Biomedical subjects

M L Hicks

Publications and source records attributed to M L Hicks.

At least 19 recordsLinked to original sources

PubMed1992

Factors influencing temporal effects with notched-noise maskers.

Temporal effects in simulataneous masking were studied by measuring the reduction in the amount of masking produced by a gated masker when that masker was preceded by a 400-ms noise (the precursor) that was usually spectrally identical to the masker. The signal frequency (fs) was 1.0 or 4.0 kHz. Experiment 1 revealed a temporal effect only when there was a spectral notch (centered at fs) in the masker and precursor. For a relative notchwidth of 0.4 fs, the temporal effect was larger at 4.0 than at 1.0 kHz. In experiment 2. where the masker and precursor both consisted of two bands of noise separated by a spectral notch of 0.4 fs, the size of the temporal effect remained essentially constant as the bandwidth of these noise bands increased from 0.2-0.8 kHz. The results from experiment 3 indicated that the temporal effect was largest when the level fo the precursor was equal to the level of the masker. Finally, the results from experiment 4 suggested that the temporal effect may depend upon the frequency region below as well as above fs, but that the frequency region above fs is probably more important.

Acoustic Stimulation↗

PubMed1992

Conservative surgery plus adjuvant therapy for vulvovaginal rhabdomyosarcoma, diethylstilbestrol clear cell adenocarcinoma of the vagina, and unilateral germ cell tumors of the ovary.

Significant progress has been made in the 1980s in early-stage vulvovaginal rhabdomyosarcoma, diethylstilbestrol (DES) clear cell adenocarcinoma of the vagina, and unilateral germ cell tumors of the ovary. In an early state of vulvovaginal rhabdomyosarcoma, systemic vincristine, dactinomycin, and cyclophosphamide (VAC) chemotherapy followed by local excision or local radiation results in a high cure rate with retention of future fertility. Similarly, early-stage DES-related adenocarcinoma of the vagina treated by wide local excision and localized vaginal radiation also results in retention of fertility and a high cure rate. Finally, significant progress has been made in unilateral germ cell tumors of the ovary in which surgical treatment by unilateral salpingo-oophorectomy followed by cisplatin, etoposide, and bleomycin results in not only high cure rates and retention of fertility but will probably be standard therapy for all germ cell tumors of the ovary, including dysgerminoma, a disease most frequently treated in the past by radiation therapy with loss of subsequent fertility.

Adenocarcinoma↗

PubMed1991

Effectiveness of halothane used with ultrasonic or hand instrumentation to remove gutta-percha from the root canal.

This study compared halothane and chloroform used with hand or ultrasonic instrumentation to remove gutta-percha and sealer from root canals. Apically extruded debris, residual debris, time for filling removal, and amount of solvent used were determined. The differences in extruded apical debris and radiographically visible residual debris were not significant (p greater than 0.05). Ultrasonic instrumentation required significantly less time to remove the root canal filling than did hand instrumentation (p = 0.02). The only significant difference in the amount of solvent used occurred when the ultrasonic-chloroform group was compared with the hand instrumentation-chloroform group (p = 0.05). Halothane was found to be an acceptable alternative to chloroform for removing gutta-percha and sealer from the obturated root canal.

Analysis of Variance↗

PubMed1991

The effect of pure-tone forward masking on overshoot.

The overshoot effect can be reduced by temporary hearing loss induced by aspirin or exposure to intense sound. The present study simulated a hearing loss at 4.0 kHz via pure-tone forward masking and examined the effect of the simulation on threshold for a 10-ms, 4.0-kHz signal presented 1 ms after the onset of a 400-ms, broadband noise masker whose spectrum level was 20 dB SPL. Masker frequency was 3.6, 4.0, or 4.2 kHz, and masker level was 80 dB SPL. Subject-dependent delays were determined such that 10 or 20 dB of masking at 4.0 kHz was produced. In general, the pure-tone forward masker did not reduce the simultaneous-masked threshold, suggesting that elevating threshold with a pure-tone forward masker does not sufficiently simulate the effect of a temporary hearing loss on overshoot.

Adolescent↗

PubMed1990

Alternative solvents to chloroform for gutta-percha removal.

The purpose of this study was to evaluate new or previously identified solvents for effectiveness in dissolving gutta-percha. The solubility of a standardized weight of gutta-percha was tested in 5-ml quantities of 32 solvents. Ten samples of 30 solvents were tested at both 22 and 37 degrees C for 15 min. If the gutta-percha samples dissolved within 15 min, the times were recorded and statistically analyzed. There was no significant difference (p greater than 0.05, one-way analysis of variance and Scheffe's test) between dissolving times of chloroform and trichloroethylene at 22 and 37 degrees C. At 22 degrees C, three solvents dissolved the gutta-percha sample, whereas at 37 degrees C, nine solvents dissolved the gutta-percha. At 37 degrees C, halothane (Fluothane) was twice as effective as cineole and demonstrated many favorable working qualities. An important finding from the experimentation with halothane was the discovery of a potential obturating material, which was termed "halopercha".

Chloroform↗

PubMed1990

Management of advanced endodermal sinus tumor of the ovary with preservation of reproductive function.

Endodermal sinus tumor of the ovary occurs primarily in children and young adults. This tumor is classified as a germ cell tumor which comprises approximately 5% of all ovarian tumors. In the past, patients with this highly malignant tumor had low survival. However, with the evolution of effective adjunctive chemotherapeutic regimens, specifically vincristine, actinomycin D, and cyclophosphamide, survival rates have improved. In an attempt to continuously improve survival rates, other combination chemotherapeutic regimens are currently under investigation. Unlike epithelial ovarian malignancies, endodermal sinus tumor can be monitored by a specific tumor marker, alpha-fetoprotein (AFP). Serum levels of AFP can be followed from the preoperative period through the course of chemotherapy. When elevated, AFP has excellent predictability that persistent disease is present. Because this disease presents primarily in young females, preservation of reproductive function is of utmost importance. We report a case of advanced endodermal sinus tumor which was managed with conservative surgery only, followed by radical combination chemotherapy, resulting in preservation of normal reproductive function and total resolution of disease documented by second-look laparotomy.

Adolescent↗

PubMed1990

Acquired immunodeficiency syndrome and Pneumocystis carinii infection in a pregnant woman.

Human immunodeficiency virus (HIV) infections are being seen with greater regularity by the obstetrician-gynecologist. Acquired immunodeficiency syndrome (AIDS), the extreme of the spectrum of HIV infections, is associated with Pneumocystis carinii infection in more than half of newly diagnosed cases. Four cases of AIDS and P carinii pneumonia complicating pregnancy have been reported in the literature, and all have caused maternal death. We report a case in which the mother survived. Treatment was similar to that used in the other reported cases except that steroids were added. A limited number of patients with AIDS and P carinii infection have been treated with trimethopterim-sulfamethoxazole and steroids, with good results. Steroids should be considered for cases in which other efforts are failing.

Acquired Immunodeficiency Syndrome↗

PubMed1989

Bacteriological comparison of ultrasonic and hand instrumentation of root canals in dogs.

This study compared the effectiveness of hand and ultrasonic instrumentation for removing a standardized inoculum of pigmented Serratia marcescens from the root canal system of premolars in dogs. Forty-four premolars from nine beagle dogs were divided into two experimental groups of 20 and 24 teeth, respectively. The experimental teeth were inoculated with approximately 10 colony-forming units of S. marcescens. After the bacterial were allowed to colonize for 1 wk, the experimental teeth were instrumented with either hand instruments or the Cavi-Endo device. The teeth were extracted, crushed, and assayed for recoverable colony-forming units of S. marcescens. Statistical comparisons of the ratio of inoculated to recovered colony-forming untis were made. The results indicated that the difference between the positive controls and the experimental groups was significant. There was no significant difference between the two instrumentation groups.

Animals↗

PubMed1989

Vertical root fractures in curved roots under simulated clinical conditions.

The purpose of this study was to determine the incidence of vertical root fractures in the mesial roots of extracted human mandibular molars that were endodontically prepared by hand or ultrasonic instrumentation and obturated with laterally condensed gutta-percha and sealer using finger and hand spreaders. One-hundred twenty mesiofacial canals were prepared by hand or ultrasonic instrumentation. After placing the teeth in a simulated alveolus, they were obturated by laterally condensing gutta-percha and sealer with B-finger or D11T hand spreaders. Teeth were obturated using forces in the range of 1 to 3 kg or 4.5 to 7.5 kg. Three teeth obturated with the D11T hand spreader using 7.0 to 7.3 kg of force demonstrated vertical root fractures. The results suggest that in vitro the range of forces reported as most commonly used by endodontists to laterally condense gutta-percha (1.0 to 3.0 kg) and those of a higher magnitude up to 4.9 kg are safe and will not result in vertical root fractures of mesial roots of mandibular molars.

Dental Pulp Cavity↗

PubMed1989

A comparison of four root canal filling techniques.

This study compared the apical seal produced by four obturation techniques. Sixty-four extracted human teeth were prepared and obturated using lateral condensation of gutta-percha that was either unmodified or was dipped in chloroform, eucalyptol, or eucapercha paste. After storage in normal saline and 0.02% azide solution at 37 degrees C for 200 days, the teeth were immersed in India ink for 48 h. The most coronal extent of leakage of India ink into the canal was then determined. Significantly more apical leakage occurred in the eucapercha group than in the other three groups. All other comparisons were equivalent. The results suggest that modification of the gutta-percha master cone with solvent does not improve the apical seal in vitro. If modification is desired, then dipping the master cone in either eucalyptol or chloroform produces an apical seal superior to that achieved with eucapercha.

Chloroform↗

PubMed1989

Effects of sonic instrumentation on the apical preparation of curved canals.

This study compared apical transportation produced in curved (45- to 60-degree) molar canals instrumented with two MM-3000 Sonic Air test files (Rispi-Sonic and Trio-Sonic) with apical transportation from instrumentation with conventional K-type files. Seventy-five extracted human permanent mandibular molars were equally divided into three groups. Results showed that 92 (61%) of 150 measurements demonstrated no transportation, and only 7 (5%) had transportation between 0.25 and 0.5 mm. Most of the transportation was 0.25 mm or less, and no file produced transportation greater than 0.5 mm in a buccolingual or mesiodistal direction. Statistical analysis (chi-square test and analysis of variance) showed no significant difference (p greater than 0.05) in the amount of apical transportation in canals prepared with the Kerr K-type, Rispi-Sonic, or Trio-Sonic files.

Dental Pulp Cavity↗

PubMed1988