Biomechanical Response in Mandibular Bone due to Mastication Loading on 3-Unit Fixed Partial Dentures

An understanding of functional responses in oral bone is a crucial component of dental biomechanics. The purpose of this study was to investigate the potential biological remodelling response during mastication on the mandibular pre- and post-insertion of a fixed partial denture (FPD). A series of three-dimensional (3D) finite element analysis (FEA) models were presented pre- and postextraction to determine the biomechanical responses to masticatory loading in the anterior mandible. Equivalent strains were analysed at lingual/buccal and mesial/distal areas of the premolar to molar region and quantified to anticipate bone remodelling response. Mandibular bone incorporating an FPD experienced substantially greater stress/strain magnitudes than that prior to placement of fixed prosthodontics, which is suggestive of engagements of bone remodelling. The results suggest similar outcomes to those reported clinically. Developing a simulation reflecting the outcomes of restorative treatment can provide meaningful insight into restorative treatment planning, clinical outcomes, and fixed prosthodontics designs

CYP3A7*1C allele: linking premenopausal oestrone and progesterone levels with risk of hormone receptor-positive breast cancers

Funder: Breast Cancer Now (BCN); doi: https://doi.org/10.13039/100009794Funder: Cancer Research UK (CRUK); doi: https://doi.org/10.13039/501100000289Funder: RCUK | Medical Research Council (MRC); doi: https://doi.org/10.13039/501100000265Funder: U.S. Department of Health & Human Services | National Institutes of Health (NIH)Funder: Wellcome Trust (Wellcome); doi: https://doi.org/10.13039/100004440Funder: EC | EC Seventh Framework Programm | FP7 Ideas: European Research Council (FP7-IDEAS-ERC - Specific Programme: "Ideas" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013)); doi: https://doi.org/10.13039/100011199; Grant(s): HEALTH-F2-2009-223175, HEALTH-F2-2009-223175Funder: Genome Canada (Génome Canada); doi: https://doi.org/10.13039/100008762Funder: Gouvernement du Canada | Canadian Institutes of Health Research (Instituts de Recherche en Santé du Canada); doi: https://doi.org/10.13039/501100000024Funder: Quebec Breast cancer Foundation Genome QuebecFunder: U.S. Department of Health & Human Services | NIH | U.S. National Library of Medicine (NLM); doi: https://doi.org/10.13039/100000092Funder: EC | EC Seventh Framework Programm | FP7 Ideas: European Research Council (FP7-IDEAS-ERC - Specific Programme: "Ideas" Implementing the Seventh Framework Programme of the European Community for Research, Technological Development and Demonstration Activities (2007 to 2013))Funder: European Union’s Horizon 2020Funder: Deutsche Krebshilfe (German Cancer Aid); doi: https://doi.org/10.13039/501100005972Funder: BCAST - European Union’s Horizon 2020Funder: Breast Cancer Now; doi: https://doi.org/10.13039/501100007913Abstract: Background: Epidemiological studies provide strong evidence for a role of endogenous sex hormones in the aetiology of breast cancer. The aim of this analysis was to identify genetic variants that are associated with urinary sex-hormone levels and breast cancer risk. Methods: We carried out a genome-wide association study of urinary oestrone-3-glucuronide and pregnanediol-3-glucuronide levels in 560 premenopausal women, with additional analysis of progesterone levels in 298 premenopausal women. To test for the association with breast cancer risk, we carried out follow-up genotyping in 90,916 cases and 89,893 controls from the Breast Cancer Association Consortium. All women were of European ancestry. Results: For pregnanediol-3-glucuronide, there were no genome-wide significant associations; for oestrone-3-glucuronide, we identified a single peak mapping to the CYP3A locus, annotated by rs45446698. The minor rs45446698-C allele was associated with lower oestrone-3-glucuronide (−49.2%, 95% CI −56.1% to −41.1%, P = 3.1 × 10–18); in follow-up analyses, rs45446698-C was also associated with lower progesterone (−26.7%, 95% CI −39.4% to −11.6%, P = 0.001) and reduced risk of oestrogen and progesterone receptor-positive breast cancer (OR = 0.86, 95% CI 0.82–0.91, P = 6.9 × 10–8). Conclusions: The CYP3A7*1C allele is associated with reduced risk of hormone receptor-positive breast cancer possibly mediated via an effect on the metabolism of endogenous sex hormones in premenopausal women

Do Nonsteroidal Anti-Inflammatory Drugs Cause Endoprosthetic Loosening? Mid- to Long-Term Follow-Up of 100 Total Hip Arthroplasties after Local NSAID Infiltration

We evaluated the effect of local infiltration of NSAIDs on prosthetic fixation at mid- to long-term follow-up of total hip arthroplasties. Intra-articular local NSAID (ketorolac) was injected into hip joints and surrounding tissues intraoperatively and postoperatively as a part of multimodal pain management protocol. Clinical and radiographic evaluation was performed for any evidence of component loosening or failure and clinical outcomes in 100 total hip joint arthroplasties with a mean follow-up of 7.3 years (4.9 to 11 yrs). Radiographic analysis at the most recent follow-up showed no evidence of loosening, subsidence, or migration and no evidence of impending failure. Clinical outcomes showed improved Harris hip scores. Intra-articular NSAID used in the intraoperative/postoperative period in hip arthroplasty showed no evidence of prosthetic loosening at mid- to long-term follow-up

Clinical equipoise in sleep surgery: investigating clinical trial targets

Objective. Surgical approaches for alleviating snoring and/or obstructive sleep apnea (OSA) have been questioned because of a lack of evidence from high-quality randomized controlled trials (RCTs). An ethical requirement for RCTs is that they must test questions where community equipoise (ie, uncertainty) exists as to the correct treatment. We aimed to measure perceived importance, community equipoise, and willingness to enroll patients in 5 potential trial targets among members of the Australian Society for Otolaryngology Head and Neck Surgery (ASOHNS). Study Design, Setting, and Subjects. All ASOHNS members were surveyed using a multistage mail, email, Internet, and phone-based questionnaire. Methods. Equipoise was measured for each of the scenarios using a bidirectional linear scale comparing 2 treatments. Responses were categorized into 1 of 3 groups: (A) preferred treatment 1, (B) completely undecided, and (C) preferred treatment 2. The resulting proportions are called equipoise ratios: A:B:C. Using tick boxes, the authors queried the general clinical importance and willingness to enroll patients for all scenarios. Results. A total of 167 of 313 surgeons responded (53.4%). Three of the 5 trial scenarios exhibited evidence of community equipoise, but 2 scenarios, radiofrequency ablation plus uvulopalatopharyngoplasty (UPPP) versus UPPP alone and upper-airway reconstruction versus mandibular advancement splint (MAS), did not have strong support for enrolling patients. Informal feedback indicates one of these may be feasible in a smaller number of specifically trained surgeons. Conclusion. We suggest 2 potential RCT targets: septoplasty and turbinate reduction versus conservative measures for snoring and airway reconstruction versus MAS for OSA, where importance, clinical equipoise, and willingness all exist

The all-ceramic, inlay supported fixed partial denture. Part 5, Extended finite element analysis validation

Background: This study is the last in a series detailing an investigation into the all-ceramic, inlay supported fixed partial denture, the major concern of which has been the examination of the stress responses of the bridge via the use of finite element analysis (FEA) and its validation. The progression from a classic FEA to the current extended or enriched FEA (XFEA) will be described and the validation performed. Methods: XFEA modelling was compared and validated against the experimental model analysis (EMA) as described in a previous study. Results: The two EMA load case fracture strengths of 160 N and 313 N compared favourably with the best two fracture predictions from the XFEA of 185 N and 213 N (maximum principal stress criterion) respectively, with the origin of fracture and overall trajectory and pattern of crack propagation agreeing very well. Conclusions: XFEA load prediction is within 15% of the EMA in the best case. The sensitivity of the bridges to loading position variations was accurately predicted by the XFEA, together with the change in fracture origin from the molar to premolar embrasures. With this, the authors believe that they have provided a convincing validation, both qualitatively and quantitatively, of an anatomically realistic dental bridge

Fracture behavior of inlay and onlay fixed partial dentures : an in-vitro experimental and XFEM modeling study

Objectives: This study aimed to explore the “sensitivity” of the fracture load and initiation site to loading position on the central occlusal surface of a pontic tooth for both all-ceramic inlay retained and onlay supported partial denture systems. Materials and methods: Three dimensional (3D) finite element (FE) inlay retained and onlay supported partial denture models were established for simulating crack initiation and propagation by using the eXtended Finite Element Method (XFEM). The models were subjected to a mastication force up to 500 N on the central fossa of the pontic. The loading position was varied to investigate its influence on fracture load and crack path. Results: Conclusions The fracture load and cracking path were found to be very sensitive to loading position in the all-ceramic inlay and onlay FPDs. The study provides a basis for improved understanding on the role of localized contact loading of the cusp surface in all-ceramic FPDs. Small perturbation of the loading position caused the fracture load and crack pattern to vary considerably. For the inlay fixed partial dentures (FPDs), the fracture origins changed from the bucco-gingival aspect of the molar embrasure to the premolar embrasure when the indenter force location is slightly shifted from the mesial to distal side. In contrast, for onlay FPDs, cracking initiated from bucco-gingival aspect of the premolar embrasure when the indenter is slightly shifted to the buccal side and from molar embrasure when the indenter is shifted to the lingual side. Conclusions: The fracture load and cracking path were found to be very sensitive to loading position in the all-ceramic inlay and onlay FPDs. The study provides a basis for improved understanding on the role of localized contact loading of the cusp surface in all-ceramic FPDs

Computational biomechanics of bone's responses to dental prostheses : osseointegration, remodeling and resorption

Clinical and experimental studies showed that human bone has the ability to remodel itself to better adapt to its biomechanical environment by changing both its material properties and geometry. As a consequence of the rapid development and extensive applications of major dental restorations such as implantation and fixed partial denture (FPD), the effect of bone remodeling on the success of a dental restorative surgery is becoming critical for prosthetic design and pre-surgical assessment. This paper aims to provide a computational biomechanics framework to address dental bone’s responses as a result of dental restoration. It explored three important issues of resorption, apposition and osseointegration in terms of remodeling simulation. The published remodeling data in long bones were regulated to drive the computational remodeling prediction for the dental bones by correlating the results to clinical data. It is anticipated that the study will provide a more predictive model of dental bone response and help develop a new design methodology for patient-specific dental prosthetic restoration