Does Stronger Mean Better?
Aggressive marketing techniques employed by most businesses—to which the business of dentistry is no exception—have indoctrinated us on the importance of "faster" and "stronger" on our path to success. As a self-employed ceramist in a dental laboratory that specializes in restorations and the proper use of restorative materials, I, along with the majority of all dentists and technicians in this field, am fully cognizant of the importance and necessity of an awareness, appreciation, and understanding of the strength and durability of the dental products and materials used in our work.
In dentistry, the tensile strength of most restorative materials is represented in megapascals (MPa), but it may not be the most complete metric for comparing dental materials. Tensile strength is a measure of compressive strength usually used for concrete or building materials. Its main purpose is to understand how much pressure can be applied before the material breaks. Therefore, its usefulness is limited, and further information is needed to fully understand the products that are used in dentistry. While tensile strength adequately demonstrates the breaking point of a material, it does little to provide relevant data in regard to flexibility, rebound, or elongation.
In examining human esthetics and mechanics, our basic dental structure is almost flawless. Every tooth position, angle, tissue process, periodontal ligament, etc, is designed to protect its environment and harness food to its proper path. The strength and resilience of human teeth are based on both their composition and functional placement. Nature has taught us that the true definition of material strength lies in both rigidity and flexibility. A natural tooth is comprised of the external enamel, which is mineralized, compact, and one of the hardest materials in the human body, and the underlying dentin, which has a tubular nanocrystalline structure made of collagen and is softer and much more flexible. Some would be very surprised to learn that, if we evaluated a natural human tooth the same way we do restorative materials, its breaking point is less the 120 MPa. Nonetheless, the combination of rigidity and flexibility, the stomatognathic system, the shock-absorbing periodontal ligament, and the proprioceptive response system together determine the strength of our teeth—not merely their tensile strength.
In our role of restoring dentition, we as technicians must aspire to a more complete understanding of what we are replacing and which materials will benefit our patients. As our work on restorations moves forward, our focus should remain on the development and improvement of materials to restore and possibly advance what nature has already given. After all, the hardness of teeth is an important feature, but only insofar as it remains consistent with the ongoing functional and esthetic health of our patients. A higher MPa does not necessarily mean a better restoration or a better fit for the human body. Knowledge of materials—both natural and manufactured—will be our strength as we strive to restore what has been damaged.
About the Author
Peter Pizzi, MDT, CDT
Editor-in-Chief
ppizzi@aegiscomm.com
