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Abstract

I teach at an orthodontic program. Recently, a resident presented a case that caused much discussion. The patient had a Class I skeletal relationship but a full Class II molar relationship, with no crowding in the mandible and the maxillary canines completely blocked out. Some faculty members thought the treatment should include extracting the maxillary premolars, leaving the molars in a Class II relationship. Others argued that maxillary premolar extractions should be reserved for severe overjet problems in nongrowing patients. They suggested that achieving a Class I molar relationship should always be the goal and said they would extract all 4 premolars and treat the mandibular arch with minimum anchorage. Their reasoning was that the occlusion in a Class II molar situation is so awkward that it will not stand the test of time, and the results would show significant instability over time. Is there any validity to that point of view? The issue is whether treating the patient to a Class II molar relationship provides a final occlusion that is unacceptable enough to justify extracting premolars in a presumably ideal mandibular arch to achieve a Class I molar relationship. Treating patients to a Class II molar relationship presents a number of challenges and is indeed awkward. First, rather than having distal tip and distal rotation, the maxillary molars should be upright and rotated in on the mesial in the Class II position. Upper molar brackets are not designed to provide this positioning. Therefore, 1 of 3 adjustments must be made: special Class II bracket designs must be used to provide the Class II position, custom archwire bends must be made, or normal molar bands must be placed with the brackets positioned up on the mesial and toward the distal of the crown. If 1 of these changes is not made, the final Class II molar relationship will be less than acceptable. Second, other occlusion problems must be considered when treating to a Class II molar relationship, or the occlusion might not stand the test of time because the results are unstable. The nonextraction mandibular arch often shows some proclination of the incisors, but the extraction maxillary arch might show undertorqued incisors. The result of these factors is often a lack of adequate overbite and overjet, or open extraction sites in the maxillary arch. However, with a combination of proper torque control, some interproximal reduction in the mandibular arch, and occasional bonding of the maxillary lateral incisors, these situations can often be avoided. Removing the mandibular premolars and closing the extraction sites by bringing the molars forward 7 mm is very difficult and invariably leads to some undesirable retraction of the mandibular incisors. Although there are challenges in achieving an acceptable Class II molar relationship, it would seem to pose fewer difficulties than extracting premolars in an ideal mandibular arch and attempting to bring the molars forward 7 mm to achieve a Class I molar relationship. My preference would be to remove the maxillary premolars, treat the mandibular arch nonextraction, and leave the molars in a Class II relationship. However, if this Class I patient has a Class III growth tendency, then maxillary and mandibular second premolar extractions might be indicated. This would allow for proclination of the maxillary incisors and retraction of the mandibular incisors as growth occurred. Class I occlusion a false goal?American Journal of Orthodontics and Dentofacial OrthopedicsVol. 127Issue 5PreviewThe proposition by Dr C J Ruff’s colleagues to extract teeth in an uncrowded mandible to compensate for maxillary premolar extractions, with the aim of achieving Class I molar occlusion, was interesting, but Dr McLaughlin’s thorough discussion of treatment mechanics did not directly address the issue (Ask Us. Am J Orthod Dentofacial Orthop 2004;126(1):17A). Any validity ascribed to such an approach is misconstrued because it is based on a false belief that one should always endeavour to establish “normal” Class I occlusion—a concept that has been arbitrarily determined. Full-Text PDF