A Core Curriculum in the Biological and Biomedical Sciences for Dentistry

INTRODUCTION: The biomedical sciences (BMS) are a central part of the dental curriculum that underpins teaching and clinical practice in all areas of dentistry. Although some specialist groups have proposed curricula in their particular topic areas, there is currently no overarching view of what should be included in a BMS curriculum for undergraduate dental programmes. To address this, the Association for Dental Education in Europe (ADEE) convened a Special Interest Group (SIG) with representatives from across Europe to develop a consensus BMS curriculum for dental programmes. CURRICULUM: This paper summarises the outcome of the deliberations of this SIG and details a consensus view from the SIG of what a BMS curriculum should include. CONCLUSIONS: Given the broad nature of BMS applied to dentistry, this curriculum framework is advisory and seeks to provide programme planners with an indicative list of topics which can be mapped to specific learning objectives within their own curricula. As dentistry becomes increasingly specialised, these will change, or some elements of the undergraduate curriculum may move to the post-graduate setting. So, this document should be seen as a beginning and it will need regular review as BMS curricula in dentistry evolve

The effect of mechanical loading on peri-implant osteogenesis

The use of endosseous oral implants, fixed into bone by means of direct bone contact, became a predictable treating modality during the eighties. To obtain osseointegration, an initial uneventful healing period for several months has been recommended for decades. However, patient inconveniences such as a prolonged treatment time are associated with this protocol. Therefore, loading implants immediately or soon after their placement is gaining acceptance among clinicians. It is no longer believed that immediate loading per se leads to fibrous encapsulation of implants. On the contrary, a certain amount of micro-strain may enhance osseointegration. However, accurate long-term studies for specific clinical conditions are lacking and the healing-loading relations are not yet fully understood either. The overall aim of this thesis was, by means of animal experimental research, to contribute to the understanding of the mechanobiology of implants subjected to immediate loading. In Chapter I, a general description of the existing knowledge on load-free implant healing is given. Some basic mechanobiological principles that are thought to guide tissue differentiation are discussed. Then, it is questioned whether healing under load is allowed and to what extent it may promote interfacial bone formation. Because this thesis mainly deals with mechanical bone stimulation through the implant, we further questioned the importance of the implant geometry and surface characteristics for an optimal biomechanical coupling. The rabbit bone chamber methodology, described in chapter II, was developed for investigation of the sensitivity of peri-implant tissue differentiation to well-defined and well-controlled mechanical conditions. The bone chamber primarily consists of dual-structure perforated hollow cylinders with a centrally positioned implant. Via perforations, bone grows into the bone chamber. A loading device allows a controlled mechanical stimulation of the implant. Repeated sampling of the bone chamber allows conducting several experiments within the same animal. A protocol for the quantification of the tissue growth and bone response to implant loading was designed, with assessments of the tissue and bone tissue filling of the chamber, as well as the fraction of (non)-mineralized bone tissue within the chamber and in contact with the implant surface. Chapter III describes the tissue response around immediately loaded and unloaded cylindrical turned implants at two different observation periods. The sensitivity of tissue differentiation and bone healing to the mechanical conditions at the peri-implant site was demonstrated. Implant micro-motion had a significant effect on the bone formation around cylindrical turned implants. Micro-movement up to 50 µm displayed a positive effect on the bone formation in the implant’s surroundings and at its interface. Certain implant designs promote bone formation and osseointegration by providing a favourable local mechanical environment. Threaded-type implants are generally recommended for immediate loading due to their higher resistance to vertical movement and shear forces compared to the cylinder-type implant. In chapter IV, the bone formation around immediately loaded implants was compared to the unloaded control with the implant configuration as independent variable. The findings of the study confirmed that well-controlled immediate implant loading accelerates tissue mineralization at the interface of implants. The screw-shaped implant design promoted osseointegration by rendering a more favourable local mechanical environment for bone formation compared to the cylindrical implant. Corroboration of mechanoregulatory tissue differentiation models by comparison with experimental data is necessary to determine their predictive power. In chapter V, three mechanoregulatory models were applied to simulate the osseointegration process for a loaded screw-shaped and cylindrical implant in the bone chamber and compared both qualitatively and quantitatively with the experimental observations. Histologically, no differences were found between the two implant geometries for the amount of bone formation in a narrow circular zone around the implant, whereas a significantly larger amount of bone-to-implant contact was observed for the screw-shaped implant compared to the cylindrical one. In the simulations, the screw-shaped implants were predicted to give rise to higher bone-to-implant contact incidence. However, other experimental observations could not be predicted for any of the investigated mechanoregulatory models. Mathematical models with implementation of the biological processes observed during peri-implant osteogenesis are missing. Also implant surface characteristics are of special importance for initial osteogenesis. It is generally accepted that roughening an implant surface results in a faster bone formation and in an increased mechanical interlocking. In chapter VI, a turned surface was compared with a roughened one under loaded and unloaded conditions. In unloaded conditions, osseointegration was accelerated at a roughened surface compared with a turned one. In the presence of loading however, the topographic dependency of the osteogenic activity at the interface was overruled by the loading-related bone response. In chapter VII, the effect of various degrees of relative movement (0–30–90 µm) on the tissue differentiation around a roughened screw-shaped immediately loaded implant was investigated. Again, it was found that controlled micro-motion at the interface did not impair the process of osseointegration. Micro-motion up to 90 µm at the interface of a roughened screw-shaped implant stimulated initial osteogenesis. This thesis has shown the importance of the local mechanical environment on the bone formation at the implant surface. Healing under load is beneficial for the establishment of osseointegration, provided a careful selection of the loading protocol and the implant macro- and micro-design. Future research should consider the cellular and molecular foundation underlying the osseointegration process. This will lead to a better understanding of the mechanism(s) of the bone cell response to mechanical loading in the peri-implant environment.Chapter I: Introduction: Mechanobiology at the interface of implants Chapter II: The rabbit bone chamber model to investigate peri-implant osteogenesis Chapter III: Histodynamics of bone tissue formation around immediately loaded cylindrical implants in the rabbit Chapter IV: The influence of controlled immediate loading and implant design on peri-implant bone formation Chapter V: Application of mechanoregulatory models to simulate the histodynamics of peri-implant bone tissue formation in an in vivo bone chamber Chapter VI: The effect of implant surface roughness and loading on peri-implant bone formation Chapter VII: The influence of micro-motion on the tissue response around immediately loaded roughened titanium implants in the rabbit Chapter VIII: General discussion and future perspectives Chapter IX: Summary Chapter X: Samenvattingnrpages: 1-151status: publishe

Fracture strength of resin-bonded dental prostheses with a rigid vs non-rigid joint. An in vitro study

This in vitro study investigated whether a resin-bonded dental prosthesis (RBDP) with a hyperstatic, rigid joint was preferable to an isostatic, nonrigid construction in terms of debonding and fracture strength. RBDPs replacing a missing molar with a rigid (design I) or a resilient model (design II) were compared to a commercially available system (Crownless Bridge Work) (design III, control). All groups were subjected to thermocycling (TC) and dynamic mechanical loading (ML) in a dual-axis chewing simulator (TC: 6,000 x 5 degrees C/55 degrees C; ML: 1,200,000 x 49 N x 1.4 Hz). None of the RBDPs of design III showed movement or fracture during the test period. Significant differences between designs I and III (P= .0049) and between designs II and III (P = .0007) were noted. Despite a tendency for lower fracture values of design I, no significant differences could be established between the test designs with a rigid or nonrigid construction. The commercially available dental prosthesis with a nonrigid joint was confirmed to resist a 5-year survival simulation.status: publishe

The effect of loading on peri-implant bone: a critical review of the literature

In the 90s, there was a general belief that mechanical overloading was one of the main reasons for late implant failure. This triggered research to assess the role of mechanical loading on the establishment and the maintenance of oral implant osseointegration. Animal experimental studies indeed suggested the potential detrimental effect of excessive mechanical load on peri-implant bone, although randomised or controlled clinical trials of treatment interventions of oral implants designed to study overload are lacking. The lack of quantification of so-called overload at the implant level in the intra-oral setting is one of the main shortcomings in the literature. The level of evidence of the studies on bone response to implant loading is weak and does not indicate that overload can lead to peri-implant bone loss, except in case of inflammation. Clinical and animal experimental studies on early and immediate implant loading, however, provide information on the impact of mechanical loading on the process of osseointegration. It is obvious that micromotion between the implant and host tissues compromises osseointegration. However, in case of an efficient force transfer between implant and surrounding tissues, mechanical loading might even stimulate peri-implant bone formation and therefore osseointegration.status: publishe

Pathways in multidisciplinary oral health care as a tool to improve clinical performance

PURPOSE: To investigate the optimization of multidisciplinary and interdisciplinary oral health care through the introduction of pathways. MATERIALS AND METHODS: A prospective randomized clinical trial was carried out in a tertiary referral academic institution. Ninety-one patients admitted for multidisciplinary oral health care from January 1, 2001, to March 31, 2003, were randomized to the test group (n = 50) or to the control group (n = 41). Pathways were implemented by means of the Medical Patient Management program, a computerized planning and coordination system specifically developed for a population with multidisciplinary oral rehabilitation needs. The efficiency of pathways in interdisciplinary oral health care was assessed. RESULTS: Statistically significant differences between test and control groups were found for variables regarding the process of care, such as "number of planned versus actual disciplines," "length of planned versus actual treatment," and "average length of a treatment session." For variables regarding patient satisfaction, significant differences between test and control groups were found for questions regarding patient involvement with the treatment and patient satisfaction with the outcome of multidisciplinary treatment. Regarding practitioner satisfaction, the results of the questionnaire indicate that implementation of pathways into everyday clinical practice is desired but remains difficult. CONCLUSION: The findings of this study show that the implementation of pathways in multidisciplinary oral health care improved some aspects of the process of care and increased patient satisfaction. The predictive capability of the Medical Patient Management program in managing oral health care has been demonstrated.status: publishe

Occlusal overload and bone/implant loss

Aim The aim of this search was to assess the biological consequences that overload might have on already osseointegrated oral implants through a systematic screening of the scientific literature. Method Detailed searches through PUBMED, OVID, EMBASE and LILACS databases were made. Articles published up to December 2011 and those reported on the clinical, radiographic and/or histological outcome of oral implants subjected to so-called overload were considered eligible for inclusion. Identified studies were assessed by one non-blinded reviewer according to well-defined inclusion and exclusion criteria. When doubt arose, the co-authors were counselled until final agreement was obtained. The PICO questions formulated was:“what is the effect of overload vs. no overload on bone/implant loss in clinically stable implants?” Results The database searches as well as additional hand searching, resulted in 726 potentially relevant titles. Eventually, 16 clinical and 25 animal studies were considered relevant to the topic. After inclusion/exclusion criteria assessment, all clinical studies and all but three animal studies and one systematic review were considered at high risk of bias and excluded. The included animal studies did not reveal an association between overload and peri-implant bone loss in the absence of peri-implant inflammation, whereas in its presence, overload seemed to aggravate the peri-implant tissue breakdown. Conclusions The effect of implant overload on bone/implant loss in clinically well-integrated implants is poorly reported and provides little unbiased evidence to support a cause-and-effect relationship. The PICO question remained unanswered. At the animal level, “overload”, mimicked by supra-occlusal contacts acting in an uninflamed peri-implant environment, did not negatively affect osseointegration and even was anabolic. In contrast, supra-occlusal contacts in the presence of inflammation significantly increased the plaque-induced bone resorption.status: publishe

Computer-aided designed/Computer-assisted manufactured composite resin versus ceramic single-tooth restorations: a 3-year clinical study

PURPOSE: No clinical evidence has been provided to suggest that metal-free all-composite resin indirect restorations are a functional and esthetic alternative to all-ceramic restorations. The aim of this study was to evaluate the clinical performance of single-tooth computer-aided design/computer-assisted manufacturing (CAD/CAM)-generated all-composite resin and all-ceramic crowns after 3 years of function. MATERIALS AND METHODS: In a prospective trial, 200 all-composite resin and all-ceramic crowns were rated over a 3-year period. Restorations were evaluated at 3 weeks and 1 and 3 years after insertion by the California Dental Association quality evaluation index, the patient's self-assessment, marginal fit, periodontal parameters, volume loss, and wear patterns of the veneering material. Statistical analysis was performed using t tests (a = .05). RESULTS: Cumulative survival and success rates after 3 years were 87.9% and 55.6% for all-composite resin and 97.2% and 81.2% for all-ceramic crowns, respectively (P < .05 for success rates). Restoration loosening occurred exclusively for all-composite resin crowns cemented on a cast post. All-ceramic restorations demonstrated satisfactory esthetic results. All-composite resin crowns resulted in significantly more mean total volume loss and mean vertical wear at occlusal contact areas after 6 months and 3 years of function. The clinical performance of the CAD/CAM-generated all-ceramic crowns used in this study was similar to that of other all-ceramic CAD/CAM systems. CONCLUSION: For up to 3 years of function, all-composite resin single-tooth restorations have inferior success rates compared to all-ceramic restorations. Due to the inferior esthetics and wear resistance of all-composite resin crowns, all-ceramic crowns remain the preferred treatment for CAD/CAM-generated metal-free single-tooth restorations.status: publishe

Overnight storage of removable dentures in alkaline peroxide-based tablets affects biofilm mass and composition

BACKGROUND: Clinical guidelines for denture care are available, but evidence for optimal nocturnal storage is scarce. The aim of the study was to compare the role of the overnight storage state on plaque growth and composition on acrylic removable dentures. METHODS: In a parallel-group randomized controlled trial of 51 institutionalized participants, 3 denture overnight preservation methods were considered: (i) in water, (ii) dry or (iii) in water with added alkaline peroxide-based cleansing tablet. Biofilm samples were taken on day 7 (developing biofilm - dBF) and day 14 (maturing biofilm - mBF) from a mechanically uncleaned, standardized region, situated distally to the second lower premolars. Total and individual levels of selected perio-pathogenic and commensal species (n=20), and of Candida albicans were calculated by PCR. Differences between storage conditions (water/dry/tablet) and between the samples (dBF/mBF) were assessed by means of unpaired and paired t-tests respectively, with α=5%. RESULTS: Overnight denture storage with cleansing tablet significantly decreased the total bacterial level of dBF and mBF up to 13.8%. Fn, Ec, Cs, Sc, Ao and Vp counts were particularly affected by tablet care. Significant lower amounts of Candida albicans for tablet storage compared to water preservation were recorded in dBF and mBF (-69.3 ± 3.8% and -75.9 ± 3.2% respectively). The mass and pathogenicity of dBF and mBF was equal, irrespective of the overnight storage intervention. CONCLUSIONS: The use of cleansing tablets for acrylic removable denture overnight storage reduces denture biofilm mass and pathogenicity compared to dry and water preservation, and may contribute to the overall systemic health. CLINICAL SIGNIFICANCE: Evidence-based clinical guidelines for overnight storage of removable acrylic dentures are lacking. The findings of this study indicate that alkaline peroxide-based cleansing tablets decrease bacterial and Candida levels in denture biofilms in case of poor oral hygiene. This provides evidence for a clinical guideline to minimize microbial load of dentures, thereby reducing associated systemic health risks.publisher: Elsevier articletitle: Overnight storage of removable dentures in alkaline peroxide-based tablets affects biofilm mass and composition journaltitle: Journal of Dentistry articlelink: http://dx.doi.org/10.1016/j.jdent.2013.08.002 content_type: article copyright: Copyright © 2013 The Authors. Published by Elsevier Ltd.status: publishe

Can fermentation be used as a sustainable strategy to reduce iron and zinc binders in traditional African cereal porridges and gruels?

Many weaning and complementary foods in Africa are plant based and thus are not good sources of bioavailable iron and zinc owing to the presence of anti-nutritional factors, in particular phytic acid, phenolic compounds, and, to some extent, dietary fiber. Several strategies are being developed to increase the levels of bioavailable iron and zinc in plant-based diets. These strategies range from fortification, biofortification, dietary diversification, and use of household processing methods such as soaking, cooking, germination, and fermentation. Fermentation poses a great potential as a significant amount of these foods in Africa involve a natural fermentation step. Exploration of this process could offer a more economical and sustainable way to reduce iron and zinc binders and consequently increase the bioavailability of the minerals in diets consisting of fermented cereals