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PubMedDate not supplied

The effect of load angulation on fracture resistance of teeth restored with cast post and cores and crowns.

The purpose of this study was to determine if loading post-restored teeth at different angles would affect their fracture resistance. Thirty maxillary central incisors were treated endodontically to within 5.0 mm of the apex. Standardized cast post and cores were fabricated using plastic #4 Parapost patterns. Post and cores were cemented using zinc phosphate cement, followed by crowns of average dimensions. Ten teeth each were loaded at 110, 130, and 150 degrees to the long axis of the tooth. Mean failure loads were: 110 degrees = 372.4 N +/- 140.8 (SD); 130 degrees = 597.6 N +/- 138.5 (SD); 150 degrees = 1274.3 N +/- 429.9 (SD). There were significant differences in fracture resistance between teeth tested at the following angles: 110 degrees versus 150 degrees (P < .0001), and 130 degrees versus 150 degrees (P < .0001), but not for 110 degrees versus 130 degrees (P = .2016). Mean failure loads increased as load angle approached parallelism to the long axis of the teeth. Significant differences in fracture resistance of post-restored teeth can occur as a result of load angle.

Analysis of Variance↗

PubMed2002

[An experiment study on repairing residual dental root with a horn-shaped orifice by different materials].

When a traditional method is used to repair residual dental root with horn-shaped orifice, this kind of dental root often has to be extracted since the success rate in clinic is very low. The main reason is that the stress often concentrates on the neck and root apex, therefore the wall at the orifice is too thin to bear this kind of pressure. A new repairing method is proposed trying to preserve the residual dental root with horn-shaped orifice. Then compare the anti-fracture ability of this kind of tooth with that of no repairing. The results show that it is very effective to prevent the fracture of residual dental root repaired by chemical hard synthetic resin followed by making the post and core. However, there is no obvious difference between non-repaired and residual dental root groups repaired by traditional glass ionic adhesives. The results also provide the great possibility to preserve the residual dental root with horn-shaped orifice in clinic.

Dental Restoration, Temporary↗

PubMed1985

Biomedical image processing for age measurements of intact teeth.

With increasing age the roots of teeth undergo sclerosis. The degree of dental root sclerosis can be demonstrated visually if light is transmitted through the specimen. However, this resultant image is only a two-dimensional (2-D) visualization which misrepresents what in truth is a three-dimensional (3-D) characteristic. We have described an image acquisition and computer processing system for imaging intact teeth, with special reference to the root transparency, which tends to progress from the root apex towards the neck of the teeth as a function of age. The components of our system involve: an energy source with light transmission through table-mounted dental specimens; an image processor with a digitizer; a step motor with a holder to rotate the tooth specimen; and a software package to computerize and reconstruct the sectional digital images. After rotating the position of the specimen, while at each rotation obtaining a 2-D image of the sample, we then can reconstruct the true 3-D cross-sectional or longitudinal morphology or both from these 2-D images. With this new approach, the reconstructed dental images represent segments from different angles of the tooth specimen. Picture element values in each image, quantitatively indicate the optical density, expressing the age dependent pattern of the 3-D anatomy in toto.

Age Determination by Teeth↗

PubMed1994

Interpretation of endodontic file lengths using RadioVisiography.

The purpose of this investigation was to compare RadioVisioGraphy (RVG) imaging with conventional radiography in determining endodontic file length adjustment. Human cadaver sections with first or second molars were used. Files were inserted into canals at randomly selected lengths, from 4 mm short of the radiographic apex to 3 mm beyond. Radiographs and RVG images were evaluated to determine the adjustment needed to place the file 0.5 mm from the radiographic apex. Results showed no significant difference in the ability of endodontists to make accurate file length adjustments using conventional radiography versus RVG. In this study, it was found that: (a) accurate file length adjustments can be made from an image two times larger than the actual tooth; (b) RVG is not significantly better than conventional radiography; and (c) if both methods are available, RVG is preferred because of the significant reduction in radiation dose.

Analysis of Variance↗

PubMed1992

Anatomical study of the root apex in the maxillary anterior teeth.

The purpose of this study was to investigate anatomically the apical portion of the root canal of human maxillary anterior teeth. Thirty maxillary central incisors, 30 maxillary lateral incisors, and 30 maxillary cuspids were used. These were teeth from patients ranging in age from 11 to 73 yr. The root apex and main apical foramen coincided in 16.7% of central incisors and cuspids and in 6.7% of the lateral incisors. The labiolingual diameter of the root canal at the apical constriction of the central incisors, lateral incisors, and cuspids averaged 0.425 mm, 0.369 mm, and 0.375 mm, respectively; and the respective vertical distances between apex and apical constriction were 0.863 mm, 0.825 mm, and 1.010 mm.

Adolescent↗

PubMed1995

New philosophy for the treatment of avulsed teeth.

The success rate of replanted avulsed teeth has been low. This poor success rate results from the use of only one treatment regimen. This treatment regimen, replantation as quickly as possible regardless of circumstances, ignores much of the dental research that shows this regimen to not be efficacious. In addition, the profession has disregarded much of the research that shows many recommended storage media damaging to avulsed teeth. This article reviews the pertinent research on avulsed teeth and recommends a new treatment philosophy of avulsed teeth that delineates 10 treatment categories based on the type of storage medium used, the length of extraoral time, and the stage of development of the root apex.

Air↗

PubMed1996

An evaluation of root resorption incident to orthodontic intrusion.

A new radiographic method was developed for measuring changes in root length. With this technique, orthodontic intrusion was investigated as a potential cause of apical root resorption of maxillary incisors. The experimental group consisted of 17 patients with excessive overbite who were treated with a Burstone-type intrusion arch, which delivered a low level of force (about 15 gm per tooth). A control group was made up of 17 patients in full-arch fixed appliances who were randomly selected. After a period of approximately 4 months, the intrusion group had only slightly more root resorption than the controls, 0.6 mm versus 0.2 mm (statistically significant difference). Intrusion measured at the center of resistance of the central incisor averaged 1.9 mm. The amount of resorption was not correlated with the amount of intrusion. A weak correlation, r = 0.45, was found between resorption and movement of the apex (i.e., in addition to intrusion, there was often palatal root movement). Results of this study seem to indicate that intrusion with low forces can be effective in reducing overbite while causing only a negligible amount of apical root resorption.

Adolescent↗

PubMed2002

Nonlinear stress-strain behavior of periodontal ligament under orthodontic loading.

Previous studies of the periodontal ligament (PDL) have applied high forces to the dental units to examine the stress-strain behavior of this soft tissue. In this study, cadaveric specimens of mandibular premolars from 2 young adult and 2 elderly adult donors were tested to determine the biomechanical behavior of the PDL over an orthodontic force range. Transverse specimens were prepared from 9 premolars and subjected to loading in intrusion and extrusion. Stress-strain curves for both loading directions had distinct toe and linear regions, demonstrating nonlinear behavior of the PDL. The average linear shear modulus was higher for intrusion than for extrusion. The toe extrusive modulus was higher for the young group, and extrusive toe size was larger for the elderly group. In extrusion, the average modulus was higher for the cervical margin and the apex regions than for the midroot regions. The size of the toe region was smaller for intrusion than extrusion. The results indicate age-dependent, location-dependent, and load-direction-dependent nonlinear properties of the human PDL and suggest that analytical computer simulations of orthodontic tooth movements might benefit from incorporating the nonlinear material properties of the PDL.

Adult↗

PubMed1994

Power density and external temperature of laser-treated root canals.

The purpose of this study was to determine the power and time parameters for an argon laser that would result in the removal of pulpal tissue without excessively elevating the external temperature of the root. External temperatures were measured by attaching thermistors to the surfaces of the teeth at the cemento-enamel junction (CEJ) areas and at the root apices. Results indicate that a 1-W power setting with a pulse duration of 0.1 sec and a 1 sec interval between pulses produced a mean temperature rise of 0.89 +/- 0.27 degrees C at the cemento-enamel junction area and a mean temperature increase of 2.04 +/- 0.47 degrees C at the apex. A 2-W power setting with a 0.1 sec pulse duration and a 1 sec interval between pulses resulted in a mean temperature increase of 1.58 +/- 0.45 degrees C at the CEJ and a mean temperature rise of 2.59 +/- 0.20 degrees C at the apex. Based upon the results of this study, it was concluded that an argon laser operating at 1 or 2 W of power with a 0.1 sec pulse duration could be used to remove pulpal tissue without creating an excessive increase in the external temperature of the tooth.

Dentin↗

PubMed1986

Gingival and alveolar bone reaction to marginal fit of subgingival crown margins.

Interproximal subgingival marginal discrepancies of full coverage restorations were compared with adjacent crevicular fluid flow and percentage radiographic periodontal bone loss. A total of 88 patients with 116 premolar crowns were evaluated. Patients were selected at random from student treatment records, Institute of Dental Prosthetics, Royal Dental College, Copenhagen, Denmark. Crevicular fluid collected on filter paper strips from the interproximal area was stained with 0.2% ninhydrin solution and the length of the area measured. Marginal fit was determined by measuring the marginal excess or deficit recorded in a polyether impression. The amount of bone around each crowned tooth was measured on five times magnified prints of radiographs. Percentage bone loss was calculated by dividing the distance from the alveolar crest to the most coronal level at which the periodontal space retained its normal width by the distance from the alveolar crest to the root apex. Correlating marginal fit with crevicular fluid within gingival index scores showed r = 0.32 (G.I.1) and r = 0.42 (G.I.2). Fit vs percentage bone loss showed r = 0.68 and r = 0.59, respectively (P less than or equal to 0.001). Differentiation was further made within the 0.0-0.2 mm range discrepancy by categorizing the data in four groups. Comparing fit relative to crevicular fluid and bone loss, most of these groups were significantly different when analyzed statistically using the Mann-Whitney U-Test. Small defects less than or equal to 0.050 mm were associated with significantly less fluid flow and bone loss than defects exceeding this value.

Age Factors↗

PubMed2000

Alveolar bone resorption and the center of resistance modification (3-D analysis by means of the finite element method).

The main goal of this research was to study the behavior of initial tooth displacements associated with alveolar bone loss situations when loaded by a force of 1 N. The analysis of displacements was carried out by the finite element method. Six 3-dimensional models of an upper central incisor (designated Geramy 391 to 396) with 1 to 8 mm of alveolar bone loss were formulated and used by the author. Center of rotation and center of resistance were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement toward the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted toward the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes center of resistance changes as a result of the alterations in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.

Adolescent↗

PubMed2006

Vital pulp therapy of mandibular incisors: a case report with 11-year follow up.

This report describes a case of a young patient in whom all the mandibular incisor teeth suffered complicated crown fractures because of a car accident. For all mandibular incisors, pulpotomy with calcium hydroxide were performed in order to achieve apexogenesis and the teeth were restored with a double-seal of glass ionomer cement and composite resin. The patient was reviewed over 11 years. All the mandibular incisor teeth showed continued root development and complete apex formation. Pulp canal obliteration was observed in only the mandibular right central incisor.

Accidents, Traffic↗

PubMedDate not supplied

[Endodontic treatment of a periapical lesion causing root separation].

A case is presented of a periapical lesion of a rather large size, which produced an important separation of two inferior incisor roots. The root canal was treated, with calcium hydroxide overextending the apex. Clinic and radiographic control after two years complete reparation of the periapex.

Adult↗

PubMed2006

Three-dimensional finite element analysis of strain and stress distributions in endodontically treated maxillary central incisors restored with different post, core and crown materials.

OBJECTIVES: The present comparative analysis aimed at evaluating which combination of restorative materials resulted in the most homogeneous stress and strain distributions. METHODS: A three-dimensional finite element analysis was performed. All the nodes on the external surface of the root were constrained in all directions. Eighteen experimental models with different material properties and configurations were simulated. An arbitrary load of 10N was applied at 60 degrees angle with tooth longitudinal axis on the palatal surface of the crown. Von Mises (equivalent stresses) energetic criterion was chosen. RESULTS: In all the models the values of both strain and stress recorded at the middle third of the buccal aspect of the root surface were at their maxima. On the contrary, the minimum values were noticed at level of both the apical portion of the post and the root apex. The maximum stresses were evidenced at level of the cemento-enamel junction (CEJ) on both the buccal and palatal aspects of root cement and dentin. Stress progressively decreased from the outer to the inner part of the root and from the CEJ towards the incisal margin of the crown as well. SIGNIFICANCE: The results of the present study would allow clinicians to make an informed choice from among available materials to restore endodontically treated teeth.

Cementation↗

PubMed1985

Endodontic therapy on an African lion (Panthera leo).

The endodontic therapy used on an African lion was similar to procedures performed on humans and other exotic animals with the same condition. The procedure involved removal of the pulpal tissue to the apex of the root in three canine teeth. The internal aspect of the root canal was sterilized and filled with a rubber-like material (gutta percha) which was cemented in place. Chrome cobalt alloy crowns were fabricated and cemented to the top two canine teeth. The lower canine tooth received a silver amalgam restoration.

Animals↗

PubMed1991

A clinical evaluation of the Endocater--an electronic apex locator.

The purpose of this study was to evaluate the accuracy of an electronic apex locator, the Endocater, in determining the location of the apical constriction or cementodentinal junction (CDJ). Measurements made by the Endocater were also compared with the adjustments recommended by an experienced endodontist. A total of 69 teeth with 99 canals from nine patients were evaluated. The results indicated that the evaluator was 95.8% and the Endocater 67.7% accurate in positioning the probe within +/- 1.000 mm from the CDJ. Thirty-three canals or 34.4% appeared to be clinically acceptable radiographically and no adjustments were deemed necessary by the evaluator. There was a significant difference (p less than 0.003) between the evaluator's ability to adjust the electronically generated file length radiograph to acceptable clinical standards and the Endocater's ability to determine the location of the CDJ. A total of 59 canals (59.6%) of the electronically determined working lengths were beyond the CDJ (n = 99). In 27 canals, the tip of the probe was greater than 1 mm beyond the constriction. Without radiographs to confirm working lengths, many canals in this study would have been overinstrumented. Future research with electronic apex locators is needed before accepting the technique as a substitution for radiographic working length determination.

Dental Pulp Cavity↗

PubMed1998

Lateral condensation in treatment of pulpitis and pulp gangrene: studies on dog canine teeth.

The clinical investigation, carried out in dogs, comprises selected cases of chronic pulpitis and pulpal gangrene of canine teeth resulting from injuries. A group of 20 teeth (group 1) underwent extirpation of pulp, as well as elaboration of a root canal and its filling with Endomethasone paste, under general anaesthesia during a one-stage procedure. The second group of 20 teeth differed from the first in an additional concentration of the paste, due to an introduction of gutta-percha points (lateral condensation). This sealing modification proved to diminish the risk of leaving empty spaces after pulp removal in the pulpitis state. However, in teeth where gangrenous pulp extirpation was performed, lateral condensation was endangered by pushing the paste through beyond the apex. Both anomalies were likely to predispose to the development of apical periodontitis.

Animals↗

PubMed2004

Wedged cervical lesions produced by toothbrushing.

PURPOSE: To compare the morphology of experimentally induced cervical toothbrush abrasion lesions to teeth demonstrating non-carious cervical lesions in vivo. METHODS: Eighteen premolars extracted for orthodontic reasons were each subjected to 80 hours (1.4 million strokes) of horizontal brushing in a custom fabricated toothbrushing machine. Toothpaste slurry was applied continuously and specimens were subjected to 300 gms of toothbrushing force. Denture base resin was used to simulate gingival recession of 1 mm and a sulcus width of 0.1 mm. Cervical abrasions were analyzed by optical and scanning electron microscopy and classified as either V-shape/wedged vs. U-shape/rounded lesions. When lesions exhibited both shapes, they were classified as mixed. Shapes of experimentally induced lesions then were compared to naturally occurring ones found on extracted premolars. RESULTSts: Experimentally induced toothbrush abrasion duplicated the classical clinical shapes. Half (9/18) of the experimentally induced toothbrush abrasions exhibited wedged lesions, 28% (5/18) showed a mixed wedged/rounded lesion, and 22% (4/18) showed rounded lesions. Serial photography showed progression of the morphology of the lesions. Toothbrush abrasion apparently begins apical to the cemento-enamel junction, progresses to dentin, and then undermines enamel with loss of the original cemento-enamel junction. Wedged lesions may appear with the apex oriented coronal or apical, or may be symmetrical.

Bicuspid↗