Effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials: An in vitro investigation.

The aim of the study was to evaluate the effects of erosion and abrasion on resin-matrix ceramic CAD/CAM materials [CERASMART (GC); VITA ENAMIC (VITA Zahnfabrik); Lava Ultimate (3 M)] in comparison to feldspar ceramic (VITABLOCS Mark II, VITA Zahnfabrik) and resin composite materials (ceram.x universal, Dentsply Sirona). Daily brushing and acid exposure were simulated using a brushing apparatus and a solution of 0.5 vol% citric acid. Microhardness, surface roughness, and substance loss were measured at baseline and after simulation of 1 and 3 years of function. All materials showed a decrease in microhardness after 3 years and an increase in surface roughness (Ra) after 1 and 3 years. The Ra increase was statistically significantly lower for the resin-matrix ceramics than for feldspar ceramic and similar to composite material. After 3 years, only feldspar ceramic showed no significant substance loss. In conclusion, resin-matrix ceramics demonstrate reduced roughening compared to feldspar ceramics, potentially improving restoration longevity by preventing plaque buildup, but differences in abrasion resistance suggest the need for further material-specific research. Future research should aim to replicate clinical conditions closely and to transition to in vivo trials.

The effect of long-term use of tooth bleaching products on the human enamel surface.

The aim of this in vitro study was to evaluate the long-term effect of bleaching on human enamel. Four groups of enamel specimens were prepared (n = 20): group 1: bleaching with Opalescence Boost [40% hydrogen peroxide (H2O2), 3 × 20 min/week]; group 2: control group (the specimens were stored in human saliva); group 3: beaching with Vivastyle Paint on Plus (6% H2O2, 2 × 10 min/day), and group 4: bleaching with Opalescence PF 16% [16% carbamide peroxide (CP), 6 h/day]. After each bleaching session the specimens were stored in human saliva. Knoop microhardness and surface roughness were measured: before bleaching, after 2-week and after 8-week bleaching. After 2-week treatment, surface roughness was significantly increased in all experimental groups (p < 0.05), while among them no significant difference was found (p > 0.05). The roughness changes exerted after 8-week bleaching were not significantly higher than the ones after 2 weeks (p > 0.05). After 8-week treatment, the increase in roughness caused by 16% CP was significantly higher (p < 0.05) than the one caused by 40% H2O2. Microhardness increased in all groups including control; however, only 40% H2O2 increased the microhardness significantly (p < 0.05). The effect of bleaching on enamel was not shown to be dependent on the method or the H2O2 concentration. Bleaching with CP 16% resulted in higher roughness than bleaching with H2O2, while 40% H2O2 caused the higher microhardness increase. The present study showed that in-office bleaching with 40% H2O2 seems to be at least as safe as home bleaching as far as their effects on human enamel are concerned.

Evaluation of Surface Roughness of Ceramic and Resin Composite Material Used for Conservative Indirect Restorations, after Repolishing by Intraoral Means.

PURPOSE: To evaluate and compare the mean surface roughness (Ra) of one ceramic and one resin composite material used for indirect restorations, after grinding and repolishing by intraoral means. MATERIALS AND METHODS: The materials used were the lithium disilicate glass ceramic IPS e.max Press (EMP) and the indirect resin composite restoration system Gradia (GR). Twelve specimen disks were prepared from each material according to the manufacturer of each material. Five initial measurements of the Ra (Ra1 ) were made on each specimen as a referral basis, and the specimens were ground with a fine (red) diamond bur. The specimens were repolished using (a) Komet Dialite Polishing Kit for EMP and (b) Enhance Finishing and Polishing System and Prisma Gloss Polishing Paste for GR. Five final Ra (Ra2 ) measurements were performed on each specimen. All measurements were made using a laser profilometer. Scanning electron microscopy (SEM) was also used to visualize the initial surface morphology and the morphological changes on the specimens' surface after repolishing. RESULTS: A highly significant difference was found between Ra1EMP and Ra2EMP (p < 0.001), between Ra1GR and Ra2GR (p < 0.001), as well as between Ra2EMP and Ra2GR (p < 0.001), when compared in pairs. A highly significant difference (p < 0.001) was also found between ΔRaEMP and ΔRaGR , with ΔRaGR being higher than ΔRaEMP . The RaGR values were higher than the RaEMP values at all times. SEM revealed that both EMP and GR repolished surfaces presented with irregularities; however, in GR specimens major voids and craters were present. CONCLUSIONS: EMP was found to perform better when polished by intraoral means compared with GR. Both materials exhibited Ra2 above the critical threshold for increased plaque accumulation and periodontal inflammation. If enamel-to-enamel roughness found in occlusal contact areas is considered as baseline, both materials were clinically acceptable after repolishing.

Effect of gaseous ozone on Enterococcus faecalis biofilm-an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the antimicrobial effect of gaseous ozone compared to conventional methods against Enterococcus faecalis. MATERIALS AND METHODS: One hundred twenty-five teeth were infected by E. faecalis and were incubated for 72 h to form biofilm. Teeth were distributed among five groups. In the first group, ozone was used; in the second group, teeth were rinsed with 20 % ethylenediaminetetraacetic acid (EDTA); in the third group, with 3 % sodium hypochlorite (NaOCl). Group 4 combined 20 % EDTA with ozone. NaOCl and ozone were combined in group 5. After treatment, the samples with paper points were taken, followed by dentin samples taken with K-file, and cultured for 24 h. Then bacterial colonies were counted. RESULTS: All treatments reduced significantly (p < 0.05) the bacteria. Paper points' samples showed 85.38 % reduction after ozone. The highest reduction was observed in NaOCl group (99.98 %). EDTA reduced bacteria by 80.64 %. Combination of NaOCl and ozone eradicated 99.95 % of the bacteria. Combination of EDTA and ozone reduced E. faecalis up to 91.33 %. The dentin chips showed the following: the highest CFU counts were observed in EDTA group, followed by ozone and NaOCl group. The lowest CFU counts were found in NaOCl-ozone group and EDTA-ozone group. CONCLUSIONS: Ozone reduced E. faecalis, even organised in a biofilm, however, lower than NaOCl. No treatment reduced totally the bacteria. CLINICAL RELEVANCE: Used as an adjuvant, ozone can increase the efficacy of conventional rinsing like EDTA and presents an alternative treatment when NaOCl cannot be used e.g. in teeth with a wide-open apical foramen.

A temporary filling material during endodontic treatment may cause tooth fractures in two-surface class II cavities in vitro.

OBJECTIVES: To investigate the effect of a zinc oxide/zinc sulphate-based cement as a temporary filling material during root canal treatment on the occurrence of cracks within the filling material or the tooth. MATERIALS AND METHODS: Root canals of 122 extracted human molars were prepared using ProTaper instruments. Standardized occlusal-distal cavities were prepared. After placing calcium hydroxide into the root canals, the teeth were divided randomly into four groups containing 33 specimens each. In the Coltosol group, the cavity was completely filled with Coltosol® F. In the Coltosol-Clearfil group, a 2-mm layer of Coltosol® F was placed into the apical part of the pulp chamber, and in the Clearfil group, a foam pellet was placed into the coronal pulp chamber. The remaining cavities were filled with Clearfil™. In the control group, the cavities were not restored. The teeth were stored at 37 °C for 14 days and examined every 24 h under a stereomicroscope. RESULTS: Fractures of the filling and/or the tooth were only observed in the Coltosol group. All Coltosol® F restorations had cracks after 24 h. Tooth fractures were found in 25 (76 %) teeth. Among these teeth, 21 (84 %) had crown fractures, four (16 %) had root-crown fractures. All root-crown fractures were vertical. CONCLUSION: Coltosol® F when used alone led to tooth fractures in two-surface class II cavities in teeth undergoing root canal treatment. CLINICAL RELEVANCE: Coltosol® F solely used as restorative material may lead to tooth fractures in two-surface class II cavities.

Water sorption and water solubility of self-etching and self-adhesive resin cements.

STATEMENT OF PROBLEM: The long-term success of indirect restorations depends on the clinical behavior of luting cements. In the oral environment, properties such as water sorption and solubility negatively affect the cements' clinical performance over time, jeopardizing the restoration's longevity. PURPOSE: The purpose of this in vitro study was to compare the water sorption and solubility characteristics of self-etching, self-adhesive, and conventional resin cements. MATERIAL AND METHODS: One conventional (Calibra), 1 self-etching (Panavia F), and 2 self-adhesive (Clearfil SA, G-Cem Automix) dual-polymerized resin cements were used. Fourteen disks of each material were prepared. Water sorption and solubility were calculated according to International Organization for Standards (ISO) specification 4049:2009. RESULTS: According to the water sorption test, all materials were found to interact with water. No statistically significant differences were found between the water sorption of Panavia F and Clearfil SA (P=.911). These cements exhibited higher water sorption values than the other materials (P<.05), whereas Calibra exhibited the lowest values (P<.05). Statistically significant differences were found among all materials regarding their water solubility (P<.05). Panavia F and Clearfil SA were found to have higher solubility values than the other materials. G-Cem Automix and Calibra exhibited negative solubility. However, all water sorption and solubility values were below the threshold values proposed by the ISO standard. CONCLUSIONS: Within the limitations of the present in vitro study, the interaction of resin cements with water is not type-related (conventional, self-etching, or self-adhesive).

Efficacy of tooth bleaching with and without light activation and its effect on the pulp temperature: an in vitro study.

The aim of this in vitro study was to evaluate the colour stability of bleaching after light activation with halogen unit, laser, LED unit or chemical activation up to 3 months after treatment. Four groups of teeth (n = 20) were bleached with Opalescence Xtra Boost (38% hydrogen peroxide) using four different methods: activation with halogen, LED, laser or chemical activation only. All teeth were bleached in one session for four times (4 × 15 min) and the colour was evaluated using a spectrophotometer at the following time points: before bleaching, immediately after bleaching, 1 day, and 1 and 3 months after the end of bleaching. Between the tested time points, the teeth were stored in 0.9% NaCl solution. Additionally, the temperature increase in the pulp chamber was measured using a measuring sensor connected to a computer. Bleaching with the halogen unit showed the highest colour change. Halogen unit, laser and chemical activation resulted in whiter teeth after 1 and 3 months compared to the colour after the end of the bleaching procedure (p ≤ 0.05). Three months after the end of bleaching, the shade changes observed were-halogen: 7.1 > chemical activation: 6.2 > LED: 5.4 > laser: 5.2. Halogen showed the highest temperature increase (17.39°C ± 1.96) followed by laser (14.06°C ± 2.55) and LED (0.41°C ± 0.66) (p < 0.0001). Chemical activation did not affect the temperature in the pulp chamber. The use of light activation did not show any advantages compared to chemical bleaching. Although halogen unit showed the higher shade's change, its use resulted also in the higher pulp temperature. According to the present findings, light activation of the bleaching agent seems not to be beneficial compared to bleaching without light activation, concerning the colour stability up to 3 months after bleaching and the pulp temperature caused during the bleaching procedure.

Elution of monomers from three different bonding systems and their antibacterial effect.

The aim of the present study was to evaluate the release of monomers from three bonding systems and to correlate it with their antibacterial effect. Three bonding systems (Optibond FL(®), Xeno III(®) and Clearfil™ Protect Bond) were tested after storage in ethanol 75 % and human saliva. Twenty samples (n = 10/medium) of each bonding material were prepared and polymerized according to the manufacturers' instructions. Each sample was stored in 1 ml of the respective storage medium. The medium was renewed after 24 h, 7 days, and 28 days and was analysed by LC-MS/MS for the release of substances. Additionally, the antibacterial effect of the unpolymerized components of each bonding system and their polymerized mixture was tested using agar disc-diffusion test with Streptococcus mutans. Only HEMA was found to be released. The amount of HEMA detected in the ethanol samples was significantly higher compared to the saliva samples (p < 0.0001). The release of HEMA was as follows: Clearfil™ Protect Bond < Optibond FL(®) < Xeno III(®.) According to the agar disc-diffusion test, all materials exhibited certain antibacterial activity. The release of HEMA from all tested materials even after storing in human saliva increases the concerns about their toxicity. Their antibacterial effect seems not be due to the release of substances.

Effect of dental composite dust on human gingival keratinocytes.

OBJECTIVE: The aim was to investigate the effect of particles released during grinding of dental composites on human gingival keratinocytes (HGK). METHODS: Specimens from Filtek™ Supreme XTE and ceram.x® universal were prepared and ground to dust. The dust was filtered (≤ 5 µm) and the particle size distribution was examined using NANO-flex®-180° dynamic light scattering (DLS). Suspensions at five concentrations (3, 10, 30, 100 and 300 µg/mL) were prepared using keratinocyte growth medium (KGM). These suspensions, as well as a positive (CuO) and a negative control (KGM) were added to HGK. The cells treated with Filtek™ Supreme XTE suspensions were analyzed by real-time monitoring using RTCA iCELLigence™. In addition, light and scanning electron microscopic images of the exposed cells were taken. Indirect immunofluorescence staining was performed to detect the extracellular matrix protein fibronectin. RESULTS: In distilled water, DLS showed similar particles' range (171.9 nm- 2.7 µm) for both composites. In saliva, larger particles were detected (Filtek™ Supreme XTE: 243 nm-6,5 µm; ceram.x® universal: 204 nm- 4,6 µm). iCELLigence™ revealed similar results of cell growth parameters for HGK incubated with composite dust (≤ 5 µm) at different concentrations. The microscopic images indicated unaltered cell structures and formation of large agglomerates with high particle concentration (> 100 µg/mL). Exposure to composite dust resulted in upregulation of fibronectin expression. SIGNIFICANCE: Grinding of dental composite materials generates dust particles of different sizes. The particle size distribution seems to be more influenced by the suspending medium than the material itself. While cell growth of HGK seem not to be affected by the particles, an upregulation of fibronectin in the intercellular space concomitant by increasing particle concentration may indicate an increase of cell migration/mobility.

Method development for the intraoral release of nanoparticles from dental restorative materials.

OBJECTIVE: The aim of this study was the development of a novel in-vitro method to evaluate the intraoral release of wear particles with a diameter< 1 µm from dental restorative materials. METHODS: Test fixtures for a dual-axis chewing simulator (CS-4.8, SD Mechatronik, Feldkirchen-Westerham, Germany), consisting of three components to mount the specimens and a solvent (distilled water) as well as a zirconia antagonist to transfer the masticatory forces onto the specimen was developed. Ceram.x Spectra™ ST HV (CS) and Filtek™ Supreme XTE (FS) specimens (n = 3) were fixed into the mounts and immersed in 25 ml solvent. All specimens were subjected to 500.000 wear cycles with a load of 49 N. The particle size distribution of the suspensions were examined by dynamic light scattering (DLS). The collected particles were characterised by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). For wear quantification, the surfaces of the specimens were photo-optically scanned and the wear was measured. For the statistical analysis, one-way ANOVA and post-hoc Scheffé tests were applied. RESULTS: DLS showed particle diameters< 1 µm (CS: 18.06 nm-1.64 µm, FS: 72.30 nm-2.31 µm). SEM/EDS indicated an association between the detected elements and the materials' composition. FS showed significantly higher volume loss (p = 0.007) and maximum depth of the wear profile (p = 0.005) than CS, but no significant differences in the surface loss (p = 0.668). SIGNIFICANCE: The novel method is able to detect material dependent particles to the size of nanoscale after in-vitro abrasion.

The antibacterial effect of gas ozone after 2 months of in vitro evaluation.

The aim of this study was to evaluate the effect of HealOzone on two microorganisms, 4 and 8 weeks after treatment, using a tooth cavity model. Four groups of caries-free third molars (n = 12) were used (A, B, C and D). Three cavities were prepared into each tooth. After sterilization, groups A and B were inoculated with Streptococcus mutans, and groups C and D, with Lactobacillus casei for 48 h. One cavity of each tooth was used to evaluate the infection. After inoculation, groups B and D were treated with ozone (60 s), and groups A and C were used as controls. Then, the two cavities of each tooth were filled with composite, and the teeth were stored in sucrose medium. The restorations were removed after 4 and 8 weeks, respectively; dentin chips were collected, and the amount of microorganisms was determined. Ozone treatment reduced significantly the amount of S. mutans compared to the control group (p ≤ 0.05). This antibacterial effect was able to be seen after 4 (p = 0.0005) and 8 (p = 0.0002) weeks. No significant difference was found between the control and treated group as far as L. casei is concerned (p > 0.05). HealOzone (60 s) can provide some antibacterial treatment against S. mutans even after 8 weeks. However, an elimination of the microorganisms through HealOzone seems not to be possible. L. casei was more resistant to ozone. Although ozone exerts a significant antibacterial effect against S. mutans, it is probably not enough as the only antibacterial method, during the fillings therapy.

Response of human gingival keratinocytes to hybrid CAD/CAM material eluates.

OBJECTIVES: The aim of this study was to investigate the influence of hybrid CAD/CAM-blocks on immortalized human gingival keratinocytes (HGK). METHODS: Samples of two different hybrid CAD/CAM materials [Lava™ Ultimate (3 M); VITA Enamic® (VITA Zahnfabrik)], a composite material [ceram.x® universal (Dentsply Sirona)] and a CAD/CAM ceramic [VITABLOCS® (VITA Zahnfabrik)] were stored in cell culture medium for 72 h to prepare eluates according to ISO-10993-12:2012. HGK were exposed to eluates for 6, 24 and 48 h. Cell monitoring was performed by RTCA iCELLigence™ system. The morphological changes were evaluated using phase contrast imaging. Specific biomarkers of apoptosis and terminal differentiation (Caspase-3, Involucrin) were analyzed semi quantitatively by indirect immunofluorescence (IIF). Protein levels and activation of MAP kinases ERK1/2 (p44/42) were quantified by Western blot. Data were statistically analyzed by unpaired t-test (p < 0.05). RESULTS: Regarding Vita Enamic® and Lava™ Ultimate, results of RTCA iCELLigence™ and Western blots showed no statistically significant differences (p > 0.05) compared to the negative control (HGK in native keratinocyte growth medium). No aberrant expression of Caspase-3 and Involucrin was detected in cells incubated with Vita® Enamic eluates Cells incubated with Lava™ Ultimate showed a higher expression of Involucrin after 24 h of incubation compared to the negative control. Statistically significant differences (p < 0.01) were found between cells incubated with ceram.x® universal and the negative control in RTCA iCELLigence™ assay and in quantitative measurements of Western blots after 6 h against phospho-p44/42 (p = 0.044). Increased expression of Caspase-3 and Involucrin were detected by IIF in cells after incubation with eluates of ceram.x® universal. SIGNIFICANCE: The present data show no significant effect of hybrid materials on analyzed functions of cell behavior. A cytotoxic influence of ceram.x® universal eluates was observed in HGK in terms of a strong modulation of proliferation, morphology and protein expression.

Cytotoxic and inflammatory response of human lung epithelial cells A549 to particles released from dental restorative materials during dry and wet grinding.

OBJECTIVES: The aim was to evaluate the release of particles from dental materials during wet and dry grinding and test their effects on human lung epithelia cells in-vitro. METHODS: Four dental restorative materials were used: two composites [Ceram.x® universal (Dentsply Sirona) and Filtek™ Supreme XTE (3 M)], one ceramic [VITABLOCS® Mark II (VITAy)] and a ceramic-resin material [Lava™ Ultimate (3 M)]. Material samples were ground to powder under standardized wet and dry conditions in an isolated dental room. During grinding, the particle concentrations were measured with LAS and CPC. Baseline values were measured before grinding. The particles' size was evaluated using DLS and SEM. Water was used as control. The cytotoxicity and inflammatory response of the lung cells (A549) after exposure to different concentrations (1, 3, 10, 30, 100, 300 µg/mL) of the generated dust were analyzed with LDH, WST-1 and ELISA. RESULTS: LAS and CPC revealed a high concentration of particles< 10 µm and< 1 µm respectively, into the air. Particles showed high tendency to agglomerate. DLS showed particle size distribution between 150 nm and 18 µm independently of the material composition. All materials induced significant effects (p < 0.05) on the cell membrane integrity and viability of the A549 cells. Only the ceramic particles showed a significant increase in hydroxyl radical formation at low concentrations (p < 0.05), for both wet and dry conditions. All materials except ceramic, induced a significant release of IL-8 in A549 cells at 300 µg / mL (p < 0.05). SIGNIFICANCE: Wet and dry grinding of dental materials result in release of ultrafine and fine particulate matter into the air. The in-vitro findings on the cellular response of lung cells to generated dust indicate a potential risk for human health due inhalation of the released particles. The use of water-cooling seems to be beneficial resulting in reduced release of particles compared to dry grinding.

Release of monomers from four different composite materials after halogen and LED curing.

PURPOSE: To evaluate the release of monomers from four different composite materials (Ceram X, Filtek Supreme XT, Tetric Flow, Tetric EvoCeram), polymerized using either halogen or LED unit. METHODS: Ten specimens were made for each material/unit combination. Each specimen was stored in 1 ml 75% ethanol. The storage medium was renewed after 1, 7 and 28 days. Aliquots of this medium were analyzed by LC-MS/MS. RESULTS: The effect of the curing unit on monomers' release differed significantly among the materials (P < 0.0001). The amount of BisGMA and TEGDMA released from Ceram X was not influenced by the unit used (P > 0.05). Curing with LED reduced the amount of Bisphenol A released from Ceram X compared to halogen. For Filtek Supreme XT, the type of unit exerted a significant effect on the elution of BisGMA (P < or = 0.05). LED curing resulted in a higher release of TEGDMA and UDMA compared to halogen (P < or = 0.05). For Tetric Flow, LED curing resulted in lower monomer release (P < 0.0001). For Tetric EvoCeram, the amounts of BisGMA, UDMA and Bisphenol A were higher when polymerizing with LED compared to halogen. The release of substances was more material dependent and less influenced by the curing unit used.

Low-dose Bisphenol A and its analogues Bisphenol F and S activate estrogen receptor ß and slightly modulate genes in human gingival keratinocytes.

OBJECTIVES: This study investigated the putative activation of estrogen receptor ß (ERß) and possible effects related on gene expression in oral mucosal cells in response to the endocrine disruptor Bisphenol A (BPA) and its analogues Bisphenol F (BPF) and Bisphenol S (BPS). METHODS: Human gingival keratinocytes (HGK) were exposed to BPA-, BPF-, and BPS-solutions in concentrations of 1.3 µM, 0.16 µM and 11.4 nM as well as 200 pM and 100 nM estradiol (E2) for 6 h, 24 h and 4 d. Indirect immunofluorescence (IIF) was performed to detect a possible ERß activation. Additionally, transcription of keratinocyte-relevant biomarkers was analyzed by quantitative real-time PCR (qRT-PCR). A linear mixed model and pairwise comparisons were applied for statistical analyses. RESULTS: The tested concentrations of BPA, BPF, BPS and E2 revealed distinct activation of ERß at all time periods, whereat 100 nM E2 induced the most pronounced activation. Despite the detected ERß activation, the concentrations of BPA and its analogues induced only moderate modulation of the tested keratinocyte-relevant biomarker genes at all time periods. This also applied to 200 pM E2, while in case of 100 nM E2 significant changes (p < 0.05) were detected for almost all analyzed genes. SIGNIFICANCE: Though BPA and its analogues induce activation of ERß irrespective from the chosen concentrations and incubation periods, they lack significant modulation of gene expression of keratinocyte-relevant biomarkers. Although limited to a selected number of genes, the sparse modulation of gene expression may give a hint that the substances do slightly affect transcription of gingival-keratinocyte-innate genes, since the concentrations applied to HGK were of physiological importance.

Detection of Bisphenol A in dental wastewater after grinding of dental resin composites.

OBJECTIVES: This study evaluated the release of bisphenol A (BPA) in wastewater after grinding of resin composites and tested three filtration materials. METHODS: Three resin composites (Ceram X, Filtek Supreme XTE and Core-X flow) were used. Samples (5mm×2mm, n=10) were prepared using a metal mold and were polymerized for 20s according to manufacturers' instructions. A dental unit was disconnected from wastewater circulation and composite samples were ground under standardized procedures (200,000rpm; 90s). Wastewater was collected in glass bottles. Water samples were collected as control by performing the same procedure without grinding resin composite. All samples were stored at 7°C for 6 months to simulate storage. Then they were analyzed by HPLC-FLD. Three filtration materials (Zeosorb, Katalox Light and Catalytic Carbon) were used for water treatment to remove BPA. BPA-water solutions were prepared; corresponding to the highest amount released by the resin composites. These solutions were analyzed before and after filtration by HPLC-FLD and their efficacy (%) was calculated. RESULTS: BPA was detected in all composite solutions: Ceram X and Filtek Supreme XTE showed similar findings (p>0.05) which were significantly higher than the control (p<0.001) and Core-X flow (p=0.001). The efficacy of the filtration materials was: Katalox Light (5.09%)

Long-term release of monomers from modern dental-composite materials.

The elution of monomers from composite materials influences the biocompatibility of dental restorations. The purpose of the present study was to investigate the elution of monomers [bisphenol A glycidyl methacrylate (BisGMA), triethylene glycol dimethacrylate (TEGDMA), urethane dimethacrylate (UDMA), and bisphenol A (BPA)] from two light-cured materials (nanohybrid and ormocer) and from a chemically cured composite material, after different curing times (0, 20, 40 and 80 s) and different storage periods (24 h, 7 d, 28 d, and 1 yr after curing). Each specimen was stored in 1 ml of 75% ethanol. This medium was renewed after 24 h, 7 d, 28 d, and 1 yr. The ethanol samples were analyzed using liquid chromatography tandem mass spectrometry (LC-MS/MS). The amount of monomers released from the nanohybrid and the chemically cured composite was significantly higher than released from the ormocer. The curing time exerted a significant effect on the release of monomers. For the nanohybrid, less monomer was released after increasing the curing time. For the ormocer, 80 s of curing resulted in a higher degree of monomer release. The effect of storage differed between the monomers. Although the elution of TEGDMA was significantly decreased after storage for 28 d and 1 yr, a similar amount of BisGMA was released at each storage time-point analyzed, even after 1 yr. The present study showed that ormocer released a very small amount of monomers compared with the other materials.

Prosthodontic Rehabilitation with Fixed Monolithic Translucent Zirconia Restorations: A Case History Report.

Recent attempts in the development of novel zirconia ceramics aim at improving its optical characteristics by increasing the yttria content to up to 5 mol% so that these ceramics can be used for the fabrication of stable and esthetic monolithic restorations. However, clinical evidence on the outcomes of such restorations is sparse. In this case report, monolithic inlays, partial crowns, tooth- and implant-supported single crowns, and fixed dental prostheses were fabricated out of a zirconia ceramic doped with 5 mol% yttria. The restorations in the present case history report showed a satisfying esthetic outcome and are in situ as inserted 18 months after insertion.

The efficacy of three different in-office bleaching systems and their effect on enamel microhardness.

This in vitro study evaluated and compared the efficacy of three in-office bleaching systems and investigated their effect on enamel microhardness. Three groups of 12 teeth (third molars) each were bleached as follows: Group A: Opalescence Xtra Boost (38% HP), Group B: Easywhite Ready (30% HP) with plasma unit and Group C: Zoom2 system (25% HP with the Zoom2 unit). The teeth were stained with tea for 24 hours, followed by the appropriate bleaching procedure. Each bleaching cycle was conducted for 15 minutes. The bleaching procedure was repeated until a shade change of six tabs (VITA shade guide) was obtained. The shade of the teeth was evaluated before, immediately after bleaching and one month later, both visually and digitally. Additionally, the "change of shade tabs per minute" was calculated. For the digital evaluation, the photos were taken under the same circumstances and the L*a*b* values were calculated using Photoshop. Five additional enamel samples for each group were prepared, and Knoop microhardness was evaluated before and after 15 minutes of bleaching. According to the visual shade evaluation, the treatment cycles required to reach the defined level of bleaching were: 1.58 for Group A (23.7 minutes), 1.02 for Group B (16.2 minutes) and 1.25 for Group C (18.7 minutes). Immediately after bleaching, a significant difference was found between Groups A and B (p = 0.0094). However, one month after the bleaching procedure, no significant difference could be observed among the three groups. According to the digital evaluation, no significant differences were found among the three bleaching systems for each of the L*a*b* values and the three times tested (p > 0.05). No significant difference (p = 0.055) was noticed among the three groups regarding microhardness after bleaching.

Elution of monomers from two conventional dental composite materials.

OBJECTIVE: The aim of this study was to determine the elution of monomers of two conventional resin composite materials after different polymerization and storage times. METHODS: Two resin composites (a hybrid and a flowable) were used. Four groups (n=10, diameter: 4.5mm, thickness: 2mm) of each material were fabricated, one for each polymerization time of: 0s, 20s, 40s, and 80s. The samples were stored in 1ml of 75% ethanol at room temperature, and the storage medium was renewed after 24h, 7 days, and 28 days. From the storage medium that was removed, samples were prepared and evaluated, with LC-MS/MS. RESULTS: Bisphenol A and UDMA were not detected in the samples. Regardless of the polymerization time, the material or the storage time, a higher amount of BisGMA was eluted compared to TEGDMA. The amount of monomer that was released from the polymerized samples of the hybrid resin composite (Tetric Ceram) was significantly higher (p<0.0001) compared to the flowable (Tetric Flow). No significant difference was found between samples polymerized for 20s compared to 40s concerning the elution of monomers. Only a polymerization time of 80s resulted in a decreased release of monomers. The release of TEGDMA decreased after 28 days; however, the elution of BisGMA remained at high levels. SIGNIFICANCE: The release of monomers remains at a high level for a long time (7-28 days) after polymerization. The 40s that are usually used for the polymerization of resin composites seems insufficient in order to prevent a high release of monomers.