Effectiveness of the addition of water-soluble photoinitiator into the self-etching primers on the adhesion of a resin composite to polished dentin and enamel

A review of the developments of self-etching primers and adhesives -Effects of acidic adhesive monomers and polymerization initiators on bonding to ground, smear layer-covered teeth

This paper reviews the developments of self-etching primers and adhesives, with a special focus on the effect of acidic adhesive monomers and polymerization initiators on bonding to ground, smear layer-covered teeth. Ionized acidic adhesive monomers chemically interact with tooth substrates and facilitate good bonding to ground dentin. Polymerization initiators in self-etching primers further promote effective bonding to ground dentin. To promote bonding to both dentin and enamel, phosphonic acid monomers such as 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) were developed. These novel adhesive monomers also have a water-soluble nature and are hence endowed with sufficient demineralization capability. A new single-bottle, self-etching, 2-hydroxyethyl methacrylate (HEMA)-free adhesive comprising 6-MHPA and 4-acryloyloxyethoxycarbonylphthalic acid (4-AET) was developed. This novel adhesive enabled strong adhesion to both ground enamel and dentin, but its formulation stability was influenced by pH value of the adhesive. To develop hydrolytically stable, single-bottle, self-etching adhesives, hydrolytically stable, radical-polymerizable acidic monomers with amide or ether linkages have been developed.

A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites

This paper reviews our recent studies on radical photopolymerization initiators, which are used in the design of light-curing dental adhesives and resin composites, by collating information of related studies from original scientific papers, reviews, and patent literature. The photopolymerization reactivities of acylphosphine oxide (APO) and bisacylphosphine oxide (BAPO) derivatives, and D,L-camphorquinone (CQ)/tertiary amine were investigated, and no significant differences in degree of conversion (DC) were found between BAPO and CQ/amine system (p>0.05). In addition, a novel 7,7-dimethyl-2,3-dioxobicyclo[2.2.1]heptane-1-carbonyldiphenyl phosphine oxide (DOHC-DPPO=CQ-APO) was synthesized and its ultraviolet and visible (UV-VIS) spectral behavior was investigated. CQ-APO possessed two maximum absorption wavelengths (λmax) at 350-500 nm [372 nm (from APO group) and 475 nm (from CQ moiety)], and CQ-APO-containing resins exhibited good photopolymerization reactivity, excellent color tone, relaxed operation time, and high mechanical strength. It was also found that a newly synthesized, water-soluble photoinitiator (APO-Na) improved adhesion to ground dentin.

Curing effectiveness of a light emitting diode on dentin bonding agents

This study tested the hypothesis that dentin bonding agents (DBAs) cured with a light emitting diode (LED) light curing unit (LCU) would not show a statistically significant different dentin shear bond strength (DSBS) relative to a halogen LCU, when the LED and halogen LCUs had a supposedly similar irradiance. Five commercial DBAs were tested: ScotchBond Multipurpose, Single Bond, One Step, Clearfil SE Bond, and Adper Prompt. The LCUs used in this study were a VIP (Bisco) for the halogen light and an Elipar FreeLight (3M ESPE) for the LED. First, the emission spectrum and spectral irradiance of both LCUs were investigated. Next, the DSBS of the DBAs cured with each LCU was measured. Two-way analysis of variance was used to analyze whether there were differences in DSBS resulting from the type of LCU and DBA used. The halogen LCU showed a higher total irradiance value relative to the LED LCU, but the difference of spectral irradiance was reduced in the efficient wavelength ranges for camphoroquinone activation. Although the DBAs cured with both types of LCUs showed similar DSBS values, Clearfil SE Bond showed the highest DSBS value when cured with a halogen light. Therefore, the null hypothesis of this study was rejected, indicating that the curing effectiveness of the LED LCU on some DBAs can be lower than that of a halogen LCU in terms of bond strength.

Curing Dental Resins and Composites by Photopolymerization

The development and continued evolution of photopolymerizable dental materials, particularly dental composite restoratives, represent a significant, practical advance for dentistry. The highly successful integration of the light-activated curing process for dental applications is described in this review. The basic mechanisms by which the photoinitiators efficiently convert monomers into polymers are discussed along with the variety of factors that influence the photopolymerization process. The conventional camphorquinone-amine visible light photoinitiator system used in most dental restorative materials is illustrated in addition to some alternative initiator systems that have been studied for dental materials applications.

CLINICAL SIGNIFICANCE

Photopolymerization has become an integral component of the practice of dentistry. A better appreciation of the photopolymerization process as well as its potential and limitations may aid the dentist in the delivery of both esthetic and restorative dental care.