Mandibular shape and skeletal divergency. (1/174)

Pre-treatment lateral cephalograms of 41 skeletal Class I girls aged 11 to 15 were divided according to MP-SN angle: lower than 28 degrees (hypodivergent, 10 girls), between 31 and 34 degrees (normodivergent, 18 girls), or larger than 37 degrees (hyperdivergent, 13 girls). The mandibular outlines were traced and digitized, and differences in shape were quantified using the elliptic Fourier series. Size differences were measured from the areas enclosed by the mandibular outlines. Shape differences were assessed by calculating a morphological distance (MD) between the size-independent mean mathematical reconstructions of the mandibular outlines of the three divergency classes. Mandibular shape was different in the three classes: large variations were found in hyperdivergent girls versus normodivergent girls (MD = 4.61), while smaller differences were observed in hypodivergent girls (MD versus normodivergent 2.91). Mean size-independent mandibular shapes were superimposed on an axis passing through the centres of gravity of the condyle and of the chin. Normodivergent and hyperdivergent mandibles differed mostly at gonion, the coronoid process, sigmoid notch, alveolar process, posterior border of the ramus, and along the mandibular plane. A significant size effect was also found, with smaller mandibles in the hyperdivergent girls.  (+info)

Long-term effect of the chincap on hard and soft tissues. (2/174)

The short- and long-term effects of the chincap used in combination with a removable appliance to procline upper incisors were analysed cephalometrically in 23 patients with Class III malocclusions. The overall changes were compared with growth changes in a closely matched control sample of untreated Class III patients. There was no evidence that the chincap retarded growth of the mandible. During treatment, there was an increase in mandibular length and facial height. The lower incisors retroclined and the upper incisors proclined. The incisor relationship was corrected. Soft tissue changes included an increase in nasolabial angle and improvement in soft-tissue profile, including the nose. Skeletal post-treatment changes included further mandibular growth associated with an increase in angle SNB and Wits measurement. Facial height also increased significantly. The Class I overjet was maintained, although slightly diminished. The soft tissue nose, upper and lower lip, and chin moved anteriorly, and the nasal tip and chin moved inferiorly. At the end of the study period there were no significant skeletal or soft tissue differences between the treated and control groups. The only significant contrasts were in the overjet and the overbite. Chincap therapy combined with an upper removable appliance to procline the upper incisors is effective in producing long-term correction of the incisor relationship by retroclination of lower incisors, proclination of upper incisors, and redirection of mandibular growth in a downward direction. The direction of growth at the chin is maintained subsequent to treatment, as are the changes in incisor inclination, although in diminished form. There are corresponding improvements in the soft tissue profile.  (+info)

Random errors in localization of landmarks in postero-anterior cephalograms. (3/174)

The aim of the present study was to evaluate the random error in localization of the most common landmarks in postero-anterior cephalograms (PAC). The study took place at the Department of Orthodontics of Aarhus University during the period 1993-1995. The material consisted of 30 standardized PAC taken in natural head position. Five examiners had to identify 34 landmarks on each cephalogram. Subsequently, all examiners had to identify again the same 34 landmarks on one randomly selected cephalogram five times with a time interval of at least 24 hours. All landmarks were digitized, related to an X-Y co-ordinate system, and an arithmetical mean was calculated. The accuracy of digitizing was evaluated by digitizing one randomly selected cephalogram 10 times. The main findings of this study are: (1) The digitizing error is negligible compared to the errors introduced by landmark identification. (2) Each landmark has its own characteristic pattern of variance, which is very similar on both sides. (3) Significant differences in accuracy exist between the various postero-anterior landmarks. The six most accurate landmarks are mastoid left (l) and right (r), latero-orbitale (l) and (r), and antegonion (l) and (r). The six least accurate landmarks are coronoid (l) and (r), condylar (l) and (r), and mandibular foramen (l) and (r). (4) A significant difference in the accuracy of landmark identification between the five examiners was only seen for seven of the 34 landmarks. (5) No evidence was found that one examiner was consistently better/worse than the others. (6) No improvement in the accuracy was found after repeated identification, thus there seems to be no short-term 'learning process'. Refereed Paper  (+info)

The effect of clustered versus regular sleep fragmentation on daytime function. (4/174)

Previously, we found that regular sleep fragmentation, similar to that found in patients with sleep apnoea/hypopnoea syndrome (SAHS), impairs daytime function. Apnoeas and hypopnoeas occur in groups in patients with REM or posture related SAHS. Thus, we hypothesised that clustered sleep fragmentation would have a similar impact on daytime function as regular sleep fragmentation. We studied 16 subjects over two pairs of 2 nights and 2 days. The first night of each pair was for acclimatisation. On the second night, subjects either had their sleep fragmented regularly every 90 s, or fragmented every 30 s for 30 min every 90 min, the remaining 60 min being undisturbed. We fragmented sleep with tones to produce a minimum 3 s increase in EEG frequency. During the days following each pair of nights we tested subjects daytime function. Total sleep time (TST) and microarousal frequency were similar no both study nights. We found significantly less stage 2 (55 SD 4, 62 +/- 7%; P = 0.001) and more slow wave sleep (21 SD 3, 12 +/- 6%; P < 0.001) on the clustered night. Mean sleep onset latency was similar on MSLT (clustered 10 SD 5, regular 9 +/- 4 min; P = 0.7) and MWT (clustered 32 SD 7, regular 30 +/- 7 min; P = 0.2). There was no difference in subjects mood or cognitive function after either study night. These results suggest that although there is more slow wave sleep (SWS) on the clustered night, similar numbers of sleep fragmenting events produced similar daytime function whether the events were evenly spaced or clustered.  (+info)

A comparison of chincap and maxillary protraction appliances in the treatment of skeletal Class III malocclusions. (5/174)

The purpose of this retrospective investigation was to compare cephalometrically the treatment effects of chincap and maxillary protraction appliances in subjects with a Class III skeletal malocclusion with a combination of an underdeveloped maxilla and prominent mandible. Twenty-four patients were divided into two groups according to the treatment type; the chincap group (mean age 11.03 years, n = 12) and the Delaire type maxillary protraction appliance group (mean age 10.72 years, n = 12). In both groups, a significant increase in ANB, molar relationship, and overjet showed the effect of the appliances in the treatment of Class III malocclusions. In comparing the two groups, the maxilla was displaced more anteriorly and the molar relationship correction was greater in the maxillary protraction appliance group (P < 0.05). Angular and dimensional parameters for lower incisor/NB and nasolabial angle showed significant differences between the groups (P < 0.05).  (+info)

Describing shape changes in the human mandible using elliptical Fourier functions. (6/174)

Elliptical Fourier functions (EFF) were generated for the boundary outline of the mandibular form in 24 non-orthodontic growth study subjects at 9, 11, 13, and 15 years of age. The mean residual fit (observed versus predicted points) of the mandibular form was 0.11 mm, with a range from 0.09 to 0.14 mm, suggesting an accurate fit. The mean plot for each of the four age groups was area standardized and superimposed on the centroid. Shape changes in males and females were found to be similar. No significant shape changes were found between 9 and 11 years. Shape changes were observed in the lower incisor area, the mental region, the body of the mandible, and the gonial angle area between 11 and 15 years. These changes coincided with the onset of the pubertal growth spurt.  (+info)

Open bite: stability after bimaxillary surgery--2-year treatment outcomes in 58 patients. (7/174)

Stability after bimaxillary surgery to correct open bite malocclusion and mandibular retrognathism was evaluated on lateral cephalograms before surgery, 8 weeks post-operatively, and after 2 years. The 58 consecutive patients were treated to a normal occlusion and good facial aesthetics. Treatment included the orthodontic alignment of teeth by maxillary and mandibular fixed appliances, Le Fort I osteotomy, and bilateral sagittal split ramus osteotomy. Twenty-six patients also had a genioplasty. Intra-osseous wires or bicortical screws were used for fixation. Twenty-three patients had maxillo-mandibular fixation (MMF) for 8 weeks or more, six for 4-7 weeks, 14 for 1-3 weeks, and 15 had no fixation. At follow-up 2 years later, the maxilla remained unchanged and the mandible had rotated on average 1.4 degrees posteriorly. Seventeen patients had an open bite. Among them, eight patients had undergone segmental osteotomies. The relapse was mainly due to incisor proclination. The most stabile overbite was found in the group with no MMF after surgery.  (+info)

Sleep fragmentation: comparison of two definitions of short arousals during sleep in OSAS patients. (8/174)

The measurement of arousals during sleep is useful to quantify sleep fragmentation. The criteria for electroencephalography (EEG) arousals defined by the American Sleep Disorders Association (ASDA) have recently been criticized because of lack of interobserver agreement. The authors have adopted a scoring method that associates the increase in chin electromyography (EMG) with the occurrence of an alpha-rhythm in all sleep stages (Universite Catholique de Louvain (UCL) definition of arousals). The aim of the present study was to compare the two scoring definitions in terms of agreement and repeatability and the time taken for scoring in patients with obstructive sleep apnoea syndrome (OSAS) of varying severity. Two readers using both ASDA and UCL definitions scored twenty polysomnographies (PSGs) each on two occasions. The PSGs were chosen retrospectively to represent a wide range of arousal index (from 6-82) in OSAS patients. There was no difference in the arousal indices between readers and between scoring methods. The mean+/-SD difference between the two definitions (the bias) was 1.1+/-3.76 (95% confidence interval: -0.66-2.86). There was a strong linear relationship between the arousal index scored with the two definitions (r=0.981, p<0.001). Mean+/-SD scoring duration was significantly shorter for UCL than for ASDA definitions (18.5+/-5.4 versus 25.3+/-6.6 min, p<0.001). In conclusion, it has been found that in obstructive sleep apnoea syndrome patients, the American Sleep Disorders Association and Universite Catholique de Louvain definitions were comparable in terms of agreement and repeatability.  (+info)