residual ridge resorption 2021

Residual ridge resorption (RRR)
The size of the residual ridge is reduced most rapidly in the first six months, but the bone resorption activity of the residual ridge 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 reduction. The rate of RRR is different among persons &even at different times &sites in the same person. Residual ridge remodeling affects the function of removable prostheses, which rely greatly on the quantity &the architecture of jaw bones.
Residual ridge reduction: the reduction of residual ridge is chronic, progressive, irreversible, &cumulative. On average, RRR is greater in mandible than maxilla. Ratio may be 4:1.
Factors effecting the residual ridge reduction:
• Anatomic.
• Biologic/metabolic.
• Mechanical.

Include quality &quantity of residual bony ridge, period of edentulism, age &sex.
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.

Bone resorptive factors, bone formation factors.
RRR= bone resorptive factors/ bone formation factors.
General body metabolism is the net sum of all the building up (anabolism) &the tearing down (catabolism) going on in the body. In equilibrium the two antagonistic actions (of osteoblasts &osteoclasts) are in balance. In growth, although resorption is constantly taking place in the remodeling of bones as they makes up for the bone destruction. Whereas in osteoporosis, osteoblasts are hypoactive, &, in the resorption related to hyper para thyroidism, increased osteoblastic activity is unable to keep up with the increased osteoclastic activity.
Bone resorptive factors:
• Localize biochemical factors, involved in periodontal disease.
• Dental plaque endotoxin.
• Osteoclasts activating factor.
• Prostaglandins.
• Human gingival bone resorption stimulating factor.
• Heparin within mast cells.
• Trauma under an ill-fitting denture.
• Reduces vascularity &oxygen tension.
Hormonal &nutritional factors:
Parathyroid hormone maintains Ca balance in kidneys, intestine &lactating mammary glands. Increased PTH mobilizes excess Ca from bones. Phosphorus also moves from bone to plasma but it is excreted in urine.
Growth hormone: it prevents resorption indirectly. It increases the skeletal mass by increasing the osteoblastic activity.
Thyroclacitonin: It attracts Ca to bone, thus reducing serum Ca levels. It also inhibits resorption by reducing the number of osteoclasts.
Vitamin D regulates bone resorption of dietary calcium from intestine. Vit.B complex &vit.C, these are essential to maintain the integrity of periodontium. They play an important role in wound healing &resistance to infections.

Periodontitis previously involved bone may be prone to increased resorption under prosthesis.
Diabetes mellitus poorly controlled diabetes, whether insulin dependent or non-insulin dependent can be associated with a greater prevalence of severe periodontitis.
Acromegaly lengthening of the mandibular ramus, continuous alveolar bone apposition &increased vertical dimension of occlusion are considerable features affecting the design of prosthesis.
Osteoporosis it primarily occurs among elderly. It may occur due to decreased estrogen levels, lack of calcium intake &or failure in calcium absorption &transportation.
Fibrous dysplasia it is a combination of bone resorption, fibrosis of marrow structure &disarrangement of bony architecture. It can be of variable types.
Paget s disease (bone maintenance disorder) simultaneous increase of pronounced resorptive process & accelerated bone deposition. This alternate activity results in a typical mosaic pattern of the affected bone, known as "cotton wool appearance".

• Amount of forces.
• Frequency of forces.
• Direction of forces.
• Duration of forces.
• Biting forces.
• Para functional forces.
• Dampening effect by the mucoperiosteum, RRR force factor dampening effect.
RRR= Force factor/ dampening effect.
Other factors:
- Post-operative scar tissue.
- Surgical trauma.
- Overly retentive denture.
Healthy jaw bone structures are required for the retention of teeth &for maintaining good oral health. Periodontal disease is only one of several conditions that will, if left untreated, will slowly attack &destroy otherwise healthy bone tissues, natural teeth are attached to our jaw bones via a root structure. Depending on the location &size of any given tooth, these root structures will vary in size, depth &complexity. The behaviors of biting &chewing (forces of mastication)produce physical stimulation of each &every root structure which in turn stimulates the immediate bone material that the root is attached to.
Sequel of tooth loss:
? Resorption: the socket gradually remodels until it assumes the shape of rounded edentulous ridge.
? Tilting.
? Drifting.
? Occlusal disharmony leads to discomfort, pain, or damage to TMJ.
Residual ridge reduction: residual ridge is a term used to describe the shape of the clinical alveolar ridge after healing of bone soft tissues following tooth extraction.
Histologic evidence of active bone formation in the bottom of the socket is seen as early as 2weeks after the extraction &the socket is progressively filled with newly formed bone about 6 months.
Ridge classification (Atwoodt s classification):
Six orders of residual ridge form:
Order I: Pre-extraction.
Order II: Post-extraction.
Order III: High, well rounded.
Order IV: Knife edge.
Order V: Low, well rounded.
Order VI: Depressed.
Loss in external width &height of the bone volume:
? Decreased bone width.
? Superior genial tubercles (which are 2 cm below the crest of bone in dentate state), eventually occupy the superior aspect of the anterior mandibular ridge.
? Muscle attachment levels gradually shift occlusally. In extreme cases muscles may attach on or very close to the crest of the ridge.



Common causes of jaw bone deterioration:
Numerous events, oral disease, dental conditions &a patient s history of dental treatments can compromise important jaw bone characteristics. Some of the more common causes are listed here:
- Trauma: events that cause a tooth to be knocked out or broken off to the extent that no biting surface exists (such as broken off at the gum line), bone stimulation ceases.
- Extractions :as soon as an adult tooth is removed, & not replaced, bone stimulation ceases for that particular site.
- Dentures: low cost, unanchored dentures are designed to ride or rest on top of gum tissue. Contrary to what many people want to believe, there is no direct stimulation of jaw bone material. Rather, there may be accompanying loss of gum tissue while the all-important underlying bone structure slowly resorbs.
- Bridge work: custom bridges are a popular treatment for replacing missing teeth. The bone structure underlying the span of missing teeth will undergo deterioration (only the anchoring teeth continue to provide important bone stimulation).
- Gross malalignment: alignment issues due to growth factors, trauma &untreated extractions can cause situations where certain tooth structures do not have an opposing tooth structure. The unopposed tooth may super erupt &also undergo underlying bone deterioration.
- Abnormalities in the bite occlusal relationship: dentists routinely maintain a close focus on bite &occlusion. Assessment of the biting surfaces assures normal bite characteristics, overall dental function &patient comfort. Long standing wear &tear & certain TMJ-TMD problems can cause abnormal physical forces that disrupt the balance of the occlusal relationship. When significant, bone deterioration can occur with certain tooth structures.
- Advanced gum disease: periodontitis, if left untreated, causes whole sale devastation of all tissues at the site of infection. Bone tissue, gingival tissue &connective tissue all undergo destructive changes that may or may not be fully restorable.
Rate of resorption:
Most rapid in the first year after extraction &can be as high as 4.5mm/year. After healing of residual ridge, annual rate of reduction in height is about 0.1-0.2mm in mandible. Annual rate of reduction in height is about 4X greater in mandible than in maxilla.
Pattern of resorption
In maxilla: resorption is up wards &inwards (smaller).
In mandible: the resorption is downwards &outwards (wider).
Masticatory loads:
Significantly lower than that produced by natural teeth. Natural teeth can produce forces up to 175pounds but usually 40 to 50pounds.
Denture wearers: the average force was in the region of 22-24pounds in molar-bicuspid region. CD wearers are able to generate forces that are only 10-15% of those with natural teeth.