The effect of digital diagnostic setups on orthodontic treatment planning

Introduction

This study aimed to evaluate whether viewing digital treatment simulations influenced orthodontic treatment planning decisions or practitioners’ confidence in their selected plans.

Methods

Records of 6 patients representing different case types (eg, missing teeth, crowding, sagittal discrepancies) were collected. A total of 22 orthodontists and 7 orthodontic residents viewed these records and formulated treatment plans for each case, indicating their most recommended plan and up to 2 alternative plans. After treatment planning each case, digital setups of each treatment plan indicated by the practitioner were shown. The practitioners were then asked if they still recommended their original plan, or if they would now recommend a different plan. Their confidence levels in the success of their plans were recorded before and after viewing the setups.

Results

After viewing the digital setups, there was a significant change in the treatment plan for 9.2% of the cases. These included modifications like changing the extraction pattern or proposing space closure rather than opening space for an implant. In an additional 14.4% of the cases, treatment plans underwent partial changes, like adding interproximal reduction or temporary anchorage devices. Practitioner confidence levels increased after viewing the setups. In cases where the treatment plan changed, the practitioner’s confidence level in the plan increased the most, and the final confidence level was uniformly high among all practitioners. Practitioners reported the most helpful features of digital setups were the ability to superimpose the setup with the original model, determine the amount of tooth movement needed, check the final incisal relationship (overjet and overbite), and establish the amount of interproximal reduction required.

Conclusions

Viewing digital setups resulted in changes to the treatment plans in about 24% of the cases. The use of digital setups was associated with higher levels of confidence in the selected plans.

Highlights

  • Digitally viewing multiple setups for a patient affects treatment decisions.

  • Viewing digital setups increased a practitioner’s overall confidence level.

  • Superimposing the setup and initial model was a helpful feature.

  • Tooth movement chart, checking final overjet and overbite, and estimating the interproximal reduction needed were also helpful features.

Since Kesling first recommended their use in 1947, diagnostic setups have been used to simulate different treatment options and aid decision making when treatment planning. Creating multiple setups to represent different treatment plans can help when considering extraction patterns, interproximal reduction (IPR), anchorage management, and other treatment mechanics. Setups also help when presenting the case to the patient and planning treatment with other dentists.

With the transition to digital study models, diagnostic setups can now be created digitally, which are as accurate and reliable as wax setups. Working with digital setups offers new advantages that were not possible with plaster, such as the ability to superimpose the setup with the original models and the ability to determine the precise amount of movement for each tooth. Many clinicians are already routinely creating digital setups as part of clinical practice because of the increased use of clear aligner therapy and other digital orthodontic techniques (ie, custom brackets and custom wires).

When designing treatment with any digital orthodontic system, a digital setup must be created to set the final result. Although this digital setup can be seen as a byproduct of the manufacturing process, the setup actually represents an additional data point for clinicians to consider while treatment planning. Some clinicians may already generate multiple digital setups using clear aligner software when deciding between different treatment decisions. For example in the case of mandibular anterior crowding, the clinician may ask for the first setup to be created with no IPR to evaluate the final proclination of the incisors and overjet, and then decide to add IPR to certain areas for the second setup. Or alternatively, the clinician may ask for one setup with mandibular IPR and then a second setup with the extraction of one mandibular incisor to compare the 2 options.

Although setups are generally regarded as useful, the magnitude of the effect of these digital setups on treatment planning has yet to be quantified. This study examined whether viewing a digital setup resulted in changes to an orthodontist’s treatment plan or in changes to the orthodontist’s level of confidence in the selected plan.

Material and methods

This study was reviewed and approved by the University of Washington Institutional Review Board. A panel of 4 orthodontists reviewed cases treated at the UW Graduate Orthodontics Clinic and selected 6 cases for this study. Cases were selected based on multiple viable treatment options and a range of case difficulties. The panel felt that 6 cases were a reasonable number to ask a practitioner to the treatment plan without occupying too much time or causing fatigue.

Assembled records included intraoral and extraoral photos, panoramic and lateral cephalometric radiographs, cephalometric tracing and measurements, Bolton analysis, and digital models of the teeth. The digital models were imported into SureSmile software (OraMetrix, Richardson, Tex) to generate digital setups. The same panel of 4 orthodontists identified as many potential treatment plans as possible for each case so that these setups could be prepared in advance. For 6 cases, a total of 44 digital setups were created, with an average of 7 setups per case. Each setup was reviewed by at least 3 orthodontists on the panel to ensure they simulated realistic biomechanics and anchorage management. Examples of digital setups in the software can be seen in Figures 1 and 2 .

Fig 1
Digital setup with tooth movement chart showing the exact movements of each tooth in the maxillary arch. In this case, the maxillary left second molar was not moved in order to indicate the anchorage loss required visually.

Fig 2
Overlay of the initial ( teal ) and final ( white ) tooth positions of the maxillary arch for bilateral canine substitution in a case with missing maxillary lateral incisors. The maxillary second molars were not moved to visualize anchorage loss needed.

In order to participate, practitioners must be enrolled in or have graduated from an orthodontic residency program and must not have been involved with the treatment of any of the cases selected for the study.

Orthodontists were shown the records of the 6 selected cases in random order. Upon viewing the records, orthodontists were asked to list up to 3 treatment plans (the most recommended plan, the second most recommended plan, and the third most recommended plan) using a treatment planning worksheet ( Fig 3 ). Practitioners were asked to indicate their confidence level in the successful outcome of their most recommended plan on a visual analogue scale.

Fig 3
Treatment planning worksheet, part 1.

After writing down their treatment plans, practitioners were shown the digital setups for only the plans that they had indicated on the treatment planning worksheet. If a practitioner proposed a treatment plan that had not been previously anticipated, the setup was created and shown to the practitioner within several days. After viewing the setups, practitioners were asked which plan was now their most recommended treatment plan and to state their confidence level in the successful outcome of this plan ( Fig 4 ).

Fig 4
Treatment planning worksheet, part 2.

Based on simulation modeling, a sample size of 29 orthodontists and orthodontic residents was set. This number of participants would provide an expected margin of error between 5% and 6% if the probability of switching treatment plans after viewing digital setups was between 10% and 30%.

For further statistical analysis, the orthodontists were divided into 3 groups: current residents, those with ≤ 5 years in practice, and those with > 5 years in practice. The study was focused on answering 3 specific questions: (1) how often did practitioners change their most recommended plan after viewing the setups; (2) did practitioners’ confidence level in their treatment plan change after viewing the setups; and (3) did the rate of treatment plan change and confidence level change differ among the 3 groups of orthodontists.

Data were analyzed using SPSS version 19 (IBM Corp, Armonk, NY). The probability of changing the most recommended treatment plan and associated confidence intervals were estimated using a binomial regression model with a log link using a generalized estimating equation for accounting multiple observations per practitioner. This technique was also used to compare changes among the different experience levels. A linear regression on change in confidence using a generalized estimating equation was used with case and plan change incorporated into the model to determine the change in the confidence interval.

Results

A total of 29 practitioners were recruited to participate in this study. The practitioners were stratified into 3 groups based on experience ( Table I ), with 7 second- or third-year orthodontic residents (residents), 13 orthodontists with 5 or fewer years in practice (newer practitioners), and 9 orthodontists with more than 5 years in practice (experienced practitioners). The group of newer practitioners had an average of 2.1 years in practice with a range of 1 to 4 years of experience. The group of experienced practitioners had an average of 25.1 years in practice with a range of 8 to 40 years of experience.

Table I
Description of practitioners in the study
Parameters No. of practitioners Average years in practice (range) Average years in residency
Residents 7 2.3 (2-3)
≤ 5 years in practice 13 2.1 (1-4)
> 5 years in practice 9 25.1 (8-40)

The 6 cases selected for study and the top 2 most recommended treatment plans by the practitioners in the study are described in Table II . Of the 6 cases selected, 3 were adolescent patients and 3 were adult patients. In addition, 3 cases were Class I, 2 cases were Class II, and 1 case was a Class III tendency.

Table II
Description of cases and most recommended treatment plans
Case no. Description of case Most recommended treatment plans
1 15-year-old female, Class I, full profile, proclined incisors, mild maxillary, and mandibular crowding
  • (1)

    Extract all first premolars

  • (2)

    Extract all second premolars

2 21-year-old female, Class I, thin upper lip, 95% overbite, moderate mandibular anterior crowding
  • (1)

    Nonextraction with mandibular IPR

  • (2)

    Extract one mandibular incisor

3 36-year-old male, Class I, excess overjet/overbite, retained maxillary left primary canine, missing maxillary left permanent canine, missing one mandibular incisor, moderate mandibular arch length deficiency
  • (1)

    Replace missing UL3 with an implant and maxillary IPR

  • (2)

    Close UL3 space by protracting maxillary left posterior teeth

4 13-year-old male, Class II subdivision, straight profile, thin lips, severe maxillary, and mandibular crowding
  • (1)

    Extract all first premolars

  • (2)

    Extract 4 of 5 on the right and 4 of 4 on the left

5 12-year-old female, end-on Class II, convex profile, thin lips, excess overjet, and minimal overbite, missing maxillary lateral incisors
  • (1)

    Bilateral canine substitution to close missing lateral incisor space

  • (2)

    Open space for maxillary lateral implants

6 48-year-old female, Class III tendency, increased overjet and overbite, severe mandibular anterior crowding, recently extracted number 10 because of root fracture
  • (1)

    Nonextraction with mandibular IPR

  • (2)

    Extract one mandibular incisor

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May 12, 2020 | Posted by in Orthodontics | Comments Off on The effect of digital diagnostic setups on orthodontic treatment planning
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