Fracture behavior of short fiber-reinforced CAD/CAM inlay restorations after cyclic fatigue aging.

The aim of this study was to assess the fracture behavior of molar teeth restored with MOD inlays made of experimental short fiber-reinforced CAD/CAM composite block (SFRC CAD) before and after cyclic fatigue aging. Standardized MOD cavities were prepared on 60 intact mandibular molars. Three groups of CAD/CAM made inlay restorations (Cerasmart 270, Enamic, and SFRC CAD) were fabricated (n = 20/group). All restorations were luted with self-adhesive dual-cure resin cement (G-Cem One). Half of restored teeth per each group (n = 10) were quasi-statically loaded until fracture without aging. The other half underwent cyclic fatigue aging for 500,000 cycles (Fmax = 150 N) before being loaded quasi-statically until fracture. Then, the fracture type was visually inspected. The microstructure and elemental content of CAD/CAM materials were assessed using SEM and EDS. Two-way analysis of variance (ANOVA) was used to statistically examine the data, and it was followed by the Tukey HSD test (α = 0.05). ANOVA demonstrated that both material type and aging had a significant effect (p < 0.05) on the load-bearing capacity values of the restorations. Teeth restored with SFRC CAD showed significantly the highest (p < 0.05) load-bearing capacity (2535 ± 830 N) after fatigue aging among all groups. SEM images showed the ability of short fibers in SFRC CAD composite to redirect and hinder crack propagation. With regard to fracture mode, Enamic group revealed 85% of catastrophic failure (vs. 45% and 10% for Cerasmart 270 and SFRC CAD, respectively). Large MOD cavities on molar teeth were most favorably restored with SFRC CAD inlays, yielding the highest load-bearing capacity and more restorable failures.

Co-Influence of Restoration Bonding and Inlay Cavity Design on Fracture Load of Restored Tooth.

INTRODUCTION: The aim of this study was to investigate the co-influence of indirect mesio- occlusal-distal (MOD) cavity geometry and inlay restoration bonding on quasi-static fracture load of the restored tooth. METHODS: Forty-eight intact human molar teeth were selected and prepared for standardized edge-shaped or round-shaped MOD cavities. The resin composite (Cerasmart, GC) inlays were bonded with the state-of-the-art inlay bonding protocol or with intentionally deteriorated bonding using n-hexane-wax solution for preconditioning. Restored teeth were loaded along the long axis of the tooth. Ultimate fracture load was recorded, and the type of fracture was visually determined and classified. Statistical analysis of load values was performed by Kruskal-Wallis test. RESULTS: Round-shaped cavity design with bonded restoration presented the highest fracture load (1658N). Bonding had significant influence on the fracture load of roundshaped cavity design (p=0.0003), whereas cavity design had no influence when the bonding was deteriorated (p=0.8075). In the case of deteriorated bonding, either the inlay or tooth fractured separately whereas in the bonded inlays fractures were commonly found both in the tooth and inlay. CONCLUSIONS: According to this study, bonded inlay restoration increased fracture resistance, while cavity design had no statistical difference on fracture resistance of the restored tooth.

Evaluation of fracture behavior in short fiber-reinforced direct and indirect overlay restorations.

OBJECTIVES: The aim was to assess how incorporating a short-fiber composite (SFC) core would affect the fracture behavior of direct and indirect overlays. Furthermore, to examine the relationship between the thickness ratio of SFC core to particulate-filled composite (PFC) veneering and the fracture-behavior of bilayered-structured restorations. MATERIALS AND METHODS: A total of 120 molars were used to create MOD cavities, with palatal cusps removed. Four different groups of direct overlays were then made (n = 15/group), all of which featured a SFC core (everX Flow) with varying thicknesses (0, 1, 4, and 5 mm), as well as a surface layer of PFC (G-aenial Posterior), with the overall thickness of the bilayered-structured restoration set at 5 mm. Additionally, four groups of CAD/CAM restorations were created (Cerasmart 270 and Initial LiSi Block), with or without 2 mm of SFC core reinforcement. Following the fabrication of these restorations, cyclic fatigue aging was carried out for a total of 500,000 cycles, with an applied maximum load (Fmax) of 150 N. Subsequently, each restoration underwent quasi-static loading until fracture. The fracture mode was subsequently evaluated using optical microscopy and SEM. RESULTS: There were no statistically significant differences (p > 0.05) observed in the fracture resistance of indirect overlays reinforced with a 2-mm SFC core compared to those made solely from restorative materials. Direct overlays constructed using plain SFC or with a 4-mm layer thickness of SFC core exhibited significantly higher fracture resistance values (2674 ± 465 and 2537 ± 561 N) (p < 0.05) when compared to all other groups tested, according to the statistical analysis ANOVA. CONCLUSIONS: The most effective method for restoring large MOD cavities was found to be direct restoration using SFC either alone or as a bulk core in combination with PFC composite. CLINICAL RELEVANCE: The use of SFC as bulk reinforcing base will significantly improve the loading performance of directly layered restorations.

A comparative assessment of color stability among various commercial resin composites.

OBJECTIVES: The aim was to evaluate the color stability of six commercial restorative resin composites after being exposed to commonly consumed beverages. Repolishing impact on the stained composite was also assessed. METHODS: One-hundred and fifty disc specimens (8 mm diameter & 3 mm thickness) were prepared from Filtek™ Universal Restorative, SDR flow+, everX Flow, G-ænial A'CHORD, G-ænial Universal Flo and G-ænial Universal Injectable. To assess the color stability in five various beverages, 25 specimens from each material were randomly distributed into five groups (n = 5), according to the utilized staining solution. Group 1: distilled water, Group 2: coffee, Group 3: red wine, Group 4: energy drink, Group 5: coke. The color changes (∆E) for all materials were measured using spectrophotometer at the baseline, after 84 days of staining and after repolishing. Data was collected and analyzed using ANOVA (α = 0.05). RESULTS: Both material type and staining solution had a significant effect on the color stability of specimens (p < 0.05). Compared to other beverages, the color value of the specimens submerged in coffee and wine showed the most statistically significant (p < 0.05) mean ∆E. SDR flow + in coffee and wine presented the highest ∆E when compared to other tested materials (p < 0.05). After staining of the composites, repolishing was successful in lowering the ∆E value. CONCLUSIONS: All the beverages had an impact on the color stability of the tested resin composites, with coffee and wine demonstrating the most significant effects. The variations in color stability varied depending on the specific material utilized. Dentists should possess awareness regarding the chemical interactions that occur between different beverages and various types of resin composites. Additionally, repolishing serves as an effective technique for eliminating surface discoloration in composite restorations.

Influence of short-fiber composite base on fracture behavior of direct and indirect restorations.

OBJECTIVES: The aim was to examine the influence of short-fiber composite (SFC) core on the fracture-behavior of different types of indirect posterior restorations. In addition, the effect of thickness ratio of SFC-core to the thickness of the veneering conventional composite (PFC) on fracture-behavior of bi-structured composite restorations was evaluated. MATERIALS AND METHODS: MOD cavities with removed palatal cusps were prepared on 90 intact molars. Five groups of direct overlay restorations (n = 10/group) were fabricated having a SFC-core (everX Flow) with various thicknesses (0, 1, 2, 3, 4 mm) and layer of surface PFC (G-aenial Anterior), remaining the thickness of the bi-structure restoration to be 5 mm. Four groups of CAD/CAM-made restorations (Cerasmart 270 and e-max CAD) were fabricated either with 2-mm layer of SFC-core or without fiber reinforcement. Intact teeth (n = 10) were used as control group. Restorations were statically loaded until fracture. Fracture patterns were evaluated visually. Data were analyzed using ANOVA (p = 0.05). RESULTS: With indirect overlay restorations, no statistically significant differences (p > 0.05) were observed in the load-bearing capacities between restorations reinforced by 2-mm SFC-core (bi-structured) and those fabricated from plain restorative materials. ANOVA displayed that direct overlay restorations made from 4-mm layer thickness of SFC-core had significantly higher load-bearing capacities (3050 ± 574 N) (p < 0.05) among all the groups tested. CONCLUSIONS: Restorations (direct/indirect) combining SFC-core and a surface layer of conventional material demonstrated encouraging achievement in reference to fracture behavior. CLINICAL RELEVANCE: The use of flowable short-fiber composite as reinforcing base with large direct and indirect restorations may result in more repairable failure.

Microstructure and Surface Characteristics of Short- Fiber Reinforced CAD/CAM Composite Blocks.

OBJECTIVE: The aim was to investigate certain surface properties and microstructure of an experimental short fiber-reinforced CAD/CAM composite block (SFRC) in comparison with different CAD/CAM, 3D-printing and manually-made commercial composites (Cerasmart 270, GC Temp PRINT, Pro3dure GR-17, Essentia U, Gradia Plus and everX Flow). METHODS: A wear-test was performed using a chewing-simulator with 15000 cycles. Wear depth (n=6) was assessed by 3D optical-profilometer. Surface roughness (SR) before and after wearing-test was evaluated. A Vickers-indenter was utilized for evaluating surface microhardness (VH) and glossmeter was utilized to measure the surface gloss at 60°. The surface microstructure of each composite was investigated with SEM. Data were statistically analyzed with analysis of variance ANOVA (p=0.05). RESULTS: Significant differences in the surface properties were found according to the type of composite (p⟨0.05). Cerasmart 270 exhibited the highest VH (94.8 V) and lowest SR (0.18 Ra) values (p⟨0.05) among the composites tested. The lowest wear depth measurement was located for GC Temp PRINT (19.3 µm) which was not significantly different (p⟩0.05) from Cerasmart 270 (20.7 µm). CONCLUSION: Incorporation of fibers to the composite of the CAD/CAM block did not negatively influence the surface characteristics of composite.

Influence of Short Fiber- Reinforced Composites on Fracture Resistance of Single-Structure Restorations.

OBJECTIVE: The aim was to determine the load-bearing capacity of anterior crowns prepared using two types of single-structure short fibre-reinforced composites (SFRCs). Furthermore, fracture toughness (FT), flexural strength (FS) and flexural modulus (FM) of tested composites were measured. METHODS: Seven groups of composite crowns were designed for an upper central incisor (n=8/group). Two groups were CAD/CAM fabricated made of Cerasmart 270 and experimental single-structure SFRC blocks. Two groups were 3D-printed made of GC Temp PRINT and Pro3dure GR-17 composites. Two groups were made of conventional light-cured composites (Essentia and Gradia Plus). The last group was a single-structure SFRC made of commercial flowable SFRC (everX Flow). Crown restorations were loaded until fracture. Failure-modes were then visually examined. FT, FS and FM were determined for each tested composite (n=8). The data were analysed using analysis of variance (p=0.05) followed by Tukey's post-hoc test. RESULTS: ANOVA revealed that crowns made of experimental SFRC blocks had significantly higher load-bearing capacities (1650 ±230 N) (p⟨0.05) among all the groups tested. Experimental SFRC blocks exhibited the highest FT (2.9 MPa m1/2) and FS (245.8 MPa) values (p⟨0.05) among tested composites. CONCLUSION: CAD/CAM fabricated restorations made of experimental SFRC blocks demonstrated encouraging performance related to their fracture-behaviour.

Fiber Reinforcement of Endodontically Treated Teeth: What Options Do We Have? Literature Review.

The restoration of endodontically treated teeth (ETT), even though practiced for many years, remains a major concern in dentistry. There is a variety of materials and clinical techniques advocated for restoring ETT and hundreds of studies devoted to this subject have been published in the dental literature. This narrative review article was undertaken to answer a question regarding restoration of ETT with available evidence: What fiber reinforcement options do we have other than prefabricated fiber post? Using a Medline search (up to 2019) and resulting cross-references, authors selected original research on the topic of fiber-reinforced composite (FRC) and restoration of ETT. Of the assessed articles selected (n=79), most were laboratory-based research with various test specimen designs and only 15 articles were clinical reports. From the reviewed studies, using individually formed FRC posts and short-FRC resin showed promising characteristics, and therefore, might be recommended as an alternative treatment option in restoring ETT. However, long-term clinical trials are needed in order to evaluate the usefulness of these alternatives.

On-farm deaths of dairy cows are associated with features of freestall barns.

On-farm death (OFD) of a dairy cow is always a financial loss for a farmer, and potentially a welfare issue that has to be addressed within the dairy industry. The aim of this study was to explore the associations between OFD of dairy cows, housing, and herd management in freestall barns. To achieve the goal, we followed 10,837 cows calving in 2011 in 82 herds. Data were gathered with observations and a structured interview during farm visits and from a national dairy herd improvement database. The hazard of OFD was modeled with a shared frailty survival model, with SAS 9.3 PHREG procedure (SAS Institute Inc., Cary, NC). The study population was 58% Ayrshire and 42% Holstein cows. The median herd size and mean milk yield in the study herds were 116 cows and 9,151 kg of milk per cow per year. The overall probability of OFD was 6.0%; 1.8% of the cows died unassisted and 4.2% were euthanized. Variation in OFD percentage between individual herds was large, from 0 to 16%, accounting for 0 to 58% of all removals in the herds. Keeping close-up dry cows in their own group was associated with higher hazard of OFD [hazard ratio (HR) = 1.37] compared with keeping them in the same pen with far-off dry cows. Higher hazard on OFD was observed when barns had only one kind of calving pen; single (HR = 2.09) or group pens (HR = 1.72), compared with having both of those types. The hazard of OFD was lower if the whole herd was housed in barns or pens that had only 1 type of feed barrier at the feed bunk, namely post-and-rail (HR = 0.51) or a type with barriers between the cow's heads (HR = 0.49), compared with having 2 types. Lower OFD hazard was observed with wider than 340 cm of walking alley next to the feeding table (HR = 0.75), and with housing a whole herd in pens with only 1 type of walking alley surface, specifically slatted (HR = 0.53) or solid (HR = 0.48), compared with having both types. The hazard of OFD was higher with stalls wider than 120 cm (HR = 1.38) compared with narrower stalls. The hazard of OFD was also associated with breed, parity, and calving season. This study identified many factors that contribute to the incidence of OFD of dairy cows. The solutions for reducing on-farm mortality include housing, management, and breeding choices that are most probably herd specific.

Effect of Distance on Light Transmission Through Polymerized Resin Composite.

OBJECTIVE: Light transmittance of dental composites varies between products and shades, but also light curing units differ to each other in their irradiance and fiber optic structure of curing tip. The aim of this study was to investigate whether there is linear relationship between the distance of the curing tip to the resin composite and irradiance at lower surface of the resin composite. MATERIALS AND METHODS: Disks of 1 mm thickness (6mm diameter) were fabricated. Light transmittance (intensity) through the disk was measured at distance of 0, 2, 4, 6, 8, 10 mm from the light tip with two light curing units Elipar S10 (3M-ESPE) and Silverlight (GC). Irradiance ratio (irradiance on the sensor surface without the composite disk / with the composite disk) was calculated and plotted against the distance of the light curing tip. Statistical analysis was carried out using analysis of covariance (ANCOVA, Tukey's, α =0.05). RESULTS: Irradiance ratio varied between 18% to 24% with Silverlight and 21% to 26% with Elipar S10 light curing units. There were statistically significant differences between the ratios with different distances of the light curing tip (p⟨0.05). Interestingly, the highest irradiance ratio for Elipar S10 unit was found with 4 mm distance of the tip, whereas Silverlight unit had the highest ratio with 6 mm distance. Out of two tested resin composites, the flowable composite showed higher irradiance ratio than regular packable resin composite. CONCLUSIONS: Increase of distance of the light curing tip from the composite surface decreased the absolute irradiance underneath of composite, as expected. However, there seemed to be device dependent optimal distance of 4-6 mm to reach the most efficient irradiance ratio through the composite resin keeping in mind that most efficient transmission of light through the material is reached by having light curing tip in contact to the material.

Effect of several intracanal medicaments on the push-out bond strength of ProRoot MTA and Biodentine.

AIM: To evaluate the effect of prior application of several intracanal medicaments on the push-out bond strength of ProRoot MTA and Biodentine. METHODOLOGY: Sixty freshly extracted maxillary anterior teeth were sectioned below the cementoenamel junction, and the root canals instrumented using rotary files. Thereafter, a parallel post drill was used to obtain a standardized root canal dimension. The roots were randomly assigned into one of the following groups with respect to the intracanal medicament applied: group 1: calcium hydroxide (CH) powder (Merck, Darmstadt, Germany) mixed with distilled water; group 2: a mixture of metronidazole, ciprofloxacin and minocycline (triple antibiotic paste); group 3: a combination of amoxicillin and clavulanic acid (Augmentin; Champs Pharmacy, San Antonio, TX, USA); group 4: an antibiotic-corticoid compound paste (Ledermix; Riemser, Greifswald, Germany); and group 5: no medicament (control). Following removal of medicaments with instrumentation and irrigation, the roots were cut into 1-mm-thick parallel transverse sections in a coronal-to-apical direction (5 slices/tooth). Thereafter, the specimens were divided into two subgroups according to the calcium silicate cement applied (n = 30/group): (i) ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK, USA) and (ii) Biodentine (Septodont, Saint-Maur-des-Fosses, France). A push-out test was performed, and the data were analysed statistically using two-way anova and Tukey's post hoc test. RESULTS: Regardless of the type of intracanal medicament used, Biodentine had significantly higher bond strength than MTA (P < 0.05). The highest push-out bond strength results were obtained in CH-treated dentine. Compared with other medicaments, this value was only significantly higher than that of Ledermix (P < 0.05). In both the MTA and Biodentine groups, pairwise comparisons between other medicaments showed similar debonding values (P > 0.05). CONCLUSIONS: Biodentine had a higher bond strength to root canal dentine than ProRoot MTA. Prior CH in distilled water intracanal placement increased the dislodgment resistance of both calcium silicate cements.

Clinical Performance of Short Fibre-reinforced Glass Ionomer Cement Restorations in Cervical Carious Lesions: 12-Month Randomized Clinical Trial.

The aim was to assess the clinical performance of experimental short fiber-reinforced glass-ionomer cement (FR-GIC) in the treatment of cervical caries lesions. A total of 45 patients were randomly enrolled in this trial according to the split-mouth design. The FR-GIC was prepared by adding short glass fibers at a mass ratio of 20% into the powder portion of Fuji II LC. The cervical lesions in the intervention group were restored with FR-GIC, while unmodified Fuji II LC was applied as the control. Clinical evaluation was performed by two blinded operators at baseline, at 6, and 12 months using modified USPHS criteria. The data were analyzed using Friedman's test, followed by the Nemenyi post hoc test with a significance level of α = 0.05. After 1 year, all restorations were fully retained. There was no statistically significant difference (p⟩0.05) between the two materials based on the evaluated criteria. Both groups had 4 (10%) cases with Bravo scores for cavos-surface marginal discoloration. Regarding marginal integrity, Bravo scores were observed in 5 (12.5%) cases in the intervention group and 4 (10%) cases in the control group. Both materials in the treatment of cervical caries lesions demonstrated satisfactory clinical outcome throughout the 12-month follow-up.

Effect of monomer composition of polymer matrix on flexural properties of glass fibre-reinforced orthodontic archwire.

To compare force levels obtained from glass fibre-reinforced composite (FRC) archwires. Specifically, FRC wires were compared with polymer matrices having different dimethacrylate monomer compositions. FRC material (E-glass provided by Stick Tech Ltd, Turku, Finland) with continuous unidirectional glass fibres and four different types of dimethacrylate monomer compositions for the resin matrix were tested. Cross-sectionally round FRC archwires fitting into the 0.3 mm slot of a bracket were divided into 16 groups with six specimens in each group. Glass fibres were impregnated by the manufacturer, and they were initially light-cured by hand light-curing unit or additionally post-cured in light-curing oven. The FRC archwire specimens were tested at 37°C according to a three-point bending test in dry and wet conditions using a span length of 10 mm and a crosshead speed of 1.0 mm/minute. The wires were loaded until final failure. The data were statistically analysed using analysis of variance (ANOVA). The dry FRC archwire specimens revealed higher load values than water stored ones, regardless of the polymer matrix. A majority of the FRC archwires showed higher load values after being post-cured. ANOVA revealed that the polymer matrix, curing method, and water storage had a significant effect (P < 0.05) on the flexural behaviour of the FRC archwire. Polymer matrix composition, curing method, and water storage affected the flexural properties and thus, force level and working range which could be obtained from the FRC archwire.

Flexural strength,water sorption and solubility of a methylmethacrylate-free denture base polymer reinforced with glass fibre reinforcement.

A methylmethacrylate-free denture base polymer (Eclipse) in comparison to a conventional denture base polymer (Palapress vario) was evaluated after water saturation and Stick glass fibre reinforcement. The data were analysed with ANOVA at a = 0.05. Water-storage caused a decrease in the flexural strength and stiffness of the materials (p > 0.05). Conventional denture base material with fibre reinforcement gave highest flexural strength (201.1 MPa) compared to fibre reinforced Eclipse (79.1 MPa) (p < 0.05). Water sorption after 76 days was 2.08% (Palapress vario) and 1.55% (Eclipse). Fibre-reinforcement of methylmethacrylate-free material was not as successful as conventional denture base and needs to be further optimized.

Effect of interfacial surface treatment on bond strength of particulate-filled composite to short fiber-reinforced composite.

Objective: The aim was to investigate the effect of different interfacial surface treatments on the shear bond strength (SBS) between a short fiber-reinforced flowable composite (SFRC) and a particulate-filled flowable composite (PFC). In addition, SBS between two successive layers of similar materials was evaluated. Materials and methods: One-hundred and forty-four specimens were prepared having either SFRC (everX Flow) as a substructure composite and PFC (G-aenial Flo X) as a surface composite or having one of the two materials as both substructure and surface layer. Eight groups of specimens were created (n = 18/per group) according to the interfacial surface protocol used. Group 1: no treatment; Group 2: ethanol one wipe; Group 3: ethanol three wipes; Group 4: phosphoric acid etching + bonding agent; Group 5: hydrofluoric acid etching + bonding agent; and Group 6: grinding + phosphoric acid etching. Group 7: only PFC layers and Group 8 (control) only SFRC layers without any surface treatment. After one-day storage (37 °C), SBS between surface and substructure composite layers was measured in a universal testing machine, and failure modes were visually analyzed. SEM was used to examine the bonding surface of the SFRC composite after surface treatment. SBS values were statistically analyzed with a one-way analysis of variance (ANOVA) followed by the Tukey HSD test (α = .05). Results: The SBS between successive SFRC layers (Group 8) was statistically (p < .05) the highest (43.7 MPa) among tested groups. Surface roughening by grinding followed by phosphoric acid etching (Group 6) resulted in a higher SBS (28.8 MPa) than the remaining surface treatments. Conclusion: Flowable composite with glass fibers (everX Flow) showed higher interlayer SBS compared to PFC flowable composite. Interfacial surface roughness increases the bonding of PFC to the substructure of SFRC.

Can Specular Gloss Measurements Predict the Effectiveness of Finishing/Polishing Protocols in Dental Polymers? A Systematic Review and Linear Mixed-effects Prediction Model.

PURPOSE: The current gold standard measure to assess polishing efficacy is surface roughness (SR) assessed in laboratory research. Specular gloss (SG) has been negatively correlated to SR, which raises the following question: Can SG be used to accurately determine the effectiveness of a finishing/polishing procedure in direct resin composites? METHODS: A systematic approach and search strategy, following Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, was developed and conducted in five electronic databases: PubMed/Medline, Scopus, Web of Science, EMBASE (Ovid), and SciELO/LILACS to identify laboratory studies that assessed SR and SG, simultaneously, of resin composites, without date or language restriction. Risk of bias assessment was carried out by two reviewers, independently. From the extracted quantitative data of SG/SR, regression analyses were performed, and a linear mixed-effects prediction model was derived using the nimble package in R (v4.0.3). RESULTS: A total of 928 potential studies were found, out of which, 13 were eligible after criterion screening. Experimental groups featured 31 resin composites of six different filler types, with the most common being microhybrids followed by nanohybrids. More than half of the studies initially reported a linear correlation between SR and SG, which ranged from r2 = 0.34-0.96. Taking into account the regression analysis and prediction model posteriorly performed, the corresponding SG threshold for 0.2 µm is estimated to be >55 GU. Most of the evidence was classified as moderate or high risk of bias. CONCLUSION: SG is universally correlated to SR in polymers, and a reference value of >55 GU is proposed, above which samples are considered well polished.

The effect of chlorhexidine and dimethyl sulfoxide on long-term sealing ability of two calcium silicate cements in root canal.

OBJECTIVES: To evaluate the long-term effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) on the sealing ability and biomineralization of two different calcium silicate cements (CSC) in root canal. METHODS: Sixty human third molar root canals were obturated with ProRoot MTA or Biodentine. Before obturation the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage was tested after three days and after six months. After additional six months (12 months after root filling) the roots were cut into 2 mm thick dentine discs. The discs were stored in artificial saliva for one year. The bond strength was measured with the push-out method, and the failure mode was evaluated with a stereomicroscope. The most apical disc of each tooth was used for Vickers hardness test. RESULTS: No significant differences between the groups was found in initial microleakage. The leakage increased significantly during the 6-month storage in all groups except in Biodentine-CHX group and Biodentine-DMSO group. CHX and DMSO irrigation significantly increased the leakage with ProRoot MTA with time, but there was no statistically significant difference compared to the ProRoot MTA-control group at six months' time point. CHX significantly reduced the push-out bond strength of ProRoot MTA. With Biodentine irrigation with CHX or DMSO resulted with significantly higher push-out strength compared to the Biodentine control group. Fracture analysis showed statistically significant difference in the distribution of the fractures between the groups, but neither CHX nor DMSO change the fracture pattern statistically significantly. With Vickers hardness test ProRoot MTA with and without DMSO as the final irrigant showed significantly higher dentin hardness than any Biodentine-group. SIGNIFICANCE: Considering that aging increased the leakage in all groups except with Biodentine-DMSO and the differences in the push-out strength and surface microhardness data, it appears that the time-related biomineralizing effect of MTA and Biodentine does not improve sealing to dentin. CHX significantly reduced ProRoot MTA bond strength and increased pure adhesive failures with both cements.

Effects of heat treatment of wood on hydroxylapatite type mineral precipitation and biomechanical properties in vitro.

Wood is a natural fiber reinforced composite. It structurally resembles bone tissue to some extent. Specially heat-treated birch wood has been used as a model material for further development of synthetic fiber reinforced composites (FRC) for medical and dental use. In previous studies it has been shown, that heat treatment has a positive effect on the osteoconductivity of an implanted wood. In this study the effects of two different heat treatment temperatures (140 and 200 degrees C) on wood were studied in vitro. Untreated wood was used as a control material. Heat treatment induced biomechanical changes were studied with flexural and compressive tests on dry birch wood as well as on wood after 63 days of simulated body fluid (SBF) immersion. Dimensional changes, SBF sorption and hydroxylapatite type mineral formation were also assessed. The results showed that SBF immersion decreases the biomechanical performance of wood and that the heat treatment diminishes the effect of SBF immersion on biomechanical properties. With scanning electron microscopy and energy dispersive X-ray analysis it was shown that hydroxylapatite type mineral precipitation formed on the 200 degrees C heat-treated wood. An increased weight gain of the same material during SBF immersion supported this finding. The results of this study give more detailed insight of the biologically relevant changes that heat treatment induces in wood material. Furthermore the findings in this study are in line with previous in vivo studies.

Bone tissue responses to glass fiber-reinforced composite implants--a histomorphometric study.

OBJECTIVES: The aims of this study were to evaluate bone-to-implant contact (BIC) and the osteoconductive capacity of bioactive fiber-reinforced composite implant (FRC) in vivo. MATERIAL AND METHODS: Threaded sand-blasted FRC implants and threaded FRC implants with bioactive glass (BAG) were fabricated for the study. Titanium implants were used as a reference. Eighteen implants (diameter 4.1 mm, length 10 mm) were implanted in the tibia of six pigs using the press-fit technique. The animals were sacrificed after 4 and 12 weeks. Histomorphometric and scanning electron microscopic (SEM) analyses were performed to characterize BIC. RESULTS: In general, the highest values of BIC were measured in FRC-BAG implants, followed by FRC and Ti implants. At 4 weeks, the BIC was 33% for threaded FRC-BAG, 27% for FRC and 19% for Ti. At 12 weeks, BIC was 47% for threaded FRC-BAG, 40% for FRC and 42% for Ti. Four weeks after implantation, all the implants appeared biologically fixed by a newly formed woven bone arranged in the thin bone trabeculae filling the gap between the implant and the bone of the recipient site. Twelve weeks after implantation, the thickness of the woven bone trabeculae had increased, especially around the FRC-BAG implants. CONCLUSION: Our results suggest that the FRC implant is biocompatible in bone. The biological behavior of FRC was comparable to that of Ti after 4 and 12 weeks of implantation. Furthermore, the addition of BAG to the FRC implant increased peri-implant osteogenesis and bone maturation.

The Effect of Chlorhexidine and Dimethyl Sulfoxide on Long-Term Microleakage of Two Different Sealers in Root Canals.

OBJECTIVE: The aim of root canal obturation is to prevent leakage and inhibit microbial invasion. This study aimed to determine the effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) as final irrigants on microleakage of root filling immediately and after 18 months. The hypothesis was that either CHX or DMSO would not affect the immediate or long-term microleakage. METHODS: A total of 120 human third molar root canals were obturated with RealSeal SE or Topseal and gutta percha. Before obturation, the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage of half of each groups (n=10) was measured after 3 days, and of the other half was measured after 18 months with fluid filtration method. RESULTS: In immediate measurements, RealSeal SE performed significantly better in CHX-irrigated group (p=0.035; Mann-Whitney test). For both sealers, DMSO had the lowest mean microleakage values, which were also statistically significantly lower than with CHX irrigation within sealers (p<0.009 for Topseal and p=0.04 for RealSeal SE; Mann-Whitney test). With RealSeal SE, the microleakage with CHX was significantly higher than that in controls (p=0.022; Mann-Whitney test). CONCLUSION: Neither final irrigant showed statistically significant differences in the immediate microleakage within the two sealers. Irrigation with DMSO caused significantly less microleakage than CHX for both sealers after 18 months.