(1/447) The root surface in human teeth: a microradiographic study.

In an attempt to clarify the nature of the human cemento-dentinal junction, ground sections of incompletely formed and fully formed extracted teeth were prepared and their histology compared with their microradiographic appearances. The results showed that incompletely formed teeth possess distinctive surface layers outside the granular layer of Tomes. The evidence indicates that these layers are of dentinal origin; their presence during development supports previous explanations by the author of the hyaline layer of Hopewell-Smith and of so-called intermediate cementum. The results also indicate that the granular layer of Tomes does not represent the outer limit of root dentine. The relationship of these surface layers to the definitive cementum which is present in fully formed teeth was studied in both young and older patients. From the results it was concluded that cementum formation begins in the more apical region of the teeth at a time when root formation is well advanced, and that it spreads towards the crown rather than in the generally accepted reverse direction.  (+info)

(2/447) Arrested eruption of the permanent lower second molar.

The incidence of retention/impaction of the permanent lower second molar (M2inf) lies between 0.6/1000 and 3/1000. Therefore, the purpose of the present study was to investigate the craniofacial morphology, the frequency of dental anomalies and the inclination of the affected M2inf and the adjacent first molar in patients with arrested eruption of M2inf. The overall goal was to elucidate the aetiology of arrested tooth eruption and to present the characteristics of these patients in order to improve diagnosis and treatment planning. Radiographic material (profile radiographs and orthopantomograms) from 19 patients (nine females and 10 males; 13-19 years of age at the time of referral) were analysed. The ages of the patients when profile radiographs were taken for cephalometric analysis varied from 8 to 16 years. The study shows that this group of patients, compared with a reference group, had an increased sagittal jaw relationship (Class II). Specifically, the mandibular prognathism was less, the mandibular gonial angle smaller, the mandibular alveolar prognathism enlarged and the maxillary incisor inclination less than in the reference group. Furthermore, this group of patients had a more frequent occurrence of morphological tooth anomalies, such as root deflections, invaginations, and taurodontism. However, none of the patients with arrested eruption of M2inf had agenesis of the lower third molar. The study did not reveal an association between the degree of inclination of the M2inf and that of the first molar in the same region. The results of this investigation show that conditions such as the craniofacial morphology and deviations in the dentition are associated with arrested eruption of M2inf. Therefore, it is important to evaluate these conditions in future diagnosis and treatment planning of patients with arrested eruption of M2inf.  (+info)

(3/447) Histological and histochemical quantification of root resorption incident to the application of intrusive force to rat molars.

This study was conducted to investigate the nature of root resorption resulting from intrusive forces applied to the rat lower molars, by means of histological and histochemical techniques with tartrate resistant acid phosphatase (TRAP). Thirty-eight 13-week-old Wistar strain male rats were used. Intrusive force was created by a fixed appliance which was adjusted to exert an initial force of 50 g for the duration of 1, 2, and 3 weeks. The degree of root resorption and distribution of TRAP positive cells were evaluated. On the root surface, the TRAP positive scores were low in the apical regions. Significant differences in the scores were found in the inter-radicular region of the roots between the experimental and control groups for the 2- and 3-week groups. More active resorption of bone occurred during the experimental period, as denoted by greater TRAP positive scores on the bone than on the root surface. Root resorption scores in the apical root region were larger in the 2- and 3-week groups than in the 1-week group. Significant differences in the root resorption scores were also found between the 1- and 3-week groups in the inter-radicular region, indicating that intrusive force application of a longer duration may lead to a higher frequency of root resorption. It is shown that, irrespective of the level of TRAP positive cells and root resorption scores, the degree of root resorption activity is higher in the apical root region than in the inter-radicular area. These results indicate that cellular cementum may be resorbed more easily because of its richer organic components and low mineralized structure.  (+info)

(4/447) The effect of tooth position on the image of unerupted canines on panoramic radiographs.

The purpose of this study was to evaluate whether panoramic tomograms, which are routinely used in orthodontic practice, can provide adequate information to localize an impacted canine. The effect of changes in position and inclination of an impacted canine on orthopantomograms was investigated in an experimental set-up. An upper canine was removed from a human skull and replaced in a positioning system, enabling simulated positional variations in impactions. In comparison with the image of a contralateral well-aligned canine, the length of the impacted tooth always decreased or remained unchanged, whereas the tooth width increased or remained unchanged. The angulation of the image was unaffected by varying the position of the impacted canine, but altered when the inclination of the tooth in a sagittal or frontal direction was changed. If there was any transversal shift of the impacted canine on the orthopantomogram, it was always towards the mid-sagittal plane. The curvature of the tooth increased after dorsal inclination and decreased after ventral inclination (in comparison with the contralateral well-aligned canine).  (+info)

(5/447) Evolution of periodontal regeneration: from the roots' point of view.

Tissues lost as a consequence of periodontal diseases, i.e. bone, cementum and a functional periodontal ligament (PDL), can be restored to some degree. Nevertheless, results are often disappointing. There is a need to develop new paradigms for regenerating periodontal tissues that are based on an understanding of the cellular and molecular mechanisms regulating the development and regeneration of periodontal tissues. As one approach we have developed strategies for maintaining cementoblasts in culture by first determining the gene profile for these cells in situ. Next, cells were immortalized in vitro using SV 40 large T antigen (SV40 Tag) or by using mice containing transgenes enabling cellular immortality in vitro. Cementoblasts in vitro retained expression of genes associated with mineralized tissues, bone sialoprotein and osteocalcin, that were not linked with periodontal fibroblasts either in situ or in vitro. Further, cementoblasts promoted mineralization in vitro as measured by von Kossa and ex vivo using a severely compromised immunodeficient (SCID) mouse model. These cells responded to growth factors by eliciting changes in gene profile and mitogenesis and to osteotropic hormones by evoking changes in gene profile and ability to induce mineral nodule formation in vitro. The ultimate goal of these studies is to provide the knowledge base required for designing improved modalities for use in periodontal regenerative therapies.  (+info)

(6/447) High-altitude illness induced by tooth root infection.

High-altitude illness may occur after recent pulmonary infection, but high-altitude illness after root canal therapy has not been described previously. A 44-year-old man is presented who skied to a 3333 m high peak in the Eastern Alps one day after he had undergone root canal therapy because of a tooth root infection. After 4 hours above 3000 m severe symptoms of high-altitude illness, including pulmonary oedema, developed. His condition improved after immediate descent. The next day he presented with local and general signs of infection which were successfully treated with gingival incisions and antibiotics. In conclusion, acute tooth root infection and root canal therapy may induce high-altitude illness at an altitude just above 3000 m.  (+info)

(7/447) A mathematic-geometric model to calculate variation in mandibular arch form.

A mathematic-geometric model was used to evaluate the variation of mandibular dental arch length with respect to the incisor inclination, but without modifying the intercanine width. In analytical terms, the equations of the curves representing the lower dental arch, before and after incisor inclination of 1 mm and of 1 degree, with controlled and uncontrolled tipping, were studied. The length of the mandibular dental arch changed in the parabolic arch form by 1.51 mm for each millimetre of incisor inclination with respect to the occlusal functional plane, by 0.54 mm for each degree of controlled tipping and by 0.43 mm for each degree of uncontrolled tipping. In the elliptical arch form (e = 0.78), it changed by 1.21, 0.43, and 0.34 mm, respectively, in the hyperbolic form by 1.61, 0.57, and 0.46 mm, in the circular form by 1.21, 0.43, and 0.34 mm, and in the catenary form by 2.07, 0.74, and 0.59 mm. The results show that by changing the arch form without modifying the dimension of the dental arch, different arch lengths can be gained for each millimetre of proclination. In addition, by controlled tipping an inter-incisive arch one-fifth longer than by uncontrolled tipping can be obtained. It would be advisable in orthodontic treatment planning to evaluate the type of dental arch, since the space available or the space required changes depending on the arch form and on the orthodontic tooth movement.  (+info)

(8/447) Predominant cultivable flora isolated from human root surface caries plaque.

Plaque samples were obtained from tooth surfaces exhibiting typical lesions of root surface caries and were immediately cultured by a continuous anaerobic procedure. The bacterial composition of root caries flora was determined on individual samples. Representative isolates from each specimen were characterized by morphological and physiological criteria. In addition, fluorescent antibody reagents were used to confirm the identification of Streptococcus mutans and Actinomyces viscosus. The plaque samples could be divided into two groups on the basis of the presence or absence of S. mutans in the plaque. In group I plaques, S. mutans comprised 30 percent of the total cultivable flora. S. sanguis was either not found or was present in very low number. In group II plaques, S. mutans was not detected, and S. sanguis formed 48 percent of the total plaque flora. A. viscosus was the dominant organism in all plaque samples, accounting for 47 percent of the group I isolates and 41 percent of the group II isolates.  (+info)