Crestal Bone Loss Around Dental Implants; A Short Communication

Abstract

Many studies described several parameters which are supposed to determine success or failure in longterm evaluations of dental implants. However, the relationship between crestal bone loss around implants and the location of implant-abutment connection in the bone still needs further investigations.The subgingival microgap between the implant and the abutment, which creates higher bone level resorption as a result of plaque accumulation, the polished surface of the implant, and the reestablishing of a biologic width are all possible factors which may increase the bone loss around dental implants which are inserted with a distance between the implant shoulder and the bone crest (DIB) 1 and >2 mm were recorded for 29.7% and 2.5% of the sides, respectively (3). To attain patients’ esthetic expectations regarding implantsupported restorations, it has been recommended that the rough/smooth implant border of non submerged implants be moved to slightly below the crest of the alveolar bone, resulting in a microgap/interface being located 1 to 2 mm below the gingival margin. To accomplish such a subgingival located implant shoulder, the apical part of the relatively smooth machined titanium surface is placed subcrestally. However, there is evidence both from experimental as well as from clinical studies that relatively smooth machined titanium surfaces are associated with additional crestal bone loss in such scenarios. It has therefore been recommended that the placement of the rough/smooth implant border into a subcrestal location is not favorable from a biological standpoint especially in esthetic regions or in areas of limited vertical bone height. In a study by Becker and his colleagues (4), it has been shown that cumulative survival rates for machined, screwshaped titanium fixtures placed in one and two stages as well as one-stage titanium plasma-sprayed screws up to the 2to 3-year follow-up examination were similar, indicating excellent clinical results. Radiographic measurements for changes in crestal bone loss were clinically insignificant for fixtures placed in one stage. For two-stage fixtures, maxillary changes were insignificant, whereas mandibular bone loss was statistically significant but clinically insignificant. Crestal Bone Loss Around Dental Implants; A Short Communication 2 of 4 Haemmerle et al. (1996) studied different amounts of bone loss which occurs when ITI implants are placed 1 mm subcrestal to the border of the rough to the polished surface (5). In this study it was found that a higher amount of bone loss is present when implants are placed with their polished surface in contact to the bone. Nowadays, it is believed that increased bone loss around implants with implant shoulder-to-bone crest distance (DIB) 0.5 mm. It has been shown that marginal bone loss (>0.5 mm) at implants was observed in 30% of subjects and 16% of implant sites. More advanced loss of marginal bone occurred in much fewer subjects and sites. Sites with marginal bone loss were in the sub-sample characterized by bleeding on probing, but only occasionally with deep (?6 mm) pockets. No matter whether bone loss around dental implants is the result of increased plaque accumulation, or an insufficient biologic width, probably also affected by the polished surface, it can be stated, that at least 1 mm of DIB should be present when dental implants are inserted. The location of implant-abutment connection regarding DIB may be an important factor that affects the success rates of dental implants.