A New Perspective on the Endodontic Restorative Continuum - Dr. Liviu Steier
The introduction of rotary nickel titanium (NiTi) instrumentation to endodontic instrumentation
procedures has provided an inherent capacity for the maintenance of a greater degree of
dentin thickness and as such preservation of tooth structure in the critical buccal lingual
direction is maximized. The use of posts to rehabilitate the structure of endodontically treated
teeth remains fraught with increasing uncertainty as new instrumentation protocols abound
and as the adhesion era in dentistry flourishes resulting in more conservative non-invasive
protocols. Retrospective studies demonstrate that non-metallic post systems will produce
significantly more positive results than with prefabricated metallic posts (1,2). As the
developments in adhesive restorative technologies and techniques enable functional and
aesthetic reconstruction of debilitated tooth structure without traditional post/core
construction, a more conservative non-invasive rehabilitation is possible for rebuilding the
integrity of the residual tooth structure.
All these advances raise highly relevant questions; are posts still necessary? are the new
composite reinforced fibre posts evidence based? are chairside fabricated composite
reinforced fiber post systems preferable? are restorations without posts reliable and
predictable? are there other ways to reinforce teeth? what parameters apply to the choice of
reinforcement? what is a the ideal adhesive restorative procedure for endodontically
retreated teeth.
The relevance of the need for post placement is definitely in question Adhesion of the
newest generation of composite core materials to the remaining tooth structure has been
shown to be more effective without post placement that with post placement provided the
placement protocol is exacting(3). Numerous studies have shown that fibre reinforced posts
demonstrate reduced stress vectors with a distribution literally approaching that of a tooth
without a post. Increasingly, the literature validates the use of composite reinforced fibre
posts in preference to metal systems (4,5).
Chairside fabricated composite reinforced fiber posts are an alternative to customized ones
(6). Using improved restorative materials that stimulate the physical properties and other
characteristics of natural teeth in combination with the proper design principles, the clinician
can develop a tooth-restorative complex with optimal functional and esthetic results (7,8).
Restorations without custom made posts are also reliable and predictable in special cases
and represent a viable option to traditional post/core construction. The cases presented in
this article will amplify this approach.
The American Association of Endodontics has a white paper on the considerations for choice
of the post-endodontic restorative modality. The considerations are; 1) the amount of
remaining sound tooth structure, 2) occlusal function, 3) opposing dentition, 4) position of the
tooth in the arch, as well as length, width and curvature of the root(s). The philosophy further
states that, “The primary purpose and main indication for a post is to retain a core that can
be used to support the final restoration. Posts do not reinforce endodontically treated teeth,
and a post is not necessary when substantial tooth structure is present after a tooth has been
prepared. In actuality, placing a post can predispose a tooth to fracture. In response to the
discovery that posts do not strengthen teeth - they only serve to retain the core - research
into design, shape, diameter, and length of posts now focuses on issues of retention.”
The policy of the American Association of Endodontists in regard to the endodonticrestorative
continuum is as follows: In anterior teeth with intact marginal ridges, cingulum,
and incisal edges, the placement of a lingual or palatal dentin-bonded composite resin is the
treatment of choice. In posterior teeth, contemporary thought, in both research and clinical
practice, supports the placement of a protective restoration with full cuspal coverage on
these teeth. The research however, continues to question the concepts espoused.
Macpherson and Smith have shown that combining of materials to reinforce weakened cusps
is a worthy cost effective alternative to removing the cusp entirely and making a crown or
protecting the cusp with a cuspal coverage gold inlay (9).
The buccal cusps of endodontically treated mandibular molars reinforced with a combination
of horizontal pins and dentin adhesive were not significantly weaker than intact teeth. Of the
restored teeth, those which had buccal cusps reinforced with horizontal pins and those
treated with complete cuspal coverage amalgam restorations exhibited the most favorable
restorative prognosis following cusp fracture (10). By using the current generations of
restorative materials that simulate the physical properties and other characteristics of natural
tooth in combination with proper design principles, the clinician can develop a toothrestorative
complex with optimal functional and esthetic results.
Vertical loading of the teeth did not generate harmful concentrations of stress. More
challenging situations were encountered during working and nonworking micro motions, both
of which generated inverted stress patterns. Supporting cusps were generally well protected
during both working and nonworking cases (mostly subjected to compressive stresses).
Nonsupporting cusps tended to exhibit more tensile stresses. High stress levels were found
in the central groove of the maxillary molar during nonworking micro motion and at the lingual
surface of enamel of the mandibular tooth during single-contact working micro motion. The
occlusal load configuration as well as geometry and hard tissue arrangement had a marked
influence on the stress distribution within opposing molars (11).
It may well be that full cuspal coverage is not mandated for predictable success of the
restoration of the endodontically treated tooth. For the moment, there is not substantive
evidence to suggest that maximal reduction and restoration will provide optimal long term
success. Continued testing as new materials with more dramatic properties and possibilities
come to the marketplace will invariably provide the answer this conundrum.
References
1. Ferrari M, Vichi A, Garcia-Godoy F. Clinical evaluation of fiber-reinforced epoxy resin
posts and cast post and cores. Am J Dent. 2000 May;13(Spec No):15B-18B.
2. Reid LC, Kazemi RB, Meiers JC. Effect of fatigue testing on core integrity and post
microleakage of teeth restored with different post systems. J Endod. 2003
Feb;29(2):125-31.
3. Krejci I, Duc O et al. Marginal adaptation, retention and fracture resistance of
adhesive composite restorations on devital teeth with and without posts. Oper Dent.
2003 Mar-Apr;28(2):127-35.
4. Glazer B. Restoration of endodontically treated teeth with carbon fibre posts: A
prospective study (J Can Dent Assoc. 2001 Feb;67(2):70-1.)
5. Fredriksson M, Astback J, Madeleine et al. A retrospective study of 236 patients with
teeth restored by carbon fiber-reinforced epoxy resin posts. (J Prosthet Dent
1998;80:151-7).
6. Hornbrook DS, Hastings JH. Use of bondable reinforcement fiber for post and core
build-up in an endodontically treated tooth: maximizing strength and aesthetics (Pract
Periodontics Aesthet Dent. 1995 Jun-Jul;7(5):33-42; quiz 44.)
7. Eskitascioglu G, Belli S.: Use of a bondable reinforcement fiber for post-and-core
buildup in an endodontically treated tooth: a case report (Quintessence Int. 2002 Jul-
Aug;33(7):549-51)
8. Terry DA, Triolo PT Jr, Swift EJ Jr.: Fabrication of direct fiber-reinforced posts: a
structural design concept (J Esthet Restor Dent. 2001;13(4):228-40.)
9. Macpherson LC, Smith BG. Reinforcement of weakened cusps by adhesive
restorative materials: an in-vitro study.Br Dent J. 1995 May 6;178(9):341-4.
10. Uyehara MY, Davis RD, Overton JD. Cuspal reinforcement in endodontically treated
molars Oper Dent. 1999 Nov-Dec;24(6):364-70.
11. Magne P, Belser UC. Rationalization of shape and related stress distribution in
posterior teeth: a finite element study using nonlinear contact analysis “(Int J
Periodontics Restorative Dent. 2002 Oct; 22(5):425-33.) |
