Chinese Journal of Dental Research, 02/2021

The endoplasmic reticulum has emerged as a modulator that is essential for cellular homeostasis and human health. It is an extensive membranous organelle that acts as a hub for the physiological and pathological processes. In recent years, it has become a topic of interest in studies on the relationship between endoplasmic reticulum homeostasis and system diseases. Periodontal disease is a prevalent chronic disease that affects tooth-supporting tissues, initiated by the interaction between pathogenic bacterial infection and immune defence and resulting in tooth loss. The endoplasmic reticulum participates in the responses to the fluctuating microenvironments in periodontal pathogenesis and regulates periodontal homeostasis. In this review, we present an overview of the significance of endoplasmic reticulum regulation as a multidimensional mediator in periodontal disease and highlight the potential strategies for periodontal regeneration. Keywords: endoplasmic reticulum, periodontal disease, periodontal regeneration

Wnt signalling pathways have been the focus of intense research activity for decades due to their fundamental role in skeletal and dental development. Wntless, an exclusive chaperone protein for the exocytotis of Wnt ligands, was identified in 2006. In the last decade, the molecular biological studies of Wntless and its genetic studies in human and mice have highlighted the importance of this protein in mineralised tissues, including bone, cartilage and teeth. This article reviews recent developments and discrepancies in the role of Wntless in skeletal and dental development based on mutant phenotypes, as well as the underlying mechanism involved in its molecular and physiological regulation. We conclude that, though some controversial phenotypes exist due to different Cre line resources, Cre recombinase activity and detection time points, Wntless undeniably exerts a context- and stage-dependent regulatory function during the development and homeostasis of both skeletal and dental tissue. Keywords: odontogenesis, osteogenesis, Wnt signalling, Wntless

Objective: To estimate the prevalence and distribution of tooth wear among groups of adolescents and adults in Shanghai, China through an epidemiological survey, and explore the associated factors. Methods: Multistage, stratified, constant volume and cluster sampling methods were used in an epidemiological survey conducted in Shanghai in 2014. The basic erosive wear examination (BEWE) index was used to screen for tooth wear in different age groups: 12 years, 15 years, 18 to 35 years, 36 to 49 years and 50 to 74 years. A previously published questionnaire collected information including dietary habits, oral hygiene habits and general conditions. Results: This survey reports the results for 1806 participants in Shanghai. The prevalence of tooth wear was 59.7% in adolescents (BEWE ≥ 1) and 93.1% in adults (BEWE ≥ 2). The prevalence and severity of disease increased with age (P < 0.01). The teeth most susceptible to wear were the central incisors and first molars. Multivariate analysis of covariance (ANCOVA) results showed that soft drinks, alcoholic drinks, pickled vegetables and hard food, gastroesophageal reflux disease (GERD), xerostomia and poor tooth brushing habits were statistically correlated with tooth wear in different age groups. Conclusion: The prevalence of tooth wear appears to be high in adolescents and adults in Shanghai. Frequent consumption of soft or alcoholic drinks, GERD, xerostomia and poor tooth brushing habits were positively associated with tooth wear in different age groups. Keywords: adolescents, adults, basic erosive wear examination index, epidemiological survey, tooth wear

adolescents aged 12 to 15 years based on the 4th National Oral Health Survey and to explore its associated factors. Methods: Students aged 12 to 15 years were recruited using to a multistage stratified random sampling method. All the subjects received oral examination and completed a questionnaire. Information relating to OHRQoL was collected through a Mandarin version of the child oral impacts on daily performances (Child-OIDP) questionnaire. The relationship between the Child-OIDP scores and independent variables was assessed using a Mann-Whitney U-test, Kruskal-Wallis test and a multivariate Poisson regression. Results: A total of 89,582 subjects were included in the analysis, of whom 76.6% reported oral impacts in the last 6 months. Eating was the most affected daily performance. The results of the regression analysis showed that factors associated with adolescents’ OHRQoL included sex, location of residence, region, only child status, parents’ level of education, frequency of sugar consumption, self-perception of general/oral health, dental appointments in the past 12 months, oral health knowledge status, age, decayed, missing and filled teeth (DMFT) index and number of teeth with gingival bleeding. Conclusion: Oral impacts were common among Chinese adolescents, although most were not so severe. Eating was the most commonly affected performance. Sex, location of residence, region, only child status, parents’ level of education, frequency of sugar consumption, selfperception of general/oral health status, dental appointments in the previous 12 months, oral health knowledge status, age, DMFT index and number of teeth with gingival bleeding were found to be associated with OHRQoL. Keywords: adolescents, associated factors, child OIDP, China, oral health–related quality of life

Objective: To compare the efficiency of a new sonic powered irrigation system named EDDY (VDW, Munich, Germany), passive ultrasonic irrigation (PUI) and conventional needle irrigation (CNI) in root canal sealer penetration. Methods: A total of 45 mandibular premolars were instrumented up to size 30, 0.9 taper and randomly divided into three groups (n = 15) depending on the final irrigation activation technique: EDDY, PUI or CNI. After the final irrigation procedures, the root canals were obturated with labelled sealer mixed with 0.1% rhodamine B. Transverse sections at 3, 5 and 7 mm from the root apex were examined using confocal laser scanning microscopy. The maximum depth and total area and percentage of sealer penetration were measured using ImageJ analysis software (National Institutes of Health, Bethesda, MD, USA). Results: In the EDDY group, the penetration depth was higher compared to the CNI group in the apical and middle sections and compared to the PUI group in the apical section (P ˂ 0.05). The penetration area in the EDDY group was higher compared to the CNI group in all sections and compared to the PUI group in the coronal section (P ˂ 0.05). The percentage of penetration was higher in the EDDY group compared to the CNI group in all sections and compared to the PUI group in the coronal section (P ˂ 0.05). Conclusion: In the present study, sealer penetration was superior in the EDDY group than the CNI group in the apical section. In the middle and coronal sections, sealer penetration was similar for the EDDY and PUI groups. Keywords: EDDY, passive ultrasonic irrigation, sealer penetration, sonic irrigation

Objective: To evaluate the microshear bond strength (μSBS) of resin cement to a lithium disilicate glass ceramic conditioned with different surface treatment procedures. Methods: Crystallised slices of lithium disilicate glass ceramic were randomly divided into five groups (n = 10) according to different surface treatment procedures: the no surface treatment (NT) group was untreated; the hydrofluoric acid (HF) group was conditioned with 4.5% HF; the silane (S) group was conditioned with a silane coupling agent; the hydrofluoric acid and silane (HFS) group was conditioned with HF followed by the silane coupling agent; and the Monobond Etch & Prime (MEP) (Ivoclar Vivadent, Schaan, Liechtenstein) group was conditioned with the one-step self-etching primer MEP. Resin cement was applied to the ceramic surfaces and irradiated. A μSBS test was performed. Failure analysis, surface roughness tests, surface topography examination and elemental analysis were also conducted. The data were analysed with a one-way analysis of variance (ANOVA) and Tukey honestly significant difference test (P < 0.05). Results: The MEP group resulted in comparable μSBS to the HFS group (16.9 ± 4.3 MPa and 16.0 ± 2.2 MPa, respectively), but a significantly higher μSBS than the NT (1.0 ± 0.9 MPa), HF (8.9 ± 3.9 MPa) and S (12.6 ± 2.5 MPa) groups. Adhesive failure was mainly observed in the NT and HF groups, while the S, HFS and MEP groups demonstrated the most mixed failure. Though micrographs revealed a roughened surface in the HF group, no significant difference was found with any other groups. Conclusion: Within the limitations of this study, it can be concluded that the μSBS of resin cement to lithium disilicate glass ceramic etched with MEP is as efficient as that treated with HF and silane. Keywords: bond strength, lithium disilicate glass ceramic, self-etching primer, surface treatment

Objective: To compare the reduction of residual dentine thickness of two different post preparation methods on the mandibular second molars with a C-shaped root canal configuration. Methods: A total of 26 extracted right mandibular second molars with a C-shaped root canal configuration were selected and paired based on similar canal morphology. Each of the paired teeth was randomly allocated to the heat and ultrasonic instruments group (HU group) or Peeso Reamer (Mani, Utsonomiya, Japan) group (PR group) (n = 13) and received post preparation with different instruments after the same endodontic treatment. The reduction of residual dentine thickness and the minimal remaining dentine thickness at the apical sections at 4 or 7 mm below the cementoenamel junction (CEJ) were recorded. The data were analysed using an independent samples t test (α = 0.05). Results: The reduction of residual dentine thickness for the HU group was less than that for the PR group in the two sections. Moreover, at the section 7 mm below the CEJ, the teeth reduction of the distolingual wall in the HU group (0.022 ± 0.007 mm) was significantly lower than that in the PR group (0.101 ± 0.013 mm) (P < 0.01). Conclusion: Using heat and ultrasonic instruments to perform post preparation could follow the original canal configuration to save more tooth structure in the remaining root canal wall, minimise the reduction of residual dentine thickness and decrease the incidence of root canal perforation. Keywords: C-shaped canal, mandibular second molars, post preparation, teeth reduction