A comparison of two histological validating techniques for occlusal caries

Microindentation hardness and calcium/phosphorus ratio of dentin following excavation of dental caries lesions with different techniques

BACKGROUND

The aim of this in vitro study was to evaluate the microindentation hardness and chemical composition of residual dentin left at the cavity bottom following removal of carious dentin using the Carisolv chemomechanical and Er:YAG laser caries excavation methods in comparison with the conventional tungsten-carbide bur excavation.

METHODS

Sixty-nine extracted permanent teeth with occlusal dentin caries were assigned into three groups according to caries removal technique. Carious dentin excavation was guided by tactile method and a caries-staining dye. In stereomicroscope images (100×) of the samples, the presence or absence of residual caries was defined. The Knoop hardness value of the cavity floor was determined and atomic analysis of treated cavities was performed by energy dispersive X-ray spectroscopy.

RESULTS

The Knoop hardness value of residual dentin left at the cavity bottom was lower (One-way ANOVA, Dunnett-C, p < 0.05) and the percentage of samples with remaining carious dentin was higher after Carisolv excavation than those obtained after conventional and laser excavations (Kruskal-Wallis, Mann-Whitney U, p < 0.05). No significant differences were found between the quantities of calcium content (Ca wt%), phosphorus content (P wt%) and calcium/phosphorus ratio of the cavities treated by three techniques (Kruskal-Wallis, Mann-Whitney U, p > 0.05).

CONCLUSION

The results indicated that Er:YAG laser was more comparable to conventional bur excavation than chemomechanical method in the efficacy of caries removal with regard to microindentation hardness of remaining dentin and both Carisolv gel and Er:YAG laser did not alter chemical composition of residual dentin in the treated cavities.

Quantitative characterization and micro-CT mineral mapping of natural fissural enamel lesions

OBJECTIVES

The aim of this study was to characterize the mineral distribution pattern of natural fissural enamel lesions and to quantify structural parameters and mineral density of these lesions in comparison to proximal white spot enamel lesions.

METHODS

Imaging was undertaken using a high-resolution desktop micro-computed tomography system. A calibration equation was used to transform the grey level values of images into true mineral density values. The value of lesion parameters including the mineral density and the thickness of the surface layer of the enamel lesion were extracted from mineral density profiles.

RESULTS

The thickness of the surface layer showed variation among different lesions and it ranged from 0-90 μm in proximal lesions and 0-137 μm in fissural lesions. The average thickness of surface layer in fissural lesions was significantly higher than smooth surface proximal lesions. Sound fissural enamel showed lower mineral density compared to proximal enamel.

CONCLUSION

Micro-CT and the suggested de-noising and visualization method provide an efficient high-resolution approach for non-destructive evaluation of fissural lesions. Using these methods, the current study revealed the exclusive pattern and structure of fissural enamel lesions which may provide a basis for future studies on prevention and remineralization of these lesions.

CLINICAL SIGNIFICANCE

The common demineralization pattern of fissural lesions, which indicates the extension of the lesion in two directions towards the pulp horns, may explain the early inflammation and symptoms of the pulp in fissural lesions even when the lesion base appears far from the pulp roof in normal radiographs. In addition, the presence of the surface layer, indicates that vigorous probing of the occlusal fissures may lead to breakage and cavitation of the enamel lesions.

Comparison of photographic and visual assessment of occlusal caries with histology as the reference standard

Background

The purpose of this study was to compare diagnostic performance for the detection of caries using photographs with an established visual examination method and histological sections as the reference standard.

Methods

50 extracted permanent teeth were assessed for the presence of occlusal caries by 9 examiners using two methods; traditional visual examination developed by BASCD and photographs produced by an intra-oral camera. For both methods, diagnoses were made at “caries into dentine” level. The teeth were histologically sectioned and the diagnostic decisions using visual and photographic assessment were compared to the histological reference standard. Inter- and intra- examiner reliability for the methods was assessed and weighted kappa values were calculated.

Results

The visual examination method had a median sensitivity value of 65.6% and a median specificity value of 82.4%. The photographic assessments method had a median sensitivity of 81.3% and a median specificity of 82.4%.

Conclusions

The photographic assessments method had a higher sensitivity for caries detection than the visual examination. The two methods had comparable specificities and good intra- and inter- examiner reliability.

Comparison of validation methods for the diagnosis of occlusal caries in primary molars

AIM

To evaluate the reproducibility of 7 validation methods used for caries diagnosis in primary teeth.

METHODS

Seventy-two occlusal sites were selected on 40 primary molars. The sites were evaluated independently by 3 experienced examiners using validation methods that involved direct assessment, i.e. by using a (1) magnifying glass (8×) and (2) stereomicroscope (35×), or indirect assessment i.e. by using (3) photographs, (4) slide projections of photographs, (5) stereomicroscope (35×) photographs, (6) stereomicroscope (35×) slide projections, and (7) projections of polarised light microscope slides. Cohen's kappa coefficients were calculated and subjected to the Kruskal-Wallis test at a significance level of 5%.

RESULTS

The mean inter-examiner kappa values for the validation methods were 0.31-0.51. There were statistically significant differences (p<0.05) between methods 1 and 3, 1 and 4, 2 and 4, 4 and 5, 4 and 6, and 4 and 7. Moderate agreement was observed for all methods except methods 1 and 4, for which the agreement was fair.

CONCLUSIONS

The inter-examiner agreement for all validation methods for caries diagnosis was moderate, except for the method based on indirect assessment by slide projection, which showed low agreement.

Validity of MicroCT for in vitro detection of proximal carious lesions in primary molars

OBJECTIVE

This study aimed to validate the MicroCT for detection of proximal carious lesions in primary molars, using histology as the gold standard.

METHODS

Forty-eight proximal surfaces of primary molars were examined. Two calibrated examiners conducted the examinations independently. Proximal surfaces were visually scored, using ICDAS. Bitewing radiographs, Micro-CT and histological analyses used caries scores: 0=sound; 1=outer enamel; 2=inner enamel; 3=not spread dentine; 4=outer dentine; 5=inner dentine. Axial and sagital images were used for Micro-CT analysis, whilst for histology, tooth sections (400μm) were analyzed stereomicroscopically (×15).

RESULTS

Inter-examiner agreement ranged from 0.87 to 0.93 kappa coefficient (k). Histological analysis revealed a frequency of sound tooth surfaces (18.8%) enamel carious lesions (E1) (48%) and dentine carious lesions (D1) (33.3%). MicroCT showed high correlation with histology (r(s)0.88). At both diagnostic thresholds (E1 and D1), sensitivity and accuracy were higher for MicroCT. Inter-device agreement between MicroCT and histology was k=0.81. No difference was found between MicroCT and histology as gold standards for detecting carious lesions using ICDAS.

CONCLUSION

MicroCT can be used as a gold standard for detecting carious lesions in proximal surfaces in primary molars.

Diagnostic performance of the visual caries classification system ICDAS II versus radiography and micro-computed tomography for proximal caries detection: an in vitro study

OBJECTIVES

The purpose of this study was: (a) to compare the visual caries classification system ICDAS II with conventional (CR) and digital radiography (DR) for diagnosis of non-cavitated caries on free proximal surfaces, (b) to examine the potential of micro-computed tomography (MCT) to substitute histological examination for the in vitro caries assessment.

METHODS

Both proximal surfaces of 20 teeth received classification separately by two examiners by means of the diagnostic modalities examined. The teeth were sectioned and assessed for depth of the lesion. The modalities were compared in terms of degree of inter-examiner agreement, sensitivity, specificity, accuracy, positive and negative predictive value and validity. Two diagnostic thresholds were applied: no caries versus all caries scores (D1), and no dentin caries versus dentin caries (D3).

RESULTS

The weighted kappa values for inter-examiner reproducibility for all diagnostic modalities were 0.51-0.81. Visual examination (ICDAS II) reached significant higher sensitivity (0.92-0.96) and negative predictive value (0.9-1) than radiography. Likewise, the radiographic modalities presented significantly higher specificity (0.93-1) and positive predictive values (0.92-1) than the ICDAS II criteria. The overall accuracy performance of radiographic modalities was related to the diagnostic threshold. MCT did not agree with histological validation at each disease severity scale.

CONCLUSIONS

The ICDAS II criteria are a promising tool for caries diagnosis on free proximal surfaces. DR and CR radiography present comparable performance. Furthermore, MCT is not capable of constituting a reliable alternative to histological examination for caries research.

Performance of laser fluorescence at tooth surface and histological section

This study aimed to evaluate a laser fluorescence device (the DIAGNOdent) and a visual classification system (ICDAS-II) for occlusal caries diagnosis. It also aimed to determine whether fluorescence measurements taken at the tooth surface correlate with the fluorescence measurements taken within the body of the lesion. The occlusal surfaces of 100 extracted permanent teeth were examined using ICDAS-II and DIAGNOdent (LF-tooth). Serial sections were made and lesion depth was assessed histologically. DIAGNOdent readings were also taken from the sections (LF-section). There were significant positive strong correlations between ICDAS-II and histology (r(S) = 0.71) and LF-section and histology (r(S) = 0.70), and only moderate correlations between LF-tooth and histology (r(S) = 0.51) and LF-tooth and LF-section (r(S) = 0.60). Diagnostic accuracy for ICDAS-II was generally better than for LF-tooth. While the DIAGNOdent device provides an objective reading for detection and monitoring of carious lesions, using the cut-off ranges previously suggested leads to inferior performance.

In situ and in vitro comparison of laser fluorescence with visual inspection in detecting occlusal caries lesions

The aim of this study was to compare the in situ and in vitro performances of a laser fluorescence (LF) device (DIAGNOdent 2095) with visual inspection for the detection of occlusal caries in permanent teeth. Sixty-four sites were selected, and visual inspection and LF assessments were carried out, in vitro, three times by two independent examiners, with a 1-week interval between evaluations. Afterwards, the occlusal surfaces were mounted on the palatal portion of removable acrylic orthodontic appliances and placed in six volunteers. Assessments were repeated and validated by histological analysis of the tooth sections under a stereomicroscope. For both examiners, the highest intra-examiner values were observed for the visual inspection when in vitro and in situ evaluations were compared. The inter-examiner reproducibility varied from 0.61 to 0.64, except for the in vitro assessment using LF, which presented a lower value (0.43). The methods showed high specificity at the D(1) threshold (considering enamel and dentin caries as disease). In vitro evaluations showed the highest values of sensitivity for both methods when compared to the in situ evaluations at D(1) and D(2) (considering only dentinal caries as the disease) thresholds. For both methods, the results of sensitivity (at D(1) and D(2)) and accuracy (at D(1)) showed significant differences between in vitro and in situ conditions. However, the sensitivity (at D(1) and D(2)), specificity and accuracy (both at D(1)) of the methods were not significantly different when the same condition was considered. It can be concluded that visual inspection and LF showed better performance in vitro than in situ.

Occlusal caries: Evaluation of direct microscopy versus digital imaging used for two histological classification systems

OBJECTIVE

Histology is frequently used as a gold standard to validate caries detection devices. Poor assessment consistency could lead to apparent changes in diagnostic accuracy. In multi-center, multi-examiner studies electronic transfer of information would be convenient, provided there is no deteriation in quality. This study tested the hypothesis that examiner reproducibility in the assessment of caries lesion depth when viewing photographic images of histological sections on a computer monitor, is comparable with viewing the same sections under a microscope using two histological classification systems.

METHODS

166 investigation sites (96 teeth) were selected for visual examination (ICDAS-II) and sections made using a novel technique which reduced risk of section damage and allowed accurate allocation of section to each investigation site. Digital images of the sections were produced and four examiners viewed the sections under a microscope and on a separate occasion corresponding digital images on a computer monitor. Presence and extent of caries was scored according to two histological classification systems (Downer, ERK).

RESULTS

The inter- and intra-examiner reproducibility for both histological classification systems and both examination techniques was substantial to almost perfect (weighted kappa=0.63-0.90). Comparing the kappa values between microscopy and viewing digital images, there was no effect or only a small effect between both examination techniques (effect size 0.00-0.28). There was also a strong relationship between the two viewing techniques (r(s)=0.748-0.844).

CONCLUSIONS

Viewing digital images of tooth sections produces results comparable to viewing images directly under a microscope and therefore has potential benefits for multi-centre studies.

Reproducibility and accuracy of the ICDAS-II for detection of occlusal caries in vitro

AIM

The aim of this study was to assess inter- and intra-examiner reproducibility and accuracy in the detection and assessment of occlusal caries in extracted human teeth using a newly developed visual method for caries diagnosis (International Caries Detection and Assessment System, ICDAS-II). Serial sectioning and microscopy were used as the 'gold standard'.

METHODS

The occlusal surfaces of 100 teeth were examined by 4 dentists using the ICDAS-II graded scores 0-6. Thereafter the teeth were serially sectioned and assessed for depth of the lesion with two histological classification systems.

RESULTS

The weighted kappa values for inter- and intra-examiner reproducibility for the ICDAS-II examination were 0.62-0.83. There was a moderate relationship between the visual and both histological examinations (r(s) = 0.43-0.72). At the D1 diagnostic threshold (enamel and dentine lesions) specificity was 0.74-0.91 and sensitivity was 0.59-0.73. At the D3 diagnostic threshold (dentine lesions) specificity was 0.82-0.94 and sensitivity was 0.48-0.83 for the 4 examiners.

CONCLUSION

The ICDAS-II system has demonstrated reproducibility and diagnostic accuracy for the detection of occlusal caries at varying stages of the disease process which are comparable to previously reported data using similar visual classification systems.

The challenges of validating diagnostic methods and selecting appropriate gold standards

Caries diagnostic methods are usually methods for caries lesion detection and measurement. Caries lesions occur on a continuous scale of tissue damage, from subclinical surface changes to macroscopic cavities reaching the pulp. Any change of a lesion on this continuous scale offers the opportunity for the diagnosis of disease activity or remission. Research aimed at remineralizing agents may focus on lesions that are amenable to remineralization, and select a method that will measure small changes in early lesions. General caries management strategies depend on detecting all stages of lesion development, and methods covering early to late stages are preferred. This paper addresses some methodological issues in validating caries diagnostic methods. The available gold standards for caries lesions are discussed, with their suitability in different applications, and their "validity" as far as it is known or can be inferred. The gold standards are compared as far as their measurement of lesion parameters and reproducibility is concerned. Tentative conclusions are formulated, and recommendations for future research are given.