We would like to thank Dr. Evers for his interest in our research, and we are pleased that he is concerned enough about the standards of our profession that he would share his opinions so enthusiastically.
We agree with him that cast gold in the form of a cuspal coverage restoration would be a suitable restorative option for the rehabilitation of many of the incompletely fractured teeth we treated in our study. That does not, however, imply that amalgam is an inappropriate material for a cuspal coverage restoration.
The scientific literature clearly supports the use of amalgam for the restoration of the occlusal surfaces of posterior teeth. In a retrospective review of the clinical longevity of cuspal-coverage amalgam restorations, Robbins and Summitt (
Oper Dent 1988;13:54–57[Medline]
) found the half-life of complex amalgam restorations to be
11
years. In a prospective study, Smales found that 72 percent of cuspal-coverage amalgam restorations were functioning satisfactorily after 15 years (
Oper Dent 1991;16: 17–20[Medline]
).
Thus, based on the near 100 percent symptom resolution resulting from the treatment provided in our study, combined with the support found for complex amalgam restorations in the scientific literature, we contend that either a gold casting or a complex amalgam restoration could serve the needs of the patient with an incompletely fractured molar.
In fact, this was mentioned in the discussion section of our article: "A cuspal-coverage amalgam restoration may be placed as a definitive treatment or as an interim restoration designed to protect the cracked tooth until a cast restoration can be completed."
We would disagree with Dr. Evers’ recommendation to restore these fractured teeth with onlays, if the onlay design were to include any intracoronal resistance features. The slightest misfit of an internally retained casting could cause the crack to be significantly enlarged. Even with the best fit possible, the hydraulic forces of the cement could wedge the cracked segments apart.
Despain and colleagues (March 1974 JADA) found that cement would track through a crack in the dentin when a crown was seated. They also found that an amalgam core prevented cement from being forced into the crack. Now that we have access to resin cements, one could seal the crack with a dentin bonding agent, which should keep cement out of the crack. However, the cementing forces of internally retained castings spreading the cusps could still increase the size of the crack. If a casting were used to restore cracked molar teeth, we would recommend either a three-fourths, seven-eighths or full veneer crown.
An added advantage of using the complex amalgam restoration is that it allows the dentist the opportunity to evaluate the pulpal prognosis of the tooth while protecting the tooth from further structural damage.
In a recent investigation, Krell and Rivera followed 127 cracked teeth for up to six years, and found that about 20 percent of the cracked teeth that were restored with crowns required endodontic treatment within six months. They reported that if the pulp survived six months, there was little likelihood of further pulpal degeneration (American Association of Endodontists Oral Research and Poster Research Abstracts 2000; page 11, abstract 17).
These findings, in combination with the other literature cited, would indicate that a cuspal-coverage amalgam restoration is a reasonable, and perhaps a better, choice for the immediate restoration of cracked teeth.
By restoring the cracked tooth with a complex amalgam restoration, the dentist has the opportunity to evaluate the health of the pulp for six months or more. If the pulpal prognosis appears to be good, then the dentist has the option of using the amalgam as a restorative substructure for a casting or leaving the amalgam as the definitive restoration. Should endodontic treatment be needed, the root canal could be completed through the amalgam restoration, without violating the integrity of the cast restoration.
While Dr. Evers might argue that a provisional resin restoration might serve the same purpose (giving the dentist the opportunity to evaluate the pulpal prognosis), we would contend that six months is too long to expect a temporary restoration to last, especially in the mouth of a patient who generates sufficient occlusal force to fracture tooth structure.
We also contend that the use of amalgam does not insinuate a "patch" mentality, as Dr. Evers believes, nor, as he claims, does it "violate the most basic principles of restorative dentistry." Though it is possible to misuse amalgam and end up with an inferior restoration, the inadequacy of the result is not so much an indictment of the material as it is a commentary on the skill and attention to detail of the clinician using it.
In conclusion, we would like to clarify the objectives of our article. The goal was not to promote the use of amalgam in preference to other restorative materials. The objective was to compare, for the benefit of clinicians who use amalgam, the efficacy of resin-bonded vs. conventionally retained complex amalgam restorations in the treatment of incompletely fractured teeth.
