Effects of ovariectomy-induced osteoporosis and two photobiomodulation protocols on the repair of apical periodontitis in Wistar rats: A microCT study.

AIM: Osteoporosis is a disease that is related to a higher prevalence and greater volumes of apical periodontitis. The purpose of this study was to evaluate the effect of ovariectomy-induced osteoporosis and high- or low-level laser photobiomodulation (PBM) on the repair of apical periodontitis (AP) in adult female Wistar rats.

METHODOLOGY: Sixty female Wistar rats (n = 120) were randomly allocated into four control (n = 6 teeth) and 8 experimental (n = 12 teeth) groups, according to procedure and time of evaluation: healthy control (GCS14/GCS28), osteoporotic control (GCO14/GCO28), sham (SHAM14/SHAM28), osteoporotic (OVX14/OVX28), low-level laser (OVX-LLL14/OVX-LLL28) and high-level laser (OVX-GEM14/OVX-GEM28). All groups were submitted to bilateral ovariectomy, except for the healthy control and sham. Eight weeks later, AP was induced bilaterally in mandibular first molars' mesial roots in experimental groups, and after 21 days, their endodontic treatment (RCT) was conducted. For 14 or 28 days, PBM was applied three times/week, as follows: sham application (SHAM and OVX groups); low-level laser (OVX/LLL groups); defocused high-power laser (OVX/GEM groups). After the respective experimental periods, the animals were euthanized. Tibias and hemi-mandibula were obtained and submitted to computed microtomography. Bone volume fraction (BV/TV), trabeculae number (Tb.N), spacing (Tb.Sp) and thickness (Tb.Th) were obtained for tibias, while RCT apical limit, periodontal ligament and AP volumes (APvol) were recorded for hemi-mandibula. Data were subjected to statistical analysis through generalized estimating equations (GEE), ANOVA and chi-square tests (5% significance level).

RESULTS

Ovariectomy tibias showed lower BV/TV and Tb.N (p < .0001) and higher Tb.Th (p = .020) and Tb.Sp (p < .0001) when compared to sham groups. For hemi-mandibula, lower APvol values were found in SHAM14 when compared to OVX/LLL14 and OVX/GEM14 groups (p < .05), which were not different from each other. Over the 28-day period, the OVX/LLL28 group showed higher AP volumes when compared to OVX28 and OVX/GEM28 (p < .05). Analysing variables effects on APvol, time, PBM and RCT apical limit showed no effect (p > .05), while ovariectomy showed a significant increase (p = .004).

CONCLUSIONS

Ovariectomy-induced osteoporosis in Wistar rats led to a reduction in AP repair, and PBM was unable to counteract this effect.