Abstract

Computer-assisted surgery is based on computerized tomography (CT) scan technology to plan the placement of dental implants and a computer-aided design/computer-aided manufacturing (CAD-CAM) technology to create a custom surgical template. It provides guidance for insertion implants after analysis of existing alveolar bone and planning of implant position, which can be immediately loaded, therefore achieving esthetic and functional results in a surgical stage. The absence of guidelines to treat dentulous areas is often due to a lack of computer-assisted surgery. The authors have attempted to use this surgical methodology to replace residual teeth with an immediate implantoprosthetic restoration. The aim of this case report is to show the possibility of treating a dentulous patient by applying a computer-assisted surgical protocol associated with the use of a double surgical template: one before extraction and a second one after extraction of selected teeth.

Introduction

To achieve osseointegration of dental implants, the Branemark surgical protocol recommended that dental implant placement occur after a 6- to 9-month healing period from the time of tooth extraction.1 

Transient edentulism can be a serious problem for many patients because it reduces the quality of life by compromising esthetics, speech, and mastication.2 In an effort to decrease anxiety and discomfort, the one solution is immediate loading. The scientific-based evidence for successful postextraction implant immediate loading is well documented.38 

Advantages of postextraction immediately loaded implants are the reduction of alveolar resorption, decreased timing for prosthetic finalization, reduced number of surgical phases, reduced postoperative prosthesis mobility, increased patient satisfaction, and improved patient compliance.911 

The computer-assisted surgery methodology permits perioperative evaluation, therefore, achieving a faster and safer solution for more complex clinical cases.12,13 

Predictable results can be accomplished because the computer software analyzes implant position and angulation prior to the surgical procedure.14 Immediate loading of a cross-arch 4-implant-supported prosthesis can achieve multiple implant prosthetic steps in a single stage, therefore transforming from edentulous to dentulous immediately.15 Unfortunately, there are no guidelines addressing immediately loaded prosthetic rehabilitation for postextractive implants using computer-assisted technology.

This report describes a clinical case using a somewhat different protocol than the conventional one. Four postextractive implants are positioned and immediately loaded using 2 surgical templates. Immediate rehabilitation is achieved and transient edentulism avoided, with good esthetic and functional results.

Materials and Methods

In November 2007, a 44-year-old woman was referred to the Dentistry and Maxillofacial Surgery Clinic at the University of Verona for dental restoration. Clinical and radiographic examinations revealed the need to extract 6 anterior mandibular teeth because of multiple endoperiodontal and carious lesions (Figures 1 and 2).

Figure 1

Figure 1. Preoperative orthpantomography.

Figure 2. Preoperative oral condition.

Figure 3. Three-dimensional software elaboration of mandible.

Figure 1

Figure 1. Preoperative orthpantomography.

Figure 2. Preoperative oral condition.

Figure 3. Three-dimensional software elaboration of mandible.

Since time was a factor for the patient, she required immediate restoration and refused a removable prosthesis. The clinical challenge was to achieve tooth extraction, implant insertion, and immediate provisionalization in only 1 surgical stage. A prefabricated prosthesis can be created in the dental laboratory before surgical procedures if implant position and angulation are clearly pre-established.

It was decided to use a computer-assisted surgical system (NobelGuide, Nobel Biocare AB, Göteborg, Sweden) to meet the patient's expectations. A surgical protocol was arranged: planning, placement of implants, and creation of a surgical template according to 3-dimensional (3D) image data.

The patient presented with no contraindications to the surgical procedure. The inclusion criteria were presence of adequate width of the keratinized gingiva or mucosa to permit a hermetic and resistant suture of the flap and optimal healing, plus a 50-mm mouth opening, which would ensure that the upper teeth would not interfere with the bur position during implant placement.

Preoperatively, an impression was obtained with silicone (Impregum Penta Soft 3M ESPE, Milan, Italy) to obtain the cast. A radiographic guide was constructed with acrylic resin (Eco-Acryl, Foresta-Dental, Zeist, NL) including 12 gutta-percha (Hygienic, Coltène/Whaledent Inc, Mahwah, NJ) markers positioned in different sites. An occlusal index was not fabricated because residual teeth constituted a sufficient reference basis.

Following evaluation of the guide stability, a computerized tomography (CT) scan including guide positioning was obtained. Consecutively, another CT scan of the guide alone was performed.

The CT scan data were formatted using planning software (NobelGuide, Nobel Biocare AB, Göteborg, Sweden) to create a 3D image of the maxillary area and the radiological guide, following the NobelGuide protocol (Figures 3 and 4).

Figure 4 and 5

Figure 4. A software elaboration with the first and second surgical template.

Figure 5. First and second surgical template.

Figure 4 and 5

Figure 4. A software elaboration with the first and second surgical template.

Figure 5. First and second surgical template.

During 3D image analysis, the central incisors were disregarded; therefore, an ideal space for the first implant (MK III TiU, Nobel Biocare, AB) could be attained. This was necessary to transfer from the first surgical template to the second one. Likewise, other residual teeth were also ignored to obtain proper space for the second surgical template necessary for the placement of the other 3 implants (MK III TiU, Nobel Biocare, AB).

The implant insertion was achieved with the use of 2 surgical templates: the first template was necessary for the placement of the first implant. The first implant was positioned using references of residual teeth and 3 anchor pins (Nobel Biocare, AB). The second template was necessary for the placement of the other 3 implants. This second template uses the first implant and 3 anchor pins as references, following tooth extraction. All 4 implants were planned in suitable prosthetic locations.

The CT scan data were sent to the Procera workstation and used to create the 2 surgical templates and a provisional prosthesis through computer-aided design/computer-aided manufacturing (CAD-CAM) technology (Figure 5). The first template contains 1 sleeve for the first implant and 3 other sleeves for the anchor pins. The second template contains 4 sleeves for all implants and 3 other sleeves for the anchor pins. The provisional prosthesis was prepared to adapt to the 4 implants planned.

Local anesthesia with mepivacain 3% and adrenaline 1∶100 000 (Mepivacain, Monico S.p.a., Venezia, Italy) was administered, and disinfection with chlorhexidine (Corsodyl, Glaxosmithkline, Milano, Italy) was performed followed by the removal of the previous prosthesis and remaining teeth.

The first surgical template guide was positioned and stabilized by anchor pins and the residual teeth. The initial implant site was prepared followed by implant insertion (Figure 6).

Figure 6–10

Figure 6. First implant inserted.

Figure 7. Atraumatic extraction of residual teeth.

Figure 8. Other implant inserted.

Figure 9. One-year control orthopantomography.

Figure 10. Postoperative oral condition.

Figure 6–10

Figure 6. First implant inserted.

Figure 7. Atraumatic extraction of residual teeth.

Figure 8. Other implant inserted.

Figure 9. One-year control orthopantomography.

Figure 10. Postoperative oral condition.

The first template was then removed, and the selected teeth in the mandible were extracted in an atraumatic manner; the alveolar sockets were curetted and irrigated.

A limited crestal flap was performed to expose the alveolar ridge, which was flattened and stretched (Figure 7). This aided implant positioning and soft-tissue healing.

After placing and stabilizing the second surgical template through the first implant and the anchor pins, the remaining implant sites were prepared to allow the insertion of the 3 implants (Figure 8).

The mounts were removed and the abutments (Multi-unit Abutment, Nobel Biocare, AB) positioned on all 4 implants.

The provisional prosthesis was placed and fixed immediately (Figure 9), therefore achieving immediate function. Eventually, the discrepancy between prosthesis and implants may be corrected through an acrylic resin (Paladur Heraeus Kulzer GmbH, Hanau, Germany) rebase procedure.

The patient was included in a maintenance program to maintain optimal hard- and soft-tissue healing (Figure 10).

Results

This case report indicates that computer-assisted surgery can be applied to patients who are in need of rehabilitation of dentulous areas. The procedures described by the authors represent a possible guideline for combining 3D planning and immediate loading of implants. The choice of computer-assisted surgery offers advantages for evaluating and effectively treating complex clinical cases.

Discussion

A computer-assisted surgical system allows for correct positioning and placement of dental implants, abutments, and provisional prostheses in a single stage.16 

The computer software offers numerous advantages in the implant-prosthetic rehabilitation for totally or partially edentulous patients. These advantages include visualization of anatomic structures, evaluation of implant position and angulation for evaluating accuracy of implant insertion, and realization of prefabricated prostheses.17 Thus, computer-assisted technology permits accurate insertion of dental implants after analysis of alveolar bone. It does this by allowing proper planning of implant position and by using the entire residual alveolar bone, which aids in implant osseointegration.18 

This does not preclude the need to respect all guidelines of immediate loading, thereby avoiding the risk of osseointegration failure.19 

In this technique, the high-dose radiation exposure patients must undergo during CT scan is a matter of concern. The effective dose was assessed during CT used for dental implants.20,21 

The American Academy of Oral and Maxillofacial Radiology and the European Association for Osseointegration have recommendations for the cross-sectional imaging for patients receiving implants.22,23 Clark et al24 demonstrated that CT scan technology delivers a greater absorbed radiation dose than linear tomography, panoramic radiographs, or intraoral radiographs.

Moreover, we have to recognize that newer CT scan systems have been developed: spiral/helical-type scanners,25 multislice scanners,26 tuned aperture CT,27 and cone-beam/digital volume CT technology.25 The latter technologies have incorporated many advantages, especially very low radiation doses.2830 

A literature review reveals several computer-assisted surgery-related scientific articles.12,1618,31 However, few deal with surgical templates in postextractive sites,32,33 and none have been published concerning computer-assisted surgery for immediate-load dental implants with the use of a surgical template in postextractive sites.

The treatment outlined in this case report is an important deviation from previous protocols because it provides a protocol for the use of computer-assisted surgery in patients requiring prosthetics following tooth removal and providing immediate-loaded dental implants.

By ignoring teeth subject to extraction, the computer software permits the clinician to observe the hard tissue on the CT scan image and to arrange the implants 3 mm under the cement-enamel junction of the existing teeth destined for extraction. It permits the operator to decide the location of the implants and to define the suitable prosthetic position for the postextractive implants.

It is possible to create 2 surgical templates: before and after tooth extraction, respectively, as previously described. The double surgical template is extremely important for maintaining the correlation between CT scan and reality. With previous methods following tooth extraction, the surgical template reference points would vanish, whereas with this technique, the first implant and 3 anchor pins inserted before tooth extraction permit new reference points and subsequent implant insertion.

The use of the double template created with CAD-CAM technology allows an accurate insertion and the immediate prefabricated prosthetic provisionalization. It also allows the clinician to avoid the necessity of an intraoperative impression for provisional prosthetic restoration.

Ignored teeth and projecting surgical templates requires more protracted training times and is more difficult to elaborate data than with the original NobelGuide protocol. However, ignoring teeth and the greater time spent during the analysis and planning phases is an obstacle that is compensated for by the easy implant placement and prosthetic steps.

By carefully reproducing initial oral conditions, the clinician increases the patient's compliance and comfort. Undesirable phonetic, esthetic, or neuromuscular disorders are avoided.16,18,34 

This technique combines the advantages of immediate-load postextractive implants and those of flapless surgery. These advantages include preservation of alveolar height and width, reducing patient discomfort and distress.11,35,36 Furthermore, this technique presents cost-effective advantages for the patient compared with multiple-step techniques because it reduces the number of surgical and prosthetic phases.16 

Conclusion

In this case report, 4 immediately loaded implants were inserted in 1 patient; during the 12-month follow-up, no failure was observed, resulting in a 100% survival rate. No technical complication such as screw loosening, resin fracture, oral abscess, or neurological deficit was registered. The patient did not report any persistent pain or excessive swelling; therefore, the patient's quality of life was not altered during the postoperative recovery.

This surgical and prosthetic rehabilitation enabled the clinician to obtain an acceptable esthetic outcome. Additional clinical cases are required to evaluate dental implant and prosthesis survival rates to confirm the clinical effectiveness of this protocol. Prospective studies would confirm the clinical predictability and reproducibility of this technique.

Abbreviations

     
  • 3D

    3-dimensional

  •  
  • CAD-CAM

    computer-aided design/computer-aided manufacturing

  •  
  • CT

    computerized tomography

Note

The authors have no financial interest in any company or any of the above-mentioned products.

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Author notes

1

Department of Maxillofacial Surgery and Dentistry, Faculty of Medicine, University of Verona, Verona, Italy.

2

Department of Oral Surgery and Dentistry, University of Milan, Milan, Italy.

3

Department of Dentistry, University of Padova, Padova, Italy.