Posterior Palatal Seal

Guided by:-Dr Akshey SharmaDr Rajesh BhanotDr Pardeep BansalDr Gagan Chahal

Submitted by:-Dr Aditi GhaiPG 2nd yearDIRDS, Faridkot

INTRODUCTION

• The Posterior Palatal Seal area is the posterior most limiting structure in the maxillary denture.

• Horizontal forces and lateral torquing forces of the maxillary denture

can be resisted only by adequate border seal.• So, diagnostic evaluation and placement of the posterior palatal seal is

of great importance.

• The posterior border of maxillary denture has definite anatomic andphysiologic boundaries ,once understood, make the placement of theplacement of posterior palatal seal a quick and easy procedure withpredictable result.

DEFINITIONS

• POSTERIOR PALATAL SEAL :- The seal area at the posterior border of maxillary removable dental prosthesis.

• POSTERIOR PALATAL SEAL AREA :- The soft tissues along the junction of the hard and soft palate on which pressure within the physiologic limits of the tissue can be applied by the denture to aid in the retention of the denture – GPT 8

3

ANATOMY AND PHYSIOLOGY:-

Soft palate :-

• Musculo-membranous curtain.

• Functions as flap valve closes off nasopharynx during swallowing.

• Part of a dual valve system which separates the oropharynx from the oral space and the nasopharynx from the nasal space.

4dimensions and displacement patterns of posterior palatal seal, Silverman, j

prosthet dent, may 1971

• The function of the soft palate in these dual valving actions requiresfreedom of movement in three dimensions or planes of space, i.e.,superoinferiorly, mediolaterally and anteroposteriorly.

• An impression should be made when the soft palate is placed at adesired denture border position.

• The functional position is achieved when patient is seated in uprightposition, with head flexed 30 degrees forward and placing the tongueunder tension against either handle of impression tray or dentist’sfingers, and should not protrude beyond lips.

5dimensions and displacement patterns of posterior palatal seal, Silverman, j prosthet

dent, may 1971

MUSCLES OF SOFT PALATE

6

4. Palatoglossus

• Origin – Palatine aponeurosis

• Insertion - Side of tongue

• Action - Draws palate down, raises tongue

5.Palatopharyngeus:-

• Origin – Arises as 2 fasciculi – Posterior fasciculi arises from palatine aponeurosis and anterior fascicule from posterior border of hard palate.

• Insertion – Lamina of thyroid cartilage, wall of pharynx and its median raphe.

• Action – Helps in pulling up the wall of pharynx and shortens it during swallowing.

7

Clinical Significance

• Tensor Veli Palatini - When taut, can influence the denture contour in the hamular notch area.

• Levator Palati - Closing of the oropharynx from the nasopharynxduring swallowing and determining the position of the vibrating line.

• Palatoglossus – On contraction, draw the tongue and soft palate towards each other.

8

STRUCTURES RELATED TO POSTERIOR PALATAL SEAL (winkler)

• Hamular process

• Pterygomaxillary notch or Hamular notch

• Median palatal raphe

• Fovea palatini

9

1. Hamular process

• 2-4mm postero-medial to the distal limit of the maxillary residual ridge.

• Affects the length and direction of the pterygomaxillary seal.

• Covered by mucous membrane and should not be covered by denture.

10

2. Pterygomaxillary notch

• Band of loose connective tissue lying between the pterygoid hamulusof the sphenoid bone and the distal portion of the maxillary tuberosity.

• Lateral boundaries for the PPS.

11

3. Median palatal raphe :-

• This overlies the medial palatal suture, contains little or no submucosaand will tolerate little compression.

• According to heartwell and rahn, this band of tissues is not meant to be compressed, rather should be relieved id prominent

12

5. Fovea palatini

• Two glandular openings within the tissues of posterior portion of hard palate, usually lying on either side of midline.

• They are the ductal openings into which the ducts of other palatal mucosal glands drain

• Doesnot represent the junction of hard and soft palate and should be used only as a guideline to placement of posterior palatal seal.

13

Disagreements regarding position-

• Sicher (1952) :- Posterior to the location of hard and soft palate.

• Nagle and Sears (1958) :- Posterior limit of hard palate.

• Fenn and associates (1961) :- Glandular region of soft palate.

• Swenson (1970) :- Vibrating line 2mm in front of fovea palatini.

• Lye (1975) :- 1.31mm anterior to the anterior vibrating line.

• Chen (1981) :- Located either on or behind the anterior vibrating line.

14

PTERYGOMAXILLARY SEAL:-

• Extends through pterygomaxillary notch continuing 3-4 mm anterolaterally approximating the mucogingival junction.

• Occupies the entire width of hamular notch.

15

VIBRATING LINE-

• The imaginary line across the posterior part of the palate marking thedivision between the movable and immovable tissues of the soft palatewhich can be identified when the movable tissues are moving.

• POST PALATAL SEAL:- Area between the anterior and posteriorvibrating line found medially from one tuberosity to another.

16

ANTERIOR VIBRATING LINE

• An imaginary line located at the junction of the attached tissues overlying the hard palate and the movable tissues of the immediately adjacent soft palate.

• Cupid bow’ shaped due to the projection of posterior nasal spine.

• Always on soft palatal tissues.

• To locate anterior vibrating line patient is asked to perform valsalvamaneuver(both nostrils are held firmly while patient blows gently through the nose)

• Also located by visualizing the area while instructing the patient to say ‘ah’ with short vigorous bursts(sharry)

17

POSTERIOR VIBRATING LINE

• Imaginary line at the junction of aponeurosis of Tensor veli palatinemuscle and the muscles of soft palate.

• Represents the demarcation between the part of soft palate that haslimited movement during function and the remainder of soft palatethat is markedly displaced during functional movements.

• Visualized by instructing the patient to say “ah” in short bursts in anormal unexaggerated fashion.

• Marks the most distal extension of the denture base.

19

CLASSIFICATION OF SOFT PALATE(WINKLER)

• Based upon the angle the soft palate makes with the hard palate.

• The more acute the angle of the soft palate in relation to the hardpalate, more muscular activity will be necessary to effectvelopharyngeal closure (closing of the nasopharynx).

• So the more the soft palate is markedly displaced in function, the lessthat can be covered by the denture base.

• Determined when the patient is in upright position with the head helderect.

20

CLASS I

• A soft palate that is rather horizontal as it extends posteriorly with minimal muscular activity.

• Wide posterior palatal seal

• Most favorable configuration as more tissue surface can be covered.

21

• CLASS II :- Palatal contours between a class I and class II

• CLASS III :- Most acute contour in relation to the hard palate

• Marked elevation of the musculature to effect velopharyngeal closure

• Seen along with a high V-shaped vault usually.

• Smaller in width but deeper posterior palatal seal area

22

HOUSE CLASSIFICATION OF PALATAL THROAT FORM:-

• Class I :- Large and normal in form with a relatively immovable band of resilient tissue 5-12 mm distal to a line drawn across distal edge of the tuberosities.

• Class II :- Medium size and normal in form with relatively immovable resilient band of tissue 3-5 mm distal to a line drawn across distal edge of the tuberosities.

• Class III :- Usually accompanies a small maxilla. The curtain of soft tissues turns down abruptly 3-5 mm anterior to a line drawn across distal edge of the tuberosities.

23

FUNCTIONS OF POSTERIOR PALATAL SEAL-(winkler)

1. Retention of the maxillary denture base by resisting the horizontalforces and lateral torquing of the maxillary denture.

2. Maintains contact of the denture with the anterior portion of softpalate during functional movements.

3. Reduces patient’s awareness of the denture and reduction in the gagreflex as there is no separation of denture base and soft palate duringnormal functional movements.

24

4. Reduces food accumulation beneath the posterior aspect of thedenture due to proper utilization of tissue compressibility.

5. Reduces patient discomfort when contact occurs between the tongueand the posterior end of the denture base as the posterior denturewill closely approximate the soft palatal tissues.

6. Compensate for the volumetric shrinkage that occurs during thepolymerization of methylmethacrylate resin.

25

REVIEW OF LITERATURE:-

• 1958, Hardy and Kapur stated - Retention and stability derived fromthe forces of adhesion cohesion and interfacial surface tension resistonly the dislodging forces acting perpendicular to the denture and failto resist the dislodgement of the dentures by horizontal forces andlateral torques.

• This dislodgement can be resisted by the retention provided by thepartial vacuum created by the denture border seal.

26

• In the posterior region sealing is done by developing a posterior palatalseal.

• Such a seal will create a partial vacuum that will not operatecontinuously, but one that will come into play only when horizontal ortipping thrusts tend to dislodge the denture and then only long enoughto overcome the emergency.

• This partial vacuum is unlikely to operate long enough to do anydamage to the supporting or border tissues.

27

• Sidney Silverman (1971) conducted a study and concluded complete maxillary dentures can be extended for an average of 8.2mm dorsally to the vibrating line or flexion line, where the soft palate joins the hard palate.

• This extension varies from 4-12mm dorsally to a transverse region.

28

• Antolino Colon, Keki Kotwal and David Mangessdorff (1982)found that the form of the palate has direct influence on the retentionof complete dentures and will aid in the selection of the type ofposterior palatal seal needed.

• Rajeev M. Narvekar and Marc B. Appelbaum in 1989 usedultrasound instrumentation as an non-invasive procedure to locate theanatomic structures in the PPS region.

• In 1997, Izharul Haque Ansari described a method to establishposterior palatal seal during the final impression stage.

29

PARAMETERS OF PPS :-

• Size

• Shape

• Location

30winland and young, maxillary complete denture posterior palatal seal: variation in

shape, size and location, j prosthet dent, march 1973

I. SIZE:• According to Hardy and Kapur (1958) , the dimension of PPS was 2 mm at the

midpalatal region and hamular notch and 4mm at the greatest curvature region ofPPS.

• Silverman performed a study on 92 patients & found the following –

The greatest mean anteroposterior width of PPS is 8.0 mm (with 5-12 mm ofrange)

The mean width was found to be different for right (8.2mm) and left side (8.1mm).

The interhamular notch was found to be 35.8 mm (25-48mm range)

The interhamular notch distance was found to be different for males (37.1 mm)and females (35.6 mm)

31

II. SHAPE-

• John M. Young and Roger D. Winland

32

Bead posterior palatal seal extending through hamular notch

Double Bead posterior palatal seal. Posterior bead located on posterior limit of denture

Butterfly posterior palatal seal with width and depth depending on amount of displacement of tissues

Butterfly posterior palatal seal with a bead on posterior limit of denture

CROSS-SECTIONAL VIEWS OF VARIOUS POSTERIOR PALATAL SEALS-

• Bead

• Double Bead

• Butterfly

• Butterfly With Bead

33

winland and young, maxillary complete denture posterior palatal seal: variation in shape, size and location, j prosthet dent, march 1973

III. Dimension

Class I – modified butterfly approx. 3-4mm wide

Class II – modified butterfly approx. 2-3mm wide

Class III – a bead

TECHNIQUES FOR RECORDING POSTERIOR PALATAL SEAL(winkler)

• Prior to the corrective wash impression procedure, the posteriordenture border must be fully extended, which means that all of the softpalate that is to be covered by the denture has been captured in theborder molded custom tray.

• Intact tissue that is 1 to 2 mm distal to the expected denture bordershould also be present in the impression tray to protect against anyovertrimming of the processed denture base.

35

The rationale for the placement of a seal in the impression tray :

• To establish positive contact posteriorly to prevent the final impression material from sliding downs the pharynx.

• To serve as a guide for positioning the impression tray

• To create slight displacement of the soft palate

• To determine if adequate retention and seal of the potential denture border is present.

36

Classification of techniques of recording PPS-

Hardy and Kapur (1958) –

• Functional :- Final impression is border molded in PPS area with softstick modeling compound / wax by sucking movements performed bythe patient.

• Semi functional :- Border molding is done by the dentist.

• Empirical :- Developed on the cast by grooving the cast to the desireddepth.

37hardy and kapur, posterior palatal seal- its rationale and importance, j prosthet dent, may

1958

The techniques used to mark posterior palatal seal are:

1. Conventional technique

2. Fluid wax technique

3. Arbitrary scraping of the master cast

4. Extended palate technique

5. Adding PPS to an existing denture

6. Determination of PPS by ultrasound

38

CONVENTIONAL TECHNIQUE (winkler)

• Final impression is made, boxed, and poured.

• A well-adapted resin/shellac tray is fabricated on the stone cast.

• The posterior palatal area is then dried with gauge; a “T” burnisher /a mouth mirroris used to palpate for the hamular process and marked with an indelible pencil

39

• The instrument (“T” burnisher/mouth mirror) is then placed along the posterior angle of the tuberosity until it drops into the pterygomaxillary notch.

• A line is placed with an indelible pencil, through the notch and extended 3-4mm anterolateral to the tuberosity, approximating the mucogingival junction.

• The same procedure is then performed on the opposite side. This will complete the outlining of the pterygomaxillary seal.

40

• The patient is asked to say “ah” in short bursts in an unexaggerated fashion.

• While observing the movement of the soft palate the posterior vibrating line ismarked with an indelible pencil.

• By connecting the line through the pterygomaxillary seal with the line just drawndemarcating the “postpalatal”seal (posterior vibrating line), the posterior dentureextension is delineated.

41

• The resin /shellac tray is then inserted into the mouth and the indelible pencil lines aretransferred to the tray, which is returned to the mastercast to complete the transfer ofposterior border and tray is trimmed.

• The palatal tissues anterior to the posterior border are palpated with the “T”burnisher/mouth mirror to determine their compressibility in width and depth.

• The use of Valsalva maneuver / visualizing the area when the patient says “ah” withshort vigorous bursts may also be used.

• This line is marked with the indelible pencil and transferred to the master cast

42

• A Kingsley scraper is used to scrape the cast.

• The deepest area of the seal are located on the either side of themidline, one third the distance anteriorly from the post vibrating line.

• It is scraped to the depth of the approximately 1-1.5mm.

• The tissue covering the median palatal raphe has little submucosa andcannot withstand the same compressive force on the tissues lateral toit. It is scraped to the depth of approximately 0.5-1.0mm.

43

• Just posterior to the deepest portion of the seal, it is also tapered to the posterior vibrating line. Failure to taper the seal posteriorly may lead to tissue irritation.

• Shellac can be readapted to conform to the scored palatal seal area and tried in the mouth to evaluate the retentive qualities of the trial base.

44

ADVANTAGES

• More retentive trial base , which can produce more accurate maxillomandibular records.

• Patients are able to experience the retentive qualities of the trial base giving them the psychological security of knowing that retention will not be a problem.

• The dentist is able to understand the retentive qualities of the finished denture.

• The posterior extension of the denture can be understood by the patient.

45

DISADVANTAGES

• Not a physiological technique and so depends upon the accurate transfer of vibrating lines and careful scraping of the cast.

• More potential for overcompression of the tissue.

46

FLUID WAX TECHNIQUE

• Similar to the conventional technique except that in this technique the indelible transfer markings are recorded on the final wash impression.

• All the procedures for location and transfer marking of the anterior andposterior vibrating lines are same as for the conventional approach.

• Indelible transfer markings are recorded on the final wash impression.

47

• Zinc oxide and eugenol /plaster are preferred over the elasticimpression material, as they set rigid.

• 4 types of wax –

1. Iowa Wax (White) – Dr. Earl S. Smith

2. Korecta Wax no.4 (Orange) – Dr. O.C. Applegate

3. H-L physiologic paste (Yellow-White) – Dr. C.S. Howkins

4. Adaptol (Green) – Dr. Nathan G. Kyne

48

• Designed to flow at mouth temperature.

• The melted wax is painted onto the impression surface with theoutline of the seal area and allowed to cool to below mouthtemperature to increase its consistency and make it more resistant toflow.

• The impression is carried to the mouth and held in the place undergentle pressure for 4-6 minutes to allow time for the material to flow.

49

• After 4-6 minutes, the impression tray is removed from the mouth andthe wax examined for uniform contact through out the posteriorpalatal seal area.

• If tissue contact has not been established, the wax will appear dull. Ifthe tissue has been contacted, the wax will have a glossy appearance.

• Where the wax appears dull, more wax should be applied and the procedure repeated.

• The secondary impression is reinserted and held for 3-5 minutes of firm pressure applied to the midpalatal area of the impression tray.

50

PRECAUTIONS:

• The patient should not protrude his tongue beyond the approximated position of the incisal edge as this may shorten the posterior border of the final impression.

• The patient should be cautioned against rinsing with cold water as this may contract the tissues and reduce the flow properties of wax.

• The borders of the wax should terminate in feather edge towards the vibrating line .If a butt joint is formed, proper flow may have not taken place.

51

ADVANTAGES

1. Physiologic technique displacing tissues within their physiologically

acceptable limits.

2. Overcompression of the tissues is avoided

3. Posterior palatal seal is obtained increasing retention at an early

stage.

4. Mechanical scraping of the cast is avoided.

52

DISADVANTAGES

• More time is needed

• Difficulty in handling the material

53

EXTENDED PALATAL TECHNIQUE:(Silverman 1971)

• Denture border is extended 8mm approximately beyond the anterior vibrating line.

• Not widely used currently.

Method -

1. After border molding tray is extended by adding compound.

2. Green stick compound is added to the seal area and record is made with head flexed 30 degree downward.

BOUCHERS TECHNIQUE• Stage of recording- during jaw relations

• Method the posterior vibrating line is located and transferred on to the master cast.

• The temporary denture base is reduced to this line.

• This will create a raised narrow and sharp bead along the posterior portion of the denture which sinks into the tissues and forms a seal.

• Advantage: According to Boucher a narrow bead like seal is more effective.

ARBITRARY SCRAPING OF THE MASTER CAST

• Anterior and the posterior vibrating lines are visualized by examining the patient’ mouth and approximately marked on the mastercast.

• Least accurate and leaves a chance at insertion appointment since it relies on dentist’s recollection of palatal configuration and tissue compressibility.

• Inaccurate and not physiological.

56

ADDING POSTERIOR PALATAL SEAL TO THE EXISTING DENTURE

• Mark the vibrating line in the mouth with an indelible marker.

• Form the desired thickness and extension of the PPS on the denture in the patient’s mouth with softened green modeling compound

• Transfer the locations of the vibrating line to the denture

• Make a cast of the intaglio surface of the denture with putty material; the cast must include all of PPS addition and extend 5 to 6 mm posteriorly

• After putty material has set, use a scalpel to cut channels which will allow excess autopolymerizingacrylic resin to escape.

• Remove the green stick compound and replace with autopolymerizing resin in a pressure pot.

57Izharul Haque Ansari, J Prosthet Dent 1994;72;449

Arthur Nimmo - Suggested correction of posterior palatal seal by using a visible light cured resin.

• Identify and mark the vibrating line in the mouth with an indelible marking stick

• Roughen the denture surface in the posterior palatal seal area with a carbide bur.

• Adapt the VLC resin

• Place the denture in the mouth and allow it to remain in place for approximately 3 minutes. During this time the material will flow.

58

• Position a hand-held visible light source near the border of the denture and apply light directly to the region for several minutes.

• Remove any excess resin with a carbide bur and smooth the junction between the seal and the polished surface of the denture.

ADVANTAGES

1. No exothermic reaction to irritate the oral tissues.

2. Minimal volumetric shrinkage during curing.

3. More closely approximates a physiologic technique.

4. Can be performed with relatively little chair time.

59

Rajeev M. Narvekar, and Marc B. Appelbaum

• Investigated the anatomic position of posterior palatal seal by ultrasound.

• Ultrasound refers to sound with frequencies higher than the audible range (20 to 20,000 Hz).

• Basic elements of an ultrasound scanning system include –

1. Transducer

2.Couplant

60

Ultrasonic transducer

• The active element that has piezoelectric properties which transform mechanical energy into electric energy and vice versa

61

Couplant

• Necessary between the ultrasonic transducer and the skin because air is a poor conductor of sound energy.

B mode (Brightness modulation)

• The brightness or shade of gray in the display represents the amplitude of the echoes received from the anatomic cross section of the patient.

62

RESULTS OF THE STUDY

• The distance from the junction of the hard and soft palates varied froma maximum of 4.3mm to a minimum of 2 mm, with a patient averageof 2.5 mm.

• The average distance from the posterior vibrating line to the junctionof the hard and soft palates was 2.9 mm.

• The average width of the posterior palatal seal is considered to beapproximately 4 to 6 mm. Therefore, part of the seal would lie on theglandular posterior third of the hard palate.

63

TROUBLESHOOTING

• Under extension

• Over extension

• Under post damming

• Over post damming

64

UNDER EXTENSION

• Most common cause for failure of the seal in the posterior palatal area

Causes

• Practitioner’s use of the fovea palatine as the landmark for terminating the denture base. By doing, so he may be depriving the patient of as much as 4 to 12 mm of tissue coverage.

• Failure of the dentist to carefully examine the hard and soft palates, making note of the palatal configuration

• Over trimming of posterior border by laboratory technician

• Due to fear of gagging

65

UNDERPOSTDAMMING

• May be the result of recording the tissue when the mouth was wide open during the final impression.

• When the mouth is in the wide open position, the pterygomandibularfold becomes taut.

• When the patient assumes any position other than a wide open position, a space will be present between the denture base and the tissue since the fold is no longer activated.

66

Diagnosis :- place the wet denture base into the mouth and slowly press

in the midpalatal region until it is firmly seated while observing the distal denture border.

• If air bubbles are seen escaping from beneath the distal border, then at that point the denture base is underpostdammed.

67

Correction –

• Further scrap the cast and readapting the trial base if the conventional approach is used

• Add more wax and remind the patient to refrain from opening the mouth so wide if the fluid wax technique employed.

68

OVERPOSTDAMMING

• Over scrapping of master cast and the posterior palatal seal displaces too much tissue.

• Significant overpostdamming especially in the pterygomaxillary seal area -posterior border will be displaced inferiorly.

• Moderately overpostdammed - tissue irritation across the posterior palatal region

• Selective reduction of the denture border with carbide bur, followed by lightly pumicing the area while maintaining its convexity.

69

OVEREXTENSION

• The most frequent complaint from the patient will be that swallowing ispainful and difficult. Small ulcerated areas in the region of the soft palatewill be evident.

• If the hamuli are covered by the denture base, the patient will experiencesharp pain, especially during function.

• By marking the lesion with an indelible pencil and transferring it to thedenture base, the precise position of the overextension can be removedwith a bur and then carefully repolished.

70

CONCLUSION

• The recording of PPS is of great significance because it is vital factor in establishing the peripheral seal which enhances retention by utilizing the atmospheric pressure.

• The PPS of a maxillary complete denture can be established during the making of the preliminary impression, during the making of final impression, by scoring the final cast or by incorporating the seal in the final denture.

• The posterior palatal seal is obtained through intimate contact and the application of pressure within the physiologic limit by the denture in this region.

• This would require an intimate knowledge of the anatomy, functions and movements of the tissues of the region.

71

REFERENCES

• Zarb Bolender, Mosby,Prosthodontic treatment for edentulous patients,12th edition

• Sheldon Winkler ,A.I.T.B.S. Publishers,Essentials of complete denture Prosthodontics,2nd edition

• Arthur O. Rahn & Charles M. Heartwell, Elsevier,Textbook of complete dentures,5th edition

• B.D. Chaurasia , Human Anatomy- Vol.3 Head and Neck• Grays Human Anatomy• Hardy I R, Posterior border seal –its rationale and importance, J

Prosthet Dent 1958:8;386-97

72

• Silverman S.L. “Dimensions and displacement patterns of the posterior palatal seal”. J Prosthet Dent 1971:25;470-88

• Winland RD, Young JM, Maxillary complete denture posterior palatal seal: Variations in size, shape & location , J Prosthet Dent 1973:29;256-61

• Lye TL, The significance of the fovea palatine in complete denture prosthodontics. J Prosthet Dent 1975:33;504-10

• Nikoukari H, A study of posterior palatal seals with varying palatal forms, J ProsthetDent 1975:34;605-13

• Chen MS, Reliability of the fovea palatini for determining the posterior border of the maxillary denture. J Prosthet Dent 1980:43;13-37

• Antolino Colon et al, Analysis of the posterior palatal seal and the palatal forms as related to the retention of complete dentures. J Prosthet Dent 1982:47;23-27.

• Ming-Sheh Chen et al, Methods taught in dental schools for determining the PPS region. J Prosthet Dent 1985:53; 380-83

73

• Nimmo A.,Correction of the posterior palatal seal by using a visible-light cure resin : A clinical report J Prosthet Dent 1988:59;529-30

• Narvekar RM, Appelbaum MB, An investigation of the anatomic position of the posterior palatal seal by ultrasound, J Prosthet Dent 1989:61;331-36

• Izharul Haque Ansari , A procedure for adding posterior palatal seal to an existing denture in dental office, J Prosthet Dent 1994:72;449

• Izharul Haque Ansari “Establishing the posterior palatal seal during the final impression stage”. J Prosthet Dent 1997:78;324-26

• Yuuji Sato , Immediate maxillary denture base extension , J Prosthet Dent 2000:83;371-73

• Aaron Y J,Terry E D.Engaging the posterior palatal seal with the framework of maxillary complete overdenture.J Prosthet Dent 2009;101:3:214-5.

74