COSMETIC & RESTORATIVE CAREAn 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 resistance• Micro leakage• Secondary caries• Lack of appropriate proximal

contact

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

formulations

• Significantly improved wear resistance• good proximal contact and contour• P olymerization shrinkage remains the bi

ggest challenge

Polymerization shrinkage • Def:

– formation of a gap between resin-based composite and the cavity wall

– 縮合體積量＝ 1.67 to 5.68 percent of the total volume

• Effect:– postoperative sensitivity and recurrent carie

s– bonding failure

Stress from polymerization shrinkage is influenc

by

• restorative technique• modulus of resin elasticity• polymerization rate• Cavity configuration or “C-factor.”

C-factor • ＝ bonded / unbonded

surfaces• an increase in this r

atio results in increased polymerization stress

-Three-dimensional cavity preparations (Class I) have the highest (most unfavorable)

To minimize the stress from polymerization shrinkage

(I)improving placement techniques(II)improving material and composite for

mulation(III) improving curing methods

Placement techniques and issues.

• The incremental technique• Direct shrinkage• Bulk technique

(I)The incremental technique

• polymerizing with resin-based composite layers less than 2-millimeters thick

• achieve good marginal quality• prevent distortion of the cavity wall• ensure complete polymerization of

the resin-based composite

• Horizontal technique– occlusogingival layering – generally used for small restorations– increases the C-factor.

• Three-site technique– clear matrix and reflective wedges– guide the polymerization vectors

toward the gingival margin.

• Oblique technique– wedge-shaped composite increments – prevent distortion of cavity walls and reduce

the C-factor– polymerization first through the cavity walls

and then from the occlusal surface– direct vectors of polymerization toward the

adhesive surface (indirect polymerization technique)

• Successive cusp buildup technique– the first composite increment is

applied to a single dentin surface without contacting the opposing cavity walls

– And then wedge-shaped composite increments

– Each cusp then is built up separately– to 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

(II)Resin-based composite materials

• By experimenting with particle size, shape and volume, manufacturers have introduced resin-based composites with differing physical and handling properties

– microfill,– hybrid– microhybrid– packable – flow-able

RESIN-BASED COMPOSITE CLASSIFICATION AND PHYSICAL PRPERTIES.

COMPOSITE TYPE

AVERAGE PARTICLE SIZE

(MICROMETERS ＝um)

FILLER PERCENTAGE(VOLUME %)

PHYSICAL PROPERTIES

Wear Resistance抗磨性

Fracture Toughness斷裂韌性

Polishability磨光性

Microfill 0.04-0.01 35-50 E F E

Hybrid 1-3 70-77 F-G+ E G

Microhybrid 0.4-0.8 56-66 E E G

Packable 0.7-20 48-65 P-G+ P-E+ P

Flowable 0.04-1 44-54 P P F-G+

E: Excellent G: good F: fair P:poor+ Varying among the same type of resin-based composite

TABLE 1

CLINICAL INDICATIONS OF RESIN-BASED COMPOSITES.

COMPOSITE TYPE CLINICAL INDICATIONS

Microfill Enamel replacement in Class III, IV and V restorationsMinimal correction of tooth form and localizeddiscoloration

Hybrid Posterior resin-based composite restorationClass V restorationDentin build-up in Class III and IV restoration

Microhybrid Posterior and anterior direct composite restorationVeneerCorrection of tooth form and discoloration

Packable Posterior resin-based composite restoration

Flowable Pit and fissure restorationLiner in Class I, II and V restoration (dentin)

TABLE 2

(II’)Dentin-enamel adhesive system

• Contemporary DAS(dentin-enamel adhesive systems) – around 22 Mpa– early bond strength to dentin ranged from 1 to 10

megapascals

……………..

(III)Curing methods

soft-start” polymerization

• “soft-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 stress

• high–C-factor restorations • high-modulus composites

– transmit more polymerization shrinkage forces to the tooth

RECOMMENDED PHOTOCURING INTENSITIES AND TIMES FOR ENAMEL AND DENTIN BUILDUP.

BUILDUP LOCATION

COMPOSITE SHADE (PRODUCT NAME)

POLYMERIZATION TECHNIQUE

INTENSITY MW/CM2†)‡

INTENSITY MW/CM2†)‡

Proximal Enamel

Pearl Smoke Pearl Neutral/Pearl Frost (Vitalescence)

Pulse 200 (300) 3 (40)

Dentin A2 (flowable, PermaFlo) A3.5-A3-A2-A1 (Vitalescence)

Progressive curing

(300) (40)

Occlusal Enamel

Pearl Smoke/Pearl Neutral/Pearl Frost Trans Smoke/Trans Mist/Trans Frost (Vitalescence)

Pulse 200 (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).

TABLE 3

Clinical Case

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. Enamel’s and dentin’s 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.

1 2

3 4

5 6

7 8

Before After

To minimize the stress from polymerization shrinkage

• improving placement techniques– placing successive layers of

wedge-shaped composite(1- to 1.5-mm) to decrease the C-factor

To minimize the stress from polymerization shrinkage

• improving material and composite formulation– select different composite materials t

o restore dentin (flowables and microhybrids) and enamel (microhybrids)

To minimize the stress from polymerization shrinkage

• curing methods– “soft-start” polymerization

EXPERIMENTAL ARTICLE REVIEW

The suitability of packable resin-based composites for posterior restorations

• Modulus of elasticity• Vickers hardness• Depth of cure

– Scraping– Producing a hardness profile

RESTORATIVE MATERIALS INVESTIGATED.MATERIAL CATEGORY

BRAND NAME

SHADE

FILLER VOLUME (%)

FILLER WEIGHT (%)

AVERAGE FILLER SIZE (µm)†

MANUFACTURER

Packable Resin-Based Composite

Solitaire

A20 90 66 2.0 - 20 Heraeus Kulzer, Wehrheim, Germany

Definite A2 61 77 1.0 Degussa AG, Hanau, Germany

SureFil A2 66 82 0.8 Dentsply De Trey, Konstanz, Germany

Alert A2 70 84 0.7 (glass fibers: 60 -

80)

Jeneric/Pentron, Wallingford, Conn.

Hybrid Composite

Tetric Ceram

A2 60 78 0.7 Ivoclar Vivadent, Schaan, Liechtenstein

Ion-Releasing Composite

Ariston pHc

universal 59 79 1.3 (alkaline

glass: 1.6)

Ivoclar Vivadent, Schaan, Liechtenstein

* Based on information from individual manufacturers.+ micrometer.

TABLE 1

MEAN VALUES AND STANDARD DEVIATIONS.COMPOSITE MATERIAL†

ELASTIC MODULUS (GPa)‡

VICKERS HARDNESS (HV§ 0.2/40)

CURING DEPTH (mm*)

By Producing Hardness Profile

By Scraping

Solitaire 4.4 (0.3)a 41.7 (3.5)a 3.0 (0.2)c,d 2.6 (0.2)a,b

Definite 6.3 (0.9)b 65.8 (1.6)c 2.5 (0.0)a,b 2.6 (0.3)a,b

SureFil 9.3 (0.9)c 70.4 (9.0)c,d 2.7 (0.3)b,c 2.8 (0.3)b

Alert 12.5 (2.1)d 75.2 (10.9)d 3.5 (0.6)e 3.5 (0.4)c

Tetric Ceram 6.8 (0.5)b 54.8 (1.1)b 3.2 (0.3)d,e 2.9 (0.2)b

Ariston pHc 7.3 (0.8)b 66.5 (2.6)c 2.2 (0.3)a 2.3 (0.3)a

*Superscript letters indicate statistically homogeneous subsets (Tukey test, = .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.

TABLE 2

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