Comparison of Two Luting Agents Used for the Retention of Cast Dowel and Cores

PURPOSE: The first purpose of this study was to compare the retentive values of zinc phosphate and Panavia F resin cements when used for luting cast dowel and cores. The second purpose was to determine whether the use of a lubricant when making the resin pattern for a custom dowel and core would have an effect on the final retention of dowels cemented with either zinc phosphate or Panavia F cements. METHODS AND MATERIALS: Sixty-three caries-free extracted single-rooted human teeth were randomly divided into three groups of 21. Root canal preparations were standardized for all 63 teeth. Clinical protocols for fabricating and cementing dowel and core restorations were examined, comparing zinc phosphate and Panavia F resin cements. Direct dowel patterns were fabricated using the Para Post system and cast in a noble metal alloy. Group I dowel spaces were lubricated with GC lubricant prior to dowel pattern fabrication and cleaned with Cavidry solvent before cementing the cast dowel and core with zinc phosphate cement. Group II dowel spaces were rinsed with water only prior to dowel pattern fabrication. The dowels and cores in this group were cemented with Panavia F resin cement. Group III dowel spaces were lubricated with GC lubricant prior to dowel pattern fabrication; the dowel spaces were cleaned with Cavidry solvent before the cast dowel and cores were cemented with Panavia F cement. The tensile force necessary to remove the cast dowel and cores was determined using a universal testing machine. Results were statistically analyzed using one-way ANOVA and Tukey's HSD test. RESULTS: The dowels and cores in Group I had significantly higher retentive values than either of the two Panavia F groups (p< or = 0.001). No difference in retentive values (p > 0.05) was found between dowels luted with either of the lubricating agents in the Panavia F groups. CONCLUSIONS: Zinc phosphate cement had higher retentive values when cementing cast dowel and cores than Panavia F. The type of lubricant used for the resin dowel fabrication (water or GC lubricant that was removed with a solvent) had no effect on the retention of cast dowels cemented with Panavia F.     

Self-adhesive resin cement versus zinc phosphate luting material: A prospective clinical trial begun 2003

ObjectivesThe literature demonstrates that conventional luting of metal-based restorations using zinc phosphate cements is clinically successful over 20 years. This study compared the clinical outcomes of metal-based fixed partial dentures luted conventionally with zinc phosphate and self-adhesive resin cement.MethodsForty-nine patients (mean age 54 ± 13 years) received 49 metal-based fixed partial dentures randomly luted using zinc phosphate (Richter & Hoffmann, Berlin, Germany) or self-adhesive resin cement (RelyX Unicem Aplicap, 3M ESPE, Germany) at the University Medical Center Regensburg. The core build-up material was highly viscous glass ionomer; the finishing line was in dentin. The study included 42 posterior, 5 anterior crowns and two onlays. Forty-seven restorations were made of precious alloys, 2 of non-precious alloys. The restorations were clinically examined every year. The clinical performance was checked for plaque (0–5; PI, Quigley-Hein), bleeding (0–4; PBI; Mühlemann) and attachment scores. The examination included pulp vitality and percussion tests.StatisticsMeans of scores, standard deviation, cumulative survival and complication rates were calculated using life tables.ResultsThe mean observation time was 3.16 ± 0.6 years (min: 2.0; max: 4.5 years). During that time no restoration was lost, no recementation became necessary. One endodontic treatment was performed in the self-adhesive composite group after 2.9 years. At study end bleeding (1.44 RelyX Unicem vs. 1.25 zinc phosphate) and plaque (1.64 RelyX Unicem vs. 1.0 zinc phosphate) scores showed no statistically significant difference.SignificanceThe self-adhesive resin cement performed clinically as well and can be used as easily as zinc phosphate cement to retain metal-based restorations over a 38-month observation period.     

Cytotoxicity of alloying elements and experimental titanium alloys by WST-1 and agar overlay tests

ObjectiveThis study was performed to evaluate the biocompatibility of nine types of pure metals using 36 experimental prosthetic titanium-based alloys containing 5, 10, 15, and 20 wt% of each substituted metal.MethodsThe cell viabilities for pure metals on Ti alloys that contain these elements were compared with that of commercially pure (CP) Ti using the WST-1 test and agar overlay test.ResultsThe ranking of pure metal cytotoxicity from most potent to least potent was: Co > Cu > In > Ag > Cr > Sn > Au > Pd > Pt > CP Ti. The cell viability ratios for pure Co, Cu, In, and Ag were 13.9 ± 4.6%, 21.7 ± 10.4%, 24.1 ± 5.7%, and 24.8 ± 6.0%, respectively, which were significantly lower than that for the control group (p < 0.05). Pure Pd and Pt demonstrated good biocompatibility with cell viabilities of 93.8 ± 9.6% and 97.2 ± 7.1%, respectively. The Ti–5Pd alloy exhibited the highest cell viability (128.4 ± 21.4%), which was greater than that of CP Ti. By alloying pure Co or Cu with Ti, the cell viabilities for the Ti–xCo and Ti–xCu alloys increased significantly up to 10 wt% of the alloying element followed by a gradual decrease with a further increase in the concentration of the alloying element. Based on the agar overlay test, pure Ag, Co, Cr, Cu, and In were ranked as ‘moderately cytotoxic’, whereas all Ti alloys were ranked as ‘noncytotoxic’.SignificanceThe cytotoxicity of pure Ag, Co, Cr, Cu, and In suggests a need for attention in alloy design. The cytotoxicity of alloying elements became more biocompatible when they were alloyed with titanium. However, the cytotoxicity of titanium alloys was observed when the concentration of the alloying element exceeded its respective allowable limit. The results obtained in this study can serve as a guide for the development of new Ti-based alloy systems.     

Effect of eugenol-containing and resin endodontic sealers on retention of prefabricated metal posts cemented with zinc phosphate and resin cements

PurposeThe aim of this study was to compare the effects of two endodontic sealers on the retention of posts cemented with zinc phosphate or resin cement.Materials and methodsCrowns of 72 mandibular premolars were removed at the cementoenamel junction. Root canals were prepared and specimens were randomly divided into two groups of 36. In each group, 12 specimens were obturated with gutta percha only; 12 specimens with gutta percha/ZOE sealer and 12 specimens with gutta percha/AH26. In the first group, 10 mm Post spaces were prepared with Peeso reamers size 4 and, size 5 stainless steel Paraposts were cemented in with zinc phosphate. In the second group, 10 mm Post spaces were prepared with Fiber Lux size 5.5 drills and size 5 Paraposts were cemented with Panavia F_2.0. After mounting in resin blocks, posts were pulled out by universal testing machine at 1 mm/min and results were analyzed by two-way ANOVA and Dunnett test.ResultsMean forces (in Newtons) required to remove posts cemented with zinc phosphate in canals obturated without sealer, with ZOE, and with AH26 sealers were 270 ± 83, 281 ± 128 and 266 ± 67, respectively; and for posts cemented with Panavia F_2.0 were 520 ± 290, 464 ± 212 and 229 ± 108, respectively. Statistical analysis showed that AH26 significantly reduced retention of posts cemented with Panavia F_2.0 (p < 0.05).ConclusionDifferent sealers had no significant effect on retention of posts cemented with zinc phosphate. However posts cemented with Panavia F_2.0 showed reduced retention in canals obturated with AH26.     

Effect of different investments and mold temperatures on titanium mechanical properties

PurposeThe aim of the present study was to evaluate commercially pure titanium (CP Ti) casting quality when a specific to titanium and a conventional phosphate bonded investments were used under different mold temperatures. For this, the evaluated parameters were surface roughness, bending strength, Vickers microhardness, casting quality by radiographies and microstructure of CP Ti.MethodsWax patterns (28 mm × 3 mm × 1 mm) were invested using two phosphate bonded investments: Rematitan Plus (REM), specific to titanium, and Castorit Super C (CAS), a conventional investment, fired and cooled until reaching two mold temperatures: 430 °C (430) and room temperature (RT). Specimens were cast from CP Ti by plasma. After casting, specimens were radiographically examined and submitted to Vickers microhardness, roughness and bending strength evaluation. Microstructure was analyzed in the center and at the surface of specimen.ResultsQualitative analysis of radiographs showed that specimens which were cast using CAS-RT presented more casting porosities while the specimens which were cast with REM-430 did not present any casting porosity. No significant difference was noted among the groups in the surface roughness and Vickers microhardness data, but the bending strength of the specimens cast using CAS was greater than REM groups. The microstructure of the specimens of the different groups was similar, presenting a feather-like aspect.ConclusionCasting porosities found in the specimens cast using conventional investments (CAS) and lower mold temperatures would limit their use, even mechanical properties were similar than in specimens cast using specific to titanium investment (REM) at temperatures recommended by the manufacturer.     

Effect of types of luting agent on push-out bond strength of zirconium oxide posts

ObjectiveThe aim of this study was to investigate the effect of different luting agents on the bond strength of zirconium oxide posts in root canals after artificial ageing.Material and methodsThirty single-rooted extracted teeth were collected. Post spaces were prepared. Custom milled zirconium oxide posts (Cercon, Degudent) were fabricated. Specimens were divided into 3 groups (n = 10), according to the luting agents used: group RA, conventional resin luting agent (RelyX ARC); group RU, self-adhesive resin luting agent (RelyX Unicem); and group Z, zinc phosphate luting agent (DeTrey). Specimens were subjected to thermocycling and water storage at 37 °C. Specimens were horizontally sectioned into three sections and subjected to a push-out test with 0.5 mm/min crosshead speed. The failure mode was assessed by scanning electron microscopy. Data were analysed by using 2-way ANOVA.ResultsThe following bond strength values were obtained: group RA – 8.89 MPa, group RU – 10.30 MPa and group Z – 9.31 MPa. There was no significant difference in bond strength among the groups (P = 0.500). Adhesive failure mode at the cement/post bonded interface was seen in 100%, 66.67% and 83.3% of examined sections in groups RA, RU and Z, respectively. There was no significant difference in bond strength among different root regions (P = 0.367).ConclusionThe type of luting agent had no significant effect on the push-out bond strength of zirconium oxide posts after artificial ageing.Clinical significanceConventional luting agents, such as zinc phosphate cement, seem to provide comparable retention to resin luting agents for cementing custom milled zirconium oxide posts.     

Effect of pulpal pressure on the microtensile bond strength of luting resin cements to human dentin

ObjectivesThe objectives of this study were to examine the effect of pulpal pressure on the microtensile bond strength (mTBS) of luting resin cements to human dentin and the permeability of dentin surfaces pre-treated with an adhesive and a self-etching primer.MethodsCylindrical composite blocks were luted with resin cements (RelyX ARC, 3M ESPE: ARC; Panavia F, Kuraray Medical Inc.: PF; RelyX Unicem, 3M ESPE: UN) in the absence or presence of simulated pulpal pressure. The application of Adper Single Bond 2 (3M ESPE) and ED primer 2.0 (Kuraray) was performed under 0 cm H₂O. After each resin cement was applied, the pulpal pressure group was subjected to 20 cm H₂O of hydrostatic pressure for 10 min during the initial setting period. Testing for mTBS was performed on 0.9 mm × 0.9 mm sectioned beams after 24 h water-storage. Scanning electron microscopy was performed to investigate the fractured surfaces after mTBS testing and additional dentin surfaces that were treated by an etchant, ED primer 2.0 and UN. Fluid permeability was measured on dentin surfaces that were applied with Adper Single Bond 2 and ED primer 2.0.ResultsApplication of pulpal pressure reduced mTBS significantly in groups ARC and PF. Porous bonding interfaces due to water permeability through the cured adhesive were observed on fractured surfaces. Dentin surfaces that were applied with the adhesive and the primer were more permeable than smear layer-covered dentin. The mTBS of UN was significantly lower than ARC and PF regardless of the absence/presence of pulpal pressure.SignificanceFluid permeation during the initial setting period deteriorated the bonding quality of resin cements.     

Effect of chlorhexidine application on long-term shear bond strength of resin cements to dentin

PurposeThe purpose of this study was to investigate the effect of chlorhexidine [CH] on dentin bond strength of three resin cements after 1 year of water storage.MethodsA flat middle dentin surface was prepared on 120 extracted premolars. The teeth were randomly divided into 6 groups of 20 specimens each according to the resin cement used: Panavia F2.0, Variolink II, and RelyX Unicem, with or without CH application. After cementation of an indirect composite rod [Z250], one subgroup [n = 10] was tested after 24 h in water at 37 °C and the other subgroup [n = 10] was tested after 1 year storage in water plus thermocycling. A shear bond strength [SBS] test was performed. The data [in MPa] were analyzed with ANOVA and Tukey tests [P < 0.05].ResultsThree-way ANOVA [resin cement, CH and time] indicated that Variolink II had the highest strength [16.65 ± 3.60] and RelyX Unicem had the lowest strength [9.30 ± 4.07]. Chlorhexidine application increased SBS [13.31 ± 4.61] compared to samples without CH [12.16 ± 5.04] [P = 0.04]. Initial SBS [15.63 ± 4.37] was significantly higher than after 1 year of storage [9.85 ± 3.36] [P < 0.001]. Separate two-way ANOVA for 24-h and 1-year data showed that cement had a significant effect but CH and its interaction had no significant effect at 24 h, whereas at 1 year the two factors and their interaction differed significantly [P ≤ 0.001].ConclusionsChlorhexidine 2% can diminish the loss of bonding effectiveness over time associated to etch-and-rinse and self-etch cements, although it appears not have any effect on self-adhesive cement.     

Curing potential and color stability of different resin-based luting materials

PurposeTo determine the curing potential and color stability of resin-based luting materials for aesthetic restorations.Material and MethodsFour resin-based luting agents were tested: traditional dual-activated resin cement (RelyX ARC, ARC), amine-free dual-activated resin cement (RelyX Ultimate, ULT), light-activated resin cement (RelyX Veneer, VEN), and pre-heated restorative resin composite (Filtek Supreme, PHC). Degree of C = C conversion was determined by infrared spectroscopy (n = 3) with direct light exposure or with interposition of 1.5-mm-thick ceramic (e.max Press HT) between the luting material and light. The curing potential considered the ratio between these two scenarios. Color difference (n = 6) was determined by CIELAB (ΔE_ab) and CIEDE2000 (ΔE₀₀) methods, by spectrophotometer measurements made 24 h after photoactivation and 90 days after storage in water. Data was submitted to ANOVA and Tukey’s test (α = 0.05).ResultsThe luting agents affected both conversion and color stability. With ceramic, ARC produced the highest conversion among the tested groups (75 ± 1%) and the pre-heated composite (PHC) the lowest one (51 ± 3%), but the curing potential was similar for all materials. ULT produced lower ΔE_ab than ARC. PHC presented the lowest color difference when considered both CIELAB and CIE2000 methods (ΔE_ab 2.1 ± 0.4; ΔE₀₀ 1.6 ± 0.2).SignificanceAll luting strategies presented high curing potential. Amine-free dual-activated material was able to reduce color difference than that formulated with the amine component. Pre-heated composite produced the least color variation after storage.     

Misfit and microleakage of implant-supported crown copings obtained by laser sintering and casting techniques,luted with glass-ionomer,resin cements and acrylic/urethane-based agents

ObjectivesThis study evaluated the marginal misfit and microleakage of cement-retained implant-supported crown copings.MethodsSingle crown structures were constructed with: (1) laser-sintered Co–Cr (LS); (2) vacuum-cast Co–Cr (CC) and (3) vacuum-cast Ni–Cr–Ti (CN). Samples of each alloy group were randomly luted in standard fashion onto machined titanium abutments using: (1) GC Fuji PLUS (FP); (2) Clearfil Esthetic Cement (CEC); (3) RelyX Unicem 2 Automix (RXU) and (4) DentoTemp (DT) (n = 15 each). After 60 days of water ageing, vertical discrepancy was SEM-measured and cement microleakage was scored using a digital microscope. Misfit data were subjected to two-way ANOVA and Student–Newman–Keuls multiple comparisons tests. Kruskal–Wallis and Dunn's tests were run for microleakage analysis (α = 0.05).ResultsRegardless of the cement type, LS samples exhibited the best fit, whilst CC and CN performed equally well. Despite the framework alloy and manufacturing technique, FP and DT provide comparably better fit and greater microleakage scores than did CEC and RXU, which showed no differences.ConclusionsDMLS of Co–Cr may be a reliable alternative to the casting of base metal alloys to obtain well-fitted implant-supported crowns, although all the groups tested were within the clinically acceptable range of vertical discrepancy. No strong correlations were found between misfit and microleakage. Notwithstanding the framework alloy, definitive resin-modified glass-ionomer (FP) and temporary acrylic/urethane-based (DT) cements demonstrated comparably better marginal fit and greater microleakage scores than did 10-methacryloxydecyl-dihydrogen phosphate-based (CEC) and self-adhesive (RXU) dual-cure resin agents.     

In vitro assessment of retention of four esthetic dowels to resin core foundation and teeth

STATEMENT OF PROBLEM: Several new esthetic dowel systems are currently available for the restoration of endodontically treated teeth. These dowel systems enhance the esthetic quality of all-ceramic restorations better than metallic dowel systems. PURPOSE: The purpose of this study was to evaluate the retentive strength of composite and ceramic endodontic dowel systems to the tooth and to the core foundation. MATERIAL AND METHODS: The following dowel systems were tested: resin dowels (Fibrekor [FR]; Luscent [LU]; Twin Luscent Anchor [TLU]); ceramic dowels (Cerapost [CR]; Cosmopost [CO]); and a titanium dowel (ParaPost XH [Ti]). In Part I of the study, core retention was tested by forming Bis-Core resin (n=12) cores around dowels followed by separation using a universal testing machine. In Part II, 60 (n=12) extracted human canines were endodontically treated, and dowel spaces were prepared using the corresponding drill for each dowel system. Nine-millimeter resin and ceramic dowels were cemented with C & B resin luting agent. Additionally, 2 groups (n=12) of Ti dowels cemented with C & B resin luting agent and zinc phosphate luting agent served as control groups. Retention was tested using a universal testing machine to separate the dowels from teeth. One-way analysis of variance and Student Newman-Keuls tests were conducted for statistical analysis (alpha=.05). Surface texture of all dowel systems tested was examined using SEM at original magnification x25 and x250. RESULTS: Core retention of Ti was higher than all esthetic dowels tested (alpha<.05), but FR had higher core retention than the other esthetic dowels tested. Resin dowels had better retention to teeth than ceramic dowels (alpha<.05). CONCLUSION: The esthetic dowel systems were less retentive for the resin core material than the titanium control. Resin dowel systems were more retentive in the root than the ceramic dowels but were similar to the titanium control.     

Challenges in luting fibre posts: Adhesion to the post and to the dentine

Objective

To investigate the relationship between physicochemical interactions of resin luting cements with dentine and retention of fibre posts in root canals.

Effect of water aging on microtensile bond strength of dual-cured resin cements to pre-treated sintered zirconium-oxide ceramics

ObjectivesTo evaluate the hydrolytic stability of different dual-cure resin cements when luted to zirconia ceramic.MethodsEighteen cylinder-shaped zirconia blocks (Cercon Zirconia, Dentsply) were conditioned with: Group 1, no treatment; Group 2, sandblasting (125 μm alumina–Al₂O₃-particles); Group 3, tribochemical silica coating (50 μm silica-modified Al₂O₃ particles). Ceramic blocks were duplicated in composite resin (Tetric Evo Ceram, Ivoclar-Vivadent). Composite disks were luted to pre-treated ceramic surfaces using: (1) Clearfil Esthetic Cement (CEC; Kuraray); (2) Rely X Unicem (RXU; 3M ESPE); (3) Calibra (CAL; Dentsply Caulk). After 24 h, bonded samples were cut into microtensile sticks (1 mm²). Half of the sticks were loaded in tension until failure (cross-head speed of 0.5 mm/min). The remaining half was tested after 6 months of water storage at 37 °C. Data was analyzed with three-way ANOVA and Tukey’s test (P <0.05). Fractographic analysis was performed by SEM.ResultsAfter 24 h, bond strength of CEC to zirconia was significantly higher than that of RXU and CAL, independently from the ceramic pre-treatment (P <0.001). Using CAL, all samples failed prematurely except when luting to sandblasted surfaces. After 6 months of water aging, bond strength of CEC significantly decreased. RXU did not significantly alter bond strengths. Adhesion of sandblasted specimens luted with CAL fell over time. Micromorphological alterations were evident after water storage.SignificanceResin–ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. CEC and RXU were both suitable for luting zirconia. Water aging played an important role in the durability of zirconia-to-composite chemical bonds.     

Corrosion mechanism of Ti–Cr alloys in solution containing fluoride

ObjectiveThe objective of this study was to clarify the influence of chromium content on surface reaction of Ti–Cr alloys in an acidic fluoride-containing saline solution.MethodsFour Ti–Cr alloys containing 5, 10, 15 or 20 mass% chromium were characterized in terms of dissolution of metals in an acidic fluoride-containing saline solution and surface structure by X-ray photoelectron spectroscopy and Auger electron spectroscopy.ResultsTotal amount of metals dissolved from each alloy decreased with increase in chromium content. The surface oxide films of Ti–Cr alloys before and after immersion in an acidic fluoride-containing saline solution consisted of titanic and chromic species, such as oxide, hydroxide, and hydrate. The [Cr]/([Ti] + [Cr]) ratio in the surface oxide film on as-polished Ti–Cr alloys was closely correlated with chromium content. However, the ratio in any alloy approximately doubled after immersion. Although thick oxide films were observed after immersion, all alloys showed a thinner oxide film than commercially pure titanium.SignificantIn all alloys, concentration of chromic species such as oxide and hydroxide in the surface oxide film was associated with chromium content, and chromic species improved corrosion resistance to fluoride.     

Laser surface treatment to improve mechanical properties of cast titanium

ObjectiveThe aim of this study was to investigate the effect of laser surface treatment on the mechanical properties of cast titanium and to compare with those of the Co–Cr alloy.MethodsDumbbell-shaped cast specimens were prepared for commercially pure titanium (grade 2) and Co–Cr alloy. The cast titanium specimens were laser-treated on the surface using a dental Nd:YAG laser machine at 240 V and 300 V. After laser treatment, tensile testing was conducted to obtain the tensile strength, percent elongation and modulus of elasticity. The hardness depth profile was made from the cast subsurface (25 μm) to 1500 μm in depth using the cross-sections of the cast rods with the same diameter as the dumbbell. The data were statistically analyzed by ANOVA/post hoc tests (p < 0.05).ResultsThe highest tensile strength was obtained for the titanium specimens laser-treated with 300 V followed by the 240 V and the control specimens. The laser-treated titanium specimens with 300 V showed a tensile strength equivalent to the Co–Cr alloy. Although the highest modulus of elasticity was found for the specimens laser-treated with 240 V, there were no significant differences in elastic modulus among 240 V, 300 V and Co–Cr. The laser-treated groups showed significantly lower hardness at the subsurface of 25 μm and maintained their hardness until the depth of 400 μm. The hardness of the control group was very high at 25 μm depth, and dramatically decreased until the 200 μm depth.ConclusionThe results of tensile testing and hardness depth-profiling indicated that the laser treatment significantly improved the mechanical properties of cast titanium by improving the surface integrity of the cast surface contamination.     

Effect of Ag on the corrosion behavior of Ti–Ag alloys in artificial saliva solutions

ObjectivesThe purpose of this study was to investigate the corrosion behavior of Ti–Ag alloys in artificial saliva solutions.MethodsThe corrosion behavior of experimental Ti–Ag alloys in artificial saliva was examined by means of potentiodynamic polarization measurements. The surface passive film formed was analyzed by means of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) methods.ResultsThe alloys were found to develop surface passive films after immersion for 1.8 × 10³ s. In comparison with commercially pure Ti, the Ti–Ag alloys exhibited better corrosion resistance with lower anodic current densities, larger polarization resistances, and higher open-circuit potentials. The passive film formed was predominantly composed of TiO₂, as determined by XPS. When fluoride ions were added in the solution, the TiO₂ passive film was destroyed and Na₂TiF₆ was formed.SignificanceAddition of Ag was found to be effective in reducing the corrosion current density and increasing the open circuit potential of titanium in artificial saliva environment. Addition of fluoride ions in the solution severely reduced the corrosion resistance of Ti–Ag alloys.     

Microhardness of resin cements in the intraradicular environment: Effects of water storage and softening treament

ObjectivesTo analyze the microhardness of four dual-cure resin cements used for cementing fiber-reinforced posts under the following conditions: after 7 days of storage in water, after additional 24 h of immersion in 75% ethanol, and after 3 months of storage in water. Hardness measurements were taken at the cervical, middle and apical thirds along the cement line.MethodsRoot canals of 40 bovine incisors were prepared for post space. Fibrekor^® glass fiber-reinforced posts (Jeneric/Pentron) of 1 mm in diameter were cemented using Panavia F 2.0 (Kuraray), Variolink (Ivoclar-Vivadent), Rely X Unicem (3M ESPE) or Duolink (Bisco) (N = 10). After 7 days of water storage at 37 °C, half the sample (N = 5) was longitudinally sectioned and the initial microhardness measured along the cement line from cervical to apex. These same samples were further immersed in 75% ethanol for 24 h and reassessed. The remaining half (N = 5) was kept unsectioned in deionized water at 37 °C for 3 months, followed by sectioning and measuring. Data were analyzed by a series of two-way ANOVA and Tukey tests at α = 5%.ResultsStatistically significant differences were identified among the cements, thirds and conditions. Significant interactions were also observed between cements and thirds and between cements and conditions. Panavia F exhibited significantly higher initial microhardness than the other three cements, which showed no statistical difference among themselves. Variolink and Duolink showed significantly higher microhardness values in the cervical third, without significant difference among the thirds for the other cements. Immersion in ethanol significantly reduced the hardness values for all cements, regardless of the thirds. Storage in water for 3 months had no influence on the hardness of most of the cements, with the exception of Unicem that showed a significant increase in the hardness values after this period.SignificanceResults showed heterogeneity in the microhardness of the cements inside the canal. All cements presented some degree of softening after ethanol treatment, which suggests instability of the polymer. The quality of curing of resin cements in the root canal environment seems unpredictable and highly material dependent.     

Initial oral biofilm formation on titanium implants with different surface treatments: An in vivo study

ObjectiveThe aim of this study was to examine in vivo the initial bacterial adhesion on titanium implants with different surface treatments.DesignTen subjects wore oral splints containing machined pure titanium disks (Ti-M), acid-etched titanium (Ti-AE) and anodized and laser irradiated disks (Ti-AL) for 24 h. After this period, disks were removed from the splints and adherent bacteria were quantified by an enzymatic assay to assess total viable bacteria and by Real Time PCR to evaluate total bacteria and Streptococcus oralis levels. Additionally, the initial adherent microorganisms were visualized by scanning electron microscopy (SEM). Titanium surface morphology was verified using SEM, and roughness was evaluated by profilometer analysis.ResultsRegarding titanium surface roughness, Ti-AL (1.423 ± 0.397) showed significantly higher Ra values than did Ti-M (0.771 ± 0.182) and Ti-AE (0.735 ± 0.196) (p < 0.05, ANOVA – Tahame). Ti-AE and Ti-AL presented roughened micro-structure surfaces characterized by open pores, whereas Ti-M showed long grooves alternating with planed areas. Comparing the Ti-M, Ti-AE and Ti-AL groups for viable bacteria (MTT assay), total bacteria and S. oralis quantification (qPCR), no significant differences were observed among these three groups (p > 0.05, ANOVA – Tahame). SEM images showed similar bacterial adhesion on the three titanium surfaces, predominantly characterized by cocci and several bacilli, indicating an initial colonization of the oral biofilm.ConclusionIn conclusion, roughness and microtopography did not stimulate initial biofilm formation on titanium surfaces with different surface treatments.     

Probability of interface imperfections within SEM cross-sections of adhesively luted GFP

ObjectivesTo calculate the probability of interface imperfections within SEM cross-sections of adhesively luted GFP depending on the level of analysis and the cement application method by means of LOM (light-optical microscopic evaluation method).Material and methodsFour groups of artificial root canals received GFPs (n = 5) under following experimental conditions: I = RelyX? Unicem, applied with application aid, II = RelyX? Unicem, III = Panavia F 2.0 and IV = Variolink II. In groups II–IV only posts were loaded with cement (i.e. conventional post cementation). After GFP cementation, standardized photographs were taken perpendicularly to post surface under light-optical microscope from two opposite sides. The length of homogenous cement interface areas were measured using surface-analyzing software. The homogenous areas were related to length of apical, middle, cervical post section and to complete post length to generate the probabilities (%) of hitting imperfections when using SEM cross-section analysis.ResultsThe probabilities (%) of hitting imperfections within SEM cross-sections for cervical, middle, and apical level of analysis were: I = 78, 64, 82; II = 89, 98, 99; III = 72, 91, 99; and IV = 85, 91, 97, respectively. For complete post length median values of probabilities (%) were: I = 75; II = 95; III = 87; and IV = 91.SignificanceThe probabilities show, that SEM cross-section evaluation concerning detection of cement interface imperfections of adhesively luted GFPs depends on the cement application method and the level of analysis and seeming therefore not always unrestricted representative for the whole specimen.     

Osseointegration of fiber-reinforced composite implants: Histological and ultrastructural observations

ObjectivesThe aim of this study was to evaluate the bone tissue response to fiber-reinforced composite (FRC) in comparison with titanium (Ti) implants after 12 weeks of implantation in cancellous bone using histomorphometric and ultrastructural analysis.Materials and methodsThirty grit-blasted cylindrical FRC implants with BisGMA–TEGDMA polymer matrix were fabricated and divided into three groups: (1) 60 s light-cured FRC (FRC-L group), (2) 24 h polymerized FRC (FRC group), and (3) bioactive glass FRC (FRC–BAG group). Titanium implants were used as a control group. The surface analyses were performed with scanning electron microscopy and 3D SEM. The bone–implant contact (BIC) and bone area (BA) were determined using histomorphometry and SEM. Transmission electron microscopy (TEM) was performed on Focused Ion Beam prepared samples of the intact bone–implant interface.ResultsThe FRC, FRC–BAG and Ti implants were integrated into host bone. In contrast, FRC-L implants had a consistent fibrous capsule around the circumference of the entire implant separating the implant from direct bone contact. The highest values of BIC were obtained with FRC–BAG (58 ± 11%) and Ti implants (54 ± 13%), followed by FRC implants (48 ± 10%), but no significant differences in BIC or BA were observed (p = 0.07, p = 0.06, respectively). TEM images showed a direct contact between nanocrystalline hydroxyapatite of bone and both FRC and FRC–BAG surfaces.ConclusionFiber-reinforced composite implants are capable of establishing a close bone contact comparable with the osseointegration of titanium implants having similar surface roughness.