Dental implant treatment is increasingly common and a number of studies have suggested that treatment outcomes are less favourable in patients who smoke. This review aimed to test the null hypothesis of no difference in the implant failure rates, risk of postoperative infection, and marginal bone loss for smokers versus non-smokers, against the alternative hypothesis of a difference.

Methods

Searches were conducted in PubMed/Medline, Web of Science, the Cochrane Oral Health Group Trials Register and supplemented by handsearching of relevant dental journals. There were no time or language restrictions for the publications. Clinical studies, either randomized or not, providing outcome data for dental implant failure in smokers and non-smokers, in any group of patients (of any age, race, or sex), with no follow-up restrictions were considered. Three reviewers carried out study selection independently and study quality was assessed using the Newcastle–Ottawa scale (NOS).

Results

• 107 studies (4 RCTs; 16 CCTs; 16 prospective studies; 71 retrospective studies) were included.
• 85 studies were considered to be of high quality; 22 moderate quality.
•  7 CCTs controlled for patient smoking habits
• 4 RCTs and 9 CCTs included did not control for smoking habit
• Only 39 out co 107 publication in total clearly defined the patients’ smoking behaviours.
• 3 studies did not provide information on implant failure rates separately between smokers and non-smokers only marginal bone loss.
• Implant failures in smokers for 104 studies are shown in the table below.

	Smokers	Non-smokers
No. of implants placed	19,836	60,464
No. of implant failures (%)	1259 (6.35%)	1923(3.18%).

•  For smokers compared with non-smokers meta-analysis found
  • a higher risk for implant failure;  relative risk (RR) = 2.23 (95% CI 1.96–2.53) (P < 0.00001; I² = 51%).
  • A higher risk of post-operative infection RR= 2.01, 95% CI 1.09–3.72; P = 0.03 I² = 0%).
  • Marginal bone loss; mean difference (MD) = 0.32, 95% CI 0.21–0.43; P < 0.00001 I² = 95%).
• The relative risk of implant failure:
  • Maxillary implant only; RR= 2.2 (95% CI 1.63–3.01) P = 0.005; I² = 49%
  • Mandibular implants only; RR = 2.61 (95% CI 0.92–7.39) P = 0.09; I² = 48%

Conclusions

The authors concluded:

The results of the present review should be interpreted with caution due to the presence of uncontrolled confounding factors in the included studies. Within the limitations of the existing investigations, the results of the present study suggest that the insertion of dental implants in smokers affects the implant failure rates, the incidence of postoperative infections, as well as the marginal bone loss.

Comments

This review is another by the same group of authors that have used the same methodological approach choosing to adopt broad study acceptance criteria including both randomised and non-randomised studies as well as those with a pro and retrospective design. This is an approach that many methodologists do not favour. In their discussion the authors highlight many potential confounders e.g. failure to report details related to smoking habits in the included papers or whether any other risk factors were present. Having more restrictive inclusion criteria would help but also restricts the number of studies available for inclusion.

However, as the authors indicate in their conclusion while the findings suggest negative effects on dental implants from smoking, the findings do need to be interpreted with caution. The results for this review for implant failure are similar to a 2013 review by Chen et al that also considered the risk factors diabetes and osteoporosis. The Chen review included 54 studies for smoking and found a relative risk for implant failure in smokers RR = 1.92; (95% CI, 1.67-2.21).

Links

Chrcanovic BR, Albrektsson T, Wennerberg A. Smoking and dental implants: A systematic review and meta-analysis. J Dent. 2015 May; 43(5):487-498. doi:10.1016/j.jdent.2015.03.003. Epub 2015 Mar 14. Review. PubMed PMID: 25778741.

Chen H, Liu N, Xu X, Qu X, Lu E. Smoking, radiotherapy, diabetes and osteoporosis as risk factors for dental implant failure: a meta-analysis. PLoS One. 2013 Aug 5;8(8):e71955. doi: 10.1371/journal.pone.0071955. Print 2013. PubMed PMID: 23940794; PubMed Central PMCID: PMC3733795.

Dental Elf – 3^rd Feb 2014 – Currently little evidence to support smoking as a risk factor for peri-implantitis

Dental Elf – 18^th June 2012 – Helping your patients give up smoking