[The omega connector--a module for jointed coupling of titanium total prostheses in the middle ear]. / Der Omega-Connector: ein Modul zur gelenkigen Ankopplung von Titantotalprothesen im Mittelohr.

BACKGROUND: Hearing improvement after reconstruction of a defect ossicular chain depends on material, design and - crucially - coupling of the prosthesis. Coupling a total ossicular replacement prosthesis to the stapes footplate can be problematic and lead to prosthesis instability. In order to solve this problem, the Omega Connector was developed, a module allowing the middle ear surgeon to couple a titanium total prosthesis to the stapes footplate in a flexible, angle-variable manner. MATERIAL AND METHOD: The Omega Connector is made of pure titanium and consists of three compenents: head, neck and base plate. The head allows a jointed coupling to the stem of a titanium total prosthesis. Positioned between the remnants of the stapes crura, the bas plate proves for a stable connection with the stapes footplate. RESULTS: The Omega Connector was implanted during 14 revisions surgeries. In 10 of these surgeries a total ossicular replacement prosthesis was removed which was implanted at an earlier date and which was fixed and no longer functioning. In all 14 cases it was possible intraoperatively to position the Omega Connector correctly and to couple it to a titanium total prosthesis. The postoperative hearing gain was between 10 to 25 dB, with an average of 18 dB. CONCLUSION: For the first time, the Omega Connector offers to the surgeon the option to couple a titanium total prosthesis via a micro ball joint. Hearing results achieved so far are satisfying. The results confirm the advantages of the Omega Connector during implantation of a titanium total prosthesis. For a final evaluation, long-term studies have yet to be made.

[Variable length titanium prostheses for type III tympanoplasty. Intraoperative length adjustment and fixation of the cartilage overlay]. / Längenvariable Titanprothesen bei Typ-III-Tympanoplastik. Intraoperative Längeneinstellung und Fixation der Knorpelauflage.

INTRODUCTION: For type III tympanoplasty by partial ossicular replacement prosthesis (PORP) or total ossicular replacement prosthesis (TORP), the length of the prosthesis must match the individual intraoperative anatomical and physiological characteristics. MATERIALS AND METHODS: Databanks were used to determine the necessary sizer length of the sizer disc. The measurement template for the size of the cartilage to overlay the prosthesis headplate was derived from the headplates of the Tübinger titanium prostheses (TTP) and the Dresdener titanium prostheses. Finally all functions were integrated into a synthetic plate. RESULTS: The result was a simple and reasonably priced disposable multifunctional instrument (Tübinger sizer disc TSD) which allowed an exact measurement for every prosthesis in TORP and PORP. For the TTP-Variac, the TSD enabled the simple intraoperative production of prostheses with the length desired by the surgeon. For PORP the TSD enabled an adaptation of the diameter of the prosthesis foot for TTP, TTP-Vario and TTP-Variac and provided a template for the size determination of the cartilage overlay of the titanium prosthesis head. The sizers and the resulting prostheses were used for initial tympanoplastic operations. Audiometric investigations carried out 6 weeks postoperatively gave results corresponding to those previously obtained in a study with TTP and TTP-Vario using the old instrumentation. CONCLUSIONS: The new instrumentation leads to an improvement of the intraoperative practicability and a simplification. The audiological results remain the same.

Acoustomechanical properties of open TTP titanium middle ear prostheses.

OBJECTIVE: The purpose of the study was to identify acoustcomechanical properties of various biostable and biocompatible materials to create a middle ear prosthesis with the following properties: (i) improved handling including a good view of the head of the stapes or footplate and adjustable length, (ii) improved acoustical characteristics that are adequate for ossiculoplastic. The identified material should serve to build CE and FDA approved prostheses for clinical use in patients. METHODS: Test models made of Teflon, polyetheretherketone, polyethylenterephtalate, polysulfone, gold, Al2O3 ceramics, carbon and titanium were investigated for their potential to fulfill the requirements. Acoustical properties were investigated by laser Doppler velocimetry (LDV) in mechanical middle ear models (MMM). Measured data were fed in to a recently created computer model of the middle ear (multibody systems approach, MBS). Using computer-aided design (CAD) measured and computed data allowed creation and fine precision of titanium prostheses (Tübingen Titanium Protheses, TTP). Their handling was tested in temporal bones. Acoustomechanical properties were investigated using the MBS and mechanical middle ear models. MAIN OUTCOME MEASURES: Input impedance, mass, stiffness, and geometry of test models and prostheses were determined. Furthermore, their influence on the intraprosthetic transfer functions and on coupling to either tympanic membrane or stapes was investigated. RESULTS: Final results were FDA- and CE-approved filigreed titanium prostheses with an open head that fulfilled the four requirements detailed above. The prostheses (TTP) were developed in defined lengths of between 1.75 and 3.5 mm (partial) and 3.0 and 6.5 mm (total) as well as in adjustable lengths (TTP-Vario). CONCLUSIONS: The results suggest acoustomechanical advantages of TTPs because they combine a significantly low mass with high stiffness. In contrast to closed prostheses, the open head and filigreed design allow an excellent view of the prosthesis foot during coupling to the head or footplate of stapes, contributing to an improved intraoperative reliability of prosthesis coupling.

Landscape metrics for assessment of landscape destruction and rehabilitation.

This investigation tested the usefulness of geometry-based landscape metrics for monitoring landscapes in a heavily disturbed environment. Research was carried out in a 75 sq km study area in Saxony, eastern Germany, where the landscape has been affected by surface mining and agricultural intensification. Landscape metrics were calculated from digital maps (1912, 1944, 1973, 1989) for the entire study area and for subregions (river valleys, plains), which were defined using the original geology and topography of the region. Correlation and factor analyses were used to select a set of landscape metrics suitable for landscape monitoring. Little land-use change occurred in the first half of the century, but political decisions and technological developments led to considerable change later. Metrics showed a similar pattern with almost no change between 1912 and 1944, but dramatic changes after 1944. Nonparametric statistical methods were used to test whether metrics differed between river valleys and plains. Significant differences in the metrics for these regions were found in the early maps (1912, 1944), but these differences were not significant in 1973 or 1989. These findings indicate that anthropogenic influences created a more home geneous landscape.

Bonding of enamel-dentin crown fragments after crown fracture. An experimental study using bonding agents.

Previous experimental studies into the use of dentin bonding agents for reattachment of enamel-dentin crown fragments have demonstrated fracture strength about 50-60% of that of intact teeth. In the clinic this has been reflected in the frequent need of repeated bonding of the treated incisors due to refracture. Recently newer bonding agents have been developed which can bond equally well with enamel and dentin. Employing the same experimental model, these bonding agents (All-Bond 2, Scotchbond MP) were used to reattach crown fragments to the remaining portion of sheep incisors. Loading of teeth bonded with these agents in an Instron testing machine at a speed of 1 mm/min demonstrated similar fracture strengths as those previously achieved with Gluma, Scotchbond 2 or Tenure. A second study was carried out whereby fragments were bonded with Scotchbond MP and loaded at various speeds. The results demonstrated that the fracture strength decreased exponentially with increased loading speed. By extrapolation, it was concluded that the strength was nil at a loading speed of approximately 2 m/min. It was concluded that the weak link in the bond between tooth fragment and remaining tooth structure is the bonding resin. Theoretically, a resin which is slightly elastic might act as a shock absorber to withstand functional stress. However, studies carried out with resins of varying moduli of elasticity gave disappointing results probably due to their low flexural strength.(ABSTRACT TRUNCATED AT 250 WORDS)