Indirect vs direct bonding of mandibular fixed retainers in orthodontic patients. Which one is better?
Posted on 13th April 2017 at 17:23
After a long planning, patient education, careful follow-up and a lot of patience, an orthodontic treatment is finally completed. The patient is happy because his teeth are going to be set free of all the wires and braces. However another phase of the treatment is about to begin, to maintain the orthodontic results for the long-term. A lot of questions come to our mind, which retainer is going to be used?. When it's about the fixed retainer we also have to wonder: Which technique are we going to use to bond it? direct or indirect ?. Here's an interesting study that's going to help you to answer these questions.
Quoting Dr. Alpern DDS, MS: “How long should we retain?” many notable orthodontic teachers have replied, “How long do you want the teeth to stay straight?” This implies permanent retention is the best way to go. Because the patient won't have to feel the need or the responsibility to use another kind of device inside his mouth. The fixed retainer is always going to be there doing its job. But why is this necessary?. The answer is very simple, alveolar bone, muscular system, and periodontal ligaments require more time to remain stable in time. Some people call this "periodontal memory".
The fixed technique consist in bonding all the anterior teeth with a wire in their lingual surface. A mandibular fixed retainer from canine to canine is the most used and accepted method for long-term retention, as described by Zachrisson in 1977. Although a wire retainer bonded on the lingual surface of mandibular canines only, is described as solid and easy to place. Some authors have reported that it does not prevent relapse of the incisors. This was mainly related to the boding method.
The direct bonding method requires the construction of a retainer on the patient's cast, subsequently bonded and light-cured in the mouth, after using a transfer key to keep the retainer wire in the right position.
The indirect bonding method relies on the preparation of composite pads on the patient's cast to be bonded using a transfer tray covering the retainer and composite pads. Indirect bonding of a mandibular fixed retainer is a clinically faster procedure than direct bonding.
A systematic review about fixed retainers reported a wide variety in protocols, including numbers of bonded teeth, in their conclusion they indicate that most fixed retainer failures occur during the first 3 to 6 months, whereas the probability of failure significantly drops after a year. So many differences in protocols and different laboratory and operators can offer different results. This inspired a different study with a more right methodology conducted by Fabienne Egli, Efstathia Bovali, Stavros Kiliaridis and Marie A. Cornelis from the University of Geneva, Switzerland and Aarhus University of Denmark. They've conducted a parallel randomized controlled trial. The same operator was used for both direct and indirect bonding technique, same laboratory and results were evaluated by a different investigator who didn't know which bonding technique was used in each patient.
Patients were reviewed after 1, 2, 4, and 6 months, and impressions and lateral cephalogram were taken after 6 months and 2 years. 60 patients were initially distributed randomized in 2 groups in blocks of 4 (using an online randomization service) to either the direct or the indirect bonding method (30 for each). The following measurements were made on dental casts: 1)Inter canine and inter premolar distances and 2) Changes in torque and rotations of the mandibular teeth.
A, Mandibular cast at pretreatment; B, immediately after treatment and C and D, occlusal and frontal views, respectively, at the 2-year follow-up. The arrow shows the lingual displacement of the canine. The double arrow indicates the displacement of the contact point between the left lateral incisor and canine. Taken from Fabienne et al (2017).
After 2 years follow up their hypotheses were confirmed: (1) there is no difference in the risks of failure 2 years after bonding mandibular fixed retainers with indirect or direct bonding, and most debondings occurred within the first year after bonding; and (2) there seem to be fewer unexpected post-treatment changes (failure of stability) with the indirect compared with the direct bonding method.
If you want to check this study detailed findings, you can download the original article by clicking here. Also don't forget to leave your comments below.
Egli F, Bovali E, Kiliaridis S, Cornelis M. Indirect vs direct bonding of mandibular fixed retainers in orthodontic patients: Comparison of retainer failures and posttreatment stability. A 2-year follow-up of a single-center randomized controlled trial. American Journal of Orthodontics & dentofacial orthopedics. 2017; 151(1):15-27.
Tagged as: Orthodontics
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