Home About us Contact
|
Home About us Contact | ||
|
|
||
Universal Testing Machine (universal + testing_machine)
Kinds of Universal Testing Machine Selected AbstractsEvaluation of fracture resistance in simulated immature teeth using resilon and ribbond as root reinforcements , An in vitro studyDENTAL TRAUMATOLOGY, Issue 4 2009Hiremath Hemalatha Material and Methods:, Sixty five freshly extracted human maxillary anterior teeth were prepared with a Peeso no. 6 to simulate immature teeth (Cvek's stage 3 root development). After instrumentation, each root was irrigated with sodium hypochlorite and with ethylene diamino tetra acetic acid to remove the smear layer. To simulate single visit apexification technique a 4,5 mm white Pro Root mineral trioxide aggregate plug was placed apically using schilder carrier. The teeth were divided into three experimental groups and one control group. Group I , control group (root canals instrumented but not filled); Group II , backfilled with thermoplastisized gutta-percha using AH plus sealer; Group III , reinforced with Resilon using epiphany sealer; Group IV , reinforced with Ribbond fibers using Panavia F luting cement. A Universal Testing Machine was used to apply a load, at the level of the lingual cementoenamel junction with a chisel-shaped tip The peak load to fracture was recorded and statistical analysis was completed using student's t -test. Results:, Values of peak load to fracture were 1320.8, 1604.88, 1620, and 1851newtons for Group I to Group IV respectively. The results of student's t -test, revealed no significant difference (P > 0.05,) between Group II and Group III. Comparison between Group IV and Group III and between Group IV and Group II revealed highly significant difference (P > 0.001). Conclusions:, Teeth reinforced with Ribbond fibers using Panavia F luting cement showed the highest resistance to fracture. Resilon could not strengthen the roots and showed no statistically significant difference when compared with thermopasticised gutta-percha in reinforcing immature tooth when tested with universal testing machine in an experimental model of immature tooth. [source] Physicochemical properties of low-fat and full-fat Cheddar cheesesINTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 3 2006E KÜÇÜKÖNER Low-fat (6% fat) and full-fat (32% fat) Cheddar cheese was manufactured and aged up to 6,9 months at 5°C. The objective was to study the impact of fat on the physicochemical properties of Cheddar cheese. Total soluble nitrogen (TSN) and protein nitrogen (TPSN) in aqueous extracts were determined by the Kjeldahl method. The peptide content of each cheese was determined with reverse phase chromatography (RPC). Low-fat Cheddar (LFC) had a markedly higher peptide content than full-fat Cheddar (FFC). The overall peptide quantity increased with age with a marked increase in hydrophobic peptide content. Rheological properties were determined using an Instron Universal Testing Machine. LFC had significantly higher stress values, indicating hard and rubbery texture, than FFC. Furthermore, LFC had lower strain values, indicating crumbliness. [source] The effect of coagulants on the texture of chhana (an acid and heat coagulated product made from milk)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2005Mahuya Bandyopadhyay Summary Chhana (a heat and acid coagulated milk protein mass and an Indian equivalent to cottage cheese) can be used as a raw material for the manufacture of various types of sweets popular all over India. Texture Profile Analysis (TPA), using an Instron Universal Testing Machine, was used to determine the effect of different coagulants on the textural characteristics of chhana. Chhana was made using three different coagulants: citric acid, lactic acid and calcium lactate, at five different concentrations, 0.5, 1, 2, 4 and 8%. Two types of dilution media, distilled water and acid whey, were used. The textural characteristics obtained when aqueous 0.5% citric acid, aqueous 0.5% lactic acid and 4,8% calcium lactate solutions, using acid whey as the solvent, gave similar TPA readings to normal chhana. [source] KINETICS of QUALITY CHANGE DURING COOKING and FRYING of POTATOES: PART I. TEXTUREJOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2003F. NOURIAN ABSTRACT Kinetics of texture change during cooking and frying of potatoes were evaluated in this study. Potatoes were cut into cylinders (diameter × height: 20 mm × 20 mm for cooking, and 10 mm × 20 mm for frying) and cooked in a temperature controlled water bath at 80,100C or fried in a commercial fryer at 160,190C for selected times. the cooked samples were water cooled while the fried samples were air cooled immediately after the treatment. Test samples were then subjected to a single cycle compression test in a computer interfaced Universal Testing Machine and three textural properties (hardness, stiffness and firmness) were derived from the resulting force-deformation curves. Texture parameters of cooked potatoes decreased with progress of cooking time and the rate of texture changes associated with each temperature was found to be consistent with two pseudo first-order kinetic mechanisms, one more rapid than the other. Textural values of fried potatoes were found to increase with frying time and also followed a first order kinetic model. Temperature sensitivity of rate constants was adequately described by Arrhenius and z-value models. [source] Effect of Auxiliary Grooves on Molar Crown Preparations Lacking Resistance Form: A Laboratory StudyJOURNAL OF PROSTHODONTICS, Issue 2 2008DClinDent, GradDipClinDent, Po-Ching Lu BDSc(Hons) Abstract Purpose: To investigate the effect of auxiliary grooves on resistance to dislodgment of crowns on compromised molar preparations lacking resistance form. Materials and Methods: Thirty human molar teeth were randomly assigned to three groups of ten, and prepared to a height-to-width ratio of 0.3 with a total convergence of 50°, and 1-mm shoulder margin. Base metal alloy copings were constructed with a 45° loading platform and cemented with zinc phosphate cement under a 50 N load. Initially, resistance testing was conducted using a Universal Testing Machine (Instron) at 1 mm/min for all 30 specimens. Following crown dislodgment, Group 1 copings were recemented and retested, Group 2 had one axial groove added, and Group 3 had two axial grooves added. New copings for Groups 2 and 3 were made, cemented, and again tested for resistance. Standardized radiographs were taken prior to initial cementation and scanned into digital images. The percentage of area occupied by the pulpal chamber above the acrylic mounting (PS), and the closest distance to pulp from the preparation surface (CD) were measured. Results: Recementation or the addition of one groove did not affect the dislodgment values (p > 0.05), but addition of two grooves caused a highly significant increase in resistance (p < 0.001). Regression analysis showed an inverse relationship between initial resistance values and pulpal space area. Lower resistance values were observed when the pulpal space area was large (p= 0.004). Conclusions: Crowns can be recemented without affecting resistance to dislodgment. Two grooves should be incorporated into compromised molar crown preparations to increase resistance form. Teeth with large pulps and therefore less coronal dentine have poorer resistance form, and therefore would benefit from placement of auxiliary grooves. [source] The Effect of Denture Cleansing Solutions on the Retention of Yellow Hader Clips: An In Vitro StudyJOURNAL OF PROSTHODONTICS, Issue 3 2007Reena M. Varghese DMD Purpose: To evaluate the retention of yellow Hader clips after exposure to various denture cleansers. Methods: Seven groups of 18 yellow Hader clips each were soaked for the equivalent of 6 months of clinical use in the following denture cleansing solutions: Polident Regular, Polident Overnight, Efferdent, 5.25% Sodium Hypochlorite (NaOCl, 1:10 dilution) 15 min/day, NaOCl (1:10 dilution) 8 hours/day, water and dry (control) group. A Universal Testing Machine, set at a crosshead speed of 2 in/min, pulled each clip once, and the peak load-to-dislodgement was recorded and used as a measure to reflect changes in the retention of the Hader clips. Data were analyzed by a one-way analysis of variance followed by Tukey's HSD test. A p value , 0.05 was considered significant. Results: Denture cleansing solutions affected the retentive values of yellow Hader clips (F= 6.102, p, .0001). Sodium hypochlorite solution, 15 min/day for 6 months, caused an increase in the retentive values of the clips tested with a mean peak load-to-dislodgement of 22.63 ± 1.29 N. In addition, clips soaked in water showed no difference in retentive values when compared with all other groups. Furthermore, Polident Regular, Polident Overnight, Efferdent, and NaOCl (8 hours/day) had no effect on the retentive values of yellow Hader clips. Conclusion: This in vitro study demonstrated that the retention of yellow Hader clips used in implant overdentures is unaffected when soaked in commercial effervescent denture cleansers (Polident 5 Minute, Polident Overnight, and Efferdent) for six simulated months. Sodium hypochlorite statistically increased the single-pull retentive values of the clips, an effect that may not be beneficial. Increased retentive values may be associated with reduced durability of clips; further research is needed to address this issue. [source] The effect of thermocycling on peel strength of six soft lining materialsJOURNAL OF ORAL REHABILITATION, Issue 6 2002A. Sertgöz The bond strength of two heat-cured and four cold-cured soft lining materials was compared using a peeling test method before and after thermocycling. Tested soft lining materials were Molloplast B, Mollosil, Ufigel P, Ufigel C, Permaquick and Permaflex. Six specimens, 6·5 × 2 × 0·3 cm, for each group were prepared according to the manufacturers' instructions. Control groups were stored in a humidor for 24 h, whereas the others were thermocycled in a water bath between the 5 and 55 °C for 5000 cycles. Peel strength of samples were measured using an Instron Universal testing machine at a cross-head speed of 5 mm min,1. The types of failure were observed using an electron microscope. The highest peel bond strength values were calculated for Permaflex and Permaquick before and after thermocycling, respectively. Molloplast B, Mollosil, Ufigel P and Permaquick demonstrated an increase in peel strength after thermocycling, with Permaquick lining material having statistically significant increase. However, decrease in peel strength was observed for Ufigel C and Permaflex after thermocycling. Failure mode within the control groups was cohesive for Molloplast B, Permaquick and Permaflex, whereas adhesive for Ufigel P and Ufigel C. Mollosil demonstrated a mixed mode of failure for both thermocycled and control groups. [source] Tensile bond strengths of four different dentin adhesives on irradiated and non-irradiated human dentin in vitroJOURNAL OF ORAL REHABILITATION, Issue 9 2001C. R. Gernhardt This study evaluated the influence of irradiation on dentin bond strength. Sixty irradiated and 60 non-irradiated human third molars were used. The irradiation dose of 60 Gy was fractionally applied over 6 weeks (2 Gy day,1, 5 days week,1). All teeth were prepared in a special manner allowing the simulation of intra-pulpal pressure and dentin perfusion. Dentin specimens with a thickness of 2·0 mm were obtained under standardized conditions. The specimens were randomly assigned to four experimental groups. Tensile bond strength of four different dentin bonding agents (ScotchbondÔ 1, Solobond Plus®, Prime&BondÔ 2·1 and Syntac®) was evaluated using an Instron Universal testing machine. Pairwise comparison did not show any significant differences between the irradiated and non-irradiated groups. The influence of the different dentin adhesives was significant (P=0·0001; ANOVA). Compared with Solobond Plus® and Prime&BondÔ 2·1, the use of ScotchbondÔ 1 resulted in a significantly higher tensile bond strength in non-irradiated specimen (P< 0·05; closed test procedure based on Kruskal,Wallis test). Within the limitations of an in vitro study, it can be concluded that adhesive restoration procedures can be successfully used in patients irradiated for cancer of the head and neck. [source] Evaluation of fracture resistance in simulated immature teeth using resilon and ribbond as root reinforcements , An in vitro studyDENTAL TRAUMATOLOGY, Issue 4 2009Hiremath Hemalatha Material and Methods:, Sixty five freshly extracted human maxillary anterior teeth were prepared with a Peeso no. 6 to simulate immature teeth (Cvek's stage 3 root development). After instrumentation, each root was irrigated with sodium hypochlorite and with ethylene diamino tetra acetic acid to remove the smear layer. To simulate single visit apexification technique a 4,5 mm white Pro Root mineral trioxide aggregate plug was placed apically using schilder carrier. The teeth were divided into three experimental groups and one control group. Group I , control group (root canals instrumented but not filled); Group II , backfilled with thermoplastisized gutta-percha using AH plus sealer; Group III , reinforced with Resilon using epiphany sealer; Group IV , reinforced with Ribbond fibers using Panavia F luting cement. A Universal Testing Machine was used to apply a load, at the level of the lingual cementoenamel junction with a chisel-shaped tip The peak load to fracture was recorded and statistical analysis was completed using student's t -test. Results:, Values of peak load to fracture were 1320.8, 1604.88, 1620, and 1851newtons for Group I to Group IV respectively. The results of student's t -test, revealed no significant difference (P > 0.05,) between Group II and Group III. Comparison between Group IV and Group III and between Group IV and Group II revealed highly significant difference (P > 0.001). Conclusions:, Teeth reinforced with Ribbond fibers using Panavia F luting cement showed the highest resistance to fracture. Resilon could not strengthen the roots and showed no statistically significant difference when compared with thermopasticised gutta-percha in reinforcing immature tooth when tested with universal testing machine in an experimental model of immature tooth. [source] Influence of contamination on resin bond strength to nano-structured alumina-coated zirconia ceramicEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2010Shanchuan Zhang Zhang S, Kocjan A, Lehmann F, Kosma, T, Kern M. Influence of contamination on resin bond strength to nano-structured alumina-coated zirconia ceramic. Eur J Oral Sci 2010; 118: 396,403. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The purpose of this study was to evaluate the influence of contamination and subsequent cleaning on the bond strength and durability of an adhesive resin to nano-structured alumina-coated zirconia ceramic. Zirconia ceramic disks were coated with nano-structured alumina, utilizing the hydrolysis of aluminum nitride powder. After immersion in saliva or the use of a silicone disclosing agent, specimens were cleaned with phosphoric acid etching or with tap water rinsing only. Uncontaminated specimens served as controls. Plexiglas tubes filled with composite resin were bonded with a phosphate monomer [10-methacryloxydecyl-dihydrogenphosphate (MDP)]-containing resin (Panavia 21). Subgroups of eight specimens each were stored in distilled water at 37°C, either for 3 d without thermal cycling (TC) or for 150 d with 37,500 thermal cycles from 5 to 55°C. The tensile bond strength (TBS) was determined using a universal testing machine at a crosshead speed of 2 mm min,1. The topography of the debonded surface was scrutinized for fractographic features, utilizing both optical and scanning electron microscopy. The TBS to uncontaminated nano-structured alumina-coated zirconia ceramic was durable, while contamination significantly reduced the TBS. Phosphoric acid cleaning was effective in removal of saliva contamination from the coated bonding surface but was not effective in removal of the silicone disclosing agent. Nano-structured alumina coating improves resin bonding to zirconia ceramic and eliminates the need for air-abrasion before bonding. [source] Enamel microhardness and bond strengths of self-etching primer adhesivesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2010Olabisi A. Adebayo Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self-etching primer adhesives. Eur J Oral Sci 2010; 118: 191,196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (,SBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the ,SBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min,1 until bond failure occurred. The mean ,SBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and ,SBS. The weights used were the inverse of the variance of the ,SBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the ,SBS. These results suggest that the ,SBS of the self-etch adhesive systems are not influenced by enamel surface microhardness. [source] Effects of additional and extended acid etching on bonding to caries-affected dentineEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 5 2004César Augusto Galvão Arrais This study evaluated the effects of additional and extended acid etching on microtensile bond strength (µTBS) of two adhesive systems to sound (SD) and caries-affected dentine (CAD). Flat surfaces of CAD surrounded by SD of 36 extracted carious third molars were assigned to four treatments (i): self-etching adhesive system (Clearfil SE Bond) applied to dentine surfaces following manufacturer's instructions (MI); (ii) after additional etching for 15 s (35% phosphoric acid, PA); (iii) total-etch one-bottle adhesive (Single Bond) applied to dentine surfaces following MI; or (iv), after etching for 45 s with PA. Composite ,blocks' were built on bonded surfaces and restored teeth were vertically sectioned to obtain bonded slices of 0.7 mm thick. Slices were trimmed to create hourglass-shaped specimens (cross-sectional area of 1 mm2), which were tested under tension in a universal testing machine. Additional CAD and SD samples were prepared for scanning electron microscopy observations. Additional and extended etching significantly increased µTBS to CAD; however, µTBS of both adhesives to CAD were significantly lower than to SD. Additional and extended etching can improve bonding to CAD; however, adhesives applied on SD showed the best results for bonding. [source] Fracture resistance of root filled molar teeth restored with glass fibre bundlesINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2010F. B. Rodrigues Rodrigues FB, Paranhos MPG, Spohr AM, Oshima HMS, Carlini B, Burnett LH Jr. Fracture resistance of root filled molar teeth restored with glass fibre bundles. International Endodontic Journal, 43, 356,362, 2010. Abstract Aim, To evaluate the effect of unidirectional or woven glass fibre tapes inserted into MOD cavity preparations on the fracture resistance of root filled molar teeth. Methodology, Extracted human molar teeth were randomly divided into six groups (n = 15) : G1 , sound teeth, control; G2 , MOD cavity preparation; G3 , MOD + root canal treatment (Endo); G4 , MOD + Endo + composite resin restoration (Resin); G5 , MOD + Endo + unidirectional fibre (UF) + Resin; G6 , MOD + ;Endo + woven fibre (WF) + Resin. The teeth were subjected to a compressive fracture test in a universal testing machine. After testing, two failure modes were classified: pulp chamber floor or cusp. Results, The highest and the lowest mean fracture strengths were found in sound teeth (G1) (4960N) and MOD + root canal treatment (G3) (612.84N), respectively, with significant differences from the other groups (P < 0.05). The remaining groups had statistically similar means. In G5 and G6, there was a tendency for fracture to occur in the pulp chamber floor compromising tooth integrity. Conclusions, The insertion of glass fibres into MOD cavity preparations and restoring them with composite resin was not different than molar teeth filled with composite resin only in terms of fracture resistance. Fibres placed into MOD cavities do not reinforce teeth. [source] The effect of irrigation time, root morphology and dentine thickness on tooth surface strain when using 5% sodium hypochlorite and 17% EDTAINTERNATIONAL ENDODONTIC JOURNAL, Issue 3 2010O. E. Sobhani Sobhani OE, Gulabivala K, Knowles JC, Ng Y-L. The effect of irrigation time, root morphology and dentine thickness on tooth surface strain when using 5% sodium hypochlorite and 17% EDTA. International Endodontic Journal, 43, 190,199, 2010. Abstract Aim, To evaluate the effect of irrigation with 5% sodium hypochlorite (NaOCl) alone and in conjunction with 17% ethylenediaminetetraacetic acid (EDTA) on tooth surface strain (TSS) and to analyse the influence of irrigation time, root morphology and dentine thickness. Methodology, Thirty-six single-rooted pre-molars with single canals had their crown and enamel reduced and root canals prepared using a standardized protocol. Teeth were grouped according to anatomical criteria and randomly distributed to experimental irrigation groups: (A) saline (negative control); (B) 5% NaOCl (positive control); (C) 5% NaOCl alternated with 17% EDTA. TSS was measured using electrical strain gauges bonded to the cervico-proximal part of the tooth. Teeth, mounted in clear acrylic resin placed in a universal testing machine, were subjected to nine consecutive 10-min irrigation periods followed by non-destructive occlusal loading to record TSS. Statistical analysis was carried out using two-way hierarchical anova and post hoc multiple comparisons. Results, Two groups showed an increase in TSS from the baseline (initial 10-min irrigation with saline). Group A showed a negligible reduction of 1.2% (343,339 ,,), which was not statistically significant (P = 0.7). Group B showed a highly significant (P = 0.001) increase in TSS by 53.7% (178,253 ,,), and group C showed a significant (P = 0.02) increase in TSS by 17.4% (163,192 ,,). The rate of change in TSS was significantly different between test groups. The length of the tooth (P = 0.04) as well as the mesio-distal (P = 0.05) width had significant effects on TSS. Conclusions, Irrigation with 5% with or without 17% EDTA increased TSS. The increase was significantly greater with 5% NaOCl alone than with 5% NaOCl alternated with 17% EDTA in contrast to previous findings with longer duration of irrigant exposure. Tooth length and mesio-distal root width significantly contributed to the increase in TSS. [source] Polymerization stress, flow and dentine bond strength of two resin-based root canal sealersINTERNATIONAL ENDODONTIC JOURNAL, Issue 10 2009S. F. C. Souza Abstract Aim, To compare two resin-based root canal sealers (AH Plus and dual cure Epiphany) in terms of flow, polymerization stress and bond strength to dentine. Methodology, Flow was evaluated by measuring the diameter of uncured discs of sealer (0.5 mL) after 7 min compression (20N) between two glass plates (n = 5). Polymerization stress was monitored for 60 min in 1-mm thick discs bonded to two glass rods (Ø = 5 mm) attached to a universal testing machine (n = 3). Bond strength was analyzed through micropush-out test (n = 10) and failure mode was examined with scanning electron microscope (100× and 2500×). Data were statistically analyzed using the Student's t -test (, = 0.05). Results, Polymerization stress was 0.32 ± 0.07 MPa for Epiphany self-cure, 0.65 ± 0.08 MPa for Epiphany light-cure and zero for AH Plus (P < 0.05). Flow data and bond strength values were 30.9 ± 1.1, 28.6 ± 0.7 mm and 6.3 ± 5.3, 17.8 ± 7.5 MPa for Epiphany and AH Plus, respectively (P < 0.001). Failure mode was predominantly cohesive in the sealer for both materials. Conclusions, Epiphany had higher flow and polymerization stress and lower bond strength values to dentine than AH Plus. In view of these findings it can be implied that AH Plus would provide a better seal. [source] Fracture strength of bovine incisors after intra-radicular treatment with MTA in an experimental immature tooth modelINTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2007E. A. Bortoluzzi Abstract Aim, To evaluate, using an experimental immature tooth model, the fracture resistance of bovine incisors submitted to different reinforcement treatments with mineral trioxide aggregate (MTA). Methodology, An immature tooth model was created by sectioning the coronal and apical portions of 40 bovine incisors 8 mm above and 12 mm below the cementoenamel junction. The root canals were irrigated with 1.0% sodium hypochlorite. They were enlarged both coronally and apically using number 703 carbide burs (ISO: 500,104-168-007-021) and their internal diameter was standardized to 2.1 mm. The specimens were assigned to four groups (n = 10): GI-control (without filling); GII-apical MTA plug + filling with gutta-percha and endodontic sealer; GIII-filling with MTA; GIV-apical MTA plug + filling with MTA + metallic post (Reforpost I). A polyether impression material was used to simulate the periodontal ligament. The specimens were submitted to a compressive load at a crosshead speed of 0.5 mm min,1 in a servo-hydraulic universal testing machine (MTS 810) applied at 45° to the long axis of the tooth until failure. Data were submitted to statistical analysis by the Kruskal,Wallis test at 5% significance level. Results, GIV presented the highest fracture resistance (32.7N) and differed significantly from the other groups (P < 0.05). No statistically difference was found between GII (16.6N) and GIII (23.4N) (P > 0.05). GIII had a significantly higher fracture resistance than GI (P < 0.05). Conclusions, The use of MTA + metallic post as an intra-radicular reinforcement treatment increased the resistance to fracture of weakened bovine teeth in an experimental immature tooth model. [source] Effect of bleaching agents on bonding to pulp chamber dentineINTERNATIONAL ENDODONTIC JOURNAL, Issue 4 2005S. Timpawat Abstract Aim, To determine the effect of intracoronal bleaching agents on adhesion of bonding agents to pulp chamber dentine. Methodology, Forty extracted human maxillary anterior teeth were randomly divided into four groups of 10 teeth each. Bleaching agents were sealed in pulp chambers for 7 days, as in clinical use. Group 1 (control): distilled water, group 2: 35% hydrogen peroxide, group 3: sodium perborate mixed with water, and group 4: sodium perborate mixed with 35% hydrogen peroxide. Teeth were stored in saline at 37 °C for 7 days. After the bleaching agent was removed, teeth were leached in water for a further 7 days prior to bonding. The crown was cut vertically from mesial to distal and the labial pulp chamber dentine was prepared for bonding with Clearfil SE-Bond and filled with resin composite (Clearfil AP-X). The bonded specimens were kept moist at 37 °C for 24 h. Microtensile bond strengths were determined using a universal testing machine. Additional teeth were prepared using the same bleaching procedures to investigate the scanning electron microscopic appearance of the dentine surface. Results, Mean values (±SD) of microtensile bond strength for the experimental groups were: group 1: 5.29 ± 2.21 MPa, group 2: 5.99 ± 1.51 MPa, group 3: 9.17 ± 1.65 MPa and group 4: 3.99 ± 1.31 MPa. Dentine treated with sodium perborate in water (group 3) had significantly higher mean bond strength when compared with the other three groups (P < 0.05, Tukey's test). Mean bond strength was lowest when dentine was treated with sodium perborate plus hydrogen peroxide (group 4). Conclusions, In terms of subsequent bond strength during restoration, sodium perborate mixed with distilled water appears to be the best intracoronal bleaching agent. [source] Effect of Er:YAG laser and EDTAC on the adhesiveness to dentine of different sealers containing calcium hydroxideINTERNATIONAL ENDODONTIC JOURNAL, Issue 7 2003F. Picoli Abstract Aim, To evaluate the effect of 15% EDTAC solution and Er:YAG laser irradiation on the adhesiveness to dentine of root canal sealers containing calcium hydroxide. Methodology, The crowns of 60 maxillary human molars were ground until dentine was exposed. The teeth were divided into three groups of 20 teeth: group I, the dentine surface received no treatment; group II, 15% EDTAC solution was applied to the dentine; group III, the dentine received Er:YAG laser application (11 mm focal distance with perpendicular incidence to dentine surface; 4 Hz frequency; 200 mJ energy; 2.25 W potency; 62 J total energy; 1 min application time). Aluminium cylinders filled with the sealers, Sealer 26, Apexit, Sealapex and CRCS, were then applied to the treated surfaces. Adhesiveness was measured with a universal testing machine, with traction results given in MegaPascals (MPa). These results were submitted to anova tests. Results, Statistical analysis showed significant differences (P < 0.01) amongst adhesiveness values of the sealers and treatments tested. Thus, sealers could be ranked in decreasing adhesiveness values: Sealer 26, CRCS, Apexit, Sealapex. Er:YAG laser irradiation and EDTAC solution application increased adhesiveness values only for Sealer 26 and Apexit. Laser irradiation was superior to EDTAC application only for Sealer 26 adhesiveness values. Conclusions, Er:YAG laser is as efficient as EDTAC solution in increasing adhesiveness of root canal sealers containing calcium hydroxide to human dentine. [source] Celite-mediated linking of polyurethane block copolymers and the impact on the shape memory effectJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Yong-Chan Chung Abstract Celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, was used as a cross-linker of polyurethane (PU) copolymer chains to improve its shape memory and mechanical properties. PU copolymers with different Celite contents were prepared and characterized by IR, DSC, and universal testing machine. The glass transition temperature of PU copolymers was maintained around 20°C independent of Celite content. The shape memory and mechanical properties were dependent on when Celite was added during the polymerization reaction. The reaction in which Celite was added at the middle stage of polymerization showed the best shape memory and mechanical properties. The best shape recovery of PU was found at 0.3 wt % Celite and increased to 97% even after the third cycle. Likewise, the shape retention also maintained a remarkable 86% after three cycles. The reasons underlining the high shape recovery and shape retention by adopting Celite as a cross-linker are discussed in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation and investigation of ethylene,vinyl acetate copolymer/silicone rubber/clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Shoulin Fang Abstract In this article, the combination of silicone rubber (SR) elastomer with synthetic iron montmorillonite (Fe-MMT) to form a kind of new flame-retardant system based on an ethylene,vinyl acetate (EVA) copolymer is first reported. Also, the flame retardancy of the EVA/SR/Fe-MMT hybrid are compared with that of EVA/SR/natural sodium montmorillonite. The structures of the nanocomposites were characterized with X-ray diffraction and transmission electron microscopy. Cone calorimeter tests and thermogravimetric analysis were used to evaluate the flame-retardant properties and thermal stability of the composites, respectively. In addition, tensile tests were carried out with a universal testing machine, and the morphology of the fracture surface was observed with environmental scanning electron microscopy. We found that SR/organophilic montmorillonite (Fe-OMT) was more effective in reducing the primary peak heat release rate of the nanocomposite, and the EVA/SR/Fe-OMT hybrid had a higher thermal stability in the deacetylated polymer than EVA/SR/sodium organophilic montmorillonite. Moreover, the exfoliated EVA/SR/Fe-OMT nanocomposite displayed excellent mechanical properties because of a better dispersion of Fe-OMT in the polymer matrix, and a possible mechanism is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Effects of adhesive systems and luting agents on bonding of fiber posts to root canal dentinJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Francesca Monticelli Abstract The study evaluated the influence of different luting materials on the microtensile bond strength of glass fiber posts to root canal dentin. Thirty extracted maxillary premolars were endodontically treated, and the roots were prepared for post cementation using the FRC Postec system (Vivadent). Two luting materials (Multilink, Vivadent and Clearfil Photo Core, Kuraray) were used in combination with three adhesive: Multilink Primer (Vivadent), Clearfil Photo Bond, and Clearfil New Bond (Kuraray). A composite build-up was performed around the root to provide adequate gripping during testing. Specimens were cut to obtain beams with the post in the center and with the radicular dentin overlaid by the composite build-up on each side. Microtensile testing was performed with a universal testing machine at a cross-head speed of 0.5 mm/min. The failure mode was classified under a stereomicroscope and four representative beams of each group were selected for SEM analysis. Bond strength data that were analyzed with two-way ANOVA and Student-Newman-Keuls multiple comparisons tests revealed that adhesive systems, luting materials, and the interaction between these two factors significantly influenced the bond strength results (p < 0.01). Multilink applied with its own adhesive system obtained the best results, while the lowest bond strength was achieved with clearfil photo core in combination with multilink primer. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] OXYGEN-INHIBITED LAYER IN ADHESION DENTISTRYJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 5 2004Byoung I. Suh MS ABSTRACT Purpose:: Characteristics of the oxygen-inhibited layer, including bond strength, photoinitiator decomposition, and post-curing degree of conversion, were investigated. Materials and Methods: To investigate shear bond strength, BisCover (Bisco, Inc., Schaumburg, IL, USA) and D/E Resin (Bisco, Inc.) were placed on disks of Renew composite (Bisco, Inc.) and cured both with and without an oxygen-inhibited layer. Light-Bond composite (Reliance Orthodontic, Itasca, IL, USA) was placed in a gelatin capsule and light cured over the cured resin. After soaking in water for 2 hours at 37°C, specimens were sheared to failure using a universal testing machine (Model 4466, Instron Inc., Canton, MA, USA). To investigate microtensile bond strength, composite substrates prepared using Renew A2 composite were light cured either in air or under nitrogen. Light-Core (Bisco, Inc.) was placed on each substrate and light cured. The resulting specimens were sectioned into composite beams and stressed to failure using a microtensile tester (built by Bisco, Inc.). To determine camphorquinone (CQ) decomposition, an experimental CQ resin was placed between two glass plates and irradiated for different time intervals. The absorption spectrum was obtained using a Cary 50 Bio UV-Visible Spectrometer (Varian, Mulgrave, Australia). To explore the degree of conversion, polyester film strips (Mylar, DuPont, Wilmington, DE, USA) coated with the CQ resin were pre-cured in air for different time periods, and then post-cured at low intensity for 5 minutes under nitrogen. A Spectrum 1000FTIR Spectrometer (Perkin Elmer, Norwalk, CT, USA) was used to measure the degree of conversion. Results: Bond strength tests resulted in no significant difference between samples with or without an oxygen-inhibited layer. The oxygen-inhibited layer contained reduced amounts of photoinitiator. The degree of conversion of post-cured oxygen-inhibited layers was lower than that for the control. Conclusion: An oxygen-inhibited layer is not necessary for bonding with composite resin. [source] Fracture Resistance of Endodontically Treated Teeth Restored with Three Different Prefabricated Esthetic PostsJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 1 2003PAULO C. A. MACCARI DDS ABSTRACT Purpose: This study was undertaken to evaluate the role of composition of prefabricated esthetic posts in fracture resistance of endodontically treated teeth in vitro. Materials and Methods: Thirty human, single-rooted teeth (maxillary central incisors and canines) with similar root dimensions, extracted for therapeutic reasons, were used in this study. The crowns were removed below the cementoenamel junction to obtain a standard root length of 17 mm. The roots were endodontically treated following the conventional manual technique and randomly assigned to three groups (n = 10) according to the post used: Aestheti-Post, Bisco, Schaumberg, Illinois; FibreKor Post, Jeneric/Pentron, Wallingford, Connecticut; and CosmoPost, Ivoclar Vivadent, Schaan, Liechtenstein. The root canals were rendered patent, and the root preparations were standardized through flaring with the manufacturers' drills included in the respective kits. The posts were cemented with an adhesive system and a resin cement (All-Bond 2 and C & B, Bisco, respectively), according to the manufacturers' directions. Composite resin (Tetric Ceram, Ivoclar Vivadent) crowns were built up using a preformed polyester matrix, and the specimens were mounted in metallic rings with cold-cure acrylic resin and kept in saline solution at 4°C for 24 hours. Fracture resistance was then determined using an EMIC DL-2000 universal testing machine. The crosshead speed was 0.5 mm/min with the 45-degree compressing load at the middle third of the crown. Data were analyzed using one-way analysis of variance and Tukey'stest (p<.001). Results: Mean fracture resistance was as follows: Aestheti-Post, 83.5 kgf; FibreKor Post, 85.7 kgf; and CosmoPost, 36.5 kgf. The fracture strength of CosmoPost was significantly lower than that of the other posts. Teeth restored with CosmoPost had post fractures, and in three specimens, those were associated with root fractures. Teeth restored with the other two posts presented fractures on the composite crowns. CLINICAL SIGNIFICANCE Compared with ceramic posts, carbon-fiber and glass-fiber prefabricated esthetic posts provide endodontically treated teeth higher fracture resistance. [source] Effect of preparation convergence on retention and seating discrepancy of complete veneer crownsJOURNAL OF ORAL REHABILITATION, Issue 10 2004D. C. N. Chan summary, The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0° to 70° and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4·58 ± 1·13 to 73·13 ± 78·32 ,m. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4·03 ± 0·61 to 12·12 ± 0·33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0·62), and retention (r = ,0·91). Complete veneer crown retention and marginal discrepancy were influenced by the preparation convergence design. [source] Fracture strength of copy-milled and conventional In-Ceram crownsJOURNAL OF ORAL REHABILITATION, Issue 7 2001Jung-Won Hwang The purpose of this study was to compare the fracture resistance of copy-milled and conventional In-Ceram crowns. Four groups of 10 uniform sized all-ceramic anterior crowns were fabricated for this test: (1) In-Ceram Spinell (2) In-Ceram Alumina (3) Celay In-Ceram Spinell, and (4) Celay In-Ceram Alumina crowns. All specimens were cemented on stainless steel master die with resin cement and stored in 37 °C water for one day prior to loading into a universal testing machine. Using a steel ball at a crosshead speed of 0·5 mm min,1, the crowns were loaded at 30 °C angle until catastrophic failure occurred. Mean fracture strength was analysed and compared. Under the conditions of this study and the materials used, the following conclusions were drawn: 1. The strength of Celay In-Ceram anterior crowns had a slightly higher fracture strength than conventional In-Ceram crowns. 2. In-Ceram Alumina crowns had a significantly higher fracture strength than In-Ceram Spinell crowns in both conventional and copy milling methods. [source] Degradation of repaired denture base materials in simulated oral fluidJOURNAL OF ORAL REHABILITATION, Issue 3 2000C.-T. Lin This in vitro study evaluates the degradation of repaired denture bases upon immersion in a simulated oral fluid. Denture base materials (Luciton 199®), after being repaired by Repair Material® and Triad®, using three different joint surface designs (butt, round and 45 ° bevel), were immersed onto 99·5 vol.% ethanol/water solution (with similar solubility parameter) for various amounts of time (0,72 h). The flexural loads of the six combination of groups were measured by the three-point bending tests using a universal testing machine. Acoustic emission (AE) during sample fracturing were processed using the MISTRA 2001 system. The fracture pattern and surface details of the interface were examined with a scanning electronic microscope (SEM). Data were analysed using three-way anova and Tukey LSD tests. SEM micrographs of the fracture interface were used to differentiate the fracture mode. The flexural loads (2·72±0·51 Kgf) of the round joint specimens were significantly higher (P<0·05) than those (butt: 1·66±0·38 Kgf, 45 ° bevel: 1·93±0·41 Kgf) of the other two designs. This corresponds to the microscopic examination in which more cohesive failure mode was found for the round joint group after storage. The flexural loads (2·54±0·39 Kgf) of the specimens repaired with Triad® were significantly higher (P<0·05) than those (1·59±0·40 Kgf) of specimens repaired with Repair Material®. Significant progressive reduction of the flexural load and/or AE signals of the specimens was noted in proportion to the length of time of the immersion in the simulated oral fluid. Mechanical strength of a denture base repaired with a round joint design and light-cured material is significantly higher after immersion in simulated oral fluid. [source] Evaluation of the Bond Strength of Denture Base Resins to Acrylic Resin Teeth: Effect of ThermocyclingJOURNAL OF PROSTHODONTICS, Issue 5 2009Juliê Marra DDS Abstract Purpose: The purpose of this study was to evaluate the thermocycling effects and shear bond strength of acrylic resin teeth to denture base resins. Materials and Methods: Three acrylic teeth (Biotone, Trilux, Ivoclar) were chosen for bonding to four denture base resins: microwave-polymerized (Acron MC), heat-polymerized (Lucitone 550 and QC-20), and light-polymerized (Versyo.bond). Twenty specimens were produced for each denture base/acrylic tooth combination and were divided into two groups (n = 10): without thermocycling (control groups) and thermocycled groups submitted to 5000 cycles between 4 and 60°C. Shear strength tests (MPa) were performed with a universal testing machine at a crosshead speed of 1 mm/min. Statistical analysis of the results was carried out with three-way ANOVA and Bonferroni's multiple comparisons post hoc analysis for test groups (,= 0.05). Results: The shear bond strengths of Lucitone/Biotone, Lucitone/Trilux, and Versyo/Ivoclar specimens were significantly decreased by thermocycling, compared with the corresponding control groups (p < 0.05). The means of Acron/Ivoclar and Lucitone/Ivoclar specimens increased after thermocycling (p < 0.05). The highest mean shear bond strength value was observed with Lucitone/Biotone in the control group (14.54 MPa) and the lowest with QC-20/Trilux in the thermocycled group (3.69 MPa). Conclusion: Some acrylic tooth/denture base resin combinations can be more affected by thermocycling; effects vary based upon the materials used. [source] Mechanical Properties of Magnetic Attachments for Removable Prostheses on Teeth and ImplantsJOURNAL OF PROSTHODONTICS, Issue 8 2008Arne F. Boeckler DMD Abstract Purpose: Magnetic attachments on teeth and implants may be used to improve stability, support, and retention of removable prostheses. Various forms of magnetic attachments are available, divided according to the design, the mechanical properties of the attachments, and the clinical indication. Recently developed attachment systems are small and promise improved retentive capacity, while existing magnetic attachments continue to be technologically modified and improved. This investigation reviewed and compared maximum retentive forces and characteristic curves for magnetic attachments indicated for use as root anchors and on implants. Materials and Methods: Twenty-four samarium-cobalt (SmCo) and neodym-iron-boron (NeFeB) magnetic attachments (12 tooth- and 12 implant-borne) were evaluated. Specimens were delivered by the manufacturers or fabricated according to their instructions. Five magnet pairs of each product and each combination were tested 10 times in a calibrated universal testing machine using a nonmagnetic test device (s = 40 mm, v = 20 mm/min). Results were recorded electronically and compared to manufacturers' details. Results: Maximum retentive forces for root keepers ranged from 1.4 to 6.6 N. Maximum retentive forces for magnetic attachments on implants ranged from 0.7 to 5.8 N. After a distance of 0.1 mm, a complete reversed distribution of the different systems became obvious. The retentive force provided by the manufacturer was achieved in one implant abutment, with retentive force (as compared to those provided by the manufacturers) for root keepers ranging between 42.5% and 92.9% and for implant abutments between 43.0% and 99.4%. Conclusion: There were differences between magnetic attachments for both the initial retentive capabilities and the characteristic curves. Recently introduced products provided relatively high initial retentive forces despite their small size. The measured retentive forces and the manufacturer's information differed in the majority of magnetic systems evaluated. [source] Effect of Aluminum Oxide Addition on the Flexural Strength and Thermal Diffusivity of Heat-Polymerized Acrylic ResinJOURNAL OF PROSTHODONTICS, Issue 6 2008Ayman E. Ellakwa BDS Abstract Purpose: This work was undertaken to investigate the effect of adding from 5% to 20% by weight aluminum oxide powder on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin. Materials and Methods: Seventy-five specimens of heat-polymerized acrylic resin were fabricated. The specimens were divided into five groups (n = 15) coded A to E. Group A was the control group (i.e., unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with aluminum oxide (Al2O3) powder to achieve loadings of 5%, 10%, 15%, and 20% by weight. Specimens were stored in distilled water at 37°C for 1 week before flexural strength testing to failure (5 mm/min crosshead speed) in a universal testing machine. Results were analyzed by one-way analysis of variance and post hoc Tukey paired group comparison tests (p < 0.05). Weibull analysis was used to calculate the Weibull modulus, characteristic strength, and the required stress for 1% and 5% probabilities of failure. Cylindrical test specimens (5 specimens/group) containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70°C). Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 99.45, 119.92, 121.19, 130.08, and 127.60 for groups A, B, C, D, and E, respectively. The flexural strength increased significantly after incorporation of 10% Al2O3. The mean thermal diffusivity values of the heat-polymerized acrylic resin (in m2/sec) were 6.8, 7.2, 8.0, 8.5, and 9.3 for groups A, B, C, D, and E, respectively. Thermal diffusivities of the composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler, which suggested that the proper distribution of alumina powders through the insulating polymer matrix might form a pathway for heat conduction. Conclusion: Al2O3 fillers have potential as added components in denture bases to provide increased flexural strength and thermal diffusivity. Increasing the flexural strength and heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction. [source] Flexural Strength, Elastic Modulus, and pH Profile of Self-etch Resin Luting CementsJOURNAL OF PROSTHODONTICS, Issue 4 2008Egle Saskalauskaite DDS Abstract Purpose: To determine the flexural strength, modulus of elasticity, and 24-hour pH profile of three self-etching resin luting cements and to obtain comparative data for representative conventional resin and resin-modified glass ionomer luting cements. Materials and Methods: Three self-etching resin luting cements [RelyX Unicem (3M ESPE), Maxcem (Kerr), Embrace Wetbond (Pulpdent)] were tested and compared with two conventional resin cements [RelyX ARC (3M ESPE), Linkmax (GC)] plus two resin-modified glass ionomer luting cements [Fuji Plus (GC), RelyX Luting Plus (3M ESPE)]. Flexural strength and modulus of elasticity were determined using bar-shaped specimens (2 × 2 × 25 mm3) at 24 hours, using an Instron universal testing machine. Setting pH was measured using a flat-surface pH electrode at 0, 2, 5, 15, and 30 minutes and 1, 2, 4, 6, and 24 hours after mixing. Testing was performed under both dual-cured and self-cured conditions for all dual-cure cements. Data analysis included ANOVA and Tukey's test (p < 0.05). Results: The self-etching cements showed similar flexural strength to the conventional resin cements, except for Embrace Wetbond self-cured, which was considerably lower. Modulus of elasticity results were both higher and lower than for conventional resin cements. All photopolymerized conventional and self-etch dual-cure cements showed markedly higher flexural strength and modulus than when solely self-cured. The resin-modified glass ionomer cements were characterized by lower flexural strength and elastic modulus. Self-etching resin cements showed lower initial pH (2.0 to 2.4) than conventional resin cements (4.8 to 5.2) and a wide range of final pH values (3.9 to 7.3) at 24 hours. One self-etching cement (Unicem) revealed a unique pH profile characterized by a more rapid rise in pH to neutrality both when dual-cured (15 minutes) and when auto-cured (1 hour). Conclusions: The self-etching resin cements evaluated in this study displayed disparate properties and cannot be considered a homogeneous group. Flexural strength properties were most uniform and were similar to those of the conventional resin cements, whereas moduli of elasticity showed greater variation. Setting pH profiles differed, depending on the brand and mode of cure, even within the same category of luting cement. All cements with dual-cure capability, both conventional and self-etch, showed significantly superior properties when photopolymerized. [source] | ||||||||||||||||