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At least 1,225 records · Page 68Linked to original sources
PubMed2006

Incisal orientation and biting efficiency.

Broad-edged 'spatulate' upper and lower incisors are distinctive of catarrhines and platyrrhines who use them in various ways to peel fruits, remove bark, and strip leaves from branches. The incisors of modern humans not only control the bite size of foods during ingestion, but often grip items in a number of non-food related tasks. Such uses have long been implicated for Neandertals as well. Despite the evolutionary importance of incision and the fact that the incisors feature prominently in clinical dentistry (via orthodontic practices designed both to correct incisal misalignments and adjust their orientation), little is known about what affects their functional efficiency. Few mechanical analyses of incisal action have been published and none that seem to take note of the mechanisms of both fracture and friction at the tooth-food interface. Here, we modeled the incisal tip as a wedge, finding that the efficiency of biting foods that fracture elastically is strongly dependent on both the apex angle of the incisor and the coefficient of friction. Based on apex angle measurements from a small sample of human central incisors, the overall efficiency of upper central incisors is predicted to be greatest when the angle between the apex bisector and the direction of applied force is zero. However, this is complicated greatly by friction, particularly for the lower incisors. The analysis probably applies not only to the use of incisors by humans, but also to some extent to frugivorous primates. This model should clarify the mechanics behind incision and can provide a basic foundation upon which more advanced models can be built on in the future.

Animals↗
PubMed1995

The adaptation of mechanically softened gutta-percha to the canal walls in the presence or absence of smear layer: a scanning electron microscopic study.

The objective of this study was to compare the adaptation of mechanically softened gutta-percha to the root canal wall in the presence and absence of smear layer. The root canals of 20 freshly extracted human maxillary incisors were cleaned and shaped. Prior to obturation, 10 root canals were irrigated with 20 ml of 50% citric acid followed by 20 ml of 5.25% sodium hypochlorite. All canals were obturated with mechanical compaction of gutta-percha and AH-26 sealer. After 72 h, each tooth was fractured in half. Scanning electron microscopy demonstrated that the sealer had formed a continuous layer in contact with the canal walls, becoming progressively thinner towards the apex. The sealer penetrated into the dentinal tubules along with projections of gutta-percha only in those teeth without smear layer.

Bismuth↗
PubMed1989

Age assessment based on translucent dentine.

The purpose of this investigation was to examine the relationship between age and the area of translucent dentine (TA) at root apex, and to compare these findings with those obtained by using the methods of Bang & Ramm and of Johanson. The material consisted of 500 teeth, 50 of each tooth type, molars excluded. For statistical analyses an XT microcomputer and SPSS/PC regression programme were used. The correlation between age and ATD varied from 0.83 to 0.57 for different types of teeth. In stepwide multiple regression analyses ATD was preferred to other types of measurement of the translucency. The factors (ATD) and sex contributed significantly to the regression for some types of teeth. Regression analyses using several factors according to Johanson's method resulted in a stronger correlation for most teeth, while the method of Bang & Ramm resulted in a weaker correlation except in the case of mandibular first premolars.

Age Determination by Teeth↗
PubMed1978

Root canal morphology of mandibular premolars.

Four hundred mandibular first premolars and 400 mandibular second premolars were decalcified, injected with dye, and made transparent to determine the number of root canals, their type, the ramifications of the main root canal, the location of apical foramina and transverse anastomoses, and the frequency of apical deltas. The mandibular first premolar had one canal at the apex in 74.0% of the teeth, two canals at the apex in 25.5%, and three canals at the apex in 0.5% of the teeth. The mandibular second premolar had one canal at the apex in 97.5% and two canals at the apex in 2.5% of the teeth.

Bicuspid↗
PubMed1990

[Experimental evaluation of an electronic apical locating instrument: study of 100 clinical cases].

A statistical study has been conducted in order to study the efficiency of an "R.C.M. apex locator" in endodontometry. The study is based on 97 electronic measurements in vivo, all samples being controlled in vitro by X-Ray examination after extraction of the teeth, the instrument remaining in the canal. Results showed that the "R.C.M. apex locator" allows a success rate of 85% length recorded being short of beyond the apex by 0.5 mm.

Dental Pulp Cavity↗
PubMed1999

Unusual case of bilateral talon cusp associated with dens invaginatus.

CASE REPORT: This paper presents a rare case of bilateral talon cusp in permanent maxillary central incisors, one on the labial and another on the lingual surface of each tooth. The condition was associated with dens invaginatus in a maxillary permanent lateral incisor, but no developmental syndrome was identified. The left central incisor required no treatment because the aesthetic appearance was satisfactory and neither occlusal interferences nor caries were present. After careful investigation of the right lateral incisor, a sealant was applied. Root canal treatment was indicated for the right central incisor that had a wide open apex with thin, weak, divergent walls, and an apical radiolucency.

Adult↗
PubMedDate not supplied

Morphometric analysis of mandibular canal: clinical aspects.

Results of morphometric analysis of the mandibular canal (MC), carried out on 105 conserved mandibles, 70 being dentate and 35 edentate, was performed. The analysis was carried out on consecutive sections, at mutual intervals of 0.5 cm. In the mandibular ramus sections were carried out obliquely, approximately in the frontal plane, and horizontally, from mandibular foramen to the lowest region of the vertical part of the MC (all together two sections). In the mandibular corpus, consecutive transversal sections were carried out between existing teeth, or at mutual intervals of 0.5 cm in edentate regions. The obtained results pointed out the very close relationship between the MC and lingual cortical plate of the mandibular ramus. In its horizontal part, the average diameter of the MC was 2.6 mm. It was situated more lingually in the molar region; towards the front, it approached the vestibular cortical plate, being closest to it in the region of the second premolar. Similar relationships of the MC and both cortical plates existed in edentate jaws. Relationships of the MC and tooth root apices varied; however, the MC was closest to the apices of the third molar. Mesially from the mental foramen, a clearly defined incisive canal was present in 92% of the dentale mandibles, but only in 31% of the edentate ones. The nearest to the incisive canal was the apex of the first premolar. The authors point out the importance of presented results in everyday practice, especially in oral and maxillofacial surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1985

Tooth root growth impairment after mantle radiation in long-term survivors of Hodgkin's disease.

The tooth root growth impairment that resulted from 35 to 37 Gy mantle port radiation in 47 long-term survivors of childhood Hodgkin's disease was quantified and related to specific age groups and categories of teeth. Root measurements of the mandibular permanent canines, first and second premolars, and first and second molars were made from sequential panoramic radiographs taken at the time of radiation therapy and after the closure of root apexes. The severity of root growth impairment was greatest in patients who received radiation during the early stages of odontogenesis. With later stages of odontogenesis, and as the age increased at the time of treatment, less impairment occurred. The potential difficulties of using repeated panoramic radiographs to assess tooth lengths in longitudinal studies also were discussed.

Adolescent↗
PubMed1995

Estimation of age from dentin by using the racemization reaction of aspartic acid.

To confirm the usefulness of the whole dentin in longitudinal sections for estimating age using the racemization ratio (D/L ratio) of aspartic acid, we compared longitudinal and transverse sections prepared from bilateral teeth in the same jaw of the same subjects. The D/L ratio was measured by gas chromatography. A better correlation between the D/L ratio and true age was observed when using longitudinal sections (r = 0.995) than when using transverse sections (r = 0.984-0.987). In the low age group, the D/L ratio was high in the crown and decreased toward the root apex. In the middle-advanced age groups, however, the D/L ratio was high in the crown as well as the area close to the root apex. The racemization reaction rate was higher in longitudinal than in transverse sections. These results suggest that the whole dentin in longitudinal sections of the central area of the tooth should be examined for accurate estimation of age.

Adolescent↗
PubMedDate not supplied

[A trial of densitometry in the objective assessment of the x-ray image of the apices of the interdental membranes in periodontal lesions].

The authors suggest a method to assess the quality of filling dental contact surfaces, based on determination of the relative contrast index (RCI) of the x-ray image of interdental septal apexes at the site of filled and intact teeth on the same image. Analysis of their own findings has lead the authors to a conclusion that assessment of the tooth filling with the use of periodontal and hygienic indexes is not strictly consistent because it is subjective, whereas the RCI permits a follow-up of changes in the mineral content of the bone in the examined site over time.

Absorptiometry, Photon↗
PubMed1975

Replantation of avulsed teeth. A review.

Time is a critical factor in successful replantation. The avulsed tooth is simply washed and replaced immediately. Where contamination with soil occurs anti-tetanus prophylaxis is given and some form of splinting is necessary for 3-4 weeks. Endodontic therapy is performed prior to replacement if there is a delay of more than two hours and where apex formation is complete it should be commenced within 10 days. Calcium hydroxide is useful as a root canal dressing and in controlling resorption. The value of immediate replacement and treatment should be publicised.

Adolescent↗
PubMed1993

Dynamics of tissue changes found after mechanical loading of the rat incisor. II. A three-dimensional longitudinal study of the histopathologic aspects.

The study comprised 60 lower left rat incisors subjected to 2 weeks of loading (19.7 +/- 1.6 gm) and 5 control teeth. After the loading period, 10 rats were killed with the springs in situ, and the remainder were killed in groups of 5 at intervals of 1 through 10 weeks after the springs were removed. The teeth were cross-sectioned serially (2 microns). The distance of each section from the apex and the time of its tissue formation in relation to load removal were calculated. Bone remodeling and dental and periodontal trauma were plotted according to their location on the tooth axis and circumference. Vigorous bone remodeling continued throughout the observation period, apposition and resorption sites intermingling around the tooth. Directionality, as expressed by the resorption/apposition ratio, for the formerly tensed and stressed areas was 0.61 +/- 0.07 and 1.79 +/- 0.52, respectively. However, in some of the groups directionality was negligible or reversed. New lesions of dentin (folding and resorption) were formed for 6 weeks after loading, whereas new damage to the enamel organ and enamel matrix appeared until week 9. The integrity of the PDL deteriorated for the first 8 weeks, as evidenced by edema, cell loss, scarring, and collagen fiber disorientation. Necrosis occurred throughout the recovery period. Fiber to bone attachment was disrupted by formation of big sinusoids adjacent to the bone. The frequency of most lesions decreased toward the end of the observation period. It is suggested that tissue recovery proceeds in subsiding cycles of tissue injury/tissue repair, a process that is much more prolonged than is generally believed.

Alveolar Bone Loss↗
PubMedDate not supplied

[Evaluation of dental age using qualitative radiographic analysis. 2].

The Authors evaluated the stage of growth of seven left mandibular teeth and their eruption sequence on 157 op. The growth accomplishment happened earlier in this study as compared to others. Males showed one year gap compared to females in reaching the full dental growth, identified by the apex closure.

Adolescent↗