Problems of Residual ridge resorption Dr Balendra pratap singh MDS, MAMS, FISDR, FPFA, FAAMP, ICMR-IF Assistant professor Deptt. Of Prosthodontics

“Alveolar bone is defined as the bony portion of the maxilla and the mandible in which roots of the teeth are held by fibers of periodontal ligament”. [GPT-8]

“Residual alveolar ridge is that portion of the alveolar ridge and its soft tissue covering which remains following the removal or loss of teeth”. [GPT-8]

The residual ridge resorption is a life-long process. The rate of reduction in size of the residual ridge is maximum in the first 3-6 months and then gradually tapers off.

Changes in the Residual Ridge after tooth extraction

Bone is Dynamic! Bone is constantly remodeling and recycling Coupled process between: Bone deposition by osteoblasts Bone resorption by osteoclasts 5-7% of bone mass recycled weekly All spongy bone replaced every 3-4 years. All compact bone replaced every 10 years. Prevents mineral salts from crystallizing; protecting against brittle bones and fractures

The rate of RRR varies, from one individual to another; at different phases of life and even at different sites in the same person. The clinical significance of such remodelling is that the functionality of removable prostheses, which rely greatly on the quantity and architecture of the residual ridge, may be adversely affected.

According to the American college of prosthodontists : According to the American college of prosthodontists : McGarry et al, J Prosthodont 8(1):27-39, 1999 Based on Bone Height (Mandible only) Type I : Residual bone height of 21 mm or greater measured at the least vertical height of the mandible. Type II : Residual bone height of 16 - 20 mm measured at least vertical height of the mandible. Type III : Residual alveolar bone height of 11 - 15 mm measured at the least vertical height of the mandible. Type IV : Residual vertical bone height of 10 mm or less measured at the least vertical height of the mandible.

EPIDEMIOLOGY OF RRR : RRR occurs worldwide in Males and females Young and old Sickness and health With or without dentures Unrelated to primary reason for the extraction of teeth ( caries & pdl disease ) Studies also suggest incresed knife edge tendency in mandibular residual ridge in women compared to men. RRR is accelerated in the first 6 months with more loss in mandible than maxilla.

Amount and rate of bone Resorption According to Boucher, During the first year after tooth extraction, the reduction in residual ridge height in the midsagittal plane is 2-3 mm for maxilla 4-5 mm for mandible Annual rate of reduction in height 0.1-0.2 mm for mandible 4 times less in the maxilla

direction of bone resorption Maxilla resorbs upward and inward to become progressively smaller because of the direction and inclination of the roots of the teeth and the alveolar process. The opposite is true of the mandible, which inclines outward and becomes progressively wider according to its edentulous age. This progressive change of the edentulous mandible and maxilla makes many patients appear prognathic.

RRR is generally more in mandible than in maxilla and but the reverse may also occur…. So one must treat the “PARTICULAR PATIENT, NOT THE AVERAGE PATIENT!”!

Mechanical/Prosthetic Etiology of RRR : Acc. To Atwood…..RRR is a multifactorial biomechanical disease caused by a combination of ANATOMIC FACTORS MECHANICAL FACTORS METABOLIC FACTORS Anatomic Mechanical/Prosthetic Biologic/metabolic

1. ANATOMIC FACTORS RRR α Anatomic factors It is postulated that RRR varies with the quantity and quality of the bone of residual ridges.. i.e. the more bone there is, the more RRR will ultimately be.

2.METABOLIC FACTORS RRR varies directly with certain systemic or localized bone resorptive factors and inversely with certain bone formation factors. RRR  BONE RESORPTION FACTORS BONE FORMATION FACTORS

SYSTEMIC LOCAL BONE RESORPTION FACTORS - Correct amount of circulating estrogen, thyroxine, growth hormone,calcium,phosphorus,vitamin D ,fluoride -Osteoporosis - Hypophosphetemia Parathormone Calcitonin -Endotoxins from dental plaque -Osteoclast activating factor(OAF) -Prostaglandins -Human gingival bone resrption factor -Heparin -Trauma due to ill fitting dentureswhich leads to increased or decreased vascularity and changes in oxygen tension

Mechanical factors Bone that is used by regular and physical activity will tend to strengthen within certain limits, than the bone that is in “disuse atrophy”, while others postulated that due to denture wearing RRR is caused due to an “abuse” bone resorption. Perhaps there is truth is both the hypotheses. The fact is that with or without dentures some patients have little or no RRR and some have severe RRR.

Consequences of RRR : Apparent loss of sulcus width and depth. Displacement of muscle attachment close to the ridge. Loss of vertical dimension of occlusion. Reduction of the lower face height. Increase in relative prognathia

Changes in inter alveolar relationship following RRR Morphological changes of the alveolar bone such as sharp, spiny uneven residual ridges. Location of mental foramina close to the ridge crest.

Treatment and prevention “Treatment of RRR is ideally by preventing it.” Prevention of loss of natural teeth Change in design of denture Impression procedures Minimal pressure impression technique. Selective pressure impression technique: places stress on those areas that best resist functional forces Adequate relief of non stress bearing areas eg. Crest of mandibular ridge. Broad area of coverage helps in reducing the force /unit area (Snow Shoe Effect)

Avoidance of inclined planes to minimize dislodgment of dentures and shear forces. Centralization of occlusal contacts to increase stability and maximize compressive forces. Provision of adequate tongue room to improve stability of denture in speech and mastication. Adequate interocclusal distance during jaw rest to decrease the frequency and duration of tooth contact. Occlusal table should be narrow

Diet counseling for prosthodontic patients is necessary to correct imbalances in nutrient intake. Denture patients with excessive RRR report lower calcium intake and poorer calcium phosphorus ratio, along with less vitamin D.

Pre-prosthetic surgery Excessive RRR leads to loss of sulcus width and depth with displacement of muscle attachment more to the crest of residual ridge, osseous reconstruction surgeries, removal of high frenal attachments, augmentation procedures, vestibuloplasties etc may be required to correct these conditions.

Immediate dentures: Some authors claim that extraction followed by immediate dentures reduces the ridge resorption but this has still to be proved.  

Overdenture: tooth or implant supported 1.The denture bearing mucosa of the residual ridges are spared abuse. 2.Maintenance of the alveolar bone 3.Sensory feedback 4.Minimal load thresholds 5.Tactile sensitivity discrimination 6.Masticatory performance 7.Reduction of Psychological trauma

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