ABSTRACT
Objectives: maintaining pulp vitality is a main goal in restorative dentistry. Introduction of pulp capping agents paved the way to eliminate the shortcomings of these materials and obtain successful restorations. On the other hand, nanotechnology is an emerging field of science with increasing use in dental materials. This study sought to assess the effect of addition of nano-TiO[2], nano-SiO[2] and nano-Al[2]O[3] on compressive strength of five hydraulic cements
Methods: in this in vitro, experimental study, three experimental formulations of nano hybrid MTA, MTA Angelus and MTA Angelus+ nano-oxide particles cements were placed in molds measuring 4+/-0.1mm in internal diameter and 6+/-0.1mm in height made of stainless steel [ISO9917-1]. Ten samples were fabricated for each of the five groups of materials. Sound samples were stored at 37degreeC and 95+/-5% humidity and were subjected to compressive strength testing in a universal testing machine at a crosshead speed of 0.5mm/minute after 24 hours and one month. Two-way ANOVA, one-way ANOVA and independent samples t-test were used for comparison of compressive strength of groups at different time points
Results: the highest compressive strength belonged to MTA Angelus+ nanohydroxyapatite and nano-hybrid MTA C at 24 hours and 30 days, respectively. The lowest compressive strength belonged to nano-hybrid MTA B and MTA Angelus at 24 hours and 30 days, respectively [P<0.05]
Conclusion: addition of nanoparticles affected the compressive strength of cements. Compressive strength significantly increased over time in all groups
ABSTRACT
Objective: Despite the high strength of zirconia restorations, aging in the oral environment and masticatory loading may result in transformation of tetragonal to monoclinic phase and decrease their strength. Statements in this regard are controversial. This study sought to compare the flexural strength [FS] of Zirkonzahn [ZirkonZahn, Cercon, Ceramill] and Mamut [Dubai Medical Equipment LLC, Dubai, UAE] zirconia ceramics and assess the effect of thermal and mechanical aging on their FS
Methods: In this in vitro experimental study, 40 bar-shaped specimens measuring 20×5×2 mm were cut from Zirkonzahn and Mamut zirconia blocks and polished. Specimens in the aging groups were subjected to thermocycling [12,000 cycles, 5-55[degree sign], dwell time of 20 seconds]. Next, they were subjected to mechanical stress in a chewing simulator [40,000 cycles, 200N force]. The three-point flexural strength [TPFS] was determined in megapascal [MPa] using a Universal Testing Machine at a crosshead speed of 0.5 mm/min. Data was analyzed using two-way ANOVA
Results: The mean and standard deviation [SD] of TPFS of Zirkonzahn and Mamut specimens in the no aging group was 809.57 [205.95] and 708.53 [158.72] MPa, respectively. These values were 810.53 [158.96] and 839.06 [217.49] MPa for the Zirkonzahn and Mamut specimens subjected to aging, respectively. Type of zirconia [Zirkonzahn or Mamut] and exposure to aging process [p=0.27] had no significant effect on TPFS of specimens
Conclusion: Within the limitations of this study, the results showed that the process of aging did not decrease the TPFS of Zirkonzahn and Mamut specimens. Thus, these ceramics may be successfully used in the clinical setting