Introduction

With a dramatic increase in the esthetic requirements during the last decade and a need to seek alternatives to amalgam, composite resins have been used more frequently in the posterior region of the oral cavity ₁ . Initially it was amalgam and cast gold restorations which were the material of choice for posterior restorations ₂ . But since the development of Bis-phenol-A glycol dimethacrylate by R. Bowen in 1962 composites have come a long way to aid as posterior restorative materials ₃ . Gradual improvements of these materials have been achieved and today many clinical investigations have confirmed acceptable restoration performance not only in anterior but also in stress bearing posterior region ₄ .

Dental resins composite, specially advocated for use in posterior teeth, were introduced in the early 1980s and have become increasingly popular in restorative dentistry. The introduction of the material was surrounded by much speculation about their clinical performance. Therefore, few materials, if any, in the modern history of clinical dentistry have given rise to more investigations and publications than resin composites ₅ .

Resin composite materials have been used in anterior teeth for many years, where as their use in posterior region have been questioned. The reason for concern has been in regard to polymerization shrinkage and their tendency to wear. Many techniques and systems are available for tooth-colored composite restorations, and many in-vitro tests have been designed to predict the durability of direct composite restorations in clinical practice. Even with carefully designed simulations of clinical circumstances, the conditions vary considerably from those in vivo. For example, the outward flow of fluids through the dentinal tubules, the surface tension, and the functional stresses caused by mastication can not be simulated with in-vitro tests ₅ . Today, most investigators of resin composite believe that clinical success cannot be predicted only on the basis of material properties determined in the laboratory. Therefore documented clinical success should serve as guidance to practitioners in everyday practice.

In recent years, there has been an emphasis on relatively short-term studies to provide an early prediction of the long term clinical performance of posterior composites ₆₇ . Clinical trials require objectives, reliable, and relevant criteria to access the performance of restorations. The United States Public Health Services (USPHS) evaluation system, also known as Ryge’s criteria, is the most commonly used direct method for quality control of restorations ₈₉₁₀ .

This study clinically evaluates different posterior composite restorative materials in class I and class II restorations for a period of six months. The materials used in this study are Ceram-X Duo (Dentsply Detrey) and Heliomolar (Ivoclar Vivadent) which are Nano-hybrid and Micro-filled composite restorative materials respectively and have not been yet clinically evaluated together.

Material and methods

Patient selection

25 patients (14 females and 11 males) within the age group of 18-40 years, having either class I or class II cavities in posterior teeth indicated for composite restoration were selected randomly from the out patients coming to department (Table I).

Figure 1

TABLE I -NUMBER AND TYPE OF RESTORATIONS AT BASELINE

Written patient consent was obtained at the start of procedure. Their oral hygiene and condition of associated soft tissues needed to fall within the range of acceptability for patients of their particular age. No more than three teeth per patient were included in the study. Exclusion criteria were restorations requiring cuspal coverage, mental or severe handicap likely to prevent cooperation during the study, patient who could not be available for follow-up, patients with Para-functional habits (bruxism) and patients with high caries index.

Restorative materials

Operative procedure

A written patient consent was taken and the whole procedure of the study was explained to each participant. Information was also given regarding the possible risks and benefits of the composite resin restorations. Only those patients who were willing for the treatment and could be present for further follow-ups were selected.

Restorative procedure was undertaken by a single operator who followed standard procedures and manufactures recommendations. Adhesive preparation design with no margin beveling was performed for any restoration. The restorations could be classified as small to moderate (Table II).

Figure 2

TABLE II- SIZES OF RESTORATIONS

The operating field was isolated using rubber dam, cotton rolls and saliva ejector was used and the cavity preparation was done using tungsten carbide burs (#245 and #330), KG Sorensen). Deeper cavities were covered with calcium hydroxide (Dycal, Dentsply, Petropolis, RJ Brazil). All enamel and cavosurface margins were acid etched and coated with a bonding agent according to manufacturer’s recommendations.

Prior to restoring class II preparation a sectional matrix band (Composi-Tight sectional matrix system, Garrison Dental Solutions) was applied, contoured and firmly wedged to closely adapt the matrix to the gingival margin of preparation and to achieve a degree of tooth separation to facilitate the restoration of the contact area. Resin composites were inserted using an incremental technique. The increments were no more than 2mm. In case of a class II cavity first increment was placed in one corner of the proximal gingival floor. Light curing was done for 40 seconds (QHL75, Dentsply Asia, 575mW/cm ² intensity)

After completion of the restoration, finishing procedures were undertaken using fine diamond burs and multi-fluted carbide burs. Final polishing procedure were carried out with aluminum oxide discs (Sof-Lex Pop-on Discs, 3M Dental), coarse to fine to achieve a smooth surface.

Clinical evaluation

All the restoration were evaluated using United States Public Health Services (USPHS) or Ryge’s direct criteria (Table III) at baseline and there after at an interval of 1, 3 and 6 months. Each restoration was evaluated by two clinicians trained in the technique. In case of a disagreement decision was made by discussion and reevaluation of the restoration. Colored photographic records of each evaluation were taken at baseline and at 1, 3 and 6 months interval (Figure1-Figure 6).

Figure 3

COLORED PHOTOGRAPHIC RECORDS

Figure 4

Figure 5

TABLE III- RYGE’S DIRECT EVALUATION CRITERIA

Statistical analysis

Results

The restorations in this study were divided into four groups (Table IV). When the results (Table V and VI) obtained from this study were subjected to statistical analysis using Friedman test to evaluate the overall changes in the parameters for a period of six months, it was seen that, no statistical significance was found between group I and II in regard to any of the parameters tested, however clinically significant results were seen with regard to color match, cavosurface margin discoloration, and surface texture (Table VII).

Figure 6

TABLE IV- STUDY GROUPS

Figure 7

TABLE V- RESULTS FOR GROUP I AND GROUP II - CLASS I RESTORATIONS

Figure 8

TABLE VI-RESULTS OF GROUP III AND IV- CLASS II RESTORATIONS

Figure 9

TABLE VII- COMPARISON BETWEEN DIFFERENT PARAMETERS OF GROUP I AND GROUP II DURING THE 6 MONTH PERIOD USING FRIEDMAN TEST

In case of group III and IV no statistical significance was found in regard to any of parameters tested, however clinically significant results were obtained with regard to color match in group III and IV and with regard to cavosurface margin discoloration, marginal adaptation, anatomical form and surface texture in group IV(Table VIII) .

Figure 10

TABLE VIII- COMPARISON BETWEEN DIFFERENT PARAMETERS OF GROUP III AND GROUP IV DURING THE 6 MONTH PERIOD USING FRIEDMAN TEST

In general no statistically significant difference was found between the two materials for any of the parameters tested over a period of six months. None of the restorations were rated Charlie (C) or Delta (D) for any of the parameters during the 6 months evaluation period.

Discussion

Improvements in resin-based composite technology have increased the acceptance of this class of materials among dental professionals, particularly for restoring posterior teeth.

In the recent years, there has been emphasis on relatively short-term studies to provide an early prediction of long-term clinical performance ₆₇ . The complexity of some masticatory system variables like temperature changes, occlusal stress and pH alterations makes reproduction of oral physiology difficult. Therefore, only the clinical environment may be determinant in assessing dental materials or restorative techniques ₁₂ .

In the present study two posterior composites, Ceram-X Duo (Dentsply Detrey) and Heliomolar (Ivoclar Vivadent) were evaluated for their clinical performance over a period of six months using Ryge’s (USPHS) Direct Evaluation Criteria in class I and class II cavities.

Composite restoration quality was evaluated using a system of clinical parameters developed by Gunnar Ryge while working in United States Public Health Service in San Francisco and is known as the United States Public Health Services (USPHS) criteria or Ryge criteria or Direct evaluation criteria ₈ . Most of the existing information on posterior composite restoration performance is based on this system. Usually two examiners evaluate the restorations independently and then compare their scoring. If there are any discrepancies between the two examiners, the examiners evaluate the restoration a third time together and determine the score by consensus. The parameters included in the evaluation were chosen because they were considered the most important feature that a dentist would evaluate to establish his/her treatment plan. Call signs are used to delineate the score for each parameter. Alfa (A) indicate satisfactory-meets all standards, Bravo (B) indicate satisfactory–but needs observation at next visit, Charlie (C) indicate not satisfactory- needs replacement for prevention and Delta (D) indicate not satisfactory-needs replacement immediately ₉₁₀ .

During this study a 100% of recall rate was observed which was probably due to the short duration of study period that is 6 months.

Only small to moderate cavities were selected for this study ₁₁ . Adhesive preparation design with no margin beveling was performed for all the restoration ₁₃₁₄ . A “butt-joint,” clean-cut non-beveled preparation is preferred to a beveled cavosurface outline. A beveled preparation results in a thin marginal fin of composite material which could fracture, leaving a ledge –type defect in the marginal region. The resin composite was inserted using an incremental technique. The increments were no more than 2mm. This can help to achieve good marginal quality, prevent distortion of cavity wall (thus securing adhesion to dentin) and ensure complete polymerization of the resin- based composite. All the restorations were performed under rubber dam isolation.

The results of this study showed that no statistical significant difference existed between the two materials at 6 month evaluation period for any of the parameters evaluated in class I and class II restorations. However, incase of few parameters clinically significant results were observed. None of the restorations received Charlie (C) or Delta (D) ratings during the evaluation period.

Although Color matching ability of both the materials was found to be clinically acceptable, restorations restored with Ceram-X showed more consistent color matching over a period of 6 months. 100% of class I and 90% of class II restorations restored with Ceram-X received Alfa (A) rating after 6 months evaluation period. These results were similar to the one obtained by Schirrmeister JF, Huber K & Hellwig E, Hahn P ₁₅ . The reason could be firstly its double translucency shade system that allows for better color matching ability and secondly the presence of nano-hybrid filler particles, which impart greater translucency and polishability to the restoration.

Heliomolar also showed good results with 80% of class I and 77% of class II restorations remaining unchanged after 6 month evaluation period. Although these results were not statistically significant but were clinically significant. The sub-micron sized filler particle allows for greater polishability and capability to retain luster. The mismatch observed was slight and was clinically acceptable. To put this issue in better perspective, it is important to remember that all restorations were acceptable in terms of color match, and especially when compared with an amalgam restoration, theses restorations represent great esthetic improvement. Further, a slight mismatch in an area where esthetics is not crucial is viewed by many as an aid to future clinical evaluation.

With regard to cavosurface margin discoloration only one (10%) class I and one (10%) class II restoration restored with Heliomolar were rated Bravo (B). Microfill composites are prone to marginal breakdown leading to crevice formation or ditching ¹⁷ . This undesirable characteristic could reduce esthetics under some instances. For instance, in certain patients who are heavy smokers and coffee or tea drinkers, stains tend to accumulate along the edges of these defects. But in the present study the presence of cavosurface marginal discoloration around two restorations was attributed to the arrested caries that was not included in the cavity preparation at the time of restoration to preserve tooth structure, thus it would not be related to secondary caries or microleakage around the margin.

Both the materials have shown excellent results in term of marginal adaptation and anatomical form with only one (10%) class II restoration restored with Heliomolar receiving Bravo (B) rating for marginal adaptation and one (10%) class II restoration restored with Heliomolar receiving Bravo (B) for anatomical form after 6 month evaluation period. The tendency for the microfilled composite to form crevice at the tooth restoration interface has been attributed to lowered tensile fatigue strength of smaller filler particle ₁₁ . In the present study, the result regarding marginal adaptation could be a direct result of a fracture of slightly overlapping marginal excess.

Surface texture remained unchanged for restorations restored with Ceram-X with 100% of restorations receiving Alfa (A) rating after 6 months evaluation period. These results were in accordance to a study done by Schirrmeister JF, Huber K & Hellwig E, Hahn P ₁₅ . In case of Heliomolar also, results were very promising with only one (10%) class I and one (10%) class II restoration receiving a Bravo (B) rating after 6 months. The results were in accordance to the findings made by Collins & others, 1988 ₆ .

None of the restorations had any evidence of caries along the margin of the restorations, thus all were rated Alfa (A) at six month evaluation period. The clinical success obtained by the absence of secondary caries in this study was probably a result of the adequate restorative technique and good oral hygiene of the patients.

The general results of this clinical investigation showed a satisfactory performance for both the composite materials during a 6 month evaluation period. Although no statistically significant difference is found between the two materials for any of the parameters tested, it was seen that the initial 6 month period after placement of the restorations, does produce certain changes in the restorations that were clinically significant. Long term studies have to be undertaken to know the exact consequence of these changes.

Conclusion

Six months may seem too short a time in which judgments about a restorative material can be drawn. However it is believed that even at 6 months, clinical trials offer the profession meaningful information regarding the early changes in restorative materials that could predict its future performance. Under the parameters of this study, the two composite resins exhibited satisfactory clinical performance after 6 months of direct evaluation in class I and class II restorations. There was no significant difference found between these two materials for any clinical parameters evaluated. Nevertheless, the occurrence of even slightest of changes, despite lack of statistical relevance, is troubling. Long-term evaluation is needed to affirm the excellence of these materials for use in posterior teeth.