As a dangerous factor in vertical root fracture, dentinal crack formation is often associated with root canal instruments. We conducted this meta-analysis to compare the influence of two types of nickel titanium (NiTi) instruments that have different movements (reciprocating single-file versus full-sequence rotary file systems) on dentinal cracks formation during root canal preparation. Searches were conducted in PubMed, ISI Web of Knowledge, Embase and Cochrane Library using a combination of keywords. Titles and abstracts of all articles were independently assessed by two reviewers in accordance with the predefined inclusion criteria. Relevant studies were acquired in full-text form. Data in these articles were independently extracted. A meta-analysis was conducted using Review Manager 5.3. The results showed that the WaveOne and Reciproc files with a reciprocating motion produced significantly fewer dentinal cracks than the conventional rotational ProTaper technique.
We have shown that Computed Microtomography (CMT) is able to map the internal distribution of the filler particles in ProTaperTM, LexiconTM, and GuttaCoreTM materials, and explain the differences in their tensile and ductility properties, prior to mechanical manipulation. Working of uncrosslinked ProTaperTM and LexiconTM samples resulted in a five-fold increase in ductility and the tensile elongation at break. CMT mapping of the internal structure showed that large, periodic, striations formed across the interior of the sample corresponding to the formation of regions with low filler particle density. In contrast to metals which harden upon working, this migration of particles away from the high stress regions resulted in stress softening, as predicted by the Mullins effect. The results indicate that CMT is an effective method for 3-D visualization of the internal particle distribution which permits the determination of structure-property relationships and facilitates the design of new materials.
A guided bone regeneration (GBR) membrane has been extensively used in the repair and regeneration of damaged periodontal tissues. One of the main challenges of GBR restoration is bacterial colonization on the membrane, constitutes to premature membrane degradation. Therefore, the purpose of this study was to investigate the antibacterial efficacy of triple-layered GBR membrane composed of poly(lactic-co-glycolic acid) (PLGA), nanoapatite (NAp) and lauric acid (LA) with two types of Gram-negative periodontal bacteria, Fusobacterium nucleatum and Porphyromonas gingivalis through a disc diffusion and bacterial count tests. The membranes exhibited a pattern of growth inhibition and killing effect against both bacteria. The increase in LA concentration tended to increase the bactericidal activities which indicated by higher diameter of inhibition zone and higher antibacterial percentage. It is shown that the incorporation of LA into the GBR membrane has retarded the growth and proliferation of Gram-negative periodontal bacteria for the treatment of periodontal disease.
The objective was to evaluate the effect of adding silver nanoparticles into three commercial adhesive systems (Excite™, Adper Prompt L-Pop™ and AdheSE™). Nanoparticles were prepared by a chemical method then mixed with the commercial adhesive systems. This was later applied to the fluorotic enamel, and then micro-tensile bond strength, contact angle measurements and scanning electron microscopy observations were conducted. The commercial adhesive systems achieved the lowest micro-tensile bond strength (Excite™: 11.0±2.1, Adper Prompt L-Pop™: 14.0±5.4 and AdheSE™: 16.0±3.0 MPa) with the highest adhesive failure mode related with the highest contact angle (46.0±0.6º, 30.0±0.5º and 28.0±0.4º respectively). The bond strength achieved in all the experimental adhesive systems (19.0±5.4, 20.0±4.0 and 19.0±3.5 MPa respectively) was statistically higher (p<0.05) than the control and showed the highest cohesive failures related to the lowest contact angle. Adding silver nanoparticles in order to decrease the contact angle improve the adhesive system wetting and its bond strength.
The objective of this investigation was to compare alternative framework designs of molar zirconia crowns veneered with various overpressing ceramics and to predict the biomechanical behavior based on the stress evaluation. The hypothesis of the study is that the zirconia framework design and type of the veneering material, using the same technological procedure, may influence the biomechanical behavior of the restorations. Three geometric models with differential coping designs (uniform thickness, cutback and buccal reduction) were developed and two types of hot-pressed ceramics (leucite and lithium disilicate reinforced) were analyzed for the veneers. Using finite element analysis (FEA), maximum principle stresses were recorded in the tooth structures and in the restorations for all the developed designs. Results led to the conclusion that the hypothesis was accepted.
Quantitative metallurgical and phase analyses employing neutron diffraction technique were conducted on two as-received commercial rectangular austenitic stainless steel orthodontic archwires, G&H and Azdent, 0.43×0.64 mm (0.017×0.025 inch). Results showed a bi-phase structure containing martensitic phase (45.67% for G&H and 6.62% for Azdent) in addition to the expected metastable austenite. The former may be a strain-induced phase-transformation arising during the cold working process of wire fabrication. Further neutron resonance capture analysis determinations provided atomic and isotopic compositions, including alloying elements in each sample, complementary to the results of traditional energy dispersive X-ray spectroscopy. Together, these results assist in relating commercial alloying recipes and processing histories with mechanical performance, strength and ductility in particular.
The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create 3D crown models and evaluated using FEA. The zirconia/composite crowns subjected to static occlusal load showed comparable results to the zirconia/porcelain crowns. Zirconia/composite crowns showed higher stress on the zirconia substructure at 63.6 and 50.9 MPa on the zirconia substructure veneered with porcelain. In conclusion, zirconia/composite crowns withstood high occlusal loads similar to zirconia/porcelain crowns with no significant difference. However, the zirconia/composite crowns showed higher stress values than the zirconia/porcelain crowns at the zirconia substructure.
The purpose of this study was to investigate the flexural strength of all-ceramics with varying core thicknesses submitted to aging. In-Ceram Alumina (IC), IPS e.max Press (EM) and Katana (K) (n=40), were selected. Each group contained two core groups based on the core thickness as follows: IC/0.5, IC/0.8, EM/0.5, EM/0.8, K/0.5 and K/0.8 mm in thickness (n=20 each). Ten specimens from each group were subjected to aging and all specimens were tested for strength in a testing machine either with or without being subjected aging. The mean strength of the K were higher (873.05 MPa) than that of the IC (548.28 MPa) and EM (374.32 MPa) regardless of core thickness. Strength values increased with increasing core thickness for all IC, EM and K regardless of aging. Results of this study concluded that strength was not significantly affected by aging. Different core thicknesses affected strength of the all-ceramic materials tested (p<0.05).
This study compared different irrigation techniques in triple antibiotic paste (TAP) removal from root canals. Fifty-six maxillaryanterior-teeth were filled with TAP for 28 days, and assigned into 5 experimental groups (n=10): Syringe irrigation (SI), NaviTip FX (NFX), Vibringe-Syringe irrigation (V-SI), NaviTip FX-Vibringe (V-NFX), passive ultrasonic irrigation (PUI) and positive and negative control groups (n=3 for each). Following the removal of the medicament, the remaining medicament was evaluated using 4-grade scoring-system. V-NFX and NFX showed similar performances (p>0.05) while V-NFX was significantly more efficient than SI and PUI (p<0.05) at all parts of root canals. VSI was less efficient at apical part when compared to NFX and V-NFX (p<0.05) while not significantly different from PUI and SI at all parts of the root canals (p>0.05). Regarding different parts of the root canals, V-SI and PUI were significantly less efficient at the apical part (p<0.05). In conclusion, the brush form of irrigation delivery with and without sonic activation improved the removal of TAP from the root canals when compared to ultrasonic activation, syringe irrigation or sonic activation alone.
The purpose of this study was to investigate methods for evaluating objectively the removability of three commercially available home reliners (Cushion Correct, Tafugurippu Pink A and Liodent Pink). After immersing each of the reliners in distilled water at 37ºC for 24 h, we compared their removability using the peel test with a finger, which was evaluated based on a visual analogue scale and the percentage of the residual area. An experimental rake-up test was also undertaken to quantify removability, evaluated based on the total amount of work required to remove it. The Tafugurippu Pink A product was easier to remove with a finger than the other two home reliner products, and required the least total amount of work to be removed in the experimental rake-up test. Furthermore, the rake-up test performed could possibly be used for objective evaluation of the removability of home reliner.
The antibacterial efficacy of intracanal medicaments for 2 and 7 days, in open apex root canals contaminated with Enterococcus faecalis biofilms was compared. One hundred and thirty-eight standardized uniradicular human roots were inoculated with E. faecalis. Colony forming units (CFU) were recorded before and after medication. Samples were divided in two (2/7 days), and subdivided (n=8/group): triple antibiotic paste (TAP); double antibiotic paste (DAP); dental base paste (DBP), consisting of calcium hydroxide, propylene glycol and calcium carbonate; DBP+0.2% chlorhexidine (CHX); DBP+0.2% cetrimide (CTR); DBP+0.2% CHX+0.2% CTR; 2.5% sodium hypochlorite (NaOCl); and distilled water. At both periods TAP, DAP, DBP+0.2% CHX, DBP+0.2% CTR and DBP+0.2% CHX+0.2% CTR exhibited no growth (NG) of E. faecalis. Distilled water and 2.5% NaOCl obtained the lowest CFU reduction. No growth with DBP was reached only at 7 days. CHX and/or CTR pastes were as effective as DAP and TAP. A 2-day period provided an effective disinfection.
A novel chitosan/polycaprolactone (CS/PCL) nanofibrous membrane by electrospinning was developed for guided tissue regeneration (GTR) to improve mechanical properties and to promote osteogenic differentiation. Firstly, chitosan and PCL solutions of different weight ratios (0/100, 30/70, 50/50) were mixed and then electrospun. Our data demonstrated that the CS/PCL (30/70) nanofibrous membrane promoted an increased rBMSCs proliferation when compared to the CS/PCL (50/50) membrane and pure PCL (0/100) membrane. The highest ALP activity and extracellular calcium deposit were observed on the CS/PCL (30/70) nanofibrous membrane, followed by the CS/PCL (50/50) and pure PCL nanofibrous membrane. Furthermore, the expression of osteocalcin (OCN) and Runx2 were also significantly higher on the CS/PCL (30/70, 50/50) nanofibrous membrane as compared to the pure PCL nanofibrous membrane. In conclusion, the electrospun CS/PCL nanofibrous membrane was found to be a biocompatible material that could stimulate osteogenic differentiation, suggesting that the novel CS/PCL membrane has an interesting potential as use for GTR.
Preventing microorganisms from adhering to the denture surface is important for ensuring the systemic health of elderly denture wearers. Silica coating agents provide high hydrophilicity but lack durability. This study investigated solutions to improve the durability of the coating layer, determine an appropriate solid content concentration of SiO2 in the silica coating agent, and evaluate the effect of adding platinum (Pt) and diamond nanoparticles (ND) to the agent. Five coating agents were prepared with different SiO2 concentrations with/without Pt and ND additives. The contact angle was measured, and the brush-wear test was performed. Scanning electron microscopy was used to investigate the silica coating layer. The appropriate concentration of SiO2 was found to be 0.5–0.75 wt%. The coating agents with additives showed significantly high hydrophilicity immediately after coating and after the brush-wear test. The coating agents with/without additives formed a durable coating layer even after the brush-wear test.
Effect of variation in morphology and size of filler particles, temperature and increase in condensation speed on packability of resincomposites was investigated. Eight experimental light-cured resin-composites (RZDn series) were tested. Each material was placed in a cylindrical mould at 26 or 32ºC. A flat-ended stainless-steel probe (φ=6 mm) was mechanically lowered with two different speeds 2 and 8 mm/s onto and into at the surface of the unset sample until a compressive force of 1 N was reached. This was repeated for five cycles, and from each cycle Fp was calculated. All spherical and irregular filler particle resin-composites showed a decrease in Fp with increase in number of compressions. Increase in temperature also decreased Fp, but this effect was not very prominent in the case of irregular filler resin-composites. Filler particle morphology, increase in temperature and compression cycle speed has a prominent effect on packability of resin-composites.
The aim of this study was to histologically evaluate direct pulp capping using different all-in-one adhesives in rat teeth. Five all-in-one adhesives and a control material (MTA) were used. Each material was applied on the exposed pulp, and each cavity was subsequently restored with the resin composite. Rats were sacrificed 14 days after the surgical procedure. Serial stained sections were histologically evaluated for examining pulp tissue disorganization (PTD), inflammatory cell infiltration (ICI), dentin bridge formation (DBF), and bacterial penetration (BP). We found that rat pulps, which were direct capped with all-in-one adhesives, showed various degrees of PTD, ICI, and DBF depending on the material, and that there were no complete dentin bridges. In contrast, rat pulps capped with MTA showed no PTD and ICI, and there were complete dentin bridges in all, but one specimen. No BP was observed in any specimen.
To examine the bonding state of metal-free CAD/CAM onlay restorations made from two popular resin composite blocks and a typical glass-ceramic block after cyclic loading, with and without immediate dentin sealing (IDS). Standardized mesial-distal-occlusalbuccal (MODB) cavities in 24 extracted human molars were prepared. The intra-cavity dentin surfaces of half of the cavities were immediately sealed with all-in-one adhesive and flowable composite, while those of the other half were not. All cavities were scanned, from which CAD/CAM onlays were fabricated from three types of block and cemented with an adhesive resin cement system. The restored specimens were subjected to cyclic loading and the intra-cavity microtensile bond strength was measured. IDS improves not only the internal bond strength, but also the bond reliability of metal-free CAD/CAM onlay restorations. The resin composite block seems to be more effective than a typical glass-ceramic block for achieving both high bond strength and excellent bond reliability.
This study was performed to compare the antibacterial activities of three cavity disinfectants [chlorhexidine (CHX), NaOCl, urushiol] and to evaluate their effect on the microtensile bond strength of Scotchbond Universal Adhesive (3M-ESPE, St. Paul, MN, USA) in class I cavities. In both experiments, class I cavities were prepared in dentin. After inoculation with Streptococcusmutans, the cavities of control group were rinsed and those of CHX, NaOCl and urushiol groups were treated with each disinfectant. Standardized amounts of dentin chips were collected and number of S. mutans was determined. Following the same cavity treatment, same adhesive was applied in etch-and-rinse mode. Then, microtensile bond strength was evaluated. The number of S. mutans was significantly reduced in the cavities treated with CHX, NaOCl, and urushiol compared with control group (p<0.05). However, there was a significant bond strength reduction in NaOCl group, which showed statistical difference compared to the other groups (p<0.05).
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