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Quality of Class II Cavity Preparations Performed by Preclinical Students With and Without Magnifying Loupes

May 11, 2016
by Akshay Satwik, Undergraduate Student; Prasanna Neelakantan, MDS, Assistant Professor

The objective of preclinical dental training of undergraduate students is focused towards orientation, improvisation of performance and spatial perception of learners. These abilities combined with application of preclinical training to clinical practice are essential.1 Preclinical training offers enhancement of dexterity (motor skills) along with cognitive development. One of the main specialties wherein this dexterity is required is operative dentistry (conservative dentistry) and endodontics. Although numerous developments have taken place in the field of operative dentistry, one innovation, which appears to greatly enhance quality of treatment offered, is the use of magnification via magnifying loupes and microscopes.2

It has been demonstrated that the use of microscopes significantly improved the accuracy score and fine motor skills in endodontic treatment.2 However, there is limited evidence to include the use of magnifying loupes as an essential requirement in preclinical training in operative dentistry. It is not known if the use of magnifying loupes significantly improves the quality of work performed by preclinical dental students. The assessment of work quality is important to monitor and modify teaching strategies as well as curriculum development. It is also essential to establish the basic level of competency and standard of care required.3-5 The objective of this study was the evaluate the quality of Class II cavity preparations for amalgam restorations, performed by preclinical students with and without the use of magnifying loupes. The null hypothesis was that there was no significant difference in the quality of work performed with and without magnifying loupes.

Materials and methods

Preclinical dental students (n=92) were enrolled in this study based on a study protocol approved by the Institutional Review Board and Ethics Committee of the university. These students had been trained in an orientation program to perform Class I cavities with and without magnifying loupes at 2.5x magnification (Orascoptic, Middleton, WI, USA). The magnification loupes were supplemented with a light source (Zeon Lumen Arc Light System, Orascoptic) and the working distance was standardized at 16.5 inches. This distance was evaluated before, during and after each test to confirm maintenance of standard working distance.


Under rubber dam isolation, students performed Class II (distoocclusal) cavities in the right lower mandibular molar typodont tooth of an articulated jaw model (Nissin Dental Products Inc, Kyoto, Japan) with and without magnifying loupes. Preparation armamentarium was standardized. All students used a turbine handpiece (PanaMax Plus, NSK, Tochigi, Japan) with continuous water spray, using a No.245 tungsten carbide bur (Tri Hawk Inc, NY, USA). Following completion of the preparations, all teeth were collected, labeled and evaluated by two calibrated examiners in a blinded manner. Where there were different scores, the examiners discussed over the differences and decided on a common grade. The examiners evaluated the cavities using a mouth mirror, probe, William’s periodontal probe without magnifying loupes. The preparations were graded for a maximum score of 10 as: excellent (scores 9-10), minor errors but clinically acceptable preparation (scores 5-8), major errors and needs repetition (scores 1-4). The criteria defined for each of the grading segments is outlined in Table 1.

TABLE 1. Parameters used for grading Class II cavity preparations performed by students
TABLE 1. Parameters used for grading Class II cavity preparations performed by students
The data of scores were presented as means and standard deviation. Statistical analysis of the data was performed using SPSS software for Windows (SPSS Inc., Chicago, IL, USA). Paired t-test was used to compare scores between groups.


The scores obtained by the students are presented as means and standard deviations (Table 2). The examiners agreed with themselves and each other 100% of the time and hence a test to assess examiner reliability was deemed unnecessary.

TABLE 2. Scores (means ± standard deviations) obtained by students for each grading segment with and without magnification (n=92)
Neelakantan Table 2

In cavity preparations performed without loupes, 38% of the preparations needed “to be repeated”, while 54.5% were graded as “clinically acceptable” and 7.5% were graded as “excellent”. The number of preparations graded as “to be repeated” in the preparations performed with loupes was 3.6% while preparations graded as “clinically acceptable” and excellent were 72.5% and 23.9% respectively. Statistical analysis of the mean scores showed that there was significant difference between the scoring segments (needs to be repeated, clinically acceptable and excellent) within each group (with loupes and without loupes)(P<0.05). Between the groups, there was significant difference in all the scoring segments (P<0.05).


This study aimed at evaluating the quality of work performed by preclinical students with and without the use of magnifying loupes. The results showed that the percentage of students and mean scores obtained by students in the three scoring segments were significantly higher in the preparations performed with magnifying loupes than without loupes. Hence, the null hypothesis needs to be rejected. The results of this work are in concurrence with those of Maggio et al. who showed that the use of magnification loupes enhanced student performance during preclinical dental education.6

To minimise operator variables, the same commercial brand of loupes, teeth, light source, turbine and burs were provided to the operators. The loupes had an adjustable inter pupillary distance. The operators were also calibrated by performing 15 Class I cavity preparations using magnifying loupes. The reasons for better performance in the preparations could be attributed to postural reasons7 as well as self-assessment of details under magnification.8

The present study used certain rigid criteria for evaluation of Class II cavity preparations. The parameters (outlined in Table 1) included measurements of the width and depth of the cavity, height of axial wall, width of the gingival seat and marginal ridge thickness. Where possible, a digital calliper was used for measurements. For other measurements, a periodontal probe was used. The use of loupes definitely has a learning curve and hence time taken for completion of work was not evaluated in this preliminary study.

The reasons why these criteria were employed for evaluation are based on their clinical significance. Amalgam restorations are retained by mechanical retention and hence cavity design is of essence for retention and resistance forms.9 This also includes conservation of tooth structure. Towards this aim, the width of the cavity and width of the marginal ridge after cavity preparation were measured. A depth of 0.5 mm into dentin (measured as 1.5mm from the central pit in a typodont tooth) is essential to offer bulk of amalgam to establish resistance form.10 Furthermore, an increased depth of the cavity can decrease the remaining dentin thickness or involve the pulp in the clinical scenario.11 Hence, accurate measurement of cavity depth is an important factor for assessment. The gingival cavosurface bevel is a very important step to be performed in Class II cavity preparations for amalgam to remove the undermined enamel rods along the gingival cavosurface margin.12

Preclinical dental training modules contribute to a major proportion of teaching hours in the undergraduate curriculum. The activities that are formulated in the preclinical program are to develop early development of psychomotor skills that are very relevant to operative dentistry and endodontics.13 With the increasing innovations in dentistry, it is imperative to train students to be well equipped for the future. The teeth that were used in this work had qualities similar to those of natural tooth structure. This ensures that the proprioception experienced by the operators was not greatly different from those of natural teeth.

The use of approaches that help a student plan, analyse and evaluate/assess their work is an important part of the perpetual ability.14 However, it must be understood that the results of performance in preclinical work cannot be directly correlated to clinical work. Limitations in clinical work include variations in mouth opening, other anatomical and physiological factors as well as postural requirements of the operator.15 However, increasing the number of exercised performed using magnifying loupes in preclinical training can help overcomes these challenges in the clinical situation.


The use of magnifying loupes increased the scores (quality of work) of preclinical dental students in Class II cavity preparations. The number of preparations graded as excellent were significantly higher in the group performed with magnifying loupes. The use of loupes should be made an essential requirement in preclinical and clinical training for undergraduate students.OH

Neelakantan Prasanna, MDS, Assistant Professor, Department of Conservative Dentistry and Endodontics, Saveetha Dental College and Hospitals, Saveetha University, Chennai, Tamil Nadu, India.

Oral Health welcomes this original article.

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