The 20 Principles of the Alexander Discipline, Volume 2. R.G. "Wick" Alexander

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СКАЧАТЬ result was a “collapse” of the anterior section of the mandibular arch (Fig 1c). Was this collapse a result of the mandibular lateral incisors’ eruption causing the exfoliation of the canines? Or were these teeth extracted to gain temporary space, allowing the lateral incisors to erupt? This is a question we could not answer.

      Although there are exceptions to every rule, my clinical advice is to not extract mandibular primary canines to make space for the incisors. Keep them as long as possible because they maintain the intercanine width and the alveolar bone in this region.

      Examination and diagnosis

      In observing the panoramic radiograph, it was noted that the mandibular left second premolar was congenitally missing. The root development from the other unerupted permanent teeth was slow, which meant treatment time would perhaps take longer because these teeth require more time to develop.

      Cephalometrically, the patient had a significant skeletal Class II (ANB of 5 degrees) pattern with a sagittal SNMP angle of 36 degrees. This, along with her nicely shaped symphysis, tells us that we can predict good skeletal correction with a cooperative patient. The maxillary incisors were flared labially and the mandibular incisors were excessively upright due to the lack of support from the missing primary canines.

      Treatment timing

      Under normal circumstances, it would be acceptable to delay treatment until the unerupted teeth had longer roots. However, because of the protrusive maxillary incisors, it was deemed necessary to begin maxillary anterior retraction to hopefully prevent any possible trauma to these teeth.

      The most difficult decision to make in this case was the resolution of the missing mandibular second premolar. There were three options available:

      1 Nonextraction: Leave space and later place a dental implant. Although dental implants are much more common today, my general philosophy regarding missing permanent teeth is to close space orthodontically when possible. The final occlusion is acceptable and long-term stability is excellent.

      2 Extraction: Extract opposite mandibular second premolar and maxillary first premolars. Extracting three other premolars is an interesting option and very well could have allowed the case to be more stable. The only disadvantage would be the resulting concave soft tissue profile, and this is a major disadvantage.

      3 Nonextraction: Close space unilaterally. Unilateral space closure would need special mechanics to prevent the mandibular midline from shifting toward the missing left second premolar space.

      Treatment plan

      Orthopedically increase the transverse dimension through the use of a maxillary rapid palatal expander (turn once a day for 30 days) and mandibular lip bumper (wear 24 hours/day for 6 months). Sagittally, the patient will wear a cervical facebow (8–10 hours/day).

      Use special mechanics to close space unilaterally: After maxillary expansion, brackets and archwires were placed on the maxillary four anterior teeth to improve arch form. During this time, the lip bumper improved the anterior mandibular arch dramatically. Between pretreatment and posttreatment, the anterior teeth have moved labially into normal positions and the intercanine width has expanded significantly. However, these positions are only temporary.

Fig 1 (a) Pretreatment profile. (b and c) Pretreatment occlusal views.

Fig 2 (a) Final profile. (b and c) Final occlusal views.

Fig 3 (a) Profile 14 years posttreatment. (b and c) Occlusal views 14 years posttreatment.

      Another issue to address is the fact that the lip bumper will upright the mandibular molars distally, so why use it when the plan is to move the left first molar mesially? The answer is based on the mechanics for individual tooth movement. Before attempting to move one molar mesially, the proper anchorage must be in place:

      1 The maxillary arch should have a 17 × 25 stainless steel (SS) tied-back archwire for elastic anchorage.

      2 The mandibular arch should have a 16 × 22 SS archwire with a unilateral closing loop distal to the left first premolar.

      3 After activating the closing loop by “cinching” back, a single ¼-inch, 6-oz, Class II elastic (left side only) is worn for 72 hours. The patient is then seen in 4 to 5 weeks.

      4 This sequence is repeated monthly until the space is closed. The molar will tip mesially even though it has a –6-degree bracket and reverse curve in the archwire.

      5 After the space is closed, a 17 × 25 SS archwire with reverse curve will level the arch.

      Discussion

The treatment time was relatively long (32 months), mostly due to the delayed eruption of the premolars. The final results demonstrated some excellent changes in overbite, overjet, arch forms, and especially a balanced soft tissue and skeletal correction. Her final profile (Fig 2a), frontal view, and smile fit all the criteria of a superior result.

      The unilateral closing mechanics, as described earlier, kept the dental and facial midline intact. The final occlusion (Figs 2b and 2c) demonstrated excellent results on the patient’s right side. The Class III occlusion on the left side was acceptable in this compromised occlusion. Treatment brought about dramatic positive changes in the arch forms.

      Cephalometrically, the orthopedic and dental corrections were excellent. The final panoramic radiograph demonstrated good root positioning, except in the mandibular incisor region.

      Evaluation

      The patient returned to our office 14 years posttreatment (11 years postretention) concerned about her crowded mandibular anterior teeth. A new set of diagnostic records was taken to evaluate her condition and compare with her previous records. She was 26 years 8 months old.

The good news was that (1) the patient’s soft tissue profile (Fig 3a), frontal view, and smile had excellent long-term results; (2) the overbite, overjet, and buccal occlusion were very stable; and (3) the maxillary arch form had slightly changed toward a more V-shaped arch (Fig 3b). However, the bad news was that the mandibular anterior teeth had collapsed (Fig 3c), resulting from tipping and crowding of the incisors and constriction of the intercanine width.

      But why did this СКАЧАТЬ