Change in the width of the mandibular body from 6 to 23 years of age: an implant study.
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After the ossification of the mandibular symphysis, shortly after birth, changes in mandibular width would be expected to occur only by surface apposition or resorption on the buccal surfaces of the left and right mandibular halves. However, evidence for an opening hinge movement of the two mandibular halves around a vertical axis located in the region of the mandibular symphysis was recently found in longitudinal studies of 29 subjects with unilateral implant markers in the mandible. These subjects were followed from 8.5 to 15.5 years of age (Korn and Baumrind, 1990; Baumrind and Korn, 1992). The aim of the present investigation was to examine whether the presence of such an age-related increase in mandibular body width could be confirmed in a sample with bilateral implant markers in the mandible. The sample comprised 10 subjects (3F, 7M) from the files of another longitudinal study with implant markers (Bjork, 1968). A total of 122 pairs of annual lateral and postero-anterior (p-a) cephalometric records were available, covering longitudinal observation periods ranging from 8 to 16 years within an age interval of between 6 and 23 years. The width between a right and left side mandibular implant marker was measured with digital callipers on all p-a radiographs. Each measurement was corrected mathematically for various sources of radiographic enlargement. A small, but statistically significant increase in the distance between the right and left implant markers, i.e. in the bilateral width of the mandibular body, was observed in all subjects. The total increase in width in each subject ranged from 0.7 to 1.7 mm for the various periods of observation (P < or = 0.01). For the 12-year period from 6 to 18 years, the average total increase was 1.6 mm (P < or = 0.001, SD = 0.42), i.e. 0.13 mm/year. After this age there was no systematic trend. The mechanism for this increase in width is unknown. It is suggested that during postnatal growth, an increasing load from the masticatory occlusal forces might influence endosteal bone remodelling in the mandibular body, thus producing or allowing a gradual permanent outward bending of the right and left mandibular halves. (+info)
Statistical methods for the comparison of measurements derived from orthodontic imaging.
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Biometric comparison procedures for dental imaging methods with continuous outcome were reviewed, mainly concentrating on assessment and comparison of accuracy and precision according to the study design. Univariate graphical and numerical representations of corresponding deviations were summarized to derive a 'check list' of minimum information necessary to compare the measurement methods. The methods reviewed in this investigation are illustrated by the comparison of conventional (radiographic) cephalometry versus assessment using the DigiGraph in 50 female children. A paired t-test and the corresponding confidence interval approach were used to assess deviations in location of two imaging methods; the test procedures of Maloney/Rastogi, Hahn/Nelson, and Grubbs were surveyed as proposals for the comparison of precisions in paired data. The Krippendorff coefficient was used as an aggregate measure for method concordance. Since these methods can be performed by simple modification of standard options available in most statistical software packages, this review intends to enable dental researchers to choose the correct methods, and perform adequate data analysis and representation. (+info)
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)
A comparative MRI study of the relationship between neuroanatomical asymmetry and interhemispheric connectivity in primates: implication for the evolution of functional asymmetries.
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The authors tested the theory that hemispheric specialization evolved as a consequence of reduced interhemispheric connectivity by examining whether neuroanatomical asymmetries were associated with variation in the ratio of corpus callosum size to brain volume (CC:VOL) and to neocortical surface area (CC:NEO) in human and nonhuman primates. Magnetic resonance images were collected in a sample of 45 primates including 8 New World monkeys, 10 Old World monkeys, 4 lesser apes, 17 great apes, and 6 humans. CC:VOL and CC:NEO were determined and correlated with measures of brain asymmetry. The results indicate that brain asymmetry significantly predicted CC:VOL and CC:NEO. Subsequent analyses revealed that species variation in functional asymmetries in the form of handedness are also inversely related to CC:NEO. Taken together, these results support the hypothesis that leftward brain asymmetries may have evolved as a consequence of reduced interhemispheric connectivity. (+info)
A cephalometric comparison of subjects with snoring and obstructive sleep apnoea.
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This prospective study analysed the upright lateral cephalometric radiographs of 115 dentate, Caucasian males. Forty-five subjects exhibited proven obstructive sleep apnoea (OSA), 46 were simple snorers, and the remaining 24 subjects, who had no history of respiratory disease and did not snore, acted as controls. Radiographs were traced and digitized, and comparisons were made of the dento-skeletal, soft tissue, and oropharyngeal features of the three groups. Differences were also sought between the snoring and OSA subjects. Of the hard tissue measurements, only the cranial base angle and mandibular body length showed significant inter-group differences (P < 0.001 and P < 0.05, respectively). When the airway and associated structures were examined, both snorers and OSA subjects exhibited narrower airways, reduced oropharyngeal areas, shorter and thicker soft palates, and larger tongues than their control counterparts. Comparison of the two sleep disordered breathing groups showed no differences in any of the skeletal or dental variables examined. However in OSA subjects, the soft palate was larger and thicker (P < 0.05), both lingual and oropharyngeal areas were increased (P < 0.01 and P < 0.05, respectively) and the hyoid was further from the mandibular plane (P < 0.05). Thus, whilst the dento-skeletal patterns of snorers resembled those of subjects with OSA, some differences in soft tissue and hyoid orientation were apparent. There was not, however, a recognizable gradation in size of the airway and its associated structures from control through snoring to OSA subjects. This suggests that there may be a cephalometrically recognizable predisposition towards the development of sleep disordered breathing, but that this is only one facet of the condition. (+info)
Surgical mandibular advancement and changes in uvuloglossopharyngeal morphology and head posture: a short- and long-term cephalometric study in males.
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The aim of the present study was to investigate, by means of an extensive cephalometric examination, the alterations which took place in hyoid bone position, head posture, position and morphology of the soft palate, and tongue and sagittal dimensions of the pharyngeal airway after mandibular advancement osteotomy for the correction of mandibular retrognathism. The sample consisted only of adult males who underwent mandibular advancement by bilateral sagittal ramus split osteotomy (BSRO) with rigid fixation. Profile cephalograms were obtained 1-3 days before surgery (20 subjects), and 6 months (20 subjects) and 3 years (19 subjects) after the surgery. Statistical evaluation was performed by paired Student's t-test and Pearson product moment correlation analysis. At the short-term follow-up, hyoid bone and vallecula assumed a more superior (AH perpendicular FH, AH perpendicular ML, AH perpendicular S, V perpendicular FH) and anterior position (AH-C3 Hor, V-C3), which was maintained at the long-term follow-up. The soft palate (NL/PM-U) became more upright at the short-term follow-up. The tongue demonstrated a transient increase in height (H perpendicular VT) and a less upright position (VT/FH) at the long-term observation. In addition, a more upright cervical spine (OPT/HOR, CVT/HOR) was recorded at the long-term follow-up. The pharyngeal airway space at the level of the oropharynx (U-MPW) and the retroglossal space at the base of the tongue (PASmin) showed an increase in the sagittal dimension at the short-term follow-up. Significant widening at the PASmin level was sustained at the long-term follow-up, indicating that mandibular advancement osteotomy could increase airway patency and be a treatment approach for sleep apnoea in selected patients. (+info)
Surgical mandibular setback and changes in uvuloglossopharyngeal morphology and head posture: a short- and long-term cephalometric study in males.
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A detailed cephalometric analysis was conducted on a sample of 31 adult males who underwent correction of mandibular prognathism by mandibular setback osteotomy (BSRO) with rigid fixation to evaluate the changes in uvuloglossopharyngeal morphology, hyoid bone position and head posture. Lateral cephalograms were obtained 1-3 days prior to the operation and at standardized 6 months and 3 years post-operative follow-up. Statistical evaluation was performed by paired Student's t-test and Pearson product moment correlation analysis. Inferior position of the hyoid bone (AH perpendicular FH, AH perpendicular ML, AH perpendicular S) and valeculla (V perpendicular FH) was recorded at the 6-month follow-up, a transient finding as at 3 years almost complete recovery to their pre-surgical position was noted. No posterior displacement of the above structures (AH-C3 Hor, V-C3) was recorded. Soft palate length (pm-U) was increased and maintained at the long-term follow-up while its posture (NL/pm-U) became less upright. The tongue showed increased length (V-T) and sagittal area (TA) and a more upright posture (VT/FH) at the late follow-up. Increased contact length between tongue and the soft palate (CL) and less residual oropharyngeal area [area not occupied by soft tissues, (TA + SPA)/OPA] was found at the long-term follow-up. Craniocervical agulation (NSL/OPT, NSL/CVT) was increased indicating cervical hyperflexion at the 3-year follow-up. Reduction of the sagittal dimension of the oropharyngeal airway space (U-MPW) appeared at the first follow-up and was sustained at the longest follow-up which, in conjunction with the decrease in residual oropharyngeal area, could raise questions regarding airway patency after mandibular setback osteotomy. (+info)
Trigonocephaly in rabbits with familial interfrontal suture synostosis: the multiple effects of premature single-suture fusion.
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Previous studies from our laboratory have characterized the craniofacial morphology and growth patterns of an inbred strain of rabbits with autosomal dominant coronal suture synostosis. A number of rabbit perinates from this colony have been collected sporadically over a 5-year period with premature interfrontal suture synostosis. The present study describes the very early onset of craniofacial dysmorphology of these rabbits and compares them to similar-aged normal control rabbits. A total of 40 perinatal New Zealand White rabbits were used in the present study. Twenty-one comprised the sample with interfrontal suture synostosis and ranged in age from 27 to 38 days postconception (term = 31 days) with a mean age of 33.53 days (+/-2.84 days). Nineteen rabbits served as age-matched, normal controls (mean age = 33.05 days +/-2.79 days). Lateral and dorsoventral radiographs were collected from each rabbit. The radiographs were traced, computer digitized, and 12 craniofacial measurements, angles, and indices were obtained. Mean measures were compared using an unpaired Student's t-test. All synostosed rabbits were stillborn or died shortly after birth. Grossly, these rabbits exhibited extreme frontal bossing, trigonocephaly with sagittal keeling, and midfacial shortening. No somatic anomalies were noted. Radiographically, rabbits with interfrontal suture synostosis had significantly (P < 0.05) narrower bifrontal widths, shorter cranial vault lengths, kyphotic cranial base angles, and different cranial vault indices (shapes) compared to controls. Results reveal severe and early pathological and compensatory cranial vault changes associated with premature interfrontal suture synostosis in this rabbit model. The 100% mortality rate noted in this condition may be related to the inheritance of a lethal genetic mutation or to neural compression from reduced intracranial volume. Results are discussed in light of current pathogenic hypotheses for human infants with premature metopic suture synostosis. (+info)