3D Printer-Assisted Layered Fabrication of a Novel Appliance for Oral Myofunctional Therapy and Functional Evaluation of Its Effects on Orofacial Muscles During Wear.

Aim Balanced function of the orofacial muscles is important for normal occlusion and dentition; however, patients with malocclusion often present with myofunctional disorder (MFD). Myofunctional therapy (MFT) has received much attention as a method for reducing MFD. Moreover, prefabricated functional appliances (PFAs) have been developed as a method to eliminate abnormal muscle pressure and guide the tongue into the correct position. However, PFAs have disadvantages, such as poor intraoral retention, limited usage time due to discomfort and poor patient compliance, and changes in the axis of the mandibular anterior teeth. Therefore, this study aimed to develop a new custom-made splint-type orthodontic appliance with CAD/CAM technology. Moreover, we evaluated the characteristics of the appliance and conducted functional tests to determine the effects of the appliance on the orofacial muscles and the discomfort associated with its use. Materials and methods Twenty-five volunteers (nine females and 16 males; mean age 28.4 ± 3.4 years) with normal swallowing function were included in the study. Lip-closing strength (LCS), electromyogram during swallowing, oxygen saturation, and pulse rate were measured and compared when the appliance was not worn and when it was worn. In addition, tongue habits were evaluated, and the maximum tongue pressure was measured when the appliance was not worn. The subjects were asked to answer a questionnaire using a numerical rating scale (NRS) regarding discomfort when wearing the appliance. The evaluation items were swallowing difficulty, speaking difficulty, and breathlessness, which were rated on an 11-point scale ranging from 0 to 10. Statistical tests were conducted using IBM SPSS version 28.0.1 (IBM, Armonk, NY, USA) with the Shapiro-Wilk and Levene's test, followed by the Wilcoxon signed rank sum test. The significance level was set at α = 0.05. The measurement error for each measurement item was evaluated using an intraclass correlation coefficient. Results A new custom-made splint-type orthodontic appliance was fabricated for each subject. The fit and retention of the appliance in the mouth were good when fitted, and a comparison of the functional test measurements of 25 subjects with and without the appliance showed that the LCS decreased significantly (p<0.05) before and after wearing the appliance. However, no statistically significant differences were found for the other items. The Mann-Whitney U test regarding the effects of sex, previous orthodontic treatment, or MFT, and oral habits did not statistically significantly influence the effects of wearing the device. In the NRS results, "difficulty swallowing" was observed in half of the subjects, "difficulty breathing" was rarely observed, and "difficulty speaking" was observed in all subjects. Conclusions A novel custom-made splint-type orthodontic appliance was designed and fabricated using digital workflow and 3D printing technology. This appliance was designed to correct oral habits and was made from a new material classified as a class II medical appliance according to the international harmonized classification.

Application of multi-directional forged titanium for prosthetic crown fabrication by CAD/CAM.

Titanium are often used as dental materials, pure titanium present low strength and titanium alloy is reported poor biocompatibility, respectively. To overcome the problem, we fabricated high-strength multi-directional forged (MDF) titanium with improved mechanical properties without changing the chemical composition and evaluated its applicability in prosthetic crowns. Cutting tests: the average absolute value of the difference before and after cutting was calculated as the uncut amount. Surface evaluations: MDF titanium, pure titanium, and the Ti-6Al-4V alloy were the surface properties (the surface roughness, the contact angles, glossiness) of the samples were evaluated. The fitness test used digital data. These demonstrated that the good workability of high-strength MDF titanium. The surface-roughness and contact-angle properties of MDF titanium and pure titanium were similar. The fitness test showed no significant differences between MDF titanium and pure titanium crowns. These results suggest that MDF titanium is promising for fabricating prosthetic crowns in dental applications.

Influence of ultraviolet irradiation treatment on porcelain bond strength of titanium surfaces.

To determine the effect of titanium (Ti) surface modification by ultraviolet irradiation (UVI) on the bond strength between Ti and porcelain. Grade 2 Ti plates were allotted to five groups: sandblasted (SA), 15 min UVI (UV), SA+5 min UVI (SA+UV5), SA+10 min UVI (SA+UV10), and SA+15 min UVI (SA+UV15). After surface treatment, porcelain was added. A precious metal (MC) was used for comparison with Ti. The effects of 24-h storage at room temperature versus thermal cycling only at 5 and 55°C in water were evaluated. Subsequently, the tensile strength of each sample was tested. Data were analyzed using one-way analysis of variance and the Tukey test. In both the room temperature and thermal cycling groups, the MC and SA+15 min UVI samples showed significantly greater bond strengths than the other samples (p<0.05). UVI processing efficiently increases the bond strength between porcelain and the Ti surface.

Evaluation of denture base resin after disinfection method using reactive oxygen species (ROS).

The effects of certain disinfectants on the stability of a polymethyl methacrylate denture base resin were investigated, including those of a novel disinfection method using reactive oxygen species (ROS). The surface roughness and flexural strength were analyzed to assess the effects of the disinfectants on material properties. The following disinfectants were tested: 5% sodium hypochlorite, 70% alcohol, and ROS. Furthermore, the attachment of Candida albicans to the resin surface was investigated. The disinfection method using sodium hypochlorite significantly increased the surface roughness and decreased flexural strength. The surface roughness and flexural strength of the ROS-treated specimens did not significantly differ from those of the control specimens, and the ROS-treated specimens exhibited diminished Candida attachment. These results demonstrate that the ROS disinfection method preserves acceptable material stability levels in polymethyl methacrylate resins.