Nonextraction orthodontic therapy: posttreatment dental and skeletal stability

To assess the long-term stability of nonextraction orthodontic treatment, the dental cast and cephalometric records of 28 cases were evaluated. Thirty cephalometric and seven cast parameters were examined before treatment, posttreatment, and an average of almost 8 years postretention. Results showed overall long-term stability to be relatively good. Relapse patterns seen were similar in nature, but intermediate in extent, between untreated normals and four first premolar extraction cases. Significant decreases were seen in arch length and intercanine width during the postretention period despite minimal changes during treatment. Incisor irregularly increased slightly postretention; intermolar width, overjet, and overbite displayed considerable long-term stability. Mandibular incisor mesiodistal and faciolingual dimensions were not associated with either pretreatment or posttreatment incisor crowding. Class II malocclusions with large ANB values and shorter mandibular lengths showed increased incisor irregularity, shorter arch lengths, and deeper overbites at the postretention stage, suggesting that the amount and direction of facial growth may have been partially responsible for maturational changes seen during the postretention period.     

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 dimensions and crowding

Previous authors have suggested that well-aligned mandibular incisors are narrower mesiodistally than incisors which crowd and that reducing mesiodistal dimensions of the mandibular incisors to fit a specific size range will prevent future malalignment. This study examined 164 cases from the records of the University of Washington Department of Orthodontics, 134 of which had been orthodontically treated and were a minimum of 10 years postretention. Measurements were made from the postretention plaster casts and from serial cephalometric head films. Statistical tests showed that there was a weak association between incisor widths or MD/FL dimensions ratio and irregular alignment over the long term. Mean dimensional differences between crowded and uncrowded incisors were small in the few pooled or segregated groups in which statistically significant differences were found. When incisor dimensions were combined with pretreatment, posttreatment, or long-term cephalometric and cast measurements, only weak and not clinically useful associations were found with long-term incisor alignment. While there was a weak tendency for narrower incisors to be associated with better alignment in some instances, narrower mesiodistal widths of mandibular incisors did not ensure long-term stability in orthodontically treated cases.     

Evaluation of the relationship between the anterior component of occlusal force and postretention crowding.

The aim of this study was to investigate whether a relationship exists between the anterior component of occlusal force (ACF) and postretention crowding in the mandibular incisor area. The study group comprised 32 adults who had undergone fixed orthodontic treatment in the department clinic at Marmara University in Istanbul, Turkey. In 13 subjects, the mandibular arch was treated without extractions; in 19, it was treated with bilateral first premolar extractions. The average postretention period was 3.5 years. The ACF created in the left side of the mandibular dentition was determined by measuring interdental frictional forces at each contact point mesial to the first molar and distal to the canine. Anatomic contact point displacements between the left mandibular anterior teeth (lateral incisor-canine, central incisor-lateral incisor, and central incisor-central incisor) were measured on plaster casts and summed to provide the irregularity index for these teeth. Correlation analysis was used to assess the relationship between the ACF values at each contact and the irregularity index. In the nonextraction group, statistically significant positive correlations were observed between the ACF and the irregularity index at the 3 contact points that were measured. The strongest correlation was found at the canine-first premolar contact (r = 0.65). In the extraction group, a positive correlation was found between the ACF and the irregularity index (r = 0.49, P <.05) at the second premolar-first molar contact, but no correlation was found at the canine-second premolar contact.     

Stability of anterior open bite nonextraction treatment in the permanent dentition.

This study cephalometrically evaluated the long-term stability of anterior open bite nonextraction treatment in the permanent dentition after a mean period of 5 years. The experimental group consisted of 21 patients who had undergone orthodontic treatment with fixed appliances from whom cephalometric headfilms were obtained at the pretreatment, posttreatment, and postretention stages. Two control groups were used. The first, with ages comparable with the experimental group before treatment, was used only to characterize it. The second control group, with normal occlusion, was longitudinally followed for a period comparable with the posttretention period and was used to compare the changes between groups during this period. The differences between the observation stages in the experimental group were analyzed with paired t tests, and the postretention changes were compared with the changes of the second control group with independent t tests. A statistically significant decrease of the obtained anterior overbite was demonstrated at the end of the postretention period. The primary factor that contributed to the overbite decrease was the smaller vertical development of the maxillary and mandibular incisors in the postretention period. Neither the pretreatment anterior open bite amount nor the magnitude of correction was associated with the long-term overbite decrease. However, 61.9% of the sample had a clinically stable open bite correction.     

Stability and relapse of mandibular anterior alignment: a cephalometric appraisal of first-premolar-extraction cases treated by traditional edgewise orthodontics

Assessment at least 10 years postretention of fifty-four cases previously treated in the permanent-dentition stage with first-premolar extractions, traditional edgewise mechanotherapy, and retention revealed considerable variation among patients. The long-term response to mandibular anterior alignment was unpredictable; no cephalometric parameters, such as maxillary and mandibular incisor proclination, horizontal and vertical growth amounts, mandibular plane angle, etc., were useful in establishing a prognosis. Few associations of value were found between cephalometric parameters and dental-cast measurements, such as overbite, arch length, intercanine width, and overjet. Only a slight tendency was found for incisor inclination to return toward the pretreatment value during the postretention period. It was possible to predict, on the basis of an analysis of pre- and posttreatment cephalometric records, those cases which had greater than 4 mm deepening of overbite postretention as well as those cases which had decreases of 3 mm or more in arch-length postretention. The practical use of these predictions were of limited clinical value, however.     

Relapse in Angle Class II Division 1 Malocclusion treated by tandem mechanics without extraction of permanent teeth: A retrospective analysis.

Ideal orthodontic treatment should achieve long-term stability of the occlusion. The mandibular incisor segment has been described as the segment that is most likely to exhibit relapse after treatment and retention. Therefore, relapse of this is a challenge that clinicians need to address. The purpose of this study is to evaluate the amount of relapse that may occur in Angle Class II Division 1 patients, treated orthodontically with tandem mechanics. All cases in this study were treated without extraction of permanent teeth, and the patients were followed for at least 2 years after the end of the retention phase of treatment. Six predictors were investigated at pretreatment, posttreatment, and postretention periods. A synopsis of this study shows the correction of lower incisor crowding as measured by the irregularity index was stable over 5.2 years of postretention follow-up; but longer follow-up time revealed increased relapse of incisor irregularity. Intermolar width increased during treatment and remained stable in the follow-up period. Overjet and overbite corrections and changes in the lower incisor to mandibular plane angle were also stable in the follow-up period. In addition, the amounts of overjet correction and loss of expansion of intercanine distance after treatment were associated with increased irregularity index in the follow-up period. It appears the discrepancies between this and previously published works are sufficiently dramatic that the whole question of treatment philosophy and long-term stability may need to be reevaluated.     

Long-term stability of combined rapid palatal expansion-lip bumper therapy followed by full fixed appliances.

INTRODUCTION: The purpose of this study was to evaluate the long-term postretention stability of rapid palatal expansion-lip bumper therapy followed by full fixed appliances. METHODS: The sample included 20 treated patients (11 women and 9 men) who were recalled to obtain postretention records. The subjects were out of retention for a minimum of 4 years and an average of 7.9 years. They had begun treatment in the late mixed dentition at a mean age of 11.1 with considerable incisor crowding but, on average, no tooth size-arch length discrepancies. Pretreatment, posttreatment (mean age, 13.6 years), and postretention (mean age, 24.3 years) models were digitized, and the computed measurements were compared with untreated reference data. RESULTS: The majority of treatment increases in maxillary and mandibular arch dimensions were statistically significant (P < .05) and greater than expected for untreated controls. Although many measurements decreased postretention, net gains were maintained for 21 of the 30 measurements evaluated. The notable exception was arch perimeter, which decreased to less than pretreatment values. Postretention incisor irregularity increased 0.5 +/- 1.2 mm in the maxillary arch and 1.1 +/- 1.5 mm in the mandibular arch. CONCLUSIONS: Based on the good long-term stability observed in this study, we concluded that use of rapid palatal expansion-lip bumper expansion therapy in the late mixed dentition followed by full fixed appliances is an effective form of treatment for patients with up to moderate tooth size-arch length discrepancies.     

A long-term study of the relationship of third molars to changes in the mandibular dental arch

The purpose of this study is to determine the relationship of third molars to changes in the mandibular dental arch. The sample for this study consisted of four groups and subgroups. The groups consisted of premolar extraction treated, nonextraction treated with initial generalized spacing, nonextraction treated, and serial extraction untreated subjects. The subgroups were divided into persons who had mandibular third molars that were either impacted, erupted into function, congenitally absent, or extracted at least 10 years before postretention records. The mean postretention time interval was 13 years, with a range of 10 to 28 years. The mean postretention age was 28 years 6 months, with a range of 18 years 6 months to 39 years 4 months. Two-way analysis of variance with repeated measures was used to compare the changes over time (before treatment, at end of active treatment, and after retention) of groups and third molar subgroups. With time, mandibular incisor irregularity increased while arch length and intercanine width decreased. The eruption patterns of mandibular incisors and first molars were similarly dispersed in all groups studied. The findings between the subgroups in which mandibular third molars were impacted, erupted into function, congenitally absent, or extracted 10 years before postretention records revealed no significant differences between any of the subgroups for the parameters studied. No significant differences in mandibular growth were found between the third molar subgroups; this suggests that persons with third molars erupted into satisfactory function do not have a significantly different mandibular growth pattern than those whose third molars are impacted or congenitally missing. In the majority of cases some degree of mandibular incisor crowding took place after retention, but this change was not significantly different between third molar subgroups. This finding suggests that the recommendation for mandibular third molar removal with the objective of alleviating or preventing mandibular incisor irregularity may not be justified.     

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.     

序列拔牙与恒牙期拔牙矫治的稳定性比较

目的：比较序列拔牙及恒牙期拔牙矫治的稳定性。方法：20例序列拔牙矫治患者、20例恒牙期拔除4个第一双尖牙矫治患者,均采用直丝弓矫治技术治疗,平均戴用保持器2年。主动治疗结束时（T2）、保持结束后5年（T3）测量下颌模型6项指标、头颅定位侧位片9项指标,用配对t检验对数据进行统计分析。结果：与T2时相比,两组患者在T3时下颌尖牙间宽度、磨牙间宽度、牙弓长度均减小;拥挤度、覆、覆盖有所增大;上中切牙与SN夹角、IMPA、下中切牙与NB距离略有增加;上下切牙夹角减小。组间差异无统计学意义。结论：两组均表现一定程度的复发,序列拔牙与恒牙期拔牙矫治在观察阶段的稳定性无统计学差异。     

The effectiveness and long-term stability of overbite correction with incisor intrusion mechanics.

BACKGROUND: Correction of deep overbite with subsequent achievement of long-term stability is difficult. The purpose of this study was to investigate the effectiveness and long-term stability of overbite correction with incisor intrusion mechanics. METHODS: The treated group consisted of 25 subjects (13 female, 12 male) with deep overbite of at least 4 mm (mean overbite, 5.9 mm). The orthodontic treatment was initiated in the late mixed or early permanent dentition, and all patients were treated nonextraction. All patients had lateral cephalometric radiographs taken at pretreatment (T1), posttreatment (T2), and postretention (T3). The treatment included cervical headgear and lever arches to intrude mainly the maxillary incisors and occasionally the mandibular incisors. Premolars were not included in the fixed appliances during the treatment. The untreated group consisted of 25 age- and sex-matched subjects from the Bolton Growth Study. RESULTS: The mechanics used were effective in overbite correction. During the posttreatment period, overbite increased by 0.7 mm. CONCLUSIONS: Although this change was statistically significant, the amount was small and is considered clinically insignificant, given the severity of the overbite pretreatment. Furthermore, a net overbite correction (T3-T1) of 3.3 mm and postretention overbite on 2.6 mm is an excellent clinical outcome.     

An evaluation of growth and stability in untreated and treated subjects

This retrospective longitudinal study compared skeletal and dental changes in orthodontically treated patients with changes in a comparable untreated group to evaluate the relationship between skeletal changes and mandibular incisor crowding. Cephalograms and models of 44 untreated subjects from the Broadbent-Bolton Growth Study and 43 treated patients were evaluated at "posttreatment" (14.3 +/- 1.5 and 15.2 +/- 1.1 years, respectively) and at "postretention" (23.2 +/- 3.4 and 28.9 +/- 3.6 years, respectively). Cranial base and mandibular superimpositions were used to measure cephalometric changes. Tooth-size-arch-length discrepancy, contact irregularity, and space irregularity were measured. In both groups, growth in the vertical dimension was twice that in the horizontal dimension. The untreated subjects, who were younger, exhibited greater yearly vertical growth increments than did the treated subjects. The treated subjects exhibited greater overjet and overbite increases than did the untreated subjects. Yearly changes in tooth-size-arch-length discrepancy were greater in the untreated than in the treated subjects, but there were no differences in the changes in irregularity between the 2 groups. A multivariate regression model, relating posterior facial height (Ar-Go) increase and lower incisor eruption to change in space irregularity, explained 42% of the variation in the untreated group (r = 0.64; P <.001). A weaker relationship was found in the treated group. Overjet change was negatively correlated with tooth-size-arch-length discrepancy. Changes in lower incisor crowding were related to growth in the vertical dimension and lower incisor eruption in both untreated (r = 0.64) and treated (r = 0.51) subjects.     

Long-term stability of anterior open bite extraction treatment in the permanent dentition.

The purpose of this study was to cephalometrically evaluate the long-term stability of anterior open bite extraction treatment in the permanent dentition after a mean period of 8.35 years. Cephalometric headfilms were obtained at pretreatment, posttreatment, and postretention stages from 31 patients who had undergone orthodontic treatment with fixed appliances. Two control groups were used. The first, with an age similar to that of the experimental group before treatment, was used only to characterize it. The second, with normal occlusion, was followed longitudinally for a period comparable with the posttreatment period and was used to compare changes during this period. The differences between the observation stages in the experimental group were analyzed with paired t tests, and the posttreatment changes were compared with the changes of the second control group with independent t tests. There was no statistically significant decrease of the obtained anterior overbite at the end of the posttreatment period. The primary factors that contributed to the nonsignificant decrease of the overbite were the normal vertical development of the maxillary and mandibular incisors, the smaller vertical development of the mandibular molars, and the consequent smaller increase in lower anterior face height, as compared with the control group in the long-term posttreatment period. Additionally, 74.2% of the sample had a "clinically stable" open bite correction.     

Changes in mandibular incisor position in Class II Division 1 malocclusion treated with premolar extractions

The aim of this study was to investigate the magnitude of mandibular incisor retraction to be expected during full fixed appliance mechanotherapy in Class II Division 1 malocclusions treated with premolar extractions when mandibular incisor retraction was not part of the treatment plan. The material consisted of pretreatment and posttreatment cephalometric films and dental casts of 70 Class II Division 1 malocclusion patients (33 males and 37 females) treated with the preadjusted edgewise appliances. The mandibular first premolars were extracted in 31 subjects, and the mandibular second premolars were extracted in 39. The pretreatment factors that suggested a basis for the extraction choice in the mandibular arch in these patients were found to include the ratio between posterior and anterior facial heights, the maxillary-mandibular plane angle, and the residual space in the mandibular arch. The mandibular incisors were retracted in only 65% of the patients. On average, the mandibular incisors were retracted by 1.02 mm relative to the nasion-pogonion line; there was no significant difference between the 2 extraction groups. Multiple regression analysis showed that the change in the mandibular incisor position is significantly correlated with the residual space in the mandibular arch, the initial distance between the mandibular incisor and the nasion-pogonion line, maxillary-mandibular angle, and the duration of crown labial torque in the mandibular incisors. In combination, these 4 factors could explain 61% of the change in the mandibular incisor position.     

Long-term stability of Class I premolar extraction treatment.

This study evaluates Class I, 4-premolar-extraction patients who were treated with the edgewise appliance by 1 practitioner, according to the philosophy of Tweed, and who had been out of retention a minimum of 5 years. The sample includes 32 patients, who started treatment at an average age of 12.8 years and who were examined a mean of 15 years posttreatment (11.7 years postretention). Cephalometric and model analyses were conducted to evaluate treatment and posttreatment tooth movements. The results showed that irregularity, as measured by the irregularity index, decreased 5.3 mm during treatment and increased 0.7 mm (SD 1.1 mm) during the posttreatment period. Eighty percent of the patients had satisfactory (<3.5 mm) mandibular incisor alignment over 10 years postretention, and none was in the severe category (>6.5 mm). Mandibular intercanine width increased (1.7 mm) during treatment, whereas intermolar width decreased (-2.1 mm). Maxillary molar widths remained unchanged posttreatment, and mandibular intercanine width decreased 1.4 mm from immediately posttreatment to postretention. Arch lengths decreased during treatment because of molar protraction and incisor retraction. Mandibular arch length continued to decrease posttreatment (-1.4 mm) because of mesial molar movement rather than distal incisor movement. Satisfactory long-term results can be achieved for most Class I, 4-premolar-extraction patients for whom evidence-based treatment objectives-including minimal alteration of the mandibular arch form and the retraction and uprighting or maintenance of mandibular incisors in their original position-have been met.     

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.     

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.     

Dental crowding in primary dentition and its relationship to arch and crown dimensions among preschool children of Davangere

The purpose of the present study was to evaluate dental crowding in the deciduous dentition and its relationship to the crown and the arch dimensions among preschool children of Davangere. Stratified randomized selection of one hundred, 3-4 year old healthy children with all primary teeth erupted was done and divided into two groups. One group had children with anterior crowding in both the arches while the other had spacing. Alginate impressions of the upper and lower arches were made and the study casts were obtained. The tooth and arch dimensions were determined. Mesiodistal dimensions of all the teeth were significantly larger in the crowded arch group. However, the buccolingual dimensions of the maxillary right central incisor, mandibular lateral incisors and the maxillary molars and the crown shape ratio of maxillary lateral incisors, mandibular canines and mandibular right second molar was statistically different. No significant correlation was found between the arch width and the presence of crowding of deciduous dentition. The arch depth of the spaced dentition was greater when compared to the crowded ones. The arch perimeter of the crowded arches was significantly less than the spaced arches.     

Evaluation of posttreatment changes in Class II Division 1 patients after nonextraction orthodontic treatment: cephalometric and model analysis.

BACKGROUND: The aim of this retrospective study was to evaluate changes in patients with Class II Division 1 malocclusions treated with cervical headgear and full fixed orthodontic appliances and without extractions. METHODS: Lateral cephalograms and dental casts of 18 patients were obtained at the beginning and the end of treatment and at the postretention period. Pretreatment records were taken at 11.9 +/- 2.6 years, and the mean treatment time was 2.8 +/- 1.2 years. All patients were asked to use maxillary and mandibular Hawley retainers for 1 year. The average postretention interval was 5.3 years. RESULTS: The assessment of cephalometric findings showed that maxillary growth was restricted; maxillary incisor inclination, overjet, and overbite were decreased; the mandibular incisors were proclined; and a slight mandibular posterior rotation occurred at the end of treatment. At the postretention period, the maxilla remained stable, the mandible moved anteriorly, and the overjet increased slightly (1.25 mm, P < .01). The dental cast changes indicated that both maxillary and mandibular irregularity index values decreased significantly during treatment but increased after 5 years. Mandibular intercanine width decreased 0.47 mm ( P < .01) during the postretention period. CONCLUSIONS: The redirection of maxillary growth remained stable in patients with Class II malocclusions treated with cervical headgear and fixed orthodontic appliances and without extractions, but treatment-induced mandibular rotations tended to return to their original patterns. Various dental changes occurred during the postretention period.