Simplified Upper Molar Intrusion With Modified Interim Goshgarian-Type Palatal Arch
Hyperdivergent skeletal class III malocclusions with a combination of maxillary retrognathism and mandibular prognathism pose an orthodontic-orthognathic challenge to the clinician. In such cases, banding of the second molars is usually deferred till the late phases of presurgical orthodontic decompensation to prevent further hinge opening of the mandible and consequent lengthening of the lower face. However, in severe class III cases with a prolonged preparatory presurgical orthodontic phase, overeruption of upper second molars may result in marginal ridge discrepancies in the vertical plane between the upper first and second molars. Such occlusal interferences pose a hindrance in setting the desired postsurgical occlusion with at least three-point contact during model surgery. This article describes a modified interim Goshgarian-type Palatal Arch (MIGPA) which is simple to fabricate and may be effectively used to intrude overerupted molars during orthodontic treatment.
The palatal arch was fabricated using a rigid 0. 036" stainless steel wire with a distally oriented single central round loop parallel to the long axis of first molars. Two sections of 0. 038” stainless steel wire ending into J-hooks (in line with the second molars to be intruded) were soldered on either side of the central loop. A 3-mm-long NiTi closed coil spring (150 g; GAC Inc) was used to apply a force of 100g on right side and a closed elastic power chain (Rocky Mountain Orthodontics Inc, Denver, CO) applied a force of 80g on the left side. The chain was made taut by twisting and was further secured by a building up the mesiolingual cusp with composite resin to prevent its slippage. Since in this case, the degree of intrusion required on either side wasn’t similar, the amount and method of force application used on the right and left side was different.
To effectively control the direction of tooth movement, bilateral J hooks were used to apply force parallel to the tooth’s long axis. Towards the completion of intrusion, a step-up bend with palatal root torque was placed in the sectional wire on the buccal aspect, mesial to second molars to eliminate rotational moments. Various complex and invasive modalities adopted for the correction of overerupted molars include corticotomy with use of repelling rare-earth magnets, miniscrews, onplants, zygomatic wires and skeletal anchorage.
Significant grinding of an overerupted tooth usually necessitates the ensuing need of endodontic treatment. The modified palatal arch precludes the need for above mentioned expensive and cumbersome appliances, and offers advantages of ease of fabrication with simple mechanics. Combination of a buccal fixed appliance and MIGPA helps provide a balanced force system for effective intrusion of molar.
The MIGPA is a simple, non-invasive and inexpensive appliance which can be successfully used to intrude supra erupted maxillary molars, at the same time providing the benefits of patient comfort and reduced chairside time.
