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PubMed1999

Immortalized cementoblasts and periodontal ligament cells in culture.

Cementum, a mineralized tissue lining the surface of the tooth root, is required for formation of a functional periodontal ligament attachment during development. Additionally, during regeneration of tissues after disease, cementum is thought to play a critical role in the reparative process. Research efforts aimed toward understanding mechanisms involved in periodontal development and regeneration, and in particular the formation of root cementum, have been hampered by an inability to isolate and culture cells involved in cementum production, i.e., cementoblasts. Using classical techniques for osteoblast isolation, immortalized, heterogeneous cementoblast/periodontal ligament cell (CM/PDL) populations were established from cells lining the tooth root surface of: 1) CD-1 mice, where cells were immortalized using SV40, or 2) H-2KbtsA58 "immorto" mice, where cells containing an immortalizing transgene were removed and cultured. CM/PDL populations were derived from tissues adherent to developing tooth root surfaces, while tissues adherent to the surrounding alveolar bone were specifically excluded from the population. Immortalized CM/PDL cells were characterized to ensure their phenotype reflected that previously demonstrated in situ and in primary, nonimmortalized cultures. Proteins/mRNAs associated with bone/cementum and known to be expressed by root lining cementoblasts, but not by PDL cells, in situ, e.g., bone sialoprotein, osteopontin, and osteocalcin, were expressed by cells within the immortalized populations. Furthermore, CM/PDL cells, in vitro, attached to bone sialoprotein in an arginine-glycineaspartic acid (RGD)-dependent manner, promoted mineral nodule formation and exhibited a PTH/PTHrP-mediated cAMP response. These immortalized heterogeneous populations, containing both CM and PDL cells, provide a unique opportunity to study cells involved in cementogenesis and to enhance our knowledge of the mechanisms controlling development, maintenance, and regeneration of periodontal tissues.

Animals↗
PubMed1991

[Physiological tooth migration in hydroxyapatite grafts with bony regeneration. Animal study].

Tooth migration into jaw segments where granular hydroxy apatite had been implanted was studied in rats. To prevent premature contact with the ceramic granules, tooth germs were completely removed in the animals at the age of 10 days. Tooth root contact with the ceramo-osseous complex as a result of physiological tooth migration had deleterious effects. In the light of these findings the implantation of granular hydroxy apatite in the vicinity of tooth roots is not advisable.

Animals↗
PubMed2002

Survival of intentionally retained permanent incisor roots following crown root fractures in children.

Retaining tooth roots, following crown loss, confers a number of benefits including the preservation of alveolar bone. Intentional root retention in adults has been widely investigated but little is known about this treatment approach in children. Therefore, the aim of the present study was to investigate the clinical outcomes associated with permanent anterior root retention in a young population. The study group comprised 53 children who had received treatment in the paediatric dentistry clinic, Charles Clifford Dental Hospital, Sheffield, UK, over the past 10 years, following a complicated crown root fracture of a permanent maxillary incisor at or below the gingival margin. Data relating to patient age at crown root fracture, gender, previous trauma history, tooth vitality, treatments performed and clinical outcomes were obtained retrospectively using patient records. The mean age of the subjects at initial crown root fracture was 12.1 years (range 8.3-15.8 years) and there were more than twice as many males (n = 37, 70%) as females (n = 16, 30%). In just over half of the cases seen (n = 29, 54%), the tooth involved was already nonvital at the time of crown root fracture. For the majority of these nonvital teeth (n = 27, 93%), primary treatment had comprised placement/replacement of a calcium hydroxide root dressing. The remaining two teeth did not require root treatment as a satisfactory gutta percha root filling was already present. A variety of treatments was undertaken for the 24 vital roots: in 15 (63%) cases the pulp was extirpated and calcium hydroxide placed; three (12%) cases were subject to a pulpotomy; five (21%) cases were left untreated with the hope that vitality would be maintained following gingival healing and in one case the radicular pulp was extirpated and immediately obturated with gutta percha. The mean time that the roots were kept under review was 2.6 years (+/- 1.57, range 0.6-6.8). During this period, only five roots (9%) had to be removed due to persistent periapical infection. There were no complications associated with the five cases where vital root submergence had been permitted but all three cases which had initially undergone a pulpotomy subsequently presented with pulpal necrosis necessitating pulpal extirpation and calcium hydroxide therapy. These findings indicate that efforts to retain permanent anterior roots in a young population are justified in view of the high clinical success rate of over 90% over a 2-year period.

Adolescent↗
PubMed2000

Localization of cathepsin D in human odontoclasts. a light and electron microscopical immunocytochemical study.

Odontoclasts are dentine and cementum resorbing cells whose relationship to bone resorbing osteoclasts is not clear. Like osteoclasts, they possess different cathepsins which are involved in mineralized tissue degradation during the tooth root resorption process in deciduous teeth. Whether cathepsin D, which in osteoclasts probably functions as an activator of other cathepsins, can be found in odontoclasts, has, however, not been investigated before. In order to determine its occurrence and localization, cathepsin D immunocytochemistry was applied to paraffin-embedded sections from 30 human deciduous tooth roots undergoing resorption. Using immunogold postembedding immunocytochemsitry on LR-Gold embedded specimens, the distribution of cathepsin D was investigated at the ultrastructural level. We identified tartrate-resistent acid phosphatase-positive mono- and multinuclear odontoclasts near and on the periodontal surfaces of tooth roots. Nearly all of these cells showed cytoplasmic granular cathepsin D immunoreactivity. At the electron microscopical level, gold labelling was seen on vacuoles and vesicles of the odontoclasts, which were identified as secondary lysosomes and phagosomes. Extracellularly it was seen along the ruffled border and in neighboured resorption areas of dentine and cementum. These findings indicate that cathepsin D is secreted into the resorbing area of human odontoclasts in order to participate in degradation of mineralized tooth matrix, but may also function as an activator of other proteases in lysosomal organelles.

Cathepsin D↗
PubMed2006

Traumatic intrusion of permanent teeth. Part 2. A clinical study of the effect of preinjury and injury factors, such as sex, age, stage of root development, tooth location, and extent of injury including number of intruded teeth on 140 intruded permanent teeth.

A prospective study of 140 intruded permanent teeth was done to evaluate the following healing complications: pulp necrosis (PN), root resorption (surface, inflammatory and replacement resorption) (RR) and defects in marginal periodontal healing (MA). These complications were related to various preinjury and injury factors. Age appeared to be related to all three healing complications in that patients younger than 12 years had the lowest complication rate. Stage of root formation at the time of the injury was very strongly related to PN and MA, with immature root formation (i.e. incomplete root formation or completed root formation with wide open apex) having better prognosis than more mature root development. Lateral incisors showed significantly more defects in MA, a finding possibly explained by the observation that lateral incisors were more often involved in multiple intrusions compared to other teeth and noting that multiple intrusions had a significantly higher frequency of MA. An associated crown fracture with exposed dentin resulted in more frequent PN, a finding possibly related to bacterial invasion through dentinal tubules into an ischemic pulp. The presence of a gingival laceration added to both PN and MA. The extent of intrusion (in mm) showed some relation to both RR with intrusion 1-3 mm having the lowest frequency of RR, whereas PN and MA showed no significant relation to the extent of intrusion. Finally, multiple adjacent intruded teeth were more frequently involved in a significantly greater loss of interproximal marginal bone (MA) than single intrusions. In conclusion, the relationship between healing complications and preinjury and injury factors could generally be explained by better healing possibilities in teeth with immature root formation. A possible explanation for that could be the softer bone surrounding the tooth, whereby trauma to the periodontium might be diminished.

Adolescent↗
PubMed2005

Posts and the root-filled tooth.

It is clear that teeth often require significant reconstruction following root canal treatment. It is also evident that there is an enormous variety of ways that can be used to achieve this. Although there is some debate about the relative contributions of the root filling and coronal restoration to endodontic success, it is agreed that the best results are gained with a good root filling and a well-sealed coronal restoration. Posts, pins and/or bonding are all possible solutions to retain the coronal restoration but it is often difficult to decide, on the basis of evidence rather than fashion or anecdote, which is preferable.

Humans↗
PubMed2003

[The effect of rehabilitation of flared root canal on the fracture resistance of root and post-core system].

OBJECTIVE: To assess the effect of rehabilitation of flared root canal on the fracture resistance of root and post-core system. METHODS: Thirty-two simulated tooth roots made of polymethyl methacrylate were divided into 4 groups, including the normal root canal group and 3 flared root canal groups. One flared root canal group was rehabilitated by light-cared composite, another group was rehabilitated by amalgam, and the third flared root conal group was not treated. Casting post and core restored every simulated tooth root. Each specimen was embedded in acrylic resin and then fixed in a special jig on the universal load-testing machine. A compressive load was applied at a 90-degree angle to the long axis of the core until fracture, at a crosshead speed of 1 mm/min; the maximum of load was recorded. RESULTS: The means of load in normal root canal group, light-cared composite rehabilitated group, amalgam rehabilitated group, not treated group were 202.92 N, 194.60 N, 146.89 N, 142.09 N. It was shown that the load of normal root canal group is significantly greater than the load of not-treated group (P < 0.01); the light-cared composite rehabilitated group is significantly stronger than the not-treated group (P < 0.01), but there is no significant difference between the light-cared composite rehabilitated group and normal root canal group, and no significant difference between the amalgam rehabilitated group and not-treated group (P > 0.05). CONCLUSION: The rehabilitation of flared root canal using suitable material not only changes the shape of root canal, but also increases the fracture resistance of root canal because of its thicker and stronger root canal wall which obviously improves the fracture resistance of post and core.

Acrylic Resins↗
PubMed2000

Parathyroid hormone-related protein regulates extracellular matrix gene expression in cementoblasts and inhibits cementoblast-mediated mineralization in vitro.

Parathyroid hormone-related protein (PTHrP) has been implicated in regulating tooth eruption and/or development. Formation of cementum, a mineralized tissue covering the tooth root surface, is a critical biological event for tooth root development. To test the hypothesis that PTHrP targets cementoblasts (CMs) and acts to regulate cementogenesis, CM cell lines were established and their responsiveness to PTHrP stimulation was determined, in vitro. First, subclones were derived from two immortalized murine cell populations that contained CMs; SV-CM/periodontal ligament (PDL) cells were obtained from the root surface of first mandibular molars of CD-1 mice and immortalized with SV40 T-antigen (TAg), and OC-CM cell population was established from OC-TAg transgenic mice in which their cells harbor an osteocalcin (OC and/or OCN) promoter-driving immortal gene SV40 TAg. Based on our previous in situ studies, CM subclones were identified as cells expressing bone sialoprotein (BSP) and OCN transcripts, while PDL cell lines were designated as cells lacking BSP and OCN messenger RNA (mRNA). CMs exhibited a cuboidal appearance and promoted biomineralization, both in vitro and in vivo. In contrast, PDL cells (PDL subclones) displayed a spindle-shaped morphology and lacked the ability to promote mineralized nodule formation, both in vitro and in vivo. Next, using these subclones, the effect of PTHrP on cementogenesis was studied. CMs, not PDL cells, expressed PTH/PTHrP receptor mRNA and exhibited PTHrP-mediated elevation in cyclic adenosine monophosphate (cAMP) levels and c-fos gene induction. PTHrP stimulation repressed mRNA expression of BSP and OCN in CMs and blocked CM-mediated mineralization, in vitro. Collectively, these data suggest that CMs possess PTH/PTHrP receptors and, thus, are direct targets for PTHrP action during cementogenesis and that PTHrP may serve as an important regulator of cementogenesis.

Animals↗
PubMed2002

Differential diagnosis between dentigerous cyst and benign tumor with an embedded tooth.

It has been generally recognized that the radiological appearances of cysts and tumors related to an embedded tooth are similar. However, based on their clinical experience, Abrams et al. pointed out that there was a difference between the two lesions at the attachment point to the embedded tooth. To investigate this difference, we conducted a study employing the radiographs of patients who visited Nihon University Dental Hospital at Matsudo and were pathologically defined as having a cyst or tumor. Using radiographs of these patients, we investigated the attachment point to the embedded tooth, and expressed the results as the proportion of the attachment point to the embedded tooth root length. The study was carried out in 100 patients with cysts (87 dentigerous cysts and 13 odontogenic keratocysts), and 27 patients with benign tumors (24 ameloblastomas and three adenomatoid odontogenic tumors). Prior to treatment based on the numerical results, the distribution of the results was examined. Thus, we evaluated several methods of examining the distributions, and found the best method to be discriminant analysis. The results showed that the discriminated boundary value (from the cemento-enamel junction) was 0.38 for the embedded tooth root length. The cases showing a boundary value of less than 0.4 for the cemento-enamel junction were judged to be cysts, and those showing a value of 0.4 or more were judged to be benign tumors. The rate of misjudgement was 28% in the cyst group and 33.3% in the benign tumor group.

Adolescent↗
PubMed2006

Tissue engineering of tooth crown, root, and periodontium.

Tissue engineering of teeth requires the coordinated formation of correctly shaped crowns, roots, and periodontal ligament. Previous studies have shown that the dental mesenchyme controls crown morphogenesis and epithelial histogenesis during tooth development in vivo, but little is known about the inductive potential of dissociated mesenchymal cells used in ex vivo cultures. A 2-step method is described in which, by using different types of reassociations between epithelial and mesenchymal tissues and/or cells from mouse embryos, reassociations were cultured in vitro before in vivo implantation. In vitro, the reassociated tissues developed and resulted in tooth-like structures that exhibited normal epithelial histogenesis and allowed the functional differentiation of odontoblasts and ameloblasts. After implantation, the reassociations formed roots and periodontal ligament, the latter connected to developing bone. The shape of the crown, initially suspected to depend on the integrity of the mesenchyme, could be modulated by adjusting the number of dissociated mesenchymal cells reassociated with the epithelial compartment. Based on these results, we propose a refined strategy for tooth tissue engineering that may help to eventually generate morphologically defined teeth.

Animals↗
PubMed1989

[Root resorption and endodontic treatment].

Some types of tooth root resorption respond favourably to endodontic treatment. Sometimes compromising factors demand particular treatment approaches and techniques. These will be described, in connection with their genesis.

Humans↗
PubMed2004

Root lengths in 47,XYY males' permanent teeth.

Studies on individuals with sex chromosome anomalies have demonstrated the promoting effect of the Y chromosome on tooth crown enamel and dentin growth. The present research investigated permanent tooth root lengths in 47,XYY males. The measurements were made from panoramic radiographs. The results indicate longer tooth roots in 47,XYY males compared with those in control males and females. The promoting effect of the Y chromosome on dental growth thus continues in the form of root dentin after the completion of crown growth. The results, together with those on tooth crown sizes in 47,XYY males, suggest that growth excesses are evident and final, beginning a few months after birth and continuing up to the age of 14 years, at least. The excess root dentin growth in 47,XYY males, as well as sexual dimorphism in the growth of crown and root dentin, might be caused by the same factor on the Y chromosome.

Adolescent↗
PubMed1994

[The direct transplantation of desmodont fibroblasts onto the necks of the teeth--a step in the expansion of the treatment potentials in orthodontics?].

The loss of periodontal support, especially of the periodontal ligament, presents the orthodontist with a constraining factor precisely in the treatment of patients who have reached adult and senior citizen age. Given this situation it was decided to take small biopsies of periodontal ligament cells, grow them, amplify them in vitro, and then with the help of different types of membranes, some of which consisted of resorbable materials, which served as cell carriers, transplant them onto tooth roots. The work reported here constitutes a starting point for research aimed at actively and directly re-populating tooth roots with periodontal ligament fibroblasts and thus, by improving the overall periodontal condition, widen the spectrum of treatment possibilities open to the orthodontist.

Adult↗
PubMed1975

Strontium content of deciduous teeth in northern and southern Finland.

A possible connection has been suggested between strontium and a low prevalence of dental caries. An investigation of this subject was initiated by measuring the strontium content of deciduous teeth by atomic absorption spectrophotometry in different regions in Finland. The material analysed consisted of a total of 2,482 tooth crowns and 392 tooth roots. The results showed that the Sr content of the tooth crowns in northern Finland was about two-fold that in the south, about 400 and 200 mug/gCa, respectively. The difference was apparently caused by corresponding differences in dietary strontium. The tooth roots contained much more Sr than the crowns, about 600 and 200 mug/gCa, respectively, in southern Finland, presumably owing to changes occurring in the dietary habits of the child during the development of the crowns and roots of the deciduous teeth.

Dental Caries↗
PubMed2000

A strain gauge and photoelastic analysis of in vivo strain and in vitro stress distribution in human dental supporting structures.

Strain gauge and photoelastic experiments have been workhorses of experimental stress analysis for over 50 years. In this study, both were used to analyse the nature of stress distribution from the tooth root surface to the supporting alveolar bone. Such studies help in understanding the behaviour of dental supporting structures under physiological function. In the strain gauge experiment, the mechanical strains were measured on the supporting bone surface and the root surface of the tooth under applied bite force. It was found that higher strains were distributed along the cervical region of the supporting bone and the root surface. The photoelastic study was also done to evaluate the stress distribution pattern from the root surface to the supporting bone under clinical conditions. The stress patterns were found to decrease from the cervical to the apical region of the root surface. These studies highlight the role of the periodontium in stress distribution and bone remodelling.

Alveolar Process↗
PubMed1996

Therapeutic delivery of calcitonin to inhibit external inflammatory root resorption. II. Influence of calcitonin binding to root mineral.

Experimentally-induced external inflammatory tooth-root resorption can be inhibited by therapeutic doses of calcitonin. Such doses can be delivered by an intrinsically slow diffusion pathway, from a reservoir in endodontically-debrided root canals, via the dentinal tubules. While the kinetics of this journey have been followed in an earlier report, the binding characteristics of calcitonin to the tooth mineral, which will be responsible, in part, for these kinetics, have not been reported before. The current study examines the binding potential of calcitonin to root mineral and addresses the potential role of non-specific binding proteins. A modified Scatchard plot indicated that a simple non-reactive type of ligand binding exists between calcitonin and root mineral, represented by a small number of identical binding sites. This interaction is both strong and reversible. Furthermore, it appears to be time-dependent with more time being required for the residual ligands to interact with the diminishing numbers of free calcitonin-binding sites. While preloaded [125I]-calcitonin could be incompletely (75-91%) displaced from dental-root material by non-radioactive calcitonin, its release was slow over 23 h. Calcitonin was four times as effective as bovine-serum albumin in competing for common "calcitonin binding sites" on macerated dental-root material. Thus, even in the presence of extraneous protein, calcitonin will bind tightly but reversibly to tooth-root material, making it a good candidate for therapeutically protracted delivery to external root surfaces from root canals.

Adolescent↗
PubMed1994

Bone sialoprotein is localized to the root surface during cementogenesis.

Bone sialoprotein (BSP), an RGD-containing protein with cell attachment properties, is believed to play a regulatory role in the biomineralization of various connective tissues. To determine its possible role in tooth root formation, murine dentoalveolar tissues at sequential phases of development were analyzed immunohistochemically for the presence of BSP. BSP was localized to alveolar bone and cementum at time points associated with initial mineralization of these tissues. In addition, northern blot analyses of dental follicle tissue at day 27 of tooth development indicated that BSP mRNA is expressed by dental follicle cells at a time point coincident with the initiation of cementogenesis on the peripheral tooth root surface. Collectively, these findings indicate that BSP may play an important role in the formation and mineralization of cementum.

Animals↗