Biological considerations of maxillary impressions/ courses for dentistry


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Biological considerations of maxillary impressions/ courses for dentistry

  2. 2. CONTENTS-  Introduction  Definition  Supporting structures 1. Bone 2.Mucous membrane  Peripheral or limiting structures
  3. 3.  Anatomy of limiting structures in maxillary region  Anatomy of supporting structures in maxillary region  Conclusion  References
  4. 4. INTRODUCTION- If dentures and their supporting tissues are to coexist for a reasonable length of time, the prosthodontist must fully understand the macroscopic and microscopic anatomy of edentulous mouth of the patient.
  5. 5.  Anatomic landmark- “ a recognizable anatomic structure used as a point of reference.” GPT-8  In both maxilla and mandible anatomic landmarks has been divided in- -supporting structures -peripheral or limiting structures
  6. 6. SUPPORTING STRUCTURES  Def- “Those areas of maxillary and mandibular edentulous ridges that are considered best suited to carry the forces of mastication when dentures are in function.” (GPT-8)
  7. 7.  Maxillary and mandibular dentures transfer occlusal loads to these so called supporting structures .  The ultimate support for a denture is provided by the underlying bone which is covered by mucous membrane. Support is provided by maxillae and palatine bone in case of maxillary denture. For mandibular denture support is provided by mandible.
  8. 8.  In both maxilla and mandible type of bone and mucous membrane overlying it, differs from area to area.  Each type of tissue found in oral cavity has its own characteristic ability to resist external forces depending on its nature and histological makeup i.e type of bone and mucous membrane.  Stress bearing and relief areas
  9. 9. Hard tissues-  The requirement of ideal support is the presence of tissues that are relatively resistant to remodeling and resorptive changes.
  10. 10.  2 types of bones are seen -compact or cortical bone -cancellous or trabecular bone
  11. 11.
  12. 12.
  13. 13.
  14. 14.
  15. 15. DIFFERENCE IN RIDGE RESORPTION IN COMPACT AND CANCELLOUS BONE-  It has been suggested that bone resorption at any site is a chemotactic phenomenon, that is it is initiated by release of some soluble factors that attract circulating monocytes to the target site. Osteoclasts, the cells responsible for bone resorption are nothing but modified monocytes.  Degree of mineralization is less in cancellous bone, so effects of resorption are more pronounced in cancellous bone.
  16. 16. Oral Mucous Membrane - The bone of upper and lower edentulous jaws, and the oral cavity is lined with a soft tissue that is known as ‘mucous membrane’. Denture bases rest on the mucous membrane, which serve as a cushion between denture base and supporting bone. The mucous membrane composed of :- (i) Mucosa (ii) Sub mucosa
  17. 17. 1) Mucosa: - Mucosa is formed by stratified squamous epithelium cells. There is subjacent narrow layer of connecting tissue to the mucosa, known as lamina propria.
  18. 18. 2) Sub mucosa: - Sub mucosa is formed by connective tissue. Connective tissue varies in character from dense to loose alveolar tissue and also varies considerably in thickness. It may contain glandular, fat or muscle cells. Submucosa transmit the blood and nerve supply to the mucosa. Sub mucosa attaches mucosa to the periosteal covering of the bone.
  19. 19.
  20. 20.  Some parts of the masticatory mucosa are without a distinct submucous layer, yet dense connective tissue of the lamina propria firmly binds the mucosa to underlying periosteum. Although not as effective in providing resiliency, this connective tissue layer serves as a protective base for the mucosa.
  21. 21.
  22. 22. Classification of oral mucosa- Depending on its location in mouth, oral mucosa classified into three categories – Oral mucous membrane Masticatory Lining Specialized
  23. 23. Limiting structures-  The functional anatomy of mouth determines the extent of the basal surface of denture.  The denture base should include the maximum surface possible within the limits of the health and function of the tissues it covers and contacts i.e it should cover all the available basal seat tissues without interfering in action of any of the structures that contact or surround it.  The anatomy in consideration is anatomy in function rather than descriptive anatomy.
  24. 24.  Term ‘Border area’ refers to the mucosal surface area which contacts the denture borders and surrounds the spaces which are occupied by denture flanges.  Border molding procedures are used to record limiting structures properly. There are 2 main objectives of border molding in recording the limiting structures- 1. to establish correct flange length and border thickness 2. to achieve retention through border seal.
  26. 26.  Labial frenum  Labial vestibule  Buccal frenum  Buccal vestibule  Hamular notch  Vibrating lines  Fovea palatinae
  27. 27. 1. LABIAL FRENUM  Term frenum or frenulum refers to a connecting fold of mucous membrane serving to support or retain a part.  labial frenum, is a fold of mucous membrane extends from the labial mucous membrane reflection area to or towards the slop or crest of residual ridge at the median line.
  28. 28.
  29. 29.  It divides the labial vestibule into approximately equal but asymmetrical left and right labial vestibule.  It starts superiorly in a fan shape and converges as it descends to its terminal attachment on the labial side of the ridge.  It contains no muscle and has no action of its own.
  30. 30.  The action of the lip in this area is mainly vertical so the labial notch in maxillary denture must be just wide and deep enough to allow the frenum to pass through it.  The denture borders should not only be cut lower, but also have less thickness adjacent to labial notch.
  31. 31. House classified frenal attachment in 3 classes-  class1- high in maxilla or low in mandible with respect to crest of ridge.
  32. 32.  class 2- medium
  33. 33.  class 3- freni encroach on the crest of the ridge and may interfere with denture seal, might require surgical correction.
  34. 34. Vertical incisive pads-  When lip is raised and pulled horizontally forward, a pad of submucosal soft tissue in the shape of vertical column is sometimes observed on each side of maxillary labial frenum, are known as vertical incisive pads.
  35. 35.  These are attachments of the superior incisive muscles, which course up from their attachments.  The basal surface of labial flange of the denture should be relieved to allow for these attachments.
  36. 36. Anterior nasal spine-  It is not a limiting structure under normal circumstances, but in instances of severe ridge resorption, the anterior labial border of denture should be relieved to avoid impingement upon the mucosa overlying the anterior nasal spine, which frequently becomes a prominent, knife edged, limiting structure.
  37. 37. Labial vestibule  The portion of the oral cavity that is bounded on one side by the teeth , gingiva and alveolar ridge (or residual ridge) and on the other by the lips anterior to the buccal frenum. GPT-8 •The labial vestibule is divided into a left and right labial vestibule by the labial frenum.
  38. 38. Three objectives which are apparent in the labial vestibular region are- 1. The thickness of the labial flange of the final impression must be developed according to the amount of bone that has been lost from the labial side of the ridge. 2. The labial flange of the impression must have sufficient height to reach the reflecting mucous membrane of the vestibular space, but should not over extend it. 3. There must be no interference of the labial flange with action of the lip in function.
  39. 39.  The main muscle of the lip, which forms the outer surface of the labial vestibule, is the orbicularis oris.  It’s tone depends on the support it receives from the labial flange and the position of the teeth.  Because the fibers run in a horizontal direction, the orbicularis oris has only an indirect effect on the extent of an impression and hence on the denture base.
  40. 40. BUCCAL FRENUM  Buccal frenum is a fold of mucous membrane, extends from the buccal mucous membrane reflection area to or towards the slop or crest of residual ridge. • The buccal frenum forms the dividing line between the labial and buccal vestibules.
  41. 41.  It is sometimes a single fold of mucous membrane, sometimes double, and in some mouth, broad and fan shaped.
  42. 42. Three muscles are attached in this region 1. The levator anguli oris (caninus) muscle attaches beneath the frenum and affects it’s position. 2. The buccinator pulls it backward. 3. Orbicularis oris pulls it forward.
  43. 43.  Because of muscle attachments, it requires more clearance for its action( in both horizontal and vertical direction) than the labial frenum does.  Inadequate provision for the buccal frenum or excess thickness of the flange distal to the buccal notch can cause dislodgement of the denture when the cheeks are moved posteriorly as in broad smile.
  44. 44.  It records in the impression as a buccal notch which is properly relieved and molded. • It should be cresentric in form, rather than ‘V’ shaped.
  45. 45. Buccal vestibule  It is defined as “the portion of oral cavity that is bounded on one side by the teeth, gingiva and alveolar ridge (residual alveolar ridge) and on the lateral side by the cheek posterior to the buccal frenula”. GPT-8
  46. 46.  The buccal vestibule lies opposite the tuberosity and extends from the buccal frenum to the hamular notch.
  47. 47. The size of the buccal vestibule varies with  contraction of the buccinator muscle,  the position of the mandible, and  the amount of bone lost from the maxilla.
  48. 48.  The extent of the buccal vestibule can be deceiving because the coronoid process obscures it when the mouth is opened wide. Therefore it should be examined with the mouth as nearly closed as possible.  This space usually is higher than any other part of the border.
  49. 49.  The size and shape of the distal end of the buccal flange of the denture must be adjusted according to the ramus and the coronoid process of the mandible.
  50. 50.  Coronomaxillary Space - (J.Prosthet.Dent 1987:57; 186-190. N.S.Arbree, A.A.Yurkstas, and J.H.Kronman.)  Definition:- The coronomaxillary space is that anatomic region that lies medial to the coronoid process and lateral to the maxillary tuberosity.
  51. 51.
  52. 52.  Terms used to identify the coronomaxillary space,are :-  1- Buccal space or vestibule, 2- Buccal pocket, 3- Tuberosity sulcus 4- Distobuccal angle of the vestibule, 5- Buccal sulcus, 6- Buccal pouch, 7- Buccal mucous membrane reflection region, 8- Postmalar area, 9- Retrozygomatic space.
  53. 53. Clinical Implications:-  To get the maximum retentive qualities of the prosthesis, each patient should be evaluated for variation in the coronomaxillary space size during mandibular opening, as the size of the space is primarily influenced by the action of the coronoid process.
  54. 54.  In some patients coronoid process appears to flare laterally at its height. For these patients space often remain same or becomes wider during opening of the mouth.
  55. 55.  The coronoid Process may be relatively straight or constricting medially . For these patients opening of the mandible can result in narrowing of the space.
  56. 56.  If the space narrows during opening, any horizontal overextension into the space would result in denture base contact and loss of retention.  In this region border molding procedure should include opening and closing, together with protrusion, and lateral movements of the jaw.
  57. 57.  If coronomaxillary space broadens or remains of same size on opening, the functional filling of this space with the denture flange becomes important. border molding should not be done with open wide, protrude, or any lateral movements. •Here a gentle molding of the region is done by pulling the cheek out, down and inwards.
  58. 58. Microscopic features of labial and Buccal vestibule - - The mucous membrane lining of vestibule is relatively thin. - The submucosal layer is thick and contains large amount of loose areolar tissue and elastic fiber. - The mucosa of the vestibular space is classified as lining mucosa. - Mucosa is devoid of keratinized layer and is freely movable with the tissue to which it is attached because of the elastic nature of the lamina propria.
  59. 59.
  60. 60. Hamular notch  Hamular notch is a displaceable area, about 2mm wide between the tuberosity of the maxilla and the hamular process of the medial pterygoid plate. Also called as pterygomaxillary notch
  61. 61.
  62. 62. Clinical Significance -  This notch is used as a boundary of the posterior border of the maxillary denture, back of the tuberosity.  The impression should not end on the tuberosity, otherwise it will result in nonretentive denture because peripheral seal is not possible in nonresilient area of tuberosity.  The tissue in the centre of the deep part of the hamular notch, can be safely displaced by the posterior palatal border of the denture to help in achieving a seal in this region called as pterygo- maxillary seal.
  63. 63.  The tip of the pterygoid hamulus is 2-3 mm posteromedial to the distal limit of maxillary residual ridge. However it may be located on the line with crest of ridge or sometimes even lateral to this line.  This variation is significant in that it affects the length and the direction of pterygomaxillary seal so it becomes very important to determine the location of hamulus by palpation.
  64. 64.  Pterygomaxillary seal occupies the entire width of hamular notch. The seal begins at pterygomaxillary notch and usually extends 5-7 mm anteromedially.
  65. 65.  Also overextensions at the hamular notches will not be tolerated because of pressure on the pterygoid hamulus and interference with the pterygomandibular raphe.  Special care should be taken in the grossly resorbed alveolar ridge, where hamular notch disappears and raphe becomes more prominent.
  66. 66.  When the mouth is opened wide, the pterygomandibular raphe is pulled forward. If the denture extends too far into the hamular notch, the mucous membrane covering the raphe will be traumatized
  67. 67. PALATINE FOVEA REGION-  The fovea palatinae are indentations near the midline of the palate in posterior region formed by coalescence of several mucous membrane ducts.  They are very prominent in some individuals, whereas in others they are barely visible or may be absent.
  68. 68.
  70. 70. Review of Literature (1) J Prosthet Dent: 1975; 33,504-510. T.L.Lye conducted clinical, radiographic and histological studies of fovea palatine and concluded that, fovea palatine were positioned 1 .31 mm in front of the vibrating line in 70% of the cases. Histologically, complex nerve endings were found just anterior to the fovea and spreading to the soft palate.
  71. 71. Dental.J.1983:28; 166-70.  A clinical study was conducted by S.B.Keng and ROW A.M.,on edentulous patients to determine the distance of the vibrating line to the fovea palatine. The results indicated that the vibrating line is located 2.62 mm. (mean of 160 subjects) anterior to the fovea palatine.  There was a significant correlation between the distances of vibrating line to the fovea for different type of soft palate contour. Soft palate with deep slope (class III) has the vibrating line at or just in front of the fovea, while class II medium contour was 2.3 m.m. anterior to fovea, and class I flat contour of the soft palate line located approximately 4 m.m. anterior to the fovea palatine.
  72. 72. FOVEA PALATINI AND POSTERIOR BORDER OF DENTURE  According to Boucher as fovea palatini are close to vibrating line and always in soft tissues, which makes them an ideal guide for location of posterior border of denture.  According to Winkler fovea palatini should be used only as guidelines to the placement of posterior palatal seal. The dentist who observes the fovea and utilizes these anatomic landmarks as posterior extent of denture base can deprive his patients of several millimeters up to a centimeter or more of tissue coverage depending on the palatal configuration.
  73. 73.  Anterior vibrating line-  Anterior vibrating line is 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. Vibrating lines of
  74. 74.  This can be located either by valsulva maneuver or by instructing patient to say “ah” with short vigorous bursts.  Due to projection of posterior nasal spine anterior vibrating line is not a straight line between hamular processes.  At the midline it usually passes about 2 mm in front of the fovea palatinae.
  75. 75.  Posterior vibrating line is an imaginary line at the junction of the aponeurosis of tensor veli palatini muscle and the muscular portion of the soft palate.  It represents the demarcation between that part of the soft palate that has limited or shallow movement during function and the remainder of soft palate that is markedly displaced during function.  Posterior vibrating line is visualized by instructing the patient to say “ah” in a normal unexaggerated fashion.
  76. 76.  Direction of the vibrating line usually varies according to the shape of palate ; the higher the vault , the more abrupt and forward the vibrating line. In a mouth with flat vault , the vibrating line is usually farther posterior and has a good curvature, affording a broader PPSA.  The M.M.House classification is customarily used to designate the shape of the soft palate and it describes the amount of posterior tissue that will accept the posterior palatal seal –
  77. 77. Class I – More than 5mm of movable tissue available for post damming .  ideal for retention. Class II – 1-5 mm of movable tissue available for post damming.  retention is usually possible. Class III – Less than 1 mm movable tissue available for post damming.  Retention is usually poor.
  78. 78. 1. Irving R. Hardy and Krishan K. Kapur. Posterior border seal –Its rationale and importance J Prosthet Dent.1958;8;386-397 • Due to the relative instability of the denture base materials generally used, we have to take added precaution of scoring the cast at the deepest point of the posterior palatal seal to counteract the warpage of the denture. • If this bead causes any irritation when the denture is worn, it can be buffed off very easily, and it may make the difference between excellent and merely passable retention.
  79. 79. 2. J prosthet.Dent.1971;25,470-488. Sidney I. Silverman-  He did a study on 500 patients who required complete denture. The clinical findings were evaluated during speech, swallowing and respiratory posture.  Silverman concluded that complete maxillary denture can be extended for an average of 8.2 mm. dorsally to the vibrating line.  The extension varies from 4 to 12 mm.
  80. 80. 3. J.Prosthet.Dent1973:23:484-93. William E. Avant did a study to do comparison of different type of palatal seal in relation of complete denture retention.  Conclusions of this study were – 1. A posterior palatal seal is necessary for optimum retention of maxillary complete dentures. 2. Each type of posterior palatal seal tested in this study increased retention effectively. 3. No one type of posterior palatal seal that was tested ,proved to be superior than other.
  81. 81. 4) J.Prothet .dent.1975:34; 605-13. H.Nikoukari did a study at school of dentistry, Mashad, Iran. This study was designed to measure the dimension and displacement pattern of the posterior palatal seal in different palatal shapes .The effect of different materials on the displacement of tissue in the posterior palatal area were also evaluated .  It was concluded that the best posterior palatal seal can be achieved by using green modeling compound or korecta wax no 4 .  For establishing the posterior palatal seal area ,the posterior border should only be scraped on the cast for better adaptation.  No apparent changes of tissue displacement were found in different palatal shapes. However width of the posterior palatal seal area in flat palate was greater than deep and medium palate.
  82. 82. 5.Journal of prosthetic dentistry 2003;12 :265-270 Behnoush Rashedi and Vicki K Petropoulos, conducted a survey of U.S. dental schools in 2001 ,to determine the concepts, techniques used for establishing the post palatal seal Results from this survey show that  Combinations of clinical methods were most frequently taught for locating the vibrating line.  The phonation of the “ah” sound was the most popular single method taught for locating the vibrating line.  Most dental schools (87.5%) teach students to carve the posterior palatal seal on maxillary master cast.  Most dental school (93.9%) take the compressibility of the palatal tissue into consideration when carving the depth of posterior palatal seal in maxillary master cast.
  83. 83. Anatomy of supporting structures in maxillary region-
  84. 84.  The foundation for dentures is made up of bone of the hard palate and residual ridge, covered by mucous membrane. The denture base rests on the mucous membrane, which serves as a cushion between the base and the supporting bone.
  85. 85. Residual alveolar ridge- Definition (According to GPT-8) – “The portion of the alveolar ridge and its soft tissue covering ,which remains following the removal of teeth.”  The socket that surrounds the root of each natural tooth is called alveolus and the bony ridge that supports the teeth is the alveolar ridge.
  86. 86.  When the natural teeth are removed, the alveoli begin to fill up with the new bone. At the same time bone around the margins of tooth sockets begin to shrink away.  This shrinkage or resorption is rapid at first six weeks of tooth removal, and it continues at a reduced rate throughout the life and is responsible for the formation of RAR.
  87. 87. The alveolar ridges vary greatly in size, shape and their ultimate form. This is dependent on the following factors -  Variation in bone size and its degree of calcification in individuals.  Teeth show wide individual variation in size. Large teeth are supported by bulky ridges and smaller teeth by narrow ones.  The amount of bone lost prior to the extraction of teeth.  The amount of alveolar process removed during extraction of teeth.
  88. 88.  Rate and degree of resorption: - During the first six weeks after the extraction of teeth, the rate of resorption is rapid, thereafter it continues throughout the life at an ever decreasing pace.  The effect of previous denture: - ill fitting denture, or dentures with occluding natural teeth, may cause rapid resorption of the alveolar process in the areas where they cause excessive pressure or lateral stresses.  The relative length of the time for which different parts of the jaw has been edentulous.  Person’s general health.
  89. 89.  According to size RAR can be- -large -medium -small
  90. 90. large medium small
  91. 91.  According to shape RAR can be- - smooth - irregular - knife edge - flat
  92. 92. IrregularSmooth Knife-edgeFlat
  94. 94. square to gently rounded This is most favorable kind of ridge because –  The centre of the palate presents an almost flat horizontal area and this will aid in retention.  The roomy sulcus allows for the development of good peripheral seal. Flat surface  The well developed ridges resist lateral and anteroposterior movement of the denture.
  95. 95. tapering or V’ Shaped • It is usually associated with thick bulky ridges. This is an unfavorable formation. The forces of adhesion and cohesion are not at right angles to surface when counteracting the normal displacing forces of gravity. V’ shaped
  96. 96. (iii) Flat palate with small ridges This is an unfavorable formation because –  The poorly developed ridges do not resist lateral and anterior-posterior movement of the denture.  Shallow Sulcus do not form a good Peripheral seal. Shallow Flat Palate
  97. 97.  Unsupported alveolar soft tissues are frequently found in the edentulous anterior maxilla which has been opposed by an island of natural anterior teeth with an edentulous posterior mandible.  During mastication the upper denture ‘see-saws’ leading to disproportionate resorption.
  98. 98.  Soft tissues are compressible and the denture develops increasing instability.  Excessive soft tissue needs surgical removal.
  99. 99. MICROSCOPIC FEATURES OF RESIDUAL RIDGES  The mucous membrane is attached to the periosteum of the bone by the connective tissue of the sub mucosa.  The stratified squamous epithelium is thickly keratinized.  The sub mucosa is devoid of fat or glandular cells and it is characterized by dense collegenous fibers that are contiguous with lamina propria.
  100. 100.  The outer surface of bone in the region of crest of RAR (most coronal portion of ridge) is usually compact in nature. This compact bone in combination with tightly attached keratinized mucous membrane makes crest of RAR histologically best able to provide primary support for the denture.
  101. 101. RAR- a primary stress bearing area ???  According to Prosthodontic Treatment for Edentulous Patients by Zarb and Bolender- “the bone in this region is subject to resorption, which limits it’s potential for support, unlike the palate, which is resistant to resorption. Because of this, ridge crest should be looked on as a secondary supporting area.”
  102. 102.  They Consider “horizontal portion of hard palate lateral to midline” as primary supporting area for denture.
  103. 103.  In a patient where tooth were extracted long time back (years), ridge becomes smaller and crest of ridge in many cases is completely devoid of smooth cortical bony surface.  Horizontal part of palate lateral to midline should definitely be considered a primary stress bearing area in these patients.
  104. 104. PALATAL REGION- Rugae area-  Rugae are the raised area of dense connective tissue radiating from the median suture in the anterior one third of the palate.  Consists of series of ridges in the anterior part of the hard palate  Mucosa is keratinized and the submucosa is fibrous  In the area of the rugae, the palate is set at an angle to the residual ridge and is rather thinly covered by soft tissue.
  105. 105.  This area contributes to the stress-bearing role as well as to retention although in a secondary capacity.  It resists forward movement of denture.  It should be recorded without pressure, if it distorts while making impression it can rebound and unseat the denture.  These folds of the mucosa play an important role in speech so dentures should reproduce this contour making it very comfortable for the patient.
  106. 106.
  107. 107. Mid palatine raphe-  This presents as slightly elevated bony ridge along the midline of hard palate.  Adequate relief should be provided in this area as- - mucosa covering the raphe is extremely thin and is traumatized easily. -mucosa is less resilient than that covering the ridges so it can act as fulcrum along which denture rocks when vertical forces are applied.
  108. 108.  This area provides primary support to denture as it offers maximum resistance to resorption. Horizontal portion of hard palate lateral to midline-
  109. 109. Lateral surface of hard palate It is divided in  anterolateral part containing adipose tissue in submucosa  posterolateral part containing glandular tissue. Both of these areas are displaceable they do not provide significant support to the denture but this region should be covered to provide retention.
  110. 110. Anteriolateral View Posteriolateral View
  111. 111.  These areas should be recorded in resting condition because when they are displaced in the final impression, they tend to return to natural form within the completed denture base, and creating an unseating force on the denture or causing soreness in the patients mouth. For recording these tissue in undistorted form, proper relief should be given in the final impression tray.
  112. 112. INCISIVE PAPILLA-  This covers the incisive foramen and is located in the midline immediately behind and between central incisors.
  113. 113. Prosthodontic significances:  It lies nearer to the crest of the ridge as resorption progresses. Thus the location of the incisive papilla gives an indication as to the amount of resorption that has taken place.
  114. 114.  Incisive papilla acts as a guide for antero-posterior positioning of the teeth, the labial surfaces of the central incisors are usually 8-10 mm in front of the papilla.
  115. 115.  Incisive papilla is used to locate the midline of the dental arch.
  116. 116. The nasopalatine nerves and blood vessels pass through the foramen, and care should be taken that the denture base does not impinge on them.
  117. 117. 1. Harold R. Ortman, and Ding H. Tsao :Relationship of the incisive papilla to the maxillary central incisors. J Prosthet Dent 1979;42; 492-496  A study on 38 maxillary casts found that the average distance between the most anterior point of maxillary central incisors and most posterior point of the incisive papilla was 12.454 mm .
  118. 118. 2.J.prosthet.Dent 1981:45;592-97. G.M.Retechie did a study at dental school London ,UK. An investigation of 64 angle skeletal class I dental students showed that the incisive papilla provides a stable anatomic landmark for arranging the labial surface of the central incisors labial surface is 10.2mm anterior to the posterior border of the papilla.
  119. 119. 3) Journal Indian Dent.Asso.1984:56;425-28. Kharat D.U. and Madan R.S. carried out a study on 200 subjects (108 men,98 women) of different age group ranging 20-65 years ,to determine the distances from incisal edge of the maxillary central incisor to the papilla.  The findings of the study showed that the mean distance of maxillary incisal edge to the incisive papilla was 8.16 + 1.26 mm for men and 7.41 + 0.98 mm for women.  Conclusion of their study was, the distance from maxillary incisal edge to the incisal papilla in dentulous men is more than the women and this distance remains constant throughout the life.
  120. 120. (4) J.Prosthet.Dent. 1987:57;712-14 A.M.H.grave and P.J.Becker compared the position of incisive papilla, in between the two groups in their study. The first group consisted of existing complete upper dentures of 67 patients(34 men,33 women). And another group consisted of cast obtained from the 60 young adults.
  121. 121.  The results of the study suggests that the labial surface of the maxillary incisors should be 12-13 mm from the posterior border of the incisive papilla. These measurements was significantly smaller in the sample of dentures examined , which suggests a tendency for anterior teeth to be placed too far posteriorly in artificial denture.
  122. 122. (5) J.prosthet.Dent. 1989:61;51-53. H.F. Grove and L.Cristensen did a study on 58 subjects to determine the orthographic distances from the posterior of the incisive papilla to the line intersecting the distal contact point of the maxillary canine. In 92% of subjects the posterior point of incisive papilla was approximately 3mm anterior to the line between the distal points of the canines. Neither gender, age, nor maxillary arch form affected this distance.
  123. 123.  Also called malar process is located opposite the first molar region and is commonly seen in mouth that has been edentulous for long. Zygomatic process-
  124. 124.  Some dentures require relief over the area to aid in retention and to prevent soreness of underlying structures.
  125. 125. MAXILLARY TUBEROSITY-  Maxillary tuberosity represents most distal portion of maxillary alveolar ridge.
  126. 126.  The tuberosity region often hangs abnormally low when maxillary posterior teeth are retained after mandibular molars are lost and not replaced, the max. teeth extrude bringing the tuberosity with them.  Often the low hanging tuberosity prevents proper location of occlusal plane.
  127. 127.
  128. 128.  Most often tuberosity enlargements are only fibrous in nature.  In either case invasion of interalveolar space in the tuberosity area may prevent the posterior extension of denture .
  129. 129. REVIEW OF LITERATURE- 1.JADA vol. 103, Dec 1981, 894. Ryle A. Bell, and Richardson. 2.Quintessence international 1987 :18;465. Sherif E, John unger and Carl Stone  They have presented techniques of non surgical managemant of overhanging tuberosities for CD patients.  Overhanging tuberosities in these cases reduced intermaxillary space to less than 3 mm. This space did not allow for the adeqate thickness of U and L acrylic denture bases.
  130. 130.  Before the record bases were constructed, the tuberosities were outlined on the cast. In these areas either type-3 gold alloy or co-cr alloy was used as denture base material in place of acrylic resin.
  131. 131. 3.J.Prosthet.Dent. 2004;92:128-31. Leonard Garth Lowe presented a clinical report for the non surgical management of bilateral undercut in tuberosity region. They made decision to incorporate flexible flanges in the undercuts using resilient silicon lining material to allow adequate height and thickness of the denture flange.
  132. 132.
  133. 133. Sharp spiny processes-  There are sharp spiny processes on max. and palatal bone that are normally deeply covered by soft tissues but in patients with considerable RAR resorption these processes irritate soft tissues .  Canal leading from a posterior palatine foramen often has a sharp overhanging edge that may irritate palatal mucosa.
  134. 134.
  135. 135. Torus palatinus-  Seen as a hard bony enlargement that occurs in midline of the roof of mouth is called torus palatinus.  Seen in nearly 20% of population  2 types -almost entirely soft tissue, loose and flabby - thin layer of mucosal tissue covering the bone  Dentures require relief over this area to aid retention and prevent soreness of the underlying tissues.
  136. 136.  A smooth rounded small torus does not normally create much problem as denture plate may be cut away to avoid tori or can be extended over it with proper relief.
  137. 137.  A large, irregular, lobbed tori should be treated surgically as cutting away the denture plate significantly reduces denture retention and also leads to excessive ridge resorption.
  139. 139. 1. R. T. Hill. Anatomy of interest to the prosthodontist. J Prosthet Dent.1955; 5; 109-111 2. G. A. Lammie. Aging changes and the complete lower denture. J Prosthet Dent.1956; 6; 450-464 3. John O. Neufeld. Changes in the trabecular pattern of the mandible following the loss of teeth. J Prosthet Dent.1958; 8; 685-697 4. Irming R. Hardy and Krishan K. Kapur posterior border seal – its rationale and importance. J Prosthet Dent. 1958; 8; 386-397
  140. 140. 6. Joseph S.Landa. Trouble shooting in complete denture prosthesis. Part I. Oral Mucosa and border extension. J Prosthet Dent.1959; 9; 974-987 7. Rovert B. Lytle Soft tissue displacement beneath removable partial and complete dentures. J Prosthet Dent.1962; 12; 34-43 8. Thomas E. J. Shanahan. Stabilizing lower dentures on unfavorable ridges. J Prosthet Dent.1962; 12; 420-424 9. H. R. Kolb. Variable denture-limiting structures of the edentulous mouth. J Prosthet Dent. 1966; 16; 194-201 10. H. R. Kolb. Variable denture limiting structures of the edentulous mouth. J Prosthet Dent. 1966; 16; 202-212
  141. 141. 11. Donald E. Van Scotter and Louis J. Boucher. The nature of supporting tissues for complete dentures. J Prosthet Dent.1965; 15; 285-294 12. Ellsworth K. Kelly. The prosthodontist, the oral surgeon and the denture-supporting tissues. J Prosthet Dent. 1966; 16; 464-478 13. Philip M Jones and LeRoy K. Nakayama. Surgical experiences of complete denture patients. J Prosthet Dent. 1967; 18; 12-18 14. K. W. Tyson. Physical factors in retention of complete upper dentures. J Prosthet Dent. 1967; 18; 90-97
  142. 142. 15. Sidney I. Silverman. Dimensions and displacement patterns of the posterior palatal seal. J Prosthet Dent. 1971; 25; 470-488 16. John L. Shannon. The mentalis muscle in relation to edentulous mandibles. J Prosthet Dent. 1972; 27; 477- 484 17. Wlodzimierz Jozefowicz. Cushioning properties of the soft tissues forming the basal seat of dentures. J Prosthet Dent. 172; 27; 471-476 18. L. Lye. The significance of the fovea palatini in complete denture prosthodontics. J Prosthet Dent. 1975; 33; 504-510 19. H. Nikoukari a study of posterior palatal seals with varying palatal forms. J Prosthet Dent. 1975; 34; 605- 613 20. Harold R. Ortman and Ding H. Tsao. Relationship of the incisive papilla to the maxillary central incisors. J Prosthet Dent. 1979; 42; 492-496
  143. 143. 21. Ming-Sheh Chen. Reliability of the fovea palatini for determining the posterior border of the maxillary denture. J Prosthet Dent. 1980; 43; 133-147 22. Aust.Dent.J.1981:26;218-21. 23. Ian b. Watson and D. Gordon Macdonald. Regional variation in the palatal mucosa of the edentulous mouth. J Prosthet Dent. 1983; 50; 853-859 24. T. E. Jacobson and A. J. Krol. A contemporary of the factors involved in complete denture retention, stability, and support. Part I: Retention. Part II: stability Part III support. J Prosthet Dent. 1983; 49; 5,165,306 25. J.Prosthet.Dent.1987:57;712-14 26. J.Oral.Rehab.1988:15;133-39. 27. H. F. Grove and L. V. Christensen. Relationship of the maxillary canines to incisive papilla. J Prosthet Dent. 1989; 61; 51-53
  144. 144. 28. G. C. D. Kau and R. F. K. Clark. The relationship of the incisive papilla to the maxillary central incisors and canine teeth in southern Chinese. J Prosthet Dent. 1993; 70; 86-93 29. J.Prosthet.Dent. 2004;92:128-31 30. Sheldon Winkler. Essentials of complete denture prosthodontics. 2nd edition 31. Zarb-Bolender Prosthodontic treatment for edentulous patients.12th edition 32. Fenn, liddelow and Gimsons`s :Clinical dental prosthetics. 3rd edition 33. Verrill G. Swenson: Complete dentures 4th edition 34. Charles M. Heartwell: textbook of complete dentures. 5th edition
  145. 145. T H A N K Y O U THANK YOU For more details please visit