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. 2022 Sep 29;9(1):84-91.
doi: 10.1080/26415275.2022.2122468. eCollection 2022.

Optical coherence tomography systems for evaluation of marginal and internal fit of ceramic reconstructions

Hiba Al-Imam  1   2 , Ana R Benetti  2 , Pete Tomlins  3 , Klaus Gotfredsen  1
Affiliations

Optical coherence tomography systems for evaluation of marginal and internal fit of ceramic reconstructions

Hiba Al-Imam et al. Biomater Investig Dent. .

Abstract

Purpose: To evaluate the marginal and internal fit of lithium disilicate and zirconia crowns using two optical coherence tomography (OCT) systems in order to estimate inter-system variations.

Materials and methods: Ten lithium disilicate and 10 cubic stabilized zirconia crowns were placed on prepared artificial teeth without cement. Marginal discrepancy and internal cement gap of the crowns were assessed on images obtained using a swept source OCT (SS-OCT) and a spectral domain OCT (SD-OCT). Medians and interquartile ranges were calculated for both materials and OCT systems. Thereafter, Wilcoxon signed rank test was carried out.

Results: No significant difference was found between the two OCT systems for absolute marginal discrepancy of either lithium disilicate (SS-OCT: 182 µm, SD-OCT: 214 µm; p = .922) or zirconia crowns (SS-OCT: 116 µm, SD-OCT: 121 µm; p = .232). Regarding internal cement gap, no significant difference was found between the two OCT systems for lithium disilicate crowns (SS-OCT: 128 µm, SD-OCT: 128 µm; p = .064). However, for zirconia crowns the SD-OCT showed significantly higher (p = .027) internal cement gap (92 µm) than the SS-OCT (68 µm). Moreover, it was not possible to assess the internal fit of zirconia crowns in 47% and 34% of the sites using SD-OCT and SS-OCT, respectively.

Conclusions: No significant difference was noted in the ability of SS-OCT and SD-OCT to assess the marginal and internal fit of lithium disilicate crowns, nor the marginal fit of zirconia crowns. On the contrary, drawbacks regarding the assessment of internal fit of zirconia crowns using both OCT systems were observed.

Keywords: Optical coherence tomography; lithium disilicate; zirconia.

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Conflict of interest statement

No potential conflict of interest was reported by the authors.

Figures

Figure 1.
Figure 1.
Experimental set-up using (a) the commercial SS-OCT (Santec IVS-300, Japan) and (b) the non-commercial SD-OCT (Queen Mary University of London, London, UK).
Figure 2.
Figure 2.
Details of measurement method: black lines cervically on the ceramic crown placed on the abutment tooth indicate the area for OCT imaging (left). B-scans (center) were obtained from five sites at the facial surface, 250 µm apart. On the B-scans, measurement sites were defined. Lines delimiting the marginal horizontal (a) and vertical (b) discrepancies were used to calculate the absolute marginal discrepancy (c), and measurement areas were delimited for assessment of internal fit. The internal cement gap was defined as the distance between two peaks on the gray value intensity plot (right).
Figure 3.
Figure 3.
Box-plots representing (a) absolute marginal discrepancy (µm) and (b) internal cement gap (µm) of lithium disilicate crowns assessed by SD-OCT and SS-OCT.
Figure 4.
Figure 4.
Box-plots representing (a) absolute marginal discrepancy (µm) and (b) internal cement gap (µm) of zirconia crowns assessed by SD-OCT and SS-OCT.
Figure 5.
Figure 5.
Percentage of measured and missing internal cement gap values for lithium disilicate and zirconia crowns according both OCT system.
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