Treating the Edentulous Mandible: Immediately Loaded Implants

The literature has demonstrated that dental implants can be successfully used for the rehabilitation of edentulous jaws.1-3 Adell, et al1 and Bränemark et al4, after an empirical review of a large number of clinical series, proposed a stress-free waiting period of 3 to 6 months. The predictability of the original treatment protocol has led to developments aimed at simplifying the technique and reducing the healing time.5,6 Many authors, using single-stage implants, have reported favorable clinical outcomes.7-14 However, a healing period is required before the imlants can be put into use.
The resistance of some patients to the idea of wearing a removable prosthesis, and the search for simplified treatment protocols with reduced healing times, gave rise to a single-stage procedure that includes subjecting implants to loading immediately after placement. Several authors established protocols for immediate loading of implants in the rehabilitation of patients with totally edentulous mandibles. These treatments allow the patient to wear a fixed prosthesis during the osseointegration period without compromising long-term success. The protocol presented by Bränemark, et al5, involves prefabricated components and surgical guides (Bränemark Novum system). It allows the attachment of the permanent fixed prosthesis on the same day using only 3 implants.
Another protocol, also involving prefabricated components and surgical guides (Speed Master system [Conexão Sistema de Próteses]) was presented by Vasconcellos, et al.15 It involves the placement of 4 implants in the edentulous mandible with a permanent fixed prosthesis fabricated over a premanufactured titanium bar. The bar is attached to the implants on the day of implant placement.
The purpose of this article is to present a case report of a patient who was rehabilitated with a hybrid prosthesis supported by 4 immediately loaded implants provided on the day of implant placement.

CASE REPORT

Figure 1. A and C: Preoperative photographs. B and D: Preoperative models of the maxilla and mandible.

Figure 2. A diagnostic wax-up was used to clinically assess the occlusion.

A 60-year-old man presented with an edentulous mandible at the São José dos Campos School of Dentistry clinic (São Paulo State University, Brazil) complaining about the instability of his total prosthesis. An immediately loaded implant procedure was proposed for the mandibular arch using the Speed Master system. The patient was in good health and was a nonsmoker. Although some wear facets were noted on the maxillary cuspids and bicuspids, the patient did not have signs of severe bruxism.
The patient was evaluated preoperatively with respect to jaw size, bone quality/volume, jaw relations, maxillomandibular distance, and occlusion. Preoperative analysis of the anatomic conditions was performed with panoramic radiography. Impressions were made of the maxilla and mandible, and laboratory casts were fabricated. The mold and shade were selected for the prosthetic teeth to be used, and a wax trial denture was fabricated for the mandibular arch. The diagnostic wax-up was also used to clinically assess his occlusion (Figures 1 and 2). The approval of the patient was requested, especially with regard to the aesthetic aspects of the treatment.
Prior to surgery, the correct vertical dimension was registered by measuring the distance between 2 reference points marked on the patient’s face; one on the chin and the other on the nose base. One hour before the surgery he was premedicated with amoxicillin (2.0 g), dexamethasone (4 mg) and diazepam (5 mg). Local anesthesia (2% mepivacaine with 1:100,000 epinephrine) was also administered.
Surgery began with a crestal incision, from the position of the right first molar to that of the left first molar. The mandible was exposed, and the mental foramina were identified. The crestal bone in the anterior region was reduced under profuse irrigation with sterile saline solution to create a 4- to 5-mm wide bone platform to accommodate the surgical guide template (Figures 3a and 3b). Direction indicators helped to determine the final position of the template before fixation with 3 temporary screws (Figure 3c). This template had 4 orifices of gradually increasing dimensions for the insertion and removal of prefabricated drill guides during implant site preparation. The drill guides were identified by their different colors (silver for the start drill and the 2.0-mm twist drill, yellow for the 3.0-mm twist drill (Figure 3c), blue for the 3.15-mm twist drill, and purple for the 3.35-mm twist drill). Each drill was used successively, beginning with the start drill, to prepare sites for the 4 implants. The drill guide system (the template) ensured that drilling was always performed in the same position and at the same angulation. In addition to the conventional drill irrigation, frontal perforations in the template allowed profuse irrigation to compensate for the increased risk of heat generation. Implants were seated with a torque wrench to 50 Ncm. When all 4 dual acid-etched cylindric screw-shaped internal hex implants (Connect AR; [Conexão]) were in place (Figure 3d), the temporary fixation screws and the template were removed.
Abutments were connected to the implants (Conexão) with 20 Ncm torque (Figure 3e). The soft tissue was readapted around the abutments and sutured into position. Four retaining screws were used to connect a prefabricated titanium bar to the abutments. Acrylic resin (DuraLay [Reliance Dental Manufacturing Company]) was used for indexing the maxillary teeth to the titanium bar in the mandible (Figure 3f). The distance between facial-reference marks registered prior to surgery was used to establish the correct vertical dimension.

Figure 3. a: The crestal bone in the anterior region has been reduced to create a 4- to 5-mm wide bone platform to accommodate the surgical guide template. b: Surgical guide template fixed. c: Direction indicators. Yellow drill guide for the 3.0-mm twist drill. d: The last acid-etched cylindric screw-shaped internal hex implants. e: Abutments connected to the implants (20 Ncm torque). f: Four retaining screws were used to connect a prefabricated titanium bar to the abutments. Duralay acrylic resin indexes the maxillary teeth to the titanium bar in the mandible.

Figure 4. a: Final cast of the mandible fixed partial denture. b: The fixed partial denture at delivery.

The titanium screws were then removed, and impression screws were used to attach the prefabricated titanium bar to the abutments. A polyvinyl siloxane (PVS) silicone impression (Aquasil [DENTSPLY Caulk]) was taken using a custom open tray. The impression screws were loosened and the bar was gently removed inside the impression. Abutment analogs (10100; [Conexão]) were connected to the bar, and the impression was poured in stone (Durone [DENTSPLY]) to make the working cast.
Next, the maxillary cast was mounted in a semiadjustable articulator, and the mandibular cast was mounted based on the acrylic resin index. A tooth arrangement was then placed on the titanium bar. Light-cured composite resin (Versyo [Heraeus Kulzer]) was used as the denture base material to reduce laboratory time (Figure 4a). After curing, the polymerized prosthesis was finished and polished prior to delivery.
At delivery, the fixed partial denture was connected to the abutments by fastening the titanium retaining screws with the torque wrench to 20 Ncm (Figure 4b). Screw holes were closed with the same light cured composite resin used for the denture base. The necessary occlusal adjustments were made, and the marginal adaptation of the bars to the abutments was confirmed with periapical radiographs.
An antibiotic (1.5g amoxicillin/d) was prescribed for 7 days postoperatively. Dipyrone was also prescribed (as needed). The patient was instructed to use ice packs on his face during the first 24 hours following the surgery, and to rinse the mouth 4 times a day using chlorhexidine digluconate (0.12%) for 7 days. During the first month, the patient was advised to consume easily chewable food. He also received oral hygiene instructions to do at home and given a follow-up schedule.

DISCUSSION

A tendency is observed within implant dentistry to reduce treatment time. This is done to simplify procedures with the purpose of increasing patient tolerance and reducing the probability of complications16. The literature has reported the advantages of the treatment of the edentulous mandible with immediate-load implants.5,17-20 The diagnostic phase was done carefully, during which a preliminary evaluation of the desired final outcome was performed. The clinical, surgical, prosthetic, occlusal, and aesthetic aspects, as well as the patient’s expectations, were assessed before proceeding.
The protocol (utilizing the Speed Master system) for immediate placement of implants and immediate loading with customized implant-supported, nonremovable prosthesis on the same day has been demonstrated. A patient becomes a candidate for immediate loading of dental implants after his or her medical and dental history and clinical and radiographic appearance are thoroughly assessed, establishing a clear understanding of the patient’s needs and desires. The ability of the patient to withstand a minor surgical procedure as well as availability of good bone quality is important criteria. The bone quality has to be good enough to provide primary stability for the implant.
A precise fit between the implant abutment and superstructure and subsequent absence of bone stress are important factors for the long-term success of implant-supported restorations. The misfit of the prosthesis introduces a stress into the implant system with the start of problems such as the following: screw loos-ening, fracture of the prosthetic components or implants, and peri-implant bone loss. The misfit may be present many years after placement because of the ankylotic character of the osseointegration.21,22 When an im-mediate load is done, the static stresses caused by prosthetic misfit are dissipated during the first weeks of osseointegration.22 Also, the osseo-integration in immediate load can indeed be reached with a percentage of bone-to-implant contact that is similar to, or even higher than, that found with unloaded implants. This would account for the greater implant stability observed.6,22,23
The system used in this case has a rigid metallic structure to splint the implants, as recommended by some authors.5,16,17,20,23,24 Any micromovement is reduced by the metal reinforcement that provides resistance to forces in all directions, and allows osseointegration to occur safely.
Studies done by Vasconcellos, et al15 on the Speed Master system in a group of 15 edentulous mandible patients showed survival rates of 100%. On the final follow-up time, the mean marginal bone loss was 1.11 mm, and bleeding on probing was not observed. Only 6.7% of the patients reported any discomfort during treatment, and all patients would recommend the procedure to others. Studies by Branemark, et al5 reported 2% of failure rates with the Novum protocol. This might be explained by the fact that the failures in that investigation were not considered a consequence of the same-day prosthetic loading concept, but rather of excessive heat generation from wide-diameter drills used in dense bone during the drilling sequence.
In the case reported, the implants placed were numerous enough to be distributed in different segments around the arch. Four implants distributed along the arch, as proposed by the system used, can compose a polygonal sustaining base with favorable distribution of oc-clusal forces, thus maintaining the level of micromotion below the critical threshold.23,25 Also, the use of more than 3 implants allows the continued use of the prosthesis in the event of a single-implant failure.
The 4 implants in this case demonstrated good initial stability after placement, which is a basic requirement for successful immediate loading. When using the Speed Master system, conventional drill irrigation is combined with irrigation through frontal perforations in the template, allowing profuse irrigation with sterile saline solution. This compensates for the increased risk of heat generation. Also, standard-diameter implants were used in the present study (3.75), reducing the number and diameter of the drills used during the drilling sequence.
Predictable osseointegration of oral implants is important. One key factor when dealing with immediate loading is the primary implant stability. To maintain osseointegration, the secondary stability must be kept at a high level. Therefore, apart from the surgical approach, healing time intervals and implant surface characteristics, as well as a prosthetic design with proper distribution of forces among the supporting implants, are mandatory.

CONCLUSION

Immediate mandibular loading, using prefabricated components and surgical guides (Speed Master surgical and prosthetic protocol), can be a viable alternative to classic delayed-loading protocols. The edentulous mandible is rehabilitated with the permanent fixed prostheses on the same day of the implant surgery. This therapeutic approach has proven to be highly advantageous for the comfort of patients, thus increasing their treatment acceptance and overall satisfaction. Furthermore, this technique does not show any additional risk to the process of osseointegration.

References

Dr. Nishioka is a professor in the Department of Dental Materials and Prosthodontics, São José dos Campos Dental School, São Paulo University (UNESP), São José dos Campos, Brazil. He can be reached by e-mailing nishioka@fosjc.unesp.com.br.

Dr. Garcia-Júnior is a professor in the Department of Surgery and Integrated Clinic at São Paulo State University’s Araçatuba Dental School. He can be reached by e-mailing idelmo@foa.unesp.br.

Dr. Souza is a post-graduate student in the Department of Surgery and Integrated Clinic at the Araçatuba Dental School, São Paulo State University, and can be reached by e-mail at f.avilasouza@ig.com.br.

Dr. Luvizuto is a post-graduate student in the Department of Surgery and Integrated Clinic at the Araçatuba Dental School, São Paulo State University. She can be reached by e-mailing eloaluvizuto@hotmail.com.

Disclosure: The authors have no financial interest in any of the companies mentioned in this article and received no compensation for writing this article.