Biomedical subjects

W E Roberts

Publications and source records attributed to W E Roberts.

At least 55 records · Page 3Linked to original sources

PubMed1997

Adjunctive orthodontic therapy in adults over 50 years of age. Clinical management of compensated, partially edentulous malocclusion.

Increasing numbers of adults, with a wide range of compensated partially edentulous (CPE) malocclusions, could benefit from adjunctive orthodontic therapy. Because loss of teeth is a risk factor for osteoporosis (OP) and restoration of occlusion depends on a positive bone response, all subjects in a prospective clinical trial were screened for OP risk factors and other bone-related metabolic problems. The sample consisted of 16 potential orthodontic patients (3 males, 13 females) over the age of 50. Based on risk factor analysis, six (44%, 1 male and 6 females) were referred for medical evaluation including bone mineral density (BMD) measurement. Ultimately, five osteopenic/osteoporotic patients, along with four patients reporting no significant osteoporotic risk factors, completed multidisciplinary treatment including adjunctive orthodontics. All were successfully treated to what was considered to be optimal esthetics and function with no substantial complications. It was concluded that patients over 50 years of age of both sexes can be effectively treated orthodontically if they have a healthy periodontium, retain an adequate residual dentition, can be controlled medically, and are compliant with treatment recommendations. Overall, orthodontics was a readily accepted, cost-effective aspect of treatment that substantially improved the esthetics and function of patients with moderate to severe CPE malocclusion.

Aged↗

PubMed1997

Multidisciplinary management of congenital and acquired compensated malocclusions: diagnosis, etiology and treatment planning.

Restoration of optimal occlusal function, consistent with desirable esthetics and a favorable long-term prognosis, is the clinical goal for management of compensated malocclusions in partially edentulous patients. An appropriate diagnostic work-up includes a careful assessment of etiology, relative to both genetic and environmental factors. Esthetic and cost-effective restoration of occlusal function often requires adjunctive orthodontic therapy, integrated into a comprehensive treatment plan. Alignment of abutments, management of edentulous space and enhancement of soft tissue contours are important preprosthetic objectives. Osseointegrated dental implants provide occlusal stops to open the vertical dimension of occlusion and serve as rigid anchorage for three-dimensional orthodontic alignment of the residual dentition. Carefully coordinated preprosthetic treatment to establish bilateral posterior occlusion (molars and/or implants) is an important goal for achieving a biomechanically-optimized restoration of occlusion. Fundamental diagnostic and treatment planning procedures are reviewed for the multidisciplinary management of partially edentulous, compensated malocclusions. Determining the probable etiology of a malocclusion is an important prerequisite for formulating a treatment plan with a reasonable probability of success. Diagnostic considerations are presented and clinical examples of specific orthodontic methods are illustrated. To demonstrate the application of fundamental principles at the clinical level, a case report is presented with a diagnosis and treatment plan for a malocclusion with both genetic and functional implications.

Adolescent↗

PubMed1996

Forceps and vacuum delivery: a survey of North American residency programs.

OBJECTIVE: To document resident instruction in operative vaginal delivery by forceps and vacuum. METHODS: A survey was sent to all 291 obstetrics-gynecology training programs in the United States and Canada. RESULTS: The overall response rate was 72% (210 of 291). Most programs (60%) have an operative vaginal delivery rate of 10% or less. Nearly all of the responding programs (199 of 209, 95%) teach operative vaginal delivery via the vacuum route; metallic cups are used in only 14% of centers. Forceps are the primary instrument in most programs (68%), but nearly one-third of responding centers use the vacuum method more often than forceps. Instruction in midpelvic operative vaginal delivery is offered in 64% of the programs, with forceps being more common by nearly a two-to-one ratio. Deep transverse arrest is handled initially by forceps by half of the respondents, whereas 28 and 22% would proceed with cesarean or attempt a vacuum extraction, respectively. CONCLUSION: Instruction in both types of operative vaginal delivery is found in most programs. The forceps are used more commonly, but vacuum is the preferred instrument in about one-third of training programs. Instruction in midpelvic delivery is offered in 64% of programs, but we noted a declining trend.

Canada↗

PubMed1996

Angiogenic induction and cell migration in an orthopaedically expanded maxillary suture in the rat.

The purpose was to examine the effect of an angiogenic factor on cell migration patterns and osteoblast histogenesis during the 96 h following orthopaedic expansion of the anterior maxillary suture. Fifty rats were divided into four groups: (1) a control group that received only angiogenic induction via injection of 5 ng/g body wt recombinant human endothelial-cell growth factor; (2) an experimental group that received orthopaedic expansion and angiogenic induction; (3) a sham group that received orthopaedic expansion and normal saline injection; and (4) a baseline group that received no expansion or injection. The experimental and sham groups were subdivided to conduct experiments over 1, 2, 3 or 4 days. The anterior portion of each maxilla was dissected free and demineralized. Sections (4 microns thick) were cut from every block and stained with Mayer's haematoxylin and eosin. Cell migration was analysed using a previously established cell-kinetics model. The osteoprogenitor cells were divided into four categories according to nuclear volume: A cells (40-79 microns3), B cells (80-119 microns3), C cells (120-169 microns3) and D cells (> or = 169 microns3 A' cells are the portion of the A cell population that responds to osteogenic stimulus. As previously defined in periodontal ligament, the reciprocal association of a decreasing number of less differentiated (A + A) cells and an increasing number of C + D cells, as a function of distance from the nearest major blood vessel, was consistently found in all groups. This suggests a vascularly oriented gradient of progressively more differentiated osteoprogenitor cells. Also, A + A' cells were predominately located within 20 microns of the nearest major blood vessel whereas the C + D cells were found at a distance > 30 microns from the nearest major blood vessel. These results suggest that the A'-->C shift occurs 20-30 microns from the nearest major blood vessel. In the angiogenic induction groups, the numbers of committed osteoprogenitors (A + A') were significantly higher than in the sham group at day 1. At day 3, the numbers of preosteoblasts (C + D) in angiogenic sutures were significantly higher than in the sham groups. This enhancement of preosteoblast population strongly suggests the possible role of activated pericytes in expanded sutures as a source of osteoprogenitor cells.

Analysis of Variance↗

PubMed1996

Operative vaginal delivery: a survey of fellows of ACOG.

OBJECTIVE: To document operative vaginal delivery rates of ACOG Fellows and to stratify practice patterns with regard to mid-pelvic delivery and deep transverse arrest by the time elapsed since residency. METHODS: A survey was mailed to a random sample of 1600 ACOG Fellows. Of the 597 respondents (37%), 558 who still practice obstetrics formed the study group. Selection bias regarding recipients of the survey was reduced by randomization by an uninvolved third party. The length of time since residency was categorized as 10 years or fewer ("recent," 31%), 11-20 years ("intermediate," 43%), and more than 20 years ("remote," 26%). RESULTS: The majority of respondents (338 of 558, 61%) reported an operative vaginal delivery rate of 15% or less. One hundred forty-two (25%) use only forceps, whereas 78 (14%) use vacuum extraction exclusively. More than half have abandoned mid-pelvic operative vaginal deliveries, and of the 41% who still perform these operations, about half use forceps. In cases of deep transverse arrest, about 25% perform cesarean delivery, whereas 26% and 42% use forceps or vacuum, respectively. Resident training and practice in vacuum delivery were more common in the recently trained groups (recent > intermediate > remote; P < .001). There were no differences among the groups with respect to attempting mid-pelvic operative vaginal delivery (P = .29), but the remote group was more likely to use forceps, whereas the recent group was more likely to use vacuum (P = .039). A large disparity existed among the groups regarding the management of deep transverse arrest, with vacuum use associated with group assignment (P < .001). CONCLUSIONS: The majority of respondents have an operative vaginal delivery rate of no more than 15%. Most respondents have abandoned mid-pelvic operative vaginal delivery. Practice patterns reflect differences in residency training; the more recently trained Fellows more often were taught and use vacuum for delivery.

Data Collection↗

PubMed1996

Rate of mesial translation of mandibular molars using implant-anchored mechanics.

Retromolar dental implants served as anchorage to close first molar extraction sites in five adult patients. Rates of unidirectional space closure for mandibular second molars were assessed with periapical radiographs superimposed on anatomical landmarks and retromolar anchorage implants. Regression analysis revealed that mesial displacement of the midroot area of the leading root was less variable (r = 0.97) than for other landmarks on the same teeth: crown (r = 0.83), alveolar crest (r = 0.82) or apex (r = 0.90). When mesial root movement (uprighting) was the principal feature of the initial mechanics (4 of the 5 patients), mesial movement of the apex was about 0.60 mm/mo for the first 8 months and then decreased to about 0.34 mm/mo as the trailing (distal) root of the second molar engaged the relatively dense bone formed by the leading (mesial) root. During the last year of space closure, radiolucent foci were noted 1-2 mm ahead of the distal root. These data suggest: (1) sustained orthodontic translation is a physiological manifestation of bone modeling and remodeling throughout the adjacent alveolar process, and (2) rate of mandibular molar translation is inversely related to the apparent radiographic density of the resisting alveolar bone.

Adult↗

PubMed1996

Intrapartum amniotic fluid index. A poor diagnostic test for adverse perinatal outcome.

OBJECTIVE: To determine if an intrapartum amniotic fluid index (IAFI) < or = 5.0 cm, or any other level, is associated with abdominal delivery for fetal intolerance to labor or Apgar scores < 7 at one and five minutes. STUDY DESIGN: Prospectively IAFI was obtained in the latent phase of labor in 1,000 parturients at > 26 weeks. Receiver operating characteristic curves were utilized to determine if any IAFI could be utilized to predict adverse outcome among (1) the entire population, (2) complicated pregnancies, (3) uncomplicated pregnancies, (4) term, or (5) preterm gestation. RESULTS: The frequencies of abdominal delivery for suspected fetal intolerance and low Apgar scores were similar among patients with IAFI < or = 5.0 cm (n = 288) versus those with IAFI > 5.0 cm. All five receiver operating characteristic curves indicated that IAFI is a poor predictor of adverse outcomes. At all the discriminatory IAFIs (0-20 cm), the false positive rate was virtually identical to the true positive rate. CONCLUSION: IAFI appears to be a poor screening test for identifying those at risk for abdominal delivery for presumed fetal distress or for birth of an infant with low Apgar scores.

Amniotic Fluid↗

PubMed1995

The irritable uterus: a risk factor for preterm birth?

OBJECTIVE: Our aim was to determine the incidence and preterm delivery rate along with the indication for delivery in patients with uterine irritability. STUDY POPULATION: In this retrospective, descriptive study, 17,186 patients with well-defined high-risk factors were compared with 2637 women with uterine irritability. RESULTS: The incidence of preterm labor in patients with uterine irritability was 18.7%, significantly less than in those with other high-risk factors (odds ratio 0.35, 0.31 < odds ratio < 0.38). However, women with uterine irritability who experience preterm labor, compared with other high-risk factors, are much more likely to deliver before 34 weeks' gestation (odds ratio 2.50, 2.07 < odds ratio < 3.03) and more than twice as likely to deliver as a result of advanced preterm labor or membrane rupture (odds ratio 2.20, 1.75 < odds ratio < 2.78). CONCLUSIONS: The incidence of preterm labor in women with uterine irritability is not as frequent as in patients with other high-risk factors. However, preterm labor does occur in patients with uterine irritability at a rate higher than that in the general obstetric population (18.7% vs 11.0%). Because it appears that women with uterine irritability have more resistance to conventional tocolytic therapy, this condition should prompt the physician to use more aggressive perinatal assessment.

Adult↗

PubMed1995

Delivery of the nonvertex second twin: breech extraction versus external cephalic version.

OBJECTIVE: Our purpose was to compare the maternal and perinatal outcomes of twin gestations in which the nonvertex second twin was delivered by total breech extraction versus those delivered by external cephalic version. STUDY DESIGN: The intrapartum courses of 284 consecutive twin gestations were analyzed retrospectively. Once those with actual birth weight < 600 gm, unrecognized multifetal pregnancy, multiple congenital anomalies, cesarean delivery, and/or antepartum intrauterine fetal death were excluded, 23 mothers were delivered by total breech extraction and 21 underwent external cephalic version. RESULTS: The two groups were similar for mean (+/- SD) maternal age, gravidity, parity, gestational age at delivery, ultrasonographic estimate of birth weight for twin B, incidence of breech or transverse presentation for the second fetus, and actual birth weight of the first or second newborn. Suspected fetal distress that led to cesarean delivery occurred significantly more often in parturients who underwent attempted external version (4/21) than total breech extraction (0/23, p = 0.04). The incidence of eventual abdominal delivery was also significantly higher in patients who underwent attempted external cephalic version (10/21) rather than breech extraction (1/23, p = 0.001). For twin B the occurrence of low Apgar scores at 1 minute was significantly higher for infants after attempted external version (7/21) rather than breech extraction (1/23, p = 0.02), but the mean pH, number with Apgar scores < 7 at 5 minutes, and number of neonatal intensive care unit admissions were similar. No perinatal traumatic injury occurred in either group. CONCLUSION: On the basis of our experience, total breech extraction of the nonvertex second twin is preferable to external cephalic version because it appears to be associated with a significantly lower incidence of fetal distress and abdominal delivery with comparable neonatal outcome.

Adult↗

PubMed1995

Stress analysis of bone modeling response to rat molar orthodontics.

The purpose of this project was to determine if alveolar bone modeling could be associated with altered mechanical environment. Finite element stress analysis of an orthodontically tipped rat molar periodontium was performed. The distributions of mechanical components within the periodontal ligament and cortical bone were compared to the well-documented bone formation and resorption patterns in the alveolus of the tooth. It was concluded that in orthodontically induced bone modeling activity, locations of osteogenesis uniquely coincided with increased tension within the periodontal ligament, while bone resorption areas could be associated with increases in other components (minimum principal and maximum shear stresses, strain energy density, and von Mises) within the bone itself.

Alveolar Process↗

PubMed1995

Statistical analysis of differential lissajous EMG from normal occlusion and Class III malocclusion.

The method of differential lissajous electromyography (DL-EMG) was applied to investigate the relationship among the integrated EMG activity, timing, and coordination of the bilateral superficial anterior temporal and masseter muscle activities in normal occlusion and Class III malocclusion subjects. In both Class III malocclusion and normal occlusion subjects, the working side muscles showed a higher mean cumulative voltage (MCV) and mean maximum peak voltage (MMPV) compared with the balancing side. In addition, a higher MCV and MMPV of the working side masseter was observed in the normal occlusion group compared with that seen in the Class III group during both right and left side chewing (p < 0.01). Discriminant analysis applied to examine the distribution, the size and the shape of DL-EMG pattern further indicated a statistical difference between subject groups (p < 0.01). Finally, there was a significantly higher percentage of clockwise DL-EMG pattern-generation in the normal group compared with that seen for Class III subjects (p < 0.01). These data indicate that, compared with normal subjects, patients with a Class III malocclusion have a demonstrably abnormal masticatory muscle balance which is well characterized by the DL-EMG method.

Adolescent↗

PubMed1995

Remodeling dynamics of bone supporting rigidly fixed titanium implants: a histomorphometric comparison in four species including humans.

The long-term maintenance of a rigid bone-implant interface (osseointegration) is the clinical goal of most dental implant systems, although the biological mechanism for retaining a foreign object in living bone is unclear. Little data are available on the physiological turnover (remodeling) of the supporting osseous tissue. The objective of this study was to histomorphometrically assess bone remodeling surrounding rigidly integrated titanium implants in multiple species. Implants, in place from 6 months to 5 years, were recovered from human, monkey, dog, and rabbit subjects. With the use of stereological point-hit and linear-intercept methods, indices of bone formation and resorption were determined. Remarkably similar patterns emerged among all investigated species. Repeated-measures ANOVA showed a 3 to 9 fold increase in remodeling within 1 mm of the bone-implant interface (P<0.001; data expressed as percent turnover / month, mean +/- SEM for n = 3-11). All morphometric indices (percent new bone, percent fluorochrome-labeled bone, percent resorption space) showed similar trends. These data suggest that the physiological mechanism for maintaining rigid osseous integration (osseointegration) is a sustained elevation of remodeling adjacent to the bone-implant interface.

Alveolar Process↗

PubMed1995

Mechanical response to functional and therapeutic loading of a retromolar endosseous implant used for orthodontic anchorage to mesially translate mandibular molars.

Three finite element models were created to investigate the potential of rigid osseous fixation (osseointegration) for orthodontic anchorage: a mandible without an implant; a mandible with an implant; and a mandible and implant with a superimposed orthodontic load. Force was applied to different locations and the stresses were computed. The mechanical stress distributions adjacent to the implant were not affected by different biting forces, hence only one case needed to be analyzed. The stresses adjacent to the bone-implant interface changed drastically due to implantation, with major changes occurring on the buccal and mesiobuccal sides. A strong, concordant gradient for intraosseous stress and bone remodeling rate was observed that reflects a mismatch in the moduli of elasticity between the implant and the supporting bone. These results suggest important clinical implications. Osseointegration of symmetrically threaded titanium implants appears to be maintained by a sustained elevation of the mechanical stresses that continuously stimulate the bone remodeling activity within 1 mm of the implant surface. It is unlikely that a rigidly fixed (osseointegrated) implant will lose integration due to an orthodontic load superimposed on normal function.

Alveolar Process↗

PubMed1995

Intrapartum detection of a macrosomic fetus: clinical versus 8 sonographic models.

The purpose of this study was to determine whether clinical or sonographic models have 1) the highest accuracy in differentiating newborns with birth-weights > or = 4,000 g (macrosomia) versus < or = 3,999 g, and 2) among macrosomics which method of predicting birth-weight has the lowest percentage error. Prospectively, 602 consecutive parturients at term had a clinical estimate of birth-weight followed by sonographic measurement of fetal parts. The sonographic prediction of birth-weight was derived using 8 different models that utilize either 1 measurement or a combination of 2 to 4 parameters. The incidence of macrosomia was 11.1% (67 of 602). Analysis of ROC curves indicated that clinical predictions (w = 0.85) were significantly better than 4 of the 8 sonographic models. The mean standardized absolute error among macrosomic newborns is significantly lower when predictions are derived clinically (99 +/- 70 g/kg) than using 1 or 2 fetal parts. Sonographic assessment of birth-weight is not significantly more accurate in the detection of a macrosomic fetus than clinical predictions.

Adult↗

PubMed1995

Emergent obstetric management of postpartum hemorrhage.

Early PPH remains a significant problem in obstetrics with serious maternal morbidity and mortality. Many patients at risk for PPH can be antenatally identified. Such identification allows these patients delivery at medical facilities where personnel, blood banking, laboratory, and radiographic expertise exist to expeditiously manage PPH. Even so, some patients without antecedent risk factors suffer PPH. This discussion provides a practical approach to establish an accurate diagnosis of PPH and an expeditious application of medical, surgical, and radiographic management. It is the responsibility of every obstetric health care provider to maintain proficiency in the diagnosis and management of PPH to reduce its incidence and associated morbidity and mortality to an unpreventable minimum.

Blood Transfusion↗

PubMed1995

Risk of preterm delivery from preterm labor in high-risk patients.

This study aimed to determine the incidence of preterm labor and birth (< 37 weeks' gestation) in patients at high risk for early delivery. In this retrospective, descriptive study, 17,186 women with high-risk factors for early delivery were studied over a five-year period (1986-1990). Study groups included women with prior preterm delivery, multifetal gestations, uterine abnormalities and cervical factors. The rate of preterm labor for all patients averaged 40% (range, 30-46%). The rate of preterm delivery in the four groups ranged from 14% to 30% and averaged 19.7%. In those who experienced preterm delivery, only 32% of cases were due to preterm labor with advanced cervical dilatation, failed tocolysis or preterm premature rupture of membranes. The majority of early deliveries were due to medical or obstetric disorders as well as to patient/physician factors. The incidence of preterm labor remains significant when women have high-risk factors for preterm delivery. However, the incidence of preterm delivery, particularly that due to avoidable factors, such as failed tocolysis and preterm rupture of the membranes, is considerably lower than that quoted in the literature.

Adult↗

PubMed1995

Management of immune thrombocytopenia purpura at a military medical center.

OBJECTIVE: To investigate whether fetal platelets in immune thrombocytopenia purpura (ITP) may be predicted by antepartum assessment. METHODS: A prospective analysis was conducted of 28 pregnant women with ITP out of 8,056 deliveries. Of the 28 patients, 13 were evaluted by fetal scalp sampling and 11 were evaluated by percutaneous umbilical blood sampling (PUBS). RESULTS: The mean fetal and maternal platelet counts prior to delivery were 146,000 and 176,000, respectively. The mean fetal and maternal platelet counts after delivery were 245,000 and 149,000, respectively. Fetal cord platelet counts could not be predicted by maternal platelet count, the presence/absence of maternal direct/indirect anti-platelet antibodies, steroid therapy, or history of splenectomy. PUBS for fetal platelet assessment correlated well with fetal postdelivery counts. CONCLUSIONS: Patients with ITP rarely exhibit complications. No antepartum characteristic enhances reliable prediction of neonatal outcome. Method of delivery should be based on obstetric guidelines.

Adolescent↗

PubMed1994

Plasma exchange for preeclampsia: II. Unsuccessful antepartum utilization for severe preeclampsia with or without HELLP syndrome.

OBJECTIVE: To explore the efficacy of plasmapheresis/plasma exchange as the primary therapy to arrest and reverse the progression of severe preeclampsia with or without HELLP syndrome in order to postpone delivery and improve perinatal outcome in very preterm pregnancies. STUDY DESIGN: In this case series of patients managed over a 4-year period from 1984 to 1987, seven gravidas with severe preterm preeclampsia underwent 1-2 plasmaphereses/plasma exchange procedures using the IBM 2997 Cell Separator with continuous electronic fetal heart rate monitoring (n = 7 patients) and central cardiovascular monitoring (n = 3 patients). RESULTS: The seven patients (one with HELLP syndrome, six without HELLP) presented between 24 and 30 weeks gestation and, despite plasmapheresis/plasma exchange, the severity of each study subject's preeclampsia persisted without clinically significant improvement. Maternal-fetal deterioration required cesarean delivery in all cases within 48 (in four patients within < 36) hours of therapy. No clinically significant adverse effect of plasma exchange therapy was recorded during cardiovascular and laboratory monitoring; two fetuses developed repetitive late decelerations during exchange despite adequate maternal fluid preload. The only patient with HELLP syndrome developed eclampsia as her third plasma exchange within 25 hours was being initiated. Significant problems with fluid retention and displacement (variable amounts of pulmonary edema, pleural effusions, large volume ascites) were encountered in all patients. Four neonates died (24-27 weeks/438-820 g) and three survived intact (740, 950, and 1,280 g). One mother (case 5) developed end-stage renal disease 21 months postpartum. CONCLUSIONS: The application of plasmapheresis/plasma exchange therapy as described in order to prolong very preterm pregnancies in the undelivered patient with severe preeclampsia/eclampsia with or without HELLP syndrome did not produced encouraging results. Patients in general were exposed to additional medical and surgical risk without a corresponding improvement in perinatal outcome.

Adolescent↗