Invisalign® treatment in the anterior region: were the predicted tooth movements achieved?

OBJECTIVE: Based on our previous pilot study, the objective of this extended study was to compare (a) casts to their corresponding digital ClinCheck® models at baseline and (b) the tooth movement achieved at the end of aligner therapy (Invisalign®) to the predicted movement in the anterior region. MATERIALS AND METHODS: Pre- and post-treatment casts as well as initial and final ClinChecks® models of 50 patients (15-63 years of age) were analyzed. All patients were treated with Invisalign® (Align Technology, Santa Clara, CA, USA). Evaluated parameters were: upper/lower anterior arch length and intercanine distance, overjet, overbite, dental midline shift, and the irregularity index according to Little. The comparison achieved/predicted tooth movement was tested for equivalence [adjusted 98.57% confidence interval (- 1.00; + 1.00)]. RESULTS: Before treatment the anterior crowding, according to Little, was on average 5.39 mm (minimum 1.50 mm, maximum 14.50 mm) in the upper dentition and 5.96 mm (minimum 2.00 mm, maximum 11.50 mm) in the lower dentition. After treatment the values were reduced to 1.57 mm (minimum 0 mm, maximum 4.5 mm) in the maxilla and 0.82 mm (minimum 0 mm, maximum 2.50 mm) in the mandible. We found slight deviations between pretreatment casts and initialClinCheck® ranging on average from -0.08 mm (SD ± 0.29) for the overjet and up to -0.28 mm (SD ± 0.46) for the upper anterior arch length. The difference between achieved/predicted tooth movements ranged on average from 0.01 mm (SD ± 0.48) for the lower anterior arch length, up to 0.7 mm (SD ± 0.87) for the overbite. All parameters were significantly equivalent except for the overbite (-1.02; -0.39). CONCLUSION: Performed with aligners (Invisalign®), the resolvement of the partly severe anterior crowding was successfully accomplished. Resolving lower anterior crowding by protrusion of the anterior teeth (i.e., enlargement of the anterior arch length) seems well predictable. The initial ClinCheck® models provided high accuracy compared to the initial casts. The achieved tooth movement was in concordance with the predicted movement for all parameters, except for the overbite.

Accuracy of Invisalign® treatments in the anterior tooth region. First results.

AIM: To analyse (a) to what extent the pretreatment model at the beginning of the treatment corresponds to the initial position in the ClinCheck® and (b) to what extent the predicted treatment result corresponds to the actual result of the therapy at the end of the treatment. MATERIAL AND METHODS: Pre- and posttreatment models as well as the initial and final position of the ClinCheck with a total of 35 patients aged between 15 and 59 were measured; all of whom were treated by using the Invisalign® technology (Invisalign®, Align Technology, S.C., Calif., USA). The measurement of the initial and final models was conducted by using an electronic digital calliper rule, i.e. that of ClinCheck® using the measurement tool ToothMeasure® of Invisalign® Software. The following parameters in the anterior region were measured: Overjet, Overbite, dental midline shift. RESULTS: Pretreament models and the initial ClinChecks® revealed slight deviations in the parameters overjet 0.08 mm (standard deviation (SD) 0.3), overbite 0.3 mm (SD 0.4) and dental midline deviation 0.1mm (SD 0.4). The final model and the final ClinCheck® revealed larger deviations: the differences for the Overjet were on average 0.4 mm (SD 0.7), Overbite 0.9 mm (SD 0.9) and dental midline shift 0.4 mm (SD 0.5). CONCLUSIONS: The IT-based transmission of mal-aligned teeth into the ClinCheck® presentation provides sufficiently good accuracy. Tooth corrections in the vertical plane were more difficult to realize. A vertical overcorrection in the final ClinCheck®, a case refinement at the end of the treatment or additional measures (e.g. horizontal beveled attachments or vertical elastics) seems useful to achieve the individually intended therapeutic goal.