Functional treatment of bilateral posterior crossbite improves mandibular kinematics during chewing.

OBJECTIVES: To evaluate the effects of treatment of bilateral posterior crossbite (BPXB) on mandibular kinematics by the percentage of reverse chewing cycles (RCCs) during soft and hard bolus chewing before and after the correction of the malocclusion with function-generating bite (FGB). MATERIALS AND METHODS: This prospective study included 71 subjects: 19 patients with occlusally symmetric BPXB (M = 9; F = 10; mean age 9.3 ± 2.2[yr.mo]), 32 patients with occlusally asymmetric BPXB (19 with more teeth in crossbite on the right side (right prevalent side), M = 7; F = 12; mean age 8.2 ± 1.6 [yr.mo] and 13 on the left side, M = 7; F = 6; mean age 9.6 ± 1.9 [yr.mo]) and 20 controls without malocclusion (M = 8; F = 12; mean age 10.2 ± 1.7 [yr.mo]). Masticatory patterns were recorded before (T0) and after (T1) the correction of the malocclusion with FGB, with the K7-I® kinesiograph using standardized soft and hard boluses. RESULTS: BPXB was corrected in all included patients. At T0, the percentage of RCCs in BPXB was significantly increased compared to controls (P < .0001); symmetric BPXB showed no difference in RCCs between the sides, whereas asymmetric BPXB showed significantly more RCCs on the side with more teeth in crossbite (prevalent side). After treatment with FGB (T1), the percentage of RCCs was significantly reduced in both symmetric BPXB patients (soft bolus, P = .003; hard bolus, P < .001) and asymmetric BPXB patients (prevalent side: soft and hard bolus, P < .00001; non-prevalent side: soft bolus, P = .01 and hard bolus, P = .0002). CONCLUSION: Functional correction of BPXB with FGB significantly improved mandibular kinematics during chewing.

Correlation between oral muscle pressure and malocclusion in mixed dentition: a cross-sectional study.

OBJECTIVE: To investigate the relationship between oral muscle pressure and malocclusion in the mixed dentition. MATERIALS AND METHODS: Maximum tongue, lip and cheek pressure was measured using the Iowa Oral Performance Instrument (IOPI) in 3 patient cohorts: patients with (1) posterior crossbite, (2) class II relationship and (3) a control group of patients without malocclusion. Linear models were used to compare the mean differences in muscle pressure between groups, with correction for age and gender. The imbalance between lips and tongue and between lips and cheeks was calculated by the Delta z-scores of each group. RESULTS: A total of 146 participants were included, 46 (mean age 8.71±0.85), 41 (mean age 11.74±1.17) and 35 (mean age 10.71±1.92) in groups 1, 2 and 3 respectively. Patients with malocclusion showed significantly higher lip and lower cheek pressure and imbalance favouring the lips over the tongue compared to controls. Class II,1 patients showed significantly higher tongue pressure than Class II,2. No differences were found in muscle pressure or imbalance between crossbite and Class II nor between crossbite types. CONCLUSION AND CLINICAL RELEVANCE: These findings suggest that oral muscle pressure may be associated with malocclusion. This highlights the importance of functional diagnosis and its implications on the prevention and treatment of malocclusion, as well as on orthodontic stability.

Oro-facial function and quality of life in children and adolescents with large horizontal maxillary overjet-A case-control study.

BACKGROUND: Large horizontal maxillary overjet (overjet) is associated with reduced bite force (BF) and number of contacts, which influence the chewing effectivity (CE). Oral health, oro-facial function (OF) and malocclusion have great impact on psychological well-being and quality of life (QoL). OBJECTIVES: The aims of the study were to examine OF, temporomandibular disorders (TMD), BF, CE, QoL and well-being in children and adolescents with large overjet. METHODS: The study was a case-control study including healthy children with large overjet in the study group compared to a control group of healthy children with neutral occlusion, all 9-14 years old. OF was examined by use of Nordic Orofacial Test-Screening (NOT-S), Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and registration of morphological and functional occlusion. QoL and well-being were examined using KIDSCREEN-10 and Strengths and Difficulties Questionnaire. RESULTS: The study and control groups included 37 and 32 participants, respectively. Significantly increased NOT-S score (p < .001) and reduced BF (p = .011), numbers of contacts (p < .001) and CE (p = .005) were found in the study group. BF, numbers of contacts and CE were negatively associated with erupting canines and premolars. No significant difference was found in age, gender, dental eruption, TMD diagnosis or QoL between the groups. Significantly increased emotional symptoms (p = .007), hyperactivity (p = .043) and total difficulties score (p = .009) were found in the study group. CONCLUSION: The study group showed higher NOT-S score and reduced BF, number of contacts and CE. No difference in QoL were found between the groups, although reduced well-being and increased emotional symptoms, hyperactivity and total difficulties were found in the study group.

The Influence of the Type of Breathing on the Masticatory Muscle Patterns in Children.

Background and Objectives: The aim was to compare the activity of the masseter muscles in children with different types of breathing. Materials and Methods: A cross-sectional study was conducted including patients aged 6-12 years with mixed dentition, who came for oral care at the Master's Degree in Pediatric Dentistry program at the Complutense University of Madrid (UCM), according to inclusion and exclusion criteria. The sample was divided into three groups: nasal breathers without dental alterations (control group), oral breathers with dental malocclusion, and oral breathers with previous orthodontic treatment. An electromyography was performed, and statistic methods were conducted with a 95% confidence to contrast hypothesis. Results: A total of 122 children were analyzed and distributed into three groups. The electrical muscle activity of masseters was significantly different between the study groups (p < 0.001 for all comparisons). Pairwise comparisons revealed a significantly higher electrical muscle activity in the control group (nasal breathers) during chewing compared to both groups of oral breathers (p < 0.001 for both comparisons). Orthodontic treatment decreased electrical muscle activity during isometric contraction in oral breathers compared to nasal breathers (p < 0.001), but did not significantly affect electrical muscle activity during chewing. Higher decompensation values were obtained in oral breathers without previous orthodontic treatment compared the other study groups (p < 0.001 for both comparisons), although electrical muscle activity values were similar in both groups of oral breathers (p > 0.05 for both comparisons). Conclusions: Differences in electrical muscle activity between nasal and oral breathers can be confirmed. Oral breathers with and without orthodontic treatment showed lower electrical muscle activity of masseters during chewing than nasal breathers, while at isometric contraction, only oral breathers with previous orthodontic treatment showed lower electrical activity. Higher decompensation values were found in oral breathers without previous orthodontic treatment, in comparison to the control group and oral breathers with previous orthodontic treatment.

Effects of Rapid Palatal Expansion on Chewing Biomechanics in Children with Malocclusion: A Surface Electromyography Study.

Malocclusion during childhood may affect both morphology and masticatory function and could greatly affect the subsequent growth and development of the jaws and face. The purpose of this study was to evaluate the efficiency of surface electromyography in describing the effects of the rapid palatal expansion (RPE) on Masseter (M) and Temporalis Anterior (T) muscles' activity in 53 children with different types of malocclusion: bilateral posterior crossbite (BPcb), underdeveloped maxillary complex without crossbite (NOcb) and unilateral posterior crossbite on the right (UPCBr) and on the left (UPCBl). The muscular activities during chewing tasks were assessed bilaterally before and after RPE application and three months after removal. Both the envelope's peak (µV) and its occurrence (% of chewing task) were extracted from the surface electromyography signal. Our results showed the presence of statistically significant differences (p < 0.05) on temporomandibular joint muscles, across different assessments, in all the tested populations of subjects. Surface electromyography demonstrated a relationship between the correction of a maxillary transverse discrepancy and the restoration of a muscle's activation patterns comparable to healthy subjects for both T and M.

Dental occlusion and body balance: A question of environmental constraints?

BACKGROUND: In the past few years, growing interest was given to the relationship between the dental occlusion and the body balance. While most research focused on this relationship at static conditions, it is evident that the contribution of the sensory information for balance control is different depending on the environmental constraints. RESEARCH QUESTION: The aim of the present paper was to elucidate whether the stomatognathic system (SS) contributes differently on body balance regulation according to the presence of external disturbances. METHODS: Literature regarding the different sources involved in the proprioceptive information to the SS was reviewed. The influence of dental occlusion on balance control at different external environments was then explored. RESULTS: The main findings are: (a) a plausible evidence between the masticatory and cervical muscles can be described; (b) a reciprocal connection between the trigeminal and vestibular nuclei supports the influence of the SS on body balance; (c) traditionally, research involving the relationship between the SS and balance control has focused on strictly controlled situations, thus, ignoring the sensory reweighting which occurs depending on the external disturbances; and (d) the afferences of dental occlusion for balance control seem strengthened when more difficult conditions are present. CONCLUSION: Results of the present review suggest that afferent signals from dental occlusion effectively contribute to balance control when more external perturbations are present, that is unstable support surface, fatigue and tasks being performed. However, more studies are needed to elucidate the mechanisms by which dental occlusion may influence balance control focusing on different external environments.

Pre-operative parafunctional or dysfunctional oral habits are associated with the temporomandibular disorders after orthognathic surgery: An observational cohort study.

BACKGROUND: Temporomandibular disorders (TMDs) are frequent and disabling, and hence, preventing them is an important health issue. Combining orthodontic and surgical treatments for malocclusions has been shown to affect temporomandibular joint (TMJ) health. However, publications regarding the risk factors that predict negative TMJ outcomes after orthognathic surgery are scarce. OBJECTIVE: Present prospective cohort study was conducted to identify an association between pre-operative dysfunctional/parafunctional oral habits and the presence of TMD symptoms after orthognathic surgery. METHOD: We included 237 patients undergoing orthodontics and surgical treatment for malocclusions associated with dentofacial deformities within the Department of Oral and Maxillofacial Surgery of the University of Lille. Their parafunctional and dysfunctional oral habits were recorded through clinical examination along with the presence of TMD symptoms before and after the surgery. According to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) classification, the TMD symptoms studied were myalgia, arthralgia, disc displacement with or without reduction. RESULTS: Multivariate analysis revealed significant associations among bruxism (odds ratio [OR] 3.17 [1.066; 9.432]), lingual interposition (OR 4.241 [1.351; 13.313]), as well as primary swallowing (OR 3.54 [1.225; 10.234]) and the presence of postoperative symptoms of myalgia. Moreover, a significant association was observed between the presence of any dysfunctional oral habit and postoperative disc displacement with reduction (OR 4.611 [1.249; 17.021]). CONCLUSION: Bruxism and dysfunctional oral habits were shown to be risk factors for the presence of TMD symptoms also after combined orthodontic and surgical treatment. Treating such habits before orthognathic surgery should help prevent TMD.

Analysis of dental compensation in patients with facial asymmetry using cone-beam computed tomography.

INTRODUCTION: The purpose of this research was to evaluate dental compensation in facial asymmetry and its correlation with skeletal variables using cone-beam computed tomography. METHODS: Sixty adult patients were retrospectively divided into asymmetry (mean age, 21.8 ± 5.4 years) and symmetry groups (mean age, 28.1 ± 4.1 years); both groups comprised 30 patients. Independent and paired t tests were used for comparisons between the asymmetry and symmetry groups and between deviated (Dv) and nondeviated (NDv) sides of the asymmetry group, respectively. Pearson correlation between dental and skeletal variables was performed. RESULTS: The mean value of menton deviation was 9.4 mm in the asymmetry group. Compared with the symmetry group, the direction and amount of dental compensation of the asymmetry group were as follows: 2.5-mm extrusion of the maxillary first molar (UM6) at NDv (P <0.05); 1.8-mm higher position of the mandibular canine (LC) from the mandibular horizontal plane using mental foramen (MHP_mf) at NDv (P <0.05); 6°-more buccoversion of UM6 at Dv; 3.7°-more linguoversion of UM6 at NDv; 4.8°-more buccoversion of the maxillary canine (UC) at Dv; 4.9°-more buccoversion of the mandibular molar (LM6) at NDv; and 2.6°-more linguoversion of LC at Dv. Dental compensation correlated or marginally correlated with skeletal variables of the deviated mandible. CONCLUSIONS: Dental compensations, extrusion of the maxillary molars on the NDv, and buccal tipping of the maxillary teeth and lingual tipping of the mandibular teeth on the Dv, were observed. The mandibular body length was associated with linguoversion of the mandibular molars on the Dv. The ramal inclination was related to the extrusion of the maxillary molars on the NDv.

Factors associated with spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction.

INTRODUCTION: This study aimed to identify significant factors affecting the spontaneous angular changes of impacted mandibular third molars as a result of second molar protraction. Temporary skeletal anchorage devices in the missing mandibular first molar (ML-6) or missing deciduous mandibular second molar (ML-E) with missing succedaneous premolar spaces provided traction. METHODS: Forty-one mandibular third molars of 34 patients (10 male and 24 female; mean age 18.3 ± 3.7 years) that erupted after second molar protraction were included in this study. They were classified into upright (U) and tilted (T) groups. Linear and angular measurements were performed at the time of treatment initiation (T1) and of ML-6 or ML-E space closure (T2). Regression analyses were used to identify significant factors related to third molar uprighting. RESULTS: Nolla stage (odds ratio [OR] 4.1), sex (OR 0.003 for male), third molar angulation at T1 (OR 1.1), missing tooth space (OR 0.006), rate of third molar eruption (OR 23.3), and rate of second molar protraction (OR 0.2) significantly affected third molar uprighting. Age, third molar angulation at T1, rate of third molar eruption, and rate of second molar protraction were significant factors for predicting third molar angulation at T2. CONCLUSIONS: Available space for third molar eruption before and after second molar protraction is not associated with uprighting of erupting third molars. Older patients whose third molars are in greater Nolla stage, are in a more upright position at T1, and have a greater eruption rate have a greater chance for third molar uprighting. Alternatively, an increase in second molar protraction rate results in mesial tipping of the third molars.

Evaluation of masticatory muscle activity in patients with unilateral posterior crossbite before and after rapid maxillary expansion.

Objectives: The relationship between unilateral posterior crossbite (UPCB) and the possible asymmetric activation of the jaw muscles in children is still under debate. This study aimed at evaluating the jaw muscle activity of children with UPCB before and after rapid maxillary expansion (RME) by means of surface electromyography and a standardized sampling protocol. Subjects and methods: Twenty-nine children with UPCB (UPCB-group, mean age 9.6 ± 1.6 years) and 40 UPCB-free controls (Control-group, 10.5 ± 1.1) were recruited. The activity of the left and right anterior temporalis (AT) and superficial masseter muscles (MM) was recorded during maximum voluntary clenching and a chewing task (T0). In the UPCB-group, data were collected, also, after the correction of the UPCB with RME (T1) and 6 months later (T2), without any further treatment. Electromyographic indices comparing the activity of paired muscle were computed via software to estimate the extent of asymmetric AT and MM activity. Paired and unpaired t-test or Wilcoxon-signed rank and Mann-Whitney U test, ANOVA or Friedman test and chi-squared test were used in the statistical analysis. Results: Both groups presented with asymmetric activity of the muscles, which did not differ between groups (T0, all P > 0.05). The treatment determined a decrease in muscular activity (T1, P = 0.040), and a more asymmetric pattern of muscle activation during chewing (T1, P = 0.040), which returned similar to baseline values at T2 (all P > 0.05). Conclusions: UPCB does not contribute to an asymmetric activation of AT and MM during functional tasks. The treatment of UPCB by RME did not determine a more symmetric activity of the assessed muscles.

Effects of crown movement on periodontal biotype: a digital analysis.

Orthodontic treatment has important correlations with periodontal changes. Various mechanical and biological factors are involved in determining such changes, but anatomical and morphological variables, generally addressed as periodontal biotype, play a key role. In measurement of such modifications, digital and non-contact reverse engineering technologies may be of tremendous advantage. The aim of this study is to retrospectively evaluate, in a series of digitized dental casts, some of the parameters addressing periodontal biotype and correlate them to extent and direction of tooth movement. Pre- (T0) and post-treatment (T1) dental casts of 22 patients were scanned by 3Shape TRIOS 3® scanner. A number of variables (crown ratio, gingival margin position, gingival contour, papillae position, gingival scallop) were investigated and their variations calculated after digital measurements on single casts at T0 and T1, or after direct measurement (T1 vs T0) on the superimposition and alignment of digital models. Univariate and multivariate statistics were then performed. No significant correlation was detected between the sagittal or vertical movement of dental crown and displacement of the gingival margin. On the other hand, vestibular gingival contour resulted significantly altered by vestibular and extrusion movements. Further studies are needed to ascertain the differential effect of bone and soft tissue on such modifications. The relationship between orthodontic treatment and the periodontium overcomes the consideration of gingival recession and includes all the concepts of periodontal biotype with its characteristics. Digital technologies and non-contact reverse engineering techniques now available have the potential to allow a more precise definition of such a relationship.

Relationship between tongue pressure and maxillofacial morphology in Japanese children based on skeletal classification.

During childhood, perioral muscle function is closely associated with malocclusion. To clarify the effects of tongue function on maxillofacial morphology in children, tongue pressure and maximum lip-closing force (LCF) were measured and the relationship between perioral muscle function and maxillofacial morphology was evaluated according to the skeletal classification. Maximum tongue pressure (MTP) and swallowing tongue pressure (STP) were measured on the anterior palatine rugae in 100 children (Hellman's dental stages IIIA-IIIC) using a balloon-type tongue pressure measurement device. Lip-closing force was measured using an LCF measurement device. Lateral cephalograms were examined to classify subjects into skeletal (S)-I, S-II and S-III groups. Correlations of skeletal classification with tongue pressure and LCF were examined. Correlations of lateral cephalometric measurements with palatal volume (PV), measured using a three-dimensional optical scanner, were evaluated. Maximum tongue pressure was significantly lower in the S-II group than in other groups. Swallowing tongue pressure was significantly lower in the S-II group than in the S-III group. Lip-closing force was significantly higher in the S-III group than in other groups. Swallowing tongue pressure was positively correlated with MTP and PV. Correlations between tongue pressure and anteroposterior skeletal classification indicated the importance of quantitative tongue function assessment.

Anxiety and malocclusion are associated with temporomandibular disorders in adolescents diagnosed by RDC/TMD. A cross-sectional study.

BACKGROUND: Temporomandibular Disorders (TMD) is a multifactorial condition, which could be associated to occlusal and psychological factors, such as anxiety. OBJECTIVE: Investigate if anxiety and malocclusion are associated with the prevalence of TMD in adolescents. METHODS: To ensure a population-based representative sample, 934 adolescents aged 10 to 14 years old from Curitiba-PR, Brazil were randomly selected and examined according to Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and malocclusion by a single-calibrated examiner (Kappa > 0.80). Anxiety was assessed according to trait anxiety (STAI-T), categorised as high, moderate and low levels. For occlusal exam, it was considered: Angel's molar relationship, anterior and posterior crossbite, excessive overjet, open and deep bite. The associations were analysed by the crude and adjusted prevalence ration (RPa ) of TMJ, calculated by a Poisson multivariate regression with robust variance (α = 0.05). RESULTS: The prevalence of at least one type of malocclusion was found in 52.3%. Anxiety was found in high level (12.2%), moderate (70.4%) and low (17.5%). Presence of high anxiety was significantly associated with the prevalence of TMD symptoms (RPa  = 4.06, P < 0.001), as well as the prevalence of myofascial pain (RPa  = 24.78; P < 0.001) and prevalence of disc displacement with reduction (RPa  = 11.08, P < 0.001). Adolescents Class II had higher prevalence of myofascial pain (Class II RPa  = 1.73; P < 0.015) than adolescents Class I. Adolescents Class III presented higher prevalence of myofascial pain (PRa 2.53; P = 0.004) than adolescents Class I. CONCLUSION: Anxiety is strongly associated with TMD in adolescents. Presence of Class II or III is associated with higher prevalence of myofascial pain in adolescentsPLESAE check and approve the edit made in the article title.

Compensations in Bone Morphology and the Dentition in Patients With Untreated Unilateral Cleft Lip and Palate: A Cone-Beam Computed Tomographic Analysis.

OBJECTIVE: The purpose of this study was to quantitatively assess dentoalveolar and skeletal compensations in patients with untreated unilateral cleft lip and palate (UCLP). We hypothesized that there are significant skeletal and dental adaptations in UCLP cases compared to a comparison maxillary crossbite group. DESIGN: A convenience retrospective sample of 30 patients with UCLP and a comparison group of 30 patients with unilateral posterior crossbite without CLP. Cone-beam computed tomography scans (CBCTs) were used to evaluate dental and skeletal compensations. In addition, alveolar bone thickness was measured at 2-mm increments in mesiodistal and faciolingual cross-sectional views along the long axis of the central incisors. Alveolar bone height was measured, and the percentage of root length supported by bone was calculated. RESULTS: Compensations for unilateral cleft lip and palate were restricted to the cleft site and adjacent structures. Dental compensations include alteration in the position of cleft-adjacent maxillary incisors and maxillary canines. No gross skeletal compensations were found. Alveolar support of cleft adjacent incisors was similar to controls except for measurements in the most coronal and apical regions. The cleft group contralateral incisors exhibited buttressing effects and had significantly higher alveolar thickness in the coronal half of the tooth. There was less (5%) alveolar coverage of the cleft-facing aspect of the central incisor root than all other incisors. CONCLUSION: The bone adaptation to the presence of a cleft was localized in the vicinity of the cleft, and adaptations in the mandible were not apparent.

Gastric emptying rate before and after orthodontic treatment examined with the [13C] breath test: A pilot study.

INTRODUCTION: Orthodontic patients with malocclusion have significantly lower masticatory and gastrointestinal digestive function than persons with normal occlusion. Although several studies have suggested that masticatory function is improved after orthodontic treatment, the relationship between such improvement and change in gastrointestinal symptoms has not been quantitatively evaluated. In this study, we aimed to investigate the change in masticatory function and the gastric emptying rate in patients with malocclusion, before and after orthodontic treatment. METHODS: Seven women with malocclusion, before (pretreatment group) and after orthodontic treatment (posttreatment group), and 7 healthy dentate female volunteers (control group) underwent a 13C-acetate breath test (13CO2) with a liquid meal and the color changeable gum test, along with completing the frequency scale for symptoms of gastroesophageal reflux and a questionnaire on food intake. Between-group differences were evaluated. RESULTS: The pretreatment group had significantly longer maximum 13CO2 exhalation time and lower masticatory function, quantified using a higher red-color value on the gum test and the questionnaire on food intake, than did the posttreatment and control groups. No significant differences were identified between the posttreatment and the control groups. CONCLUSIONS: We provide evidence of improvement of masticatory function after orthodontic treatment, which was associated with a faster rate of gastric emptying.

Determinant factors of malocclusion in children and adolescents with cerebral palsy.

INTRODUCTION: Cerebral palsy (CP) is an encephalic static lesion characterized as a nonprogressive disorder of movements and posture with functional deficits that may favor the occurrence of various malocclusions. We looked for a possible association between overall functional impairment and malocclusion in this population. METHODS: Seventy patients from the Center of Attendance for Special Needs Patients, ages 6 to 18 years and with a CP diagnosis, were involved in the research. The overall degree of functional impairment was assessed with the Gross Motor Function Classification System, and malocclusion was evaluated with the criteria established by the World Health Organization and selected occlusion characteristics. To test the associations, univariate and multiple logistic Poisson regression analyses were used, and prevalence ratio values were calculated. RESULTS: Patients with limited or severely limited mobility (Gross Motor Function Classification of 4 or 5) (P = 0.003), parafunctional habits (P = 0.001), and a caregiver who was not the mother had 3 to 4 times more risk for open bite. Patients with dyskinetic CP are 4 times more likely to develop deepbite (P = 0.005). CONCLUSIONS: The results showed that the type of CP, the degree of motor involvement, and the presence of parafunctions are important factors to be considered to establish a correct diagnosis of malocclusion in persons with CP.

Effects on nasal airflow and resistance using two different RME appliances: a randomized controlled trial.

Objectives: To evaluate and compare the effects of tooth-borne (TB) and tooth-bone-borne (TBB) rapid maxillary expansion (RME) on nasal airflow and resistance. Material and methods: Fifty-four consecutive patients who met the eligibility criteria were recruited from September 2010 to December 2015. Of these 54 subjects, 40 agreed to participate in the part of the study involving evaluation of nasal flow and resistance. The 40 subjects were allocated to either the TB group, mean age 9.7 years (SD 1.5), or the TBB group, mean age 10.2 years (SD 1.4). All subjects performed rhinomanometric registration at baseline (T0), but only 30 attended the post-expansion registration (T1), of whom 16 had been randomized to the TB group and 14 to the TBB group. The study outcomes, nasal airflow and nasal airway resistance, were evaluated with linear regression adjusted for baseline variable of the outcome to compare the study groups with complete cases strategy as well as after multiple imputation (MI). Randomization: Participants were randomly allocated in blocks of different sizes, using the concealed allocation principle in a 1:1 ratio. The randomization list was computer generated to ensure homogeneity between groups. Blinding: Blinding was done only for outcome assessor due to clinical limitations. The care providers at the ENT unit who conducted all the rhinomanometry examinations were blinded to which group the patients were allocated to. Results: Complete case analysis showed significantly higher post-expansion nasal airflow values for the TBB group compared with the TB group, mean difference 51.0 cm3/s (P = 0.018). The evaluation after MI showed a similar significant mean difference, 52.7 cm3/s (P = 0.020) in favour of the TBB group when taking into account the missing values from the T1 examination. Even reduction in nasal airway resistance showed similar pattern in favour of the TBB group. Limitations: Our results represent the short-term effects. A longer follow-up period would have been preferable. Conclusions: The TBB RME induced significantly higher nasal airway flow and lower nasal resistance values than TB RME. It might be wiser to use TBB RME in cases with constricted maxilla and upper airway obstruction. Registration: This trial was not registered in any external sites. Protocol: The protocol was not published before trial commencement.

Comparison of EMG activity and blood flow during graded exertion in the orbicularis oris muscle of adult subjects with and without lip incompetence: a cross-sectional survey.

Background/Objectives: The peri-oral muscles-including orbicularis oris-are critical in maintaining equilibrium in tooth position. Lip incompetence (LI) can thus be a factor in malocclusion. We therefore aimed to validate a technique to evaluate not only muscle activity via electromyography (EMG) but also muscle endurance and fatigue via blood flow (BF) for LI. Subjects/Methods: Subjects were classified into increased muscle tension/lip incompetent (experimental) and normal muscle tension/lip competent (control) groups. Each subject then exerted force on a custom-made traction plate connected to a tension gauge. Using laser speckle imaging and electromyographic measurements, we characterized muscle activity and corresponding BF rates in these subjects in various states of resting, loading, and recovery. Results: Results showed a significant difference between the experimental and control groups, notably in the rate of change in BF to the inferior orbicularis oris muscle under conditions of increasing load (graded exertion). Furthermore, the data suggested that the muscles in the control group undergo a more prolonged (and therefore presumably more complete) recovery than muscles in the experimental group. These factors of reduced BF and short recovery may combine to accelerate muscle fatigue and produce LI. Limitations: The sample used here was controlled for malocclusion (including open bite) to eliminate this type of confounding effect. Conclusions/Implications: From these findings, we conclude that reduced BF and inadequate recovery in the orbicularis oris muscles may be more significant than EMG activity in the assessment of LI.

Growing patients with Duchenne muscular dystrophy: longitudinal changes in their dentofacial morphology and orofacial functional capacities.

Aim: The aim of this study was to describe the longitudinal changes in facial morphology, dental arch alterations and oral functional capacities that occur in growing patients with Duchenne muscular dystrophy (DMD) in order to identify the effects of the progression of the disease. Subjects and Methods: Twelve DMD patients (6.5-17.5 years of age) and 12 matched controls were screened on two different occasions (T1 and T2), 2 years apart. Dental casts, lateral cephalometric radiographs, maximal posterior bite force and labial force were measured to determine changes in their functional capacities and dentofacial morphology. Furthermore, the thickness and echogenicity of the masseter muscle were measured during clenching. Statistical evaluation: Unpaired t-tests were performed to evaluate the differences between the DMD patients and their healthy matched controls; paired t-tests were used to assess the changes that occurred within each group between T1 and T2. Results: Between T1 and T2 the following changes were observed: widening of the lower dental arch for the DMD patients of 2.6mm (±0.9mm) compared to a slight reduction of -0.1mm (±0.8mm) for the control group (P = 0.001). We found a statistically significant reduction of the sagittal skeletal intermaxillary relationship (ANB-angle) of 2.0° (±2.0°) in the DMD group (P = 0.012). In T1 and T2, the maximal posterior bite force and the labial force were lower for the DMD patients compared to the control group (P = 0.001), who showed an increase during this period. Conclusion: The results indicate that DMD influences the facial morphology, dental arch dimensions and oral functional capacities. The longitudinal perspective of this study revealed that the worsening of most of the measured parameters is associated with the progression of the disease. Besides the expected deterioration of the functional measurements, we found in all patients, a marked transverse increase of the posterior part of the dental arches, more in the lower than in the upper, resulting in posterior crossbites, as well as a tendency towards a skeletal Class III relationship.

Effect of different masticatory functional demands on the 3D mandibular condyle morphology of growing rats using posterior bite-blocks.

Background and objectives: Apart from the primary effect of bite-blocks on tooth position, they may also influence the mandibular condylar growth. Our aim was to investigate their influence on the condylar morphology, with variable masticatory forces. Material and methods: Fifty-two 4-week old male rats were divided into hard and soft diet groups in order to create individuals with different masticatory muscle capacity. Two weeks later, they were equally divided into bite-block and control groups. After a total of 6 weeks experimental time, the animals were sacrificed. The mandibles were scanned with high-resolution micro-CT and 3D analysis was performed on the condylar neck and head of the condyle. The volume and the length of the condylar process were measured. Statistical analysis was done with a one-way analysis of variance. Results: The use of bite-blocks decreased the length of the condylar process (P = 0.001) as well as the volume of the condylar neck (P = 0.001) and head (P = 0.006). The soft diet decreased the volume of the condylar neck (P < 0.001) and head (P < 0.001) two to three times more than the bite-blocks but did not affect the condylar process length. The interaction between the two variables was not statistically significant. Conclusions: Both the bite-block appliance and weak masticatory muscle function reduced the volume at all regions of the condylar process, although the functional factor had a substantially greater effect. However, only the bite-block appliance affected the condylar process length. In the presence of both factors, an additive effect was found but no interaction detected.