Cone-Beam Computed Tomography Analysis on the Relationship between the Mandibular Third Molar and the Position of the Mandibular Canal in Koreans from the Yanbian Area and the Han People.

Objective: To analyze differences in the positional relationships between the mandibular third molar (MTM) and the mandibular canal in Korean and Han patients using cone-beam computed tomography (CBCT) and to provide a basis for preoperative risk assessments. Materials and Methods: The CBCT imaging data of 260 Korean and Han patients were collected. The patients' genders, ages, impaction types and depths, relative positions between the MTMs and the mandibular nerve canals, and the shortest distances and shapes at the root tips and cortical bones were all recorded and analyzed. All data were compared using the nonparametric test, ordered logistic regression analysis, a chi-square test, and Fisher's exact test. Results: The relationship between the mandibular canal and the relative position of the MTM differed between Korean and Han patients, mainly in the different types of impactions, and the difference was statistically significant (P < 0.05). The shortest distance between the mesioangular and horizontally impacted mandibular canals and the buccal side of the MTM in Korean patients was less than in Han patients, and the difference was statistically significant (P < 0.05). For horizontal impactions, the probability of cortical bone interruption was 1.980 times greater in Korean patients than in Han patients, and the difference was statistically significant (P < 0.05). The significance threshold was set at 0.05. Conclusion: There are some differences in the positional relationship between the mandibular canal in the MTM region and the rate of cortical bone disruption between Koreans from the Yanbian area and the Hans. This should gain clinical attention.

Cytotoxicity and reactive oxygen species production induced by different co-monomer eluted from nanohybrid dental composites.

BACKGROUND: Safety issues for dental restorative composites are critical to material selection, but, limited information is available to dental practitioners. This study aimed to compare the chemical and biological characteristics of three nanohybrid dental composites by assessing filler particle analysis, monomer degree of conversion (DC), the composition of eluates, and cytotoxicity and reactive oxygen species (ROS) production in fibroblasts. METHODS: Three nanohybrid composites (TN, Tetric N-Ceram; CX, Ceram X Sphere Tec One; and DN, DenFil NX) were used. The size distribution and morphology of the filler particles were analysed using scanning electron microscopy (n = 5). The DC was measured via micro-Raman spectroscopy (n = 5). For the component analysis, methanol eluates from the light-polymerised composites were evaluated by gas chromatography/mass spectrometry (n = 3). The eluates were prepared from the polymerised composites after 24 h in a cell culture medium. A live/dead assay (n = 9) and Water-Soluble Tetrazolium-1 assay (n = 9) were performed and compared with negative and positive controls. The ROS in composites were compared with NC. Statistical significance in differences was assessed using a t-test and ANOVA (α = 0.05). RESULTS: Morphological variations in different-sized fillers were observed in the composites. The DC values were not significantly different among the composites. The amounts of 2-hydroxyethyl methacrylate (HEMA) were higher in TN than DN (p = 0.0022) and triethylene glycol dimethacrylate (TEGDMA) in CX was higher than in others (p < 0.0001). The lowest cell viability was shown in CX (p < 0.0001) and the highest ROS formation was detected in TN (p < 0.0001). CONCLUSIONS: Three nanohybrid dental composites exhibited various compositions of filler sizes and resin components, resulting in different levels of cytotoxicity and ROS production. Chemical compositions of dental composites can be considered with their biological impact on safety issues in the intraoral use of dental restorative composites. CX with the highest TEGDMA showed the highest cytotoxicity induced by ROS accumulation. DN with lower TEGDMA and HEMA presented the highest cell viability.

Synergistic effects of arginine-glycine-aspartic acid and phosphatidylserine on the surface immunomodulation and osseointegration of titanium implants.

The control of macrophage polarization is important in bone tissue regeneration such as osseointegration. In this study, a coating method was developed to improve the osseointegration of titanium (Ti) implants by generating an immunomodulatory effect. The surface of the Ti discs was coated with a poly(lactide-co-glycolide)(PLGA) polymer, phosphatidylserine (PS), and arginine-glycine-aspartic acid (RGD) peptide conjugated phospholipid. In in vitro assay using mouse bone marrow-derived macrophages (BMDMs), the most significant expression of the M2 marker genes (Arg-1, YM-1, FIZZ1) and CD206, an M2 surface marker, was obtained with coatings containing 6 mol% RGD conjugates and phospholipids consisting of 50 mol% PS. The M2-inducing effect of RGD and PS was also verified in rat femurs where coated Ti rods were implanted. The RGD and PS coating significantly enhanced the osseointegration of the Ti implants. Moreover, a biomechanical push-out test showed that the RGD and PS coating increased the interfacial binding force between the bone and implants. These results indicate that PS and RGD can be applied to the solid surface of implantable biomedical devices to improve immunomodulation and tissue regeneration.