The limited durability of resin-dentin bonds severely compromises the longevity of composite resin restorations. Resin-dentin bond degradation might occur via degradation of water-rich and resin sparse collagen matrices by host-derived matrix metalloproteinases (MMPs). This review article provides overview of current knowledge of the role of MMPs in dentin matrix degradation and four experimental strategies for extending the longevity of resin-dentin bonds. They include: (1) the use of broad-spectrum inhibitors of MMPs, (2) the use of cross-linking agents for silencing the activities of MMPs, (3) ethanol wet-bonding with hydrophobic resin, (4) biomimetic remineralization of water-filled collagen matrix. A combination of these strategies will be able to overcome the limitations in resin-dentin adhesion.

The aim of this study was to examine that thick dentin bonding agent application or low modulus composite restoration could reduce stresses on dentin bonding agent layer.

A mandibular first premolar with abfraction lesion was modeled by finite element method. The lesion was restored by different composite resins with variable dentin bonding agent thickness (50µm, 100µm, 150µm). 170N of occlusal loading was applied buccally or lingually. Von Mises stress on dentin bonding agent layer were measured.

When thickness of dentin bonding agent was increased von Mises stresses at dentin bonding agent were decreased in both composites. Lower elastic modulus composite restoration showed decreased von Mises stresses. On root dentin margin more stresses were generated than enamel margin.

For occlusal stress relief at dentin boning agent layer to applicate thick dentin bonding agent or to choose low elastic modulus composite is recommended.

The purpose of this study was to compare the effect of various dentin bonding systems on microtensile bond strength of immediate dentin sealing (IDS) and delayed dentin sealing (DDS). Eighteen extracted permanent molars were used in this study. The teeth for DDS group were restored with a provisional restorations, and immersed in saline solution for 1 week, and divided into 3 subgroups according to various dentin bonding adhesives; SB subgroup (3 step total-etch adhesive), SE subgroup (2 step self-etch adhesive), XE subgroup (1 step self-etch adhesive). In IDS group, the teeth were divided into 3 subgroups, and applied with bonding adhesives as in DDS group. The teeth were restored with provisional restorations, and immersed in saline solution for 1 week. Indirect composite disc was cemented with resin cement, and all specimens were subjected to microtensile bond strength. The data were statistically analyzed with one-way ANOVA and Student t-test.

The results were as follows:

The IDS group showed significantly higher µTBS than DDS group in 3 step total-etch and 2 step self-etch adhesive (p < 0.05).

This study was conducted to evaluate the influence of the C-factor on the bond strength of a 6th generation self-etching system by measuring the microtensile bond strength of four types of restorations classified by different C-factors with an identical depth of dentin.

Eighty human molars were divided into four experimental groups, each of which had a C-factor of 0.25, 2, 3 or 4. Each group was then further divided into four subgroups based on the adhesive and composite resin used. The adhesives used for this study were AQ Bond Plus (Sun Medical, Japan) and Xeno III (DENTSPLY, Germany). And composite resins used were Fantasista (Sun Medical, Japan) and Ceram-X mono (DENTSPLY, Germany).

The results were then analyzed using one-way ANOVA, a Tukey's test, and a Pearson's correlation test and were as follows.

There was no significant difference among C-factor groups with the exception of groups of Xeno III and Ceram-X mono (p < 0.05).

It was concluded that the C-factor of cavities does not have a significant effect on the microtensile bond strength of the restorations when cavities of the same depth of dentin are restored using composite resin in conjunction with the 6th generation self-etching system.

The objective of this study was to compare dentin shear bond strength (DSBS) of dentin bonding agents (DBAs) cured with a plasma arc (PAC) light curing unit (LCU) and those cured with a light emitting diode (LED) LCU. Optical properties were also analyzed for Elipar freelight 2 (3M ESPE); LED LCU, Apollo 95E (DMT Systems); PAC LCU and VIP Junior (Bisco); Halogen LCU. The DBAs used for DSBS test were Scotchbond Multipurpose (3M ESPE), Singlebond 2 (3M ESPE) and Clearfil SE Bond (Kuraray). After DSBS testing, fractured specimens were analyzed for failure modes with SEM.

The total irradiance and irradiance between 450 nm and 490 nm of the LCUs were different. LED LCU showed narrow spectral distribution around its peak at 462 nm whereas PAC and Halogen LCU showed a broad spectrum. There were no significant differences in mean shear bond strength among different LCUs (P > 0.05) but were significant differences among different DBAs (P < 0.001)

The fracture toughness test is believed as a clinically relevant method for assessing the fracture resistance of the dentinal restoratives. The objectives of this study were to measure the fracture toughness (K_1C) and microtensile bond strength of dentin-resin composite interface and compare their relationship for their use in evaluation of the integrity of the dentin-resin bond.

A minimum of six short-rod specimens for fracture toughness test and fifteen specimens for microtensile bond strength test was fabricated for each group of materials used. After all specimens storing for 24 hours in distilled water at 37℃, they were tensile-loaded with an EZ tester universal testing machin. Statistical analysis was performed using ANOVA and Tukey's test at the 95% confidence level, Pearson's coefficient was used to verify the correlation between the mean of fracture toughness and microtensile bond strength. FE-SEM was employed on fractured surface to describe the crack propagation.

Fracture toughness value of Clearfil SE Bond (SE) was the highest, followed by Adper Single Bond 2 (SB), OptiBond Solo (OB), ONE-STEP PLUS (OS), ScotchBond Multi-purpose (SM) and there was significant difference between SE and other 4 groups (p < 0.05). There were, however, no significant difference among SB, OB, OS, SM (p > 0.05). Microtensile bond strength of SE was the highest, followed by SB, OB, SM, OS and OS only showed significant lower value (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. FE-SEM examination revealed that dentin bonding agent showed different film thickness and different failure pattern according to the film thickness.

From the limited results of this study, it was noted that there was statistically no correlation between K1C and µTBS. We can conclude that for obtaining the reliability of bond strength test of dentin bonding agent, we must pay more attention to the test procedure and its profound scrutiny.

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration.

Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then Ca(OH)₂ and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at 36.5℃ for experiment period (7 days, 30 days). After removing IRM and Ca(OH)₂, each dentin adhesives were treated on dentin surfaces.

Composite resin (Z-250, 3M) was placed with 5 mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into 1.0 × 1.0 mm² cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and µTBS test was performed. SEM analysis was performed to examine the fractured surfaces.

The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.

To evaluate the effect of vital tooth bleaching agent and alcohol pretreatment on dentin bonding, flat dentin windows were produced on the buccal side of the crowns of fifty-five extracted, human premolars. A bleaching gel, Opalescence® with 10% of carbamide peroxide (Ultradent Product, USA) was daily applied on the teeth of three experimental groups for six hours for 10 consecutive days, while teeth of a control group were not bleached. After 6 hours of bleaching gel application, the specimens were washed and stored in saline until the next day application. After application of One-step® dentin bonding agent (Bisco, USA), Z-250® resin (3M-ESPE, USA) was bonded to dentin with a mount jig. Shear bond strength was measured with an Instron machine (Type 4202, Instron Corp., USA) after 24 hours. The results were analyzed using one-way ANOVA and Duncan's multiple range test at p < 0.05.

Immediate bonding group showed significantly lower bond strength than un-bleached control group (p < 0.05).

Ethanol-treated group showed significantly higher bond strength compared to immediate bonding group (p < 0.05). However, the bond strength of the ethanol treatment group was lower than that of the un-bleached control group (p < 0.05).

There were no significant difference in shear bond strength between the 2-week delayed bonding group and the ethanol-treated group (p > 0.05) and between delayed bonding group and un-bleached control group (p > 0.05).

In the condition of the present study, it seems that alcohol pretreatment after bleaching procedure can reduce the adverse effect of vital bleaching agent on dentin bonding.

This study compared the dentin shear bond strengths of currently used dentin bonding agents that were irradiated with an LED (Elipar FreeLight, 3M-ESPE) and a halogen light (VIP, BISCO). The optical characteristics of two light curing units were evaluated. Extracted human third molars were prepared to expose the occlusal dentin and the bonding procedures were performed under the irradiation with each light curing unit. The dentin bonding agents used in this study were Scotchbond Multipurpose (3M ESPE), Single Bond (3M ESPE), One-Step (Bisco), Clearfil SE bond (Kuraray), and Adper Prompt (3M ESPE). The shear test was performed by employing the design of a chisel-on-iris supported with a Teflon wall. The fractured dentin surface was observed with SEM to determine the failure mode.

The spectral appearance of the LED light curing unit was different from that of the halogen light curing unit in terms of maximum peak and distribution. The LED LCU (maximum peak in 465 ㎚) shows a narrower spectral distribution than the halogen LCU (maximum peak in 487 ㎚). With the exception of the Clearfil SE bond (P < 0.05), each 4 dentin bonding agents showed no significant difference between the halogen light-cured group and the LED light-cured group in the mean shear bond strength (P > 0.05).

The results can be explained by the strong correlation between the absorption spectrum of cam-phoroquinone and the narrow emission spectrum of LED.

The purpose of this study was to evaluate the penetration pattern of dentin adhesives according to the orientation of dentinal tubules with confocal laser scanning microscopy. Specimens having perpendicular, parallel and oblique surface to dentinal tubules were fabricated. The primer of dentin adhesives (ALL BOND® 2, CLEARFIL™ SE BOND and PQ1) was mixed with fluorescent material, rhodamine B isothiocyanate (Aldrich Chem. CO., Milw., USA). It was applied to the specimens according to the instructions of manufactures. The specimens were covered with composite resin (Estelite, shade A2) and then cut to a thickness of 500 µm with low speed saw (Isomet™, Buehler, USA). The adhesive pattern of dentin adhesives were observed by fluorescence image using confocal laser scanning microscopy.

The results were as follows.

For the groups with tubules perpendicular to bonded surface, funnel shape of resin tag was observed in all specimen. However, resin tags were more prominent in phosphoric acid etching system (ALL BOND® 2 and PQ1) than self etching system (CLEARFIL™ SE BOND).

The objectiveness of this study was to evaluate whether low-viscosity composite can bond effectively to dentin surface without bonding resin. The low-viscosity composites being 50wt% filler content were made by the inclusion of bonding resin of two self-etching systems(Clearfil SE Bond, Unifil Bond) varied with contents as 0, 10, 20, 30, 40, 50wt%.

Exposed dentin surfaces of extracted 3rd molars are used. Dentin bond strengths were measured. The tests were carried out with a micro-shear device placed testing machine at a CHS of 1mm/min after a low-viscosity composite was filled into an iris cut from micro tygon tubing with internal diameter approximately 0.8mm and height of 1.0mm.

Flexural strength and modulus was increased with the addition of bonding resin.

Low viscosity composite including some functional monomer may be used as dentin bonding resin without an intermediary bonding agent. It makes a simplified bonding procedure and foresees the possibility of self-adhesive restorative material.