Dental materials journal最新文献

Dental titanium implants and their surface modifications markedly improve implant biocompatibility. However, studies evaluating the mechanical biocompatibility of implants are scarce. In particular, the analysis of mechanical biocompatibility deficiencies leading to stress shield-induced bone resorption. Recently, we focused on using PEEK as a dental material. This study explored the hypothesis that PEEK implants improve the stress shielding of titanium. In this study, artificial bone surfaces were examined to measure strains on the artificial bone surface under compressive loading with the implants in place. Additionally, 3D image analysis of the fracture state inside the bone tissue was performed using micro-CT (µCT). This hypothesis was supported by µCT imaging analysis of bone tissue changes under stress, which revealed that PEEK implants transfer greater loads than titanium implants. µCT imaging and statistical analysis showed that bone porosity had little effect on stress shielding.

The objective of this study was to investigate the effects of repetitive removal/insertion and a load equivalent to the occlusal force on the retentive force of rest plate-I bar (RPI) clasps fabricated by selective laser melting (SLM) on powder bed fusion. RPI clasp fabricated by SLM and casting were evaluated to the retentive force by repetitive removal/insertion (SLM-RI and Cast-RI), and the retentive force of RPI clasp by SLM was also evaluated by repetitive removal/insertion under load (SLM-L). SLM-RI group was kept superior retentive force during repetitive removal/insertion than Cast-RI group. SLM-L group showed the decrease of retentive force, and all specimens fractured during less than 7,000 repetitive removal/insertion. In SLM-L, the fracture of RPI clasp occurred at minor connector due to stress concentration. In conclusion, the RPI clasp by SLM demonstrated the superior retentive force and fitting for repetitive removal/insertion, yet improvements were necessary to withstand a load equivalent to occlusal force.

The purpose of this study was to construct an artificial intelligence object detection model to detect the articular disk from temporomandibular joint (TMJ) magnetic resonance (MR) images using YOLO series. The study included two experiments using datasets from different MR imaging machines. A total of 536 MR images were retrospectively examined. The performance of YOLOv5 and YOLOv8 in detecting the TMJ articular disk in both normal and displaced conditions was evaluated. The impact of image-processing techniques, such as histogram equalization (HE) and contrast-limited adaptive HE (CLAHE) on model performance, was also examined. The results showed that the YOLO series could detect the articular disk regardless of displacement, with superior performance on images of normal disk position. The results suggest the applicability of object detection models in improving the diagnosis of TMJ disorders.

Enamel microcracks are often apparent in the teeth of elderly individuals. However, accurate clinical diagnosis of enamel microcracks is very difficult. The purpose of this study was to examine the utility of inspections for enamel microcracks using a near-infrared light transillumination device with fluorescence staining. Human upper incisors with typical enamel microcracks were selected. Grayscale pictures of each tooth specimen were then taken by digital camera under visible light as control. Every tooth specimen was stained using indocyanine green solutions, then examined, and photographed under visible light. All digital images were compared with the background enamel surface and measured using image analysis software. Inspection using near-infrared light transillumination with indocyanine green solution was effective for detecting the presence of enamel microcracks. This method offers a non-invasive method of chair-side diagnosis and appears effective for detecting the presence of enamel microcracks.

This study investigates the moments generated when applying third-order bends to lingual brackets with different slot shapes and wires made of different materials. Three types of lingual brackets with different slot shapes: 0.018×0.018-inch square slot self-ligation bracket (AL-bracket); 0.018×0.025-inch slot self-ligation bracket (CL-bracket); 0.018×0.025-inch slot self-ligation bracket (ST-bracket). Wires of three different materials were measured. The torque value generated during torque application was measured using a torque gauge. The AL-bracket had a significantly larger torque moment than the CL- and ST-brackets at the same angles. The CL-bracket had the smallest torque moment of the three for the square wire; however, the CL-bracket revealed a larger torque moment than the ST-bracket for the rectangular wire. The torque moment of Ti-Ni wires was observed the smallest. In lingual orthodontic treatment, the results suggested the shape of the lingual bracket slot and the wire material should be considered when adjusting and applying third-order bends.

The material concept of resin cements capable of disintegrating due to near-infrared (NIR) radiation was verified. The cements were prepared by adding silicon carbide (SiC), which heats upon absorbing NIR rays, and thermally expandable particles (TEPs) to 4-META/MMA-TBB resin cement. The microtensile bond strength (µTBS) and cytocompatibility of the cements were evaluated. The resin cements with 5 mass% SiC and 20-40 mass% TEPs had significantly lower µTBS after NIR radiation than before NIR radiation, and their cytocompatibility was not decreased by SiC and TEPs additions. Furthermore, in vitro thermal damage tests were performed using the resin cement with 5 mass% SiC and 20 mass% TEPs, a typical composition. The results demonstrated conditions that significantly reduced µTBS and minimized thermal damage by NIR radiation. Although these data are only proof of concept, the possibility that dental devices bonded with these cements could be detached by NIR radiation was demonstrated.

This study evaluated the effects of HEMA and 10-MDP in the bonding agent in a 2-step self-etch adhesive system, Clearfil SE Bond 2, on water sorption (W_sp) and elastic modulus (E) of the polymerized bonding agent. The microtensile bond strength (µTBS) to dentin was also evaluated initially and after 10,000 thermal cycles (TC10,000). Four bonding agents were tested: the original, H-free (excluding HEMA), M-free (excluding 10-MDP), and HM-free (excluding HEMA and 10-MDP). HEMA increased W_sp and decreased E. Initial µTBS (TC0) was highest for the original and lowest for HM-free. After TC10,000, the original maintained the highest µTBS, indicating the importance of HEMA and 10-MDP. TC10,000 did not reduce µTBS for any groups. HEMA and 10-MDP compromised mechanical property and increased water sorption, suggesting these components could potentially compromise adhesive stability.

In dental practice, there are two major diseases: dental caries and periodontal disease. Although dental treatment techniques have advanced along with advances in dental materials, some diseases such as root surface caries and horizontal bone resorption have not yet achieved satisfactory treatment results. Since these diseases are infections caused by oral bacteria, we believe that materials with long-lasting antimicrobial properties would help control these diseases. In addition, materials that can adhere to wet hard tissues would contribute to treatment. In this review, new materials developed based on this idea, the antimicrobial material "cetylpyridinium chloride-montmorillonite" and the hard tissue adhesive implantable material "phosphorylated pullulan" was introduced.

The aim was to compare different surface pretreatments on definitive resin crown materials manufactured additively or subtractively in terms of shear bond strength (SBS) values. Seven subgroups (n=10) were formed from additively manufactured VarseoSmile Crown Plus (VS) and subtractively manufactured Cerasmart270 blocks (CS) according to different surface pretreatments applied; sandblasting (subgroup SB), hydrofluoric acid (subgroup HF), Multi Primer (subgroup MP), subgroup SB-HF, subgroup SB-MP, subgroup SB-HF-MP, and control subgroup. A 3-mm-diameter composite was cemented onto each sample by self-adhesive resin cement. SBS values were measured and failure modes were analyzed after thermocycling. Data were analyzed with two-way ANOVA and Tukey HSD tests. The mean SBS value of VS was found significantly higher than CS (p<0.001). Subgroups SB-HF-MP, HF, SB-MP, and MP of VS exhibited the highest SBS values (p<0.001). The VS exhibited mostly cohesive failure, while CS exhibited mostly adhesive failure.

This study evaluated the influence of phosphoric acid and primer on enamel bonding performance using Panavia V5. Ground bovine enamels were assigned: using K-etchant syringe and Tooth Primer (CT), using K-etchant syringe (PA), using Tooth Primer (TP), neither K-etchant syringe nor Tooth Primer was used (NC). The micro-tensile bond strength values of CT and PA were significantly higher than TP. After thermal cycling, the values were higher in CT and PA. In the leakage test, line-shaped signal pattern at the adhesive interface was detected in NC, and the signal was partially detected in PA and TP. Observation of the adhesive interface after acid and base challenge confirmed tooth-like structures in groups except NC. Large spaces were observed between the enamel and cement in NC. Limited in this study, the lack of application of phosphoric acid or Tooth Primer may affect the enamel bonding performance.