Class III subdivision malocclusion corrected with asymmetric intermaxillary elastics

Patient compliance in using asymmetric Class III elastics was crucial for success. The effects of Class III elastics caused a small maxillary protrusion, and
the mandible had a small retrusion, probably consequent to the backward and downward rotation that this apical base experiences when Class III elastics are used11,16,22 (Table). These changes in the apical anteroposterior position contributed to the improvement in their relationship. Accordingly, concomitant increases in the growth pattern angles were observed, with the exception of the occlusal plane angle to SN. However, these are also  expected changes with Class III elastics. 7,11,16,18,22 The occlusal plane experienced a small counterclockwise rotation under the influence of the Class III elastics; this is a normal result from these elastics.11,16,23-25 The maxillary incisors were labially tipped and protruded, and the mandibular incisors were 
lingually tipped and retruded. The vertical component of the elastics produced small extrusions of the maxillary molars and mandibular incisors. As a consequence of these skeletal and dentoalveolar changes, there was a decrease in the nasolabial angle, protrusion of the upper lip, and retrusion of the lower lip, significantly improving his facial profile (Table, Figs 5-8).
If the patient’s compliance had not been good in using the elastics, another option would have been to extract the mandibular left first premolar.  According to Class III subdivision malocclusion characteristics, with the maxillary midline coincident to the midsagittal plane and the mandibular midline deviated to the right, this could be considered the best choice to correct the midline deviation and the occlusal discrepancy.1 However, this would not be a favorable treatment alternative for the desired soft-tissue changes because the anterior crossbite would be corrected by retraction of the mandibular incisors with little or no protrusion of the maxillary incisors; this would cause less improvement in the facial profile than the nonextraction alternative. On the other hand, it could be argued that the use of asymmetric Class III elastics could deviate the maxillary midline to the right as an unfavorable side effect. Yes, this  could be possible, but in choosing between these 2  treatment options one must select the protocol that will fulfill most of the treatment objectives, with the fewest collateral side effects. Based on this, it was thought that the nonextraction option would provide a more favorable profile change, and that the resulting unfavorable maxillary midline deviation would be within acceptable limits. According to Johnston et al,26 deviations up to 2 mm of the dental midline to the midsagittal plane can be clinically satisfactory. The final extraoral smiling photograph confirms this (Fig 5).
It has been stated that anteroposterior intermaxillary elastics produce significant vertical adverse effects.16,18,20,25,27,28 This can be true if their use is
not properly monitored. Use of the correct resistant torques in the maxillary and mandibular incisors to counteract the Class III elastic forces on these teeth is essential. In this patient, the adverse effects seem to have been well controlled, because only small extrusions of the maxillary molars and mandibular incisors were apparent (Fig 8). Inclusion of the second molars might also have helped in controlling the adverse effects of the elastics.20,27 Class III elastics especially are believed to cause counterclockwise rotation of the occlusal plane and inversion of the natural esthetic smile line.11,16 A small counterclockwise rotation of the occlusal plane occurred, but with no significant negative influence on the smile line because of proper control of its use (Figs 5 and 8). The use of Class III elastics also causes backward and downward mandibular rotation.7,11,16,25 The backward mandibular rotation is favorable for correcting a Class III malocclusion because it improves the anteroposterior discrepancy of the apical bases. In this patient, the downward rotation was acceptable because of his predominant horizontal growth pattern characteristics.11,16,25,29
Stability of the correction was addressed by using Class III elastics during 5 months of nighttime wear, after correction of the anteroposterior  iscrepancy. For this amount of asymmetric Class III anteroposterior discrepancy, it can be considered satisfactory.11 Concerns with stability in corrected Class III adults are not as critical as in growing patients because there is no adverse growth to reestablish the problem.23,30,31 Therefore, the chances are greater for stability in treated Class III adults. Nevertheless, follow-ups every 6 months are recommended for at least 2 years.11,31 Two years after treatment, the occlusal and esthetic results have remained stable, despite small cephalometric changes (Figs 9 and 10). This stability is probably
consequent to the association of the procedures described above. Cephalometrically, from posttreatment to the 2-year follow-up, there were slight labial tipping and protrusion of the maxillary incisors and mandibular incisors (Fig 11, Table). Because the mandibular incisors were lingually tipped and retruded during treatment, possibly this was consequent to a small relapse tendency of the mandibular incisors to return to their original position. 
32,33 Consequently, the maxillary incisors also experienced some labial tipping through their relationship with the mandibular incisors. The occlusal
plane angle also slightly increased, showing a tendency to return to its original angulation. This might have contributed to the small relapse of the Class III apical base discrepancy evaluated by the Wits appraisal. The mild counterclockwise rotation of the mandible shows the temporary characteristic of the
mandibular rotation after treatment.34,35 However, these posttreatment cephalometric changes were small and did not compromise the occlusal and esthetic results. Treatment with intermaxillary elastics is also suspected of causing much relapse.36 This might be true if active retention is not used for a sufficient amount of time after correcting the anteroposterior Class II or Class III discrepancy. Nevertheless, this is not valid only for treatment with intermaxillary elastics but for most Class II and Class III anteroposterior discrepancy correction. Class II nonextraction treatment with headgears and
removable or fixed functional appliances also needs some time of active retention to be stable.37-39 Therefore, it seems that it is not the orthodontic
appliance or device that determines treatment stability but the way it is used and especially if enough active retention time was used before the patient was finished. Therefore, the stability obtained in this patient, treated with asymmetric Class III intermaxillary elastics, seems to illustrate this principle.
Evidently, An orthodontic-surgical approach could have produced greater skeletal correction of the Class III discrepancy, but the treatment should aim to solve the patient’s primary concern.7,8,40 Because this patient’s concern was primarily his dental appearance, the clinician obtained the most from the orthodontic mechanics available to satisfy his needs.