Mandible In Subjects Research Articles

Mandibular response after rapid maxillary expansion in mixed dentition children with different vertical growth patterns: a retrospective study.

This study evaluated the mandibular development induced by rapid maxillary expansion (RME) therapy in mixed dentition patients with different vertical growth patterns through long-term observation. The research utilized a retrospective design that included two cohorts: a control group consisting of pediatric subjects with individualized malocclusions, and an experimental group received RME therapy. A total of 60 subjects were included; 37 in the RME group (17 males and 20 females) and 23 in the control group (13 males and 10 females). Based on mandibular plane angles, 19 pertinent cephalometric variables were quantified with Dolphin Imaging software, and participants were subclassified into high-angle and normal-angle subgroups. Changes in the groups during the observation period were statistically analyzed with a t-test. Compared to the control group, both sagittal parameters tended to decrease after treatment in the RME group (p < 0.05), and none of the vertical correlations were statistically different (p > 0.05). Within the normal-angle experimental subgroup, sagittal parameters markedly decreased when contrasted with their normal-angle control group (p < 0.05). Notably, a substantive decrease in overjet was solely observable in the sagittal dimension among the high-angle expansion subgroup when compared to the high-angle control subgroup (p < 0.05). In the vertical dimension, neither the normal-angle nor high-angle subgroups exhibited any statistically significant differences from their respective control cohorts (p > 0.05). Based on long-term observation, RME therapy promotes mandible sagittal growth of the mandible in subjects with normal-angle vertical growth patterns. A similar tendency was not observed in subjects with high-angle vertical growth patterns. In addition, the mandibular plane angle did not increase after RME in children with high-angles.

Establishment of soft tissue norms for sagittal discrepancy for maxilla and mandible in central Gujarat population

Objective: To establish the cephalometric norms of ‘Zero meridian line’ and ‘Mew line’ to assess the sagittal discrepancy in the maxilla and mandible of subjects in the Central Gujarat population Materials and methods: The sample was screened from the records from the hospital. 100 individuals (50 males, 50 females) of the age group between 18-50 years, native of Central Gujarat, with acceptable pleasing profile, no skeletal asymmetry, normal Class I occlusion having ideal anterior bite, less than 2 mm crowding and no history of previous orthodontic treatment were selected for the study. Lateral cephalograph were taken in natural head position. The linear measurements between points of soft tissue pogonion to the Zero Meridian line (vertical line dropped from soft tissue nasion) and distance of Mew line (the biting edge of the upper front teeth to the tip of the nose) was taken on cephalograms. Result: Mean value for soft tissue pogonion to the Zero meridian line on cephalograms was 0.2 mm for female and 0.8 mm for male and mean value for Mew line on cephalograms was 39 mm for female and 42 mm for male subjects. Conclusion: Normal value for soft tissue pogonion to the Zero meridian line is 0.8 + 1.8 mm for males and 0.2 + 1.7 mm for females, and normal value for Mew line is 41.2 + 3.2 mm for male and 39.4 + 2.2 mm for female in Central Gujarat population. Values other than normal suggests skeletal sagittal discrepancy of maxilla and/or mandible, which is helpful in diagnosis and treatment planning.

Changes in the pharyngeal airway after different orthognathic procedures for correction of class III dysplasia

ObjectiveThis study was conducted to compare changes in pharyngeal airway after different orthognathic procedures in subjects with class III deformity.MethodsThe study included CBCT scans of 48 skeletal class III patients (29 females and 19 males, mean age 23.50 years) who underwent orthognathic surgery in conjunction with orthodontic treatment. The participants were divided into three groups of 16, as follows: Group 1, mandibular setback surgery; group 2, combined mandibular setback and maxillary advancement surgery; and group 3, maxillary advancement surgery. CBCT images were taken 1 day before surgery (T0), 1 day (T1), and 6 months (T2) later. The dimensions of the velopharynx, oropharynx, and hypopharynx were measured in CBCT images.ResultsIn all groups, there was a significant decrease in airway variables immediately after surgery, with a significant reversal 6 months later (P < 0.05). In subjects who underwent maxillary advancement, the airway dimensions were significantly greater at T2 than the T0 time point (P < 0.05), whereas in the mandibular setback and bimaxillary surgery groups, the T2 values were lower than the baseline examination (P < 0.05). The alterations in airway variables were significantly different between the study groups (P < 0.05).ConclusionsThe mandibular setback procedure caused the greatest reduction in the pharyngeal airway, followed by the bimaxillary surgery and maxillary advancement groups, with the latter exhibiting an actual increase in the pharyngeal airway dimensions. It is recommended to prefer a two-jaw operation instead of a mandibular setback alone for correction of the prognathic mandible in subjects with predisposing factors to the development of sleep-disordered breathing.

Three‐dimensional analysis of the temporal bone and mandibular morphology in mandibular prognathism with facial asymmetry

AbstractThe aims of this study were to perform a three‐dimensional analysis of the craniofacial area, in particular, the temporal bone and to examine the morphological relationship between the temporal bone and asymmetry of the mandible in subjects with mandibular prognathism and facial asymmetry. Subjects were 50 adult orthognathic patients with facial asymmetry and mandibular prognathism. The initial computed tomographic data were reconstructed into three‐dimensional and multiplanar reconstruction images. Linear and angular measurements of the temporal bone and the mandible were obtained. Then deviated and non‐deviated sides were compared and the relationship between the temporal bone and mandibular morphology was investigated. The lengths of the mandibular body and ramus, the anteroposterior and vertical positions of the mandibular fossa, and the slant angle of the posterior surface of the petrous pyramid were significantly smaller (P &lt; .05) on the deviated side than on the non‐deviated side. Further, the left‐right differences in the temporal bone were positively correlated with a deviation of the mandible and differences in the lengths of the mandibular body and ramus (P &lt; .05). The results suggest that asymmetry of the temporal bone is closely related to mandibular asymmetry and might have an important role in the mechanism of facial asymmetry.

Three-dimensional measurement and analysis of mandibular characteristics in subjects with impacted mandibular second molars.

To investigate the morphological characteristics of the mandible in subjects with impacted mandibular second molars by measuring and analysing the mandible in three dimensions. In this retrospective study, the data of a total of 52609 subjects who underwent cone-beam computed tomography (CBCT) for diagnosis and treatment were reviewed. According to the inclusion and exclusion criteria, 183 subjects with impacted mandibular second molars and 176 age- and sex-matched controls were included. A retrospective case-control study was designed. The 183 subjects were divided into two groups: group 1 (G1) comprised 120 patients with unilaterally impacted mandibular second molars, and group 2 (G2) comprised 63 patients with bilaterally impacted mandibular second molars. Group 3 (G3) contained 176 age- and sex-matched controls. The mandible was reconstructed with nineteen landmarks using Mimics software. Twelve linear lengths and 3 angles were measured. The bilateral germination gap, mandibular body width and gonion width in G1 were significantly lower than those in G3 (P<.05), while the gnathion angle and first molar width values in G1 were significantly higher than those in G3 (P<.05). The results in G2 were similar to those in G1, but the differences between G2 and G3 were greater than those between G1 and G3. There were no significant differences in the other measurements among the groups. The mandibles of the subjects with impacted second molars were constricted in terms of the sagittal length and transverse width.

Buccal cortical bone thickness in different sagittal skeletal relationship

PurposeTo assess buccal cortical bone thickness of the alveolar process in the maxilla and mandible in subjects with different skeletal relationship as an aid in orthodontic miniscrew placement. Materials and methodsThe study was carried out using cone-beam computed tomography (CBCT) images of 94 adult subjects with skeletal Class I, II or III sagittal relationship and normal mandibular plane angle. Buccal cortical bone thickness was obtained at the alveolar processes from canine to second molar at 2 different vertical levels (6, and 8mm) from the cementoenamel junction (CEJ). Analysis of variance (ANOVA) was used to analyse differences in cortical bone thickness. ResultsThe difference in mean values of buccal Cortical thickness was significant between the three skeletal classes in both arches and all sites except for the site between first and second mandibular molars (P<0.05). In the mandible, buccal cortical plate was thickest between first and second molar in all skeletal classes. In the maxilla, the highest cortical bone thickness for Class I subjects was between first and second molar, for Class II subjects was between canine and first premolar, and for Class III subjects was between first and second premolar. Mandibular measurements increase apically and posteriorly in all skeletal classes. ConclusionsBuccal cortical bone thickness could be influenced by skeletal relationship. The mandible shows a similar pattern for all skeletal classes. In the maxilla each skeletal relationship shows a different pattern. Skeletal relationship need to be considered in site choice for miniscrew placement.

Transverse dimension of the alveolar bone in different masticatory patterns

Aim: The aim of this study was to evaluate, through cone beam computed tomography (CBCT), the transverse dimension of the alveolar bone in the posterior region of the maxilla and mandible in subjects with different patterns of mastication, comparing both sides of the arches according to the performance of the masticatory function. Methods: 39 subjects not orthodontically treated, with normal occlusion or symmetrical malocclusion, and normal periodontal condition were selected. Twenty-one subjects (54%) were identified as having preferential unilateral mastication, 11 subjects (28%) had bilateral mastication and 7 (18%) had exclusive unilateral mastication. All participants were submitted to CBCT and the buccolingual dimension of the posterior regions was evaluated at a height of 2, 4, 6, 8, and 10mm from the alveolar crest. Results and Conclusion: Subjects with bilateral mastication showed statistically significant difference between the right and left sides at the heights of 6 (p=0.030) and 8mm (p=0.023) between the first and second maxillary premolars. There was no difference in the transverse dimension of the alveolar bone in the posterior regions of maxilla and mandible between preferred and non-preferred sides in subjects with preferred unilateral mastication and between right and left sides in subjects with bilateral mastication.

Evaluation of the laterality of the tissue oxygen saturation of masticatory muscles in subjects with facial asymmetry

PurposeIn subjects with facial asymmetry (FA), both morphological and functional lateralities in the masticatory muscles have been reported in literature. However, most studies evaluated masticatory muscle activity by electromyography. No report has analyzed tissue oxygen saturation (StO2) in subjects with FA. In this study, we aimed to investigate the hemodynamic laterality by measuring the bilateral masticatory muscle StO2 in subjects with FA. Materials and methodsThe subjects were divided into three groups: Group A, Class III skeletal relationship with mandibular deviation of ≥3.0mm; Group B, Class III skeletal relationship with mandibular deviation of <3.0mm; and Group C, normal skeletal relationship and occlusion. We used near-infrared spectroscopy to measure the bilateral masticatory muscle StO2 at rest, immediately after maximum clenching for 10s, and 30s after maximum clenching. We calculated the reduction rate of StO2 after maximum clenching and its recovery rate after 30s from the end of clenching, and statistically compared both sides within each group. ResultsWith regards to the reduction and recovery rates of StO2, significant difference was not found between sides in Groups B and C. However, a significant difference was observed in Group A; the reduction rate was significantly larger, and the recovery rate was significantly smaller in the side of mandibular deviation. ConclusionsHemodynamic laterality was found in the masticatory muscles between the deviated and non-deviated sides of the mandible in subjects with FA.

Assessment of Interradicular Spaces for Miniscrew Placement in Class I Subjects

Objectives: To assess interradicular spaces of maxilla and mandible in subjects with class I sagittal skeletal relationship as an aid for miniscrew placement. Materials and Methods: The study was carried out using cone-beam computed tomography (CBCT) images of 47 adult subjects with class I skeletal relationship. Interradicular spaces were obtained at the alveolar processes from first premolar to second molar at 2 different vertical levels (6 and 8mm) from the cementoenamel junction (C.E.J). Results: In the maxilla, the highest interradicular space existed between second premolar and first molar. In the mandible, the highest interradicular space existed between first and second molar. All mandibular measurements were higher than their respective maxillary measurement. Generally, availability of interradicular space increases apically in both arches, but the difference is not significant. In the maxilla, male subjects’ measurement were significantly higher at 8 mm level between second premolar and first molar and between first and second molar Conclusions: Interradicular spaces in the maxillary and mandibular alveolar spaces are available for miniscrew placement. In both arches, a more apical location provides more interradicular space. However, careful planning is needed to avoid sinus perforation.

Are all mandibles golden? A cephalometric study of mandibular morphology as compared to the golden proportion

Objective: To evaluate the ratio of the condylar axis and corpus axis of the mandible in subjects with different growth pattern and sagittal skeletal relation. To assess if the above ratio is similar to the golden ratio in all the groups of patients. Materials and Methods: pretreatment lateral cephalograms of adult patients were analyzed and six groups were selected with 30 patients in each group. (male: 15, female: 15). The characteristics of each group were: Group 1 - patients with average growth pattern, Group 2 - horizontal growth pattern, Group 3 - vertical growth pattern, Group 4 - class-I skeletal bases, Group 5 - class-II skeletal bases, and Group 6 - class-III skeletal bases. The cephalograms were traced manually and the ratio between condylar and corpus axis was calculated using Golden ratio software ( http://www.markuswelz.de/software2/index.html ). The mean ratio for each group was calculated and this ratio was compared with the golden ratio (0.6180) using sample t test. P value was set at 0.05. Results: No statistically significant difference ( P > 0.05) was found between the mean value of the ratio of condylar to corpus axis of the mandibles and the golden ratio in all groups except the vertical growth pattern group ( P Conclusion: In the sample studied, the ratio of condylar axis to corpus axis in all groups closely matches the golden ratio except in the vertical growth pattern patients where the ratio was significantly reduced (0.6151).

Morphologic quantification of the maxilla and the mandible with cone-beam computed tomography

The purpose of this pilot study was to use cone-beam computed tomography (CBCT) to determine the volumes of the maxilla and the mandible in subjects with skeletal Class I, Class II, and Class III malocclusions. Hypothesis 1 was that the volume (size) of a skeletal Class II maxilla is larger than those of Class I and Class III. Hypothesis 2 was that the volume of a skeletal Class III mandible is larger than those of Class I and Class II. Thirty women patients were classified into 3 groups according to their skeletal pattern: skeletal Class I (0 degrees < or =ANB <6 degrees ), Class II (ANB > or =6 degrees ) and Class III (ANB <0 degrees ). The volumes of the maxilla and the mandible were measured with CBCT. CB MercuRay (Hitachi Medico, Tokyo, Japan) and CB works software (CyberMed, Seoul, Korea) were used to process the images. There was a trend that skeletal Class III subjects might have significantly greater mandibular volume compared with Class II subjects (P = 0.089). The ratios of maxilla-to-mandible volumes between the skeletal Class II and Class III groups were significantly different (P = 0.005). Differences were observed in the ratios of maxillary and mandibular volumes across the 3 groups. Hypotheses 1 and 2 were rejected; there was no trend for Class III subjects to have larger mandibles (P = 0.089) compared with Class II subjects. The ratio of the maxilla and mandible volumes in skeletal Class III subjects was significantly larger (P = 0.005) compared with Class II subjects.

Age-related disruption of the lamina dura: Evidence in the mandibular horizontal incompletely impacted third molar

Changes in the lamina dura are associated with dental diseases around the root of the tooth and with systemic diseases; however, the lamina dura below the crown of horizontal, incompletely impacted third molars has not been studied. Using orthopantomography, we studied the age of subjects with and without the lamina dura in 419 subjects. The participants were between the ages of 21 and 89 years. Mean age in men with the lamina dura was 30.29 +/- 9.92 and without the lamina dura was 47.64 +/- 16.32 (P < 0.0001), and in women with a lamina dura it was 29.65 +/- 8.19 and without a lamina dura 41.97 +/- 11.07 (P < 0.0001). To study the effect of aging, the relationship between the lamina dura and dental status was assessed in subjects over the age of 31 years. Alveolar bone resorption in the canine and the first molar of the ipsilateral mandible in subjects without the lamina dura was not significantly higher than in those with the lamina dura. There were no significant differences in the number of teeth lost, except in men, the number of treated teeth and the number of decayed teeth differed between groups. Disruption of the lamina dura was related to age, but with no alveolar bone resorption in the mandible.

Longitudinal study of temporomandibular joint disc status and craniofacial growth

The objective of this retrospective cohort study was to assess the association of temporomandibular joint (TMJ) disc status and craniofacial growth. Seventy-nine subjects (52 female, 27 male) with and without TMJ disc abnormalities were followed for a mean time of 3 years 8 months. Of this sample, 40 subjects (21 female, 19 male) received orthodontic treatment. Disc displacement and disc length measurements from magnetic resonance imaging of the jaw joints were used to evaluate TMJ disc status. A principal component analysis was used to produce a single disc status score per subject. Horizontal and vertical growth changes were obtained from cephalometric radiographs. The Fishman skeletal maturation index system was used to obtain the percentage of the total craniofacial growth attained. In addition, previous orthodontic treatment and time frames between the follow-up cephalometric radiographs were considered. A stepwise multiple linear regression analysis was used to evaluate the influence of TMJ disc status and orthodontic treatment on the displacement vectors between initial records (T1) and final records (T2) for each cephalometric point. Less horizontal and vertical growth was found in specific regions of the maxilla and the mandible in subjects with TMJ disc abnormalities, although their respective determination coefficients were mild (R2 <11.2%). TMJ disc abnormality was associated with reduced forward growth of the maxillary and mandibular bodies. TMJ disc abnormality was associated with reduced downward growth of the mandibular ramus.

Morphometric Analysis of the Mandible in Subjects with Class III Malocclusion

This study evaluated the deformations that contribute to Class III mandibular configuration, employing geometric morphometric analysis. Lateral cephalograms of male and female groups of 100 young adults and 70 children with Class III malocclusion were compared to those of counterparts with normal occlusion. The sample included an equal number of both genders. The cephalographs were traced, and 12 homologous landmarks were identified and digitized. Average mandibular geometries were generated by means of Procrustes analysis. Thin-plate spline analysis was then applied to mandibular configurations to determine local form differences in male and female groups of adults and children with normal occlusion and Class III mal-occlusion. The mandibular morphology was significantly different between these two groups of male and female adults, and children (p < 0.0001). This spline analysis revealed an anteroposterior elongation of the mandible along the condylion-gnathion axis, showing an extension in the regions of the mandibular condyle and ramus, and of the anteroinferior portion of the mandibular symphysis in Class III groups. More extension was evident in Class III adults. The deformations in subjects with Class III malocclusion may represent a developmental elongation of the mandible anteroposteriorly, which leads to the appearance of a prognathic mandibular profile.

Mandibular morphology and growth with and without hypodontia in subjects with Pierre Robin sequence

Mandibular micrognathia is the hallmark of Pierre Robin sequence (PRS). A high prevalence of mandibular hypodontia has been reported in subjects with PRS. The hypothesis of this study is that the morphology of the mandible in subjects with PRS and mandibular hypodontia is different from that in subjects with PRS but without mandibular hypodontia. The study was conducted at the craniofacial center of The Hospital for Sick Children in Toronto. The study sample comprised 16 caucasian children with nonsyndromic PRS (7 boys, 9 girls) with mandibular hypodontia and 18 white children with nonsyndromic PRS (6 boys, 12 girls) without hypodontia. Longitudinal lateral cephalograms were available before orthodontic treatment (T1; mean age, 11.7 years) and after orthodontic treatment but before orthognathic surgery (T2; mean age, 16.6 years). A new, customized cephalometric analysis with additional landmarks and measurements to study mandibular morphology was performed. Differences in measurements were studied by using analysis of variance adjusted for age and sex. Cephalometric measurements were smaller in the group with mandibular hypodontia at T1: mandibular length (3.36 mm, P = .04), ramal length (2.78 mm, P = .04), posterior facial height (3.97 mm, P = .03), and mandibular molar eruption (1.96 mm, P = .02). At T2, the differences increased: mandibular length (4.56 mm, P = .02), ramal length (4.04 mm, P = .002), posterior facial height (5.98 mm, P = .001), and mandibular molar eruption (2.08 mm, P = .04). Comparison of growth increments between the 2 groups from T1 to T2 showed a greater cranial base deflection increment in the group with mandibular hypodontia (0.88 degrees, P = .02) and a larger posterior facial height increment in the group without mandibular hypodontia (2.02 mm, P = .04). Children with nonsyndromic PRS with mandibular hypodontia had smaller mandibles than children with nonsyndromic PRS and normal complements of mandibular teeth. Their patterns of growth did not improve during adolescence, and the magnitude of differences increased.

Mandibular growth in subjects with infraoccluded deciduous molars: a superimposition study.

The aim of this longitudinal cephalometric study was to analyze the growth characteristics of the mandible in subjects with infraocclusion of the mandibular deciduous molars. A group of 28 subjects with bilateral infraocclusion of mandibular deciduous molars (IG) were enrolled in a prospective longitudinal study on the growth characteristics of the mandible and compared with a control group (CG) of 28 subjects. Lateral cephalograms were collected in both groups at T1 and at T2, after a mean 19-month interval in the IG and after a mean 16-month interval in the CG. All subjects were observed in the early mixed dentition before the pubertal peak and did not receive any orthodontic treatment during the observation interval. Cephalometric analysis at T1 and superimposition of tracings at T1 and T2 were performed, and statistical comparisons between the two groups were carried out by means of independent sample t-tests. Discriminant analysis on the superimposition data identified Co-Gn angle (angle formed by line Co-Gn at T1 and at T2) as the single discriminant variable between IG and CG. There were significant differences between the two groups as to morphological changes of the mandible and direction of condylar growth, thus demonstrating anterior growth rotation of the mandible in subjects with infraocclusion. Because of the high levels of alveolar bone turnover and remodeling in anterior rotating mandibles, this study suggested that skeletal growth characteristics of the mandible may influence the clinical expression of infraocclusion.

Vertical changes following orthodontic extraction treatment in skeletal open bite subjects.

The purpose of this investigation was to assess the vertical changes occurring in skeletal open bite patients treated orthodontically with different extraction patterns. The study was conducted using lateral cephalometric radiographs taken before and after treatment. Fifteen patients who had an anterior open bite (AOB) only were treated with first premolar extractions (Group E4). Seventeen patients with an AOB extending to the posterior teeth were grouped according to the extractions: extraction of second premolars (Group E5) and first molars (Group E6). Cephalometric data were analysed according to the 'two-factor experiment with a repeated measure on one factor' model. The treatment group factor had three levels, E4, E5, and E6, and the time factor two levels, pre- and post-treatment. The differences between the pre- and post-treatment periods were statistically significant for all the cephalometric variables (P < 0.001, P < 0.0001), except for ANS-Me/Na-Me. The time and group interaction were found to be statistically significant for the variables where the time factor is important, such as SN-GoGn angle, SGn-NBa angle, ANS-Me dimension, Na-Me dimension, forward movement of the maxillary and mandibular molars, and the distance to the mandibular plane of the lower molars. The severity of vertical dysplasia did not change in group E4. Generally, however, within the appropriate indications, extraction of the second premolars or the first molars led to a closing rotation of the mandible in subjects with a skeletal AOB extending to the posterior teeth.

Mandibular alveolar bone resorption: A vertical assessment

T he extraction of teeth is invariably followed by continuous and irreversible loss of residual alveolar bone.’ This continuing resorption takes place in both maxillary and mandibular residual ridges, although mandibular resorption presents a more serious problem to the prosthodontist. The alveolar ridges provide retention and support for complete dentures as well as for some forms of partial dentures; therefore, a technique by which the degree of alveolar bone resorption could be quantified would provide the dentist with valuable information. For example, the dentist could assess effects of various forms of prosthodontic treatment on the rate of alveolar bone resorption. Wical and Swoope* investigated the possibility of using the inferior border of the mental foramen as a reference point to estimate the original retrospective bone height of the edentulous mandible. They assumed that the relationship of the mental foramen to the splenium (lower border of the mandible from gonian to gnathion), as described by GabrieJ3 remains relatively constant in spite of increasing age or resorption of the residual ridge above the mental foramen. They postulated that if it could be demonstrated that the relatively stable bone below the foramen had a constant proportional relationship to the “full” bone height of the body of the mandible in subjects with no bone resorption, then this relationship might be used to estimate the original height of an edentulous mandible that had undergone resorption. To test their hypothesis, Wical and Swoope* measured the full bone height of the body of the mandible as well as the distance between the lower border of the mental foramen and the splenium. These measurements were made from radiographic images of panoramic radiographs of the jaws of adult subjects with little or no evidence of residual resorption. From these measurements they established a mean proportional ratio of