| Abstract|| |
Background: The restoration of noncarious cervical lesions (NCCLs) often poses a challenge to the clinician. Various restorative materials are available in the market for the restoration of the same. Each material has various advantages and shortcomings.
Aim: The aim of this study was to compare and to evaluate the clinical performance of capsulated resin-modified glass ionomer cement (RMGIC), flowable composite, and polyacid-modified composite resin (PMCR) in NCCLs.
Materials and Methods: A total of 101 restorations were placed among healthy controls in this clinical trial. A total of 101 restorations were divided into three groups with n = minimum 32 per group (Group 1: 33 restorations, Group 2: 34 restorations, and Group 3: 34 restorations). The restorative materials used were capsulated RMGIC, flowable composite and PMCR. After the placement, the restorations were evaluated for the United States Public Health Services criteria for six parameters, namely retention, marginal adaptation, marginal discoloration, color stability, surface roughness, and sensitivity. The restorations were evaluated at baseline, 6 and 12 months.
Statistical Analysis: Statistics was performed using SPSS 21.0 version. Chi-square test was done to compare the proportions between groups. Fisher's exact test was used to compare proportion change between time points.
Results: There was no statistically significant difference seen among the three groups for retention, color stability, surface roughness, and hypersensitivity. RMGIC had shown superior characteristics in marginal adaptation and marginal discoloration compared to flowable composite and PMCR, and the difference was statistically significant.
Conclusion: Within the limitations of this study, all the three restorative materials are clinically acceptable for the restoration of NCCLs. RMGIC is superior regarding marginal adaptation and esthetics for restoring NCCLs.
Keywords: Flowable composites; noncarious cervical lesions; polyacid-modified composite resins; resin-modified glass ionomer cement; United States Public Health Services criteria
|How to cite this article:|
Hussainy SN, Nasim I, Thomas T, Ranjan M. Clinical performance of resin-modified glass ionomer cement, flowable composite, and polyacid-modified resin composite in noncarious cervical lesions: One-year follow-up. J Conserv Dent 2018;21:510-5
|How to cite this URL:|
Hussainy SN, Nasim I, Thomas T, Ranjan M. Clinical performance of resin-modified glass ionomer cement, flowable composite, and polyacid-modified resin composite in noncarious cervical lesions: One-year follow-up. J Conserv Dent [serial online] 2018 [cited 2020 Jun 2];21:510-5. Available from: http://www.jcd.org.in/text.asp?2018/21/5/510/241199
| Introduction|| |
A noncarious cervical lesion (NCCL) is defined as the loss of tooth structure at the cementoenamel junction, which is unrelated to dental caries. These lesions have a multifactorial etiology and often present diagnostic and restorative challenges for the dental profession. The NCCLs in human teeth have been conventionally and broadly classified according to their etiology and pathogenesis as abrasion, erosion, and tooth flexure. In 1991, Grippo described tooth flexure as abfraction, which is a pathological loss of dental hard tissue caused by biomechanical forces. Historically, these NCCLs were classified according to their appearance as wedge-shaped, disc-shaped, flattened, irregular, or smooth.
Noncarious loss of tooth structure in the cervical region is a very common clinical condition with the fact that the prevalence and severity of these lesions have been found to increase with age. The consequences of these lesions are sensitivity and high wear besides suboptimal esthetics. Thus, restoration of these lesions is quite often necessary, along with proper control of the likely causal effect, which is generally related to the occlusal problems.
Self-cured glass ionomer cements (GIC) have a wide range of clinical applications in NCCLs. However, the conventional GICs are relatively unesthetic and have poorer mechanical properties than the composite resins. To overcome the disadvantages of GIC, resin-modified GIC has been developed. In these materials, the addition to light-curing resin components, and in some systems, additional self-curing resin components, have led to a higher resistance to early moisture contact and desiccation, better mechanical characteristics, and equal fluoride release.
The introduction of RMGICs was followed by the development of “polyacid-modified composite resin (PMCR).” PMCR consists of ion-leachable glass particles and polymerizable acidic monomers. An acid-base reaction which is typical in the setting of GICs s does not occur in PMCR. They set through a free radical polymerization reaction. The proposed nomenclature for these materials is PMCR because they are resin-based materials rather than GICs.
More recently, composites have imposed themselves as restorative alternatives to GIC for the restoration of NCCL due to their improved esthetic properties, improved adhesive capacity due to modern dentin adhesives, and increased mechanical properties. Shortcomings of composite restorations in cervical areas have been associated with stress generation on the tooth restoration interface, as a consequence of polymerization shrinkage, and tensile stress caused by oblique occlusal loading. To address the problem of debonding as a consequence of polymerization shrinkage, flowable composites have been proposed as a restorative option, due to their low-elasticity module.
The available literature does not show any studies comparing RMGIC, flowable composite, and PMCR. Hence, the purpose of this study was to evaluate and to compare the clinical performance of RMGIC (Fuji II LC capsules), Flowable composite (Filtek Z 350 XT) and PMCR (Dyract extra) in NCCLs. The null hypothesis was that there is no difference in clinical performance of any of the materials tested in NCCLs.
| Materials and Methods|| |
Approval for the project was obtained from the Institutional Review Board. Based on the study done by Jyothi et al. 2011, comparing the clinical performance of two restorative materials using United States Public Health Services (USPHS) criteria, sample size estimation was calculated using a priori by G*Power 3.1.2 software. The minimum sample size of each group was calculated, following these input conditions: power of 0.8 and P ≤ 0.05 and sample size arrived was minimum 32 teeth per group. Considering dropouts, the final restorations were placed in 33 teeth for Group 1, 34 teeth for Group 2 and 34 teeth for Group 3. The eligibility criteria for the study included individuals with NCCLs, individuals with hypersensitivity, healthy persons between the age group of 18 and 65 years who signed the inform consent, vital teeth, teeth with occlusion and interproximal contact, and individuals with fair oral hygiene. Individuals with evidence of parafunctional tooth wear, carious teeth, discolored teeth, poor oral hygiene, and teeth that underwent root canal therapy were excluded from the study. The study participants for the study were recruited from the pool of patients in the Department of Conservative Dentistry and Endodontics. Randomization was done well in advance by a third person who was not related to the study. Randomization was done using block randomization procedures with unknown block sizes to the investigators until the end of the study. Sequentially numbered, opaque, sealed envelopes method was implemented for allocation concealment which conceals the sequence until interventions were assigned. Patients and the evaluator were unaware about the type of treatment and treatment protocol and they were blinded.
Before the treatment, a careful medical and dental history was taken. Preoperative data for each patient was recorded in the predesigned patient's chart which includes age, sex, tooth number, and intensity of sensitivity before the treatment. The treatment and the study design were explained to the qualifying patients, and informed consent was obtained from the voluntary patients who were willing to participate in the study.
The lesions were classified being as saucer shaped or V shaped. The presence of sensitivity was recorded by taking the history and clinical examination. The selected lesions in each participant were randomly assigned to either RMGIC, PMCR, or flowable composite.
All the participants underwent oral prophylaxis within 2 weeks before the placement of restorations. The lesions were not prepared with rotary instruments following the guidelines of the American Dental Association Acceptance program for dentin and enamel adhesive materials that do not allow placement of bevels. The lesions were cleaned with prophylaxis paste and rubber cup to remove the topped deposits at the time of restoration. Shade selection was done using a Vitapan classic shade guide (Zanfabrik H. Ranter Gmbhand Co, KG Germany). Isolation of the area was achieved using cotton rolls and saliva ejector. Retraction cord was placed in case of subgingival lesions.
All restorations were placed according to manufacturer's instructions. For Group 1 restorations, GC Fuji II LC capsule is available in premeasured unit dose capsules for no-mess mixing. Teeth restored with Fuji II LC capsules received a 10 s application of GC cavity conditioner. After the activation of capsule, cement was placed in the cavity, restoration was contoured, excess cement was removed, and light cured for 40 s. For Group 2 restorations, teeth restored with Filtek Z 350 XT were etched for 15 s using 37% phosphoric acid. Dentin primer (Scotch bond multipurpose) was applied for 5 s and allowed to dry. Dentin adhesive (Scotch bond multipurpose) was applied without air thinning and light cured for 10 s. Filtek Z 350 XT was applied incrementally and light cured. For Group 3 restorations, teeth restored with Dyract flow were etched for 15 s. After etching, the lesion was rinsed for 10 s and dried to remove excess water, leaving a moist surface. Prime and Bond NT (Dentsply) was applied to the whole surface with a brush and left undisturbed for 15 s. The solvent was removed for 5 s with a gentle stream of air, and the adhesive was light cured for 10 s. Dyract Flow (Dentsply) was applied to the lesion incrementally, as mentioned above, and each layer was light cured for 40 s.
After 24 h, all the three group restorations were finished under water coolant with fine and superfine diamond points (Diaburs, Mani). Polishing was done with soflex discs (3M ESPE). Subjects were instructed to use soft brush with toothpaste. One week after placement, baseline records were taken that included color photographs and clinical evaluation. Clinical evaluation included the assessment of retention, color match, marginal discoloration, marginal adaptation, color stability, surface roughness, and sensitivity according to USPHS criteria. The participants were called at the end of 6 and 12 months for evaluation of restorations by a single calibrated investigator using mirror and explorer under good operating light using USPHS criteria. The investigator was blinded about the restorative materials used in the study.
The data were entered into spreadsheets and statistically analyzed applying software SPSS version 21 (SPSS, Chicago, IL, USA). Chi-square test was used to compare the proportions between groups. The performance of restorations at the baseline and after 6 and 12 months' recall times was evaluated by McNemar's test. A level of 0.05 was adapted to determine the statistical significance of differences (P < 0.05).
| Results|| |
All the participants were available for recall at 6 and 12 months. The data for retention, marginal adaptation, marginal discoloration, color stability, surface roughness, and sensitivity for the tested materials for each of the periods are summarized in [Table 1]. The retention score of RMGIC was 100% Alfa at 6 and 87.9% Alfa at 12 months. Among 33 restorations placed, 3 had a score bravo, and 1 restoration was lost at 12 months. There was a loss of retention for 2 restorations at 6 months when restored with flowable composite, and 3 restorations had a score bravo after 12 months. Out of 34 restorations placed with PMCR, there was a loss of one restoration at 6 months, and 3 restorations had a score bravo at 12 months. When marginal adaptation is considered, there was much variation among the restorative materials. The Alfa score for RMGIC is 90.9%, flowable composite is 64.7%, and PMCR is 67.6% at the end of 12 months.
|Table 1: Evaluation of United States Public Health Services criteria for three restorative materials at baseline, 6 and 12 months|
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The percentage of Alfa ratings for marginal discoloration are 90.9% for RMGIC, 58.8% for flowable composite, and 67.6% for PCMR at the end of 12 months. There was a statistically significant difference between the RMGIC compared to flowable composite and polyacid-modified resin composite regarding marginal adaptation and marginal discoloration at 12 months with P value of 0.039 and 0.015 [Table 2]. When color stability was evaluated RMGIC, and flowable composite had shown a score of 100% Alfa at 6 months. 1 restoration of PMCR had shown a score of bravo at 6 months. After 12 month recall, 2 restorations of RMGIC, 4 restorations of flowable composite, and 2 restorations of PMCR had shown Bravo score. When surface roughness was evaluated at a 6 month recall, 1 restoration of RMGIC had shown a bravo score. After 12 months recall, 5 restorations of RMGIC and PMCR each and 3 restorations of flowable composite showed bravo rating. Neither of restorations placed with RMGIC and PMCR had presented postoperative sensitivity at 6 and 12 months recall. At 12 month recall, 2 restorations placed with flowable composite presented with sensitivity.
| Discussion|| |
This study evaluated and compared the clinical performance of RMGIC, flowable composite and PMCR in NCCLs using USPHS criteria which are widely used for long-term evaluation of restorations and is considered valid for comparison purpose among studies at different observation periods.
The retention rate for RMGIC and PMCR was 97% and 94.1% for flowable composite at the end of 12 months. In this study, the filler content of the restorative materials is 63.3% for flowable composite and 38% for PMCR. According to low-filler content, flowable composites shrink more upon polymerization when compared with conventional composites. It has been suggested that the materials with the most polymerization shrinkage obtain the lowest bond strength values. This may be the reason for the low retention rate. Heintze and Cavalleri reported long-term degradation mechanisms (e.g., hydrolysis) acting on the composite/dentin interface play a more crucial role when dealing with the loss of retention of Class V restorations. Other studies revealed a multifactorial etiology for the restoration failure, according to which success of retention seems to depend on patient selection, location, occlusal stress, presence of sclerotic dentin, shape of the lesions, as well as on the properties of the materials used.,
In general, failure of marginal adaptation may be due to thermal and mechanical stresses in the oral environment, viscoelastic property of the restorative material, water sorption, hydrolysis, and unique stress patterns at the cervical margin of the tooth. Cervical areas are morphologically and histologically different from the crown and the root portions of the tooth. In this study, the ratings of marginal discoloration correspond within certain limits to that of the marginal adaptation. The similar ratings provide evidence that the poor marginal adaptation can predispose to marginal discoloration.
RMGIC had shown superior performance compared to flowable composite and PMCR in regarding marginal adaptation and marginal discoloration. Results have shown that there was a statistically significant difference by Fishers Exact test among three materials in both marginal adaptation (P = 0.039) and marginal discoloration (P = 0.015) at 12 months. The flowable composite resins due to their lower filler content have higher polymerization shrinkage, coefficient of thermal expansion, and inferior mechanical properties. Stresses from shrinkage create forces that compete with the adhesive bond, and this may disrupt the bond to cavity walls, and is the primary causes of marginal failure and micro leakage., Moreover, in cervical lesions, the lack of enamel at the gingival margin aggravates the situation. This could be the reason for flowable composite restorations for not performing better regarding marginal adaptation and discoloration. However, the importance of perfect seal for success and longevity of class V resin restorations must be considered at the time of restorative treatment. Especially, in case of PMCR, several restorations showed excess at the margins placed on enamel and had moderate discoloration. According to Folwaczny et al. 2001, this excess at PMCR restoration margins is most likely due to water sorption which leads to swelling. Some authors postulate that the combination of excess and deformation to which cervical restorations are subjected might be responsible for the breakdown of the bond and fracturing of the material at the margins, leading to marginal discoloration and discrepancies.
One of the most challenging tasks related to rising esthetic demands in dentistry is to achieve a restoration that matches the color and appearance of a natural tooth. In this study, the prevalence of discoloration was significantly higher for the PMCR. Many restorations did not match well with tooth color. Maneenut and Tyas mentioned incomplete polymerization, residual HEMA molecules after light activation, susceptibility to water sorption and desiccation as factors that may affect the color stability of PMCRs.
The chemical composition, type, and amount of filler can alter the wear on restorations. Even studies evaluating the alterations in surface morphology of flowable composites have attributed increased wear due to reduced filler loading. The reduced filler content increases better polish ability but reduces the overall wear resistance.
All the three materials had shown clinically acceptable performance at the end of tested time periods so the null hypothesis can be considered as accepted. All materials tested in this study resulted in retention rates above 95% at 12 months. RMGIC has shown superior performance than flowable composite and PMCR regarding marginal adaptation and marginal discoloration, and the results were statistically significant. When color stability was evaluated, RMGIC had shown better results followed by PMCR and flowable composite. The flowable composite had shown least surface roughness among the tested groups. No postoperative sensitivity was found in groups restored with RMGIC and PMCR and 5.9% restorations placed with flowable composite has shown sensitivity.
| Conclusion|| |
Within the limitations of this study, it has been concluded that all the three restorative materials are clinically acceptable for the restoration of NCCLs.
Higher rates of restoration loss were associated with flowable composite; however, the results were not statistically significant.
Clinically, RMGIC showed an overall better performance than the other two materials. However, more studies conducted over a longer period and with a higher number of samples are required to conclusively compare these three materials.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Iffat Nasim
Department of Conservative Dentistry and Endodontics, Saveetha Dental College, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai - 600 010, Tamil Nadu
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]