NewsletterDifferent biomaterials are used to prevent fractures under the varying occlusal loads posed by this patient’s challenging dentition.
By George V. Duello, DDS, MS
In 2011, the Federal Aviation Administration and the European Aviation Safety Agency certified the Boeing 787 Dreamliner for commercial passenger transportation.1 This revolutionary aircraft is 80% composite by volume. The new flagship model for Lamborghini, the Aventador LP-700-4, is a two-seater performance supercar with a composite carbon fiber uni-body mono-coupe serving as the framework for the chassis. Using composite materials in these two applications can allow for durability, weight reduction, and energy savings. The strength-to-weight ratio of these specialized composites allows for the manufacturing of materials strong enough specifically for load-bearing components.
Synthetic composite resins have also been used in the field of dentistry for restorative and prosthetic products. Their use has been advocated due to the ease of application, esthetics, and cost. New-generation composites can provide biomaterials that are insoluble in the oral environment and are resistant to dehydration. Initially, composites were manufactured only for the replacement of tooth enamel damaged as a result of caries, congenital deformities, and traumatic fractures. Today, dental composites have been manufactured with varying fillers and colors in paste and flowable systems to replace the soft and hard tissues in dental prosthetics.
Traditionally, full-arch prosthodontics on dental implants relied on the application of acrylic materials over a cast or CAD/CAM substructures to replace the gingival and enamel esthetics. These materials can provide acceptable esthetics and reasonable durability over time. However, acrylic and polymethylmethacrylate (PMMA) can fracture and de-bond under occlusal loading, leaving the patient and dentist with an appliance that may require removal to repair. Patients with screw-retained fixed implant prostheses can lose their masticatory efficiency and facial esthetics when appliances require in-laboratory repairs.
This article will focus on the use of a new series of products in implant prosthodontics for the lamination of titanium CAD/CAM-fabricated screw-retained frameworks. These materials can provide high abrasion resistance, excellent elasticity, and brilliant esthetics, while allowing extra- and intraoral repairs in the event of an emergency. A patient requiring full-mouth rehabilitation will be the focus of this report on new materials for the lamination of the prosthetic framework.
A 46-year-old man was referred by his general dentist for oral facial pain associated with chronic advanced generalized periodontitis and dental caries (Figure 1). Objective and subjective clinical data were obtained via pretreatment interview and clinical examinations. Panoramic and CBCT radiographic examinations were supplemented by extraoral and intraoral photographs for consultations and treatment planning (Figure 2). Based on a review of the clinical data and informed consent documentation, the existing dentition’s long-term prognosis was deemed very doubtful. Several prosthetic treatment options were discussed, including complete removable dentures; single- or complete-arch implant overdentures; and complete-arch, screw-retained, fixed-implant prosthetics. After further deliberations with the clinical team, the patient elected to have full-mouth rehabilitation with traditional fixed implant technologies advocated by Branemark3 and Malo.4
The patient started treatment by returning to the general dentist for fabrication of maxillary and mandibular immediate removable dentures. After a staged extraction sequence of posterior and anterior teeth, the patient underwent major alveoloplasty to provide interocclusal spaces for appropriate dental materials and bioengineering. After the bone reduction, five dental implant fixtures were placed in the mandible, and four dental implants from Nobel BiocareTM (Nobel Biocare, www.nobelbiocare.com) were placed in the maxillary arch using clear duplicate denture guides and a metal malleable guide.5 All nine external hexed fixtures achieved 35-Ncm primary stability and were attached to multiunit transmucosal abutments to facilitate the fabrication of an all-acrylic, screw-retained provisional denture. The multiunit abutments also would serve as the prosthetic platform for a dual-arch definitive prosthetic after the implants achieved osseointegration after immediate loading.
After 2 months of healing with the provisional fixed prosthesis, the patient presented with an emergency fracture of the acrylic around a titanium temporary abutment. An extraoral repair was performed with the aid of a jig prefabricated on implant analogs with denture acrylic. Subsequent to this initial fracture, two additional fractures of the acrylic occurred, as did delamination of a denture tooth (Figure 3). In response to these clinical findings, the decision was made to fabricate the final prosthesis in such a manner as to minimize fractures/wear with a durable lightweight substructure that would provide adequate mass to resist the tension, compression, and tensile forces of occlusion. A titanium framework was designed to be uniformly veneered in pink, and white-colored composites were the long-term prosthetic solution suggested for this patient. This prosthesis would be followed by permissive and protective occlusal guards for added nocturnal and athletic protection.
Multi-unit level impressions were taken using a customized intraoral verification jig to fabricate master casts poured from a low-expansion stone developed for laser scanning. The master casts were mounted in centric relation from intraoral records using a deprograming anterior jig. After base plates were fabricated on the master casts, the laboratory professional applied pink wax and PMMA denture teeth in a mold selected by the patient and restorative dentist. Once esthetic, phonetic, and occlusal approvals were secured from the dentist and patient, the final phase of the laboratory was initiated using the wax try-in as the template for the definitive prosthesis.
Back in the laboratory, the wax try-in dentures were duplicated in resin, followed by a 2-mm circumferential cutback reduction for the final copy-mill pattern for laser scanning. Both copy mill patterns were scanned in a Nobel Biocare laser scanner, with the subsequent files being sent electronically to Nobel Biocare’s milling facilities in Mahwah, New Jersey. CNC titanium alloy frameworks were milled from the Procera® (Nobel Biocare) file and returned to the laboratory (Figure 4). The frameworks were sandblasted, and an A1 opaquer was applied over the titanium followed by a light-curing bond LC from Anaxdent6 (www.anaxdent.com), for the connection of the veneering composites.
The wax try-ins were reattached to the master model in universal flasks and invested in clear silicone. Vulcanization of the silicone was achieved under pressure, followed by deflasking and attachment of sprues for injection of composite. A base of A1 shade dentin was applied for a 6-minute cure; then an incisal cutback was performed for the final application of the incisal and body composite, anaxBLEND from Anaxdent, based on the pre-selected shade (Figure 5). Final composite finishing was chemically performed with a barrier gel. Pink gingival esthetics were manually applied with a combination of pastes and flowable composites, anaxGUM from Anaxdent, for the artistic interpretation of the laboratory technician (Figure 6). Final curing was completed with an airbag for the 6 minutes with cover gel procedure. The composite was finished with grey paste polishing, steam cleaning, and buff polish.
Upon completion of the laboratory procedures, the final prosthesis was returned to the general dentist for seating and adjustments as needed (Figure 7). Intraoral adjustments could be made on the composite using recommended burs, wheels, and polish tips. Once the occlusal anatomy was refined, impressions were taken for immediate fabrication of a maxillary permissive composite occlusal guard and a soft vacuum-form athletic guard. The final procedure for the active phase of treatment was a panoramic radiograph to confirm fit and document the bone levels for recall comparisons (Figure 8). Future repairs could be made intraorally and/or extraorally as needed with additional application of paste and/or flowable composite with light curing. After an appropriate period of wear under normal function or parafunction, the composite could be stripped from the titanium frameworks with the new application of new composite.
Because of the natural history of this patient’s dentition and the clinical breakage demonstrated during the provisional prosthetic phase, it was determined to use biomaterials that differed from the conventional fabrication of screw-retained implant prostheses. Traditional fixed hybrid prostheses have a bar that is wrapped in pink denture acrylic with PMMA denture teeth. It was the opinion of the clinical team involved in this interdisciplinary case that a different set of biomaterials might allow for better bioengineering and prevent fractures under varying occlusal loads. The application of a new generation of dental composites over computer-aided design titanium frameworks may provide the patient with a more durable dental prosthesis.
Contributors to this article included Steve Raney, a general dentist in Columbia, Illinois, and Robert Sarno CDT, of Pinnacle Dental Lab, St. Louis, Missouri.
The author received an honorarium from Nobel Biocare for writing this article, and is also a paid consultant and lecturer for the company.
1. Boeing 787: A Matter of Materials—Special Report: Anatomy of a Supply Chain. IndustryWeed.com, December 1, 2007.
2. Lamborghini technical specifications. Available at: www.lamborghini.com/en/models/aventador/lp-700-4/technical-specifications/. Accessed August 23, 2012.
3. Adell R, Lekholm U, Rockler B, Brånemark PI. A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg. 1981;10
(6):387-416.
4. Malo P, Rangert B, Nobre M. “All-on-Four” immediate function concept with Branemark system implants for completely edentulous maxillae: a 1-year retrospective clinical study. Clin Implant Dent Relat Res. 2005:7(suppl 1);588-594.
5. Data on file. Nobel Biocare, Nobel Biocare AG, Zurich, Switzerland. www.nobelbiocare.com.
6. Data on file. Anaxdent, Anaxdent GmbH Olgastrasse 120a, 70180 Stuttgart. www.anaxdent.com.
George V. Duello, DDS, MS
Masters Institute
St. Louis, Missouri
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