Early complications and short-term failures of zirconia single crowns and partial fixed dental prostheses Juha Pihlaja,a Ritva Näpänkangas, DDS, PhD,b and Aune Raustia, DDS, PhDc Institute of Dentistry, University of Oulu, Oulu, Finland; Oulu University Hospital, Oulu, Finland Statement of problem. Ceramic single crowns fabricated from newer materials, especially zirconia, have shown relatively high survival rates. However, early reversible complications may increase the risk of an irreversible failure later. Purpose. The purpose of the study was to evaluate the early complications and short-term failures of zirconia single crowns and partial fixed dental prostheses (FDPs) made by predoctoral dental students. Material and methods. Data were collected from the patient records. Altogether, 264 zirconia single crowns and 120 FDPs (342 abutments and 190 pontics) were fabricated for 173 patients between 2007 and 2010. Early complications were recorded during the prosthetic treatment phase, and short-term failures were recorded during the first year in use. Results. The most frequent early complications were localized gingival irritation (1.9% of single crowns and 2.5% of FDP) and postoperative tooth sensitivity (0.4% of single crowns and 3.3% of FDPs). Pulp exposure during preparation was recorded in 3 abutment teeth of the FDPs. The most frequent short-term failure was chipping of the veneering porcelain (0.8% for single crowns, 0.8% for FDPs). One crown lost cementation because of poor retention (0.4%), and 2 FDPs failed because of framework fractures (1.7%). Conclusions. The most frequent early complications were localized gingival irritation and postoperative tooth sensitivity, and the most frequent short-term failure was chipping of the veneering porcelain. (J Prosthet Dent 2014;-:---)
Clinical Implications Patients should be told that tooth sensitivity may occur after preparation but is usually transient. In the case of localized gingival irritation with single crowns or the abutment teeth of fixed dental prostheses, an examination may reveal excess cement. The chipping of porcelain is more common in zirconia restorations than in metal ceramic ones and can occur shortly after cementation. Conventional metal ceramic single crowns and partial fixed dental prostheses (FDP) have been used in dentistry for decades and have earned worldwide acceptance.1 Nowadays, they are regarded as the gold standard because of their low failure rates and good longterm clinical results.2,3 Nevertheless, the a
emerging demands for metal-free, more biocompatible, and highly esthetic restorations have directed materials research and development toward ceramics. Numerous advances have been made in the mechanical properties and fabrication methods of ceramic materials since the introduction of leucite-
reinforced glass ceramics (IPS Empress; Ivoclar Vivadent) and the InCeram technique (Vita Zahnfabrik; H. Rauter GmbH & Co KG).4,5 Currently, a wide range of ceramic materials is available for clinical use. On the basis of recent studies, fixed ceramic prostheses fabricated from newer
Dental student, Institute of Dentistry, University of Oulu. Senior lecturer, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Oulu, Finland; and Specialist, Oral and Maxillofacial Department, Oulu University Hospital. c Professor, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Oulu, Finland; and Chief, Oral and Maxillofacial Department, Oulu University Hospital. b
Pihlaja et al
2
Volume materials, especially zirconia, have shown relatively high short-term and mediumterm survival rates, comparable to those of metal ceramics.4-19 This evidence suggests that, especially in the absence of parafunctional habits, clinicians may choose from any of the recent ceramic materials, depending on the esthetic and functional needs of the patient.6 Because of its excellent mechanical properties, zirconia is more widely used in restorative dentistry than other ceramics.20 The high strength and fracture toughness of zirconia has changed the most frequent reasons for the failure of ceramic partial fixed dental prostheses (FDPs) from severe framework fracture to minor technical complications, such as the chipping of veneering porcelain.12 This problem seems to be the biggest weakness of zirconia restorations when compared to metal ceramic ones.21 Early repairable chipping of veneering porcelain can increase the risk for irreparable porcelain damage later.22,23 In addition, Sagirkaya et al16 found in a 4-year followup that 4 out of 5 failures occurred in the first year. However, the use of monolithic zirconia with no veneering porcelain has increased and the risk for the fractures has diminished.24 To our knowledge, no published studies have focused completely on the early complications of zirconia restorations during the prosthetic treatment phase or on short-term failures during the first year in use. The hypothesis was that complications are few during and shortly after prosthetic treatment. Thus, the objective of the study was to evaluate the early complications and shortterm failures of zirconia single crowns and FDPs made by predoctoral dental students.
approved by the ethical committee of the Northern Ostrobothnia Hospital District. Data, which consisted of patients treated with zirconia single crowns and FDPs by predoctoral dental students, were collected from patient records. A total of 173 patients (94 women and 79 men, mean age 55 years, range 18-79 years) were treated with zirconia single crowns or FDPs between 2007 and 2010. Altogether, 264 zirconia single crowns were placed in 88 patients (mean 3 crowns per patient, range 1 to 12 crowns), mostly to the maxillary anterior region (Fig. 1). The names and manufacturers of the zirconia frameworks in single crowns were Zirkonzahn Zirconia (Zirkonzahn), NobelProcera Zirconia (Nobel Biocare), and Prettau Zirconia (Zirkonzahn). In addition, 102 patients were treated with 120 zirconia FDPs (range 3 to 12 units, mean 4.5 units). The names and manufacturers of the zirconia frameworks in FDP were Zirkonzahn Zirconia (Zirkonzahn), NobelProcera Zirconia (Nobel Biocare), and Prettau Zirconia (Zirkonzahn). These FDPs consisted of 342 abutments and 185 pontics (Fig. 2), of which 5 were cantilevers.
MATERIAL AND METHODS This retrospective study of the early complications of zirconia restorations during the prosthetic treatment phase and short-term failures during the first year in use was conducted at the Institute of Dentistry, University of Oulu, Finland. The study protocol was
The Journal of Prosthetic Dentistry
-
Issue
-
The abutment teeth were usually maxillary canines and incisors, and mandibular premolars and second molars. The maxillary pontics were distributed evenly in the dental arch, but in the mandible, the first molars were the most common pontics. The most common indications for zirconia restorations were excessive loss of tooth substance (crowns), renewal of the existing restorations (crowns), and tooth loss (FDPs). All patients received periodontal treatment before prosthetic treatment, including education, instructions for proper home care, and a professional tooth cleaning. The preprosthetic treatment also included caries and endodontic treatment as well as occlusal adjustment, if needed. All the preparations were made in accordance with international treatment guidelines.25 For the crowns and abutment teeth of FDPs, the teeth were prepared with 1.5 mm axial clearance (total convergence 6 degrees) and a 2 mm anatomically adequate occlusal or incisal reduction with a functional cusp bevel to ensure sufficient material thickness. The heavy chamfer finish line was placed slightly below the free
45 40 35 30 25 20 15 10 5 0
0 5 10 15 20 25 30 35 40 45
Maxillary teeth Mandibular teeth
1 Distribution of zirconia single crowns (n¼264).
Pihlaja et al
-
2014
3 45 40
Pontics
35
Abutments
30 25 20 15 10 5 0
Maxillary teeth Mandibular teeth
0 5 10 15 20 25 30 35
Pontics
40
Abutments
RESULTS
45
2 Distribution of abutment teeth and pontics of zirconia partial fixed dental prostheses (n¼120). gingival margin (0.5 mm) in anterior teeth and marginally (equigingival) in posterior teeth. Composite resin (Filtek Z250; 3M ESPE) was used for the foundation when needed, and a fiber post (RelyX Fiber post; 3M ESPE) was used in endodontically treated teeth. All the treatment procedures were performed under the supervision of qualified clinical instructors. For Zirkonzahn Zirconia and Prettau Zirconia, the frameworks were fabricated with manual milling and designed for the uniform thickness of the veneering porcelain layer. The minimal thickness of the framework was 0.4 mm. The connector design requirement was 9.0 mm2. The veneering porcelain (GC Initial Zr; GC Europe) was layered on the frameworks. In NobelProcera Zirconia, the frameworks were fabricated by using computer-aided design/ computer-assisted manufacture and designed for the uniform thickness of veneering porcelain layer. The minimal thickness of the frameworks in single crowns was 0.4 mm in the anterior area and 0.7 mm in the posterior area and in FDP 0.6 mm. Briefly, for the FDPs, the
Pihlaja et al
patients were asked to make contact in case of emergency, and no scheduled examination at the clinic was performed after the 6-month follow-up visit. Patient records were checked for possible failures between 6 months and 12 months after the definitive cementation. The complications were divided into early complications and short-term failures. Early complications included complications recorded during the prosthetic treatment until definitive cementation. Short-term failures included failures recorded during the first year in use after the definitive cementation. Both early complications and short-term failures were divided into biological and technical categories.
connector design requirement was 6.0 mm2 in the anterior area and 9.4 mm2 in the posterior area. The veneering porcelain (Vita VM 9; Vita Zahnfabrik) was layered on the frameworks. Before the definitive cementation of the restorations, their esthetic appearance and occlusion were confirmed. The clinical instructor evaluated the fit of the restoration and the patients were asked whether they were satisfied with the color and esthetics of the restoration. The restorations were bonded with dual-polymerizing, self-adhesive, universal resin cement (RelyX Unicem; 3M ESPE) according to the manufacturer’s instructions. The single crowns were cemented with definitive cement immediately, but the FDPs were first cemented with interim cement (TempBond NE; Kerr Corp), and definitive cementation took place about 1 week later. The first follow-up was scheduled 1 to 2 weeks after the definitive cementation of the crowns and FDP. At the 6month follow-up, the restorations, surrounding tissues, and occlusion were thoroughly examined. Thereafter,
The biological early complications found were localized gingival irritation (5 of 264 single crowns, 1.9%; 3 of 120 FDP, 2.5%) and postoperative tooth sensitivity (1 of 264 single crowns, 0.4%; 4 of 120 FDPs, 3.3%) (Table I). Localized gingival irritation was caused by excess cement (except in 1 instance) and was relieved by cement removal. The tooth sensitivity of abutments required no additional treatment for the single crowns and 2 of the FDPs, but 2 of the FDPs had to be left with interim cement for a longer period of time. The most common technical early complication during the prosthetic treatment phase was unacceptable color. Three (1.1%) of the 264 single crowns and 1 (0.8%) of 120 FDPs had to be remade because of unacceptable color. Poor fit of the framework was recorded in 3 (2.5%) of 120 FDPs. Pulp exposure during the preparation occurred in 3 (2.5%) of 120 FDPs. In 2 abutment teeth, visible exposure occurred during preparation. In 1 abutment, the FDP was cemented with interim cement and endodontically treated afterward, and in the other, mineral trioxide aggregate was used to protect the abutment tooth by pulp capping. In addition, 1 patient developed symptoms of pulpitis, and the
4
Volume
Table I.
-
Issue
-
Early complications during prosthetic treatment of zirconia single crowns (n¼264) and partial FDPs (n¼120)
Single Crown Complication Type Biological
FDP
Complication Description
n
%
n
%
Localized gingival irritation
5
1.9
3
2.5
Postoperative tooth sensitivity
1
0.4
4
3.3
Unacceptable final color
3
1.1
1
0.8
Framework did not fit
0
0
3
2.5
Perforation during preparation
0
0
3
2.5
Restoration left with temporary cement
0
0
2
1.7
Loss of existing filling
1
0.4
0
0
Total
10
3.8
16
13.3
Technical
FDP, fixed dental prosthesis.
Table II.
Short-term failures in year after definitive cementation of zirconia single crowns (n¼264) and FDP (n¼120)
Single Crown Complication Type
FDP
Complication Description
n
%
n
%
Biological
.
0
0
0
0
Technical
Porcelain chipping, irreparable
2
0.8
0
0
Porcelain chipping, reparable
0
0
1
0.8
Framework fracture
0
0
2
1.7
Loss of retention
1
0.4
0
0
Total
3
1.1
3
2.5
FDP, fixed dental prosthesis.
abutment tooth had to be endodontically treated and restored with a fiber post before the impression phase. No biological short-term failures of single crowns or FDPs occurred during the first year after definitive cementation (Table II). Of the technical failures, chipping of the veneering porcelain was recorded in 2 (0.8%) of 264 crowns (a maxillary lateral incisor and a mandibular central incisor) and loss of retention in 1 (0.4%) of 264 crowns. Chipping of porcelain occurred during the first month in use. Both crowns were considered unrepairable (Grade 3 according to Heintze and Rousson1), and the crown was remade. The crown with loss of retention was recemented. Framework fracture was noted in 2 (1.7%) of 120 FDPs, and the restorations had to be remade. In 1 (0.8%) of 120 FDPs, a minor reparable porcelain fracture (Grade 21) was observed in a
maxillary premolar abutment and was repaired with composite resin (Table II). None of the 120 FDPs lost retention during the observation period.
DISCUSSION The most common early complications were localized gingival irritation and postoperative tooth sensitivity. The most common short-term failure was chipping of the veneering porcelain, as has also been reported in previous studies when compared to metal ceramic restorations.1,19 The framework fracture was noted in 1.7% of FDPs, which can be considered a high percentage when compared to Sailer et al,19 who in a systematic review reported the annual failure rate of zirconia framework fracture to be 0 to 0.48%. The first framework fracture
The Journal of Prosthetic Dentistry
occurred in the connector area of 2 premolar abutments when the FDP was removed after interim cementation. The other framework fracture occurred in an occlusal area of a molar abutment tooth after the definitive cementation. The cause of the fracture in this prosthesis is unknown. The most common abutment teeth for mandibular zirconia FDPs were molars. The indications for the use of zirconia in the mandibular posterior region rather than metal ceramic were related to an interest in using a metalfree, high-strength material with reported promising results.19 In addition, the zirconia frameworks were less expensive for the patient. Although a year is short time in the expected life of a restoration, identifying initial problems that may be rectifiable is important. However, if the material fails at this point, it is more
Pihlaja et al
-
2014
likely caused by material weakness or errors during the fabrication process rather than patient factors, such as bruxism or diet. Localized gingival irritation was a problem during the prosthetic treatment. It was mainly related to excess cement and was managed with cement removal, professional cleaning, and improved home instructions. In some studies, no significant periodontal differences between the control teeth and abutments were noted.13 However, in 3-year followups, Tartaglia et al10 and Tinschert et al13 found that abutment teeth tended to have increased pocket depths. Ortorp et al,11 in a 3-year follow-up, reported that only 4 of 25 crowns were free from gingival bleeding and calculus. Although postoperative tooth sensitivity has rarely been mentioned as a biological complication in follow-up studies, tooth sensitivity was relatively common in this study. Only Roediger et al18 have also described sensitivity as a common problem. However, postoperative tooth sensitivity is usually a transient symptom, as Roediger et al18 also stated, and only 2 patients in this study in whom the FDP was left on with interim cement for a longer period of time needed additional treatment. Abutment preparation is always a risk to pulp vitality because the preparation may lead to pulp reactions or exposure. Although the treatment procedures were made by predoctoral students, the definitive preparations and restorations were supervised by qualified dental instructors. In the present study, pulp exposure occurred in 3 abutments during preparation, all in the abutment teeth of FDPs. In 1 tooth, the pulp was successfully capped with mineral trioxide aggregate, but the other 2 required endodontic treatment. In this study, 2 (0.8%) of 264 single crowns and 1 (0.8%) of 120 FDPs had chipping of the veneering porcelain during the first year. Only a minor reparable chip-off fracture (Grade 21) was noted in the FDP, but both single crown fractures occurred within the first few weeks of use and were considered irreparable (Grade 31).
Pihlaja et al
5 A limitation of this study is the impossibility of comparing zirconia manufacturing systems with one another; patient records did not specify which systems were used for every patient. Sagirkaya et al16 reported that because porcelain systems are different, survival rates may differ with 3 to 6 unit FDPs when different systems are used. Differences in marginal accuracy may also be noted when different systems and techniques are used.16 Recording accurate treatment information with the precise details of materials and manufacturers is essential, especially with ceramic materials, because when zirconia materials are chosen, numerous processing techniques and materials are available. Short-term and medium-term studies have demonstrated the excellent biological and mechanical properties of zirconia,10-14,16-21 but long-term follow-up studies of zirconia restorations will be needed to compare different fabrication processes and to investigate how time affects the materials.
CONCLUSIONS The results of this retrospective study showed that with zirconia single crowns and FDPs made by predoctoral students, the most usual early complications were localized gingival irritation and postoperative tooth sensitivity, and the most usual short-term failure was chipping of the veneering porcelain.
REFERENCES 1. Heintze SD, Rousson V. Survival of zirconiaand metal-supported fixed dental prostheses: a systematic review. Int J Prosthodont 2010;23:493-502. 2. Näpänkangas R, Raustia A. Twenty-year follow-up of metal-ceramic single crowns: a retrospective study. Int J Prosthodont 2008;21:307-11. 3. Näpänkangas R, Raustia A. An 18-year retrospective analysis of treatment outcomes with metal-ceramic fixed partial dentures. Int J Prosthodont 2011;24:314-9. 4. Conrad HJ, Seong WJ, Pesun IJ. Current ceramic materials and systems with clinical recommendations: a systematic review. J Prosthet Dent 2007;98:389-404.
5. Pjetursson BE, Sailer I, Zwahlen M, Hämmerle CH. 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 I: single crowns. Clin Oral Implants Res 2007;18(suppl 3):73-85. 6. Della Bona A, Kelly JR. The clinical success of all-ceramic restorations. J Am Dent Assoc 2008;139:8-13. 7. Sorrentino R, Galasso L, Tetè S, De Simone G, Zarone F. Clinical evaluation of 209 all-ceramic single crowns cemented on natural and implant-supported abutments with different luting agents: a 6-year retrospective study. Clin Implant Dent Relat Res 2012;14:184-97. 8. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns: a two-year report. J Am Dent Assoc 2010;141:10-4. 9. Heintze SD, Rousson V. Fracture rates of IPS Empress all-ceramic crowns-a systematic review. Int J Prosthodont 2010;23:129-33. 10. Tartaglia GM, Sidoti E, Sforza CA. 3-year follow-up study of all-ceramic single and multiple crowns performed in a private practice: a prospective case series. Clinics (Sao Paulo) 2011;66:2063-70. 11. Ortorp A, Kihl ML, Carlsson GE. A 3-year retrospective and clinical follow-up study of zirconia single crowns performed in a private practice. J Dent 2009;37:731-6. 12. 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. 13. Tinschert J, Schulze KA, Natt G, Latzke P, Heussen N, Spiekermann H. Clinical behavior of zirconia-based fixed partial dentures made of DC-Zirkon: 3-year results. Int J Prosthodont 2008;21:217-22. 14. Al-Amleh B, Lyons K, Swain M. Clinical trials in zirconia: a systematic review. J Oral Rehabil 2010;37:641-52. 15. Peláez J, Cogolludo PG, Serrano B, Lozano JF, Suárez MJ. A prospective evaluation of zirconia posterior fixed dental prostheses: three-year clinical results. J Prosthet Dent 2012;107:373-9. 16. Sagirkaya E, Arikan S, Sadik B, Kara C, Karasoy D, Cehreli M. A randomized, prospective, open-ended clinical trial of zirconia fixed partial dentures on teeth and implants: interim results. Int J Prosthodont 2012;25:221-31. 17. Sailer I, Fehér A, Filser F, Gauckler LJ, Lüthy H, Hämmerle CH. Five-year clinical results of zirconia frameworks for posterior fixed partial dentures. Int J Prosthodont 2007;20:383-8. 18. Roediger M, Gersdorff N, Huels A, Rinke S. Prospective evaluation of zirconia posterior fixed partial dentures: four-year clinical results. Int J Prosthodont 2010;23:141-8. 19. Sailer I, Pjetursson BE, Zwahlen M, Hämmerle CH. 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.
6
Volume 20. Manicone PF, Rossi Iommetti P, Raffaelli L. An overview of zirconia ceramics: basic properties and clinical applications. J Dent 2007;35:819-26. 21. Augstin-Panadero R, Fons-Font A, RomanRodriguez JL, Granell-Ruiz M, del RioHighsmith J, Sola-Ruiz MF. Zirconia versus metal: a preliminary comparative analysis of ceramic veneer behavior. Int J Prosthodont 2012;25:294-300. 22. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. An 18-year retrospective survival study of full crowns with or without posts. Int J Prosthodont 2006;19:136-42.
23. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. A 20-year retrospective survival study of fixed partial dentures. Int J Prosthodont 2006;19: 143-53. 24. Rinke S, Fischer C. Range of indications for translucent zirconia modifications: clinical and technical aspects. Quintessence Int 2013;44:557-66. 25. Shillingburg HT, Staher DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, et al. Fundamentals of fixed prosthodontics. 4th ed. Chicago: Quintessence Publishing Co; 2012. p. 131-48, 161-2.
The Journal of Prosthetic Dentistry
-
Issue
-
Corresponding author: Dr Ritva Näpänkangas Department of Prosthetic Dentistry and Stomatognathic Physiology Institute of Dentistry, University of Oulu Box 5281, FIN-90014 Oulu FINLAND E-mail: ritva.napankangas@oulu.fi Acknowledgments The authors thank Vuokko Anttonen and Päivi Harju for their help collecting patient files. Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
Pihlaja et al
Clinical Implications Patients should be told that tooth sensitivity may occur after preparation but is usually transient. In the case of localized gingival irritation with single crowns or the abutment teeth of fixed dental prostheses, an examination may reveal excess cement. The chipping of porcelain is more common in zirconia restorations than in metal ceramic ones and can occur shortly after cementation. Conventional metal ceramic single crowns and partial fixed dental prostheses (FDP) have been used in dentistry for decades and have earned worldwide acceptance.1 Nowadays, they are regarded as the gold standard because of their low failure rates and good longterm clinical results.2,3 Nevertheless, the a
emerging demands for metal-free, more biocompatible, and highly esthetic restorations have directed materials research and development toward ceramics. Numerous advances have been made in the mechanical properties and fabrication methods of ceramic materials since the introduction of leucite-
reinforced glass ceramics (IPS Empress; Ivoclar Vivadent) and the InCeram technique (Vita Zahnfabrik; H. Rauter GmbH & Co KG).4,5 Currently, a wide range of ceramic materials is available for clinical use. On the basis of recent studies, fixed ceramic prostheses fabricated from newer
Dental student, Institute of Dentistry, University of Oulu. Senior lecturer, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Oulu, Finland; and Specialist, Oral and Maxillofacial Department, Oulu University Hospital. c Professor, Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Oulu, Oulu, Finland; and Chief, Oral and Maxillofacial Department, Oulu University Hospital. b
Pihlaja et al
2
Volume materials, especially zirconia, have shown relatively high short-term and mediumterm survival rates, comparable to those of metal ceramics.4-19 This evidence suggests that, especially in the absence of parafunctional habits, clinicians may choose from any of the recent ceramic materials, depending on the esthetic and functional needs of the patient.6 Because of its excellent mechanical properties, zirconia is more widely used in restorative dentistry than other ceramics.20 The high strength and fracture toughness of zirconia has changed the most frequent reasons for the failure of ceramic partial fixed dental prostheses (FDPs) from severe framework fracture to minor technical complications, such as the chipping of veneering porcelain.12 This problem seems to be the biggest weakness of zirconia restorations when compared to metal ceramic ones.21 Early repairable chipping of veneering porcelain can increase the risk for irreparable porcelain damage later.22,23 In addition, Sagirkaya et al16 found in a 4-year followup that 4 out of 5 failures occurred in the first year. However, the use of monolithic zirconia with no veneering porcelain has increased and the risk for the fractures has diminished.24 To our knowledge, no published studies have focused completely on the early complications of zirconia restorations during the prosthetic treatment phase or on short-term failures during the first year in use. The hypothesis was that complications are few during and shortly after prosthetic treatment. Thus, the objective of the study was to evaluate the early complications and shortterm failures of zirconia single crowns and FDPs made by predoctoral dental students.
approved by the ethical committee of the Northern Ostrobothnia Hospital District. Data, which consisted of patients treated with zirconia single crowns and FDPs by predoctoral dental students, were collected from patient records. A total of 173 patients (94 women and 79 men, mean age 55 years, range 18-79 years) were treated with zirconia single crowns or FDPs between 2007 and 2010. Altogether, 264 zirconia single crowns were placed in 88 patients (mean 3 crowns per patient, range 1 to 12 crowns), mostly to the maxillary anterior region (Fig. 1). The names and manufacturers of the zirconia frameworks in single crowns were Zirkonzahn Zirconia (Zirkonzahn), NobelProcera Zirconia (Nobel Biocare), and Prettau Zirconia (Zirkonzahn). In addition, 102 patients were treated with 120 zirconia FDPs (range 3 to 12 units, mean 4.5 units). The names and manufacturers of the zirconia frameworks in FDP were Zirkonzahn Zirconia (Zirkonzahn), NobelProcera Zirconia (Nobel Biocare), and Prettau Zirconia (Zirkonzahn). These FDPs consisted of 342 abutments and 185 pontics (Fig. 2), of which 5 were cantilevers.
MATERIAL AND METHODS This retrospective study of the early complications of zirconia restorations during the prosthetic treatment phase and short-term failures during the first year in use was conducted at the Institute of Dentistry, University of Oulu, Finland. The study protocol was
The Journal of Prosthetic Dentistry
-
Issue
-
The abutment teeth were usually maxillary canines and incisors, and mandibular premolars and second molars. The maxillary pontics were distributed evenly in the dental arch, but in the mandible, the first molars were the most common pontics. The most common indications for zirconia restorations were excessive loss of tooth substance (crowns), renewal of the existing restorations (crowns), and tooth loss (FDPs). All patients received periodontal treatment before prosthetic treatment, including education, instructions for proper home care, and a professional tooth cleaning. The preprosthetic treatment also included caries and endodontic treatment as well as occlusal adjustment, if needed. All the preparations were made in accordance with international treatment guidelines.25 For the crowns and abutment teeth of FDPs, the teeth were prepared with 1.5 mm axial clearance (total convergence 6 degrees) and a 2 mm anatomically adequate occlusal or incisal reduction with a functional cusp bevel to ensure sufficient material thickness. The heavy chamfer finish line was placed slightly below the free
45 40 35 30 25 20 15 10 5 0
0 5 10 15 20 25 30 35 40 45
Maxillary teeth Mandibular teeth
1 Distribution of zirconia single crowns (n¼264).
Pihlaja et al
-
2014
3 45 40
Pontics
35
Abutments
30 25 20 15 10 5 0
Maxillary teeth Mandibular teeth
0 5 10 15 20 25 30 35
Pontics
40
Abutments
RESULTS
45
2 Distribution of abutment teeth and pontics of zirconia partial fixed dental prostheses (n¼120). gingival margin (0.5 mm) in anterior teeth and marginally (equigingival) in posterior teeth. Composite resin (Filtek Z250; 3M ESPE) was used for the foundation when needed, and a fiber post (RelyX Fiber post; 3M ESPE) was used in endodontically treated teeth. All the treatment procedures were performed under the supervision of qualified clinical instructors. For Zirkonzahn Zirconia and Prettau Zirconia, the frameworks were fabricated with manual milling and designed for the uniform thickness of the veneering porcelain layer. The minimal thickness of the framework was 0.4 mm. The connector design requirement was 9.0 mm2. The veneering porcelain (GC Initial Zr; GC Europe) was layered on the frameworks. In NobelProcera Zirconia, the frameworks were fabricated by using computer-aided design/ computer-assisted manufacture and designed for the uniform thickness of veneering porcelain layer. The minimal thickness of the frameworks in single crowns was 0.4 mm in the anterior area and 0.7 mm in the posterior area and in FDP 0.6 mm. Briefly, for the FDPs, the
Pihlaja et al
patients were asked to make contact in case of emergency, and no scheduled examination at the clinic was performed after the 6-month follow-up visit. Patient records were checked for possible failures between 6 months and 12 months after the definitive cementation. The complications were divided into early complications and short-term failures. Early complications included complications recorded during the prosthetic treatment until definitive cementation. Short-term failures included failures recorded during the first year in use after the definitive cementation. Both early complications and short-term failures were divided into biological and technical categories.
connector design requirement was 6.0 mm2 in the anterior area and 9.4 mm2 in the posterior area. The veneering porcelain (Vita VM 9; Vita Zahnfabrik) was layered on the frameworks. Before the definitive cementation of the restorations, their esthetic appearance and occlusion were confirmed. The clinical instructor evaluated the fit of the restoration and the patients were asked whether they were satisfied with the color and esthetics of the restoration. The restorations were bonded with dual-polymerizing, self-adhesive, universal resin cement (RelyX Unicem; 3M ESPE) according to the manufacturer’s instructions. The single crowns were cemented with definitive cement immediately, but the FDPs were first cemented with interim cement (TempBond NE; Kerr Corp), and definitive cementation took place about 1 week later. The first follow-up was scheduled 1 to 2 weeks after the definitive cementation of the crowns and FDP. At the 6month follow-up, the restorations, surrounding tissues, and occlusion were thoroughly examined. Thereafter,
The biological early complications found were localized gingival irritation (5 of 264 single crowns, 1.9%; 3 of 120 FDP, 2.5%) and postoperative tooth sensitivity (1 of 264 single crowns, 0.4%; 4 of 120 FDPs, 3.3%) (Table I). Localized gingival irritation was caused by excess cement (except in 1 instance) and was relieved by cement removal. The tooth sensitivity of abutments required no additional treatment for the single crowns and 2 of the FDPs, but 2 of the FDPs had to be left with interim cement for a longer period of time. The most common technical early complication during the prosthetic treatment phase was unacceptable color. Three (1.1%) of the 264 single crowns and 1 (0.8%) of 120 FDPs had to be remade because of unacceptable color. Poor fit of the framework was recorded in 3 (2.5%) of 120 FDPs. Pulp exposure during the preparation occurred in 3 (2.5%) of 120 FDPs. In 2 abutment teeth, visible exposure occurred during preparation. In 1 abutment, the FDP was cemented with interim cement and endodontically treated afterward, and in the other, mineral trioxide aggregate was used to protect the abutment tooth by pulp capping. In addition, 1 patient developed symptoms of pulpitis, and the
4
Volume
Table I.
-
Issue
-
Early complications during prosthetic treatment of zirconia single crowns (n¼264) and partial FDPs (n¼120)
Single Crown Complication Type Biological
FDP
Complication Description
n
%
n
%
Localized gingival irritation
5
1.9
3
2.5
Postoperative tooth sensitivity
1
0.4
4
3.3
Unacceptable final color
3
1.1
1
0.8
Framework did not fit
0
0
3
2.5
Perforation during preparation
0
0
3
2.5
Restoration left with temporary cement
0
0
2
1.7
Loss of existing filling
1
0.4
0
0
Total
10
3.8
16
13.3
Technical
FDP, fixed dental prosthesis.
Table II.
Short-term failures in year after definitive cementation of zirconia single crowns (n¼264) and FDP (n¼120)
Single Crown Complication Type
FDP
Complication Description
n
%
n
%
Biological
.
0
0
0
0
Technical
Porcelain chipping, irreparable
2
0.8
0
0
Porcelain chipping, reparable
0
0
1
0.8
Framework fracture
0
0
2
1.7
Loss of retention
1
0.4
0
0
Total
3
1.1
3
2.5
FDP, fixed dental prosthesis.
abutment tooth had to be endodontically treated and restored with a fiber post before the impression phase. No biological short-term failures of single crowns or FDPs occurred during the first year after definitive cementation (Table II). Of the technical failures, chipping of the veneering porcelain was recorded in 2 (0.8%) of 264 crowns (a maxillary lateral incisor and a mandibular central incisor) and loss of retention in 1 (0.4%) of 264 crowns. Chipping of porcelain occurred during the first month in use. Both crowns were considered unrepairable (Grade 3 according to Heintze and Rousson1), and the crown was remade. The crown with loss of retention was recemented. Framework fracture was noted in 2 (1.7%) of 120 FDPs, and the restorations had to be remade. In 1 (0.8%) of 120 FDPs, a minor reparable porcelain fracture (Grade 21) was observed in a
maxillary premolar abutment and was repaired with composite resin (Table II). None of the 120 FDPs lost retention during the observation period.
DISCUSSION The most common early complications were localized gingival irritation and postoperative tooth sensitivity. The most common short-term failure was chipping of the veneering porcelain, as has also been reported in previous studies when compared to metal ceramic restorations.1,19 The framework fracture was noted in 1.7% of FDPs, which can be considered a high percentage when compared to Sailer et al,19 who in a systematic review reported the annual failure rate of zirconia framework fracture to be 0 to 0.48%. The first framework fracture
The Journal of Prosthetic Dentistry
occurred in the connector area of 2 premolar abutments when the FDP was removed after interim cementation. The other framework fracture occurred in an occlusal area of a molar abutment tooth after the definitive cementation. The cause of the fracture in this prosthesis is unknown. The most common abutment teeth for mandibular zirconia FDPs were molars. The indications for the use of zirconia in the mandibular posterior region rather than metal ceramic were related to an interest in using a metalfree, high-strength material with reported promising results.19 In addition, the zirconia frameworks were less expensive for the patient. Although a year is short time in the expected life of a restoration, identifying initial problems that may be rectifiable is important. However, if the material fails at this point, it is more
Pihlaja et al
-
2014
likely caused by material weakness or errors during the fabrication process rather than patient factors, such as bruxism or diet. Localized gingival irritation was a problem during the prosthetic treatment. It was mainly related to excess cement and was managed with cement removal, professional cleaning, and improved home instructions. In some studies, no significant periodontal differences between the control teeth and abutments were noted.13 However, in 3-year followups, Tartaglia et al10 and Tinschert et al13 found that abutment teeth tended to have increased pocket depths. Ortorp et al,11 in a 3-year follow-up, reported that only 4 of 25 crowns were free from gingival bleeding and calculus. Although postoperative tooth sensitivity has rarely been mentioned as a biological complication in follow-up studies, tooth sensitivity was relatively common in this study. Only Roediger et al18 have also described sensitivity as a common problem. However, postoperative tooth sensitivity is usually a transient symptom, as Roediger et al18 also stated, and only 2 patients in this study in whom the FDP was left on with interim cement for a longer period of time needed additional treatment. Abutment preparation is always a risk to pulp vitality because the preparation may lead to pulp reactions or exposure. Although the treatment procedures were made by predoctoral students, the definitive preparations and restorations were supervised by qualified dental instructors. In the present study, pulp exposure occurred in 3 abutments during preparation, all in the abutment teeth of FDPs. In 1 tooth, the pulp was successfully capped with mineral trioxide aggregate, but the other 2 required endodontic treatment. In this study, 2 (0.8%) of 264 single crowns and 1 (0.8%) of 120 FDPs had chipping of the veneering porcelain during the first year. Only a minor reparable chip-off fracture (Grade 21) was noted in the FDP, but both single crown fractures occurred within the first few weeks of use and were considered irreparable (Grade 31).
Pihlaja et al
5 A limitation of this study is the impossibility of comparing zirconia manufacturing systems with one another; patient records did not specify which systems were used for every patient. Sagirkaya et al16 reported that because porcelain systems are different, survival rates may differ with 3 to 6 unit FDPs when different systems are used. Differences in marginal accuracy may also be noted when different systems and techniques are used.16 Recording accurate treatment information with the precise details of materials and manufacturers is essential, especially with ceramic materials, because when zirconia materials are chosen, numerous processing techniques and materials are available. Short-term and medium-term studies have demonstrated the excellent biological and mechanical properties of zirconia,10-14,16-21 but long-term follow-up studies of zirconia restorations will be needed to compare different fabrication processes and to investigate how time affects the materials.
CONCLUSIONS The results of this retrospective study showed that with zirconia single crowns and FDPs made by predoctoral students, the most usual early complications were localized gingival irritation and postoperative tooth sensitivity, and the most usual short-term failure was chipping of the veneering porcelain.
REFERENCES 1. Heintze SD, Rousson V. Survival of zirconiaand metal-supported fixed dental prostheses: a systematic review. Int J Prosthodont 2010;23:493-502. 2. Näpänkangas R, Raustia A. Twenty-year follow-up of metal-ceramic single crowns: a retrospective study. Int J Prosthodont 2008;21:307-11. 3. Näpänkangas R, Raustia A. An 18-year retrospective analysis of treatment outcomes with metal-ceramic fixed partial dentures. Int J Prosthodont 2011;24:314-9. 4. Conrad HJ, Seong WJ, Pesun IJ. Current ceramic materials and systems with clinical recommendations: a systematic review. J Prosthet Dent 2007;98:389-404.
5. Pjetursson BE, Sailer I, Zwahlen M, Hämmerle CH. 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 I: single crowns. Clin Oral Implants Res 2007;18(suppl 3):73-85. 6. Della Bona A, Kelly JR. The clinical success of all-ceramic restorations. J Am Dent Assoc 2008;139:8-13. 7. Sorrentino R, Galasso L, Tetè S, De Simone G, Zarone F. Clinical evaluation of 209 all-ceramic single crowns cemented on natural and implant-supported abutments with different luting agents: a 6-year retrospective study. Clin Implant Dent Relat Res 2012;14:184-97. 8. Fasbinder DJ, Dennison JB, Heys D, Neiva G. A clinical evaluation of chairside lithium disilicate CAD/CAM crowns: a two-year report. J Am Dent Assoc 2010;141:10-4. 9. Heintze SD, Rousson V. Fracture rates of IPS Empress all-ceramic crowns-a systematic review. Int J Prosthodont 2010;23:129-33. 10. Tartaglia GM, Sidoti E, Sforza CA. 3-year follow-up study of all-ceramic single and multiple crowns performed in a private practice: a prospective case series. Clinics (Sao Paulo) 2011;66:2063-70. 11. Ortorp A, Kihl ML, Carlsson GE. A 3-year retrospective and clinical follow-up study of zirconia single crowns performed in a private practice. J Dent 2009;37:731-6. 12. 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. 13. Tinschert J, Schulze KA, Natt G, Latzke P, Heussen N, Spiekermann H. Clinical behavior of zirconia-based fixed partial dentures made of DC-Zirkon: 3-year results. Int J Prosthodont 2008;21:217-22. 14. Al-Amleh B, Lyons K, Swain M. Clinical trials in zirconia: a systematic review. J Oral Rehabil 2010;37:641-52. 15. Peláez J, Cogolludo PG, Serrano B, Lozano JF, Suárez MJ. A prospective evaluation of zirconia posterior fixed dental prostheses: three-year clinical results. J Prosthet Dent 2012;107:373-9. 16. Sagirkaya E, Arikan S, Sadik B, Kara C, Karasoy D, Cehreli M. A randomized, prospective, open-ended clinical trial of zirconia fixed partial dentures on teeth and implants: interim results. Int J Prosthodont 2012;25:221-31. 17. Sailer I, Fehér A, Filser F, Gauckler LJ, Lüthy H, Hämmerle CH. Five-year clinical results of zirconia frameworks for posterior fixed partial dentures. Int J Prosthodont 2007;20:383-8. 18. Roediger M, Gersdorff N, Huels A, Rinke S. Prospective evaluation of zirconia posterior fixed partial dentures: four-year clinical results. Int J Prosthodont 2010;23:141-8. 19. Sailer I, Pjetursson BE, Zwahlen M, Hämmerle CH. 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.
6
Volume 20. Manicone PF, Rossi Iommetti P, Raffaelli L. An overview of zirconia ceramics: basic properties and clinical applications. J Dent 2007;35:819-26. 21. Augstin-Panadero R, Fons-Font A, RomanRodriguez JL, Granell-Ruiz M, del RioHighsmith J, Sola-Ruiz MF. Zirconia versus metal: a preliminary comparative analysis of ceramic veneer behavior. Int J Prosthodont 2012;25:294-300. 22. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. An 18-year retrospective survival study of full crowns with or without posts. Int J Prosthodont 2006;19:136-42.
23. De Backer H, Van Maele G, De Moor N, Van den Berghe L, De Boever J. A 20-year retrospective survival study of fixed partial dentures. Int J Prosthodont 2006;19: 143-53. 24. Rinke S, Fischer C. Range of indications for translucent zirconia modifications: clinical and technical aspects. Quintessence Int 2013;44:557-66. 25. Shillingburg HT, Staher DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, et al. Fundamentals of fixed prosthodontics. 4th ed. Chicago: Quintessence Publishing Co; 2012. p. 131-48, 161-2.
The Journal of Prosthetic Dentistry
-
Issue
-
Corresponding author: Dr Ritva Näpänkangas Department of Prosthetic Dentistry and Stomatognathic Physiology Institute of Dentistry, University of Oulu Box 5281, FIN-90014 Oulu FINLAND E-mail: ritva.napankangas@oulu.fi Acknowledgments The authors thank Vuokko Anttonen and Päivi Harju for their help collecting patient files. Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
Pihlaja et al
