Effects of different luting cements and light curing units on the sealing ability and bond strength of fiber posts.

This study evaluated the sealing ability and push-out bond strength of two luting cements cured with two different types of light curing units (LCU): light-emitting diode (LED) versus quartz tungsten halogen (QTH). Forty teeth were divided into four groups(n=10/group). Quartz fiber posts (D. T. Light-Post) were luted to coronal or apical section of root canals using two types of resin cements (Panavia F or RelyX) cured with either LED LCU (Elipar FreeLight II) or QTH LCU (Optilux 501). Highest push-out bond strength was exhibited by QTH-cured RelyX, which was not significantly different from LED-cured RelyX but was higher than QTH-cured Panavia F. The push-out bond strength of Panavia F did not differ with LCU type (p>0.05), but exhibited lower values than both QTH- and LED-cured RelyX. Fluid filtration test revealed that sealing ability was not influenced by luting cement type, but was significantly influenced by LCU type in favor of QTH light source: QTH-cured specimens displayed better seal than LED-cured ones (p<0.05).

Do resin cements alter action potentials of isolated rat sciatic nerve?

OBJECTIVES: The purpose of this study was to explore the effects dual-cure resin cements on nerve conduction. METHODS: Panavia F, RelyX ARC, and Variolink II polymerized either by light-emitting diode (LED) or quartz tungsten halogen (QTH) were used in the study (n=10). The conductance of sciatic nerves of 50 rats were measured before and after contact with the specimens for 1 h. RESULTS: The time-dependent change in nerve conductance and the comparison of LED versus QTH showed that differences between groups are significant (P<.05). For both polymerization techniques, pair-wise comparisons of resin cements showed that the nerve conductance between groups is different (P<.05). RelyX ARC elicited irreversible inhibition of compound action potentials (more than 50% change) and Panavia F and Variolink II polymerized by LED and QTH did not alter nerve conduction beyond physiologic limits. CONCLUSIONS: Resin cements may alter nerve conductance and even lead to neurotoxic effects.

Effect of different polymerization methods on the cytotoxicity of dental composites.

OBJECTIVES: The aim of this study was to compare the cytotoxic effects of various dental composites polymerized with two different curing units. METHODS: Disc-shaped test samples of composites Filtek Z250, Filtek A110, Filtek P60, Filtek Supreme, and SDI Rok were polymerized using one quartz tungsten halogen (QTH) and one light emitting diode (LED) light curing unit (LCU), namely Optilux 501 (QTH) and Elipar Freelight 2 (LED). L-929 mouse fibroblast cultures (3x10(4) cells/ml) were incubated with the samples in 96 well culture plates for evaluation after 8, 24, 48, 72 h. At the end of each period, the cells were counted and examined under a light microscope, and a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay was performed. The degree of cytotoxicity for each sample was determined according to the reference value represented by the cells in a control group (a culture without sample). RESULTS: A significant 3 factor interaction occurred among LCUs, composites, and time factors (P<.005). In general, the test materials cured with the LED LCU demonstrated higher cell survival rates when compared with those cured with halogen LCUs. CONCLUSIONS: This study shows that polymerization of dental composites with a light emitting diode LCU positively influences the L-929 mouse fibroblast cell viability.

Vascular smooth muscle contraction/relaxation of rat carotid artery is not altered by bone grafting substitutes in vitro.

PURPOSE: The aim of this study was to explore the effects of various bone grafting substitutes (Osteosponge, Perioglas, Tutoplast, and Surgibone) on vascular smooth muscle tonus. METHODS: Bilateral carotid arteries were removed from rats and contraction/relaxation of isolated vessel rings were measured before and after contact with the biomaterials and then, for dose-dependent epinephrine and papaverin administrations, by a force displacement transducer. The data of each biomaterial group were collected by a computerized system and corresponding software at a sample rate of 1,000 kHz and were converted to contraction force. RESULTS: Vascular contraction forces were influenced in response to biomaterials tested except for Osteosponge (P < 0.05), although the differences between groups were insignificant (P > 0.05). There was a dose-dependent vascular response to epinephrine and papaverine administration upon biomaterial contact (P < 0.05). The dose-dependent vascular responses to epinephrine and papaverine administration were almost similar for all biomaterials tested (P < 0.05), suggesting that the biomaterials led to reversible effects on vascular contraction/relaxation behavior, which resulted in recovery. CONCLUSIONS: Osteosponge, Perioglas, Tutoplast, and Surgibone do not alter vascular smooth muscle tonus and vitality and therefore would, presumably, not jeopardize the angiogenesis of fresh blood vessels and full vascularization during tissue healing.

Water Absorption and HEMA Release of Resin-Modified Glass-Ionomers.

OBJECTIVES: The aim of this study was to evaluate the water absorption and the amount of hydroxyethyl metacrylate (HEMA) level released from various resin modified glass ionomer cements. METHODS: Advance, Vitremer and Protec-Cem resin modified glass ionomer cements were used to evaluate the HEMA release. Ten specimens were fabricated from each cement in 10 x 1 mm height. Thirty specimens were immersed in glass containers filled with 20 ml deionized water. 1 ml solution was taken from the container at 10 minutes, 1 hour, 24 hour and 7 days intervals from each group and analyzed with high performance liquid chromatography (HPLC) machine and the results are presented in ppm. The data were subjected to Kruskal-Wallis, Mann-Whitney and Wilcoxon tests at a 0.05 significance level. RESULTS: At all time intervals Vitremer showed highest HEMA release ( 10 min: 54.2 ppm; 1 h: 86.8 ppm; 24 h: 93.4 ppm) (P=0.0001). At the end of 10 minutes and first hour, following Vitremer, HEMA release was highest for Protec-Cem (10 min: 14.8 ppm; 1 h: 23.6 ppm) and then Advance (10 min: 5.5 ppm; 1 h: 18.8 ppm) (P<.05). Water absorption tests were performed according to the specifications of ISO 4049. Water absorption was highest for Vitremer and lowest for the Protec-Cem and the difference among cement groups was significant (P<.005). CONCLUSIONS: Vitremer showed the highest HEMA release and water absorption values and Protec-Cem showed the lowest values. HEMA release by time was significant for Advance cement. This release may be relevant both to the risk of adverse pulpal responses in patients and to the risk of allergy in patients and dental personnel.