Evaluating parameters of osseointegrated dental implants using finite element analysis--a two-dimensional comparative study examining the effects of implant diameter, implant shape, and load direction.

Finite element analysis (FEA) has been proven to be a precise and applicable method for evaluating dental implant systems. By means of FEA, a parasaggital model was digitized from a computed tomography (CT)-generated patient data set, and various single-tooth, osseointegrated, two-dimensional dental implant models were simulated. The specific aims of the study were to: (1) examine the effect of implant diameter variation (3.8 mm-6.5 mm) of both a press-fit, stepped cylindrical implant type and a press-fit, straight cylindrical implant type as osseointegrated in the posterior mandible; (2) compare the stress-dissipating characteristics of the stepped implant versus the straight implant design; and (3) analyze the significance of bite force direction (vertical, horizontal, and oblique 45 degrees) on both implant types. The results of the FEA suggested that (1) using the widest diameter implant is not necessarily the best choice when considering stress distribution to surrounding bone, but within certain morphological limits, for both implant types, an optimum dental implant exists for decreasing the stress magnitudes at the bone-implant interface; (2) stress is more evenly dissipated throughout the stepped cylindrical implant when compared to the straight implant type; and (3) it is important in FEA of dental implants to consider not only axial forces (vertical loading) and horizontal forces (moment-causing loads), but also to consider a combined load (oblique bite force), since these are more realistic bite directions and for a given force will cause the highest localized stress in cortical bone. The theoretical analysis performed implies that clinically, whenever possible, an optimum, not necessarily larger, dental implant should be used based on the specific morphological limitations of the mandible and that a stepped cylindrical design for press-fit situations is most desirable from the standpoint of stress distribution to surrounding bone.

Comparison of soft tissue healing and osseointegration of IMZ implants placed in one-stage and two-stage techniques: a pilot study.

The osseointegration of endosseous dental implants is well documented. Implants have proven to be a viable treatment option for the replacement of missing teeth. The surgical phase of implant dentistry for most implant systems involves two stages--the placement of the implant and its subsequent uncovering. The IMZ (Interpore International) implant system is classically a two-stage system. No significant differences were demonstrated in osseointegration and soft tissue healing for IMZ implants placed in one-stage and two-stage procedures in this pilot study.

Comparison of Periotest values of integrated implants with and without healing abutments: a pilot study.

The role of the Periotest in the clinical evaluation of osseointegration has been well documented. Some clinicians have used the initial Periotest values at second-stage surgery as a baseline to measure changes in integration at the bone-implant interface over time. The purpose of this pilot study was to compare Periotest values made with and without healing abutments in place. A statistically significant difference was found between the Periotest values that were recorded with and without healing abutments, with the values without the healing abutments being more negative and suggestive of greater osseointegration.

Evaluation of osseointegration of endosseous implants in radiated, vascularized fibula flaps to the mandible: a pilot study.

PURPOSE: This study clinically evaluated the osseointegration of implants placed into vascularized fibula flaps used in mandibular reconstruction of cancer patients following radiation treatment and subsequent hyperbaric oxygen (HBO) therapy. MATERIALS AND METHODS: Five head and neck cancer patients had mandibular resection and immediate reconstruction with a vascularized fibula flap. Subsequent therapy included greater than 50 Gy of radiation to the fibula flap over a 6 to 8-week period. Two to 6 weeks following radiation therapy each patient received 20 90-minute daily sessions of HBO at 2.4 atmosphere pressure. Stage 1 implant surgery was performed placing two to six implants (15 mm in length and 3.75 to 4.0 mm in width) into each fibula flap. This was followed by 10 postoperative HBO sessions using the previously mentioned protocol. The stage 2 procedure was performed 6 months after the stage 1 procedure. Osseointegration was assessed clinically using manual force and an electronic device at the time the implants were uncovered and monthly over a 6-month period. RESULTS: All 20 implants placed in the fibula flaps were osseointegrated clinically at the time the implants were uncovered and during the 6-month follow-up. CONCLUSION: In this pilot study, mandibular reconstruction with a vascularized fibula flap and endosseous osseointegrated implants, following radiation of the fibula, was successful. It was concluded that factors such as the graft having its own blood supply and the use of HBO contributed to the successful osseointegration of these implants.

The status of undergraduate implant education in dental schools outside the United States.

Over the past 20 years the incorporation of implant dentistry into academia has been documented in some detail for North American dental schools but has not been pursued on an international level. In June of 1993, we surveyed 51 dental schools outside of the United States affiliated with the University of Pennsylvania School of Dental Medicine's Office of International Relations concerning their teaching involvement with implant dentistry. Results from the 44 (86 percent) responding schools suggest that implant dentistry is being incorporated into predoctoral curriculums. Industrialized countries were more inclined to provide implant education. Insufficient time and the thought that the predoctoral level was not the place for implant dentistry were cited as some of the reasons for not incorporating implant dentistry into the curriculum. Oral surgery, prosthodontics, and periodontics departments developed and administered the implant curriculum. Formats varied among schools with respect to allotted time, curricular placement, laboratory experience, and clinical participation. Didactic material most frequently presented included a historical overview, diagnosis and treatment planning, classification of dental implants, and surgical and prosthetic concepts. Clinical involvement varied from actual implant placement to observation of prosthodontic procedures. Results were categorized based on the TOEFL (Test of English as a Foreign Language) classification of countries in six regions.

Reconstruction of the head and neck cancer patient with a vascularized fibula flap and dental implants: preliminary clinical report.

Reconstruction and rehabilitation of the head and neck cancer patient is challenging. Vascularized fibula grafts can be used to reconstruct mandibular defects after resection of the malignancy and the surrounding bone. Prosthodontic treatment can restore function and esthetics. This preliminary report discusses the use of endosseous implants in radiated mandibular vascularized fibula grafts after surgical resection.

An investigation of the Impac custom abutment for root form dental implants.

PURPOSE: This study measured the tensile force required to separate a custom implant abutment fixture that had been cast onto a machined component using the Impac custom abutment system (Vident, Baldwin Park, CA). The characteristics of the interface between the cast and machined components were also investigated by scanning electron microscopy x-ray and energy-dispersive (JEOL T330A, Peabody, MA) analysis (Kevex Delta Level I, San Carlos, CA). MATERIALS AND METHODS: A polycarbonate custom abutment component, attached to a gold alloy component of the abutment, was invested in a phosphate-bonded investment and cast in a type III gold alloy (Argenco, Argen Precious Metals, San Diego, CA). Eight samples were cast after a burn-out of 900 degrees F and 13 samples were cast after a burn-out at 1300 degrees F. The abutment components were pulled in tension in a universal Testing Machine (Instron 4204, Canton, MA) until failure. The interface of as-cast and failed samples were examined by electron microscopy. RESULTS: Samples burned out at 1300 degrees F failed at a mean force of 2477 +/- 295 N (545 +/- 65 lb), and samples burned out at 900 degrees F failed at a mean force of 2182 +/- 91 N (484 +/- 20 lb). Electron microscopy of the interface between the cast and machined components showed retentive tags provided in the design of the machined components. There was also a zone of diffusion between components shown by a zone of void formation within the casting. Failure occurred at the interface of the cast and machined components for all samples. CONCLUSION: The cast component was retained by a combination of mechanical and chemical mechanisms.

Nasopharyngeal impression technique for fabrication of a radiation carrier.

A new technique for intracavitary application of Iridium 192 seeds in carcinoma of the nasopharynx is described. This technique allows for accurate construction of a nasopharyngeal carrier that permits the radiotherapist to deliver an adequate dose of irradiation to the nasopharynx.