Fixed Retention

INTRODUCTION

It has been shown by a number of long-term studies that following a course of orthodontic treatment, relapse occurs in approximately 70% of cases. Some of this will be due to orthodontic relapse, and some will be due to normal changes with time, such as continued facial growth.

Posttreatment relapse is perhaps the most common risk of orthodontic treatment, and planning for postretention stability should be part of the initial treatment plan and discussed with the patient during the informed consent process before treatment, so that any relapse is not a disappointment for either the clinician or patient.

Reasons such as initial spacing, severe rotations, periodontal involvement, or the inclination of the lower labial segment have been proposed as influencing the choice of retainer.

Vacuum formed retainers (VFRs) are relatively inexpensive and can be quickly fabricated on the same day as appliance removal. They are the retainers most commonly used by orthodontists in the UK and Ireland and are also becoming more popular in the USA. VFRs are discreet and are well accepted by patients from an aesthetic and comfort perspective.There is also evidence that VFRs are more cost-effective and better at retaining the alignment of the anterior teeth than Hawley-type retainers although the sizes of the differences are small. They can be modified to produce minor active tooth movements if required and prosthetic teeth can be incorporated in cases with hypodontia. Full posterior occlusal coverage, including the most distal molars, is advisable in order to reduce the risk of over-eruption of these teeth during retention. It is important to remind patients not to eat or drink with the vacuum formed retainers in place. This is a particular concern if the patient drinks cariogenic drinks with the retainer in situ.

These types of retainers are robust and, unlike VFRs, Begg and Hawley retainers can be worn when eating without becoming damaged. Hawley retainers (Fig. 5) have the advantage of facilitating posterior occlusal settling during retention. However this is of less importance if good posterior intercuspation has been established by the time of appliance removal. The labial bow can be modified to accomplish simple active tooth movements if required and an anterior bite plane can be incorporated to help retain corrected deep overbites.

There are several designs of fixed retainer. A multi-strand wire bonded to all six anterior teeth or a sandblasted round stainless steel wire bonded only to the canines is the most commonly used . Fixed retainers are discreet and reduce the demands on patient compliance. However, they are associated with a significant long-term failure rate. One study reported that a third of patients experienced retainer failure within 30 months15 with de-bonding from at least one tooth in 22% of patients, and 17% having total retainer loss. Fracture of the retainer wire was uncommon, with less than 1% of patients having this type of failure. Particular care is required when placing upper bonded retainers to minimise occlusal contacts with the opposing lower teeth as such contacts have been shown to increase failure rates. A composite with high filler content is preferred to improve resistance to wear.

Conclusion The degree of relapse that is likely to occur following a course of fixed appliance therapy is unlikely to be affected by the choice of retainer, vacuum-formed or Hawley. Therefore, when deciding on the type of retainer to be fitted following fixed appliance therapy, other factors such as cost may play a more significant role.

Results The findings of this investigation support those of most previous studies, which demonstrate that relapse in the lower labial segment occurs even with a fixed retainer in place

Conclusion

  • Relapse as measured by Little’s index can occur in the lower labial segment with both bonded and modified Hawley retainers.
  • There is no statistically significant difference in the relapse seen in the lower labial segment teeth with either bonded or modified Hawley removable appliances.

This study demonstrated once again, that even with bonded retainers in place, relapse still occurs; the study results support the finding of previous studies. This suggests that either deformation of the

stainless steel multistrand wire allows some tooth movement or that the wire was not passive whenplaced. The thickness of the bonded retainer wire may have influenced relapse. A review of the literature by Bearn  recommended the use of 0.0215-inch multistrand wire instead of the 0.0175-inch wire used in this study. More rigid, larger diameter wires will increase the force required for permanent deformation and hence possibly reduce relapse, although this is not always supported by the evidence

Some relapse is likely after fixed appliance therapy irrespective of retainer choice, and this is minimal in most patients at 6 months after debond.

Bonded retainers have a better ability to hold the mandibular incisor alignment in the first 6 months after treatment than do vacuum-formed retainers.

  1. Fabricate digital model.
  2. Make sure all plaque and calculus is removed
  3. Place rubber dam. Adapt the lingual wire passively to the lingual surfaces of the teeth to be bonded. Wire diameter should be .0195" or .0215". Cut the wire to the required length.  Pumice/air abrade the lingual surface of all teeth to be included in the retainer.
  4. Check the position of the retainer wire in the mouth, and adjust if necessary. Due to unintentional wear of stone during wire adaptation, the fit may be good on the working model, but inaccurate in the mouth.
  5. Etch surfaces to be bonded with 37% phosphoric acid for one minute. Rinse and dry completely. The use of sealant is not necessary on lingual surfaces.

  6. The retainer wire, adjusted to fit the lingual contour entirely passively, may be held in place with very light elastics or > dental floss, steel ligatures, wax, a compound index, or acrylic stabilizers outside the retainer wire, or hand held while the retainer is bonded in a two-step procedure:
    >.  Tacking >  Tack the wire to one tooth with a small amount flowable composite. Check the passiveness of the wire, and then tack another tooth in a similar manner. This initial tacking is vital for strength. Since the wire cannot now be displaced, the bulk of adhesive can be added with totally undisturbed setting.
    >> Bond retainer wire to all teeth with medium filled composite resin.
  7. Check with a mouth mirror that enough adhesive is used. Add more adhesive when required.
  8. Trim along gingival margin and contour bulk with a No. 7006 latch-type oval tungsten carbide bur. This bur is ideal for optimum contouring of the adhesive , and excellent on the lingual surfaces at the time of retainer debonding. A smaller, oval bur (No. 2) and a tapered tungsten carbide fissure bur (No. 1172) may be used to supplement the oval bur for finishing.
  9. Instruct the patient in proper oral hygiene and the use of dental floss with a floss threader.

3 Pearls

  • discussion of short Hawley labial bow crossing at upper 3/4 may disrupt occlusion. Versus long bow soldered to Adams clasps on 6 with no crossing the 3 or 4
  • for high canines that want to vertically re intrude post treatment, I put the Hawley loop opposite upper 4 not upper 3-then I place a composite blob on buccal of 3 and place wire gingival to that-this stops the upper 3 from re-intruding
  • Another problem with Hawley retainer is patient clicks it in and out and wire breaks (-in practice at retainer delivery I have the kid break a paper clip by flexing it. Then I told them extra $ to repair, so don’t click retainer)

Conclusions

 Long-term age changes in skeletal and soft tissues surrounding the teeth mean that relapse after orthodontic treatment is unpredictable, but likely.

• As it is difficult to predict which cases will relapse, every case should be treated on the basis that it has the potential to relapse and long-term or life-long retention may be required.
• Patients should only proceed with orthodontic treatment if they are prepared to wear retainers.
• Removable retainers allow the patient to remove them to maintain oral hygiene, but their success depends on long-term compliance.
• In some situations, bonded retainers are required as full-time retention is necessary. The patient must maintain excellent oral hygiene around the bonded retainers to reduce the chance of dental disease. *I like ti make a VFR or Hawley to combine with FBRs.

• The GDP has important roles in orthodontic retention. These include informing patients that they will need to wear retainers after orthodontic treatment; motivating patients to continue wearing their retainers during the retention period; monitoring and if necessary replacing or repairing retainers; and liaising with the orthodontist as required.

• There remains a need for further randomised clinical trials to evaluate the use of different types of retainers and retention protocols.

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