Reliability of an Innovative Slab Shear versus Microtensile Bond Strength Test: Mechanical and Finite Element Analysis.

OBJECTIVE: The aim of this study was to evaluate the efficiency of slab shear bond strength test (Slab_SBS) versus the microtensile in evaluation of the bond strength of different substrates. MATERIALS AND METHODS: Forty-eight extracted caries-free human third molars were utilized for teeth specimens' preparation. After flattening of all molars' occlusal table, the specimens were divided into two groups based on the type of utilized restorative material: nanohybrid resin composite and resin-modified glass ionomer (RMGI). Each group was further subdivided into three subgroups according to the subsequently applied bond strength test and specimen width; microtensile bond strength test (µTBS), Slab_SBS [2 mm] and Slab_SBS [3 mm]. Both testing methods were additionally applied on CAD/CAM specimens, nanohybrid resin composite blocks (composite-to-composite), and ceramic blocks (ceramic-to-ceramic). CAD/CAM specimens were prepared and cemented and then sectioned and subdivided as followed for teeth specimens' preparation. Pretest failures (PTF), bond strength, and failure mode of each specimen were recorded. Representative three-dimensional (3D) finite element analysis (FEA) models were developed to simulate µTBS and Slab_SBS specimens. Data were statistically analyzed using Shapiro-Wilk test and Weibull analysis. RESULTS: Pretest failures were only noted in the µTBS subgroups. Slab_SBS provided comparable bond strength to the µTBS of all substrates with adhesive mode of failure. CONCLUSION: Slab_SBS is easier to prepare with consistent and predictable outcome with no pretest failures during specimen preparation and better stress distribution.

The Effect of Polyacrylic Acid and Sodium Trimetaphosphate on Dentin Hybrid Layer Remineralization: An In Vitro Study.

Background: Adhesive monomers are not able to fully encapsulate collagen fibrils in hybrid layer leaving them vulnerable to time-dependent hydrolytic degradation. The current in vitro study was designed for investigation of the remineralization of the resin-dentin hybrid layer using biomimetic analogs by nanoleakage investigation. Material and Methods: Firstly, occlusal enamel of thirty human molars was removed exposing flat surface of dentin, then randomly divided into three main groups according to the different remineralizing protocols (n=10) (R): control group (R0), STMP group (R1), and biomimetic remineralizing group (R2). The dentin surface of the STMP and biomimetic remineralizing groups (R1 and R2) was treated with STMP solution, followed by self-etch adhesive application on dentin surface of all groups, and restored with double 2-mm thick layers of resin composite. Each tooth was sectioned perpendicularly to the resin-dentin interface for producing 1-mm thick slaps. Each group was subdivided into four subgroups according to the incubation time to 24 hours, one month, three months, and 4 months. Retrieved slabs were prepared for nanoleakage for evaluation of metallic silver particles distribution percentage at the resin-dentin interface using digital image analysis software. Results: There was a statistically significant increase in nanoleakage over time in all three groups. However, the third group showed the least increase in metallic silver uptake over time. Conclusions: Hybrid layer could be remineralized by using dual-biomimetic analogs (PAA and STMP). Key words:Hybrid layer, remineralization, nanoleakage, polyacrylic acid, sodium trimetaphosphate.

Effect of phytic acid on bond strength and interfacial integrity of universal adhesive to deep dentin.

This study investigated the effect of phytic acid (IP6) in different concentrations and application times on microtensile bond strength (µTBS) and interfacial integrity of universal adhesive to deep dentin. Flat deep dentin surfaces of 48 human molars were either etched with 37% phosphoric acid (PA) for 15 sec (control); or received no acid treatment and universal adhesive was applied directly in a self-etch mode (SE); or divided according to IP6 concentration (C) into two main groups: C1, 0.5%, and C2, 1%. Specimens of IP6 groups were further subdivided into three subgroups according to application time of IP6 (T) where; T1, 15 sec; T2, 30 sec and T3, 60 sec. Single Bond Universal Adhesive was then applied and resin composite blocks were built-up. Forty Specimens were then sectioned to produce resin/dentin beams that were used for µTBS testing using a universal testing machine. The remaining eight specimens were sectioned into slabs that were immersed into ammonical silver nitrate solution and nanoleakage was observed using a field emission scanning electron microscope (FE-SEM). The results showed that the application of IP6 in 0.5% and 1% produced significantly higher µTBS and less nanoleakage compared to PA and SE groups. Also, the application of IP6 for 60 sec recorded the highest µTBS and the lowest nanoleakage followed by 30 sec, and 15 sec respectively. Therefore, conditioning of deep dentin with IP6 enhances µTBS and interfacial integrity of universal adhesive to deep dentin in comparison to PA etching or using the universal adhesive in SE mode.

Effect of phytic acid on bond strength and interfacial integrity of universal adhesive to deep dentin

Abstract This study investigated the effect of phytic acid (IP6) in different concentrations and application times on microtensile bond strength (µTBS) and interfacial integrity of universal adhesive to deep dentin. Flat deep dentin surfaces of 48 human molars were either etched with 37% phosphoric acid (PA) for 15 sec (control); or received no acid treatment and universal adhesive was applied directly in a self-etch mode (SE); or divided according to IP6 concentration (C) into two main groups: C1, 0.5%, and C2, 1%. Specimens of IP6 groups were further subdivided into three subgroups according to application time of IP6 (T) where; T1, 15 sec; T2, 30 sec and T3, 60 sec. Single Bond Universal Adhesive was then applied and resin composite blocks were built-up. Forty Specimens were then sectioned to produce resin/dentin beams that were used for µTBS testing using a universal testing machine. The remaining eight specimens were sectioned into slabs that were immersed into ammonical silver nitrate solution and nanoleakage was observed using a field emission scanning electron microscope (FE-SEM). The results showed that the application of IP6 in 0.5% and 1% produced significantly higher µTBS and less nanoleakage compared to PA and SE groups. Also, the application of IP6 for 60 sec recorded the highest µTBS and the lowest nanoleakage followed by 30 sec, and 15 sec respectively. Therefore, conditioning of deep dentin with IP6 enhances µTBS and interfacial integrity of universal adhesive to deep dentin in comparison to PA etching or using the universal adhesive in SE mode.

Resumo Este estudo investigou o efeito do ácido fítico (IP6) em diferentes concentrações e tempos de aplicação na resistência da ligação microtensiva (µTBS) e na integridade interfacial do adesivo universal à dentina profunda. As superfícies planas de dentina profunda de 48 molares humanos foram preparadas com ácido fosfórico (PA) a 37% durante 15 seg. (controlo); ou não receberam tratamento ácido e o adesivo universal foi aplicado diretamente em modo de auto-adesivo (SE); ou dividido de acordo com a concentração de IP6 (C) em dois grupos principais: C1, 0,5%, e C2, 1%. Os espécimes dos grupos IP6 foram ainda subdivididos em três subgrupos de acordo com o tempo de aplicação do IP6 (T) em que; T1, 15 seg; T2, 30 seg e T3, 60 seg. Aplicou-se então Single Bond Universal Adhesive e construíram-se blocos compostos de resina. Quarenta espécimes foram então seccionados para produzir feixes de resina/dentina que foram usados para testes µTBS usando uma máquina de testes universal. Os restantes oito espécimes foram seccionados em placas que foram imersas em solução amoniacal de nitrato de prata e observou-se uma nano-infiltração utilizando um microscópio eletrônico de varrimento de emissões de campo (FE-SEM). Os resultados mostraram que a aplicação de IP6 em 0,5% e 1% produziu µTBS significativamente mais elevado e menos nano-infiltração em comparação com os grupos PA e SE. Além disso, a aplicação de IP6 durante 60 seg registou o µTBS mais alto e o mais baixo de nano-infiltração seguido de 30 seg, e 15 seg respectivamente. Portanto, o condicionamento da dentina profunda com IP6 melhora o µTBS e a integridade interfacial do adesivo universal à dentina profunda em comparação com a gravação de PA ou utilizando o adesivo universal no modo SE.

Impact of Immediate Dentin Sealing Using Universal Adhesive under Simulated Pulp Pressure on Microtensile Bond Strength of Indirect Resin Composite Restorations and Dentin Permeability.

OBJECTIVE: The aim of this study was to investigate the effect of immediate dentin sealing (IDS) technique using universal adhesive under simulated pulp pressure on microtensile bond strength (µTBS) of indirect resin composite restorations and dentin permeability. MATERIALS AND METHODS: Fifty extracted caries-free human third molars were used for specimens' preparation. Each molar's occlusal table was abraded flat and their roots were separated under continuous water cooling. Forty specimens were used for microtensile bond strength test (µTBST) evaluation. The µTBST specimens were randomly assigned to two groups according to the dentin sealing time; Immediate dentin sealing (IDS) and delayed dentin sealing (DDS). Each group was further subdivided into two subgroups according to the adhesive system used for dentin sealing: iBOND self-etch adhesive and GLUMA Bond Universal. All specimens were exposed to simulated pulp pressure for 1 week then restored using computer-aided design/computer-aided manufacturing (CAD/CAM) resin composite blocks. The µTBS was evaluated for all tested subgroups after 24 hours and 6 months of water storage. The remaining 10 teeth were used for the preparation of dentin discs for dentin permeability evaluation. They were divided into two groups according to type of self-etch adhesive used. Fluid filtration rate was evaluated after etching, with smear layer and after adhesive application. Results obtained were statistically analyzed using Shapiro-Wilk test and Weibull analysis. RESULTS: Statistically significant difference was recorded between µTBS mean values of both IDS and DDS techniques at 24 hours and after 6 months of water storage. GLUMA Bond Universal adhesive had significantly higher bond strength compared with iBond at both IDS and DDS techniques, but both adhesives showed a significant reduction in the Weibull characteristic strength after 6 months of water storage. Significant reduction in dentin permeability was recorded by both adhesives without any significant difference between them. CONCLUSIONS: The IDS technique using universal adhesive in self-etch mode is an effective strategy for improving the final bond strength of CAD/CAM resin composite restorations and reducing dentin permeability.

Microtensile Bond Strength, Marginal Leakage, and Antibacterial Effect of Bulk Fill Resin Composite with Alkaline Fillers versus Incremental Nanohybrid Composite Resin.

OBJECTIVE: This study aimed to investigate the microtensile bond strength (µTBS), microleakage, and antibacterial effect of bulk fill resin composite with alkaline fillers (alkasite) (alkaline fillers such as barium aluminum silicate glass and ytterbium trifluoride) in comparison to incremental nanohybrid resin composite. MATERIALS AND METHODS: µTBS was evaluated by using 30 human mandibular molars. Teeth were randomly divided into three groups (C): nanohybrid resin composite (C0), self-cured alkasite (C1), and dual-cured alkasite (C2). Each group was subdivided into two subgroups according to the bulk thickness: 4 mm (T1) and 6 mm (T2). The occlusal enamel of teeth was removed and the resin composite was applied to a flat dentin surface. Then, teeth were sectioned into beams to be tested under tension. For microleakage testing, mesio-occlusal class II cavities were prepared in 15 molars and divided into three groups as mentioned before. Following this, cavities were restored, thermocycled, immersed in a dye, sectioned mesiodistally, and then dye penetration was assessed. The antibacterial effect of both tested materials was evaluated using agar disc diffusion and broth dilution methods against chlorhexidine as a control positive group. RESULTS: There was no significant difference in µTBS between all tested groups. Bulk fill self-cured alkasite showed the lowest microleakage value followed by bulk fill dual-cured alkasite and incremental nanohybrid resin composite, respectively. Also, cervical microleakage showed significantly higher mean value than the occlusal one. The antibacterial effect of alkasite was less than chlorhexidine. Alkasite showed maximum broth clarity at lowest tested bacterial concentration. CONCLUSION: Resin composite with alkaline fillers was characterized by good µTBS and marginal integrity with weak antibacterial effect.

Effect of Galla Chinensis on Remineralization of Early Dentin Lesion.

OBJECTIVE: This study aimed to investigate the efficacy of the Galla chinensis extract (GCE) on early dentin lesion remineralization. MATERIALS AND METHODS: Seventy-two dentin specimens were divided into three groups according to the treatment solution. In group S1, specimens were treated with GCE; in group S2, the specimens were treated with sodium fluoride (NaF); meanwhile, specimens of group S3 were treated with distilled water (DW). Each group was further subdivided into two subgroups according to the treatment time (1 minute and 5 minutes). An in vitro pH-cycling model for 12 days was done. Subsequently, surface microhardness (SMH) of the specimens, elemental analysis, and their micromorphological appearance were evaluated. STATISTICAL ANALYSIS: Data were statistically analyzed. One-way analysis of variance was used to compare numerical (parametric) data between more than two separate groups followed by post hoc Tukey. RESULTS: There was no significant difference between the mean SMH of dentin between NaF and GCE groups. Regarding the time, the 5-minute treatment with NaF and DW groups recorded higher mean SMH value of dentin than the 1-minute treatment group. Meanwhile, for GCE groups, the 1-minute immersion recorded higher mean SMH value than the 5-minute immersion without any significant difference between them. The microhardness results were confirmed by environmental scanning electron microscope and energy dispersive X-ray analysis results. CONCLUSION: GCE could be used as an effective alternative for dentin remineralization.