Bilge Turhan Bal

Clinical study on the insertion torque and wireless resonance frequency analysis in the assessment of torque capacity and stability of self-tapping dental implants

Resonance frequency (RF) analysis is a non-invasive, objective and sensitive technique developed for implantology where it measures the stability of the implant in osteotomy site. Although many studies were performed by the previous electronic version of RF analyzer, a very limited number of studies were carried out with the new magnetic wireless version. The aim of the study was to evaluate the relation between insertion torques, primary and secondary stability of self-tapping tapered implant systems. Thirteen subjects were treated with 42 endosseous implants using two-stage surgical procedure. The maximal insertion torque values were recorded prior to RF analysis during surgery. Six months after surgery, the secondary stability values were measured by the RF analysis. The average maximal insertion torque and primary and secondary magnetic RF values were 33 +/- 11 N cm and 66 +/- 12 ISQ and 71.9 +/- 6 ISQ for 42 implants respectively. The correlation between insertion torque and RF values were indicated to be statistically significant (P < 0.01). Significantly higher maximal insertion torque, and primary and secondary magnetic RF values were achieved in mandibular sites compared with maxillary areas (P < 0.01). No significant differences were measured for all parameters when both systems were compared with each other (P > 0.05). There was a strong correlation between the insertion torque, primary and secondary magnetic RF values of self-tapping tapered endosseous implant used. Further studies are needed to understand the impact of the wireless magnetic RF analysis technique in clinics.

Effect of fatigue on biaxial flexural strength of bilayered porcelain/zirconia (Y-TZP) dental ceramics

OBJECTIVES The aim of this study was to evaluate the effect of fatigue on biaxial flexural strength of bilayered disks of two Y-TZP cores. METHODS Twenty bilayered veneer/zirconia disks were fabricated from each material (Lava veneer+core, 3M/ESPE, and Cercon veneer+core, Densply). Ten specimens from each material were tested for biaxial flexural strength either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load) in a universal testing machine (1mm/min). Stresses generated at the core and the veneer, at the top and the bottom surfaces, and the interface of bilayered disk were calculated using Hueshs solutions. Data were statistically analyzed using Weibull statistics. The fractured core was also examined via Raman spectroscopy and the monoclinic fraction was calculated at the top, the middle of thickness, and the bottom of the cross-section of fractured core. The results of monoclinic fraction were statistically analyzed by Three-Factor ANOVA with Repeated Measures on One Factor. RESULTS Weibull modulus (m) of Cercon control (CC), Cercon fatigue (CF), Lava control (LC) and Lava fatigue (LF) were between 11.8 and 14.3, 7.1 and 13.1, 9.4 and 13, and 7.1 and 8.2, respectively. There were no significant differences between characteristic strength (σ(0)) of CC (970.9 MPa) and CF (947.7 MPa) (p>0.05). For Lava, σ(0) of LF (1444.8 MPa) was significantly higher than LC (1240.5 MPa) (p<0.05). At the interfaces, σ(0) values of CC and CF groups were not significantly different while LF showed significantly higher σ(0) than LC. The monoclinic zirconia was significantly lower for CF than CC and significantly higher for LF than LC. SIGNIFICANCE Fatigue showed different effects on the strength of Cercon and Lava ceramic systems. Decreases in m values were observed at the interfaces of two materials after fatigue.

Effect of fatigue on fracture toughness and phase transformation of Y‐TZP ceramics by X‐ray diffraction and Raman spectroscopy

The aim of this study was to evaluate the effect of fatigue on fracture toughness and phase transformation of yttria-stabilized zirconia polycrystal materials (Cercon and Lava). The specimens were tested for indentation fracture toughness either with or without being subjected to fatigue (20,000 cycles, 2 Hz, 200 N load). X-ray diffraction (XRD) analysis was used to examine the phase composition of specimens. The indentation images were analyzed using Raman spectroscopy at indentation center (p1), indentation corner (p2), points on crack 100 μm (p3), and 200 μm (p4) away from the corner and a point ∼80 μm away from the crack (p5). Fracture toughness results were statistically analyzed by two-way analysis of variance (ANOVA); XRD and Raman spectroscopy results were analyzed by three-way ANOVA. Fracture toughness of Cercon control (CC) and fatigue (CF) groups were 6.8 and 6.9 MPa√m, respectively, with no significant difference (p > 0.01). Fracture toughness of Lava fatigue (LF; 7.3 MPa√m) was significantly higher than Lava control (LC; p < 0.01). XRD analyses showed CC and LC consisted of tetragonal zirconia, monoclinic zirconia detected after fatigue. After indentation, relative amount of monoclinic phase significantly increased in CC, CF, and LC; decreased in LF. The Raman spectroscopy results indicated that monoclinic fraction was the highest at p2, subsequently at p1 and decreased at p3, p4, and p5 for all groups. Mechanical cycling increased fracture toughness of Cercon and Lava, the second being significant. Phase transformation was also detected after fatigue, which is higher in Lava. Analysis of indentations showed that transformation was highest was at the corner, second at center.

Finite element analysis of stress distribution with splinted and nonsplinted maxillary anterior fixed prostheses supported by zirconia or titanium implants.

PURPOSE The aim of the present study was to evaluate the effect of splinting titanium (Ti) or zirconia (Zr) implants supporting maxillary anterior fixed prostheses on the stress levels and patterns in the implants, prostheses, and the surrounding bone; and to compare the effects of Zr and Ti implant materials on the stress distribution in splinted and nonsplinted designs via finite element modeling. MATERIALS AND METHODS Zr and Ti dental implants and the anterior maxilla were modeled. In the nonsplinted design (D1), implants were placed into the maxillary left central incisor and canine regions, and a three-unit zirconia fixed prosthesis was modeled. In the splinted design (D2), a symmetric model of D1 was generated and the two prostheses were splinted together to create a six-unit prosthesis. Loading was applied horizontally and obliquely. Von Mises, tensile, and compressive stresses were evaluated in the implants, prostheses, and surrounding bone. RESULTS Under both loading conditions, the stresses on the D2 implants were lower than those in the D1 implants. Stresses were concentrated on the neck of the implant and decreased through the apex. All of the stress values in cortical bone in D1 were slightly higher than in D2 for both implant materials under both loading conditions. CONCLUSION When the implants were splinted together, stresses were reduced in the supporting bone and implants in both loading conditions, but increased stress was observed in the prostheses under oblique loading. Intense stress concentrations were found in the connector of the splinted prosthesis and the cervical region of the nonsplinted prosthesis. Zr and Ti implants showed very similar stress distributions in all materials. Under oblique loading, lower stresses occurred in implants and the prosthesis core material when Ti implants were used.

Which device is more accurate to determine the stability/mobility of dental implants? A human cadaver study

Non-invasive devices including resonance frequency (RF) analysis and mobility measuring (MM) damping capacity assessment are used to measure implant stability/mobility. The aims of the study were to compare the primary stability of implant inserted into extraction sockets by using RF with cable, RF wireless and new wireless MM device, to clarify the relation between these devices and to understand the correlations between peri-implant bone levels and implant stability. A total of 30 screw-type implants (3.75 x 11 and 4.2 x 11 mm) were inserted into extraction sockets of eight mandibular pre-molar regions of human cadavers. The primary stability of implants was measured by three devices after insertion. Peri-implant vertical defects were created in millimetre increments ranging between 0 and 5 mm, and stability/mobility of implants were analysed. At placement, the mean implant stability quotient of RF with cable, RF wireless and MM device values was 46 +/- 1, 57.8 +/- 9 and -5.4 +/- 1, respectively. Statistical correlations were demonstrated between these devices (P = 0.001). Statistically significant differences were presented for all peri-implant detects ranging between 0 and 5 mm for RF with cable and RF wireless at all increments. However, only a significant decrease was found between 0 and 1 mm defects, and 4 and 5 mm defects in MM device. Although RF with cable and RF wireless seem to be suitable to detect peri-implant bone loss around implants in 1 mm increments, the new MM device may not be suitable to detect the 1 mm peri-implant bone changes in human dried cadaver mandibles.

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.

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.

Initial Stability of Two Dental Implant Systems: Influence of Buccolingual Width and Probe Orientation on Resonance Frequency Measurements

BACKGROUND Although many factors seem to have an impact on the resonance frequency (RF) values of implants, there is a lack of evidence about some other parameters, which may have an influence on implant stability. PURPOSE The aims of the study were to determine whether initial stability of a dental implant differs when the buccolingual width of the bone changes, to determine whether different orientations affect the RF measurements in the RF device, and to investigate two dental implants with different morphologies with regard to their initial stability. MATERIALS AND METHODS Two implant systems (Tidal Spiral Dental Implant Systems, Huntsville, AL, USA, and MIS Seven, MIS Implants Technologies Ltd., Shlomi, Israel) with diameters of 3.75 mm and 4.2 mm and with a length of 13 mm were used. Following the insertion of implants, buccolingual thinning of the models was performed in 2-mm increments ranging between 0 and 8 mm. RESULTS A statistically significant decrease for implant stability quotient (ISQ) values was noticed for both diameters and both systems for all dimensional time points of the blocks (p < .05). The second system (more number of threads) resulted with higher ISQ values for both diameters than the first system (lower number of threads) (p < .001). The orientation of the probe influenced the measurements, where a standard orientation is advisable for the magnetic RF device. CONCLUSION Different implant surface geometries seem to behave in different patterns in terms of initial stability. Dimensional changes in buccolingual direction seem to have an impact on the initial stability, where wider implants also presented higher ISQ values than narrow ones.

Fracture strength of CAD/CAM fabricated lithium disilicate and resin nano ceramic restorations used for endodontically treated teeth

The purpose of the present study was to evaluate and compare the fracture strength and failure modes of endocrowns, zirconia post, and fiber post supported restorations and predict the clinical outcomes of six different prostheses used for endodontically treated teeth. Sixty (n=10) maxillary central incisors were restored with zirconia post/resin-nano-ceramic crown (ZrRNC), fiber post/resinnano-ceramic crown (FbRNC), zirconia post/lithium disilicate ceramic crown (ZrLDS), fiber post/lithium disilicate ceramic crown (FbLDS), resin-nano-ceramic endocrown (EndoRNC), and lithium disilicate ceramic endocrown (EndoLDS). Fracture strength test was performed. Fracture loads and modes were determined. The EndoLDS group had the highest fracture strength, followed by ZrRNC and EndoRNC group. However the results were not significantly different among groups (p>0.05). The failure modes of the restorations changed according to the restorative materials. Endodontically treated anterior teeth might be restored with endocrowns as well as other post-core restorations, however tooth fracture failures should be considered that affect reliability of endocrowns.