Publications by authors named "Garry J P Fleming"
A critical examination of the literature for dental wear publications highlighted three distinct areas, clinical data, laboratory data and the simulation of the clinical situation data. The imprecision of the clinical data values from direct and indirect in vivo methods renders the clinical data compromised at best. Laboratory data showed a focus on finding a correlation between simplistic laboratory abrasive wear resistance studies and established materials science laboratory techniques, but with no actual correlation identified.
View Article and Find Full Text PDFObjective: The fabrication of all-ceramic restorations using Computer Aided Design and Computer Aided Manufacturing (CAD-CAM) most commonly involves subtractive machining which results in strength-limiting, surface and sub-surface damage in the resultant prosthesis. The objective was to explore how clinically relevant machining-process variables, and material variables, affect damage accumulation in lithium silicate glass-ceramics.
Methods: Three commercial lithium silicate glass-ceramics (IPS e.
Objectives: Despite developments in polycrystalline ceramics, glassy dental-ceramic materials provide the optimum cosmetic option in most clinical situations to mimic the natural dentition. The clinical success of glassy dental-ceramic materials is often attributed to resin-adhesive bonding techniques. In this study we explore whether shrinkage stresses generated on photo-polymerisation of the resin-cement are sufficient to induce ceramic surface defect stabilization, and we quantify the transient nature of the induced stresses.
View Article and Find Full Text PDFObjective: To assess the cuspal deflection of standardised large mesio-occluso-distal (MOD) cavities in third molar teeth restored using conventional resin-based composite (RBC) or their bulk fill restorative counterparts compared with the unbound condition using a twin channel deflection measuring gauge. Following thermocycling, the cervical microleakage of the restored teeth was assessed to determine marginal integrity.
Methods: Standardised MOD cavities were prepared in forty-eight sound third molar teeth and randomly allocated to six groups.
Objectives: Characterisation of the interaction between crack extension, crack stabilisation and stress/strain relaxation in the polymeric matrix, the interplay between stress corrosion cracking and the mechanical response of a resin-based luting adhesive within a surface defect population could extend PLV restoration longevity by optimising cementation protocols. The aim was to investigate the influence of stress corrosion cracking and the viscoelastic behaviour of a resin-based luting adhesive independently by controlling the environmental conditions operative during test specimen fabrication.
Methods: The effects of stress corrosion at ceramic crack tips and potential viscoelastic responses to loading of the resin-coated impregnating cracks were isolated.
Objective: To investigate the fundamental wear mechanisms of six resin-based composite (RBC) formulations during short-term in vitro wear testing.
Materials: RBC materials were condensed into rectangular bar-shaped specimens and light irradiated using the ISO 4049 specimen manufacture and irradiation protocol. Wear testing (n=10 specimens for each RBC) was performed on a modified pin-on-plate wear test apparatus and wear facets were analysed for wear volume loss using a white light profilometer.
Objective: To identify the minimum data acquisition variables in the x- and y-planes required when using three-dimensional (3D) profilometry to produce accurate mean total volumetric wear and mean maximum wear depth measurements for a range of wear facets produced by an oral wear simulator.
Methods: The Oregon Health Science University (OHSU) oral wear simulator was employed to wear an experimental resin-based composite formulation from 25,000 to 400,000 wear cycles. Mean total volumetric wear and mean maximum wear depth were determined using a contact profilometry at a measurement speed of 1mm/s.
Objective: To investigate the use of a three-dimensional (3D) digital scanning method in determining the accuracy of the wear performance parameters of resin-based composites (RBCs) determined using a two-dimensional (2D) analogue methodology following in-vitro testing in an Academisch Centrum for Tandheelkunde Amsterdam (ACTA) wear machine.
Methods: Specimens compatible with the compartments of the ACTA wear machine specimen wheel (n=10) were prepared from one commercial and four experimental RBCs. The RBC specimens were rotated against an antagonist wheel in a food-like slurry for 220,000 wear cycles.
Dental pulp tissue can be damaged by a range of irritants, however, if the irritation is removed and/or the tooth is adequately restored, pulp regeneration is possible (Mjör and Tronstad, 1974 [1]). At present, dental restorative materials limit healing by impairing mineralization and repair processes and as a result new biologically-based materials are being developed (Ferracane et al., 2010 [2]).
View Article and Find Full Text PDFDirect application of histone-deacetylase-inhibitors (HDACis) to dental pulp cells (DPCs) induces chromatin changes, promoting gene expression and cellular-reparative events. We have previously demonstrated that HDACis (valproic acid, trichostatin A) increase mineralization in dental papillae-derived cell-lines and primary DPCs by stimulation of dentinogenic gene expression. Here, we investigated novel genes regulated by the HDACi, suberoylanilide hydroxamic acid (SAHA), to identify new pathways contributing to DPC differentiation.
View Article and Find Full Text PDFObjectives: To investigate the single-edge notched (SEN) bend fracture toughness (KIC) testing methodology as a reproducible and discriminatory mechanical testing protocol for encapsulated and hand-mixed glass-ionomers (GI).
Methods: SEN bend test-pieces (35.0±0.
Objectives: The study aims to characterise a low and high viscosity giomer bulk fill resin restorative with established low and high viscosity resin-based composite (RBC) restoratives at simulated clinical relevant specimen depths.
Methods: The irradiance of a light curing unit (Bluephase 20i) was measured on a laboratory-grade spectrometer at distances up to 10mm from the light tip (in 1mm increments). Polymerization kinetics (real-time decrease of CC double bond and degree of cure, DC) and micro-mechanical properties (Vickers hardness/HV; Depth of cure/DOC; Indentation modulus/E) were assessed at varying specimen depths (0.
Objectives: The development of glass-ionomers (GIs) from the earliest experimental GI formulations to the modern day commercially available GIs was reviewed. The aim of the review was to identify the developments in the glass powder and polyacid liquid constituents of GIs since their inception in the late 1960s.
Data: The glass powder has undergone major changes from the earliest GI powder formulation (G200) in an effort to enhance the reactivity with the polyacid liquid.
Objectives: To assess the cuspal deflection and cervical microleakage scores of standardised large mesio-occlusal-distal (MOD) cavities filled with different restoration protocols: (1) conventional resin restoratives, (2) bulk fill flowable base materials 'capped' with a conventional dimethacrylate resin-based composite (RBC) or (3) bulk fill resin restorative materials.
Methods: Standardised MOD cavities were prepared in sixty-four sound maxillary premolar teeth and randomly allocated to eight groups. Restorations were placed in conjunction with a universal bonding system and resin restorative materials were irradiated with a quartz-tungsten-halogen light-curing-unit.
Objectives: To identify a reproducible and discriminatory mechanical testing methodology to act as a performance indicator for hand-mixed glass-ionomer (GI) restoratives.
Methods: Groups of 20 (five batches of four) cylinders (6.0±0.
Objectives: As CAD/CAM technologies improve we question whether adhesive lamination of ceramic materials could offer mechanical advantages over monolithic structures and improve clinical outcomes. The aim was to identify whether an adhesive interface (a chemically cured resin-cement) would influence the biaxial flexure strength (BFS) and slow-crack growth in a machinable dental ceramic.
Methods: Monolithic and adhesively laminated (with a chemically cured dimethacrylate resin-cement) feldspathic ceramic discs of identical dimensions were fabricated.
The dental market is replete with new resorative materials marketed on the basis of novel technological advances in materials chemistry, bonding capability or reduced operator time and/or technique sensitivity. This paper aims to consider advances in current materials, with an emphasis on their role in supporting contemporary clinical practice.
View Article and Find Full Text PDFObjectives: Recently all-ceramic restorative systems have been introduced that use CAD/CAM technology to fabricate both the Y-TZP core and veneer-ceramic layers. The aim was to identify whether the CAD/CAM approach resulted in more favourable stressing patterns in the veneer-ceramic when compared with a conventionally sintered Y-TZP core/veneer-ceramic.
Methods: Nominally identical Vita VM9 veneer-ceramic disc-shaped specimens (0.
Objectives: To assess the cuspal deflection and cervical microleakage of standardized mesio-occluso-distal (MOD) cavities restored with a dimethacrylate resin-based-composite (RBC) placed with one 3-step, one 2-step and three 1-step bonding systems and compared with the unbound condition.
Methods: Forty-eight sound maxillary premolar teeth with standardized MOD cavities were randomly allocated to six groups. Restoration was performed in eight oblique increments using a quartz-tungsten-halogen (QTH) light curing unit (LCU) with the bonding condition as the dependent variable.
Aim: To investigate the inter-examiner variability of contact point displacement measurements (used to calculate the overall Little's Irregularity Index (LII) score) from digital models of the maxillary arch by four independent examiners.
Methods: Maxillary orthodontic pre-treatment study models of ten patients were scanned using the Lava(tm) Chairside Oral Scanner (LCOS) and 3D digital models were created using Creo(®) computer aided design (CAD) software. Four independent examiners measured the contact point displacements of the anterior maxillary teeth using the software.
Objectives: To assess the adhesive performance of three universal bonding systems (self-etch and total-etch protocols) with cuspal deflection and cervical microleakage score.
Methods: Fifty-six standardised sound maxillary premolar teeth with uniform mesio-occlusal-distal (MOD) cavities were randomly allocated to six groups. Restoration with resin-based composite (RBC) was performed in conjunction with a universal bonding system facilitated by a quartz-tungsten-halogen light-curing-unit.
Objectives: To investigate if resin-cementation of a soda lime glass dental analogue could elucidate information regarding the pattern of resin-reinforcement when coated in an environment actively scavenged of moisture.
Methods: 192 soda lime disc-shaped specimens (alumina particle air abraded, hydrofluoric acid-etched and silane coated) were randomly assigned to eight groups (n=24 per group) prior to resin-coating at seating loads of 5 N (Groups A-D) and 30 N (Groups E-H) in an environment where moisture was actively scavenged and maintained below 15 ppm. Following one week storage the discs were tested in biaxial flexure at crosshead rates of 0.
Objectives: To compare contact point displacement measurements, used to determine the Little's Irregularity Index (LII) score on study casts and digital models of study casts by an independent examiner.
Methods: The contact point displacement measurements of the six maxillary anterior labial teeth were measured on ten study casts using digital callipers and their associated digital models using Creo Parametric software on five occasions following scanning using a LAVA Chairside Oral Scanner (LCOS) three-dimensional (3D) intra oral scanner. Means, standard deviations and coefficients of variation (CoV) were determined, data analyses (Pearson's correlation coefficients (PCCs) and Intraclass correlation coefficients (ICCs)) and statistical analyses (three and two-way analyses of variance (ANOVAs) and Independent Sample Student's t-tests) were carried out (p<0.
Objectives: The study employed a three-dimensional (3D) human-derived oral mucosal model to assess the biocompatibility of base-metal dental casting alloys ubiquitous in fixed prosthodontic and orthodontic dentistry.
Methods: Oral mucosal models were generated using primary human oral keratinocyte and gingival fibroblast cells seeded onto human de-epidermidised dermal scaffolds. Nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) base-metal alloy immersion solutions were exposed to oral mucosal models for increasing time periods (2-72h).
Objective: To assess the depth of cure claims of two bulk-fill flowable RBC bases (SDR and x-tra base) using Fourier transform infrared (FTIR) spectroscopy, biaxial flexure strength (BFS), and Vickers hardness number (VHN) for specimen depths of 8mm (in 1mm increments).
Methods: The degree of conversion (DC) was measured by monitoring the peak height (6164cm(-1)) of specimens (11.0±0.