Comparative evaluation of the surface roughness of a microhybrid and nanohybrid composites using various polishing system: A profilometric analysis

Kevin Lin Kovoor; Shruthi H Attavar

doi:10.4103/jioh.jioh_130_23

ORIGINAL RESEARCH

Year : 2023 | Volume : 15 | Issue : 4 | Page : 372-376

Comparative evaluation of the surface roughness of a microhybrid and nanohybrid composites using various polishing system: A profilometric analysis

Kevin Lin Kovoor, Shruthi H Attavar
Department of Conservative and Endodontics, A B Shetty Memorial Institute of Dental Sciences, Nitte (Deemed to be university), Mangalore, Karnataka, India

Date of Submission	01-Jun-2203
Date of Decision	12-Jul-2023
Date of Acceptance	17-Jul-2023
Date of Web Publication	31-Aug-2023

Correspondence Address:
Dr. Shruthi H Attavar
Department of Conservative and Endodontics, A B Shetty Memorial Institute of Dental Sciences, Nitte (Deemed to be university), Deralakatte, Mangalore 575018, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jioh.jioh_130_23

Abstract

Aim: To assess the effectiveness of various polishing systems on nanohybrid and microhybrid composite restorative materials. Materials and Methods: The present study was an experimental in vitro analysis. A total of 64 cylindrical specimens were divided based on random sampling method into two groups: Group I (n = 32): micro hybrid composite Te-ecoconom Plus (IvoclarVivadent) and Group II (n = 32): nanohybrid composite Beautifil II (Shofu Inc.). The two groups were further subdivided on the basis of polishing system used into four subgroups. The control subgroup (n = 8) did not receive any finishing or polishing. Subgroup A (n = 8)—Sof-Lex XT (3M ESPE). Subgroup B (n = 8)—OneGloss (Shofu Inc.). Subgroup C (n = 8)—Super-Snap X-TREME Technique Kit (Shofu Inc.). A surface profilometer was used to evaluate the surface roughness following the finishing and polishing processes. The measured value was analyzed using independent sample t test. The findings were computed using SPSS Software version 20. Results: On comparing the composites and polishing systems using independent sample t test, it was found that Beautifil II group using Super-Snap X-TREME polishing system showed a significant difference when compared to the Beautifil II group using OneGloss system and the Te-econom Plus group using the Super-Snap X-TREME system generating P value of 0.009 and 0.004, respectively, which is <0.05 hence considered to be statistically significant. Conclusion: Within the limitations of this study, the nanohybrid composite resin showed a better polishability as compared with the micro hybrid composite. The three polishing system used significantly influenced the surface roughness with Super-Snap X-TREME, Sof-Lex multistep polishing system producing a smoother surface compared to OneGloss one step polishing system.

Keywords: Dental restoration, finishing and polishing systems, photopolymerization, resin composites

How to cite this article:
Kovoor KL, Attavar SH. Comparative evaluation of the surface roughness of a microhybrid and nanohybrid composites using various polishing system: A profilometric analysis. J Int Oral Health 2023;15:372-6

How to cite this URL:
Kovoor KL, Attavar SH. Comparative evaluation of the surface roughness of a microhybrid and nanohybrid composites using various polishing system: A profilometric analysis. J Int Oral Health [serial online] 2023 [cited 2023 Sep 25];15:372-6. Available from: https://www.jioh.org/text.asp?2023/15/4/372/384655

Introduction

Effective finishing and polishing are one of the most important aspects of dental restorations since it increases their durability and aesthetic value.^[1] Plaque buildup, gingival inflammation, periodontal issues, demineralization of enamel, discoloration, cavities, and poor aesthetics can all be caused by improper surface finishing of restorations. Surface changes as small as 0.3 mm can be quickly recognized from the tongue tip. Consequently, the smooth surface quality of a dental repair is crucial. It can be accomplished by polishing and completing repairs. While polishing eliminates particles less than 25 μm, using the finishing procedure, additional material with particles larger than 25 μm may be eliminated.^[2]

The primary goal of composite restorations has always been to create a smooth surface, not just for aesthetic reasons but also for oral health. Several variables, including filler particle size, filler loading and resin amount, filler type, and particle shape, affect the surface quality of composite resin. When smaller particles are utilized, as in microfilled composites, polishability is stated to rise, but their mechanical qualities are said to be inferior to those of nanohybrid and nanofilled composites.^[3],[4] Surface roughness above 0.2 µm can lead to plaque retention on the surface of the composite, increasing the likelihood of periodontal disease and cavities. Surface roughness affects the restoration’s natural shine and stain-resistance.^[5],[6] For composite restorations, using a Mylar strip produces the smoothest surface while curing. The restoration is then coarsely contoured before completing. Polishing is done to smooth out the restoration material’s surface and eliminate the scratches made during finishing. The type of product used largely determines how polishing processes affect composites. Therefore, the purpose of this study is to assess the effectiveness of various polishing processes on nanohybrid and microhybrid composite restorative materials.^[7]

The different manufacturers state the beneficial polishability of composite materials with their systems, but the efficiency of the polishing systems depends on a number of factors, including the material composition, the hardness of composite and hardness concerning abrading molecule, the rate at which the abrasive polishing system is applied to the composite, and the use of lubricants during the polishing process. The effectiveness toward one step over multiple step polishing procedures on the surface polishability of the two recently introduced composite resins is the main focus of the current investigation. This in vitro study was performed to evaluate the polishability of various composites and compare the surface roughness of composites produced using various polishing techniques.^[8]

Materials and Methods

Study setting and sampling criteria

The current research study was carried out in the school of conservative dentistry and endodontics ABSM dental sciences. The current study was an experimental in vitro investigation that was created using the modified Consolidated Standards of Reporting Trials (CONSORT).

The current study primarily emphasizes two elements.

1) Type of composite: Nanohybrid composites, Microhybrid composite.

2) Polishing system: Sof-Lex XT, OneGloss, and Super-Snap X-TREME.

The analysis of the surface roughness was done using random sampling method. The two composite resins were divided based on the various polishing systems used in the present in vitro experimental research.

Sample size calculation

In the present study, nMaster software (STATA, EpiInfo, nQuery, etc.) version 2.0 was used for determining the sample size, with 80% power and alpha error of 0.05 that the sample size of 64 would be required for the study.

Outcome

Primary outcome

The surface of the composite resin pellets was subjected to profilometric analysis to analyze the surface roughness and the result of the polishing systems regarding the surface topography of the polymeric material.

Secondary outcome

The surface of the composite resins with a good surface polish will reduce the plaque accumulation and therefore decrease the secondary caries formation.

Specimen preparation

A total of 64 disk-shaped specimens of microhybrid composite Te-econom Plus (IvoclarVivadent, Zurich, Switzerland) and nanohybrid composite Beautifil II (Shofu Inc., Kyoto, Japan) were prepared [Table 1].

Table 1: Composition of the restorative material used in the study

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A total of 32 specimens from every material combination were produced and bound in Mylar strips in the cylindrical grooves of a special mold which was 6 mm in width and 2 mm deep. The material was coated with an additional transparent Mylar strip on over the entire full mold when the loading of the mold was finished. To remove excess material from the mold to produce an even surface, a slide of glass was gently pushed on the highest point of the transparent Mylar strip. Following curing, every specimen was polymerized utilizing a 1-mm thickness glass plate with activated light measured at around 600 mW/cm². An intensitometer was used to determine the intensity. Each of the samples was light cured for 20 s from both surfaces (top and bottom). All specimens were removed from the mold, and the polymerization process was allowed to finish for incubator at 37°C for 24 h and 100% relative humidity.^[9]

Composition regarding the restorative material utilized in the research [Table 1].

Grouping and randomization

Group I (n = 32)—Microhybrid composite Te-econom Plus (IvoclarVivadent).

Group II (n = 32)—Nanohybrid composite Beautifil II (Shofu Inc.).

Each group is further divided into four subgroups. Control subgroup (n = 8)—composites did not receive any finishing or polishing.

Subgroup A (n = 8): Sof-Lex XT (3M ESPE, Bayern, Germany)

The Sof-Lex XT Finishing and Polishing Discs (coarse, medium 40 m, fine 24 m, and superfine 8 m) were used to polish the composite surface. The Sof-Lex XT Discs were consecutively utilized in a low-speed handpiece with periodic light pressure and no water cooling. The coarse-grit disc was utilized for 5 s at medium speed (about 10,000 rpm). The disc was then dried using a 3-in-1 air syringe after being cleaned with water. It was then followed by 15 s of medium-grit disc polishing without the use of water at around 10,000 rpm. Now, the fine-grit Sof-Lex XT Disc was used for 15 s at a high speed (about 30,000 rpm). Each disc was given a final polish using the superfine grit Sof-Lex XT Disc at a high speed (about 30,000 rpm) for 15 s after further washing and drying. Presently, the fine-grit Sof-Lex XT Disc was employed for 15 s at a high speed (about 30,000 rpm). Each disc received a final polish using the superfine grit Sof-Lex XT Disc at a high speed (about 30,000 rpm) for 15 s after further washing and drying.

Subgroup B (n = 8): OneGloss (Shofu Inc.)

OneGloss polishing system consists of a one-step finisher and polisher which was used in an electric handpiece with light pressure at 15,000 rpm on the cylindrical shaped composite samples for 20 s without water coolant.

Subgroup C (n = 8): Super-Snap X-Treme Technique Kit (Shofu Inc.)

It is finishing and polishing system, in which first the Course (black) and Medium (violet) polishing discs were used on the composite samples at 10,000 rpm. Followed by the Fine (green) and Super fine (red) polishing discs were used at 20,000 rpm for 20 s.^[10]

Polishing procedure

The specimens had been cleaned with water for 10 s to eliminate any dirt, further they were air dried for 10 s before polishing with a disc with a lower grit. The details of polishing system, that is, single step and multistep polishing systems have been mentioned above. To avoid heat accumulation or the emergence of surface grooves, mild pressure was exerted using a continuous, repeated stroking motion in one direction. A single individual polished the samples, and the polishing speed was standardized by using an electric handpiece. A surface profilometer was used to determine the average surface roughness following finishing and polishing processes.^[11] The data were analyzed and tabulated.

Surface roughness analysis

A physical computerized profilometer was used to measure the surface roughness of all samples (Taylor Hobson Ltd.). The instrument consists essentially of a stylus coupled to a prolonged stretch arm that moves along its surface and detects the stylus’s vertical and horizontal movements. It additionally permits enabling surface roughness evaluation by generating mean surface roughness values, which represent where the mathematical average of how high of the roughness constituent variations off an average line observed during the specimen’s length; the larger this number, the coarser the surface appears.^[12]

Statistical analysis

The quantitative data were shown as mean and standard deviation. The information was assessed in order to verify the normal distribution and ensure variance equality. Independent sample t test was done to analyze the level of significance and P value < 0.05 was considered statistically significant. The findings were computed using SPSS Software version 20 (IBM, Armonk, NY, USA).

Results

Independent sample t test was showing the contrast amongst two distinct polymers and polishing systems [Table 2][Table 3][Table 4]. The statistical analysis was done to denote the significant difference for the surface polishability between the two composites, that is, Group I Te-econom Plus which is the microhybrid composite and Beautifil II; Nanohybrid composite resin. Further the analysis of the surface roughness was done to compare the significant difference among the various subgroups Sof-Lex, OneGloss, and Super-Snap polishing systems.

Table 2: Independent sample t test showing the comparison between Group I and subgroups

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Table 3: Independent sample t test showing the comparison between Group II and subgroups

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Table 4: Independent sample t test showing the comparison between Group I and Group II

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According to [Table 2], the comparison was done between Group I Microhybrid composite with the control and subgroups A, B, and C. The findings revealed a statistically significant difference among control subgroup and group polished with Super-Snap and OneGloss with a P value 0.044 and 0.000, respectively, which is <0.05.

According to [Table 3], the comparison was done between group II nanohybrid composite with the control and subgroups A, B, and C. The results demonstrated a statistically significant value between the Beautifil II composite polished with Super-Snap and OneGloss polishing system with the P value of 0.009, which is <0.05.

According to [Table 4] independent sample t test was done to compute the significant difference among the two groups. Beautifil II nanohybrid composite showed a significant difference when polished with Super-Snap and OneGloss polishing system with P value of 0.001 and 0.004, respectively.

Discussion

The present research compared polishing systems with two different polymeric structures on the level of surface roughness with various filler contents. The results showed that polishing methods at baseline reduced surface roughness. Differing polishing techniques and resin composites, however, had a substantial impact on the surface roughness after polishing, contradicting both null assumptions.^[13],[14]

It has been demonstrated that the particle size, hardness, and quantity of filler have an impact after finishing and polishing on the surface morphology of resin composites. Harder filler particles remain exposed on the surface after polishing because hybrid composites preferentially remove the softer resin matrix. To protect the resin matrix from abrasives, filler particles should be placed as closely as possible together. Particles with a wider distribution and smaller dimensions can be loaded with more filler, which improves the mechanical characteristics of the polymer and reduces shrinkage during polymerization.^[5],[15]

Whereas polishing techniques eliminate minor flaws, finishing techniques remove a significant amount of material. As a smooth surface enhances the restoration’s aesthetics and patient comfort, polishability of composite resins is an essential quality. Previously, it was thought that roughness values more than 0.2 m increased the formation of biofilm and the danger of secondary caries. In nonclinical trials, this surface roughness threshold, however, did not accurately predict the production of biofilms.^[16] Literature has also reported various clinical factors that are impacted by surface roughness. A smooth and well-polished restoration with values approximating 0.25 and 0.50 µm mean surface roughness can be connected with a more comfortable patient experience. In this case, all examined materials would be suitable independent of the polishing procedure in order to get a reduced discomfort sensation. Taking into account the findings of the present in vitro study, the surface roughness of the composites will become suitable for clinical use solely following the finishing and polishing.^[17]

The study’s findings indicate that Super-Snap X-TREME and Sof-Lex polishing systems, followed by OneGloss polishing systems, produce the smoothest surface. The aluminum oxide polishing discs from Super-Snap X-TREME and Sof-Lex is the likely cause of generating a smoother surface on both composites that were used because they seem to finish or tend to sand the surface material without displacing the filler particles. The flexibility of the Super-Snap X-TREME and Sof-Lex polishing systems due to them being thin discs also encourages uniform filler and resin matrix abrasion.

This occurs as these discs will curve on the slightest use of any excessive force during polishing on the composites. As opposed to the OneGloss polishing system which uses more rigid silicone polishers, which are less flexible. Leaving the polish that this system creates less precise as the surface roughness can vary based on the pressure applied by the operator. The resulting tests demonstrated that the OneGloss polishing system produced the least smooth surfaces. This is likely due to the fact that it abrades softer resin matrices more rapidly while retaining the harder filler particles in the composite which stick out from the surface giving it a more uneven polish.^{[18],[19],[20]}

Conclusion

Among the constricts of the experimental in vitro study the three polishing systems used significantly influenced the surface roughness with Super-Snap X-TREME, Sof-Lex multistep polishing system producing a smoother surface compared to OneGloss one step polishing system, which indicate that multi-step polishing techniques namely Super-Snap X-TREME and Sof-Lex that use flexible discs outperformed the one-step system OneGloss which uses a silicone polisher. Nanohybrid composite has also shown improved polishability when compared to microhybrid composites.

Acknowledgments

Nil.

Author contribution

Dr. Kevin Lin Kovoor was responsible for the research’s idea and design, as well as gathering information, evaluation, and assessment. Dr. Shruthi H. Attavar drafted the article or critically revised it for key intellectual content, and all authors approved the final version to be published.

Acknowledgement

Not applicable.

Financial support and sponsorship

Self funded.

Conflicts of interest

There is no conflict of interest.

Authors contributions

Concept and design of study or acquisition of data or analysis and interpretation of data was done by Dr Kevin Lin Kovoor. Drafting the article or revising it critically for important intellectual content was done by Dr Shruthi H Attavar ; and Final approval of the version to be published was approved by all the authors.

Ethical policy and institutional review board statement

The study has been approved by the institution ethical committee. All the procedures have been performed as per the ethical guidelines laid down by the Declaration of Helsinki 2023.

Patient declaration of consent

Not applicable.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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