The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study. (17/1457)

Changes in the functional shift of the mandibular midline and the condyles were studied during treatment of unilateral posterior crossbite in six children, aged 7-11 years. An expansion plate with covered occlusal surfaces was used as a reflex-releasing stabilizing splint during an initial diagnostic phase (I) in order to determine the structural (i.e. non-guided) position of the mandible. The same plate was used for expansion and retention (phase II), followed by a post-retention phase (III) without the appliance. Before and after each phase, the functional shift was determined kinesiographically and on transcranial radiographs by concurrent recordings with and without the splint. Transverse mandibular position was also recorded on cephalometric radiographs. Prior to phase I, the mandibular midline deviated more than 2 mm and, in occlusion (ICP), the condyles showed normally centred positions in the sagittal plane. With the splint, the condyle on the crossbite side was displaced 2.4 mm (P < 0.05) forwards compared with the ICP, while the position of the condyle on the non-crossbite side was unaltered. After phase III, the deviation of the midline had been eliminated. Sagittal condylar positions in the ICP still did not deviate from the normal, and the splint position was now obtained by symmetrical forward movement of both condyles (1.3 and 1.4 mm). These findings suggest that the TMJs adapted to displacements of the mandible by condylar growth or surface modelling of the fossa. The rest position remained directly caudal to the ICP during treatment. Thus, the splint position, rather than the rest position should be used to determine the therapeutic position of the mandible.  (+info)

Incremental growth charts for condylar growth between 6 and 16 years of age. (18/1457)

This study provides sex specific reference data for the incremental growth of the mandibular condyle. The results pertain to a mixed-longitudinal sample of 113 males and 108 females followed annually between 6 and 16 years of age (total of 1647 observations). Growth of condylion was evaluated using naturally stable mandibular reference structures. The mean growth curves were estimated by multilevel models using iterative least squares procedures; between subject variation was estimated based on the sample's percentile distributions. Mean yearly velocities of condylar growth for males ranged between 2.1 and 3.1 mm/year. Growth rates decreased during childhood, increased during adolescence, and attained a maximum of 3.1 mm/year at approximately 14.3 years of age. Females showed a more constant rate of condylar growth during childhood (2.0-2.7 mm/year), a smaller adolescent peak (2.3 mm/year) at approximately 12.2 years and rapid deceleration after the peak. These reference data offer orthodontists an objective means of evaluating growth potential and treatment outcome in individual patients. Charts are provided for evaluating condylar growth of individual patients.  (+info)

A comparison of sagittal and vertical effects between bonded rapid and slow maxillary expansion procedures. (19/1457)

The purpose of this study was to determine the vertical and sagittal effects of bonded rapid maxillary expansion (RME), and bonded slow maxillary expansion (SME) procedures, and to compare these effects between the groups. Subjects with maxillary bilateral crossbites were selected and two treatment groups with 12 patients in each were constructed. The Hyrax screw in the RME treatment group and the spring of the Minne-Expander in the SME treatment group were embedded in the posterior bite planes, which had a thickness of 1 mm. At the end of active treatment these appliances were worn for retention for an additional 3 months. Lateral cephalometric radiographs were taken at the beginning and end of treatment, and at the end of the retention period. The maxilla showed anterior displacement in both groups. The mandible significantly rotated downward and backward only in the RME group. The inter-incisal angle and overjet increased in both groups. No significant differences were observed for the net changes between the two groups.  (+info)

Anthropometry of patients with osteogenesis imperfecta. (20/1457)

Standing height, sitting height, armspan, subischial leg length, head circumference, and growth hormone-insulin-like growth factor I (IGF-I) axis were determined in 86 patients with osteogenesis imperfecta. The aim of this study was to determine standing height and body proportions and their variability among osteogenesis imperfecta types and collagen defects. Mean standing height was reduced in all groups of patients, to the greatest extent and variability in osteogenesis imperfecta type III/IV and in those with qualitative collagen defects. The mean standing height of patients with osteogenesis imperfecta was lower than that of their unaffected first degree family members. Truncal height of patients with osteogenesis imperfecta was reduced; head size was increased, and this was more pronounced in patients with osteogenesis imperfecta type III/IV and qualitative collagen defects than in patients with osteogenesis imperfecta type I and quantitative collagen defects. Mean concentrations of IGF-I and IGF binding protein 3 (IGFBP-3) were low, but most values were within age specific reference values. The reduction of standing height appears to correlate with osteogenesis imperfecta type and the type of collagen defect. A relatively short trunk is typical and head circumference and body length are disproportionate.  (+info)

Linear and angular changes in dento-facial dimensions in the third decade. (21/1457)

The object of the study was to examine changes in dento-facial dimensions and relationships during the third decade of life, and consisted of a prospective cephalometric study. The data used consisted of 90 degree left lateral cephalometric radiographs of 21 males and 26 females at ages 18 years (T1) and 21 years (T2), and for 15 of the males and 22 of the females at 28 years (T3). Various dimensions representative of dento-facial morphology were measured and the changes in dimensions over time were calculated and tested for significance with the one sample t-test. In general, skeletal and dental relationships remained relatively stable. Face height and jaw length dimensions increased by small amounts.  (+info)

Reduction cranioplasty for macrocephaly. Two case reports. (22/1457)

Multi-stage reduction cranioplasty was performed on two children with severe macrocephaly secondary to hydrocephalus. One patient underwent a four-stage operation, and the other underwent a two-stage operation. The postoperative course of both patients was uneventful. Reduction cranioplasty improved quality of life for both patients, and good cosmetic results were achieved. Reduction cranioplasty is effective for the treatment of macrocephaly, and multi-stage surgery can reduce the associated risks.  (+info)

The effects of increasing the reverse curve of Spee in a lower archwire examined using a dynamic photo-elastic gelatine model. (23/1457)

This paper describes the development and testing of a dynamic in vitro photo-elastic model for evaluating the effects of orthodontic mechanics on an entire arch of teeth. A model of a mandibular arch was made and the teeth were embedded in a gelatine material with a high level of mechanical creep which permitted tooth movement in response to orthodontic forces. The excellent photo-elastic properties of this material also facilitated the analysis of the stress distribution around the roots of the teeth. The model of a mandibular arch was used to investigate the tooth movements and stress distributions produced by increasing the reverse curve of Spee in a 0.018 x 0.025-inch stainless steel archwire. The results revealed that a 1-mm reverse curve of Spee increased the arch length by 1.6 mm, but increasing the reverse curve of Spee to 5 mm did not increase arch length further. Photo-elastic analysis showed an increased stress distribution around the roots of the incisors and molars as the reverse curve of Spee was increased in the archwire.  (+info)

Thin-plate spline analysis of treatment effects of rapid maxillary expansion and face mask therapy in early Class III malocclusions. (24/1457)

An effective morphometric method (thin-plate spline analysis) was applied to evaluate shape changes in the craniofacial configuration of a sample of 23 children with Class III malocclusions in the early mixed dentition treated with rapid maxillary expansion and face mask therapy, and compared with a sample of 17 children with untreated Class III malocclusions. Significant treatment-induced changes involved both the maxilla and the mandible. Major deformations consisted of forward displacement of the maxillary complex from the pterygoid region and of anterior morphogenetic rotation of the mandible, due to a significant upward and forward direction of growth of the mandibular condyle. Significant differences in size changes due to reduced increments in mandibular dimensions were associated with significant shape changes in the treated group.  (+info)