Meral Arslan Malkoc

Evaluation of the marginal fit of full ceramic crowns by the microcomputed tomography (micro-CT) technique.

Objective: To evaluate the marginal gap (MG) and absolute marginal discrepancy (MD) of full ceramic crowns with two finish line designs, shoulder and chamfer, using microcomputed tomography (micro-CT) before and after cementation. Materials and Methods: Sixty extracted human maxillary premolar teeth were divided into two groups based on the finish line design: Group I: 90° shoulder and Group II: 135° chamfer. The specimens were further grouped based on the type of full ceramic crown they received: Group A: Feldspathic Cerec inLab ceramic system, Group B: Cerec inLab aluminum oxide ceramic system and Group C: Lithium disilicate press ceramic system. Before cementation, five crowns from each group were scanned using micro-CT in two sections, sagittal and coronal, to determine the MG and MD values for four regions of the crown (sagittal buccal, sagittal lingual, coronal mesial and coronal distal). After cementation and thermal cycling, the scanning was repeated. Measurements were obtained from 10 points for each region, 80 points totally, to evaluate the MG and MD values. Files were processed using NRecon and CTAn software. Results were statistically analyzed using one- and two-way ANOVA and Tukey HSD tests (P = 0.05). Results: Full ceramic systems showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system generally presented the lowest variance, except in the MG values of the coronal mesial region. The MG and MD values of all ceramics increased significantly after cementation, except in the shoulder preparation design (sagittal buccal region) for MG and in the chamfer preparation design (sagittal lingual region) for MD values. Conclusions: Full-ceramic crowns showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system (Vitablocs Mark II) generally presented the lowest variance when compared with the other ceramics, except for the MG values on the mesial surface of the coronal section.

Level of residual monomer released from orthodontic acrylic materials

OBJECTIVE To quantify, with high-pressure liquid chromatography (HPLC), the amount of residual monomer leached from different orthodontic acrylic materials prepared with two different manipulation methods. MATERIALS AND METHODS Eighty cylindrical specimens (5 × 25 mm) were divided into eight groups (n  =  10). The specimens were prepared with four acrylic materials-Orthocryl Neon Blue (Dentaurum), Orthocryl EQ (Dentaurum), Orthoplast (Vertex), and O-80 (Imicryl)-and with two different manipulation methods: doughing and spray-on. HPLC measurements were made at intervals of 2 hours, 6 hours, 1 day, 1 week, and 3 months. One-way analysis of variance (ANOVA) and Tukeys honestly significant difference multiple-comparison test were used to assess the amount of monomer eluted from the various groups. To assess the differences within each group over the various periods, repeated-measures ANOVA and paired t-tests were used. RESULTS Statistically significant differences were found within the groups in the amount of residual monomer in the specimens at different time intervals (P < .001). HPLC showed statistically significant differences among the groups (P < .05) in the amount of eluted monomer. Evaluation of the manipulation techniques showed that the monomer release rate was higher in the specimens prepared with the doughing method. When the four acrylic materials were compared, the specimens made from Orthoplast (Vertex) showed the highest rate of monomer release with both manipulation techniques. CONCLUSION The spray-on method can be recommended to clinicians for the preparation of orthodontic appliances.

Evaluation of mineral content of dentin treated with desensitizing agents and neodymium yttrium-aluminium-garnet (Nd:YAG) laser

The aim of this study was to evaluate the mineral content of dentin prepared using three different desensitizing agents and the Nd:YAG laser. The occlusal third of the crowns of 30 molar teeth were cut with a slow-speed diamond saw sectioning machine under water cooling. Dentin slabs from the 30 teeth were randomly divided into five experimental groups, each comprising six slabs. The five groups were treated as follows: group A, no treatment; group B, treatment with oxalate-containing desensitizing agent (BisBlock); group C, treatment with resin-based desensitizing agent (Admira Protect); group D, treatment with glutaraldehyde-containing desensitizing agent (Systemp); and group E, irradiation with the Nd:YAG laser (DEKATM ) at 0.40 W. The levels of Mg, P, Ca, K, and Na in each slab were measured by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Data were analyzed by one-way analysis of variance and the Tukey HSD test. The effect of desensitizing agents and laser irradiation on the dentin surface were evaluated using a scanning electron microscope. There were no significant differences between the groups (p > 0.05). Group E was showed the lowest Ca/P ratio. SEM showed that the resin-based agent occluded the dentinal tubules, the glutaraldehyde-containing agent increased the Ca/P ratio, and Nd:YAG laser irradiation decreased the Ca/P ratio. The mean percentages by weight of Ca, Mg, K, Na and P were not affected by Nd:YAG laser irradiation or any of the desensitizing agents.

The effect of repeated porcelain firings on corrosion resistance of different dental alloys

PURPOSE The aim of this study was to evaluate the effects of repeated porcelain firing process on the corrosion rates of the dental alloys. MATERIALS AND METHODS Cr-Co, Cr-Ni and Pd-Ag alloys were used for this study. Each metal supported porcelain consisted of 30 specimens of 10 for 7, 9 and 11 firing each. Disc-shaped specimens 10 mm diameter and 3 mm thickness were formed by melting alloys with a propane-oxygen flame and casted with a centrifuge casting machine and then with the porcelain veneer fired onto the metal alloys. Corrosion tests were performed in quintuplicate for each alloy (after repeated porcelain firing) in Fusayama artificial saliva solution (pH = 5) in a low thermal-expansion borosilicate glass cell. Tamhane and Sheffe test was used to compare corrosion differences in the results after repeated firings and among 7, 9 and 11 firing for each alloy. The probability level for statistical significance was set at α=0.05. RESULTS The corrosion resistance was higher (30 mV), in case of 7 times firing (Commercial). On the other hand, it was lower in case of 11 times firing (5 mV) (P<.05). CONCLUSION Repeated firings decreased corrosion resistance of Pd-Ag, Cr-Co and Cr-Ni alloys. The Pd-Ag alloy exhibited little corrosion in in vitro tests. The Cr-Ni alloy exhibited higher corrosion resistance than Cr-Co alloys in in vitro tests.

3D micro-CT analysis of void formations and push-out bonding strength of resin cements used for fiber post cementation

PURPOSE To investigate the void parameters within the resin cements used for fiber post cementation by micro-CT (µCT) and regional push-out bonding strength. MATERIALS AND METHODS Twenty-one, single and round shaped roots were enlarged with a low-speed drill following by endodontic treatment. The roots were divided into three groups (n=7) and fiber posts were cemented with Maxcem Elite, Multilink N and Superbond C&B resin cements. Specimens were scanned using µCT scanner at resolution of 13.7 µm. The number, area, and volume of voids between dentin and post were evaluated. A method of analysis based on the post segmentation was used, and coronal, middle and apical thirds considered separately. After the µCT analysis, roots were embedded in epoxy resin and sectioned into 2 mm thick slices (63 sections in total). Push-out testing was performed with universal testing device at 0.5 mm/min cross-head speed. Data were analyzed with Kruskal–Wallis and Mann–Whitney U tests (α=.05). RESULTS Overall, significant differences between the resin cements and the post level were observed in the void number, area, and volume (P<.05). Super-Bond C&B showed the most void formation (44.86 ± 22.71). Multilink N showed the least void surface (3.51 ± 2.24 mm2) and volume (0.01 ± 0.01 mm3). Regional push-out bond strength of the cements was not different (P>.05). CONCLUSION µCT proved to be a powerful non-destructive 3D analysis tool for visualizing the void parameters. Multilink N had the lowest void parameters. When efficiency of all cements was evaluated, direct relationship between the post region and push-out bonding strength was not observed.

Bond strength of veneering porcelain to zirconia after different surface treatments

Abstract Aim: The aim of this study was to evaluate the effect of various surface treatments on the bond strength of veneering feldspathic porcelain to zirconia. Methods: Fifty yttria-stabilized tetragonal zirconia polycrystalline specimens were divided into five groups (n = 10) according to various surface treatments. The groups were as follows: Group 1: control group with liner application and no further surface treatment; Group 2: air-particle abrasion with 110 μm of alumina (Al2O3) particles; Group 3: grinding with a diamond disk; Group 4: Nd:YAG laser irradiation (the laser and the energy parameters were 10 Hz, and 2 W and 200 mJ, and the pulse duration (short pulse) range was up to 180 μs); Group 5: selective infiltration etching (SIE). After surface treatments, a liner application was performed for all surfaces according to the manufacturer’s instructions. Veneering porcelain was applied on zirconia surfaces using a Teflon mold. Shear bond strength was tested using a universal testing machine. The fractured surface morphologies were examined with scanning electron microscopy. The data were statistically analyzed using Mann–Whitney U and Kruskal–Wallis tests (α = .05). Results: The Megapascal values of the bonding groups were as follows: G1 = 8.62 ± 1.12, G2 = 13.87 ± 5.08, G3 = 12.31 ± 3.35, G4 = 17.32 ± 6.16, and G5 = 16.17 ± 4.55. Statistically significant differences were observed between the control group and the other groups (p < 0.05). Group 4 had the highest bond strength while G1 showed the lowest bond strength. No significant differences were found between the Nd:YAG, grinding, sandblasting, and SIE groups. Conclusion: Surface treatments had different effects on the shear bond strength of feldspathic porcelain to zirconia. Surface treatment techniques used in this study can be used on zirconia specimens prior to liner application to obtain an acceptable bond strength of veneering porcelain to zirconia. The effect of Nd:YAG laser irradiation and SIE techniques on bond strength of veneering ceramic to zirconia should be evaluated with further studies.

Cytotoxicity of temporary cements on bovine dental pulp-derived cells (bDPCs) using realtime cell analysis

PURPOSE To evaluate the cytotoxicity of temporary luting cements on bovine dental pulp-derived cells (bDPCs). MATERIALS AND METHODS Four different temporary cements were tested: Rely X Temp E (3M ESPE), Ultratemp (Ultradent), GC Fuji Temp (GC), and Rely X Temp NE (3M ESPE). The materials were prepared as discs and incubated in Dulbeccos modified eagles culture medium (DMEM) for 72 hours according to ISO 10993-5. A real-time cell analyzer was used to determine cell vitality. After seeding 200 µL of the cell suspensions into the wells of a 96-well plate, the bDPCs were cured with bioactive components released by the test materials and observed every 15 minutes for 98 hours. One-way ANOVA and Tukey-Kramer tests were used to analyze the results of the proliferation experiments. RESULTS All tested temporary cements showed significant decreases in the bDPCs index. Rely X Temp E, GC Fuji Temp, and Rely X Temp NE were severely toxic at both time points (24 and 72 hours) (P<.001). When the cells were exposed to media by Ultratemp, the cell viability was similar to that of the control at 24 hours (P>.05); however, the cell viability was significantly reduced at 72 hours (P<.001). Light and scanning electron microscopy examination confirmed these results. CONCLUSION The cytotoxic effects of temporary cements on pulpal tissue should be evaluated when choosing cement for luting provisional restorations.

Evaluation on Shear Bond Strength of Different Glass Ionomer and Hydroxy Apatite Cements Used in Ossiculoplasty

BACKGROUND Glass ionomer cements (GIC) have been widely used in dentistry for many years. In recent years, GIC have also been used for ossiculoplasty. The bond strength of GIC used in ossiculoplasty and the way they may change over the years in the cementation area are being questioned. The bonding strength of the substance may be of importance for long-term outcomes. AIMS The aim of this study was to investigate the bond strength of different GIC on ossicles. STUDY DESIGN In vitro study. METHODS Twenty ossicles were obtained from patients who had undergone ear surgery. All specimens were randomly divided into four subgroups. All specimens were inserted into a specially designed apparatus for shear bond strength (SBS) testing. The tested materials [Aqua Meron (AM), Aqua Cem (AC), Ketac Cem (KC), and Otomimix CPB (OH)] were prepared and applied according to the manufacturers instructions. The SBS was tested using a universal testing machine at a crosshead speed of 0.5 mm/min. RESULTS The mean SBSs were found to be 13.28 MPa, 23.43 MPa, 8.51MPa, and 1.78 MPa for AM, AC, KC, and OH, respectively. AC had the highest SBS, which was statistically significantly different from that of KC and OH (p<0.05). Both AM and KC had higher SBS than OH (p<0.05). CONCLUSION The results obtained in this study by investigating the bone-bonding strength of cements widely used in ossiculoplasty demonstrate that some of these substances have a greater ability to bond to ossicles compared to others. Further clinical investigations are needed to test different parameters.

The effect of repair protocols on shear bond strength to zirconia and veneering porcelain

Abstract The aim of this study was to evaluate the shear bond strength (SBS) of a new repairing material including zirconia primer to zirconia and veneering porcelain after various surface treatments. A total of 60 specimens (30 zirconia-Zr and 30 feldspathic porcelain-Feld) were prepared and divided into 6 groups (n = 10). Two surface preparations (air abrasion-AA and Erbium Yag (Er-YAG) Laser-Las) were applied to the specimens. Zr and Feld specimens treated with a grinding bur according to manufacturer advice, were used as control (C). Repair material (Cimara Zircon, VOCO, Germany) was applied to the specimens 2 mm in height. The SBS was measured in a universal testing machine at 1 mm/min crosshead speed. The SBS data (MPa) were analyzed using two-way ANOVA and Tukey HSD multiple comparison tests (α = 0.05). Significant effects of the material type (p = 0.005) and the surface treatment strategy (p = 0.000) were found. Interaction terms were also significant (p = 0.000). While the Zr-C (68,4 MPa) showed the highest SBS (p < 0.05), Zr-Las (16,4 MPa) had the lowest SBS (p < 0.05). The highest SBS value was obtained when both zirconia and veneering porcelain were treated with a grinding bur without any additional surface treatment.

Physical Properties of Different Orthodontic Composites

ABSTRACT Objective: The aim of this study was to compare the water sorption, solubility, and compressive strength of 3 traditional orthodontic composites and 1 flowable composite after 1, 7, and 30 days of immersion in water. Materials and Method: The traditional orthodontic composites used in this study were ORTHO Bracket Paste (Bisco, Schaumburg, IL, USA), Transbond XT (3M, Monrovia, CA, USA), and Light Bond (Reliance, Itasca, IL, USA). The flowable composite used was Tetric EvoFlow (Ivoclar Vivadent, Schaan, Liechtenstein). The specimens were subjected to water sorption and solubility tests based on the ISO 4049 and ADA No. 8 requirements. Mechanical tests were performed with an Instron Universal Test Machine. Results: There were no significant differences in solubility among the 4 materials after 1 and 7 days (p > 0.05). Tetric EvoFlow had a lower compressive strength than the traditional orthodontic composites (p > 0.05) and exhibited significantly higher water sorption than the traditional orthodont...