Stability/ dentistry dental implants


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  • Latin word –hub of a wheel
    Meating pt. Of eight muscles-distinct conical prominance at the corner of the mouth.
  • If the thumb is placed inside the corner of the mouth and the fingre outside on the prominance and then the lip and cheek are contracted, the modiolus feel like a a knot
  • It can be fixed more anteriorly as when the word “Hoe” is pronounced or posteriorly as in case of “He”.
  • This pouch is called Anthropoidal pouch Coz its more prominent in monkeys they use it to store food
  • 1)coz the tissues covering the massetor be displaced anteriorly.
  • Although everyone has a normal tongue at birth, some looses it and as a result acquire retracted tongue position
  • The functional renge refers to the positions through which the lower jaw moves horizontally during normal speech, swollowing and mastication.
  • The frictional resistance between the wide occlusal table of the zero degree teeth may contribute horizontal forces to the denture bases. Thus both the anatomic and flat plane bith tyoes if teeth leads to in stabilty of lower denture.
  • In the eccentric positions also the forces will act in same position over the residual ridge as that of centric position.
  • Is it possible?
  • But this position is essential for esthetics and function, so balanced occlusion is necessary.
  • This leads to slight crossbie relation when teeth are extracted, which may goes un detected.
  • But since the maxillry dentures are more retentivr which in turns aid in stability, we tends to abuse it thiss results in rapid latral resorption of alveolar ridge.
  • This compramises stability and makes control of the food bolus and denture more difficult.
  • Various anatomical landmarks such as Stensons duct and retromalar pad should be taken in to consideration while planning for occlusal plane
  • They can be soft tissue and hard tissue sugeries ------ bony deformities- exostisis tori , and genial tubercle
  • Dramitic change in stability of denture can be obsereved bu long term clinical follow up studies are not reported.
    In one clinical study it is reported to be 8 times less than conventional dentures
  • Stability/ dentistry dental implants

    1. 1.
    3. 3. CONTENTS • INTRODUCTION. • DEFINITION. • FACTORS CONTRIBUTING STABILITY: I. The relationship of the denture base to the underlying tissues. II. The relationship of the external surface and border to the surrounding orofacial musculature. III. The relationship of the opposing oclusal surfaces IV. other
    4. 4.
    5. 5. CONTENTS • Methods to improve stability. • Conclusion. • References.
    6. 6. Success of complete denture
    7. 7. Biological factors, physical factors, mechanical factors support Longevity Stability Physiologic comfort Prosthesis Retention Psychological comfort
    8. 8. • Retention resistance to vertical dislodgement Stability resistance to horizontal forces • Retention psychological comfort Stability physiologic comfort
    9. 9. Retention is the most spectacular yet probably the least important of the three denture properties Stability is the most important of these
    10. 10.
    11. 11. Definition (GPT-8) • STABILITY:- • 1)That quality of maintaining a constant character or position in the presence of forces that threaten to disturb it; the quality of being stable; to stand or endure. • 2)The quality of a removable prosthesis to be firm, steady or constant to resist displacement by functional horizontal or rotational stresses. • 3) Resistance to horizontal displacement of prosthesis.
    12. 12. • Denture stability:- • The resistance of a denture to movement on its tissue foundation, especially to lateral (horizontal) forces as opposed to vertical displacement (termed denture retention). • A quality of a denture that permits it to maintain a state of equilibrium in relation to its tissue foundation and/ or abutment teeth.
    13. 13. Factors contributing to stability • Ridge height. • Base adaptation • Residual ridge relationships • Occlusal harmony • Neuromuscular control • Retention • Proper form and contour of polished surface • Patient education
    14. 14. • Neutral zone. • Tongue anatomy. • Denture surrounding structures.
    15. 15. • FISH (1948) described three denture surfaces. • Tissue surface. • Polished surface. • Occlusal surface. • All the three surfaces helps in determining stability of the complete denture.
    16. 16. • The relationship of the denture base to the underlying tissues. • The relationship of the external surface and border to the surrounding orofacial musculature. • The relationship of opposing occlusal surfaces. • Others.
    17. 17. The relationship of the denture base to the underlying tissues.
    18. 18. Residual ridge anatomy • Retention is available to all patients regardless of the condition of the ridge…….. • But stability gets limited. • A poor ridge simply indicates that its inability to exert an equal and opposite pressure against a functional force tending to dislodge the denture.
    19. 19. • Large, square, broad ridges offers a greater resistance to lateral forces than do small, narrowed tapered ridges.
    20. 20. • Stability is mainly obtained by incorporating the surfaces of the maxillary and mandibular ridges which are right angle to the occlusal plane.
    21. 21. • The contacting of the labial and buccal flanges with labial and buccal slopes is one of the critical factors contributing stability. • Small and rounded irregularities present on the vertical walls of the ridges also contribute. So alveoloplasty should be limited.
    22. 22. • The arch form – square or tapered arches tends to resist rotation of the prosthesis better than the ovoid arches. • Shape of palatal vault – stability is limited by the length and angulations of the palatal ridge slopes. • A steep or high arched palate enhances the stability by providing greater area of contact and long inclines approaching at right angle to the direction of force.
    23. 23.
    24. 24. Denture base adaptation • The relationship of the tissue surface of the denture base to the underlying tissues is dependent on the impression procedures of the clinician. • Maximum coverage without undue displacement of tissue, the development of a good border seal, and close adaptation helps in improving stability. • Maximum buccal extension of the mandibular denture in the buccinator attachment zone, retromylohyoid region, sublingual cresent area are desirable
    25. 25.
    26. 26. Mandibular lingual flange • Most desirable feature of lingual slopes approaches 900 to the occlusal plane. • Effectively resist horizontal forces. • Although the posterior fibres of the mylohyoid muscle attach more superiorly than anterior, they descend nearly vertically to attach hyoid bone • So the posterior lingual flange can be extended more
    27. 27.
    28. 28. • Musculature of the floor of the mouth may also influence the degree of intimate contact allowed. • Any flange extension below the mylohyoid ridge must incline medially away from the mandible to allow for the mylohyoid muscle contraction. • Presence of a thin mucosa overlying the bony ridge slopes that may require relief make the close contact impossible.
    29. 29. Sublingual crescent area. • The crescent shaped area on the anterior floor of the mouth formed by the lingual wall of the mandible and the adjacent sublingual fold. It the area of the anterior alveolingual sulcus.(GPT-8) • Extension of the denture over the resting tissues of the sublingual crescent area completes the border seal.
    30. 30. • Its coverage by denture results in • 1)Increased stability by allowing the tongue to aid in holding the denture in place. • 2) Increased retention of the denture.
    31. 31. • Making the impressions with minimal pressure on the floor of the mouth while tongue is at rest position allows greater mobility of the underlying muscles without denture dislodgement and without occlusion of the sublingual gland duct. •JPD1992;67:205- 210
    32. 32.
    33. 33. Relationship of the external surface and periphery to surrounding orofacial musculature
    34. 34. • Both stability and retention depend upon the relationship of polished surface and surrounding orofacial musculature. • Also normal functioning of certain muscle groups enhance the stability. • Alteration in external denture base contour can lead to dynamic seating and stabilizing action directed towards the prosthesis.
    35. 35. • Action of certain muscle groups must be permitted to occur without interference by the denture base so that they will not dislodge the denture, - they compromise the stability. • The action of the levator anguli oris, depressor anguli oris (triangularis), mentalis, mylohyoid and genioglossus muscles can dislodge the denture if the denture base does not provide freedom for these muscle action.
    36. 36. • The basic geometric design of denture bases should be triangular. • In the frontal cross section, the maxillary and mandibular dentures should appear as two triangles whose apexes correspond to the occlusal surface. •JPD1983;49:165-174
    37. 37. • The buccal and labial flanges of the maxillary and mandibular dentures should be concave to permit positive seating by the cheeks and the lips. • The primary muscles of cheeks and lips are orbicularis oris and buccinator. • These muscles are active in mastication, deglutition and speech.
    38. 38. • The proper contour of the denture flanges permits the horizontally directed forces, that occur during contraction of these muscles, to be transmitted as vertical forces tending to seat prosthesis.
    39. 39.
    40. 40. • To direct a seating action on the mandibular denture, the tongue should rest against a lingual flange inclined medially away from the mandible and somewhat concave. The degree of inclination depends on the balance of the muscular forces of the tongue as opposed to the mylohyoid and superior constrictor muscle.
    41. 41. • Inclination of the lingual flange must be designed to guide the tongue to rest over the flange and permit any horizontal forces generated against the denture base to be transmitted as seating forces.
    42. 42. Modiolus • The musculi cruculi modioli or modiolus and their associated musculatures has various actions on the denture. • The modiolus or tendinous node is an anatomical landmark near the corner of the mouth that is formed by the intersection of several muscles of the cheeks and lips.
    43. 43. • These muscles are:- • Orbicularis oris. • Buccinator. • Caninus (levator anguli oris). • Triangularis (depressor anguli oris). • Zygomaticus major. • Risorius. • Quadratus labii superioris. • Depressor labii inferioris.
    44. 44.
    45. 45. • Because none of these muscles contains fibres that have more than one bony attachment, they depend on fixation of the modiolus to allow isometric contraction. • E.g.-contraction of the triangularis, caninus, and zygomaticus muscles fixes the modiolus, allowing the buccinator muscle to contract
    46. 46. • Isotonic contraction of the buccinator muscle in the absence of modiolus fixation would pull the corner of the mouth posteriorly. • The same is the situation of orbicularis oris and other muscles.
    47. 47. • The denture base must be contoured to permit the modiolus to function freely. • In the premolar region the mandibular denture should exhibit both a shortened and narrowed flange to permit the action that draws the vestibule superiorly and the modiolus medially against the dentures.
    48. 48. • The buccinator muscle may be divided in to superior, middle, and inferior divisions.
    49. 49. • According to Fish, • Superior fibers acts to seat the maxillary denture. • Middle fibres controls the bolus of food. • The inferior fibres contributes to mandibular denture stability.
    50. 50. • While the middle fibres contract, controlling the bolus, the inferior fibres relax to form a pouch capable of storing food until needed to form another bolus. • Extension of a concave denture base into this pouch allows the cheek to lie over the flange.
    51. 51. Action of some other muscles. Dislocating muscles Fixing muscles vestibular Masseter Mentalis Depressor labii inferioris Buccinator Orbicularis oris lingual Internal pterigoid Palatoglossus Styloglossus mylohyoid Genioglossus Intrinsic muscles of tongue JPD1965;15:401-417
    52. 52. • Masseter muscle- if an impression is made while masseter is relaxed, the denture tends to be displaced when this muscle contracts.
    53. 53. • Mentalis muscle:- the origin of the mentalis muscle is located closer to the crest of the residual ridge than the mucosal reflection in the alveolabial sulcus. • Consequently the bottom of the sulcus is lifted when the mentalis muscle contracts; and thereby, the depth and space of the oral vestibule can be decreased considerably.
    54. 54. • Depressor labii inferioris originates from very near the crest of the residual ridge and extends down and beneath the alveololabial sulcus. • So during contraction, the denture space reduces .
    55. 55. • Internal pterygoid muscle- it determines the extension of the denture in the lower, posterior and lingual part. • Palatoglossus muscle during deglutition, it reduces the lumen of the isthmus faucium. The mucosa covering the lower part of the muscle is lifted superiorly, anteriorly and medially. The terminating part of alveololingual sulcus is affected by it’s contraction • Styloglossus
    56. 56. • Pterygomandibular raphe:- when mouth is opened widely, the pterygomandibular raphe stretches. So a denture that has been extended onto this structure may be dislodged during an energetic opening movement of the mandible.
    57. 57. • Tendon of the genioglossus muscle:- when the apex of the tongue is lifted, the tendaneous origin of the genioglossus muscle as well as the lingual frenum will be passively streched and lifted, thus easily being capable of dislodging the lower denture
    58. 58. Tongue • As the patient becomes edentulous, the continuous destruction of residual ridges occurs. • Because of these changes the tongue will expand in the space formerly occupied by the teeth. • This occurs partly due to a growth of tongue and has been named Proptosis lingualis.
    59. 59. • A small, narrow tongue contributes to the ease of impression making but jeopardizes the lingual seal for mandibular denture. • An extremely large tongue (macroglossia) poses additional problems during impression making and impairs denture stability.
    60. 60. Normal tongue. • A normal tongue fills the floor of the mouth. • The apex rests on the lingual surface of the mandibular anterior teeth and the sides rest against the lingual surfaces of the posterior teeth and extend slightly over their occlusal surfaces.
    61. 61.
    62. 62. • When mouth is opened, the tongue can rest on the mandibular teeth and stabilizes a mandibular denture. • During mastication, the sides of the tongue press food outward over the posterior teeth in opposition to inward pressure of the middle fibres of the buccinator muscle.
    64. 64. The retracted tongue position is sometimes referred to as an awkward tongue position, and has the following characteristics:
    65. 65.
    66. 66. (1) The tongue is pulled back into mouth and the floor of the mouth is exposed. (2) The lateral borders are either inside or posterior to the ridge. (3) The tip of the apex of the tongue sometimes lies in the posterior part of the floor of the mouth or may be withdrawn into the body of the tongue.
    67. 67. The neutral zoneThe neutral zone • Definition: (GPT-8) • The potential space between the lips and cheeks on one side and tongue on the other; that area or position where the forces between the tongue and cheeks or lips are equal.
    68. 68. • The basic concept is to establish harmony between the polished surface of denture and the associated musculature. • The musculature should functionally mold not only the borders but also the entire polished surface.
    69. 69. • The teeth are placed within the “neutral zone” where facial and lingual forces generated by the musculature of the lips, tongue and cheeks are balanced. • This functional rather than anatomic arrangement of teeth is believed to further enhance the stability of the dentures by minimizing active forces.
    70. 70.
    71. 71. Relationship of opposing occlusal surfaces
    72. 72. • Harmony developed between the opposing occlusal surfaces also contributes stability. • The dentures must be free of interferences within the functional range of movements of the patient.
    73. 73. • During both functional and parafunctional movements movements the occlusal surfaces should not strike prematurely in localized areas. • Such contacts cause uneven stresses to be transmitted to the denture during function resulting in lateral and torquing forces that destabilize the denture.
    74. 74. • Geometric classification of occlusion. [J.P.Frush –1966] 1) One-dimensional (linear) occlusion. 2) Two-dimensional (flat plane) occlusion. 3) Three-dimensional (cusped) occlusion This is based on the dimensional contacts between occluding posterior teeth. J. PROSTHODONT2004;
    75. 75. Anatomic occlusal scheme. • Maximum intercuspation. • Surface contact between posterior anatomic teeth consists of multidirectional but equalized, vectors.
    76. 76. • The directional forces change in eccentric position, and there is a significant lateral force component exerted on the denture bases.
    77. 77. Balanced occlusion • The bilateral, simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions. (GPT-8) • The bilateral balance is more important during activities such as swallowing saliva, closing to reseat the dentures, and the bruxing of the teeth.
    78. 78. • Patients with balanced occlusion do not upset the normal static, stable and retentive position. • Absence of occlusal balance will result in leverage of the denture during mandibular movement, compromising stability.
    79. 79. Zero degree teeth. • They can be arranged in a single plane (monoplane/ flat plane). • If they are set in a curve, balancing can be achieved. But this results in additional planes. • These inclined planes can cause skidding of the denture bases and induce excessive friction.
    80. 80. • A monoplane scheme reduces the horizontal force components because of direction of forces between zero degree teeth in centric and eccentric position is essentially vertical.
    81. 81. • However in eccentric positions there is an inequity in the opposing surface area contact between working and non-working side and there is a shift in the location of the forces between the occluding surfaces.
    82. 82. Linear occlusion. • William H. Goddard. • The basic parameters. 1)Zero degree (flat plane) teeth are opposed by bladed (line contact) teeth in which the blade is in a precisely straight line over the crest of ridge.
    83. 83.
    84. 84. 2) Maxillary teeth are set to a flat (monoplane) occlusal plane. 3) There is no anterior tooth interference to protrusive or lateral movement.
    85. 85.
    86. 86. • The size of the requiring the greatest stability may determine the arch receiving the bladed teeth. • The occluding forces between a zero degree and a bladed tooth are vertical in centric and eccentric positions.
    87. 87. • Force of vectors are vertical and equalized in both centric and eccentric positions.
    88. 88. • The blade line contact with the zero degree (flat plane) reduces the width component of the force seen in other zero degree denture occlusion and increases the force per unit area of contact. • Noninterceptive occlusion provides a consistent vertical seating force in both centric and eccentric movement; transverse force vectors are essentially eliminated.
    89. 89. ESTHETICS? • If non-anatomic or linear occlusal scheme is followed, esthetics gets compromised, especially in the maxillary premolar region. • Occlusal scheme with advantages of a linear occlusal scheme yet providing good esthetics………. Gysi (1927); Payne (1941)
    90. 90.
    91. 91. LINGUALIZED OCCLUSION. • Principles of lingualized occlusion. • Anatomic posterior (30/330 ) teeth are used for the maxillary denture. Tooth form with prominent lingual cusps are helpful. • Nonanatomic or semianatomic teeth are used for the mandibular denture. Either a shallow or flat cusp form is used. A narrow occlusal form is preferred.
    92. 92. • Modification of the mandibular posterior teeth by selective grinding of central fossae of the mandibular teeth, lower marginal ridges and to form slight buccal and lingual inclines. • Maxillary lingual cusps should contact mandibular teeth BUT the mandibular buccal cusps should not contact the upper teeth in centric occlusion.
    93. 93.
    94. 94. • Balancing and working contacts should occur only on the maxillary lingual cusps. • Protrusive balancing contacts should occur only between the maxillary lingual cusps and the lower teeth. • Since in lingualized occlusion, vertical forces are centralized on the mandibular teeth, it is proposed to aid in stability.
    95. 95. Tooth position and occlusal plane. • Anterior and posterior teeth should be arranged as close as possible to the position once occupied by the natural teeth, with only slight modifications made to improve leverages and esthetics.
    96. 96. • When forces act on a body in such a way that no motion results, there is a balance or equilibrium. • This should be the primary consideration with the forces that act on the teeth and the denture bases with their resultant effect on the movement of the base. • A stable base is the ultimate goal.
    97. 97. • Total stability is not possible because of the yielding nature of the supporting structures. • ‘Lever balance’ is the basis of balanced occlusion.
    98. 98. Some rules in teeth arrangement. • The wider and larger the ridge and closer the teeth are to the ridge, greater is the lever balance. • Wider the ridge, narrower teeth bucco- lingually greater the balance and vice- versa.
    99. 99. • More lingual the teeth placed in relation to the ridge crest, greater the balance, more buccal the placement of teeth, poorer the balance. • More centered the forces of occlusion antero-posteriorly greater the stability of the base.
    100. 100. Maxillary anterior tooth position: • The arch curvature should correspond to curvature of alveolar ridge, facial contour and maxillary lip position.
    101. 101. • Arranging teeth in to a square arch form on a tapering or ovoid residual alveolar ridge causes canines to be labial to crest of the maxillary ridge than central incisors.
    102. 102. • This results in bicuspids being more buccal to the ridge than they should be. • Working side occlusal pressure produces a displacing tendency, the ridge crest acting as a fulcrum.
    103. 103. • The labial axial inclination of the natural anterior tooth places the incisal edge labial to the center of rotation of the tooth, if prosthetic tooth is placed exactly in the same position as the natural crown it will be labial to the ridge support. • Incisal pressure causes a displacing torque.
    104. 104. Mandibular anterior tooth position. • It should be in harmony with the maxillary anterior tooth position. • Errors in maxillary tooth position will be transferred to the mandibular arch. • For maximum stability, overbite should be as minimum as possible.
    105. 105. Maxillary posterior tooth position. • Natural posterior maxillary teeth have a buccal axial inclination and the mandibular teeth have a normal lingual axial inclination.
    106. 106.
    107. 107. • The normal residual alveolar ridge resorption pattern leads to increased cross bite relationship. • Tendency to avoid crossbite arrangement results in placing maxillary teeth in buccal position or mandibular teeth in lingual to desired position. • Both leads to impaired stability.
    108. 108. • In such cases, the working side occlusal pressure causes a displacing tendency because the line of force is buccal to the fulcrum.
    109. 109. Mandibular posterior teeth. • The buccal cusps and fossae of the posterior mandibular teeth should be directly over the crest of the ridge.
    110. 110. •If placed more buccally, working side occlusal pressure causes a displacing tendency because the line of force is buccal to the fulcrum. •If placed more lingually, tongue will displace the denture
    111. 111. OCCLUSAL PLANE • The superior-inferior position of the occlusal plane also a recognized factor influencing stability. • A mandibular occlusal plane that is too high can result in reduced stability.
    112. 112. 1]Lateral tilting forces directed against the teeth are magnified as the plane is raised. 2]The mandibular denture needs to be controlled by the musculature of the tongue, lips, and cheeks. An elevated occlusal table prevents the tongue from reaching over the food table into the buccal vestibule.
    113. 113. • A raised mandibular occlusal plane is usually present when the vertical dimension of occlusion is increased excessively. • Bisecting the interridge distance distance improves the mechanical advantage of the mandibular denture.
    114. 114. • The best stability is obtained when the occlusal plane is parallel to and evenly divided between the ridges.
    115. 115. • If the occlusal plane is is tipped, there will be shunting effect and a loss of stability. • If the occlusal plane is lower in molar area, there will be a tendency for upper denture to be displaced posteriorly and lower denture anteriorly.
    116. 116. Patient education Eating • Patients must be advised that chewing is not random but an intentional and selective activity. The eating skills must be slowly developed and refined. Initially patient should limit themselves to soft foods and avoid tough fibrous foods that will overtax the capacity of their residual ridges. •
    117. 117. • What to eat depends on effective patient guidance . • How to eat with dentures is a skill that has to be learned • Basically chewing with dentures is more methodical than with natural teeth. Patients must be instructed to divide the normal spoonful of food into half and place each half posteriorly and bilaterally
    118. 118. TONGUE POSITION
    119. 119. • In order to determine whether the patient has normal tongue position or an abnormal retracted tongue position, ask the patient to open just wide enough to accept food and observe the dorsal surface of tongue and occlusal surfaces of the teeth. • The tongue is in contact with lingual surface of denture and floor of mouth is at normal level. The mandibular denture should be stable and able to resist a gentle push on mandibular incisors. If not, the denture will be unstable and easily dislodged.
    120. 120. • Thus the patient should be aware of importance of tongue position, demonstrate proper tongue positions and subsequent increase in denture retention and stability. • The patient must practice opening and closing while tongue assumes normal position. • Some patients with Parkinson’s disease stroke will have difficultly in coordinating tongue movements. These patients have difficultly in speaking and require help of speech therapist.
    121. 121. Checking stability of the patient • Pressure is applied with the ball of the finger in the premolar-molar regions of each side alternatively.this pressure must be at right angle to the occlusal surface. If pressure on one side causes the denture to tilt and raise on the other side, it indicates that the teeth on the side on which the pressure was applied are outside the ridge.
    122. 122. • Checking stability in centric closure- patient is asked to close in centric relation, if forceful closure causes skidding of the denture, dentures are said to be unstable. • If balanced occlusion is provided to the patient,patient is asked to do all the eccentric movements, the denture should remain firm and steady.
    123. 123. • Stability can be evaluated by grasping the denture and attempting to rotate it or displace it laterally. The amount of movement must be considered relative to shape and character of the supporting structures (e.g. resiliency of the underlying tissue).
    124. 124. Maximizing stability. • Maximum coverage of denture bearing area within physiologic limit. • Giving due respect to muscle actions. • Use of neutral zone impression technique. • Proper positioning of teeth. • Proper positioning of occlusal plane.
    125. 125. • Occlusal scheme selection best suited for individual patient. • Non interceptive occlusion. • Proper patient education regarding tongue position, diet habit etc. • Denture modifications. • Use of denture adhesives.
    126. 126. Improving patient’s denture foundation and ridge relations. Non surgical methods- providing rest for denture supporting tissues, good nutrition and conditioning of patient’s musculature. Surgical methods- they are more popularly known as pre-prosthetic surgeries.
    127. 127. • Surgeries for ridge correction- Frenectomies, excision of hyperplastic tissues,correction of bone deformities. • Surgeries for ridge extension:- Vestibuloplasty, ridge augmentation procedures. • Placement of tooth root analogues.
    128. 128. Overdentures • Dentures get more ridge support, this enhances the retention of the denture and ultimately stability gets improved. • Rate of resorption of residual ridge decreases. • Preservation of periodontal membrane- preservation of proprioceptive impulses- retains myofacial nervous complex- improved neuromuscular control – improved manipulation of denture in mouth.
    129. 129. • Improving borders and peripheral extensions by using soft relining materials.
    130. 130. • Using composite impression technique for recording flabby ridges.
    131. 131. Myloc system The surface of a lower denture facing the tongue is fitted with small bars shaped like wings. These wings lay underneath the tongue providing a purchase point to help stabilize the denture.
    132. 132. MYLOFLEX DENTURESMYLOFLEX DENTURES • . It incorporates a positional memory  insert and an extended flange that takes  advantage of the undercut available in the  submandibular fossa. • When placed in the mouth, the myloflex  denture captures the lower mandible with  it's bilateral spring action. The tension is  slight, but significant enough to aid in  stabilization and retention of the denture
    133. 133.
    134. 134. Review of literature
    135. 135. Influence of functional design on the stability of complete maxillary dentures. F.Floystrand , J.Orstavik Journal of dental research 1982 vol.61 Reprinted abstract – JPD 1983;49(1):4 A clinical study - stability of complete maxillary denture was measured as resistance against dislodgment provoked by unilateral occlusal loading of denture in premolar region
    136. 136. • The results confirmed the beliefs that lingualized occlusal contact, functionally determined filling in of the vestibulum by the denture borders and full palatal coverage to the vibrating line all contribute toward improved stability of complete dentures.
    137. 137. The maxillary denture: its palatal relief and posterior palatal seal. Laney WR,Gonzalez JB JADA 1967;75:1182-1187. V- shaped maxillary ridge with essentially no hard palate; not conducive to development of good complete denture stability and retention.
    138. 138. • U-shaped maxillary ridge with horizontal hard palate; favorable for support and retention. • Palates with torus complicate retention and stability as they are covered by thin mucoperiosteum.
    139. 139. • The influence of the retromylohyoid extension on mandibular complete denture stability. C.H.Jooste, C.J. Thomas IJP1992;5:34-38 The contribution of retromylohyoid extension in complete mandibular impression was tested in six individuals by means of cineradiography and placement of metal marker. It was concluded that the retromylohyoid extension has a stabilizing effect on mandibular complete denture.
    140. 140. Prospective clinical evaluation of mandubular implant overdentures part-I retension stability and tissue responses, DR Burns et al JPD1995;73 • The study shown superior statistics of implants as an treatment alternatative to increase stability than ridge augmentation or vestibular extension procedures.
    141. 141. A comparison of different treatment strategies in patients eith atrophic mandibles- a clinical evaluation. W. Kalk et al. IJP 1992;5. • In this 6.5 years clinical follow up study, the stability was assessed in three groups: 1)those patients who needed pre-prosthetic surgery but which was contraindicated , had received new dentures.
    142. 142. 2) same as group 1 but were treated with vestibuloplasty and lowering of the floor of the mouth before denture fabrication. 3)Control groups without residual ridge problems who were treated with new complete dentures • The least displacement of the mandibular denture occurred in group2 and group3, with group 1 being the greatest.
    143. 143. CONCLUSION. • Stability prevents anterioposterior shunting of the denture base . • It has been cited as the most significant property in providing physiology comfort to the patient. • Denture instability adversely affect retention & support & results in deleterious forces on the edentulous ridge during function & parafunction.
    144. 144. • It is important to know factors affecting stability. • Though to fabricate the perfectly stable denture may not be truly possible , we should still try to achieve the maximum possible.
    145. 145. REFERANCES. • Boucher’s Prosthodontic treatment for edentulous patients. • Sheldon Winkler: Essentials of complete denture prosthodontics. • John J. Sharry: complete denture prosthodontics.
    146. 146. • David J. Lamb: problem and solutionas in complete denture prosthodontics. • William R. laney: Diagnosis and treatment in prosthodontics. • Evaluation of the factors necessary to develop stability in complete dentures. Corwin R. Wright JPD 1966;16:414-30. reprint JPD2004;92:509-18
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