Effect of different polishing methods on roughness and color stability of air-abraded restorative materials after artificial accelerated aging.

PURPOSE: To evaluate the effect of air abrasion and polishing procedures on roughness and color stability of ceramic and composite materials after artificial accelerated aging. METHODS: In this study, six restorative materials were tested: feldspathic ceramic (CEREC Blocks), glass ceramic (IPS e.max CAD), resin-based hybrid ceramic (Cerasmart), microhybrid composite (Charisma Classic), nanohybrid composite (Charisma Diamond) and nanoceramic composite (CeramXOne). Forty square-shaped composite specimens were fabricated from each composite and CAD-CAM ceramic material. Initial surface roughness measurements were performed using a profilometer and color measurements of each specimen with a spectrophotometer. Ten control specimens for each group did not receive air abrasion. The other specimens were treated by an air abrasion device and then were randomly divided into three subgroups of 10 specimens (n= 10). After air abrasion, 10 specimens of each group did not receive polishing (Air abrasion group) and others were repolished with Sof-Lex kit (Sof-Lex group) or a rubber kit (Rubber group). Surface roughness and color measurements were repeated before and after 300 hours of artificial accelerated aging (AAA). The univariate test and then three-way ANOVA and two-way ANOVA were performed for comparison of groups (α= 0.05). RESULTS: The univariate statistical analysis revealed that the restorative materials were differently affected after air abrasion, polishing methods and AAA (P< 0.001). Three-way ANOVA showed that the surface roughness of the restorative materials increased after air abrasion and AAA (P< 0.001). Two-way ANOVA showed statistically significant differences between color changes of ceramic (CEREC and IPS e.max CAD) and composite based restorative materials (P< 0.001). CLINICAL SIGNIFICANCE: Clinicians should be aware that air abrasion at a specified power and time significantly changes the surface roughness of the materials except for CEREC. Additionally, polishing procedures (Sof-Lex, Rubber) did not significantly reduce the surface roughness of the ceramic groups. After air abrasion, depending on the material type used clinically, restorations should be repolished to reduce roughness and ensure color stability.

Comparison of fracture strength, surface hardness, and color stain of conventionally fabricated, 3D printed, and CAD-CAM milled interim prosthodontic materials after thermocycling.

PURPOSE: The purpose of this in vitro study was to investigate the fracture resistance, surface hardness, and color stain of 3D printed, CAD-CAM milled, and conventional interim materials. MATERIALS AND METHODS: A total of 80 specimens were fabricated from auto polymerizing polymethyl methacrylate (PMMA), bis-acryl composite resin, CAD-CAM polymethyl methacrylate resin (milled), and 3D printed composite resin (printed) (n = 20). Forty of them were crown-shaped, on which fracture strength test was performed (n = 10). The others were disc-shaped specimens (10 mm × 2 mm) and divided into two groups for surface hardness and color stainability tests before and after thermal cycling in coffee solution (n = 10). Color parameters were measured with a spectrophotometer before and after each storage period, and color differences (CIEDE2000 [DE00]) were calculated. The distribution of variables was measured with the Kolmogorov Smirnov test, and one-way analysis of variance (ANOVA), Tukey HSD, Kruskal-Wallis, Mann-Whitney U tests were used in the analysis of quantitative independent data. Paired sample t-test was used in the analysis of dependent quantitative data (P < .05). RESULTS: The highest crown fracture resistance values were determined for the 3D printed composite resin (P < .05), and the lowest were observed in the bis-acryl composite resin (P < .05). Before and after thermal cycling, increase in mean hardness values were observed only in 3D printed composite resin (P < .05) and the highest ΔE00 value were observed in PMMA resin for all materials (P < .05). CONCLUSION: 3D printing and CAD-CAM milled interim materials showed better fracture strength. After the coffee thermal cycle, the highest surface hardness value was again found in 3D printing and CAD-CAM milled interim samples and the color change of the bis-acryl resin-based samples and the additive production technique was higher than the PMMA resin and CAD-CAM milled resin samples.

Shear bond strength of a self-adhesive resin cement to dentin surface treated with Nd:YAG and femtosecond lasers.

This study aims to evaluate the effect of Nd:YAG and femtosecond lasers irradiation on the shear bond strength (SBS) of a self-adhesive resin cement to the human dentin surface. One hundred extracted third molar teeth were randomly divided into 10 experimental groups according to dentin surface treatments; with and without the bonding agent, Nd:YAG 302 J/cm2 and 440 J/cm2, femtosecond 4 J/cm2 and 7 J/cm2, and control groups were prepared. After surface treatments, a self-adhesive resin cement was luted by using a bonding jig (Ultradent Products Inc.). The specimens were then subjected to shear test at a crosshead speed of 0.5 mm/min, and failure loads were recorded as megapascal (MPa). Two-way analysis of variance and Tukey HSD tests were performed (p Ë‚ 0.05). Representative specimens from each experimental subgroup were examined by means of SEM. The highest SBS values were obtained in Group 302 J/cm2 Nd:YAG with bonding agent, and there is no statistical difference between Group 440 J/cm2 Nd:YAG with bonding and Group 7 J/cm2 femtosecond with bonding (p > 0.05). The lowest SBS values were observed in Group control without bonding agent. Nd:YAG and femtosecond laser treatments improved the adhesion between the dentin surface and the self-adhesive resin cement.

Effect of fabrication techniques on the optical properties of zirconia-based systems.

STATEMENT OF PROBLEM: How the optical properties of zirconia restorations are affected by their differing processing techniques is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effects of 5 different fabrication techniques on the optical properties of zirconia-based systems, including the color difference between the corresponding shades (ΔE∗ab, ΔE00), translucency parameter, opalescence parameter, and fluorescence (ΔE∗ab-FL). MATERIAL AND METHODS: Sixty zirconia disks (IPS e.max ZirCAD) were prepared (0.5 ±0.01mm thick) and veneered by using different techniques (n=15): Group L - layering with fluorapatite ceramic; Group P - pressing with fluorapatite ceramic; Group CB - veneered with pressing followed by layering technique; Group CO - digitally veneered with lithium disilicate glass-ceramic; and Group FZ - prepared from monolithic zirconia (inCoris TZI) (n=15). All the specimens were set to 1.5 ±0.02 mm in thickness. Color measurements were made with a spectrophotometer. Data were statistically analyzed with 1-way ANOVA and the Tukey honestly significant difference, Kruskal-Wallis, Bonferroni (α=.05), Pearson, and Spearman correlation tests (α=.01). RESULTS: Significant differences were found among the groups for all the optical parameters (P<.05). All the groups showed color differences higher than the perceptibility and acceptability thresholds for ΔE∗ab and ΔE00, except the P and FZ groups that showed values lower than the acceptability threshold (ΔE∗ab<2.7). Translucency parameter, opalescence parameter, and ΔE∗ab-FL values ranged between 5.77 and 9.95, between 4.72 and 7.07, and between 1.93 and 3.14, respectively. Strong positive correlations were found between ΔE∗ab and ΔE00, as well as between translucency parameter and opalescence parameter (P<.001). CONCLUSIONS: The optical properties of the zirconia-based systems were significantly affected by the fabrication techniques even when the same nominal shade was used. Therefore, the color reproduction, translucence, opalescence, and fluorescence of the selected materials should be considered for acceptable color matching.

Effect of a Home Bleaching Agent on the Ion Elution of Different Esthetic Materials.

PURPOSE: To investigate the effect of a 16% carbamide peroxide home bleaching agent on the ion elution of different esthetic restorative materials and to determine if the released ions exceed the minimal risk levels. MATERIALS AND METHODS: Ceramic materials comprising a low-fusing porcelain (Vita VM7), lithium disilicate glass-ceramics (IPS e.max Press and IPS e.max CAD), zirconium substructure materials (IPS e.max ZirCAD and Vita In-Ceram YZ for InLab), and ceromers (Estenia and Tescera ATL) were chosen. Thirty disk-shaped specimens (2 mm thickness and 10 mm diameter) were fabricated from each material and then were divided into 3 experimental groups to receive one of the following solutions: acetic acid (positive control), a bleaching agent and distilled water (negative control) (n = 10/group). For the bleaching agent, the specimens were subjected to a 16% carbamide peroxide solution (VOCO Perfect Bleach) for 2 hours per day for 14 days. A 4% acetic acid solution was applied at 80°C for 16 hours according to the ISO 6872:2015 protocol and specimens of negative control group were immersed in distilled water for 16 hours. Ion elution measurements were conducted with inductively coupled plasma atomic emission spectroscopy (ICP-AES) after immersion in the solutions, and the weight loss of the materials was measured with a precision scale. Changes in the surface topography were investigated by a scanning electron microscopy (SEM).The results were evaluated using multivariate analysis of variance (MANOVA). RESULTS: Among the specimens tested, the most ion elution was observed in the Tescera ATL group, and the least ion elution was observed in the e.max ZirCAD group in all solutions. Ion elution was found to be greater in the bleaching agent than in the acetic acid and distilled water groups. Sodium was the most released ion, and zinc and lithium were the least released among the elements tested. CONCLUSIONS: It should be noted that the bleaching-related ion release may exceed toxic doses even if restorative materials meet ISO 6872 standards, and the materials should be protected before home bleaching to prevent ion elution.

Comparison of color stability of two laminate veneers cemented to tooth surfaces with and without preparation.

OBJECTIVE: The aim of this study was to determine the effects of preparation vs nonpreparation of tooth surfaces and the types of porcelain laminate veneers (PLVs) on color changes after 300 hours of artificially accelerated aging (AAA). MATERIALS AND METHODS: Forty extracted maxillary central incisors were used. The teeth were divided into four groups (n = 10) to evaluate preparation methods and porcelain types: Group A: tooth preparation with IPS e.max computer-assisted design (CAD), group B: tooth preparation with IPS e.max press, group C: nonpreparation with IPS e.max CAD, and group D: nonpreparation with IPS e.max press. Veneers were fabricated and cemented using a dual-polimerized cement. Initial color measurement was performed and repeated after AAA. Color changes were calculated with the CIEDE 2000 (ΔE00 ) formula. Color differences were analyzed with two-way ANOVA (P < .05). RESULTS: The two-way ANOVA test showed no significant difference among the groups (P > .05). The highest color change value was observed in group C, followed by groups B, A, and D. CONCLUSION: Preparation of veneers caused more color changes in PLVs than nonpreparation. However, IPS e.max CAD systems for fabrication of nonprepared PLVs increased the color change of the PLVs measured after AAA. CLINICAL SIGNIFICANCE: The results provide information on the effect of the amount of preparation and the type of porcelain on color change in porcelain laminate veneers. In terms of esthetic dentistry, IPS e.max press and non-prep treatment should be used in the anterior region, where esthetics are important.

Effect of mucosa thicknesses on stress distribution of implant-supported overdentures under unilateral loading: Photoelastic analysis.

INTRODUCTION: The aim of this study was to evaluate the effect of different heights of attachment and mucosa thicknesses on the stress distribution of two implant-retained mandibular overdenture designs under loading using the photoelastic stress analysis method. MATERIALS AND METHODS: Six photoelastic models of an edentulous mandibula were fabricated with two solitary implants that were placed in the canine regions. The attachment systems studied were ball and locator stud attachments. Both the ball and locator groups included three models that had different residual ridge heights so as to provide different mucosa thicknesses (1 mm-1 mm, 1 mm-2 mm, 1 mm-4 mm). A static vertical force of 135 N was applied unilaterally (each on the right then the left side) to the central fossa of the first molars. Models were positioned in the field of a circular polariscope to observe the distribution of isochromatic fringes around the implants and the interimplant areas under loading. The photoelastic stress fringes were monitored and recorded photographically. RESULTS: The ball attachment groups showed higher stress values than did the locator groups under loading. Both attachment systems produced the lowest stress values in stimulated 1 mm-1 mm mucosa thickness models. The models with 1 mm-2 mm mucosa thicknesses showed higher stress values than did other models for both attachment systems. The highest stress value observed around both attachment systems was the moderate level in all test models. CONCLUSION: In different height mucosa thicknesses, locator attachment models distributed the load to the other side of the implant and its surrounding tissue, whereas the ball attachment did not. Regardless of mucosal thickness and attachment type, the implant on the loading side was subjected to the highest stress concentration.

Evaluation of Stress Distribution on Mandibular Implant-Supported Overdentures With Different Bone Heights and Attachment Types: A 3D Finite Element Analysis.

The biomechanical behavior of the edentulous mandible with bone irregularities that has been rehabilitated with implant-supported overdentures has become an important factor for treatment planning. Restorative options, including dental implants with various attachments, affect the stress distribution. The purpose of this study was to evaluate the stress distribution of cortical bone around the implant neck and implant structures in overdentures with two different attachment types at the edentulous mandible and with different bone heights using three-dimensional finite element analysis. Five three-dimensional models of an edentulous mandible were designed and implemented. Ten models were constructed with ball and locator attachments. Static bilateral and unilateral vertical and oblique occlusal loads with magnitudes of 100 N were applied to the overdentures. The principal stresses were higher in the presence of oblique loads compared to vertical loads in all the analyzed models. Maximum principal stresses were observed around the mesial side of the contralateral implant, and the minimum principal stresses were noted around the distal side of ipsilateral implant during unilateral vertical loading. These patterns were reversed during oblique loadings. The ball attachment models yielded lower von Mises stress values than the locator models at all the loading conditions, while the stress distributions were similar in the models with the same and different bone levels. Correspondingly, bone corrections due to irregularities may not be necessary in terms of biomechanics. The results of this study may provide clinicians a better understanding for the mandibular overdenture design in the cases at which different bone heights exist.

Effect of Veneering Techniques on Shear and Microtensile Bond Strengths of Zirconia-Based All-Ceramic Systems.

PURPOSE: To evaluate shear (SBS) and microtensile (µTBS) bond strengths of zirconia cores veneered using different fabrication techniques. MATERIALS AND METHODS: Seventy-five IPS e.max ZirCAD plates were fabricated and divided into three groups according to the following veneering techniques: layering, pressing, and CAD-on. The specimens of the layering group were veneered with IPS e.max Ceram, and the specimens of the pressing group were veneered with IPS e.max Zir- Press. Veneering ceramics in the CAD-on group were milled from IPS e.max CAD, fused with the core by using a glass-fusion ceramic, and then crystallized. Bond strength tests were performed using a universal testing machine at a crosshead speed of 0.5 mm/min for the SBS test and 1 mm/min for the µTBS test. Mean SBS and µTBS (MPa) were analyzed with one-way ANOVA and Tukey's HSD test (p < 0.05). RESULTS: Significant differences in SBS were observed between the groups (p < 0.05). The mean SBS for the CAD-on group was significantly higher (31.89 ± 5.83 MPa) than those of the layering (14.27 ± 4.45 MPa) and pressing (12.23 ± 3.04 MPa) groups. However, the mean µTBS of the CAD-on (30.41 ± 8.64 MPa), layering (21.71 ± 3.40 MPa) and pressing (20.74 ± 6.36 MPa) groups were not statistically significant (p > 0.05). CONCLUSION: The CAD-on technique showed the highest shear bond strengths of the tested groups, and most of the specimens failed cohesively instead of failing at the adhesive interface.

Color Stability of CAD/CAM Fabricated Inlays after Accelerated Artificial Aging.

PURPOSE: To investigate the influence of accelerated artificial aging on the color stability of three different inlay restorations produced with a CAD/CAM system. MATERIALS AND METHODS: Thirty non-carious human mandibular molar teeth were used. The teeth were embedded in autopolymerizing acrylic resin blocks. Standard Class I inlay cavities were prepared, and the teeth were randomly divided into three groups (n = 10) to fabricate inlay restorations: (1) a feldspathic-ceramic group, (2) a resin nano-ceramic group, and (3) a leucite glass-ceramic group. Optical impressions were made with CEREC software, and the restorations were designed and then milled. The inlays were adhesively cemented with a dual-polymerizing resin cement and left in distilled water at room temperature for 1 week. Color measurements were performed with a spectrophotometer before and after accelerated aging in a weathering machine with a total energy of 150 kJ/m(2) . Changes in color (∆E, ∆L, ∆a, ∆b, ∆C) were determined using the CIE L*a*b* system. The results were assessed using a one-way ANOVA and Tukey's HSD test (p = 0.05). RESULTS: The color changes of the materials ranged from 2.1 to 9.29. The highest color change was seen in the resin nano-ceramic material. This change was not clinically acceptable (∆E > 5.5). No significant differences were found in the ∆L and ∆a values of the test groups. CONCLUSIONS: Color changes were observed in each evaluated material after accelerated aging. All CAD/CAM inlays became darker in appearance, more saturated, a little reddish, and more yellow.

Management of restricted mouth opening caused by radiation: A clinical report.

Trismus, a commonly observed sequela in patients who have undergone radiation therapy to treat malignancies of the head and neck, causes a loss of function that reduces patients' overall quality of life. Radiation can cause intense fibrosis in the masticatory muscles, and this fibrosis may lead to trismus. This clinical report describes the management of a patient with radiation-induced trismus who was treated with a custom-made mouth-opening device. The device had maxillary and mandibular sections, was made of a thermoactive acrylic resin material, and was connected with 2 vertical screws in the right and left canine regions. The screws were adjusted daily to increase the oral opening, such that each turn of the screws increased the opening by 0.25 mm. With the help of this device, at the end of a 4-month follow-up period, the patient's maximal interdental distance had increased from 7.16 mm to 19.50 mm. The intraoral opening device described in this study is useful for achieving a vertical opening sufficient to perform dental treatment.

Effect of Nd:YAG laser bleaching and antioxidizing agents on the shear bond strength of brackets.

OBJECTIVE: The aims of this study were to evaluate the effect of hydrogen peroxide bleaching agents, both nonactivated and activated by a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, and of antioxidant treatment on the shear bond strength (SBS) of orthodontic brackets. BACKGROUND DATA: Nd:YAG laser activation is expected to accelerate the bleaching therapy without decrease shear bond strength. MATERIALS AND METHODS: Ninety extracted maxillary central incisors were divided into two experimental groups and a control group. Group I was the control group, Group II was bleached with 35% hydrogen peroxide and had no photoactivation, and Group III was bleached with 35% hydrogen peroxide with activation by a Nd:YAG laser (4.0 W, 60 Hz frequency, 1 mm distance, 20 sec). Each group was divided into two subgroups: Subgroup A was immersed in artificial saliva for 2 weeks, and then bonded using the total etch system, whereas subgroup B was treated with an antioxidant agent (10% sodium ascorbate) and then bonded using the same system. The samples were stored in water for 24 h at 37°C, and thermocycled. The SBS in megapascals (MPa) was determined by a shear test with 1 mm/min crosshead speed, and failure types were classified with modified adhesive remnant index scores. The data were analyzed with two way analyses of variance, Tukey, and χ(2) tests at the α = 0.05 level. RESULTS: In both Groups II and III, the SBSs of brackets bonded after bleaching (Group II 15.16, Group III 17.50 MPa) were significantly lower than those of brackets in the bonded unbleached group (Group I 22.13 MPa); however, sodium ascorbate treatment significantly increased the SBSs of brackets in the bleached groups (Group II 21.52, Group III 22.43 MPa), but had an insignificant effect on the SBS of the control group (Group I 23.66MPa). CONCLUSIONS: Hydrogen peroxide bleaching agents reduce the SBSs both with and without Nd:YAG laser activation; however, treatment of the bleached enamel surface with 10% sodium ascorbate prior to bonding negates the effect.

Amelogenesis imperfecta and generalized gingival overgrowth resembling hereditary gingival fibromatosis in siblings: a case report.

Amelogenesis imperfecta (AI) is a group of hereditary disorders primarily characterized by developmental abnormalities in the quantity and/or quality of enamel. There are some reports suggesting an association between AI and generalized gingival enlargement. This paper describes the clinical findings and oral management of two siblings presenting both AI and hereditary gingival fibromatosis (HGF) like generalized gingival enlargements. The treatment of gingival enlargements by periodontal flap surgery was successful in the management of the physiologic gingival form for both patients in the 3-year follow-up period. Prosthetic treatment was also satisfactory for the older patient both aesthetically and functionally.

Effects of fibers on the color change and stability of resin composites after accelerated aging.

Composite resins were reinforced with glass and polyethylene fibers in this study, and the effect of fiber reinforcement on the color change of composite resins was investigated. After accelerated aging, the effect of fiber reinforcement on the color stability of composite resins was also examined. There were three experimental groups (n=12 disks per group): non-fiber-reinforced composite (non-FRC control), polyethylene fiber (Ribbond-THM)-reinforced composite, and glass fiber (everstick NET)-reinforced composite. According to the critical remarks of color change of National Bureau of Standarts (NSB), glass fiber-reinforced anterior composites showed trace color change and polyethylene-fiber reinforced composites showed slight color change before accelerated aging. After accelerated aging, both control and fiber-reinforced composite groups showed noticeable color change. It was concluded that both the types of fiber reinforcement and composite resin influenced the color change of fiber-reinforced composite resins.

Single tooth replacement using a ceramic resin bonded fixed partial denture: A case report.

This article describes the use of an all ceramic resin-bonded fixed partial denture as a conservative solution for the replacement of an incisor. It is a minimally invasive technique that does not discolor the abutment teeth.

Influence of the supporting die structures on the fracture strength of all-ceramic materials.

This study investigated the influence of the elastic modulus of supporting dies on the fracture strengths of all-ceramic materials used in dental crowns. Four different types of supporting die materials (dentin, epoxy resin, brass, and stainless steel) (24 per group) were prepared using a milling machine to simulate a mandibular molar all-ceramic core preparation. A total number of 96 zirconia cores were fabricated using a CAD/CAM system. The specimens were divided into two groups. In the first group, cores were cemented to substructures using a dual-cure resin cement. In the second group, cores were not cemented to the supporting dies. The specimens were loaded using a universal testing machine at a crosshead speed of 0.5 mm/min until fracture occurred. Data were statistically analyzed using two-way analysis of variance and Tukey HSD tests (α = 0.05). The geometric models of cores and supporting die materials were developed using finite element method to obtain the stress distribution of the forces. Cemented groups showed statistically higher fracture strength values than non-cemented groups. While ceramic cores on stainless steel dies showed the highest fracture strength values, ceramic cores on dentin dies showed the lowest fracture strength values among the groups. The elastic modulus of the supporting die structure is a significant factor in determining the fracture resistance of all-ceramic crowns. Using supporting die structures that have a low elastic modulus may be suitable for fracture strength tests, in order to accurately reflect clinical conditions.

Complex midfacial reconstruction with an implant-supported framework.

This clinical report describes the treatment of a patient with osseointegrated extraoral implants supporting a framework retainer and acrylic resin mesostructures and a large silicone midfacial prosthesis. A metal framework was used to splint the implants together and provided satisfactory retention for the facial prosthesis. A 2-piece prosthesis that composed of an obturator and facial prosthesis was fabricated. Cosmetic improvements as well as the ability to speak, swallow, and, to a lesser degree, chew, were achieved for this patient.

The effect of different surface treatments on roughness and bond strength in low fusing ceramics.

The aim of this study was to evaluate the influence of different surface treatments (air abrasion, acid etching, and laser irradiation) on the surface roughness and bond strength of a low fusing ceramic. Thirty-six discs of low fusing ceramic (Finesse, Ceramco) were prepared (10 mm in diameter and 2 mm in thickness) according to the manufacturer's instructions. Specimens were divided into three groups (n = 12), and the following treatments were performed: Air abrasion with alumina particles (50 µm), acid etching with 5% HF and Nd:YAG laser irradiation (distance: 1 mm, 100 mJ, 20 Hz, 2 W, and 141.54 J/cm(2)). Following determination of surface roughness (R(a)) by profilometry, specimens were examined with scanning electron microscopy (SEM). The luting cement (Clearfil Esthetic Cement) was bonded to the ceramic specimens using Teflon tubes. After 24 h of water storage, shear bond strength test was performed using a universal testing machine at a crosshead speed of 1 mm/min. The data were analyzed with two-way analysis of variance (ANOVA) and Tukey HSD tests (α = .05). Two-way ANOVA indicated that surface roughness was significantly affected by surface treatments (p < .001). Tukey honestly significant difference (HSD) indicated that the air abrasion group had a significantly higher mean value (p < .05) than the other groups. Shear bond strength was significantly affected by surface treatments (p < .001). Tukey HSD indicated that the air abrasion group had a significantly higher mean value (p < .05) than the other groups. No significant difference was found between the acid-etching and laser-irradiation groups (p > .05). The SEM image of the laser irradiation surface appeared to be relatively smooth as compared to the images of other the groups. Air abrasion of low-fusing porcelain surfaces was effective in improving the bond strength as compared to the acid-etching and laser-irradiation methods.

Effect of different finishing techniques for restorative materials on surface roughness and bacterial adhesion.

STATEMENT OF PROBLEM: The formation of biofilm and bacterial accumulation on dental materials may lead to the development of gingival inflammation and secondary caries. PURPOSE: The purpose of this study was to examine the effect of different surface finishing and polishing methods on surface roughness and the adhesion of S. mutans bacteria to 2 new-generation indirect composite resins, 1 direct composite resin, and 1 ceramic material. MATERIAL AND METHODS: Forty specimens (10 x 10 x 2 mm) of each material, indirect composite resins (SR Adoro, Estenia), direct composite resin (Tetric), and a ceramic material (VITABLOCS Mark II), were fabricated. Specimens were divided into 4 groups (n=10) that were treated with 1 of the following 4 surface finishing techniques: diamond rotary cutting instrument, sandpaper discs (Sof-Lex), silicone-carbide rubber points (Shofu), or a felt wheel with diamond paste. Surface roughness was measured with a profilometer. Test specimens were covered with artificial saliva and mucin to produce pellicle. Bacterial suspension (10(9) CFU/ml) was then added to the pellicle-coated specimens, and bacterial adhesion was determined using a confocal laser microscope and image analyzing program. Data were analyzed with 2-way ANOVA, followed by Tukey HSD test, Pearson correlation, and regression analysis (alpha=.05). RESULTS: The highest surface roughness values were recorded in SR Adoro and diamond rotary cutting instrument groups. The lowest vital S. mutans adhesion was seen in the ceramic group and in SR Adoro indirect composite resin (P<.05). CONCLUSIONS: Bacterial adhesion to indirect composite resin materials differed from that to ceramic material after surface treatments. A positive correlation was observed between surface roughness and the vital S. mutans adhesion.

The finite element analysis of the effect of ferrule height on stress distribution at post-and-core-restored all-ceramic anterior crowns.

The purpose of this study was to compare the effect of ferrule with different heights on the stress distribution of dentin and the restoration-tooth complex, using the finite element stress analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with an all-ceramic crown were prepared. Three-dimensional models were varied in their ferrule height (NF: no ferrule, 1F: 1-mm ferrule, and 2F: 2-mm ferrule). A 300-N static occlusal load was applied to the palatal surface of the crown with a 135 degrees angle to the long axis of the tooth. In addition, two post and core materials with different elastic modulus were evaluated. The differences in stress transfer characteristics of the models were analyzed. Maximum stresses were concentrated on force application areas (32.6-32.8 MPa). The stress values observed with the use of a 2-mm ferrule (14.1/16.8 MPa) were lower than the no-ferrule design (14.9/17.1 MPa) for both the glass fiber-reinforced and zirconium oxide ceramic post systems, respectively. The stress values observed with zirconium oxide ceramic were higher than that of glass fiber-reinforced post system. The use of a ferrule in endodontically treated teeth restored with an all-ceramic post-and-core reduces the values of von Mises stresses on tooth-restoration complex. At rigid zirconium oxide ceramic post system, stress levels, both at dentin wall and within the post, were higher than that of fiber posts.