Cutaneous vasoconstriction with subsequent decrease in tissue microperfusion and flow rate, together with a decrease in white cell function and number may be responsible for impairment in wound healing which has been demonstrated as more prominent in smokers. Smoking has been shown to decrease the success rates for the integration of oral implants, particularly in the maxilla. Much of the previous research in this area has been on groups treated with smooth surface implants. Advancements in surface technology have led to the introduction of rough surface implants which in their various manifestations appear to show earlier histomorphometric healing. While some studies have shown no survival risk for rough surface implants in smokers, this study aimed to identify any correlation between survival rates of smooth and rough surface implants placed in smokers and non smokers.
Material and Methods A retrospective review of the records of 1498 consenting patients treated in one clinic, who were labelled as either smokers or non smokers was undertaken over two distinct time periods. The first involved 593 patients who received 2182 smooth surface implants (Brånemark System, Nobel Biocare) while the second involved 905 patients who received 2425 rough surface implants (TiUnite, Nobel Biocare). Various data parameters such as age, gender, jaw etc. were recorded and the correlation between these variables determined. Results were gathered and survival time from placement to failure or review calculated. Failure was defined as the absence of an inserted implant at the time of review. The results were adjusted using hazard models and subjected to statistical analysis.
Results In the smooth surface group, 17.5% were smokers, 54.3% were female and the mean age (SD) was 51.3 (±18.5) years. 111 implant losses were identified in 65 patients and the survival rate was 94.0% at 5 years. Smoking was found to be significant in implant failure (P<0.001). Of the rough surface group, 10.5% were smokers, 59.6% were female and the mean age (SD) was 48.2 (±17.8) years. 85 implant losses were identified in 64 patients and the survival rate at 5 years was 94.5%. Smoking was not found to be significant in implant failure (P=0.68). Among smokers in the study, implant losses in the smooth surface group was more than three times that of the rough surface group, especially within the first year. In both smokers and non smokers, the intraoral location of the rough surface implants was not significantly (P=0.45) associated with their loss. Conversely the intraoral location of smooth surface implants did significantly affect their survival, P=0.004, but only in smokers. Overall, the survival rate was lowest in the posterior maxilla of smokers who had received smooth surface implants.
Discussion and Conclusion Smoking has long been associated with an increased risk of failure for smooth surface titanium implants. The advent of a new generation of dental implants with rough surface characteristics has been found to improve early integration and bone to implant contact, such that overall success rates are comparable between smokers and non-smokers, regardless of jaw and location. The results of the current study reinforce this. The surface characteristics of rough surface implants allow for a greater initial bone to implant contact encouraging osseoconductive bone formation at the implant surface. Optimized platelet attraction and propagation on the rough surface precedes effective osteogenic differentiation and osteogenesis. The efficiency of this process on rough surface implants may outweigh the suppressive effects of smoking on healing and osseointegration. In contrast, the decreased bone to implant contact and subsequent impact on the effectiveness of integration alongside the decreased healing ability in smokers may be responsible for the reduced success rates found with smooth surface implants particularly when placed in areas of lower bone density such as the posterior maxilla.
In conclusion, while the results of this study are significant in corroborating previous findings, they incorporate many variables which necessitate further prospective studies to reinforce these conclusions.