IADR Abstract Archives

Effect of Photoinitiator on Adhesive Resin Conversion and Dentin Bonding

Adequate degree of conversion (DC) of resin adhesives is critical to resin-dentin bond strength and clinical durability. Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) is a promising alternative photoinitiator compared to redox initiators based on camphorquinone for resin adhesives. Photoinitiator combinations may provide broader light absorptivity and more reactive radicals with the potential to enhance polymerization.

Objectives: Evaluate effect of five photoinitiator systems on DC and resin/composite-dentin shear bond strength (SBS).

Methods: DCs of hydrophilic (PMGDM/HEMA) and hydrophobic (BisGMA/TEGDMA) resins containing 5 photoinitiator systems; BAPO, BAPO/benzoyl peroxide (BAPO/BPO), camphorquinone/ethyl-4-dimethylaminobenzoate (CQ/4E), CQ/BAPO, and CQ/BPO were measured at 24-hour by FTIR using Near-infrared (NIR; 1.8mm-thick resins) for both resins and Mid-infrared (Mid-IR;25 micron-thick resins) for BisGMA/TEGDMA (n=5). 50 sound molars were randomly divided into 5 groups by photoinitiator system. All teeth were flattened and ground with #320-grit SiC papers to completely remove coronal enamel before application of a 3-step etch-and-water rinse, primer and bonding resin adhesive (35% phosphoric acid etchant, PMGDM/HEMA/50%acetone primers, and BisGMA/TEGDMA bonding resins) and a commercial resin-based composite (TPH3, Dentsply). SBS (knife-edge chisel-on-iris) was evaluated at 24-hour followed by fracture mode evaluation under a light microscope.

Results:

Photoinitiators	DC at 24h (%) by NIR		Mean SBS at 24h (MPa)
Photoinitiators	Bis-GMA/TEGDMA7:3 by mass	PMGDM/HEMA 3.3:1 by mass.	Mean SBS at 24h (MPa)
BAPO (1%)	81.37(±0.52)^A,a	76.58(±0.46)^B,b	35.31(±6.87)^A
BAPO (1%) BPO (1%)	81.97(±0.78)^A,a	79.20(±0.53)^A,b	35.58(±7.56)^A
CQ (0.25%) 4E (1%)	76.61(±1.08)^B,a	67.53(±0.55)^C,b	27.22(±9.04)^B
CQ (0.25%) BAPO (1%)	80.06(±1.84)^A,a	76.70(±1.61)^B,b	21.17(±5.92)^B
CQ (0.25%) BPO (1%)	74.35(±0.72)^C,a	58.68(±0.78)^D,b	14.28(±2.35)^C
Groups with same upper case letters within columns and same lower case letters within rows are not significantly different (p > 0.05).

NIR measured significantly higher DC of BisGMA/TEGDMA resin at 24-hour compared to Mid-IR; BAPO=59(±1.6)%, BAPO/BPO=61(±1.6)%, CQ/4E=54(±1.5)%, CQ/BAPO=62(±1.6)%, CQ/BPO=59(±0.5)%. No cohesive failures were observed. Groups with lower SBS had a higher percentage of joint failures; while groups with higher SBS had a higher percentage of mixed failure.

Conclusion: The use of BAPO alone and in combination with BPO and CQ increased DC of both hydrophobic and hydrophilic resins over resins containing CQ/4E. Only BAPO and BAPO/BPO demonstrated significantly higher SBS over resins containing CQ/4E. Supported by NIST, NIDCR Interagency agreement (Y1-DE-7005), ADAF PRC, and University of Iowa.

Division: IADR/AADR/CADR General Session
Meeting: 2011 IADR/AADR/CADR General Session (San Diego, California)
Location: San Diego, California
Year: 2011
Final Presentation ID: 1564
Abstract Category|Abstract Category(s): Dental Materials 1: Adhesion - Bond Strength Testing and Mechanisms

Authors

Talungchit, Supitcha ( University of Iowa, Iowa City, IA, USA )

Dickens, Sabine ( American Dental Association Foundation, Gaithersburg, MD, USA )

Schumacher, Gary E. ( American Dental Association Foundation, Gaithersburg, MD, USA )

Armstrong, Steven ( University of Iowa, Iowa City, IA, USA )

Jessop, Julie ( University of Iowa, Iowa City, IA, USA )

Qian, Fang ( University of Iowa, Iowa City, IA, USA )

Cobb, Deborah S. ( University of Iowa, Iowa City, IA, USA )

Geraldeli, Saulo ( University of Iowa, Iowa City, IA, USA )

Antonucci, Joseph M. ( National Institute of Standards and Technology, Gaithersburg, MD, USA )

SESSION INFORMATION

Oral Session
Durability of Adhesion to Dentin
03/18/2011