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Background:With the aim of developing methods that could increase the fracture resistance of structurally compromised endodontically treated teeth, this study was conducted to compare the effect of three esthetic post systems on the fracture resistance and failure modes of structurally compromised and normal roots.Materials and Methods:Forty five extracted and endodontically treated maxillary central teeth were assigned to 5 experimental groups (n=9). In two groups, the post spaces were prepared with the corresponding drills of the post systems to be restored with double taper light posts (DT.Light-Post) (group DT.N) and zirconia posts (Cosmopost) (group Zr.N). In other 3 groups thin wall canals were simulated to be restored with Double taper Light posts (DT.W), double taper Light posts and Ribbond fibers (DT+R.W) and Zirconia posts (Zr.W). After access cavity restoration and thermocycling, compressive load was applied and the fracture strength values and failure modes were evaluated. Data were analyzed using two-way ANOVA, Tukey and Fisher exact tests (P<0.05).Results:The mean failure loads (N) were 678.56, 638.22, 732.44, 603.44 and 573.67 for groups DT.N, Zr.N, DT.W, DT+R.W and Zr.w respectively. Group DT+R.W exhibited significantly higher resistance to fracture compared to groups Zr.N, DT.W and Zr.w (P<0.05). A significant difference was detected between groups DT.N and Zr.W (P=0.027). Zirconia posts showed significantly higher root fracture compared to fiber posts (P=0.004).Conclusion:The structurally compromised teeth restored with double taper light posts and Ribbond fibers showed the most fracture resistance and their strengths were comparable to those of normal roots restored with double taper light posts. More desirable fracture patterns were observed in teeth restored with fiber posts.

Background:As the use of different irrigants to eliminate residual debris and smear layer in the field of endodontic is unavoidable, by considering the effect of irrigants on the bond strength of resin composite restorations, this study was designed to evaluate the effect of a mixture of a tetracycline isomer, an acid, and a detergent (MTAD) on the shear bond strength of two self-etch adhesives, Clearfil SE Bond and Adper Prompt L- Pop to dentin.Materials and Methods:The crowns of 80 extracted premolars were transversally sectioned to expose dentin. Flat dentin surfaces were wet abraded with 320-grit abrasive paper and randomly assigned to eight groups according to two self-etch adhesive and four dentin surface treatments: direct application over smear layer (no treatment), etching with 35% phosphoric acid for 15s, 1 min 5.25% NaOCl/1 min MTAD and 20min 1.3% NaOCl/5min MTAD. Shear bond strength was tested 24 h after storage in distilled water at 37°C in incubator. Data were analyzed using one-way ANOVA followed by duncan post-hoc (α=0.05).Results:Phosphoric acid etching prior to SE Bond application significantly decreased the shear bond strength to dentin (P<0.05). Application of MTAD clinical protocol (20min 1.3% NaOCl/5min MTAD) did not significantly decrease the shear bond strength of self-etch adhesives to dentin (P=0.745)Conclusions:Based on the results of present investigation, it seems that the use of clinical protocol of 1.3% NaOCl as a root canal irrigant and a 5-min application of MTAD as a final rinse to remove the smear layer has no adverse effect on the shear bond strength of self-etch adhesives to dentin.

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BackgroundThe purpose of orthognathic surgery is to correct facial deformity and dental malocclusion and to obtain normal orofacial function. However, there are controversies of whether orthognathic surgery might have any negative influence on temporomandibular (TM) joint. The purpose of this study was to evaluate the influence of orthognathic surgery on articular disc position and temporomandibular joint symptoms of skeletal CI II patients by means of magnetic resonance imaging.Material and MethodsFor this purpose, fifteen patients with skeletal CI II malocclusion, aged 19-32 years (mean 23 years), 10 women and 5 men, from the Isfahan Department of Oral and Maxillofacial Surgery were studied. All received LeFort I and bilateral sagittal split osteotomy (BSSO) osteotomies and all patients received pre- and post-surgical orthodontic treatment. Magnetic resonance imaging was performed 1 day preoperatively and 3 month postoperatively. Descriptive statistics and Wilcoxon and Mc-Nemar tests were used for statistical analysis. P<0.05 was considered significant.ResultsDisc position ranged between 4.25 and 8.09 prior to surgery (mean=5.74±1.21). After surgery disc position range was 4.36 to 7.40 (mean=5.65±1.06). Statistical analysis proved that although TM disc tended to move anteriorly after BSSO surgery, this difference was not statistically significant (p value<0.05).ConclusionsThe findings of the present study revealed that orthognathic surgery does not alter the disc and condyle relationship. Therefore, it has minimal effects on intact and functional TM joint. Key words:Orthognathic surgery, skeletal class 2, magnetic resonance imaging, temporomandibular disc.