Endodontics Restoring teeth that are endodontically treated through existing crowns. Part iii: Material usage and prevention of bacterial leakage Glenn Trautmann, DMDVJames L. Gutmann, DDS^/Martha E. Nunn, DDS, David E. Witherspoon, BDSc, MS^/Charles W. Berry, MS, PhDVGiancarlo G. Romero, DDS, Objective: This study was undertaken to determine if any current materiais can prevent coronai ieal<age in the restoration of endodontic access openings in permanently fixed crowns foiiowing nonsurgicai root canal therapy. Method and materials: Sixty mandibuiar first moiars and 36 maxiiiary centrai incisors were assigned into 1 of 8 compiete-coverage crown groups. Endodontic access openings were made through the restorations and randomly placed in 1 of 5 access restorative modalities. A culture of Proteus vulgaris was placed into the coronal reservoir of each assembly of a leakage assessment apparatus for 30 days. Specimens were examined weekly, and turbidity was recorded. Results: Chi-square tests and Fisher's exact test were used for statistical evaluation, A total of 51% of specimens (41/80) demonstrated turbidity. The findings did not indicate a statistically significant association between the materials used and the presence of bacterial leakage. All-metal noble crowns demonstrated the lowest rate of turbidity (20%), and all-porcelain crowns exhibited the highest rate of turbidity (70%) among posterior teeth. Anterior teeth were more than 3.5 times as likely to exhibit bacterial leakage as posterior teeth. Conclusion: When chal- lenged with bacteria, all materials allowed significant leakage. All-porcelain crowns demonstrated more leakage than the other types of crowns. Anterior crowns leaked the most, regardless ot crown or restora- tion type. (Quintessence Int 2001:32:27-32) Key words: amalgam, bacterial leakage, complete-coverage crown, glass-ionomer cement, nonsurgicai root canal treatment, Proteus vulgaris, resin composite CLINICAL RELEVANCE: Further evaluations are war- ranted for the identification of a leak-proof material and placement technique to restore endodontic access cavi- ties in complete-coverage crowns. 'Graduate Resident of Graduate Endodontios, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M University System, Health Science Center, Dallas, Texas, ^Professor and Director of Graduate Endodontics, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M University System, Health Science Center, Dallas, Texas, ^Assistant Professor, Department of Public Health Sciences, Baylor College of Dentistry, Texas A&M University System, Health Science Center, Dallas, Texas, "Assistant Professor of Graduate Endodontics, Department of Restorative Sciences, Baylor College of Dentistry, Texas A&M University System, Health Science Center, Dallas, Texas, ^Professor of Biomédical Sciences, Baylor College of Dentistry, Texas A&M University System, Health Science Center, Dallas, Texas, «Private Practice, Houston, Texas, Reprint requests: Dr James L, Gutmann, Baylor College of Dentistry, Graduate Endodontics (Room 335), 3302 Gaston Avenue, Dallas, Texas 75246. E-mail: jgutmann@tambcd.edu M ore than 50% of all teeth with complete-coverage crown restorations require nonsurgicai root canal treatment (NSRCT).' This can he due to the extensive effects of restorative procedures, the possible leakage of bacteria and their by-products at imperfect crown margins, or recurrent marginal caries that can- not always be detected clinically.'* Following NSRCT on these teeth, the crowns are not always replaced. The endodontic access openings in teeth with preexisting complete-coverage crowns are routinely restored with amalgam, resin composite, or glass-ionomer cement, bonded or not bonded. However, there is no evidence-based support for the choice of material for the restoration and no data on its clinical performance over time.' Material choice is critical because coronal leakage of bacteria and their by-products is an important factor in the failure of nonsurgicai root canal treatment.'-^*^''^ The need for re-treatment may arise from continued marginal leak- age at the tooth-crown interface or the coronal access-crown interface. Therefore, if the crown is determined to be intact clinically at the interface with the tooth and is to be retained, the integrity of the Quintessence International 27