Bjørn L. Dahl

Occlusal wear of teeth and restorative materials: A review of classification, etiology, mechanisms of wear, and some aspects of restorative procedures

This paper is a literature review of various aspects of the wear of occluding tooth surfaces. It presents classification and terminology of occlusal tooth wear, and discusses etiology and differential diagnosis. It may be difficult to differentiate among abrasion, attrition, and erosion because there is nearly always a combination of the various processes. These processes of wear are described, and the in vitro and in vivo wear of some restorative materials is discussed. Treatment of severe tooth wear is considered difficult; prophylactic measures are therefore important. Some guidelines for restorative treatment of patients with extensive occlusal tooth wear are given, with special emphasis on the type of treatment, the vertical dimension of occlusion, the space available, and choice of material for the restorations.

An index for evaluating wear of teeth

An index for evaluation of dental wear based on Ryges system comprising three satisfactory and two not acceptable categories was tested in two different age groups of individuals with brain damage. Group 1 consisted of 12 individuals, 3 women and 9 men, with a mean age of 34.5 years. Group 2 consisted of 13 individuals, 4 women and 9 men, with a mean age of 45.1 years. The wear was evaluated by three examiners, two dentists and one dental hygienist. The examiners worked independently, having available at all times the written criteria and a photographic guide illustrating the lowest limit of each category. Each tooth was given a rating in accordance with the index, and the interexaminer agreement of 612 such evaluations was approximately 85%. Each person was given an individual wear rating corresponding to the most severe category comprising 90% of the tooth ratings. The difference in the distribution of individual ratings between the two groups was tested for significance by the ridit method. Significantly greater wear was observed in group 2 than in group 1, indicating a good sensitivity of the index.

Negative affectivity, somatic complaints, and symptoms of temporomandibular disorders

This study examined the relationship between trait anxiety, subjective somatic symptoms, and pain associated with temporomandibular disorders (TMD) in a combined cross-sectional and prospective study. Compared with the initial measurements, a significant reduction in anxiety and pain was observed in the follow-up phase (two years after evaluation and therapy). No change in general somatic complaints was found. In both the initial phase and the follow-up phase, a consistent relationship between anxiety, somatic complaints, and TMD-related pain was demonstrated. The results are in agreement with a conceptualization of negative affectivity (e.g., anxiety, distress, tension) as a general dimension of somatopsychic distress. The best predictors of later TMD pain were general somatic complaints, followed by initial pain, and trait anxiety. Significant moderate correlations between anxiety, somatic complaints, and response to muscle palpation (feelings of tenderness) were also found. It is concluded that studies of TMD should incorporate measures of negative affectivity and general somatic complaints because these factors are important predictors of TMD pain, response to treatment, and chronicity.

Signs and symptoms of craniomandibular disorders in two groups of 19-year-old individuals, one treated orthodontically and the other not

Fifty-one individuals (28 girls and 23 boys) who had received orthodontic treatment were compared as to signs and symptoms of craniomandibular disorders with 47 individuals (19 girls and 28 boys) without such treatment. All were 19 years old. An average of 5 years had elapsed since the termination of the treatment. The examinations enabled calculations of the anamnestic, the clinical dysfunction, and the occlusal indices of Helkimo. There were no statistically significant differences between the groups except with regard to the anamnestic index. Subjects who had not received orthodontic treatment reported most symptoms, but none were severe. In conclusion, there were no substantial differences as to signs and symptoms of craniomandibular disorders in these two groups of individuals.

The Effect of a Partial Bite-Raising Splint on the Inclination of Upper and Lower Front Teeth

In a previous paper it was maintained that the effect of the permanent use of an anterior partial bite-raising splint was an intrusion of the front teeth and an eruption of the others. However, the effect might have been merely a change in the inclination of the front teeth. The present study comprised the same material as earlier. Linear and angular changes in the position of upper and lower incisors were measured on cephalometric radiographs. In the upper jaw a possible average proclination occurred, whereas in the lower jaw no or only a very small retroclination took place. The values were well within the method error, and it was concluded that the effect of the splint had been one of intrusion of the upper and lower front teeth and not merely a change in their inclination.

The suitability of a new index for the evaluation of dental wear

The suitability of a new index for rating dental wear by different observers was tested. Four dentists, who were first calibrated using the scoring system and then subjected to an inter-examiner agreement test before and after a field study, rated 167 individuals in total in their private dental practices. The incisal/occlusal state of the teeth with regard to restorations and dental wear was recorded. The inter-examiner agreement test proved satisfactory when rating main groups of wear but not so good when rating subcategories. However, a marked improvement in agreement developed between the first and the second test. The individuals composing the field study group are probably not representative of Scandinavian populations in general. Relatively few teeth were missing, and the teeth were well restored. Only the highest age group (80-89 years) displayed the most severe degree of wear to any extent. However, wear into the dentin was observed in 20% of the teeth already in the youngest age group (20-29 years). These teeth were solely incisors and canines of both jaws. In conclusion, we found that the index should be well suited for the evaluation of dental wear in large groups of people by different investigators after adequate training in use of the system has been provided and that tooth wear may be a relatively small problem in urban Scandinavian populations with regular dental care.

Differences in functional variables, fillings, and tooth wear in two groups of 19-year-old individuals

Fifty-one individuals (28 girls and 23 boys) who had received orthodontic treatment were compared with 47 subjects (19 girls and 28 boys) without such treatment as to maximal mandibular mobility, chewing muscle tenderness, morphologic occlusion, occlusal/incisal state, and degree of tooth wear. All were 19 years old. There were no statistically significant differences between the groups except for the number of teeth present and maximal mouth opening, which were both smallest in those who had received treatment. The first finding is evident, extraction of premolars being an accepted mode of orthodontic treatment. The reduced mouth opening capacity was related to an increased number of individuals with four or more palpably tender muscle sites in that group of individuals.

Bonding properties and dimensional stability of hydrocolloid impression systems in fixed prosthodontics

Four hydrocolloid impression systems for fixed prosthodontics and one conventional alginate were tested for bonding properties between the syringe and the tray materials of the systems. Their dimensional stability was tested also after the impressions were kept in a humidor for 1, 3, and 24 hours before casts were poured. Findings showed that there was a true bond between the syringe and the tray materials for all combinations. The precision tests gave a mean percent difference between the master model and the cast of less than 0.15 for all material combinations at both the 1- and 3-hours observations. The same was true at the 24-hours observation, except for one combination. From a clinical point of view, all the materials can be used for fixed prosthodontic impressions even if kept for 1 and 3 hours in 100% humidity before pouring the casts; however one material was unsuitable if kept for 24 hours before pouring.

Antibacterial effect of two luting cements on prepared dentin in vitro and in vivo.

Dahl, B.L. Antibacterial effect of two luting cements on prepared dentin in vitro and in vivo.The antibacterial effect of a polycarboxylate cement (Durelon®) and a zinc phosphate cement (De Treys Zink Zement Improved®) was studied in vitro and in vivo.For in vitro experiments a streptomycin resistant strain of Streptococcus mutans (Strep. mutansPRSR) was used. In one experimental series 1 ml of an overnight bacterial culture was suspended in 20 ml of nutrient agar, and poured to set in Petri dishes. Holes 5 mm in diameter were punched in the gel and filled with freshly mixed cement. The antibacterial effect was estimated by measuring the diameter of the zone of bacterial growth inhibition surrounding the holes after 24 h. In another experimental series two cavities were cut into the dentin of newly extracted human third molars. On the floor of both cavities a circular disc of filter paper saturated with Strep. mutans PRSR was placed. A sterile brass cylinder with freshly mixed cement covered one of the p...

Effect of cleansing procedures on the retentive ability of two luting cements to ground dentin in vitro.

A method has been described to measure the retention of luting cements to ground dentin in vitro. Using a specially designed apparatus, a circular disc of cement was produced on a ground dentin surface of equal diameter. In a universal testing machine a tensile stress was applied to the cement disc pulling it parallel with the dentin surface at right angles to the diamond grooves until separation. The effect of two different cleansing procedures on the retentive ability of two dental cements was investigated. The cleansing procedures were: rubbing ground dentin with Tubulicid or polishing with wet pumice. The cements studied were a polycarboxylate cement (Durelon) and a zinc phosphate cement (De Treys Zink Zement Improved). The retentive ability of the polycarboxylate cement showed values from six to seventeen times those of the zinc phosphate cement. The retentive ability of zinc phosphate cement was only slightly affected by the two cleansing procedures, while for polycarboxylate cement it was somewhat reduced following rubbing with Tubulicid and greatly improved after polishing with pumice and water.