Evaluation of dental arch width and form changes after orthodontic treatment and retention with a new computerized method.

The purpose of this study was to evaluate longitudinal arch width and form changes and to define arch form types with a new computerized method. Maxillary and mandibular models of 21 Class II Division 1 patients were examined before treatment (T(0)), after treatment (T(1)), and an average of 3 years after retention (T(2)). Arch width measurements were made directly on scanned images of maxillary and mandibular models. Arch form changes at T(0)-T(1) and T(1)-T(2) were evaluated by superimposing the computer-generated Bezier arch curves with a computer program. Types of dental arch forms were defined by superimposing them with the pentamorphic arch system, which included 5 different types of arch forms: normal, ovoid, tapered, narrow ovoid, and narrow tapered. Maxillary arch widths were increased during orthodontic treatment. Mandibular posterior arch widths were also increased. The expansion of the mandibular arch forms was less than in the maxillary arch forms. Arch width changes were generally stable, except for reduction in maxillary and mandibular interlateral, inter-first premolar, and mandibular intercanine widths. Pretreatment maxillary arch forms were mostly tapered; mandibular arch forms were tapered and narrow tapered. In maxillary arch forms, 76% of the treatment changes were maintained. Mandibular arch form was maintained in 67% of the sample, both during treatment and after retention. In mandibular arches, 71% of orthodontically induced arch form changes were maintained.     

Mandibular second premolar extraction--postretention evaluation of stability and relapse

The dental casts and cephalometric radiographs of 46 patients, treated with mandibular second premolar extraction and edgewise orthodontic mechanotherapy, were evaluated for changes over a minimum 10-year postretention period. The sample was divided into two groups: early (mixed dentition) extraction of mandibular second premolars and late (permanent dentition) extraction of mandibular second premolars. Results showed no difference in long-term stability between the two groups. Arch length and arch width decreased with time and incisor irregularity increased throughout the postretention period. No predictors or associations could be found to help the clinician in determining the long-term prognosis in terms of stability. The sample was regrouped according to the postretention degree of incisor irregularity. Statistically significant differences in cephalometric measurements were found between the minimally crowded group and the moderately to severely crowded group.     

The stability of the arch-expansion effects of Fr?nkel appliance therapy

To assess the long-term stability of the arch expansion effects of the functional regulator, mandibular dental casts were evaluated for treatment and postretention changes in intercanine width, width between first premolars, width between second premolars, intermolar width, incisor irregularity, and arch length. This study was comprised of 11 cases that were treated with the Fr?nkel appliance (mean = 27 mo.) and were and average of 4 years and 4 months out of active treatment. Results showed overall stability to be good, with some variability present in individual responses. Intercanine width, width of first premolars, width of second premolars, and intermolar width all demonstrated maintenance of treatment increases. Correction of incisor irregularity displayed better stability than has been reported in other stability studies. Arch length decreased with treatment and continued to decrease during the postretention period, although to a lesser extent than has been previously reported. The results of this study support the statements of Fr?nkel concerning the stability of this type of arch expansion.     

Mandibular incisor alignment and dental arch changes 1 year after extraction of deciduous canines

This study investigated the early effects on mandibular incisor irregularity and rotation together with dental arch dimensions of the extraction of four deciduous canines. Children, during early mixed dentition, were randomized into one extraction (n = 32) and one control (n = 41) group. Dental casts from baseline (T0) and 1 year follow-up (T1) were used to evaluate changes in the irregularity index and in mandibular incisor rotation, dental arch dimensions, overjet, and overbite. Median mandibular incisor irregularity decreased over time, significantly more in the extraction than the control group (1.2 versus 0.7 mm; P < 0.01), with wide ranges in both groups. Rotational changes greater than 10 degrees for lateral incisors were twice as common in the extraction group (42 versus 20 per cent; P < 0.01). Central incisors displayed only minor changes in both groups. The correlation between changes in irregularity index and changes in incisor rotation was weak in both groups (r(s) < 0.3 not significant). According to professional assessment of overall alignment, 84 per cent in the extraction group versus 34 per cent in the control group (P < 0.001) improved from T0 to T1. A significant decrease in maxillary and mandibular arch length and circumference from T0 to T1 was recorded in the extraction group (1.3, 1.1 mm and 2.4, 2.0 mm, respectively; P < 0.001), while arch dimensions were preserved in the control group. To conclude, 1 year after extraction of the deciduous canines, small improvements in mandibular incisor alignment were seen, together with reduced arch dimensions. Little's index underestimated malalignment related to tooth rotation.     

Evaluation of posttreatment stability after orthodontic treatment in the mixed and permanent dentitions

Objective:To investigate posttreatment changes in the maxillary and mandibular arches in patients who underwent orthodontic treatment during the mixed and permanent dentitions.Materials and Methods:The sample was collected retrospectively from three private practices and consisted of 42 patients who were at least 10 years out of orthodontic treatment. The longitudinal records of study casts and cephalometric radiographs were analyzed to quantify posttreatment changes.Results:Minimal changes in maxillary and mandibular irregularity occurred after an average of 16.98 years from completion of treatment. More than 10 years posttreatment, approximately 81% of the maxillary anterior teeth and 88% of the mandibular anterior teeth showed clinically acceptable incisor alignment (<3.5 mm). Mandibular fixed retainers greatly aided in maintaining the stability of the mandibular incisor alignment. However, posttreatment changes in maxillary incisor irregularity did not appear to be influenced by the presence of a mandibular fixed retainer. When compared with longitudinal changes observed in untreated subjects, the increase in incisor irregularity resembled a pattern similar to the regression line of untreated subjects and seems to be entirely age related. Arch width and arch depth was consistently decreased after treatment, but the magnitude of change was minimal at about 1 mm. No associations were found between any of the cephalometric measurements and changes in incisor irregularities.Conclusions:Orthodontic treatment stability can be achieved and mandibular fixed retention appears to be a valuable contributor, especially in patients with further growth expected.     

Nickel-titanium mandibular bonded lingual 3-3 retainer: for permanent retention and solving relapse of mandibular anterior crowding.

An innovative technique that involves a nickel-titanium mandibular bonded lingual 3-3 retainer was used to treat relapse of mandibular anterior crowding. The purpose of this study was to demonstrate clinical procedures and to study the effects of a new mandibular bonded lingual 3-3 retainer on the mandibular dental arch. In 18 patients, changes in the irregularity index and in arch dimensions (intercanine width, arch length, and arch depth) were measured against the patients' mandibular dental casts, which were obtained at completion of the previous orthodontic treatment (T(0)). These measurements were taken at the beginning of retreatment (T(1)), and 2 (T(2)), 4 (T(3)), and 6 (T(4)) months after initiation of retreatment. During the period of relapse (T(0)-T(1)), the irregularity index increased from 1.3 to 3.5 mm and the mandibular arch dimensions decreased. Four months after a segment of.018-in nickel-titanium archwire was bonded lingually from canine to canine, the irregularity index decreased from 3.5 to 1.0 mm and the arch dimensions increased and recovered their original posttreatment dimensions. The nickel-titanium archwire was left in place for permanent retention after the period of retreatment. This simple technique effectively solved relapse of mandibular anterior crowding in 4 months. This mandibular bonded lingual 3-3 retainer could be used both actively, to re-treat mandibular anterior crowding without the use of lingual brackets, and passively, for maintenance as a bonded lingual retainer.     

上颌中切牙内收与消耗牙弓间隙量的相关性研究

目的 探究上颌中切牙内收量与其消耗牙弓间隙量的比例关系。方法 选择拔除上颌第一前磨牙的前牙深覆盖成年正畸患者203例,对治疗前、后的锥形束CT进行三维重建,测量上颌中切牙内收量(X₁)、尖牙间宽度变化量(X₂)及尖牙远中移动量。数字化扫描仪扫描治疗前的上颌石膏模型,测量上颌前段牙弓拥挤度。将上颌中切牙内收量、尖牙间宽度变化量与消耗的总牙弓间隙量(Y)进行相关分析、线性回归分析。结果 上颌中切牙内收量与牙弓间隙的消耗量呈强正相关(r=0.726,P＜0.001),尖牙间宽度变化量与牙弓间隙消耗量呈负相关(r=-0.317,P<0.001),消耗的总牙弓间隙量(Y)与上颌中切牙内收量(X₁)、尖牙间宽度变化量(X₂)的回归方程为Y=1.25X₁-0.494X₂-2.299。结论 上颌中切牙每内收1 mm,消耗的牙弓间隙为1.250 mm;尖牙间宽度每缩减1 mm,消耗的牙弓间隙为0.494 mm。     

An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects

The purpose of this study was to examine dimensional changes in the maxillary arch following the extractions of maxillary first or second premolars. Pre- and posttreatment records of 71 patients treated by one experienced orthodontist were randomly selected from completed premolar extraction cases. Forty-five patients involved the extraction of maxillary first premolars; of these, 15 also had extractions of mandibular first premolars and 30 had extractions of mandibular second premolars. Twenty-six patients involved the extraction of maxillary second premolars, and all of these also had extractions of mandibular second premolars. Pretreatment factors that seemed to suggest a basis for the extraction choice in this sample included incisal overjet, molar relationship, and maxillary incisor protrusion. Mean reductions with treatment in the anteroposterior arch dimension were similar within all premolar extraction groups. There was evidence of greater mean maxillary intermolar-width reduction following the extractions of maxillary second premolars than following extractions of maxillary first premolars. Greater mean maxillary incisor retraction was found in the maxillary first premolar extraction group than in the maxillary second premolar group. A wide range of individual variation in incisor and molar changes did, however, accompany treatment involving both maxillary premolar extraction sequences.     

上下颌唇挡对替牙晚期儿童牙(牙合)的影响

目的研究上下颌唇挡同时应用对替牙晚期儿童牙(牙合)的影响.方法选择替牙晚期上下牙列轻度或中度拥挤患儿12例,上下颌均采用唇挡治疗8个月,进行治疗前后X线头影测量分析和模型测量分析,并对治疗前后的测量值变化进行配对t检验.结果唇挡治疗后,SNA、SNB分别增加1.02°和0.97°(P＜0.05),上下切牙前移均是牙冠向近中倾斜,而根尖相对固定的控制性倾斜,旋转中心接近根尖.上下磨牙远中倾斜效果不同,上磨牙远中倾斜直立,旋转中心接近牙冠;下磨牙远中倾斜移动,旋转中心接近阻抗中心;上颌磨牙间牙弓宽度、牙弓周径分别增加4.12mm和5.09mm(P＜0.01),下颌磨牙间牙弓宽度、牙弓周径分别增加4.07mm和6.86mm(P＜0.01).结论在儿童生长发育高峰期,唇挡可有效地引起上下颌牙弓横向和纵向变化,减轻或解除上下牙弓拥挤.     

Rapid maxillary expansion followed by fixed appliances: a long-term evaluation of changes in arch dimensions

The purpose of this longitudinal study was to evaluate the short- and long-term changes in dental arch dimensions in patients treated with rapid maxillary expansion (RME) followed by fixed edge-wise appliances. The records of 112 patients in the treated group (TG) were compared with those of 41 untreated controls. Serial dental casts were available at three different intervals: pretreatment (T1), after expansion and fixed appliance therapy (T2), and at long-term observation (T3). The mean duration of the T1-T2 and T2-T3 periods for the TG group was three years two months +/- five months and six years one month +/- one year two months, respectively. Treatment by RME followed by fixed appliances produced significantly favorable short- and long-term changes in almost all the maxillary and mandibular arch measurements. In comparison with controls, a net gain of six mm was achieved in the maxillary arch perimeter, whereas a net gain of 4.5 mm was found for the mandibular arch perimeter of treated subjects in the long term. The duration of retention with a fixed lower appliance in the posttreatment period did not appear to affect the long-term outcomes of the treatment protocol significantly. The amount of correction in both maxillary and mandibular intermolar widths equaled two-thirds of the initial discrepancy, whereas treatment eliminated the initial deficiency in maxillary and mandibular intercanine widths. The amount of correction for the deficiency in maxillary arch perimeter was about 80%, whereas in the mandible a full correction was achieved.     

Is the postretention relapse of maxillary and mandibular incisor alignment related?

Previous studies suggest a poor association between initial and postretention pattern of incisor irregularity. One explanation may be that the incisor movements are limited by the boundaries provided by the incisors in the opposite arch. If so, postretention malalignment of the maxillary and mandibular incisors may be related. To test this hypothesis, long-term postretention study models of 96 patients with acceptable occlusion at the time of appliance removal were examined. The occlusal surfaces of the postretention study models were photocopied, and tooth anatomical contact points were digitized. An algorithm was used to fit the dental arch to the digitized points. The amount of incisor rotation and anatomical contact point displacement of maxillary and mandibular anterior teeth, relative to their respective dental arches, were computer generated. Overbite, the number of occlusal contact points in the anterior segment, and concavity of the lingual surfaces of the maxillary incisors were recorded manually. Statistical analyses demonstrated a significant association (P <.05) between the overall irregularity of the maxillary and mandibular incisors. The association did not differ among subgroups that were stratified according to overbite or number of occlusal contacts. No associations were found for the overall amount of incisor rotation in the 2 arches (P >.05). The amount and direction of displacement of antagonistic pairs of maxillary and mandibular central incisors were also associated (P <.05), but not the amount and direction of rotation (P >.05). The lingual configuration of the maxillary incisors did not affect the pattern of mandibular incisor malalignment.     

Stability of transverse expansion in the mandibular arch.

This was a retrospective, longitudinal cephalometric and cast study of 29 white patients at pretreatment, posttreatment, and an average of 6 years 3 months postretention. The goal was to assess changes with treatment and retention with the expanding mandibular lingual arch appliance in conjunction with fixed edgewise treatment. Seven mandibular cast measurements were assessed, including arch crowding, arch perimeter, arch length, and arch width at the permanent canines, first premolars, second premolars, and first molars. Cephalometric radiographs were digitized, and 16 cephalometric measurements were made. Repeated-measures analysis of variance and 2-sample t tests were used to determine statistically significant changes. It was found that the expanding lingual arch used for less than 6 months with the mandibular fixed edgewise appliance caused an increase in both the transverse and sagittal dimensions of the mandibular dental arch. Transverse expansion was more stable in the posterior region of the mandibular dental arch than in the anterior region. Mandibular intercanine width increase could be maintained only by fixed retention. Although the maxillary and mandibular incisors were advanced and proclined, lip protrusion did not occur.     

Longitudinal craniofacial changes in Japanese adults with untreated maxillary and mandibular protrusions

This study evaluates the craniofacial change during the third decade of life and compared the changes that occurred in subjects with normal occlusion and untreated malocclusions. 10 cases each of normal occlusion, untreated maxillary protrusion and mandibular protrusion were subjected to cephalometric analysis and model analysis. The mean age at the beginning of the observation (T1) was 24 years, and the observation period (T2) was approximately 13 years in three groups. There was no significant difference in any cephalometric values between T1 and T2 in the normal occlusion group. The SNB angle was slightly decreased, the Y-axis was increased, and upper incisors were lingually inclined in the maxillary protrusion group and increasing of overjet and decreasing of overbite was observed in the mandibular protrusion group. In model analysis, the arch length discrepancy (ALD) and the inter-molar width (IMW) were slightly increased in the lower arch in the normal occlusion group and the upper arch length (AL) had decreased in the mandibular protrusion group. In conclusion, significant differences were found in the changes of several skeletal and dental parameters between normal occlusion and untreated malocclusion subjects in the third decade of life. These changes in the third decade of life should be considered in order to plan the orthodontic treatment and evaluate the long-term stability in the patients with maxillary and mandibular protrusion.     

Dental arch dimensions in patients with unilateral cleft lip and palate

In this investigation, dental arch dimensions during different ages were studied in 72 children with unilateral cleft of the lip, alveolar process, and palate and were compared with those of normal children. All the children with clefts were treated surgically by surgeons of the Lancaster Cleft Palate Clinic. The dental arch dimensions were studied with the use of dental casts during the time of full deciduous dentition (3 to 4 years of age), mixed dentition (8 to 9 years of age), and permanent dentition (12 years of age). The major findings were: (1) all maxillary interdental widths and lengths were significantly smaller than the normal dimensions at all ages, except for intermolar width at age 12 years; and (2) the mandibular arch dimensions seemed to be related to changes in the maxillary arch; however, the influence of surgical procedures in the maxillary arch is not reflected severely in mandibular arch dental position.     

20例错牙合正畸治疗和保持后的模型分析研究

目的：评估错He畸形经治疗和保持后牙弓的变化情况，为临床治疗同类错He提供依据。方法：选择拔除4颗第一双尖牙的患者20例，采用方丝弓技术治疗。对治疗前后和保持器停截1年后的模型进行测量。结果：治疗前后除上下牙弓尖牙宽度增加外，其余指标均不同程度减少，去除保持器1年后，上下尖牙宽度和前牙覆He，覆盖出现复发，而上下牙弓中，后段宽度和上下牙弓长度继续减少。结论：治疗后上颌尖牙宽度净增加量较下颌稳定，经治疗和保持后，上下牙弓宽度和长度并非一定会复发。     

Mandibular growth rotation effects on postretention stability of mandibular incisor alignment

OBJECTIVE: To test the hypotheses that pronounced forward and backward mandibular growth rotation may be risk factors for postretention relapse of mandibular incisor alignment, and that morphologic parameters at adolescence may be predictive of the remaining type of mandibular growth. MATERIALS AND METHODS: Cephalograms and study models were made before (T1) and after (T2) active treatment and at a minimum of 10 years postretention (T3) of three groups of orthodontic patients with acceptable occlusion at the time of appliance removal. The groups were short facial height (n = 46), angle between the sella-nasion line and the mandibular plane (SN/MP) or= 38 degrees at T2. RESULTS: The groups were similar regarding age at T2, gender ratio, incisor irregularity (IRI), intercanine (3-3) width at T1, change of 3-3 width from T1 to T2, and time from T2 to T3 (P > .05). IRI increased in all groups from T2 to T3 (P < .05), but there were not any intergroup differences in this increase (P > .05). Minor differences were detected among the groups in mandibular growth rotation from T2 to T3. Males experienced more forward rotation than females (P < .001) and more increase in IRI from T2 to T3 (P < .01). Male gender, T1-T2 increase in 3-3 width, and T2-T3 reduction in 3-3 width were included in the model explaining T2-T3 increase in IRI. CONCLUSION: High-angled and low-angled facial patterns at time of appliance removal are not associated with increased risk of postretention relapse of mandibular incisor malalignment, and in adolescent orthodontic patients are poor predictors of type of posttreatment growth.     

Dental arch morphological and dimensional characteristics in Jordanian children and young adults with beta-thalassaemia major

OBJECTIVE: The aim of this study was to examine the arch dimensions of Jordanian patients with beta-thalassaemia major in comparison with an unaffected control group. METHODS: The sample consisted of 24 patients who suffered from beta-thalassaemia major (mean age = 13.9 +/- 3.1 years) and an unaffected control group (mean age = 13.5 +/- 2.9 years) matched for dental age, sex, and incisor and molar relationships. The unaffected control group was randomly selected from four public schools in the Governate of Irbid-Jordan. Alginate impressions were taken of the maxillary and mandibular dental arches of all participants. All measurements of the arch dimensions were made on the casts using an electronic digital sliding calliper. RESULTS: In the mandibular arch, when compared with the patients with thalassaemia, the unaffected control group subjects showed a (statistically) significantly larger incisor width, larger arch depth, and larger left and right anterior arch lengths (1.18, 2.58, and 1.85 and 1.12 mm, respectively). In the maxillary arch, there was a statistically significant difference in the mean incisor width (+/- 2.16 mm), arch depth (+/- 3.14 mm), inter-molar width (+/- 1.21 mm) and in the left anterior arch length (+/- 1.97 mm). The canine widths, premolar widths, left and right posterior arch length, and curve of Spee of both arches showed no statistically significant differences between the two groups. CONCLUSION: When compared to unaffected subjects, patients with beta-thalassaemia major exhibited: a narrower maxilla; a shorter maxilla and mandible; and smaller incisor widths for the maxillary and mandibular arches.     

Combined orthodontic-orthognathic surgical treatment of a Class II, Division 1 malocclusion

This case report shows the need to extract four first premolars in addition to orthognathic surgery, even though the initial treatment plan involved a nonextraction strategy. The extractions were necessary to reduce maxillary dental protrusion and proclination and also to recover from the mandibular incisor proclination that occurred as a consequence of leveling the mandibular arch. (Am J Orthod Dentofac Orthop 1997;111:640-5.)     

A new method of evaluating posterior occlusion and its relation to posttreatment occlusal changes.

The purpose of this study was to assess the relationship between posterior occlusion and posttreatment changes in other occlusal variables. Pretreatment (T1), posttreatment (T2), and postretention (T3) records were obtained for 49 Class I (n = 23) and Class II (n = 26) extraction cases. Overbite, overjet, mandibular incisor irregularity, right and left molar deviations, midline deviation, and mandibular arch length were measured, and occlusal registrations were made of each set of dental casts. The proximity of posterior occlusal surfaces was measured as the contact or near-contact areas at or below 300 microm thickness, based on the optical densities of scanned images of the posterior occlusal registrations. The treatment changes for overbite, overjet, right and left molar deviation, and arch length were significantly greater in the Class II group, and the reductions in incisor irregularity were greater in the Class I group. No other class differences were found. Overbite, overjet, and incisor irregularity increased after treatment, and arch length continued to decrease, with no significant class differences. Contact and near-contact areas at or below 300 microm constituted 7% of the functional occlusal table for both classes at the end of treatment, having decreased significantly in both groups (21% in Class I and 29% in Class II) during treatment. Because contact and near-contact areas increased in some patients and decreased in others, there were no significant posttreatment changes. Negative correlations were found between contact and near-contact areas at T2 and changes in overjet from T2 to T3, and between contact and near-contact areas at T3 and changes in overbite from T2 to T3. No relationships were found between posterior contact and near-contact area and incisor irregularity. We concluded that (1) the area of actual and near contacts at or below 300 microm decreased significantly with treatment, indicating that, despite excellent treatment results by conventional standards, the proximity of posterior occlusal surfaces lessened; (2) the proximity of the posterior occlusal surfaces should not be expected to increase posttreatment; (3) posttreatment contact and near-contact areas may be factors in overbite and overjet stability; and (4) posttreatment contact and near-contact areas are not related to incisor irregularity.     

Soft tissue profile changes following orthodontic treatment of Chinese adults with Class III malocclusion

Thirty-eight adult Chinese patients (mean age 24.3 +/- 3.2 years) exhibiting true Class III dental and skeletal malocclusions were treated orthodontically with the edgewise appliance and extractions of mandibular first premolars together with simultaneous anterior expansion of the maxillary arch. A retrospective cephalometric study was undertaken to determine the soft tissue profile changes at least 6 months postretention. Significant cephalometric changes included decrease in the mandibular incisor protrusiveness by 6.4 mm (P less than .001) and accompanying lower lip protrusiveness by 4.4 mm (P less than .01), together with a slight forward movement of the maxillary incisors by 1.7 mm (P less than .05) and, consequently, a slight increase in upper lip protrusiveness by 1.2 mm (P less than .05) and decrease in nasolabial angle (P less than .05). The overall improvement in lip profile provided by this mandibular arch contraction/maxillary arch expansion orthodontic approach appears to be a viable alternative in mild-to-moderate Class III patients who decline orthognathic surgery.