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PubMed1981

Tridimensional planning for surgical/orthodontic treatment of mandibular excess.

The dentofacial deformity of mandibular excess is frequently complicated by significant discrepancies in the anteroposterior position of the maxilla and mandible. Disproportionality of facial height as a result of increased or decreased vertical growth of the jaws, labiomental contour, transverse arch relationships, and/or asymmetries also complicate this deformity. Planning treatment for mandibular prognathism must entail diagnostic consideration of all three dimensions of space if maximum results are to be obtained with contemporary surgical techniques. In this article some of these diagnostic considerations, pre- and postsurgical orthodontic objectives, surgical techniques, orthodontic sequencing, timing of treatment, and clinical results are delineated to acquaint the orthodontist with contemporary treatment planning for this deformity in order to obtain optimum function, esthetics, and relative stability. Tridimensional facial proportionality, occlusal balance, and good dental and skeletal stability were achieved in five patients (average age, 17.5 years) with relative or absolute mandibular prognathism. These patients, who were observed for an average postoperative follow-up period of 24 months, were treated by multiple maxillomandibular surgical procedures in concert with orthodontic treatment.

Adolescent↗

PubMed1987

Recognition of profile change after simulated orthognathic surgery.

Fifty-one oral and maxillofacial surgeons, 52 orthodontists, 51 orthognathic surgery patients, and 100 lay persons evaluated life-size lateral photographs of two male and two female subjects that had been altered to simulate varying amounts of surgical correction of mandibular retrognathism and prognathism. A horizontal change at pogonion of less than 4 mm was generally not recognized by more than half of the lay groups. The dental groups were more accurate, but even they did not achieve better than 80% recognition until 6 mm of change. Both the dental and lay groups recognized change more easily in the female and the prognathic subjects. When asked which feature appeared changed, dentists generally indicated the chin and lay groups the lips.

Chin↗

PubMed1988

Self-assessment of profile and body image among orthognathic surgery patients before and two years after surgery.

Ninety patients undergoing surgery at two major university hospitals completed self-ratings of their profile, perceived deviations from the ideal profile, and a measure of body image. Identical measures were obtained presurgically and two years following surgery. Patients diagnosed with mandibular hypoplasia perceived themselves significantly more prognathic on the maxillary dimension and most retrognathic on the mandibular dimension; their self-drawings reflected a shorter vertical dimension. These perceptions approached the normal range at the postsurgical assessment. Patients treated for maxillary hypoplasia, however, rated themselves in the mandibular prognathic range both before and after surgery. These patients were also more likely to perceive other deviations from the ideal in their facial features 2 years after surgical correction. Body image did not differentiate among diagnostic categories, but showed overall improvements for all patients from presurgery to postsurgery. Profile drawings appear to be the most statistically and clinically useful method of determining patients' self-assessments of deviations from normal, and their perceptions of treatment needs.

Body Image↗

PubMed1992

The biomechanical effects of a sagittal split ramus osteotomy on the relationship of the mandible, the hyoid bone, and the cervical spine.

The effects of a sagittal split ramus osteotomy in correcting mandibular retrognathism and prognathism were studied cephalometrically in a group of 25 patients. The patients were divided into two groups, 18 patients with retrognathic mandibles and 7 patients with prognathic mandibles to be corrected by means of a sagittal split ramus osteotomy according to Obwegeser Dal Pont. The major complications of this type of surgical intervention have been documented in literature and are known as (1) a certain degree of relapse, i.e., mandibular instability and (2) the development of a permanently disturbed head balance. The displacement of the dental, skeletal, and neuromuscular components within the craniomandibular complex requires a large adaptive capacity and suggests that the patient will develop a forward head posture (anteroposition of the head) after both types of surgical intervention. In mandibular advancement, however, the initiating mechanism to develop a forward head posture starts in the cervicothoracic transition (C6-C7-T1-T2). In mandibular set-back, the discussed mechanism will start in the upper cervical area (C0-C1-C2-C3). The different pattern of movement of C2 and C3 in mandibular advancement and mandibular set-back, respectively, confirmed the conclusion that the initiating mechanisms, may be found in the cervicothoracic transition and the upper cervical region, respectively.

Adolescent↗

PubMed2006

Methods to evaluate profile preferences for the anteroposterior position of the mandible.

INTRODUCTION: Facial profile disharmonies in the anteroposterior (AP) position of the mandible are among the most frequent reasons that patients seek orthodontic treatment. Various methods are available for assessing profile preferences, and differences between them could affect treatment decisions. The purposes of this study were to compare and contrast 3 methods of evaluating profile preferences for the AP position of the mandible. METHODS: Facial profile preferences of white orthodontists (n = 28) and white (n = 56) and Japanese-American (n = 55) laypeople were evaluated. The esthetic significance of variations in the AP position of the mandible was investigated by using 3 methods: a traditional semantic differential scale, the Perceptometrics method (Health Programs Intl, Wellesley, Mass), and the implicit association test (IAT). RESULTS: Findings from the semantic differential scale show that, overall, there is a general preference among orthodontists and laypeople for an orthognathic profile (P <.001). Findings from the Perceptometrics method indicate that orthodontists consider the most pleasing profile to be more forward than do lay subjects (P <.001). The IAT results show a positive bias among all 3 groups toward orthognathic profiles and a negative bias toward profiles with mandibular retrognathism or prognathism. The IAT suggested that laypeople were more tolerant of mandibular prognathism in men than in women (P <.01), and more tolerant of mandibular retrognathia in white women than in men (P = .03). CONCLUSIONS: These results support the benefits of using both implicit and explicit methods to assess facial profile preferences.

Adult↗

PubMed2005

Changes in the chewing path of patients in skeletal class III with and without asymmetry before and after orthognathic surgery.

PURPOSE: The purpose of this study was to examine the relation between changes in the condylar long axis and the chewing path before and after mandibular ramus osteotomy for patients with prognathism with and without asymmetry. PATIENTS AND METHODS: Eleven men and 16 women with mandibular prognathism were divided into groups on the basis of symmetry and osteotomy procedure. Preoperative and postoperative frontal chewing paths were recorded. The chewing path consisted of 4 components: deviated side range, undeviated side range, vertical range, and incisal path angle. The angle of the condylar long axis and the 4 components of the chewing path were compared between groups and the differences were analyzed statistically. RESULTS: No significant differences in each of the 4 chewing path components were found between groups on the basis of symmetry or osteotomy procedure. A positive correlation was found between the changes in incisal path angle when chewing on the undeviated side and condylar long axis angle on the undeviated side (P < .05). A positive correlation was also found between the changes in undeviated side range when chewing on the deviated side and condylar long axis angle on the deviated side (P < .05). CONCLUSION: This study suggests that surgically induced increase in the condylar long axis is correlated with increase in side range and incisor path angle, although surgical orthodontic treatment does not significantly change the chewing pattern.

Adult↗

PubMed2006

Anatomical study of the complications of intraoral vertico-sagittal ramus osteotomy.

PURPOSE: The present study was performed to determine the variations in anatomical features of the ramus and the course of the maxillary artery to reduce the risk of injury during intraoral vertico-sagittal ramus osteotomy (IVSRO). MATERIALS AND METHODS: The locations and sizes of anatomical features of the medial aspect of mandibular rami were measured in 94 bilateral sides of 47 dry mandibles as a control group, and the results were compared with 3-dimensional computed tomography images of 44 sides of 22 patients with prognathism. We also dissected 12 sides of 6 mandibles from cadavers in a simulated IVSRO procedure to determine the course of the maxillary artery near the medial aspect of the ramus. RESULTS: In the dry mandibles and patients with prognathism, the mandibular foramen was located slightly posterior to the center of the width of the mandibular ramus, and the lingula tip was located about one third the distance from the sigmoid notch to the inferior border of the ramus. The distance from the lateral margin of the mandibular foramen to the lateral surface of the mandibular ramus ranged from 3.1 to 4.4 mm. However, these distances showed various ranges. In the mandibles from Asian cadavers, the maxillary artery approached close to the ramus and passed lateral to the lower head of the lateral pterygoid muscle. CONCLUSIONS: The position of the mandibular foramen in rami varies among individuals and, therefore, should be confirmed preoperatively on axial CT images. In addition, the maxillary artery approaches close to the medial aspect of the sigmoid notch in many cases. Therefore, the medial aspect from the sigmoid notch should be exposed carefully in the IVSRO procedure to avoid damaging the maxillary artery.

Anthropometry↗

PubMed2000

Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: a preliminary report.

PURPOSE: This study examined bite force and occlusal contact area in prognathic patients before and after bilateral sagittal split ramus osteotomy of the mandible using a newly developed pressure-sensitive sheet (Dental-Prescale, Fuji Photo Film Co, Tokyo, Japan). PATIENTS AND METHODS: Twenty-five prognathic patients were examined. Bite force and occlusal contact area were measured preoperatively, at 2, 4, and 8 weeks, and at 3 and 6 months after surgery. The bite force and occlusal contact area of 20 healthy subjects were also measured. RESULTS: Both bite force and occlusal contact area of the patients were the lowest 2 weeks after surgery and recovered to the preoperative level between 8 weeks and 3 months. Subsequently, they increased slowly and exceeded the preoperative level at 6 months after surgery. However, even at 6 months, both the bite force and the occlusal contact area of the patients were still only about half or less than that of healthy subjects. CONCLUSION: This pressure-sensitive device can be used as a simple indicator of postoperative recovery and occlusal improvement in patients following orthognathic surgery.

Adolescent↗

PubMed1999

Differences in soft tissue profile changes following mandibular setback in Chinese men and women.

PURPOSE: This study investigated the soft tissue profile changes after surgical correction of mandibular prognathism in Chinese patients and evaluated the sex differences in the ratios of soft tissue to hard tissue change. PATIENTS AND METHODS: Forty-three adult Chinese patients (18 men and 25 women) with mandibular prognathism were treated by intraoral oblique or vertical ramus osteotomy. Lateral cephalometric radiographs were taken presurgically and between 6 to 12 months postsurgically, and specific soft and hard tissue points were digitized and analyzed with a computer-aided system. RESULTS: As a result of surgical setback of the mandible, the soft tissue to hard tissue change ratios were: Li:Ii = 0.71:1, Si:B = 0.90:1, Pg':Pg = 0.94:1 for the males; and Li:Ii = 0.82:1, Si:B = 0.92:1, Pg':Pg = 1.06:1 for the females. CONCLUSION: The changes in soft tissue were closely correlated with the hard tissue movement after surgical setback of mandible. The average ratios of soft tissue to hard tissue change in horizontal direction appear to show a gender difference, which suggests the need for different ratios when predicting the results of orthognathic surgery.

Adult↗

PubMed1999

Temporomandibular joint reconstruction in children using costochondral grafts.

PURPOSE: The aim of this study was to evaluate the postoperative growth of the mandible after reconstruction of the condylar process using costochondral grafts in children. PATIENTS AND METHODS: Temporomandibular joint (TMJ) ankylosis was surgically treated and the joint reconstructed with a costochondral graft (CCG) in two boys and eight girls with a mean age of 7.4 years. Two children had bilateral ankylosis. Postoperative changes and craniofacial growth were monitored by lateral and posteroanterior (PA) cephalograms annually from 2 to 6 years (mean of 4 years). RESULTS: Postoperatively, in the eight children with unilateral TMJ reconstruction, the mandible (Co-Gn) grew an average of 14.7 mm in length on the affected side and 15.1 mm on the nonaffected side; ramus length (Co-Go) increased an average of 7.1 mm on the affected side and 7.3 mm on the nonaffected side. However, in five of the children the chin progressively deviated toward the nonaffected side after TMJ reconstruction. The CCGs tended to have a more vertically directed condylar growth pattern and a more laterally positioned condyle. In the two cases with bilateral TMJ reconstruction, the CCGs grew until there was a mandibular prognathism that required orthognathic surgery to set back the mandible. CONCLUSIONS: Using CCGs to reconstruct TMJ ankylosis in children provides a functional condyle with growth potential. However, there is a possibility of excessive growth of the graft, resulting in deviation of the chin and mandibular prognathism years later.

Ankylosis↗

PubMed1994

A study of nasal respiratory resistance and craniofacial dimensions in white and West Indian black children.

Two studies have shown that there are morphologic differences in the nasopharynx between the major racial groups. This investigation was conducted to see whether these morphologic differences affected nasal respiration. Twenty-two West Indian and 24 white children (mean age of 13 years 11 months) were studied to examine the relationship between nasorespiratory function and nasopharyngeal and dentofacial structure. The nasorespiratory function was measured in terms of nasal respiratory resistance, NRR, (Pascals/cm3 per second), both by anterior and posterior methods, with a computerized rhinomanometer. Nasopharyngeal structure was described in terms of cephalometric variables. The West Indian cephalometric profile generally conformed to its existing description in the literature including prognathic jaws and bimaxillary proclination; in addition, the West Indians were found to have a greater bony nasopharyngeal width (posterior nasal spine-basion) and shallower nasopharyngeal roof angle (posterior nasal spine-hormion-basion). All rhinomanometric measurements were significantly lower in the West Indian group, especially when posterior rhinomanometry was used. The correlation coefficients between the cephalometric and the rhinomanometric measurements were statistically significant but low. In addition, the measure of mandibular prognathism (angle SNB) was also found to be significantly correlated with the nasorespiratory resistance.

Adolescent↗

PubMed1999

Long-term application of chincup force alters the morphology of the dolichofacial Class III mandible.

The conventional orthopedic Milwaukee brace exerts a large and continuous force that induces malocclusion and a significant deformation of the mandible. Our previous chincup study examined its use in moderately severe mandibular prognathism without retrusion of the maxilla. The orthopedic force was approximately 500 g at the center of chin and was applied during sleep for 6 to 24 months. For mandibular prognathism subjects (means, 1.0 degrees and -1.3 degrees of ANB angle in the prepubertal and pubertal subjects), the resultant changes were maintained after retention. However, research reported that the changes obtained during chincup treatment (average, 4 (1/2) years' use) were often not maintained in severe skeletal Class III malocclusion. The aim of this clinical study was to investigate the immediate and long-term effects of prolonged use (mean, 7 years 2 months) of chincup appliances in subjects with dolichofacial Class III mandibles. Thirty-six female subjects with severe skeletal Class III malocclusions, associated with large gonial angles, were selected from the dental records of a private clinic. At posttreatment (T1, 65 months' duration) and postretention (T2, 56 months after T1), Ar-Me and Wits appraisal cephalometric parameters were significantly different (P <.01) between patients and control subjects (n = 230). Furthermore, the Go-Me parameter in treated subjects was longer than that of the controls at T0 but became significantly shorter at T2 (P <.01). Treatment was associated with a finding that the Ar-Go parameter increased less than the controls at T2. Our results indicate that long-term use of the chincup appliance (>5 years) is effective in subjects with severe skeletal Class III abnormality.

Case-Control Studies↗

PubMed1994

Shape of the craniofacial complex in patients with Klinefelter syndrome.

The shape and size of the craniofacial complex in 35 adults with Klinefelter syndrome (47,XXY) were analyzed cephalometrically and compared with 60 control males. Twenty-four angular and 18 linear measurements were obtained for each subject. The results showed that the 47,XXY males were different from the controls in several areas of the craniofacial skeleton. Most of the differences were located in the cranial base and the cranial base angle (p < 0.02). The length of the maxillary base was greater (p < 0.05) and more prognathic (p < 0.01) in the study group. The mandible was also longer and more prognathic (p < 0.01).

Adult↗

PubMed1998

Mandibular morphology in subjects with Class III malocclusions: Finite-element morphometry.

The absence of physical restraint may be associated with a mandibular allometry that contributes to mandibular prognathism. Cephalographs of 73 prepubertal children of European American descent with untreated Class III malocclusions were traced and eight mandibular landmarks digitized. The resulting eight-noded geometries were normalized, and the mean Class III geometry compared with the equivalent Class I average. Procrustes analysis established statistical difference (p < 0.05) between these mean configurations. A color-coded finite-element (FEM) analysis was used to localize differences in morphology. Comparing Class III and normal mandibular configuration for changes in size, FEM revealed positive allometry of the mandibular corpus and around supramentale (15% increase in size), with reductions (30%) between the incisor alveolus and menton. For changes in shape, mandibular configurations were predominantly isotropic, with the exception of the anisotropic anterior region in the Class III subjects. Incremental growth differences are consistent with the view that the absence of physical restraint is associated with mandibular prognathism.

Case-Control Studies↗

PubMed1999

Arrested eruption of the permanent lower second molar.

The incidence of retention/impaction of the permanent lower second molar (M2inf) lies between 0.6/1000 and 3/1000. Therefore, the purpose of the present study was to investigate the craniofacial morphology, the frequency of dental anomalies and the inclination of the affected M2inf and the adjacent first molar in patients with arrested eruption of M2inf. The overall goal was to elucidate the aetiology of arrested tooth eruption and to present the characteristics of these patients in order to improve diagnosis and treatment planning. Radiographic material (profile radiographs and orthopantomograms) from 19 patients (nine females and 10 males; 13-19 years of age at the time of referral) were analysed. The ages of the patients when profile radiographs were taken for cephalometric analysis varied from 8 to 16 years. The study shows that this group of patients, compared with a reference group, had an increased sagittal jaw relationship (Class II). Specifically, the mandibular prognathism was less, the mandibular gonial angle smaller, the mandibular alveolar prognathism enlarged and the maxillary incisor inclination less than in the reference group. Furthermore, this group of patients had a more frequent occurrence of morphological tooth anomalies, such as root deflections, invaginations, and taurodontism. However, none of the patients with arrested eruption of M2inf had agenesis of the lower third molar. The study did not reveal an association between the degree of inclination of the M2inf and that of the first molar in the same region. The results of this investigation show that conditions such as the craniofacial morphology and deviations in the dentition are associated with arrested eruption of M2inf. Therefore, it is important to evaluate these conditions in future diagnosis and treatment planning of patients with arrested eruption of M2inf.

Adolescent↗

PubMed1999

Adult craniocervical and pharyngeal changes--a longitudinal cephalometric study between 22 and 42 years of age. Part I: Morphological craniocervical and hyoid bone changes.

The purpose of this study was to investigate longitudinally, by cephalometric means, alterations in craniocervical morphology and hyoid bone position in adult males and females, in three different age groups at 10-year intervals, and to compare the changes between the two genders. The material consisted of three series of cephalograms of 26 males and 24 females with approximately a 10-year interval between each series. Alterations with increasing age in males and females included: 1 An increase in anterior and posterior facial height in both genders, a reduction in mandibular prognathism, and an increase in the mandibular plane angle in females only. 2 The hyoid bone assumed a more inferior position in relation to different skeletal structures for both sexes. 3 Head posture alterations were similar for the male and female group over time. The overall significant inter-sex changes over a 20-year period were a reduction in mandibular prognathism, an increase in the mandibular plane angle in females, and a more inferior position of the hyoid bone in males.

Adult↗

PubMed2005

Craniofacial development in obese adolescents.

The purpose of this study was to investigate craniofacial morphology in obese adolescents and to compare the morphological data with those of normal adolescents. The study was based on measurements of lateral cephalometric roentgenograms of adolescents who had been diagnosed as obese. Linear and angular measurements were obtained from cephalometric tracings of 27 females (mean age 15.6 +/- 0.83 years) and 23 males (mean age 13.9 +/- 0.98 years). The data were compared with corresponding measurements of gender and age matched controls. The results showed that both males and females in the obesity group exhibited significantly larger mandibular and maxillary dimensions than the controls. On average, mandibular length (Cd-Pgn) was 10 mm greater in males and 8 mm greater in females. Maxillary length (Pm-A) was 3.5 mm greater in males and 3 mm greater in females. When considering vertical dimensions, lower anterior (Ans-Gn) and posterior (S-Go) face height were 4 and 5 mm greater in the obese males, respectively, while in the obese females both these distances were 4 mm greater compared with the controls. Both maxillary (SNA) and mandibular (SNB, SNPg) prognathism were more pronounced in the obesity group than in the control group. This also influenced the average soft tissue profile, which was less convex in the obesity groups. The mandibular plane angle (ML/SN) was smaller in the obesity group than in the control group. Craniofacial morphology differs between obese and normal adolescents. In general, obesity was associated with bimaxillary prognathism and relatively greater facial measurements.

Adolescent↗

PubMed2006

The change of stress distribution on the condyle after mandibular setback surgery.

The rigid-body spring model (RBSM) theory was incorporated into a model as a discrete method for analysing problems of limit, such as the stress distribution on the condyle. The purpose of this study was to evaluate the two-dimensional RBSM for determining stress on the temporomandibular joint (TMJ) in patients after orthognathic surgery. Thirty-two patients (five males and 27 females, mean age 21.4 +/- 4.9 years) with mandibular prognathism underwent bilateral sagittal split ramus osteotomy (SSRO) and setback; 48 subjects were recruited as controls. Anatomical landmarks were traced from pre- and post-operative lateral cephalograms and the information was processed using the Fortran analysis program. The force vector on the condyle, its degree, its direction, and the displacement co-ordinates (x, y) and rotation (theta) at the gonial angle were calculated. When muscular power was assumed to be 1, the post-operative degree of the force vector was higher than the pre-operative value (P < 0.05). The X co-ordinate, x, and rotation, theta, of the displacement vector in the pre-operative patients with mandibular prognathism were significantly higher than those in the control subjects (P < 0.05). There were still significant differences between the displacement values post-operatively between the patients and controls (P < 0.05). The results suggest that the degree and direction of the force vector and the resulting displacement co-ordinates can be used as parameters in a surgical model. The RBSM may also be useful in evaluating the pre- and post-operative skeletal morphology of jaw deformities.

Adult↗