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تأثیر آموزش دانشجویان دندان پزشکی در شاخص نیاز درمانی ارتدنسی

Efficacy of training dental students in the index of orthodontic treatment need
Am J Orthod Dentofacial Orthop 2002;122:456-62
November 2002 • Volume 122 • Number 5
Columbus, Ohio
Orthodontic studies over several decades have found generally inconsistent opinions among dentists when evaluating orthodontic treatment need. There has also been recent concern that dental school education does not sufficiently prepare dentists to diagnose malocclusion and make appropriate referrals of potential orthodontic patients. The purpose of this study was to investigate the efficacy of using the index of orthodontic treatment need (IOTN) as a tool to improve dental students’ ability to assess orthodontic treatment need. Fourth-year dental students were randomly divided into control, sham-control, and experimental groups stratified for mean grade point average. On 2 occasions, the subjects evaluated 30 orthodontic study models with a gold standard previously established by an expert panel of 15 orthodontists for orthodontic treatment need. The experimental group reevaluated the models after IOTN instruction. Kappa statistics, sensitivity, and specificity were calculated for each subject. Analysis of covariance (ANCOVA) showed that the experimental group had significantly higher agreement with the expert panel after IOTN training than did either control group. IOTN is a promising teaching aid for improving educational outcomes for orthodontic referral.

In 1899, Edward H. Angle1 stated: “I am impressed with the belief that although diagnosis is the question of greatest importance, it is yet apparently the least intelligently studied and comprehended.” Angle’s Classification of Malocclusion helped to define both occlusion and the orthodontic specialty. A century later, this classification is still the accepted method of classifying occlusion for communication among dental practitioners. However, Angle’s classification is based primarily on anteroposterior molar relationships and has low validity in determining orthodontic treatment need.2 Increasingly, malocclusion is considered an expression of normal biologic variation, and treatment need is often based as much on psychosocial concerns as on proven oral health risks attributable to malocclusion. Associations between malocclusion and secondary oral disease such as periodontitis, caries, and temporomandibular disorders are tenuous at best.3,4 The criteria for determining who receives or needs orthodontic treatment is controversial, and there is no infallible test for confirming treatment need. These factors make it particularly difficult for the general dentist to determine for whom orthodontic treatment is indicated, but the traditional pathway to orthodontic care passes through the

general dentist’s office. Shaw et al5 found that 70% of orthodontic patients initially were prompted to seek orthodontic care by their general dentists. However, a 1994 study by Richmond et al6 showed that a panel of 74 dentists could not agree on what constituted a need for orthodontic treatment on the basis of dental health. In some instances, the intraobserver agreement was equivalent to chance. In a study of orthodontists by Keeling et al,7 excellent subjective reliability existed only for evaluating the presence of a posterior crossbite (_ _ .79).

he genesis of this diagnostic shortcoming was recently illuminated by an education outcomes assessment by Brightman et al,8 whose study was initiated because orthodontists in northern Ohio were concerned about their lack of referrals from general dentists. Concomitantly, fourth-year dental students at the closest dental school (Case Western Reserve in Cleveland) expressed concern that they had no clinical experience in orthodontics and did not know how to apply didactic knowledge to clinical situations. Brightman et al8 concluded that, although didactic knowledge increased,

orthodontic diagnostic skills did not substantially improve during undergraduate dental education. Consequently, the ability to make appropriate referrals for treatment did not improve during dental education. Students “ . . . had difficulty recognizing instances of spacing, crowding, overbite, overjet, and crossbite” and “did not recognize unusual dental conditions such as congenitally absent, supernumerary, or impacted teeth.” The dental health component (DHC) of IOTN specifically addresses the deficiencies noted in this academic outcomes study. The DHC (Table I) of IOTN is a distillation of the factors currently believed to be related to the deleterious health effects of malocclusion. The 5 traits assessed by the DHC are missing teeth, overjet, crossbites, displacement of contact points (crowding), and overbite. The aesthetic component (AC) of the IOTN (Fig 1) satisfies a mandate from the 1993 American Association of Orthodontists Orthodontic Indices Conference9 that an index should include an esthetic or psychosocial component. The AC of the IOTN consists of a 10-point scale, illustrated by a series of numbered photographs. Brook and Shaw10 originally developed the IOTN as a second-generation occlusal index with 2 components to provide a balanced approach to allocating need. The

IOTN’s validity and reliability have been extensively verified both abroad and in the United States.11-14

The referral of patients for orthodontic care is an arbitrary process that depends as much on the observer as on the malocclusion. Inconsistent or invalid standards for orthodontic referral result in some patients attending unnecessary orthodontic evaluations and other patients missing out on timely referrals for treatment. This exposes a deficiency in the diagnostic ability of dental school graduates and in the dental school educational process. The purpose of this study was to test the use of the IOTN as an educational tool in predoctoral dental education.

MATERIAL AND METHODS

Subject selection

Fourth-year dental students at The Ohio State University College of Dentistry volunteered to participate

in this study. Students were excluded if they had any experience with occlusal indexes. Three stratified, random sample groups were formed with nearly equivalent mean grade point averages (GPAs). Group 1 was the control; Group 2 was a sham-control group to control for the Hawthorne Effect,15 and Group 3 was the experimental group. Each group initially contained 29 participants. Between 21 and 25 volunteers came for the baseline assessment, and attrition from the first

assessment (T1) to the second assessment (T2) further reduced the number to 20 per group. A power analysis indicated that a sample size of 20 was adequate. A group of orthodontic study models was previously duplicated from the archives of the University of Pittsburgh. This sample was used by DeGuzman et al16

for peer assessment rating (PAR) validation; Younis et al11 to validate the IOTN, handicapping malocclusion assessment, handicapping labiolingual deviations, and PAR; and by Beglin12 to validate the dental aesthetic index, California modification of the handicapping labiolingual index, and IOTN. In addition, Beglin12 established this set of casts as a viable gold standard by showing a high agreement between the opinions of orthodontists in western Pennsylvania and central Ohio (_ _ .83). In Beglin’s study, orthodontic raters assigned a score to each cast on an adjectival scale where 1 equaled none/minimal need and 7 equaled very great need.12 The raters then established an indicated treatment point at which orthodontic treatment was indicated. This cutoff point was calculated to be 3.53. All casts below this point were in the no-treatment category, and all models at or above were in the treatment category. Thirty models were selected that ranged from

2.00 to 5.13 on the 7-point scale. Models at either end of the malocclusion spectrum were excluded because borderline cases are more difficult for the students to categorize.17 This yielded a more challenging test of their diagnostic abilities both at baseline and after training.

In a pilot study, 6 students assessed 11 casts from adjectival grades 1 to 7 for orthodontic treatment need. For _, the mean was .711 with an SD of .182. For an level of .05 and a power of 80%, a sample size of 20 was required to detect a change in _ of greater than or equal to .12. The selected 30 casts were arranged on a table in archival numbered order that had no relation to treatment need. The subjects were asked to determine orthodontic treatment need using the same instructions that were given to the orthodontic raters who established the gold standard. The word “referral” was substituted for “treatment” to reflect the subjects’ nonspecialist status. The instructions were as follows: You are the consultant for a private corporation for which a fund has been established to provide orthodontic

treatment for personnel. You are to evaluate these study casts and answer the following question:

In your opinion, does this occlusion need referral for orthodontic treatment? All subjects made baseline decisions of yes or no at T1 for orthodontic treatment referral. The time from T1 to T2 was minimized to lessen the chance for other dental school training or communication between the groups to influence the results. The IOTN group was tested last to prevent knowledge of IOTN procedures from filtering out to the 2 control groups. The time from T1 to T2 for most subjects was 9 days but ranged up to 20 days.

At T2, groups reevaluated the casts exactly as before. Before T2, the sham-control group participated

in an exercise on posterior-anterior cephalometrics. The subjects viewed a computer-displayed presentation and drew vertical and horizontal planes from Grummon’s analysis18 on provided tracings. They then reevaluated the casts exactly as before. Before T2, the experimental group viewed a computer presentation similar in content to Burden et al’s19 “A Guide to Assessing the Need for Orthodontic Treatment.” (This was a self-paced study guide made available to general dentists to improve the appropriateness of their referrals without requiring that they attend a time-intensive calibration session.) Instruction manuals identical to the presentation were also provided to be viewed concurrently with a familiarization exercise for both the AC and the DHC. Two of the sets

of models used in the presentation demonstrated several IOTN measurable traits and were duplicated so that each participant could grade the same models. Once all participants demonstrated accurate grading of each trait, the group moved on to the next IOTN trait. The acronym MOCDO (missing, overjet, crossbite, displacement of contact points, and overbite) was used to enhance learning. After the presentation, there was an opportunity for participants to ask questions and clarify the instructions. To facilitate learning and accommodate schedule conflicts, subgroups of 3 to 7 were taught over a 3-week period. One investigator provided all instruction. It was thought that the standard 1 or 2-day IOTN calibration session would be impractical in a dental school setting. Therefore, the instruction session

was designed to fit the time constraints of a standard lecture period, from 30 to 45 minutes. At the conclusion of the instruction, the experimental group subjects reassessed the models with IOTN and then made a referral or no referral decision on the basis of their findings. Optimal cutoff points as established by Beglin were used (DHC _ 3; AC _ 5).

Statistical analysis

We used _ to measure interobserver agreement on diagnostic tests.20 This experiment used a binary yes or no decision with no rank ordering, so a simple _ was used. Unlike percentage agreement, _ controls for agreement because of chance. Sensitivity (those correctly indicated for referral/

those requiring referral) was used as a measurement of the students’ ability to identify patients requiring referral for orthodontic evaluation. Specificity (those correctly not indicated for referral/those not requiring referral) was used to measure the students’ ability to identify those who did not require referral for orthodontic evaluation. For sensitivity and specificity, the numerator is the students’ decision, and the denominator is the orthodontic gold standard. Final scores of the 3 dependent variables, _, sensitivity, and specificity, were analyzed for significant differences because of treatment effect (IOTN training) with analysis of covariance (ANCOVA), with the initial value as the covariate. ANCOVA adjusts the final score to reflect baseline differences.

RESULTS

There were no significant pre-experimental group differences for gender or GPA (Table II). For _, the

ANCOVA showed a significant group effect (P _ .0001); the experimental group’s ability to assess orthodontic treatment need was significantly improved by IOTN training compared with the sham and the control

groups (Table III; Fig 2). There was also a significant gender effect (P _ .0289); males showed significantly better agreement with the gold standard. There was no significant group-by-gender interaction. For sensitivity, there were no significant effects (Table IV;; Fig 3). For specificity, there was a significant group effect (P _ .0001) and a significant gender effect (P _ .0377), but no significant group-by-gender interaction (Table V; Fig 4).

DISCUSSION

This study demonstrated that the IOTN is an effective educational resource to improve the orthodontic

diagnostic abilities of dental students. At T1, _ scores for the 3 groups ranged from fair to moderate strength of agreement. This finding is consistent with previously cited literature2,6,7 on the subjective agreement among dentists when evaluating orthodontic treatment need. At T2, the experimental group’s final adjusted mean showed substantial agreement, whereas the control and the sham-control groups still had only fair to moderate agreement21 (Table VI). IOTN training did not increase sensitivity to a significant degree. Because sensitivity started relatively high, there was little room for a positive effect. At baseline, the dental students could correctly identify the majority of patients who would benefit from orthodontic treatment. However, this high sensitivity was achieved partially at the expense of a relatively lower specificity. Mean adjusted specificity values in the experimental

group were significantly higher than in the shamcontrol group, but not significantly higher than in the

control group. This might be partly attributable to a positive treatment effect on the men in the experimental group and partly to a decline in performance of the women in the sham-control group.

This study also detected a performance difference between genders. Group composition did not differ

significantly as a result of gender, and analysis of GPA distribution by gender showed no significant difference (P _ .5065). The men had significantly better final adjusted mean _ and specificity values compared with the women. It is not known whether these differences are attributable to systematic biases in the research design, learning differences, or innate gender differences

when assessing orthodontic treatment need. A literature search for gender differences in dental education yielded no matches.

Current research3,4 finds the links between ideal occlusion and oral-facial health to be equivocal; this might leave the general dentist in a quandary regarding whom to refer. An index provides some measure of objectivity so that the referring dentist might confidently counsel patients on the relative need for orthodontic treatment as a part of comprehensive treatment planning.

The findings of this study give credence to Burden et al’s19 field trial in Great Britain of an IOTN learning package for general dentists. Formal IOTN training might take 1 or 2 days in a calibration session. Burden et al19 thought that presenting the information in a self-taught format would be more time efficient and acceptable to the general dentists. In a randomized controlled trial, dentists were separated into an IOTNtrained group and a group with no IOTN training. Their orthodontic referral patterns were then evaluated. A significant improvement was found in the odds that a patient referred by the test group definitely needed orthodontic treatment compared with patients referred by the control group.

Prioritization (therefore limitation) of orthodontic care through national health care plans in European

countries has been a prime factor behind the development of indexes such as the IOTN. Occlusal indexes in the United States have often been associated with efforts to allocate (limit) access to government-funded orthodontic care. There has been little incentive for private practitioners to embrace the use of indexes and surrender professional decision-making autonomy to insurance or welfare organizations. The limits of occlusal indexes are exposed when they are used to make fine  ifferentiations between patients seeking care. The level of confidence is much higher when an index such as the IOTN is used because it places patients in broader groups. A score of 4 compared with 3 under the IOTN reliably identifies a patient in greater need of orthodontic treatment. The same cannot be said for a grade of 44 compared with 43 on a scale that has finer gradations. The history and limitations of occlusal indexes have constrained their application in the United States. A key point of this study is that IOTN training improved the agreement of prospective general dentists, not with a bureaucratic standard, but with theirn local orthodontists. The educational community is increasingly adopting quality improvement methods from the business world. Establishing baseline performance levels and monitoring outcomes of improvement initiatives are cornerstones of the quality improvement movement. Although limited in scope to 1 school, dental students’ baseline orthodontic diagnostic performance might be inferred from the work of Brightman et al.8 The dental school experience might adequately prepare a student to take the National Board but do little to improve a student’s clinical orthodontic diagnostic expertise. This study validated a potential method to improve orthodontic educational outcomes. The IOTN might now be viewed not only as a valid and reliable occlusal index

but also as an efficacious resource for dental education.

CONCLUSIONS

Teaching dental students the IOTN significantly improved the agreement of their orthodontic evaluations

compared with an expert panel of orthodontists as measured by _. It was possible to train the students with a combination of computer-generated and hands-on instruction in a time period compatible with the constraints of a dental school curriculum.

REFERENCES

1. Angle EH. Classification of malocclusion. Dent Cosmos 1899; 41:248-64.

2. Gravely JF, Johnson DB. Angle’s classification of malocclusion: an assessment of reliability. Br J Orthod 1974; 1:79-86.

3. Howat A. Orthodontics and health: have we widened our perspectives? Community Dent Health 1993;10(Suppl 2):29-37.

4. Katz RV. An epidemiological study of the relationship between various states of occlusion and the pathological conditions of dental caries and periodontal disease. J Dent Res 1978;57:433-9.

5. Shaw WC, Gabe MJ, Jones BM. The expectations of orthodontic patients in South Wales and St Louis, MO. Br J Orthod 1980;7:75-80.

6. Richmond S, O’Brien KD, Roberts CT, Andrews M. Dentists variation in the determination of orthodontic treatment need. Br J Orthod 1994;21:65-8.

7. Keeling SD, McGorray S, Wheeler TT, King GJ. Imprecision in orthodontic diagnosis: reliability of clinical measures of malocclusion. Angle Orthod 1996;66:381-91.

8. Brightman BB, Hans MG, Wolf GR, Bernard H. Recognition of malocclusion: an education outcomes assessment. Am J Orthod Dentofacial Orthop 1999;116:444-51.

9. AAO Proceedings of the orthodontic indices consensus conference. St Louis: American Association of Orthodontists; 1993.

10. Brook PH, Shaw WC. The development of an index of orthodontic treatment priority. Eur J Orthod 1989;11:309-20.

11. Younis JW, Vig KW, Rinchuse DJ, Weyant RJ. A validation study of three indexes of orthodontic treatment need in the United States. Community Dent Oral Epidemiol 1997;25:358-62.

12. Beglin FM. Validation of three indices of orthodontic treatment need [thesis]. Columbus: The Ohio State University; 1997.

13. Shaw WC, Richmond S, O’Brien KD, Brook P, Stephens CD. Quality control in orthodontics: indices of treatment need and treatment standards. Br Dent J 1991;170:107-12.

14. Brook PH, Shaw WC. The development of an index of orthodontic treatment priority. Eur J Orthod 1989;11:309-20.

15. Roethlisberger FT, Dickson WJ. Management and the worker. Cambridge (Mass): Harvard University Press; 1939.

16. DeGuzman L, Bahiraei D, Vig KW, Vig PS, Weyant MS, O’Brien K. The validation of the Peer Assessment Rating Index for malocclusion severity and treatment difficulty. Am J Orthod

Dentofacial Orthop 1995;107:172-6.

17. Popovich F, Thompson GW. A longitudinal comparison of the orthodontic treatment priority index and the subjective appraisal of the orthodontist. J Public Health Dent 1971;31:2-8.

18. Grummons DC, Kappeyne van de Coppello MA. A frontal asymmetry analysis. J Clin Orthod 1987;21:448-65.

19. Burden DJ, Garvin W, Patterson CC. A field trial of an orthodontic treatment need learning package for general dental practitioners. Br Dent J 1997;183:123-9.

20. Cohen AJ. A coefficient of agreement for nominal scales. Educational and Psychological Measurements 1960;20:37-46.

21. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74.


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