Impaction of Mandibular First Molar by Tooth-Like Hard Tissue.

Impaction of permanent teeth during the mixed dentition stage is relatively common in clinical practice, but impaction of mandibular first molars is rare. This case report presents an impaction of the mandibular first molar due to a tooth-like hard tissue lesion. An 8-year-old girl was diagnosed with an impacted mandibular first molar. The roots of the impacted molars were almost completely developed. A spherical tooth-like hard tissue with a diameter of approximately 2 mm was observed at the alveolar crest between the impacted mandibular first and second molars. The lesion causing the impaction was excised, and the first molar was fenestrated and allowed to erupt naturally. We showed that even if the tooth root is almost complete, natural eruption can be expected if the lesion is removed and space for eruption is secured.

Radiological and histochemical study of bone regeneration using the costal cartilage in rats.

PURPOSE: The purpose of this study was to conduct basic research on the possibility of using cartilage tissue for hard-tissue reconstruction and to observe morphological changes in the transition of the cartilage to bone. METHODS: A 4-mm diameter bone defect was created in the right mandibular angle of rats. Cartilage, autologous bone, and artificial bone were grafted into the defect. Computed tomography (CT) was performed to measure the increase in bone volume. Further histological evaluation of the grafted site was performed. RESULTS: At 12 weeks, CT show that bone formation in the costal cartilage group was comparable to that in the autogenous bone group. Histologically, in the artificial bone group, a clear boundary was observed between the existing bone and defect, whereas in the costal cartilage and autologous bone groups, laminar plate bone repair of the defect was observed. CONCLUSION: The findings in this study suggest that bone reconstruction achieved with cartilage grafting is almost equivalent to that with autogenous bone grafting and that bone reconstruction using cartilage is clinically feasible. In future, if regenerated cartilage is successfully applied clinically, bone reconstruction using regenerated cartilage may be feasible.

Clinical Research on the Safety Evaluation of Platelet-rich Plasma Treatment in Oral Diseases: A Study Protocol.

Background: Platelet-rich plasma (PRP) is a biological product obtained from autologous blood that contains growth factors, promoting the healing and regeneration of human tissues. Several oral diseases require surgical intervention, producing residual wounds that undergo a healing process, accompanied by pain, swelling, superinfections, and bone remodeling. This protocol study aims to evaluate the safety of PRP use for the following dental procedures: post-extraction socket healing, periodontal tissue regeneration, maxillary sinus floor elevation, tooth transplantation, and intentional tooth replantation. Methods: Ten patients will be enrolled and subjected to the required treatment with the addition of PRP, after appropriate hematological and biochemical evaluations. The participants will then be subjected to an observation period of 4 weeks to monitor adverse events through clinical observation. Secondary outcomes will regard pain, and clinical evolution of the treated site. Among these, presence of infection, swelling, wound healing, stability of the transplanted tooth. Discussion: Safety of medical procedures represents the first requirement for their introduction in routine practice. A careful evaluation of clinical response during follow-up period and registration of adverse effects is fundamental for safety confirmation and subsequent use of PRP for the proposed dental procedures. Trial registration: Japan Registry of Clinical Trials (https://jrct.niph.go.jp/, registry number: jRCTc030190273, jRCTc030190274, jRCTc030190275, jRCTc030190276, jRCTc030190277; Date of registration: 31 March 2020).

Medication-Related Osteonecrosis of the Jaw Subsequent to Peri-Implantitis: A Case Report and Literature Review.

The aim of this report was to document a rare case of medication-related osteonecrosis of the jaw (MRONJ) that developed around the already osseointegrated implants in the maxillary right molar region. A 73-year-old woman presented at our university dental hospital in May 2017 with a chief complaint of discomfort near a maxillary implant. Her first visit was in 2006, and the maintenance treatment began in 2007 after the periodontal treatment. During the implant maintenance period there were no complications; however, the patient began taking alendronate sodium hydrate (Fosamac tablets, 35 mg, once weekly), an oral bisphosphonate (BP) since 2013, for treatment of osteoporosis. Eight years after starting implant maintenance, in 2016, peri-implantitis occurred, for which mechanical cleaning and antimicrobial therapy were performed. Peri-implantitis symptoms disappeared, and the medical condition improved. Nonetheless, in 2017, MRONJ developed 4 years after she commenced taking the BP. The patient underwent implant removal and sequestrectomy. There was no postoperative recurrence. Since it was such a rare case, we performed a literature review but only discovered a few similar cases. Because various triggers may lead to the development of MRONJ, even if already osseointegrated implant, it is important to note that implants in patients taking BPs should be more carefully maintained.

Mechanical analysis of the effects of implant position and abutment height on implant-assisted removable partial dentures.

PURPOSE: An increasing number of clinical reports describe the use of dental implants as abutments in implant-assisted removable partial dentures (IARPD). We used three-dimensional finite element analysis to evaluate IARPD as a unilateral mandibular distal extension denture. Specifically, the mechanical effects of implant position and abutment height on the abutment tooth, denture, and denture-supporting tissue were assessed. METHODS: The models analyzed were defects of the left mandibular second premolar and first and second molars prosthetically treated with an IARPD using one implant for each tooth position. There were two abutment heights: one equal to that of the mucosa and another that was elevated 2 mm above the mucosa. Six models were constructed. RESULTS: For mucosal-level abutments, movement of the abutment tooth was lower for implants positioned distal to the abutment tooth than for those positioned medial to the abutment tooth. For elevated abutments, movement of the abutment tooth was lower for implants positioned medial to the abutment tooth than for those positioned distal to the abutment tooth. CONCLUSIONS: The mechanical effects on abutment teeth at the same implant position differed in relation to implant abutment height.

Bone marrow-derived mesenchymal stem cells enhance bone marrow regeneration in dental extraction sockets.

Bone marrow-derived mesenchymal stem cells (BMMSCs) remain the most widely used source of osteogenic cells in bone tissue engineering research. A cell-based treatment for alveolar ridge augmentation has received attention as an alternative to bone grafting. In the present study, BMMSC transplantation into tooth extraction sockets of C57BL/6J mice was evaluated for alveolar ridge regeneration. The first right maxillary molars were extracted, and then BMMSCs (PDGFRα+ Sca-1+ CD45- TER119- cells) isolated from femoral and tibial bone marrow were immediately transplanted into the extraction sockets. A control group underwent the same procedure except for BMMSC transplantation. Bone formation in the sockets was evaluated using micro-computed tomography and histological and immunohistochemical analyses. At 3 weeks, bone formation in the sockets was more advanced in the experimental group than in the control group. Histological analysis at 6 weeks after transplantation showed that the sockets in the experimental group also contained a greater quantity of bone marrow. Interestingly, socket bone mineral density was lower in the experimental group than in the control group at 6 weeks. These findings suggest that BMMSC transplantation accelerates bone healing and augments bone marrow formation in tooth extraction sockets.

Three-dimensional finite element analysis of the effects of implant diameter and photofunctionalization on peri-implant stress.

Previous finite element analyses of peri-implant stress assumed a bone-implant contact (BIC) ratio of 100%, even though the BIC ratio is known to be approximately 50% or less. However, the recent development of ultraviolet treatment of titanium immediately before use, known as photofunctionalization, significantly increased the BIC ratio, to 98.2%. We used a unique finite element analysis model that enabled us to examine the effects of different BIC ratios on peri-implant stress. A three-dimensional model was constructed under conditions of vertical or oblique loading, an implant diameter of 3.3, 3.75, or 5.0 mm, and a BIC ratio of 53.0% or 98.2%. Photofunctionalization and larger implant diameters were associated with reduced stress on surrounding tissues. Under vertical loading, photofunctionalization had a greater effect than increased implant diameter on stress reduction. Under oblique loading, increased implant diameter had a greater effect than photofunctionalization on stress reduction.

Diverse calcification patterns of ameloblastic fibro-odontoma on radiographic examination.

The occurrence of ameloblastic fibro-odontoma (AFO) in the oral region is unusual and accounts for 1-3% of all odontogenic tumors. AFO presents mixed radiopaque patterns within the lesion with diverse findings; therefore, it is important to compare this tumor with other odontogenic tumors that radiographically present with calcified bodies. Herein, we observed the calcification patterns within the lesion in seven AFO cases (five males, two females; mean age, 8.3 years; age range, 4-13 years). Periapical and panoramic radiographs were obtained from all seven cases. Five cases underwent conventional computed tomography (CT) scanning, and one underwent cone beam CT. Classification of the calcifications primarily involved the following two characteristics on the X-rays: appearance and location of the lesions. All seven cases were located in the molar regions of the mandible in association with impacted teeth. The calcification patterns of these AFOs were mixed or inhomogeneous within the lesion with various findings, including complex odontoma-like calcifications. However, the patterns differed between panoramic radiography and CT in some cases. The radiolucent lesions in AFO demonstrated varying calcification patterns and were associated with impacted teeth on the CT images.(J Oral Sci 58, 533-537, 2016).

Current status of implant prosthetics in Japan: a survey among certified dental lab technicians.

BACKGROUND: There are many implant cases in which dental technicians take initiative with regard to the design of implant prostheses, and to a certain extent, this area of care is one in which dentists do not necessarily play the leading role. Moreover, inadequate communication between dental technicians and dentists and insufficient instructions for technicians has been highlighted as issues in the past. The purpose of this questionnaire is to improve the quality of implant prostheses and thereby contribute to patient service by clarifying, among other aspects of treatment, problem areas and considerations in the fabrication of implant prostheses, conceptual-level knowledge, and awareness of prosthodontics on the part of the dentists in charge of treatment and methods for preventing prosthetic complications. METHODS: A cross-sectional survey was given to 120 certified dental technicians. To facilitate coverage of a broad range of topics, we classified the survey content into the following four categories and included detailed questions for (1) the conditions under which implant technicians work, (2) implant fixed prostheses, (3) implant overdentures, and (4) prosthetic complications. RESULTS: Out of 120 surveys sent, 74 technicians responded resulting in a response rate of 61.6%. CONCLUSIONS: This survey served to clarify the current state of implant prosthodontics, issues, and considerations in the fabrication of implant prostheses, and the state of prosthetic complications and preventive initiatives, all from a laboratory perspective. The results of this survey suggested that, to fabricate prostheses with a high level of predictability, functional utility, and aesthetic satisfaction, it is necessary to reaffirm the importance for dentists to increase their prosthetic knowledge and work together with dental technicians to develop comprehensive treatment plans, implement an organized approach to prosthesis design, and accomplish occlusal reconstruction.

Relationship between growth of facial morphology and chronologic age in preschool children with obstructive sleep apnea.

BACKGROUND: The purpose of this study was to evaluate the relationship between facial morphology using cephalometry and chronologic age in preschool children with obstructive sleep apnea (OSA). MATERIALS AND METHODS: From a group of lateral cephalometric radiographs taken of 35 children with OSA for diagnostic purposes, 15 were selected for the present investigation based on head position. The subjects consisted of preschool children with both OSA and primary dentition, all of them with a lowest documented SpO(2) <90% and a lowest 0

Videofluorographic evaluation of dysphagia before and after modification of the flap and scar in patients with oral cancer.

Dysphagia is an important postoperative problem in patients with oral cancer. We evaluated the usefulness of a technique to modify the flap and scar for the alleviation of swallowing disorders. The modifications were made while tongue pressure was being measured to improve excursion of the residual tongue in nine patients. They had been operated on for oral cancer and reconstruction was with a forearm free flap, or the wound was closed primarily. After a 5 ml bolus of liquid barium had been given orally, lingual movement, barium inflow into the pharynx before swallowing, stasis in the epiglottic valleculae, and stasis in the oral cavity after swallowing, were evaluated by videofluorography before and after modification. Oral transit time, pharyngeal transit time, and total transit time were also measured. Lingual movement improved in eight patients. Barium inflow into the pharynx before swallowing improved slightly in all patients. Stasis in the epiglottic valleculae was improved in six patients. Stasis in the oral cavity improved in all patients. Oral transit time and total transit time were significantly shorter after modification of the flap and scar than before operation. Pharyngeal transit time was unchanged. We conclude that our technique for modification of the flap and scar can alleviate postoperative swallowing dysfunction in patients with oral cancer.

Masticatory efficiency before and after surgery in oral cancer patients: comparative study of glossectomy, marginal mandibulectomy and segmental mandibulectomy.

This study evaluated the effect of oral cancer surgery on masticatory efficiency. Masticatory efficiency was measured using the ATP absorption method. Eating ability was measured using a questionnaire. Two groups were employed as controls: The "normal occlusion group" consisted of subjects who had a complete set of natural maxillary teeth opposed to mandibular teeth, and the "unilateral occlusion group" consisted of subjects who had lost their molar and premolar teeth on one side of the mandible as a result of caries or periodontal diseases. Three treatment groups, each of 6 patients, were studied: a glossectomy group, a marginal mandibulectomy group and a segmental mandibulectomy group. There were no differences in masticatory efficiency between two control groups. Masticatory efficiencies of the three oral cancer treatment groups were lower than in the unilateral occlusion group, even 12 months after surgery. Masticatory efficiency of the glossectomy group was significantly higher 12 months after surgery compared with pre-surgery. Masticatory and eating abilities of the marginal mandibulectomy group and the segmental mandibulectomy were reduced at 3 and 6 months after surgery. The masticatory efficiency 12 months after surgery was higher in the marginal mandibulectomy group than the segmental mandibulectomy group, although the difference was not statistically significant. The self assessed eating ability 12 months after surgery was significantly higher in the marginal mandibulectomy group than the segmental mandibulectomy group. These results suggest that discontinuation of the mandible may lead patients to eat only foods that do not require a substantial amount of chewing. Hence, the quality of life of patients in the marginal mandibulectomy group was considered to be better than that in the segmental mandibulectomy group.