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At least 1,099 records · Page 61Linked to original sources
PubMed1993

Alteration of nerve growth factor-receptor expression in the periodontal ligament of the rat during experimental tooth movement.

This pilot study deals with the initial responses of neural elements showing nerve growth factor-receptor (NGFR) immunoreactivity in the periodontal ligament of rats to orthodontic forces. The animals were killed at intervals of 1, 2, 6, 12 h and 1, 3, 5, 7 days after the insertion of elastic bands between the maxillary first and second molars. Serial frozen sections, prepared from each animal, were processed immunohistochemically to demonstrate NGFR, after which the periodontal ligament of the mesial root of the maxillary second molar was examined microscopically. In control sections, NGFR-positive neural elements were predominantly distributed at the apex of the bony socket on the distal side of the periodontal ligament. After 1 h of tooth movement, NGFR positively-stained nerve fibres tended to disappear slightly in both the intermediate and coronal regions of the distal periodontal ligament. By the third day of tooth movement, the periodontal ligament nerve fibres showed more intense NGFR-immunoreactivity; thick, positively stained nerve fibres were recognized on the distal side in which active bone remodelling was occurring, and a few of these fibres were densely distributed around blood vessels or near Howship's lacunae. The distribution of NGFR-positive neural elements on the mesial side increased at 5 days of tooth movement. Finally, at 7 days of tooth movement, staining intensity for NGFR appeared to decrease. These findings demonstrate that an alteration in the distribution and the intensity of immunoreactive staining for NGFR in the periodontal ligament is associated with the bone remodelling induced by orthodontic tooth movement.

Animals↗
PubMed1984

Endodontic treatment of a cementoblastoma.

The benign cementoblastoma (true cementoma, osteoblastoma, giant osteoid osteoma) appears to be a true neoplasm of functional cementoblasts which proliferate at the apex of teeth to form an expansile tumor. It remains intimately attached to the tooth roots and occasionally involves the root canals themselves. Although the pulpal tissue remains vital, treatment has historically consisted of extraction of the involved tooth along with extirpation of the tumor. This mode of therapy for the benign cementoblastoma should not be confused with the entity called periapical cemental dysplasia (that is cementoma, periapical osteofibroma or osteofibrosis, cementifying fibroma, localized fibro-osteoma, and periapical fibrous dysplasia). In this latter lesion the treatment consists of simply recognizing the condition and establishing a schedule for periodic evaluation of the patient. In the case presented here enucleation of the cementoblastoma and endodontic therapy were selected as treatment modalities, despite the presence of buccal and lingual expansion of the cortical plates. There has been no recurrence of this growth during the 4-year follow-up period.

Adult↗
PubMed1999

Analysis of stress in the periodontium of the maxillary first molar with a three-dimensional finite element model.

The aim of this study was to simulate the stress response in the periodontium of the maxillary first molar to different moment to force ratios, and to determine the moment to force ratio for translational movement of the tooth by means of the finite element method. The three-dimensional finite element model of the maxillary first molar consisted of 3097 nodes and 2521 isoparametric eight-node solid elements. The model was designed to dissect the periodontal ligament, root, and alveolar bone separately. The results demonstrate the sensitivity of the periodontium to load changes. The stress pattern in the periodontal ligament for a distalizing force without counterbalancing moments showed high concentration at the cervical level of the distobuccal root due to tipping and rotation of the tooth. After various counterrotation as well as countertipping moments were applied, an even distribution of low compression on the distal side of the periodontal ligament was obtained at a countertipping moment to force ratio of 9:1 and a counterrotation moment to force ratio of 5:1. This lower and uniform stress in the periodontal ligament implies that a translational tooth movement may be achieved. Furthermore, high stress concentration was observed on the root surface at the furcation level in contrast with anterior teeth reported to display high concentration at the apex. This result may suggest that the root morphology of the maxillary first molar makes it less susceptible to apical root resorption relative to anterior teeth during tooth movement. The stress patterns in the periodontal ligament corresponded with the load types; those on the root appeared to be highly affected by bending and the high stiffness of the root.

Alveolar Process↗
PubMed1994

An in vitro test of a simplified model to demonstrate the operation of electronic root canal measuring devices.

This article describes an in vitro test of the accuracy of a model for demonstrating the operation of electronic canal length measuring devices (ECLMDs). The model is made from commercially available gelatin which is mixed with sterile saline solution. Extracted human canine and anterior teeth with fully formed apices had access preparations and complete pulpectomies before drying the canals with paper points. The tooth length was determined with an Exact-A-Pex using the gelatin test model. When the apex locator green light-emitting diode indicated 1.5 mm from the apex, the file length to the nearest 0.5 mm was measured with a rubber stop. This length was compared with the length determined by visualization of the tip of a #10 K-Flex file at the foramen. This method was repeated with the Foramatron IV using the instrument's digital reading of zero as the apex location and root canal length. There was complete agreement as to canal length between electronic root canal measuring devices and visual observations. This indicates that the gelatin test model is an accurate in vitro method of determining canal length.

Cuspid↗
PubMed1990

[Finite element analysis on physiological mobility of individual teeth].

The initial movement of the tooth was investigated by the finite element method. The mechanical properties of the periodontal membrane were estimated from the results of the simulation. The analysis was made by using an 8 point isoparametric finite element method. The upper central incisor with an axial directional load was simulated. The concept of the apparent elastic modulus was introduced to the stress-strain relation of the soft tissue, that is, soft tissue such as the periodontal membrane and the gingiva was considered to have stress dependent elastic moduli. At the first stage of the simulation, the stress and strain distributions in the paradentium were calculated by the conventional method. From the next stage, the apparent elastic moduli for the soft tissue were introduced to the calculation, that is, the elastic moduli for the soft tissue were computed from the calculated equivalent stresses of the previous stage. The calculations were repeated until the displacement values converged. The initial displacement of the tooth was not proportional to the applied load but showed a non-linear relationship. The relationship between load and displacement was approxiated by the n-th power equation. These results were in agreement with the clinical experimental results. The periodontal membrane is built up of different elastic moduli. The elastic moduli were low at the alveolar edge and the root apex. The equivalent stresses of the periodontal membrane were marked low in the alveolar edge and the root apex. In conclusion, the concept of the apparent elastic modulus is useful to investigate the initial movement of the tooth and estimate the mechanical properties of the periodontal membrane.

Computer Simulation↗
PubMed1997

Development of the computerized dental cast form analyzing system--three dimensional diagnosis of dental arch form and the investigation of measuring condition.

To analyze the functional and morphological harmonies of the tooth and dental arch, a computerized system to measure a dental cast and to detect the apex of dental cusps and angle points of incisors was developed. Detailed morphology in the measured dental cast could be displayed distinctively by computer graphics (CG) with a surface model. Accuracy in determining the position of the apex of the dental cusp was examined by increasing the measuring pitch from 50 microns to 400 microns, the error increased gradually with increased measuring pitch. Taking the measuring error, the time for measurement and the memory size for analysis into account, a measuring pitch of 200 microns was determined to be reasonable. Three-dimensional data measurements from the apex of the dental cusp in molar, and the mesial and distal angles in canine and incisor were fitted to a polynomial formula. In the present measured model, the 4th order polynomial formula was used for the dental arch, and the 2nd order polynomial formula was used for the anteroposterior and lateral occlusal curves. These formulae could be simultaneously superimposed on the surface model of the dental cast, and displayed using CG.

Computer Graphics↗
PubMed1985

Accuracy of tooth length measurements from periapical radiographs.

This study was undertaken to investigate and assess two radiographic techniques for measuring tooth length. The result of this study demonstrated the inadequacy of determining tooth lengths using radiographs alone without the introduction of instruments into the canal as close as possible to the root apex. Neither of the techniques proved ideal, however, the Paralleling Extension Tube Technique seemed relatively more accurate and reliable than the Bisecting-Angle Technique.

Adult↗
PubMed1987

Pulp re-innervation in re-implanted canine teeth of the cat.

This was investigated 24 weeks post-operatively by light and electron microscopy. The number of axons in the pulp at the root apex ranged from 7.5 to 76.2 per cent of the number in the contralateral control tooth. The myelinated fibres were smaller and did not penetrate as far as the coronal pulp.

Animals↗
PubMed1981

Endodontic treatment of teeth with periapical radiolucent areas in a general dental practice.

Clinical details of 192 teeth with preoperative periapical radiolucent areas, treated endodontically, are described. The presenting signs and symptoms as well as some postoperative observations are listed. Periapical radiolucent areas were most frequently found related to maxillary teeth: 55 percent were adjacent to teeth with a single root canal and 30 percent related to teeth with three root canals. Radiographic follow-up 1 or more years after therapy was possible in 125 of the root-filled teeth: of those teeth, 59 percent shows disappearance of the radiolucent area and 29 percent exhibited a decrease in size of the area. The degree of success did not appear to be related to the number of root canals filled per tooth but, rather, to whether or not the root filling was short of the radiographic apex. In addition, the prognosis made at the time of root filling was accurate in most cases when compared to the estimated success rates.

Adolescent↗
PubMed1995

Neural elements in dental pulp and dentin.

This article addresses the structural and quantitative aspects of human tooth innervation and briefly considers the functions and clinical relevance of tooth axons. The classification of peripheral axons, the pulpal and dentinal innervation, and the theories of dentin sensitivity are discussed. Quantitative studies on tooth innervation are also reviewed. Human premolars receive about 2300 axons at the root-apex of which about 13% are myelinated and 87% are nonmyelinated fibers. Most apical myelinated axons are fast-conducting A delta-fibers with their receptive fields located at the pulpal periphery and inner dentin. These fibers are probably activated by a hydrodynamic mechanism and conduct impulses that are perceived as a short well-localized sharp pain. Most C-fibers are slow-conducting fine sensory afferents with their receptive fields located in the pulp and transmit impulses that are experienced as dull poorly localized and lingering pain. In addition to the nociceptive alarm signaling, the intradental sensory axons may play a regulatory role in the maintenance and repair of the pulpodentinal complex.

Animals↗
PubMed1996

Differential distribution of lumican and fibromodulin in tooth cementum.

The objectives of this study were to isolate and characterize the major proteoglycans of tooth cementum in relation to the tissue's mineralization. Cementum was collected from the root apex region of bovine molars and pulverized. It was first extracted with 6M guanidine-HCI, pH 7.4 (G-extract, mineral-unassociated) and then demineralized and extracted with 0.5M EDTA (E-extract, mineral-associated). Both extracts were applied to anion exchange and then molecular sieve chromatography to isolate proteoglycans. The fractions collected were assayed for chondroitin-(CS) and keratan sulfate (KS) containing proteoglycans using the monoclonal antibodies 2-B-6 and 5-D-4, respectively. It was found that the KS was the major glycosaminoglycan and was enriched in the G-extract fraction. The major KS fraction was then applied to 7.5% SDS-PAGE. The major broad band (69 kDa) was 5-D-4 positive in Western blot analysis and separated into two bands (46 kDa and 50 kDa) after treatment with keratanase II and endo-beta-galactosidase. These two proteins were transfered to PVDF membrane and analyzed for amino acid sequence. The results showed the major band (46 kDa) to be lumican and the minor (50 kDa) fibromodulin. In addition, based on the immunohistochemical study using a number of mono- and polyclonal antibodies including 5-D-4, anti-lumican core protein as well as anti-fibromodulin core protein antibodies, the KSPGs were found to be located almost exclusively in nonmineralized portions of cementum such as precementum and the pericementocyte area. These biochemical as well as immunohistochemical data suggest that the major KSPGs of cementum, lumican and fibromodulin, have a specific tissue distribution and may have regulatory roles in cementum mineralization.

Amino Acid Sequence↗
PubMedDate not supplied

[The treatment of periodontitis with prolonged-action propolis preparations (clinical x-ray research)].

A 4% alcohol solution of bee glue is suggested to be added to the filler for root-canal filling, besides the traditional treatment of the root canals with bee glue solution. Clinical and x-ray examinations have demonstrated a high efficacy of such technique in acute, exacerbated, and chronic forms of periodontitis. This filler is characterized by an anesthetizing effect; it resolves behind the root canal apex within 3-12 months, is preserved in the root canals, does not stain the tooth crown, promotes regeneration of the bone structures, and prolongs the effect of 0.4% water-alcohol bee glue emulsion.

Delayed-Action Preparations↗
PubMed1976

[The disposition of the apices of the roots of multirooted teeth in the alveolar processes of the upper jaw].

Specific features of the disposition of root apexes of premolars and molars in the alveolar process of the upper jaw were studied in 148 skulls and 67 tooth-jaw cuts. The least thickness of the alveolar process was found to be at the level of the first premolar (10,41 +/- 0,33 mm), and the greatest--at the level of the first molar (14,075 +/- +/- 0,456 mm). Strong correlation of the alveolar process was established between the levels of the premolars and the last two molars. The distance from the apexes of cheek roots of the first molar to the bottom of the maxillary sinus is 2,05--2,92 mm, and the palatal roots -- 2,02 mm. On roentgenograms the molar roots are often projected on the sinus bottom.

Adult↗
PubMed2003

Maxillary incisor impaction and its relationship to canine displacement.

This study aimed to examine the eruption status of unerupted maxillary permanent canines in patients who also had an impacted central incisor. Seventy-five unilateral cases of the incisor anomaly were retrospectively examined. Using the initial panoramic films, we assessed the positions of the ipsilateral and contralateral canines and the lateral incisors and the timing (eruption progress) of the canines. The final position of the canines was evaluated from patient records and progress photographs. The data showed a significant increase in prevalence and severity of displaced canines in the ipsilateral side (41.3%) compared with the contralateral side (4.7%). Palatally displaced canines occurred in 9.5%, buccally displaced canines in 30.2%, and canine-lateral incisor transposition in 1.6% of the patients. Half of the buccally displaced canines in the ipsilateral side were pseudotransposed with the adjacent lateral incisor. The eruption timing of ipsilateral undisplaced canines was either similar or delayed, relative to the contralateral tooth, but never accelerated. The ipsilateral lateral incisor was strongly angulated because of a more distally located apex (5 mm) rather than a mesially tipped crown. The ipsilateral canine was relatively more superiorly positioned (undererupted). Patients who had trauma had a significantly higher prevalence and severity of canine displacement and more distally displaced lateral incisor apices. Initial height of incisor impaction did not influence the results. These data provide evidence of a significant environmental influence of an impacted maxillary central incisor in delaying and altering the eruption path of the ipsilateral maxillary canine.

Adolescent↗