Comparative study of removable & fixed orthodontic appliance

Department of OrthodonticsNorth Bengal Dental College & Hospital

Comparative study of Removable & Fixed Orthodontic Appliances

Why Orthodontics?

•Psychological implications of malocclusions which hampers the facial appearance causing low self –esteem and restricted social activities of the patient.

•Problems with clarity and articulation of speech.

•Difficulty in mastication due to certain malocclusions.

•Inability to keep lips closed which causes discomfort to the patient.

•Pain in the lower anterior teeth or palate in severe deep bite.

•Hypersensitivity of teeth and anterior teeth getting worn down.

•Pain in the TMJ.

Orthodontic treatment aims at improving the aesthetics and function of the oro-facial region.

Aims of Orthodontic Treatment

Jackson’s Triad

Functional Efficiency

Structural Balance Aesthetic Harmony

Most of these changes are brought about by using devices that move teeth or modify the growth of jaws, these devices are called Orthodontic Appliances.

Orthodontic appliances are devices by means of which mild pressure may be applied to a group of teeth and their supporting structures so as to bring about necessary changes within the bone, which will allow tooth movement.

Orthodontic Appliances

Classification of Orthodontic Appliances

Removable appliances as the name suggests are appliances which can be inserted into and removed from the oral cavity by the patient at will.

Removable Appliances

Fixed appliances are those that are fitted onto the tooth surface and can only be removed by the operator.

Fixed Appliances

Components of Removable Appliances

Retentive components- various types of clasps

Active components- bows, springs, retractors, screws.

Base plate- acrylic part.

Active components- arch wires, springs, elastics, separators.

Passive components- bands, brackets, buccal tubes, lingual attachments, lock pins, ligature wires

Components of Fixed Appliances

Easy to construct and manage, requires minimum chair side time.

Needs less inventory, relatively less expensive than fixed appliances.

The removable nature of appliance makes it possible for the patient to maintain good oral hygiene, minimum food debris accumulation.

Patient can wear without fear, if trauma occurs the patient has the freedom to remove it (damaged appliances the apply undesirable forces can be removed by the patient)

Advantages of Removable Appliances

Most malocclusions requiring tipping type of tooth movement can be readily carried out using removable appliances.

Lesser forces are required than those needed for bodily tooth movement. Hence, strain on the anchor teeth is lesser than in fixed appliance therapy.

Type of Tooth Movement

Patient cooperation is dispensed, the orthodontist does not have to depend on the patient for timely wear and management of the appliance.

Multiple tooth movements are possible simultaneously. Therefore, treatment duration is considerably reduced.

More precise tooth movements and detailing of occlusion is possible using fixed appliances.

Fixed appliances offer better control over anchorage.

Advantages of Fixed Appliance

Unlike the removable appliances it is possible to bring about various types of tooth movements such as bodily tooth movement, rotation, intrusion, extrusion and even possible simultaneously in the same treatment.

Type of Tooth Movement

Removable appliances work by applying a single force onto the crown of the teeth. Thus, removable appliance acts by tipping the tooth around its centre of resistance.

Tipping can be brought about in mesio-distal or bucco-lingual direction.

Removable appliances are generally ineffective in bringing about bodily translation, derotation and uprighting of teeth due to single point of contact of the appliance.

Action of Removable Appliances

Bodily movement- implies an equal movement of both crown as well as the root in the same direction.

Action of fixed Appliance

Tipping – the crown moves in the direction of force around a fulcrum in the apical region of the root, the root apex moves in the opposite direction

Torquing- implies root movement in the labial or lingual direction.

Uprighting- the crown of certain teeth will be tipped in the mesio-distal direction and the roots tipped in the opposite direction

Rotation- displacement of the body, produced by a couple, characterized by centre of rotation coinciding with the centre of resistance that is movement of point of tooth along the area of circle with centre of resistance being the centre of the circle.

Intrusion and Extrusion- it refers to the vertical movements of teeth along their long axis

The major limitation of removable appliances is that they are capable of only tipping tooth movement (uncontrolled tipping).

Patient cooperation is vitally important for the success of the treatment. It can only be used when less than 4.5 mm of tooth movement is required.

Multiple tooth movement correction should b e carried out 1 at a time, therefore, treatment duration is prolonged.

In cases of extraction, residual space closure by forward movement of posterior teeth is very difficult.

Disadvantages of Removable Appliances

The most important disadvantage is oral hygiene maintenance becomes very difficult (Plaque and food debris tend to accumulate around the attachments).

Fixed appliances are time consuming, they take up more chair side time unlike removable appliances.

Unless modern tooth colored appliances are used, they are unaesthetical.

They require lot of special skill and training of the operator. Otherwise there is a greater possibility of producing adverse tooth movements.

Fixed appliances are by far more expensive than removable.

Disadvantage of Fixed Appliances

Comparative Analysis

Correction of mild to moderate crowding.

Correction of anterior cross bite.Correction of posterior cross bite .

Correction of deep bite.

Scope of Removable Appliances

Arch expansion

Correction of anterior crossbite

Correction of posterior crossbite

Correction of flared incisors

Other uses for removable appliances

Growth modification

Correction of oral habits Correction of habits such as:

1. Thumb sucking

2. Mouth breathing

3. Toungue thrusting

Use of an anterior bite block which will allow the passive erruption of the posterior teeth to an extent causing the correction of deep bite

Deep bite correction

Case Study

Before Treatment

Removable appliances may cause inappropriate results if used alone.

The upper first premolars have been extracted and the overjet reduced by tipping the teeth. Since tipping alone is not sufficient in this case the result is poor.

The upper model shows the compromised result produced by use of a removable appliance alone

Inappropriate use of a removable appliance has simply converted a Class II division 1 maloccusion in an unaesthetic and unappealing result due to torque limitation. In other words, even though removable appliances have varied scope in orthodontics but it may require an adjunctive use with fixed appliance for a number of purposes.

Post Treatment

In total Removable appliances can be used for all comprehensive orthodontic treatment but due to its certain short comings or side effects they are now rarely used in expense of fixed appliances.

The main difference between the removable appliances and fixed appliances lies in their mode of action.

Removable appliances work by simple tipping movements of the crowns of the teeth about a fulcrum close to the middle of the tooth. They differ from fixed appliances, which are capable of complex movements of multiple teeth, including bodily movement, torque and rotation.

Conclusion

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