Academic literature on the topic 'Adhesive dentistry'

Subject. Dental restoration includes work on tissue restoration by filling, using inlays, veneers, and artificial crowns. Adhesive systems are used in therapeutic dentistry for working with composites, compomers and some glass-ionomer cements, for adhesive fixation of all types of indirect structures, repairing chips of composite and ceramic linings; in pediatric dentistry for sealing fissures, for fixing orthodontic structures. Currently, there are eight generations of adhesives on the market of dental materials. The first two generations of adhesives required only enamel etching and transformed the dentin layer, while the third already provided for conditioning of the dentin, and the fourth and fifth ― and all-out etching. The sixth, seventh and eighth generations of adhesives are self-etching analogues. This article presents the results of a survey of practical health care dentists in choosing an adhesive system. The goal is to evaluate the preferences of the choice of adhesive systems by dentists. Methodology. 30 dental therapists and orthopedic dentists took part in the survey. Results. The results of the questionnaire analysis showed that the majority of dentists prefer to use fifth-generation adhesives in their practice (46 %), the sixth generation of adhesive systems is in second place in popularity (31 %), followed by the "gold standard" ― the fourth generation (13 %), and the seventh (10 %) in last place. Conclusions. The fifth-generation adhesive systems surpassed the other generations in efficiency and reliability. This is why the majority of dentists surveyed chose this generation.

Composite materials based on acrylate UV-cured polymers (Bis-GMA/TEGDMA) as a matrix and reinforcements that can be selected in order to adjust the properties of the obtained composite are used in the field of dental technology. The role of reinforcement is to adjust the mechanical properties, but also to control the shrinkage during curing. As reinforcement, alumina particles doped with iron oxide (Al2O3 Fe) synthesized using the sol-gel technique were selected. In order to simulate the process of adhesive application in real conditions, in vitro testing technique and adhesion properties of synthesized adhesive were used, where tooth tissue was used as a substrate. Comparison with standard adhesives used in dentistry was used to compare adhesion. The quality of the adhesive joint was evaluated using the microhardness testing method using different loads where it is estimated how the adhesive makes a connection with the substrate. It was shown that the synthesized adhesive showed significantly enhanced adhesion compared to the standard adhesive used in dentistry (836%).

ABSTRACT Aim The goal of this study was to evaluate nanoleakage within the hybrid layer yielded by etch-and-rinse and self-etch adhesive systems, with different solvents and compositions. Materials and methods Four adhesives were applied onto 20 human dentin disks: group A: Adper Scotchbond 1XT™ (3M ESPE), group B: One Coat Bond® (Coltène Whaledent), group C: AdheSE® (Ivoclar Vivadent) and group D: Xeno-V® (Dentsply). The samples were immersed in aqueous ammoniacal silver nitrate for 24 hour, prepared and observed under field-emission scanning electron microscopy with backscattered electrons. Microphotographs were scanned and data were processed. The mean value and standard deviation were calculated. KruskalWallis and Mann-Whitney tests were used (p < 0.05). Results All the adhesives showed nanoleakage within the hybrid layer: Adper Scotchbond 1XT™ (218.5 μm ± 52.6 μm), One Coat Bond® (139.6 μm ± 79.0 μm), AdheSE® (92.7 μm ± 64.8 μm) and Xeno-V® (251.0 μm ± 85.2 μm). AdheSE® yielded less nanoleakage than Adper Scotchbond-1XT™ (p = 0.003) and than Xeno-V® (p = 0.007). No other statistically significant differences were detected. Conclusion Two-step self-etch adhesive system (AdheSE®) might contribute for lower nanoleakage deposition and thus better performance in dentin adhesion. Clinical significance The two-step self-etch adhesive system showed the lowest nanoleakage deposition compared with the other adhesive systems evaluated, which seems to indicate a better behavior when a restoration is performed in dentin and possibly can lead to a durable adhesion along time. How to cite this article Ferreira JC, Pires PT, Azevedo AF, Oliveira SA, Melo PR, Silva MJ. Influence of Solvents and Composition of Etch-and-Rinse and Self-Etch Adhesive Systems on the Nanoleakage within the Hybrid Layer. J Contemp Dent Pract 2013;14(4):691-699.

SUMMARY Objective: The purpose of this study was to evaluate the effect of reduced application times of universal adhesives on enamel bond fatigue and surface morphology of the treated enamel with constant force atomic force microscopy (AFM). Methods: Four universal adhesives—Adhese Universal (AU), Clearfil Universal Bond Quick (CU), G-Premio Bond (GP), and Scotchbond Universal Adhesive (SU)—were evaluated in a laboratory for their ability to adhesively bond resin composite to enamel. Shear bond strengths were initially determined using 15 specimens per test group for each adhesive. Shear fatigue strengths were then determined using 20 specimens per test group for each the adhesives. The fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. AFM observations, surface Ra roughness measurements, and geometric surface area evaluations of enamel surface treated with the adhesive agents were also conducted. Results: A strong relationship was found between the initial shear bond strength and shear fatigue strength for enamel surface Ra roughness but not for geometric surface area. The initial shear bond strength and shear fatigue strength of CU and GP were not influenced by different application times, unlike those of AU and SU. While the surface area of enamel treated with the adhesive agents was not significantly influenced by different application times and type of adhesive, surface Ra roughness of the enamel in the AU and SU groups significantly increased with increasing application time, unlike CU and GP. Conclusions: The results of this study suggest that universal adhesives, used with reduced application times, have adequate Ra surface roughness to provide sufficient resistance to enamel bond fatigue at application times from &lt;1 second to 20 seconds, while the geometric surface area of adhesive-treated enamel did not show any significant changes at these different application times.

The phenomena of adhesion and cohesion are reviewed and discussed with particular reference to dentistry. This review considers the forces involved in cohesion and adhesion together with the mechanisms of adhesion and the underlying molecular processes involved in bonding of dissimilar materials. The forces involved in surface tension, surface wetting, chemical adhesion, dispersive adhesion, diffusive adhesion, and mechanical adhesion are reviewed in detail and examples relevant to adhesive dentistry and bonding are given. Substrate surface chemistry and its influence on adhesion, together with the properties of adhesive materials, are evaluated. The underlying mechanisms involved in adhesion failure are covered. The relevance of the adhesion zone and its importance with regard to adhesive dentistry and bonding to enamel and dentin is discussed.

Aim: The aim of this study was to evaluate a new method for measuring the retention values of different denture adhesives. Methods: The adhesive strength values of three different commercial denture adhesives (Corega powder, Corega adhesive tape and Ultra Corega cream) were evaluated using three different moisturizing agents (distilled water, artificial saliva and natural saliva). The adhesive test was performed on a universal testing machine, after applying the adhesive products to acrylic resin specimens, under two different test conditions (wetting or dipping). Tensile bond strength values in MPa were obtained for each denture adhesive presentation and test condition. Viscosity of the denture adhesives mixed with the different moisturizing agents was determined using a rotary rheometer. Maximum viscosity values were analyzed using the one-way ANOVA test. Tensile bond strength data was analyzed using Kruskal-Wallis and the Tukey’s test. Pooled data of each denture adhesive presentations for all test conditions was also carried out. Correlation between viscosity and pooled tensile strength values was analyzed through linear regression analysis. A significance level of α=0.05 was set for all analyses. Results: Results showed that statistically higher adhesion strength was obtained with tape and cream adhesives when using natural saliva as moisturizing agents (p<0.05). The adhesive strength values obtained with the dipping method were similar to those obtained with the conventional wetting method. The denture retention strength was influenced by both the denture adhesive type and moisturizing agent used. Conclusion: The dipping method showed to be a reliable test capable to simulate the oral conditions and should be better explored in further studies.

Restorative dentistry is based on a continuous development of materials that make the best possible connection with dental tissues. Thus, dental adhesives have been researched with increasing interest. A successful adhesive system depends very much on its chemistry, as well as on the clinical procedures that must be appropriate for that type of dental adhesive. This review presents a retrospective of dental adhesives focusing on research into new types of adhesive systems that involves the use of nanoparticles. Dental adhesive systems are used in most clinical procedures related to restorative dentistry and can be classified into “etch-and-rinse” adhesives and “self-etch” adhesives. Recently, both types of adhesive systems have been modified, being loaded with different types of nanoparticles to try to improve them in terms of the thickness of the adhesive layer, but also to induce other special qualities. Therefore, in order to avoid compromising the restorative procedures by losing the restorations or by affecting the dental pulp due to cytotoxicity, several factors must be considered in choosing the adhesive system.

According to the ‘Adhesion–Decalcification’ concept, specific functional monomers within dental adhesives can ionically interact with hydroxyapatite (HAp). Such ionic bonding has been demonstrated for 10-methacryloyloxydecyl dihydrogen phosphate (MDP) to manifest in the form of self-assembled ‘nano-layering’. However, it remained to be explored if such nano-layering also occurs on tooth tissue when commercial MDP-containing adhesives (Clearfil SE Bond, Kuraray; Scotchbond Universal, 3M ESPE) were applied following common clinical application protocols. We therefore characterized adhesive-dentin interfaces chemically, using x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), and ultrastructurally, using (scanning) transmission electron microscopy (TEM/STEM). Both adhesives revealed nano-layering at the adhesive interface, not only within the hybrid layer but also, particularly for Clearfil SE Bond (Kuraray), extending into the adhesive layer. Since such self-assembled nano-layering of two 10-MDP molecules, joined by stable MDP-Ca salt formation, must make the adhesive interface more resistant to biodegradation, it may well explain the documented favorable clinical longevity of bonds produced by 10-MDP-based adhesives.

Abstract Objective Bonding to different dentin substrates influences resin composite restoration outcomes. This study investigated the influence of different adhesion protocols on the shear bond strength of universal adhesive systems to sound and artificial caries-affected dentin (CAD). Materials and Methods Occlusal enamel of 80 premolars were wet grinded to obtain flat midcoronal dentin. Specimens were equally divided according to the substrate condition: sound and CAD by subjecting to pH-cycling for 14 days. Each dentin substrate was bonded with the adhesive systems used in this study: Single Bond universal adhesive or Prime&Bond universal (applied either in etch-and-rinse or self-etch adhesion protocol). Adhesive systems were utilized according to manufacturers’ instructions, then resin composite was built up. Specimens were tested for shear bond strength. The data were analyzed by three-way analysis of variance, and failure modes were determined using stereomicroscope. Results There was no statistically significant difference between the two tested adhesive systems on artificially created CAD with different adhesion protocols. On sound dentin, Single Bond universal, either in the etch-and-rinse or self-etch adhesion protocols, revealed higher statistically significant shear bond strength mean values compared with CAD. Conclusion Single Bond universal adhesive in an etch-and-rinse adhesion protocol improved only bonding to sound dentin, while no added positive effect for the etching step with Prime&Bond universal adhesive was found when bonded to both sound and CAD substrates. The influence of CAD on the performance of the universal adhesives was material-dependent.

2012/2013
The subject of this thesis is the stability of the adhesive interface in dentistry. Success in adhesive dentistry means long lasting restorations. However, there is substantial evidence that this ideal objective is not achieved. Current research in this field aims at increasing the resin-dentin bond durability. This doctoral research examines the fundamental processes responsible for the aging mechanisms involved in the degradation of resin-bonded interfaces, as well as some potential approaches to prevent and counteract this degradation. Resin-dentin bond degradation is a complex process that is not completely understood, involving the hydrolysis of both the resin and the collagen component of the hybrid layer. The hydrophilic and acidic characteristics of current dentin adhesives have made hybrid layers highly prone to water sorption, which causes polymer degradation and results in decreased resin-dentin bond strength over time. These unstable polymers inside the hybrid layer may result in an incomplete encapsulation of collagen fibers, which become vulnerable to mechanical and hydrolytical fatigue, as well as degradation by host-derived proteases with collagenolytic activity. These enzymes, such as matrix metalloproteinases (MMPs) and cysteine cathepsins, have a crucial role in the degradation of type I collagen, the organic component of the hybrid layer. The first part of this thesis aims to review the current knowledge regarding adhesion to the tooth substrate (Chapter 1), focusing on the fundamental processes that are responsible for the degradation of the adhesive interface (Chapter 2). Since the permeability of adhesives to water is particularly evident in simplified adhesive formulations, the research activity was focused on self-etch and universal adhesive systems’ behavior. Thus, the research study reported in Chapter 3 showed that the bond strength and nanoleakage expression of two-step and one-step self-etch tested bonding systems were affected by storage for 6 month and 1 year in artificial saliva. Although it is generally accepted that the permeability of adhesives to water is particularly evident in simplified adhesive formulations, the stability over time was not related to the number of steps of bonding systems, but to their chemical formulations. The performance of a new universal (or multi-mode) adhesive system through storage in artificial saliva was also investigated. The original results presented in Chapter 4 found that improved bonding effectiveness of the tested universal adhesive system on dentin was obtained when the adhesive was applied with the self-etch approach. Indeed, the etch-and-rinse approaches tested (both on wet and dry dentin) resulted in immediate bond strength comparable to the self-etch mode but expedited long-term aging resulted in reduced bond strength and increased nanoleakage expression, irrespective of dentin wetness. Moreover, the results of the zymographic analysis showed evident changes in dentinal MMP-2 and -9 enzyme activities after the application of the tested adhesives, revealing differences in the extent of enzyme activation. These findings exhibit that the activation of endogenous MMPs is not related to the adhesive system or the strategy employed. Thus, regardless of the approach and the material used in bonding procedures, a stable and durable bond is not achieved. Therefore, experimental strategies that aim to enhance the adhesive interface, particularly improving the durability of the resin-dentin bond strength by inhibiting intrinsic collagenolytic activity and increasing the resistance of dentin collagen matrix to enzymatic degradation are needed. The last part of the thesis is focused on both the strategies to inhibit the proteolytic and collagenolytic activity of the endogenous proteases and the methods to increase the mechanical strength of collagen network and its resistance to enzymatic degradation (Chapter 5). Chlorhexidine (CHX) has been used as a non-specific MMP inhibitor to prevent degradation of hybrid layers. However, CHX is water-soluble and may leach out of hybrid layers, compromising its long-term anti-MMP effectiveness. An entirely different approach is to treat the acid-etched dentin containing activated matrix-bound MMPs with cross-linking agents that inactivate the catalytic site of proteases. In particular, the ability of a cross-linker agent, 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide (EDC), to prevent collagen degradation was evaluated under occlusal cycle loading. Previous research successfully utilized EDC to increase the durability of resin-dentin bonds by increasing the mechanical properties of the collagen matrix; however, the 1 to 4 hrs required for that procedure was clinically unacceptable. For this reason, the purpose of the last part of the research, presented in Chapter 6, was to evaluate the ability of 0.5 M EDC short-time (1 min) pre-treatment to improve the stability of demineralized dentin collagen matrices by quantifying the release of telopeptide fragments over time. The results showed that EDC application for 1 min may be a clinically relevant and effective means for stabilizing the collagen network not only by strengthening the fibrils, but also by reducing the enzymatic degradation rate. Thus, dentin collagen reinforcement and strengthening through EDC cross-linking might be of importance to improve the bond strength and structural integrity of the resin-dentin interface over time against the enzymatic and hydrolytic degradation.
La tesi qui presentata riguarda la stabilità dell'interfaccia adesiva in odontoiatria. Il successo delle moderne terapie conservative è rappresentato dalla longevità dei restauri adesivi. Tuttavia, vi è una sostanziale evidenza che questo obiettivo ideale non sia raggiunto. La stabilità dell’interfaccia adesiva dipende dalla formazione di uno strato ibrido, compatto e omogeneo, durante l’impregnazione del substrato dentinale da parte dei monomeri adesivi. Poiché lo strato ibrido rappresenta un’entità complessa, in cui interagiscono componenti biologiche diverse (matrice dentinale collagenica e cristalli d’idrossiapatite residui) e non (monomeri resinosi e solventi), i fenomeni d’invecchiamento interessano in maniera sinergica sia la porzione resinosa che quella dentale. L’articolato processo che porta alla degradazione dell’interfaccia adesiva coinvolge infatti la componente resinosa, attraverso l’idrolisi della resina negli spazi interfibrillari, e quella organica, attraverso la disorganizzazione delle fibre collagene dovuta ad un incompleto incapsulamento delle stesse, nonché alla degradazione da parte di proteasi intrinseche con attività collagenolitica. È stato dimostrato come questi enzimi, le metalloproteinasi della matrice (MMP) e le catepsine, abbiano un ruolo cruciale nella degradazione del collagene di tipo I, la principale componente organica dello strato ibrido. Inoltre le caratteristiche idrofile e acide degli attuali sistemi adesivi dentinali hanno reso lo strato ibrido molto suscettibile all'assorbimento di acqua, comportando, attraverso l’idrolisi, la degradazione dello stesso e andando così a contribuire ad una diminuzione della forza di legame nel tempo. Attualmente l’interesse della comunità scientifica mira ad aumentare la durata del legame adesivo con il substrato dentinale. Dopo un’attenta analisi delle attuali conoscenze riguardanti adesione al substrato dentale (Capitolo 1), la prima parte della tesi si propone di valutare i processi fondamentali che sono responsabili della degradazione dell'interfaccia adesiva (Capitolo 2). Poiché la permeabilità all’acqua degli adesivi è particolarmente evidente nelle formulazioni semplificate, l'attività di ricerca si è concentrata sull’analisi del comportamento dei sistemi adesivi self-etch e dei recenti sistemi adesivi universali. I risultati riportati nel Capitolo 3 ha dimostrato come la forza di legame e l’espressione del nanoleakage dei sistemi adesivi self-etch two-step e one-step testati sia negativamente influenzata dall’invecchiamento in saliva artificiale per 6 mesi e 1 anno. Sebbene sia generalmente accettato che la permeabilità degli adesivi all'acqua è particolarmente evidente in formulazioni di adesivi semplificati, la stabilità nel tempo non è stata correlata al numero di passaggi dei sistemi adesivi, bensì alle loro composizioni chimiche. Sono state in seguito analizzate anche le prestazioni di un nuovo sistema adesivo universale (o multimodale). I risultati presentati nel Capitolo 4 hanno stabilito una migliore efficienza adesiva del sistema universale, testato sul substrato dentinale, quando l'adesivo è stato applicato con l'approccio self-etch. Infatti, la tecnica etch-and-rinse, testata sia su dentina umida che secca, ha comportato una forza di adesione immediata paragonabile alla modalità self-etch, ma a tempi di invecchiamento incrementali si è evidenziata una diminuzione della forza di legame e una maggiore espressione del nanoleakage, a prescindere dalla condizione di umidità dentinale. Inoltre, i risultati dell'analisi zimografica hanno mostrato evidenti variazioni dell’attività enzimatica delle metalloproteinasi MMP-2 e -9 dopo l'applicazione degli adesivi testati. Questi risultati dimostrano come l'attivazione delle MMP endogene non sia correlata al sistema adesivo o alla strategia adottata. Ne evince che, indipendentemente dal metodo e dal materiale utilizzato nelle procedure adesive, non si è in grado di stabilire un legame affidabile e duraturo. Pertanto si avverte l’esigenza di strategie sperimentali che mirino a migliorare la stabilità dell’interfaccia adesiva, in particolare incrementando la durata della forza di legame in dentina inibendo l'attività collagenolitica intrinseca e aumentando la resistenza del collagene alla degradazione enzimatica. L'ultima parte della tesi è focalizzata quindi sulle strategie per inibire l'attività proteolitica e collagenolitica delle proteasi endogene e sui metodi per aumentare la resistenza meccanica del collagene alla degradazione enzimatica (Capitolo 5). Un potente agente antibatterico, la clorexidina (CHX), è stato usato come inibitore non specifico delle MMP al fine di impedire la degradazione dello strato ibrido. Tuttavia la CHX, essendo solubile in acqua, può dissolversi nello strato ibrido, compromettendo la sua efficacia anti-MMP a lungo termine. Un approccio completamente diverso è quello di trattare la dentina mordenzata con agenti cross-linker. In particolare, simulando il carico occlusale, è stata valutata la capacità di un agente cross-linker, l’1-etil-3-(3-dimetilammino-propil) carbodiimmide (EDC), per prevenire la degradazione del collagene. Precedenti ricerche hanno utilizzato con successo l’EDC con lo scopo di aumentare la durata dell’interfaccia adesiva, aumentando le proprietà meccaniche della matrice di collagene; tuttavia, il tempo necessario (da 1 a 4 ore) richiesto per tali procedure è clinicamente inaccettabile. Per questo motivo, lo scopo dell’ultima parte della ricerca, presentata nel Capitolo 6, è stato quello di valutare la capacità di 0,5 M EDC nel breve periodo di pretrattamento (1 min), andando a quantificare il rilascio di frammenti di telopeptidi di collagene nel corso del tempo. I risultati hanno dimostrato che l'applicazione di EDC per 1 min può essere un approccio clinicamente rilevante ed efficace nello stabilizzare il collagene, non solo rafforzando le fibrille, ma anche riducendo la velocità di degradazione enzimatica. Di conseguenza, l’utilizzo di questo cross-linker può garantire una valida strategia per migliorare la forza di legame e l'integrità strutturale dell'interfaccia adesiva nel tempo contro l’attività enzimatica intrinseca del collagene e la degradazione idrolitica.
XXVI Ciclo
1985

Objective: To assess the effects of ceramic opacity and thickness on delivered radiant exposure and degree of conversion and microhardness of the light-cured resin cement. Materials and Methods: IPS e-Max ceramic discs (Ivoclar Vivadent) were fabricated in 3 thicknesses (0.5, 1.0, and 1.5mm) and 4 opacities (HT, LT, MO, HO) (n=3/per group). Light-cured resin cement (Variolink Veneer Luting Cement - shade MVO, Ivoclar Vivadent) 50µm thick was cured through these ceramics disks using a quartz tungsten halogen curing light unit (Optilux 501, Kerr) with its radiant exposure measured by MARC from a fixed distance (1.5mm). Knoop microhardness was used to evaluate the bottom degree of cure and was correlated with the radiant exposure deliverd. Descriptive statistics were conducted. One- and two-way ANOVA with post-hoc Tukey's HSD test, Pearson correlation test, the simple linear regression analysis were used for the statistical analyses (alpha=0.05). Results: Significant interaction was found between ceramic thickness and opacity on radiant exposure (p=0.0078). Subsequent analyses demonstrated that there was a significant simple effect for opacity and for thickness on radiant exposure under different conditions of thickness and opacity. A significant relationship was found between resin cement microhardness and radiant exposure (p=0.0001) below 4.5 J/cm2. Moreover, the Pearson correlation coefficient of 0.93 indicated a strong correlation between the two variables below 4.5 J/cm2 of radiant exposure delivered. Conclusion: Ceramic opacity and thickness affect the polymerization of light-cured resin cements and need to be considered and compensated for when bonding indirect restorations. Based upon the findings of this preliminary study, the final study is ongoing.

Purpose: This study evaluated microleakage associated with cast restorations that were luted with a resin-modified glass ionomer cement (RelyX) following obturation of the dentinal tubules with either a desensitizing agent (Gluma Desensitizer) or an adhesive system (Scotchbond Multipurpose Dental Adhesive). The effect of acid etching on the removal of the smear layer and its influence on the extent of microleakage associated with the adhesive system was also evaluated. Materials and Methods: Extracted mandibular premolars (N = 48) were prepared for complete cast restorations and divided into 4 groups (N = 12). In group A ( control), neither a desensitizing agent or a component of the adhesive system was applied prior to luting. In group B, Gluma Desensitizer was used to obturate the dentinal tubules. In group C, Scotchbond Multipurpose Dental Adhesive System was applied to tooth preparations according to the manufacturer's instructions. Tooth preparations in group D received the same dentin surface treatment as in group C, but no acid etching was performed. Cast restorations in all 4 groups were then luted with the resin-modified glass ionomer luting cement RelyX. All specimens were subjected to thermocycling between 8° and 55°C for 500 cycles in water baths, placed in a solution of 0.5% basic fuchsin dye for 24 hours, and then sectioned twice longitudinally, once mesiodistally and then buccolingually. All specimens were examined at X30 magnification with a stereomicroscope equipped with a digital camera. Photographs of all sections were made and the extent of microleakage along the tooth-cement interface was measured in millimeters using an image analysis software. Microleakage was perceived to have occurred along a segment of the tooth-luting cement interface when dye penetration from that segment into the dentinal tubules was detected. One-way analysis of variance (α = 0.05) was performed to identify differences in mean microleakage among the luting groups, followed by Tukey's Honestly Significant Difference Test for pairwise comparisons. Results: Large standard deviations were found in all 4 groups. No statistically significant difference was found among the control (0.64 ± 0.50 mm), Gluma Desensitizer (0.42 ± 0.24 mm), and Scotchbond Multipurpose without etching (0.67 ± 0.40 mm) groups. However, a statistically significant difference was found between the Scotchbond Multipurpose with etching (1.51 ± 0.92 mm) group and each of the other groups. Conclusions: The large standard deviations obtained implied a marked amount of variability in microleakage within each group, which might be the result of the small sample size used. The increase in microleakage when 35% phosphoric acid was used prior to dentin bonding is difficult to explain. Within the limitations of the study, the results suggest that the use of a nonpolymerizing, resin-based (Gluma Desensitizer) material or a photopolymerizing, resin-based (Scotchbond Multipurpose) system without etching had no effect on microleakage under cast restorations luted with the resin-modified glass ionomer luting cement RelyX. The increase in microleakage when etching with 35% phosphoric acid was preformed might be explained by the phenomenon known as nanoleakage, but further investigation is recommended in this area.

Oral Biology
M.S.
Objectives: While bracket debonding has been explored through shear bond-strength tests with debonding linked to the type of material used, the technique of adhesive application, and contamination, the contribution of internal voids in orthodontic adhesives is unknown. Voids may result in fracture or bond-failure, either within the adhesive or at the tooth-adhesive-bracket interfaces. The aim of this thesis is to quantify the internal volumetric voids and bonding strength of three generations of bracket adhesives. Methods: Extracted third molars were bonded with three groups of orthodontic brackets including conventionally-pasted (CP), pre-coated (PC), or pre-coated flash-free (FF) (n=5 per group). The three-dimensional internal structure of the adhesive was evaluated with Micro Computed Tomography (micro-CT) using the Skyscan micro-CT (maximum resolution of 5 microns). Data from the micro-CT were analyzed with SkyScan software to perform 3D reconstructions, image processing, and qualitative and quantitative analysis of the adhesive’s structure. The amount of void was determined by measuring the percentage of voids at the bonded interfaces (Vint) and within the adhesive (Vbulk). The total amount of void was also calculated (Vtot= Vint+ Vbulk). Differences in void between the groups were assessed using one-way ANOVA with post-hoc Tukey tests (α=0.05). The bonding strength of the three adhesives systems was evaluated via shear bond strength tests. Results: Our void quantification results showed that FF brackets had a statistically higher (p0.05) for any the analyzed locations (Vint, Vbulk). Our results indicate the majority of voids were found at bonded interfaces (Vint) compared to within the bulk (Vbulk) for all three groups, with statistically significant (p<0.05) differences for CP and FF. Our bonding strength evaluation revealed the pre-coated group (PC) to have on average the highest bond strength compared to conventionally-pasted (CP) and pre-coated flash-free (FF) groups. Conclusions: The overall amount of void in the pre-coated flash-free adhesive brackets is significantly higher compared to conventionally-pasted and pre-coated groups. The majority of the void was identified to be located at the bonded interfaces (tooth/adhesive and bracket/adhesive) rather than within the bulk of the adhesive for all groups. Our bonding strength results indicate the pre-coated brackets to have the highest bond strength compared to pre-coated flash-free and conventionally-pasted. Our preliminary set of results indicate an inverse relationship between bonding strength and amount of void of brackets adhesives, with the pre-coated exhibiting the highest bond strength and least void. However, due to a limited sample size additional data are needed to validate these conclusions and find solid relationships between adhesive voids and bonding strength.
Temple University--Theses

The objective of this work was to develop a short-term, clinically simulative, biofilm-based aging/storage model for lab testing of newer dental adhesives in order to predict their long-term performance. To do this we tested the hypothesis that 15 days of biofilm challenge with cariogenic bacterial species, Streptococcus mutans (SM) and Streptococcus sobrinus (SS), would produce similar or a greater reduction in microtensile bond strength (μTBS) of dental adhesives as compared to a standard 6 months of water storage (WS). Thirty-one molars were flattened to dentin, restored using Optibond-FL adhesive and Z-100 dental composite, sectioned and trimmed into four dumbbell-shaped specimens and randomly distributed according to aging conditions (n=31): A) Water storage for 6 months, B) Water storage for 5.5 months + S. mutans-biofilm challenge for 15 days, C) S. mutans-biofilm challenge for 15 days and D) S. sobrinus-biofilm challenge for 15 days. Specimens were gripped centrally with respect to the test axis with a non-gluing passive gripping device. Microtensile bond strength testing was performed using a Zwick Material Testing Machine at a crosshead speed of 1 mm/min and failure modes were classified using light microscopy. Mixed model ANOVA and Weibull regression analysis revealed that the type of storage condition significantly affected the microtensile bond strength (p<0.0001). Mean microtensile bond strength observed within group A (49.69 ± 15.53MPa) was significantly higher than those in groups B (19.26 ± 6.26MPa), C (19.92 ± 5.86MPa) and D (23.58 ± 7.88MPa). Also, microtensile bond strength obtained with group D was significantly greater than that with groups B and C, while no difference was seen between the latter two groups. Chi-square statistical analysis indicated that specimens from groups B (74.2%), C (83.9%) and D (80.6%) were more likely to have cohesive failures in dentin than specimens from group A (54.8%). Within the limitations of the study, it can be concluded that 15 days of Streptococcus mutans- and Streptococcus sobrinus- based biofilm challenge produced more reduction in microtensile bond strength of dental adhesive than 6 months of water storage and appear to be a promising in vitro accelerated aging model.

The data of modern research on adaptation processes and our own research on ways to improve adaptation to removable dentures are summarized. The material is illustrated by drawings. The manual is intended for students of dental faculties, clinical residents, graduate students, teachers and dentists.

Adhesive systems are used in many specialties in dentistry. These systems provide chemical attachment of prosthetic and restorative materials to the tooth surface. The first stage of adhesive systems is the etching process. In the commonly used Total etch systems, acid agent is applied to the tooth first to create roughness on the tooth surface, then the applied bond agent enters this rough surface to ensure retention. The acid agent used is 37% phosphoric acid gel. Normally, phosphoric acid is liquid. It should be applied in gel form in order to be applied in a controlled manner to a certain surface of the tooth and to remain on the desired surface for a long time. Commercially used phosphoric acid gels are produced by a single method and contain the carbomer chemical. Another way to produce gel is silicium dioxide. Acid gels produced with carbomer have a glossy appearance, while acids produced with Silicium have a matte appearance. In this study, we aimed to see the difference in retention of the phosphoric acid gel produced with silicium dioxide compared to the carbomeric acid gel. In this study, we prepared phosphoric acid gel with silicium dioxide and phosphoric acid with carbomer. In our study, 50 extracted caries-free human teeth were used. Orthodontic buttons were attached to the buccal surfaces of the teeth in 2 groups. Phosphoric acid gel prepared with Carbomer was applied for 40 seconds on 25 teeth and phosphoric acid gel prepared with silicium dioxide for 40 seconds on 25 teeth. Afterwards, the teeth were washed with water for 10 seconds and dried, and the orthodontic buttons were adhered with blue light for 40 seconds with Tokuyama bond and flowable composite, and a tensile test was applied to them. There was a statistically significant difference between the tensile force resistance of the buttons attached with two different methods. The teeth in which the gel prepared with silicium dioxide was used showed an average of 6% more resistance to tensile force than the other group. In this study, adhesion strength was measured for the first time by changing the gel base material in acid. We recommend this preparation of acids in adhesive systems, and we believe it can be beneficial for all dentists.

This work is focused on the experimental investigations for wear properties of rapid tooling with nano scale fillers for grinding applications. The rapid tooling has been prepared by using composite material feed stock filament (consisting of Nylon6 as a binder, reinforced with biocompatible nano scaled Al2O3 particles on fused deposition modeling (FDM) for the development of grinding wheel having customized wear resistant properties. A comparative study has been conducted under dry sliding conditions in order to understand the tribological characteristics of FDM prints of composite material and commercially used acrylonitrile butadiene styrene (ABS) material. This study also highlights the various wear mechanisms (such as adhesive, fatigue and abrasive) encountered with newly prepared composite material while grinding. The FDM printed parts of proposed composite material feedstock filament are more suitable for grinding applications especially in clinical dentistry.