We used cephalograms to investigate the correlation between the craniofacial morphology of skeletal Class I craniofacial morphology in Japanese adults and the mandibular symphysis, measuring the angles between the mandibular plane and symphysis, and the angles between the symphysis and mandibular central incisor. We observed the correlations between ∠SNA and Thickness Point B and Thickness Pogonion; between ∠SNB and Thickness Point B and Thickness Pogonion; between ∠ANB and Idm-Me; between FMA and Idm-Me, Thickness Point B, and Thickness Pogonion; between IMPA and ∠Idm-X to MP, ∠L1 to Idm-X, Thickness Point B and Thickness Pogonion; and between Gn-Cd and Idm-Me and Thickness Pogonion. In females, correlations were observed between ∠SNA and Thickness Point B and Thickness Pogonion (mm); between ∠SNB and ∠Idm-Me to MP, Thickness Point B, and Thickness Pogonion; between FMA and ∠Idm-Me to MP, ∠Idm-X to MP, ∠X-Me to MP, Idm-Me, and Thickness Point B; between IMPA and ∠Idm-Me to MP, ∠Idm-X to MP, ∠L1 to Idm-X, and Thickness Point B; and between Gn-Cd and Idm-Me. These results suggested the importance of monitoring movement of the mandibular anterior teeth during orthodontic treatment because skeletal differences affect the inclination of these teeth and the morphology of the symphysis. (J Osaka Dent Univ 2023; 57: 1-9)

Candidalysin is a recently identified peptide toxin produced by Candida albicans and is recognized to play a critical role in the onset of candidiasis. Secreted candidalysin interacts with epithelial cells and destabilizes the plasma membrane resulting in cell damage. Epithelial cells, on the other hand, recognize the presence of candidalysin via a not fully understood mechanism and initiate innate immunity. Previously we reported that oral epithelial cells release interleukin (IL)-1α shortly after candidalysin treatment. The released IL-1α is indispensable for the candidalysin-mediated activation of the nuclear factor kappa B (NF-κB) signaling pathway and the subsequent production of IL-8 and granulocyte-macrophage colony-stimulating factor (GM-CSF). The inhibitor of nuclear factor kappa Bζ (IκBζ) is an NF-κB-dependent gene and works with NF-κB as a cofactor in macrophages. In the present study, we examined the role of IκBζ in the induction of NF-κB-dependent cytokine production in candidalysin-treated oral epithelial cells. We found that the silencing of IκBζ in oral epithelial cells decreased the production of IL-6 in response to candidalysin exposure. Although not having the predominant role observed in LPS-stimulated macrophages, IκBζ has a role in inducing secondary response genes of NF-κB in candidalysin-treated oral epithelial cells. (J Osaka Dent Univ 2023; 57: 11-15)

Ferroptosis is a newly discovered form of cell death that exhibits effective tumor suppression in various cancer cell types. Since ferroptosis efficiently decreases the viability of cancer cells undergoing epithelial-mesenchymal transition (EMT), it may exert anti-tumor effects on highly malignant oral squamous cell carcinoma (OSCC) in EMT. xCT is a subunit of a the cystine-glutamate antiporter. Ferroptosis occurs due to increased oxidative stress by inhibiting xCT. We induced EMT in OSCC cells and examined the effects of the induction of ferroptosis by inhibiting xCT in these cells. We investigated whether xCT inhibitor erastin induced ferroptosis in OSCC cells in vitro. Furthermore, we induced the EMT state in OSCC cells by the administration of transforming growth factor-β1 and examined the sensitivity of OSCC cells to ferroptosis in the presence or absence of the EMT state. Erastin induced ferroptosis in the OSCC cells. Ferroptosis-induced reductions in cell viability were greater in OSCCs of the mesenchymal state by EMT than in those in the normal state. OSCC cells in the mesenchymal state induced by EMT were highly susceptible to ferroptosis. The mesenchymal properties induced by EMT increase the malignancy of cancer cells. Therefore, therapy involving the induction of ferroptosis has potential in the treatment of advanced OSCC with invasion and metastasis. (J Osaka Dent Univ 2023; 57: 17-24)

Although fluctuations in glucose concentration have been reported to regulate osteogenic differentiation, the effect on periodontal ligament cells (PDLCs) is not clear. We investigated the effect of fluctuating glucose concentrations on the cellular functions of PDLCs. Variations in glucose concentration were examined in four ways. Group A was incubated in 100 mg/dL glucose for 14 days. Group B was incubated in 100 mg/dL glucose for 7 days, the culture medium was replaced with 0 mg/dL glucose, and the group was then incubated for another 7 days. Group C was incubated in 0 mg/dL glucose for 7 days, the culture medium was replaced with 100 mg/dL glucose, and the group was then incubated for another 7 days. Group D was incubated in 0 mg/dL glucose for 14 days. We evaluated the osteogenic differentiation capacity by alkaline phosphatase (ALP) activity, ALP staining, calcium deposition and alizarin red staining after the 14 days of culturing. We found that the osteogenic differentiation of PDLCs was enhanced in the presence of glucose, suggesting that glucose metabolism regulates the osteogenic differentiation of PDLCs, especially in the early stages of differentiation. (J Osaka Dent Univ 2023; 57: 25-29)

In recent years, there has been a tremendous increase in interest in dental esthetics. In prosthodontic clinical practice, patients are highly concerned with tooth color, among other esthetic requirements, and they have a strong desire to have white teeth. However, it is not clear what impression a person's tooth color gives to others, nor is it clear whether there is a difference between the impression men and women have. The purpose of this study was to determine the influence of different teeth colors have on the impression female smiles give by using the semantic differential method and factor analysis. The subjects were 52 students undergoing clinical training at the School of Dentistry, Osaka Dental University. The average face of 10 adult women whose tooth color had been converted by image processing to C4, A2 or NW0 according to the shade guide was used as the stimulus image, and an impression measurement was performed. As part of the statistical analysis, an exploratory factor analysis was conducted on the impression structure of different tooth colors on the impression of female smiles. The extracted factors were subjected to two-way analysis of variance (mixed design), with tooth color and gender as factors. In the factor analysis, two factors were extracted: "gorgeous" and "natural". The analysis of variance revealed a difference in the main effect of tooth color for both factors. These findings suggest that differences in tooth color have an influence on the impression female smiles give to dental students, irrespective of their gender. (J Osaka Dent Univ 2023; 57: 31-40)

The fit of mouthguards fabricated using working models produced by a 3D printer based on impressions taken with an intraoral scanner were compared with the fit of those fabricated by conventional methods, i.e. mouthguards formed on plaster models using a pressure thermoforming machine. A maxillary dentition model was used as the master model. A total of 20 working models were replicated with hard plaster. The master model was scanned using an intraoral scanner, and 10 working models were produced using a 3D printer. A pressure thermoforming machine was used for 10 of the working models, and a vacuum former was used for the other 10. Mouthguard sheets were formed on 10 plaster models and 10 3D printer models using a pressure thermoforming machine. Similarly, the mouthguard sheets were formed on 10 plaster models using a vacuum former. The fit of the mouthguards fabricated by thermoforming on the working model fabricated by the 3D printer was not comparable to that of those fabricated by the conventional method. However, it was better than that of the mouthguards fabricated using the vacuum former. We concluded that, the fit of the mouthguards fabricated by thermoforming on a working model fabricated by a 3D printer is clinically acceptable. (J Osaka Dent Univ 2023; 57: 41-46)

Understanding the effect of smoking on oral pathologies at the molecular and cellular level is required for the stable progress of oral medicine. In the present study, we investigated the effect of tobacco smoke components (TSCs) and mechanical stimulation on the senescence of periodontal ligament cells. We cultured human periodontal ligament fibroblasts (HPdLFs) for different durations that were exposed to TSCs collected by our own original procedures. Proliferative activity and cellular senescence after TSC treatment was examined at different points in time. Our results demonstrated that HPdLFs continuously treated with TSCs exhibited characteristics of senescence. Moreover, there was an increased expression of the senescence-related gene when the senescent HPdLFs were cultured with a stretching stimulation. This result clearly suggests that stretching stimulation aggravates cellular senescence. (J Osaka Dent Univ 2023; 57: 47-53)

Although the complement cascade is the basis of innate immunity, little is known about its mechanism. NGF acts as an important mediator of the cascade acting downstream of the C5a receptor 1 (C5aR1). Although NGF is known to be involved in inflammatory pain, the mechanism by which NGF causes pain remains unclear. It is known that an injection of Complement 5a (C5a) into the hind paw skin of mice elicits painful behavior and enhances NGF expression in dermal macrophages. Sorting Nexin25 (SNX25) is part of a family of proteins that play important roles in membrane trafficking, intracellular signaling, membrane remodeling, and organelle motility, some of which also contribute to the immune system. Using the macrophage cell-line, J774.1, we examined whether SNX25 is involved in C5a-induced NGF expression at the cellular level. Treatment of J774.1 with C5a enhanced NGF and SNX25 expression. Western blotting revealed that C5a-induced NGF expression was reduced by Snx25 siRNA. Snx25+/- mice had lower NGF levels and showed a pain-insensitive phenotype in response to C5a. We propose that the expression level of C5a-induced NGF is controlled by macrophages through SNX25 signaling. (J Osaka Dent Univ 2023; 57: 55-62)

We calculated the utility scores for various oral conditions using the time trade-off (TTO) method which is an index-type scale. A nationwide survey was conducted in Japan among the general population using the internet. The utility score was calculated for each participant using the TTO method for 17 hypothetical oral conditions presented on a computer according to five assumed tooth loss conditions and medical interventions for each. When we analyzed the survey responses obtained from 2193 individuals, we found that the utility score declined as the number of missing teeth increased for the different tooth loss conditions. Furthermore, a histogram of the data representing the utility score exhibited a bimodal pattern for all oral conditions, and the bimodal data shifted with medical intervention, showing an increase in the utility score. These results enabled the calculation of utility scores for oral conditions in Japanese individuals and demonstrated that tooth loss affected the utility score. (J Osaka Dent Univ 2023; 57: 63-69)

The purpose of this study was to examine the reliability and interpretability of mandibular activity obtained from two different signal processing methods employing a three-axis accelerometer during mastication of mastication initiation training foods using the generalizability theory. The subjects were 17 healthy dentulous individuals with a mean age of 23.2±1.3 years who had no problems with mastication or swallowing. We calculated two types of mandibular activity, namely the mandibular activity (MA) detected from the central region of the chin and corrected mandibular activity that corrected MA using the activity of the forehead. For each subject, there were two measurement days at 1-week intervals, and three repeated measurements. To examine reliability, a generalizability study (two-facet crossed design) was performed with the subjects being the object of measurement, and the date of measurement and the number of measurements as the two facets. We found that when measuring mandibular activity, the use of mandibular activity corrected for forehead motion (head sway) and the use of the mean measurement over multiple days improved reliability and interpretability. (J Osaka Dent Univ 2023; 57: 71-81)

Antibacterial, antiviral and antimycotic activities of the photocatalytic semiconductor TiO2 have been demonstrated in recent years. The purpose of this study was to determine the antibacterial properties against bacteria in saliva of a synthetic dental filling resin containing TiO2. The test material contained anatase TiO2 microparticles that had been irradiated under light from a light-emitting diode for 2 h in saline. The material was then embedded in a mouthpiece and set in an oral cavity for 30 min. It was removed and washed in saline, and a bacterial suspension was collected from the wash solution and inoculated in fixed amounts onto blood agar plates that were then incubated anaerobically for 48 h. The bacterial counts were then calculated from photographic images of the plates. The packing density of viable bacteria on the plates (the percentage occupied by bacterial colonies) was found to be 16.3-87.6% without TiO2, and 0.5-24.1% with TiO2. The viable bacteria on the plates were 191-506×108 colony-forming units per milliliter (CFU/mL) in the non-TiO2 group, and 1-74×108 CFU/mL in the TiO2 group. Significant differences were seen between the two groups (p<0.01) for both packing density and viable cell counts. The results showed that light irradiation of the synthetic preventive dental filling resin containing TiO2 had an antibacterial effect on whole saliva. (J Osaka Dent Univ 2023; 57: 83-88)

Certain siderophores have recently been reported to inhibit the growth of cancerous cells. Here, we assessed the cytotoxic effects of two siderophores, deferriferrichrysin (Dfcy) and bisucaberin, on the human oral squamous cell carcinoma (OSCC) cell lines HSC-3 and SAS. The iron-chelating ability of Dfcy and bisucaberin was measured using an iron assay kit utilizing the ferrozine chromogenic method. Cell viability was measured using the WST-8 assay, and caspase-3 activity was determined using a caspase-3 assay kit. Apoptotic, anti-apoptotic, and cell cycle markers were assessed by western blot analysis. Dfcy chelated ferric iron in a dose-dependent manner. In addition, 10 μg/mL bisucaberin chelated approximately 75% of the iron. Dfcy and bisucaberin inhibited the proliferation of HSC-3 and SAS cells in a dose-dependent manner. Bisucaberin-treated SAS cells exhibited significantly increased caspase-3 activation. Cleaved poly (ADP-ribose) polymerase (PARP) was also increased in bisucaberin-treated HSC-3 and SAS cells and in Dfcy-treated SAS cells. Bisucaberin treatments alone upregulated cleaved caspase-3 in SAS cells. However, Dfcy had no effect on OSCC cell apoptosis. The results show that bisucaberin exerts potential anticancer effects against SAS cells by inducing apoptosis. (J Osaka Dent Univ 2023; 57: 89-97)

We investigated the relationship between sella turcica size and maxillofacial morphology in skeletal Class III malocclusion among Japanese adults.The subjects were 115 patients visiting the Osaka Dental University Hospital between May 2014 and March 2019 with ∠ANB<1.0°, negative overjet, and an absence of congenital abnormalities in the skeletal Class III malocclusion group. Individuals with 1.0° ≤ ∠ANB ≤ 4.0° were included as controls (n=122). Lateral cephalometric analysis was performed to measure the overbite depth indicator (ODI), the maximum anteroposterior width (W) of the sella turcica, depth (De) of the sella turcica, and diameter (Di) of the sella turcica; and interclinoid distance (I), among other parameters.

In the skeletal Class III malocclusion group, Di and I were significantly smaller among the males, and De was significantly larger among females. In males, a positive correlation was observed between De and ODI. In females, a positive correlation was observed between W and Pog to NB, De and ∠ANB, ∠Occlusal pl to SN, and ∠GoGn to SN. These findings indicate the possibility of predicting maxillofacial growth based on sella turcica morphology, which could help improve orthodontic treatment. (J Osaka Dent Univ 2023; 57: 99-106)

In the current World Health Organization (WHO) classification, oral epithelial dysplasia (OED) is classified using a two- or three-grade system. However, no useful auxiliary diagnostic method for determining the OED grade of specimens by this system has yet been established. In this study, specimens of not only OED, but also epithelial hyperplasia (Hp) and oral squamous cell carcinoma (OSCC) were examined immunohistochemically to investigate expression levels/rates of various antibodies. Six specimens of Hp, 13 of mild epithelial dysplasia (MiD), 11 of moderate epithelial dysplasia (MoD), 11 of severe epithelial dysplasia (SD), and 9 of OSCC obtained from the First Department of Oral and Maxillofacial Surgery at Osaka Dental University Hospital were examined immunohistochemically to determine the expression levels of CK13, CK17, CK19, Ki-67, p53, p63, p21, p27 and cyclin D1. The dysplasia grade was negatively correlated with expression of CK13 and CK17. As the dysplasia grade increased, expression rates of Ki-67, p53, p63, p21 and cyclin D1 increased, while the expression rate of p27 decreased. The expression rate of Ki-67 differed significantly between SD and OSCC, as did the expression of p53 between MoD and SD as well as between SD and OSCC. The expression rate of p63 differed significantly between MiD and MoD as well as between MoD and SD, as did the expression rate of p27 between SD and OSCC (p<0.05). These results suggest that not only CK13, CK17, Ki-67 and p53, but also p63, p21, p27 and cyclin D1 may be linked to dysplasia. The results also suggest that calculation of Ki-67, p53, p63 and p27 expression rates could be used for OED grading and auxiliary diagnosis of OSCC. (J Osaka Dent Univ 2023; 57: 107-117)

Transplantation of mesenchymal stem cells (MSCs) has been demonstrated to induce regeneration of periodontal tissues. Stem cell derivatives including paracrine factors, cell extract, and exosomes from MSCs are attracting attention as a novel cell-free treatment. We investigated the effect of cell extract from MSCs (MSC-extract) on the proliferation of periodontal ligament cells (PDLCs). We obtained MSC-extract from immortalized bone marrow-derived MSCs using freeze-thaw cycles and centrifugation. Water-soluble tetrazolium (WST)-8 assay and immunostaining of Ki67 were used to examine cell proliferation and detect cells in a proliferation state, respectively. Cycloheximide (CHX) was used to inhibit protein synthesis of MSCs. In the WST-8 assay, we found that MSC-extract increased the proliferation of PDLCs in a concentration dependent manner. MSC-extract significantly increased the number of Ki67-positive cells after 72 hours. Additionally, heat treatment of MSC-extract diminished the proliferation of PDLCs, and the MSC-extract obtained from CHX-treated MSC showed significantly lower proliferative effect on PDLCs. These results suggest that MSC-extract enhances the proliferation of PDLCs through its protein components. Our new findings may provide important information for the development of novel periodontal regenerative therapy. (J Osaka Dent Univ 2023; 57: 119-124)

Oral care from a young age is important for the prevention of dental caries and periodontal disease, as well as systemic diseases. Propolis, which has been used in traditional medicine for centuries, has value as a new oral care product because of its low toxicity, low allergenicity, and antimicrobial activity. However, the chemical composition of propolis extracts are extremely complex and influenced by region in the area where honey been live. In order to use propolis in oral care products, it is necessary to find out what ingredients it contains and how active they are. In this study, we evaluated the antimicrobial activity of a new Bahia propolis against oral pathogens. The results showed that the product has antimicrobial activity against the periodontopathogenic bacteria Porphyromonas gingivalis (P. gingivalis) and early colonizer Actinomyces oris. In particular, the effect on P. gingivalis was comparable to that of antimicrobials and disinfectants. Our results showed that the new Bahia propolis is a promising antimicrobial agent that may prevent oral infections. (J Osaka Dent Univ 2023; 57: 125-129)

We investigated the effect of blue light-emitting diode (LED) irradiation on the cariogenic bacteria Streptococcus mutans (S. mutans) and the gingival epithelial cell line GE-1 cells. Light-emitting diodes with a wavelength of 465 ± 10 nm were used to irradiate the S. mutans and GE-1 cells, and the cell viability was measured. The induction of the antioxidant enzyme heme oxygenase-1 was evaluated using quantitative reverse transcription polymerase chain reaction and western blotting. The results showed that blue LED irradiation with vitamin B partly suppressed the growth of S. mutans, and induced reactive oxygen species in GE-1 cells, thereby reducing cell viability. (J Osaka Dent Univ 2023; 57: 131-136)

Subcutaneous injection of enamel matrix derivative into rat back tissue results in the formation of eosinophilic round bodies (ERBs). When a large amount of ERBs are formed, they induce cartilage. Our previous studies have shown that ERB is a part of amelogenin exon-5. We therefore artificially created synthesised peptide (SP) with the same sequence as ERB. Subcutaneous injection of SP into rat back tissue induces bone and endochondral bone formation. Since amelogenin plays many important roles, we hypothesised that ERB, which is a part of amelogenin, may also play an important role. For this reason we produced a mouse monoclonal antibody (A-ERB) using SP, to investigate the function of ERB. In the present study, immunohistochemical staining with A-ERB was performed on oral cystic lesions in the expectation that A-ERB would react with odontogenic epithelium. We selected as test material seven human oral cystic lesions, the radicular cyst, dentigerous cyst, dermoid cyst, epidermoid cyst, orthokeratinised odontogenic cyst, odontogenic keratocyst, and unicystic ameloblastoma. They were sectioned and immunohistochemically stained using A-ERB. Although ERBs were expressed in the lining epithelium of dermoid cysts, they were not expressed in the epidermoid cysts. Although epidermis with cutaneous appendages expressed ERB, epidermis without cutaneous appendages did not. Dermoid and epidermoid cysts are now classified as the same lesion. However, the character of the lining epithelium of the two is different. Perhaps the two lesions should not be in the same category. (J Osaka Dent Univ 2023; 57: 137-146)

Dental hygienists need to understand basic anatomy in periapical radiographs to gather information and support imaging in oral health care. However, to date, few studies have analyzed how hands-on periapical radiography training (HPRT) enhances understanding of imaging anatomy for these students. The degree of knowledge in imaging anatomy required for second-year students was assessed using an objective test before the HPRT. For the hands-on training, the students were divided into two groups, the lecture only group and the lecture and hands-on training group. After the hands-on training, an objective test and subjective evaluation by a questionnaire were conducted. In the hands-on group, all the objective items of the students' knowledge of anatomy improved. The rate of increase was significantly greater than that for the group that had only the lecture. In the post-hands-on training questionnaire, the subjective evaluation was high except for the item related to willingness to learn more. This study showed that hands-on training was superior to lectures alone in understanding imaging anatomy. In the future, it is necessary to create classes that will motivate students to learn more about oral radiology. (J Osaka Dent Univ 2023; 57: 147-152)

We investigated the effect of low-temperature atmospheric plasma treatment on the bond strength between denture materials and self-curing resin. Cubical blocks of 15 mm each were fabricated from polymethyl methacrylate (PMMA) denture material. The surfaces of the blocks were polished to #280 water-resistant abrasive paper, and the surface was treated. A silicon mold with an inner diameter of 10 mm was filled with self-curing resin, cured for 15 minutes, and the mold was then removed. The experimental specimens were kept at room temperature for one week or immersed in water at 37°C, and then shear bonding tests were performed. After the shear test, the fracture surface was observed. The results of the shear bonding test showed that the shear bonding strength was greater with plasma treatment than without, regardless of whether the specimens were immersed in water. Plasma treatment was effective in improving the bond strength between the denture materials and self-curing resin. (J Osaka Dent Univ 2023; 57: 153-157)

We evaluated the effect of light irradiation on the bond strength between root canal dentin and six commercially available resin adhesives, as well as core composite resins. The root canal dentin was used as the bonding substrate. The light irradiation conditions were divided into four groups: 1) the bonding resin and core resin were not irradiated with light, 2) light was irradiated only on the core composite resin, 3) light was irradiated only on the bonding resin, and 4) light was irradiated on both the bonding resin and composite resin. The bonding procedures were performed according to the manufacturers' instructions. Resin-dentin bonded specimens were prepared, and the bond strength was measured. After the bond tests, the fractured surfaces were observed using a scanning electron microscope. The results showed that light irradiation increased the bond strengths in two of the systems, while no significant difference was found in the bond strength between the cases with or without light irradiation in the other four resin systems. The bond strength was not influenced by the light-irradiation in four of the six systems studied. It is suggested that a stable bond strength was obtained in the absence of light irradiation in these four bonding resin/core composite resin systems because of chemical polymerization. (J Osaka Dent Univ 2023; 57: 159-167)

We studied the effect of background color on the results of shade matching of natural teeth with shade guides. We photographed shade tab A2 and the maxillary right central incisors of four men and one woman with a mean age of 20.2 ± 0.4 years using a digital camera with lighting by a light emitting diode (LED) in a dark room. Digital image color analysis software was used to quantify the digital images using the CIE L*a*b* color space. For colorimetry, the shade tabs and natural teeth were divided into 12 regions. Background conditions were categorized as no background paper, and use of black, gray, or white background papers. The shade tab and natural teeth were affected differently by the background color. The shade tab results and the color difference between no background and the others were significant for all regions. The incisal area of natural teeth is easily affected by the background. This study suggests that, in the assessment and recording of shade tab results and the color of natural teeth, dental technicians and dentists need to use the same background color, and that when dental technicians make esthetic prostheses, they need to consider the background color. (J Osaka Dent Univ 2023; 57: 169-178)

We used cephalograms to investigate each measurement item of the maxillofacial morphology of skeletal Class I Japanese adult males and females with individualized normal occlusion. We also calculated the standard values of the Steiner analysis, which is widely used for setting treatment goals in orthodontic practice. In comparison with pre-existing Japanese measurements on growing children, in males, our results showed larger values for ∠SNB, ∠SND, U1 to NA (mm), U1 to NA (angle), Po to NB, Interincisal angle, SL, and SE, and smaller values for ∠ANB, L1 to NB (angle), ∠Occl to SN, and ∠GoGn to SN. In females, ∠SNB, ∠SND, U1 to NA (angle), Po to NB, Interincisal angle, SL, and SE showed large values, while ∠ANB, L1 to NB (angle), ∠Occl to SN, and ∠GoGn to SN, showed smaller values. Based on the results of our study, it is necessary to consider a new ratio for the relationship between the distances L1 to NB (mm) and Po to NB (mm) in Japanese because of Japanese facial features. (J Osaka Dent Univ 2023; 57: 179-186)

We investigated the effectiveness of four household vacuum cleaners in removing upper airway obstructions in the home. The researchers used three battery-powered vacuum cleaners and one powered from an electric wall socket outlet to measure suction performance. They found that the wall-socket powered vacuum cleaner had a negative pressure of 15.5 KPa, about four times greater than that of the battery-powered models, and a suction volume of 208 mL/sec, about twice that of the LT-105 battery-powered model. The results suggest that household vacuum cleaners may be a feasible option for removing upper airway obstructions in a domestic setting. However, further research is needed to determine their safety and efficacy compared to other methods such as back slaps and abdominal thrusts. (J Osaka Dent Univ 2023; 57: 187-189)

A 22-month prognostic study covering a total of 180 CAD/CAM crowns reported that 9 (5.0%) of them came off and 1 (0.6%) fractured.1 The purpose of this study was to clarify the effect of plasma treatment on the bond strength between resin blocks used for fabrication of CAD/CAM crowns that had contaminants, and the adhesive resin cement used to place them in the patient. Cerasmart Prime was used as the resin block, Panavia V5 as the cement, and Clearfil Ceramic Primer Plus as the primer. Silicone oil and machine oil were used as the contaminants. The materials were divided into those subjected to and not subjected to alumina blasting and plasma treatment. The resin blocks were bonded to stainless steel blocks. And shear bonding tests were then conducted. Two-way analysis of variance was performed for statical analysis. Plasma treatment and the type of contaminant were considered factors. There was a significant difference attributable to plasma treatment, but no difference for the contaminant factor. Specimens contaminated with machine oil and treated with plasma had the highest adhesive strength. Cohesive failure was observed within the block, indicating that plasma treatment is effective in removing the surface contaminants. (J Osaka Dent Univ 2023; 57: 191-195)

The digital images of abutment teeth obtained by optical scanners tend to have rounded sharp edges. This rounding can result in an ill-fitting fixed prosthesis. Ridgeline reconstruction restores the rounded edges of the digital abutment tooth image back to sharp edges, improving the margin accuracy of the CAD/CAM crown. However, the reproducibility of ridgeline reconstruction, including the associated manual operations, has not been clarified. In this study, we investigated this reproducibility. Prepared artificial teeth were scanned with a laboratory scanner, and standard tessellation language (STL) data were obtained. The region of the scan data corresponding to the finish line of the abutment tooth was manually isolated, and ridgeline reconstruction was performed with polygon editing software. We then measured the area above the finish line of the digital abutment tooth, the increased volume, and the length of the finish line. Systematic error for these three measured items were examined with repeated measures ANOVA and the magnitude of random error was examined with intraclass correlation coefficients. The reproducibility of ridgeline reconstruction indicated no systematic errors and relatively good reproducibility. (J Osaka Dent Univ 2023; 57: 197-202)

Reaming and filing are used fot pulp extraction and cleaning infected root canals. The smear layer is a residue of softened dentin in the dentin tubules. In endodontic treatment, the removal of the smear layer is very important in terms of infection control. Poly Ether Ether Ketone (PEEK) material has excellent resistance to heat, hydrolysis, chemical breakdown, radiation, and flames. It is widely used in industry for cleaning automobile parts such as gears. This study used PEEK material, which was developed as a root canal expander. A scanning electron microscope was used to evaluate its effect on the removal of the smear layer in the root canal. (J Osaka Dent Univ 2023; 57: 203-208)

We investigated how the extraction of mandibular second premolars, which tends to contribute to an increase in retromolar space, can affect the eruption process of third molars. Mandibular third molars rotate and change their position within the jawbone during development and erupt into the oral cavity at later stages of root maturation. This study targeted patients with mandibular third molars whose root maturation was nearing completion at the end of orthodontic treatment. Those having erupted third molars at the end of treatment were designated as the erupted group, while those having impacted third molars at the end of treatment were designated as the impacted group. Degree of root maturity was determined based on the Demirjian staging of tooth development where in Stage G the root apex remains open despite parallel root walls and in Stage H the root apex is completely closed. We examined 23 erupted third molars from 14 patients, and 28 impacted third molars from 15 patients. The first, second, and third molar axes were measured on panoramic radiographs taken at the start and end of treatment. The results showed no change in the first molar axis. Changes in the second molar axis were observed in both the erupted and impacted groups, showing significant uprighting after the end of treatment. At the start of treatment a significant difference between the two groups was found only in the second molar axis, with the erupted group showing a greater mesial inclination. The two groups showed no significant difference in the third molar axis at the start of treatment. These suggest that, given the same third molar axis, a mild mesial inclination of the second molars at the start of treatment may be a factor promoting the eruption of the third molars. (J Osaka Dent Univ 2023; 57: 209-215)

"Kissing molars" (KMs) are defined as the situation when the root apices of two impacted molars face each other so that their occlusal surfaces come into contact, and the crowns are located within a single follicle. Until now, only 14 cases of bilateral KMs, including this case, have been reported in the literature. We encountered a 41-year-old female in whom panoramic radiographs and computed tomography scans revealed bilateral impaction of the mandibular second and third molars. The occlusal surfaces of the impacted molars were in contact with each other, and their root apices were facing in opposite directions. In addition, the affected crowns were covered by clearly delineated, unilocular, round, cystic lesions. Tooth extraction and extirpation were performed under general anesthesia, and the lesions were histopathologically diagnosed as dentigerous cysts. The patient's postoperative course has been good with no recurrence of the lesions for 24 months. (J Osaka Dent Univ 2023; 57: 217-222)