Effects of a three-dimensional bimetric maxillary distalizing arch.
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This study aimed to investigate the dental effects of a three-dimensional (3D) bimetric maxillary distalizing arch. The Wilson rapid molar distalization appliance for Class II molar correction was used in 14 patients (10 girls and four boys with a mean age of 12.18 years). The open coil springs were activated with bent Omega stops and Class II intermaxillary elastics. The mandibular anchorage was gained by a 0.016 x 0.016 utility arch with a 3D lingual arch or a lip bumper with a standard lingual arch. The lateral cephalograms taken before and after treatment formed the material of the research. A Wilcoxon test was used to statistically evaluate the treatment effects. The results showed that the distal tipping of the maxillary first and second molars, and first and second premolars and canines were statistically significant. Significant distal movement occurred in all posterior and canine teeth. The maxillary first molar distalization was found to be 3.5 mm. The maxillary incisor showed significant proclination and protrusion. The decrease in overbite was found to be statistically significant. The mandibular plane angle significantly increased by a mean of 0.5 mm. In addition, significant soft tissue changes were observed. (+info)
Long-term stability of dental arch form in normal occlusion from 13 to 31 years of age.
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Based on observations of longitudinal changes in dental arch dimensions, it has been stated that an individuality of arch form and an integrity of this form exists. However, longitudinal studies evaluating arch form changes have rarely been reported in the literature. The purpose of this investigation was to use a computer-assisted method for the description and analysis of maxillary and mandibular arch form in a sample of normal occlusion subjects, and to evaluate the long-term stability in dental arch form from the age of 13-31 years. The study was carried out on 30 subjects of Scandinavian origin with normal occlusion, recorded at a mean age of 13.6 years and at follow-up at 31.1 years. Arch form analysis was based on a standardized photographic procedure, digitization of morphological landmarks, and a computerized form analysis in which arch form was described using eccentricity values of conics. No specific arch form could be found to represent the sample. Age changes occurred in arch form, although with large individual variations. For the mandible, a significant change to a more rounded arch form with age was found, which in males was accompanied by a significant increase in inter-molar distance and reduction in arch depth. There was also a significant correlation between change in mandibular arch form and increased irregularity of the lower incisors. These findings of lack of stability in arch form in normal occlusion subjects, when passing from adolescence into adulthood, further question the possibility of achieving stability post-orthodontically. (+info)
Temporomandibular disorders in relation to craniofacial dimensions, head posture and bite force in children selected for orthodontic treatment.
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The present study examined the associations between craniofacial dimensions, head posture, bite force, and symptoms and signs of temporomandibular disorders (TMD). The sample comprised 96 children (51F, 45M) aged 7-13 years, sequentially admitted for orthodontic treatment of malocclusions entailing health risks. Symptoms and signs of TMD were assessed by 37 variables describing the occurrence of headache and facial pain, clicking, jaw mobility, tenderness of muscles and joints, and the Helkimo Anamnestic and Dysfunction indices. Craniofacial dimensions (33 variables), and head and cervical posture (nine variables) were recorded from lateral cephalometric radiographs taken with the subject standing with the head in a standardized posture (mirror position). Dental arch widths were measured on plaster casts and bite force was measured at the first molars on each side by means of a pressure transducer. Associations were assessed by Spearman correlations and multiple stepwise logistic regression analyses. The magnitudes of the significant associations were generally low to moderate. On average, temporomandibular joint (TMJ) dysfunction was seen in connection with a marked forward inclination of the upper cervical spine and an increased craniocervical angulation, but no firm conclusion could be made regarding any particular craniofacial morphology in children with symptoms and signs of TMJ dysfunction. Muscle tenderness was associated with a 'long face' type of craniofacial morphology and a lower bite force. Headache was associated with a larger maxillary length and increased maxillary prognathism. A high score on Helkimo's Clinical Dysfunction Index was associated with smaller values of a number of vertical, horizontal, and transversal linear craniofacial dimensions and a lower bite force. (+info)
Morphological parameters as predictors of successful correction of Class III malocclusion.
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The aim of the study was to assess pre-treatment cephalometric parameters and measurements of the size of the apical bases as predictors of successful orthodontic correction of Class III malocclusions. Pre- and post-treatment lateral cephalograms and study models of 80 completed Class III subjects were examined to obtain 23 cephalometric parameters taken mainly from the analyses of McNamara and Schwarz, and to measure the size of the apical bases. Success of occlusal correction was evaluated as the percentage change of peer assessment rating score during treatment, which was used as the dependent variable in multivariate statistical analyses testing the predictive value of the parameters assessed. No improvement in the Class III skeletal pattern occurred during treatment and the treatment effects were confined to dentoalveolar changes. With the exception of the percentage midfacial length/mandibular length ratio, the net sum of maxillary and mandibular length differences, the mandibular ramus height/mandibular body length ratio and the gonion angle, most cephalometric parameters of pre-treatment craniofacial morphology assessed were poor predictors of successful correction of Class III malocclusions. Assessment of the size relationship of the maxillary and mandibular apical bases was the strongest predictor of occlusal correction achieved and may serve as a valuable diagnostic addition in the prediction of successful treatment outcome. (+info)
Maxillary morphology in obstructive sleep apnoea syndrome.
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The aim of this case-control study was to test the hypothesis that maxillary morphology differs between obstructive sleep apnoea (OSA) patients and non-snoring, non-apnoeic subjects. Forty randomly selected patients [36 M, 4 F; mean age 49 +/- 2 (SEM) years] with varying degrees of OSA (mean Apnoea/Hypopnoea Index 32 +/- 4/hour) were compared with 21 non-snoring, non-apnoeic control subjects (18 M, 3 F; mean age 40 +/- 2 years). An intra-oral assessment of the occlusion was carried out, particularly for the presence or absence of posterior transverse discrepancies. Maxillary dental arch width was assessed by standardized lateral inter-tooth measurements (inter-canine, inter-premolar, and inter-molar) from dental models. Palatal height and maxillary depth were also measured. The maxillary dental arch was described by a 4th order polynomial equation. The ratios of maxillary to mandibular width (max/mand) and maxillary to facial width (max/facial) were determined from standardized postero-anterior cephalometric radiographs in a subgroup of patients (n = 29) and all controls. Twenty patients (50 per cent) had evidence of posterior transverse discrepancies compared with one control subject (5 per cent; P < 0.01). All patients had significantly reduced inter-canine, inter-premolar, and inter-molar distances (P < 0.05). The maxillary depth was also shorter (P < 0.05), but palatal height was not different. The quadratic coefficient of the polynomial equation was greater in the patients than in the controls (P < 0.05), indicative of greater arch tapering. Patients had smaller maxillary to mandibular and maxillary to facial width ratios (P < 0.01). These results suggest that OSA patients have narrower, more tapered, and shorter maxillary arches than non-snoring, non-apnoeic controls. Further work is required to determine the relevance of these findings in the pathophysiology of OSA. (+info)
An experimental study on mandibular expansion: increases in arch width and perimeter.
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The purpose of this study was to estimate the increase in arch perimeter associated with mandibular lateral expansion. The mandibular expansion was simulated using a three-dimensional (3D) finite element method (FEM) and a computer graphics technique (3D simulation). The centre of rotation of molars during movement accompanied by lateral expansion was calculated using 3D FEM. The geometry of the model was determined using the mandibular bone of an East Indian skeletal specimen and 1 mm computer tomogram (CT) slices. The 3D set-up simulation was then conducted using 3D computer graphics instead of performing a manual set-up. Rotational movement was induced in the buccal segment, from the first premolar to second molar, in the 3D set-up model around the location of the centre of rotation (4.5 mm below the root apex of the first molar) derived from the FEM. According to 3D simulation, the model showed an opening space of 1.43 mm between the canine and first premolar, and thus a change in arch perimeter of 2.86 mm. The tip of the mesio-lingual cusp of the first molar moved 3.88 mm laterally, resulting in a change in inter-molar width of 7.76 mm. These values mean that a 1 mm increase in arch width resulted in an increase in arch perimeter of 0.37 mm. This result would be of value clinically for prediction of the effects of mandibular expansion. (+info)
The effect of maceration on the dental arches and the transverse cranial dimensions: a study on the pig.
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The dimensional change of the dental arches and the transverse cranial dimensions were studied in the pig to gain information on cranial post mortem changes and thus improve the possibilities of comparison between modern and skeletal samples. Dental arch dimensions were registered in 17 pigs within 30 minutes after they had been killed. The following day, the skulls were registered on lateral and axial radiographs. The animals were prepared, and storage and preparation included freezing and treatment in hot water. The water temperature did not exceed 65 degrees C. After this process, the skulls were again registered on lateral and axial radiographs. The skulls were then allowed to dry for 2 weeks and the direct measurements were repeated. The dimensions showed shrinkage of between 0 and 3.3 per cent. The mandible showed a greater change transversally in the posterior region than the cranium, which may have been due to its shape. The more deviant values for dimensional change were probably due to technical errors and the shrinkage may be expected to vary from 0.3 to 1.7 per cent, with greater values occurring in the posterior transverse parts of the mandible. A differential shrinkage in the maxilla could not be excluded and the values varied between 0.3 and 1.9 per cent. The results indicate that the crania in skeletal samples can be expected to be 0.3-1.7 per cent smaller than in vivo. (+info)
Maxillary retention: is longer better?
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Two different maxillary retention regimes were compared to ascertain if differences in posttreatment relapse existed. The patient pool was derived from subjects being treated at two orthodontic departments in the west of Scotland. Group 1 (20 patients) followed a 6 month regime using removable upper Hawley retainers for a period of 3 months full time and 3 months nights only. Group 2 (18 patients) followed a 1 year regime of 6 months full time and 6 months nights only. The results revealed that maxillary incisor alignment, as determined by Little's irregularity index, had relapsed by an average of 50 per cent of the end of retention value 3 months out of retention in Group 1 but only 23 per cent in Group 2. Although the actual mean values for relapse were 0.77 and 0.23 mm, respectively, seven subjects in Group 1 showed relapse of more than 3 mm as compared with only one in Group 2. This suggests that retaining a case for 1 year rather than 6 months is clinically beneficial. (+info)