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rev port estomatol med dent cir maxilofac . 2021;62(3):150-156 151

Influência do cimento na resistência à fratura de coroas de resina
nanocerâmica sobre margens knife-edge: Estudo piloto

r e s u m o

Palavras-chave: Objetivo: Avaliar a influência do tipo de cimento na resistência à fratura de coroas de recobri-
Blocos de CAD/CAM mento total de resina nanocerâmica cimentadas sobre preparações com margens knife-edge.
Resistência à fratura Métodos: Um dente tipodonte pré-molar inferior direito foi preparado com uma redução ax-
Cimento de ionómero de vidro ial de 1.5 mm, redução oclusal de 2.0 mm e uma margem vertical do tipo knife-edge. A partir
modificado por resina da leitura digital da preparação, foi desenhada uma coroa anatómica em software CAD/CAM.
Resina nanocerâmica Seguidamente, foram fresadas 20 coroas a partir de blocos CAD/CAM de resina nanocerâmi-
Cimento de resina auto-adesivo ca (Cerasmart270™) e uma réplica da preparação dentária em liga de crómio-cobalto. As 20
coroas foram divididas aleatoriamente em 2 grupos. No grupo 1 foram cimentadas com ci-
mento de resina auto-adesivo (G-CEM LinkAce™) e no grupo 2 com cimento de ionómero de
vidro modificado por resina (FujiCEM™ 2). Posteriormente, foram sujeitas a teste de resistên-
cia numa máquina de testes universal Instron até ocorrer fratura. Os resultados obtidos foram
analisados utilizando o teste paramétrico t de Student (α=0.05).
Resultados: O tipo de cimento utilizado demonstrou ter um efeito estatisticamente significa-
tivo na resistência à fratura das coroas (p<0.001). O grupo 1 apresentou uma média de
1284.3±340.19 Newtons, bastante superior à média registada no grupo 2, de 417.9±106.35
Newtons, verificando-se um aumento de 207.3% da resistência à fratura.
Conclusões: As coroas de resina nanocerâmica cimentadas com cimento de resina auto-ade-
sivo apresentaram resistência à fratura consideravelmente maior do que as cimentadas com
cimento de ionómero de vidro modificado por resina. (Rev Port Estomatol Med Dent Cir
Maxilofac. 2021;62(3):150-156)
© 2021 Sociedade Portuguesa de Estomatologia e Medicina Dentária.
Publicado por SPEMD. Este é um artigo Open Access sob uma licença CC BY-NC-ND
(http://creativecommons.org/licenses/by-nc-nd/4.0/).

9
inlays, onlays, and veneers. These materials have shown a
Introduction
modulus of resilience greater than dental ceramics’, and al-
Technological advances in digital impression methods and though they are less resistant to wear, they cause less abrasion
production systems have led to the increasing use of CAD/CAM to the opposing dentition. 9,10 Furthermore, manufacturers
(computer -aided design/computer -aided manufacturing) sys- claim they are less susceptible to fracture and chipping be-
tems in the manufacture of indirect prosthetic restorations. 1 -3 cause their modulus of elasticity is close to that of dentin. 3
Several materials with different compositions and physical In general, polymer -based materials developed for CAD/CAM
properties are currently available to use with these systems. use performed better in flexural testing than analogous ceram-
3
Ceramics (glass or polycrystalline), characterized as resistant, ic materials due to the combination of a relatively high flex-
4,9
rigid yet brittle, and having excellent esthetics and high wear ural strength with a low modulus of elasticity. This results
resistance, are examples of this development. 3,4 in an increased ability to withstand occlusal loading by under-
Composite resin -based materials were later introduced going more elastic deformation before fracture, being more
and nowadays serve as an alternative to conventional ceram- flexible and less brittle than purely ceramic materials. 4,9,10
ics. These materials have gained popularity due to their me- Additionally, they exhibited flexural properties similar to those
3
chanical properties, high esthetic potential, wear similar to of dentin, making them an acceptable choice for single -unit
tooth enamel’s, and easy repair of minor defects induced by prosthetic restorations. 9,10
function. 3 -5 Composite resins for use with CAD/CAM systems Although no single property can be used to predict a ma-
usually come in blocks or disks consisting of a polymeric ma- terial’s clinical success or failure, parameters such as flexural
trix reinforced by inorganic fillers (porcelains, glasses, ceram- strength, fracture resistance, modulus of elasticity, and mod-
ics, or glass ceramics), differing in type, size, and amount of ulus of resilience provide important information about the
filler. 6,7 dynamic behavior of these materials. Previous studies have
11
In an attempt to combine the favorable characteristics of shown that the type of cement significantly affects the frac-
ceramics with those of composite resins, new materials were ture resistance of crowns, but the materials tested were most-
7,8
developed and classified as resin nanoceramics. These ma- ly feldspathic and glass ceramics. 12,13 Other studies have eval-
terials contain a polymeric matrix with the addition of refrac- uated the influence of cement on the fracture resistance of
7
tory inorganic compounds (>50% by weight). They are recom- different indirect composite resins. 5,14-17 However, until now,
mended for indirect restorations, such as full -contour crowns, there is a lack of available literature regarding its influence on