Continuing Education The Role of Cements in Dental Implant Success, Part 2 Authored by Chandur P. K. Wadhwani, BDS, MSD, and Kwok-Hung (Albert) Chung, DDS, MS, PhD Course Number: 162 Upon successful completion of this CE activity 2 CE credit hours may be awarded A Peer-Reviewed CE Activity by Opinions expressed by CE authors are their own and may not reflect those of Dentistry Today. Mention of specific product names does not infer endorsement by Dentistry Today. Information contained in CE articles and courses is not a substitute for sound clinical judgment and accepted standards of care. Participants are urged to contact their state dental boards for continuing education requirements. Dentistry Today, Inc, is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in indentifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Concerns or complaints about a CE provider may be directed to the provider or to ADA CERP at ada.org/goto/cerp. Approved PACE Program Provider FAGD/MAGD Credit Approval does not imply acceptance by a state or provincial board of dentistry or AGD endorsement. June 1, 2012 to May 31, 2015 AGD PACE approval number: 309062
Transcript
Continuing Education
The Role of Cements inDental Implant Success,
Part 2Authored by Chandur P. K. Wadhwani, BDS, MSD, and
Kwok-Hung (Albert) Chung, DDS, MS, PhD
Course Number: 162
Upon successful completion of this CE activity 2 CE credit hours may be awarded
A Peer-Reviewed CE Activity by
Opinions expressed by CE authors are their own and may not reflect those of Dentistry Today. Mention of
specific product names does not infer endorsement by Dentistry Today. Information contained in CE articles and
courses is not a substitute for sound clinical judgment and accepted standards of care. Participants are urged to
contact their state dental boards for continuing education requirements.
Dentistry Today, Inc, is an ADA CERP Recognized Provider. ADA CERP isa service of the American Dental Association to assist dental professionalsin indentifying quality providers of continuing dental education. ADA CERPdoes not approve or endorse individual courses or instructors, nor does itimply acceptance of credit hours by boards of dentistry. Concerns orcomplaints about a CE provider may be directed to the provider or to ADA CERP at ada.org/goto/cerp.
Approved PACE Program ProviderFAGD/MAGD Credit Approval doesnot imply acceptance by a state orprovincial board of dentistry orAGD endorsement. June 1, 2012 toMay 31, 2015 AGD PACE approvalnumber: 309062
This is part 2 of a 2-part article series. Part 1 of this serieswas published in the April 2013 issue of Dentistry Todayand can be found within the Online Courses listing of thedentalcetoday.com Web site.
LEARNING OBJECTIVESAfter participating in this CE activity, the individual will learn: • The fluid mechanics and flow involved with implantluting cements so that flow can be manipulated andcontrolled effectively, and
• How the abutment can be used as a repository forexcess cement to reduce the amount extruded outthrough the restorative margin.
ABOUT THE AUTHORSDr. Wadhwani received his specialtycertificate in prosthodontics with amaster’s degree from the University ofWashington School of Dentistry. He iscurrently in private practice in Bellevue,Wash, and is past president of the
Washington State Society of Prosthodontics. He is anaffiliate instructor at the University of Washingtondepartment of restorative den tistry. He has authoredseveral technique and research papers on the subject ofimplants and is involved in numerous research projects. Hecan be reached via e-mail at [email protected].
Disclosure: Dr. Wadhwani reports no disclosures.
Dr. Chung graduated from the NationalDe fense Medical Center, Taiwan, with aDDS degree. He received his PhDdegree in biomaterials from theNorthwestern University at Chicago anda certificate in advanced prosthodontics
from the University of Texas Health Science Center at
San Antonio. He was ap pointed by the University ofWashington as a full professor of the restorative dentistrydepartment in 2006. Dr. Chung is a Fellow of Academy ofDental Materials, has published more than 90 articles inpeer-reviewed journals, and has lectured internationally. He can be reached at (206) 543-5948 or via e-mail [email protected].
Disclosure: Dr. Chung reports no disclosures.
INTRODUCTIONCementation as a means of attaching a restoration such asan inlay, onlay, crown, or bridge to a natural tooth has beenused for close to 100 years. The process serves to unitecomponents of the same or different materials together. Thecementing media used can result in a union that is primarilyfrictional (eg, zinc phosphate cement) where some form ofme chanical or micromechanical interlocking occurs, oradhesive in nature where a chemical bond unites thestructures (eg, self-etching resin systems and dentine), orboth, depending on the materials joined.
With the advent of dental implants and the subsequentintroduction of the cement-retained implant restoration hascome the emergence of new issues that are not commonlyobserved when restoring teeth.1-4 The cement-retainedimplant restoration may be more vulnerable to the effects ofcement entering the soft tissues and residual excesscement on the implant restoration when compared to atooth.5 Although there are tens of thousands of articleswritten on cements, highlighting compressive, tensile, andshear strengths, their properties, and clinical applications,very little is reported about the way in which cements flowduring the cementation process, how to optimize theirapplication, or the amount of cement required to achieve theideal cementation results.
The occlusion of the cemented crown can be altered bythe quality and quantity of cement applied to the internalaspect of the crown. This has been reported by severalauthors who have studied cement application techniqueswith respect to vertical displacement.6-8
Having a sealed restorative margin is considered aprerequisite for a tooth to eliminate ingress of bacteria thatcould cause sub sequent caries.9 With implant restorations, a
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bacterial marginal seal providedby cement lute may not be a greatconcern, especially when oneconsiders the success that screw-retained restorations have, whereno seal exists.10 Marginal adapta-tion of an implant crown has notbeen shown to be problematic.Jemt11 found no issue with theexposed set cement that filledmarginal space between theimplant abutment and crown.However, marginal seal may beim portant with respect to cementlute wash out during luting (con-tamination from crevicular fluids),and after luting (dissolution of thecement) the restoration. Residualexcess cement extrusion fromaround the margin of the cementedrestoration of im plants is a problem and has also been de scribed in the literature.12
The purpose of this article is to provide an overview ofhow cement flows within an implant abutment crownsystem and how this may be altered to reduce thepossibility of peri-implant disease. The discussion fo cuseson cement application and how to manage the flow patternsin relation to implant restorations. A visual reference as tohow cement may be affected by the site placed, amountapplied, and modifications to the abutment is described.Part 1 of this article reviewed differences be tween teeth andimplants with regard to cement selection.
HOW MUCH CEMENT SHOULD WE USE?A recent survey of more than 400 dentists evaluatedcement application techniques specifically for implantcrowns.13 The data revealed a large difference inapplication technique and site. Most dentists (55%) ap pliedcement on the internal surface with a brush; 28% of thosesurveyed applied ce ment arbitrarily by loading the inside ofthe crown; and a smaller proportion (17%) preferentiallyloaded the internal margin of the crown (Figure 1). Thestudy13 concluded that there appeared to be little
consensus on the most appropriate site or technique whenconsidering cementation of implant crowns.
A second part of the survey13 in volved weighing theamount of cement placed into the crowns and comparing itto the ideal amount re quired such that the crown completelyseated with complete cement lute space filled with cementand no ex cess. This was determined to be 3% of the totalcrown volume. What was of significant interest was therange of cement placed within the crowns. Some surveyeddentists loaded the crowns with greater than 50 times theamount of cement required. Others placed only one quarterof the ideal amount needed (Fig ures 2a and 2b).
The clinical significance of the ce ment application andvolume data indicates a large variation in thought processes,with very few dentists able to provide the appropriate volumeof cement. Too little cement and the crown may not stay inplace; too much cement may result in cement extrusion intothe tissues and result in peri-implant disease.1 It should beunderstood that the laboratories fabricating the restorationsprovide the clinician with a limited finite volume for cement,usually in some form of relief such as a die spacer, eitherpainted onto the abutment if fabricated by conventionaldental techniques, or “built in” with CAD/CAM technology.
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Figure 1. Actual examples of loading patterns and site of cement from a survey of more than 400 dentistson how they place cement for an implant crown.
Group 1 Group 2 Group 3
Gross Application Brush Application Rim Application
This usually equates to about 20 µm to 50µm of space, or as thick as a one to 2 layersof nail varnish.
CEMENTS AS LIQUIDSClinicians should be aware of howmaterials such as liquids behave. While thisis beyond the scope of this text, a very briefsummary will be given. Cements vary intheir physical nature, predominantly de-pendent up on their chemical composition,but in general, cements are consideredviscous fluids. Fluids can be loosely definedby their behavior when ex posed to anapplied force. Many liquids, in cluding water,have New tonian fluid properties. Regard -less of the forces acting on such a fluid, theviscosity re mains un changed, so the fluidwill flow, taking up the shape of thecontainer it is in (Figure 3a).
In dentistry, most polymers (manycements are polymers) are considered non-Newtonian fluids; al though they may ap pearas liquids, they have unusual flow properties.Their viscosities change with the applied strain rate. Fluidsmay not flow into containers as does water (Figure 3b), thusthey are considered non-Newtonian in nature.
MODELING CEMENT FLOW: A SIMPLEDEMONSTRATION The closed solid abutment onto which a restoration issubsequently cemented frequently has a simple form,usually circular in cross section, and similar to a flat topcone with an occlusal convergence taper of approximately6° to 10° (Figure 4). Cement flow can be easily modeled todemonstrate the influence of placement site, amount used,and abutment mod ifications. To do this, the model systemshould allow the ce ment flow to be visualized—in other words,the mo del system should ideally be transparent. The 2 modelstructure should conform to the shape of a crown and the im plant abutment.
One simple model system is to use clear plastic drinkingbeak ers (Figures 5a to 5c). For demonstration pur poses,
the cement and flow behavior can be mimicked by usingshaving cream.
One documented meth od for loading ce ment into acrown prior to seating onto an implant abutment is toarbitrarily or gross fill the restoration, and then seat it ontothe abutment. The amount loaded is usually far in excess ofwhat is required to ideally fill the cement space provided forthe clinician during crown fabrication.13 Of ten, the crown isfurther seated by the application of a seating force of ap proximately 5 kg (the pa tient bites on a wood stick orcotton wool, holding the restoration as the ce ment set
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Figures 2a and 2b. (a) This group of dentists overfilled the crowns with cement—someplaced more than 50 times the ideal amount required. (b) This group underfilled the crownswith insufficient cement to fill the lute space.
a b
Figures 3a and 3b. (a) This body of water has Newtonian properties. It fills this container andwill flow according to Newtonian laws when a force is applied to it. (b) This liquid does not follow Newtonian laws. It does not flow into the container and will behave differently thanwater when force is applied.
a b
Figure 4. Typical formof a posterior implantabutment: flat top cone,circular in cross section, occlusalconvergence taper 6º to 10º.
commences).14 To simulate the ce ment flowwhen this technique is used, the crowncomponent of the model system is half filledwith the shaving foam, then seated onto thebeaker, representing the implant abutment.The “crown” has to be forced down toovercome the hydrostatic pressureresistance from the occlusal cement layerthat traps be tween the 2 horizontal surfaces.Liquids (cements prior to setting) areresistant to compression, unlike water. Oncethe ap plied force is great enough toovercome this compression, the cementflows down onto the axial walls of the“abutment,” and the excess cement willeventually be extruded out of the crown/abutment marginunder great pressure (Figures 6a and 6b). The pressuremay be so great that the vulnerable soft-tissue hemi-desmosomal at tachment to the implant may be damagedand even detached, which could allow cement to flow wellbeneath the tissues.5
In this demonstration, note the ex cess and theblanching of the fingers indicating the amount of forcerequired to seat the “crown.” Large amounts of excesscement are extruded out through the margin of thecrown/abutment because the amount of cement loaded intothe crown is poorly controlled.
Some studies6,7 have suggested that the axial wall ofthe abutment, near to but not including the occlusal surfaceitself, should have cement applied to it (Figures 7a to 7c).When this is modeled, as the crown component is seated,the applied force, which is provided by seating pressure,works to shear the cement. The result is that the cement isforced down the abutment axial walls, leaving a void nearthe occlusal aspect of the abutment.7 Less excess cementextrusion is seen at the margin when compared to the grossapplication technique due to less cement material appliedin the first instance. However, the incomplete fill of thecement space makes this process potentially problematic,with potential reduction of retentive force capabilities.
When the cement is applied to the internal aspect of thecrown near to, but not including the crown margin, thenseated onto the abutment, a different effect is seen15
(Figures 8a to 8c). The cement appears to flow against thedirection of the seating force. In effect, it flows “up.” As thecrown is seated, the cement contacts the axial walls of theabutment. The seating force acts to compress the cementagainst the axial walls, which are round and tapered. Thiscompression forces the cement to flow up, until the occlusaltable is reached. At this point, the vector of force no longeracts as it lies perpendicular to the seating force. The
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Figures 5a to 5c. (a) The model system: Clear drinking beakers—note total occlusal convergence recorded with a protractor (10º total); (b) beakers designed to “fit” directly to oneanother similar to a crown and an abutment; and (c) shaving foam represents the cement.
a b c
Figures 6a and 6b. Cement applied in the form of gross application.Two effects are noted: (a) The occlusal cement is in compression andresists seating forces, propping the “crown” up. (b) The cement extrudedis under great force; this may damage the soft tissue attaching to theimplant surface. The crown is on average 50% filled with cement; onlyabout 3% is actually required, so too much is used and most of it mustbe extruded out of the system.
a b
remainder of the cement is forced downtoward the margins, with much less extrusionoutward than compared with either of the 2former techniques. The cement fill is alsomore ideal.
OCCLUSAL VENTING EFFECT AND THEINTERNAL VENTED ABUTMENTThe cement flow toward the occlusal surface(Figure 9) is of interest especially whereimplant restorations are involved. It isconsidered common practice to close anabutment screw access before the crown iscemented; in fact, all of the US dental schoolsadvocate this16 (Figure 10). One conceptrecently developed is to leave the screwaccess chamber open and not seal it off.17
This provides a reservoir for excess cement tobe retained within the crown abutment system,rather than have excess cement be extrudedout of the crown margin. This is beneficial fromseveral aspects:
1. Less cement extrusion may re ducethe potential for cement induced peri-implant disease.
2. Cleanup of a reduced amount ofcement is considered easier and faster.
3. There is the ability to improveretentive capabilities as the surface area ofthe cement contact area with the abutmentis increased.
Using the abutment screw chamber as a reservoir hasbeen studied and proven to reduce the amount of cementextruded out of the crown abutment margin as well aschange the retention capabilities of the cement used. Oneother feature that has also been investigated is modifyingthe abutment by placing vent holes internally.17 The internalvent abutment (IVA) (Figure 11) has 2 holes, 180° apartapproximately 3 mm below the occlusal surface. It has theadded advantage of changing the way cement flows toenhance the amount of cement kept within the abutmentcompared to keeping the chamber open (Figures 12a and12b). With such modifications as the IVA, cement flow can
be modified simply, which can also increase the retentivecapabilities of a given cement18 and reduce residualcement extrusion when compared to closing off theabutment, or leaving it open (Tables 1 and 2).
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Figures 7a to 7c. Application of cement to the axial wall, near but not on the occlusal surface, results in cement flow in the same direction as the applied seating force. Theocclusal aspect remains unfilled; considerably less excess extrusion is noted when comparedto the gross application.
a b c
Figures 8a to 8c. Application of the cement near the inner crown margin results in a flow pattern that forces cement occlusally initially, then as the model crown seats, the cementflows down toward the margin, with small amounts of excess cement.
a b c
Figure 9. The occlusalsurface is partially filledas a result of compres-sion forces vectoring thecement upward againstthe taper of theabutment.
When considering the IVA, the ventholes should only be placed in materials thatare not weakened by the inclusions, andtherefore, are not recommended for zirconiaor ceramic abutment materials. The numberand sites of the vents required is currentlybeing evaluated; presently it is consideredadequate to have 2 vents, 180° apart, withone at the mesial aspect of the implant, oneat the distal, and 3 mm from the occlusalsurface. Further study may be required tooptimize their position. The screw headshould always be protected by a spacer toprevent cement getting into the screwdriverengagement site; currently the recom-mended material is polytetrafluoroethylenetape.19 This material can be sterilized, is easyto manipulate, is radiopaque, and is lessassociated with malodor when retrieved.
Some abutments do not contain a screwaccess chamber (eg, Strau mann Solidabutment). For these abutments, otherforms of selectively applying cement havebeen de scribed.8 This involves loading thecrown then seating it onto an analog outsideof the mouth to pre-extrude excess cementand coat the inside of the crown with a layerof cement. One technique suggests the useof the laboratory analog that is used tofabricate the crown.20 However, the clinicianshould be aware that the laboratory analogis actually larger than the abutment that isused for the patient; the laboratoryabutment has die spacer built into it. Thiswould likely leave a layer of cement that isinadequate for cementation needs. A moreappropriate technique is to either use acopy abutment of the identical size,8 or anappropriately smaller sized abutment than the one used forthe patient.21 Making a copy Blu-mousse abutment(Parkell) as a pre-extrusion device appears to provide
almost exactly the correct amount of cement lute and canalso be used for multiple abutments for a bridge orconjoined im plant restoration.
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Figure 10. Examples of abutments that haveclosed off abutment screw access holes, as advocated by US dental schools.
Figure 11. The open screw access chamberand the internal vented abutment (IVA). Bothprovide a space for excess cement to flowwithin. The addition of the vent holes in theIVA improve both the amount of cement keptinside the system as well as the retentivetensile strength of the cemented crown.
Figures 12a and 12b. Cement flow was improved in the IVA compared to the open screwaccess (OA) abutment, indicating more excess cement would be extruded out from the OAsystem.
a b
SUMMARYSimple modeling systems can be used todemonstrate how cement flows, helping withthe understanding of how luting cements workas liquids, knowledge of how much is required,application techniques, and how simplemodifications to abutment design can be ofbenefit to the implant restoring dentist.
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EXCESSE
XCESS
EXCESS0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
Cem
ent W
eight (g)
CLOSED OPEN INTERNAL VENT
Table 1. Comparison of the Amount of Cement Retained Internally in Each System; In All Cases the Same Amount of Cement Was Used Initially
250
200
150
100
50
0
Retentive force (N)
CLOSED OPEN IVA
X 1.5X 2X
Table 2. Comparison of Abutment Modification and TensileRetentive Force to Remove Cemented Crown;Closed Was Approximately Half the Value of the IVA
REFERENCES1. Wilson TG Jr. The positive relationship between excess
cement and peri-implant disease: a pro spective clinicalendoscopic study. J Periodontol. 2009;80:1388-1392.
2. Pauletto N, Lahiffe BJ, Walton JN. Complicationsassociated with excess cement around crowns onosseointegrated implants: a clinical report. Int J OralMaxillofac Implants. 1999;14:865-868.
3. Gapski R, Neugeboren N, Pomeranz AZ, Reissner MW.Endosseous implant failure influenced by crowncementation: a clinical case report. Int J Oral MaxillofacImplants. 2008;23:943-946.
4. Callan DP, Cobb CM. Excess cement and peri-implantdisease. Journal of Implant & Advanced ClinicalDentistry. 2009;1:61-68.
6. Assif D, Rimer Y, Aviv I. The flow of zinc phosphatecement under a full-coverage restoration and its effecton marginal adaptation according to the location ofcement application. Quin tes sence Int. 1987;18:765-774.
7. Cardoso M, Torres MF, Rego MR, Santiago LC.Influence of application site of provisional cement onthe marginal adaptation of provisional crowns. J ApplOral Sci. 2008;16:214-218.
8. Santosa RE, Martin W, Morton D. Effects of acementing technique in addition to luting agent on the uniaxial retention force of a single-tooth im plant-supported restoration: an in vitro study. Int J OralMaxillofac Implants. 2010;25:1145-1152.
9. Goodacre CJ, Bernal G, Rungcharassaeng K, et al.Clinical complications in fixed prosthodontics. J Prosthet Dent. 2003;90:31-41.
10. Weber HP, Kim DM, Ng MW, Hwang JW, Fiorellini JP.Peri-implant soft-tissue health surrounding cement- and screw-retained implant restorations: a multi-center,3-year pro spective study. Clin Oral Implants Res.2006;17:375-379.
11. Jemt T. Cemented Cera One and porcelain fused toTiAdapt abutment single-implant crown res torations: a10-year comparative follow-up study. Clin Implant DentRelat Res. 2009;11:303-310.
12. Wadhwani C, Rapoport D, La Rosa S, Hess T, Kret -schmar S. Ra dio graphic detection and char acter isticpatterns of residual excess cement associated with ce ment-retained im plant restorations: a clinical re port. J Prosthet Dent. 2012;107:151-157.
13. Wadhwani C, Hess T, Piñ eyro A, Opler R, Chung KH.Cement application tech niques in luting im plant-supported crowns: a quantitative and qualitative survey.Int J Oral Max illofac Im plants. 2012;27:859-864.
14. Jorgensen KD, Petersen GF. The grain size of zinc phos-phate cements. Acta Odon tol Scand. 1963;21:255-270.
15. Assif D, Azoulay S, Gorfil C. The degree of zinc phos -phate cement coverage of complete crown preparationsand its effect on crown retention. J Prosthet Dent.1992;68:275-278.
16. Tarica DY, Alvarado VM, Truong ST. Survey of UnitedStates dental schools on cementation pro tocols forimplant crown restorations. J Prosthet Dent.2010;103:68-79.
17. Wadhwani C, Piñeyro A, Hess T, Zhang H, Chung KH.Effect of im plant abutment modification on the extrusionof ex cess ce ment at the crown-abutment margin for ce -ment-retained implant res tor ations. Int J Oral Max illofacImplants. 2011;26:1241-1246.
18. Wadhwani C, Hess T, Piñ eyro A, Chung KH. Effects ofabut ment and screw ac cess channel modification ondislodgement of ce ment-retained implant-supportedrestorations. Int J Pros thodont. 2013;26:54-56.
19. Moráguez OD, Belser UC. The use of polytetrafluoro -ethylene tape for the management of screw accesschannels in implant-supported prostheses. J Pros thetDent. 2010;103:189-191.
21. Wadhwani C, Piñeyro A. Technique for controlling thecement for an implant crown. J Prosthet Dent.2009;102:57-58.
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POST EXAMINATION INFORMATION
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POST EXAMINATION QUESTIONS
1. A recent survey of dentists revealed a largedifference in cement application techniques forimplant restorations. Most dentists applied cementon the internal surface with a brush.
a. The first statement is true, the second is false.
b. The first statement is false, the second is true.
c. Both statements are true.
d. Both statements are false.
2. During the fabrication of cemented restorations,dental laboratories usually provide some form ofrelief, often in the form of die spacer, to allow for:
a. Rotation of the restoration.
b. Space for cement.
c. Air space so the model does not get damaged.
d. Easier alignment.
3. Relief is commonly built into conventional andCAD/CAM restorations providing a space betweenthe crown/bridge and the abutment of ____ µm.
a. 5 to 10.
b. 10 to 20.
c. 20 to 50.
d. 50 to 70.
4. The average amount of cement required to ideally fillthe space between abutment and restoration is in theorder of about ____ of the total volume of therestoration.
a. 1%.
b. 2%.
c. 3%.
d. 5%.
5. A survey of dentists found very little differences incement application technique for implant crowns. Thesurvey concluded that there is major consensusregarding the most appropriate cementationtechnique.
a. The first statement is true, the second is false.
b. The first statement is false, the second is true.
c. Both statements are true.
d. Both statements are false.
6. Most dental cements are considered non-Newtonianliquids. Although they may appear as liquids theyhave unusual flow properties.
a. The first statement is true, the second is false.
b. The first statement is false, the second is true.
c. Both statements are true.
d. Both statements are false.
7. Water as a liquid is considered to have Newtonianproperties because:
a. When a force is applied to water, its viscosity changes.
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b. Water follows Newton’s laws and flows into the vesselcontaining it and takes up the shape.
c. When a force is applied to water, its viscosity remainsunchanged.
d. Both b and c.
8. How much force is usually applied to seating of acemented restoration when a patient bites on a woodstick or cotton wool?
a. 0.5 kg.
b. 5.0 kg.
c. 50 kg.
d. 500 kg.
9. Leaving the screw access channel open for acemented implant abutment:
a. Provides a hole that must be sealed.
b. Provides a potential reservoir for cement to be keptwithin the abutment.
c. Should not be done.
d. Increases the chance of screw loosening.
10. For a cement-retained implant-supported restoration,when a definite amount of cement is used studiesshow:
a. The more cement that stays inside the system,proportionally more will be extruded outside of themargin.
b. The more cement that stays inside the system,proportionally less will be extruded out of the system.
c. All cement always stays inside the abutment.
d. All cement always is extruded out of the system.
11. Cements prior to setting are resistant to compres-sion. In this regard, cements are the same asNewtonian fluids, which are also resistant tocompression.
a. The first statement is true, the second is false.
b. The first statement is false, the second is true.
c. Both statements are true.
d. Both statements are false.
12. Abutment modifications can change the way cementflows, which can be of benefit for the followingreason(s):
a. Improves retention of the restoration.
b. More cement can be retained within the abutment.
c. Less cement is extruded out through the abutmentcrown margin.
d. All of the above.
13. Internal venting is only useful with metal abutmentsthat are not weakened by the inclusions. Internalventing is not recommended for zirconia or ceramicabutments.
a. The first statement is true, the second is false.
b. The first statement is false, the second is true.
c. Both statements are true.
d. Both statements are false.
14. For internal vent abutments the following is/areconsidered adequate:
a. Two vents.
b. Vents 180º apart.
c. Vents 3 mm from the occlusal surface.
d. All of the above.
15. For abutments that have no screw access channel, a useful means of controlling the amount of cementused is:
a. Paint a layer of cement on the inside of the crown—studies have shown this is a predictable way to applythe ideal amount required.
b. Use the laboratory abutment to pre-extrude cement—it is the same size as the actual abutment for thecrown.
c. Use a copy abutment that is appropriately smaller insize than the actual abutment to pre-extrude cementprior to seating the restoration.
d. There are no such abutments—the solid abutmentdoes not exist.
16. Polytetrafluoroethylene tape is now being used as aspacer material on top of the screw head to preventcement getting into the screwdriver engagement sitebecause it is:
a. Easy to manipulate.
b. Radiopaque.
c. Can be sterilized.
d. All of the above.
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The Role of Cements in Dental Implant Success, Part 2
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Continuing Education
The Role of Cements in Dental Implant Success, Part 2
ANSWER FORM: COURSE #: 162Please check the correct box for each question below.
1. � a � b � c � d 9. � a � b � c � d
2. � a � b � c � d 10. � a � b � c � d
3. � a � b � c � d 11. � a � b � c � d
4. � a � b � c � d 12. � a � b � c � d
5. � a � b � c � d 13. � a � b � c � d
6. � a � b � c � d 14. � a � b � c � d
7. � a � b � c � d 15. � a � b � c � d
8. � a � b � c � d 16. � a � b � c � d
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