Sixteen Cellular Senescence-associated DNA Methylation Signature Predicts Overall Survival in Patients with Head and Neck Squamous Cell Carcinoma.

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.

[Clinical comparative study of efficacy of Er:YAG laser for debonding different veneers].

PURPOSE: To compare the debonding time of IPS e.max CAD lithium disilicate glass-ceramic veneers in different thickness and transparency using Er:YAG laser, and evaluate the effect of Er:YAG laser on the surface topography of the veneers and the underlying tooth. METHODS: A total of twelve maxillary first premolar teeth were collected and prepared, then veneers were made by computer aided design and computer aided manufacture(CAD/CAM) system. The veneers were divided into four groups according to different thicknesses and transparency: e.max HT with 0.5 mm and 1.0 mm thickness, e.max LT with 0.5 mm and 1.0 mm thickness. Three veneers of each group were cemented to prepared premolar with resin cement and then stored in normal saline solution at room temperature for 7 days. All veneers were debonded with Er:YAG laser and the debonding time of all-ceramic veneers of all groups was recorded. Scanning electron microscopy(SEM) observation was performed to detect the surface topography of the veneers and the underlying tooth. SPSS 19.0 software package was used for statistical analysis. RESULTS: The debonding time of 1.0 mm-thick groups were longer than 0.5 mm-thick groups. When the veneer thickness was 0.5 mm, the average debonding time of e.max LT group was longer than e.max HT. Consistent with the finding of 0.5 mm, the longer debonding time was found in the e.max LT group of 1.0mm. No cracks and crater structure were found in SEM observation of veneers after Er:YAG laser irradiation. Teeth surface was covered with bonding cement with no signs of ablation or damage of the enamel. CONCLUSIONS: Er:YAG laser can completely debond lithium disilicate glass-ceramic veneers, and the debonding time depends on the transparency and thickness of the veneers. The lower translucent porcelain veneers (e.max LT) and thicker ones (1.0 mm-thick) had a longer debonding time. Moreover, Er:YAG laser does not damage the morphology and topography of the veneer and the teeth surface.

Validation of Digital Evaluation in Systematic Training on Tooth Preparation in Aesthetic Veneer Rehabilitation.

OBJECTIVE: To evaluate the outcome of systematic video training on tooth preparation in veneer restoration and the practicability of the application of the digital evaluation system of scan design and assessment software. METHODS: Ten residents were selected from a group enrolled on the first-year programme for the National Standard Training of Dentistry in the Department of Prosthodontics, College of Stomatology, Ninth People's Hospital Affliated with Shanghai Jiao Tong University, School of Medicine. First, each student prepared five teeth based on their knowledge and clinical experience, and then received systematic video training on veneer preparation. Before and after the training, the evaluation of the effects of training was conducted on the prepared teeth by measuring the continuity of the finishing line and tooth reduction amount automatically using the prepCheck 2.0 (Dentsply Sirona, Charlotte, NC, USA) CAD/CAM system. RESULTS: The results showed a significant difference in the quality of finishing line continuity pre- and post-training. Furthermore, the data for tooth reduction after training, which met standard values, improved remarkably, increasing from 32.40 ± 7.82% to 60.50 ± 5.48%. CONCLUSIONS: Video training could significantly enhance the quality of tooth preparation for veneers. Moreover, the digital evaluation system could serve as an ideal alternative for tooth preparation evaluation for preclinical students, offering new insights for clinical education.