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 Table of Contents  
Year : 2023  |  Volume : 23  |  Issue : 1  |  Page : 38-44

In vitro comparison of the color degradation of two computer-aided design/computer-aided manufacturing provisional materials: A 12-month simulation

1 Department of Prosthodontics, Saint Joseph University of Beirut, Beirut, Lebanon
2 Department of Pediatrics, McGill University, Saint Joseph University of Beirut, Beirut, Lebanon

Date of Submission07-Mar-2022
Date of Decision15-Jul-2022
Date of Acceptance29-Jul-2022
Date of Web Publication29-Dec-2022

Correspondence Address:
Suzanna Maria Sayegh
Saint Joseph University, Beirut
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jips.jips_119_22

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Aim: This study evaluated the color aging of two computer aided design/computer aided manufacturing (CAD/CAM) provisional materials of different compositions (polymethyl methacrylate and composite resin) after exposure to thermal aging and immersion in coffee for 3, 6, and 12 intraoral months.
Setting and Design: The current in vitro study was conducted from September to December 2021 at the Craniofacial laboratory at the Saint Joseph University in Beirut, Lebanon.
Materials and Methods: The shades of 2.0 mm thick, 10.0 mm in diameter disk shaped specimens of VITA CAD Temp® and Ceramill® TEMP were measured using the VITA Linearguide 3D MASTER® and a conversion table to extract the CIE L*a*b* values on a white background (n = 30).
Statistical Analysis Used: The color differences ΔE at 3, 6, and 12 months were calculated and analyzed by repeated measures ANOVA followed by Bonferroni multiple comparisons, univariate analyses, and one sample t tests.
Results: The mean ΔET1/T0, ΔET2/T0, and ΔET3/T0 values were significantly higher than the cutoff values for acceptability and perceptibility for the VITA CAD Temp® and the Ceramill® TEMP groups. In addition, the increase in ΔE overtime was significantly greater in the Ceramill® TEMP group compared to the VITA CAD Temp® group.
Conclusions: The Ceramill® TEMP changed color more and faster than the VITA CAD Temp®. In addition, whether at 3, 6, or 12 months, the color variations of both materials are not only perceptible but also unacceptable compared to the initial shade.

Keywords: Color, composite resin, computer-aided manufacturing/computer-aided manufacturing, in vitro, materials, polymethyl methacrylate, stability, temporary

How to cite this article:
Sayegh SM, Daou M, Najjar G, Zebouni E. In vitro comparison of the color degradation of two computer-aided design/computer-aided manufacturing provisional materials: A 12-month simulation. J Indian Prosthodont Soc 2023;23:38-44

How to cite this URL:
Sayegh SM, Daou M, Najjar G, Zebouni E. In vitro comparison of the color degradation of two computer-aided design/computer-aided manufacturing provisional materials: A 12-month simulation. J Indian Prosthodont Soc [serial online] 2023 [cited 2023 Feb 6];23:38-44. Available from: https://www.j-ips.org/text.asp?2023/23/1/38/365936

  Introduction Top

In fixed prostheses, the temporization phase is the most important,[1] especially because of its role in restoring esthetics, its diagnostic value, restoring function (chewing and phonation), and protection of underlying and surrounding structures.[2] Whether for the patient or for the practitioner, the provisional will make it possible to choose the best permanent crowns as wisely as possible at the end of treatment.[1] Discoloration of these temporary teeth would lead to patient dissatisfaction, the need to replace them, and the surge of additional costs on the practitioner. It is therefore based on this reasoning that the quest for temporization materials[2] that combine mechanical resistance, biocompatibility, and esthetic longevity has been intensified.[3] When treatment plans are long and require long temporization periods of up to 12 months, practitioners then resort to materials manufactured industrially under optimal conditions: computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured materials, more stable mechanically and chemically,[4],[5],[6],[7] and available mainly in two types: methacrylic resins and composite resins.

The aim of this study was first, to confirm or refute the theory that claims that composite materials are more vulnerable than others to color change, to determine which of the two materials (PMMA and composite) changes color more and quicker, to determine whether this change in color is perceptible or not and acceptable or not by the patient, and finally, to deduce which of the two materials should be chosen for provisional restorations for long term prosthetic treatments in an esthetic region.

The answers to the above were found after calculating and analyzing the color changes (ΔE) after thermal aging and immersion in coffee[7],[8],[9],[10],[11],[12] of two CAD/CAM-manufactured materials: the VITA CAD-Temp® (Bad Säckingen, Germany) from VITA, a microfiller-reinforced polyacrylic (MRP) composed of a matrix of cross-linked acrylate polymer, exempt of fibers and supplemented with microfillers, and the Ceramill® TEMP (Koblach, Austria) from Amann Girrbach made of polymethyl methacrylate (PMMA) and methacrylic acid ester-based cross-linked polymers.

  Materials and Methods Top

In the present study and as aforementioned, two CAD/CAM materials used for the fabrication of temporary crowns were compared, one made of PMMA resin, the Ceramill® TEMP (Koblach, Austria) PMMA from Amann Girrbach, and the other a composite resin, the Vita CAD-Temp® (Bad Säckingen, Germany) from VITA. Both materials, manufactured in the same way, were exposed to the same staining factor, the most dreaded according to previous studies:[7],[8],[9],[10],[11],[13] coffee. Ethical Committee approval reference number, it's the following: USJ-2020-236.

Materials and specimens' fabrication

VITA CAD-Temp® is a material consisting of a high-molecular-weight cross-linked acrylate polymer matrix supplemented with microfillers; this material is called MRP. VITA CAD-Temp® is used for the fabrication of multiunit provisional bridges in cases requiring long-term temporization. Ceramill® TEMP is a PMMA that is also suitable for long-term temporary restorations with a wearing time of up to 3 years. According to the recommendations of their respective manufacturers, both materials have the same indications for use.

Thirty specimens of each material, both of shade 1M2 (n = 30, n = 60), were milled according to the ISO recommendations for this kind of experiment, i.e., 1 cm diameter and 2 mm thick discs [Figure 1] with the Ceramill® Motion 2 (Koblach, Austria) milling machine from Amann Girrbach AG [Figure 2]. The 60 specimens were numbered from 101 to 130 (VITA CAD-Temp®) and from 201 to 230 (Ceramill TEMP®) on one side (by engraving) and polished on the other side by the same operator using a diamond polishing paste (Renfert Polish® by Renfert). Specimens were polished for 15 s with a polishing disc mounted on an electric handpiece at 15,000 rpm using the diamond polishing paste. Before initial color measurement, visual observation of the respective polished surfaces of all specimens was made to ensure that surfaces were exempt of any porosity. This was followed by washing and storing the discs in distilled water.
Figure 1: One centimeter diameter and 2 mm thick disc-shaped specimens

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Figure 2: Specimens' design and milling

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Preparation of the staining solution

Coffee is one of the most popular drinks in the world. In Lebanon, Turkish coffee is the most consumed, with 65%[14] of the total consumption, whereas instant coffee is only 35% of the total consumption (Espresso 0.34% and filter coffee almost 0%).[14] To prepare the coffee solution and to standardize it, the preparation was done with the Raqwa® (Beirut, Lebanon) machine of Café Najjar, which allowed to obtain the exact same solution each time by the capsule system.

Implementation of the protocol

The specimens were artificially aged by thermocycling (each cycle = 30 s in the −5°C tray, 5 s of rest, and 30 s in the 55°C tray) [Figure 3]. After each thermocycling step (2500, 5000, and 10,000 cycles, respectively, equivalent to 3, 6, and 12 months[15]), soaking was performed to simulate the consumption of three cups of coffee per day over 3, 6, and 12 months (24 h of soaking being equivalent to 1 month of consumption; therefore, 72 h for 3 months, 144 h for 6 months, and 288 h for 12 months.[16],[17],[18]).
Figure 3: Thermocycling step

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Color measurements [Figure 4] were performed after each pair of manipulations (thermocycling + soaking) using the VITA Linearguide 3D-MASTER® (Bad Säckingen, Germany) and after rinsing the specimens for 3 min using distilled water and drying them with absorbent paper towels. First of all, the initial shade of the specimens was double-checked before soaking, and the baseline color values at T0 were noted down. Moreover, since visual color examination is influenced by the light environment and the visual fatigue of the practitioner, the specimens were positioned on a white background, allowing better visualization of color changes in addition to a better accentuation of the nuances.[19],[20] This was done on the same working surface, and facing the same window, between noon and 3 o'clock, every single time. These precautions aimed to lessen, as much as possible, the bias related to the light environment. Furthermore, the color was measured twice each time, 1 h apart, and by a practitioner with a trained eye and good eyesight (no glasses worn), to eliminate any bias that might be caused by visual fatigue of the practitioner. The color difference (ΔE) after 3, 6, and 12 months was then calculated.
Figure 4: Specimens and shade guides on the white background used for color measurement

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[Figure 5] concretizes the chronology of the manipulations and the measurements in time.
Figure 5: Chronology of the applied protocol

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Statistical analyses

Statistical analyses were performed using IBM SPSS Statistics for Windows (IBM Corp., Armonk, NY, USA) (version 25.0). The level of significance was set at – P ≤ 0.05. The primary outcome variable of this study was the variation of ΔE within time.

Repeated measures analysis of variance with one within-subject factor (time) and one between-subject factor (VITA and AG) was applied to compare the mean Δ E between the groups. This test was followed by univariate analyses and Bonferroni multiple comparisons. The 95% confidence interval of the mean Δ E values was calculated in each group. One-sample t-tests were used to compare the mean ΔE with the cutoffs of 1.2, 2.767, and 3.368.

  Results Top

As shown in [Table 1], the mean ΔET1/T0, ΔET2/T0, and ΔET3/T0 values were significantly higher than the cutoff of acceptability and perceptibility for the VITA (P < 0.001) and AG groups (P < 0.001).
Table 1: MeanΔE variation among groups (VITA and Amann Girrbach [AG])

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These ΔE values significantly increased over time for the VITA (P < 0.001) and AG groups (P < 0.001); however, the increase in ΔE over time was significantly greater in the AG group compared to the VITA group (statistical interaction: P < 0.001).

Hence, for VITA, the ΔE has significantly increased between T1/T0 and T2/T0 by +1.341 (P < 0.001), between T2/T0 and T3/T0 by +3.394 (P < 0.001), and between T1/T0 and T3/T0 by +4.735 (P < 0.001). The increase of +1.341 was not perceptible (P = 0.342), the increase of +3.394 was perceptible (P < 0.001) and acceptable (P = 0.882), and the increase of +4.735 was perceptible (P < 0.001) but not acceptable (P < 0.001).

For the AG group, the Δ E has significantly increased between T1/T0 and T2/T0 by +1.781 (P < 0.001), between T2/T0 and T3/T0 by +3.98 (P < 0.001), and between T1/T0 and T3/T0 by +5.761 (P < 0.001).

The increase of +1.781 was perceptible (P = 0.005). The increase of +3.980 was perceptible (P < 0.001) but not acceptable (P < 0.001), and the increase of +5.761 was perceptible (P < 0.001) but not acceptable (P < 0.001).

  Discussion Top

This study's primary aim was to compare the color stability of two provisional CAD/CAM materials of two different compositions, the Vita CAD-Temp® from VITA and the Ceramill® TEMP from Amann Girrbach, after exposure to thermal aging and immersion in coffee for 3, 6, and 12 intraoral months.

First, statistical analysis showed that the Ceramill® TEMP changed color more and faster than VITA CAD-TEMP®, making the latter a better choice for long-term esthetic provisional restorations, thus invalidating the theory stating that composite materials are more prone than others to color change[21],[22] and thereby refuting the hypothesis of the current study. The aforementioned results are in line with the ones of another recently published study by Kul et al. that compared these two materials.[8]

However, whether at T1, T2, or T3, the color variations of both materials were shown to be not only perceptible but also unacceptable compared to the initial shade when the temporary crowns were placed in the mouth. This was deduced after comparing the ΔEs obtained to perceptibility and acceptability thresholds, the perceptibility threshold (3368) being the visually detectable color difference, and the acceptability threshold[1],[2] being the magnitude of color difference that is acceptable by the patient for esthetic outcomes.[16] Practically, this means that after 3 months in the mouth, the patient could complain about the change in color of the provisional crowns and demand their replacement, and the situation would deteriorate further 3 and 9 months later (at 6 and 12 months).

This allows to deduce that first, after 3 months in the mouth in a patient drinking three cups of coffee a day, even these high-performance materials are not ideal from an esthetic point of view since their color change is already perceptible and unacceptable at 3 months, and that second, the color stability of prefabricated temporary blocks for CAD/CAM systems still needs to be improved, as also mentioned by Kul et al.[8]

Nevertheless, going into the details of the results, it is noticeable that between T1 and T2, during the period extending between the 3rd and 6th months after the delivery of the provisional crowns, the color change is not perceptible with the VITA CAD-Temp® and is perceptible and acceptable with the Ceramill® TEMP. Furthermore, between T2 and T3, during the 6 months extended from the 6th to the 12th month after delivery of the provisional crowns, the color change is perceptible and acceptable for VITA CAD-Temp® but perceptible and not acceptable for Ceramill® TEMP.

The above two results suggest a lesser degradation of the materials after 3 intraoral months, thus a less important color change than during the first 3 months. Further studies analyzing the changes affecting the materials in particular at the level of their sorption and thus of their capacity of absorption of the coloring substances at shorter intervals are necessary to confirm this hypothesis, as it was done in a previous study.[16] This hypothesis is also supported by another study which underlines the fact that the degradation of color during the first 4 weeks of simulation is less important than that appearing after 8 weeks;[4] the time factor would therefore be quite delicate after the 1st month of manipulation,[23] and it would have been interesting to have included measurements at 1 month of simulation in the present study.

Moreover, it can then be deduced that when planning for treatments including long-term temporization in an esthetic region, the VITA CAD-Temp® is a better choice than the Ceramill® TEMP, without omitting the fact that the color stability of CAD/CAM blocks must be further improved in future to meet the expectations of practitioners and patients, since the color change in both materials was noticeable and not acceptable after 3, 6, and 12 months.

In addition, this study provided more precise results than several other studies (sometimes even very recent) of the same kind,[8] given several facts. First, most studies only soaked specimens without prior thermocycling,[7],[8],[9],[12] which does not accurately reproduce the intraoral conditions. Second, in other studies,[8],[9] the color measurements are made with spectrophotometers on the VITA CAD-Temp® specimens, knowing that the values given by the most advanced dental spectrophotometers on the market are not validated on this material (according to the scientific research team of VITA Zahnfabrik who were contacted). Third, the coffee staining solutions used in this study are highly standardized since they were prepared through a capsule system (Raqwa® from Café Najjar). Fourth, the population represented was poorly included in previous studies, since the type of coffee used in the vast majority if not all of the previous studies is filter coffee or instant coffee, types of coffee that are far from being the most popular in the Arab region. A last important advantage is the fact that the manipulations simulated 12 intraoral months, a duration exceeding those simulated in similar studies. This makes this study a continuation of previous ones that have underlined the limitation due to short simulation periods.[4]

It is nevertheless important to underline the fact that, in the oral environment, apart from exposure to coffee and temperature variations, restorative materials are also exposed to many other liquids and coloring substances, as well as to functional and parafunctional load constraints and toothbrushing. One of the limitations of this in vitro study would therefore be that the clinical environment and its effect on the discoloration of the CAD/CAM blocks have not been fully reproduced. Therefore, further investigation and more sophisticated handling is recommended to assess the effect of all the exogenous factors contributing to the long-term discoloration of CAD/CAM materials.[16],[24] Furthermore, a detailed dissection of the filler and resin matrix composition of each material and an analysis of the surface quality and composition-related properties of the materials after each soaking cycle would have possibly brought clarifications as to the influence of endogenous factors on color aging, as it was highlighted in other studies.[12],[13],[16],[24] Therefore, a more comprehensive strategy should be developed to test the exogenous and endogenous influences on the color stability of provisional prosthetic materials. Although combining factors will not provide information on the influence of any single factor, it might better mimic intraoral conditions and provide valuable supplementary findings.

An additional limitation of the present study is the fact that the color measurement was done twice, but by a single observer, it is recommended for it to be done by at least two different observers.

Finally, it would be interesting to investigate starting how many weeks this deterioration becomes perceptible and unacceptable in order to be able to predict the maximum duration of acceptability of the provisional by the patient. An analysis of the modification of the surface properties of the materials, in particular the modifications of their water sorption,[25] would provide further explanation as to the dynamics and intensity of color aging of the materials studied.

  Conclusions Top

Within the limitations of this study, it was concluded that:

  1. “Composite“ does not automatically mean less efficient, quite the contrary: on the basis of the results obtained, it is concluded that the VITA CAD-Temp® composite material from VITA Zahnfabrik exhibited a less important color aging than the noncomposite Ceramill TEMP® PMMA material from Amann Girrbach
  2. The Ceramill TEMP® PMMA aged more and quicker than the VITA CAD-Temp® composite material
  3. The color change is both perceptible and not acceptable by the patient whether it is after the simulation of 3, 6, or 12 intraoral months
  4. Despite all the technological advances with regard to dental materials, in particular materials for temporary restorations, improvements in physical properties still need to be made in order to obtain materials whose color stability is sufficient for long-term treatments to avoid the need for their replacement due to patient dissatisfaction. Nevertheless, if a choice has to be made between the two materials used in this study, the VITA CAD-Temp® would be preferred
  5. The spectrophotometers on the market are not yet ideal, their measurements not being validated with certain materials including composite ones. Improvements in these instruments can still be made.


The authors would like to thank VITA Zahnfabrik for the donation of their materials, Zirconnet Dental Laboratory (Mr. Marwan Khoury and Ms. Laureine Hamdar) for the milling of the specimens, and Pr. Maha Daou and Dr. Georges Najjar for their assistance and guidance in the laboratory work.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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Perry RD, Magnuson B. Provisional materials: Key components of interim fixed restorations. Compend Contin Educ Dent 2012;33:59-60, 62.  Back to cited text no. 2
Comisi JC. Provisional materials: Advances lead to extensive options for clinicians. Compend Contin Educ Dent 2015;36:54, 56-9.  Back to cited text no. 3
Song SY, Shin YH, Lee JY, Shin SW. Color stability of provisional restorative materials with different fabrication methods. J Adv Prosthodont 2020;12:259-64.  Back to cited text no. 4
Rayyan MM, Aboushelib M, Sayed NM, Ibrahim A, Jimbo R. Comparison of interim restorations fabricated by CAD/CAM with those fabricated manually. J Prosthet Dent 2015;114:414-9.  Back to cited text no. 5
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1]


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