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Biomedical subjects

W H Christie

Publications and source records attributed to W H Christie.

15 recordsLinked to original sources
PubMed1996

The maxillary second molar: variations in the number of roots and canals.

A retrospective study was undertaken of 520 completed endodontic treatments of maxillary second molar teeth which were selected from a specialty endodontic practice. Radiographs were reviewed and studied, a classification of antomical root and canal variations was devised, and the frequency with which each variant occurred was recorded. There were six variants which occurred frequently enough to be considered as separate anatomic categories and their frequency of occurrence is illustrated. The six variants found in the study and their frequency of occurrence are as follows: (1) three separate roots and three separate canals (56.9%); (2) three separate roots and four canals (two in the mesiobuccal root) (22.7%); (3) three roots and canals whose mesiobuccal and distobuccal canals combine to form a common buccal with a separate palatal (9%); (4) two separate roots with a single canal in each (6.9%); (5) one main root and canal (3.1%); and (6) four separate roots and four separate canals including two palatal (1.4%). Clinical examples of these deviant variations are also presented.

Dental Pulp Cavity↗
PubMed1994

Canal configuration in the mesiobuccal root of the maxillary first molar: a clinical study.

Surgical telescopes, headlamps, and a modified access preparation were used clinically to aid in the search for mesiolingual canals in the mesiobuccal roots of 208 maxillary first molars. In 148 (71.2%) of the mesiobuccal roots two canals were located and treated. Of these, 66 (31.7%) had two separate apical foramina (Weine Type III) and 82 (39.4%) had two canals that joined (Weine Type II). In 60 (28.9%) cases only one canal was located.

Adult↗
PubMed1994

The importance of endodontic access in locating maxillary and mandibular molar canals.

The principle of straight-line access is discussed with particular reference to endodontic access of either maxillary or mandibular molar teeth. Modifications to the traditional triangular access opening are described that will make it easier for a practitioner to locate and instrument the fourth canal system commonly found in molar teeth. The high frequency of a fourth canal in molar teeth makes it essential to anticipate and find all canals during molar endodontic therapy. Quite frequently, the general practitioner attempting molar endodontic therapy should expect to locate a second canal in the mesiobuccal root of the maxillary molar and a second canal in the distal root of a mandibular molar. The possibility of extra roots over and above the norm should also be anticipated and looked for carefully. Proper angulation and interpretation of radiographs help to identify chamber and root anatomy. A two-step access opening is advocated when making access openings on molar teeth if a coronal crack in the crown is to be seen early in treatment. A method of unroofing the pulp chamber and pre-flaring the canal orifice to facilitate the subsequent shaping of the entire root-canal system is described. Clinical and laboratory examples are pictured to illustrate modifications or errors in the standard endodontic access opening.

Dental Pulp Cavity↗
PubMed1993

Clinical observations on a newly designed electronic apex locator.

The introduction of alternative electronic principles and circuitry has produced the next generation of electronic apex locators, which have fewer clinical limitations and greater ease of use, on a routine basis, than their predecessors. The history of how the electronic apex locator was developed over the past 30 years and the limitations of the machines designed on earlier principles are reviewed. Clinical examples of root canal systems measured using a newly-designed, frequency-dependent apex locator are presented in order to illustrate the spectrum of cases that can be read. All measurements were made on canals irrigated previously with electro-conducting solutions, which would have made readings from earlier machines problematic. Single-rooted and molar teeth as well as teeth with vital tissue in the root canal system or with necrotic pulp tissue and periapical lesions have been treated with equal ease and results. The electronic apex locator is being advocated to supplement instrumentation technique and to improve the identification of the apical terminus of the root canal system. The routine use of these devices is advocated to ensure an accurate placement of root canal fillings rather than to eliminate the need for radiographs.

Dental Pulp Cavity↗
PubMed1991

Maxillary molars with two palatal roots: a retrospective clinical study.

Clinical records and radiographs were reviewed for 15 patients who had endodontic treatment performed on 16 maxillary molars with two palatal roots. These cases, plus six extracted teeth or slides, were evaluated. From the morphology of these roots, a classification of three types is proposed.

Dental Pulp Cavity↗
PubMed1990

The endo-perio problem in dental practice: diagnosis and prognosis.

The relationships between endodontics and periodontics are explored. Diagnosis, prognosis, and treatment planning are discussed for the primary endodontic lesion and the primary endodontic lesion with secondary periodontal involvement. These endodontic lesions are compared with primary periodontal lesions and primary periodontal lesions with secondary endodontic participation. The "true" combined lesion is also reviewed. Clinical photographs and radiographs are used to illustrate specific aspects.

Dental Pulp Diseases↗
PubMed1978

Mass spectrometry of N-nitrosamines.

The preparation of a series of N-nitrosamines for carcinogenicity studies presented an opportunity to study mass spectral fragmentation schemes in detail. Condensed spectra are listed for 146 N-nitrosamines of widely differing structures, including nitroso derivatives of commercial drugs and insecticides. Aliphatic nitrosamines were generally characterized by molecular ions and loss of OH. Subsequent fragmentation via alpha-cleavage is similar to that of aliphatic amines. The loss of OH is believed to result in a cyclic ion. Subsituted aliphatic nitrosamines varied in fragmentation schemes with structure and position of the substitutent groups. However, most showed alpha-cleavage at some point in fragmentation. When substituted with aromatic groups prominent peaks due to the aromatic moiety were observed. The alicyclic nitrosamines showed losses of NO, NOH and OH and subsequent alpha-cleavages. Nitrosamides were characterized by rupture of the carbonyl to nitrogen bond. Spectra of substituted ureas usually showed charge retention by the carbonyl fragment, while carbamate esters showed ions from both fragments.

Carcinogens↗
PubMed1975

Non chromatographic colorimetric assay for total taurine-conjugated bile acids: application of measurements of glycine: taurine ratio in bile.

A direct colorimetric assay for total conjugated taurine from bile-rich duodenal aspirates is described. The method is based on complete acetylation of the free hydroxyl groups by acetic anhydride at 100 degrees C. of both the tri- and di-hydroxy bile acids in Folch extracted bile samples. Taurine-conjugated bile acids are measured by ion pair formation with Azure A and subsequent extraction of the complex into the organic phase of a biphasic system. Absorption at 645 nm. of this complex directly quantifies total taurine-conjugated bile acid. Total bile acids are then estimated by the 3alpha-hydroxysteroid dehydrogenase assay. The difference between the concentration of the total conjugated bile acid and of the total conjugated taurine determines the concentration of glycine conjugates and the glycine:taurine ratio. Potentially interfering materials such as sulphalipids, certain phospholipids, and unconjugated bile acids are removed by Folch extraction. The 3-hydroxysteroid sulfates (cholesteryl sulfate, lithocholate sulfate, and glycocholate sulfate) are not measurable by heating in acetic anhydride and do not interfere. Taurolithocholate-3-sulfate, under identical conditions, gives a measurable but very low color yield and in normal physiologic concentrations would contribute negligible color. As previously reported, this assay under prescribed conditions is selective for long-chain amphipathic sulfates or sulfonates with no measurable color yield with glycine conjugates, unconjugated bile acids, free fatty acids, or lecithin. Values for glycine:taurine ratios by the above-described method in both normal bile extracts and extracts from patients with either elevated or depressed ratios relate closely to those determined by thin-layer chromatography.

Acetates↗