In three studies from the same research group, female rats with ovariectomy-induced (OVX) osteoporosis were included [31,32,33]. Although the same research group performed the studies, the results were based on diverse animal populations, as it can be inferred from the studies. Rats receiving a high dose of SRAN (SRAN_H, 1000 mg/kg/day) showed an increased ratio between bone and total voxels in direct contact to the implant (1.9-fold) compared with a non-supplemented OVX group. Similar trends were observed regarding trabecular thickness (by 1.2-fold), bone volume/tissue volume (by 1.1-fold), trabecular number (by 90%), and connectivity density (by 85.1%), evaluated by microtomography. In fact, the OVX + SRAN_H group showed similar or even statistically significantly better values regarding the above-mentioned parameters when compared with a non-osteoporotic group, while the improvements induced with a smaller dose of SRAN (SRAN_L, 500 mg/kg/day) did not reach statistical significance [32] compared with the control group. However, SRAN_L animals showed improved implant osseointegration (as assessed by microtomography and histomorphometric evaluation) compared to a non-supplemented OVX group [33], but did not enhance bone-quality-related parameters when compared with a group receiving bisphosphonates (zolendronated and alendronate) [31]. Animals receiving bisphosphonates, however, showed significantly increased bone mineral density, and bone-to-implant contact and implant push-out values, when compared with a non-supplemented OVX group [31].

According to SYRCLE’s risk of bias tool for animal studies [28], the studies were classified in relation to the risk of bias regarding their selection, performance, detection, attrition, and reporting characteristics. All studies successfully met the criterion of not reporting their outcomes in a selective manner, and all proposed aims and elaborated hypotheses were adequately addressed in the results and discussion sessions of the papers. On the other hand, most studies were unclear regarding relevant steps, e.g., the housing of the animals, allocation concealment of the animals, whether outcome assessment was blinded, and whether incomplete outcome data existed and were not reported. Another possible source of bias may be the lack of consistent reporting regarding selection and justification of the posology of Sr supplementation. All these parameters represent relevant biases regarding the findings of the selected studies. The overall scoring for the included studies is presented in Table 3.