Computer Approach in Dental Implantology

5.3.1 Introduction

Materialise is market leader in oral implantology simulation software. Implant placement and surgery simulation packages offer increased opportunities for developing state-of-the-art techniques for minimally invasive procedures.

SimPlant® software, a software for 3D modelling and interactive 3D-based implant planning, makes it possible to create a complete planning environment from CT scanning images by reformatting of the dataset (cross-sections, panoramic image) and 3D visualization. The following crucial step in implant placement is the transfer from the preoperative plan to the surgical field. Accurate transfer of treatment planning is necessary to obtain the desired result. SurgiGuide® personalized drilling guides are designed to fit perfectly on the irregular jawbone. The irregular shape of the jawbone ensures a stable and unique positioning of the drilling guide, necessary to provide an accurate transfer of the planning.

5.3.2 Virtual 3D planning environment: SimPlant®

Although panoramic X-rays have traditionally been used to launch an implant treatment plan, many implant clinicians now realize that X-ray films are often insufficient and can even provide misleading information. A CT scan provides non-distorted data describing the patient's bone quality and quantity and hence comprehensive and accurate presurgical information.

A SimPlant®® CT study creates a complete planning environment (Figure 5.19), allowing simultaneous viewing of cross-sectional, axial, panoramic and 3D images in an interactive

Simplant Virtual Abutments

Figure 5.19 Overview SimPlant*® planning environment

Figure 5.19 Overview SimPlant*® planning environment setting. From these, plan treatment scenarios to ensure optimal implant placement can be confidently planned.

A variety of measurement and simulation tools are included to assist in establishing the plan. SimPlant® gives access to information about bone density, measurements, sinus graft volumes, bite forces and much more. Various tools are available to visualize vital structures like the alveolar nerve channel. Virtual implants can be inserted and fully evaluated. With SimPlant®®, the precise number of implants to be placed and their position, sizes and abutments will be known presurgically.

  1. 3.3 Guide to accurate implant treatment: SurgiGuide®
  2. 3.3.1 General concept of SurgiGuide®®

The SimPlant®® treatment plan is precisely conveyed to the SurgiGuide®® and ultimately to the patient's mouth at the time of surgery.

During the operation, the SurgiGuide®R is placed on the jawbone, on the mucosa or on the teeth. Owing to its precise design and intricate shape, the fit of the SurgiGuide®® will be unique and stabile (Figure 5.20).

The SurgiGuide®R guides the surgeon's drills to the planned position. With millimetric precision, the implant surgeon can prepare the osteotomies and place the implants with full certainty of the implant location.

SurgiGuides® are custom manufactured for each patient. A SurgiGuide®® set contains consecutive guides, each with guiding cylinders following the drilling sequence specified. The consecutive SurgiGuides®R fit exactly to the same position.

The production of SurgiGuides®R uses stereolithography. This technology incorporates the high accuracy needed to guarantee a unique fit on the jaw. The drill guide materials have FDA approval to be used in contact with human tissue.

Surgiguide
Figure 5.20 Schematic representation of a SurgiGuide®®

5.3.3.2 Different types of SurgiGuide® Tooth-supported SurgiGuide®

A tooth-supported SurgiGuide®® fits on the soft tissue and teeth of the patient's partially edentulous jaw. This type of guide can be used when one or a few teeth are missing.

In combination with the implant treatment plan, a plaster cast accurately representing the patient's preoperative situation is needed to create the SurgiGuide®®. This method can overcome limited distortion from scattering of artefacts which is often present owing to amalgane dental fillings or non-removable metal appliances.

Bone-supported SurgiGuide®

A bone-supported SurgiGuide®® fits on the jawbone of the patient. This type of SurgiGuide®® can be used for patients with edentulous and partially edentulous jaws.

Bone-supported SurgiGuides®® are used when there is sufficient supporting bone surface to guarantee a stable and unique position of the guide. The fabrication of this type of SurgiGuide®® requires that there is not too much residual metal (bridges, metal crowns, etc.) causing scatter artefacts on the scanner images.

During surgery, a ridge incision is made and mucoperiosteal flaps are raised to free the bone surface. The SurgiGuide®® is placed on the bone surface and guides the drill in the planned position. The raising of the mucoperiosteal flaps also enables a good visibility during operation.

Case study of a bone-supported SurgiGuide®®: the use of implant simulation in prosthetic rehabilitation of a class II maxilla

Dr Thierry Claeys - maxillofacial surgeon, Belgium - and Lth. Johan Kint(1) - prosthodontist, Belgium - work closely together as a team, combining their skills to produce the best possible surgical, aesthetical and functional results for their patient.

Their philosophy is that implant treatment should begin with the patient's prosthetic needs. After the type of prosthetic reconstruction is chosen, the appropriate number of implants is determined. Then, with the help of different imaging modalities, Dr Claeys and Lth. Kint evaluate the patient's jaw to determine the available bone quality and volume. The following case illustrates their methodology.

The patient was a 67 year old doctor whose maxilla had been totally edentulous for more than 20 years. It was the desire of the patient to have a stable and retentive prosthetic reconstruction without prior surgical intervention. To obtain the final treatment plan, the following examinations were performed:

  1. Temporary teeth set-up. The wax set-up in the articulator showed a large intermaxillary gap in the distal region. Based on this and the fact that the anatomy of the edentulous maxilla was flat with a shallow palate, they concluded that it was not possible to create a fixed prosthesis in the distal area.
  2. Medical imaging. Although the clinical examination and the panoramic radiographs showed adequate bone volume, the CT scan revealed an atrophic maxilla. Horizontal and vertical bone resorption was evident in the anterior, and the alveolar height in the posterior was also inadequate for implants.

(1) Lth. = licentiaat tandheelkunde (Dutch dentist).

Figure 5.21 Scan prosthesis

3. Implant simulation. Since the final location and angulation of the implants determine the aesthetical and functional results, it was decided that a SurgiGuide® drill guide would be required to achieve precise implant placement in a predictable fashion. Based on the temporary teeth set-up, a radiopaque CT scan appliance was made (Figure 5.21). The patient was then scanned on a CT scanner with the appliance in place. Then the CT data were processed to produce a SimPlant® study that included 2D and 3D images of the maxilla with the desired location of the teeth to be restored provided by the CT scan appliance. Dr. Claeys and Lth. Kint then used SimPlant®® software to simulate possible treatment planning solutions, choosing the most ideal treatment plan for their patient (Figure 5.22).

The SimPlant1® treatment plan was then used to produce a SurgiGuide®® (Figure 5.23) drill guide that would fit perfectly on the patient's maxillary bone, with drill guides accurately to position each implant exactly as it had been simulated in the SimPlant®® treatment plan.

The implants were quickly and easily placed using the SurgiGuide®® and the healing abutments were immediately positioned (Figure 5.24).

After an integration period of 6 months, the implants were uncovered and the prosthesis was installed. Because of the accurate placement of the implant, the prosthesis could be created with the normal prosthetic lab techniques. Dr Claeys and Lth. Kint use SurgiGuides® when:

  • accurate and predictable location and angulation of multiple implants are required;
  • adequate bone volume is doubtful.
Figure 5.22 SimPlant1® treatment plan
Figure 5.23 Jaw model with a SurgiGuide®
Figure 5.24 Surgery outcome

Dr Claeys and Lth. Kint concluded that, when using a SurgiGuide®®, based on a computer-based treatment plan, the placing of the implants is more accurate and predictable and the surgery is simpler.

DrTh. Claeys, maxillofacial surgeon, St ElisabethZiekenhuis,Zottegem, andDr J. Kint, prosthodontist - dental treatment under general anaesthesia, St Elisabeth Ziekenhuis, Zottegem Published in DentistNews, Volume 6, September 2002 (Apollonia cv, Ieper, Belgium).

Mucosa-supported SurgiGuide®

A mucosa-supported SurgiGuide®® is a custom-manufactured drill guide made for a unique and stable fit on the soft tissue of the patient's jaw. This type of SurgiGuide®® can be used for patients with edentulous jaws. A scan of the patient together with a scan prosthesis is obligatory. This also visualizes clearly the desired tooth set-up in the CT images for improved implant planning.

During surgery, the SurgiGuide®®, placed on the soft tissue in the unique and stable position for which it was created, guides the drill in the planned position. This technique leads to minimal invasive surgery.

Case study of a mucosa-supported SurgiGuide®®: immediate loading of mandibular implants in a case with bleeding tendency using the mucosal-supported SurgiGuides® The current trend in implant dentistry is to provide the patients with immediate function with dental implants. In order to do this, we have to prepare the patients for precision surgery.

Figure 5.25 Scan prosthesis

With the development of computer-guided implantology, the preparation work for immediate loading of dental implants is simplified.

The following case report illustrates the extra benefit for a patient with bleeding tendency to receive immediate loading of the mandibular implants using the mucosal-supported SurgiGuides®R.

The patient, a 62 year old lady, was known to have cardiac arrhythmia. She had undergone pacemaker implantation and was currently on anticoagulant therapy. She was wearing complete upper and lower dentures for her edentulism. However, she was suffering from pain and inadequate masticatory function owing to the instability of her lower denture.

Considering her medical condition, we decided to perform flapless surgery for implant placement in her mandible and to provide her with a fixed provisional prosthesis for immediate loading (the Hong Kong bridge protocol).

For the preparation, a duplicate of her lower denture had been made with BaSO4 and it was used as the radiographic stent during CT scan investigation (Figure 5.25). The CT scan data were converted to computer images and then virtual model surgery was carried out accordingly (Figure 5.26). A series of mucosal-supported SurgiGuides® was produced, and subsequently a provisional prosthesis (Hong Kong bridge) was fabricated with respect to the model surgery (Figure 5.27).

On 12 September, 2002, the patient underwent the implant surgery under intravenous sedation with Midazolam. Two Replace Select Tapered®R and two Replace Select Straight®R implants with TiUnite® surface were placed in the interforaminal region of the anterior mandible without raising a muco-periosteal flap (Figure 5.28). Immediately, the final abutments were connected and the provisional prosthesis was converted to a screw-retained fixed prosthesis by bonding to the temporary cylinders with cold-cured acrylics (Figures 5.29 and 5.30).

Figure 5.26 SimPlant® treatment plan
Figure 5.27 SurgiGuide®
Figure 5.28 Surgery with SurgiGuide®®
Figure 5.29 Provisional prosthesis
Figure 5.30 Provisional prosthesis

Postoperative recovery was uneventful and the patient was ready for the making of the final prosthesis.

Dr J. Chow Kwok Fai, oral and maxillofacial surgeon (private practice), Honorary Assistant Professor in Oral and Maxillofacial Surgery, The University of Hong Kong, pioneer in Asia for immediate loading for dental implants.

SurgiGuide® for special implants

This type of SurgiGuide®® (Figure 5.31) is a custom-manufactured drill guide used for placement of special implants, like zygoma implants. Both bone-supported and mucosa-supported SurgiGuides® for special implants can be manufactured. A good positioning and small angle deviation of these types of implant is extremely important. The preoperative planning is translated to the surgery by the use of a SurgiGuide®®, obtaining the best possible results for implant placement.

A model with coloured planned implants will be delivered together with the SurgiGuide®®. In this way, the surgeon can check and verify the planning and the fit of the SurgiGuide®®.

Rapid Prototyping Implants
Figure 5.31 SurgiGuide®® for special implants

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