Evaluation of a nanometric hydroxiapatite covered implant surface. In vivo study in rats submitted to cigarette smoke inhalation

Field: Dentistry (Health Sciences)

Background: The habit of smoking may contribute to impaired healing and increased risk of loosing dental implants. Nicotin reduces osteogenic activity, increases periodontal and periimplant bone loss and may lead to implant failure. Chemical and topographic modifications on the surface of the implants have been proposed to improve osseointegration process. Previous studies have shown that the addition of nano-hydroxyapatite to titanium implants may contribute to an accelerated bone healing.Aim: This study aimed to analyze, in rats submitted or not to intermittent cigarette smoke inhalation, by Quantitative Real-Time PCR assessments, the biological response to an implant surface modified by the addition of nano-hydroxyapatite, evaluating bone regeneration related gene expression. Material and methods: Mini implants (1.4 mm in diameter and 2.7 mm in length) with 3 types of surface (machined = MAC, double acid etched = DAE and with the addition of nano-hydroxyapatite = NHA; 24 implants of each type) were installed in the tibias of healthy (n=36) and submitted to cigarette smoke inhalation (n=36) rats. The rats were divided into six experimental groups (n=12 each): G1(HM), MAC installed in healthy rats; G2(HAE), DAE installed in healthy rats, G3(HN), NHA installed in healthy rats; G4(SM), MAC installed in smoke inhalation (SI) rats; G5(SAE), DAE installed in SI rats; and G6(SN), NHA installed in SI rats. The animals were euthanized 7 and 30 days (7d and 30d) after implant placement, and bone biopsies around implants were collected and processed. Gene expressions for osteoprotegerin (OPG), RANK and ostopontin (OPN) were determined by quantitative real-time PCR evaluation. Intra and Inter-groups differences were assessed using One-way Analysis of Variance + Tukey tests (p<0.05).Results: The intergroup analysis showed, for OPG, statistically significant differences between G6(SN) 7d (1,18 u00b1 0,23) versus G4(SM) 7d (0,51 u00b1 0,03); between G6(SN) 30d (1,61 u00b1 0,26) versus G4(SM) 30d (0,50 u00b1 0,02) and versus G5(SAE) 30d (0,74 u00b1 0,18); for RANK, there were significant differences between G1(HM) 30d (1,77 u00b1 0,06) versus G2 (HAE) 30d (1,37 u00b1 0,05) and G3(HN) 30d (0,58 u00b1 0,08), between G2(HAE) 30d versus G3(HN) 30d, between G1(SM) 30d (0,12 u00b1 0,02) versus G2(SAE) 30d (0,53 u00b1 0,02) and G3(HN) 30 d (0,81u00b10,09), and between G2(SAE) 30d versus G3(HN) 30 d; for OPN, there were signicant diferences between G3(HN) 30d (0,56 u00b1 0,04) versus G2 (HAE) 30d (1,18 u00b1 0,07) and G1 (HM) 30d (1,30 u00b1 0,05), and between G6(SN) 30d (0,73 u00b1 0,04) versus G5(SAE) 30d (0,34 u00b1 0,01) and G4 (SM) 30d (0,10 u00b1 0,00). Intragroup analysis showed, for OPG, statistical diferences between 7d and 30d for all groups in healthy rats and only for nano-hydroxyapatite surface in smoke inhalation animals; for RANK and OPN, statistical diferences between 7d and 30d for all groups only in smoke inhalation rats.Conclusions and clinical implications: The present results indicate that the implant surface modified by the addition of nano-hydroxyapatite promoted an up-regulation in the osteogenesis gene expression when compared to machined or double acid etched surfaces, both in systemically healthy rats as well as in rats submitted to intermittent cigarette smoke as an impaired bone model, mainly in late (30 days after implant insertion) healing period. Smoke inhalation negativelly impacted the results of all the evaluated surfaces.