Superfast Set, Strong and Less Degradable Mineral Trioxide Aggregate Cement

Purpose. Despite the good sealing ability and biocompatibility of mineral trioxide aggregate (MTA), its slow setting, high degradation, and weakness limit its use in surgical endodontics and high stress-bearing areas. This study aimed to develop two new liquids to control these drawbacks. They were prepared from calcium chloride, fumed silica, and hydroxyapatite or calcium phosphate and coded “H” and “P,” respectively. Methods. Portland cement, Grey ProRoot® MTA, and white ProRoot MTA were mixed with distilled water (control) or liquid “H” or “P.” The pH, setting time, degradation rate, leachant/precipitate’ composition, compressive strength, and morphology were assessed. Results. Both liquids maintained MTA’s high alkalinity and reduced the setting time by 1-2 orders of magnitude. Both liquids, H in particular, significantly reduced the degradation rate of Grey ProRoot and White ProRoot MTA®. Calcite has been identified as the main phase of the leachant or precipitate formed during the cement’s degradation. Calcium hydroxide or hydroxyapatite was also identified with Grey ProRoot MTA mixed with H liquid. These liquids also significantly increased the compressive strength with no statistical differences between them; this was associated with the production of dense, consolidated structures. Conclusions. The modified MTA could be used in surgical endodontics and high stress-bearing areas

Effect of environment on cyclic fatigue of ProTaper Next rotary files

Aim: The aim of the study was to evaluate the effect of different irrigation solutions on cyclic fatigue of ProTaper Next (PTN) rotary files. Materials and Methods: A total of 50 files were divided into 5 groups according to the environment in which cyclic fatigue test was carried out as follows: chlorhexidine (CHX) 2%, ethylenediaminetetraacetic acid 17%, saline, sodium hypochlorite 6%, and air (control group). A specially designed testing device was assembled utilizing an artificial canal made of a heat-resistant glass tube. The tube had a 1.2 mm diameter, an angle of curvature of 60°, and a radius of curvature 6 mm. Before each fatigue test, the tube was filled with fresh irrigation solution except air group, which was left dry. The mean number of cycles to failure was counted then fractography and length of broken segment were analyzed after failure. Statistical analyses were performed using one-way ANOVA test. Results: The CHX group was the most resistant to cyclic fatigue compared to all groups (P 0.05). Fractographic analysis of all groups showed signs of a fatigue failure. A crack site was seen followed by a striation area leading to a dimples overload area. The length of broken segments was not significantly different among all groups (P = 0.37). Conclusion: Although liquid media may function as lubrication, all irrigants except CHX failed to increase the fatigue life of PTN files when compared to dry conditions

Sodium Hypochlorite Irrigation and Its Effect on Bond Strength to Dentin

Effective shaping and cleaning of root canals are essential for the success of endodontic treatment. Due to the complex anatomy of root canal spaces, the use of various instrumentation techniques alone is not effective in producing bacteria-free root canal spaces. Irrigation, disinfectants, rinses, and intervisit medications are used in conjunction with the mechanical instrumentation to ensure the success of endodontic treatment. Sodium hypochlorite (NaOCl), a halogenated compound, is routinely used to irrigate the root canal during endodontic treatments. NaOCl has been known for its antibacterial action, proteolytic and dissolution capacity, and debridement properties. NaOCl, however, can alter the composition of dentin and hence its interaction with the adhesive resins used to bond the restorative materials to treated dentin. This review therefore covers in depth the action of NaOCl on dentin-adhesive resin bond strength including both enhancement and reduction, then mechanisms proposed for such action, and finally how the adverse action of NaOCl on dentin can be reversed

The root canal shaping ability of WaveOne and Reciproc versus ProTaper Universal and Mtwo rotary NiTi systems

Aim: The aim of this study is to compare the root canal shaping ability of two reciprocating instruments: WaveOne and Reciproc versus two rotary instruments – ProTaper Universal (PTU) and Mtwo. Materials and Methods: A total of 160 simulated root canals in resin blocks were constructed with two curvatures located at two positions creating four different combinations: 20°/8 mm, 20°/12 mm, 40°/8 mm, and 40°/12 mm. Canals were prepared using continuous rotation (PTU and Mtwo) or reciprocating (WaveOne and Reciproc) instruments according to the manufacturer's recommendations. Each system was used to prepare 10 canals of each shape. Each file or a set of files was used to prepare one canal. Using Image Analysis Software, pre- and post-instrumentation matching images were superimposed and analyzed for canal width and transportation. Instrument fractures, time of preparation, and change in working length were also recorded. The effect of instrument and canal type on shaping ability were analyzed using two-way ANOVA test followed by post hoc Pearson Chi-square test and sum of squares test at level of significance 5%. Results: The largest mean canal width and transportation values were associated with the Mtwo system (P < 0.001) and 40°/8 mm canals (P < 0.001). Canal aberrations were limited to rotary instruments mainly in canals with 40° curves. The reciprocating instruments prepared canals significantly faster than continuous rotation systems (P < 0.001). Conclusions: Continuous rotation and reciprocating files were safe and maintained the original canal anatomy. However, continuous rotation instruments have a higher tendency for canals transportation and aberrations, especially with larger curvatures. Reciprocating files were faster than continuous rotation files in shaping simulated root canals in resin blocks

The Effect of Repeated Pressing on the Flexural Strength, Color Stability, Vickers Hardness, and Surface Topography of Heat-Pressed Lithium Disilicate

The aim of this study was to investigate the effect of repressing leftover heat-pressed lithium disilicate material on its mechanical and optical properties. A lithium disilicate ingot (IPS e.max® Press, IvoclarVivadent, Schaan, Liechtenstein) shade (A1) low translucency was first heat-pressed to yield ceramic bars and disks. Then, the second and third presses were fabricated from the leftovers of the previous pressing cycles. A total of 36 bars and 15 disk specimens were fabricated and divided into three groups according to the number of pressing cycles (n = 12 bars and n = 5 disks): P1: first press (control), P2: second press, and P3: third press. The specimens were tested for flexural strength, color change, Vickers hardness, and surface topography under scanning electron microscopy. One-way ANOVA testing was used to evaluate flexural strength and hardness, while an independent t-test was performed to evaluate color change. There was no significant difference in flexural strength as the number of heat-pressed cycles increased (p = 0.283). Similarly, there was no significant difference in the microhardness values between all groups (p = 0.220). The overall color change ∆E between P1–P2 and P1–P3 were 2.01 and 2.14, respectively. The SEM images showed evenly distributed and densely packed lithium disilicate crystals in the P1 group. However, larger and less densely packed crystals were noticeable in P2 and P3. The IPS e.max Press could be repressed up to two times without an adverse effect on mechanical properties or color stability. These results may support the reuse of pressed lithium disilicate for economical purposes, but further clinical evaluation should be conducted to confirm these findings