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Biomedical subjects

R E Walton

Publications and source records attributed to R E Walton.

At least 37 records · Page 2Linked to original sources
PubMed1995

Vertical root fracture in nonendodontically treated teeth.

Vertical root fractures have been reported to occur primarily in endodontically treated teeth due to condensation forces and/or with post placement. This study describes 11 Chinese patients with 12 molars that developed vertical root fractures without endodontic or post procedures. These showed characteristics of a true vertical root fracture as confirmed after extraction. Fractured teeth showed a consistent pattern. The majority were severely attrited mandibular molars in males. All had clinically intact crowns with no or minimal restorations.

Aged↗
PubMed1995

Cross-sectional configuration of endodontic files compared with manufacturers' design.

The cross-sectional configuration of seven files at coronal and apical levels were compared with diagrams presented by manufacturers. The presence of cutting edges was also examined. Ground-twisted (K-file, K-Reamer, and K-flex) and machined files (Flex-R, Unifile, S-file, and Hedstrom) were included in #10, #25, and #40. Twelve files of each size and brand comprised the samples. Files were embedded in acrylic, which was then cut in cross-section in the apical and coronal parts of the flutes. These were photographed under a microscope. Six clinicians viewed the slides projected onto a screen for comparison with manufacturers' design and evaluation of visible cutting edges. The inconsistencies were primarily in machined files, smaller sizes, and apical sections of the instruments. Data showed that overall the cross-sections and presence of cutting edges compared well with the designs intended by the manufacturers.

Dental Instruments↗
PubMed1995

Anaerobic tissue-dissolving abilities of calcium hydroxide and sodium hypochlorite.

Closed root canals likely have an oxygen-free environment; most bacteria in canals are anaerobic. These bacteria and other debris are difficult to remove. Unknown is tissue dissolution with chemicals under these anaerobic conditions. This study evaluated and compared dissolving properties of calcium hydroxide (Ca(OH)2) and sodium hypochlorite (NaOCl) on bovine pulp tissue in aerobic and anaerobic environments. Sixty bovine pulp specimens were dried, then randomly divided into six groups. Groups A and B were immersed in Ca(OH)2 + water solution, whereas group C and D were in 2.5% NaOCl. Groups E and F (controls) specimens were placed in distilled water. Groups A, C, and E were incubated anaerobically, and groups B, D, and F were incubated under regular atmospheric conditions, all for 7 days. Percentages of weight loss were compared between groups. Results showed the following: (a) both chemicals partially dissolved pulp tissue, (b) anaerobic environment did not alter tissue-dissolving properties of Ca(OH)2 or NaOCl, and (c) Ca(OH)2 and NaOCl were equal and more effective than water.

Anaerobiosis↗
PubMed1995

Electrothermal debracketing: patient acceptance and effects on the dental pulp.

Adhesives bond ceramic brackets so effectively that their removal by mechanical forces can fracture the brackets and may damage the tooth surface. Electrothermal debracketers have been developed to facilitate removal; whether the heat generated will damage the underlying pulp is unclear. In our experiment, a prototype device with a high heat tip was used to remove brackets from premolars in patients. The following parameters were evaluated: (1) time required for removal, (2) patient acceptance, and (3) histologic effect on the pulp. Forty-eight experimental teeth planned for orthodontic extraction were bonded by a filled Bis-GMA composite resin and a monocrystalline sapphire bracket. After the chemically cured composite set, debracketing was performed according to the manufacturer's recommendations. Seventeen premolars were not etched or bracketed and served as controls. The interval between heat application and removal of the bracket was timed. Patients were questioned as to sensations during debracketing. Teeth were extracted at 5 to 7 or 28 to 32 days and histologically prepared. Pulps were evaluated for alterations. Brackets were removed in an average of 2.1 seconds, usually at the bracket/composite interface. Patient acceptance was generally positive. Pulpal necrosis was not observed but, in a number of specimens, slight inflammation and odontoblastic disruption occurred at both observation periods.

Acid Etching, Dental↗
PubMed1994

Extensive idiopathic apical root resorption. A case report.

Multiple idiopathic external apical root resorption is an unusual phenomenon. A brief review of cases in the literature is presented as well as a report of a patient with severe resorption. No significant systemic, dental, or familial findings could be identified as a possible cause. Careful chronologic radiographic documentation showed that roots with normal length began to resorb several years earlier, and the resorption continued over a defined period of time, terminating spontaneously before tooth loss or obvious pulp damage. Because the pathogenesis is generally unknown, no specific treatment modalities exist at present.

Adult↗
PubMed1994

Vasculature of the dental pulp of atherosclerotic monkeys: light and electron microscopic findings.

Arteriosclerosis is a pathological condition in which there is a severe luminal narrowing of arterioles, resulting in tissue ischemia and necrosis. Arteriosclerosis has been reported in the dental pulp of normotensive persons as young as 40 yr of age. To date, no corroboration of these findings have been published. Our study examined pulp from atherosclerotic monkeys for such changes under controlled conditions. The lingual artery and canines from 11 nonatherosclerotic (control) and 11 atherosclerotic (experimental) cynolmolgus monkeys were histologically evaluated with light and transmission electron microscopy. Lingual arteries from controls did not exhibit atherosclerotic plaques, whereas those of the experimental monkeys did show fibro-foamy plaques. However, neither experimental nor control animals exhibited any arteriosclerotic alterations in the pulp. Our study concluded that, in this animal model, which did demonstrate atherosclerosis in the oral cavity, no similar alterations were found in the pulp.

Animals↗
PubMed1994

Characterization of induced pulpal hypoxia using 3H-misonidazole.

Tritiated misonidazole (3H-MISO) is a bioreductively activated marker which preferentially binds to cells with decreased oxygen tension (hypoxia). Detection of hypoxia may be an important indicator of metabolic imbalance. For 3H-MISO to be functional as a marker, normal oxygen (normoxic) levels must be distinguishable from increased hypoxic retention. This investigation characterized retention of 3H-MISO in: (a) normoxic pulp, (b) induced hypoxic pulp, and (c) reoxygenated hypoxic pulp. Rats were injected intraperitoneally with either 3H-MISO, unlabeled MISO, or saline, then divided into normoxic and hypoxic groups with appropriate controls. Normoxic animals were maintained at ambient pressure. Hypoxia was induced by placing animals in a hypobaric chamber at 0.5 atm. Pulps were then removed and prepared for liquid scintillation counting. Hypoxic pulps retained significantly more 3H-MISO than normoxic pulps (analysis of variance, p = 0.001). Hypoxic 3H-MISO retention was unaffected by subsequent, transient tissue reoxygenation. 3H-MISO detects changes in pulpal oxygen status that deviate from normal.

Analysis of Variance↗
PubMed1994

Bacterial retention in canal walls in vitro: effect of smear layer.

When dentin is planed by endodontic instruments, a smear layer forms. Whether this layer should be removed is unknown and controversial. This study was conducted to assess the effect of the smear layer on retention of bacteria using an in vitro root canal bacterial colonization model. Canals of 26 extracted human canines were step-back prepared using 2.5% NaOCl. Teeth were then randomly divided into two groups based on the type of high volume final flush: 1-20 ml of sterile saline (0.85% wt/vol) or (2-10 ml of 17% EDTA followed by 10 ml of 2.5% NaOCl which removes smear layer. Streptococcus anginosus (milleri) was cultured in trypticase soy broth supplemented with 0.5% yeast extract at 37 degrees C in 5% CO2. Cells were harvested by centrifugation and resuspended in fresh media. Serial dilutions were performed to achieve inocula of 10(6) colony-forming units in a 30-microliters volume. Teeth were inoculated and incubated for 2 h in 5% CO2 at 37 degrees C. Following incubation, teeth were split and processed for microbiological analysis. Numbers of colonizing bacteria were determined by a spiral-plating system. Enumeration of the numbers of bacteria revealed a reproducible, order of magnitude difference (p = 0.0002) between teeth with smear layer (10(4) colony-forming units) versus teeth without smear layer (10(5) colony-forming units). This suggests that smear layer produced during root canal therapy may inhibit bacterial colonization of root canals. One suggested mechanism is that smear layer may block bacterial entry into dentinal tubules.

Bacterial Adhesion↗
PubMed1994

Coronal leakage: bacterial penetration through obturated canals following post preparation.

Coronal leakage of bacteria from saliva into root canal filling materials is a potential cause of failure. This problem may be more pronounced when only a small volume of obturating material remains in the canal, such as after post preparation. In this study, coronal leakage of bacteria through unsealed, apically obturated canals was investigated using a new in vitro model system.

Dental Leakage↗
PubMed1993

Healing of induced periapical lesions in ferret canines.

A previous study showed that the ferret canine is an appropriate model for inducing periapical lesions. Ferret canines were used in this study to study changes in periapical lesions after root canal treatment (RCT). After periapical pathosis was induced in the maxillary and mandibular canines of six ferrets, RCT was performed on three of the four canines in each animal. Each ferret received periodic intraperitoneal injections of Procion red dye. Two animals were killed at each of 4, 8, and 12 wk after RCT. Apices and surrounding lesions were evaluated radiographically, histologically, and by fluorescent microscopy. Periapical radiolucencies increased in size during induction but showed no changes after RCT. Lesions in untreated teeth showed features of granulomatous inflammation, mainly the presence of macrophages and lymphocytes. After RCT, there was histological evidence of healing in the form of cementum deposition, increased vascularity, and increased fibroblastic and osteoblastic activity. Fluorescent staining showed cementum deposition of variable thickness in the treated specimens.

Animals↗
PubMed1993

Adaptation of thermafil components to canal walls.

The desired result of the Thermafil system is described as a centered carrier encased by gutta-percha in apposition to the canal walls. This study examined, in curved canals, the intracanal relationships of: (a) the metal carrier; (b) the surrounding gutta-percha; and (c) the sealer. Following the manufacturer's recommended techniques, 20 resin blocks that had canals prepared with conservative flaring were obturated. Cross-sections were made in the cervical, middle, and apical thirds and were evaluated with a stereomicroscope and scanning electron microscope to determine the location of the Thermafil components. In an additional 20 resin canal preparations obturated with the Thermafil system, the sealer was stained with dye to evaluate coating patterns. Then, these blocks were sectioned at the apex and examined under the stereomicroscope for adaptation at the apical extent of the preparation. In most preparations, the carrier abutted the canal wall in the cervical and middle sections but was usually surrounded by gutta-percha in the apical one third. The adaptation of components showed the most variability at the most apical extent of the preparation; complete encasement of the carrier did not occur in any specimen. Sealer distribution was variable throughout, usually being absent in the apical canal.

Dental Pulp Cavity↗
PubMed1993

Cleaning of oval canals using ultrasonic or sonic instrumentation.

This study investigated the effect of direction of file oscillation on the amount of debris and smear remaining within oval canals. Sixty-five lower premolars were allocated to six experimental groups (n = 10) and one control group (n = 5). Canals were prepared using Gates Glidden burs and hand instruments. Preparations were completed using either an ultrasonic size 15 K file or a sonic size 15 shaper file. Three preparation techniques were used: (a) file oscillation toward oval recesses within the canal, (b) file oscillation at right angles to the recesses, and (c) rotational movement of handpiece. Canals were examined under the scanning electron microscope and blindly scored for debris and smear layer. Log linear analysis revealed no significant difference (p > 0.05) between sonic or ultrasonic instrumentation as to debris or smear layer remaining. File oscillation directed toward oval recesses left the least amount of debris (p < 0.05). Smear layer remained unaffected by all techniques.

Chi-Square Distribution↗
PubMed1993

Prophylactic penicillin: effect on posttreatment symptoms following root canal treatment of asymptomatic periapical pathosis.

It has been reported that administration of prophylactic penicillin may prevent flare-ups or other undesirable posttreatment sequelae following root canal treatment. To test this hypothesis in a prospective study, 80 patients with a diagnosis of pulp necrosis and chronic apical periodontitis were divided into three groups: group A (prophylactic penicillin, AHA recommendation), group B (placebo, same regimen), and group C (no medication). Medications and evaluations were double-blinded. Patients reported their posttreatment events including incidence of flare-ups, incidence and severity of pain/swelling, and occurrence of adverse side effects. Differences in the three groups were determined statistically using chi-square tests. The outcome showed no significant difference (p = 0.68) among the three groups. That is, administration/nonadministration of penicillin prophylactically was unrelated to posttreatment signs and symptoms following canal preparation. Incidence of flare-ups was very low (1 of 80). Occurrence of pain in the mild-moderate levels was fairly high (approximately 70% overall), but was primarily in the mild category. Overall incidence of side effects was also very low (2 of 80). Severe levels of pain/swelling and flare-up incidence were low with no difference between administration or nonadministration of antibiotics. Based on our data, using penicillin (a potentially dangerous drug) prophylactically to control posttreatment symptoms is not recommended in cases of pulp necrosis and asymptomatic periapical pathosis.

Adolescent↗
PubMed1992

Canal Master files: scanning electron microscopic evaluation of new instruments and their wear with clinical usage.

Canal Master instruments have a short, fluted cutting area and a small flexible shaft; they may be predisposed to rapid wear and breakage. This study examined new and used files as to tip, flute, and shaft design when new and with increasing time of canal preparation. One hundred files prepared 140 curved canals. Sizes #20, #40, and #60 files were examined unused and after 1, 3, 5, and 7 min of use. Evaluation was for uniformity when new and for deterioration and breakage with usage. The smaller sizes (#20 and #40) had some inconsistencies when new and were most predisposed to wear and breakage with time. Findings suggest that smaller files could have had improved quality control by the manufacturer. Also, they should be used with caution and discarded after short times of use in small, curved canals. This should minimize instrument separation and maximize cutting efficiency.

Dental Cavity Preparation↗
PubMed1992

Histological evaluation of the presence of bacteria in induced periapical lesions in monkeys.

In endodontic periapical lesions, both presence and location of bacteria are controversial. Various experimental techniques have produced differing results perhaps related to potential artifacts such as contamination during specimen recovery. Our objective was to examine for bacteria in uncontaminated, undisturbed periapical lesions in an animal model. Pulp necrosis was induced by exposing molars in nonhuman primates and closing the exposure after 1 week with amalgam. Lesions developed at 18 apices. After 7 months, block sections including tooth and surrounding tissues were removed, processed histologically, and Gram stained. Bacteria, primarily Gram positive, were consistently identified in necrotic tissue in canals. Two canals demonstrated bacterial masses to the apical foramen. No bacterial colonies, only intracellular microorganisms, were seen periapically. Inflammatory lesions seemed to resist the spread of bacteria, confining them to the canal space. Bacterial masses at the apical foramen could contaminate periapical tissues during surgery or extraction and give a false positive upon microbiological sampling.

Animals↗
PubMed1992

Effect of precurving endosonic files on the amount of debris and smear layer remaining in curved root canals.

Endosonic files are prone to constraint; this reduces their efficiency, particularly in the apical third and in curved root canals. Precurving the file may reduce constraint, thereby improving the file's ability to debride. This investigation was undertaken to compare both straight and precurved endosonic files as to debris and smear layer removal. Thirty-six curved root canals were randomly allocated into six groups. Each group was prepared using a step-down technique, then instrumented with either a straight or precurved endosonic file of size 15, 20, or 25. The tooth roots were split and examined under the scanning electron microscope. Blind examinations were made for debris and smear layer removal and evaluation scores were analyzed using a log linear approach. The root canals instrumented with the precurved files had a significantly lower debris score than those prepared with straight files. Precurving did not affect smear layer removal. In conclusion, precurving of files decreased the amount of debris but did not affect smear layer removal.

Dental Cavity Preparation↗