Early postnatal development of the mandibular permanent first molar in infants with isolated cleft palate.

BACKGROUND: Based on measurements on dental casts, smaller permanent teeth in children with cleft palate have previously been reported in the literature; however, the early maturation of teeth and the size of the follicles and crowns have not been investigated. HYPOTHESIS: The maturation of the mandibular permanent first molar (M1(inf)) is delayed, and the mesiodistal diameters of the follicle and crown of M1(inf), respectively, are reduced in children with isolated cleft palate (ICP). DESIGN: Retrospective, longitudinal. Cephalometric X-rays were available for 2 and 22 months old children with clefts (64 children with ICP, and a control group of 38 children with unilateral incomplete cleft lip). The width of the follicle and the crown of M1(inf), and the maturation of M1(inf) were assessed. Intra-observer error was acceptable. RESULTS: M1(inf) maturation was delayed in children with ICP at both 2 and 22 months of age. The mesiodistal diameter of the crown of M1(inf) in the ICP group was reduced. Thus, the two hypotheses could not be refuted. CONCLUSIONS: Children with ICP showed smaller dimensions of the M1(inf) , and in addition, the maturation of M1(inf) was delayed.

Requirement of alveolar bone formation for eruption of rat molars.

Tooth eruption is a localized event that requires a dental follicle (DF) to regulate the resorption of alveolar bone to form an eruption pathway. During the intra-osseous phase of eruption, the tooth moves through this pathway. The mechanism or motive force that propels the tooth through this pathway is controversial but many studies have shown that alveolar bone growth at the base of the crypt occurs during eruption. To determine if this bone growth (osteogenesis) was causal, experiments were designed in which the expression of an osteogenic gene in the DF, bone morphogenetic protein-6 (Bmp6), was inhibited by injection of the first mandibular molar of the rat with a small interfering RNA (siRNA) targeted against Bmp6. The injection was followed by electroporation to promote uptake of the siRNA. In 45 first molars injected, eruption was either delayed or completely inhibited (seven molars). In the impacted molars, an eruption pathway formed but bone growth at the base of the crypt was greatly reduced compared with the erupted first-molar controls. These studies show that alveolar bone growth at the base of the crypt is required for tooth eruption and that Bmp6 may be essential for promoting this growth.

Mandibular third molar space in different antero-posterior skeletal patterns.

Retromolar space has long been identified as a major factor in the aetiology of mandibular third molar impaction. The aims of this study were to compare mandibular third molar space between the different antero-posterior (A-P) skeletal patterns, between erupted and impacted third molars in the different A-P skeletal patterns, and to report on the status of third molar eruption/impaction among the studied subjects. A total of 432 mandibular third molars in 270 subjects (132 females and 138 males) were investigated from dental pantomograms (DPTs) and lateral cephalograms (LC). The average age for the total sample was 20.80 ± 2.03 years. The subjects were divided into three groups according to their ANB angle as follows: skeletal Class I (144 third molars in 90 subjects), skeletal Class II (145 third molars in 95 subjects), and skeletal Class III (143 third molars in 85 subjects). Each group was subdivided into impacted and erupted subgroups. DPT and LC were traced and the following variables were measured: retromolar space width, third molar width and angulation, ß angle, second molar angulation, mandibular length, and gonial angle. Independent t-test, analysis of variance, and chi-square test were used for statistical analysis. Retromolar space width in the Class III subjects was smaller than in the Class I subjects (P < 0.05). Mandibular third molars were recorded as impacted in 26, 32, and 42 per cent of the Class I, II, and III subjects, respectively (P < 0.001). The impacted groups had a reduced retromolar space width, increased ß angle, and reduced third molar angulation in all A-P skeletal patterns. Class III subjects showed increased mandibular third molar impaction with reduced retromolar space width.

Presencia de lesiones quísticas en sacos pericoronarios de terceros molares mandibulares / Presence of cystic lesions in pericoronary sacs of mandibular third molars

Introducción: a pesar de que un tercer molar no erupcionado repre- senta un riesgo de formación quística, la práctica clínica desestima el análisis histopatológico de los folículos de dichos molares. Objetivo: identificar la frecuencia de lesiones quísticas en los sacos pericoronarios de terceros molares mandibulares. Material y métodos: estudio des- criptivo, transversal, analítico y observacional, en donde se incluyeron sacos pericoronarios de terceros molares mandibulares para su análisis histopatológico, descripción de características clínico-radiográficas y su asociación con la presencia de cambios histológicos o lesiones quís- ticas. Resultados: se incluyeron 48 muestras de sacos pericoronarios, la histopatología de los sacos pericoronarios mostró que 83.3% tenían algún tipo de alteración: 13 quistes paradentales (27.1%), cuatro quistes dentígeros (8.3%), 12 folículos hiperplásicos (25.0%) y 11 folículos inflamados (22.9%). La presencia de lesiones quísticas en la población fue de 35.4%. Se detectó asociación estadísticamente significativa entre el sexo y la presencia de lesiones quísticas (p = 0.039) y entre el nivel de erupción y la presencia de cambios histológicos (p = 0.046). Con- clusiones: la frecuencia de lesiones quísticas o cambios histológicos en folículos de terceros molares mandibulares es alta, principalmente en molares parcialmente erupcionados o submucosos y sin importar la ausencia de sintomatología o alteraciones radiográficas (AU))

Introduction: although a non-erupted third molar represents a risk of cystic formation; clinical practice rejects the histopathological analysis of the follicles of said molars. Objective: identify the frequency of the histopathological changes in pericoronary sacs of mandibular third molars. Material and methods: descriptive cross- sectional, observational and analytic study, where pericoronary sacs of mandibular third molars were included for histopathological analysis, description of clinical-radiographic characteristics and their association with the presence of histological changes or cystic lesions. Results: 48 samples of pericoronary sacs were included, the histopathology of the pericoronary sacs showed 83.3% had some type of alteration: 13 paradental cysts (27.1%), four dentigerous cysts (8.3%), 12 hyperplastic follicles (25.0%) and 11 inflamed follicles (22.9%). The presence of cystic lesions in the population was 35.4%. A statistically significant association was detected between sex and the presence of cystic lesions (p = 0.039); and between the level of eruption and the presence of histological changes (p = 0.046). Conclusions: the frequency of cystic lesions or histological changes in mandibular third molar follicles is high, mainly in partially erupted or submucosal molars and regardless of the absence of symptoms or radiographic alterations (AU)

Experimental study in the dog of the non-active role of the tooth in the eruptive process.

The role of the tooth in eruption was studied radiographically and histologically after experimental manipulations of the crowns of permanent mandibular premolars in dogs. Crowns were removed and dead crown shells or metal or silicone replicas were substituted into dental follicles just prior to scheduled eruption. These replacements erupted on schedule after formation of the usual eruption pathways and formation of trabecular bone from the base of the bony crypt. Removal of crowns, but without adding replacements, also exhibited these same hallmarks of eruption. We conclude that tooth eruption is a series of metabolic events in alveolar bone characterized by bone resorption and formation on opposite sides of the dental follicle and the tooth does not contribute to this process.

Radiographic and histological analysis of tooth eruption through calcium phosphate ceramics in the cat.

The effect of implanting calcium phosphate ceramics (CPC) into metabolically active sites within kitten mandibles during permanent premolar tooth eruption was examined. Forty kittens, 3-4 months of age were used: the deciduous second and third mandibular premolars were extracted and their sockets implanted with autologous blood clot, autogenous cancellous marrow, and the calcium phosphate ceramics, non-porous beta-tricalcium phosphate or porous hydroxylapatite. Animals were killed at 1, 2, 3, 4 and 5 months after implantation and undermineralized sagittal sections were evaluated by light microscopy. Eighty percent of hydroxylapatite implanted mandibles showed delay in tooth eruption concurrent with distortion in crown development, and a dense cellular fibro-proliferative response within the follicle of unerupted teeth. This response occurred in only one specimen with tricalcium phosphate, whereas normal eruptive patterns and crown development were routinely noted. Both the tricalcium phosphate and hydroxylapatite were integrated into the surrounding alveolar bone without evidence of an inflammatory response. Thus hydroxylapatite initiated a dense cellular fibrous network within the dental follicle preventing formation of an eruptive pathway, delaying tooth eruption and causing crown deformation. This was rarely seen with tricalcium phosphate, and may be due to the resorbability of tricalcium phosphate when compared to hydroxylapatite. Hydroxylapatite should therefore be used with caution for implanting into areas containing unerupted teeth with a metabolically active dental follicle.

Temporal and spatial patterns of transforming growth factor-beta 1 expression in developing rat molars.

Regulatory peptides of the TGF-beta family affect various aspects of embryonic development. Recent immunolocalization and in situ hybridization studies have demonstrated a specific time- and tissue-dependent expression of TGF-beta 1 in the developing mouse embryo. The purpose of this study was to evaluate the distribution of TGF-beta 1 within rat molars at different stages of development, using a well-characterized antibody, highly specific for TGF-beta 1, and immunohistochemical methods of detection. TGF-beta 1 was immunolocalized intensely within the ectodermally derived stellate reticulum and the mesenchyme of the dental papilla at the bell stage of development. Marked immunostaining was also evident in the papillary layer and the reduced dental organ subjacent to ameloblasts in the differentiation and secretory phases of amelogenesis. During the formation of coronal tissues and in the pre-eruptive phase, immunoreactive TGF-beta 1 was localized conspicuously within the dental follicle overlying the tooth germ. This temporospatial pattern of expression of TGF-beta 1 appears to correlate with specific events in morphogenesis, histogenesis and cytodifferentiation during tooth development.

The small dentigerous cyst. A diagnostic dilemma.

The dentigerous (follicular) cyst is recognized as one of the most common lesions of the jaws. Clinical, radiographic, histologic, and prognostic characteristics are well established for medium to large pericoronal cysts that are lined by nonkeratinized stratified squamous epithelium. However, it can be difficult, if not impossible, to distinguish between a small dentigerous cyst and a large dental follicle despite the availability of both radiographic and histologic information. Epidemiologic data derived from a comparative study of 1662 dentigerous cysts and 824 dental follicles showed considerable overlap in age distribution and site predilection and were therefore of minimal use in reaching a final diagnosis. At present, it appears that identifying a cystic cavity at the time of surgery may be the only reliable way to arrive at a definitive diagnosis when radiographic and histologic features are insufficient to distinguish between a small dentigerous cyst and a large dental follicle.

Does the canine dental follicle cause resorption of permanent incisor roots? A computed tomographic study of erupting maxillary canines.

We performed computed tomography (CT) on 107 children and adolescents aged 9-15 years with 176 unerupted maxillary canines (152 erupting ectopically and 24 erupting normally) to determine whether there is an association between widened dental follicles of the maxillary canines and resorption of the adjacent incisors during eruption. Contiguous axial (transverse) CT scans were obtained through the maxilla in the region of the canines. The width and shape of the dental follicles were recorded, as were any contacts between the follicles and the crowns of the maxillary canines and neighboring incisors. Fifty-eight lateral incisors (38%) and 14 central incisors (9%) had some type of root resorption. The position of the maxillary canine in relation to the root of the lateral incisor varied greatly, as did the width and shape of the canine dental follicle. Follicle width ranged from 0.5 mm to 7.0 mm. The mean +/- SD width of dental follicles was, on average, larger for the ectopically positioned canines (2.9 +/- 0.8 mm) than for the normally erupting canines (2.5 +/- 0.8 mm) (P < or = .01). We found that during eruption, the follicle of the erupting maxillary canine frequently resorbed the periodontal contours of adjacent permanent teeth but not the hard tissues of the roots. We concluded that the dental follicle did not cause root resorption of permanent teeth. Resorption of neighboring permanent teeth during maxillary canine eruption was most probably an effect of the physical contacts between the erupting canine and the adjacent tooth, active pressure during eruption, and cellular activities in the tissues at the contact points, all of which are part of the eruptive mechanism. The findings also confirm an association between root resorption of deciduous canines and the dental follicles of erupting permanent canines.

Immunohistochemical analysis of human homologue of drosophila patched (PTCH) in dental follicles of impacted third molars / Análisis imunohistoquímico del homólogo humano del gen parcheado de drosofila (PTCH) en folículos dentales de terceros molares retenidos

This study investigated the immunodetection of PTCH in epithelial components of dental follicles associated with impacted third molars without radiographic signs of pathosis. One hundred and five specimens of dental follicles associated with impacted third molars with incomplete rhizogenesis (between Nolla's stage 6 and 9) were surgically removed from 56 patients. Epithelial cell proliferation was determined by using immunohistochemical labeling. Statistical analysis was performed using Fisher exact test and a level of significance of 5 percent. Of the 105 dental follicles collected, 3 were PTCH-positive. The specimens with squamous metaplasia and epithelial hyperplasia had higher rates of positivity for PTCH, as well as those with active remnants of odontogenic epithelium. This study suggests that the odontogenic cells of the dental follicle might be proliferating during the rhizogenesis, while the squamous metaplasia and hyperplasia of the epithelial lining and proliferative odontogenic epithelial rests show the differentiation potential of dental follicles.

Se investigó la inmunodetección de PTCH en los componentes epiteliales de los folículos dentales asociados a terceros molares retenidos sin signos radiográficos y morfológicos de patología. Fueron quirúrgicamente extraídos de 56 pacientes 105 muestras de folículos dentales asociadas a terceros molares retenidos con rizogénesis incompleta (entre el estadio de Nolla 6 y 9). La proliferación de células epiteliales se deteminó mediante inmunohistoquímica. El análisis estadístico se realizó mediante la prueba exacta de Fisher. De los 105 folículos dentales recogidos, 3 fueron PTCH-positivos. Las muestras con metaplasia escamosa e hiperplasia epitelial tuvieron mayores tasas de positividad para PTCH, así como aquellos con los restos de proliferación del epitélio odontogénico. En conclusión, este estudio sugiere que las células odontogénicas del folículo dental podrían estar proliferando durante la rizogénesis, mientras que la metaplasia escamosa e hiperplasia del epitelio y de restos epiteliales odontogénicos en proliferación muestran el potencial de diferenciación de los folículos dentales.

Current concepts of the biology of tooth eruption.

Tooth eruption is defined as the movement of a tooth from its site of development within the jaws to its position of function within the oral cavity. We present a critical review of evidence for the mechanisms and regulation of the intraosseous and supraosseous phases of eruption, with an emphasis upon the canine premolar model studied by the authors. Analyses at different stages of premolar eruption indicate that selective fragmentation of dental follicle protein DF-95 correlates with the presence of elevated levels of follicular collagenase and stromelysin, and with the onset of premolar movement. A dramatic decrease in these metalloproteinases followed initiation of movement. A biochemical and cell biological model for regulation of tooth eruption is proposed based upon these new and existing data.

Relación entre las características de la celularidad epitelial y el espesor de la pared de los sacos foliculares de los dientes retenidos / Relationship between the features of epithelial cellularity and wall thickness of follicular sacs of impacted teeth

Esta investigación se realizó con el objetivo de describir las características de disposición de los restos epiteliales inmersos en los sacos pericoronarios (SP) de dientes retenidos y su relación con la edad, el sexo, la localización anatómica y el espesor de la pared. Se estudiaron 115 SP de dientes cuyas raíces habían completado 2/3 o más y sus coronas estaban totalmente inmersas en el tejido óseo circundante. Las muestras se fijaron en formol al 10 por ciento y se colorearon con hematoxilina y eosina. Para la evaluación de la población celular epitelial inmersa en los SP se establecieron convencionalmente los siguientes criterios: AUSENTES, ESCASAS Y ABUNDANTES. El espesor de los sacos fue determinado mediante un dispositivo ocular de micromediciones con escala graduada, desplazando la preparación histológica en la platina de tal forma que la escala ocular quedara perpendicular al eje mayor de corte. El procesamiento matemático de los datos fue realizado de acuerdo al estadígrafo Chi-cuadrado. Entre los resultados estadísticos resulta interesante que no hay razones estadísticas para rechazar la independencia entre las variables estudiadas

Calcificaciones en los folículos de dientes retenidos / Calcifications in the follicles of impacted teeth

Los sacos foliculares, representan una estructura de frecuente manejo quirúrgico por parte de los odontólogos. La relativa escasa información de los mismos, así como su reconocida relación con neoformaciones de diferentes complejidades biológicas, conforman el propósito general del presente trabajo. Con el objetivo de precisar la relación existente entre las calcificaciones observadas en los SF y diferentes variables tales como la edd, sexo, localización anatómica y la presencia de restos epiteliales, se estudiaron 75 especímenes de acuerdo a un conjunto de criterios de exclusión. Los mismos fueron procesados por la técnica de inclusión en parafina y coloreados con hematoxilina y eosina, PAS y von Kossa. Los datos obtenidos fueron volcados en gráficos confeccionados al efecto para su ulterior análisis matemático. Se plantea una discusión sobre la presencia de las calcificaciones en estas estructuras como resultado de un fenómeno distrófico o metaplásico. Del mismo modo, se presentan ilustraciones que describen las más frecuentes formas de presentación de estas calcificaciones inmersas en los SF. Es de destacar que el procedimiento estadístico evidenció dependencia entre la variable localización anatómica y las calcificaciones

Análise histológica de folículos pericoronários / Histologic analysis of pericoronary follicle

Avaliou-se a correlação histológica entre o epitélio odontogênico de folículos pericoronários de molares semi-inclusos de adultos jovens com história de sintomatologia e infiltrado inflamatório. Observou-se epitélio em 75,6% dos espécimes, 50,6% inativos e 48,4% hiperplásicos, bem como infiltrados inflamatórios (70,3%), a maioria crônico e intenso, exibindo associação (p<0,001) entre infiltrado inflamatório e os remanescentes epiteliais

Aspectos de biologia molecular envolvidos no processo de erupçäo dentária / Molecular biology aspects involved in the tooth eruption process

O presente trabalho de revisäo discorre sobre os eventos celulares e moleculares envolvidos no processo de erupçäo dentária. Descreve o folículo dentário como o tecido que desempenha o papel central no processo, estando envolvidas células mononucleares (monócitos) e osteoclastos. Apresenta as principais moléculas conhecidas como iniciadoras e reguladoras da erupçäo, que säo: IL-1, CSF-1, TGF-1, TGF-ß e EGF, as quais estäo presentes em células do retículo estrelado e/ou do folículo dentário