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At least 919 records · Page 51Linked to original sources

PubMed2003

Surgical extraction of a fractured, non-vital deciduous tooth in a tiger.

A 10-month-old, female/intact tiger (Panthra tigris) was presented for a fractured deciduous mandibular right canine tooth, mandibular swelling, and a cutaneous draining tract ventral to the apex of the fractured tooth. The tooth had chronic pulpal exposure and was considered non-vital with periapical osteomyelitis. This case report describes treatment to optimize normal development and eruption of the permanent mandibular right canine tooth.

Animals↗

PubMed2005

Three-dimensional finite element analysis of stress in the periodontium.

The aim of this study is to calculate the stress produced in the periodontium at different bone levels under occlusal load. Four finite element models of maxillary incisors were designed consisting of the tooth, pulp, periodontal ligament and alveolar bone at various levels of bone height (25%, 50% and 75%). An occlusal load of 24 kg at an angle of 50 degrees to the long axis of the tooth was applied on the palatal surface, at the level of the middle third of the crown. All the models were assumed to be isotropic, linear and elastic and the analysis was performed on a Pentium IV computer using the NISA II Display III software. The results showed that maximum stress in the tooth was seen at the cervical region and to a greater extent at the apex for all the models. In periodontal ligament, maximum stress was seen at the alveolar crest in models with normal alveolar bone height and with reducing alveolar bone height maximum stress was at the apex. There was no significant stress distribution in alveolar bone, while no stress was seen on the pulp. The results of the study demonstrated a significant increase in stress concentration at the apex with loss of alveolar bone height.

Alveolar Process↗

PubMed2003

Microtensile bond strength between adhesive cements and root canal dentin.

OBJECTIVES: The hypotheses tested were that the bond strength of adhesive cements to root canal dentin (1) would be reduced as a function of configuration factor, polymerization process and type of luting material and (2) would be lowered near the apex of the tooth. METHODS: Human canines and premolars were prepared for post cementation using Single Bond/Rely X ARC, ED Primer/Panavia F, C and B Metabond, and Fuji Plus. The specimens were divided into two groups. For intact roots, the posts were luted using standard clinical procedures. For flat roots, the posts were applied directly into flat ground canals. All roots were sectioned into 0.6 mm thick slices, trimmed mesio-distally and stressed to failure at 1 mm/min. The muTBS of each slab was calculated as the force at failure divided by the bonded cross-sectional surface area. The results were compared using a one-way ANOVA and Tukey multiple comparison intervals (alpha=0.05). Least squares linear regression analysis was used to assess the effect of dentin location on bond strength. RESULTS: All cements showed significantly (p</=0.05) lower bond strengths in intact vs. flat roots. The muTBS of posts to intact roots were not significantly different for Single Bond/Rely X ARC and Panavia F, but both were significantly lower (p</=0.05) than the bonds produced by C and B Metabond and Fuji Plus cements. For Single Bond/Rely X ARC and Fuji Plus a significant decrease in bond strength was observed in dentin closer to the apex of the root. SIGNIFICANCE: Stresses from polymerization shrinkage and problems with adequate access to the root canal complicate the formation of high-strength bonds when cementing endodontic posts with resin cements.

Analysis of Variance↗

PubMed1997

Orthodontic-endodontic treatment planning of traumatized teeth.

Occasionally, an orthodontic patient will accidentally traumatize a maxillary anterior tooth before or during orthodontic treatment. In some situations, the trauma will be substantial and avulse the tooth. In other accidents, the tooth may not avulse, but the pulp becomes nonvital. If the pulp is devitalized, and the root has not fully formed, the apex of the root canal may be wide. In this situation, the endodontist may recommend apexification procedures to help close the apex before conventional obturation of the root canal. If the patient is currently undergoing orthodontic movement of the traumatized incisor, what effect will the tooth movement have on the success of the apexification? If the tooth were avulsed, replanted, and then ankylosed, should it be extracted? If so, when should the ankylosed incisor be removed? What effect will further facial growth have on the ankylosed tooth and the potential to achieve a successful esthetic restoration? The answers to these questions are important during the interdisciplinary treatment planning of the patient with traumatized teeth. This article will elucidate the endodontic-orthodontic considerations for patients with traumatized anterior teeth.

Adolescent↗

PubMed1980

Enameloid in the teleost fish Lophius. An ultrastructural study.

The ultrastructural and chemical differences between mature enameloid and dentine in the teleost fish Lophius were demonstrated using transmission (TEM) and scanning (SEM) electron microscopy, X-ray diffraction analysis, electron diffraction analysis and electron microprobe analysis. An enameloid cap (about 50 micron thick) and a thin layer (1 micron thick) of collar enameloid were revealed in the scanning (SEM) and transmission (TEM) electron microscopes. Collar enameloid, structurally different from dentine both in SEM and TEM, proved to be less mineralized than the cap as revealed by electron microprobe analysis. The enameloid cap was seen to differ from dentine by (i) its electron density in TEM; (ii) the structural arrangement perpendicular to the underlying dentine, observed in SEM and TEM and corroborated by electron diffraction data, which showed a preferred orientation of enameloid crystallites; (iii) its higher F content decreasing gradually from the apex of the tooth to the junction with dentine and falling suddenly below this junction; and (iv) its lower Mg content. Establishment of a classification of enameloids is proposed, similar to that for dentines, in which selachian enameloid would be a reference standard.

Animals↗

PubMed1990

Post preparation techniques and their effect on the apical seal.

It is accepted clinical procedure to extend post preparations to such a depth that 3 mm to 5 mm of gutta-percha remains at the apex of the tooth. Clinicians use numerous techniques to achieve this goal. This investigation quantitatively analyzed the effect of the method of gutta-percha removal on the apical seal and evaluated apical leakage in teeth with different levels of remaining gutta-percha. The methods evaluated included the GPX instrument, heated pluggers, and Gates-Glidden drills. Groups of 25 extracted teeth were prepared with each of the three methods leaving 3 mm or 5 mm of gutta-percha remaining apically. Spectrophotometry (optical density) was used to assess apical leakage. Significantly less leakage was observed with the heated plugger technique at the 3 mm and 5 mm levels when compared to the 3 mm and 5 mm levels in both the GPX and Gates-Glidden groups.

Analysis of Variance↗

PubMed1983

Spontaneous expulsion of a retrograde filling. Report of a case.

The placement of a retrograde filling is designed to seal the apex of a tooth when conventional procedures have either failed or cannot be performed. This case report describes the mechanical failure of this procedure, as well as the expulsion of the filling material from the oral cavity.

Adult↗

PubMed1987

Radiographic reproduction of endodontic "working length" comparing the paralleling and the bisecting-angle techniques.

The reproduction of a metal indicator simulating a root canal instrument at the apex of a tooth was examined as a function of paralleling, modified paralleling, and bisecting-angle radiographic techniques. Radiographs exposed according to the paralleling and modified paralleling principles demonstrated good correlation between the radiographic position of the metal indicator and its position on direct inspection. The bisecting-angle technique, either correctly or incorrectly angulated, produced the least accurate results. The apical location of the metal indicator was significantly more reliable with the paralleling principle than with the bisecting-angle technique (p less than 0.05).

Equipment Design↗

PubMed2005

Light microscopic study of periapical lesions associated with asymptomatic apical periodontitis.

The purpose of the study has been to evaluate the degree of chronic inflammation in tissues surrounding the apex of the tooth root in patients with apical periodontitis in the remission phase. The material included 37 apical granulomas and radicular cysts obtained as a result of apiectomy, and 20 teeth which were removed together with the focus of the periapical inflammation. Routine histological techniques, as well as the immunofluorescent and immuno-chemical methods were used to examine the material. Despite the absence of clinical symptoms in 23 of 57 cases, the morphological signs of chronic inflammation were observed in the apical area of the tooth root. Morphological signs of viral invasion of epithelial and stromal cells in the radicular cyst wall were revealed in six cases. The presence of the virus of Herpes simplex I in epithelial cells (five cases) and adenoviral invasion (one case) was confirmed by immuno-fluorescent and immuno-chemical methods. Histological examination often reveals morphological signs of an active inflammatory process in the periapical tissues of patients treated during clinical remission. In our opinion, the presence of viruses in the epithelial cells of the radicular cyst may contribute to the persistence of the active stage of the inflammatory process.

Adult↗

PubMed1992

The mental foramen: 3. Size and position on panoramic radiographs.

Panoramic radiographs were made of 75 dry, adult human mandibles. The size and position of the mental foramen in relation to the second premolar was determined. The mental foramen on panographic radiographs was slightly larger than reported on periapical radiographs. The average position of the foramen was mesial and below the radiographic apex of the tooth. Panoramic radiography may account for a distal shift of the foramen and a 23% increase in size of the mandibles examined.

Bicuspid↗

PubMed1999

Effects of alternating and direct electrical current application on the odontoblastic layer in human teeth: an in vitro study.

AIM: The aim of this study was to investigate the influence of a low intensity alternating current on the odontoblasts and odontoblast layer and compare this with the effects of a direct current. METHODOLOGY: Teeth extracted for orthodontic reasons were immersed in physiological saline stabilized with thymol crystals. Within 1 h of extraction, an alternating or direct current was applied on the crown in the direction of the apex of the tooth for 120-360 s. The current doses were 12, 30, 60, 600, 1800, 3600, 7200, 24,000 and 144,000 microC. The teeth were fixed in Bouin or Baker fluids, the pulps removed, dehydrated and immersed in paraffin, then sectioned, stained with haematoxylin and eosin, and studied under a light microscope. RESULTS: Neither direct nor alternating current, similar to that applied in electrical caries diagnosis caused histological changes in the odontoblasts. CONCLUSIONS: There was no difference between direct and low intensity alternating current in the response of the odontoblast.

Adolescent↗

PubMed2002

The contribution of trabecular bone to the visibility of the lamina dura: an in vitro radiographic study.

OBJECTIVE: The objective of this study was to determine the degree to which trabecular bone contributes to the radiographic visibility of lamina dura. STUDY DESIGN: Segments of human cadaver mandible were obtained and split longitudinally. Two identical radiographs were made of each segment (1) before the removal of any additional bone and after (2) the removal of a small amount of the lamina dura at the apex of a tooth, (3) block removal of trabecular bone, and (4) smoothing of the endosteal surface of the external cortex. The radiographs were projected in random pairs for each sample. Six dentists judged whether a difference in the amount of lamina dura could be detected between 2 sets of radiographs. RESULTS: Chi-square analysis revealed a significant radiographic difference between radiographs made initially and after removal of the lamina dura and trabecular bone. CONCLUSIONS: Fewer than half of the changes of lamina dura loss alone could be detected radiographically by the observing dentists, whereas nearly all cases of the loss of periapical lamina dura in conjunction with loss of trabecular bone could be detected.

Aged↗

PubMed2002

In vitro measurement accuracy of an electronic apex locator in teeth with simulated apical root resorption.

The purpose of this in vitro study was to evaluate the accuracy of Root ZX apex locator to determine the working length in teeth with simulated apical root resorption. Fifty extracted, single-rooted, human teeth with mature apices were used in this study. An irregular cavity defect was drilled at the apex of each tooth simulating an apical root resorption. Three operators used the Root ZX to measure the working lengths, comparing the electronic readings with the direct visual measurements. The Root ZX was 62.7%, 94.0%, and 100.0% accurate to within 0.5 mm, 1 mm, and 1.5 mm of the direct visual measurements, respectively. Statistically significant differences were observed between operator A and B and A and C (p < 0.01), but no significant differences were detected between operator B and C (p > 0.01).

Dental Pulp Cavity↗

PubMed1989

The heat generated on the external root surface during post space preparation.

The heat generated on the external root surface of human premolar teeth during post space preparation was measured in vitro. The rise in temperature was recorded at a point 6 mm from the apex of the tooth using a thermocouple attached to a chart recorder. The temperature rise was greatest when the removal of gutta-percha was combined with post channel preparation. Temperature rises of up to 31 degrees C were recorded. Instruments that only removed gutta-percha did not generate the same amount of heat. The results from this study suggest that the use of engine-driven drills to prepare post channels in teeth may generate temperature rises that may cause periradicular tissue damage, and caution should be exercised during their use.

Crowns↗

PubMed2004

The impact of image compression on diagnostic quality of digital images for detection of chemically-induced periapical lesions.

OBJECTIVES: To test the hypothesis that there is no significant difference in the detectability of chemically-induced periapical lesions between a non-compressed image and one subjected to a Joint Photographic Experts Group (JPEG) lossy compression technique at a ratio of 23:1 or less. METHOD: Chemically-induced periapical lesions were created by placing a solution of 70% perchloric acid at the apex of extracted teeth in 13 human jaw cadaver specimens. Acid was applied in seven incremental time periods from 0-32 h. Extracted teeth were replaced in the socket and images were made using the Schick CDR digital sensor. Using a JPEG lossy compression algorithm, five compression ratios of 2:1, 14:1, 23:1, 28:1 and 47:1 were applied to the images. Images were viewed three times by three observers who ranked the presence or absence of a lesion at three sites, the mesial area, distal area and apex of the tooth, on a 5-point confidence scale. Intraobserver and interobserver agreement and agreement between the compressed and the original images were assessed with intraclass correlation coefficients (ICCs). RESULTS: Overall ICCs for measuring intraobserver agreement using all images were 0.77, 0.84, and 0.50 for the three observers, respectively. The overall ICC for assessing agreement between observers was 0.57. There was no significant difference (P>0.05) between compressed and original images for any site at compression ratios of 2:1, 23:1 and 28:1. There were significant differences for a compression ratio of 47:1. CONCLUSION: JPEG compression does not impact detectability of artificial periapical lesions at low and moderate compression ratios up to and including 28:1.

Algorithms↗

PubMed2004

Clinical significance of the structural integrity of the superior aspect of the mandibular canal.

BACKGROUND: Sparse data can be found regarding the structural integrity of the superior aspect of the mandibular canal. In many cases, the mandibular canal must be carefully evaluated prior to defining patient treatment. METHODS: In this case report, a 54-year-old patient presented with a periapical infection involving the mesial root of the mandibular right second molar (#31). Radiographic evaluation revealed that the periapical lesion extended from the apex of the tooth to the superior aspect of the mandibular canal. Upon surgical removal of the tooth, an apical communication between the extraction socket and mandibular nerve was located. A guided bone regeneration procedure was performed to protect the nerve from subsequent damage and to prepare the site for future implant placement. Implants were placed in the area approximately 5 months following the regenerative procedure. RESULTS: After implant placement, the patient experienced normal function and no mandibular symptomatology. Implants have been in function for the past 4 years. CONCLUSIONS: Many factors, both pathologic and developmental, can lead to a discontinuity of the superior aspect of the mandibular canal. Normally, a thin cortical plate of bone protects the nerve. When a lack of structural integrity of the canal roof is discovered, enucleation of a periapical infection or subsequent implant placement can lead to potential disruption of the nerve. Limited information is available regarding the integrity of this protective cover. This case report underscores the importance of proper clinical diagnosis before implant placement in the posterior mandible.

Bone Regeneration↗

PubMed1980

Sensory differences between crown and root dentin in human teeth.

Earlier ultrastructural investigations of human teeth have revealed differences in the innervation between crown and root dentin. In the present investigation, an intradental comparison of human teeth was made to estimate the sensitivity to different stimuli applied to two cavities, one in the buccal cusp and the other half-way between the cervix and the apex of the tooth. It was found that the pain produced by the different stimuli in the cuspal cavity was described as "sharp" or shooting, while the same stimuli applied to the root cavity provoked "dull" pain, often of a longer duration. Gentle stimuli, such as dry absorbent paper, only produced pain in the cuspal cavities. Ultrastructural examination revealed no nervous elements in the vicinity of the ground surface of the tested cavities in the crown or in the root. Odontoblastic cells including nuclei, were a common finding in the dentinal tubules of both the roots and the cusps, indicating aspiration of these cells. In some cases, in the cuspal areas, accompanying nerve-fibres had also been aspirated. The conclusion of the present investigation is that there are differences in sensibility between crown and root dentin. These differences are observed in both intensity and modality, supporting earlier findings of morphological discrepancies in the innervation of the coronal and root dentin.

Adolescent↗

PubMed1992

Dentinogenesis and the calciotraumatic response to the injection of lead or fluoride ions.

A number of ions can disturb the formation of dentine resulting in a calciotraumatic response. The calciotraumatic response following the injection of sodium fluoride was investigated using backscattered electron imaging in the scanning electron microscope and compared with the response to lead acetate. With fluoride, there was formation of a hypermineralized band succeeded by a relatively hypomineralized band, but with lead acetate, only a hypomineralized band was produced. However, there were some differences in the response between the labial and lingual dentine with both ions. In the labial dentine following injection of sodium fluoride, the onset of hypermineralization was less abrupt than in the lingual dentine. Furthermore, the transition from hypermineralization to relative hypomineralization was more abrupt in the labial dentine. Sometimes there was an increased thickness of labial dentine between the hypermineralized layers towards the apex of the tooth and this dentine was less homogeneously mineralized. Normal incremental lines were occasionally seen both labially and lingually. Lead acetate produced a more severe disruption of dentine formation labially than lingually. These differences in response may be related to the pattern of mineralization labially and lingually and to the systemic effects following the injection of sodium fluoride.

Animals↗