Third Molar Assessment: Examiners Agreement about the Radiographically Determined Anatomical Parameters

Research Article

Austin J Dent. 2017; 4(3): 1074.

Third Molar Assessment: Examiners Agreement about the Radiographically Determined Anatomical Parameters

Abdurrahman A. Al-Samman*

Department of Oral Surgery, Tikrit Specialized Dental Center, Salahiddin Health Directorate, Iraq

*Corresponding author: Abdurrahman A. Al- Samman, Department of Oral Surgery, Tikrit Specialized Dental Center, Salahiddin Health Directorate, Ministry of Health, Iraq

Received: March 14, 2017; Accepted: April 18, 2017; Published: May 03, 2017


Objective: This study aimed to evaluate the reproducibility of the radiographically determined anatomical parameters related to the lower third molar (L3M) by analyzing the results of examiners agreement degree.

Study Design: An observational study of 50 L3M was made from twentyfive digital panoramic radiographs, which analyzed by four examiner groups (oral and maxillofacial surgeons, dental specialists, general dental practitioners (GDP), and post-rotation dentists) through the evaluation of the position and angulation of L3M along with the root forms and their relation to the inferior dental nerve (IDN). Intra and interexaminer agreement were determined by descriptive analysis and variance test.

Results: Only evaluation of tooth angulation showed both intra and inter-group agreement among examiners (82.3%, P= 0.128), whereas mean agreement about tooth position was 80.7% for intragroup analysis with statistical significant difference to position variable in intergroup analysis.

Root form and tooth-IDN relation variables revealed lowest intragroup mean of agreement with lack of inter-group reproducibility with greater disagreement to the GDP and specialist group (P< .05).

Conclusion: The intra and interexaminer reproducibility of subjective L3M evaluation was only associated to tooth angulation. These results suggest the need for using an objective measurement method to minimize the error introduced by observer interpretation.

Keywords: Examiner agreement; Third molar assessment; Anatomical parameters


A diverse range of anatomic positions and angulations are commonly associated with lower third molar (L3M) that result in a high degree of tooth impaction [1]. Classically, L3M have been classified according to the Pell & Gregory’s and winter’s criteria that classify them according to the relative depth respect to the occlusal plane, the position in relation to the mandibular ramus and the inclination of the longitudinal axis [2]. Other variables like root form and the relation to the inferior dental nerve were put in accounts by other studies [3-5]. These radiologically determined anatomical parameters have provided information influencing the precision of treatment planning.

Prediction of the extraction difficulty of L3M is crucial when designing a treatment plan [6], and optimizes the patient’s preparation and minimizes postoperative complications [7].

Despite the importance of Pell & Gregory’s and Winter’s classifications in addition to L3M relation to the inferior dental nerve in the field of L3M surgery, a limited number of researchers were investigated the reproducibility of such classifications [8-10] and relation [11]. Moreover, and up to our best knowledge, there has been no previous research in the literature, which has tested the reproducibility of root form evaluation criteria.

Therefore, the aim of the present study was to evaluate the reliability of Pell & Gregory’s and Winter’s classifications along with root form and the relation to the inferior dental nerve evaluation criteria though the assessment of the intra- and inter-group examiners agreement in different dental disciplines.

The null hypothesis is that there is no disagreement among examiners in their assessment of L3M anatomical parameters. The alternative hypothesis is that in L3M anatomical evaluation, there is lack of agreement among examiners.

Material and Methods

A descriptive, observational study design was made according to the guidelines of the ethical committee of the Iraqi Ministry of Health, in which digital panoramic radiographs were selected from the database of Al-Zuhoor Dental Imaging Center, Mosul city.

The study included high-quality digital radiographs showing completely formed L3M. Those radiographs with absent lower second molar (L2M) or largely destroyed L2M or L3M were excluded. Subsequently, twenty-five radiographs were selected for inclusion in the research, totalizing 50 L3M for the agreement analysis.

Before the radiographic analysis, information about the Pell & Gregory’s and Winter’s classification of third molars were provided to all examiners ensuring that this study was to estimate the agreement degree among examiners. In addition, Examiners asked to list down the factors (from most to least important) considered on radiograph when evaluating extraction difficulty. These digital radiographs were printed on photo paper (at a resolution of 150 ppi) and numbered from 1 to 25, then analyzed separately by 40 examiners to evaluate the position (vertical and horizontal) and angulation of L3M according to the Pell & Gregory’s and Winter’s criteria in addition to the root forms and their relation to the inferior dental nerve (IDN). The following options given for root form: convergent, straight, divergent, and bulbous. Distant, close proximity, contact/seems contact were the options of tooth relation to IDN.

The examiners set in four groups; ten for group. First group comprising oral and maxillofacial surgeons (the average of their experience is 9.7 years), second group including dental specialists (10.8 years of experience), general dental practitioners in the third group (9.2 years of experience), and post-rotation junior dentists included in the group 4 (1.8 years of experience). Each examiner had a copy of digital radiographs to be compiled one week later with his/ her own evaluation recorded on answer sheet.

The data was analyzed using IBM SPSS Statistic 23 (SPSS Inc., Chicago, IL, USA) applying the following statistical tests: Analysis of variance (One-way ANOVA test) was applied to know if there was intergroup significant difference (the level of significance set at 5%). Only in the statistically significant variables, a post-test (Duncan Test) was used to identifywhich examiner group demonstrated disagreement. The intragroup agreement of examiners was evaluated by descriptive analysis where mean value =0.90 indicates excellent agreement, mean values of 80-89.9 reflects very good agreement, mean values of 70-79.9 represents good agreement, while values <70 indicates moderate-poor agreement.


When evaluating the extraction difficulty factors as recorded by examiners, the most important one was the tooth angulation as reported by 37.5% of examiners followed by vertical tooth position, relation to the IDN, horizontal tooth position, and root form (25%, 15%, 12.5%, and 10% respectively). Table 1 illustrates the priority of extraction difficulty factors as considered by examiners. The estimation of extraction difficulty demonstrated that junior dentists recorded the highest mean value (5.98) whereas the GDP reported the least mean value (4.61). Surgeons and specialist groups recorded comparable results (5, 5.28).