Single crowns have long been the mainstay, the bread and butter, of general dental practices ever since insurance reimbursement levels plummeted for restorative "fill and bill" procedures. When completed skillfully, crowns are a profitable and satisfying part of a typical day in a GP's office.
It's important for a general practitioner to become proficient in this most basic of procedures. As is surely common to any practitioner after 25 years of dentistry, I've developed a technique and flow that serves me well.
The goal of this article isn't to claim superiority over any colleagues in technique or ability; rather, it's to publicize what has worked well for me and has stood the test of time.
The end goal for every restorative procedure done in my office is to align the patients' goals with my own ability to reach that end. As it relates to a crown, a patient's unspoken goals are simple: A "cap" that is aesthetic and comfortable and will allow him or her to chew food. It is my duty to satisfy these patient goals; however, my professional responsibilities toward the patient must be more sophisticated and further reaching.
No patient has ever asked me to avoid impinging upon his or her biologic width; to have wide, broad contacts; or to avoid lateral excursive interferences. No patient has asked me to have a crown in which floss "snaps" through the contacts or for me to create a crown whose properly engineered prep will allow the laboratory to fabricate a prosthesis with a shape that allows for physiologic deflection of food debris.
The implementation of these additional goals is what assures me that I have fulfilled my responsibilities to my patient and enables me to maintain the Hippocratic Oath I pledged upon receiving my degree.
Case Review:
Oral hygiene instruction
and crown buildup
My patient's past dental history was complicated, even for an individual who was only 24 years of age. A lack of adequate family finances, poor oral hygiene and inadequate overseas professional care all contributed to his present situation, which included bilateral lower edentulous sites as well as drifted and supererupted teeth (Figs. 1–3).
After an initial period of oral hygiene instruction, followed by caries control and extractions of nonrestorable teeth (Fig. 4), an RN MIS implant was placed in site #19 (Fig. 5) instead of a WN implant because of inadequate buccal/lingual width of bone.
After a three-month implant healing period, attention was directed to tooth #14, where the supereruption would have caused us to restore the opposing implant with an uneven occlusal scheme unless it, too, were treated (Figs. 6–7). The endodontically treated tooth was fully excavated to eliminate existing caries (Fig. 8).
A liner of TheraCal LC was syringed over the orifices and then light-cured. TheraCal LC is a resin-modified calcium silicate material that performs as a barrier and protectant to the dental pulpal complex. It is indicated for direct and indirect pulp capping and as a protective base/liner under restorative materials, including composite, amalgam and cement.1
In this case, however, TheraCal LC was used simply as a barrier between the root canal orifices and the crown buildup material as well as to increase the bondable surface area. Clearfil SE by Kuraray, a light-cured self-etch, was my bonding system of choice because of its high strength and its sealing properties.
Premier's CompCore AF was injected as the buildup material and cured. CompCore AF, which is a dual-cured, fluoride-releasing, radiopaque composite core buildup material used in vital and nonvital teeth,2 has been my core buildup material of choice for years because it flows well and does not slump. The material cuts like dentin—smoothly and without ditching (Fig. 9).
Qualities of PFM crowns
PFM crowns have two main drawbacks:
- Their veneer of feldspathic porcelain causes abrasion, sometimes severe, of the opposing tooth.
- They're bilayered restorations, so there's a chance they will come apart.
Despite the apparent drawbacks to the PFM, a decision was made to proceed with its use for one main reason: The opposing tooth was to be an implant crown, and implant crowns are always adjusted in my office to extremely light occlusion to avoid the two potential issues discussed above.
As a side note, I wish to add that in my practice, PFMs are used in more than 90 percent of all clinical cases. All my crowns are inserted with light contacts and with all lateral interferences resolved. This alone has eliminated the main drawbacks of PFMs in my office, and I continue to use a restoration that has stood the test of time.
In short, clinically I have seen little if any wear on opposing teeth and actual separation of the feldspathic porcelain from the metal coping is essentially a nonexistent event in my office.
Prep, crown lengthening
and taking impressions
Attention is first directed to occlusal reduction with the aid of Premier's Two Striper football diamond #285.52. The point of the diamond is always inclined toward the central fossa to follow the natural contours of the tooth.
I complete the occlusal preparation with Premier's Two Striper 240C diamond, which will provide the laboratory with adequate central fossa reduction to create proper intercuspation. After breaking through the contacts with a thin tapered diamond, the supragingival portion of the crown is completed using the workhorse of my burs, Premier's Two Striper 724.10C. This thick, flat-end tapered diamond enables speedy bulk reduction, and prepares an extremely smooth, easily readable shoulder in preparation for the bevel.
Beveling is important to the success of the crown. In my hands, the bevel adds 1–1.5mm of additional tooth structure to provide strength and additional surface area for retention. It also seals off the tooth from bacterial ingress. In addition, the action of creating the bevel reduces the circumferential width of the tooth in the critical cervical area, thereby decreasing the emergence profile of the crown.
For anterior teeth and premolars, a needle-shaped 860/010 diamond is placed under the sulcus and angulated toward the prepped tooth. Its cutting motion is used circumferentially around the neck of the tooth, always angulated coronally. For molars, a wider needle-shaped diamond 860/016 is used. I then carefully inspect for tissue attachment to the bevel region. Any tissue left adhering will negatively affect my impression and is removed with a periodontal curette.
In this case, a crown-lengthening procedure was required to avoid biologic width invasion. I have performed closed-tissue crown-lengthening procedures for years with great success. It is simple to take a Brasseler USA 957, 958 or 959 FG End Cut bur and quickly eliminate interfering osseous structures (Fig. 10).
Subgingival preparation is traumatic to the gingiva, and a fair amount of bleeding can be expected. It is critical to control the heme before impressions are taken. Ultradent's Astringent, an aqueous 15.5 percent ferric sulfate solution, is vigorously rubbed circumferentially in the sulcular region until bleeding has slowed. The astringent is washed away and the second part of my tissue management protocol is used.
Premier's Traxodent is applied directly into the sulcus, and a compressive Premier Retraction Cap is fitted over the tooth. The cotton cap guides the Traxodent into the sulcus, completes the hemostatic cascade began by the astringent and then retracts the gingiva by turning into a claylike material after it dehydrates.
Astringent and Traxodent are two of my "can't live without them" products. Two minutes later, after I have washed away the Traxodent, I am looking at a tooth that is fluid-free, with wide open sulcular regions (Fig. 11), ready for Impregum Monophase to be injected around it. Impressions such as the one featured in Fig. 12 are commonplace after following these steps for hemostasis and retraction.
Conclusion
Some years ago, I placed a quote I read in a dental journal on my office pegboard. "A crown and bridge impression is merely a reflection of the dentist's integrity. Nothing more, nothing less." I have reflected on this quote often during my career. This article reflects the present-day care that I provide to my crown and bridge patients. It is the combination of rigid adherence to my methodology, combined with the utilization of the highest quality, up-to-date products that allow me to insert crowns with perfect marginal integrity and to give my best to the patients who give me their trust. Dentists are privileged to play an integral part of a patient's health care team and, in turn, we owe them our utter refusal to accept compromise on our standards (Figs. 13–14).
The author would like to thank his laboratory, Ceramtech Dental Studio in Fair Lawn, New Jersey, for excellence in all it does. The author also thanks Zev Schulhof, DMD, MD, of North Jersey Oral & Maxillofacial Surgery for his expertise regarding the oral surgical aspects of the case.
References
1 The Dental Advisor Volume 29 Number 10 December 2012
2 The Dental Advisor Volume 25 Number 09 November 2008