The use of technologies that merge computerized tomography X-ray imaging and 3-dimensional (3D) planning software allow the surgeon to digitally elaborate on the computer the position, length, and diameter of every implant to be placed. Following this approach, the placement is guided in a 3D digital model, and the implants are placed in the final position avoiding eventual anatomic structures. In this case report, the patient's remaining mandibular teeth were extracted, and the patient received 8 implants with the help of a computer surgical guide. The case was planned using SimPlant and a bone-supported guide. Because of the high precision of the planning, it was possible to realize a provisional rehabilitation before the actual surgery. The planning allows placement of parallel implants to optimize the prosthetic procedure and outcome. An immediate provisional implant was fixed with a flow composite on the temporary abutments and then refined in the dental laboratory. The patient received the provisional rehabilitation the same day of the surgery. After 6 weeks of healing, the final impression was taken and the prosthesis was finalized with a computer-aided design/computer-aided manufacturing titanium full-arch screwed framework with composite veneering. A 6-month follow-up showed good integration of the prostheses and success of all 8 implants. The use of surgical computer-guided planning changes the surgeon's approach: whereas before the use of conventional guides permitted a certain degree of offset from what was planned, the use of computer guides allows the implant to be inserted in a far more precise way. It is obvious that careful planning is the key factor to avoid implant misplacement.

Introduction

The standard surgical protocol for implant surgery comprises a diagnostic step (clinical examination and X-ray examination), a planning step (type of rehabilitation needed), and a surgical step, where the surgeon tries to implement what was planned.

The use of technologies that merge computerized tomography (CT) X-ray imaging and 3-dimensional (3D) planning softwares allows the surgeon to digitally elaborate on the computer the position, length, and diameter of every implant to be placed. Furthermore, it helps prevent damage to vital structures and helps find the most suitable sites for implant placement. The use of a custom-built surgical guide on the surgical plan defined by the surgeon allows implants to be placed in the exact position for each site, although some authors have found it not to be so precise.1,2 Following this approach, the placement is guided using a 3D digital model and the implants are placed in the final position avoiding eventual anatomic structures.36 

Furthermore, such precise planning may produce a provisional restoration before the actual surgery, thus allowing, when the surgical condition will permit it, an immediate loading protocol to be applied.7 

The following case report shows the use of a bone-supported surgical guide for open flap surgery (Surgiguide, Materialise Dental, Leuven, Belgium) for a patient needing full mandibular rehabilitation.

Clinical Report

A 79-year-old man presented with few compromised natural teeth in the lower jaw. He showed no systemic pathology and was not a smoker. He had been wearing a fixed partial denture on his natural teeth for a long time and was unhappy with the esthetics and the occasional inflammation that occurred because of difficulties in removing debris around the teeth. After careful evaluation, all remaining anterior teeth in the lower jaw appeared to be hopeless (Figures 1 and 2).

The alternative presented to the patient was the removal of all teeth in the mandible (except for a left molar), the use of a removable provisional, and the subsequent placement of implants and the load with a provisional and then a definitive fixed partial denture supported by implants. The strong request of the patient to try everything possible to avoid a provisional mobile restoration convinced the surgeon and the prosthodontist to apply a more complex treatment.

The patient was then instructed about the possibility of applying a postextractive implant placement with eventual immediate loading. Such a surgical plan was to be considered under strict computer planning to evaluate whether the patient was an ideal candidate for such a protocol. The patient was instructed that only at the end of the surgical procedure would the surgeon decide if the implants were in condition to support an immediate loading or not.

After a full mandibular cone beam CT, the digital imaging and communications in medicine (DICOM) files were converted and opened with SimPlant (Materialise Dental). Afterward it was possible to analyze the data in order to plan the surgery.

The patient showed a marked resorption in the posterior areas, allowing the insertion of 6 implants of 8 × 4.8 mm. The position of the implants was planned in a prosthetically driven approach with the help of the existing rehabilitation. Two implants placed in ideal position were found to possibly lack sufficient primary stability for an immediate loading. The information on the quality of the bone provided by the software is useful in such cases. Five postextractive implants were planned in the anterior areas, and the other 3 implants were evenly distributed in the posterior areas. The number of implants was discussed with the patient, and the risk of not being able to immediately load all implants at the same time, and convinced him that accepting more implants now would provide enough stability that more implants would not be needed later. Therefore, a total of 8 Straumann tissue level SLActive implants (6 regular neck 4.1 × 10 mm implants, 1 wide neck 4.8 × 8 mm implant, and 1 wide neck 4.8 × 6 mm implant; Straumann, Basel, Switzerland) were planned (Figures 3 through 5).

The information was sent to Materialize Dental for the construction of a stereolithographic model and a surgical guide (Figure 6). With the use of such a model it was possible to produce a provisional fixed restoration on the future implants. In particular, the stereolithographic model was articulated with the antagonist jaw, with the help of the remaining lower molar tooth. The surgical guide was seated on the model, and the drills were used to create implant sites in the model, simulating the actual surgery. Implant analogs were seated in the model and the provisional implant was created on top of temporary abutments. The surgical guide was constructed to be bone supported in order to apply an open-flap surgery to prepare for the eventual presence of thread exposure in the postextractive sites.

After removing the compromised teeth, an open-flap surgery was performed and the surgical guide was set directly on the residual alveolar bone (Figures 7 and 8). The seating of the guide was not straightforward because of the need to elevate a large vestibular and lingual flap. Minor lingual reduction of the guide was applied. Besides that, the seating was stable and only minor bone trimming was necessary in the anterior postextractive sites. Implants were inserted with the help of a specific surgical kit (Straumann Guided Surgery), and there was no need to change from what was planned (Figures 9 and 10).

In the anterior areas, minor bone defects (foretold by the software elaboration) were corrected with autogenous bone (collected with bone scrapers) and covered with Bio-Oss and Bio-Guide (Geistlich Pharma AB, Wolhusen, Switzerland). The suture was realized with a 6/0 polyamide.

Implant stability was sufficient (>35 N/cm measured with a torque spring) for 6 of the 8 implants; therefore, an immediate loading protocol was applied. Two implants were not restored immediately.

Six temporary abutments were screwed on the implants, and the prosthetic rehabilitation was fixed to the abutments with flowable composite resin (Figure 11). The holes in the provisional were pretreated with composite bonding, and after being seated on the abutments, a small amount of flowable composite was inserted in the holes to achieve a mechanical locking of the prostheses to the abutments. The vertical dimension was checked and modified properly. The provisional implant was then sent to the dental laboratory for refining and polishing. The provisional implant was set into place after 3 hours and the occlusion was checked (Figure 12).

After 6 weeks of healing, the first impression was taken. The final prosthesis was delivered 9 weeks after surgery (Figures 13 and 14).

The 6-month follow-up visit showed good integration of the implants and demonstrated good precision for the position of the planned implants in respect to the actual position (Figures 15 through 19).

Discussion

Correct diagnosis and accurate implant planning are key for success in implant rehabilitation. The use of advanced planning, for example, computer-based planning using CT scans, allows the surgeon to reduce the risk of damaging nearby structures and allows for more precise planning than use of conventional printed CT scans.8 These new techniques, although some authors have shown some skepticism about their utility, are more precise than conventional surgical guides produced by the dental laboratory on the information given by the soft-tissue contours.

Increasingly, studies confirm the high predictability of 3D planning software in regards to their ability to offer absolute precision between what is planned and what is accomplished surgically.9 The use of surgical computer-guided planning changes the surgeon's approach: whereas the use of conventional guides permitted a certain degree of offset from what was planned, the use of computer guides allows implants to be inserted in a far more precise way. It is obvious that careful planning is the key factor in order to avoid implant misplacement.1 

Summary

The use of such computer guides have several advantages: the reduced risk of damaging nearby structures, the ability to place implants more precisely in complex cases, the capacity to foretell the final results and the eventual surgical difficulties, a sensible reduction of surgery duration, better patient postoperative conditions, and the possibility of producing a provisional implant for immediate loading without having to take complete impressions. Still, the surgery must be conducted carefully by an expert surgeon who is knowledgeable about computer-aided surgical guides and has undergone several hours of training in the use of the software. The combination of a nonexpert surgeon and an error in planning could result in a clinical disaster.

Abbreviations

     
  • 3D

    3-dimensional

  •  
  • CT

    computerized tomography

  •  
  • DICOM

    digital imaging and communications in medicine

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