Chinese Journal of Dental Research, 04/2023

Dentine is a major component of teeth and is responsible for many of their functions, such as mastication and neural sensation/transduction. Over the past decades, numerous studies have focused on dentine development and regeneration using a variety of research models, including in vivo, ex vivo and in vitro models. In vivo animal models play a crucial role in the exploration of biochemical factors that are involved in dentine development, whereas ex vivo and in vitro models contribute mainly to the identification of biophysical factors in dentine regeneration, of which mechanical force is most critical. In the present review, research models involved in studies related to dentine development and regeneration were screened from publications released in recent years and summarised comprehensively, particularly in vivo animal models including prokaryotic microinjection, Cre/LoxP, CRISPR/Cas9, ZFN and TALEN, and scaffold-based in vitro and ex vivo models. The latter were further divided by the interactive forces. Summarising these research models will not only benefit the development of future dentine-related studies but also provide hints regarding the evolution of novel dentine regeneration strategies. Keywords: dentine development, dentine regeneration, research models, scaffolding system, transgenic mice

Birth defects have always been one of the most important diseases in medical research as they affect the quality of the birth population. Orofacial clefts (OFCs) are common birth defects that place a huge burden on families and society. Early screening and prevention of OFCs can promote better natal and prenatal care and help to solve the problem of birth defects. OFCs are the result of genetic and environmental interactions; many genes are involved, but the current research has not clarified the specific pathogenesis. The mouse animal model is commonly used for research into OFCs; common methods of constructing OFC mouse models include transgenic, chemical induction, gene knockout, gene knock-in and conditional gene knockout models. Several main signal pathways are involved in the pathogenesis of OFCs, including the Sonic hedgehog (SHH) and transforming growth factor (TGF)-β pathways. The genes and proteins in each molecular pathway form a complex network to jointly regulate the formation and development of the lip and palate. When one or more genes, proteins or interactions is abnormal, OFCs will form. This paper summarises the mouse models of OFCs formed by different modelling methods, as well as the key pathogenic genes from the SHH and TGF-β pathways, to help to clarify the pathogenesis of OFCs and develop targets for early screening and prevention. Keywords: mouse models, orofacial clefts, Sonic hedgehog pathway, transforming growth factor-β pathway

Objective: To radiographically evaluate the effect of intact periosteum in guided bone regeneration (GBR) for the treatment of peri-implant ridge defects in posterior region. Methods: Twenty-eight patients who satisfied the criteria were included in this study. Buccal dehiscence defects were regenerated using demineralised bovine bone mineral (DBBM). Subjects were divided into two groups: the control group (conventional GBR, buccal trapezoidal flap and DBBM with collagen membrane coverage, n = 14) and the test group (modified GBR, buccal pouch and DBBM with collagen membrane coverage, n = 14). CBCT images obtained immediately after and 3 to 7 months following GBR were used to assess buccal bone thickness (BBT) at a level of 0, 2, 4 and 6 mm below the implant platform. Results: Immediately after surgery, BBT at 0 mm and 2 mm below the implant platform presented a significant difference between the two groups (P < 0.05) with significantly thicker buccal bone in the control group in terms of BBT-0 (3.83 ± 1.01 mm) and BBT-2 (4.88 ± 1.15 mm) than in the test group (2.33 ± 0.66 mm and 3.60 ± 1.10 mm, P = 0.000 and P = 0.008, respectively). After 3 to 7 months of healing, the BBT at all levels showed no significant difference between the two groups (P > 0.05), but more bone graft resorption (BBR) in the control group in terms of BBR-0 (2.45 ± 1.14 mm), BBR-2 (2.09 ± 0.94 mm) and BBR-0% (65.37% ± 26.62%) than the test group (BBR-0 1.07 ± 0.51 mm, P = 0.001; BBR-2, 1.22 ± 0.63 mm, P = 0.008; BBR-0% 45.70% ± 15.52%, P = 0.024). Conclusion: In the short term, all treatment modalities achieved similar coronal BBT and the intact periosteum had a positive effect on keeping ridge dimensions even. Keywords: alveolar ridge augmentation, bone regeneration, CBCT, dental implants

Objective: To construct a cellular senescence–related DNA methylation model to act as an independent prognosis predictor for patients with head and neck squamous cell carcinoma (HNSCC). Methods: Methylome, transcriptome and clinical information for 499 HNSCC patients were received from The Cancer Genome Atlas (TCGA) as a training set. An extra independent methylation dataset of 54 patients with oral squamous cell carcinoma (OSCC) was downloaded from the NCBI Gene Expression Omnibus (GEO) database as the validation set. To assess the cellular senescence level of each sample, the senescence score (SS) of each patient was calculated using the transcriptome data via single-sample gene set enrichment analysis (ssGSEA). Least absolute shrinkage and selection operator (LASSO) Cox regression analyses were conducted to confirm Cytosine, phosphoric acid and Guanine (CpG) sites for the development of a cellular senescence–related DNA methylation signature. Results: Based on the SS of each HNSCC patient in the TCGA cohort, the patients were divided into high- and low-SS subgroups. The high-SS group showed a better prognosis than the low-SS group. Moreover, 3,261 differentially methylated CpG sites (DMCs) were confirmed between the two groups. Among them, 16 DMCs were included to develop a 16-DNA methylation signature for evaluation of HNSCC prognosis using LASSO and multivariate Cox regression analysis. Conclusion: A novel cellular senescence–related 16-DNA methylation signature was determined, which can be used as an independent index to evaluate the prognosis of HNSCC patients and select appropriate treatment strategies. Keywords: cellular senescence, diagnostic predictor, DNA methylation signature, head and neck squamous cell carcinoma, oral squamous cell carcinoma

Objective: To compare calcium silicate–based endodontic sealer and epoxy resin–based sealer remnants on root canal walls after post space preparation and their influence on the bond strength of fibre posts fixed with a dual-cured resin cement. Methods: Thirty-six extracted single-root mandibular premolars were instrumented and divided randomly into two equal groups with different endodontic sealers. iRoot SP (Innovative BioCeramix, Vancouver, Canada) was employed in the experimental group and AH Plus (Dentsply Sirona, Charlotte, NC, USA) was used in the control group. Sealer remnants were observed under an endodontic microscope after root canal therapy and post space preparation. Fibre posts were fixed with dual-cured resin cement. Specimens were taken at each third of the post space. The push-out bond strength was measured using a universal testing machine and fracture modes were assessed. Statistical analysis was performed using an independent samples t test and one-way analysis of variance. Results: There was no statistically significant difference in bond strength of fibre posts between the control and experimental group (P > 0.05); however, sealer remnants were observed in 38.9% of the samples treated with iRoot SP and none of the samples treated with AH Plus. The major fracture mode in samples treated with iRoot SP was adhesive failure between the resin cement and the post, and no adhesive failure between the resin cement and dentine occurred at the site of the sealer remnant. The presence of iRoot SP remnants on the root canal walls after post space preparation did not interfere with bonding. Conclusion: iRoot SP is a viable option for root canal obturation before fibre post cementation. Keywords: AH Plus, bond strength, calcium silicate–based sealer, endodontic sealer, fibre post, iRoot SP

Objective: To evaluate the effects of powered and manual tooth brushing on gingival inflammation in a Chinese population with mild to moderate gingivitis. Methods: The present randomised, single-blind, parallel clinical trial was conducted in five cities in China. Generally healthy participants aged 18 to 65 years, who were non-smokers and had at least 20 sites of gingival bleeding, were included as eligible subjects. The subjects were randomly assigned to either the powered tooth brushing (PTB) group or standard manual tooth brushing (MTB) group. All subjects were supplied with a fluoride-containing toothpaste, Gingival Bleeding Index (GBI), Modified Gingival Index (MGI) and the Turesky modification of the Quigley-Hein Plaque Index (MPI) were used to evaluate the outcomes. Results: A total of 235 subjects completed the study, 118 in the PTB group and 117 in the MTB group. The mean age and sex distribution for the PTB and MTB groups were 34.40 ± 9.99 years, 89 women and 29 men, and 34.20 ± 10.14 years, 82 women and 35 men, respectively. After 6 months, the percentage decrease in MGI was 26.150% ± 26.897% for the PTB group and 14.768% ± 38.544% for the MTB group (P = 0.0092). Statistically significant differences between types of tooth brushing were also observed at 6 months for GBI, and at all time points for MPI. Conclusion: Tooth brushing with a powered toothbrush twice a day was shown to be more effective than use of a manual toothbrush in reducing gingival inflammation, gingival bleeding and surface plaque after a 6-month period. Both kinds of toothbrushes were safe for the oral tissues. Keywords: dental hygiene, gingivitis, oral hygiene, public health

Renal cell carcinoma (RCC) is often diagnosed in advanced stages and a third of patients have distant metastasis at diagnosis. Metastasis may be the first evidence of clear cell RCC in many cases. RCC most often metastasises to the lung, liver, bone, brain and thyroid; however, metastatic disease to the oral cavity, especially the mandible, is rare. The purpose of this study is to report a case of clear cell RCC metastatic to the mandible and review the literature. The mandible lesion underwent radical excision in this case. Notably, no metastatic lesions were detected in the lungs and liver in this patient until 15 months after the mandibulectomy. The patient lived for around 2.5 years after the diagnosis of RCC. Keywords: mandible, mandibular metastasis, renal cell carcinoma (RCC)

Oral submucous fibrosis (OSF) is a chronic, progressive and potentially malignant oral mucosal disease. Patients often have a habit of chewing betel nuts. Areca catechu has been listed as a Class 1 carcinogen by the International Agency for Research on Cancer (IARC), and its main active component, arecoline, is classified as a Group 2B carcinogen by the IARC. The World Health Organization (WHO) categorises OSF as an oral potentially malignant disorder (OPMD). The present guideline describes the risk factors, clinical symptoms and clinical signs of OSF. Clinical staging, auxiliary examination methods, basis for diagnosis and differential diagnosis and the need to improve bad lifestyle habits are proposed and addressed, and local treatment drugs, therapies, dosage and course of treatment, possible adverse reactions, and oral treatment drugs, dosage and course of treatment are proposed. The guideline also addresses the indications for surgical treatment, alternative non–drug treatment methods, selection of treatment plans for different clinical stages, criteria for efficacy evaluation, and preventive measures. Keywords: carcinogenic, chewing betel nut, oral potentially malignant disorders, oral submucous fibrosis, risk factors