The effect of resin cement type and cleaning method on the shear bond strength of resin cements for recementing restorations

Effect of Dentin Contamination with Hemostatic Agents and Cleaning Techniques on Bonding with Self-Adhesive Resin Cement

BACKGROUND Dentin contamination with hemostatic agents before bonding indirect restorations negatively affects the bond strength. However, the consensus on which materials could be used to clean contamination of hemostatic agents has not been explored. The aim of this study was to assess the effect of Katana Cleaner applied on the surface of dentin contaminated with hemostatic agents on the shear bond strength (SBS) of self-adhesive resin cement by comparing it with three other surface cleaners. MATERIAL AND METHODS Ninety dentin specimens were divided into a no contamination group (control) (n=10), 4 groups contaminated with 25% aluminum chloride (Viscostat Clear) (n=40), and 4 groups contaminated with 20% ferric sulfate (Viscostat) (n=40). Subsequently, 4 different cleaners were used for each contamination group (water rinse, phosphoric acid, chlorhexidine, and Katana Cleaner). Then, self-adhesive resin cement was directly bonded to the treated surfaces. All specimens were subjected to 5000 thermal cycles of artificial aging. The shear bond strength was measured using a universal testing machine. RESULTS Two-way analysis of variance showed that the contaminant type as the main factor was statistically non-significant (p=0.655), cleaner type as the main factor was highly significant (p<0.001), and interaction between the contaminant and cleaner was non-significant (p=0.51). The cleaner type was the main factor influencing the bond strength. Phosphoric acid and chlorhexidine showed better performance than Katana Cleaner. CONCLUSIONS Cleaning dentin surface contamination with phosphoric acid and chlorhexidine had better performance than with Katana Cleaner.

Evaluation and Comparison of Two Different Cleaning Procedures on Mechanical Properties for Recemented Restoration Using Two Conventional Glass Ionomer Cement Types: An In Vitro Study

Background In modern dentistry, fixed dental prostheses are often the preferred and the most complex treatment procedures. However, the success of these procedures depends to a great extent on the durability and consistency of the ongoing reconstruction. This paper aimed to compare the shear bond characteristics of conventional glass ionomer cement types, namely, Vivaglass luting cement and GC fuji 1 cement, after being subjected to two different dentin-cleaning techniques: the tungsten carbide bur and the prophy jet. This would help determine whether the castings that have been cleaned and recemented are just as tenacious as when they were initially placed. Methodology A total of 60 human teeth extracted due to periodontal disease were collected for this study. The teeth were cleaned and stored in a thymol arrangement after carefully removing any leftover fragile tissue. They were randomly grouped as follows: luted with Vivaglass cement (N = 30) in group A and GC fuji 1 cement (N = 30) in group B. Each group's debonded surfaces were arbitrarily split into three subgroups, with each containing 10 samples. This was done to comply with dentin-cleaning techniques for recementation. Results The intergroup bond strengths calculated were compared among the subgroups. The mean strength for subgroup IA was 2.78 ± 0.24 MPa, subgroup IB was 2.60 ± 0.30 MPa, subgroup IIA was 4.39 ± 0.19 MPa, subgroup IIB was 3.80 ± 0.23 MPa, subgroup III A was 4.52 ± 0.22 MPa, and subgroup IIIB was 3.63 ± 0.17 MPa. An analysis of variance test showed there was a significant difference between the subgroups (F = 117.60; P = 0.001). The results revealed that there was a significant difference between the subgroups. Shear bond strength testing was performed using common testing equipment. The results indicated that there was not any significant difference between the mean increases in the shear bond strength of the two luting cement types. However, the GC fuji 1 cement showed greater initial shear bond strength than the Vivaglass cement. Additionally, when the tungsten carbide bur was used as a cleaning technique before recementing, it showed greater shear bond strength compared to the prophy jet. Conclusions The initial shear bond strength of GC fuji 1 (Group B) luting cement was slightly higher than that of Vivaglass (Group A), and the bond strength achieved after recementation with GC fuji 1 and surface cleaning with the carbide bur was the highest among the other three groups.

Shear bond strength of ceramic laminate veneers to finishing surfaces with different percentages of preserved enamel under a digital guided method

Background

The purpose of this in vitro study was to evaluate the effect of the percentages of preserved enamel on ceramic laminate veneers’ (CLVs) shear bond strength (SBS).

Methods

Seventy extracted human maxillary central incisors were scanned and reconstructed into three-dimensional models. The extracted teeth were then embedded and randomly divided into seven groups (n = 10 per group). Based on digital analyses of the three-dimensional models, guided tooth preparation and bonding procedures were performed individually to form seven different percentages (100%, 80%, 60% 50%, 40%, 20% and 0%) of remaining enamel thickness on the bonding surface. Finally, the SBS test was performed, and the data were statistically analysed by one-way ANOVA with LSD post hoc test (α = 0.05).

Results

The complete enamel surface exhibited the highest SBS (19.93 ± 4.55 MPa), followed by 80% enamel (19.03 ± 3.66 MPa), 60% enamel (18.44 ± 3.65 MPa), 50% enamel (18.18 ± 3.41 MPa), 40% enamel (17.83 ± 3.01 MPa) and 20% enamel (11.32 ± 3.42 MPa) group. The lowest SBS (9.63 ± 3.46 MPa) was detected in 0% enamel group. No significant difference was observed among the 40–100% enamel groups, while the 20% or 0% enamel group demonstrated a significantly lower mean SBS than the 40% enamel group (p < 0.05).

Conclusion

The SBS value of CLVs bonded to 100% enamel on the finishing surfaces (nearly 20 MPa) was twice that which bonded to 0% enamel (nearly 10 MPa). Bonding to 100% enamel is the most reliable treatment. When dentin exposure is inevitable, enamel should be preserved as much as possible to maintain good bonding. In addition, 40% of preserved enamel on the bonding surface was the minimal acceptable value to fulfil the requirements of good bonding strength.

Influence of resin removal treatments on the surface topography and strength of de-bonded lithium disilicate ceramic

AIM

This study aims to assess the influence of resin removal treatment regimes on the surface topography and compressive strength of de-bonded ceramic surfaces.

MATERIAL AND METHODS

Sixty-five lithium disilicate ceramic (LDC) discs were prepared, cleaned, and polished with carbide paper. All samples were etched using 9.6% hydrofluoric acid (HFA). Fifteen samples were taken as positive controls; the remaining 50 samples were subjected to the process of silanization. Resin build-up using dual-cure cement was performed incrementally and light cured. Based on different methods of resin cleaning from de-bonded LDC, the samples were divided into five groups, n=10 each: group 1 (no treatment), group 2 (slow-speed diamond bur), group 3 (1 min heat treatment), Group 4 (6 min heat treatment), and group 5 (sandblasting with Al₂O₃). Following resin removal, LDC samples were tested under compressive failure load in a universal testing machine. Five disc specimens from each group were sputter coated with gold for scanning electron microscopy (SEM). Analysis of variance (ANOVA) and Tukey's post hoc test was used for descriptive statistics. Level of significance was established at p<0.05.

RESULTS

The highest compressive strength with significant difference among all experimental groups was found in group 5 (321.54 ± 13.25 MPa) (p<0.05). The lowest compressive strength values, presenting significant difference compared with all other groups, were displayed in group 1 (158.57 ± 5.22 MPa) (p<0.05). Compressive strength among group 2 (231.54 ± 15.55 MPa), group 3 (237.81 ± 10.81 MPa), and group 4 (255.53 ± 8.95 MPa) specimens was statistically comparable (p>0.05). On SEM, heat-treated specimens confirmed coarser granules, with mild porosities and roughening, whereas sandblasted specimens exhibited consistent evenness with moderate porosity and loss of glazed surface.

CONCLUSION

De-bonded LDC surface, treated with heat treatment and sandblasting procedures, exhibited removal of residual resin and significantly high compressive strength compared with non-cleansed ceramic surface.

Influence of endodontic sealers with different chemical compositions on bond strength of the resin cement/glass fiber post junction to root dentin

OBJECTIVE

This study evaluated the influence of endodontic sealers with different chemical compositions on bond strength of resin cement/glass fiber post junction to root dentin.

MATERIALS AND METHODS

Seventy-two maxillary canines roots were instrumented with Reciproc (#R50) and distributed in 6 groups (n = 12) according to endodontic sealers: G1-control (no sealer); G2-Endofill; G3-Sealapex; G4-AH Plus; G5-Sealer Plus; G6-EndoSequence BC. The glass fiber post was cemented with Panavia F in 10 of the specimens. Two specimens from each group did not receive post and were analyzed by SEM to verify presence of filling material. Three slices were obtained from each third. The first slice was subjected to push-out test and type of failure. The second slice was imaged using laser confocal microscopy for evaluation of dentin/resin cement adhesive interface. Bond strength (BS) data were analyzed using two-way ANOVA and Tukey's post hoc tests; for LCM data, we used Kruskal-Wallis and Dunn's tests.

RESULTS

Endofill yielded the lowest BS values (p < 0.05). The control and AH Plus groups differed from all others (p < 0.05). In all groups, adhesive to dentin failure predominated. Most specimens of control and AH Plus groups had acceptable interfaces, while those of EndoSequence BC, Sealapex, and Sealer Plus groups ranged between acceptable and poor interfaces. Overall, few filling material remnants were observed on the dentin.

CONCLUSION

EndoSequence BC, Sealapex, Sealer Plus, and Endofill negatively interfere with BS of glass fiber post/resin cement junction to root dentin.

CLINICAL RELEVANCE

In cases whose restoration planning includes a post cemented with resin cement, it is recommended that endodontic sealer be based on epoxy resin.

Evaluation of rebonding strengths of leucite and lithium disilicate veneers debonded with an Er:YAG laser

Resin cements create a high bond between the tooth and ceramic surfaces, thus making it impossible to remove the restoration in one piece. The aims of this study were to evaluate (i) the efficiency of an Er:YAG laser for debonding, and (ii) the changes in the rebonding strength values of all-ceramic veneers, which were removed after laser application. A tooth reduction of 120 extracted human maxillary central incisors was made to provide two different bonding surfaces (60 enamel and 60 dentin). Sixty leucite and 60 lithium disilicate discs (1-mm thickness, 5-mm diameter) were cemented to prepared surfaces with a dual-cure resin cement. Each group was divided into two subgroups (n = 15): control and laser-irradiated. Er:YAG laser (2940 nm) was applied for 9 s at 3 W power (10 Hz, 300 mJ) with 100 μs pulse duration. Shear bond strength (SBS) test was made with a universal testing machine. After the tested laser-irradiated specimens had been rebonded, the SBS test was performed again and rebonding strengths were measured. The statistical evaluations were performed by using repeated measures one-way ANOVA and post hoc Bonferroni tests (p < 0.05). Significant differences were found between the control and laser-irradiated groups (p < 0.001). While the required SBS values for control groups were between 30.04 and 24.66 MPa, the values for laser-irradiated groups were between 6.60 and 4.09 MPa. There was no significant difference between the control and rebonded groups. Er:YAG laser-irradiation is an effective method for removing all-ceramic restorations without affecting the rebonding strength.

The contribution of ceramic thickness and adhesive type on the de-bonding strength of dental ceramic veneers using Er,Cr:YSGG laser

Purpose: De-bonding strength of ceramic veneers by laser use needs to be evaluated in detail. The aim of this study, is to determine the contribution of ceramic thickness and cementing agents to the de-bonding strength of ceramic veneers using Er,Cr:YSGG laser. Methods: A total of 120 maxillary central incisors specimens were randomly divided into twelve groups on the basis of disc thickness, cementing agent, and Er,Cr:YSGG laser use. Under laboratory conditions, 120 IPS Empress II system discs 0.5mm, 1mm, and 2mm in thickness were applied to the tooth surfaces, for laser use. An Er,Cr:YSGG laser system was applied to the central surface of the IPS Empress II discs on specimens in all laser groups (Groups 1,3,5,7,9,11). Then the shear bond strength (SBS) for all specimens were tested with a testing machine at a speed of 0.5mm/min. The SBS values were considered as the de-bonding strength. Results: The mean de-bonding strength values for Groups 9 and 11 (0,5 mm disc thickness + laser application) have the lowest median load (0.000 N), while Group 4 (2mm disc thickness + no laser) has the highest median load (573.885 N). The de-bonding strengths of all the groups without laser application were higher than those of all groups with laser use. When laser is applied, the mean de-bonding strength decreases with decreasing disc thickness, and it reaches zero at 0.5mm thickness of discs cemented by self- or total-etch adhesives. Conclusions: The de-bonding strength decreases with laser use, and decreasing disc thickness. In the absence of laser, the mean de-bonding values of discs cemented by a total etch adhesive system are always higher than those of discs cemented with a self-etch adhesive system. Without any extra load, all 0.5mm thick discs were dislodged from teeth while applying or testing the laser.