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

Expert consensus on pediatric orthodontic therapies of malocclusions in children

Malocclusion, identified by the World Health Organization (WHO) as one of three major oral diseases, profoundly impacts the dental-maxillofacial functions, facial esthetics, and long-term development of ~260 million children in China. Beyond its physical manifestations, malocclusion also significantly influences the psycho-social well-being of these children. Timely intervention in malocclusion can foster an environment conducive to dental-maxillofacial development and substantially decrease the incidence of malocclusion or reduce the severity and complexity of malocclusion in the permanent dentition, by mitigating the negative impact of abnormal environmental influences on the growth. Early orthodontic treatment encompasses accurate identification and treatment of dental and maxillofacial morphological and functional abnormalities during various stages of dental-maxillofacial development, ranging from fetal stages to the early permanent dentition phase. From an economic and societal standpoint, the urgency for effective early orthodontic treatments for malocclusions in childhood cannot be overstated, underlining its profound practical and social importance. This consensus paper discusses the characteristics and the detrimental effects of malocclusion in children, emphasizing critical need for early treatment. It elaborates on corresponding core principles and fundamental approaches in early orthodontics, proposing comprehensive guidance for preventive and interceptive orthodontic treatment, serving as a reference for clinicians engaged in early orthodontic treatment.

Relation between Maximum Oral Muscle Pressure and Dentoalveolar Characteristics in Patients with Cleft Lip and/or Palate: A Prospective Comparative Study

BACKGROUND

Perioral muscle function, which influences maxillofacial growth and tooth position, can be affected in patients with oral clefts due to their inherent anatomical characteristics and the multiple surgical corrections performed. This research aims to (1) compare the maximum oral muscle pressure of subjects with and without isolated cleft palate (CP) or unilateral cleft lip and palate (UCLP), (2) investigate its influence on their dentoalveolar characteristics, and (3) investigate the influence of functional habits on the maximum oral muscle pressure in patients with and without cleft.

MATERIAL AND METHODS

Subjects with and without CP and UCLP seeking treatment at the Department of Orthodontics of University Hospitals Leuven between January 2021 and August 2022 were invited to participate. The Iowa Oral Performance Instrument (IOPI) was used to measure their maximum tongue, lip, and cheek pressure. An imbalance score was calculated to express the relationship between tongue and lip pressure. Upper and lower intercanine (ICD) and intermolar distance (IMD) were measured on 3D digital dental casts, and the presence of functional habits was reported by the patients. The data were analyzed with multivariable linear models, correcting for age and gender.

RESULTS

44 subjects with CP or UCLP (mean age: 12.00 years) and 104 non-affected patients (mean age: 11.13 years) were included. No significant differences in maximum oral muscle pressure or imbalance score were detected between controls and clefts or between cleft types. Significantly smaller upper ICDs and larger upper and lower IMDs were found in patients with clefts. A significant difference between controls and clefts was found in the relationship between oral muscle pressure and transversal jaw width. In cleft patients, the higher the maximum tongue pressure, the wider the upper and lower IMD, the higher the lip pressure, the smaller the upper and lower ICD and IMD, and the higher the imbalance score, the larger the upper and lower IMD and lower ICD. An imbalance favoring the tongue was found in cleft patients. The influence of functional habits on the maximum oral muscle pressure was not statistically different between clefts and controls.

CONCLUSION

Patients with CP or UCLP did not present reduced maximum oral muscle pressure compared with patients without a cleft. In cleft patients, tongue pressure was consistently greater than lip pressure, and those who presented a larger maxillary width presented systematically higher imbalance scores (favoring the tongue) than those with narrow maxillae. Therefore, the influence of slow maxillary expansion on maximum oral muscle pressure in cleft patients should not be underestimated.

Effects of tongue lesions and palatal coverage on oral sensory functions

STATEMENT OF PROBLEM

Oral stereognosis (OS) plays a significant role in the oral rehabilitation of patients with edentulism, as it influences their adaptation to new prostheses. Because of the essentially tactile characteristic of oral sensory perception, the tongue and palate appear to have a crucial function in OS. However, little is known about the influence of tongue lesions on OS and sensorial function. In addition, controversies remain regarding the role of the palate.

PURPOSE

The purpose of this clinical study was to evaluate whether tongue lesions and palatal coverage are disruptive to OS and gustatory function.

MATERIAL AND METHODS

Seventy participants (mean age=30.7 ±6.7 years) were divided into a tongue lesion group (experimental; n=35) and a control group (n=35). The tongue lesion group included participants with geographic, fissured, or hairy tongue. OS was evaluated with the oral stereognosis ability (OSA) test. Gustatory function was assessed with exposure to flavored solutions. After completing the above tests, the participants received a palate covering device, and then OS and gustatory function were immediately reevaluated. Data were analyzed with the Mann-Whitney and Wilcoxon tests (α=.05).

RESULTS

OSA and gustatory function scores did not differ among the tongue lesion and control groups with and without palatal coverage (all P>.05). After palatal coverage, the tongue lesion group took more time to perform the OSA test than the control group (P<.05).

CONCLUSIONS

Neither the presence of tongue lesions nor palatal coverage influenced OS or gustatory function. The OSA test response times were longer for the tongue lesion group after they had received palatal coverage.

Impact of Maximum Tongue Pressure in Patients with Jaw Deformities Who Underwent Orthognathic Surgery

Malocclusion and morphological abnormalities of the jawbone often affect the stomatognathic function and long-term postoperative stability in patients with jaw deformities. There are few reports on the effect of maximum tongue pressure (MTP) in these patients. We investigated the relationship between the MTP and jawbone morphology and the effect of the MTP on surgery in 42 patients with jaw deformity who underwent surgical orthodontic treatment at Hiroshima University Hospital. The MTP was measured using a tongue pressure measurement device; the average value was considered as the MTP. Based on the MTP measured before surgery, patients were classified into the high- or the low-MTP group. The clinical findings and results of the cephalometric analysis were compared. Posterior movement of the mandible in the high-MTP group was significantly lower than that in the low-MTP group. The ANB angle, overjet, and overbite in the high-MTP group were significantly smaller than those in the low-MTP group. On the other hand, there was no difference between the two groups in the measured values, indicating a labial inclination of the anterior teeth (U1 to SN, U1 to FH, IMPA, and FMIA). MTP has been suggested to affect mandibular prognathism in patients with jaw deformities.

Oral support for patients with severe motor and intellectual disabilities

BACKGROUND

Oral support during feeding was clinically provided to patients with severe motor and intellectual disabilities (SMID) for the prevention of dysphasia. The present study investigated the advantages of oral support anatomically and functionally.

METHODS

A videofluoroscopic swallowing study was conducted on nine patients with SMID (age = 5-41 years; mean age = 15.0; four males, five females) and 24 healthy adults (age = 26-67 years; mean age = 44.3; 16 males, eight females). The movements of the hyoid bone and mandible during pharyngeal swallowing were tracked, and the pharyngeal residues were evaluated. The temporal and spatial features of the movements were compared between patients with and without oral support as well as healthy adults.

RESULTS

The mandible moved downward earlier and showed larger displacement in the patients with SMID. The patients also had insufficient anterior displacement of the hyoid, which was associated with the pharyngeal residue. This displacement was enhanced, and the pharyngeal residue decreased with oral support.

CONCLUSIONS

Oral support to hold the mandible successfully improved hyoid excursion and reduced pharyngeal residue during swallowing, which is a simple and reliable strategy for the prevention of dysphasia in patients with SMID.

Hyoid bone movement during swallowing and mechanism of pharyngeal residue in patients with profound intellectual and multiple disabilities

OBJECTIVES

Dysphagia is linked to mortality risk among patients with profound intellectual and multiple disabilities (PIMD); the present study therefore aimed to clarify the characteristics of hyoid movements during swallowing and to examine the mechanism of dysphagia in patients with PIMD.

METHODS

A retrospective video fluoroscopic swallowing study was conducted on 43 patients with PIMD (mean age = 25.4; 25 males, 18 females) and 24 healthy adults (mean age = 44.3; 16 males, 8 females). The movements of the hyoid bone and mandible were tracked frame by frame in the video footage, and their range of movements and trajectories were analyzed.

RESULTS

Most patients showed atypical movement trajectories of the hyoid, such as insufficient anterior movement and increased range of mandibular downward movement, compared with normal adults. Moreover, the mechanism of dysphagia was revealed by structural equation modeling, indicating that insufficient anterior movement could lead to pharyngeal residue in the pyriform sinus.

CONCLUSION

The insufficient anterior movement of the hyoid could be caused by weak ventral suprahyoid muscles and atypical head and neck posture characteristic of patients with PIMD. It may be useful to predict pharyngeal residue from the range of hyoid movements and trajectories for the prevention of aspiration.

Analyses of Swallowing Function and Its Related Factors in Community-Dwelling Elderly Patients: A Case-Control Study

This retrospective case-control study evaluated the prevalence of declined swallowing function and the association with oral functions and gender in community-dwelling elderly patients. Their profiles, the results of swallowing function (Eating Assessment Tool: EAT-10) and other oral functions (oral dryness, maximum occlusal force (MOF), tongue-lip motor function (oral diadochokinesis: ODK), maximum tongue pressure (MTP) and masticatory performance (MP)) were extracted for analyses. The patients were categorized into three groups according to EAT-10 score (Group 1: 0, Group 2: 1 and 2, Group 3: ≥3). In total, 242 patients were enrolled and 46 of them (19.0%) were categorized into declined swallowing function (Group 3). In two-group comparisons (Group 1, 2 versus Group 3), significant differences were identified in age and the number of remaining teeth, but they were not identified in three-group comparisons. The patients with declined swallowing function (Group 3) had significantly lower function in ODK and MTP. Multiple logistic regression analyses identified that declined swallowing function was independently associated with declined functions in ODK /ka/ (OR: 5.31, 95% CI: 1.03-27.23, p = 0.04) and in MTP (OR: 2.74, 95% CI: 1.12-6.66, p = 0.03). This study could confirm the critical role of tongue functions in swallowing in community-dwelling elderly patients.

Changes in oral and cognitive functions among older Japanese dental outpatients: A 2-year follow-up study

BACKGROUND

The relationship between oral and cognitive functions among older people is highly debated.

OBJECTIVE

To examine whether oral functions are related to changes in the levels of mild cognitive impairment (MCI) biomarkers in older Japanese outpatients.

METHODS

This observational study included 52 outpatients aged ≥65 years who underwent dental examinations at the Fukuoka Dental College Hospital. The Mini-Mental State Examination (MMSE) was performed, and MCI blood biomarker levels were assessed at baseline and after 2 years. The present dental and periodontal conditions and the oral functions (tongue pressure and masticatory performance) were evaluated. Changes in parameters from baseline to follow-up were compared using the Wilcoxon signed-rank test, McNemar test or chi-squared test. Associations among changes in the parameters were analysed using Spearman's rank correlation coefficient.

RESULTS

The follow-up rate in this study was 67%. The masticatory performance was improved (p < 0.001), whereas gingival inflammation was decreased (p < 0.001) over the 2-year period. A significant increase in the MMSE score (p < 0.001) and a decrease in MCI risk (p < 0.001) were noted. The decrease in MCI risk was correlated with the increase in both masticatory performance (ρ = -0.34; p < 0.05) and MMSE score (ρ = -0.56; p < 0.01).

CONCLUSION

A decrease in MCI risk, as demonstrated by the levels of the blood biomarkers, was correlated with an increase in the masticatory performance in Japanese outpatients.

Low Tongue Strength and the Number of Teeth Present Are Associated with Cognitive Decline in Older Japanese Dental Outpatients: A Cross-Sectional Study

To mitigate the impact of dementia, initiating early intervention is important. This study aims to investigate the associations between deterioration in oral function and cognitive decline in older outpatients whose oral health was maintained in the dental clinic. This study included 50 outpatients aged ≥65 years. We used the Japanese version of the Montreal Cognitive Assessment (MoCA-J) to assess cognitive decline. Oral function was evaluated by tongue pressure, masticatory performance, and swallowing ability. A full-mouth periodontal examination was conducted, and the occlusal support and number of teeth were recorded. Odds ratios (ORs) and 95% confidence intervals (CIs) for cognitive decline (MoCA-J score ≤ 25 points) were calculated using logistic regression models. The age, number of teeth, tongue pressure, and masticatory performance were significantly correlated with cognitive decline (p < 0.05). Logistic regression analyses revealed that cognitive decline was independently associated with age (OR: 1.25; 95% CI: 1.03-1.52; p = 0.024), number of teeth (OR = 0.83; 95% CI: 0.76-1.00; p = 0.047), and lower tongue pressure (OR: 0.87; 95% CI: 0.77-0.98; p = 0.022). Lower tongue pressure and a small number of remaining teeth may be associated with cognitive decline in Japanese outpatients.

Preterm Birth Impacts the Timing and Excursion of Oropharyngeal Structures during Infant Feeding

Swallowing in mammals requires the precise coordination of multiple oropharyngeal structures, including the palatopharyngeal arch. During a typical swallow, the activity of the palatopharyngeus muscle produces pharyngeal shortening to assist in producing pressure required to swallow and may initiate epiglottal flipping to protect the airway. Most research on the role of the palatopharyngeal arch in swallowing has used pharyngeal manometry, which measures the relative pressures in the oropharynx, but does not quantify the movements of the structures involved in swallowing. In this study, we assessed palatopharyngeal arch and soft palate function by comparing their movements in a healthy population to a pathophysiological population longitudinally through infancy (term versus preterm pigs). In doing so, we test the impact of birth status, postnatal maturation, and their interaction on swallowing. We tracked the three-dimensional (3D) movements of radiopaque beads implanted into relevant anatomical structures and recorded feeding via biplanar high-speed videofluoroscopy. We then calculated the total 3D excursion of the arch and soft palate, the orientation of arch movement, and the timing of maximal arch constriction during each swallow. Soft palate excursion was greater in term infants at both 7 and 17 days postnatal, whereas arch excursion was largely unaffected by birth status. Maximal arch constriction occurred much earlier in preterm pigs relative to term pigs, a result that was consistent across age. There was no effect of postnatal age on arch or soft palate excursion. Preterm and term infants differed in their orientation of arch movement, which most likely reflects both differences in anatomy and differences in feeding posture. Our results suggest that the timing and coordination of oropharyngeal movements may be more important to feeding performance than the movements of isolated structures, and that differences in the neural control of swallowing and its maturation in preterm and term infants may explain preterm swallowing deficits.

Preliminary study: evaluating the reliability of CBCT images for tongue space measurements in the field of orthodontics

INTRODUCTION

Accurately measuring tongue space is challenging, but this information can be useful to many dental specialties. This study was intended to estimate the reliability of using cone-beam computed tomography (CBCT) to measure tongue space, which includes tongue volume and the oral cavity air capacity.

METHODS

For this preliminary study, CBCT images from ten participants (five females and five males, mean age of 29.8 ± 3.3 years) were available for evaluation. Each participant was radiographed two times (T0 and T1). The average time between T0 and T1 was 15.8 ± 3.7 days. CBCT scans were standardized to reduce variability. Three-dimensional landmarks were established to identify tongue space and 3D image analysis software (SimPlant^® 17 Pro; Materialise Dental, Leuven, Belgium) was used to measure the volume circumscribed by the landmarks. Two investigators independently calculated airway, tongue dimensions, and total tongue space for CBCT image T0 twice (day 1 and day 14), and T1 once. Intraclass correlation coefficients (ICCs) were used to estimate intra-rater and inter-rater reliability. Bland-Altman charts were constructed to demonstrate agreement within and between raters.

RESULTS

The intra-rater and inter-rater ICCs of the CBCT measurements at T0 were excellent (> 0.90). Measurements for T0 vs. T1 show good (0.75-0.90) intra-rater and excellent (> 0.90) inter-rater reliability. Bland-Altman charts show that 90-95% of the total measurements fall within the 95% limits of agreement for both intra- and inter-rater pairs CONCLUSIONS: The results of this preliminary study suggest that the landmarks chosen to measure the overall tongue space are reproducible and can be measured clearly using CBCT.

Tongue function and swallowing in individuals with temporomandibular disorders

The tongue participates in the oral phase of swallowing by pushing the food bolus toward the oropharynx. This relationship between tongue function and swallowing is little addressed addressed in individuals with temporomandibular dysfunction (TMD).

Description of tongue movements on swallowing patterns

OBJECTIVE

The purpose of this study was to compare the different swallowing patterns regarding tongue movement during saliva swallowing in healthy participants.

DESIGN

Seventeen participants (23.0 ± 3.6 years old) were included in this cross-sectional study. The movement of the tongue (anterior, middle and posterior portions) on the three axes of space (inferior-superior, anterior-posterior and medial-lateral) was recorded using a 3D electromagnetic articulograph. The tongue movement patterns registered during saliva swallowing were classified according to Bourdiol et al. (2014) into Type I, II or III.

RESULTS

Three swallowing patterns were identified (Type I, 64.7 %; Type II, 5.9 %; and Type III, 29.4 %). On the anterior-posterior axis, the displacement of the three portions of the tongue was significantly higher in Type III pattern compared with the Type I pattern. Furthermore, on the superior-inferior axis, the displacement of the anterior portion was significantly higher in Type III pattern compared with Type I pattern. In Type I pattern, on the inferior-superior axis, the smallest range of displacement occurred in the anterior portion of the tongue, followed by the middle and, finally, the posterior portion. In the analysis of Type III swallowing pattern, no significant differences were found on the range of displacement of the tongue portions on the three axes.

CONCLUSION

Statistical differences were found between swallowing patterns Type I and III regarding tongue movement. The frequency of pattern II found in the participants of this study was not high enough to compare the three patterns. However, the results obtained indicate that the methodology applied could be used to identify the patterns based on quantitative data.

Lower Arch Dimensions in Children with Anterior Open Bite and Normal Vertical Overbite: A Cross-sectional Study

Aim

Dental arch is a dynamic structure and its size depends on genetic and environmental factors. The aim of this study was to determine lower arch dimensions in children between 8 and 16 years with anterior open bite (AOB) and normal vertical overbite (NVO).

Materials and Methods

A cross-sectional study was performed in 132 individuals with AOB and 132 with NVO between 8 and 16 years selected from public schools. Intercanine width, arch length, intermolar and interpremolar distances, and arch perimeter of the lower arch were measured in previously digitalized models using the GOM inspection program and an optical three-dimensional scanner.

Results

Individuals with NVO presented smaller lower arch size with statistical differences in intercanine (P = 0.024, 95% confidence interval [CI]: 0.01, 0.02) and intermolar (P = 0.000, 95% CI: -1.76, -0.53) width and nonsignificant differences in the arch perimeter (P = 0.239, 95% CI: -1.57, 0.39) according to Mann-Whitney U-test.

Conclusion

Individuals between 8 and 16 years of age with NVO showed smaller lower dental arch than individuals with AOB in most dimensions.

Supplied Food Consistency and Oral Functions of Institutionalized Elderly

Background

Maintaining good oral function is one of the goals of dental treatment. The Japanese national insurance system newly introduced the concept of management of oral function according to the life stage. For the application of management of oral functions of the elderly, seven kinds of examination is a must for the diagnosis: xerostomia, oral hygiene status, maximum occlusal pressure, tongue and labium function, tongue pressure, chewing ability, and swallowing function. We analyzed the relationship between oral functions and supplied food consistency.

Methods

Oral functions and supplied food consistency of sixty-nine institutionalized elderly were investigated. There were 13 men and 56 women, and their mean age was 86.23 ± 7.02. Oral functions were measured and evaluated according to the Japanese insurance system. Data were analyzed by item response theory analysis, ROC analysis, and decision analysis.

Results

By the item response theory analysis, tongue pressure and swallowing functions had high discrimination ability. The subjects who had malfunction of the tongue and labium all had processed food. The subjects with difficulty in swallowing, even without malfunction of the tongue and labium, all had processed food.

Conclusion

Supplied food consistency may depend on the oral functions. However, as oral function has some dimension, a systematic evaluation system is necessary to decide the supplied food consistency.

Multiscale modeling of the neuromuscular system: Coupling neurophysiology and skeletal muscle mechanics

Mathematical models and computer simulations have the great potential to substantially increase our understanding of the biophysical behavior of the neuromuscular system. This, however, requires detailed multiscale, and multiphysics models. Once validated, such models allow systematic in silico investigations that are not necessarily feasible within experiments and, therefore, have the ability to provide valuable insights into the complex interrelations within the healthy system and for pathological conditions. Most of the existing models focus on individual parts of the neuromuscular system and do not consider the neuromuscular system as an integrated physiological system. Hence, the aim of this advanced review is to facilitate the prospective development of detailed biophysical models of the entire neuromuscular system. For this purpose, this review is subdivided into three parts. The first part introduces the key anatomical and physiological aspects of the healthy neuromuscular system necessary for modeling the neuromuscular system. The second part provides an overview on state-of-the-art modeling approaches representing all major components of the neuromuscular system on different time and length scales. Within the last part, a specific multiscale neuromuscular system model is introduced. The integrated system model combines existing models of the motor neuron pool, of the sensory system and of a multiscale model describing the mechanical behavior of skeletal muscles. Since many sub-models are based on strictly biophysical modeling approaches, it closely represents the underlying physiological system and thus could be employed as starting point for further improvements and future developments. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Analytical and Computational Methods > Computational Methods Models of Systems Properties and Processes > Organ, Tissue, and Physiological Models.

Voice and swallowing outcomes following hypoglossal nerve stimulation for obstructive sleep apnea

OBJECTIVE

Hypoglossal nerve stimulation is an effective treatment for a subset of patients with Obstructive Sleep Apnea (OSA). Although multiple clinical trials demonstrate its efficacy, no previous literature explores the potential impact the stimulator has on swallowing and voice. Our primary objective is to evaluate patient reported post-operative changes in voice or swallowing following hypoglossal nerve stimulator placement.

STUDY DESIGN

Prospective cohort study.

SETTING

Tertiary care hospital.

SUBJECT AND METHODS

Patients scheduled to receive a hypoglossal stimulator were enrolled. Participants completed baseline Voice Handicap Index-10 (VHI-10) and Eating Assessment Tool-10 (EAT-10) questionnaires preoperatively and again at 1week, 3months, and 6months post-operatively following placement of a hypoglossal nerve stimulator.

RESULTS

9 males and 5 females completed the study. The mean pre-operative VHI-10 and EAT-10 score was 3 and 0.8 respectively. Using linear mixed models, a clinically and statistically significant increase in the mean EAT-10 score was observed post-operatively at 1week (p=0.007), which was not observed at the time points the stimulator was active. A clinically and statistically significant decrease in VHI-10 score was observed following 2months of active stimulator use (p=0.02), which was not observed at any other time point.

CONCLUSION

The implantation and use of the hypoglossal nerve stimulator over 5months did not demonstrate any sustained, patient reported changes in voice handicap and swallowing function. While larger studies are warranted, our findings can be used to provide further informed consent for hypoglossal nerve stimulator implantation.

Occlusal loading during biting from an experimental and simulation point of view

OBJECTIVES

Occlusal loading during clenching and biting is achieved by the action of the masticatory system, and forms the basis for the evaluation of the functional performance of prosthodontic and maxillofacial components. This review provides an overview of (i) current bite force measurement techniques and their limitations and (ii) the use of computational modelling to predict bite force. A brief simulation study highlighting the challenges of current computational dental models is also presented.

METHODS

Appropriate studies were used to highlight the development and current bite force measurement methodologies and state-of-the-art simulation for computing bite forces using biomechanical models.

RESULTS

While a number of strategies have been developed to measure occlusal forces in three-dimensions, the use of strain-gauges, piezo-electric sensors and pressure sheets remain the most widespread. In addition to experimental-based measurement techniques, bite force may be also estimated using computational models of the masticatory system. Simulations of different bite force models clearly show that the use of three-dimensional force measurements enriches the evaluation of masticatory functional performance.

SIGNIFICANCE

Hence, combining computational modelling with three-dimensional force measurement techniques can significantly improve the evaluation of masticatory system and the functional performance of prosthodontic components.

Influence of bruxism and splint therapy on tongue pressure against teeth

OBJECTIVES

This study estimated the maximum tongue pressure (MTP) against teeth in bruxers, and verified the effect of a stabilization splint.

METHOD

Forty subjects (mean age: 26.57 years) were assigned to two groups (n520): bruxers and nonbruxers. Sleep bruxism was diagnosed by self-report, presence of tooth wear and tongue indentation, and by using a BiteStrip2 device. Maximum tongue pressure was measured by intraoral appliances containing pressure sensors. After baseline evaluation, bruxers received a stabilization splint and non-bruxers received a palatal splint, both for nocturnal use. Maximum tongue pressure was reassessed after 30 and 60 days. Data were submitted to repeated-measures ANOVA and Tukey test (Pv0.05).

RESULTS

Bruxers showed an increased MTP against teeth (Pv0.05). Splint therapy decreased MTP for bruxers and non-bruxers.

DISCUSSION

Bruxers present tongue indentations or ulcerations; however, there is no evidence on their MTP. Further research should focus on therapies to avoid tongue ulcerations in bruxers.

A randomised clinical trial to determine the abrasive effect of the tongue on human enamel loss with and without a prior erosive challenge

OBJECTIVES

To investigate the abrasive effect of the tongue on human enamel loss with and without a prior dietary acid challenge in an in situ model.

METHODS

A single centre, single blind, randomly allocated, split mouth, four treatment regimen, in situ study in healthy adult volunteers was undertaken. Twenty four subjects wore two lower intra-oral appliances each fitted with 4 human enamel samples 6h/day for 15 days. The samples were treated with either 50ml orange juice or water for 5min ex vivo 4x/day; prior to being licked or not licked with the subject's tongue for 60s. There were 2 samples per group per subject. Surface loss was measured by contact profilometry.

RESULTS

23 subjects completed the study with no adverse events. The mean loss of enamel at 15days was: 0.08μm for water without licking, 0.10μm with water and licking; 1.55μm with orange juice alone, 3.65μm with orange juice and licking. In the absence of erosive challenge, licking had no detectable effect on enamel loss p=0.28. Without licking, orange juice had a highly significant effect on loss compared to water, p<0.001. Erosive challenge followed by licking more than doubled the loss of enamel p<0.001.

CONCLUSIONS

When enamel was exposed to orange juice prior to licking, tissue loss as a result of tongue abrasion of the eroded surface was increased, and double that of the erosive challenge alone. Licking enamel with the tongue had no perceptible effect on enamel loss in the absence of the erosive challenge.

CLINICAL SIGNIFICANCE

Enamel wear resulting from tongue abrasion on tooth surfaces softened by acid challenge, can be an unavoidable consequence of oral function. This may account for the pattern of erosive toothwear on palatal and occlusal tooth surfaces, reinforcing the importance of restricting the frequency of dietary acid challenge in susceptible individuals.

Magnetic resonance imaging of swallowing-related structures in nasopharyngeal carcinoma patients receiving IMRT: Longitudinal dose-response characterization of quantitative signal kinetics

BACKGROUND

We aim to characterize serial (i.e., acute and late) MRI signal intensity (SI) changes in dysphagia-associated structures as a function of radiotherapy (RT) in nasopharyngeal cancer (NPC) patients.

MATERIALS AND METHODS

We retrospectively extracted data on 72 patients with stage III-IV NPC treated with intensity-modulated RT (IMRT). The mean T1- and T2-weighted MRI SIs were recorded for the superior pharyngeal constrictor (SPC) and soft palate (SP) at baseline, early-after IMRT, and last follow up, with normalization to structures receiving <5 Gy.

RESULTS

All structures had a significant increase in T2 SIs early after treatment, irrespective of the mean dose given. At last follow-up, the increase in T2 SI subsided completely for SPC and partially for SP. The T1 SI did not change significantly in early follow-up images of both structures; on late follow-up, patients with mean doses >62.25 Gy had a significant decrease in the corresponding T1 SI for SPC (1.6 ± 0.4 vs. 1.3 ± 0.4, P=0.007) but decreased non-significantly for SP.

CONCLUSIONS

Serial MRI acquisitions enable the identification of both early and late radiation-induced changes in swallowing structures after definitive IMRT for NPC. Dose dependent decrease in late T1 SI is associated with higher RT doses to the superior pharyngeal constrictor muscle; while dose independent increase in SI for both structures in early post-RT T2 images is observed and subsides after therapy. Further efforts will seek to elucidate the relationship between dose-dependent muscle SI changes and functional alteration of swallowing muscles.