Anatomically planned and functionally optimal implant placement has long been a major goal of implant dentistry (Drago, 1994.; Garber & Belser, 1995). Many surgical procedures are necessary to the optimal placement of the implant. Thus, it would be of great clinical advantage for patients to have dental implants placed flapless and immediately loaded with prosthesis, delivered just after surgery. Post-operative morbidity and treatment times could be reduced significantly (Cannizzaro et al., 2008;Meloni et al., 2010). Thereby the growing interest for flapless surgery in conjunction with immediate loading of the edentulous patients has led to the development of software programs that allow treatment planning, fabrication of a surgical template, as well as the production of a prosthesis that can be secure to the patient immediately after the placement of the implants (Fuster-Torres et al., 2009).
However, the accurate diagnostic is the main factor for the treatment success. The edentulous patients generally have resorption when they loose their teeth.
The resorption can be related to bone loss and bone loss associated with the soft tissue. The type of resorption is decisive to determine the kind of fixed implant supported prosthesis. Patients who lost soft tissue and underlying supporting bone in addition to teeth may be considered to have a composite defect. To evaluate the relative amount of soft tissue deficiency, it is suggested to utilize a denture or denture set-up in wax that has been confirmed for proper tooth position, border extension, and relationship between the arcs (Bedrossian et al., 2008). So, an appropriate selection of the type of prosthesis is fundamental in the beginning of the treatment planing using implants.
There are two main objectives of computer-aided design (CAD), computer-aided machining (CAM): guided dental implant placement and restoration. The first allow the precise planning of implant positions on computed tomography scans, and the second is to generate an accurate surgical guide that permits the surgeon to place implants precisely into planned positions allowing the immediate prosthesis placement (Fuster-Torres et al., 2009).
Thus the objective of this chapter is to discuss the indications, contraindications, protocol preparation, maintenance problems and postoperative-guided in implantology.
2. Guided surgery
The use of software associated with digital images, acquired from computerized tomography, it is a new trend in dentistry. The CAD/CAM technologies associated with stereolithography provide to the professional tools to improve the planning and the rehabilitation with more security.
The use of software combined with three-dimensional images obtained by computerized tomography enables the professional to evaluate the optical density, to measure the bone thickness and, therefore, to choose the implant size and its appropriate positioning in the arch (Spin-Neto et al. 2011).
The guided surgery is a highly accurate in implantology. By this technique, the extensive amount of information obtained in a virtual planning is transferred for the surgical field by means of surgical guides manufactured in stereolithography (Parel & Triplett, 2004). Later, the advantages and limitation of the surgical guide will be discuss.
The guided surgery is indicated both for total edentulous patients (Casap et al., 2005 ;Van Steenberghe et al., 2005) as for partially edentulous patients (Fortin et al. 2003; Kupeyan et al., 2006; Marchack, 2007; Serry et al., 2007).
The guided surgery is counter-indicated for patients with reduced mouth opening that jeopardizes positioning of surgical instruments on the guide (Almeida et al., 2010).
This technique has several advantages compared to the conventional open flap surgery. These are the preservation of the vital anatomical structures, minimal invasive surgery, faster and simpler technique and leads to less discomfort to the patient after the surgery (Kupeyan et al., 2006; Van Steenberghe et al., 2005; Becker et al., 2005; Widmann et al., 2010) as well as lower risk of infection. However, due to the use of a range of sophisticated technology and specialized instrumentals, the guided surgery technique has a higher cost compared to the conventional surgery. In addition, some authors reports that the surgical guide can be unstable for completely edentulous patient mainly when only remaining soft tissue is present. (Bedrossian, 2007; Holst et al., 2004).
Before the tomography, some steps are necessary to assist the planning, as a specific clinical exam. In this session, it is important to evaluate the existing prosthesis of the patient, relationship between the arches, the dental oclusal pattern and the inter maxillary distance. An initial clinical exam is accomplished to evaluate the relationship among the arches, the oclusal pattern and the inter maxillary distance.
For the total edentulous patients, it is fabricated the total prosthesis with appropriate vertical dimension of occlusion (Figure 1). After that, the prosthesis should be duplicated to facilitate the tomography guide construction. To associate the edentulous arches to the tomographic guide at the software the radiopaque marks of barium sulfate are made in the guide near the canine or molar region (Figure 2). The relationship of the maxillary and mandibular arches is registered using condensation silicone.
The virtual planning has two steps in the computed tomography (CT): the double scanning technique of the patient (Widmann et al., 2007) with both tomographic guide in position and the CT of the guide alone to superimpose the images later in the software. During the CT the complete denture should have adequate positioning in relation to the antagonist arch and the anatomy of the soft tissues. The patient can be asked to use an adhesive to improve stabilization of the denture during the scanning (Almeida et al., 2010). Afterwards, the CT is transformed in 3D images with DICOM extension. It is necessary conversion to a planning guide software, as DentalSlice® (Bioparts, prototipagem biomédica, São Paulo, Brazil).
At this moment, the virtual planning can be made into the software by the prosthodontics and surgery professionals. They can choose the best three-dimensional position of each implant based in the quantity and quality of bone and at emergence profile of the artificial teeth represented by the image of the guide. Wherever possible, it is recommended to plan the posterior implant more distant to the anterior in order to reduce the cantilever. (Figure 3).
After the prototyping and the guide confection, the guide is tested to verify the adequate position to the edentulous area and the dental position. The guide should touch the edentulous area being passive and avoiding ischemic areas (Figure 4).
The guides should be sterilized according to the manufacturer indications.
At the moment of the surgery, the first step is the distant local anesthesia because the region can develop edema areas and prevent the guide adaptation.
Later, the guide is stabilized at the planned dental occlusion using the silicone and the retaining pins are screwed at the buccal region to stabilize the guide in the correct position (Figure 6).
Afterwards, the mucous membrane can be removed bellow the drill guide by punch (Figure 7). The perforations should respect the progressive sequence of drills with their guides corresponding to the diameter of the drill to be used (Slice-guide, Conexão Sistema de Prótese Ltda, Arujá, SP).
The sequence of drill was used with its respective guide with intermittent movement and abundant irrigation to avoid heating of the bone tissue. The speed of the drill can vary from 400 to 800 rpm, depending on the bone quality. The long length of the drill is a limitation of this technique for reduced mouth opening.
After the drill perforations, it is recommended to start the installation of the implants by the intermediary positions ones to avoid the guide displacement (Figure 8).
When the last implant is installed, all screws and the palate fixation are removed together with the guide (Figure 9).
For the placement of an immediate prosthesis, all implants should have an appropriate primary stability, in other words, an initial torque around 40N.cm.
There are two options for prosthesis confection: prosthesis fabricated before the implants installation surgery or prosthesis fabricated after the surgery.
2.3. MANUFACTURING OF THE PROSTHESIS
Prosthesis fabricated after the guided surgery:
Firstly, the impression cooping are attached to the implant and the surgical guide is positioned (Figure 10). Thereafter, the impression cooping are conected with auto polimerized resin (Pattern Resin LS; GC America, Alsip, Ill) to record the implant position (Figure 11).
Impression cooping are carried out in both arches using the same surgical guide and condensation silicone (Zetaplus/Oranwash; Zhermack, Rovigo, Italy) (Figure 12). Then, the analogs are attached to the transfer copings before dental stone pouring. In laboratorial phase, the implant superstructure and the teeth in wax are positioned on a base of light-polymerized resin on the working cast (Margonar et al., 2010a). The implant superstructure is attached to the implant to verify the passive fit (Figure 13). Later, the teeth in wax on the base of light-polymerized resin are tested on the superstructure (Sterngold ImplaMed, São Paulo, Brazil) during the same clinical session (Margonar et al., 2010a) (Figure 14).
On the second day, the immediate implant-supported fixed dentures are inserted and the occlusion is evaluated in order to favor the force distribution (Figure 15). The appropriate three-dimensional positioning of the implants was verified by panoramic radiography and computed tomography and that can preview the success of the treatment (Figure 16 and 17).
Prosthesis fabricated before the guided surgery:
Some techniques have been cited in the literature for the fabrication of prosthesis before the guided surgery. These techniques use the passive cementation. One of them uses the Nobel Biocare system. In this technique the surgical guide is used to make a master model, the abutments are selected, and then the titanium cylinders are placed onto the abutments for the bridge manufacture, that is immediately secured to the implants, installed by the guided surgery (Bedrossian et al., 2008).
Another technique is the technique of the cemented cylinder (Siirilä et al. 1988; López, 1995). In this technique the components installation in the mouth is done after the guided surgery. They are selected previously with torque from 20 to 32N.cm. It is accomplished the molding of the components for the fabrication of an index. And it is made the cementation of the cylinders inside the prosthesis in agreement with the index. Then, it is made the cementation of the prosthesis in the mouth (Siirilä et al. 1988; López, 1995).
The complications in guided surgery can be divided in early complications and late complications:
Early complications: lack of primary stability (Yong & Moy, 2008), loosening of prosthesis screw (Young & Moy, 2008), slight genial tumefaction (Gillot et al., 2010), difficulty in speech and bilateral cheek occlusion (Young & Moy, 2008), jugal hematoma (Gillot et al., 2010) and heating of tissues (Figure 18).
Margonar et al., 2010b, evaluated bone tissue heating and the wear drills after repeated osteotomies for implants, simulating the guided surgery technique and comparing it with the classical technique. According to that study, the heating of the bone tissue due to the guide surgery technique was higher when compared with the conventional open flap surgery during the preparation of the surgical site, but both techniques have not reached the threshold temperature that causes immediate necrosis.
Late complications: persistent pain (Gillot et al., 2010), gingival recession (Yong & Mo, 2008), osseointegration loss (Yong & Moy, 2008). The success rate ranges from 83 to 100% (Canizzaro et al., 2008; Komiyama et al., 2008; Schneider et al., 2009; Van Steenberghe et al., 2005).
2.4. MISTAKES IN GUIDED SURGERY
The computer-guided surgery has a sequence from the diagnostic stage to the prosthetic, and mistakes may occur in different stages. The most common mistakes found in the literature are as follows:
Inaccurate fixation of the guide resulting in displacement during perforation (Valent et al., 2009).
Mechanical errors caused by angulation of the drills during perforation that may cause lateral deviations (Valent et al., 2009).
Changed positioning of surgical instruments due to reduced mouth opening (Valent et al., 2009).
Human mistakes as not using the whole length of the drill during perforation (Valent et al., 2009).
The guided surgery is an excellent option of treatment for patients with satisfactory bone quantity for implant insertion. The guided surgery can be indicated for complete and partially edentulous arches in the maxilla and/or mandible.
When properly prescribed and monitoring, the virtual planning and the guide surgery are excellent tools used in implantology to perform surgical procedures with more safety, confort and predictability to the patient.