Stem/progenitor cells isolated from human dental follicles differentiate into osteogenic cells. To investigate factors associated with osteogenic differentiation/mineralization in human dental follicle cells (hDFCs), we performed gene expression profiling of hDFCs during osteogenic differentiation. Cyclooxygenase (COX)-1 and -2 were up-regulated in hDFCs cultured in osteogenic induction medium(OIM)compared to growth medium (GM). Prostaglandin E₂ (PGE₂), which is the most studied prostanoid derived from arachidonic acid through the actions of COXs, may regulate bone metabolism. All PGE₂ E-type prostanoid receptors (EP), EP1-EP4, were expressed in hDFCs. Real-time PCR showed that the expression of EP2 and EP4 was increased in hDFCs cultured in OIM and GM at days 10 and 17 compared to day 0. We investigated the action of PGE₂ in osteogenic differentiation using hDFCs. PGE₂ decreased gene expression levels of osterix and alkaline phosphatase, which are factors associated with osteogenic differentiation. PGE₂ elicited inhibitory action on matrix mineralization of hDFCs as seen with alizarin red S staining. These findings suggest that PGE₂ may inhibit osteogenic differentiation/mineralization of stem/progenitor cells.

　The purpose of this study was to assess condylar fracture risk according to the classification of the mandibular inferior cortical shape using pantomography.

　This retrospective study was approved by the Institutional Review Board (EC15-12-009-1). 254 patients with suspected condylar fractures who underwent both pantomography and MDCT from April 2006 to December 2016 were included in this study. The mandibular inferior cortical shape was evaluated by pantomography on both sides of the mandible, distal to the mental foramen by specialist of two oral and maxillofacial radiologists, and classified into three types as follows; Type l: normal cortex, Type 2: mildly to moderately eroded cortex and Type 3: severely eroded cortex. Moreover, the patients were divided into two groups; Group I: normal bone mineral density (Type 1) and Group II: low bone mineral density (Types 2 and 3).

　Of the 254 patients, condylar fractures were seen in 158 patients (62.2%). Of the 158 patients with condylar fractures, 27 patients were in Group I (17.1%) and 131 patients were in Group II (82.9%). Of the 96 patients without mandibular fracture, 57 patients were in Group I (59.4%) and 39 patients were in Group II (40.6%). There was a statistically significant difference between Group I and Group II in the prevalence of condylar fractures (p < 0.05).

　Our results suggest that classification of the mandibular inferior cortical shape on pantomography may provide a risk assessment of condylar fractures.

Purpose: In this study, to elucidate the ability of Ga-Al-As laser treatment to induce hard tissue formation, human dental pulp cells (hDPCs) stimulated with high concentration prostaglandin E₂ (PGE₂), which inhibits hard tissue formation, were irradiated with lasers at 660 or 810 nm. Differences in the molecular mechanisms underlying hard tissue formation using Ga-Al-As lasers at these wavelengths, including signaling via the bone morphogenetic protein (BMP)/SMAD pathway, were examined and compared.

Methods: hDPCs were harvested from third molars extracted under aseptic conditions from 20-year-old patients undergoing orthodontic treatment. hDPCs were cultured for up to 30 days. After adding PGE₂, hDPCs were irradiated with a Ga-Al-As laser at an output of 300 mW and wavelengths of 660 or 810 nm, approximately 10 cm above the culture supernatant. The laser irradiation time period was set to 600 seconds. BMP2, phosphorylated- (p-) SMAD1/5/8 and SMAD6 production were evaluated and calcified nodules stained.

Results: Ga-Al-As laser treatment resulted in decreased SMAD6 mRNA and increased protein expression of p-SMAD1/5/8 in groups irradiated at both wavelengths, compared with hDPCs stimulated with PGE₂. Moreover, those irradiated at 810 nm exhibited lower BMP2 mRNA expression, but no definite difference in SMAD6 protein expression,compared with cells stimulated with PGE₂.

Conclusion: Using Ga-Al-As lasers at the same output power, our results suggest that irradiation at 660 nm enhanced the ability of hDPCs to form hard tissue by suppressing SMAD6 expression; however, irradiation at 810 nm enhanced hard tissue generation via a different route that did not involve BMP2 and SMAD6.

　A mesiodens is the most common supernumerary tooth present in the maxillary incisor area. There have been many reports regarding the prevalence and treatment for supernumerary teeth; however, the etiology of the condition is still unknown. This study aimed to identify genes associated with susceptibility to mesiodens formation. The study population comprised 24 patients with mesiodens and 24 controls. Genomic DNA was obtained from the soft tissue of extracted supernumerary teeth or saliva samples. Genotypes and allele frequencies of single nucleotide polymorphisms (SNPs) in genes associated with the initiation of odontogenesis, including TP63, PITX2, LEF1, BMP2, BMP4, FGF9, FGF20, WNT10A, WNT10B, EDA, EDAR, MSX1, MSX2, PAX9, LHX6, and RUNX2 were compared between mesiodens group and controls using chisquared tests. In addition, SNPs in genes associated with supernumerary incisor formation in rodents, including SOSTDC1, LRP4, APC, PAX6, and CEBPB were tested. No positive polymorphisms were found in the tested SNPs between the two groups. These results suggest that these SNPs might not be candidates of genetic marker for mesiodens formation.

　Fibronectin, which is an extracellular matrix component, is broken down by several matrix degradation enzymes. Fibronectin-fragments (FN-fs), with molecular sizes of 29-200 kDa, are present at high levels in synovial fluid from osteoarthritis patients. The roles of FN-fs in temporomandibular joint (TMJ) arthritides were investigated. The 120 kDa FN-f was the most potent inducer of the expression and production of CXCL1, also called growth-related oncogene α (GROα), compared to 30 kDa and 45 kDa FN-fs in synovial fibroblasts (SF) from human temporomandibular joints. Therefore, further investigation was carried out using the 120 kDa FN-f. Microarray analysis indicated that 120 kDa FN-f treatment of SF upregulated the expressions of CXCL1 and chemokines. Real-time PCR analysis showed that the gene expressions of CXCL1, CXCL2, and CXCL3 were significantly higher in 120 kDa FN-f-treated SF than in untreated controls. CXCL1 protein production was increased by the 120 kDa FN-f in a time-dependent manner. Furthermore, signal inhibitor experiments indicated that 120 kDa FN-f-mediated induction of CXCL1 was transduced via activation of NFκB signaling. These results suggest that the 120 kDa FN-f is associated with the inflammatory progression of TMJ arthritides.