Fourth Molar Research Articles

INTERESTING CASE: Kissing molars

The fourth molar is the second most common supernumerary tooth after the mesiodens, which usually presents as a solitary impacted tooth in the maxilla.

Atrição dental em Didelphis albiventris e D. marsupialis (Marsupialia, Didelphimorphia, Didelphidae) do Sul do Brasil

Pesquisou-se o nível de desgaste dental (atrição e/ou abrasão) em 168 espécimes de Didelphis albiventris e D. marsupialis (gambás) do sul do Brasil. O desgaste foi muito importante, com elevada freqüência de dentina terciária e de exposição da câmara coronária e/ou do canal radicular, devido à associação de fraturas e desgaste, pois as fraturas predispõem ao desgaste e este favorece as fraturas. O grau de desgaste aumentou com a idade dos animais. A ordem crescente na freqüência de dentina terciária nos dentes caudais aos caninos foi: primeiro, segundo e terceiro molares, terceiro e segundo pré-molar, e quarto molar. Diferentemente de outros onívoros, em Didelphis o desgaste dentário parece mais relacionado às fraturas devidas aos alimentos (seguida de atrição/abrasão) do que ao contato entre os dentes. Ao contrário da literatura, os molares tribosfênicos não parecem "ideais" para tal dieta onívora, o que é evidenciado pela elevada freqüência de desgaste, fraturas e exposição da câmara coronária ou do canal radicular.

Supernumerary Fourth and Fifth Molars: A Report of Two Cases

Panoramic radiographs of two female patients ages 22 and 21 revealed the presence of two impacted bilateral upper fourth molars and unilateral (right) upper fourth and fifth molars. All of the teeth were distomolars. The supernumerary teeth had normal tooth morphology with regard to their crowns and roots but were slightly smaller than the existing third molars. Their crowns were either two or three tuberculated and they all had single roots.

Endodontic therapy in a fused mandibular molar

This case report describes the endodontic management of fusion involving a mandibular third molar and a fourth molar (distomolar).

Mandibular Molar Teeth and the Development of Mastication in the Miniature Pig (<i>Sus scrofa</i>)

The only components of the orofacial complex that are fully developed as soon as they establish function are the occlusal surfaces of teeth. It is usually assumed that the occlusal surface of the molar teeth influences the orientation of the power stroke in spite of the fact that the data supporting this claim are lacking. The purpose of this longitudinal study was therefore to determine whether or not this hypothetical form-function relationship existed during development and whether or not it was related to growth. Serial dorsoventral and lateral radiography, and dorsoventral cineradiography were performed during natural feeding of 5 Hanford miniature pigs (Sus scrofa) of both genders between their 8th and 18th weeks. Sequences of power strokes were analyzed frame by frame and compared between sessions, and related to the position of the fourth primary mandibular molar (dm4). The changes in direction of the power stroke and in position of the dm4 relative to the midline were subsequently related to growth. The results of this study indicate that changes in orientation of the power stroke, though significant only on the balancing side, occur independently of the repositioning working and balancing side mandibular molars, as well as of skeletal growth. The null hypothesis that the mandibular primary molars influence the transverse orientation of the power stroke during growth is therefore refuted.

The fourth molar in a mandible found in a Jomon skeleton in Japan

AbstractA fourth molar in a mandible occurs very rarely, even in clinical surveys involving a large number of modern people. Having encountered a case with the fourth mandibular molar in a prehistoric skull in Japan, we would like to report on the macroscopic morphology of the case using X‐rays, and to discuss the case with reference to literature concerning supernumerary teeth in the molar region.

Fusion of third and fourth mandibular molars?

Fusion of third and fourth mandibular molars?

Hypodontia and hyperdontia of permanent teeth in Hong Kong schoolchildren

This study was performed to determine the prevalence of hypodontia and hyperdontia of permanent teeth amongst Southern Chinese children in Hong Kong. The sample consisted of 1093 12-yr-old children on whom a panoramic radiograph was taken. The prevalence of congenitally missing teeth (third molars excluded) was 6.1% in boys, 7.7% in girls, and 6.9% for both sexes combined. On the average, each child was missing 1.5 teeth. The most commonly absent tooth was the mandibular incisor, affecting 58.7% of the children with hypodontia. Thirty children (2.7%) had supernumerary teeth, with a male:female ratio of 6.5:1; in four cases the tooth had erupted. Three children had fourth molars and one case of a supplemental premolar was recorded (all unerupted). Four cases of a maxillary supernumerary tooth and hypodontia in the mandible were seen.

A case of the fusion of the third and fourth molars in the mandible

A case of the fusion of the third and fourth molars in the mandible

The incidence of unerupted permanent teeth and related clinical cases

The impacted or mal-erupted tooth and its associated pathosis provide great diagnostic challenges to the dentist. The frequency of occurrence of impaction was found to be over 10,000 in 5,000 Army recruits. The type and position of impaction are summarized in tables. The incidence of impactions was higher than previously reported and may reflect some sampling bias. The incidence of impacted second and fourth molars is higher than expected. Impactions or mal-eruptions were seen to involve every permanent tooth except the mandibular incisors and first molars. Impactions can occur because of malpositioning of the tooth bud or obstruction in the path of eruption. However, the exact mechanism is still unknown. Six unusual cases of impacted permanent teeth are described to illustrate the importance of panoramic radiographs in the discovery of some anomalously located impactions.

Enamel and dentine ultrastructure in the early Jurassic therian Kuehneotherium

Three fragmentary molars of Kuehneotherium from Wales were progressively abraded by grinding and studied by scanning electron microscopy. A fourth molar was reduced to small blocks, thin sections of which were examined by transmission electron microscopy. Enamel showed a ‘preprismatic’ pattern, consisting of columns of crystals disposed as pinnae but not separated by an interprismatic substance. No enamel tubules were observed. Incremental lines were present. Inner dentine was permeated by numerous tubules not surrounded by peritubular dentine but a peripheral dentine layer adjacent to the enamel-dentine junction was atubular. Calcified deposits were occasionally observed in the lumen of dentine tubules, some of which were interpreted here as dentinal sclerosis consecutive to masticatory wear.

Third and fourth molar fusion

Third and fourth molar fusion

Maxillary fourth and fifth molars: an unusual radiological finding

Maxillary fourth and fifth molars: an unusual radiological finding

Completely fused third and fourth molars

Completely fused third and fourth molars

Impacted second, third, fourth, and fifth molars

Impacted second, third, fourth, and fifth molars

Fourth Molar in Mandible

Supernumerary teeth develop rarely in the mandibular molar region compared to the maxillary molar region and are apt to be impacted. Therefore the role of roentgenographic examination is important. Having encountered 4 cases with such teeth in the mandible (the socalled fourth molars) we would like to report on the outline of these cases, their x-ray findings and discuss the Japanese literature dealing with supernumerary teeth in the maxillary and mandibular molar region.

Four impacted fourth molars

Four impacted fourth molars

A Supernumerary Tooth in the Lower Molar Region: A Case Report

AbstractSupernumerary teeth in the upper third molar region are relatively common but cases in the lower jaw are rare. In his survey of supernumerary teeth Stafne (1932) saw 131 upper but only 10 lower fourth molars. The following is a report of a single supernumerary tooth in the lower third molar region.

A fourth pair of mandibular molars in a white-tailed deer.

A fourth pair of mandibular molars in a white-tailed deer(Odocoileus virginianus) was located posterior to the third pair. There was a distinct gap between the third and fourth molars on both left and right sides.

Presence of fourth molars in a group of dental students.

Presence of fourth molars in a group of dental students.