The breakdown of bone around oral implants following excessive occlusal load or plaque accumulation was evaluated in monkeys. 5 screw type implants of pure titanium (Astra) were inserted in the mandible of 4 monkeys (Macaca Fascicularis). 2 implants were placed in each of the lateral segments and 1 in the frontal area. Each monkey was provided with 2 cemented splints covering the premolars and molars in the right and left side of the maxilla, respectively. 6 months after insertion of the fixtures, a fixed partial prosthesis was mounted on the 2 implants in one of the lateral segments. The prosthesis was in supra-occlusal contact with the antagonizing splint. Each prosthesis was replaced during the course of the experiment. The renewed prosthesis caused a lateral displacement of the mandible during occlusion, and therefore resulted in a lateral rather than axial excessive occlusal load. Implants retaining the prosthesis were brushed 1 x a week and subgingival cleaning was performed 1 x a month. The remaining implants were never cleaned and, additionally, a cotton cord was placed passively around each of these to promote plaque accumulation. 5 out of 8 implants with excessive occlusal load lost osseointegration (mobility and peri-implant radiolucency). The loss of osseointegration was observed 4.5 months to 15.5 months after the occlusal overload was commenced. None of the implants with plaque accumulation lost osseointegration, although an average loss of 1.8 mm in the radiographic bone level was assessed after 18 months.

Occlusal forces affect an oral implant and the surrounding bone. According to bone physiology theories, bones carrying mechanical loads adapt their strength to the load applied on it by bone modeling/remodeling. This also applies to bone surrounding an oral implant. The response to an increased mechanical stress below a certain threshold will be a strengthening of the bone by increasing the bone density or apposition of bone. On the other hand, fatigue micro-damage resulting in bone resorption may be the result of mechanical stress beyond this threshold. In the present paper literature dealing with the relationship between forces on oral implants and the surrounding bone is reviewed. Randomized controlled as well as prospective cohorts studies were not found. Although the results are conflicting, animal experimental studies have shown that occlusal load might result in marginal bone loss around oral implants or complete loss of osseointegration. In clinical studies an association between the loading conditions and marginal bone loss around oral implants or complete loss of osseointegration has been stated, but a causative relationship has not been shown.

Breakdown of bone around oral implants following occlusal overload or plaque accumulation was evaluated in monkeys. 5 screw-type implants of pure titanium (Astra Tech) were inserted in the mandible of 4 monkeys (Macaca Fascicularis). 6 months after insertion of the implants a fixed partial prosthesis was mounted on the 2 implants in 1 of the lateral segments. The prosthesis was in supra-occlusal contact with an antagonizing splint and caused a lateral directed excessive occlusal load (overload). Implants retaining the prosthesis were brushed 1 x week and subgingival cleaning was performed 1 x month. The remaining implants were never cleaned and, additionally, a cotton cord was placed around the abutments of these implants to promote plaque accumulation. 6 out of 8 implants with occlusal overload became loose. 2 of these were lost, whereas the remaining 4 were retained in the jaws. After 18 months of occlusal load or plaque accumulation, the monkeys were sacrificed. Tissue blocks with the implants were infiltrated and embedded in acrylic resin. Approximately 50 microns thick sections of the implants and surrounding tissues were made. All implants with plaque accumulation were osseointegrated, but exhibited an average histologic marginal bone loss of 2.4 mm (range: 0.8-4.0 mm). Of the 6 implants with occlusal overload available for histologic analysis, 2 implants in 1 monkey had lost osseointegration completely and 2 other implants were osseointegrated in the apical part only, whereas the remaining 2 were still osseointegrated but exhibited a bone loss of 1.8-1.9 mm.

The aim of the present study was to evaluate the long‐term (5 yr.) effect of surgical and non‐surgical periodontal treatment. 16 patients with advanced periodontal disease participated in the study‐ All patients were subjected to initial treatment comprising supra‐ and subgingival scaling and instruction in performing proper oral hygiene. Modified Widman flap surgery was always employed in a quadrant in both the maxilla and mandible. Reverse bevel flap surgery or root planing under local anesthesia were used in the contralteral quadrants. During the 1st 2 wk after surgery or root planing the patients rinsed twice daily with 0.2% chlorhexidine digluconate They were then recalled for professional tooth cleaning once every 2nd wk for the 1st yr. every 3rd month during the 2nd yr, and every 6th month during the last 3 yr. Subgingival scaling was performed at each recall appointment during the last 4 yr. Surgical as well as non‐surgical treatment resulted in a considerable reduction in probing pocket depth which was maintained during the 5‐yr observation period. A small gain of probing attachment (0.0‐0.4 mm) was assessed 3 months after treatment for all procedures, but after 5 yr a small loss of attachment (0.0‐0.2 mm) bad occurred in surgically treated areas, whereas a gain of 0.3 mm was maintained in the areas treated with root planing. The changes in bone level were minute following both surgical and non‐surgical treatment. Less than 5% of the tooth surfaces exhibited a loss of probing attachment of more than 2 mm or a loss of alveolar bone of 15% or more of the “normal” bone height alter 5 yr. The number of deteriorating sites in each individual did not correlate with the level of self‐performed oral hygiene.

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