Shigaku = Odontology

This study investigated the prevalence and distribution of anomalies of permanent dentition in the current Japanese population by examining an unbiased sample. We conducted a survey of dental anomalies by mass dental screening at eight high schools in 2012. Participants were all students with permanent dentition. Dental anomalies were classified as hypodontia, supernumerary teeth, peg-shaped teeth, fused teeth, and talon cusps. Students with one or more dental anomalies on oral examination were given a differential diagnosis by three specialists. The final sample comprised 9584 participants (5062 boys, 4522 girls). Hypodontia was present in 372 students (3.88 %) with no significant sex difference (191 boys, 181 girls). Frequent sites were the right or left mandibular second premolar, right or left maxillary second premolar, and right or left maxillary lateral incisor. Supernumerary teeth were observed in three boys (0.06 %) and one girl (0.02 %). Peg-shaped teeth were observed in 74 students (0.77 %; 27 boys, 47 girls), differing significantly between sexes; they were most prevalent among maxillary lateral incisors. Of affected students, 18 students (0.19 %) also had hypodontia (3 boys, 15 girls). Fused teeth were present in two boys (0.04 %) and three girls (0.07 %) (gemination in one boy and fusion in the remaining four students). Sites were limited to maxillary and mandibular central and lateral incisors. Talon cusps were observed in two boys (0.04 %) and four girls (0.09 %). The present survey of a large unbiased sample can be considered to reflect the prevalence and distribution of anomalies of permanent dentition in the current Japanese population.

This study aims to evaluate the effects of etching with sulfuric acid (SA) and vinyl sulfonic acid (VSA) on the bond strength between a light-curing indirect resin composite and polyetherketoneketones (PEKK). PEKK specimens were ground with 600 silicon carbide papers, etched with 90% SA for 5 s (90-5 SA) or 95% VSA for 30 s (95-30 VSA), and then modified with a phosphate primer; afterward, a light-curing resin composite was veneered on the specimens. Two control groups were also prepared without etching (unetched/unprimed and unetched/primed). After 20,000 thermocycles in water at 4 and 60 °C, the shear bond strengths of the specimens were determined and subjected to a nonparametric (Steel–Dwass) test (α = 0.05, n = 8). The etched surfaces were observed by scanning electron microscopy (SEM) at 2000× magnification. Higher bond strengths were obtained when the PEKK surface was etched with 90-5 SA or 95-30 VSA (90-5 SA/unprimed 24.3 ± 4.3 MPa, 90-5 SA/primed 26.2 ± 3.2 MPa, 95-30 VSA/unprimed 23.7 ± 2.5 MPa, 95-30 VSA/primed 24.3 ± 4.1 MPa), and these values were not statistically different, whereas the two control groups exhibited significantly lower bond strengths (unetched/unprimed 12.2 ± 1.7 MPa, unetched/primed 9.5 ± 2.7 MPa). SEM observations revealed that 95-30 VSA led to a microporous (felt-like) surface, which was different from the surface structure etched with 90-5 SA. Etching the PEKK surface with SA or VSA significantly improved the bond strength between resin composite and PEKK in contrast with the application of the phosphate primer. Appropriate chemical etching could be a useful option when fabricating prostheses using PEKK-based materials and indirect resin composites.

The purpose of this clinical trail was to assess the clinical behavior of posterior composite restorations supported by a substantial foundation of flowable short fiber-reinforced composite SFRC (everX Flow, GC, Japan) used without proximal surface coverage with particulate filler resin composite (PFC). Seventy patients (20 males, 50 females; mean age: 30 ± 10 years) were randomly enrolled in this trial. Patients received direct restorations of either SFRC covered only on the occlusal surface (1–2 mm) by conventional PFC composite (G-ænial Posterior, GC), or plain conventional PFC composite without fiber-reinforcement, in Class II cavities in premolar and molar vital teeth. One operator made all restorations using one-step, self-etch bonding agent (G-ænial Bond, GC) according to manufacturers’ recommendations. Two blinded trained operators evaluated the restorations at baseline, at 6, 12 and 18 months using modified USPHS criteria. Results indicated that, in both groups and at different follow-up intervals, according to evaluated criteria, restorations were rated mostly with best score (Alpha) (p > 0.05). For the marginal integrity after 6 months, a single case in the intervention [increased to 3 (8.8%) after 18 months] and 3 (9.7%) cases of the control group [increased to 4 (12.9%) after 18 months] had Bravo score but with no significant difference (p > 0.05). For color match measured after 6 and 18 months, three (8.8%) cases had Bravo score in the intervention group. The use of flowable SFRC composite without any PFC surface coverage proximally in Class II restorations demonstrated satisfactory clinical outcome throughout the 18-month follow-up.

The aim of this study was to investigate the effect of two different priming agents and/or sandblasting on the shear bond strength of self-adhesive resin cement to the resin composite for core build-up to CAD/CAM blocks. A CAD/CAM ceramic block (GN I CERAMIC BLOCK, GC) and a CAD/CAM resin composite block (CERASMART 270, GC), a self-adhesive resin cement (G-CEM ONE, GC) and two different primers, i.e., a multipurpose primer (MP; G-Multi Primer, GC) and a ceramic primer (CP; Ceramic Primer II, GC), were examined. Five different surface treatments with priming and/or sandblasting and no surface treatment (control) were performed on the block. Disk specimens (6 mm in diameter and 4 mm in thickness) made from core composites were cemented to the blocks after the surface treatments. Then, the 24-h shear bond strength of the resin cement between the block and the resin composite core was determined (n = 15). Sandblasted specimens had greater bond strength than controls for both blocks (p < 0.05). Priming to both blocks significantly increased the bond strength of resin cement compared to that of controls (p < 0.05). Although Weibull moduli were not significantly changed among all surface treatments for both blocks, the strengths with 5% and 95% failure probability of sandblasted and/or primed blocks were estimated to be greater than those of controls. The combination of priming and sandblasting to the CAD/CAM composite and ceramic surface was effective in increasing the bond strength of the resin cement.

Emerging evidence suggests the use of less invasive therapy such as pulpotomy in treating permanent teeth with pulp exposure and signs of pulpitis. Hence, this umbrella review aims to evaluate the available systematic reviews on pulpotomy treated permanent teeth. Articles published between January 1970 and May 2021 were searched in ten electronic databases and five textbooks. Only systematic reviews published in English that examined the use of pulpotomy on either carious or traumatic pulpal exposed in mature or immature permanent teeth with signs of pulpitis were selected. The Corrected Covered Areas (CCAs) were calculated to identify the overlap in primary studies, whereas the AMSTAR 2 assessment tool was used to analyze the risk of bias in each included review. Nine systematic reviews were chosen of which two systematic reviews focused solely on coronal pulpotomy, one on partial pulpotomy, and the remaining focused on both coronal and partial pulpotomies. Overall, only two reviews were rated as ‘High Quality’. Umbrella analyses showed that both coronal and partial pulpotomies revealed overall high success rates ranging from 88.5% to 90.6%. However, the currently available evidence on the effects of different pulpal medicaments and restorative materials on the success rate of pulpotomy were still inconclusive. Pulpotomy can be regarded as a promising modality in treating mature and immature permanent teeth with carious pulpal exposure or signs of pulpitis. Nonetheless, further high-quality clinical trials with long-term follow-up and better control of confounding factors are warranted in the future.

The aim of this systematic review (SR) compared the effect of xenogeneic collagen matrix (XCM) vs. connective tissue graft (CTG) for the treatment of multiple gingival recession (MGR) Miller Class I and II or Cairo type I. Five databases were searched up to August 2022 for randomized clinical trials (RCTs) comparing the clinical effects of XCM vs. CTG in the treatment of MGR. The random effects model of mean differences was used to determine reduction of gingival recession (GR), gain in keratinized tissue width (KTW), gain in gingival thickness (GT) and gain in clinical attachment level (CAL). The risk ratio was used to complete root coverage (CRC) at 6 and 12 months. 10 RCTs, representing 1095 and 649 GR at 6 and 12 months, respectively, were included in this SR. The meta-analysis showed no statistically significant difference in GR reduction, KTW gain GT gain or CAL gain between groups at 6 months. However, at 12 months of follow-up, differences favoring the control group were observed (p < 0.05). CRC was significantly higher in the CTG group at 6 and 12 months. Regarding dentine hypersensitivity (DH), no statistically significant differences were found between groups at 6 and 12 months of follow-up (p < 0.05). At 12 months, CTG showed significantly superior clinical results in the treatment of MGR: however, this difference was not observed in the decrease of DH.

It is widely accepted that fibrosis is frequently observed in the gingiva of smokers. However, the mechanisms by which smoking results in pathological changes in periodontal tissue that lead to fibrosis are not entirely clear. Our former report showed that type I collagen synthesis was promoted by nicotine via CCN family protein 2 in human periodontal tissue cells. Here, we evaluated other aspects of nicotine function from a viewpoint of extracellular matrix (ECM) remodeling. Human gingival fibroblasts (n = 4) and periodontal ligament cells (n = 3) were isolated. The cells were treated with nicotine at a variety of concentrations for 12–48 h. Modulators of matrix remodeling were measured using enzyme-linked immunosorbent assays. Cell migration and morphology were also evaluated. As a result, following treatment with 1 μg/ml nicotine, tissue inhibitor of metalloproteinase-1 and transforming growth factor-β1 production in both cell lysates and supernatants, and matrix metalloproteinases-1 production in cell lysates, were significantly increased (p < 0.05). Compared to controls, cell migration was significantly inhibited (p < 0.005) by nicotine in a time-dependent manner. Electron microscopic analysis revealed the presence of a number of vacuoles in nicotine-treated cells. These results indicate that nicotine not only impairs fibroblast motility, and induces cellular degenerative changes, but also alters ECM-remodeling systems of periodontal cells. Induction of matrix remodeling molecules, combined with type I collagen accumulation, may account for the molecular mechanism of nicotine-induced periodontal fibrosis.

In the clinical situations, the time intervals between material mixing and light exposure during bracket bonding, using light-cured resin-reinforced glass ionomer cement (LCGIC), may vary for each individual bracket. This study determined the tensile bond strengths of LCGIC subjected to various time intervals, and evaluated the durability with thermocycling. Comparisons were made between LCGIC and light-cured composite resin (LCR). Two hundred and forty bovine teeth were chosen as specimens. Light exposure was performed 5, 10, 20, and 40 min after the commencement of powder/liquid mixing. The durability was evaluated by thermocycling for 2000 times at temperatures between 5°C and 55°C, with a 30-s dwell time. Tensile bond strengths of LCGIC and LCR after 5 min, representing the general condition in clinical use, equaled 5.7 ± 1.5 MPa and 5.1 ± 2.6 MPa, respectively. For the LCGIC groups, no significant differences were seen between bond strengths with and without thermocycling. Also, no significant differences were noted among any time intervals. For the LCR groups, there were also no significant differences with and without thermocycling. The tensile bond strength of LCR showed highly significant differences within groups across time. Compared with LCR, the failure sites for brackets bonded with LCGIC appeared to be predominantly at the bracket/adhesive interface. The standard deviations of LCR were high when compared with those of LCGIC. The bond strength of LCGIC with or without thermocycling surpassed the clinically required minimum. LCGIC may be an advantageous alternative to LCR for orthodontic bracket bonding.

The purpose of this study was to clarify the relationship between two types of dental prescale systems. Forty healthy subjects were asked to maximally clench for about 3 s, and the maximum occlusal force before and after cleaning was calculated using an Occluzer FPD707 for dental prescale (P1) and a bite force analyzing system for dental prescale II (P2). The maximum occlusal forces measured by P1 and P2 were compared before cleaning and after cleaning. Next, the relationship between the maximum occlusal force by P1 and maximum occlusal force by P2 was investigated. In addition, comparisons were made between males and females. The maximum occlusal force after cleaning was significantly smaller than before cleaning for both P1 and P2. The reduction rate of the occlusal force was 4.1% for P1 and 25.9% for P2. Significant linearity was observed between the maximum occlusal forces of P1 and P2 (regression linear equation: y = 1.191x − 30.521, r = 0.980, p < 0.001). The maximum occlusal forces measured by P1 and P2 were both significantly larger in males than in females. It was suggested that there was a certain relationship between the maximum occlusal forces measured by dental prescale and dental prescale II, suggesting that it is possible to compare the results of both by applying corrections using a regression equation.

It has been revealed that atherosclerosis and periodontal disease may have a common mechanism of “chronic inflammation”. Several reports have indicated that periodontal infection is related to atherosclerosis, but none have yet reported such an investigation through the cooperation of local clinics. This study was performed in local Japanese clinics to examine the relationship between periodontal disease and atherosclerosis under collaborative medical and dental care. A pilot multicenter cross-sectional study was conducted on 37 medical patients with lifestyle-related diseases under consultation in participating medical clinics, and 79 periodontal patients not undergoing medical treatment but who were seen by participating dental clinics. Systemic examination and periodontal examination were performed at baseline, and the relationships between periodontal and atherosclerosis-related clinical markers were analyzed. There was a positive correlation between LDL-C level and plasma IgG antibody titer to Porphyromonas gingivalis. According to the analysis under adjusted age, at a cut-off value of 5.04 for plasma IgG titer to Porphyromonas gingivalis, the IgG titer was significantly correlated with the level of low-density lipoprotein cholesterol (LDL-C). This study suggested that infection with periodontal bacteria (Porphyromonas gingivalis) is associated with the progression of atherosclerosis. Plasma IgG titer to Porphyromonas gingivalis may be useful as the clinical risk marker for atherosclerosis related to periodontal disease. Moreover, the application of the blood examination as a medical check may lead to the development of collaborative medical and dental care within the local medical clinical system for the purpose of preventing the lifestyle-related disease.