Current research: new findings on crown preparation ferrule needs

July 10, 2011
Dr. Gordon Christensen explains the findings of a recent study and gives his advice about the use of ferrules in crown preps.

By Gordon J. Christensen, DDS, MSD, PhD

Extracted human central incisors were divided into three groups: no ferrule, 0.5 mm ferrule, and 1.0 mm ferrule. Each tooth received a fiber-reinforced composite post, a composite core, and a ceramic crown cemented with resin cement. The specimens were subjected to 6 kg of load at 135 degrees to the long axis of the teeth. The no-ferrule group had the most failure; the 0.5 mm-ferrule group survived more fatigue cycles; and the 1.0 mm-ferrule group showed all specimens reaching the upper cycle limit.

Ma PS, Nicholls JI, Junge T, Phillips KM. Load fatigue of teeth with different ferrule lengths, restored with fiber posts, composite resin cores, and all-ceramic crowns. J Prosthet Dent. Oct. 2009; 102(4):229-234.

Dr. Gordon Christensen comments: The conclusion of this study suggests that the longer the ferrule, the better, and that 1 mm was better than less tooth structure. I still prefer 1.5 mm to 2.0 mm of ferrule.

Gordon J. Christensen Guide for Preferred Clients Jan./Feb. 2011; Vol. 16, Issue 1

Click here to read more clinical tips and current research from Dr. Gordon Christensen.

Author bio
Dr. Gordon Christensen is a practicing prosthodontist in Provo, Utah, and a diplomate for the American Board of Prosthodontics. He is the founder and director of Practical Clinical Courses, an international continuing education organization initiated in 1981 for dental professionals. Dr. Christensen is a cofounder (with his wife, Rella) and senior consultant of CLINICIANS REPORT (formerly Clinical Research Associates), which has conducted research in all areas of dentistry since 1976. Dr. Christensen is an adjunct professor for Brigham Young University and the University of Utah.