Search PubMed⌕ Search

Biomedical subjects

M J Tyas

Publications and source records attributed to M J Tyas.

At least 37 records · Page 2Linked to original sources
PubMed2000

The influence of the modification of etched bovine dentin on bond strengths.

OBJECTIVE: The aim of this study was to modify demineralized bovine dentin surfaces by application of either 12.5% sodium hypochlorite (NaOCl), or 0.1% (w/w) Type I collagenase, after conditioning with phosphoric acid, to observe the demineralized surface and to investigate the effect on tensile bond strength. METHODS: The NaOCl was applied to etched dentin for 30 s, 1 or 2 min and the collagenase for 1, 3 or 6 h. A control group was used without NaOCl or collagenase treatment. Prior to bonding, treated surfaces were examined using an Atomic Force Microscope (AFM). A 2.3 mm diameter area of dentin was conditioned, treated and bonded with either One Coat Bond or Single Bond following each manufacturer's instructions, and a resin composite rod attached. Bonds were stressed in tension at a rate of 1 mm/min until failure. Mean bond strengths were calculated (MPa) and mode of failure was determined by observation at 20x magnification. Results were analyzed using multiple regression analysis and LSD test at the 95% level of confidence (n = 12). RESULTS: AFM results showed progressive changes of the surface collagen as the treatment time of NaOCl or collagenase increased. For both bonding systems, the bond strengths of 1 min NaOCl and 3 h collagenase treatments were significantly higher than the control or other treatment groups (p < 0.05). Bond failure consisted of mostly adhesive failure between dentin and resin combined with small regions exhibiting cohesive failure of resin. SIGNIFICANCE: Bond strengths were not dependent on the thickness of the hybrid layer, but rather quality of the hybrid layer.

Acid Etching, Dental↗
PubMed2000

Strain patterns in cervical enamel of teeth subjected to occlusal loading.

OBJECTIVES: This study was planned to investigate the variations in strains in enamel under different patterns of occlusal loading, using three-dimensional finite element analysis (3D FEA) and strain gage measurements in extracted teeth. METHODS: A 3D FEA model of a mandibular second premolar was used to investigate effects of occlusal load on enamel surface strains, particularly in response to oblique directions of cuspal loading. Point loads of 100 N were applied axially and at 45 degrees from the vertical on the buccal or lingual incline of the buccal cusp, either in the bucco-lingual plane or at varying mesio-distal angulations (up to +/- 20 degrees). Patterns of strain observed in the FEA model were confirmed experimentally using strain gages on extracted premolars mounted in a servohydraulic testing machine. RESULTS: Strains predicted from the FEA model were in excellent agreement with the strain gage measurements. Strains were concentrated near the cementoenamel junction (CEJ) regardless of load direction. A vertical load on the buccal cusp tip resulted in compressive strains on the buccal surface but small tensile strains in lingual cervical enamel. Strains resulting from oblique loads on buccal cusp inclines were complex and asymmetric, with either tension or compression occurring in any location depending on the site and angle of loading. SIGNIFICANCE: The magnitude, direction and character of strains in cervical enamel are highly dependent on patterns of loading. The asymmetric pattern of strains in buccal cervical enamel in response to oblique occlusal forces is consistent with the common clinical picture of asymmetric non-carious cervical lesions.

Analysis of Variance↗
PubMed2000

Nanoleakage patterns of four dentin bonding systems.

OBJECTIVES: The purpose of this study was to evaluate the nanoleakage patterns of four dentin bonding systems. METHODS: The dentin bonding systems used in this study were: Single Bond, One Coat Bond, Prime & Bond NT/Non Rinse Conditioner (NRC), and PermaQuik. Flat occlusal dentin surfaces from extracted human molars were finished with wet 600-grit silicon carbide paper, and bonded with one of the dentin bonding systems. After 24 h storage at 37 degrees C in water, margins were finished with polishing discs and the surrounding tooth surfaces coated with nail varnish. The samples were immersed in a 50% (w/v) solution of silver nitrate for 24 h, and exposed to photodeveloping solution for 8 h. The samples were cut longitudinally, polished, and mounted on stubs, carbon coated and observed in a Field Emission-SEM using backscattered electron mode. RESULTS: Different nanoleakage patterns were observed with the different adhesive systems. However, accumulations of silver particles were often noted at the base of the hybrid layer for all materials. Single Bond and One Coat Bond demonstrated uptake of silver particles both within the hybrid layer and the adhesive resin. Prime & Bond NT/NRC showed silver staining throughout almost the entire thickness of the hybrid layer. The leakage pattern of PermaQuik revealed loose silver deposition within the hybrid layer. The composition of each adhesive system may play a role in forming the different leakage patterns. SIGNIFICANCE: The current dentin bonding systems used in this study do not achieve perfect sealing at the restoration/dentin interface, which may influence the durability of the bond to dentin.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2000

Microtensile bond strengths of glass ionomer (polyalkenoate) cements to dentine using four conditioners.

OBJECTIVES: The purpose of this study was to measure the microtensile bond strengths of three glass ionomer cements to dentine (Photac-Fil Quick; Fuji II LC; Fuji IX GP) using four different conditioners (Ketac Conditioner; Dentin Conditioner; Cavity Conditioner; and an experimental conditioner, K-930). METHODS: Superficial occlusal dentine of extracted human third molars was exposed, finished with wet 600-grit silicon carbide paper, and each of the above glass ionomer cements bonded using the four conditioners according to the manufacturers' instructions. After 24h in tap water at 37 degrees C, the teeth were sectioned to obtain 3-4 bar-shaped specimens. Ten specimens were prepared for each group and shaped to an hour-glass form of (1.2+/-0.02)mm diameter. The specimens were mounted in a jig and stressed in tension at a crosshead speed of 1mm/min until failure. The mean bond strengths were calculated and compared using one-way ANOVA and LSD tests, and the fracture modes were examined by scanning electron microscopy. RESULTS: Mean microtensile bond strengths for Photac-Fil Quick were not significantly different from Fuji II LC for each of the conditioners used. However, the bond strengths for Photac-Fil Quick were significantly greater than Fuji II LC when no conditioner was applied. Mean microtensile bond strengths of conditioned specimens of Fuji II LC were significantly greater than non-conditioned specimens. Mean microtensile bond strengths of non-conditioned specimens of Fuji IX GP were not significantly different from conditioned specimens. The fracture mode of all specimens demonstrated mostly cohesive failure within the cement. SIGNIFICANCE: The use of surface conditioners resulted in improvement in bond strength of Fuji II LC, while Photac-Fil Quick and Fuji IX GP showed no difference.

Acrylic Resins↗
PubMed2000

Clinical evaluation of EBS dentine bonding agent: one year results.

There are numerous dentine bonding agents currently on the market, the majority of which adhere by means of infiltration of a hydrophilic polymerizable diacrylate into dentinal collagen exposed by acid treatment. The purpose of the present study was to evaluate the clinical performance of one such product, EBS dentine bonding, in non-undercut caries-free cervical lesions. Forty cavities were restored in eight patients of mean age 53 years. The manufacturer's instructions were followed, which involved essentially etching the enamel and dentine for 20 seconds with 32 per cent phosphoric acid, application and evaporation of EBS Primer, followed by placement and curing of EBS Bond, and restoring the cavity with Pertac II (ESPE) hybrid resin composite. Restorations were photographed at base line and one year for evaluation of marginal discolouration on a continuous linear rating scale. At six months, one patient with four restorations was not available; the remaining 36 restorations were all present. At one year, one restoration was missing, giving a cumulative retention rate of over 97 per cent. One of the 36 restorations exhibited very mild marginal discolouration.

Acid Etching, Dental↗
PubMed2000

Minimal intervention dentistry--a review. FDI Commission Project 1-97.

The concept of minimal intervention dentistry has evolved as a consequence of our increased understanding of the caries process and the development of adhesive restorative materials. It is now recognised that demineralised but noncavitated enamel and dentine can be 'healed', and that the surgical approach to the treatment of a caries lesion along with 'extension for prevention' as proposed by G V Black is no longer tenable. This paper gives an overview of the concepts of minimal intervention dentistry, describes suggested techniques for a minimally invasive operative approach, and reviews clinical studies which have been carried out in this area.

Composite Resins↗
PubMed2000

Field-emission scanning electron microscopy of resin-dentin interface morphology of seven dentin adhesive systems.

PURPOSE: The purpose of this study was to evaluate the resin-dentin interface morphology of 7 resin-based dentin adhesive systems (Solid Bond, EBS-Multi, PermaQuik, One Coat Bond, Gluma One Bond, Prime & Bond NT/NRC, and Clearfil Liner Bond 2V). MATERIALS AND METHODS: Fourteen dentin disks 1.0 mm thick were obtained from superficial occlusal dentin of extracted human third molars, and finished with wet 600-grit silicon carbide paper. Two dentin disks were bonded using each of the adhesives above according to the manufacturers' instructions, and a thin layer of flowable resin composite was applied. The specimens were kept in tap water for 24 h at 37 degrees C, and then assigned to one of two observational techniques: a fracture technique and an acid-base technique. Fracture technique: shallow grooves were cut, fixed in 10% buffered formalin, and dehydrated in an ascending ethanol series up to 100%, critical-point dried, and fractured along the prepared grooves. Acid-base technique: the specimens were embedded in epoxy resin, sectioned through the center, polished with diamond paste down to 0.25-micron particle size, and treated with 10% orthophosphoric acid for 10 s and 5% sodium hypochlorite for 5 min. All the specimens were mounted on aluminum stubs, gold sputter coated, and observed using field-emission scanning electron microscopy (FE-SEM). RESULTS: All the dentin adhesive systems showed hybrid layer formation, but the thickness varied depending on the bonding system used. The self-etching priming systems (Prime & Bond NT/NRC and Clearfil Liner Bond 2V) showed the thinnest hybrid layer at 1 to 2 microns, whereas the "single-bottle" system (Gluma One Bond) exhibited the thickest hybrid layer at 8 to 16 microns. CONCLUSION: The ultramorphological structures of dentin bonding systems are determined by the composition of each system. Characterization of the interface of the adhesive system using the fracture technique provides additional information regarding the pattern of resin infiltration in some dentin bonding systems.

Adhesives↗
PubMed2000

Micromorphological investigation of noncarious cervical lesions treated with demineralizing agents.

PURPOSE: The purpose of this study was to examine the micromorphology of noncarious cervical lesions (NCCL) and the change occurring after acid conditioning. MATERIALS AND METHODS: Nine wedge-shaped lesions, 9 saucer-shaped lesions, and 5 third molars with prepared cervical cavities were used. All NCCLs exhibited a hard, smooth surface with no discoloration. The teeth were sectioned and divided into three groups, each containing the three lesion types. Teeth in Group I were not etched, and teeth in Groups II and III were etched with 35% phosphoric acid and 20% polyacrylic acid/3% aluminum chloride, respectively. Field emission SEM and atomic force microscopy were used to examine the lesion surfaces. RESULTS: The surfaces of the prepared cervical (control) lesions were covered with a smear layer. Treatment with phosphoric acid and polyacrylic acid resulted in removal of the smear layer, although some residual smear layer was found on the surface treated with polyacrylic acid. The images of the untreated surfaces of NCCL showed highly mineralized dentin with complete obliteration of the dentinal tubules. After treatment with phosphoric and polyacrylic acids, the images revealed demineralization of the surface, which was more pronounced on those treated with phosphoric acid. CONCLUSION: The mineral deposits on the surface of NCCL decreased the effect of acid conditioning. Although there was no apparent difference between the two forms of NCCL used in this study, further work is needed to better understand these lesions.

Acid Etching, Dental↗
PubMed2000

Nanoleakage of cervical restorations of four dentin bonding systems.

PURPOSE: The aim of this study was to evaluate the degree of nanoleakage of restorations placed in cervical preparations with dentin bonding systems. MATERIALS AND METHODS: The dentin bonding systems used were Single Bond, One Coat Bond, Prime & Bond NT/NRC, and PermaQuik. Ten saucer-shaped cervical preparations were bonded with one of the dentin bonding systems and restored with Silux Plus resin composite in each group. After 24 hours storage in 37 degrees C water, restorations were finished and the surrounding tooth surfaces were coated with nail varnish. The samples were immersed in 50% w/v solution of silver nitrate for 24 hours, and exposed to photodeveloping solution for 8 hours. The samples were cut longitudinally through the center, polished, carbon coated and observed in a Field Emission SEM using backscattered electron mode. The degree of silver penetration along the preparation wall was observed and calculated as a percentage of the total preparation wall length. Results were analyzed by one-way ANOVA and LSD tests. RESULTS: PermaQuik demonstrated the lowest leakage score and the least silver deposition within the hybrid layer, while Prime & Bond NT/NRC showed the greatest leakage scores and the most silver deposition within the hybrid layer. Different nanoleakage patterns were observed for the different adhesive systems. CONCLUSION: First, the composition of each adhesive system may play a role in the different leakage patterns. Second, the current dentin bonding systems used in this study did not achieve perfect sealing at the restoration-dentin interface. This may influence the durability of the bond to dentin.

Acid Etching, Dental↗
PubMed1999

The effect of dentine location and tubule orientation on the bond strengths between resin and dentine.

This study determined the influence of dentine structure on the micro-tensile bond strengths between resin and dentine of two different dentine adhesive systems (Single Bond, 3M Dental Products, St Paul, MN; MF-102 (experimental self-etching primer), GC Corporation, Tokyo, Japan). The study was separated into two main parts: bond strength measurement and investigation of the bonding interface. Twenty-two human premolars were used for the bond strength measurement. Each tooth was cut vertically, separating the tooth into mesio-distal halves. One half of the tooth was used to bond to a surface perpendicular to the dentinal tubules and other half to bond to a surface parallel to the tubules. For each half, six locations of dentine were bonded. Each material was used in accordance to the manufacturer's directions. Cylindrical hourglass-shaped specimens of 1.2 mm diameter at the bonded interface were manufactured. The bonds were stressed in tension at a crosshead speed of 1 mm/min. Mean bond strengths were compared using LSD, one-way ANOVA, and Student's t-test. The fractured surfaces were examined under a scanning electron microscope, and the frequency of fracture modes was compared using the Kruskal-Wallis and Mann-Whitney U tests. For the investigation of the bonded interface, four teeth were prepared by the same procedure used for the bond test specimens. The bonded interfaces were observed after an acid-base treatment or fracturing across the bonded interface, prior to investigation with a field-emission scanning electron microscope. For Single Bond, the bond strengths for mid-root dentine were significantly lower than for other locations (p < 0.05). For MF-102, there was no significant difference for all locations (p > 0.05). MF-102 bonded well to all locations of dentine while Single Bond showed a porous zone at the base of the hybrid layer. The bonds were not influenced by tubule orientation. The results indicate that the bond for Single Bond may be affected by its ability to penetrate demineralised dentine in different locations of a tooth. The self-etching primer of MF-102 produces a good bond and is independent of the position on the tooth.

Analysis of Variance↗
PubMed1999

1-year clinical evaluation of one-step in non-carious cervical lesions.

PURPOSE: To evaluate the 1-year clinical retention rate of restorations of non-carious cervical lesions placed using a "one-bottle" adhesive (One-Step) and one of two low modulus resin-based composite (RBC) restorative materials (AEliteflo or Bisco Glaze) or a microfilled RBC (Silux Plus). MATERIALS AND METHODS: 105 non-carious cervical lesions in 14 patients, mean age 60 years, were restored using either AEliteflo, Bisco Glaze or Silux Plus with One-Step dentin bonding agent. The dentin surface was lightly roughened with a fine diamond stone, cleaned with pumice and water and restored according to the manufacturers' instructions. Patients were recalled at 6 months and 1 year, and the restoration sites examined. RESULTS: At 6 months all restorations were present. At 1 year, five restorations were missing (two Silux, three AEliteflo), three of which were in one patient. A cumulative retention rate of 95% was recorded. A small number of restorations exhibited marginal discoloration, but this was believed to be due to excess RBC on unetched enamel.

Adult↗
PubMed1999

Bond strengths of orthodontic brackets to restorative resin composite surfaces.

In orthodontic practice, it is not uncommon to bond brackets to resin composite restorations. With this in mind, this study was designed to compare first the shear/peel strengths of metal, ceramic and polycarbonate brackets bonded to microfilled resin composite (RC), using either a light-cured resin-modified glass ionomer cement (Fuji Ortho LC), a chemical-cured composite (System 1+) or a light-cured composite adhesive (Transbond XT); and then to examine the effects of thermocycling on the shear/peel strengths of these systems. Four different brackets were used: two stainless steel (Victory and Optimesh), one ceramic (Transcend 6000) and one polycarbonate (Spirit MB). Seventy-two specimens of each bracket were divided into three groups for bonding with one of the three adhesives. Half the specimens from each group were also thermocycled. Mean shear/peel bond strengths were found to be significantly different for the four different brackets, although not influenced by the three adhesives used within each group. All groups were found to have clinically-acceptable mean bond strengths, except for Spirit MB-System 1+. After thermocycling, both Optimesh-Transbond XT and Victory-System 1+ groups showed superior mean bond strengths (26.8 and 24.4 MPa, respectively) when compared with all other groups (p < 0.05). Applying the Weibull survival analysis for groups utilising Victory, Transcend 6000 and Spirit MB brackets, those with 90 per cent or greater probabilities of survival included Victory-System 1+, Transcend 6000-Fuji Ortho LC, Victory-Fuji Ortho LC and Spirit MB-Transbond XT groups. In all groups, bond failure was mainly (64 per cent) cohesive within the RC restorative surface. The thermocycled Spirit MB-Transbond XT group had the highest frequency of undamaged RC failure interfaces. Despite the focus of this study being on bond strength and the potential for surface damage, it was noted that these properties should always be considered alongside other factors such as the strength of the bracket itself, friction within the bracket slot, patients' wishes, cost of the materials and the presenting malocclusion.

Acrylic Resins↗
PubMed1998

Effect of cross-sectional surface area on bond strengths between resin and dentin.

OBJECTIVES: This study was conducted to determine the effect of the bonding area on the micro-shear and micro-tensile bond strengths of four dentin adhesive systems (Scotchbond MP Plus, 3M Dental Products, St. Paul, MN; OptiBond FL, Kerr Corp., Orange, CA; OptiBond Solo, Kerr Corp., Orange, CA; One-Step, Bisco, Inc., Itasca, IL). METHODS: Sixty extracted human molars were cut vertically and occlusal enamel removed, one half of the tooth was used for tensile testing and one half for shear. The occlusal dentin was bonded according to manufacturers' directions with a resin composite block and sectioned to obtain up to three square bar-shaped specimens, which were shaped with a high speed diamond bur on a lathe to produce cylindrical specimens of 1.2, 1.4 or 2.0 mm diameter at the bonded interface. The bonds were stressed in shear or tension at a crosshead speed of 1 mm min-1. The mean bond strengths were compared using one-way ANOVA, two-way ANOVA and Student's t-test. The fractured surfaces were examined under a scanning electron microscope and the frequency of fracture modes was compared using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: For all materials, the 2.0 mm diameter group showed significantly lower bond strengths than the 1.2 mm diameter group in both shear and tensile tests (p < 0.05). Most specimens of 1.2 mm or 1.4 mm diameter exhibited adhesive failure at the interface between the dentin and the adhesive resin. SIGNIFICANCE: The results indicate that small surface areas of test specimens are associated with higher bond strengths and that the effect on tensile and shear values is similar.

Analysis of Variance↗
PubMed1998

The influence of cross-sectional shape and surface area on the microtensile bond test.

OBJECTIVES: The purpose of this study was to determine the effect of the cross-sectional area shape (cylindrical vs. rectangular) and the bonding surface area on the microtensile bond strengths and stress distribution of four dentin adhesive systems (Scotchbond MP Plus, OptiBond FL, OptiBond Solo, One-Step). In addition, finite element analysis (FEA) models were developed to investigate stress distributions. METHODS: Extracted human molars were cut vertically and the occlusal enamel removed; one-half of the tooth was used for rectangular specimens, the other half for cylindrical specimens. The occlusal dentin was bonded according to the manufacturers' directions and covered with a block of resin composite. For the cylindrical specimens, the bonded dentin was shaped with a diamond bur on a lathe to produce specimens of area 1.1, 1.5 or 3.1 mm2 at the bonded interface. The rectangular specimens were sectioned to obtain bar-shaped specimens, which were shaped to produce hour-glass shaped specimens with the same area as the round specimens. Bonds were stressed in tension at a speed of 1 mm min-1. The mean bond strengths were compared using two-way ANOVA, one-way ANOVA, LSD and Student's t tests. The fractured surfaces were examined by scanning electron microscopy, and the frequencies of the fracture modes were compared using the Kruskal-Wallis and Mann-Whitney U tests. FEA models were created simulating the cross-sectional areas for bonding to determine the stress distribution. RESULTS: The 3.1 mm2 bonding area groups showed significantly lower bond strengths than the 1.1 mm2 bonding area groups (p < 0.05), except for the rectangular specimens using Scotchbond MP Plus and One-Step. Most cylindrical specimens of bonding area 1.1 or 1.5 mm2 exhibited adhesive failure at the interface between the dentin and the adhesive resin. No differences were determined between cylindrical and rectangular specimens. The fracture mode matched the stress distribution patterns calculated from the FEA modeling. SIGNIFICANCE: The results indicate that the test methods using small surface areas produce higher bond strengths than those using larger surface areas, and that cross-sectional shape has little effect. This is probably a result of fewer defects occurring in the small-area specimens.

Analysis of Variance↗
PubMed1998

The evaluation of resin composite consistency.

OBJECTIVE: To evaluate a method for the assessment of the consistency of unset resin composite. METHODS: Fourteen commercial resin composites were selected, which had a range of consistencies as assessed subjectively. The material was placed in a cylindrical mold with 8 mm diameter and 8 mm depth, and a glass rod with 4.37 mm diameter driven into the composite at 24.4 mm min-1 for 6 s, i.e., to a depth of 2.44 mm. The maximum force reached during the 6 s period was recorded, and used as a measure of consistency. RESULTS: Consistency values ranged from 0.33 N to 31.3 N, with the highest values being found for some of the recently introduced 'packable' materials. The reliability of the test was high. SIGNIFICANCE: The test may be useful as a standard method of assessing resin composite consistency.

Analysis of Variance↗
PubMed1998

Direct resin-bonded, fibre-reinforced anterior bridges: a clinical report.

Direct resin composite cantilever bridges were placed in patients to replace 26 single upper anterior teeth and one upper premolar. Twenty-four bridges were simple cantilevers, and three were fixed-fixed bridges. The bridges were constructed with hybrid resin composite placed around a resin-impregnated plasma-etched polyalkane fibre bundle bonded to the abutment tooth enamel by the acid-etch technique. Twenty-five bridges were assessed at 10 +/- 1 months. Two had fractured due to trauma, however, in both cases the pontic remained attached to the abutment tooth by the fibre bundle. This method of tooth replacement is viewed as a rapid, simple, cost-effective means of replacing anterior teeth in selected patients.

Acid Etching, Dental↗
PubMed1998

Determinants of quality in operative dentistry.

The definition of quality in operative dentistry has often, at least in part, been related to how well a cut preparation compares with an ideal preparation. The ideal preparation follows well-defined design principles. These design principles have their roots in empirical dentistry and scientific evaluations, the latter often being conducted in vitro. Because of the complexity of following these design principles practically, a large portion of dental education consists of perfecting cavity preparations. By focusing on how to cut these cavity preparations as closely as possible to the ideal preparation, dentists with high psycho-motor skills have been able to provide the public with restorative procedures of high standards over the years. However, because of the tendency of relating quality in operative dentistry to the ideal preparation, we found it justifiable to review the literature dealing with the cavity design principles of the Class II amalgam preparation. What triggered this review was a request from the International Dental Federation (FDI) to start a process leading to a scientifically based quality definition of dental restorations, a definition that determines how different factors, including cavity design principles, affect the longevity of both tooth and restoration. From our review, we conclude that patient response and restoration performance over time, rather than how closely a cavity preparation compares with the ideal preparation, will be of more significance in determining the longevity of a Class II amalgam restoration.

Dental Amalgam↗