J Pharm Bioallied Sci.2011 Jan-Mar;3(1): 170172.doi:10.4103/0975-7406.76505PMCID:PMC3053518Biofunctional prosthetic system: A new era complete dentureVandana SainiandRuchi SinglaFaculty of Dentistry, Dr. H.S.J. Dental College, Punjab University, Chandigarh, India. E-mail:teena2982@yahoo.co.inCopyright Journal of Pharmacy and Bioallied SciencesThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Sir,This clinical report describes the prosthetic rehabilitation of an edentulous patient,who was dissatisfied from her 8-year-old denture. To give her a better fit, we opted Biofunctional Prosthetic System (BPS) for the new prosthesis. BPS is the system designed to work with the body in a biologically harmonious way, maximizing function, and giving comfort and natural appearance to the patient. The functional impression technique and simulation of the jaw movements by the Stratos 200 articulator in BPS ensure that BPS denture meets most exacting requirements.[1]BPS denture meets the esthetic demand of patients with its unique Ivoclear teeth, which replicate anatomy of the natural tooth Ivoclear teeth are made up of 3 layers of cross-linked acrylic resins that contribute to a life-like appearance and resistance to wearing. BPS system uses a controlled heat/pressure polymerization procedure during which time the exact amount of material flows into the flask to compensate for shrinkage, which ensures a perfect fit. This pressure also optimizes the physical properties of the denture. [2]A 60-year-old edentulous woman with a chief complaint of compromised function and esthetics was treated in the clinic. Intraoral examination showed resorbed ridges and masticatory dysfunction [Figure 1]. An extraoral examination revealed flattened mandibular plane. She was wearing dentures with attrited teeth and worn out denture base. A significant loss of vertical dimension affected the temporomandibular joint. Hence, a BPS denture was planned to give her a better fitted prosthesis.The BPS recommends impression making similar in principle to the mucostatic method that minimally compresses tissues, using a combination of irreversible hydrocolloids of varying densities together in the same impression.[3] Low-density impression material (syringe Acc Gel) was syringed into the vestibular area and the occlusal centric tray was loaded with high-density hydrocolloid and inserted into the patients mouth to get the initial vertical dimension [Figure 2]. This vertical dimension was used for mounting the casts obtained from initial impressions, taken with Accu-trays (different from conventional denture trays) with an extra flange to cover the vestibular areas and extended distal part to cover the retromandibular pad area more efficiently [Figure 3]. Custom trays were made on the primary casts. The Gnathometer M tracing device was attached to the casts, which facilitates the clinical procedures of secondary impression making, face-bow record and jaw registration [Figure 4].The secondary impression was taken with zinc oxide eugenol impression paste [Figure 5]. Casts were poured and a wax-up denture was made for the trial [Figure 6]. After checking the fit and occlussal relations, the denture was sent to the laboratory. Dentures were cured with injection molding technique [Figure 7] using Ivocap high-impact plus denture base material.[4] Necessary adjustments were done and the dentures were delivered to the patient.The patient was recalled after 6 months and examined. There was no occlusal disharmony or sore spots. The patient was very much satisfied with her new prosthesis and she showed her gratification for the comfortable prosthesis and a younger look.AcknowledgmentsWe are grateful to Mr. Chauhan, Dental Technician, Chauhan Dental Lab, Sec-32, Chandigarh, India, for his laboratory work.References1.Available from: BPS Dentures smilebydesign_in Best Dentist In Delhi[Last cited in 2010]2.Available from:http://www.familydentalhealthcentre.com/completedenture[Last cited in 2010]3.Roraff AR, Stansbury BE. Errors caused by dimensional change in mounting materials.J Prosthet Dent.1972;28:24752.[PubMed: 4558968]4.Patel BN. Acrylic removable prosthesis- an integral part of modern Day Dentistry.Famdent.2005;6:624.Figures and TablesFigure 1

Resorbed ridgesFigure 2

Occlussal centric tray loaded with impression for recording initial vertical dimensionFigure 3

Biofunctional prosthetic system impression traysFigure 4

Bite registration through Gnathometer MFigure 5

Secondary impression-making with zinc oxide eugenol pasteFigure 6

Wax-up trial for the patientFigure 7

Acrylized denture

Articles fromJournal of Pharmacy & Bioallied Sciencesare provided here courtesy ofMedknow PublicationsJoint Vibration Analysis in Routine Restorative DentistryWritten by Mark W. Montgomery, DMDFriday, 10 September 2010 12:46INTRODUCTIONClinical ConsiderationsThe urgency for taking the temporomandibular joint (TMJ) condition into account is the pervasiveness of occlusion-related disease and the recent advances in restorative and prosthetic systems. Clinical best practices would include the screening and diagnosis of the temporomandibular condition in the evaluation and treatment of the occlusion-related diseases such as abfractions, wear, mobility, periodontal damage, fractured teeth, and abnormal parafunctional muscle activity.During routine dentistry, in the vast majority of dental practices, 2 oversimplified assumptions are made that then determine the course of occlusion, mastication, and dental anatomy decisions for the patient. These assumptions are: (1) that the asymptomatic TMJ is either healthy, or as healthy as can be expected for this patient, and (2) that maximum intercuspal position (MIP) is the most stable position in which to reference the patients dental care.

Figure 1.Preoperative photo.Figure 2.Deprogramming appliance (in anterior contact only).

Figure 3.Stabilized bite registration for Joint Vibration Analysis (JVA) (BioRESEARCH) testing.Figure 4.Maximum intercuspal position versus stable condylar position on the articulator.

Figures 5a and 5b.Preoperative JVA with disc derangement.

Figures 6a and 6b.Before and after JVA.

Figure 7.Before and after case photos.

These 2 assumptions are commonly adopted as the default scenario for dental care for several reasons. Namely, the clinical manifestations of TMJ derangements are often encountered at a later or more chronic stage that does not lend itself easily to diagnosis and/or treatment. Many of these later-stage, chronic disc derangements are often asymptomatic before and after routine dental care. Furthermore, most of these later-stage TMJ derangements are not correctable withroutinedentistry.Also, the MIP is seemingly the most easily determined position of the interface between the maxilla and mandible due to patient accommodation and preference of interdigitated teeth. Additionally, the facet-to-facet interdigitation of the teeth is routinely utilized to relate the maxillary teeth to the mandibular teeth on laboratory models of the patients dentition.Relying on either or both of these assumptions creates or perpetuates the existing conditions, pathologies, and the position of the mandibular condyles and their respective disc and ligament apparatus. This perpetuation of the current status puts even the most limited restoration in jeopardy of early failure or worsening of the patients condition.While the majority of patients without reported symptoms will accommodate or continue to accommodate to this condition/position of the condyles, the glaring signs of occlusal disease and pathology are staring the practitioner in the face. These signs are primarily being treated symptomatically or ignored, rather than systematically evaluated and treated at the source of the problem.This situation is frustrating for dentists, as they often feel that they dont have the opportunity or urgency of symptoms to be able to take control of the problems. Additionally, there has been a challenge to integrate the concepts of occlusion with the condylar position. Many dentists have studied with various occlusion camps only to become confused regarding the relevance of the condylar position or which condylar position is correct. This debate has continued for years as to the best way to define and establish what a normal condylar position is. As a result, the only established norms for occlusion have relied on the systems created to produce successful clinical results and idealistic concepts that are perpetuated in texts and academia.Consequently, dentists end up discussing their philosophy of occlusion without regard to routine objective measurements that could establish the relative health or normality of the stomatognathic system.This situation is also frustrating for patients, as they are at a loss as to what is normal for them. How much deterioration of their dentition is acceptable? Why, when they return to the dentist year after year, is something wrong, every time? And which of their symptoms are important enough to report to their dentist? They often end up years down the road with thousands of dollars of dentistry done only to discover that their wear and/or pain continues, and their condition is never truly under control, despite their best intentions and investment.Technological Implications ofJoint Vibration Analysis

Lou Shuman, DMDDr. Peter Dawson wrote, on page 3 of his latest text Functional Occlusion: From TMJ to Smile Design, that all occlusal analysis begins with the TM joints. The temporomandibular joint (TMJ) is widely considered to be the skeletal base of the stomatognathic system. As dentists, we understand that TMJ stability is critical to a stable and predictable occlusion. It has become clear that a key component of the stomatognathic health is the interplay among the teeth, muscles, and the TMJs. Without a pair of stable TMJs, a stable occlusion is next to impossible, and this has a direct and obvious impact on the success or failure of our restorative, cosmetic, and orthodontic treatments. Without a clear objective and detailed assessment of TMJ function, we cannot predict the future success (or failure) of our dental treatments, nor can we determine if subsequent TMJ pathologies previously existed, or were the result of our dental work.We need a tool that can alert us to subclinical pathology before we begin treatment, one that can quickly and accurately assess TMJ function (or dysfunction) and compare it to previous screenings to see if our patients TMJs are improving, stable, or getting worse. We also need a tool that can immediately assess the impact of our treatments on TMJ function. A suitable device for screening, assessment of pathology progression, and treatment outcome analysis has been hard to find.The TMJ has been the subject of much confusion because the quick and inexpensive methods of screening for TMJ pathology are either subjective and unreliable (auscultation, palpation, patient report, and Doppler); or they are expensive, invasive, and provided only static images of the joint with no information on the dynamic function of these unique joints (computed tomography scans, cone beam tomography, magnetic resonance imaging). In fact, the most recent research from the British Institute of Radiology indicates that the interobserver agreement on MRI scans is fair at best.1Enter Joint Vibration Analysis (JVA) (BioRESEARCH). The JVA system brings objectivity and predictability to the assessment of TMJ function and stability. Normal TMJs have smooth, well-lubricated surfaces in a proper biomechanical relationship and produce almost no vibration. But surface changes, such as those caused by degeneration, tears, or displacements of the disk, generally produce friction and vibration. Different disorders can produce different vibration patterns or signatures. PC-assisted vibration analyses helps identify these patterns and helps you distinguish among various TM disorders.JVA provides a fast, noninvasive, and repeatable measurement of TMJ function to aid in the diagnosis of TMJ condition. Understanding TMJ function is vital any time you are changing the vertical, lateral, or the anterior/posterior position of the mandible. Common dental treatments can change mandibular position. In addition to TMD treatment, orthodontics, prosthodontics, restorative, and sleep dentistry can all benefit from JVA testing.A JVA recording takes 10 seconds of patient time, and less than 2 minutes of staff time. In less than 5 minutes, your staff can be trained to take accurate, repeatable data. Simply searching JVA 60-second instructional video on youtube.com will give you an idea of how fast and easy it is to get this data on every one of your patients.

Reference1. Butzke KW, Batista Chaves KD, Dias da Silveira HE, Dias da Silveira HL. Evaluation of the reproducibility in the interpretation of magnetic resonance images of the temporomandibular joint.Dentomaxillofac Radiol. 2010;39:157-161.

Fortunately, we currently are in a new place of discussion regarding the diagnosis and possible therapies for occlusal, masticatory, and temporomandibular care. With an objective test for TMJ condition, better treatment plans can be devised for occlusal disease.This new place where we are is directly related to the development and usage of biometric technology that gives the doctor objective data from which to make decisions and measured documented treatment results.The past attempts to record and/or measure the condylar position and condition included axiopath recordings of joint position and border movements, transcranial and tomographic radiography with objective and subjective interpretation, comparison of condylar position on articulators with multiple jaw position bite recordings, magnetic resonance imaging (MRI) and functional MRI scans, computed tomography (CT) and cone beam CT scans, contrast arthrography, computerized mandibular positions based on transcutaneous electrical nerve stimulation pulsed muscle contractions irrespective of the condylar position, face-bow mounted casts on various articulators referenced to numerous closure paths from speech to swallowing, from controlled manipulation to deprogrammed patient closure. At best, these methods were expensive and time consuming; and at worst, these techniques were dependent on the clinicians experience and subjective analysis.The current biometric standard with the Joint Vibration Analysis (JVA), a system of equipment and software manufactured by BioRESEARCH(bioresearchinc.com), allows the dentist to easily and objectively measure the condition of the condyles quickly, affordably, and irrespective of treatment philosophy. The mandate from the ADA, as stated in 1990 and 1992, calls upon the dentist to document, assess, note, describe, evaluate, and record the presence, location, loudness, timing, consistency, and quality of joint vibrations. This mandate then encourages us to consider biometrics that will accomplish this effectively and affordably with high levels of sensitivity and specificity. The JVA system achieves this standard and creates a 21st-century documentation of objective information that will afford the treating dentist the ability to diagnose the patients condition and monitor the patient throughout preventive or therapeutic care. By establishing objective measurements of the condylar condition, the dentist can evaluate the effect of future events such as injury, accident, or therapy. The doctor can also begin to correlate the condylar condition with other data, such as bite force analysis (with T-Scan) and/or electromyography (BioPAK [BioRESEARCH]) measurements of the muscles of mastication. In addition this JVA system can be overlaid on data regarding mastication analysis (BioPAK), range of motion, and mandibular position.CASE REPORTA patient presented to our office with severe occlusal-related disease. Examination revealed abfractions, anterior wear into the dentin, and periodontal attachment loss. The patient desired a long-term restorative solution that would include aesthetic enhancement of the smile (Figure 1).The case was designed with a mock-up of the anterior smile zone, followed by a determination that the envelope of function would be well controlled without having to restore the vertical dimension. The development of the anterior envelope of function was accomplished by first deprogramming the avoidance pattern muscle engrams with an anterior contact (only) appliance. In the deprogrammed patient, the mandibular position is determined by an anterior contact composite ball bite (open-bite centric). This open-bite registration is then tested with the JVA and compared to the preoperative JVA. By testing the stability of the TMJs at the time of bite registration, we can be confident that our diagnostic wax-up will be designed not only to the desired aesthetic result, but also that the provisionals and final restoration will be accomplished with the condyles in a more smooth and stable position (Figures 2 and 3).The patients preoperative casts and mock-up casts were mounted, and cross mounted, at the most stable condylar position allowing for the desired smile design and functional anterior zone. This mounting with the apex of force centric open-bite registration can then be studied on the articulator for a comparison of the condylar position with the condylar position that is associated with the preoperative MIP interdigitation (Figure 4).Commonly, the cases that have avoidance-related anterior wear and muscle engrams also show a condylar position discrepancy between the MIP condylar position and the stabilized mandibular restorative position. These small dislocations of the condyle in the MIP are frequently associated with disc movement and subtle changes in the morphology of the posterior band of the meniscus. This increases the frequency of inflammation in the joint and the likelihood that the patient will suffer a partial- or full-disc displacement, along with the associated popping and possible retrodiscal impingement and pain (Figures 5a and 5b).The condyle position discrepancy between stable/normal and the MIP dislocation can be in almost any direction and position. The clinical manifestation of this discrepancy is usually referred to as a slide, or as a closure interference. Rarely does this dental slide actually show up as the condyle being on the disc and downward and forward on the eminence. Rather, the abnormal MIP condyle is pulled downward and away from the disc and eminence, thus destabilizing the disc and allowing for the disc movement that is observed on the JVA.JVA Practice Management Ramifications

Amy MorganIf part of your practices vision is to implement the very latest technologies and cutting-edge clinical skills to enhance your patients experience, Joint Vibrational Analysis (JVA) (BioRESEARCH) can be a very significant addition. Using JVA as a tool for diagnosing and educating your patients in a holistic approach to their overall oral health and well-being by addressing temporomandibular Joint diesease prior to treatment is essential.The initial investment in the equipment necessary to perform JVA is approximately $10,000. This includes the training needed to incorporate it into the practice. In our interviews with various practitioners, all have reported increased case acceptance, increased fabrication of appliances, decreased restorative remakes, and an increased number of referrals (from both patients and specialists); translating into a significant potential return on investment. The more passive or qualitative returns include more predictability in results, becoming another tool to exceed patients expectations and confidence in the treatment results.The most impacted team members are the chairside assistants (and possibly the hygienists, depending on its incorporation into the periodic examination schedule). Team members are trained in-office. This helps to promote immediate comfort in utilizing this new tool in the real environment. The learning curve for the team can be fairly rapid. We have reports that clinical team members can learn the mechanics of the instrument within 10 minutes! These new skills are very empowering and can enhance each clinical job description, thus providing opportunities for improvement and growth.Lets not forget the educational impact on the dentist as well! An extensive 3-day course provides the initial training for the doctor in interpretation of the data. Continued training online and or additional off-site provide opportunities for the doctor and team to finish certification on JVA.The impact on the practice is usually minimal regarding scheduling. Simply incorporating it into your new patient evaluation as an additional screening tool is a common approach. Patients of record can be exposed to JVA during your periodic or status exams. Screening questions about headaches, tension, joint sounds, or pain are asked and patients with positive answers are given the JVA quick test (approximately 3 minutes). Reading and interpretation of this screening either leads to no further action (negative results), or, if positive indicators result, the patient is scheduled for further services. Patients are intrigued by the JVA and feel this technology is yet another sign of a progressive, high-tech, and comprehensive approach to their care. This can definitely create a buzz and additional referrals.For dentists and team members who are passionate about doing everything possible to improve the health of their patients, JVA is another option to take to improve your processes and procedures.

Consequently, we now pay very close attention to any joint vibration that occurs during the time that the teeth are sliding into MIP, or in the timeframe just before closure. These are the early, subclinical vibrations that can be easily treated by elimination of the closure interferences and/or re-establishing the normal vertical dimension of occlusion. Certainly, the treatment plan does not have to include a change in vertical dimension or a full-mouth rehabilitation; however, it must ensure that the closure interferences (slides) are eliminated and that any hyperactivity of the lateral pterygoid muscles related to working or nonworking interferences be controlled with appropriate occlusal therapy. This occlusal therapy can include subtractive coronoplasty on the interferences, but more frequently depends on appropriate additive coronal enhancement of the anterior and canine teeth.The use of the JVA during treatment design and provisionalization as well as postoperatively gives us the assurance that we are not only aware of any pretreatment problems or red flags, but most importantly, that in the course of any dentistry that influences tooth contact or occlusion patterns, we have not made changes that result in a more unstable TMJ apparatus than we noted before treatment. We would always like the patient to finish our care better off than when we first started (Figures 6a to 7).DISCUSSIONRegardless of other biometrics or treatment philosophy, the JVA provides objective information to the treating doctor as to the stability or instability of the TMJ condylar apparatus. This information can be easily utilized in the decision as to whether (or not) MIP would be the best choice in making dental treatment plans for the best long-term patient prognosis. Certainly, an unstable condyle being present in the attempt to treat occlusal disease would necessitate the treating doctor to consider and document the effect of his or her treatment of the dentition on the stomatognathic system, including the TMJs. In the authors experience, in utilizing the JVA system in literally hundreds of full-mouth rehabilitations during the last 11 years, several conditions of the patient bring this technology to bear.The most enlightening finding from JVA recordings has been the diagnosis of subclinical problems that represent early or unstable condyle-disc problems that are not perceptible with any other technology, especially palpation or auscultation. This condition shows up as disc movement, joint laxity, and/or TMJ inflammation. The ability to diagnose this subclinical condition has revealed that appropriate treatment of the dentition can result in stabilizing or correcting the problem in the condyle disc apparatus. This is the missing link in the conversation of the connection between the occlusion and the TMJ condition.If problems can be detected before they become permanent ligament or disc damage, then stabilization through effective occlusal therapy will afford the patient the best possibility for long-term health and function

INDIAN DENTAL ACADEMYIndian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats and courses we offer Dental Implantology, fixed orthodontics, rotary endodontics,General dentistry. and various online dental courses having best faculty of world wide repute Fixed orthodontics training online orthodontic training advanced Implant dentistry courses Fixed orthodontics training certified orthodontic online courses Rotary Endodontic coursesWednesday, July 24, 2013ESTHETICS IN COMPLETE DENTURES

ESTHETICS IN COMPLETE DENTURECONTENTSIntroductionReview of LiteratureDentogenicsDiscussionConclusionBibliography

INTRODUCTIONAn acceptable cosmetic effect in any dental restoration has always been regarded as important to good dentistry. A well-made prosthesis will fail if it is deficient in this respect.Esthetics includes the appreciation and response to the beautiful in art and nature. Esthetics has been given many definitions in dentistry but according to Young. It is apparent that beauty, harmony, naturalness and individuality are major qualities of esthetics. The dentist must visualize esthetics in relation to the patient and then translate that visualization into an acceptable esthetic result. The success of his efforts depends upon his artistic ability, his powers of observation and his experience.The selection of anterior teeth for an edentulous patient is a most important and often difficult problem for the dentist. He should select teeth which not only embody the proper form and size, but the most ideal shade as well.The art of selection of teeth for edentulous patients has been lost in the maze of tooth guides, folders and pamphlets and the numerous methods of selection advocated by researchers.An attempt has been made in this seminar to briefly describe the various methods advocated in the literature and to reach a practical method.For the sake of clarity and simplicity, the matter has been dealt with under the following sub headings.-Introduction-Review of LiteratureoEvolution of TechniquesoDentogenicsoThe Golden Proportion-Discussion-Conclusion

REVIEW OF LITERATUREI)Evolution of TechniquesYoung in 1954 described the evolution of various techniques used in the selection of the anterior tooth mold.Technique 1During the ivory age and early porcelain period, teeth were selected or created mostly by dimensional measurements of the denture space and arch size with little regard to esthetics.Technique 2Technique of Correspondence and Harmony projected by J.W. White in 1872. By this time, the temperamental theory was fading out of medicine but white reached over and suggested that the temperaments called for similarity of formin faces and teeth.The temperamental theory is a theory of the fluids of the body, especially the blood, the phlegm and the bile. It was conceived by Hippocrates in the 5thcentury BC and was used continuously by the medical profession in diagnosis and treatment until the nineteenth century, when it gave way to demonstrate science.Choleric temperament predominance of yellow bile characterized by anger, irritability, a jaundiced view of life. Body structures are small and finely textured.Melancholic due to predominance of black bile and characterized by depression.Phlegmatic temperament due to abundance of phlegm in respiratory passages. Alleged to make people stolid, apathetic and undemonstrative. A physical decline occurs due to phlegm in the blood.Sanguine temperament attributed to a predominance of blood and characterized by cheerfulness and optimism. Red complexion, large body, strong musculature and vigorous action.This was the introduction of the temperamental theory into dentistry but it was not widely used till after 1885 when temperamental forms of teeth were manufactured as named sets.Technique 3The Typical form concept projected by W.R. Hall in 1887. This was the initiation of the geometric theory later presented by Williams.The basis of this classification was two-fold, the major basis was the tooths labial surface curvatures (transverse and gingivo-incisal), outline form and neck width.Hall gave the classification of ovoid, tapering and square.The minor basis was the labio-lingual inclination of the upper incisors in relation to profile types. This classification apparently exerted little influence on practice procedure at that time.Technique 4The temperamental technique was the first technique of selecting tooth form from the point of view of influence and universal acceptance. It required several years to associate and establish dental characteristics of the temperaments and to incorporate them in manufactured tooth forms, this occurred by 1885.Dentists like Flagg, Laycock, Hutchinson, Kingsley et al and artists like Madame Schimmelpeinik, spurzheim and Jacques contributed to the development and acceptance of this theory.However, only rarely could two dentists agree on exactly what the theory meant, what it taught and what it required. It had an intangible quality which could not be defined in any authoritative way.Technique 5Berrys biometric ratio method 1906.Berry projected in 1903 that the outline form of the inverted central incisor tooth closely approximated the outline form of the face. Therefore the outline form of the edentulous face indicated the outline form of the anterior teeth to be chosen for a denture patient.Berrys continued investigation into the correlation between faceform and tooth form resulted in the discovery that the maxillary central incisor was 1/16ththe width of the face and 1/20thits length. Subsequent research by M.M. House and others proved the 1/16thwidth ratio but the 1/20thlength ratio which was frequently not possible to use due to interference by ridge bulk. Difficulty in practical applications discouraged the use of this technique.Mavroskoufis et al in 1981 concluded that the inter-alar nasal width is a reliable guide for selecting the mold of anterior teeth. The tips of the canines were found to lie on a projection of two perpendicular lines drawn from the outer surfaces of the nasal alae.Thus the mesiodistal width of the artificial anterior teeth should be determined by adding 7mm to the patients nasal width.They found no relationship between the nasal width and the total/overall width of the four incisors.The authors advocate that the tips of the canine be set on a line which passes through the posterior border of the incisive papilla which proved to be a stable anatomic land mark.The incisive papilla can also be used as a guide for arranging the labial surface of the central incisors at 10mm anterior to the posterior border of the papilla.Kern in 1967 studied various anthropometric parameters of tooth selection by examining over 6000 skulls. He concluded that:1.The bizygomatic measurement did not show a high percentage consistency ratio to the width of the crowns of the maxillary central incisors.2.Nor did the skull length measurement prove reliable for the determination of the length of the maxillary central incisor crown.Significantly consistent ratios were found to occur in:1.The nasiomenton (internasal and nasofrontal sutures and the chin) measurement and the length of the maxillary central incisor crown showed a 11:1 ratio in 81 per cent of skulls. However this has little significance in edentulous patients whose nasiomenton measurements depends on the degree of mouth opening and the orientation of the occlusal plane.2.The cranial circumference and the widths of the maxillary anteriors showed a ratio of 10:1 in 91 percent of skulls. This has been reported by Sears also.3.93% of skull showed equal or near equal measurements between the nasal widths, nasal aperture and the width of the four maxillary incisors.4.The maxillary and mandibular anterior teeth showed a high percentage ratio of 5:4 in 90% of skulls. Sears also reported similar findings.Technique 6Clapps tabular dimension table method 1910.Teeth were selected based on the overall dimension of six anterior teeth arranged on the Bonwill circle and the vertical tooth space available in the patient.A table with illustrations of molds allowed the dentist to select and specify the mold to be used by number.

Technique 7Valderramas Molar tooth Basis was projected in 1913. This method of only historical value used varying measurements between combinations of cusp points to indicate the size of the individual and overall tooth measurements. The basic problem with this technique is that edentulous patients have no molars.Valderrama also predicted a selection of tooth size on a 1/4thincrement of the size of a Bonwill triangle, determined by measuring the edentulous mandible.Technique 8Cigrande 1913 advocated the use of the outline form of the fingernail to select the outline form of the upper central incisor. The size was modified to meet the requirements of tooth space and other relationships.Technique 9The Geometric method or Law of Harmony.Williams Typal form method projected by J. Leon Williams in 1914 is based on the geometric pattern created by the outline form of the bony face frame the ovoid, square and tapering forms. William arrived at this classification after extensive anthropological study and was able to interest a manufacturer. The Dentists supply company to produce his systematized molds of teeth. Thus the typal form method or geometric method of anterior tooth selection gained universal acceptance. However further investigation by Wright in 1936, Bell in 1978 and Mavroskufis et al in 1980 invalidate this method of selection. But this method is probably still the way in which most dentists select anterior artificial teeth.Technique 10Young proposed the selection of tooth form by Mold guide sample as the 10thtechnique (in approximate chronological order).Technique 11Wavrin Instrumental Guide Technique presented in 1920 was based on Berrys Biometric ratio method and Williams Typal form teeth but its use was limited to a single manufacturers product.Technique 12Maxillary Arch outline form projected by Nelson in 1920. This technique assumed that the arch outline form was a valid method since it was related to an individuals anatomy. This was invalidated by changes in arch form due to resorption.

Technique 13Wrights Photometric method proposed in 1936 was based on using a photograph of the patient with natural teeth and establishing a ratio by comparative computation of measurements of like areas of the face and photograph. The simple unknown mathematical fomula could be used to select teeth or to create correct vertical dimension. Minute inaccuracies in measurements tended to diminish greatly the reliability of the technique so it has enjoyed little usage.Technique 14The multiple choice method introduced by Myerson in 1937 was based on a need for a selective range in labial surface characteristic of transparent labial and mesial surfaces, varying surface colour tone, and chracterization of teeth by time and wear. Harmony of tooth size and shape with face size and shape was associated with this technique.Technique 15Steins coordinated size technique presented in 1940 was based on the coronal index of 70 to 100 commonly used in prosthetic on 4 model teeth representing the range of maximum frequency of use and on the common variability in size of individual natural teeth. The index is the width percent of the length. The variability is 0.5mm ; model size varied from 7.2 to 8.7 mm.Technique 16Anthropometric Cephalic index method projected by Sears in 1941 was based on the fact that the width of the upper central incisor could be determined by dividing either the transverse circumference of the head by 13 or the bizygomatic width by 3.3. Tooth length was in proportion to face length.Technique 17Frame Harmony method by the Justi company in 1949, is based on the fact that the size and proportions of the teeth are in harmony with the general bony proportions of the skeleton. The overall tooth size is selected by a mathematical formula, 1/7ththe total dimension of the upper and lower edentulous ridges, with the dimensions of the individual anterior teeth correlated with a developed table of tooth dimensions to give the indicated over-all dimension. Other characteristic of tooth form are based on genetics, and the comparison of such dental qualities of a near relative.Technique 18Bioform technique proposed by the Dentists Supply company in 1950 is based on the geometric outline forms of face and teeth the House classification for 4 basic and 3 combination typal forms, and 3-dimensional harmony of tooth form and face form. It is associated with the tabular and mold guide systems. This is currently in use.Technique 19The Trubyte tooth indicator or Selection Indicator Instrument method advocated by the Dentists supply company which is correlated with Williams and Houses Typal form theory and the Tabular technique.Technique 20House instrumental method of projecting typal outline and profile silhouettes onto the face by means of a telescopic projector instrument and silhouette form plates. This was correlated with designated mold numbers and size variation. This was proposed by House in 1939 and by the Dentists Supply company in 1950.Technique 21Automatic instant selector guide of the Austenal company in 1951 correlated form, size and appearance in such a manner that only a single reading was required to select the appropriate tooth mold based on dimensions of denture space and harmony of face and tooth form.These were the twenty one techniques detailing the evolution of the selection of anterior teeth as described by Young in 1954.Then in September 1955 Frush and Fisher created a revolution in the field of dental esthetics by the introduction of Dentogenics. In a series of six articles published between 1955 and 1959 they described various means to more natural dentures and many tips on how to avoid the denture look.Krajicek in 1956 proposed methods involving the duplication of the patients natural teeth either before or after extraction. Klein (1960), Hayward (1968), Kafandaris and Theodoros (1974) suggested incorporating the patients natural teeth in the denture. Van Victor in 1963 proposed the mold guide cast technique.

DENTOGENICSFrush and Fisher in the first, of a series of six articles, published in 1955 introduced the dental community to Dentogenic restorations. According to them, there was nothing in the field of esthetics that had not been considered before. Yet a vacuum existed and the Denture look prevailed.Dentogenics describes a denture that is eminently suitable to the wearer in that it adds to the persons charm, character, dignity or beauty in a fully expressive smile. Dentogenics then means the art, practice and techniques used to achieve that esthetic goal in dentistry.The authors describe the origin of the concept Frush in 1952 met in Zurich, Switzerland, a master sculptor by the name of Wilhelm Zech who ground and formed teeth for his dentist father. Zech experimented with the molding, spacing and arrangement of teeth in artificial dentures with an artists concept of what belonged in the mouth of a living human. His work inspired Frush to take anew look at denture prosthetics and the Swissedent foundation was established in Los Angeles, California in 1952, from where through seminars and workshops, the concepts of dentogenics have disseminated.Frush and Fisher in 1956 advocated sex identity in dentures by the application of Dentogenics. According to them, the feminine form is characteristically spherical with a roundness, smoothness and softness that is typical of women. Whereas the masculine form is cuboidal, with the hard, muscular, vigorous appearance which is typical of men.The procedure therefore is to select a basically Feminine or Masculine mold and then harmonize it to the individual patient depending upon the personality and age factors by modifying individual teeth.The authors describe a procedure they call depth grinding which involves the accentuation of the third dimensional depth to eliminate the first appearance of the artificial upper anterior teeth. With a soft stone, the mesio-labial line angle of the central incisor is ground in a definite and flat cut, following the same curve as the mesial contour of the tooth in order to move the deepest visible point of the tooth further lingually. After this cut has been made, a careful rounding and smoothing of the sharp angle made by the stone must be accomplished and a perfect polish must be given to the ground surface.It is necessary to develop the desired effect in depth grinding by a consideration of these main factors A flat thin, narrow tooth is delicate looking and fits delicate women and involves little depth grinding. Whereas a thick, Bony, big sized tooth, heavily carved on its labial face is vigorous and is to be used exclusively for men. This involves rather severe depth grinding.For the average patient, a healthy women or a less vigorous man, the depth grinding will be an average between delicate and vigorous, the feminine or masculine characteristics being given by other tooth shaping, incisal grinding and the positioning of the teeth.Depth grinding reduces the width of the central incisors according to the severity of grinding to be accomplished. Therefore, to maintain the normal harmony of contrast in size between the six anterior teeth, a larger sized central incisor of the same mold should be selected.Again in 1956, Frush and Fisher discussed another aspect of Dentogenics the personality of a patient. They stated that the foundation for dentogenic restorations is the personality of the patient simply because the basic male or female tooth form is a refinement of that tooth form which has its inception in the personality factor. Likewise age is a refinement of the personality factor. They devised the personality spectrum and explained the precise prosthodontic application of the otherwise abstract word personality by the 3 divisions of the personality spectrum.1.Delicate meaning fragile, frail, the opposite of robust.2.Medium pleasing meaning normal, moderately robust, healthy and of intelligent appearance.3.Vigorous meaning the opposite of delicate, hard and aggressive in appearance, the extreme male animal, muscular type almost primitive, ugly.The personality spectrum can be used in our artistic endeavour to inject a variety of tooth form and tooth position, at the comprehensive level of individual patient personality analysis. A small percentage of patients are delicate, and a slightly larger percentage are vigorous. The remaining majority of patients fall into the medium section of the personality spectrum, but all of these have either vigorous or delicate tendencies.The use of the dentogenic concept is made easier by considering the smile as the primary objective personality trait of the patient. This primary objective personality trait and the personality spectrum is used for the selection of the mold category. These fundamental shapes must then be subjected to the refining procedure of sex and age modifications.The age factor in dentogenics, considered by Frush and Fisher in 1957, determines the selection of the shade of the mold to be used in the denture. Light shades are considered appropriate for young people and darker shades are considered esthetic for older people. Also bluish incisal tinges are preferred for the young and grayish shades for the older. Mold refinement is done by producing worn incisal edges and cuspid tips, attritional and abrasional facets, development of diastemata to indicate tooth loss and subsequent drifting.Thus the dignity of advancing age may be portrayed in the denture.In 1958, Frush and Fisher propounded the Dynesthetic interpretation of the dentogenic concept. Dynesthetics is a compounded word. The prefix dyn is from the Greek word dynamis meaning power. It implies movement, action, change and progression in the esthetic phase of prosthodontics. This dynamic value has been described as making the difference between an artifact, any object without life-like effect such as a spoon, and a work of art or visual objects that are alive in meaning such as a statue.Therefore the application of dynesthetics allows a denture to be a work of art and have a life-like effect against a denture lacking artistic treatment and thus remain an artifact.The dynesthetic techniques are rules which concern the 3 important divisions of denture fabrication.1.The tooth.2.Its position.3.Its matrix (visible denture base).The selection and modification of the tooth according to dentogenics has already been described. The positioning and denture base considerations are beyond the scope of this seminar.THE GOLDEN PROPORTIONOf particular interest is the so called Golden proportion that exists between the perceived widths of the upper anterior teeth.Lombardi in 1973 and Levin in 1978 demonstrated that the width of the central incisor is in golden proportion to the width of the lateral incisor. The width of the lateral incisor to thewidth of the canine is also in golden proportion as is the width of the canine to the first premolar. The golden proportion exists when the ratio between a larger part B (for example) to a smaller part A (for example) is 1.618.

DISCUSSIONA practical approach to the selection of the anterior teeth is to consider the size, form and color.SIZE:May be determined from:-Pre extraction records.-Marking the corners of the mouth on the occlusal rim gives the width of the 6 anterior teeth.-Marking the inter alar width on the occlusal rim gives the width of the 6 anterior teeth from cuspid tip to cuspid tip.-Length may be determined by noticing visibility of the incisal edges and relating this to lip length and dentogenics.FORM:Inspite of the body of research that invalidates Williams Typal theory, clinically, it is observed to provide esthetic results and as stated by William Observance of this rule will always give you perfect harmony the harmony of opposition of line.The form may also be selected considering first the personality of the patient and then modified according to the sex and age of the patient to individualize the mold.Pre extraction records may also be of value in the selection of the form of the anterior teeth.COLOR:Color of the teeth is to be determined by the skin coloring of the individual. The color selected should be so inconspicuous so as not to attract attention to the teeth. The squint test may be helpful in evaluating colors of the teeth with the complexion of the face. With the eyelids partially closed to reduce light, the dentist compares prospective colors of artificial teeth held along the face of the patient. The color that fades from view first is the one that is least conspicuous in comparison with the color of the face.The age of the patient will also effect the color of the teeth. The general rule is that darker teeth are more appropriate in older patients and lighter teeth are more harmonious in young patients.This rule however must be overruled for the patient who does not smoke and takes food of slight pigmentation and may continue to have a relatively light tooth body together with the normal color texture. This is an application of dentogenics to the color selection.CONCLUSIONThe selection of anterior teeth is an important part of the esthetic phase of denture fabrication. It is essential not to be embroiled by the various techniques aimed at making the task easier. What is necessary is the development of an esthetic sense by the observation of natural dentitions in response as well as in function so as to be able to create dentures that are living things belonging to a human being and not just mere artifacts that are poor replicas of what has been lost.

BIBLIOGRAPHY1.BELL R.A. : The geometric theory of selection of artificial teeth : Is it valid ?. JADA 97 : 637, 1978.2.CLAPP G.W. : How the science of esthetic tooth form selection was made easy. J. Prosthet. Dent. 5 : 596, 1955.3.Dorlands Illustrated Medical Dictionary. W.B. Saunders, 28thEd. Pg 1666.4.FENN, LIDELOW, GIMSON (1989) : Clinical Dental Prosthetics, 3rdEd., Wright.5.FRUSH J.P. and FISHER R.D. : Introduction to dentogenic restorations. J. Prosthet. Dent. 5 : 586, 1955.6.FRUSH J.P. and FISHER R.D. : How dentogenic restorations interpret the sex factor. J. Prosthet. Dent. 6 : 160, 1956.7.FRUSH J.P. and FISHER R.D. : How dentogenics interpret the personality factor. J. Prosthet. Dent. 6 : 441, 1956.8.FRUSH J.P. and FISHER R.D. : The age factor in dentogenics. J. Prosthet. Dent. 7 : 5, 1957.9.FRUSH J.P. and FISHER R.D. : The dynesthetic interpretation of the dentogenic concept. J. Prosthet. Dent. 8 : 558, 1958.10.HAYWARD D.E. : Use of natural upper teeth in complete dentures. J. Prosthet. Dent. 19 : 359, 1968.11.HICKEY J.C., ZARB G.A., BOLENDER C.L., (1985) : Bouchers prosthodontic treatment for edentulous patients, 9thEd., Mosby, S. Louis.12.HEARTWELL C.M. and RAHN A.O. (1986): Syllabus of complete dentures, 4thEd., Lea and Febiger, Philadelphia.13.KERN B.E. : Anthropometric parameters of tooth selection. J. Prosthet. Dent. 17 : 431, 1967.14.KAFANDARIS N.M. and THEODOROU T.P. : Complete denture technique using natural teeth. J. Prosthet. Dent. 33 : 571, 1974.15.KLEIN I.E. : Immediate denture prosthesis. J. Prosthet. Dent. 10 : 14, 1960.16.KRAJICEK D.D. : Personalized acrylic resin anterior teeth. J. Prosthet. Dent. 6 : 29, 1956.17.LEVIN E.I. : Dental esthetics and the Golden proportions. J. Prosthet. Dent 40 : 244, 1978.18.MAVROSKOUFIS F. et. al : The face form as a guide for the selection of maxillary central incisors. J. Prosthet. Dent. 43 : 501, 1980.19.MAVROSKOUFIS F. et. al : Nasal width and incisive papilla as guides for the selection and arrangement of maxillary anterior teeth. J. Prosthet. Dent. 45 : 592, 1981.20.PICARD C.F. : Complete denture esthetics. J. Prosthet. Dent. 8 : 252, 1958.21.SEARS V.H. : Selection of anterior teeth for artificial dentures. JADA 23 : 1512, 1936.22.VAN VICTOR A. : The mold guide cast Its significance in denture esthetics. J. Prosthet. Dent. 13 : 406, 1963.23.WRIGHT W.H. : Selection and arrangement of artificial teeth for complete dentures. JADA 23 : 2291, 1936.24.YOUNG H.A. : Selecting the anterior tooth mold. J. Prosthet. Dent. 4 : 748, 1954.

INDIAN DENTAL ACADEMYIndian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats and courses we offer Dental Implantology, fixed orthodontics, rotary endodontics,General dentistry. and various online dental courses having best faculty of world wide repute Fixed orthodontics training online orthodontic training advanced Implant dentistry courses Fixed orthodontics training certified orthodontic online courses Rotary Endodontic coursesTuesday, July 30, 2013HIGH SPEED CUTTING INSTRUMENTS IN PROSTHODONTICS

HIGH SPEED CUTTING INSTRUMENTS IN PROSTHODONTICSIntroductionIn order to perform the intricate and detailed procedures associated with restorative dentistry, the dentist must have a complete knowledge of the purpose and application of the many instruments required. During each day of his clinical experience the dentist operates on vital tissues within the oral cavity where a millimeter or a fraction there of, is a very significant dimension. A skillful application of sharp hand and rotary instruments requires ability and coordination gained only by extensive training.Before the advent of rotary instruments, removal of tooth tissue was accomplished with sharp edged chisels, hatchets, and hoes. These hand instruments possessed a cutting capability, which was used for clearing away unsupported and undermined enamel resulting from dental caries. Walls and floors of the cavity were formed by a planning and lateral scraping action of these sharp edged instruments. At best, such efforts were crude, time consuming and often difficult.The first, rotary instruments for cutting tooth tissue were modified hand instruments. These, drill or bur heads could be twisted in the fingers to produce a cutting or abrading action. In 1846 the finger ring was introduced with a drill socket attached for adapting a series of long bundled burs or drills. This was the primitive application of the rotary principle. The first drill having flexible cable drive and the first angle hand piece were introduced by Charles Merry between 1858 and 1862. In 1871, Morrison modified and adapted the dental foot engine from the Singer Sewing machine. This was followed by the introduction of the electric dental engine utilizing a cable arm in 1883. In 1910 the endless cord on a jointed arm was made available. The earlier dental hand pieces were capable of speeds from 4500 to 6000 rpm.In 1940 the use of diamond abrasive paints became widespread. The diamond point is compared of a number of small diamond particles bound on a rotary blank.In 1945 Dr. G.V. black, published a report on the non mechanical preparation of cavities and in doing so introduced the air abrasive technique. The impact of Dr. Blacks revolutionary cutting technique on the dental profession was considerable. This was the first significant break in the long established traditional method of cavity preparation. The air abrasive principle utilized particles of aluminium oxide propelled against the tooth surface by a carbon dioxide stream under the pressure of 110 psi, and funneled through a tungsten carbide nozzle with a lumen of 0.018 inch. The penetration of enamel and dentin was rapid but some what difficult to control.In 1949 Walsh and Symons published their initial findings relating to the removal of tooth tissue with diamond points at rotational speeds upto 70,000 rpm. This report indicated the use of lighter forces and a resulting increased cutting efficiency at these higher speeds.In early 1950, the ball-bearing hand piece was introduced.In 1963, following the work of Nelson the first fluid turbine type handpiece was introduced. This instrument was capable of rotational speeds of approximately 50,000 rpm and was limited to diamond instruments operated at one speed only. In 1954, air-driven hand pieces were developed. A continuous belt-driven contra-angle which utilized a friction grip chuck and bur was introduced, making possible cutting speeds of upto 150,000 rpm.By 1957, many dentists were using rotational speeds upto 3,00,000 rpm. The introduction of air-bearing hand piece in the early 1950 made possible greater rotational speeds of approximately 5,00,000 rpm.In 1953, an ultrasonic method of tooth tissueremoval was also introduced, which used suitably shaped tips vibrating at frequencies ranging from 2,50,000 to 3,00,000 cycles per seconds.This brief historical back ground reveals that the profession has been searching for a suitable method of tooth tissue removal. Only during last 30 years, this hunt has slowed down still the profession is trying to refine the procedure and instruments.Review of literatureA search through literature reveals various methods used in the past for removal of tooth tissue. The continuous development of newer methods till 1960, indicatesthat the earlier instruments had some disadvantages. Inspite of the introduction of numerous tooth reduction instruments, and procedures, the principles and the biologic objectives have remained the same. These are as follows.1.The operator should remove the least amount of tooth tissue consistent with necessary mechanical retention.2.This should be done with the least barm to the periodontal tissues and the pulp.3.It should be done with the least discomfort to the patient.4.No pathologic reactions should be initiated in the pulp.Advantages of high speeds1.Smaller stones can be used at the increased speeds.2.Less fatigue results both for the patient and operator.3.Due to high speed, very light pressure is required.4.Less vibrations are felt by the patient.5.The chairside time for a given preparation is considerably reduced.6.Trauma to the pulp is reduced.7.The efficiency and life of the cutting tools is increased.8.Because of small tools, control is easy.9.Removal of old amalgam and gold restorations is easy.Disadvantages of high speeds1.The increased speed creates increased temperatures in the tooth. Therefore some method of cooling the tooth more efficiently is required not to injure the pulp. This necessitates additional equipment.2.When a dentist changes from the lower speeds, which utilize a pressure in pounds, to high speeds which need only a pressure in ounces, he must develop a new technique and retrain himself to a new tactile sense.3.To operate at high speeds good visibility of the cutting instrument is necessary to avoid over cutting.4.Due to the ease with which tooth tissue is removed, caution must be taken not to injure the proximal enamel of the adjacent healthy tooth and the gingiva.5.High speeds result in greater wear on the working parts of the handpiece, necessitating more frequent repairs and replacements.6.Unless used properly, high speeds have a tendency to create striations on a tooth surface.7.The ideal preparation for any type of restoration cannot be accomplished by using high speed equipment alone. The final exactness and finishing line can best be established by instruments revolving at moderate speeds.Types of high speed instrumentsHand piece can be divided into four types depending upon their speeds as follows.1.Low speed upto 10,000 rpm.2.Intermediate speed 25,000 to 45,000 rpm.3.High speeds 50,000 to 1,00,000 rpm.4.Ultra high speeds 1,00,000 rpm and over.Kilpatric has further classified the ultra high speed handpiece into three classes.Type I the gear driven centre-angle handpiece, upto1,25,000 rpm.Type II the belt driven contra-angle handpiece upto 2,00,000 rpm.Type III turbine driven air contra-angle handpiece upto 3,00,000 rpm and higher.Heat generation:Knowledge of the physics tells us that, whenever there is friction between two surfaces, heat is generated, which may bring about rise in temperature of either or both the surfaces. The same applies in the tooth reduction procedures. Here the rotating cutting tools come in contact with the tooth surface and the heat is generated.It was not until 1930 that the workers began to investigate the heat rise in the dental pulp.There are many factors that influence the rise in temperature which takes place in cutting operations. The greater the speed of rotation of the cutting tool, the faster the tool revolves, the higher the resultant temperature. It has been found that the temperature rise develops within 10-12 seconds, after the cutting operation is started. Size of the cutting instrument has an important bearing on heat generation, since, its diameter affects the cutting speed at its periphery. Larger the size of the cutting tool more the host generation.A third factor is the pressure applied by the dentist during cutting operation. As the pressure increases, greater will be the rise in temperature.Hudson and associates in 1954 conducted a study on temperature developed in dental cutting instruments from their study they have concluded that,1.The temperatures produced by dental burs in cutting human dentin ranged from 125F to 275F. Since these temperatures are above those, said to be tolerated by normal human dentin, it would seem advisable to use some form of coolant.2.A significant decrease in time required to accomplish a given operation is apparent, when high operating speeds are used.3.The amounts of heat transferred to the tooth from the bur decreases, at speeds above 12000 rpm, since cutting time at these speeds is reduced and bur temperature remains.Substantially constant and there is less heat trauma to the vital structures.Coolants:From the study of Hudson and Sweeney, it is evident that the temperatures reached during tooth reduction procedures are above those said to be tolerated by normal human dentins. This indicates that, some form of coolant must be used, during the cutting operations, particularly when high speeds are used.Every means should be employed to keep the temperature down as much as possible during cutting operations. Coolants must employed which, to be effective, should be applied at the point of contact between the cutting instrument and the tooth tissue. There are three types of coolants usually employed in dental practice.1.Water.2.Spray of air and water3.Air alone.Peyton has shown that at speeds ranging from 30000 rpm to 170000 rpm and with an application of four ounces of pressure, a temperature rise within the tooth of less than 15C occurred when water or air-water sprays were employed. He also found that even with a water coolant, excessive temperatures developed, when large diameter instruments or excessive pressure were applied with increased operating speeds. This indicates that the use ofa coolant, does not eliminate the danger of excessive temperature rise.A reduction in concentration of the amount of water used during cutting procedure shows the significant temperature rise of the dental bur.The minimum volume of water to be applied was estimated at 1.5 ml per minute.The question whether water in spray form should be used at mouth or temperature seems to have no significance as far as temperature rise in the tooth was concerned. Tylman is of the opinion that if the water reservoir is kept at 100F, it is most comfortable to the patient, less liable to be harmful to the pulp and still reduces the heat of friction during cutting.There are certain other problems associated with the use of the highspeed cutting tools. Most of the hand pieces are so designed that a spray or stream of water is directed from the head of the handpiece directly onto the cutting operation. Where the water strikes the tooth and the cutting tool directly, full benefit is obtained from the coolant. Where however, the abrasive on the cutting tool, is on the surface away from the stream of water, water does not flood the tooth surface being cut, resulting in excessive temperature rise. The overcome this difficulty perforated disks have been developed, which permit the water to go through the openings and lubricate the disk and tooth on the cutting side. The use of perforated disk results in less temperature rise. Consequently when disks are non perforated, and when the stream of water cannot be directed to the cutting contact areas, they should be used at speeds not exceeding 10,000 rpm.Another advantage of a water coolant lies in the fact that the tooth debris from the cutting is removed rapidly, preventing the clogging of the cutting tools. This results in greater cutting efficiency of the stone. Also, it prolongs the life and effectiveness of the instrument. It is essential that the water be in intimate contact with the revolving instrument and the tooth tissue.To do this more effectively, Nelson recommended the addition of a wetting agent to the water spray.Because the high speed technique requires a larger quantity of water as a coolant, there is the problem of removing this water from the mouth. To have the dentist stop frequently to allow the patient to spit out the excess water is time consuming. The customary saliva ejector has insufficient removal capacity.To solve this problem, Thompson has suggested a washed field technique.This technique adapts the suction or vacuum principle. It established and maintains a powerful but gentle negative pressure of air in the mouth, close to the field of operation.Accompanying the air stream, is a flow of isothermal water which is projected copiously onto the operative field. This water is entrained into the vacuum air stream, which draws it rapidly across the operative area. The irrigant pulls away with it tooth cuttings and debris. These are taken into the vacuum air stream and disposed off in a filter system. A clean, clearly visible operative field is provided. This technique has the distinct advantages that it facilitates the use of high speed instruments, maintains visibility during copious irrigation of the operative field, reduces operating time, improves the patients well being and introduces a new concept of cleanliness. Human tissues are maintained in their natured wet safe pain, trauma and postoperative complication, which may arise due to ingestion of tooth debris are reduced.Desiccation of hard and soft tissues is avoided. Heat is eliminated thus preserved the tissues.Vibration:Cutting a tooth may be very annoying and unpleasant to the patient but still not be painful. In pain there is usually an involvement of the nerve endings, either by trauma or extreme irritation, resulting in an acute, painful reaction. Most patients associate the sensation of vibration, noise, pressure and the slight increase in cutting temperature with the sensation of pain. Consequently, if the factors of vibration, heat and pressure are reduced to a minimum, the patient usually experience reduced or no pain.One mechanical factor that influences vibration is the dental handpiece, whether it is friction-bearing, ball bearing, high speed belt driven or turbine ultra speed. When the friction bearing, conventional type of handpiece is used at a speed of 4500 rpm to 6000 rpm, it is connected by the conventional belt and pulley system of the dental engine. In this case one may expect a high order of vibration depending upon the condition of various mechanical parts, their adjustment and speeds of their operation.Pulleys that are worn, a worn belt, or an improperly adjusted belt will cause vibrations that are transmitted down to the cutting tool. Similarly hand piece which do not hold the cutting tool properly, which have worm bearing or are out of adjustment will also cause vibration.The investigations of Walsh and Symmoss showed that vibration, when applied to tooth, produced the most unfavorable response when the frequency was between 100 cps and 200 cps. When the frequencies were above 1000 cps, they were generally beyond the upper threshold of perception of the average patient. It is the lower frequencies, in the range of 100 200 cps, that are usually developed at the lower speeds, especially if the equipment is worm and maladjusted.Hudson and Sweeney have reported the importance of having centricity in the cutting tool. They found that eccentric burs when rotated at 6000 to 10000 rpm produced a lower frequency in the range of 100-200 cps, whereas a true running bur at 10000 rpm produced vibrations in the frequency range above the upper threshold.Tamner pointed out that only a part of an eccentric cutting tool is used as it rotates, thus causing unfavorable impacts and vibrations, which fall into the most annoying frequency range. The disks and stones that are unmounted and are screwed onto a mandrel very frequently are eccentric and therefore should not be used in high speed cutting operations. The permanently mounted instruments are indicated in preference to unmounted type.Poorly built burs with blades not evenly cut or chipped will likewise cause vibration. In using carbide burs, it is very important the see that none have chipped blades.Correct adjustment of the belt is important in the reduction on and elimination of vibration. A belt that is too loose increases the vibration pattern transmitted directly to the tooth.In the ultra highspeed hand pieces the metal chuck holding the cutting instrument often is replaced by a rubber or plastic chuck. This lessens the vibration transmitted to the cutting instrument and facilitates the more rapid cutting action.In cutting with a water turbine handpiece at 45,000 rpm the intensity of vibrations was well tolerates by the patient.Morrison and Grinnel made the following observations.The deleterious effects of vibration are two fold in origin.1.Amplitude.2.Undesirable modulating frequencies.If we minimize or eliminate these factors, we can then reduce the undesirable effects of vibration.Amplitude:The wave of vibration consists of frequency and amplitude.At conventional speeds, amplitude is greater but frequency is less. At higher speeds the reverse is true. The greatest harm is caused by the amplitude of vibration which is the factor, most destructive of instruments and which causes the most apprehension in the patient and the greatest fatigue in the dentist.By increasing operating speeds, the amplitude and its effects are reduced and a more satisfactory result is attained.Vibration waves are measured in cycles per second. It has been shown that rotation of approximately 6000 rpm sets up a vibrational wave of approximately 100 cps. As the rpm is increased the cps of the fundamental vibration wave are increased until, at ranges of 100000 rpm, we have a vibration wave of 1600 cps. It has been demonstrated that at wave of vibration of over 1300 cps, vibration is practically imperceptible to the patient. The reason for this is not fully understood, but there are two theories for this phenomenon.(1)The Wedensky inhibition phenomenon frequency increased to a point where vibratory perception diminishes due to failure to perceive vibration. This is because Stimulation occurs during Refractory Period of Recovery.(2)Vibratory perception depends upon the product of the amount of stimulation (i.e. pressure) multiplied by the frequency of stimulation necessary for a reaction. This is called Chronaxie. As the speeds above 1,00,000 rpm, due to light pressure and high speeds, chronaxie is attained, which is necessary for reaction.Thus it can be concluded that, the more the rpm, the less the amplitude, and the greater the frequency. Vibratory perception will be lost in the ultra highspeed range of 1,00,000 rpm or more.Spread of pathogenic organisms by Ultra speed cutting procedures:Atmospheric contamination through the spread of oral organisms particularly from air turbine action has been a concern of the dental profession for some time. Dental procedures tend to expose the operator to infectious diseases. Recent studies suggest that the extent of aerosol produced by air turbine may increase the normal hazard. A report involving patients with pulmonary tuberculosis cultures were demonstrated on all petri dishes exposed during cutting procedures, with the heaviest concentration being at 2 feet in distances from the patients mouth. This indicates that the dentist and his assistant are exposed to a serious health hazard when operating with an ultra speed exposed instrument on patients having such pathogens in their oral flora. When a patients history suggests the existence of tuberculosis, pneumonia, influenza, infections hepatitis or any infectious diseases including the common cold, a protective face mask should be worn by both dentist and assistant. During all ultrahigh speed cutting procedures, protective eye-glasses should be worm routinely.SUCK-BACK PHENOMENON-The operation of the turbine is switched off by closing the compressed-air valve abruptly. Then, owing to its own kinetic energy, the turbine continues its rotation, so that the turbine starts operating as an air pump. This causes a negative pressure in the area of the turbine shaft. The negative pressure sucks air from the environment that can be contaminated by aerosols of saliva and blood of the patient.Size of cutting instrument and cutting speeds:It has been pointed out by Peyton, and Nelson that, the important factor of increased operating speeds is the instrument surface speed in fact per minute rather than the revolution per minute of the instrument.The larger the diameter of the cutting instrument, the slower the speed required at the spindle. The specific phase in preparation of an abutment should determine the size of the cutting instrument and the rpm that should be used. Employing superspeed for all operations places unnecessary strain upon the patient and equipment. If the same effect can be accomplished by using a larger instrument at a lower speed, but still remaining above the threshold of perception, this should be done. However, oversized cutting tools should not be used at super speeds due to the difficulty of instrument control and accuracy of cutting.VIBRATION SYNDROME :the perception of vibration, pain, touch and temperature deteriorates. The negative effect of local vibrations occurs within the range 5-1400 hz, the most harmful being those below 16 hz. mechanical vibrations arise because the various machines operating at the dentists workplace contain moving parts. The main source is vibrating power-driven or air-driven instruments, such as low- and high-speed handpieces as well as ultrasonic instruments.The vibrations emitted by these machines travel directly from the handles to the operators hand. These are local vibrations.Biologic response of dentin and pulp to high speed cutting:Dentin:As the contents of the dentinal tubules are in direct continuity with the odontoblasts, and pulp, cutting or grinding the dentin causes a reaction in the pulp and this may lead to changes in the dentin.An early experimental investigation into the effect of cavity preparation on the dentin and pulp was carried out by Fish in 1932. He cut cavities in the teeth of dogs and left the cavities open to the saliva. By sealing dyes into the pulp chambers of the treated teeth he has shown that one of two reactions is produced in the dentin.In some cases there was sclerosis of the cut dentinal tubules which forms a protective some sealing off the pulp from the injury and underneath this region, there is a further growth of tubular dentine. These reactions are produced by the stimulation of the odontoblasts. The other reaction that resulted was the formation of dead tracts. With this lesion some or all of the odontoblasts, that are in connection with the cut tubules die. On the pulpal aspect of these tubules, hyaline mineralized barrier, secondary dentine is laid down, thereby sealing the lesion from the pulp.Pulp:The changes in the pulp have been studied by Langeland and Morslard and Shovelton. They state that the damage to the pulp is to a large extent due to the heat generated. They have shown that when precautions are taken to minimize heat production by using burs rotated slowly in a speed reducing handpieces, the only evidence of pulp damage was a slight reduction of the odontoblast layer with the displacement of a small number of odontoblasts into the dentinal tubules. When speeds upto 5,000 rpm were employed, there was more extensive displacement of odontoblasts associated with marked vacuolization of the odontoblast layer, and local hemorrhages may be seen in the pulp. As the speed was increased, the changes became more severe. When tooth reduction was done under a stream or spray of water, the damage to the pulp was markedly reduced.Pulp changes associated with tooth reduction using the air abrasive technique have been studied by Kennedy and using ultrasonic technique by Mitchell and Jenson. The changes in both the cases are similar to those produced at the speeds of 5,000 rpm.The effects on the pulp of using high speed rotary instruments such as the air turbine have been investigated by Marsland and Shovelton. The changes found are no severe than those produced at lower operating speeds provided that adequate cooling of the cutting instrument by water jet or air/water spray is ensured.Alterations in the hard tissues of tooth cut by air turbines have been observed. The enamel over a wide area of crown may show minute cracks and the dentin shows altered staining reactions as a result a local overheating.RECENT DEVELOPMENT:ANTI-SUCK BACK-Planmeca compact dental units, the turbine drive air is not shut off abruptly but controlled down by allowing the driving air to decrease gradually. The software of the dental unit will keep on supplying the drive air into the turbine according to carefully chosen parameters. This way there is no possibility for the build-up of a vacuum effect that would cause suck-back.Ceramic bearings- no need of lubrication and more resistant to autoclave sterlization.Use of quartz rods instead of fibre-optic.Easy-to-use push-button bur releases.Swivel systems.Titanium handpieces.Smaller head size.ELECTRICAL HIGH SPEED HANDPIECESadvantages are:More power and torque than air turbine handpieces.Better bur concentricity.Less vibration and noise.Broad, controllable speed ranges.Forward/reverse option are available.With appropriate attachments, one system can be used for restorative, prosthodontics, prophies and endodontics.Disadvantages are :Heavier than air turbine.More expensive.Learning curve may be required.Attachment heads not as small as the small-head air turbines.May not be able to fully replace the air turbine.Infection control concerns.DiscussionIt is for more than 125 years, that rotary instruments have been in use, for tooth reduction operations, in different forms, from a hand rotary instrument to ultra sonic instruments, which have the rotational speeds ranging from very low speeds in case of band rotary instruments to 5,00,000 rpm in case of air bearing hand piece. These remarkable advances in the instruments have greatly reduced fatigue in the operator because of the physical case of manipulation and have considerably increased the comfort to the patient by reducing the actual working time and pressures required for tooth reduction, thereby minimizing the factors of heat generation and pain. Though high speed techniques have been a born to the dental profession, they have their can limitations. It is interesting to not that, in spite of considerable improvements in tooth reduction procedures and the instruments used for the same, the principles and biologic objectives have not changed.These improved methods of tooth tissue removal have a potential to damage the healthy teeth and surrounding structures, if they are used without proper understanding of their working and if they are used without taking proper care. Improper handling of these modern equipment may also be different to the longevity and working capacity of the instruments themselves.For successful and efficient use of those cutting tools, certain factors should be given consideration. Heat that is generated, while the tooth tissue is being removed must be kept, down to the minimum and at the sametime, whatever heat is generated, must be eliminated as efficiently and as quickly as possible by employing coolants, in any one of three forms commonly used i.e. water, air/water spray or air alone. Simultaneously with the coolant, if water or air/water spray is used, an efficient mechanism for remove of the water from the oral cavity must be employed. Otherwise, the clinical procedure is delayed, if the patient has to spit out the water, every now and then. By eliminating the water evacuation equipment, we are losing one of the advantages of these high speed instruments i.e. reduced working time for a particular preparation. Use of efficient coolants, not only eliminate the heat generated, but at the same time, keeps the operating area clean and free of any debris.High speed cutting methods have a further advantages in that, they reduce the annoyance that may be caused to the patient, when low speeds are used with the modern high speed cutting devices, the vibration produced is of a frequency that is generally beyond the upper threshold of perception of the average patient.Pressures that have to be employed in the use of high speeds are considerably reduced, in comparison with those needed for low speeds.Thus, when the factors of pressure, temperature and vibration are kept within the tolerance limits, the patient comfort is certainly improved.Size of the cutting tool to be used for particular tooth reduction procedure is an important consideration, particularly while using high speeds. Oversized cutting tools should be avoided, as they are difficult to control and at the same time, the accuracy of tooth preparation on procedure is also adversely affected.Biologic reactions of the tooth tissues, particularly dentin and pulp, should not be over locked, when high speeds are employed for tooth reduction operation. These responses have been studied by a number of people and they have shown that, the response are not significantly different from those, when low speeds are used, provided, effective coolants are employed.Thus it can be concluded that, high speed equipments for tooth reduction if used with proper understanding and due care, provide definite advantages over the conventional low speed cutting procedures. This fact places the high speed devices at definitely a higher level as against their low speed counterparts.Conclusions1.High speed cutting devices, if used with a thorough understanding of their mechanism and due care to the biologic integrity of teeth and surrounding structure, are a boon to dentistry.2.In the process of tooth reduction using high speeds considerable amount of heat is generated and an effective coolant is a must for preservation of tooth integrity and patient comfort.3.Vibration is increased with the increase in speed, but it is beyond the threshold of prerception of the normal human beings and hence not harmful.4.Biologic reactions of the dentin and pulp, to high speed cutting, cannot be overlooked.SummaryA brief history of rotary instruments has been presented. A critical evaluation of the high speed cutting devices, as to their advantages, disadvantages, and precautions to be taken during their use, has been assessed at length. Biologic reactions of dentin and pulp, to high speed cutting have been discussed in brief.

ContentsI.IntroductionII.Review of Literaturea.Advantages of high speedsb.Disadvantages of high speedsc.Types of high speed instrumentsd.Heat generatione.Coolantsf.Vibrationg.Spread of pathogenic organismsh.Size of cutting instruments and cutting speedsi.Biologic responses of dentin and pulp to high speed cuttingIII.DiscussionIV.ConclusionV.

Summary

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FINISH LINES IN FPDFinish LinesINTRODUCTIONThe ultimate goal in fixed and removable prosthodontics is the maintenance and preservation of the remaining dentition. The execution of this goal can be achieved initially by tooth preparations that are clinically sound and will increase the longevity of the abutments. Likewise, proper tooth preparation and contoured restorations that are periodontically acceptable are of major importance in maintaining optimal periodontal health, restoration of occlusal harmony, and stability of the restored dentition. Restoration of teeth is possible only if sufficient space is created for the application of the appropriate thickness of material required. Preference for the shoulder with a bevel preparation allows ample room for the periodontal tissues and the bulk of the restorative materials (metal crowns with acrylic resin veneers or porcelain-fused-to metal). The indications and contraindications for each type of full coverage preparation will be reviewed.

TYPES OF FINISH LINESOver the years there is often discussion about the various types of full coverage preparations and their advantages and disadvantages. There are four types of finishing lines for full coverage restorations:1.Knife edge.2.Chamfer.3.Shoulder.4.Beveled shoulder.Knife-Edged Preparations:A knife-edge, or a feather-edge preparation that is basically designed so that as the tooth is prepared zero cutting results at the gingival termination. The dentist employs the rotary instrument and leans the cutting stone or bur inward by rotating on that gingivaltermination and cutting mostly at the occlusal end. It is a process of tipping the rotary instrument occlusally. When planning the taper of this type of preparations, a number of problems are observed, especially with a short crowned tooth or on a tooth with a normal anatomic crown where the preparation ends at the cementoenamel junction.1.When using ceramometal restorations and aesthetic considerations are critical, because there is zero cutting at the gingival termination and aesthetic concerns are of primary concern and a metal collar is not to be used, then the resultant slip joint type of crown becomes overcontoured gingivally. Concomitant with this, the entire contour of the crown becomes greater, as without overcontouring, color cannot be achieved in the gingival portion.2.The retention and resistance form of the preparation is compromised. As the preparation becomes overtapered, the ability of the crown to be retained on the tooth structure becomes diminished. As an illustration, altering the taper from a perfectly parallel preparation to one with a 6-degree taper, which is considered the ideal because it is achievable, almost 50 per cent of the retention is lost. With alteration from a 5-degree taper to about 20 degrees, 25 per cent of the retention remains. Thus, retention is developed on the basis of the luting strength of the cement. Cement has a crystalline structure, so it does not fracture at one time. Each time this cement is challenged, more fracturing of the crystals occur until, finally, enough of the crystals are fractured to enable the restorations to loosen. Thus, these overtapered preparations have compromised long-term retention.3.Another negative aspect of overtapered preparations is that they develop internal stress wedging. As force is applied into the ceramometal crown with a conically shaped preparation, it will act like a wedge. The crown exerts a force on the preparation, even if cement is in between. All materials have flow, even though they are solid. That flow is enough to cause wedging of the metal. The veneering material is strong under compression but is weak under tension. The internal stress wedging tends to expand the metal substructure, causing the porcelain veneer to craze and fracture over a period of time.However, there is a place for a knife-edge preparation in the dentists armamentarium. This is the type of preparation that the clinician should utilize with long clinical crowns found with postperiodontal surgery cases. With a postperiodontal case, the clinical crown encompasses the anatomic crown and part of anatomic root structure. If the preparation extends to the tissue because of old restorations, root caries, root sensitivity, and aesthetics, very long preparations will be developed. A shoulder preparation cannot be developed, because once the practitioner cuts past the junction of the enamel and onto the cementum, the root may begin to taper severely. Thus, the roots become narrower, the farther apically the tooth is prepared. In these compromised cases, if a shoulder is cut, the resultant long, thin preparation will fracture easily. Interestingly, a knife-edge preparation when employed with a long clinically crowned tooth is not a overtapered as on short clinical crowned tooth; therefore, diminished retention of a normal sized preparation is not a concern with long preparations.4.Another problem with knife-edged preparations is the resistance form. Resistance form is the ability of a crown to withstand displacement from eccentric or lateral forces. A lateral force is applied when the mandible goes into eccentric movements. This is a rotational force that tends to dislodge a crown.5.Three factors reduce the resistance to dislodgement from rotation.a . The longer preparation the more resistant to dislodgment.b. The more parallel a preparation, the more resistant to rotation forces.c.The smaller diameter the crown, the more resistant to rotation forces.For example, given the same length and taper, a bicuspid is more resistant to being dislodged by rotation that a molar. The molar then becomes the liability. In consequences, in the case of a long-span fixed partial denture extending from a cuspid to a second molar, cementation wash out occurs on the molar. Rarely, is it on the anterior tooth, as the molar has the larger diameter and thus the least resistance to dislodgment. As a result the management of a large-diameter tooth requir