Packable composites: overview and technical considerations

Effect of light curing tip distance and resin shade on microhardness of a hybrid resin composite

Resin composite shades and resin composite polymerization performed with a distanced light tip are factors that can affect polymerization effectiveness. Thisin vitro study aimed to evaluate the influence of curing tip distance and resin shade on the microhardness of a hybrid resin composite (Z250 - 3M ESPE). Forty-five resin composite specimens were randomly prepared and divided into nine experimental groups (n = 5): three curing tip distances (2 mm, 4 mm, and 8 mm) and three resin shades (A1, A3.5, and C2). All samples were polymerized with a continuous output at 550 mW/cm². After 24 hours, Knoop microhardness measurements were obtained on the top and bottom surfaces of the sample, with a load of 25 grams for 10 seconds. Five indentations were performed on each surface of each sample. Results showed that bottom surface samples light-cured at 2 mm and 4 mm presented significantly higher hardness values than samples light-cured at 8 mm. The resin shade A1 presented higher hardness values and was statistically different from C2. The resin shade A3.5 did not present statistical differences from A1 and C2. For the top surface, there were no statistical differences among the curing tip distances. For all experimental conditions, the top surface showed higher hardness values than the bottom surface. It was concluded that light curing tip distance and resin shade are important factors to be considered for obtaining adequate polymerization.

Dynamic and static elastic moduli of packable and flowable composite resins and their development after initial photo curing

OBJECTIVE

The purpose of this study was to evaluate the dynamic (storage) shear modulus and the static shear modulus of elasticity of packable and flowable composite resins and to investigate their development after initial photo-curing.

METHODS

Three pairs of a packable versus a flowable composite and a microfill composite resin were tested (Alert/Flow It, Filtek P60/Filtek Flow, Admira/Admira Flow, A 110). Cylindrical specimens (0.85 mm x 18 mm) were made for each material. All specimens were conditioned and tested dry at 21 degrees C. The specimens were tested at 30 min, 24h and 1 week after the end of photo curing. Storage shear modulus and loss tangent were determined by conducting dynamic torsional loading in the frequency range from 1 to 150 Hz. Static shear modulus measurements were made by applying a constant load (below the proportional limit of the materials) for 10s and recording the angular deformation of the specimens. Data were analyzed by ANOVA and Duncan's Post hoc test (alpha=0.05).

RESULTS

Storage shear moduli (at 1 week measurement) ranged from 3.39 to 9.67 GPa, and loss tangents from 0.0735 to 0.0235; static shear moduli ranged between 2.66 and 9.80 GPa. High values of elastic moduli and low tandelta values were obtained with packable composites, while low moduli values were obtained with flowable composites. Statistically significant (alpha=0.05) differences were recorded between materials of the same category. Storage time, 24h and 1 week after initial polymerization, resulted in significant increases in both moduli of elasticity. Dynamic shear storage moduli were highly correlated to the static ones (r(2)=0.92; P<0.05).

SIGNIFICANCE

The results of the aging studies showed that the rigidity of these materials increases significantly even 1 week after the clinician turns off the curing unit.

Fatigue behavior of packable composites

The aim of this study was to investigate the flexural fatigue behavior of 11 packable composites. Of each material 30 rectangular samples (1.2 x 5 x 35 mm) for flexural fatigue test were prepared. The clamped fracture strength and flexural fatigue limit (FFL) of each material were determined using a custom-made fatigue machine, after storage of the samples for one month in water at 37 degrees C. All data were analyzed using one-way ANOVA and Bonferroni/Dunn's test for multiple comparisons (p<0.05). Regression analysis was used to evaluate the relationship between elastic modulus (Abe et al., 2001), clamped fracture strength or FFL and inorganic filler fraction (vol%). The fracture strengths of all but two materials were in between those of the compact-filled densified composites and the microfine ones. The FFL of the packable composites tested were significantly lower than those of the compact-filled densified composites. Three of the tested materials showed even significantly lower FFL than did the microfine composites. There were statistically significant relationships between both the elastic modulus and the volumetric filler fraction (R(2)=0.974, p=1.990 x 10(-7)). The great diversity in packable composites makes clinical assessment necessary with regard to a justified use in posterior teeth.

Does the wear resistance of packable composite equal that of dental amalgam?

BACKGROUND

There is little evidence that packable composites are sufficiently wear resistant to be used as an alternative to amalgam.

PURPOSE

The purpose of this study was to evaluate wear rates of packable composites compared with hybrid resin composites and amalgams by an in vitro wear test.

MATERIALS AND METHODS

The following composites were used: three packable composites (SureFil, Dentsply/Caulk, Milford, DE, USA; Alert, Pentron Clinical Technologies, Wallingford, CT, USA; and Solitaire, Heraeus Kulzer, Wehrheim, Germany), two hybrid resin composites (TPH Spectrum, Dentsply/Caulk; and Pyramid enamel, Bisco Inc., Schaumburg, IL, USA), and two amalgams (Tytin, Kerr Manufacturing Co., Romulus, MI, USA; and Dispersalloy, Dentsply/ Caulk). Cylindrical Class I cavities prepared on occlusally flattened, extracted human molars were restored with respective materials according to the manufacturers' instructions. Generalized, localized, and antagonistic enamel wear tests were carried out by a University of Alabama at Birmingham (UAB) wear simulator according to previously reported methods. Seven specimens were tested for each group, and the wear depths were measured on profilometric tracings. The data for each wear mode were independently analyzed by one-way analysis of variance and Fisher's exact test (p < or = .05).

RESULTS

The generalized wear values for SureFil (7.0 +/- 3.5 microm), Alert (8.6 +/- 1.8 microm), and Pyramid (3.9 +/- 0.5 microm) were not statistically different from those of amalgam materials (Tytin 5.8 +/- 0.7 microm, Dispersalloy 6.0 +/- 0.9 microm) but were different from those of Solitaire (23.9 +/- 2.6 microm) and TPH (30.6 +/- 5.5 microm). The localized wear values for SureFil (19.8 +/- 14.2 microm) and Alert (28.0 +/- 1.6 microm) were significantly smaller than for all other materials. For antagonistic enamel wear, Solitaire exhibited a minimal value (3.4 +/- 0.9 microm), whereas values of SureFil (12.6 +/- 5.6 microm) and Alert (12.0 +/- 6.6 microm) were not statistically different from those of TPH (11.0 +/- 4.0 microm) and amalgams (Tytin 14.5 +/- 4.3 microm, Dispersalloy 7.8 +/- 3.3 microm).

CONCLUSIONS

It can be concluded that SureFil and Alert packable composites possess similar wear resistance and abrasiveness to amalgam on the basis of the limitations of this study, which simulated 3 years of clinical wear.

Fracture resistance of class II packable composite restorations with and without flowable liners

This study evaluated fracture resistance in class II slot packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Thirty-six sound, caries-free human mandibulary molar teeth were used. Separate mesio-occlusal and disto-occlusal class II slot cavity preparations were made in each tooth. The prepared teeth were randomly divided into three groups of 12 teeth. Two packable composites (Surefil, Filtek P60) and one microhybrid composite (Filtek Z250) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The marginal ridges of the restorations were loaded at an angle of 13.5 degrees to the long-axis of the tooth in an Instron Testing Machine until failure. The data were analysed using a one-way anova. There was no significant difference in fracture resistance between composite restorations with and without flowable liners.

Dynamic mechanical analysis of viscoelastic functions in packable composite resins measured by torsional resonance

The objective of this study was to evaluate the viscoelastic functions of packable composite resins with the use of a resonant dynamic mechanical analysis technique in torsion. The materials tested were: Alert (Jeneric Pentron), Prodigy Condensable (Kerr Corporation), Surefil (Dentsply DeTrey), and Filtek P60 (3M Dental Products). Dynamic torsional loading was conducted in the frequency range from 1 to 150 Hz. Composite specimens were tested after storage in water at 37 degrees C for 24 h. One group was thermal cycled for 3000 cycles with temperatures of 5-37-50 degrees C. Measurements were taken at 21 degrees C dry, and at 37 and 50 degrees C wet. Storage modulus, loss tangent, and other viscoelastic parameters were determined from the amplitude/frequency curves. Data for storage modulus and loss tangent of the materials were analyzed by means of ANOVA and Student-Newman-Keuls test (alpha = 0.05). It was found that there were significant differences (P < 0.001) in storage modulus and loss tangent among the packable composites tested. The highest value of storage modulus, in measurements at 21 degrees C, was for Alert (10.3 GPa), followed by Filtek P60 (9.31 GPa), Surefil (7.29 GPa), and Prodigy Condensable (6.74 GPa). There were significant differences (P < 0.001) in storage modulus and loss tangent among the four different conditions tested. Storage modulus decreased at higher temperatures, whereas the loss tangent increased. Thermal cycling increased storage modulus and decreased loss tangent. The results showed that both monomer and filler composition and filler loading of the materials significantly affect their viscoelastic functions, and the mechanical properties of the products cannot be characterized from the packability alone.

Wear Resistance of Packable Resin Composites after Simulated Toothbrushing Test

PURPOSE

The purpose of this study was to determine the wear resistance of five different packable composites versus two different composite controls using a laboratory toothbrushing simulation test.

MATERIALS AND METHODS

Twelve samples measuring 5 mm in diameter and 3 mm thick were prepared from the following resin composites: Packable resin composites SureFil (Dentsply Ind. Com. Ltda, Petrópolis, Rio de Janeiro, Brazil), Alert (Jeneric Pentron Incorporated, Wallingford, CT, USA), Filtek P60 (3M ESPE Dental Products, St. Paul, MN, USA), Prodigy Condensable (sds Kerr, Orange CA, USA), Solitaire (Heraeus Kulzer GmbH, Wehrheim, Germany), and control resin composites Z100 Restorative (3M ESPE) and Silux Plus (3M ESPE). Finishing and polishing were conducted with Sof-Lex disks (3M ESPE), and baseline weight (grams) and surface roughness (measured with Hommel Tester T 1000, Hommelwerke, GmbH, Alte Tuttinger Strebe 20. D-7730 VS-Schwenningen, Germany) were recorded. Specimens were aged for 2 weeks until they reached a weight that remained constant for 5 consecutive days, and then were subjected to 100,000 cycles of brushing (representative of 4.2 yr) using a toothbrushing testing machine. Toothbrush heads with soft bristle tips (Colgate Classic, Colgate-Palmolive Co., Osasco, São Paulo, Brazil) with dentifrice suspension (Colgate MFP, Colgate-Palmolive Co.) in deionized water were used under a 200 g load. Changes in weight and surface roughness were determined after toothbrushing cycles.

RESULTS

Significant differences of weight loss and surface roughness were found (paired t-test, p < .05). Weight loss percentage (mean [SD]) ranged from 0.38 to 1.69% (analysis of variance and Tukey's least significant difference, p < .05); the weight loss of the materials ranked from least to most as follows: SureFil (0.38 [0.56]), Alert (0.52 [0.18]), Z100 (1.16 [0.27]), Filtek P60 (1.31 [0.17]), Solitaire (1.51 [0.45]), Prodigy Condensable (1.55 [0.471), and Silux Plus (1.69 [0.66]). Regarding surface roughness, Prodigy Condensable (0.19 [0.08]), Solitaire (0.28 [0.06]), and Z100 (0.30 [0.07]) became less rough after toothbrushing, whereas all the others were rendered rougher: Alert (0.49 [0.29]), Filtek P60 (0.28 [0.08]), Silux Plus (0.39 [0.091), and SureFil (0.81 [0.32]).

CONCLUSION

SureFil and Alert were statistically more resistant to wear (less weight loss) than were the other materials. SureFil became significantly rougher than did all the others.

CLINICAL SIGNIFICANCE

Overal, packable resin composites are unlikely to show superior wear resistance with regard to weight loss and surface roughness compared with current resin composites also indicated for posterior restorations.

Evaluation of performance of dental providers on posterior restorations: does experience matter? A data envelopment analysis (DEA) approach

The purpose of this study is to discern what factors affect the longevity of amalgam and of composite restorations by dentists who perform posterior restorations. Data are obtained from the Washington Dental Service and contain 1.5 million patient encounters representing visits to 23,000 providers from January 1993 through 31 December 1999. Analysis of provider performance is estimated through Data Envelopment Analysis. The principal finding is that the most efficient dentists produce posterior restorations that survive almost 5 months (4.6 months) longer than those by inefficient providers (chi2 = 18.98, p < 0.0001). The findings suggest that there is no difference in restoration longevity between amalgam and composite restorations when the restoration is performed by efficient provider.

Clinical evaluation of packable and conventional hybrid resin-based composites for posterior restorations in permanent teeth: results at 12 months

BACKGROUND

Packable resin-based composites and simplified resin bonding systems are marketed to offer many advantages over conventional posterior hybrid composites and total-etch bonding systems. The authors conducted a study to evaluate 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 resin-based 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 microm 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.

Surface Roughness of Packable Composite Resins Polished with Various Systems

PURPOSE

The aim of this study was to evaluate the surface roughness of four packable composite resins, SureFil (Dentsply, Petrópolis, Rio de Janeiro, Brazil), Prodigy Condensable (Kerr Co., Orange, CA, USA), Filtek P60 (3M do Brasil, São Paulo, Brazil), and ALERT (Jeneric/Pentron, Inc., Wallingford, CT, USA) and one microhybrid composite resin (Filtek Z250, 3M do Brasil) after polishing with four finishing systems.

MATERIALS AND METHODS

Twenty specimens were made of each material (5 mm in diameter and 4 mm high) and were analyzed with a profilometer (Perthometer S8P, Perthen, Mahr, Germany) to measure the mean surface roughness (Ra). The specimens were then divided into four groups according to the polishing system: group 1--Sof-Lex (3M do Brasil), group 2--Enhance (Dentsply), group 3--Composite Finishing Kit (KG Sorensen, Barueri, São Paulo, Brazil), and group 4--Jiffy Polisher Cups (Ultradent Products, Inc., South Jordan, UT, USA). The specimens were polished and then evaluated for Ra, and the data were subjected to analysis of variance, analysis of covariance, and Tukey's test (p = .05).

RESULTS

The mean Ra of SureFil polished with Sof-Lex was significantly lower than that of KG points. Prodigy Condensable polished with Enhance showed a significantly less rough surface than when polished with Sof-Lex. Filtek P60 did not exhibit a significant difference with the various polishing systems. For ALERT the lowest mean Ra was obtained with Sof-Lex and the highest mean Ra with KG points. Regarding Filtek Z250, polishing with KG and Jiffy points resulted in a significantly lower mean Ra than when polished with Enhance.

CONCLUSIONS

Packable composite resins display variable roughness depending on the polishing system used; the Sof-Lex disks and Jiffy points resulted in the best Ra values for the majority of the materials tested.

CLINICAL SIGNIFICANCE

The Sof-Lex disks and the Jiffy points produced the smoothest surfaces for the tested resin composites. As a result, they should be considered for clinical use as preferred polishing systems for these resin composites.

Direct Composite Resin Restorations: A Review of Some Clinical Procedures to Achieve Predictable Results in Posterior Teeth

The interest of patients in having tooth-colored restorations and the development of techniques and materials that make these restorations easier have contributed to make the esthetic restoration of posterior teeth popular. The direct use of composites in posterior teeth is a technique-sensitive procedure. Some difficulties, nevertheless, can be overcome or at least minimized by a heedful clinician by paying thorough attention to the various stages of the restorative technique. The present article seeks to review some concepts about this adhesive restorative procedure and to illustrate the possibilities of the technique with clinical reports.

CLINICAL SIGNIFICANCE

The direct posterior composite restorative technique offers the possibility of closely matching the natural optical characteristics of the lost tooth structure. Aimed at showing the potential of this technique, this article presents two step-by-step case reports and also reviews some concepts related to these clinical procedures.

Two-year clinical performance of a packable posterior composite with and without a flowable composite liner

The aim of the study was to evaluate the clinical performance of a packable fine hybrid dental composite (Prodigy Condensable) and the influence of the additional application of a flowable resin composite (Revolution, SDS Kerr) layer on marginal integrity after 2 years in stress-bearing posterior cavities according to the Ryge criteria. In 50 patients (40.5+/-17.5 years of age), 116 class II fillings (metal matrix system, glass ionomer-cement-base in 36%, rubberdam isolation in 70%) were placed, with at least two restorations per patient. The adhesive Optibond Solo Plus was used for all the restorations. In one of the two fillings in each patient, an additional layer of the flowable composite Revolution was applied in the entire cavity and separately light-cured. Baseline scores have been rated Alfa in > or =95% and Bravo in <5%. After 2 years, the results [%] of the Ryge evaluation for the two groups with/without the additional use of Revolution were: (1) Marginal Adaptation: Alfa:78/70, Bravo:16/27, Charlie:0/0, Delta:6/4; (2) Anatomic Form: Alfa:89/95, Bravo:6/2, Charlie:6/4; (3) Secondary Caries: Alfa:98/100, Bravo:2/0; (4) Marginal Discoloration: Alfa:76/68, Bravo:24/32, Charlie:0/0; (5) Surface: Alfa:90/91, Bravo:4/5, Charlie:0/0, Delta:6/4; (6) Color Match: Oscar:56/57, Alfa:44/39, Bravo:0/4, Charlie:0/0. Within the observation period (recall rate: 95%), three restorations out of 116 at baseline fractured, one restoration showed a secondary caries, one tooth received endodontic treatment, and all other restored teeth remained vital. After 2 years, no statistically significant difference (Chi-square test) in the overall survival rate between the group with the additional use of Revolution (92.8%) and that without Revolution (94.6%) was found. The combined survival rate for both groups together was 93.7% of clinically acceptable restorations.

Cytotoxic effects of packable and nonpackable dental composites

OBJECTIVE

Advanced dental packable and nonpackable composite materials have been recently introduced onto the market as 'amalgam alternatives' for the restoration of posterior teeth. Most established composites are applied in increments of no more than 2mm and light cured to ensure complete polymerization, whereas new formulations have been claimed to be suitable for application in increments of 4-5mm. The aims of the present study were to analyze the cytotoxicity of these new composites in comparison to an established nonpackable composite using standardized cell culture systems and to examine the influence of thickness of the light cured increments on the cytotoxicity of these materials.

METHODS

Specimens were prepared in polyethylene tubes covered with mylar. All materials were light cured in 2.5 or 5mm increments with a Demetron curing light (light intensity: 550 mW/cm(2)). Specimens were added to the cultures immediately after production or after preincubation for 1, 2, 7 days or 6 weeks under cell-culture conditions. Specimens were incubated with L-929 fibroblasts for 72 h and cell numbers determined by flow cytometry. In a different series of experiments, dopaminergic cells were incubated with composite supernatants.

RESULTS

Results with L-929 fibroblasts demonstrated that all freshly prepared composite materials reduced cell numbers (p<0.05) in comparison to controls. The cytotoxicity of all substances diminished after increasing preincubation times (p<0.0001). In a rank order of cytotoxicity, the established composite and two of the advanced composite materials exhibited least cytotoxicity, whereas the other advanced composites showed moderate or severe cytotoxic effects. The cytotoxicity of each material was much higher when polymerized in 5mm increments than in 2.5mm composite increments (p<0.0001).

SIGNIFICANCE

Our data demonstrate that the advanced composites tested show similar or more severe cytotoxicity than an established nonpackable composite and that cytotoxicity of all materials investigated increases when applied in a 5mm bulk increment.

Stickiness prior to setting of some light cured resin-composites

OBJECTIVES

To describe and evaluate a method for deriving a laboratory measure of stickiness, and to compare a set of dental resin-composites by this procedure.

MATERIALS AND METHODS

Twelve commercial resin composites were selected. Each material was placed in a cylindrical mold (phi=6.1 x 2.2 mm(2) depth) held either at 23 or at 37 degrees C. A flat-ended stainless-steel instrument was placed onto the surface of the unset sample with a force 350 g. After 2s it was moved vertically at 2 cm/s. This caused a sticky composite to be elevated to a maximum height between 0.2 and 1.8 mm until detachment from the instrument occurred. The elevated material was immediately solidified by light curing at 600 mW/cm(2) for 40s. These elevated profiles were mapped for both height and projected area of elevation. An instrument was constructed for this purpose in our laboratories. Both the projected heights and areas were evaluated as potential measures of stickiness. One-way ANOVA and Duncan's multiple range test were used for statistical analysis.

RESULTS

Projected heights ranged from 0.2 to 1.8 mm and projected areas of elevation ranged from 4.0 to 23.9 mm(2). The greatest values were found for microfine anterior composites (Silux plus, Filtek A110). There was a significant difference (p<0.05) between the material (SX) with the highest stickiness and all of the others. The set of profile height and area values were found to be strongly correlated (r(2)=0.9600).

SIGNIFICANCE

Once inserted and the load removed, the ideal material stays in place. This is generally assisted by an increase in viscosity and a decrease in stickiness. The stickiness test described is original and may prove to be useful as a standard test method for characterizing the handling stickiness of resin composite materials.

A novel filling technique for packable composite resin in Class II restorations

The use of composite resin restorations in posterior teeth has increased considerably in the past few years. Specific composite resins for posterior teeth, as well as new operative techniques, have been developed to overcome some clinical difficulties. The present article describes a new technique to reconstitute the interproximal contour and contact of Class II restorations using a packable composite resin. Two lower first molars from the same patient are reported in detail, illustrating the technique step by step. The technique indicates the use of a metallic matrix band and wood wedges to provide an interproximal contour and contact with the adjacent tooth as well as to provide an adequate cervical adaptation. The first increment of the packable composite resin is applied on the gingival wall of the proximal box, packed cervically near the axial wall and, automatically, the resin climbs up in contact with the inner surface of the matrix band. This increment is sculpted and light-cured and the metallic matrix band is removed. Thus, the Class II cavities are transformed into Class I, with free access for light-curing. Small incremental layers of composite fill the remaining cavities. This technique is faster than conventional techniques and permits appropriate embrasure, better contour, and contact points.

CLINICAL SIGNIFICANCE

Packable composite resins present primarily new handling characteristics that permit the development of novel filling techniques. The technique proposed in this article allows easier Class II buildup, with proper proximal contact and proximal smooth surfaces, once there are no irregularities among the composite increments. Another advantage is that there is adequate light exposure for polymerization, because the metal matrix can be removed during the restorative procedure.

An alternative method to reduce polymerization shrinkage in direct posterior composite restorations

BACKGROUND

Polymerization shrinkage is one of dental clinicians' main concerns when placing direct, posterior, resin-based composite restorations. Evolving improvements associated with resin-based composite materials, dental adhesives, filling techniques and light curing have improved their predictability, but shrinkage problems remain.

METHODS

The authors propose restoring enamel and dentin as two different substrates and describe new techniques for placing direct, posterior, resin-based composite restorations. These techniques use flowable and microhybrid resin-based composites that are polymerized with a progressive curing technique to restore dentin, as well as a microhybrid composite polymerized with a pulse-curing technique to restore enamel. Combined with an oblique, successive cusp buildup method, these techniques can minimize polymerization shrinkage greatly.

CONCLUSIONS

Selection and appropriate use of materials, better placement techniques and control polymerization shrinkage may result in more predictable and esthetic Class II resin-based composite restorations.

CLINICAL IMPLICATIONS

By using the techniques discussed by the authors, clinicians can reduce enamel microcracks and substantially improve the adaptation of resin-based composite to deep dentin. As a consequence, marginal discoloration, recurrent caries and postoperative sensitivity can be reduced, and longevity of these restorations potentially can be improved.

From vulcanite to vinyl, a history of resins in restorative dentistry

This article provides historical background on the development of resin-based dental restorative materials. With an understanding of the evolution of these materials, clinicians can better appreciate both the complexity of and similarities among the wide variety of resins and polymerization techniques available today. Common problems associated with the use of resin-based materials are explained, and more advanced resin-based systems currently under development are briefly reviewed.

Do condensable composites help to achieve better proximal contacts?

OBJECTIVES

Obtaining acceptable contact areas with adjacent teeth is a significant challenge when placing direct resin composite in Class II preparations. It was the purpose of this laboratory study to evaluate the influence of the type of resin composite ('packable' vs conventional) and of the matrix system on the quality of the proximal contact area in Class II composite restorations.

METHODS

A standardized DO cavity was prepared in 170 frasaco teeth. Two operators each filled 85 teeth in the same frasaco model using four resin composites [Solitaire (S), Surefil (Su), P60, Z100], three matrix systems [Automatrix (A), Palodent (P), Lucifix matrix (L)] and one hand instrument specially designed to achieve better proximal contacts [Belvedere Composite Contact Former (B)]. The teeth were subdivided into 17 groups (Z100/1-A, Z100/1-P, Z100/1-L, S-A, S-P, S-L, Z100/1-A-B, Z100/1-L-B, Su-A, Su-P, Su-L, P60-A, P60-P, P60-L, Z100/2-A, Z100/2-P, Z100/2-L). Each operator made five fillings of each group. The quality of the proximal contacts was assessed by measuring the maximum mesio-distal (M-D) diameter of the restored teeth using a digital micrometer and the tightness of the proximal contact area using standardized metal blades. All data were analyzed using two-way ANOVA and Bonferroni/Dunn's test for multiple comparisons with a significance level of P<0.05.

RESULTS

Regarding the matrix system, a significant larger M-D diameter and a stronger proximal contact area was achieved with the Palodent matrix system. The use of the Belvedere Composite Contact Former together with Lucifix matrix and Automatrix contributed to significantly stronger proximal contact areas. Concerning the type of resin composite, no significant differences were noted for both evaluation criteria when Palodent was used. Using Automatrix or Lucifix matrix, the more condensable resin composite P60 scored slightly better than Surefil and Z100. There was no operator effect. Both operators underwent a learning process. The longer they worked with a specific material/technique, the better proximal contacts they achieved.

SIGNIFICANCE

The best proximal contact areas in Class II composite restorations were obtained using a sectional matrix system. The 'packability' of the resin composite did not help to achieve better proximal contacts.

Dynamic elastic modulus of 'packable' composites

OBJECTIVE

A new type of so-called 'packable', 'condensable' or 'mouldable' composite has been developed and aims at replacing amalgam for posterior restorations. The purpose of the present investigation was to study the dynamic elastic modulus of 12 packable composites, and to follow the evolution of this property following prolonged water absorption.

METHODS

Of each material ten rectangular samples (1.5x5x35 mm) were prepared. The elastic modulus (GPa) of each sample was determined with a non-destructive dynamic method using a Grindo-Sonic after 24 h of dry storage at room temperature, and after 24h, 1, 3 and 6 months of wet storage at 37 degrees C. All data were analyzed using two-way ANOVA, Bonferroni/Dunn's test for multiple comparisons and paired t-test with a significance level of p<0.05. In addition, inorganic filler volume percentages were derived from the phenomenological model introduced by Braem et al. [11].

RESULTS

The studied materials varied widely in terms of elastic modulus, ranging between composites classified as Compact-Filled Densified (elastic modulus of 23.4+/-2.4 GPa) and as Microfine (elastic modulus of 8.5+/-2.1 GPa).

SIGNIFICANCE

The great diversity observed in the elastic modulus of this type of composites necessitates clear specifications with regard to 'first' the definition of marketing terms such as packable and so on, and 'second' the justified use in posterior teeth.

Posterior resin-based composite restorations: clinical recommendations for optimal success

Resin-based composites are increasingly used for the restoration of defects in posterior teeth. This review describes, illustrates and discusses important clinical aspects of the posterior composite technique. A relatively new stratification concept oriented to the development of functional and anatomic restorations is proposed.

Using packable composites for direct posterior placement

BACKGROUND

Although dentists have been using resin-based composites successfully to restore posterior teeth in Class II situations for several years, creating a functional, anatomical proximal contact remains a clinical challenge for many clinicians.

OVERVIEW

This article presents a step by-step technique for creating a predictable proximal contact using a packable resin-based composite as the restorative material. Using a technique that is similar to that for amalgam will enable the dentist to make a successful transition to using composite as an alternative to amalgam in some posterior teeth.

PRACTICE IMPLICATIONS

More patients today are well-informed about dental care and are seeking tooth-colored restorative alternatives. Excellent materials and proven techniques are making the transition from traditional metallic restorations easier and more predictable. With this article, the authors aim to help dentists gain confidence in their technique and enable them to provide this service for their patients.

Properties of packable dental composites

The introduction of many new packable composites suggests that these products are rapidly gaining popularity. The purpose of this study was to evaluate the in vitro properties of a variety of packable composites and to determine if significant enhancements in physical and mechanical properties have been achieved for these materials compared with two popular nonpackable posterior composites. For the five packable and two regular composites tested (ALERT, Pyramid-Dentin, Pyramid-Enamel, Solitaire, SureFil, Heliomolar, and Z100), the values for fracture toughness, flexure strength, flexure modulus, hardness, and volumetric polymerization shrinkage were determined. In general, although the packable composites were of heavier consistency, they had mechanical properties that were intermediate to (ALERT, Pyramid, and SureFil) or lower than (Solitaire) those of the nonpackable materials. These results could have been predicted based on the similar methacrylate resin chemistry and filler volumes of the various composites. No composite had adequate depth-of-cure when tested in increments greater than 2 mm thick. Polymerization contraction of the packable composites was similar to or higher than that of the nonpackable composites. In addition, the radiopacity of at least one material, Solitaire, was not considered to be adequate (less than 2 mm of aluminum). The results of this study suggest that these packable composites are unlikely to offer improved clinical performance over well-placed nonpackable composites.

Polymerization contraction stress in light-cured packable composite resins

OBJECTIVE

Determination of the polymerization contraction stress of packable composites (ALERT, Surefil, Solitaire, Solitaire 2) and a packable ORMOCER material (Definite) in comparison with a conventional hybrid composite (Tetric Ceram).

METHODS

Contraction force generated by the test materials (10 replications each) was measured by polymerizing the composites filled in a plastic tray between two aluminum attachments mounted in a Stress-Strain-Analyzer testing machine (specimen size: 4x4x2 mm, C-factor=0.33). Contraction force was recorded for 300s under a standard exposure condition (40s, 800mW/cm(2)). Maximum contraction stress (MPa), force rate (N/s), relative force rate (%/s) of each material were statistically analyzed by ANOVA (alpha=0.05) and post-hoc Tukey's test.

RESULTS

Maximum contraction stresses of the packable materials were 4.60 +/- 0.32MPa (ALERT), 4.16 +/- 0.18MPa (Definite), 3.36 +/- 0.08MPa (Solitaire 2), 3.33 +/- 0.23MPa (Solitaire) and 3.13 +/- 0.18MPa (Surefil), which were significantly higher than that of Tetric Ceram (2.51 +/- 0.14MPa). Tetric Ceram exhibited the significantly lowest force rate. Force/time curves were S-shaped. Solitaire especially showed a longer pre-gelation phase before contraction force was recorded.

SIGNIFICANCE

High contraction stress and rapid contraction force development can lead to failure of bond to tooth structure. This study suggested that, packable composite resins are less capable of reducing the contraction stress during the early setting stage, thus not superior in maintaining the bond with cavity walls to conventional hybrid composite Tetric Ceram.

Effects of flowable composite lining and operator experience on microleakage and internal voids in class II composite restorations

STATEMENT OF PROBLEM

When inexperienced clinicians perform class II composite restorations, improper placement techniques can lead to problems, including marginal adaptation and void formation.

PURPOSE

The aim of this study was to determine the influence of flowable composite linings on marginal microleakage and internal voids in class II composite restorations performed by practitioners with different levels of experience.

MATERIAL AND METHODS

Eighty extracted molars were prepared with mesial and distal class II cavity preparations and divided into 4 groups. Each group was restored separately with the following materials: Prodigy/Revolution lining (group I), Prodigy (group II), Tetric Ceram/Tetric Flow lining (group III), and Tetric Ceram (group IV). Each group was equally divided and restored by 2 practitioners, one experienced and another untrained in composite restorations. After restoration, all teeth were stored for 24 hours, thermocycled (at 5 degrees C to 60 degrees C) 1500 times, and soaked in 2% basic Fuchsin dye for 24 hours. After soaking, the teeth were sectioned, and gingival marginal microleakage and internal voids (at the gingival wall interface and in the cervical and the occlusal parts) were recorded. Data were analyzed with the Kruskal-Wallis test.

RESULTS

There was no significant reduction in microleakage for either practitioner. There were fewer interface voids within pairs with or without flowable composite linings made by the experienced practitioner (P<.05).

CONCLUSION

When flowable composite lining was placed at the gingival floor of a class II composite restoration by an experienced practitioner, voids in the restored interface were reduced. Gingival marginal sealing was not improved by the same technique.

The new posterior resins and a simplified placement technique

BACKGROUND

New heavy-body (packable) composites have been developed for use in posterior direct resin restorations. These materials are promoted as having better handling characteristics and higher physical properties than previous microhybrid composites.

METHODS

The authors describe an incremental layering technique that takes advantage of the improved handling characteristics and proposed reduced shrinkage and greater depth of cure.

CLINICAL IMPLICATIONS

When this new technique is used with one-bottle adhesives and improved instrumentation, posterior heavy-body composites can be placed faster, easier and possibly more predictably than when medium-body resins and previous techniques are used.