Expansion of the lower arch concurrent with rapid maxillary expansion

Hyrax versus Leaf expander in growing patients, what about adverse dental effects? A retrospective study

OBJECTIVES

Transverse discrepancy is a Common problem in young patients. Many devices are employed to expand the palatal dimension, with different characteristics and biomechanical aspects. The Leaf expander, a new-born appliance containing nickel-titanium springs, free from activation by parents. We compared the maxillary and mandibular dental effects of Leaf expander to conventional Hyrax in growing patients.

METHODS

All patients who met the eligibility criteria between the period from January 2017 to December 2019 were included. The patients had transverse inter-arch discrepancy of at least 5mm and were treated with Hyrax expander (HEX) or Leaf expander (LEX). All patients had complete follow-up of expansion by remote monitoring. An algorithm established distances between the teeth. It was also used to measure the change in dental axes.

RESULTS

In the maxilla, LEX caused more tipping on the canines and premolars but significantly less on the molars compared to HEX: -0.154̊ vs. 3.05̊ (P<0.001). In the mandible, LEX caused a greater increase in arch widths and tipping (P<0.02) in the molars and second premolars, but not in the other teeth. No correlation was demonstrated between mandibular dental movements and increased maxillary arch widths. Alternatively, for the two devices, expansion and tipping were correlated within each dental arch (r>0.4).

CONCLUSIONS

The LEX produced more tooth movement on average than the HEX, except for the maxillary first molars. Several correlations exist between the movements within each arch for the two devices, most often between tipping and expansion.

A pilot study of mandibular expansion in combination with a fixed-appliance for increasing the effective space of the mandibular arch: Finite element analysis and three-dimensional cone-beam computed tomography

Techniques for enhancing the effective space of the mandibular arch are urgently needed. Therefore, this study aimed to perform mandibular expansion in combination with a fixed-appliance technique, with preliminary monitoring by finite element analysis and 3-dimensional cone-beam computed tomography (CBCT).Finite element models were structured according to CBCT images of a 14-year-old girl. The von Mises stress of the alveolar bone and tooth displacement were assessed in different models. The technique was also applied in an 11-year-old boy. CBCT was performed at post-expansion, post-retention, post-treatment and 2 years after treatment. Tooth movement and alveolar bone stress were assessed by the CAD software.Finite element analysis suggested that the teeth tended to stand upright in the buccal side in the expander model compared with the expander-remove model. However, minimum tooth change was observed in the normal model, indicating highest stability. The von Mises stress of the alveolar bone was decreased in the normal model compared with the expander model, suggesting that buccal-inclined teeth could more easily lead to alveolar bone stress than normal ones. Based on CBCT data and the 3D mandibular dentition model fitting, mandibular teeth tended to be upright in the buccal side after retention compared with the post-expansion condition, which somewhat differed from finite element analysis results. Furthermore, dehiscence and fenestration were not observed.This expansion technique is expected to increase the effective space after mandibular expansion and reduce buccal alveolar bone stress.

Three-dimensional assessment of transverse dentoskeletal mandibular dimensions after utilizing two designs of fixed mandibular expansion appliance: A prospective clinical investigation

The aim of this clinical study was to evaluate and compare the dentoskeletal transverse mandibular arch dimensions following the use of two designs of fixed mandibular expanders using cone beam computed tomography (CBCT). Twenty orthodontic patients, 12 females and 8 males, with mean age of 13.4 ± 0.5 years were selected and randomly divided into two equivalent groups; group A consisted of 10 patients (4 boys, 6 girls) who were treated with modified Williams expander and group B consisted of 10 patients (4 boys, 6 girls) who were treated with a two-arm fixed expander. Consistent expansion instructions were given to all patients according to a standardized slow protocol of one quarter turn twice/week for both expanders. Routine orthodontic records as well as mandibular CBCTs were obtained before (T1) and immediately after expansion (T2) to estimate changes in dentoskeletal mandibular transverse dimensions. The data was statistically analyzed and the significance level was set at p ≤ 0.05. Mandibular intercanine, inter-premolar, intermolar widths; and arch perimeter were significantly increased (p ≤ 0.05) following expansion with both fixed expanders. However, the changes in inter-premolar width, intercanine width, and arch perimeter were significantly augmented in two-arm fixed expander group than modified Williams’s group. In contrast, their effects on the skeletal mandibular body width were non-significant (p > 0.05). Both expanders yielded significant and equivalent dentoalveolar effects that were more evident with two-arm fixed expander than the William one. Both fixed designs enhanced mandibular transverse dental dimensions; however, they were unsuccessful to create any considerable skeletal effects.

Dental inclination with self-ligating and conventional fixed appliances, with and without rapid maxillary expansion

OBJECTIVE

To compare the labio- and buccolingual inclination of the anterior and posterior teeth in subjects treated with self-ligating and conventional fixed appliances with and without rapid maxillary expansion.

METHODS

Seventy-one subjects with Class I malocclusion were divided into three groups. Group 1 comprised 24 subjects (17 female; seven male, with a mean age of 13.94 ± 2.87 years), treated with Roth's pre-adjusted fixed appliances. Group 2 comprised 24 subjects (14 female; 10 male, with a mean age of 13.85 ± 1.83 years) treated with Rapid Maxillary Expansion followed by Roth's pre-adjusted fixed appliances. Group 3 comprised 23 patients (12 female; 11 male, with a mean age of 14.75 ± 1.34 years) treated with Damon self-ligating bracket system. Buccolingual inclination was measured on digital dental models using a 3D software. Intergroup changes comparison was performed with one-way ANOVA, followed by Tukey tests.

RESULTS

The left maxillary lateral incisor showed labial inclination in the conventional and RME groups, and palatal inclination in the Damon group. The Damon group showed greater buccal inclination in most posterior mandibular teeth during treatment than the conventional and RME groups. The right mandibular canine and lateral incisor showed greater labial inclination in the Damon group than in the RME group.

CONCLUSIONS

There was greater buccal inclination of the posterior mandibular teeth and labial inclination of the right mandibular canine and lateral incisor in the Damon group.

Maxillary and mandibular dentoalveolar expansion with an auxiliary beta-titanium arch

Traditionally, adult patients with mild to moderate transverse discrepancies are treated with a combination of slow maxillary expansion with palatal appliances and expanded archwires. In this case report, we describe an alternative approach for anterior crowding and excessive buccal corridors in a 20-year-old man who was treated using a beta-titanium auxiliary expansion archwire. The perceived benefit of this approach was related not only to the esthetic improvement of the smile resulting from elimination of the anterior crowding and reduction of the buccal corridors, but also to the minimal disruption of the patient's speech, which was his main functional concern.

Arch-width changes in extraction vs nonextraction treatments in matched Class I borderline malocclusions

INTRODUCTION

The aims of this study were to identify a sample of borderline Class I extraction and nonextraction patients and to investigate posttreatment changes in arch-width and perimeter measurements.

METHODS

A parent sample of 580 Class I patients was subjected to discriminant analysis, and a borderline subsample of 62 patients, 31 treated with extraction of 4 first premolars and 31 treated without extractions, was obtained. The patients' plaster casts were digitally scanned, and the maxillary and mandibular intercanine and intermolar widths and perimeters were assessed.

RESULTS

The extraction group showed increases in maxillary and mandibular intercanine widths (P <0.001) and decreases in mandibular intermolar width and in maxillary and mandibular perimeters (P <0.001). The nonextraction group showed increases in all 4 arch-width measurements (P ≤0.003), whereas the maxillary and mandibular perimeters were maintained. The posttreatment differences between the 2 groups showed significant differences in the maxillary (P <0.001) and mandibular intermolar widths (P <0.001). Also, the comparison of the arch perimeters between the 2 treatment groups showed adjusted differences of -8.51 mm (P <0.001) and -8.44 mm (P <0.001) for the maxillary and mandibular arches, respectively. The intercanine widths showed no changes between the 2 treatment groups.

CONCLUSIONS

Borderline Class I patients treated with extraction of 4 first premolars had decreased maxillary and mandibular intermolar and perimeter measurements compared with nonextraction patients. The maxillary and mandibular intercanine widths showed no significant difference between the 2 treatment groups.

Rapid palatal expansion effects on mandibular transverse dimensions in unilateral posterior crossbite patients: a three-dimensional digital imaging study

Background

The purpose of this controlled study was to investigate indirect effects on mandibular arch dimensions, 1 year after rapid palatal expansion (RPE) therapy.

Methods

Thirty-three patients in mixed dentition (mean age 8.8 years) showing unilateral posterior crossbite and maxillary deficiency were treated with a RPE (Haas type) cemented on the first permanent molars. Treatment protocol consisted of two turns per day until slight overcorrection of the molar transverse relationship occurred. The Haas expander was kept on the teeth as a passive retainer for an average of 6 months. Study models were taken prior (T1) and 15 months on average (T2) after expansion. A control group of 15 untreated subjects with maxillary deficiency (mean age 8.3 years) was also recorded with a 12-month interval. Stone casts were digitized with a 3D scanner (3Shape, DK).

Results

In the treated group, both mandibular intermolar distance (+1.9 mm) and mandibular molar angulation (+9°) increased. Mandibular incisor angulation showed an increase of 1.9°. There was little effect on intercanine distance and canine angulation. Controls showed a reduction in transverse arch dimension and a decrease in molar and canine angulation values.

Conclusions

RPE protocol has indirect widening effects on the mandibular incisors and first molars.

Comparison between rapid and mixed maxillary expansion through an assessment of arch changes on dental casts

Background

Aim of this retrospective observational study was to compare upper and lower dental changes in patients treated with Rapid Maxillary Expansion (RME) and Mixed Maxillary Expansion (MME), assessed by dental cast analysis.

Methods

Treatment groups consisted of 42 patients: the RME group (n = 21) consisted of 13 female and 8 male subjects with the mean age of 8.8 years ± 1.37 at T0 and 9.6 years ± 1.45 at T1; the MME group (n = 21) consisted of 12 female and 9 male patients with a mean age of 8.9 years ± 2.34 at T0 and 10.5 years ± 2.08 at T1. The upper and lower arch analysis was performed on four dental bilateral landmarks, on upper and lower casts; also upper and lower arch depths were measured. The groups were compared using independent sample t-test to estimate dental changes in upper and lower arches.

Results

Before expansion treatment (T0), the groups were similar for all examined variables (p>0.05). In both RME and MME group, significant increments in all the variables for maxillary and mandibular arch widths were observed after treatment. No significant differences in maxillary and mandibular arch depths were observed at the end of treatment in both groups. An evaluation of the changes after RME and MME (T1) showed statistically significant differences in mandibular arch depth (p<0.001) and maxillary intercanine widths (p<0.05). Differences in maxillary arch depth and arch width measurements were not significant.

Conclusions

RME and MME can be considered two effective treatment options to improve transverse arch dimensions and gain space in the dental arches. A greater lower arch expansion was observed in the MME group, which might be attributed to the “lip bumper effects” observed in the MME protocol.

Comparison between rapid and mixed maxillary expansion through an assessment of dento-skeletal effects on posteroanterior cephalometry

Background

The aim of this study is to compare the dento-skeletal effects of rapid maxillary expansion (RME) and mixed maxillary expansion (MME), assessed on posteroanterior (PA) cephalograms.

Methods

Treatment groups consisted of 42 patients; mean age in RME group (n = 21,13 female and 8 male subjects) was 8.8 years ± 1.37 at T0 and 9.6 years ± 1.45 at T1 and mean age in MME group (n = 21, 12 female and 9 male patients) was 8.9 years ± 2.34 at T0 and 10.5 years ± 2.08 at T1. Seventeen bilateral anatomic landmarks, 16 linear (12 skeletal and 4 dental) and 4 angular measurements were assessed for each patient at T0 and T1. Data from the two groups were compared using independent sample t test (p < 0.05).

Results

At T0, the groups were similar for all examined variables (p > 0.05). Significant and equal increase of lateronasal and maxillary and upper and lower molar widths (p < 0. 01) occurred in both groups at T1. Significant but different increases were observed for maxillary incisal, upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001 vs. p < 0.05). Significant increases were reported for upper inter-incisal width apex (p < 0.001) and upper right first molar-lateroorbitale angle (p < 0.05) only in the RME group. At T1, differences in maxillary incisal angle (p < 0.05), upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001) were noted.

Conclusions

RME and MME were both effective to increase skeletal transverse dimensions by opening mid-palatal suture in growing patients, while MME was associated with minor dental side effects than RME.

A comparative in-vivo evaluation of the alignment efficiency of 5 ligation methods: A prospective randomized clinical trial

Objectives:

To conduct a prospective randomized study comparing the efficiency of 5 different ligation systems (ELL; elastomeric ligature, SSL; stainless steel ligature, LL; leone slide ligature, PSL; passive self-ligation and ASL; active self-ligation) over the duration of mandibular crowding alleviation.

Materials and Methods:

Fifty consecutive patients (54.2% male, 45.8% female; mean age: 16.69 years) satisfying the inclusion criteria were randomly allocated to 5 ligation groups with an equal sample size of 10 per group. The 5 groups received treatment with 0.022-inch MBT pre-adjusted edge-wise technique (ELL: Gemini 3M Unitek, SSL: Gemini 3M Unitek, LL: Gemini 3M Unitek, PSL: SmartClip 3M Unitek and ASL: In-Ovation R Euro GAC International). The models and cephalograms were evaluated for anterior arch alignment, extraction space closure, and lower incisal inclinations at pre-treatment T₁ and at the end of initial alignment T₂. Analysis of variance (ANOVA) and Post-hoc tests were used for data analysis.

Results:

Forty-eight participants completed the study, and SL systems showed a significant difference over CL groups in time to alignment, passive space closure, and incisal inclination. Multiple regression showed a reduction of 5.28 days in time to alignment by changing the ligation group in the order of ELL to ASL group and 1 mm increase in initial irregularity index increases time to alignment by 11.68 days.

Conclusion:

Self-ligation brackets were more efficient than conventional ligation brackets during initial leveling and alignment.

CBCT of skeletal changes following rapid maxillary expansion to increase arch-length with a development-dependent bonded or banded appliance

OBJECTIVE

To assess the three-dimensional (3D) skeletal response to a standardized 5 mm of rapid maxillary expansion (RME) in growing children (6-15 years) with maxillary width deficiency and crowding.

MATERIALS AND METHODS

A bonded appliance was used prior to the eruption of the maxillary first premolars (Mx4s), and a banded appliance was used thereafter. A consecutive sample of 89 patients (29 boys and 60 girls) from a large pediatric dentistry and orthodontics practice was divided into four groups: 1) 6-8 years old (n = 26), 2) 9-11 years old with unerupted Mx4s (n = 21), 3) 9-11 years with erupted Mx4s (n = 23), and 4) 12-15 years (n = 19). For all patients, the 3D evaluation of dental and skeletal effects was performed with cone-beam computed tomography (CBCT).

RESULTS

For both appliances in all patients, CBCT confirmed a triangular pattern of expansion in both the frontal and sagittal planes. Overall, both appliances produced significant maxillary expansion (>80% of the 5-mm activation), but older children showed a progressively more dental (less skeletal) response. Comparison of the two types of expanders in the crossover sample, children aged 9-11 years, showed that the bonded RME produced the most efficient skeletal expansion in the preadolescent sample. Increased maxillary width at the level of the zygomaticomaxillary suture was the best indicator for development of maxillary arch circumference.

CONCLUSION

Development-dependent appliances (bonded RPE before Mx4s erupt, and a banded device thereafter) provided optimal RME treatment for all children from age 6-15 years.

Magical NiTi expander

A 24-year-old male patient was referred to our department for expansion of the constricted maxillary arch as a presurgical procedure for the correction of congenital facial disfigurement. On examination, the patient had a convex profile, increased interlabial gap, tongue thrust, limited mouth opening, posterior crossbite, asymmetric 'V'-shaped maxillary arch with severe constriction, crowding of anterior teeth in the maxillary arch and a massive open bite. Radiographic investigations included orthopantomograph and occlusal radiographs. The patient photographs and models were analysed. On careful evaluation, the treatment for maxillary arch expansion was planned with a nickel titanium (NiTi) slow maxillary expander along with fixed mechanotherapy for alignment of teeth. An unexpectedly successful outcome was appreciated from the treatment. An emphasis should be laid on selecting and treating the case of constricted arches with a surgical or non-surgical approach, as expansion can be achieved orthodontically by using NiTi expanders.

Mandibular dental arch changes associated with treatment of crowding using self-ligating and conventional brackets

The purpose of this study was to investigate the effect of treatment of mandibular crowding with self-ligating and conventional brackets on dental arch variables. Fifty-six patients were selected from a pool of subjects satisfying the following inclusion criteria: non-extraction treatment in the mandibular or maxillary arches, eruption of all mandibular teeth, no spaces and an irregularity index greater than 2 mm in the mandibular arch, and no adjunct treatment such as etxra- or intraoral appliances. The patients were assigned to two groups: one group received treatment with the self-ligating bracket and the other with a conventional edgewise appliance, both with a 0.022 inch slot. Lateral cephalometric radiographs obtained at the beginning (T1) and end (T2) of treatment were used to assess the alteration in mandibular incisor inclination, and measurements of intercanine and intermolar widths were made on dental casts to investigate changes associated with the correction. The results were analysed with bivariate and multivariate linear regression analysis in order to examine the effect of the bracket systems on arch width or lower incisor inclination, adjusting for the confounding effect of demographic and clinical characteristics. An alignment-induced increase in the proclination of the mandibular incisors was observed for both groups; no difference was identified between self-ligating and conventional brackets with respect to this parameter. Likewise, an increase in intercanine and intermolar widths was noted for both bracket groups; the self-ligating group showed a higher intermolar width increase than the conventional group, whereas the amount of crowding and Angle classification were not significant predictors of post-treatment intermolar width.

Maxillary expansion in the mixed dentition: rapid or semi-rapid?

The purpose of this study was to investigate the effects of rapid maxillary expansion (RME) and semi-rapid maxillary expansion (SRME) in the mixed dentition period. The SRME group consisted of 18 patients (11 girls and 7 boys) with a mean age of 8.63 +/- 1.09 years and the RME group 17 patients (11 girls and 6 boys) with a mean age of 8.78 +/- 1.21 years. A splint type tooth- and tissue-borne modified bonded RME appliance was used, with the patients activating the screw two-quarter turns per day for the first week, followed by one-quarter turn every other day in the SRME group and two-quarter turns per day throughout treatment in the RME group. The average treatment time was 57.16 +/- 21.52 and 21.23 +/- 8.36 days for the SRME and RME groups, respectively. A Wilcoxon signed rank test was used to evaluate the treatment effects [pre-(T(0)) - post-(T(1)) treatment changes] for both the SRME and RME groups and a Mann-Whitney U-test to determine the differences between the two groups (T(0)-T(1) changes SRME versus T(0)-T(1) changes RME). For both groups, the maxillary base, nasal cavity width and upper intercanine and intermolar distances were increased, and the upper molars tipped buccally. The only statistically significant (P < 0.05) difference between two groups was in inferior movement of posterior nasal spine (PNS) relative to the SN plane (SN upper left and right quadrantsPNS). This measurement increased in both groups yet significantly more in the RME group. The results suggest that RME and SRME have similar effects on dentofacial structures both in the transverse, vertical, and sagittal planes.

[Early treatment with rapid palatal expander and 3D Quad Action mandibular appliance: evaluation of a comprehensive approach in 22 patients]

The aim of this retrospective study in mixed dentition was to quantify dental arches and radiographic changes with a rapid maxillary expander followed by a transpalatal bar with arms and a 3D Quad action mandibular appliance, at the end of the treatment (T1) and six months afterwards (T2).

MATERIAL AND METHODS

Thirty Class II patients in mixed dentition with tooth size-arch length discrepancies were studied (22 treated). We obtained measurements from dental casts before treatment, at T1 and T2 and radiographic changes at T1. The breathing was appraised.

RESULTS

We found a significant (p < 0.05) increase of maxillary (+7.41 mm) and mandibular (+2.96 mm) dental arch perimeter, of intercanine gingival width (maxillary +3.25 mm, mandibular +1.57 mm) and of intermolar gingival width (maxillary +5.32 mm, mandibular +2.32 mm). There is a statistically significant increase of SNB angle. All posterior cross bites were corrected. We obtained a better position for the maxillary canine on radiography. All patients had nasal breathing at T1. Non treated subjects showed no improvement. In conclusion, this interceptive treatment corrected posterior cross bites, improved breathing and suggests an amelioration of tooth size-arch length discrepancy.

Self-ligating vs conventional brackets in the treatment of mandibular crowding: a prospective clinical trial of treatment duration and dental effects

INTRODUCTION

The aim of this study was to investigate the duration of mandibular-crowding alleviation with self-ligating brackets compared with conventional appliances and the accompanying dental effects.

METHODS

Fifty-four subjects were selected from a pool of patients satisfying the following inclusion criteria: nonextraction treatment in the mandibular or maxillary arches; eruption of all mandibular teeth; no spaces in the mandibular arch; irregularity index greater than 2 in the mandibular arch; and no therapeutic intervention planned with any extraoral or intraoral appliance. The patients were randomly assigned to 2 groups: 1 group received treatment with a self-ligating bracket (Damon 2, Ormco, Glendora, Calif) and the other with a conventional edgewise appliance (Microarch, GAC, Central Islip, NY), both with 0.022-in slots. The irregularity index of the mandibular arch was normalized between the groups, and the time to alignment was estimated in days. Treatment duration was assessed by data modeling with the Cox proportional hazard regression. Lateral cephalometric radiographs were used to assess the alteration of mandibular incisor position before and after alignment. Measurements of intercanine and intermolar widths were also made on dental casts to determine changes associated with correction.

RESULTS AND CONCLUSIONS

Overall, no difference in the time required to correct mandibular crowding with Damon 2 and conventional brackets was observed. For moderate crowding (irregularity index <5), however, the self-ligating group had 2.7 times faster correction. This difference was marginally insignificant for subjects with irregularity index scores greater than 5. Greater crowding prolonged treatment by an additional 20% for each irregularity index unit. Increases in intercanine and intermolar widths associated with crowding correction regardless of bracket group were noted. The self-ligating group showed a statistically greater intermolar width increase than the conventional group. Also, an alignment-induced increase in the proclination of the mandibular incisors was observed for both bracket groups, but no difference was found between Damon 2 and conventional brackets for this parameter.

Long-term Stability of Unilateral Posterior Crossbite Correction

OBJECTIVE

To evaluate the stability of orthodontically corrected unilateral posterior crossbite in patients treated either by rapid maxillary expansion or with slow expansion devices in the early (mean age 7.2 years, n = 50) or late mixed dentition (mean age 9.9 years, n = 50).

MATERIALS AND METHODS

The observation periods were approximately 8 years for the early treatment groups and 6.5 years for the late treatment groups. The measurements were made on plaster casts at the following time points: before treatment (T1), after crossbite correction (T2), at the end of active orthodontic treatment (T3), and about 2 years after the end of active treatment (T4). Midline deviation and the skeletal classification of the malocclusion were also evaluated.

RESULTS

Almost 80% of the treated patients showed long-term stability of the corrected unilateral posterior crossbite. More than 70% of the patients were treated for the mandibular midline deviation. At the end of active treatment, 50% of the patients showed a skeletal Class III craniofacial morphology.

CONCLUSIONS

The results emphasize that determination of the correct treatment approach for the individual patient is the basic principle underlying the therapeutic success in unilateral crossbite cases. In patients where a broad lower arch is a cofactor in the etiology of the lateral crossbite, the treatment approach should be focused on both arches and not be limited to the constricted upper arch.

Long-term stability of unilateral posterior crossbite correction

OBJECTIVE

To evaluate the stability of orthodontically corrected unilateral posterior crossbite in patients treated either by rapid maxillary expansion or with slow expansion devices in the early (mean age 7.2 years, n = 50) or late mixed dentition (mean age 9.9 years, n = 50).

MATERIALS AND METHODS

The observation periods were approximately 8 years for the early treatment groups and 6.5 years for the late treatment groups. The measurements were made on plaster casts at the following time points: before treatment (T1), after crossbite correction (T2), at the end of active orthodontic treatment (T3), and about 2 years after the end of active treatment (T4). Midline deviation and the skeletal classification of the malocclusion were also evaluated.

RESULTS

Almost 80% of the treated patients showed long-term stability of the corrected unilateral posterior crossbite. More than 70% of the patients were treated for the mandibular midline deviation. At the end of active treatment, 50% of the patients showed a skeletal Class III craniofacial morphology.

CONCLUSIONS

The results emphasize that determination of the correct treatment approach for the individual patient is the basic principle underlying the therapeutic success in unilateral crossbite cases. In patients where a broad lower arch is a cofactor in the etiology of the lateral crossbite, the treatment approach should be focused on both arches and not be limited to the constricted upper arch.

Meta-analysis of immediate changes with rapid maxillary expansion treatment

BACKGROUND

The authors conducted a literature review to evaluate immediate transverse, anteroposterior, and vertical dental and skeletal changes produced by rapid maxillary expansion (RME).

TYPES OF STUDIES REVIEWED

The authors reviewed clinical trials that assessed immediate dental and/or skeletal changes after RME using cephalometric analysis, model casts or both. No surgical or other simultaneous treatment was accepted during the evaluation period.

RESULTS

The authors searched electronic databases and found 31 articles that met the initial inclusion criteria. The authors later rejected 12 of these articles because they did not report immediate changes, three because they lacked detailed descriptions of their results and two because of their nonconventional appliance designs. Fourteen articles satisfied th final inclusion criteria; however, they had methodological deficiencies.

CLINICAL IMPLICATIONS

The greatest changes resulting from RME in the studies analyzed were dental and skeletal transverse changes. Few vertical and anteroposterior immediate changes were statistically significant, though they probably are not clinically important.

Spontaneous mandibular arch response after rapid palatal expansion: a long-term study on Class I malocclusion

The purpose of this study was to investigate the spontaneous mandibular arch response to rapid palatal expansion as the sole orthodontic intervention. Particular attention was paid to clinically significant effects and long-term (mean age, 11.3 years) posttreatment stability in 30 Class I malocclusion patients treated during the early and mid mixed dentition. Measurements were made directly on 120 dental casts obtained at 4 assessment stages: pre-expansion (A1), short-term follow-up (A2), progress (A3), and long-term follow up (A4). Comparisons between A1 and A2 showed statistically significant (P < .001) increases for intermolar widths (lingual and occlusal values). During the transition to the permanent dentition, a significant (P < .001) decrease occurred in arch length and arch perimeter. There was a 25% intermolar width (occlusal value) decrease from the initial net gain, whereas the lingual values remained unchanged. Comparisons between A2 and A4 showed an intermolar width (occlusal value) net gain of 50% and a significant (P < .001) decrease for the arch length and arch perimeter. There was remarkable stability in intermolar width (lingual value) and intercanine width (occlusal value), indicating that the increase in the mandibular arch width dimension was in response to the orthopedic effects of rapid palatal expansion in the early and mid-mixed dentition and that the stability was maintained until adulthood.

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.

Maxillary and mandibular width changes studied using metallic implants

The purpose of this implant study was to evaluate the transverse stability of the basal maxillary and mandibular structures. The sample included 25 subjects between 12 and 18 years of age who were followed for approximately 2.6 years. Metallic implants were placed bilaterally into the maxillary and mandibular corpora before treatment. Once implant stability had been confirmed, treatment (4 first premolar extractions followed by fixed appliance therapy) was initiated. Changes in the transverse maxillary and mandibular implants were evaluated cephalometrically and two groups (GROW+ and GROW++; selection based on growth changes in facial height and mandibular length) were compared. The GROW++ group showed significant width increases of the posterior maxillary implants (P <.001) and the mandibular implants (P =.009); there was no significant change for the anterior maxillary implants. The GROW+ group showed no significant width changes between the maxillary and mandibular implants. We conclude that (1) there are significant width increases during late adolescence of the basal mandibular and maxillary skeletal structures and (2) the width changes are related with growth potential.

Biomechanics of mandibular distractor orientation: an animal model analysis

PURPOSE

Previous reports suggest that device orientation may be one of the most important parameters affecting the successful application of osteodistraction. However, only computer models or cadaver mandibles have been used to investigate the biomechanical effects of device orientation during mandibular distraction osteogenesis. Therefore, the purpose of this study was to compare two different device orientations during bilateral mandibular osteodistraction in an animal model.

MATERIALS AND METHODS

Fifteen skeletally mature beagle dogs underwent 10 mm of bilateral mandibular lengthening by intraoral distraction osteogenesis. The dogs were divided into two groups based on the orientation of the distraction device relative to the mandible when viewed occlusally: either parallel to the body of the mandible (group I) or parallel to the axis of distraction (group II). The effects of device orientation during osteodistraction were then analyzed clinically, radiographically, and by dental cast measurements.

RESULTS

Distractors oriented parallel to the body of the mandible caused an increase in the anterior width of the proximal mandibular segments. This lateral displacement of the proximal segments led to several clinical complications, including screw fixation failure and bone resorption under the fixation plates. These effects were minimized when the device was oriented parallel to the axis of distraction.

CONCLUSIONS

Device orientation plays an important role when applying distraction osteogenesis in a clinical setting. Although other intrinsic and extrinsic factors affect the success of osteodistraction, the devices should be oriented parallel to the axis of distraction to minimize adverse biomechanical effects during bilateral mandibular lengthening.

A retrospective study of Angle Class I malocclusions treated orthodontically without extractions using two palatal expansion methods

The correction and relapse of mandibular anterior crowding was evaluated in a population of 58 patients with Angle Class I malocclusion who were treated orthodontically without extraction of permanent teeth. The subjects were retrospectively evaluated from records taken before treatment, posttreatment, and postretention. The postretention period averaged 8 years (minimum of 4 and maximum of 20 years). All cases in Groups A and B were given orthopedic treatment to develop the maxillary apical base in the transverse and anteroposterior planes. Group A was treated with expansion of the inner bow of the face bow appliance (Kloehn), and Group B was treated with the Haas palatal expansion appliance. Both groups were then treated orthodontically with tandem mechanics. The response variables measured were: overbite, overjet, intercanine distance, intermolar distance, and irregularity index. Study groups A and B were not significantly different for subject age, retention, or postretention time. Moreover, the groups did not show significant difference for any of the response variables before treatment. However, there was a statistically significant difference in the treatment times (P =.0133). A statistically significant treatment effect was observed for most response variables in the groups. Overbite, overjet, and irregularity index were significantly reduced, intermolar distance was significantly increased, and intercanine distance showed no significant change in Groups A and B. In the postretention period, there was a tendency for variables to change slightly toward their before treatment values but no compromise of orthodontic correction was noted. The irregularity index in Group A was corrected from 4.8 to 1.1 mm and remained at 1.1 mm in the postretention period. The irregularity index in Group B was corrected from 5.1 to 1.2 mm (P =.0001) and changed slightly from 1. 2 to 1.7 mm (P =.0540) in the postretention period. We concluded that mandibular incisors tended to become more crowded postretention. However, in contrast to previous reports, we calculate this relapse to be small. Neither before treatment nor posttreatment variables were predictive of relapse.

Rapid maxillary expansion with incisor intrusion: a study of vertical control

This is a prospective study of 20 consecutively treated patients needing maxillary expansion and incisor intrusion. The patients were treated with a bonded maxillary expansion appliance, intrusion of the incisors with either a one-piece or three-piece base arch and anchorage augmented by the use of vertical-pull chincup therapy. Because rapid palatal expansion and intrusion of maxillary incisors both produce extrusion of posterior teeth, this study was undertaken to determine if a combination of controlled forces could prevent undesirable increases in vertical dimension. The maxillae were widened approximately 8 mm, the incisors were intruded 3 mm, the maxillary molars stayed the same or were intruded slightly, and the mandibular plane angle stayed essentially the same. In addition, A-point was retracted slightly and the occlusal plane was rotated in a counter-clockwise direction.

Retention and stability: a review of the literature

Long-term posttreatment stability is an issue of great concern to all orthodontists. This article highlights the factors reported to play a role in posttreatment crowding and reviews the long-term retention studies evaluating the stability of various treatment modalities. Recommendations, based on well-documented basic principles, are made to try to insure greater posttreatment stability of our orthodontically treated cases.

Dynamic relationships of the mandibular anterior segment

The hyperbolic cosine function is shown to be an accurate representation of the form of the mandibular anterior teeth from the canine/first premolar contact on one side around the perimeter to the opposite side (r = 0.951). On the basis of this mathematical function, the changes in canine width, anterior segment depth, arch perimeter, and their related incisor angular alterations are forecastable. This knowledge will allow the clinician to predict the effects on various aspects of the anterior segment arch form as one or more of these variables are altered without resorting to trial and error or performing a wax-up. For example, the clinician can predict the change in the anterior segment arch depth and incisor angulation that would occur with alterations in canine width.

Resolution of mandibular arch crowding in growing patients with Class I malocclusions treated nonextraction

The purpose of this study was to determine the manner in which mandibular arch crowding was resolved in Class I growing patients who were treated nonextraction. A retrospective study was completed with 30 patients from a postgraduate orthodontic clinic, treated with a variety of treatment modalities. Eight study models and six cephalometric parameters were examined before treatment and at the end of active treatment (posttreatment). The results showed that statistically significant increases in arch width occurred at the canine (0.9 mm), first premolar (1.6 mm), second premolar (1.8 mm), and first molar (1.2 mm). The incisors were advanced an average of 2.1 mm and proclined 6.1 degrees. The molars showed no anteroposterior movement. Arch perimeter increased 2.3 mm and arch depth increased 1.6 mm. Multiple linear regression analysis revealed that 52% of the variance in crowding resolution was accounted for by an increase in arch perimeter. It was concluded that the resolution of crowding, in this group of patients with Class I malocclusions, was achieved by generalized expansion of the buccal segments, along with advancement of the lower incisors. In some cases, these changes may be consistent with treatment objectives; in others, they may be undesirable. It is therefore important for practitioners to carefully evaluate treatment outcome irrespective of the treatment modality, to determine whether treatment objectives are being met.

Leeway space and the resolution of crowding in the mixed dentition

The leeway space provides adequate space to resolve crowding that is present in the mixed dentition in the majority of individuals. This space can be maintained by preserving arch length with a lingual arch as the primary teeth begin to exfoliate, unless conditions such as the premature loss of a primary canine require earlier intervention. A lip bumper can also be inserted after the eruption of the first premolars to preserve arch length.

Changes concurrent with orthodontic treatment when maxillary expansion is a primary goal

A retrospective study of dental and maxillary skeletal changes occurring during a period of orthodontic treatment was made from pretreatment and posttreatment dental casts. Sixty maxillary expansion cases were examined. Thirty cases had maxillary expansion accomplished with a fixed rapid palatal expander and 30 were expanded with a quadhelix appliance. All cases were finished with full fixed edgewise appliances. Multiple linear regression analyses were completed for both groups with upper molar width change as the criterion and age, tipping of the upper molars, palatal width change and maxillary tipping as the predictors. All predictors were included in the analysis for the quadhelix group with a significant R2 value of 0.55. For the rapid expansion group, a significant R2 value of 0.33 was achieved with the inclusion of palatal width change and age only. The other variables did not meet the level of significance for entry into the model. Although both groups demonstrated similar amounts of maxillary dental expansion, the rapid expansion group demonstrated greater average skeletal expansion. In addition, there was a significant relationship between skeletal and dental expansion for the rapid expansion group, but not the quadhelix group. Palatal depth increased more on average in the rapid expansion group suggesting that there was greater dental eruption in that group. Expansion across the mandibular molars was greater on average in the quadhelix group. There was no difference in the degree of upper molar rotation or final upper and lower arch forms between the two groups.

Transverse development of the human jaws between the ages of 8.5 and 15.5 years, studied longitudinally with use of implants

We report longitudinal data on the transverse widening of the maxilla and mandible from a sample of normal subjects (11 males and 20 females) with metallic implants of the Bjork type. Data were from measurements on lateral and frontal (posterior-anterior) cephalograms generated at annual intervals between the ages of 8.5 and 15.5 years (although data were not available for all subjects at all time points). The maxillary data were, in general, similar to those reported by Bjork and Skieller (1974, 1977) for a smaller sample of slightly younger boys. During the age interval studied, transverse widening was greater in the more posterior part of the palate. [The mean annual rate of change in the posterior-most (zygomatic) region was 0.43 mm, sd = 0.18 mm; p less than 0.001.] Although the rate of palatal widening was not large in absolute terms, widening appeared to continue throughout the age interval under study, and there was no evidence to support the conventionally accepted idea that palatal growth in the transverse dimension tapers off substantially or even ceases during the age interval under observation. Evidence of statistically significant widening of the mandibular arch by means of transverse rotation of the osseous matrix was noted in nine of the 29 subjects for whom three-dimensional mandibular information was available. For these nine subjects, the estimated annual increase in mandibular arch angle ranged from 0.52 degrees to 1.40 degrees. As far as we are aware, this is the first report of mandibular matrix rotation in the transverse direction from a sample of subjects with metallic implants. The finding that spontaneous changes in this dimension are relatively common raises the possibility that classical attitudes concerning the immutability of osseous relationships in the symphyseal region during growth may be inappropriate.

Mandibular arch length increase during the mixed dentition: postretention evaluation of stability and relapse

Increasing mandibular arch length to resolve crowding has long been debated as a treatment method. Twenty-six patients with records obtained before treatment, after treatment, and a minimum of 6 years out of retention were assessed. All the patients showed a loss of treatment arch length increase with only 6 of 26 patients showing any gain over pretreatment dimensions. Width constriction was a consistent finding, as was crowding of anterior teeth after retention. In 89% the postretention record demonstrated clinically unsatisfactory alignment. Lateral cephalometric superimposition of mandibles showed variable molar and incisor change after retention. As teeth erupted after treatment, mesial molar movement and lingual tipping of incisors were the most common cephalometric findings.