Evaluation of shade matching of monochromatic versus polychromatic layering techniques in restoration of fractured incisal angle of maxillary incisors: A randomized controlled trial

Basma Badry Hashem; Mohammed Adel Khairy; Omar Osama Shaalan

doi:10.4103/jioh.jioh_176_22

ORIGINAL RESEARCH

Year : 2023 | Volume : 15 | Issue : 1 | Page : 43-51

Evaluation of shade matching of monochromatic versus polychromatic layering techniques in restoration of fractured incisal angle of maxillary incisors: A randomized controlled trial

Basma Badry Hashem, Mohammed Adel Khairy, Omar Osama Shaalan
Department of Conservative Dentistry, Faculty of Dentistry, Cairo University, Cairo, Egypt

Date of Submission	07-Aug-2022
Date of Decision	19-Oct-2022
Date of Acceptance	06-Nov-2022
Date of Web Publication	28-Feb-2023

Correspondence Address:
Dr. Omar Osama Shaalan
Department of Conservative Dentistry, Faculty of Dentistry, Cairo University, 35 Mohamad Farid Street El Hay El Motamayz, Sixth of October City, Giza
Egypt

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_176_22

Abstract

Aim: To evaluate shade matching potential of monochromatic layering technique (Filtek Universal) compared to polychromatic layering technique (Filtek Z350XT) in restoration of fractured incisal angle. Materials and Methods: A total of 26 patients received 26 class IV restorations divided randomly between groups (n = 13) using either; monochromatic layering technique (Filtek Universal) or polychromatic layering technique (Filtek Z350XT) in a parallel study design with superiority framework. After preparation, class IV resin composite restorations were performed according to manufacturers’ instructions. Shade matching of class IV restorations was evaluated by two blinded and calibrated assessors using the modified USPHS criteria and digital photography at baseline and after three-days. Association between the layering technique for restoration of fractured incisal angle and shade matching potential was done using the chi square test; statistical significance was set at P ≤ 0.05. Results: Inter-group comparison between layering techniques for shade matching using the modified USPHS criteria have shown statistically significant difference at baseline (P = 0.0001), while there was no statistically significant difference after 3 days (P = 0.2864). Intra-group comparison between follow-up periods within monochromatic layering technique have revealed statistically significant difference (P = 0.0001), while within polychromatic layering technique there was no statistically significant difference (P = 0.2864). Inter-group comparison between both layering techniques using digital photography have shown no statistically significant difference at baseline (P = 0.3592), while after 3 days there was statistically significant difference (P = 0.0071). Intra-group comparison between follow-up periods within monochromatic layering technique have shown statistically significant difference (P = 0.0002), while within polychromatic layering techniquethere was no statistically significant difference (P = 0.3592). Conclusions:Monochromatic resin composite restorations showed satisfactory shade matching potential when compared to polychromatic resin composite restorations.

Keywords: Class IV, Color, Composite, Monochromatic, Polychromatic, Shade, USPHS

How to cite this article:
Hashem BB, Khairy MA, Shaalan OO. Evaluation of shade matching of monochromatic versus polychromatic layering techniques in restoration of fractured incisal angle of maxillary incisors: A randomized controlled trial. J Int Oral Health 2023;15:43-51

How to cite this URL:
Hashem BB, Khairy MA, Shaalan OO. Evaluation of shade matching of monochromatic versus polychromatic layering techniques in restoration of fractured incisal angle of maxillary incisors: A randomized controlled trial. J Int Oral Health [serial online] 2023 [cited 2023 Apr 1];15:43-51. Available from: https://www.jioh.org/text.asp?2023/15/1/43/370748

Introduction

Composite resins have earned appeal as restorative materials since their inception, owing to their attractive characteristics and conservation of tooth structure. Over the past decades, resin composite technology had advanced rapidly. Composite resin is currently the most popular restorative material for both anterior and posterior teeth. Restoring anterior teeth with direct composite restoration has been practiced for more than 40 years by dentists worldwide. Despite direct procedures are consistently more conservative for the valuable tooth structure than indirect methods, restorative methods by the means of direct composite can be a challenge due to technique sensitivity.^[1]

Restoration of fractured anterior teeth is clinically complicated, as it must meet several criteria, including shape, function, phonetics, esthetics, as well as imitating the remaining tooth structure and neighboring teeth. In class IV cavities each third of the tooth has its own chromatic appearance due to the various thicknesses of enamel and dentine in its composition. Furthermore, natural teeth are not monochromatic and possess other characteristics such as translucency, opalescence, and fluorescence that must be mimicked by resin composite materials in the restorative procedures to obtain satisfactory esthetic results. Small filler particles are often used in anterior composites to enhance smoothness and polishabilty. Nanotechnology has permitted significant advancements in resin composite restorations, as a consequence, a new type of composite resins known as nano-composites has emerged with enhanced mechanical characteristics and polishability due to increased filler loading.^[2]

Polychromatic layering technique was considered the gold standard for restoration of anterior teeth through mimicking the natural appearance and optical characteristics.^[3]However, polychromatic layering technique is considered technique sensitive; it is significantly more complicated than a basic dual or monoshade approach, needing sophisticated technical potentials and prolonged clinical sessions.^[4]Monochromatic layering technique with just body shade has been introduced to replace enamel and dentin, it is less technique-dependent than polychromatic layering and has an opacity that is halfway between enamel and dentin.^[5]Filtek Universal is a newly introduced resin composite utilizing the monochromatic body shade technology, available in a universal opacity and shows a beneficial chameleon effect. In daily clinical practice, general dentists are concerned that composite resin market is becoming excessively complicated, and they are more inclined to do monochromatic resin composite restorations for most of their cases, which allows them to achieve top-line aesthetics in a more straightforward manner within a sensible chair time, instead of being laden with sophisticated systems with various tints, opacities, and characterizers.^[6]

To our knowledge, there is deficiency in the current evidence regarding clinical performance of Filtek Universal in restoration of fractured incisal angle. Therefore, it was found beneficial to assess shade matching potential of monochromatic layering technique (Filtek Universal) compared to polychromatic layering technique (Filtek Z350XT) in restoration of fractured incisal angle. The null hypothesis tested, that there was no difference in shade matching between monochromatic technique compared to polychromatic technique in the restoration of fractured incisal angle.

Materials and Methods

Trial registration, study design and grouping

The present randomized clinical trial was performed in the Faculty of Dentistry at Cairo University, Egypt. Protocol of the current study was pre-registered in ClinicalTrials.gov database (NCT04355208). All the procedures completed in the present study were in agreement with the standards of the Research Ethics Committee (REC) of Faculty of Dentistry at Cairo University (Ref. 16-6-20). The design of the current study was double blinded, parallel, two-armed study with superiority framework and 1:1 allocation ratio.

Sample size calculation

According to Demirci et al. (2018),^[2] the probability of alpha score for shade matching of polychromatic resin composite restorations was (0.929), probability of bravo score was (0.071) with effect size w=0.858. If the estimated probability of alpha score for shade matching of monochromatic resin composite restorations was (0.95), probability of bravo score was (0.05) with effect size w=0.9. After setting statistical significance at 0.05 and power at 80%, the total sample size was (21). Sample size was increased by (20%) to compensatefor possible dropouts to be a total of (26) cases i.e. (13) for each group.

Eligibility criteria

Patients with fractured incisal angle in vital maxillary permanent incisors, age range between 13 to 30 years and good oral hygiene were included. Patients with non-vital, endodontically treated teeth, active periodontal disease, sever medical complications, malocclusion or parafunctional habits were excluded.

Recruitment

Screening of patients from clinic of Conservative Dentistry, Faculty of dentistry at Cairo University seeking dental care continued until the target population was achieved 1 months prior to intervention according to the eligibility criteria. Out of 32 patients examined, 26 patients fulfilled the eligibility criteria and informed consent was signed by the eligible participants before enrolment in the present trial. [Figure 1] shows the CONSORT flow diagram of participants in the current research.

Figure 1: CONSORT flow diagram

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Randomization, sequence generation and blinding

Simple randomization was done by generating numbers from 1:26 into 2 columns (www.randomization.com) representing the intervention or comparator groups. Principal investigator chose between the generated random numbers for treatment allocation from opaque sealed envelopes, the patients and outcome assessors were blinded to the material assignment, while the investigator was not blinded due to the difference in the protocol of application of the restorative materials, which prohibited blinding of the operator.

Interventions

Class IV cavities were restored using either Filtek Universal (3M™ ESPE, St. Paul, Minnesota, USA) using monochromatic layering technique or Filtek Z350XT (3M™ ESPE, St. Paul, Minnesota, USA) using polychromatic layering technique. Filtek Universal is a nanofilled resin composite with universal opacity and utilizing chameleon effect. Both resin composites were used conjunction with Scotchbond™ Universal Etchant and Single Bond Universal adhesive (3M™ ESPE, St. Paul, Minnesota, USA) in selective enamel etching mode.

Clinical procedures

Cavity preparation procedures

Before cavity preparation, pre-wedging was done for interdental separation and to depress the papilla apically to achieve better rubber dam inversion, this was followed by multiple isolation using rubber dam (Sanctuary Dental Dam, Perak, Malaysia). Beveling of cavo-surface margin was done using a red coded diamond bur (Mani, Tochigi, Japan) in a 75° direction, followed by using a coarse Soflex disc (3M ESPE, San Paul, MN, USA).

Bonding procedures

Selective enamel etching was done using Scotchbond Universal Etchant (3M ESPE, St. Paul, MN, USA) by applying the gel for 15–20 seconds on enamel only, followed by rinsing for 20 seconds. Drying of etched enamel surface was done using oil free air from triple way syringe of the dental unit, dry etched enamel should appear matte and chalky white. Bonding agent was applied by placing one coat of Single Bond Universal (3M ESPE, St. Paul, MN, USA), followed by agitation for 20 seconds. Air thinning was done afterwards to remove excess adhesive and allow homogenous distribution. Finally, light curing was done for 20 seconds using LED light curing unit (Elipar S10, 3M ESPE, St. Paul, MN, USA).

Composite application

Both resin composites were applied according to manufacturers’ instructions. For monochromatic layering technique, the palatal shell was built using Filtek Universal (3M ESPE, St. Paul, MN, USA) against a celluloid strip (TOR VM, Moscow, Russia) till the incisal edge followed by light curing for 20 seconds, then afterwards celluloid strip was removed and replaced with transparent sectional contoured matrix (TOR VM, Moscow, Russia) to build the proximal wall. Remaining cavity was restored to the desired shape and contour, while using a modeling resin (GC Corporation, Bunkyo-ku, Tokyo, Japan) to facilitate composite placement and contouring, followed by light curing for 20 seconds for each increment.

For polychromatic layering technique, a celluloid transparent strip (TOR VM, Moscow, Russia) was used to build the palatal shell using enamel shade with a thickness of 0.5 mm to give space for the subsequent layers of dentin and enamel shades, followed by curing for 20 seconds, then afterwards celluloid strip was removed and replaced with transparent sectional contoured matrix (TOR VM, Moscow, Russia) to build the proximal wall using enamel shade with a thickness of 0.5 mm as well. This was followed by placement of dentin shade to fill most of the prepared cavity and covering the bevel, misura instrument (LM-Dental, Parainen, Finland) was used to remove the excess material of dentin shade and leave about 0.5 mm for subsequent enamel shade. A final layer of enamel shade was used to restore the remaining cavity to the desired shape and contour, a modeling resin (GC Corporation, Bunkyo-ku, Tokyo, Japan) was used to facilitate composite placement and contouring, followed by light curing for 20 seconds.

Finishing and polishing procedures

Gross finishing was done using yellow coded diamond finishing stones (Mani, Tochigi, Japan). Primary anatomy was corrected by using both Soflex discs (3M ESPE, St. Paul, MN, USA) and Perio-bur #831 (Komet Dental, Lemgo, Germany), starting by adjusting incisal edge length and thickness using Soflex discs followed by drawing line angles on both central incisors using a pencil in order to determine the proper width of restoration in relation to the contralateral tooth, then line angles were contoured using Soflex discs and Perio-bur #831.

Secondary and tertiary anatomies were reproduced according to their presence in the contralateral tooth. They were detected by using an articulating paper and pushing it in a cervico-incisal direction on the air-dried remaining tooth structure, the restoration, and the contralateral tooth, then the detected surface topography was reproduced by the by the means of Perio-bur #831 (Komet Dental, Lemgo, Germany).

Occlusion was checked for any premature contacts or interferences using articulating paper (Bausch, Nashua, New Hampshire, USA). Polishing was done using rubber cup, flame and wheel polishing tip (Kenda, Vaduz, Liechtenstein). [Figure 2] shows the clinical procedures for Class IV restoration using Filtek Universal.

Figure 2: Clinical procedures for Class IV restorations using Filtek Universal: (A) preoperative, (B) rubber dam isolation, (C) beveling of cavity margins, (D) acid etching, (E) application of bonding agent, (F) composite placement, (G) immediate postoperative, and (H) 3 days’ postoperative

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Outcome assessment

Dental restorations were evaluated at baseline and after 3 days for shade matching using modified USPHS criteria and digital photography. Outcome assessment was performed by two calibrated assessors for each case under standardized lightening conditions and chair position, in case of conflict, they discussed to reach for a consensus [Table 1].

Table 1: Outcome assessment

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Statistical analysis

Data was analysed using Medcalc software, version 19 for windows (MedCalc Software Ltd, Ostend, Belgium). Categorical data was described as frequency and percentage, comparisons between categorical variables was performed using the chi square test. A P value less than or equal to 0.05 was considered statistically significant and all tests were two tailed.

Results

Demographic data

The currenttrial was performed on 26 patients that were randomly assigned to the intervention and the comparator arms (n = 13). After 3 days all participants were assessed with 100% retention rate. There were 10 males (38.5%) and 16 females (61.5%) in the current study, there was no statistically significant difference regarding gender distribution among groups (P = 0.1138). Mean age in the current study was 17.3 ± 2.8, there was no statistically significant difference regarding age between groups (P = 0.147).

Shade matching (modified USPHS criteria)

Inter-group comparison between layering techniques using modified USPHS criteria have shown statistically significant difference at baseline (P = 0.0001), while there was no statistically significant difference after 3 days (P = 0.2864). Intra-group comparison between follow-up periods within monochromatic layering technique have revealed statistically significant difference (P = 0.0001), while within polychromatic layering technique there was no statistically significant difference (P = 0.2864) [Table 2].

Table 2: Frequency and percentage for shade matching scores using USPHS criteria for the intergroup comparison between materials within each follow-up and intragroup comparison within each material between different follow-up periods

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Shade matching (digital photography)

Inter-group comparison between both layering techniques using digital photography have shown no statistically significant difference at baseline (P = 0.3592), while after 3 days there was statistically significant difference (P = 0.0071). Intra-group comparison between follow-up periods within monochromatic layering technique have shown statistically significant difference (P = 0.0002), while within polychromatic layering technique there was no statistically significant difference (P = 0.3592) [Table 3].

Table 3: Frequency and percentage for shade matching scores using digital photography for the intergroup comparison between materials within each follow-up and intragroup comparison within each material between different follow-up periods

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Discussion

The shade matching potential of monochromatic layering technique compared to polychromatic layering technique in restoration of fractured incisal angle was evaluated in the current study. In restorative dentistry, randomized clinical trials (RCTs) are used to evaluate a new or modified dental material or restorative technique and recommend its validity for its specific indication of intraoral use, such as restoring function, improving/maintaining aesthetics, and not causing any harm to adjacent biological tissues, as well as to determine whether the proposed material/technique can be applied by the majority of dental healthcare professionals who will perform a similar procedure.^[7]

Reproduction of natural color and appearance of esthetic anterior resin composite restoration is a significant determinant for success. Many strategies for placing composite restorations have been presented, including mono-shade technique, dual-shade technique, and multi-shade approach, because of the availability of new composite materials that have increased the possibilities of aesthetic restorations. Even though layering approach has shown to provide appropriate shade matching results. However, it is more complicated than a standard dual or single shade technique, requiring superior technical abilities and more chair time. In addition, clinicians favor resin composite procedures and restorative techniques to be simple in order to reduce technique sensitivity.^[8]

The incisal third’s unique characteristics influence whether a single shade could be used with one opacity or a blend of tones with two or more opacities is required. Some patients will have minimal to no intrinsic effects based on these criteria, suggesting that a monochromatic approach will suffice. Other patients, on the other hand, will have a combination of translucency, white spots, and a halo effect, necessitating additional clinical attention.^[9]

In the current study, a bevel on the facial side was made by means of a fine, tapered diamond stone at a 75° angle, followed by a course Soflex disc to create an infinite bevel by finishing the outer margin of the bevel, this was done to mask the fracture line and avoid any line of demarcation to appear after completion of the final restoration. In dentistry, bevels were originally utilized to improve the retention of resin composite on acid etched enamel prisms. Though retention is an important aspect of the bevel, the visual transition from restoration to natural tooth is as important. Bevels not only reveals the enamel rods ends for acid etching, allowing for enhanced adhesive bonding, but they as well assist the resin-based composite blend in better with the native tooth structure by establishing a transition area, enabling the fracture line to be hidden.^[9]

In the current research, the operating field was isolated using rubber dam. The use of a rubber dam is regarded as the best technique of moisture control for a reliable adhesive restorative procedure. Retraction cords, wedges anddental floss ligatures may be utilized after isolation with rubber dam to improve the seal and stop the dam from partly covering neighboring teeth that are being used to guide restorative form.^[10]

In the current study universal adhesive system was preceded by selective enamel etching to enhance bond strength.^[11],[12] A wedged celluloid matrix strip was applied to avoid contamination of the adjacent teeth with adhesive system. For reproduction of optimum proximal contact, pre-contoured transparent sectional matrix was used in the current research to enhance curvature, anatomic shape, and contacts.^[13]

For standardization of thickness of resin composite increments during application of polychromatic composite restoration, Misura tool (LM Arte, Finland) was used. Until recently, clinically calibrating a uniform 0.5 mm thickness in an intraoral restoration required extraordinary abilities from the operator. Misura was designed for this purpose, this tool features a conical end with a thinner tip that will be held against the sound enamel, and a thicker conical section that will press the uncured dentin shade composite to the proper thickness allowing for a room to place enamel shade.^[14]

Polychromatic resin composite system was selected as a comparator in the current study being regarded as the gold standard technique for restoration of fractured incisal angle. Enamel and dentin possess different translucency and opacity due to their composition and thickness. Finding the optimal translucency and opacity of the material, which is crucial to reach the optical behavior of enamel and dentin, is a significant issue for manufacturers when producing resin composite. Filler content and distribution has previously been observed to be directly connected to translucency and opacity.^[8] Because enamel and dentin have distinct structural features, they interact with light waves in different ways. Because of its extremely mineralized prismatic structure, low organic content, and small amount of water, enamel transmits more light than dentin; dentin has less mineral content, an organic tubular structure, greater water content, and is less transparent. Moreover, resin composites’ translucency is inversely related to their thickness. Translucency and value were shown to have a significant relationship, with deeper shades having less translucency.^[4],[8]

Surface texture of the teeth has an impact on their appearance. The texture of an object’s surface is divided into macro- and micro-textures. The macro-textures on the enamel’s surface such as emerging grooves represent topographical variations, macro-textures generate large patches of light reflection. The micro-textures are generated by ameloblasts depositing hydroxyapatite crystals on the enamel surface throughout tooth germ development, resulting in small parallel grooves. A vivid parallel groove surface lowers the translucency of the tooth surface, causing diffuse reflection zones to appear.^[9],[10]

The finishing procedures in the current research was started using discs in descending sequence from coarse to fine, this was followed by finishing diamond stones and perio bur, following the outlines and surface characterizations of the contralateral tooth reproducing primary, secondary and tertiary anatomy. Even though the surface created using a transparent matrix is completely smooth, it is dense with organic resin. As a result, finishing and polishing processes that remove the outermost layer of resin tend to produce a tougher, more wear-resistant, and hence more aesthetically stable surface.^[9],[10] Regarding polishing, a polishing system was used in the present study in order to reproduce a highly polished lustrous surface, according to Jaramillo-Cartagena et al..^[15] Finishing and polishing procedures of resin composite restorations are crucial steps in improving the appearance, color stability and longevity of anterior restorations.

In the current study, shade matching was assessed using modified USPHS criteria. Cvar and Ryge published modified USPHS criteria for clinical assessment of restorative materials’ regarding color stability and shade matching in 1971, and it is a well-established technique in clinical research. Visual comparisons of a restoration and neighboring tooth structure are utilized to give ratings (Alfa, Bravo, and Charlie) depending on whether the restoration and adjacent tooth structure match perfectly and, if not, if the discrepancy is beyond the normal range of tooth color, shade, or translucency.^[16]

In the current study restorations were evaluated under standardized lightening conditions and chair position. Different light sources may alter color perception, light has a chief role in shade matching and restoration outcomes. Color is frequently regarded as a critical component of a restoration’s aesthetic success. However, minor faults in that parameter, may go unnoticed if other requirements such as shape, surface texture, and opacity, are all fulfilled. Value is the most important factor in the three-color components, afterwards come chroma and hue.^[17],[18]

Visual assessments using digital photography was performed in this study using a scale from 1 to 5, where score “1” represented total mismatch while score “5” represented exact match.^[19] Visual assessment using digital photography has demonstrated efficiency for evaluating color in a more practical way by previous studies.^{[4],[8],[20],[21]} In this study camera settings used was adjusted to ISO125, shutter speed 1/125 and aperture F 25. For capturing high-resolution digital photographs for color research, DSLR cameras and cross-polarizing filters have proven to be viable tools. Clinicians will benefit from the simplicity of use and flexibility to alter the white balance of cross-polarized digital pictures, helping to eliminate misleading color casts.^[8]Cross-polarized photography, which combines polarizing filters with digital photography permits for a more thorough examination of the depth, features, characteristics, transparencies of dental structures and the underlying dentin’s characteristics.^[22]

In the current clinical trial, there was no clinically or statistically significant difference in the shade matching between monochromatic and polychromatic layering techniques after 3 days, but there was statistically significant difference at baseline. After 3 days, assessment of shade matching using modified USPHS criteria showed no statistically significant difference between both techniques, while evaluation of shade matching using the digital camera showed statistically significant difference. This could be attributed to the sensitivity of the visual scoring system^[18] used in the current study. Moreover, the differences in the current study between both measuring techniques could be accredited to the higher sensitivity of the digital camera that pointed out differences that could not be seen with the naked eye during using modified USPHS Criteria.^[21],[22]

It has been discovered that the degree of hydration of dental tissue has a significant impact on enamel translucency. In the present study there was statistically significant difference in shade matching with the remaining tooth structure at baseline between monochromatic and polychromatic layering techniques, this could be attributed to the dehydration phenomenon produced by rubber dam isolation, which may have altered the chameleon effect of monochromatic composite, however due to the rehydration after 3 days, monochromatic composite matched exactly the shade with the remaining tooth structure and there was no difference between both materials either statistically or clinically.^[23]

The current study was consistent with Magne et al.,^[17] they found that a single shade system utilizing body shade performed better than multiple shade systems in terms of optical integration. When employing more complex techniques, single shading is preferable over dual shading, which requires more time. Universal composites with improved color matching might make anterior restorations easier to perform and reduce clinical errors.^[8] Color perception was influenced by the thickness of their layers, which indicated that the esthetic outcome of a multi-layer composite restoration is significantly affected by layer thickness and the proportion of dentin and translucent shade thicknesses.^[24]

Monochromatic resin composite systems with only body shade have been utilized to replace enamel and dentin and have an opacity that is midway between enamel and dentin due to their filler content.^[5] Filtek Universal have non agglomerated and non-aggregated 20 nm silica fillers with 76.5% filler loading by weight, where these particles may attribute to the opacity which explained the acceptable shade matching potential. In addition to the presence of nanoclusters that could be accountable for the translucency and light transmission.^[25]

Habib et al.^[26] found that the resulting translucency of resin composite restoration was influenced by the filler chemical composition, filler loading and size. The particle size had an inverse effect on the translucency, with smaller particles producing substantially larger transparency, this could be due to smaller particles have less light scattering, reflection and are smaller than the wavelength of the light.

Prior research indicated that composites with high filler loading and small filler particle size had higher translucency values than those with lower loading and larger filler particle size, and that the higher the translucency, the greater the blending effect.^[8] This was in agreement with Sulaiman et al.,^[27] they found that filler particle type is a factor that could affect the light transmission, where nanofilled composite (Filtek Universal) was considered the most color stable with the smallest alteration in their translucency after aging which was attributed to the high weight percentage of filler and small filler particle size.

Despite there was statistically significant difference between monochromatic layering technique and polychromatic layering technique when evaluated using the digital photography-based scoring system, yet both techniques exhibited nearly similar esthetic performance with close or exact match to the tooth structure. This could be attributed to the similarity between Filtek Universal and Filtek Z350XT in their composition. Filtek Universal have a filler loading of 76.5% which is nearly equal to Filtek Z350XT with a filler loading ranging from (72.5% to 78.5%) depending on the shade translucency.^[28] This was in agreement with Korkut and Özcan,^[28] where they found no difference between monochromatic and polychromatic layering techniques for restoring fractured anterior teeth and they attributed this to the similarity in the composition and filler loading of both resin composite materials.

The outcomes of the current randomized clinical trial showed similar shade matching potential of monochromatic and polychromatic layering techniques after 3 days. Consequently, the null hypothesis cannot be rejected. The limitations of the present clinical trial were relatively small sample size and short-term baseline assessment. A larger sample size is recommended to provide more accurate results, detect any differences between both layering techniques and enhance generalizability to the population. Moreover, the short-term follow up period of only 3 days might be insufficient to assess the color stability. To our knowledge the present study was one of the pioneer trials evaluating the shade matching potential of monochromatic layering technique using the new universal nanofilled resin composite (Filtek Universal) in comparison to polychromatic layering technique using (Filtek Z350XT) in restoring fractured incisal angle. Yet, more clinical trials are recommended to confirm the current findings.

Conclusions

Monochromatic resin composite restorations showed satisfactory shade matching potential when compared to polychromatic resin composite restorations for restoration of fractured incisal angles

Monochromatic layering technique provided a more simplified approach in restoring fractured incisal edges with less time-consuming procedures.

Clinical recommendations

Monochromatic layering technique has been introduced to replace enamel and dentin in class IV restorations; it is less technique-dependent than polychromatic layering and has an opacity that is halfway between enamel and dentin.

Universal monochromatic composite can be recommended in cases with less incisal edge details such as incisal translucency, incisal halo and dentin map.

Monochromatic layering using universal restorative shades may be recommended to undergraduate dental students due to less technique sensitivity and easier shade selection.

Polychromatic layering technique using enamel and dentin shades is still the gold standard technique for cases of increased incisal edge details.

Acknowledgments

Not applicable.

Financial support and sponsorship

Self-funded.

Conflict of interest

The author declared no conflict of interest.

Authors’ contribution

BBK: Idea, definition of intellectual content, study design, review of literature, principal investigator, data collection, and manuscript preparation. MK: Idea, definition of intellectual content, study design, guarantor and manuscript editing and review. OS: Idea, definition of intellectual content, study design, auditing, data collection, statistical analysis and manuscript preparation, editing, and review.

Ethical policy and institutional review board statement

The protocol of the present trial was pre-registered ClinicalTrials.gov (NCT04355208). All procedures were in agreement with the standards of the Research Ethics Committee (REC) of the Faculty of Dentistry at Cairo University (Ref. 16-6-20).

Patient declaration of consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Data availability statement

Raw data are available from the corresponding author upon reasonable request.

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