无机填料含量对流动树脂挠曲强度和压缩强度影响体外研究

目的 研究无机填料含量对流动树脂的挠曲强度和压缩强度的影响。方法 于2012年4月在北京大学口腔医学院口腔材料研究室测定Clearfil Flow、Filtek Flow、DenFil Flow、Filtek Z250复合树脂无机填料的质量分数、挠曲强度和压缩强度。结果 流动树脂中无机填料的质量分数与其挠曲强度的变化顺序相一致,由小到大依次为DenFil Flow、Filtek Flow、Clearfil Flow、Filtek Z250。DenFil Flow与其余3组间挠曲强度差异均有统计学意义（P < 0.05）,Filtek Flow与Clearfil Flow、Filtek Z250间挠曲强度差异亦均有统计学意义（P＜0.05）,但Clearfil Flow与Filtek Z250间挠曲强度差异无统计学意义（P＞0.05）。4种材料压缩强度差异均无统计学意义（P＞0.05）。结论 高填料型流动树脂的挠曲强度远高于普通流动树脂,并且可达到我国医药行业标准规定牙合面修复材料的要求;压缩强度与前后牙通用树脂相近,可以满足临床应用的需要。     

�޻����Ϻ�����������֬����ǿ�Ⱥ�ѹ��ǿ��Ӱ�������о�

目的研究无机填料含量对流动树脂的挠曲强度和压缩强度的影响。方法于2012年4月在北京大学口腔医学院口腔材料研究室测定Clearfil Flow、Filtek Flow、DenFil Flow、Filtek Z250复合树脂无机填料的质量分数、挠曲强度和压缩强度。结果流动树脂中无机填料的质量分数与其挠曲强度的变化顺序相一致,由小到大依次为DenFil Flow、Filtek Flow、Clearfil Flow、Filtek Z250。DenFil Flow与其余3组间挠曲强度差异均有统计学意义（P〈0.05）,Filtek Flow与Clearfil Flow、Filtek Z250间挠曲强度差异亦均有统计学意义（P〈0.05）,但Clearfil Flow与Filtek Z250间挠曲强度差异无统计学意义（P〉0.05）。4种材料压缩强度差异均无统计学意义（P〉0.05）。结论高填料型流动树脂的挠曲强度远高于普通流动树脂,并且可达到我国医药行业标准规定面修复材料的要求;压缩强度与前后牙通用树脂相近,可以满足临床应用的需要。     

Flowable composites as intermediate agents without adhesive application in resin composite repair

PURPOSE: To evaluate the effect of different intermediate resin agents on composite-to-composite microtensile bond strength (microTBS). METHODS: Composite disks (8 x 4 mm) of Gradia Direct Anterior (N = 15) and Filtek Supreme XT (N = 15), stored in a saline solution at 37 degrees C for 1 month, were sandblasted (Microetcher, 50 microm-Al2O3), cleaned (35% H3PO4), and randomly divided into five groups (N = 3) according to the intermediate agent applied. Two flowable composites (Gradia LoFlo; Filtek Supreme XT Flow) and two adhesives (Adper Scotchbond 1XT, Scotchbond Multi-Purpose) were used. As a control, no intermediate agent was applied. Each disk was incrementally repaired (8x8 mm) with the same resin as the respective substrate. By serially cutting each repaired specimen, multiple sticks of about 0.8 mm2 in cross-section were obtained and loaded in tension until failure at a cross-head speed of 0.5 mm/minute. Data were statistically analyzed. Failure mode was examined by stereo- and scanning electron-microscopy (SEM). Additional specimens were prepared to morphologically evaluate the composite-to-composite interfacial quality by SEM analysis. RESULTS: Composite substrate and intermediate agent were significant factors (Two-way ANOVA, P < 0.001). Bond strengths achieved with Gradia Direct Anterior were higher than Filtek Supreme XT. The application of flowable composites resulted in statistically superior microTBS than adhesives and control (Tukey test, P < 0.001). Failure mode was predominantly cohesive (flowable composites), cohesive/adhesive (adhesives) and adhesive (no treatment). Flowable composites and adhesives showed a good interfacial quality.     

In vitro evaluation of the erosive potential of viscosity-modified soft acidic drinks on enamel

Objective

The objective of this in vitro study was to investigate the effect of viscosity-modified soft acidic drinks on enamel erosion.

Materials and methods

A total of 108 bovine enamel samples (??=?3 mm) were embedded in acrylic resin and allocated into six groups (n?=?18). Soft acidic drinks (orange juice, Coca-Cola, Sprite) were used both in their regular forms and at a kinetic viscositiy of 5 mm²/s, which was adjusted by adding hydroxypropyl cellulose. All solutions were pumped over the enamel surface from a reservoir with a drop rate of 3 ml/min. Each specimen was eroded for 10 min at 20 °C. Erosion of enamel surfaces was measured using profilometry. Data were analyzed using independent t tests and one-way ANOVAs (p?<?0.05).

Results

Enamel loss was significantly higher for the regular (Coca-Cola, 5.60?±?1.04 μm; Sprite, 5.49?±?0.94 μm; orange juice, 1.35?±?0.4 μm) than for the viscosity-modified drinks (Coca-Cola, 4.90?±?0.34 μm; Sprite, 4.46?±?0.39 μm; orange juice, 1.10?±?0.22 μm).

Conclusion

For both regular and viscosity-modified forms, Coca-Cola and Sprite caused higher enamel loss than orange juice. Increasing the viscosity of acidic soft drinks to 5 mm²/s reduced enamel erosion by 12.6–18.7 %.

Clinical relevance

The erosive potential of soft acidic drinks is not only dependent on various chemical properties but also on the viscosity of the acidic solution and can be reduced by viscosity modification.     

Shear strength evaluation of composite-composite resin associations

OBJECTIVE: The aim of this study was to investigate the shear strength between distinct associations of different commercial composite resins and their fracture modes. METHODS: Nine composite-composite associations (n=90) were prepared for shear strength evaluation and separated into the following groups: Z/Z (Filtek Z250 UD+Filtek Z250 A2); Z/D (Filtek Z250 UD+Durafill VS A2); Z/S (Filtek Z250 UD+Filtek Supreme YT); C/C (Charisma OA2+Charisma A2); C/D (Charisma OA2+Durafill VS A2); C/S (Charisma OA2+Filtek Supreme YT); H/H (Herculite XRV B2D+Herculite XRV B2E); H/D (Herculite XRV B2D+Durafill VS A2); H/S (Herculite XRV B2D+Filtek Supreme YT). Shear tests were carried out using universal mechanical test equipment with a load of 200kgf and speed of 0.5mm/min. Ultimate shear strength data (MPa) from all tested groups were submitted to analysis of variance (one-way ANOVA) and the Tukey test. The fractured surfaces of the test samples were visually evaluated by binocular stereomicroscope at 20 times magnification. Fractures were classified as either adhesive or cohesive or mixed. RESULTS: The highest ultimate shear strength observed for composite-composite associations was found for the groups: Z/Z, C/S, H/H, H/S, Z/S and C/C. Those associations containing the Durafill resin were weaker than the others. CONCLUSION: Microparticle RBC associations presented lower shear strength than hybrid and/or nanoparticle RBC associations, once the only significant difference was found when the Durafill resin was involved.     

Gradual surface degradation of restorative materials by acidic agents

The aim of this study was to investigate the effect of acidic agents on surface roughness and characteristics of four restorative materials. Fifty-two discs were created from each restorative material: metal-reinforced glass ionomer cement (Ketac-S), resin-modified glass ionomer cement (Fuji II LC), resin composite (Filtek Z250), and amalgam (Valiant-PhD); each disc was 12 mm in diameter and 2.5 mm thick. The specimens were divided into four subgroups (n=13) and immersed for 168 hours in four storage media: deionized water (control); citrate buffer solution; green mango juice; and pineapple juice. Surface roughness measurements were performed with a profilometer, both before and after storage media immersion. Surface characteristics were examined using scanning electron microscopy (SEM). Statistical significance among each group was analyzed using two-way repeated ANOVA and Tukey's tests. Ketac-S demonstrated the highest roughness changes after immersion in acidic agents (p<0.05), followed by Fuji II LC. Valiant-PhD and Filtek Z250 illustrated some minor changes over 168 hours. The mango juice produced the greatest degradation effect of all materials tested (p<0.05). SEM photographs demonstrated gradual surface changes of all materials tested after immersions. Of the materials evaluated, amalgam and resin composite may be the most suitable for restorations for patients with tooth surface loss.     

Color stability of different composite resins after polishing

The goals of the present study were to evaluate, in vitro, the staining of different composite resins submitted to different common beverages, and to compare the staining effect of each of these solutions. A total of 288 specimens were randomly divided into six groups and immersed for 4 weeks in five staining solutions represented by red wine, orange juice, coke, tea and coffee or in artificial saliva as a control group. When analyzed over a black background, mean ΔE00 values varied from 0.8 for Venus Diamond, Saremco Microhybrid and ELS in saliva and Estelite Posterior in coke to 37.6 for Filtek Supreme in red wine. When analyzed over a white background, mean ΔE00 values varied from 0.5 for Saremco Microhybrid in saliva to 51.1 for Filtek Supreme in red wine. All materials showed significant changes in color after 4 weeks of immersion in staining solutions. Significant differences were found between the tested composite resins and also between the staining solutions.     

Evaluation of the wear resistance of new nanocomposite resin restorative materials

STATEMENT OF PROBLEM: The use of composite resins for the restoration of posterior teeth is popular because of the improved performance and appearance of these materials. Wear resistance continues to be of particular importance when restoring large occlusal areas in posterior teeth. PURPOSE: The purpose of this study was to evaluate the relative wear characteristics of 2 recently introduced nanofiller-based composite resins (Filtek Supreme, Premise) and compare them to the more traditional microhybrid (Point 4) and microfill (Heliomolar RO) materials that have been used for many years. MATERIAL AND METHODS: Six specimens (2 mm thick and 15 mm in diameter) of each material were subjected to 3-body wear tests using the Oregon Health Sciences University Oral Wear Simulator to produce abrasive wear and attrition for all specimens using human enamel as the opposing cusp. Profilometric tracings of the worn surfaces were used to determine the relative abrasive wear, attrition wear, and roughness (Ra) of the composite resin substrate. The mean diameter of the antagonist enamel wear facets was determined under a measuring microscope. Qualitative SEM analysis was also used to assess the surface appearance of the resulting enamel and composite resin wear facets. The data were analyzed by 1-way ANOVA and Tukey's multiple range post hoc test (alpha=.05). RESULTS: The results indicated that the composite resin type did not significantly affect the amount of measured attrition (P=.15) but did significantly affect abrasive wear (P=.02). The conventional microfill composite resin (Heliomolar RO) exhibited significantly less abrasive wear than the nanohybrid material (Premise). There was no significant difference in the average size of the opposing enamel wear facet generated by the different composite resin materials. Heliomolar RO resulted in a significantly rougher surface within the wear track than either nanohybrid composite resin (Premise) or microhybrid composite resin (Point 4) but was not significantly different than nanofilled composite resin (Filtek Supreme). CONCLUSIONS: The incorporation of nanofillers in 2 of the composite resin materials tested did not significantly improve their wear resistance or the amount of opposing cusp wear when compared to the traditional materials tested.     

Three-dimensional surface profile analysis of different types of flowable restorative resins following different finishing protocols

AIM: The aim of this study was to investigate the surface roughness of different types of flowable restorative resins and compare the effectiveness of diamond finishing burs followed by aluminum oxide discs with aluminum oxide discs alone in producing smooth surfaces. METHODS AND MATERIALS: Twenty-four specimens (10 mm X 2 mm) for each flowable resin (flowable microhybrid composite, flowable liquid microhybrid composite, flowable compomer, and flowable ormocer) were fabricated in an acrylic mold and randomly assigned to three groups. In group I samples were left undisturbed after the removal of a Mylar strip (control). In group II samples were polished with diamond finishing burs, followed by aluminum oxide discs. In group III samples were finished with only aluminum oxide discs. The mean surface roughness (Ra, microm) was determined with 3-D non-contact interferometry. Data were subjected to one way analysis of variance (ANOVA), and post hoc comparison was accomplished using Tukey's HSD. RESULTS: Although significant differences in surface roughness (Ra) values were observed among the materials using a Mylar strip (control), no significant differences between restorative materials were found when all finishing/polishing methods were combined. For all flowable restorative resins tested, the Mylar strip produced surfaces smoother than those produced by a diamond finishing bur followed by a disc or by using discs alone. Surface roughness values were statistically similar for a diamond finishing bur followed by a disc and for disc treated surfaces within each material except for Dyract Flow, a flowable compomer. CONCLUSION: Although the surface roughness of flowable restorative resins differs among the types, this difference can be overcome with different finishing/polishing methods.     

The effect of finishing and polishing procedures on the surface roughness of composite resin materials

AIMS: The aims of this study were to evaluate the effect of various finishing and polishing procedures on the surface roughness of six different composite resin materials (Artemis Enamel, TPH Spectrum, Filtek A-110, Filtek Supreme Enamel, Solitaire 2, and Filtek P-60) as well as to evaluate the effectiveness of the surface sealant application (BisCover) on the surface roughness after finishing and polishing procedures of tested composites. METHODS AND MATERIALS: Specimens (n=168) measuring 5 mm in diameter x 2 mm in thickness were fabricated in a plexiglass well covered with a Mylar strip using six composite resins. A control group of seven specimens of each material received no polishing after being cured under the Mylar strip. Twenty-one specimens for each composite were randomly divided among three finishing and polishing groups (n=7). Each group was polished using a different system: Carbide bur/Sof-Lex disc, Carbide bur/Enhance disc with polishing paste, and Carbide bur/Edenta composite finishing kit. The average surface roughness (Ra, microm) of the control and treated specimens were measured with the Mitutoyo Surftest-402 Surface Roughness tester. After a surface sealant (BisCover) was applied to all treated specimens, according to manufacturer's instructions, the average roughness (Ra) was measured again. Results were statistically analyzed using analysis of variance (ANOVA) and the post-hoc Scheffe's test at a p<0.05 significance level. RESULTS: Significant differences were found for the surface roughness (p<0.05) with interaction among composite resins and the finishing systems used (p<0.05). Enhance/Biscover finishing and polishing procedure surface was not significantly different from the Mylar strip surface groups (p>0.05). The Mylar strip group was not significantly different from the Sof-Lex/BisCover and Edenta/BisCover groups. The ranking of mean Ra values by materials was as follows: Filtek Supreme Enamel < Filtek A110 < TPH Spectrum < Artemis 相似文献   

The effect of proximal contour on marginal ridge fracture of Class II composite resin restorations

OBJECTIVES: To compare the marginal ridge fracture strength of Class II composite resin restorations placed with a straight or contoured matrix band using composite resins with different modulus of elasticity. METHODS: In 60 artificial first molars standardized MO-preparations were ground. Two matrix systems were used: (1) A straight matrix (Standard Tofflemire Matrix, KerrHawe) in Tofflemire retainer (Produits Dentaire). (2) A contoured matrix (Standard matrix, Palodent, Dentsply). In both groups, a wooden wedge and separation ring (Composi-Tight Gold, GDS) were placed and the matrix was burnished against the adjacent tooth. Three composite resins together were used (Filtek Supreme: e-modulus 13.3GPa (3M ESPE), Clearfil AP-X: 16.6GPa (Kuraray) and Clearfil Majesty Posterior: 22.0GPa (Kuraray)), resulting in six groups (n=10). Teeth were mounted into a MTS servo hydraulic testing machine (Mini Bionix II, MTS, USA) with stylus placed on the marginal ridge. Samples were loaded at a crosshead speed of 1.0mm/min until fracture occurred. Fracture resistance data were statistically analyzed using ANOVA and Scheffé's post hoc test for multiple comparison of groups (p<0.05). RESULTS: Contoured proximal surfaces (365.5+/-87.6N) resulted in significant stronger marginal ridges compared to straight surfaces (290.5+/-64.2N) (p<0.001). Clearfil AP-X (378.1+/-94.63N) provided a higher resistance to fracture than Filtek Supreme (301.4+/-67.3N) (p=0.001) and Clearfil Majesty Posterior (304.5+/-70.6N) (p=0.002). No differences were found between Filtek Supreme and Clearfil Majesty Posterior (p=0.890). CONCLUSION: Within the limitations of this in vitro study it was shown that use of a contoured matrix results in a stronger marginal ridge of a Class II composite resin restoration.     

Surface roughness of novel resin composites polished with one-step systems

OBJECTIVES: This study: 1) analyzed the surface roughness of five novel resin composites that contain nanoparticles after polishing with three different one-step systems and 2) evaluated the effectiveness of these polishers and their possible surface damage using scanning electron microscope (SEM) analysis. METHODS: The resin composites evaluated in this study include CeramX, Filtek Supreme XT, Grandio, Premise and Tetric EvoCeram. A total of 100 discs (20/resin composites, 10 x 2 mm) were fabricated. Five specimens/resin composites cured under Mylar strips served as the control. The samples were polished for 30 seconds with PoGo, OptraPol and One Gloss discs at 15,000 rpm using a slow speed handpiece. The surfaces were tested for roughness (Ra) with a surface roughness tester and examined with SEM. One-way ANOVA was used for statistical analysis (p = 0.05). RESULTS: For all the composites tested, differences between the polishing systems were found to be significant (p < 0.05). For Filtek Supreme XT, Mylar and PoGo created equally smooth surfaces, while significantly rougher surfaces were obtained after OptraPol and One Gloss applications. For Grandio, Mylar and PoGo created equally smooth surfaces, while OptraPol and One Gloss produced equally rougher surfaces. Tetric EvoCeram exhibited the roughest surface with OptraPol, while no significant differences were found between Premise and CeramX. According to SEM images, OptraPol and One Gloss scratched and plucked the particles away from the surface, while PoGo created a uniform finish, although the roughness values were not the same for each composite. CONCLUSION: Effectiveness of the polishers seems to be material dependent.     

Light transmission on dental resin composites.

OBJECTIVES: The purposes of this study was: (1) to examine the light transmittance characteristics of two light-cured resin composites, for different thickness, (2) to correlate the light transmittance through the resin composites and the filler contents, and (3) to determine the penetration depth of the light as a function of the wavelength. METHODS: Two resin composites (Filtek Z250, shade A2 and Filtek Supreme XT, shade A2E) were used. Specimens of six different thicknesses (0.15, 0.25, 0.30, 0.36, 0.47 and 0.75 mm) were prepared (n=3). The transmittance at wavelengths from 400 to 800 nm was measured using a UV-visible spectrophotometer, before and after light polymerization. RESULTS AND SIGNIFICANCE: Significant differences were found in the wavelength dependence of transmittance between the two materials, and between the unpolymerized and polymerized stages of each resin composite. At lower wavelengths, the light transmittance of the Filtek Supreme XT resin composite was lower than the Filtek Z250. At the higher wavelengths, however, Filtek Supreme XT presented higher light transmittance. For both resin composites, the penetration depth was higher after polymerization. However, Filtek Supreme XT showed a higher gain in transmittance at the 0.15 mm thickness. The difference in light transmittance characteristics of the resin composites may affect their depth of polymerization.     

Flowable composites as "filled adhesives:" a microleakage study

OBJECTIVE: The purpose of this in vitro study was to investigate the microleakage at dentin margins of a flowable resin composite associated with an adhesive, either light cured separately or co-cured, in Class V cavities. MATERIALS AND METHODS: Twenty four recently extracted human molars were prepared with standardized box-shaped Class V cavities of 3.0 mm (mesial-distal), 2.0 mm (occlusal-gingival), and 2.0 mm depth with margins located on enamel and dentin/cementum on the buccal or lingual surfaces. The cavities were randomly assigned into three groups (n=8): Group I - Single Bond + Filtek Z250 (control); Group II - Single Bond + Filtek Flow (light cured separately) + Filtek Z250; and Group III - Single Bond + Filtek Flow co-cured (light cured simultaneously) + Filtek Z250. After being immersed in tap water for 24 h, the specimens were thermocycled (1000x, 5 degrees -55 degrees C, 30 sec dwell time) and immersed in a 0.5% basic fuchsine solution for 24 h. The restorations were sectioned longitudinally and gingival margins were evaluated for microleakage using a 0-4 scale. Data were subjected to the Kruskal-Wallis test at p<0.05. RESULTS: A statistically significant difference at p = 0.0044 between Groups 1 and 3 and Groups 2 and 3 was observed. Although Group 2 performed slightly better than Group 1, no significant difference was observed. CONCLUSION: The use of a flowable resin composite cured simultaneously with an adhesive yielded the worst results in this study. As no statistical differences were seen between Groups 1 and 2, the use of a flowable composite as a means of minimizing microleakage at dentin margins may be questioned.     

Microtensile bond strength of adhesive systems to dentin with or without application of an intermediate flowable resin layer

This study evaluated the effect of flowable composite resin application on the microtensile bond strength (muTBS) of adhesive systems to dentin. Occlusal surfaces of human third molars were ground to obtain flat dentin surfaces. The crown of each tooth was sectioned occluso-gingivally into four quarters with a water-cooled diamond saw. One of the following adhesive systems was applied to dentin surface in each quarter of the same tooth, following manufacturers' instructions: Scotchbond Multipurpose, Single Bond Adper Prompt and Clearfil SE Bond. Experimental and control groups received the same treatment, except for the fact that a layer of flowable composite (Filtek Flow) was placed and light-cured on top of the adhesive layer in the specimens of the experimental groups. Resin composite (Filtek Z250) crown buildups were then made on the bonded surfaces and incrementally light-cured for 20 s. The restored teeth were stored in water at 37 masculineC for 24 h. Each tooth quarter was serially cut in a longitudinal direction in order to obtain several bonded sticks (0.9-mm(2) in cross-section). Maximal microtensile stress (in MPa) at failure was recorded using a universal testing machine. Data were analyzed by two-way ANOVA and Tukey's test at 5% significance level. Placement of a low-viscosity resin to the hybridized dentin increased the muTBS for all tested adhesive systems. However, such increase was significant only for Clearfil SE Bond (p<0.05). When the restorations were placed without low-viscosity resin, Clearfil SE Bond presented higher muTBS than Adper Prompt (p<0.05). For the groups treated with flowable composite, Clearfil SE Bond produced the highest muTBS means to dentin. In conclusion, the effect of the addition of an intermediate flowable composite layer on muTBS to dentin was material-dependent and resulted in an increased adhesion for all tested materials, though with significance only for Clearfil SE Bond.     

Cuspal deflection and microleakage in premolar teeth restored with resin-based composites with and without an intermediary flowable layer

OBJECTIVES: To assess cuspal deflection and cervical enamel microleakage with and without an intermediary flowable RBC layer for the incremental restoration of mesio-occluso-distal (MOD) cavities with two resin-based composites (RBCs). METHODS: Forty sound upper premolar teeth had standardised MOD cavities prepared. Restoration of the teeth involved the placement of the RBCs (Filtek P60 or Filtek Supreme) in eight increments with the appropriate bonding system with and without an intermediary flowable RBC layer (Filtek Flow). Buccal and palatal cusp deflections were recorded post-irradiation using a twin channel deflection measuring gauge. Following restoration, the teeth were thermocycled, immersed in a 0.2% basic fuchsin dye for 24h, sagittally sectioned and examined for cervical enamel microleakage. RESULTS: A significant reduction in cuspal deflection was evident when both RBC materials were used to restore the cavity by employing an intermediary flowable (P<0.001) compared with when no intermediary flowable was utilised. No statistically significant differences were identified in microleakage between the teeth restored with Filtek P60 or Filtek Supreme when an intermediary flowable (Filtek Flow) was employed. CONCLUSIONS: The results of the current study suggest that there was a benefit to the operator in terms of a reduction in cuspal deflection but not from the maintenance of the synergism of the adhesive bond, namely microleakage at the cervical enamel cavosurface margin, when an intermediate layer of a flowable RBC was used under higher elastic modulus RBCs.     

EFFECTS OF POLISHING PROCEDURES ON COLOR STABILITY OF COMPOSITE RESINS

The purpose of this study was to investigate the effect of different polishing methods on color stability of posterior, universal and nanohybrid composite resin restorative materials upon exposure to a staining agent. Twenty-five specimens were prepared for each of 5 different composite resins (Filtek Z250, Filtek P60, Quadrant LC, Grandio and Filtek Supreme). Specimens were divided into 5 groups and different polishing procedures, including polishing discs (Pd), polishing discs then diamond polishing paste (PdP), polishing discs then a liquid polishing system (Biscover) (PdB), and combinations of these (PdPB) were used. Unpolished specimens served as the control (C). The specimens were stored for 48 h in a coffee solution. The color of all specimens was measured before and after exposure with a colorimeter, and total color change ∆E*) were calculated. The data were analyzed with a two-way ANOVA and the means were compared by Tukey HSD test (α=0.05). The lowest color difference was observed in the groups PdP and C, while the highest color difference was observed in PdPB, and PdB. When comparing the five different restorative materials, no significant difference was observed between FiltekP60 and FiltekZ250, and these materials demonstrated significantly less color change than Quadrant LC and the nanohybrid materials (Grandio, Filtek Supreme). The posterior (Filtek P60) and universal (Filtek Z250) composite resin restorative materials, which do not contain tetraethyleneglycol dimethacrylate (TEGDMA), were found to be less stainable than the nanohybrid (Grandio, Filtek Supreme) and universal (Quadrant LC) composite resins, which contain TEGDMA. The use of diamond polishing paste after polishing with polishing discs significantly decreased staining when compared to the groups that used polishing discs alone, for all restorative materials tested. The highest color change values were obtained for the specimens that were polished with the Biscover liquid polish system (PdB and PdPB groups).     

Prevention by means of fluoride of enamel erosion as caused by soft drinks and orange juice

Fluoride has been suggested to prevent erosion of the teeth, either after a topical treatment of the teeth or by addition of fluoride to the acidic drink. The main aim of the present study was to describe the dissolution of calcium fluoride in some soft drinks and orange juice and compare it with the amounts of calcium fluoride left on the enamel surfaces after a topical treatment. A further aim was to describe the dissolution of enamel in soft drinks and juice saturated for 3 days with solid calcium fluoride. Solid calcium fluoride was suspended in each of 10 soft drinks and orange juices and gently agitated for 72 h, after which the drinks were analyzed for calcium, phosphate and fluoride and pH was determined. To examine the erosion-preventive effect of the calcium fluoride-rich drink, intact teeth were exposed to the drinks with or without calcium fluoride. It was found that from 6 to 45 mg of calcium fluoride was dissolved per liter of drink. The more acidic the drink, the more calcium fluoride was dissolved, presumably due to HF formation. The teeth exposed to the soft drinks all showed erosion-like lesions. Very little effect of the 4-6 ppm ionic fluoride dissolved in the soft drinks was observed. In orange juice, however, the dissolved calcium fluoride established a saturation with respect to fluorapatite and consequently, the erosion-like lesion was replaced by a caries-like lesion. In conclusion, the acidic soft drinks are capable of dissolving considerable amounts of calcium fluoride and the erosion-preventive effect of even high fluoride concentrations is limited.     

The effect of bonding system and composite type on adaptation of different C-factor restorations

This study evaluated the effect of two adhesive systems and four resin-based composites on the marginal sealing and cavity wall adaptation of restorations with different C-factors. Cylindrical cavities, 1 mm deep and 3 mm in diameter (C-factor=2.3) or 2 mm in diameter (C-factor=3), were prepared on superficial bovine dentin surfaces. The teeth were restored with Clearfil SE Bond or Single Bond adhesive system followed by hybrid (Photo Clearfil Bright or Z100) or flowable (Filtek Flow or Estelite LV) resin composite. After thermocycling, a dye penetration test was carried out to evaluate the degree of marginal leakage and cavity-wall gap formation. Cavity-wall gap formation increased when the C-factor increased from 2.3 to 3, except for Estelite LV resin composite. In terms of marginal sealing, Clearfil SE Bond showed better performance than Single Bond. When using Clearfil SE Bond, flowable composites improved resin composite adaptation to the cavity wall compared with hybrid composites.     

Analysis of camphorquinone in composite resins as a function of shade.

OBJECTIVE: To identify and quantify the camphorquinone (CQ) used in different brands of composite resins as a function of the shade analyzed. MATERIALS AND METHODS: Filtek Z250 A3 (FZA3), Filtek Z-250 Incisal (FZI), Pyramid Enamel A1 (PEA1), Pyramid Enamel Translucent (PET), Filtek Supreme A3E (FSA3) and Filtek Supreme GT (FSGT) were used. Five hundred milligrams of each resin were weighed and then dissolved in 1.0 ml of methanol. The samples were centrifuged to accelerate the sedimentation of the inorganic particles. 0.8 ml of the supernatant solution was collected with a pipette and assessed under gas chromatography coupled to the mass spectrometer (GC-MS). The results were compared to pure CQ solutions, used as a standard. Student's t-test, (p=0.05) significant at the level of 5%, compared the results of each brand shade. RESULTS: A smaller amount of camphorquinone was found in Filtek Z-250 (FZI) resin incisal shade when compared to (FZA3) A3 shade. On the other hand, Filtek Supreme resin featured a statistically larger camphorquinone amount in the incisal shade. In Pyramid Enamel resin camphorquinone was found only in shade A1, while the photoinitiator used in the Translucent shade was not identified. SIGNIFICANCE: Based on the data obtained, it is possible to conclude that a single composite resin brand may feature differences in amount and type of photoinitiator used.