Retention and Mechanical Behavior of Attachment Systems for Implant-Retained Auricular Prostheses

Effect of in vivo aging on the surface and electrochemical properties of magnetic attachments used in facial prostheses: A retrieval analysis study

STATEMENT OF PROBLEM

Reasons associated with the failure of facial prosthesis are of major concern and may be associated with deterioration of both elastomeric materials and magnetic attachments. However, the extent of deterioration of these components is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate selected retrieved facial prostheses and provide information regarding the electrochemical characterization of the recovered magnetic attachments.

MATERIAL AND METHODS

Five facial prostheses (RP1, RP2, RP3, RP4, RP5) fabricated at the University of Texas, M.D. Anderson Cancer Center were retrieved following clinical use. The intaglio and external surfaces of the prostheses along with the incorporated magnetic attachments were photographed. The areas with the detected failures on the retrieved prostheses, as well as the recovered magnetic attachments, were evaluated under a reflected light stereomicroscope at ×16 nominal magnification and photographed with a digital camera. Five magnetic attachments recovered from the prostheses (retrieved group RT) were evaluated for degradation of their corrosion resistance after electrochemical testing in artificial sweat solution and were compared with 5 unused magnetic attachments (control group, CT). To identify the elemental composition of the intact magnet surface, 1 specimen from the control group was investigated by X-ray energy dispersive spectroscopy (EDS). Means and standard deviations of the open circuit potential (EOCP), the zero-circuit potential (Ecorr), and Icorr were calculated and statistically analyzed by a t test (α=.05 for all tests).

RESULTS

The main reasons of failure were discoloration, degradation and rupture of the silicone elastomer, marginal misfit, and delamination of the polyurethane sheet. Additional findings were tarnish and discoloration of the magnetic attachments accompanied by considerable smear build-up. EDS results verified the Ni plating of tested magnets. Electrochemical testing revealed that retrieved magnets showed significantly lower OCP (P<.001) and Ecorr (P<.001) but similar Icorr (P=0.083) while the pseudopassivity region of unused magnets vanished in the retrieved group, denoting a degradation of electrochemical properties after clinical use.

CONCLUSIONS

In vivo aging exerts extended degradation on the elastomer part of facial prostheses as well as deterioration of their surface integrity and electrochemical properties.

Effect of spatial arrangement and clinical service lifetime simulation on the retention of magnetic units used in implant-anchored orbital prostheses

STATEMENT OF PROBLEM

Evidence for the optimal spatial arrangement of magnetic attachments in implant-supported orbital prostheses is lacking.

PURPOSE

The purpose of this in vitro study was to assess the effect of 6 different spatial arrangements on the retentive force of magnetic attachments following the in vitro simulation of clinical service by insertion-removal test cycles and the contribution of artificial aging to the morphological alterations induced on the magnetic surfaces.

MATERIAL AND METHODS

Ni-Cu-Ni plated disk-shaped neodymium (Nd) magnetic units (d=5 mm, h=1.6 mm) were secured on leveled (50×50×5 mm, n=3) and angled (40×45×40 mm, interior angle=90 degrees, n=3) pairs of test panels in 6 different spatial arrangements: triangular_leveled (TL), triangular_angled (TA), square_leveled (SL), square_angled (SA), circular_leveled (CL), and circular_angled (CA) generating corresponding test assemblies (N=6). TL and TA arrangements included 3 magnetic units (3-magnet groups) and SL, SA, CL, and CA 4 (4-magnet groups). The retentive force (N) was measured at a mean crosshead speed of 10 mm/min (n=10). Each test assembly was subjected to insertion-removal test cycles with a 9-mm amplitude, ν=0.1 Hz, and n=10 consequent retentive force measurements at a crosshead speed of 10 mm/min at 540, 1080, 1620, and 2160 test cycles. Surface roughness alterations following the 2160 test cycles were measured by calculating the Sa, Sz, Sq, Sdr, Sc, and Sv parameters with an optical interferometric profiler with 5 new magnetic units used as a control group. Data were analyzed with 1-way ANOVA and Tukey HSD post hoc tests (α=.05).

RESULTS

The 4-magnet groups had statistically significantly higher retentive force than the 3-magnet ones at baseline and following the 2160 test cycles (P<.05). In the 4-magnet group, the ranking at baseline was SA<CA<CL<SL (P<.05) and following the test cycles SA=CA<CL<SL (P<.05). No statistically significant differences were found in the surface roughness parameters (Sa, Sz, Sq, Sdr, Sc, and Sv) following the 2160 test cycles among the experimental groups tested (P>.05).

CONCLUSIONS

Four magnetic attachments placed on an SL spatial arrangement resulted in the highest retention force but presented with the highest force reduction following the in vitro simulation of clinical service by insertion-removal test cycles.

Bar-clip versus magnet-retained auricular prostheses: A prospective clinical study with a 3-year follow-up

STATEMENT OF PROBLEM

Implant-retained auricular prostheses, on a bar-clip or with a magnetic retention system, are considered successful treatment for missing ears. However, which of these 2 retention systems is preferred by patients is unknown.

PURPOSE

The purpose of this clinical study was to assess which retention system is mostly preferred by patients wearing implant-retained auricular prostheses: bar-clip retention or magnetic retention.

MATERIAL AND METHODS

All consecutive patients visiting the clinic between March 2014 and November 2014 for a routine follow-up of their implant-retained auricular prostheses on a bar-clip retention system were asked to enroll in this descriptive study comparing patient preference for the retention system: bar-clip versus magnets. Participants were asked to complete a questionnaire to obtain patient satisfaction scores regarding their auricular prosthesis before and 3 months after changing to a magnetic-retained auricular prosthesis. After 3 months, participants were asked to state their preference for either their previous bar-clip system or the new magnetic system. If they did not prefer the magnetic system, participants were able to return to their previous bar-clip system. The study follow-ups were performed at 6, 12, 24, and 36 months. Again, patient satisfaction was scored with the aid of the same questionnaire, and prosthetic care and aftercare were also assessed.

RESULTS

Of 20 eligible patients, 17 participants (12 men, 5 women) enrolled in the study. The mean score for patient satisfaction for the bar-clip system at the start of the study was high (8 ±1.62). After 3 months, 2 participants wanted to return to their previous bar-clip system, followed by 1 more at the 6-month evaluation and 2 more at the 1-year evaluation. After 3 years, 9 of 16 participants (57%) preferred the magnetic-retained auricular prosthesis. During the 3 years of follow-up, aftercare was considered minor for both the bar-clip and the magnetic system. No participants developed peri-implantitis. All participants indicated that cleaning and placing the magnetic-retained auricular prosthesis was easier than the bar-clip system.

CONCLUSIONS

The majority of the participants (59%) in this study, especially the elderly participants, preferred the magnetic retention system. When compared with the bar-clip system, no additional aftercare was needed.