Blur reduction of conventional film-based tomograms for pre-surgical evaluation of potential mandibular implant sites

Comparison of linear tomography and direct ridge mapping for the determination of edentulous ridge dimensions in human cadavers

OBJECTIVE

The purpose of this study was to compare the accuracy of linear tomography (LT) and direct ridge mapping (RM) for determining alveolar ridge dimensions.

STUDY DESIGN

One site in the posterior mandible was selected for evaluation in each of 5 cadaver heads. Vacuum-formed stents made from models of the cadaver ridges were used to identify 3 sets of measurement points for each specimen: coronal (intersection of coronal and middle third of ridge), middle (intersection of middle and apical third), and apical (base of vestibule). The imaging stent contained 2-mm metal balls at each point, while the RM stent had holes drilled at corresponding locations. Linear tomograms and periapical radiographs (PA) were taken of the selected sites. RM measurements were made with calipers. Five blinded examiners measured ridge width at the designated measurement points with both LT and RM as well as distance from the ridge crest to mandibular canal (using PAs for RM group). Mandibles were then sectioned and an independent examiner made direct measurements (DM). MANOVA was used to determine whether LT and RM differed significantly from DM.

RESULTS

There were no significant differences between LT and RM for ridge width measurements. However, both techniques underestimated ridge dimensions compared to DM ( P < .05). Measurement of mandibular canal height was accurate when determined by periapical radiographs but not by LT.

CONCLUSION

Neither LT nor RM proved to be completely accurate in determining ridge width in the posterior mandible.

Evaluation of accuracy of insertion of dental implants and prosthetic treatment by computer-aided navigation in minipigs

The survival of loaded implants is critically dependent on their biomechanical stability. We have used a computer-guided navigation technique to evaluate the accuracy of computer-assisted insertion for immediately-loaded implants in minipigs. On the basis of computed tomographical data, the Robodent system was used for preoperative planning and guidance of inserting the implant. An optical tracking system allowed positioning of the implant and immediate prosthetic rehabilitation by inserting it in a plaster model and during the operation. Postoperative computed tomograms (CT) showed that the implants were placed precisely in the preoperatively planned position. The accuracy achieved corresponded well with the spatial resolution of the CT used. Immediate placement of the prefabricated crowns resulted in favourable occlusal positioning. Histological cross-sections showed that the implants were biomechanically stable. The accuracy of insertion of oral implants illustrated here suggests that insertion and prosthetic modelling of implants may benefit from computer-assisted navigation.

Imaging technique selection for the preoperative planning of oral implants: a review of the literature

BACKGROUND

As the use of oral implants for the treatment of partially as well as fully edentulous patients has increased the past two decades, more specialized radiographic techniques have become available for the preoperative planning of oral implant placement.

PURPOSE

The goal of this article was to enable clinicians to select the appropriate imaging techniques when planning for oral implants.

MATERIALS AND METHODS

This artide reviews the available literature about various imaging techniques and their indication for the preoperative planning of oral implants. The advantages and drawbacks of each technique are described. A dosimetric overview is given relative to different radiologic techniques used in various clinical situations.

RESULTS

For preoperative planning of implant placement, advantages and drawbacks of the available imaging techniques have been considered, which allows guidelines for image technique selection to be formulated based on the clinical situation provided, considering the diagnostic yield of each technique and the radiation doses involved.

CONCLUSIONS

From the available literature, it can be stated that many clinical situations demand the use of cross-sectional imaging techniques for optimal preoperative planning of implant placement. Nevertheless, such techniques are not required in cases in which the clinical examination reveals sufficient bone width and where standard radiographic examinations, such as intraoral and panoramic radiography, reveal adequate bone height and space for implant placement.

Evaluation of mandibular implant sites: correlation between panoramic and linear tomography

The reliability of the linear tomography and panoramic radiography made with X-ray equipment was evaluated (Vera View Scope X-600; Morita). The sample was composed of 20 dry human hemimandibles, in which the area selected for analysis was 1.5 cm distal from the limit set before the mental foramen. Four measurements were made. The images obtained were drawn on acetate paper and the hemimandibles cut at the demarcated area. The measurements were made using a digital electronic pachymeter. The values found for the radiographic images were compared to those obtained in the mandibular specimens and submitted to statistical evaluation by the Wilcoxon test. It was concluded that both techniques were reliable for the accomplishment of vertical linear measurements in the selected area. However, a 2.0 mm safety margin is recommended.

Use of an image-guided navigation system in dental implant surgery in anatomically complex operation sites

INTRODUCTION

Recent developments in computer assisted surgery have brought major improvements to maxillofacial surgery. Computer systems for intra-operative navigation have been introduced enabling the surgeon to locate the continually updated position of the instruments and the operation site on the patient's three-dimensional reconstructed image data set displayed on a monitor in the operating room. Complex surgical procedures can be performed according to the preoperative plan based on CT and/or MRI data minimizing surgical risks and optimizing clinical results. Nowadays computer-assisted-surgery has also proved effective in dental implantology.

AIM

The objective of this study was to compare the accuracy of conventional and computer-assisted dental implantation planning and surgery. Analyzing our early experiences, we aimed to evaluate the benefit from utilising computer assisted surgery (CAS).

PATIENTS

Five patients were treated with the aid of CAS, a total of 18 dental implants being placed. Only difficult operation sites, e.g. following bone augmentation or anatomically malformed jaws were included in this study.

METHOD

An infra-red light based navigation system (Vector Vision 2, BrainLAB, Munich, Germany) including a three-dimensional planning approach for maxillofacial surgery was used. Placement of dental implants in the maxilla included direct visualization when drilling the implant socket according to the axis previously planned on radiographs and CT scans.

RESULTS

In two cases the conventionally planned implant location had to be changed due to insufficient bone being available. With four implants, it proved possible to insert longer fixtures after the CAS system had evaluated all parameters of the surgical region. In one case a shorter implant was installed due to insufficient bone at the designated location.

CONCLUSION

The use of an image-guided navigation system provides a valuable tool in implant dentistry and proved superior to conventional implant surgery especially in difficult anatomical regions.

Positioning of dental implants using computer-aided navigation and an optical tracking system: case report and presentation of a new method

A navigation system for computer-aided surgery (Virtual Patient System, VPS) has been described in previous studies for different indications in oral and maxillofacial surgery. The aim of the system is the intraoperative transfer of preoperative planning on radiographs or CT scans on the patient, in real-time, and independent of the position of the patient's head. Until now an electromagnetic tracking system has been used for intra-operative position measurement. For placement of dental implants, the electromagnetic tracking system is not suitable since the motor of the implant drill leads to a considerable distortion of the magnetic field, thus direct visualization of drilling the implant socket was not possible. To overcome this problem, an optical tracking system which is not disturbed by conductive materials was integrated in the VPS system. The first patient operated on with this system had a posttraumatic loss of the upper incisors; three implants have been placed according to the prosthetic axis previously planned on radiographs and CT scans. The experience gained in this intervention led to the conclusion that computer-aided surgery provides a valuable tool in implant dentistry.