Clinical performance of one shade universal composite resin and nanohybrid composite resin as full coronal esthetic restorations in primary maxillary incisors: A randomized controlled trial : Journal of Indian Society of Pedodontics and Preventive Dentistry

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Original Article

Clinical performance of one shade universal composite resin and nanohybrid composite resin as full coronal esthetic restorations in primary maxillary incisors

A randomized controlled trial

Zulekha, ; Vinay, C; Uloopi, KS; RojaRamya, Kakarla Sri; Penmatsa, Chaitanya; Ramesh, MV1

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Journal of Indian Society of Pedodontics and Preventive Dentistry 40(2):p 159-164, Apr–Jun 2022. | DOI: 10.4103/jisppd.jisppd_151_22
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It is prudent to restore the early childhood caries involved teeth to preserve the integrity of primary dentition until its exfoliation and eruption of permanent teeth. Resin composite strip crowns or crown formers are the first choice of treatment for many clinicians, mainly because of the superior esthetics and the ease of repair if the crown subsequently chips or fractures.[12] However, shade-matching of resin composite to the surrounding tooth structure remains a problem to be resolved.[3]

The tendency to produce more and more so-called natural shades of restorative material has led to a plethora of shade choices that complicates the shade matching procedure, requires more inventory, and increases cost and chairside time.[4] Moreover, artificial emulation of all the inherent features of the tooth is not always an easy task because the enamel and dentin have disparate thickness distributions in the dental crown, structure, composition, and especially optical properties.[5] The trend of shortening the restorative procedure time and simplifying color matching led to competition between dental manufacturers to develop a universal resin composite (single shade), which could match a wide range of classical shades.[6]

Omnichroma is a newly developed single-shade resin composite. The manufacturer claims it is the first material that used structural color as the primary color mechanism in composite dentistry and can mimic the color of the surrounding tooth, irrespective of its shade.[7] The structural color phenomenon is based on the discrimination of wavelengths by the interaction of incident light with nanostructures such as thin films, diffraction gratings, or photonic crystals.[8] It consists of uniform-sized supra-nano spherical filler particles of silicon dioxide (SiO2) and zirconium dioxide (ZrO2) with a particle size of 260 nm, which interact with the incident light and change the transmission of light along the red-to-yellow zone of the color spectrum, thereby allowing it to match the color of the patient's surrounding dentition.[9]

A recent study reported that Omnichroma with 260 nm spherical filler particles exhibited structural color and that their color adaptation to denture teeth of various shades was excellent.[10] However, its clinical success in various shades of human teeth, especially the primary teeth, remains unclear. Therefore, this study was carried out with an aim to evaluate the clinical performance of the novel one shade universal composite, Omnichroma®, in comparison with nanohybrid resin composite, Tetric-N-Ceram® as full coronal restorations in primary maxillary incisors.

Materials and Methods

This double-blinded randomized controlled trial was carried out from July 2020 to July 2021. The clinical trial design was reviewed and approved by the Institutional review board and the ethical committee and the protocol was in accordance with the ethical standards laid down by the Helsinki declaration. The study was registered with the Clinical Trials Registry of India (CTRI/2020/03/024302).

The sample size was calculated from the previous study by Pereira Sanchez et al.[10] The Gpower software version (Heinrich-Heine-Universitat Dusseldorf, Dusseldorf, Germany) for power analysis indicated that a total of 32 teeth (corresponding to achieve 80% power with 95% confidence) were required. Given the possibility of 20% attrition in subsequent follow-ups, nine teeth were added to each group, and therefore, a total of 25 teeth were included per group.

After screening the children attending the outpatient department of Pediatric and Preventive dentistry, 25 children aged 3–5 years with multi-surface carious lesions in primary maxillary incisors involving enamel or enamel and dentin only with at least two carious surfaces, and at least two-thirds of the crown persisting after caries removal and those requiring complete coronal restoration were included in the study. Children having deep carious lesions with pulpal involvement or any signs of abscess/sinus tract/root resorption, medically compromised patients, and those participating in other studies were excluded. Details of the study were shared with the patients and parents before the start of the trial, and informed consent was obtained from the participants parents.

The present study was carried out using a split-mouth design, and a total of 50 primary maxillary incisors were included. Computer-generated block randomization technique was used to randomly allocate the teeth into the two treatment groups: Group I – One shade universal composite, Omnichroma (Tokuyama, CA, USA) (test group), Group II – Conventional composite, Tetric-N-Ceram (Ivoclar Vivadent, Schaan) (control group). The outcome assessor and data analyst were kept blinded to the allocation, whereas the operator could not be blinded since the control group requires shade selection.

Shade selection was made for the control group. Appropriate-sized strip crowns were selected for both groups, and rubber dam isolation was done to avoid moisture contamination. Then, the caries was excavated with round diamond burs. Tooth preparation was done by reducing the tooth interproximally by 0.5–1.0 mm, and the incisal edge by 1.5 mm using a tapered fissure bur. The labial surface was reduced by 1 mm using tapered fissure bur, and the lingual surface was reduced by 0.5 mm using flame-shaped bur. A feather edge margin was created, and the strip crowns were adapted to the cingulum of the maxillary anterior tooth by cutting the gingival margin using scissors. Vent holes were placed on the crown's mesial and distal incisal angles to remove excess material.

The prepared tooth surfaces were etched for 15 s with 37% phosphoric acid gel and then rinsed thoroughly with water. Excess moisture on the tooth surfaces was blotted out; a layer of bonding agent was applied, and light-cured for 20 s. Then, the celluloid/strip crowns were filled with corresponding composite material and inserted onto the prepared tooth, and excess resin was removed. Then, the material was light-cured, and the strip crowns were peeled off using an explorer. Postoperative occlusion was checked and adjusted accordingly. The children were recalled at 6- and 12-month interval for follow-up evaluation. Clinical photographs of teeth 51 and 61 treated with Tetric-N-Ceram and Omnichroma are illustrated in Figures 1 and 2.

Figure 1:
Clinical photographs of teeth 51 and 61 treated with Tetric-N-Ceram and Omnichroma, respectively. (a) Preoperative photograph; (b) immediate postoperative photograph; (c) 6-month follow-up photograph; (d) 12-month follow-up photograph
Figure 2:
Clinical photographs of teeth 51 and 61 treated with Tetric-N-Ceram and Omnichroma, respectively. (a) Preoperative photograph; (b) immediate postoperative photograph; (c) 6-month follow-up photograph; (d) 12-month follow-up photograph

Evaluation of the color matching with the adjacent tooth tissues at baseline, color stability, and retention at 6 and 12 months were done using the Modified United States Public Health Services criteria.[11] The restorations were evaluated by two independent examiners trained in the assessment technique at the start of the study. They were precalibrated at 90% reliability on 10 patients who were not included in the study. The kappa values for inter-examiner reliability were 0.840–1.0 for Omnichroma and 0.615–1.0 for Tetric-N-Ceram groups. The agreement between the examiners was observed to be substantial to almost perfect.

The obtained data were tabulated and subjected to statistical analysis using nonparametric tests. The Wilcoxon signed-rank test was used for intra-group comparison and Mann–Whitney U test for intergroup comparison. Values of P ≤ 0.05 and P ≤ 0.000 were considered for statistical significance and high significance, respectively.


Participation of children through the study is depicted in the CONSORT flow diagram [Figure 3]. All the children were available for the follow-up without any dropouts.

Figure 3:
CONSORT flow diagram

Color match

On intergroup comparison of the color match at baseline, 84% (n = 21) of restorations in the Omnichroma group and 80% (n = 20) of restorations in the Tetric-N-Ceram group were graded Alpha, the best score that represents perfect shade and translucency match with adjacent tissues. However, the difference was not statistically significant (P = 0.716), indicating that the color match of both the restorative materials was comparable [Table 1].

Table 1:
Intergroup comparison of test parameters at 6- and 12-month intervals

Color stability

On intragroup comparison of color stability at 6- and 12-month interval, the difference was found to be statistically significant in both Omnichroma (P = 0.001) and Tetric-N-Ceram (P = 0.001) groups, indicating that the color stability of restorations was better at 6-month interval compared to 12-month interval [Table 2].

Table 2:
Intra-group comparison of test parameters at 6- and 12-month intervals

On intergroup comparison of color stability, no statistically significant difference was found at both 6- and 12-month intervals (P = 0.575 and 0.990, respectively), indicating that the color stability of both the restorative materials was similar [Table 1].


On intragroup comparison of retention, in the Omnichroma group, 100% of restorations at 6-month interval and 92% of restorations at 12-month interval displayed the Alpha code which represents fully intact restoration. In the Tetric-N-Ceram group, 92% of restorations at 6-month interval and 80% of restorations at 12-month interval were graded as Alpha. A statistically significant difference was observed in both Omnichroma (P = 0.025) and Tetric-N-Ceram (P = 0.014) groups, indicating that the retention of restorations was better at 6-month interval compared to 12-month interval [Table 2].

On intergroup comparison of retention, no statistically significant difference was found at both 6- and 12-month intervals (P = 0.153 and 0.226, respectively), suggesting that retention of both the restorative materials was comparable [Table 1].


The use of esthetic restoration has become an essential aspect of pediatric dentistry, and color matching is paramount for the success of resin composite restorations. Few studies have investigated the color adjustment potential of Omnichroma, and currently, there is limited evidence of its in vivo performance. Furthermore, there are no studies on its use in primary teeth. Hence, the current clinical trial was conducted to evaluate and compare the clinical performance of Omnichroma with Tetric-N-Ceram in primary teeth.

The broad color-matching ability of Omnichroma eliminates the need for a shade-matching procedure and reduces composite inventory, allowing clinicians to minimize chair time, the wastage of unused composite shades, and reduce reliance on shade-matching procedures.[4] Other potential benefits include less change in the shade over time due to reduced photochemical degradation and less color distortion since their filler particle arrangement corresponds to the wavelengths of the visible light.[101213]

Results of the current study showed that clinically the color matching ability of single shade composite, Omnichroma was comparable to multi-shade composite, Tetric-N-Ceram in primary teeth. The uniformly sized and shaped supra-nano-filled particles might have contributed largely to the shade matching ability of this novel esthetic composite resin. Similarly, Durand et al. and Pereira Sanchez et al. concluded that Omnichroma exhibited a significant and most pronounced color adjustment potential than the frequently used resin composites such as Filtek Supreme Ultra, TPH Spectra, Herculite Ultra, and Tetric EvoCeram.[910]

On the contrary, studies conducted by de Abreu et al. and AlHamdan et al. showed that multi-shade composites presented better color matching ability than the single-shade composite.[1415] This was attributed to the difference in optical behavior of restoration in the anterior or posterior segment of the dental arch. The dark background of the oral cavity might influence the translucency of anterior restorations, resulting in greyish restorations. The use of the blocker agent provided by the manufacturer of Omnichroma in class III restorations and restorations lacking lingual wall that compensates for the dark background of the oral cavity could be one viable answer for this problem.[16]

Color stability is the ability of materials to retain their original color. Degradation of the color of composite resins can be related to intrinsic or extrinsic factors. Internally induced discolorations are permanent and are caused by various factors, including filler type and quantity, polymer quality, insufficient polymerization as well as the photoinitiator system. Under the influence of light or heat, other components of the photoinitiator cascade, such as tertiary aromatic or aliphatic amines, tend to turn yellow or brown.[17]

In the current study, the color stability of Omnichroma was equivalent to Tetric-N-Ceram at both 6- and 12-month time intervals. Both the groups did better at 6-month time intervals. than at 12-month time interval, demonstrating that the color of the restorations deteriorated over time, though the change was clinically acceptable. This might be due to the similar amount of filler content in both materials. Omnichroma comprises uniformly shaped supra-nano spherical filler particles, which would eventually give a smoother finish to the restoration, lesser spaces between the resin-filler interface, reduces bacterial adhesion and microleakage, thereby reducing surface stains over time.

These results are in accord with an in vitro study by AlHamdan et al., who concluded that Omnichroma exhibited comparable color stability with that of a conventional composite, Filtek[15] and a study by Sensi et al., who demonstrated that Omnichroma showed the least discoloration when subjected to artificial aging.[18] Contradictory results were demonstrated by Bajabaa et al., where Omnichroma showed the highest microleakage compared to Tetric-N-Ceram. This may be explained by the presence of TEGDMA in the resin matrix of Omnichroma, which has a low-molecular-weight when compared to Bis-GMA and UDMA in Tetric-N-Ceram which considerably reduces polymerization shrinkage and microleakage.[19] Microleakage would lead to water sorption, stain penetration, and eventually discoloration.[19]

The longevity of restorations is probably the most critical factor for measuring the success of restorative therapy. Many variables affect the retention of resin composite restorations, including patient, operator, material, and tooth-related factors.[20] In the current study, Omnichroma and Tetric-N-Ceram performed similarly in terms of retention at both 6- and 12-month time intervals. However, the clinical performance of both groups was better at 6-month than at 12-month time intervals. The comparable results may be explained by the similar amount of filler content that reduces polymerization shrinkage, use of the same clinical technique, bonding agent, isolation protocol, and exposure to the same oral environment.

Clinically, Omnichroma performed similarly to Tetric-N-Ceram with excellent color match, good color stability and retention over 12 months, proving the null hypothesis. Hence, this novel single-shade resin composite can be employed as an alternative to multi-shade nanohybrid composite in pediatric patients where chair side time and child behavior are essential concerns.


One shade universal composite resin, Omnichroma performed similarly to multi-shade nanohybrid composite, Tetric-N-Ceram in terms of the color match at baseline. The color stability and retention of Omnichroma were comparable to Tetric-N-Ceram at both 6- and 12-month intervals. In both Omnichroma and Tetric-N-Ceram, color stability and retention were reduced over time.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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Crowns; deciduous teeth; early childhood caries; esthetics; resin composite; retention

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