[Color stability of three composite resins following accelerated artificial aging: an in-vitro study]

Discoloration is among the most common problems of composite restorations. Color change over time compromises the main advantage of composite resins namely their high esthetics. In such cases, the restoration needs to be replaced. .The aim of this in-vitro study was to evaluate the effect of accelerated artificial aging [AAA] on the color stability of three composite resins [Filtek Z250, Filtek Z250XT, and Filtek Supreme]. In this experimental study, 7 composite specimens with equal dimensions were fabricated of each composite resin. The initial color of specimens was measured using a spectroradiometer according to the CIE L*a*b* system. The specimens were then submitted to AAA for 384h and underwent color assessment again. Before and after aging, the surface roughness of one specimen from each group was determined by Atomic Force Microscopy [AFM]. The obtained color parameters were analyzed by one-way ANOVA and Tukey's test. The color change of Filtek Z250 was significantly lower than that of Filtek Z250XT and Filtek Supreme [P 0.05]. All composite resins showed color change above the clinically acceptable threshold [delta >/= 3.3]. Z250 microhybrid composite was more color stable than nano-composites [Z250XT and Supreme]. AAA increased the surface roughness in all groups but it was within the clinically acceptable range

[Effects of casein phosphopeptide amorphous calcium phosphate and casein phosphopeptide amorphous calcium phosphate fluoride on alterations of dental plaque pH following sucrose consumption]

Plaque pH drop after consumption of sugary materials may dis-solve enamel minerals. Casein phosphopeptide amorphous calcium phosphate [CPP-ACP] is a paste enriched with calcium and phosphate. The new formulation of this paste, casein phosphopeptide amorphous calcium phosphate fluoride [CPP-ACPF], contains 900 ppm fluoride. This paste can neutralize the low pH of bacterial plaque. This study compares the efficacy of CPP-ACP and CPP-ACPF for neutralizing plaque acidity at different time points. This clinical trial was conducted on 40 students. Plaque pH at the distal of first molar was measured before and 10 minutes after the consumption of 10% sucrose solution. In the next step, CPP-ACP and CPP-ACPF pastes were applied as recommended by the manufacturers to the tooth surface. Plaque pH was measured at 30 minutes, 60 minutes and 24, 48, 72 and 96 hours. Data was recorded and analyzed by repeated measures ANOVA [P<0.05]. Both CPP-ACP and CPP-ACPF increased plaque pH similarly in the first 48 hours. However, the pattern changed from this time point on. CPP-ACP and CPP-ACPF had similar efficacy for up to 48 hours, but CPP- ACPF was capable of keeping the pH high by up to 96 hours

Evaluation of volume-targeted versus pressure-limited ventilation for Preterm Neonates with respiratory distress

Objectives: To evaluate the efficiency of volume targeted versus pressure-limited ventilation for preterm infants with respiratory distress

Methods: 60 newborn infants with gestational age 28-34 weeks in the NICU at Alexandria University Children's Hospital randomly divided in to 2 groups ventilated with either volume targeted ventilation [VTV] or pressure limited time cycled ventilation [PLV] as primary mode or secondary to failure of NCPAP using SLE 4000 or 5000 ventilators

Results: The demographic and clinical characteristics, values of tidal volume [VT], peak inspiratory pressure [PIP], mean airway pressure [MAP], fraction of inspired oxygen [Fio2], alveolar arterial oxygen gradient [A-aDo2], carbon dioxide tension, and pH were similar for all participating infants initially. During the follow-up, the PIP, MAP and FIO2 levels were significantly decreasing in the VTV group during the first 48 hrs. Moreover, The VTV group showed significantly lower incidence of hypocarbia and non-permissible hypercarbia. The VTV group showed significantly shorter duration of ventilation. There was no statistical significant difference between both groups as regards IVH, air leaks BPD, PDA or nosocomial infection

Conclusion: The use of VTV achieves adequate gas exchange using lower MAP and with less variability in tidal volume reducing the risk of hypocarbia and non-permissible hypercarbia. The use of VTV also shortens the duration of ventilation in premature infants with respiratory distress

In vitro evaluation of the effect of different times of sandblasting on the bond strength of feldspathic porcelain to composite resin

Intraoral repair of fractured porcelain is an acceptable method to avoid replacement and therefore saving time and cost. The purpose of this study was to determine the in-vitro shear bond strengths of composite resin to feldspathic porcelain after different durations of sandblasting and to compare the effect of sandblasting with that of hydrofluoric acid [HF]. In this in-vitro study, 40 porcelain disks were fabricated and randomly divided into 4 groups [n=10]. Porcelain surface in group 1 was etched with 9.5% HF for 2 minutes. Groups 2, 3 and 4 were sandblasted with 50am alumina particles for 5, 10 and 15 seconds, respectively. All specimens received the same silane agent, bonding agent and composite resin. The samples were subjected to 5000 thermal cycles and then underwent shear bond strength testing. The mean bond strength was analyzed with one-way ANOVA. The mode of failure was determined using stereomicroscope and scanning electron microscope. An additional porcelain sample was fabricated and prepared according to the aforementioned protocols in each group and its surface topography was observed by SEM. The mean bond strength was 15/28 [ +/- 3/64], 13/82[ +/- 4/03], 15/77[ +/- 3/94] and 16/54[ +/- 3/73] MPa in the 4 groups, respectively. There were no statistically significant differences among groups. The most common mode of failure was cohesive in porcelain. No statistically significant difference was found in SEM results of different durations of sandblasting. The shear bond strength was not significantly different after various durations of sandblasting treatment. The bond strength after sandblasting was similar to that of HF. SEM showed that HF acid etching and sandblasting patterns were different

[Effect of tea on color change of silorane and methacrylate based composite resins]

At present, stainability and color instability of tooth-colored restorations following the consumption of colored beverages are among the problems commonly encountered in restorative dentistry. Filtek P90 composite resin comprising of Oxirane and Siloxane functional moieties was recently introduced aiming at reducing the polymerization shrinkage. The aim of this study was to evaluate the effect of tea on color change of P90 and Z250 composite resins using spectrophotometry. For this experimental study, 20 composite discs were fabricated in metal molds from Z250 and P90 composite resins and light cured using LED light-curing unit. Specimens were stored in distilled water at 37° C for 24 hours to allow completion of polymerization. Color of specimens was then measured at baseline and after 5 days of storage in water and tea solution using spectrophotometer. Data were analyzed using independent sample t-test and two-way ANOVA. The color change of P90 and Z250 composites after storage in distilled water was not significant in comparison to their baseline color [P>0.05]. However, both composite resins showed a significant change in color after storage in tea solution [P<0.05]. Stainability of Z250 composite in tea was significantly greater than that of P90; but in distilled water P90 showed greater color change than Z250. Within the limitations of this study, Z250 composite demonstrated significantly greater color change in comparison to P90 after immersion in tea solution

In-vitro evaluation of water sorption and solubility of G-Cem and Fuji Cem in water and acid

Solubility is among the negative characteristics of dental materials leading to structural degradation of cements and decreased longevity of restorations. The present study sought to assess the water sorption and solubility of FujiCem resin-modified glass ionomer [RMGI] and G-Cem self-adhesive resin cement in water and acid. In this experimental study, 5 discs were fabricated from each understudy cement for solubility testing in lactic acid and 5 other disc-shaped specimens were made for evaluation of water sorption and solubility. Specimens were immersed in distilled water for 7 days and immediately weighed afterwards [M2]. Discs were then transferred to a desiccator again to reach a constant weight of M3. Water sorption and solubility were calculated using the respective equations. For acid solubility testing, specimens were immersed in lactic acid for 24h. Independent t-test was applied for statistical analysis of results. Solubility in distilled water was 0.0000139 +/- 0.0001 microg/m[3] for FujiCem and 0.0000016 +/- 0.000005 microg/m[3] for G-Cem [P=0.480]. Water sorption was 0.0000197 +/- 0.000234 for FujiCem and 0.0000025 +/- 0.00004 for G-Cem [P0=001]. Acid solubility was 0.0059414 +/- 0.0016 for FujiCem and 0.0039115 +/- 0.0016 microg/m[3] for G-Cem [P=0.348]. The two understudy cements had no significant difference in water or acid solubility but FujiCem RMGI showed greater water sorption than G-Cem self-adhesive resin cement

[Comparison of adherence of Candida Albicans on amalgam, light cure composite and glass ionomer: an In vitro study]

Statement of Problem: Candidiasis is the most common fungal infection in the human oral cavity. 85% of this infection is caused by Candida albicans. Although there is considerable information about the adhesion of Candida albicans to the epithelial cells and prosthetic materials, there are very few studies in regard to the adhesion of Candida albicans to various restorative dental materials

Purpose: This study aimed to compare the adhesion of Candida albicans to three restorative materials, amalgam, light cure composite and glass ionomer

Materials and Method: In this experimental study, 54 specimens of amalgam, light cure composite and glass ionomer [18 specimens from each group] were transferred to tubes containing suspensions of Candida albicans [1× 10[6] cell/ml]. After 40, 80 and 120 minutes, the specimens of restorative materials were suspended in tubes containing 1ml of saline solution and then 100 microlitre of this suspension were plated in Sabouraud Dextrouse Agar. After 48 hours of incubation, the number of candida colonies was counted. Finally, the data were analyzed using kruskal wallis and Mann-Whitney tests

Results: In the composites and amalgams specimens, the adhesion of Candida albicans increased with time and this differences was statistically significant [p < 0.05]. In glass ionomer specimens, no statistically significant difference was observed in different periods of time. The highest value of adhesion was related to composite at 120 minutes and the lowest was observed on a amalgam specimens at 40 minutes

Conclusion: The results of this study show that glass ionomer is an appropriate choice as a dental restorative material especially in patients who are susceptible to candidiasis infections

Effect of composite elasticity and filler concentration on shear bond strength of composite to dentin

Resin composites are one of the most popular tooth colored restorative materials. Their enamel and dentin bonding ability are based on many factors, including elasticity and filler concentration. This study was undertaken to evaluate the effect of volumetric filler percentage and modulus of elasticity of six composites by measuring shear bond strength to dentin of the bovine teeth as experimental bonding substrate. Eighty bovine incisors were prepared and divided into eight groups. Tetric Ceram, Tetric Flow, Compo glass F, Helimolar RO, Definite, and Degufill Mineral were applied respectively. A fifth generation of dentin bonding system [Single Bond [3M, USA]] was used for all the groups. The volumetric filler percentage of each composite was obtained from their specification data. The modulus of elasticity was determined, using the formula presented by Bream et al [1986]. Then, in last two groups Heliomolar RO and Definite were bonded using their own bonding systems, Syntac Multicomponent, and Definite Multibond. The shear bond strength was measured according to the ISO/TR 11405. Pearson's correlation test was used to compare the result with groups 4 and 5. The results indicated that the relationship between both the filler percentage and the modulus of elasticity with the shear strength was 16% [P < 0.005]. There was a significant difference between groups 4 and 7, but no significant difference was observed between groups 5 and 8. Using composites with a higher filler content and modulus of elasticity resulted in higher shear bond strength in dentin bonding system. Our results showed that the corresponding dentin bonding system of composites had better results

Non-functioning pituitary adenoma: clinicopathological study of 85 cases

Background and Purpose: Pituitary adenomas without clinically active hypertension are termed as non-functioning adenoma [NFPA]. These tumors represent about one quarter of all pituitary tumors. Immunohistochemical methods are the gold standard methods of identifying them. The Ki-67 is a nuclear antigen detected by the monoclonal antibody MIB-1, whose labeling index [LI] is considered as a marker of normal and abnormal cell proliferation

Methods and Materials: In this clinicopathological study, 85 cases of NFPAs were analyzed immunohistochemically

Results: MIB-1 LI was measured in all surgical specimens, which was higher than 5% only in 5 cases. Also, 18 cases were immunoactive to one or two adenohypophysial hormones

Conclusion: NFPAs comprise several pathologically different types of tumors, some of which are potentially hormone producing tumors. However, probable defects in hormone secretion may be the cause of not increasing the adenohypophysial hormone levels in the serum and consequent syndromes