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100 rev port estomatol med dent cir maxilofac. 2019;60(3):96-103

Table 2. Descriptive statistics for microtensile bond strength (µTBS) results (MPa).
Adhesive strategy n Mean ± SD Min Max 95% CI
Immediate 40 52.5 ± 13.56 a 22.17 89.78 [48.26; 56.71]
SBU
4 years 35 26.0 ± 6.50 b 11.76 34.73 [23.27; 28.64]
Immediate 43 59.3 ± 12.39 a 32.37 80.59 [55.52; 62.97]
SBU + HL
4 years 37 32.5 ± 5.72 b 12.33 39.16 [30.24; 34.67]
Means with different superscript lower-case letters indicate statistically significant differences (p<0.05).
Number of specimens (n), mean ± standard deviation (SD), minimum (Min) and maximum (Max) values, and lower/upper bound for mean at a
95% confidence interval (CI).
SBU, Scotchbond TM Universal Adhesive; SBU + HL, Scotchbond TM Universal Adhesive + hydrophobic layer.

Figure 3 shows the distribution of the failure patterns of
the experimental groups. No statistically significant differenc-
es were detected in the distribution of the failure mode, as
evidenced by the chi-square test. The most common failure
mode was cohesive for all adhesive strategies employed.

Discussion

Universal or multi-mode adhesives represent the latest gen-
eration of adhesive systems and have been developed under
the ‘‘all-in-one’’ concept of the already existing one-step self-
etch adhesives. Concerning most universal adhesives, in vitro
studies report consistently that a similar immediate dentin
microtensile bond strength can be achieved using either the
etch-and-rinse or the self-etch adhesive strategy while exhib-
iting a relatively high performance. 4,23 Nevertheless, when
Figure 2. Effect of water storage on the microtensile
bond strength (μTBS) to dentin. Squares represent mean adhesive interfaces were subjected to aging processes, sever-
and the corresponding 95% confidence interval. Notice al studies concluded that the self-etch approach resulted in
that water storage promotes an approximately 50% more stable long-term bond characteristics. 6,9,24 One me-
reduction in μTBS for both groups. ta-analysis of in vitro studies that evaluated nanoleakage re-
lated to universal adhesives reported divergent results and
highlighted that etching modes influenced significantly and
dissimilarly the nanoleakage of universal adhesives. Namely,
the etch-and-rinse technique significantly reduced the nano-
leakage of the Peak Universal and G-Bond Plus adhesives,
whereas the self-etch mode reduced the nanoleakage of All-
Bond Universal. In comparison, the etching technique did not
significantly modify the nanoleakage pattern of either
Prime&Bond Elect or Scotchbond Universal, which presented
the lowest nanoleakage. 25
The mean immediate dentin μTBS obtained in the present
study with the application of Scotchbond TM Universal, an ul-
tra-mild adhesive (pH=2.7), using the self-etch mode is in
agreement with previously reported data at the upper thresh-
old, in which bond strengths ranged from 32.3 to 59.9 MPa. In
previous studies, when the same adhesive system was ap-
plied in the etch-and-rinse mode, μTBS was within a similar
range of values (32.3 to 55.7 MPa). 5,17,20,26-29 In this study, the
group with the application of an additional hydrophobic res-
in layer showed better bond-strength values both immediate-
ly and after 4 years of water storage. However, for both peri-
ods, no statistically significant differences were detected
Figure 3. Distribution of the failure patterns of the between adhesive strategies. Therefore, the first null hypoth-
experimental groups in percentage.
esis is rejected.