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Biomedical subjects

S S Porter

Publications and source records attributed to S S Porter.

16 recordsLinked to original sources
PubMed2001

Long-term performance of Osseotite implants: a 6-year clinical follow-up.

In this prospective, multicenter study, 147 Osseotite implants were placed in 75 patients (32 men and 43 women with a mean age of 54 years) using a conventional two-stage surgical protocol with 3 months of healing time in the mandible and 6 months in the maxilla. Of the 147 implants, 69% were inserted in posterior sites and 64% were short implants of 10 mm or less. From the time of implant insertion to second-stage surgery, 5.1 months (+/- 2.4 months) elapsed. Restorative treatments included 25 single-tooth replacements (28.4%), 58 short span fixed bridges (65.9%), 1 full-arch reconstruction (1.1%), and 4 overdentures (4.5%). The mean time from implant placement to final recall was 74.1 months (+/- 8.9 months). At second-stage surgery and at 6-month and annual follow-up examinations, implants were evaluated for mobility, peri-implant radiolucency, gingival health, signs and symptoms of infection, neuropathies, paresthesia, and crestal bone levels. A 3-year interim report identified 5 implant failures, 4 of which occurred as a clustering phenomenon in a single, medically compromised patient. Using the life table analysis method, the cumulative implant success rate was calculated at 96.6%. The 3-year interim report indicates that the implants developed an extended, functional osseous state that remained stable for more than 6 years.

Adult↗
PubMed2001

An evaluation of a case of agenesis of the corpus callosum with Rourke's nonverbal learning disorder model.

This article evaluates the case of an 11-year-old male with congenital agenesis of the corpus callosum, against Rourke's NLD models. A comprehensive neuropsychological assessment was completed, and impairments with attention, movement, fine motor and sensory perception, visuo-spatial organization, and verbal memory were identified. Additionally, a volumetric analysis of the magnetic resonance image (MRI) was completed. Although no gross structural abnormalities, beyond agenesis, were present, the possibility of unobservable abnormalities was considered. Many predicted NLD deficits were clearly evidenced in this case, including associated behavioral problems. This study concludes that although Rourke's NLD model is descriptive of many aspects of white matter impairments, it may not account for the full range or severity of deficits that may be observed. In callosal agenesis, children may exhibit verbal learning, auditory attentional, and verbal expressive difficulties.

Clinical Conference↗
PubMed1999

A human histologic analysis of osseotite and machined surfaces using implants with 2 opposing surfaces.

A human histologic study was conducted to compare the percentage of bone-to-implant contact (BIC) at 6 months for Osseotite and machined, commercially pure titanium implant surfaces. To eliminate potential influences caused by differences in bone density at different intraoral locations, 2 mm x 5 mm, threaded, 2-surfaced titanium implants were manufactured; 1 side received the Osseotite surface modification and the opposite side maintained a machined surface. In each of 11 patients, 1 test implant was placed in the posterior maxilla (Types III and IV bone) during conventional dental implant surgery. Following 6 months of unloaded healing, the conventional implants were uncovered, and the test implants and surrounding hard tissue were removed. Histologic analysis indicated that at 6 months of unloaded healing, the mean BIC value for the Osseotite surfaces (72.96% +/- 25.13%) was statistically significantly higher (P < 0.05) than the mean BIC value for the machined surfaces (33.98% +/- 31.04%). When the BIC values for the machined and Osseotite surface pairs were ranked from high to low based on the machined BIC value range of 93% to 0%, the upper 50th percentile (20 surface pairs) mean BIC value was 86.1% +/- 16.7% for the Osseotite surfaces and 60.1% +/- 18.3% for the machined surfaces. The lower 50th percentile (19 surface pairs) mean BIC value was 59.1% +/- 25.3% for the Osseotite surfaces and 6.5% +/- 10.8% for the machined surfaces. Differences between mean BIC values for the 2 surfaces in both the upper and lower 50th percentiles were statistically significant (P < 0.05). The results of this study indicate that in the poorer quality bone typically found in the posterior maxilla, a statistically significantly higher percentage of bone contacts Osseotite surfaces when compared to opposing machined surfaces on the same implant.

Alveolar Process↗
PubMed1998

A prospective multicenter study evaluating loading of osseotite implants two months after placement: one-year results.

Historically, the recommended time between placement and functional loading of machined-surface dental implants has been 3 months for the mandible and 6 months for the maxilla. However, such recommendations are a result of evaluating randomly chosen healing times during the initial phase of implant development and are based on the subsequent clinical outcome of either implant integration or mobility. In recent years, histologic and experimental studies have shown that specifically designed micro-topographic implant surfaces can result in increased bone-to-implant contact at earlier healing times than obtained with machined-surface implants. Histologic and clinical studies investigating early and immediate implant loading support the premise that implants can be placed into function earlier than previously recommended. With the development of specifically designed implant surfaces and the utilization of time-saving surgical (one-stage surgical protocol) and prosthetic (implant position indexing) techniques, patients are now being restored and returning to function sooner than previously thought possible. The purpose of this multicenter clinical investigation is to evaluate the efficacy of loading Osseotite dental implants (3i-Implant Innovations Inc., Palm Beach Gardens, Florida) at 2 months and to determine the effect of early loading on implant performance and survival. A total of 429 Osseotite implants were placed in 155 patients (87 females and 68 males; mean age 54.0 +/- 13.7 yr), at 10 study centers, and subsequently loaded 2.1 +/- 0.7 months following placement. A single-stage surgical protocol was followed, with implants indexed immediately or impressed 4 to 6 weeks following placement. Patient restorative treatments included placement of 83 single-implant provisional restorations and 129 splinted, two-, three-, and four-implant supported maxillary and mandibular provisional restorations. The mean time from prosthetic loading to the most recent follow-up evaluation was 10 +/- 1.3 months. Seven of the 429 implants did not integrate; of these, six were identified prior to loading and one was identified 1 month after loading. The cumulative implant survival rate was 98.5% at 12.6 months. The cumulative post-loading implant survival rate was 99.8% at 10.5 months. The preliminary results of this clinical investigation suggest that successful functional loading of the Osseotite dental implant is possible at 2 months following noncomplicated implant placement.

Adult↗
PubMed1991

Somatosensory-evoked potential monitored during total hip arthroplasty.

One hundred consecutive patients were monitored using somatosensory-evoked potential (SEP) monitoring to detect intraoperative sciatic nerve compromise during total hip arthroplasty. The peroneal nerve was stimulated using the contralateral extremity to rule out systemic influences on the SEP tracings. Loss of amplitude or an increase in latency of greater than 10% was considered significant. Of the 18 patients who exhibited changes that met these criteria, 16 were female. Two patients had loss of amplitude of the tracings at the time of closure, and both of these patients exhibited postoperative sciatic nerve palsies. There were no false negatives. Femoral reaming and reduction are the surgical events most commonly associated with nerve reactions. Patients who have had prior hip procedures appear to be at higher risk. There was no correlation with intraoperative SEP changes and age, weight, surgical approach, or leg lengthening. Compared with unmonitored patients, there was no reduction in the incidence of sciatic palsy.

Evoked Potentials, Somatosensory↗
PubMed1989

Apparent fracture toughness of all-ceramic crown systems.

This study measured apparent fracture toughness (Kc) and elastic modulus-to-hardness ratio (E/H) of dental restorations made with five all-ceramic crown systems. An indentation technique was used whereby Kc was calculated from the length of radial cracks formed on the release of a Vickers Diamond. Twenty-four crowns were made by using five different crown systems: Cerestore, DICOR, Hi-Ceram, Renaissance, and Vitadur-N. After the crowns were fired and glazed, they were embedded, polished, gold-coated, and indented under oil. In addition Knoop indentations were made for E/H calculation. Cerestore had a mean Kc of 1.79 MPa.m1/2 and E/H of 13.9, DICOR 2.10 and 26.8, Hi-Ceram 1.96 and 17.8, Renaissance 2.02 and 24.2, and Vitadur-N 1.96 and 22.3. Statistically significant differences (p less than 0.05) were found between DICOR and Cerestore materials for Kc and between DICOR, Renaissance, and Cerestore materials for E/H. For comparison, previous work found Vita VMK metal ceramic crowns to have a mean Kc of 1.91 MPa.m1/2 and E/H of 20.2.

Aluminum↗
PubMed1989

Apparent fracture toughness of metal ceramic restorations with different manipulative variables.

Apparent fracture toughness (Kc) is a measure of the strain absorption capacity of brittle materials. It relates to the level of tensile stress that must be exceeded at the tip of a crack before failure occurs. Using an indentation technique, this study measured Kc and elastic modulus-to-hardness ratio (E/H) of 65 metal ceramic crowns made with 13 different variables. The variables studied were (1) brand of porcelain, (2) firing temperature, (3) condensation, and (4) modeling liquid. Statistically significant differences in Kc and E/H were found in respect to porcelain brand and between two of the modeling liquids. No significant differences were found in respect to altering firing temperature or condensation.

Chemical Phenomena↗
PubMed1989

Intraoperative cortical somatosensory evoked potentials for detection of sciatic neuropathy during total hip arthroplasty.

Approximately 3% of patients undergoing hip arthroplasty develop postoperative sciatic neuropathy. The factors associated with changes in somatosensory evoked potentials (SSEP) and sciatic neuropathy were examined in patients undergoing hip arthroplasty, to evaluate whether the use of intraoperative SSEP could help reduce the incidence of postoperative sciatic neuropathy. Eighty-eight patients were assigned to either monitored or unmonitored groups. SSEP were recorded following peroneal nerve stimulation, using contralateral stimulation to detect systemic influences on SSEP. Amplitude reduction of less than 50% of control and/or latency increase of greater than 10% of control was considered significant, and surgical intervention was attempted to restore SSEP. Previous surgery and a lateral incision approach tended to be associated with sciatic neuropathy (p less than 0.053). The incidence of sciatic neuropathy in the monitored group (4.3%) was not different from the unmonitored group (2.4%). Isolated reduction in amplitude or prolongation in latency of the SSEP was not predictive of postoperative neurologic function of the sciatic nerve. Six patients, two of whom developed sciatic neuropathy, demonstrated complete flattening of the SSEP. Both of these patients had flattened SSEP for two or more surgical events (p less than 0.01) and flattened SSEP were present at the end of the surgical procedure. There were no false-negative SSEP changes. Simultaneous amplitude and latency changes appear to be predictive of sciatic nerve function following hip arthroplasty.

Evoked Potentials, Somatosensory↗
PubMed1989

Colour measurements of all ceramic crown systems.

The objectives of this study were: (i) to determine variability among colour parameters of five different ceramic crown systems; and (ii) to measure the effect of using coloured luting agents on restoration colour. The crown systems studied were Cerestore, Dicor, Hi-Ceram, Renaissance, and Vitadur-N. Five crowns for each system were made according to manufacturer's instructions with the same nominal shade (Vita Lumin Vacuum A2) to fit an Ivorine central incisor tooth. Restoration thickness was adjusted to within +/- 0.1 mm (+/- 0.05 mm in the mid-facial area where colour measurements were to be made) with the aid of a dial calliper prior to glazing or, in the case of Dicor, surface staining. Where a core was part of the system this was fabricated to the minimum recommended thickness. The crowns were cemented using luting agents of five different colours in a randomly chosen sequence. The colour of each restoration/cement combination was measured three times using a small-area colorimeter (Minolta CR-121). The variance of each colour parameter (L*, a*, b*) was statistically compared for each crown system using an analysis of variance procedure, as was the effect of the cement. Observed differences were related to visual perception by using the colour difference formula. There were statistically significant differences among the variances of the crown systems and the cements, with significant interactions between crown systems and direction of colour and between cement and direction of colour. Restorations made with different ceramic crown systems had noticeably different colour despite having the same nominal shade. Changing the shade of the luting agent had a perceivable effect on Dicor crowns and, to a lesser extent, on Vitadur-N crowns but not on the other systems due, presumably, to the opacity of their core materials.

Color↗
PubMed1988

Comparison of intravenous nitroprusside, nitroprusside-captopril, and nitroglycerin for deliberate hypotension during posterior spine fusion in adults.

Three techniques for deliberate hypotension (mean arterial pressure, 60 to 70 mmHg) were prospectively compared in adults undergoing posterior spine fusion. Patients received either IV sodium nitroprusside, sodium nitroprusside with oral captopril pretreatment, or IV nitroglycerin. Patient groups were comparable in age, sex, weight, baseline hemodynamic and laboratory parameters, duration of surgery, and duration of hypotension. Absolute blood loss was significantly less in the group receiving nitroglycerin; however, there were no differences between groups when corrected for operative exposure (milliliter per spine segment exposed). Nitroprusside was effective in producing target blood pressure in all patients. Nitroglycerin was ineffective in two patients and two other patients required greater than 20 micrograms/kg/min. Both groups receiving nitroprusside developed significant postinfusion increases in arterial pressure. Blood pressure fell significantly after induction of anesthesia in patients receiving captopril. Cardiac index, heart rate, pulmonary capillary wedge pressure, intrapulmonary shunt, and arterial blood gases were comparable and did not change significantly in any group. Systemic vascular resistance fell during infusion in all groups and remained depressed after infusion in patients receiving nitroglycerin. Plasma renin activity was significantly increased in the group receiving captopril due to loss of feedback inhibition of renin release and rose significantly during infusion in those patients receiving nitroprusside alone. There were no complications. Nitroprusside with and without captopril pretreatment was associated with postoperative increases in arterial pressure, although not to hypertensive levels, probably due to loss of captopril activity after single-dose administration. The use of nitroglycerin was limited by lack of potency. There was no demonstrable clinical advantage for any of the three techniques.

Administration, Oral↗
PubMed1986

Intraoperative allergic reactions to hydroxyethyl starch: a report of two cases.

The presentation, evolution, and treatment of two cases of intraoperative allergic reactions are described. In each case, the offending agent was felt to be hydroxyethyl starch (HES), a synthetic polymer colloid solution used for intravascular volume expansion. Symptoms included urticaria, angioedema, and hypotension in the first patient, and urticaria, hypoxia, and haemoconcentration in the second patient. Both patients had earlier received multiple drugs and/or blood products. However, HES administration in both patients immediately produced allergic symptomatology. The first patient had concurrent depression of serum total complement levels (CH50) and no elevation of plasma histamine levels, which suggested a complement-mediated reaction to HES. Levels of CH50 and histamine were not obtained from the second patient. Direct stimulation of mast cell degranulation by the offending agent, complement activation, or conventional antigen-antibody interaction in a previously exposed patient may initiate intraoperative allergic reactions. Anaesthesia personnel should be aware of the risk of intraoperative allergic reactions to HES and be prepared to treat them rapidly and effectively.

Adolescent↗
PubMed1985

Spinal cord and cerebral blood flow responses to subarachnoid injection of local anesthetics with and without epinephrine.

Subarachnoid anesthesia with lidocaine, mepivacaine, or tetracaine with and without added epinephrine (1:100 000) produced no demonstrable changes in average cerebral (CBF) or segmental spinal cord blood flow (SCBF) in 38 cats anesthetized with pentobarbital. Blood flow was measured by the injection of radioactive microspheres. Seven groups of cats received either lidocaine 15 mg, lidocaine 15 mg with epinephrine, mepivacaine 10 mg, mepivacaine 10 mg with epinephrine, tetracaine 5 mg, tetracaine 5 mg with epinephrine, or saline with epinephrine 1:100 000. Mean arterial pressure (MAP) decreased significantly (P less than 0.05) in Groups I-VI. Added epinephrine had no effect on the decrease in MAP. Amplitude of the somatosensory cortical evoked response decreased significantly in Groups I-VI, but did not change from control in Group VII. No significant change in CBF or SCBF was demonstrated in any group at any time. Plasma lidocaine and mepivacaine levels were significantly less at 5 min after subarachnoid injection in the groups receiving epinephrine compared to those not receiving epinephrine (P less than 0.05). The data appear to support the hypothesis of a vasoconstrictive reduction in systemic absorption of intrathecal local anesthetics, but suggest that significant segmental spinal cord ischemia does not occur. Maintenance of total flow in the face of a decrease in MAP suggests that autoregulation in brain and spinal cord may be maintained. Changes in regional SCBF or CBF may have been present but were not examined in this study. Further studies of brain and spinal cord blood flow dynamics, regional flow changes, and regulation of flow after intrathecal agents are necessary.

Anesthesia, Spinal↗
PubMed1984

Venous air embolism in a child undergoing posterior fossa craniotomy: a case report.

The incidence of venous air embolism in children undergoing neurosurgical procedures in the sitting position may be as high as 33 per cent. It may be more serious in children because smaller total volumes of air can produce serious physiologic disturbances or fatalities, and the risk of systemic air embolism through a patent foramen ovale or patent ductus arteriosus may be greater than in adults. The case of a six-year-old child who sustained four separate episodes of air embolism while undergoing posterior fossa exploration is presented. Early episodes were well tolerated, but later episodes produced clinical instability. A total of 11 cc of air was recovered from an indwelling right atrial catheter, and the patient recovered uneventfully. This case report illustrates the physiologic changes produced by venous air embolism and reviews the importance of adequate monitoring techniques and early treatment.

Astrocytoma↗
PubMedDate not supplied

A prospective multicenter clinical study of the Osseotite implant: four-year interim report.

This article reports the 4-year interim results of a multicenter study evaluating the clinical performance of the Osseotite dental implant. At 4 study centers, 485 Osseotite implants were consecutively placed in 181 patients (219 were placed in the mandible and 266 in the maxilla). A total of 355 implants were placed in posterior regions. Short implants (10 mm or less) represented 31.5% (n = 153) of all implants placed in this study. Patients were restored with 210 restorations, distributed as 123 short-span prostheses, 58 single-tooth replacements, 28 long-span prostheses, and 1 maxillary overdenture. At this 4-year interim evaluation, the mean time from implant placement to the most recent evaluation was 52.6 +/- 3.0 months, with a mean loading time of 43.3 +/- 3.8 months. Of the 485 implants placed, there have been 6 failures. All implant failures occurred prior to loading and were categorized as early implant failures. Five of the 6 failures occurred in the maxilla. Only one of the 153 short implants failed to integrate. Baseline radiographs were obtained at prosthesis connection. Radiographic analysis 1 year post-restoration showed a mean bone loss of 0.09 +/- 0.7 mm. From baseline to the end of the second year of function, an overall mean bone loss of 0.13 +/- 0.8 mm was recorded, indicating no additional bone was lost after the first year of implant function. At 4 years, the cumulative implant success rate for all implants placed in this study was 98.7%, with a 99.4% success rate in the posterior mandible and 98.4% success rate in the posterior maxilla. Results of this 4-year interim analysis indicate that this implant achieved a high success rate in posterior regions and that all failures with this implant in this patient population occurred prior to implant loading. When the clinical success of implants 10 mm or shorter was compared to that of implants greater than 10 mm in length, the shorter implants in this study performed similarly to longer implants.

Adolescent↗