Browsing by Author "Oyar, Perihan"

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Citation Count: 0
Comparison of fatigue lifetime of new generation CAD/CAM crown materials on zirconia and titanium abutments in implant-supported crowns: a 3D finite element analysis
(Walter de Gruyter Gmbh, 2024) Deste Goekay, Gonca; Durkan, Rukiye; Oyar, Perihan; Durkan, Rukiye; Protetik Diş Tedavisi / Prosthetic Dental Treatment
Objectives Due to the dynamic character of the stomatognathic system, fatigue life experiments simulating the cyclic loading experienced by implant-supported restorations are critical consideration. The aim of this study was to examine the effect of different crown and abutment materials on fatigue failure of single implant-supported crowns.Methods Models were created for 10 different designs of implant-supported single crowns including two zirconia-reinforced lithium silicates (crystallized and precrystallized), monolithic lithium disilicate, polymer-infiltrated ceramic networks, and polyetheretherketone supported by zirconia and titanium abutments. A cyclic load of 179 N with a frequency of 1 Hz was applied on palatal cusp of a maxillary first premolar at a 30 degrees angle in a buccolingual direction.Results In the models with titanium abutments, the polymer-infiltrated ceramic network model had a lower number of cycles to fatigue failure values in the implant (5.07), abutment (2.30), and screw (1.07) compared to others. In the models with zirconia abutments, the crystallized zirconia-reinforced lithium silicate model had a higher number of cycles to fatigue failure values in the abutment (8.52) compared to others. Depending on the fatigue criteria, polyetheretherketone implant crown could fail in less than five year while the other implant crowns exhibits an infinite life on all models.Conclusions The type of abutment material had an effect on the number of cycles to fatigue failure values for implants, abutments, and screws, but had no effect on crown materials. The zirconia abutment proved longer fatigue lifetime, and should thus be considered for implant-supported single crowns.
Citation Count: 0
Comparison of the effect of different metal alloys on the esthetic appearance of dentin porcelain
(Korean Assoc Crystal Growth, inc, 2022) Gokay, Gonca Deste; Durkan, Rukiye; Oyar, Perihan; Gokcimen, Gulsum; Protetik Diş Tedavisi / Prosthetic Dental Treatment
The purpose of this study was to examine the effect of aurofilm masking agents applied to various metal alloys on the color of porcelain in metal-ceramic restorations (MCRs). The study was conducted with 2 different base-metal alloys (Ni-Cr, Co-Cr) and 2 different noble alloys (Pd-based, Au-Pd) used for MCRs, as well as 1 high noble alloy (Au-based) that served as a control group. Eight experimental groups (n=7) and 1 control group were used in this study. An aurofilm masking agent was applied to 4 groups (AuPdM, PdM, CoCr, NiCrM). Opaque porcelain and dentin body porcelain were applied to all groups. CIEL*a*b* color coordinates were measured. The Pd group had the highest mean a* value (-5.82); however, in comparison to the control group, the differences in a* values were statistically significant only for the Cr-Co alloy groups (CoCr and CoCrM). The Pd group had the highest mean b* value (7.89). The AE value (2.13) of the CoCr group was significantly higher than all other alloy groups. Metal alloy substrate and aurofilm masking agents significantly affected the color of porcelain MCRs. However, color differences between base-metal and noble alloys and the control group were within clinically acceptable limits (Delta E<3.5).
Citation Count: 0
The effect of different abutment and restorative crown materials on stress distribution in single-unit implant-supported restorations: A 3D finite element stress analysis
(Wiley, 2023) Gokcimen, Gulsum; Durkan, Rukiye; Gokay, Gonca; Oyar, Perihan; Protetik Diş Tedavisi / Prosthetic Dental Treatment
PurposeTo evaluate the effect of restorative materials with or without resin content, modeled on zirconia and titanium abutment materials, on the stress distribution on the alveolar bone, implant, and prosthetic crowns with a 3D finite element stress analysis. Material and MethodsTitanium and zirconia abutments were combined with three implant-supported crown materials (polymer infiltrated hybrid ceramic (PICN), lithium disilicate (LD), and zirconia-reinforced lithium silicate (ZLS)) to create six experimental groups. The 40 x 30 x 20 mm alveolar bone, 3.75 x 10 mm implant, esthetic abutment, and maxillary first premolar crown bonded over the abutment were the components of the finite element models. On the lingual cusp of the crown, the 150 N occlusal loading was applied in the buccolingual direction at a 30 & DEG; angle. Equivalent von Mises stress and maximum and minimum principal stresses were used for both the qualitative and quantitative evaluation of the stress distribution of the created models. ResultsThe von Mises stress in implant and abutment did not differ according to the crown materials. The use of a zirconia abutment resulted in higher von Mises stress values in the abutment but lower stress values in the implant. The highest stress values were obtained in ZLS (196.65 MPa) and LD (194.05 MPa) crowns. The use of titanium abutments, regardless of crown materials, resulted in higher von Mises stress values in restorative crowns than in zirconia abutments. The principal stress values in alveolar bone showed similar distribution and concentration in all models. ConclusionsChanges in crown material did not affect stress distribution in the implant and peripheral bone. However, the zirconia esthetic abutment resulted in a lower stress concentration on the implant.
Citation Count: 0
The effects of heating rate and sintering time on the biaxial flexural strength of monolithic zirconia ceramics
(Walter de Gruyter Gmbh, 2023) Oyar, Perihan; Durkan, Rukiye; Protetik Diş Tedavisi / Prosthetic Dental Treatment
The strength of zirconia ceramic materials used in restorations is dependent upon sintering. Varying sintering protocols may affect the biaxial flexural strength of zirconia materials. This in vitro study was conducted to investigate the effects of sintering parameters on the biaxial flexural strength of monolithic zirconia. Two different monoblock zirconia ceramics were used. Following coloration, samples of both types of ceramics were divided into groups according to whether or not biaxial flexural strength testing was performed directly after sintering or following thermocycling. Biaxial flexural strength data was analysed with a Shapiro Wilk normality test, followed by 1-way ANOVA, Tukey post hoc tests for inter-group comparisons, and paired samples t-tests for intra-group comparisons. A significant difference was found between the biaxial flexural strengths of Zircon X and Upcera ceramics before thermocycling (p < 0.05). In both Zircon X and Upcera ceramic groups, the thermocycling process created a significant difference in the biaxial flexural strength values of the ceramic samples in Group 6 (p < 0.05) which had the slowest heating rate and longest holding time. The zirconia ceramics have higher BFS at higher heating rates either before or after thermocycling. The holding time has significant effects on thermocycling and flexural strength. The zirconia achieved its optimum strength when it sintered at longer time regardless of heating rates.
Citation Count: 4
Effects of repeated use of tungsten carbide burs on the surface roughness and contact angles of a CAD-CAM PMMA denture base resin
(Mosby-elsevier, 2022) Oyar, Perihan; Durkan, Rukiye; Durkan, Rukiye; Protetik Diş Tedavisi / Prosthetic Dental Treatment
Statement of problem. The surface roughness (Ra) and wettability of complete denture base materials must meet certain clinical requirements. Although computer-aided design and computer-aided manufacturing (CAD-CAM) systems have recently become popular for the fabrication of complete dentures, the effects of the repeated usage of milling burs on the surface properties of CAD-CAM denture base acrylic resins have not yet been fully investigated. Purpose. The purpose of this in vitro study was to evaluate the effects of new and used burs on the Ra and contact angles (wettability) of a CAD-CAM polymethylmethacrylate (PMMA) denture base material. Material and methods. A total of 40 O2x10-mm disks were fabricated from 1 brand of CAD-CAM PMMA resin (Polident). Half of the specimens (group N) were milled with a new tungsten carbide bur set, while the other half (group U) was milled with a used tungsten carbide bur set. Moreover, half of the specimens (groups NT and UT) were subjected to thermocycling before Ra and contact angle testing. Ra was tested by using a profilometer, and the surfaces were also examined by scanning electron microscopy (SEM). The contact angle was measured by using the sessile drop method. Data were analyzed with the Kruskal-Wallis and Dunn Pairwise Comparison tests (alpha=.05). Results. The mean contact angle was highest for group U (80 degrees) and lowest for group UT (66 degrees) (P<.05). Ra values were highest for group N (1.3 mu m) and lowest for group U (0.93 mu m) (P<.05). Conclusions. Specimens milled with new tungsten carbide burs had lower mean contact angles and higher Ra values than specimens milled with used burs. The contact angles of CAD-CAM PMMA resin specimens milled with used burs decreased significantly after thermocycling. Regardless of whether or not thermocycling was performed, contact angle values decreased as Ra values increased.
Citation Count: 0
Geleneksel PMMA, Modifiye MMA ve Poliamid Protez Kaide Materyallerinin Farklı İçeceklere Karşı Renk Stabilitesi
(Galenos Publ House, 2023) Durkan, Rukiye; Gökay, Gonca Deste; Oyar, Perihan; Durkan, Rukiye; Gürbüz, Ayhan; Protetik Diş Tedavisi / Prosthetic Dental Treatment
Amaç: Bu çalışmanın amacı, yaygın olarak tüketilen içeceklerin farklı zaman aralıklarında protez kaide materyallerinin renk stabilitesi üzerindeki etkisini değerlendirmektir. Gereç ve Yöntemler: Konvansiyonel polimetilmetakrilat (PMMA) (Meliodent), modifiye metilmetakrilat (MMA) (Bre-Crystal ve Acryfee) ve poliamid (Bre-Flex, Flexinylon ve T Crystal) akrilik rezinlerden oluşan 20 disk şeklinde (10 mm çap, 2 mm kalınlık) örnek pürüzsüz ve pürüzlü yüzeylerde hazırlandı. Tüm örneklerin başlangıç rengi kolorimetre ile ölçüldü (T0). Her örnek kahve, kola, çay ve distile suya daldırıldı. Örneklerin rengi 1 günlük (T1), 12 günlük (T2) ve 36 günlük (T3) daldırma sürelerinden sonra tekrar ölçüldü. Her örnek için ortalama renk değişikliklerini (∆E) hesaplamak için CIE L*a*b* sistemi kullanıldı. Elde edilen veriler 0,95 güven aralığında ANOVA ve Bonferroni testleri kullanılarak istatistiksel olarak karşılaştırıldı.Bulgular: Pürüzsüz ve pürüzlü yüzeyler arasında renk değişimi açısından zaman veya içecekten bağımsız olarak anlamlı fark yoktu (p>0,05). Tüm zaman aralıklarında, modifiye MMA (Bre-cystal) daha yüksek renk stabilitesi gösterdi (p<0,05). Zamandan bağımsız olarak, kolaya daldırılan modifiye MMA (Acryfree) ve konvansiyonel PMMA (Meliodent) örnekleri, istatistiksel olarak anlamlı derecede daha düşük renk stabilitesi sergiledi (p<0,05). Sonuç: Çalışmada kullanılan içecekler, T1 ve T3 periyodlarından sonra distile suya göre istatistiksel olarak anlamlı bir renk değişimine neden olmadı. NBS sistemine göre T3 periyodundan sonra renk değişimleri “hafif” ile “çok” arasındaydı. Modifiye MMA rezin (Brecrystal), uzun süreli kullanımda yüksek renk stabilitesi nedeniyle PMMA alerjisi olan hastalarda protez kaide materyali olarak öne çıkabilir.
Citation Count: 0
Impact of various aging treatments on the microhardness and surface roughness of CAD-CAM monolithic restorative materials
(Wiley, 2024) Goekay, Gonca Deste; Durkan, Rukiye; Durkan, Rukiye; Protetik Diş Tedavisi / Prosthetic Dental Treatment
PurposeDental ceramics deteriorate as a result of thermal aging and exposure to acidic solutions, which change their microhardness and surface roughness. This study assessed the resistance of several computer-aided design and computer-aided manufacturing (CAD-CAM) restorative dental materials in terms of surface roughness and microhardness following exposure to acidic solutions and thermal aging.Materials and MethodsFive different monolithic CAD-CAM restorative materials, two leucite-reinforced glass ceramics (G-Ceram and CEREC Blocs), a zirconia-infiltrated lithium silicate (Celtra Duo), a resin nanoceramic (Grandio), and monolithic zirconia (inCoris TZI), were used to create 2-mm-thick rectangular specimens (n = 100). After being immersed in either acidic saliva (pH = 4.0) (ST) or gastric juice (pH = 1.2) (GT), each material was subjected to 10,000 cycles of thermal aging. The Vickers microhardness and average surface roughness of the specimens were assessed at baseline, following thermal aging and exposure to either gastric juice or acidic saliva. The surface properties were examined using an atomic force microscope. The Mann-Whitney U test with Bonferroni correction and the Wilcoxon signed-rank test was used for statistical analysis (a = 0.05).ResultsThe surface roughness of two leucite-reinforced glass ceramics (G-ceram and CEREC) significantly decreased with ST (p = 0.027 and p = 0.044). Only the CEREC was affected when the aging protocols were compared, and the ST group had a significant reduction in roughness (p = 0.009). The microhardness values significantly decreased after both aging protocols in all groups except for the ST subgroup of G-Ceram. Only inCoris was affected when the aging protocols were compared, and the GT group exhibited a significant reduction in microhardness (p = 0.002).ConclusionThe surface roughness of the tested materials was not affected by the GT. Only leucite ceramics exhibited a decrease in surface roughness in the ST stage. Both aging processes produced a significant decrease in the microhardness of the tested ceramics. Leucite-reinforced glass-ceramic materials may be advantageous for patients with gastroesophageal reflux disease and those with a diet high in acidic foods due to their lower values for changes in microhardness and surface roughness compared to those of other CAD-CAM materials.
Citation Count: 0
Mechanical response of different frameworks for maxillary all-on-four implant-supported fixed dental prosthesis: 3D finite element analysis
(Walter de Gruyter Gmbh, 2022) Guclu, Zekiye Begum; Durkan, Rukiye; Gokay, Gonca Deste; Durkan, Rukiye; Oyar, Perihan; Protetik Diş Tedavisi / Prosthetic Dental Treatment
This study's purpose is to assess the stress distribution in the peri-implant bone, implants, and prosthetic framework using two different posterior implant angles. All-on-four maxillary prostheses fabricated from feldspathic-ceramic-veneered zirconia-reinforced lithium silicate (ZLS) and feldspathic-ceramic-veneered cobalt-chromium (CoCr) were designed with 17 or 30-degree-angled posterior implants. Posterior cantilever and frontal vertical loads were applied to all models. The distribution of maximum and minimum principal stresses (sigma max and sigma min) and von Mises stress (sigma VM) was evaluated. Under posterior cantilever load, with an increase in posterior implant angle, sigma max decreased by 4 and 7 MPa in the cortical bone when ZLS and CoCr were used as a prosthetic framework, respectively. Regardless of the framework material, 17-degree-angled posterior implants showed the highest sigma VM (541.36 MPa under posterior cantilever load; 110.79 MPa under frontal vertical load) values. Regardless of the posterior implant angle, ZLS framework showed the highest sigma VM (91.59 MPa under posterior cantilever load; 218.99 MPa under frontal vertical load) values. Increasing implant angle from 17 to 30 degrees caused a decrease in sigma max values in the cortical bone. Designs with 30-degree posterior implant angles and ZLS framework material may be preferred in All-on-four implant-supported fixed complete dentures.
Citation Count: 0
Static and dynamic stress analysis of different crown materials on a titanium base abutment in an implant-supported single crown: a 3D finite element analysis
(Bmc, 2024) Gokay, Gonca Deste; Durkan, Rukiye; Gokcimen, Gulsum; Durkan, Rukiye; Protetik Diş Tedavisi / Prosthetic Dental Treatment
Background This Finite Element Analysis was conducted to analyze the biomechanical behaviors of titanium base abutments and several crown materials with respect to fatigue lifetime and stress distribution in implants and prosthetic components.Methods Five distinct designs of implant-supported single crowns were modeled, including a polyetheretherketone (PEEK), polymer-infiltrated ceramic network, monolithic lithium disilicate, and precrystallized and crystallized zirconia-reinforced lithium silicates supported by a titanium base abutment. For the static load, a 100 N oblique load was applied to the buccal incline of the palatal cusp of the maxillary right first premolar. The dynamic load was applied in the same way as in static loading with a frequency of 1 Hz. The principal stresses in the peripheral bone as well as the von Mises stresses and fatigue strength of the implants, abutments, prosthetic screws, and crowns were assessed.Results All of the models had comparable von Mises stress values from the implants and abutments, as well as comparable maximum and minimum principal stress values from the cortical and trabecular bones. The PEEK crown showed the lowest stress (46.89 MPa) in the cervical region. The prosthetic screws and implants exhibited the highest von Mises stress among the models. The lithium disilicate crown model had approximately 9.5 times more cycles to fatique values for implants and 1.7 times more cycles to fatique values for abutments than for the lowest ones.Conclusions With the promise of at least ten years of clinical success and favorable stress distributions in implants and prosthetic components, clinicians can suggest using an implant-supported lithium disilicate crown with a titanium base abutment.