Effects of class II intermaxillary elastics on masticatory muscle activity balance, occlusal contact area and masticatory performance: A multicenter randomised controlled trial.

BACKGROUND: Bilateral Class II intermaxillary elastics (CII elastics) are commonly used in orthodontics; however, the effects of CII elastics on masticatory muscle activity and the occlusal contact area have not been studied. OBJECTIVES: To evaluate the short-term effects of CII elastics on masticatory muscle activity balance, occlusal contact area and masticatory performance in a group of adult orthodontic patients after 3 months. MATERIALS AND METHODS: Forty-three patients with a <3 mm Class II molar relationship receiving ongoing treatment with fixed appliances were recruited. The experimental group (n = 21) wore CII elastics (100-150 g/side) full time; the control group (n = 22) did not wear CII elastics. Surface electromyography, the areas of occlusal contact and near contact (ACNC) and the median particle size of a test food were assessed prior to (T0) and after one (T1) and 3 months (T2). Within- and between-group differences were analysed and the relationships between changes in dependent variables were examined (α = 0.05). RESULTS: At T2, the experimental group showed better masticatory muscle activity balance (p < .001) and masticatory performance (p < .05) than controls. Both masticatory muscle activity balance (p < .001) and masticatory performance (p < .001) significantly improved in the experimental group between T0 and T2. The changes in masticatory muscle activity balance and masticatory performance were significantly related (p < .05). No significant changes in cumulative ACNC or ACNC balance were observed (p > .05). CONCLUSION: After 3 months, CII elastics improved masticatory muscle activity balance, which led to better masticatory performance.

Overbite recognition and factors affecting esthetic tolerance among laypeople.

OBJECTIVES: To determine recognition ability and the levels of esthetic tolerance of deep bite and anterior open bite (AOB) among laypeople and investigate the factors affecting levels of tolerance. MATERIALS AND METHODS: Using a questionnaire, laypeople (N = 100) were examined, and overbite was measured. They were tested for whether they recognized deep bite and AOB. Esthetic tolerance thresholds for deep bite and AOB were selected by incremental depiction in grayscale images. Stepwise logistic regression analyses were used to quantify the effect of recognition and other factors (age, sex, education level, occupation, history of orthodontic treatment, interest in orthodontic treatment or retreatment, and overbite presence) affecting the tolerance of overbite problems (α = 0.05). RESULTS: Of the participants, 55% and 94% recognized deep bite and AOB, respectively. Participants with a deep bite were significantly more likely to esthetically tolerate deep bite compared with those without a deep bite (odds ratio [OR], 3.57; 95% confidence interval [CI], 1.29-9.89). Participants who recognized a deep bite problem had significantly lower esthetic tolerance to deep bite compared with participants who did not recognize a deep bite (OR, 0.17; 95% CI, 0.06-0.45). None of the other eight chosen factors significantly affected the tolerance level of AOB (P > .05). CONCLUSIONS: Participants with a deep bite or those who did not recognize a deep bite had significantly higher esthetic tolerance of deep bite than those without or those who recognized the problem (P < .05).

Mandibular incisor root volume changes between anterior bite planes fabricated from acrylic resin and thermoplastic materials: a prospective randomized clinical trial.

OBJECTIVES: To compare mandibular incisor root volume change (RVC) after 6 months between an anterior bite plane fabricated from acrylic resin (ABP) and thermoplastic materials (TBP) in a group of growing patients. MATERIALS AND METHODS: Thirty-four deep bite patients (age: 11.57 ± 1.30 years) were randomized into the ABP or TBP group. The RVC from before treatment (T0) to 6 months after treatment (Tct) at the labio-coronal (La1), labio-middle (La2), labio-apical (La3), linguo-coronal (Li1), linguo-middle (Li2), and linguo-apical (Li3) segments were investigated from cone beam computed tomography (CBCT) images. Cephalometric changes between T0 and the visit that normal overbite was achieved (Tcep) were also assessed (α = 0.05). RESULTS: Thirty-four patients completed the trial. Treatment duration was 5.0 ± 2.9 months. Significant decrease in root volume (RV) was found at the La2, La3, and Li3 segments of the ABP group (P < .05). No significant RVC was found in any segment of the TBP group (P ≥ .05). Comparing between groups, the RVC at La3 and Li3 of the ABP group was significantly greater than that of the TBP group (P < .05). However, total RVC between groups was not significantly different (P ≥ .05). CONCLUSIONS: Growing patients undergoing deep bite correction for 6 months with ABP displayed more apical RVC of mandibular incisors than those who used TBP. However, total RVC between appliances was not significantly different.

Effects of anterior bite planes fabricated from acrylic resin and thermoplastic material on masticatory muscle responses and maximum bite force in children with a deep bite: A 6-month randomised controlled trial.

BACKGROUND: Anterior bite planes are bite-raising appliances used for deep bite correction. However, muscle responses to anterior bite planes of different harnesses may vary. OBJECTIVES: To prospectively evaluate masticatory muscle activity, muscle balance and maximum bite force (MBF) responses to anterior bite planes fabricated from acrylic resin (ABP) or bi-laminate thermoplastic (TBP) over 6 months in children with a deep bite. METHODS: Sixty-six children were randomly assigned to the ABP, TBP or untreated control groups. Masticatory muscle activity, activity index (AC) and percentage overlapping coefficient (POC) were assessed by surface electromyography; MBF, using a custom-made bite force sensor. Data were collected before, immediately after appliance insertion and after 2 weeks and 1, 3 and 6 months of treatment. Within- and between-group differences were analysed using the one-way ANOVA/Kruskal-Wallis and Mann-Whitney U tests (α = .05); Friedman's tests were used to assess within-group differences over time (α = .08). RESULTS: At rest, no dependent variables changed throughout the study. At maximum clenching, masticatory muscle activity immediately dropped significantly but returned to baseline values and was equal to the control group at 1-3 months. The ABP group had significantly lower masseter activity and AC than the TBP group after insertion. Neither POC nor MBF were significantly different within or between groups. CONCLUSION: Masticatory muscle activity reduced after anterior bite plane insertion but returned to baseline after 1-3 months. Masseter activity decreased significantly more in the ABP group than TBP group. Neither appliance significantly affected POC or MBF. CLINICAL TRIAL REGISTRATION: Thai Clinical Trial Registry (TCTR20210330002).

Are occlusal contact area asymmetry and masticatory muscle activity asymmetry related in adults with normal dentition?

Objective: To examine whether asymmetry in the area of occlusal contact and near contact (ACNC) and asymmetrical masticatory muscle electromyographic activity are correlated in healthy dentate adults.Methods: Ninety-one healthy subjects with full dentition were included. Seven levels of ACNC were registered, and the asymmetry indexes (AsI) for each level of ACNC (AsI-ACNC) were determined. Surface EMG was used to record bilateral anterior temporalis activity and masseter muscle activity. The AsI for the anterior temporalis, masseter, and the combination of both muscles were calculated.Results: Pearson's correlation analysis revealed all levels of AsI-ACNC were significantly, negatively correlated with the AsI of the anterior temporalis and the combination of both muscles (p < 0.05), but not the AsI of the masseter muscle (p > 0.05).Conclusion: The side with greater ACNC has significantly lower anterior temporalis activity and combined anterior temporalis and masseter muscle activity on the ipsilateral side.

Masticatory performance is influenced by masticatory muscle activity balance and the cumulative occlusal contact area.

OBJECTIVE: To investigate the influence of masticatory muscle activity balance, occlusal contact area balance and the area of occlusal contact on masticatory performance in healthy dentate adults. DESIGN: This cross-sectional study included ninety-three healthy subjects with complete dentition. Surface electromyography (sEMG) was used to record bilateral anterior temporalis activity and masseter muscle activity during maximum voluntary clenching and while chewing a test food. Seven levels of area of occlusal contact and near contact (ACNC) were registered and calculated cumulatively. The percentage overlapping coefficients were calculated for both muscle groups at maximum voluntary clenching and chewing and all levels of ACNC. Masticatory performance was measured by determining the median particle size of frankfurter sausage after 15 chewing cycles. Pearson's correlation and stepwise multiple linear regression analyses were used to assess the correlations between variables and the influence of the variables on masticatory performance, respectively, at the 0.05 level of significance. RESULTS: Muscle balance during clenching and chewing, all near contact levels of cumulative ACNC and ACNC balance correlated negatively with median particle size (P <  0.05). The model based on stepwise multiple linear regression analysis showed muscle balance during clenching and cumulative ACNC at < 250 µm influenced median particle size. CONCLUSION: Masticatory muscle activity balance during maximum voluntary clenching and the cumulative amount of near contact area were associated with masticatory performance, suggesting the amount of occlusal contact area-as well the balance of masticatory muscle activity-play a role in masticatory performance.

Alveolar bone response to maxillary incisor retraction using stable skeletal structures as a reference.

OBJECTIVES: To evaluate alveolar bone change in relation to root position change after maxillary incisor retraction via cone-beam computed tomography (CBCT) using stable skeletal structures as a reference. MATERIALS AND METHODS: A total of 17 subjects (age 24.7 ± 4.4 years) who required retraction of the maxillary incisors were included. Labial and palatal alveolar bone changes and root change were assessed from preretraction and 3 months postretraction CBCT images. The reference planes were based on stable skeletal structures. The Kruskal-Wallis test and Wilcoxon signed-rank test were used to compare changes within and between groups, as appropriate. Spearman rank correlations were used to identify the parameters that correlated with alveolar bone change. The significance level was set at .05. RESULTS: The labial alveolar bone change after maxillary incisor retraction was statistically significant (P < .05), and the bone remodeling/tooth movement (B/T) ratio was 1:1. However, the palatal bone remained unchanged (P > .05). The change in inclination was significantly related to labial alveolar bone change. CONCLUSIONS: Using stable skeletal structures as a reference, the change in labial alveolar bone followed tooth movement in an almost 1:1 B/T ratio. Palatal alveolar bone did not remodel following maxillary incisor retraction. The change in inclination was associated with alveolar bone change.

Assessment of the relationship between masticatory performance, occlusal contact area, chewing time and cycles, and gastric emptying scintigraphy in dentate subjects.

BACKGROUND: Good mastication is thought to help digestion in the stomach, hence promoting the health of the gastrointestinal system. However, the correlation between masticatory and gastric function has been controversial. This is partly explained by different food types used to assess the performance of the two organs. Recently, frankfurter sausage has been proposed to be suitable for both masticatory performance and gastric emptying tests. OBJECTIVES: To examine the relationship between masticatory performance, occlusal contact area, chewing time and cycles, and gastric emptying scintigraphy parameters in healthy dentate adults. MATERIALS AND METHODS: Forty healthy subjects (15 men: 25 women, age 23.9 ± 3.8 years) underwent masticatory performance tests and gastric emptying scintigraphy using frankfurter sausage as a test food. Masticatory performance was calculated as the median particle size (MPS) of chewed frankfurter sausage cubes after 30 chewing cycles. Gastric emptying scintigraphy was performed using frankfurter sausage mixed with technetium-99 m-labelled microwaved egg meal. Cumulative occlusal areas of contact-near contact (cACNC) were determined by silicone bite registration and image-analysed. Chewing time and cycles before swallowing were also recorded. RESULTS: No significant differences in MPS, cACNC, chewing time and cycles, or gastric emptying parameters were observed between gender. Bivariate correlation showed masticatory performance, occlusal contact area, chewing time and cycles were not correlated with gastric emptying parameters (P > 0.05). CONCLUSION: Using the same test food to assess the masticatory and gastric function in dentate subjects, the present study showed that masticatory performance, occlusal contacts, chewing time and cycles did not affect gastric emptying.

Effects of two frequencies of vibration on the maxillary canine distalization rate and RANKL and OPG secretion: A randomized controlled trial.

OBJECTIVES: To investigate the effects of 30 and 60 Hz vibratory stimulus on canine distalization and RANKL and OPG secretion. SETTING AND SAMPLE POPULATION: Sixty patients requiring canine distalization at the Orthodontic Clinic, Prince of Songkla University. MATERIALS AND METHODS: Patients were randomly assigned to 30 Hz vibration (n = 20), 60 Hz vibration (n = 20), or the control group (n = 20). Modified electric toothbrushes were used to apply vibration to the randomly selected canine for 20 min/day by the investigator combined with 60 cN continuous distalization force from day 1 to day 7. RANKL and OPG were analysed before (T1) and 24 hours (T2), 48 hours (T3) and 7 days (T4) after initiation of distalization. From day 8, vibratory devices were used by the subjects at home. Rate of canine distalization (T1 to 3 months after initiation [T5]) was calculated. Kruskal-Wallis tests were used for multiple comparisons (significance level, 0.05). RESULTS: Canine distalization rate was not different between groups (median; 0.82, 0.87, and 0.83 mm/month for 30, 60 Hz, and control group, respectively; P > 0.05). No within- or between-group differences in RANKL and OPG were observed (P > 0.05), except RANKL on the compression side of the control group was significantly higher at T2, T3 and T4 than T1 (P < 0.001). CONCLUSION: In the clinic, 30 and 60 Hz vibratory stimulus have no additive effect on rate of canine distalization rate, RANKL and OPG secretion or RANKL/OPG ratio.

Alveolar bone response to light-force tipping and bodily movement in maxillary incisor advancement: A prospective randomized clinical trial.

OBJECTIVE: To compare alveolar bone thickness and height changes between untreated incisors (control), incisors advanced with light-force tipping, and incisors advanced with bodily movement mechanics. MATERIALS AND METHODS: Forty-three subjects (aged 9.49 ± 1.56 years) with anterior crossbite were allocated into an untreated group (control), tipping group, or bodily movement group. Lateral cephalograms were taken before advancement (T0) and after obtaining normal overjet (T1). Changes in labial and palatal alveolar bone thickness and height surrounding maxillary incisors were evaluated with limited field-of-view cone-beam computed tomography before advancement (CT0) and 4 months after normal overjet was obtained (CT1). Wilcoxon matched-pairs signed-rank and Kruskal-Wallis one-way ANOVA tests were used to compare changes within and between groups, as appropriate. The significance level was set at .05. RESULTS: Labial alveolar bone thickness at the midroot and apical levels were significantly decreased in the bodily movement group ( P < .05). However, between groups, there was no statistically significant difference in labial bone thickness changes at any level. Palatal and total alveolar bone thickness at the midroot and apical levels were significantly decreased in the tipping group compared with the control and bodily movement groups ( P < .05). Neither labial nor palatal bone height changes were significantly different among groups. CONCLUSIONS: Maxillary incisor advancement with light-force tipping and bodily movement in growing patients resulted in labial alveolar bone thickness and labial and palatal alveolar bone height changes that were similar to the untreated group.

Vibratory stimulation increases interleukin-1 beta secretion during orthodontic tooth movement.

OBJECTIVES: To investigate the effects of application of vibratory stimuli on interleukin (IL)-1ß secretion during maxillary canine distalization. MATERIALS AND METHODS: Split-mouth design study in 15 subjects (mean age, 22.9 years; range 19-25 years) whose bilateral maxillary first premolars were extracted with subsequent canine distalization. On the experimental side, light force (60 g) was applied to the canine for 3 months in combination with vibratory stimuli provided using an electric toothbrush 15 minutes a day for 2 months; only orthodontic force was applied to the contralateral control canine. Gingival crevicular fluid (GCF) was collected from the mesial and distal sides of each canine at each monthly appointment. IL-1ß levels were analyzed using an enzyme-linked immunosorbent assay. Canine movement was measured monthly. RESULTS: Overall, enhanced IL-1ß secretion was observed at the pressure sites of experimental canines compared to control canines (mean, 0.64 ± 0.33 pg/µL vs 0.10 ± 0.11 pg/µL, respectively, P < .001). The accumulative amount of tooth movement was greater for the experimental canine than for the control canine (mean, 2.85 ± 0.17 mm vs 1.77 ± 0.11 mm, respectively, P < .001). CONCLUSIONS: This study demonstrates that, in combination with light orthodontic force, application of vibratory stimuli using an electric toothbrush enhanced the secretion of IL-1ß in GCF and accelerated orthodontic tooth movement.

Changes of anterior maxillary alveolar bone thickness following incisor proclination and extrusion.

OBJECTIVE: To investigate changes in maxillary alveolar bone thickness after maxillary incisor proclination and extrusion during anterior crossbite correction in a group of growing patients with Class III malocclusion. MATERIALS AND METHODS: Maxillary incisors of 15 growing patients with anterior crossbite were proclined and extruded with 0.016″ beta-titanium advancing loops and Class III elastics. Lateral cephalograms were recorded before advancement (T0) and 4 months after a normal overjet and overbite were achieved (T1). Changes in alveolar bone thickness surrounding the maxillary incisors at the crestal (S1), midroot (S2), and apical (S3) levels were measured using cone-beam computed tomography (CBCT). Paired t-tests were used to determine the significance of the changes. A Spearman rank correlation analysis was performed to explore the relationship between thickness changes and the rate and amount of incisor movements. RESULTS: Although statistically significant decreases were observed in palatal and total bone thickness at the S2 and S3 level (P < .05), the amounts of these changes were clinically insignificant, ranging from 0.34 to 0.59 mm. Changes in labial bone thickness at all levels were not significant. Changes in palatal bone thickness at S3 were negatively correlated with changes in incisor inclination. (r  =  -0.71; P < .05). CONCLUSION: In a group of growing patients with Class III malocclusion undergoing anterior crossbite correction, controlled tipping mechanics accompanied by extrusive force may produce successful tooth movement with minimal iatrogenic detriment to the alveolar bone.

Mother-child agreement on the child's past food exposure.

OBJECTIVE: To assess mother-child agreement on the child's past food exposure, and factors affecting response discrepancy. METHODS: Twelve- to 14-year-old children and their mothers (n = 78) in an urban community, a rural community, and 2 orthodontic clinics completed a 69-item food questionnaire to determine mother-child level of agreement on the child's past consumption frequency; response discrepancies; the frequencies that the mother cooked for and ate together with her child; food types; mother-child pair effect; and food item effect. RESULTS: Sixty-eight percent of food items had moderate to good agreement (Kqw > or = 0.41). Rural pairs had lower odds of producing response discrepancy (odds ratio = 0.55). Variances of the mother-child pair and food item random effects were 0.87 and 0.08, respectively. CONCLUSIONS AND IMPLICATIONS: The child's past food exposure recall by the mother and the child had moderate to good agreement, especially among rural mother-child pairs. Mother-child disagreement was not affected by the food items.