The Effect of Curing Light Source on Polymerization Contraction Stress and Degree of Conversion Over Time in an Orthodontic Adhesive PDF Download
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Author: Kari K. Borgen
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
Author: Kari K. Borgen
Publisher:
ISBN:
Category :
Languages : en
Pages : 92
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Book Description
Author: Barton L. Carter
Publisher:
ISBN:
Category :
Languages : en
Pages : 148
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Author: Mounir Iskandar
Publisher:
ISBN:
Category :
Languages : en
Pages : 130
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Book Description
The purpose of this study was 1) To determine the impact of eliminating or delaying the photo-activation procedure on the polymerization contraction stress (PCS)and degree of conversion (DC) of a dual-cured resin luting agent, and 2) To determine the amount of delay in photo-initiation of the dual-cured resin cements that can achieve a reduced PCS value with the highest possible DC. The amount of PCS and DC of a dual-cured resin luting agent was determined using a tensometer and ATR spectroscopic technique, respectively. Photo-activation delay in seven tested groups was 0 min, 2 min, 4 min, 6 min, 8 min, 10 min and no photoactivation. Five samples for each group were tested. There were two hypotheses for this study: 1) A significant decrease in the amount of PCS associated with delayed photo-activation, and 2) A significant increase in DC associated with delayed photo-activation. The PCS of the chemical-cure luting agent had significantly lower value than all of the light-cure groups. For the light-cure groups, those with a 4-min delay had higher PCS than those with delays of 0 min, 2 min, 6 min, 8 min, and 10 min. The zero (0)-min and 2-min delay had higher PCS than the 6-min, 8-min, and 10-min delay; and the 6-min delay had higher PCS than the 8-min and 10-min delay. The PCS decreased 0.086 MPa per minute of delay. The DC of the chemical-cure luting agent had significantly lower value than the 2-min, 4-min, 6-min, 8-min, and 10-min delaylight cure. For the light-cure groups, 0-min delay had a lower DC than the 2-min, 4-min, 6-min, 8-min, and 10-min delay; 2-min delay had lower DC than 4-min, 6-min, 8-min, and 10-min delay. The 4-min and 6-min delay had lower DC than the 8-min and 10-min delay; and the 8-min delay had a lower degree of conversion by peak area than the 10- minute delay. The DC increased 0.021 per minute of delay. Extending the stress relief period of the dual-cured luting agents by delaying light activation has a significant impact on PCS and DC values. There was significant decrease in PCS with the delayed light curing of the resin luting agent. Significant increase in DC was noticed when light activation was delayed in the dual-cured resin luting agents.
Author: Maram Shaabin
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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Book Description
Polymerization shrinkage is one of the most significant problems associated with resin-matrix composite. Shrinkage results in contraction stress in the resin, leading to possible debonding in certain areas of the adhesive joint and potentially adversely affecting the bond strength. The reduction in the stress may improve the adaptation of the resin restoration, and decrease the problems that are associated with contraction stress, such as postoperative pain and recurrent caries. Recently, it has been found that varying the inhibitor concentration would reduce the polymerization shrinkage without affecting mechanical properties. In this study, we investigated the effects of varying the initiator and initiator levels on polymerization shrinkage stress, strength, and degree of conversion. An experimental composite was prepared by using a blend of BisGMA: UDMA: TEGMA (1:1:1 weight ratio) with 70 wt% silanated glass fillers. Four levels of inhibitors (BHT 0.0 %, 2%, 6%, 20%) and initiators (CQ 2%, 6%, 20%, 60%) were used (total of 16 combinations). A tensiometer was used to measure the polymerization contraction stress, contraction stress rate and gel time for each resin. FTIR was used to measure the degree of conversion. The flexural strength and flexural modulus were determined using the three-point bending test. Resin-matrix composite with 0.0-percent BHT and 2.0-percent CQ showed the highest contraction stress and stress rate and the shortest gel time, while resin-matrix composite with the 6.0-percent BHT and 6-percent CQ showed the lowest contraction stress and stress rate and the longest gel time. At an extremely high concentrations of CQ (20 percent and 60 percent) and high BHT concentration (20 percent) low degree of conversion values were observed. Overall, from the collected data, group F (2-percent BHT and 6-percent CQ) and G (6-percent BHT and 6-percent CQ) provide the most desirable combination of strength (above 80 MPa) and stress (below 3 MPa) are present as a potential dose combination range of CQ and BHT. In conclusion, the effect of inhibitors and initiators appears to change in different resin formulation. Increasing the levels of both the inhibitor and the initiator decrease the polymerization contraction stress and stress rate, and the impact on the conversion is unpredictable. In this study, we found a decrease in both the conversion value and depth of cure.
Author: Rachel Claire Soyland
Publisher:
ISBN:
Category :
Languages : en
Pages : 69
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Author: Nazir Lalani
Publisher: National Library of Canada = Bibliothèque nationale du Canada
ISBN:
Category : Dental bonding
Languages : en
Pages : 58
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Book Description
The objective of this study was to determine the efficiency of an argon laser in polymerizing a light cure orthodontic adhesive. Metal brackets were bonded to 37 buccal and 148 lingual surfaces of 185 premolars. Five groups of 37 premolars were cured as follows: Light 40 seconds buccal, light 40 seconds lingual, laser 5 seconds lingual, laser 10 seconds lingual and laser 15 seconds lingual. All bonded specimens were placed in distilled water for 30 days at 37$\sp\circ$C and thermal cycled for 24 hours. The brackets were detached using a shear load on an Instron machine and the site of bond failure was examined under 10X magnification.
Author: John M. Powers
Publisher: Mosby
ISBN:
Category : Medical
Languages : en
Pages : 668
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Book Description
Presenting a comprehensive exploration of restorative dental materials, this book provides the information readers need to know to correctly use dental materials in the clinic and dental laboratory. Ranging from fundamental concepts to advanced skills, it also provides the scientific basis for technical procedures and manipulation of materials.
Author: Jess Thomas
Publisher:
ISBN:
Category : Dental glass ionomer cements
Languages : en
Pages :
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Book Description
Introduction: The polymerization and acid-base reactions in resin-modified glass-ionomers (RMGI) are thought to compete with and inhibit one another. The objective of this study was to examine the effect of visible light-cure (VLC) delay on the polymerization efficiency and orthodontic bond strength of a dual-cured RMGI. Methods: An RMGI light-cured immediately, 2.5, 5, or 10 minutes after mixing comprised the experimental groups. Isothermal and dynamic temperature scan differential scanning calorimetry (DSC) analysis of the RMGI was performed to determine extents of VLC polymerization and acid-base reaction exotherms. Human premolars (n = 18/group) were bonded with the RMGI. Shear bond strength and adhesive remnant index (ARI) scores were determined. Results: DSC results showed the 10 minute delay RMGI group experienced significantly (P 0.05) lower VLC polymerization compared to the other groups. Acid-base reaction exotherms were undetected in all groups except the 10 minute delay group. No significant differences (P0.05) were noted among the groups for mean shear bond strength. A chi-square test showed no significant difference (P = 0.428) in ARI scores between groups. Conclusions: Delay in light-curing may reduce polymerization efficiency and alter the structure of the RMGI, but orthodontic shear bond strength does not appear to be compromised.
Author: Dale Anne Featheringham
Publisher:
ISBN:
Category :
Languages : en
Pages : 102
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Author: Vesna Miletic
Publisher: Springer
ISBN: 3319609610
Category : Medical
Languages : en
Pages : 310
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Book Description
This book covers both basic scientific and clinically relevant aspects of dental composite materials with a view to meeting the needs of researchers and practitioners. Following an introduction on their development, the composition of contemporary composites is analyzed. A chapter on polymerization explains the setting reactions and light sources available for light-cured composites. The quality of monomer-to-polymer conversion is a key factor for material properties. Polymerization shrinkage along with the associated stress remains among the most challenging issues regarding composite restorations. A new classification of dental composites is proposed to offer more clinically relevant ways of differentiating between commercially available materials. A review of specific types of composites provides an insight into their key issues. The potential biological issues of dental composites are reviewed in chapters on elution of leachable substances and cariogenicity of resin monomers. Clinical sections focus on material placement, finishing procedures, and the esthetics and clinical longevity of composite restorations. Bonding to tooth tissues is addressed in a separate chapter, as is the efficiency of various composite repair methods. The final chapter discusses future perspectives on dental composite materials.
