Development of a new quantitative gas permeability method for dental implant-abutment connection tightness assessment

Background  

Most dental implant systems are presently made of two pieces: the implant itself and the abutment. The connection tightness between those two pieces is a key point to prevent bacterial proliferation, tissue inflammation and bone loss. The leak has been previously estimated by microbial, color tracer and endotoxin percolation.     

Optical assessment of dental pulp vitality

The assessment of dental pulp vitality is an important part of oral diagnosis. Conventional tests stimulate the nerves in the pulp and rely on a subjective response from the patient. The use of an optical method for assessment of pulp vitality has been investigated. Fibre optic light guides were used to transmit light to and from the tooth and signal processing was employed to enhance the resulting signal. Valid pulse signals were differentiated from artefactual signals by analysis of signal parameters. Artefactual signals were found to have coefficients of variability that are greater than 40% for amplitude and greater than 25% for phase. With this technique it has been possible to recognize a pulse signal from over 70% of healthy teeth. Further work is in progress to develop the technique to a state where it can be used as a routine clinical tool.     

Skeletal age, dental age, and the maturation of KNM-WT 15000

The skeleton of the Homo erectus boy from West Lake Turkana, Kenya (KNM-WT 15000), is remarkably complete, and this individual has thus provided a case study for several researchers examining Homo erectus growth. Using data from a longitudinal study of Montreal French-Canadian children, it is shown that while dental and skeletal ages match reasonably well at the level of a sample of children, individuals can display differences between skeletal and dental ages of 2 years or more. Furthermore, the relationship between these two markers may change over time in individual children. It is also possible to find children with patterns of dental maturation similar to KNM-WT 15000's pattern in the Montreal sample. Therefore, neither the discrepancy between skeletal age and dental age alone nor the pattern of dental maturation as assessed by dental stages precludes a human-like pattern of growth, including an adolescent growth spurt, for this individual. Some indicators (e.g., estimated body size for predicted age, and enamel formation) do suggest possible growth-patterning differences from modern humans, and therefore earlier maturation is a reasonable hypothesis, but caution is warranted, given the large degree of modern human variation in developmental markers and the inherent uncertainty in precise estimation of KNM-WT 15000's maturational parameters.     

A new correction procedure for calibrating dental caries frequency

The incisors and canines and the premolars and molars show differential resistance to cariogenic factors. The anterior teeth have a lower caries frequency than the posterior teeth. However, these tooth classes are lost differentially in postmortem stages due to their anatomical structures. This differential postmortem tooth loss distorts proportions between the anterior and posterior tooth classes. The disproportionality can affect the calculation of total caries prevalence. In this paper, we propose a new calibration procedure which removes this disproportionality and call it the proportional correction factor. For this procedure, the caries rates of anterior and posterior teeth are corrected by multiplying the anterior teeth by three-eighths and the posterior teeth by five-eighths. These fractions are derived from the human dental formula which contains three anterior and five posterior teeth by side. The correction factor is more effective if the proportion of anterior to the posterior teeth is extremely distorted. When this procedure is used with the caries correction factor, it provides a useful way to approach to an almost true caries prevalence. Am J Phys Anthropol 108:237–240, 1999. © 1999 Wiley-Liss, Inc.     

A new system of dermatomes

A new system for tangential excision (deepidermization, debridement, and graft harvesting) was devised and clinically tested. The system comprises three sizes of dermatomes for use in all body areas and tangential excision purposes. We trust that the presented system will offer the surgeon new possibilities and access and will facilitate the currently used procedures.     

A new approach for environmental risk assessment

Environmental problems, such as global warming, the limited supply of sustainable energy, the depletion of natural resources, hazardous emissions released into the atmosphere and waste, are increasing global concerns. Therefore, individuals, communities, and businesses need to address environmental protection and sustainability. Environmental impact assessments are needed to identify, mitigate, and control aspects that affect the environment or a company's products, services, or activities. In this study, a general environmental aspect and impact assessment approach, which can be applied to any company that is involved in the production or service sector, is created. An environmental impact pattern that consists of 10 main and 32 sub-categories was formed based on the ISO 14001, environmental studies and field applications. The developed approach was applied to the dyeing units of a manufacturing firm. Sixteen environmental aspects were identified and assessed using the environmental impact template via the environmental failure mode and effect analysis (E-FMEA) method. The developed-approach can be applied to each sector, which will enable us to perform a detailed analysis of the environmental aspects in the environmental impact category. This approach provides a checklist for the environmental impact studies of businesses and has been pioneered as an effective method for company resources to improve their environmental performance.     

MicroWeaR: A new R package for dental microwear analysis

Mastication of dietary items with different mechanical properties leaves distinctive microscopic marks on the surface of tooth enamel. The inspection of such marks (dental microwear analysis) is informative about the dietary habitus in fossil as well as in modern species. Dental microwear analysis relies on the morphology, abundance, direction, and distribution of these microscopic marks. We present a new freely available software implementation, MicroWeaR, that, compared to traditional dental microwear tools, allows more rapid, observer error free, and inexpensive quantification and classification of all the microscopic marks (also including for the first time different subtypes of scars). Classification parameters and graphical rendering of the output are fully settable by the user. MicroWeaR includes functions to (a) sample the marks, (b) classify features into categories as pits or scratches and then into their respective subcategories (large pits, coarse scratches, etc.), (c) generate an output table with summary information, and (d) obtain a visual surface‐map where marks are highlighted. We provide a tutorial to reproduce the steps required to perform microwear analysis and to test tool functionalities. Then, we present two case studies to illustrate how MicroWeaR works. The first regards a Miocene great ape obtained from through environmental scanning electron microscope, and other a Pleistocene cervid acquired by a stereomicroscope.     

A new method for ageing wild boar using dental measures

Over the last decades, wild boar (Sus scrofa) populations in Europe have increased with impacts on agriculture, livestock and biodiversity. Thus, changes in population management for wild boar are increasingly important. Knowledge of the age structure of the population is crucial to designing effective management plans. However, the costs and efforts required to estimate the age of wild boar, primarily in the oldest animals, is problematic for managers and researchers. Here, we describe a new method to estimate wild boar age based on simple dental measures (the external aperture of the pulp cavity, root length and crown length from primary and secondary incisors). Our study was based on data from 93 wild boar of known age belonging to two different populations in central and south-eastern Spain. We propose a model based on Boosted Regression Trees (BRT). Our results show a final age estimation model that included all the explanatory variables proposed (dental measures) and showed a high percentage of estimated deviance (61%), obtained by cross-validation. Thus, at least in Iberian wild boar populations, our method constitutes a low-cost and reliable method for wild boar age estimation.     

A new approach for calibrating dental caries frequency of skeletal remains

It is a fact that researchers make use of various calibration methods for calculating and correcting dental caries frequency. The lack of standardization and accuracy of such methods has made it difficult for the researchers to draw reliable and differentiated conclusions from caries frequencies. Besides, the number of studies on how far the calculation methods reflect the "real" caries frequency is very limited. In this study, various methods for calculating caries frequency in skeletal samples are discussed and a new calculation method is proposed for estimating "real" caries frequency. The Hardwick's correction, which is one of the methods discussed in this study, is not successful in estimating "real" caries frequency as it proposes standard values for different life styles and dietary habits. The decayed and missing index is also considered inefficient as it assumes that all antemortem tooth loss is due to caries. The caries correction factor, proposed by Lukacs, achieves more successful results by considering factors other than caries in antemortem tooth loss, but because it does not differentiate between the anterior and posterior tooth groups during calculation, the results to be obtained therefrom may deviate from actual figures. In order to correct any such deviation, the caries correction factor must be applied separately for the anterior and posterior teeth groups since the resistance of each group to cariogenic factors is different. All the methods outlined above do not consider the effects of postmortem tooth loss on caries frequency. As a result, these methods are still far from reflecting a reliable caries frequency. The application of a proportional correction factor--as a technique newly introduced here--corrects the deviation caused by postmortem tooth loss and achieves more realistic results.     

Incremental lines of dental cementum in biological age estimation

The aim of this study is to evaluate the use of counting incremental lines of dental root cementum for biological age determination, and to compare it with alternative methods. Two samples were taken: 51 teeth from 49 individuals of known age obtained at the Stomatological Clinic, Vilnius University, as well as the canine teeth from the remains of 48 individuals from the mass graves of Tuskulenai in Vilnius (inhumed 1944-47). In the latter sample, the chronological age of 43 individuals was known through personal identification. Undecalcified teeth were sectioned with the Leica SP 1600 microtome diamond saw, and incremental line count as a blind test was made on sections of 35 to 100 microns thickness. Incremental line count was possible in 82-86 percent of cases. The results of three independent counts showed that intra-observer bias has no significant impact. Biological age was estimated by adding incremental line number to the average age of tooth eruption. It was found that mean absolute error was 6.46 years for the 1st sample, 6.27 years for the 2nd sample, and in some cases exceeded 10 years. For the 2nd sample, the results were compared to those of other methods such as endocranial suture ossification, pubic symphysis morphology and the "combined" method of Nemeskéri. All four methods yield a similar correlation in regard to an individual's chronological age. The highest correlation was found for the combined method, and the lowest one for public symphysis morphology. All correlations had a similar standard error. Thus our assessment is less enthusiastic than in some past studies; it is suggested that the incremental lines rather have a similar use as other methods.     

Performance assessment of a new optimization system for robotic SBRT MLC-based plans

PurposeTo assess the performance of a new optimization system, VOLO, for CyberKnife MLC-based SBRT plans in comparison with the existing Sequential optimizer.MethodsMLC-plans were created for 25 SBRT cases (liver, prostate, pancreas and spine) using both VOLO and Sequential. Monitor units (MU), delivery time (DT), PTV coverage, conformity (nCI), dose gradient (R50%) and OAR doses were used for comparison and combined to obtain a mathematical score (MS) of plan quality for each solution. MS strength was validated by changing parameter weights and by a blinded clinical plan evaluation. The optimization times (OT) and the average segment areas (SA) were also compared.ResultsVOLO solutions offered significantly lower mean DT (−19%) and MU (−13%). OT were below 15 min for VOLO, whereas for Sequential, values spanned from 8 to 160 min. SAs were significantly larger for VOLO: on average 10 cm² versus 7 cm². VOLO optimized plans achieved a higher MS than Sequential for all tested parameter combinations. PTV coverage and OAR sparing were comparable for both groups of solutions. Although slight differences in R50% and nCI were found, the parameters most affecting MS were MU and DT. VOLO solutions were selected in 80% of cases by both physicians with 88% inter-observer agreement.ConclusionsThe good performance of the VOLO optimization system, together with the large reduction in OT, make it a useful tool to improve the efficiency of CK SBRT planning and delivery. The proposed methodology for comparing different planning solutions can be applied in other contexts.     

DNA-expressed human cytochrome P450s: a new age of molecular toxicology and human risk assessment

It has long been recognized that a large degree of species differences exists among drug and carcinogen metabolizing enzymes. In particular, differences in cytochrome P450s, the principal enzymes of metabolic activation of procarcinogens, are widespread and may determine species and individual susceptibility to cancer causing chemicals. Although species differences in both the regulation and catalytic activities of P450s are quite large, roden-based systems are mainly used as the means to determine the degree of hazard of environmental pollutants, pesticides, drugs and other environmental chemicals to humans. During recent years, a large effort has been expended on analyzing directly the structure, properties and catalytic activities of P450s from human tissues. In vitro mutagen testing systems, based on activation by human P450s, are being developed that will supplement other test systems in order to more accurately predict human risk to chemical exposure.