Scanning acoustic microscopy study of titanium-ceramic interface of dental restorations

Bonding between titanium and dental porcelain: a systematic review

OBJECTIVES

The aims of this literature review are to provide answers to questions on how to improve bonding between titanium and dental porcelain and how to further implement, in clinical practice, ceramic-veneered titanium as an alternative to conventional metal-ceramic systems.

MATERIAL AND METHODS

A literature search of PubMed and also among referenced published scientific papers was performed and 24 fulfilled the search criteria, namely mentions of titanium, ceramics and bond strength. These papers were compiled for comparison and evaluated regarding the bond strength achieved with different methods.

RESULTS

The results strongly indicate that there are possibilities to improve both the present materials and methods for titanium-ceramic veneering.

CONCLUSIONS

The results indicate that present knowledge is sufficient to conclude that veneering titanium with low-fused porcelain for crowns and fixed partial dentures can be recommended for routine clinical use.

The effect of surface modifications on titanium to enable titanium–porcelain bonding

OBJECTIVES

Titanium-ceramic restorations are currently used, despite the pending problem of titanium-ceramic bonding, which has only been partially solved. The surface treatment of the metal proposed by the manufacturer promotes lower bond strength between titanium and porcelain when compared to the conventional metal-ceramic systems. The objective of this study was to evaluate the influence of acid and caustic baths on the bonding characteristics of specific titanium porcelain bonded to cast commercially pure titanium (CP Ti).

METHODS

Eighty strips of cast CP Ti were obtained in dimensions of 25mm x 3mm x 0.5mm, and divided into eight groups (n=10) which were subjected to surface treatment by immersion in one of the follow solutions-group HF: HF 10%; group NaOH+HF: NaOH 50%-CuSO(4).5H(2)O 10% followed by HF 10%; group HCl: HCl 35%; group NaOH+HCl: NaOH 50%-CuSO(4).5H(2)O 10% followed by HCl 35%; group HNO(3): HNO(3) 35%-HF 5%; group NaOH+HNO(3): NaOH 50%-CuSO(4).5H(2)O 10% followed by HNO(3) 35%-HF 5%; control group: treated according to the manufacturer's instructions; NaOH+control group: treated according to the manufacturer's instructions followed by immersion in NaOH 50%-CuSO(4).5H(2)O 10%. Low fusion porcelain (Vita Titankeramik) was applied to the center of one of the sides of each CP Ti sample with dimensions of 8mm x 3mm x 1mm. All groups were submitted to a three-point flexure test. Scanning electron microscopy (SEM) photomicrographs were taken to characterize the failed surfaces at the titanium-porcelain interface. Anova and Tukey's multiple comparison tests were used to analyze the data at a 5% probability level.

RESULTS

All groups treated with NaOH 50%-CuSO(4).5H(2)O 10% solution showed significant superior values when compared to groups treated exclusively with acid solution. There were no significant differences between HF (21.2MPa) and HCl (23.4MPa) groups; control (25.2MPa), HCl (23.4MPa) and HNO(3) (26.6MPa) groups; NaOH+HF (29.9MPa) and NaOH+HCl (30.8MPa) groups; NaOH+HNO(3) (34.8MPa) and NaOH+control (32.1MPa) groups. SEM analysis indicated a combination of cohesive and adhesive fractures in NaOH+HNO(3) and NaOH+control groups, while mainly adhesive fractures were found in the other groups.

SIGNIFICANCE

Bond strength between porcelain and cast CP Ti can be increased by use of a caustic bath prior to porcelain firing.

SEM/EDS evaluation of porcelain adherence to gold-coated cast titanium

The adhesion between titanium and dental porcelain is related to the diffusion of oxygen to the reaction layer formed on cast-titanium surfaces during porcelain firing. The diffusion of oxygen could be suppressed by coating the titanium surface with a thin gold layer. This study characterized the effects of gold coating on titanium-ceramic adhesion. ASTM grade II CP titanium was cast into a MgO-based investment (Selevest CB, Selec). The specimen surfaces were air abraded with 110-microm Al(2)O(3) particles. Gold coating was applied on titanium surfaces by three methods: gold-paste (Deck Gold NF, Degussa-Ney) coating and firing at 800 degrees C for three times, single gold-paste coating and firing followed by sputter coating (40 mA, 500 s), and sputter coating (40 mA, 1000 s). Surfaces only air abraded with Al(2)O(3) particles were used as controls. An ultra-low-fusing dental porcelain (Vita Titankeramik, Vident) was fused on titanium surfaces. Specimen surfaces were characterized by SEM/EDS and XRD. The titanium-ceramic adhesion was evaluated by a biaxial flexure test (N = 8), and area fraction of adherent porcelain (AFAP) was determined by EDS. Numerical results were statistically analyzed by one-way ANOVA and the Student-Newman-Keuls test at alpha = 0.05. SEM fractography showed a substantial amount of porcelains remaining on the gold-sputter-coated titanium surfaces. A new Au(2)Ti phase was found on gold-coated titanium surface after the firing. Significantly higher (p <.05) AFAP values were determined for the gold-sputter-coated specimens compared to the others. No significant differences were found among the other groups and the control. Results suggested that gold coatings used in this study are not effective barriers to completely protect titanium from oxidation during the porcelain firing, and porcelain adherence to cast titanium can be improved by gold-sputter coating used in the present study.

Evaluation of low-fusing ceramic systems combined with titanium grades II and V by bending test and scanning electron microscopy

The bond strength by three point bending strength of two metal substrates (commercially pure titanium or grade II, and Ti-6Al-4V alloy or grade V) combined to three distinct low-fusing ceramic systems (LFC) and the nature of porcelain-metal fracture by scanning electron microscopy (SEM) were evaluated. The results were compared to a combination of palladium-silver (Pd-Ag) alloy and conventional porcelain (Duceram VMK68). Sixty metal strips measuring 25x3x0.5mm were made - 30 of titanium grade II and 30 of titanium grade V, with application of the following types of porcelain: Vita Titankeramik, Triceram or Duceratin (10 specimens for each porcelain). The porcelains were bonded to the strips with dimensions limited to 8x3x1mm. The control group consisted of ten specimens Pd-Ag alloy/Duceram VMK68 porcelain. Statistical analyses were made by one-way analysis of variance (ANOVA) and Tukey test at 5% significance level. Results showed that the bond strength in control group (48.0MPa ± 4.0) was significantly higher than the Ti grade II (26.7MPa ± 4.1) and Ti grade V (25.2MPa ± 2.2) combinations. When Duceratin porcelain was applied in both substrates, Ti grade II and Ti grade V, the results were significantly lower than in Ti grade II/Vitatitankeramik. SEM analysis indicated a predominance of adhesive fractures for the groups Ti grade II and Ti grade V, and cohesive fracture for control group Pd-Ag/Duceram. Control group showed the best bond strength compared to the groups that employed LFC. Among LFC, the worst results were obtained when Duceratin porcelain was used in both substrates. SEM confirmed the results of three point bending strength.