Effect of Sodium Fluoride on the endogenous MMP Activity of Dentin Matrices.

OBJECTIVES: This study evaluated the effect of incorporating increasing concentrations of sodium fluoride in incubation media, on the loss of dry mass and solubilization of collagen from demineralized dentin beams incubated for up to 7 days. The effect of fluoride on the inhibition of matrix-bound metalloproteinases (MMPs) was also measured. METHODS: Dentin beams were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass, the beams were divided into six groups (n=10) and incubated at 37°C either in buffered media containing sodium fluoride (NaF) at 75, 150, 300, 450, 600 ppm or in fluoride-free media (control) for seven days. Following incubation, dry mass was re-measured. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HYP) as an index of solubilization of collagen by endogenous dentin proteases. Increasing concentrations of fluoride were also evaluated for their ability to inhibit rhMMP-9. RESULTS: Addition of NaF to the incubation media produced a progressive significant reduction (p<0.05) in the loss of mass of dentin matrices, with all concentrations demonstrating significantly less mass loss than the control group. Significantly less HYP release from the dentin beams was found in the higher fluoride concentration groups, while fluoride concentrations of 75 and 150 ppm significantly reduced rhMMP-9 activity by 6.5% and 79.2%, respectively. CONCLUSIONS: The results of this study indicate that NaF inhibits matrix-bound MMPs and therefore may slow the degradation of dentin matrix by endogenous dentin MMPs.

Cytotoxicity of endodontic sealers after one year of aging in vitro.

The in vitro cytotoxic response to endodontic sealers was assessed for one year. AH-Plus (AHP), Epiphany (EPH), EndoRez (ER), Guttaflow (GF), InnoEndo (IN), and Pulp Canal Sealer (PCS) were exposed to mouse osteoblasts and human monocytes after curing, 52 weeks of aging, and after resurfacing post-aging; cellular response was estimated by succinate dehydrogenase (SDH) activity. The effect of materials on TNFα secretion from activated (LPS) and inactivated monocytes also was measured. Cell responses were compared with ANOVA and Tukey post hoc analysis (α = 0.05). Initially, all materials except GF suppressed osteoblastic SDH activity compared with Teflon (Tf) controls. SDH activity in cells exposed to some aged sealers improved significantly; but IN and ER remained cytotoxic. When aged materials were resurfaced then tested, AHP, ER, GF, and IN did not change. EPH and PCS were more toxic. Monocytes responded similarly to the osteoblasts. No endodontic sealer activated monocytic TNFα secretion (p > 0.05 vs. -LPS Tf-controls). LPS-activated monocytes exposed to unresurfaced AHP and IN significantly suppressed TNFα secretion. When activated monocytes were exposed to the resurfaced sealers, differential suppression of TNFα secretion was observed for three of the four sealers tested (EPH, IN, and PCS). The results suggest that long-term aging may be a useful adjunct to in vitro assessment of these materials.

Dysregulation of monocytic cytokine secretion by endodontic sealers.

Recent studies have reported that sealers may alter the secretion of specific cytokines from THP1 monocytic cells in vitro. In this study, a cytokine array was used to determine if endodontic sealers changed secretion of 42 cytokines. White mineral trioxide aggregate (WMTA), MTA preparation (CS), AH-Plus (AHP), and Pulp Canal Sealer (PCS) were mixed, allowed to set for 72 h, then "aged" in buffered-saline for 12 weeks. Aged specimens were placed in direct contact with THP1 for 72 h and their cytotoxicity (MTT assay) was assessed. Materials that were not severely toxic were then exposed to THP1 with or without lipolysaccharide (LPS), and the culture medium was assayed for cytokine secretion. Secretion of cytokines was quantified using infrared scanning (Odyssey(®)); replicate pairs were averaged. PCS severely suppressed MTT activity and was not assessed for its influence on cytokine secretion. WMTA, CS, and AHP induced a broad-based increase in cytokine secretion (>20% vs. Teflon controls), but AHP induced the greatest increase (>100% in 17 of 42 cytokines). The effects of the sealers on LPS-activated THP1 were biphasic, with some increases and decreases cytokine secretion of >20%, but few larger effects. This work shows endodontic sealers may alter the secretion of a broad cross section of cytokines from monocytic cells.

Cytotoxic response of three cell lines exposed in vitro to dental endodontic sealers.

The in vitro cytotoxicity of five endodontic sealers was measured >8-12 weeks using L929 mouse fibroblasts, osteoblastic cells (ROS) 17/2.8 rat osteoblasts, and MC3T3-E1 mouse osteoblasts. Discs (n = 6) of AH-plus Jet (AHP), two versions of Endo Rez (ER, ERx), Epiphany (EPH), and Pulp Canal Sealer (PCS) were prepared. The sealers and Teflon (Tf, negative control) were placed in direct contact with cells after immersion in phosphate-buffered saline for 1-12 wk. Cellular succinate dehydrogenase (SDH) activity was estimated using the MTT method (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a yellow tetrazole), and activities were normalized to Teflon® controls. The cellular responses to the materials were compared using analysis of variance with Tukey posthoc analyses (α = 0.05). Initially, all sealers suppressed normalized SDH activity of L929 fibroblasts by >90%. After 12 weeks of immersion in saline, AHP exhibited the SDH activity above Tf (120%), followed by ERx (78%), ER (58%), PCS (38%), and EPH (28%), all statistically distinct (p < 0.05). In general, the three cell lines responded similarly to the sealers. However, AHP caused unique responses: ROS cells were significantly (p < 0.05) less sensitive initially, and AHP was severely cytotoxic to MC3T3 cells (<35% of Tf) through 8 weeks. The data suggest that with "aging" in saline, current endodontic sealers decrease in in vitro cytotoxicity at different rates.

Two-year clinical performance of Clearfil SE and Clearfil S3 in restoration of unabraded non-carious class V lesions.

This study was undertaken to evaluate the two-year clinical performance of a self-etching primer and a self-etching adhesive, both of which employ the same acidic monomer. Forty pairs of restorations of AP-X hybrid resin composite (Kuraray Co, Ltd, Osaka, Japan) were placed in caries-free cervical erosion/abfraction lesions. Based on insensitivity to air, the dentin in 62% of these lesions was considered to be sclerotic. The restorations were placed with no abrasion of tooth surfaces, except for cleaning with plain pumice and no use of phosphoric acid etching, which is counter to the manufacturer's instructions that call for etching of unprepared enamel. One restoration from each pair was placed using Clearfil SE Bond, an adhesive employing a self-etching primer, and the other was placed using Clearfil S3 Bond, a self-etching adhesive. To emulate the results likely to occur in a private practice, the restorations were placed by well-educated, experienced clinicians who had no particular expertise in adhesive dentistry research and who placed the restorations according only to their interpretation of the manufacturer's instructions. The restorations were clinically evaluated at baseline and at 6, 12 and 24 months, using modified Ryge/USPHS criteria. For both products, retention of 81%-84% of the restorations was observed over two years, which is lower than has been previously observed with these products and is likely due to limitations in the manufacturer's instructions compounded by inexperience of the operators in adhesive dentistry research. One restoration placed with each adhesive demonstrated secondary caries, which was probably attributable to the study being conducted in a non-fluoridated area and which reduced the percentages of clinically successful restorations to 78%-81%. No statistically significant difference (p = 0.50) between the two adhesives was observed in overall performance.

Inflammatory suppression by endodontic sealers after aging 12 weeks In vitro.

Dental endodontic sealers are in intimate contact with tissues around the root apex (periapical area) for extended periods. New endodontic sealers have been developed in the past decade, but the biological responses to many new products are not well documented. In this study, we assessed in vitro monocytic cytotoxic and inflammatory responses to several contemporary endodontic sealers. AH-Plus (AH), Pulp Canal Sealer (PC), Epiphany (EPH), Endo-Rez (ER), and an experimental Endo-Rez (ERx) were initially placed in buffered-saline for 12 weeks to simulate in vivo use. After "aging," specimens were placed in direct contact with THP1 monocytes for 72 h and their cytotoxicity (mitochondrial response; MTT) or ability to trigger or suppress cytokine secretion (ELISA; TNFalpha, IL1beta, IL=6; +/- lipopolysaccharide (LPS) exposure) were measured relative to Teflon (Tf) negative controls. Cellular responses among conditions were compared with ANOVA and Tukey post-hoc analysis (alpha = 0.05). Two of the five sealers, EPH and PC, still suppressed cell mitochondrial activity by 70% or more after 12 weeks of conditioning in saline. No sealer alone activated monocytic TNFalpha, IL1beta, or IL6 secretion (p > 0.05 vs. +LPS controls). When THP1 were activated by LPS after exposure to the sealers, differential suppression of TNFalpha, IL1beta, and IL6 secretion was observed for two of the five sealers tested. (EPH and PC) This data suggest that common endodontic sealers do not activate monocytic TNFalpha, IL1beta, and IL6 secretion in vitro by themselves, but degradation products of the sealers may suppress activation of monocytes.

In vitro cytotoxic response to lithium disilicate dental ceramics.

OBJECTIVES: The use of lithium disilicate dental ceramics is increasing in dentistry and previous reports have suggested that they may have greater biological risks than previously thought. We tested a hypothesis that composition and processing influence the biological properties of these ceramics. METHODS: The cytotoxicity of two machined and three pressed lithium disilicate materials (n=6) were tested in vitro using mouse fibroblasts in direct contact with the materials for 72h. Cellular response was estimated by mitochondrial succinate dehydrogenase activity (MTT method). Mitochondrial activity was expressed as a percentage of Teflon controls, then compared to Teflon using 2-sided t-tests (alpha=0.05). Polished materials were aged in artificial saliva and tested for cytotoxicity periodically over 6 weeks, then were repolished (320grit SiC paper), aged and tested again for 4 weeks. RESULTS: All materials significantly (50-70%) suppressed cellular mitochondrial activity in the initial week, but suppression decreased by 25-30% over the next 2 weeks. In weeks 4 and 6 some materials exhibited a cytotoxic 'relapse' of 10-20%. The cytotoxic response was no different for machined or pressed materials, but the presence of ZnO had at least an association with longer-term cytotoxicity and relapse. Repolishing to 320grit did not increase cytotoxicity significantly. SIGNIFICANCE: Our results suggest that lithium disilicates are not biologically inert, and that many have a similar cytotoxicity dynamic regardless of small differences in composition or processing.

The effect of light curing source on the residual yellowing of resin composites.

PURPOSE: This study evaluated the amount of residual yellow in cured resin composites when polymerizing with either a quartz-tungsten-halogen (QTH) or blue light-emitting diode (LED). MATERIAL AND METHODS: Twelve shades (bleaching to conventional shades) of microfill, hybrid and microhybrid resin composite specimens (n = 10) were polymerized with both light types. All the materials contained only camphorquinone as the photoinitiator. After exposure, the specimens were stored in the dark for 24 hours. Then, the specimen color parameters were recorded (L*, a*, b* and C*(ab)) and color differences (deltaE*(ab)) were determined by examining for changes among the test combinations. Group comparisons were examined using ANOVA and the Tukey-Kramer post-hoc test, and pairwise comparisons were made using the Student's t-tests at a pre-set alpha of 0.05. RESULTS: When a significant difference in the shade of yellow was noted, the QTH light produced a greater yellow tinge than most comparisons using the LED. The potential for producing more residual yellowing could not be anticipated with respect to composite filler classification or shade, as this effect may be more dependent on individual product composition. The extent to which residual yellowing differences were noted between light curing units fell within levels considered detectable by the human eye (deltaE > 2.0). CONCLUSION: The selection of light curing unit to polymerize resin-based restorative materials can have a significant influence on the amount of residual yellow present, with the QTH light tending to leave more yellow than an LED unit.

The effect of chlorhexidine on dentin hybrid layers in vivo.

This in vivo study evaluated by TEM the degradation of dentin hybrid layers in deep occlusal resin composite restorations. Caries-free premolars scheduled for extraction as part of orthodontic treatment were prepared, restored and evaluated after two and six months. The adhesive used was a single-bottle etch-and-rinse product (Single Bond Plus, 3M ESPE). Control group restorations were placed according to the manufacturer's instructions, while the experimental group received application of a 2% solution of chlorhexidine digluconate after etching. No degradation was observed in either group after two months. Slight degradation was found in the control group after six months, but none was observed in the experimental group. In vitro testing showed no significant difference in microtensile bond strength between the control and experimental adhesive protocols.

Penetration of fluids into periodontal pockets using a powered toothbrush/irrigator device.

UNLABELLED: This study was a single-blind, randomized, controlled clinical trial. The researchers evaluated a powered brush/irrigating device (HydraBrush Oral Health System; OHS) for its safety and ability to deliver a solution to the bottom of 5-6 mm pockets, compared to rinsing alone with a solution following brushing with a powered toothbrush (Sonicare Elite 7800; SE). An evaluation technique to measure the quantity and quality of solution able to enter the pocket was also introduced in this project. METHODS: Subjects were randomized in one of two-groups: brush plus simultaneous irrigation (OHS) versus brush plus rinsing (SE). Subjects used their devices at home for two weeks. At the measurement visit, subjects used the OHS to irrigate and brush simultaneously for 1 minute (30 seconds per each side of the mouth) with a 0.01% erythrosine disclosing solution in 10 oz of distilled water. Control subjects brushed for 2 minutes with a SE followed by a 1 minute rinse with an identical disclosing solution. A blinded evaluator collected six samples of approximately of 1 microL of sucular fluid from six 5-6 mm evaluation sites. This was accomplished by inserting a microcapillary tip with a 20 microL micropipette in the sulcus. Two-group repeated measures ANOVA was used to examine differences in two measures of the disclosing solution between OHS and SE subjects; the spectrometer reading of the disclosing solutions, and by visual inspection of the samples (positive/negative) to determine the presence or absence of solution in the samples. Subjects' diaries were collected. Bleeding and discomfort during the evaluation period was reported. RESULTS: Visually, OHS had a significantly greater proportion of solution taken from the base of 5-6 mm sites than the SE (p=0.0001). However, there was no statistical difference between the two groups (p=.1359) in the spectrophotometer readings. CONCLUSION: The experimental device is more efficient in delivering a solution to the base of 5-6 mm pockets than rinsing following use of a control powered toothbrush. Both devices have demonstrated they are safe and well accepted by patients. The technique developed provides a useful method for quantitative and qualitative studies of solutions from the base of periodontal pockets.

Restoration of proximal contact in direct class II resin composites.

Although this technique performed well in the case presented, it becomes more advantageous with larger restorations. This would be especially true for core build-up restorations of missing cusps, although such cusps must be restored prior to placement of separating rings. Clear plastic matrices are available and permit effective curing of resins, but the authors find the preset contours of these matrices not sufficiently adaptable to differing clinical situations and prefer metal matrices, even though these necessitate additional light curing after matrix removal.

Eighteen-month clinical performance of a self-etching primer in unprepared class V resin restorations.

This study evaluated the clinical performance of unprepared Class V resin composites, placed using a self-etching primer and a single-bottle adhesive, over a period of 18 months. Thirty-eight pairs of restorations of Renew hybrid resin composite (BISCO, Inc) were placed using adhesives from the same manufacturer in caries-free cervical erosion/abfraction lesions. Based on insensitivity to air, the dentin in 76% of these lesions was considered to be sclerotic. The restorations were placed without abrasion of tooth surfaces, except for cleaning with plain pumice. One of each pair was placed using Tyrian, a self-etching primer and the other was placed using One-Step, a single-bottle adhesive placed after acid etching. Both the etchant and self-etching primer were applied for 20 seconds. The restorations were clinically evaluated at baseline, 6, 12 and 18 months, using modified Ryge/USPHS criteria. For both adhesives, very low retention of 50% to 56% of the restorations was observed over 18 months, leading to the conclusion that tooth surfaces must receive some additional treatment prior to restoration with these adhesives. No statistically significant difference (p=0.75) between the two adhesives was observed in overall performance, and dentinal sclerosis and axial depth did not appear to be important factors in the study.

Two-year clinical performance of Class V resin-modified glass-lonomer and resin composite restorations.

While a one-year report had been previously published, this study was undertaken to evaluate the clinical performance and appearance of a resin-modified glass ionomer and a resin composite over two years. Thirty-seven pairs of restorations of FujI II LC and Z 250/Single Bond were placed in caries-free cervical erosion/abfraction lesions without tooth preparation. Restorations were clinically evaluated at baseline, 6, 12, 18 and 24 months using modified Ryge/USPHS criteria. No statistically significant difference (p = 0.13) was observed in the overall performance of the materials. Retention was 96% for the resin-modified glass ionomer and 81% for the resin composite, with no additional restorations of either material lost after one year. As previously reported, retention of the Z 250 restorations at six months was below the minimum specified in the ADA Acceptance Program for Dentin and Enamel Adhesives. The resin composite restorations generally had a better appearance, with a 100% alpha rating in color match, versus 85% for the resin-modified glass ionomer.