Improving implant fixation by immediate loading

Modified recommendations regarding patient treatment protocol for immediate loading, derived from the patient study The results of the animal experiments were reviewed critically to derive from them a number of recommendations as to the loading regimes that oral implants should be subjected to shortly after implantation in order to avoid adverse bone reaction, or even in order to stimulate the osseointegration process. These recommendations were integrated into a protocol for a pilot study on patients with a limited number of patients. The patients were given guidelines as to the best type of food to be eaten, and the chewing habits that are preferable. A number of ten patients was foreseen. The results of the follow-up of the ten patients were interpreted together with the results of the animal experiments. A final recommendation was made as to the optimal bone loading protocol that has to be recommended to patients after one stage placement of their implant and immediate loading with an oral prosthesis. The prescribed oral rehabilitation protocol, specifying food, behaviour, oral hygiene etc. for control patients resulted in zero failures after 1 year of loading. Animal experiments proved that mechanical loading has no negative outcome for the healing of the freshly installed implants. On the contrary, there was an increase in peri-implant bone mass observed in directly loaded implants. These results enhance the scientific basis for the clinical immediate loading protocol.

Devices to apply controlled loads to a dental implant in vivo. a. A novel non-invasive loading device utilising magnetic forces combined with a magnetic core residing in the implant. This concept has been evaluated and although not feasible in terms of development for this current project. Further development work will be required to advance the concept and technology in exploring feasibility and if positive then progression to a prototype device. We propose that the innovation should be noted at this stage. b. A device for application of loads directly to the dental implant using either pneumatically driven actuators for low frequency loading regimens or electromagnetic driven actuators for both high and low frequency loading applications. The osteogenic frequencies reported in the literature at the 20-30Hz level could not be induced with a pneumatic system. The project, therefore designed and developed the electromagnetic system used to impose a variable range of frequency and load. This concept involves a linear motor actuator used in the project for direct intra-oral loading of dental implants at frequencies of 3 and 30Hz. This device was developed and validated as a prototype and then refined for use in the project to load oral implants in Berkshire pigs.

Smart Prosthesis for autonomous monitoring of implant loading with user feedback Licensing of "smart prosthesis" (patent) A patent on the smart prosthesis technology needed to be filed to allow "protected" publications and interviews with dentists/patients (necessary for the final market analysis by Astra Tech (Task 4a.4, D23). K.U.Leuven/Medical Sensor Lab has taken the lead in drafting this patent application, together with the legal department of K.U.Leuven Research & Development. The patent has been filed in "The Patent Office" in South Wales, United Kingdom by LRD-K.U.Leuven. Submission date: 25/10/2004. The record is known under reference LRD-GB-1-523. The patent is entitled "Implantable Strain Controlling Unit". A PCT version was also filed. Reflections about the current smart prosthesis concept: The current concept of real time capturing information based on abutment deformation (strain gauges) is very valuable as a study design, and has never been performed until now, in an out-of-hospital setting. However the current "smart" prosthesis is: -Too bulky to function comfortable for the patient -Very painful when the smart prosthesis is seated deep into the gingiva (anaesthesia), due to the strain gauged abutments. -Has a battery autonomy of only 48 h. at best -Is technique sensitive -Has an uncertain but probably rather high cost for the patient -Does not have a readily marketable design To achieve a marketable design, it is necessary to build-in a warning device into the prosthesis and not at the abutment level. The warning signal should prevent the patients not to over-stress the bone at the implant-interface. Probably a device adaptable in time is wanted (i.e. more loads are allowed as time progresses).

UWCM contributed to the 3D modelling effort in the project: 1. Parametric modelling of implant designs Parametric finite element models of dental implant-bone complex were developed combining non-linear contact analyses and optimisation numerical routines aimed at optimising implant design in a way that it would lead to optimal long-term osseointegration. To this end, the models should be integrated with a bone re-modelling algorithm 2. Integration of bone remodelling algorithms with FE software -A robust methodology was developed to build 3D finite element models of composite structures (including cancellous and cortical bone, bone marrow and artificial dental implants) -A robust methodology was developed to perform optimised (performance/accuracy) non-linear finite element analyses of complex structures made of artificial biomaterials and biological tissues and structures. -The integration of an advanced bone adaptation algorithm into a commercial finite element framework that can be used to predict bone growth/resorption and remodelling still needs fine-tuning. The mathematical constitutive framework is based on a rigorous thermodynamically sound theory of continuum damage-repair. KULeuven used the robust methodology to build FE models of selected guinea pigs from the in vivo experiments and from selected patients from the pilot study. The bone- remodelling algorithm was applied to the guinea pig cases and the need for fine- tuning confirmed. All the methodologies described above can be combined in a computational environment to predict in vivo osseointegration in human subjects. An external partner is envisaged to integrate this environment into oral implant planning software. Examples of such software are Simplant (Materialise), Oralim (Medicim), etc.

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