Purpose: Recently, low reactive level laser therapy (LLLT), which involves applying photobiomodulation (PBM) to living organisms, has been used for periodontal treatment, but there are few reports on its molecular biology, and further research is needed for clinical application. The aim of this study was to elucidate the biological effects of laser irradiation based on PBM at human gingival epithelial cells (HGKs) by analyzing gene expression and their interactions over time.

 Methods: HGKs were irradiated at 0.31 J/cm² (0.1 J, 30 pps, 10 s). DNA microarray analysis was performed at 6 hours after irradiation. We extracted differentially expressed genes (DEGs) and analyzed their biological processes (BPs). Among the included BPs, we focused on ‘cellular response to stress’ and searched for key genes that were significantly associated with multiple genes by investigating protein-protein interactions (PPIs). Chronological gene expression of the key genes was analyzed at 1, 3, 6, 12, and 24 hours after laser irradiation.

 Results: We identified 10 key genes, cyclin dependent kinase inhibitor 2A (CDKN2A), fas cell surface death receptor (FAS), interleukin-6 (IL6), interferon regulatory factor 3 (IRF3), MDM2 proto-oncogene (MDM2), replication factor C subunit 3 (RFC3), replication protein A1 (RPA1), sirtuin 6 (SIRT6), sirtuin 7 (SIRT7), and X-linked inhibitor of apoptosis (XIAP), among the PPIs in the BP ‘cellular response to stress’. The results of chronological expression analysis inferred directions of interactions between the key genes.

 Conclusion: LLLT increased the expression of 2,756 genes involved in cell proliferation. The influences on CDKN2A, FAS, IRF3, MDM2, RFC3, RPA1, SIRT6, SIRT7, and XIAP among the major genes of BP ‘cellular response to stress’ with LLLT were new discoveries in the dental field. The effects of LLLT on HGKs were related to inflammation, such as IL6, which was expressed immediately after irradiation, and related to cell repair, such as MDM2, which was upregulated over time. Among the key genes, MDM2 and IL6 were considered to play an important role in the associations with other genes and MDM2 had a role in the duration of the effect.

 Purpose: Human gingival crevicular fluid (GCF) comprises various bioactive substances, including tissue-destructive factors such as matrix metalloproteinases (MMPs) and inflammatory cytokines, and has the potential to be used as a bioinformatics tool without invasive sampling. In 2017, the Classification of Periodontal and Peri-Implant Diseases and Conditions was reported at the World Workshop jointly held by the American Academy of Periodontology and the European Federation of Periodontology. However, the criteria for biomarkers of gingival sulcal exudate in the Grade Classification are without sufficient advantages or evidence data. In this study, we analyzed the correlation between GCF volume, total protein concentration, changes in tissue-destructive factors (MMP), tissue-destructive inhibitors (tissue inhibitors of metalloproteinases, TIMP), and clinical profiles such as probing depth (PD), bleeding on probing (BOP) rate, and periodontal inflamed surface area (PISA) for each patient classified according to Grade in the Periodontal Disease Classification (2017) at the initial visit. We aimed to improve the accuracy of diagnosis by Grade based on tissue-destructive factors in GCF by analyzing the correlations between clinical profiles, such as PD, BOP, and PISA.

 Methods: In total, 184 patients (Grade A: 38, Grade B: 124, Grade C: 22) with chronic periodontitis and 14 healthy volunteers (Control) were included in this study. Periodontal clinical parameters were recorded, GCF was obtained at the initial visit, and the concentrations of MMP-8, MMP-9, TIMP-1, and TIMP-2 were measured using antibody membrane assay and enzyme-linked immunosorbent assay. Correlations with BOP rate and PISA were also evaluated.

 Results: The GCF volume and total protein concentration increased with Grade progression (p＜0.05); BOP rate (r＝0.569) and PISA (r＝0.622) showed a positive correlation with the GCF volume. MMP-8 and MMP-9 expressions increased with the progression of Grade (p＜0.05), whereas TIMP-1 expression decreased after Grades B and C (p＜0.05). When comparing the correlation with BOP rate and PISA, MMP-8 and MMP-9 showed a positive correlation, whereas TIMP-1 showed a negative correlation (BOP rate: MMP-8, r＝0.850; MMP-9, r＝0.517; TIMP-1, r＝−0.657; PISA: MMP-8, r＝0.837; MMP-9, r＝0.459; TIMP-1, r＝−0.571).

 Conclusion: The expression levels of MMP-8, MMP-9, and TIMP-1 in GCF were useful indicators in differentiating the Grade.

 Purpose: In current dentistry, resin composites with excellent color matching properties that develop by applying structural color have emerged and are used clinically. Resin composites have unique characteristics, and many investigations related to color have been reported, such as shade matching, optical behavior, and resistance to discoloration, but few reports have examined shrinkage stress in detail. We therefore compared shrinkage stresses in a resin composite that develops structural color with those in a conventional resin composite that develops color with dyes. In addition, the depth of concavity on the free surface caused by polymerization shrinkage was measured and this shrinkage depth was discussed.

 Methods: Omnichroma (Tokuyama Dental, Tokyo, Japan, OM) as a structurally chromogenic resin-based composite and Estelite Σ Quick A2 shade (Tokuyama Dental, ES) as a dye-colored resin-based composite were used as experimental materials. Each material was filled into a cavity mold simulating a Class 1 cavity, then generated shrinkage stress was measured with a servo-driven shrinkage stress-measuring device from the start of light curing until 24 h later. Shrinkage depth was calculated by measuring the distance from the outer edge of the free surface of the cavity mold to the deepest part of the concavity formed by shrinkage using a 3D optical profilometer. Statistical analysis was performed using Student’s t-test at the 5％ level of significance.

 Results: Shrinkage stresses of OM and ES showed similar changes from the start to the end of measurement. Both OM and ES showed a rapid increase in shrinkage stress during light curing and a gradual increase after completing light curing. Maximum shrinkage stress was recorded within 24 h for all samples. Statistical analysis showed significantly smaller shrinkage stress at only 10 s after starting light curing for OM, but no significant difference between OM and ES in shrinkage stress or maximum shrinkage stress at other measurement times. Concavity of the free surface of the cavity mold was more clearly observed in OM than in ES. As a result, shrinkage depth was significantly higher in OM than in ES.

 Conclusion: Shrinkage stresses for OM, which is structurally chromogenic, and ES, which is chromogenic due to dyes, showed almost the same changes over time, except in the very early stage of polymerization.

 Purpose: The purpose of this study was to elucidate the effect of a wet environment around the root on dimensional changes in resin-based root canal sealers during setting.

 Methods: Human extracted teeth collected at The Nippon Dental University Hospital were used for the experiments (NDU-T2021-53). In Experiment 1, both a cut root test piece and an acrylic resin test piece with cylindrical cavities 3.0 mm in diameter and 5.0 mm in depth were prepared. Three types of root canal sealers (sealer) were used: methacrylate resin-based (MR), epoxy resin-based (ER), and zinc oxide eugenol-based (ZE). For each sealer, three environments were set: a water group (-W) and a dry group (-D) using cut root test pieces, and a negative control group (-N) using acrylic resin test pieces, for a total of nine groups (n＝8 each). The setting time for each group was measured using a Gilmore needle. In Experiment 2, using the same conditions as Experiment 1, a CMOS laser application sensor was used to irradiate the sealer area with a laser and measure non-contact dimensional changes from immediately after injection to double the setting time. In Experiment 3, to evaluate water penetration into sealer, root test pieces were prepared from root portions of extracted teeth. As in Experiments 1 and 2, three sealer groups, MR-R, ER-R, ZE-R (n＝8 each), were injected, with 2.0 mm of the root apex immersed in 1％ Rhodamine B and the rest in physiological saline solution. After the setting time, sections were cut perpendicularly along the root axis every 1.0 mm and fluorescence intensity was measured by confocal laser scanning microscopy. In the statistical analysis, significance was checked using the Kruskal-Wallis test and multiple comparisons were made using the Steel-Dwass test (p＜0.05).

 Results: Experiment 1 showed significant differences between environments for MR and ZE. Experiment 2 showed significant differences between environments for MR and ER. W group comparisons showed significant differences between MR-W and both ER-W and ZE-W before and after the setting time. Experiment 3 showed a significant difference between MR-R and the other two groups at 2.0 mm.

 Conclusion: This study showed the effects of the wet environment around the root on setting reactions and dimensional changes in resin-based root canal sealers during setting. It is considered that the MR in the methacrylate sealer expanded by taking up water around the root during setting.

 Purpose: The purpose of this study was to elucidate the roles of the neurotransmitter calcitonin gene-related peptide (CGRP) and innate immune regulation to investigate dentin regeneration during the pulp healing process.

 Methods: Experimental dental pulp injury was induced in 8-week-old Wistar rats by making group cavities in the mesial proximal surface of the maxillary first molars. Histologic analyses were performed postoperatively at 1, 3, 5, 7, and 14 days. The pathological condition of the dental pulp and periapical periodontal tissues was examined by hematoxylin and eosin staining; the dynamics of odontoblasts were evaluated with anti-nestin antibodies; apoptosis was assessed by TdT-mediated dUTP nick-end labeling (TUNEL) assay; cell proliferation was measured with anti-Ki67 antibodies; and the dynamics of nerve fibers, M2 macrophages and dendritic cells, and CGRP expression patterns were analyzed with anti-PGP9.5, anti-CD206, and anti-CGRP antibodies, respectively.

 Results: Infiltration of inflammatory cells, mainly of polymorphonuclear leukocytes and macrophages, was strong on postoperative day 1 and decreased over time. In contrast, the positivity rates for nestin, PGP9.5, and Ki-67 peaked between postoperative days 3 and 5 and then decreased. CGRP positivity rates increased at the dentin-pulp interface directly beneath the cavity from postoperative day 7 to day 14, and the area of reparative dentin also increased from postoperative day 5.

 Conclusion: In dental pulp tissue, the anti-infection function of innate immune-related cells, enhanced by neuropeptide CGRP production, promotes the formation of reparative dentin during the pulp healing process after dental injury.

 Purpose: Chemokine (C-C motif) ligand 28 (CCL28), the most recently identified chemokine, was reported in 2000 and has chemotactic and bactericidal activity. CCL28 is expressed in various tissues, including the salivary glands; however, whether CCL28 is expressed in human dental pulp is unclear. Therefore, this study investigated CCL28 expression in inflamed human dental pulp tissue and whether CCL28 and its receptor, C-C motif chemokine receptor 10 (CCR10), are expressed in cultured human dental pulp cells in response to inflammatory stimuli.

 Methods: CCL28 expression in human dental pulp tissue was analyzed using immunohistochemistry. CCL28 and CCR10 mRNA and protein expression in cultured interleukin one beta (IL-1β) -stimulated human dental pulp cells was examined using real-time PCR and western blotting. CCL28 and CCR10 protein expression was analyzed using fluorescent immunocytochemical staining.

 Results: In inflamed human dental pulp tissue, strong CCL28 signals were detected in dental pulp cells located at sites of intense inflammation accompanied by infiltration of inflammatory cells. Furthermore, IL-1β enhanced CCL28/CCR10 mRNA and protein expression in cultured human dental pulp cells. These findings suggest that CCL28 produced by dental pulp fibroblasts may act in an autocrine and paracrine manner during dental pulp inflammation and may be involved in the inflammatory cascade in the dental pulp.

 Conclusion: CCL28/CCR10 may be involved in the immune response in inflamed human dental pulp. Understanding the role of CCL28 in dental pulp tissue provides insights into the progression of pulp inflammation through CCR10.

 Purpose: This case report describes the restoration of a missing lower second premolar using a direct resin-bonded fixed partial denture (RBFPD), employing the composite resin injection technique with a digital workflow and a transparent silicone index. While conventional direct composite RBFPD can be technique-sensitive, this approach simplifies and standardizes the process, making it less dependent on the operator’s experience.

 Methods: A 50-year-old male patient sought restoration of a missing lower second premolar, preferring to avoid cutting intact teeth or surgical interventions such as dental implants. Thus, a direct composite RBFPD was chosen. The restoration was digitally designed, and a transparent silicone index was fabricated from a 3D-printed dental model, which featured mesial and distal, narrow bucco-lingual extensions to prevent overflow of the composite resin. After the adjacent abutment teeth were bonded with a two-step self-etching adhesive, a highly filled universal-shade flowable composite resin was injected through the opening of the occlusal surface of the silicone index.

 Results: The procedure proved to be straightforward, with the success of treatment being less dependent on clinical technique sensitivity. In the laboratory, the need for conventional free-hand wax-up with paraffin wax was eliminated in favor of digital wax-up. The design resulted in less overflow of the flowable composite resin in the cervical area, enhancing cleanability with interdental brushes. A functional and esthetic replacement of the missing premolar was achieved without tooth preparation.

 Conclusion: This technique provides a minimally invasive and cost-effective solution with predictable clinical outcomes, establishing it as a potential definitive restorative option.

 Introduction: It can be difficult for inexperienced dentists to properly treat root canals. In recent years, the use of a dental operating microscope (hereafter referred to as “microscope”) has become widespread in root canal treatment for closely examining root canal morphology. This study reports that even a second-year postgraduate dentist could treat a maxillary first molar with six root canals, without missing any, by using a microscope.

 Case: A 34-year-old male patient underwent a pulpectomy under anesthesia on the maxillary left first molar due to acute suppurative pulpitis, which was performed by a second-year postgraduate dentist. During treatment, percussion pain was observed, but after repeated exploration of the root canal under the microscope, six root canals, including two mesiobuccal, three distobuccal, and one palatal canal, were successfully treated without missing any. The symptoms disappeared, and good treatment results were obtained.

 Results: The patient was in good condition at 7 months after treatment, and the X-ray images showed no abnormalities.

 Discussion: Even dentists with limited treatment experience can properly perform root canal treatment on teeth with numerous root canals by conducting the treatment under a microscope while paying attention to changes in clinical symptoms. It was observed that a microscope is effective for helping inexperienced dentists treat root canals without missing them.

 Conclusion: A dentist with limited treatment experience could properly treat a maxillary first molar with six root canals using a microscope.

 Immature teeth are roots that have not completely formed. Once the pulp of an immature tooth has become devitalized, there is no prospect of root development, and since the root is short and the tooth structure thin, it is at higher risk of fracture. However, treatment to enable the long-term preservation of teeth that have become diseased is important for the stability of the dentition and to maintain occlusal function.

 Case: A boy, aged 11 years 10 months, presented with the chief complaint of swelling of the gingiva in the lower left premolar region. Dental X-rays showed that the root of the lower left second premolar was not completely formed, and a periapical radiolucency was evident from the apex to the central part of the root. A radio-opacity thought to be a dentin bridge was seen at the root canal foramen, and partial pulpotomy had been conducted in the vicinity of the tooth neck in previous treatment. There was no vital response on electric pulp testing. It was thought that, despite vital pulp therapy, the pulp of the lower left second premolar had become devitalized, and periapical periodontitis had occurred. Given the results of these investigations, The diagnosis was based on AAE criteria. Pulpal diagnosis was pulp necrosis, and apical diagnosis was chronic apical abscess.

 Pulp necrosis and chronic apical abscess was diagnosed. Since the root formation of this tooth was incomplete, we decided to conduct apexification, but with no evident improvement in symptoms. Cone-beam computed tomography (CBCT) was performed to clarify the root canal morphology. Diagnostic imaging with CBCT showed that there was a transverse fracture of this root near its apex. In axial section, a radio-opacity believed to be the lesion extended to the root of the left first premolar and the mesial root of the left first molar. Because the condition was not cured by regular root canal treatment, it was decided to conduct endodontic microsurgery.

 Course: There were no symptoms after two years. The patient continues to heal, since X-rays show that the radiolucency has contracted.

 Conclusion: Based on the findings of CBCT, endodontic microsurgery of an immature tooth with failed vital pulp therapy was performed and achieved adequate functional recovery following a good postoperative course.

 Purpose: Conservative treatment of vertical root fractures (VRF) is challenging. Bonding treatments for VRF using adhesive materials have recently been reported. There are two types of bonding treatments for VRF: internal adhesive therapy, in which the fractured tooth is bonded nonsurgically through the root canal, and a combination of adhesive therapy and intentional replantation, in which the fractured tooth is extracted, bonded extraorally, and replanted. This report describes a long-term case of a mandibular molar with complete VRF successfully restored using adhesive therapy and intentional replantation.

 Case: The patient was a 50-year-old female with a complaint of discomfort in the first molar of the left mandible. A sinus tract was observed in the buccal gingiva. The periodontal pocket depth was 9 mm on the buccal aspect of the mesial root and 3 mm in other areas, and the mobility was 0 degree. Dental radiography showed halo radiolucency around the mesial root. The condition was diagnosed as a complete VRF of the mesial root of the mandibular left first molar. Treatment methods included adhesive therapy and intentional replantation.

 Treatment: The tooth was extracted with forceps to avoid damage to the periodontal ligament and immediately preserved in a preservative solution. The infected root canal contents and fractured surfaces were removed. The root canal and fractured fragments were bonded using a one-step adhesive and filled with a dual-cure core resin. A 0.9-mm U-shaped wire was embedded in the root canal for reinforcement. The end of the root apex was retro-filled with MTA. The tooth was replanted into the socket and loosely fixed using simple sutures. The stitches were removed after seven days. Three months after surgery, a dental radiograph showed a reduction in bone radiolucency; however, bone loss was observed in the root furcation area. One year and one month after surgery, dental radiography revealed bone formation around the mesial root, and bone radiolucency had almost disappeared. Four years and six months after surgery, a dental radiograph showed the lamina dura around the mesial root and bone formation in the root furcation area. Seven years and one month after surgery, no recurrence of the root fracture was observed on dental radiography.

 Conclusion: Successful healing can be expected by applying adhesive therapy using a dual-cure core resin and a metal wire and intentional replantation of mandibular molars with complete VRF. The patient remains in good condition at seven years and one month of follow-up.