Tentative Opinion on Clenching

Abstract

Since Gibbs published “Cuspal Fracture Odontalgis” in 1954, a large number of researchers have presented papers on tooth fractures. However, most of them were concerned with teeth that had been treated with root canal fillings or restorations. I found that there was clenching, and that hairline fractures had arisen even in the intact vital teeth of patients that had not received any dental treatment and whose oral cavities had absolutely no caries or periodontal disease. I also noticed that the fracture lines followed the central grooves or fissures in the buccal and lingual surfaces. Therefore, in such cases it seems that the fractures arose solely as a result of so called “stress” or “occulusion” which is composed and affected by the gnathostomatic system. However, dental treatment would not be a causative factor here at all.
I studied a sample of 83 subjects who clenched their teeth. Group A was comprised of 14 subjects who actually had hairline fractures. Four of them refused to allow occlusal analysis involving diagnosis of the occlusion. Group B was comprised of 21 subjects who had no hairline fractures and no defects in the teeth, although they clenched their teeth. Group C was 48 subjects who clenched their teeth and had dental defects that seemed associated with this clenching.
Examination and analysis were carried out on the above 83 subjects. Standardized models were fabricated based on the HIP plane of three of the subjects from group A who had hairline fractures in teeth that had never received any dental treatment. In order to examine the condition of the mesiodistal and buccolingual contacts and the occlusion of the occluded maxillary and mandibular models, two sets of each model were cemented with adhesive cement after reference lines were scribed where sectioning was planned at the pits, fissures and cusp tips of the models. Following the lines where sectioning was planned, one of the models was sectioned mesiodistally, and the other buccolingually, and photographs were taken.
Based on the findings, the occlusal conditions were graphed, each physical characteristic of the structural elements of the teeth was incorporated, and finite element analysis was carried out. In addition, specimens were carefully taken from extracted impacted wisdom teeth, the wet compressive strength was determined, and investigations were also made as to how the fracture of the tooth structural elements would occur.
It became clear that the fracture line would run vertically along the central groove and fissures on the buccal and lingual surfaces. I would like to make it clear that the hairline fractures to which I am referring are limited to the above mentioned definition, and are fundamentally different from previously reported cuspal fractures, root fractures that occur in endodontically filled teeth, and traumatic fractures.
Based on the above fundamentals, I would like to report how to identify those patients who are likely to have the primary factors that might produce hairline fractures, and discuss prevention and treatment methods.