Oral behaviours and wake-time masseter activity in patients with masticatory muscle pain.

BACKGROUND: Little is known about wake-time masseter activity of patients with masticatory muscle pain in real-life settings. OBJECTIVES: The aims of this study were (1) to assess wake-time masseter activity of women with masticatory muscle pain (MMP) and compare it with that of pain-free women; and (2) to investigate the association between objectively measured masseter contractions and self-reported oral behaviours. METHODS: Adult women (N = 27) diagnosed with MMP were age-matched with pain-free women (N = 26). The electromyographic (EMG) activity of the masseter muscle when awake was recorded unilaterally for two consecutive days. The number of contraction episodes and relative contraction time (%) were calculated using cut-off thresholds of 3%, 5% and 10% of maximum voluntary contraction (MVC). Self-reported daytime oral activity was assessed using the Oral Behaviours Checklist (OBC, items 3-21). Data were analysed using univariate tests and mixed-model analyses. RESULTS: The number of contraction episodes was similar between groups for all detection thresholds, but the relative contraction time at the lower detection thresholds (i.e. 3% MVC and 5% MVC) was significantly longer (1.5-fold) in the MMP than in the pain-free group. The OBC scores were significantly higher in the women with MMP than in controls, but no positive association could be found between EMG variables and OBC scores. CONCLUSION: Women with MMP engage in low-level masseter muscle contractions, which last longer than those of pain-free controls. There was no relationship between self-reported oral behaviours and masseter activity when awake. These findings support the notion that prolonged low-level clenching when awake may play a role in the pathophysiology of MMP.

Occlusal Features and TMJ Clicking: A 30-Year Evaluation from a Cohort Study.

Occlusal features that deviate from normative values have been historically considered risk factors for temporomandibular joint (TMJ) disorders. Nowadays, a putative association between dental occlusion and TMJ disorders remains controversial, with research findings on associations being inconsistent and inconclusive. We hypothesized that putative occlusal features identified during adolescence are associated with TMJ clicking later in life. The Dunedin Multidisciplinary Health and Development Study is a longitudinal birth cohort study investigation of 1,037 children (48.4% female) born in Dunedin, New Zealand, between April 1, 1972, and March 31, 1973, and assessed repeatedly since then. Associations between posterior crossbite, overbite, and overjet at age 15, as well as both self-reported and clinically assessed TMJ clicking sounds at age 45, were studied. Data were analyzed using multivariate logistic regression, after controlling for sex, emotional style, self-reports of tooth clenching and sleep bruxism, and history of orthodontic treatment. Self-reported and examiner-reported TMJ clicking at age 45 affected 18.3% and 23.8% of the study sample, respectively, and were not associated with the presence of a posterior crossbite or abnormal overjet/overbite values during adolescence. Self-reported history of tooth clenching and emotional style were associated with self-reported TMJ clicking later in life. In addition, there is a suggestion that high overbite during adolescence is negatively associated with TMJ clicking later in life. A history of orthodontic treatment was not associated with TMJ clicking. Abnormal occlusal features, such as posterior crossbite and high and low overjet/overbite in adolescence, are not associated with higher prevalence of TMJ clicking later in life. Personality also appears to influence self-reports of TMJ clicking later in life.

Halitosis: prevalence, risk factors, sources, measurement and treatment - a review of the literature.

Halitosis, an offensive breath odour, has multiple sources and negative impacts on people's social interactions and quality of life. It is important for health care professionals, including general physicians and dental professionals, to understand its aetiology and risk factors in order to diagnose and treat patients appropriately. In this study, we have reviewed the current literature on halitosis regarding its prevalence, classification, risk factors, sources, measurement and treatment.

Maternal Smoking during Pregnancy Is Associated with Offspring Hypodontia.

Little is known about environmental risk factors for hypodontia. The objective of this study was to investigate the association between hypodontia and common environmental risk factors, such as maternal smoking and alcohol and caffeine consumption during pregnancy. Eighty-nine hypodontia cases with 1 or more missing permanent lateral incisors and/or 1 or more missing premolars were enrolled in this clinic-based case-control study. Some 253 controls with no missing teeth were frequency matched to cases by age and sex. Hypodontia was diagnosed using panoramic radiographs. Sociodemographic data were collected from both the participants and their mothers, with maternal self-reported active and passive smoking, as well as alcohol and caffeine consumption during pregnancy, assessed by a questionnaire. Odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated with logistic regression to assess the strength of association between risk factors and hypodontia. OR estimates were then adjusted for possible confounders, such as maternal age at delivery, sex and gestational age of the child, and household socioeconomic background. Significant associations were found between hypodontia and maternal cigarette use during pregnancy, as well as the number of cigarettes smoked per day. The consumption of 10 or more cigarettes per day during pregnancy was associated with greater odds of having a child with hypodontia (adjusted OR, 4.18; 95% CI, 1.48-11.80; P = 0.007). Observed associations between hypodontia, second-hand smoke, and alcohol and caffeine consumption were not statistically significant. Maternal smoking during pregnancy is associated with hypodontia. Larger samples and prospective observational study designs, however, are needed to investigate this association further.

Self-report of temporomandibular joint clicking and psychological factors: is there an association?

The objectives of this study were to test the hypothesis that self-reported TMJ clicking sounds in adolescents are positively associated with non-specific somatic symptoms, self-perception of body image and care-seeking behaviour. A cross-sectional study was carried out in 353 young adolescents (48·4% females) recruited from community (N = 272) and orthodontic clinic (N = 81) settings. Assessments included self-reported TMJ clicking, non-specific physical symptoms, body image concerns and for the clinic sample only, the source of motivation for treatment. TMJ sounds were self-reported by 19% of the sample and were associated with higher scores for non-specific physical symptoms and body image concerns (P < 0·001). Adolescents who were self-motivated to seek orthodontic treatment had greater scores for non-specific physical symptoms, more body image concerns and tended to report TMJ sounds more often (26·3% and 7·7% respectively; P = 0·41) than those who were solely parent/family-motivated to seek treatment. Self-reported TMJ sounds in adolescents were associated with a propensity to somatisation and concerns with body image. Care-seeking adolescents have greater non-specific physical symptoms and body image concerns and tend to report more frequent TMJ sounds.

Effect of weather on temporal pain patterns in patients with temporomandibular disorders and migraine.

Patients with masticatory muscle pain and migraine typically report that the intensity of pain fluctuates over time and is affected by weather changes. Weather variables, such as ambient temperature and humidity, may vary significantly depending on whether the individual is outdoor or indoor. It is, therefore, important to assess these variables at the individual level using portable monitors, during everyday life. This study aimed to determine and compare the temporal patterns of pain in individuals affected with facial and head pain and to investigate its relation with weather changes. Eleven patients (27·3 ± 7·4 years) with chronic masticatory muscle pain (MP) and twenty (33·1 ± 8·7 years) with migraine headache (MH) were asked to report their current pain level on a visual analogue scale (VAS) every hour over fourteen consecutive days. The VAS scores were collected using portable data-loggers, which were also used to record temperature, atmospheric pressure and relative humidity. VAS scores varied markedly over time in both groups. Pain VAS scores fluctuate less in the MP group than in the MH group, but their mean, minimum and maximum values were higher than those of migraine patients (all P < 0·05). Pain scores <2 cm were more common in the MH than in the MP group (P < 0·001). Perceived intensity of pain was negatively associated with atmospheric pressure in the MP group and positively associated with temperature and atmospheric in the MH group. Our results reveal that patients with masticatory muscle pain and patients with migraine present typical temporal pain patterns that are influenced in a different way by weather changes.

Accounts of bullying on Twitter in relation to dentofacial features and orthodontic treatment.

Social media offers an accessible resource for gaining valuable insights into the social culture of bullying. The purpose of this study was to qualitatively analyse Twitter posts for common themes relating to dentofacial features, braces and bullying. Twitter's database was searched from 2010 to 2014 using keywords relevant to bullying, teeth and orthodontics. Two investigators assessed the Twitter posts, and selected those that conveyed the experiences or opinions of bullying victims. The posts were qualitatively analysed using thematic analysis. Of the 548 posts screened, 321 were included in the final sample. Four primary categories relating to 'dental-related bullying' were identified: (i) morphological features, (ii) psychological and psychosocial impact, (iii) coping mechanisms and (iv) the role of family. Bullied individuals reported a diverse range of psychological impacts and coping mechanisms. Secondary categories were also identified. Family members, for example, were found to play both a contributory and mediatory role in bullying. In summary, social media can provide new and valuable information about the causal factors and social issues associated with oral health-related bullying. Importantly, some coping mechanisms may mitigate the negative effects of bullying.

Self-reported oral behaviour habits in hyperdivergent and normodivergent facial types.

The relationship between facial morphology and jaw function remains controversial. The purpose of this study was to investigate differences in self-reported oral behaviour habits between individuals with normodivergent and hyperdivergent facial types. Some 80 cases and controls were individually matched on age, sex ethnicity and treatment stage. The participants were recruited from an orthodontic clinic, and included both adolescents and adults. Habitual oral activity was assessed using the Oral Behaviour Checklist (OBC) based on their experiences in the past 4 weeks. Univariate and bivariate analyses were performed. The sample had a mean age of 17·2 years (SD = 4·6; range = 12-49 years), and was predominantly female (65·0%) and of New Zealand European origin (91·3%). The prevalence of reporting one or more frequently performed habitual muscular behaviour in either study group was over 85% (P > 0·05). There was no difference in total OBC score between the hyperdivergent (25·6; SD: 9·0) and normodivergent group (25·3; SD: 9·9). Moreover, there was no difference in the prevalence of either nocturnal or daytime oral behaviours between the two groups. While this study did not include any objective measures of functional or habitual activity, we found no differences in self-reported oral behaviour habits between normodivergent and hyperdivergent individuals. The findings do not support an association between vertical facial form and habitual muscular activity.

Factors affecting intra-oral pH - a review.

One of the greatest challenges to modern dentistry is the progressive destruction of tooth material due to chemical erosion. Dental erosion is the loss of dental hard tissue, without the action of bacteria, in which demineralisation of enamel and dentine results due to a decrease in intra-oral pH. The aim of this review was to appraise the scientific literature on the factors that can affect intra-oral pH. The review will examine (i) the protective role of human saliva, in terms of its mineral composition, flow rates and buffering systems and (ii) sources of in-mouth acids such as extrinsic acids, which are derived from the diet and environment, as well as intrinsic acids, which are related to disorders of the gastro-oesophageal tract. This review may assist clinicians to identify the risk factors for tooth wear and to recommend adequate preventive measures to patients.

Simultaneous wireless assessment of intra-oral pH and temperature.

OBJECTIVES: Intra-oral pH plays an important role in the pathogenesis of tooth erosion and decay, but there is limited information about its variation in real life settings. The aims of this research were to: 1) develop a wireless device, which can be used to continuously monitor intra-oral pH and temperature in real-time; 2) test and validate the device under controlled laboratory conditions; and 3) collect data in a natural environment in a sample of healthy volunteers. METHODS: A wireless device for measuring pH and temperature simultaneously was developed, calibrated and validated against the gold standard glass electrode pH meter. A smart phone was used as data logger. The wireless device was embedded in an oral appliance and worn by eleven participants (mean age 31.1±6.9years) for 24h, while conducting standardised drinking tasks and regular daily activities. RESULTS: The wireless device could accurately measure pH and temperature both in vitro and in vivo. The recovery time following the swallow of a standard acidic drink varied markedly among individuals (mean=1.3±0.9min). The intra-oral pH and temperature recorded in the natural environment also showed a large inter- and intra-individual variability. The average intra-oral pH when asleep (6.7±0.5) was lower (p<0.001) than when awake (7.2±0.5). The average intra-oral temperature during sleep (35.6±0.5°C) was higher (p<0.001) than when awake (34.5±0.7°C). CONCLUSIONS: Intra-oral pH and temperature can be continuously and wirelessly assessed in real-life settings, and show individual-specific patterns with circadian variations. Intra-oral pH becomes slightly acidic during sleep while intra-oral temperature increases and fluctuates less. CLINICAL SIGNIFICANCE: We propose a wireless device that is capable of measuring intra-oral pH over a 24-h period. We found marked inter-individual variation after acidic stimuli, and day to sleep time variation of both intra-oral temperature and pH. Our approach may provide new insight into the relationship between oral pH, tooth wear and decay.

Effect of occlusal vertical dimension on swallowing patterns and perioral electromyographic activity.

Abnormal swallow patterns have been associated with specific dentofacial traits, such as an anterior open bite, but the cause-effect relationship between swallowing and malocclusion remains highly controversial. The aim of this research was to determine the effects of acute change in occlusal vertical dimension (OVD) on intraoral pressure swallow patterns and perioral electromyographic activity (EMG) during swallowing. Ten volunteers (five female, five male; 27-32 years) repeated standardised swallowing tasks as the OVD was progressively increased using mandibular trays of different heights. Standardised swallowing tasks were performed repetitively with each tray in place. Individual swallowing waveforms were quantitatively and qualitatively analysed. Peak pressure, swallow duration, time to peak pressure and lip EMG peak activity were assessed for each swallow. Data were analysed using mixed-model analysis. As OVD increased, lip peak pressure during swallowing increased almost threefold (+2·1 kPa; P ≤ 0·001), whereas swallow duration increased by 12·7 per cent (+160 ms; P = 0·01) at lip level and by 26·4 per cent (+270 ms; P < 0·001) at tongue level. Perioral muscle activity during swallows increased by 43·7 per cent (P ≤ 0·01) up to the OVD where resting lip seal was not attainable. Swallowing waveforms varied markedly between individuals, but interindividual waveforms were only minimally affected. The adaptive response and the waveform similarities associated with OVD variation supports the existence of a central control mechanism for swallowing, which may be modified by peripheral inputs.

Incidence of temporomandibular joint clicking in adolescents with and without unilateral posterior cross-bite: a 10-year follow-up study.

Among different malocclusions, posterior cross-bite is thought to have a strong impact on the correct functioning of the masticatory system. The association between unilateral posterior cross-bite (UPCB) and temporomandibular joint (TMJ) clicking, however, remains still controversial. The aim of this study was to investigate whether the presence of UCPB during early adolescence increases the risk of reporting TMJ clicking after a long-term follow-up. A longitudinal survey design was carried out in a group of 12-year-old young adolescents, who were examined at baseline for TMJ clicking sounds and unilateral posterior cross-bite. After 10 years, 519 subjects could be reached by a telephone survey. Standardised questions were used to collect self-reported TMJ sounds and to determine whether participants had received an orthodontic treatment. Logistic regression analysis revealed a significant association between unilateral posterior cross-bite and subjectively reported TMJ clicking (odds ratio = 6·0; 95% confidence limits = 3·4-10·8; P < 0·0001). The incidence of TMJ clicking was 12%. At a ten-year follow-up, self-reports of TMJ clicking were significantly associated with the presence of UPCB at baseline, but not with the report of having received an orthodontic treatment. Within the limitation of this study, the presence of unilateral posterior cross-bite in young adolescents may increase the risk of reporting TMJ sounds at a 10-year follow-up. The provision of an orthodontic treatment, however, does not appear to reduce the risk of reporting TMJ sounds.

Continuous measurement of intra-oral pH and temperature: development, validation of an appliance and a pilot study.

To describe a novel approach for continuous measurement of intra-oral pH and temperature in individuals carrying out normal daily activities over 24 h. We designed, validated and constructed a custom-made appliance fitted with a pH probe and a thermocouple. Six subjects wore the appliance over a 24-h period for two non-consecutive days, while the intra-oral pH and temperature were measured continuously and recorded. Intra-oral pH and temperature were very similar across different recording days, the difference being not statistically significant (P ≥ 0.14). There was a noticeable difference in the pattern of variation of pH between day and night. During the day, the mean pH was 7.3 (±0.4) and dropped markedly only after consumption of acidic food and drinks. The intra-oral pH decreased slowly during sleep with an average pH of 6.6 (±0.4) being recorded. The difference between day and night was statistically significant (P = 0.002). The mean intra-oral temperature was 33.9 °C (±0.9) during daytime and 35·9 °C (±0·5) during sleep (P = 0.013) with minor fluctuations occurring over 24 h. The continuous and simultaneous intra-oral pH and temperature measurement system described in this report is reliable, easy to construct, able to measure variables over a sustained period and may serve as a future diagnostic tool in a number of applications.

3D assessment of mandibular growth based on image registration: a feasibility study in a rabbit model.

BACKGROUND: Our knowledge of mandibular growth mostly derives from cephalometric radiography, which has inherent limitations due to the two-dimensional (2D) nature of measurement. OBJECTIVE: To assess 3D morphological changes occurring during growth in a rabbit mandible. Methods. Serial cone-beam computerised tomographic (CBCT) images were made of two New Zealand white rabbits, at baseline and eight weeks after surgical implantation of 1 mm diameter metallic spheres as fiducial markers. A third animal acted as an unoperated (no implant) control. CBCT images were segmented and registered in 3D (Implant Superimposition and Procrustes Method), and the remodelling pattern described used color maps. Registration accuracy was quantified by the maximal of the mean minimum distances and by the Hausdorff distance. RESULTS: The mean error for image registration was 0.37 mm and never exceeded 1 mm. The implant-based superimposition showed most remodelling occurred at the mandibular ramus, with bone apposition posteriorly and vertical growth at the condyle. CONCLUSION: We propose a method to quantitatively describe bone remodelling in three dimensions, based on the use of bone implants as fiducial markers and CBCT as imaging modality. The method is feasible and represents a promising approach for experimental studies by comparing baseline growth patterns and testing the effects of growth-modification treatments.

Factors associated with pain induced by orthodontic separators.

Pain resulting from the application of orthodontic forces varies markedly across individuals. The reasons of this variability are still largely unknown. To investigate factors that may be associated with orthodontic pain following the application of orthodontic separators. One hundred and seven participants were screened for pain response over 48 h following placement of orthodontic elastomeric separators. The highest (n = 10) and lowest (n = 10) pain responders were identified, and data collected on tooth pain sensitivity to electrical stimulation in conjunction with using the Pain Catastrophising Scale (PCS), Dental Anxiety Scale (DAS) and cold pressor test (CPT). There were statistically significant differences between high- and low-pain responders in catastrophising score (P ≤ 0.023). For every PCS magnification score of 1 unit higher, the relative risk of being a high-pain responder was 1.6 (P = 0.002); those scoring higher on helplessness had a lower risk of being so. DAS scores of high-pain responders were twice as high as those of low-pain responder (P = 0.043). During the first 2 min of CPT, the high-pain responders experienced more pain than the low-pain responders (P ≤ 0.029). Tooth pain thresholds did not differ between the two different pain responder groups. Pain catastrophising, dental anxiety and cold sensitivity appear to modify the pain experienced following placement of orthodontic separators. Further research is needed to determine the validity of screening questions to identify at-risk patients prior to commencing orthodontic treatment.

Efficacy of air/water syringe tip sterilization.

BACKGROUND: Dental procedures involve contact between instruments and the patient's tissues, blood or saliva. This study evaluated the efficacy of the standardized sterilization of non-disposable air/water syringe tips and corrosion and contaminant build-up in these tips. METHODS: The bacterial contamination of single-use and multiple-use non-disposable air/water syringe tips after routine use and sterilization was compared to that of single-use disposable tips by microbial culturing on PCA and blood agar plates. The effect of flushing the syringe tips prior to sterilization was also measured. The amount of corrosion in single-use and multiple-use non-disposable syringes was measured by SEM and EDS analyses. RESULTS: Non-disposable syringe tips had significantly (p < 0.05) greater bacterial contamination than single-use disposable tips. There were no statistically different levels of contamination between flushed and non-flushed non-disposable syringes or between single-use and multiple-use non-disposable syringes. SEM and EDS analyses showed greater evidence of corrosion and contaminant build-up in multiple-use syringes compared to single-use non-disposable syringes. CONCLUSIONS: Sterilization of non-disposable air/water syringes is not completely effective and rinsing, or the number of uses, does not affect the effectiveness of sterilization. There may be a lower risk of cross-infection from the use of disposable air/water syringe tips, instead of non-disposable ones.

A qualitative analysis of orthodontic-related posts on Twitter.

OBJECTIVE: To investigate the content of orthodontic-related Twitter posts in order to improve our understanding of orthodontic patients' perceptions and treatment experiences. MATERIALS AND METHODS: Some 131 consecutive posts were collected from Twitter over a 5-day period. Twitter's advanced-search function was used to limit the sampling frame to New Zealand. The posts were qualitatively analyzed for themes using discourse analysis. RESULTS: Four main themes were identified: (1) excitement about getting braces off, (2) problems with braces, (3) positive comments about braces, and (4) negative comments about braces. Various language tools and symbols were often used to convey different degrees of emotion. The present study explores these themes and discusses how they relate to modern-age orthodontics. CONCLUSION: This is the first study to qualitatively analyze orthodontic-related posts in the social media era. Our findings suggest that orthodontic patients use social media sites such as Twitter to convey positive and negative feelings about braces.

Neck and shoulder muscle activity during standardized work-related postural tasks.

The aim of the present study was to assess the activity levels of the sternocleidomastoid muscle and upper trapezius muscle during static postures under controlled and standardized conditions, and to determine whether the muscle activity differed between sexes. Electromyographic (EMG) activity was recorded unilaterally from the sternocleidomastoid and upper trapezius muscle in 17 participants whilst they were performing various postural tasks. EMG amplitude was measured by the root mean square values of the raw signals and normalized to peak maximum contractile values for each muscle (%MVC). The intensity of muscle activity was ranked as light (<3%MVC), moderate (3%MVC ≤ EMG ≤ 8%MVC), and substantial (>8%MVC). During most tasks the two muscles contracted light to moderately. Head leaning and shoulder shrugging postures yielded substantial muscle activity in both muscles. Muscle activity did not differ significantly between male and female participants (F = 3.1; p = 0.078). Our findings provided normative values, which will enhance future studies of muscle activity during work in a natural, unrestrained environment.

The role of oral soft tissues in swallowing function: what can tongue pressure tell us?

Tongue pressure data taken from healthy subjects during normal oral activities such as mastication, speech and swallowing are providing us with new ways of understanding the role of the tongue in craniofacial growth and function. It has long been recognized that the sequential contact between the tongue and the palate plays a crucial role in the oropharyngeal phase of swallowing. However, because the focus of most research on intraoral pressure has been on the generation of positive pressure by the tongue on the hard palate and teeth, generation and coordination of absolute intraoral pressures and regional pressure gradients has remained unexplored. Ongoing research in our laboratory has uncovered highly variable individual pressure patterns during swallowing, which can nonetheless be divided into four stages: preparatory, primary propulsive, intermediate and terminal. These stages may further be sub-classified according to pressure patterns generated at the individual level as tipper or dipper patterns in the preparatory stage, roller or slapper in the primary propulsive and monophasic or biphasic during the intermediate stage. Interestingly, while an increase in bolus viscosity can result in significant changes to pressure patterns in some individuals, it has little effect in others. Highly individual responses to increased viscosity are also observed with swallowing duration. The above, together with other findings, have important implications for our understanding of the aetiology of widely differing conditions such as protrusive and retrusive malocclusions, dysphagia and sleep apnoea, as well as the development of novel food products.