The effect of nicotine-containing products on peri-implant tissues: A systematic review and network meta-analysis.

INTRODUCTION:Smokers have a higher chance of developing peri-implant diseases and are therefore considered an at-risk population. Our aim was to compare peri-implant characteristics in users of electronic cigarettes (EC), waterpipes (WP), cigarettes (CS), smokeless tobacco (ST), and non-smokers (non-users of any nicotine and tobacco product; NS). METHODS:A systematic search of four electronic databases (PubMed, EMBASE, Web of Science, CENTRAL) was performed until April 2023, restricted to English language. Thirty-nine observational studies were included in the qualitative synthesis, of which 32 studies were included in a Bayesian network meta-analysis. Using a predesigned form, two researchers independently collected data about marginal bone loss (MBL), probing pocket depth (PPD), plaque index (PI), bleeding on probing (BOP), modified plaque index (mPI), probing pocket depth > 4mm (PPD>4), gingival index (GI), peri-implant sulcular fluid (PISF) volume, and TNF-α and IL-1β levels. QUIPS and CINeMA were used to evaluate the risk of bias and certainty of evidence. RESULTS:NS had the smallest MBL. Most nicotine-containing product users had significantly higher MBL (CS, MD:1.34 CrI: 0.85, 1.79; WP, MD:1.58 CrI: 0.84, 2.35; ST, MD:2.53, CrI: 1.20, 3.87) than NS. EC did not show significant difference compared to NS (MD:0.52 CrI: -0.33, 1.36). In secondary outcomes NS were ranked in first place. Subset analysis based on smoking habit, implant duration, and maintenance control revealed no differences in ranking probability. CONCLUSION:Most nicotine-containing product users presented worse peri-implant parameters compared to non-smokers, while EC users did not show significant differences to NS in many outcomes. IMPLICATION:Alternative nicotine-containing products are gaining popularity and are often considered less harmful by the general public compared to traditional cigarettes. This is the first network meta-analysis comparing users of four nicotine-containing products and non-smokers. This study shows that CS, WP and ST have a detrimental effect on the overall health of peri-implant tissues. EC users also presented inferior parameters compared to NS, however, the difference was not significant in many outcomes. It is essential to educate patients who are using nicotine-containing products, and to provide proper maintenance and appropriate cessation support. Well-designed multi-armed studies are needed for direct comparison of different products, including heated tobacco products. Greater transparency of confounding factors is needed regarding smoking habit and oral hygiene.