Saudi Journal of Oral Sciences

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 5  |  Issue : 2  |  Page : 75--79

In vitro assessment of simulation teeth in a preclinical teaching program


James Dudley 
 Department of Prosthodontics, Adelaide Dental School, The University of Adelaide, South Australia, Australia

Correspondence Address:
James Dudley
Adelaide Dental School, Adelaide Health and Medical Sciences Building, Faculty of Health Sciences, The University of Adelaide, South Australia 5005
Australia

Abstract

Introduction: The aim of this study was to investigate the effect of two processes (cycles of incubator drying and sectioning with a diamond blade) on the weight of different anatomical types of simulation teeth used in the proposed assessment process in a preclinical dental teaching program. Materials and Methods: Sixty-eight new unprepared reference plastic Columbia teeth of 17 different anatomical types were cleaned, dried, and sectioned with a diamond blade and the change in weight recorded. Four hundred and four teeth including 210 teeth prepared for a variety of different crown preparations, 68 reference teeth of 17 different anatomical types and 68 sectioned teeth of 17 different anatomical types were cleaned, dried, and subjected to three incubator cycles of 60°C for 24 h. The change in weight was recorded before and after each cycle. Results: The average percentage of tooth lost through sectioning for all teeth was 2.7% which varied from 2.3% in smaller diameter teeth to 3.1% in larger diameter teeth. There was no significantly different percentage tooth loss between the different anatomical tooth types (global P = 1.0000). The average loss of tooth weight over the duration of all incubator cycles for all teeth was 1.64%. When controlled for clustering, there was no statistically significant difference in weight across the time periods within each of the tooth groups. Conclusion: The testing conditions employed in this study did not produce a statistically significant loss in tooth weight and showed initial promise in the proposed protocol of assessment of simulation teeth on a large scale.



How to cite this article:
Dudley J. In vitro assessment of simulation teeth in a preclinical teaching program.Saudi J Oral Sci 2018;5:75-79


How to cite this URL:
Dudley J. In vitro assessment of simulation teeth in a preclinical teaching program. Saudi J Oral Sci [serial online] 2018 [cited 2019 Jun 20 ];5:75-79
Available from: http://www.saudijos.org/text.asp?2018/5/2/75/241168


Full Text



 Introduction



Simulation teaching is used extensively in modern day undergraduate dental curricula in both preclinical and end-point teaching modalities. Students typically complete a sequence of formative practical exercises culminating in a summative practical assessment.

Historically, the assessment of practical exercises has been performed by the expert opinion of what is thought to represent satisfactory or unsatisfactory “tooth shapes” that can be open to individual interpretation. Challenge and critique of these methods have led to the development of marking rubrics and use of scanning technology as standardized and reproducible assessment methods.[1],[2]

In the search for improved efficiencies often in large class sizes, streamlined methods of assessment are desirable utilizing standardized semi-automated or fully automated processes. Ideally, such methodologies would be based on established protocols and guidelines from the vast volume of in vitro research.

In vitro materials testing has broad applications, is usually simple to perform and involves subjecting materials to selected conditions in a controlled environment that are thought to simulate some or all of an in vivo environment. However, a lack of validation represents the major limitation of the large volume of in vitro materials research and reliance on the minimal volume of clinical trials that has been reported to be represented by [3]

The International Organization for Standardization (ISO) standards have been created that provide requirements, specifications, guidelines, or characteristics that can be used consistently to ensure that materials, products, processes, and services are fit for their purpose.[4] ISO standards are, by their very nature, open to some degree of debate because they are created in response to requests from industry or stakeholders using a consensus-based expert opinion approach often taking 3 years.[5] In the field of dental materials, a number of standards have been produced for dental (prosthodontic) materials, but in the ever-increasing body of in vitro dental materials research, it appears many of the publications use testing conditions that have not been validated.[6]

The current study formed the precursor to an overarching study that provided an initial screening assessment of the quality (by volume reduction) of different types of crown preparations performed by undergraduate dental students during a preclinical teaching program in a dental simulation clinic. The proposed method of assessment involved comparing the weights of teeth prepared for various types of crowns with standardized teeth before further phases of assessment.

The aim of this study was to investigate the effect of two experimental conditions (cycles of incubator drying and sectioning with a diamond blade) on the weight of different anatomical types of plastic simulation teeth used in the proposed assessment process in a preclinical dental teaching program. The tested null hypotheses were:

The loss of weight from sectioning teeth with a diamond wafering blade was not significantly different between the different anatomical tooth typesThere was no significant difference in loss of tooth weight within the different tooth groups resulting from repeated cycles of drying teeth in an incubator for 24 h at 60°C.

 Materials and Methods



The study was conducted at The University of Adelaide and utilized teeth prepared for a variety of different crown preparations by undergraduate dental students during a preclinical teaching program in a dental simulation clinic, unprepared reference teeth, and sectioned teeth. Ethics approval (H-2016-025) was obtained from The University of Adelaide Human Research Ethics Committee.

Two separate assessments were carried out.

Sectioning teeth

Sixty-eight new unprepared (whole) reference plastic Columbia teeth (Columbia Dentoform, Long Island City, NY, USA) of 17 different anatomical types were assessed. Each tooth was manually cleaned with gauze and dried with pressurized air.

The teeth were dried in an incubator for 24 h at 60°C in reference to similar previous investigations.[7],[8],[9] After allowing to cool to 21°C for 30 min, the weight of each tooth was recorded by positioning the tooth in the center of a calibrated Mettler AE260 DeltaRange analytical balance (Mettler-Toledo, Columbus, Ohio, USA) secured on a fixed absorption base.

The teeth were sectioned with a 0.3 mm thick IsoMet ™ Diamond Wafering blade (Buehler, Lake Bluff, IL, USA) at the designated cementoenamel junction and the two remaining components manually cleaned with gauze and dried with pressurized air then weighed using the same analytical balance.

For each of the 17 tooth types, average values were calculated for the weight of the whole tooth before sectioning and each of the two components after sectioning. The percentage of tooth loss from sectioning was calculated for each tooth type. Statistical analysis of the differences in the percentage of tooth loss between tooth types was carried out using a linear regression model and SAS 9.4 (SAS Institute Inc., Cary, NC, USA) software.

Incubator cycles

A total of 414 teeth or teeth segments were studied in four groups (crown prepared teeth, reference teeth, crown sections, and root sections) comprising of 210 teeth prepared for a variety of different crown preparations [Figure 1], 68 unprepared (whole) reference teeth of 17 different anatomical types, and 68 sectioned teeth of 17 different anatomical types (resulting in 68 crown segments and 68 root segments). Each tooth or tooth segment was manually cleaned with gauze and dried with pressurized air.{Figure 1}

The initial weight of each tooth or tooth segment was recorded by positioning the tooth or tooth segment in the center of a calibrated Mettler AE260 DeltaRange analytical balance (Mettler-Toledo, Columbus, Ohio, USA) secured on a fixed absorption base.

Each tooth or tooth segment was then dried in an incubator for 24 h at 60°C in reference to similar previous investigations.[7],[8],[9] The teeth or teeth segments were then left for 30 min at 21°C and weighed again before being placed in incubator for a further cycle for 24 h at 60°C. This process was repeated for a total of three incubator cycles resulting in a total of six weight measurements.

Average weights were calculated for each of the four tooth groups at each time period. Statistical analysis of the change in tooth weights was carried out within each tooth group using a linear regression model and SAS 9.4 (SAS Institute Inc., Cary, NC, USA) software.

 Results



Results for the two separate assessments are presented.

Sectioning teeth

The average percentage of tooth weight lost from sectioning with upper and lower 95% Confidence Intervals for each tooth type is presented in [Table 1]. Post hoc pairwise comparisons established there was no significantly different percentage tooth loss between the different anatomical tooth types (global P = 1.0000).{Table 1}

The average percentage of tooth weight lost through sectioning for all teeth was 2.6621%.

The null hypothesis was upheld because the observed changes in weight were not statistically significantly different between the different anatomical tooth types.

Incubator cycles

The average weight for each of the four tooth groups with upper and lower 95% Confidence Intervals at the six-time measurements is presented in [Table 2]. The average weight for each of the four tooth groups at the six-time measurements is presented in graphs for comparison noting the different initial weights of the different teeth or teeth segments [Figure 2], [Figure 3], [Figure 4], [Figure 5]. Time periods 2, 4, and 6 represent measurements after 24 h in the incubator following cooling for 30 min.{Table 2}{Figure 2}{Figure 3}{Figure 4}{Figure 5}

The average loss of tooth weight over the duration of the testing for each tooth group (time 6 compared with time 1) was 1.86% (crown prepared teeth), 1.51% (reference teeth), 1.54% (crown sections), and 1.66% (root sections), and for all teeth and teeth segments combined was 1.64%.

When controlled for clustering, there was no statistically significant difference in weight loss across the time periods within each of the tooth groups: crown prepared teeth (global P = 0.9985), reference teeth (global P = 1.0000), crown sections (global P = 1.0000), or root sections (global P = 1.0000).

The null hypothesis was upheld because the observed changes in weight were not statistically significantly different within each of the different tooth groups.

 Discussion



Loss of weight from incubator cycles

The average loss of tooth weight resulting from the repeated incubator cycles of 1.86% (range 1.51%–1.86%) throughout all teeth is an important consideration for studies of this type where weight is used as a measure of performance. The factors that contribute to changes of weight and subsequently influence the final results must be known and accounted for.

The findings of this study are in agreement with the pilot study results of previous research for teeth stored in an incubator.[7],[8],[9] The current study and past research have demonstrated a focus on the requirement to have appropriate tooth storage conditions and the potential effect of water uptake and loss on the results.

In other similar studies, it has been reported that resin materials tend to absorb water depending on the storage conditions.[7],[8],[9] In the current study, it is more likely the uptake and loss of moisture from teeth [as illustrated in [Figure 2], [Figure 3], [Figure 4], [Figure 5] was the main contributor to the observed changes in weight rather than a change in the composition of the actual tooth as the teeth were observed to be subtly porous particularly when cut. It is possible subtle variations in room humidity played some role in weight changes.

Although commencing with different initial weights, the different tooth groups reacted in the same manner as demonstrated by comparing [Figure 2], [Figure 3], [Figure 4], [Figure 5]. This means the crown prepared reference and sectioned teeth can be confidently managed in the same manner in the proposed assessment protocol.

Loss of weight in sectioning teeth

The observed loss of weight from sectioning teeth might naturally be expected but to date has not been quantified. The sectioning process produced an average weight loss of 2.7% throughout all teeth that varied from 2.3% in smaller diameter teeth to 3.1% in larger diameter teeth but the difference showed no statistical significance between the different anatomical tooth types. It is proposed that larger diameter teeth lost more tooth structure than smaller diameter teeth due to their greater surface area requiring greater sectioning time by the blade. The loss of weight from sectioning teeth in studies involving weighing the residual components should be considered in results.

Validation of experimental conditions

The experimental conditions used in this study were employed because they were simple and repeatable but have not been previously validated as appropriate nor is there any guiding ISO standard for research of this type. When there is a lack of previous guidelines and ISO Standards to guide research, researchers are required to apply the best judgment and common sense to test materials appropriately.

Limitations

As with all in vitro research, the major limitation is the very nature of simulation-based investigations. This study was subject to potential observer bias as one researcher selected the experimental conditions and conducted all measurements.

It is appropriate to consider the reasons for selecting certain experimental conditions, for example, the time period of 24 h for drying the samples in the incubator. It appears that in some research, experimental conditions do not relate to accurately simulating in vivo conditions and may be selected purely for reasons of convenience. This research raises some questions and should provoke thought regarding the selected in vitro testing conditions.

 Conclusion



Repeated incubator cycles resulted in loss of tooth weight that was not statistically significantly different within the different groups of simulation teeth used in this study. Sectioning teeth produced an average weight loss of 2.7% that was not statistically significantly different between the different anatomical tooth types but should be considered in the analysis of results. The testing conditions employed in the current study showed initial promise in the proposed streamlined and time efficient large-scale assessment protocol of simulation teeth.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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