The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study.
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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)
A comparison of sagittal and vertical effects between bonded rapid and slow maxillary expansion procedures.
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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)
Thin-plate spline analysis of treatment effects of rapid maxillary expansion and face mask therapy in early Class III malocclusions.
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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)
Rapid palatal expansion in treatment of Class II malocclusions.
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A technique which combines the use of rapid maxillary expansion and fixed appliance in growing patients, is presented. The treatment in three patients with Class II division 1 malocclusion and different skeletal patterns is described, and relative advantages highlighted. (+info)
How much space is created from expansion or premolar extraction?
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The aim of this study was first to investigate the relationship between maxillary arch expansion and change in arch depth (overjet), and secondly to quantify the reduction in maxillary arch depth following extraction of 4\4 with complete space closure. A model of maxillary typodont teeth was constructed to allow expansion and premolar removal. Arch dimensions were recorded using a reflex microscope. A linear relationship was found between arch expansion and reduction of the arch depth. When the premolars were removed, there was a greater reduction in arch depth than the mesio-distal width of these teeth. (+info)
Effect of rapid maxillary expansion on skeletal, dental, and nasal structures: a postero-anterior cephalometric study.
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The purpose of this study was to compare the transverse dimensions of skeletal, dental, and nasal structures of a group of patients with maxillary narrowness before and after rapid maxillary expansion (RME) with an untreated control group using postero-anterior (PA) cephalometric radiographs. The material consisted of PA cephalograms of 25 children with a posterior crossbite (mean age 13 years 4 months), and 25 age- and sex-matched controls (mean age 13 years 11 months). Both groups consisted of 20 females and five males. Thirty-four reference points were digitized using the Dentofacial Planner software program. The 17 variables studied consisted of six skeletal, four dental, and seven intra-nasal linear measurements. Student's t-tests were used to compare the differences between the groups, and the effect of RME on skeletal, dental, and nasal structures. RME produced small, but statistically significant changes in maxillary width, upper and lower molar widths, the width between upper central incisor apices, and intra-nasal width. When compared with previous studies, the changes observed were similar for patients of a similar age group, but less than reported for a younger population. There is some evidence that the pattern of expansion produced by RME will vary depending on the age and maturity of the subject. (+info)
Mandibular advancement using an intra-oral osteogenic distraction technique: a report of three clinical cases.
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Osteogenic distraction has been used for decades to lengthen limbs and now attention is focused upon its use within the craniofacial skeleton. This paper addresses distraction of the mandible. It is proposed that mandibular osteogenic distraction could be a possible adjunct to the orthodontic treatment of those adult patients with skeletal anomalies, who would benefit from combined orthodontic/orthognathic treatment. Three consecutive cases from one unit are presented, where adult patients with severe Class II division 1 malocclusions have undergone orthodontic treatment combined with mandibular osteogenic distraction, instead of conventional bilateral sagittal split osteotomies. (+info)
Rapid palatal expansion in mixed dentition using a modified expander: a cephalometric investigation.
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The aims of this investigation were to cephalometrically study the short-term skeletal and dental modifications induced by rapid palatal expansion in a sample of 20 patients (10 male, 10 female), aged 6-10 years (mean age 8 years) in mixed dentition with a uni- or bilateral posterior crossbite, a mild skeletal Class II malocclusion, and an increased vertical dimension (FMA, SN/\GoGn), and to compare them with an untreated matched control group of 20 subjects (10 male and 10 female), mean age 8 years. Cephalometric analysis showed that the maxilla displayed a tendency to rotate downwards and backward, resulting in a statistically significant increase of the SN/\PP angle (T0 = 9*95 degrees, T1 = 11*60 degrees, P < 0*01) and the SN-ANS linear value (T0 = 49*50 mm, T1 = 51*10 mm, P < 0*05). In addition, there was a statistically significant alteration of the anterior total facial height N-Me (T0 = 113*15mm, T1 = 114*15 mm, P < 0*05) and for the dental upper molar measurement U6-PP (T0 = 19*70 mm, T1 = 20*30 mm, P < 0*05). The small alterations found in the anterior total facial height and in the sagittal angles agree with previous studies, and suggest that RPE can be also used in subjects with a tendency to vertical growth and a skeletal Class II malocclusion. (+info)