Impact of cone-beam computed tomography on orthodontic diagnosis and treatment planning

Impact of cone-beam computed tomography on orthodontic diagnosis and treatment planning

American Journal of Orthodontics and Dentofacial Orthopedics, 2013-05-01, Volume 143, Issue 5, Pages 665-674, Copyright © 2013 American Association of Orthodontists

Introduction

In this study, we measured the impact of cone-beam computed tomography (CBCT) on orthodontic diagnosis and treatment planning.

Methods

Participant orthodontists shown traditional orthodontic records for 6 patients were asked to provide a diagnostic problem list, a hypothetical treatment plan, and a clinical certainty. They then evaluated a CBCT scan for each patient and noted any changes, confirmations, or enhancements to their diagnosis and treatment plan.

Results

The number of diagnosis and treatment plan changes varied widely by patient characteristics. The most frequently reported diagnosis and treatment plan changes occurred in patients with unerupted teeth, severe root resorption, or severe skeletal discrepancies. We found no benefit in terms of changes in treatment plan for patients when the reason for obtaining a CBCT scan was to examine for abnormalities of the temporomandibular joint or airway, or crowding. Orthodontic participants who own CBCT machines or use CBCT scans frequently in practice reported significantly more diagnosis and treatment plan changes and greater confidence after viewing the CBCT scans during the study.

Conclusions

The results of this study support obtaining a CBCT scan before orthodontic diagnosis and treatment planning when a patient has an unerupted tooth with delayed eruption or a questionable location, severe root resorption as diagnosed with a periapical or panoramic radiograph, or a severe skeletal discrepancy. We propose that CBCT scans should be ordered only when there is clear, specific, individual clinical justification.

Radiographs are an indispensible tool in the evaluation of the bony structures of the head and neck in pretreatment orthodontic diagnosis and treatment planning. Previous research has shown that lateral cephalograms and panoramic, anterior periapical, and posterior bitewing radiographs provide sufficient information for most orthodontic patients. These radiographic techniques provide 2-dimensional information about the maxillomandibular relationship, the position of the dentition in relation to basal and alveolar bones, the airway, skeletal or dental disease, root anatomy and angulation, and a gross visualization of the osseous anatomy of the temporomandibular joint (TMJ).

With the advent of cone-beam computed tomography (CBCT), it became possible to evaluate the hard and soft tissues of the maxillofacial region in 3 dimensions and in high spatial detail. Additionally, visualization of the craniofacial complex in 3 dimensions is also possible with surface reconstruction views. Such information has the potential to improve orthodontic diagnosis and treatment planning, including airway analysis, TMJ evaluation, positions of impacted teeth, orthognathic surgical planning, evaluation of skeletal asymmetries, root position and structure, and miniscrew placement. However, the use of CBCT entails both financial costs and potential risks from radiation exposure.

Some researchers have provided recommendations for ordering CBCT scans based on specific characteristics, including facial asymmetry, sleep apnea, impacted teeth, intent to use dental mini-implants, consideration of rapid maxillary expansion, and persistent TMJ symptoms. Others have advocated the routine used of CBCT in standard orthodontic diagnosis and treatment planning because of the additional diagnostic information that is potentially available. The decision to use any imaging modality before orthodontic treatment is justified when there is a reasonable expectation that a radiograph will result in a clinical benefit. This study was designed to measure the impact of CBCT in orthodontic diagnosis and treatment planning, and to determine the extent to which patient characteristics might provide benefits to clinicians in diagnosis and treatment planning.

Material and methods

The records and study models of 6 patients treated in the orthodontic clinic at the University of California at Los Angeles were selected and duplicated. The patient case records included, at a minimum, medical and dental histories; stone study models trimmed to centric relation; images of the full-mouth intraoral and extraoral photographs; lateral cephalometric, panoramic, and full-mouth series views; and the initial CBCT examination. All CBCT scans were made on a NewTom 3G machine (QR S.r.l., Verona, Italy) with a 12-in field of view and reconstructed with a 0.5-mm slice thickness.

The cases were selected to represent a broad range of clinical characteristics commonly encountered in orthodontic practices, including Class I, Class II, and Class III molar relationships, canine impactions, anterior open bites, anterior and posterior crossbites, dental crowding, airway and TMJ problems, and severe skeletal asymmetries ( Table I ). The cases exposed the participants to common patient characteristics, especially problems where CBCT has been suggested to be beneficial, but without regard to prevalence. For example, the prevalence of impacted maxillary canines is 1% to 2.5%, but in our study, impacted maxillary canines were present in 2 of the 6 cases.

Table I
Patient case characteristics
Patient case Age Sex Angle class Unerupted tooth Root position/resorption Severe skeletal discrepancy TMD Airway problem Crowding Case severity
1 13 y 0 mo M II N N N N N N Low
2 7 y 3 mo F III Y N N N N Y Low
3 15 y 3 mo M I N N N N Y Y Medium
4 11 y 6 mo F II Y Y N N N Y High
5 20 y 1 mo F II Y N Y Y Y N High
6 16 y 1 mo M III N N Y N Y Y Medium
M , Male; F , female; N , no; Y , yes; TMD , TMJ disorder.

Letters briefly describing the study and inviting participation were sent via e-mail to 219 members of the Pacific Coast Society of Orthodontists who resided in the Southern California area. A letter was also sent to the program directors of the 3 regional orthodontic programs: University of California, Los Angeles; University of Southern California, Los Angeles; and Loma Linda University, Loma Linda, Calif. Those who responded were contacted and told that participation would consist of 1 interview (estimated to last about 2 hours) during which the participant would be shown orthodontic cases and asked to provide hypothetical diagnoses and treatment plans. The participants were assured that the accuracy of their diagnosis and treatment plan was not being evaluated, but, rather, the investigators wished to determine the information used to formulate their diagnoses and treatment plans. This study was approved by the institutional review board of the University of California at Los Angeles.

A standardized interview was used. Descriptive data were gathered about the participants (sex, orthodontic program and year of graduation, whether they owned a CBCT device, and for what percentage of their patients did they order CBCT scans before treatment). The participants were shown the case records for the 6 patients. One case, selected by the investigators as an easy diagnostic one, was always presented first to familiarize the participants with the process. The order of presentation of the other 5 cases was systematically varied to prevent changes to the outcome variables associated with fatigue.

Each case was presented on a 15.4-in screen (MacBook Pro; Apple, Cupertino, Calif) with software (Dolphin Imaging, Chatsworth, Calif). The participants were given each patient’s medical and dental histories and shown the study models, intraoral and extraoral photographs, and lateral cephalometric, panoramic, and full-mouth series radiographs. The participant was allowed to rotate and manipulate all images (except the CBCT images) during this part of the interview. They were asked to describe their diagnostic problem list. They were also asked to provide their degree of certainty with their diagnosis using a visual analog scale ranging from 0% (complete guess) to 100% (absolutely certain). This process was repeated for the treatment plan.

The participants were then asked whether they would request a CBCT scan for this patient and their rationale. Regardless of whether they requested a CBCT scan, the participants were asked to evaluate the CBCT examination and note any changes, enhancements, or confirmations to their diagnosis and treatment plan, including reasons for these changes. Next, the participants were given preconstructed images of the TMJ, impacted teeth, and teeth with root resorption. They were also encouraged to view the multi-planar reconstructions and to create any other cross-sections from the CBCT scan that would contribute to their diagnosis and treatment plan.

After data collection, the considerations for ordering CBCT scans and associated diagnostic and treatment plan changes were grouped into the following 8 categories: unerupted tooth, root position or resorption (>2 mm), severe skeletal discrepancy (−2° ≥ ANB ≥ 6°, or asymmetry ≥4 mm), TMJ disorder (signs or symptoms of clicking, popping, or pain), airway problems, crowding (>5 mm in either arch), medico-legal reasons, and financial costs. During the analysis, a hierarchy of change, enhancement, and confirmation was established, with a change having the greatest impact. For example, if a participant reported a change and an enhancement to a diagnosis, both were recorded but only the change was used for analysis.

The participants then provided final percentages of certainty for both their diagnoses and treatment plans. At the conclusion of each case, the participants were asked how the CBCT scan was useful in their diagnosis and whether the information from it would have influenced the treatment outcome for that patient. They were allowed to explain any radiographs or other diagnostic aids that they would have ordered if the CBCT scan were unavailable.

Statistical analysis

The P values for comparing binary outcomes (percentages) from the same participants across patient profiles were computed by using the Cochran Q procedure, a generalization of the McNemar test for balanced 2 × k tables, where k is the number of subjects. For comparisons across categories when participant-patient was the unit of analysis, this was expanded to a repeated-measure logistic model with a random participant effect to take into account nonindependence.

The P values for comparing continuous confidence score outcomes across patients from the same participants were computed by using the nonparametric Friedman test for repeated-measure comparisons, a generalization of the Wilcoxon signed rank test for paired continuous data.

Results

Twenty-four participants began the interview process, and 23 finished all 6 patient cases; 1 participant finished 5. The participants were mostly men (n = 21), trained at 10 orthodontic programs, and had an average of 24 years of experience (range, 1-44 years). The participants reported using CBCT examinations for 0% to 100% of their patients in their practices (mean, 12.1%; median, 5%) ( Fig 1 ).

Participants' self-reported use of CBCT in private practice.
Fig 1
Participants’ self-reported use of CBCT in private practice.

There were 64 CBCT scans ordered (45% of opportunities) during the interview process ( Table II ). The number of CBCT requests for each case ranged from 2 to 22, and 64% of the CBCT scans requested were for cases 4 and 5. For case 1, only 2 CBCT scans were requested. Two participants never requested a CBCT during their review of the 6 cases, 16 participants ordered 2 to 4 CBCT scans, and 2 participants requested a CBCT scan for all 6 cases ( Table III ).

Table II
Number of CBCT scans ordered for each patient
Patient case CBCT scans ordered Differences
n % SE
1 2 8 ±6 2, 3, 4, 5, 6
2 6 25 ±9 1, 4, 5
3 7 29 ±10 1, 4, 5
4 22 92 ±6 1, 2, 3, 6
5 19 79 ±9 1, 2, 3, 6
6 8 35 ±10 1, 4, 5
Total 64 45 ±2.8

Significantly fewer than all other cases ( P <0.05).

significantly more than cases 1-3 and 6 ( P <0.05).

Table III
CBCT scans ordered by participants
CBCT scans requested (n) Participants (n)
0 2
1 3
2 8
3 4
4 4
5 1
6 2

There were 26 changes to the participants’ diagnoses after viewing the CBCT scans (18% of opportunities) and 28 changes to the treatment plans (20% of opportunities) ( Table IV ). The number of changes varied widely by patient case, ranging from 1 to 11, with cases 4 and 5 together comprising over 67% of the changes to the diagnoses (18 of 26 changes) and treatment plans (19 of 28 changes).

Table IV
Changes and enhancements to the diagnoses and treatment plans
Patient case Diagnosis changes Treatment plan changes
n % SE n % SE
1 1 4 ±4 2 8 ±6
2 2 8 ±6 2 8 ±6
3 1 4 ±4 1 4 ±4
4 9 38 ±10 8 33 ±10
5 9 38 ±10 11 46 ±10
6 4 17 ±8 4 17 ±8
Total 26 18 28 20

Significantly different from cases 1, 2, and 3 ( P <0.05).

significantly different from cases 1, 2, 3, and 6 ( P <0.05).

The number of CBCT scans ordered and the number of resulting changes to the diagnoses and treatment plans varied by patient characteristics ( Table V ). Multiple characteristics were present in each case; thus, participants gave multiple reasons for ordering a CBCT scan and for a change to a diagnosis or treatment plan.

Table V
Summary of changes to diagnosis and treatment plan by patient characteristic
Patient characteristic n Characteristic present CBCT scan ordered Diagnosis change Treatment plan change
n % SE (%) n % SE (%) n % SE (%)
Unerupted tooth 71 N 2 3 2 0 0 0 0 0 0
72 Y 39 54 6 15 21 5 16 22 5
Root position/resorption 119 N 8 7 2 2 2 1 0 0 0
24 Y 13 54 10 3 13 7 6 25 9
Severe skeletal discrepancy 96 N 3 3 2 0 0 0 1 1 1
47 Y 6 13 5 5 11 5 6 13 5
TMD 119 N 9 8 2 6 5 2 1 1 1
24 Y 4 17 8 3 13 7 2 8 6
Airway problem 72 N 3 4 2 3 4 2 3 4 2
71 Y 11 15 4 3 4 2 3 4 2
Crowding 48 N 2 4 3 1 2 2 0 0 0
95 Y 8 8 3 2 2 1 4 4 2
N , No; Y , yes; TMD , TMJ disorder.

Values significantly different ( P <0.05).

For 5 of the 6 patient characteristics, participants ordered CBCT scans more frequently ( P <0.05) when the characteristic was present. An unerupted tooth was the most frequently cited reason for ordering a CBCT scan (64% of orders), followed by root resorption (33% of orders). Of the 72 observations on patients with unerupted teeth, a CBCT scan was ordered 39 times when the characteristic was present (54%) and only twice when the characteristic was not present. Root resorption was cited as the rationale for ordering the CBCT scan 13 times when the characteristic was present (54%) and 8 times (7%) when the characteristic was not present. Severe skeletal discrepancy, TMJ disorders, and airway problems were cited less frequently, yet still significantly more frequently when the characteristic was present. Crowding was offered as a reason for ordering a scan but was not statistically significant.

For 3 of the 6 patient characteristics—unerupted tooth, root resorption, and severe skeletal discrepancy—the participants reported changes to the diagnosis and treatment plan significantly more frequently when the characteristic was present. An unerupted tooth was the most frequently cited reason for changes to the diagnosis (15 instances, or 21% of the cases with the characteristic present) and treatment plan (16 instances, or 22%). It was never mentioned in cases without the characteristic present. Root position or resorption was present in fewer cases, and CBCT scans were ordered for diagnostic reasons both when the characteristic was present (3 times) and when it was not (2 times). In proportion, it was the most common reason for treatment plan changes (6 times, or 25%). Severe skeletal discrepancy was reported as a reason for a change to the diagnosis 5 times (11%). For the treatment plan, 6 changes occurred when there was a severe skeletal discrepancy and once when it was not present. There was no significant difference in the reasons cited for ordering by the presence or absence of the characteristics for TMJ disorder, airway problem, and crowding.

Treatment outcome was defined as the expected result of treatment as reported by the participants. We evaluated the association between treatment plan changes and expected effect on treatment outcome as reported by the participants ( Table VI ). The presence of unerupted teeth resulted in 16 treatment changes, and the participants expected that 7 (44%) of these would affect patient outcome. For the other patient characteristics, the participants reported that the changes would affect patient outcome for between 67% and 100% of the treatment plans.

Table VI
Treatment plan changes and effect on expected treatment outcome
Patient characteristic Treatment plan changes Treatment plan change and outcome affected Proportion (%) SE (%)
Unerupted tooth 16 7 44 12
Root position/resorption 6 5 83 15
Severe skeletal discrepancy 7 7 100 0
TMD 3 2 67 27
Airway problem 6 5 83 15
Crowding 4 4 100 0
Total 42 30 71
TMD , Temporomandibular joint disorder.

The participants’ initial confidence ranged from 75% to 97% for diagnoses, and from 83% to 95% for treatment plans ( Fig 2 ). Patient cases 4 and 5 had the lowest mean initial diagnosis confidence values; case 1 had the highest value. Significant increases in the mean percentages of confidence in the diagnoses and treatment plans were demonstrated for patient cases 2 to 6 after the participants viewed the CBCT scans ( Fig 3 ).

Mean confidence intervals in the initial diagnoses and treatment plans. Error bars represent standard deviations.
Fig 2
Mean confidence intervals in the initial diagnoses and treatment plans. Error bars represent standard deviations.
Mean changes in diagnoses and treatment plans. Error bars represent standard deviations. *Significant change ( P <0.05).
Fig 3
Mean changes in diagnoses and treatment plans. Error bars represent standard deviations. *Significant change ( P <0.05).

We evaluated whether sex, practice experience, CBCT use in private practice, or ownership of a CBCT machine influenced the outcome variables ( Table VII ). Sex was not significantly associated with any outcome variable. Orthodontists in practice for a decade or less ordered significantly fewer CBCT examinations than did more experienced orthodontists. Two orthodontists who reported ordering CBCT scans for 90% to 100% of their patients in private practice ordered significantly more CBCT examinations than did the other orthodontists (100% vs 40%). These orthodontists also reported significantly more changes to their diagnoses (75% vs 13%) and treatment plans (83% vs 14%), and greater gains in confidence than the 22 who ordered CBCT examinations for 0% to 15% of their private practice patients. Similarly, the 4 orthodontists who owned a CBCT machine ordered more CBCT examinations (79% vs 38%) and reported more changes to their diagnoses (63% vs 9%) and treatment plans (67% vs 12%) and greater gains in confidence than did the 20 who did not own a CBCT machine.

Table VII
CBCT scan ordering patterns, number of changes to diagnosis and treatment plan, and mean change in participant’s percentage of confidence
Participant characteristic n Number (%) of CBCT scans ordered Number (%) of changes Mean confidence change (%)
Diagnosis Treatment plan Diagnosis Treatment plan
Sex
M (n = 21) 125 56 (45) 25 (20) 27 (22) 10 9
F (n = 3) 18 8 (44) 1 (6) 1 (6) 3 3
Years in practice
1-10 (n = 6) 36 8 (22) 4 (11) 5 (14) 10 11
11-29 (n = 7) 42 22 (52) 7 (17) 9 (21) 10 9
30+ (n = 11) 65 34 (52) 15 (23) 14 (22) 7 6
% of patients having CBCT scan
0-15 (n = 22) 131 52 (40) 17 (13) 18 (14) 6 6
90-100 (n = 2) 12 12 (100) 9 (75) 10 (83) 35 33
Own CBCT
N (n = 20) 119 45 (38) 11 (9) 14 (12) 5 5
Y (n = 4) 24 19 (79) 15 (63) 16 (67) 26 25
M , Male; F , female; N , no; Y , yes.

Significantly different ( P <0.05).

Discussion

This study was designed to (1) investigate patients’ clinical characteristics associated with a decision by orthodontists to order CBCT examinations and (2) measure the utility of these examinations in terms of their influence on diagnoses and treatment plans. Fryback and Thornbury described a hierarchical model for efficacy of studies in diagnostic imaging. These range from radiographic studies assessing the technical efficacy of the imaging system (level 1) to studies measuring the societal benefit of imaging (level 6). Our study measured diagnostic thinking and therapeutic efficacy, whether the CBCT examination influences the treatment plan (level 4) and, to some extent, patient outcome efficacy, and whether the findings from the examination are likely to change the patient’s outcome (level 5).

The number of CBCT examinations requested varied widely by participant, ranging from 2 participants who never requested a scan to another 2 participants who always ordered a scan, with most participants ordering few CBCT scans. This pattern mirrored their stated ordering practices in their private practices. These findings suggest no wide agreement, at least among these orthodontists with far-ranging experience and educational backgrounds, regarding the appropriate indications for making CBCT examinations.

Our participants requested a CBCT scan during diagnosis and treatment planning substantially more often than they reported using CBCT scans for patients in their private practices (45% vs 12%). This discrepancy might be attributable to the higher prevalence of patient problems we selected for our test cases than in private practice. For example, 33% of the patients in this study had an impacted canine, whereas the prevalence of impacted maxillary canines is 1% to 2.5%. Also, it might have simply been easier to order a CBCT scan as a part of this study when there was no financial or radiation cost associated with it. Three participants stated that they requested a CBCT scan “only if cost is not a factor.”

The number of CBCT scans ordered was associated with case severity. Patient cases 4 and 5 were rated as the most difficult by the investigators and an orthodontic faculty member at the University of California at Los Angeles, and those cases had the most CBCT scans ordered by the participants (22 and 19, respectively). Cases 1 and 2 were categorized as having a low degree of difficulty, and they had 2 and 6 CBCT scans, respectively, requested by the participants. This suggests that most participants thought that traditional radiographs were sufficient to diagnose and plan these cases.

Of the 6 patient characteristics cited as reasons for a change to the diagnosis or treatment plan, unerupted tooth, root resorption, and severe skeletal discrepancy were the most frequent. For these characteristics, there were significantly more changes to the diagnoses and treatment plans when the case had the characteristic when compared with cases without the characteristic. This suggests that a benefit is gained from CBCT scans when a patient has an unerupted tooth, root resorption as diagnosed on a periapical or panoramic view, or a severe skeletal discrepancy diagnosed on a lateral cephalometric view. These patient characteristics were also reported by Kapila et al as those most likely to benefit from a CBCT examination. TMJ disorders, airway difficulties, and crowding, however, were not associated with significant changes in the diagnosis or treatment plan. Because of our small sample size and the selection of patient cases, the possibility of a benefit from a CBCT scan for some patients with these characteristics cannot be ruled out.

We considered the possibility that valuable information might be discovered serendipitously: ie, findings on the images ordered for reasons not related to the patient characteristic prompting an examination. Indeed, 19 of the 60 reasons reported for a change to the diagnosis or treatment plan occurred when a CBCT scan was ordered for an unrelated reason. However, among the 79 instances when a CBCT scan was not ordered, no changes were reported in the subsequent evaluations of these examinations. These findings suggest that there is little utility to an examination made without a clinical indication. Furthermore, a recent study associated an increase in ionizing radiation exposure in children to leukemia and brain cancer, emphasizing the importance of the benefit of ionizing radiation outweighing the risk. Because the likelihood of finding a significant abnormality is small, and most likely magnified due to the relatively high number of problems in our cases, we do not advise ordering a CBCT scan for patients not otherwise indicated solely because of a chance of finding something that will provide valuable information.

Diagnosis and treatment plan changes can range from mild to major. To assess the clinical significance of a change, the participants indicated whether they thought that the information obtained from the CBCT scan would influence the patient’s treatment outcome. The presence of unerupted teeth resulted in the most changes, yet had the least likelihood of affecting the expected treatment outcome. Many treatment changes from unerupted teeth had to do with the position of the unerupted tooth in relation to the roots of adjacent teeth and the mechanics that would be applied to bring it into occlusion. Although this change is significant, many participants believed that this would not substantively change the eventual outcome of the treatment. On the other hand, changes associated with skeletal discrepancies and dental crowding affected the expected treatment outcome 100% of the time. The treatment changes to skeletal problems usually resulted in a decision whether to have orthognathic surgery, which would have a pronounced impact on the outcome of the treatment. Although treatment plan changes for crowding were relatively few, the change was usually from a decision whether to extract teeth; this can influence the eventual positions of teeth and the length of treatment.

The availability of a CBCT examination significantly increased the confidence of orthodontists in their diagnostic and treatment plans. The greatest increases in confidence were found in the 2 participants who reported making examinations of 90% to 100% of their private patients or the 4 who own a CBCT machine. Atchison et al found that the average confidence values in the diagnosis and treatment plan after analyzing study models, photographs, patient history, and 2-dimensional radiographs were 87% and 84%, respectively. Our study began with analysis of all records plus 2-dimensional radiographs; despite different patient cases and different participants, we found comparable initial confidence values in the diagnoses and treatment plans (87% and 78%, respectively). The increases in the confidence percentages after examining the CBCT images was statistically significant for cases 2 through 6, suggesting that our participant orthodontists received benefits for 5 of the 6 cases.

Those who own a CBCT machine or reported using CBCT for more that 90% of their patients in private practice ordered more CBCT examinations and reported higher percentages of changes to the diagnosis and treatment plan, and greater changes in their confidence after viewing the CBCT images. This study was designed to allow participants the freedom to manipulate the CBCT data; thus, participants with more knowledge and experience with CBCT should be better at extracting information from the CBCT data. Those who had less than 10 years of experience in practice (5 of the 6 had less than 3 years of practice experience) had received extensive instruction on the use of CBCT in residency programs. Despite their familiarity with CBCT examinations however, these recent graduates were not significantly different when compared with those who graduated before CBCT training was available in residency programs with respect to changes in diagnoses or treatment plans. They ordered these examinations significantly less frequently than did their colleagues who had been in practice longer. In this study, we allowed for subjective responses on whether the diagnosis and treatment plan changed, and the amount of confidence that was gained. It might be that the greater number of CBCT examinations ordered by those who own a CBCT machine or use CBCT for more that 90% of their private patients, and their higher rates of changes to diagnoses and treatment plans, and higher levels of change in confidence, all primarily reflect a personal preference of orthodontic records.

There were several limitation to this study. First, it relied on self-selected participants; thus, the sample could be biased from nonprobability sampling. This sample size was sufficient to identify clear differences among patient cases and 3 patient characteristics with regard to the impact of CBCT on the diagnostic and treatment planning process. However, with more cases, we might have found significant differences for other patient characteristics. A larger sample of cases would also allow for a broader range of severity of the patient characteristics to be evaluated, providing further information as to when a CBCT scan should be ordered. For example, we found that a CBCT scan is beneficial for patients with severe root resorption, but CBCT might contribute to cases with less severe root resorption if those cases were available to show participants. Although we demonstrated that CBCT scans contribute to the diagnosis and treatment planning process in some cases, we did not attempt to evaluate the accuracy of the diagnoses and treatment plans provided.

Conclusions

The results of this study support obtaining a CBCT scan before orthodontic diagnosis and treatment planning when a patient has an unerupted tooth with delayed eruption or a questionable location, severe root resorption as diagnosed with a periapical or panoramic radiograph, or a severe skeletal discrepancy. Obtaining a CBCT scan to examine for abnormalities of the TMJ, airway, or crowding did not result in significant changes in the diagnosis or the treatment plan. We propose that CBCT scans should only be ordered when there is a clear, specific, and clinical justification for the patient. Our findings do not support a CBCT examination of every patient.

We thank the 24 orthodontists who gave generously of their time for this project, Kang Ting for his guidance, and Jeffrey Gornbein for his statistical support.

The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.

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Impact of cone-beam computed tomography on orthodontic diagnosis and treatment planning Ryan J. Hodges , Kathryn A. Atchison and Stuart C. White American Journal of Orthodontics and Dentofacial Orthopedics, 2013-05-01, Volume 143, Issue 5, Pages 665-674, Copyright © 2013 American Association of Orthodontists Introduction In this study, we measured the impact of cone-beam computed tomography (CBCT) on orthodontic diagnosis and treatment planning. Methods Participant orthodontists shown traditional orthodontic records for 6 patients were asked to provide a diagnostic problem list, a hypothetical treatment plan, and a clinical certainty. They then evaluated a CBCT scan for each patient and noted any changes, confirmations, or enhancements to their diagnosis and treatment plan. Results The number of diagnosis and treatment plan changes varied widely by patient characteristics. The most frequently reported diagnosis and treatment plan changes occurred in patients with unerupted teeth, severe root resorption, or severe skeletal discrepancies. We found no benefit in terms of changes in treatment plan for patients when the reason for obtaining a CBCT scan was to examine for abnormalities of the temporomandibular joint or airway, or crowding. Orthodontic participants who own CBCT machines or use CBCT scans frequently in practice reported significantly more diagnosis and treatment plan changes and greater confidence after viewing the CBCT scans during the study. Conclusions The results of this study support obtaining a CBCT scan before orthodontic diagnosis and treatment planning when a patient has an unerupted tooth with delayed eruption or a questionable location, severe root resorption as diagnosed with a periapical or panoramic radiograph, or a severe skeletal discrepancy. We propose that CBCT scans should be ordered only when there is clear, specific, individual clinical justification. Radiographs are an indispensible tool in the evaluation of the bony structures of the head and neck in pretreatment orthodontic diagnosis and treatment planning. Previous research has shown that lateral cephalograms and panoramic, anterior periapical, and posterior bitewing radiographs provide sufficient information for most orthodontic patients. These radiographic techniques provide 2-dimensional information about the maxillomandibular relationship, the position of the dentition in relation to basal and alveolar bones, the airway, skeletal or dental disease, root anatomy and angulation, and a gross visualization of the osseous anatomy of the temporomandibular joint (TMJ). With the advent of cone-beam computed tomography (CBCT), it became possible to evaluate the hard and soft tissues of the maxillofacial region in 3 dimensions and in high spatial detail. Additionally, visualization of the craniofacial complex in 3 dimensions is also possible with surface reconstruction views. Such information has the potential to improve orthodontic diagnosis and treatment planning, including airway analysis, TMJ evaluation, positions of impacted teeth, orthognathic surgical planning, evaluation of skeletal asymmetries, root position and structure, and miniscrew placement. However, the use of CBCT entails both financial costs and potential risks from radiation exposure. Some researchers have provided recommendations for ordering CBCT scans based on specific characteristics, including facial asymmetry, sleep apnea, impacted teeth, intent to use dental mini-implants, consideration of rapid maxillary expansion, and persistent TMJ symptoms. Others have advocated the routine used of CBCT in standard orthodontic diagnosis and treatment planning because of the additional diagnostic information that is potentially available. The decision to use any imaging modality before orthodontic treatment is justified when there is a reasonable expectation that a radiograph will result in a clinical benefit. This study was designed to measure the impact of CBCT in orthodontic diagnosis and treatment planning, and to determine the extent to which patient characteristics might provide benefits to clinicians in diagnosis and treatment planning. Material and methods The records and study models of 6 patients treated in the orthodontic clinic at the University of California at Los Angeles were selected and duplicated. The patient case records included, at a minimum, medical and dental histories; stone study models trimmed to centric relation; images of the full-mouth intraoral and extraoral photographs; lateral cephalometric, panoramic, and full-mouth series views; and the initial CBCT examination. All CBCT scans were made on a NewTom 3G machine (QR S.r.l., Verona, Italy) with a 12-in field of view and reconstructed with a 0.5-mm slice thickness. The cases were selected to represent a broad range of clinical characteristics commonly encountered in orthodontic practices, including Class I, Class II, and Class III molar relationships, canine impactions, anterior open bites, anterior and posterior crossbites, dental crowding, airway and TMJ problems, and severe skeletal asymmetries ( Table I ). The cases exposed the participants to common patient characteristics, especially problems where CBCT has been suggested to be beneficial, but without regard to prevalence. For example, the prevalence of impacted maxillary canines is 1% to 2.5%, but in our study, impacted maxillary canines were present in 2 of the 6 cases. Table I Patient case characteristics Patient case Age Sex Angle class Unerupted tooth Root position/resorption Severe skeletal discrepancy TMD Airway problem Crowding Case severity 1 13 y 0 mo M II N N N N N N Low 2 7 y 3 mo F III Y N N N N Y Low 3 15 y 3 mo M I N N N N Y Y Medium 4 11 y 6 mo F II Y Y N N N Y High 5 20 y 1 mo F II Y N Y Y Y N High 6 16 y 1 mo M III N N Y N Y Y Medium M , Male; F , female; N , no; Y , yes; TMD , TMJ disorder. Letters briefly describing the study and inviting participation were sent via e-mail to 219 members of the Pacific Coast Society of Orthodontists who resided in the Southern California area. A letter was also sent to the program directors of the 3 regional orthodontic programs: University of California, Los Angeles; University of Southern California, Los Angeles; and Loma Linda University, Loma Linda, Calif. Those who responded were contacted and told that participation would consist of 1 interview (estimated to last about 2 hours) during which the participant would be shown orthodontic cases and asked to provide hypothetical diagnoses and treatment plans. The participants were assured that the accuracy of their diagnosis and treatment plan was not being evaluated, but, rather, the investigators wished to determine the information used to formulate their diagnoses and treatment plans. This study was approved by the institutional review board of the University of California at Los Angeles. A standardized interview was used. Descriptive data were gathered about the participants (sex, orthodontic program and year of graduation, whether they owned a CBCT device, and for what percentage of their patients did they order CBCT scans before treatment). The participants were shown the case records for the 6 patients. One case, selected by the investigators as an easy diagnostic one, was always presented first to familiarize the participants with the process. The order of presentation of the other 5 cases was systematically varied to prevent changes to the outcome variables associated with fatigue. Each case was presented on a 15.4-in screen (MacBook Pro; Apple, Cupertino, Calif) with software (Dolphin Imaging, Chatsworth, Calif). The participants were given each patient's medical and dental histories and shown the study models, intraoral and extraoral photographs, and lateral cephalometric, panoramic, and full-mouth series radiographs. The participant was allowed to rotate and manipulate all images (except the CBCT images) during this part of the interview. They were asked to describe their diagnostic problem list. They were also asked to provide their degree of certainty with their diagnosis using a visual analog scale ranging from 0% (complete guess) to 100% (absolutely certain). This process was repeated for the treatment plan. The participants were then asked whether they would request a CBCT scan for this patient and their rationale. Regardless of whether they requested a CBCT scan, the participants were asked to evaluate the CBCT examination and note any changes, enhancements, or confirmations to their diagnosis and treatment plan, including reasons for these changes. Next, the participants were given preconstructed images of the TMJ, impacted teeth, and teeth with root resorption. They were also encouraged to view the multi-planar reconstructions and to create any other cross-sections from the CBCT scan that would contribute to their diagnosis and treatment plan. After data collection, the considerations for ordering CBCT scans and associated diagnostic and treatment plan changes were grouped into the following 8 categories: unerupted tooth, root position or resorption (>2 mm), severe skeletal discrepancy (−2° ≥ ANB ≥ 6°, or asymmetry ≥4 mm), TMJ disorder (signs or symptoms of clicking, popping, or pain), airway problems, crowding (>5 mm in either arch), medico-legal reasons, and financial costs. During the analysis, a hierarchy of change, enhancement, and confirmation was established, with a change having the greatest impact. For example, if a participant reported a change and an enhancement to a diagnosis, both were recorded but only the change was used for analysis. The participants then provided final percentages of certainty for both their diagnoses and treatment plans. At the conclusion of each case, the participants were asked how the CBCT scan was useful in their diagnosis and whether the information from it would have influenced the treatment outcome for that patient. They were allowed to explain any radiographs or other diagnostic aids that they would have ordered if the CBCT scan were unavailable. Statistical analysis The P values for comparing binary outcomes (percentages) from the same participants across patient profiles were computed by using the Cochran Q procedure, a generalization of the McNemar test for balanced 2 × k tables, where k is the number of subjects. For comparisons across categories when participant-patient was the unit of analysis, this was expanded to a repeated-measure logistic model with a random participant effect to take into account nonindependence. The P values for comparing continuous confidence score outcomes across patients from the same participants were computed by using the nonparametric Friedman test for repeated-measure comparisons, a generalization of the Wilcoxon signed rank test for paired continuous data. Results Twenty-four participants began the interview process, and 23 finished all 6 patient cases; 1 participant finished 5. The participants were mostly men (n = 21), trained at 10 orthodontic programs, and had an average of 24 years of experience (range, 1-44 years). The participants reported using CBCT examinations for 0% to 100% of their patients in their practices (mean, 12.1%; median, 5%) ( Fig 1 ). Fig 1 Participants' self-reported use of CBCT in private practice. There were 64 CBCT scans ordered (45% of opportunities) during the interview process ( Table II ). The number of CBCT requests for each case ranged from 2 to 22, and 64% of the CBCT scans requested were for cases 4 and 5. For case 1, only 2 CBCT scans were requested. Two participants never requested a CBCT during their review of the 6 cases, 16 participants ordered 2 to 4 CBCT scans, and 2 participants requested a CBCT scan for all 6 cases ( Table III ). Table II Number of CBCT scans ordered for each patient Patient case CBCT scans ordered Differences n % SE 1 2 ∗ 8 ±6 2, 3, 4, 5, 6 2 6 25 ±9 1, 4, 5 3 7 29 ±10 1, 4, 5 4 22 † 92 ±6 1, 2, 3, 6 5 19 † 79 ±9 1, 2, 3, 6 6 8 35 ±10 1, 4, 5 Total 64 45 ±2.8 ∗ Significantly fewer than all other cases ( P <0.05). † significantly more than cases 1-3 and 6 ( P <0.05). Table III CBCT scans ordered by participants CBCT scans requested (n) Participants (n) 0 2 1 3 2 8 3 4 4 4 5 1 6 2 There were 26 changes to the participants' diagnoses after viewing the CBCT scans (18% of opportunities) and 28 changes to the treatment plans (20% of opportunities) ( Table IV ). The number of changes varied widely by patient case, ranging from 1 to 11, with cases 4 and 5 together comprising over 67% of the changes to the diagnoses (18 of 26 changes) and treatment plans (19 of 28 changes). Table IV Changes and enhancements to the diagnoses and treatment plans Patient case Diagnosis changes Treatment plan changes n % SE n % SE 1 1 4 ±4 2 8 ±6 2 2 8 ±6 2 8 ±6 3 1 4 ±4 1 4 ±4 4 9 ∗ 38 ±10 8 ∗ 33 ±10 5 9 ∗ 38 ±10 11 † 46 ±10 6 4 17 ±8 4 17 ±8 Total 26 18 28 20 ∗ Significantly different from cases 1, 2, and 3 ( P <0.05). † significantly different from cases 1, 2, 3, and 6 ( P <0.05). The number of CBCT scans ordered and the number of resulting changes to the diagnoses and treatment plans varied by patient characteristics ( Table V ). Multiple characteristics were present in each case; thus, participants gave multiple reasons for ordering a CBCT scan and for a change to a diagnosis or treatment plan. Table V Summary of changes to diagnosis and treatment plan by patient characteristic Patient characteristic n Characteristic present CBCT scan ordered Diagnosis change Treatment plan change n % SE (%) n % SE (%) n % SE (%) Unerupted tooth 71 N 2 3 2 0 0 0 0 0 0 72 Y 39 ∗ 54 6 15 ∗ 21 5 16 ∗ 22 5 Root position/resorption 119 N 8 7 2 2 2 1 0 0 0 24 Y 13 ∗ 54 10 3 ∗ 13 7 6 ∗ 25 9 Severe skeletal discrepancy 96 N 3 3 2 0 0 0 1 1 1 47 Y 6 ∗ 13 5 5 ∗ 11 5 6 ∗ 13 5 TMD 119 N 9 8 2 6 5 2 1 1 1 24 Y 4 ∗ 17 8 3 13 7 2 8 6 Airway problem 72 N 3 4 2 3 4 2 3 4 2 71 Y 11 ∗ 15 4 3 4 2 3 4 2 Crowding 48 N 2 4 3 1 2 2 0 0 0 95 Y 8 8 3 2 2 1 4 4 2 N , No; Y , yes; TMD , TMJ disorder. ∗ Values significantly different ( P <0.05). For 5 of the 6 patient characteristics, participants ordered CBCT scans more frequently ( P <0.05) when the characteristic was present. An unerupted tooth was the most frequently cited reason for ordering a CBCT scan (64% of orders), followed by root resorption (33% of orders). Of the 72 observations on patients with unerupted teeth, a CBCT scan was ordered 39 times when the characteristic was present (54%) and only twice when the characteristic was not present. Root resorption was cited as the rationale for ordering the CBCT scan 13 times when the characteristic was present (54%) and 8 times (7%) when the characteristic was not present. Severe skeletal discrepancy, TMJ disorders, and airway problems were cited less frequently, yet still significantly more frequently when the characteristic was present. Crowding was offered as a reason for ordering a scan but was not statistically significant. For 3 of the 6 patient characteristics—unerupted tooth, root resorption, and severe skeletal discrepancy—the participants reported changes to the diagnosis and treatment plan significantly more frequently when the characteristic was present. An unerupted tooth was the most frequently cited reason for changes to the diagnosis (15 instances, or 21% of the cases with the characteristic present) and treatment plan (16 instances, or 22%). It was never mentioned in cases without the characteristic present. Root position or resorption was present in fewer cases, and CBCT scans were ordered for diagnostic reasons both when the characteristic was present (3 times) and when it was not (2 times). In proportion, it was the most common reason for treatment plan changes (6 times, or 25%). Severe skeletal discrepancy was reported as a reason for a change to the diagnosis 5 times (11%). For the treatment plan, 6 changes occurred when there was a severe skeletal discrepancy and once when it was not present. There was no significant difference in the reasons cited for ordering by the presence or absence of the characteristics for TMJ disorder, airway problem, and crowding. Treatment outcome was defined as the expected result of treatment as reported by the participants. We evaluated the association between treatment plan changes and expected effect on treatment outcome as reported by the participants ( Table VI ). The presence of unerupted teeth resulted in 16 treatment changes, and the participants expected that 7 (44%) of these would affect patient outcome. For the other patient characteristics, the participants reported that the changes would affect patient outcome for between 67% and 100% of the treatment plans. Table VI Treatment plan changes and effect on expected treatment outcome Patient characteristic Treatment plan changes Treatment plan change and outcome affected Proportion (%) SE (%) Unerupted tooth 16 7 44 12 Root position/resorption 6 5 83 15 Severe skeletal discrepancy 7 7 100 0 TMD 3 2 67 27 Airway problem 6 5 83 15 Crowding 4 4 100 0 Total 42 30 71 TMD , Temporomandibular joint disorder. The participants' initial confidence ranged from 75% to 97% for diagnoses, and from 83% to 95% for treatment plans ( Fig 2 ). Patient cases 4 and 5 had the lowest mean initial diagnosis confidence values; case 1 had the highest value. Significant increases in the mean percentages of confidence in the diagnoses and treatment plans were demonstrated for patient cases 2 to 6 after the participants viewed the CBCT scans ( Fig 3 ). Fig 2 Mean confidence intervals in the initial diagnoses and treatment plans. Error bars represent standard deviations. Fig 3 Mean changes in diagnoses and treatment plans. Error bars represent standard deviations. *Significant change ( P <0.05). We evaluated whether sex, practice experience, CBCT use in private practice, or ownership of a CBCT machine influenced the outcome variables ( Table VII ). Sex was not significantly associated with any outcome variable. Orthodontists in practice for a decade or less ordered significantly fewer CBCT examinations than did more experienced orthodontists. Two orthodontists who reported ordering CBCT scans for 90% to 100% of their patients in private practice ordered significantly more CBCT examinations than did the other orthodontists (100% vs 40%). These orthodontists also reported significantly more changes to their diagnoses (75% vs 13%) and treatment plans (83% vs 14%), and greater gains in confidence than the 22 who ordered CBCT examinations for 0% to 15% of their private practice patients. Similarly, the 4 orthodontists who owned a CBCT machine ordered more CBCT examinations (79% vs 38%) and reported more changes to their diagnoses (63% vs 9%) and treatment plans (67% vs 12%) and greater gains in confidence than did the 20 who did not own a CBCT machine. Table VII CBCT scan ordering patterns, number of changes to diagnosis and treatment plan, and mean change in participant's percentage of confidence Participant characteristic n Number (%) of CBCT scans ordered Number (%) of changes Mean confidence change (%) Diagnosis Treatment plan Diagnosis Treatment plan Sex M (n = 21) 125 56 (45) 25 (20) 27 (22) 10 9 F (n = 3) 18 8 (44) 1 (6) 1 (6) 3 3 Years in practice 1-10 (n = 6) 36 8 (22) ∗ 4 (11) 5 (14) 10 11 11-29 (n = 7) 42 22 (52) 7 (17) 9 (21) 10 9 30+ (n = 11) 65 34 (52) 15 (23) 14 (22) 7 6 % of patients having CBCT scan 0-15 (n = 22) 131 52 (40) 17 (13) 18 (14) 6 6 90-100 (n = 2) 12 12 (100) ∗ 9 (75) ∗ 10 (83) ∗ 35 ∗ 33 ∗ Own CBCT N (n = 20) 119 45 (38) 11 (9) 14 (12) 5 5 Y (n = 4) 24 19 (79) ∗ 15 (63) ∗ 16 (67) ∗ 26 ∗ 25 ∗ M , Male; F , female; N , no; Y , yes. ∗ Significantly different ( P <0.05). Discussion This study was designed to (1) investigate patients' clinical characteristics associated with a decision by orthodontists to order CBCT examinations and (2) measure the utility of these examinations in terms of their influence on diagnoses and treatment plans. Fryback and Thornbury described a hierarchical model for efficacy of studies in diagnostic imaging. These range from radiographic studies assessing the technical efficacy of the imaging system (level 1) to studies measuring the societal benefit of imaging (level 6). Our study measured diagnostic thinking and therapeutic efficacy, whether the CBCT examination influences the treatment plan (level 4) and, to some extent, patient outcome efficacy, and whether the findings from the examination are likely to change the patient's outcome (level 5). The number of CBCT examinations requested varied widely by participant, ranging from 2 participants who never requested a scan to another 2 participants who always ordered a scan, with most participants ordering few CBCT scans. This pattern mirrored their stated ordering practices in their private practices. These findings suggest no wide agreement, at least among these orthodontists with far-ranging experience and educational backgrounds, regarding the appropriate indications for making CBCT examinations. Our participants requested a CBCT scan during diagnosis and treatment planning substantially more often than they reported using CBCT scans for patients in their private practices (45% vs 12%). This discrepancy might be attributable to the higher prevalence of patient problems we selected for our test cases than in private practice. For example, 33% of the patients in this study had an impacted canine, whereas the prevalence of impacted maxillary canines is 1% to 2.5%. Also, it might have simply been easier to order a CBCT scan as a part of this study when there was no financial or radiation cost associated with it. Three participants stated that they requested a CBCT scan “only if cost is not a factor.” The number of CBCT scans ordered was associated with case severity. Patient cases 4 and 5 were rated as the most difficult by the investigators and an orthodontic faculty member at the University of California at Los Angeles, and those cases had the most CBCT scans ordered by the participants (22 and 19, respectively). Cases 1 and 2 were categorized as having a low degree of difficulty, and they had 2 and 6 CBCT scans, respectively, requested by the participants. This suggests that most participants thought that traditional radiographs were sufficient to diagnose and plan these cases. Of the 6 patient characteristics cited as reasons for a change to the diagnosis or treatment plan, unerupted tooth, root resorption, and severe skeletal discrepancy were the most frequent. For these characteristics, there were significantly more changes to the diagnoses and treatment plans when the case had the characteristic when compared with cases without the characteristic. This suggests that a benefit is gained from CBCT scans when a patient has an unerupted tooth, root resorption as diagnosed on a periapical or panoramic view, or a severe skeletal discrepancy diagnosed on a lateral cephalometric view. These patient characteristics were also reported by Kapila et al as those most likely to benefit from a CBCT examination. TMJ disorders, airway difficulties, and crowding, however, were not associated with significant changes in the diagnosis or treatment plan. Because of our small sample size and the selection of patient cases, the possibility of a benefit from a CBCT scan for some patients with these characteristics cannot be ruled out. We considered the possibility that valuable information might be discovered serendipitously: ie, findings on the images ordered for reasons not related to the patient characteristic prompting an examination. Indeed, 19 of the 60 reasons reported for a change to the diagnosis or treatment plan occurred when a CBCT scan was ordered for an unrelated reason. However, among the 79 instances when a CBCT scan was not ordered, no changes were reported in the subsequent evaluations of these examinations. These findings suggest that there is little utility to an examination made without a clinical indication. Furthermore, a recent study associated an increase in ionizing radiation exposure in children to leukemia and brain cancer, emphasizing the importance of the benefit of ionizing radiation outweighing the risk. Because the likelihood of finding a significant abnormality is small, and most likely magnified due to the relatively high number of problems in our cases, we do not advise ordering a CBCT scan for patients not otherwise indicated solely because of a chance of finding something that will provide valuable information. Diagnosis and treatment plan changes can range from mild to major. To assess the clinical significance of a change, the participants indicated whether they thought that the information obtained from the CBCT scan would influence the patient's treatment outcome. The presence of unerupted teeth resulted in the most changes, yet had the least likelihood of affecting the expected treatment outcome. Many treatment changes from unerupted teeth had to do with the position of the unerupted tooth in relation to the roots of adjacent teeth and the mechanics that would be applied to bring it into occlusion. Although this change is significant, many participants believed that this would not substantively change the eventual outcome of the treatment. On the other hand, changes associated with skeletal discrepancies and dental crowding affected the expected treatment outcome 100% of the time. The treatment changes to skeletal problems usually resulted in a decision whether to have orthognathic surgery, which would have a pronounced impact on the outcome of the treatment. Although treatment plan changes for crowding were relatively few, the change was usually from a decision whether to extract teeth; this can influence the eventual positions of teeth and the length of treatment. The availability of a CBCT examination significantly increased the confidence of orthodontists in their diagnostic and treatment plans. The greatest increases in confidence were found in the 2 participants who reported making examinations of 90% to 100% of their private patients or the 4 who own a CBCT machine. Atchison et al found that the average confidence values in the diagnosis and treatment plan after analyzing study models, photographs, patient history, and 2-dimensional radiographs were 87% and 84%, respectively. Our study began with analysis of all records plus 2-dimensional radiographs; despite different patient cases and different participants, we found comparable initial confidence values in the diagnoses and treatment plans (87% and 78%, respectively). The increases in the confidence percentages after examining the CBCT images was statistically significant for cases 2 through 6, suggesting that our participant orthodontists received benefits for 5 of the 6 cases. Those who own a CBCT machine or reported using CBCT for more that 90% of their patients in private practice ordered more CBCT examinations and reported higher percentages of changes to the diagnosis and treatment plan, and greater changes in their confidence after viewing the CBCT images. This study was designed to allow participants the freedom to manipulate the CBCT data; thus, participants with more knowledge and experience with CBCT should be better at extracting information from the CBCT data. Those who had less than 10 years of experience in practice (5 of the 6 had less than 3 years of practice experience) had received extensive instruction on the use of CBCT in residency programs. Despite their familiarity with CBCT examinations however, these recent graduates were not significantly different when compared with those who graduated before CBCT training was available in residency programs with respect to changes in diagnoses or treatment plans. They ordered these examinations significantly less frequently than did their colleagues who had been in practice longer. In this study, we allowed for subjective responses on whether the diagnosis and treatment plan changed, and the amount of confidence that was gained. It might be that the greater number of CBCT examinations ordered by those who own a CBCT machine or use CBCT for more that 90% of their private patients, and their higher rates of changes to diagnoses and treatment plans, and higher levels of change in confidence, all primarily reflect a personal preference of orthodontic records. There were several limitation to this study. First, it relied on self-selected participants; thus, the sample could be biased from nonprobability sampling. This sample size was sufficient to identify clear differences among patient cases and 3 patient characteristics with regard to the impact of CBCT on the diagnostic and treatment planning process. However, with more cases, we might have found significant differences for other patient characteristics. A larger sample of cases would also allow for a broader range of severity of the patient characteristics to be evaluated, providing further information as to when a CBCT scan should be ordered. For example, we found that a CBCT scan is beneficial for patients with severe root resorption, but CBCT might contribute to cases with less severe root resorption if those cases were available to show participants. Although we demonstrated that CBCT scans contribute to the diagnosis and treatment planning process in some cases, we did not attempt to evaluate the accuracy of the diagnoses and treatment plans provided. Conclusions The results of this study support obtaining a CBCT scan before orthodontic diagnosis and treatment planning when a patient has an unerupted tooth with delayed eruption or a questionable location, severe root resorption as diagnosed with a periapical or panoramic radiograph, or a severe skeletal discrepancy. Obtaining a CBCT scan to examine for abnormalities of the TMJ, airway, or crowding did not result in significant changes in the diagnosis or the treatment plan. 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