Reparative dentine formation and pulp morphology

Bone-like material growth in a replanted immature central incisor following avulsion

BACKGROUND

Avulsion is one of the most complicated types of trauma to the teeth. After replantation of an avulsed immature tooth, numerous pulpo-dentinal responses may occur.

CASE REPORT

This study reports a case of a seven-and-a-half-year-old boy in whom an immature maxillary permanent central incisor was replanted following avulsion due to a fall from a tree, and a bone-like growth was observed in the pulp chamber 6 months after the trauma, with a thin radiolucent line on the inner surface of the dentinal walls. The bone-like structure eventually filled the pulp chamber of the tooth.

FOLLOW-UP

The tooth was followed up 4 years after the replantation with no evidence of pathology.

CONCLUSION

This case demonstrates an immature avulsed tooth which did not present positive vital signs, but still maintains the potential of survival, and endodontic intervention may not be required. Instead, follow-up visits are recommended as long as there are no pathologic signs, especially in teeth with questionable prognosis.

Dentin phosphophoryn promotes cellular migration of human dental pulp cells

Dentin phosphophoryn (DPP) is a dentin sialophosphoprotein gene product that has an RGD motif and repeat sequences of aspartic acid and phosphoserine. To date, the function of DPP in the early stage of reparative dentin formation still remains unclear. The objective of this study was to evaluate the effects of DPP on pulp cell migration and proliferation. DPP promoted cell migration in a concentration-dependent manner, thus increasing it by about 3-fold at 1000 ng/mL compared with the control, but it had no effect on cell proliferation. Dephosphorylated DPP also promoted cell migration, similarly to DPP. However, cell migration was significantly suppressed by the addition of alphavbeta3 integrin antibody to the medium. Furthermore, porcine DPP-derived RGD peptide, but not its mutant RAD peptide, significantly promoted cell migration. These results indicated that the RGD motif of DPP plays an important role in the migration of human dental pulp cells.

Bioengineered teeth from tooth bud cells

Advances in tissue engineering and materials science have led to significant progress in hard and soft tissue repair and regeneration. Studies demonstrate the successful application of tissue engineering for bioengineering dental tissues. The ability to apply tissue engineering to repair or regenerate dental tissues and even whole teeth is becoming a reality. Current efforts focus on directing the formation of bioengineered dental tissues and whole teeth of predetermined size and shape. Advances in dental progenitor cell characterizations, combined with improved methods of fabricating biodegradable scaffold materials, bring closer the goal of making tooth tissue engineering a clinically relevant practice.

Autotransplantation of teeth: requirements for predictable success

The aim of this article is to summarize the biologic principles required for successful autotransplantation of teeth. Indications, armamentarium, technique and prognosis will be discussed.

Apexification of an infected untreated immature tooth

A case of a traumatized permanent young tooth in which apexification occurred without the benefit of endodontic treatment is reported. It illustrates how a immature incisor that underwent pulp necrosis and periapical inflammation could progress to complete apical formation.

Analysis of low affinity nerve growth factor receptor during pulpal healing and regeneration of myelinated and unmyelinated axons in replanted teeth

Nerve regeneration was examined in rat molars that were briefly extracted and then replanted in the socket for 1-90 days. Immunocytochemistry was used to evaluate neural and nonneural immunoreactivity (IR) for low affinity nerve growth factor receptor (p75-NGFR) and for laminin and calcitonin gene-related peptide (CGRP). Three different types of pulpal response to replantation were found. Type I: Some replanted teeth had mild injury and still contained coronal odontoblasts and associated fibroblasts that retained p75-NGFR-IR; they continued regular dentin formation and had excellent reinnervation. Type II: Teeth with intermediate injury lost most or all of the coronal pulp tissue, but they regenerated odontoblast-like cells that formed irregular dentin, they had numerous dispersed p75-NGFR-IR fibroblasts in crown pulp during early regeneration, and they had excellent reinnervation. Type III: Severely injured teeth lost their original pulp; they filled with dense connective tissue and bone and had poor reinnervation. After Type I or II injury the Schwann cells around degenerating myelinated and unmyelinated axons had increased expression of p75-NGFR by 1-3 days. By 7-10 days those Schwann cells had formed hollow tubes (bands of Bungner) along the degenerating axon tracks. They maintained their increased p75-NGFR-IR during and after regeneration of unmyelinated axons, whereas Schwann cells involved in remyelination lost p75-NGFR-IR at that stage. The number of CGRP-IR axons in the regenerating pulp increased from 7 to 90 days. Laminin-IR increased in all replanted teeth at 3-10 days and only returned to normal patterns in teeth with Type I or Type II response at 20-90 days. The special p75-NGFR-IR of pulpal fibroblasts of adult rat molars did not usually persist in regenerated, reinnervated pulp. The extensive depletion of fibroblast p75-NGFR-IR and the continuing enhanced p75-NGFR-IR in unmyelinated nerve fibers at 90 days show that altered growth factor conditions characterize regenerated pulp of replanted teeth.

Secondary dentin in replanted teeth--a histometric study

To quantify the secondary dentin formation in replanted teeth, 16 human premolars with a postoperative observation period of 6, 12 and 24 weeks were studied histometrically. In spite of marked intra- and interindividual variations, a regression analysis revealed a significant correlation (r = 0.70) between observation time and the quantity of secondary dentin in the coronal pulp registered by histometry. A comparison with a previous semiquantitative interpretation of the same material showed that the histometric method was more accurate.

Dentin and osteodentin matrix formation in apicoectomized replanted incisors in cats

The reestablishment and rate of osteodentin and dentin matrix formation in 27 apicoectomized replanted and 20 control incisors in cats were studied after Procion H8-BS vital staining. In control teeth the pattern of matrix formation differed in the various pulpal zones, with a higher rate of matrix formed toward apical areas, most dominantly in maxillary incisors. Osteodentin formation could be traced after a lag period of more than 10 days after replantation. Thirty and 60 days postoperatively osteodentin matrix was found in the total pulpal length in 83% and 73% of the teeth, respectively. A common finding was a tubular osteodentin matrix in the pulpal apical third in the replanted teeth. Tubular osteodentin matrix was, however, present most incisally in some teeth 60 days postoperatively. Internal resorption corresponding to outer cervical lesions dominated the pulpal reactions in the maxillary replanted teeth after 60 days. It is concluded that under the present experimental conditions the pulp tissue possesses a high healing potential and that the osteodentin formation reflects the pulpal healing pattern after replantation traumas. The results also indicate that successful pulpal healing depends on unexposed dentinal tubules.

A histological investigations of isografts of immature mouse molars to an intrabony and extrabony site

Partially-developed teeth with remnants of their periodontal ligaments isografted to the tibial shaft medulla and renal subcapsular site were capable of progressive regeneration characterized by renewed tubular dentine formation. Bone formation occurred in relation to grafts at the renal site as well as the tibial shaft; evidence of periodontal fibre reorganization was observed in grafts at both sites. Despite post-transplantation dentine and cementum formation, continued development of roots of normal morphology did not occur, perhaps due to disappearance of epithelial root sheath.

The effect of wear on the cheek teeth and associated dental tissues of the lizard Uromastix aegyptius (Agamidae)

Serial coronal sections of the teeth and their surrounding tissues in the agamid lizard, Uromastix aegyptius, were examined with the light microscope in order to determine how these structures change as the teeth wear. Because new teeth are added only at the posterior end of the tooth row and older teeth are not replaced, the series of sections included the youngest as well as the oldest teeth. Two types of changes occur as the teeth become older: bone under the teeth changes from cancellous to compact, and the pulp chamber of the tooth is obliterated. Although the labial surface of the dentary lacks a periosteal covering and some of the bone lacks any covering at all, it remains functional throughout the life of the animal.

A classification of dysplastic forms of dentin

Considerable effort has been made in the past to describe the morphologic changes in dentin which characterize various developmental disturbances of teeth. However, there appears to be no previous attempt to describe the spectrum of changes which may be exhibited by abnormal dentin. This paper presents a classification of dysplastic forms of dentin with definitions and illustrations of each abnormality. The classification was derived from reviewing the literature and from a study of 82 odontomas, examples of specific developmental disorders of dentin, regional odontodysplasia, and systemic conditions affecting dentin.