Increasing levels of smoking may increase the relative risk of dental implant failure

Journal of Evidence Based Dental Practice

Available online 15 September 2020, 101493

Summary

Subjects or Study Selection

The authors searched PubMed, Embase, Web of Science and Scopus databases for randomly controlled clinical trials, cohort studies, case control studies and case series of subjects with dental implants who smoked, who also reported implant failures and the number of cigarettes they smoked. Two authors graded the quality of the studies using the nine-point Newcastle-Ottawa scale, and they retained studies that scored greater than six points. The initial search identified 5,035 studies, 23 of which met the criteria for inclusion in the meta-analysis, with 1 clinical trial, 6 prospective studies, and 16 retrospective studies, and a total of 31,129 implants. Though not reported in the paper, the number of subjects (10,902) was calculated from the online supplemental Table S2A; however, the actual number of subjects was higher because one paper in the table did not report the number of subjects.

Key Study Factor

Systematic review and meta-analysis of 23 studies comparing the effects of smoking on failure rates of dental implants; all studies had to include the level of smoking expressed as numbers of cigarettes smoked, and at least two categories, such as light versus heavy smoking.

Main Outcome Measure

The main outcome measure was a statistically significant increase (P<0.05) in the relative risk of implant failure with increased numbers of cigarettes smoked. Because studies categorized cigarette smoking levels differently, separate meta-analyses were performed for groups of studies based on how they categorized smoking. The groups were: 1) none, <10, or >10 cigarettes; 2) none, <15, or >15 cigarettes; 3) none, <20, or >20 cigarettes; and, 4) none, <10, 10-20, or >20 cigarettes. They also performed separate meta-analyses based on implant-related and patient-related data (each implant was considered as a separate subject). Finally, separate sub-group meta-analyses were performed based on implant surface type (rough vs. smooth), and on implants placed in grafted sinuses.

Main Results

Subjects who smoked >20 cigarettes per day, compared to non-smokers, had a relative risk of 2.48 (C.I. 1.46-4.22, p= 0.001) for implant failure on an implant-level basis, and 4.0 (C.I., 2.72-5.89, p<0.001) on a subject level basis. High heterogenicity (I²=72%) was reported for the implant related findings but was low (I²=7.9%) for the patient related findings. Statistically significantly higher relative risks were also found for subjects who smoked any number of cigarettes compared to none, however, the effect sizes were lower and less consistent. Comparisons between levels of smoking that excluded non-smokers were inconsistent.

Funnel plot inspections and Egger’s tests for all meta-analyses performed detected no evidence of publication bias.

Conclusions

The authors concluded that the risks of implant failure increased as the number of cigarettes smoked increased, and that smoking more than a pack of cigarettes per day can be considered a risk for implant failure.