Clinical evaluation of packable and conventional hybrid resin-based composites for posterior restorations in permanent teeth

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COVER STORY

he use of posterior resin-based composites is increasing, despite their higher costs and shorter longevity in comparison with amalgam and gold.1,2 Packable or high-density posterior resin-based composites are marketed extensively as amalgam substitutes. Their handling properties are claimed to be similar to those of dental amalgam, in Both types of terms of allowing faster placement and composite tighter interproximal contacts with placed with a Class II restorations than are possible simplified with conventional posterior resin-based 3 bonding system composites. The physical properties of in posterior packable composites—such as wear resistance, surface hardness, fracture permanent toughness, and compressive, tensile and teeth showed flexural strengths—are comparable with satisfactory those of conventional resin-based comand similar posites.4-10 Overall, their polymerization 11,12 Thereresults after shrinkage also is comparable. fore, it has been assumed that a pack12 months. able composite (such as SureFil,

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KEVIN H.-K. YIP, B.D.S., M.Ed., M.Med.Sc., Ph.D.; BELINDA K.M. POON, B.D.S., B.Dent.Sc., M.D.S.; FREDERICK C.S. CHU, B.D.S.(Hons), M.Sc.; ERIC C.M. POON, B.D.S.; FIONA Y.C. KONG, B.D.S.; ROGER J. SMALES, M.D.S.(Hons), D.D.SC.

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Results at 12 months

Background. Packable resin-based composites and simplified resin bonding systems are marA D A J keted to offer many advan✷ ✷  tages over conventional posterior hybrid composites and total-etch bonding N C U U IN systems. The authors conG ED A 1 RT ducted a study to evaluate ICLE the initial clinical performances of a packable and a conventional hybrid resin-based composite used with a simplified bonding system. Methods. A total of 57 Class I and 45 Class II restorations were placed in the permanent teeth of 65 adult patients. The carious lesions were restored with either packable resin-based composite (SureFil, Dentsply DeTrey GmbH, Konstanz, Germany) or conventional hybrid resin-based composite (SpectrumTPH, Dentsply DeTrey GmbH), using a resin adhesive (Non-Rinse Conditioner and Prime & Bond NT, both manufactured by Dentsply DeTrey GmbH). The authors evaluated the restorations using U.S. Public Health Service-Ryge modified criteria (in which Alfa is the highest rating) and by using color transparencies and die stone replicas. Results. Three SureFil restorations failed before their baseline evaluation. There were no failures among the 78 SpectrumTPH restorations evaluated at 12 months. For both resinbased composites, Alfa ratings were 90 percent or higher for marginal discoloration, anatomical form, surface texture and surface staining. Lower percentages of restorations were rated Alfa for color match, marginal integrity and gingival health. Occasional mild postoperative sensitivity was reported for four SureFil restorations and one SpectrumTPH restoration. The mean occlusal wear rate was 38 micrometers for the larger SureFil restorations and 25 µm for the smaller SpectrumTPH restorations. Conclusions. The 12-month clinical performances of the two restorative materials were satisfactory and not significantly different for each of the parameters evaluated. Clinical Implications. A packable and a conventional hybrid resin-based composite placed with a simplified bonding system in posterior permanent teeth showed satisfactory and similar results after 12 months. CON

Clinical evaluation of packable and conventional hybrid resin-based composites for posterior restorations in permanent teeth

ABSTRACT

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TABLE 1

receiving care at The Prince Philip Dental HosRESTORATIVE MATERIALS USED IN THE STUDY. pital, Hong Kong. Each volunteer subject signed an MATERIAL COMPOSITION informed consent form Bis-GMA,† TEGDMA,‡ bis-EMA,§ barium fluoroalumiSureFil* before participating in the noborosilicate glass, fumed silica (filled 82 percent by weight, average size 0.8 micrometers), stabilizers, study. Approval for the photoinitiators clinical trial was obtained Bis-GMA, bis-EMA, TEGDMA, barium aluminosilicate Spectrum * from the ethics committee glass, fumed silica (filled 77 percent by weight, average of the hospital’s faculty of size 0.8 µm), stabilizers, photoinitiators dentistry. Itaconic and maleic acids, water Non-Rinse Conditioner * We required each subject UDMA,¶ PENTA,# R5-62-1 resin, T-resin, D-resin, silica Prime & Bond NT * to have no more than four nanofiller (particle diameter of 7 nanometers), cetylamine vital permanent premolars hydrofluoride, photoinitiators, stabilizers, acetone and/or molars with clini* Manufactured by Dentsply DeTrey GmbH, Konstanz, Germany. cally or radiographically † Bis-GMA: Bisphenol A glycidyl methacrylate. ‡ TEGDMA: Triethylene glycol dimethacrylate. detectable primary caries § Bis-EMA: Ethoxylated bisphenol-A dimethacrylate. that required restoration. ¶ UDMA: Urethane dimethacrylate. # PENTA: Dipentaerythritol penta acrylate monophosphate. The selected teeth had to have opposing teeth present. Otherwise, as in general practice, there Dentsply DeTrey GmbH, Konstanz, Germany) were no other constraints. Table 1 shows the comwill perform at least as well as a conventional ponents of the materials used; Table 2 shows the minifilled hybrid composite (such as SpectrumTPH, distribution of the subjects and of the restorations Dentsply DeTrey GmbH). placed and evaluated. One subject received four Prime & Bond NT, or PBNT, Dual Cure Adherestorations, 26 received two restorations each, sive (Dentsply DeTrey GmbH), is a self-priming and four subjects received three restorations resin adhesive that contains nanofillers approxieach. Thirty-four subjects received only one restomately 7 nanometers in diameter. The manufacration each. No subject received both restorative turer claims that it provides superior bond strengths to enamel and dentin when compared materials. with other current so-called fifth-generation Operative procedure. The dentists on the bonding agents.13,14 The associated use of a Nonresearch team (K.H.-K.Y., B.K.M.P., F.C.S.C.) Rinse Conditioner, or NRC (Dentsply DeTrey made the shade selection before the restorative GmbH), simplifies the restoration placement tech- procedure while the teeth were moist. With few nique. The reduction of treatment steps not only exceptions, all teeth were treated by one of the saves time, but also should result in less postopthree dentists under local anesthesia and isoerative sensitivity.15 In addition, the adhesive lated with rubber dam. Cavity preparation system appears to have adequate in vitro enamel involved conservative adhesive designs. For deep and dentin bond strengths for clinical success.16-20 cavities, the dentists placed a light-cured glass We undertook a study to compare the clinical ionomer cement liner (Fuji Lining LC, GC Corpoperformance of SureFil and SpectrumTPH when ration, Tokyo) under the restorations to protect used with the NRC and PBNT bonding system for the pulp. For Class II restorations, the dentists posterior restorations in permanent teeth. The used metal matrix bands (Tofflemire, Teledyne null hypothesis we were testing was that there Waterpik Technologies, Fort Collins, Colo.) and are no significant differences between the clinical wooden wedges. They removed excess water from performances of the two restorative materials the cavities with a soft airblow, leaving a moist when they are placed using a simplified bonding surface. system. In each case, the dentist applied NRC to the preparation surfaces for 20 seconds before SUBJECTS, MATERIALS AND METHODS removing excess liquid with a gentle air blow. He Subjects. We recruited 65 healthy adult subjects, or she then applied PBNT liberally and left it for 16 male and 49 female, with a mean age of 30 20 seconds before also removing excess solvent years (aged 18 to 66 years), from among patients with a gentle air blow. He or she checked the surTPH

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TABLE 2 faces to confirm that they were uniformly glossy before light curing them for NUMBERS OF SUBJECTS, WITH RESTORATIONS PLACED AND EVALUATED. 10 seconds. The dentist placed MATERIAL PERIOD SUBJECTS RESTORATIONS SureFil and SpectrumTPH Class I Class II Total sequentially in two separate groups of subjects. Initially, SureFil* Placement 38 29 33 62 he or she applied a thin Baseline 36 29 29 58 layer of composite to the 12 months 28 24 21 45 exposed dentin in the preparation and cured it for Spectrum * Placement 27 30 13 43 20 seconds while holding Baseline 25 28 12 40 any matrix band firmly 12 months 21 22 11 33 against the adjacent proximal tooth contact. Incre* Manufactured by Dentsply DeTrey GmbH, Konstanz, Germany. ments of 2 to 3 millimeters were cured for 40 seconds. After removing the matrix band, the dentist restorations are also satisfactory, although not directed additional curing toward the buccal and ideal, with a range of acceptability. Charlie restolingual embrasures. A standard halogen lightrations are not of acceptable quality and should curing unit (Spectrum 800, Dentsply Caulk, Milbe replaced or corrected for preventive reasons.) ford, Del.) was used for curing the resin adhesive Gingival bleeding adjacent to Class II restoraand the restorations. tions was recorded using World Health OrganizaThe dentists finished the restorations immedition plastic Community Periodontal Index ately after curing, using multifluted carbide finprobes.22 The assessors recorded this parameter ishing burs for contouring and removal of excess or factor as either absent or present, as they did restorative material. They achieved additional with restoration expansion and postoperative senrefinements by using finishing and polishing sitivity (both of which were determined by the points and discs (Enhance Finishing and Poltwo assessors who interviewed the subjects and ishing Points and Discs, Dentsply Caulk). A final by clinical examination). luster was achieved by applying polishing pastes Indirect evaluations. Either the dentists or (Prisma-Gloss or Prisma-Gloss Extrafine, the assessors took color transparencies at ×1.0 Dentsply Caulk). magnification of the carious teeth before treatDirect evaluations. Two clinical assessors ment, after restoration, at baseline and at 12 (E.C.M.P., F.Y.C.K.) evaluated the restorations months after restoration placement to confirm within two weeks of their placement at baseline any color mismatch and marginal or surface disand at the subsequent 12-month review. They coloration observed clinically. worked with the principal investigator (K.H.-K.Y.) Either the dentists or the assessors made an impression of each restored tooth with polyvinyl to establish evaluation criteria, and the principal siloxane impression material (Aquasil, Dentsply investigator trained them before the baseline Caulk) after cavity preparation, and after restoevaluation. All evaluations were carried out ration at baseline and at 12 months. Dental techunder a dental operating light, using frontnicians at The Prince Philip Dental Hospital, surfaced mouth mirrors and dental explorers. The Hong Kong, poured the impressions in a reinassessors directly evaluated restoration retention, forced stone, and the assessors then evaluated color match, marginal discoloration, marginal the replicas against a standard semiquantitative integrity, recurrent caries (cavitation or softness ivorine tooth model (Rheinberger, Ivoclarto probing), anatomical form, surface texture and Vivadent, Schaan, Lichtenstein) to estimate the surface staining according to United States Public restorations’ amount of occlusal wear. The cavoHealth Service, or USPHS, -Ryge modified crisurface margin showing the most severe wear or teria.21 (These criteria are as follows: Alfa restoramaterial loss determined the rating given for tions are of satisfactory quality and meet all clineach restoration. The assessors confirmed the ical standards with a range of excellence. Bravo TPH

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evaluations of interproximal contacts, marginal integrity and any expansion of the restorations from the stone replicas. They also measured the approximate dimensions of the cavity preparations from the stone replicas by using a graduated metal probe. They made measurements at the cavosurface margins for restoration width and length, and from the deepest region of the pulpal floor to the cavosurface margins for restoration depth. Statistical analysis. The assessors entered all data into a spreadsheet program (Excel Version 7.0, Microsoft, Redmond, Wash.). Another of the investigators (R.J.S.) analyzed the data using statistical software (Prism Package, Version 2.01, GraphPad, San Diego). He used the Fisher exact test and the Student t test to determine statistical differences between the two composites. We considered a probability value of P ≤ .05 to be statistically significant. The investigator calculated cumulative failures using the formula given in the American Dental Association Acceptance program guidelines for dentin and enamel adhesive materials.23 RESULTS

Twelve subjects who were seen at baseline did not return for the 12-month evaluation. These people accounted for restoration dropouts of 22 percent for SureFil and 18 percent for SpectrumTPH over 12 months. Table 2 shows the numbers of restorations that were available for evaluation. There was no significant difference between the two composites for restoration class numbers at 12 months (Fisher exact test, P = .24). Four molar teeth with large SureFil restorations placed in deep Class II preparations required further treatments before they were evaluated at baseline. Two restorations that failed because of bulk fracture were replaced by amalgam restorations in one subject, and one failed cracked restoration was replaced by a cast gold onlay in another subject. A third subject required endodontic therapy for one tooth in which the restoration originally was intact. Shortly after the baseline evaluations, two additional subjects each had one tooth with similar deep molar preparations and originally intact restorations that developed a need for endodontic therapy. The three intact SureFil restorations in teeth requiring endodontic therapy should be classified as apparent and not true restorative material 1584

failures, as the pulpal problems were not directly related to the resin-based composite material. The other three failed SureFil restorations that required replacements before their baseline evaluations resulted in a cumulative failure rate after 12 months of 6.3 percent. None of the SpectrumTPH restorations failed. The three failed Class II SureFil restorations had a mean ± standard deviation cavity volume of 254 ± 45 cubic millimeters with a cavity depth of 5.7 ± 1.8 mm, while the intact Class II restorations had a much smaller mean volume of 76 ± 23 mm3 with a depth of 4.0 ± 0.3 mm. By comparison, for SpectrumTPH, the intact Class II restorations had a mean cavity volume of 30 ± 7 mm3 with a depth of 3.6 ± 0.3 mm. Rating of the restoration parameters and factors. The assessors recorded only Alfa and Bravo ratings for the baseline and 12-month evaluations of the restoration parameters or factors (Figures 1 and 2). They gave no Charlie or unsatisfactory ratings (Table 3, page 1586). Color match. Initially, the assessors gave Alfa ratings to 97 percent of the SureFil and 92 percent of the SpectrumTPH restorations. At the 12month review, the Alfa ratings had decreased to 78 percent for the SureFil and 85 percent for the SpectrumTPH restorations. The assessors rated the color match for the other restorations as Bravo. Marginal discoloration. None of the restorations showed marginal discoloration at baseline. At the 12-month review, 91 percent of the SureFil and 90 percent of the SpectrumTPH restorations received Alfa ratings. Any staining present was minor and confined to short sections of the margins of the affected restorations. It was more readily detected from the color photographs. Marginal integrity. Many restorations had small marginal defects at the 12-month evaluation. The defects were related to minor deficiencies or fractured excesses of material, which may have been attributable partly to the finishing technique used during placement of the restorations. Alfa ratings had decreased at 12 months to 56 percent for the SureFil and 75 percent for the SpectrumTPH restorations. Anatomical form/occlusal wear. Only slight wear changes were detected by direct clinical examination at the 12-month review. Alfa ratings were 93 percent for the SureFil and 97 percent for the SpectrumTPH restorations. However, the net mean (SD) occlusal wear as measured from the stone replicas was 38.2 (10.1) micrometers for the

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SureFil and 24.9 (9.9) µm for the SpectrumTPH restorations, without statistical significance (t = 0.877, df = 25, P = .39). The mean ± SD occlusal surface area was 16.5 ± 4.1 square millimeters for the SureFil and 12.7 ± 2.9 mm2 for the SpectrumTPH restorations, without statistical significance (t = 0.662, df = 25, P = .51). This is equivalent to an occlusal wear rate of 2.3 µm/mm2 and 2.0 µm/mm2, respectively. The assessors noted no open proximal contact gaps from the stone replicas for either material. Surface texture and staining. Initially, almost all of the restorations exhibited a smooth surface comparable to the adjacent enamel. At the 12month review, Alfa ratings were 93 percent for the SureFil and 97 percent for the SpectrumTPH restorations. No restoration had observable surface staining. Expansion. For both materials, we detected no expansion of the restorations from baseline clinically or on the stone replicas at 12 months. Gingival bleeding. At the baseline evaluation, the assessors rated almost all of the gingival tissues adjacent to the Class II restorations as being healthy. However, at the 12-month evaluation, Alfa ratings for the absence of gingival bleeding to blunt probing had decreased to 57 percent for the SureFil and 91 percent for the SpectrumTPH restorations. The mean ± SD widths of the Class II cavity preparations, which probably reflected the widths of the proximal boxes, were 3.6 ± 0.3 mm for SureFil and 2.7 ± 0.2 mm for SpectrumTPH, which was of borderline significance (t = 1.882, df = 28, P = .06). Larger proximal restoration surfaces may offer larger areas for plaque retention and, consequently, increased gingivitis. Postoperative sensitivity. Initially, subjects reported tooth sensitivity for 7 percent of the SureFil and 3 percent of the SpectrumTPH restorations. At the 12-month evaluation, subjects reported some sensitivity for 9 percent of the SureFil and 3 percent of the SpectrumTPH restorations. The sensitivity was mild and only occasional in response to temperature changes. In two of the sensitive teeth restored with SureFil, the cavities were 6.0 mm and 6.5 mm deep. The mean ± SD depth of all the other cavities in affected teeth was 3.6 ± 0.7 mm. At 12 months, there were no statistically significant differences between the clinical performances of the two restorative materials for any of the parameters evaluated. Therefore, the null hypothesis was accepted.

Figure 1. SureFil (Dentsply DeTrey GmbH, Konstanz, Germany) disto-occlusal restoration in first premolar rated Alfa for color match and Bravo for marginal integrity and marginal discoloration at 12 months (using the United States Public Health Service-Ryge modified criteria21).

Figure 2. SureFil (Dentsply DeTrey GmbH, Konstanz, Germany) disto-occlusal restoration in first molar rated Alfa for marginal discoloration and Bravo for marginal integrity and color match at 12 months (using the United States Public Health Service-Ryge modified criteria21).

DISCUSSION

The two resin-based composite restorative materials evaluated in this study were used in combination with a simplified bonding system. Pretreatment of the cavity with NRC, which does not require rinsing after its application, followed by PBNT self-priming bonding resin, simplified the treatment procedure. While such a system is convenient to use, its effectiveness with packable com-

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TABLE 3

EVALUATION RESULTS FOR SUREFIL* AND SPECTRUM TPH* RESTORATIONS. PARAMETER

RATING

SUREFIL BASELINE

SPECTRUMTPH BASELINE

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%

No.

%

P VALUE†

SUREFIL 12-MONTH EVALUATION

SPECTRUMTPH 12-MONTH EVALUATION

No.

%

No.

%

P VALUE†

Retention

A‡ B¶

58 0

100 0

40 0

100 0

N/A§

45 0

100 0

33 0

100 0

N/A

Color Match

A B

56 2

97 3

37 3

92 8

0.40

35 10

78 22

28 5

85 15

0.56

Marginal Discoloration

A B

58 0

100 0

40 0

100 0

N/A

41 4

91 9

30 3

90 10

1.00

Marginal Integrity

A B

58 0

100 0

40 0

100 0

N/A

25 20

56 44

25 8

75 25

0.10

Recurrent Caries

A B

58 0

100 0

40 0

100 0

N/A

45 0

100 0

33 0

100 0

N/A

Anatomic Form/Wear

A B

58 0

100 0

40 0

100 0

N/A

42 3

93 7

32 1

97 3

0.63

Surface Texture

A B

58 0

100 0

39 1

97 3

0.41

42 2

93 7

32 1

97 3

1.00

Surface Staining

A B

58 0

100 0

40 0

100 0

N/A

45 0

100 0

33 0

100 0

N/A

Expansion

Absent Present

58 0

100 0

40 0

100 0

N/A

45 0

100 0

33 0

100 0

N/A

Gingival Bleeding (Class II)

Absent Present

29 0

100 0

10 2

84 16

0.08

12 9

57 43

10 1

91 9

0.11

Postoperative Sensitivity

Absent Present

54 4

93 7

39 1

97 3

0.65

41 4

91 9

32 1

97 3

0.39

* Manufactured by Dentsply DeTrey GmbH, Konstanz, Germany. † Fisher exact test. ‡ A: Alfa rating according to the U.S. Public Health Service-Ryge modified criteria.21 § N/A: Not applicable. ¶ B: Bravo rating according to the U.S. Public Health Service-Ryge modified criteria.21

posites has yet to be established. The marketing of packable or high-density composites as amalgam substitutes has included the advertising of similar handling properties and occlusal wear, the ability to displace nonsectional matrix bands for achieving tight proximal contacts, fast bulk placement and deep light-curing of the composites. However, several packable composites have given unsatisfactory short-term clinical performances.24 Several of the materials also have performed more poorly than expected in terms of packability, polymerization shrinkage, depth of light curing and displacement of matrix bands, together with greater-than-expected microleakage at margins placed in dentin.3,11,25,26 In addition, their range of shades is limited, they 1586

cannot be carved and their surfaces may be less smooth and may wear more than those of minifilled conventional hybrid composites.6,27 The failed SureFil restorations all were placed in large, deep molar cavity preparations, and the vital pulps of several teeth apparently had been compromised before their restoration. With hindsight, it may have been inappropriate to restore such teeth with a resin-based composite material, although the packable composites are being marketed extensively as amalgam substitutes, and although we first placed a glass ionomer cement as a base. Retention. According to a recent laboratory study, the use of NRC with PBNT produced a thinner hybrid layer and shorter resin tags in

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dentin than was found with phosphoric acid– that packable composites are less capable of conditioned dentin and PBNT.16 However, the reducing contraction stress during the early setNCR-PBNT combination has shown satisfactory ting stage than is a conventional hybrid resin in vitro enamel and dentin bond strengths,17,19,28 composite.34 In another study, the use of a although the highest bond strengths to enamel syringeable composite resulted in significantly were achieved with a combination of phosphoric better restoration adaptation and fewer voids acid etch and PBNT.17,29 than did a packable composite.35 Unsatisfactory Although we used a simplified cavitycavity sealing at the restoration-tooth interface conditioning method in this study—instead of can result in microleakage and, therefore, many either a separate phosphoric acid etching of researchers have recommended the use of flowenamel only, or the total-etch technique—the able liners with the high-viscosity packable combonding of the two restorative materials was sufposites to reduce microleakage at dentinal ficient to provide adequate retention over 12 margins.36-39 months. In our study, marginal defects were often Color match/surface texture and observed for both materials, but marginal discolstaining/gingival bleeding. Incorrect shade oration was minimal and infrequent. Many of the selection, together with a restrictive range of minor defects appeared to result from the fracture lighter shades for SureFil (A, B and C only), may of thin flashes of composite material extended have accounted for some initial misonto noninstrumented enamel surmatches. The dentists involved in faces adjacent to the cavity marthe study selected six shades of In our study, marginal gins. The use of phosphoric acid SpectrumTPH. One other study etching may reduce the occurrence defects were often reported some concerns after 12 of such defects, especially in highobserved for both months with the color matching and stress–bearing regions, because of materials, but surface texture of SpectrumTPH, but the improved enamel etching.16 marginal discoloration 30 not with SureFil. Another small One 12-month study, which used a was minimal and study noted some instances of surtotal-etch technique with Prime & face staining for SureFil after 12 infrequent. Bond 2.1 (Dentsply Caulk), months in subjects who smoked,31 reported 100 percent Alfa ratings and further instances of surface for the marginal integrity of Class staining were apparent after two II SureFil restorations.31 The rat32 years. We observed no surface staining in our ings remained unchanged after two years.32 study. Both restorative materials exhibited relaAnatomical form and occlusal wear. tively smooth surfaces after polishing, in comparSureFil has been advertised by the manufacturer ison with the adjacent enamel surfaces. Thereto offer “everything you demand of an amalgam” fore, the increased gingivitis observed with the and to “deliver amalgamlike wear rates.” HowClass II SureFil restorations may have been ever, such claims have not been substantiated by related to their larger sizes and, consequently, independent research,40 and amalgam has shown greater areas of plaque-retentive proximal lower in vitro wear rates.41 One study concluded surfaces. that “these new packable composites would not Marginal discoloration and integrity. offer improved clinical performance over current Marginal discoloration usually results from non-packable composites in terms of wear defects present between the tooth-colored restoraresistance.”4 tion and the cavity margins and walls. Defects After one and two years, another clinical study may be caused by inadequate restoration placeof SureFil found mean occlusal wear rates of 2.3 ment and finishing procedures, by unsatisfactory µm and 13.8 µm, respectively.31,32 In our 12-month bonding and by subsequent stress fatigue. Resinstudy, using the same semiquantitative Vivadent based composites shrink on polymerization and wear scale, SureFil’s mean occlusal wear was can generate high stresses at bonded surfaces in higher (38.2 µm), but the wear for SpectrumTPH 33 confined cavity preparations. According to the (24.9 µm) approximated that for another earlier manufacturer, the volumetric shrinkage for composite (Prisma TPH, Dentsply Caulk) SureFil is 2.2 percent and that for SpectrumTPH is (23.6 µm) in a similar study involving primary 2.5 percent.13,14 However, one study suggested molars.42 In these latter two studies, the cavosurJADA, Vol. 134, December 2003 Copyright ©2003 American Dental Association. All rights reserved.

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face margin showing the most severe wear determined the rating given for each restoration. A different rating method, which averaged the score for each restoration, was used in the former study.31,32 The semiquantitative Vivadent wear scale has been shown to achieve a higher level of agreement regarding restoration wear and more uniform scores among different evaluators than have other comparable methods.43 The stone replicas showed good proximal contacts for both resin-based composites, without any obviously superior results for high-viscosity materials such as SureFil.3,44 Postoperative sensitivity. Anecdotal and some limited clinical trial evidence suggests that postoperative sensitivity is reduced considerably when using self-etching bonding systems.15,45 In our study, although several restored teeth with initially deep carious lesions continued to show some occasional mild sensitivity after 12 months, the overall findings support the effectiveness of the NRC/PBNT bonding system. CONCLUSION

Our initial 12-month findings showed that the clinical performances of a packable resin-based composite, SureFil, and a conventional hybrid resin-based composite, SpectrumTPH, when used with a simplified bonding system, were satisfactory and not significantly different. Longer-term observations are required to monitor the performances of the two posterior composite materials and the bonding system used. ■ Dr. Yip is an associate professor in oral diagnosis, Faculty of Dentistry, The University of Hong Kong, The Prince Philip Dental Hospital, 34 Hospital Road, Hong Kong SAR, PR China, e-mail “Kevin.H.K. [email protected]”. Address reprint requests to Dr. Yip. Dr. Belinda Poon is an honorary assistant professor in conservative dentistry, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, PR China. Dr. Chu is an assistant professor in oral diagnosis, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, PR China. At the time this article was written, Dr. Eric Poon was a dental student, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, PR China. He is now working as a general dental practitioner, Howloon, Hong Kong SAR, PR China. At the time this article was written, Dr. Kong was a dental student, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, PR China. She is now working as a general dental practitioner, Howloon, Hong Kong SAR, PR China. Dr. Smales is a visiting research fellow, Dental School, The University of Adelaide, Adelaide, South Australia. The authors gratefully acknowledge financial assistance from the Committee of Research and Conference Grants, The University of Hong Kong (grant 10202573). This clinical trial was conducted independently

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