|Year : 2015 | Volume
| Issue : 1 | Page : 41-45
Prosthetic rehabilitation of a traumatic mandibular defect using alveolar distraction and an implant-supported hybrid prosthesis: A clinical report
Sohil Rajkumar Daswani1, Meena A Aras1, Vikas Dhupar2, Sanket Gavhane2
1 Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa, India
2 Department of Oral and Maxillofacial Surgery, Goa Dental College and Hospital, Bambolim, Goa, India
|Date of Web Publication||12-Aug-2015|
Sohil Rajkumar Daswani
Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Prosthetic rehabilitation of edentulous sites with concomitant alveolar deficiency is always an esthetic and functional challenge. In the current case, the advantages of distraction osteogenesis and hybrid prosthesis with a cast metal framework were used to restore esthetics and function. The surgical elegance of distraction osteogenesis combined with the variety of features of hybrid prosthesis ensured successful rehabilitation, patient comfort and ease of maintenance. This case report highlights the need for meticulous preoperative planning and selection of the right options, both surgical and prosthetic to effectively restore complex oral defects using implants. Traumatic defects are mostly accompanied by hard and soft tissue loss. This report describes the surgical and prosthetic treatment of a patient with a traumatic mandibular defect. The trauma resulted in the loss of numerous mandibular teeth and extensive loss of bone particularly in the anterior mandible. In order to restore the lost hard and soft tissues, the treatment plan comprised of alveolar distraction osteogenesis in the anterior mandible followed by an implant supported screw-retained FP-3 prosthesis. This article also describes a technique to ensure a passive well-fitting cast metal framework for the fixed removable screw-retained hybrid prosthesis.
Clinical Relevance to Interdisciplinary Dentistry
- Placement of implants in compromised edentulous ridges often results in a compromised final prosthetic outcome.
- This case report describes an interdisciplinary approach to manage hard and soft tissue ridge defects using alveolar distraction osteogenesis, followed by implant placement and prosthetic rehabilitation using a hybrid denture. The integration of the faculties of prosthodontics, oral and maxillofacial surgery, and oral and maxillofacial radiology was the key factor that determined the successful completion of this complex and technically demanding case.
Keywords: Alveolar distraction, hybrid prosthesis, resorbed ridge
|How to cite this article:|
Daswani SR, Aras MA, Dhupar V, Gavhane S. Prosthetic rehabilitation of a traumatic mandibular defect using alveolar distraction and an implant-supported hybrid prosthesis: A clinical report. J Interdiscip Dentistry 2015;5:41-5
|How to cite this URL:|
Daswani SR, Aras MA, Dhupar V, Gavhane S. Prosthetic rehabilitation of a traumatic mandibular defect using alveolar distraction and an implant-supported hybrid prosthesis: A clinical report. J Interdiscip Dentistry [serial online] 2015 [cited 2019 Dec 12];5:41-5. Available from: http://www.jidonline.com/text.asp?2015/5/1/41/162744
| Introduction|| |
While rehabilitating ridge defects with oral implants, an important aspect to be considered is the distribution of masticatory loads and the final esthetic outcome. This is largely dependent on the number, size, and position of the implants.  In many cases, the patients residual alveolar bone quantity and quality hinders the optimal placement of dental implants.
Insufficient alveolar height often means that the crown-height to implant length ratio is too large  which results in unfavorable loading of the implants.
Distraction osteogenesis has been used in the treatment of vertical resorption of edentulous areas, to allow the installation of osseointegrated implants, with predictable results. ,
Distraction osteogenesis of the edentulous alveolar ridges may be considered an alternative to many other surgical techniques, such as alloplastic graft augmentation, autogenous onlay bone grafting, and guided bone regeneration. 
The advantages of alveolar distraction osteogenesis (ADO) include attainment of larger augmentations and formation of mucoperiosteum and gingiva without requiring the patient to undergo donor site surgery. 
A hybrid denture is fabricated over a metal framework and retained by screws threaded into the implant abutments. This kind of prosthesis is particularly indicated in situations where the prosthesis is expected to restore extensive defects of both hard and soft tissue nature. 
The importance of precision of fit for implant restorations has been reported by several authors. ,, Framework misfits cause excessive stresses to the implants and the surrounding bone.  Screw-retained implant prosthesis frameworks cast by dental alloys involve certain risks such as distortion and stress from heating and cooling during the lost-wax technique. , This article describes a technique to overcome the problem of casting shrinkage and helps to achieve a passive well-fitting framework.
| Case report|| |
A 32-year-old male reported to the Department of Prosthodontics, Goa Dental College and Hospital with a chief complaint of missing teeth. The patient gave a history of a motor vehicular accident that resulted in the loss of the majority of his mandibular teeth. Clinical examination revealed extensive hard and soft tissue defects, particularly in the anterior mandible [Figure 1]. After a detailed examination and thorough diagnosis of the condition, a treatment plan comprising of ADO in the anterior mandible followed by implant supported hybrid prosthesis was finalized.
Alveolar distraction osteogenesis
The patient underwent surgery under local anesthesia to incorporate the distractor in the anterior mandible based on the following sequence: A midcrestal incision and two vertical releasing incisions were initially given to raise a mucoperiosteal flap and expose the buccal alveolar ridge. A piezosurgical saw was then used to perform one horizontal and two vertical osteotomies (Resista; Omenga, Italy) [Figure 2]; the lingual periosteum was left untouched to ensure proper vascularization. The osteotomized segment (24 mm × 12 mm) was mobilized using a chisel and mallet. The alveolar distractor was fixated to this segment using mini screws (A. K. Instruments, Mumbai, India) [Figure 3]. Interocclusal clearance was evaluated, and the flap sutured. A panoramic radiograph was taken to evaluate the placement of the distractor [Figure 4].
A 7 days latency period was required prior to distractor activation. The distraction was executed at a rate of 1 mm/day, by turning the transport rod a single turn daily for a period of 7 days. The patient was instructed on maintaining oral hygiene and placed on a regular follow up schedule.
After a 4-month consolidation phase, the distractor was removed, and five implants were placed in the edentulous regions of the mandible.
A partial denture with radiopaque Gutta-Percha markers was used as a radiographic stent and a cone beam computed tomography scan was performed to aid in planning the proper positioning of the five implants. This radiographic stent was then converted into a surgical stent that aided in the prosthetic positioning of the implants. Four 3.8 mm × 13 mm implants (Alpha Bio Spiral SPI™ ) were placed in the right first molar, right first premolar, right canine and left first premolar regions of the edentulous mandible. One 3.5 mm × 11.5 mm implant (Alpha Bio Spiral SPI™ ) was placed in the mid symphysis region [Figure 5]. Care was taken to avoid the distraction osteotomy sites during implant placement. A few threads of the implant in the left first premolar region were exposed after implant placement, alloplastic bone graft material NovaBone Dental Putty (NovaBone Products, Alachua, Florida, USA) was placed along with a resorb able collagen membrane (Periocol, Eucare Pharmaceuticals Private Limited, Chennai, India) to cover the threads and the flap was sutured. The implants were allowed to osseointegrate undisturbed for 4 months after which prosthetic rehabilitation was performed.
The implants were uncovered and healing abutments were placed [Figure 6] for 2 weeks to ensure good soft tissue contour around the implants. Five open tray impression copings were splinted to one another using auto polymerizing resin [Figure 7] (Pattern Resin™ LS, GC America, Inc., Alsip, IL, USA) and an open tray impression was made using medium body polyvinylsilicone impression material in an acrylic custom tray. After the model was obtained the wax-up was performed on castable abutments and auto polymerizing acrylic resin (Pattern Resin™ LS, GC America, Inc., Alsip, IL, USA) was used to fabricate a framework for the screw-retained hybrid prosthesis which was then cast in cobalt chrome. The cobalt chrome framework was then tried in the patient's mouth to evaluate fit and passivity of the framework.
|Figure 7: Open tray impression coping splinted together with auto polymerizing resin|
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Both on clinical and radiographic evaluation [Figure 8], it was evident that the metal framework failed to passively fit onto the implants due to casting shrinkage commonly associated with the lost-wax technique. In order to overcome this dimensional change the frame work was sectioned into two parts [Figure 9]. The two parts of the sectioned frame work were fit passively onto their respective abutments and then joined intraorally using auto polymerizing acrylic resin [Figure 10] (Pattern Resin™ LS, GC America, Inc., Alsip, IL, USA). A long bur shank was attached to the two parts of the framework to prevent any movement of the attached framework in the horizontal plane. This entire assembly was embedded in type IV gypsum material and stabilized extraorally. The resin between the two parts of the framework was burnt out using a solder torch [Figure 11]. The two parts of the framework were joined together using silver solder. The framework was finished and tried again in the patient's mouth to check for a passive-fit. The fit was also confirmed radiographically [Figure 12]. The abutments were removed from the implant fixtures and healing abutments reconnected. The mandibular denture teeth were waxed to the hybrid framework, and a final wax try-in was performed to verify and correct maxillomandibular relations. The denture was invested and acrylization was completed using injection molding technique (SR Ivocap; IvoclarVivadent). The prostheses was finished and polished, a clinical remount was performed to allow refinement of occlusal contacts.
|Figure 8: Clinical and radiographic failure of the framework to passively fit onto the implants|
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|Figure 10: Two parts of the sectioned framework stabilized intraorally with autopolymerizing resin|
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|Figure 11: Sectioned framework embedded in type IV gypsum and burn out of resin|
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|Figure 12: Clinical and radiographic evaluation of the passive-fit of sectioned framework after soldering|
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The occlusion was adjusted such that there were no contacts on the implant supported teeth during light closure and equal intensity contacts on both implant supported and natural teeth during heavy closure. A group function occlusal scheme was provided for working side contacts to allow distribution of forces during eccentric movements. No contact of the teeth on the balancing side. A shallow anterior guidance was provided to cause disocclusion of the posterior teeth on the protrusion. The hybrid prosthesis was screw-retained with a final insertion torque of 35 Ncm as per manufacturer recommendations. The screw channels were packed with cotton and composite resin (TempBond; Kerr) was used to cover screw access holes [Figure 13]. A panoramic radiograph was taken postoperatively to evaluate radiographically the final implant-supported restoration [Figure 14].
The patient was instructed to use a standard soft bristle toothbrush without toothpaste for hygiene maintenance on the facial, lingual and occlusal surfaces of the prosthetic superstructure. A nylon coated interdental brush was advised for plaque removal on the gingival side of the superstructure and proximal surfaces of abutments. A flossing cord (Super Floss; Oral-B) specifically designed for dental implants was advised to polish the transmucosal abutments and gingival side of the prosthesis. 
The patient was recalled 24 h, 1-week and 3 weeks after delivery of the prosthesis to check for screw loosening, plaque, and calculus formation and evaluate patients motivation toward oral hygiene maintenance.
Patient was put on a follow-up protocol which includes a recall visit every 3 months.  Protocols for radiographic evaluation include follow-up radiographs at 6 months, 1-year and 3 years after prosthesis insertion. Thereafter, radiographs are taken at 3 years intervals or as needed for necessary evaluation. 
| Discussion|| |
The osteogenic distraction is a method of lengthening the bone tissue by the modulation of the osseous clavi. The process involves an osteotomy, followed by the controlled and continuous gradual distraction (separation) of the osseous segments, creating tension in the bone callus that stimulates the local histogenesis.  The tension activates cellular metabolism, increasing the protein synthesis and the mitotic index, which results in the formation of hard and soft tissues, adjacent to the space produced by distraction. 
The vertical bone gain aids in reducing the crown-height space (distance from the crest of the bone to the incisal edge), and thus reduces the risk of abutment screw fracture and the subsequent failure of the prosthesis. 
| Summary and conclusion|| |
Producing a passive-fitting substructure for fixed removable screw-retained hybrid prosthesis is arguably one of the most technically complex tasks in implant dentistry. Distortions commonly occur during impression making, cast pouring, waxing, casting, indexing, and result in errors in the fit of the metal framework.  The gap between an implant fixture and an abutment should be 10 micron or less to be considered passive.  This degree of fit may be almost impossible with the geometry of most cast screw-retained fixed detachable hybrid prostheses. This simple technique of sectioning the cast metal framework and joining the two fragments by soldering can help obtain a cast framework with the clinically acceptable fit and ensure long-term success of the implant supported prosthesis.
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