Ivar A. Mjör

The density and branching of dentinal tubules in human teeth

Detailed knowledge of dentine structure, and especially that of the dentinal tubules, is essential in order to understand dentine permeability and to interpret data from investigations on dentine adhesive materials. The aim here was to examine the density and branching of dentinal tubules in human teeth by light and scanning electron microscopy. Stained and unstained demineralized sections and undemineralized fractured specimens were studied. Statistically significant differences in the density of tubules were found depending on location. Differences in density of tubules between the peripheral and inner aspects were more marked in the crown than in root. The mean number of dentinal tubules in the middle part of the root was significantly lower than in the middle part of the crown. The density of the tubules in the outer dentine at the cusp location was also significantly different from that subjacent to the occlusal fissure. The number of branches of dentinal tubules was particularly abundant in locations where the density of tubules was low. The branching patterns revealed an intricate and profuse canalicular, anastomosing system, criss-crossing the intertubular dentine. Three types of branches, major, fine and microbranches, were identified on the basis of size, direction and location. Major branches, 0.5-1.0 micron dia., were the typical delta branchings found peripherally. Fine branches, 300-700 nm dia., forked off at 45 degrees and were abundant in areas such as in the root where the density of the tubules was relatively low. Microbranches, 25-200 nm dia., extended at right angles from the tubules in all parts of the dentine. The findings emphasize the need for detailed characterization of dentine substrates for adhesive testing and of samples used in permeability studies.

An Overview of Reasons for the Placement and Replacement of Restorations

Aim Surveys on reasons for the placement and replacement of restorations have been conducted in various countries. The purpose of this paper is to bring together and review the data of 10 such surveys with similar methodology. Method The studies reviewed are all based on the protocol described by Mjör in 1981. Results The surveys reviewed provide data on the reasons for the placement and replacement of a total of 32,777 restorations. Notwithstanding differences between countries, different groups of practitioners and minor variations in methodology, the data included in the selected surveys indicate that everyday clinical practice in Scandinavia, UK and USA during the 1980s and 1990s has involved more replacement than initial restorations, with the ratio of initial to replacement restorations ranging from 1:1.1 to 1:2.4 for amalgam and 1:1.1 to 1:3.8 for composite materials. Primary caries has been consistently found to be the principal reason for the provision of initial restorations of amalgam and composite. The principal reason for the replacement of restorations of amalgam and composite has remained secondary caries as diagnosed clinically. Material failures (marginal degradation, discoloration, bulk fracture and loss of anatomic form) accounted for the replacement of more restorations of composite than amalgam. Recent surveys have reported secondary caries as the principal cause of failure of restorations of glass-ionomer cements and related materials. Conclusions The clinical diagnoses of caries may continue to be found to account for the placement and replacement of most intracoronal restorations. Surveys of the type reviewed provide valuable insight into patterns of provision of dental care and highlight research priorities in relation to direct restorations.

The reasons for replacement and the age of failed restorations in general dental practice

A cross-sectional survey among practitioners in Sweden treating adult patients was initiated to record the reasons for replacement of composite, amalgam, and glass ionomer restorations and to compare the findings with those obtained about 16 years ago. The age of the failed restorations was also recorded. The clinical diagnosis of secondary caries was the main reason for the replacement of all three types of restorations. The diagnosis was significantly higher for amalgam restorations than for composite and glass ionomer restorations. No statistically significant differences could be found in the diagnosis of secondary caries between composite and glass ionomer restorations. Major changes in the reasons for replacement of composite restorations were noted by comparing the present results with those from 16 years ago. A notable difference was seen with regard to a decrease in the relative frequency of replacements due to composite degradation/wear and an increase in the replacements due to bulk and marginal fractures. The reasons for replacement of amalgam restorations had remained much the same over the 16 years. The report that half the glass ionomer restorations replaced had the diagnosis secondary caries was by far the most surprising result. The age of the failed restorations were reported for a limited number of restorations. The median age was about 6 years for composite, almost 9 years for amalgam, and just more than 3 years for glass ionomer restorations.

Placement and longevity of tooth-colored restorations in Denmark

A survey has been made of the use of materials and the reasons for placement of 2542 tooth-colored restorations in Denmark. In adults 38% of all the restorations were inserted because of primary caries, and 62% were replacements of failed restorations. In children primary caries was the reason for placing 68% of the restorations in deciduous teeth and 77% of those in permanent teeth. Resin-based materials were the most frequently used tooth-colored restorative, except in the treatment of deciduous teeth, for which glass ionomer cement was used preferentially. Silicate cement was used for less than 2% of the tooth-colored restorations, and the few old silicate cement restorations were most often replaced with resin materials. The reasons for replacement of resin restorations were dependent on dentition, age of the patient, and type of restoration. Secondary caries, fracture of restoration, and loss of fillings were the most frequently recorded failures. The age of the resin restorations replaced ranged from 0 to 19 years, and half of the failed restorations in adults were more than 6 years old. In permanent teeth in children half of the failed resin restorations were replaced within 2 years, whereas half of those in primary teeth were replaced within 1 year.

Age of restorations at replacement in permanent teeth in general dental practice.

The ages of 6,761 restorations replaced in permanent teeth, 6,088 in adults ≥19 years of age and 673 in adolescents ≤18 years, were available for analyses. The results showed that the median age of amalgam restorations in adults was 11 years and that of resin-based composite restorations 8 years. This difference in longevity was significant (P = 0.0001). The median age of failed conventional glass ionomer restorations in adults was 4 years and for resin-modified glass ionomer 2 years. In adolescents, the median longevity of failed amalgam restorations was 5 years and that of composite restorations 3 years, while both types of glass ionomers had a median longevity of 2 years. The data were subdivided based on clinician gender and practice setting. The results showed that the median age of amalgam and composite restorations replaced by male clinicians was higher than that for female clinicians irrespective of clinical setting. The median age of amalgam and composite restorations replaced by salaried dentists was significantly lower than that by private practitioners. Minor differences were noted in longevity of restorations between male and female patients. The age of replaced restorations was shortest for the group of clinicians with the least clinical experience and highest for those that graduated ≥ 30 years ago. Keywords: Amalgam composite; gender differences; glass; ionomer; practice setting

FDI World Dental Federation: clinical criteria for the evaluation of direct and indirect restorations—update and clinical examples

In 2007, new clinical criteria were approved by the FDI World Dental Federation and simultaneously published in three dental journals. The criteria were categorized into three groups: esthetic parameters (four criteria), functional parameters (six criteria) and biological parameters (six criteria). Each criterion can be expressed with five scores, three for acceptable and two for non-acceptable (one for reparable and one for replacement). The criteria have been used in several clinical studies since 2007, and the resulting experience in their application has led to a requirement to modify some of the criteria and scores. The two major alterations involve staining and approximal contacts. As staining of the margins and the surface has different causes, both phenomena do not appear simultaneously. Thus, staining has been differentiated into marginal staining and surface staining. The approximal contact now appears under the name “approximal anatomic form” as the approximal contour is a specific, often non-esthetic issue that cannot be integrated into the criterion “esthetic anatomical form”. In 2008, a web-based training and calibration tool called e-calib (www.e-calib.info) was made available. Clinical investigators and other research workers can train and calibrate themselves interactively by assessing clinical cases of posterior restorations which are presented as high-quality pictures. Currently, about 300 clinical cases are included in the database which is regularly updated. Training for eight of the 16 clinical criteria is available in the program: “Surface lustre”; “Staining (surface, margins)”; “Color match and translucency”; Esthetic anatomical form”; “Fracture of material and retention”; “Marginal adaptation”; “Recurrence of caries, erosion, abfraction”; and “Tooth integrity (enamel cracks, tooth fractures)”. Typical clinical cases are presented for each of these eight criteria and their corresponding five scores.

Placement and longevity of amalgam restorations in Denmark

A survey has been made of the reasons for placement of 4932 amalgam restorations in Denmark. In patients more than 16 years of age 39% of all restorations were made because of primary caries, and 61% were replacements of failed restorations. In children 74% of the restorations in primary teeth and 84% of those in permanent teeth were inserted because of primary caries. The reasons for replacement of restorations depended on dentition, age of the patient, and type of restoration. Secondary caries was the most frequent reason for replacement of failed restorations in permanent teeth and accounted for 38% of all failures. Marginal discrepancies and bulk fracture of fillings were the other two major reasons. In primary teeth fracture and loss of fillings were the commonest reasons, whereas secondary caries accounted for only a quarter of all restorations replaced. The age of the restorations replaced ranged from 0 to 46 years, and half of the failed restorations in permanent teeth of adults were more than 8 years old. A shorter longevity of failed restorations was noted in primary teeth and permanent teeth of children.

Restorative treatment pattern and longevity of amalgam restorations in Denmark

A survey has been made of the reasons for placement and replacement of 6052 amalgam restorations in Denmark. In patients more than 16 years of age 48% of all restorations were made because of primary caries, and 52% were replacements of failed restorations. In primary teeth 64% and in permanent teeth of children 83% of the restorations were made because of primary caries. The reasons for replacement of restorations were dependent on dentition, age of the patient, and type of restoration. Secondary caries was the most frequent reason for replacement of failed restorations in permanent teeth, comprising a third of all replacements. Marginal discrepancies and bulk fracture of fillings were the other two major reasons. In primary teeth fracture and loss of fillings were the two major reasons for replacement of amalgam restorations, whereas secondary caries caused less than a quarter of all restorations to be replaced. The age of the restorations replaced ranged from 0 to 38 years, and half of the restorations replaced in permanent teeth of adults were less than 7 years old. A shorter longevity of failed restorations was noted in primary teeth and permanent teeth of children.

The age of restorations in situ

In a cross-sectional survey the age of restorations in situ was recorded in three patient groups. Group A were randomly examined regular attenders, group B were irregular attenders randomly chosen from patient treatment records, and in group C the age of posterior gold and composite resin restorations was recorded in selected regular attenders. The study material included 8310 restorations in group A, 1281 in group B, and 500 restorations in group C. The three materials amalgam, composite, and gold accounted for more than 90% of all restorations. In group A 3.3% of the restorations were scheduled for replacement. The most prevalent reasons for replacement were secondary caries, bulk fractures of the restoration, and tooth fractures. The median age of the failed restorations was fairly similar to the median age of the acceptable restorations in situ among the regular patients (group A). The data indicate median ages of 20 years for gold restorations, 12-14 years for amalgam restorations, and 7-8 years for composite resin restorations. The restoration ages were influenced by the type and size of the restoration, the restorative material used, and possibly also the intra-oral location of the restorations.

Increasing the Longevity of Restorations by Minimal Intervention: A Two-year Clinical Trial

UNLABELLED This investigation assessed the effectiveness of alternative treatments for the replacement of amalgam and resin-based composite restorations. Sixty-six patients (age 18 to 80 years, mean = 26.6) with 271 (amalgam [n = 193] and resin-based composite [n = 78]) defective restorations were randomly assigned to one of five different treatment groups: A) Repair (n = 27); B) Sealing of margins (n = 48); C) Refurbishing (n = 73); D) Replacement (n = 42) and E) Untreated (n = 81). USPHS/Ryge criteria were used to determine the quality of the restorations. Two calibrated examiners (Cohens Kappa 0.74) assessed the restorations independently at the beginning of the study (baseline) and at two years after treatment using seven parameters from the USPHS/Ryge criteria (Marginal Adaptation, Anatomic Form, Roughness, Marginal Stain, Occlusal Contact, Secondary Caries and Luster). RESULTS Two-hundred and fifty-six restorations (178 amalgam and 78 resin-based composite) were examined at the two-year recall exam. The sealing of marginal defects showed significant improvements in marginal adaptation (p < 0.05). Refurbishing of the defective restorations significantly improved anatomic form (p < 0.0001), luster (p < 0.016), marginal adaptation (p < 0.003) and roughness (p < 0.0001). The repair significantly improved anatomic form (p < 0.002) and marginal stain (p < 0.002). Replacement showed significant improvements for all parameters (p < 0.05). The Untreated group showed significant deterioration on marginal adaptation (p < 0.013). CONCLUSIONS The two-year recall examination showed that sealant, repair and refurbishing treatments improved the clinical properties of defective amalgam and resin-based composite restorations by increasing the longevity of the restorations with minimal intervention.