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Date: 4th. Nov. 2017
This article will present an in-depth view of retention and relapse in orthodontics, need for retention, causes of relapse, different types of retainers, dos and don’ts in usage, and techniques for fabrication of retainers.
Retention is also called orthodontic contention and is defined as maintenance of newly moved teeth in position long enough to aid in stabilising their correction. It is aimed at minimizing unwanted dental movements and maintaining the corrections obtained during the initial period following the removal of braces or other appliances used for correction.
Relapse is defined as the loss of any correction achieved by orthodontic treatment.
Orthodontic retainers are devices usually made of wires or clear plastics that hold teeth in position after straightening them, or any other method of realigning teeth. Today newer materials are available for the same.
During orthodontic treatment the teeth are held in position by braces but once the braces are removed stretched elastic fibres in the gums try to pull back teeth to their previous positions that were present before the treatment started. The reason for this is that malocclusion is a stable occlusion. It takes lot of time for the periodontal ligaments to remould and stop pulling on teeth.
The patient is at the maximum risk of orthodontic relapse just after the braces have been removed as compared to later on when the teeth are slowly stabilising. But it doesn’t mean that as time goes by the patient can stop wearing his retainers. To guarantee that teeth stay put, retainers are a lifelong commitment – thankfully they are both comfortable and discreet.
The aim of orthodontic treatment is getting those pearly whites in a straight and the goal of retention is maintaining them in that position. As with most interventions in healthcare, maintenance is the key. If the patient makes retainer wearing a habit then he is ensured of successful orthodontic treatment and a gorgeous smile that will last for a lifetime.
Bone has the capacity to change and remodel for a lifetime that’s why a fractured bone can heal in time. From 20-50 years of age, faces mature and teeth continue to push forward causing crowding of lower front teeth. This happens regardless of whether wisdom teeth are present or absent, extraction of teeth to gain space, or previous orthodontic treatments in the same patient.
Orthodontic treatments are both a heavy investment of time and money, thus their results need to be retained, or else it can pose a big problem for the dentist and an unhappy situation for the patient.
Thus, let us look at the causes of relapse in orthodontic treatment:
1. Incomplete Orthodontic Treatment
The first and foremost reason for relapse is full orthodontic treatment not completed. The reason for this common phenomenon is that at the beginning of the treatment patients are very enthusiastic about the whole concept of treatment but as time goes by the very same enthusiasm wanes and they want their braces out for reasons like a sudden weeding in the family, change in location due to the prospects of a new job et al. if the full course of the treatment is not completed then failure is obvious.
2. Failure to Correct Cause of Malocclusion
Let’s consider a apertognathism patient – if the causative factor is not removed, then the chances of failure is high. Thus, before starting such cases the dentist must factor in tasks like molar intrusion to retain the closed bite. In case of a deep bite, it must be found out before treatment if the patient has habits like thumb sucking or tongue thrusting. This would eliminate the etiological factors and help in long term.
3. Lack of Monitoring and Follow Ups
This is a very important task to be carried out in all patients who are growers. For example, vertical growers for whom excessive growth tendencies and continuous eruption of posterior teeth pose a problem and ruin the result given to the patient. In these patients open bites are retained by high pull headgears to upper molars or use of bite block appliances like posterior bite planes that stretch the musculature and produce intrinsic forces on dentition.
4. Final Occlusal Setting Not Done Post Alignment
Sometimes, settling of occlusion is needed to eliminate small occlusal gaps between upper and lower teeth and achieve maximum intercuspation. This is done using red elastics between upper and lower teeth to encompass the whole gap. A very flexible wire like 014 NITI can be used in this case as it brings the required flexibility.
The elastics can be used by the patient himself; with an elastic lasting for a day or two. Usually 5-6 weeks are given to close these gaps using red elastics to bring about the settling of occlusion. The centric relation and occlusion should coincide or the slide from centric relation to centric occlusion should not be more than 1.5-2mm in order to prevent relapse.
Presence of habits like clenching, bruxism, nail biting, lip biting, are important part of relapse. Thus, the dentist must aim for a very stable intercuspation when the jaws are closed and for harmonious occlusal contacts during functional movements of the teeth and jaws.
5. Poor Patient Compliance
If the patient misses appointments and is not serious about treatment, then the proper treatment can’t be given. Moreover, there are a lot of unwanted movements of teeth which again change the original treatment plan. This is of particular importance in the growing patient. Follow ups are very important to study the eruption of second and third molars to see if their eruption can bring about any changes to the original treatment plan.
6. Lack of Adequate periods of Rest
Many a times, patients are in such a hurry to complete orthodontic treatment that they keep pressurizing the dentist to complete the treatment as soon as possible. Contrary to this, adequate periods of rest must be given during the treatment to allow the periodontal ligament to reorganise and for the alveolar bone to adapt so that new fibres are formed. Thus, when braces are removed the relapse occurs.
Retainers are classified into 2 types: Fixed and Removable
Removable Retainer
Let us first discuss Hawley’s retainer. It is one of the oldest retainers used in orthodontics,. designed by Charles Hawley’s in 1920. It consists of Adam’s clasps on the first molars and a short labial bow extending from canine to canine having adjustment loops. The Adam’s class on first molars aid in retaining the appliance.
Fabrication involves traditional debonding of the fixed orthodontic appliance followed by impressions that are poured into quick setting stone and sent to the ortho lab for processing and then delivered to the patient. Adjustments are usually minimal.
Fixed Retainer (Lingual Bonded Retainer)
The technique for fabrication of fixed retainer is as follows:
The patient is comfortably seated in the dental chair. The lingual surfaces of the teeth are thoroughly scaled and polished. Use of rubber dam is advised. Interproximal wedges are placed in the embrasures areas to prevent excess composite resin from flowing interproximally and creating a cervical overhang.
The bite is checked with articulating paper, both in centric and excursive movement. Accordingly, the lingual surface of the enamel is etched with 37 percent phosphoric acid. Which is then washed with a gentle stream of water, following which a bonding agent is lingually applied.
This is then cured, following which a multi-stranded wire which is adapted on to the lingual surfaces of the teeth, taking into account the patients bite. On one end of the wire, light cured composite is placed and cured. Moving on to the next tooth, the wire is adapted further, and composite is placed extremely close to the wire and tooth, and then cured.
This is done from canine to canine in both the arches. The composite is then finished and polished. Any sharp end of the wire is cut to avoid any irritation to the patient’s tongue and surrounding soft tissues. Bite is rechecked to prevent any interference during centric relation and excursive movements. The braces can now be removed and the labial surfaces are freed of any remnants of previously used composites. Post – Ortho procedures can be carried out thus.
Instead of a multi-stranded wire, Interlig can also be used to create a lingual bonded retainer. Interlig is a braided glass fibre impregnated with light cure composite resin. It is easy to cut (special scissors are not required) It has high flexural strength and since it is pre- impregnated, it is ready to use and saves time and material. It is also malleable and easy to adjust.
Techniques:
Use of rubber dam is mandatory for isolation. In orthodontics we would like the splint to last for a long time. Thus, we start by making horizontal grooves on the lingual surfaces of the teeth involved. This is to provide room for the fibre resulting in a thinner splint, which is more comfortable. The groove must be restricted to enamel with a depth of around one mm. This is to ensure maximum bonding strength.
Now, place wedges in the interproximal areas to avoid cervical over hang and maintain embrasures. Use dental floss to measure the length of interlig that will be needed. After that, any normal scissor can be used to cut the fibre. Etch teeth with 37 percent phosphoric acid for 30 seconds following which wash the teeth for one minute and air dry gently.
Next, apply bonding agent and cure. A layer of flowable resin is used to provide better adaptation of fibre. After the insertion of the fibre, each segment is cured for 20 seconds. A layer of hybrid or micro-hybrid must cover the full length of the fibre. Do not expose the fibre to the oral environment, like blood or saliva, because interlig can absorb liquids and its properties can be impaired. Finish and polish the composite resin all over as for the multi-stranded wire and proceed with post ortho procedures.
Fabrication of bonded lingual retainer using a seated template:
In the past stainless steel or blue elgiloy wire was adapted to the lingual surfaces of the anterior teeth. The technique followed by dentists was thus: post ortho procedures were carried out and the orthodontic appliance was completely debonded first. A cast was then poured from impressions made of the same patient.
The labial and lingual surfaces of the teeth in the patient’s mouth were then thoroughly scaled and polished. The stainless steel or elgiloy wire was then adapted to the lingual surfaces of the teeth from canine to canine. The retainer wire was then stabilised on the cast of the patient with water soluble adhesive.
An impression was then made from the cast with the wire in place firmly held by the adhesive. Material used for this case was a rubber based heavy body. Thus, a seating template was created. The seating template was used to position the retainer wire against the lingual surfaces of the teeth. Using light cured composite resin, the wire was bonded at both the ends.
Essix Retainer:
Introduction: Essix retainers are transparent and cover the entire arch of the teeth because they are uniquely moulded to the shape of the patients’ teeth. Since they are relatively invisible, they are very popular among patients. They are made using clear plastic. They may also be called overlay retainers because they fully cover the teeth and even some of the surrounding gum tissues. They were first introduced in the early 1970’s.
Construction: An impression is made from the patient’s teeth following routine post ortho debonding procedures. The impression is poured into a plaster cast. A thin sheet of plastic (0.030 inch) is heated and using a vacuum unit is sucked down over the cast. The finished appliance is trimmed away and given to the patient.
Usage: These essix retainers look very similar to invisalign aligners but instead of replacements every few weeks like invisalign or clear path, they are to be worn indefinitely.
Advantages and disadvantages: High patient compliance because of clear appearance. They are easy to use and very comfortable. Maintaining oral hygiene is very easy with essix retainers, provided the patient removes the retainer and maintains oral hygiene.
Some patients consume too many carbonated and fizzy drinks and put the retainer on without washing the teeth. This exponentially increase the bad effects of these carbonated soft drinks and may promote tooth decay. The same is true with sugary rinks and junk food. Since the teeth are snugly covered by the retainers, it acts as a haven for bacteria, thus creating a problem for patients. Hence, optimum oral hygiene is mandatory if the patient wishes to use these retainers.
Over a period of time these retainers will wear, thus the patient will need another set of retainers. These retainers are to be worn a lifetime if the patient wants to maintain his smile.
These retainers are very popular among invisalign patients. In fact, invisalign Inc. makes essix retainers under the brand name vivera retainers.
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