Comparative clinical evaluation of a self-adhering flowable composite with conventional flowable composite in Class I cavity: An in vivo study.

Context: The purpose of this study was to evaluate the efficiency of self-adhering flowable composite with that of a time-tested conventional flowable composite. Since the self-adhering composite reduces chair time and is convenient to use, its clinical behavior was monitored for a year. Aim: This study aimed to evaluate the clinical behavior of self-adhering flowable composite - Fusio Liquid Dentin - in small-sized Class I cavities and also to compare it with conventional flowable composite - Tetric N-Flow - bonded to the tooth structure with fifth-generation two-step-etch-and-rinse adhesive. Subjects and
Methods: A total of 60 cavities were restored using flowable composite materials (30 cavities in each group) and evaluated at baseline, 1 month, 3 months, 6 months, and 1 year with modified United States Public Health Service criteria. The statistical analysis for the study was done using Fisher's exact test for intergroup comparison and Chi-square test for intragroup comparison. P < 0.05 was considered statistically significant.
Results: Statistically no significant differences were observed in Fusio Liquid Dentin restorations during the recall visits. Statistically significant differences were found in color match evaluated for Tetric restorations during the recall visits.
Conclusion: Based on the data acquired, the novel self-adhering composite material demonstrated good clinical behavior. As a result, at this point in the prospective clinical study, the use of Fusio Liquid Dentin to repair Class I cavities is acceptable. Copyright:

INTRODUCTION

With the discovery of acid etching by Buonocore and Bis-GMA by Bowen, restorative dentistry entered an era in which adhesives were inevitable. Adhesion-based restorative dentistry is extremely promising and predictable, but it is also quite a technique sensitive and time consuming.

The bonding agents have been developed with the aim of reducing steps, thus easing the procedure and saving working time. Fifth, sixth, and seventh generations of bonding agents are presently in use. The fifth generation, also known as total etch, uses 37% phosphoric acid for etching,[1] following which primer and bonding agent are applied together. They have been proven to show excellent clinical performance in terms of durability and bond strength.[2] The sixth and seventh generations are self etch adhesives which contain agents that conditions and prime enamel and dentin at the same time.[3]

Self-etch adhesives can be categorized into two groups: (1) two-bottle system where one bottle contains the etchant and primer together, and the second bottle contains the adhesive (sixth generation) and (2) one-bottle system where all the components are mixed together (seventh generation).

Composite restoration, including packable and flowable composites, has a broad range of indications. Although flowable composites lack mechanical properties when compared to packable composites due to lower filler content, they are commonly used as a pit and fissure sealant in Class III, Class V, and Class I restorations that do not involve areas of occlusal loading, or as a liner in large restorations, and so on.[4]

Self-adhering flowable composites were introduced to the market a few years ago to eliminate procedural stages and thereby save chairside time. Two products are now available in the market: Vertise Flow (Kerr, Orange, USA) and Fusio Liquid Dentin (Pentron, Wallingford, Connecticut, United States).

The current study aimed to evaluate the 1-year clinical performance of self-adhering flowable composite (Fusio Liquid Dentin) in posterior small Class I restorations. Its performance was also compared with Tetric N-Flow (Ivoclar Vivadent, Schaan, Liechtenstein) that uses the two-step-etch-and-rinse adhesive.

The null hypothesis for the study was as below:

For Fusio Liquid Dentin, there would be no difference in the criteria evaluated at the recall visits

For Tetric flow, there would be no difference in the criteria evaluated at the recall visits

There would be no difference in clinical performance between Fusio Liquid Dentin and Tetric flow restorations for the criteria evaluated at recall visits.

SUBJECTS AND METHODS

This is a prospective, single-center, single-blinded randomized controlled clinical trial. The study was conducted at the department of conservative dentistry and endodontics. The study protocol was approved by institutional ethics committee and followed the CONSORT guidelines perspicaciously. A total of 30 individuals aged between 18 and 54 years with at least two Class I restorations in maxillary or mandibular first or second molar were included for this study. A total of 60 cavities were restored and evaluated at baseline, 1 month, 3 months, 6 months, and 1 year with modified United States Public Health Service criteria (USPHS).[5]

For the experimental group, Fusio Liquid Dentin was used, which is a 4-methacryloxyethyl trimellitic acid-based self-adhering flowable composite. It is unique in way that its hydrophilic, acidic, and negatively charged carboxylic acid groups of methacrylate monomers bond to the mineral ions in the tooth: As the carboxylic acid monomers polymerize, they become incorporated into the tooth surface and provide bonding. The filler content includes nano-sized amorphous silica and glass. Fusio Liquid Dentin is available in four shades, and the curing time for 1–2 mm increment is 10 s. It reduces the steps of etching and bonding.

For the control group, Tetric N-Flow (Ivoclar Vivadent, Schaan, Liechtenstein) flowable composite was used using fifth-generation etch-and-rinse technique. For that, N-etch (Ivoclar Vivadent, Schaan, Liechtenstein) and Tetric N-bond (Ivoclar Vivadent, Schaan, Liechtenstein) were used along with flowable composite.

Before restoring the teeth, clinical and radiographic examination of the teeth along with a vitality test was done, including cold and electric pulp testing. Moreover, pain scale for each patient was recorded, only patients who scored zero were considered for the study.

The clinical procedure for the study is as below:

The whole procedure was done under × 2.5 loupes (Cricvision, Mumbai, India). The patient's occlusion was checked and preoperative radiographs (Kavo Scan eXam One, Brea, California) were taken, followed by shade selection. Under rubber dam isolation (Hygienic, Coltene, Altstatten, Switzerland), caries removal was done by slow speed tungsten carbide burs (Mani, INC, Tochigi, Japan), followed by cavity preparation with high-speed handpiece using round diamond burs (Mani, INC, Tochigi, Japan). After cavity preparation, the cavity was cleaned with water and air and finally restored with flowable composites.

For the teeth to be restored with Fusio Liquid Dentin, 1 mm composite dispensed and brushed using applicator tips (ORO, India) on the tooth surface for 15–20 s, then cured for 10 s. After that, 2 mm increments were added and cured using Bluephase C5 (Ivoclar Vivadent, Schaan, Liechtenstein). For the teeth to be restored with Tetric N-flow, first etching was done with 37% phosphoric acid (Tetric N-etch, Ivoclar Vivadent, Schaan, Liechtenstein) for 15 s, rinsed with water for 30 s dried with chip blower or blotting paper, bonding agent was applied and brushed for 10 s and light cured for 10 s, the second layer of bonding agent was applied, and the procedure was repeated. Then, the cavity was restored with Tetric N-flow in 2 mm increments and cured for 20 s each.

After removing the rubber dam, occlusion was checked with articulating paper and corrected with yellow band burs (Mani, INC, Tochigi, Japan). Polishing was done with universal polishing paste (Ivoclar Vivadent, Schaan, Liechtenstein) and fiber Occlubrush and concave OptiShine (Kerr, Orange, California, United States).

The restorations were examined with mirror and probe at baseline, after 1 month, 3 months, 6 months, and 1 year. At each recall, data regarding color match, marginal discoloration and adaptation, secondary caries, anatomic form, surface roughness, fracture, and postoperative sensitivity were collected with reference to the modified USPHS criteria/Ryge criteria as given in Table 1.

Table 1

Modified United States Public Health Service criteria with score interpretation for clinical assessment of restorative materials

Criteria	Score	Score interpretation
Color match*	Alpha	The restoration matches the adjacent tooth tissue in color, shade, or translucency
	Bravo	There is a slight mismatch in color, shade, or translucency but within the normal range of adjacent tooth structure
	Charlie	There is a slight mismatch in color, shade, or translucency but outside of the normal range of adjacent tooth structure
Marginal discoloration*	Alpha	There is no discoloration anywhere along the margin between the restoration and adjacent tooth structure
	Bravo	Discoloration is present but has not penetrated along the margin in a pulpal direction
	Charlie	Discoloration has penetrated along the margin in a pulpal direction
Secondary caries†	Alpha	No caries is present at the margin of the restoration, as evidenced by softness, opacity, or etching at the margin
	Bravo	There is evidence of caries at the margin of the restoration
Anatomic form‡	Alpha	The restoration is continuous with the existing anatomic form
	Bravo	The restoration is discontinuous with the existing anatomic form, but missing material is not sufficient to expose the dentin or base
	Charlie	Sufficient restorative material is missing to expose the dentin or base
Marginal adaptation (Alfa, Bravo‡ Charlie, Delta§)	Alpha	There is no visible evidence of a crevice along the margin into which the explorer penetrates
	Bravo	There is visible evidence of a crevice along the margin into which the explorer penetrates or catches
	Charlie	The explorer penetrates the crevice, and dentin or base is exposed
	Delta	The restoration is mobile, or missing, either in part or total
Surface roughness§	Alpha	The restoration surface is as smooth as the surrounding enamel
	Bravo	The restoration surface is rougher than the surrounding enamel
	Charlie	There are a crevice and fracture on the restoration
Retention	Alpha	Restoration is present
	Delta	Restoration is partially or totally missing
Postoperative sensitivity¦	Alpha	Normal reaction to the stream of air compared to that of nonrestored teeth
	Bravo	Increased sensitivity
	Charlie	Spontaneous pain

*Visual inspection, †To detect secondary caries, the presence of softness, opacity, etching, or white spot was considered as evidence of undermining or demineralization in areas where the explorer catches or resists the removal after insertion. Radiographs were also taken at each follow-up, ‡Visual inspection and explorer, §Explorer, ¦Postoperative sensitivity was assessed as the patient comfort with the restoration under function, and by blowing a stream of compressed air for 3 s at 2–3 cm away from the restoration

The statistical analysis for the study was done using Fisher's exact test for intergroup comparison and Chi-square test for intragroup comparison. P < 0.05 was considered statistically significant.

RESULTS

The performance of both the restorative materials was different at the different recall visits as compared to the baseline. When comparing Fusio Liquid Dentin restorations at different recall visits [Graphs 1 and 2], changes were seen in color match, anatomic contour, marginal integrity, surface texture, and postoperative sensitivity. The number of restorations showed unacceptable scores, which increased as the time elapsed. Hence, the first null hypothesis was partially rejected. All restorations scored alpha for secondary caries and retention at all the recall visits.

Graph 1

The results of the clinical evaluation in different intervals with alpha score

Graph 2

The results of the clinical evaluation in different intervals with alpha score

In the Tetric N-flow group, though changes were seen in the different parameters such as color match, marginal discoloration, marginal integrity, surface texture, and postoperative sensitivity at the different recall visits, no significant difference was seen up to 6 months, but there was a significant difference noticed in results at 1-year follow-up. Except for color match, scores achieved for all the parameters were statistically nonsignificant. Hence, there was a rejection of the second null hypothesis.

No statistically significant difference was seen in intergroup comparisons between Fusio Liquid Dentin and Tetric N-flow restorations. Hence, there was acceptance of the third null hypothesis.

DISCUSSION

Flowable composites contain less filler and have properties such as lower modulus of elasticity, higher flexibility (to reduce curing stress), and low viscosity, but they are thought to have compromised mechanical properties, a higher coefficient of thermal expansion, and a higher rate of polymerization shrinkage.[6] Reduced filler load (weight: 60%–70%; volume: 46%–65%), on the other hand, may weaken the restorations’ resistance to deformation during function. As a result, they are recommended for usage in nonstress bearing regions such as tiny Class I cavities.[7]

Since the performance of Tetric flow has been found to be better than the other flowable composites tested in terms of shear bond strength, flexural strength, flexural modulus, modulus of elasticity, linear polymerization shrinkage, and marginal integrity,[8910] it was chosen as a material for comparison.

Considering 5% alpha and 80% power value, the minimum sample size was calculated as 30 per group.

Two Class I cavities were prepared for each patient. One was restored with Fusio Liquid Dentin and the other with Tetric N-flow. Few important parameters such as masticatory forces, occlusal habits, chemicals and abrasives, temperature fluctuations, humidity variations, bacterial by-products, and salivary enzymes all contribute as uncontrollable factors that affect the longevity of composite restorations. To avoid the threat of control-selection bias and to increase efficiency, a self-control design was used in the current study; hence, both the test and control materials were placed in Matching pairs in the same patient with the same oral environment.

In the Fusio Liquid Dentin (FLD) group, at 1-year follow-up, the difference from baseline was not significant. Four restorations (13.3%) scored Bravo score (slight mismatch in color, shade, or translucency but within the normal range as of adjacent tooth structure. Tetric group showed five restorations (16.7%) that scored Bravo at 1-year follow-up which was statistically significant. Change in the color of composite over time period is a multifactorial process. The size and distribution of filler particles are important factors contributing to the color change. Larger the filler particles, more is the susceptibility for the color change due to the hydrolysis at the filler-matrix interface.[11] Similar results were achieved in an in vivo study conducted by Heintze et al. where they assessed both materials in Class V cavities for 18 months; the reason for inferior color match in this study is said to be due to the large filler particles in the Tetric N-flow material. Moreover, for posterior restorations, color match is not as critical as compared to anterior restorations.[12]

In the FLD group, four restorations (13.3%) scored Bravo for anatomic form at 1-year follow-up which was statistically nonsignificant. Change in anatomic form of the restorations may be attributed to the wear of the material and its flexural strength.[13] However, the maximum flexural strength of FLD has been found to be 150 MPa and that of Tetric flow to be 102 MPa.

At 1 year, five FLD restorations (16.7%) had a Bravo score for surface roughness, which was statistically insignificant. They determined in research that the nano-sized amorphous silica and glass filler in the FLD material may have smoothed the surface.[12]

For retention, secondary caries, and marginal discoloration, all the restorations scored alpha at 1-year follow-up. Similar results were seen for retention in a study done by Shaalan et al. with a different SAFC at 6-month follow-up.[14]

To alleviate postoperative sensitivity at the end of 1 year in the Fusio group, five restorations (16.7%) scored Bravo and two restorations (6.7%) scored Charlie, which is statistically insignificant. Self-adhering composites have less flow than typical flowable composites, which may impede appropriate sealing of dentinal tubules and, in certain situations, produce postoperative discomfort.[15]

CONCLUSION

Within the limitations of this study,

Statistically nonsignificant differences were observed in Fusio Liquid Dentin restorations during the recall visits

Statistically significant differences were found in color match evaluated for Tetric restorations during the recall visits

Based on the collected data, the new self-adhering composite material gave proof of a satisfactory clinical behavior. Therefore, at this stage of the prospective clinical trial, the use of Fusio Liquid Dentin to restore Class I cavities can be accepted.

Financials support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.