COSMETIC & RESTORATIVE CARE An alternative method to reduce polymerization shrinkage in direct posterior composite restorations

SIMONE DELIPERI, D.D.S.; DAVID N. BARDWELL, D.M.D., M.S.

Spreafico RC, Gagliani M. Composite resin restorations on posterior teeth. InAdhesion

The silent revolution in dentistry. Chicago: Quintessence; 2000:253-76.

Yoshikawa T, Sano H, Burrow MF, Tagami J, Pashley DH. Effects of dentin depth and cavity configuration on bond strength. J Dent Res 1999;78:898-905.

In three decades ago resine-based composite was..Wear resistanceMicro leakageSecondary cariesLack of appropriate proximal contact

In the past 10 years dramatic improvement in newer-generation bonding agents and resin-based composite formulations

Significantly improved wear resistancegood proximal contact and contourpolymerization shrinkage remains the biggest challenge

Polymerization shrinkage

formation of a gap between resin-based composite and the cavity wall1.67 to 5.68 percent of the total volume postoperative sensitivity and recurrent cariesbonding failure

Stress from polymerization shrinkage is influenc by

restorative technique modulus of resin elasticity polymerization rate cavity configuration or C-factor.

C-factor is

ratio between bonded and unbonded surfacesan increase in this ratio results in increased polymerization stress -Three-dimensional cavity preparations (Class I) have the highest (most unfavorable)

To minimize the stress from polymerization shrinkageimproving placement techniquesimproving material and composite formulationcuring methods

Placement techniques and issues.

The incremental techniqueDirect shrinkageBulk technique

The incremental technique

polymerizing with resin-based composite layers less than 2-millimeters thickachieve good marginal qualityprevent distortion of the cavity wallensure complete polymerization of the resin-based composite

Horizontal techniqueocclusogingival layering generally used for small restorationsincreases the C-factor.

Three-site techniqueclear matrix and reflective wedgesguide the polymerization vectors toward the gingival margin.

Oblique techniquewedge-shaped composite increments prevent distortion of cavity walls and reduce the C-factorpolymerization first through the cavity walls and then from the occlusal surfacedirect vectors of polymerization toward the adhesive surface (indirect polymerization technique)

Successive cusp buildup techniquethe first composite increment is applied to a single dentin surface without contacting the opposing cavity wallsAnd then wedge-shaped composite increments Each cusp then is built up separatelyto minimize the C-factor in 3-D cavity preparations

Figure 1. Schematic representation of wedge-shaped composite increments (1-6) used to build up the enamel proximal surface. F: Facial aspect. L: Lingual aspect.

Figure 2. Schematic representation of the flowable composite increment (1) and wedge-shaped increments (2-7) used to build up dentin;two increments (8 and 9) are used to build up enamel using the successive cusp buildup technique. F: Facial aspect. L: Lingual aspect.

Resin-based composite materials &Dentin-enamel adhesive systems

Resin-based composite materialsBy experimenting with particle size, shape and volume, manufacturers have introduced resin-based composites with differing physical and handling properties

microfill,hybridmicrohybridpackable flow-able

TABLE 1

RESIN-BASED COMPOSITE CLASSIFICATION AND PHYSICAL PRPERTIES.COMPOSITE TYPEAVERAGE PARTICLE SIZE(MICROMETERS)FILLER PERCENTAGE(VOLUME %)PHYSICAL PROPERTIESWear ResistanceFracture ToughnesspolishabilityMicrofill0.04-0.0135-50EFEHybrid1-370-77F-G+EGMicrohybrid0.4-0.856-66EEGPackable0.7-2048-65P-G+P-E+PFlowable0.04-144-54PPF-G+E: Excellent G: good F: fair P:poor+ Varying among the same type of resin-based composite

TABLE 2

CLINICAL INDICATIONS OF RESIN-BASED COMPOSITES.COMPOSITE TYPECLINICAL INDICATIONSMicrofillEnamel replacement in Class III, IV and V restorations Minimal correction of tooth form and localized discoloration

HybridPosterior resin-based composite restoration Class V restoration Dentin build-up in Class III and IV restoration

MicrohybridPosterior and anterior direct composite restoration Veneer Correction of tooth form and discoloration

PackablePosterior resin-based composite restoration

FlowablePit and fissure restoration Liner in Class I, II and V restoration (dentin)

Dentin-enamel adhesive systems Bonding to dentin introduced more recently and has improved over the years

contemporary DAS(dentin-enamel adhesive systems) around 22 Mpaearly bond strength to dentin ranged from 1 to 10 megapascals

..

Curing methods

soft-start polymerizationsoft-start polymerization (Miyazaki et al.)composite exhibited improved physical properties when cured at a low intensity and with slow polymerization vs. higher intensity and faster polymerization

initially uses low-intensity curing for a short period to provide sufficient network formation on the top composite surface delaying until the gel point final high-intensity polymerization

highly mineralized tissue (Enamel) resulting in a lower flexibility and decreased ability in relief of shrinkage stresshighC-factor restorations high-modulus compositestransmit more polymerization shrinkage forces to the tooth

TABLE 3

RECOMMENDED PHOTOCURING INTENSITIES AND TIMES FOR ENAMEL AND DENTIN BUILDUP.BUILDUP LOCATIONCOMPOSITE SHADE (PRODUCT NAME)*POLYMERIZATION TECHNIQUEINTENSITY MW/CM2)INTENSITY MW/CM2)Proximal EnamelPearl Smoke Pearl Neutral/Pearl Frost (Vitalescence)Pulse200 (300)3 (40)

DentinA2 (flowable, PermaFlo) A3.5-A3-A2-A1 (Vitalescence)Progressive curing(300)(40)Occlusal EnamelPearl Smoke/Pearl Neutral/Pearl Frost Trans Smoke/Trans Mist/Trans Frost (Vitalescence)Pulse200 (600)3 (10 occlusal], 10 [facial], 10 [palatal])

Vitalescence and PermaFlo are manufactured by Ultradent Products Inc., South Jordan, Utah. mW/cm2: Milliwatts per square centimeter. Intensity at first polymerization (intensity after waiting period). Photocuring time at first polymerization (time after waiting period).

Figure 3. Preoperative occlusal view of tooth no. 3.

Figure 4. Tooth no. 3 after a rubber dam was placed, caries was removed and the cavity preparation was completed with a gingival butt joint and no bevel either on the axial or occlusal surface

Figure 5. A matrix was placed to protect adjacent tooth structure during cavity preparation and etching. Then etching was performed using 35 percent phosphoric acid.

Figure 6. Enamels and dentins glossy appearances after application of a fifth-generation, 40 percent filled ethanol-based adhesive system.

Figure 7. A sectional matrix, plastic wedge and G-ring placed to reconstruct the proximal surface.

Figure 8. Tooth no. 3 after the enamel proximal surface was built up using the Pearl Neutral enamel shade of the microhybrid composite (Vitalescence, Ultradent Products Inc., South Jordan, Utah).

Figure 9. Tooth no. 3 after the sectional matrix, plastic wedge and G-ring were removed and the A2 shade of the flowable composite (PermaFlo, Ultradent Products Inc., South Jordan, Utah) was applied to a single dentin surface.

Figure 10. A and B. Tooth no. 3 after wedge-shaped composite increments of A3. 5, A3 and A2 shades of the microhybrid composite (PermaFlo, Ultradent Products Inc., South Jordan, Utah) were used to reconstruct dentin

Figure 11. Tooth no. 3 after Pearl Neutral enamel shade of the microhybrid composite (Vitalescence, Ultradent Products Inc., South Jordan, Utah) was used to build up the occlusal surface according to the successive cusp buildup technique.

Figure 12. Postoperative occlusal view of tooth no. 3.

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BeforeAfter

To minimize the stress from polymerization shrinkageimproving placement techniquesplacing successive layers of wedge-shaped composite(1- to 1.5-mm) to decrease the C-factor

To minimize the stress from polymerization shrinkageimproving material and composite formulationselect different composite materials to restore dentin (flowables and microhybrids) and enamel (microhybrids)

To minimize the stress from polymerization shrinkagecuring methodssoft-start polymerization

EXPERIMENTAL ARTICLE REVIEW

The suitability of packable resin-based composites for posterior restorations

Modulus of elasticityVickers hardnessDepth of cureScrapingProducing a hardness profile

TABLE 1

RESTORATIVE MATERIALS INVESTIGATED.*MATERIAL CATEGORYBRAND NAMESHADEFILLER VOLUME (%)FILLER WEIGHT (%)AVERAGE FILLER SIZE (m)MANUFACTURERPackable Resin-Based CompositeSolitaireA2090662.0 - 20Heraeus Kulzer, Wehrheim, GermanyDefiniteA261771.0Degussa AG, Hanau, GermanySureFilA266820.8Dentsply De Trey, Konstanz, GermanyAlertA270840.7 (glass fibers: 60 - 80)Jeneric/Pentron, Wallingford, Conn.Hybrid CompositeTetric CeramA260780.7Ivoclar Vivadent, Schaan, LiechtensteinIon-Releasing CompositeAriston pHcuniversal59791.3 (alkaline glass: 1.6)Ivoclar Vivadent, Schaan, Liechtenstein* Based on information from individual manufacturers. + micrometer.

TABLE 2

MEAN VALUES AND STANDARD DEVIATIONS.*COMPOSITE MATERIALELASTIC MODULUS (GPa)VICKERS HARDNESS (HV 0.2/40)CURING DEPTH (mm**)By Producing Hardness ProfileBy ScrapingSolitaire4.4 (0.3)a41.7 (3.5)a3.0 (0.2)c,d2.6 (0.2)a,bDefinite6.3 (0.9)b65.8 (1.6)c2.5 (0.0)a,b2.6 (0.3)a,bSureFil9.3 (0.9)c70.4 (9.0)c,d2.7 (0.3)b,c2.8 (0.3)bAlert12.5 (2.1)d75.2 (10.9)d3.5 (0.6)e3.5 (0.4)cTetric Ceram6.8 (0.5)b54.8 (1.1)b3.2 (0.3)d,e2.9 (0.2)bAriston pHc7.3 (0.8)b66.5 (2.6)c2.2 (0.3)a2.3 (0.3)a*Superscript letters indicate statistically homogeneous subsets (Tukey test, a = .05).Manufacturers are as follows: Solitaire, Heraeus Kulzer, Wehrheim, Germany; Definite, Degussa AG, Hanau, Germany; Surefil, Dentsply De Trey, Konstanz, Germany; Alert, Jeneric/Pentron; Tetric Ceram and Ariston pHc, Ivoclar Vivadent, Schaan, Liechtenstein.GPa: Gigapascal.HV: Vickers hardness.**mm: Millimeters.

Figure. Determination of curing depth of the tested materials by scraping vs. producing a hardness profile (r2 = 0.9945). mm: Millimeters. Manufacturers are as follows: Ariston pHc and Tetric Ceram, Ivoclar Vivadent, Schaan, Liechtenstein; Definite, Degussa AG, Hanau, Germany; Solitaire, Heraeus Kulzer, Wehrheim, Germany; SureFil, Dentsply De Trey, Konstanz, Germany; Alert, Jeneric/Pentron.

CONCLUSIONS

Packable composites that are promoted for the restoration of stress-bearing posterior carious lesions are quite different in their mechanical and physical properties