Chinese Journal of Dental Research, 03/2022

Objective: To investigate the synergistic changes of the astrocytes and neurons in the sensorimotor cortex during the process of implant osseointegration after insertion. Methods: A total of 75 rats were allocated into three groups (n = 25): non-operated, extraction and implant. The rats in the latter two groups underwent extraction surgery of three maxillary right molars. One month later, the implant group received one titanium implant in the healed extraction socket. The rats were sacrificed on days 1, 3, 7, 14 and 28 after implantation. The brain sections, including sensory centre S1 and motor centre M1, were selected for further immunofluorescence for measurement of the synergistic morphological and quantitative changes of astrocytes and neurons. Results: In layer IV of S1, the number of astrocytes in the implant group showed a descending trend with time; on days 1, 3, 7 and 14, the number of astrocytes in both the extraction group and the implant group was significantly higher than that in the non-operated group, and there was no difference between the extraction group and the implant group; however, on day 28, the number of astrocytes in the implant group was significantly lower than that in the extraction group. In layer V of M1, on days 7, 14 and 28, the number of astrocytes in the implant group was significantly lower than that in the extraction group; on days 14 and 28, the number of astrocytes in the extraction group was significantly higher than that in the non-operated group. In layer IV of S1 or layer V of M1, the number of neurons showed no significant changes between the three groups. Conclusion: The astrocytes in the face sensorimotor cortex were activated as a reaction to oral environment changes. This kind of neuroplasticity can be reversed by oral rehabilitation with dental implants. The motor cortex may be intimately related to osseointegration and osseoperception. Keywords: motor cortex, neuroplasticity, oral implant, osseointegration, sensory cortex

Objective: To investigate the differences between temporomandibular articular fossa bone surface and the envelope surface of the mandibular condyle movement. Methods: Thirty-four healthy adults underwent skull base and mandible scans using CBCT and performed mandibular border movement using the mandibular movement recording system. Landmarks of the fossa and tubercle were indicated and distance and angle parameters were measured on the 3D models reconstructed from the CBCT. The condyle movement envelope surfaces were formed according to models reconstructed from CBCT and the mandibular movement trajectory using computer simulation. The highest and lowest points of the envelope surface were indicated to create parameters. The data were analysed using a paired t test in SPSS (version 24.0, IBM, Armonk, NY, USA). Results: The mandibular fossa bone surface was statistically different to the envelope surface for the height of the first peak of the envelope surface (3.280 ± 1.319 mm) and depth of the mandibular fossa (6.338 ± 2.389 mm) (the ratio was 51.75%), the height of the second peak of the envelope surface (1.463 ± 0.745 mm) and the height of the tubercle (2.000 ± 0.968 mm) (the ratio was 73.15%), and the downwards angle of the envelope surface (25.933 ± 7.539 degrees) and the posterior slope angle of the articular tubercle (35.059 ± 5.224 degrees) (the ratio was 73.97%). Conclusion: The downwards angle of the envelope surface was statistically significantly smaller than the posterior slope angle of the articular tubercle, suggesting that the condyle movement is flatter than the mandibular fossa bone surface. Keywords: artificial fossa component, condyle movement, envelope surface, mandibular fossa bone surface, temporomandibular joint

Objective: To determine the prevalence, frequency and distribution of dental anomalies that were detectable on panoramic radiographs in a large sample Turkish population, and the associations among the anomalies. Methods: This study was conducted retrospectively on panoramic radiographs of 43,880 patients who were admitted to the Faculty of Dentistry at Trakya University, Edirne, Turkey. Patients’ files were examined by two observers and radiographic images of 2265 patients with at least one dental anomaly were included. Dental anomalies were classified as anomalies in the number, structure, position and shape of teeth. The interactions between the groups were analysed using chi-square tests. Results: The study group consisted of 1336 women (59%) and 929 men (41%) with a mean age of 33.3 ± 14.4 years. A total of 2265 patients, with a prevalence of 5.2% (2265/43880), had at least one dental anomaly. The most frequent anomalies were in position (2.7%) and number (2.1%). Structure anomalies were least common, affecting 0.02% of patients. Among the study group of patients with dental anomalies, 12.2% presented more than one kind of anomaly. Conclusion: Position anomalies were the most common dental anomaly, whereas structural anomalies were least common in a Turkish sample. The prevalence of anomalies varies between populations, confirming the role of racial factors. Keywords: fused teeth, impacted tooth, panoramic radiography, supernumerary tooth, tooth abnormalities.

Objective: To undertake a joint analysis of the influence of fracture width, dental thickness and distance of the fracture from the cortical bone on the radiographic diagnosis of vertical root fractures. Methods: Thirty-six uniradicular bovine teeth were endodontically treated and distributed into three groups according to the remaining root dentine thickness: 1.2 mm, 1.5 mm and 1.8 mm. Each group comprised 12 teeth, six with vertical root fracture and six without. Scanning electron microscopy (SEM) images of the fractured tooth groups were obtained and the fracture lines were measured. All specimens were inserted into bone defects created in bovine ribs, at different distances from the external cortical bone. Digital periapical radiographs were randomly evaluated by three blinded examiners (presence or absence of fractures). Results: The specificity for periapical radiography was found to be 89% and the accuracy rate was 57.4%. The mixed-model regression using the generalised estimating equation (GEE) model showed that the width of the fracture line and the thickness of the dental remnant play an important role in radiographic detection of vertical root fractures. There is a lower chance of correct diagnosis with fracture line widths < 0.2 mm (odds ratio [OR] 0.294, 95% confidence interval [CI] 0.103 to 0.836; P = 0.022) and tooth thicknesses < 1.2 mm (OR 0.342, 95% CI 0.157 to 0.747; P = 0.007). Conclusion: Fracture line widths < 0.2 mm and smaller root thicknesses lead to a less accurate diagnosis of vertical root fractures on periapical radiographs. Keywords: diagnosis, endodontically treated teeth, radiograph, vertical root fracture

Objective: To determine the impact of social support on perceived stress in Latin American and Caribbean dental students and dental practitioners during mandatory social isolation within the coronavirus (COVID-19) pandemic in 2020. Methods: A cross-sectional study was conducted with a sample of 1812 dental students and dental practitioners from 21 Latin American and Caribbean countries. Perceived stress was assessed using the perceived stress scale (PSS-14), and the influence of social support was addressed using the Duke-UNC-11. Additionally, sociodemographic variables, knowledge of and preventive behaviour against COVID-19 and health status were considered. A descriptive, bivariate and multivariate analysis was performed through multiple linear regression. Results: In the multivariate analysis, model 4 presented R2% = 21.20 (P < 0.001), a constant of 40.049; within the model, the social support variable had a non-standardised regression coefficient (b) of −4,527 (95% CI – 5.646 to −3,408; P < 0.001), the self-perceived level of concern regarding COVID-19 was b = 1.838 (95% confidence interval [CI] 0.887 to 2.790; P < 0.001), the self-perceived health status was b = −2.191(95% CI −2.944 to −1.437; P < 0.001), the number of days in compulsory isolation was b = −0.965 (95% CI −1.908 to −0.022; P = 0.045), while the level of confinement was b = 0.923 (95%CI: 0.106-1.740; P = 0.027), age was b = −1.743 (95% CI −2.625 to −0.860; P < 0.001), sex was b = 1.324 (95% CI 0.311 to 2.337; P = 0.011) and the economic income level was b = −1.539 (95% CI −2.434 to −0.644; P = 0.001). Conclusion: An association was determined between perceived stress and social support, as well as the variables of concern about the disease, self-perceived health status, number of days and level of confinement, age, sex and economic income level, based on the experience of dental practitioners and dental students in mandatory isolation. Keywords: coronavirus, dental practitioners, dental students, psychological stress, social support

Objective: To evaluate the accuracy of 10 intraoral scanners for single-crown and three-unit preparation models. Methods: A maxillary partially edentulous model was fabricated. A dental cast scanner was used to obtain standard tessellation language (STL) data. Ten intraoral scanners, namely Trios 2 (TR2; 3Shape, Copenhagen, Denmark), True Definition (TD; 3M, Saint Paul, MN, USA), CEREC AC Omnicam (OM; Dentsply Sirona, Charlotte, NC, USA), Organical Scan Oral (OS; R+K, Berlin, Germany), PlanScan (PS; Planmeca, Helsinki, Finland), DWIOP (DW; Dental Wings, Montreal, Canada), Xianlin (XL; Hangzhou Xianlin, Hangzhou, China), DL-100 (DL; Guangzhou Longcheng, Guangzhou, China), Trios 3 (TR3; 3Shape) and i500 (MD; MEDIT, Seoul, South Korea) were used to obtain stereolithography data as test groups. Trueness, precision and surface accuracy were evaluated by deviation analysis using 3D image processing software. One tooth with a three-unit preparation for each test group was registered with the reference scan data, and the absolute distance from another tooth was calculated as the absolute accuracy. The data were analysed using a Mann-Whitney U test and Dunn-Bonferroni test (α = 0.05). Results: The best trueness, precision and surface accuracy of scanning single crown preparation were recorded with TD (trueness 2.9 μm and precision 1.9 μm) and XL (surface accuracy 20.3 ± 2.9 μm). The best trueness, precision, surface accuracy and absolute accuracy of three-unit preparations were recorded with TD (2.6 μm), XL (1.9 μm), OM (27.1 ± 5.2 μm) and TR3 (79.2 ± 19.6 μm), respectively. There was no statistically significant difference in trueness between single- and multiple-unit preparations for any of the intraoral scanners (P > 0.05). A statistically significant difference in the surface accuracy between single and multiple preparations was found for TR2, TD, OM, DW, XL, DL and MD (P < 0.05). Conclusion: The trueness and precision of intraoral scanners for scanning three-unit preparations were nearly the same as those for single-crown preparations; however, with the exception of OS, PS and TR3, the surface accuracy of single-crown preparations was significantly better than that for three-unit preparations. Keywords: intraoral scanner, scanning accuracy, single crown preparation, surface accuracy, three-unit fixed denture preparation

Objective: To evaluate the prevalence of temporomandibular disorder (TMD) in dental faculty students in different years of education and investigate the relationship between TMD and oral habits or quality of life.  Methods: The Fonseca Anamnestic Index (FAI) questionnaire was used to determine the prevalence and severity of TMD, the Oral Behaviors Checklist (OBC) questionnaire served to determine the severity of harmful oral habits/parafunctions and the Oral Health Impact Profile-14 (OHIP-14) questionnaire was used to evaluate the quality of life in a total of 452 dentistry students (269 women and 183 men) in different years of education. Results: With regard to incidence of TMD, a total of 215 women had TMD (215/269, 79.9%), which was significantly higher than that in men (87/183, 47.5%) (P < 0.001). According to the OBC and OHIP-14 questionnaire results, harmful oral habits and quality of life showed a low to moderately significant correlation with TMD (P < 0.05). Conclusion: The Fonseca, OHIP-14 and OBC questionnaires allow early and inexpensive determination of oral habits that increase the prevalence of TMD. The prevalence of TMD in dentistry students at the clinical education stage is higher than those who have not progressed to the clinical education stage. Keywords: Fonseca questionnaire, oral behaviours checklist, oral health impact profile-14, temporomandibular disorder

Traditional techniques for fabricating interim, immediately loaded implant-supported full-arch prostheses are complex and time-consuming. The present study presents an efficient technique for fabricating interim prostheses with prefabricated multipurpose rigid connecting bars. This technique can minimise the misfit attributed to the polymerisation shrinkage of resin and expansion of the working cast, and simultaneously facilitate impression taking and occlusal records in one visit, thus reducing laboratory and chair time. Due to its ease of use and clinical efficiency, the present technique is considered particularly beneficial for immediate loading rehabilitation. Keywords: dental implant, full-arch, immediate loading, implant impressions, interim prostheses