Evaluation of the efficacy of calcium silicate vs. glass ionomer cement indirect pulp capping and restoration assessment criteria: a randomised controlled clinical trial-2-year results.

OBJECTIVES: Assess calcium silicate cement (Biodentine™) vs. glass ionomer cement (Fuji IX™, control) as indirect pulp capping (IPC) materials in patients with reversible pulpitis after a 2-year follow-up. Evaluate the integrity of the overlying resin composite restorations using modified USPHS criteria and FDI criteria. Investigate the sensitivity of the modified USPHS criteria compared to the FDI criteria in the assessment of the restorations. MATERIALS AND METHODS: Seventy-two restorations (36 Biodentine™, 36 Fuji IX™) were placed randomly in 53 patients. Periapical radiographs were taken at pre-treatment (T0), 12-month (T12), and 24-month (T24) review. Restorations were assessed using the modified USPHS and FDI criteria at T12 and T24. RESULTS: At 24 months, 15 teeth had failed to maintain vitality (6 Biodentine™, 9 Fuji IX™). Clinical success rate of IPC for both materials was 72% and is related to the intensity of reversible pulpitis symptoms. No difference was found between T12 and T24 in the periapical (PA) radiographs and in the integrity of the resin composite restorations overlying Biodentine™ compared to Fuji IX™. There was no difference in the efficacy of the USPHS criteria compared to the FDI criteria in the assessment of the resin composite restorations. CONCLUSIONS: Biodentine™ and Fuji IX™ were clinically effective when used as IPC materials in teeth with reversible pulpitis at T24. Resin composite restorations overlying both materials performed well at T24. Using the USPHS or FDI criteria is equally efficient at T24; however, longer term follow-up is needed to establish whether there are sensitivity differences between these assessment criteria. CLINICAL SIGNIFICANCE: Teeth with deep carious lesions approaching the pulp and with signs of reversible pulpitis can be treated successfully by indirect pulp capping using either Biodentine™ or Fuji IX™. Using the USPHS or FDI criteria to assess restorations is equally effective at 2 years. TRIAL REGISTRATION: NCT02201641.

An in vitro investigation of pre-treatment effects before fissure sealing.

BACKGROUND: Fissure sealants prevent occlusal caries in permanent molars. Enamel preparation methods are used before fissure sealing. AIMS: To investigate effects of bioglass air-abrasion pre-treatment with and without an adhesive, on fissure enamel of permanent teeth, with respect to etchability, microleakage and microtensile bond strength. DESIGN: Half of the occlusal surfaces of 50 extracted premolars underwent bioglass air-abrasion. Dye was applied to the entire occlusal surface. Photographs were taken to score etched surface by dye uptake. Adhesive was applied to 25 of the bioglass-treated areas and all teeth were fissure sealed, sectioned, and evaluated using confocal microscopy. Buccal and lingual surfaces of a further eight premolars were acid-etched and randomly received: air-abrasion, adhesive, both, or none before sealant application for microtensile bond strength measurement in half of the samples immediately and half following 6 months of water immersion. RESULTS: Linear mixed models and multinomial logistic regression were used (P = 0.05). Bioglass air-abrasion significantly improved enamel etchability and reduced microleakage. The addition of an adhesive made no difference to either microleakage or microtensile bond strength. The combination of bioglass abrasion and adhesive led to more cohesive, rather than adhesive, failure. CONCLUSIONS: Bioglass air-abrasion improved enamel etchability and reduced microleakage irrespective of the adhesive use but neither pre-treatment affected the microtensile bond strength.

Penetration depth of monomer systems into acrylic resin denture teeth used as pontics.

STATEMENT OF PROBLEM: The ways of softening and dissolving the surface of acrylic resin denture teeth need to be specified to obtain more durable prosthetic treatments that include resin denture teeth. PURPOSE: The purpose of this study was to analyze the penetration depth of 4 monomer systems applied during different exposure times on the acrylic resin denture teeth used as pontics of directly fabricated fiber-reinforced composite fixed dental prostheses. The penetration depth contributes to the adhesion of the tooth to the adhesive resin. MATERIAL AND METHODS: Ninety-six specimens were divided into 3 groups according to the acrylic resin denture tooth used: Artic 8 (Heraeus Kultzer), experimental tooth (GC), and Vitapan (Vita). Each group was divided into 4 subgroups according to the monomer system used: methylmethacrylate (99%), composite primer, a flowable composite resin, and a photopolymerizing dimethacrylate resin. The 4 monomer systems were labeled with rhodamine B to determine their penetration depth into the acrylic resin denture teeth. After exposure times of 1, 5, 15, and 60 minutes, the monomers were photopolymerized for 5 minutes, with the exception of methylmethacrylate. The specimens were cut orthogonally from gingival to occlusal in 4 slices (n=8/subgroup). The penetration depths of monomers were measured by a confocal scanning type microscope. Differences in the penetration depths were evaluated with ANOVA. RESULTS: ANOVA (R(2)=.699) revealed significant differences in the penetration depths according to the exposure times (P<.001), monomers (P<.001), brands used (P=.047), and their mutual interaction (P<.001). CONCLUSIONS: The ability of monomers to penetrate the surface of acrylic resin denture teeth was influenced by the monomer systems, which might improve the bond between the pontics and the fiber-reinforced composite frameworks of fixed dental prostheses.

Influence of air-abrasion executed with polyacrylic acid-Bioglass 45S5 on the bonding performance of a resin-modified glass ionomer cement.

The aim of this study was to test the microtensile bond strength (µTBS), after 6 months of storage in PBS, of a resin-modified glass ionomer cement (RMGIC) bonded to dentine pretreated with Bioglass 45S5 (BAG) using various etching and air-abrasion techniques. The RMGIC (GC Fuji II LC) was applied onto differently treated dentine surfaces followed by light curing for 30 s. The specimens were cut into matchsticks with cross-sectional areas of 0.9 mm(2). The µTBS of the specimens was measured after 24 h or 6 months of storage in PBS and the results were statistically analysed using two-way anova and the Student-Newman-Keuls test (α = 0.05). Further RMCGIC-bonded dentine specimens were used for interfacial characterization, micropermeability, and nanoleakage analyses by confocal microscopy. The RMGIC-dentine interface layer showed no water absorption after 6 months of storage in PBS except for the interdiffusion layer of the silicon carbide (SiC)-abraded/polyacrylic acid (PAA)-etched bonded dentine. The RMGIC applied onto dentine air-abraded with BAG/H(2)O only or with BAG/PAA-fluid followed by etching procedures (10% PAA gel) showed no statistically significant reduction in µTBS after 6 months of storage in PBS. The abrasion procedures performed using BAG in combination with PAA might be a suitable strategy to enhance the bonding durability and the healing ability of RMGIC bonded to dentine.

Bioactive effects of a calcium/sodium phosphosilicate on the resin-dentine interface: a microtensile bond strength, scanning electron microscopy, and confocal microscopy study.

This study evaluated, through microtensile bond strength (µTBS) testing, the bioactive effects of a calcium/sodium phosphosilicate (BAG) at the resin-dentine interface after 6 months of storage in phosphate buffer solution (PBS). Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were also performed. Three bonding protocols were evaluated: (i) RES-Ctr (no use of BAG), (ii) BAG containing adhesive (BAG-AD), and (iii) BAG/H (3) PO (4) before adhesive (BAG-PR). The dentin-bonded specimens were prepared for µTBS testing, which was carried out after 24 h or 6 months of storage in PBS. Scanning electron microscopy ultramorphology analysis was performed after debonding. Confocal laser scanning microscopy was used to evaluate the morphological and nanoleakage changes induced by PBS storage. High µTBS values were achieved in all groups after 24 h of storage in PBS. Subsequent to 6 months of storage in PBS the specimens created using the BAG-AD bonding approach still showed no significant reduction in µTBS. Moreover, specimens created using the BAG-AD or the BAG-PR approach showed an evident reduction of nanoleakage after prolonged storage in PBS. The use of BAG-containing adhesive may enhance the durability of the resin-dentine bonds through therapeutic/protective effects associated with mineral deposition within the bonding interface and a possible interference with collagenolytic enzyme activity (matrix metalloproteinases) responsible for the degradation of the hybrid layer.

Therapeutic effects of novel resin bonding systems containing bioactive glasses on mineral-depleted areas within the bonded-dentine interface.

This study aimed in evaluating the effects of two experimental resin bonding systems containing conventional Bioglass 45S5 (BAG) or Zinc-polycarboxylated bioactive glass (BAG-Zn) micro-fillers on the resin-bonded dentine interface after storage in a simulated body fluid solution (SBFS). Three resin bonding systems were formulated: Resin-A: (BAG containing); Resin-B; (BAG-Zn containing); Resin-C (no filler). The ability of the experimental resins to evoke apatite formation was evaluated using confocal Raman spectroscopy. Acid-etched dentine specimens were bonded, and prepared for AFM/nano-indentation analysis in a fully-hydrated status to evaluate the modulus of elasticity (Ei) and hardness (Hi) across the interface at different SBFS storage periods. Further resin-dentine specimens were tested for microtensile bond strength after 24 h or 3 months of SBFS storage. SEM examination was performed after de-bonding and confocal laser microscopy was used to evaluate the ultramorphology of the interfaces and micropermeability. The resin A and B showed a consistent presence of apatite (967 cm(-1)), reduced micropermeability within the resin-dentine interface and a significant increase of the Ei and Hi along the bonded-dentine interface after prolonged SBFS storage. Bond strength values were affected by the resin system (P < 0.0001) and by storage time (P < 0.0001) both after 24 h and 3 months of SBFS storage. In conclusion, resin bonding systems containing bioactive fillers may a have therapeutic effect on the nano-mechanical properties and sealing ability of mineral-depleted resin-dentine interface.

Glass-ionomer and calcium silicate-based cements interactions with human dentine in health and disease: Two-photon fluorescence microscopy and Raman spectroscopy analysis.

OBJECTIVES: To investigate the potential mineralising effects of calcium silicate-based dentine replacement material (Biodentine™) in comparison with glass-ionomer cement (GIC) (Fuji IX™) on different human dentine substrates using a multimodal non-invasive optical assessment. METHODS: Cements were applied on artificially demineralised or naturally carious dentine and stored for 4 weeks in phosphate-rich media +/- tetracycline used for mineralisation labelling. Interfacial dentine was examined from the same sample and location before and after aging using two-photon fluorescence microscopy, fluorescence lifetime imaging (FLIM) and second harmonic generation (SHG) imaging. Additionally, Raman spectroscopy was used to detect changes in the mineral content of dentine. RESULTS: Significant changes in the fluorescence intensity and lifetime were detected in partially demineralised dentine and caries-affected dentine underneath both tested cements, after storage (p < 0.001). This was associated with a significant increase in the mineral content as indicated by the increased intensity of the phosphate Raman peak located at 959 cm-1 (p < 0.0001). Caries-infected dentine showed significant fluorescence changes under Biodentine™ after storage (p < 0.001), but not under GIC (p = 0.44). Tetracycline binding induced a reduction in the fluorescence lifetime with comparable increase in the fluorescence intensity in both cements' groups within the affected dentine (p < 0.001). Significance Two-photon fluorescence microscopy can be used efficiently for non-destructive in-vitro dentine caries characterisation providing a technique for studying the same dentine-cement interface over time and detect changes. Biodentine™ demonstrated comparable remineralising potential to GIC, in addition to inducing remineralisation of caries-infected dentine. This may suggest using Biodentine™ as part of minimally invasive operative dentistry (MID) in caries management.

An in vitro evaluation of selective demineralised enamel removal using bio-active glass air abrasion.

Unnecessary over-preparation of carious enamel often occurs clinically during operative caries management. The working hypothesis to be investigated in this study is the potential for bio-active glass air abrasion to remove selectively only demineralised enamel in artificial enamel lesions when compared to equivalent alumina air abrasion, so potentially minimising cavity over-preparation. Bisected artificial, paired smooth surface enamel lesions on ethics-approved, extracted sound human molars were created and subsequently air abraded with 27 µm alumina (n = 19) and bio-active glass (n = 19). The difference between pre-operative lesion boundary and post-operative cavity margin was calculated following optical confocal fluorescent assessment of the lesion boundary. Data indicated mean% over-preparation (sound enamel removal) of 176% with alumina and 15.2% for bio-active glass (p = 0.005). Bio-active glass abrasion removed completely the demineralised enamel from artificial lesions with clinically insignificant over-preparation of sound tissue, indicating technique selectivity towards grossly demineralised enamel. Alumina air abrasion resulted in substantial enamel removal in both sound and demineralised tissues indicating the operator selectivity required to use the techniques effectively in clinical practice.

Effects of common dental materials used in preventive or operative dentistry on dentin permeability and remineralization.

The aim of this study was to evaluate the dentin remineralization induced by bioactive substances contained in common dental materials used in preventive and operative dentistry. Several materials were applied on human dentin segments. Dentin permeability was quantified using a fluid filtration system working at 20 cm H(2)O. Micro-Raman, SEM-EDX, and microhardness calculation were used to evaluate changes in the mineralization of dentin. Dentin treated with the prophylactic materials showed different dentin permeability values, in particular subsequent to immersion in remineralizing solutions (RSS). The bioactive glass (Sylc) was the only substance able to reduce dentin permeability after immersion in remineralizing solution and to show hydroxyapatite precipitation as a sign of dentin remineralization. The reduction in dentin permeability obtained after the application of the other prophylactic materials used in this study was due to the presence of the remnant material in the dentinal tubules, with no remineralization effect after storage in remineralizing solution. In conclusion, the results indicated that bioactive glass prophy powder may induce immediate remineralization of dentin.

Effect of resin coating and occlusal loading on microleakage of Class II computer-aided design/computer-aided manufacturing fabricated ceramic restorations: a confocal microscopic study.

OBJECTIVE: To evaluate the effect of resin coating and occlusal loading on microleakage of class II computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic restorations. MATERIAL AND METHODS: Molars were prepared for an mesio-occlusal-distal (MOD) inlay and were divided into two groups: non-coated (controls); and resin-coated, in which the cavity was coated with a combination of a dentin bonding system (Clearfil Protect Bond) and a flowable resin composite (Clearfil Majesty Flow). Ceramic inlays were fabricated using the CAD/CAM technique (CEREC 3) and cemented with resin cement (Clearfil Esthetic Cement). After 24 h of water storage, the restored teeth in each group were divided into two subgroups: unloaded or loaded with an axial force of 80 N at a rate of 2.5 cycles/s for 250,000 cycles while stored in water. After immersion in 0.25% Rhodamine B solution, the teeth were sectioned bucco-lingually at the mesial and distal boxes. Tandem scanning confocal microscopy (TSM) was used for evaluation of microleakage. The locations of the measurements were assigned to the cavity walls and floor. RESULTS: Loading did not have a significant effect on microleakage in either the resin-coated or non-coated group. Resin coating significantly reduced microleakage regardless of loading. The cavity floor exhibited greater microleakage compared to the cavity wall. TSM observation also revealed that microleakage at the enamel surface was minimal regardless of resin coating. In contrast, non-coated dentin showed extensive leakage, whereas resin-coated dentin showed decreased leakage. CONCLUSIONS: Resin coating with a combination of a dentin-bonding system and a flowable resin composite may be indicated prior to impression-taking when restoring teeth with CAD/CAM ceramic inlays in order to reduce microleakage at the tooth-resin interface.

Durability of resin cement bond to aluminium oxide and zirconia ceramics after air abrasion and laser treatment.

PURPOSE: The erbium laser has been introduced for cutting enamel and dentin and may have an application in the surface modification of high-strength aluminum oxide and zirconia ceramics. The aim of this study was to evaluate the durability of the bond of conventional dual-cured resin cements to Procera Al(2)O(3) and zirconium oxide ceramics after surface treatment with air abrasion and erbium laser. MATERIALS AND METHODS: One hundred twenty Al(2)O(3) and 120 zirconia specimens measuring 3 × 3 × 0.7 mm(3) were divided equally into three groups, and their surfaces treated as follows: either untreated (controls), air abraded with Al(2)O(3) particles, or erbium-laser-treated at a power setting of 200 mJ. The surface of each specimen was then primed and bonded with one of two dual-cured resin cements (either SCP-100 Ceramic Primer and NAC-100 or Monobond S and Variolink II) using a 1-mm thick Tygon tube mold with a 0.75-mm internal bore diameter. After 24 hours and 6 months of water storage at 37°C, a microshear bond strength test was performed at a crosshead speed of 1 mm/min. Surface morphology was examined using a confocal microscope, and failure modes were observed using an optical microscope. The data were analyzed using the Kaplan-Meier nonparametric survival analysis. RESULTS: In the case of zirconia, air abrasion and Erbium:yttrium-aluminum-garnet (Er:YAG) laser treatment of the ceramic surface resulted in a significant reduction in the bond strengths of both resin cements after 6 months water storage; however, when the zirconia surface was left untreated, the SCP-100/NAC-100 group did not significantly reduce in bond strength. In the case of alumina, no treatment, air abrasion and Er:YAG laser treatment of the surface led to no significant reduction in the bond strengths of the three SCP-100/NAC-100 groups after 6 months water storage, whereas all three Monobond S/Variolink II groups showed a significant reduction. CONCLUSION: Er:YAG laser treatment of the zirconia surface did not result in a durable resin cement/ceramic bond; however, a durable bond between a conventional dual-cured resin cement and Procera All Ceram and Procera All Zirkon was formed using a ceramic primer containing the phosphate monomer, MDP, without any additional surface treatment.

Flexural strength of glass fibre-reinforced posts bonded to dual-cure composite resin cements.

The aims of this study were to evaluate the flexural strength of two different types of glass fibre-reinforced posts bonded to dual-cure composite resin cements. Forty glass methacrylate-based fibre posts (GC Fiber Post) and 20 glass fibre inter-polymerizing network posts (everStick POST) were divided into three groups. Group 1 contained 20 GC posts that were bonded to a dual-cure composite cement (UnifilCore). Group 2 contained 20 Stick Tech posts that had adhesive applied (Scotchbond Multipurpose resin) and were bonded to a dual-cure composite resin cement (RelyX Unicem). Group 3 contained 20 GC posts that were pretreated with a silane-coupling agent before being treated with resin and composite, as in group 1. A 4-point bend test was carried out to failure on all of the groups. Failure modes were determined using scanning electron microscopy. Pretreatment of the post surface with the silane-coupling agent did not increase the flexural strength. The flexural strength of the Stick Tech post was significantly lower than the flexural strength of the GC post. The mode of failure for the GC Posts was adhesive, whereas the Stick Tech posts failed cohesively. Different flexural strengths and failure modes were observed among the two fibre post-resin systems.

Effect of resin coating on adhesion and microleakage of computer-aided design/computer-aided manufacturing fabricated all-ceramic crowns after occlusal loading: a laboratory study.

This study investigated the effect of resin coating and occlusal loading on adhesion and microleakage of all-ceramic crowns. Molars were prepared for an all-ceramic crown and were divided into two groups: non-coated (control) and resin-coated with Clearfil Tri-S Bond. Crowns were fabricated using CEREC 3 and cemented using Clearfil Esthetic Cement. After 24 h of storage in water, the restored teeth in each group were divided into two subgroups: unloaded, or loaded while stored in water. Mechanical loading was achieved with an axial force of 80 N at 2.5 cycles s(-1) for 250,000 cycles. After immersion in Rhodamine B, the specimens were sectioned and processed for microleakage evaluation by confocal microscopy, which was followed by further sectioning for microtensile bond testing. Loading had no significant effect on microleakage in either the resin-coated or non-resin-coated groups. Resin coating did not reduce the microleakage at the dentine interface but increased the microleakage at the enamel interface. All the beams fractured during slicing when non-coated and loaded. The bond strengths of non-coated and unloaded, resin-coated and unloaded, and resin-coated and loaded groups were 15.82 +/- 4.22, 15.17 +/- 5.24, and 12.97 +/- 5.82 MPa, respectively. Resin coating with Clearfil Tri-S Bond improved the bonding of resin cement to dentine for loaded specimens. However, it was not effective in reducing the microleakage, regardless of whether it was loaded or unloaded.

Prevention of water contamination of ethanol-saturated dentin and hydrophobic hybrid layers.

PURPOSE: This in vitro study evaluated the amount and distribution of outward fluid flow that occurred when an experimental etch-and-rinse hydrophobic adhesive was applied to ethanol-saturated dentin before and after oxalate pretreatment. MATERIALS AND METHODS: Measurements of dentin permeability were performed under a constant pulpal pressure of 20 cm H2O in deep and middle dentin. A lucifer yellow solution was placed in the pulp chamber to determine the distribution of the water contamination of the hybrid layers. RESULTS: The distribution of fluorescence in dentin specimens that were not pretreated with oxalate revealed that the dye permeated around the resin tags and filled the hybrid layer. Dentin specimens pretreated with oxalate prior to resin bonding, showed 80% to 83% less (p < 0.05) water contamination compared to controls. The dentin permeability results obtained before and after oxalate pretreatment showed that oxalate decreased dentin permeability by 98% (p < 0.05) compared to acid-etched controls. This prevented outward fluid movement during bonding, resulting in better resin sealing of dentin due to the formation of a double seal of resin tags over calcium oxalate crystals in the tubules. CONCLUSION: Outward dentinal fluid flow may contaminate hybrid layers during adhesive bonding procedures. Pretreatment of acid-etched dentin with 3% oxalic acid prior to bonding procedures can prevent outward fluid flow during bonding and water contamination of the hydrophobic hybrid layers.

An in-vitro investigation of the effects of variable operating parameters on alumina air-abrasion cutting characteristics.

Air-abrasion is a tooth preparation technology developed in the 1940s that is currently gaining popularity due to its compatibility with adhesive restorations. Variables, including propellant pressure, powder flow rate, nozzle angle and distance to the tooth surface abrasion time, can affect the cutting rate of the air-abrasion unit. A static setup and a more clinically realistic dynamic experimental setup have been used to assess the effect of these parameters of the cutting rate on an enamel analogue. By keeping each parameter fixed, its effect on the cutting rate was examined. The results showed that increasing the propellant pressure (20-100 PSI) caused an almost linear increase in the cutting rate in both setups. Increasing the powder flow rate (0.5 - 3 g/minute) concurrently increased the powder flow and caused an increase in the cutting rate but with a plateau differing for the different propellant pressures. The nozzle angles producing the highest cutting rates were 60 degrees and 75 degrees for static and dynamic cutting, respectively, with smaller and larger angles producing lower rates. Increasing abrasion time in static cutting and the nozzle advancement rate in dynamic cutting both caused an increase in the cutting rate. These findings are relevant for both clinicians, who might wish to alter the cutting rate of their instrument, and researchers, who should always control the numerous parameters in studies involving air-abrasion in order to control the variables, which can influence the end effect of air-abrasion.

Deproteinization effects of NaOCl on acid-etched dentin in clinically-relevant vs prolonged periods of application. A confocal and environmental scanning electron microscopy study.

Complete removal of the collagen matrix with sodium hypochlorite (NaOCl) as an adjunctive step of restorative and adhesive dentistry is still a subject for debate. This study evaluated the efficacy of a 12 w/v% NaOCl solution for complete removal of exposed collagen matrices from acid-etched dentin surfaces within a maximum clinically possible period of 120 seconds and a longer period of application (10 minutes) using confocal reflection/immuno-fluorescence microscopy and ESEM. An extended period (45 minutes) of NaOCl application was also performed as a negative control. Unstained and immunohistochemically-stained collagen fibrils were imaged using a confocal laser-scanning microscope for the reflection/fluorescence experiment. Fully-hydrated specimens were also examined with an ESEM. Unetched dentin was devoid of exposed collagen fibrils. Conversely, confocal microscopy showed demineralized collagen after acid-etching, which appeared as a hydrogel-like layer during ESEM examination. The application of NaOCl for two minutes left remnants of dentin collagen on intertubular and intratubular surfaces. The ESEM examination confirmed the presence of remnants of a hydrogel-like layer. After 10 minutes of NaOCl application, residual collagen reflection and immuno-fluorescence signals were detected around dentinal tubules, appearing as spike-like projections during the ESEM investigation. Complete dissolution of the collagen presence was achieved after 45 minutes of NaOCl treatment. Complete deproteinization of acid-etched dentin is unachievable in a maximum clinically possible period of 120 seconds.

Chitosan-bioglass complexes promote subsurface remineralisation of incipient human carious enamel lesions.

OBJECTIVES: To test the in vitro subsurface remineralisation efficacy of chitosan-bioglass complex on artificial white spot lesions. METHODS: 64 artificial enamel white spot lesions were created by acidic gel and equally separated for static and 7d pH-cycling models. In each model, samples were assigned to 4 groups: (1) bioglass application on chitosan pre-treated lesions (CB); (2) chitosan-bioglass slurry (CBS); (3) "standard" remineralisation solution (RS - positive control); (4) deionised water (NC - negative control). Before each treatment using remineralising agents, 3-minute pellicle was formed on lesions' surfaces. Mineral content changes, surface and subsurface microhardness and ultrastructure were evaluated by Raman intensity mapping, Knoop microhardness and scanning electron microscopy, respectively. Data were statistically analysed using one-way ANOVA with Tukey's test (p < 0.05 is considered as significant). RESULTS: Chitosan-bioglass complexing was found to exhibit greater mineral regain and recovery of surface and subsurface microhardness compared to "standard" remineralisation solution and control groups, after static and dynamic pH-cycling remineralisation for 7 days (p < 0.05). Specifically, dense precipitations with Ca/P ratios similar to that in pure hydroxyapatite (HA) were observed on surfaces and subsurfaces which filled the porosities in the dynamic pH-cycling group, leaving no prismatic enamel structure exposed. CONCLUSIONS: Chitosan-bioglass complex is positive in promoting subsurface mineral deposition in spite of the presence of a short-term salivary pellicle. Clinical significance chitosan-bioglass complexing may provide an alternative clinical strategy in remineralising early enamel carious lesions as well as desensitizing exposed porous vital dental tissues clinically.

An in vitro investigation of the effectiveness of bioactive glass air-abrasion in the 'selective' removal of orthodontic resin adhesive.

The process of clinically debonding orthodontic brackets causes histomorphological damage to enamel that needs to be quantified and minimized. This study compared three methods for removing residual resin adhesive following bracket debonding. The surface finish following removal of residual adhesive using a slow-speed eight-bladed tungsten carbide bur (group 1), alumina air-abrasion (group 2), and bioactive-glass air-abrasion (group 3) and following polishing, was examined using scanning electron microscopy imaging of resin replicas. Contact profilometry was used to image surfaces before and after debonding for quantifiable volumetric analysis of enamel damage. Surface scarring was seen on scanning electron micrographs from group 1, a sharp pitted surface was identified in group 2, while group 3 exhibited similar, but subjectively smoother, pits. The surface finish following polishing was similar for groups 2 and 3 but did not completely remove the scarring evident from group 1. Quantifiable enamel lost was as follows: group 1, 0.285 mm(3); group 2, 0.386 mm(3); and group 3, 0.135 mm(3); statistical differences were observed between groups 2 and 3. From these results, bioactive-glass air-abrasion more consistently caused less physical damage to enamel and achieved a clinically smooth surface finish following polishing and is therefore to be recommended for clinical use.

Micropermeability of current self-etching and etch-and-rinse adhesives bonded to deep dentine: a comparison study using a double-staining/confocal microscopy technique.

Water sorption decreases the mechanical properties and the bond strengths of resin-bonded dentine. The aim of this study was to evaluate the micropermeability of several self-etching and etch-and-rinse adhesives. Optibond FL, Silorane, Scotchbond 1XT, G-Bond, and DC-Bond were bonded under simulated pulpal pressure. A 10 wt% solution of ammoniacal silver nitrate and a 1 wt% solution of rhodamine B were injected into the pulp chamber at 20 cm of water pressure. The dentine-adhesive interfaces were examined using a confocal scanning microscope. Micropermeability was detected in all the adhesives. DC-Bond, G-Bond, and Scotchbond 1XT showed voids along the resin-bonded interface. Silorane and Optibond FL showed an adhesive layer that was free from water trees and micropermeability. The double staining technique is a method that gives accurate results in the study of the resin-dentine micropermeability. Each class of adhesive has a different distribution of micropermeability. The higher the micropermeability, the higher the risk of defects at the resin-dentine interface, which may represent the pathway for hydrolytic and enzymatic degradation of resin-dentine bonds over time.

An investigation of the effect of powder reservoir volume on the consistency of alumina powder flow rates in dental air-abrasion devices.

OBJECTIVES: To investigate the effect of powder reservoir fill volume on the emitted alumina powder flow rate of four dental air-abrasion units. The null hypothesis examined was that powder reservoir fill volume has no effect on alpha-alumina powder flow rate. METHODS: The spent alumina powder from the four air-abrasion units tested (Abradent, Crystalmark, Clendale, CA, USA; Aquacut, Velopex, Horesham, UK; MicroPrep Associate Lares, Chico, CA, USA; Rondoflex 360, KaVo, Lake Zurich, IL, USA) was gathered in a collecting chamber over a 60s running period. The difference in the weight pre- and post-collection was noted and flow rate calculated for different reservoir fill volumes (100%, 75%, 50% and 25%). RESULTS: The powder flow rate of each machine was significantly affected by a change in powder reservoir volume (p<0.05). In all devices a partially empty reservoir caused a significant decrease in powder flow rate, compared to that at maximum fill volume. The maximum percentage difference seen using the Rondoflex was similar for 27 microm and 50 microm abrasive (70% and 69%, respectively), whereas, smaller differences were seen with the Abradent (59%), Aquacut 29 microm and 53 microm abrasive (62% and 30%) and MicroPrep (35%) machines. CONCLUSION: It was shown that the fill of the reservoir affects the powder flow rate of air-abrasion units, thus disproving the null hypothesis. In a clinical setting and in future research studies, the powder reservoir should be filled to a set level to achieve a constant and reproducible cutting performance of the tested units.