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Background Having an adverse impact on systemic health, periodontitis is an inflammatory disease which is characterized by the loss of integrity in tooth-supporting tissues. Middle-aged human (MAH) have been reported to have a higher incidence of periodontitis and a greater extent of bone loss. Although middle-aged monkey (MAM) shares similar dental anatomy and physiology with humans, it is still unclear whether they both display same disease phenotype or not, given that literature comparing the periodontal status between MAH and MAM is limited. CBCT examination and histological analysis were performed to characterize the periodontal condition, while 16 s rRNA sequencing was carried out to evaluate the possible mechanism that may explain the difference between these two primates. Results The present study revealed a more severe disease phenotype in MAH than in MAM, along with significantly higher levels of alveolar bone loss accompanied with increased blood vessels and inflammatory cells infiltration. High-throughput gene sequencing based on 16S rRNA gene demonstrated that the diversity of salivary microorganisms in MAH was lower than that of MAM. In addition, at the phylum level, the relative abundance of Proteobacteria in the MAH was higher than MAM, while Bacteroidetes showed a totally opposite trend. At the genus level, the relative abundances of Alloprevotell, Aggregatibacter, Haemophilus, Gemella and Porphyromonas in the MAH group were significantly less than that of the MAM group. One of the possible factor that may explains for this observation would be the dietary factors, affecting the oral microbial composition and diversity, and subsequently contributing to the alterations of periodontal status. Conclusions Altogether, these results demonstrated a potential link that may explain for the difference in inflammatory status in the oral cavity of MAH and MAM – the oral microbiota, prompting further investigation to explore specific roles of these bacterial population in the maintenance of oral health.

Background: Having an adverse impact on systemic health, periodontitis is an inflammatory disease which is characterized by the loss of integrity in tooth-supporting tissues. Middle-aged human (MAH) have been reported to have a higher incidence of periodontitis and a greater extent of bone loss. Although the similar dental anatomy and physiology as humans, whether middle-aged monkey (MAM) has the same disease phenotype as MAH is unclear. Furthermore, literature comparing the periodontal status between MAH and MAM is limited. Methods: Therefore, four female middle-aged Macaca fascicularis and five middle-aged woman were used to evaluate the periodontal status before evaluating possible mechanism that may explain the difference between these two primates. CBCT examination and histological analysis were performed to characterize the periodontal condition, while 16s rRNA sequencing was done to explore the oral microbial profiles of two groups. Results: The present study revealed a more severe disease phenotype in MAH than in MAM, along with significantly higher levels of alveolar bone loss and increased blood vessels and inflammatory cells infiltration. High-throughput gene sequencing demonstrated that the diversity of salivary microorganisms in MAH was lower than that of MAM. In addition, at the phylum level, the relative abundance of Proteobacteria in the MAH was higher than MAM, while Bacteroidetes showed a totally opposite trend. At the genus level, the relative abundances of Alloprevotell, Aggregatibacter, Haemophilus, Gemella and Porphyromonas in the MAH group were significantly less than that of the MAM group. Conclusions: Altogether, these results demonstrated a potential link that may explain for the difference in inflammatory status in the oral cavity of MAH and MAM – the oral microbiota, prompting further investigation to explore specific roles of these bacterial population in the maintenance of oral health.

Background: This study aims to compare the percentage of dentin removed, instrumentation efficacy, root canal filling and load at fracture between contracted endodontic cavities and traditional endodontic cavities in premolars. Methods: Forty extracted intact human first premolars were imaged with micro-CT and randomly assigned to CEC or TEC groups. Minimal CECs were prepared with the aid of 3D-printed guide template, canals were prepared with a 0.04 taper M-Two rotary instrument and cavities were restored with resin. The specimens were loaded to fracture in an Instron Universal Testing Machine after a fatigue phase. The data were analyzed by the independent samples T test and Mann-Whitney U test, appropriate post hoc tests. Results: In the premolars tested in vitro, CECs conserved coronal dentin in premolars with two dental roots but no impact on the instrument efficacy, the root canal filling or the biomechanical responses compared with TECs. Conclusion: The results of this study did not suggest that CEC could improve the fracture resistance of the endodontically treated premolars. The instrumentation efficacy and the percentage of filling material did not significantly differ between CECs and TECs in the premolars.