Degradation of resin-dentin bonds of etch-and-rinse adhesive system to primary and permanent teeth

Enhancing adhesive-dentin interface stability of primary teeth: From ethanol wet-bonding to plant-derived polyphenol application

OBJECTIVES

To investigate whether the adhesive-dentin interface stability of primary teeth would be enhanced by epigallocatechin-3-gallate (EGCG) with ethanol wet-bonding.

METHODS

Non-caries primary molars were sliced to achieve a flat dentin surface and etched then randomly distributed into five groups in accordance with different treatments: group 1, no treatment; group 2, applying absolute ethanol wet-bonding for 60 s; groups 3-5, applying 0.1%, 0.5%, and 1% (w/v) EGCG-incorporating ethanol wet-bonding (0.1%, 0.5%, and 1% EGCG) for 60 s. Singlebond universal adhesive was then applied followed by resin composite construction. Microtensile bond strength, fracture mode, and nanoleakage at adhesive-dentin interface were evaluated after 24 h of water storage or 10,000 times of thermocycling. Zymography of hybrid layer, biofilm formation of Streptococcus mutans by CLSM, FESEM, and MTT test, and cytotoxicity by CCK-8 assay were respectively assessed.

RESULTS

Irrespective of thermocycling, the dentin bond strength was preserved with reduced nanoleakage in the 0.5% and 1% EGCG groups. Furthermore, the activity of endogenous proteases and the growth of Streptococcus mutans biofilm were inhibited after treatment with 0.5% and 1% EGCG/ethanol solutions (groups 4 and 5). CCK-8 results of the 0.1% and 0.5% EGCG groups showed acceptable biocompatibility.

CONCLUSIONS

Treatment by EGCG/ethanol solutions effectively enhanced the bond stability of primary teeth at the adhesive-dentin interface.

CLINICAL SIGNIFICANCE

Synergistic application of EGCG and ethanol wet-bonding suggesting a promising strategy to improve dentin bonding durability with bacterial biofilm inhibition, thus increasing resin-based restorations' service life in primary dentition.

Long-term microtensile bond strength of self-etch adhesives and influence of 7-s phosphoric acid etching on adhesion of a 3-step etch-and-rinse adhesive to the dentine of primary teeth

BACKGROUND

The immediate microtensile bond strength (µTBS) of self-etch (SE) adhesives to primary dentine is promising, but evidence about the durability is scarce.

AIM

To assess the long-term µTBS of SE adhesives to primary dentine and to examine the effect of 7-s etching on µTBS of a 3-step etch-and-rinse (ER) adhesive.

DESIGN

The enamel of 115 caries-free human primary teeth was ground flat, and bonding was performed according to group assignment: G-aenial™ Bond/GC [GB], Clearfil™ SE Bond/Kuraray [CS], OptiBond™ XTR/Kerr [OX], Scotchbond™ Universal/3M™ [SU], Prime&Bond^® NT™/Dentsply [PB], and OptiBond™ FL/Kerr [OF]. After storage (24 h, 6 mos., 12 mos.), 1,762 beams were cut for µTBS testing. Fracture analysis was performed using light/fluorescence microscopy. Resin-dentine interfaces were exemplarily analyzed using SEM.

RESULTS

After 24 h, OX and SU showed significantly higher estimated mean µTBS than GB, which exhibited the lowest µTBS at all stages (p < .05). μTBS within each adhesive group showed slight variations over time (p > .05). OF_SE produced acceptable µTBS. Etching increased the mean immediate µTBS for OF (p > .05) and the percentage of cohesive fractures.

CONCLUSIONS

SE adhesives achieved durable μTBS to primary dentine. 7-s etching may improve the immediate µTBS of a 3-step ER adhesive.

Influence of 2% Chlorhexidine on the Bond Strength of Three Adhesive Systems on Primary Molars: An In Vitro Study

The hydrolysis of the collagen matrix by metalloproteinases (MMPs) is one of the paradigms that currently arouses most interest due to its close relationship with a decrease in bond strength (BS) and consequent restoration failure. Chlorhexidine 2% has demonstrated its ability to inhibit MMPs’ activity in the permanent dentition, improving the duration of resin–dentine, but there are few studies on deciduous dentition and its possible repercussions. Aim: To determine the influence of 2% chlorhexidine digluconate (CHX) as a dentine pretreatment on the BS of three adhesive systems on primary molars. Methods: 128 primary extracted molars were assigned to eight groups at random. BS in vitro was recorded by micropush-out test, and analyzed by two-way ANOVA. Results: BS values oscillated from 15.01 MPa to 20.41 MPa. There was no statistically relevant variation between the BS total mean of those adhesive groups that had received CHX pretreatment versus those that did not. Adper Prompt L-Pop was the self-etching adhesive with the best BS. Adper Scotchbond 1XT was the total-etch adhesive with the best BS values. Conclusions: Application of 2% chlorhexidine for 60 s as dentine pretreatment did not affect the immediate BS of several adhesive systems used in primary dentition.

Degradation of resin-dentine bond of different adhesive systems to primary and permanent dentine

AIM

To evaluate the water storage degradation of resin-dentine bonds of different adhesive systems to primary and permanent human dentine.

METHODS

Flat occlusal human dentine surfaces of 15 primary molars and 15 permanent molars were randomly assigned according to adhesive systems: Adper Single Bond 2; Clearfil SE Bond and One Up Bond F Plus. After bonding procedures, the adhesives were applied according to the manufacturers' instructions and composite resin blocks were built. Restored teeth were sectioned rendering rectangular sticks (RS) (0.4 mm²). The RS were submitted to microtensile bond strength (µTBS) test according to the water storage time: 24 h, 1-year, and 2-years. Mean µTBS values were analysed by three-way analysis of variance (mixed design) and Tukey post hoc test (α = 0.05). The failure mode was analysed at 400× magnification.

RESULTS

All three factors isolated showed significant influences on µTBS, as did the cross-product interactions between material vs. storage time (p = 0.01) and substrate vs. storage time (p = 0.002). Bond strength means to primary dentine were lower than to permanent dentine (34.7 ± 10.1 and 45.8 ± 12.9 mPa, respectively) after 2-years of water storage. The one-step self-etch adhesive (One Up Bond F Plus) showed less stable bond strength after 2-years of water storage.

CONCLUSION

The resin-dentine bond of primary teeth was more prone to degradation over time compared to permanent dentine.

Effect of composite/amalgam thickness on fracture resistance of maxillary premolar teeth, restored with combined amalgam-composite restorations

Background

Combined amalgam-composite restorations have been used through many years to benefit from the advantages of both dental amalgam and composite resin. Two variations have been mentioned for this technique, this study investigated the fracture resistance of maxillary premolar teeth with extended mesio-occluso-distal (MOD) cavities, restored with the two variations of combined amalgam-composite restorations.

Material and Methods

Sixty intact extracted premolar teeth were randomly divided into 6 groups (G1-G6) of 10 teeth. G1; consisted of intact teeth and G2; consisted of teeth with MOD preparations were assigned as the positive and negative control groups respectively. Other experimental groups after MOD preparations were as follows: G3, amalgam restoration; G4, composite restoration; G5 combined amalgam-composite restoration with amalgam placement only on 1mm of the gingival floor of the proximal boxes; G6, combined amalgam-composite restoration with amalgam placement to the height of contact area of the proximal surface of the tooth. Fracture strength of the specimens was measured and the data were analyzed using one-way analysis of variance (ANOVA). The level of significance was P<0.05. Fracture mode of the specimens was also recorded.

Results

G1 had the highest value of fracture resistance (1736.90 N). G2 and G3 had the lowest fracture resistance (775.70 N and 874.70 N, respectively). The difference between G 4, 5 and 6 was not statistically significant. However, G4, G5 and G6 showed significantly higher resistance to fracture compared to G2 and G3. Fracture modes were favorable in all of the study groups except in G6.

Conclusions

Fracture resistance of the premolars restored with the two variations of combined amalgam-composite restoration was similar to that achieved with composite restoration alone and more than that of amalgam restoration alone. It can be concluded that the thickness of amalgam in combined amalgam-composite restorations did not affect fracture resistance of the teeth.

Key words:Amalgam, composite, fracture resistance, restoration.