Complete mouth reconstruction with implant-supported fixed partial dental prostheses fabricated with zirconia frameworks: A 4-year clinical follow-up Shweta Puri, BDS,a Ewa C. Parciak, DDS,b and Mathew T. Kattadiyil, BDS, MDS, MSc Loma Linda University School of Dentistry, Loma Linda, Calif Few scientiﬁc reports regarding the success of complete mouth partial ﬁxed dental prostheses frameworks fabricated with zirconia are available, especially when dental implants serve as the abutments. A complete mouth reconstruction with zirconia frameworks veneered with feldspathic porcelain is reported involving a 65-year-old white woman who presented with partial edentulism and an unrestorable remaining dentition. After examination, 14 implants were planned (8 in the maxillary arch and 6 in the mandibular arch), and implant-supported zirconia framework screw-retained partial ﬁxed dental prostheses (ISZPFDPs) were fabricated and made in sections for easier retrievability and management. No major complications were encountered during follow-up appointments at 6-month intervals for 4 years. However, minor fractures of the veneering ceramic were noted 4 years after placement. The ISZPFDPs were well accepted by the patient and had a favorable outcome in terms of patient acceptability and success, despite some complications. (J Prosthet Dent 2014;-:---) Over the past decade, zirconia technology has had a signiﬁcant impact on dentistry because of its biocompatibility,1 esthetics,1 and material strength.2-4 These properties have led to the increasing use of zirconia in the fabrication of partial ﬁxed dental prosthesis (PFDP) frameworks. In vitro studies of zirconium dioxide specimens demonstrate a ﬂexural strength of 900 to 1200 MPa and a fracture toughness of 9 to 10 MPa$m½.3,5 Additionally, the white color of zirconia makes it beneﬁcial in esthetic areas of the oral cavity, and its ability to transmit light makes it a suitable material for anterior restorations. Zirconia frameworks present a less noticeable transition compared to metal framework substructure should tissue recession occur in patients with a thin gingival biotype.6 Clinical studies have reported varying degrees of success and survival for zirconia-based multiunit substructures on natural teeth. A prospective study by Schmitt et al7 reports a survival rate of 92% at 5 years for 3- and 4-unit PFDPs made with zirconia frameworks. The most
common complications reported were minor and major chipping of the veneering porcelain. Complications associated with veneering porcelain on zirconia frameworks have been reported.8-11 The scientiﬁc literature lacks data regarding complete mouth PFDP frameworks fabricated from zirconia layered with feldspathic porcelain, especially with dental implants as abutments. Clinical reports have evaluated restorations with a zirconia structure supported by implants, and the outcomes of these prostheses continue to be of signiﬁcant interest.12,13 A patient situation is presented that discusses the treatment considerations and prosthodontic complications associated with a complete mouth rehabilitation with implant-supported PFDPs fabricated with zirconia frameworks layered with feldspathic porcelain.
CLINICAL REPORT A 65-year-old white woman presented to the graduate prosthodontics clinic at Loma Linda University School of
Dentistry with an unrestorable remaining dentition due to caries. Her reduced salivary ﬂow, caused by the onset of Sjögren syndrome, had accelerated the carious process. After the assessment and diagnosis of the clinical situation,14 different treatment options were presented including maxillary and mandibular conventional complete dentures, implant retained overdentures, a maxillary complete denture opposing a mandibular ﬁxed complete denture, and a complete mouth rehabilitation with implant-supported PFDPs, from which she selected deﬁnitive implantsupported PFDPs to rehabilitate her mouth after extractions (Fig. 1). Her remaining teeth were extracted and immediate complete dentures placed. A diagnostic waxing with teeth arrangement was performed after 4 months to establish appropriate esthetics, phonetics, and occlusal vertical dimension. Adequate bone was available for the placement of dental implants to support individual PFDPs. The bone volume was conﬁrmed with a cone beam computerized tomograph (CBCT) made
Presented as a poster at the American Equilibration Society meeting, Chicago, Ill, February 2012. a
Graduate student, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry. Graduate student, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry. c Professor and Director, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry. b
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1 Occlusal views of edentulous ridges. A, Maxilla. B, Mandible.
2 Diagnostic templates in place. A, Intraoral view. B, View revealing low smile line. C, Proﬁle view of side with ﬂange. D, Proﬁle view of side without ﬂange. with the maxillary and mandibular radiographic templates (fabricated by duplicating the tooth arrangements) in place. The tooth arrangement was also duplicated in clear autopolymerizing resin (Splint acrylic resin; Great Lakes Orthodontics) to create a template,
which was evaluated intraorally after sectioning one half of the labial ﬂange on the left side. This allowed the objective evaluation of the lip support and the visibility of teeth in an exaggerated smile (Fig. 2) to help conﬁrm the treatment option for the implant-
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supported zirconia framework screwretained partial ﬁxed dental prostheses (ISZPFDPs). Surgical templates were fabricated, and 14 root form dental implants (Nobel Replace; Nobel Biocare USA), 8 in the maxillary and 6 in the mandibular arch ranging in diameter
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3 Occlusal view of mandibular frameworks. from 3.5 to 5.0 mm, were placed. A 1stage technique was used and healing abutments placed on implants. A CBCT was made to conﬁrm the appropriate placement of the implants. During the healing period, the patient reported pain in the maxillary left premolar area, and a radiographic evaluation revealed periimplant radiolucency. The implant was easily removed with a screwdriver, conﬁrming the lack of osseointegration. Another implant was placed distal to the site of the removed implant. Implant-level deﬁnitive open tray impressions were made with polyvinyl siloxane (Examix; GC America Inc), and maxillomandibular relationship records were made at an appropriate occlusal vertical dimension with maxillary and mandibular occlusion rims and deﬁnitive casts mounted on a semiadjustable articulator (Panadent PCH articulator; Panadent Corp). Protrusive records were made to program the articulator. Complete mouth diagnostic wax patterns (Renfert wax; Renfert GmbH) were made with a group function occlusal scheme. After a veriﬁcation index15 conﬁrmed the accuracy of the impressions, acrylic resin (Alike; GC America Inc) interim restorations were fabricated by using the wax patterns as a template to assess esthetics, phonetics, and the planned group function occlusion at the determined occlusal vertical dimension. After 2 uneventful weeks and positive feedback from the patient regarding the interim restorations, the wax patterns were duplicated with autopolymerizing
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4 Frontal view in maximal intercuspal position of maxillary and mandibular ISZPFDPs.
5 Panoramic radiograph of deﬁnitive restorations. acrylic resin (Pattern resin; GC America Inc) and cut back to accommodate a uniform thickness of veneering porcelain. The resin patterns were scanned with a computer-aided design and computer-aided manufacturing (CAD/ CAM) scanner (Procera Forte scanner; Nobel Biocare USA) to produce 6 PFDP zirconia frameworks, 3 per arch (Fig. 3), with the Nobel Procera CAD/CAM system. These frameworks were evaluated clinically and radiographically for ﬁt15 and then veneered with a compatible feldspathic porcelain (Nobel Rondo; Nobel Biocare USA). The group function occlusal scheme was duplicated from the diagnostic wax patterns. The prostheses were placed and adjusted, and the group function occlusion was conﬁrmed. They were tightened into place following the manufacturer’s recommendations (35 Ncm) (Figs. 4-6). The patient was given oral hygiene
instructions and shown how to clean interproximal and ridge lap areas with ﬂoss (Super Floss; Oral-B Inc) in addition to a conventional brushing technique. Follow-up appointments at 24 hours, 1 week, and 2 weeks revealed excellent patient response and satisfaction. At 2 weeks, impressions and new centric relation records were made to fabricate an occlusal device (Fig. 7). The patient was instructed to wear the device at night to avoid damage to the ISZPFDPs from parafunctional forces. Follow-up appointments were carried out at 6-month intervals for 4 years. Initially, no major complications were encountered. However, fracture of the veneering porcelain was detected on the distal marginal ridge of the maxillary right ﬁrst molar at 19 months and at the incisal edges of the maxillary right canine, lateral incisor, and right and left central incisors at the 4-year follow-up
6 Occlusal view of deﬁnitive restorations. A, Maxillary occlusal view. B, Mandibular occlusal view. Arrow identiﬁes ﬁrst fracture at 19 months.
7 Occlusal device in place. appointment (Figs. 6B, 8). After consideration of the patient’s masticatory pattern, it was decided that a repair of maxillary right ﬁrst molar was not required. Regarding the anterior PFDP, the patient was given an option to have the fractured veneering porcelain repaired with composite resin, but she declined, stating that this fracture was not a concern esthetically or functionally; the prosthesis was removed, smoothed, polished, and reinserted. Interestingly, the fractures did not occur at the interphase of the zirconia and veneering porcelain but within the veneering porcelain itself. With the design for easy retrievability, if additional and signiﬁcant chipping fractures occur in the future, repairs are possible without compromising the prostheses. No complications have been noted in relation to the zirconia framework itself.
8 Fracture within veneering porcelain at 4-year follow-up.
DISCUSSION Zirconia is a biocompatible and esthetic material1 that may be used for PFDP frameworks. Some clinical studies have reported varying degrees of success for zirconia-based multiunit substructures on natural teeth.7 Clinical reports have addressed complete arch restoration with implant-supported zirconia frameworks.12,13 Alhashim et al12 reported favorable outcomes from a 4-year follow-up of the rehabilitation of a mandibular arch with cementable zirconia-reinforced ﬁxed dental prosthesis. The prosthesis was designed with an acrylic resin encircling a zirconia framework opposing a maxillary complete denture. Cheng et al13 reported on a 1-year follow-up of a mandibular completely edentulous arch rehabilitated with monolithic zirconia
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implant-supported PFDPs. They also reported satisfactory outcomes at the 1-year follow-up. The present clinical report describes the use of multiple, short-span screwretained ISZPFDPs in a complete mouth restoration. The patient was selected for treatment with a zirconia framework on the basis of the history of absence of any obvious signs and symptoms of parafunctional habits in her natural dentition. The PFDPs were planned to be screw retained and were made in sections, considering the need for retrievability and easier management of complications. Although incidences of minor chipping fracture did occur, the restoration was considered successful because the fractures were only grade 1 and could be repaired by polishing alone and without compromising esthetics and function.16 Veneering porcelain
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fractures in this patient were detected in 5 of the 24 units within the ﬁrst 4 years after placement. The veneering porcelain crack formation observed in this patient was in contrast with the report by White et al,4 who found that catastrophic failure after initial crack progression often involved the porcelain-zirconia interface. The observations in the present study are similar to those reported by Larsson et al,8 who found minor superﬁcial fractures in 34% of the units evaluated. Raigrodski et al9 and Sailer et al,10 in their respective systematic reviews, concluded that chipping of the veneering porcelain was the most common concern in ZPFDPs. Pjetursson et al11 also reported that the most common technical complication in implantsupported PFDPs was the fracture of veneering materials. In the present patient, cracks in the veneering porcelain were the main complication but were not catastrophic. Nonetheless, each of the planned screw-retained, short-span ISZPFDP is retrievable, should an individual unit fail in the future. The continuing fracture of the veneering porcelain is a cause for concern. Because the veneering porcelain did not reveal fracture at the zirconia interface, the authors speculated that there was an inherent ﬂaw in the handling of the veneering porcelain during fabrication. Another reason could be the internal stresses created at placement when tightening the screw-retained zirconia frameworks. However, the 4-year time line of 4 of the 5 fractures seen does not lend much support to this argument.
SUMMARY ISZPFDPs demonstrated a favorable outcome in terms of patient acceptability and success. However, the chipping fractures observed at the 4-year follow-up is a concern. On the basis
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5 of 4 years of follow-up data for this patient, along with the inherent limitations of a clinical report, the following conclusions can be drawn: 1. Careful patient selection, planning larger reconstructions on implants with retrievability for repairs, and an appropriate occlusal scheme are critical for a successful outcome with these types of prostheses. 2. Because of the relatively recent introduction of zirconia in dentistry, the inherent properties of the material are yet to be completely understood. Clinicians should be cautious when using ﬁxed zirconia frameworks veneered with feldspathic porcelain in complex restorative situations. 3. Studies with diverse and large patient populations are recommended to assess the long-term success rates of multiple- and single-unit ISZPFDPs in complete mouth reconstructions.
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8. Larsson C, Vult von Steyern P, Nilner K. A prospective study of implant-supported full-arch yttria-stabilized tetragonal zirconia polycrystal mandibular ﬁxed dental prostheses: three year results. Int J Prosthodont 2010;23:364-9. 9. Raigrodski AJ, Hillstead MB, Meng GK, Chung KH. Survival and complications of zirconia- based ﬁxed dental prostheses: a systematic review. J Prosthet Dent 2012;107: 170-7. 10. Sailer I, Pjetursson BE, Zwahlen M, Hammerle CHF. A systematic review of the survival and complication rates of all-ceramic and metal-ceramic reconstructions after an observation period of at least 3 years. Part II: ﬁxed dental prostheses. Clin Oral Implants Res 2007;18(suppl 3):86-96. 11. Pjetursson BE, Bragger U, Lang NP, Zwahlen M. Comparison of survival and complication rates of tooth-supported ﬁxed dental prostheses (FDPs) and implantsupported FDPs and single crowns (SCs). Clin Oral Implants Res 2007;18(suppl 3): 97-113. 12. Alhashim A, Kamel M, Brackett WW. Four-year follow-up of the rehabilitation of a mandibular arch with a cementable zirconia-reinforced ﬁxed dental prosthesis: a clinical report. J Prosthet Dent 2012;108: 138-42. 13. Cheng CW, Chien CH, Chen CJ, Papaspyridakos P. Complete-mouth implant rehabilitation with modiﬁed monolithic zirconia implant-supported ﬁxed dental prostheses and an immediate-loading protocol: a clinical report. J Prosthet Dent 2013;109: 347-52. 14. Bidra AS, Agar JR. A classiﬁcation system of patients for esthetic ﬁxed implant-supported prostheses in the edentulous maxilla. Compend Contin Educ Dent 2010;31:366-8. 370, 372-4. 15. Simon H, Marchak CB. Implant veriﬁcation cast-a predictable restorative system in implant prosthodontics. J Calif Dent Assoc 2010;38:571-81. 16. Anusavice KJ. Standardizing failure, success, and survival decisions in clinical studies of ceramic and metal-ceramic ﬁxed dental prostheses. Dent Mater 2012;28:102-11. Corresponding author: Dr Shweta Puri Advanced Specialty Education Program in Prosthodontics Room 2242 11092 Anderson Street Loma Linda, CA 92350 E-mail: [email protected]
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