Evaluation of patient satisfaction and shade matching of Vita Suprinity versus lithium disilicate (E-max) ceramic crowns in the esthetic zone: a randomized controlled clinical trial

Introduction

In dentistry, accurate and predictable shade matching between natural teeth and restorative materials represents a challenge for clinicians and laboratory technicians. For decades, visual shade matching was most commonly used for the shade selection in the dental clinics as it is easy and does not require expensive equipment^1,2. Several studies reported that the color of the shade tabs is uniformly distributed and the shade guide enables accurate shade matching with the natural teeth^3,4. Other studies stated that the number of correct matches might increase if the Vitapan 3D-Master shade guide is used^4–6. They also suggested the use of Vitapan 3D-Master along with shade mapping, as in this study, to allow the exclusion of the effect of operators’ experience on shade-matching process and to ensure correct placement of different shade effects and characterizations^4–6.

However, many factors may negatively affect the quality of shade matching clinically, including tooth texture, lighting conditions, the surroundings and background⁷, as well as the subjective nature of human color observation, through color blindness or color perception defects^8,9. Differences in gender¹⁰, variations in experience of the evaluators, lighting conditions, metamerism and eye fatigue that could affect proper shade selection¹¹. Additionally, factors such as tooth dehydration as result of prolonged clinical procedures¹² and color alteration of shade tabs after chemical disinfection can cast a significant effect on the final shade matching^13–15.

Therefore, in order to eliminate the confounders during the color matching process, instrumental methods have been introduced¹⁶. Greater correlation in several studies have been found between both the objective (spectrophotometer) and the subjective (visual) shade selection methods with respect to color dimension of value or lightness, followed by hue and finally chroma^17–19. It was concluded that combination of both methods should be used for a successful esthetic outcome. While other studies found that using a spectrophotometer for shade matching is more accurate than using a conventional shade guide^20–24. In other studies, instrumental color matching was suggested as a supplementary tool for a better esthetic outcome^18,19,22.

In addition, the final color of all-ceramic restorations is affected by different factors including the porcelain layering technique²⁵, dental ceramic type, ceramic brand²⁶, veneering ceramic thickness^27–29, and firing temperature and conditions^30–32. Moreover, clinical parameters, including type³³, color³⁴, and thickness^35,36 of cement can also influence the final result³⁷.

Therefore, the esthetic needs of the patients during treatment should be taken into consideration, otherwise patient satisfaction will not be achieved, which has a significant effect on patient self-perception and quality of life^38,39. A survey looking at patient satisfaction with esthetic treatment found that the restoration color was the primary cause for patient dissatisfaction, as 89.3% of patients were not satisfied of their esthetic treatment because of the color of their restoration⁴⁰. Other studies found that tooth color and gender also affect patient satisfaction, with females more dissatisfied than males^41,42.

Newly introduced ceramic systems with improved optical properties may lead to improve clinical shade matching and patient satisfaction. VITA SUPRINITY, introduced by VITA Zahnfabrik, is a glass ceramic material enriched with approximately 10% zirconia by weight. This very fine homogenous dual microstructure resulted in high flexural strength while simultaneously providing a high percentage of glassy matrices. These structural effects provide the ceramic with good optical and polishing properties and allow delivery of restorations with excellent esthetics^43,44.

Lithium disilicate ceramic (such as IPS e.max CAD, manufactured by Ivoclear Vivadent) is considered one of the more esthetic ceramics due to the glass matrix embedded with needle-like lithium disilicate crystals that results in reduction of internal scattering of the light as it passes through the material. There are also other optical properties for better mimicking of adjacent natural teeth, which include the chameleon effect^45,46.

Therefore, this study was conducted to evaluate patient satisfaction according to the visual analogue scale (VAS) and shade-matching of VITA SUPRINITY versus (IPS e-max CAD) lithium disilicate all ceramic crowns in esthetic zone using the modified United States Public Health Service (USPHS) criteria in a prospective controlled randomized clinical trial. The null hypothesis of the study was that there would be difference in patient satisfaction and shade matching of VITA SUPRINITY if compared with lithium disilicate ceramic crown used in the esthetic zone.

Methods

Intervention

Two crown systems (IPS e.max CAD and VITA SUPRINITY ceramics) were selected for this study (Table 1). All treatment procedures were performed by the same clinician (S.A.). Scaling and polishing were performed for each patient before shade selection in order to remove any dental plaque, calculus and staining, which will affect the accurate shade selection. The tooth color was recorded visually using VITA 3D-Master shade guide system (VITA, Zahnfabrik, Germany) in accordance to the contra-lateral/adjacent tooth under different light conditions: natural day light, incandescent light and color-corrected light (using Smile Lite, Smile Line, Switzerland) to avoid metamerism. This was done with the help of three prosthodontists, who had performed Ishihara's test to determine deficiency in color vision⁴⁹. Their results showed no color blindness.

Table 1. The materials investigated in the study.

Material name	Composition	Manufacturer
IPS e.max CAD	Lithium disilicate glass-ceramic	Ivoclar Vivadent (Germany)
VITA SUPRINITY	Zirconia reinforced lithium silicate ceramic	Vita Zahnfabrik (Germany)

Visual shade selection was carried out within a standardized environment at midday, when incident daylight is most balanced with the visible light spectrum⁵⁰. While the patients were positioned on dental chair so that his/her mouth was at the same level and 40 cm apart from observers’ eyes. All bright colors were removed from the field of view (as makeup, tinted eye glasses) and a neutral gray patient bib masked clothing colors. Upper and lower teeth were separated with the tongue retracted. Both tooth (the contra-lateral/adjacent tooth) and shade tab were placed in the same plane with neutral gray background (Flexipalette Color Match, Smile line, Switzerland). Shade selections were done in three areas of the tooth (incisal, middle and cervical third) to match the subject's maxillary contra-lateral/adjacent tooth^5,51. (Figure 1)

Figure 1. Shade selection under natural day light of upper left central incisor.

The color-corrected light, with a color correlated temperature of 5,500K, 1,500 lux at a distance of approximately 10 cm and a color rendering index (CRI) of 92, was used as a confirmatory procedure. The evaluators were asked to stand opposite the targeted tooth so that shade matching was performed from the see-thru rectangular window (Figure 2)^52–54.

Figure 2. Shade selection using color corrected light of upper left central incisor.

Shade matching was also confirmed with Vita Easyshade V spectrophotometer (VITA, Zahnfabrik, Germany). It was calibrated before starting each measurement. As stated by the manufacturer, the measurement was acknowledged when three consecutive, identical readings were generated using tooth area measurement mode for shade selection (Figure 3)²². Vita Easyshade V was used as a confirmatory tool for better shade selection by the operator only and wasn’t used for the clinical evaluation or assessment procedure of the final restorations.

Figure 3. Shade selection corresponding to upper right central incisor.

Preparation of teeth for full coverage restoration were performed with smooth, round contours and line-angles, chamfer finish lines of 1 mm in diameter with round internal angles, and incisal reduction of 2 mm^46,55,56. The shade of the prepared abutment tooth was recorded visually using the IPS Natural Die Material shade guide (Ivoclar Vivadent) under natural day light and color corrected light in order to fabricate a die mimicking the oral situation for optimum desired final esthetic results (Figure 4)^46,57.

Figure 4. Tooth stump shade selection of upper left central incisor.

Vinyl polysiloxane elastomeric impressions (Honigum impression material, DMG, Germany) were made, and provisional restorations (Structur 2 SC, VOCO, Germany) were cemented with non-eugenol provisional cement (RelyX Temp NE, 3MESPE, USA)⁵⁵.

The construction of the all-ceramic crowns was performed using CAD/CAM Cerec InLab MC X5 milling machine, with Cerec 15.0.0 software. The fitting surfaces of the all-ceramic crowns were treated and silanated according to the manufacturer's instruction and abutment teeth were prepared where self-etch adhesive protocol was obeyed using adhesive resin cement (Bifix-QM, VOCO, Germany) (Figure 5)^58,59.

Figure 5. After cementation of the crown of upper left central incisor.

(A) Frontal view. (B) Palatal view.

Results

The patient satisfaction associated with restorations for both groups is highlighted in Table 2 and Figure 6. Raw data are available on Open Science Framework⁴⁷.

Figure 6. Column chart of aesthetics scores associated with restoration for both groups.

According to the visual analogue scale (VAS), 100% of patients were satisfied while 0% were dissatisfied by the restoration in both groups. This was statistically non-significant as verified by chi square test (p>0.05). Table 2 and Figure 6. No harms were recorded.

Regarding shade matching, no statistical difference was found between the two tested groups (p >0.05). According to the modified USPHS criteria, 100% of the patients were Alpha score with 0% for Bravo, Charlie and Delta scores in both groups (Table 3 and Figure 7).

Figure 7. Column chart of shade match associated with restoration for both groups.

Discussion

Concerning shade matching results, all patients recorded no color difference between their restorations and adjacent/contra-lateral teeth which might be attributed to the strict and meticulous shade matching protocol followed in respect to the staining procedure in accordance to each material used. In addition to the similarity in microstructure of both materials being lithium silicate-based glass-ceramics. This was in accordance with several studies that stated that in order to achieve a tooth-colored restoration, two different steps are required: select the proper shade using a shade guide and/or an electronic shade-taking device, and reproduce this shade with a suitable dental material^37,63.

Concerning IPS e.max CAD all-ceramic crowns, Fasbinder et al.⁶⁴ stated that no color change was noted for CAD/CAM lithium disilicate crowns after 2 years of service. Rauch et al.⁶⁵ reported USPHS alpha scores for all monolithic lithium disilicate crowns in the posterior zone upon evaluation after 6 and 10 years. Contradicting to our results those found by Chaiyabutr et al.⁴⁶, who found color variation in CAD/CAM lithium disilicate glass-ceramic restorations. They explained that this may be due to the optical characteristics of the material, which allows the underlying tooth shade stump to affect the final color of the crown. They reported that the final color of 1 mm ceramic thickness in the cervical area combined with low-translucency ceramic blocks may be affected by intense discoloration of underlying abutment tooth color. This was avoided in our current study, as severely discolored abutments were among our exclusion criteria.

Rinke et al.⁶⁶ found the excellent esthetic properties of VITA SUPRINITY may be related to the homogenous dual microstructure, consisting of very fine lithium disilicate and lithium metasilicate crystals with average size of 0.5–0.7 μm which are four to eight times smaller than lithium disilicate crystallites. The result is very fine microstructure that provides a higher ratio of glass matrix/zirconium oxide in solution.

However, contradicting our results, Jirajariyavej et al.²⁹ found that the different ceramic materials affected the final esthetic outcome of the restoration. This color difference may be due to difference in translucency between the silicate-based glass-ceramic materials, with the IPS e.max CAD being more translucent than VITA SUPRINITY.

Concerning patient satisfaction results, all the patients were satisfied with their restorations. Additionally, there was no statistically significant difference between the two groups. This might be attributed to the meticulous shade matching protocol and laboratory procedure followed in this study. Ballard et al.⁵⁵ found that patients reporting high satisfaction ratings may have been affected by the high value of the restoration. Al-Wahadni et al.⁶⁷ found that patients’ satisfaction increased when the restorations were received in an academic institution, denoting that patients’ confidence in the school or good relationship with the dental student may have elevated their opinions of the care received.

Contradicting our results are those by Shah et al.⁴¹ who found the overall rating of patient satisfaction was acceptable (USPHS Bravo and Charlie scores). They explained that patient level of education might affected the results. Well-educated patients tended to be more satisfied with their tooth color compared to patients with primary level of education. Samorodnitzky-Naveh et al.⁴⁰ found discrepancies between overall satisfaction with tooth appearance and satisfaction with tooth color. They explained that age might have a significant effect on patient satisfaction, as the selected young cohort of subjects might have been excessively sensitive about the appearance of their teeth. This was avoided in our study by selecting large age range between 20 and 60 years old.

Finally, the hypothesis was rejected as no statistical difference was found between the two tested groups (IPS e.max CAD and VITA SUPRINITY).

Conclusions

VITA SUPRINITY and IPS e.max CAD full coverage restorations revealed excellent patient satisfaction and color matching. This indicates that both materials can be recommended as full coverage restorations in clinical situations for optimum esthetic outcome. The choice depends on the dentist's preference.

Data availability

Reporting guidelines

Open Science Framework: CONSORT checklist for article “Evaluation of patient satisfaction and shade matching of Vita Suprinity versus lithium disilicate (E-max) ceramic crowns in esthetic zone: a randomized controlled clinical trial”. https://doi.org/10.17605/OSF.IO/ZH6SC⁶⁷.

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).