In vitro study of the correlation between the simulated clinical and radiographic examination of microgaps at the implant-abutment interface.

OBJECTIVES: To analyze the diagnostic value of the clinical and radiographic investigation of the interface of two-piece implant systems under the variables crevice size of the microgap, clinical experience, radiograph exposure time, prosthesis design, and type of evaluation. METHOD AND MATERIALS: A simulated mandibular cast with five screw-retained implants (Straumann) providing three different prosthesis designs displayed artificially created proximal, visually inaccessible microgaps of unequal sizes or junctions without any measurable gap formation. Three groups of 15 investigators each with a different degree of clinical experience evaluated the implant-abutment interfaces of the cast clinically and radiographically. The investigation was conducted on the basis of a scoring form adapted from the receiver operating characteristic (ROC) 5-choice method. Radiographs were prepared in two exposure times (0.1 second, 0.2 second) for each junction. Radiographs of the initial situation without any measurable gap formation were shown as a control and to detect false-positive scores for each gap size. A 10-point SEM measurement of the junctions served for standardization purposes. Statistical methods included ROC analysis, kappa analysis, and a regression analysis (alpha = .05). RESULTS: Gaps greater than 150.9 microm (P < .001) were detected 227% more frequently and gaps greater than 189.7 microm 292% more frequently via radiographic examination. Kappa values were adequate for the radiographic examination and unsatisfactory for clinical examination. Prosthetic superstructure and exposure time did not adversely affect the diagnosis. Clinical experience improved the detection of microgaps significantly. CONCLUSION: A relationship between the size of microgaps and the examiners' ability to detect them can be established. Whereas tactile examination alone is not accurate enough, radiographic analysis affiliated with a certain degree of clinical experience possesses features for an adequate clinical management of restoration defects.

Comparative study of in vitro caries-like lesions and natural caries lesions at crown margins.

PURPOSE: Secondary caries at crown margins and the influence of preparation techniques are major clinical problems. It was therefore the aim of this study to compare natural caries lesions at crown margins with experimental caries lesions. MATERIALS AND METHODS: Five extracted caries-free human molars were restored with gold cast crowns and afterwards covered with wax leaving a 3 x 3 mm window at the crown margin. These teeth were then incubated in acidified gel (pH 4.7) for 50 days. After incubation these teeth and five other crowned extracted teeth exhibiting natural caries lesions were embedded in Technovit 9100. Serial sections with a thickness of 80 microm were cut through the lesions and investigated with polarized light microscopy (PLM) and scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) analysis for quantitative element analysis of Ca, P, and C. The results of the quantitative element analysis were statistically evaluated using the nonparametric ANOVA test for repeated measurements. RESULTS: PLM of the experimental lesions showed homogeneous lesions with no transparent zone, or dead tracts. The natural caries lesions exhibited a demineralized zone, translucent zone, and dead tracts. Quantitative element analysis showed a statistically significant difference (p < 0.01) of Ca, P, and C between sound dentin and demineralized dentin in natural and experimental caries lesions. CONCLUSION: The experimental model reproduces the demineralization pattern of secondary caries but does not simulate the vital dentin reactions of peritubular and intratubular mineralization.

Secondary caries in crowned teeth: correlation of clinical and radiographic findings.

STATEMENT OF PROBLEM: The diagnostic value of radiographs for interproximal caries detection on nonrestored teeth is well investigated. However, little is known about the use of radiographs in the diagnosis of secondary caries localized at crown margins. PURPOSE: The aim of this study was to correlate clinical findings with regard to secondary caries with the findings of a radiographic evaluation. MATERIALS AND METHODS: One hundred randomly selected patients who underwent restorations with fixed prostheses and were exhibiting at least one secondary carious lesion were included in the study. A total of 820 restorations (test group, 730 interproximal surfaces of 365 single crowns and 910 interproximal surfaces of 455 fixed partial denture retainer crowns) and 1024 interproximal surfaces of 512 nonrestored teeth (control group) were investigated clinically, with the use of modified California Dental Association criteria, and radiographically for interproximal carious lesions. The extension of the lesions was rated to be initial (with no cavitation), early (with cavitation limited to orthodentin), or deep (with cavitation). The data were statistically analyzed for normal distribution, and the frequency of the findings was calculated in absolute numbers and as a percentage. Statistically significant differences were determined by use of the chi(2) test (P<.05). A linear regression model was applied for the correlation between the percentage of secondary caries and the duration of the crowns in situ. RESULTS: Secondary caries was diagnosed clinically in 11.2% of 1640 interproximal surfaces but only in 8.3% radiographically. In contrast, the frequency of interproximal carious lesions diagnosed clinically in nonrestored teeth increased with the use of radiographs from 3.3% to 4.1%. CONCLUSION: Within the limits of this study, the results confirm that radiographs improve the diagnostic sensitivity for interproximal caries in nonrestored teeth. However, for the diagnosis of secondary caries in crowned teeth, the clinical examination is more reliable than the radiographic evaluation.

Histologic and radiographic assessment of caries-like lesions localized at the crown margin.

STATEMENT OF PROBLEMS: Little is known about the impact of crown margins on the demineralization and remineralization process or on the interpretation of radiographs for the detection of early secondary caries. PURPOSE: The aim of this study was to correlate the findings from 2 different radiographic techniques with the results of a histologic assessment of carieslike lesions at the crown margin. MATERIAL AND METHODS: Ten fully impacted third molars were extracted and restored with complete metal crowns with chamfer preparations. For each tooth, the prepared margin ended in enamel on one side and extended into cementum/dentin on the other. After being thoroughly cleaned, the teeth were covered with wax except for a 2- x 3-mm window at the crown margin in each of 2 test areas localized at the interproximal enamel and cementum/dentin junction. During demineralization with 6% hydroxyethyl cellulose gel at pH 4.9, direct digital radiographs or conventional radiographs were made at baseline and after 7, 14, 21, and 28 days. Each radiograph was blinded and examined for the presence/absence of lesions by 3 calibrated observers who used predetermined criteria required for receiver operating characteristic (ROC) analysis. After 28 days, the teeth were imbibed with methyl methacrylate and serially ground sectioned for assessment of the lesions in polarized light. Morphometric analysis of lesion extension included the calculation of mean values and standard deviations. Kappa and ROC analysis were applied to assess radiographs made at different demineralization time periods, localization of the crown margins in enamel or cementum/dentin, and direct digital and conventional radiographs. Data were tested for normal distribution (QQ plot), and statistical differences were calculated with Tukey's honestly significant difference post hoc test. RESULTS: Radiographic evaluation revealed only slight interexaminer agreement (Kappa) for enamel lesions (direct digital 0.19, conventional radiographs 0.2) and a fair interexaminer agreement for cementum/dentin lesions (direct digital 0.35, conventional radiographs 0.33). ROC analysis revealed no differences between the radiographic techniques. Lesions localized in cementum/dentin (direct digital 0.86 +/- 0.14, conventional radiographs 0.86 +/- 0.09) were diagnosed more reliably than those in enamel (direct digital 0.79 +/- 0.05, conventional radiographs 0.72 +/- 0.10). As microscopically assessed, the depth of lesions in enamel was less than that of lesions in cementum/dentin (49.3 +/- 7.3 microm vs 89.5 +/- 13.2 microm). Erosions were found in cementum/dentin (depth 25.2 +/- 5.3 microm). CONCLUSION: Within the limitations of this study, small artificial lesions were detected equally well by conventional and direct digital radiography. However, because of low interexaminer agreement, the radiographic assessment did not reproduce true histopathologic lesion characteristics documented by morphometry of serial ground sections.