Second premolar extraction: Not always a second choice.

Extraction is a recognized and widely accepted procedure in orthodontic treatment. The selection of teeth for orthodontic extraction is an important decision and they are modified according to the individual patient. This case report describes the management of 18-year old female patient with moderate crowding which was treated with second bicuspid extraction. At the end of treatment, patient had pleasing profile, good intercuspation, ideal overjet, and overbite. The occlusion remained stable even 3 years after orthodontic treatment.

Introduction

Malocclusions can involve arch-size/ tooth-size discrepancies that have to be resolved by premolar extractions. Treatment planning in such cases usually involves removing either first or second premolars. Orthodontic treatment planning is important for resolution of a malocclusion, and the orthodontist has to make a decision after careful analysis. In borderline cases, the choice of teeth to be extracted is determined by the degree of discrepancy and the amount of retraction required during treatment. In patients with mild to moderate crowding, acceptable incisor positions, and facial profiles, the second premolar would be a better choice.[12345678]

This case report describes the management of such a case with second premolar extraction who had mild crowding and proclination in upper and lower arch.

Diagnosis and etiology

An 18-year-old female patient reported to the author's private clinic with chief complaint of unesthetic appearance of her smile. Medical history and family history revealed no significant finding. The patient had a mild convex profile and symmetric face. Clinically she had a pleasing profile and normal nasolabial angle [Figure 1].

Figure 1

Pretreatment extraoral and intraoral photographs

Intraorally the patient had a Super Class I molar (SI 11) relationship and Class I canine on both sides with an overjet of 3 mm and an overbite of 2 mm with mild anterior crowding and proclination. Her lower right canine and upper right lateral incisor were in cross bite.

Cephalometric analysis indicated a skeletal Class I relationship with average growth pattern. The maxillary and mandibular incisors were mildly proclined with the normal nasolabial angle [Figure 2 and Table 1].

Figure 2

Pretreatment lateral ceph and orthopantomogram

Table 1

Cephalometric

Treatment Objectives

The treatment objectives were:

To correct proclination in both the arches

To correct canine cross bite on the right side

To relieve the crowding

To correct the dental midline

To establish a Class I molar relationship and to maintain a Class I canine relationship

To obtain ideal overjet and overbite.

To accomplish these objectives, second premolar extraction was recommended. Less space would be utilized for crowding and retraction to maintain her facial profile.

Treatment alternative involving extraction of all first premolars was not recommended since this patient had a prominent chin. Excessive retraction would create dished in appearance.

Treatment Progress

Orthodontic tooth movement is initiated with 0.022 slot MBT bracket system in both the arches. 0.016 NiTi was the initial wire, followed 0.017 × 0.025 NiTi, 0.019 × 0.025 NiTi, 0.019 × 0.025 SS. In the maxillary arch premolars and canines retracted separate followed by upper anterior retraction. In the mandibular arch, en masse retraction was carried out. Debanding was done after establishing good sagittal and intercuspal relation [Figure 3]. After removal of fixed appliance, a wrap around the retainer in the upper arch and a 4-4 lingual bonded retainer in the lower arch were placed [Figure 4].

Figure 3

Settling before debanding

Figure 4

Posttreatment extra oral and intraoral photographs

Treatment Results

Overall active treatment time was 18 months. The post treatment records showed that all the treatment objectives were achieved. The facial photographs showed drastic improvement in the profile. Super Class I molar relation was corrected to Class I. Class I canine relation is maintained. Good intercuspation was achieved. The curve of spee was leveled. Dental midlines were coinciding. Ideal overbite and overjet were established. A posttreatment panoramic radiograph showed root parallelism [Figure 5]. Cephalomeric analysis showed good incisor inclinations. Nasolabial angle improved after treatment [Table 1]. Pre- and post-treatment superimposition showed changes were mainly dental and overjet and overbite improved.[6] Patient was recalled and records were made at regular intervals of 1 year after debanding to check the stability of treatment. The occlusion remained stable even after 3 years [Figure 6].

Figure 5

Posttreatment lateral ceph and orthopantomogram

Figure 6

Three years after retention

Discussion

Choosing an extraction pattern is a skill and requires careful analysis. The indication for first and second premolar extraction is different and varies with the malocclusion.

The benefit of second premolar extraction is limited lingual migration of the mandibular anterior segment, minimal increase in the curve of spee and overbite. The maintenance of lower incisor position minimizes facial profile flattening during the reduction of an arch length deficiency malocclusion. Extraction of the second premolar is preferred in borderline cases because it helps in preserving the width/length ratio and zenith position. This will also avoid the formation of unesthetic black triangles following orthodontic treatment. Dewel,[12] Logan[3] and Nance[4] recognized the advantages of second premolar extraction and stated that the extraction of the second premolar not only aids in rapid space closure but also maintains good marginal relationship between the contact point of mandibular first molar. Schoppe[5] advocated second premolar extraction, which permits molar protraction and less incisor retraction. As this happens simultaneously extraction space closure is faster. He also suggested that if the arch length discrepancy was 7.5 mm or less when there was no indication for incisor retraction, it would be advisable to consider second rather than first premolar if teeth were to be extracted.

While addressing a group at an Angle Society Meeting, Nance said that second premolar extraction was an excellent, but often overlooked facet of orthodontic practice.[5] Salzmann[6] advocated second premolar extraction when extraction space would be utilized for tooth alignment and mesial movement of the molar. de Castro[9] stated anchorage values and soft-tissue analyses are the principal factors that dictate one's decisions concerning which teeth to extract. He considered permanent dentition, as an arrangement of three independent segments namely an anterior segment (from canines to canine) and two posterior segments (from first premolar to molars). When a second premolar is extracted in the middle of the posterior segment, only the posterior segment is affected and shortened. However, therapeutic removal of first premolars not only affects the posterior segment but also disturbs the anterior segment. Proffit[10] sought to quantify differences in incisor retraction and mesial molar movement with different extraction patterns through clinical observation. He concluded that extraction of second premolar should be considered when anchorage conservation is minimum.

Careful attention to anchorage is critical in any extraction case. Anchorage concern in this case was moderate to establish Class I molar relation. Mesialization of upper first premolar helped in achieving Class I molar relation. After initial alignment, it was important to establish Class I molar relationships and to maintain Class I canine and anterior relationships.

Good incisor inclination is also an important factor in esthetic smile. In this case, during the finishing stage, 0.019 × 0.025 reverse curve NiTi with posterior box elastic was used in the lower arch. This not only helped in settling but also controlled unwanted lingual inclination. Pre- and post-superimposition showed mainly dental changes [Figure 7]. Extraction space was utilized by both incisor retraction and molar protraction. Incisors were retracted to 5 mm in the upper arch and 4 mm in the lower arch [Table 1]. Upper and lower molars were moved 3 mm and 1.5 mesially [Table 1]. Nasolabial angle improved after the treatment. Cephalometric values showed [Table 1] there was not much change in a vertical dimension.

Figure 7

Pre- and post-treatment superimpositions (a) overall (b) maxilla, mandible

Conclusions

Careful management of the residual extraction space preserves normal lip support and facial profile. Second premolars are a good choice in borderline cases with minimal or no profile alteration and mild to moderate anterior space requirement.