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Effect of Preoperative Occlusal Matrices on the V ickers Microhardness of Composite Disks Polymerized with QTH and LED Lamps
Author(s) -
CastilloOyagüe Raquel,
Milward Paul J.,
MartínCerrato Alicia,
Lynch Christopher D.
Publication year - 2015
Publication title -
journal of esthetic and restorative dentistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.919
H-Index - 60
eISSN - 1708-8240
pISSN - 1496-4155
DOI - 10.1111/jerd.12156
Subject(s) - materials science , indentation hardness , composite number , composite material , scanning electron microscope , curing (chemistry) , polymerization , microstructure , polymer
Purpose This study aimed to assess the reliability of the preoperative occlusal matrix technique in terms of the surface V ickers microhardness ( VMH ) of the underlying composite restorative material. Materials and Methods Two hundred microhybrid composite cylinders were built up and light‐cured in a single‐layer step, forming two experimental groups ( N = 100) according to their heights (1.5 mm/2 mm). Each group was divided into five subgroups ( N = 20) depending on the matrix thickness (no matrix/0.5 mm/1 mm/2 mm/3 mm). Half the specimens per subgroup ( N = 10) were randomly polymerized with a quartz‐tungsten‐halogen ( QTH ) light‐curing unit ( LCU ). The remaining half were cured using a light‐emitting diode lamp. The top and bottom samples' sides were tested for VMH at 1 hour and 24 hours post‐curing using a universal VMH machine. A multiple analysis of variance with repeated measurements for the “surface” factor and the Student– N ewman– K euls test were run ( α = 0.05). Bottom/top microhardness ratios were compared with the empirically accepted limit (0.8). Surface topography was analyzed under a scanning electron microscope. Results The thinnest matrices provided the significantly best VMH values. LCU , disc height, and time also contributed to VMH . At 24 hours, 2‐mm high discs polymerized with QTH resulted in inadequate microhardness ratios when 1‐mm thick to 3‐mm thick matrices were used. Conclusion The thinnest matrices are the most recommendable ones. Clinical Significance The esthetics and occlusal reproducibility achieved with customized occlusal matrices fabricated before cavity preparation have been widely demonstrated. However, their effect on the physical properties of the restorations deserves further investigation. Although more studies are necessary, the thinnest matrices seem to be the most suitable to preserve the composite surface VMH and the curing depth.