Available online 16 April 2024

Author links open overlay panel, , , , AbstractStatement of problem

Three-dimensional (3D) printing has become popular in dentistry, but studies on the influence of incorporating organic and inorganic nanofillers on 3D printed materials are lacking.

Purpose

The purpose of this in vitro study was to assess the flexural strength, color, and antimicrobial efficacy of 3D printed photopolymerizable resin upon adding titanium dioxide nanoparticles (TiO2 NPs) and silanized chitosan nanoparticles (sCS NPs).

Material and methods

A stereolithographic material (VarseoSmile Crown plus; Bego) was used as a control group (VSC resin), and 3 nanocomposite resin groups were prepared by adding nanoparticles as follow: titanium dioxide group (VSC resin + 0.4% wt. TiO2 NPs), chitosan group (VSC resin + 0.4% wt. sCS NPs), and hybrid group (VSC resin + 0.2% wt. TiO2 NPs + 0.2% wt. sCS NPs). A total of 132 specimens were designed by using a free computer-aided design software program, printed, postpolymerized, and divided into 4 groups. The nanocomposite resins were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR). Bar shaped specimens (n=44) were tested for 3-point flexural strength using a universal testing machine followed by the color measurement of disk-shaped specimens (n=44) with a spectrophotometer. Antimicrobial capacity was measured with Streptococcus mutans, and absorbance was measured using a microplate reader (n=44). Statistical assessments were made with 1-way ANOVA followed by the Tukey post hoc test with Bonferroni adjustment (α=.05).

Results

The hybrid group recorded the highest mean value of flexural strength 135.51 MPa, showing a significant difference compared with that of the control group (P=.022). Regarding color, the mean ∆E00 for titanium was 1.18, for chitosan was 4.26, and for the hybrid group was 3.23 (P<.001). The optical density of the chitosan (2.42) was significantly higher than that of the titanium 1.36 (P=.007) and that of the control 1.63 (P=.042).

Conclusions

The incorporation of nanofillers resulted in an increase in flexural strength, but it adversely affected the color of nanocomposite resins. Antimicrobial efficacy was improved by incorporating titanium nanofillers.

Section snippetsMATERIAL AND METHODS

The material investigated was a 3D printed dental crown resin (VarseoSmile Crown plus; BEGO) (VSC). A total of 132 specimens were divided into 1 control group and 3 test groups, (n=33). The control group contained 3D printed resin (VSC) without modification, whereas the remaining 3 nanocomposite resin test groups were prepared by incorporating 0.4% by weight of TiO2 NPs7 (<10 nm - spherical like shape), sCS NPs (<50 nm – spherical shaped), and hybrid NPs (0.2% TiO2 and 0.2% sCS NPs) (Table 1).

RESULTS

The morphological topographical distribution of NPs incorporated into the 3D printed resin was characterized through SEM (Fig. 1). The VSC resin surface demonstrated a consistent uniformity devoid of distinct features. In contrast, the morphological characteristics of TiO2, sCS, and hybrid nanocomposite resin surfaces revealed an uneven topography, with particle clusters randomly distributed across the surface.

The EDX analysis (Fig. 2) showed that the control specimen (VSC) had a composition of

DISCUSSION

The null hypothesis that flexural strength, color, and antimicrobial efficacy would not be affected significantly upon adding titanium dioxide nanoparticles (TiO2 NPs) and silanized chitosan nanoparticles (sCS NPs) into the 3D printed photopolymerizable resin used for a 3D printed crown material was rejected. Consistent with a previous study,7 0.4% TiO2 NPs provided the best dispersion in comparison with 1 wt% and 2.5 wt% TiO2 and, as expected, increased mechanical properties. Silane coupling

CONCLUSIONS

Based on the findings of this in vitro study, the following conclusions were drawn:

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A significant increase was observed in the flexural strength of the hybrid group compared with the control group.

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The inclusion of sCS and TiO2 NPs led to noticeable changes in color, suggesting implications for the esthetics of dental restorations. Therefore, its use is recommended for definitive restorations of deciduous teeth, posterior restorations, or long-term interim restorations.

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The introduction of TiO2

CRediT authorship contribution statement

Noha S. ElMalah: Conceptualization, Methodology, Investigation, Formal analysis, Resources, Writing - original draft. Seham A. Hanafy: Conceptualization, Methodology, Visualization, Writing - review and editing, Supervision. Essam M. Osman: Conceptualization, Methodology, Validation, Data curation, Writing - review and editing, Supervision. Salma A. Aboulgheit: Conceptualization, Investigation, Methodology, Data curation, Writing - review and editing, Supervision. Amira S. Baz:

Acknowledgments

The authors thank Dr Dawlat Mostafa for her academic help and guidance; Dr Yomna Saad for her help with UTM software; and Dr Hams Abdelrahman for her assistance with the statistical analysis.

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