Mandibular Intercanine Width Research Articles

Arch-width and perimeter changes in patients with borderline Class I malocclusion treated with extractions or without extractions with air-rotor stripping

The aim of this study was to compare dental arch-width and perimeter changes in patients with borderline Class I occlusion, treated with extractions or without extractions with air-rotor stripping (ARS). The study was conducted with 26 sets of pretreatment and posttreatment dental models of patients with borderline Class I occlusion. Thirteen patients (mean age, 18.1 +/- 3.7 years) were treated with 4 premolar extractions, and 13 (mean age, 17.8 +/- 2.4 years) were treated without extractions but with the ARS technique. Mean maxillary and mandibular crowding values were 5.7 +/- 1.5 and 5.9 +/- 1.4 mm in the extraction group, and 5.0 +/- 1.3 and 5.9 +/- 1.3 mm in the nonextraction group, respectively. A digital caliper was used to measure maxillary and mandibular intercanine and intermolar arch widths and arch perimeters. The Wilcoxon test was used to evaluate treatment changes in each group. The Mann-Whitney U test was used to compare the pretreatment and posttreatment values and the treatment changes between the 2 groups. At the start of treatment, the maxillary and mandibular intercanine and intermolar widths and the arch perimeters of both groups did not differ statistically. The maxillary intercanine widths were maintained in both groups. The maxillary and mandibular intermolar widths and arch perimeters decreased in the extraction group. In the nonextraction group, intermolar widths decreased, but arch perimeters did not change significantly. After treatment, the maxillary and mandibular intercanine widths were not different between the groups. In Class I borderline patients with moderate crowding, extraction therapy with minimum anchorage did not result in narrower dental arches, and nonextraction treatment with ARS preserved the intercanine arch widths and arch perimeters.

Dental arch widths in the early and late permanent dentitions of a Nigerian population

Objective: This study was carried out in a Nigerian population to assess arch widths at two different stages of dentition, to observe the comparative changes which may occur, and to determine the presence or absence of sexual dimorphism in arch dimensions. Material: The study population consisted of two groups of 150 subjects. Group 1 consisted of 75 males and 75 females aged 10-13 years (early permanent dentition); while Group 2 consisted of 75 males and 75 females aged 18-25 years (late permanent dentition). Measurements taken included maxillary and mandibular inter-canine, inter-premolar and inter-molar widths for both groups. Result: In the early permanent stage, the mean maxillary inter-canine, inter-premolar and inter-molar widths were 36.37mm, 45mm and 55.22mm respectively in males and 34.35mm, 42.62mm and 51.56mm respectively in females. All findings were significantly greater in males. In the mandibular arch, findings recorded in males were also significantly greater than females with the exception of the inter-canine widths. In the late permanent dentition the mean maxillary inter-canine, inter-premolar and inter-molar arch widths were 37.65mm, 46.25mm and 57.35mm respectively in males and 37.07mm, 45.21mm and 55.30mm respectively in females. Conclusion: Comparative changes in arch widths between early and late permanent dentition stages were seen with greater increases in arch widths in the maxilla when compared to the mandible. Significant sexual dimorphism was observed in almost all dimensions measured. Key words: Dental arch widths, Nigerians

Age-Related Long-Term Posttreatment Occlusal and Arch Changes

To evaluate differences in long-term postretention changes between adolescents and adults. The sample included 96 subjects, 51 adolescents and 45 adults (14.2 +/- 0.8 and 21.5 +/- 6.8 years of age, respectively, at the end of treatment) retained for 3 years and followed approximately 16 years post treatment, who were randomly selected from two private practices. Prior to treatment, 38 and 58 had Class I and Class II malocclusions, respectively. With the exception of adult midlines, all of the occlusal variables (overjet [0.50-0.77 mm], overbite [0.85-0.95 mm], the maxillary incisor irregularity [0.69-0.80 mm], the mandibular incisor irregularity [0.85-1.50 mm] and the PAR score [0.86-1.92 points]) showed significant increases over time. Adolescents consistently showed greater increases of the occlusal variables than adults, with mandibular incisor irregularity and the PAR index attaining statistically significant (P < .05) levels. Arch length and mandibular intercanine width showed statistically significant decreases over time in both groups; maxillary intercanine and intermolar widths did not change significantly. Overjet increased significantly more in Class II patients than in Class I patients, whereas Class I patients showed significantly greater decreases in mandibular intermolar width than Class II patients. Over the 16-year posttreatment period, adolescents showed significantly greater increases in mandibular incisor irregularity, and the PAR index than adults. Treated Class I patients demonstrated less increase in overjet and greater decreases in mandibular intermolar width than Class II patients.

Comparative study of dental arch width in plaster models, photocopies and digitized images

The aim of this study was to comparatively assess dental arch width, in the canine and molar regions, by means of direct measurements from plaster models, photocopies and digitized images of the models. The sample consisted of 130 pairs of plaster models, photocopies and digitized images of the models of white patients (n = 65), both genders, with Class I and Class II Division 1 malocclusions, treated by standard Edgewise mechanics and extraction of the four first premolars. Maxillary and mandibular intercanine and intermolar widths were measured by a calibrated examiner, prior to and after orthodontic treatment, using the three modes of reproduction of the dental arches. Dispersion of the data relative to pre- and posttreatment intra-arch linear measurements (mm) was represented as box plots. The three measuring methods were compared by one-way ANOVA for repeated measurements (alpha = 0.05). Initial / final mean values varied as follows: 33.94 to 34.29 mm / 34.49 to 34.66 mm (maxillary intercanine width); 26.23 to 26.26 mm / 26.77 to 26.84 mm (mandibular intercanine width); 49.55 to 49.66 mm / 47.28 to 47.45 mm (maxillary intermolar width) and 43.28 to 43.41 mm / 40.29 to 40.46 mm (mandibular intermolar width). There were no statistically significant differences between mean dental arch widths estimated by the three studied methods, prior to and after orthodontic treatment. It may be concluded that photocopies and digitized images of the plaster models provided reliable reproductions of the dental arches for obtaining transversal intra-arch measurements.

Sheldon Friel Memorial Lecture 2007: Myths and Legends in Orthodontics

Opinions and procedures, which are incorrect or invalid but continue to exist, are discussed. Eight seldomly criticised subjects have been selected which are relevant for the theory and practice of orthodontics. First, the idea that all individuals have or can reach an occlusion with contact between all opposing teeth is commented upon. Second, interest and preferences of editors and referees in the acceptance of manuscripts is clarified and the neglecting of published information explained. Third, the reliability of conclusions drawn from lateral roentgenocephalograms is reviewed in regard of the accuracy of commonly used bony landmarks. Fourth, the interpretation of growth data concerning visual interpretation, error of the method and reliability of conclusions based on cephalometric data, is treated. Fifth, the need of lateral roentgenocephalograms and recently developed digital techniques for diagnostic purposes is evaluated. Sixth, the validity of facial orthopedics, and particularly its supposed contribution to the improvement of facial configuration and beauty is analysed. Seventh, the idea that the increase of mandibular intercanine width is the cause of the occurrence of mandibular incisor irregularities after alignment by treatment is challenged. Eight, the usefulness of traditional removable retainers as the Hawley and "wrap-around" appliance, is questioned and an approach and design, adapted to the change from banding to bonding of fixed appliances, is presented.

Arch Widths in Adults with Class I Crowded and Class III Malocclusions Compared with Normal Occlusions

To test the hypothesis that there is no difference between adults with Class I crowded (CICR), Class III (CIII), and Class I normal (CIN) occlusions with respect to (1) arch widths, (2) width of the maxillary and mandibular arches, (3) gender dimorphism within groups, and (4) gender comparisons. Samples of 39 CICR subjects, 40 CIII subjects, and 40 CIN subjects were studied. All subjects were white Americans with no history of orthodontic treatment. An analysis of variance and Duncan's test statistically compared the groups and genders. The CICR group had mean maxillary and mandibular intermolar and alveolar arch widths significantly smaller than the CIN group. The CIII group had mean maxillary intermolar and alveolar arch widths significantly smaller than the CIN group. Mean maxillary and mandibular intercanine arch widths were similar in the three groups. The CICR and CIN groups had similar mean maxillary/mandibular intermolar and alveolar differences significantly larger than the negative differences observed in the CIII group. Gender dimorphisms were identical in the CIII and CIN groups. The CICR group differed by not having a gender dimorphism in the maxillary alveolar width and having a gender dimorphism in the mandibular intercanine width. Gender comparisons between groups were similar in intercanine widths but differed in other widths. The hypothesis was rejected by the findings of this study.

Association of the canine guidance angle with maxillary and mandibular intercanine widths and anterior alignment relapse: Extraction vs nonextraction treatment

Long-term stability is an important measure of the success of orthodontic treatment. Research in the 1970s suggested that premolar extraction treatment had poor stability over the long term. The purpose of this prospective follow-up study was to investigate changes in intercanine widths and the irregularity index during the postretention phase in patients treated with and without extractions. Associations between the maxillary canine guidance angle and the mandibular intercanine widths and the mandibular irregularity index were also examined. Two groups of 30 patients each, with and without premolar extractions, were studied and the results compared. Records were taken at pretreatment, at bracket removal, at the end of retention, and out of retention. The times out of retention were 6.3 years for the nonextraction group and 6.5 years for the extraction group. Stone casts were mounted on an articulator with an anatomical facebow and a central wax record. The measurements were made with a 3-dimensional digitizer. Maxillary and mandibular intercanine distances behaved differently. The mandibular intercanine distance showed a net decrease between pretreatment and follow-up, whereas the maxillary arch had a net increase. The maxillary canine guidance angle at the end of retention, measured to the axis-orbital plane, was highly associated with relapse of mandibular anterior alignment and change of the mandibular intercanine distance. Methods are needed that consider the anatomical configuration of the teeth for bracket selection before treatment. Individualized brackets (torque) should then be coordinated with the guidance angle of the maxillary teeth.

Aging in the Craniofacial Complex

To describe the dental arch changes occurring after adolescence through the sixth decade of life. Longitudinal dental casts from 40 patients (20 male and 20 female) were digitized and analyzed. Measurements were recorded after the presumed cessation of circumpubertal growth (T1), at approximately 47 years of age (T2), and at least one decade later (T3) were compared. The majority of the measurements were found to have a significant time effect, demonstrating at least some level of change throughout the aging process (T1-T3). Exceptions to this observation were the posterior maxillary arch width measurements, mandibular intermolar and interpremolar (as measured at the second premolars) widths, the maxillary incisor irregularity index, overjet, overbite, and curve of Spee. The T1-T3 changes reflected for the most part the T1- T2 changes, while the T2-T3 changes affected overall modifications only for the mandibular intercanine width and maxillary depth, as measured at the second premolars. All changes reflected a decrease in arch width, depth, and perimeter, with a significant increase in the mandibular incisor irregularity index. The dental arches continue to change and adapt throughout life and into the sixth decade, though the degree of change decreases with time.

Long-term effectiveness of the continuous and the sectional archwire techniques in leveling the curve of Spee

The correction of a deep overbite with the subsequent achievement of long-term stability is a difficult problem for orthodontists. The role of leveling the curve of Spee (COS) in bite opening and the success of orthodontic treatment has been well documented in the literature. The aim of this study was to investigate whether leveling the COS, by using 2 orthodontic treatment techniques, produces stable results on a long-term basis. We compared the long-term stability of leveling the COS with the straight-wire Alexander technique and the bioprogressive sectional-arch technique. The randomly selected subjects for this retrospective study were obtained from the private practices of Drs R. G. Alexander and Ruel Bench. Study models taken 2 months before treatment (T1), 2 months after treatment (T2), and after retention (T3) were evaluated. Measurements of the COS were made on the mandibular casts with a commercially available palatometer. Mandibular intercanine width, overbite, overjet, mandibular incisor irregularity, and mandibular arch length were also recorded. Both techniques produced highly significant reductions in the COS (T1 to T2). Statistically significant, but clinically insignificant, postretention relapse of the COS occurred (T2 to T3). For both techniques, a statistically significant difference was seen in the incidence of the relapse of the COS between patients who were completely leveled posttreatment and those who were not. We did not find a correlation between pretreatment COS and relapse in any of the other occlusal traits studied.

A descriptive study of mandibular incisor alignment in untreated subjects

The development of mandibular incisor crowding appears to be a continuous process throughout life, but more evidence is needed to understand why changes occur. In this study, we describe the longitudinal dental changes in untreated children (n = 15) who had records at 3 times and in an untreated adult group (n = 18) (parents) who had records for 2 times. The mean numbers of years between initial and final observations were 29.8 years for the children and 33.7 years for the parents. All subjects were participants in the original Burlington Growth Research Project at the University of Toronto. The following variables were measured to an accuracy of 0.01 mm: overjet, overbite, mandibular intercanine width, mandibular interfirst premolar width, mandibular intermolar width, mandibular arch length, Little's incisor irregularity index, mandibular anterior space analysis, and Carey's space analysis. There were no statistically significant (P >.01) differences between the sexes for the variables measured. Little's irregularity index continued to increase in all groups (P <.01), although this rate appeared to be lower in the parent group. Intercanine and interfirst premolar widths and arch lengths continued to decrease with age. These results underline the importance of studies showing that untreated dentitions change over time. Orthodontic patient education is imperative about retention protocols and late developmental crowding.

Relationship between dental arch width and vertical facial morphology in untreated adults

The objectives of this study were to investigate if a relationship exists between dental arch width and the vertical facial pattern determined by the steepness of the mandibular plane, and to examine the differences in dental arch widths between male and female untreated adults. Lateral cephalograms and dental casts were obtained from 185 untreated Caucasians (92 males, 93 females) between 18 and 68 years of age with no crossbite, minimal crowding, and spacing. The angle of the mandibular plane (MP) to the anterior cranial base (SN) was measured on cephalograms of each patient. Dental casts were used to obtain comprehensive dental measurements including maxillary and mandibular intercanine, interpremolar, and intermolar widths, as well as the amount of crowding or spacing. The arch widths of males and females were analysed and the differences between them were tested for significance using a Student's t-test. Regression analysis was used to determine the statistical significance of the relationships between MP-SN angle and dental arch width and crowding or spacing. The results showed that male arch widths were significantly larger than those of females (P < 0.05). For both males and females, there was a trend that as MP-SN angle increased, arch width decreased. It was concluded that dental arch width is associated with gender and facial vertical morphology. Thus, using individualized archwires according to each patient's pre-treatment arch form and width is suggested during orthodontic treatment.

Arch Widths in Class II-2 Adults Compared to Adults with Class II-1 and Normal Occlusion

To compare (1) arch widths in adults with Class II division 2 (II-2), Class II division 1 (II-1), and Class I normal occlusions, (2) genders, (3) gender dimorphism, (4) differences between maxillary and mandibular arch widths, and to (5) develop adult norms for arch widths. Subjects were white Americans with no history of orthodontic treatment. Arch width dimensions measured were: intercanine, intermolar, and molar alveolar in both arches. Analysis of variance (ANOVA) and Duncan's test were used to compare groups. Comparison of pooled genders showed the II-2 group had maxillary arch widths significantly smaller than the normal occlusions and significantly larger than the II-1 group. All groups had similar mandibular intercanine and alveolar widths. The II-2 and II-1 groups had similar mandibular intermolar widths, both significantly smaller than normal occlusions. The II-2 group had a maxillary/mandibular intermolar difference significantly smaller than the normal occlusions, and significantly less negative than the II-1 group. Gender comparisons in two of six widths showed normal and II-2 male subjects were similar, and in six of six widths normal and II-2 female subjects were similar; in five of six widths II-2 and II-1 male and female subjects were similar. Gender dimorphism occurred in five of six widths in normal occlusions, four of six widths in II-2, and one of six widths in II-1. Arch width dimensions of II-2 subjects were intermediate between normal and II-1 occlusions. In both Class II malocclusions, the process that narrows arch widths was more pronounced in male than in female subjects.

Transverse features of subjects with sucking habits and facial hyperdivergency in the mixed dentition

The aim of this study was to analyze the transverse characteristics of subjects with sucking habits and hyperdivergency in the mixed dentition. The test group consisted of 80 subjects with sucking habits and hyperdivergency in the intermediate mixed dentition, and it was compared with a control group of 185 subjects. The prevalence rate of posterior crossbite was recorded. Maxillary and mandibular intercanine and intermolar widths, and anterior and posterior transverse interarch discrepancies were measured on the dental casts. The statistical comparisons between the test and control groups were performed with independent sample t tests and chi-square tests (P <.05). The prevalence rate of posterior crossbite in the test group was significantly greater (52%) than in the control group (14%) (P <.001). The test group had significantly smaller maxillary intermolar and intercanine widths and significantly greater posterior transverse discrepancy (P <.01). No significant differences were found for mandibular intermolar and intercanine widths or anterior transverse discrepancy. Prolonged sucking habits and hyperdivergency in the mixed dentition were associated with narrow maxillary intermolar and intercanine widths, increased posterior transverse discrepancies, and increased prevalence of posterior crossbites.

Facial and dental characteristics of Padaung women (long-neck Karen) wearing brass neck coils in Mae Hong Son Province, Thailand

Women of the Padaung tribe in Thailand are known to wear brass neck coils (BNC) all their lives. The purpose of this study was to identify the effects of these coils on facial morphology and dental characteristics. This study sample included 61 subjects wearing BNC (group I) and 32 subjects not wearing BNC (group II). Each group was subdivided into younger (5-15 years old) and older (more than 15 years old) groups. Facial morphologic variables were assessed by using photographic analysis and direct facial measurements. Dental variables were assessed by model analysis. Total and lower face heights in group I were significantly shorter than in group II (P = .04, P <.001, respectively). Upper and lower lip lengths in group I were significantly shorter than in group II (P = .01, P <.001, respectively). Overjet in group I was significantly larger than in group II (P = .01). Mandibular intercanine width in group I was significantly narrower than in group II (P = .04). Maxillary and mandibular incisor inclinations in the older subset of group I were more proclined than in the older subgroup of group II (P = .04, P = .03, respectively). Palatal height in the older subgroup of group I was less than in the older subgroup of group II (P <.001). Maximum mouth opening in group I was significantly less than in group II (P = .02). The findings indicated considerable effects on facial morphology and dental characteristics in Padaung women wearing BNC. Deformations could be avoided if they gave up this custom.

Treatment effects and short-term relapse of maxillomandibular expansion during the early to mid mixed dentition

The treatment effects and the short-term (0.9 +/- 0.45 years) relapse potential of phase I slow maxillary expansion, with a bonded palatal expander or a quad-helix appliance combined with a mandibular banded Crozat/lip bumper and followed by 12 to 15 months of retention, were examined. Pretreatment (8.8 +/- 1.7 years) and posttreatment (11.1 +/- 1.7 years) models of 54 patients were used to evaluate treatment effects. Posttreatment (11.0 +/- 1.3 years) and follow-up (11.9 +/- 1.4 years) models of 23 patients who returned for phase II treatment were used to evaluate relapse over the 11 months, during which no retention was used. The models were digitized, and 15 measures were computed. Significant treatment increases were observed for all measurements in both arches. Treatment gains in arch perimeter (6%-8%) were due more to increases in intermolar width (11%-15%) than to increases in arch depth (5%). Posttreatment relapse was significant (P <.05) for all measures except mandibular intercanine width and maxillary molar arch depth. After accounting for normal growth, net changes (pretreatment to follow-up) indicated significant increases for all measures except maxillary molar arch depth. In addition to maintaining leeway space, the maxilla and the mandible showed net perimeter gains of 2.9 and 1.0 mm, respectively. Slow maxillary expansion combined with a mandibular banded Crozat/lip bumper during the early mixed dentition produced clinically useful increases in arch dimensions that subsequently underwent mild-to-moderate amounts of relapse after removal of all retention appliances.

Relapse of anterior crowding in patients treated with extraction and nonextraction of premolars

The purpose of this study was to evaluate long-term stability of incisor crowding in orthodontic patients treated with and without premolar extractions. Dental casts and cephalometric records of 98 patients were evaluated before treatment (T1), at posttreatment (T2), and at postretention (T3). Half of the patients had been treated with extractions, and half were treated nonextraction. Irregularity, as measured by the irregularity index, decreased 5.51 mm in the extraction group and 2.38 mm in the nonextraction group. Mandibular incisor irregularity increased 0.97 mm in the extraction group and 0.99 mm in the nonextraction group, respectively, in the postretention period. Maxillary incisor irregularity relapse was smaller than mandibular incisor relapse for both groups. Intercanine width expanded during treatment. At T3, mandibular intercanine width decreased in both groups, but the differences were not statistically significant. At T3, intermolar width was stable, arch depth decreased, overbite and overjet slightly increased, SN mandibular plane angle decreased, and incisor positions in both groups tended to return to T1 values. Clinically acceptable stability was obtained. With the exception of the interincisal angle, no statistically significant differences were recorded between the extraction and nonextraction groups from T2 to T3. No statistically significant correlations were found between any variables studied and mandibular incisor irregularity at T1, T2, and T3.

A comparative study of cephalometric and arch width characteristics of Class II division 1 and division 2 malocclusions

The aim of this compound cephalometric and arch-width study was to determine any dental and/or skeletal differences between subjects with Class II division 1 and Class II division 2 malocclusions. The dento-skeletal characteristics of Class II subjects were evaluated using lateral cephalometric radiographs and dental casts of 90 untreated patients. The sample included 46 Class II division 1 patients (19 girls and 27 boys) with a mean age of 15.27 +/- 2.48 years, and 44 Class II division 2 patients (27 girls and 17 boys) with a mean age of 15.95 +/- 3.25 years. The intermolar, interpremolar and intercanine measurements were carried out on study models. The radiographs were digitized and processed using Dolphin Imaging software. In addition to standard descriptive statistical calculations, an independent samples t-test was carried out in order to compare the two groups. The non-parametric Mann-Whitney U test was utilized for the parameters for the data which were not normally distributed. The only statistically significant difference between the groups for the study model measurements was mandibular intercanine width. The cephalometric results revealed that SNB angle was responsible for the skeletal sagittal difference between the two groups. In addition, the Class II division 1 group had higher vertical proportions and the Class II division 2 group a more concave profile with a prominent chin. The sagittal skeletal pattern of Class II division 2 subjects was found to be very similar to the Class I skeletal relationship, with no evidence of any mandibular restriction.

Changes in arch width. A 20-year longitudinal study of orthodontic treatment.

The changes in the dental arch dimensions that occur as a result of growth and treatment are of interest to the orthodontist and require careful consideration during treatment planning. A greater understanding of these changes could influence the patient's expectations from treatment as well as the formulation of the treatment and retention plans by the clinician. A retrospective study of the maxillary and mandibular canine and molar arch width changes in 60 patients over 20 years was carried out. Approximately half were treated orthodontically, and measurements were made on dental casts taken at four time points during the study: 1981, 1985, 1989, and 2001. Between baseline and final follow-up, the treated group demonstrated a statistically significant increase in maxillary intercanine arch width and statistically significant decreases in maxillary intermolar and mandibular intercanine and intermolar widths. No significant changes were observed for the untreated group. When comparing the orthodontically treated group with the untreated group, there was a significantly greater increase in maxillary intercanine width and a significantly greater reduction in mandibular intercanine width in the treated group over the duration of the study. No significant difference was observed between treated and untreated groups for maxillary and mandibular intermolar width changes. Sex had no statistically significant effect on these treatment differences. Type of orthodontic treatment had no effect on arch width changes within the treated group; however, the effect of tooth extraction needs further investigation.

Arch width changes in extraction and nonextraction treatment in class I patients.

The aim of this retrospective study was to examine the dental arch width changes of extraction and nonextraction treatment in Class I patients. The study was performed on pretreatment and posttreatment dental casts of 60 patients (30 extraction and 30 nonextraction). The mean ages were 14.3 +/- 2.02 years for the extraction group and 14.1 +/- 2.9 years for the nonextraction group. The maxillary and mandibular crowding was -6.7 +/- 3.1 and -6.3 +/- 2.8 mm for the extraction group and -4.5 +/- 3.6 and -2.1 +/- 3.5 mm for the nonextraction group, respectively. The intercanine and intermolar arch width measurements were measured using a digital caliper. Paired samples t-test was used to evaluate the treatment changes within each group. To compare the changes between groups, independent samples t-test was performed. At the start of treatment, the maxillary and the mandibular intercanine and intermolar widths of both groups did not differ statistically. At the end of treatment, maxillary and mandibular intercanine widths of both groups increased significantly. The mandibular intermolar width decreased significantly for the extraction group and the maxillary intermolar width increased significantly for the nonextraction group. The decrease in maxillary intermolar width for the extraction group and the increase in mandibular intermolar width for the nonextraction group were not significantly different. No differences were observed between the groups in maxillary and mandibular intercanine widths. Maxillary and mandibular intermolar width indicated a significantly larger value in the nonextraction group than that in the extraction group.

Posttreatment stability of four first bicuspid extraction cases treated with the Alexander technique--model analysis

To evaluate the posttreatment stability of four first bicuspid extraction cases with the Alexander technique. Fifteen patients, 8 males and 7 females in the permanent dentition were selected. The age range of the patients was 10.3 to 16.2 years old. Four first bicuspids of every patient were extracted and all patients were treated with the Alexander technique. The study casts were taken before (T(1)), after treatment (T(2)) and 27.8 months averagely follow-up (T(3)). Data were correlated by means of paired t tests. Although maxillary and mandibular intercanine widths were increased by 0.98 mm and 0.87 mm, respectively, during treatment, they were decreased by 0.37 mm and 0.72 mm, respectively, during follow-up period. Maxillary and mandibular crowding were increased by 0.53 mm and 0.98 mm, respectively, during follow-up period. No statistical significance were found. Upper and lower arch depth were decreased significantly due to retraction of anterior teeth and remained stable during follow-up period. According to this study, the design of the Alexander appliance and the Alexander technique are helpful for stability of extraction therapy. Follow-up is still necessary to evaluate the long-term stability.