Particle Size Modification of Endodontic Cement (Mechanical Activation VS Chemical synthesis)

Abstract

Objective: Initial setting time is one of the most important properties of calcium silicate cements (CSCs) such as white mineral trioxide aggregate (WMTA). This study aimed to evaluate the effect of two methods used to reduce the particle size of WMTA, mechanical activation and chemical synthesis. Methods: WMTA without bismuth oxide (WMTA-B) was provided and divided into four groups (n=5) including: WMTA-B, WMTA-B+10 min milling, WMTA-B+30 min milling, and sol-gel. In groups 2 and 3, the milling was performed by using tungsten carbide balls in a ratio 1:15 (w/w) and a vibration frequency of 30 Hz together with absolute ethanol. For the fourth group, polyethylene glycol (PEG), calcium acetate (Ca(C 2 H 3 O 2 ) 2 ), SiO 2 , and aluminum oxide (Al 2 O 3 ) were used for the sol-gel process. After preparation, sample powders were mixed with distilled water and placed in cylindrical molds, covered with water-moistened gauze, and incubated at 37°C for 24 hours. The Vicat needle test analyzed the initial setting time. Data were analyzed by ANOVA and Tukey tests at a significance level of P<0.05. The correlation between particle size and setting time was determined. Results: Initial setting time of the sol-gel and WMTA-B+30 min milling was significantly lower than in the other two groups (P<0.05). A significant correlation was noticed between particle size and initial setting time (P<0.05). Conclusion: Sol-gel process introduces a promising alternative strategy for the reduction of initial setting time of CSC materials. While both methods increased surface area, mechanical activation was not as successful in reducing surface area and initial setting time as effectively as the sol-gel process.

Calcium silicate and calcium aluminate cements for dentistry reviewed

“…Spherical particles have been made with sol-gel processing, but are not known to be commercialized. 134 Some researchers have speculated on the manufacturing techniques 135,136 used for the calcium silicate cements; however, compositions and methods are proprietary trade secrets. Many other dental materials have an industrial or cosmetic grade counterpart, such as calcium sulfate or methyl methacrylate (PMMA).…”

“…181 Recent products 180,182,183 meet the film thickness requirement of <50 µm, which may be attributed to finer cement particle sizes, and alternative water or organic liquids developed for mixing with the cement powders. 134,[184][185][186] The particle sizes of the calcium silicate dental cements are finer than Type 1 Portland cement. 185 See Table 2B which lists the particle size ranges of prominent calcium silicate dental cements.…”

Influence of Ultrasonic Activation on the Physicochemical Properties of Calcium Silicate-Based Cements

“…Group II, with activation: all cements were manipulated as described in Group I; then, they were activated using an ultrasound applied directly in the center of the mixture for 30 s. A noncutting insert (# 20, taper 0.01) (E1-Irrisonic, Helse Dental Technology, Santa Rosa de Viterbo, SP, Brazil) coupled with the piezoelectric ultrasonic unit (P100, EMS-Electro Medical System, Switzerland) at 30% power, with frequency at 24–32 Hz [ 8 – 10 ], was used. The MTA was put in a sterile plastic capsule, whereas for the MTA Repair HP and Biodentine, their respective capsules were used.…”

“…The mechanical manipulation of cements can provide a uniform and homogeneous mixture between powder and liquid, and the reduction of the particles' size [ 7 , 8 ] provides greater interaction of the cement with dentin [ 9 ], increasing the contact area between them during the hydration process [ 10 ]. These processes can also allow greater interaction with dentin and, consequently, a deeper penetration into the dentinal tubules and material adaptation to the retrograde cavity [ 9 ].…”

Characterisation of glass ceramic wasteforms using quantitative image analysis of electron micrographs

“…Moreover, many refinement techniques require a starting model and structural understanding of the material [1,2]. Micrographic image analysis is not an uncommon technique to research areas such as cementitious materials, as it can be particularly well utilised to measure pore sizes efficiently and determine aggregate size distribution [3]. Quantitative phase analysis by electron micrograph thresholding across contrast regions has been observed in the literature, though in this example, the technique was facilitated by proprietary-hard-coded microscope software with limited flexibility and user parametrisation [4].…”