ABSTRACT
Objective: The purpose of the study was to compare the fracture resistance of ceramic veneers
and composite resin veneers with and without dental preparation. Materials and Methods: Forty freshly extracted mandibular premolars were selected and randomly assigned
into four groups (n = 10): Group NPR = no dental preparation and direct veneer with 0.2 mm thick composite
resin (Amelogen Plus, Ultradent); Group NPC = no dental preparation and 0.2 mm thick
lithium disilicate ceramic veneer (IPS e.max Press, Ivoclar Vivadent); Group P2C =
Tooth preparation of 0.2 mm and 0.2 mm thick ceramic veneer (IPS e.max Press); and
Group P5C = Tooth preparation of 0.5 mm and 0.5 mm-thick ceramic veneer (IPS e.max
Press). In all groups, the restorations covered 1 mm of the occlusal surface of the
buccal cusp, and the thickness of this area was the same of the buccal area (0.2 mm
or 0.5 mm). After the luting procedure, all groups were thermocycled (10,000 cycles,
5°C–55°C) and subjected to fracture resistance test under compression (Instron 4444
with a crosshead speed of 0.5 mm/min). The mode of failure analysis was performed
under a ×10 magnification. Data were subjected to one-way ANOVA and Duncan's post hoc test (P < 0.05). Results: The mean fracture resistance (men ± standard deviation) was NPR = 690.33 ± 233, NPC
= 790.52 ± 408, P2C = 1131.34 ± 341, and P5C = 983.56 ± 202. There were significant
differences of the fracture resistance values between all groups (P = 0.013). NPR and NPC groups showed mean values of fracture resistance significantly
lower than P2C. However, P5C presented intermediate values without a significant difference
from the other groups. The mode of failure for all groups was mixed (60%), cohesive
failures (20%), root failures (15%), and adhesive failures (5%). Conclusion: Minimally invasive tooth preparation (0.2-mm) allowed to achieve higher fracture
resistance in premolars restored with lithium disilicate ceramic veneers. Attention
should be given to the 0.5 mm preparation since catastrophic fractures only happened
when this preparation depth was performed.
Key words:
Ceramic veneers - fracture resistance - lithium disilicate - mode of failure - resin
composite
