Influence of anterior load and restorative procedure on maxillary incisors with different cervical wear morphologies / Influência do procedimento restaurador e de contato anterior em incisivos superiores com diferentes morfologias de desgaste cervical

The aim of this study was to evaluate the influence of different anterior load type and restorative procedure on stress distribution of maxillary incisors with different noncarious cervical lesions (NCCLs) morphologies. Three-dimensional models of a maxillary incisor were generated. Beyond the sound model (SO), five NCCLs morphologies were simulated: shallow (SH), notched (NO), concave (CO), wedge-haped (WS) and irregular with dual center (IR' and IR"). Composite resin restoration of all the models was simulated (R). Two different anterior loads were applied: 100N on palatine middle third (ML) and 500 N on palatine incisal third (IL). The data were obtained in MPa using the Maximum Principal Stress and Von Mises criteria and the statistical analysis was performed (paired t-test with 95% confidence level). The IL provided higher compressive stress than ML, mainly on WS (-136.3MPa), IR" (-117.5) and NO (-71.1 MPa). The highest tensile stress found within the restored models was on NOR with IL (19,1 MPa). The Von Mises results showed higher stress concentration on non-restored and IL models (p<0.001). The anterior load type and restorative status were determinant factors on stress distribution pattern changes, whereas NCCLs morphologies had little influence in maxillary incisors.

O objetivo deste estudo foi avaliar a influência de diferentes tipos de contatos anteriores e procedimentos restauradores na distribuição de tensões de incisivos superiores com diferentes morfologias de lesões cervicais não-cariosas (NCCLs). Modelos tridimensionais de um incisivo central superior foram gerados. Além do modelo hígido (SO), foram simuladas cinco morfologias de NCCLs: rasas (SH), entalhadas (NO), côncavas (CO), em forma de cunha (WS) e irregulares com centro duplo (IR' e IR''). Restauração com resina composta em todos os modelos foi simulada (R). Dois contatos anteriores diferentes foram aplicadas: 100N no terço médio palatino (ML) e 500N no terço incisal palatino (IL). Os dados foram obtidos em MPa utilizando os critérios de Tensão Máxima Principal e de Von Mises e a análise estatística foi realizada (teste t pareado com nível de significância de 95%). A IL proporcionou maior estresse compressivo que ML, principalmente em WS (-136,3MPa), IR "(-117,5) e NO (-71,1 MPa). A maior tensão de tração encontrada nos modelos restaurados foi na NOR com IL (19,1 MPa). Os resultados de Von Mises mostraram maior concentração de estresse nos modelos não restaurados e IL (p <0,001). O tipo de contato anterior e a presença de restauração foram fatores determinantes nas alterações do padrão de distribuição de estresse, enquanto as morfologias dos NCCLs tiveram pouca influência nos incisivos superiores.

Shear bond strength of a self-adhesive resin cement to resin-coated dentin / 대한치과보철학회지

PURPOSE: The aims of this study were to evaluate the effect of a resin coating on the shear bond strength of indirect composite restoration bonded to dentin with a self adhesive resin cement and to compare the shear bond strength with that of a conventional resin cement. MATERIALS AND METHODS: The occlusal enamels of thirty six extracted non-carious human molars were removed until the dentin flat surfaces of the teeth were exposed. Then, they were divided into 3 groups. The dentin surfaces of group 1 and 3 were left without any conditioning, while the dentin surfaces of group 2 were resin-coated with Clearfil SE bond and a flowable resin composite, Metafil Flo. After all specimens were temporized for 24 hours, indirect composite resin blocks fabricated by Tescera were bonded to dentins by Unicem for group 1 and 2, and by Panavia F for group 3. After 48 hours of water storage, shear bond strengths were measured. The data was analyzed with one-way analysis of variance and multiple comparison test (Tukey method). RESULTS: The shear bond strengths of Unicem applied to resin coated dentin surfaces were significantly higher than those of Unicem and Panavia F used to uncoated dentin surfaces (P<.0001). CONCLUSION: Application of a resin coating to the dentin surface significantly improved the shear bonding strength of a self adhesive resin cement in indirect restoration.

Influence of rebonding procedures on microleakage of composite resin restorations / 대한치과보존학회지

During a composite resin restoration, an anticipating contraction gap is usually tried to seal with low-viscosity resin after successive polishing, etching, rinsing and drying steps, which as a whole is called rebonding procedure. However, the gap might already have been filled with water or debris before applying the sealing resin. We hypothesized that microleakage would decrease if the rebonding agent was applied before the polishing step, i.e., immediately after curing composite resin. On the buccal and lingual surfaces of 35 extracted human molar teeth, class V cavities were prepared withthe occlusal margin in enamel and the gingival margin in dentin. They were restored with a hybrid composite resin Z250 (3M ESPE, USA) using an adhesive AdperTM Single Bond 2 (3M ESPE). As rebonding agents, BisCover LV (Bisco, USA), ScotchBond Multi-Purpose adhesive (3M ESPE) and an experimental adhesive were applied on the restoration margins before polishing step or after successive polishing and etching steps. The infiltration depth of 2% methylene blue into the margin was measured using an optical stereomicroscope. The correlation between viscosity of rebonding agents and mciroleakage was also evaluated. There were no statistically significant differences in the microleakage within the rebonding procedures, within the rebonding agents, and within the margins. However, when the restorations were not rebonded, the microleakage at gingival margin was significantly higher than those groups rebonded with 3 agents (p < 0.05). The difference was not observed at the occlusal margin. No significant correlation was found between viscosity of rebonding agents and microleakage, except very weak correlation in case of rebonding after polishing and etching at gingival margin (r = -0.326, p = 0.041).

The effect of Er,Cr:YSGG irradiation on microtensile bond strength of composite resin restoration / 대한치과보존학회지

The purpose of this study was to evaluate the effect of Er,Cr:YSGG laser irradiation with hypersensitivity mode on microtensile bond strength of composite resin. Twenty extracted permanent molars were randomly assigned to six groups, according to the irradiation of Er,Cr:YSGG laser, adhesive system (Optibond FL or Clearfil SE bond) and application time of etchant (15 sec or 20 sec). Then composite resin was build up on each conditioned surface. The restored teeth were stored in distilled water at room temperature for 24 h and twelve specimens for each group were prepared. All specimens were subjected to microtensile bond strength and the fracture modes were evaluated. Also, the prepared dentin surface and laser irradiated dentin surface were examined under SEM. The results were as follows: 1. The microtensile bond strength of laser irradiated group was lower than that of no laser irradiated group. 2. Regardless of laser irradiation, the microtensile bond strength of Optibond FL was higher than that of Clearfil SE bond. And the microtensile bond strength of 20 sec etching group was higher than that of 15 sec etching group when using Optibond FL. 3. The SEM image of laser irradiated dentin surface showed prominent peritubular dentin, opened dentinal tubules and no smear layer.

Effect of calcium hydroxide on bond strength of dentin bonding systems / 대한치과보존학회지

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration. Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then Ca(OH)2 and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at 36.5degrees C for experiment period (7 days, 30 days). After removing IRM and Ca(OH)2, each dentin adhesives were treated on dentin surfaces. Composite resin (Z-250, 3M) was placed with 5 mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into 1.0 x 1.0 mm2 cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and microTBS test was performed. SEM analysis was performed to examine the fractured surfaces. The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.

Effect of calcium hydroxide on bond strength of dentin bonding systems / 대한치과보존학회지

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration. Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then Ca(OH)2 and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at 36.5degrees C for experiment period (7 days, 30 days). After removing IRM and Ca(OH)2, each dentin adhesives were treated on dentin surfaces. Composite resin (Z-250, 3M) was placed with 5 mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into 1.0 x 1.0 mm2 cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and microTBS test was performed. SEM analysis was performed to examine the fractured surfaces. The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.