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Table of Contents   
ORIGINAL ARTICLE  
Year : 2016  |  Volume : 19  |  Issue : 4  |  Page : 306-310
Two-year clinical evaluation of resin composite in posterior teeth: A randomized controlled study


1 Department of Prosthetic Dentistry, Federal University of Espírito Santo, Vitória, ES, Brazil
2 Department of Physics, Federal University of Ceará, Fortaleza, CE, Brazil
3 Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil
4 Department of Operative Dentistry, Federal University of Ceará, Fortaleza, CE, Brazil

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Date of Submission04-Mar-2016
Date of Decision06-May-2016
Date of Acceptance29-Jun-2016
Date of Web Publication18-Jul-2016
 

   Abstract 

Background: Clinical evaluations as fundamental method to prove the efficiency of restorative materials.
Aim: This study evaluated the clinical performance of restorative systems during 2 years of clinical service.
Materials and Methods: This study assessed the clinical performance of restorative systems (Filtek Z250 and P60), during 2 years of clinical service, using the US Public Health Service system. The randomized and double-blind study comprising thirty volunteers. The restorations were evaluated at baseline, 6, 12, and 24 months. It was used the following criteria: marginal discoloration (MD), marginal integrity (MI), superficial texture (ST), wear (W), postoperative sensitivity (PS) and recurrent caries (RC).
Results: Statistic analysis was performed using Fisher's and McNemar's exact tests and Pearsons's Chi-square in a significance level of 5%. The results at baseline and 24 months for Group I were: MD – 100, 100%; MI – 100, 88.6%; ST – 100, 94.3%; W – 100, 94.3%; PS – 100, 100%; RC – 100, 100%, of alpha scores; Group II: MD – 100, 97.1%; MI – 100, 91.4%; ST – 100, 94.3%; W – 100, 91.4%; PS – 100, 100%; RC – 100, 100%, of alpha scores. It was observed no statistical difference in the evaluated criteria and period.
Conclusions: After 24 months of evaluation, both restorative systems exhibited acceptable clinical performance.

Keywords: Clinical trial; composite resins; dental materials; randomized controlled trial

How to cite this article:
Gianordoli-Neto R, Padovani GC, Mondelli J, de Lima Navarro MF, Mendonša JS, Santiago SL. Two-year clinical evaluation of resin composite in posterior teeth: A randomized controlled study. J Conserv Dent 2016;19:306-10

How to cite this URL:
Gianordoli-Neto R, Padovani GC, Mondelli J, de Lima Navarro MF, Mendonša JS, Santiago SL. Two-year clinical evaluation of resin composite in posterior teeth: A randomized controlled study. J Conserv Dent [serial online] 2016 [cited 2019 Jul 24];19:306-10. Available from: http://www.jcd.org.in/text.asp?2016/19/4/306/186446

   Introduction Top


With the advancement of dentistry and the growing interest in the developments of ideal materials to replace lost dental tissue, resin-based composites have been widely used to restore posterior teeth.[1] Concerns about aesthetics, the content of mercury in amalgam restorations and the possibility of more conservative restorations, using the minimally invasive technique, has been essential in the selection of these materials in stress-bearing areas.[2],[3] However, some intrinsic characteristics from resin composite, for example, polymerization shrinkage and elastic modulus different of dental structure can produce several problems [4] including postoperative sensitivity, secondary caries, pulp inflammation, tooth or restoration fractures, and marginal defects of the composite with the adjacent tooth structure.[5] The failure of such treatment is a public health problem which increases the cost of dental treatment and decreases dental health.

Frequently, a range of experimental resins is launched on the market aiming to better physical and chemical properties, and consequently, an increase in the longevity of restorations. Thus, variations in the form and amount of inorganic particles in the polymeric matrix,[6],[7],[8] in the photoinitiator system,[9],[10],[11] handling, indications, among other factors, are increasingly frequent. However, the characteristics and effects of these composites are not yet fully elucidated, especially in the short term (early failure) and associated a clinical performance, making it difficult to choose the ideal restorative material.

The measure of success of a restorative treatment appears to be strongly associated to its longevity.[12] Although laboratory tests can provide relevant information on the restoration longevity, the long-term performance of these systems still depends on clinical evaluations. However, clinical studies require a more effective approach and greater precision in the experimental design due to several variables which can influence the results such as: Difficulty of patient compliance, difficulty of evaluating the restorations longevity as an objective factor (operator, patient, and material), and difficulty to acquire a heterogenic group such as that present in clinical routine.[13] Hence, several studies [14],[15] have used selective groups (e.g., dental students). However, these groups are not truly representative because they have distinguished prevention and hygiene practices.

Therefore, all factors observed in several studies served as a base to the development of this study. The purpose of this randomized and double-blind study was to assess the clinical performance of two composites for posterior tooth, in Class I and II restorations, using public health service system, during baseline, after 6-, 12-, and 24-months. The null hypothesis tested was that there is no significant difference in clinical performance between Z250 and P60 resin systems when using in posterior teeth.


   Materials and Methods Top


Patient selection and description of the groups

The study design was approved by the Human Ethics Committee Process #224. A total of seventy restorations were placed in molar and premolars in thirty patients (14 females and 16 males; 18–40 years). The following parameters were set for sample size calculation: the expected proportion was 0.8, the relative standard error was of 10%, the power of the test was calculated to be 80% (beta error), and the two-tailed alpha error of 5% was 2-sided. Based on these data, a sample size of 25 subjects was found to be necessary. Taking into consideration a possible loss during the study, a 20% increase in sample size was set totalizing 30 subjects. All patients received dental treatment in a public health service system, allowing the formation of a heterogeneous sample, during 24-months. The following criteria were used to select subjects to the study: Good oral hygiene, low caries index, no periodontal disease neither parafunctional habits, the patients should have at least two posterior teeth (molars and/or premolars) with initial carious lesions to be treated, and/or teeth with unsatisfactory restorations which needed to be replaced. The relationship between Class I and Class II restorations was 1:2.[16],[17]

Patients committed to attend the annual recall by participating in the study, and they were divided into two study groups according to the tested materials [Table 1]. Each subject received at least two restorations with evaluated materials. The randomization process that has allocated the cavities and materials were performed by software SPSS-Statistical Package for Social Science, Software version 12, SPSS Inc., Chicago, IL, USA. Furthermore, aiming to secure a blind study, patients and examiners were unaware of any data from the randomization process.
Table 1: Groups, composition and lot of materials used in the study

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Clinical procedures

Restorative procedures were carried out by an experienced clinician, who was submitted to a calibration process that consisted of performing 10 repeated restorations of each material under direct supervision of the project's coordinator. The operator's questions were addressed, and consensus was obtained during the calibration session. Teeth were carefully cleaned with pumice/water slurry, rinsed with water, and air-dried. All restorations were placed under rubber dam isolation. Bitewing radiographs were only taken when they were appropriate for diagnostic examination.

Amalgam and/or resin composite restorations considered unsatisfactory and cavity preparation were carried out with 245 carbide burs (Jet Burs, Beavers Dental Division of Sybron, Canada). All internal angles were rounded, and dislodged enamel prisms at gingival wall were removed with a gingival margin trimmer. Cavosurface angles were sharp with no bevel external surface. The criteria used in the evaluation of unsatisfactory restorations were restoration failure, dentin or base was exposed, contact point was missing (present periodontal inflammation), color and/or translucency beyond the normal range of tooth colors, marginal staining penetration in the direction of the pulp, marginal gap exhibiting the enamel–dentin junction, fractured, loose filling that is missing partly or completely, and presence of caries (associated with the filling).[3]

Every detail of cavity preparation such as cavity depth, enamel presence at the cervical margin, sclerotic dentin, possible pulp exposition, fissures and defects in the enamel, and cavity extension were recorded. Therefore, four teeth were covered with calcium hydroxide (Dycal Dentsply Ind e. Com. Ltda., Petrópolis, RJ, Brazil) and resin-modified glass ionomer cement (Vitrebond; 3M Dental Products, St. Paul, MN, USA) since the thickness of the remaining dentin was less than approximately 0.5 mm.

Enamel was etched for 30 s and dentin for 15 s with 37% phosphoric acid gel (Scotchbond Etchant; 3M Dental Products, St. Paul, MN, USA), washed for 30 s, and gently dried with air jet. The adhesive system (Single Bond, 3M Dental Products, St. Paul, MN, USA) and the resins composite were applied to the dental substrates in accordance with the manufacturer's instructions. To provide the largest free surface area, the resins composite were inserted in 2 mm thick increments. Each increment was light-cured for 40 s using a halogen curing light (Curing Light XL 3000, 3M Dental Products, St. Paul, MN, USA), with minimum light intensity of 600 mW/cm 2 and checked by a light-curing meter (Hilux Dental Curing Light Meter, Benlioglu Dental Inc., Turkey). Class II cavities, the proximal wall, was reconstructed to transform into a Class I cavity, with the aid of polyester strip matrix (K-Dent Quimidrol, Joinville, Santa Catarina, Brazil) and dental interproximal wedges (TDV Dental Ltda, Pomerode, Santa Catarina, Brazil). Resin insertion in the occlusal box was performed in cone-shaped increments according to progressive waxing technique.

The restorations were immediately finished by removing excess material, whereas the finishing and polishing were performed after 1 week, using a 12-fluted tungsten carbide burs (Jet Burs, Beavers Dental Division of Sybron, Canada), the Enhance Polishing System (Dentsply, Rio de Janeiro, Brazil) and Sof-Lex Polishing discs (3M Dental Products, St. Paul, MN, USA).

Clinical evaluation

The restorations were evaluated by two calibrated examiners, and they were unaware of which material had been used. The examiners were calibrated before the baseline evaluation using picture slides representing each condition to be assessed in the study, and any disagreements during evaluation were resolved by consensus among the examiners. Modified US Public Health Service (USPHS) criteria [Table 2] were used to evaluate marginal discoloration, marginal integrity, surface texture, wear, postoperative sensitivity, and recurrent caries [18],[19] at baseline, after 6-, 12-, and 24-months. The data collection form used at baseline and all recall periods were identical.
Table 2: Modified-USPHS rating criteria

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The restorations were classified and demonstrated by scores: Alpha - ideal clinical situation, Bravo - clinically acceptable, and Charlie - clinically unacceptable situation.

Statistical analysis

Interexaminer reliability was assessed using kappa index (0.90). Comparisons of ratings for restorations and between baseline and follow-up examinations were analyzed by Fisher's and McNemar's Chi-square tests for each category. The value P ≤ 0.05 was set as the standard value considered to demonstrate statistically significant differences. The statistical analyses were carried out with SPSS 16.0 (SPSS Inc., Chicago, IL, USA).


   Results Top


The sample (30 subjects, 14 females and 16 males, 18–40 years), the number of restorations (35 per material), the distribution of restoration (maximum of three pairs in the same patient), the relationship between Class I and Class II (1:2) followed American Dental Association guidelines for new material testing.[16]

The distribution of restorations and recall characteristics for both tested groups are described in [Table 3]. The returns showed a collaboration rate of patients of 96.6% during 6 months, and after 24 months, 28 patients were examined, representing 93.3%.
Table 3: Distribution of restorations and recall characteristics for both tested Groups

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The results of this study revealed an excellent quality of resin composite restorations, which showed no cases of nonacceptable restorations in any aspect. No statistically significant differences between the two materials were found at 2 years with respect to evaluated criteria. The only criterion that presented a numerical, but not statistically, difference was marginal integrity. Thus, given the experimental conditions, our results demonstrated no material-time-dependency. The results are showed in [Table 4].
Table 4: Evaluation of the materials at baseline, 6, 12 and 24 months (Alfa score Percentage)

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   Discussion Top


Given the limitation of the method, USPHS recommendations are critically reviewed. Clinical evaluation of restorative procedures requires (a) choices of clinically relevant criteria, (b) assessment using simple nominal scales, (c) calibration of evaluators, (d) two independent evaluations, and (e) nonparametric statistical analysis that recognizes the patient (and not the restoration) as the independent variable.[19] Furthermore, USPHS evaluates only the degree of deviation from ideal restoration.[20] However, there is still no complete and accurate method that can evaluate all these numerous variables.

Problems in tooth restoration interface such as marginal integrity, marginal stain, and secondary caries are associated to materials physics and mechanics properties - elasticity modulus, thermal expansion coefficient, and curing shrinkage - and overall to enamel marginal finishing. A low elasticity modulus determines a greater material deformation when force is applied, damaging adhesive bonding due to fatigue in tooth restoration interface. Tooth and restorative materials show different thermal expansion coefficient; therefore, temperature change that takes place in oral cavity leads to stress in adhesive interface breaking hybridization bonding. That situation plus curing shrinkage ends up with leakage and marginal discoloration.[3],[21]

Marginal integrity criteria showed distinct values; nevertheless, there was no significant statistically difference. Both materials showed a slight degradation along the time, noticed through the changing in restoration scores from alpha to Bravo along the 6 and 24 months. In the first 6 months, Group I (Single Bond and Filtek Z250) showed 100% alpha score, after 12 months 97.1% and 2.9% Bravo, and after 24 months showed 88.6% alpha score and 11.4% Bravo score. Group II (Single Bond and Filtek P60) showed after 6 months 6% Bravo score, and after 12 and 24 months 91.4% to alpha score and 8.6% to Bravo score. This could probably be due to small fracture of the cavosurface margin and material. According to marginal discoloration, both materials showed similar score, showing after 12 months 100% Alpha score and after 24 months 97.1% alpha score. Concerning secondary caries both materials showed identical clinical behavior after 24 months which was 100% alpha score. Those results matched the findings from Türkün and Oguz,[18] Leinfelder,[22] Cenci et al., and [23] Gianordoli Neto et al.[24]

Analyzing the results for postoperative sensitivity, it was noticed that both materials (Group I and Group II) showed 100% alpha score in all evaluated periods. All cavity margins had enamel present which increases significantly the restorative adhesive system sealing capacity, decreasing possibility of marginal microleakage, and its consequences such as postoperative sensitivity.

It was observed in present research that there was no statistical difference between materials. Nevertheless, there was a numerical difference (percentage) to marginal integrity in Group I, which is presented in [Table 4]. The resins composite are both indicated for posterior restorations but differ in terms of handling characteristics. However, the lack of difference occurred due to similarities in the chemical composition of the composites used [Table 1]. P60 is filled to 61% by volume with zirconia/silica filler particles having a size range of from 0.01 to 3.5 µm, contain a greater number of smaller particles and the total load is approximately to 84% for weight. Z250 is filled to 60% by volume with zirconia/silica particles having a size range of 0.01–3.5 µm and an average size of 0.6 µm, contains also a greater number of smaller particles and the total load is approximately to 78% for weight. Probably, the difference may occur in longer observation periods.

Since materials were distributed likewise in the same patient, the variable patient factor cannot be used as a cause of greater wear. It was observed no wear after 12 months, only notice after 24 months, which matched the results from Türkün and Oguz,[18] Gianordoli Neto et al.[24] That happened because the improving of composites physic properties. New formulations decreasing tremendously the average size of particles have been developed over the last decade. Besides that, the incremental technique favored better clinical results, once lower increments decreased inner porosity and improved composite conversion rate, which reduced the observed wear.

All restorations in this research had final polishing and finishing after 7 days. The polishing consists of making the restoration surface look as enamel. After evaluation of superficial texture in different periods (baseline, 6, 12, and 24 months), Filtek Z250 (Group I) restorations showed 100% after 12 months and 94.3% alpha score after 24 months and Filtek P60 (Group II) showed after the same period 97.1% and 94.3%.

Both restorative adhesive systems used are hybrid and have as inorganic phase extremely small silica and zircon particles. It is associated to resin matrix with components (triethylene glycol dimethacrylate) increasing the molecular bonding and a higher conversion rate of double linking during curing process, which leads to a great resistant organic matrix. According to Anusavise [21] and Leinfelder,[22] decreasing size, changing composition, and increasing quantity of particles made nowadays composites 10–15 times superior than the previous ones in wear resistance and surface texture maintenance. In accordance with the results of the present study, few clinical alterations were observed in the resin composite wear and surface texture. This leads us to accept the null hypothesis.

All restorations after 24 months appeared to be clinically acceptable but are important to follow-up these restorations for a longer period to analyze the clinical performance of the resin composite systems. Long-term clinical trials are certainly needed because they remain the ultimate way to collect scientific evidence on the clinical effectiveness of restorative treatments.


   Conclusions Top


On the basis of the results and despite the limitations of this study, it seems reasonable to conclude that all direct resin composite restorations were clinically satisfactory and no significant differences were found among them over an evaluation period of two years.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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Correspondence Address:
Prof. SÚrgio Lima Santiago
Rua Monsenhor Furtado, s/n - Rodolfo Teofilo, CEP 60430-355, Fortaleza-CE
Brazil
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.186446

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