The Impossible Dream: A Sterile Field Beneath Modern Day Restorations
By Timothy W. Fraser, D.D.S., M.A.
A hypothesis can be made that current restorative failures and high rates of recurrent decay are indicators of dental materials that function poorly in vivo. Fontana, DDS, PhD and Gonzales-Cabezas, DDS, PhD recently reported that 71% of all restorative treatments are performed on previously restored teeth with recurrent caries as the predominant cause. (1) Terry Donovan, DDS, Director of Advanced Education in Prosthodontics, USC, reported a vast discrepancy in the longevity of various types of restorations with an emphasis on gold restorations. One short term study reported a 50% failure of Class II gold inlays within seven years. A study of one dentist’s gold restorations conducted by Donovan included 1,314 cast gold restorations covering 114 patients. The dentist’s restorations presented a 97% survival rate at 9 years, 90.3% at 20 years, 94.9% at 25 years, 98% at 29 years, 96.9% at 30 years, and 94.1 % greater than 40 years. All of these restorations were cemented with zinc phosphate cement. (2) Improvements can be made in current dental therapeutics so that the results seen by Donovan can become more commonplace.
A review of dental history combined with new insights has yielded a solution. This paper proposes that the concept of a sterile field is biologically unobtainable and the illusion of an attainable sterile field has led dentistry toward luting cements that are seemingly more stable yet disappointing in vivo. In reference to dentin bonding cements, Gordon J. Christensen DDS, MSD, PhD states, “These failures present a confusing phenomenon, since dentin bond strengths in vitro show values as strong as or stronger than bonds to enamel”(3). Christensen went on to propose that even with dentin bonding, mechanical retention was advisable (3). The last thirty-five years has been dominated by the concept of a perfect seal created by perfect bonding and dentistry unsurprisingly returns to mechanical retention.
A review of literature by Ralph Steinman, DDS, Loma Linda University, explains that the metabolism of teeth and the overall oral cavity are extensions of the overall metabolism of the human body (4). Based on Steinman’s work and research, a viable, biocompatible and practical solution to the problem of recurrent decay will be presented. A new generation of galvanically activated copper containing cements will be considered in light of current biofilm research. New galvanically activated copper cements will be proposed as a sensible approach to solving the problems of recurrent decay and improving the patients’ oral health.
Genesis of Tooth Decay
Many models regarding the genesis of tooth decay have been proposed, however reviewing the research and literature of the past fifty years, it is possible to extrapolate a model based on solid research and biological reality. This model focuses on Steinman’s proving an interactivity between the oral cavity and the metabolism of the whole body. The occurrence of decay is not due primarily to external contamination of the tooth through acid producing foods and bacteria, but through the internal action on the metabolism of the tooth through its relationship to biological systems of the body. (4)
Teeth are not solid, but rather a series of dentin tubules and parallel enamel rods. (4) Steinman proved that substances moved from within the body, through the pulp chamber, through the intestinal fluid to within the dentin tubules and even through the enamel and into the mouth. He demonstrated this fact by directly injecting acriflavin hydrochloride into the abdominal cavities of rats and recovering this radioactive material in the dentin tubules within six minutes, and in the enamel within an hour. He believed this to be a self-cleansing mechanism. This constant flushing of the tooth structure prevents the movement of microbes into the tooth and the destructive effects of acids formed by foods (4).
Major problems occur when endocrine function, poor diet or circulatory problems, associated with ill health or aging leads to a reverse flow within dentin tubules. (4) Stagnation can be postulated as resulting from less tooth vitality as well. (4)
A reverse flow “sucks” bacteria, acids and other materials from the mouth or, surrounding periodontium into the tooth. (4) Steinman produced many slides demonstrating this flow going in both directions and related reverse flow to diet, age, stress, and hormonal imbalances. (4)
Dr. Steinman’s most dramatic discovery was that if you plot the course of dental decay, as with any other disease, function is altered initially by the reversal of the dentin tubules fluid flow. (4) Next, inflammation occurs in the pulp chamber next to the dentin, and finally, the disease spreads to the enamel, before the clinical appearance of a cavity. As part of the decay process, he identified the early loss of magnesium, copper, iron and manganese, all active in cellular oxidation and necessary for the energy-production that allows the cleansing flow through dentin tubules. (4)
In studies quoted by Steinman, the addition of copper, iron, and manganese when added to the decay producing diet, almost abolished the decay rate. (4) This fact was taken into account in the formulation of one of the new galvanically activated copper containing cements.
Although it is generally accepted that a good diet, good hygiene and overall good health is beneficial to oral health, what can the dental practitioner do clinically to prevent redecay? Removing existing decay and sealing the tooth with a restoration, while necessary, will only suffice until the next attack on the system. Although it is well understood that decay cannot occur without bacteria, it should be evident that since teeth are not solid, a sterile field cannot be maintained on a purely mechanical basis. There is no perfect seal.
A Return of Antimicrobial Cements
Historically, copper-containing cements consisted of zinc phosphate cements to which copper was added. (5) The pure copper phosphate cement also existed and was widely used but discolored teeth and proved toxic. Many present day dentists have discovered old, ill fitting and worn-out gold swaged crowns and amalgams with red cement still present and a baffling absence of recurrent decay. Copper cements were eventually termed toxic, probably because of the true copper phosphate cement produced by Ames and containing 97% cupric oxide (Black). It may be remembered that copper is an essential metabolite found in all healthy teeth. Copper increases local and general immunity and prohibits chronic, inflammation and infection in tissues associated with local dental procedures, and with the decay process. (6) Copper supports tissue metabolism and detoxification (6). Copper cements contained anywhere from 2% copper to 97% copper. (5) Often cements containing low concentrations of copper were shown to be just as germicidal as those with higher concentration. (5) This fact was not fully explainable until around 2000 when biofilm research entered dentistry.
Dr. Marcus Ward came to the conclusion that the effectiveness of copper containing cements depended on the germicidal quality of the copper salt used as well as the infinitesimal solubility of the cement in its set phosphate form. Ward rightfully stated, “Our chief interest is what may happen beneath fillings”. (5)
In 1931 in the text “Metallurgy for Dental Students” by K.W. Ray, the use of copper containing cements was staunchly advocated. (7) Dr. Ray went so far, as to say whenever copper cements were used; no need for thorough cavity preparation presents itself. (7) Antimicrobial cements reached a zenith of popularity and acceptance before falling into disfavor. The problems with the true copper phosphate cements (97%) could have been overcome but not the new ideas about perfect marginal seal and a sterile field. In “The Science of Dental Materials” by Dr. W.E. Skinner we find the following: “ if the cavity has been properly sterilized before the cement is applied, and if a tight cement filling is possible, it is difficult to understand why a germicidal cement is needed”. (7)
Michael Dumas and Marvin Blush came to the conclusion in 1956, “ In view of the contradictory evidence and the definite advantages of a germicidal cement, especially where carious dentin removal may cause pulp exposure, it would seem that further investigation and reappraisal of the copper containing cements is indicated”. (7)
It is interesting that the term “copper containing cements” associated with toxicity did not concern itself with percentages of copper. Paul Poetshke (Caulk Laboratories), Dr. M.R. Smirnow (Yale Medical School), Dr. Raymond F. Bacon (Melon Institute) and Marcus Ward (Ann Arbor, Michigan), all found that zinc phosphate cements containing 2% cuprous iodide were far more antimicrobial than the standard zinc phosphate cements. (5) Recall that the exquisitely resilient restorations in Donovan’s recent article were gold restorations all cemented with zinc phosphate cement containing bismuth, an antibiofilm agent.
Around the year 2000, new scientific methods changed dental microbiology from its focus on planktonic forms of bacteria to biofilm research. This discovery further challenged the then current thoughts concerning the role of bacteria in dental disease. More than 400 bacteria have been discovered associated with dental disease with perhaps twice that amount as a potentially accurate number. (8) These microbes share nutrients and genetic information and in unison produce a mucopolysaccharide (slime) layer. This layer as well as the fact that outer colonies protect inner colonies, presents a barrier, that is not permeable to antibiotics and traditional medicaments (9). These bacterial colonies become invisible to the immune system. All that is required for biofilm success is a surface on which to adhere an initial bacterial attachment. Tooth surfaces, porous composite surfaces, etched ceramic surfaces, stagnant dentin tubules, and metal surfaces are perfect for biofilm attachment. Where biofilms reside, bacteremias prove resistant to almost all forms of treatment except mechanical removal and the use of galvanically activated copper. (10)
The Center for Biofilm Engineering (CBE), Bozeman, Montana, under the directions of William Costerton, PhD began a search for a surface for medical prosthesis and devices which would resist biofilm formation and the subsequent untreatable chronic bacteriemia that followed their formation. Many antimicrobial agents, including copper and silver were considered. Used alone, none of these materials were able to penetrate the biofilm slime layer and destroy associated bacteria. It was then discovered that when copper and silver ions were placed in solution together, the cations, due to mutual repulsion, became highly galvanically activated allowing them to disrupt the metabolism of biofilms. (11)
The author had been privately researching the concept that copper salts were much more effective when mixed with highly dissimilar cations. A red copper cement was produced using copper and iron salts in a zinc phosphate cement along with bismuth as an antibiofilm agent, based on the resistance of human blood vessels to biofilm formation. Blood might resist biofilm formation because of the copper/iron relationship found in erythrocyte formation. A similar galvanic activation was obtained in white copper cement by combining copper, silver and bismuth. Upon hearing Dr. Costerton at a meeting in Denver, Colorado, Doc’s Best™ Cements underwent testing at CBE. All of Doc’s Best™ Products were found to be 100% resistant to the biofilms of Staphylococcus aureus, Lactobacillus paracasei, and Streptococcus mutans. All other cements tested proved nonresistant (12).
Cooley & Cooley Ltd, Houston, TX working with the author improved copper containing cements which would retain the best qualities of older formulas while eliminating problems associated with some of these earlier copper cement blends. Together a new group of low concentration copper containing cements was developed, based on the interaction of copper with the cations silver and iron. Combining these materials with a zinc phosphate base proved necessary because infinitesimal solubility found in all zinc phosphate cements is essential if minerals are to remain in circulation within the fluids flowing through dentin tubules. In this manner, antimicrobial and antibiofilm activity is long lasting and compensatory for the inherent structure assuring that no sterile field can exist within a tooth.
Many of the minerals found in Doc’s Best™ cements are restorative to the health of the tooth according to Dr. Ralph Steinman’s findings, “Minerals normally lost during the inflammatory process are available within their inherent metabolic functions”. (4)
Currently biofilm resistant cements exist in red cement, designed for gold and post cementations, and white cement used with porcelain margins. Powder may be mixed with composite resin for a buildup resistant to bacterial infestation. The red cement is also suggested for the cementation of root canal post and for post failures where softening has occurred around a previous post. White copper cement concerns itself with anterior esthetics. A pulp canal sealer was developed to prevent bacterial infestation within the stagnant dentin tubules of nonvital teeth.
Conclusion
The
author has used these cements clinically for fifteen years with only minor
modifications. Many documented case studies reflect the ability of the cements
to render decay inactive and to promote secondary dentin formation with pulpal
health remaining positive. Root calcification was not evident in any of these
cases. Cooley & Cooley Ltd’s COPALITE® dental varnish is always used before
placing a phosphate cement. It was discovered that a few drops of this
particular varnish when mixed with a small amount of the cement powder provides
rapid penetration into decayed areas that must be allowed to heal in order to
prevent pulpal exposure within vital teeth. According to a recent study
performed by Yiming Li DDS, MSC, PhD, at Loma Linda University, the combination
of the cement powder mixed with COPALITE® varnish is not cytotoxic and is well
accepted at the cellular level. The statement that copper cements are toxic has
been proven false. In the 1950’s, the “baby was thrown out with the bathwater”.
These highly anticariogenic, biocompatible cements can now be used with
confidence for the benefit of patients and dentists wishing to promote dental
health through caries control.
Bibliography