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 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.     

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 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.     

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 mandibular dental arch: Part I, lower incisor position.

The position of the lower incisor with respect to hard tissue references has been evaluated. Two samples were used for this purpose: one containing 78 patients with posttreatment records having a postretention period of at least 4 years, and the other composed of 82 normal occlusions. The results indicated: 1) There was no significant difference in relapse of lower incisor crowding between cases where the lower incisor had been moved lingually, labially, or held in the same relative position during treatment. 2) The position of the maxilla should be considered when placing the lower incisor. The APo plane adequately serves as a guide to this purpose, whereas other reference lines such as mandibular plane or facial plane do not. 3) The positions of the incisors with respect to popular cephalometric reference lines such as APo, NB, or mandibular plane were not correlated with the relapse of mandibular crowding. Therefore, other clinical guides might be more successful for determining stability.     

Effect of reverse curve mushroom archwire on lower incisors in adult patients: a prospective study.

This prospective clinical study was undertaken to analyze adult skeletodental changes induced by a reverse curve mushroom archwire during the initial stage of treatment. Lateral cephalograms from before treatment and immediately after bite opening were evaluated from 8 female adult patients who were undergoing lingual orthodontic treatment. Before treatment the patients had a mean overbite of 3.9 mm. Six linear and 5 angular measurements were selected for cephalometric analysis. The mean change in the cephalometric parameters was subjected to paired t-tests to determine whether the change was significant. There was a highly significant overbite reduction (-1.9 mm, P < .001) leaving a postintrusion overbite of 2.0 mm. The lower incisors were intruded 1.5 mm (P < .001) and the lower incisor edge was in an approximately stable sagittal position (L1 to NPg = -0.2 mm, NS). Some lower incisor proclination (L1 to MP = 1.2 degrees) was seen, which was not of significance. The mandibular molars were not significantly extruded. After bite opening the mandibular plane angle was not significantly altered. Consequently, the lower anterior face height was not significantly increased. The results of this study revealed that the use of reverse curve mushroom archwire is capable of intruding the lower incisors with minimal side effects on the posterior teeth.     

Postretention assessment of deep overbite correction in Class II Division 2 malocclusion

The purposes of this study were to evaluate the long-term stability of deep overbite correction in Class II Division 2 malocclusion and to search for predictors of postretention overbite. The sample of 62 (31 males, 31 females) was limited to Class II Division 2 patients with initial deep overbite and successful orthodontic treatment as judged clinically at the end of treatment. Study models and cephalograms were analyzed before treatment, after treatment, and out of retention (average 15 years). The sample was divided into two groups according to the degree of postretention overbite: Group 1 (N=33; overbite > or = 4.0 mm at T3, mean = 5.17 +/- 0.87) and group 2 (N=29; overbite <4.0 mm at T3, mean = 2.95 +/- 0.87). The results showed that patients with very upright pretreatment maxillary and mandibular incisors tended to have deeper initial overbite and a tendency to return to their original relationship by the postretention stage. Posttreatment vertical growth contributed to maintenance of overbite correction. By stepwise multiple regression analysis, initial overbite was selected as the most important predictor of postretention overbite. Initial overbite was positively related with postretention overbite.     

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.     

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 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.     

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.     

Vertical components of overbite change: a mathematical model.

The purpose of this study was to better understand the multidimensional nature of overbite changes that occur during adolescence. The study used longitudinal cephalograms of 181 untreated children (102 males, 79 females) taken at ages 10 and 15. Four major components that directly affect overbite were measured: (1) maxillary vertical displacement, (2) mandibular vertical displacement, (3) upper incisor vertical change within the bone, (4) lower incisor vertical change within the bone. Cranial base, maxillary, and mandibular superimpositions were performed for each subject to assess the vertical changes that occurred in these 4 components and to assess overbite. A multiple regression analysis was used to develop a mathematical model describing the relationships of these components to changes in overbite. The model was validated with an independent subsample and a comparison of subjects whose overbites decreased and those whose overbites increased. The results showed that overbite changed minimally (0.2 mm) over the 5-year period; variation ranged from a 2.4 mm decrease to a 5.6 mm increase. The regression model indicated that the mandibular skeletal changes were twice as important as the mandibular dental changes and about 2.5 times as important as the maxillary changes in effecting overbite change. Within the mandibular skeletal component, vertical growth was more important than mandibular rotation in determining overbite change. The model demonstrated that a multivariate approach is necessary to understand overbite changes. More effective orthodontic treatment might be achieved by focusing on the primary components effecting overbite change, especially those with the greatest potential for therapeutic modification.     

Orthodontic treatment of openbite and deepbite high-angle malocclusions.

The aim of the investigation was to assess the effect of orthodontic treatment on dentoskeletal morphology in children with openbite and deepbite high-angle malocclusion. Subjects (n = 54) in the mixed dentition with a hyperdivergent mandibular plane angle (high-angle, NSL/ML > or =40 degrees) were surveyed. Pre- and posttreatment lateral roentgenographic cephalograms were analyzed. Subjects were divided into three subgroups according to the amount of pretreatment overbite: < 0 mm = insufficient/no compensation (openbite); 0-4 mm = acceptable compensation (normal overbite); >4 mm = overcompensation (deepbite). Pretreatment, 20% of the high-angle cases exhibited insufficient dentoskeletal compensation (overbite <0 mm), and 35% displayed overcompensation (overbite >4 mm). Influences of habits such as lip sucking and tongue-thrust swallowing were more common in the openbite group. No major difference in treatment approach could be found between subgroups. In 82% of the openbite group and 90% of the deepbite group, overbite was corrected by orthodontic treatment. The mandibular plane angle was unaffected in both groups. The mechanisms of overbite correction differed between groups. The openbite group exhibited a significant decrease in interjaw-base angle. Increases in anterior and posterior dentoalveolar heights were comparable. The deepbite group showed no significant changes in skeletal morphology. The increase in dentoalveolar height was approximately twice as large posteriorly as anteriorly. The majority of children (80%) with high-angle morphology had a positive pretreatment overbite, thus exhibiting compensation of jaw-base hyperdivergency. Orthodontic treatment of high-angle malocclusions did not influence the mandibular plane angle in openbite or deepbite cases. Overbite correction was accomplished by tipping the maxilla downward anteriorly in openbite subjects, and by controlling incisor eruption in deepbite subjects.     

Bilateral congenital absence of maxillary lateral incisors: a craniofacial and dental cast analysis

The dental casts and cephalometric records of forty-three patients exhibiting bilateral congenital absence of maxillary lateral incisors were evaluated to determine the nature and extent of any concurrent craniofacial and dental anomalies. The effects of bilateral orthodontic space closure were evaluated on a subsample of twenty-two cases. The data revealed normal dental arch length, arch width, overjet, and overbite, while significant tooth size discrepancies were found in several anterior and posterior teeth. Craniofacial deviations from normal included smaller maxillary length, smaller mandibular length, smaller anterior cranial base, and nasal bone. Vertical facial dimensions, both anterior and posterior, were significantly less, as was the mandibular plane angle. Soft-tissue examination revealed a 10 degrees greater nasiolabial angle, which was increased a further 5 degrees as a result of a mean incisor retraction of 1.5 mm during space closure. The craniofacial anomalies noted in the present sample were similar to those seen in persons with clefts and may reflect a common etiology related to a developmental disturbance during fusion of the facial processes in utero. In the treatment of patients with bilateral congenital absence of maxillary incisors, mechanotherapy designed to open the mandibular plane, increase the vertical dimension, and move the maxillary posterior teeth forward is recommended in order to prevent worsening the Class III tendency and to minimize maxillary incisor and upper lip retraction. Most cases will require significant mesiodistal reduction in tooth size in order to achieve an optimal occlusion.     

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.     

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.     

Mandibular incisor extraction--postretention evaluation of stability and relapse.

Pretreatment, posttreatment and 10-year postretention dental cast and lateral cephalogram records of 42 patients were evaluated. Each patient had undergone edgewise orthodontic treatment following removal of one or two mandibular incisors and various maxillary teeth. Seven of 24 patients (29%) in the single-incisor extraction group and 10 of 18 (56%) patients in the two-incisor extraction group demonstrated unacceptable mandibular incisor alignment at the postretention stage. This result was considerably more favorable than the results of previously reported premolar extraction cases (70% unacceptable alignment at postretention). Intercanine width decreased during treatment and continued to decrease postretention in most cases. Overbite and overjet remained acceptable. No associations could be found to predict the amount of relapse.     

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.     

Tooth movements associated with deep overbite correction in Class II division 1 malocclusions

The orthodontic profession has assumed much of the responsibility for the improvement in function of the teeth and jaws. Since function is closely associated with overbite, the correction of vertical overbite discrepancies comprises a major part of clinical orthodontics. This investigation was undertaken to describe the movements that teeth undergo during the correction of excessive overbites and to correlate these movements to the change in overbite. A total of 87 cases were selected from the records of the Indiana University School of Dentistry, Department of Orthodontics. The selected cases had an excessive pre-treatment overbite of 4.0 mm or more as seen cephalometrically and a satisfactory post-treatment result. In addition, they were clinically determined to be post-pubertal, indicating essentially no growth potential during the treatment period. Pre and post-treatment tracings of the cephalograms were made and measurements collected from the tracings. Superimpositions were prepared of the pre and post-treatment radiographs and the general trends that appeared were noted. The change in overbite was correlated to tooth movements of the Class II Division 1 correction using the Pearson test of correlation coefficients. The results indicate that the tooth movements most commonly seen in treatment to reduce excessive overbite occur mainly in the mandibular arch. In Class II Division 1 cases, the change was significantly correlated to the reduction in vertical height of the mandibular incisor and to the increase in the angulation of the mandibular incisor to the mandibular plane. Not all measurements recorded were significantly correlated to the change in overbite.(ABSTRACT TRUNCATED AT 250 WORDS)