Comparison of Corrosion Products From Implant and Various Gold-Based Abutment Couplings: The Effect of Gold Plating
This study compared titanium (Ti), palladium (Pd), platinum (Pt), and gold (Au) ion release following induced accelerated tribocorrosion from three Au alloy abutment groups coupled with Ti implants over time; investigated contacting surface structural changes; and explored the effect of Au plating. Three abutment groups, G (n = 8, GoldAdapt, Nobel Biocare), N (n = 8, cast UCLA, Biomet3i), and P (n = 8, cast UCLA, Biomet3i, Au plated), coupled with implants (Nobel Biocare), immersed in 1% lactic acid, were cyclically loaded. Ions released (ppb) at T1, T2, and T3, simulating 3, 5, and 12 months of function, respectively, were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and compared. Surface degradation and fretted particle composition after T3 were evaluated with scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). ICP-MS data were nonparametric, expressed as medians and interquartile ranges. SEM/EDX showed pitting, crevice corrosion, and fretted particles on the components. Released ion concentrations in all groups across time significantly decreased for Pd (P < .001, median range: 1.70–0.09), Pt (P = .021, 0.55–0.00), and Au (P < .001, 1.01–0.00) and increased for Ti (P = .018, 2.49–5.84). Total Ti release was greater than other ions combined for G (P = .012, 9.86–2.30) and N (P < .001, 13.59–5.70) but not for P (P = .141, 8.21–3.53). Total Ti release did not differ between groups (P = .36) but was less variable across group P. On average, total ion release was 13.77 ppb (interquartile range 8.91–26.03 ppb) across the 12-month simulation. Tribocorrosion of Ti implants coupled with Au abutments in a simulated environment was evidenced by fretted particles, pitting, and crevice corrosion of the coupling surfaces and release of ions. More Ti was released compared with Pd, Pt, and Au and continued to increase with time. Abutment composition influenced ion release. Au-plated abutments appeared to subdue variation in and minimize high-concentration spikes of titanium.
The 3 types of abutments. G, GoldAdapt cast-to; N, nonplated UCLA; P, gold-plated UCLA.
Left: schematic representation of the loading apparatus. Right: specimen container was tightened in a 30° jig on the testing machine.
(a) Preloading scanning electron microscopy (SEM) of the internal surface of the hex of an implant showing a smooth, uniform machined surface (×150). (b) Postloading SEM of the same area showing the presence of pitting (×150). This implant was connected to an Au-plated abutment. (c) Preloading SEM of the external area of the coupling surface of an implant showing a smooth, uniform machined surface (×500). (d) Postloading SEM of the same area showing the presence of pitting and particles (×500). This implant was connected to a nonplated abutment.
Figure 4. Box plots of ion release throughout the experiment time across the 3 groups (ppb). Note that each vertical axis has a different ppb scale. (a) Titanium. (b) Palladium. (c) Platinum. (d) Gold. P values for related tests are documented in Table 3. Figure 5. Box plots of the comparison of titanium (Ti) ion release from the implants compared with the combined release of platinum (Pt) + palladium (Pd) + gold (Au) ions from the abutments (ppb). There was a significant difference between ion release in groups G (P = .012) and N (P < .001) but not in group P (P = .141). Figure 6. (a) Box plots of the distribution of the total amounts of each element (titanium [Ti], platinum [Pt], palladium [Pd], gold [Au]) released across the 3 groups (ppb). Ti release was significantly greater than each of the other 3 elements in all 3 groups (P < .001). (b) Box plots of the distribution of the total amounts of Pt, Pd, and Au released from the abutments in the 3 groups. Figure 7. Box plots of the total ion release over the 3 time points (ppb). There was no significant difference between the groups (P = .32).
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