Interproximal Open Contacts Between Implant Restorations and Adjacent Teeth. Prevalence - Causes - Possible Solutions.

PURPOSE: To present the prevalence and contributing factors of interproximal contact loss (ICL) between implant restorations and adjacent teeth, and to provide recommendations for possible prevention and treatment of this complication. MATERIALS AND METHODS: The authors explored the dental literature on PubMed on ICL between implants and adjacent teeth, interproximal contacts, open contacts, teeth migration causes, facial bone formation, and facial bone changes. RESULTS: ICL between fixed implant prostheses and adjacent teeth has been reported. A literature search revealed 7 studies showing a high prevalence of ICL between implant prostheses and adjacent teeth. The literature indicates that this ICL is greater in the mesial aspect in comparison with the distal. As identified by the literature review, ICL in the maxilla ranged between 18% and 66% versus 37% to 54% in the mandible. ICL might occur as early as 3 months after prosthetic treatment. The literature review documented possible tooth migration causes, crown-related causes, and bone formation/growth-related causes of ICL. CONCLUSIONS: ICL is a common multifactorial implant complication. The clinical condition will dictate if the implant crown needs to be modified/replaced or the natural tooth needs to be restored to reestablish interproximal contact between an implant prosthesis and adjacent tooth. Periodic evaluations of interproximal contacts between implant restorations and the adjacent teeth and the use of screw-retained restorations due to ease of removal is recommended to diagnose and mitigate the problem. An orthodontic retainer or occlusal guard may help prevent ICL between the implant restoration and the adjacent tooth.

Efficiency, effectiveness and treatment stability of clear aligners: A systematic review and meta-analysis.

OBJECTIVES: The objective of this study was to perform a systematic review of the orthodontic literature with regard to efficiency, effectiveness and stability of treatment outcome with clear aligners compared with treatment with conventional brackets. METHODS: An electronic search without time or language restrictions was undertaken in October 2014 in the following electronic databases: Google Scholar, the Cochrane Oral Health Group's Trials Register, Scopus, CENTRAL, MEDLINE via OVID, EMBASE via OVID and Web of Science. We also searched the reference lists of relevant articles. Quality assessment of the included articles was performed. Two authors were responsible for study selection, validity assessment and data extraction. RESULTS: Four controlled clinical trials including a total of 252 participants satisfied the inclusion criteria. We grouped the trials into four main comparisons. One randomized controlled trial was classified as level 1B evidence, and three cohort studies were classified as level 2B evidence. Clear aligners appear to have a significant advantage with regard to chair time and treatment duration in mild-to-moderate cases based on several cross-sectional studies. No other differences in stability and occlusal characteristics after treatment were found between the two systems. CONCLUSIONS: Despite claims about the effectiveness of clear aligners, evidence is generally lacking. Shortened treatment duration and chair time in mild-to-moderate cases appear to be the only significant effectiveness of clear aligners over conventional systems that are supported by the current evidence.

Prevalence of Interproximal Open Contacts Between Single-Implant Restorations and Adjacent Teeth.

PURPOSE: The aim of this study was to determine the prevalence of interproximal open contacts between singleimplant prostheses and adjacent teeth, as well as to provide guidelines to prevent interproximal contact loss (ICL). MATERIALS AND METHODS: This was a retrospective, cross-sectional study. One hundred twenty-eight patients (174 single-implant restorations) from Columbia University College of Dental Medicine and a private faculty clinic with a single-implant restoration in the posterior or anterior region were selected to participate in this study. Patients between the ages of 19 and 91, both male and female, were included in this pilot study. The period of evaluation after implant restoration insertion was between 3 months and 11 years. Participants were seen at random intervals to identify ICL. Interproximal contacts were evaluated with 0.07-mm-thickness dental floss and visual confirmation. Contact was considered open if floss passed without resistance from adjacent teeth. RESULTS: The results of this study revealed a significant percentage of ICL, 52.8%, between single-implant restorations and adjacent teeth; 78.2% were identified on the mesial surfaces and 21.8% on the distal surfaces. ICL was noted in 57.9% of the maxillary implant restorations and 49% of the mandibular implant restorations. Eight implant restorations in women demonstrated mesial and distal openings. Among the patients with ICL, a significant percentage, 40%, were aware of the presence of ICL and food impaction. CONCLUSION: In this study, 52.8% of implant restorations demonstrated ICL. This result dictates that ICL should be included as a prosthetic implant complication. The high prevalence of ICL is justification for proper informed consent, and associated clinical problems need to be addressed. Possible causative factors were presented, but further research is necessary to identify the causative factors for ICL. The authors suggest the use of an Essix retainer to prevent ICL between single-implant restorations and adjacent teeth. Evaluation of interproximal contact between implant restorations and the adjacent teeth should be periodically monitored.

Retention procedures for stabilising tooth position after treatment with orthodontic braces.

BACKGROUND: Retention is the phase of orthodontic treatment that attempts to keep teeth in the corrected positions after treatment with orthodontic braces. Without a phase of retention, there is a tendency for teeth to return to their initial position (relapse). To prevent relapse, almost every person who has orthodontic treatment will require some type of retention. OBJECTIVES: To evaluate the effects of different retention strategies used to stabilise tooth position after orthodontic braces. SEARCH METHODS: We searched the following databases: the Cochrane Oral Health Group's Trials Register (to 26 January 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) (2015, Issue 12), MEDLINE via Ovid (1946 to 26 January 2016) and EMBASE via Ovid (1980 to 26 January 2016). We searched for ongoing trials in the US National Institutes of Health Trials Register (ClinicalTrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform. We applied no language or date restrictions in the searches of the electronic databases. We contacted authors of randomised controlled trials (RCTs) to help identify any unpublished trials. SELECTION CRITERIA: RCTs involving children and adults who had had retainers fitted or adjunctive procedures undertaken to prevent relapse following orthodontic treatment with braces. DATA COLLECTION AND ANALYSIS: Two review authors independently screened eligible studies, assessed the risk of bias in the trials and extracted data. The outcomes of interest were: how well the teeth were stabilised, failure of retainers, adverse effects on oral health and participant satisfaction. We calculated mean differences (MD) with 95% confidence intervals (CI) for continuous data and risk ratios (RR) with 95% CI for dichotomous outcomes. We conducted meta-analyses when studies with similar methodology reported the same outcome. We prioritised reporting of Little's Irregularity Index to measure relapse. MAIN RESULTS: We included 15 studies (1722 participants) in the review. There are also four ongoing studies and four studies await classification. The 15 included studies evaluated four comparisons: removable retainers versus fixed retainers (three studies); different types of fixed retainers (four studies); different types of removable retainers (eight studies); and one study compared a combination of upper thermoplastic and lower bonded versus upper thermoplastic with lower adjunctive procedures versus positioner. Four studies had a low risk of bias, four studies had an unclear risk of bias and seven studies had a high risk of bias. Removable versus fixed retainers Thermoplastic removable retainers provided slightly poorer stability in the lower arch than multistrand fixed retainers: MD (Little's Irregularity Index, 0 mm is stable) 0.6 mm (95% CI 0.17 to 1.03). This was based on one trial with 84 participants that was at high risk of bias; it was low quality evidence. Results on retainer failure were inconsistent. There was evidence of less gingival bleeding with removable retainers: RR 0.53 (95% CI 0.31 to 0.88; one trial, 84 participants, high risk of bias, low quality evidence), but participants found fixed retainers more acceptable to wear, with a mean difference on a visual analogue scale (VAS; 0 to 100; 100 being very satisfied) of -12.84 (95% CI -7.09 to -18.60). Fixed versus fixed retainersThe studies did not report stability, adverse effects or participant satisfaction. It was possible to pool the data on retention failure from three trials that compared polyethylene ribbon bonded retainer versus multistrand retainer in the lower arch with an RR of 1.10 (95% CI 0.77 to 1.57; moderate heterogeneity; three trials, 228 participants, low quality evidence). There was no evidence of a difference in failure rates. It was also possible to pool the data from two trials that compared the same types of upper fixed retainers, with a similar finding: RR 1.25 (95% CI 0.87 to 1.78; low heterogeneity; two trials, 174 participants, low quality evidence). Removable versus removable retainersOne study at low risk of bias comparing upper and lower part-time thermoplastic versus full-time thermoplastic retainer showed no evidence of a difference in relapse (graded moderate quality evidence). Another study, comparing part-time and full-time wear of lower Hawley retainers, found no evidence of any difference in relapse (low quality evidence). Two studies at high risk of bias suggested that stability was better in the lower arch for thermoplastic retainers versus Hawley, and for thermoplastic full-time versus Begg (full-time) (both low quality evidence).In one study, participants wearing Hawley retainers reported more embarrassment more often than participants wearing thermoplastic retainers: RR 2.42 (95% CI 1.30 to 4.49; one trial, 348 participants, high risk of bias, low quality evidence). They also found Hawley retainers harder to wear. There was conflicting evidence about survival rates of Hawley and thermoplastic retainers. Other retainer comparisonsAnother study with a low risk of bias looked at three different approaches to retention for people with crowding, but normal jaw relationships. The study found that there was no evidence of a difference in relapse between the combination of an upper thermoplastic and lower canine to canine bonded retainer and the combination of an upper thermoplastic retainer and lower interproximal stripping, without a lower retainer. Both these approaches are better than using a positioner as a retainer. AUTHORS' CONCLUSIONS: We did not find any evidence that wearing thermoplastic retainers full-time provides greater stability than wearing them part-time, but this was assessed in only a small number of participants.Overall, there is insufficient high quality evidence to make recommendations on retention procedures for stabilising tooth position after treatment with orthodontic braces. Further high quality RCTs are needed.

The effect of simvastatin on relapse of tooth movement and bone mineral density in rats measured by a new method using microtomography.

PURPOSE: To evaluate the effect of simvastatin on relapse of tooth movement in rats using microtomography (micro CT), as well as the correlation of bone density with the orthodontic relapse. METHODS: Twenty-five adult male Wistar rats, divided into two groups, had stainless steel springs installed on left maxillary first molar. The molars were moved for 18 days, and after removing the springs, were applied by oral gavage, 5mg/kg of simvastatin in the experimental group for 20 days. Tooth relapse was assessed with a micro CT scanner, and the images chosen through the Data Viewer software 1.5.0.0 had their measurement guides made and checked by the software Image ProR plus 5.1, and compared by Mann-Whitney test. After rats were sacrificed, bone mineral density was evaluated by micro CT through the software CT Analyzer 1.13 and compared by independent T-test, as well as by Spearman correlation test. RESULTS: Relapse and bone mineral density (BMD) was lower in the experimental group than in the control group, however without a statistically significant difference. CONCLUSION: Simvastatin did not inhibit the relapse of tooth movement in rats, and there was no correlation between bone density and orthodontic relapse.

The effect of simvastatin on relapse of tooth movement and bone mineral density in rats measured by a new method using microtomography

PURPOSE: To evaluate the effect of simvastatin on relapse of tooth movement in rats using microtomography (micro CT), as well as the correlation of bone density with the orthodontic relapse. METHODS: Twenty-five adult male Wistar rats, divided into two groups, had stainless steel springs installed on left maxillary first molar. The molars were moved for 18 days, and after removing the springs, were applied by oral gavage, 5mg/kg of simvastatin in the experimental group for 20 days. Tooth relapse was assessed with a micro CT scanner, and the images chosen through the Data Viewer software 1.5.0.0 had their measurement guides made and checked by the software Image ProR plus 5.1, and compared by Mann-Whitney test. After rats were sacrificed, bone mineral density was evaluated by micro CT through the software CT Analyzer 1.13 and compared by independent T-test, as well as by Spearman correlation test. RESULTS: Relapse and bone mineral density (BMD) was lower in the experimental group than in the control group, however without a statistically significant difference. CONCLUSION: Simvastatin did not inhibit the relapse of tooth movement in rats, and there was no correlation between bone density and orthodontic relapse. .

The aetiology and management of labial and vertical migration of maxillary incisors: 'do you catch my drift?'.

Labial and vertical migration of maxillary incisors is a common complaint seen in general and specialist practices alike. Tooth movement in the aesthetic zone may cause significant concern to the patient, and a challenging management case for the dental team. This paper describes the aetiology, stabilisation and management of such cases.

Intrusion and uprighting teeth for fixed prosthesis with temporary anchorage device.

The mandibular first permanent molar is usually first to erupt around the age of six. Therefore, if the oral hygiene is not impeccable, it is usually also the first permanent tooth decayed in a child's mouth. A plethora of circumstances may lead to pulpal involvement, periapical pathosis, and endodontic treatment and in unfortunate situations, removal of this tooth. If this tooth is not replaced, or the extraction space is not retained for a considerable amount of time, the posterior occlusion will collapse. The most common occurrence is tipping of teeth in juxtaposition to the extraction site and extrusion of at least one opposing tooth. This article will describe efficient uprighting and intrusion of offending teeth prior to placement of fixed prosthesis. The author will explain the procedure step by step, first on acrylic models and then on the actual patient.

Anterior alveolar segmental osteodistraction with a bone-borne device: clinical and radiographic evaluation.

PURPOSE: Anterior alveolar osteodistraction is a common method for enlargement of the dentoalveolar process, and bone-borne distraction devices are hypothesized to avoid the risk of dental tipping and periodontal impairment during distraction. The aim of this study was to objectify this thesis and to determine the reliability of bone-borne osteodistraction of the anterior alveolar process. PATIENTS AND METHODS: The study group consisted of 18 consecutive patients who underwent anterior alveolar segmental distraction with a bone-borne distraction device for the treatment of dental crowding or alveolar retrusion from 2008 through 2011. Clinical and radiologic changes within the apical base and dentoalveolar process were analyzed after bone-borne distraction osteogenesis. All measurements were carried out using cone-beam computed tomography. RESULTS: Surgery and the postoperative period were uneventful in all patients. Mean alveolar movement was 8.2° ± 2.4°. Skeletal movement was 97.6% and absolute dental tipping was 2.4%. A mean change in the occlusal plane of 1.9° ± 1.1° was verified. The apical base enlargement showed a mean of 7.9 ± 1.4 mm, and the dentoalveolar arch a mean increase of 12.7 ± 2.1 mm. Within the distraction zone, a mean vertical bone loss of 3.5 ± 0.7 mm and a mean horizontal bone loss of 3.9 ± 0.8 mm were seen. After orthodontic gap closure, both were clinically irrelevant, with no need for additional bone grafts. Periodontal impairment (gingival recessions of 1 mm) was observed in 7 patients but affected only the teeth bordering the vertical osteotomy line. CONCLUSIONS: Bone-borne anterior alveolar osteodistraction is sufficient for enlargement of the apical base and the dentoalveolar arch of the mandible. Skeletal movement of the alveolar segment was predictable and dental tipping was clinically irrelevant. This technique presents further indications and approaches in orthognathic surgery.

In vitro determination of the mechanical and chemical properties of a fibre orthodontic retainer.

The aim of this study was to analyse, in vitro, the chemical and mechanical properties of a new fibre retainer, Everstick, comparing its characteristics with the requirements for an orthodontic retainer. Chemical analysis was used to examine seven fibre bundles exposed to a photocuring lamp and then to different acids and resistance to corrosion by artificial saliva fortified with plaque acids. The mechanical properties examined were tensile strength and resistance to flexural force. Ten fibre samples were tested for each mechanical analysis and the mean value and standard deviation were calculated. Wilcoxon signed rank test was used to evaluate change in weight after treatment in each group. To determine changes over time between the groups for each acid considered separately, both repeated measures analysis of variance (ANOVA) on original data and on rank transformed data were used. If the results were different, ANOVA on rank-transformed data was considered. Acetic acid was found to be the most corrosive and caused the most substance loss: both pure and at the salivary pH value. Hydrofluoric acid was the most damaging. For all acids analysed in both groups (lactic, formic, acetic, propionic), changes after treatment were statistically different between two groups (P < 0.001 for lactic, acetic, propionic; P = 0.004 for formic acid).The mean Young's modulus value was 68 510 MPa. Deformation before the fibre separated into its constituent elements (glass fibre and composite) was 3.9 per cent, stress to rupture was 1546 MPa, and resistance to bending was 534 MPa. The deflection produced over a length of 12 mm was 1.4 mm. The fibre bundle was attacked by acids potentially present in the oral cavity; the degree of aggressiveness depending on the acid concentration. To preserve fibre bundles long term, careful plaque control is necessary, especially in the interproximal spaces, to avoid acid formation. The tested product was found to be sufficiently strong to oppose flexural and occlusal forces.

Modified distal shoe appliance for the loss of a primary second molar: a case report.

Preservation of primary teeth until their normal exfoliation plays a crucial role in preventive and interceptive dentistry. Premature loss of the primary second molar prior to the eruption of the permanent first molar in the absence of the primary second molar can lead to mesial movement and migration of the permanent molar before and during its eruption. In such cases, an intra-alveolar type of space maintainer to guide the eruption of the permanent first molar is indicated. In certain cases, however, the conventional design is not practical. This paper describes a new design for distal shoe appliances in cases of primary second molar loss prior to the eruption of the permanent mandibular first molar.

[Retention and relapse. Review of the literature]. / Retenció és recidiva az ortodonciában. Irodalmi áttekintés.

The retention after orthodontic intervention is just as important part of the therapy as the activ treatment. It is difficult to find statistical data about the frequency and the average degree of the relapse, but some restitution in lower denture is observable in the 70-90% of the cases, in the postretention period. The upper jaw is also frequently touched, but the prevalence and the rate is milder. The authors of this article tried to collect all the factors which are responsible for the orthodontic relapse and to determine the rules should be kept by the planning and the management of the therapy. The age and the maturity of the patients, the result of the orthodontic intervention, the origin and the character of the anomaly, the type of the retainer, the compliance of the patients; all can influence the chance of the relapse. There are some anomalies which more frequently relapse, contrarily some orthodontic irregularities have quite good long-term prognosis. In the first 6 month after the orthodontic treatment any kind of retainer has to be worn nearly 24 hours/day, later 12-14 hours daily wear seems to be satisfactory. The retention period should be twice longer than the activ orthodontic treatment, posteriorly the appliance can be left gradually. Certainly the length of the retention depends on compliance of the patients. Among the retention appliances the fixed retainers are suggested in the lower front area, because the lower incisors are most frequently relapsed.

Elastic training for the prevention of mandibular drift following mandibulectomy in dogs: 18 cases (2005-2008).

OBJECTIVE: To describe a noninvasive method for preventing mandibular drift (MD) after mandibulectomy in dogs. STUDY DESIGN: Technique description and case series. ANIMALS: Dogs (n=18) that had mandibulectomy involving resection of a portion of the mandible caudal to the 2nd mandibular premolar tooth. METHODS: One orthodontic button was attached to the lingual aspect of the canine tooth of the intact mandible and 1 to the buccal aspect of the ipsilateral maxillary 4th premolar tooth. An orthodontic elastic rubber chain was attached to the buttons creating tension sufficient for maintaining normal occlusion. The rubber chain was replaced weekly by the clients. Follow-up appointments were scheduled 2, 6, 10 weeks postoperatively and monthly thereafter if indicated. The appliance was removed when dogs had resumed normal occlusion of the canine teeth. RESULTS: All dogs maintained normal occlusion, normal jaw function, had no apparent disfigurement, and resumed preoperative activity levels while wearing the appliance. Eight dogs achieved temporomandibular joint stability and normal occlusion 4.5-6 months postoperatively and 8 did not, resulting in MD. One dog was lost for follow-up and 1 was euthanatized. CONCLUSION: Elastic training using orthodontic buttons and power chain is a viable option for prevention of MD but requires good client compliance. More data and longer follow-up are required to determine the long-term mandibular stabilizing potential of this technique. CLINICAL RELEVANCE: Elastic training is a quick, simple, cost-effective and noninvasive technique, preserving normal occlusion and function in many dogs after mandibulectomy.

Postorthodontic root approximation after opening space for maxillary lateral incisor implants.

INTRODUCTION: Orthodontic space opening during adolescence is a common treatment for congenitally missing maxillary lateral incisors. Because of continued facial growth and compensatory tooth eruption, several years can elapse between completion of orthodontic treatment for a teenage patient and implant placement. There are reports that, after successful orthodontic opening of the implant space, the central incisor and canine roots reapproximate during retention and prevent implant placement. METHODS: To study this phenomenon, the records of 94 patients with missing maxillary lateral incisors were collected. Periapical and panoramic radiographs were used to measure intercoronal and interradicular distances between the central incisor and the canine adjacent to the missing lateral incisor before and after orthodontic treatment and at implant placement. RESULTS: Although root approximation between the adjacent central incisor and canine during retention did not occur consistently, 11% of the patients experienced relapse significant enough to prevent implant placement. CONCLUSIONS: To ensure sufficient space for implant placement, we recommend at least 6.3 mm of intercoronal space and 5.7 mm of interradicular space between the adjacent central incisor and canine. A bonded wire or resin-bonded bridge will help to reduce root approximation that might occur during retention.

Results of a survey-based study to identify common retention practices in the United States.

INTRODUCTION: The purpose of this descriptive study was to use a carefully constructed, pilot-tested survey instrument to identify the most common orthodontic retainers and retention protocols prescribed in the United States as reported by active members of the American Association of Orthodontists. METHODS: We randomly selected 2000 active members, stratified by region of practice, for the study. Information gathered included, but was not limited to, the types of retainers prescribed in the maxillary and mandibular arches, duration of full-time and part-time wear, use of fixed retainers, appliances fabricated in office vs commercial laboratories, the number of debonds per year, and retention appointment schedules. The survey consisted of 20 questions. Data were gathered on a categorical scale and analyzed. RESULTS: We received 658 responses (32.9%) during a 12-week period. Maxillary Hawley retainers (58.2%) and mandibular fixed lingual retainers (40.2%) were the most commonly used. Most orthodontists prescribed less than 9 months of full-time wear of removable retainers and thereafter advised part-time, but lifetime wear. Most orthodontists (75.9%) did not instruct patients to have the fixed lingual retainers removed at a specific time. More orthodontists who prescribed Hawley retainers recommended longer full-time wear compared with clear thermoplastic retainers. The timing of scheduled retention appointments varied among clinicians and depended on the number of years in practice, the volume of patients debonded, and the type of prescribed retainer. The only regional difference associated with retainer design was the Northeast region, where mandibular fixed lingual retainers were used less frequently. Female orthodontists did not use mandibular fixed lingual retainers as often as their male counterparts. CONCLUSIONS: Maxillary Hawley and mandibular fixed lingual retainers are most commonly used. This study is the first to describe retention protocols and the scheduling of retention appointments in the United States.

Local delivery of osteoprotegerin may be a way of reinforcing orthodontic anchorage.

One of the most challenging problems in orthodontics is anchorage. The traditional mechanical methods of reinforcing anchorage are limited by multiple factors, but a pharmacological approach aimed at utilizing the known biological mechanisms underlying tooth movement may provide an ideal way of reinforcing orthodontic anchorage. So we make the hypotheses that if the resorptive process of modeling during tooth movement can be inhibited, tooth movement may be inhibited as well. Since osteoprotegerin (OPG) has been found to be a key factor in the inhibition of osteoclast differentiation and activation, and involved in mechano-modulation of bone modeling, its local delivery adjacent to the anchorage teeth may provide a novel pharmacological approach for preventing unneeded tooth movement that is highly desirable for reinforcing orthodontic anchorage.

Effectiveness of lingual retainers bonded to the canines in preventing mandibular incisor relapse.

INTRODUCTION: A retainer bonded to the lingual surfaces of the mandibular canines (3-3 retainer) is a widely used type of retention. Our aim in this study was to assess the effectiveness of the 3-3 mandibular lingual stainless steel retainer to prevent relapse of the orthodontic treatment in the mandibular anterior region. METHODS: The sample consisted of the dental casts of 235 consecutively treated patients (96 boys, 139 girls) from the archives of the Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Center, The Netherlands, who received a 3-3 mandibular lingual stainless steel retainer at the end of active orthodontic treatment. The casts were studied before treatment (Ts), immediately after treatment (T0), and 2 years (T2), and 5 years (T5) posttreatment. RESULTS: The main irregularity index decreased significantly from 7.2 mm (SD, 4.0) at Ts to 0.3 mm (SD, 0.5) at T0; it increased significantly during the posttreatment period to 0.7 mm (SD, 0.8) at T2 and 0.9 mm (SD, 0.9) at T5. The irregularity index was stable during the 5-year posttreatment period (T0-T5) in 141 patients (60%) and increased by 0.4 mm (SD, 0.7) in 94 patients (40%). The intercanine distance increased 1.3 mm between Ts and T0 and remained stable during the posttreatment period. CONCLUSIONS: The 3-3 mandibular lingual stainless steel retainer (bonded to the canines only) is effective in preventing relapse in the mandibular anterior region in most patients, but a relatively high percentage will experience a small to moderate increase in mandibular incisor irregularity.

Effects of posttreatment skeletal maturity measured with the cervical vertebral maturation method on incisor alignment relapse.

INTRODUCTION: Our aim was to test the hypothesis that relapse of incisor alignment is associated with skeletal maturity at the end of treatment, as assessed with the cervical vertebral maturation (CVM) method. METHODS: This was a case-control study with information from the postretention database at the University of Washington. Mandibular incisor irregularity (II) at least 10 years out of retention (T3) was used to define the subjects (II >6 mm, relapse group) and the controls (II <3.5 mm, stable group). The following model measurements were made: II at pretreatment (T1), II at posttreatment (T2), and intercanine width at T1 and T2. On cephalograms taken T2, the CVM status was determined. Logistic regression analyses were used to determine the association between relapse and CVM status after treatment. The models were adjusted for potentially confounding variables (II at pretreatment and posttreatment, intercanine width change during treatment, sex, age at T2, and treatment alternatives). RESULTS: No association between CVM stage at T2 and relapse was found (P = 0.89). Both groups had similar distributions of the CVM stages (P >0.05). Pretreatment II and postretention time were found to be correlated with long-term incisor stability (P = 0.007 and 0.034, respectively). Sex was not related to relapse (P = 0.33). CONCLUSIONS: Maturity of craniofacial structures at the end of treatment evaluated with the CVM method is not associated with long-term stability of incisor alignment.

Effect of the transpalatal arch during extraction treatment.

INTRODUCTION: The transpalatal arch (TPA) can be used as an adjunct during orthodontic treatment to help control the movement of the maxillary first molars in 3 dimensions, including producing molar rotation and uprighting, maintaining transverse dimensions posteriorly during treatment, and maintaining leeway spaces during the transition of the dentition. The purpose of this retrospective cephalometric study was to test an additional function of the TPA: its ability to enhance orthodontic anchorage during extraction treatment. METHODS: Records consisting of pretreatment and posttreatment cephalograms were gathered from several orthodontic practices that used an .018 x .025-in preangulated appliance. All patients were white and had 4 first premolars extracted as part of their treatment protocol. Patients were treated either with or without a TPA of the soldered Goshgarian design. Patients were excluded if headgear or any other auxiliary anchorage device beside the TPA was used during treatment. Matched samples of 30 patients were identified based on sex, age at the start of treatment, treatment duration, and cervical vertebral maturation stage. Statistical comparisons were made with nonparametric statistical tests. RESULTS: Analysis of the changes from pretreatment to posttreatment for the TPA and the no-TPA groups showed no statistically significant differences in any of the variables examined. The net difference for both vertical and mesial movement of the maxillary first molar in relation to the maxilla between the 2 groups was 0.4 mm, with the no-TPA group in a more downward and forward position. CONCLUSIONS: Although the usefulness of the TPA for the abovementioned functions is not negated, it does not provide a significant effect on either the anteroposterior or the vertical position of the maxillary first molars during extraction treatment.