Effect of titanium preoxidation on wrought pure titanium to ceramic bond strength.

STATEMENT OF PROBLEM: The creation of high bond strength between machined computer-manufactured pure titanium and porcelain remains a problem. However, machined titanium does not form the thick titanium oxide film found in cast titanium. PURPOSE: The purpose of this study was to investigate the effects of different preoxidation treatments on the bond strength of a machined pure titanium ceramic system. MATERIAL AND METHODS: Specimens of commercially pure titanium (25 × 3 × 0.5 mm) were divided equally into 6 groups (n=8), which received different preoxidation treatments (3 hour natural oxidation; 600°C, 650°C, 700°C, 750°C, and 800°C for 3 minutes). Bond strengths were evaluated by using a 3-point bend test. The results were analyzed by using 1-way ANOVA and the least significant difference test. Twelve additional specimens of commercially pure titanium (15 × 3 × 0.5 mm) were cut for interface observation and divided equally into 6 groups that received the preoxidation treatments described previously. Scanning electron microscopy and energy dispersive spectrum were used to observe microscopic features of the interface between Ti and ceramic. RESULTS: The bond strength values of the 6 groups ranged from 23.72 ±2.53 MPa to 36.99 ±3.92 MPa, with significant differences (P<.05). The specimen that received 750°C preoxidation had the highest bond strength. The main interface elements of the 6 groups were O, Si, Ti, Sn, Al, Na, and K. Ti showed a sigmoidal diffusion curve in each group, and Si showed a sigmoidal diffusion curve in most groups. Sn was enriched in each group's interface. CONCLUSIONS: Preoxidation under vacuum before porcelain firing can effectively improve the bond strength of machined pure titanium-porcelain systems.

[Clinical study of submental artery island myocutaneous flap for reconstruction of oral and maxillofacial defects following operation].

OBJECTIVE: To evaluate the outcome and indication of the reconstruction of oral and maxillofacial postoperative defects by submental artery island myocutaneous flaps. METHODS: Sixty eight cases with the reconstruction of oral and maxillofacial defects by submental artery island myocutaneous flaps from January 2006 to May 2010 were analysed retrospectively. Primary lesions included carcinomas originating from tongue (28 cases), palate (13 cases), mouth floor (9 cases), gingiva (4 cases), buccal mucosa (6 cases), lip (3 cases), and other malignant or benign tumors (5 cases). The ages ranged from 25 to 84 years (mean 58 years); 47 males and 21 females. The sizes of skin paddle varied from a minimum of 4 cm × 4 cm to a maximum of 15 cm × 10 cm. RESULTS: Of the 68 flaps, 62 were survival, 4 had partial necrosis but healed with treatments, and 2 failed due to complete necrosis. Appearance and functions of recipient sites were satisfactory. The followed-up time was 3 - 24 months, local recurrence occurred in 5 cases and cervical lymph node metastases were found in 15 patients. CONCLUSION: Submental island flap is reliable for the reconstruction of postoperative defects in early oral cancer without regional lymph node metastasis or in benign tumor.

[Effect of different heat treatment on the bonding strength of porcelain and Co-Cr alloy].

PURPOSE: To investigate and compare the effect of different heat treatment on the metal- ceramic bonding strength and the interfacial microstructure of the Co-Cr alloy. METHODS: Thirty specimens were made according to ISO 9693,and then divided into 3 groups (n=10) through the measurements .Group A(degassed 60s):degassed and then maintained 60s in 980 degrees centigrade Group B(degassed 60s and preoxidation 60s): degassed and maintained 60s in 980 degrees centigrade, then were maintained continuously for 60s in 980 degrees centigrade after re-gassed,Group C(degassed 120s): degassed and maintained 120s in 980 degrees centigrade. The bonding strengths of the three groups were evaluated through three point bending test. Six specimens divided into 3 group were made in the same method to observe the metal-ceramic interface through scanning electronic microscope(SEM) and energy dispersive spectrum(EDS).The bonding strength data were analyzed using ANOVA and Bonferroni's test by SPSS13.0 software package. RESULTS: The mean value of bonding strength was (39.03±2.70)MPa for group A, (34.43±2.36)MPa for group B, (31.65±1.49)MPa for group C, respectively. There were significant difference between every two groups (P<0.05). SEM demonstrated that the width of interfacial transition layer was 12.3-16.4µm in group A, 15.2-21.8µm in group B and 26.3-32.2µm in group C. CONCLUSIONS: Higher metal-ceramic bonding strength for Co-Cr alloy will be formed under the situation of degassed,and maintained 60s in 980 degrees centigrade ; while extending degassed time, prolonging the heat maintained time and preoxidation after degassing will reduce metal-ceramic bonding strength.