Intergonial Width Research Articles

Use of a Mandibular Plate to Maintain Intergonial Width in a Partially Edentulous Patient Undergoing Mandibular Symphysis Reconstruction

One of the most challenging and essential aspects of management of patients with traumatic or ablative deformities involving the mandibular symphysis is maintenance of intergonial width. Classically, the use of occlusal splints has been a simple and cost-effective solution to this problem. Patients who are edentulous, the use of Gunning splints with circummandibular wires is an alternative strategy. In the present report, we describe the use of a mandibular fixation plate for maintenance of intergonial width in an edentulous patient with a postablative mandibular symphysis defect.

Evaluation of Facial Anthropometric Parameters in 11-17 Year Old Boys

Anthropometry is the study of qualitative specifications based on linear and angular measurements of human body. The aim of the present study was to determine anthropometric parameters of 11-17 year old boys of northeast Iran. This cross-sectional analytical study was conducted on 583 boys of Fars ethnicity living in Mashhad with Class I skeletal and dental relationships. Digital photographs in natural head position were transferred to a computer and the desired anthropometric landmarks were traced on each image. Anthropometric parameters including the width of the forehead, the width of the face, the width of the cranial base, intergonial width, intercanthal width, binocular width, nasal width, mouth width, facial and nasal height and depth of superior, middle and inferior one-third of the face were measured by "Smile Analyzer" software. ANOVA, Tukey test, and linear regression were used for statistical analysis. Most of the parameters studied increased gradually with age. A growth spurt was evident at the ages of 15-16 years old for binocular width, nasal width, nasal height and depths of middle and inferior one-third of the face. Facial height was among some parameters which were found to increase slightly after 16. Unlike the other parameters, intercanthal width showed an irregular pattern of changes and statistical analysis did not show any significant differences among different age groups (P-value = 0.362). Aging of the face occurs in spurts and at different periods of life. During the studied time span, significant growth in most anthropometric parameters except intercanthal width was obvious.

The stability of mandibular prognathism corrected by bilateral sagittal split osteotomies: a comparison of bi-cortical osteosynthesis and mono-cortical osteosynthesis

This study evaluated the differences in surgical changes and post-surgical changes between bi-cortical and mono-cortical osteosynthesis (MCO) in the correction of skeletal Class III malocclusion with bilateral sagittal split osteotomies (BSSOs). Twenty-five patients had bi-cortical osteosynthesis (BCO), 32 patients had mono-cortical fixation. Lateral and postero-anterior cephalometric radiographs, taken at the time of surgery, before surgery, 1 month after surgery, and on completion of orthodontic treatment (mean 9.9 months after surgery), were obtained for evaluation. Cephalometric analysis and superimposition were used to investigate the surgical and post-surgical changes. Independent t-test was performed to compare the difference between the two groups. Pearson's correlations were tested to evaluate the factors related to the relapse of the mandible. The sagittal relapse rate was 20% in the bi-cortical and 25% in the mono-cortical group. The forward–upward rotation of the mandible in the post-surgical period contributed most of the sagittal relapse. There were no statistically significant differences in sagittal and vertical changes between the two groups during surgery and in the post-surgical period. No factors were found to correlate with post-surgical relapse, but the intergonial width increased more in the bi-cortical group. The study suggested that both methods of skeletal fixation had similar postoperative stability.

Effect of gender, facial dimensions, body mass index and type of functional occlusion on bite force

ObjectiveSome factors such as gender, age, craniofacial morphology, body structure, occlusal contact patterns may affect the maximum bite force. Thus, the purposes of this study were to determine the mean maximum bite force in individuals with normal occlusion, and to examine the effect of gender, facial dimensions, body mass index (BMI), type of functional occlusion (canine guidance and group function occlusion) and balancing side interferences on it.Material and MethodsThirty-four individuals aged 19-20 years-old were selected for this study. Maximum bite force was measured with strain-gauge transducers at first molar region. Facial dimensions were defined by standardized frontal photographs as follows: anterior total facial height (ATFH), bizygomathic facial width (BFW) and intergonial width (IGW). BMI was calculated using the equation weight/height2. The type of functional occlusion and the balancing side interferences of the subjects were identified by clinical examination.ResultsBite force was found to be significantly higher in men than women (p<0.05). While there was a negative correlation between the bite force and ATFH/BFW, ATFH/IGW ratios in men (p<0.05), women did not show any statistically significant correlation (p>0.05). BMI and bite force correlation was not statistically significant (p>0.05). The average bite force did not differ in subjects with canine guidance or group function occlusion and in the presence of balancing side interferences (p>0.05).ConclusionsData suggest that bite force is affected by gender. However, BMI, type of functional occlusion and the presence of balancing side interferences did not exert a meaningful influence on bite force. In addition, transverse facial dimensions showed correlation with bite force in only men.

Transverse Displacement and Angulation of the Proximal Segment After Mandibular Setback by Means of Bilateral Intraoral Vertico-Sagittal Ramus Osteotomy

The purpose of this study was to assess the transverse displacement and angulation of the proximal segment after a bilateral intraoral vertico-sagittal ramus osteotomy (IVSRO) and its relation with mandibular setback. Sixty patients were recruited into this study and underwent a mandibular setback with bilateral IVSRO with wire fixation. Posteroanterior and lateral cephalometric radiographs were obtained 1 month before and 1 month after surgery. The transverse displacement and angulation of the proximal segments after surgery were measured on posteroanterior radiographs, via the best-fit method. The correlation of the amount of mandibular setback with the amount of transverse displacement and angulation of proximal segment was also assessed. A statistically significant increase was seen in intergonial width (P < .001), and inter-ramus width (P < .001) with a mean of 2.25 mm (SD, 0.82) and 4.45 mm (SD, 1.18), respectively. Both the right and left ramus angles showed an increased angle on average: mean, 1.70° (SD, 0.91) and 1.43° (SD, 0.66), respectively. There was a statistically significant increase in both angles 1 month after surgery (P < .001). There was a statistically significant relation between the amount of mandibular body setback measured at B point and increase in intergonial width (P = .012, r = 0.45), inter-ramus width (P = .018, r = 0.42), left ramus angle (P = .007, r = 0.48), and right ramus angle (P = .008, r = 0.47). This study suggested that IVSRO leads to an increase in intergonial width and inter-ramus width, as well as the outward angulation of the condylar fragment. In addition, there was a significant correlation between the amount of setback and intergonial width, inter-ramus width, and medial ramus angles.

Evaluation and selecting indications for the treatment of improving facial morphology by masseteric injection of botulinum toxin type A

Few reports exist on effective methods of evaluating the effects and selecting indications for the treatment of improving facial morphology by masseteric injection of botulinum toxin type A. The method for selecting indicative factors, as determined by the change of masseteric area volume at a standard frontal view when tightly clenching teeth, was used in this study. Patients with varying masseteric area volume were randomly enrolled. Bilateral masseteric muscles were treated with multi-point percutaneous intramuscular injections of botulinum toxin type A, 30-50 u for each side. Changes in facial appearance and satisfaction of patients were observed and standard frontal view photographs were taken pre-treatment and 2-3 months post-treatment. Following this, the anterior facial height(FH), bizygomatic facial width (FWz) and intergonial width (FWg) were measured from the photographs. The indices of FH/FWz and FWg/FWz were calculated and analysed. The results showed that the volume of masseteric area was reduced and the facial morphology was improved at 2-4 weeks post-injection, with maximum reduction at 2-3 months post-injection. All of the 32 patients were satisfied with the clinical effects. The pre-treatment and post-treatment values of FH/FWz were 0.8309±0.0423 and 0.8331±0.0382, respectively, and FWg/FWz values were 0.8281±0.0209 and 0.7925±0.0206 (P<0.01), respectively. In conclusion, the appropriateness of masseteric injection of botulinum toxin type A for improving facial morphology can be determined by the changes in masseteric area volume at a standard frontal view of tightly clenched teeth. In addition, the facial index of FWg/FWz can be used to evaluate the treatment.

Characteristics and Corrective Outcome of Face Asymmetry by Orthognathic Surgery

This study was conducted to identify the characteristics of facial asymmetry before surgery and to evaluate the facial skeletal changes and stability after 2-jaw orthognathic surgery. The ideal "double-cross grid" as fitting the key landmarks to the reference planes on posteroanterior cephalograms was set as the treatment goal. Twenty-seven adult patients, 18 female and 9 male subjects, were evaluated before and after surgery and at completion of orthodontic treatment. Cephalometric measurements of posteroanterior and lateral cephalograms were obtained at 3 timings. Measurements of frontal facial photographs were recorded before and after treatment. Data from each time set were compared to evaluate surgical achievement and postsurgical stability. All patients had original malocclusion of Class III in at least 1 side of the dentition except 1 patient. Total treatment duration was 15 +/- 3.5 months on average. Laterality of the patients demonstrated left-side dominance in 18 patients and right-side dominance in 9 patients. After surgery, face symmetry was improved by correction of the occlusal plane cant, incisal dental axis, and chin deviation. Symmetry of bilateral gonial width was also improved significantly with good stability. Intergonial width was reduced by 3.4 mm during treatment. Soft tissue presented similar correction by leveling oral commissures and correcting chin deviation. The maxilla was moved forward 1.25 mm and upward 1.20 mm, and the mandible was setback 4.3 mm and upward 1.5 mm as measured from lateral cephalograms. All sagittal changes remained stable after surgery. Fitting skeletal landmarks into a double-cross grid on posteroanterior cephalogram is an attainable guide and goal for 2-jaw orthognathic correction of facial asymmetry. Symmetry was achieved and facial profile was improved after surgery and remained stable afterward. The decrease of intergonial width indicated considerable remodeling of the bilateral gonial angle after surgery.

Facial dimensions, bite force and masticatory muscle thickness in preschool children with functional posterior crossbite

Posterior crossbite may affect craniofacial growth and development. Thus, this study aimed to associate facial dimensions (by standardized frontal photographs) to masseter and anterior portion of the temporal muscle thickness (by ultrasonography) and maximal bilateral bite force in 49 children with deciduous and early mixed dentitions. They were distributed in four groups: deciduous-normal occlusion (DNO, n = 15), deciduous-crossbite (DCB, n = 10), mixed-normal occlusion (MNO, n = 13) and mixed-crossbite (MCB, n = 11). Anterior facial height (AFH), bizygomatic width (FWB), and intergonial width (FWI) were determined and associated with muscle thickness and bite force, applying Pearsons coefficients and multiple logistic regression, with age, gender, body weight and height as the covariates. FWB and FWI were correlated positively with the masseter thickness, whereas AFH/FWB and AFH/FWI ratios had negative correlation, except in the DNO group. The correlation between AFH/FWB and bite force in the MCB group was significantly negative. A higher AFH/FWB in MNO and MCB led to a significantly higher probability for functional crossbite development. In the studied sample, it was observed that children in the early mixed dentition with a long-face trend showed lower bite force and higher probability to present functional posterior crossbite, without significant influence of the covariates.

Transverse Displacement of the Proximal Segment After Bilateral Sagittal Osteotomy: A Comparison of Lag Screw Fixation Versus Miniplates With Monocortical Screw Technique

The purpose of the present study was to compare lag screw fixation versus miniplates with monocortical screw technique with respect to the amount of transverse displacement of the proximal segment after bilateral sagittal osteotomy (BSO) for mandibular advancement surgery. We conducted a multicenter, retrospective investigation of 82 patients who underwent a mandibular advancement with BSO and rigid internal fixation. Forty-five patients from Denmark and Sweden, the miniplate fixation group, received a rigid fixation consisting of miniplates with monocortical screws. Thirty-seven patients from the Mayo Clinic, the lag screw fixation group, received a rigid fixation with lag screw fixation of the mandible. The transverse displacement and angulation of the proximal segments were measured on posterior-anterior cephalometric radiographs, using the best-fit method. After BSO, 44 of 45 patients in the miniplate fixation group showed an increased transverse intergonion distance with a mean of 5.0 mm and an increase transverse interramus width with a mean of 2.4 mm. Thirty-six of 37 patients in the lag screw fixation group had an increased intergonial width with a mean of 5.6 mm, and 35 of 37 patients showed an increased transverse interramus width with a mean of 3.3 mm. t tests showed that there were no significant differences between the 2 groups with respect to these 2 variables. Our results indicate that transverse displacements of the proximal segments occur after BSO surgery with both miniplate or lag screw fixation technique. Attention and future studies should focus on possible complications that transverse displacement of the proximal segment may cause.

Longitudinal study of facial skeletal growth completion in 3 dimensions

Previous authors have suggested that transverse facial skeletal growth is completed before either anteroposterior or vertical growth and that anteroposterior growth is completed before vertical growth. Our purpose in this study was to examine this concept. Twenty-four subjects (11 male, 13 female) who had annual lateral and posteroanterior cephalograms up to and including age 17 or 18 and again at age 25 or older were identified from the Iowa Facial Growth Study. Transverse, anteroposterior, and vertical facial dimensions were measured longitudinally into adulthood by using key skeletal landmarks. Descriptive statistics were calculated, and nonparametric Wilcoxon signed rank tests were performed separately for the sexes to determine the age at which each anteroposterior, vertical, and transverse growth variable reached adult size. For both sexes, an overlap exists at any age in the amount of growth completed for the various measurements in the transverse, anteroposterior, and vertical dimensions. Although some transverse measures (cranial width and interjugal width) attain adult size before any anteroposterior or vertical ones, there is evidence of continued growth for other transverse parameters (interzygomatic width and intergonial width). A similar overlap is seen in the anteroposterior and vertical dimensions. A distinct separation, by time and dimension, is not seen in the amount of facial growth completed during development. Instead, a dramatic spread and an overlap of growth curves are observed throughout the developing years.

Transverse Displacement of the Proximal Segment After Bilateral Sagittal Split Osteotomy Advancement and Its Effect on Relapse

To evaluate the transverse displacement of the proximal segment and its association with horizontal relapse post-treatment. Retrospective study of 25 patients (10 males, 15 females) who underwent bilateral sagittal split osteotomy (BSSO) advancement and Le Fort I osteotomy with rigid internal fixation (RIF) using bicortical lag screws. Posteroanterior and lateral cephalograms obtained preoperatively (T1), early postoperatively (T2), and after orthodontic treatment completion (T3) were used to assess: the angulation of each proximal segment relative to the upper orbital margin line and obtain the sum of both angles (total angle), mandibular intergonial width (IGW), mandibular length (Ar-B), B point position, and condylion position. Paired t tests were used to determine statistically significant (P < .05) changes within the variables between various time points (T2-T1; T3-T2; T3-T1). Correlations between variables were estimated by calculating Pearson's correlation coefficients. T2-T1 findings: all 25 patients showed an increase in IGW with a mean of 6.5 +/- 2.5 mm and the angulations of the proximal segments increased 3.2 +/- 2.6 degrees (total angle change). Ar-B increased 3.8 +/- 3.4 mm. B point moved anteriorly 4.8 +/- 2.9 mm. T3-T2 findings: IGW decreased 1.8 +/- 1.5 mm; angulation of the right and left proximal segments decreased 1.2 +/- 2.8 degrees (total angle change). Condylion moved superiorly 1.5 +/- 2.0. Statistically significant changes occurred in transverse width and angulation of proximal segments of patients who underwent BSSO advancement with Le Fort I osteotomy. No clinically significant associations were found between transverse displacement of the proximal segments and horizontal relapse.

Effect of Mandibular Setback via Bilateral Sagittal Split Ramus Osteotomy on Transverse Displacement of the Proximal Segment

The purpose of this study was to evaluate if a correlation exists between: a) transverse changes in the proximal segments because of mandibular setback surgery and b) postsurgical horizontal relapse of the mandible. A total of 42 patients underwent bilateral sagittal split ramus osteotomy setback with rigid fixation and Le Fort I osteotomy performed by 1 surgeon between 1986 and 2000. The radiographic material for this study consisted of posteroanterior and lateral cephalometric radiographs for each patient taken preoperatively (T1), early postoperatively (T2), and late postoperatively (T3). Twenty-four of the 42 identified patients had T1, T2, and T3 radiographs, while the remainder of the patients had only T1 and T2 radiographs available. The posteroanterior radiographs were used to evaluate the angulation of the proximal segment and the intergonial width. Statistically significant increases in intergonial width and proximal segment angulation occurred from T1 to T2. In fact, all 42 patients had an increased intergonial width from T1 and T2. From T2 to T3, most patients underwent some relapse in their transverse dimension changes (21 of 24 patients had a decrease in their intergonial width). Overall, the intergonial width and the proximal segment angulations were significantly increased from T1 to T3. However, there was no significant correlation between the amount of transverse displacement of the proximal segment and horizontal postsurgical relapse of the mandible. The results show that statistically significant changes in the transverse width and angulation between proximal segments occur in patients undergoing bilateral sagittal split ramus osteotomy for mandibular setback with rigid fixation. However, the magnitude of the changes was small, and it is still uncertain as to whether these changes are of any clinical significance.

Masseter muscle thickness in growing individuals and its relation to facial morphology

It is widely accepted that an interaction exists between masticatory muscle function and craniofacial growth. In adults, correlations have been found between facial dimensions and jaw-muscle cross-sectional area, and between facial dimensions and masseter muscle thickness. Little is known about growth of the human masticatory muscles and its relation with facial dimensions at different ages. In 329 Greek individuals, aged 7–22 yr, masseter muscle thickness was measured by ultrasonography. Muscle thickness was related to age, stature and weight, and to facial dimensions, measured by means of anthropological calipers. Muscle thickness was statistically assessed by univariate analysis of variance, after the males and females had been divided into three age groups. Facial dimensions were assessed by multivariate analysis of variance, age being considered as a covariate. The relation between muscle thickness and facial dimensions was subjected to stepwise multiple regression analysis. Masseter muscle thickness increased with age in both sexes. No differences were found between the left- and right-hand side. For each age group (and corrected for stature and weight), males had significantly thicker masseters than females ( p < 0.01). Variation in muscle size and facial dimensions mainly coincided with variation in age, stature and weight. Apart from these, muscle thickness showed a significantly negative relation with anterior facial height and mandibular length, and a significantly positive relation with intergonial width and bizygomatic facial width.

Frontal cephalometric evaluation of transverse dentofacial morphology and growth of children with isolated cleft palate

The transverse dentofacial morphology and growth of 64 children operated on for clefting of the hard and soft palate was studied by means of a frontal proportional cephalometric analysis and was compared to a normal sample at the ages 3-4, 8-9 and 12 years. The cross-sectional comparison of the cleft palate and normal samples at the three periods indicated: (a) The presence in the cleft group of significantly increased ratios of the inner orbital width to the interorbital width and of the width of the nasal cavity to the interorbital width; (b) the absence of any significant differences in the ratio of the maxillary intermolar width to the interorbital width; and (c) the presence of almost identical ratios of the intergonial width of the mandible to the interorbital width and of the width of the maxilla to the intergonial width of the mandible. Evaluation of the changes of all cephalometric variables during the period 8-12 years showed the absence of any significant difference between the cleft palate and normal groups.

Frontal cephalometric study of dentofacial morphology in children with bilateral clefts of lip, alveolus and palate

The transverse dentofacial morphology of 36 children with bilateral cleft lip, alveolus and palate was studied by means of a frontal proportional cephalometric analysis at the ages of three, eight and twelve years. Comparison of the variables of the cleft group was made with the normal dimensions as obtained from the Bolton cephalometric templates. The results indicated that the BCLP group presented characteristics and significant differences from the normal in the dimensions of the nasal septum width and the mandibular intergonial width as they are both related to the interorbital width, the maxillary intermolar width as it is related to the mandibular intermolar width and the maxillary width as it is related to the mandibular intergonial width at all three ages. The maxillary base and intermolar widths, although significantly different at the ages of three and eight years, showed no significant deviation from normality at the age of twelve years. Following orthodontic treatment between the ages of seven to twelve years, the maxillary intermolar width of the treated subgroup was significantly larger than in the untreated subjects.

Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics.

The relationship between human craniofacial morphology and the biomechanical efficiency of bite force generation in widely varying muscular and skeletal types is unknown. To address this problem, we selected 22 subjects with different facial morphologies and used magnetic resonance imaging, cephalometric radiography, and data from dental casts to reconstruct their craniofacial tissues in three dimensions. Conventional cephalometric analyses were carried out, and the cross-sectional sizes of the masseter and medial pterygoid muscles were measured from reconstituted sections. The potential abilities of the muscles to generate bite forces at the molar teeth and mandibular condyles were calculated according to static equilibrium theory using muscle, first molar, and condylar moment arms. On average, the masseter muscle was about 66% larger in cross section than the medial pterygoid and was inclined more anteriorly relative to the functional occlusal plane. There was a significant positive correlation (P less than 0.01) between the cross-sectional areas of the masseter and medial pterygoid muscles (r = 0.75) and between the bizygomatic arch width and masseter cross-sectional area (r = 0.56) and medial pterygoid cross-sectional area (r = 0.69). The masseter muscle was always a more efficient producer of vertically oriented bite force than the medial pterygoid. Putative bite force from the medial pterygoid muscle alone correlated positively with mandibular length and inversely with upper face height. When muscle and tooth moment arms were considered together, a system efficient at producing force on the first molar was statistically associated with a face having a large intergonial width, small intercondylar width, narrow dental arch, forward maxilla, and forward mandible. There was no significant correlation between muscle cross-sectional areas and their respective putative bite forces. This suggests that there is no simple relationship between the tension-generating capacity of the muscles and their mechanical efficiency as described by their spatial arrangement. The study shows that in a modern human population so many combinations of biomechanically relevant variables are possible that subjects cannot easily be placed into ideal or nonideal categories for producing molar force. Our findings also confirm the impression that similar bite-force efficiencies can be found in subjects with disparate facial features.