Detection of Dentinal Microcracks Using Infrared Thermography

doi:10.1016/j.joen.2012.06.033

Journal of Endodontics

Volume 39, Issue 1, January 2013, Pages 88-91

https://doi.org/10.1016/j.joen.2012.06.033 Get rights and content

Abstract

Introduction

It is difficult to make a definite diagnosis of a cracked tooth solely based on an inspection within the root canal, especially in case of microcracks. At present, there seems to be no established method to detect dentinal microcracks in roots; therefore, the current detection techniques need to be improved. Vibrothermography (VibroIR) helps to detect microcracks by the friction heat generated from ultrasonic vibration. The purpose of this study was to establish a novel method using VibroIR to detect dentinal microcracks.

Methods

The root canals of 20 roots with cracks and control roots were prepared after removing the tooth crowns. A tapered indenter was inserted into the root canal and pressed until a microcrack was created under an optical microscope. Using VibroIR, the detection trials for dentinal microcracks were performed with an ultrasonic vibration power ranging from 0.43 to 1.48 W at an angle of 0°, 30°, 45°, 60°, and 90° between the ultrasonic vibration point and the microcrack line. After the detection test, the microcrack width was measured with an optical microscope.

Results

Frictional heat was detected in the microcracks with thermography at 0.89 to 1.48 W and at an ultrasonic vibration point angle less than 60° from the crack line for 10 seconds. Microcracks with a width of 4 to 35.5 μm were detected with this method.

Conclusions

VibroIR may be an effective method for the diagnosis of root dentinal microcracks.

Section snippets

Preparation of Cracked Teeth

A total of 20 freshly extracted human teeth were obtained from dental clinics. Soon after extraction, the teeth were stored in Hank's balanced salt solution (GIBCO 14170 Hank's Balanced Salt Solution; Invitrogen, Irvine, CA) at 4°C. The teeth were decoronated using a low-speed diamond wheel saw at the cementoenamel junction under water irrigation. The root canals were cleaned and shaped with K-files #40 (Mani, Tokyo, Japan) and a Large Peeso Reamer (Dentsply, Ballaigues, Switzerland). The roots

Results

The dentinal microcracks could be detected from the increase in temperature with vibration (Fig. 2B). In the case of the controls, the microcrack was not detected with vibration (Fig. 2E). Figure 3 indicates that the detection time with an ultrasonic power of 0.89 W to 1.48 W at 0°, 30°, 45°, and 60° was not significantly different according to one-way analysis of variance (P > .05). The evaluation of the ultrasonic power as described earlier showed no significant difference in the detection

Discussion

The results clearly show that the VibroIR method can be useful for detecting microcracks. Particularly, it can detect microcracks as wide as 4 to 35.5 μm that are difficult to identify with commonly used detection methods. When the crack is narrow, the area of contact between the crack surfaces increases. This makes it easy to generate frictional heat between the surfaces (24). On the other hand, when the crack width exceeds 42 μm, it becomes difficult to find by means of the VibroIR method,

Acknowledgments

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

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Sonic-IR (Infrared) imaging technique was applied to detect defects of cementitious materials in the temperature rise of thermal imaging by ultrasonic excitation and infrared thermography on the target surface. It was investigated in this study to identify the fracture regions with cracks inside mortar and quantifying the epoxy resin filling situation at repaired crack in concrete. As the results, it was found that sonic-IR imaging technique can be utilized for detecting the fracture area and the crack propagation zone, although it is known that the technique is usually introduced for metals or composite materials which have high thermal conductivity. In particular, the shear fracture surface formed due to compressive stress could be detected as well as X-ray CT imaging. It was also enabled to quantitatively clarify the fracture progress with damage degree of mortar subjected to the compression stress and the epoxy resin injected depth at the simulated crack in concrete.
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In addition,Chunliangzhang[107] et al. established a set of digital image processing system to simulate the stress change of cracked teeth during chewing, which provides a new reference method for clinical diagnosis of cracked teeth. The principle of Vibrothermography (VibroIR) is that the defect generates heat by friction under ultrasonic vibration.And the defect is detected by the temperature change,moreover,the smaller the crack width is the more obvious the temperature change is.Matsushita TM[108] et al. tried to detect artificially created cracks extending to the root with different parameters of VibroIR.The experimental results show that the depth of dentin crack can be detected by using VibroIR under appropriate parameters.However, whether vibration will increase the crack range and its effect on dental pulp needs to be considered. The application of nondestructive testing technology in industry and other fields is becoming more and more mature, and extending it to more disciplines will be the direction that related majors should strive for.
Cracked tooth is a common dental hard tissue disease.The involvement of cracks directly affects the selection of treatment and restoration of the affected teeth.It is helpful to choose more appropriate treatment options and evaluate the prognosis of the affected tooth accurately to determine the actual involvement of the crack.However, it is often difficult to accurately and quantitatively assess the scope of cracks at present.So it is necessary to find a real method of early quantitative and non-destructive crack detection.This article reviews the current clinical detection methods and research progress of cracked tooth in order to provide a reference for finding a clinical detection method for cracked tooth.
Detecting Dentinal Microcracks Using Different Preparation Techniques: An In Situ Study with Cadaver Mandibles
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Further progress is clearly needed to detect microcracks in teeth in an in vivo scenario. Various methods have been used to detect the presence of microcracks in teeth including strain gauges (25), infrared thermography (26), optical coherence tomography (27), and LED transillumination (20, 28). Moreover, magnetic resonance imaging of root canal anatomy was described by Baumann (29).
This study assessed the frequency of dentinal microcracks using a cadaver mandible model in teeth instrumented with TRUShape (TS; Dentsply Sirona, York, PA), WaveOne Gold (WO, Dentsply Sirona), or K-files (KF) compared with an uninstrumented control group (CG).
Fifteen human mandibles with 95 single-rooted teeth were randomly distributed into the following groups: CG (no preparation, n = 11), TS (n = 28), WO (n = 28), and KF (step-back preparation with K-Flex-o-files [Dentsply Sirona], n = 28). Teeth were prepared to apical sizes of #25/.06 or #25/.07; overlying bone was removed, and then teeth were lifted out of the socket and sectioned at 3, 6, and 9 mm from the apex using a low-speed saw. Resulting slices were photographed at 20× and 25× magnification. Three independent and blinded evaluators assessed the images for the presence of dentinal microcracks and their extension, direction, and location. The chi-square test was used for statistical analysis (P < .05).
In the final sample of 83 teeth for the 4 groups, microcracks were found in 10 of 33, 13 of 66, 16 of 69, and 21 of 81 sections for CG, TS, WO, and KF, respectively. There were no significant differences in the frequency of microcracks among the CG, TS, WO, or KF instruments overall or when comparing section levels (3 mm [P = .9], 6 mm [P = .18], or 9 mm [P = .69], respectively, from the apex). There were also no significant differences in the extension, direction, or location of the dentinal microcracks among all groups (P > .05).
There was no difference in the frequency of microcracks among the experimental groups instrumented with TS, WO, and KF or uninstrumented controls.
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Conventional dental diagnostic aids based upon imagery and patient symptoms are at best only partially effective for the detection of fine structural defects such as cracks in teeth.
The purpose of this clinical study was to determine whether quantitative percussion diagnostics (QPD) provided knowledge of the structural instability of teeth before restorative work begins. QPD is a mechanics-based methodology that tests the structural integrity of teeth noninvasively.
Eight human participants with 60 sites needing restoration were enrolled in an institutional review board-approved clinical study. Comprehensive examinations were performed in each human participant, including QPD testing. Each site was disassembled and microscopically video documented, and the results were recorded on a defect assessment sheet. Each restored site was then tested using QPD. The normal fit error (NFE), which corresponds to the localized defect severity, was correlated with any pretreatment structural pathology.
QPD agreed with clinical disassembly in 55 of 60 comparisons (92% agreement). Moreover, the method achieved 98% specificity and 100% sensitivity for detecting structural pathologies found later upon clinical disassembly. Overall, the NFE was found to be highly predictive of advanced structural pathology.
The data from the present in vivo study support the hypothesis that QPD can provide the clinician with advance knowledge of the structural instability of teeth before restorative work begins.
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Several recent studies have evaluated the presence of dentinal defects after root canal preparation in extracted human teeth by using the root sectioning methodology. The objective of this research was to investigate whether light-emitting diode (LED) transillumination enhances the visualization of dentinal defects by using a root sectioning methodology.
Forty mesial roots of mandibular molars were sectioned at 3, 6, and 9 mm from the apex with a low-speed saw under water cooling. Microscopic pictures of the specimens were taken by using ×19.2 magnification for the 3-mm slice and ×12.8 magnification for the 6- and 9-mm slices. The LED transillumination was done by positioning an LED probe at 4 different locations (mesial, distal, buccal, and lingual). The root canal lumen was masked, and 2 independent evaluators assessed the presence of dentinal defects on the non-LED and LED images. The number of dentinal defects was recorded, and χ² test was used for statistical analysis (P < .05).
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There are several methods to assess the weakening of the tooth after different endodontic procedures. Matsushita-Tokugawa et al (20) used infrared thermography to detect dentinal cracks and reported that thermography has some limitations because of the size of the thermography equipment. Ribeiro et al (21) used an Instron testing machine to assess the fracture resistance of roots filled with different endodontic filling materials.
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The control group had no cracks, and the difference between the control group and the experimental groups was statistically significant (P < .001). The ProTaper Next and TF Adaptive systems produced significantly less cracks than the ProTaper Universal and WaveOne systems in the apical section (3 mm) (P < .05).
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: Supported by KAKENHI Grant-in-Aid for Scientific Research (B) (19390483) and (B) (22390358).

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Basic ResearchDetection of Dentinal Microcracks Using Infrared Thermography

Abstract

Introduction

Methods

Results

Conclusions

Section snippets

Preparation of Cracked Teeth

Results

Discussion

Acknowledgments

J Endod

J Endod

J Endod

J Endod

J Endod

J Endod

J Endod

J Endod

J Endod

J Endod

Int J Fatigue

Infrared Phys Technol

Oral Surg Oral Med Oral Pathol Oral Radiol Endod

Seven-year clinical evaluation of painful cracked teeth restored with a direct composite restoration

J Endod

Basic Research
Detection of Dentinal Microcracks Using Infrared Thermography