Orthodontic Retainers

Abstract

One of the most challenging phase for an orthodontist is to retain the corrections achieved during the course of orthodontic treatment. Retainers are passive orthodontic appliances that help in maintaining and stabilizing the position of teeth long enough to permit reorganization of supporting structures after the active phase of orthodontic therapy. This article provides a comprehensive review about the various types of orthodontic retainers available today.

Keywords: Orthodontic retainers, Removable retainers, Bonded retainers, Essix retainers.

INTRODUCTION

Retention is the phase of orthodontic treatment which maintains the teeth in their orthodontically corrected positions following the cessation of active orthodontic tooth movement. If teeth are not maintained in its new position it tends to “relapse”. The major causes of relapse after orthodontic treatment include the • Elasticity of gingival fibers • Cheek/lip/tongue pressures, • Jaw growth. • Gingival fibers and soft tissue pressures are especially potent in the first few months after treatment ends, before PDL reorganization has been completed. • Unfavourable growth is the major contributor to changes in occlusal relationships1. Orthodontic retainers resist the tendency of teeth to return to their pre-treatment positions under the influence of periodontal, occlusal and soft tissue forces, and continuing dentofacial growth.

HISTORY

Knierim2 in the year 1973 reported the use of direct bonding fixed retainers. In 1977, Zachrisson stated the importance of using multistranded wires for constructing the bonded retainers. Later in 1982, Artun and Zachrisson3 introduced a clinical technique of bonding retainer from canine to canine. Soon after Zachrison stressed the importance of using multistranded wires for bonding due to its increased mechanical retention and flexibility4,5,6.

FACTORS WHICH MAY MODIFY THE RETENTION PROTOCOL

1. Corrected rotations of anterior teeth7.
2. Lower incisor alignment8.
3. Changes in the antero-posterior lower incisor position9.
4. Correction of deep overbite9.
5. Patients with a history of periodontal disease or root resorption9.
6. Correction of anterior open bites9.
7. Growth modification treatment10.
8. Correction of posterior and anterior crossbites14.
9. Adult Patients11.
10. Spaced dentitions12.

GRABERS CRITERIA FOR IDEAL RETAINER

• Should retain all teeth that have been moved into desired positions.
• Should permit normal functional forces to act freely on the dentition.
• Should be self‐cleansing.
• Should permit oral hygiene maintenance.
• Should be strong enough to bear the rigors of day‐to‐day usage.

REMOVABLE RETAINERS

Removable retainers are the most common retainers because they are patient friendly and can be removed and reinserted by the patient.

1.Hawley’s Retainer

This retainer was designed in 1920 by Charles Hawley. It is by far the most frequently used retainer till date. It Consists of claps on molars and a short labial bow extending from canine to canine having adjustment loops13.

2.Begg’s retainer

Consists of a labial wire that extends till the last erupted molar and curves around it to get embeded in acrylic that spans the palate. Advantage: There is no cross over wire that extends between the canine and premolar thereby eliminating the risk of space opening14.

3.Clip – on retainer / spring aligner

This appliance is made of a wire frame work that runs labially over the incisors and then passes b/w the canine and premolar and is reserved to lie over the lingual surface. Both the labial as well as lingual segments are embedded in a strip of clear acrylic. It brings about corrections of rotations commonly seen in lower anterior region15.

4.Wrap around retainer

It is a type of spring aligner. It consists of wire that passes along the labial as well as lingual surfaces of all erupted teeth which is embedded in a strip of acrylic. It helps in stabilizing a periodontally weak dentition15.

5.Kesling tooth positioner

It is made of thermoplastic rubber like material that spans the inter – occlusal space and covers the clinical crowns of the upper and lower teeth and a small portion of the gingiva. It needs no activation at regular intervals and is durable17.

Drawbacks: - difficulty in speech - risk of TMJ problems.

6.Invisible retainers

Fully cover the clinical crowns and a part of the gingival tissue. It is made of ultra thin transparent thermoplastic sheets using a Biostar machine. It is esthetic and highly popular due to its invisible form18.

7.Crozat retainer

A 4-4 Crozat appliance has cribs on the first bicuspids, recurved double lapping lingual finger springs and a labial bow. Advantages are firm retention, labiolingual control of anterior teeth, flexible, maintenance of adequate oral hygiene, because it is removable and esthetic. The major disadvantages of the appliance are: It is cost effective and it is breakable19 .

8.Vander linden retainer

The Vander linden retainer is constructed to offer complete control over the maxillary anterior teeth, with firm fixation provided by clasps on the canines. This retainer does not usually interfere with the occlusion20.

9.Kansals Retainer

It is a removable tooth borne orthodontic retainer which has acrylic and wire components. The wire components include modified labial bow,Kansals bow and pin head clasps. The main advantage of this retainer is that it is less bulky, low food accumulation and easy to clean21.

10.Osamu Invisible Retainer

It is a retainer made up of thin thermoplastic sheets.They extend from the clinical crowns of the teeth to the part of the adjacent gingiva22.

ADVANTAGES OF REMOVABLE APPLIANCE

• It is removable
• Effective for simple malocclusions
• Smaller anchorage requirement
• Uncompromised oral hygiene
• Short chair side time
• Ease of adjustment.
• Less professional training for management.

DISADVANTAGES OF REMOVABLE APPLIANCES

• Dependant on patient compliance
• Unable to perform complex malocclusion
• Difficulty in speech
• Prone to breakage and loss

FIXED RETAINERS

Fixed retainers are a type of invisible retainers which are either banded or bonded to the lingual surface of the teeth,hence it is not visible to the naked eye.It is indicated where prolonged retention is required and involves miminal or no patient cooperation.They are fixed to the teeth and hence cannot be removed by the patient.

1.Band and spur retainers

It is indicated where a single tooth has been orthodontically treated for rotation correction or labiolingual displacement. The tooth that has been moved banded and spurs are soldered onto the bands so as to overlap the adjacent teeth.

2.Banded canine to canine retainer

It is commonly used in lower anterior region.Canines are banded and a thick wire is contoured over the lingual aspects and soldered to canine bands.

3.Bonded lingual retainers

They are bonded on lingual aspects following anterior curvature. The ends are curved over the canines where it is bonded [23].

ADVANTAGES OF FIXED RETAINER

• Reduced need for patient co-operation
• Can be used when conventional retainers cannot provide same degree of stability.
• Bonded retainers are more esthetics
• No tissue irritation unlike what may been seen in tissue bearing areas of Hawley’s retainer
• Can be used for permanent and semi permanent retention.
• Do not affect speech.

DISADVANTAGES OF FIXED RETAINERS

• More cumbersome to insert
• Increased chair side time
• More expensive
• Loss of healthy tooth material
• Tend to discolour

CONCLUSION

Retention forms an integral part of orthodontic treatment. Compared to removable retainers,fixed retainers have shown to have better treatment stability. However more clinical trials have to be carried out to prove the efficiency of both removable and fixed retainers.

REFERENCES