Mastication, EMG activity and occlusal contact area in subjects with different facial types

Evaluation´ of mandibular alveolar bone in patients with different vertical facial patterns : A cross-sectional CBCT study

PURPOSE

The study aimed to investigate the morphological and structural differences of mandibular alveolar bone between different vertical facial patterns (VFP).

METHODS

In all, 66 CBCT scans of patients were selected for the study: 24 were designated as hyperdivergent, 25 as normodivergent, and 17 as hypodivergent. Fractal values of the interdental alveolus were measured at the incisor, canine, premolar, and molar regions. The minimum trabecular bone width (MTBW) of the alveolus, the buccal and lingual cortical bone thicknesses, and the total alveolar width (AW) at the minimum trabecular bone level were measured. One-way analysis of variance and Tukey test were used to compare the groups. The correlations between FMA (Frankfurt mandibular plane angle) and other measurements were analyzed by Pearson analysis.

RESULTS

No significant differences were detected in fractal values and buccal and lingual cortical bone thicknesses between the groups. The MTBW and AW of the hypodivergent individuals were found to be higher in the anterior and premolar interdental sites. FMA was found to be significantly correlated with MTBW and AW.

CONCLUSIONS

The patients with different VFPs did not exhibit significant differences in the trabecular complexity of the mandibular alveolus. Hypodivergent patients tend to have thicker trabecular and alveolar bone widths than normodivergent and hyperdivergent individuals.

General and local predictors of mandibular cortical bone morphology in adult females and males: the seventh survey of the Tromsø Study

OBJECTIVES

To analyze factors predicting mandibular cortical width (MCW) and mandibular cortical index (MCI) in adult females and males.

MATERIAL AND METHODS

Data on 427 females and 335 males aged 40-84 from The Tromsø study: Tromsø7 were used. T-score, age, menopausal status (for females), remaining teeth, and periodontal status were analyzed in linear and logistic regression analyses as predictors of MCW and MCI, respectively.

RESULTS

T-score, age, and the number of remaining teeth significantly predicted MCW in females but not males. Standardized β coefficients were 0.286, -0.231, and 0.131, respectively. The linear regression model explained 24% of MCW variation in females. MCI in females was significantly predicted by T-score, age, and remaining teeth with the Wald values of 9.65, 6.17, and 5.83, respectively. The logistic regression model explained 16.3-23% of the variation in MCI in females. In males, T-score was the only significant predictor of the eroded cortex, and the logistic model explained only 4.3-5.8% of the variation in MCI.

CONCLUSIONS

The T-score demonstrated a stronger relationship with MCW and MCI than other factors in females, which supports the usefulness of those indices for osteoporosis screening. Conversely, the T-score exhibited no association with MCW and remained the only significant predictor of MCI in males, yet to a lesser extent than in females.

CLINICAL RELEVANCE

Understanding factors affecting mandibular cortical morphology is essential for further investigations of MCW and MCI usefulness for osteoporosis screening in females and males.

Correlation of masticatory muscle activity and occlusal function with craniofacial morphology: a prospective cohort study

OBJECTIVES

Masticatory function, including masticatory muscle activity and occlusal function, can be affected by craniofacial morphology. This study aimed to investigate the relationship between craniofacial morphology and masticatory function in participants who had completed orthodontic treatment at least two years before and had stable occlusion.

MATERIALS AND METHODS

Fourty-two healthy participants were prospectively enrolled and divided into three vertical cephalometric groups according to the mandibular plane angle. Masticatory muscle activity (MMA) in the masseter and anterior temporalis muscles was assessed using surface electromyography. The occlusal contact area (OCA) and occlusal force (OF), defined as occlusal function in this study, were evaluated using occlusal pressure mapping system. Masticatory muscle efficiency (MME) was calculated by dividing MMA by OF. The craniofacial morphology was analyzed using a lateral cephalogram. The masticatory function was compared using one-way analysis of variance. Pearson correlations were used to assess relationships between craniofacial morphology and masticatory function.

RESULTS

The hypodivergent group had the lowest MMAand the highest MME in the masseter (167.32 ± 74.92 µV and 0.14 ± 0.06 µV/N, respectively) and anterior temporalis muscles (0.18 ± 0.08 µV/N, p < 0.05). MMA in the masseter showed a positive relationship with mandibular plane angle (r = 0.358), whereas OCA (r = -0.422) and OF (r = -0.383) demonstrated a negative relationship (p < 0.05). The anterior temporalis muscle activity negatively correlated with ramus height (r = -0.364, p < 0.05).

CONCLUSIONS

Vertical craniofacial morphology was related to masticatory function. Hypodivergent individuals may have low MMA and high occlusal function, resulting in good masticatory muscle efficiency.

CLINICAL RELEVANCE

Hypodivergent individuals require careful consideration in orthodontic diagnosis and prosthetic treatment planning.

Evaluation of trabecular bone and mandibular cortical thickness in adults with different vertical facial types

OBJECTIVES

This study investigated differences in trabecular structure and mandibular cortical thickness in adults related to vertical facial type (VFT), sex, and their interactions.

STUDY DESIGN

Lateral cephalometric radiographs (LCRs) and panoramic radiographs (PRs) of 256 patients were reviewed. The VFT classification into low-angle, normal, and high-angle groups was determined using angular and linear measurements on LCRs. Fractal dimension (FD) values and mandibular radiomorphometric indices (RMIs) were calculated on PRs.

RESULTS

Two-way analysis of variance revealed significant differences in FD overall among VFT groups in all sites (P < .001), with pairwise comparisons indicating the greatest values in the high-angle group in the condyle (P < .05) but in the low-angle group elsewhere (P < .001). RMIs were significantly different overall regarding VFT only in the posterior mandible (P = .004), with pairwise comparisons revealing low-angle and normal group values greater than high-angle group values (P < .05). Patient sex and the interaction of facial type and sex had no significant effect on any bone measurements.

CONCLUSIONS

VFT had significant effects on trabecular structure at all measured sites, but cortical thickness was affected only in 1 location.

Chewing Patterns and Muscular Activation in Deep Bite Malocclusion

Background: Deep bite, a frequent malocclusion with a high relapse rate, is associated with craniofacial features that need to be considered in the course of orthodontic treatment. Methods: This study included 81 patients with deep bite malocclusion (11.4 ± 1.1 [yr.mo]; M = 32 and F = 49), and 14 age- and gender-matched controls (9.11 ± 1 [yr.mo]; M = 5 and F = 9). The patients with deep bite malocclusion were treated with functional therapy. The chewing cycles and masticatory muscle EMG activity were recorded concomitantly before treatment in both groups (n = 95). Following correction of the malocclusion, a second recording took place (n = 25). Results: The kinematic variables showed the same dependency on bolus hardness in those with deep bite and in the controls. The masticatory muscle EMG activity was increased in those with deep bite, but decreased as a result of functional treatment. The chewing patterns showed a tendency towards a reduced lateral component, which significantly increased after treatment, indicating that functional therapy impacts the neuromuscular coordination of mastication, as well as dental positioning. Conclusions: Deep bite is a complex malocclusion, involving alterations in chewing and masticatory muscle activity. Orthognathodontic treatment should not only consider and correct the teeth position, but should also address muscular hyperactivity.

Electromyographic features and efficacy of orofacial myofunctional treatment for skeletal anterior open bite in adolescents: an exploratory study

BACKGROUND

Due to the multifactorial aetiology and unpredictable long-term stability, skeletal anterior open bite (SAOB) is one of the most intractable conditions for orthodontists. The abnormal orofacial myofunctional status (OMS) may be a major risk factor contributing to the development and relapse of SAOB. This study is aimed at evaluating the OMS and the efficacy of orofacial myofunctional therapy (OMT) alone for SAOB subjects.

METHODS

Eighteen adolescents with SAOB (4 males, 14 females; age: 12-18 years) and eighteen adolescents with normal occlusion (2 males, 16 females; age: 12-18 years) were selected. The electromyographic activity (EMGA) associated with mastication and closed mouth state was measured. Lateral cephalography was used to evaluate craniofacial morphology. Wilcoxon signed rank tests and t-tests were performed to evaluate myofunctional and morphological differences. Pearson or Spearman correlation analysis was used to investigate the correlations between EMGA and morphological characteristics. SAOB subjects were given OMT for 3 months, and the EMGA was compared between before and after OMT.

RESULTS

During rest, anterior temporalis activity (TAA) and mentalis muscle activity (MEA) increased in SAOB subjects, but TAA and masseter muscle activity (MMA) decreased in the intercuspal position (ICP); and upper orbicularis activity (UOA) and MEA significantly increased during lip sealing and swallowing (P < 0.05). Morphological evaluation revealed increases in the FMA, GoGn-SN, ANS-Me, N-Me, L1-MP, U6-PP, and L6-MP and decreases in the angle of the axis of the upper and lower central incisors and OB in SAOB subjects (P < 0.05). TAA, MMA and anterior digastric activity (DAA) in the ICP were negatively correlated with vertical height and positively correlated to incisor protrusion. MEA was positively correlated with vertical height and negatively correlated with incisor protrusion; and the UOA showed a similar correlation in ICP, during sealing lip and swallowing. After SAOB subjects received OMT, MEA during rest and TAA, MMA and DAA in the ICP increased, while UOA and MEA decreased (P < 0.05).

CONCLUSION

SAOB subjects showed abnormal OMS features including aberrant swallowing patterns and weak masticatory muscles, which were interrelated with the craniofacial dysmorphology features including a greater anterior facial height and incisor protrusion. Furthermore, OMT contributes to OMS harmonization, indicating its therapeutic prospect in SAOB.

Evaluation of mandibular morphologic measurements and trabecular structure among subgroups of impacted mandibular third molars

OBJECTIVE

To investigate mandibular morphologic measurements and trabecular structures that may cause mandibular third molar (MM3) impaction according to MM3 subgroups.

METHODS

A total of 150 MM3 of 2175 panoramic radiographs (PRs) were reviewed. MM3s according to Winter (vertical), Pell & Gregory Class 1 and group: A, B, C on PRs were included in the study group. Fractal dimensions (FD) and mandibular morphologic measurements were evaluated. Statistical analysis for parametric values was performed using one-way analysis of variance (ANOVA). Statistical analysis for non-parametric values was performed using the Kruskal-Wallis H test.

RESULTS

Statistically, a significant difference was found only in terms of angle of impaction among the groups of MM3 (p < 0.05) [Winter (vertical), and Pell & Gregory Class 1 and group A, B, C]. There was no difference among groups A, B, C in mandibular morphology and trabecular structure, but group C showed different characteristics than the other groups only in terms of impaction angle.

CONCLUSION

The trabecular structure and morphometric properties except for the angle of impaction do not affect impacted MM3s with adequate retromolar space and vertical angle.

Effects of gum chewing exercise on maximum bite force according to facial morphology

Development of the masticatory system is influenced by functional needs. Furthermore, masticatory exercise can improve masticatory function. The aim of this study was to evaluate the potential effect of the gum chewing exercise on the maximum bite force (MBF) in adult subjects with different facial morphologies. MBF was measured by a portable occlusal force gauge and lateral cephalogram was used for evaluation of craniofacial morphology in 19 individuals (7 males and 12 females) with a mean age of 25.4 years (SD ± 4.3). The volunteers underwent gum chewing exercise for 5 min twice a day for 4 weeks. MBF was measured before (T1) and after the 4‐week exercise (T2). The facial morphology of the subjects was classified into the brachy (n = 7), mesio (n = 7), and dolicho (n = 5) facial types. In all three groups, exercise was associated with a significant increase in MBF, though the percent increase was highest in the dolicho facial type. We conclude that gum chewing exercise can improve masticatory performance, especially in individuals with dolicho facial morphology.