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At least 595 records · Page 33Linked to original sources
PubMed1999

Age-related morphometry of equine incisors.

In the present study the age-related morphological characteristics of 948 equine incisors were investigated. After extraction, total incisival length and root length were measured at the vestibular side of the teeth. Equine incisors reach their maximal length 2-3 years after eruption. Notwithstanding severe occlusal wear, this maximal length is maintained during most of the horses' life due to prolonged root formation. Root formation, at the rate of 2.5 mm per year, starts at the age of 5-6 years and continues until the age of 17. As the root of the incisor develops, its apical foramen narrows and changes position. In young horses the apical foramen is situated at the apex of the tooth, whereas in older individuals it is located at the mesial, distal, or lingual side of the tooth at a distance of 5-15 mm from the dental apex. In horses aged over 20 years apical foramina are still present. Radiographic imaging is a good method with which to obtain reliable information concerning the total incisival length and the size and position of the apical foramen.

Aging↗
PubMed2006

[The role of the maxillary incisors in the development of the base of the nose. Applications in dento-facial orthopedics].

The neonatal respiratory distress observed in the event of a solitary median maxillary central incisor compels us to reconsider some of the traditional concepts relative to the transverse growth of the nasal level of the face. The "container-contents" connections associating maxillary incisor odontogenesis with the development of the premaxillary and facial envelopes draw the attention to the significant geometrical and mechanical expression of this morphogenesis. They require attributing to the maxillary incisors an important motor role in this development. They lead to granting the ontogenetic bonds, between malocclusions and disturbed nasal breathing, the place they deserve, taking into account the morphological integration combining them. They eventually open a new therapeutic prospect: the optimization of the development of the growing face, with regard to the various tissue mechanics and physiologies, becoming the best guarantor for the prevention of relapse after dentofacial orthopedics.

Animals↗
PubMed2000

Location of the apex of the lower central incisor.

Clinicians have always had difficulty finding the apex of the lower central incisor on a lateral cephalometric radiograph. This study was undertaken to define the radiographic anatomy surrounding the true apex. Standard cephalograms were taken of 38 skulls with metallic markers in the socket apex of 1 lower central incisor. Similar cephalograms were taken with the lower central incisor apex positioned in the central ray of the x-ray source. The comparison of the marked apices in the complete skulls and their separate mandibles showed that there was no distortion. Measurements from the markers to the lingual and labial symphyseal borders located the apices labial of center.

Adolescent↗
PubMed2000

Triangular-shaped incisor crowns and crowding.

The purpose of this study was to establish if there is a correlation between the shape of the labial crowns of the incisors and crowding. Plaster cast models of 69 untreated individuals (30 males and 39 females) were evaluated. The casts were selected randomly from the collection at Seoul National University and Ajou University. With the use of Little's irregularity index, the sample was divided into 2 groups, a crowded group and a normal group. Repeated measurements of the maximum mesiodistal width of the incisal and cervical areas of the incisors were taken by means of a digital vernier caliper and a ratio of these measurements was calculated. The mean value for the crowded group was significantly larger in the incisal area (P <.01) and smaller in the cervical areas (P <.01) than corresponding values in the normal group. These ratios were correlated with the irregularity index (Pearson r(2) from 55% to 65%). The value obtained from the incisor width ratio in the normal group can be useful for the diagnosis and treatment of crowded malocclusion.

Case-Control Studies↗
PubMed2002

Treatment of a patient with a crowded Class I malocclusion and a congenitally missing mandibular incisor.

This case report describes the management of maxillary and mandibular crowding in a patient with facial esthetic concerns and a tooth-size discrepancy due to a missing mandibular central incisor. The treatment included extracting the remaining mandibular central incisor and the 2 maxillary first premolars. The mandibular canines were repositioned to substitute for lateral incisors, and the mandibular premolars were used as canines.

Adolescent↗
PubMed2003

Effects of post-core design and ferrule on fracture resistance of endodontically treated maxillary central incisors.

STATEMENT OF PROBLEM: Studies concerning the effects of post-core design and ferrule on the fracture resistance of endodontically treated teeth remain controversial. PURPOSE: The purpose of this study was to investigate in vitro the effects of post-core design and ferrule on the fracture resistance of root canal treated human maxillary central incisors restored with metal ceramic crowns. MATERIAL AND METHODS: Forty-eight extracted human maxillary central incisors were endodontically treated and divided into 4 groups of 12. The following treatments were evaluated: group A: restored with metal ceramic (porcelain fused to metal [PFM]) crowns as control; group B: 2-mm ferrule/custom cast post-core/PFM crowns; group C: no ferrule/custom cast post-core/PFM crowns; and group D: 2-mm ferrule/prefabricated post and resin core/PFM crowns. Each specimen was subjected to load (N) on the lingual surface at a 135-degree angle to the long axis with a MTS 810 material testing machine until fracture at a crosshead speed of 0.02 cm/min. One-way analysis of variance and nonparametric chi-square test were used to compare the results. A significant analysis of variance result was followed by Newman-Keuls pairwise multiple comparisons (P<.05). RESULTS: There were significant differences among the 4 groups studied (P<.01). Group B had the highest fracture strength (1793.59 +/- 387.93 N). There was no significant difference among the fracture resistances of the other 3 groups (group A: 958.49 +/- 286.02 N; group C: 992.98 +/- 291.00 N; group D: 994.94 +/- 285.04 N). CONCLUSION: Within the limitations of this study, not all of the post-core structures tested improved the strength of the endodontically treated teeth. Those prepared with a 2-mm dentin ferrule more effectively enhanced the fracture strength of custom cast post-core restored endodontically treated maxillary central incisors.

Analysis of Variance↗
PubMedDate not supplied

Histopathological study on the PTHrP-induced incisor lesions in rats.

Parathyroid hormone related peptide (PTHrP) was discovered as a causative factor of humoral hypercalcemia of malignancy (HHM). The present study elucidates the histopathological characters of incisor lesions in the HHM rat model. Nude rats were implanted with PTHrP-expressing tumor (LC-6) cells, maintained for 12 weeks, after which the mandibular incisors were collected. Incisor fractures were observed grossly. Microscopically, hypercalcified dentin, dentin niche with osteodentin, and thinning of dentin were observed. Hypercalcified dentin was observed as a basophilic line of calcified dentin without associated odontoblastic changes, whereas dentin niche and thinning of dentin occurred with osteodentin and loss of cell height, respectively. In contrast with hypercalcified dentin, which was distributed throughout the dentin, dentin niche and thinning of dentin were localized to the labial area of the apical and middle region, and to the labial and lingual areas of the middle and incisal region, respectively. These results suggest that hypercalcemia affected the entire calcification process resulting in hypercalcified dentin, and that high PTHrP concentrations affected selective populations of odontoblasts resulting in formation of dentin niche and thinning of dentin. The localization of dentin niche and thinning of dentin also suggest that PTHrP may also be involved odontoblastic development in the rat.

Animals↗
PubMed2005

Histopathological study of time course changes in PTHrP-induced incisor lesions of rats.

Parathyroid hormone related peptide (PTHrP) was discovered as a causative factor of humoral hypercalcemia of malignancy (HHM). In the present study using HHM model rats, the time course of odontoblastic response to PTHrP and its relation to incisal fracture were elicited. Nude rats were implanted with PTHrP-expressing tumor (LC-6) cells, mandibular incisors were collected at several time points. Microscopically 3 distinctive types of odontoblastic/dentin lesions were observed. Hypercalcfied dentin, which was reported as hypercalcemia-induced lesion in previous reports, observed in all areas of the dentin from week 5-10 samplings. Dentin niche, observed solely in week-10 sampling point, exhibited a nature identical to that of reparative odontoblast reported in the literatures of various cytotoxic agents. Since cytotoxicites were neither observed prior to the lesions nor reported as a role of PTHrP, the reparative response may have derived from highly sustained levels of PTHrP. Loss of columnar odontoblasts height was initially observed at week-5 time point in the middle section of the incisor. This primary loss of cell height prior to incisor fracture was considered to be the earliest response to the increased PTHrP levels of this model.

Animals↗
PubMed2005

PTHrP and PTH/PTHrP receptor 1 expression in odontogenic cells of normal and HHM model rat incisors.

Parathyroid hormone related peptide (PTHrP) was discovered as a causative factor of humoral hypercalcemia of malignancy (HHM). We examined PTHrP and its receptor (PTHR1) expression patterns in odontogenic cells in normal and HHM model rat incisors. Nontreated nude rats serving as the normal control and HHM model rats produced by implantation of PTHrP-expressing tumor (LC-6) cells were prepared. HHM rats fractured its incisor, and histopathologically, restrict population of odontoblasts showed findings classified as "shortening of high columnar odontoblasts" and "dentin niche." The incisors were immunostained against PTHrP and PTHR1. In normal rats, PTHrP and PTHR1 colocalized in ameloblasts, cementoblasts, and odontoblastic cells from mesenchymal cells to columnar odontoblasts. In high columnar odontoblasts, PTHrP solely expressed. In the HHM animals, although the expression patterns were identical to those of the normal rats in normal area, the shortened high columnar odontoblasts maintained PTHR1 expression and dentin niche comprising odontoblastic cells expressed both proteins. In the HHM model, the protein expression patterns changed in the odontoblastic cells with histological anomalies, and thus direct relations between the anomalies and PTHrP/PTHR1 axis are suggested.

Animals↗
PubMed2002

Development of enamel defects in rat mandibular incisor after thyro-parathyroidectomy.

Previous studies with scanning electron microscopy (SEM) demonstrated the presence of small hypoplastic defects in the incisal third of incisors and deep hypoplasia in the apical third of the incisors after thyro-parathyroidectomy in the rat. These studies provided a morphological description of the defects, but uncertainty remained concerning their development throughout amelogenesis. The aim of the present investigation was to study, with SEM operated in the backscattered mode, the development of the hypoplastic defects, from the beginning of the secretion to the end of the maturation zone of the enamel, in the lower incisor of thyroparathyroidectomized rats. The results of the present study showed that the large and small defects developed are separate entities that do not develop into the other. The distribution of large defects might be linked to a reduction of the eruption rate in these rats. The pathogenesis of these defects needs further investigation.

Animals↗
PubMed1990

Familial trends in palatal canines, anomalous lateral incisors, and related phenomena.

Our previous studies have established a strong link between small, peg-shaped and missing lateral incisors, and palatally-displaced maxillary canine teeth. Since these anomalies of lateral incisor development are known to be under strong genetic control, the hypothesis was that first degree relatives of patients with palatal canines would themselves show a raised prevalence of the anomalies. The present study also investigated a possible link between palatal canines and lateness in development of the dentition, and a relative absence of crowding, both of which are phenomena that have been mentioned both by us and elsewhere as similarly linked phenomena. Results showed that anomaly of the lateral incisors was found to be four times that of the general population and that positive links with late development of the dentition and a relative absence of crowding were also seen.

Adolescent↗
PubMed1994

The alignment of permanent mandibular incisors in children. A longitudinal prospective study.

The aim was to study the alignment of mandibular incisors before and after eruption of the canines, and if possible to find a method of predicting space deficiency. Fifty-three children with normal occlusion or untreated mild post-normal occlusion had plaster models taken at 7, 9, 10, and 13 years of age. An estimation of the space situation for the mandibular incisors was made using a scale with five levels. Measurements of intercanine distance, width of each incisor and space available between the canines were made. Greater crowding was seen before the eruption of permanent canines than after the start of eruption. Estimation of space showed significant correlations to measurements of inter-canine distance. Children with an excess of incisal space had a wider mandibular inter-canine distance compared with those with a deficiency of space. Among 7-, 9-, and 10-year-old children an inter-canine distance of less than 26 mm was associated with crowding. A distance of 28 mm or more was estimated as no risk for crowding.

Child↗
PubMed1996

Mandibular incisor extraction: indications and long-term evaluation.

The extraction of a lower incisor constitutes a therapeutic alternative limited to certain occlusal situations, i.e. supernumerary incisors, tooth size anomalies (peg-shaped upper laterals), ectopic eruption and anterior crossbites. The effect of the extraction of a single incisor on the out of retention alignment of lower anterior teeth was studied in 26 treated cases. Initial (T1), final (T2) and 5-8 years out of retention (T3) dental casts were measured. Mean crowding at the start of treatment (T1 = 3.86 mm) relapsed out of retention (T3 = 1.49 mm), with a net mean improvement of 2.37 mm. Little's irregularity index at the start of treatment (T1 = 6.44) relapsed out of retention (T3 = 2.53), with a net mean improvement of T1-T3 = 3.91. Alignment stability seems to be better than that achieved in cases subjected to premolar extraction.

Adolescent↗
PubMed2003

The eruption of permanent incisors and first molars in prematurely born children.

The purpose of this work was to examine whether the clinical eruption of the permanent first molars and incisors is affected by pre-term birth. The data applied to 328 prematurely born white and black children and 1804 control children who participated in the Collaborative Perinatal Project (USA) in the early 1960s and 1970s. The dental examinations had been performed in a cross-sectional manner at ages varying from 6 to 12 years in 95 per cent of cases (range 5-14 years). Dental casts were placed in matched pairs by sex, race and conceptional age for comparison of the four clinical stages of eruption of the permanent incisors and first molars between the pre-term and control children. The results showed significantly (P < 0.05) earlier tooth eruption in the pre-term children. The findings suggest that the eruption process is earlier in those teeth that go through a sensitive period circumnatally, being at the pre-eruptive stages and entering the first phases of mineralization under the influence of various neonatal systemic factors and accelerated growth period (catch-up growth) with related unknown mechanisms, which may influence the eruption of the permanent incisors and first molars in prematurely born children.

Adolescent↗
PubMed1998

The effect of extraction of third molars on late lower incisor crowding: a randomized controlled trial.

The problem of late mandibular incisor crowding is a well established phenomenon, the cause of which has been the substance of considerable debate over the years. A central issue is the possible role of the third molars though no definitive conclusions have been consistently drawn. This prospective study was designed to investigate the effects of randomly assigned early extraction of third molars on late crowding of the mandibular incisors. One-hundred-and-sixty-four patients entered the study from 1984 following completion of retention after orthodontic treatment. Seventy-seven patients (47%) returned for records up to a mean of 66 months later, and their start and finish study casts were digitized on a reflex microscope to determine Little's index of irregularity, intercanine width and arch length. Forty-four of the patients had been randomized to have third molars removed. There was no evidence of responder bias. Where third molars were extracted the mean increase in lower labial segment irregularity was reduced by 1.1 mm from a mean of 2.1 mm for the group where third molars were retained (P = 0.15, not statistically significant). This difference was also not considered to be clinically significant. The principal conclusion drawn from this randomized prospective study is that the removal of third molars to reduce or prevent late incisor crowding cannot be justified.

Adolescent↗
PubMed1989

Incisor edge-centroid relationships and overbite depth.

Interincisor angulation is commonly held to be a critical factor in determining overbite depth, where there is incisor contact. In this study significant correlations between these variables were found in Class II, division 2 malocclusions although interincisor angle explained less than a third of the variance in overbite depth. It was found that the anteroposterior relationship of the lower incisor edge to the upper incisor root centroid is more strongly related to overbite depth and it is suggested that this is a useful factor to take into account in planning treatment in Class II cases.

Dental Occlusion, Centric↗
PubMed2000

A supernumerary tooth fused to the facial surface of a maxillary permanent central incisor: case report.

A case of a supernumerary tooth fused to the facial surface of a maxillary permanent central incisor is reported. Root canal therapy on the maxillary central incisor was performed due to pulpal communication between the supernumerary tooth and the maxillary central incisor after removing the supernumerary tooth structure. The communication was sealed with mineral trioxide aggregate. The difference between fusion and gemination is discussed.

Aluminum Compounds↗
PubMed1997

Evaluation of X-ray beam angulation for successful twin canal identification in mandibular incisors.

This study was undertaken to determine the most effective horizontal beam angulation for the diagnosis of twin canals in mandibular incisors. Two hundred extracted mandibular incisor teeth, in groups of four, were aligned in the form of a lower dental arch and radiographed using a beam alignment device at 10 degrees intervals between 0 degree and 50 degrees from both right and left sides. Five observers with varying degrees of experience were asked to assess the number of canals in each of the four teeth from these radiographs. A further radiograph of each individual tooth was taken at 90 degrees through the mesio-distal plane to identify the number of twin canals present. A random sample of 10% of the radiographs were viewed for a second time 3 months later to assess intra-observer variation. The 20 degrees right and 30 degrees left horizontal beam angulations showed significantly more accurate diagnosis of twin canals than the ortho-radial view (0 degree) by all five observers. Analysis of the inter-observer results suggests that the experienced viewers were no better but more consistent at identifying twin canals in mandibular incisors.

Dental Pulp Cavity↗