## 4 Discussion  
The purpose of preclinical dental courses is to simulate as closely as possible the actual circumstances that patient care entails. The use of mannequins as representative of human head anatomy is the classic method of presenting dental students with these parameters. Included in this model are replicas of the jaws and teeth, on which instruction is given by skilled educators as to the steps required to perform appropriate dental preparations [6]. The most common mode of this type of education is to observe the instructor as they perform and explain the needed tasks. Furthermore, said instructors are required to evaluate each student's endeavors in order to gauge their progress. However, the majority of instructors are solo practitioners, which tends to produce uneven standards in technique and insular scales of evaluation. Previous studies have described the educational shortcomings of evaluating preclinical dental student performance due to inconsistency within and among examiners [9; 10; 11]. In addition, the use of magnifications (i.e., loupes) for evaluating cavity preparation might further enhance the procedure [22]. The present study is an effort to alleviate the issues of the reliability and accuracy of the evaluation of clinical performance by instructors. The former refers to the consistency of earned marks regardless of who administers them or when [20]. To fulfill this definition, we developed a novel analog model of human teeth with multicolored layers using 3D digital printing. These are designed to follow the margins of an ideal cavity preparation (border of white and green) in all dimensions, with strata of green, yellow, and red beneath an outer ivory surface [19]. The removal of material from these analogs provides both student and instructor with direct visual feedback as to the performance of the given procedure. The ability to discern even minor deviations in this manner is superior to and more objective than the traditional method using monochromatic plastic teeth. The results of this study show that, by using the novel multicolored 3D-printed teeth, both intra- and inter-examiner reliability was improved. [PERSON] (1994) [23] described commonly cited ranges for the qualitative rating of agreement based on ICC values, i.e., \"good\" for values between 0.6 and 0.74, and \"excellent\" for values between 0.75 and 1. In our study, the ICC was used to measure the inter-examiner reliability in both the multicolored 3D-printed and the conventional plastic teeth. The agreement between examiners was found to be excellent for both the first (ICC = 0.929), and second (ICC = 0.768) evaluations on multicolored 3D-printed teeth. When conventional plastic teeth were used to test this, it was found to be low at the first (ICC = 0.314) and moderate at the second (ICC = 0.672) evaluations. These findings are different from those reported by [PERSON] et al. (2018) [21], who reported that inter-examiner reliability was excellent for both methods of digital assessment by CEREC software and conventional visual assessment of cavity preparation on regular plastic teeth (ICC from 0.77-0.87). However, [PERSON] et al. (2016) [24], who compared a conventional visual assessment with a computerized laser-scanning cavity preparation skill evaluation system (CPSES) of class I cavity preparation by clinical instructors, reported thatthe CPSES gave consistent inter-examiner reliability and excellent intra-examiner reliability (ICC 1), in contrast to the conventional method (ICC from 0.56 to 0.77). The use of digital tools in modern dentistry permits the rapid scanning of student cavity preparation and comparison with standardized cavity preparation models. This can generate 3D feedback data using computer-based evaluation systems such as PrepCheck [15], CEREC [21], and CPSES [24].