Browsing by Author "Bottino, Marco"

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    Cuspal Deflection in Premolar Teeth Restored with Bulk-Fill Resin-Based Composite Materials
    (2015) Elsharkasi, Marwa M.O.; Platt, Jeffrey A.; Cook, Norman Blaine; Hara, Anderson T.; Matis, Bruce A.; Bottino, Marco
    Objectives: To investigate the effect of bulk-fill resin based composite materials on cuspal deflection in large slot mesio-occlusal-distal cavities (MOD) in premolar teeth. Methodology: Thirty-two sound maxillary premolar teeth with large slot MOD cavities were distributed to four groups (n=8). Three groups were restored with bulk-fill resin composite materials (Tetric EvoCeram, x-tra fil, and Sonic Fill, respectively) in a single increment. The conventional composite group, Filtek Z100, was used to restore the cavities in 2mm increments. Cusp deflection was recorded post irradiation using a Nikon measurescope UM-2 (Nikon, Tokyo, Japan), by measuring the changes in the bucco-palatal width of the premolar teeth at 5 minutes, 24 hours, and 48 hours after completion of the restoration. The cuspal deflection was obtained by recording the difference between the baseline measurements and the other measurements for each tooth. Results: Cuspal deflection was significantly higher in Conventional Composite than in Tetric EvoCeram Bulk Fill (p=0.0031), x-tra Fil Bulk (p=0.0029), and SonicFill Bulk (p=0.0002). There was no significant difference in cuspal deflection for Tetric EvoCeram Bulk, X-tra Fil Bulk, and SonicFill Bulk Composites. Conclusions: All the investigated bulk-fill resin composites exhibited cuspal deflection lower than conventional resin composite. One of the aims of research and studies on the resin composite materials is improving their clinical longevity, and simplifying their use. For that purpose bulk-fill materials are considered promising materials and further clinical studies should be conducted.
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    Effect of Chlorhexidine-Encapsulated Nanotube-Modified Adhesive System on the Bond Strength to Human Dentin
    (2019) Kalagi, Sara Arfan; Cook, N. Blaine; Diefenderfer, Kim; Bottino, Marco; Feitosa, Sabrina
    Introduction: The resin-dentin interface undergoes degradation by endogenous matrix metalloproteinases (MMPs) after adhesive procedures. Application of several MMP inhibitors such as chlorhexidine (CHX) to the demineralized collagen dentin matrix after acid-etching has been suggested to be a successful approach to prevent degradation of the hybrid layer. Further, nanotubes (HNT) have been used as a reservoir for encapsulation and controlled delivery for several therapeutic drugs with sustained release. Therefore, HNT can be encapsulated with CHX and incorporated into dentin adhesives for the possibility of enhancing the longevity and durability of the hybrid layer. Objective: To evaluate the effect of a CHX-encapsulated nanotube-modified primer/PR and adhesive/ADH on the microtensile resin bond strength (µTBS) to dentin. Materials and Methods: A commercial adhesive and its respective primer were modified by adding CHX-encapsulated nanotubes at two distinct concentrations (10 and 20 wt.%). The experimental adhesives were evaluated by degree of conversion (DC) and viscosity. Meanwhile, only viscosity was determined for the experimental primers. The prepared HNT-encapsulated with CHX (10 and 20 wt.%) powders were incorporated into the primer and/or adhesive according to the groups: ADH (control); HNT (control); 0.2% CHX; PR+CHX10%; PR+CHX20%; ADH+CHX10%; ADH+CHX20%. Human molars were selected and autoclaved; mid-coronal dentin surfaces were exposed for bonding purposes. Dentin surfaces were etched, followed by primer and adhesive application, and restored with a resin composite. After 24 hours, the teeth were sliced into beams for µTBS testing; beams collected for each tooth were equally assigned into two testing condition groups: 24 hours and 6 months. Microtensile bond strength was tested using a universal testing machine, and the types of failure were classified as adhesive, mixed, and cohesive failure. Data from DC and viscosity tests were analyzed using one-way ANOVA. Bond strength data were analyzed by pair-wise comparisons using the Sidak method to control the overall significance level at 5% for each aging time separately. Weibull-distribution survival analysis was used to compare the differences in the microtensile bond strength results among the groups after 24 hours and 6 months. Results and Conclusion: DC analysis revealed no significant differences among adhesive groups. However, ADH group had a significantly lower viscosity than modified adhesive groups, and a significantly higher viscosity than modified primer groups. Test results of stress value (MPa) by each group for each aging time revealed no significant differences among groups after 24 hours. However, after 6-month storage, modified primer groups (PR+CHX10%, PR+CHX20%) and 0.2%CHX group showed a significant difference in µTBS compared to control groups (ADH, HNT) and modified adhesive groups (ADH+CHX10%, ADH+CHX20%) in the same aging time testing (p < 0.05). When comparing the µTBS after 24 hours and 6 months, there were no significant differences among the groups except for the ADH+CHX20% group, for which MPa values were higher after 24 hours than 6 months (p = 0.0487). In conclusion, this study has demonstrated the great potential of modified dental primers with CHX-encapsulated nanotubes in preservation of the resin-dentin bond strength over a 6-month time period. Additionally, modification of dental primers and adhesives was a successful approach that didn’t compromise the characteristics or the mechanical properties of the materials and has a promising long-term effect on resin-dentin bond strength.
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    Influence of dentrifice abrasivity and toothbrush stiffness on the development of non-carious cervical lesions
    (2016) Binsaleh, Fahad; Hara, Anderson T.; Lippert, Frank; Bottino, Marco; Cook, Norman Blaine; Diefenderfer, Kim Edward
    Background: Non-carious cervical lesions (NCCLs) can be defined as the loss of dental hard tissue near the cemento-enamel junction without bacterial involvement. Abrasion, erosion and abfraction have been mentioned as common etiological factors of NCCLs. Abrasion is the loss of tooth structure due to friction by materials such as toothbrushes or abrasives in toothpaste. In contrast, dental erosion is the loss of tooth structure driven by acids. Abfraction, on the other hand, starts due to the weakening of the tooth structure in areas of concentrated stress as a result of cuspal flexure from heavy and repeated occlusal loading, which progresses to dental hard-tissue loss. Purpose: The present study focused on the abrasion aspect of NCCLs. Specifically, it aimed to investigate the influence of dentifrice abrasivity and toothbrush stiffness on the development of NCCLs in vitro Hypothesis: NCCL development is affected by both the abrasive level of the dentifrice and the stiffness of the toothbrush, as well as their interaction. Materials and Methods: A total of 288 extracted human upper first premolars, free of any dental caries and root defects, were selected. The teeth were be cleaned with a hand periodontal scaler and randomly assigned into twelve groups (total of 24 teeth/group). Specimens were brushed in an automated toothbrushing machine, using simulated toothpaste slurries of varying abrasivity and toothbrushes of varying stiffness. This study examined three experimental factors: 1. Toothpaste abrasivity, at four levels: high, medium, low, and non-abrasive slurry (as negative control); 2. Toothbrush stiffness, at three levels: soft, medium, and hard; 3. Toothbrushing cycles at three levels: baseline, 35k, and 65k strokes. Specimens were analyzed by optical profilometry at baseline and after each brushing level. The response variable was the dentin volumetric loss, in mm3. All toothbrushes caused significantly higher tooth wear when associated to the high abrasive slurry, compared to medium- and low-abrasive slurries. Medium- caused more tooth wear than low-abrasive slurry, which in turn led to more tooth wear than the control. Hard and medium toothbrushes were not significantly different, but both caused significantly higher volumetric loss than Soft toothbrushes. There were no differences among toothbrushes, when used with the non-abrasive (control) and low- abrasive slurries. Overall, 35k strokes resulted in significantly less tooth volumetric loss than 65k.
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    Step-growth thiol-ene photopolymerization to form degradable, cytocompatible and multi-structural hydrogels
    (2014-01-17) Shih, Han; Lin, Chien-Chi; Xie, Dong; Bottino, Marco
    Hydrogels prepared from photopolymerization have been used for a variety of tissue engineering and controlled release applications. Polymeric biomaterials with high cytocompatibility, versatile degradation behaviors, and diverse material properties are particularly useful in studying cell fate processes. In recent years, step-growth thiol-ene photochemistry has been utilized to form cytocompatible hydrogels for tissue engineering applications. This radical-mediated gelation scheme utilizes norbornene functionalized multi-arm poly(ethylene glycol) (PEGNB) as the macromer and di-thiol containing molecules as the crosslinkers to form chemically crosslinked hydrogels. While the gelation mechanism was well-described in the literature, the network properties and degradation behaviors of these hydrogels have not been fully characterized. In addition, existing thiol-ene photopolymerizations often used type I photoinitiators in conjunction with an ultraviolet (UV) light source to initiate gelation. The use of cleavage type initiators and UV light often raises biosafety concerns. The first objective of this thesis was to understand the gelation and degradation properties of thiol-ene hydrogels. In this regard, two types of step-growth hydrogels were compared, namely thiol-ene hydrogels and Michael-type addition hydrogels. Between these two step-growth gel systems, it was found that thiol-ene click reactions formed hydrogels with higher crosslinking efficiency. However, thiol-ene hydrogels still contained significant network non-ideality, demonstrated by a high dependency of hydrogel swelling on macromer contents. In addition, the presence of ester bonds within the PEGNB macromer rendered thiol-ene hydrogels hydrolytically degradable. Through validating model predictions with experimental results, it was found that the hydrolytic degradation of thiol-ene hydrogels was not only governed by ester bond hydrolysis, but also affected by the degree of network crosslinking. In an attempt to manipulate network crosslinking and degradation rate of thiol-ene hydrogels, different macromer contents and peptide crosslinkers with different amino acid sequences were used. A chymotrypsin-sensitive peptide was also used as part of the hydrogel crosslinkers to render thiol-ene hydrogels enzymatically degradable. The second objective of this thesis was to develop a visible light-mediated thiol-ene hydrogelation scheme using a type II photoinitiator, eosin-Y, as the only photoinitiator. This approach eliminates the incorporation of potentially cytotoxic co-initiator and co-monomer that are typically used with a type II initiator. In addition to investigating the gelation kinetics and properties of thiol-ene hydrogels formed by this new gelation scheme, it was found that the visible light-mediated thiol-ene hydrogels were highly cytocompatible for human mesenchymal stem cells (hMSCs) and pancreatic MIN6 beta-cells. It was also found that eosin-Y could be repeatedly excited for preparing step-growth hydrogels with multilayer structures. This new gelation chemistry may have great utilities in controlled release of multiple sensitive growth factors and encapsulation of multiple cell types for tissue regeneration.