Class II correction: Extraction or nonextraction?

The patient with a Class II malocclusion, proclination, or moderate crowding of the mandibular anterior teeth, and a moderate-to-low mandibular plane angle is a treatment-planning challenge. The records of 3 patients are presented. For 2 of them, extraction treatment was used to resolve the Class II malocclusion problem. Each of these patients was treated with the removal of maxillary first premolars and mandibular second premolars. The third patient was treated with Class II elastics without extractions. The clinician must weigh the pros and cons of each approach and decide which approach will give the patient the best long-term benefit.

Highlights

  • Facial balance and harmony are major goals of Class II malocclusion correction.

  • A patient with a moderate-to-low MP angle and Class II can be treated with premolar extractions.

  • Mandibular incisor proclination should not be a result of Class II correction.

The patient with a Class II malocclusion and a moderate-to-low mandibular plane angle and mandibular incisor crowding or flaring has unique and, at times, difficult problems that must be resolved. As with any orthodontic patient, the differential diagnosis requires a careful analysis of the face, skeletal pattern, and dentition so that the treatment plan and subsequent treatment will yield long-term esthetic and functional benefits.

The facial esthetics of patients must be a primary consideration for the clinician. Uprighting of the mandibular incisors can harm the facial balance of many patients who have a moderate to diminished lower anterior facial height. If this is the case, the mandibular incisors should be left in their pretreatment positions. Other patients, however, have a facial pattern that requires at least some mandibular incisor uprighting to give the face more balance and harmony. The clinician must discern the difference and plan accordingly. If patients have mandibular incisor crowding, these teeth should not be proclined to eliminate this crowding. A deep curve of Spee is an additional treatment complexity because leveling it requires space. If the curve of Spee is deep or there is mandibular incisor crowding, it is not prudent to flare the mandibular incisors to correct these problems. To flare or, conversely, to overly upright the mandibular incisors can often unfavorably impact the facial profile.

The patient with a moderate-to-low mandibular plane angle is generally a forward rotator who has diminished dentoalveolar development in the maxillary arch. Barring a surgical approach, the clinician must move the teeth to the desired position or maintain them in the pretreatment position.

When the dentition is considered, space-analysis rules are essentially the same as they are for most orthodontic patients. If the mandibular incisors of a patient with a Class II malocclusion are in a good position over basal bone, but moderately crowded or flared, maxillary first and mandibular second premolar extractions can be considered if Class II buccal-segment correction is the goal. This extraction pattern will allow the clinician to maintain the anteroposterior mandibular incisor position, align the crowded mandibular incisors or upright them if they are proclined, protract the mandibular molars, and retract flared maxillary incisors. If the mandibular second premolars are extracted, the clinician must have a command of the mechanics used to upright the roots of the teeth adjacent to the extraction sites into the sites. If the uprighting is not done properly, the extraction spaces will reopen after appliance removal.

The other issue that must be controlled by the clinician is the amount of mandibular molar protraction vs premolar and incisor retraction that will occur during mandibular space closure. If the space is to be closed primarily with molar protraction, temporary anchorage devices (TADs) can be used to minimize premolar and incisor retraction.

Another option for malocclusion correction for these patients is to distalize the entire maxillary arch while holding the mandibular dentition in its pretreatment position. If this option is selected, it is generally prudent to carefully analyze the amount of space that is available in the posterior maxillary dentition area. The maxillary third molars might need to be extracted to create space for distalization of the remaining maxillary teeth. If this option is chosen, some sort of TAD augmented anchorage or skeletal anchorage, either of which will facilitate distal movement of the maxillary teeth, can be considered. This type of anchorage will minimize the use of Class II elastics, which are generally contraindicated due to their propensity to flare the mandibular incisors.

Another viable option for many Class II patients is to treat them with removal of the maxillary first premolars and mandibular third molars—if the mandibular arch has minimal crowding, if the mandibular incisors have an acceptable inclination over basal bone, and if the curve of Spee is not excessive. This treatment plan generally requires excellent maxillary posterior anchorage because anchorage loss in the posterior part of the maxillary arch will limit retraction of the maxillary anterior teeth and result in some overjet with poor canine coupling at the end of treatment. Mandibular third molar removal, if these teeth are half to two thirds developed and immediately distal to the mandibular second molars, creates space in the posterior part of the mandibular arch so that the curve of Spee can be leveled by buccal segment uprighting rather than incisor proclination. To level the curve of Spee in this manner will require a force system to the mandibular arch that holds the anterior teeth in their pretreatment positions.

These treatment plans, as well as a nonextraction treatment plan, can all be considered to correct a patient with a moderate-angle Class II malocclusion. The plan that is chosen must depend on the malocclusion. The clinician must select a plan that is appropriate.

These clinical case reports will describe the treatment of 2 patients who were treated with removal of the maxillary first premolars and mandibular second premolars because this plan can be used to correct many moderate-to-low angle Class II malocclusions that are complicated by flared or crowded mandibular incisors and a deep curve of Spee. The patient with this type of malocclusion can receive significant facial and dental benefits if treatment with this extraction pattern is properly accomplished. The third patient, whose treatment is described was treated without premolar removal.

Patient 1

The pretreatment facial photographs of this 13-year-old girl ( Fig 1 ) show mandibular lip eversion, convexity of the facial profile, and mentalis strain. The casts confirm an Angle Class II malocclusion with a deep overbite, a full-step dental Class II relationship, a mild curve of Spee, and no crowding in the maxillary and mandibular arches. The pretreatment panoramic radiograph shows a healthy dentition; the pretreatment cephalogram and its tracing confirm a relatively low mandibular plane angle of 20°, mandibular incisors that are proclined to 105°, and an ANB angle of 7°. The profile line—a line from chin point tangent to the most prominent lip—is several millimeters in front of the nose. This profile line to nose relationship is confirmation of the relative protrusion of the lips ( Fig 2 ). Due to these problems and the desire to correct the Class II occlusion, the treatment planning process led to the conclusion that the maxillary first premolars and mandibular second premolars should be extracted. The extraction of the mandibular second premolars was done to provide space to move the mandibular molars forward and upright the mandibular incisors by a small amount so that lip protrusion could be reduced. The maxillary first premolars were extracted because the maxillary anterior teeth needed to be intruded and retracted.

Fig 1
Patient 1: pretreatment facial and cast photographs.

Fig 2
Patient 1: pretreatment panoramic radiograph, cephalogram, and tracing.

A nonextraction option for this patient was requested by the parent, who agreed with the extraction option after incisor position, facial profile considerations, and occlusal correction were explained. Mandibular incisors must be kept in their pretreatment positions or moderately uprighted if necessary.

The patient was banded and bonded with a standard edgewise appliance. The maxillary canines were retracted on an 0.018 × 0.025-in archwire with high-pull J-hook headgear. The mandibular arch was leveled with an 0.018 × 0.025-in edgewise archwire. During maxillary canine retraction, the mandibular first molars were protracted with closing loops in the extraction spaces. Molar protraction was augmented with elastomeric chain. These mandibular space closure procedures were done on a 0.020 × 0.025-in edgewise archwire that had 6.5-mm closing loops just distal to the first premolars. The tie-back that was used to open the closing loop was bent into the wire just distal to the loop. This tie-back was then ligated tightly to the first molar to open the closing loop approximately 1 mm per activation. This system used all other anterior teeth plus the premolars as anchorage units and pitted these 8 teeth against the molars. When this system is used, the clinician must carefully monitor mandibular incisor positions. Mandibular incisors must be kept in their pretreatment positions or moderately uprighted if necessary. Their positions must be carefully monitored during space closure. After the maxillary canines were retracted and the mandibular molars were protracted, the maxillary anterior teeth were retracted with a 0.020 × 0.025-in maxillary closing loop archwire with hooks soldered for J-hook headgear attachment so that the maxillary incisors could be intruded as they were being retracted. During maxillary anterior tooth retraction, the mandibular first molars were uprighted carefully with a 0.019 × 0.025-in archwire with second-order bends after the mandibular second molars had been uprighted. Mandibular space closure was maintained. During the finishing stages of treatment, maxillary and mandibular 0.020 × 0.025-in finishing archwires were used. Mild Class II elastics were worn combined with an anterior vertical elastic and high-pull J-hook headgear attached to hooks soldered to the maxillary archwire between the maxillary central and lateral incisors. Treatment time was 22 months. This archwire sequence has been described in detail because it seemed to work well for a patient who needed this type of treatment.

The posttreatment facial photographs confirm less convexity of the facial profile. Lip eversion was eliminated. The posttreatment casts confirm correction of the Class II dental relationship, opening of the deep overbite, and leveling of the curve of Spee. Arch form was maintained ( Fig 3 ). The posttreatment panoramic radiograph shows significant uprighting of the teeth into the extraction spaces. The developing third molars will probably need to be extracted. The posttreatment cephalogram and its tracing confirm maintenance of the mandibular plane angle, mild uprighting of the mandibular anterior teeth, some retraction of point A, and a favorable change in the relationship of the profile line to the lips and the nose ( Fig 4 ).

Fig 3
Patient 1: posttreatment facial and cast photographs.

Fig 4
Patient 1: posttreatment panoramic radiograph, cephalogram, and tracing.

Superimpositions were done on the cranial base using the anterior curvature of sella and cranial base structures. The superimpositions of the maxilla were made by using the curvature of the palatal plane as well as the key ridge. Mandibular superimpositions were based on the lingual curvature of the mandibular symphysis and the inferior alveolar nerve canal. Pretreatment and posttreatment superimpositions confirm mesial molar movement, mild mandibular incisor uprighting, and a positive change in the relationship of the mandible to the maxilla ( Fig 5 ).

Fig 5
Patient 1: pretreatment and posttreatment superimpositions.

The patient was recalled 4 years later. She had not worn retainers for 2 years. The facial photographs 4 years after treatment ( Fig 6 ) confirm the balance and harmony of an orthognathic face. The protrusion has been eliminated. Lip support is good, and there is no mentalis strain upon closure. The retention casts show settling of the dentition into an ideal Angle Class I dental relationship with stability of the arch form, which was not changed during treatment. It is hoped that the stability of the dentition will continue throughout her life. Yes, the teeth will experience some minor changes, but because she was treated with maintenance of the arch form and without expansion of the mandibular canines, stability should be reasonably good. The recall panoramic radiograph confirms that the third molars have been removed. The recall cephalogram and its tracing ( Fig 7 ) confirm a stable maxillomandibular relationship. The pretreatment, posttreatment, and recall cephalogram superimposition tracings ( Fig 8 ) illustrate continued favorable changes in the spacial relationship of the mandible to the maxilla.

Fig 6
Patient 1: recall facial and cast photographs.

Dec 8, 2018 | Posted by in Orthodontics | Comments Off on Class II correction: Extraction or nonextraction?
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