residual ridge resorption

management of residual ridge resorption

1. RESIDUAL RIDGE RESORPTION

2. CONTENTS INTRODUCTION DEFINITION CLASSIFICATION OF RRR PATHOLOGY OF RRR PATHOPHYSIOLOGY OF RRR PATHOGENESIS OF RRR EPIDEMIOLOGY OF RRR ETIOLOGY OF RRR CLINICAL FEATURES OF RRR MANAGEMENT CONCLUSION REFERENCES

3. INTRODUCTION Residual ridge is the portion of the residual bone and its soft tissue covering that remains after the removal of teeth. It consists of the denture-bearing mucosa, submucosa and periosteum, and the underlying residual alveolar bone. alveolar bone.

4. •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.

5. 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 phenomenon has been described as RESIDUAL RIDGE RESORPTION (RRR).

6. Definition : The diminishing quantity and quality of the residual ridge after teeth are removed (GPT8).

7. In the maxillae, the labial and buccal alveolar plates resorb much faster than the palatal plates, while, in the mandible, the amounts of bone resorbed at the lingual and labial plates are approximately the same. Swenson stated that after tooth extraction the alveolar process of the maxillae resorbs upward and inward to become progressively smaller because of the direction and inclination of the roots of the teeth. Alveolar ridge resorption following tooth extraction: J Prosthet Dent January 1967

8. Consequently, the older the edentulous maxillae, the smaller is the potential tooth-bearing area. He felt the opposite to be true in the mandible, which inclines outward and becomes progressively wider with edentulous age. Alveolar ridge resorption following tooth extraction: J Prosthet Dent January 1967

9. CLASSIFICATION Atwood’s classification Order 1 : Pre-extraction Order 2 : Post-extraction Order 3 : High, Well Rounded Order 4 : Knife Edged Order 5 : Low, Well Rounded Order 6: Depressed Post-extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent.1963 Sep 1;13(5):810-24.

10. Order I: Pre-extraction : The lower central incisor is in its socket with very thin labial and lingual cortical plates merged with the lamina dura Order II: Post-extraction : The healing period includes clot formation, clot organization, filling of the socket to the height of the cortical plates with new trabecular bone, and epithelization over the socket site. The edges of the residual ridge are still sharp Post-extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent.1963 Sep 1;13(5):810-24.

11. Order III: High, Well-Rounded Residual Ridge : The cortical plates are rounded off, narrowing of the crest of the ridge has begun, and remodeling of the internal trabecular structure has taken place . Order IV: Knife-Edge Residual Ridge : There is marked narrowing of the labiolingual diameter of the crest of the ridge with a compensatory internal remodeling which sometimes leads to an incredibly sharp crest of the ridge Post-extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent.1963 Sep 1;13(5):810-24.

12. Order V.: Low Well-Rounded Residudal Ridge : The end result of progressive labiolingual narrowing of a knife-edge ridge is the disappearance of the knife-edge portion. A more widely rounded, but considerably lower residual ridge remains Order VI: Depressed Residual Ridge : Resorption has continued below the level of the genial tubercle. Post-extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent.1963 Sep 1;13(5):810-24.

13. Class I - dentate. Class II - immediately post extraction. Class III - well-rounded ridge form, adequate in height and width. Class IV - knife-edge ridge form, adequate in height and inadequate in width. Class V - flat ridge form, inadequate in height and width. Class VI - depressed ridge form, with some basalar loss evident. A classification of the edentulous jaws. Int. J. Oral Maxillofac. Surg. 1988; 17:232-236 According to Cawood and Howell.

14. PATHOLOGY OF RRR 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.

15. Longitudinal radiographic cephalometric studies have provided excellent visualization of the gross patterns of this bone loss from a lateral viewpoint. The careful superimposition of portions of tracings of these lateral cephalograms has clearly shown the gross reduction of bone in size and shape that occurs on the external surface on the labial, crestal, and lingual aspects of the residual ridge.

16. Dry specimens of mandible shows that while external cortical surfaces of the maxilla and mandible are uniformly smooth, the crestal areas of residual ridges have a different appearance and show more porosities and imperfections. Bones with the most severe RRR (Orders V and VI) may display the gross porosity of medullary bone on the crest of the ridge and eventually may even display the uncovering of the inferior alveolar canal on the mandible

17. Lateral cephalometric radiographs provide the most accurate method for determining the amount of residual ridge and the rate of RRR over a period of time .

18. RRR does not stop with the residual ridge, but may go well 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.

19. The panoramic radiographic technique described by Wical and Swoope is a simple, useful method for arriving at a gross estimate of the amount of RRR to date in a given patient. Class I- Upto one third of the original vertical height lost. Class II- From one third to two third of the vertical height lost. Class III- Two third or more of the mandibular height lost. Studies of residual ridge resorption. II. The relationship of dietary calcium and phosphorus to residual ridge resorption. J Prosthet Dent 1974;32:13–22.

20. MICROSCOPIC PATHOLOGY Microscopic studies have revealed evidence of osteoclastic activity on the external surface of the crest of residual ridges. The scalloped margins of Howship’s lacunae contain visible osteoclasts. Frequently, the scalloped external surface seems inactive, without visible bone-resorbing cells, and is covered by fibrous non-osteogenic periosteum.

21. A micro-radiographic study of 21 edentulous mandibles has shown wide variation in the configuration, density, and porosity of not only the residual ridges but also the entire cross-section of the anterior mandible. Reduction of residual ridges: a major oral disease entity. J Prosthet Dent. 1971 Sep;26(3):266-79

22. In addition, there was micro-radiographic evidence of mandibular osteoporosis including: a. Increased variation in the density of osteons, b. Increased number of incompletely closed osteons, c. Increased endosteal porosity, d. Increased number of plugged osteons in about half the specimens. A microradiograph of the inferior border of a mandible showing evidence of moderate osteoporosis with increased variation in the density of osteons, increased number of incompletely closed osteons, and increased endosteal porosity ( x 15)

23. PATHOPHYSIOLOGY OF RRR It is a normal function of bone to undergo constant remodeling throughout life through the processes of bone resorption and bone formation. Except during growth, when bone formation exceeds bone resorption, bone resorption and bone formation are normally in equilibrium.

24. Osteoporosis is a generalized disease of bone in which bone is in negative balance, because bone resorption exceeds bone formation. In periodontal disease, there is a localized destruction of the bone around teeth, perhaps due to certain local pathologic processes. In both generalized osteoporosis and localized periodontal disease, when bone matrix is lost it does not ordinarily return.

25. Physiologic process of internal bone remodeling goes on even in the presence of this pathologic external osteoclastic activity. Remodeling must take place in three 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 it should be replaced by a new cortical layer that is formed by simultaneous endosteal bone formation.

26. If endosteal bone growth fails to keep pace with the external osteoclastic activity, there will be absence of a cortical layer and exposure of the medullary layer to the external surface of the bone, resulting in defects on the crest of the ridge .

27. PATHOGENESIS OF RRR Immediately following the extraction (Order II), any sharp edges remaining are rounded off by external osteoclastic resorption, leaving a high, well-rounded residual ridge (Order III). As resorption continues from the labial and lingual aspects, the crest of the ridge becomes increasingly narrow, ultimately becoming knife edged (Order IV).

28. As the process continues, the knife edge becomes shorter and eventually disappears, leaving a low well-rounded or flat ridge (Order V). Eventually, this too resorbs, leaving a depressed ridge (Order VI). RRR is chronic, progressive, irreversible, and cumulative.

29. EPIDEMIOLOGY There have been no large-scale studies of RRR in man. RRR is worldwide, occurs in males and females, young and old, in sickness and in health, with and without dentures. It is unrelated to the primary reason for the extraction of the teeth (caries or periodontal disease).

30. ETIOLOGY It is postulated that RRR is a multifactorial disease and that the rate of RRR depends not on one single factor but on the concurrence of two or more factors, which may be called cofactors. For convenience, possible factors could be divided into four categories : Anatomic, Metabolic, Functional, And Prosthetic. f Since all of these factors may vary from one patient to the next, these different co-factors may combine in an infinite variety of ways, thus explaining the variations in RRR between patients.

31. The anatomic factors include things such as the size and shape of the ridge, the type of bone, and the type of mucoperiosteum. The metabolic factors include age, sex, hormonal balance, osteoporosis, etc. The functional factors include the frequency, direction, and amount of force ap plied to the ridge. The prosthetic factors include the type of denture base, the form and type of teeth, the interocclusal distance etc

32. For further convenience, since the functional factors must function through the prosthetic factors, they may be grouped together as mechanical factors . This gives us three groups of cofactors-anatomic, biologic, and mechanical Some clinical factors related to rate of resorption of residual ridges . J Prosthet Dent. 1962;441-50.

33. Anatomic Factors It is postulated that RRR varies with the quantity and quality of the bone of the residual ridges. RRR anatomic factors  

34. Amount of Bone More bone there is, the more RRR there will ultimately be. Broad, high ridge may have a greater potential 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 the bone.

35. 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.

36. Another way to evaluate the anatomic factors is to consider the mechanical factors that would be favorable to stability and retention of a denture. Thus, large well-rounded ridges and broad palates would seem to be favourable anatomic factors.

37. Metabolic Factors RRR varies directly with certain systemic or localized bone resorptive factors and inversely with certain bone formation factors: RRR RRR is a localized loss of bone on the crest of the residual ridge. Local biochemical factors in relation to periodontal disease play an important role in RRR.  

38. These factors include: Endotoxins from dental plaque, Osteoclast-activating-factor (OAF), Prostaglandins , Human gingival bone-resorption stimulating factor, and others. Heparin , a cofactor in bone resorption, is associated with mast cells, and can be observed in microscopic sections of residual ridges close to the bone margin. Other local bone resorption factors are related to trauma, which leads to increased or decreased vascularity and changes in oxygen tension.

39. Local bone resorbing factors must be considered in the environment of the systemic factors that influence the balance between normal bone formation and bone resorption . Some patients have a natural resistance to unfavorable local factors whether it be Calculus or bacteria; Occlusal force in patients with natural teeth; Vertical dimension, Cusp form, Other prosthetic factors in denture wearers.

40. Perhaps such individuals have the correct amounts of circulating: Estrogen , Thyroxine, Growth hormone, Androgens, Calcium, Phosphorus, Vitamin D, Protein, Fluoride, and so on to compensate for poor local factors

41. Bone has its own specific metabolism and undergoes equivalent changes. The four main levels of bone activity are equilibrium , growth , atrophy , resulting from decreased osteoblastic activity, as in osteoporosis and in disuse atrophy, and resorption , caused by increased osteoclastic activity, as in hyperparathyroidism and in pressure resorption.

42. In equilibrium the two antagonistic actions (of osteoblasts and osteoclasts) are in balance. 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.

43. 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.

44. 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.

45. Some clinical factors related to rate of resorption of residual ridges . J Prosthet Dent. 1962;441-50.

46. Mechanical Factors 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. Masticatory and non-masticatory force is ordinarily transmitted to the dento -alveolar bone through the periodontal ligament. Some postulate that RRR is an inevitable “ disuse atrophy .”

47. Others postulate that RRR is an “ abuse” bone resorption due to excessive forces transmitted through dentures. Hence both hypothesis are true which states with or without dentures some patients have little or no RRR and some have severe RRR.

48. It is not the amount of force that is taken into concern, but also The frequency of force, The duration of force, The direction of force, The area over which force is distributed and The damping effect of the underlying tissue.

49. Abnormal parafunctional forces from clenching and grinding of teeth may last up to several hours per day which likely leads to pathologic loads on the residual ridges. Force is a cofactor in RRR that can be expressed as: There is a tendency for more RRR in the mandible than in the maxilla. RRR FORCE  

50. The amount of force applied to the bone may be affected inversely by the “damping effect,” or energy absorption. This cofactor may be expressed as follows: The “damping effect” may take place in the mucoperiosteum which can be considered a viscoelastic material. RRR    

51. Muco-periosteum varies in its viscoelastic properties from patient to Patient and from maxilla to mandible, its energy absorption qualities may influence the rate of RRR. Maxillary residual ridge is frequently broader, flatter, and more cancellous than its mandibular counterpart and may be a factor in the frequently observed differences in the RRR of the two jaws.

52. The traditional design of dentures includes many features whose goal is to reduce the amount of force to the ridge and thereby to reduce RRR. These prosthetic factors include: Broad-area coverage (to reduce the force per unit area); Decreased number of dental units, Decreased bucco -lingual width of teeth, Improved tooth form (to decrease the amount of force required to penetrate a bolus of food); Avoidance of inclined planes (to minimize dislodgement of dentures and shear forces);

53. Centralization of occlusal contacts (to increase stability of dentures and to maximize compressive forces ) Provision of adequate tongue room (to improve stability of denture in speech and mastication) Adequate inter-occlusal distance during rest jaw (to decrease the frequency and duration of tooth-contacts)

54. In addition to the three major categories of factors (anatomic, metabolic, and mechanical), the importance of the time since extraction to the bone-loss curves, should be emphasized by adding an inverse relation. RRR  

55. Osteoporosis: Osteoporosis results from the loss of bone, especially the spongy spicule that supports the weight bearing parts of the skeleton. It is more common where heavy loads are present: (e.g. in vertebral column, epiphyses of long bones, pelvis, the maxillae and fingers). Osteoporosis is common in aging individuals, especially post menopausal women when the estrogenic blood level is low.

56. Osteoporosis is caused by a variety of factors such as calcium loss, calcium deficiency, hormonal deficiency, change in protein nutrition and decreased physical activity. Progressive loss of alveolar bone may be a manifestation of osteoporosis.

57. In patients whose residual ridges are low, osteoporosis should be considered, especially in women. Massler had reported that Prosthodontists are in a strategic position to intercept early evidence of osteoporosis and educate the geriatric patient towards good nutrition.

58. CLINICAL FEATURES OF RRR The depth and width of the sulcus is reduced due to the resorption of the ridge till the level of the muscle attachment. Decreased vertical dimension at occlusion (VDO). Reduction of the lower facial height (due to decreased VDO). Anterior rotation of the mandible

59. Increase in relative prognathism. Resorption is centripetal (towards the centre ) in the maxilla, and centrifugal (away from the centre ) in the mandible. Sharp, spiny and uneven ridge appear in the crest due to difference in rate of resorption from one place to another. Long-term resorption affects support stability and retention of dentures.

60. The mandible's rotation may produce the following consequences: Loss of centric occlusion in the dentures. Changes in the structures that support the upper denture. Movement of the lower denture in a backward direction. This may lead to traumatic changes in the supporting structures of the mandible. Movement of the lower jaw anteriorly, with an ensuing prognathic appearance.

61. MANAGEMENT OF RRR The best treatment is to avoid total tooth extraction, preserve a few teeth, and make overdentures, which are associated with much lower rates of bone resorption. The placement of dental implants and the insertion of an implant-supported prosthesis have been shown to reduce bone loss in the edentulous jaw. Clinical morbidity and sequelae of treatment with complete dentures. J Prosthet Dent 1997;79:17-23.

62. MOUTH PREPARARTION 1. Physical health . Any systemic illness that is contributing to the degenerative bone condition must be corrected or stabilized. In cases where only limited help can be rendered, the patient must be carefully counseled as to the effect this will have on dental health.

63. 2. Diet. T he patients need a diet high in protein, vitamin, and mineral content. They should totally eliminate refined carbohydrates, white flour, and white sugar or, specifically, sucrose and glucose.

64. 3. Pre-prosthetic surgery. Its role may be considered where the following procedures are necessary: (1) removal of local prosthetic problems such as high frenal attachments, (2) increase in the height of the alveolus, (3) repositioning of attachments of the soft tissues to the jaws, so increasing the denture-bearing area, and (4) insertion of subperiosteal implant dentures.

65. It includes the following surgical procedures: • Ridge correction. • Ridge extension/ vestibuloplasty . • Ridge augmentation • Surgical correction of maxillomandibular relation .

66. 4. Tissue treatment therapy. The use of soft conditioning material to rejuvenate the tissue-bearing area has been well established.

67. Soft liners. Used routinely for patients with severe alveolar resorption, in two clear instances: (1) Where non-surgically removable alveolar irregularities are traumatizing the denture-bearing mucosa and (2) where maximum stability and minimum soft-tissue loading have been incorporated into a prosthesis and the denture-bearing mucosa is still unable to accept the load.

68. Disadvantages: A soft liner will not aid denture stability, and care must be taken to ensure that the prosthesis to which it is fitted has good balanced occlusion. The soft liner should be used where there is adequate bulk is and must be carefully processed if its properties are to be retained and separation from the denture base avoided.

69. Accessory aids to retention Magnets: Magnets have been employed embedded either in the alveolar process and denture, so as to attract the denture to the alveolus, or in the dentures alone, normally in the molar region, with the poles placed so that they repel each other.

70. Springs Used as an aid to retention although they tend to stabilize the denture antero-posteriorly. Also, the constant pressure they produce on the bone may be a factor in further alveolar resorption. The length and site of insertion of the springs must be very carefully chosen, for if too short they tend to expel the dentures from the mouth when opened, and if too long they impinge upon the cheeks.

71. Prosthetic management: Impression techniques. Denture base selection. Teeth selection and arrangement. Implant supported prosthesis.

72. 1.Impression techniques • 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.

73. Mc-Cord and Tyson’s admixed technique Impression compound and green tracing stick compound in the ratio of 3 : 7 parts by weight are placed in a bowl of water at 60 C and kneaded to a homogenous mass that provides a working time of about 90 seconds. Wax spacer is removed; this homogenous mass is loaded and patient is made to do various tongue movements.

74. All Green Technique Green stick compound is kneaded to a homogenous mass and is loaded on the special tray and border movements are done. Final impression is made using zinc oxide eugenol.

75. Winkler’s technique (Closed mouth functional impression) In this technique, denture bases with occlusal rim are fabricated on primary cast. Jaw relations are done to record appropriate horizontal and vertical dimensions. Three applications of tissue conditioner material are done at an interval of 8–10 minutes and functional movements are made by the patients.

76. Tissue conditioning material is applied on the tissue surface of mandibular denture base and patient is asked to close the mouth in the prerecorded vertical dimension and do various functional movements such as puffing, blowing, whistling, and smiling. Final impression is made with light body addition silicone material with closed mouth technique.

77. Cocktail Impression Technique In this technique customized tray is fabricated with autopolymerizing acrylic resin according to Dynamic Impression Technique. A tray with 1 mm wax spacer and cylindrical mandibular rests in the posterior region is made at increased vertical height. Patient is advised to close his mouth so that the mandibular rests fit against the maxillary alveolar ridge. This helps to stabilize the tray in position by preventing anteroposterior and mediolateral displacement of the tray during definitive impression.

78. Lingual surfaces of mandibular rests are made concave to provide space for the tongue to move freely during functional movements. McCord and Tyson’s technique for flat mandibular ridges is followed for definitive impression.

79. For recording the functional state, patient is instructed to run his tongue along his lips, suck in his cheeks, pull in his lips, and swallow by keeping his mouth closed, as in closed mouth impression technique, till the impression material hardens. The retrieved impression is visually inspected for surface irregularities and disinfected and is poured in dental stone.

80. Elastomeric Technique Tray adhesive is applied over the border, internal and external surface of the acrylic custom tray, to facilitate the retention of the silicone border moulding material. An addition silicon putty with an extended working time is loaded along the borders of special tray. The special tray is placed in the mouth and its border is molded; the patient is asked to move the tongue according to standard impression procedures.

81. The tray is removed from the mouth, and the impression is examined. Light-body addition of silicon impression material is loaded in the impression and inserted in the mouth.

82. The patient is instructed to repeat the tongue movements, more vigorously, while the light-body impression material is border molded along the buccal and labial flange areas. After the material has set, the impression was removed from the mouth and examined for any discrepancy

83. 2. 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 The degenerative denture ridge—Care and treatment. J Prosthet Dent. 1974 Nov;32(5):477-92

84. 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. The degenerative denture ridge—Care and treatment. J Prosthet Dent. 1974 Nov;32(5):477-92

85. Cast metal bases Main 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 .

86. 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.

87. 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.

88. The following requirements have to be met during teeth arrangement: Stability of occlusion in centric relation. Balanced occlusion for eccentric contacts. 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.

89. 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.

90. Implant Supported Prosthesis The 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.

91. 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.

92. 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.

93. SUMMARY Reduction of residual ridges (RRR) needs to be recognized for what it is a major unsolved oral disease which causes physical, psychologic, and economic problems. RRR is a chronic, progressive, irreversible, and disabling disease, probably of multifactorial origin. Much is known about the pathology and the pathophysiology of this oral disease, but we need to know much more about its pathogenesis, epidemiology, and etiology .

94. 4. The ultimate goal of research of RRR is to find better methods of prevention or control of the disease. 5. More research in RRR with new methods and new thinking are badly needed in order to provide the best possible oral health care for millions of edentulous patients.

95. REFERENCES Sheldon Winkler. Essentials of complete denture prosthodontics. 2nd edition A local pathophysiologic mechanism of the resorption of residual ridges: Prostaglandin as a mediator of bone resorption. Current perspectives in residual ridge remodeling and its clinical implications: A review. (J Prosthet Dent 1998;80:224-37.) Post-extraction changes in the adult mandible as illustrated by microradiographs of midsagittal sections and serial cephalometric roentgenograms. J Prosthet Dent.1963 Sep 1;13(5):810-24. Studies of residual ridge resorption. II. The relationship of dietary calcium and phosphorus to residual ridge resorption. J Prosthet Dent 1974;32:13–22.

96. Reduction of residual ridges: A maior oral disease entity. J Prosthet Dent. 1971 Sep;26(3):266-79 Some clinical factors related to rate of resorption of residual ridges . J Prosthet Dent. 1962;441-50. The management of gross alveolar resorption. J Prosthet Dent. 1973 Apr;29(4):397-404. Factors of bone resorption of the residual ridge . J Prosthet Dent. 1960; 10: 605–611.

97. A classification of the edentulous jaws. Int. J. Oral Maxillofac. Surg. 1988; 17:232-236 Clinical morbidity and sequelae of treatment with complete dentures. J Prosthet Dent 1997;79:17-23. The degenerative denture ridge—Care and treatment. J Prosthet Dent. 1974 Nov;32(5):477-92 Changes caused by a mandibular removable partial denture opposing a maxillary complete denture. J Prosthet Dent 1972;27:140–50.

98. Dynamic impression methods.Tryde , G., Olsson, K., Jensen, S. A., Cantor, R., Tarsetano , J. J., & Brill, N. (1965). The Journal of Prosthetic Dentistry, 15(6), 1023–1034. Modified fluid wax impression for a severely resorbed edentulous mandibular ridge. J Prosthet Dent 2009;101:279-282 Cocktail Impression Technique: A New Approach to Atwood’s Order VI Mandibular Ridge Deformity. J Indian Prosthodont Soc (Jan-Mar 2011) 11(1):32–35.

99. Comparison of Different Final Impression Techniques for Management of Resorbed Mandibular Ridge: A Case Report. Yadav, B., Jayna, M., Yadav, H., Suri, S., Phogat , S., & Madan, R. (2014).Case Reports in Dentistry, 2014, 1–6.