Rare root canal morphology of maxillary second molars: A report of three cases.

Key Clinical Message: Endodontists should be aware that some maxillary second molars can have more than three roots. If any unusual anatomical features are detected during dental radiography or endodontic procedures, it is necessary to conduct cone-beam computed tomography (CBCT) scanning to prevent procedural mishaps. Abstract: CBCT can provide three-dimensional reconstructed images of the root canal system. With the help of CBCT, variations in tooth root number and root canal morphology, such as extra canals, apical ramifications, apical deltas, and lateral canals, can be identified. Knowledge of the variations is very important for the success of endodontic treatment. This report suggests that endodontists must not assume that a MSM has only three tooth roots, which is the most prevalent number.

Successful regenerative response of a severe bone defect in a right lower central incisor affected by a cemental tear.

Cone-beam computed tomography and clinical examinations including pulp vital testing and pocket probing depth showed a cemental tear with a severe labial alveolar bony defect, but no endodontic lesions, in #25, which had a sinus tract at the labial site, in a 75-year-old woman.

Endodontic Approach and Periodontal Regenerative Therapy for a Mandibular Right Central Incisor Affected by a Perforation and Cemental Tear.

A cemental tear involves complete or incomplete separation of the cementum on the root surface along the cementodentinal junction. Because a cemental tear can lead to periodontal breakdown and mimic endodontic and periodontal lesions, diagnosing clinical cases can be difficult and requires special examinations. A 72-year-old woman presented with a localized periodontal defect on the labial and interproximal surfaces of the mandibular right central incisor. Performing CBCT scans and a biopsy during periodontal surgery allowed definitive diagnosis of a cemental tear and perforation of the site. First, the perforation was repaired with endodontic therapy. Periodontal regenerative therapy using recombinant human fibroblast growth factor-2 (rhFGF-2) was then performed after removing granulomatous tissue and cementum fragments. Examination of the biopsy specimen showed bacterial colonies. This case showed successful clinical and radiographic outcomes at the 18-month follow-up.

A mandibular second molar with a middle mesial root canal.

The present case report describes the clinical detection and root canal management of a rare middle mesial canal of a Japanese mandibular second molar by troughing preparation using an operating microscope and cone-beam computed tomography.

Sinus floor elevation with platelet-rich fibrin alone: A Clinical retrospective study of 1-7 years.

BACKGROUND: Several sinus floor elevation procedures for implant placement have been introduced. The present study aimed to evaluate the implants placed with Platelet-rich fibrin (PRF) alone in atrophic posterior maxillae and survival rates and the potential factors associated with implant loss. MATERIAL AND METHODS: This retrospective study evaluated 71 implants in 34 patients after 1-7 years' follow-up time. Statistical models were used to determine the implant survival and the potential factors associated with loss. RESULTS: Overall, 7 implants were lost, and the cumulative survival rate at 7 years by implant-based and patient-bases analyses were 85.5% and 85.7%, respectively. The mean residual bone height (RBH) was 4.26 mm. The implant survival rate was significantly lower at RBH < 4 mm than RBH ≥ 4 mm. CONCLUSIONS: This retrospective study showed that sinus floor elevation with PRF alone could be applied in cases of lower RBH. However, it should be carefully performed in cases of RBH < 4 mm before surgery. Key words:Platelet-rich fibrin, dental implant, sinus augmentation, retrospective study.

Sinus Augmentation by Platelet-Rich Fibrin Alone: A Report of Two Cases with Histological Examinations.

In sinus floor augmentation of an atrophic posterior maxilla, platelet-rich fibrin (PRF) has been used as a graft material. We herein report two cases with histological evaluations of PRF after the surgery. The first case was a 28-year-old female with an atrophic right posterior maxilla who was treated with sinus floor augmentation and simultaneous implant placement using PRF as the sole graft material in our hospital. Twenty-four months after surgery, the implant was unfortunately removed because of occlusal overloading by parafunctional habits. During implant replacement, a tissue sample was obtained from the site of augmentation with PRF and was evaluated histologically. The second case was a 58-year-old man with severe alveolar atrophy of the right maxilla who underwent lateral sinus augmentation using only PRF in a two-stage procedure in our hospital. Samples were obtained at the second-stage surgery and histological examinations were performed. As a result, new bone formation was confirmed histologically in both cases. Our findings show that the use of PRF as a graft material during sinus floor augmentation induces natural bone regeneration.

Extracellular inorganic phosphate regulates gibbon ape leukemia virus receptor-2/phosphate transporter mRNA expression in rat bone marrow stromal cells.

In mammalian cells, several observations indicate not only that phosphate transport probably regulates local inorganic phosphate (Pi) concentration, but also that Pi affects normal cellular metabolism, which in turn regulates apoptosis and the process of mineralization. To elucidate how extracellular Pi regulates cellular functions of pre-osteoblastic cells, we investigated the expression of type III sodium (Na)-dependent Pi transporters in rat bone marrow stromal cells and ROB-C26 pre-osteoblastic cells. The mRNA expression level of gibbon ape leukemia virus receptor (Glvr)-2 was increased by the addition of Pi in rat bone marrow stromal cells, but not in ROB-C26 or normal rat kidney (NRK) cells. In contrast, the level of Glvr-1 mRNA was not altered by the addition of extracellular Pi in these cells. The induction of Glvr-2 mRNA by Pi was inhibited in the presence of cycloheximide (CHX). Moreover, mitogen-activated protein kinase (MEK) /extracellular-signal-regulated kinase (ERK) pathway inhibitors; U0126 (1.4-diamino-2, 3-dicyano-1, 4-bis [2-amino-phenylthio] butadiene) and PD98059 (2'-Amino-3'-methoxyflavone) inhibited inducible Glvr-2 mRNA expression, but p38 MEK inhibitor SB203580 [4-(4'-fluorophenyl)-2-(4'-methyl-sulfinylphenyl)-5-(4'pyridyl) imidazole] did not inhibit the induction of Glvr-2 mRNA expression, suggesting that extracellular Pi regulates de novo protein synthesis and MEK/ERK activity in rat bone marrow stromal cells, and through these, induction of Glvr-2 mRNA. Although Pi also induced osteopontin mRNA expression in rat bone marrow stromal cells but not in ROB-C26 and NRK cells, changes in cell viability with the addition of Pi were similar in both cell types. These data indicate that extracellular Pi regulates Glvr-2 mRNA expression, provide insights into possible mechanisms whereby Pi may regulate protein phosphorylation, and suggest a potential role for the Pi transporter in rat bone marrow stromal cells.

Type I collagen regulated dentin matrix protein-1 (Dmp-1) and osteocalcin (OCN) gene expression of rat dental pulp cells.

In this study, we investigated the effect of type I collagen on dentin matrix protein-1 (Dmp-1) and osteocalcin (OCN) gene expression of dental pulp cells. The mRNA level of Dmp-1 gene was down-regulated; however, OCN gene expression was up-regulated by the culture of dental pulp cells with type I collagen. These findings imply that type I collagen regulates mRNA level of Dmp-1 and OCN gene that are predominantly expressed in active odontoblasts. The change of gene expression by type I collagen was suppressed by the blocking of collagen-integrin interaction. We could conclude that the effect of type I collagen was mediated via binding of collagen to integrin receptors.

Alpha E- and alpha N-catenin expression in dorsal root ganglia and spinal cord.

The localization of alpha E- and alpha N-catenin in dorsal root ganglia and spinal cord was examined immunocytochemically. Alpha E- and alpha N-catenin appeared to be co-localized in cell bodies of neurons in dorsal root ganglia, but alpha N-catenin was not expressed in cell bodies of neurons in the ventral horn that showed alpha E-catenin expression. These findings indicate the possibility that the type of alpha catenin expressed in neurons differs with its functional property (e.g. sensory or motor).

Endosseous implants in horizontal alveolar ridge distraction osteogenesis.

PURPOSE: This study evaluated horizontal distraction of the narrow alveolar ridge in dogs and the possibility of achieving osseointegration of implants placed into the distracted site during a consolidation period. MATERIALS AND METHODS: Six beagle dogs weighing approximately 9 to 10 kg were used in this experiment. Twelve weeks after extraction of the mandibular premolars, horizontal alveolar ridge distraction was performed using an originally designed lengthening apparatus. Twelve days after the completion of distraction, screw-type implants were placed into the distracted site. RESULTS: Twelve weeks after the placement of implants, thin lamellar bone rose horizontally from the transport segment toward the surface of the implant. Twenty-four weeks after their placement, the implants were fully embedded in mature lamellar bone, and direct bone contact with the implant surface could be seen. DISCUSSION: Horizontal alveolar ridge distraction was performed successfully by using a lengthening apparatus in the narrow alveolar models. Osseointegration was achieved even though the implants were placed into the distracted site during the consolidation period. CONCLUSION: Horizontal alveolar ridge distraction can be a beneficial technique in the placement of implants In the narrow alveolar ridge in the dog population.