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Residual ridge resorption /certified fixed orthodontic courses by Indian dental academy

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Residual ridge resorption /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
  2. 2. RESIDUAL RIDGE RESORPTION www.indiandentalacademy.com
  3. 3. CONTENTS •Introduction. •Basic concept of bone. •Mechanism of bone resorption •Pathology of RRR •Pathophysiology of RRR •Pathogenesis of RRR •Changes in maxilla and mandible www.indiandentalacademy.com
  4. 4. •Epidemiology of RRR •Etiology of RRR •Calcium homeostasis and RRR •Osteoporosis and RRR •Management of RRR •Summary •Conclusion •References www.indiandentalacademy.com
  5. 5. Introduction Residual ridge is a term used to describe the shape of the clinical alveolar ridge after healing of bone and soft tissues after tooth extractions. It consists of the denture-bearing mucosa, submucosa and periosteum, and the underlying residual alveolar bone. www.indiandentalacademy.com
  6. 6. •After tooth extraction, a cascade of inflammatory reactions is immediately activated, and the extraction socket is temporarily closed by the blood clot. •Epithelial tissue begins its proliferation and migration within the first week and the disrupted tissue integrity is quickly restored. •The most striking feature of the extraction wound healing is that even after the healing of wounds, the residual alveolar ridge bone undergoes a life-long catabolic remodeling. www.indiandentalacademy.com
  7. 7. •The size of the residual ridge is reduced most rapidly in the first 6 months, but the bone resorption activity continues throughout life at a slower rate, resulting in removal of a large amount of jaw structure. •This unique phenomena has been described as RESIDUAL RIDGE RESORPTION (RRR). •The rate of RRR is different among persons and even at different sites in the same person. www.indiandentalacademy.com
  8. 8. The mechanical aspect of bone remodeling is usually associated with Wolff’s law of bone transformation (1892) which states that “EVERY CHANGE IN THE FORM AND FUNCTION OF BONE , OR OF THEIR FUNCTION ALONE,IS FOLLOWED BY CERTAIN DEFINITE CHANGES IN THEIR INTERNAL ARCHITECTURE, AND EQUALLY DEFINITE ALTERATION IN THEIR EXTERNAL CONFORMATION, IN ACCORDANCE WITH MATHEMATICAL LAWS.”, which simply means that bone remodels in response to the forces applied. However, the mere reference to ‘Wolff’s law’ in relation to bone resorption is an inadequate explanation of this complex physiologic process. www.indiandentalacademy.com
  9. 9. Consequences of RRR •Apparent loss of sulcus width and depth. •Displacement of the muscle attachment closer to the crest of the residual ridge. •Loss of vertical dimension of occlusion. •Reduction of lower face height. •An anterior rotation of the mandible. •Increase in relative prognathia. www.indiandentalacademy.com
  10. 10. •Changes in inter-alveolar ridge relationship. •Morphological changes such as sharp, spiny, uneven residual ridges. •Resorption of the mandibular canal wall and exposure of the mandibular nerve. •Location of the mental foramina close to the top of the mandibular residual ridge. This provides serious problems to the clinician on how to provide adequate support, stability and retention of the denture. www.indiandentalacademy.com
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  12. 12. Basic concept of bone: A basic concept of bone structure and its functional elements must be clear before bone resorption can be understood. The structural elements of bone are: a) Osteocytes found in bone lacunae. b) The intercellular substance or bone matrix consisting of fibrils and calcified cementing substance. c) Osteoblasts. d) Osteoclasts www.indiandentalacademy.com
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  14. 14. (a) Osteocytes: These are small, flattened and rounded cells embedded in the bone lacunae. They are the main cells, of the developed bone and are derived from the matured osteoblasts. Function: • Help to maintain bone as a living tissue because of their metabolic activity. • Play an important role in maintaining the exchange of calcium between bone and extra cellular fluid. (b) Calcified cementing substance: Consists of mainly polymerized glycoproteins and mineral salts namely CaCo3 and phosphate which are bound to these protein substances. www.indiandentalacademy.com
  15. 15. (c) Osteoblasts: Concerned with bone formation and are situated on the outer surface of bone in a continuous layer. Functions: • Responsible for synthesis of bone matrix. • Role in calcification. (d) Osteoclasts: They are the giant multinucleated cells found in the lacunae of bone matrix. Functions: • Responsible for bone resorption during bone remodeling. Bone resorption always requires the simultaneous elimination of organic and inorganic components of the intercellular substance. www.indiandentalacademy.com
  16. 16. Mechanism of bone resorption •The organic components of the intercellular substance are removed by proteolytic action of the osteoclasts. •Then, the Ca salts (inorganic) are dissolved by a chelating action of the osteoclasts. •As resorption takes place, the osteocytes released may revert to osteoblasts or become osteoclasts, depending on the physiologic and pathologic demands. • Histologically, bone apposition and resorption take place in close approximation, making possible the bone balance of shape and size. www.indiandentalacademy.com
  17. 17. Pathology of RRR www.indiandentalacademy.com
  18. 18. Gross pathology: The basic structural change in RRR is a reduction in the size of the bony ridge under the mucoperiosteum. It is primarily a localized loss of bone structure. In some situations, this loss of bone may leave the overlying mucoperiosteum excessive and redundant. In order to provide a simplified method for categorizing the most common residual ridge configurations, a system of six orders of RR form has been described. Order 1 Pre extraction Order 2 Post extraction Order 3 High, well-rounded Order 4 Knife edge Order 5 Low, well-rounded Order 6 Depressed www.indiandentalacademy.com
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  20. 20. •It is clear that RRR does not stop with the residual ridge , but may well go below where the apices of the teeth were, sometimes leaving only a thin cortical plate on the inferior border of the mandible or virtually no maxillary alveolar process on the upper jaw. •Sometimes a knife edge ridge maybe masked by a redundant or inflamed soft tissue, which can be detected by palpation or by Lateral cephalometric radiographs. www.indiandentalacademy.com
  21. 21. Microscopic pathology: • Studies have revealed evidence of osteoclastic activity on the external surface of the crest of the residual ridges. The scalloped margins of Howship’s Lacunae sometimes contain visible osteoclasts . •Studies have shown total absence of periosteal lamellar bone on the crest of the residual ridge, and a presence of cortical layer consisting of an endosteal type of bone, or no cortical layer but simply a medullary type of trabecular bone. •Varying degrees of inflammatory cells ,including lymphocytes and plasma cells, have also been seen. www.indiandentalacademy.com
  22. 22. PATHOPHYSIOLOGY OF RRR www.indiandentalacademy.com
  23. 23. •It is a normal function of bone to undergo constant remodeling throughout life through the process of bone resorption and bone formation. •Growth : ↑ Bone formation. •Osteoporosis/localized periodontal disease: ↑ Bone resorption. www.indiandentalacademy.com
  24. 24. •RRR is a localized pathologic loss of bone that is not built back by simply removing the causative factors. •Yet, the physiologic process of internal bone remodeling goes on even in the presence of this pathologic external osteoclastic activity that is responsible for the loss of so much of bone substance. •It has been shown that remodeling takes place in 3 dimensions such that certain portions of bone become narrower to the extent that all existing cortical bone in that area is removed by external osteoclastic activity and is replaced by a new cortical layer that is formed by simultaneous endosteal bone formation. www.indiandentalacademy.com
  25. 25. •Even if a great deal of RR is removed in total, there is often a cortical layer of bone over the crest of the ridge. This means that new bone has been laid down inside the RR in advance of the external osteoclastic removal of bone. •The mechanism of the reduction of the mandibular residual ridge actually represents a modified version of the Enlow’s “V” principle, showing external resorption accompanied by endosteal deposition. www.indiandentalacademy.com
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  27. 27. Based on the clinical fact that : •RRR is not inevitable • Its rate varies • The rate of resorption is greater that the rate of formation in some patients , ….RRR should be considered a pathologic process. www.indiandentalacademy.com
  28. 28. Pathogenesis of RRR www.indiandentalacademy.com
  29. 29. Order I: pre-extraction: The tooth is in its socket with thin labial and lingual cortical plates merged with the lamina dura. Order II: postextraction: The healing period includes clot formation and organisation, filling of the socket with the trabecular bone and epithelisation over the socket site. The edges of the residual ridge are still sharp. Order III: High , well rounded residual ridge: The cortical plates are rounded off by external osteoclastic resorption, narrowing of the crest of the ridge begins and remodelling of the internal trabecular structure takes place. www.indiandentalacademy.com
  30. 30. Order IV: Knife edge RR : Sharp narrowing of the labiolingual diameter of the crest of the ridge with a compensatory internal remodelling leading to a sharp crest of the ridge. Order V: Low well rounded RR : Progressive labio lingual narrowing of knife edge ridge leads to a widely rounded and lower residual ridge. Order VI: Depressed RR: Eventually further progression of the resorption leads to a flat, depressed ridge. www.indiandentalacademy.com
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  33. 33. •RRR is chronic, progressive, irreversible and cumulative. Usually, RRR proceeds slowly over a long period of time flowing from one stage imperceptibly to the next. Autonomous regrowth has not been reported. Annual increaments of bone loss have a cumulative effect leaving less and less residual ridge. www.indiandentalacademy.com
  34. 34. Changes In The Maxilla And The Mandible www.indiandentalacademy.com
  35. 35. •Maxillary teeth are generally directed downward and outward, so bone reduction generally is upward and inward. Since the outer cortical plate is thinner than the inner cortical plate, resorption from the outer cortex tends to be greater and more rapid. As the maxilla becomes smaller in all dimensions, the denture bearing area (basal seat) decreases. •The bone of the maxillae resorbs primarily from the occlusal surface and from the buccal and labial surfaces. •Thus the maxillary residual ridge looses height and maxillary arch becomes narrower from side to side and shorter anteroposteriorly. www.indiandentalacademy.com
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  38. 38. •The anterior Mandibular teeth generally incline upward and forward to the occlusal plane, whereas the posterior teeth are either vertical or incline slightly lingually. •The mandibular ridge resorbs primarily from the occlusal surface. •Because the mandible is wider at its inferior border than at the residual alveolar ridge in the posterior part of the mouth, resorption, in effect, moves the left and right ridges progressively farther apart. www.indiandentalacademy.com
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  41. 41. •The mandibular arch appears to become wider, while the maxillary arch becomes narrower. •Thus, RRR is centripetal in maxilla and centrifugal in mandible. •The cross section shrinkage in the molar region, is downward and outward. In the anterior region it is first downward and backward ,and then moves forward. •The surface of the arches maybe resorbed out of parallelism which can result in diminished stability of dentures. •Severe ridge resorption can also result in increased inter arch space. www.indiandentalacademy.com
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  43. 43. Epidemiology of RRR: •To date, it would appear that RRR is world-wide, occurs in males and females, young and old, sickness and in health, with and without dentures and is unrelated to the primary reason for the extraction of the teeth (Caries / periodontal disease). •Rate of RRR is variable -between persons. -within the same person at diff. times. -within the same person at diff. sites. www.indiandentalacademy.com
  44. 44. Etiology of RRR www.indiandentalacademy.com
  45. 45. It is postulated that RRR is a multifactorial, biomechanical disease that results from a combination of: • Anatomic. • Metabolic. • Functional. • Prosthetic factors. www.indiandentalacademy.com
  46. 46. ANATOMIC FACTORS: It is postulated that RRR varies with the quantity and quality of the bone of the residual ridges: RRR α anatomic factors The amount of bone: • It is not a good prognostic factor for the rate of RRR, because it has been seen that some large ridges resorb rapidly and some knife edge ridges may remain with little changes for long periods of time. •Although the broad ridge may have a greater potential for bone loss, the rate of vertical bone loss may actually be slower than that of a small ridge because there is more bone to be resorbed per unit of time and because the rate of resorption also depends on the density of bone. www.indiandentalacademy.com
  47. 47. Quality of bone: On theoretic grounds, the denser the bone, the slower the rate of resorption because there is more bone to be resorbed per unit of time. METABOLIC FACTORS. Generally, body metabolism is the net sum of all the building up (anabolism) and the tearing down (catabolism) going on it the body. RRR α bone resorption factors bone formation factors www.indiandentalacademy.com
  48. 48. •In equilibrium the two antagonistic actions (of osteoblasts and osteoclasts) are in balance. In growth, although resorption is constantly taking place in the remodeling of bones as they grow, increased osteoblastic activity more than makes up for the bone destruction. •Whereas in osteoporosis, osteoblasts are hypoactive, and, in the resorption related to hyperparathyroidism, increased osteoblastic activity is unable to keep up with the increased osteoclastic activity. The normal equilibrium may be upset and pathologic bone loss may occur if either bone resorption is increased or bone formation is decreased, or if both occur. www.indiandentalacademy.com
  49. 49. •Since bone metabolism is dependent on cell metabolism, anything that influences cell metabolism of osteoblasts and osteoclasts is important. •The thyroid hormone affects the rate of metabolism of cells in general and hence the activity of both, the osteoblasts and osteoclasts. •Parathyroid hormone influences the excretion of phosphorous in the kidney and also directly influences osteoclasts. •The degree of absorption of Ca, P and proteins determines the amount of building blocks available for the growth and maintenance of bone. •Vit C aids in bone matrix formation. •Vit D acts through its influence on the rate of absorption of calcium in the intestines and on the citric acid content of bone. •Various members of Vit B complex are necessary for bone cell metabolism. www.indiandentalacademy.com
  50. 50. •According to Reifenstein, in the young person, there is a relative predominance of anabolic hormones (estrogen and testosterone) over the anti anabolic hormones( cortisone and hydrocortisone) resulting in continued growth of skeleton. •He further states that, as people get older, the anabolic hormones are so reduced that the antianabolic hormones are in relative excess with the result that bone resorption may take place faster than bone formation and that bone mass may be reduced. www.indiandentalacademy.com
  51. 51. FUNCTIONAL FACTORS •Forces within the physiological limits are beneficial in their massaging effect. On the other hand, increased or sustained pressure produces bone resorption. •Bone that is used as by regular physical activity will tend to strengthen within certain limits , while bone that is in disuse will tend to atrophy. www.indiandentalacademy.com
  52. 52. Disuse atrophy •It is directly proportional to the extent of disuse. •It does not result from the direct loss of non functional bone, but the lack of replacement of bone not needed for function. •After the loss of natural teeth, bone cannot be stimulated by a denture base as the teeth did internally. The lack of internal stimuli contributes to the disuse atrophy. www.indiandentalacademy.com
  53. 53. •The amount and frequency of stress and its distribution and duration are important factors. •The reaction of bone to pressure can cause both apposition and resorption. •Whenever pressure interferes with the blood or nerve supply of the bone, resorption occurs. •The interference maybe due to pressure directly from the bone or inflammatory in origin. www.indiandentalacademy.com
  54. 54. PROSTHETIC FACTORS  Excessive stress resulting from artificial environment: • Human tissues have not evolved in nature to accept ranges of artificial things and the denture acts as an artificial entity.  Abuse of tissues from lack of rest: • Abused tissues are always manifested with a slung, glistering surface. Bone is moldable. It can tolerate masticatory forces within the limits of physiologic tolerance but exceeding that it causes damaging forces which will result in resorption of the alveolar bone and alteration in tissue form . www.indiandentalacademy.com
  55. 55.  Long continued use of ill fitting dentures: • In ill fitting dentures, there is an improper relation of the denture base to the supporting tissue. Ill fitting dentures may be due to : • Long use • Loss of bone • Incorrect occlusion • Incorrect jaw relation  UNDER EXTENDED DENTURES: • Lead to less retentive dentures and increase load per unit area. Common sites are: • Lingual flange • Buccal shelf area • Retromylohyoid area • Retromolar pad www.indiandentalacademy.com
  56. 56.  Faulty improper procedures employing compression forces: • Before impression procedures, care has to be taken on selection of trays. If the tray selected is too large, it will distort the tissues around the borders of the impression, away from the tissues. If it is too small, the border tissues will collapse inward onto the residual ridge. This will reduce the support of the lips by the denture flange. • The use of minimal and selective pressure impression techniques should be implicated in order to avoid distortion of the mucosa and ridge area which may be under considerable pressure otherwise. www.indiandentalacademy.com
  57. 57.  Error in relating maxilla to the cranial landmarks (orientation relation): The plane of the maxilla should be oriented to the facial reference line (Camper’s plane or ala tragus line). If not, may cause instability of denture leading to resorption.  Lack of freeway space due to increased vertical dimension of occlusion: Freeway space is present in the teeth in the physiologic rest position. It is normally 2-8mm but in complete dentures it is around 2mm. At times, due to lack of freeway space the bone resorbs because of increased vertical height in an attempt to create the space. www.indiandentalacademy.com
  58. 58.  Incorrect Centric relation record: If the Centric relation is not recorded properly, the mandibular teeth will not occlude properly with those on the maxillary arch. This proper occlusion is essential to the health of bony support. Otherwise, during eccentric movement, it causes pressure on bone due to failure of denture stability. Hence resorption of base occurs. www.indiandentalacademy.com
  59. 59. Faults in selection and placement of posterior teeth: The selection of proper tooth size is based on : •Capacity of ridges to receive and resist the forces of mastication. •Space available for the teeth. •When the ridge is weak, resorbed and covered by only lining mucosa, then the use of the posterior teeth should be smaller. This will limit the occlusal surface, which in turn will minimize the forces directed to such a ridge. www.indiandentalacademy.com
  60. 60.  If occlusal corrections are not done: • These errors which may be caused due to processing techniques if not corrected causes premature contacts resulting in increased stress. • Selective grinding should be done to minimize lateral stress and resulting tissue trauma.  Overclosure • The loss of proper vertical dimension after the insertion of complete dentures results in the triggering of a cyclic series of events detrimental to the health of the residual alveolar ridge. • Overclosure causes the mandible to be moved or rotated in an upward and forward direction causing occlusal disharmony and excessive trauma to anterior region . www.indiandentalacademy.com
  61. 61. Bone resorption and Ca homeostasis: The only sources of Ca for the body are •Diet •Bone reservoir. Ca homeostasis is maintained by controlling Ca obtained from these 2 sources. This can occur by altering internal absorption mechanisms (income) or tubular reabsorption (recycling) or by liberation of Ca from the skeleton via resorption (savings). There is a reciprocal relationship between Ca concentration and bone resorption to maintain Ca homeostasis. As the level of serum calcium develops, resorption is stimulated and factors that would inhibit resorption are depressed. www.indiandentalacademy.com
  62. 62. •Skeletal depletion of calcium occurs as a result of stimulation of parathyroid gland and the alveolar bone is the first to be affected. This is due to the function of parathyroid hormone in maintaining the blood calcium level by mobilizing it from bones by osteoclastic activity. •Simultaneously , there is an increased renal excretion of phosphate, which disturbs the blood calcium:phosphorous ratio by raising the blood calcium level. This results in mobilization of phosphates from bones by osteoclastic activity. •Under these conditions , alveolar bone becomes susceptible to diseases like osteoporosis. www.indiandentalacademy.com
  63. 63. Osteoporosis and RRR •Osteoporosis is characterized by low bone mass and micro architectural deterioration of the bone, which leads to increased bone fragility and risk of fracture. •It has two forms. •The more prevalent Type I (post menopausal) affects women for a decade or so after menopause. •The Type II ( senile or idiopathic) attacks males and females at any age for no obvious reason. •RRR maybe a manifestation of Type I osteoporosis . •Both cortical and trabecular bone are affected. www.indiandentalacademy.com
  64. 64. Treatment for osteoporosis •Estrogen replacement therapy •Ca supplement •Good nutrition and regular exercise •New drugs for systemic osteoporosis are under evaluation, including biophosphonates to inhibit osteoclasts and injections and calcitonin to reduce resorption. Detection of bone loss i.e. radiographs •Digital subtraction radiography •Dual energy x-ray absorptiometry www.indiandentalacademy.com
  65. 65. Methods of evaluation of bone loss in RRR • Radiographs: - Cephalometrics . - Panoramic. • Tetracycline labeling • Mercury porosimetry • Anatomic studies • Remount jig procedure www.indiandentalacademy.com
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  69. 69. Management of RRR www.indiandentalacademy.com
  70. 70. Systemic evaluation Diet Tissue treatment therapy Pre prosthetic surgery Prosthetic management: -Impression techniques. -Denture base selection. -Teeth selection and arrangement. -Implant supported prosthesis. www.indiandentalacademy.com
  71. 71. Systemic evaluation •Any systemic condition that can contribute to the degeneration of the bone condition should be corrected and stabilized, for e.g.: osteoporosis, hyperparathyroidism, diabetes mellitus. •Any dental treatment should follow only after the condition is under control and the patient is fit for treatment. •In cases where limited help can be given, the patient should be counseled about its effect on dental health. www.indiandentalacademy.com
  72. 72. Diet. •Patients with bone disease need a diet high in proteins, vitamins and mineral content. •Should reduce or stop intake of refined carbohydrates, white flour, and white sugar. •In all dietary prescriptions , the consistency of food prescribed must take into account the patients ability to masticate. Tissue Treatment Therapy. •Soft conditioning materials can be used to rejuvenate the tissue-bearing area. •Hypertrophied tissues, previously treated by surgery, can be reconditioned by using this material. www.indiandentalacademy.com
  73. 73. Pre-prosthetic surgery It aims at providing a good healthy surface for the insertion of the dentures. It includes all the surgical procedures by virtue of which an ideal smooth, healthy U shaped ridge , without any unfavourable undercuts or bony growths and with sufficient vestibular depth is achieved. It includes the following surgical procedures: •Ridge correction. •Ridge extension/vestibuloplasty. •Ridge augmentation www.indiandentalacademy.com •Surgical correction of maxillomandibular relation.
  74. 74. Ridge Corrective surgery Soft tissue deformities •Labial frenectomy. •Lingual frenectomy. •High buccal frenal attachments. •Hyperplasia of soft tissues. Bony deformities •Sharp irregular ridge. •Alveoloplasty. •Alveolectomy. www.indiandentalacademy.com •Excision of tori and genial tubercles.
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  77. 77. Ridge extension surgery/vestibuloplasty •Labial. •Lingual. •High mental foramen. •Zygomaticoplasty. •Tuberoplasty. www.indiandentalacademy.com
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  81. 81. Ridge augmentation It is aimed at : •Increase in the ridge height and width providing a large denture bearing area , •Protection of neuro vascular bundles •Restoration of proper maxillomandibular arch relationship. Ridge augmentation has been tried with: •Bone transplants •Autogenous and homogenous cartilage •Hydroxylapatite •Acrylic implants. www.indiandentalacademy.com
  82. 82. Prosthetic management. Impression technique In patients with severely resorbed ridges, lack of ideal amount of supporting structures decreases support and the encroachment of the surrounding mobile tissues onto the denture border reduces both stability and retention. Thus the main aim of the impression procedure is to gain maximum area of coverage. For e.g., in mandibular ridge, obtaining a fairly long retromylohyoid flange helps to achieve a better border seal and retention. Selection of proper trays and the correct impression procedure is very essential for an accurate impression. www.indiandentalacademy.com
  83. 83. • Selective pressure technique This technique is most widely advocated to manage RRR. It makes it possible to confine the forces acting on the denture to the stress bearing areas . This helps in better withstanding the mechanical forces induced by denture wearing. • Winkler describes a technique which uses tissue conditioners. An over extended primary impression of alginate is made. Occlusal wax rims are constructed and the borders are adjusted so that the lingual flange and sublingual crescent area are in harmony with the resting and acting phases of the floor of the mouth by an open and closed – mouth technique. www.indiandentalacademy.com
  84. 84. 3 applications of conditioning material are used – each application approximately 3-10 minutes. The third and final wash is made with a light bodied material. This technique results in the impression that has tissue placing effect with relatively thick, buccal, lingual and sublingual crescent area borders. •Miller used mouth-temperature waxes instead of tissue conditioners . www.indiandentalacademy.com
  85. 85. Mucodynamic technique. It is intended to integrate the changes in the shape of the vestibules when functional movements are made. A highly viscous thermoplastic reversible impression material is placed in the custom tray, then carefully adapted to the residual ridge and held with light and uniform pressure while the functional movements are made. As soon as the entire surface is smooth and the buccal and lingual borders are molded to the outer circumference without any folds, the impression is complete. www.indiandentalacademy.com
  86. 86. Selection of denture base For degenerative ridge patients there are three types of denture bases: •Methyl methacrylate resin denture bases •Cast metal bases •Processed resilient , lined denture bases www.indiandentalacademy.com
  87. 87. Methyl methacrylate resin denture bases •These are the standard bases normally used. •These bases are quickly and easily processed. •Dimensionally stable. •But in a short time the base appears to soften and change color, and is not strong. www.indiandentalacademy.com
  88. 88. Cast metal bases. •Main advantage is the great accuracy of fit to the tissues by surface tension, than acrylic denture bases. •They maybe of gold, chromium cobalt or aluminium. Processed resilient , lined denture bases. Its greatest advantage is its cushioning effect on the mucosa and its ability to distort and spring back. Indications: •Patients with severely undercut ridges, but for whom surgery is contraindicated. •Patients with parafunctional mandibular movement habits. •Patients with flat ridge and delicate tissues. www.indiandentalacademy.com
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  90. 90. Limitations: •They can be used only under a hard-processed acrylic resin base, and the lining works best when there is a 2 mm thickness. •Deterioration of the liner in some mouths. In spite of this , it can be held up well in dentures by proper cleansing and brushing with soft tooth brush. www.indiandentalacademy.com
  91. 91. Teeth selection and arrangement Teeth can be selected acc. to their form and size: •Anatomic or cuspal teeth •Semi anatomic teeth •Non anatomic or zero degree teeth. The following requirements have to be met during teeth arrangement: •Stability of occlusion in centric relation. •Balanced occlusion for eccentric contacts. •Unlocking of the cusps mesio distally to accommodate the settling of denture bases. www.indiandentalacademy.com
  92. 92. •Control of horizontal force by buccolingual cusp height reduction acc. to residual ridge shape and inter arch space. •Functional balance by favorable tooth to ridge crest position. •Cutting and shearing efficiency. •Anterior clearance of teeth during mastication. •Minimal occlusal stop areas for reduced pressure during function. •Teeth should be placed in neutral zone to create co ordination between the primary and secondary masticatory organs. www.indiandentalacademy.com
  93. 93. •Relative to each other, the maxillary and mandibular residual ridges are known to be in a favorable position for normal arrangement of posterior teeth if the connecting line between the midridge line of the max. and mand. residual ridges are at an angle of more than 80 degrees. •An angle less than 80 degrees necessitates a cross bite or reverse occlusion arrangement of posterior teeth. •A prognathic mandible necessitates the arrangement of anterior teeth in a reverse occlusion. www.indiandentalacademy.com
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  95. 95. •Non anatomic teeth have known to cause fewer denture sore spots and lesser ridge resorption. •Semi anatomic reverse curve posterior teeth favor the lower ridge •Anatomic posterior teeth cause more denture soreness and ridge resorption. •Few studies state that anatomic posterior occlusion favors lower dentures and non anatomic posterior teeth favor upper denture. www.indiandentalacademy.com
  96. 96. Implant supported prosthesis. The various problems associated with RRR and stability of removable soft tissue borne dentures have aroused interest in dental implantology to provide stable mechanical support to the dental prosthesis. This is because of the following advantages offered by implant supported prosthesis: •Maintenance of alveolar bone •Maintenance of occlusal vertical dimension. •Height of alveolar bone is found to be maintained as long as the implant remains healthy. •Improved psychological health. www.indiandentalacademy.com
  97. 97. •Regained proprioception. •Increased stability, retention and phonetics. •Maintenance of structure and function of muscles of mastication and facial expression. •Immune to caries. •Increased trabeculation and density of bone. •Overall volume of bone is maintained. •Efficiency to take up stress and strain. •There is 20 fold decrease in the loss of structure with implants when compared with resorption that occurs with removable prosthesis. •Preventive implant is given following extraction to retard ridge resorption. www.indiandentalacademy.com
  98. 98. Prosthodontic classification of implants. FP-1 : Fixed prosthesis replacing only crown. FP-2 : Fixed prosthesis replacing crown and portion of root. FP-3 : Fixed prosthesis replacing missing crowns and portion of the edentulous site. RP-4 : Removable prosthesis : overdenture supported by implants. RP-5 : Removable prosthesis : overdenture supported by both soft tissue and implant. www.indiandentalacademy.com
  99. 99. www.indiandentalacademy.com
  100. 100. www.indiandentalacademy.com
  101. 101. •The success of implant supported prosthesis, however, depends on the technical knowledge and mastery of the implantologist, and is directly related to the selection of patient and implant, surgical technique, follow up procedures and patient acceptability. www.indiandentalacademy.com
  102. 102. Summary www.indiandentalacademy.com
  103. 103. •Residual ridge resorption is a chronic, progressive, irreversible, and disabling disease , of multifactorial origin. •Much is known about its pathology and pathophysiology, but a lot remains to know about its pathogenesis, epidemiology and etiology. •RRR requires a multiple approach for diagnosis and treatment planning. •The cause must be detected, by the aid of a physician, and then eliminated or stabilized before dentures are constructed. •Construction of a stable functioning denture and a regular follow up treatment can help in the restoration of function, and thus, the restoration of the physical and mental vitality of the patient. www.indiandentalacademy.com
  104. 104. Conclusion www.indiandentalacademy.com
  105. 105. •The preservation of supporting tissues is a sacred trust that cannot be ignored. •The application of the basic concepts and the advances made in the basic sciences will help to keep this trust in the hands of the dental profession. •As prosthodontists, we need to perform the most meticulous and intelligent prosthodontic care of the patient within our capabilities. •…and then , it would not seem a nebulous hope that some day there will be control over residual ridge resorption. www.indiandentalacademy.com
  106. 106. References www.indiandentalacademy.com
  107. 107. •Ortman HR: Factors of bone resorption of the residual ridge. J Prosthet Dent 1962;12,3:429-440. •Atwood DA: Reduction of residual ridges: A major oral disease entity. J Prosthet Dent 1971;26:266-279. •Atwood DA: Some clinical factors related to rate of resorption of residual ridges. J Prosthet Dent 2001;86:119125. •Wendt DC: The degenerative denture ridge – Care and treatment. J Prosthet Dent 1974;32,5:477-492. •Ortman HR : The role of occlusion in preservation and prevention in complete denture prosthodontics. J Prosthet Dent 1971;25,2:121-138. •Sobolik FC : Alveolar bone resorption. J Prosthet Dent 1960;10,4:612-619. www.indiandentalacademy.com
  108. 108. •Jahangiri L, Devlin H, Ting K et al :Current perspectives in residual ridge remodelling and its clinical implications: A review. J Prosthet Dent 1998;80;224-237. •Atwood DA : Post extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent 1963;13:810-824. •Winkler S : Essentials of complete denture prosthodontics. 2nd edition,2000. •Boucher CO : Prosthodontic treatment for edentulous patients. 12th edition,2004. •Alfred H G :Color Atlas of Dental Medicine – Complete Denture and Overdenture Prosthetics.2nd edition,1993. •Misch CE : Contemporary implant dentistry. 2nd edition,1999. •Eroshenko VP : di Fiore’s Atlas of histology. 7th edition.1993. www.indiandentalacademy.com
  109. 109. Thank you www.indiandentalacademy.com

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