Retainer Wear Research Articles

Comparison of the effects of modified and full-coverage thermoplastic retainers on occlusal contacts

The purpose of this prospective study was to determine the number of contacts in centric occlusion during retention with modified and full-coverage thermoplastic Essix retainers. This research was based on 36 patients who were randomly assigned to wear either modified (18 patients) or full-coverage (18 patients) Essix retainers. Silicone-based bite registrations were used to record occlusal contacts at the beginning (T1), end of full-time (6 months; T2), and end of night-time (3 months; T3) wear of retainers. The occlusal contacts determined in treated patients were compared with the values of 18 untreated "normal" Class I subjects. Bonferroni-adjusted Wilcoxon and Kruskal-Wallis tests were used to evaluate intra- and intergroup differences. Total posterior contacts increased significantly at T3 compared to T1 and T2 only in the modified Essix group. Non-ideal and total contacts on premolars, non- ideal and actual contacts on first molars, and actual contacts on second molars increased significantly at T3 in the modified Essix group. No significant increase was determined in the final total posterior contacts in the full-coverage Essix group. Actual contacts on premolars and first molars and total posterior actual contacts were significantly greater at T3 in the modified Essix group compared to the full-coverage Essix Group. Also the number of final posterior ideal contacts in the modified Essix group was greater than in the normal sample. Total anterior contacts decreased significantly in the modified Essix group, whereas they increased significantly in the full-coverage Essix group. Increase in posterior contacts was achieved only during night-time wear of modified Essix retainers.

Residents' journal review

Residents' journal review

Patient Compliance to Wear Orthodontic Retainers During Postretention may Vary by Age, Gender, and Time Since Braces Were Removed

To evaluate and quantify compliance of orthodontic retainer wear and predictors for noncompliance during the postretention phase. Information not available. Survey. Level 3: Other evidence. Not applicable.

Residents’ journal review

Residents’ journal review

Patient compliance with orthodontic retainers in the postretention phase

Retention is an important, even critical, component of orthodontic treatment. There is little research on practice protocols and patient compliance with long-term or short-term retention. This lack of information leaves our specialty with many opinions and practice protocols. The purposes of this study were to evaluate and quantify orthodontic retainer wear according to several variables, including patient age, sex, time in retention, and retainer type, and to identify predictors of compliance and reasons for noncompliance with removable orthodontic retainers. Questionnaires were mailed to patients who finished full fixed appliance therapy in either the orthodontic graduate clinic or the orthodontic faculty practice at the University of Kentucky within the past 6 years. Of the 1085 questionnaires mailed, 280 were returned (25.8%). A logistic regression model that described the probabilities of retainer wear was created (P <0.0001). Patient compliance was greater with vacuum-formed retainers (VFRs) for the first 2 years after debonding. However, compliance with VFRs decreased at a much faster rate than with Hawley retainers. Because of this, patient compliance was greater with Hawley retainers at any time longer than 2 years after debonding, and patient compliance overall was greater with Hawley retainers. This evidence disagrees with the current anecdotal trend of orthodontists who favor switching from Hawley retainers to VFRs. An unexpected finding was that patients reported few esthetic concerns about retainers, and the few that were reported were equally distributed between Hawley retainers and VFRs.

Left/right asymmetries and open/closed differences of interdental forces in the mandible

The aim of the present investigation was to study the variation in interdental forces between mandibular canines and lateral incisors of 19 volunteers (9 males and 10 females) aged 20-26 years for four configurations (mandible open/closed and left/right side). These forces were derived by pulling a stainless steel matrix strip between these teeth, six times per configuration, and registering the time variation with a high-resolution transducer. The repeated median smoothing algorithm was applied to find the maximum of each curve and a bootstrap method estimated the 95 per cent confidence intervals (CIs) for all 76 configurations. Seventy-six per cent of all paired force differences were found to be significant. Asymmetry phenomena were observed: the interdental forces differed significantly between the left and right sides and also between the open and closed position of the mandible. The interdental forces (4-21 N) showed a pattern modulated by volunteer-specific features: in 91 per cent of the configurations, the interdental forces were larger when the mouth was open. This observed pattern contributes to the instability observed in clinical practice, thus necessitating permanent fixed lower retainer wear.

Retainer wear and compliance in the first 2 years after active orthodontic treatment

The purpose of this descriptive study was to estimate retainer wear and compliance among orthodontic patients in the first 2 years after active orthodontic treatment. A random sample of 1200 orthodontic patients was selected from 4 offices. Data were collected by a self-administered questionnaire that consisted of 6 items: type of retainer prescribed, age, sex, length of time since debond, and hours per day and nights per week that patients wore their retainers. Responses were solicited by mail or the Internet. Data were gathered on a categorical scale and analyzed. The overall response rate was 36% during a 6-week period. In the first 3 months after debond, 60% of patients were wearing their retainers more than 10 hours during a 24-hour cycle, and 69% were wearing the retainers every night. At 19 to 24 months after debond, 19% of the patients were not wearing their retainers, and 81% wore their retainers at least 1 night per week. Compliance rates during the periods of 0 to 3, 4 to 6, 7 to 9, 10 to 12, 13 to 18, and 19 to 24 months were 69%, 76%, 55%, 62%, 45%, and 45%, respectively. Age, sex, and type of retainer did not influence the levels of compliance. Most continued to wear their retainers at least 1 night per week, with compliance rates, as defined, tending to decrease in our sample. It was encouraging that 81% of the patients in this sample largely maintained their orthodontic result.

Posterior occlusion changes with a Hawley vs Perfector and Hawley retainer

To characterize postorthodontic settling of the posterior occlusion of patients wearing Hawley retainers vs patients who initially wore Perfector retainers and then switched to Hawley retainers. This follow-up study was based on 40 patients (25 Perfector and 15 Hawley), who were part of a larger sample of 50 patients randomly assigned to wear either Hawley or Perfector retainers. The Perfector patients were given Hawley retainers 2 months after retainer delivery. Occlusal bite registrations were scanned and traced to quantify posterior areas of contact and near contact (ACNC). A seven-item questionnaire was used to assess the patient's perception of occlusion. Measurements were obtained at the on the day of retainer delivery, 2 months post delivery, 6 months post delivery, and 8 months post delivery. ACNC increased significantly (P < .05) during the first 6 months of retainer wear. The ACNC of the Hawley and Perfector/Hawley groups increased by 129% and 105%, respectively, over 8 months of retention. The greatest increases in ACNC occurred during the first 2 months. The ACNC further increased between 2 and 6 months in both groups. The Perfector/Hawley group also showed slight increases in ACNC between 6 and 8 months. Overall group differences were not statistically significant. The Perfector/Hawley group perceived greater improvements in occlusion than the Hawley group, but group differences after 8 months were small. Substantial amounts of settling occurred at decelerating rates during the first 6 months after retainer delivery. No significant differences in ACNC were found between the Hawley and Perfector/Hawley groups after 8 months of retainer wear.

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

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. 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. 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. 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.

Longitudinal measurements of tooth mobility following orthodontic treatment

Objective: The aim of the present study was to evaluate the changes in tooth mobility following orthodontic treatment and to obtain information regarding the guideline of retainer wear duration during the post-treatment period. Methods: The sample consisted of twenty patients who had been treated with edgewise appliances. The mobility of the maxillary teeth from the central incisor to the first molar was measured bilaterally by way of the Periotestⓡ, a non-invasive, electronic device that provides an objective measurement of the reaction of the periodontium to a defined impact load. Tooth mobility was monitored at the time of the removal of the orthodontic appliances and subsequently at three-month intervals during the two years following appliance removal. Results: Tooth mobility decreased rapidly for the first six months and then decreased at a slower rate during the next six months; no statistically significant decrease in mobility was observed during the second year following appliance removal. Conclusions: The results of the present study suggest that adequate tooth stabilization is critical during the first six months following appliance removal and that continued wearing of retainers is recommended at least until twelve months after the completion of orthodontic treatment.

A randomized clinical trial of thermoplastic retainer wear

The purpose of this study was to determine whether thermoplastic retainers need to be worn full-time for a limited period or whether part-time wear from the outset is adequate to maintain tooth position, arch form, and occlusion. This study was a randomized clinical trail, conducted in a district general hospital. Sixty-two participants were enrolled in the study. Group 1, full-time wear, consisted of 30 patients (12 males and 18 females, aged 13.6 +/- 1.5 years) and group 2, part-time wear, 32 patients (14 males and 18 females, aged 13.8 +/- 1.5 years). Each patient was assigned to one of the groups by random number generation. Clinical records in the form of study models were taken at the start of active treatment (T1), at debond (T2), 6 months into the retention phase (T3), and 1 year post-debond (T4). The irregularity index, intercanine width, intermolar width, arch length, overbite, overjet, and Peer Assessment Rating (PAR) scores were measured on study models using digital callipers. A Mann-Whitney test was used to evaluate the treatment changes within each group. The only statistically significant difference was found to be at T3 and T4 for overbite (P = 0.05 and P = 0.02, respectively). PAR scoring showed more variable changes in group 2. There was good correlation for the measurement method. There was no statistical difference for the two groups for overjet, arch length, intermolar width, intercanine width, and irregularity index at any time point.

Hawley retainers full- or part-time? A randomized clinical trial

The aim of this trial was to compare two different orthodontic retention regimens: is night-only wear of upper and lower Hawley retainers for 1 year as effective as 6 months full-time followed by 6 months night-only wear? Sixty-seven consecutive patients attending for orthodontic debond were randomly allocated to wear upper and lower Hawley retainers either for 1 year night-only (group 1) or for 6 months full-time followed by 6 months night-only (group 2). In group 1, 41.2 per cent were males and 58.8 per cent were females and their mean age was 15.6 years [standard deviation (SD) 1.6 years]. In group 2, 24.2 per cent were males and 75.8 per cent were females and their mean age was 15.8 years (SD 1.2 years). Study models were taken at the start (T0) and end (T1) of treatment and 1 year post-debond (T2). Digital callipers were used to measure upper and lower labial segment irregularity using Little's index and upper and lower labial segment crowding. To evaluate differences between groups 1 and 2 t-tests were used. There were no statistically significant differences between the two retention regimens at T2 for labial segment irregularity or crowding (P > 0.05). Since both retention regimens were equally effective during the 1 year retention period, it would seem clinically acceptable to ask patients to wear their retainers at night only.

Microsensor technology to help monitor removable appliance wear

Retention is routinely prescribed after orthodontic treatment to prevent relapse. Orthodontists often notice a discrepancy between what a patient reports about retainer wear and what a clinical examination shows. In these cases, is the patient misreporting wear, or is the retainer at fault? Scientific Compliance (Atlanta, Ga) has invented, patented, and produced the Smart Retainer environmental microsensor that can be easily incorporated into many types of removable orthodontic appliances to monitor compliance. The technology behind the Smart Retainer environmental microsensor is possible because of recent reductions in electronic component sizes and power requirements. A proprietary USB-powered Smart Reader uses wireless technology to download information about actual usage from the Smart Retainer. The information is decrypted and analyzed, and can be shown to the patient in easy-to-understand charts. The orthodontist can use this information to discuss actual retainer usage vs prescribed retainer usage with the patient or parent and make data-driven recommendations about future retention.

A laser pointer surveyor to detect an undercut in fixed partial denture preparation

1. Rudd RW, Bange AA, Rudd KD, Montalvo R. Preparing teeth to receive a removable partial denture. J Prosthet Dent 1999;82:536-49. 2. Alfonso C, Toothaker RW, Wright RF, White GS. A technique to create appropriate abutment tooth contours for removable partial dentures. J Prosthodont 1999;8:273-5. 3. Kawano F, Ohguri T, Ichikawa T, Matsumoto N. Influence of thermal cycles in water on flexural strength of laboratoryprocessed composite resin. J Oral Rehabil 2001;28:703-7. 4. Takahashi Y, Hisama K, Sato H, Chai J, Shimizu H, Kido H, et al. Probability of failure of highly filled indirect resin-veneered implant-supported restorations: an in vitro study. Int J Prosthodont 2002;15:179-82. 5. Davenport JC, Hawamdeh K, Harrington E, Wilson HJ. Clasp retention and composites: an abrasion study. J Dent 1990;18:198202. 6. Tietge JD, Dixon DL, Breeding LC, Leary JM, Aquilino SA. In vitro investigation of the wear of resin composite materials and cast direct retainers during removable partial denture placement and removal. Int J Prosthodont 1992;5:145-53. 7. Chow TW, Chung RW, Chu FC, Newsome PR. Tooth preparations designed for posterior resin-bonded fixed partial B 1 A, Definitive cast of preparations. B, Intaglio surface of highly filled composite resin partial coverage restoration. A

Patients’ attitudes towards compliance with retainer wear

Abstract Objectives: The objectives of this survey were to determine patients’ attitudes towards retainers and their compliance in wearing retainers. Methods: Three hundred dental school patients were selected at random and survey questionnaires were distributed. Twelve private orthodontists were willing to participate in the survey and each was given 20 questionnaires for distribution to their patients. The questionnaire was designed to gather information regarding compliance in wearing removable retainers, perception of the comfort level of retainers and acceptance of the appearance of removable and fixed retainers. Results: The results revealed that compliance in wearing an upper retainer was related to its comfort level and acceptance. Discomfort was the main reason given by dental school patients and forgetfulness was the major reason given by private patients for not wearing retainers. Higher proportions of patients found fixed retainers more comfortable to wear and were more willing to accept the appearance of fixed retainers. A higher proportion of private patients accepted the appearance of retainers compared with dental school patients, while a higher proportion of dental school patients found retainers less comfortable to wear than private patients. Conclusions: There was a strong relationship between compliance and comfort level in wearing upper removable retainers. Patients found fixed retainers more acceptable than removable types because of appearance and comfort.

Wear of visible light-cured restorative materials and removable partial denture direct retainers.

This study measured the in vitro wear of visible light-cured restorative materials and removable partial denture direct retainers. An aluminum test die was produced by replicating the facial contours of an extracted human molar (model). The replica's cervical contour was modified by placement of a restorable Class V cavity preparation. The test die became a fixed component of a testing apparatus. The restorative materials tested were Z100 (fine particle filled resin composite), Silux Plus (microfilled resin composite), and Photac-Fil (hybrid glass ionomer). Cast round, half round, I bar, and wrought-wire retainers were designed to engage a 0.254-mm undercut. Caliper measurements of the wear of restorative materials were made at intervals during testing, and after 7,500 retainer placements and removals. The measurements of material- and retainer-wear were subjected to ANOVA and Tukey tests. Generally, retainers with round profiles caused less wear of the restorative materials than those featuring flat contact surfaces. Wear of the materials ranged from 14 +/- 5.5 microns (Silux Plus by cast round) to 70 +/- 10.0 microns (Photac-Fil by cast half round). Mean wear of retainers, however, ranged only from 2 +/- 4.5 microns for six of 12 possible retainer-material pairings up to 12 +/- 4.5 microns (cast half round by Z100). Regardless of their design features, the direct retainers of this study exhibited little wear when paired with any of the restorative materials. Overall, material wear appeared to be greater than retainer wear by a factor of five. When paired with practically any retainer type, the hybrid glass ionomer (Photac-Fil) exhibited more wear than either of the two resin composites (Z100 or Silux Plus). Although not established clearly, retainers with round profiles (wrought-wire and cast round) appeared to produce less wear of restorative materials than their I bar and cast half round counterparts.

Effects of retainers on the articulation of speech

Articulation abilities of 15 patients were evaluated at the end of orthodontic treatment with the initiation of removable upper and lower retainer wear. A test of articulation, based on consonants and vowels (cv), (vcv), (vc), (cvc) nonsense syllables, was used to evaluate the articulatory distortions with no retainers and with maxillary and mandibular retainers worn respectively and together. The test was performed (a) on the first day, (b) 24 hours later, and (c) 1 week later. Statistically significant articulatory distortions with the /t/ and /d/ sounds on the first day with upper retainer only and with both retainers worn together were noted. Also significant distortion of the /k/ sound with both retainers worn was observed. These distortions, due to the wearing of retainers, decreased to an insignificant level or disappeared completely on the seventh day showing the ability of tongue adaptation in a very short period of time. (Am J Orthod Dentofac Orthop 1996;110:534-40.)