An evaluation of the stress effect of different occlusion concepts on hybrid abutment and implant supported monolithic zirconia fixed prosthesis: A finite element analysis

PURPOSE@#The aim of this study is to evaluate the effects of canine guidance occlusion and group function occlusion on the degree of stress to the bone, implants, abutments, and crowns using finite element analysis (FEA). @*MATERIALS AND METHODS@#This study included the implant-prosthesis system of a three-unit bridge made of monolithic zirconia and hybrid abutments. Threedimensional (3D) models of a bone-level implant system and a titanium base abutment were created using the original implant components. Two titanium implants, measuring 4 × 11 mm each, were selected. The loads were applied in two oblique directions of 15º and 30º under two occlusal movement conditions. In the canine guidance condition, loads (100 N) were applied to the canine crown only. In the group function condition, loads were applied to all three teeth. In this loading, a force of 100 N was applied to the canine, and 200-N forces were applied to each premolar. The stress distribution among all the components of the implant-bridge system was assessed using ANSYS SpaceClaim 2020 R2 software and finite element analysis. @*RESULTS@#Maximum stress was found in the group function occlusion. The maximum stress increased with an increase in the angle of occlusal force. @*CONCLUSION@# The canine guidance occlusion with monolithic zirconia crown materials is promising for implant-supported prostheses in the canine and premolar areas.

An evaluation of the stress effect of different occlusion concepts on hybrid abutment and implant supported monolithic zirconia fixed prosthesis: A finite element analysis

PURPOSE@#The aim of this study is to evaluate the effects of canine guidance occlusion and group function occlusion on the degree of stress to the bone, implants, abutments, and crowns using finite element analysis (FEA). @*MATERIALS AND METHODS@#This study included the implant-prosthesis system of a three-unit bridge made of monolithic zirconia and hybrid abutments. Threedimensional (3D) models of a bone-level implant system and a titanium base abutment were created using the original implant components. Two titanium implants, measuring 4 × 11 mm each, were selected. The loads were applied in two oblique directions of 15º and 30º under two occlusal movement conditions. In the canine guidance condition, loads (100 N) were applied to the canine crown only. In the group function condition, loads were applied to all three teeth. In this loading, a force of 100 N was applied to the canine, and 200-N forces were applied to each premolar. The stress distribution among all the components of the implant-bridge system was assessed using ANSYS SpaceClaim 2020 R2 software and finite element analysis. @*RESULTS@#Maximum stress was found in the group function occlusion. The maximum stress increased with an increase in the angle of occlusal force. @*CONCLUSION@# The canine guidance occlusion with monolithic zirconia crown materials is promising for implant-supported prostheses in the canine and premolar areas.

Influence Of Different Bleaching Systems On The Bond Strength Of Laminate Veneer To Enamel

Purpose:The objective of this in-vitro study was to examine the microtensile bond strength of a porcelain laminate veneer (PLV) to tooth surface bleached with photoactivation by blue light-emitting diode (LED) or diode laser. Methods:Eigthteen extracted human central incisors were randomly divided into three groups. Two sticks were obtained from each tooth (n=12). Before surface treatments; teeth were prepared to provide space for PLVs. The first group teeth were bleached with Whiteness HP which is contain 35% hydrogen peroxide (HP) and then photoactivated with a LED for 20 seconds. The second group were bleached with Laserwhite 20 which is contain 46% HP and photoactivated with a diode laser for 30 seconds. The third group received no surface treatment and served as the control group. IPS Esthetic ceramic veneers were luted with Variolink II veneer cement . The teeth were sectioned to obtain porcelain-resin-enamel/dentin sticks and submitted to a MTB testing device. The maximum load at fracture was recorded. Data were analyzed using one-way ANOVA followed by the Tukey HSD post-hoc test at a preset α of 0.05. Results:One-way ANOVA revealed that there was significant difference between LED unit group and control group (p<.05) but no statistical differences were observed with diode laser group (p>.05) The LED unit group presented significantly lower bond strength value (6.49±2.3 MPa) than diode laser (8.49±3.1 MPa) and control groups (9.53±2.7 MPa). Conclusion:The results suggested that bleaching therapy with activation by LED or diode laser reduced the bond strength of IPS Esthetic ceramic veneers to tooth surfaces.

The effect of a diode laser and traditional irrigants on the bond strength of self-adhesive cement

PURPOSE: The purpose of this study was to compare the effect of a diode laser and traditional irrigants on the bond strength of self-adhesive cement. MATERIALS AND METHODS: Fifty-five incisors extracted due to periodontal problems were used. All teeth were instrumented using a set of rotary root canal instruments. The post spaces were enlarged for a No.14 (diameter, 1.4 mm) Snowlight (Abrasive technology, OH, USA) glass fiber reinforced composite post with matching drill. The teeth were randomly divided into 5 experimental groups of 11 teeth each. The post spaces were treated with the followings: Group 1: 5 mL 0.9% physiological saline; Group 2: 5 mL 5.25% sodium hypochlorite; Group 3: 5 mL 17% ethylene diamine tetra acetic acid (EDTA), Group 4: 37% orthophosphoric acid and Group 5: Photodynamic diode laser irradiation for 1 minute after application of light-active dye solution. Snowlight posts were luted with self-adhesive resin cement. Each root was sectioned perpendicular to its long axis to create 1 mm thick specimens. The push-out bond strength test method was used to measure bond strength. One tooth from each group was processed for scanning electron microscopic analysis. RESULTS: Bond strength values were as follow: Group 1 = 4.15 MPa; Group 2 = 3.00 MPa; Group 3 = 4.45 MPa; Group 4 = 6.96 MPa; and Group 5 = 8.93 MPa. These values were analysed using one-way ANOVA and Tukey honestly significant difference test (P.05). CONCLUSION: Orthophosphoric acid and EDTA were more effective methods for removing the smear layer than the diode laser. However, the diode laser and orthophosphoric acid were more effective at the cement dentin interface than the EDTA, Therefore, modifying the smear layer may be more effective when a self-adhesive system is used.

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 alpha=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.

Effect of different provisional cement remnant cleaning procedures including Er:YAG laser on shear bond strength of ceramics

PURPOSE: The purpose of this study was to evaluate the effect of provisional cement removal by different dentin cleaning protocols (dental explorer, pumice, cleaning bur, Er:YAG laser) on the shear bond strength between ceramic and dentin. MATERIALS AND METHODS: In total, 36 caries-free unrestored human third molars were selected as tooth specimens. Provisional restorations were fabricated and cemented with eugenol-free provisional cement. Then, disc-shaped ceramic specimens were fabricated and randomly assigned to four groups of dentin cleaning protocols (n = 9). Group 1 (control): Provisional cements were mechanically removed with a dental explorer. Group 2: The dentin surfaces were treated with a cleaning brush with pumice Group 3: The dentin surfaces were treated with a cleaning bur. Group 4: The provisional cements were removed by an Er:YAG laser. Self-adhesive luting cement was used to bond ceramic discs to dentin surfaces. Shear bond strength (SBS) was measured using a universal testing machine at a 0.05 mm/min crosshead speed. The data were analyzed using a Kolmogorov Smirnov, One-way ANOVA and Tukey HSD tests to perform multiple comparisons (alpha=0.05). RESULTS: The dentin cleaning methods did not significantly affect the SBS of ceramic discs to dentin as follows: dental explorer, pumice, cleaning bur, and Er:YAG laser. CONCLUSION: The use of different cleaning protocols did not affect the SBS between dentin and ceramic surfaces.

relationship of some patients factors with shade of their teeth measured by spectrophotometry in Turkish people

To investigate the relationships of some patients' factors with the shade of their teeth in Turkish people. Four Hundred subjects who had no defects in their natural right maxillary central incisors were examined in this study. Shade of teeth was measured with a spectrophotometer. Eye colours were classified as brown, honey, hazel, green, black and blue respectively. Skin complexions were determined by using the Fitzpatrick Skin Type Classification. Tooth shades were placed into 13 categories using the vita shade scale, and skin complexion in 6 categories. The Pearson Chi-Square and Likelihood Ratio statistical tests were used to analyze the data. There was no correlation between the skin complexion and tooth shade [P > 0.05]. Statistically significant differences were found between gender and tooth shade [P < 0.05]. People with their ages between 14-30 and 31-45 generally had A2 tooth shade, and those who were between the ages of 46-60 and 61-80 generally had A3 tooth shade. There was a statistically significant correlation between age and tooth shade [P < 0.05]. People having hazel, brown, blue and black eyes had A2 shade teeth and those with honey and green eyes generally had teeth with the A3 shades. There were no statistically significant correlations between eye and tooth shade [P > 0.05]. Within the limitations of this study, there were no significant relationships between skin complexion, eye color and tooth shade. Younger people generally had A2 shade teeth. Elderly people were more likely to have darker teeth