Gastroesophageal reflux disease and tooth erosion

The increasing prevalence of gastroesophageal reflux disease (GERD) in children and adults, and of “silent refluxers” in particular, increases the responsibility of dentists to be alert to this potentially severe condition when observing unexplained instances of tooth erosion. Although gastroesophageal reflux is a normal physiologic occurrence, excessive gastric and duodenal regurgitation combined with a decrease in normal protective mechanisms, including an adequate production of saliva, may result in many esophageal and extraesophageal adverse conditions. Sleep-related GERD is particularly insidious as the supine position enhances the proximal migration of gastric contents, and normal saliva production is much reduced. Gastric acid will displace saliva easily from tooth surfaces, and proteolytic pepsin will remove protective dental pellicle. Though increasing evidence of associations between GERD and tooth erosion has been shown in both animal and human studies, relatively few clinical studies have been carried out under controlled trial conditions. Suspicion of an endogenous source of acid being associated with observed tooth erosion requires medical referral and management of the patient as the primary method for its prevention and control.Sarbin Ranjitkar, John A. Kaidonis, and Roger J. Smale

Effects of non-carious cervical lesion size, occlusal loading and restoration on biomechanical behavior of premolar teeth

Accepted manuscript online: 15 DEC 2015Information on fracture biomechanics has implications in materials research and clinical practice. The aim of this study was to analyze the influence of non-carious cervical lesion (NCCL) size, restorative status and direction of occlusal loading on the biomechanical behavior of mandibular premolars, using finite element analysis (FEA), strain gauge tests and fracture resistance tests.Ten buccal cusps were loaded on the outer and inner slopes to calculate the strain generated cervically. Data were collected for healthy teeth at baseline and progressively at three lesion depths (0.5 mm, 1.0 mm and 1.5 mm), followed by restoration with resin composite. The magnitude and distribution of von Mises stress and maximum principal stress were simulated at all stages using FEA, and fracture strength was also determined (n = 7 per group).There were significant effects of the lesion size and loading directions on stress, strain and fracture resistance (p<0.05). Fracture resistance values decreased with increase in lesion size, but returned to baseline with restorations.Combined assessment of computer-based and experimental techniques provide an holistic approach to characterize the biomechanical behaviour of teeth with both unrestored and restored NCCLs. This article is protected by copyright. All rights reserved.LF Zeola, FA Pereira, AC Machado, BR Reis, J Kaidonis, Z Xie, GC Townsend, S Ranjitkar, PV Soare

Genetically Determined Plasma Lipid Levels and Risk of Diabetic Retinopathy: A Mendelian Randomization Study.

Results from observational studies examining dyslipidemia as a risk factor for diabetic retinopathy (DR) have been inconsistent. We evaluated the causal relationship between plasma lipids and DR using a Mendelian randomization approach. We pooled genome-wide association studies summary statistics from 18 studies for two DR phenotypes: any DR (N = 2,969 case and 4,096 control subjects) and severe DR (N = 1,277 case and 3,980 control subjects). Previously identified lipid-associated single nucleotide polymorphisms served as instrumental variables. Meta-analysis to combine the Mendelian randomization estimates from different cohorts was conducted. There was no statistically significant change in odds ratios of having any DR or severe DR for any of the lipid fractions in the primary analysis that used single nucleotide polymorphisms that did not have a pleiotropic effect on another lipid fraction. Similarly, there was no significant association in the Caucasian and Chinese subgroup analyses. This study did not show evidence of a causal role of the four lipid fractions on DR. However, the study had limited power to detect odds ratios less than 1.23 per SD in genetically induced increase in plasma lipid levels, thus we cannot exclude that causal relationships with more modest effect sizes exist

An anthropological perspective: Another dimension to modern dental wear concepts

Extent: 6p.For many years, research on tooth wear by dental academics has been diametrically opposite to that of anthropological research, with each discipline having a different understanding as to the nature of the wear processes. Dental focus revolved around preventive and restorative considerations while the anthropological focus was a biological understanding related to human evolution, diet, environment, form, and function and included all the craniofacial structures. Introducing the anthropological perspective into modern dentistry gives an insight into the “bigger picture” of the nature and extent of tooth wear. By combining anthropological evidence with clinical knowledge and experience, it is most likely to provide the best-informed and biologically based approach to the management of tooth wear in modern societies.John A. Kaidonis, Sarbin Ranjitkar, Dimitra Lekkas, and Grant C. Townsen

Differential nuclear and mitochondrial DNA preservation in post-mortem teeth with implications for forensic and ancient DNA studies

Major advances in genetic analysis of skeletal remains have been made over the last decade, primarily due to improvements in post-DNA-extraction techniques. Despite this, a key challenge for DNA analysis of skeletal remains is the limited yield of DNA recovered from these poorly preserved samples. Enhanced DNA recovery by improved sampling and extraction techniques would allow further advancements. However, little is known about the post-mortem kinetics of DNA degradation and whether the rate of degradation varies between nuclear and mitochondrial DNA or across different skeletal tissues. This knowledge, along with information regarding ante-mortem DNA distribution within skeletal elements, would inform sampling protocols facilitating development of improved extraction processes. Here we present a combined genetic and histological examination of DNA content and rates of DNA degradation in the different tooth tissues of 150 human molars over short-medium post-mortem intervals. DNA was extracted from coronal dentine, root dentine, cementum and pulp of 114 teeth via a silica column method and the remaining 36 teeth were examined histologically. Real time quantification assays based on two nuclear DNA fragments (67 bp and 156 bp) and one mitochondrial DNA fragment (77 bp) showed nuclear and mitochondrial DNA degraded exponentially, but at different rates, depending on post-mortem interval and soil temperature. In contrast to previous studies, we identified differential survival of nuclear and mtDNA in different tooth tissues. Furthermore histological examination showed pulp and dentine were rapidly affected by loss of structural integrity, and pulp was completely destroyed in a relatively short time period. Conversely, cementum showed little structural change over the same time period. Finally, we confirm that targeted sampling of cementum from teeth buried for up to 16 months can provide a reliable source of nuclear DNA for STR-based genotyping using standard extraction methods, without the need for specialised equipment or large-volume demineralisation steps.Denice Higgins, Adam B. Rohrlach, John Kaidonis, Grant Townsend, Jeremy J. Austi

Targeted sampling of cementum for recovery of nuclear DNA from human teeth and the impact of common decontamination measures

Background: Teeth are a valuable source of DNA for identification of fragmented and degraded human remains. While the value of dental pulp as a source of DNA is well established, the quantity and presentation of DNA in the hard dental tissues has not been extensively studied. Without this knowledge common decontamination, sampling and DNA extraction techniques may be suboptimal. Targeted sampling of specific dental tissues could maximise DNA profiling success, while minimising the need for laborious sampling protocols and DNA extraction techniques, thus improving workflows and efficiencies. We aimed to determine the location of cellular DNA in non-degraded human teeth to quantify the yield of nuclear DNA from cementum, the most accessible and easily sampled dental tissue, and to investigate the effect of a common decontamination method, treatment with sodium hypochlorite (bleach). We examined teeth histologically and subsequently quantified the yield of nuclear DNA from the cementum of 66 human third molar teeth. We also explored the effects of bleach (at varying concentrations and exposure times) on nuclear DNA within teeth, using histological and quantitative PCR methods. Results: Histology confirmed the presence of nucleated cells within pulp and cementum, but not in dentine. Nuclear DNA yields from cementum varied substantially between individuals but all samples gave sufficient DNA (from as little as 20 mg of tissue) to produce full short tandem repeat (STR) profiles. Variation in yield between individuals was not influenced by chronological age or sex of the donor. Bleach treatment with solutions as dilute as 2.5% for as little as 1 min damaged the visible nuclear material and reduced DNA yields from cementum by an order of magnitude. Conclusions: Cementum is a valuable, and easily accessible, source of nuclear DNA from teeth, and may be a preferred source where large numbers of individuals need to be sampled quickly (for example, mass disaster victim identification) without the need for specialist equipment or from diseased and degraded teeth, where pulp is absent. Indiscriminant sampling and decontamination protocols applied to the outer surface of teeth can destroy this DNA, reducing the likelihood of successful STR typing results.Denice Higgins, John Kaidonis, Grant Townsend, Toby Hughes and Jeremy J. Austi

Tooth wear development in the Australian Aboriginal dentition from Yuendumu: a longitudinal study

The analysis of dental wear, at both the microscopic and macroscopic scale, is one of the most widely used tools in archeology and anthropology to reconstruct the diet and lifestyle of past human populations. Biomechanical studies have indicated that tooth wear helps to dissipate the mechanical load over the crown surface, thus reducing the risk of tooth fracture. To date, there are only a few studies that have examined functional tooth wear variation in modern humans. Here we propose to study masticatory efficiency through the use of the Occlusal Fingerprint Analysis method, a well-developed digital approach that allows the reconstruction of the occlusal dynamics occurring during mastication. The aim of this study is to provide the first longitudinal quantitative data of molar and premolar macrowear patterns within a functional context. We examined the mixed and permanent dentition of one Australian Aboriginal child (from ages 8 to 17) from Yuendumu, using high-resolution surface scans of dental casts including both upper and lower arches. Our results suggest that the occlusal macrowear patterns of this individual did not significantly change through time. Occlusal contact parameters such as functional area, inclination and direction remain relatively unaltered throughout childhood and adolescence, indicating little change in the masticatory function of this individual. The functional tooth wear pattern in this individual did not change longitudinally indicating the degree of masticatory efficiency has most probably remained unaltered.Jinyoung Lee, Sarah Fung, Robin Yong, Sarbin Ranjitkar, John Kaidonis, Alistair R. Evans, Luca Fiorenz

Managing caries:the need to close the gap between the evidence base and current practice

Underpinned by a changing knowledge of the aetiology of caries and its sequelae, and assisted by established and advancing dental materials, there is growing evidence supporting less invasive management of dental caries based on the principles of minimal intervention dentistry. This narrative review assesses both the evidence and the adoption of less invasive caries management strategies and describes ways in which the gap between evidence and practice might be overcome. While there is increasing data supporting less invasive management of carious lesions, these are not standard in most dental practices worldwide. Usually, clinical studies focused on efficacy as outcome, and did not take into consideration the views and priorities of other stakeholders, such as primary care dentists, educators, patients and those financing services. Involving these stakeholders into study design and demonstrating the broader advantages of new management strategies might improve translation of research into practice. In theory, clinical dentists can rely on a growing evidence in cariology regarding less invasive management options. In practice, further factors seem to impede adoption of these strategies. Future research should address these factors by involving major stakeholders and investigating their prioritised outcomes to narrow or close the evidence gap.</p

Genome-Wide Association Study to Identify Genetic Variants Associated With Diabetic Maculopathy

PURPOSE. Diabetic maculopathy (including diabetic macular edema [DME]) is the leading cause of vision loss in people with diabetes. We aimed to identify the genetic determinants of diabetic maculopathy. METHODS. We conducted a genome-wide association study (GWAS) in two cohorts with a meta-analysis. The Australian cohort comprised 551 cases of DME and 599 controls recruited from the states of South Australia and Tasmania. The Scottish cohort comprised 1951 cases of diabetic maculopathy and 6541 controls from the Genetics of Diabetes Audit and Research in Tayside Scotland study (GoDARTS). Genotyping, imputation, and association analysis using logistic regression were conducted in each cohort, before combining summary statistics in a meta-analysis using the GWAMA package. RESULTS. A locus on chromosome 7 reached genome-wide significance in GoDARTS but showed the opposite direction of effect in the Australian cohort. The meta-analysis identified two suggestive associations (P &lt; 5 × 10−6) for diabetic maculopathy risk with similar effect direction; one at chromosome 1 close to the RNU5E-1 gene and one at chromosome 13 upstream of the ERICH6B gene. The two loci were evaluated in silico for potential functional links to diabetic maculopathy. Both are located in regulatory regions and have annotations indicating regulatory functions. They are also expression quantitative trait locus (eQTLs) for genes plausibly involved in diabetic maculopathy pathogenesis, with links to folate metabolism and the regulation of VEGF. CONCLUSIONS. The study suggests several promising SNPs and genes related to diabetic maculopathy risk. Despite being the largest genetic study of diabetic maculopathy to date, larger, homogeneous cohorts will be required to identify robust genetic risk loci for the disease.</p

Three-year randomised clinical trial to evaluate the clinical performance, quantitative and qualitative wear patterns of hybrid composite restorations

The aim of the study was to compare the clinical performance, quantitative and qualitative wear patterns of conventional hybrid (Tetric Ceram), micro-filled hybrid (Gradia Direct Posterior) and nano-hybrid (Tetric EvoCeram, TEC) posterior composite restorations in a 3-year randomised clinical trial. Sixteen Tetric Ceram, 17 TEC and 16 Gradia Direct Posterior restorations were placed in human molars and evaluated at baseline, 6, 12, 24 and 36 months of clinical service according to US Public Health Service criteria. The gypsum replicas at each recall were used for 3D laser scanning to quantify wear, and the epoxy resin replicas were observed under scanning electron microscope to study the qualitative wear patterns. After 3 years of clinical service, the three hybrid restorative materials performed clinically well in posterior cavities. Within the observation period, the nano-hybrid and micro-hybrid restorations evolved better in polishability with improved surface gloss retention than the conventional hybrid counterpart. The three hybrid composites showed enamel-like vertical wear and cavity-size dependant volume loss magnitude. Qualitatively, while the micro-filled and nano-hybrid composite restorations exhibited signs of fatigue similar to the conventional hybrid composite restorations at heavy occlusal contact area, their light occlusal contact areas showed less surface pitting after 3 years of clinical service