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Biomedical subjects

R E Walton

Publications and source records attributed to R E Walton.

At least 55 records · Page 3Linked to original sources
PubMed1992

Induced periapical lesions in ferret canines: histologic and radiographic evaluation.

Ferrets have been utilized in endodontic research to study periapical responses. However, various aspects of induction and healing of periapical pathosis in ferrets are unclear. This study evaluated the radiographic and histopathologic features of induced periapical lesions. Periapical pathosis was consistently produced in 8 canines of 2 ferrets by extirpating the pulp, leaving the cavities open for a week, then sealing for 12 weeks. The resulting lesions were evaluated radiographically every two weeks. The animals were then killed and the induced lesions evaluated histologically and histobacteriologically. Four untreated canines from 2 other ferrets were used as controls. Results showed that periapical rarefactions were visible in all teeth in the experimental group within 4 weeks. Histologically, the induced lesions consisted principally of a mononuclear inflammatory infiltrate, dominated by macrophages but with numerous lymphocytes. With Brown & Brenn staining, bacteria were demonstrated in the pulp space of teeth in which the lesions were induced and in the apical arborization of the canal system. Only one specimen had bacteria within the periapical lesion.

Animals↗
PubMed1992

Histologic evaluation of three endodontic instrument/preparation techniques.

33 curved canals were prepared to quantify both the increase in canal area and predentin removal in the apical region. Compared were three different file designs/instrumentation techniques, that is "stepback" with K-flex file, "balanced force" with Flex-R file, and the Canal Master system. Following canal preparation and histological processing, cross-sections at 1 and 3 mm levels were examined using the Bioquant image analysis system. Results showed that, at the 3 mm leve, the mean increase in canal area and predentin removal showed no statistically significant difference (p > 0.05) between the techniques. At 1 mm, the step-back technique (with K-flex files) resulted in a significant increase in canal area and greater predentin removal than did the "balanced forces" (with Flex-R files) or the Canal Master system. However, although there were statistical differences, the actual differences were small; these may not translate to clinically significant differences in the 3 techniques.

Dental Cavity Preparation↗
PubMed1992

Managing local anesthesia problems in the endodontic patient.

Root canal therapy has a poor public image related to occasional and sometimes severe pain, and to dentists' inability to obtain profound anesthesia. Patients' apprehension, in combination with tissue inflammation, significantly lowers the pain threshold, which decreases the anesthetic's effectiveness. The best and also the first approach to achieving anesthesia is to administer a conventional block or infiltration. If profound anesthesia does not occur after this attempt, use a supplemental technique such as lingual infiltrations, PDL or intrapulpal injections. Because infiltrations are generally not effective, PDL and intrapulpal injections are preferred. The PDL is better than the intrapulpal injection because it is non-painful, safe and usually effective. The intrapulpal injection is limited and may be uncomfortable. Administer both the PDL and intrapulpal injections under back-pressure to achieve effective, but short-lived anesthesia. Special injection devices (for example, pressure syringes for the PDL) are not required for either technique. Two anesthetic types are useful. Administer 2 percent lidocaine with epinephrine for conventional and supplemental injections. For emergencies and long procedures, administer 0.5 percent bupivacaine with epinephrine to provide effective, long-lasting anesthesia and analgesia.

Anesthesia, Dental↗
PubMed1992

Tooth discoloration resulting from long-term tetracycline therapy: a case report.

Administration of tetracycline to children or pregnant women is known to adversely affect the color of developing teeth. This case report suggests the possibility that discoloration from tetracycline may not be limited to tooth development in the child, but may also affect the adult dentition. When given over long periods of time in adults, the tetracycline molecule is incorporated into the continuously forming secondary dentin. It is possible that chronic sun exposure of the incorporated tetracycline may cause the formation of a reddish-purple oxidation product, resulting in discoloration of the permanent teeth.

Acne Vulgaris↗
PubMed1992

Pulp response to bases and cavity depths.

In cavities of ferret canines, preparation depth and bases were compared as to their effect on odontoblasts and to rate of dentin formation. These were measured by injecting 3H-proline at 0, 20 and 40 days post-preparation. Odontoblast activity was determined by label density in each band; inter-band distances indicated the amount of dentin formed. Correlations were by Pearson's coefficient. The following were determined: 1) cavity depth (remaining dentin thickness) was the major factor in odontoblast response and in dentin formation; deeper cavities suppressed odontoblasts with less subsequent dentin formation at all time periods; 2) basing materials had little effect on odontoblast activity or on the rate of dentin formation. An exception was in deep cavities, with Ca(OH)2 showing more label; this activity was temporary with no increased dentin formation; 3) there was no evidence of a "rebound" response.

Animals↗
PubMed1992

Current concepts of canal preparation.

Canal preparation is a complex procedure, performed with inadequate instruments and chemicals in a restricted environment. With these limitations, it is surprising that the success rate for root canal treatment is good, although not as high as is commonly reported. The preparation of the canal is divided into two actions, cleaning and shaping. Both are quite different and require different criteria for evaluation. Specifically, cleaning is debridement, whereas shaping is preparing the canal for obturation. Cleaning (debridement) depends on straight-line access, and requires the action of both intracanal instruments and irrigants. Files should contact and plane as many walls as possible to loosen debris. This is followed by irrigation, which has the primary function of flushing debris from the canal space. The chemical action of the irrigant is less important, but is an aid in total debridement. Shaping of the canal depends on the obturating material and the condensing instruments. Because gutta-percha is the preferred material, and lateral condensation the most common technique (although not necessarily superior), preparations should be flared. It has been shown that the taper should be sufficient to permit deep penetration of the spreader or plugger alongside the gutta-percha during lateral condensation. Hand instrumentation remains the preferred approach for canal preparation. There are variations including standardized and flaring, with the flaring (or step-back) the most commonly taught and used. The step-back approach encourages a small apical preparation with larger instruments used at successively decreasing lengths to create a taper. An advantage is that this method tends to minimize procedural errors such as transportation, ledging, and apical perforation. Automated techniques continue to be of interest as the dentist searches for easier, faster, and generally more efficient techniques. Ultrasonic and sonic devices have generated considerable interest. Research has not demonstrated these instruments to be as effective as hand techniques unless employed in a special manner. Other types of engine-driven instruments are generally not indicated and may in fact be dangerous.

Humans↗
PubMed1991

Vertical root fracture and relative deformation during obturation and post cementation.

There are several speculated etiologies of vertical root fractures such as pressure exerted during post placement and excessive forces during lateral condensation. However, there are no reports comparing these two forces by use of the same measurement system. This study determined and compared on single-rooted teeth (1) the amount of strain to the root that occurs during obturation and post cementation and (2) the incidence of incomplete and complete vertical root fractures occurring during the aforementioned procedures. Canals of 32 extracted maxillary central incisors were step-back prepared. Teeth were randomly divided into negative and positive controls and experimental groups. The amount of root distortion was recorded with a strain gauge during each of the following procedures: (1) lateral condensation, and (2) lateral condensation plus cementation of a cast gold post. Relative deformations were compared statistically. Teeth were examined by transillumination and stereomicroscopy for incomplete and complete fractures and compared among groups. Data showed significantly more relative deformation with placement of a post and loading than with obturation alone. The accumulation of strain from both procedures did not significantly increase incidence of vertical root fractures. The results indicate that stresses from cementation of posts is more likely to cause relative deformation of roots.

Cementation↗
PubMed1991

The efficacy of step-down procedures during endosonic instrumentation.

The step-back method of root canal preparation may not be suitable for endosonic files as they may be prevented from working efficiently within the apical region. This study determined the debris present in the apical portion of the canal after using three different endosonic instruments and compared the step-back versus the step-down technique; the latter involves initial preparation of the upper regions of the root canal which may reduce file constraint. Thirty-six teeth were prepared by either the step-back or step-down method using endosonic generators (magnetostrictive, piexoelectric, and sonic). Preparation times were standardized so that files were used for the same period. From scanning electron micrographs, debris removal was scored on a four-point scale by four clinicians. A log linear analysis showed that there was significantly less debris present with the step-down method using piezoelectric and sonic devices. More debris was present when files driven by a magnetostrictive instrument were used with the step-back method. This study showed that the step-down method may be useful when using certain types of endosonic generators.

Dental Cavity Preparation↗
PubMed1990

The periodontal ligament injection as a primary technique.

The periodontal ligament injection has been promoted as a primary anesthesia technique. To be useful, however, any anesthetic approach must meet several criteria. First, there must be adequate depth of anesthesia; second, onset of anesthesia should be sufficiently rapid; third, duration must be sufficient to complete the procedure; fourth, discomfort should be minimal during and after the injection; and fifth, the injection must be safe to periodontium and pulp during operative or other procedures. In reviewing the clinical and experimental literature as to the factors described above, the periodontal ligament injection does not meet all of the necessary requirements for a primary technique. It is, however, apparently safe to the periodontium and to the pulp when used in conjunction with certain operative procedures.

Anesthesia, Dental↗
PubMed1990

A comparison of techniques for cleaning endodontic files after usage: a quantitative scanning electron microscopic study.

One-hundred ten new endodontic files were used to prepare canals and were then cleaned using three different techniques: (a) gauze soaked with alcohol, (b) sponge soaked with alcohol, and (c) ultrasonic bath. The cleaning ability of each of these techniques immediately after use and after 1 h of delay were compared. Identical areas on each file were examined by using a custom-made jig. Morphometric analysis of debris was carried out using a Bioquant image analysis system. Sponge/alcohol was the worst cleaning method; this was significantly different from the other two techniques. The gauze/alcohol and ultrasonic bath were similar. The 1-h delay before instrument cleaning did not affect the ability of any of the techniques tested. None of the methods tested were able to totally clean the files.

Decontamination↗
PubMed1990

Comparison of the radiographic appearance of root canal size to its actual diameter.

Clinically, the apparent radiographic diameter size does not always seem to correspond to the true canal size. The objective of this study was to compare canal size on periapical radiographs with the actual canal diameter as determined histologically. Periapical radiographs were exposed on 36 teeth on 5 human cadavers. Mesial-to-distal boundaries of canals were measured in the cervical, middle, and apical thirds. The teeth were extracted, the roots histologically processed, and cross-sections made in the cervical, middle, and apical thirds. Measured values of diameter from radiographs were compared with true canal widths as measured from the corresponding level of histological sections by using a correlated t test. All sections of all roots demonstrated a canal histologically, although some regions had no canal visible radiographically. In general, there was statistically no difference (p less than 0.001) between the histological and radiographic measurements even when pulpal calcifications were present. However, in some roots there were marked discrepancies between radiographs and histological sections as to canal diameter.

Dental Pulp Calcification↗
PubMed1990

Vertical root fracture and dentin deformation in curved roots: the influence of spreader design.

The effect of lateral condensation using different tapered spreaders was evaluated. Curved mesiobuccal roots of maxillary molars were step-back prepared. Strain gauges applied to the root surfaces measured dentin deformation (distortion) during controlled lateral condensation with either fine finger or D11 spreaders. After obturation, roots were cross sectioned and analyzed under the stereomicroscope to detect the presence and pattern of fractures. The results showed no statistical difference between spreader designs as to mean distortion and the incidence of fractures; however several specimens in the D11 group showed high root distortion measurements. When fractures occurred, there were no consistent patterns of fracture in either spreader group. In conclusion, although there were no significant differences in mean deformation or fracture incidence in curved roots between the spreaders, the roots showing high deformation readings in the D11 group may be more susceptible to future vertical root fractures.

Dental Cavity Preparation↗
PubMed1989

Vertical root fracture and root distortion: effect of spreader design.

The incidence of vertical root fractures and the amount of root distortion created during lateral condensation of gutta-percha with either D11 spreaders or B-finger pluggers were evaluated in vitro. Fifty-five extracted human, single-rooted teeth were instrumented using the step-back flare technique. Ten teeth served as positive controls (obturation to the point of fracture) and five teeth as negative controls (prepared but not obturated). Strain gauges were attached to the root surfaces. In the experimental group, 20 teeth were obturated using a D11 spreader and 20 with a B-finger plugger. Recordings were made of root distortion (expansion) created during obturation. Then, after sectioning the teeth, root surfaces of obturated samples were examined for fractures under the scanning electron microscope. Only the more tapered spreader, the D11, produced vertical root fractures, although very few in number. Also, the D11 spreader caused greater root distortion than did the B-finger plugger.

Dental Stress Analysis↗
PubMed1989

Molar access: shape and outline according to orifice locations.

This study was designed to relate, in molars, the access outline on the occlusal surface to the canal orifices. The occlusal surfaces of maxillary and mandibular molars were photographed and prints made. The crowns were then sectioned at the level of the pulpal floor to expose the canal orifices. Transparent photographs of the orifices were taken and projected on the occlusal photograph; the orifice locations were marked directly on the print. Orifice location demonstrated a fairly regular pattern relative to the occlusal surface in all four molar groups. The resulting outline scribed from the orifices tended to be centered mesiodistally on the crown of each group and did not extend to the marginal ridges. The results indicate that classic access drawings are too far mesial.

Dental Pulp Cavity↗
PubMed1989

Case of mistaken identity: periapical cemental dysplasia in an endodontically treated tooth.

A case of a patient with a history of root canal treatment and re-treatment and a persistent periapical radiolucency is reviewed. Following surgery, biopsy material was submitted and diagnosed as periapical cemental dysplasia (PCD). With careful diagnosis, PCD should be readily differentiated from endodontic pathosis, thus avoiding unnecessary root canal treatment. In this case, surgery was necessary to rule out other inflammatory disease or benign odontogenic entities.

Adult↗
PubMed1988

Patterns of innervation of the maxillary first molar: a dissection study.

Human maxillae were dissected with the aim of tracing nerves from maxillary first molar root apices to their parent superior alveolar nerve branches. The contribution of the posterior, middle, and anterior superior alveolar nerves to the innervation of the first molar was assessed. The posterior superior alveolar nerve was found to contribute innervation 100% of the time; the middle superior alveolar nerve, when present, contributed innervation 28% of the time. The anterior superior alveolar nerve did not supply any innervation to the first molar.

Adult↗