Chinese Journal of Dental Research, 02/2022

The ultimate goal of periodontal treatments is the regeneration of all lost periodontal tissues including bone, cementum and the periodontal ligament (PDL). Until now, the clinical methods for periodontal regeneration have been associated with significant failure or incomplete success. Various studies have reported the promising effects of growth factors/cytokines on periodontal regeneration. Growth factors/cytokines include proteins or steroid hormones that bind to cellular receptors, known as signalling molecules, and that trigger cellular responses that eventually stimulate cell proliferation and differentiation. The present review aims to provide an overview of the main growth factors that play an important role in and have been used in the regeneration of periodontal components. Keywords: growth factors, cementogenesis, osteogenesis, periodontal regeneration, stem cells

Objective: To compare the sequential healing of maxillary sinuses grafted with two different xenogeneic bone substitutes processed at either a low (300°C) or high (1200ºC) temperature. Methods: A sinus augmentation procedure was performed bilaterally in 20 rabbits and two different xenogeneic bone grafts were randomly used to fill the elevated spaces. Healing was studied after 2 and 10 weeks, in 10 rabbits during each period. Results: After 2 weeks of healing, very small amounts of new bone were observed in both groups, and were mainly confined to close to the sinus bone walls and osteotomy edges. After 10 weeks of healing, new bone was found in all regions, with higher percentages in those close to the bone walls and to the osteotomy. In this period of healing, the proportion of new bone in the 300°C group was 20.0% ± 4.3%, and in the 1200ºC group it was 17.2% ± 4.3% (P = 0.162). In the 1200ºC group, translucent, dark fog-like shadows in regions of the grafts were hiding portions of new bone (interpenetrating bone network). Conclusion: Both biomaterials provided conditions that allowed bone growth within the elevated space, confirming that both biomaterials are suitable to be used as a graft for sinus floor augmentation. Keywords: animal study, bone healing, histology, sinus floor augmentation, sinus membrane

Objective: To investigate the composition and abundance of candidate phyla radiation (CPR) in the oral cavity in caries patients and a healthy population. Methods: The raw macrogenomic sequencing data for a total of 88 subjects were downloaded from the National Centre for Biotechnology Sequence Read Archive (NCBI SRA) public database according to the public data usage specifications. Trimmomatic (Department for Metabolic Networks, Potsdam, Germany) and Bowtie 2 (University of Maryland, College Park, MD, USA) were used to quality control and dehost the host sequences. Species annotation was made using Kraken2 (Johns Hopkins University, Baltimore, MD, USA) and Bracken (Johns Hopkins University) based on the reference database. According to the results of the species annotation, the species-significant differences and species correlation of caries and healthy oral microbiota in species composition and microbiota diversity were analysed to study the distribution and abundance differences of CPR in the oral environment. Results: Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria and Fusobacteria were the main components. The relative abundance of TM7 (Candidatus Saccharibacteria) and GN02 (Candidatus Gracilibacteria) of CPR is second only to the aforementioned five bacteria, indicating that CPR is an important part of the oral microbiota. TM7 and GN02 were common to both the caries patients and healthy patients and were detected in all samples, suggesting that CPR is the ‘core microbiome’. There was a correlation between CPR and a variety of oral microbiota, among which the positive correlation with Capnocytophaga was the strongest, suggesting that Capnocytophaga might be the potential host bacteria of CPR. Conclusion: CPR is an indispensable part of the oral microbiota. It is the ‘core microflora’ of the oral cavity and may play an important role in the stability and function of the oral microecological environment. Capnocytophaga may be the potential host bacteria of CPR. Keywords: candidate phyla radiation, caries, core microbiome, metagenomics, oral microbiota

Objective: To assess the accuracy of transfer learning models for age estimation from panoramic photographs of permanent dentition of patients with an equal sex and age distribution and provide a new method of age estimation. Methods: The panoramic photographs of 3000 patients with an equal sex and age distribution were divided into three groups: a training set (n = 2400), validation set (n = 300) and test set (n = 300). The ResNet, EffiecientNet, VggNet and DenseNet transfer learning models were trained with the training set. The models were subsequently tested using the data in the test set. The mean absolute errors were calculated and the different features extracted by the deep learning models in different age groups were visualixed. Results: The mean absolute error (MAE) and root mean square error (RMSE) of the optimal transfer learning model EfficientNet-B5 in the test set were 2.83 and 4.59, respectively. The dentition, maxillary sinus, mandibular body and mandibular angle all played a role in age estimation. Conclusion: Transfer learning models can extract different features in different age groups and can be used for age estimation in panoramic radiographs. Keywords: age estimation, deep learning, forensic odontology, panoramic radiograph, transfer learning

Objective: To evaluate the change in demineralisation depth (DD)and mineral density (MD) over time in primary teeth exposed to a demineralisation protocol with microcomputed tomography (microCT). Methods: Caries lesions were artificially induced on the labial surfaces of 9 primary incisors by way of a demineralisation protocol using 0.1 M lactic acid with 10% methylcellulose gel for 7 and 14 days. The specimens were scanned with microCT and CTAn software (Bruker, Billerica, MA, USA) was used to analyse the changes in DD and MD. Statistical analyses were performed using SPSS software (IBM, Armonk, NY, USA). Repeated analysis of variance (ANOVA) test and Pearson bivariate correlation were used and the level of significance was set at P < 0.05. Results: The DD ranged from 0.00 to 0.99 μm (mean ± standard deviation [SD] 0.70 ± 0.43 μm) at baseline, 11.18 to 29.5 μm (18.15 ± 5.23 μm) at 7 days and 18.00 to 55.30 μm (34.20 ± 8.70 μm) at 14 days. The MD for all specimens (n = 9) ranged from 1.48 to 1.76 g/cm3 (1.65 ± 0.08 g/cm3) at baseline, from 1.47 to 1.74 g/cm3 (1.62 ± 0.08 g/cm3) at 7 days demineralisation and 1.33 to 1.72 g/cm3 (1.54 ± 0.13 g/cm3) at 14 days. There were statistically significant differences in DD (P < 0.001) and MD (P = 0.016) between different durations of demineralisation. Conclusion: DD and MD change with time after being exposed to demineralising solution. MicroCT is a nondestructive method that allows repeated MD evaluations of the same sample. Keywords: demineralisation, lesion depth, microcomputed tomography, mineral density, primary teeth

Objective: To investigate the relationship between chewing sugar-free gum (SFG) and dental caries status in China. Methods: A total of 860 teenagers (aged 12 to 15 years) and 490 adults (aged ≥ 18 years) were recruited using a multistage stratified cluster method from economically developed areas (Beijing, Guangdong) and less economically developed areas (Hubei, Xinjiang). Each participant completed a questionnaire including oral health-related knowledge of SFG and chewing habits of SFG and agreed to undertake a clinical assessment. Potential factors associated with chewing conditions were analysed through a chi-square statistical test. A negative binominal regression analysis was performed to quantify the relationship between dental caries and consumption of SFG. Results: The overall percentage of the survey population who consumed SFG was 43.4%, and SFG-related knowledge and awareness was only 19.4%. For decayed, missing and filled permanent teeth (DMFT), the mean value was 1.63 ± 2.41 and 2.29 ± 3.65 in the chewing group and non-chewing group, respectively. According to the negative binominal regression analysis, the caries status in the SFG chewing group was better than in the non-chewing group (adjusted prevalence rate ratio [PRR] 0.73; 95% confidence interval [CI] 0.62–0.87). Conclusion: The chewing condition and oral health-related knowledge and awareness of SFG is low. Chewing SFG is related to a better dental caries status, so regular consumption of SFG should be recommended when promoting oral health. Keywords: caries prevention, China, sugar-free gum

Objective: To gather the available scientific evidence about the oral health of migrants in south-south contexts. Methods: A scoping review methodology was applied through a comprehensive search in databases of scientific and grey literature: PubMed/Medline, Scopus, LILACS, EMBASE, Google Scholar and the International Centre for Migration, Health and Development. A descriptive analysis of the characteristics of the selected studies was conducted. Results: The search yielded 23 papers. Seventeen studies (17/23, 73.9%) were conducted on the Asian continent and 91.3% (21/23) were cross-sectional. Studies were focused on oral health problems such as dental caries and periodontal disease with diverse findings when comparing immigrants with natives. Some studies found poor oral health indexes in migrants. Migrants face barriers to dental health services. Other oral health variables addressed in the studies were oral health–related quality of life, beliefs, knowledge and practices in oral health. Determining factors related to oral health were evidenced, such as migration status, sociodemographic, cultural, psychological, living, economic and material conditions, social support, oral health practices and previous oral and general health status. Studies reported conceptual and methodological gaps and limitations that must be considered when interpreting the results. Conclusion: According to the scientific evidence, immigrant populations in south-south migratory contexts show poor oral health indicators, and this translates into social vulnerability in this group. Further research is needed to increase the scientific body about the social and contextual determinants in oral health and understanding of the social construction of this phenomenon. Keywords: dental health services, emigrants, immigrants, oral health

Dental implants are widely used in the rehabilitation of patients with edentulous jaws caused by periodontitis. The success of implants is closely related to their framework material and patients’ periodontal health. Polyetheretherketone (PEEK) is a kind of high polymer material that has broad prospects as the framework for full-arch dental prostheses, but long-term follow-up data are lacking. The present clinical report demonstrates the use of a PEEK framework for the construction of an implant-supported full-arch fixed dental prosthesis for a patient diagnosed with periodontitis. With the guidance of biological width, a provisional retained restoration was achieved to create the emergence profile, resulting in a 3D printed PEEK framework with good aesthetics and biological functions. Keywords: gingival modification, high polymer framework, implant-supported fixed prosthesis, staged extraction