Influence of universal adhesives and silane coupling primer on bonding performance to CAD-CAM resin-based composites: A laboratory investigation.

OBJECTIVE: Obtaining strong resin bonds to computer-aided design and computer-aided manufacturing (CAD-CAM) resin-based composites with dispersed fillers (CCRBCs) poses a challenge. Therefore, this study aimed to assess the effect of three universal adhesives and a two-component silane coupling agent on the shear bond strength to three (CCRBCs). MATERIALS AND METHODS: Eight hundred and sixty-four specimens of Brilliant Crios, Lava Ultimate, and Tetric CAD were polished or grit blasted, bonded with Adhese Universal DC, One Coat 7 Universal (OC7), and Scotchbond Universal Plus Adhesive (SBU) with or without a silane primer. Shear bond strength was measured after 24 h and 10,000 thermocycles. Linear regressions were performed (α = 0.05). RESULTS: After thermocycling, bond strengths were similar for the universal adhesives on polished Brilliant Crios and Lava Ultimate (p ≥ 0.408). Grit blasted Tetric CAD showed no significant differences (p ≥ 0.096). The silane primer had minimal impact on grit blasted Tetric CAD (p ≥ 0.384). The silane primer increased the bond strength of OC7 to Brilliant Crios (p = 0.001) but decreased the adhesion of SBU to Brilliant Crios and Lava Ultimate (p ≤ 0.018). CONCLUSIONS: Bond strength of universal adhesives varied with CCRBC type. The two-component silane coupling agent showed mixed effects on adhesive performance. CLINICAL SIGNIFICANCE: Selecting universal adhesives from the same CCRBC product line does not always guarantee superior bond strength. The efficacy of silane coupling agents differs based on the bonding substrate.

Impact of Irradiation on the Adhesive Performance of Resin-Based Dental Biomaterials: A Systematic Review of Laboratory Studies.

Head and neck cancers are a significant global health burden, with radiation therapy being a frequently utilized treatment. The aim of this systematic review was to provide a critical appraisal of laboratory studies that assessed the effect of irradiation on the adhesive performance of resin-based biomaterials. The analysis included 23 laboratory studies obtained from five databases, with most studies using human enamel, dentin, or both, and bonding procedures involving the fabrication of direct restorations, standardized specimens, bonding of orthodontic brackets, and luting of endodontic fiber posts. The protocols used for irradiation varied, with most studies exposing specimens made from extracted teeth to irradiation using cabinet irradiators to simulate treatment of head and neck cancer. The findings indicate that irradiation reduces the bond strength of dental adhesives and resin-based composites on flat, ground enamel and dentin specimens, with different adhesives and timing of irradiation having a significant impact on adhesive performance. Irradiation also increased microleakage in most studies. The effect of irradiation on marginal adaptation of direct resin-based composite restorations was inconclusive. This systematic review indicates that irradiation has detrimental effects on the adhesive performance of resin-based biomaterials and highlights the need for further clinical and laboratory studies evaluating the performance of adhesive materials and approaches to improve it.

Debulking different Corona (SARS-CoV-2 delta, omicron, OC43) and Influenza (H1N1, H3N2) virus strains by plant viral trap proteins in chewing gums to decrease infection and transmission.

Because oral transmission of SARS-CoV-2 is 3-5 orders of magnitude higher than nasal transmission, we investigated debulking of oral viruses using viral trap proteins (CTB-ACE2, FRIL) expressed in plant cells, delivered through the chewing gum. In omicron nasopharyngeal (NP) samples, the microbubble count (based on N-antigen) was significantly reduced by 20 µg of FRIL (p < 0.0001) and 0.925 µg of CTB-ACE2 (p = 0.0001). Among 20 delta or omicron NP samples, 17 had virus load reduced below the detection level of spike protein in the RAPID assay, after incubation with the CTB-ACE2 gum powder. A dose-dependent 50% plaque reduction with 50-100 ng FRIL or 600-800 µg FRIL gum against Influenza strains H1N1, H3N2, and Coronavirus HCoV-OC43 was observed with both purified FRIL, lablab bean powder or gum. In electron micrographs, large/densely packed clumps of overlapping influenza particles and FRIL protein were observed. Chewing simulator studies revealed that CTB-ACE2 release was time/dose-dependent and release was linear up to 20 min chewing. Phase I/II placebo-controlled, double-blinded clinical trial (IND 154897) is in progress to evaluate viral load in saliva before or after chewing CTB-ACE2/placebo gum. Collectively, this study advances the concept of chewing gum to deliver proteins to debulk oral viruses and decrease infection/transmission.

Effect of Preirradiation Fluoride Treatment on the Physical Properties of Dentin.

Objective: To determine the effects of preirradiation fluoride treatments on the Knoop hardness of dentin. Materials and Methods: Human posterior teeth mounted into acrylic resin molds were polished with silicon carbide (SiC) abrasives and 3-micron diamond paste. The Knoop hardness of dentin was measured with a Leco hardness instrument. The teeth were divided into groups of ten teeth per group as follows: no treatment (control), treatment with silver diamine fluoride (SDF), MI varnish (MI), and cavity shield (CS). The teeth were exposed to 2 Gy of daily radiation for six weeks using an X-Rad 320ix biological irradiator. Hardness was measured weekly, before, during, and after irradiation. The teeth were stored in artificial saliva at 37oC between radiation treatments. Results: In preirradiation dentin, a Knoop hardness value of 58.8 (14.1) KHN was obtained. Treatment with SDF significantly increased KHN before irradiation. Immediately after radiation treatment, hardness was significantly reduced in all experimental groups. Postirradiation fluoride treatments increased the hardness of dentin to varying degrees. Conclusions: Preirradiation fluoride treatment does not provide protection from decreases in the hardness of dentin. Treatment of teeth with fluoride formulations after radiation progressively restores the hardness of dentin to different degrees.

Ceramic Printing - Comparative Study of the Flexural Strength of 3D Printed and Milled Zirconia.

PURPOSE: To determine and compare the mechanical properties of 3D-printed yttriastabilized zirconia to milled isostatic pressed yttria-stabilized zirconia, with the following hypotheses: (1) The flexural strength of 3D-printed yttria-stabilized zirconia is comparable to milled yttria-stabilized isostatic pressed zirconia; and (2) thermocycling and chewing simulation do not affect the flexural strength of 3D-printed yttria-stabilized zirconia. MATERIALS AND METHODS: A total of 30 bars of an experimental 3D-printed 3 mol% yttriastabilized zirconia (LithaCon 3Y 230, Lithoz) and 10 bars of milled isostatic pressed zirconia (Prettau Zirconia, Zirkonzahn) were utilized. The printed zirconia bars were divided into three groups (n = 10 bars per group): (1) untreated (control); (2) thermocycled; and (3) tested after chewing simulation. A flexural strength test was performed on all samples using a three-point bend test in an Instron Universal testing machine. One-way analysis of variance on ranks was used to compare milled to printed zirconia. The effects of thermocycling and load cycling on 3D-printed zirconia were also determined. RESULTS: The flexural strength values for milled and printed zirconia were 936.3 ± 255.0 MPa and 855.4 ± 112.6 MPa, respectively. There was no statistically significant difference in flexural strength between the milled and printed zirconia (P = .178). No statistically significant differences were observed between the control 3D-printed zirconia group and the thermocycled (888.4 ± 59.3 MPa) or load-cycled printed zirconia (789.6 ± 133.8 MPa; P = .119). CONCLUSION: Printed 3 mol% yttria-stabilized zirconia has comparable flexural strength to milled yttria-stabilized isostatic pressed zirconia. The thermocycling and chewing simulation used in this study did not significantly alter the flexural strength of the printed 3 mol% yttria-stabilized zirconia. These results indicate a promising role for 3D printing in the fabrication of zirconia restorations. Additional studies are needed to explore the full potential of this technology.

Influence of cleaning methods on bond strength to saliva contaminated zirconia.

OBJECTIVE: To evaluate the influence of saliva contamination and cleaning procedures on shear bond strength (SBS) of a self-adhesive resin cement (SAC) to zirconia surfaces. MATERIALS AND METHODS: A total of 160 sandblasted zirconia blocks were randomly divided into eight groups as follows: No saliva contamination, no cleansing (NC-NC); contamination with saliva, no cleansing (SC-NC); no saliva contamination, cleansing with a zirconia primer (ZP; Z-Bond, Danville Materials, Inc., S. Ramon, California) (NC-ZP); contamination with saliva, cleansing with ZP (SC-ZP); no saliva contamination, cleansing with hydrofluoric acid (HF; Ultradent Porcelain Etch; Ultradent Products, South Jordan, Utah) followed by cleansing with ZP (NC-HF-ZP); contamination with saliva, cleansing with HF followed by cleansing with ZP (SC-HF-ZP); cleansing with ZP, contamination with saliva, cleansing with ZP (ZP-SC-ZP); application of ZP, contamination with saliva, cleansing with HF followed by cleansing with ZP (ZP-SC-HF-ZP). Cylindrical resin composite blocks were luted to the zirconia surfaces with SAC (Clearfil SA Cement Automix, Kuraray, Inc., Tokyo, Japan). Specimens were subjected to shear forces at a cross-head speed of 0.5 mm/min. Data were analyzed with Analysis of Variance and Tukey tests (α = 0.05). RESULTS: The bond strength values to zirconia were significantly influenced by saliva contamination (P < .05). The SC-NC group showed the lowest bond strength values (5.6 ± 1.4 MPa; P < .05). All cleansing or pretreatment agents improved the bond strengths when compared to noncleansing groups, NC-NC and SC-NC. CONCLUSION: In situations where saliva contamination is deemed unavoidable, application of ZP after try-in of the zirconia restoration could be beneficial for the accurate cementation. CLINICAL SIGNIFICANCE: During try-in sessions of fixed dental prostheses, zirconia ceramic restoration may come into contact with saliva and surfaces should be cleansed to obtain an optimal surface for adhesion. Application of zirconia primer to the sandblasted zirconia surface is recommended whether the surface is contaminated with saliva or not.

Flexural strength of fiber reinforced posts after mechanical aging by simulated chewing forces.

This study evaluated the effect of simulated chewing forces on the flexural strength of fiber reinforced posts (FRPs). Four different brands of FRPs were selected as main group for the study: RelyX Fiber Post (RX), IceLight (ICE), Unicore Posts (UC), FlouroPost (FP). Ten posts in each main group didn't receive any aging process and tested as baseline (BL), other ten posts were subjected to simulated chewing forces/mechanical aging (MA) as follows: Post spaces were prepared in acrylic with drill. Depth of preparation was adjusted to leave 4-mm coronal part of posts protruding from canals. Coronal parts were incrementally restored with resin-composite (Clearfil Majesty Posterior A2, Kuraray, Osaka, Japan). Prepared samples were subjected to chewing cycles in a chewing simulator (Chewing Simulator CS-4, Mechatronik, Germany). Flexural strengths of all groups were measured with three-point bending test. Data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). After MA, flexural strengths of all posts were significantly decreased when compared with BL for all FRPs tested (p < 0.05). At BL, highest flexural strength values were obtained for ICE. After MA, similar to BL, highest flexural strength values were obtained for ICE. Only RX showed statistically significant difference when compared with ICE (p < 0.05). UC and FP showed similar flexural strength values with ICE (p > 0.05). It may be concluded that chewing forces on post-core systems may reduce the flexural strengths of FRPs.

Surface characteristics of bioactive Ti fabricated by chemical treatment for cartilaginous-integration.

Artificial hip joints are generally expected to fail due to wear after approximately 15years and then have to be replaced by revision surgery. If articular cartilage can be integrated onto the articular surfaces of artificial joints in the same way as osseo-integration of titanium dental implants, the wear of joint implants may be reduced or prevented. However, very few studies have focused on the relationship between Ti surface and cartilage. To explore the possibility of cartilaginous-integration, we fabricated chemically treated Ti surfaces with H2O2/HCl, collagen type II and SBF, respectively. Then, we evaluated surface characteristics of the prepared Ti samples and assessed the cartilage formation by culturing chondrocytes on the Ti samples. When oxidized Ti was immersed in SBF for 7days, apatite was formed on the Ti surface. The surface characteristics of Ti indicated that the wettability was increased by all chemical treatments compared to untreated Ti, and that H2O2/HCl treated surface had significantly higher roughness compared to the other three groups. Chondrocytes produced significantly more cartilage matrix on all chemically treated Ti surfaces compared to untreated Ti. Thus, to realize cartilaginous-integration and to prevent wear of the implants in joints, application of bioactive Ti formed by chemical treatment would be a promising and effective strategy to improve durability of joint replacement.

A retrospective survey on long-term survival of posterior zirconia and porcelain-fused-to-metal crowns in private practice.

OBJECTIVES: This retrospective survey assessed the clinical survival of zirconia-based crowns (PFZ) and conventional porcelain- fused-to-metal (PFM) crowns on posterior teeth in private practice. METHOD AND MATERIALS: A print survey of 13 private practitioners was conducted to assess the long-term survival of previously placed full-coverage crowns. The practitioners reported a total of 2,182 premolar (n = 881) and molar (n = 1,301) full-coverage single crowns, 1,102 PFZ and 1,080 PFM, fabricated by one dental laboratory (Cusp, Boston) and followed over 7.4 years. All post-cementation complications (eg, porcelain fractures and chippings) were recorded as failures. In the PFZ group, one veneering porcelain (CZR, Kuraray Noritake) was used in combination with three coping systems (Lava, 3M ESPE; Procera, Nobelbiocare; Katana, Kuraray Noritake). Kaplan-Meier survival analysis was used for statistical analyses. RESULTS: The probability of survival of posterior crowns investigated over the period of study (7.4 years) was 99.3% for PFM and 99.2% for PFZ restorations. There was no statistically significant difference (P = .614) between PFZ and PFM groups. In the PFZ group, probability of survival was 97.7% for Lava, 100% for Procera, and 99.5% for Katana. There were no statistically significant differences (P = .34) between the three PFZ systems or the location of the crowns (premolar or molar; P = .454). CONCLUSION: PFZ crowns fabricated with CZR and three commercial zirconia coping systems revealed excellent long-term success rates. Survival times and survival probabilities of posterior PFZ crowns did not differ from PFM crowns and were independent of type of coping system and location (molar or premolar teeth).

Relationship between air-blowing duration and bond strengths of three adhesive systems to dentin after thermal aging.

The purpose was to evaluate the effect of air-blowing duration of three different adhesive systems on immediate or thermal aged resin-dentin shear bond strength (SBS). Human dentin surfaces were bonded with: one-step (Bond Force, BF), two-step (FL-Bond II, FLB) and three-step (Scotch Bond Multi-Purpose, SBMP) adhesive systems. Bonded surfaces from each group were air-blown for 0, 5, or 10 s and cured. Composite cylinders were built on the treated surfaces and cured. Half of the specimens from each group were tested immediately and the other halves were tested after thermal aging. Statistical analysis showed significant decrease in SBS after thermal aging compared to immediate testing in all groups, except BF after 5 s air-blowing or FLB and SBMP with no air-blowing (p>0.05). The results suggested that 5 s air-blowing is necessary to obtain a stable SBS for BF. However, extended airblowing duration of FLB and SBMP decreased the SBS significantly after thermal aging.

Postoperative tooth sensitivity with a new self-adhesive resin cement--a randomized clinical trial.

OBJECTIVES: This study evaluated and compared sensitivity of teeth after cementation of full-coverage crowns with a new self-adhesive resin cement (SARC). A resin-modified glass ionomer cement (RMGIC) served as control. MATERIALS AND METHODS: Eighty-eight full-coverage crowns were cemented to vital teeth with either the self-adhesive cement iCem (Heraeus Kulzer; n = 44) or the RMGIC GC Fuji PLUS (GC, n = 44). Before preparations, patients were questioned for sensitivity (patient sensitivity, PS). In addition, air was blown for 2 s onto the buccal cementoenamel junction (air sensitivity, AS), and ice spray was applied in the cementoenamel junction area (ice sensitivity, IS). Patient responses were recorded with a visual analog scale. After cementation of the crowns, patients were recalled for follow-up (f/u) visits at 1 day, 1 week, and 3 weeks. PS, AS, and IS were recorded during each visit. Data were analyzed with Mann-Whitney U tests. RESULTS: The two groups revealed comparable sensitivity scores at baseline. SARC showed significantly lower PS sensitivity scores at 1 day (p = 0.02) and significantly lower AS scores at 1-week follow-up (p = 0.01). IS generally produced the highest sensitivity scores with SARC revealing significantly lower scores at all follow-up visits. CONCLUSION: Cementation of crowns with the SARC tested in this study resulted in overall lower postoperative sensitivity than with the RMGIC. CLINICAL RELEVANCE: Among other clinical advantages, some self-adhesive resin cements seem to lower postoperative sensitivity of crowned teeth.

The current state of adhesive dentistry: a guide for clinical practice.

Adhesive dentistry is key to minimally invasive, esthetic, and tooth-preserving dental restorations. These are typically realized by bonding various restorative materials, such as composite resins, ceramics, or even metal alloys, to tooth structures or other materials with composite resin luting agents. For optimal bond strengths and long-lasting clinical success, however, these material and tooth substrates require their respective pretreatment steps, based on their natures and compositions. Today, dental adhesion is used in almost all dental specialties. This article summarizes key aspects and guidelines for clinical success with adhesive dentistry and summarizes information presented at the 5th International Congress on Adhesive Dentistry.

Comparison of retention and strain energies of stud attachments for implant overdentures.

PURPOSE: The retentive forces and the strain energies absorbed during dislodging of implant overdenture stud attachments are useful parameters to consider in the selection of attachments. The purpose of this study was to compare the retentive forces and strain energies of the Nobel Biocare standard ball, Nobel Biocare newer generation ball (Yorba Linda, CA), Zest Anchor, Zest Anchor Advanced Generation (Escondido, CA), Sterngold-Implamed ERA white, and Sterngold-Implamed orange attachments (Attleboro, MA) on an implant-retained in vitro overdenture model. MATERIALS AND METHODS: The attachments were tested using two permanently placed Brånemark system implants on a test model attached to an Instron machine. Each attachment had one part embedded in a denture-like housing, and the other part screwed into the implants. Dislodging tensile forces were applied to the housings in two directions simulating function: vertical and oblique. Eight tests were done in two directions with six specimens of each attachment. Retentive forces generated and strain energies absorbed during displacement were determined. A 1-way ANOVA followed by the Tukey studentized range test was used to determine groups that were significantly different at the p < 0.05 level. RESULTS: The Zest Anchor Advanced Generation attachment had significantly the highest retentive vertical and oblique forces [37.2 (5.5) N and 25.9 (3.2) N, respectively]. The Zest Anchor had the lowest vertical force [10.8 (4.2) N], and Nobel Biocare Standard had the lowest oblique retentive force [10.6 (3.0) N]. The Nobel Biocare Standard Ball attachment had the highest strain energies [29.7 × 10(-3) (11.9 × 10(-3)) J, 30.3 × 10(-3) (14.3 × 10(-3)) J, respectively, in the vertical and oblique directions]. The Sterngold-Implamed ERA White and Zest Anchor had the lowest strain energies [5.3 × 10(-3) (3.2 × 10(-3)) J and 4.5 × 10(-3) (1.1 × 10(-3)) J, respectively, in the vertical and oblique directions]. CONCLUSION: The retentive forces and strain energies of implant overdenture stud attachments are different and should be considered during prosthesis selection.

Friction between various self-ligating brackets and archwire couples during sliding mechanics.

INTRODUCTION: The aim of this study was to evaluate the frictional resistance between active and passive self-ligating brackets and 0.019 × 0.025-in stainless steel archwire during sliding mechanics by using an orthodontic sliding simulation device. METHODS: Maxillary right first premolar active self-ligating brackets In-Ovation R, In-Ovation C (both, GAC International, Bohemia, NY), and SPEED (Strite Industries, Cambridge, Ontario, Canada), and passive self-ligating brackets SmartClip (3M Unitek, Monrovia, Calif), Synergy R (Rocky Mountain Orthodontics, Denver, Colo), and Damon 3mx (Ormco, Orange, Calif) with 0.022-in slots were used. Frictional force was measured by using an orthodontic sliding simulation device attached to a universal testing machine. Each bracket-archwire combination was tested 30 times at 0° angulation relative to the sliding direction. Statistical comparisons were performed with 1-way analysis of variance (ANOVA) followed by Dunn multiple comparisons. The level of statistical significance was set at P <0.05. RESULTS: The Damon 3mx brackets had significantly the lowest mean static frictional force (8.6 g). The highest mean static frictional force was shown by the SPEED brackets (83.1 g). The other brackets were ranked as follows, from highest to lowest, In-Ovation R, In-Ovation C, SmartClip, and Synergy R. The mean static frictional forces were all statistically different. The ranking of the kinetic frictional forces of bracket-archwire combinations was the same as that for static frictional forces. All bracket-archwire combinations showed significantly different kinetic frictional forces except SmartClip and In-Ovation C, which were not significantly different from each other. CONCLUSIONS: Passive self-ligating brackets have lower static and kinetic frictional resistance than do active self-ligating brackets with 0.019 × 0.025-in stainless steel wire.

Bond strength of luting cements to core foundation materials.

PURPOSE: The purpose was to compare the shear bond strength of luting cements to foundation materials and to determine the effect of storage in lactate buffer solution. MATERIALS AND METHODS: Disks that were 8 mm in diameter and 2-mm thick were fabricated from foundation substrates: amalgam, composite resin, resin-modified glass ionomer, and glass ionomer (n = 20). Cylinders that were 2 mm in diameter and 4 mm in length of resin luting cement, resin-modified glass ionomer luting cement, and a glass ionomer luting cement were bonded to the foundation substrate materials. Shear bond strength of each foundation substrate material/cement pair was determined with a universal testing machine after 24 hours. A second set of specimens was tested after storage in a 0.01M lactate buffer solution for 24 hours. A three-way analysis of variance followed by pair-wise comparisons was performed to compare bond strengths (P < .05). RESULTS: The resin cement provided the highest (P < .05) bond strengths to amalgam, composite resin, and resin-modified glass ionomer foundation materials while the glass ionomer cement showed the lowest bond strength (P < .05) to composite resin and glass ionomer foundation restoration materials. After immersion in a 0.01M lactate buffer solution, the shear bond strength of all the material combinations was significantly lower (P < .05) than nonimmersed specimens, except the bonds between composite resin foundation and resin luting cement, which significantly increased (P < .05) in strength. CONCLUSION: The resin cement had the highest bond strength to most foundation substrates investigated. The highest bond was observed between the composite resin foundation and resin cement. This bond was also the most durable on immersion in lactic acid.

In vitro comparative bond strength of contemporary self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion.

This study compared shear bond strengths of six self-adhesive resin cements to zirconium oxide ceramic with and without air-particle abrasion. One hundred twenty zirconia samples were air-abraded (group SB; n = 60) or left untreated (group NO). Composite cylinders were bonded to the zirconia samples with either BisCem (BC), Maxcem (MC), G-Cem (GC), RelyX Unicem Clicker (RUC), RelyX Unicem Applicator (RUA), or Clearfil SA Cement (CSA). Shear bond strength was tested after thermocycling, and data were analyzed with analysis of variance and Holm-Sidak pairwise comparisons. Without abrasion, RUA (8.0 MPa), GC (7.9 MPa), and CSA (7.6 MPa) revealed significantly higher bond strengths than the other cements. Air-particle abrasion increased bond strengths for all test cements (p < 0.001). GC (22.4 MPa) and CSA (18.4 MPa) revealed the highest bond strengths in group SB. Bond strengths of self-adhesive resin cements to zirconia were increased by air-particle abrasion. Cements containing adhesive monomers (MDP/4-META) were superior to other compositions.

Effect of liquid rubber additions on physical properties of Bis-GMA based dental resins.

OBJECTIVE: The aim of this investigation was to determine the effect of an experimental liquid rubber (LR) toughening agent on fracture toughness, crosslink density and Barcol hardness of polymerized mixtures of 50/50 wt% Bis-GMA and TEGDMA. METHODS: An experimental LR, was added to a solution of Bis-GMA and TEGDMA containing 1wt% dimethylamino ethyl methacrylate and 0.5 wt% camphoroquinone at concentrations 0-10%. The composites were polymerized by exposure to a visible light curing unit for 60s. Fracture toughness was determined according to ASTM. 399. Crosslink density was evaluated using a swell test in ethanol. RESULTS: Mean fracture toughness values ranged from 0.39 MPa m(1/2) for samples containing 6% to 1.24 MPa m(1/2) for samples containing 8% LR. Fracture toughness of samples containing 2%, 4%, and 8% LR were significantly higher than controls. The highest degree of cross-linkage was obtained in controls and lowest for samples containing 2% LR. Barcol Hardness values ranged from 36.7 for the control and 4% LR composition to 31.2 for samples containing 10% LR. SIGNIFICANCE: Addition of 2, 4 and 8% LR increases the fracture toughness of Bis-GMA/TEGDMA composites. Addition of LR shows promise as a method of improving the fracture toughness of Bis-GMA based dental composites.

A new resin-bonded retrograde filling material.

OBJECTIVE: This study determined the physical properties and cytotoxicity of a novel root-end filling material (NRC). STUDY DESIGN: NRC is a powder and liquid system. The liquid is composed of hydroxyethylmethacrylate, benzoyl peroxide, toluidine, and toluenesulfinate. And the powder is made of calcium oxide, calcium silicate, and triphenylbismuth carbonate. The setting time, compressive strength, and pH change of NRC and gray and white mineral trioxide aggregate (MTA) were determined according to ISO standardization. MC3T3-E1 cells were cultured on NRC and white MTA for determining MTT scores. The absorbance of formazan was measured at 570 nm with a spectrophotometer. The MTT assay was performed in triplicate and repeated in 2 cultures. One-way analysis of variance was used to determine statistical differences in physical properties and MTT assay (P < .05). RESULTS: Mean setting time of materials tested were: NRC 12.5 +/- 0.3 minutes, gray MTA 345.5 +/- 96.2 minutes, and white MTA 318.0 +/- 56.0 minutes. After 24 hours, the mean compressive strengths were: NRC, 21.6 +/- 5.5 MPa, gray MTA: 7.7 +/- 3.3 MPa, and white MTA, 18.9 +/- 3.2 MPa. The pH of the test materials were: NRC 12.0, gray MTA 12.2, and white MTA 11.9. There were no statistically significant differences in compressive strength and pH between white MTA and NRC. The compressive strength of gray MTA was significantly lower than white MTA and NRC (P < .05). The setting time of NRC was significantly lower than white and gray MTA. In MTT assay, both NRC and white MTA were not cytotoxic to MC3T3-E1 cells. CONCLUSIONS: It was concluded that the setting time, compressive strength, pH, and initial biocompatibility results of NRC are favorable for a root-end filling material.

Comparative osteogenesis of maxilla and iliac crest human bone marrow stromal cells attached to oxidized titanium: a pilot study.

OBJECTIVES: Severe alveolar bone loss affects dental implant placement. Bone augmentation by grafting iliac crest bone rich in osteoprogenitor cells such as bone marrow stromal cells (BMSCs) requires a second surgical procedure in non-orofacial bone. Skeletal site-specific osteogenesis indicates maxilla and mandible BMSCs are highly proliferative and exhibit osteogenic properties superior to iliac crest BMSCs. Alveolar bone can be easily obtained during routine dental surgery, but it is unclear if titanium-attached alveolar BMSCs will retain their superior osteogenic properties. This study evaluated and compared in vitro osteogenic properties of titanium-attached maxilla and iliac crest BMSCs in same individuals. MATERIAL AND METHODS: Primary culture of maxilla and iliac crest BMSCs from four normal healthy volunteers was expanded in culture. In 24-well plates, first passage BMSCs were seeded directly (1 x 10(4) cells/well) on oxidized titanium disks (1.27 cm diameter and 2 mm thickness) or tissue culture plate. Each cell type was assessed for affinity for titanium, post-attachment survival and osteogenic differentiation based on alkaline phosphatase and osteopontin expressions. RESULTS: There was no difference in the affinity of maxilla and iliac crest BMSCs to titanium. However, titanium-attached maxilla BMSCs were apparently more osteogenically responsive than iliac crest cells based on calcium accumulation and gene expression of alkaline phosphatase and osteopontin. But these differences were not statistically significant in this small patient sample. CONCLUSION: Maxilla and iliac crest BMSCs have similar attachment affinity for titanium. This pilot study indicates that titanium-attached maxilla BMSCs are more osteogenically responsive and may be a viable and more readily available donor graft material in implant dentistry.

In vitro changes in hardness of sealed resilient lining materials on immersion in various fluids.

PURPOSE: During clinical use, resilient lining materials undergo changes in hardness that make them ineffective. The aims of this investigation were (1) to determine the effect of a resilient lining sealer on the hardness of four resilient denture liners; and (2) to determine the effect of the sealer on hardness after immersion in various solutions. MATERIALS AND METHODS: Two sets of specimens of four resilient liners, Coe-comfort (CC), PermaSoft (PS), Tokuyama soft reline (TK), and Total-Soft (TS), 6-mm diameter by 4-mm thickness, were fabricated. Two coats of Permaseal, a soft reline sealant, were applied to one set of specimens of each material according to manufacturers' instructions. Sealed and unsealed samples were divided into four groups (n = 10). Each group was immersed in one of the following solutions: artificial saliva at 37 degrees C, Efferdent, Efferdent with once daily scrubbing with a soft toothbrush, and 50% ethanol. Shore A hardness numbers were obtained at 0, 1, 3, 7, 30, and 90 days. A two-way ANOVA test was performed using materials (treated and untreated) and immersion solution as independent variables. The percentage change in hardness after the 90-day immersion period was the dependent variable. RESULTS: The results show that the application of sealant significantly improved the durability of CC, PS, and TS in immersion solutions by maintaining hardness close to preimmersion values or delaying the softening effect of the solutions. The hardness of sealed and unsealed TK showed the significantly (p < 0.05) lowest change after immersion in the test solutions. Ethanol caused the most severe decrease in hardness of all solutions, followed by saliva. Immersion in Efferdent and daily brushing after immersion in Efferdent showed only a mild effect on the hardness of the soft reline agents. CONCLUSION: The use of a sealer can play an important role in the preservation of the hardness of some resilient lining materials.