Characterizing and evaluating the bonding between TiO2 nanotubes and dental porcelain
thesisposted on 16.02.2016, 00:00 by Himani Nadgauda
The following body of work aims to strengthen the bonding between titanium and dental porcelain through achieving mechanical interlocking at the interface. Electrochemical anodization was used to create titanium dioxide nanotubes on the titanium surface in hopes that when porcelain was added on top of the metal, the resulting increased surface area would lead to stronger bond strength between the two materials. Titanium samples were electrochemically anodized at 60 V for 0, 1, 5, 15, and 30 minutes so as to grow nanotubes of different lengths. Dental porcelain was added onto the titanium and the metal-ceramic samples were subsequently fired in a furnace. The bond strength of these samples was evaluated using the 3-point bending method, following ISO 9693 standards. Results showed that the highest average debonding strength values for both the grade 2 and grade 5 samples occurred for the 0 min anodization time (grade 2: 16.1±2.4 MPa, grade 5: 16.9±3.0 MPa) and 5 min anodization time groups (grade 2: 15.8±2.5 MPa, grade 5: 18.5±2.9 MPa). It was found that the grade 2 and 5 samples without nanotubes adhered to the ceramic equally well as the grade 2 and 5 samples that had been anodized for 5 min. These two groups were able to withstand the highest average load during the 3-point bending test compared to the grade 2 and 5 samples at the other anodization times used (1, 15, and 30 min). The ANOVA analysis of the results revealed that the debonding strength, , of the grade 5 metal-ceramic samples was greater than that of grade 2 metal-ceramic samples. Student t-test results showed that the mean of grade 2 metal-ceramic samples anodized for 1 and 15 min and grade 5 metal-ceramic samples anodized for 1 min was significantly lower than the un-anodized metal-ceramic samples. Rutile formation may have occurred on the titanium samples during the porcelain firing process due to the exposure to high temperatures in the dental furnace. This may have caused collapse of some of the TNTs on the metal-ceramic samples. For every metal-ceramic sample, the break during the 3-point bending test occurred in a jagged fashion; the break appeared to be both a substrate failure and cohesive failure. These findings suggested that there is a need for further research on developing a coating that can withstand the high temperatures in the dental furnace, lead to successful wetting of porcelain on the metal surface, and successfully achieve stronger bonding between the titanium and dental porcelain during the firing process.