[show abstract][hide abstract] ABSTRACT: This in-vitro study investigated the marginal fit of two all-ceramic copings with 2 finish line designs.
Forty machined stainless steel molar die models with two different margin designs (chamfer and rounded shoulder) were prepared. A total of 40 standardized copings were fabricated and divided into 4 groups (n=10 for each finish line-coping material). Coping materials tested were IPS e.max Press and Zirkonzahn; luting agent was Variolink II. Marginal fit was evaluated after cementation with a stereomicroscope (Leica MZ16). Two-way analysis of variance and Tukey-HSD test were performed to assess the influence of each finish line design and ceramic type on the marginal fit of 2 all-ceramic copings (α =.05).
Two-way analysis of variance revealed no statistically significant differences for marginal fit relative to finish lines (P=.362) and ceramic types (P=.065).
Within the limitations of this study, both types of all-ceramic copings demonstrated that the mean marginal fit was considered acceptable for clinical application (⩽120 μm).
European journal of dentistry. 04/2012; 6(2):163-8.
[show abstract][hide abstract] ABSTRACT: To investigate the effects of different acids and etching times on the bond strength of glass fiber-reinforced composite (FRC) posts to composite core material.
Twenty-six FRC posts (FRC Postec Plus) were randomly divided into 13 groups (each n = 2). One group received no surface treatment (control). The posts in the other groups were acid etched with 35% phosphoric acid and 5% and 9.6% hydrofluoric acid gel for four different etching times (30, 60, 120, and 180 seconds). A cylindric polytetrafluoroethylene mold was placed around the treated posts and filled with dual-cure composite core material (MultiCore Flow). All samples were light cured for 60 seconds. After 24 hours of water storage, the specimens were sectioned perpendicularly to the bonded interface under water cooling to obtain 2-mm post-and-core specimens. Eight specimens were made from each group. Push-out tests were performed at a crosshead speed of 0.5 mm/min using a universal testing machine. Data were analyzed by one-way ANOVA followed by the Tukey honestly significant difference test (alpha = .05).
The lowest bond strength was observed in the control group (12.51 megapascal [MPa]). No statistical significant difference was observed among group H5-120 (20.31 MPa), group H9-120 (20.55 MPa), or group P-180 (20.57 MPa) (P > .05). These groups demonstrated the highest bond strength values (P < .05).
For the FRC posts, all acid-etching procedures tested showed significantly increased bond strength when compared with the control group. Acid-etching with 5% hydrofluoric acid and 9.6% hydrofluoric acid for 2 minutes and with 35% phosphoric acid for 3 minutes (groups H5-120, H9-120, and P-180, respectively) demonstrated the highest bond strength values between the FRC post and composite core material. Although the bond strength was increased by prolonged acid etching, the microstructure of the FRC posts might have been damaged.
[show abstract][hide abstract] ABSTRACT: The objectives of the study were to evaluate the effect of the finishing methods on the surface roughness, and to investigate changes in CIE L*a*b* color coordinates of all-ceramic systems after different finishing methods and accelerated aging. Sixty specimens were prepared, 20 specimens each for Vitadur-N, IPS Empress II, and Cerec Vita Block Mark II. The surface roughness (Ra) following treatment with the different finishing methods was measured using a profilometer. Surface examinations in all groups were made by using a scanning electronic microscope. CIE L*a*b* values of the specimens were determined. After all specimens were subjected to accelerated aging, color measurements were repeated, and the total color differences (ΔE) were calculated. Data were analyzed statistically. Significant differences in surface roughness among all-ceramics were found (P < 0.05). No significant differences were found between the surface roughness of the glazed and polished all-ceramics (P > 0.05). After accelerated aging, all groups had acceptable color changes (ΔE < 2).Research Highlights► Surface modifications are essential for correcting occlusal interferences of ceramic restorations, and improving the esthetic appearance and surface smoothness of porcelain restorations. ► A smooth surface texture is important for the color of the restoration, since a smooth surface will reflect a greater amount of light than a rough surface. ► The purpose of this in vitro study was to investigate the effects of different porcelain finishing techniques on the color change and surface roughness of a full porcelain.
Journal of Non-Crystalline Solids 01/2011; 357(6):1499-1503. · 1.60 Impact Factor
[show abstract][hide abstract] ABSTRACT: The biomechanical behavior of the superstructure plays an important role in the functional longevity of dental implants. However, information about the influence of framework design on stresses transmitted to the implants and supporting tissues is limited. The purpose of this study was to evaluate the effects of framework designs on stress distribution at the supporting bone and supporting implants.
In this study, the three-dimensional (3D) finite element stress analysis method was used. Three types of 3D mathematical models simulating three different framework designs for implant-supported 3-unit posterior fixed partial dentures were prepared with supporting structures. Convex (1), concave (2), and conventional (3) pontic framework designs were simulated. A 300-N static vertical occlusal load was applied on the node at the center of occlusal surface of the pontic to calculate the stress distributions. As a second condition, frameworks were directly loaded to evaluate the effect of the framework design clearly. The Solidworks/Cosmosworks structural analysis programs were used for finite element modeling/analysis.
The analysis of the von Mises stress values revealed that maximum stress concentrations were located at the loading areas for all models. The pontic side marginal edges of restorations and the necks of implants were other stress concentration regions. There was no clear difference among models when the restorations were loaded at occlusal surfaces. When the veneering porcelain was removed, and load was applied directly to the framework, there was a clear increase in stress concentration with a concave design on supporting implants and bone structure.
The present study showed that the use of a concave design in the pontic frameworks of fixed partial dentures increases the von Mises stress levels on implant abutments and supporting bone structure. However, the veneering porcelain element reduces the effect of the framework and compensates for design weaknesses.
European journal of dentistry. 10/2010; 4(4):374-82.
[show abstract][hide abstract] ABSTRACT: The aim of this study was to determine the effect of different surface treatments on the flexural strength of four different ceramic specimens. The four ceramic systems investigated in this study were lithium disilicate reinforced, zirconium oxide reinforced, glass-infiltrated alumina reinforced, and feldspathic ceramic. For the first group, grinding burs, for the second group polishing kit and for the third group glazing procedures were applied for surface treatment. Surface roughness, mean fracture toughness, and a SEM were used to describe surface features. The surface treatments affected the flexural strength and surface roughness of the ceramic systems evaluated.
International Journal of Applied Ceramic Technology 10/2009; 8(2):437 - 445. · 1.15 Impact Factor
[show abstract][hide abstract] ABSTRACT: To test the hypothesis that there is no difference in the number of occlusal contacts in centric occlusion in patients treated with bonded and removable retention procedures and a control group during a 1-year retention period.
Twenty-five patients received a removable Hawley retainer, and 25 patients received maxillary and mandibular bonded retainers. The retainer patients were compared with 20 control subjects with normal occlusions. Silicone-based impression bites were used to record occlusal contacts. Paired-sample t-test, analysis of variance (ANOVA), and Tukey tests were used to evaluate intragroup and intergroup differences.
An increased number of occlusal contacts were recorded in total-arch and posterior combined (actual/near) teeth during the retention period as compared with the control group. In the Hawley group, actual and total contacts on the first and second molar and actual contacts on the premolar and canine showed statistically significant increases. In the bonded retainer group, near and total contacts on the first and second molars and premolars showed statistically significant increases. Slight occlusal changes were seen in the control sample during the observation period, presumably from growth and development. ANOVA comparisons of total contacts of anterior and posterior teeth indicated statistically significant differences in the three groups on posterior segments.
The hypothesis is rejected. Both retention procedures allowed relative vertical movement of the posterior teeth, but the number of contacts on the posterior segment was increased more in the bonded retainer group than in the Hawley and control groups at the end of retention.
The Angle Orthodontist 10/2009; 79(5):867-72. · 1.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to compare the fracture resistance of implant-supported all-ceramic fixed partial dentures, which have three different pontic designs.
Two implants were placed in a metal model simulating mandibular left second premolar and mandibular left second molar. Thirty standardized 3-unit all-ceramic fixed partial dentures with biconvex, convex or concave pontic designs were fabricated using IPS e.max system (n=10). Afterwards, specimens were centrally loaded on the pontics until failure with a universal testing machine. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests at 5% significance level.
The fracture resistance values of all-ceramic fixed partial dentures designed with biconvex, convex or concave pontics were 349.71, 438.20 and 300.78 N, respectively. There were no statistically significant differences between the fracture resistances of the groups (p>0.05), except for convex and concave groups (p<0.05 and p=0.009, respectively).
Convex design showed the best mechanical properties as demonstrated by the high values of fracture resistance.
Journal of applied oral science: revista FOB 01/2009; 17(5):533-8. · 0.39 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this in vitro study was to compare the shear bond strengths of resin, glass-ionomer, and ceramic-based core materials to all ceramic discs. Five core materials (Core max, Sankin; Clearfil AP-X, Kuraray; Empress Cosmo, Ivoclar-Vivadent; Photocore, Kuraray; Dyract Extra, Dentsply) were prepared as discs 10 mm in diameter and 2 mm in height according to the manufacturer's instructions. Ten disc specimens per group were prepared, and dentin served as the control. All resin specimens were embedded in autopolymerizing acrylic resin, with one surface facing up. All ceramic discs (IPS Empress I, Ivoclar-Vivadent) 3 mm in diameter and 2 mm in height were prepared and bonded to core specimens with a dual-curing luting resin cement (Variolink II, Vivadent). Specimens were stored in distilled water at 37 degrees C. Shear bond strength of each sample was measured after 24 h using a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed with one-way analysis of variance and Tukey HSD tests (alpha = 0.05). Shear bond strength varied significantly depending on the core material used (p < 0.05). Clearfil AP-X and Photocore showed the highest shear bond strength value while Empress Cosmo provided the lowest (p < 0.05). There were no statistically significant differences among Clearfil AP-X, Photocore, and Core-Max (p > 0.05). And also there were no statistically significant differences between Dyract Extra and the control group (p > 0.05). In vitro shear bond strengths of ceramic discs bonded to resin-based core materials showed higher bond strength values than ceramic-based core material.
Journal of Biomedical Materials Research Part A 04/2008; 89(2):466-71. · 2.83 Impact Factor
[show abstract][hide abstract] ABSTRACT: To evaluate retentive strength and film thickness of complete metal crowns cemented to overtapered teeth with 3 different cements after the application of airborne-particle abrasion.
Sixty extracted maxillary molar teeth were embedded in autopolymerizing resin. Crowns were prepared with 30-degree overtapered axial walls and a 1-mm shoulder margin using a water-cooled cylindrical airborne-particle abrasion device. Then, 60 complete crowns were made from a nickel-chromium alloy. Teeth and crowns were assigned to 2 groups, 30 to the control group and 30 to the experimental group to undergo airborne-particle abrasion. In the first part of study, 30 teeth from the experimental group were submitted to the silicon-replica technique and their buccolingual cross sections were measured so that cement film thickness could be measured before airborne-particle abrasion. Three measurements using a light microscope were made in 7 regions of each tooth. In the second part of study, complete metal crowns with and without airborne-particle abrasion were distributed into 3 groups with 10 teeth each to be cemented with zinc phosphate, polycarboxylate, or resin-modified glass ionomer. All specimens were subjected to a tensile bond test in an universal testing machine at a crosshead speed of 0.1 mm/min until failure. The results were then evaluated with Student t test at a 5% level of significance.
The film thickness showed no statistically significant differences among groups (P > .05). There was a significant difference between the control and experimental groups, with an increase in all 3 cements after airborne-particle abrasion (P < .05). The highest retentive strength in the control group was found with resin-modified glass ionomer (141.4 +/- 56.7 N), but there was no significant difference between the resin-modified glass ionomer (141.4 +/- 56.7 N) and zinc phosphate (121.4 +/- 24.2 N) (P > .05). Retentive strength of polycarboxylate was the lowest (78.03 +/- 16 N) (P < .05). For the experimental group, the difference among the zinc phosphate (220.5 +/- 83.8 N), polycarboxylate (185.4 +/- 60.8 N), and resin-modified glass ionomer (228.9 +/- 62.4 N) was not statistically significant (P > .05).
Airborne-particle abrasion had a positive effect on the retention of complete metal crowns when the crowns were cemented with zinc phosphate cement, polycarboxylate cement, or resin-modified glass-ionomer cement.
[show abstract][hide abstract] ABSTRACT: The purpose of this article is to report on the long-term clinical evaluation of patients treated with dental implants. A total of 106 implants were placed in 34 patients and restored with fixed partial dentures and overdentures. The 12-year cumulative implant survival and success rates were 95.2% and 90.2%, respectively. Probing depths around mandibular implants were significantly lower than those around maxillary implants (P < .05). The cumulative implant success rate in nonsmokers was 97.7%, but this dropped to 75.81% in smokers. Also, patients rehabilitated with implant-supported overdentures had more peri-implant tissue inflammation than patients with fixed prostheses.
The International journal of periodontics & restorative dentistry 08/2007; 27(4):358-67. · 1.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this follow-up study was to evaluate the number of contacts in centric occlusion during a 1-year retention period in patients treated with 2 retention procedures and in a control sample.
Twenty patients received modified wraparound Hawley retainers, and 20 received maxillary Jensen plates with mandibular fixed retainers. These retention patients were compared with a control group of 20 subjects with normal occlusions. Silicone-based impression bites were used to record occlusal contacts. Paired and independent-sample t tests were used to evaluate intragroup and intergroup differences.
Contacts increased in the total arch and the posterior combined (actual/near) during the retention period compared with the control group. In the Hawley retainer group, actual contacts on the second molars (P <.05), near contacts on the premolars (P <.05), and total contacts on the first molars (P <.05) and premolars (P <.01) had statistically significant increases. In the maxillary Jensen plate and mandibular fixed lingual retainer group, the number of actual contacts on the posterior segment increased. Actual contacts on the first molars (P <.01), second molars (P <.01), premolars (P <.05), and canines (P <.05), and total contacts on the first (P <.05) and second (P <.05) molars had statistically significant increases. During the observation period, some slight occlusal changes were seen in the control sample, presumably from growth and development. At the end of the study, during the 1-year follow-up period, no statistically significant occlusal contact differences were observed in the 3 groups.
Retention procedures carried out in this study allowed relative vertical movement of the posterior teeth.
American journal of orthodontics and dentofacial orthopedics: official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics 03/2007; 131(3):357-62. · 1.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast-B) to alumina-abraded or lased heat-cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning-electron microscopy (SEM) was also determined. Laser-treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina-abraded and untreated (control-group) specimens (p < 0.05). There were no statistically significant differences in surface roughness between alumina-abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > 0.05). Molloplast-B applied to alumina-abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser-treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material.
Journal of Biomedical Materials Research Part B Applied Biomaterials 10/2004; 71(1):196-200. · 2.31 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of this study was to examine the effect of glass fibre reinforcement on the dimensional changes and water sorption of a heat-polymerising denture acrylic polymer and a microwave-polymerising denture acrylic polymer. Fifteen specimens from each group were prepared with 2% by weight (18 mg) E-glass fibre and 15 without glass fibre. The dimensional change measurements were made at three different stages on the 60 specimens. The water sorption calculations were made on specimens immersed in distilled water at 37 degrees C +/- 1 degree C for 0, 1 and 7 days. Glass fibre reinforcement and processing method do not affect the dimensional change of test specimens, but as the time increased the dimensional change decreased. The glass fibre reinforcement decreased water sorption, but the two processing methods failed to show a significant difference.
The European journal of prosthodontics and restorative dentistry 10/2003; 11(3):129-32.
[show abstract][hide abstract] ABSTRACT: Inflammatory changes in periimplant soft tissues and loss of alveolar bone can develop as in periodontal diseases. This clinical phenomena has been described as periimplantitis. Microorganisms such as Gram-negative anaerobic rods, spirochetes, and bacteroides that are seen in subgingival flora in periodontitis have also been found in sulcular microflora in periimplantitis. The purpose of this study was to evaluate periimplant tissue changes in totally edentulous patients who had implant-supported overdentures for 3 to 8 years (5-5.5 years) clinically from both a subjective and an objective point of view. The clinical parameters used in this study can be helpful in the evaluation of periimplant tissue health.
[show abstract][hide abstract] ABSTRACT: In this study, the functional stresses in alveolar bone created by restorative materials used in implant-supported prostheses were determined by the photoelastic stress analysis method. A photoelastic resin mandibular model, hollow-cylinder implants (3.5 mm diameter, 10 mm length), and fixtures and superstructures made of five different prosthetic materials were used. Vertical and 45-degree inclined loads were applied to the model. Subsequently, color photographs of the force line distribution observed on a polariscope were taken. Differences between vertical and inclined loads were statistically significant for all prosthetic materials (P < 0.01). The greatest stress distribution around the apex of the implant was observed with Ceramco II porcelain, followed by Biodent acrylic. The ArtGlass and Elcebond CCV composite materials had equal values, whereas Verebond Ni-Cr alloy showed minimum stress distribution.
[show abstract][hide abstract] ABSTRACT: Anterolateral alveolar osteotomy was performed in a patient who experienced facial trauma in a traffic accident. Bony sequela had remained in the maxilla after the emergency surgery, affecting the facial appearance. A different technique of osteotomy for this unusual type of deformity is presented.
The International journal of adult orthodontics and orthognathic surgery 02/1998; 13(4):327-31.
[show abstract][hide abstract] ABSTRACT: The objective of this experimental study is to determine electrical discharge machining (EDM) parameters that offer the best
adhesion at the interface of a machined titanium–porcelain composite. First of all, with Taguchi method, machining parameters
that will be effective in the bonding strength as well as their interactions on each other were determined in the test. Then,
multiple level experiments were conducted to determine how the effective parameters varied over a wide area. Slopes of the
curves obtained in these tests were studied, and then, final tests were conducted to obtain the best bonding strength possible.
In this way, machining parameters that would offer the highest bonding strength of the titanium–porcelain matrix in a stepwise
adjustable EDM machine were obtained. By taking into consideration the steps on the EDM machine where the tests were conducted,
it is seen that, when a full factorial experiment is undertaken, 5 power × 2 polarity × 2 type of dielectric × 2 sandblasting
or non-sandblasting × 2 kind of electrode × 10 pulse-on time, it necessitates 800 different tests to be executed, but, with
the applied method, 16 + 18 + 3 yields 37 different tests where the results that include all possible alternatives were obtained.
As a result, EDM machining parameters that offer the highest adhesion and are relatively higher, 31.5N/mm2, than the acceptable minimum value of 25N/mm2 were specified.
International Journal of Advanced Manufacturing Technology 45(1):55-61. · 1.21 Impact Factor