For four sixes, revisited

Rarely is the extraction of the four first molars the ideal choice in the course of orthodontic treatment, particularly in older patients. Although this approach can offer distinct advantages in carefully selected patients, it is also associated with a number of well-recognized problems, including the extension of treatment times, anchorage management, and control of second molars during space closure. However, by careful use of contemporary materials and techniques, a high standard of treatment can be achieved, even in patients with complex malocclusions. This is illustrated in a report of a case that highlights both the challenges and some of the solutions this treatment modality can offer.


  • Extraction of 4 first molars can be considered for carefully selected patients.

  • Well-planned treatment will add only a few months to treatment duration.

  • The patient will benefit by ending treatment with 2 premolars in each quadrant.

  • The need for dental restorations or prosthetic replacement can be avoided.

Although there has been considerable debate over the years about the use of extractions in orthodontics, the removal of permanent teeth remains an effective and predictable way to create space for the relief of crowding and to allow correction of anteroposterior discrepancies. The most frequently extracted teeth are premolars as their position in the arch allows for relief of both labial and buccal crowding and retraction of the labial segments in patients with Class II and III malocclusion.

Although there are few situations clinically when first molars are the first choice for extraction in patients as a part of orthodontic treatment, it is usually a decision reached because of the poor prognosis of one or more of the teeth. Historically this has been a result of the high incidence of caries associated with first molars. More recently with falling rates of caries, it is often because of molar incisor hypomineralisation.

There are clinical situations when the extraction of first molars might specifically help with the correction of the malocclusion, including crowding in the posterior segments (see Case Report), correction of Class III malocclusion, and treatment of anterior open bite and hyperdivergent facial form.

The case presented below illustrates how a successful outcome can be achieved even in difficult malocclusion with the extraction of first molars.

Case report

A 13-year-old male presented with a Class I incisor relationship on a mild Class II skeletal base with average Frankfort-mandibular plane angle and lower face height with mild to moderate crowding, impacted mandibular first premolars, and heavily restored mandibular right and maxillary left first molar ( Fig 1 ). The maxillary left second premolar was rotated through 180°. Radiographically all teeth were present, including the third molars, and there was evidence of secondary caries under the restoration in the mandibular right first molar ( Fig 2 ). The lateral cephalogram confirmed the clinical findings. This cephalogram was taken before the panoramic radiograph and showed a retained second primary molar that was subsequently removed by the patient’s general dentist ( Fig 3 ).

Fig 1
Patient with Class I incisor relationship on mild Class II skeletal base with average lower anterior face height, mild to moderate crowding, impacted mandibular first premolars, and heavily restored mandibular right and maxillary left first molar.

Fig 2
Panoramic radiograph. R, right; L, left.

Fig 3
Pretreatment lateral cephalogram.

Consideration was initially given to avoid extraction, using the space in the mandibular arch with an interproximal reduction to create space for the impacted mandibular first premolars. However, the mandibular second molars were distally angulated and only partially erupted, indicative of crowding in the back of the arch. In addition, the long-term prognosis of the mandibular right first molar was doubtful. It was therefore decided to treat the patient with the extraction of all four first molars. As the morphology of the buccal and palatal cusps of the maxillary left second premolar was similar, it was decided to accept the rotation.

After the extractions, a transpalatal arch with a Nance button was fitted to prevent anchorage loss, and a labial preadjusted edgewise appliance bonded. Lacebacks were placed in all four quadrants, and a closed coil was placed on the mandibular archwire across the extraction sites. A light nickel-titanium (NiTi) push coil was placed between the mandibular canines and second premolars to start creating a space for the mandibular first premolars ( Fig 4 ). The first premolars started erupting within 3 months of placing the fixed appliance. At 6 months into treatment, enough space was available, and they had erupted sufficiently to allow brackets to be placed for full alignment.

Fig 4
Initial aligning archwire 0.014-in NiTi with a palatal arch with Nance button, steel tubing to protect the wire in extraction spaces, and light push coil to open space for impacted first premolars.

After alignment, the transpalatal arch was removed, and a working 0.019 × 0.025-in stainless steel (SS) archwire was placed; space closure commenced using NiTi closing coils. Class II intermaxillary traction was run on the left side to aid in centerline correction. Final space closure was achieved in the maxillary arch using closing loops ( Fig 5 ).

Fig 5
Final space closure using space closing loops.

After the removal of the appliances, a mandibular bonded retainer was placed to maintain alignment of the lower labial segment facilitated by part-time wear of vacuum-formed retainers. To prevent space opening up in the mandibular arch, bonded retainers were placed between the mandibular second premolars and molars ( Fig 6 ). The oral panoramic radiograph taken toward the end of active treatment showed all third molars were in a good position with evidence of root development ( Fig 7 ). The near end of treatment lateral cephalogram showed that although there had been some growth, this had been mostly vertical ( Figs 8 and 9 ). The total treatment time was 26 months.

Jun 12, 2021 | Posted by in Orthodontics | Comments Off on For four sixes, revisited
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