The inter-relation between epithelial cells of Malassez and vessels studied immunohistochemically in the periodontal membrane of human primary and permanent teeth

The long-term fate of persisting deciduous molars and canines in 42 patients with severe hypodontia: a 12-year follow-up

OBJECTIVES

The decision to preserve or to extract a deciduous tooth without a successor hinges upon whether it can be expected to be stable over time. This study aimed to record the number and location of deciduous teeth and to examine the condition of deciduous canines and molars in a group of patients with severe hypodontia, both at baseline and at follow-up.

MATERIAL AND METHODS

A total of 50 patients participated in a follow-up study. The average age was 13.9 years (range 7-25 years) at baseline and 25.6 years (range 18-38 years) at follow-up. Of the 50 subjects, 44 had at least one persisting deciduous tooth at follow-up and 42 had at least one deciduous canine or molar at baseline. The presence of persisting deciduous teeth was identified on panoramic radiographs. Deciduous canines and second molars were classified as good or poor based on infraocclusion, root resorption, and restorations.

RESULTS

The mean number of persisting deciduous teeth per patient was 6.3 (range 1-16) at baseline and 2.6 (range 0-9) at follow-up. The tooth types with the highest tendency to remain were canines and second molars, and in particular canines in the mandible. Among the 42 participants with a deciduous canine or molar, 183 teeth were present at baseline, of which 112 were classified as good. At follow-up, 86 (77 per cent) of these were still present, with 65 (58 per cent) classified as good. The number of teeth classified as poor due to infraocclusion decreased much more from baseline to follow-up than those classified as poor due to root resorptions and restorations, indicating that infraoccluded teeth were lost during the observation period.

CONCLUSIONS

Preserving deciduous canines and molars in good condition is often a dependable choice. Early infraocclusion is detrimental to the prognosis and often leads to tooth loss. Teeth with short roots proved to be more stable over time.

[Ectoderm, mesoderm and neuroectoderm are tissue types of importance for understanding and preventing root resorption. Clinical guidelines]

INTRODUCTION

This three-part article summarizes ideas already described elsewhere by the author. Part 1. New way of diagnosing the dentition. For diagnostic purposes origin and appearance of the three tissue types - ectoderm, mesoderm (ectomesenchyme) and peripheral nerves - are depicted on orthopantomograms. Same tissue types are marked on the root surface (peri-root sheet). Part 2. Factors provoking root resorption. Resorption can be explained from the composition of the peri-root sheet. Deviations (inborn or acquired) in each of the three tissue layers can provoke inflammation, resulting in resorption. Orthodontic forces resulting in resorption can occur in normal peri-root sheets, but also in peri-root sheets with inborn deviations, important to diagnose. Part 3. How to prevent root resorption - Clinical guidelines. General diseases and different dental morphologies are signs predisposing for root resorption (ectoderm and mesoderm), so are local or general virus attacks (neuroectoderm). Resorption often occurs in dentitions never treated orthodontically.

MATERIAL AND METHOD

The author performed a review of the literature in order to present a new diagnostic approach incorporating histological and embryological concepts.

RESULTS

The review revealed different etiologies and sites involved in root resorption. Patients presenting variations of the peri-root sheet are most exposed to root resorption.

DISCUSSION

At this stage, it is difficult to diagnose these variations. The author offers diagnostic recommendations to be followed prior to orthodontic treatment. Even when no orthodontic treatment is given, root resorption can occur unexpectedly. In these cases, resorption prevention is currently impossible.

Mechanism of human tooth eruption: review article including a new theory for future studies on the eruption process

Human eruption is a unique developmental process in the organism. The aetiology or the mechanism behind eruption has never been fully understood and the scientific literature in the field is extremely sparse. Human and animal tissues provide different possibilities for eruption analyses, briefly discussed in the introduction. Human studies, mainly clinical and radiological, have focused on normal eruption and gender differences. Why a tooth begins eruption and what enables it to move eruptively and later to end these eruptive movements is not known. Pathological eruption courses contribute to insight into the aetiology behind eruption. A new theory on the eruption mechanism is presented. Accordingly, the mechanism of eruption depends on the correlation between space in the eruption course, created by the crown follicle, eruption pressure triggered by innervation in the apical root membrane, and the ability of the periodontal ligament to adapt to eruptive movements. Animal studies and studies on normal and pathological eruption in humans can support and explain different aspects in the new theory. The eruption mechanism still needs elucidation and the paper recommends that future research on eruption keeps this new theory in mind. Understanding the aetiology of the eruption process is necessary for treating deviant eruption courses.

Autotransplantation of maxillary second premolars to mandibular recipient sites where the primary second molars were impacted, predisposes for complications

OBJECTIVE

The aim of the study was to elucidate whether ankylosis of a transplanted permanent tooth can be predicted based on an evaluation of the primary and permanent dentitions.

MATERIALS AND METHODS

The study comprised 162 maxillary second premolars and 49 third molars transplanted to the mandibular second premolar region in 157 patients treated in the period 1980-2003.

SELECTION CRITERIA

panoramic radiograph available; agenesis of the mandibular permanent premolar/s; persistence of the primary molar at the recipient site. The 211 transplanted teeth were observed for a period of between 1-29 years.

RESULTS

Seven per cent (95% confidence interval, CI = 3-11%) of the transplanted second premolars ankylosed during the first 10 years after operation. The success rate for transplantation of the third molar to the mandibular second premolar region was significantly lower (p = 0.001), as 40% (95% CI = 24-57%) of the third molars had ankylosed 10 years after operation. A significant association (p = 0.022) was found between ankylosis of a second premolar and infra-position of the primary second molar located at the recipient site. The infraposition group had 13% (CI = 4-23%) ankylosis after 10 year, whereas the non-infraposition group had 5% (CI = 1-9%) ankylosis after 10 years.

CONCLUSIONS

The present study concludes that there is an increased risk of ankylosis of the transplanted permanent tooth if the primary tooth at the recipient site is in infraposition. This observation may be decisive for treatment planning, especially in young individuals in whom excessive growth of the alveolar process is expected from the cephalometric analysis.

Regional aggressive root resorption caused by neuronal virus infection

During orthodontic treatment, root resorption can occur unexplainably. No clear distinction has been made between resorption located within specific regions and resorption occurring generally in the dentition. The purpose is to present cases with idiopathic (of unknown origin) root resorption occurring regionally. Two cases of female patients, 26 and 28 years old, referred with aggressive root resorption were investigated clinically and radiographically. Anamnestic information revealed severe virus diseases during childhood, meningitis in one case and whooping cough in the other. One of the patients was treated with dental implants. Virus spreading along nerve paths is a possible explanation for the unexpected resorptions. In both cases, the resorptions began cervically. The extent of the resorption processes in the dentition followed the virus infected nerve paths and the resorption process stopped when reaching regions that were innervated differently and not infected by virus. In one case, histological examination revealed multinuclear dentinoclasts. The pattern of resorption in the two cases indicates that innervation is a factor, which under normal conditions may protect the root surface against resorption. Therefore, the normal nerve pattern is important for diagnostics and for predicting the course of severe unexpected root resorption.