Chinese Journal of Dental Research, 03/2020

Objective: To explore the effects of Sirtuin 7 (SIRT7) on the gene expression profile of stem cells from the apical papilla (SCAPs). Methods: SCAPs were isolated and cultured. SIRT7 short hairpin ribonucleic acid (shRNA) was used to knock down the expression of SIRT7 in SCAPs. After library construction and RNA sequencing (RNA-seq), differentially expressed genes were identified using Cuffdiff with a false discovery rate (FDR) ≤ 0.05 and fold change ≥ 2. Pathway and Gene Ontology (GO) analyses were conducted to elucidate the changes in important functions and pathways after SIRT7 gene knockdown. Gene set enrichment analysis (GSEA) was performed and enrichment of a gene set with an FDR lower than 0.25 was considered significant. Results: The most striking GO terms related to SIRT7sh SCAPs and Consh SCAPs were response to nucleus, nucleolus, cytoplasm, protein binding and intrinsic apoptotic signalling pathway. Signalling pathway analysis revealed the top five pathways to be metabolic, pyrimidine metabolism, protein processing in endoplasmic reticulum, phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signalling and p53 signalling. The results of GSEA showed that genes were mainly enriched in cell cycle, cell proliferation, transforming growth factor beta (TGF-β) signalling and cytokine–cytokine receptor interaction pathways. Conclusion: SIRT7 may affect the functions of SCAPs through cell cycle, cell proliferation and apoptosis pathways. Keywords: RNA sequencing, SIRT7, stem cells from the apical papilla

Objective: To investigate the role of microbiota in dentine formation and the characteristics of dental pulp stem cells (DPSCs) in mouse incisors. Methods: The influence of microbiota on dentine was detected via microcomputed tomography (microCT), microhardness testing and haematoxylin-eosin (HE) staining in incisors from germ-free (GF), specific pathogen–free (SPF) and conventionalised (ConvD) mice. Cell Counting Kit-8 (CCK-8) assay, alizarin red staining and expression of dentine sialophosphoprotein (DSPP), alkaline phosphatase (ALP) and bone sialoprotein (BSP) via real-time polymerase chain reaction (PCR) were used to evaluate the biological characteristics of DPSCs derived from mice of different microbiota status. Results: MicroCT showed that the incisors in the GF and ConvD groups had comparable dentine thickness to those in the SPF group. Microhardness testing showed a lower dentine hardness value in GF incisors compared to SPF, while HE staining showed that GF incisors exhibited thicker predentine than SPF incisors. There was no difference between the ConvD and SPF groups. DPSCs from GF mice showed no significant difference in proliferation rate to SPF and ConvD DPSCs. DPSCs from GF mice formed less mineral deposition and expressed lower levels of osteo-/odontogenic differentiation–related genes including ALP, BSP and DSPP than SPF and ConvD DPSCs. The absence of microbiota in GF mice resulted in a lower dentine hardness value, thicker predentine and impaired osteo-/odontogenic differentiation capacity. Conclusion: The absence of microbiota impaired the dentine mineralisation and osteo-/odontogenic differentiation abilities of DPSCs. Keywords: dental pulp stem cells, dentinogenesis, germ-free, microbiota, mineralisation

Objective: To design and fabricate 3D-printed rigid constraint guides for the tooth preparation for laminate veneers and to evaluate the accuracy of guide-assisted preparation. Methods: Twenty maxillary right central incisor resin artificial teeth were randomly divided into two equal groups and prepared for laminate veneers. Tooth preparations were performed, assisted by guides in the test group and by depth gauge burs in the control group, and both were finished by freehand operation. The typodonts were 3D scanned before preparation, after initial preparation and after final preparation. The tooth preparation depths at each step, including initial preparation depth, final preparation depth and loss of tooth tissue during polishing, were measured by 3D deviation analysis. Statistical analyses were conducted to investigate differences. Results: The initial preparation depth was 0.488 mm (median, quartile 0.013 mm) in the test group and 0.521 mm (median, quartile 0.013 mm) in the control group. A statistically significant difference was found between them (P 0.05). The final preparation depth in the test group (0.547 ± 0.029 mm) was significantly less than that in the control group (0.599 ± 0.051 mm) (P 0.05), and closer to the predesigned value (0.5 mm). There was no statistically significant difference in the loss of tooth tissue during polishing between the test group (0.072 ± 0.023 mm) and the control group (0.089 ± 0.038 mm) (P > 0.05). Conclusion: In maxillary central incisors, the tooth preparation for laminate veneers could be conducted using 3D-printed rigid constraint guides, the accuracy of which is better than that of depth gauge burs. Keywords: 3D printing, computer-aided design (CAD), dental veneers, guide, tooth preparation

Objectives: To investigate whether the levels of serum C-reactive protein (CRP), salivary interleukin (IL)-6 and IL-lβ in metabolic syndrome (MS) patients can be potential monitors for inflammation in MS patients with severe periodontitis. Methods: A total of 114 MS patients and 49 systemically healthy subjects were enrolled. CRP in serum and IL-1β and IL-6 in non-stimulated whole saliva were collected from these patients and subjects and analysed by enzyme-linked immunosorbent assay (ELISA). Dental examinations were performed and the participants completed a questionnaire. Results: The serum CRP level of MS patients was higher than that of systemically healthy subjects, and increased as the number of components increased (P 0.05). No difference was observed in the salivary level of IL-6 and IL-1β between MS patients and controls or between MS patients with different components. The level of salivary IL-6 in MS patients with moderate/severe periodontitis was significantly higher than in MS patients with good periodontal health/mild periodontitis (P 0.05). After adjustment for age, sex and smoking habits, multivariate analysis showed that the corresponding odds ratio (OR) for MS combined with moderate/severe periodontitis was 1.21 (95% confidence interval [CI] 1.04–1.39, P = 0.012) for subjects with high serum CRP and salivary IL-6 and IL-1β were not risk indicators for MS combined with moderate/severe periodontitis. Conclusions: MS patients might be burdened by high levels of serum CRP. Serum CRP could be a potentially valuable biomarker to detect inflammation in MS patients with severe periodontal disease. Keywords: cytokines, inflammation, metabolic syndrome, periodontitis

Objective: To investigate the bilateral symmetry of double root canals, variation in root canal bifurcation and position of canal orifices in mandibular incisors in a Chinese population. Methods: A total of 149 subjects with mandibular incisors with two canals were selected from 866 patients based on CBCT images and divided into three groups: group 1 ( 21 years), group 2 (21–40 years) and group 3 (> 40 years). The prevalence of bilateral symmetry of double root canals (type III and type V), the distance between the cementoenamel junction (CEJ) and the bifurcation (D1) and the distance between the two canal orifices (D2) were calculated and analysed. Results: The bilateral symmetry of type III for mandibular central incisors (MCIs) (44.4%) was significantly lower than that for mandibular lateral incisors (MLIs) (63.4%). D1 was greater in group 1 (4.63 ± 1.35mm) than in group 2 (3.99 ± 1.02 mm) and group 3 (3.90 ± 1.95 mm). D2 was shorter in in MCIs (0.65 ± 0.20 mm) than in MLIs (0.74 ± 0.22 mm). Conclusion: Special attention is required in the root canal treatment of mandibular incisors, especially in patients aged above 21 years. Keywords: bilateral symmetry, CBCT, double root canals, mandibular incisors

This report describes the cases of two patients with a maxillary lateral incisor with palatogingival groove and extensive endodontic-periodontal lesions. Although it is reported that acceptable periodontal status is of great importance in case selection in intentional replantation, it is suggested in this report that intentional replantation could be chosen instead of immediate extraction if extensive endodontic-periodontal lesions exist in a tooth with palatogingival groove. The gingival margin position and gingival papilla were well preserved and the bone defect was almost completely repaired. This was beneficial to the aesthetic prosthodontic treatment and implantation, although external root resorption was observed. Keywords: bone repair, endodontic-periodontal lesion, external root resorption, intentional replantation, palatogingival groove

The main goal of this report was to solve a clinical case of a 73-year-old man with diabetes, partial edentulism and a pathological occlusion with biocorrosion using conservative and adhesive techniques. A complete rehabilitative treatment was performed, increasing the vertical dimension of occlusion using indirect restorations with composite resins on teeth and resin crowns on implants and returning function using mutually protected occlusion. A 6-month posttreatment clinical and radiographic follow-up was performed. Keywords: composite resins, dental implants, dental prosthesis, implant-supported, tooth wear, vertical dimension