The effect of thermal aging on the color matching of Class III and Class V restorations with universal resin composites in various-shade human teeth: an instrumental and visual evaluation

Abstract

Objectives: This in vitro study aimed to assess the color matching of two single-shade and one group-shade universal composite resins for Class III and Class V restorations in extracted human teeth of different shades and evaluate the impact of thermal aging on these restorations using both instrumental and visual methods.

Materials and methods: Forty-five extracted human central incisors in a range of Vita Classical shades (A1, A2 and A3) were used. Three composite resins (Zenchroma (ZC), Charisma Diamond One (CDO), and Neo Spectra ST (NEO)) were tested. Each tooth received both Class III and Class V restorations (2 mm depth and 4 mm diameter) with the same composite resin. Color measurements were made immediately after restoration, 24 h, and after thermal aging using an intraoral spectrophotometer. Color differences (ΔE₀₀) were calculated using the CIEDE2000 formula. Visual assessments were scored from 0 (perfect fit) to 4 (significant mismatch) by three dental specialist. Data were analyzed using IBM SPSS V23. A Generalized Linear Model (GLM) was used to assess main and interaction effects, and Tukey's test was applied for multiple comparisons. A significance level of p < 0.05 was considered.

Results: NEO showed statistically significantly lower ΔE₀₀ values (2.45 ± 1.29) compared to the other composite resins (p < 0.001). Class III restorations (3.41 ± 1.48) exhibited lower ΔE₀₀ values than Class V restorations (4.56 ± 2.23, p < 0.001). ΔE₀₀ values decreased after aging (p = 0.007).

Conclusion: Class III restorations demonstrated better color matching than Class V restorations in both visual and instrumental evaluations. The group-shade composite resin showed better color matching compared to the single-shade composite resins. Although visual matching improved over time, some instrumentally measured color differences remained above the clinically acceptable threshold (ΔE₀₀>1.8).

Clinical relevance: Clinicians should consider both composite type and cavity configuration when selecting materials for aesthetic restorations.

Keywords: Color; Esthetics; Resin composite; Spectrophotometry.

Fig. 1

Flowchart of the study

Fig. 2

Class V restorations are indicated by symbol A, and Class III restorations are indicated by symbol B. Color was measured using a spectrophotometer from three different points on the tooth surface surrounding the restoration and once directly over the restoration itself

Fig. 3

Color match scores of the groups immediately after time (ZC = Zenchroma, CDO = Charisma Diamond One, NEO = Neo Spectra ST)

Fig. 4

Color match scores of the groups 24 h later (ZC = Zenchroma, CDO = Charisma Diamond One, NEO = Neo Spectra ST)

Fig. 5

Color match scores of the groups after aging (ZC = Zenchroma, CDO = Charisma Diamond One, NEO = Neo Spectra ST)