Planning implants crown down--a systematic quality control for proof of concept.

PURPOSE: We evaluated an innovative approach for conventional surgical or transmucosal implantation applying backward planning with bone oriented crown down implant positions, followed by immediate restoration. MATERIALS AND METHODS: Our workflow combined computer-assisted preoperative planning with the well-known intraoperative handling of surgical templates. To guarantee optimal accuracy, the complete process was bone borne, not soft tissue borne. Furthermore, in this concept, the definite prosthesis was manufactured on a plaster cast and fixed with technical implants inserted into the model using the same drilling template applied for intraoperative guidance of the drill. This bone-based workflow avoids the accumulation of errors throughout all steps of the treatment. In the present study, we have provided a concise quantitative quality control using 4 in vivo implants. This goal was accomplished by image matching of the preoperative plan with the corresponding postoperative computed tomography scan, applying descriptive statistics, the 1-sample t test, and the Student t test. RESULTS: Statistical evaluation showed that the bone-borne drilling template provides sufficient accuracy for immediate restoration with the definite prosthesis at the end of the operation. Deviation in the apex plane was 0.8 ± 0.42 mm, with 0.33 at the maximum. The angular deviation was 3.18° ± 0.78°. CONCLUSIONS: Our workflow is a promising approach with respect to handling, accuracy, and intraoperative safety.

Clinical experiences with resorbable ultrasonic-guided, angle-stable osteosynthesis in the panfacial region.

PURPOSE: In this study we report our experiences with the treatment of midfacial fractures and various other indications in regions with low load bearing (eg, dysmorphias) using the biodegradable Osteosynthesis System (SonicWeld Rx by KLS Martin, Tuttlingen, Germany), comprising biomechanical and histological aspects. PATIENTS AND METHODS: Seventy-five patients were included in this study. We describe the application of this system for the treatment of fractures of the zygomamaxillary complex, frontal bone impression fractures, surgical treatment of mukocele in the frontal sinus, isolated fractures of the orbital floor, complex midfacial trauma and bone cap fixation, craniosynostoses, and fixation of a distracted bone fragment. RESULTS: The pin insertion could be finished with a total failure rate of lower than 5%. In 3 patients, soft tissue swellings in regions with less subcutaneous fat were observed 6 to 8 months postoperatively. No fracture dislocations occurred. Scanning electron micrograph of the experimentally acquired connection between the resorbable plate and 2 pins clearly demonstrates a tight and reliable fusion to bone, both at the cortical as well as at the spongy compartment. Conventional histology leads to corresponding findings as scanning electron micrography, and shows a close fusion between all components. CONCLUSION: This retrospective study shows the general feasibility, sufficient mechanical stability, and efficient intraoperative handling of this angle-stable, ultrasonic-guided resorbable Osteosynthesis System (ResorbX and SonicWeld Rx) for a wide variety of indications in craniomaxillofacial surgery.

Clinical evaluation of mechanically optimized plates for the treatment of condylar process fractures.

OBJECTIVE: In this study we report on finite element calculation to verify the mechanical stability induced by the new geometry of a novel condylar process plate. We report our clinical experiences in the treatment of condylar process fractures using the novel plate. The plate has been designed according to finite element calculations in order to optimize mechanical stability and stiffness. The potential influence of this plate on the postoperative complication rate was assessed. STUDY DESIGN: Thirty-five mandibular condylar process fractures in 30 patients (20 male, 10 female, age: 34.3 +/- 11.5 years) were treated with the Modus condylar process plates (Medartis, Basle, Switzerland) and are included in this study. The time periods for postoperative follow-ups were 6 weeks and 6 months. RESULTS: No plate fractures occurred and there was no injury to the facial nerve. In one patient a screw loosening was observed. Two patients showed inadequate reduction without functional impairment. CONCLUSION: The newly developed condylar process plate proved to provide sufficient mechanical stiffness to avoid plate fractures. The postoperative complication rate can be reduced significantly. Statistical comparison to other osteosynthesis methods of the condylar process was performed and showed significant differences (single miniplates: P = .006 and minidynamic compression plates: P = .055). We conclude that a single Modus condylar process plate shows results comparable to 2 miniplates.

Comparison of laser surface scanning and fiducial marker-based registration in frameless stereotaxy. Technical note.

The authors compared the accuracy of laser surface scanning patient registration using the commercially available Fazer (Medtronic, Inc.) with the conventional registration procedure based on fiducial markers (FMs) in computer-assisted surgery. Four anatomical head specimens were prepared with 10 titanium microscrews placed at defined locations and scanned with a 16-slice spiral computed tomography unit. To compare the two registration methods, each method was applied five times for each cadaveric specimen; thus data were obtained from 40 registrations. Five microscrews (selected following a randomization protocol) were used for each FM-based registration; the other five FMs were selected for coordinate measurements by touching with a point measurement stylus. Coordinates of these points were also measured manually on the screen of the navigation computer. Coordinates were measured in the same manner after laser surface registration. The root mean square error as calculated by the navigation system ranged from 1.3 to 3.2 mm (mean 1.8 mm) with the Fazer and from 0.3 to 1.8 mm (mean 1.0 mm) with FM-based registration. The overall mean deviations (the arithmetic mean of the mean deviations of measurements on the four specimens) were 3.0 mm (standard deviation [SD] range 1.4-2.6 mm) with the Fazer and 1.4 mm (SD range 0.4-0.9 mm) with the FMs. The Fazer registration scans 300 surface points. Statistical tests showed the difference in the accuracy of these methods to be highly significant. In accordance with the findings of other groups, the authors concluded that the inclusion of a larger number of registration points might improve the accuracy of Fazer registration.

Computer-aided navigation in dental implantology: 7 years of clinical experience.

PURPOSE: This long-term study gives a review over 7 years of research, development, and routine clinical application of computer-aided navigation technology in dental implantology. Benefits and disadvantages of up-to-date technologies are discussed. MATERIALS AND METHODS: In the course of the current advancement, various hardware and software configurations are used. In the initial phase, universally applicable navigation software is adapted for implantology. Since 2001, a special software module for dental implantology is available. Preoperative planning is performed on the basis of prosthetic aspects and requirements. In clinical routine use, patient and drill positions are intraoperatively registered by means of optoelectronic tracking systems; during preclinical tests, electromagnetic trackers are also used. RESULTS: In 7 years (1995 to 2002), 55 patients with 327 dental implants were successfully positioned with computer-aided navigation technology. The mean number of implants per patient was 6 (minimum, 1; maximum, 11). No complications were observed; the preoperative planning could be exactly realized. The average expenditure of time for the preparation of a surgical intervention with navigation decreased from 2 to 3 days in the initial phase to one-half day in clinical routine use with software that is optimized for dental implantology. CONCLUSIONS: The use of computer-aided navigation technology can contribute to considerable quality improvement. Preoperative planning is exactly realized and intraoperative safety is increased, because damage to nerves or neighboring teeth can be avoided.