The metabolic inter-relationships between changes in waist circumference, triglycerides, insulin sensitivity and small, dense low-density lipoprotein particles with acute weight loss in clinically obese children and adolescents.

OBJECTIVE: Small, dense low-density lipoprotein (LDL) particles are highly atherogenic and strongly associated with obesity-related dyslipidemia. The metabolic inter-relationships between weight loss induced changes in waist circumference, triglycerides, insulin sensitivity and small-dense LDL particles in clinically obese children and adolescents have not been studied. METHODS: Seventy-five clinically obese boys and girls (standardized body mass index 3.07 ± 0.59, aged 8-18 years) were recruited. Anthropometric, body composition and cardiometabolic risk factors were measured pre- and post-weight loss. RESULTS: There were highly significant reductions in anthropometric, body composition and cardiometabolic risk factors. Triglyceride change was positively correlated with LDL peak particle density and percentage LDL pattern B changes (relative abundance of small, dense LDL particles). Multiple regression analyses showed that changes in triglyceride concentration accounted for between 24 and 18% of the variance in LDL peak particle density and percentage LDL pattern B change, respectively. Changes in waist circumference and insulin sensitivity did not predict these changes in LDL characteristics. CONCLUSION: Acute and highly significant weight loss significantly decreased LDL peak particle density and percentage LDL pattern B. The change in triglycerides was a strong predictor of LDL peak particle density and percentage LDL pattern B change.

Ceramics in implant dentistry (Working Group 1).

INTRODUCTION: The remit of this working group was to update the existing knowledge base in ceramics in implant dentistry. The reviews from working group 1 formed the basis for this update. Moreover, clinical applications as well as suggestions for further research have been formulated. MATERIALS AND METHODS: The papers in the working group critically reviewed the literature on the topic. Manuscripts were produced on: 1. The performance of ceramic and metal implant abutments supporting fixed implant reconstructions. 2. The viability of ceramic implants as alternatives to titanium implants. 3. The survival and complications of CAD-CAM reconstructions as compared with FDPs which have been fabricated using conventional techniques. RESULTS: The results and conclusions of the review process are presented in the following papers, together with the group consensus statements, clinical implications and directions for future research: Sailer I., Philipp A., Zembic A., Pjetursson B. E., Hämmerle C. H. F., Zwahlen M. A systematic review of the performance of ceramic and metal implant abutments supporting fixed implant reconstructions. Andreiotelli M., Wenz H. J., Kohal R.-J. Are ceramic implants a viable alternative to titanium implants? A systematic literature review. Harder S., Kern M. Survival and complications of CAD-CAM vs. conventionally fabricated reconstructions: a systematic review.

Dental endosseous implants in the medically compromised patient.

The literature contains numerous observations on the significance of systemic disorders as contraindications to dental endosseous implant treatment, but the justification for these statements is often apparently allegorical. Although implants are increasingly used in healthy patients, their appropriateness in medically compromised patients is less equivocal. Perhaps surprisingly, the evidence of their efficacy in these groups of patients is quite sparse. Indeed, there are few if any randomized controlled trials (RCTs) in this field. Furthermore, any health risks from the placement of implants are unclear. We review the current evidence for the risks associated with endosseous implants in a range of systemic disorders. There is clearly a need for prospective systematic trials. The degree of disease-control may be far more important that the nature of the disorder itself, and individualized assessment, including the medical condition, quality of life and life expectancy is indicated. The benefits of implants to many of these patients may outweigh any risks. However, proper informed consent is mandatory.

Biomechanical aspects of oral implants. Consensus report of Working Group 1.

The method used by the working group was an iterative process based upon a structured review of the relevant literature by a group of reporters. The review papers were circulated to the members of the group before the conference and formed the basis for subsequent discussions. Each paper was subject to detailed collective analysis and subsequently modified on the basis of the panel's discussions and referenced to additional relevant literature where appropriate. The group assessed the levels of evidence for the statements made in the supporting documentation and recognized that it was necessary to adopt a compromise between acceptance of the lowest level, resulting in the largest body of material, and the highest level, which, in some cases, produced little evidence. While this approach does not represent endorsement of lower evidence levels per se, it was designed to provide conclusions of clinical utility within the existing knowledge base. The consensus statements were prepared after a detailed consideration of the papers submitted to the workshop by the working group. The papers were scrutinized, amended and approved by the group. The basis of each paper is described in the section on 'search strategy' and defines the parameters within which the consensus statements were prepared.

The management of ectodermal dysplasia and severe hypodontia. International conference statements.

An international conference on ectodermal dysplasias and hypodontia, held in London in 2004, featured a session devoted to the management of the ectodermal dysplasias and severe hypodontia. This paper presents a set of statements prepared by an international specialist panel, including representatives of patient support groups, who presented and subsequently debated a series of papers on this subject. The following topics were explored: potential roles of patient support groups; core care standards, including the roles and composition of medical and dental multidisciplinary teams for treating these conditions; the format of a baseline data set for patients with an ED; and priorities for research in ectodermal dysplasias, with particular regard to laboratory and clinical studies, and research methodology. The statements are intended to form an international framework for developing patient care pathways, and collaborative research in this field.

Adhesion of bone cells to ion-implanted titanium.

The use of ion-implantation to encourage osseointegration has been investigated using an in vitro model cell culture system and surface analysis. Polished titanium discs were implanted with calcium, potassium and argon ions. The adhesion of bone-derived cells was measured using radioactively labeled cells and the morphology examined using scanning electron microscopy. Similar numbers of cells were found to adhere to the potassium and argon-implanted titanium as to control (non-implanted) titanium. However, adhesion to the calcium-implanted titanium discs was significantly reduced. Moreover, although the cells were found to be well spread on the calcium and potassium-implanted titanium, a much greater proportion of cells appeared to remain rounded and poorly attached on the argon-implanted surface. These differences are discussed in relation to the observed surface roughness and chemistry, which were assessed using interferometry and X-ray photoelectron spectroscopy, respectively.

Root resorption in retained deciduous canine and molar teeth without permanent successors in patients with severe hypodontia.

AIMS: The ability to predict the morbidity of retained deciduous teeth with no permanent successors, a characteristic of hypodontia, would be of considerable value in treatment planning, but is hampered by lack of data. METHODS: This problem was studied using 356 orthopantomogram radiographs (OPGs) from the records of 249 patients who had attended a specialist hypodontia clinic, and had retained deciduous teeth with no permanent successors. Due to their clinical importance, canine and molar teeth were chosen for examination. Resorption was assessed subjectively by three experienced clinicians. RESULTS: Un-weighted Kappa values for reproducibility were > 0.8, and for interobserver error 0.60-0.83. Gender related differences were minimal. Regardless of gender or radiographic age, the lower canines appear to show the least amount of resorption and the upper first molars the most. The upper and lower second molars have particularly unpredictable life spans. Whilst the lower first molars have a predictable life span that is poor, the life span for the upper first molars is slightly worse. CONCLUSIONS: Lower canines have a predictable life span that appears to be good, as do upper canines, but of lesser duration than lower canines. Molars have poorer and less predictable life spans.

A comparison of written and multimedia material for informing patients about dental implants.

A study was undertaken to compare the effectiveness of an information leaflet with a multimedia program in informing potential implant patients attending a dental hospital. The results show that both methods of presenting information are effective in informing patients; however, where the information to be presented is visual in nature, a multimedia presentation can have a more positive short-term effect than an equivalent leaflet.

Functional mandibular deformation in edentulous subjects treated with dental implants.

PURPOSE: The purpose of this study was to measure medial convergence, dorsoventral shear, and corporal rotation in the human mandible. MATERIALS AND METHODS: Measurements were made using custom-fabricated strain gauge displacement transducers in 6 edentulous subjects who had been treated with mandibular endosseous dental implants. These were mounted on the most distal of the mandibular implants on each side, and measurements were made in real time using a multichannel analogue/digital converter and a personal computer for data storage and analysis. Measurements were made while the implants were loaded, and the subjects opened and closed their mouths and made lateral mandibular excursions. Medial convergence was measured as a linear change at the site of the most distal implant. Dorsoventral shear was expressed as a relative rotation of the right and left mandibular bodies projected onto the median sagittal plane, and corporal rotation was expressed as the relative rotation of the most distal implant. RESULTS: Jaw deformation was found to occur immediately on opening and was related to closing forces and jaw position. Medial convergence of up to 41 microns was observed, with values for corporal rotation of up to 6 degrees and dorsoventral shear of up to 19 degrees. CONCLUSION: The study demonstrated clinically for the first time 3 different and simultaneous patterns of functional mandibular deformation.

Effects of cellular mediator agonists on cortisol and steroid acute regulatory (StAR) protein in bovine zona fasciculata (ZF) cells.

Primary cultures of bovine ZF cells were incubated for 1 h or 6h with the agonists 8-bromo-cyclic AMP (8-Br-cAMP) an activator of protein kinase A (PKA), the phorbol ester phorbol 12-myristate 13-acetate (PMA) a protein kinase C (PKC) activator, the Ca2+ ionophore, A23187, or the L-type Ca2+ channel agonist Bay K8644. Both cortisol secretion (determined by radioimmunoassay of cell medium) and cellular StAR protein levels (quantified by western blotting) were significantly increased at 6h, by all agonists. However, while all agonists stimulated cortisol secretion at 1h, StAR protein levels remained unchanged by these treatments. We conclude that in bovine ZF cells, StAR protein synthesis can be regulated by mechanisms involving activation of PKA, PKC and Ca2+ influx. However, a net increase in cellular StAR protein does not appear to be essential for the initiation for the first stage of acute steroidogenesis.

Effects of superstructure type and design on force transmission via implant-stabilised mandibular prostheses.

Forces to which individual implant units are subjected when an implant-stabilised mandibular over-denture is loaded have been measured using a carbon-fibre reinforced epoxy resin replica of an edentulous mandible mounted in a loading rig which simulated physiological conditions. Three different retentive designs were used; ball attachments, a fixed-fixed bar cranked anteriorly, and a similar design with posterior cantilevers. Forces exerted on the implants were measured using resistance strain gauges mounted on their trans-mucosal abutments and the dentures were loaded at individual tooth positions with a strain gauge beam. Ball attachments were associated with the lowest detected forces on the abutments. It is concluded that variations in superstructure design affect the forces transmitted by implants stabilising a complete mandibular over-denture, when the mandible is suspended and loaded in a physiological manner.

The influence of mandibular deformation, implant numbers, and loading position on detected forces in abutments supporting fixed implant superstructures.

STATEMENT OF PROBLEM: Forces may arise in association with the use of implant stabilized mandibular fixed partial dentures as a result of functional jaw deformation, yet the phenomenon has received little attention and is rarely included as a variable when investigating implant biomechanics. PURPOSE: This in vitro investigation tested the hypothesis that functional mandibular deformation influences force distribution in the jaw/implant/superstructure complex. MATERIAL AND METHODS: Six Brånemark implants were mounted in an acrylic resin replica of an edentulous human mandible. Applied forces were measured with 4-element resistance strain gauges mounted on each of 6 standard titanium abutments. The mandible was supported either on its lower border or suspended in a frame that simulated the natural situation. A cast gold superstructure was a mounted on varying combinations of implants, loaded occlusally in different locations, and the resultant forces at each supporting transmucosal abutment measured. RESULTS: The suspended ("natural") support configuration was associated with considerable differences in patterns of force transmission as compared with bench support. Loads were more widely spread, and large extrusion forces were detected, particularly where several implants were connected. CONCLUSIONS: Functional mandibular deformation is a significant factor in the design of mandibular implant stabilized prostheses, and calls into doubt the value of modeling techniques that do not allow for this phenomenon.

A comparison between the wear resistance of three types of denture resin to three different dentifrices.

This study compares the abrasive effects of three dentifrices on three different denture base resins, a heat cured acrylic resin, a self cured acrylic resin and a light activated urethane dimethacrylate-based resin. Specimens of the resins were subjected to a regimen of mechanical brushing using measured amounts of paste on standard toothbrushes driven by a reciprocating device. The apparent wear of each specimen was assessed qualitatively using scanning electron microscopy and quantitatively using profilometry and reflex microscopy. The study showed that cleaning pastes play a significant role in the wear of conventional acrylic resins, the relative abrasivity of the dentifrices being substrate related. However, wear was less evident on the light activated urethane dimethacrylate resin. Brushing with water alone produced no detectable wear on any of the specimens.

Functional adaptability to changes in lower denture shape.

Forces exerted on the right and left lingual and buccal flanges of Kennedy Type I mandibular dentures were studied using an 8 channel recording technique, during resting, swallowing, talking, reading and simulated mastication. The effects of adaptation, head position and incremental thickening of the flanges were determined. Highest forces were recorded when swallowing, with smaller differences between the other activities. Lingual forces were higher than buccal, and posterior forces higher than anterior ones. There was a highly significant relationship between increases in flange thickness of 2 and 3mm and increases in peak forces. Evidence for adaptation and effects related to head position was weaker.

An in vivo quantitative analysis of the fit of Nobel Biocare implant superstructures.

Loss of osseointegration of implant fixtures and mechanical failure of superstructures have been attributed to failure to achieve a passive fit between the superstructure and the transmucosal abutment (TMA). The fit of five mandibular superstructures, fabricated on Nobel Biocare implants, was investigated in vivo, using a polyvinyl siloxane impression material to record the discrepancies. Following sectioning of the impressions, the vertical and horizontal discrepancies were analysed at four locations using a travelling microscope. The discrepancies obtained were measured both when the gold cylinder screws were maximally tightened by hand and when tightened with a torque driver to the recommended value of 10 Ncm. The vertical discrepancies for the hand tightened abutments ranged from 0 micron to 63 microns with a mean of 14 microns. In the mechanically tightened group, the vertical discrepancies ranged from 0 micron to 130 microns with a mean of 21 microns. The horizontal discrepancies for the mechanically tightened abutments ranged from 0 micron to 140 microns with a mean of 31 microns, compared with a mean of 46 microns and range of 0 micron to 113 microns, for the hand-tightened abutments. A close fit was seldom achieved. It is concluded that considerable discrepancies existed around superstructures that had been judged to have a clinically acceptable fit. These were reduced in the vertical direction by hand tightening of the gold screws.

The influence of occlusal scheme on masticatory forces using implant stabilized bridges.

The objectives of this study were to determine the effects on masticatory forces of using implant stabilized mandibular bridges with occlusal schemes providing either balanced or unbalanced articulation. The investigation was carried out in a group of six subjects who had dentate, or restored dentate maxillary arches and who used implantstabilized mandibular prostheses. Peak masticatory forces, chewing frequency and load rate were determined when chewing bread, carrots and nuts. The mean peak masticatory force varied markedly from subject to subject, and, together with the masticatory load rate were lowest when eating bread and highest when chewing nuts, with values for chewing carrots between the two. There was no detectable difference in mean peak masticatory force or load rates associated with chewing bread with the two occlusal schemes; however, these were lower with balanced occlusion when chewing nuts and carrots. The ranking of subjects in terms of mean peak masticatory force and load rate was consistent and peak load rates of up to 2000 N/sec were recorded. Chewing frequency was relatively consistent for a particular subject irrespective of the foodstuff.

Load distribution on implants with a cantilevered substructure: an in vitro pilot study.

The forces distributed on six Nobelpharma implants were analyzed by strain gauges fixed to various implant combinations that were placed in a replica of a human edentulous mandible and connected to a cast gold alloy superstructure. The mandible was supported on its lower border and the superstructure loaded in different locations. Although force distribution was found to be asymmetrical, statistical analysis revealed no significant differences. Loads applied to one side of the superstructure were largely carried by the implants on that side, demonstrating torquing of the casting in the midline. Loads applied to the cantilever resulted in large extension forces in implants on the opposite side of the fulcrum. The magnitudes of the loads distributed on the screw varied as a result of the combinations, inter-implant spaces, and implant locations.

The effects of superstructure fit and loading on individual implant units: Part 2. The effects of loading a superstructure with varying degrees of fit.

This study investigated force transmission in an implant supported bridge with varying degrees of fit. The project utilised an in vitro model of five implant fixtures mounted linearly and rigidly. These supported a well-fitting cast gold superstructure via implant abutments fitted with strain gauges so as to function as force transducers. Gaps of 10-110 microns were created at the middle and one terminal abutment and loads of 50N applied over the cantilever and 230N between the terminal abutments. Force distribution was uneven, compression, tension and torque observed, and loading of the cantilever noted to generate large forces.