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Aim: To assess the Vickers hardness of plastic brackets, after in vitro aging. The morphology and structure of corresponding retrieved brackets were also studied to assess the reliability of in vitro set-up in imposing effects comparable to intraoral aging., Materials and Methods: Four types of plastic brackets were selected. Specimens were immersed in a buffer solution to induce artificial aging; brackets of two groups were retrieved after orthodontic treatment. The wings of brackets were subjected to Knoop hardness testing, and scanning electron microscopy was employed to study the morphology and microstructure of retrieved brackets. The results were statistically analyzed by two-way analysis of variance and Tukey test (alpha = 0.05)., Results: Differences were identified between the brands of brackets, but not between the new and in vitro-aged appliances. The retrieved appliances showed significant reduction in hardness when compared with their as-received counterparts. Evidence of degradation was seen in the retrieved appliances., Conclusions: The inability of ex vivo experimental configuration to simulate clinical conditions is stressed; several clinical implications related to torque control, friction, and tie-wing strength of brackets are discussed.

The purpose of this study was to qualitatively and quantitatively characterize the substances released from orthodontic brackets and nickel-titanium wires and to comparatively assess the cytotoxicity of the ions released from these orthodontic alloys. Two full sets of stainless steel brackets of 20 brackets each (weight 2.1 g) and 2 groups of 0.018 x 0.025 Ni-Ti archwires of 10 wires each (weight 2.0 g) were immersed in 0.9% saline solution for a month. The immersion media were analyzed with inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and the ionic content was statistically analyzed with 1-way analysis of variance (ANOVA). Human periodontal ligament fibroblasts and gingival fibroblasts were exposed to various concentrations of the 2 immersion media; nickel chloride was used as a positive control for comparison purposes. The cytotoxic or cytostatic activity of the media was investigated with the MTT and the DNA synthesis assays. The results of the cytotoxicity assay were analyzed with 2-way ANOVA and the Tukey test with solution and concentration variants as discriminating variables (alpha=0.05). The results indicated no ionic release for the nickel-titanium alloy aging solution, whereas measurable nickel and traces of chromium were found in the stainless steel bracket-aging medium. Concentrations of the nickel chloride solution greater then 2 mM were found to reduce by more than 50% the viability and DNA synthesis of fibroblasts; however, neither orthodontic materials-derived media had any effect on the survival and DNA synthesis of either cells.

The purpose of this study was to assess the chemical composition, structure and degree of double bond conversion of retrieved bone cement from 29 total hip replacement revision arthroplasties, employing a multi-technique approach. Scanning electron microscopy revealed a porous cement surface, which replicated the characteristics of bone or femoral stem surface irregularities. Fourier transform infrared spectroscopy indicated that the retrieved bone cement samples were covered by a well-organized proteinaceous film rich in amides and alcohols, probably because of the adsorption of species from body tissues and fluids. X-ray fluorescence spectrometry showed the presence of potassium, sodium, calcium and phosphorus, implying the development of a mineralization process of the adsorbed biofilm. X-ray microtomography demonstrated a dense porous network in the bulk material comprised of macropores with a mean diameter >1 mm. FTIR analysis of the degree of double bond conversion of retrieved samples was in the order of 70%, similar to that of samples prepared in vitro in air, but 30% lower relative to their counterparts mixed in vitro and set in water. The effect of the adsorption of species onto bone cement surface on the reactivity of the material with the surrounding tissues and materials, is currently unknown. The results of this investigation reveal that the in vivo aging pattern of bone cements may involve alterations, which cannot be simulated under current in vitro protocols, emphasizing the necessity for adopting in vivo approaches including retrieval studies in assessing bone cement properties., (Copyright 2003 Kluwer Acadamic Publishers)

Aim: The purpose of the present study was to investigate the composition and to assess the microhardness and structure of as received, retrieved, and recycled stainless steel brackets., Materials and Methods: New, used, and recycled brand-, slot size-, and prescription-matched appliances were subjected to scanning electron microscopy (SEM), energy dispersive (EDS) electron probe microanalysis, metallographic analysis, and Vickers microhardness testing. Elemental analysis was performed on randomly selected bulk material base and wing areas. Basic metal content and microhardness results were statistically analyzed using a two-way ANOVA and the Tukey test, with treatment (as received, retrieved, and recycled) and bracket region (base, wing) serving as discriminating variables (alpha = 0.05)., Results: The results showed that there was no alteration in the bulk composition of the brackets among the three conditions. In contrast, differences were noted between bracket base and wing with respect to elemental composition among all groups, implying that the base and wings were manufactured from different alloys. The metallographic etching identified no difference in grain structure between the bracket base and wing components for all groups, regardless of treatment. Vickers microhardness demonstrated significant differences in hardness between base and wing for all groups and between recycled and retrieved states for the wing component.

The purpose of this study was to qualitatively and quantitatively assess the nickel, chromium, and ferrous levels in a population of 17 orthodontic patients undergoing treatment, compared with seven untreated individuals, employing a novel methodological approach and a new analytical technique. Salivary samples obtained from patients before and after rinsing with double distilled water were processed for Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) for simultaneous estimation of the concentration of the metallic elements. No statistically significant difference was detected between control and patient groups with respect to salivary metal content, regardless of element. The range of salivary metal levels found did not exceed those of daily intake through food and air. The lack of a continuous monitoring scheme for salivary metal concentrations in real time may impose substantial obstacles to defining the release rate of metals in vivo. The results of this study emphasize the necessity of incorporating the dimension of time in assessing the release potential of orthodontic alloys.

Objective: To evaluate the in vivo vs the in vitro anticariogenic potential of glass-ionomer and resin composite restoratives, utilizing a standardized interfacial gap model., Methods: (a) In vitro study. Box shaped cavities were prepared at the buccal surfaces of extracted premolars limited to enamel. The incisal cavity walls received no treatment and were covered with 40 microm-thick metal spacers. The cavities were restored with a glass-ionomer (Ketac-Fil, n=8) and a fluoride-free resin composite (Scotchbond MP Plus/Z100, n=8). After 4 weeks immersion in an acidic gel (pH 4), thin sections were produced and examined under polarized-light microscopy.(b) In vivo study. Four low caries activity volunteers, with first four premolars, each planned to be extracted for orthodontic reasons, participated in the study. Cavities were prepared as before and filled contralaterally per patient with glass-ionomer (n=8) and resin composite (n=8). After 6 months in vivo, the teeth were extracted, sectioned and investigated by polarized-light microscopy, Raman microspectroscopy and SEM-EDS X-ray microanalysis. Unpaired t-test (lesion dimensions) and one-way ANOVA and Newman-Keuls tests (Ca, P wt%, Ca/P ratios) were used to identify statistically significant differences in lesion analysis (alpha=0.05)., Results: (a) In vitro study. All restorations developed lesions at incisal and cervical margins. At gap-free regions glass-ionomers showed reduced lesion dimensions compared to those of composites (p<0.05). At regions with gaps, no significant differences were found in lesion depth between the restorative groups tested. Lesion length was increased in composite, and decreased in glass-ionomer, whereas lesion depth in both restorative groups was increased in comparison to gap-free regions (p<0.05).(b) In vivo study. No lesions were observed at gap-free regions. At gap regions, 75.5% of glass-ionomer and 62.5% of composite restorations developed lesions. The lesion dimensions were significantly greater in glass-ionomer (p<0.05). A reduction in PO4(3-), CO3(2-), Ca and P was found in lesions compared to intact tissues. No F was detected and no CaF2 lattice vibrations were found at the enamel margins facing the gap adjacent to glass-ionomers., Significance: In the presence of a standardized interfacial gap, no preventive effect was exerted in vivo from the glass-ionomer to protect the adjacent enamel wall from secondary caries attack. The lack of any correlation between the in vivo and in vitro models tested implies that artificial caries experiments have a negligible clinical relevance in predicting the in vivo effect.

The purpose of this study was to investigate the composition of as-received, retrieved, and recycled stainless steel brackets. New, used, and recycled brand-matched, slot size-matched, and prescription-matched appliances were subjected to scanning electron microscopy and energy dispersive electron probe microanalysis. Elemental analysis was performed on randomly selected surface bracket base and wing areas, and metal content was statistically analyzed with the 2-way ANOVA and the Tukey test, with treatment (as-received, retrieved, and recycled) and bracket regions (base and wing) serving as discriminating variables (alpha = 0.05). The results showed that there was no difference in the surface composition of the base; however, surface area-wing analysis indicated that nickel content was decreased in retrieved and recycled specimens, implying that an ionic release effect occurred in vivo. Differences were noted between bracket base and wing with respect to elemental composition for the same brackets, implying that the base and wings are manufactured from different alloys.

The purpose of this study was to investigate the reactivity with water of a moisture-insensitive orthodontic primer (Transbond MIP), in conjunction with a no-mix orthodontic adhesive (Unite), and a moisture-insensitive adhesive (Smartbond), and to assess their bond strength to wet and saliva-contaminated enamel relative to the conventional application of the no-mix adhesive. The reactivity of the moisture-insensitive products with water was investigated by micro-multiple internal reflectance Fourier transform infrared spectroscopy (micro-MIR FTIR). Sixty premolars were divided into two groups of 30 teeth each and, on the buccal enamel surfaces, a standardized volume (0.1 ml) of water or fresh whole saliva was applied. Standard edgewise stainless steel brackets were then bonded to enamel surfaces as follows: (a) Unite, (b) Unite with the Transbond MIP, and (c) Smartbond. The brackets were debonded under shear force at a speed of 2 mm/min and the debonded enamel surfaces were subjected to fractographic analysis. The statistical analysis of the bond strength values was performed by two-way ANOVA with condition (water, saliva) and adhesive type serving as discriminating variables (n = 10, alpha = 0.05). The results of the fractographic analysis were evaluated by chi 2 test (alpha = 0.05). FTIR analysis showed that only Smartbond set in the presence of water. Application of water in Transbond MIP increased the extent of carboxyl ionization without inducing any setting reaction. Transbond MIP did not improve bond strength values when combined with the no-mix adhesive. Most adhesive-enamel condition combinations showed a trend to present lower bond strength in the presence of saliva; however, this was not confirmed statistically. Fractography of enamel and bracket base surfaces showed that Unite + Transbond MIP resulted in the most adhesive fractures (leaving no resin on enamel surface), whereas Smartbond presented the highest frequency of cohesive fractures (adhesive left on bracket and enamel surfaces).

Objectives: The purpose of this study was to investigate whether monomer separation occurs in single-bottle adhesives applied on acid-etched dentin surfaces., Methods: Smear-layer covered dentin specimens produced from sound premolars, were acid-etched and analyzed by micro-MIR FTIR spectroscopy, before and after treatment with the single-bottle adhesives One-Step, Prime and Bond 2.1, Scotchbond 1 and Syntac-Sprint. The difference spectra (etched, and primed minus etched of the same dentin surfaces) were plotted and compared with original adhesive spectra. The C=C/C...C (aromatic adhesives) and C=C/C=O (aliphatic adhesives) peak area ratios were used to evaluate the extent of monomer separation relative to original adhesive spectra at the uppermost 2 microm of the resin-dentin interdiffusion zone. Three dentin specimens were used for each adhesive. One-way ANOVA and Newman-Keuls tests were performed to assess the statistically significant differences (alpha=0.05)., Results: All the adhesives demonstrated separation of monomer components on etched dentin ranging in mean values from 68.7 to 81.9% relative to reference. High molecular weight hydrophobic (i.e. BisDMA, BisGMA, BisGMA adducts) and hydrophilic monomers (i.e. BPDMA) predominated at the region probed. Prime and Bond 2.1 demonstrated the highest extent of monomer separation., Significance: Heterogeneous monomer distribution following application to etched dentin may affect the curing performance of single-bottle adhesives within the resin infiltrated region and consequently, the mechanical and chemical stability of the network formed.

The effect of intraoral aging of biomaterials on the modification of their surface properties has mostly been unknown. The purpose of this study was to investigate and characterize surface alterations of retrieved inner face-bow headgear components. Specimens were prepared from 3 areas of retrieved headgear wires: inner-outer face-bow soldered junction, buccal segment, and projection entering the buccal tube. Specimens from as-received headgear wires that matched the brand and size of the retrieved wires were also fabricated; all specimens were then subjected to multitechnique characterization. Optical microscopy revealed extensive biofilm islands of amorphous precipitants and accumulated microcrystalline particles. Micro-multiple internal reflectance Fourier transform infrared spectroscopy investigation of the retrieved wire samples demonstrated the presence of a proteinaceous biofilm, the organic constituents of which were mainly amide, alcohol, and carbonate. Scanning electron microscopy and radiographic microanalysis showed that the elemental species precipitated on the material surface were mainly calcium and phosphorus, forming calcium-phosphorus precipitates with thicknesses reaching 300 microm, whereas radiograph fluorescence spectrometry provided evidence of integument calcification through identification of calcium and phosphorus peaks. The clinical implication of the aging pattern that was identified relates to the potential protective role or induction of disintegration by the biofilm adsorbed on the wire that affected the biocompatibility of the alloy. Whereas further investigation is suggested for the clarification of the effect of intraoral aging on ionic release, the results of this study emphasize the necessity for the incorporation of in vivo approaches, including retrieval analyses, in the study of the biologic performance of orthodontic materials.

"Ease of use," as applied to dental materials and techniques, means different things to different people. Factors that may contribute to ease of use include a minimum number of application stages, easy application and shaping ability, quickness of use, lack of stick, and moisture sensitivity. Ease of use may also imply that a material or technique does not cause stress for the dentist and patient, is cost effective, is easy to learn, and should provide the operators with a sense of satisfaction with their work. Similarly, "clinical effectiveness" of the treatments prescribed for patients is not always capable of being accurately defined. Suggested factors that may contribute to clinical effectiveness include a lack of patient complaints with respect to longevity and/or cost, no secondary caries, and preservation of the remaining tooth structure during functional loading. Ease of use and clinical effectiveness are not necessarily related, but they must be combined for a technique to be successful. The achievement of this demands a partnership between clinicians, manufacturers, and patients.

The purpose of this study was to evaluate the enamel colour changes associated with bonding of brackets with a no-mix (one-phase) adhesive resin (Unite) and a glass-ionomer adhesive (GC Fuji Ortho). Thirty recently extracted premolars were used in the investigation. Black rectangular pieces of adhesive tape with a 3-mm diameter window were used to standardize the enamel surface intended for analysis. The teeth were divided into two groups of 15 teeth each, brackets (Starfire TMB) were bonded with the two adhesives, and the enamel surfaces were colourimetrically evaluated at three time intervals: (a) before bonding (baseline), (b) following debonding and cleaning, and (c) after artificial photo-ageing for 24 hours. The CIE colour parameters (L*, a*, b*) were recorded and averaged for each material, interval group, and the corresponding colour differences (delta E) were calculated. The results were statistically analysed using two-way ANOVA repeated measures, and Scheffé multiple range test at alpha = 0.05 level of significance. All differences noted exceeded the threshold for clinical detection (delta E = 3.7). The highest differences were recorded for the baseline-debonding interval for both adhesives used. No difference was found with respect to delta E between etching-mediated and no etching-mediated bonding implying that the debonding cleaning process involving adhesive grinding may be more invasive relative to acid etching with regard to enamel colour alterations.

Purpose: The purpose of this study was to evaluate the curing efficiency of 8 light- and dual-cured denture reliners., Materials and Methods: The curing efficiency was measured with Fourier infrared micromultiple internal reflectance spectroscopy, calculating the percentage of remaining carbon double bonds on the top and bottom surfaces of each specimen immediately after exposure to the extraoral light-curing unit according to the manufacturer's instructions and after 1 week of storage in dark and dry conditions. Another group of specimens was photopolymerized initially through a denture base resin prior to the extraoral light-curing polymerization. Five specimens of each reliner were tested., Results: The dual-cured reliners showed no statistically significant differences (P > 0.05) between top and bottom surfaces after immediate exposure to the light-curing unit. On the contrary, light-cured reliners revealed significant differences. The majority of the reliners showed reduction of the percentage of remaining carbon double bonds at both surfaces after 1 week of storage in dark and dry conditions. Photopolymerization of light-cured reliners through a denture base resin induced an increased amount of remaining carbon double bonds, whereas no effect was observed in dual-cured materials., Conclusion: Dual-cured denture liners exhibited distinct advantages over light-cured ones concerning the curing efficiency.

The purpose of this study was to estimate the degree of cure (DC) of a light-cured, and a two- and a one-phase (no-mix) chemically-cured, as well as a dual-cured commercially available orthodontic adhesive resin. Forty stainless steel brackets were divided into four groups of 10 brackets each, and the bracket bases were covered with a standardized volume of adhesive. They were then pressed firmly onto a yellowish background surface of 75 per cent reflectance covered with cellulose film to facilitate detachment of the system and recovery of the set material. The visible light- and dual-cured adhesives were photopolymerized by irradiation from the incisal and cervical edges of the bracket for 10 seconds each, while another group of ceramic brackets was used to assess the differential interference of transparent relative to opaque material in the DC. Micro-multiple internal reflectance Fourier transform infrared spectroscopy was employed for the estimation of the DC of the adhesives (alpha = 0.05, n = 10), utilizing a method proposed previously. The dual-cured product demonstrated the highest DC followed by the light-cured combined with the ceramic bracket, and the no-mix and the chemically-cured adhesives. The combination of the metallic bracket with the light-cured product resulted in a DC comparable with that of the chemically-cured material.

Objective: The aim of this study was to investigate the relationship between the degree of conversion (DC) and shrinkage strain values of two representative resin-composites when irradiated by two light intensity levels, for different time periods., Methods: The DC of Z100 and Tetric Ceram was measured by FTIR spectroscopy immediately post-cure and shrinkage strain values were obtained continuously for 30 min from photoinitiation with the bonded-disk technique. All samples were photopolymerized at an initial temperature of 23 degrees C with the Elipar Highlight unit under the following modes of variable light intensity (I) 40 s at 750 mW/cm2; (II) a two-step 'soft-start' irradiation mode of 10 s at 200 mW/cm2 plus 30 s at 750 mW/cm2; (III) 40 s at 200 mW/cm2; and (IV) 10 s at 200 mW/cm2. Temperature effects of the light and curing exotherm were not eliminated., Results: Mode II of irradiation did not reduce the DC for each material, relative to the values obtained with mode I (p > 0.05). The corresponding shrinkage strain values after 30 min were also not significantly different (p > 0.05). However, the effects of reduced light intensity levels for 10 s and 40 s (modes III and IV), were in agreement with previous findings implying reduced shrinkage strain levels. For both resin composites, data from all curing times and light-intensities gave a linear regression relationship (with r2 > 0.99) between the bonded-risk shrinkage strain versus DC values., Significance: For the materials and light-intensities studied, the correlation between DC and shrinkage strain values means that some reductions in the problems of shrinkage may be achieved by an acceptable reduction in DC. However, this must also be consistent with generating adequate curing performance in the resin-network. Nevertheless, DC is not the exclusive parameter describing network character and a fuller understanding of the latter is an important research goal.

The objectives of this study were to investigate the structural characteristics of open and closed elastomeric modules in the as-received condition, and following (a) 24-hour in vitro loading determined as a 50 per cent extension relative to their original length; (b) 24-hour intra-oral exposure; (c) 3-week intra-oral exposure. Ten specimens of each type (open and closed) of the three brands of elastic chains were included in the study (total of 60). All specimens were subjected to (a) optical transmission microscopy utilizing phase contrast and polarized light modes, (b) micro MIR FT-IR spectroscopy, and (c) scanning electron microscopy and electron probe X-ray microanalysis. Stretched elastomers demonstrated a honeycomb pattern of filament detachment corresponding to strained areas. The chains possessing a well-differentiated inter-modular link presented higher strain concentration gradients located in the link. Phase contrast imaging revealed that the stress adsorption mechanism of these materials involved macromolecular chain orientation and elongation co-axially to the applied load. The specimens retrieved after 24 hours had acquired a proteinaceous film rich in alcohol groups with minimal evidence of phosphate mineralization, while the 3-week retrieved specimens presented precipitation of Ca- and P-forming calcium phosphates. The high protein content of the biofilm organized on the surface of these materials, as well as the calcification pattern found, were similar to a non-specific mechanism of film adsorption of biomaterials exposed to body fluids. The results have clinical implications for aspects of retraction control through sliding mechanics with the use of elastomeric ligatures, and the potential detrimental effects on dental and periodontal tissues such as decalcification and gingival inflammation, respectively. In addition, the experimental protocols adopted for the in vitro study of the force decay of elastomerics should be modified to include parameters pertinent to adsorption phenomena and calcification processes documented to occur in vivo.

Objectives: The purpose of this study was to assess the effect of two commercial primers and distilled water on the morphology, molecular composition and collagen conformation of acid-demineralized dentin in situ., Methods: Dentin specimens etched with Scotchbond Etchant were imaged by tapping mode AFM and analyzed by MIR-FTIR spectroscopy. They were then primed with Scotchbond Multi-Purpose Plus Primer, Scotchbond 1 Adhesive or distilled water and imaged and analyzed again. The chemical modifications induced on the uppermost 2 microns of primed dentin were studied after water and original primer subtraction. The conformational changes of type I collagen at this region were evaluated by deconvoluting the amide I band components. The absorbance ratio An(1655/1627) was used to semiquantitatively assess, on a relative basis, the extent of collagen denaturation., Results: All the priming treatments swelled the collapsed dentin collagen left after etching. No evidence of primary bonding was found after priming treatments, while approximately 50% of the conditioned dentin collagen appeared denatured. Treatment with distilled water did not change the status of denatured collagen, however, application of the commercial primers refolded the alpha-helix to approximately 95% of the extent found on the native reference dentin., Significance: The dynamic response of dentin collagen to demineralization and priming treatments reveals the critical role of some primers in rapidly restoring the conformational status of acid-denatured collagen. Implementation of reactive adhesive groups in alpha-helix recovery may provide an associative means of modifying the mechanical properties of the demineralized collagen based on the extent of their intermolecular bonding.

Studies on the titanium porcelain interface have shown the presence of alumina, attributed mainly to the sandblasting procedure. In this study, an investigation of the effect of the sandblasting procedure on the microstructure and roughness of a cast commercially pure titanium surface was undertaken using three different particle size alumina powders. The analysis showed that in all cases alumina particles are embedded into the surface layer of titanium. The use of a large particle size alumina seems to be advantageous in reducing the weight of alumina remaining on the titanium surface and while increasing the surface roughness, thus promoting mechanical interlocking with porcelain.

The articular surfaces of 10 retrieved ultrahigh molecular weight polyethylene acetabular sockets were studied by optical microscopy, X-ray fluorescence spectrometry, multiple internal reflectance FTIR spectroscopy, scanning electron microscopy, and wavelength dispersive X-ray microanalysis. The results revealed characteristic wear patterns including polishing, scratching, pitting, cratering, folding, shredding, burnishing, cracking, embedding of particles, and development of acquired biofilms with various degrees of mineralization. The biofilms formed were mainly of proteinaceous origin, and mineralized regions were composed of calcium phosphates with carbonate impurities. The crystallinity of the polyethylene at the articular surfaces was enhanced compared to the bulk, which was possibly due to the cold work produced in vivo. The mineralized regions were classified into two groups based on the grey levels of the backscattered images obtained. The high-contrast regions that were mainly composed of Ca and P with traces of Al and Si were associated with bone fragments; the low-contrast regions composed of K, Na, Ca, Mg, Si, Al, Fe, Cl, and P were associated with acquired biofilm calcification, which implies the active engagement of biofilms in the long term performance of acetabular sockets in vivo., (Copyright 1999 John Wiley & Sons, Inc.)

Objective: The aim of the study was to evaluate the extent of the acid-base reaction and F- release in Compoglass (Vivadent) and Dyract (Dentsply/DeTrey) restoratives., Methods: For evaluation of the extent of the acid-base reaction, two groups of three specimens (7 mm x 5 mm x 1 mm) were prepared for each material. The first group was immersed in distilled water, while the second was kept in dark and dry conditions. Micro-MIR FTIR spectroscopy was used to determine the extent of the acid-base reaction on directly irradiated material surfaces immediately after irradiation and following water storage for 30 min, 3 d, 1, 2, 4, 8 and 12 wks. The in-depth extent of the acid-base reaction of the specimens stored in water for 4 weeks was studied by sequential spectra acquisition after removal of the uppermost 20, 70, 100, 240 and 400 microns layer by controlled grinding and 1 wk re-immersion in water of the 400 microns reduced specimens. For the F- release measurements, five disk-shaped specimens (10 mm x 1.5 mm) were prepared from each material and stored in distilled water. The amount of F- released for the storage periods reported above was measured using an ionometer with an F- electrode. Statistical analysis was performed by ANOVA, Scheffé's test and regression analysis., Results: Storage in water promoted the development of an acid-base reaction on directly irradiated surfaces which reached a saturation point after 4 weeks. Depth profiling of the 4 wk immersed specimens revealed high salt concentration at the uppermost 100 microns layer. Re-immersion in water for 1 week of the 400 microns reduced specimens increased the salt concentration again at the uppermost region. Statistically significant differences were found in the acid-base rates and the in-depth salt yields between the materials (p < 0.05). The fluoride release after a 1 week initial "bursting" period was stabilized below 2 mg l-1 (p > 0.05) in both products. No positive correlation was found between acid-base reaction and fluoride release., Significance: The development of a carboxylate-rich surface layer on polyacid-modified composite restoratives after water storage may explain their lower wear resistance compared with resin composites. The dynamic nature of these surfaces may provide several advantages regarding their interaction potential with hard dental tissues and their anticariogenic properties, but also some disadvantages concerning the quality of the surface texture obtained.

Objectives: An experimental method was used to assess the glass ionomer and resinous character in three "dual-cure" (Fuji II LC, Photac-Fil, Variglass) and a "triple-cure" (Vitremer) resin-modified glass ionomer restoratives to evaluate their acid-base and free-radical setting mechanisms., Methods: Four groups (A-D) of three specimens (5 x 4 x 1 mm) were prepared from each material and subjected to the following treatments: A: mixing; B,C: mixing, 60 s irradiation, 20 min dark/dry storage; and D: mixing, 20 min dark/dry storage and then 60 s irradiation. Micro-multiple internal reflectance FTIR spectroscopy was used to determine: 1) the curing efficiency of the products immediately after irradiation; 2) the effect of irradiation 20 min after dark/dry storage on the curing efficiency; and 3) the extent of the acid-base reaction on irradiated and non-irradiated specimens after 20 min dark/dry storage., Results: The curing efficiency immediately after irradiation was determined from the percentage of residual double bonds which ranged from 33-50% for these materials. Irradiation after 20 min dark/dry storage significantly reduced curing efficiency in all the products, except Variglass. The latter showed no acid-base reaction under the conditions of this study. Non-irradiated specimens after the dark storage period demonstrated higher carboxylate yields compared to their irradiated analogues. Non-irradiated specimens from Vitremer had the highest carboxylate yield and a curing efficiency of approximately 50% residual double bonds., Significance: Photopolymerization seemed to greatly reduce the acid-base reaction during the early setting stages of resin-modified glass ionomer restoratives. The free-radical formation rates are slower than those achieved by chemically initiated polymerization, but they produce adequate conversion and high carboxylate salt yields. This study demonstrated an experimental model for identification and characterization of the acid-base reaction in water-containing resinmodified glass ionomer restoratives.

The purpose of this study was to investigate the microstructure and bonding mechanisms for four types of ceramic brackets by using information from several methods. Two of the bracket types provided exclusively micromechanical retention as a bonding mechanism, with the use of microspheres or microcrystals to achieve a rough structure for the bracket base. A silane layer that provided chemical adhesion was found to cover the bases of the two other types of brackets; one type also used central regions of increased roughness to provide additional micromechanical retention. Polarized-light optical microscopy showed that the silane layer was not continuous. Small area x-ray photoelectron spectroscopy analysis (SAXPS) of the silane layer was consistent with the presence of gamma-methacryloxypropyl trimethoxysilane. The study of the ceramic bracket bases revealed a wide variety in composition, structure, morphologic condition, and coating treatment that implies different bonding mechanisms to orthodontic adhesives.

The purpose of this study was to evaluate quantitatively the fluoride uptake by enamel from an experimental visible light-cured orthodontic adhesive (VP-862) based on YbF3 filler. Sixteen contralateral premolars were extracted from 10 orthodontic patients and were classified in four groups (A, B, C, D) of four buccal surfaces each. Standardized enamel areas located on these surfaces were acid etched and were subjected to the following adhesive treatments: (A) VP-862; (B) Heliosit Orthodontic; (C) Heliobond + VP 862; and (D) Heliobond + Heliosit Orthodontic. Groups B and D were used as a reference. After 9 months in vivo, the teeth were extracted and cross-sectioned, and the enamel-adhesive interfaces were studied by combined wavelength-energy dispersive electron probe microanalysis. According to the results, the cumulative fluoride uptake by enamel from the experimental adhesive was not statistically different from the fluoride detected in the reference groups. No effect of the liquid resin, Heliobond, on the fluoride uptake gradients of enamel could be differentiated.

The purpose of this study was to examine the electrochemical behavior of silver points in vivo. The apices of silver points removed from teeth with successful or failed endodontic treatments were subjected to complete surface characterization by small-area ESCA, scanning electron microscopy, and electron probe microanalyzer. Cross-sections of the points near the apex were examined with scanning electron microscopy and electron probe microanalyzer to identify the depth of corrosion involvement. According to the results, all silver points manifested evidence of corrosion attack. Electron probe microanalyzer showed no difference in the elemental distribution found on the points. ESCA analysis of the uppermost 5-nm point layer revealed the presence of N on silver points removed from failed treatments. The examination of cross-sections manifested deep S penetration in the bulk of the points removed from failed treatments. Considering the results of this study, no direct association seems to exist between the extent of the corrosion involvement and the prognosis of the treatment. Handling factors and the presence of bacteria are probably the parameters determining the outcome of a treatment.

The purpose of this study was to evaluate the form and microstructure of three types of ceramic bracket and to assess their interfacial surface shapes and bond strengths with visible light-cured and chemically cured adhesives after thermocycling. One monocrystalline and two polycrystalline structures were identified. The form of the bonding bases implied three types of bonding with the adhesive: a chemical bonding, a combination of mechanical retention and adhesion, and a combination of micromechanical retention and adhesion. All the ceramic bases were covered with a layer of gamma-methacryloxypropyltrimethoxysilane coupling agent. The thickness of the adhesive layer was affected by the design of the bracket bases. The highest bond strength was obtained from the brackets by a combination of micromechanical retention and adhesion, with the site of failure located at the resin/bracket interface. The other types of ceramic brackets had a greater amount of resin left on the enamel and some cases of cohesive bracket fractures.

This study assessed the effect of an air-powder abrasive instrument (Prophy Jet) on the surface integrity of a series of restorative materials. Four types of amalgam alloys (Amalcap, Dispersalloy, Tytin, Ana 2000), three types of composite resins (Silux, Brilliant Lux, Adaptic II), a heat-cured resin (SR Vivadent), and porcelain (Vita VMK) fused to a Gr-Ni alloy at 1 mm and 2.5 mm thickness were subjected from 5 mm distance to the abrasive stream at 100 psi for 5 seconds. The resulting surface topography was studied under an electron probe microanalyzer. All of the amalgams presented increased surface roughness and alterations in the surface composition assigned to the destruction of the soluble gamma-2 and n phases. Composite resins showed excessive matrix disruption, exposure of the filler particles and pitting on the prepolymer surfaces. The crown and fixed partial denture resin was the most affected material. Porcelain at 2.5 mm thickness exhibited moderate stain pitting, whereas in 1 mm thickness severe glaze cracking was identified.

The clinical build up of visible light cured restorations in many cases is performed by layering different types of composites to obtain enhanced characteristics. The purpose of this study was to evaluate the interfacial strength and microleakage pattern of paired light-cured restorations. Two small particle (SP), two pure hybrid (HB) and two microfilled materials (MF) were selected. Cylindrical molds were used to prepare double layer specimens for the groups SP-HB, SP-MF, HB-MF and the controls. The last group was comprised of double layer specimens respectively. All the samples were immersed in normal saline at 37 degrees C and divided in two series. The first series included samples immersed in normal saline for 24 h and accelerated aged for 1 h in saline at 37 degrees C plus 1000 times thermal cycling between 5 degrees-60 degrees C. These samples were sheared off at 0.005 inch/min cross-head speed. The second series was composed of the samples subjected to the some experimental conditions but tested for their interfacial microleakage pattern utilizing the silver nitrate technique. According to the results pairing SP-MF, SP-HB increases interfacial strength compared to MF-MF, and HB-HB. The combination of HB-MF results in no statistical significance from MF-MF or HB-HB. Minimal leakage was detected in some cases but did not correlate to bond strength values.

The purpose of this study was to assess the surface free energy of a series of composite resin restorative materials, utilizing the concept of critical surface tension (yc). Cylindrical samples of 20 mm diameter and 2 mm in thickness were prepared from 4 microfilled, 3 hybrid and 6 small particle composite resins. The critical surface tension was determined by contact angle measurements on 1000 grit ground surfaces. A Zisman series of homologous liquids was used (Water, Glycerol, Formamide, Thiodiglycol, Dilodormethane, I-Bromonapthalane). The recorded yc means were 30.000-42.600 dyn/cm for microfilled, 42.47-44.68 dyn/cm for hybrid and 42.19-49.20 dyn/cm for small particle composites. In all the cases the work of wetting was primary attributed to non polar and dispersion forces. The type and the concentration of the reinforcing fillers is the major factor influencing yc, especially in the presence of hydrophylic particles like Ba. Microfilled materials showed decreased wetting efficiency. Hydrophobic monomers do not provide any significant advantage on the wettability of polished composite surfaces.

The structure and function of P in P-based dental adhesives have not been defined properly. The purpose of this study was to evaluate these parameters in some currently available materials. Five dental adhesives were selected: Bondlite, Clearfil New Bond, J&J Dental Adhesive, Prisma Universal Bond, and Scotchbond. High-resolution 31P-NMR spectroscopy was used to identify the phases of the incorporated P and the kinetics of monomer-bonded P in an aqueous environment. Areas of 5 mm diameter located on polished sound dentin were subjected to the corresponding adhesive treatments and covered with translucent molds of the same diameter, which were filled up to 1 mm length with a visible-light-cured hybrid composite. Following 60 sec of light exposure from lateral directions, the specimens were embedded in fast-setting resin, cross-sectioned, and analyzed in an electron probe microanalyzer. The elemental profiles of Ca, P, and Cl were determined from area and line scans. Great differences in the 31P resonance shifts were obtained from the tested adhesives, indicating the presence of monomer-bonded and free P. A rapid hydrolysis of the resin-bonded P in the presence of water was identified. The x-ray images revealed dentin demineralization, with distinct differences in the P distribution pattern and the P/Cl ratio.

The properties and the biocompatibility of root canal sealers, depend on the composition and the purity of their constituents. Four root canal sealers made in Greece are claimed to correspond to the formula proposed by Grossman. The lack of quality control on the production of these materials provided evidence for a systemic composition analysis and an evaluation of their Pb impurities. The analytical methods chosen were X-ray diffraction (XRD) and atomic absorption spectroscopy (AAS). According to the results of the study none of the tested root canal sealers agrees with Grossman formula, which was identified in the control sealer. The levels of the Pb were found significantly elevated (80-510 ppm) compared to the control (2 ppm). All these findings indicate the need for the establishment of quality control and the development of strict specifications for the manufacturing of root canal sealers.

The interfacial oxides formed during the oxidation stage of porcelain dental alloys are of primary importance. The purpose of this study was to identify the type of the oxides in three commercial alloys and to evaluate their adherence with the underlying alloy before and after porcelain application. X-ray diffraction analysis revealed the presence of PdO, Fe2O3, FeO, InO, In2O3 (precious alloy), Ga2O3, GaO, PdO, CuO, SnO2 (Hi-Pd) and NiO, Gr2O3, SiO2, MoO2, TiO2, Al2O3 (non precious) in the oxide layers removed from each alloy respectively with a 10% Br solution in methanol. The highest values of tensile strength were obtained from the non-precious alloy oxides which were further enhanced after porcelain fusion. The application of porcelain does not seem to influence metal ceramic bonding.

Despite the extensive use of the layering technique in light-cured restorations there is limited information for the interfacial strength when curing is accomplished in air and an inhibited zone is formed on the first layer. This study analyzed the nature of the inhibited zone to determine the interfacial topography, evaluated the shear interlayer bond strength in the presence of the inhibited layer, and assessed the effect of various interfacial treatments on bonding. Two microfilled, one hybrid, and three small-particle composite resins were included in the study. According to the results, the inhibited zone is primarily composed of catalyst-free monomer. The presence of this zone reduces bond strength, creating interfacial discontinuities. Removal of the inhibited layer by an organic solvent of low boiling point results in the highest strength and better interfacial topography from the tested treatments.

The purpose of the study was to evaluate quantitatively the degree of double bond conversion in nine commercially available pit and fissure sealants. The materials selected for the study were a) Nuva-Seal and Nuva Coat-UV cured b) Delton, Helioseal, Pentra Seal, Prisma Shield, Visioseal-Visible light cured and c) Delton, Concise White-Chemically cured. Infrared spectroscopy of monomer and polymer films, was used for the quantitative analysis at 37 degrees C. Monomer spectra were obtained from liquid films enclosed between two KBr plates while polymer spectra 24h after storage from 0.2 mm thick cylindrical specimens of 10mm diameter exposed to the activating lights for 1 min or mixed according to manufacturers. The results indicate that UV-cured materials provide the highest degree of double bond conversion followed by visible light cured systems. The clinical failure of UV-cured systems, despite their higher conversion rates is probably attributed to stabilization and shelf life problems of the catalyst besides the harmful side effects of UV-radiation which limited the utilization of these systems.

A newly developed denture resin based on a 4-META containing monomer became recently commercially available. It has been claimed that this resin system has the unique ability of creating bond to Cr-Co alloys without any mechanical retention. The objective of this study was to determine the chemical composition of the new resin, to study the bonding mechanism with a Cr-Co alloy and to compare its physical and mechanical properties to a commonly used acrylic denture resin. The analysis revealed that the new system contains 5% by weight 4-META in MMA liquid and 28% poly (ethyl methacrylate) in PMMA. No practical differences were noted in the stress-strain characteristics and hardness values between the resin systems. The META-DENT resin was more abrasion resistant. The bond of META-DENT to the Cr-Co alloy was greatly superior than that of the conventional resin. The bonding mechanism may be related to enhanced physical wetting due to reduced META-DENT viscosity and probably complexation of the anhydride groups with either Cr or Co.