Discussion - References.
There is little information in the literature concerning the thickness of radicular dentine. This study was carried out with the intention of providing important data on this relevant topic.
The pulp of a tooth decreases in volume with the passage of time. The teeth examined in this study were from adult subjects aged between 35 and 55 years. The teeth were extracted primarily because of periodontal disease and the canals were often narrow.
Amongst the specimens examined the presence of two canals in a single root was rare. Only one main canal was found in each of the40maxillary incisors examined. In the group of maxillary canines only one specimen was divided in the coronal third due to the presence of a dentinal island. No distinction was made between mandibular central or lateral incisors because there were no remarkable differences between the two groups. Sometimes dentine islands forming two canals were noted in the second and third sections with in a longitudinally flattened canal, however, the canals always had a single apical foramen. For the group of mandibular canines, only in one case out of the 30 teeth examined were there two roots and two canals, in all the other cases there was one single, generally wide, canal. All mandibular premolars were included in a single group because none were found with two canals and also because roots of first and second premolars were similar in shape.
The results of the anova, with the computation of the ETAsqd, show that the thickness of radicular dentine mainly varies depending on location and section factors rather than tooth type. In other words, independent of the tooth type, a similar variation of dentine thickness can be observed in all of the teeth studied.
Larger values of dentine thickness were detected near the lingual and buccal surfaces with reduced thicknesses near the mesial and distal surfaces. In many sections, the dentine was very thin. Thus, it follows that the knowledge of the radicular dentine thickness must serve as a guide to all treatment that includes the root of the tooth. Clearly, one must use the utmost caution when introducing rotating, rigid or large-diameter instruments into the canal.
Biomechanical studies suggest that at least 1mm of root dentine should remain around the post (Caputo & Standlee 1988) to avoid the risk of root fracture. There fore, during canal preparation it is advisable to remove as little dentine as possible and during post-preparation, it is advisable to follow the anatomy of the radicular canal by designing flattened posts in a mesio-distal direction, with tapered vertical walls. The dentine should mainly be removed, if necessary, in the lingual area where the thickness is greater. In the apical part, there is very little dentine available therefore in this area it is preferable not to remove any dentine but only to clean the canals of filling material.
This study has been limited to the observation of radicular dentine thickness in anterior teeth and premolars. The teeth examined belonged to adult subjects between the ages of 35 and 55 years that were extracted because of periodontal disease.
As a result, data on the dentine thickness of teeth from younger subjects is missing. This would be expected to show a smaller radicular dentine thickness due to larger dimensions of the pulp. In the future it would be desirable to conduct studies on posterior teeth and other age groups.
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