Strategies to Avoid Underdiagnosing Pit-and-Fissure Caries.

Traditionally, testing for whether pit-and-fissure caries should be restored involved probing with a sharp explorer and evaluating resistance to withdrawal (ie, "stick"). Alternative visual methods of evaluation and classification have been proposed, validated, and accepted formally in the core curriculum on caries management in both Europe and North America. This article examines the resistance to occlusal breakdown of fluoridehardened enamel despite progression of underlying dentin caries with accompanying difficulty in diagnosis. Traditional methods of pit-and-fissure caries diagnosis, including radiographs or fissure probing with an explorer, have been shown to be inaccurate and potentially destructive. The clinical process of using the visual/tactile International Caries Detection and Assessment System (ICDAS) and/or the Caries Classification System (CCS) is described and illustrated through case examples.

Dental Anatomy and Occlusion: Mandibular Incisors-Flipped Classroom Learning Module.

INTRODUCTION: This dental anatomy module is the second in a series that develops skills in analyzing the morphology, function, anomalies, and development of human teeth. Learning the visual details associated with teeth has often proven difficult using the lecture format; thus, we have utilized computer-assisted flipped learning, which has been shown to be just as effective as lectures and frees up class time for active learning. METHODS: In a flipped classroom approach, students learn basic knowledge with a self-paced, interactive tutorial prior to class. In class, students are assigned to small groups and start with a readiness assessment quiz, administered first individually and then to each team. This is followed by a review for the whole class. The teams then practice critical thinking through practical application scenarios; a laboratory exercise follows where students wax tooth #25 and tooth #26. RESULTS: Students rated faculty members who used team-based learning higher than those who used lecture format for similar morphology lectures. For the first 3 years that this flipped classroom technique was used, students consistently scored it higher than the lecture format on a 5-point Likert scale. Multiple positive comments indicated their preference for this method. DISCUSSION: Teaching students to see the subtle variations in tooth morphology takes time and attention. In a lecture, each key point is covered only once, and images appear fleetingly. A key advantage of the self-paced interactive tutorial coupled with flipped classroom activities is that each learner can take the time needed with each image in a tutorial.

Caries Management with the International Caries Detection and Assessment System II: Established Pit and Fissure Lesions.

INTRODUCTION: Operative dentistry addresses the surgical management of caries, a significant portion of dental practice. Dental students, who typically develop their skill sets in this important discipline by creating idealized preparations in plastic teeth, are often confused by the wide variety of tooth anatomy and caries presentation they see when they subsequently treat patients. To address this significant clinical transition issue, we developed this resource on preparing the moderate carious lesion using a stepwise, structured technique. METHODS: This resource consists of a flipped-classroom learning module and associated laboratory activity with an algorithm worksheet to practice critical thinking skills. Prior to the exercise, an interactive tutorial introduces the didactic background. The 4-hour class session starts with a short quiz and review, then learners use the worksheet to prepare and restore their tooth specimens. RESULTS: Learner response has been very positive. Moreover, faculty note that learners' skills in treating patients in clinic are noticeably higher and require less faculty intervention than was previously the case. DISCUSSION: Since new national curriculum standards for caries are currently being introduced, in addition to providing instruction to dental students, this resource presents an excellent opportunity to calibrate faculty members, who are a secondary learner group in this exercise, on a standard clinical protocol.

Uninfiltrated Collagen in Hybrid Layers produced after Reduced Acid-etching Time on Primary and Permanent Dentin.

AIM: This study evaluated the influence of acid-etching time on collagen exposure in adhesive interfaces established on primary and permanent dentin. MATERIALS AND METHODS: Flat dentin surfaces were produced on sound primary molars and premolars (n = 8). The surfaces were divided into mesial and distal halves, and each half was etched with phosphoric acid for 5 or 15 seconds. The teeth were randomly allocated into two groups according to the adhesive system applied: Prime & Bond NT or Prime & Bond 2.1. After the adhesive application, the specimens were processed for Goldner's trichrome staining. The thickness of the uninfiltrated collagen zone (UCZ) in the hybrid layer was measured under optical microscopy. Data were analyzed by analysis of variance and Tukey tests (α = 0.05). RESULTS: The thickness of UCZ was adhesive dependent. Within the same substrate, the specimens treated with Prime & Bond 2.1 presented thicker UCZ when etched for 15 seconds. Collagen exposure was significantly higher for the primary teeth etched for 5 seconds and treated with Prime & Bond 2.1. CONCLUSION: The thickness of UCZ in hybrid layers is directly affected by acid-etching time and by the adhesive system applied. Primary dentin seems to be more susceptible to collagen exposure than is permanent dentin. CLINICAL SIGNIFICANCE: Both acid-etching time and adhesive system can influence the amount of exposed collagen interfering on resin-dentin bond quality, especially on primary dentin.

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.

Water distribution in dentin matrices: bound vs. unbound water.

OBJECTIVE: This work measured the amount of bound versus unbound water in completely-demineralized dentin. METHODS: Dentin beams prepared from extracted human teeth were completely demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 gH2O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 gH2O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 gH2O/g dry mass (Drierite). RESULTS: Exposure of the first layer of bound water to 0% RH for 5 min produced a -0.3% loss of bound water; in the second layer of bound water it caused a -3.3% loss of bound water; in the third layer it caused a -6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a -4 and -7% loss of bound water in the second layer, respectively; and a -17 and -23% loss of bound water in the third layer. Bound water represented 21-25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 and 35% of unbound water, respectively. SIGNIFICANCE: Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75 and 79% of total matrix water, the more such water can be removed, the more resin can be infiltrated.

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.

Quaternary ammonium silane-functionalized, methacrylate resin composition with antimicrobial activities and self-repair potential.

The design of antimicrobial polymers to address healthcare issues and minimize environmental problems is an important endeavor with both fundamental and practical implications. Quaternary ammonium silane-functionalized methacrylate (QAMS) represents an example of antimicrobial macromonomers synthesized by a sol-gel chemical route; these compounds possess flexible Si-O-Si bonds. In present work, a partially hydrolyzed QAMS co-polymerized with 2,2-[4(2-hydroxy 3-methacryloxypropoxy)-phenyl]propane is introduced. This methacrylate resin was shown to possess desirable mechanical properties with both a high degree of conversion and minimal polymerization shrinkage. The kill-on-contact microbiocidal activities of this resin were demonstrated using single-species biofilms of Streptococcus mutans (ATCC 36558), Actinomyces naeslundii (ATCC 12104) and Candida albicans (ATCC 90028). Improved mechanical properties after hydration provided the proof-of-concept that QAMS-incorporated resin exhibits self-repair potential via water-induced condensation of organic modified silicate (ormosil) phases within the polymerized resin matrix.

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.

In vitro osteogenic potential of an experimental calcium silicate-based root canal sealer.

OBJECTIVE: This in vitro study compared the cytotoxicity and osteogenic potential of an experimental calcium silicate-based sealer with an epoxy resin-based sealer (AH Plus; Dentsply Caulk, Milford, DE) and a zinc oxide-eugenol-based sealer (Pulp Canal Sealer; SybronEndo, Orange, CA). METHODS: Disks prepared from the respective sealer and from Teflon (negative control) were placed in direct contact with a MC3T3-E1 osteogenic cell line at 6 weekly intervals after immersion in a culture medium. Succinic dehydrogenase activities were evaluated using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Extracts from these sealers after the 6-week immersion period were investigated also by MTT assay. Aged sealers were then switched to an osteogenic medium for examination of the alkaline phosphatase activity and mineralization of extracellular matrices produced by the differentiated cells. RESULTS: All sealers exhibited severe toxicity after 24 hours, after which toxicity decreased gradually over the experimental period except for Pulp Canal Sealer, which remained severely toxic. Toxicity of the extracts derived from the sealers was concentration dependent, with those derived from the experimental sealer being the least cytotoxic at a 1:10 dilution. Minimal alkaline phosphatase activity and no bone formation were seen with Pulp Canal Sealer. The production of alkaline phosphatase was less intense for the experimental sealer at 7 days. However, both AH Plus and the experimental sealer did not inhibit mineralization of the extracellular matrix after 28 days. CONCLUSION: The experimental calcium silicate-based sealer may be regarded as minimally tissue irritating and does not interfere with bone regeneration even when it is inadvertently extruded through the apical constriction.

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.

Color differences: polymerized composite and corresponding Vitapan Classical shade tab.

OBJECTIVES: This study compared newer composite resin restorative materials to the Vitapan Classical tabs they purported to represent. METHODS: Five Vitapan Classical tabs were studied: A3.5, B2, C1, C3, and D2 (n=3). These tabs created a variety of levels of lightness, chroma and hue. Each of these five shade tabs was removed from three different shade guides, and an intraoral spectrophotometer was used to capture CIELAB color coordinates. Three separate readings were made and all nine were averaged. The inter-tab color differences were also calculated. Five specimens approximately 4.0mm thick were fabricated for each of the shades studied using five different composite resin materials. Composite specimens were of the same size and shape as target shade tabs, and three separate recordings were made for each of them. This average was compared to five Vitapan Classical shade tabs to calculate the color differences using both CIELAB and CIEDE2000 color difference formulas. Color differences were compared to thresholds for perceptibility and acceptability reported in other studies. RESULTS: CIELAB and CIEDE2000 color differences ranged from 3.9 to 22.8 and from 2.1 to 13.8, respectively. None of the materials proved, an acceptable CIELAB color match to any of the shades tested. CONCLUSION: When various shade tabs of Vitapan Classical shade guides were compared with correspondent tabs made of direct restorative composites, no material/shade combination resulted in an acceptable mismatch relative to the used standard of acceptability. Therefore, evaluated resin composites exhibited poor match compared to target Vitapan Classical tabs.

A comparison of human raters and an intra-oral spectrophotometer.

Consistently choosing an accurate shade match is far more difficult than it appears. Recently, several electronic shade-matching devices have been marketed. One device is an intraoral spectrophotometer, Easyshade. The current study compared the accuracy and consistency of the Easyshade (ES) device to three clinicians experienced in tooth whitening trials and trained in the use of the Vitapan 3D Master shade. The maxillary anteriors of 16 participants were matched on three separate occasions one month apart. At each appointment, the three clinicians (R1, R2 & R3) and ES independently chose a single 3D Master tab. A trained research assistant used the Easyshade device to record CIE L*, C* and H* and a shade tab. In addition, color differences between shade tabs were calculated using the Delta E 2000 (delta e 00) formula. The CIE L*C*H* data were also used to establish standards for the five lightness groups of the 3D Master. An intrarater agreement was evaluated using an intraclass correlation statistic, and an inter-rater agreement was evaluated using a weighted Kappa statistic. The percentages of exact matches were: ES = 41%; R1 = 27%; R2 = 22% and R3 = 17%. Matches within a half-shade were also calculated. This represents a mismatch that is perceptible but acceptable. The percentages of matches within a half-tab were: ES = 91%; R1 = 69%; R2 = 85% and R3 = 79%. In terms of lightness, the intra-rater agreement was considered to be very good for ES and R2 and good for R1 and R3. For chroma, agreement for ES was considered good, and for the three clinicians, it was considered moderate. The mean color difference for the L*, C*, H* data recorded at each evaluation was 1.5, or only slightly greater than the color difference between the same tab on different guides (1.2). The delta e 00 data were the most accurate data collected, and they were used to establish a standard to which the tab choices of the four raters were compared. A weighted Kappa statistic was performed and, in terms of lightness, agreement was found to be good for all raters. For chroma, agreement was very good for ES and it was good for the clinicians. In terms of the number of exact matches and matches within a half-shade, the performance of ES was at least comparable to, if not better than, the dentists. Statistically, the same was true in terms of consistency and accuracy when making repeated matches of lightness and chroma using the 3D Master shade guide.

Minimally retentive gold onlays: a six-year case report.

Partial veneer gold restorations, such as gold onlays, have changed little in preparation design over the past 40 years, as evidenced by textbooks that have long been in print. Such designs must have been based on the assumption that restorations would be luted with zinc phosphate cement but have not altered, despite the introduction of stronger luting cement classes, such as resin composite and resin-modified glass ionomer cements. It is well-established that both porcelain and base metal materials, which have been etched on the intaglio surface, can be combined with resin composite luting cements to produce restorations retained largely through adhesion. However, neither of these materials can equal the combination of minimal tooth reduction and margin adaptation that is possible with high noble gold restorative materials. Although high noble gold alloys cannot be etched, air abrasion of the intaglio surface of restorations likely improves micromechanical retention, but it is unknown whether this, along with a strong luting cement, is sufficient to stabilize high noble gold alloys in preparations with considerably less retention and resistance form than traditional designs.

In vitro cytotoxicity evaluation of a self-adhesive, methacrylate resin-based root canal sealer.

This study compared the cytotoxicity of MetaSEAL (Parkell Inc, Farmington, NY), a methacrylate resin-based sealer with an epoxy resin-based (AH Plus Jet; Dentsply Caulk, Milford, DE) and a zinc oxide-eugenol-based sealer (Pulp Canal Sealer; SybronEndo, Orange, CA). Five-millimeter diameter disks prepared from the respective sealer and disks prepared from Teflon (negative control) and polymethyl methacrylate (positive control) were placed in direct contact with a rat osteosarcoma (ROS) 17/2.8 rat osteoblast-like cell line at six intervals after setting completely at 72 hours and for 5 succeeding weeks after the disks were immersed in simulated body fluid. Succinate dehydrogenase activity was evaluated by using 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide assay. All sealers exhibited severe toxicity at 72 hours, after which toxicity decreased gradually over the experimental period except for Pulp Canal Sealer, which remained severely toxic. MetaSEAL was more toxic than AH Plus Jet during the first week. Both were similar to the toxicity profile of the positive control after the first week, which was probably diffusion controlled.

Comparison of traditional and low sensitivity whiteners.

This placebo-controlled, double-blind randomized clinical trial compared five 10% carbamide peroxide tooth whitening formulations. Three products contained varying concentrations of potassium nitrate as desensitizers. One contained no desensitizers and one was a placebo. During the two weeks of active bleaching, participants used a daily diary to record the number of days of sensitivity from hot, cold, gums, tongue and/or throat. The total number of days of sensitivity experienced by the participants in each group was compared. Participants using the agent with no desensitizers did not experience any more sensitivity than those using the agent containing 3% potassium nitrate. The products that included 0.5% potassium nitrate and 0.5% potassium nitrate and 0.25% sodium fluoride were not associated with any more sensitivity than the placebo group. In addition, the shade tab change from baseline to 11 weeks following cessation of bleaching was compared. Using an active bleaching agent, no difference in color change was noted among the four groups. All four groups were associated with significantly higher color change than the placebo. The addition of a small percentage of potassium nitrate to a 10% carbamide peroxide tooth whitener was shown to significantly reduce postoperative sensitivity without reducing efficacy.

Comparison of two low sensitivity whiteners.

PURPOSE: To evaluate two commercially available doctor-supplied, patient-applied, bleaching systems for their ability to whiten the maxillary anterior teeth while at the same time not causing sensitivity. METHODS: 46 participants were randomly assigned to one of two groups: One group received Rembrandt Xtra-Comfort and the other group Nite White Excel 2Z. Bleaching stents were fabricated and the bleaching systems were used following manufacturers' instructions. Participants recorded tray use and any sensitivity on a daily basis. Participants bleached for 2 weeks followed by 2 weeks of no bleaching. Color was evaluated at the first, second and fourth week following the initial delivery of bleaching trays. Color change was measured using the Vita Classic Shade Guide arranged by value. RESULTS: As a group, participants in the NW2Z group bleached for 302 days with a total of 48 days (16%) of sensitivity recorded. The Rembrandt Xtra Comfort group bleached for 313 total days with 97 days (31%) of sensitivity recorded. The difference in sensitivity between the two products proved to be statistically significant (Chi-square analysis, P < or = 0.0001). The median shade change for both products following 2 weeks of active treatment was six tabs. At the 4-week evaluation, the median shade change was 5.5 and 6.0 tabs respectively for Rembrandt and Nite White. There was no statistical difference between the products in respect to shade change.

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.