Statement of problem
There is currently no protocol for managing endodontic access openings for all-ceramic crowns. A direct restorative material is generally used to repair the access opening, rendering a repaired crown as the definitive restoration. This endodontic procedure, however, may weaken the restoration or initiate microcracks that may propagate, resulting in premature failure of the restoration.
The purpose of this in vitro study was to evaluate how an endodontic access opening prepared through an all-ceramic crown altered the structural integrity of the ceramic, and the effect of a repair of this access on the load to failure of an all-ceramic crown.
Material and methods
Twenty-four alumina (Procera) and 24 zirconia (Procera) crowns were fabricated and cemented (Rely X Luting Plus Cement) onto duplicate epoxy resin dies. Twelve crowns of each were accessed to simulate root canal treatment therapy. Surface defects of all accessed specimens were evaluated with an environmental scanning electron microscope. The specimens were repaired with a porcelain repair system (standard adhesive resin/composite resin protocol) and were loaded to failure in a universal testing machine. Observations made visually and microscopically noted veneer delamination from the core, core fracture, shear within the veneer porcelain, or a combination thereof. A Kruskal-Wallis test was used to determine if a significant difference (α=.05) in load to failure existed between the 4 groups, and a Mann-Whitney test with a Bonferroni correction (P<.0125) was used for multiple comparisons. A Weibull analysis was also used to estimate the Weibull modulus and characteristic failure for each group.
All specimens exhibited edge chipping around the access openings. Some displayed larger chips within the veneering porcelain, and 4 zirconia crowns showed radial crack formation. There was a significant difference in load to failure among all groups with the exception of the alumina intact and repaired specimens (P=.695). The alumina crowns generally showed fracture of the coping with the veneering porcelain still bonded to the core, whereas the zirconia copings tended not to fracture but experienced veneering porcelain delamination.
Endodontic access through all-ceramic crowns resulted in a significant loss of strength in the zirconia specimens but not in the alumina specimens.
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Journal of Prosthetic Dentistry
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- Restoring teeth that are endodontically treated through existing crowns. Part II: survey of restorative materials commonly used.Quintessence Int. 2000; 31: 719-728
- Microleakage-full crowns and the dental pulp.J Endod. 1992; 18: 473-475
- Endodontic complications following periodontal and prosthetic treatment of patients with advanced periodontal disease.J Periodontol. 1984; 55: 63-68
- Endodontic access of Cerestore crowns.J Endod. 1985; 11: 555-558
- Providing endodontic care for teeth with ceramic crowns.J Am Dent Assoc. 1998; 129: 1746-1747
- Castable glass ceramic crowns and their reaction to endodontic therapy.Oral Surg Oral Med Oral Pathol. 1991; 72: 108-110
- Endodontic access of all-ceramic crowns.J Prosthet Dent. 1989; 61: 146-149
- A comparison of the effects of two burs on endodontic access in all-ceramic high lucite crowns.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2000; 89: 486-492
- Fracture surface characterization of clinically failed all-ceramic crowns.J Dent Res. 1994; 73: 1824-1832
- Dental ceramics: current thinking and trends.Dent Clin N Am. 2004; 48: 513-530
- Endodontic access cavities in porcelain jacket crowns—two methods of repair compared.Restorative Dent. 1988; 4: 56-58
- Fracture strength of amalgam crowns with repaired endodontic access.Oper Dent. 2002; 27: 254-258
- A comparison of the porcelain fracture resistance of screw-retained and cement-retained implant-supported metal-ceramic crowns.J Prosthet Dent. 2004; 91: 532-537
- Relative frequency of teeth needing endodontic treatment in 3350 consecutive endodontic patients.J Endod. 1994; 20: 399-401
- Procera AllCeram crowns followed for 5 to 10.5 years: a prospective clinical study.Int J Prosthodont. 2001; 14: 504-509
- Procera: a new way to achieve an all-ceramic crown.Quintessence Int. 1998; 29: 285-296
- Five-year clinical evaluation of Procera AllCeram crowns.J Prosthet Dent. 1998; 80: 450-456
- Anusavice K.J. Phillips R.W. Phillips' science of dental materials. 11th ed. Elsevier, St. Louis2003: 655-715
- Resistance to fracture of three all-ceramic systems.J Esthet Dent. 1998; 10: 60-66
- An in vitro study to investigate the load at fracture of Procera AllCeram crowns with various thickness of occlusal veneer porcelain.Int J Prosthodont. 2003; 16: 54-58
- Fracture resistance of three all-ceramic restorative systems for posterior applications.J Prosthet Dent. 2004; 91: 561-569
- Evaluation of porcelain surface treatments and agents for composite-to-porcelain repair.J Prosthet Dent. 1996; 76: 119-124
- Approaches for intraoral repair of ceramic restorations.Compend Contin Educ Dent. 2000; 21 (642-4): 635-639
- Fatigue life of porcelain repair systems.Int J Prosthodont. 1992; 5: 205-213
- Effect of etchant, etching period, and silane priming on bond strength to porcelain of composite resin.Oper Dent. 1998; 23: 250-257
- Clinically relevant approach to failure testing of all-ceramic restorations.J Prosthet Dent. 1999; 81: 652-661
- Stress distribution and failure mode of dental ceramic structures under Hertzian indentation.Dent Mater. 2003; 19: 542-551
- An in vitro study of the compressive load at fracture of Procera AllCeram crowns with varying thickness of veneer porcelain.J Prosthet Dent. 2003; 89: 154-160
- Shear strength of core-veneer interface in bi-layered ceramics.J Prosthet Dent. 2004; 91: 349-355
- Fracture surface analysis of dental ceramics: clinically failed restorations.Int J Prosthodont. 1990; 3: 430-440
- Lifetime-limiting strength degradation from contact fatigue in dental ceramics.J Dent Res. 2000; 79: 722-731
Marquette University School of Dentistry, Milwaukee, Wis; US Army Dental and Trauma Research Detachment, Great Lakes, Ill; Baylor College of Dentistry, Dallas, Tex
This investigation was supported by Marquette University School of Dentistry and the American Academy of Fixed Prosthodontics Tylman Research Grant Program, 2004.
© 2006 The Editorial Council of The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.