Post-treatment cephalometric changes in adolescent patients with Class II malocclusion treated using two different functional appliance systems for an extended time period: a randomized clinical trial.

OBJECTIVES: To assess the post-treatment changes in Class II adolescent patients treated with two different functional appliances for an extended time period. DESIGN: Randomized clinical trial. SETTING: One university and one district general hospital in the UK. PARTICIPANTS: Caucasian adolescent patients with a Class II malocclusion. METHODS: Pairs of patients of similar age and gender were randomly allocated to one of two functional appliance systems, the Twin Block or Dynamax appliance. The appliances were used for 15 months full time. Changes were measured from lateral cephalograms taken at the start (T1) and at the end of treatment at 15 months (T2) and 30 months (T3). RESULTS: Hundred patients completed the trial, 52 Twin Block and 48 Dynamax. Mandibular forward movement was 3.5 mm (±2.5) in the Twin Block group and 1.7 mm (±2.1) in the Dynamax group (P < 0.01; T1-T2) and, subsequently, by 0.3 mm (±2.6) and 0.9 mm (±2.5), respectively (P = 0.3; T2-T3). Mandibular length increased by 6.3 mm (±2.7) in the Twin Block group and 4.0 mm (±2.5) in the Dynamax group (P < 0.01; T1-T2) with treatment and, subsequently, by 0.5 mm (±2.3) and 1.5 mm (±3.1; P = 0.05). Anterior face height increased in both groups. CONCLUSIONS: Treatment resulted in greater mandibular growth with the Twin Block than the Dynamax. In the follow-up period, there was less growth in the Twin Block group compared to the Dynamax. TRIAL REGISTRATION: This trial was not registered on any major database of clinical trial. PROTOCOL: The protocol was not published before the commencement of the trial but can be given on request.

Royal London space analysis: plaster versus digital model assessment.

Aim: With the advent of digital study models, the importance of being able to evaluate space requirements becomes valuable to treatment planning and the justification for any required extraction pattern. This study was undertaken to compare the validity and reliability of the Royal London space analysis (RLSA) undertaken on plaster as compared with digital models. Materials and methods: A pilot study (n = 5) was undertaken on plaster and digital models to evaluate the feasibility of digital space planning. This also helped to determine the sample size calculation and as a result, 30 sets of study models with specified inclusion criteria were selected. All five components of the RLSA, namely: crowding; depth of occlusal curve; arch expansion/contraction; incisor antero-posterior advancement and inclination (assessed from the pre-treatment lateral cephalogram) were accounted for in relation to both model types. The plaster models served as the gold standard. Intra-operator measurement error (reliability) was evaluated along with a direct comparison of the measured digital values (validity) with the plaster models. Results: The measurement error or coefficient of repeatability was comparable for plaster and digital space analyses and ranged from 0.66 to 0.95mm. No difference was found between the space analysis performed in either the upper or lower dental arch. Hence, the null hypothesis was accepted. The digital model measurements were consistently larger, albeit by a relatively small amount, than the plaster models (0.35mm upper arch and 0.32mm lower arch). Conclusion: No difference was detected in the RLSA when performed using either plaster or digital models. Thus, digital space analysis provides a valid and reproducible alternative method in the new era of digital records.

An extended period of functional appliance therapy: a controlled clinical trial comparing the Twin Block and Dynamax appliances.

The aim of this clinical trial was to compare the hard- and soft-tissue effects of 15 month full-time functional appliance therapy with Twin Block (TB) and Dynamax (Dx) appliances. The effects on both hard and soft tissue were analysed using cephalograms and three-dimensional optical surface laser scans. One hundred and three subjects with a class II division 1 malocclusion, and a minimum overjet of 7mm were available for analysis following stratified randomization according to gender and age. Data was collected at the start of treatment, 15 month therapy, and after 3 month post-treatment observation. Statistical analysis was conducted using analysis of covariance. The results demonstrated both appliances corrected the overjet with significantly increased skeletal dimensional changes with the TB compared with the Dx with forward movement of pogonion of 5.2mm (TB) and 0.7mm (Dx) P = 0.003. In addition, significant changes occurred particularly in the vertical dimension where there was also an increase in total anterior face height in both groups (TB = 6.4mm, Dx = 5.5mm) and significant (P = 0.003) mandibular length changes were also observed (TB = 7.2mm, Dx = 3.8mm). The cephalometric soft-tissue changes were significantly different between the two appliances at soft-tissue pogonion (TB = 9.8mm, Dx = 4.6mm, P = 0.001). Laser scan three-dimansional changes showed significant difference in the lower labial sulcus region where forward movements were observed (TB = 8.2mm, Dx = 6.2mm; P = 0.04). Overall these changes appear to be greater and more stable than those achieved in a previous 9 month study.

Comparison of maxillary arch dimensional changes with passive and active self-ligation and conventional brackets in the permanent dentition: a multicenter, randomized controlled trial.

INTRODUCTION: The purpose of this study was to compare maxillary arch dimensional and inclination changes during alignment with conventional brackets and self-ligation. METHODS: Ninety-six patients, ages 16 years and above, were included in this multicenter, 3-group parallel randomized trial. The main outcome measures were changes in maxillary intercanine, interpremolar, and intermolar dimensions, and molar and incisor inclination changes. The patients were randomly allocated in permuted blocks of 12 subjects into 3 equal groups with the allocations concealed in opaque sealed envelopes. Each participant underwent alignment with a standard Damon Q (Ormco, Orange, Calif) wire sequence for a minimum of 34 weeks. Blinding of clinicians and patients was not possible. Data were analyzed on a per-protocol basis, since losses to follow-up were minimal. RESULTS: Complete data were obtained from 87 subjects. Bracket type had no significant effect on any of the transverse dimensional changes. No difference in molar inclination was found between passive self-ligation and conventional brackets (0.67°; 95% CI, -2.24, 3.58; P = 0.65) or active self-ligation (0.91°; 95% CI, -1.95, 3.78; P = 0.53). Similarly, incisor inclination changes with the Damon Q could not be differentiated from those developing with either conventional system (0.44°; 95% CI, -1.93, 2.8; P = 0.71) or In-Ovation C (-0.22°; 95% CI, -2.58, 2.14; P = 0.85). No harms were encountered. CONCLUSIONS: No difference in the arch dimensional or inclination changes during alignment can be expected between conventional brackets and either active or passive self-ligation.

One-carbon metabolite supplementation to heifers for the first 14 d of the estrous cycle alters the plasma and hepatic one-carbon metabolite pool and methionine-folate cycle enzyme transcript abundance in a dose-dependent manner.

The objective of this study was to determine the dose of folate and vitamin B12 in beef heifers fed rumen protected methionine and choline required to maintain increased B12 levels and intermediates of the methionine-folate cycle in circulation. Angus heifers (n = 30; BW = 392.6 ±â€…12.6 kg) were individually fed and assigned to one of five treatments: 0XNEG: Total mixed ration (TMR) and saline injections at day 0 and 7 of the estrous cycle, 0XPOS: TMR, rumen protected methionine (MET) fed at 0.08% of the diet DM, rumen protected choline (CHOL) fed at 60 g/d, and saline injections at day 0 and 7, 0.5X: TMR, MET, CHOL, 5 mg B12, and 80 mg folate at day 0 and 7, 1X: TMR, MET CHOL, 10 mg vitamin B12, and 160 mg folate at day 0 and 7, and 2X: TMR, MET, CHOL, 20 mg B12, and 320 mg folate at day 0 and 7. All heifers were estrus synchronized but not bred, and blood was collected on day 0, 2, 5, 7, 9, 12, and 14 of a synchronized estrous cycle. Heifers were slaughtered on day 14 of the estrous cycle for liver collection. Serum B12 concentrations were greater in the 0.5X, 1X, and 2X, compared with 0XNEG and 0XPOS on all days after treatment initiation (P < 0.0001). Serum folate concentrations were greater for the 2X treatment at day 5, 7, and 9 of the cycle compared with all other treatments (P ≤ 0.05). There were no differences (P ≥ 0.19) in hepatic methionine-cycle or choline analyte concentrations by treatment. Concentrations of hepatic folate cycle intermediates were always greater (P ≤ 0.04) in the 2X treatment compared with the 0XNEG and 0XPOS heifers. Serum methionine was greater (P = 0.04) in the 0.5X and 2X heifers compared with 0XNEG, and S-adenosylhomocysteine (SAH) tended (P = 0.06) to be greater in the 0.5X heifers and the S-adenosylmethionine (SAM):SAH ratio was decreased (P = 0.05) in the 0.5X treatment compared with the 0XNEG, 0XPOS, and 2X heifers. The hepatic transcript abundance of MAT2A and MAT2B were decreased (P ≤ 0.02) in the 0.5X heifers compared with the 0XNEG, 0XPOS, and 2X heifers. These data support that beef heifers fed rumen protected methionine and choline require 20 mg B12 and 320 mg folate once weekly to maintain increased concentrations of B12 and folate in serum. Furthermore, these data demonstrate that not all supplementation levels are equal in providing positive responses, and that some levels, such as the 0.5X, may result in a stoichiometric imbalance in the one-carbon metabolism pathway that results in a decreased SAM:SAH ratio.

The strategic inclusion of one-carbon metabolites, which include vitamins and minerals that are found in human prenatal vitamins, to beef cattle feeding and management protocols during the periconceptual period (the time around breeding) is a novel concept. Therefore, this study aimed to identify the feeding and injection doses of one-carbon metabolites in beef heifers to maintain increased circulating concentrations of one-carbon metabolites for use as a model from which other studies could base their treatments on. We determined that daily feeding of methionine and choline at 0.08% of dry matter and 60 g/d, respectively, and administration of vitamin B12 and folate at 20 mg and 320 mg once per week, respectively resulted in sustained elevated concentrations of one-carbon metabolites.

An investigation of cephalometric and morphological predictors of successful twin block therapy.

OBJECTIVE: To identify predictors of overjet reduction, changes in mandibular length (Co-Me) and antero-posterior changes in mandibular position (Pog-Vert) during Twin Block therapy. METHODS: Pre- and post-treatment cephalograms of 131 participants were analysed (Mean age 12.73 years +/- 1) following Twin Block therapy. RESULTS: Mean annualised overjet reduction was 7.29 mm (+/- 2.99) with chin projection improving by 2.66 mm (+/- 5.37). The magnitude of the initial overjet was a strong predictor (95% CI: 0.30, 0.77, p < 0.01) of overjet reduction and change in chin position (95% CI: 0.08, 0.77, p = 0.02). Greater forward movement of Pogonion occurred if there was greater retrusion of Pogonion at the outset (95% CI: 0.15, 0.45, p < 0.01). No prognostic relationship was noted for other potential cephalometric predictors including pretreatment mandibular lower border morphology and Co-Go-Me angle. CONCLUSION: No relationship between mandibular morphology, vertical skeletal pattern and favourable dentoalveolar and skeletal responses to Twin Block therapy could be found. These results require confirmation on an external sample.

Randomized clinical trial of orthodontic treatment efficiency with self-ligating and conventional fixed orthodontic appliances.

INTRODUCTION: Our objective was to test the hypotheses that treatment with 2 fixed orthodontic appliances (SmartClip and Victory; 3M Unitek, Monrovia, Calif) would result in no difference in (1) the duration of orthodontic treatment or (2) the number of visits required. METHODS: Sixty-six consecutive patients were randomly allocated to treatment with a self-ligating bracket system (SmartClip) or a conventional appliance (Victory). The duration of treatment and the number of visits required in addition to the initial and final peer assessment rating (PAR) scores were recorded. The number of teeth extracted during treatment and the frequency of mechanical eruption of canines were also noted. Analyses of covariance were used to assess the influence of bracket type on treatment durations, visits required, and percentage PAR score reductions. RESULTS: Fifty-four (81.8%) participants completed the study. The duration of treatment was 3 months greater in the group treated with SmartClip. However, bracket type had no statistical influence on treatment duration (P = 0.076), total visits required (P = 0.184), or percentage PAR score reduction (P = 0.255). CONCLUSIONS: Neither hypothesis could be rejected. Bracket type did not influence the duration of treatment or the number of visits required. The percentages of PAR score reductions were also unaffected by the choice of appliance.

Assessed facial normality after Twin Block therapy.

SUMMARY: The first aim of this study was to identify any difference in the perception of facial normality between orthodontists and lay people of patients with the initial presentation of a Class II division 1 malocclusion, the second is to investigate whether there was an identifiable facial change following Twin Block (TB) therapy, and lastly, the relationship between identifiable facial change and clinical measurements was explored. Animated laser scans of 16 randomly selected adolescent patients, nine males aged 12-14 years and seven females aged 11-13 years with Class II division 1 malocclusions before and after TB therapy, were assessed on a visual analogue scale (VAS) by 34 orthodontists and 35 lay people. The 'Mark and Measure' and 'Orientated' techniques were used to determine soft tissue dimensions. Overjet was also recorded. Non-parametric statistical analyses were employed, including Mann-Whitney, Wilcoxon signed value, and Spearman's rank-order correlation tests. There was no statistically significant difference in facial normality scores of adolescents before TB therapy when assessed by orthodontists (46.2 mm) and lay people (50.9 mm; P = 0.120). However, TB therapy significantly improved the assessment score of the orthodontists (54.8 mm) and lay people (57.8 mm; P = 0.000). Using a 5 per cent threshold in categorization of change in VAS scores, the majority of assessors perceived an overall 'improvement' (87.0 per cent). An increase in soft tissue lower face height (ST LFH) and overjet reduction was strongly correlated with the higher assessments of lay people (r = 0.515) and orthodontists (r = -0.505), respectively. Although orthodontists and lay people assess facial normality of patients with Class II division 1 malocclusions similarly, following TB therapy an increase in ST LFH with lay people and overjet reduction with orthodontists were most closely related to improved facial normality.

Comparison of mandibular arch changes during alignment and leveling with 2 preadjusted edgewise appliances.

INTRODUCTION: Our objective was to compare the effects of 2 preadjusted appliances on angular and linear changes of the mandibular incisors, and transverse mandibular arch dimensional changes over a minimum of 30 weeks. This was a prospective, randomized, controlled, clinical trial a the Royal London Hospital, School of Dentistry, in London and the Kent and Canterbury Hospital in Canterbury, United Kingdom. METHODS: Sixty- six consecutive patients satisfying the inclusion criteria were enrolled and randomly allocated to treatment with a self-ligating bracket system (SmartClip, 3M Unitek, Monrovia, Calif) and conventional preadjusted edgewise brackets (Victory, 3M Unitek). Initial study models and cephalograms were obtained within a month of starting the trial. All subjects received treatment with the following archwire sequence: 0.016-in round, 0.017 x 0.025-in rectangular, 0.019 x 0.025-in rectangular martensitic active nickel-titanium archwires, and 0.019 x 0.025-in stainless steel archwires. Final records, including study models and a lateral cephalogram, were collected a minimum of 30 weeks after initial appliance placement. Lateral cephalograms were assessed for treatment-related changes in mandibular incisor inclination and position. Transverse dimensional changes in intercanine, interpremolar, and intermolar dimensions, and the amount of crowding alleviated during the study period were assessed by comparison of pretreatment and posttreatment models. All measurements were made with a digital caliper (150 mm ISO 9001 electronic caliper, Tesa Technology, Renens, Switzerland). RESULTS: Sixty patients completed the study. After adjustment for pretreatment values, duration of treatment, and amount of crowding alleviated during the study period, bracket type had little effect on incisor inclination (P = 0.437) and positional changes (P = 0.35), and intercanine (P = 0.967), inter-first premolar (P = 0.495), and inter-second premolar (P = 0.905) dimensions. However, the self-ligating appliance produced slightly more expansion in the molar region, a difference that was statistically significant (P = 0.009). Pretreatment values for incisor inclination (P = 0.044) and transverse dimensions (P = 0.000) affected inclination and transverse changes, respectively, with proclination less likely when the labial segment was proclined at the outset and expansion unlikely during leveling and alignment in wider arches. Greater alleviation of crowding during the study period resulted in more incisor proclination (P = 0.000) and advancement (P = 0.000). CONCLUSIONS: There was little difference overall in the pattern of arch alignment and leveling related to the 2 preadjusted appliances. However, there was a statistically greater increase in intermolar width in the group treated with the self-ligating appliance, although the difference was only 0.91 mm.

Efficiency of mandibular arch alignment with 2 preadjusted edgewise appliances.

INTRODUCTION: The aim of this study was to compare the efficiency of mandibular arch alignment in 3 dimensions with a self-ligating bracket system (SmartClip, 3M Unitek, Monrovia, Calif) and a conventional preadjusted edgewise twin bracket (Victory, 3M Unitek) in nonextraction patients. This was a prospective, randomized, controlled clinical trial at the Royal London Hospital, School of Dentistry, and Kent and Canterbury Hospital, United Kingdom. Sixty-six consecutive patients satisfying the inclusion criteria were enrolled in the study. They were randomly allocated with a computer-generated system to 1 of the 2 bracket systems. METHODS: Pretreatment mandibular arch irregularity was measured by using a coordinate measuring machine (Merlin II, International Metrology Systems, Gloucester, United Kingdom). A 0.016-in round martensitic active nickel-titanium aligning archwire (3M Unitek) was placed in all subjects. Mandibular arch irregularity was remeasured 8 weeks later. RESULTS: Sixty-five subjects completed the study. Bracket type had little influence on alignment efficiency overall (P = 0.08), or in the buccal (P = 0.173) or labial segments (P = 0.528) after adjustment for pretreatment differences by analysis of covariance (ANCOVA). Alignment efficiency was highly correlated to pretreatment irregularity overall (P <0.001), both in the buccal (P = 0.001) and labial (P <0.001) segments. Increasing age appeared to have a negative effect on alleviation of irregularity, although this effect did not reach statistical significance (P = 0.053). CONCLUSIONS: The null hypothesis that efficiency of alignment in the mandibular arch in nonextraction patients is independent of bracket type was accepted. Alignment efficiency is largely influenced by initial irregularity.

Self-ligating appliances: evolution or revolution?

AIMS: To review the literature relating to self-ligating orthodontic appliances. METHODS: Narrative review of the relevant historic and contemporary research. RESULTS: Proposed advantages of these appliance systems include reduced friction, more efficient mechanotherapy, improved operator efficiency, and more secure ligation. Randomised clinical trials investigating these potential advantages have largely been equivocal. CONCLUSIONS: Self-ligating brackets are here to stay and continue to be refined and enhanced. Further prospective studies investigating their clinical application and performance would be welcome.

Arch form and dimensional changes in orthodontics.

In the first part of this article arch dimensional changes related to growth and fixed appliance therapy were discussed. A trend towards greater acceptance of arch development and expansion has followed advances in orthodontic appliances and arch wires. Longitudinal studies have highlighted the relapse potential related to expansion of the transverse dimension, particularly the mandibular inter-canine width. In this paper the literature related to arch expansion is considered and its implications for treatment and retention protocols discussed.

Arch form and dimensional changes in orthodontics.

The dental arch form is a composite of individual tooth position; alteration in arch dimensions may be planned to alleviate crowding, to address transverse discrepancies and may be considered to enhance smile aesthetics. Characteristic changes in arch dimensions occur throughout life including a reduction in transverse dimensions and arch length; increases in transverse dimensions are typical during orthodontic treatment. In this paper the literature relating to arch dimensional changes arising naturally with growth and produced by orthodontic treatment is reviewed and discussed.

Prospective randomized clinical trial comparing the effects of a masticatory bite wafer and avoidance of hard food on pain associated with initial orthodontic tooth movement.

INTRODUCTION: The purpose of this prospective, randomized clinical trial was to compare the use of masticatory bite wafers with the avoidance of mastication in reducing pain and discomfort associated with initial orthodontic tooth movement. METHODS: Eighty-four subjects (mean age, 14.1 years), randomly allocated to a bite-wafer group (BWG) or a reduced-mastication group (RMG), completed the study. In each subject, 1 arch was bonded and ligated with a round austenitic active 0.016-in nickel-titanium wire, and placebo instructions were given. The subjects in the BWG then performed immediate supervised mastication of the wafers for 10 minutes, and they were instructed thereafter to bite on the wafers to prevent pain for the next 7 days. The subjects in the RMG were instructed not to masticate for 3 hours after placement of the fixed appliance and to avoid masticating hard food for 7 days. Each patient's level of anxiety was assessed before treatment with standard psychometric questionnaires. Each patient recorded the level of pain immediately after archwire ligation on a 100-mm visual analogue scale (VAS) and used a pain diary with a verbal rating scale for the next 7 days. RESULTS: No statistically significant differences in the VAS immediately after ligation of the archwires were observed between the 2 groups. The median pain score for the BWG was higher for the first 4 days. The median peak difference was reached on the evening of the first day. At this maximum value, the median pain score of the BWG was higher and statistically significant (P = .006). CONCLUSIONS: Although the amount of pain and discomfort reported by the patients undergoing fixed orthodontic therapy varied, more pain was reported by those using bite wafers than by those who avoided masticatory activity after placement of fixed appliances.).

Quetiapine for treatment of refractory symptoms of combat-related post-traumatic stress disorder.

To assess the effects of adjunctive quetiapine for treatment of refractory symptoms of combat-related post-traumatic stress disorder (PTSD), charts of Vietnam veterans with war-connected PTSD who had been prescribed quetiapine were reviewed. Only patients with symptoms that had not responded to adequate therapy with two or more psychotropic medications prior to quetiapine treatment were analyzed. Addition of quetiapine to ongoing therapy resulted in further symptomatic improvements in DSM-IV PTSD criterion B (re-experiencing) for 35%, criterion C (avoidance/numbing) for 28%, and criterion D (arousal) for 65% of study subjects. Low doses of quetiapine (mean = 155 +/- 130 mg) were associated with minimal side effects. These results, although retrospective, suggest that augmentative quetiapine may benefit some refractory symptoms of PTSD in combat veterans.

The timing of significant arch dimensional changes with fixed orthodontic appliances: data from a multicenter randomised controlled trial.

OBJECTIVES: To identify the timing of significant arch dimensional increases during orthodontic alignment involving round and rectangular nickel-titanium (NiTi) wires and rectangular stainless steel (SS). A secondary aim was to compare the timing of changes occurring with conventional and self-ligating fixed appliance systems. METHODS: In this non-primary publication, additional data from a multicenter randomised trial initially involving 96 patients, aged 16 years and above, were analysed. The main pre-specified outcome measures were the magnitude and timing of maxillary intercanine, interpremolar, and intermolar dimensions. Each participant underwent alignment with a standard Damon (Ormco, Orange, CA) wire sequence for a minimum of 34 weeks. Blinding of clinicians and patients was not possible; however, outcome assessors and data analysts were kept blind to the appliance type during data analysis. RESULTS: Complete data were obtained from 71 subjects. Significant arch dimensional changes were observed relatively early in treatment. In particular, changes in maxillary inter-first and second premolar dimensions occurred after alignment with an 0.014in. NiTi wire (P<0.05). No statistical differences in transverse dimensions were found between rectangular NiTi and working SS wires for each transverse dimension (P>0.05). Bracket type had no significant effect on the timing of the transverse dimensional changes. CONCLUSIONS: Arch dimensional changes were found to occur relatively early in treatment, irrespective of the appliance type. Nickel-titanium wires may have a more profound effect on transverse dimensions than previously believed. CLINICAL SIGNIFICANCE: On the basis of this research orthodontic expansion may occur relatively early in treatment. Nickel-titanium wires may have a more profound effect on transverse dimensions than previously believed.

Prospective clinical trial comparing the effects of conventional Twin-block and mini-block appliances: Part 2. Soft tissue changes.

PURPOSE: The aims of this prospective clinical trial were to compare the soft tissue effects of Twin-block (TB) and mini-block (MB) functional appliances by using lateral cephalograms and optical surface laser scans and to evaluate the extent of posttreatment relapse with both appliances. MATERIAL: Seventy Class II Division 1 patients meeting set inclusion criteria were matched by age and sex. The matched pairs were randomly allocated to treatment with either the TB or the MB appliance. The appliances were worn full time for 9 months (phase I), followed by a 3-month observation phase of no appliance wear (phase II). Lateral cephalograms were taken at the start of treatment and at 12 months, and laser scans were taken at 0, 3, 9, and 12 months. RESULTS: Radiographically, there was a greater advancement of the soft tissue pogonion in the TB group (median, TB: 4.0 mm; MB: 1.8 mm; P = .004), whereas the soft tissue anterior face height increased similarly in both groups (median, TB: 4.4 mm; MB: 4.3 mm). Optical surface scans confirmed the cephalometric changes. There were a greater forward movement of soft tissue pogonion in the TB group during active treatment (median change, TB: 3.2 mm; MB: 3.9 mm) and similar increases in the soft tissue total anterior face height (median change, TB: 3.2 mm; MB: 3.9 mm). There were negative changes of soft tissue pogonion (median, TB: -1.0 mm; MB: -0.9 mm) and vertical face height (median change, TB: -0.7; MB: -0.6) during phase II. CONCLUSIONS: The TB appliance produced the greater overall change in the soft tissue profile. However, there were clinically significant relapse changes in the immediate postfunctional phase.

Prospective clinical trial comparing the effects of conventional Twin-block and mini-block appliances: Part 1. Hard tissue changes.

PURPOSE: The aim of this prospective clinical trial was to compare the dentoskeletal effects of a conventional and a modified Twin-block (TB) appliance. The conventional TB appliance was constructed with a large, single-step advancement. The modified appliance, termed the mini-block (MB), was incrementally advanced, incorporated a maxillary incisor torquing spring, and had a reduced bite-block height. MATERIAL: Seventy patients were placed into age- and sex-matched pairs. Patients in each pair were allocated to opposing appliance groups. Active treatment lasted 9 months, irrespective of the final overjet attained, and final cephalometric records were taken at 12 months (+/-1 month). Both groups showed pretreatment equivalence for age, sex, overjet, and cephalometric variables. RESULTS: The TB group experienced a significantly greater reduction in overjet (median, -8 mm; P = .02) compared with the MB group (median, -4 mm). This improved overjet reduction was associated with significantly greater forward movement of pogonion (median change, TB: 3.3 mm; MB: 2.1 mm; P = .02) and greater retroclination of the maxillary incisors (median change, TB: -5 degrees ; MB: -1.9 degrees ; P = .04). No significant intergroup difference was found for changes in total anterior facial height (median change, TB: 4.4 mm; MB: 4.3 mm) and mandibular incisor proclination (median change, TB: 1.3 degrees ; MB, 2.4 degrees ). CONCLUSIONS: Progressive mandibular advancement was not associated with greater mandibular growth compared with single-step advancement. The maxillary incisor torquing spring seems to be effective at reducing maxillary incisor retroclination. Reduced bite activation in the MB group did not result in less mandibular incisor proclination. There was considerable individual variation in appliance effects within both groups.