Amelogenesis imperfecta. This is a radiographic view of amelogenesis imperfecta showing the altered thickness and shape of the enamel crown that is characteristic of this disease. In this patient the

condition was inherited as an autosomal dominant trait..

Hypodontia. This radiograph shows a retained deciduous, mandibular second molar. Note that the first premolar is in place, fully erupted, and apparently functional. There may be carious involvement of the distal aspect of the crown of the deciduous second molar.

This photograph presents a clinical view of a nine-year-old boy who has ectodermal dysplasia, a condition which affects all ectodermally-derived structures. It is inherited as both an X-linked and an autosomal recessive trait. Note that the hair is sparse and there is an absence of both the eyebrows and eyelashes. Fingernails and toenails are affected as well. What oral findings might you expect?

Hypodontia associated with ectodermal dysplasia. This photograph shows an intraoral view that is characteristic of patients with ectodermal dysplasia. In this case only the two maxillary canine teeth have developed. The secondary dentition was also affected in this patient, and there were no succedaneous replacements, even for these two primary teeth. Because of the absence of teeth, alveolar bone also fails to form. Patients with ectodermal dysplasia are best treated through provision of full upper and full lower dentures, which must be replaced at regular intervals as growth takes place.

• False anodontia. This frame shows an interesting clinical phenomenon. This nine-year-old girl presented clinically with an "absence of teeth". Radiographs, however, revealed the presence of teeth beneath the existing gingiva. This condition was caused by the overgrowth of gingiva as a result of a phenomenon called gingival hyperplasia (increased cellular proliferation). In this case, the condition was triggered by the gradual and continual eruption of the teeth. As the teeth emerge from the alveolar process, the gingiva overgrows and keeps pace with the rate of eruption. Patients with this condition are best treated by regular gingivoplasty and gingivectomy to allow normal function and aesthetics. Gingival overgrowth can also be initiated in patients taking Dilantin (antiseizure medication), Cylcosporine (immunosuppressive drug) or calcium channel blocker, particularly Nifedipine (treatment of angina and hypertension). Good oral hygiene has been shown to reduce the severity of drug-induced gingival hyperplasia.

• Supernumerary teeth. This clinical view shows a supernumerary tooth which has erupted in the mid-line between the left and right maxillary central incisors. The mesiodens, as it is called, is one of the more common forms of supernumerary teeth. In this case the supernumerary tooth was acceptable aesthetically, and therefore, no treatment was provided to the patient. Not all supernumerary teeth resemble a normal tooth in either size or shape. Such teeth are often called accessory teeth.

• Supernumerary teeth. This is an example of an impacted supernumerary tooth (found in the maxilla between the lateral incisor and canine) that was found during a routine radiographic examination. Multiple supernumerary teeth, many of them impacted, are characteristically found in cleidocranial dysostosis. Gardner's Syndrome is another condition characterized by the occurence of multiple, impacted supernumerary teeth. This disease is of interest to the dental profession, because the presence of the supernumerary teeth, and multiple osteomas in the mandible and maxilla, may lead to its diagnosis.

• Dens-in-dente (Dens invaginatus). This radiograph show an example of what happens when there is a distortion of the enamel organ. As a consequence, an aberrant crown forms in which there is commonly a communication between the surface of the crown and the pulp chamber. Carious involvement of this usually deep pit in the crown leads to bacterial invasion of the dental pulp. This radiograph demonstrates bony tissue breakdown as a consequence of a severe inflammatory response in the pulp of this tooth. There is a large radiolucency at the apex of this tooth. Also note that this tooth has a widened pulp canal inconsistent with the patient's age (compare this canal with that of the adjacent canine tooth). Secondary dentin formation that would have resulted in normal narrowing of this canal did not take place because of the death of the pulp.

• Dens-in-dente. This is another example of a "tooth within a tooth", but there is no evidence of a connection between the surface of the crown and the dental pulp.

•Gemination. This clinical view reveals the presence of a rather large lateral incisor. Count the teeth. How many incisors are there? This oversized tooth is a result of gemination or twinning of the enamel organ during development. This partial splitting results in a larger template for the crown, and the clinical crown becomes much larger than normal. Such large teeth, often with clefts in their surfaces, should be considered twinned teeth if the proper number of teeth are present

•Gemination. This is a radiograph of another patient showing that in a "twinned" tooth, the pulp chamber is often divided into two chambers within the single partially divided crown of the tooth. Notice that there is a single pulp canal.

• Fusion. In this case, how many teeth are present? This is a clinical example of fusion. Fusion occurs when neighboring toothbuds fuse, which as in gemination also results in a single larger-than-normal tooth. Counting the teeth in this mandibular arch should have revealed the absence of a right lateral incisor. The lateral incisor and the central incisor have fused to make a single "macrodont" tooth. Fused teeth commonly have a clinical crown that is fissured, as you see here. They also usually have two pulp chambers and two pulp canals, but these characteristics depend on the time at which fusion took place.

• Dilaceration. This photograph show examples of dilaceration, or curving of the roots. This results from a distortion of Hertwig's root sheath during development. Such teeth may present severe problems for either endodontic treatment or extraction. They are usually vital and functional. Surprisingly, eruption does not seem to be affected by the altered shape of the roots.

• Accessory roots. This is an example of accessory root formation that can occur as a result of an alteration in root sheath development.

• Rootless tooth. A 31-year-old male patient complained of a molar that was "loose". Radiographs revealed an absence of roots. Because of the high mobility of the tooth, it was extracted. For whatever reason, proliferation of Hertwig's root sheath abruptly ceased before much of the roots were formed. The cervical line of the tooth is clearly evident.

• Rootless teeth. This is another example of a patient who complained of "loose" teeth. Radiographs revealed only short stubby roots. The cervical line of the tooth is clearly evident, and the staining is due to tetracycline. For whatever reason, proliferation of Hertwig's root sheath abruptly ceased, but is not known whether tetracycline was a factor

• Enamel pearl. An enamel "pearl" is demonstrated in this photograph of an extracted tooth. The "pearl" lies in the furca (groove) between the mesial and distal roots of this maxillary molar. The differentiation of ameloblasts, and the formation of small amounts of enamel below the level of the cervical occurs with some regularity. The production of an actual "enamel pearl" is not as commonly seen. Radiographically, this would have been recognized as a very bright radiopacity overlying the furcal area of this tooth. The presence of these ectopic enamel deposits can have significant consequences for the periodontal health of these teeth. Notice that the palatal root of this tooth is affected by dilaceration.

• Hutchinson's or "Screwdriver-shaped" incisors. This clinical photograph presents an example of peg-shaped and misshapen incisors in both the maxilla and the mandible that occur in patients with congenital syphilis. Another anomaly, "mulberry molars.” There is narrowing of the incisal third of the maxillary and mandibular incisors, a form which has been described as screwdriver-shaped. The Treponemes (T. pallidum) that cause syphilis cross the placenta, and the fate of the infected fetus depends on the duration and the stage of the mother's disease.

• Mulberry molars. This clinical photograph presents a second example of the effects of congenital syphilis on the developing dentition. The first anomaly, "screw-driver shaped" incisors is shown in the previous frame. The blebbed surface of the mulberry molar wears away rather quickly, and carious involvement of the multiple pits is not an uncommon feature of these teeth.

• Enamel Hypoplasia. Hypoplasia commonly leads to an altered tooth form as a result of a reduction in the quantity of the organic matrix produced. Not uncommonly there is also a defect in the mineralization process. Hypoplastic and hypomineralization defects usually occur as a consequence of disease states. Because of the pitting, and other structural defects, hypoplastic enamel is often more susceptible to dental caries. This clinical photograph shows severe hypoplasia in the incisal third of the crowns with loss of some of the enamel.

• Enamel Hypoplasia. In this patient, hypoplasia resulted in enamel pitting that predisposed these teeth to carious attack.

• Enamel Hypomineralization. This clinical view presents an example of "snow-capped" teeth. This phenomenon is a form of hypomineralization. Notice that all four incisor teeth are affected with the central incisors showing the greatest defect. Only the maxillary teeth were involved in this patient. This condition may be due to a dietary deficiency, a systemic disease, or to an inherited defect in mineralization.

• Enamel hypoplasia associated with rickets. This is a case of avitaminosis D that results in the clinical condition of Vitamin D-dependent rickets. Severe hypoplastic defects are present in all eight maxillary and mandibular permanent incisors. This gives some idea of the time in which the nutritional deficiency took place. In some cases, vitamin C and vitamin A deficiencies can lead to similar hypoplastic defects in enamel.

• Enamel fluorosis (mottled enamel). Low-grade pitting, followed by pigmentation of the pitted areas can be seen in teeth when exposure levels of fluoride exceed 1-2 parts per million in the drinking water, or if inappropriate fluoride supplementation is carried out during early infancy and childhood. The degree of fluorosis seen in this patient suggests that fluoride levels in the drinking water exceeded 5 parts per million. The high levels of fluoride incorporated into the hydroxyapatite crystals of the enamel renders these teeth extremely resistant to carious attack. In fact, the beneficial effects of fluoride were recognized after epidemiological studies of communities in which fluorosis was endemic revealed a significant reduction in the prevalence of dental caries.

• Amelogenesis imperfecta. This patient demonstrates an inherited form of enamel hypomineralization in which tooth form is reasonably good. Any genetically inherited form of hypomineralization or hypoplasia is called amelogenesis imperfecta, and there are at least 13 distinct inheritance patterns that have been characterized, including both autosomal and sex-linked recessive and dominant forms.. The thinness of the enamel and its poor attachment to the underlying dentin lead to the rapid loss of the enamel from the surface of the crown. The brown areas seen in this photograph represent discolored areas of exposed dentin.

• Amelogenesis imperfecta. This is different patient presenting a more severe type of amelogenesis imperfecta. In this case there is both a hypoplasia and a hypomineralization of the enamel.

• Amelogenesis imperfecta. This is a radiographic view of amelogenesis imperfecta showing the altered thickness and shape of the enamel crown that is characteristic of this disease. In this patient the condition was inherited as an autosomal dominant trait..

• Dentinogenesis imperfecta. Dentinogenesis imperfecta is often associated with a systemic condition known as osteogenesis imperfecta in which bone is affected, as well as teeth. In the latter condition, a peculiar blue coloration of the sclera of the eye may sometimes be seen. Dentinogenesis imperfecta is characterized by the presence of a pearl-gray coloration of the teeth and an early loss of the enamel, particularly from incisal and occlusal surfaces. The loss of the enamel is the result of an abnormal dentinoenamel junction. In addition, the dentin is excessively "soft" due to the high amount of interglobular dentin, which is hypomineralized, and thus support for the enamel is poor. The peculiar coloration of the tooth is a result of the obliteration the pulp chamber, which normally gives a pinkish coloration to the dentin.

• Dentinogenesis imperfecta. Dentinogenesis imperfecta is characterized by the presence of a pearl-gray coloration of the teeth and an early loss of the enamel, particularly from incisal and occlusal surfaces. The loss of the enamel is the result of an abnormal dentinoenamel junction. In addition, the dentin is excessively "soft" due to the high amount of interglobular dentin, which is hypomineralized, and thus support for the enamel is poor. The premature loss of enamel exposes the dentin to occlusal forces that can lead to severe attrition. As in this patient, full crown coverage is often used to preserve occlusal height.

• Dentinogenesis imperfecta. This is a radiograph of the previous patient showing several distinctive features of dentinogenesis imperfecta. The teeth have a "lollipop" look, i.e. a bulbous crown that appears to be attached to a narrow root. There is a marked reduction in the size of the pulp chambers and pulp canals, with an absence of the canals in at least one of these teeth. It is not uncommon for these teeth to be painful, but the cause of the pain is not fully understood. In contrast, it is uncommon for patients who have amelogenesis imperfecta to experience pain, even in teeth that have been denuded of their enamel.

• Dentinal dysplasia. This is a rare phenomenon in which there is abnormal dentin development and aberrant root formation. The dentin is poorly formed with large amounts of interglobular dentin present, and pulp chambers and pulp canals are virtually nonexistent. These teeth quickly become mobile, and are commonly extracted because they cannot withstand the forces of occlusion.

• Hypercementosis. This radiograph reveals an excessive radiopacity surrounding the root. However, careful inspection will reveal the presence of a radiolucency (the periodontal ligament space) and a radiodense line (the lamina dura).

• Concrescence. This frames shows the clinical features of the condition known as concrescence wherein hypercementosis has resulted in the union of two or more teeth. The cause of this condition is not understood, but it presents significant problems for extraction of these teeth. Normal function, however, seems to be unaffected.