Merve Bankoğlu Güngör

Effect of surface treatments on the biaxial flexural strength, phase transformation, and surface roughness of bilayered porcelain/zirconia dental ceramics

STATEMENT OF PROBLEM Veneered zirconia restorations are widely used in prosthetic applications. However, these restorations often fail because of chipping of the veneer porcelain. Surface treatments of zirconia core materials may affect the connection between the 2 layers. PURPOSE The purpose of this study was to evaluate the effect of surface treatments on the biaxial flexural strength, phase transformation, and mean surface roughness of different bilayered porcelain/zirconia ceramics. MATERIAL AND METHODS Forty disk-shaped specimens were obtained for each material (Kavo and Noritake) and divided into 4 (n=10) groups (control, airborne-particle abraded, ground, and ground and airborne-particle abraded). Airborne-particle abrasion was performed with 110-μm Al2O3 particles for 15 seconds and at 400 kPa. Diamond rotary instruments with 100-μm grain size were used for grinding. The monoclinic phase transformation and surface roughness of the specimens were measured. Then, the specimens were veneered and subjected to a biaxial flexural strength test to calculate the Weibull moduli (m values) and the stresses occurring at the layers, outer surfaces of the bilayer, and interfaces of the layers. RESULTS The Kavo airborne-particle abraded group showed higher strength values in both layers (P<.05) than those of all experimental groups. The Kavo airborne-particle abraded group showed the lowest m values at the core and veneer layers. According to the phase analysis, significantly higher Xm values were found in the ground and airborne-particle abraded groups for both materials (P<.05). In both materials, except in the airborne-particle abraded groups, the relative monoclinic phases showed no difference (P<.05). CONCLUSION Surface treatments affected the phase transformation, surface roughness, and biaxial flexural strength of Kavo and Noritake zirconia ceramics differently. Surface treatments increased the relative monoclinic phase content and average surface roughness.

Effect of surface treatments on shear bond strength of resin composite bonded to CAD/CAM resin-ceramic hybrid materials.

PURPOSE The purpose of this study was to assess the effect of surface treatments on shear bond strength of resin composite bonded to thermocycled and non-thermocycled CAD/CAM resin-ceramic hybrid materials. MATERIALS AND METHODS 120 specimens (10×10×2 mm) from each material were divided into 12 groups according to different surface treatments in combination with thermal aging procedures. Surface treatment methods were airborne-particle abrasion (abraded with 50 micron alumina particles), dry grinding (grinded with 125 µm grain size bur), and hydrofluoric acid (9%) and silane application. According to the thermocycling procedure, the groups were assigned as non-thermocycled, thermocycled after packing composites, and thermocycled before packing composites. The average surface roughness of the non-thermocycled specimens were measured after surface treatments. After packing composites and thermocycling procedures, shear bond strength (SBS) of the specimens were tested. The results of surface roughness were statistically analyzed by 2-way Analysis of Variance (ANOVA), and SBS results were statistically analyzed by 3-way ANOVA. RESULTS Surface roughness of GC were significantly lower than that of LU and VE (P<.05). The highest surface roughness was observed for dry grinding group, followed by airborne particle abraded group (P<.05). Comparing the materials within the same surface treatment method revealed that untreated surfaces generally showed lower SBS values. The values of untreated LU specimens showed significantly different SBS values compared to those of other surface treatment groups (P<.05). CONCLUSION SBS was affected by surface treatments. Thermocycling did not have any effect on the SBS of the materials except acid and silane applied GC specimens, which were subjected to thermocycling before packing of the composite resin.

An Overview of Zirconia Dental Implants: Basic Properties and Clinical Application of Three Cases

Due to the possible aesthetic problems of titanium implants, the developments in ceramic implant materials are increasing. Natural tooth colored ceramic implants may be an alternative to overcome aesthetic problems. The purpose of this article is to give information about the basic properties of dental zirconia implants and present 3 cases treated with two-piece zirconia implants. Two-piece zirconia dental implants, 4.0 mm diameter and 11.5 mm in length, were inserted into maxillary incisor region. They were left for 6 months to osseointegrate. Panoramic and periapical radiographs were obtained and examined for bone-implant osseointegration. During the follow-up period the patients were satisfied with their prosthesis and no complication was observed.

Evaluation of stress distributions occurring on zirconia and titanium implant-supported prostheses: A three-dimensional finite element analysis.

STATEMENT OF PROBLEM Titanium implants have been successfully used to support fixed dental prostheses. Zirconia implants have been suggested as support for crowns, but information on their use to support partial fixed dental prostheses is limited. PURPOSE The purpose of this finite element study was to evaluate the maximum principal, minimum principal, and von Mises stresses and their distributions on zirconia and titanium implant-supported, partial fixed dental prostheses located in the anterior maxillary region. MATERIAL AND METHODS Zirconia and titanium implants (4 mm in diameter and 11. 5 mm in length) and prostheses made from 2 different materials (lithium disilicate and zirconia) were simulated, and 4 models were generated: Titan-IPS, Titan-Lava, Zircon-IPS, and Zircon-Lava. The maxillary bone was modeled as type 3 bone. The load was applied obliquely (534 N) and horizontally (76.5 N), and the stress values and distributions were examined. RESULTS Under horizontal loading, stresses generated on the cortical bone in the Zircon models were lower than those in the Titan models. Under oblique loading, stress values were similar in the same implant material and stress type. For all types of stress among the models, the stress values that occurred on the trabecular bone were found to be similar under both horizontal and oblique loading. The maximum stress values on the bones, implants, cores, and veneers did not exceed the strength of the structures. CONCLUSIONS Different stress values resulted from the different implant types. The prosthetic materials did not change the stress distributions in bone.

Biaxial flexural strength and phase transformation of Ce-TZP/Al2O3 and Y-TZP core materials after thermocycling and mechanical loading.

PURPOSE The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. MATERIALS AND METHODS Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.

Comparison of Maximum Intercuspal Contacts of Articulated Casts and Virtual Casts Requiring Posterior Fixed Partial Dentures

PURPOSE To evaluate the accuracy of the CEREC CAD/CAM system in reproducing the maximum intercuspal contacts of the casts, which include posterior teeth preparation for a fixed partial denture (FPD). MATERIALS AND METHODS Ten pairs of gypsum casts were mounted in articulators in maximum intercuspal position (MIP) to serve as patient simulation models. Tooth #19 was removed from the cast. Occlusal contacts in MIP were identified with articulating paper, and digital impressions of the casts with unprepared teeth and buccal images in MIP were taken. Teeth #18 and #20 were prepared for an FPD, and full- and half-arch digital impressions of the casts with prepared teeth and buccal images from different sides were taken. In each situation, screenshot images of the virtual casts with occlusal contacts were saved as JPEG files. The proportions of congruence of virtual contacts with cast contacts were analyzed by superimposing screenshot images of the virtual casts onto the screenshot images of the casts with the indicated occlusal contacts in a transparent manner using an image-processing program. The data were statistically analyzed with a paired t-test. RESULTS The highest percentages of virtually indicated contacts identical to the cast contacts were observed in non-prepared full-arch digital impressions. Comparison of full-arch impressions taken before and after tooth preparation showed no difference for congruence even if the buccal image was taken from the contralateral or ipsilateral side (p > 0.05). After tooth preparation, comparing full- and half-arch digital impressions revealed that half-arch impression showed significantly lower percentages of identical contacts (p < 0.05). When comparing the buccal image side, no significant difference was detected between ipsilateral and contralateral images both for non-prepared and prepared casts (p > 0.05). CONCLUSION When there is no posterior antagonist contact following tooth preparation for an FPD, taking a full-arch digital impression and designing the restoration on full-arch virtual models can be advocated.

Fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after aging in a mastication simulator

Statement of problem. The demand for ceramic restorations has increased over the past years, and now various machinable materials can be used for chairside computer‐aided design and computer aided manufacturing (CAD‐CAM) systems. Limited studies of these new materials make it difficult to evaluate their mechanical performance, advantages, and limitations. Purpose. The purpose of this in vitro study was to investigate the fracture resistance of CAD‐CAM monolithic ceramic and veneered zirconia molar crowns after thermomechanical aging. Material and methods. A mandibular first molar tooth was prepared, and 12 different experimental groups were generated (n=10). An aging procedure was performed by subjecting the specimens to 12×105 mechanical cycles and 5000 thermocycles. Survival analysis was performed according to the thermomechanical aging. The fracture resistance (load at fracture) of all specimens was evaluated with 1‐way analysis of variance after the means had been compared using the Tukey honest significant difference test and Weibull distributions of the experimental groups (&agr;=.05). Results. According to the results, the differences between the fracture resistance of the groups were found to be significant. Restorations in the dual network ceramic crown group fractured catastrophically during thermomechanical aging. In all groups, the highest value was found for monolithic zirconia, followed by monolithic lithium disilicate crowns (P<.05). Both of the monolithic crowns made of lithium disilicate derivates and zirconia crowns veneered with lithium disilicate ceramic showed no differences from each other (P>.05). The Weibull modulus (m) ranged from 4.22 to 8.58, and conventionally veneered and overpressed zirconia showed the lowest Weibull modulus values among the tested groups, indicating greater variation of the data. Conclusions. The highest fracture resistance was observed for yttria‐stabilized zirconia crowns, followed by lithium disilicate derivates. Veneered zirconia restorations generally showed lower resistance than these ceramics. The dual network ceramic crowns fractured during thermomechanical aging.

Clinical and radiographic evaluation of new dental implant system: Results of a 3-year prospective study

Background/purpose The aim of this study was to evaluate implant survival, crestal bone level changes, and clinical parameters of IDcam dental implants over a mean follow-up period of 3 years. Materials and methods Seventy-two patients, 32 females and 40 males, received 255 implants. Implant-supported metal–ceramic fixed restorations were inserted. Following completion of restorations, each patient was re-examined at 6-month intervals. Radiographic crestal bone level changes were calculated, as well as soft tissue parameters including pocket probing depth, bleeding on probing, plaque index, and gingival index. Examination results were recorded from 18 months to 42 months. Implant survival was estimated using the Kaplan–Meier method. Associations between implant survival and recorded variables were estimated using Cox proportional regression analysis. Results The Kaplan–Meier survival analysis demonstrated a cumulative survival rate of 97.6%. Three implants in three patients failed to osseointegrate at stage 2 surgery, and three implants in three patients were lost after loading. The mean marginal bone losses were 0.35 ± 0.14 mm, 0.47 ± 0.15 mm, and 0.58 ± 0.16 mm, as determined 6 months, 12 months, and 24 months after prosthetic loading, respectively. Cox proportional regression analysis revealed that the variables such as age, sex, type of the restoration, and implant region had no significant influence on implant failure (P > 0.05). Coefficients of correlation between implant survival and crestal bone loss, pocket probing depth, bleeding on probing, plaque index, and gingival index were found to be nonsignificant (P > 0.05). Conclusion Survival and radiographic and clinical assessments of implants after 2 years of function demonstrated promising results for an IDcam dental implant system.

Göz protezi yapımında çalışma modelinin modifiye edilmesi: Olgu sunumu

Yuz bolgesinde cesitli etkenlerle meydana gelen doku kayiplari hastalarda fizyolojik, estetik ve psikolojik problemleri beraberinde getirmektedir. Yuz protezleri bozulan yuz butunlugunu gercege en yakin sekilde restore etmeyi ve hastalarin toplum icine cikabilmesini saglayan bir tedavi yontemidir. Yuz protezlerinin yapimi hem klinik hem de laboratuvar asamalari uzun zaman alan, zahmetli ve hassas bir islemdir. Yuz protezlerinin yapiminda onemli bir asama calisma modeli elde edilmesidir. Calisma modeli uzerinde protezlerin mum ornegi hazirlanir ve mum ornek uzerinde yapilan modelaj calismalari tamamlandiktan sonra calisma modeli silikonun polimerize edilecegi alci kalibin bir parcasini olusturur. Mum ornegin calisma modeline iyi bir adaptasyonunun saglanmasi ve provalar esnasinda bu adaptasyonunun bozulmamasi yapilacak silikon protezin cevre dokularla uyumlu olmasi acisindan onem tasimaktadir. Bu vaka raporunda goz protez yapimi esnasinda calisma modelinin modifiye edilmesi ile kenar kisimlarinda meydana gelebilecek deformasyonun onlenmesi anlatilmaktadir.

ÖN BÖLGE İMPLANTLARININ HASTA BAŞI CAD-CAM KİŞİSEL SERAMİK ABUTMENTLARLA REHABİLİTASYONU: 2 OLGU SUNUMU

Kisisel abutmentlar, anterior bolgeye uygulanan implant destekli protezlerde karsilasilacak bir cok problem cozmeye yardimci olur. Kisisel abutmentlarin uretiminde kullanilan tekniklerden biri de; zirkonya ve lityum disilikat abutmentlarin uretimine olanak saglayan CAD-CAM teknolojisinin kullanilmasidir. Bu vaka raporunda; anterior bolgede yetersiz mezio-distal genisligi bulunan 2 vakanin CAD-CAM teknolojisi ile tasarlanan kisisel seramik abutmentlar ile tedavisi anlatilmaktadir. Her iki vakada da sol maksiller santral dis bolgesine yerlestirilen implant, CAD-CAM sisteminde tasarlanan ve uretilen kisisel abutmentlar ile restore edilmistir. Abutmentlar, Vaka 1 icin zirkonyadan ve Vaka 2 icin lityum disilikattan uretilmistir. Daha sonra abutmentlarin uzerine lityum disilikat kronlar yapilmistir. 12 aylik takibin sonunda; her iki hasta da protezlerinden memnun olduklarini belitmislerdir. 5 ay sonunda Vaka 2’de abutment vida gevsemesi goruldu fakat 12ay suresince baska bir komplikasyon gorulmedi.