PURPOSEThe aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars.MATERIALS AND METHODSA total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (α=.05).RESULTSFiber-glass posts with composite cores showed the highest fracture resistance values (915.70±323 N), and the zirconia post system showed the lowest resistance (435.34±220 N). The corresponding mean value for the Ni-Cr casting post and cores was reported as 780.59±270 N. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests.CONCLUSIONThe fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiberglass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.

Objectives: Parafunctional habits, as one of the etiological factors of temporomandibular disorders (TMD), are an individual’s response to increased stress. During stress and depression, biomarkers such as cortisol and salivary alpha-amylase (SAA) are secreted in the saliva. The present study aimed to investigate whether there is a correlation between salivary stress biomarkers and parafunctional habits. Materials and Methods: Thirty-two cases, from May to September 2015, were selected based on two standard stress questionnaires, namely the depression anxiety stress Scale-21 (DASS-21) and the Beck Anxiety Inventory (BAI). Saliva samples were collected to examine the level of unstimulated salivary cortisol and SAA. The significance of the results was assessed via student’s t-test and Mann-Whitney test (α=0.05). Results: The mean concentrations of cortisol and SAA in unstimulated saliva were significantly higher in the case group than in the control group (P=0.01 and 0.44, respectively). The mean scores of anxiety, stress, and depression were significantly higher in the case group than in the control group (P<0.05). Conclusion: It seems that the levels of salivary cortisol and SAA, as well as stress, anxiety, and depression scores, are higher in patients with parafunctional habits.

Introduction: Myofascial pain dysfunction syndrome (MPDS) is a common temporomandibular joint disorder. Due to its multifactorial etiology, treatment usually involves more than one modality to obtain complementary results. The purpose of this study was to compare the combined effect of a low-level laser, a hard occlusal appliance, and conventional pharmacotherapy with pharmacotherapy only in the management of patients with MPDS. Methods: In this study, 15 patients with MPDS were diagnosed and randomly assigned to 3 groups (n=5). Subjects in Group 1 were treated with pharmacotherapy (PT); Group 2 received the diode laser (940 nm gallium arsenide) every other day for a total of 10 sessions, plus pharmacotherapy (PTL) and Group 3 were given hard occlusal splint 12 h/day for 4 weeks, plus pharmacotherapy (PTO). The intensity of pain was measured using the visual analog scale (VAS) prior to the treatment, 2 and 4 weeks after the onset of treatment and 2 weeks later. The maximum painless mouth opening and pain intensity at muscle palpation were also recorded. Comparisons were made between the groups via repeated measure analysis of variance (ANOVA) (P<0.05). Results: Pain relief in the subjective VAS was observed in both laser and appliance groups in the third and fourth examination sessions (P<0.05). No statistically significant reduction in pain was noted using pharmacotherapy only. The maximum painless mouth opening and muscle tenderness were not significantly different between the 3 groups (P>0.05). Conclusion: Both the laser and the occlusal appliance combined with pharmacotherapy proved to be effective for pain reduction in patients with MPDS. All groups, however, failed to result in a significant improvement in the maximum mouth opening or tenderness in masticatory muscles.

Objectives This study aimed at assessing the effect of the addition of silver nanoparticles (SNPs) to a silicone soft liner on its tensile bond strength to denture base resin. Materials and Methods SNPs were added to Mucopren cold cure soft liner in 0 (control), 0.5, 1, 2, and 3 wt% concentrations and bonded in 120 stainless steel molds with processed heat cure acrylic resin blocks. Liner/resin combination samples were divided into two groups. The first half was stored for 2 days in distilled water at 37°C and then subjected to tensile bond strength, while the other half were thermocycled 3000 times before testing. Mean bond strength, expressed in mega pascals (MPa), was determined in the tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min. Statistical Analysis Data were analyzed using SPSS via one-way analysis of variance test, t-test, and Tukey’s posthoc, at a 95% confidence level (p < 0.05). Results Addition of SNPs and thermocycling both caused a significant reduction in the tensile bond strength of Mucopren to acrylic resin; however, in the thermocycled group, the bond strength increased with the increase in the concentration of SNPs (p < 0.001). Conclusion Addition of SNPs to Mucopren soft silicone liner reduces its tensile bond strength to denture acrylic resin.

Splinting maxillary overdentures implants is associated with significant lower stress levels in the surrounding bone tissue.

Background. This study investigated the effect of the thickness of two resin cements on push-out bond strength of fiber posts to root dentin. Methods. Sixty decoronated single-rooted teeth were endodontically treated. The specimens were then randomly allocated to two groups (n=30); group 1: drill size 90 w, matching the size of fiber posts used; group 2: drill size 110, larger than the posts. The specimens in each group were divided into 2 subgroups (n=15); subgroup SE, in which the posts were cemented with self-etch Panavia F2.0 and subgroup SA, in which self-adhesive Panavia cement was used. After 72 hours, 2 slices with 1 mm of thickness were prepared from the mid-root of each specimen. Push-out bond strength test was performed in a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with two-way ANOVA and t-test. Results. The mean bond strengths of the posts cemented in matched-size spaces for SE and SA groups were 4.02±1.6 and 4.12±2.3 MPa, respectively. For posts cemented in oversized spaces, the values were 4.9±2.3 and 2.8±1.3 MPa, respectively. In matched-size spaces, there was no significant difference between the two groups. Conclusion. The results of this study suggested that increasing the cement thickness would reduce the bond strength of fiber posts to root dentin when self-adhesive cements are used; however, self-etch adhesives were not affected.

Due to proper mechanical properties, NPG post and cores seem to be a suitable choice for restoration of severely damaged anterior teeth, provided that other properties are proven to be acceptable.

Background: The current study aimed to assess the amount of fluoride released from fluoride-containing dental adhesives and its effect on micro-tensile bond strength (µTBS) and on resistance to demineralisation of dentine and enamel. Material and Methods: Two fluoride-containing dental adhesives, and a fluoride-free adhesive were used as experimental adhesives. After thermal cycling the µ-TBS of adhesives to dentine and the failure mode were assessed. The fluoride release and cross-sectional microhardness (CSMH) of specimens were measured before and after one day, 7 and 28 days of pH-cycling. The data were analysed using one-way ANOVA, Weibull statistics and repeated measures ANOVA. Results: The results indicated a significant difference between the group of FL and both the SE and LBF groups (p≤0.001). The CSMH values of both the dentine and enamel underneath the adhesives was reduced at 28 th day of the pH-cycling compared to the baseline (p≤0.001). From day 1 to day 28, the released fluoride declined in both the fluoride containing dental adhesives (p≤0.001). Conclusions: Based on the results, the released fluoride from dental adhesives may adversely influence the bond strength and durability of the resin/dentine interface. Moreover, the released fluoride didn't improve the resistance to demineralisation of adjacent enamel and dentine to bond interface.