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PubMed1998

Relationship between facial types and tooth and bone characteristics of the mandible obtained by CT scanning.

The purpose of this study was to evaluate relationships between morphological characteristics of vertical sections of the mandibular body and facial type. Of the correlation coefficients between tooth and bone inclination and facial type parameters, facial height index (FHI) was negatively associated with second premolar (P2), first molar (M1), and second molar (M2) inclinations. The angle represented by Frankfort horizontal plane to mandibular plane (FMA) was negatively associated with bone inclination of the M2 section. The buccal cortical bone was thicker in short-faced individuals than in the average and long-faced groups, while lingual cortical bone thickness of the M1 and M2 sections was greater. The basal cortical bone thickness of the L1 section was greater in the short-faced group, and the inclinations of the P2, M1, and M2 axes were significantly smaller. Teeth in the short-faced group inclined more lingually than in the average- and long-faced groups. The results of this study provide evidence that a significant but complex relationship exists between structures of the mandibular body and facial types. The morphological features that relate to masticatory function and facial types are associated with cortical bone thickness of the mandibular body and the buccolingual inclination of the first and second molars.

Bite Force↗
PubMed2001

Three-dimensional inclination of the dental axes in healthy permanent dentitions--A cross-sectional study in a normal population.

The 3-dimensional (3-D) inclination of the facial axis of the clinical crown (FACC) and the size of the clinical crowns were measured in 100 white northern Italians. The subjects consisted of 22 girls and 21 boys, ages 13-15 years (adolescents), and 31 women and 26 men, ages 16-26 years (adults), all with a complete permanent dentition and Class I dental relationships. The 3-D coordinates of dental landmarks were obtained with a computerized electromagnetic digitizer. Clinical crowns heights and FACC inclinations in the anatomical frontal and sagittal planes relative to 2 reference planes, maxillary and mandibular (between the incisive papilla and the intersection of the palatal/lingual sulci of the first permanent molars with the gingival margin), were calculated. Ages and sexes were compared by ANOVA. On average, the frontal plane FACCs of most teeth converged toward the midline plane of symmetry. In contrast, the incisors diverged from the midline plane or were nearly vertical. Within each quadrant, the inclinations of the postincisor teeth progressively increased. In the sagittal plane, most teeth had a nearly vertical FACC. FACC inclinations showed sex- and age-related differences (P < .05). In the frontal plane, the canines, premolars, and molars were more inclined in adolescents than in adults. In the sagittal plane, a large within-group variability was observed. Clinical crown height was significantly larger in males than in females in all maxillary and mandibular canines, premolars, second molars, maxillary central incisors, and first molars. With age, some degree of dental eruption was found in maxillary and mandibular canines, maxillary second premolars, and molars. The age-related decrease in FACC inclination may be the effect of a progressive buccal and mesial drift.

Adolescent↗
PubMed2001

Effects of patient age and sex on treatment: correction of Class II malocclusion with the Begg technique.

When children are treated orthodontically during a phase of active growth-notably adolescence-there is the opportunity to harness growth to achieve some of the correction, especially in the sagittal plane in which differential jaw growth can harmonize dental relationships. All correction must be from tooth movement when there is no growth. Three questions were addressed in the present study: (1) how much orthodontic correction is achieved by bone growth? (2) do the proportions of tooth and bone movement depend on patient age? and (3) do the jaws of boys and girls grow at discernibly different rates during treatment? A sample of 139 children aged 9 to 17 years at the start of treatment with Class II division 1 malocclusions was studied cephalometrically using Johnston analysis. Maxillary and mandibular growth were highest in the youngest children, with rates decreasing to effectively zero in the oldest adolescents. Means adjusted for age were significantly higher for boys than for girls for upper and lower jaw growth. Age had little influence on the amount of tooth movement except for a marked decline with age in the mesial movement of the maxillary first molar, which was greatest in the youngest patients of both sexes. The amount of orthodontic correction was independent of age, but in the youngest quartile of the sample, most of the correction (87%) was due to differential jaw growth in the youngest quartile of the sample, and the rest (13%) resulted from tooth movement, whereas in the oldest quartile, most of the correction was due to tooth movement (64% tooth movement and 36% bone growth). Overall, the influence of age and sex had significant influences on multiple skeletodental variables, suggesting that research designs need to account for these demographic sources of variability. Although all cases were treated to a Class I occlusion, the nature of the correction was affected measurably by the patient's age and sex.

Adolescent↗
PubMed1998

Posterior bite collapse--revisited.

Although there are different definitions of posterior bite collapse, only the classical definition of Amsterdam provides a definite diagnosis and treatment plan. This situation entails a subtle loss of the occlusal vertical dimension with resultant flaring of the maxillary incisors. Other causes for flaring, such as derangements of form and functions of lips and tongue, bruxism, habits, as well as the presence of advanced periodontal disease or malocclusions, should be ruled out before the diagnosis of posterior bite collapse can be made. The complexity of differential diagnosis is illustrated with three case reports.

Adult↗
PubMed2000

Posttreatment changes after successful correction of Class II malocclusions with the twin block appliance.

This investigation is a continuation of a previously published study assessing the treatment effects of the Twin Block appliance. All active treatment was carried out during the mixed dentition stage (mean starting age, 9 years 1 month) with final follow-up for the treatment group occurring in the permanent dentition (mean age, 13 years 1 month). Of the original group consisting of 28 consecutively treated severe skeletal Class II patients, 26 were available for follow-up. A comparison group of 28 untreated Class II subjects matched for age, sex, and vertical facial type was obtained from the Burlington Growth Centre according to the original study design. Of these 28 control subjects, 24 had 4-year follow-up cephalometric films available. The mean age of the controls was 12 years 11 months at the time of follow-up. During the active treatment phase, the Twin Block group experienced an average increase in mandibular unit length of 6.5 mm over a mean of 14 months (annualized rate of change of 5.6 mm per year). In comparison, the control group experienced a 2.3 mm increase in mandibular unit length during the 13-month observation period (annualized rate of 2.1 mm per year). In the posttreatment phase, the change in mandibular unit length for the Twin Block group was 6.0 mm over a 36-month period (annualized rate of change of 2.0 mm per year). The control group experienced an average increase in mandibular unit length of 6.7 mm over the posttreatment assessment period that was 34 months in duration (annualized rate of change of 2.4 mm per year). Although there was a slight reduction in mandibular growth rate after treatment, much of the significant increase in mandibular length achieved during the active phase of treatment with the Twin Block appliance was still present 3 years later when the subjects had matured into the permanent dentition stage.

Adolescent↗
PubMed1993

The spontaneous effects of lower first premolar extraction on the mesio-distal angulation of adjacent teeth and the relationship of this to extraction space closure in the long term.

This study was undertaken to examine the short- and long-term effects of uncontrolled extraction space closure on the angulation of buccal teeth in the lower arch following the extraction of all first premolars. The sample consisted of 20 subjects (12 males, 8 females). Impressions for study models were taken before premolar extraction (mean age 13 years), at monthly intervals during the first year thereafter, and at long-term follow-up (mean 13 years post-extraction). Measurements were made using the Reflex Microscope. Angulations of teeth (canines, second premolars, and first molars) were measured relative to the occlusal plane and to each other. The findings showed that although teeth tended to tip towards the extraction space, the amount of tipping was small (not exceeding 15 degrees in the majority of cases). The tipping was found to be greatest during the first 6 months following premolar extraction. In the long-term, as spaces continued to close, some uprighting was noted especially in the canine angulation. It is concluded that excessive tipping appears to be the exception rather than the rule in lower first premolar extraction cases.

Adolescent↗
PubMed1994

The association between spontaneous reversal of gingival recession in mandibular incisors and dentofacial changes in children. A 3-year longitudinal study.

In a previous 3-year longitudinal study, reversal of gingival recession in mandibular incisors was observed for 16 out of 28 participating children aged 6-13 years (Andlin-Sobocki et al., 1991). In the present report various dentofacial conditions that might be associated with this reversal were evaluated from dental casts and cephalometric radiographs by comparing the 16 children with spontaneous reversal of gingival recession (Group Rev) to the 12 children with persisting gingival recession (Group Per). Dental casts and cephalometric radiographs were obtained at baseline and after three years. The findings indicate that the children with persisting gingival recession tended to have a particular facial morphology and incisor pattern. They were likely to have a larger basal bone discrepancy between the maxillary and mandibular jaws, with somewhat more proclined and more irregularly positioned mandibular incisors. Although a reduction in incisor irregularity and a slight increase in anterior arch widths occurred for both groups during the observation period, the tooth alignment situation in Group Per at the end of the observation period was similar to that of Group Rev at baseline. Additionally, in Group Rev all facially deviating incisors with recession at baseline had self-corrected at 3 years. This was not the case for Group Per. Thus, spontaneous reversal of gingival recession in mandibular incisors seem to be related to developmental changes in the dentition favouring incisor alignment.

Adolescent↗
PubMed1994

The role of occlusal discrepancies in the long-term stability of the mandibular arch.

To assess the influence of occlusal discrepancies on the long-term stability of orthodontic treatment, the dental casts, and cephalometric records of 40 patients were evaluated, pretreatment, post-treatment, and at least 9 years post-retention. Post-treatment and post-retention casts were mounted in a semi-adjustable articulator in RCP. In addition to arch dimension measurements, discrepancies between RCP and ICP were measured in three spatial planes using a condymeter. Arch width and length decreased significantly after retention. The position of the lower incisors was relatively stable, whereas the lower molars moved forward substantially. Lower anterior irregularity increased after treatment. As a consequence, 60% of the cases had unsatisfactory lower anterior alignment after retention. The long-term records generally showed a trend towards moderate crowding. The amount of slide decreased over time and had a statistically significant, though clinically only moderate, influence on the increase in lower anterior irregularity.

Adolescent↗
PubMed1998

Therapeutic changes in extraction versus non-extraction orthodontic treatment.

Pre- and post-treatment lateral cephalograms of two extraction groups (E4: extraction of the four first premolars; E5: extraction of the four second premolars) and one non-extraction group (NE) were evaluated in patients treated with Begg appliances. It was the intention to investigate the initial amount of crowding, the changes in the position of incisors and molars, the soft tissue profile changes, and the clinical outcome. Ten linear and eight angular measurements were analysed. In order to assess the initial amount of crowding, the Arch Length Discrepancy (ALD) was measured on dental casts taken before treatment. The clinical outcome was evaluated using the PAR Index. The mean pretreatment crowding was nearly twice as large in group E4 when compared with groups E5 and NE. This difference was the main reason for the higher mean PAR score (21.4) for E4 when compared with E5 (15.4) and NE (15.2). In addition, for the cephalometric pretreatment values, some significant differences between the three groups were found: the upper and lower incisors and the lower lip region relative to the pterygomaxillary vertical plane (PMV) were more protrusive in group E5; the inter-incisal angle in both extraction groups was smaller than in the non-extraction group. During treatment, the lower incisor position relative to PMV did not change significantly, and the upper incisors moved backward approximately 2 mm in both extraction groups. This was not reflected in a significant change in lip position. In the non-extraction group, tooth alignment was accompanied by a significant proclination of the incisors, and a comparable forward movement in the lip region when measured in relation to PMV. In the three types of cases, no unfavourable changes in the facial profile were seen. A mean enlargement of about 6 degrees normalized the inter-incisal angle in both extraction groups, while in the non-extraction group the inter-incisal angle became smaller than the norm value. In the three types of cases, upper and lower molars were moved mesially. This movement was higher in group E5 than E4, and lower in the NE cases. Mainly due to the case selection (Class I or very mild Class II or Class III malocclusions), the pretreatment PAR Index was not very high. The percentage reduction for the three groups was higher than 90 per cent. With post-treatment mean PAR scores less than 2, groups E4, E5, and NE can be regarded as having an almost ideal clinical outcome.

Adolescent↗
PubMed1999

Initial tooth displacement in vivo as a predictor of long-term displacement.

In the past, the dry skull has been used as a hypothetical model to test initial orthodontic and orthopaedic force systems. However, the question as to whether this hypothetical model can be used as a predictor of long-term displacements in vivo remains unanswered. In this study, an attempt was made to compare initial tooth displacement with the long-term effect after application of the force system for a longer period of time, in six adult dogs. Tooth displacement was obtained by applying a force by means of a coil spring (push) system. Following application of a force of 50 g in the first series (n = 3) and 80 g in the second series (n = 3), initial displacements were registered by means of speckle interferometry. The long-term displacement was registered by means of standardized cephalometry in the same dog by leaving the force system in place for 5 weeks. The mean values of the displacement vectors of the second premolars in the six dogs were compared. A paired t-test revealed no significant differences between the initial and long-term displacements in any of the dogs. The results show that both groups of measurements belong statistically to the same sample and that initial tooth displacement measured by means of speckle interferometry is a valuable predictor for forecasting long-term displacement in vivo after 5 weeks.

Animals↗
PubMed1989

Stability of magnetic versus mechanical palatal expansion.

Spatial stability following palatal expansion (PE) treatment was studied longitudinally on 8 Macaca fascicularis monkeys. The sample was divided into short-term and long-term groups. The four subjects in each group received: (1) an indirect screw (IS) PE appliance (F = 2035 g), (2) an indirect magnetic (IM) PE appliance (F = 258 g and 360 g), (3) a direct magnetic (DM) PE appliance (F = 258 g and 360 g) and (4) a sham appliance. The terms direct and indirect describe force transmission directly, via pinning to the palatal shelves or indirectly, via abutment teeth. Active treatment in the long-term group was followed by a 4 month retention phase and a 2 month relapse phase. The implant study indicated the transverse stability to be greatest in the skeletally borne appliance. Correspondingly, intercanine distance relapse was 53 per cent and 23 per cent for the IS and DM subjects, respectively. Intermolar expansion was significantly more stable than intercanine expansion due to selective activity of the circum-maxillary sutures (transverse suture) and root configuration. Sagittal advancement and vertical superior translation, which are controlled by selective activity of the premaxillary suture, were particularly apparent in the magnetic appliances with a low force PE regimen. Clinical implications suggest that the use of a low force PE regimen can be of substantial benefit in young skeletal Class III patients with transverse maxillary deficiency.

Animals↗