Heritage-specific oral microbiota in Indigenous Australian dental calculus.

Background and objectives: Aboriginal Australians and Torres Strait Islanders (hereafter respectfully referred to as Indigenous Australians) experience a high burden of chronic non-communicable diseases (NCDs). Increased NCD risk is linked to oral diseases mediated by the oral microbiota, a microbial community influenced by both vertical transmission and lifestyle factors. As an initial step towards understanding the oral microbiota as a factor in Indigenous health, we present the first investigation of oral microbiota in Indigenous Australian adults. Methodology: Dental calculus samples from Indigenous Australians with periodontal disease (PD; n = 13) and non-Indigenous individuals both with (n = 19) and without PD (n = 20) were characterized using 16S ribosomal RNA gene amplicon sequencing. Alpha and beta diversity, differentially abundant microbial taxa and taxa unique to different participant groups were analysed using QIIME2. Results: Samples from Indigenous Australians were more phylogenetically diverse (Kruskal-Wallis H = 19.86, P = 8.3 × 10-6), differed significantly in composition from non-Indigenous samples (PERMANOVA pseudo-F = 10.42, P = 0.001) and contained a relatively high proportion of unique taxa not previously reported in the human oral microbiota (e.g. Endomicrobia). These patterns were robust to stratification by PD status. Oral microbiota diversity and composition also differed between Indigenous individuals living in different geographic regions. Conclusions and implications: Indigenous Australians may harbour unique oral microbiota shaped by their long relationships with Country (ancestral homelands). Our findings have implications for understanding the origins of oral and systemic NCDs and for the inclusion of Indigenous peoples in microbiota research, highlighting the microbiota as a novel field of enquiry to improve Indigenous health.

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.

A functional analysis of Carabelli trait in Australian aboriginal dentition.

OBJECTIVES: Carabelli is a nonmetric dental trait variably expressed as a small pit to a prominent cusp in the maxillary molars of modern humans. Investigations on the occurrence and expression rates of this trait have been conducted extensively, tracing its origin to genetic sources. However, there remains a lack of understanding about its potential role in chewing. In this study, we examine molar macrowear with the aim of reconstructing Carabelli trait occlusal dynamics occurring during chewing. METHODS: We have examined 96 deciduous and permanent maxillary molars of children and young adults from Yuendumu, an Australian Aboriginal population that was at an early stage of transition from a nomadic and hunter-gatherer way of life to a more settled existence. We apply a well-established method, called Occlusal Fingerprint Analysis, which is a digital approach for analyzing dental macrowear allowing the reconstruction of jaw movements required to produce wear pattern specific to each tooth. RESULTS: Carabelli trait slightly enlarges the surface functional area, especially in those molars where this feature is expressed in its cuspal form and it is closer to the occlusal plane. Moreover, the highly steep contact planes would also indicate that Carabelli wear areas contribute to increasing the shearing abilities of the occluded teeth, which are particularly important when processing fibrous and tough foods. CONCLUSIONS: The macrowear analysis suggests that Carabelli trait in the Aboriginal people from Yuendumu slightly enhanced occlusion and probably played some functional role during mastication. Future biomechanical and microwear analyses could provide additional information on the mechanical adaptation of Carabelli trait in modern human dentition.

The functional role of the Carabelli trait in early and late hominins.

The Carabelli trait is a dental feature that forms along the lingual margin of the protocone of deciduous and permanent maxillary molars. It is variably expressed, ranging from a small pit or furrow to a large cusp, and its development seems to be associated with crown size and molar cusp spatial configuration. The degree of expression of the Carabelli trait differs systematically between hominin taxa, and for this reason, it has been used extensively in the reconstruction of their phylogeny. However, the functional implications of having a large Carabelli trait remain unclear. In this study, we analyze the macrowear pattern of maxillary molars of early and late hominins using the occlusal fingerprint analysis method, an approach based on digital models of teeth that helps in reconstructing occlusal dynamics occurring during mastication. Tooth crowns with a small Carabelli cusp generally exhibit larger wear contact areas that extended cervically, while two additional new occlusal contact areas are common in teeth characterized by a large Carabelli cusp. These wear areas are created at the beginning of the chewing cycle, when occluding with the slopes of the lingual groove of the lower molars, between the metaconid and entoconid cusps. Advancing tooth wear leads to a slight enlargement of Carabelli occlusal contacts increasing their functional area. A steep inclination could be mechanically important in food reduction and in balancing the functional load distribution during mastication contacts. Steep wear areas are particularly developed in primates that process foods characterized by tough and fibrous textural properties. Future biomechanical and microwear texture analyses could provide additional information on the mechanical adaptation of this dental trait.

Titania nanotube-based protein delivery system to inhibit cranial bone regeneration in Crouzon model of craniosynostosis.

BACKGROUND: Craniosynostosis is a developmental disorder characterized by the premature fusion of skull sutures, necessitating repetitive, high-risk neurosurgical interventions throughout infancy. This study used protein-releasing Titania nanotubular implant (TNT/Ti) loaded with glypican 3 (GPC3) in the cranial critical-sized defects (CSDs) in Crouzon murine model (Fgfr2c342y/+ knock-in mutation) to address a key challenge of delaying post-operative bone regeneration in craniosynostosis. MATERIALS AND METHODS: A 3 mm wide circular CSD was created in two murine models of Crouzon syndrome: (i) surgical control (CSDs without TNT/Ti or any protein, n=6) and (ii) experimental groups with TNT/Ti loaded with GPC3, further subdivided into the presence or absence of chitosan coating (on nanotubes) (n=12 in each group). The bone volume percentage in CSDs was assessed 90 days post-implantation using micro-computed tomography (micro-CT) and histological analysis. RESULTS: Nano-implants retrieved after 90 days post-operatively depicted well-adhered, hexagonally arranged, and densely packed nanotubes with average diameter of 120±10 nm. The nanotubular architecture was generally well-preserved. Compared with the control bone volume percentage data (without GPC3), GPC3-loaded TNT/Ti without chitosan coating displayed a significantly lower volume percent in cranial CSDs (P<0.001). Histological assessment showed relatively less bone regeneration (healing) in GPC3-loaded CSDs than control CSDs. CONCLUSION: The finding of inhibition of cranial bone regeneration by GPC3-loaded TNT/Ti in vivo is an important advance in the novel field of minimally-invasive craniosynostosis therapy and holds the prospect of altering the whole paradigm of treatment for affected children. Future animal studies on a larger sample are indicated to refine the dosage and duration of drug delivery across different ages and both sexes with the view to undertake human clinical trials.

Technical note: The use of 3D printing in dental anthropology collections.

OBJECTIVES: Rapid prototyping (RP) technology is becoming more affordable, faster, and is now capable of building models with a high resolution and accuracy. Due to technological limitations, 3D printing in biological anthropology has been mostly limited to museum displays and forensic reconstructions. In this study, we compared the accuracy of different 3D printers to establish whether RP can be used effectively to reproduce anthropological dental collections, potentially replacing access to oftentimes fragile and irreplaceable original material. METHODS: We digitized specimens from the Yuendumu collection of Australian Aboriginal dental casts using a high-resolution white-light scanning system and reproduced them using four different 3D printing technologies: stereolithography (SLA); fused deposition modeling (FDM); binder-jetting; and material-jetting. We compared the deviations between the original 3D surface models with 3D print scans using color maps generated from a 3D metric deviation analysis. RESULTS: The 3D printed models reproduced both the detail and discrete morphology of the scanned dental casts. The results of the metric deviation analysis demonstrate that all 3D print models were accurate, with only a few small areas of high deviations. The material-jetting and SLA printers were found to perform better than the other two printing machines. CONCLUSIONS: The quality of current commercial 3D printers has reached a good level of accuracy and detail reproduction. However, the costs and printing times limit its application to produce large sample numbers for use in most anthropological studies. Nonetheless, RP offers a viable option to preserve numerically constraint fragile skeletal and dental material in paleoanthropological collections.

The physiological linkage between molar inclination and dental macrowear pattern.

OBJECTIVES: Exact symmetry and perfect balance between opposite jaw halves, as well as between antagonistic teeth, is not frequently observed in natural masticatory systems. Research results show that asymmetry in our body, skull, and jaws is often related to genetic, epigenetic, environmental and individual ontogenetic factors. Our study aims to provide evidence for a significant link between masticatory asymmetry and occlusal contact between antagonist teeth by testing the hypothesis that tooth inclination is one of the mechanisms driving distribution of wear in masticatory phases in addition to dietary and cultural habits. MATERIALS AND METHODS: The present work investigates the relationship between dental macrowear patterns and tooth inclinations on a sample of complete maxillary and mandibular 3D models of dental arches from 19 young and adult Yuendumu Aboriginal individuals. The analysis was carried out on first molars (M1) from all quadrants. Occlusal Fingerprint Analysis was used for the quantification of macrowear patterns, and 2D cross-sectional geometric analysis was carried out to investigate asymmetry in dental arches. RESULTS: The asymmetry is highly variable on both arches, and it is associated with differences in the inclination of upper M1 crowns. Each molar has variable inclination (buccal/lingual) which influence tooth to tooth contact, producing greater or lesser variation in wear pattern. Interindividual variability of morphological variation of the occlusal relationship has to be considered in macrowear analysis. DISCUSSION: Our results suggest that overall asymmetry in the masticatory apparatus in modern humans affects occlusal contact areas between antagonist teeth influencing macrowear and chewing efficiency during ontogeny.

Glypican-based drug releasing titania implants to regulate BMP2 bioactivity as a potential approach for craniosynostosis therapy.

Advances in molecular biology and nanomedicine based therapies hold promise to obviate the need of multiple surgical interventions (associated with current management) in craniosynostosis by preventing bone re-ossification. One such adjunctive therapy involves application of glypicans 1 and 3 (GPC1 and GPC3) that are BMP inhibitors implicated in downregulating the BMP2 activity in prematurely fusing sutures. Electrochemically anodized Titania nanotube (TNT) arrays have been recognized as a promising localized, long-term drug delivery platform for bone-related therapies. This study presents the application of nanoengineered TNT/Ti implants loaded with recombinant glypicans for craniosynostosis therapy. By using Dual luciferase Reporter assay, we tested the biofunctionality of eluted glypicans from the TNT/Ti implants for BMP2 bioactivity regulation in C2C12 murine myoblast cell line. BMP2 activity was inhibited significantly for up to 15days by the glypicans released from polymer-coated TNT/Ti implants, indicating their potential application in adjunctive craniosynostosis treatment.

Neanderthal behaviour, diet, and disease inferred from ancient DNA in dental calculus.

Recent genomic data have revealed multiple interactions between Neanderthals and modern humans, but there is currently little genetic evidence regarding Neanderthal behaviour, diet, or disease. Here we describe the shotgun-sequencing of ancient DNA from five specimens of Neanderthal calcified dental plaque (calculus) and the characterization of regional differences in Neanderthal ecology. At Spy cave, Belgium, Neanderthal diet was heavily meat based and included woolly rhinoceros and wild sheep (mouflon), characteristic of a steppe environment. In contrast, no meat was detected in the diet of Neanderthals from El Sidrón cave, Spain, and dietary components of mushrooms, pine nuts, and moss reflected forest gathering. Differences in diet were also linked to an overall shift in the oral bacterial community (microbiota) and suggested that meat consumption contributed to substantial variation within Neanderthal microbiota. Evidence for self-medication was detected in an El Sidrón Neanderthal with a dental abscess and a chronic gastrointestinal pathogen (Enterocytozoon bieneusi). Metagenomic data from this individual also contained a nearly complete genome of the archaeal commensal Methanobrevibacter oralis (10.2× depth of coverage)-the oldest draft microbial genome generated to date, at around 48,000 years old. DNA preserved within dental calculus represents a notable source of information about the behaviour and health of ancient hominin specimens, as well as a unique system that is useful for the study of long-term microbial evolution.

Biological response of human suture mesenchymal cells to Titania nanotube-based implants for advanced craniosynostosis therapy.

Titania nanotubes (TNTs) engineered on titanium (Ti) surfaces (i.e. TNT/Ti) and loaded with specific drugs have been recognised as a promising solution for localised therapeutic delivery to address several medical problems not feasible with conventional drug administration. We propose the use of TNT/Ti protein-releasing implants to treat paediatric craniofacial abnormality in craniosynostosis caused by premature fusion of cranial sutures. In this study, we have analysed the biological response of human suture mesenchymal cells (SMCs), extracted from two different patients undergoing craniofacial reconstruction surgery, at the TNT/Ti implant surface. The experimental groups included large-diameter TNT/Ti implants, with and without biopolymer surface coating (Chitosan and Pluronic-F127) while the controls comprised of flat Ti disc and tissue culture plastic. The non-loaded implant surfaces and the cellular interactions at the implant-cell interface were characterised using scanning electron microscopy (SEM). The SMC adhesion, viability and proliferation were determined by MTT assay and manual cell counting at day 1 and day 3 of cell incubation. SEM showed significant reduction in initial attachment and adhesion of SMCs at TNT-cell biointerface compared with the control Ti discs. Subsequent cell proliferation results also revealed a decrease in the number of viable cells on the TNT surfaces. The nanotopography and structural features along with the surface chemistry dictated the cellular response, with nanotubular surfaces (with and without polymer coating) impeding cell adhesion and proliferation. Our findings hold promise for the use of TNT-based cranial implants as a delivery system to prevent sutural bone growth for advanced craniosynostosis therapy.

The 'sialo-microbial-dental complex' in oral health and disease.

Biofilms are naturally found in all wet environments including the oral structures of nearly all species. Human oral biofilms have existed since our earliest ancestors and have evolved symbiotically with the dentition over many millennia within a Palaeolithic, hunter-gatherer setting. Irrespective of the plant-animal ratio, it can be argued that the Palaeolithic diet was essentially acidic, and acted as a selective force for much of the evolution of the stomatognathic system. The relationship between saliva, biofilm and teeth, the 'sialo-microbial-dental complex', provides oral health benefits and offers a different perspective to the old dental paradigm that only associated oral biofilms (plaque) with disease (caries). This new paradigm emphasises that oral biofilms are essential for the 'mineral maintenance' of teeth. Oral biofilms provide physical protection from dietary acid and together with bacterial metabolic acids cause the resting pH of the biofilm to fall below neutral. This is then followed by the re-establishment of a neutral environment by chemical interactions mediated by the saliva within the biofilm. Such pH fluctuations are often responsible for the cyclic demineralisation, then remineralisation of teeth, a process necessary for tooth maturation. However, since the advent of farming and especially since the industrial revolution, the increase in consumption of carbohydrates, refined sugars and acidic drinks has changed the ecology of biofilms. Biofilm biodiversity is significantly reduced together with a proliferation of acidogenic and aciduric organisms, tipping the balance of the 'demin-remin' cycle towards net mineral loss and hence caries. In addition, the consumption of acidic drinks in today's societies has removed the protective nature of the biofilm, leading to erosion. Erosion and caries are 'modern-day' diseases and reflect an imbalance within the oral biofilm resulting in the demineralisation of teeth.

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.

Three-dimensional profilometric assessment of early enamel erosion simulating gastric regurgitation.

OBJECTIVES: A priority research area in minimal intervention dentistry is the characterization of the early stages of dental erosion. The aim of this in vitro study was to assess the effect of short, repetitive erosive challenges to human enamel over 2 min at pH 1.5 and 3.0 under conditions simulating gastric regurgitation. METHODS: Enamel surfaces were subjected to erosive challenges at pH 1.5 (Group 1, n=10) and pH 3.0 (Group 2, n=9) for periods of 30s (stage 1), 60s (stage 2) and 120 s (stage 3). Quantitative changes were assessed longitudinally by measuring the 3D average surface roughness (Sa) values using 3D confocal microscopy. Qualitative micrographic assessment of surface changes was also conducted by using environmental scanning electron microscopy. RESULTS: Linear mixed model analysis showed significant effects of the pH values (p<0.001) and the stages (p<0.001) on the observed Sa values. Post hoc tests showed significant increases in the Sa values between baseline and other stages in both groups (p<0.01). The mean Sa values also increased significantly from stage 1 to stage 2 in Group 1 (p<0.05). Micrographic analysis displayed severely etched enamel rods in Group 1, but only subtle changes in Group 2. CONCLUSIONS: The complexity of the enamel surface is influenced by both acid concentration (pH value) and duration of acid exposure during early stages of erosion. Erosion occurring under conditions simulating GORD can be detected in its initial stages, opening up the possibilities of early diagnosis and management of this condition. CLINICAL SIGNIFICANCE: Erosive tooth wear occurs progressively and insidiously, often creating complex treatment challenges. This emphasizes the need for early diagnosis and management in accordance with minimal intervention philosophy. Our findings provide a foundation for further research that could lead to the development of highly-sensitive clinical diagnostic tools and preventive strategies.

Evaluation of carrier RNA and low volume demineralization for recovery of nuclear DNA from human teeth.

PURPOSE: Teeth and bones are frequently used in the genetic analysis of degraded and ancient human and animal remains. Standard extraction methods, including most commercially available systems, may not yield sufficient DNA to enable successful genetic analysis. Addition of a carrier molecule and demineralization (via EDTA) can increase yields from samples containing limited amounts of DNA. However the benefits of carrier molecules have not been demonstrated for bones and teeth and demineralization introduces large reagent volumes that are difficult to integrate into commercial DNA extraction systems. METHODS: We compared nuclear DNA yields recovered from small samples of partially decomposed human teeth using a commercial silica-based DNA extraction system with and without the addition of carrier RNA and/or a low-volume demineralization step. RESULTS: DNA yield was significantly improved with demineralization, but there was no significant effect of carrier RNA. The DNA content of a sample did not influence the significance of the effect of demineralization. CONCLUSION: Using a simple low-volume (1 mL) demineralization step, prior to DNA extraction with the QIAmp DNA Investigator kit (Qiagen), as little as 50 mg of tooth powder can yield more than 500 ng of nuclear DNA.

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.

Sequencing ancient calcified dental plaque shows changes in oral microbiota with dietary shifts of the Neolithic and Industrial revolutions.

The importance of commensal microbes for human health is increasingly recognized, yet the impacts of evolutionary changes in human diet and culture on commensal microbiota remain almost unknown. Two of the greatest dietary shifts in human evolution involved the adoption of carbohydrate-rich Neolithic (farming) diets (beginning ∼10,000 years before the present) and the more recent advent of industrially processed flour and sugar (in ∼1850). Here, we show that calcified dental plaque (dental calculus) on ancient teeth preserves a detailed genetic record throughout this period. Data from 34 early European skeletons indicate that the transition from hunter-gatherer to farming shifted the oral microbial community to a disease-associated configuration. The composition of oral microbiota remained unexpectedly constant between Neolithic and medieval times, after which (the now ubiquitous) cariogenic bacteria became dominant, apparently during the Industrial Revolution. Modern oral microbiotic ecosystems are markedly less diverse than historic populations, which might be contributing to chronic oral (and other) disease in postindustrial lifestyles.

An anthropological perspective: another dimension to modern dental wear concepts.

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.

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.

Oral manifestations of gastroesophageal reflux disease.

Numerous case-control and other studies involving confirmation of gastroesophageal reflux disease (GERD) by esophageal pH-metry and the assessment of dental erosions have shown significant associations between the two conditions in both adults and children. By contrast, when asked to vote on whether GERD may cause dental erosions, only 42% of physicians strongly agreed that such an association existed in adults, and just 12.5% strongly agreed for children, respectively in two global consensus reports. Part of this divergence between the perceptions of physicians and the findings of research publications may reflect a general lack of oral health education during medical training, and cursory oral examinations being made under less-than-ideal conditions. Adequate salivary secretions are essential for the protection of the teeth and the oropharyngeal and esophageal mucosa. The quantity and quality of the saliva require monitoring as many drugs, including several of the proton pump inhibitors (PPIs), can cause hyposalivation. In addition, PPIs do not always result in adequate acid suppression. Therefore, collaboration between physicians and dentists is strongly advocated to prevent or ameliorate possible adverse oral effects from both endogenous and exogenous acids, and to promote adequate saliva production in patients with GERD.