Pleiotropic roles of LAMMER kinase, Lkh1 in stress responses and virulence of Cryptococcus neoformans.

Dual-specificity LAMMER kinases are highly evolutionarily conserved in eukaryotes and play pivotal roles in diverse physiological processes, such as growth, differentiation, and stress responses. Although the functions of LAMMER kinase in fungal pathogens in pathogenicity and stress responses have been characterized, its role in Cryptococcus neoformans, a human fungal pathogen and a model yeast of basidiomycetes, remains elusive. In this study, we identified a LKH1 homologous gene and constructed a strain with a deleted LKH1 and a complemented strain. Similar to other fungi, the lkh1Δ mutant showed intrinsic growth defects. We observed that C. neoformans Lkh1 was involved in diverse stress responses, including oxidative stress and cell wall stress. Particularly, Lkh1 regulates DNA damage responses in Rad53-dependent and -independent manners. Furthermore, the absence of LKH1 reduced basidiospore formation. Our observations indicate that Lkh1 becomes hyperphosphorylated upon treatment with rapamycin, a TOR protein inhibitor. Notably, LKH1 deletion led to defects in melanin synthesis and capsule formation. Furthermore, we found that the deletion of LKH1 led to the avirulence of C. neoformans in a systemic cryptococcosis murine model. Taken together, Lkh1 is required for the stress response, sexual differentiation, and virulence of C. neoformans.

Evaluation of residual dentin thickness using quantitative light-induced fluorescence technology.

This study aimed to determine whether a correlation exists between residual dentin thickness and quantitative light-induced fluorescence (QLF) values and, if so, to analyze its tendencies. Forty extracted sound human molars were assigned to filled and unfilled groups. The teeth were submerged in a mold with clear acrylic resin. Red utility wax was inserted into the pulp chamber space in the filled group to simulate vital pulp. The specimen was sectioned longitudinally to observe the inside of the pulp space. The samples were cut horizontally from the highest point of the pulp space 2 mm apart. QLF images were then taken of 2 mm, 1 mm, and 0.5 mm samples using the QLF-D Biluminator™ 2 + system. Three operators independently evaluated the QLF images, and the statistical analysis was conducted using one-way analysis of variance, Pearson correlation coefficients, and intraclass correlation coefficients. In the filled group, the mean ΔF values for residual dentin thicknesses of 2 mm, 1 mm, and 0.5 mm were - 3.22, - 7.84, and - 11.52, respectively. In the unfilled group, the mean ΔF values were 0, - 6.90, and - 10.14, respectively. A positive correlation was found between residual dentin thickness and ΔF values (P < 0.05). The intraclass correlation coefficients for observations made by the three operators for the filled and unfilled groups were 0.831 and 0.917, respectively (P < 0.05). In conclusion, residual dentin thickness and ΔF values were significantly correlated and had a highly positive correlation regardless of the QLF device operator.

Three-dimensional evaluation of dentopalatal changes after rapid maxillary expansion in growing children.

INTRODUCTION: In growing children with transverse malocclusion problems, various types of rapid maxillary expanders (RMEs) have been effectively used in skeletal and dental expansions. We evaluated 3-dimensional dentopalatal changes in growing children who underwent maxillary expansion using RMEs and bonded RMEs. METHODS: We investigated dentopalatal changes in 20 patients treated with bonded RMEs, 19 with RMEs, and 38 control patients. Dental plaster models before and after expansion were scanned 3-dimensionally and superimposed to evaluate transverse expansion, expansion ratio, angular expansion, and palatal expansion height ratio. RESULTS: Using bonded RMEs, similar anterior and posterior dental expansions were achieved with an efficiency of 69%-76% (expansion ratio), and palatal soft-tissue expansion occurred more apically in the posterior area (palatal expansion height ratio, 1.00) than in the anterior area (palatal expansion height ratio, 0.64). Using RMEs, a larger posterior dental expansion was achieved, with an efficiency of 106%-117% (expansion ratio), than anterior dental expansion (55%-60%), and palatal soft-tissue expansion occurred more apically in the posterior area (palatal expansion height ratio, 0.99) than anterior area (palatal expansion height ratio, 0.23). CONCLUSIONS: Dental expansions in the anterior and posterior areas were similar using bonded RMEs, whereas the posterior dental expansions were larger than those of the anterior area using RMEs. The entire palatal soft-tissue slope expanded in the posterior area, whereas the occlusal part expanded in the anterior area using RMEs and bonded RMEs.

Effect of icariin surface treatment on the resorption of denuded roots after replantation in rat.

AIM: Limiting the incidence of resorption associated with delayed replantation of avulsed teeth is critical for long-term tooth survival. In this study, we assessed whether icariin, a natural product with anti-osteoclastic properties, could reduce root resorption in a rat model of tooth replantation. METHODOLOGY: Cytocompatibility of icariin (10, 20, 40 and 80 µM) was evaluated by CCK-8 proliferation assay in vitro, and an osteoclastogenesis assay was performed to evaluate the effect of icariin on the differentiation of rat bone marrow macrophages and human peripheral blood monocytes into tartrate-resistant acid phosphatase-stained (TRAP+ ) multinucleated giant cells (MNGCs). Differentiation of human periodontal ligament stem cells (hPDLSCs) treated with icariin (10 µM) was also evaluated at 5, 10 and 21 days of osteogenic induction. The first maxillary molars of five-week-old male Sprague-Dawley rats were extracted, denuded of PDL, then treated either with neutralized collagen solution (Carrier control) or icariin in collagen (3 µg/µL) before replantation into their sockets. The animals were euthanized 2 weeks post-surgery for micro-computed tomography (micro-CT) imaging and histological analyses. RESULTS: Icariin was cytocompatible and significantly reduced the differentiation of TRAP+ MNGCs in a dose-dependent manner compared to the control. Moreover, icariin enhanced alkaline phosphatase activity, expression of osteogenic marker genes and proteins, and calcium deposition in hPDLSCs. Micro-CT imaging of the replanted samples demonstrated a significantly higher volume of remaining roots in the icariin-treated group than in the control group. Histological analysis revealed a marked number of resorptive lacunae with TRAP activity in the control group, whereas icariin-treated samples showed signs of functional healing and reduced osteoclastic activity. CONCLUSIONS: Icariin was biocompatible and demonstrated potent anti-osteoclastic and pro-osteogenic properties that reduced resorption and promoted functional healing of denuded roots in a rat maxillary first molar model of replantation. These findings indicate that root surface treatment with icariin may be a clinically relevant and practical method for improving the retention and survival of teeth with compromised PDL after delayed replantation following traumatic avulsion.

Biological Function and Potential Applications of Garcinol in Human Dental Pulp Stem Cells.

INTRODUCTION: The regeneration of pulp tissue is crucial for true regenerative endodontic treatment, which requires a reduction in osteogenic differentiation. Garcinol, a histone acetyltransferase inhibitor, is a natural regulator that is known to suppress the osteogenic differentiation of dental pulp stem cells. In this study, the inhibitory effect of garcinol on the osteogenic differentiation of human dental pulp stem cells (hDPSCs) was evaluated using three-dimensional culture under in vitro and in vivo conditions. METHODS: hDPSCs were obtained from caries-free third molars and cultured with 10 µM garcinol for 7 days in an ultra-low attachment plate. The cell stemness and expression of osteogenic differentiation-related genes were analyzed using reverse transcription-polymerase chain reaction and single-cell analysis. A transplantation experiment was performed in mice to investigate whether garcinol-treated hDPSCs showed restrained osteogenic differentiation. RESULTS: hDPSCs cultured in the U-shaped ultra-low attachment plate showed the highest expression of stemness-related genes. Garcinol-treated hDPSCs demonstrated downregulation of osteogenic differentiation, with lower expression of bone sialoprotein, which is related to bone formation, and higher expression of dentin sialophosphoprotein, which is related to dentin formation. However, the garcinol-treated hDPSCs did not show any alterations in their stemness. Consistent results were observed in the transplantation experiment in mice. CONCLUSIONS: Garcinol reduced the osteogenic differentiation of hDPSCs, which can contribute to true regenerative endodontic treatment.

Three-dimensional accuracy of endodontic access preparations using novel nonrestrictive static guides: A laboratory study.

This study compared the accuracy of traditional endodontic access to conservative access cavities prepared with or without novel nonrestrictive endodontic access guides by operators with different levels of clinical experience without visual aids, using a three-dimensional volumetric accuracy analysis method. The accuracy of the preparations was analysed using a novel 3D volumetric analysis by calculating the intersection and volume of the actual cavities to the planned model cavities. The experienced operator significantly outperformed the inexperienced operator in the free hand groups, while accuracy of conservative access cavities prepared using the novel guides were comparable and significantly higher than the other groups (p < 0.05). The results demonstrated clinical experience enhanced endodontic preparations accuracy and that nonrestrictive guides achieve accurate conservative access cavities which are independent of the operator skill level. Additionally, the three-dimensional volumetric analysis is a consistent and objective method to judge the accuracy of guided endodontic techniques.

Real-time optical detection of endodontic infection using bacterial autofluorescence.

OBJECTIVES: For successful root canal treatment (RCT), it is essential to objectively assess the presence and activity of bacteria in the root canal system. However, current methods rely on subjective observations of root canal exudates. This study aimed to confirm whether real-time optical detection using bacterial autofluorescence can evaluate endodontic infection status by assessing the red fluorescence (RF) detected from root canal exudates. METHODS: During RCT, endodontic paper points were used to collect root canal exudates scored using conventional organoleptic tests to assess the severity of root canal infections. RF on the paper points was assessed using quantitative light-induced fluorescence (QLF) technology. RF intensity and area from the paper points were quantified, and their correlations with infection severity were assessed using their organoleptic scores. The oral microbiome composition of RF samples was compared with non-red fluorescent (non-RF) samples. RESULTS: The RF detection rate was nil and >98% in the non-infectious and severe groups. The RF intensity and area significantly increased with infection severity (p<0.001) and showed strong correlations with organoleptic scores (r=0.72, 0.82, respectively). The diagnostic accuracy for detecting root canal infection using RF intensity was good to excellent (AUC = 0.81-0.95) and increased with infection severity. The microbial diversity of the RF samples was significantly lower than that of the non-RF samples. Gram-negative anaerobic bacteria such as Prevotella and Porphyromonas were more predominant in RF samples. CONCLUSIONS: Optical detection using bacterial autofluorescence can objectively evaluate endodontic infection status in real-time by assessing the RF of endodontic root canal exudates. CLINICAL SIGNIFICANCE: This real-time optical technology can be utilised to detect endodontic bacterial infection without conventional incubation, allowing clinicians to determine the endpoint of chemomechanical debridement and increase the positive outcomes of RCTs.

An Endodontic Forecasting Model Based on the Analysis of Preoperative Dental Radiographs: A Pilot Study on an Endodontic Predictive Deep Neural Network.

INTRODUCTION: This study aimed to evaluate the use of deep convolutional neural network (DCNN) algorithms to detect clinical features and predict the three-year outcome of endodontic treatment on preoperative periapical radiographs. METHODS: A database of single-root premolars that received endodontic treatment or retreatment by endodontists with presence of three-year outcome was prepared (n = 598). We constructed a 17-layered DCNN with a self-attention layer (Periapical Radiograph Explanatory System with Self-Attention Network [PRESSAN-17]), and the model was trained, validated, and tested to 1) detect 7 clinical features, that is, full coverage restoration, presence of proximal teeth, coronal defect, root rest, canal visibility, previous root filling, and periapical radiolucency and 2) predict the three-year endodontic prognosis by analyzing preoperative periapical radiographs as an input. During the prognostication test, a conventional DCNN without a self-attention layer (residual neural network [RESNET]-18) was tested for comparison. Accuracy and area under the receiver-operating-characteristic curve were mainly evaluated for performance comparison. Gradient-weighted class activation mapping was used to visualize weighted heatmaps. RESULTS: PRESSAN-17 detected full coverage restoration (area under the receiver-operating-characteristic curve = 0.975), presence of proximal teeth (0.866), coronal defect (0.672), root rest (0.989), previous root filling (0.879), and periapical radiolucency (0.690) significantly, compared to the no-information rate (P < .05). Comparing the mean accuracy of 5-fold validation of 2 models, PRESSAN-17 (67.0%) showed a significant difference to RESNET-18 (63.4%, P < .05). Also, the area under average receiver-operating-characteristic of PRESSAN-17 was 0.638, which was significantly different compared to the no-information rate. Gradient-weighted class activation mapping demonstrated that PRESSAN-17 correctly identified clinical features. CONCLUSIONS: Deep convolutional neural networks can detect several clinical features in periapical radiographs accurately. Based on our findings, well-developed artificial intelligence can support clinical decisions related to endodontic treatments in dentists.

Red fluorescence for assessing longitudinal tooth fractures.

BACKGROUND: This study was designed to determine whether autofluorescence emitted from longitudinal tooth fractures (LTFs) differs between fracture types, with the aim of determining which clinical factors are related to red fluorescence at the fracture line. METHODS: Thirty-three extracted teeth were classified into cracked teeth, split teeth, and root fractures using LTF types according to the American Association of Endodontists classification. The types of LTFs were identified using an operating microscope. LTF autofluorescence was captured using a fluorescence technique. Clinical examinations were performed using the preoperative factors from clinical and radiographic findings. RESULTS: Red fluorescence was identified in 82% and 83% of cracked and split teeth, respectively. None of the vertical root fractures exhibited red fluorescence (p<0.001). When red fluorescence was identified on the outer tooth surface, it penetrated into the crack line, but fluorescence that was not red at the tooth surface did not penetrate the fracture line. Among the examined preoperative clinical factors, differences between the presence and absence of red fluorescence were identified for sinus tract formation (p = 0.021), and radiographic features (p = 0.027). Regression analysis revealed a significant factor related to the red fluorescence, with sinus tract formation having a negative effect on red fluorescence (odds ratio [OR]=0.09). The presence of comprehensive periradicular lesions in radiography had a positive effect on red fluorescence (OR=5.04). CONCLUSIONS: Cracks originating from tooth crowns in certain types of LTFs were associated with red fluorescence, and cracks with red fluorescence were associated with extensive periodontal bone resorption around the teeth roots.

Single-Cell RNA Sequencing Analysis of Human Dental Pulp Stem Cell and Human Periodontal Ligament Stem Cell.

INTRODUCTION: Many studies have investigated the transcriptome profiles of dental stem cells for regenerative medicine. However, such studies use bulk RNA and do not consider cell-level heterogeneity. Here, we investigated the characteristics and heterogeneity of human dental pulp stem cells (hDPSCs) and human periodontal ligament stem cells (hPDLSCs) at the single-cell level and examined the differences between them. METHODS: hDPSCs and hPDLSCs were obtained from caries-free premolars (n = 2). Single-cell RNA sequencing of hDPSCs and hPDLSCs was performed using a Single Emulsion Systems (Dolomite Microfluidics, Royston, UK) droplet microfluidic device and the Illumina NextSeq550 system (Illumina, San Diego, CA). Data alignment was performed using STAR v2.4.0, and further analysis was performed using the Seurat, singleR, and clusterProfiler packages in R (R Foundation for Statistical Computing, Vienna, Austria). RESULTS: hDPSCs and hPDLSCs were separated into 3 clusters. hDPSCs mainly exhibited osteogenic and neurogenic cell populations. The main populations of hPDLSCs comprised osteogenic and myofibroblastic populations. hPDLSCs showed high "scores" for osteogenic gene expression, whereas hDPSCs had high neurogenic and endogenic scores. CONCLUSIONS: Single-cell RNA sequencing of hDPSCs and hPDLSCs revealed that the genes were expressed in specific clusters. The results of these analyses can be used as reference databases and valuable resources for further research in dental therapeutics.

The Effect of Mechanical Vibration on Osteogenesis of Periodontal Ligament Stem Cells.

INTRODUCTION: Appropriate occlusal forces can prevent ankylosis after tooth replantation or transplantation. However, the "proper occlusal forces" on periodontal ligament (PDL) healing have not yet been defined due to insufficient in vitro studies and uncertain in vitro models. Herein, we presented a mechanical vibration device as an in vitro model to determine such favorable occlusal forces. METHODS: Human periodontal ligament stem cells (hPDLSCs) were exposed to mechanical vibration force with 4 frequencies (30, 90, 150, and 210 rpm). Cell viability and the expression of osteogenic differentiation-related genes and proteins were tested in vitro. The calvarial transplantation experiment was performed to assess the bone formation ability of 150 rpm mechanical vibration stimulation (MVS). RESULTS: MVS at 150 and 210 rpm significantly reduced cell viability in the early stages. The 150-rpm MVS decreased osteogenic marker expression at the early time point (3 days) but had no harmful effects at the late time point (14 days). Furthermore, hPDLSC cell sheets treated with 150-rpm MVS had potential to decrease bone formation in rat calvarial defects serendipitously and facilitated functional PDL-like tissue formation. CONCLUSIONS: We found that MVS at a frequency of 150 rpm could provide a strategy for a transient reduction in the osteogenic potential of hPDLSCs and promote PDL-like tissue formation. Thus, 150-rpm MVS could be used as a controllable proper occlusal force to prevent ankylosis and promote PDL healing after tooth replantation or transplantation.

Preserving the vitality of teeth adjacent to a large radicular cyst in periapical microsurgery: a case report with 4-year follow-up.

BACKGROUND: Radicular cysts may enlarge considerably, cause extensive bone destruction, and jeopardize the integrity of the associated vital teeth. The different treatment approaches are aimed mainly at eliminating the cystic epithelial membrane while reducing the risk of injury to vital structures. Contrary to other treatment modalities, preapical surgery offers an unequivocal single occasion resolution for the patient. However, it has been associated with higher risk of collateral damages. CASE PRESENTATION: A patient presented with a large radicular cyst originating from a maxillary lateral incisor. The adjacent central and canine teeth initially failed to exhibit responses to sensibility tests but showed signs of vitality. Microsurgical management was aimed at enucleating the cystic membrane while maintaining adjacent teeth vitality. Upon careful and controlled cyst enucleation under the dental operating microscope, the neurovascular bundle of one of the involved teeth was visualized and its integrity was maintained throughout the procedure. RESULTS: The procedure was successful and follow up recalls revealed recovery of normal sensibility of tooth 11 and 13 with complete bone regeneration around their apices. CONCLUSION: Within the limitation of the present case report, we demonstrated that complete excision of large periapical cyst can be performed without sacrificing the vitality of the adjacent teeth, by preserving the integrity of their neurovascular supply through controlled microsurgical enucleation, and by a potential apical vascular repair ensuing unintended injury. Diagnosing the pulp vitality of non-offending teeth whose apices protrude into the cystic lumen is a complex process and can be misleading. Pressure from the growing cyst can inhibit vital teeth responses to neural-based sensibility tests leading to false negative results. Thus, in such cases, the use of blood perfusion-based vitality testing is recommended for correct initial diagnosis.

Survival and prognostic factors of managing cracked teeth with reversible pulpitis: A 1- to 4-year prospective cohort study.

AIM: This prospective clinical study evaluated the clinical performance of managing cracked teeth with reversible pulpitis through a combination of internal and external splinting and investigated factors that can affect pulp survival after splinting. METHODOLOGY: Thirty-four teeth diagnosed with cracks and reversible pulpitis were enrolled and treated with bidirectional crack splinting: 1) immediate splinting with a stainless-steel band, 2) internal splinting with crack line removal and resin filling and 3) external splinting with a temporary crown followed by final crown placement. If the symptoms remained/recurred, root canal treatment was performed. Patients were followed up at 3, 6 and 12 months, then annually thereafter. Kaplan-Meier survival analysis to calculate the survival of the treated teeth and Cox univariate proportional hazards regression model to investigate prognostic factors were performed. RESULTS: Twenty-nine (97%) teeth were followed up for up to 4 years. The pulp survival rate was 72% after banding and 91% after final crown cementation. No tooth was extracted (100% tooth survival rate). In the univariate Cox proportional hazard test, pain on percussion was the only statistically significant factor (hazard ratio = 11.77). Teeth with pain on percussion at the first visit had a pulp survival rate of 46% during the follow-up period. In comparison, their counterparts without pain had a 94% pulp survival rate. CONCLUSIONS: Bidirectional splinting successfully managed cracked teeth with reversible pulpitis. Pain on percussion (mechanical allodynia) may be an important factor in deciding whether to attempt root canal treatment on symptomatic cracked teeth. A step-by-step approach with bidirectional crack splinting should be encouraged for a cracked tooth with a vital pulp without mechanical allodynia rather than pre-emptive root canal treatment.

An Update on Endodontic Microsurgery of Mandibular Molars: A Focused Review.

Endodontic microsurgery is a highly predictable treatment option in most cases when conventional endodontic treatment is not feasible. Nevertheless, mandibular molars are still considered by clinicians to be the most difficult type of teeth, with the lowest success rate. In recent years, endodontic microsurgery has been attempted more frequently with the emergence of modern cutting-edge technologies such as dental operating microscopes, various microsurgical instruments, and biocompatible materials, and the success rate is increasing. This review describes the current state of the art in endodontic microsurgical techniques and concepts for mandibular molars. Notably, this review highlights contemporary equipment, technology, and materials.

Spontaneous repair of iatrogenic root perforation by an orthodontic miniscrew: A case report.

BACKGROUND AND OVERVIEW: Orthodontic miniscrews have become popular tools for providing temporary anchorage during orthodontic treatment. Although they are easy to insert, damage to the periodontal ligament or dental root during insertion is an unfavorable iatrogenic complication. Root perforation during miniscrew insertion in human teeth has been reported in a few articles. In this article, the authors describe the spontaneous repair of an iatrogenic root perforation in a mandibular first molar that occurred during insertion of an orthodontic miniscrew in a young girl undergoing orthodontic treatment. CASE DESCRIPTION: A 15-year-old girl with malocclusion was undergoing orthodontic treatment when the mesial root of her mandibular right first molar was damaged by an orthodontic miniscrew. The miniscrew and corresponding bracket were immediately removed to avoid any unnecessary forces on the tooth. Because the pulp remained vital without any additional damage and infection for 6 months, orthodontic treatment was resumed and completed in 9 months without any pulp damage or unfavorable symptoms. Serial periapical radiographs and cone-beam computed tomographic images showed that the injured area was surrounded by reparative tissue without any apical lesion. CONCLUSIONS AND PRACTICAL IMPLICATIONS: The findings of this case suggest that immediate removal of unnecessary forces provides an environment for spontaneous repair in cases of iatrogenic root perforation by orthodontic miniscrews, even when the damage involves the pulp. If force stimulation is avoided for a certain period, which was 6 months in this case, it may be possible to complete the orthodontic treatment without unfavorable symptoms.

A One-Year Radiographic Healing Assessment after Endodontic Microsurgery Using Cone-Beam Computed Tomographic Scans.

This study aimed to evaluate one-year radiographic healing after endodontic microsurgery using CBCT with modified PENN 3D criteria and to compare the outcome with results evaluated using Molven's criteria. A total of 107 teeth from 96 patients were evaluated one year after endodontic microsurgery by using CBCT scans with modified PENN 3D criteria and periapical radiographs with Molven's criteria. Both preoperative and postoperative lesion volumes were calculated using ITK-SNAP (free software). Radiographic healing assessment using periapical radiographs and CBCT images, and preoperative and postoperative lesion volume measurements were performed independently by two examiners. The assessment using Molven's criteria resulted in 75 complete healings, 18 incomplete healings, eight uncertain healings, and six unsatisfactory healings. Based on modified PENN 3D criteria, 64 teeth were categorized as complete healing, 29 teeth as limited healing, six teeth as uncertain healing, and eight teeth as unsatisfactory healing. With the one-year follow-up, CBCT scans showed a lower healing tendency than did periapical radiography. The volumes of apical radiolucency after the surgery were reduced by 77.7% on average at one-year follow up.

Comparison of Biocompatibility of Calcium Silicate-Based Sealers and Epoxy Resin-Based Sealer on Human Periodontal Ligament Stem Cells.

The aim of this study was to evaluate the biocompatibility of calcium silicate-based sealers (CeraSeal and EndoSeal TCS) and epoxy resin-based sealer (AH-Plus) in terms of cell viability, inflammatory response, expression of mesenchymal phenotype, osteogenic potential, cell attachment, and morphology, of human periodontal ligament stem cells (hPDLSCs). hPDLSCs were acquired from the premolars (n = 4) of four subjects, whose ages extended from 16 to 24 years of age. Flow cytometry analysis showed stemness of hPDLSCs was maintained in all materials. In cell viability test, AH-Plus showed the lowest cell viability, and CeraSeal showed significantly higher cell viability than others. In ELISA test, AH-Plus showed higher expression of IL-6 and IL-8 than calcium silicate-based sealers. In an osteogenic potential test, AH-Plus showed a lower expression level than other material; however, EndoSeal TCS showed a better expression level than others. All experiments were repeated at least three times per cell line. Scanning electronic microscopy studies showed low degree of cell proliferation on AH-Plus, and high degree of cell proliferation on calcium silicate-based sealers. In this study, calcium silicate-based sealers appear to be more biocompatible and less cytotoxic than epoxy-resin based sealers.

The application of "bone window technique" using piezoelectric saws and a CAD/CAM-guided surgical stent in endodontic microsurgery on a mandibular molar case.

Apical surgery for a mandibular molar is still challenging for many reasons. This report describes the applications of computer-guided cortical 'bone-window technique' using piezoelectric saws that prevented any nerve damage in performing endodontic microsurgery of a mandibular molar. A 49-year-old woman presented with gumboil on tooth #36 (previously endodontically treated tooth) and was diagnosed with chronic apical abscess. Periapical lesions were confirmed using cone-beam computed tomography (CBCT). Endodontic microsurgery for the mesial and distal roots of tooth #36 was planned. Following the transfer of data of the CBCT images and the scanned cast to an implant surgical planning program, data from both devices were merged. A surgical stent was designed, on the superimposed three-dimensional model, to guide the preparation of a cortical window on the buccal side of tooth #36. Endodontic microsurgery was performed with a printed surgical template. Minimal osteotomy was required and preservation of the buccal cortical plate rendered this endodontic surgery less traumatic. No postoperative complications such as mental nerve damage were reported. Window technique guided by a computer-aided design/computer-aided manufacture based surgical template can be considerably useful in endodontic microsurgery in complicated cases.

The Application of "Bone Window" Technique in Endodontic Microsurgery.

Endodontic microsurgery for a tooth with a large periapical lesion and an intact cortical plate may necessitate the removal of extra bone and cause delayed or unfavorable healing. In such cases, the "bone window" technique offers excellent exposure to the operative field and preserves cortical bone without placing any additional graft material. In the reported cases, root-end surgery was performed on the maxillary and mandibular molars with a large periapical lesion. The bone window was fashioned with the aid of thin osteotomy instruments and repositioned to the original site at the end of the procedure, which resulted in minimizing bone loss and acted as an autologous graft for the surgical site. At 12- and 16-month follow-ups, clinical examinations and cone-beam computed tomographic scans revealed the healing of the lesion without symptoms or complications. Cone-beam computed tomographic imaging was used as a presurgical assessment tool for indication selection and precise design of the bone window. The use of a bone window in endodontic microsurgery, which appears to be a reliable technique, should be the method of preference when the large lesion is deeply positioned between intact buccal and lingual cortices.

Stress Analyses of Retrograde Cavity Preparation Designs for Surgical Endodontics in the Mesial Root of the Mandibular Molar: A Finite Element Analysis-Part II.

INTRODUCTION: The aim of this study was to investigate the influence of apical filling material and the modification made to the apical preparation design in surgical endodontics on the areas of stress concentration in the mesial root of a mandibular molar using finite element analysis. METHODS: The filling material was injected under 2 conditions (ie, with or without mineral trioxide aggregate retrograde filling). The apical preparation design was modified by extending the preparation mesially while maintaining a similar prepared area. We contained the displacement of all the nodes at the base of the supporting bone and applied a force of 150 N to the vertical axis. We analyzed stress generation and concentrations numerically for all cavity design groups. RESULTS: In the presence of retrograde filling, the von Mises stress decreased gradually according to the enlargement of the prepared cavity in the subgroups. When the retrograde filling was absent, the von Mises stress increased as the prepared cavity enlarged. The modification of the apical preparation extending in the mesial direction showed a drastic decrease in stress concentration. CONCLUSIONS: Within the limitations of this study, it was advantageous to perform mesial retrograde preparation within the mesial root dentin to maintain a balanced root dentin on both sides of the apical preparation and create a low-stress field. The surgeon should be careful not to wash out or dislodge the retrograde filling material during obturation to avoid failure of surgery.