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ORIGINAL ARTICLE
Year : 2015  |  Volume : 3  |  Issue : 3  |  Page : 76-79

Correlation of fracture resistance of molar teeth with weight


1 Department of Restorative Dentistry, Faculty of Dentistry, Izmir Katip Celebi University, Izmir, Turkey
2 Department of Endodontics, Faculty of Dentistry, Izmir Katip Celebi University, Izmir, Turkey
3 Department of Endodontics, Faculty of Dentistry, Ataturk University, Erzurum, Turkey

Date of Web Publication30-Oct-2015

Correspondence Address:
Dr. Bilal Yasa
Department of Restorative Dentistry, Faculty of Dentistry, Izmir Katip Celebi University, Izmir-35640
Turkey
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-4619.168734

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  Abstract 

Background: The aim of this study was to determine a standardizing model for fracture resistance test methods in which molar teeth are used. Materials and Methods: Fifty freshly extracted human mandibular molar teeth were selected. Each tooth was numbered and data were obtained by measuring the mesiodistal (MD) and buccolingual (BL) dimensions, length, and weight. Tests for fracture strength were performed using a universal testing machine, and for each sample, the force at the time of fracture was recorded in Newton. The correlations of the MD and BL dimensions, lengths, and weights of the teeth to the fracture strength values were evaluated using the Pearson correlation coefficient. Results: Significant correlations were not observed between the fracture strength values and MD dimensions (r = 0.055, P > 0.05), BL dimensions (r = 0.074, P > 0.05), and lengths of the teeth (r = 0.017, P > 0.05); however, they were observed with the weights of the teeth (r = 0.312, P < 0.05). Conclusions: The fracture resistance of molar teeth increases as their weights increases. These weights should be standardized during fracture resistance studies when distributing sample molar teeth into the study groups.

Keywords: Fracture resistance, molar teeth, sample teeth standardization, tooth weight, weight


How to cite this article:
Yasa B, Ertas H, Arslan H, Gok T, Capar ID. Correlation of fracture resistance of molar teeth with weight. J Res Dent 2015;3:76-9

How to cite this URL:
Yasa B, Ertas H, Arslan H, Gok T, Capar ID. Correlation of fracture resistance of molar teeth with weight. J Res Dent [serial online] 2015 [cited 2019 Sep 21];3:76-9. Available from: http://www.jresdent.org/text.asp?2015/3/3/76/168734


  Introduction Top


The biomechanical strength of restored endodontically-treated teeth is less than that of vital teeth.[1] The presence of nonrestorable cusp fractures is a significant reason for extracting endodontically-treated teeth with an incidence of 17.8%.[2] The reason for endodontically treated teeth's susceptibility to fracture is not its brittle nature as traditionally believed, but rather the cause can be attributed to access cavity preparation,[3] endodontic procedures,[4] post-space preparation,[5] and weakened tooth structure by caries or operative procedures.[6],[7] Therefore, preservation of tooth structure and reinforcement are important to conserve endodontically-treated teeth against fracture.[8] In the literature, there are several studies in which the fracture resistance of endodontically-treated teeth was evaluated, or the techniques for reinforcing these teeth were described.[9],[10],[11]

In order to identify treatments or materials that might improve clinical performances, it is necessary to examine an in vitro model prior to in vivo use. For this purpose, extracted human molar teeth are widely used for in vitro studies in fracture resistance tests.[8],[12] However, the standardization of these teeth is one of the most important steps, because without it there can be high standard deviations. If molar teeth are not distributed among the groups equally, these variables could affect the results of the study.

In many studies, the mesiodistal (MD) and buccolingual (BL) dimensions, as well as the lengths of the teeth, were standardized.[13],[14],[15] In spite of these standardization attempts, the standard deviations within the groups were rather high,[13],[16] rendering the results meaningless, and prompting studies using a larger number of specimens. Therefore, different variables should be evaluated in terms of standardization among the groups. Thus, the aim of this study was to determine a standardizing model for fracture resistance test methods in which molar teeth are used. The null hypothesis was that different physical properties of molar teeth would not affect the fracture strength.


  Materials and Methods Top


Fifty intact, noncarious, nonrestored human mandibular molar teeth, freshly extracted for periodontal reasons, with completed apices, were used in this study. The teeth were stored in 0.1% thymol at room temperature until they were used. The teeth were examined under a stereomicroscope to discard specimens with cracks and craze lines, and any remaining soft tissue and calculus were removed mechanically from the root surfaces using a periodontal scaler.

Each specimen was enumerated and the weights in gram were calculated using a Precisa XB 220A precision balance (Precisa, Gravimetrics AG, Dietikon, Switzerland) which has a capacity of 420 g, and a readability of 0.001 g [Figure 1]a. The lengths of teeth were measured in millimeters from apex to the highest point of crown [Figure 1]b. The MD [Figure 1]c and BL [Figure 1]d dimensions in millimeters at the prominent points of the crown were recorded with the tooth number, and the teeth were mounted into an acrylic resin, after which, fracture strength tests were performed using a universal testing machine. The upper plate of the machine included a spherical steel tip with a diameter of 4 mm. Force was loaded with a speed of 1 mm/min, parallel to the long axis of the tooth, until fracture occurred [Figure 2]. The force when the fracture occurred was recorded in Newtons for each tooth.
Figure 1: Calculation of weight (a), length (b), MD dimension (c), and BL dimension (d) of the mandibular molar. MD = Mesiodistal, BL = buccolingua

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Figure 2: Schematic design of the fracture strength test. CEJ = Cementoenamel junction

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The Pearson correlation coefficient was computed to evaluate the associations of the MD and BL dimensions, lengths, and weights of the teeth to the fracture strength values (P = 0.05). All statistical analyses were performed using the IBM® Statistical Package for Social Sciences (SPSS)® 20.0 software (IBM SPSS Inc, Chicago, USA).


  Results Top


The descriptive data of the measurements is shown in [Table 1]. The Pearson correlation coefficient revealed significant associations between the strength values and the weights of the teeth (r = 0.312, P < 0.05). However, significant correlations were not observed between the fracture strength values and the MD dimensions (r = 0.055, P > 0.05), BL dimensions (r = 0.074, P > 0.05), and lengths of the teeth (r = 0.017, P > 0.05) [Table 2].
Table 1: Descriptive data of molar teeth used in the study

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Table 2: Physical properties of the teeth along with Pearson correlation coefficients and P values

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  Discussion Top


There is the potential for large uncontrollable variations to affect the fracture strength of molar teeth. Therefore, all controllable factors have been standardized as much as possible. While some researchers who used molar teeth for fracture resistance performed standardizations according to length and the MD and BL dimensions, some did not.[14],[16],[17] In spite of the standardization efforts in such studies, high standard deviations were observed.[13],[16],[18] Therefore, the present study aimed to control factors that can affect the fracture resistance of teeth, in order to contribute to the standardization process.

The null hypothesis of present study was rejected, and the results of this study revealed that the weights of molar teeth have more statistically significant values than the lengths, and MD and BL dimensions.

During the study design, standardization was generally achieved based on the lengths, and the MD and BL dimensions of the teeth, with referrals to other studies in the literature. Naumann et al.,[19] recommended to distribute the specimens by a sort of tooth size assessment. For example, the product of the mesial-distal and buccal-palatal extension at the level of the cementoenamel junction can be calculated. Teeth of extreme size should be excluded. The remaining teeth can be randomly allocated according to a randomization plan.[19] Weight of teeth, as a factor that would affect fracture resistance of molar teeth, did not take into consideration in previous studies, except for in study of Ertas et al.,[20] evaluated effects of physical and morphological properties of roots on fracture resistance. Although the evaluated terms are different compared to aforementioned study, the present study has similarly shown that weight of teeth may affect the fracture resistance.

Thus, it is important to determine the alternative properties of the teeth, which could be useful for the standardization process in future investigations. Researchers should standardize the weights of the teeth to inhibit high standard deviations in future studies. However, further studies are necessary in order to discuss the current results.


  Conclusion Top


This is the first study in the literature to conclude that "the fracture resistance of a molar tooth increases as its weight increases". Within the limitations of this study, it can be concluded that when forming groups to evaluate fracture resistance of restorative material applied teeth, the teeth should be equally distributed according to their weights, rather than their MD and BL dimensions, since these dimensions cannot simulate the entire strength of the teeth as closely as the weight.


  Acknowledgments Top


The authors deny any conflict of interest related to this study.

 
  References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2]


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[Pubmed] | [DOI]



 

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