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At least 1,189 records · Page 66Linked to original sources
PubMed1990

Variations in the perception of ideal bracket location and its implications for the pre-adjusted edgewise appliance.

An investigation was undertaken of the variability in the perception of ideal bracket location for the pre-adjusted edgewise appliance by the same clinician (intra-clinician variability) and between different clinicians (inter-clinician variability). The effect of recent training and experience upon this variability, as well as the likely changes in crown inclination and root apex positioning, was also assessed. Results show that both intra- and inter-clinician variability for the long axis of the clinical crown (LACC) angulation was large while very small variations occurred in the location of the long axis (LA) point. Experience and training significantly reduced the variability in LACC angulation, but had little effect on the LA point location. The likely clinical implications are limited to only minor changes in crown inclination and root apex position for the majority of clinicians. However, the extreme intra-clinician variations found in LACC angulation could well result in poor root apex positioning.

Humans↗
PubMed1993

A assessment of the plastic Thermafil obturation technique. Part 1. Radiographic evaluation of adaptation and placement.

Adaptation and placement of alpha-phase gutta-percha delivered with a plastic core-carrier, Thermafil, was compared to the lateral condensation of gutta-percha in a specific tooth model. Fifty-one mandibular molar roots with separate canals, patent canal orifices and curvatures greater than 15 degrees were cleaned and shaped with K-files and 2.5% sodium hypochlorite to a size 30 at the apex, and flared with Hedstrom files to create a continuously tapering funnel preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or standard beta-phase gutta-percha with lateral condensation. Roots were radiographed from the proximal and evaluated by three examiners, based on established criteria for overall material adaptation, apical adaptation, and filling material extrusion. Thermafil provided a statistically significant better overall canal obturation (P < 0.001), while, in the apical third, both techniques were not significantly different (P > 0.05). When the apical orifice was patent there was a significant propensity for the extrusion of filling materials beyond the apex (P < 0.001) with the Thermafil technique.

Evaluation Studies as Topic↗
PubMed1998

An evaluation of Ektaspeed Plus film versus Ultraspeed film for endodontic working length determination.

Thirteen teeth in human cadaver sections were accessed and #15 K-files were placed at various lengths in one root canal of each tooth. Using a positioner to ensure duplicate views, radiographs were taken with both Ultraspeed and Ektaspeed Plus X-ray film. Each of the 26 radiographs was coded and then placed in random order. Six endodontic specialists measured the distance from the file tip to the radiographic apex on each film. The results were analyzed by analysis of variance and Cronbach's generalizability theory. It was found that 94% of the variance in measurements was due to differences among the viewers, whereas 5% was due to a combination of viewers and tooth. Only 1% was due to differences between the two types of film. It was concluded that Ektaspeed Plus film may be used for working length radiographs because it requires only approximately 50% of the radiation needed for Ultraspeed film.

Analysis of Variance↗
PubMed1990

Scanning electron microscopy of the auditory teeth along the mouse cochlear duct.

The auditory teeth in the spiral limbus of the cochlear duct are located under the limbal portion of the tectorial membrane and separated by furrows lodging the interdental cells. In this study, the shape, arrangement and distribution of the auditory teeth in the cochlear duct of adult mice were examined by scanning electron microscopy after removing the tectorial membrane and the interdental cells with chemical maceration methods. The auditory teeth appeared on the top face of the spiral limbus between the edge of the vestibular lip and the Reissner membrane. The teeth on the vestibular lip side possessed elongated upper plates and formed a continuous row resembling the keyboard of a piano; the teeth were separated by radially oriented parallel slits. The elongated teeth decreased in length from the base to the apex of the cochlear duct. The teeth on the Reissner membrane side showed star-shaped upper plates separated by slits and gaps. The population density of the star-shaped teeth decreased from the base to the apex, widening the gaps to hold the interdental cells. The upper plates of the teeth occupied about 75% of an extent of the tooth zone in the hook and first basal half turn, and about 55% in the apical turn. The regional differences of the auditory teeth are considered to be closely related to local functions of the tectorial membrane and the interdental cells.

Animals↗
PubMed2001

Biomechanical effects of cervical lesions and restoration on periodontally compromised teeth.

OBJECTIVE: The purpose of this study was to photoelastically evaluate the effects of cervical root lesions and their restoration on stress distribution in periodontally compromised teeth. METHOD AND MATERIALS: Three-dimensional composite photoelastic models of a maxillary first premolar with buccal cervical root lesions were fabricated. Two different lesion configurations, wedge- and shallow saucer-shaped, at 20% alveolar bone height reduction were tested. A 35% reduction model was given a wedge-shaped lesion. The lesions were restored with microfine resin composite. Vertical loads of 7.5 lbs were applied to the unrestored and restored models at the tip of the buccal cusp and the tip of the lingual cusp. The resulting stresses within the tooth models were monitored and recorded photographically in the field of a circular polariscope arrangement. RESULTS: For buccal cusp loading of the unrestored models, stress concentrated at the apex of the lesion regardless of the lesion shape or periodontal support conditions. The highest stress concentration was observed around the apex of the wedge-shaped lesion on the 35% reduction model. Restoring the lesions changed stress distribution. Restoration of the lesions resulted in a marked stress reduction at the lesion apex. Stress along the gingival restoration-model interface was characteristic for the restored situation. The interfacial stress followed the contour of the restoration most closely for the wedge-shaped lesion on the 20% support reduction model. CONCLUSION: The shape and dimension of the lesion as well as periodontal support status has considerable influence on stress distribution, especially around the lesion, restored or not restored.

Alveolar Bone Loss↗
PubMed1995

Risk factors for apical root resorption of maxillary anterior teeth in adult orthodontic patients.

The purpose of this study was to identify risk factors for apical root resorption in adult orthodontic patients. Standardized periapical radiographs of maxillary anterior teeth and cephalograms made before and after treatment and treatment charts of 343 adults, representing groups of consecutively treated patients from four orthodontic practices, were examined. Apical root resorption was calculated by subtracting posttreatment tooth length measurements from the corresponding pretreatment measurements. Root width was measured from the mesial to the distal outline of the roots 4 mm from the apex. Root form was scored subjectively as normal, pointed, eroded, blunt, bent, and bottle shaped. Root movement was calculated from measurements of superimposed tracings of pretreatment and posttreatment cephalograms. Proximity of the central incisor roots to the palatal cortical bone was scored subjectively as present or absent. Severity of initial malocclusion and treatment variables were collected from the charts. Multiple linear regression analyses revealed that amount of root movement, long roots, narrow roots, abnormal root shape, and use of Class II elastics were significant risk factors. However, the statistical model had a low explained variance, strongly suggesting a weak prediction power. No association was found between type of initial malocclusion, treatment time, use of rectangular arch wires, proximity of the root to the palate or treatment with maxillary osteotomy, and root resorption. Endodontic treatment was a preventive factor.

Adult↗
PubMed1989

[Clinical evaluation of the voltage gradient method for root canal measurement].

The voltage gradient method for root canal measurement was evaluated in vivo and in vitro. For the evaluation in vivo, 25 single root teeth, were employed. The working length was measured by bipolor or monopolor electrode. After measurement, the electrode was fixed on the tooth, and the tooth was extracted. Radiograph was taken from 12 directions perpendicular to longer axis of tooth, and the relation between anatomical foramen, physiological foramen and the attained position of electrode tip was assessed. In the evaluation in vitro, 7 extracted teeth were used, for which the positions of anatomical foramen and physiological foramen had been determined in advance from radiograph, in order to determine the influence of the root canal irrigants and medicaments. The electrode was fixed on electronic calipers and direct reading of the movement. Root canal irrigants and medicaments were injected into root canal, and the measurements were evaluated. The results were as follows: (1) In the cases of 22 teeth measured by monopolar electrode in vivo, the electrode tip was within 0.5mm from physiological foramen except one tooth. (2) In the cases of 3 teeth measured by monopolar electrode in vivo, the electrode tip was within 0.4mm from anatomical foramen. (3) In the cases, where electrolyte solution was filled in root canal and measurement was made by bipolar in the evaluation in vitro, the results of measurement were stable, and the electrode tip tended to be slightly closer to coronal direction from physiological foramen. (4) In the cases where non-electrolyte solution was filled in root canal and measurement was made by bipolar electrode in the evaluation in vitro, the results of measurement were not stable, and the electrode tip tended to be closer to the apex from physiological foramen. (5) In the case of the evaluation in vitro, where electrolyte solution was filled in root canal and measurement was made by monopolar electrode, the electrode tip tended to be a little closer to the front than the anatomical foramen. (6) In the evaluation in vitro, where non-electrolyte solution was filled in root canal and measurement was made by monopolar, the measurement was not achievable. (7) 10% NaOCl solution was found to be very useful as electrolyte solution filled in root canal to search physiological foramen by this measurement method. The above results suggest that the voltage gradient method for root canal measurement is highly reliable because root canal morphology at the apex can be directly in identified.

Dental Pulp Cavity↗
PubMed1995

Efficacy of argon laser irradiation in removing intracanal debris.

Endodontic instrumentation, irrigation, or intracanal medication are unable to totally remove intracanal debris. The purpose of this study was to evaluate the efficacy of argon laser irradiation in removing debris from the root canal system. After cleaning and shaping, 12 single rooted teeth were randomly divided into two groups of six teeth each. The first group, which served as the control, was not lased. In the second group, a 300 microns argon laser fiber optic was introduced into the root canal of each tooth, to its working length. Fifteen pulses of 100 msec each with an energy of 2 watts were delivered for 5 seconds at the apex. The lasing procedure was repeated at 1 mm intervals along the root canal, and the fiber tip was retrieved from the apex to the orifice. Computerized scanning electron microscopy analysis revealed that the amount of debris in the lased group was significantly lower than that in the control (p = 0.0001). On the basis of these results, it appeared that intracanal argon laser irradiation was an efficient mean of removing intracanal debris.

Argon↗
PubMed1989

[Stress analysis of post-reconstructed teeth with dead space at the apex of the post].

Reconstruction of the crowns of non-vital teeth with posts can be a very useful technique. However, there are many cases where the length of the posts are insufficient, resulting in a poor fit and dead space at the apex of the post. The purpose of this study was to compare the post length to the depth of the post preparation using parallel X-ray films of 31 teeth (incisors, canines and premolars) and to locate the dead space at the apex of the post. In addition, stress analysis of the post-reconstructed upper central incisor models having five types of posts with dead space at the apex and two levels of supporting conditions were calculated using the finite element method. The results obtained were as follows: 1. From the roentogenographic survey, the depth of the post preparations averaged two thirds of the remaining root length, and one half the length of the root in bone. However, lengths of the posts were on the average 20% shorter than the depth of the post preparation. 2. As the dead space increased and supporting levels diminished, stresses of post-reconstructed teeth were found to increase gradually and to concentrate in the remaining dentin near the apex of the post.

Crowns↗
PubMed1975

[Apex and periapical periodontium of teeth with endodontic-endosseal pin fixation].

Teeth with endodontic-endosteal pin fixation were observed for several years and radiolucencies that could be interpreted as chronic inflammation, were found in the periapical region of these teeth. The cause is sought in the iatrogenic noxa of the originally applied method. It is recommended to expose the apex of teeth to be provided with endodontic-endosteal pin fixation and to shorten the apex by grinding off 2-3 mm.

Dental Implantation, Endosseous, Endodontic↗