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Biomedical subjects

R P White

Publications and source records attributed to R P White.

At least 19 recordsLinked to original sources
PubMed1995

The accuracy of video imaging in orthognathic surgery.

Video imaging is an important emerging technology in planning orthognathic surgery and educating patients about the esthetic effects of treatment. The presurgical cephalograms of 56 patients, 41 with mandibular advancement alone and 15 with mandibular advancement plus genioplasty, were digitized, and the computer-generated soft tissue "line drawing" predictions were compared with the actual posttreatment cephalograms. Video images of the patients' presurgical lateral view were obtained, and two experienced clinicians compared the computer generated video image predictions with the actual posttreatment profile. Video images judged very good or excellent were considered acceptable for treatment planning; 60% to 83% met this criterion, depending on the profile area viewed. The percentage of acceptable images in the lower lip, labiomental fold, and chin area decreased with the addition of a genioplasty. The predicted and actual posttreatment soft tissue line drawings were quite similar for all areas except for the lower lip region, where statistically significant differences were noted, with the predicted lower lip more retrusive and thinner than the actual contours. For the lower lip and chin, a 2 mm or more discrepancy was observed in 20% of the patients. In all cases, the actual image was judged more esthetic than the predicted image, allaying fears of unrealistically optimistic computer generated predictions.

Adult↗
PubMed1994

The impact of clinical practice patterns on hospital charges for orthognathic surgery.

To assess the impact of changes in practice patterns, hospital charges (overall and component charges excluding professional fees) for 1992 were compared to 1985 data for three orthognathic surgical procedures: bilateral sagittal split osteotomy (BSSO), Le Fort I osteotomy (LFI), and a combination of both (BSSO/LFI). Data for 1992 were obtained for 59 patients (26 BSSO, 18 LFI, 15 BSSO/LFI). Secondary analysis of similar data for 1985 included 77 patients (27 BSSO, 16 LFI, 34 BSSO/LFI). Changes in clinical practice from 1985 to 1992 reduced mean length of stay (days): BSSO 3.2 to 1.2, LFI 3.7 to 1.4, BSSO/LFI 4.1 to 1.8. Mean total charges (dollars) increased: BSSO 3,086 to 5,023, LFI 3,538 to 6,784, BSSO/LFI 4,778 to 8,816. If 1992 charges are expressed in 1985 dollars, ancillary, pharmacy, and room charges all are reduced. Charges attendant to the surgical procedure (anesthesia, operating room, supply, and recovery) were just over half of total charges in 1985. By 1992, these components escalated to 80% of total charges. Most notable was the increase in supply charges. Charges for rigid fixation were a major component of increased supply charges in 1992. Surgeons minimally influence charges attendant to the operating room and postanesthesia recovery, the major components of total charges in 1992. Quality can be maintained with reduction in some charge categories, but these components total less than 25% of the patient's bill. Technology changes benefit patients, but a judgment must be made weighing benefits against increased health care costs.

Cost-Benefit Analysis↗
PubMed1993

Early assessment of neurologic deficits in the fluid percussion model of brain injury.

This study was designed to quantify the early neurologic effects of brain injury elicited by fluid percussion to the dura of cats. Propofol was used for surgical anesthesia because recovery in normal animals from an intravenous infusion was found to be nearly complete within 2 h of cessation and absolutely complete by 4 h. In addition, a cat coma scale (CCS) was developed that reflects normal (CCS, 14) to moribund (CCS, 3) behavior. The CCS values at 6 h were compared with the force of injury expressed in atmospheres (atm), maximum blood pressure change, and gross neuropathology to ascertain which parameter might best account for the behavior observed after brain injury. The results showed that decreasing neurologic scores correlated well with increasing atmospheres of injury (Pearson's r 0.71, p < 0.001) but not with the rise in systolic blood pressure caused by the trauma (n = 29). Coma scores did correlate with the cross sectional area of ponto-mesencephalic lesions (Pearson's r = 0.51, p < 0.01) and proved to be significantly different in animals grouped according to lesion size of less or more than 3 mm in length (t test, p < 0.01). Thus the CCS and the pharmacologic properties of propofol permit an early analysis of the neurologic status in the feline fluid percussion model of brain injury. These procedures could facilitate the evaluation of early biochemical changes that affect behavior and of therapies designed to ameliorate the deleterious effects of head injury.

Anesthesia↗
PubMed1993

Recovery following orthognathic surgery: mandibular bilateral sagittal split osteotomy and Le Fort I osteotomy.

Thirty-eight patients, who underwent orthognathic surgery, reported their recovery period upon returning to work or school and returning to full activity. Twenty-six patients had isolated bilateral sagittal split osteotomies (BSSO) and 12 had isolated Le Fort I osteotomies (LFI). At 1 to 2 weeks postoperatively, 50% of the BSSO group had returned to work or school while none of the LFI group had returned. By 3 to 4 weeks, 81% of the BSSO group had returned to work or school while nearly one half of the LFI group still had not returned. The BSSO group returned to full activity earlier than the LFI group, although the differences were not statistically significant. Hemoglobin, hematocrit, weight, and vital signs were determined preoperatively and for 6 weeks postoperatively. The LFI group had a larger mean estimated blood loss, length of operation, and weight loss.

Absenteeism↗
PubMed1992

Stability of surgical maxillary expansion.

Stability after transverse expansion of the maxilla via Le Fort I osteotomy with segments was evaluated in 39 patients. The average expansion was 5.4 mm at the second molars, decreasing almost linearly to 2.8 mm at the first premolars. Postsurgical relapse also was greatest at the second molars, averaging 2.6 mm. The percentage of relapse was greatest posteriorly, decreasing from 49% at the second molars to 30% at the first premolars. Considerable variability in stability followed surgery: Three-fourths of the patients had some relapse at the first molars (greater than 3 mm in 28%), but one fourth were stable. Sixty-two percent of the patients had a net posttreatment gain in arch width at the first molars. No correlation was found between transverse relapse and the type of presurgical orthodontic tooth movement, the use of rigid fixation, or the use of an auxiliary stabilizing arch wire. The amount of postsurgical relapse was significantly greater in those who had concurrent mandibular surgery. To improve clinical results with surgical expansion, we recommend (1) moderate overexpansion at surgery for major transverse changes, (2) maintenance of the occlusal splint for at least 6 weeks, and (3) use of a lingual arch wire or auxiliary labial arch wire to maintain molar width during postsurgical orthodontics.

Adult↗
PubMed1992

Recovery following orthognathic surgery and autologous blood transfusion.

Patients undergoing maxillary surgery, with or without mandibular surgery, were divided into two groups. One surgeon's patients served as controls and did not receive blood unless hemodynamically indicated. The remaining surgeons' patients were transfused regardless of their hemoglobin levels following surgery. An attempt was made to identify benefits or complications associated with the reinfusion of autologous blood, particularly in patients with "low blood loss." Patients were asked to record when they returned to their presurgical level of activity. Of the 46 patients in the study 14 (12 nontransfused, two transfused) were not back to full activity 6 weeks after surgery. Of the 32 patients that reported a return to full activity within the study period, transfused patients reported a significantly quicker return to full activity at 2 weeks, 3 weeks, and 4 weeks postoperatively than did their nontransfused counterparts, even when blood loss at surgery was minimal. No complications have occurred with this practice.

Adolescent↗
PubMed1991

Capric acid as a potent dilator of canine vessels in vitro and in vivo.

1. Pharmacodynamic effects of even numbered saturated fatty acids, C4-C16, were determined on isolated canine basilar and femoral arteries precontracted with PGF2 alpha. 2. The fatty acids relaxed the precontracted vessels. 3. The basilar artery was the most sensitive vessel and caprate (C10) was the most potent acid with an EC50 of 49 microM. 4. The relaxant effect was endothelium-independent. 5. Contractions elicited by norepinephrine, serotonin, and U46619 were also inhibited. 6. Caprate (C10) given intra-arterially increased femoral blood flow in a dose-dependent manner and the dose computed to increase blood flow 50% was 1.27 microM/kg.

Animals↗
PubMed1991

Identification of capric acid as a potent vasorelaxant of human basilar arteries.

To determine whether naturally occurring fatty acids, especially saturated ones, might act directly as vasodilators, segments of human basilar arteries and umbilical arteries were precontracted submaximally with prostaglandin F2 alpha and then exposed to different saturated fatty acids (C4 through C16) or unsaturated fatty acids (C14:1, C18:1, C18:2, and C18:3) at concentrations from 4 microM to 4 mM. The results showed caprate (C10) to be the most potent vasorelaxant and basilar arteries to be more responsive (EC50 = 63 microM) than umbilical arteries (EC50 = 780 microM). Caprate also inhibited contractions elicited by KCl, serotonin, and the thromboxane analogue U46619. The relaxation was independent of the endothelium, and potency was not related to the weak capacity of caprate to inhibit Ca(2+)-induced contractions of K(+)-depolarized basilar arteries. The pattern of potencies for the arteries differed, but among unsaturated fatty acids the monounsaturated (C14:1, C18:1) were more potent than the polyunsaturated (C18:2, C18:3). Comparing the potencies obtained with the concentrations reported for the free fatty acid content of arteries, brain, and plasma indicates that these lipids could influence vasomotion in health and disease.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Intracoronal radiolucencies within unerupted teeth. Case report and review of literature.

A panoramic radiograph obtained during orthodontic treatment revealed an intracoronal radiolucency within an unerupted permanent second molar. This unusual entity was successfully treated by surgical and endodontic intervention, followed by restorative and orthodontic treatment. These treatments enabled the tooth to maintain pulpal vitality, erupt, complete root formation, and function. This report will review the proposed etiologies for this condition, discuss the need for surgical intervention, and present the details of the case.

Calcium Hydroxide↗
PubMed1990

Eicosanoid levels in CSF of premature infants with posthemorrhagic hydrocephalus.

The cerebrospinal fluid (CSF) of 11 premature infants suffering from posthemorrhagic hydrocephalus was examined by radioimmunoassay for prostaglandin (PG) E2, PGF2 alpha, PGD2, 6-keto PGF1 alpha, thromboxane B2 (TxB2) and peptidoleukotrienes (LTC4/LTD4). The LTs were detected in the CSF of more of these patients (70%) than any of the other eicosanoids, and usually in the highest concentration. Among the 11 posthemorrhagic patients CSF eicosanoid levels were highest when determined soon after injury. Moreover, the variety of eicosanoids present, as well as concentrations, in these infants decreased with time. The types of eicosanoids most evident in the CSF of patients who required shunting were TxB2 and LTs, being present together in 5 of 6 (83%) of these infants. In contrast, 1 of 5 (20%) of the patients who did not require this neurosurgical intervention contained both TxB2 and LTs, the remaining having only one or neither eicosanoid. The highest average concentration for each eicosanoid studied was (pg/ml): PGE2, 628; PGF2 alpha, 985; PGD2, 1410; 6-keto PGF1 alpha, 544; TxB2, 486 and LTs, 1229. This study is the first to demonstrate that the CSF of preterm infants may contain a wide variety of eicosanoids and indicates that these lipids are a manifestation of neurological assault.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Who needs surgical-orthodontic treatment?

The indication for surgical-orthodontic treatment is a skeletal or dentoalveolar deformity so severe that the magnitude of the problem lies outside the envelope of possible correction by orthodontics alone. For adults, this means that satisfactory correction by tooth movement is not possible; for children, it means that the problem cannot be corrected satisfactorily by a combination of tooth movement and growth modification. Correction of the dental occlusion is not an adequate description of successful treatment; satisfactory facial esthetics must also result. Extrapolation from existing data for malocclusion in the United States suggests that there are a total of 1.2 million individuals in the present population with problems severe enough to require surgical-orthodontic treatment for satisfactory correction. Of these, 700,000 have Class II malocclusions and 300,000 have Class III malocclusions. Approximately 220,000 individuals have long-face problems and another 220,000 have other problems, but these groups have about a 60% overlap with the Class II and Class III groups.

Adolescent↗
PubMed1990

Responses of isolated cerebral arteries to vasoactive agents.

One hypothesis of cerebral vasospasm contends that the slow onset and eventual disappearance of the spasm of subarachnoid hemorrhage is caused by the finite production of spasmogens. These are generated and accumulate in the basal cisterns as the result of chemical reactions between blood elements, arterial wall, leptomeninges, and brain. The spasmogens may spread in the general direction of bulk CSF flow to affect arteries more distally. Pharmacodynamic studies performed on isolated cerebral arteries show that a vast array of naturally occurring substances are vasoactive. Among these, derivatives of arachidonate (eicosanoids) are strong candidates as spasmogens because they produce strong, prolonged contractions in human arteries and because the CSF levels of some eicosanoids are preferentially elevated in subarachnoid hemorrhage patients who experience severe spasm. The spasm may be largely refractory to treatment because the intravasation of blood elements and the coagulum serve as barriers to therapeutic agents and because cerebral arteries are devoid of vasa vasorum; however, in animal models of chronic subarachnoid hemorrhage, calcium antagonists given intrathecally will reverse the spasm. Other therapeutic strategems are being tried experimentally and clinically, including compounds like prostacyclin that relax cerebral arteries and inhibit platelets. In vitro studies indicate further that some plasma proteins (e.g., haptoglobin, antithrombin III) and several products of endothelial synthesis (PGI2, EDRF) may naturally provide protection against the genesis of vasospasm. The in vitro responses to bloody CSF are capricious but are not due to many pharmacologically defined substances, including hemoglobin. Hemoglobin and its derivatives, however, may be critical to the enhanced lipid peroxidation and free-radical production that occur in subarachnoid hemorrhage.

Animals↗