Alterations in mandibular morphology associated with glypican 1 and glypican 3 gene mutations.

OBJECTIVES: Glypican 1 (GPC1) and glypican 3 (GPC3) are bone co-regulators that act downstream in many of the signalling pathways associated with craniosynostosis. Morphometric data from GPC-knockout mice were analysed to determine whether elimination of GPC1 and GPC3 genes would alter mandibular morphology. SETTING AND SAMPLE POPULATION: The murine model included five male and five female mandibles in each of GPC1-knockout, GPC1/GPC3-knockout and wild-type (control) groups. Female GPC3-knockout mice had a very high rate of perinatal lethality, and therefore, only five males were included in this group. METHODS: The mandibular morphology of GPC1-knockout (n=10), GPC3-knockout (n=5), GPC1/GPC3-knockout (n=10) and wild-type (n=10) mice was compared by analysing five landmark-based linear dimensions: anterior and posterior lengths, as well as ascending, descending and posterior heights. Measurements were recorded on three-dimensional micro-CT reconstructions. RESULTS: GPC3-knockout mandibles were larger than wild-type mandibles for all dimensions (P<.05). Mandibular heights were more affected than lengths. A decreasing trend of mandibular dimensions across the mouse groups (GPC3-knockout>GPC1/GPC3-knockout>GPC1-knockout=wild-type) (P<.05) indicated that an increase in mandibular size was associated with increased GPC3 expression, but not GPC1. CONCLUSIONS: Alterations in GPC3 expression are likely to mediate changes to mandibular size in craniosynostosis. These findings have potential future applications in the prevention and treatment of craniosynostosis and associated craniofacial dysmorphology.

Determining the direction of tooth grinding: an in vitro study.

The analysis of microwear patterns, including scratch types and widths, has enabled reconstruction of the dietary habits and lifestyles of prehistoric and modern humans. The aim of this in vitro study was to determine whether an assessment of microwear features of experimental scratches placed on enamel, perpendicularly to the direction of grinding, could predict the grinding direction. Experimental scratches were placed using a scalpel blade on standardised wear facets that had been prepared by wearing opposing enamel surfaces in an electromechanical tooth wear machine. These control 'baseline' facets (with unworn experimental scratches) were subjected to 50 wear cycles, so that differential microwear could be observed on the leading and trailing edges of the 'final' facets. In Group 1 (n=28), the 'footprint' microwear patterns corresponding to the known grinding direction of specimens in the tooth wear machine were identified. Then, they were used to predict the direction of tooth grinding blindly in the same sample after a 2-week intermission period. To avoid overfitting the predictive model, its sensitivity was also cross-validated in a new sample (Group 2, n=14). A crescent-shaped characteristic observed in most experimental scratches matched the grinding direction on all occasions. The best predictor of the direction of grinding was a combined assessment of the leading edge microwear pattern and the crescent characteristic (82.1% in Group 1 and 92.9% in Group 2). In conclusion, a simple scratch test can determine the direction of tooth grinding with high reliability, although further improvement in sensitivity is desirable.

Opening up on airways: the purported effect of nasorespiratory obstruction on dentofacial growth.

Nasorespiratory obstruction has been purported to influence dentofacial growth adversely. This has sparked considerable debate for decades with a resurgence in interest in 'airway friendly orthodontics' among both general and specialist dental practitioners. This critical review aims to evaluate the current literature relating to two questions: does nasorespiratory obstruction alter dentofacial growth, and does early intervention targeted at alleviating nasorespiratory obstruction improve dentofacial growth? The strength of association between nasorespiratory obstruction, mouth breathing and a long face is weak. The common methodological flaws in research include unblinded and cross-sectional study designs, a lack of adequate controls, inadequate follow-up, subjective assessments and inadequate statistical power. Vertical dentofacial growth has a strong genetic influence, which implies a relatively minor contribution of environmental factors including airway obstruction. The current evidence does not support recommending procedures, such as adenotonsillectomy and maxillary expansion, with the singular aim of negating a hyperdivergent (vertical) dentofacial growth pattern. In light of low-quality evidence, both the World Health Organization guidelines and ethical principles dictate that greater emphasis is placed on avoiding harm and wastage of resources over alternative options. These findings call for quality improvement in undergraduate and postgraduate curricula and continuing professional development for health professionals.

The effect of casein phosphopeptide-amorphous calcium phosphate on erosive dentine wear.

BACKGROUND: Erosive tooth wear is a growing concern in clinical dentistry. Our aims were to assess the effect of Tooth Mousse (TM) in managing erosive dentine wear in vitro. METHODS: Opposing enamel and dentine specimens from 36 third molar teeth were worn under a load of 100 N for 75 000 cycles in electromechanical tooth wear machines. In experiment 1, TM was applied continuously at the wear interface and the mean dentine wear rate was compared with those of specimens subjected to continuous application of hydrochloric acid (HCl, pH 3.0) and deionized water (DW, pH 6.1) as lubricants. In experiment 2, specimens were subjected to TM application every 1600 cycles at both pH 3.0 and 6.1, and the mean dentine wear rates were compared with those of specimens worn with continuous application of HCl and DW lubricants. RESULTS: Dentine wear was reduced significantly with continuous application of TM compared with HCl and DW lubricants. Specimens prepared with continuous TM application displayed smooth wear facets, whereas more pronounced microwear details were observed with HCl and DW lubricants. CONCLUSIONS: Both remineralization and lubrication seem to contribute to reduction in dentine wear associated with TM application, although lubrication appears to have a more pronounced effect.

Orofacial neuralgia associated with a middle cerebral artery aneurysm.

Chronic orofacial pain of neuropathic origin can present diagnostic and management dilemmas to dental practitioners and also affects the patient's quality of life. Intracranial aneurysms are a potential cause of stroke (e.g. sub-arachnoid haemorrhage) that is usually associated with, high rates of mortality and morbidity. A patient who had been previously managed for symptoms of temporomandibular joint disorder (TMD) presented with sharp, shooting pain of moderate intensity. It was precipitated by swallowing, and radiated to the right throat, posterior border of the mandible, ear and temporomandibular joint. Clinical and radiological investigations ruled out odontogenic pain, TMD and other more common types of facial pain. Magnetic resonance imaging revealed a 7 × 6 mm aneurysm in the right middle cerebral artery (MCA) which was subsequently surgically clipped. Interestingly, the facial pain resolved after this procedure. Compression of the insular region of the brain innervated by the trigeminal, glossopharyngeal and vagus nerves provides a plausible explanation for the pain reported. To our knowledge, this is the first case of facial neuralgia associated with an aneurysm in the MCA which emphasizes the importance of a multidisciplinary approach in the diagnosis and management of unusual cases of chronic orofacial pain.

An in vitro assessment of the role of Tooth Mousse in preventing wine erosion.

BACKGROUND: The recommendation that Tooth Mousse (TM), an anticariogenic remineralizing agent, is effective for controlling dental erosion in professional wine tasters is not evidence-based. The aim of this in vitro study was to determine the effectiveness of TM in reducing erosion of coronal enamel and radicular dentine/cementum simulating a typical wine judging session. METHODS: Enamel and dentine/cementum from buccal halves (experimental sample) and palatal halves (control sample) of human maxillary premolar teeth were subjected to 1500 one-minute exposures (cycles) to white wine (pH = 3.5). TM was applied every 20 cycles to the experimental sample, but not to the control sample. Paired t-tests were used to determine whether there were significant differences in erosion depths between the experimental and control samples. RESULTS: Mean erosion depths were significantly shallower in the experimental sample than the control sample for both enamel (34.4 microm versus 49.2 microm, respectively) (p < 0.05) and dentine/cementum (143.2 microm versus 203.7 microm, respectively) (p < 0.01). CONCLUSIONS: TM may have significant role in the management of wine erosion, which is under-recognized as an occupational hazard by the Australian wine industry. Future studies are needed to compare the relative benefits of TM and other remineralizing agents, when used individually or in combination, in preventing dental erosion.

A qualitative assessment of non-carious cervical lesions in extracted human teeth.

BACKGROUND: Opinions vary about the causes of non-carious cervical lesions (NCCLs). They have been attributed to toothbrush abrasion, acid corrosion (commonly termed dental erosion), and abfraction. The purpose of this study was to examine the microwear details of NCCLs in a collection of extracted human teeth using scanning election microscopy (SEM). METHODS: Negative replicas of large NCCLs in 24 extracted human teeth were obtained in polyvinylsiloxane impression material (Light Body Imprint II, 3M ESPE) and viewed under SEM. RESULTS: All NCCLs extended from the cemento-enamel junction to the root surface and they displayed a variety of wedge-shaped appearances. There was evidence of both abrasion and corrosion in 18 of the 24 teeth (75.0 per cent), abrasion only in one tooth (4.2 per cent) and corrosion only in five teeth (20.8 per cent). Horizontal furrows with smooth edges and minor scratch marks, characteristic of abrasion and corrosion, were noted in 13 teeth (54.2 per cent). CONCLUSIONS: Based on microscopic assessment of a sample of extracted teeth, it appears that abrasion and corrosion are common associated aetiological factors in the formation of NCCLs.

Surface-Sensitive Microwear Texture Analysis of Attrition and Erosion.

Scale-sensitive fractal analysis of high-resolution 3-dimensional surface reconstructions of wear patterns has advanced our knowledge in evolutionary biology, and has opened up opportunities for translatory applications in clinical practice. To elucidate the microwear characteristics of attrition and erosion in worn natural teeth, we scanned 50 extracted human teeth using a confocal profiler at a high optical resolution (X-Y, 0.17 µm; Z < 3 nm). Our hypothesis was that microwear complexity would be greater in erosion and that anisotropy would be greater in attrition. The teeth were divided into 4 groups, including 2 wear types (attrition and erosion) and 2 locations (anterior and posterior teeth; n = 12 for each anterior group, n = 13 for each posterior group) for 2 tissue types (enamel and dentine). The raw 3-dimensional data cloud was subjected to a newly developed rigorous standardization technique to reduce interscanner variability as well as to filter anomalous scanning data. Linear mixed effects (regression) analyses conducted separately for the dependent variables, complexity and anisotropy, showed the following effects of the independent variables: significant interactions between wear type and tissue type ( P = 0.0157 and P = 0.0003, respectively) and significant effects of location ( P < 0.0001 and P = 0.0035, respectively). There were significant associations between complexity and anisotropy when the dependent variable was either complexity ( P = 0.0003) or anisotropy ( P = 0.0014). Our findings of greater complexity in erosion and greater anisotropy in attrition confirm our hypothesis. The greatest geometric means were noted in dentine erosion for complexity and dentine attrition for anisotropy. Dentine also exhibited microwear characteristics that were more consistent with wear types than enamel. Overall, our findings could complement macrowear assessment in dental clinical practice and research and could assist in the early detection and management of pathologic tooth wear.

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

BACKGROUND: Information on fracture biomechanics has implications in materials research and clinical practice. The aim of this study was to analyse the influence of non-carious cervical lesion (NCCL) size, restorative status and direction of occlusal loading on the biomechanical behaviour of mandibular premolars, using finite element analysis (FEA), strain gauge tests and fracture resistance tests. METHODS: 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). RESULTS: 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. CONCLUSIONS: 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.

Odontogenic facial swelling of unknown origin.

BACKGROUND: Current radiography techniques have limitations in detecting subtle odontogenic anomalies or defects that can lead to dentoalveolar and facial infections. This report examines the application of micro-CT imaging on two extracted teeth to enable detailed visualization of subtle odontogenic defects that had given rise to facial swelling. METHODS: Two extracted non-carious mandibular left primary canine teeth (73) associated with odontogenic infections were selected from two patients, and an intact contralateral tooth (83) from one of the patients was used as a control. All three teeth were subjected to three-dimensional micro-CT imaging at a resolution of 20 µm. RESULTS: Tooth 73 from the first case displayed dentine pores (channels) that established communication between the pulp chamber and the exposed dentine surface. In comparison, tooth 73 from the second case had a major vertical crack extending from the external enamel surface into the pulp chamber. The control tooth did not display any anomalies or major cracks. CONCLUSIONS: The scope of micro-CT imaging can be extended from current in vitro applications to establish post-extraction diagnosis of subtle odontogenic defects, in a manner similar to deriving histopathological diagnoses in extracted teeth. Ongoing technological advancements hold the promise for more widespread translatory applications.

Nanoscratch testing for the assessment of enamel demineralization under conditions simulating wine erosion.

BACKGROUND: Erosive tooth wear and dentinal hypersensitivity are common problems affecting professional wine tasters. By using nanoscratch testing, the aim of this in vitro study was to assess enamel softening under conditions simulating 10 one-minute episodes of wine erosion. METHODS: Ten enamel specimens were bathed in artificial saliva for 2 hours before being eroded for 10 episodes, with each episode comprising one minute of wine erosion followed by one minute of remineralization in artificial saliva. Nanoscratches were placed with a spherical tip (20 µm radius) in a nanoindenter under a load of 100 mN at baseline (stage 1), after a one-erosion episode (stage 2) and after 10-erosion episodes (stage 3). RESULTS: There were significant effects of erosion stages on both scratch depth (p<0.001) and surface roughness (p<0.001). Post hoc tests showed significant differences in both scratch depths and surface roughness between stages 1 and 3 (p<0.001), and between stages 2 and 3 (p<0.01). CONCLUSIONS: Enamel softening occurs at an early stage of wine tasting, emphasizing the need to implement early preventive strategies in professional wine tasters. Further research elucidating the fundamental mechanisms involved in early stages of erosion has the potential to lead to development of more effective preventive strategies.

A radiographic assessment of the prevalence of pulp stones in Australians.

BACKGROUND: Pulp stones are discrete calcified bodies found in the dental pulp. The aims of this study were to calculate the prevalence of pulp stones in young Australian adults using radiographs, and to report any associations between occurrence of pulp stones and sex, tooth type, dental arch, side and dental status. METHODS: From 217 undergraduate dental students, comprising 123 males and 94 females aged between 17-35 years, 3296 teeth were examined under 2x magnification on bitewing radiographs. Pulp stones were scored as present or absent, and associations with sex, tooth type, dental arch, side and dental status noted. RESULTS: Pulp stones were found in 100 (46.1 per cent) of the subjects and 333 (10.1 per cent) of the teeth examined. Occurrences were rare in premolars (0.4 per cent) but significantly higher in molars (19.7 per cent). Pulp stones were significantly more common in first molars than in second molars, and in maxillary first molars than in mandibular first molars. Carious and/or restored maxillary right first molars and maxillary left second molars displayed higher prevalences of pulp stones than unrestored and intact molars. CONCLUSION: Pulp stones may provide useful forensic information when examining dental records to identify deceased persons.

Application of three-dimensional computed tomography in craniofacial clinical practice and research.

Following the invention of the first computed tomography (CT) scanner in the early 1970s, many innovations in three-dimensional (3D) diagnostic imaging technology have occurred, leading to a wide range of applications in craniofacial clinical practice and research. Three-dimensional image analysis provides superior and more detailed information compared with conventional plain two-dimensional (2D) radiography, with the added benefit of 3D printing for preoperative treatment planning and regenerative therapy. Current state-of-the-art multidetector CT (MDCT), also known as medical CT, has an important role in the diagnosis and management of craniofacial injuries and pathology. Three-dimensional cone beam CT (CBCT), pioneered in the 1990s, is gaining increasing popularity in dental and craniofacial clinical practice because of its faster image acquisition at a lower radiation dose, but sound guidelines are needed to ensure its optimal clinical use. Recent innovations in micro-computed tomography (micro-CT) have revolutionized craniofacial biology research by enabling higher resolution scanning of teeth beyond the capabilities of MDCT and CBCT, presenting new prospects for translational clinical research. Even after four decades of refinement, CT technology continues to advance and broaden the horizons of craniofacial clinical practice and phenomics research.

Functional dental occlusion: an anthropological perspective and implications for practice.

Physiologic changes occur in dental occlusion throughout life, resulting from the interplay between functional demands and reciprocating adaptive responses. These changes have been reported in the anthropological literature and they reflect evolutionary changes in the human stomatognathic system during the Paleolithic, hunter-gatherer period. Specific occlusal changes occur in response to different environments, leading to extensive variation within and between extinct and extant human populations. For example, functional demands can cause occlusal and interproximal tooth wear, resulting in shortening of the dental arch, continual tooth eruption and changes in masticatory patterns. Since the advent of farming through to our current industrialized culture, functional demands on the human masticatory system, and its adaptive responses to these demands, have been reduced considerably. Indeed, it is only occasionally that functional demands are severe enough to lead to obvious pathology in the modern human dentition. In contrast to normal masticatory activity, 'modern-day conditions' such as dental caries, periodontal disease and erosion, can lead to significant changes in dental occlusion that are pathological and need to be treated. The masticatory system is a dynamic, functional unit that displays considerable change over a lifetime. In this concept paper, it is proposed that modern human populations living in industrialized environments display dental occlusions that can be considered to be 'neotenous'; that is, our dentitions tend to reflect an unworn stage of our ancestors that was only seen in infants, juveniles and young adults. Clinicians can draw on both phylogenetic and ontogenetic perspectives of 'functional dental occlusion' to differentiate continual physiological changes occurring over time that require ongoing review, from pathological responses that require intervention.

Dental phenomics: advancing genotype to phenotype correlations in craniofacial research.

The field of dental phenomics provides many opportunities to elucidate the roles of genetic, epigenetic and environmental factors in craniofacial development. To date, research findings have helped to clarify the pathogenesis of many conditions, aiding diagnosis and clinical management. This paper provides an overview of dental phenomics research in some commonly encountered oral diseases in everyday clinical practice, as well as research relating to craniofacial growth and development. Clinically, advances in cariology and periodontology have led to better diagnostic capabilities and treatment provision. In the study of growth and development, important information regarding the varying clinical presentation and pathogenesis of many disorders is now apparent through the accurate quantification of phenotypes. Improvements in two-dimensional (2D) and three-dimensional (3D) imaging and analytical techniques have allowed for accurate dental phenotyping, and efforts are ongoing to apply these in vitro techniques to the in vivo setting. The field of dental phenomics represents an exciting avenue that links research findings to practical application, and collaboration between researcher and clinicians will help advance the field further.

The teeth and faces of twins: providing insights into dentofacial development and oral health for practising oral health professionals.

The continuing studies of the teeth and faces of Australian twins and their families in the Craniofacial Biology Research Group in the School of Dentistry at the University of Adelaide began 30 years ago. Three main cohorts of twins have been recruited, enabling various objectives and specific hypotheses to be addressed about the roles of genetic, epigenetic and environmental influences on human dentofacial growth and development, as well as oral health. This paper highlights some key findings arising from these studies, emphasizing those of direct relevance to practising oral health professionals. We also draw on published literature to review the significant developments in relation to the use of precision 2D and 3D imaging equipment, the application of modern molecular techniques, and the development of sophisticated computer software for analysing genetic relationships and comparing complex shapes. Such developments are valuable for current and future work. Apart from the classical or traditional twin model, there are several other twin models that can be used in research to clarify the relative contributions of genetic, epigenetic and environmental contributions to phenotypic variation. The monozygotic (MZ) co-twin model is one particularly valuable method, given that examination of only one pair of MZ twins can provide considerable insights into underlying causes of observed variation. This model can be used in a dental practice environment, with oral health professionals having the opportunity to explore differences in orofacial structures between MZ co-twins who are attending as patients. As researchers have become more aware of the complexities of the interactions between the genome, the epigenome and the environment during development, there is the need to collect more phenotypic data and define new phenotypes that will better characterize variations in growth processes and health status. When coupled with powerful new genetic approaches, including genome-wide association studies and linkage analyses, exciting opportunities are opening up to unravel the causes of problems in craniofacial growth and common oral diseases in human populations.

Non-carious cervical lesions: influence of morphology and load type on biomechanical behaviour of maxillary incisors.

BACKGROUND: The aim of this study was to measure the effect of simulating two different loads on maxillary incisors displaying eight morphological types of non-carious cervical lesions, unrestored and restored with an adhesive restoration, by quantifying the stress distributions generated using finite element analysis. METHODS: Virtual models of maxillary incisors were generated using the CAD software (RhinoCeros). After composing virtual dental and supporting structures with and without non-carious cervical lesions, each model was meshed using a control mesh device (ANSYS Finite Element Analysis Software). All of the virtual models were subjected to two load types, oblique load and vertical load, to simulate occlusal forces of 100 N each. Comparisons were made between simulated teeth with non-carious cervical lesions, with and without composite resin restorations, and a simulated sound tooth. Data summarizing the stress distributions were obtained in MPa using von Mises criteria. RESULTS: Oblique loading on simulated non-carious cervical lesions resulted in greater stress concentration compared with vertical loading, and non-carious cervical lesions with acute angles displayed higher stress concentrations at the depth of the lesion. Restoring the lesions with an adhesive restoration, such as composite resin, appeared to overcome this stress concentration. CONCLUSIONS: Restoring NCCLs with adhesive restorative materials, such as a nanohybrid composite resin, appears to recover the biomechanical behaviour similar to sound teeth.

The effect of casein phosphopeptide-amorphous calcium phosphate on erosive enamel and dentine wear by toothbrush abrasion.

OBJECTIVE: In addition to its role as a remineralizing agent in preventing dental caries, calcium product (CPP-ACP) delivered as a mousse (Tooth Mousse, TM) can reduce erosion of enamel and dentine. The aim of this study was to determine whether CPP-ACP could also reduce erosive tooth wear involving toothbrush abrasion. METHODS: Flat, polished enamel and dentine specimens (n=72) were subjected to 10 wear regimes, with each regime involving erosion in 0.3% citric acid (pH 3.2) for 10 min followed by toothbrush abrasion in a slurry of fluoride-free toothpaste and artificial saliva (1:3 ratio by weight) under a load of 2N for 200 cycles. The specimens were immersed in artificial saliva for 2h between wear regimes. In the experimental group 1, TM (containing CPP-ACP) was applied at the beginning of each wear episode for 5 min whereas TM- (without CPP-ACP) was applied in the experimental group 2. No mousse was applied in the control group. RESULTS: TM significantly reduced enamel wear (mean+/-S.E., 1.26+/-0.33 microm in the experimental group 1 vs 3.48+/-0.43 microm in the control group) and dentine wear (2.16+/-0.89 microm in the experimental group 1 vs 10.29+/-1.64 microm in the control group), and dentine wear was significantly less in the experimental group 1 than in the experimental group 2 (5.75+/-0.98 microm). CONCLUSION: The finding that TM reduced erosive tooth wear involving toothbrush abrasion, probably by remineralizing and lubricating eroded tooth surfaces, may have implications in the management of tooth wear.