Roxana Stegaroiu

Influence of maxillary cortical bone thickness, implant design and implant diameter on stress around implants: A three-dimensional finite element analysis

PURPOSE There is no clear evidence of the factors that could improve implant biomechanics in the posterior maxilla. Thus, a finite element analysis was performed to investigate the effect of maxillary cortical bone thickness, implant design and diameter on stress around implants. METHODS A total of 12 models of the posterior maxilla with implant were computer-simulated by varying the thickness of the alveolar cortical bone (1.5, 1.0, 0.5 or 0 mm) and implant characteristics (cylindrical implant of 4.1-mm diameter, screw-type implants of 4.1-mm or 4.8-mm outer diameters). On top of each implant, forces were separately applied axially (100 N) and buccolingually (50 N), and the von Mises stresses were calculated. RESULTS Regardless of load direction, implant design and diameter, cortical and cancellous bone stresses increased with the decrease of crestal cortical bone thickness. In the absence of crestal cortical bone, cancellous bone stresses were highest and, under axial load, were transferred to the sinus floor. Implant design and diameter influenced stress to a less extent, especially under buccolingual load and in the presence of crestal cortical bone. CONCLUSIONS From a biomechanical viewpoint, to improve implant success odds in the posterior maxilla, rather than implant selection, careful preoperative evaluation of the cortical bone at the planned implant site is recommended. If this cortical bone is very thin or even lacking, implant treatment should be carried on with caution by progressive loading in the range of functional loads.

Finite element analysis of implant-embedded maxilla model from CT data: Comparison with the conventional model

PURPOSE There are no entire maxillary finite element analysis models available, as a base of reference for the dimensions of conventional segment finite element analysis models. The objectives of this study were: (1) to construct a maxillary model derived from a human skull and to investigate the strain distribution around a posterior implant embedded in it; (2) to investigate the usability of conventional segment maxillary models. METHODS CT DICOM data of a human dried skull maxilla was imported into the Mesh Generation Tools (ANSYS AI environment) and a computer-generated implant-abutment unit was bicortically embedded into it. In this Large model, Von Mises strains under axial and buccolingual loads were then calculated by a finite element program. Moreover, two simplified maxillary segments (Simplified models) were computer-generated and their Von Mises strains were similarly calculated. RESULTS Although absolute values differed markedly, strain distribution patterns in the cortical bone were similar to those in the Simplified models: high Von Mises strains in the cortical bone concentrated in the sinus floor around the implant apex under axial load, and in the alveolar crest around the implant neck under buccolingual load. CONCLUSIONS The simplified and segmented three-dimensional finite element models of the human maxilla showed the same locations of the highest equivalent strains as the full maxilla model created from CT DICOM data. If absolute strain values are not of interest, the Simplified models could be used in strain analyses of simulated posterior maxilla for diagnostic suggestions in implant placement.

A proposed core curriculum for dental English education in Japan

BackgroundGlobalization of the professions has become a necessity among schools and universities across the world. It has affected the medical and dental professions in terms of curriculum design and student and patient needs. In Japan, where medicine and dentistry are taught mainly in the Japanese language, profession-based courses in English, known as Medical English and Dental English, have been integrated into the existing curriculum among its 83 medical and 29 dental schools. Unfortunately, there is neither a core curriculum nor a model syllabus for these courses.MethodsThis report is based on a survey, two discussion forums, a workshop, and finally, the drafting of a proposed core curriculum for dental English approved by consensus of the participants from each university.ResultsThe core curriculum covers the theoretical aspects, including dental English terms and oral pathologies; and practical aspects, including blended learning and dentist-patient communication. It is divided into modules and is recommended to be offered for at least two semesters.ConclusionsThe core curriculum is expected to guide curriculum developers in schools where dental English courses are yet to be offered or are still in their early development. It may also serve as a model curriculum to medical and dental schools in countries in Asia, Europe, Africa, and Central and South America, where English is not the medium of instruction.

Changes in the Oral Moisture and the Amount of Microorganisms in Saliva and Tongue Coating after Oral Ingestion Resumption: A Pilot Study

Background and Objective: Tube feeding has been significantly associated with a higher rate of aspiration pneumonia that is mainly related to oral microorganisms and a reduced salivary flow. Thus, the difference in the mode of nutritional intake is expected to affect the oral environment, but this has not yet been fully clarified. The purpose of this study was to investigate, in tube-fed patients, changes in the oral moisture and the counts of microorganisms in saliva and tongue coating, which occur after oral ingestion resumption. Methods: Study participants were 7 tube-fed inpatients of the Niigata University Medical and Dental Hospital (72.7±8.5 years old) who received dysphagia rehabilitation at the Unit of Dysphagia Rehabilitation until oral ingestion resumption. Their oral health, swallowing, and nutrition status, oral mucosal moisture, amount of unstimulated saliva and the counts of microorganisms (total microorganisms, streptococci, Candida) in saliva and tongue coating were investigated and compared before and after the recommencement of oral intake. Results: Tongue coating, choking, oral mucosal moisture and amount of unstimulated saliva were improved significantly after resumption of oral ingestion. The other investigated parameters did not significantly change, except for the streptococci in tongue coating, which significantly increased 1 week after oral ingestion recommencement, but decreased thereafter. Conclusion: After oral intake resumption, oral mucosal moisture and amount of unstimulated saliva were improved. However, because of a transitory increase in the counts of streptococci with oral ingestion recommencement, it is important to appropriately manage oral hygiene in these patients, according to the changes in their intraoral microbiota.

The influence of temporomandibular joint movement parameters on dental morphology

Association between tooth morphology, occlusal relations and mandibular condyle/glenoid fossa morphology is still a controversial issue in dentistry. The aim of the present study was to examine the influence of three important articular parameters on the dental morphology and the crown volume, quantifying the variation for each tooth group: incisor, canine, premolar and molar. MATERIALS AND METHODS All maxillary teeth from a set of basic study models were prepared for zirconia single crowns. The models were scanned and then, using a computer aided design software, they were mounted in a virtual articulator and specific mandibular movements were defined. The crown morphology was designed and statically adapted. Ten models were obtained by dynamical adjustment of the basic model for successively modified articular parameters: sagittal condylar inclination (SCI)=30°, Bennett angle (BA)=10°, Immediate side shift (ISS)=0.5mm - for control and SCI: 40°, 50° and 60° with BA and ISS as control, BA: 15°, 20° and 25° with SCI and ISS as control, ISS: 1.5mm, 1.0mm and 0.0mm with SCI and BA as control - for the nine test models. The following measurements were performed three times on the right side of each model: volume for each tooth group, slope (S) for the central incisor, S and mesio-distal angle (MDA) for canine, S, MDA and vestibulo-oral angle (VOA) for the first premolar and molar. RESULTS When SCI was varied, statistically significant changes as compared to the controls were found for incisors and premolars S, premolars VOA and, for 50° and 60°, MDA and molars MDA (for 50°) and VOA (for 60°). When BA was varied, significant changes were found for S (canine) and, in certain models, MDA (premolar, molar). Variations of ISS significantly changed mainly MDA for molars and, in two models, premolars. CONCLUSIONS Within the limits of this study, among the articular parameters, SCI mostly influenced the dynamic tooth morphology, but canine and molar morphology was stronger influenced by BA and/or ISS.

Comprehension of Japanese oral care‐related terms among caregivers and nurses, as assessed using a newly developed instrument

OBJECTIVES (i) To assess comprehension of oral care-related terms among caregivers and nurses working at long-term care facilities, using a newly developed test; (ii) to analyse the effect of participant characteristics on their comprehension. BACKGROUND Effective mutual communication between dental professionals and caregivers/nurses is essential for providing information on daily oral care for institutionalised elders. METHODS A 36-item word-knowledge test in Japanese was developed to assess comprehension of oral care-related terms. The test was administered to a convenience sample of 236 nursing staff (198 caregivers and 38 nurses) at six long-term care facilities in Niigata City, Japan, and its reliability and validity were verified. Associations of participant characteristics with their responses were investigated by multiple regression analysis. RESULTS Mean percentage of correct responses (accuracy rate) for nursing staff was approximately 62% (highest for oral care products and lowest for prosthodontic terms). Test internal reliability was high (Cronbachs alpha >0.8). Concurrent validity (test ability to distinguish between characteristically different groups) was confirmed. Mean accuracy rate was significantly higher among nurses (78.5 ± 19.3%) than among caregivers (58.7 ± 22.8%), and among respondents with interest in oral care (64.2 ± 21.1%) than among those with no such interest (51.5 ± 28.9%). CONCLUSION The word-knowledge test was valid and reliable for nursing staff of six long-term care facilities in Niigata City. Their comprehension was low for perioral and intraoral structures, related symptom and disease names, and prosthodontics terms related to oral care. Understanding of oral care-related terms among the nursing staff was related to their occupation and interest in oral care.