Effect of nicotine exposure on the rate of orthodontic tooth movement: A meta-analysis based on animal studies.

BACKGROUND: Nicotine exposure has been reported to modify bone cell function and the osseous metabolism with potential effects on the rate of orthodontic tooth movement. OBJECTIVES: To systematically investigate and quantitively synthesize the most recent available evidence from animal studies regarding the effect of nicotine exposure on the rate of orthodontic tooth movement. SEARCH METHODS: Unrestricted searches in 7 databases and hand searching were performed until July 2020 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ProQuest Dissertations and Theses Global). SELECTION CRITERIA: We searched for controlled studies on healthy animals investigating the effect of nicotine on the rate of orthodontic tooth movement. DATA COLLECTION AND ANALYSIS: Following study retrieval and selection, relevant data was extracted and the risk of bias was assessed using the SYRCLE's Risk of Bias Tool. Exploratory synthesis and meta-regression were carried out using the random effects model. RESULTS: From the initially identified records, 5 articles meeting the inclusion criteria were selected and no specific concerns regarding bias were identified. Quantitative data synthesis showed that the rate of orthodontic tooth movement in the nicotine exposed rats was higher than in the control group animals (2 weeks of force application; 0.317 mm more movement in nicotine exposed rats; 95% Confidence Interval: 0.179-0.454; p = 0.000). No effect of the concentration or the duration force application was demonstrated following exploratory meta-regression. CONCLUSION: Rats administered with nicotine showed accelerated rates of orthodontic tooth movement. Although, information from animal studies cannot be fully translated to human clinical scenarios, safe practice would suggest that the orthodontist should be able to identify patients exposed to nicotine and consider the possible implications for everyday clinical practice.

Gingival overgrowth and dental alveolar alterations: possible mechanisms of cyclosporin-induced tooth migration. An experimental study in the rat.

The inter-incisal distance and dimension of the interdental papilla between the mandibular incisors were examined in cyclosporin A (CSA) fed rats over 6 weeks. Rats in the test group received CSA daily in mineral oil by gastric feeding (30 mg/kg body weight); the control group received mineral oil only. The inter-incisal distance and gingival dimensions, including bucco-lingual width and vertical height, were assessed biweekly from alginate impressed stone models. Animals were sacrificed at the end of the study and tissue sections were obtained from the anterior region of the mandible for histopathological evaluation. Both the inter-incisal distance and the dimension of the interdental papilla were significantly greater in CSA-exposed animals compared to control. The significant alteration appeared earlier in the papillary dimensions than that in the interdental distance. Particular histopathological alterations of the soft and hard tissues of the periodontium were observed in CSA-exposed animals. Within limitations of the study, we suggest that the CSA-induced gingival overgrowth may offer an active force contributing to observed tooth movement, however, remarkable alveolar remodeling should be considered as an undetermined factor for the movement.