The aim of this study was to retrospectively assess the frequency and localizations of bond failures (BFs) in patients treated with either lingual (TOP-Service für Lingualtechnik GmbH, a 3M Company, Bad Essen, Germany) or buccal (Mini Diamond brackets/Accent molar tubes; Ormco, Orange, Calif) full multibracket appliances in both dental arches.
Data were acquired by an independent investigator from the patient records of 3 practitioners. To establish a standardized observation period, the first year of treatment was analyzed for each patient. Statistical analysis comprised the Kruskal-Wallis, Wilcoxon, Mann-Whitney U, and Fisher exact tests. The significance level was set at P <0.05.
The mean number of BFs per patient in the first year of treatment did not differ significantly between the lingual group (n = 59; mean age, 31.1 years; mean BFs per patient, 2.63; SD, 2.77; minimum, 0; maximum, 13) and the buccal group (n = 44; mean age, 15.14 years; mean BFs per patient, 2.61; SD, 3.41; minimum, 0; maximum, 14) ( P = 0.428) or with respect to sex (lingual group, P = 0.251; buccal group, P = 0.414) or practitioner (lingual group, P = 0.755; buccal group, P = 0.060), but molar attachments were more prone to BFs than were premolar brackets (lingual group, P = 0.015; buccal group, P = 0.049), and premolar brackets were more prone to BF than anterior brackets (lingual group, P = 0.005; buccal group, P = 0.004).
With both appliances, a mean of 2.62 BFs per patient in the first year of treatment can be expected; this benchmark provides a reference for patient briefing, which is very important considering the large interindividual variances and budgeting considerations.
Since the development of the enamel etching technique by Buonocore and its application on orthodontic attachments by Newman, bonding has become the common way of attaching orthodontic brackets. Various materials and protocols have been invented and refined, but bond failures (BFs) are a common complication in orthodontic treatment with fixed appliances. Although BFs are usually easily manageable, they can increase treatment time and costs, and disturb practitioners’ schedules.
Previous studies have identified factors related to patient and process for BFs, although their conclusions do not agree. Some authors found the choice of the adhesive to have an influence on the frequency of bracket loss. Sandblasting is generally regarded as useful for increasing bond strength. However, not all authors share this conclusion.
Notably, the literature concentrates on buccal appliances. Fully individualized lingual appliances offer an esthetic alternative to buccal treatment, while minimizing impairment of patient comfort and providing higher slot precisions in contrast to standardized lingual appliances. Furthermore, lingual brackets have decisive medical advantages: eg, reduction of white spot lesions, full control of mandibular incisors with the Herbst appliance, and excellent bite opening and bite closing.
In terms of clinical handling, lingual bracket systems require various appropriate procedures, especially with respect to bonding.
This investigation was initiated with the purpose of clinically evaluating differences in the frequency of BFs per patient and year between lingual and buccal appliances. Additionally, several potential risk factors were analyzed because some studies indicate that more BFs occur in male patients, that there might be a correlation between the incidence of bracket loss and patient age, or that the location of a bracket might influence its proneness to failure.
Material and methods
This retrospective investigation took place in the Department of Orthodontics at the University of Münster in Germany. Consecutive patient records from 3 experienced practitioners (A.H., T.Z., and S.F.), each using buccal and individual lingual appliances, were processed.
Only patients needing comprehensive orthodontic treatment and full appliances in both dental arches were included.
Patients whose fixed appliance was in place for less than 1 year were excluded. Also, teeth with bands or teeth with brackets bonded on artificial surfaces were excluded from the study because the number of metal and ceramic surfaces was not equally distributed between the lingual and buccal groups, therefore causing a risk of distorted results.
Furthermore, therapies with crossover techniques (eg, buccal brackets in the mandible and lingual braces in the maxilla), partial appliances, or brackets in only 1 dental arch led to exclusion from the study. Chlorhexidine pretreatments were avoided for both systems because they adversely affect adhesion.
Two types of bracket systems were used: Incognito (lingual; TOP-Service für Lingualtechnik GmbH, a 3M Company, Bad Essen, Germany) ( Fig , left ) and Mini Diamond Brackets/Accent Molar Tubes (buccal; Ormco, Orange, Calif) ( Fig , right ).
In both the lingual and buccal groups, the respective tooth surfaces were cleaned with a polishing brush (Pluradent, Offenbach, Germany) with Remot prophylaxis paste (lege artis Pharma, Dettenhausen, Germany) and rinsed.
In the lingual group, the whole bonding procedure was performed as recommended by the manufacturer. All lingual surfaces were sandblasted for 3 to 4 seconds using 50-μm aluminum oxide powder (BEGO, Bremen, Germany). After the teeth were rinsed, dry tips (Mölnicke Health Care, Erkrath, Germany) and the NOLA dry field system (Great Lakes Orthodontics, Tonawanda, NY) were inserted. The teeth were subsequently dried and etched with 37% phosphoric acid gel (Smile Dental, Düsseldorf, Germany) on their respective surfaces with a minimum application time of 15 seconds per tooth. Bonding was carried out indirectly using a silicone transfer tray (TOP-Service für Lingualtechnik GmbH, a 3M Company), and a chemically curing adhesive (Maximum Cure Sealant A and B; Reliance Orthodontic Products, Itasca, Ill) was simultaneously applied on the surfaces to be bonded and on the brackets in the silicone transfer tray before its insertion.
In the buccal group, after the NOLA dry field system was used, and the teeth were dried and etched as in the lingual group, the brackets were bonded directly by applying Maximum Cure Sealant A and B on the teeth and Phase II Paste A and B (Reliance Orthodontic Products) on the brackets.
Data were entered into an Excel worksheet (2013; Microsoft, Redmond, Wash).
An independent investigator acquired the relevant information from patient records. In addition to patient sex, age, and treatment duration, the data included information on missing and present teeth and respective surfaces (artificial or natural) as well as specification of the respective attachment that could be a buccal or a lingual bracket or tube (the lingual brackets or tubes with or without an occlusal pad).
To establish a standardized observation period, BFs during the first year of treatment were analyzed.
The statistical analysis was conducted by means of SPSS software version 21; (SPSS, Chicago, Ill). The significance level was set at P <0.05.
The Mann-Whitney U test for independent samples was applied to assess differences in (1) influences of sex and age on the number of BFs per patient in the first year of treatment, (2) patients’ ages at the beginning of treatment in the 2 groups, (3) BF rates in the 2 groups, and (4) BF rates between brackets with and without occlusal pads in the lingual group.
The Kruskal-Wallis test for independent samples was used to assess possible (1) age-related differences in the 3 practitioners’ patient groups and (2) interpractitioner differences.
The Wilcoxon signed rank test for matched pairs served to identify differences (1) in the number of BFs per bracket between molars and premolars, as well as between premolars and canines and incisors and (2) between the maxillary and mandibular arches.
With the Fisher exact test, the sex distribution between the lingual and buccal groups was evaluated.
One hundred three patients (44 male, 59 female; average age, 24.28 years; SD, 11.75 years; minimum, 10.99 years; maximum, 55.42) with a total of 2543 brackets met the inclusion criteria. Fifty-nine patients belonged to the lingual group (21 male, 38 female; average age, 31.1 years; SD, 10.85 years; minimum, 15.45 years; maximum 55.42 years), and 44 were in the buccal group (23 male, 21 female; average age, 15.14 years; SD, 4.39 years; minimum, 10.99 years; maximum, 32.70 years) ( Table I ). The age difference between the groups was statistically significant ( P = 0.000), in contrast to the age differences between the 3 practitioners’ patient groups ( P = 0.743). The percentages of female patients were 64% in the lingual group and 48% in the buccal group, not yielding a significant difference ( P = 0.109) between the groups.
|Group||Patients (n)||BFPPY (n)|
There were 155 BFs in the lingual group (64 in male patients, 91 in female patients), averaging 2.63 BFs per patient in the first year of treatment (SD, 2.77; minimum, 0; maximum, 13) ( Table I ). No significant differences were identified between male and female patients ( P = 0.251) or between the practitioners ( P = 0.755) ( Table II shows the different sex distributions with respect to the 3 practitioners).
|Male patients (n)||9.00||6.00||6.00|
|Female patients (n)||17.00||15.00||6.00|
|Age, mean (y)||31.17||31.05||31.00|
|Age, minimum (y)||15.45||15.73||16.27|
|Age, maximum (y)||49.59||50.14||55.42|
|Age, SD (y)||10.52||9.92||13.79|
|BFPPY, mean (n)||2.27||3.05||2.67|
|BFPPY, minimum (n)||0.00||0.00||0.00|
|BFPPY, maximum (n)||8.00||11.00||13.00|
|BFPPY, SD (n)||2.01||3.07||3.68|
|Male patients (n)||6.00||11.00||6.00|
|Female patients (n)||9.00||6.00||6.00|
|Age, mean (y)||14.59||14.39||16.89|
|Age, minimum (y)||11.13||10.99||11.40|
|Age, maximum (y)||19.20||23.34||32.70|
|Age, SD (y)||2.43||3.27||6.90|
|BFPPY, mean (n)||1.20||3.00||3.83|
|BFPPY, minimum (n)||0.00||0.00||0.00|
|BFPPY, maximum (n)||5.00||14.00||11.00|
|BFPPY, SD (n)||1.61||4.11||3.61|