The evaluation of the surface micro-hardness values in different depth of resin blocks

• Published in: Cumhuriyet Dental Journal Vol. 21; no. 4; pp. 284 - 289
• Main Authors: Bek Kürklü, Zeliha Gonca, Yoldaş, Hamdi Oğuz
• Format: Journal Article
• Language: English
• Published: Cumhuriyet University 30-12-2018
• Subjects: cad/cam; composite resin blocks
• ISSN: 1302-5805; 2146-2852
• DOI: 10.7126/cumudj.401248

Objective: Computer-aided
design and manufacturing technology has shown great improvement in dentistry
since the 1980s. This technology is based on a one-stage restoration using
prefabricated blocks. Two main types of materials are used during CAD / CAM
indirect restorations:  glass-ceramic /
ceramic and resin composite. CAD / CAM resin blocks are polymerized under high
temperature and pressure. Polymerization depth affects the surface hardness of
composite resins. When preparing a restoration, different depth layers of the
resin block are used. The aim of this study is to show that adequate
polymerization is achieved in each layer of the resin blocks and that the
hardness of each layer is the same. Two composite resin block materials and one
hybrid resin block material were included in this study.
Material and
method: The CAD/CAM block materials evaluated in this study were Cerasmart,
Lava  and Vita Enamic Square specimens
(n=5/material) of approximate dimensions 10×10×2 mm blocks were sectioned (5
slices/block) from commercially available CAD-CAM materials using a diamond saw
(exakt 300 cl Apparatebau, Norderstedt, Germany) with water cooling. All
specimens were abraded followed by 500,1200,2500 grid using SiC abrasive paper
(exakt 400 cs Apparatebau, , Norderstedt, Germany). After storage in distilled
water at 37 °C for 24 hours the Knoop hardness test was performed using a
hardness testing machine (Buehler MMT 3 digital micro hardness tester, Lake
Bluff, IL, USA) using a load of 500 gf and a loading time of 10s.
Results: The
material with the highest hardness number was Vita Enamic block, whereas the
lowest numbered group was the Cerasmart. The rank order of surface hardness was
as follows: Vita Enamic> Lava Ultimate >Cerasmart.
Conclusion: The
hardness measurements of the layers of blocks were similar.