Complex implant-supported rehabilitation from the temporary to the definitive restoration
Over the past two decades, the indication range for osseointegrated oral implants has been significantly extended. This is due to progress made concerning the macro design and microstructure of implants, improved surgical protocols, and the introduction of new techniques and materials for efficient augmentation. As a consequence, implant-retained restorations have emerged as a standard treatment option.2,3,36,56,63,93 In many cases, however, patients suffer from a significant loss of hard and soft tissue, which may occur due to periodontitis, chronic periapical infection, ill-fitting dentures or trauma.29 In spite of more recent concepts that involve, for example, short or narrow implants to avoid augmentation,6,31,58 implant placement into existing bone without the preceding treatment of hard and soft tissue defects can be regarded as problematic.83,85 The requirement to restore deficient tissue is also based on the concept of restorative-driven implant placement, which has become the treatment gold standard.13,19,34,57
The contour of the alveolar ridge can be reestablished using an array of methods, including sinus floor augmentation, horizontal and vertical augmentation with bone blocks or guided bone regeneration, distraction osteogenesis, and ridge expansion techniques.4,7,18,22,49-51,53,54, 59,65,75,78,80-82,84 The concept of three-dimensional (3D) alveolar ridge reconstruction with the aid of thin cortical intraoral bone grafts and autogenous cancellous bone has been described in Chapter 4.
7.2 Specific aspects of temporary restorations
Undisturbed ossification of the augmented area is critical for the success of horizontal and vertical augmentation.53 The area must not be loaded by the temporary restoration, as loading would inevitably lead to resorption or loss of the graft.53 This, in turn, would result in an inadequate bone volume for implant placement, which finally may affect the functional and esthetic restorative outcome. During the first phase of osseointegration, loading of the implants with mucosa-supported provisional restorations should also be avoided as this could lead to the loss of osseointegration.77 Therefore, mucosa-supported provisionals are contraindicated in connection with complex augmentation (Fig 7-1a) and implant restorative procedures.53
The avoidance of a temporary denture affects patients both functionally and esthetically, considering that the period from initial surgery to final soft tissue shaping can extend over an entire year.52 As edentulousness is generally not accepted in the professional and private environment of most patients today, even for a short period, many patients still refuse implant treatment, thus denying themselves oral rehabilitation. If certain criteria are met, the insertion of a removable temporary prosthesis may be an option. However, this may also involve a certain postoperative period without restoration, the need to reline the denture with soft silicone, the inherent risk of microbial contamination and subsequent infection of the augmented area, and esthetically problematic retentive clamps.15
Since Ledermann’s investigations in the 1970s, high success rates have been demonstrated for immediate functional loading of splinted implants.11,61 More recent developments concerning implant macro-design and microsurface structure have extended the indication range for immediate or early functional loading.92,113 Implants, alone or in combination with natural teeth, can be used for the quadrangular support of an immediately loaded labside provisional.20,30,52,77–79,86,92,108 In this way, patients in need of a complex rehabilitation, including augmentation, will benefit from a functional and esthetic provisional over the entire treatment period. However, to prevent excessive micro motion and ensure osseointegration, all implants should be rigidly splinted.43,46,100,101,113
Since the 1990s, one-piece screw-type conical implants have been reported as an option for the support of temporary restorations.12 Immediately loaded transitional implants, including so-called needle implants, have demonstrated good survival rates in a number of studies.11,12,20,21,23,26,38,52,86,90,92,96,100,107 Hybrid splinting of teeth and transitional implants has also been considered.27 By definition, these implants have to be removed before the final restoration is placed (Fig 7-1a to h).
Alternatively, permanent narrow-diameter implants can be used for immediately loaded provisionals. After successful osseointegration, these implants can be included into the final implant-retained restoration. This approach has likewise demonstrated good results.5,22,24,33,104,110
Long-term provisionals can be modified in the course of treatment. For this reason, they are an excellent tool to meet patients’ esthetic preferences, which may change over time.12,108 Apart from providing pure function, long-term provisionals include all the relevant information relating to the final restoration. These provisionals can be used as a test for the augmentation of the reduced vertical dimension in cases of severe abrasion of the remaining teeth.
In cases where the temporary restoration fulfills patients’ desires from the esthetic and comfort points of view, they can also serve for the planning of the definitive restoration. In this sense, a duplicate of the provisional may be used as an optimal drilling template.25 Finally, long-term provisionals have proven to be a helpful tool to shape the emergence profile in the final soft tissue surgical phase.108,114
Clinical indications for labside long-term provisionals supported by transitional implants include:
The phase of the final prosthetic rehabilitation begins after the successful osseointegration of all implants in the augmented areas. The concept developed by Khoury involves loading of implants in the augmented areas after only 3 to 4 months.48,50,54 For a successful outcome and for long-term implant survival, the final restorative procedure must be safe and reliable. In this context, the passive fit of the suprastructure is a basic requirement. An adequate method was defined by Pape and coworkers in the 1990s.76 Transitional implants must be able to support the long-term provisional until the final restoration is placed. The following section presents in detail the restorative concept of the authors for complex cases where multiple and different bone augmentation procedures were necessary. With a minimal number of sessions, this concept offers maximum patient comfort and high predictability, with functionally and esthetically satisfactory implant-supported provisionals over the entire treatment period.
7.3 Treatment planning
Successful implant-retained restorations depend mainly on strategic treatment planning, which is based on comprehensive diagnostics.13,94,95 Before the onset of extensive treatment, it should be established whether the patient would prefer a removable denture with partial palatal coverage or a removable bridge without palatal coverage. Most patients prefer a fixed implant-retained bridge, even in cases with a high atrophic maxilla or mandible. In order to provide comprehensive advice, clinicians should overlook the possibilities and limitations of current surgical and prosthodontic concepts.
Concerning imaging modalities, conventional panoramic radiography, lateral cephalography, and dental radiographs are usually sufficient to evaluate potential abutment teeth. The use of CBCT should be left for the augmentation planning, after the cleaning and extraction therapy.
In some complex cases, facial analysis by means of profile and frontal photographs will improve strategic treatment planning. On the basis of these images, patients can be informed about potential tissue deficiencies that will have an impact on the restoration type (e.g. fixed versus removable). In terms of esthetics, the smile line is a critical parameter.95 In patients with a low smile (lip) line, i.e. when this line is on the level of the incisal edges, esthetic requirements will be easier to handle than in patients with a high smile line. In the latter case, optimal esthetic results should be the treatment goal, which implies significantly higher diagnostic and therapeutic effort.
To detect craniomandibular disorders, temporomandibular joint (TMJ) function should be thoroughly evaluated before starting the surgical treatment in complex restorations. Important information can be acquired from centric check-bites, arbitrary registration of the TMJ position, and study models mounted in a semi-adjustable articulator. With the help of these diagnostic devices, the dental technician can prepare a wax-up. This is important for the final details of the long-term provisional, especially when a fixed restoration is planned in the maxilla. The wax-up or diagnostic tooth arrangement helps the patient to participate in the restoration planning and therefore represents an important informational basis for the entire treatment.
Besides functional and tooth-related factors such as caries and endodontic problems, the periodontal prognosis of all remaining teeth should be carefully evaluated; their prognosis can, for example, be categorized as good, unreliable or hopeless. Teeth with a good prognosis can be included in the long-term provisional and the final restoration, and those with an unreliable prognosis might serve as transitional abutments during the temporary phase (Fig 7-2a to d). Teeth suffering from severe periodontal disease and important loss of periodontal attachment are categorized as hopeless and should be removed at the beginning of treatment. Whenever possible, natural teeth with a good prognosis should be retained in order to provide patients with some degree of proprioceptive control. As a rule, all decisions concerning retention or extraction of teeth should be based on the available literature28,37,41,42,44,64,66–69,97–99 as well as the clinician’s own judgment and expertise.
On the basis of all diagnostic information, including the results of study model analysis, the patient should receive comprehensive guidance concerning the envisioned treatment and options for the final restoration.
Cases where patients are to receive a fixed long-term provisional on the basis of the final design of the definitive restoration need very precise planning. Ideally, provisionals should have a quadrangular support. For this purpose, the provisional can be retained exclusively on the teeth, on the teeth and implants, or exclusively on the implants (Fig 7-3a to c). After removing teeth with a hopeless prognosis during the initial treatment phase, potential abutment teeth can be categorized as follows (see Chapters 2 and 4):
The types and positions of implants used to support the provisional should be planned with care. In very narrow alveolar ridges, one-piece transitional implants with a small diameter (1.5 to 2 mm) are indicated (Fig 7-4a to p). The ideal positions of the transitional implants in an edentulous jaw are the lateral incisor and first premolar. In this situation, it is possible to prepare a temporary restoration that fills the esthetic window from the right second premolar to the left second premolar. At the same time, it is possible to later insert implants in the canine area, which is an important key for the definitive restoration. Basically, one- or two-piece conical transitional implants can be used. As they quickly lose their congruity with the implant bed upon unscrewing, these implants are easy to remove (Fig 7-5a to t). Transitional implants are composed of an implant body with bone-compressive properties and a transmucosal conical head, which serves as a retentive element for the provisional.
As far as immediate loading supporting temporary restorations is concerned, permanent implants with a reduced diameter (3.0 to 3.4 mm) have demonstrated good results in the context of complex augmentation procedures. If successfully osseointegrated, they can also be included in the final restoration (see Fig 7-2a to d). However, depending on the final restorative concept, these implants may have to be removed at a later stage if they were not placed at the esthetically desired position. The use of a surgical guide from the beginning will prevent such inconvenience. Adhesive bridges are another temporary option after complex augmentation procedures. These restorations are retained by natural teeth, either in combination with implants or not (Fig 7-6a to l). The simplest type of provisional is a thermoformed splint with resin teeth (Fig 7-7). This option, however, results in significantly reduced comfort for the patient and a disturbance of the occlusion if used for a long time.
Interim implants are conical titanium compression screws with a rough surface and a coronal diameter between 2.0 and 3.0 mm. They have a transgingival design and are available as one- or two-piece implants. A benefit of two-piece implants (e.g. Tempion interim implant; GZG, Cologne, Germany) is the possibility of removing the abutment for surgical or restorative reasons, especially during the preparation of the final restoration (Fig 7-8a to g). Unfortunately, this implant is not delivered anymore since the company stopped producing them. As an alternative, a new temporary implant (Medical Instinct, Bovenden, Germany) was developed in the last 5 years with the aim of fulfilling the need to support functional and esthetic temporary restorations, especially in very complex situations. The new two-piece implant system is available in two lengths (10 and 12 mm) and offers additional straight or angulated abutments to allow for all types of prosthetic restorations, including for extreme and difficult situations (Fig 7-9a to u).
In cases where natural teeth are still present, a decision has to be taken regarding which teeth can be retained temporarily to support the fixed restoration. In every quadrant, two abutments are needed to support a resin-fused-to-metal restoration, closing the esthetic window and extending from the second premolars on both sides. In cases where no adequate natural teeth are present to support the temporary bridge, interim implants (minimum insertion torque 35 Ncm) can be inserted in strategic positions to support the restoration. However, during the extraction of hopeless teeth with significant bone loss, it is often very difficult to find sufficient bone into which the interim implants can be inserted in the ideal position. Therefore, some compromises must be made in order for the patient to have a fixed restoration during the healing period.
As interim implants have a conical shape with a coronal diameter between 2.0 and 3.0 mm, they can be inserted in the interdental septa or in the lingual/palatal bone of the socket. Following the extraction of the teeth and insertion of the interim implants, impressions are made with silicone-based material. The patient receives a chairside short-term temporary restoration, which is retained by the remaining teeth and the interim implants (see Fig 7-9l). One day later, the functional parameters of the long-term temporary restoration are recorded, and an esthetic setup is made. The metal-reinforced resin restoration can then be finished by the laboratory within 24 h. The main surgery with bone grafting and implant placement is usually carried out 6 to 8 weeks after this first step.
In edentulous patients with severe bone atrophy, the interim implants are inserted during the main surgery, together with the bone grafting procedure. After exposure of the bone, the interim implants are placed into the locally atrophied bone with a high torque. After the insertion of all the interim implants, the bone grafting procedure is performed with screw fixation of the bone blocks in the adequate position. Perforations of the vestibular flap are carried out to stabilize the flap over the grafted area through the abutment of the provisional implants (Fig 7-10a to f). In the mandible, the augmentation or implant procedure is carried out in combination with a vestibular incision based on Kazanjian’s method.13 Also in this situation, the flap is perforated, allowing stabilization through the temporary implants.
An impression of the interim implants is performed at the end of the surgery. One day later, the maxillomandibular relationship is recorded and the esthetic try-in carried out. As a rule, the fixed temporary reconstruction is cemented or screw-retained onto the interim implants 2 to 3 days postoperatively.