Improvement in Dental Porcelain Bonding to Milled, Noncast Titanium Surfaces by Gold Sputter Coating

Shear bond strength of the ceramic veneer to additively manufactured titanium

OBJECTIVES

The objective of this in vitro study was to evaluate the shear bond strength between the ceramic veneer and additively manufactured titanium with different surface treatments, and to compare with milled titanium. Also, to characterize the surface and the presence of an α-case layer of additively manufactured and milled titanium.

MATERIAL AND METHODS

Sixty additively manufactured titanium grade 23, and 20 milled titanium grade 4 cylindrical specimens were divided into four groups based on surface treatments, air-particle abrasion and grinding. After ceramic veneering half of each group were thermocycled. The bond strength was analyzed using a shear bond strength test. The surfaces were analyzed using interferometry and scanning electron microscopy.

RESULTS

The grinding procedure and air-particle abrading pressure had no significant effect on the shear bond strength (p = .264 and p = .344). Thermocycling showed a tendency towards an effect but not significant (p = .052). The group with the highest air-abrading pressure showed the highest surface roughness. No presence of an α-case layer was detected in any of the groups.

CONCLUSION

Additively manufactured titanium grade 23 may be veneered with ceramics without prior grinding of the surfaces.

The effect of nanocoatings of SiO2, TiO2, and ZrO2 on titanium-porcelain bonding

STATEMENT OF PROBLEM

Durable titanium-porcelain bonding is challenging because of the formation of a thick oxide layer on the surface during porcelain firing.

PURPOSE

The purpose of this in vitro study was to evaluate how atomic layer deposition (ALD) of different oxide coatings affected titanium-porcelain bonding and failure types.

MATERIAL AND METHODS

Forty-four airborne-particle abraded Type-2 titanium specimens were coated by ALD with either SiO₂, TiO₂, or ZrO₂ (n=11) at a thickness of 30 nm, whereas control specimens were left uncoated (n=11) (airborne-particle abraded only). The surface roughness of the specimens was analyzed with a profilometer before applying porcelain (Vita Titankeramic). Titanium-porcelain bonding was analyzed by using a 3-point bend test. Surface properties and titanium-porcelain interfaces were examined under scanning electron microscopy combined with energy-dispersive spectroscopy, and failure types were evaluated by using a stereomicroscope. Surface roughness and bond strength data were analyzed by 1-way ANOVA and Tukey HSD tests. Failure type data were analyzed by the Fisher-Freeman-Halton exact test (α=.05).

RESULTS

All nanocoatings increased surface roughness values, but only TiO₂ and ZrO₂ coatings showed statistically significant higher roughness than the control surfaces (P<.001). Specimens coated with SiO₂ (28.59 ±4.37 MPa) and TiO₂ (26.86 ±3.66 MPa) presented significantly higher bonding strength than control (22.04 ±4.59 MPa) specimens (P<.01). Fracture types of different groups were not statistically different (P>.05).

CONCLUSIONS

Nanocoating titanium surfaces with SiO₂ and TiO₂ by using the ALD technique significantly improved titanium-porcelain bonding.

Porcelain-titanium bonding with a newly introduced, commercially available system

STATEMENT OF PROBLEM

Titanium is widely used in implant dentistry because of its high strength, toughness, biocompatibility, and low cost. The fabrication of complex substructures is now possible with a number of automated systems. One major obstacle to broad clinical acceptance of porcelain-titanium prostheses is the poor ceramic-metal bonding.

PURPOSE

The purpose of this study was to compare titanium bonding with a traditional bonder and a newly introduced titanium bonding system. Bonding was characterized by the delamination crack initiation stress per ISO 9693:2009.

MATERIAL AND METHODS

Grade 4 titanium strips were laser machined to meet ISO 9693:2009 standards. Bonding and firing of opaque porcelain was accomplished by using a traditional titanium ceramic system and a newly introduced bonding system. Variables tested besides the bonding system included the length of the porcelain block (7 mm, 8 mm, 9 mm); the thickness of the block (1.0 mm, 1.6 mm); testing the specimens 1 mm off-center; and reusing the strips. Crack initiation stresses were calculated and compared by ANOVA and the Duncan test (α=.05).

RESULTS

The newly introduced commercially available system gave the strongest bond (41.82 ±5.7 MPa), followed by the 9 mm specimens (32.2 ±3.9 MPa), then a statistically similar group of the 8 mm, 7 mm, and 1.6 mm thick specimens with new Ti (approximately 23 MPa), and last a similar group with 7 mm, 8 mm, and 1 mm offset loading on reused Ti (approximately 16 MPa). The lower limit under ISO 9693:2009 was 23 MPa.

CONCLUSIONS

The newly introduced commercially available system achieved much higher bond strengths than traditional titanium systems, even better than those for many high-gold alloys.