Dentsply DeTrey Research Articles

Antifungal activity of dental resins containing amphotericin B-conjugated nanoparticles

ObjectivesTo evaluate the antifungal activity, biocompatibility and mechanical properties of dental resins containing silica nanoparticles functionalized with amphotericin B (SNP-DexOxAmB) against five species of Candida. MethodsDental resin composites (Spectrum, Dentsply DeTrey, GmbH, Germany) having 2% (w/w) of SNP-DexOxAmB (SNPs of 5 and 80nm, denoted as SNP5 and SNP80) were aged for 10, 20 and 30 days at 37°C, in phosphate buffer saline buffer pH 7.4 (PBS). At different time, the antifungal activity was evaluated by a direct contact assay against 1×104cells of Candida. The biocompatibility of the resins was tested against human fibroblasts, endothelial cells and red blood cells. ResultsDental resins containing SNP5-DexOxAmB have high (1×104cells killed in 5h by ∼70mg of dental resin composite containing 2% (w/w) of SNP-DexOxAmB) and durable (for at least 1 month) antifungal activity against five strains of Candida. The incorporation of the nanoparticles (NPs) had no significant change in the mechanical properties of the resin, specifically the flexural strength and modulus. Our results further show that the antifungal activity is mainly mediated by direct contact and not by leaching of NPs from the resin. Resins incorporating SNP5-DexOxAmB have longer-term antifungal activity than SNP80-DexOxAmB. The antimicrobial activity of resins with SNP5-DexOxAmB persists after 4 cycles of re-use and it is superior to the activity obtained for dental resins containing silver NPs. In addition, dental resins incorporating SNP5-DexOxAmB are non-cytotoxic against human skin fibroblasts and human umbilical vein endothelial cells, and non-hemolytic against human red blood cells. SignificanceThe incorporation of SNP5-DexOxAmB in dental resins resulted in a non-cytotoxic composite with high and durable antifungal activity.

Push-out bond strength of a newly introduced glass fiber root canal filling material.

To compare the push-out bond strength of a new glass fiber root canal filling material to that of Resilon/ Epiphany, EndoREZ, and gutta-percha/AH Plus root canal filling materials. Sixty roots were randomly divided into four groups (n = 15) according to the obturation material: group 1, Resilon/Epiphany (RE) (Pentron Clinical Technologies); group 2, gutta-percha/AH Plus (GP) (Dentsply DeTrey); group 3, EndoREZ obturation system (ER) (Ultradent); and group 4, glass fiber root canal filling (GF) (Stick Tech) and dual-curing resin sealer (MetaSeal, Parkell). Two-mm-thick horizontal sections from the coronal, middle, and apical thirds of each root were sliced for the push-out bond strength measurement. GF showed the significantly highest mean bond strength values at the coronal and middle thirds. At the apical third, GF showed significantly higher bond strength values than did RE and ER. However, there was no significant difference at the apical third between the GF and GP groups. The lowest bond strength values were recorded for ER. Glass fiber root canal filling material seems to provide promising bond strength to root canal dentin.

Retentive Strength of Two‐Piece CAD/CAM Zirconia Implant Abutments

The purpose of this study is to evaluate the retention of two-piece computer-aided design (CAD)/computer aided manufacturing (CAM) zirconia abutments after artificial aging under simulated oral conditions using three different types of resin-based luting agents. Twenty-one CAD/CAM-generated zirconia copings (CERCON Compartis, Degudent, Hanau, Germany) were bonded to a prefabricated secondary titanium implant insert (XiVE Ti-Base, Dentsply Friadent, Mannheim, Germany), using three different types of resin-based luting agents: group A: Panavia 21 (Kuraray Co, Kurashiki, Japan); group B: Multilink Implant (Ivoclar Vivadent, Schaan, Liechtenstein); and group C: SmartCem2 (Dentsply DeTrey, Konstanz, Germany). The bonding surfaces of the titanium inserts and the zirconia ceramic copings were air-abraded and cleaned in alcohol. All specimens were stored in distilled water for 60 days and subsequently thermal-cycled 15,000 times (5-55 °C). The dislodging force of the copings along the long axis of the implant/abutment complex was recorded using a universal testing machine with 2 mm/min crosshead speed. Data were analyzed descriptively and by performing the Kruskal-Wallis test. The mean retention values were 924.93 ± 363.31 N for Panavia 21, 878.05 ± 208.33 N for Multilink Implant, and 650.77 ± 174.92 N for SmartCem2. The Kruskal-Wallis test indicated no significant difference between the retention values of the tested luting agents (p = 0.1314). The failure modes of all tested two-piece abutments were completely adhesive, leaving the detached zirconia coping and titanium insert undamaged. The use of resin-based luting agents in combination with air abrasion of titanium inserts and zirconia copings led to a stable retention of two-piece CAD/CAM abutments. The bonding stability of the investigated luting agents exceeded the general limits of fracture resistance of two-piece zirconia abutments. A notable difference between the mean retention values of the tested bond materials was shown. However, the statistical analysis revealed that this difference was not significant.

Long-term Dose- and Time-dependent Effects of Endodontic Sealers in Human In Vitro Osteoclastogenesis

IntroductionThis study evaluates the concentration and time-dependent effects of endodontic sealers' extracts (AH Plus [Dentsply DeTrey, Konstanz, Germany], GuttaFlow [Roeko, Colténe/Whaledent, Germany], Tubliseal [Kerr/Sybron, Romulus, MI], Sealapex [Kerr/Sybron, Romulus, MI], and RealSeal [SybronEndo, Orange, CA]) in the differentiation and function of both unstimulated and stimulated osteoclast precursors, simulating, respectively, immature/undifferentiated precursors and cells undergoing osteoclastogenesis. MethodsThe sealers were mixed according to the manufacturers' instructions, freshly extracted with culture medium (1.3 cm2/mL, 24 hours, 37°C, 5% CO2/air), and diluted (1:20, 1:100, 1:500, and 1:2500). Human peripheral blood mononuclear cells were used as osteoclast precursor cells. After overnight attachment, peripheral blood mononuclear cell cultures were exposed to the sealers' extracts during 21 days in the absence (unstimulated) or presence (stimulated) of recombinant macrophage colony-stimulating factor and receptor for the activation of nuclear factor-κB ligand. Cultures performed in the absence of the extracts were used as the control. Cultures were characterized for osteoclastic differentiation and function. ResultsExtracts caused mostly inhibitory effects on osteoclastic cells, both in unstimulated and stimulated conditions, which were reflected by a decrease in tartrate-resistant acid phosphatase activity, the presence of actin rings, vitronectin and calcitonin receptors, the calcium phosphate resorbing ability, and the expression of osteoclastic genes. Also, the extracts induced alterations in the relative contribution of some intracellular signaling pathways involved in osteoclastogenic events. The sealers differed in the dose- and time-dependent profile. An adaptive cell response was noticed for the inhibitory effects after long-term exposure. ConclusionsEndodontic sealers affect the osteoclastic differentiation and activity, which is followed by an adaptive cell response. Our results suggest that the deleterious effect in the bone periapical tissues observed with the root canal sealers might involve, at least partially, a direct effect on the osteoclastic cells.

Effect of Various Endodontic Irrigants on the Push-out Bond Strength of Biodentine and Conventional Root Perforation Repair Materials

IntroductionThe aim of this study was to evaluate the effect of various endodontic irrigants on the push-out bond strength of Biodentine (Septodont, Saint Maur des Fossés, France) in comparison with contemporary root perforation repair materials. MethodsMidroot dentin of canine teeth was horizontally sectioned into 1-mm-thick slices. The canal space of each dentin slice was enlarged with a diamond bur to 1.4 mm in diameter. The samples were divided into 5 groups (n = 40), and the following materials were placed, respectively: Biodentine, ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK), amalgam, Dyract AP (Dentsply DeTrey, Konstanz, Germany), and intermediate restorative material (IRM, Dentsply DeTrey). The samples were wrapped in wet gauze for 10 minutes and divided into 3 subgroups (n = 10) to be immersed into 3.5% sodium hypochlorite, 2% chlorhexidine gluconate (CHX), or saline for 30 minutes. No irrigation was performed in the controls (n = 10), and a wet cotton pellet was placed over each test material. After incubation for 48 hours, the dislodgement resistance of the samples was measured using a universal testing machine. The samples were examined under a stereomicroscope to determine the nature of the bond failures. ResultsBiodentine showed significantly higher push-out bond strength than MTA (P < .05). The statistical ranking of push-out bond strength values was as follows: Dyract AP > amalgam ≥ IRM ≥ Biodentine > MTA. The push-out bond strength of Dyract AP, amalgam, IRM, and Biodentine was not significantly different when immersed in NaOCl, CHX, and saline solutions, whereas MTA lost strength when exposed to CHX. ConclusionsBiodentine showed considerable performance as a perforation repair material even after being exposed to various endodontic irrigants, whereas MTA had the lowest push-out bond strength to root dentin.

The Antioxidant Property of Pachymic Acid Improves Bone Disturbance against AH Plus–induced Inflammation in MC-3T3 E1 Cells

IntroductionThe cytotoxicity of resin-based sealer is influential on the inflammatory reaction and cell survival for oral periapical cells. In this study, pachymic acid as an antioxidant was investigated for the improvement of bone disturbance against AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany)–induced inflammation in MC-3T3 E1 cells. MethodsAH Plus was prepared according to the manufacturer's instructions. Using mouse osteoblast cells (MC-3T3 E1), a specimen of AH Plus was eluted with the culture medium for 1 day and was diluted by 30%. The cellular cytotoxicity and reactive oxygen species formation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and 2′,7′-dichlorodihydrofluorescein diacetate with fluorescence-activated cell sorting. The secretion of proinflammatory cytokines was determined by an enzyme-linked immunosorbent assay, and the expression of inflammatory and osteogenic molecules was determined by immunoblotting. ResultsCells with AH Plus elutes showed a decrease of cell viability and ALP activity. However, pachymic acid and N-acetyl-L-cysteine (control antioxidant) restored cell viability and ALP activity damaged by AH plus. The secretion of nitric oxide, tumor necrosis factor α, and interleukin-1β were increased in AH Plus–stimulated MC-3T3 E1 cells, but pachymic acid suppressed its production. Furthermore, pachymic acid reduced the receptor activator of nuclear factor-κB ligand, cyclooxygenase-2, matrix metalloproteinase-2 and -9, increased bone morphogenetic protein-2 and -7, and runt-related transcription factor 2 despite AH Plus stimuli. In addition, pachymic acid affected the removal effect of reactive oxygen species formation as did N-acetyl-L-cysteine. More importantly, pachymic acid inhibited nuclear factor-κB translocation. ConclusionsThe property of pachymic acid can mitigate the unfavorable conditions induced by AH Plus stimuli. Therefore, the use of pachymic acid is suggested to prevent the complications of oral diseases such as inflammation and alveolar destruction of the oral cavity.

Tissue Reactions to a New Mineral Trioxide Aggregate–containing Endodontic Sealer

IntroductionThe purpose of this study was to analyze the connective tissue reactions to MTA Fillapex (Ângelus Indústria de Produtos Odontlógicos Ltda, Londrina, Brazil) compared with a zinc oxide–based sealer (EndoFill; Dentsply Indústria e Comérico Ltda, Petrópolis, Brazil) and an epoxy resin–based material (AH Plus; Dentsply DeTrey GmbH, Konstanz, Germany) in Wistar rats. MethodsPolyethylene tubes containing the test materials and empty polyethylene tubes (control) were implanted in the subcutaneous tissue of 12 rats. Empty tubes were used as a negative control. After 7 and 60 days (n = 6 per period), observations were made for cellular inflammatory components, fibrous condensation, and abscess formation. Comparisons among the groups and between the experimental periods were made using 2-way analysis of variance and the Bonferroni post hoc test (P < .05). ResultsAt the end of the 7-day experimental period, all sealers scored higher than the control group for the variable lymphocytes, and MTA Fillapex presented lower fiber condensation compared with empty tubes. After 60 days, macrophages and lymphocytes scored significantly higher for MTA Fillapex and EndoFill compared with the negative control, and AH Plus showed similar results related to the empty tubes. Comparing the materials' responses at the end of the 2 evaluated periods, for EndoFill samples the variable neutrophils was detected less after 60 days. Both EndoFill and MTA Fillapex presented increased fiber condensation after 60 days. ConclusionsAlthough none of the sealers promoted ideal tissue responses, AH Plus presented the best outcomes. Although MTA Fillapex contains MTA powder, it presented no biocompatibility advantages when compared with AH Plus and EndoFill.

Degree of conversion of two-step etch-and-rinse adhesives: In situ micro-Raman analysis

ObjectivesDC of three commercial two-step etch-and-rinse adhesives across the dentine–adhesive interface was investigated using micro-Raman spectroscopy. The hypothesis tested was that no difference in DC would exist among the adhesives tested. MethodsAdper Scotchbond 1XT (3M ESPE), Prime&Bond NT (Dentsply DeTrey), and Ambar (FGM) were applied on human dentine disks (n=9). Composite increments of 2mm were then applied on the adhesive surface. Raman spectra were collected along the dentine–adhesive interface. The relative intensities of the peaks associated with the mineral (PO43− at 960cm−1) and the adhesive (CC at 1640cm−1; phenyl CC at 1610cm−1) were used to identify the adhesive within the hybrid layer and calculate its DC. ResultsAdper Scotchbond 1XT and Ambar showed similar DC (79±7% and 77±7%, respectively), while a lower DC was found for Prime&Bond NT (70±7%; p<0.05). ConclusionsThe hypothesis tested was rejected because differences were found among the adhesives tested. The difference in DC among the three adhesive systems can be attributed to different monomer compositions and solvents. Further studies are needed to correlate DC with other mechanical properties of these adhesives. Clinical significanceInsufficient polymerization of an adhesive can result in a weak hybrid layer, and the presence of unreacted monomers may result in degradation of the polymeric network, decreasing the strength and longevity of the bond. In the present study, Adper Scotchbond 1XT and Ambar performed significantly better than Prime&Bond NT.

Variability of physicochemical properties of an epoxy resin sealer taken from different parts of the same tube

To analyse several physicochemical properties of AH Plus (Dentsply DeTrey, Konstanz, Germany), including setting time, flow, radiopacity and the degree of conversion (DC); and to correlate the results with the source of the material: from the beginning, middle or end of the tubes in which they were supplied. Three experimental groups were established for each property investigated. Group 1 corresponded to material taken from the beginning of tubes A and B; Group 2 corresponded to material taken from the middle of each tube; and group 3 corresponded to that from the end of each tube. The setting time, flow and radiopacity were studied according to American National Standards Institute/American Dental Association (ANSI/ADA) Specification 57. DC was determined from infrared spectra, which were recorded at 1-h intervals for the first 6 h; then, at 2-h intervals for the next 14 h; then, at 24 and 30 h. Data were analysed statistically by analysis of variance (anova), Tukey-Kramer, Kruskal-Wallis and Dunn tests, with a significance level of 5%. Group 1 had a significantly longer setting time (2303 ± 1058 min) (P < 0.05). Group 3 had the lowest flowability (30.0 ± 0.7 mm) and the highest radiopacity (14.85 ± 1.8 mm Al) (P < 0.05). No differences were found for the DC test (P > 0.05). The results suggest that segregation occurs between the organic and inorganic components of AH Plus sealer, thereby changing the setting time, flow and radiopacity.

Two-year clinical evaluation of three adhesive systems in non-carious cervical lesions

Objectives Adhesive systems are continuously being introduced to Dentistry, unfortunately often without sufficient clinical validation. The aim of this study was to evaluate the clinical performance of cervical restorations done with three different adhesive systems. Material and methods 158 non-carious cervical lesions of 23 patients were restored with a nanofilled composite resin (Filtek Supreme, 3M/ESPE) combined with Single Bond (3M/ESPE, group SI), Clearfil SE (Kuraray Medical Inc., group CL) and Xeno III (De Trey Dentsply, group XE). In groups SI-B, CL-B and XE-B, the outer surface of the sclerotic dentin was removed by roughening with a diamond bur before application of the respective adhesive systems. In groups CL-BP and XE-BP, after removal of the outer surface of the sclerotic dentin with the bur, the remaining dentin was etched with 37% phosphoric acid and the self-etch adhesive systems Clearfil SE and Xeno III were applied, respectively. Lesions were evaluated at baseline, and restorations after 3 months, 1 year and 2 years using modified USPHS criteria. Results After 2 years, no significant difference was found between the retention rates of the groups (p >0.05). Although groups CL and SI showed significantly better marginal adaptation than group XE (p<0.05) at 2 years, no significant difference was found between the marginal adaptation of the groups SI-B, CL-B and XE-B (p>0.05). After 2 years no significant difference was observed among the marginal staining results of all groups (p>0.05). Conclusion Although all adhesive systems showed similar retention rates, Clearfil SE and Single Bond showed better marginal adaptation than Xeno III after 2 years of follow-up.

The Effect of Prior Calcium Hydroxide Intracanal Placement on the Bond Strength of Two Calcium Silicate–based and an Epoxy Resin–based Endodontic Sealer

IntroductionThe aim of this study was to investigate the effect of prior calcium hydroxide (Ca[OH]2) intracanal placement on the bond strength of AH Plus (Dentsply DeTrey GmbH, Konstanz, Germany), iRoot SP (Innovative Bioceramix, Vancouver, BC, Canada), and MTA Fillapex (Angelus Soluções Odontológicas, Londrina, PR, Brazil). MethodsThe root canals of 90 human incisor teeth were prepared with the ProTaper System (Dentsply Maillefer, Ballaigues, Switzerland) up to a master apical file size of F5. Canals were filled using the single-cone technique either immediately (the control group, n = 30) or after a 7-day Ca(OH)2 placement. Ca(OH)2 removal was performed either manually using F5 with distilled water irrigation (the Ca[OH]2 group, n = 30) or manually using Protaper F5 followed by passive ultrasonic irrigation with 2.5 % NaOCl with a final flush of 17 % EDTA and then distilled water (the PUI group, n = 30). After obturation, a 2-mm-thick middle section of each root was then subjected to push-out testing. ResultsUsing 1-way analysis of variance, AH Plus showed a higher bond strength than iRoot SP and MTA Fillapex in the control group (P < .05). With prior Ca(OH)2 placement, AH Plus and iRoot SP showed a similar bond strength (P > .05), which was higher than MTA Fillapex (P < .05). ConclusionsPrior Ca(OH)2 placement seemed to improve the dislodgment resistance of iRoot SP but did not affect AH Plus and MTA Fillapex.

Tooth discolouration: Staining effects of various sealers and medicaments

The aim of this investigation was to quantify the discolouration of tooth roots caused by various medicaments and sealers. The roots of extracted teeth were chemo-mechanically prepared and the smear layer removed. The roots were filled with either Multi-Cal (Pulpdent Corporation, Watertown, MA, USA), Ledermix (Lederle Laboratories, Wolfratshausen, Germany), 2% chlorhexadine acetate in polyethylene glycol (PEG), 5% clindamycin in PEG, PEG alone (as a vehicle control), sealers AH26 (De Trey Dentsply, Zurich, Switzerland), AH Plus (De Trey Dentsply), an experimental epoxy resin with zirconium dioxide (Millenium Chemicals, Rockingham, Western Australia) or Araldite (Selleys Pty Ltd, Sydney, Australia). The roots were maintained at 37°C in dark humid conditions and standardised images of the coronal surfaces recorded over 12 months. Ledermix caused the most darkening of the introduced medicaments, while calcium hydroxide and the materials in PEG did not cause darkening. AH26 caused more darkening than did the other sealers. It was concluded that the use of alternatives to Ledermix and AH26 should be considered when aesthetics are important.

Residual Filling Material in Dentinal Tubules after Gutta-percha Removal Observed with Scanning Electron Microscopy

IntroductionIn cases of failed root canal treatment, endodontic retreatment of the root canal system is necessary. The present study aimed to assess variation in the incidence and depth of residual filling material in dentinal tubules after gutta-percha removal with H-files, the ProTaper Universal System (Dentsply Maillefer, Ballaigues, Switzerland), and the SybronEndo K3 System (SybronEndo Corporation, Orange, CA). MethodsForty human mandibular premolars with single straight root canals were prepared with K-files (up to size 40) using the step-back technique and filled by cold lateral condensation with gutta-percha and AH Plus sealers (Dentsply DeTrey, Konstanz, Germany). After 1 year, the 40 teeth were divided into one control group and 3 retreatment groups (n = 10 each). Gutta-percha was removed using H-files, the ProTaper Universal System, or the SybronEndo K3 System. The teeth were sectioned, and the incidence and depth of residual filling material in the dentinal tubules were measured under scanning electron microscopy. ResultsThe depth of filling material in the dentinal tubules did not differ significantly among groups (P > .05). Residual filling material was present in significantly more dentinal tubules in the ProTaper (P = .043) and K3 groups (P = .001) than in the H-file and control groups. ConclusionsThe ProTaper Universal System and the SybronEndo K3 System left filling material in a greater proportion of dentinal tubules than did H-files.

Microhardness of different resin cement shades inside the root canal

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material. Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X•Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core•X flow. All materials were applied according to manufacturers’ instructions and were all photopolymerized (Bluephase LED unit, Ivoclar Vivadent, 40s). After 24 hours, roots were transversally cut into 9 slices 1 mm thick from the coronal to apical extremes, three corresponding to each root third. Then, VHNs were recorded (100 gf, 30 s) on the resin luting materials along the adhesive interface in all sections. Data were analyzed by two-way ANOVA and SNK tests (α=0.05). Results: A significant influence on microhardness of resin luting material in their respective shades (p<0.001), root third (p<0.001) and interactions between them was detected (p<0.001). RelyX Unicem cement showed the highest microhardness values and Calibra the lowest, regardless of the shade selected. All resin luting materials tested exhibited a significantly higher microhardness in the cervical third. Conclusions: Microhardness of resin luting agents tested inside the canal is dependent on material brand and resin cement shade seems to be a less relevant factor. Microhardness decreased along the root canal, regardless of the shade selected. Key words:Cement shade, degree of conversion, dual-cured resin cements, fiber posts, microhardness, root thirds.

Colorimetric comparison of single layered dental composite with double layered dental composite

Objectives: This study analyzed the difference in color caused by different thickness in enamel layer of composite resins when applied with single and layering placement technique, and evaluated if the results agreed with the shade guide from the manufacturers to verify reliability of the color matching process of the manufacturers. Materials and Methods: For single composite resin samples, 6 mm diameter and 4 mm thickness cylindrical samples were fabricated using Ceram-X mono (DENTSPLY DeTrey) and CIE values were measured with spectrophotometer. Same process was done for layering composite resin samples, making 3 dentinal shade samples, 4 mm thickness, for each shade using Ceram-X duo (DENTSPLY DeTrey) and enamel shade resins were layered in 2 mm thickness and CIE values were measured. These samples were ground to 0.2 mm thickness each time, and CIE values were measured to 1 mm thickness of enamel shade resin. Results: Color difference () between single and layering composite resin was 1.37 minimum and 10.53 maximum when layering thicknesses were between 1 mm and 2 mm and 6 out of 10 same shade groups suggested by manufacturer showed remarkable color difference at any thickness ( > 3.3). Conclusion: When using Ceram-X mono and duo for composite resin restoration, following the manufacturer's instructions for choosing the shade is not appropriate, and more accurate information for Ceram-X duo is needed on the variation and expression of the shades depending on the thickness of the enamel.

Fracture Resistance of Retreated Roots Using Different Retreatment Systems

This study was designed to evaluate the fracture resistance of retreated roots using different rotary retreatment systems. Forty eight freshly extracted human canine teeth with single straight root canals were instrumented sequentially increasing from size 30 to a size 55 using K-files whit a stepback technique. The teeth were randomly divided into three experimental and one control groups of 12 specimens each. The root canals were filled using cold lateral compaction of gutta-percha and AH Plus (Dentsply Detrey, Konstanz, Germany) sealer in experimental groups. Removal of gutta-percha was performed with the following devices and techniques: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), R-Endo (Micro-Mega, Besançon, France), and Mtwo (Sweden & Martina, Padova, Italy) rotary retreatment systems. Control group specimens were only instrumented, not filled or retreated. The specimens were then mounted in copper rings, were filled with a self-curing polymethylmethacrylate resin, and the force required to cause vertical root fracture was measured using a universal testing device. The force of fracture of the roots was recorded and the results in the various groups were compared. Statistical analysis was accomplished by one-way ANOVA and a post hoc Tukey tests. There were statistically significant differences between the control and experimental groups (P<.05). However, there were no significant differences among the experimental groups. Based on the results, all rotary retreatment techniques used in this in vitro study produced similar root weakness.

Comparing the effectiveness of self-curing and light curing in polymerization of dual-cured core buildup materials

The authors conducted an in vitro study to investigate the influence of various curing protocols on subsurface microhardness of dual-cured resin-based composites. The authors filled molds with four dual-cured resin-based composite core buildup materials: Clearfil DC Core Automix (Kuraray, Tokyo), Core•X flow (Dentsply DeTrey, Konstanz, Germany), LuxaCore Z-Dual (DMG, Hamburg, Germany) and MultiCore Flow (Ivoclar Vivadent, Schaan, Liechtenstein). They light cured the specimens for 20 or 60 seconds immediately after the filling procedure (time delay, 0 seconds) or after a 90-or 300-second delay. Self-cured specimens served as controls. The authors tested 15 specimens in each group. They measured the Knoop hardness number (KHN) at depths of 0.25, 2.00 and 5.50 millimeters two weeks after the initiation of polymerization. Light curing with Core•X flow, LuxaCore Z-Dual and MultiCore Flow did not result in significantly higher KHNs at any depth compared with those for the self-cured control specimens. For Clearfil DC Core Automix, immediate light curing for 60 seconds resulted in significantly higher KHNs than those for self-cured specimens only at a depth of 5.50 mm (P=.0171). The study results showed no significant differences in KHN at different depths for Core•X flow specimens, independent of the curing protocol. All other materials exhibited a significant decrease in KHN at increased depths in only one of the six light-cured groups. The results of this study show that photoactivation of the tested dual-cured materials provided no clinically relevant benefit compared with self-curing with regard to the degree of microhardness. The dominant self-curing mode allows placement of the tested buildup materials in areas inaccessible to a curing light.

Evaluation of Adhesive and Compressive Strength of Glass Ionomer Cements

The aim of the study was to assess, compare and evaluate the adhesive strength and compressive strength of different brands of glass ionomer cements to a ceramometal alloy. (A) Glass ionomer cements: GC Fuji II (GC Corporation, Tokyo), Chem Flex (Dentsply DeTrey, Germany), Glass ionomer FX (Shofu-11, Japan), MR dental (MR dental suppliers Pvt Ltd, England). (B) Ceramometal alloy (Ni-Cr: Wiron 99; Bego, Bremen, Germany). (C) Cold cure acrylic resin. (E) Temperature cum humidity control chamber. (F) Instron Universal Testing Machine. Four different types of Glass ionomer cements were used in the study. From each type of the Glass ionomer cements, 15 specimens for each were made to evaluate the compressive strength and adhesive strength, respectively. The 15 specimens were further divided into three subgroups of five specimens. For compressive strength, specimens were tested at 2, 4 and 12h by using Instron Universal Testing Machine. To evaluate the adhesive strength, specimens were surface treated with diamond bur, silicone carbide bur and sandblasting and tested under Instron Universal Testing Machine. It was concluded from the study that the compressive strength as well as the adhesive bond strength of MR dental glass ionomer cement with a ceramometal alloy was found to be maximum compare to other glass ionomer cements. Sandblasting surface treatment of ceramometal alloy was found to be comparatively more effective for adhesive bond strength between alloy and glass ionomer cement.

Color Changes of Dental Resin Composites before and after Polymerization and Storage in Water

The aims of this study were to: (1) evaluate the A2 shades of various types and brands of resin composites to determine if any color differences occurred before and after polymerization and after 1 month of storage in water and (2) examine the correlation among the color changes and changes in Commission internationale de l'éclairage L*, a*, and b* values after polymerization and after 1 month of storage in water. One submicron-hybrid (Spectrum TPH3, DENTSPLY DeTrey, Milford, DE, USA), one nano-filled (Filtek Supreme XT, 3 M ESPE, St. Paul, MN, USA), three micro-hybrid (Filtek Z250, 3 M ESPE; Esthet X, DENTSPLY DeTrey; and Gradia Direct, GC, Tokyo, Japan), and five nano-hybrid (Ceram X, DENTSPLY DeTrey; Clearfil Majesty Esthetics, Kuraray, Osaka, Japan; Premise, Kerr Corporation, Orange, CA, USA; Tetric Evo Ceram, Ivoclar Vivadent, Schaan, Liechtenstein and Tetric N Ceram, Ivoclar Vivadent) light-curing resin composites were tested. The specimens (N = 10 for each composite) were prepared as discs, 12 mm in diameter and 2 mm in thickness, using round molds. The measurements were performed "before polymerization,""after polymerization," and "after 1 month of storage in water" using a contact type dental spectrophotometer (Vita Easyshade, Vident, Brea, CA, USA). The range of ΔE* values after polymerization (ΔE*1) and storage in water (ΔE*2) were 4.59 to 14.13 and 1.26 to 6.29, respectively. Nested analysis of variance and post hoc tests revealed that the type of resin composites significantly affected Δa*1, Δa*2, Δb*1, Δb*2, ΔE*2-values, whereas the brand of resin composites affected the changes in all color parameters (p < 0.05). In spite of many improvements in chemical compositions and fillers of the contemporary composites, color changes after polymerization were perceptible in all resin composites. However, color changes after storage in water were in the acceptable ranges for all resin composites except Clearfil Majesty Esthetic and Gradia Direct. In spite of many improvements in chemical compositions and fillers of the contemporary resin composites, the color changes after polymerization were still perceptible in all the resin composites tested in this study, regardless of their types and brands. Such changes may cause esthetic problems clinically, thus should be taken into account when the shade selections are performed. Alternatively, a piece of unpolymerized resin material can be placed on, or adjacent to the tooth to be restored and polymerized to confirm the selected shade of the esthetic material.

PH, Calcium Ion Release, and Setting Time of an Experimental Mineral Trioxide Aggregate–based Root Canal Sealer

Introduction An experimental mineral trioxide aggregate sealer (MTAS) has been developed for use as a root canal sealer. The aim of this study was to evaluate the setting time, pH, and calcium ion release of MTAS compared with white Portland cement (CPB-40; Votorantin Cimentos, Camargo Correa SA, Pedro Leopoldo, MG, Brazil), white MTA Angelus (MTA; Angelus, Londrina, PR, Brazil), and AH Plus (Dentsply DeTrey, Konstanz, Germany). Methods For the evaluation of setting time, each material was analyzed using Gilmore-type needles. Polyethylene tubes with the materials were immersed in distilled water for the measurement of pH (digital pH meter) and calcium release (atomic absorption spectrophotometry). The evaluations were performed at 3, 6, 12, 24, and 48 hours and 7, 14, and 28 days. Data were analyzed by analysis of variance and the Tukey test at 5% significance level. Results MTAS showed higher calcium release at all experimental periods, a greater increase in pH up to 48 hours and the longest setting time. Conclusions MTAS presented favorable properties for its indication as a root canal sealer.