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Biomedical subjects

J D Brewer

Publications and source records attributed to J D Brewer.

12 recordsLinked to original sources
PubMed1998

Acceptability of shade differences in metal ceramic crowns.

STATEMENT OF PROBLEM: Application of technology that quantify color and color differences is currently used in esthetic restorative materials research. However, parameters for the size of perceptible and acceptable color differences in metal ceramic crowns have not been determined. PURPOSE: The CIELAB colorimetric system was used to study the relationship between instrumentally measured color differences (delta E) and human observer assessment of color differences in metal ceramic crowns. MATERIAL AND METHODS: Subjects were shown pairs of metal ceramic crowns whose color difference varied from indistinguishable to obvious. The subjects attempted to discern a difference in each pair's color and indicated the clinical acceptability of the shade difference between the crown pairs. RESULTS: Correlations between instrumental and visual assessment of color differences in these crown pairs did not agree in all dimensions of color space. Thresholds acceptability of color differences were 1.1 delta E units for red-varying crowns and 2.1 delta E units for yellow-varying crowns. Thresholds for perceptibility judgments were significantly lower than thresholds for acceptability judgments. CONCLUSIONS: Acceptability thresholds were found to be dependent on chromaticity. Observers were more sensitive and critical of crowns whose color differed in redness as opposed to crowns whose color differed to the same extent in yellowness.

Chi-Square Distribution↗
PubMed1996

Chronic acalculous cholecystitis: laparoscopic treatment.

From 1990 through 1993, we treated 36 patients with recurrent typical biliary colic but who showed no ultrasonic evidence of cholelithiasis by laparoscopic cholecystectomy. Associated symptoms included nausea (75%), bloating (56%), fatty-food intolerance (53%), vomiting (17%), weight loss (31%), bowel irregularity (28%), reflux or dyspepsia (25%), and fever (17%). Diagnostic evaluation included ultrasound (100%), upper gastrointestinal series (36%), oral cholecystogram (14%), computed tomographic scan (39%), endoscopic retrograde cholangiopancreatography (17%), upper gastrointestinal endoscopy (14%), and hepatobiliary scan (92%). Quantitative hepatobiliary scans in 33 patients revealed a low gallbladder ejection fraction (EF) of less than 35% in 29 patients (88%; mean EF = 9%), and 13 patients experienced reproducible pain after cholecystokinin provocation. All patients underwent attempted laparoscopic cholecystectomy; one case of unsuspected acute acalculous cholecystitis was converted to open laparotomy because of unclear anatomy. Gross and histological examination of the gallbladders revealed chronic inflammation (83%), cholesterolosis (31%), cholesterol crystals or small stones (17%), acute inflammation (8%), polyps (6%), and normal histology (6%); however, blind retrospective scoring of gallbladders revealed significant chronic inflammation in only 38%. In the 2 to 40 months (mean, 14 months) since operation, there have been no deaths (97% follow-up). Laparoscopic cholecystectomy relieved pain in 93% of patients with a low preoperative EF compared with 75% of patients with a normal EF (nonsignificant p value). Persistent abdominal or gastrointestinal complaints included flatulence (31%), loose stools or fecal urgency (29%), belching (29%), indigestion (20%), nausea (11%), and "typical" gallbladder pain (9%). We conclude that many patients with symptoms of biliary colic and scintigraphic evidence of biliary dyskinesia have histologic findings of chronic cholecystitis. Although laparoscopic cholecystectomy usually eliminates biliary colic, persistent nonbiliary complaints are frequent.

Adult↗
PubMed1996

The influence of three-dimensional video systems on laparoscopic task performance.

Many laparoscopic surgeons feel constrained by the two-dimensional (2-D) view provided by video monitors. Video-eye-hand coordination is further complicated by the diminished tactile feedback blunted by elongated instruments. Video systems capable of receiving and displaying three-dimensional (3-D) images are now available for laparoscopy. First-generation 3-D systems have been marketed with the promise of significant time savings in laparoscopic procedures compared with 2-D optics. We assessed whether laparoscopic task performance was better in 2-D or 3-D among individuals with varying levels of laparoscopic experience. Five different tasks were performed in random order using both 2-D and 3-D technology by medical students (n = 10), inexperienced surgical residents (n = 10), and laparoscopic attending surgeons (n = 10). There was no significant difference in task performance between 2-D and 3-D among groups performing simple or difficult tasks, although suturing and knot-tying were performed 12% (p = 0.06) faster in 3-D by all groups. With repetition of tasks three times, the difference between the 2-D and 3-D systems was indistinguishable. Subjective assessment of the video systems by participants revealed that only 46% (p = 0.72) preferred working in three dimensions, despite 60% (p = 0.27) sensing more motor control in 3-D. Our results suggest that first-generation 3-D video systems offer no significant advantage to the novice or expert surgeon performing laparoscopic procedures. Further trials with the next generation of 3-D video systems and a larger sample size may support the trend favoring 3-D for more complex maneuvers, such as suturing and knot-typing.

Humans↗
PubMed1995

Sutured or fibrin-glued laparoscopic choledochojejunostomy.

Minimally invasive techniques for choledochojejunostomy offer theoretical advantages for palliating unresectable periampullary neoplasms. Fibrin glue, a biologic adhesive containing concentrated fibrinogen, may obviate suturing and promote healing without stricture formation. We examined the technical ability to perform laparoscopic choledochojejunostomy (LCJ) and the applicability of thrombin-activated fibrin glue in an animal model of biliary obstruction. Domestic pigs underwent laparoscopic cholecystectomy and ligation of the distal bile duct. Three days later, a side-to-side LCJ was performed by intracorporeal sutured anastomosis (n = 7) or using four stay sutures and homologous fibrin glue (n = 7). Control animals underwent a similar bypass via open laparotomy (n = 7). The postoperative interval to ambulation and oral intake was recorded, and serial serum liver enzymes were measured. The animals were sacrificed at 6 weeks, and tensile strength of the anastomoses was assessed by tensometry. Liver function tests returned to normal values within 7 days following all methods of choledochojejunostomy. In the fibrin glue group, three anastomotic leaks (43%) occurred in the 1st postoperative week. At 6 weeks, all other anastomoses were intact and patent by cholangiogram, but there was moderate stenosis of two open and one fibrin-glue anastomosis. The sutured LCJ, while taking approximately 1 h longer to perform (P < 0.05), resulted in similar efficacy and more rapid recovery (P < 0.05) than open biliary-enteric bypass. Fibrin-glued LCJ was performed rapidly, but had less tensile strength (P < 0.05) and often leaked in the early post-operative interval. We conclude that while there may be a role for laser-activated solders for primary anastomosis, thrombin-activated fibrinogen cannot be advocated as the primary means of creating biliary anastomoses. Using intracorporeal suturing techniques, laparoscopic choledochojejunostomy may be performed safely.

Alanine Transaminase↗
PubMed1994

Laparoscopic Billroth II gastrectomy in the canine model.

The feasibility and safety of laparoscopic Billroth II gastrectomy were evaluated in an animate model. After developing the technique in acute animal experiments, laparoscopic antrectomy and Billroth II anastomosis was performed in six mongrel dogs. Video laparoscopic access to the peritoneal cavity was accomplished with six ports (five, 10 mm; one, 12-18 mm). The operations were performed without complication in 150-200 min (mean +/- SEM, 171 +/- 10 min). The animals tolerated solid oral meals on the 2nd or 3rd postoperative day. One dog developed frequent diarrheal stools and lost 3.4 kg prior to sacrifice 18 days postoperatively when a gastroileostomy was discovered. The remaining five animals did well and were sacrificed at 49-77 days postoperatively. Adhesions were minimal and the gastrojejunostomy was widely patent in all animals without evidence of leakage or obstruction. Laparoscopic Billroth II gastrectomy in the canine model is thus feasible and safe. Using laparoscopic guidance, it may be more difficult to identify the ligament of Treitz, which must be assured at the time of operation.

Anastomosis, Surgical↗
PubMed1991

Spectrophotometric analysis of a nongreening, metal-fusing porcelain.

Spectrometric analysis has been used previously to examine color differences among various porcelains and metal ceramic systems. This study determined whether nongreening porcelain of a single shade fused to high-gold and palladium-silver alloys results in the same final color. Both conventional (VMK-68) and nongreening (VMK-68N) porcelains were fused to metal coupons of high gold (Will-Ceram Y) and palladium-silver (Will-Ceram W-1) to make up four groups. CIELAB colorimetric data were collected at each of seven fabrication steps to define color differences between steps for each alloy-porcelain group as well as between groups at each step. For the shade tested, perceptible color differences between high-gold/conventional porcelain and palladium-silver/nongreening porcelain coupons did not support manufacturers' claims.

Analysis of Variance↗
PubMed1990

Clinical discrimination between autoglazed and polished porcelain surfaces.

Precementation refinements of porcelain-fused-to-metal crowns often require reglazing or polishing of the porcelain surface. This study was done to determine whether visual inspection differences exist between glazed and polished porcelain surfaces. Prosthodontists, general dentists, and students (six in each group) rated esthetic properties of 12 porcelain-fused-to-metal crowns. All crowns were initially autoglazed. For phase 1 observations, six crowns were air abraded and polished and six retained their glazed surface. For phase 2 observations, the surface treatments were reversed. At both observations, crowns were rated on 5-point Likert scales for outline form, porosity, smoothness, reflectance, texture, dullness, defects, and general esthetic appearances. Phase 1 polished and glazed crowns had different means for outline form sharpness, porosity, reflectance, dullness, and general esthetic appearance. Phase 2 crowns were different for dullness. Polished and glazed crowns alike were more dull at phase 1 than at phase 2. Glazed crowns were different between phases for reflectance and general esthetic appearance. All reported differences were significant at p less than .01. Significant differences occurred among raters with polished and glazed crowns for several variables.

Analysis of Variance↗
PubMed1985

Changes of attitude in fixed prosthodontic patients.

The results of a survey that examined the perceptions and attitudes of patients who have completed fixed prosthodontic treatment were described. The data obtained in this survey confirm the clinical experiences of many restorative dentists. Most patients desire functional, comfortable, and particularly, esthetic restorations. They are sensitive to changes that occur when provisional restorations are replaced by definitive crowns and fixed partial dentures. Tooth preparation and impression procedures are perceived as the most unpleasant steps in the treatment process. On completion of treatment, patients recognize and appreciate its benefits. The data have implications for the overall treatment process. With an appreciation for the perceptions and attitudes of fixed prosthodontic patients, the restorative dentist is prepared more completely to provide satisfying restorations. Through increased awareness of patient expectations and experiences, restorations can be planned, made and placed in harmony with the hard and soft oral tissues, and in harmony with the patient's expectations as well.

Adolescent↗
PubMed1985

Spectrometric analysis of the influence of metal substrates on the color of metal-ceramic restorations.

The development and use of ceramic alloys have created the potential for variation in the color of dental porcelain. In order to define the nature of the alterations, it is necessary to examine quantitatively the color of dental porcelain baked onto ceramic alloys. The purpose of this study was to examine spectrometrically where color differences occur in the fabrication process. One shade of Vita porcelain was baked onto coupons of three ceramic alloys (high gold, palladium-silver, base metal). Eight replications were made in each alloy at seven fabrication steps: prepared metal, oxide, first opaque, second opaque, first dentin, second dentin, and glaze. Spectrometric analyses were performed for each replication at each step. Data were tabulated every 10 nm over the recorded 380-750-nm range, for conversion to the CIE color measurement system. Tristimulus values X, Y, and Z and chromaticity coordinates x and y were calculated. Differences from spectrographic inspection were seen among the metal substrate series. The greatest variation appeared at the first dentin step between the palladium-silver and high-gold alloys and between the palladium-silver and base metal alloys. Mean tristimulus values were significantly different (p less than 0.0001) for all steps and alloys. The distribution of plotted values followed the same pattern of spectral changes throughout the seven fabrication steps. Analysis of these data shows that color differences of metal-ceramic coupons based on dissimilar metal substrates can be quantified, and that spectral reflectance values can be converted to CIE notation. As depicted spectrally, notable color differences appeared with the first dentin porcelain layer.

Chromium Alloys↗