ABSTRACT
Background/purpose: There is no consensus to date on how many repetitive pecking motions at working length (WL) should be regarded as optimal during instrumentation. Therefore, this study aimed to evaluate the effect of pecking frequency at WL on the volume of apically extruded debris using three single-file systems in curved, oval-shaped canals. Materials and methods: Forty-five single-rooted mandibular premolars with curved, oval-shaped canals were prescanned by micro-computed tomography, anatomically paired-matched, and randomly divided among three groups (n = 15 each): Reciproc Blue (RB), WaveOne Gold (WOG) and XP-endo Shaper (XPS). Samples were embedded in agarose gel to collect extruded debris. After preparation to the WL, each sample was rescanned after one, two, four, 10, and 20 pecking motions at WL, respectively. The debris volume was innovatively calculated by a modification of an existing method using micro-computed tomography. The apical preparation size was also measured. Data were compared using a two-way repeated-measures analysis of variance. Results: All single-file systems extruded debris apically, irrespective of the pecking frequency at WL. The extruded debris volume correlated positively with the minor foramen size (P < 0.05); both increased with pecking frequency for each single-file system (P < 0.05). The minor foramen size corresponded to the instrument tip size when reaching the WL once. Conclusion: To produce less debris extrusion and obtain a predictable foramen size corresponding to the instrument tip size, a single pecking motion may be preferred when using single-file systems. Caution should be exercised when applying the current results to clinical situations.
ABSTRACT
In clinical work, the main challenges for titanium (Ti) implantation are bacterial infection and aseptic loosening, which severely affect the survival rate of implants. The first 4 weeks post-operation is the infection peak phase of implants. Inhibiting implant infection caused by bacteria adhesion and proliferation during the early phase as well as promoting subsequent osteointegration is essential for implant success. Herein, we constructed a quaternary ammonium carboxymethyl chitosan (QCMC), collagen (COL â ) and hydroxyapatite (HAP) multilayers coating on Ti substrates via a modified layer-by-layer (LBL) technique and polymerization of dopamine. The QCMC/COL/HAP coating exhibited a multi-antibacterial property with a two-phase function: (1) At the first 4 weeks post-operation, the covalently bonded QCMC could be slowly degraded and demonstrated both contact-killing and release-killing properties during the infection peak phase; (2) At the second phase, osteogenesis and osseointegration-promotion capabilities were enhanced by HAP under the effective control of infection. The multifilm coating was degraded for more than 45 days under the action of collagenase â , and displayed good biocompatibility in vivo and in vitro. Most importantly, the coating exhibited a long-lasting antibacterial activity for more than 3 months, against the main pathogenic bacteria of peri-implant infections. Both in vitro studies and in vivo animal models revealed a desirable osteogenic differentiation capacity of Ti-CCH. Therefore, our study reports a two-phase, long-lasting multi-antibacterial coating on Ti-CCH and indicates potential applications of the modified LBL strategy in orthopaedic fields, which is enlightening for developing practical implant and scaffold materials.
ABSTRACT
INTRODUCTION: The present study compared the effect of the number of pecking motions at the working length (WL) on the shaping ability of single-file systems in long oval-shaped curved root canals. METHODS: Single-rooted mandibular premolars with long oval-shaped curved canals (25°-35°) were prescanned using micro-computed tomographic imaging, anatomically paired, and randomly divided into 3 groups (n = 15): XP-endo Shaper (XPS; FKG Dentaire, La Chaux-de-Fonds, Switzerland), Reciproc Blue (RB; VDW, Munich, Germany), and WaveOne Gold (WOG; Dentsply Sirona, Ballaigues, Switzerland). After preparation to the WL, each specimen underwent 1, 2, 4, 10, or 20 pecking motions to the WL and was rescanned. Morphologic parameters were measured and analyzed using a 2-factor repeated measures analysis of variance and the Scheirer-Ray-Hare test. RESULTS: The minor apical diameter and percentage increase in canal volume increased with the number of pecking motions, whereas the percentage of unprepared canal surface area decreased (P < .05). The mean minor diameters (in mm) at D0 varied between 0.29 and 0.35 after 4 pecking motions with the RB and WOG systems and between 0.35 and 0.36 after 10 pecking motions with the XPS system. No significant differences in canal transportation or centering ratio were observed among the groups at the levels of canal curvature and canal thirds (P > .05). CONCLUSIONS: Increasing the number of pecking motions improves the cutting efficacy of single-file systems without adversely altering the anatomic characteristics of oval-shaped curved canals. No more than 4 pecking motions for the RB and WOG systems and 10 pecking motions for the XPS system appear to be acceptable for the shaping of these difficult to clean root canals.
