Developmental variations of tooth morphology and periodontal disease.

Some developmental variations of tooth morphology may influence the potential for periodontal disease by allowing accumulation of bacterial plaque and calcified deposits. Mechanical plaque control becomes difficult even for the conscientious patient. Periodontal disease may be hastened in these cases. The therapist must be aware of these variations and their significance in the etiology of isolated periodontal lesions. Recognition of these anomalies and early diagnosis may improve the prognosis of the involved tooth.     

Developmental biology and genetics of dental malformations

The synthesis of tooth development biology with human studies focusing on inherited conditions that specifically interfere with tooth development is improving our understanding of normal and pathological tooth formation. The type of inherited dental malformations observed in a given kindred relate to when, during odontogenesis, the defective gene is critically expressed. Information about the protein encoded by the defective gene and the resulting dental phenotype helps us understand the major processes underway at different stages during tooth development. Genes affecting early tooth development (PAX9, MSX1, and AXIN2) are associated with familial tooth agenesis or oligodontia. Genes expressed by odontoblasts (COL1A1, COL1A2, and DSPP), and ameloblasts (AMELX, ENAM, MMP20, and KLK4) during the crown formation stage, are associated with dentinogenesis imperfecta, dentin dysplasia, and amelogenesis imperfecta. Late genes expressed during root formation (ALPL and DLX3) are associated with cementum agenesis (hypophosphatasia) and taurodontism. Understanding the relationships between normal tooth development and the dental pathologies associated with inherited diseases improves our ability to diagnose and treat patients suffering the manifestations of inherited dental disorders.     

Fundamental principles of the biology of tooth movement

The classic studies of the biology of tooth movement were observations of tissue responses as seen in clinical measurements and corroboration by histologic evidence. These useful studies show the result of a series of biological cell occurrences that turn biomechanical signals into chemical and electrical messages to which cells respond. When working in concert over time, teeth move, roots resorb, or occasionally ankylose. An understanding of how these complex events occur will lead to the clinician's ability to move teeth more efficiently or gain better retention through the modification of various host responses. This article discusses some of the biologic aspects of biomechanics that may lead to the application of molecular and cell biology currently so important in medical science, to the field of orthodontics. The next major change in the way that orthodontics will be practiced in the future is in the clinician's ability to change the host to respond to (1) the mechanical forces applied to teeth and their affect on the supporting bone or (2) the propensity for teeth in their new position to relapse. The means of doing so is through expanding the understanding of the basic biology of tooth movement. This knowledge base is at 2 distinct but related levels, the tissue biology and the cell biology of what science calls mechanical perturbation events.     

Aspiration of a bridge and a tooth.

This is a rare and unusual case in its presentation, the patient having aspirated a three unit bridge into the right bronchus and a central incisor being found in the stomach following maxillo-facial trauma. This paper also emphasizes the necessity of careful intra-oral examination before proceeding to any therapeutic manoeuvres.     

Restoration of a vertical tooth fracture and a badly mutilated tooth using canal projection.

Management of vertically fractured tooth or a perforation frequently poses problem during endodontic management. Such teeth often need a pre-endodontic restoration prior to initiation of root canal therapy to aid in the placement of rubber dam clamp. This paper describes a simple method of placement of a pre-endodontic restoration using the canal projection technique using hollow metallic needles as sleeves.     

Developmental arrest of tooth bud after correction of mandibular fracture

Abstract A case of multiple fractures of the mandible following a car accident in a five-year-old patient is reported. The fracture line passed distal to the first molar tooth bud. The fracture was treated by wire osteosynthesis and skeletal fixation. During the ensuing 18 months, a gradual arrest of the development of the first molar tooth bud was radiologically observed. The eruption process had not been disturbed, and the tooth erupted at the age of 61/2 years. Since the distal root had completely failed to develop and the mesial roots showed a diminished size, the tooth was extracted. Histopathological examination revealed disturbed dentin apposition, there was almost complete obliteration of the pulp chamber by globular dentin, and evidence of root resorption.     

Dilaceration of a primary tooth.

A case is presented in which a non-vital maxillary primary incisor failed to resorb, its root apex appeared in the labial sulcus and further investigation showed it to be dilacerated.     

Cell biology in orthodontic tooth movement： The known and the unknown

This review is aimed at providing, at the cellular level, a concise and complete overview ot the important knowledge on the mechanism of orthodontic tooth movement to orthodontists and postgraduates who are involved or interested in basic research. The construction of this article was oriented to the following key questions: Where an osteoclast starts to its first resorption site? When the cascade of a resorption cycle starts? What are the factors involved in bone remodeling and how they orchestrate? What happens before and after the formation of a resorption pit? Major findings in these aspects were summarized and discussed. In addition, related biological phenomenon such as orthodontically induced root resorption was intensively reviewed. By means of an updated and systematic review, the author intended to introduce more biological evidence to orthodontic intervention and to encourage evidence-based treatment in daily orthodontic practice.     

Restoration of a fractured anterior tooth.

A fragment of tooth missing for three years was found in the patients' lower lip. The fragment was surgically removed and cleaned. It was restored to its original position on the maxillary left incisor with an acid etch resin technique. After three months, the restoration was satisfactory.     

From a hippopotamus tooth to a porcelain tooth

The history of dentistry is written as if thousands of years of obscurity were followed by a couple of hundred years of enlightenment. The turning point was the work of the Father of Modern Dentistry Pierre Fauchard (1678-1761). But historically speaking this notion of progress has theoretical and practical disadvantages. In this article a practical example is given, that of porcelain. The production developed completely in the times of obscurity and only a simple pharmacist just saw the possibilities of the result in dentistry.