Page 27 - SPEMD_62-3

rev port estomatol med dent cir maxilofac . 2021;62(3):150-156 153

dried with an oil -free airstream to obtain a clean surface, thus structions. The RMGI was hand -mixed for 10 seconds until a
preventing contamination. homogeneous mixture was obtained. A uniform layer of ce-
Group 1 crowns were luted with dual -cure self -adhesive ment was placed on the crown’s inner surface using the spat-
™
resin cement (G -CEM LinkAce , GC Corporation, Tokyo, Japan; ula. The seating protocol was the same as in group 1. Excess
Lot 180611B; Val: 07/2020) according to the manufacturer’s in- cement was removed with the straight explorer as soon as the
structions. The self -adhesive resin cement was dispensed ho- cement achieved a rubbery consistency. The manufacturer’s
mogeneously using a self -mixing syringe. A uniform layer of recommended setting time of 4.5 minutes was applied. In the
cement was placed on the crown’s inner surface with a spat- end, the remaining excesses were cleaned up as necessary.
ula (Heidemann Spatula n.º 3 TD4173, Dental Market, Lucca, The processes of placing the die and crown set on the put-
Italy). The crown was seated onto the die with finger pressure ty base, carrying out the fracture resistance test, removing the
and then with a 5 -kg weight, equivalent to a 49 -N seating pres- remaining crown fragments and cement from the die, and re-
sure, for 1 minute. 19 During cementation, each surface was peating the procedure for all crowns were executed in the
®
light -cured for 1 second (Bluephase Style 20i, Ivoclar Viva- same way as for group 1. A single operator carried out the
dent, Schaan, Liechtenstein), and then the excess cement was cementation of all crowns.
removed with a straight explorer (Explorers No. 6 TD4006, Den- The sample size (n=20) was selected based on the study of
tal Market, Lucca, Italy). Each surface was light -cured again for Sorrentino et al., who tested the fracture resistance of Cer-
™
™
20 seconds each, with the device directed to the interface be- asmart full -contour crowns (predecessor of Cerasmart270 ),
20
tween the crown and the die to improve marginal integrity. In using a sample of ten specimens per experimental group.
the end, all excesses were cleaned up as necessary. The statistical power of the present study was 93%, with a
After cementation, the die and crown set was placed in a significance level of 0.05.
circumferential putty base (Turboflex Putty Soft Normal Set, The data were analyzed using IBM SPSS Statistics, version
R&S, France; Lot 286323; Val: 11/2020) with a 50 -mm diameter 25.0 (SPSS Inc., Chicago, Illinois, USA). Since the Shapiro -Wilk
and 5 -mm thickness and fixed to the load frame base of the and Levene’s tests revealed normality and homogeneity
testing machine. The fracture resistance test was performed (p>0.05), respectively, the data were analyzed with a paramet-
in a universal testing machine (Instron, model 4502, Instron ric Student’s t -test. A statistical significance of α=0.05 was
Ltd, Bucks, England) with a 5000 -N load cell and a 6 -mm stain- considered.
less steel spherical tip at a crosshead speed of 1 mm/minute.
The set was positioned so that the spherical tip was at the
center of the crown’s occlusal surface. Then, vertical load was Results
applied toward the crown until fracture occurred (Figure 4).
The maximum breaking load was recorded in Newtons (N). In group 1, the fracture resistance ranged from 852 N to 1855
After fracture, the remaining crown fragments and cement N, with a mean value of 1284.3±340.19 N. In group 2, it ranged
remnants were removed from the die using a straight explor- from 285 N to 648 N, with a mean value of 417.9±106.35 N (Ta-
er and a 50 -µm aluminum oxide sandblast (Basic classic 2945- ble 1). These values are depicted in a graphic (Figure 5). Statis-
-2026, Renfert GmbH, Hilzingen, Germany). The whole process
was repeated for each tested specimen.
Group 2 crowns were luted with resin -modified glass ion- Table 1. Load at fracture in Newtons (N). Descriptive
omer cement (RMGI) (FujiCEM 2, GC Corporation, Tokyo, Japan; statistics by group: mean and standard deviation (SD).
™
Lot 180804A; Val: 08/2020), according to the manufacturer’s in-
Group 1 Group 2
(Self ‑adhesive (Resin modified glass
Specimen
(n) resin cement) ionomer cement)
Fracture Load (N) Fracture Load (N)
1 1786 648

2 1314 369
3 1120 551
4 1855 285
5 1138 402
6 1489 341
7 1153 354
8 874 398
9 1262 430
10 852 401
Figure 4. Crown cemented with G -CEM LinkAce™
(GC Corporation, Tokyo, Japan) after loading test. Mean (±SD) 1284.3±340.19 417.9±106.35