and Severe Crowding Class I Cases

Tarek El-Bialy, Donna Galante, Sam Daher

Faculty of Medicine and Dentistry 7-020D Katz Group Centre for Pharmacy and Health Research University of Alberta, Edmonton, Alberta T6G 2E, Canada


Traditional approaches for treating severe crowded cases usually involve removal of some teeth with the intention to allow stable occlusion after the orthodontic treatment. However, in severe constricted cases, arch expansion could be the best approach to treat these cases without removal of permanent teeth. This chapter presents cases with severe teeth crowding and the possible treatment of these cases with clear aligners. This chapter presents moderate to severe crowding cases treated solely by clear aligners utilizing dental arch expansion. Also, this chapter presents diagnostic criteria for deciding expansion/non extraction or extraction approaches in detail.

Keywords: Class I, Expansion, Extraction, Interproximal, Malocclusion, Moderate crowding, Proclination, Severe crowding, Stripping, Spacing.

* Corresponding author Tarek El-Bialy: Faculty of Medicine and Dentistry 7-020D Katz Group Centre for Pharmacy and Health Research University of Alberta, Edmonton, Alberta T6G 2E, Canada; E-mail:


According to Proffit [1], moderate crowding can be considered when 2-4 mm of dental arch length discrepancy exists [1]. Cases with moderate dental crowding can be treated by different approaches including expansion, proclination in cases with reteroclined upper and /or lower incisors, interproximal reduction (IPR) or extraction in cases with severe skeletal problems like increased vertical dimension/hyperdivergent or open bite cases.

The first report about treatment of moderate crowded cases by Invisalign clear aligners was reported by Boyd, in 2000 [2]. Since then, there have been many reports about the possibility of using Invisalign or clear aligners in general to treat cases with moderate crowded teeth with variable degrees of success and satisfactory finishing [3]. In addition, Boyd has introduced a new protocol for managing complex cases with Invisalign or clear aligners [4]. The following cases with moderate dental crowding were treated solely by Invisalign clear aligners, details are as follows.

Case 1

This twelve-year old female presented to the clinic in June 2011 with chief complaint that upper right canine tooth is labially erupted with no room/space in the dental arch to accommodate its normal position (Fig. 6.1). The patient had relatively normal skeletal relationship, class I molars and canine relationships, upper crowding (4 mm), lower 1.5 mm crowding and upper and lower midlines coincident with facial midline.

Fig. (6.1))
Initial photographs of a twelve-year old female with labially erupted upper right canine tooth with upper 4 mm crowding and lower 1.5 mm crowding. Midlines are centered, right and left molars and canines are class I relationship. No Bolton discrepancy existed.

Problem List/Findings

  1. Labially erupted upper right canine (4 mm crowding)
  2. Slight lingually inclined upper and lower incisors
  3. Right side premolars are not fully interdigitated (Slight end to end relationship) can be seen in clincheck (Fig. 6.2).

Treatment Objectives

  1. Resolve upper and lower crowding
  2. Maintain midline relationships
  3. Maintain left buccal occlusion and improve right occlusion.

Fig. (6.2))
Right side premolars are in slight end-to-end relation, and upper right first molar is not fully sucked in (full interdigitation).

Treatment plan included sight expansion (non-extraction) of the upper and lower arches and labial crown torque of upper incisors.

Two treatment options were presented to the patient:

  1. Full fixed appliance, or
  2. Invisalign clear aligners treatment

Parents and patient were informed with limitations of each technique and both patient and parents chose Invisalign treatment. Patient was fitted with 22 aligners, utilizing class II elastics on both sides to improve buccal occlusion, providing space for upper right canine and left class II elastics were used to prevent canting of anterior occlusal plan. Also, slight proclination of the upper and lower incisors were requested 1) improve their position, and 2) provide space for the buccally erupted upper right canine. (Fig. 6.3): shows patient after 11 months in treatment with no refinement or second set of aligners. Fig. (6.4) shows superimposition of initial and final tooth position as produced by Clincheck®. It can be observed that the upper right canine moved favorably into its normal position, while midlines were maintained, buccal occlusions were improved to full class I molars and premolars.

Fig. (6.3))
Final photos after one year in treatment.

Fig. (6.4))
Model superimposition showing initial position (blue) and final toot position (white).

Retention protocol includes 24/7 earing of Vivera upper and lower retainers in the first year and night time afterwards (forever). Possible relapse without wearing retainers was explained possibly due to normal growth or facial adaptation.

Severe Crowding Cases

Severe crowding according to Proffit is defined as arch length deficiency of more than 3 mm [5]. In this regard, the case presented above may be considered severe crowding as well. The next case is definitely severe crowding and traditional orthodontic treatment plan is recommended for doing serial extraction. It has been reported that the use of lingual arch in late mixed dentition can be helpful in resolving incisor crowding [6, 7]. The idea of using lingual arch in late mixed dentition is to save leeway space (E-Space) to resolve moderate crowding (2-4 mm).

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May 6, 2017 | Posted by in Orthodontics | Comments Off on and Severe Crowding Class I Cases
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