High Intensity and Halogen Ligh-Curing of an Orthodontic Adesive Resin: shear bond strenght test

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Stress distribution in a post-restored tooth using the three-dimensional finite element method

Clinicians are opting ever more frequently for restorative materials which have an elastic modulus similar to that of dentin when reconstructing endodontically treated teeth. Metallic posts, which are capable of causing dangerous and non-homogenous stresses in root dentin, are slowly being abandoned. Ideal posts may be those made of various types of fibre (carbon, mineral and glass) and which are adhesively luted into the canal. Among the different methods for evaluating the mechanical behaviour of posts in root canals (progressive loads and photo-elastic technique) the finite element method (FEM) presents many advantages. The aim of this paper is to evaluate, utilizing three-dimensional analysis of the finite elements, what the effect of material rigidity, depth of insertion and post diameter could be on the stress distribution in the different components of the single tooth-post-core reconstruction unit. The results of the FEM analyses, expressed as the distribution of Von Mises stress values, has allowed us to conclude that (i) fibreglass-reinforced composite distributes stress better than titanium alloy or stainless steel; (ii) fibreglass-reinforced composite posts should be inserted as deeply as possible (but maintaining 5-6 mm of gutta-percha apical seal); (iii) fibreglass-reinforced composite post diameter does not affect stress distribution, therefore, as much radicular dentin as possible should be preserved

Osteotomia segmentale per il recupero chirurgico-ortodontico di un dente in anchilosi : Caso clinico = Segmental osteotomy for the management of an ankylosed permanent tooth : A case report

OBJECTIVES. The aim of this case report is to describe a method to treat ankylosed teeth, as an alternative to avulsion and replantation procedures. MATERIALS AND METHODS. The case of a 13-year-old patient is presented, who was subjected to a single tooth dento- osseous osteotomy for the treatment of an ankylosed and infraoccluded maxillary right central incisor. RESULTS. Short term evaluation revealed a good soft tissue healing. After 6 months, there was no evidence of relapse in the tooth position. The post-treatment panoramic radiograph showed good bone regeneration around the segmental osteotomies. CONCLUSIONS. Single-tooth osteotomy to reposition an ankylosed tooth, in conjunction with orthodontic treatment, is a predictable and successful procedure. This technique enables the repositioning of the ankylosed tooth, while preserving the alveolar bone

Effect of three radicular dentine treatments and two luting cements on the regional bond strength of quartz fibre posts

The purpose was to investigate by push-out tests and scanning electron microscopy (SEM)/energy-dispersive spectroscopy (EDS) the effect, after first acid etching the post space walls, of three radicular dentine treatments on the regional bond strength of quartz fibre posts placed using two heavily filled resin luting cements. The crowns of 39 extracted maxillary central incisors were sectioned transversely 2 mm coronal to the labial cement-enamel junction and the roots endodontically treated. After standardized post space preparations and etching 15 s with 32% phosphoric acid, 36 roots were randomly divided into six equal groups. Quartz fibre posts (D.T. LIGHT-POST) were placed using three radicular dentine treatments (0.9% sodium chloride (NaCl) for 60 s, 10% sodium hypochlorite (NaOCl) for 60 s, 17% ethylenediaminetetraacetic acid (EDTA) for 60 s followed by 5.25% NaOCl for 60 s) and two resin composite luting cements (ONE-STEP PLUS/DUO-LINK; ONE-STEP PLUS/LuxaCore Dual). Transverse segments (S1-S7), 1.00 mm (SD = 0.05 mm) thick, were sectioned from the coronal 8 mm of each root. Push-out bond strength tests were performed on coronal, middle and apical post space segments (S2, S4, S6) at a crosshead speed of 0.5 mm/min. Data were recorded and analyzed using a two-way mixed ANOVA design (a = 0.05). Three segments (S1, S5, S7) from roots in each group were examined using SEM/EDS. After post space preparation, acid etching and using each of the three radicular dentine treatments, the three remaining roots were sectioned longitudinally for SEM observation of the post space walls. At all root segment sites, the mean bond strengths from using 0.9% NaCl were significantly lower than for the other two radicular dentine treatments (P ≤ 0.02), and DUO-LINK cement had significantly higher mean bond strengths than LuxaCore Dual cement (P ≤ 0.01). There was a significant linear trend for reduced bond strengths from coronal to apical post space segments (P < 0.001), which was supported by the SEM/EDS observations of dentine tubule appearance and resin tag formation. Acid etching followed by either 10% NaOCl or 17% EDTA and 5.25% NaOCl dentine treatments of the post spaces provided good adhesion and resin luting cement tag infiltration of dentinal tubules in the coronal and middle segments in particular.Haiyan Mao, Yaming Chen, Kevin H-K. Yip, Roger J. Smale

Influence of core-finishing intervals on tensile strength of cast posts-and-cores luted with zinc phosphate cement

The core finishing of cast posts-and-cores after luting is routine in dental practice. However, the effects of the vibrations produced by the rotary cutting instruments over the luting cements are not well-documented. This study evaluated the influence of the time intervals that elapsed between the cementation and the core-finishing procedures on the tensile strength of cast posts-and-cores luted with zinc phosphate cement. Forty-eight bovine incisor roots were selected, endodontically treated, and divided into four groups (n = 12): GA, control (without finishing); GB, GC, and GD, subjected to finishing at 20 minutes, 60 minutes, and 24 hours after cementation, respectively. Root canals were molded, and the resin patterns were cast in copper-aluminum alloy. Cast posts-and-cores were luted with zinc phosphate cement, and the core-finishing procedures were applied according to the groups. The tensile tests were performed at a crosshead speed of 0.5 mm/min for all groups, 24 hours after the core-finishing procedures. The data were subjected to one-way analysis of variance (ANOVA) and Tukey's test (&#945; = 0.05). No significant differences were observed in the tensile strengths between the control and experimental groups, regardless of the time interval that elapsed between the luting and finishing steps. Within the limitations of the present study, it was demonstrated that the core-finishing procedures and time intervals that elapsed after luting did not appear to affect the retention of cast posts-and-cores when zinc phosphate cement was used