We appreciate Dr. Shulman’s interest in our JADA article on the relationship between occlusion and periodontal disease.
Dr. Shulman correctly points out that the terminology used to describe human occlusion can be contradictory and confusing. A large portion of occlusal terminology dates back to the first half of the 20th century. At that time, science in general and dentistry in particular were often based on observational data, as opposed to measured data. By this we mean that trained observers would describe a phenomenon to the best of their ability and, as part of this observational process, develop words and phrases to describe what they had seen.
Because many individuals were observing the same physiologic processes and then independently developing words and phrases to describe those processes, an often confusing descriptive vocabulary developed. An example would be the phrase "balancing contacts." This phrase was used to describe occlusal contacts of a denture on the side opposite the direction that the mandible was moving (that is, occlusal contacts on the teeth on the left side when the mandible moves to the right). In complete dentures, balancing contacts were considered positive due to the belief that these contacts helped hold the denture in place, hence the positive connotation of a "balance."
In the natural dentition, a significant body of research indicates that a similar contact between natural teeth may be damaging. In natural teeth, this same contact is often called a "nonworking contact." The movement and the contact are the same, but one description has an inherently positive connotation and the other has a defined negative connotation. This is extremely confusing to students learning about occlusion, and this confusion often persists beyond the student level.
Within our JADA article, we attempted to adhere to the definitions contained within the occlusal section of the 1999 International Workshop for a Classification of Periodontal Diseases and Conditions.1 The definitions contained in that document apply scientific definitions, rather than the historical observational definitions, to the field of occlusal study. As with all science, these definitions are imperfect and will evolve as additional scientific evidence is presented.
Within the Harrel-Nunn studies, which are the genesis of much of what we discussed in our JADA article, the definitions of occlusal interferences and occlusal therapy were closely defined. As with all articles that review a large body of research, we did not define each term used but referred the reader to the original research. We urge Dr. Shulman to refer to the original research articles for the definitions used by the various researchers.
Dr. Shulman discusses the concept that, in "normal occlusion function," teeth only contact briefly during chewing and swallowing. He indicates that all other contacts may be due to parafunctional movements. This concept is not universally accepted, and was beyond the scope of our article. As a clinical reality in periodontal therapy, large numbers of patients with active periodontitis present with wear facets on many of their teeth, indicating contacts far beyond a brief contact during swallowing and chewing. An integral portion of the treatment of periodontal disease consists of minimizing existing risk factors to the greatest extent possible.
This includes improving oral hygiene, urging smoking cessation, etc. It is our opinion that occlusal discrepancies, as defined in the Harrel and Nunn articles, are a treatable risk factor for periodontal disease and, therefore, amelioration of this risk factor should be a routine part of periodontal treatment for patients with active periodontal disease.
The method for this treatment is in the hands of the treating dentist. Treatment will probably include selective grinding to minimize occlusal discrepancies and, where indicated, the treatment of parafunctional habits. In our hands, the treatment of parafunctional habits is usually best addressed with some type of removable occlusal stint or night guard. It appears that Dr. Shulman recommends eliminating the stimuli that cause the patient to have parafunctional occlusal contacts.
In our experience, this is not clinically realistic for most patients with parafunctional habits who fully participate in the stresses of routine life activities.
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