CLINICAL CONSIDERATIONS CROWDING

CLINICAL CONSIDERATIONS CROWDING

CROWDING CASES TREAT MOST PREDICTABLY WHEN: Anterior teeth are retroclined or upright. Arches are narrow with posterior teeth tipped lingually, particularly cuspids and bicuspids. Clinical crowns are not short. GENERAL TREATMENT PLANNING CONSIDERATIONS Options to Resolve Crowding The three basic options to address crowding are anterior proclination (buccal crown tipping), posteriordental expansion (buccal crown tipping) and interproximal reduction (IPR). With severe crowding, extractions may be needed. A single lower incisor extraction may be indicated for an adult patient where there is significantly more lower anterior crowding than upper crowding and the posterior occlusion is very tightly interdigitated. This can be a good alternative to extensive lower anterior IPR. Please note that extractions may increase the complexity of the treatment and require auxiliary techniques to be used in combination with the aligners to close residual space. For patients with posterior crowding, carefully consider how to create space in order to bring into alignment the teeth positioned outside the arch. If space is insufficient and cannot be created, extractions may be considered, as well as leaving the posterior crowding/crossbite untreated.

Crowding and teeth inclination When the patient presents with lingually tipped anterior and/or posterior teeth, arch length can be increased by proclination of the anterior teeth and expansion of the posterior teeth (using buccal crown tipping movements). Note that proclination of the anterior teeth will create relative intrusion, and reduce the overbite. If there is a deep bite present in addition to crowding, absolute anterior intrusion can create the necessary overjet space in order to procline the lower anterior teeth. With normally inclined anterior teeth or flared anterior teeth, IPR and arch expansion will be the only means to create space to address the crowding; if this is not enough to prevent excessive proclination of the anterior teeth, you may want to consider distalization or a more complex extraction treatment plan. Crowding and tooth size discrepancy Assuming a Class I occlusion, a tooth size discrepancy (where the proportions of the upper and lower teeth don t match) may manifest itself by: 1. Excess overjet when the teeth are completely aligned if the upper teeth are proportionally wider than the lower teeth. 2. Residual spaces between the upper anterior teeth when the teeth are completely aligned since the lower teeth are wider than the upper; the alternative manifestation is for the lower teeth to be crowded if no spaces are present on the upper arch. If there is tooth size discrepancy, either the wider teeth will need to be reduced with IPR (see example on the right), or the narrower teeth will need to be widened with restorations. If the tooth size discrepancy is too large, the extraction of a single lower incisor should also be considered. When analyzing the Bolton index, this patient showed a 0.6mm anterior mandibular excess. 0.6 mm of IPR on the lower arch was planned on doctor s request to achieve the goals.

INVISALIGN SPECIFICS IPR staging If IPR is required, the teeth will first be proclined until the interproximal contacts are easily accessible, which may lead to some round-tripping. Round-tripping is tipping the teeth towards the buccal to provide access to the distal and/or mesial edges of the teeth causing the collision before retroclining them into their final position. As IPR is applied to reduce the tooth width, the teeth will be retroclined to their final aligned position. However, the doctor may request earlier IPR to reduce the amount of round-tripping. Doctors may provide additional instructions to create visible space between the crowded teeth to facilitate their alignment and prevent them from binding; note that this will increase the initial proclination needed to create the space and will result in additional bucco-lingual movements (round-tripping). Upper arch staging On treatments with lower anterior crowding, the upper anterior teeth may be proclined and spaces temporarily created on the upper anterior teeth to avoid heavy inter-arch interferences. These interferences should be monitored. For more information and treatment planning help Learn more from your peers who are successfully treating patients with both mild and severe crowding: https://learn.invisalign.com/crowding#tips

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