Purpose: The purpose of this study was to investigate the influence of substrates under the three-dimensional periodontal ligament (3D PDL) tissue on its biological functions after compressive stimulation.

Methods: A 3D PDL tissue was created using a poly(L-lactic acid) (PLLA) porous scaffold impregnated with human periodontal ligament fibroblasts (hPDLFs). It was then placed on a polyetheretherketone (PEEK) substrate, which has a comparable elastic modulus to bone and was compressed (25 g/cm²) for 1, 3, and 7 days. The morphology and biological functions of the hPDLFs in the 3D PDL tissue on the PEEK substrate were evaluated and compared with those on the polystyrene (PS) substrate.

Results: Compressive forces for the PLLA porous scaffold on the PEEK substrate were higher than those on the PS substrate. hPDLFs were present throughout the PLLA porous scaffold and there was no morphological change upon compressive stimulation. Increased expression of osteoclastogenic genes was observed after 3 days of compressive stimulation, while the level of these genes was increased by changing the substrate under the PDL tissue from PS to PEEK.

Conclusion: The substrate placed under the PDL tissue during compressive stimulation affects the biological functions of hPDLFs.

Purpose: As three-dimensional (3D) intraoral scans are becoming popular in modern dentistry, they also offer a new category of antemortem data for forensic identification. This study proposes a novel methodology for individual identification based on 3D homologous models of the maxilla.

Methods: Data from 100 maxillary plaster casts (40 monozygotic twin casts, 28 dizygotic twin casts and 32 singleton casts) were used. From the initial sample, 10 casts were randomly chosen and duplicated four times, resulting in 40 duplicates. These were divided into four groups and subjected to the following alterations: molar attrition (n = 10), canine attrition (n = 10), molar and canine attrition (n = 10), and no alteration (n = 10). All the casts were converted to 3D models and then to homologous models using a template with 24 landmarks. The 3D coordinates of each vertex in the homologous model were then calculated and used for statistical comparison of similarity between two given homologous models using the average Hausdorff distance.

Results: All four groups achieved accurate matching with their original maxillary casts, with a minimal average Hausdorff distance.

Conclusion: This method accurately identified individuals, including monozygotic twins, and exhibited robustness against minor tooth attrition, demonstrating its feasibility as an identification method in actual forensic settings.

Purpose: Inorganic polyphosphate (PolyP), a polymer of orthophosphate, strongly promotes mineralized tissue formation. This study explored the conditions necessary for PolyP to induce calcified deposits in cartilage and assessed the role of insulin in modulating PolyP-induced tissue calcification.

Methods: Murine chondrogenic ATDC5 cells were cultured under growth, mineralization, or PolyP-induced calcification conditions, with or without insulin. Calcified nodules were stained with Alizarin Red S, and conditioned media were analyzed for pH and lactate concentration using a pH meter and a lactate assay kit-WST.

Results: PolyP treatment of ATDC5 cells led to calcified deposits by day 5, both with and without insulin. However, in the presence of insulin, these deposits were nearly fully decalcified by day 14. Conditioned media with insulin had a lower pH and a higher lactate concentration compared to those without insulin, with lactate levels sufficient to demineralize the PolyP-induced calcified deposits.

Conclusion: These data suggest that treatment of ATDC5 chondrogenic cells with PolyP accelerates the formation of mineralized tissue. However, PolyP-induced calcified nodules undergo demineralization owing to lactate production by cells in the presence of insulin.

Purpose: This study investigated the law of color formation in various color mixtures of dental acrylic resin powder, with the aim of realizing quick and accurate color matching of facial prostheses.

Methods: Self-curing acrylic resin in crown, gingival, and clear colors was used to prepare 62 disk-shaped specimens (diameter, 30 mm; thickness, 5 mm). For each specimen, 2 g of different colored powders were mixed with 1 g of liquid and polymerized. Color values (L*, a*, and b*) were measured using a spectrophotometer. First-order linear (M₁), second-order quadratic (M_2S), second-order interactive (M_2I), and complete second-order (M_2C) models were applied to predict the relationship between component concentrations and color values. Multiple linear regression analysis was performed to assess the fitness of the observed and predicted colors. Differences in fitness were evaluated using repeated measures analysis of variance.

Results: M_2C showed a significantly better fit between the observed and predicted values compared with the other models.

Conclusion: The new model satisfied the requirements for clinical application. Using this formula, the mixing ratio of the powder of self-curing acrylic resin can easily be calculated to match skin colors. This formula will contribute to the fabrication of facial prostheses with suitable color, using dental material.

Purpose: This study evaluated the effects of sintering temperature on the crystal structure, optical and thermal properties, and surface roughness and topography of nanolithium disilicate ceramics (NLDS) and zirconia-reinforced nanolithium silicate ceramics (ZNLS).

Methods: One hundred and twenty specimens of each ceramics were prepared and divided into 4 groups on the basis of sintering temperature. The specimens were then subjected to X-ray diffraction (XRD), spectrophotometric analysis of optical properties, differential thermal analysis (DTA), thermal gravimetrical analysis (TGA), roughness analysis, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectrometry. The data were analyzed using one-way analysis of variance followed by Tukey’s test (α = 0.05)

Results: XRD confirmed the presence of lithium disilicate, lithium phosphate, lithium metasilicate, and quartz in NLDS and ZNLS specimens. TGA, DTA, and average roughness did not significantly differ between groups (P < 0.05). Among NLDS groups, NLDS4 had ∆E values that significantly differed from those of the other groups (P < 0.05). EDX showed that NLDS2 had the highest Si value (25.3 ± 0.1 wt%) followed by NLDS4 (24.8 ± 0.1 wt%). Among ZNLS groups, ZNLS2-4 had a clinically acceptable ∆E. EDX analysis showed no significant difference for any group.

Conclusion: Sintering temperature did not affect the evaluated properties of NLDS. However, sintering ZNLS at different temperatures might affect the tested properties.

Purpose: To evaluate the surface characteristics of hybrid ceramic-polymer materials before and after exposure to erosive and abrasive media.

Methods: Samples were prepared from Vita Enamic (VE), Cerasmart (CS), VarseoSmile Crown plus (VSC), and VarseoSmile Temp (VST). Surface roughness (SR), scanning electron microscopy (SEM), and surface hardness (SH) analyses were performed before (T0) and after exposing the samples to gastric juice (GJ), toothbrushing (TB), or both (GJ TB) for a simulated period of one (T1) or two years (T2).

Results: At T0, VSC and VST showed higher average (Ra) and maximum (Rz) roughness values, more homogeneous surfaces in SEM micrographs, and lower Vickers numbers (HV) than VE and CS. At T1 and T2, samples showed higher Ra values, greater surface damage on SEM micrographs, and reduced HV. The most pronounced changes were evident for GJ TB samples, followed in order by GJ (within VE and CS) and TB samples (within VSC and VST).

Conclusion: VE and CS showed initially lower SR and higher SH, lower resistance to GJ, and higher resistance to TB than VSC and VST, which would be essential when fabricating restorations for patients who are particularly susceptible to dental erosion and abrasion.

Purpose: The purpose of this study was to investigate swallowing function of older adults with lowered hyoid bone position.

Methods: A total of 60 older adults (23 males and 37 females, mean age: 70.1 years) with no diagnosed dysphagia participated in the study. Participants were divided into two groups (High and Low group) based on the anterior point of the hyoid bone (H) with respect to the line connecting the most inferior and anterior point on the corpus of the third cervical vertebra (C3) and Menton (Me). Swallowing function was measured using the Repetitive Saliva Swallow Test (RSST), the Eating Assessment Tool (EAT-10), jaw-opening force (JOF) and tongue pressure (TP). Each group was studied for its relationship to swallowing function. Additionally, the RSST of males and females in the Low group were compared.

Results: Males in the Low group had a significantly higher JOF (P = 0.009) in the RSST ≥ 5 group than in the RSST < 5 group. Females in the Low group had no measurements that showed significant differences between the RSST ≥ 4 and RSST < 4 groups.

Conclusion: JOF may affect swallowing function in older males with lowered hyoid bone position.

Purpose: To investigate the mineral density of artificial root caries lesions formed under varying concentrations of calcium phosphate, with or without the presence of fluoride.

Methods: Sixty-four human tooth root blocks were exposed to various lactic acid solutions for 96 h. These included a low concentration (0.16 mM) of calcium chloride and potassium dihydrogen phosphate (Group L), a low concentration (0.16 mM) of calcium chloride and potassium dihydrogen phosphate with 0.5 ppm fluoride (with sodium fluoride) (Group LF), a high concentration (2.2 mM) of calcium chloride and potassium dihydrogen phosphate (Group H), and a high concentration (2.2 mM) of calcium chloride and potassium dihydrogen phosphate with 0.5 ppm fluoride (Group HF). The mineral loss in the artificial lesions formed was measured using micro-computed tomography.

Results: The mineral loss in groups L, LF, H and HF was 35.38 ± 2.15%, 31.96 ± 2.1%, 32.58 ± 1.15%, and 27.78 ± 2.3%, respectively. A significant difference (P < 0.001) was observed between groups L and LF, groups LF and HF, groups H and HF, and groups L and HF. Calcium phosphate and fluoride exposure both had significant effects (P < 0.001) on mineral loss.

Conclusion: Artificial root caries lesions were associated with decreased mineral loss in solutions containing higher concentrations of calcium phosphate or in the presence of fluoride, compared with those formed in solutions with lower calcium phosphate concentrations or without fluoride.

Purpose: The present study investigated the effects of stabilization splints on two categories of sleep bruxism using a portable electromyographic recording system.

Methods: Twenty-six individuals confirmed as mild to severe bruxers by nocturnal masseter electromyographic episodes were enrolled in the study. Participants wore a stabilization splint during sleep for 30 nights, and masseter muscle activity was measured at baseline, immediately after, and 1 and 4 weeks after insertion of the splint. Bursts in masseter electromyographic episodes were separated into phasic bursts or tonic bursts, then each burst was analyzed in terms of duration, frequency, and magnitude of bursts.

Results: The frequency of phasic bursts significantly decreased immediately after insertion of the splint compared with the baseline. The geometric mean magnitude of tonic bursts decreased when wearing the splint compared with the baseline.

Conclusion: These findings suggest that stabilization splints reduce jaw-muscle activity during sleep in patients suffering from sleep bruxism by reducing the frequency of phasic bursts in the short term and reducing the magnitude of tonic bursts over a longer period.