Influence of prosthetic parameters on the survival and complication rates of short implants.

PURPOSE Implants shorter than 10 mm can be a long-term solution for sites with limited bone height. The purpose of this study was to determine the influence of some prosthetic factors on the survival and complication rates. MATERIALS AND METHODS Two hundred sixty-two short machined-surface Brånemark System implants were consecutively placed in 109 patients and followed for a mean of 53 months. The prosthetic parameters were recorded, and the data were examined for relation to peri-implant bone loss and biologic or biomechanical complications. RESULTS Relatively few crown-to-implant (C/I) ratios were < 1 or > 2 (16.2%). Occlusal table (OT) width ranged from 5.4 to 8.3 mm. Opposing dentition was most often natural teeth, a fixed prosthesis supported by natural teeth, or an implant-supported fixed restoration. Occlusion with a normal buccolingual maxillomandibular relationship was found in 72.7% of the cases. No significant difference in peri-implant bone loss was correlated with C/I ratio or OT. Neither cantilever length nor bruxism had a significant effect on peri-implant bone loss. Mean bone loss was 0.74 +/- .65 mm. The difference in the complication rate (15% overall) between the bruxer and the nonbruxer group was not statistically significant (P = .51). One implant was lost in a heavy bruxer after 7 years of function. DISCUSSION Increased C/I and OT values do not seem to be a major risk factor in cases of favorable loading. In 67% of the cases, the mesiodistal length of the prosthesis was less than the corresponding natural tooth length, which may have contributed to better load distribution and more favorable results. CONCLUSIONS Short implants appear to be a longterm viable solution in sites with reduced bone height, even when the prosthetic parameters exceed the normal values, provided that force orientation and load distribution are favorable and parafunction is controlled.