After two years, the clinical performances of three packable resin-based composites placed using different adhesive systems generally were considered satisfactory for the restoration of posterior teeth.^2–6 Clinical successes ranged from 93 to 100 percent, and few unsatisfactory restoration characteristics or parameters were observed. Only one of these studies did not involve the use of a separate phosphoric acid etchant as part of the adhesive procedure.⁵

Our study tests the null hypothesis that, after 3.5 years, there are no significant differences between the clinical performances of a packable resin-based composite and a conventional resin-based composite placed using a simplified self-etch resin-based adhesive system.

	SUBJECTS, MATERIALS AND METHODS

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
While we previously gave detailed descriptions about the subjects, materials and methods used in our study,¹ following are summary details.

Subjects and operative procedures. We recruited 65 healthy adult subjects from among patients receiving care at The Prince Philip Dental Hospital, Hong Kong. Each subject signed an informed consent form before participating in the study. We required each subject to have no more than four vital posterior teeth with primary caries needing restoration. In addition, the teeth had to have opposing tooth contacts.

Three dentists (including K.H.-K.Y.) placed either a packable hybrid resin-based composite (SureFil, Dentsply DeTrey GmbH, Konstanz, Germany) or a conventional hybrid resin-based composite (Spectrum^TPH, Dentsply DeTrey GmbH) in the teeth of each subject. None of the subjects received both materials. The dentists used Non-Rinse Conditioner (NRC) (Dentsply DeTrey GmbH) and Prime & Bond NT (PBNT) Dual Cure Adhesive (Dentsply DeTrey GmbH) with both restorative materials.

With few exceptions, the teeth were treated under local analgesia and isolated with a rubber dam. The dentists placed a light-cured glassionomer cement liner in deep cavities and used wedged metal matrices for Class II preparations. The dentists applied NRC and then PBNT adhesive to the preparations for 20 seconds each before gently removing excess liquid. Then they light-cured the PBNT for 10 seconds using a curing light. They incrementally added the resin-based composite materials, curing each 2- to 3-millimeter layer for 40 seconds, before using rotary finishing and polishing instruments, followed by polishing pastes to achieve a final luster.

Clinical evaluations. An independent assessor (E.C.M.P.) evaluated the restorations at the 3.5-year review. He directly evaluated restoration retention/fracture, recurrent caries, color match, marginal discoloration, marginal integrity, anatomical form/occlusal wear, surface texture and surface staining according to U.S. Public Health Service–Ryge modified criteria.⁷ These criteria are as follows:

– Alfa restorations are of satisfactory quality and meet all clinical standards with a range of excellence;

– Bravo restorations also are satisfactory, though not ideal, with a range of acceptability;

– Charlie restorations are not of acceptable quality and should be replaced or corrected for preventive reasons.

The assessor then evaluated the interproximal gingival bleeding adjacent to Class II restorations⁸ and postoperative tooth sensitivity as being either absent or present. He also procured clinical photographs and addition-cured silicone impressions for indirect evaluation of the restorations. He and a second independent assessor (R.J.S.) used the photographs to confirm any color mismatches and marginal or surface discolorations, as well as to measure the surface areas and proximal embrasure widths of the restorations by using an imaging analysis and software system. Die stone replicas were poured from the impressions, and the second independent assessor used them to confirm any marginal discrepancies and open interproximal contacts. He also used them to measure the surface wear of the restorations by using a standard semiquantitative ivorine tooth model. The cavosurface margin of the restoration showing the most severe wear or material loss determined the rating. The independent assessors also used die stone replicas of the cavity preparations to measure the approximate cavity depths from the deepest region of the pulpal floors to the cavosurface margins with a graduated metal probe.

Statistical analysis. One independent assessor (R.J.S.) analyzed the data using a statistical software package (Prism 2.01, GraphPad Software, San Diego). He used the Fisher exact test, Student t test, the nonparametric Mann-Whitney test and Kruskal-Wallis tests to determine clinical and dimensional differences between the two resin-based composites. He also calculated the cumulative survival rates for each resin-based composite.⁹ As a test of intraexaminer reliability, we redigitized 30 randomly selected color photographs and re-evaluated 30 randomly selected color photographs and 30 replicas. We used Cohen’s statistic to compare the original and duplicate evaluations.¹⁰ For all tests, we set the probability level for statistical significance at = .05.

	RESULTS

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Twelve subjects who were seen at baseline were not available at the one-year review, and 16 other subjects failed to attend the 3.5-year review. These people accounted for restoration dropouts of 50 percent for SureFil and 38 percent for Spectrum^TPH over 3.5 years (Table 1). However, we found no significant difference between the two resin-based composites in the distribution of Class I and II premolar and molar restoration numbers at any period (Fisher exact tests, P = .20-.99). We also found no significant differences between the two resin-based composites or for each resin-based composite in the occlusal surface areas of the restorations (Table 2).

Restoration failures. We show the results of the restoration evaluations in Table 3. Three large SureFil restorations placed in deep Class II molar preparations fractured just before their baseline evaluations, resulting in a cumulative failure rate of 6.3 percent after one year. None of the Spectrum^TPH restorations had failed by one year. Subsequently, three more Class II SureFil restorations failed, two from bulk fractures in a molar and a premolar, and one from recurrent marginal caries in a molar (Bravo ratings), resulting in a cumulative survival rate of 81.3 percent after 3.5 years. Two Class II Spectrum^TPH restorations also failed—one from bulk fracture in a molar and one from recurrent marginal caries in a premolar (Bravo ratings)—resulting in a cumulative survival rate of 92.0 percent after 3.5 years. The dimensions of the failed SureFil restorations generally were larger than those of the remaining intact SureFil restorations (P .08, Table 4). Although there was no significant difference between the two resin-based composites for occlusal surface area (P = .30), there were significant differences for cavity depth (P = .001) and, consequently, cavity volume (P = .04). We were unable to show any statistically significant dimensional differences between the two resin-based composites for either failed (P .86) or intact (P .16) restorations.

Color match. At baseline, the independent assessors gave Alfa ratings to 97 percent of the SureFil restorations and 92 percent of the Spectrum^TPH restorations. At the 3.5-year review, the Alfa ratings had decreased to 70 percent for the SureFil restorations and 79 percent for the Spectrum^TPH restorations. The restorations generally were lighter than the adjacent tooth structure (Figure 1).

View larger version (70K): [in this window] [in a new window]   Figure 1. The SureFil (Dentsply DeTrey GmbH, Konstanz, Germany) occlusal restoration in the second molar was rated Bravo (satisfactory, though not ideal, with a range of acceptability) for color match and surface staining and Alfa (satisfactory quality and meets all clinical standards with a range of excellence) for the other parameters at the 3.5-year review.

View larger version (80K): [in this window] [in a new window]   Figure 2. The SpectrumTPH (Dentsply DeTrey GmbH, Konstanz, Germany) occlusal restoration in the first molar was rated Bravo (satisfactory, though not ideal, with a range of acceptability) for marginal discoloration and Alfa (satisfactory quality and meets all clinical standards with a range of excellence) for the other parameters at the 3.5-year review.

Anatomical form/occlusal wear. Our direct clinical examinations detected only minor wear changes at the 3.5-year review, with Alfa ratings of 89 percent for the SureFil restorations and 79 percent for the Spectrum^TPH restorations. The net mean (± standard deviation [SD]) occlusal wear as measured from the die stone replicas was 28.9 (± 32.9) micrometers for the SureFil restorations and 33.8 (± 29.6) µm for the larger Spectrum^TPH restorations; this difference was not statistically significant (t₄₄ = .523, P = .60). This is equivalent to an annual wear rate of approximately 8 µm for SureFil restorations and 10 µm for Spectrum^TPH restorations. We noted no open proximal contact gaps for Class II restorations from the die stone replicas during the evaluations, and there were no instances of food impaction when we asked the subjects about it.

Surface texture and staining. At baseline, the independent assessors rated all restorations as Alfa, apart from one Spectrum^TPH restoration. At the 3.5-year review, they rated 89 percent of the SureFil restorations and 100 percent of the Spectrum^TPH restorations as Alfa for surface texture, while they rated 89 percent of the SureFil restorations and 96 percent of the Spectrum^TPH restorations as Alfa for surface staining. They were able to detect discrete areas of surface roughness and slight staining more readily using color photographs (Figure 1). In two instances, the small surface defects appeared to have been caused by dental instruments during finishing and polishing.

Gingival bleeding. At baseline, the independent assessors rated all but two Class II Spectrum^TPH restorations as being without adjacent gingival tissue bleeding after blunt probing. At the 3.5-year review, 69 percent of the SureFil Class II restorations and 71 percent of the Spectrum^TPH Class II restorations were without adjacent gingival tissue bleeding. The mean (± SD) widths of the Class II cavity preparations at the occlusal embrasures were 3.3 (± 0.2) mm for the SureFil restorations and 3.5 (± 0.3) mm for the Spectrum^TPH restorations; this difference was not statistically significant (t₁₄ = .624, P = .54).

Postoperative sensitivity. At baseline, subjects reported mild transient tooth sensitivity for 7 percent of the teeth restored with SureFil and 3 percent of the teeth restored with Spectrum^TPH. Subjects reported no sensitivity associated with the restored teeth at the 3.5-year review.

After 3.5 years, we found no statistically significant differences between the two resin-based composites for any of the clinical parameters evaluated (P .24). Therefore, the null hypothesis was not rejected.

	DISCUSSION

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
Twenty-eight of the 61 subjects seen at baseline did not attend the 3.5-year review. In two of these subjects, three failed SureFil restorations had been replaced just before baseline. Several other subjects had moved or we were unable to contact them, several were unable to arrange a convenient appointment time, and concerns about increased unemployment in Hong Kong prevented some subjects from taking nonessential time away from their workplaces.

Restoration failures. Failures occurred only in Class II cavity preparations and usually resulted from the bulk fracture of large molar restorations placed in deep preparations (Table 3). This situation was especially significant for the SureFil restorations (Table 4). We also detected secondary caries at the gingival margin in one instance for each resin-based composite. These failures resulted in cumulative survival rates of 81.3 percent for the SureFil restorations and 92.0 percent for the Spectrum^TPH restorations over 3.5 years. (If the three large SureFil Class II molar restorations that fractured just before baseline were not included in our calculation, then the cumulative survival rates for SureFil restorations would be 90 percent over 3.5 years).

One smaller three-year study of Class II pre-molar Spectrum^TPH restorations, in which 36 percent phosphoric acid total-etch and Prime & Bond 2.1 (Dentsply DeTrey) were used as the adhesive system, reported a 100 percent survival rate.¹²

We observed one Class II premolar Spectrum^TPH restoration with secondary caries in our study. Two two-year studies of Class I and II premolar and molar SureFil restorations, in which 34 percent phosphoric acid total-etch and Prime & Bond 2.1 were used as the adhesive system, reported survival rates of 100 percent² and 96 percent.⁶

Restoration parameter ratings. Color match/surface texture and surface staining/gingival bleeding. The limited choice of shades (A, B, C) available for SureFil precluded accurate shade matching in several instances, with the restorations usually being too light. This problem was reported in 38 percent of SureFil restorations in a two-year study.⁶ In our study, the greater range of shades available for Spectrum^TPH resulted in better shade matches. It was not possible, however, to distinguish clinically between the two resin-based composite materials from their shade matching and surface texture. The surface texture of all restorations was satisfactory, with discrete areas only of occasional surface roughness and staining evident for both resin-based composites. Other two-year studies of SureFil restorations also reported minimal surface roughness and slight staining that might have been related to smoking.^2,6 For the Class II restorations, the proximal surface textures and areas (as reflected by their occlusal embrasure widths) probably were similar for both resin-based composites, as similar percentages of SureFil restorations and Spectrum^TPH restorations were without adjacent gingival tissue bleeding after blunt probing (P = .99).

Marginal discoloration and marginal integrity. In our study, at the 3.5-year review, approximately 84 and 61 percent of all restorations received Alfa ratings for marginal discoloration and marginal integrity, respectively. Other two-year studies of SureFil restorations have reported Alfa ratings of 100 percent² and 90 percent⁶ for marginal discoloration and 91 percent² and 86 percent⁶ for marginal integrity. We were able to observe small discrete marginal discolorations and discrepancies more readily from the color photographs and replicas, respectively, than from the direct clinical examinations. In several instances, the occlusal discrepancies appeared to result from the fracture of thin flashes of resin-based composite material extended onto uninstrumented or unground enamel surfaces adjacent to the preparation margins. This also was reported in a related study, even though a 34 percent phosphoric acid etchant was used in it.⁶ However, the use of phosphoric acid etching^13–16 and aggressive self-etch adhesives¹⁷ instead of NRC with PBNT might reduce the incidence of small marginal discrepancies in high-stress regions.

Though subjects reported several instances of mild transient sensitivity for the resin-based composite–restored teeth at the one-year review, no one reported any sensitivity at the 3.5-year review.

Anatomical form/occlusal wear. We observed only minor occlusal wear changes at the 3.5-year review, with Alfa ratings of 89 percent for the SureFil restorations and 79 percent for the Spectrum^TPH restorations. A two-year study of SureFil restorations reported Alfa ratings of 96 percent for anatomical form.⁶ Another two-year study of SureFil restorations found a mean wear rate of 13.8 µm when using the same standard semiquantitative ivorine tooth model as we did in our study.² However, the authors averaged six cavosurface margin scores for each restoration to determine the score for each restoration,¹⁸ rather than selecting, as we did, the cavosurface margin showing the most severe wear. With net mean (± SD) wear rates of 28.9 µm (± 32.9) for the SureFil restorations and 33.8 µm (± 29.6) for the Spectrum^TPH restorations at the 3.5-year review, both resin-based composites appeared to meet the occlusal wear requirements of the ADA.⁹ However, the use of a semiquantitative ivorine tooth model will underestimate the actual amount of occlusal wear.¹⁹ Increased wear is to be expected for larger restorations, which probably is of more significance in our study than is the actual posterior resin-based composite restoration placed. The die stone replicas revealed no open Class II proximal restoration contacts for both resin-based composites, without any obviously superior results for the SureFil restorations.^20,21

Postoperative sensitivity. Anecdotal evidence suggests that postoperative sensitivity can be reduced considerably in general dental practice by using self-etch adhesives.²² However, the evidence from controlled clinical trials for this reduction is equivocal when it is compared with that for the use of total-etch adhesives.²³ Postoperative tooth sensitivity is attributed to many factors, and the correct application of the clinical technique chosen might be more relevant than the type of adhesive used.²³ In our study, though subjects reported several instances of mild transient sensitivity for the resin-based composite–restored teeth at the one-year review, no one reported any sensitivity at the 3.5-year review.

Packable or high-density resin-based composites and self-etch adhesive systems are marketed as improving and simplifying the clinical use of resin-based materials as amalgam alloy substitutes for posterior restorations. However, advertising claims and the expectations of dentists for these resin-based materials have been exaggerated, and they would appear to offer few advantages when compared with correctly handled older conventional posterior resin-based composites and total-etch adhesive systems.^{5,20,21,23–33}

	CONCLUSIONS

TOP ABSTRACT SUBJECTS, MATERIALS AND METHODS RESULTS DISCUSSION CONCLUSIONS REFERENCES

 
The 3.5-year findings from our study showed that a packable hybrid resin-based composite, SureFil, and a conventional hybrid resin-based composite, Spectrum^TPH, had satisfactory and similar clinical performances when used with a self-etch adhesive to restore Class I and moderate-sized Class II cavities. However, because of the increased risk of bulk fracture, the use of the two resin-based composites should be avoided in large intracoronal Class II molar cavity preparations.³⁴