Rrr

GUIDED BY: DR. A. S. KAULGUIDED BY: DR. A. S. KAULPROF AND HEAD OFPROF AND HEAD OF

DEPT OF PROSTHODONTICSDEPT OF PROSTHODONTICSK.D.D.C., MATHURAK.D.D.C., MATHURA

PRESENTED BY : PRESENTED BY : HIMANSHU GUPTAHIMANSHU GUPTA

CONTENTSCONTENTS

INTRODUCTIONINTRODUCTION DEFINITIONSDEFINITIONS RESIDUAL RIDGE RESORPTION : A MAJOR ORAL DISEASE RESIDUAL RIDGE RESORPTION : A MAJOR ORAL DISEASE

ENTITYENTITY ETIOLOGYETIOLOGY PATHOLOGYPATHOLOGY PATHOPHYSIOLOGYPATHOPHYSIOLOGY PATHOGENESISPATHOGENESIS EPIDEMIOLOGYEPIDEMIOLOGY TREATMENT AND PREVENTIONTREATMENT AND PREVENTION SUMMARYSUMMARY BIBLIOGRAPHYBIBLIOGRAPHY

INTRODUCTIONINTRODUCTION

Anatomic changes will invariably take place within the alveolar Anatomic changes will invariably take place within the alveolar processes of the jaws following dental extractions. After the processes of the jaws following dental extractions. After the extraction of teeth, the empty dental alveoli fill up with blood, extraction of teeth, the empty dental alveoli fill up with blood, which sequentially clots, is organized, and is replaced with new which sequentially clots, is organized, and is replaced with new bone. To this newly formed ridge dentures are constructed, and bone. To this newly formed ridge dentures are constructed, and the ridge undergoes changes in shape and reduces in size at the ridge undergoes changes in shape and reduces in size at varying rates in different individuals and in the same individual at varying rates in different individuals and in the same individual at different times. The ridge changes occur because of the changes different times. The ridge changes occur because of the changes in the whole distribution of forces after the extraction. The load in the whole distribution of forces after the extraction. The load is not directed to the entire bone, but is applied only on its is not directed to the entire bone, but is applied only on its surface. Alveolar bone can only tolerate this compression to a surface. Alveolar bone can only tolerate this compression to a certain extent. Over the long period of time, with the use or certain extent. Over the long period of time, with the use or without the use of dentures there is the atrophy of the residual without the use of dentures there is the atrophy of the residual alveolar ridge or alveolar ridge or REDUCTION OF RESIDUAL RIDGE.REDUCTION OF RESIDUAL RIDGE.

DEFINITIONSDEFINITIONS

RESIDUAL RIDGE RESORPTIONRESIDUAL RIDGE RESORPTION : A TERM USED FOR : A TERM USED FOR THE DIMINISHING QUANTITY AND QUALITY OF THE THE DIMINISHING QUANTITY AND QUALITY OF THE RESIDUAL RIDGE AFTER TEETH ARE REMOVED.RESIDUAL RIDGE AFTER TEETH ARE REMOVED.

RESIDUAL RIDGERESIDUAL RIDGE : THE PORTION OF THE RESIDUAL : THE PORTION OF THE RESIDUAL BONE AND ITS SOFT TISSUE COVERING THAT BONE AND ITS SOFT TISSUE COVERING THAT REMAINS AFTER THE REMOVAL OF TEETH.REMAINS AFTER THE REMOVAL OF TEETH.

RESIDUAL BONERESIDUAL BONE : THAT COMPONENT OF : THAT COMPONENT OF MAXILLARY OR MANDIBULAR BONE, ONCE USED TO MAXILLARY OR MANDIBULAR BONE, ONCE USED TO SUPPORT THE ROOTS OF THE TEETH, THAT REMAINS SUPPORT THE ROOTS OF THE TEETH, THAT REMAINS AFTER TEETH ARE LOST.AFTER TEETH ARE LOST.

REDUCTION OF RESIDUAL RIDGES : A REDUCTION OF RESIDUAL RIDGES : A MAJOR ORAL DISEASE ENTITYMAJOR ORAL DISEASE ENTITY

PATHOLOGY

PATHO-

PHYSIOLOGY

TREATMENT AND

PREVENTION

EPIDEMIOLOGY

PATHOGENESIS

ETIOLOGY

RRR : A MAJORORAL DISEASE

ENTITY

ETIOLOGYETIOLOGY

RRR depends not on one single factor but on the concurrence of RRR depends not on one single factor but on the concurrence of two or more factors, which may be called two or more factors, which may be called cofactors.cofactors.

The possible cofactors are divided into four categories:The possible cofactors are divided into four categories:

a) a) ANATOMICANATOMIC

b)b) METABOLIC METABOLIC

c) PROSTHETICc) PROSTHETIC

d)d) FUNCTIONAL FUNCTIONAL

Since the functional factors must function through the prosthetic factors, they Since the functional factors must function through the prosthetic factors, they may be grouped together as may be grouped together as MECHANICAL FACTORS.MECHANICAL FACTORS.

ANATOMIC

MECHANICALBIOLOGIC

ANATOMIC FACTORS:- It is postulated that RRR ANATOMIC FACTORS:- It is postulated that RRR varies with the quantity and quality of the bone of the varies with the quantity and quality of the bone of the residual ridges.residual ridges.

RRR RRR αα ANATOMIC FACTORS ANATOMIC FACTORS

THE ANATOMIC FACTORS TO BE CONSIDERED :THE ANATOMIC FACTORS TO BE CONSIDERED :1.1. RIDGERIDGE2.2. FACIAL MORPHOLOGYFACIAL MORPHOLOGY3.3. MANDIBULAR SHAPEMANDIBULAR SHAPE

1. 1. RIDGE FACTORS :RIDGE FACTORS :

So that states that the more bone there is, the more resorption So that states that the more bone there is, the more resorption of the residual ridges there will be.of the residual ridges there will be.

But the amount of bone is not a good prognosticator of the rate But the amount of bone is not a good prognosticator of the rate of RRR.of RRR.

Another anatomic factor to be considered is the density of the Another anatomic factor to be considered is the density of the bone.bone.

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

2. 2. FACIAL MORPHOLOGYFACIAL MORPHOLOGY : ( JPD; 41(1); 1979; 90-100) : ( JPD; 41(1); 1979; 90-100)

The longer the face, the more alveolar bone there is and the The longer the face, the more alveolar bone there is and the less chance there is for an individual to reach a stage of severe less chance there is for an individual to reach a stage of severe atrophy in wearing dentures.atrophy in wearing dentures.

The further closed the vertical dimension of occlusion, the The further closed the vertical dimension of occlusion, the more comprehensive are the forces applied on the residual more comprehensive are the forces applied on the residual ridges and the greater are the chances for an individual with a ridges and the greater are the chances for an individual with a closed vertical dimension of occlusion to reach the stage of closed vertical dimension of occlusion to reach the stage of extremely severe atrophy with the dentures, especially for the extremely severe atrophy with the dentures, especially for the mandible mandible

3. 3. MANDIBULAR SHAPEMANDIBULAR SHAPE : ( JPD; 27 (2); 1972; 120-132) : ( JPD; 27 (2); 1972; 120-132)

3. 3. MANDIBULAR SHAPEMANDIBULAR SHAPE : ( JPD; 27 (2); 1972; 120-132) : ( JPD; 27 (2); 1972; 120-132)

Correlations between the shape of the mandible and the anterior Correlations between the shape of the mandible and the anterior mandibular bone loss indicated a pronounced resorption in mandibular bone loss indicated a pronounced resorption in subjects with a marked mandibular base bend, and a less marked subjects with a marked mandibular base bend, and a less marked resorption in subjects with a flattened mandibular base.resorption in subjects with a flattened mandibular base.

METABOLIC FACTORS METABOLIC FACTORS :- :-

BONE RESORPTION FACTORSBONE RESORPTION FACTORS

RRR RRR αα

BONE FORMATION FACTORSBONE FORMATION FACTORS

BONE RESORPTION FACTORSBONE RESORPTION FACTORS :- :-

LOCAL FACTORSLOCAL FACTORS

- Endotoxins- Endotoxins

- Osteoclast activating factor- Osteoclast activating factor

- Prostaglandins- Prostaglandins

- Human gingival bone resorption stimulating factor- Human gingival bone resorption stimulating factor

- Heparin- Heparin

- Trauma- Trauma

The The locallocal bone resorbing factors must be considered in the bone resorbing factors must be considered in the enviroment of the enviroment of the systemicsystemic factors that influence the balance factors that influence the balance between normal bone formation and bone resorption.between normal bone formation and bone resorption.

Some patients who seem to have a natural resistance to Some patients who seem to have a natural resistance to unfavorable local factors have the correct amounts of circulatingunfavorable local factors have the correct amounts of circulating

estrogen, thyroxine, growth hormone, androgens, calcium, estrogen, thyroxine, growth hormone, androgens, calcium, phosphorus, vitamin D, protein, fluoride, and so on to phosphorus, vitamin D, protein, fluoride, and so on to compensate for poor local factorscompensate for poor local factors

The biochemical mediators of calcium metabolism which The biochemical mediators of calcium metabolism which predominate in control of bone resorption are :predominate in control of bone resorption are :

-Parathyroid-Parathyroid

-Vitamin D-Vitamin D

MECHANICAL FACTORSMECHANICAL FACTORS : :

FORCEFORCE

RRR RRR αα

DAMPING EFFECTDAMPING EFFECT

There are two views regarding the force factors.There are two views regarding the force factors.

1.1. Disuse atrophyDisuse atrophy

2.2. Abuse bone resorptionAbuse bone resorption

In considering force, one must concern with :In considering force, one must concern with :

1.1. Amount of forceAmount of force

2.2. FrequencyFrequency

3.3. Duration Duration

4.4. DirectionDirection

5.5. Area over which force is distributedArea over which force is distributed

The forces that act may beThe forces that act may be

1.1. FunctionalFunctional

2.2. Para functionalPara functional

Brewer has shown that normal functional masticating and Brewer has shown that normal functional masticating and swallowing contacts between dentures average less than 15 swallowing contacts between dentures average less than 15 minutes per waking day.minutes per waking day.

Ohashi et al have demonstrated that swallowing forces in 21 Ohashi et al have demonstrated that swallowing forces in 21 patients averaged 11.4 pounds.patients averaged 11.4 pounds.

Cutright et al have calculated that 1500 empty swallows per 24 Cutright et al have calculated that 1500 empty swallows per 24 hours could amount to 3500 to 4200 lbs of loading per day.hours could amount to 3500 to 4200 lbs of loading per day.

Woelfel et al have cited a patient with a projected maxillary Woelfel et al have cited a patient with a projected maxillary denture area of 4.2 inch square and a projected mandibular denture area of 4.2 inch square and a projected mandibular denture area of 2.3 inch square ( ratio 1.8:1). denture area of 2.3 inch square ( ratio 1.8:1).

If such a patient bites with a pressure of 50 lb, this calculates out If such a patient bites with a pressure of 50 lb, this calculates out to 12 lb/inch square under the maxillary denture and 21 lb/inch to 12 lb/inch square under the maxillary denture and 21 lb/inch square under the mandibular denture.square under the mandibular denture.

It is logical to postulate that such differences could be casually It is logical to postulate that such differences could be casually related to differences in the two jaws. related to differences in the two jaws.

The amount of force applied to the bone may be affected The amount of force applied to the bone may be affected inversely by the “damping effect” or energy absorption.inversely by the “damping effect” or energy absorption.

The damping effect may take place in the mucoperiosteum, The damping effect may take place in the mucoperiosteum, which can be considered as viscoelastic material.which can be considered as viscoelastic material.

The damping effect of bone itself should be considered.The damping effect of bone itself should be considered. Frost has stated, “…bones which are subjected largely to Frost has stated, “…bones which are subjected largely to

compression loads and experience no significant bending loads, compression loads and experience no significant bending loads, are composed largely of cancellous bone, which is ideally are composed largely of cancellous bone, which is ideally constructed for the absorption and dissipation of energy.constructed for the absorption and dissipation of energy.

He also points out that trabeculae in such bones are oriented He also points out that trabeculae in such bones are oriented parallel to the direction of compression deformation, allowing parallel to the direction of compression deformation, allowing maximum resistance to deformation.maximum resistance to deformation.

Applegate and his colleague recommended phasing the loading Applegate and his colleague recommended phasing the loading of an edentulous ridge to prevent sudden over loading of the of an edentulous ridge to prevent sudden over loading of the bony ridge and in the hope of strengthening and reorienting the bony ridge and in the hope of strengthening and reorienting the trabeculae on the crest of the ridge.trabeculae on the crest of the ridge.

Neufeld cut at right angles through the crest of the ridge of dry Neufeld cut at right angles through the crest of the ridge of dry human jawbones and demonstrated in some specimens that the human jawbones and demonstrated in some specimens that the trabeculae were oriented at right angles to the crest and thus trabeculae were oriented at right angles to the crest and thus parallel to the direction of occlusal forces transmitted through parallel to the direction of occlusal forces transmitted through the denture.the denture.

The traditional design of dentures include many features The traditional design of dentures include many features whose goal is to reduce the amount of forces to the ridge and whose goal is to reduce the amount of forces to the ridge and thereby to reduce the amount of force to the ridge and thereby thereby to reduce the amount of force to the ridge and thereby to reduce RRR. These factors include:to reduce RRR. These factors include:

1.1. Broad area coverageBroad area coverage

2.2. Decreased number of dental unitsDecreased number of dental units

3.3. Decreased buccolingual width of teeth and improved tooth Decreased buccolingual width of teeth and improved tooth form.form.

4.4. Avoidance of inclined planesAvoidance of inclined planes

5.5. Centralisation of occlusal contactsCentralisation of occlusal contacts

6.6. Provision of adequate tongue roomProvision of adequate tongue room

7.7. Adequate interocclusal distance during rest jaw relationAdequate interocclusal distance during rest jaw relation

PATHOLOGYPATHOLOGY

The primary structural change in the reduction of The primary structural change in the reduction of residual ridges is the loss of bone.residual ridges is the loss of bone.

The reduction of the residual ridge leads to a variety of stages The reduction of the residual ridge leads to a variety of stages of ridge forms:-of ridge forms:-

1.1. Pre-extractionPre-extraction

2.2. Post-extractionPost-extraction

3.3. High well roundedHigh well rounded

4.4. Knife edgeKnife edge

5.5. Low well roundedLow well rounded

6.6. Depressed Depressed

The reduction of the residual ridge leads to a variety of stages The reduction of the residual ridge leads to a variety of stages of ridge form.of ridge form.

Before scientific methods of comparison can be applied to this Before scientific methods of comparison can be applied to this problem, the use of ambiguous terms such as ‘ high’, ‘low’, problem, the use of ambiguous terms such as ‘ high’, ‘low’, ‘flat’ or ‘poor’ was followed.‘flat’ or ‘poor’ was followed.

LANDA suggested a classification to replace these terms LANDA suggested a classification to replace these terms based on the mandibular resorption pattern. His system based on the mandibular resorption pattern. His system arbitrarily divided the mandible into three ‘levels’ which were arbitrarily divided the mandible into three ‘levels’ which were then subdivided into nine narrower ‘levels’. No criteria or then subdivided into nine narrower ‘levels’. No criteria or anatomic reference points for clinical identification of the anatomic reference points for clinical identification of the different levels were described.different levels were described.

Several authors have affirmed the relationship of the foramen to Several authors have affirmed the relationship of the foramen to the inferior border of the mandible remains relatively constant in the inferior border of the mandible remains relatively constant in spite of increasing age or resorption of the alveolar process spite of increasing age or resorption of the alveolar process above the foramen. (JPD; 32 (1); 1974; 7-12)above the foramen. (JPD; 32 (1); 1974; 7-12)

CLASS I : Up to one third of the original vertical height lost.CLASS I : Up to one third of the original vertical height lost. CLASS II : From one third to two thirds of the vertical height CLASS II : From one third to two thirds of the vertical height

resorbed.resorbed. CLASS III : Two thirds or more of the mandibular height lost. CLASS III : Two thirds or more of the mandibular height lost.

So, it is clear that RRR does not stop with the residual ridge, but So, it is clear that RRR does not stop with the residual ridge, but may go well below where the apices of the teeth were, sometimes may go well below where the apices of the teeth were, sometimes leaving only a thin cortical plate on the inferior border of the leaving only a thin cortical plate on the inferior border of the mandible or virtually no maxillary alveolar process on the upper mandible or virtually no maxillary alveolar process on the upper jaw.jaw.

A 62-year-old woman, edentulous at the age of 30, presented A 62-year-old woman, edentulous at the age of 30, presented with complaints of pain and spontaneous “electrical shocks” in with complaints of pain and spontaneous “electrical shocks” in the mucosa under her mandibular complete denture. Upon the mucosa under her mandibular complete denture. Upon clinical examination there was no visible tissue alteration, but clinical examination there was no visible tissue alteration, but palpation of the mental region on both sides of the mandible palpation of the mental region on both sides of the mandible elicited pain and a “shock” sensation. The panoramic and elicited pain and a “shock” sensation. The panoramic and tomographic examinations revealed extensive mandibular bone tomographic examinations revealed extensive mandibular bone resorption. ( Journal of contemporary dental practice; 9 (3); resorption. ( Journal of contemporary dental practice; 9 (3); 2008)2008)

MICROSCOPIC PATHOLOGYMICROSCOPIC PATHOLOGY

Microscopic studies have revealed evidence of osteoclastic Microscopic studies have revealed evidence of osteoclastic activity on the external surface of the crest of residual ridges.activity on the external surface of the crest of residual ridges.

The scalloped margins of Howship’s lacunae contain osteoclasts.The scalloped margins of Howship’s lacunae contain osteoclasts.

A microradiographic study of 21 edentulous mandibles has A microradiographic study of 21 edentulous mandibles has shown wide variation in the shown wide variation in the configuration, density, and porosity configuration, density, and porosity of not of not just the residual ridges but also the entire cross section of the just the residual ridges but also the entire cross section of the anterior mandible.anterior mandible.

The microradigraphic study revealed The microradigraphic study revealed

1.1. Increased variation in the density of osteonsIncreased variation in the density of osteons

2.2. Increased number of incompletely closed osteonsIncreased number of incompletely closed osteons

3.3. Increased endosteal porosityIncreased endosteal porosity

All specimens had either a cortical layer consisting of an All specimens had either a cortical layer consisting of an endosteal type of bone or else no cortical layer but simply a endosteal type of bone or else no cortical layer but simply a medullary type of trabecular bone.medullary type of trabecular bone.

Microscopic studies of the mucoperiosteum have shown Microscopic studies of the mucoperiosteum have shown

1.1. Varying degrees of keratinizationVarying degrees of keratinization

2.2. AcanthosisAcanthosis

3.3. EdemaEdema

4.4. Varying degree of inflammatory cellsVarying degree of inflammatory cells

5.5. Architectural pattern of mucosal epithelium in the same Architectural pattern of mucosal epithelium in the same mouth and between subjectsmouth and between subjects

PATHOPHYSIOLOGY OF RRRPATHOPHYSIOLOGY OF RRR

It is a normal function of bone to undergo constant remodelling It is a normal function of bone to undergo constant remodelling throughout life through the processes of bone resorption and throughout life through the processes of bone resorption and bone formation.bone formation.

RRR is a localised pathologic loss of bone that is not built back RRR is a localised pathologic loss of bone that is not built back by simply removing the causative factors.by simply removing the causative factors.

Yet the physiologic process of internal bone remodelling goes on Yet the physiologic process of internal bone remodelling goes on even in the presence of this pathologic external osteoclastic even in the presence of this pathologic external osteoclastic activity that is responsible for the loss of so much bone activity that is responsible for the loss of so much bone substancesubstance

Even after a great deal resorption of residual ridges, often a thin Even after a great deal resorption of residual ridges, often a thin cortical layer of bone over the crest of the ridge is present.cortical layer of bone over the crest of the ridge is present.

This means that new bone has been laid down inside the residual This means that new bone has been laid down inside the residual ridge in advance of the external osteoclastic removal of bone.ridge in advance of the external osteoclastic removal of bone.

This is in accordance to ENLOW’S priniciple. (JPD; 26 (3); 1971)This is in accordance to ENLOW’S priniciple. (JPD; 26 (3); 1971)

PATHOGENESIS OF RRRPATHOGENESIS OF RRR

The reduction of residual ridges is The reduction of residual ridges is chronic, progressive, chronic, progressive, irreversible, and cumulative.irreversible, and cumulative.

The reduction of residual ridges usually proceeds slowly over a The reduction of residual ridges usually proceeds slowly over a long period of time from one stage to the next i.e. starting from long period of time from one stage to the next i.e. starting from order I to order VI depending upon the amount of resorption.order I to order VI depending upon the amount of resorption.

The reduction of the residual ridge leads to a variety of stages The reduction of the residual ridge leads to a variety of stages of ridge forms:-of ridge forms:-

1.1. Pre-extractionPre-extraction

2.2. Post-extractionPost-extraction

3.3. High well roundedHigh well rounded

4.4. Knife edgeKnife edge

5.5. Low well roundedLow well rounded

6.6. Depressed Depressed

Autonomous regrowth of residual ridges has not been reported.Autonomous regrowth of residual ridges has not been reported. The annual increments of bone loss have a cumultative effect, The annual increments of bone loss have a cumultative effect,

leaving less and less residual ridgeleaving less and less residual ridge In general, the rate of RRR varies between different individuals.In general, the rate of RRR varies between different individuals. Within a given individual the rate is usually most rapid in the first Within a given individual the rate is usually most rapid in the first

6 months following extraction. (JPD; 26 (3); 1971; 266-279)6 months following extraction. (JPD; 26 (3); 1971; 266-279)

In the graph, the vertical bone loss of the anterior part of the ridge In the graph, the vertical bone loss of the anterior part of the ridge in 19 years was 3 mm in the maxillae and 14.5 mm in the in 19 years was 3 mm in the maxillae and 14.5 mm in the mandible.mandible.

Because RRR is chronic and progressive, it results in repeated Because RRR is chronic and progressive, it results in repeated mucosal, functional, psychologic, esthetic, and economic mucosal, functional, psychologic, esthetic, and economic problems for denture patients.problems for denture patients.

And because it is cumultative, the patient with this disease And because it is cumultative, the patient with this disease becomes more and more dentally handicapped, ultimately a becomes more and more dentally handicapped, ultimately a “dental cripple.”“dental cripple.”

EPIDEMIOLOGY OF RRREPIDEMIOLOGY OF RRR

Epidemiology is the study of distribution and determinants of Epidemiology is the study of distribution and determinants of health related states or events in specified population, and the health related states or events in specified population, and the application of this study to the control of health problems.application of this study to the control of health problems.

Epidemiology methodology can contribute to an understanding Epidemiology methodology can contribute to an understanding of the etiology of a specific disease, especially by the use of a of the etiology of a specific disease, especially by the use of a large experimental population.large experimental population.

Epidemiologic studies are useful in trend-finding investigations Epidemiologic studies are useful in trend-finding investigations of multifactorial diseases.of multifactorial diseases.

DIFFICULTIES IN STUDYING RRRDIFFICULTIES IN STUDYING RRR : :

1.1. The disease is almost universal, but there are variations in The disease is almost universal, but there are variations in amount and rate between individuals.amount and rate between individuals.

2.2. The amount is so cumultative so that a single examination The amount is so cumultative so that a single examination does not reveal the present ratedoes not reveal the present rate

3.3. The rate is low.The rate is low.

4.4. The rate may vary at different times and in different sites The rate may vary at different times and in different sites within an individual .within an individual .

5.5. Any attempt to correlate this complex problem with a single Any attempt to correlate this complex problem with a single factor is likely to be inconclusive.factor is likely to be inconclusive.

The longitudinal study of edentulous individuals covering 25 The longitudinal study of edentulous individuals covering 25 years of complete denture wearing revealed a continued reduction years of complete denture wearing revealed a continued reduction of the residual ridges throughout the observation period. (of the residual ridges throughout the observation period. (ANTJE ANTJE TALLGREN : THE CONTINUING REDUCTION OF THE RESIDUAL ALVEOLAR RIDGES IN TALLGREN : THE CONTINUING REDUCTION OF THE RESIDUAL ALVEOLAR RIDGES IN COMPLETE DENTURE WEARERS : A MIXED LONGITUDINAL STUDY COVERING 25 YEARS; 27 COMPLETE DENTURE WEARERS : A MIXED LONGITUDINAL STUDY COVERING 25 YEARS; 27 (2); 1972; 120-132)(2); 1972; 120-132)

In group A the mean decrease in anterior height of the lower In group A the mean decrease in anterior height of the lower ridge between the seven year and 13.5 year controls was 1.4 mm ridge between the seven year and 13.5 year controls was 1.4 mm and that of the upper ridge was 0.4 mmand that of the upper ridge was 0.4 mm

The mean decrease in mandibular height during the total period The mean decrease in mandibular height during the total period of 13.5 years was 7.7 mm, and the maxillary reduction was 2.2 of 13.5 years was 7.7 mm, and the maxillary reduction was 2.2 mm.mm.

In group C the mean reduction in anterior height of the lower In group C the mean reduction in anterior height of the lower residual ridge between the 10 year and 25 year stages of denture residual ridge between the 10 year and 25 year stages of denture wear was 3 mm and that of the upper ridge was 0.8 mmwear was 3 mm and that of the upper ridge was 0.8 mm

The magnitude of alveolar resorption showed great individual The magnitude of alveolar resorption showed great individual variation variation

The marked alveolar bone loss during the first year of denture The marked alveolar bone loss during the first year of denture wearing and the gradual decrease in the rate of resorption is wearing and the gradual decrease in the rate of resorption is clearly noticeable.clearly noticeable.

TREATMENT AND PREVENTIONTREATMENT AND PREVENTION

SWENSON stated, “ The ideal ridge is one that is broad in its SWENSON stated, “ The ideal ridge is one that is broad in its bearing surface and has practically parallel sides.”bearing surface and has practically parallel sides.”

But in the degenerative denture ridge, undercut ridges, V- But in the degenerative denture ridge, undercut ridges, V- shaped ridges, thin knife edge ridges, and flat or non- existent shaped ridges, thin knife edge ridges, and flat or non- existent denture ridges may be seen.denture ridges may be seen.

Prosthodontists must correct dentures on all of these Prosthodontists must correct dentures on all of these degenerated ridges and should aim not only to replace the lost degenerated ridges and should aim not only to replace the lost structures and lost function but also to preserve the remaining structures and lost function but also to preserve the remaining ridge.ridge.

The cause of the degenerative denture ridge will determine the The cause of the degenerative denture ridge will determine the type of treatment.type of treatment.

So a detailed examination must be performed.So a detailed examination must be performed.

Complete mouth and panographic radiographs are essential.Complete mouth and panographic radiographs are essential.

If the patient is an old denture wearer then the type of denture, If the patient is an old denture wearer then the type of denture, the number of sets he had worn, and why and when he lost his the number of sets he had worn, and why and when he lost his teethteeth

Diagnostic casts and and their articulation in difficult jaw Diagnostic casts and and their articulation in difficult jaw relations is most revealing.relations is most revealing.

PREPARATION OF MOUTHPREPARATION OF MOUTH :- :- Patients with degenerate denture ridges need careful mouth Patients with degenerate denture ridges need careful mouth

health restoration before construction begins.health restoration before construction begins.

1.1. Physical health Physical health :- Any systemic illness that is contributing to the :- Any systemic illness that is contributing to the degenerate bone condition must be corrected or stabilized.degenerate bone condition must be corrected or stabilized.

2.2. Diet Diet :- One of the most neglected facets of treatment in :- One of the most neglected facets of treatment in degenerate denture ridge patients is the prescribing of a diet.degenerate denture ridge patients is the prescribing of a diet.

These patients need a diet high in protein, vitamin, and These patients need a diet high in protein, vitamin, and mineral content.mineral content.

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

PROCESSED, RESILIENT, LINED DENTURE PROCESSED, RESILIENT, LINED DENTURE BASESBASES

Its greatest advantages are its cushioning effect upon the Its greatest advantages are its cushioning effect upon the mucosa and its ability to distort and spring back.mucosa and its ability to distort and spring back.

It is really indicated in the cases of It is really indicated in the cases of

1.1. Severely undercut ridges where surgery is contraindicatedSeverely undercut ridges where surgery is contraindicated

2.2. Patients with no ridgePatients with no ridge

3.3. Patients with a flat ridge and delicate tissues.Patients with a flat ridge and delicate tissues.

4.4. Spinous ridge, tori, the mental foramen, and the genial Spinous ridge, tori, the mental foramen, and the genial tuberclestubercles

The lining is best when there is a 2 mm thickness. So, it cannot The lining is best when there is a 2 mm thickness. So, it cannot be used in the cases of small interridge distance.be used in the cases of small interridge distance.

The biggest disadvantage is deterioration of the resilient liner in The biggest disadvantage is deterioration of the resilient liner in few monthsfew months

ARTICULATING METHODSARTICULATING METHODS :- Success or failure of :- Success or failure of treatment of the degenerate ridge patient is dependent on a treatment of the degenerate ridge patient is dependent on a good occlusion and occlusal vertical dimension.good occlusion and occlusal vertical dimension.

If rehabilitation of the articulator apparatus is impossible, teeth If rehabilitation of the articulator apparatus is impossible, teeth with a flat occlusal pattern are best.with a flat occlusal pattern are best.

SELECTION OF OCCLUSAL PATTERNSSELECTION OF OCCLUSAL PATTERNS :- The patient :- The patient with impaired chewing ability should have non-anatomic with impaired chewing ability should have non-anatomic posterior teeth.posterior teeth.

The most important factor in articulation is that centric The most important factor in articulation is that centric occlusion be harmonious with centric relation.occlusion be harmonious with centric relation.

A balanced occlusion is important for denture base stabilityA balanced occlusion is important for denture base stability

POST INSERTION CAREPOST INSERTION CARE :- :- The delicate tissues will require many adjustments.The delicate tissues will require many adjustments. These should be done carefully with a pressure sensitive paste.These should be done carefully with a pressure sensitive paste. A periodic assessment of the denture and the ridge is advocated. A periodic assessment of the denture and the ridge is advocated.

It is best to see these patients every 72 hours for atleast three It is best to see these patients every 72 hours for atleast three appointments.appointments.

These patients should be seen at regular intervals of at least every These patients should be seen at regular intervals of at least every six months.six months.

PREVENTIONPREVENTION

For the adverse sequelae of residual ridge resorption to be For the adverse sequelae of residual ridge resorption to be reduced, the following should be considered :reduced, the following should be considered :

1.1. Every effort should be made to retain some teeth in Every effort should be made to retain some teeth in strategically good positions to serve as overdenture abutments.strategically good positions to serve as overdenture abutments.

VAN WAAS et al. (1993) randomly assigned 74 subjects to VAN WAAS et al. (1993) randomly assigned 74 subjects to immediate complete dentures versus immediate complete immediate complete dentures versus immediate complete dentures versus immediate complete overdenture prosthesis dentures versus immediate complete overdenture prosthesis supported on two mandibular canines. supported on two mandibular canines.

The loss of bone measured was 0.9 mm in the overdenture group The loss of bone measured was 0.9 mm in the overdenture group and 1.8 mm in the denture group in the canine area; and in the and 1.8 mm in the denture group in the canine area; and in the molar area the loss of bone was 0.7 mm and 1.9 mm molar area the loss of bone was 0.7 mm and 1.9 mm respectively. respectively.

2.2. Edentulous patients should be told the benefits of implant Edentulous patients should be told the benefits of implant supported prosthesis.supported prosthesis.

The bone under an implant supported overdenture may resorb as The bone under an implant supported overdenture may resorb as little as 0.6 mm vertically over a 5 – year period, and long term little as 0.6 mm vertically over a 5 – year period, and long term rersorption may remain at 0.1 mm per year.rersorption may remain at 0.1 mm per year.

3. The patient with complete dentures should follow a regular 3. The patient with complete dentures should follow a regular control schedule at yearly intervals so that an acceptable fit and control schedule at yearly intervals so that an acceptable fit and stable occlusal condition can be maintained. stable occlusal condition can be maintained.

SUMMARYSUMMARY

Reduction of residual ridges needs to be recognized for what it Reduction of residual ridges needs to be recognized for what it is: a major unsolved oral disease which causes physical, is: a major unsolved oral disease which causes physical, psychological, and economic problems for millions of people all psychological, and economic problems for millions of people all over the world. RRR is a chronic, progressive, irreversible, and over the world. RRR is a chronic, progressive, irreversible, and disabling disease, probably of multifactorial origin. Much is disabling disease, probably of multifactorial origin. Much is known about the pathology and pathophysiology of this oral known about the pathology and pathophysiology of this oral disease, but we need to know much more about its pathogenesis, disease, but we need to know much more about its pathogenesis, epidemiology, and etiology. The ultimate goal of research of epidemiology, and etiology. The ultimate goal of research of RRR is to find better methods of prevention or control of the RRR is to find better methods of prevention or control of the disease. So, more research in RRR with new methods and new disease. So, more research in RRR with new methods and new thinking are badly needed in order to provide the best possible thinking are badly needed in order to provide the best possible oral health care for millions of edentulous patients.oral health care for millions of edentulous patients.

BIBLIOGRAPHYBIBLIOGRAPHY

SHELDON WINKLER : ESSENTIALS OF COMPLETE DENTURE SHELDON WINKLER : ESSENTIALS OF COMPLETE DENTURE PROSTHODONTICS – SECOND EDITIONPROSTHODONTICS – SECOND EDITION

DOUGLAS ALLEN ATWOOD : REDUCTION OF RESIDUAL RIDGES : A DOUGLAS ALLEN ATWOOD : REDUCTION OF RESIDUAL RIDGES : A MAJOR ORAL DISEASE ENTITY; 26 (3); 1971; 266-279MAJOR ORAL DISEASE ENTITY; 26 (3); 1971; 266-279

ANTJE TALLGREN : THE CONTINUING REDUCTION OF THE RESIDUAL ANTJE TALLGREN : THE CONTINUING REDUCTION OF THE RESIDUAL ALVEOLAR RIDGES IN COMPLETE DENTURE WEARERS : A MIXED ALVEOLAR RIDGES IN COMPLETE DENTURE WEARERS : A MIXED LONGITUDINAL STUDY COVERING 25 YEARS; 27 (2); 1972; 120-132LONGITUDINAL STUDY COVERING 25 YEARS; 27 (2); 1972; 120-132

WICAL AND SWOOPE : STUDIES OF RESIDUAL RIDGE RESORPTION. WICAL AND SWOOPE : STUDIES OF RESIDUAL RIDGE RESORPTION. USE OF PANORAMIC RADIOGRAPHS FOR EVALUATION AND USE OF PANORAMIC RADIOGRAPHS FOR EVALUATION AND CLASSIFICATION OF MANDIBULAR RESORPTION; 32 (1); 1974; 7-12CLASSIFICATION OF MANDIBULAR RESORPTION; 32 (1); 1974; 7-12

DOUGLAS C. WENDT : THE DEGENERATIVE DENTURE RIDGE – CARE DOUGLAS C. WENDT : THE DEGENERATIVE DENTURE RIDGE – CARE AND TREATMENT; 32 (5); 1974; 477-492AND TREATMENT; 32 (5); 1974; 477-492

PAUL MERCIER AND ROGER LAFONTANT : RESIDUAL ALVEOLAR PAUL MERCIER AND ROGER LAFONTANT : RESIDUAL ALVEOLAR RIDGE ATROPHY : CLASSIFICATION AND INFLUENCE OF FACIAL RIDGE ATROPHY : CLASSIFICATION AND INFLUENCE OF FACIAL MORPHOLOGY; 41 (1); 1979; 90-100MORPHOLOGY; 41 (1); 1979; 90-100