The Influence of an Ultrasonic Cleaning Protocol for CAD/CAM Abutment Surfaces on Cell Viability and Inflammatory Response In Vitro

BACKGROUND/AIM

To evaluate the effect of an ultrasonic cleaning and disinfection method for CAD/CAM abutment surfaces on cell viability and inflammatory response in vitro.

MATERIALS AND METHODS

Untreated and manually polished surfaces of CAD/CAM generated titanium and zirconia disks were randomly assigned, either to a 3-step ultrasonic cleaning and disinfection process (test: TiUF, TiPF, ZrUF, ZrPF) or to 30 sec steam cleaning (control: TiUS, TiPS, ZrUS, ZrPS). Pre-cleaning surface analyses using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and surface profilometry were performed. Human gingival fibroblasts (HGFs) were cultured on test and control specimens and subsequently examined for cell viability and inflammatory response. Expression of acute inflammatory cytokine interleukin (IL)-6 and vascular endothelial growth factor A (VEGFA) were assessed by means of RT-qPCR.

RESULTS

Cells on all specimens exhibited a satisfactory viability, indicating firm attachment. Cells on polished zirconia samples, cleaned by means of sonication (ZrPF), exhibited significantly higher viability than cells on the same material cleaned by steam (ZrPS), p=0.019. For all other three material/ surface treatment combinations (TiU, TiP, ZrU), no such difference was observed between the cleaning methods. The messenger ribonucleic acid (mRNA) levels of IL-6 and VEGFA were between 50 and 105% of that of the control cells on the non-toxic control surface. mRNA levels of IL-6 and VEGFA correlated well with each other.

CONCLUSION

Except for higher viability of cells cultured on polished zirconia specimens, no universally applicable advantage could be found for the ultrasonic cleaning procedure for zirconia and titanium abutment surfaces regarding cell viability, IL-6 expression or VEGFA expression. The cleaning procedures did not have any negative effect either.

Influence of scaling procedures on the integrity of titanium nitride coated CAD/CAM abutments

PURPOSE

To determine the extent of treatment traces, the roughness depth, and the quantity of titanium nitride (TiN) removed from the surface of CAD/CAM abutments after treatment with various instruments.

MATERIALS AND METHODS

Twelve TiN coated CAD/CAM abutments were investigated for an in vitro study. In the test group (9), each abutment surface was subjected twice (150 g vs. 200 g pressure) to standardized treatment in a simulated prophylaxis measure with the following instruments: acrylic scaler, titanium curette, and ultrasonic scaler with steel tip. Three abutments were used as control group. Average surface roughness (Sa) and developed interfacial area ratio (Sdr) of treated and untreated surfaces were measured with a profilometer. The extent of treatment traces were analyzed by scanning electron microscopy.

RESULTS

Manipulation with ultrasonic scalers resulted in a significant increase of average surface roughness (Sa, P<.05) and developed interfacial area ratio (Sdr, P<.018). Variable contact pressure did not yield any statistically significant difference on Sa-values for all instruments (P=.8). Ultrasonic treatment resulted in pronounced surface traces and partially detachment of the TiN coating. While titanium curettes caused predominantly moderate treatment traces, no traces or detectable substance removal has been determined after manipulation with acrylic curettes.

CONCLUSION

Inappropriate instruments during regular plaque control may have an adverse effect on the integrity of the TiN coating of CAD/CAM abutments. To prevent defects and an increased surface roughness at the transmucosal zone of TiN abutments, only acrylic scaling instruments can be recommended for regular maintenance care.

Retention Strength of Conical Welding Caps for Fixed Implant-Supported Prostheses

PURPOSE

This study evaluated the retention strength of welding caps for Ankylos standard abutments using a pull-out test.

MATERIALS AND METHODS

Each sample consisted of an implant abutment and its welding cap. The tests were performed with a Zwick Roell testing machine with a 1-kN load cell.

RESULTS

The retention strength of the welding caps increased with higher abutment diameters and higher head heights and was comparable or superior to the values reported in the literature for the temporary cements used in implant dentistry.

CONCLUSION

Welding caps provide a reliable connection between an abutment and a fixed prosthesis without the use of cement.

Fatigue limits of titanium-bar joints made with the laser and the electric resistance welding techniques: microstructural characterization and hardness properties

Fatigue behavior of the titanium bars is of utmost importance for the safe and reliable operation of dental implants and prosthetic constructions based on these implants. To date, however, only few data are available on the fatigue strength of dental prostheses made with electric resistance welding and laser welding techniques. This in-vitro study highlighted that although the joints made with the laser welding approach are credited of a superior tensile strength, joints made with electric resistance welding exhibited double the minimum fatigue strength with respect to the joints made with laser welding (120 vs 60 N).