| 1. |
- Fernandes, CP, et al.
(författare)
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Reflection photoelasticity: a new method for studies of clinical mechanics in prosthetic dentistry
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:2, s. 106-117
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. This research was conducted to demonstrate the effectiveness of reflective photoelasticity as an in vivo technique for monitoring the strain/stress distribution in prosthetic devices during function. Methods. Seven subjects were selected for this study and divided into three groups according to the design of the prostheses. The buccal surfaces of the experimental prostheses were coated with a birefringent resin 2 mm thick. Using a reflection polariscope, fringe patterns were documented on video tape during standardized in vivo loadings. Strain and stress levels (gamma(max) and tau(max)) were calculated from isochromatic fringe order determinations. The intra-observer variability in counting fringe orders and the accuracy level of reflective photoelasticity as compared to strain gauge results were also studied. The strain results of in vivo loading of the prostheses were analyzed with ANOVA and Scheffes tests. The intra-observer variability was analyzed with the Friedman nonparametric test. Comparisons of photoelastic data and strain gauges were tested with Pearson's correlation. Results. Coated areas accessible to normally incident light, produced comprehensive maps of strain distribution. Significant differences were found in the in vivo gamma(max) values for the prostheses designs (p < 0.05). The test for intra-observer variability showed that no significant differences occurred in counting fringe orders. Strain values obtained with reflective photoelasticity showed a high correlation r = 0.98 and 0.99) with values obtained at the same areas using strain gauges. Significance. Reflective photoelasticity is a valid, reliable and accurate technique to be used for in vivo studies on the biomechanical behavior of prosthetic devices. (C) 2003 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.
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| 2. |
- Fernandes, Cláudio Pinheiro, et al.
(författare)
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A Novel Sensor for Bite Force Determinations
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:2, s. 118-126
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- OBJECTIVES: The clinical usefulness, accuracy and precision of a novel bite force sensor based on force sensing resistors were tested in six subjects wearing maxillary removable partial dentures retained by conical crowns. METHODS: The surfaces of the sensor were manufactured in a silicone material that had mechanical properties similar to those of tough foodstuffs. In two separate series of standardized bite force tests, submaximum force levels were recorded with the sensor and with a strain gaged bite fork. Subjects were assisted in the loading tests with visual feedback instrumentation. Reliability estimates for the bite force sensor were calculated in order to show their reproducibility. Strain gages attached to the prostheses were used to determine the pattern of force distribution during loading tests. The bite force results obtained with the new bite force sensor and with the bite fork were analyzed with ANOVA and Scheffes tests. The strain patterns registered with strain gages were analyzed with F-test. RE-SULTS: The bite force sensor and the bite fork transducer showed no statistically significant differences in respect of intra-individual bite force levels (range 50-300N). The bite forces registered with the new sensor were dependent on the loading position (p<0.05), sex (p<0.05) and test subject (p<0.05). The reliability of the new sensor for sub-maximum bite forces was calculated to be 93%. Strain gage results showed that the new sensor generated strain patterns of less variance (p<0.05) than the bite fork and therefore allowed for higher precision during biting tests. SIGNIFICANCE: The presented instrument has such clinical merits, as to favor its use in experimental clinical studies on the biomechanics of prosthetic appliances.
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| 3. |
- Fernandes, Cláudio Pinheiro, et al.
(författare)
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On the Accuracy of Some In Vitro Models for Mechanical Studies of Maxillary Removable Partial Dentures
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:2, s. 127-136
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- OBJECTIVES: Comparative in vitro/in vivo studies show wide differences in functional strain magnitudes and patterns of functional strain distribution in prosthetic devices. The aim of this study was to evaluate the accuracy of three in vitro models for biomechanical studies of prosthetic devices. METHODS: Strain gages were attached to the test RPDs of six subjects. In vitro maxillary models with simple (model A), intermediate (model B) and advanced (model C) features for the anatomical simulation of supporting structures were manufactured for each subject. The dentures were subjected to two separate series of standardized functional and laboratorial loading tests. The principal maximum strain value (epsilon (1)) obtained for each gage and experiment was used to calculate the intra-experiment variance and inter-experiment variance for the in vivo and in vitro experiments. The integrated strain gage difference value between the in vitro and in vivo data (Sigma(diff)) was calculated for every loading test and compared to the in vivo inter-experiment variance with ANOVA and Scheffes test. RESULTS: The bite forces recorded were similar for each subject and loading position and between the two loading sessions. The inter- and intra-experiment variance was found to be higher for in vivo loadings than for in vitro. Results showed that the (Sigma(diff)) values for model B and model C were significantly different from the in vivo strain interexperiment variance (p<0.05). SIGNIFICANCE: This study showed that the anatomical simulation of in vitro models is insufficient to allow for accurate mechanical analyses of maxillary RPDs and that only simple verifications of the strain levels in prosthetic appliances can be attained in vitro.
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| 4. |
- Persson-Sjögren, Solveig, et al.
(författare)
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Effects of dental materials on insulin release from isolated islets of Langerhans
- 2002
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 18:1, s. 20-25
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To investigate the possibility of using a whole organ model for evaluating the biological effects of dental restoration materials in vitro. Methods: The effect on insulin release of isolated Langerhans islets of a series of dental materials was examined. The islets were incubated for 1 h with extracts obtained from various dental materials and insulin was assayed radioimmunologically with crystalline mouse insulin. The results were analysed statistically using analysis of variance (ANOVA) and Scheffe's test at a significance level of p<0.05. Results: One dental ceramic, Vita VMK 95, significantly ( p<0.01) decreased the insulin release, whereas another dental ceramic, Empress ( p<0.01), a partly re-cast high-noble gold alloy ( p<0.001), a modified high-noble gold alloy ( p<0,05), and unalloyed copper ( p<0.001) significantly increased the release of insulin. Significance: The results demonstrate a new instance of examining the biological effects of dental restoration materials. The method provides information about the effect of different materials on organ level in vitro that can complement other in vitro tests.
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| 5. |
- van Dijken, Jan
(författare)
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A 6-year clinical evaluation of Class I poly-acid modified resin composite/resin composite laminate restorations cured with a two-step curing technique.
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:5, s. 423-428
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Polymerization shrinkage is still one of the main disadvantages of resin composite restorations (RC). Especially in cavities with a high C-factor, debonding can occur. A laminate restoration including a base with a more elastic behavior might result in a better adaptation. The purpose of this study was to evaluate the durability of a combination of two techniques suggested to counter the stress formation in direct RC restorations in cavities with the highest C-factor. METHODS: Each of the 29 patients received one or two pair(s) of Class I restorations. The first restoration was a poly-acid modified resin composite/resin composite (PMRC/RC) sandwich restoration and the second a direct RC restoration. Both restorations, except for the PMRC layer, were placed with oblique layering and two-step curing technique. Ninety restorations, 23 premolar and 67 molars, were evaluated annually with slightly modified USPHS criteria during 6 years. RESULTS: At 6 years, 41 pairs were evaluated. A cumulative failure rate of 2.4% was observed for both the RC and the laminate restorations. One laminate restoration showed non-acceptable color match, but was not replaced and one RC restoration showed non-acceptable marginal adaptation. Two cases of slight postoperative sensitivity were observed in one patient. Three restorations were partially replaced due to primary proximal caries. SIGNIFICANCE: A high durability for and no differences, were observed between both restorative techniques in Class I cavities.
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| 6. |
- van Dijken, Jan
(författare)
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Resin-modified glass ionomer cement and self-cured resin composite luted ceramic inlays. A 5-year clinical evaluation.
- 2003
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 19:7, s. 670-674
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: This study evaluated IPS Empress ceramic inlays luted with two chemical-cured luting agents, a resin-modified glass ionomer cement (Fuji Plus (F)) and a resin composite (RC) (Panavia 21 (P)). METHODS: Seventy-nine ceramic inlays were placed in Class II cavities in 29 patients. At least two inlays were placed in each patient to compare the luting techniques intra-individually. In each patient half of the inlays were luted with F and the other half with P. The inlays were evaluated clinically, according to modified USPHS criteria (van Dijken, 1986), at baseline, after 6 months, and yearly during 5 years. RESULTS: At 5 years, 71 inlays were evaluated. Two small partial fractures were observed at 3 years (1P, 1F). One inlay showed recurrent root caries at 4 years (P). Four inlays, two in each group showed non-acceptable color match (2P, 2F). Small defects were observed in 4 inlays (2P, 2F). A slight ditching of the cement margins was observed in both luting groups but did not seem to increase during the second half of the evaluation. No significant difference in durability was observed between the two luting agents. SIGNIFICANCE: IPS Empress inlays luted with the chemical-cured RC and the resin-modified glass ionomer cement functioned satisfactory during the 5 years follow-up.
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| 7. |
- Kou, Wen, 1979-, et al.
(författare)
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Numerical modeling of the fracture process in a three-unit all-ceramic fixed partial denture
- 2007
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 23:8, s. 1042-1049
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The main objectives were to examine the fracture mechanism and process of a ceramic fixed partial denture (FPD) framework under simulated mechanical loading using a recently developed numerical modeling code, the R-T(2D) code, and also to evaluate the suitability of R-T(2D) code as a tool for this purpose. METHODS: Using the recently developed R-T(2D) code the fracture mechanism and process of a 3U yttria-tetragonal zirconia polycrystal ceramic (Y-TZP) FPD framework was simulated under static loading. In addition, the fracture pattern obtained using the numerical simulation was compared with the fracture pattern obtained in a previous laboratory test. RESULTS: The result revealed that the framework fracture pattern obtained using the numerical simulation agreed with that observed in a previous laboratory test. Quasi-photoelastic stress fringe pattern and acoustic emission showed that the fracture mechanism was tensile failure and that the crack started at the lower boundary of the framework. The fracture process could be followed both in step-by-step and step-in-step. SIGNIFICANCE: Based on the findings in the current study, the R-T(2D) code seems suitable for use as a complement to other tests and clinical observations in studying stress distribution, fracture mechanism and fracture processes in ceramic FPD frameworks.
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| 8. |
- Sundh, Anders, 1958-, et al.
(författare)
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Fracture resistance of yttrium oxide partially-stabilized zirconia all-ceramic bridges after veneering and mechanical fatigue testing
- 2005
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:5, s. 476-482
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Yttria-stabilized zirconia (Y-TZP) ceramic is a high-performance material with excellent mechanical properties suitable for fixed partial dentures. The purpose of this study was to evaluate after fatigue testing, the effect of heat-treatment and veneering on the fracture resistance of frameworks manufactured using sintered and subsequently hot isostatic pressed yttrium oxide partially-stabilized zirconia (Denzir). METHODS: The specimens were subjected to dynamic loading in water. Thereafter, using a universal testing machine, the fracture resistance of three-unit fixed partial dentures was determined; (i) of the frameworks as delivered after machining, (ii) after the frameworks had been subjected to heat-treatment similar to veneering with a glass-ceramic (Eris) or a feldspar-based ceramic (Vita D) and (iii) after the frameworks had been veneered with these ceramics. In addition, the fracture resistance of frameworks as delivered after machining not subjected to dynamic loading in water was determined. RESULTS: Cyclic loading in water did not significantly (p>0.05) affect the fracture resistance. The load necessary to fracture the frameworks as delivered after machining was significantly (p<0.001) higher than for the heat-treated and veneered specimens. No significant difference was seen between the specimens veneered with Eris and those veneered with Vita D (p>0.05). For all but three specimens the fractures were located in the loading point and through one of the connectors. SIGNIFICANCE: Heat-treatment and veneering reduce fracture resistance of hot isostatic pressed zirconia. Nevertheless, the results obtained indicate that it is an interesting material for potential in all-ceramic restorations.
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| 9. |
- Altmann, Brigitte, et al.
(författare)
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Cellular transcriptional response to zirconia-based implant materials
- 2017
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 33:2, s. 241-255
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Tidskriftsartikel (refereegranskat)abstract
- Objective To adequately address clinically important issues such as osseointegration and soft tissue integration, we screened for the direct biological cell response by culturing human osteoblasts and gingival fibroblasts on novel zirconia-based dental implant biomaterials and subjecting them to transcriptional analysis. Methods Biomaterials used for osteoblasts involved micro-roughened surfaces made of a new type of ceria-stabilized zirconia composite with two different topographies, zirconium dioxide, and yttria-stabilized zirconia (control). For fibroblasts smooth ceria- and yttria-stabilized zirconia surface were used. The expression of 90 issue-relevant genes was determined on mRNA transcription level by real-time PCR Array technology after growth periods of 1 and 7 days. Results Generally, modulation of gene transcription exhibited a dual dependence, first by time and second by the biomaterial, whereas biomaterial-triggered changes were predominantly caused by the biomaterials’ chemistry rather than surface topography. Per se, modulated genes assigned to regenerative tissue processes such as fracture healing and wound healing and in detail included colony stimulating factors (CSF2 and CSF3), growth factors, which regulate bone matrix properties (e.g. BMP3 and TGFB1), osteogenic BMPs (BMP2/4/6/7) and transcription factors (RUNX2 and SP7), matrix collagens and osteocalcin, laminins as well as integrin ß1 and MMP-2. Significance With respect to the biomaterials under study, the screening showed that a new zirconia-based composite stabilized with ceria may be promising to provide clinically desired periodontal tissue integration. Moreover, by detecting biomarkers modulated in a time- and/or biomaterial-dependent manner, we identified candidate genes for the targeted analysis of cell-implant bioresponse during biomaterial research and development.
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| 10. |
- Ballo, Ahmed Mansour, et al.
(författare)
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Osseointegration of fiber-reinforced composite implants : Histological and ultrastructural observations
- 2014
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 30:12, s. e384-e395
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. The aim of this study was to evaluate the bone tissue response to fiber-reinforced composite (FRC) in comparison with titanium (Ti) implants after 12 weeks of implantation in cancellous bone using histomorphometric and ultrastructural analysis. Materials and methods. Thirty grit-blasted cylindrical FRC implants with BisGMA-TEGDMA polymer matrix were fabricated and divided into three groups: (1) 60 s light-cured FRC (FRC-L group), (2) 24 h polymerized FRC (FRC group), and (3) bioactive glass FRC (FRC-BAG group). Titanium implants were used as a control group. The surface analyses were performed with scanning electron microscopy and 3D SEM. The bone-implant contact (BIC) and bone area (BA) were determined using histomorphometry and SEM. Transmission electron microscopy (TEM) was performed on Focused Ion Beam prepared samples of the intact bone-implant interface. Results. The FRC, FRC-BAG and Ti implants were integrated into host bone. In contrast, FRC-L implants had a consistent fibrous capsule around the circumference of the entire implant separating the implant from direct bone contact. The highest values of BIC were obtained with FRC-BAG (58 ± 11%) and Ti implants (54 ± 13%), followed by FRC implants (48 ± 10%), but no significant differences in BIC or BA were observed (p = 0.07, p = 0.06, respectively). TEM images showed a direct contact between nanocrystalline hydroxyapatite of bone andboth FRC and FRC-BAG surfaces. Conclusion. Fiber-reinforced composite implants are capable of establishing a close bone contact comparable with the osseointegration of titanium implants having similar surface roughness.
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| 11. |
- Berglund, Anders, et al.
(författare)
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Dimensional change of a calcium aluminate cement for posterior restorations in aqueous and dry media.
- 2006
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 22:5, s. 470-476
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: A calcium aluminate cement has recently been developed, with claims of being an alternative to dental amalgam and resin composites in posterior cavities. However, its' mechanical properties are not well evaluated and the aim of the study was therefore, to evaluate its' dimensional stability over time. METHODS: The dimensional changes of the cement, Doxadent, and two composite resins, Esthet-X and InTen-S, were tested during 360 d. The specimens were stored at 37+/-1 degrees C either in 100% air humidity (dry) or immersed in distilled water (wet), except for the first 24h when all specimens were stored at 100% air humidity and 37+/-1 degrees C. RESULTS: During the first 24h, Doxadent decreased in volume with 0.04%, while InTen-S and Esthet-X decreased with 1.60 and 1.75%, respectively. From d 1-360, the dry Doxadent specimens increased in volume with 2.0% and in weight with 5.5%, while the corresponding increase for the wet specimens were 4.1 and 6.3%, respectively. The volume of both composites increased 0.8% or less in dry and wet conditions, while the increase in weight for InTen-S was 1.2% for the wet specimens and 0.6% for the dry. The corresponding figures for Esthet-X were 0.7 and 0.2%. SIGNIFICANCE: Doxadent was less dimensionally stable than the composites tested. Doxadent increased 2 times more in volume immersed in water than in 100% air humidity, while the increase in weight was almost similar. The clinical implications of the results found in the present study are uncertain. A material that continues to absorb water during prolonged periods and continues to react is questionable for clinical use.
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| 12. |
- Berglund, A, et al.
(författare)
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Mercury levels in plasma and urine after removal of all amalgam restorations : the effect of using rubber dams.
- 1997
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Ingår i: Dental Materials. - 0109-5641 .- 1879-0097. ; 13:5, s. 297-304
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of the present study was to determine whether removal of all amalgam restorations might significantly affect mercury levels in plasma and urine and whether the use of rubber dams might reduce patient exposure to mercury during amalgam removal. METHODS: All amalgam restorations were removed from 18 subjects during a single treatment session in which a rubber dam was used and from 10 subjects when a rubber dam was not used. All amalgam restorations were removed by the same dentist using high-speed cutting, water coolant, and high-volume evacuation. The levels of mercury in plasma and urine were analyzed both before and during the subsequent twelve months after amalgam removal. In order to determine whether removal of all amalgam restorations might cause an exposure large enough to significantly increase the mercury levels in two indicator media for mercury exposure, i.e., plasma and urine, and to determine if the removal might cause a significant decrease in the mercury levels found over time, the one-tailed, paired Students' t-test was used. For each individual, the pre-removal levels were compared with both the levels found in plasma on d 1 and in urine on d 10, and also with the levels found 1 y after removal. Furthermore, in order to examine whether the use of rubber dams had any effect on the mercury levels found after removal, the changes in the mercury levels found were compared between the groups using the Wilcoxon-Mann-Whitney rank sum test. RESULTS: After removal of all amalgam restorations, only the non-rubber dam group showed significant increases in the mercury levels found in plasma (p = 0.012) and urine (p = 0.037). However, one year later, the mercury levels in plasma and urine had sunk significantly below the pre-removal levels for both groups. When the changes in the mercury levels found were compared between the groups, the non-rubber dam group showed a significantly higher increase of mercury in plasma than the rubber dam group the day after removal (p = 0.0010). Compared to the pre-removal mercury levels in plasma and urine, the levels found 1 y after removal of all amalgam restorations were on average 52 +/- 23% (range 4-89%) lower in plasma and 76 +/- 21% (range 20-94%) lower in urine. SIGNIFICANCE: The study showed that dental amalgam had a statistically significant impact on the mercury levels found in plasma and urine in the patients tested, and that the use of a rubber dam during removal of all amalgam restorations significantly reduced the peak of mercury in plasma following removal.
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| 13. |
- Braian, Michael, et al.
(författare)
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Geometrical accuracy of metallic objects produced with additive or subtractive manufacturing : A comparative in vitro study
- 2018
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Ingår i: Dental Materials. - : Elsevier. - 0109-5641 .- 1879-0097. ; 34:7, s. 978-993
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To evaluate the accuracy and precision of objects produced by additive manufacturing systems (AM) for use in dentistry and to compare with subtractive manufacturing systems (SM). Methods. Ten specimens of two geometrical objects were produced by five different AM machines and one SM machine. Object A mimics an inlay-shaped object, while object B imitates a four-unit bridge model. All the objects were sorted into different measurement dimensions (x, y, z), linear distances, angles and corner radius. Results. None of the additive manufacturing or subtractive manufacturing groups presented a perfect match to the CAD file with regard to all parameters included in the present study. Considering linear measurements, the precision for subtractive manufacturing group was consistent in all axes for object A, presenting results of <0.050 mm. The additive manufacturing groups had consistent precision in the x-axis and y-axis but not in the z-axis. With regard to corner radius measurements, the SM group had the best overall accuracy and precision for both objects A and B when compared to the AM groups. Significance. Within the limitations of this in vitro study, the conclusion can be made that subtractive manufacturing presented overall precision on all measurements below 0.050 mm. The AM machines also presented fairly good precision, <0.150 mm, on all axes except for the z-axis. Knowledge regarding accuracy and precision for different production techniques utilized in dentistry is of great clinical importance. The dental community has moved from casting to milling and additive techniques are now being implemented. Thus all these production techniques need to be tested, compared and validated. (C) 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.
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| 14. |
- Braian, Michael, et al.
(författare)
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Production tolerance of additive manufactured polymeric objects for clinical applications
- 2016
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Ingår i: Dental Materials. - : Elsevier. - 0109-5641 .- 1879-0097. ; 32:7, s. 853-861
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. To determine the production tolerance of four commercially available additive manufacturing systems. Methods. By reverse engineering annex A and B from the ISO_12836;2012, two geometrical figures relevant to dentistry was obtained. Object A specifies the measurement of an inlay shaped object and B a multi-unit specimen to simulate a four-unit bridge model. The objects were divided into x, y and z measurements, object A was divided into a total of 16 parameters and object B was tested for 12 parameters. The objects were designed digitally and manufactured by professionals in four different additive manufacturing systems; each system produced 10 samples of each objects Results. For object A, three manufacturers presented an accuracy of <100 mu m and one system showed an accuracy of <20 mu m For object B, all systems presented an accuracy of <100 mu m, and most parameters were <40 mu m. The standard deviation for most parameters were <40 mu m Significance. The growing interest and use of intra-oral digitizing systems stresses the use of computer aided manufacturing of working models. The additive manufacturing techniques has the potential to help us in the digital workflow. Thus, it is important to have knowledge about production accuracy and tolerances. This study presents a method to test additive manufacturing units for accuracy and repeatability. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved
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| 15. |
- Bryington, M. S., et al.
(författare)
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The influence of nano hydroxyapatite coating on osseointegration after extended healing periods
- 2013
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 29:5, s. 514-520
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Studies observing early wound healing periods around dental implants demon-strate an implants ability to enhance osseointegration, the bone-implant interactions for extended healing periods though have not been thoroughly studied. Methods. Twenty threaded titanium alloy (Ti6Al4V, Grade 5) implants were inserted bilaterally, half prepared to impart stable hydroxyapatite nanoparticles onto a sand blasted and acid etched surface (HA) and half with a non-coated control surface with only heat treatment (HT), into eighteen rabbit femurs. At 12 weeks, the bone-implant blocks were retrieved for micro computed tomography (mu CT), histologic processing and histomorphometric evaluation. Results. The bone-to-implant contact for the entire threaded portion of the implant revealed 57.1% (21.0) for the HT group and 38.8% (17.7) for the HA group with a total bone area within the threads 72.5% (13.9) (HT) and 59.7% (12.5) (HA). The 3D reconstructed mu CT image corresponded to the histomorphometric results. Significance. It is suggested that multiple factors such as the change in topography and chemistry may have influenced the outcomes.
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| 16. |
- Cecchinato, Francesca, et al.
(författare)
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Modulation of the nanometer pore size improves magnesium adsorption into mesoporous titania coatings and promotes bone morphogenic protein 4 expression in adhering osteoblasts
- 2016
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Ingår i: Dental Materials. - : Elsevier. - 0109-5641 .- 1879-0097. ; 32:7, s. E148-E158
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Mesoporous (MP) titania films used as implant coatings have recently been considered as release systems for controlled administration of magnesium to enhance initial osteoblast proliferation in vitro. Tuning of the pore size in such titania films is aimed at increasing the osteogenic potential through effects on the total loading capacity and the release profile of magnesium. Methods. In this study, evaporation-induced self-assembly (EISA) was used with different structure-directing agents to form three mesoporous films with average pore sizes of 2 nm (MP1), 6 nm (MP2) and 7 nm (MP3). Mg adsorption and release was monitored using quartz crystal microbalance with dissipation (QCM-D). The film surfaces were characterized with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The effect of different Mg release on osteogenesis was investigated in human fetal osteoblasts (hFOB) using pre-designed osteogenesis arrays and real-time polymerase chain reaction (RT-PCR Results. Results showed a sustained release from all the films investigated, with higher magnesium adsorption into MP1 and MP3 films. No significant differences were observed in the surface nanotopography of the films, either with or without the presence of magnesium. MP3 films (7 nm pore size) had the greatest effect on osteogenesis, up-regulating 15 bone-related genes after 1 week of hFOB growth and significantly promoting bone morphogenic protein (BMP4) expression after 3 weeks of growth Significance. The findings indicate that the increase in pore width on the nano scale significantly enhanced the bioactivity of the mesoporous coating, thus accelerating osteogenesis without creating differences in surface roughness. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved
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| 17. |
- Coelho, Paulo G., et al.
(författare)
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Osseointegration : hierarchical designing encompassing the macrometer, micrometer, and nanometer length scales
- 2015
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Ingår i: Dental Materials. - : Elsevier. - 0109-5641 .- 1879-0097. ; 31:1, s. 37-52
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Osseointegration has been a proven concept in implant dentistry and orthopedics for decades. Substantial efforts for engineering implants for reduced treatment time frames have focused on micrometer and most recently on nanometer length scale alterations with negligible attention devoted to the effect of both macrometer design alterations and surgical instrumentation on osseointegration. This manuscript revisits osseointegration addressing the individual and combined role of alterations on the macrometer, micrometer, and nanometer length scales on the basis of cell culture, preclinical in vivo studies, and clinical evidence. Methods. A critical appraisal of the literature was performed regarding the impact of dental implant designing on osseointegration. Results from studies with different methodological approaches and the commonly observed inconsistencies are discussed. Results. It is a consensus that implant surface topographical and chemical alterations can hasten osseointegration. However, the tailored combination between multiple length scale design parameters that provides maximal host response is yet to be determined. Signcance. In spite of the overabundant literature on osseointegration, a proportional inconsistency in findings hitherto encountered warrants a call for appropriate multivariable study designing to ensure that adequate data collection will enable osseointegration maximization and/or optimization, which will possibly lead to the engineering of endosteal implant designs that can be immediately placed/loaded regardless of patient dependent conditions.
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| 18. |
- Coutinho, E., et al.
(författare)
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Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams
- 2009
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 25:11, s. 1325-1337
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Tidskriftsartikel (refereegranskat)abstract
- Current available techniques for transmission electron microscopy (TEM) of tooth biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. Objectives. The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth-biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chem. l Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clear. l SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. Methods. After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. Results. The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct "fog" or "melted look", which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct "keyhole" shape of enamel rods sectioned at 90 degrees, delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. Significance. The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial-hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.
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| 19. |
- Derand, Tore, et al.
(författare)
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Bond strength of composite luting cement to zirconia ceramic surfaces.
- 2005
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:12, s. 1158-62
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To evaluate the bond strength of dental resin agent to zirconia ceramic after surface pre-treatment with different techniques. METHODS: Specimens of hot isostatic pressed yttrium-oxide-partially-stabilized zirconia blocks (ZF) were fabricated (Procera Zircon, Nobel Biocare, Sweden) and compared to glossy dense zirconia blocks (ZG). Four groups of specimens with different surface treatment were prepared. Group I: ZF (n = 5) and ZG (n = 5) without any pre-treatment, Group II: ZF-s (n = 5) and ZG-s (n = 5) treated with silane solution, Group III: ZF-P (n = 10) and ZG-P (n = 10) treated with RF plasma spraying (hexamethyldisiloxane) using a reactor (Plasma Electronic, Germany), Group IV: ZF-p (n = 10) and ZG-p (n = 10) treated with micro pearls of low fusing porcelain (720 degrees C) on the surfaces. Composite cylinders (Charisma, Hereus Kulzer, Dormagen, Germany) were luted with Variolink II (Ivoclar-Vivadent, Schaan, Liechtenstein) to the test specimens. The specimens were then stored in air for 1 h before shear loading in a universal testing machine (LRX, Lloyd Instruments, Farnham, England) until failure. RESULTS: No statistical difference was found between the untreated ZF and ZG specimens (Group I) neither between the specimens treated with silane (Group II). Plasma spraying treatment improved bond strength by a factor of three (p < 0.001). Treatment with low fusing porcelain micro pearls increased the bond strength by a factor of 10 compared to untreated surfaces (p < 0.001). No significant difference was seen between the surfaces treated ZF-p and ZG-p specimens. The thickness of the glass pearls layer did not exceed 5 microm. SEM showed dense grain borders of ZF and a flat glossy texture of ZG. SIGNIFICANCE: Treatment of zirconia ceramic surfaces with plasma spraying or a low fusing porcelain pearl layer significantly increased the bond strength of resin cement to the ceramic surface.
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| 20. |
- Emami, Nazanin, et al.
(författare)
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Dynamic mechanical thermal analysis of two light-cured dental composites
- 2005
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:10, s. 977-983
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Tidskriftsartikel (refereegranskat)abstract
- ObjectivesClinical observations suggest that some composite resins are more often linked to post-operative sensitivity than others. These differences may relate to differences in modulus of elasticity and polymerization rates among materials. The aim of this study was to identify viscoelastic behavior of two light curable composites and determine whether significant differences in viscoelastic behavior exist between the two materials when light cured at each of three different irradiance values.MethodsTwo composites (Z100 and Z250 by 3M ESPE) were evaluated. Six specimens per composite and irradiance value (250, 500 and 850 mW/cm2) were made. The curing times were chosen to produce a fixed energy value of 30 J/cm2 independent of irradiation value. Dynamic mechanical thermal analysis (DMTA) was performed in single cantilever clamped mode.ResultsThere were significant differences in transition temperatures between the two materials and the three frequencies at their glass transition temperatures, while significant differences did not exist at the lower transitions. The glass transition of Z250 was lower and narrower than that of Z100. Z250 exhibited lower storage modulus values. The irradiance values did not affect any of the transition temperatures significantly.SignificanceThe lower and more distinct Tg of Z250 suggests that Z250 cures more efficiently than Z100. The lower storage modulus of Z250 suggests that Z250 develops less stress in the tooth than Z100 during curing if shrinkage is the same for the two materials. The findings suggest that the material chosen, rather than irradiance, determines the stress level developed during light curing.
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| 21. |
- Emami, Nazanin, et al.
(författare)
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How filler properties, filler fraction, sample thickness and light source affect light attenuation in particulate filled resin composites
- 2005
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 21:8, s. 721-730
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Tidskriftsartikel (refereegranskat)abstract
- The way by which variables such as filler type, filler surface treatment and light source affect light attenuation in particulate filled resin composites was presented. Mixture of 50 wt% bisGMA and 50wt% TEGDMA consisting of a photo-initiatior and a co-initiator was prepared. Three different filler types, HBB, SBB, and KU, which were either silane surface treated or not, were added to that mixture in eight different volume percentage. It was observed that of the two light sources, more light was absorbed by the composite when the laser light was used. It was also observed that the HBB filler absorbed most light and the KU filler the least.
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| 22. |
- Hedberg, Yolanda S., et al.
(författare)
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In-vitro biocompatibility of CoCrMo dental alloys fabricated by selective laser melting
- 2014
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 30:5, s. 525-534
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Selective laser melting (SLM) is increasingly used for the fabrication of customized dental components made of metal alloys such as CoCrMo. The main aim of the present study is to elucidate the influence of the non-equilibrium microstructure obtained by SLM on corrosion susceptibility and extent of metal release (measure of biocompatibility).Methods: A multi-analytical approach has been employed by combining microscopic and bulk compositional tools with electrochemical techniques and chemical analyses of metals in biologically relevant fluids for three differently SLM fabricated CoCrMo alloys and one cast CoCrMo alloy used for comparison.Results: Rapid cooling and strong temperature gradients during laser melting resulted in the formation of a fine cellular structure with cell boundaries enriched in Mo (Co depleted), and suppression of carbide precipitation and formation of a martensitic ε (hcp) phase at the surface. These features were shown to improve the corrosion and metal release susceptibility of the SLM alloys compared with the cast alloy. Unique textures formed in the pattern of the melting pools of the three different laser melted CoCrMo alloys predominantly explain observed small, though significant, differences. The susceptibility for corrosion and metal release increased with an increased number (area) of laser melt pool boundaries.Significance: This study shows that integrative and interdisciplinary studies of microstructural characteristics, corrosion, and metal release are essential to combine and consider during the design and fabrication of CoCrMo dental components of optimal biocompatibility. The reason is that metal release from CoCrMo alloys is dependent on the fabrication procedure.
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| 23. |
- Håff, Anna, et al.
(författare)
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A retrospective evaluation of zirconia-fixed partial dentures in general practices : an up to 13-year study
- 2015
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 31:2, s. 162-170
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: To evaluate zirconia-based fixed partial dentures (FPDs) after more than 8 years in clinical service.Methods: Patients treated between 2000 and 2004 with zirconia FPDs were identified from the records of a manufacturer of FPD substructures. Of the 45 patients who met the inclusion criteria 30 attended the appointment and 33 FPDs were evaluated using modified California Dental Association (CDA) criteria. In addition, plaque and the bleeding index were registered. Patient satisfaction with the restorations was evaluated using a 10-point visual analog scale (VAS).Results: All the FPDs were made using CAD/CAM and hot isostatic pressed yttria-tetragonal zirconia polycrystal (HIPed Y-TZP) ceramic (Denzir) and were placed within general practices. The mean observation period was 9.6 ± 1.6 years (range 3.0–13.1 years). The CDA rating was 90% satisfactory for the surface. Corresponding figures for anatomic form, color and margin integrity were 94%, 100% and 94%, respectively. Regarding surface three (9.7%) FPDs exhibited veneer chipping and were rated ‘not acceptable’. For margin integrity two (6.5%) were rated ‘not acceptable’ because of caries. For anatomic form two (6.1%) were rated ‘not acceptable’ due to two lost FPDs. No significant differences were seen between the FPDs and controls for plaque and bleeding. The Kaplan–Meier survival rate (still in clinical function) was 94%, the success rate (technical events accounted for) 91% and (biological events accounted for) 73%. Based on the VAS the mean value for patient satisfaction was 9.3 ± 1.2.Significance: Ninety-four percent of the FPDs were still in clinical function. HIPed Y-TZP could serve as an alternative for FPD treatments similar to those in the current study.
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| 24. |
- Kassapidou, Maria, et al.
(författare)
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Cobalt-chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness
- 2020
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 36:11
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To investigate the metal ion release, surface roughness and cytoxicity for Co-Cr alloys produced by different manufacturing techniques before and after heat treatment. In addition, to evaluate if the combination of materials affects the ion release. Methods. Five Co-Cr alloys were included, based on four manufacturing techniques. Commercially pure titanium, CpTi grade 4 and a titanium alloy were included for comparison. The ion release tests involved both Inductive Coupled Plasma Optical Emission Spectrometry and Inductive Coupled Plasma Mass Spectrometry analyses. The surface analysis was conducted with optical interferometry. Cells were indirectly exposed to the materials and cell viability was evaluated with the MTT (3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) method. Results. All alloys showed a decrease of the total ion release when CpTi grade 4 was present. The total ion release decreased over time for all specimens and the highest ion release was observed from the cast and milled Co-Cr alloy in acidic conditions. The cast and laser-melted Co-Cr alloy and the titanium alloy became rougher after heat treatment. All materials were within the limits of cell viability according to standards. Significance. The ion release from Co-Cr alloys is influenced by the combination of materials, pH and time. Surface roughness is influenced by heat treatment. Furthermore, both ion release and surface roughness are influenced by the manufacturing technique and the alloy type. The clinical implication needs to be further investigated. (C) 2020 The Academy of Dental Materials. Published by Elsevier Inc.
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| 25. |
- Lööf, Jesper, et al.
(författare)
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A comparative study of the bioactivnity of three materials for dental applications
- 2008
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 24:5, s. 653-659
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. The aim of this work was to investigate the in vitro bioactivity of two different experimental dental luting cement formulations based on calcium aluminate (CA) in comparison with glass ionomer cement (GIC). One of the CA-based formulations was a hybrid between CA and GIC. Methods. Samples were submerged in phosphate buffered saline and stored at 37 degrees C for four periods of time: 1 h, 1 day, 7 days and 4 weeks. After storage the samples were analyzed in order to investigate if a surface layer of hydroxyapatite had formed. The analysis techniques used included grazing incidence X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy. Results. Both the CA-containing formulations were found to be bioactive. The highest degree of bioactivity was found on the sample with only CA as active substance. A relatively thick and totally covering layer was already formed after 24 h. On the hybrid material hydroxyapatite was found after 7 days. The GIC showed no bioactivity during the test period. Significance. The utilization of a bioactive material for tooth restorations will give an opportunity for remineralization and a natural and durable seal of the tooth-material interface. Materials based on CA exhibit bioactivity.
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