Q U I N T E S S E N C E I N T E R N AT I O N A L

RESTORATIVE DENTISTRY

Ulrike Stephanie Beier

Longevity of silicate ceramic restorations Ulrike Stephanie Beier, PD, DDr, MSc 1/Herbert Dumfahrt, Prof DDr2 The demand for esthetic restorations has resulted in an increased use of dental ceramics as a biocompatible and functionally sufficient alternative to conventional restorative materials. Silicate ceramic restorations are widely used for veneers, inlays, onlays, and crowns in dentistry. Long-term data are of crucial importance to optimize clinical practice. The

purpose of the present article is to summarize data of the Innsbruck ceramic evaluation up to 261 months with the focus on longevity and failure characteristics.1-4 (Quintessence Int 2014;45:637–644; originally published in Quintessenz 2013;64(6):701–709; doi: 10.3290/j.qi.a32234)

Key words: all-ceramic, bruxism, failure, longevity, silicate ceramic

All-ceramic restoration materials can be divided into two main categories: oxide and silicate ceramics (Fig 1).5,6 Silicate ceramics are glass-based systems with crystalline fillers, typically leucite or lithium disilicate. In contrast to polycrystalline ceramics, which have little to no glass contributing to their glass-to-crystalline ratio, their glass content is decidedly higher. The glass-tocrystalline ratio influences the esthetic outcome and stability of the ceramic. The larger and more homogenous the crystalline component, the more firm is the dental ceramic. Increased stability implies more opacity, leading to a reduced esthetic outcome. According to the recommendations by the Society for Dental Ceramics (SDC), ceramic materials with a fracture strength under 350 MPa must be adhesively cemented.7 Silicate ceramic restorations are optimal to mimic the translucency and structure of natural teeth.7 These 1

Assistant Professor, Clinical Department of Restorative and Prosthetic Dentistry, Innsbruck Medical University, Innsbruck, Austria.

2

Professor, Clinical Department of Restorative and Prosthetic Dentistry, Innsbruck Medical University, Innsbruck, Austria.

Correspondence: PD DDr Ulrike Stephanie Beier, Clinical Department of Restorative and Prosthetic Dentistry, Innsbruck Medical University, MZA, Anichstrasse 35, A-6020 Innsbruck, Austria. Email: [email protected]

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properties and patients’ changing attitudes to esthetic dentistry have increased the demand for metal-free restorations. In addition to esthetic considerations when selecting a restorative material, patients have questioned the use of amalgam and nonprecious alloy filler material,8 and this has been followed by technical progress in the development of new all-ceramic materials and clinical practices. The number of dental ceramics has increased dramatically, and these vary in material and clinical properties. This technological and materials progress has resulted in increased application in dentistry.9 However, inherent brittleness, crack propagation, low tensile strength, and the potential to abrade the opposing dentition are mentioned as mechanical shortcomings of these materials.10-13 The main reason reported for ceramic failure in clinical studies is still fracture of the ceramic material.14-17 Long-term data of silicate restorations are of crucial importance to optimize clinical practice. The purpose of the present article is to summarize data of the Innsbruck ceramic evaluation up to 261 months with the focus on longevity and failure characteristics.1-4

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Dental ceramic

Fig 1

Oxide ceramic

Silicate ceramic

with low glass content

glass and crystalline systems

Glass-infiltrated

Polycrystalline

Sintered glass-infiltrated aluminum oxide

Aluminum oxide Zirconium oxide

Glass ceramic

60% to 70% feldspar

Leucite-reinforced glass ceramic Lithium-disilicate– reinforced glass ceramic Fluorapatite glass ceramic

Classification of dental ceramics.

METHOD AND MATERIALS Clinical examination Three hundred and two patients (120 men and 182 women) were examined during their regularly scheduled maintenance appointment in the Department of Restorative and Prosthetic Dentistry, Innsbruck Medical University, Austria, over a 4-month period from March 2010 to July 2010. No patients were excluded. All examined silicate ceramic restorations were fabricated following the manufacturers’ recommendations in the dental laboratory of the department between November 1987 and December 2009. Patient (sex, age, and smoking and bruxing habit), tooth (location in the oral cavity, sensitivity, in case of nonvital teeth core placement, extension of the restoration, and state of periodontal situation), and ceramic (type of restoration, material, and bonding and cementation material) specific data for every single restoration were recorded in a ceramic database after insertion. Additionally, casts were fabricated for further diagnostics. The clinical examination of the restorations was performed by two experienced dentists after careful calibration using modified California Dental Association (CDA)/Ryge criteria.18,19 The following examination issues were assessed:

638

Feldspathic porcelain

• • • •

esthetic match porcelain surface marginal discoloration marginal integrity.

If the evaluation parameters were rated “Alpha” or “Bravo”, the ceramic restoration was rated acceptable and successful. “Charlie” and “Delta” ratings were determined as unacceptable and classified as failures. Types and reasons for failures were recorded. Data concerning failures of the ceramic restoration from the examined patients before the evaluation in 2010 were collected from the patient’s chart and ceramic database and included in the study. After the clinical examination, the patient’s selfreported satisfaction with the ceramic restoration was measured with a categorical scale consisting of the following four responses: excellent, good, medium, or none.

Statistical analysis Statistical analysis was performed using the SAS 9.2 software (SAS Institute). The survival time was defined as the period of time starting from the successful fitting of the silicate ceramic restoration and ending when the restoration presented with an irreparable problem.

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Table 1

Overview of failure characteristics (n = 95) Total

Failure characteristic

Ceramic factors

n

%

Total

60

63.2

Fracture of the ceramic

32

33.7

Crack in the ceramic

23

24.2

Chipping

5

5.3

14

14.7

Caries New restoration after endodontic treatment

6

6.3

Fracture of tooth

4

4.2

Debonding

3

3.2

Marginal integrity

3

3.2

Esthetics (color or too short)

3

3.2

Hypersensitivity

2

2.1

Total

95

100

Kaplan-Meier methodology was utilized for the calculation of the survival probabilities in this study. The logrank chi-square statistic test was applied for comparison of the different groups. The Cox proportional hazards model was used to study the influence of various risk factors for veneer failure. The level of significance was established at P ≤ .05.

RESULTS In total, 470 crowns, 318 veneers, 213 onlays, and 334 inlays (1,335 restorations) were evaluated. The mean observation time for the single restoration was 102.41 ± 60.46 months. The mean age of patients at the time of cementation was 46.51 ± 13.14 years. During evaluation in 2010, 1,266 restorations were clinically examined using modified Ryge criteria, with 26 restorations rated not acceptable and unsatisfactory (“Charlie” or “Delta” rating). The study population contained 1,335 ceramic restorations because in this patient group 69 failures occurred before the evaluation in 2010. In summary, 95 restoration failures were recorded. Table 1 presents the number and frequency of the different failure characteristics.

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The Kaplan-Meier survival analysis of the different restoration types with 95 failures evaluated is shown in Table 2 and graphically in Fig 2 in detail. The log-rank test revealed no significant differences between the restoration types. Comparing the used ceramic materials as a predictor for failure, no significant differences were found. Significantly higher failure rates were observed for nonvital teeth (P < .0001) and in the luting agents: cementation using Variolink (Ivoclar Vivadent) showed significantly fewer failures than Optec Cement (Jeneric/Pentron; P = .0217) and Dual Cement (Ivoclar Vivadent; P = .0099). Figure 3 presents the distribution of the silicate restorations in the oral cavity. In total, 652 (48.8%) silicate restorations were placed in the anterior region, 442 (33.1%) in premolars, and 241 (18.1%) in molars. Of the 95 failures, 65 (68.4%) occurred in the anterior region, 19 (20%) in premolars, and 11 (11.6%) in molars. For the different regions in the oral cavity (anterior, premolar, or molar), the statistical analysis found no significant differences. In the study population, 106 (35.1%) patients showed signs of a bruxing habit or were diagnosed as bruxers. Restorations in this study population showed a significantly (P = .0045) higher failure risk, with a Hazard ratio of 2.3. On the four responses (excellent, good, medium, or none) for self-rating patient satisfaction, no patients rated medium or no satisfaction. Fifty-seven patients (4.1%) rated satisfaction as good and 1,280 patients (95.9%) rated it excellent. All of the patients, even those who had ceramic failures, regarded the ceramic restorations as an ideal type of dental restoration and would bear the ceramic procedure, time, and costs again.

DISCUSSION The most frequent reason for failure was fracture of the ceramic (33.68%). The second most frequent reason for failure was cracks in the ceramic (n = 23; 24.21%) (Table 1). Secondary caries was the reason for failure in 14 cases (14.74%). This reflects the findings of previous studies.13-16

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Table 2

Estimated survival rates (%) for different restoration types (Kaplan-Meier method)

Years

All restorations

Crowns

Veneers

Onlays

Inlays (total)

Inlay (1 surface)

Inlay (2 surfaces)

Inlay (3 surfaces)

5

97.3

97.4

94.5

98.9

98.9

100

100

97.8

8

95.6

94.1

94.1

98.1

97.3

100

100

94.5

10

93.5

90.0

93.5

92.4

96.8

100

100

93.3

12

91.1

88.5

93.5

92.4

89.6

94.7

94.4

83.4

15

85.8

83.6

85.7

no data

87.2

94.7

94.4

77.6

18

80.1

77.3

82.9

no data

81.5

94.7

94.4

63.9

20

78.5

51.2

82.9

no data

81.5

94.7

94.4

63.9

Veneer Crown Onlay Inlay

Veneer (censored) Crown (censored) Onlay (censored) Inlay (censored)

700

Inlay (3 surfaces) Inlay (2 surfaces) Inlay (1 surface) Onlay Crown Veneer

0,0,0,0

600

Number of restorations

1.0

Cumulative survival

0.8 0.6 0.4

500

337

400

127

300 99

315

0.2

28 42 24

14

200

99

100

114 100

0

50

100

150

200

250

300

33 0

3

0

0

Anterior region

Premolar region

Molar region

Observation period (months) Fig 2 Kaplan-Meier survival curves for the event failure of all restoration types.

Fig 3 Distribution of the silicate restorations in the oral cavity.

Over 80% of all restorations were placed in the anterior and premolar regions. The small number of ceramic restorations in the molar region might be responsible for the fact that, concerning the different regions in the oral cavity (anterior, premolar, or molar), no significantly higher failure rates were found in the molar region.

These findings differ from the results of Fradeani and Redemagni,20 who reported that posterior allceramic crowns are associated with a higher risk of fracture. Especially in patients with signs of bruxism, allceramic restorations show higher failure rates in the molar region, because of the higher bite forces compared to the anterior region.21-23 The dentist must pay

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Fig 4

Initial situation: anterior view.

Fig 7 Initial situation: occlusal view mandible.

Fig 5 Initial situation: protrusive movement.

Fig 6 Initial situation: occlusal view maxilla.

Fig 8 Initial situation: severe substantial teeth defects resulting from bulimia, palatal view.

Fig 9 side.

special attention to indications for ceramic crowns in the molar area. In cases where adhesive cementation is not possible because of the extension of the preparation finish line, patients should be consulted regarding an alternative restoration type, with the possibility of conventional cementation. In the study population, 106 patients reported a bruxing habit or were diagnosed as bruxers. The calculated risk for a ceramic failure was 2.3-times higher than for patients without parafunction. The results supported the hypothesis that the bruxing habit is a major factor influencing ceramic failure, especially in veneer restorations. The determined risk was 7.7-times higher for failure in bruxing patients than in patients without the bruxing habit.2 Therefore, after placing the ceramic restorations, patients at the Innsbruck clinic are provided with heat-pressed hard acrylic-resin occlusal guards to protect the definitive restorations during bruxism episodes. Significantly higher failure rates were observed for nonvital teeth (P < .0001). In general, dentists should consider that ceramic preparations increase the likelihood of eventual pulpal death.24 The creation of an

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Initial situation: facial view right

endodontic access cavity through a ceramic restoration can become difficult,25 and in some cases a new restoration might be indicated. Reasons for the high success rate are the strict adherence to the anterior-canine-guidance occlusal concept to avoid premature and balance contacts and the preparation under university conditions by experienced dentists with patients who were free of active gingival and periodontal inflammation prior to ceramic treatment.

CLINICAL CASE Figures 4 to 27 demonstrate a complex restoration with silicate ceramics in a patient with reduced vertical dimension and severe substantial teeth defects resulting from bulimia. After diagnostics the vertical dimension was increased, and malposition of the left maxillary central incisor and buccal non-occlusion of the left mandibular second premolar were corrected. The intact porcelain-fused-to-metal crown on the right mandibular second molar was substituted with a ceramic onlay to fulfill the occlusal concept and raise the bite.

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Fig 10 Initial situation: facial view left side.

Fig 11

Fig 13 Maxilla anterior region preparation, palatal view.

Fig 14 Mandible anterior region preparation, labial view.

Fig 15 Placement of retraction cords before impression taking.

Fig 16 Chair-side manufactured provisional restoration with increased vertical dimension.

Fig 17 Silver-plated gypsum model, maxilla.

Fig 18 Silver-plated gypsum model, mandible.

Fig 19

Fig 20 Palatal view of crowns in the maxilla.

Fig 21 Veneer restorations in the mandible, lingual view.

Technical work articulator.

Maxilla preparation.

CONCLUSION Silicate ceramic restorations showed a high success rate, with estimated survival rates of 93.5% at 10 years and 78.5% at 20 years. A significantly higher failure risk was found for patients with a bruxing habit and for

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Fig 12

Mandible preparation.

nonvital teeth. These risk factors should be discussed with the patient before preparation. One issue concerning all-ceramic restorations is the careful occlusal adjustment to establish canine-guided dynamic occlusion. If the bruxing habit occurs after placement of the ceramic restorations, patients should be provided with

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Fig 23 Placed restorations in the maxilla.

Fig 22 Ceramic restorations before adhesive cementation (in not entirely serious positioning).

Fig 24 dible.

Fig 25 view.

Fig 27 Placed restorations, protrusive movement.

Placed restorations, right facial

Fig 26 view.

Placed restorations, left facial

heat-pressed hard acrylic-resin occlusal guards to protect the definitive restorations during the bruxing episodes.

REFERENCES 1. Beier US, Kapferer I, Dumfahrt H. Clinical long-term evaluation and failure characteristics of 1,335 all-ceramic restorations. Int J Prosthodont 2012;25:70–78. 2. Beier US, Kapferer I, Burtscher D, Dumfahrt H. Clinical performance of porcelain laminate veneers for up to 20 years. Int J Prosthodont 2012;25:79–85. 3. Beier US, Kapferer I, Burtscher D, Giesinger JM, Dumfahrt H. Clinical performance of all-ceramic inlay and onlay restorations in posterior teeth. Int J Prosthodont 2012;25:395–402. 4. Beier US, Dhima M, Koka S, Salinas TJ, Dumfahrt H. Comparison of two different veneer preparation designs in vital teeth. Quintessence Int 2012;43:835–839.

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Placed restorations in the man-

5. Lindemann W. Dentalkeramiken-mineralogisch betrachtet. ZMK - Zahnheilkd Manage Kultur 2000;16:280–285. 6. Beier US, Kapferer I, Matkulcik M, Dumfahrt H. Klinische Erfahrungen mit silikatkeramischen Restaurationen. Stomatologie 2012;109:19–22. 7. Kern M, Kohal RJ, Mehl A, et al. Dentalkeramiken-Struktur und Einsatzzweck. In: AG Keramik (ed). Vollkeramik auf einen Blick. Ettlingen, 2010. 8. Brodbeck UR. Six years of clinical experience with an all-ceramic system. Signature 1997;43:6–13. 9. Haselton DR, Diaz-Arnold AM, Hillis SL. Clinical assessment of high-strength all-ceramic crowns. J Prosthet Dent 2000;83:396–401. 10. Qualtrough AJ, Piddock V. Ceramics update. J Dent 1997;25:91–95. 11. Sjogren G, Lantto R, Granberg A, Sundstrom BO, Tillberg A. Clinical examination of leucite-reinforced glass-ceramic crowns (Empress) in general practice: a retrospective study. Int J Prosthodont 1999;12:122–128. 12. Sjogren G, Lantto R, Tillberg A. Clinical evaluation of all-ceramic crowns (Dicor) in general practice. J Prosthet Dent 1999;81:277–284. 13. Conrad HJ, Seong W-J, Pesun IJ. Current ceramic materials and systems with clinical recommendations: A systematic review. J Prosthet Dent 2007;98: 389–404.

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14. Manhart J, Chen H, Hamm G, Hickel R. Buonocore Memorial Lecture. Review of the clinical survival of direct and indirect restorations in posterior teeth of the permanent dentition. Oper Dent 2004;29:481–508. 15. van Dijken JW, Hasselrot L. A prospective 15-year evaluation of extensive dentin-enamel-bonded pressed ceramic coverages. Dent Mater 2010;26: 929–939. 16. Peumans M, De Munck J, Fieuws S, Lambrechts P, Vanherle G, Van Meerbeek B. A prospective ten-year clinical trial of porcelain veneers. J Adhes Dent 2004;6:65–76. 17. Friedman MJ. A 15-year review of porcelain veneer failure: a clinician’s observations. Compend Contin Educ Dent 1998;19:625–628. 18. California Dental Association. Quality Evaluation of Dental Care. Guidelines for the Assessment of Clinical Quality and Performance. Sacramento, CA: CDA, 1995.

19. Ryge G. Clinical criteria. Int Dent J 1980;30:347–358. 20. Fradeani M, Redemagni M. An 11-year clinical evaluation of leucite-reinforced glass-ceramic crowns: a retrospective study. Quintessence Int 2002;33:503–510. 21. Blatz MB. Long-term clinical success of all-ceramic posterior restorations. Quintessence Int 2002;33:415–426. 22. Della Bona A, Kelly JR. The clinical success of all-ceramic restorations. J Am Dent Assoc 2008;139(Suppl):8S–13S. 23. Kelly JR. Dental ceramics: what is this stuff anyway? J Am Dent Assoc 2008;139(Suppl):4S–7S. 24. Valderhaug J, Jokstad A, Ambjornsen E, Norheim PW. Assessment of the periapical and clinical status of crowned teeth over 25 years. J Dent 1997;25:97–105. 25. Donovan TE. Factors essential for successful all-ceramic restorations. J Am Dent Assoc 2008;139(Suppl):14S–18S.

Longevity of silicate ceramic restorations.

The demand for esthetic restorations has resulted in an increased use of dental ceramics as a biocompatible and functionally sufficient alternative to...
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