Journal of oral science最新文献

Purpose: To investigate the elemental composition, corrosion resistance, and mechanical properties of computer-aided design and computer-aided manufacturing (CAD-CAM) retainers versus conventional fixed retainers (FRs).

Methods: Eight different retainer wires were investigated. Energy dispersive X-ray spectroscopy was used to determine the elemental composition. Leakage was analysed according to ISO 10271:2020 guidelines. Hardness was tested using the Vickers method with a load of 0.3 kg. The tensile force and tensile strength were evaluated. Multiple comparisons among wires of hardness, tensile force, and strength were conducted using the Welch t-test, with Bonferroni correction.

Results: Nickel was present in all wires. The CAD-CAM-FR wire, which contained more nickel than the other wires, had no measurable leakage. The gold-plated wires had the highest total leakage, but did not exceed the ISO standard limit. The hardness of the stainless-steel twisted wires was the highest and that of the CAD-CAM-FR wire was the lowest. The tensile strength of the CAD-CAM-FR wire was significantly lower than that of the other wires and similar to the other twisted-wire retainers.

Conclusion: The CAD-CAM-FR wire is likely to have high corrosion resistance and flexibility due to its low hardness.

Characterization of the metal component of dental restorations and fixed prostheses is useful for the treatment of dental metal allergies and personal identification. This study aimed to describe the composition of metal elements in dental restorations and fixed prostheses in the oral cavity of 43 cadavers of Japanese adults aged 55 years or older in forensic autopsies conducted at a university. In this study, Ag-Pd-Au alloys were most frequently detected, and the percentage of Ni alloys was smaller than that reported in patients with dental metal allergies. Furthermore, alloys containing other elements, such as Fe or Hg, were also detected in some cases.

Customized posts-and-cores have been widely used for improved fitness within a prepared post space. However, in comparison to direct restoration, they necessitate an increased number of appointments for patients. A 24-year-old man presented with a maxillary left canine that had fractured due to trauma 10 months previously. For this case, a digital process was used for simultaneous restoration with a personalized titanium post-and-core and a zirconia crown achieved with an intraoral scanner (IOS) and computer-aided design/computer-aided manufacturing (CAD-CAM). This workflow allowed the restoration to be completed in 2 visits, facilitating more effective and predictable treatment, with reduced time and cost for the patient.

Purpose: Prior studies explored factors influencing dental study choice, but shifts from BDSc to DDS degrees in some countries impact demographics and motivations, potentially affecting the dental workforce. The aim of this study was to establish Australian DDS and BOH students' sociodemographics and career motivations.

Methods: Questionnaires conducted in mid-2019 assessed sociodemographic profiles and career motivations. Statistical analysis utilized descriptive statistics and Fisher's exact test.

Results: The overall response rate was 71.3%. DDS students had an average age of 25.2 years, while BOH students averaged 21.5 years. Most BOH (80.7%) and DDS students (52.0%) were female. They were mainly single, local, Australian citizens from metropolitan areas. Self-motivation ranked highest, particularly for DDS students (P < 0.05). Significant motivators included healthcare occupation, helping others, interesting career, and flexible hours (P < 0.05). DDS students were more motivated by flexible hours and independence (P < 0.05), while females emphasized a healthcare profession (P = 0.003). International students were motivated by being their own boss (P = 0.003), and private school graduates valued lifestyle within the profession (P = 0.049).

Conclusion: Despite sociodemographic changes, the main motivations for studying dentistry remain consistent. DDS students prioritized lifestyle factors such as time and remuneration over BOH students.

Purpose: To clarify the magnification error caused by the degree of tilt of the incisor and the elevation of the X-ray focus position, and the verification effect of magnification correction when performing vertical dual-exposure panoramic radiography.

Methods: Panoramic radiographic images of a phantom embedding 26 steel balls were taken at different heights (0, 5, 10, 15, and 20 mm) and tilt angles (0°, 10°, 20°, and 30°) to evaluate vertical magnification in each condition. Error and correlation coefficients in the vertical magnifications were calculated between the measured and theoretical magnification values.

Results: The more the steel ball phantom was tilted, the more the images of the uppermost steel balls were laterally stretched. In the vertical direction, image magnification also influenced the tilt angle of the object in the incisal region. The range of error in vertical magnification was −0.35-0.30%. The Spearman’s rank correlation coefficient between the measured and theoretical magnification value was 0.983.

Conclusion: Vertical magnification correction has the potential to improve image quality when merging panoramic radiographs in vertical dual-exposure panoramic radiography.

Purpose: To compare the shear-bond-strength (SBS) of a highly-filled-flowable composite (HFFC) and a paste-type composite for indirect composite repair and to evaluate the effect of different surface treatments (ST), concerning the composite repair protocol.

Methods: Eighty-four 5 × 5 × 2 mm cylindrical specimens were prepared using Gradia Plus and SR Nexco indirect composite materials. The samples were thermocycled 5,000 times. According to the ST, the samples were divided into three groups (control, bur, and air-abrasion). After ST, the sample subgroups were divided into two sub-groups according to the repair material: paste-type composite and HFFC (n = 7). Another 5,000 cycles of aging were performed. SBS values were measured with a universal testing machine (Shimadzu, Japan). Shapiro-Wilk, 3-way ANOVA, and Tukey HSD test were used to evaluate data (P < 0.05).

Results: ST was considered significant for SBS (P < 0.001). The mean values were (13.9 ± 5.7), (17.0 ± 6.4), (20.4 ± 4.9) MPa for the control, bur and phosphoric acid, and air-abrasion groups, respectively. The surface treatment and repair material interaction was considered significant for SBS (P = 0.044). The highest mean bond strength (24.5 ± 4.5 MPa) was observed for the interaction of SR Nexco, air-abrasion ST, and HFFC repair.

Conclusion: Repairing with HFFC following air abrasion might enhance the SBS for indirect composite restorations.

Purpose: The aim of this study was to investigate the influence of different convergence angles of abutment teeth and different cement spaces on internal adaptation of anterior fixed dental prostheses (FDPs) fabricated with a computer-aided design-computer-aided manufacturing (CAD-CAM) system.

Methods: Composite resin FDPs for 99 standardized maxillary central incisors were fabricated according to nine parameters: three total convergence angles (4 [DG4], 12 [DG12], and 20 degrees [DG20]) and three cement space settings (10 [CS10], 50 [CS50], and 90 µm [CS90]). Internal space values were measured with a cement space replica technique. The Kruskal-Wallis and Steel-Dwass tests were used to evaluate differences in the total convergence angles and luting agent spaces, respectively (α = 0.05).

Results: For all three cement spaces tested, the median marginal gap values between abutment teeth and FDPs decreased significantly as the total convergence angle increased (P < 0.05). For the CS10 and CS50 groups, the internal space values at the axial area increased significantly as the total convergence angles increased (P < 0.05).

Conclusion: Total convergence angles of the abutment teeth and cement spaces affected the marginal and internal adaptation of anterior FDPs fabricated with a CAD-CAM system.

Purpose: To investigate the surface topography and nickel content of nickel-titanium (NiTi) archwires exposed to either routine oral hygiene or a prophylactic regimen with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) during orthodontic treatment.

Methods: This in vivo study involved 40 orthodontic patients with fixed appliances, who were randomly assigned to either a routine oral hygiene group or a CPP-ACP supplementary regimen group. Twenty new NiTi archwires served as controls. All archwires underwent scanning electron microscopy and energy-dispersive spectroscopy to evaluate their surface topography and elemental composition. The nickel content was quantified as a percentage of total weight and the Ni/Ti ratio, and statistical comparisons were made using pairwise tests.

Results: Wires exposed to fluoride toothpaste showed signs of pitting corrosion, deep grooves, and corrosion debris. In contrast, wires exposed to supplementary CPP-ACP exhibited smooth surface areas interspersed with microdefects and deposits. Statistically significant differences in nickel content were found between the new and retrieved archwires, as well as between wires exposed to routine oral hygiene and CPP-ACP (P < 0.001). The archwires exposed to CPP-ACP had the lowest nickel content (P < 0.001).

Conclusion: The use of CPP-ACP holds promise for application as a safe anticariogenic agent with possible protective properties during orthodontic treatment.

Purpose: The aim of the present study was to develop a novel method for distinguishing white spot lesions (WSLs) from sound enamel in human premolars using micro-computed tomography (micro-CT) and scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and to examine differences in surface morphology, chemical composition, and mineral density (MD) between these two areas.

Methods: Fourteen premolars with natural WSLs on the enamel surface of the crowns were examined. After sectioning the teeth, each specimen containing WSLs adjacent to intact enamel was examined for MD, surface morphology, and atomic percentages (At%) of chemical components using micro-CT and SEM/EDS, respectively. Differences between these areas of the same specimen were analyzed statistically using paired t-test.

Results: SEM images highlighted increased roughness and irregularity in the lesion area. EDS analysis revealed significant reductions in calcium (Ca), phosphorus (P), fluorine (F), chlorine (Cl), and sodium (Na) levels at the lesion surface in comparison to intact enamel (P < 0.05). The decreases in the MD of the lesions were statistically significant in comparison to sound enamel (P < 0.05).

Conclusion: These findings provide standard measurements for evaluating the essential characteristics of WSLs and intact enamel, being vital for assessment of treatment outcomes and development of innovative biomaterials for management of hypo-mineralized enamel lesions.

Mandibular deviation and rotation following mandibulectomy can significantly impact oral function and quality of life. The postoperative course of a 57-year-old patient who underwent mandibulectomy for oral cancer and findings over 11 years of follow-up observation to monitor changes in the mandibular position are described here. Based on the observations, it is important to raise awareness regarding the necessity of continued monitoring of mandible position and regular adjustments of prostheses for patients who have undergone mandibulectomy.