Marginal adaptation of a restorative resin polymerized at reduced rate

Uno, Shigeru; Asmussen, Erik

doi:10.1111/j.1600-0722.1991.tb01052.x

Cited by 174 publications

(194 citation statements)

References 16 publications

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“…Afterwards, high light intensity is applied to complete the polymerization process and provide proper mechanical properties 10,25 . Since the volumetric contraction of the composite can cause debonding forces and a part of this stress can be compensated during the initial phase of polymerization by the flow of the dental composite 3,4 , the extending in time of the pre-gel phase with stepped irradiation can preserve the marginal integrity of the restoration 10,13,22,26 due to a reduction in the polymerization contraction stress 5,11,24 . The stepped irradiation mode used with incremental filling techniques to restore class I cavities provided bonding strength values similar to those of the control group.…”

Section: Discussionmentioning

confidence: 99%

“…Different filling and photo-activation techniques have been developed in an attempt to reduce the shrinkage potential and produce minimal interfacial stress development 2,18 . Soft-start polymerization or stepped light intensity uses an initial low-output intensity of light followed by a higher intensity of light 13,22 , and incremental insertion of composite resin reduces the volume of the restorative material that shrinks under photo-activation 8,12,17 . Both methods have been advocated because they minimize stress generated during polymerization and improve the marginal sealing and cavity wall adaptation of restorations 18 .…”

Section: Introductionmentioning

confidence: 99%

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Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

et al. 2004

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Factors such as light-curing mode, filling technique and cavity configuration may affect the bonding strength to dentin. This study evaluated the effect of irradiation mode and filling technique on resin/dentin bonding strength on the buccal wall of class I cavities in human teeth. Occlusal enamel was removed to expose a flat dentin surface. Occlusal cavities (4 x 3 x 3 mm) were prepared in dentin. The adhesive Single Bond was applied according to the manufacturer's instructions and TPH Spectrum composite resin was placed using the following: oblique incremental, horizontal incremental or bulk filling techniques. The composite resin was light-cured either by continuous (600 mW/cm² for 40 s) or Soft-Start (250 mW/cm² for 10 s + 600 mW/cm² for 30 s) modes. Specimens of the control group were obtained by bonding the material to the flat exposed buccal wall of the cavity (C-factor = 1). The teeth were stored in water at 37 o C for 24 h and prepared for microtensile testing. Bonded beams of approximately 0.8 mm² were obtained from the buccal wall and tested with a tension of 0.5 mm/min. Results were analyzed by two-way ANOVA, Tukey's test and Dunnett's test (α = 0.05). Incremental placement techniques with both irradiation modes produced higher bonding strength values than the bulk technique (p < 0.05). Bonding strength tested in the cavities had lower values than those obtained in flat dentin surfaces (control group) (p < 0.05), except for incremental fillings using stepped irradiation. Bonding strength to the cavity walls depends on the filling technique and on the irradiation mode of composite resins. DESCRIPTORS: Composite resins; Dentin; Dental cements; Dental enamel. RESUMO:Fatores como o modo de ativação, a técnica restauradora e a configuração cavitária podem afetar a resistência adesiva à dentina. Este estudo avaliou os efeitos dos modos de ativação e das técnicas restauradoras na resistência de união compósito/dentina na parede vestibular de restaurações classe I. O esmalte oclusal dos dentes foi removido para expor uma superfície dentinária planificada. Cavidades oclusais (4 x 3 x 3 mm) foram preparadas em dentina. O adesivo Single Bond foi aplicado de acordo com as instruções do fabricante, e o compósito TPH Spectrum, inserido através de três diferentes técnicas: oblíqua incremental, horizontal incremental ou incremento único. O compósito foi ativado utilizando o método contínuo (600 mW/cm² por 40 s) ou "Soft-Start" (250 mW/cm² por 10 s + 600 mW/cm² por 30 s). O grupo controle foi obtido pela união somente à parede vestibular planificada (fator C = 1). Os dentes foram armazenados por 24 h em água a 37 o C e preparados para o ensaio de microtração (0,5 mm/min). Os espécimes apresentaram na secção transversal uma área de união de aproximadamente 0,8 mm². Os resultados foram analisados pela ANOVA (dois fatores), pelos testes de Tukey e Dunnett (α = 0,05). A técnica incremental seguida da ativação com ambas as formas de fotopolimerização produziu maiores valores de resistência de união que a técnica...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

et al. 2004

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“…The primary aim of these strategies is to allow more time for the composite to flow during setting 1 and to facilitate a certain degree of polymer chain relaxation 2 before reaching the gelation phase. In fact, some investigators have reported reduced shrinkage stress and improved marginal integrity without compromising the final double-bond conversion of the material 3,4 . Besides shrinkage stress, studies concerning the dental polymer structure resulting from different curing strategies usually concentrate on degree of conversion (DC).…”

Section: Introductionmentioning

confidence: 99%

Influence of ethanol concentration on softening tests for cross-link density evaluation of dental composites

et al. 2007

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This study investigated the influence of ethanol concentration on softening tests for cross-link density evaluation (microhardness) of dental composites. Specimens of Filtek Z100 (3M ESPE) were light-activated by standard or pulse-delay methods. After initial Knoop hardness readings (KHN 1 ), half of specimens (n = 10) for each irradiation method was stored in 100% ethanol, and half in 75% ethanol, during 24 hours, and hardness was determined anew. Hardness deterioration (ΔKHN) was recorded as the difference between pre and post-storage values. KHN 1 data were submitted to one-way ANOVA and Tukey's test (α = 0.05), and hardness deterioration was analyzed by two-way ANOVA and Tukey's test (α = 0.05). For KHN 1 , no significant differences were detected between the activation modes (p = 0.697). Samples light-activated by the pulse-delay method presented significantly higher softening compared to the standard mode when samples were immersed in 100% ethanol. Conversely, no significant differences between curing modes were detected for samples stored in 75% ethanol.

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“…[11][12] Such arguments have been used in the development of photoactivation protocols, which serve as alternatives to high irradiance continuous curing. 3,5 Generally speaking, these methods lead to the formation of a reduced number of polymer growth centers, reducing the reaction rate and increasing the opportunity for flow before the vitrification stage. 13 Among the photoactivation protocols suggested, those using an initial pulse with radiant exposure up to 1 J/cm 2 seem to be the most efficient in reducing shrinkage stress.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2] Depending on the magnitude of such stresses and the bond strength between the adhesive system and tooth substrate, problems, such as debonding, cusp deflection or cracks in enamel, may occur. [3][4][5][6] In the early stages of the reaction, volumetric contraction may be compensated for by viscous flow of the composite. [7][8] However, at very low degrees of conversion (around 1%), development of a crosslinked network (gel point) reduces flow capacity and contraction stresses become apparent.…”

Section: Introductionmentioning

confidence: 99%

Pulse-delay Curing: Influence of Initial Irradiance and Delay Time on Shrinkage Stress and Microhardness of Restorative Composites

Pfeifer

Braga

Ferracane

2006

Operative Dentistry

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©Operative Dentistry, 2006, 31-5, 610-615 CSC Pfeifer • RR Braga • JL Ferracane Clinical RelevanceNew photoactivation protocols need to be tested before being recommended for clinical use. This study suggests that pulse-delay curing may be an efficient way to reduce polymerization shrinkage stress without compromising degree of conversion or polymer network structure. SUMMARYObjectives: Evaluate the influence of pulse-delay curing on shrinkage stress and microhardness of 2 restorative composites (Herculite XRV and Tetric Ceram). Methods: Two pulse irradiances (500 and 100 mW/cm 2 ) were applied for 1 or 5 seconds, respectively (radiant exposure = 0.5 J/cm 2 ). In both cases, photoactivation was completed applying 500 mW/cm 2 for 39 seconds after a delay time of 0, 1 or 3 minutes. Shrinkage stress was monitored for 10 minutes in specimens 5-mm in diameter by 1-mm in height. Knoop hardness (KHN) was used to estimate the degree of conversion 10 minutes after photoactivation and after 48 hours of storage in distilled water (37°C) in specimens with similar geometry and dimensions. Additional KHN readings after 48 hours of storage in ethanol (37°C) were used to estimate polymer structure. The results were evaluated using ANOVA/Tukey test and Student t-test (α α=0.05). Results: For Tetric Ceram, 3-minute delay led to stress reduction compared to continuous curing at 500 mW/cm 2 (4.7±0.6 MPa and 7.0±1.3 MPa, respectively). At 100 mW/cm 2 , 1 minute delay was enough to cause significant stress reduction (5.2±0.5 MPa). For Herculite, the pulse with 3 minute delay led to stress reduction compared to no delay for both irradiances (100 mW/cm 2 : 6.3±0.5 MPa and 7.8±0.8 MPa, respectively; 500 mW/cm 2 : 6.4±0.3 MPa and 7.8±0.7 MPa, respectively). At 10 minutes, only small differences in microhardness were observed for both materials. No differences were found after water and ethanol storage (p>0.05). Conclusions: The composites behaved differently when subjected to pulse curing. Stress reduction was influenced by delay time but not by pulse irradiance. KHN results suggest that similar degrees of conversion and polymer structure were achieved with the photoactivation methods tested.

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Marginal adaptation of a restorative resin polymerized at reduced rate

Cited by 174 publications

References 16 publications

Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

Effect of irradiation mode and filling technique on resin/dentin bonding strength in class I cavities

Influence of ethanol concentration on softening tests for cross-link density evaluation of dental composites

Pulse-delay Curing: Influence of Initial Irradiance and Delay Time on Shrinkage Stress and Microhardness of Restorative Composites

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