Mandibular asymmetry and condylar position in children with unilateral posterior crossbite

Short- and long-term effects of conventional and miniscrew-assisted rapid palatal expansion on hard tissues using voxel-based superimposition of serial cone-beam computed tomography scans

INTRODUCTION

The objective of this study was to evaluate the short-term and long-term hard-tissue changes with miniscrew-assisted rapid palatal expansion (MARPE) and rapid palatal expansion (RPE) compared with a matched control group with voxel-based superimposition using 3-dimensional cone-beam computed tomography (CBCT) scans.

METHODS

A total of 180 CBCT scans were analyzed for 60 patients with a mean age of 13.9 years at 3 time points: pretreatment (T1), postexpansion (T2), and posttreatment (T3). Patients were divided into 3 groups: MARPE, RPE, and controls. Voxel-based superimposition was performed for CBCTs from T1 to T2 and T1 to T3 using the anterior cranial base as a reference. The hard-tissue surfaces were extracted after the superimposition procedure. Nine landmarks were analyzed: nasion, A-point, pogonion, left and right alar bases, zygoma, and gonion. Within-group changes were analyzed using linear mixed-effects models, including a random intercept per subject and the mixed effect of time (T1, T2, or T3) with test P values adjusted for multiple testing using Tukey's method. Between-group changes were analyzed using linear mixed-effects models, including a random intercept per subject and the mixed effects of time, group, and group × time interaction with P values adjusted for multiple testing using the Benjamin-Hochberg false discovery rate method.

RESULTS

In the short term, both MARPE and RPE led to a significant downward movement of the right gonion and lateral movement of the right alar base compared with controls at T2 (P <0.05). In addition, MARPE led to a significant downward movement of pogonion and left gonion. RPE led to a significant downward movement of the A-point and lateral movement of the left alar base compared with controls at T2 (P <0.05). However, in the long-term, no changes were observed between the groups at T3.

CONCLUSIONS

There were significant differences in pogonion, alar base, and gonion between MARPE, RPE, and control groups in the short term. However, all the hard-tissue changes were transient, as there were no differences between the 3 groups in the long term.

Three-dimensional evaluation of the temporomandibular joints after unilateral surgically assisted rapid maxillary expansion in adults: A preliminary retrospective study

BACKGROUND

Unilateral surgically assisted rapid maxillary expansion (U-SARME) is a successful method for correction of true unilateral posterior crossbite (TUPC).

OBJECTIVES

This retrospective preliminary study aimed to evaluate the position and morphology of condyles in TUPC cases and the effects of U-SARME on condyle with the help of cone beam computed tomography (CBCT).

METHODS

Fifteen patients (mean age: 18.69 ± 1.59 years) who were diagnosed as TUPC and undergone U-SARME were selected. Preoperative (T0) and after 6-month retention (T1) DICOM data of CBCT images were evaluated with MIMICs version 19.0 software. Condylar morphology (medio-lateral and antero-posterior dimensions) and position (anterior, posterior, medial and lateral joint spaces, frontal/axial axis angles, the ratio of posterior to anterior joint space and the percentage of posterior to anterior joint space) were evaluated. Student's t-test was used for intergroup (crossbite, normal) comparisons. Paired-samples t-test was used for intra-group comparisons (p = .05).

RESULTS

There were no positional or dimensional asymmetry of the condyles between crossbite and normal sides initially and after expansion. Regarding T0-T1 changes, while significant increase was determined in medial (0.3 ± 0.29 mm; p = .001) and superior (0.39 ± 0.7 mm; p = .045) joint spaces on crossbite side, posterior (0.79 ± 0.99 mm; p = .008), superior (0.5 ± 0.79 mm; p = .029) and lateral joint spaces (0.31 ± 0.54 mm; p = .042) presented significant increases on normal side. However, no significant changes were found between crossbite and normal sides at T0 and T1.

CONCLUSIONS

Condyles were symmetrical in true unilateral posterior crossbite cases and the symmetry were not disrupted following U-SARME.

"Association between posterior unilateral functional crossbite and asymmetrical spinal flexion: A prospective study"

Background

Unilateral posterior crossbite (UPC) with functional shift is a malocclusion that may have the potential to affect the masticatory function and the flexibility of the spine due to intrinsic occlusal, structural and functional asymmetries sustained by marked asymmetrical muscular activation.

Research question

To investigate whether the presence of UPC with functional shift is associated with reverse chewing pattern and altered spine flexion.

Methods

Patients with UPC and a control group of patients with normal occlusion were recorded when chewing soft and hard boluses using a Kinesiograph (Myotronics-Noromed Inc., USA) and spine alignment was assessed with an electronic inclinometer Spinal Mouse® system (Idiag AG, Switzerland).

Results

There were 87 children with UPC in the patients' group among whom 38, with median (IQR) age 8.0 (7.3-9.3) years, had measurements before and after treatment. The UPC patients showed a higher percentage of anomalous/reverse chewing patterns on the crossbite side compared with a control group (p < 0.001). Moreover, a clear difference was observed between left and right flexion angles of the spine in the patients' group (p < 0.001 and p = 0.001, paired t-test) with the crossbite side being more flexible compared to the non-crossbite side. No such differences were seen in the control group, nor post-treatment for right and left crossbite (p = 0.44 and p = 0.15 respectively, paired t-test).

Significance

This study suggests an association between UPC, asymmetrical chewing patterns and asymmetrical flexion of the spine. These results may help improve understanding of any association between dental malocclusions and spine posture and hence aid diagnosis and treatment strategies.

Normal variation of mandibular asymmetry in children

OBJECTIVE

To explore the normal variation of asymmetry in mandibles of children in the age group of 1 to 12 years.

MATERIALS AND METHODS

The study group consisted of 92 cadaveric mandibles of children with a dental age of 1 to 12 years old in possession of ACTA (Academic Centre for Dentistry Amsterdam), Faculty of Dentistry, the Netherlands. 3D models of the mandibles were obtained from CT-scans and hemimandibular volumes of all mandibles were calculated. The condylar height, ramus height, mandibular body length and the gonial angle were bilaterally determined using a novel landmark-based method, and the degree of asymmetry was calculated.

RESULTS

No relationship was found between dental age and asymmetry of the studied parameters (P < .05). The highest degree of asymmetry was found in the ramus height, whereas the gonial angle presented the lowest degree of asymmetry. A positive correlation was found between the asymmetry of the hemimandibular volume vs the height of the ramus (P < .05) and the length of the mandibular body (P < .05). An inverse correlation was found between the asymmetry of the ramus height vs the condylar height (P < .05), mandibular body length (P < .05) and gonial angle (P < .05).

CONCLUSIONS

Mandibular asymmetries in children did occur (9.8% of the included mandibles presented with a relevant overall asymmetry of ≥3%) and were unrelated to age. The different segments of the mandible seem to compensate for each other, in order to maintain a functional equilibrium.

Improvement in the transverse dimension of dental arches in mixed dentition patients with posterior crossbite treated with functional therapy

OBJECTIVES

To evaluate the effects of treatment of posterior crossbite (PXB) in the mixed dentition with the Function Generating Bite (FGB) appliance on the transverse dimension of the dental arches.

MATERIALS AND METHODS

This study included 84 PXB patients (female = 46; male = 38; mean age, 8.2 ± 1.8 years) and 69 control (C) patients (female = 31; male = 38; mean age, 8.9 ± 1.4 years). Measurements were taken with digital calipers on maxillary and mandibular study casts before (T0) and after (T1) treatment for the following measures: intermolar (IMD), intermolar gingival (IMGD), intercanine (ICD), and intercanine gingival distances (ICGD).

RESULTS

At T0, there was a significant difference in all maxillary measurements between the PXB and C groups (P < .001), reflecting maxillary hypoplasia in PXB patients. At T1, there was no difference between the groups. In PXB patients, the mean increase between T0 and T1 for IMD was 4.34 ± 2.42 mm; this difference measured 3.51 ± 2.19 mm for IMGD, 2.78 ± 2.37 mm for ICS, and 1.89 ± 1.7 mm for ICGD. There was no significant difference in mandibular measurements between groups at T0 and T1.

CONCLUSIONS

Functional therapy with FGB is effective in significantly increasing the transverse dimension of the maxillary dental arch in PXB patients. Considering its efficacy in treating masticatory dysfunction, FGB may be considered a good treatment option for the correction of PXB in growing children.

Condylar Asymmetry in Children with Unilateral Posterior Crossbite Malocclusion: A Comparative Cross-Sectional Study

Unilateral posterior crossbite (UXB) is a common, severely asymmetric malocclusion, characterized by maxillary hypoplasia and masticatory dysfunction. The aim of this research is to evaluate the asymmetry of mandibular condyles and rami in children with UXB. This comparative cross-sectional study included 33 children with UXB (girls = 15, boys = 18; mean age ± SD = 8.0 ± 1.3 years.months]) and 33 age- and gender-matched controls (girls = 15, boys = 18; mean age ± SD = 8.4 ± 1.3 years.months]). Pre-treatment OPGs were analyzed by comparing the height of condyles and rami between the sides using the method by Habets et al. (1988); the result was considered significant if the degree of asymmetry was >6%. Children with UXB showed a significantly increased asymmetry of mandibular condyles (mean ± SD = 10.7% ± 9, p < 0.001), but not of rami (mean ± SD = 1.9% ± 2.3), compared to controls. The rami did not show significant asymmetry in either group. The presence of an increased condylar asymmetry index in a developing patient with unilateral posterior crossbite is a sign of altered skeletal growth and should be considered in the diagnostic process and treatment plan.

The effectiveness of the early orthodontic correction of functional unilateral posterior crossbite in the mixed dentition period: a systematic review and meta-analysis

Objective

This systematic review and meta-analysis aimed to critically appraise the available evidence of the effectiveness of early intervention of functional unilateral posterior crossbites (FPXB) between the ages of 6 and 12 years.

Materials and methods

Electronic search in four databases (PubMed, Scopus, Embase, and Google Scholar) for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) was performed between 1^st January 1990 and 31^st October 2021. Methodological index for non-randomized studies (MINORS) for CCTs and Cochrane's risk of bias tool for RCTs were applied. The certainty of the evidence was evaluated according to the grading of recommendations, assessment, development, and evaluation (GRADE) approach.

Results

Nine studies (6 RCTs and 3 CCTs) were included in this review, and six of them were appropriate for quantitative synthesis. The meta-analysis revealed that the quad-helix (QH) was more effective than expansion plates (EP) in increasing the intermolar width (WMD = 1.25; 95% CI 0.75, 1.75; P < 0.001), and decreasing treatment time (WMD = − 3.36; 95% CI − 4.97, − 1.75; P < 0.001). The relapse rate at 5.6 years post-treatment was greater in the QH group than in the EP group (RR = 3.00); however, the difference was statistically insignificant. There was no significant difference between the QH and the EP in other outcome measures. When assessing the rapid maxillary expansion (RME), only one RCT compared the RME with an untreated control group and reported a significant increase in the maxillary intermolar and intercanine width (P < 0.001, P = 0.002, respectively) and a significant decrease in lower midline deviation (P < 0.001).

Conclusion

There is weak to moderate evidence that the treatment of functional posterior crossbite (FPXB) by the QH increased the maxillary intermolar width and the success rate and decreased the treatment duration compared to the EP. The relapse percentage was greater in the QH group. There is very weak evidence that the mandibular midline correction rate did not differ significantly between the QH and the EP modalities. The RME using the Hyrax appliance corrected the FPXB successfully; however, the strength of evidence in this regard is very low. As the quality of evidence ranged from very low to moderate in this review, we confirm the need for more RCTs with different expansion appliances in the early treatment of FPXB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40510-022-00398-4.

Mandibular asymmetry in young adult patients with unilateral posterior crossbite: A controlled retrospective CBCT study

OBJECTIVE

This study aimed to evaluate the mandibular skeletal asymmetry in pre-orthodontic patients with the unilateral posterior dental crossbite (UPCB).

MATERIALS AND METHODS

Using a retrospective design, 30 pre-orthodontic patients with a UPCB, (16 on the right side, 14 on the left side), 18 females and 12 males were selected (mean age: 21.2±4.92 years), along with 30 controls matched by age and sex with cl I occlusal relationship (mean age: 21.9±4.80 years). The patients were from an Orthodontic Department of Dental Faculty of Hamadan University of Medical Sciences and a private office from 2009 to 2013. In the UPCB group, at least one molar tooth was in the crossbite position. All the patients had initial CBCT¹ and pre-orthodontic study models. 10 linear and 3 angular measurements were performed to evaluate the mandibular skeletal asymmetry. repeated measure-ANCOVA² by controlling the effect of age and sex, T-test and paired-samples t-test were used for comparisons. Measurement's reliability was measured with ICC³ test.

RESULTS

There was a positional deviation of mandible to the crossbite side 95% CI⁴ (0.166 - 1.087). The intergroup analysis showed that Corpus Length (P≤0.014), Ramus Angle in frontal view (P≤0.046), and Condylar-Width in axial view (P≤0.029) in the crossbite side of the case group were significantly smaller than the control group. In the subjects with UPCB, mandibular condylar width was smaller in the crossbite side (17.31±2.50) relative to the non-crossbite side (18.06±2.18).

CONCLUSIONS

The adults with dental UPCB, in addition to deviation to crossbite side, may show smaller condylar head and Corpus length in crossbite side relative to the control group.

Cone beam computed tomographic evaluation of the changes in condylar position in growing patients with unilateral posterior crossbite undergoing rapid maxillary expansion followed by fixed orthodontic therapy

PURPOSE

This study aimed at assessing changes in condylar position (CP) in growing patients with unilateral posterior crossbite (UPC) undergoing rapid maxillary expansion (RME) followed by fixed orthodontic treatment (FOT) (experimental-group); and growing patients without posterior crossbite (PC) treated with FOT alone (control-group).

METHODS

Cone beam computed tomography (CBCT) images were obtained before treatment (T0), 6 months after RME (T1) and after FOT (T2) for the experimental-group (n = 19); and at T0 and T2 for the control-group (n = 22). Condylar position-related measurements including the anterior joint space (AJS), superior joint space (SJS), posterior joint space (PJS), lateral position of condyle (LC) and condylar angle (CA) were measured. Non-parametric tests were used.

RESULTS

On the crossbite side, significant increases were found in LC (P = 0.039) and CA (P = 0.007), and on the non-crossbite side significant increases were observed in SJS (P = 0.027) and LC (P = 0.001) between T0, T1 and T2 in patients with UPC. On the right and left sides in the control-group, significant increases were identified in LC (P < 0.001 and P = 0.012, respectively) between T0 and T2.

CONCLUSIONS

In growing patients with UPC, RME followed by FOT is associated with significant changes in CP-related measurements.

Evaluation of mandibular changes after rapid maxillary expansion: a CBCT study in youngsters with unilateral posterior crossbite using a surface-to-surface matching technique

OBJECTIVES

The purpose of this study was to evaluate mandibular asymmetry in youngsters with posterior unilateral crossbite (PUXB), through cone-beam computed tomography and reverse engineering technique, before and after rapid maxillary expansion (RME) treatment.

MATERIALS AND METHODS

Forty cone-beam computed tomography (CBCT) images were obtained from all patients at two time points, namely T0 acquired before the placement of a Hyrax expander and T1 after appliance removal. The CBCT scans were segmented and volume rendered into a surface there-dimensional (3D) mesh model. Thereafter, mandibular models were digitally registered by using a "best-fit" algorithm. Surface and volumetric changes, between T0 and T1, were compared by using Student's t tests.

RESULTS

A slight increase of 0.45 cm³ of the total mandibular volume was found at T1 when compared with T0 (p < 0.001). The mandibular hemi-volume on the crossbite side (CB) was slightly smaller than the non-crossbite side both at T0 and T1. However, the mean differences of hemi-volume from the CB (crossbite) and non-CB side between T0 and T1 show a decrease of 0.26 cm³ (p < 0.001). Findings for the surface-to-surface deviation analysis demonstrated a fine percentage of matching at T0 which slightly improved at T1 (p < 0.001).

CONCLUSIONS

Youngsters affected by PUXB showed a very slight and not statistically significant volumetric and morphological asymmetry between CB side and non-CB side at T0. However, the change in mean differences of 0.26 cm cannot be considered clinically relevant.

CLINICAL RELEVANCE

Mandibles in young PUXB patients exhibit only a very mild mandibular asymmetry. Although the statistically significant mean change found right after RME removal cannot be considered clinically relevant, a more consistent sample and a longer follow-up could be of interest in explaining the short-term findings.

Three-dimensional morphological and positional analysis of the temporomandibular joint in adults with posterior crossbite: A cross-sectional comparative study

OBJECTIVES

The purpose of this study was to three-dimensionally (3D) evaluate the morphological and positional features of the temporomandibular joint (TMJ) in adults with unilateral and bilateral posterior crossbite compared with aligned control subjects.

MATERIALS AND METHODS

This cross-sectional comparative study analysed cone beam computed tomography (CBCT) images of 90 adult subjects' divided into three equal groups: bilateral posterior crossbite (BCG), unilateral posterior crossbite (UCG) and control group (CG). 3D measurements of the TMJ included the following: (a) position, angulation and inclination of the mandibular condyles; (b) centralisation of the condyles in their respective mandibular fossae; and (c) volumetric measurements of the TMJ spaces. Intra- and intergroup differences were identified using the paired Student's t test and an analysis of variance (ANOVA) followed by Tukey's post hoc test, respectively.

RESULTS

Regarding the intra-group side-based comparisons, there were significant differences in the anterior and superior joint spaces and the anteroposterior condylar joint position in the UCG. Intergroup comparisons revealed significant differences in the vertical condylar inclination, medial condylar position, condylar width and height, and volumetric joint space between the unaffected side of the UCG and left sides of the other groups. There were significant differences in the anteroposterior condylar inclination, medial condylar position, condylar width and height, anterior, posterior, superior and volumetric joint spaces, and anteroposterior condylar joint position between the crossbite side of the UCG and the right sides of the other groups.

CONCLUSION

Skeletal crossbite accompanied with characteristic morphological and positional TMJ features associated with unilateral posterior crossbite and are associated with side-specific TMJ asymmetry.

Early Orthodontic Treatments of Unilateral Posterior Crossbite: A Systematic Review

We aimed to report an update of the systematic review by Petrén et al. (2003). The objective was to evaluate how orthodontic treatments can affect unilateral posterior crossbite (UPXB) in primary and early mixed dentition. Several databases were consulted, and articles published between January 2002 and March 2020 were selected. This review examines the following studies: randomized clinical trials, prospective and retrospective studies with concurrent untreated or normal control groups, and clinical trials comparing at least two treatment strategies. Among the 1581 articles retrieved from the searches, 11 studies were included. Quad-helix (QH) and expansion plate (EP) appliances were compared in three studies. One study compared rapid maxillary expansion (RME) treatment anchored on primary dentition otherwise on permanent molars. One study compared RME and a modified RME with arms extended until deciduous canine and EP. Four studies evaluated the effects of expansion appliances compared with a control group. Compared with the previous review, the quality of the included studies is higher. However, heterogeneity of treatments, different strategies in measurements, lack of a similar follow-up length, and absence of a cost-effectiveness analysis preclude the possibility of providing reliable scientific evidence on the most effective UPXB treatment in primary and early mixed dentition.

Evaluation of mandibular symmetry and morphology in adult patients with unilateral posterior crossbite: a CBCT study using a surface-to-surface matching technique

OBJECTIVES

To investigate mandibular morphology in adults affected by posterior unilateral crossbite (PUXB) and to evaluate the hemi mandibular volumes from the crossbite (CB) and non-CB sides of the same patients.

METHODS

Thirty-eight cone beam computed tomography (CBCT) images were consecutively recruited and the Digital Imaging and Communications in Medicine (DICOM)-formatted scans were volume rendered into a surface three-dimensional (3D) mesh model and volumes to obtain the 3D model of the mandibular bone. To achieve the surface point-to-point analysis of the mandibular models, a reverse engineering software was used. The same procedure was performed for an age-matched control group (19 CBCT images).

RESULTS

Total mandibular volume showed a difference of 2.46 cm3 between patients and controls, which was not statistically significant. A mean difference of 1.53 cm3 was found comparing the hemi mandibular volumes from the CB and non-CB sides of PUXB patients, this difference was statistically significant (P ≤ 0.01). Findings for the surface-to-surface deviation analysis, demonstrated a higher percentage of mismatch in patients PUXB, over 10% at 0.5 mm tolerance level.

LIMITATIONS

Limitations are related to the intrinsic surfaces matching methodology, that make difficult to evaluate discrepancies among different mandibular anatomical units.

CONCLUSION

Adult patients affected by PUXB show a greater mandibular structural asymmetry compared to controls because of a lower matching percentage obtained from the surface-to-surface matching technique.

IMPLICATIONS

Treatment of adult patients affected by PUXB should take into consideration the possibility of a mild mandibular asymmetry mainly localized at the condyle and gonial angle levels.

Evaluation of structural skeletal asymmetry of the glenoid fossa in adult patients with unilateral posterior crossbite using surface-to-surface matching on CBCT images

OBJECTIVES

To compare, using surface-to-surface (StS) matching, any shape differences between the crossbite and noncrossbite side of the glenoid fossa and articular eminence in adult patients affected by posterior unilateral crossbite (PUXB) and compare them with unaffected controls.

MATERIALS AND METHODS

32 cone beam computed tomography (CBCT) scans of patients (mean age: 23.72 ± 3.74 years) undergoing surgical maxillary expansion were analyzed to obtain three-dimensional models of the left and right glenoid fossae that were superimposed using stable anatomical reference points and then compared using StS matching to evaluate the presence of any shape differences. These findings were compared with those obtained from 16 CBCT scans of unaffected controls (mean age: 23.72 ± 3.73 years).

RESULTS

A mean difference of >11% was found between the study group and controls when comparing the matching percentages of the two sides of the glenoid fossa and articular eminence at all three levels of tolerance selected for this study. These differences were found to be highly statistically significant (P ≤ .0001).

CONCLUSIONS

According to the shape analysis findings, adult PUXB patients exhibit a higher degree of glenoid fossa and articular eminence shape differences compared to unaffected controls.

Effects of rapid maxillary expansion on temporomandibular joints

OBJECTIVE

To evaluate the impact of rapid maxillary expansion (RME) on the condylar position, disc joint, joint space, and interarticular relationship in growing patients.

MATERIALS AND METHODS

A systematic search was performed in nine databases. The clinical studies selected included those with pre- and post-magnetic resonance, conventional computed tomography or cone beam tomography in growing patients. Risk of bias assessment was performed using the Cochrane Collaboration tool for controlled clinical studies and National Heart, Lung, and Blood Institute (NHLBI) Quality Assessment for Before-After Studies With No Control Group.

RESULTS

Initially, 4303 records were identified. Only eight studies fulfilled the criteria and were included in the qualitative analysis. Of those, two were controlled clinical studies with a risk of uncertain to high bias. The remaining papers had a low to moderate risk of bias. Results showed that RME in children and adolescents promoted the following: remodeling in the head and or condylar branch, changes in condylar position and joint space, maintenance of improved symmetry between the condyles, and no ability to modify the position or shape of the articular disc.

CONCLUSIONS

RME in growing patients is able, in the short term, to modify the condyle-fossa relationship but does not change the position or shape of the articular disc. The intercondylar symmetric relationship is maintained or improved. Although the NHLBI score shows low to moderate risk of bias, the clinical relevance of these review findings is limited by Cochrane and Grades of Recommendation, Assessment, Development and Evaluation scores.

Evaluation of the Effect of Fixed Anterior Biteplane Treatment on Temporomandibular Joint in Patients with Deep Bite

OBJECTIVE

To investigate the effects of fixed anterior biteplane treatment on temporomandibular joint in deep bite patients.

METHODS

The sample comprised 17 Class II patients with deep bite and decreased lower anterior facial height. The average patient age was 9.9±0.9 years. Transcranial temporomandibular joint radiographs were obtained from the subjects before (T0) and after fixed anterior biteplane treatment (T1). Anterior joint space, posterior joint space, superior joint space, anteroposterior thickness of the condylar head, vertical height of the articular fossa, and the articular fossa slope were measured on temporomandibular joint radiographs to evaluate the position of the mandibular condyles in the glenoid fossa.

RESULTS

The average treatment duration was 8.5±2.1 months. Slope of the articular fossa, vertical height of the articular fossa, anteroposterior thickness of the condyle, posterior joint space, superior joint space, and anterior joint space showed no statistically significant difference between T0 and T1 (p>0.05).

CONCLUSION

Fixed anterior biteplane appliance treatment did not change the condyle fossa relationship in Class II deep bite patients at the time of appliance removal.

Prevalence and Severity of Mandibular Asymmetry in Non-Syndromic, Non-Pathological Caucasian Adult

Background:

Mandibular Asymmetry has been analysed in diverse, non-Caucasian groups, principally children. No large-scale analysis has been carried out on non-syndromic Caucasian adults.

Aims:

To evaluate the prevalence and severity of mandibular asymmetry; to identify gender differences and evaluate side predominance, where no actual patient concern was reported and no surgery was being contemplated.

Materials and Methods:

Dental records of 437 patients were analysed. This large patient cohort had no reports of pathology involving the rami or condyles or the TMJ. Following strict ‘Inclusion Criteria’, 200 DPTs were analysed: 96 male, 104 female patients (age range 18-93 years, average 59.41 years, SD ±13.94).

Statistical Analysis:

Intra-observer error was determined, r = 0.99. The Student t-test determined differences between the sides for ramal height measurements. and gender. The Asymmetry Index evaluated the severity of asymmetry between condylar heights and ramus.

Results:

18 % of the cohort presented substantial Mandibular Ramal Asymmetry (MRA). Male prevalence was 23.9%; female prevalence was 12.5%; severity was 18.82% and 32.88% respectively.

Conclusions:

Incidence of asymmetry, though significant, has no detrimental effect on the patient's well-being or dental health. Facial surgery that is contemplated in response to both minimal and extreme asymmetry may well be carried out as a result of other cultural demands.

Is there an asymmetry of the condylar and coronoid processes of the mandible in individuals with unilateral crossbite?

OBJECTIVES

To evaluate if there is a true skeletal asymmetry of the condylar and coronoid processes of the mandible in growing individuals with unilateral posterior crossbite (UPC) either functional or not.

MATERIALS AND METHODS

This cross-sectional study screened a total of 1120 cone beam computed tomography (CBCT) scans based on inclusion and exclusion criteria. The final sample comprised 20 CBCT images of individuals with UPC and 19 CBCT images of individuals without transverse malocclusion. The lengths of the condylar and coronoid processes were measured to evaluate asymmetry, as well as the magnitude of the mandibular lateral deviation in the UPC group.

RESULTS

There was a significant difference between the lengths of the affected and nonaffected sides of the coronoid processes in the UPC group (P < .01). The same was not observed in the condyle in the UPC group (P > .05). There were no significant differences between the groups (P > .05).

CONCLUSIONS

Although no differences in the condyle were observed, the coronoid process was asymmetric in individuals with UPC. However, this asymmetry was not considered to be clinically significant.

Correlations between dental malocclusions, ocular motility, and convergence disorders: a cross-sectional study in growing subjects

Objective

The purpose of the study was to analyze the association between dento-skeletal malocclusions, ocular motility, and convergence disorders in growing subjects.

Materials and methods

84 subjects (49 males, 35 females) with a mean age of 7.3±1.7 years were enrolled in a screening procedure for celiac disease at the Department of Gastroenterology of the University of Rome "Tor Vergata". Each child underwent an orthodontic, orthoptic, and ophtalmological examination. Pearson's Chi-Square test with Yates' correction and Fisher's exact test were conducted to assess the association between orthoptic defects and malocclusions (p<0.05).

Results

Ocular motility disorders were present in 44.9% of males and in 57.1% of females, while convergence defects were present in 10.2% of males and in 2.9% of females. Ocular motility disorders were more frequent in subjects with Angle Class III malocclusion (66.7%) than in subjects with Angle Class II (59.1%) and Class I (45.8%) malocclusion. Convergence defects were equally frequent in Angle Class I and Class II malocclusion (5.1%), while none subject presenting with Angle Class III malocclusion exhibited convergence defects. A statistically significant correlations was found between ocular motility disorders and unilateral cross-bite with midline deviation.

Conclusion

Ocular motility defects had a significant greater prevalence in subjects presenting with unilateral cross-bite and midline deviation. The importance of role of orthodontic diagnosis among interdisciplinary treatment in growing children should be recognized.

Early correction of unilateral scissor bite using transforce appliance and modified twin block appliance

Early treatment of scissor bite has been advocated mainly to prevent function jaw shift that can eventually lead to permanent skeletal asymmetry and temporomandibular joint pathosis. Although unilateral scissor bite is more common, most of the times, bilateral mandibular expansion is indicated. Lingual transforce appliance can be useful in such cases. This article presents a patient with unilateral scissor bite in mixed dentition with alveolar narrowing. Transforce appliance was used for scissor bite correction followed by modified twin block appliance for stabilization and settling of occlusion till the eruption of premolars. The case was finished with fixed mechanotherapy. Two years after completion of treatment, results were well maintained. Our results suggest that lingual transforce appliance along with careful management of occlusion is effective in the early management of severe unilateral scissor bite.

Unilateral Posterior Crossbite is Not Associated with TMJ Clicking in Young Adolescents

Unilateral posterior crossbite has been considered as a risk factor for temporomandibular joint clicking, with conflicting findings. The aim of this study was to investigate a possible association between unilateral posterior crossbite and temporomandibular disk displacement with reduction, by means of a survey carried out in young adolescents recruited from three schools. The sample included 1291 participants (708 males and 583 females) with a mean age of 12.3 yrs (range, 10.1–16.1 yrs), who underwent an orthodontic and functional examination performed by two independent examiners. Unilateral posterior crossbite was found in 157 participants (12.2%). Fifty-three participants (4.1%) were diagnosed as having disk displacement with reduction. Logistic regression analysis failed to reveal a significant association between unilateral posterior crossbite and disk displacement with reduction (odds ratio = 1.3; confidence limits = 0.6–2.9). Posterior unilateral crossbite does not appear to be a risk factor for temporomandibular joint clicking, at least in young adolescents.

Early risk factors for posterior crossbite and anterior open bite in the primary dentition

OBJECTIVE

To investigate risk factors specific to posterior crossbite and anterior open bite at the age of 3 years.

MATERIALS AND METHODS

The study included 422 children of the French EDEN mother-child cohort. The main outcomes were the presence of posterior crossbite and anterior open bite assessed by dentists at 3 years. Social characteristics (collected during pregnancy), neonatal characteristics (collected at birth), duration of breast-feeding (collected prospectively), sucking habits at 3 years, and open lips (as a proxy for mouth breathing) were studied and two logistic regressions conducted.

RESULTS

Preterm birth appears to be a risk factor specific for posterior crossbite (OR: 3.13; 95% CI: 1.13-8.68), whereas small for gestational age seems to be associated with a lower risk of posterior crossbite (OR: 0.32; 95% CI: 0.12-0.87). Ongoing pacifier or thumb sucking at 3 years is a risk factor for both posterior crossbite and anterior open bite.

CONCLUSIONS

Children born preterm seem to be more at risk for posterior crossbite than those born at term. Different mechanisms may be involved in posterior crossbite and anterior open bite.

Dental and skeletal effects of palatal expansion techniques: a systematic review of the current evidence from systematic reviews and meta-analyses

The aim was to assess the quality and to summarise the findings of the Systematic Reviews (SRs) and Meta-Analyses (MAs) on the dental and skeletal effects of maxillary expansion. Electronic and manual searches have been independently conducted by two investigators, up to February 2015. SRs and MAs on the dentoalveolar and skeletal effects of fixed expanders were included. The methodological quality was assessed using the AMSTAR (A Measurement Tool to Assess Systematic Reviews). The design of the primary studies included in each SR/MA was assessed with the LRD (Level of Research Design scoring). The evidence for each outcome was rated applying a pre-determined scale. Twelve SRs/MAs were included. The AMSTAR scores ranged from 4 to 10. Two SRs/MAs included only RCTs. The current findings from SRs/MAs support with high evidence a significant increase in the short-term of maxillary dentoalveolar transversal dimensions after Rapid Maxillary Expansion (RME). The same effect is reported with moderate evidence after Slow Maxillary Expansion (SME). However, there is moderate evidence of a non-significant difference between the two expansion modalities concerning the short-term dentoalveolar effects. With both RME and SME, significant increase of skeletal transversal dimension in the short-term is reported, and the skeletal expansion is always smaller than the dentoalveolar. Even though dental relapse to some extent is present, long-term results of the dentoalveolar effects show an increase of the transversal dimension, supported by moderate evidence for RME and low evidence for SME. Skeletal long-term effects are reported only with RME, supported by very low evidence.

The role of rapid maxillary expansion in the promotion of oral and general health

Rapid maxillary expansion (RME) is an effective orthopedic procedure that can be used to address problems concerned with the growth of the midface. This procedure also may produce positive side effects on the general health of the patient. The aim of the present consensus paper was to identify and evaluate studies on the changes in airway dimensions and muscular function produced by RME in growing patients. A total of 331 references were retrieved from a database search (PubMed). The widening of the nasal cavity base after midpalatal suture opening in growing patients allows the reduction in nasal airway resistance with an improvement of the respiratory pattern. The effects of RME on the upper airway, however, have been described as limited and local, and these effects become diminished farther down the airway, possibly as a result of soft-tissue adaptation. Moreover, limited information is available about the long-term stability of the airway changes produced by RME. Several studies have shown that maxillary constriction may play a role in the etiology of more severe breathing disorders such as obstructive sleep apnea (OSA) in growing subjects. Early orthodontic treatment with RME is able to reduce the symptoms of OSA and improve polysomnographic variables. Finally, early orthopedic treatment with RME also is beneficial to avoid the development of facial skeletal asymmetry resulting from functional crossbites that otherwise may lead to functional and structural disorders of the stomatognathic system later in life.

Mandibular asymmetry: a proposal of radiographic analysis with public domain software

Objective

This preliminary study aimed to propose a new analysis of digital panoramic radiographs for a differential diagnosis between functional and morphological mandibular asymmetry in children with and without unilateral posterior crossbite.

Methods

Analysis is based on linear and angular measurements taken from nine anatomic points, demarcated in sequence directly on digital images. A specific plug-in was developed as part of a larger public domain image processing software (ImageJ) to automate and facilitate measurements. Since panoramic radiographs are typically subject to magnification differences between the right and left sides, horizontal linear measurements were adjusted for greater accuracy in both sides by means of a Distortion Factor (DF). In order to provide a preliminary assessment of proposed analysis and the developed plug-in, radiographs of ten patients (5 with unilateral posterior crossbite and 5 with normal occlusion) were analyzed.

Results

Considerable divergence was found between the right and left sides in the measurements of mandibular length and position of condyles in patients with unilateral posterior crossbite in comparison to individuals with normal occlusion.

Conclusion

Although there are more effective and accurate diagnostic methods, panoramic radiography is still widespread, especially in emerging countries. This study presented initial evidence that the proposed analysis can be an important resource for planning early orthodontic intervention and, thus, avoid progression of asymmetries and their consequences.

Early treatment of posterior crossbite--a randomised clinical trial

Background

The aim of this randomised clinical trial was to assess the effect of early orthodontic treatment in contrast to normal growth effects for functional unilateral posterior crossbite in the late deciduous and early mixed dentition by means of three-dimensional digital model analysis.

Methods

This randomised clinical trial was assessed to analyse the orthodontic treatment effects for patients with functional unilateral posterior crossbite in the late deciduous and early mixed dentition using a two-step procedure: initial maxillary expansion followed by a U-bow activator therapy. In the treatment group 31 patients and in the control group 35 patients with a mean age of 7.3 years (SD 2.1) were monitored. The time between the initial assessment (T1) and the follow-up (T2) was one year. The orthodontic analysis was done by a three-dimensional digital model analysis. Using the ‘Digimodel’ software, the orthodontic measurements in the maxilla and mandible and for the midline deviation, the overjet and overbite were recorded.

Results

Significant differences between the control and the therapy group at T2 were detected for the anterior, median and posterior transversal dimensions of the maxilla, the palatal depth, the palatal base arch length, the maxillary arch length and inclination, the midline deviation, the overjet and the overbite.

Conclusions

Orthodontic treatment of a functional unilateral posterior crossbite with a bonded maxillary expansion device followed by U-bow activator therapy in the late deciduous and early mixed dentition is an effective therapeutic method, as evidenced by the results of this RCT. It leads to three-dimensional therapeutically induced maxillary growth effects. Dental occlusion is significantly improved, and the prognosis for normal craniofacial growth is enhanced.

Trial registration

Registration trial DRKS00003497 on DRKS

Severe facial asymmetry and unilateral lingual crossbite treated with orthodontics and 2-jaw surgery: 5-year follow-up

A 33-year-old woman with severe facial asymmetry and unilateral lingual crossbite was treated with orthodontics combined with differential maxillary impaction and intraoral vertical ramus osteotomy. After 12 months of preoperative orthodontic treatment, 2-jaw surgery was performed. The total active treatment time was 18 months. Both her occlusion and facial appearance were significantly improved by the surgical-orthodontic treatment. The occlusion was stable after 5 years of retention. Posttreatment records after 5 years showed excellent results with good occlusion and long-term stability.

A review of the oral health-related evidence that supports the orthodontic treatment need indices

BACKGROUND AND OBJECTIVES

To date, there is no evidence-based method of quantification for malocclusion. Consequently, how deviant occlusal traits should be scored and weighted relative to one another is a matter of serious debate. Orthodontic Treatment Need Indices (OTNI) use the subjective opinion of the experts, as their foundation, to define the pathological boundaries (cut-offs) of occlusal traits. This paper reviews the evidence relating malocclusions or deviated occlusal traits to oral health problems, and investigates if this evidence supports the cut-off points and the rationale used for OTNI.

MATERIALS AND METHODS

The relevant cited studies and reviews from the MEDLINE, Web of Science, Scopus, Cochrane databases, and scientific textbooks were used. The citation rate was confirmed by using the Google Scholar.

RESULTS

So far, the evidence for harmful effects of deviated occlusal traits on oral health is either lacking or exists as cross-sectional (mostly) and longitudinal (a few and primarily short-term) studies. When an association was reported between a deviated occlusal trait and an oral health problem, either the strength of that association was weak, or due to methodological issues, findings were not conclusive. Consequently, establishing a cause and effect relationship is difficult. Further, commonly used OTNI do not record a full spectrum of occlusal traits, and relating their ranking or scoring systems to the available evidence is difficult. Therefore, there is little evidence to suggest that individuals with a high need (high score), as measured by OTNI, will necessarily put at risk their oral health if they turn down orthodontic therapy.

CONCLUSION

OTNI have a role in the epidemiology and can be used for resource planning, but their predictive value to detect the future objective functional deficits or oral health problems is questionable. OTNI will need revalidation over time with emerging research findings.

Condyle fossa relationship associated with functional posterior crossbite, before and after rapid maxillary expansion

OBJECTIVE

To investigate condylar symmetry and condyle fossa relationships in subjects with functional posterior crossbite comparing findings before and after rapid maxillary expansion (RME) treatment through low-dose computed tomography (CT).

MATERIALS AND METHODS

Twenty-six patients (14 girls and 12 boys, mean age 9.6 ± 1.4 years) with functional posterior crossbite (FPXB) diagnosis underwent rapid palatal expansion with a Hyrax appliance. Patients' temporomandibular joints (TMJ) underwent multislice CT scans before rapid palatal expansion (T0) and after (T1). Joint spaces were compared with those of a control sample of 13 subjects (7 girls and 5 boys, mean age 11 ± 0.6 years).

RESULTS

Anterior space (AS), superior space (SS), and posterior space (PS) joint space measurements at T0 between the FPXB side and contralateral side demonstrated no statistically significant differences. After RME treatment (T1), all three joint spaces increased on both the FPXB side and the non-crossbite side. However, differences were statistically significant only for the SS when comparing the two sides at T1. SS increased more than AS and PS in the non-crossbite condyle (0.28 mm) and FPXB condyle (0.37 mm), and PS increased only on the FPXB side (0.34 mm).

CONCLUSIONS

There were no statistically significant differences in condyle position within the glenoid fossa between the FPXB and non-crossbite side before treatment. Increases in joint spaces were observed after treatment with RME on both sides. These changes were, however, of small amounts.

Localization of basicranium midline by submentovertex projection for the evaluation of condylar asymmetry

The purpose of this research was to compare the reliability of two different methods for cranial midline localization through cephalometric analysis of mandibular condyle asymmetries. A retrospective cohort study was performed analyzing consecutively the SMV radiograms of 47 patients undergoing oral surgery before orthodontic treatment at the Dental School, University of Trieste (Italy) from 2003 to 2008. Two different cephalometric analyses were used to identify the basicranium midline (Tracing 1: initial landmarks = craniostat ear rods; Tracing 2: initial landmarks = spinosum foramina), and the left/right symmetry ratio (SR) for four parameters (condylar length, condylar angle, intra-condylar hemidistance, extra-condylar hemidistance) was calculated. The main result showed that no significant statistical difference between the SRs of the intra-condylar and extra-condylar hemidistance obtained with the same tracing was found (t-test; P = NS; C.I. 95%). Conversely, the difference between the SRs obtained with the two different tracings was statistically significant (t-test; P < 0.000; C.I. 95%). In conclusion, if the analysis of condylar asymmetries is performed in growing subjects, utilization of anatomic references such as the neurovascular foramina seems to guarantee a lower error compared to non-fixed references such as ear rods.

Mandibular asymmetry in unilateral and bilateral posterior crossbite patients using cone-beam computed tomography

OBJECTIVE

To test the hypotheses that (1) there is no difference in mandibular asymmetry between the crossbite and normal side in a unilateral crossbite group (UCG) and between the right and left sides in a bilateral crossbite group (BCG) and a control group (CG); and (2) there is no significant difference in mandibular asymmetry among crossbite groups and control group.

MATERIALS AND METHODS

The cone-beam computed tomography scans of three groups were studied: (1) 15 patients (6 male, 9 female; mean age: 13.51 ± 2.03 years) with unilateral posterior crossbite; (2) 15 patients (8 male, 7 female; mean age: 13.36 ± 2.12 years) with bilateral posterior crossbite; and (3) 15 patients (8 male, 7 female; mean age: 13.46 ± 1.53 years) as a control group. Fourteen parameters (eight linear, three surface, and three volumetric) were measured. Side comparisons were analyzed with paired samples t-test, and for the intergroup comparison, analysis of variance (ANOVA) and Tukey tests were used at the P < .05 level.

RESULTS

According to side comparisons, no statistically significant difference was found in the UCG. There were statistically significant differences in hemimandibular (P = .008) and ramal (P = .004) volumes for the BCG and in ramal height (P = .024) and body length (P = .021) for the CG. Intergroup comparisons revealed significant differences in hemimandibular (P = .002) and body volume (P < .001) for the normal side of the UCG and left sides of the other groups, and in angular unit length (P = .025) and condylar width (P = .007) for the crossbite side of the UCG and the right sides of the other groups.

CONCLUSIONS

Contrary to UCG, CG and BCG were found to have side-specific asymmetry. Skeletal components of the mandible have significant asymmetry among the crossbite groups and the CG.

A preliminary anatomical study on the association of condylar and occlusal asymmetry

The aim of this study was to test the hypothesis that condylar and occlusion asymmetry are not associated. For each of 22 skulls, the asymmetry of condyles was graded by one examiner and the asymmetry of occlusion by another examiner, both blinded to each other's evaluation, as 0 = symmetrical, 1 = mild asymmetrical and 2 = severe asymmetrical. There were 18 condyles graded the same as to their occlusion, but in four, the grades differed by one degree. Nine were graded symmetrical, seven were mild, and six were graded severely asymmetrical condyles. The corresponding figures for occlusion were: 10 were graded symmetrical, seven were graded mildly asymmetrical, and five were graded severely asymmetrical occlusion. The relation between occlusion and condylar asymmetry was tested using Goodman-Kruskal's gamma and was found to be 0.970 (p < 0.001). The null hypothesis was not supported. The results indicate that asymmetry of occlusion and condyles are associated, which indicates the need for further studies on larger samples, and in vivo studies.

Characteristics of masticatory muscles in children with unilateral posterior crossbite

The aim of this study was to detect possible differences in the EMG (electromyography) activity, chewing rate (CR), cycle duration (CD) and preferred chewing side (PCS) between children with and without unilateral posterior crossbite. Thirty-seven children aged from 7 to 10 years were selected from the clinic of the Department of Pediatric Dentistry, Piracicaba Dental School, Brazil, and divided into two groups: unilateral posterior crossbite (UPCB group, n = 17), and normal occlusion (NOccl group, n = 20). The PCS was determined using a visual spot-checking method. The EMG activity was recorded during mastication, and two chewing sequences of 20 s were evaluated to establish each subject's CR (cycles/sec) and CD. UPCB and NOccl groups did not have a PCS. The EMG activity and the cycle characteristics did not differ between the groups. The correlations between CD, CR and EMG activity were statistically significant for the masseter and anterior temporalis muscles only in the NOccl group, in which there was also a significant correlation between the EMG activity of masseter and anterior temporalis. In conclusion, these findings suggest that although children with and without UPCB presented a bilateral masticatory pattern with similar CR and CD, balanced EMG activity of masseter and anterior temporalis muscles was observed only in the NOccl group. These results indicate that in children, UPCB can alter the coordination of masticatory muscles during mastication.

Slow or rapid palatal expansion for early treatment of unilateral posterior crossbite? Evaluation of the reverse chewing cycles correction

OBJECTIVES

It is well established that patients with a unilateral posterior crossbite, when chewing on the affected side, show an increased frequency of reverse chewing cycles. It was hypothesized that the correction of reverse cycles may be due to the characteristics of the therapy. The aim was to investigate the prevalence of reverse chewing patterns in children with unilateral posterior crossbite before and after treatment with Function Generating Bite (FGB).

MATERIALS AND METHODS

Twenty children, (9 boys, 11 girls; age, mean ± SD, 7.5 ± 1.1), 10 with a right and 10 with a left posterior unilateral crossbite were selected. Mandibular movements during chewing soft and hard boluses were measured with a kinesiograph (K7 -I, Myotronics Inc. Tukwila, Washington, USA).

RESULTS

The results showed a significant difference when comparing the percentage of reverse chewing patterns, before and after therapy with FGB, during chewing on the crossbite side both with soft and hard bolus (p<0.0001). No significant differences were observed during chewing on the non-crossbite side.

DISCUSSION

The results of this study confirmed that FGB corrects both the dental and functional asymmetries. Knowing that the rapid palatal expansion does not correct the masticatory function, it is of clinical relevance, for the orthodontists, the knowledge and the understanding of the functional outcomes with different therapies.

CONCLUSIONS

The type of treatment and the biomechanics of the appliance used are of great importance for the correction of the reverse chewing cycles and for rebalancing the functional asymmetry of children with unilateral posterior crossbite.