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At least 1,027 records · Page 57Linked to original sources
PubMed1990

Mechanical properties of the periodontal ligament in the incisor teeth of rats from 6 to 24 months of age.

Mechanical properties of the periodontal ligament of the incisor have been examined in sections of the mandibles of rats from 6 to 24 months of age. Mechanical measures estimated from the load-deformation and stress-strain curves did not show age-related changes, although the body and mandible weights increased gradually during the experimental period. It is suggested that qualitative and quantitative changes in the supporting tissues/unit area of the ligament are minor at a restricted region examined.

Aging↗
PubMed1990

Age-progressive changes in pulp widths and root lengths during adulthood: a study of American blacks and whites.

The intertwined effects of normal aging processes and time-progressive diseases produce systematic changes in many oral and dental tissues. This cross-sectional study of pulp dimensions and root lengths in sound teeth tested for changes with age in adulthood while controlling for differences in gender and race (black, white). Age was the paramount determinant of pulp size which decreases via the accumulation of secondary dentin. In some instances the rate of change increases in older adults with an inflection point at 35-40 years of age. In contrast, root lengths are statistically independent of age once gender (male greater than female) and race (black greater than white) are controlled. Causes of the lack of association with age are discussed.

Adolescent↗
PubMed2002

Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope.

Various authors have investigated the frequency of second canals (MB2) in the mesiobuccal roots of maxillary molars, predominantly first molars. Further, it has been reported that the percentage of MB2 canals that are treated during routine endodontic therapy is much lower than the number of second canals identified in vitro. It was the purpose of this study to investigate whether the use of an operating microscope may improve the diagnosis of MB2 canals in mesiobuccal roots of maxillary molars. The canal orifices of 100 maxillary first and second molars (50 of each) were initially inspected by Examiner 1 using individually-adapted x2 magnifying loupes. Subsequently, all teeth were examined by a second investigator using an operating microscope (OPM) with x8 magnification. Finally, the mesiobuccal roots of all teeth were separated. Then, the sections were analysed histologically and by SEM. The histological investigation revealed a total number of 63 MB2 canals, 39 in first, and 24 in second molars. Only 26 (41.3%) of those canals were identified using magnifying loupes, whereas 59 (93.7%) were found by means of an operating microscope.

Dental Equipment↗
PubMed2005

In vitro evaluation of three techniques to obturate 0.06 taper canal preparations.

The aim of this study was to evaluate the ability of three obturation methods to seal root canals prepared using 0.06 taper rotary instruments. Forty-five extracted human single-rooted teeth were instrumented with 0.06 taper Profile nickel-titanium rotary files and randomly divided into three experimental groups containing 15 teeth each. The first group was obturated using the System B technique with 0.06 taper standardised gutta-percha points, the second group was obturated using the System B technique with non-standardised MF gutta-percha points, the third group was obturated by cold lateral condensation technique using standardised 0.02 taper master gutta-percha points. Apical leakage of the roots was evaluated by dye penetration using a stereomicroscope after sectioning the roots. The group obturated using System B and 0.06 taper gutta-percha points showed the least dye penetration. However, the difference in the linear extent of dye penetration was not statistically significant.

Coloring Agents↗
PubMed2005

Determination of root canal curvatures before and after canal preparation (part 1): a literature review.

The continuing development of methods and materials for root canal preparation is resulting in enhanced preparation techniques with only minor alterations to the canal morphology. Improved evaluation methods are required for differentiated assessment of these innovations. One criterion for assessment of the preparation quality of curved root canals is preparation-induced straightening of the canal. The first canal curvature measurements served to divide teeth into different curvature classes. However, their actual execution represented mere angular measurement rather than root curvature assessment. This purely graphic method lacked precision, nor could it be readily applied to all tooth groups. Further developments of that method resulted in it being applicable to molars and to canals with multiple curvatures. Some years ago, the graphically determined curvature radius was added as a further parameter to measurement of the canal deviation angle, thus permitting a curvature to be correctly described for the first time in geometric and analytic terms. The first mathematically accurate description was presented by Dobó-Nagy et al., who correctly described the mean canal curvature in a two-dimensional image in concrete terms by means of fourth-degree polynomial functions. Recent developments in the application of microcomputed tomography of extracted teeth permit non-destructive three-dimensional assessment of root canal configurations. It remains to be seen whether this resource-intensive form of in vitro examination can assert itself.

Dental Pulp Cavity↗
PubMed2006

Determination of root canal curvatures before and after canal preparation (part II): A method based on numeric calculus.

The aim of this paper is to present a new method based on numeric calculus to provide data on any type of root canal curvature at any point of the long axis of the canal. Twenty severely curved, simulated root canals were prepared with rotary FlexMaster and Profile instruments in the crown-down technique and manually in the step-back technique. The inner and outer curvatures were registered in a system of coordinates before and after preparation in increments of 0.5 mm. Using an equalising function, the curvatures were first represented in graphic and algebraic form. The maximum and the mean curvature as well as the length of the arc from the apical foramen to the point of maximum curvature were determined mathematically. An increase in maximum curvature was registered for all four shaping systems investigated. The radius of the inner curvature decreased by 0.5-1.2 mm in the manual systems as a result of the preparation. The Profile system displayed the smallest changes in radius (-0.9 mm) even with the outer curvature, and manual preparation with stainless steel files the most pronounced change (-1.8 mm). The point of maximum curvature at the inner curvature was displaced by 1.6 mm to the apical foramen through manual preparation with Ni-Ti files. At the outer curvature, the maximum displacement (1.8 mm) recorded was also the result of preparation with Ni-Ti hand files, while a displacement of only 0.3 mm to the apical foramen was recorded with the other systems. The method offers a means of determining curvatures precisely without random specification of reference points. The method is also capable of registering only minor changes in curvature in the two-dimensional long axis of the canal.

Calibration↗
PubMed2006

Endodontic retreatment of a maxillary second molar with three separate buccal roots.

A rare case of a four-rooted maxillary second molar in a 39-year-old male patient is reported. After clinical and radiographic examination, two separate mesio-buccal roots were detected, and a treatment plan consisting treatment of the mesio-buccal roots and retreatment of the disto-buccal and palatal roots was made to resolve the previous treatment failure. The tooth was treated by orthograde endodontic retreatment in two visits. Mesio-buccal canals that were located in the separate mesio-buccal roots (which were missed in previous treatment) were found and treated. The case report underlines the importance of complete knowledge about root canal morphology and possible variations, coupled with full clinical and radiographic examination, in order to increase the ability of clinicians to treat difficult cases.

Adult↗
PubMed1980

Comparison of mesiodistal crown diameters of the deciduous and permanent teeth in Australian aboriginals.

Mesiodistal crown diameters of corresponding deciduous and permanent teeth were compared in 106 male and 66 female Aboriginal subjects from Yuendumu in the Northern Territory of Australia. On average, the size relationships were similar to those reported for Caucasoid groups but there was considerable variation between subjects, particularly in the deciduous first molar--permanent first premolar comparison.

Australia↗
PubMed1980

Correlations between crown diameters of the deciduous and permanent teeth of Australian Aboriginals.

Correlations between crown diameters of corresponding teeth and tooth groups in the deciduous and permanent dentitions are reported for Australian Aboriginals. Size associations for within-dentition comparisons were stronger than those for between-dentition. Furthermore, correlations tended to be greater for corresponding tooth groups than for single teeth both within and between dentitions. This co-ordination appears to be well marked in Aboriginals compared with other populations.

Australia↗
PubMed1991

Mongoloid features of the permanent mandibular second molar in Singaporean Chinese.

The permanent mandibular second molar is usually described as four-cusped, two placed buccally and two lingually. It has been reported that five-cusp forms were more commonly present in dentitions of mongoloid origin. The prevalence and features of this tooth form were examined in a Singaporean sample of 380 subjects with bilateral presence of the mandibular second molars. One-hundred and sixty four cases (43.1 per cent) were found to have bilateral occurrence of five-cusp forms and thirty-four cases (8.9 per cent) with unilateral occurrence. Six-cusp forms were detected in three cases. There was almost equal prevalence in both sexes and both sides were equally involved in unilateral cases. The extra cusp was smallest, placed disto-buccally and sometimes midway at the distal border. The occlusal outline of five-cusp second molars was rectangular with a somewhat similar groove pattern to the first molar. There was an increase in the mesio-distal width of the crown. The high incidence was comparable with other studies of mongoloid dentitions and it could be considered as an important morphological and racial characteristic of the Singaporean Chinese.

Asian People↗
PubMed1993

Coronal morphology of the mandibular second premolar in the Singaporean Chinese.

Five hundred and sixty-four patients of Singaporean Chinese origin with bilateral second premolars present were screened. Morphological features of the crown, number and position of cusps and the sex of the patient were recorded. The mesio-distal dimensions of the crowns were measured. Three hundred and seventy-four (66.3 per cent) exhibited bilateral 2-cusp forms; 143 (25.4 per cent) were 3-cusp forms; and 47 (8.3 per cent) were mixed. There was no sex predilection in the three groups. In the 2-cusp forms, the predominant occlusal pattern was H-shaped (75.9 per cent). The 3-cusp type with a Y-shaped pattern and a squarish outline is a significant morphological and racial characteristic in the local population. The presence of 2-cusp and 3-cusp forms in an individual is an unusual developmental phenomenon.

Asian People↗
PubMed1995

Agenesis of permanent maxillary lateral incisors in South Australian twins.

The frequency of agenesis of maxillary lateral incisors (I2) in a sample of South Australian twins was determined, and associations with gender, zygosity, birthweight and dental crown size were investigated. Ten of the 446 twins examined (2.24 per cent) displayed agenesis of one or both I2, a similar frequency to that reported for Australian singletons. Seven of the ten affected individuals were monozygous female twins, including two pairs, while the three affected dizygous twins were each from different male twin pairs. Five pairs of monozygous twins were identified who displayed varying expressions of normal, small, peg-shaped or missing I2. These twin pairs displayed disparate birthweights suggesting they may have been mono-chorionic. These findings are consistent with a multifactorial threshold model linking size and number of I2 with developmental influences modifying phenotypic expression in those monozygous twins whose genetic predisposition places them near to the threshold for agenesis.

Adolescent↗