Chinese Journal of Dental Research, 03/2019

Objective: To evaluate the therapeutic effect of local injection of stem cells from human exfoliated primary teeth (SHED) on periodontitis in mice. Methods: Fifteen female mice were randomly divided into three groups: normal control group, periodontitis group and SHED treatment group. A periodontitis model was established by ligating a 0.2 mm orthodontic ligation wire to the maxillary first molar. The SHED group was injected with SHED at 3 weeks post-ligation. All mice were sacrificed and their maxillae were dissected five weeks post-ligation. Clinical assessments, micro-computed tomography (micro-CT) scanning, and histologic examination were used to evaluate the outcome of tissue regeneration. Results: Micro-CT analysis showed that SHED administration significantly increased periodontal regeneration and decreased the distance between the cemento-enamel junction and the alveolar bone crest. In addition, histopathological photomicrographs showed new regenerated bone, the number of TNF-α-positive, IFN-γ-positive and CD4+ cells decreased, and osteoclasts-positive decreased in the periodontal defect area in the SHED group compared with the periodontitis group. Conclusion: SHED administration suppresses the expression of inflammatory factors, inhibits the production of osteoclasts, and promotes the regeneration of periodontal tissues. Keywords: periodontitis, stem cells from primary teeth, inflammation

Objective: To investigate the changes of the bacterial community in the oral environment of beagle dogs to gain insights on the possible causes of failed therapy in peri-implantitis. Methods: Beagles were used as models for experimental peri-implantitis. Samples from peri-implant soft tissue (supramargin and submargin), ligature and contaminated surface of peri-implantitis sites were collected and analysed by sequencing the bacterial 16S rRNA gene. Results: The residual microbial community from the curettes-treated implant surface contained a variety of microorganisms, including periodontal pathogens, which showed no changes in their composition and structure. Conclusion: It is possible that the residual bacterial community remained unchanged and this was the cause of recurrent episodes of inflammation. Keywords: peri-implantitis, microbial communities, peri-implant mucositis, peri-implant soft tissue, biofilm

Objective: To increase the awareness of oral squamous cell carcinoma (OSCC) metastasis to the parotid region and the characteristics of these cases, and to evaluate the outcomes and provide treatment suggestions. Methods: A retrospective study was conducted among the OSCC patients with metastasis to the parotid gland at the Peking University School and Hospital of Stomatology from 2000 to 2015. The demographic data and the medical records including primary tumour, treatment protocol, follow-up information and outcomes were collected and analysed. Results: A total of 10 patients with parotid metastasis (out of 1358 OSCC patients) were included in the study. The incidence of parotid metastasis was relatively low (0.74%). All the cases were poorly differentiated (Grade II/III) and the primary sites were in an advanced stage (T3/4). Parotid metastasis occurred frequently following neck dissection and radiotherapy, and the inferior parotid lymph nodes were most commonly involved. Surgery and radiotherapy were mainly salvage protocols for parotid metastasis. The 5-year survival rate of these patients was 38.9% by the Kaplan-Meier method. Conclusion: OSCC has the potential to metastasise into the parotid lymph nodes. The salvage rate and prognosis were relatively poor. Removing of the parotid tail along with the neck dissection is recommended for OSCC patients. Keywords: oral squamous cell carcinoma, parotid lymph node, metastasis

Objective: To evaluate the effect of provisional restorations using ovate pontics on the hard and soft tissues of the alveolar ridge after tooth extraction. Methods: Patients with intact buccal bone after extraction of a maxillary incisor underwent a series of treatments. The protocol included tooth extraction and provisional restoration using ovate pontics. The outcomes were assessed 1, 3 and 6 months after the procedure, regarding changes in bone volume and soft tissue dimension. Results: A total of 11 patients (6 female and 5 male) were treated using an ovate pontic provisional restoration after tooth extraction. After 6 months, bone loss at level 1, 3 and 5 mm below the most coronal section of the bone crest was 2.28 ± 0.53 mm, 1.51 ± 0.30 mm and 1.46 ± 0.41 mm, respectively. Changes in bone volume of these three levels were significantly lower (P 0.01) than changes previously reported in the literature. The mesial and distal papillae recessed 0.47 ± 0.24 mm and 0.88 ± 0.57 mm, respectively, whereas the midfacial shrinkage was 0.86 ± 0.44 mm. The dimension of the ridge contour around the socket reduced mostly at 3 and 5 mm below the coronal section and the gingival mucosa, with values of 1.68 ± 0.48 mm and 1.61 ± 0.48 mm, respectively. Conclusion: Using a provisional restoration with ovate pontics after tooth extraction may preserve the alveolar ridge by sustaining the soft tissue, in particular the gingival papilla. Keywords: ovate pontics, alveolar ridge preservation, provisional restoration, gingiva recession, bone loss

Objective: To evaluate the bond strength of fiber posts to intraradicular dentine pretreated with two root canal obturation techniques and three postspace irrigation solutions. Methods: A total of 96 human premolars were collected and treated with complete or partial root canal obturation techniques. The roots were further divided into three subgroups (n = 16) based on postspace irrigation solutions: 2.5% NaOCl, 37% phosphoric acid etching, and distilled water. The fiber posts were bonded with self-adhesive resin cement, and the roots were sectioned into three slices (cervical, middle, and apical regions) after 5,000 thermocycles. The push-out bond strengths were determined and subjected to analysis of variance (α = 0.05). A stereomicroscope was used to observe the failure modes of the specimens. Results: The irrigation solution, root canal obturation technique, and root region had significant effects on bond strength (P 0.001). The completely obturated root canals showed significantly lower bond strength than the partially obturated root canals. The 2.5% NaOCl treatment produced the highest bond strength among the three irrigation solutions. Among the root regions, the cervical part showed significantly greater bond strength than the middle and apical parts. The most common failure mode was mixed failure. Conclusion: The partial root canal obturation technique provided better bond strength of the fiber post to intraradicular dentine. Irrigation with 2.5% NaOCl solution and phosphoric acid etching before cementation improved the push-out bond strength of the fiber posts to intraradicular dentine. Keywords: root canal obturation technique, post space irrigation, bond strength, dentine

Objective: To measure the fracture resistance of mandibular premolar roots following root canal instrumentation with different sizes. Methods: A total of 100 human permanent mandibular premolars with a straight single canal were decoronated and assigned to 10 groups (n = 10) by block randomisation. In the control group, the roots were uninstrumented, whereas roots in the nine experimental groups were instrumented to different master apical files (MAF) and tapers (MAF/taper): 40/0.05, 45/0.05, 50/0.05, 55/0.05, 60/0.05, 40/0.10, 40/0.15, 45/0.10 and 45/0.15. All roots were subjected to vertical loading until fracture. Results: Fracture load values for instrumented roots were lower than the intact roots of the control group. In 50/0.05, 55/0.05, 60/0.05, 40/0.15 and 45/0.15 groups, the fracture load values were significantly lower than the fracture load value for the control group (P 0.05) with a 30% decrease. No significant differences in the fracture modes were detected among the 10 groups (P > 0.05). Conclusion: Mechanical instrumentation adversely affects the fracture resistance of roots. When the roots of mandibular premolars were instrumented to a MAF equal to or larger than 50 with a taper of 0.05 or to a MAF of 40 or 45 with a taper of 0.15, the fracture load values significantly decreased. Keywords: tooth fractures, root canal preparation, mandibular premolars

Objective: To investigate the effects of nonsurgical periodontal therapy on the serum interleukin 6 (IL-6) and high-sensitivity C-reactive protein (hsCRP) and on the carotid artery in rats with chronic periodontitis (CP) and with or without hyperlipidemia (HL). Methods: A total of 29 Sprague-Dawley rats were randomly divided into two groups: group A (CP, n = 14) and B (CP + HL, n = 15), and subjected to the corresponding treatment. Groups A and B were further divided into groups A1/B1 (without periodontal interventions) and A2/B2 (with periodontal interventions). The serum IL-6 and hsCRP levels were evaluated before periodontal intervention and at 1, 3, 5, and 7 weeks after periodontal intervention. The rats were euthanised 8 weeks after the periodontal intervention and the histopathologic changes in the carotid artery were observed. Results: The serum hsCRP and serum IL-6 levels in groups A1 and B1 were elevated with time; they were significantly higher in group B1 than in group A1 (P 0.001) at all time points. The hsCRP and IL-6 levels in groups A2 and B2 increased with time and reached the maximum level 1 week after the second intervention, and then gradually decreased. Atherosclerotic plaques, fibrous cap, and calcium salt deposits were apparent in the rats of group B1, whereas no obvious atherosclerotic changes were observed in the rats of groups A2 and B2. Conclusion: Periodontal interventions resulted in acute, short-term systemic inflammation. However, it was beneficial in long-term as it improved the carotid artery integrity. Keywords: atherosclerosis, high-sensitivity C-reactive protein, interleukin 6, periodontal intervention, periodontitis