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Biomedical subjects

R DeLong

Publications and source records attributed to R DeLong.

At least 19 recordsLinked to original sources
PubMed2001

Factors influencing optical 3D scanning of vinyl polysiloxane impression materials.

PURPOSE: Future growth in dental practice lies in digital imaging enhancing many chairside procedures and functions. This revolution requires the fast, accurate, and 3D digitizing of clinical records. One such clinical record is the chairside impression. This study investigated how surface angle and surface roughness affect the digitizing of vinyl polysiloxane impression materials. MATERIALS AND METHODS: Seventeen vinyl polysiloxane impression materials were digitized with a white light optical digitizing system. Each sample was digitized at 3 different angles: 0 degrees, 22.5 degrees, and 45 degrees, and 2 digitizer camera f-stops. The digitized images were rendered on a computer monitor using custom software developed under NIH/NIDCR grant DE12225. All the 3D images were rotated to the 0 degrees position, cropped using Corel Photo-Paint 8 (Corel Corp, Ottawa, Ontario, Canada), then saved in the TIFF file format. The impression material area that was successfully digitized was calculated as a percentage of the total sample area, using Optimas 5.22 image processing software (Media Cybernetics, LP, Silver Spring, MD). The dependent variable was a Performance Value calculated for each material by averaging the percentage of area that digitized over the 3 angles. New samples with smooth and rough surfaces were made using the 7 impression materials with the largest Performance Values. These samples were tested as before, but with the additional angle of 60 degrees. Silky-Rock die stone (Whip Mix Corp, Louisville, KY) was used as a control. RESULTS: The Performance Values for the 17 impression materials ranged from 0% to 100%. The Performance Values for the 7 best materials were equivalent to the control at f/11 out to a surface angle of 45 degrees; however, only Examix impression material (GC America Inc, Alsip, IL) was equivalent to the control at f/11/\16. At the 60 degrees surface angle with f/11/\16, the Performance Values were 0% for all the impression materials, whereas that for the control was 90%. The difference in the Performance Values for the smooth and rough surface textures was 7%, which was not significant. CONCLUSIONS: The digitizing performance of vinyl polysiloxane impression materials is highly material and surface angle-dependent and is significantly lower than the die stone control when angles to 60 degrees are included. It is affected to a lesser extent by surface texture.

Analysis of Variance↗
PubMed2001

Development of a nondestructive compliance test for resilient denture liners.

PURPOSE: Resilient denture liners are prescribed for patients who cannot adjust to hard-based dentures because of a thin mucosa or severe alveolar ridge resorption. A nondestructive test to evaluate compliance of new soft liner materials will be useful in clinical trials. The purpose of this study was to evaluate a nondestructive compliance testing technique designed to characterize long-term, silicone-based resilient denture liner materials. MATERIALS AND METHODS: Samples of thicknesses of 1.1, 2.2, 3.3, and 4.4 mm of 2 materials (MPDS-SL [Lai Laboratories, Inc, Burnsville, MN] and Molloplast-B [Buffalo Dental, New York, NY]) were assessed for compliance using a closed-loop servohydraulic testing system, applying a 3 lb force following a squarewave pattern; force and position values were recorded using a storage oscilloscope. The oscilloscope values were analyzed using computer software to determine compliance values. The effect of material thickness was examined by testing wedges of the 2 materials. RESULTS: The testing technique used showed that differing thicknesses had significantly different compliance values (p <.0001). In the materials used to evaluate the technique, MPDS-SL behaved more elastically than did Molloplast-B (p <.0001). Material thicknesses beyond 2.2 mm did not increase compliance, although MPDS-SL had a steeper thickness-compliance curve than Molloplast-B. CONCLUSIONS: The method used to test compliance proved to be sufficiently sensitive to distinguish between 2 materials and between varying thicknesses. The sensitivity and nondestructive nature of this test show its suitability for clinical evaluation of resilient denture liners.

Analysis of Variance↗
PubMed2000

Mortality of sea lions along the central California coast linked to a toxic diatom bloom.

Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans.

Animals↗
PubMed1999

Wear of enamel and veneering ceramics after laboratory and chairside finishing procedures.

PURPOSE: This in vitro study compared the wear of enamel against 3 types of ceramics with high esthetic potential (designed for layering techniques): feldspathic porcelain (Creation), aluminous porcelain (Vitadur alpha), and low-fusing glass (Duceram-LFC). Laboratory finishing (glazing/polishing) and chairside polishing with a Dialite kit were simulated to compare their respective effects on wear. METHODS: Tooth-material specimen pairs were placed in an artificial mouth using closed-loop servohydraulics. Constant masticatory parameters (13.5 N occlusal force, 0.62 mm lateral excursion; 0.23 second cuspal contact time) were maintained for 300, 000 cycles at a rate of 4 Hz. The occlusal surface of each pair was mapped and digitally recorded before and after each masticatory test. Quantitative changes were measured in terms of depth and volume of wear. Quantitative wear characteristics were assessed by SEM. RESULTS: Significant differences were observed (2-factor ANOVA, P <.05). Duceram-LFC generated increased volume loss of enamel (0.197 mm(3)) compared with Creation (0.135 mm(3)) and Vitadur alpha (0.153 mm(3)). Creation exhibited the lowest ceramic wear and lowest combined volume loss (0.260 mm(3); the sum of the data for enamel and the opposing material) compared with Duceram-LFC (0.363 mm(3)) and Vitadur alpha (0.333 mm(3)). The most significant differences among materials were observed in volume loss, not in depth of wear. For all 3 ceramic systems, qualitative SEM evaluation revealed an abrasive type of wear. Wear characteristics of chairside polished specimens were similar to those of laboratory finished specimens (glazed and polished). CONCLUSION: Duceram-LFC was the most abrasive ceramic for the antagonistic tooth. Creation ceramic was the least abrasive material and most resistant to wear. Defects, brittleness, and the possibly insufficient toughness of LFC may explain its increased abrasiveness. Laboratory and chairside finishing procedures generated similar results.

Analysis of Variance↗
PubMed1998

Dimensional changes during veneering procedures on discoloured teeth.

OBJECTIVES: The aim of the study was to determine the dimensional changes of teeth when veneering procedures are involved. METHODS: Fifteen discoloured central incisors were selected from a group of 180 veneer restorations (VRs) composed of three different types of materials (direct resin composite, indirect resin composite and porcelain). Impressions and dies were made before treatment, after preparation and after placement and finishing the restoration. Contact stylus profilometry and subsequent analysis of the 3-D surface images provided quantitative data of the differences between the various treatment phases. RESULTS: The preparation reduction was the most for indirect resin composite VRs and the least for direct resin composite VRs. All veneer restorations showed nearly the same thickness and dimensional change after treatment, except one, which resulted in an additional increase of volume of the tooth. CONCLUSION: From the results of this study it is concluded that the dimensions of a discoloured tooth treated with a veneer restoration unintentionally increased, resulting in overcontour.

Analysis of Variance↗
PubMed1998

Novel chemically modified oligonucleotides provide potent inhibition of P-glycoprotein expression.

One major form of multiple drug resistance (MDR) to cancer therapeutic agents is mediated by overexpression of P-glycoprotein, a membrane ATPase that serves as a drug efflux pump. In humans, this protein is the product of the MDR1 gene. We have used chemically modified antisense oligonucleotides to reduce expression of P-glycoprotein in multidrug-resistant fibroblasts and colon carcinoma cells. Although several types of oligonucleotides were tested, compounds having a phosphorothioate backbone and a methoxyethoxy (ME) group at the 2' position of the ribose ring proved to have the greatest potency. Thus, phosphorothioate 2'-ME oligonucleotides directed against either the AUG codon region or the stop codon region of the MDR1 message produced substantial (50-70%) inhibition of P-glycoprotein expression at concentrations of < or = 50 nM. In addition, such treatment resulted in augmented drug uptake as measured by flow cytometry. Unmodified phosphorothioate compounds of the same sequence were active only in the micromolar range. We also tested the ability of several potential delivery agents to enhance the pharmacological effectiveness of anti-MDR1 oligonucleotides. Both commercial Lipofectin, a well known liposomal transfection agent, and a liposomal preparation based on a novel "facial amphiphile" were effective in enhancing their pharmacological effects of antisense oligonucleotides. A Starburst dendrimer, a type of cationic polymer, was also effective in oligonucleotide delivery. This report emphasizes that significant improvements in antisense pharmacology can be made through judicious use of both chemical modifications of oligonucleotides and appropriate delivery systems.

3T3 Cells↗
PubMed1997

Exclusion of the expansion of CAG/CTG repeats at thirteen loci on chromosome 12 as a candidate genetic mutation in scapuloperoneal spinal muscular atrophy with anticipation.

Scapuloperoneal spinal muscular atrophy (SPSMA) is a neuromuscular disorder characterized by weakness in the distribution of shoulder girdle and peroneal muscles. We have previously described a large New England kindred with autosomal dominant SPSMA and have subsequently linked this family trait to 12q24.1-q24.31. In this family, disease expression becomes more severe and progressive in successive generations, suggesting genetic anticipation. Accordingly, we have investigated the thirteen known CAG/CTG repeat loci on chromosome 12 that could be tested by using the polymerase chain reaction as candidate genetic mutations in SPSMA. None of these loci is expanded.

Age of Onset↗
PubMed1997

Variation in tooth wear in young adults over a two-year period.

STATEMENT OF PROBLEM: Although all the processes of loss of hard tissue are important, attrition on the occlusal surfaces commands our attention. PURPOSE OF STUDY: The enamel wear rate of 18 young adults over 2 consecutive years was measured independently by volume loss and mean depth loss. Any significant differences in tooth wear resulting from gender and a clinical diagnosis of bruxism were identified. MATERIAL AND METHODS: A strict protocol for dental impressions provided epoxy models, which were digitized with a null point contact stylus. AnSur software provided a complete morphologic description of changes in the wear facets. RESULTS: The mean loss for all teeth measured was 0.04 mm3 by volume and 10.7 microns by depth for the first year. CONCLUSIONS: These numbers were approximately doubled at 2 years of cumulative wear.

Adult↗
PubMed1997

Isoflurane anesthesia in free ranging sea lion pups.

California sea lion pups, Zalophus californianus, (n = 115), were captured and anesthetized for (mean +/- SD) 17.6 +/- 7.8 min on San Miguel Island, California (USA) in November of 1992. Mask isoflurane anesthesia allowed intubation in 7.1 +/- 2.74 min. Pups recovered and walked in 7.32 +/- 4.8 min. Mask anesthesia in pups resulted in relaxation in 45 +/- 14 sec. Safe, brief anesthesia was delivered in support of weighing, medical evaluation, and short surgical procedures. Recovery character of all pups was sufficient to permit release to the free ranging state immediately after surgery, saving labor, supervision personnel, and postoperative time.

Anesthesia, Inhalation↗
PubMed1996

Linkage of scapuloperoneal spinal muscular atrophy to chromosome 12q24.1-q24.31.

Scapuloperoneal (SP) syndromes are heterogeneous neuromuscular disorders which are characterized by weakness in the distribution of shoulder girdle and peroneal muscles. SP syndromes can resemble facioscapulohumeral muscular dystrophy (FSH) due to scapular weakness or Charcot-Marie-Tooth disease (CMT) due to atrophy of peroneal muscles. Both neurogenic and myopathic SP syndromes have been described. Locus for the myopathic form of SP syndrome (scapuloperoneal muscular dystrophy, SPMD) has recently been assigned to chromosome 12q. We previously described a large New England kindred exhibiting an autosomal dominant neurogenic SP syndrome (scapuloperoneal spinal muscular atrophy, SPSMA). Disease expression was more severe and progressive in successive generations, which suggested genetic anticipation. We performed genetic linkage analysis of this family with microsatellite markers and excluded the loci for FSH, CMT, SPMD and SMA (spinal muscular atrophy) in our family. Linkage in our SPSMA family (lod score > 3) was established to seven microsatellite markers that map to chromosome 12q24.1-q24.31. The highest lod score with two-point linkage analysis was 6.67 (theta = 0.00) with marker D12S353. Multipoint analysis gave maximum lod scores of 7.38 between D12S354 and D12S79, and also 7.38 between D12S369 and NOS1 (neuronal nitric oxide synthase). The gene for SPSMA lies within the 19 cM interval between D12S338 and D12S366. This report establishes a locus for the neurogenic form of SP syndrome approximately 20 cM telomeric to the one described for the myopathic form of SP syndrome.

Chromosome Mapping↗
PubMed1994

Children with autistic spectrum disorder and a family history of affective disorder.

This paper compiles the clinical behavioral phenomenology of individuals with autistic spectrum disorder (ASD) with a family history of bipolar affective disorder (BPAD) or major depression and no identified neurological disorder, based on repeated clinical interviews during extended follow-up (ranging from six months to 21 (mean 3.9) years. Their pattern of affective and cognitive symptoms showed notable similarities across the entire group, despite wide variations in severity; was congruent with standard definitions of ASD; showed many features of childhood BPAD, including affective extremes, cyclicity, obsessive traits, special abilities, and regression after initial normal development; and differed from that of autistic children with neurological etiologies. These observations support the concept that ASD in some cases may be etiologically related to BPAD.

Adolescent↗
PubMed1994

Digital imaging of occlusal contacts in the intercuspal position.

PURPOSE: The purpose of this study was to develop an approach to the measurement of occlusal contact area and location using digitized video images of occlusal records. MATERIALS AND METHODS: Five occlusal records in the intercuspal position were made using a polyvinylsiloxane material on five subjects with intact, natural dentition. In regions of occlusal contact, the material showed a minimal film thickness without perforation. A dental cast of the mandibular arch was video digitized and followed by digitization of each of the five occlusal records in place on the cast. An impression of a calibration stepwedge was video digitized to provide the relationship between impression material thickness and pixel density. RESULTS: Contact surface areas ranged from 0.02 to 3.16 mm2 between subjects. The contact positions on a single tooth determined in five records from a single individual showed coefficients of variation between 7.4% to 36.1%. Large variations in contact size were found in this group of five records from a single individual (coefficient of variation ranged from 10.8% to 156.7%). The large difference in contact size between records may be due to variations in biting force at the time the records were made. When the cast position was changed and records redigitized, the mean area of the contact was not significantly different (P > .20) from measurements at the original position. CONCLUSIONS: For the small sample evaluated, a large variation in occlusal contact size was found in the five records. The occlusal contact location was consistent in the five records. The measurement method developed seems to provide reliable measures of occlusal contact surface area and location.

Adult↗
PubMed1994

Psychiatric family history and neurological disease in autistic spectrum disorders.

The authors obtained neurological assessments and psychiatric family history data for 40 children with autistic spectrum disorders (autism, Asperger syndrome and pervasive developmental disorder). Neurological evaluation included EEG, MRI, karyotyping and positron emission tomography as indicated. Family history data were obtained from family members during long-term follow-up. 20 probands had positive neurological findings, 18 with negative family history. 14 had no neurological findings and positive family histories; they tended to have higher function. Six had neither, and two had both. The segregation of neurological findings and familial affective disorder was highly significant. These findings suggest that an important subgroup of autistic spectrum disorders may be related etiologically to familial major affective disorders, and may represent the early-life onset of a severe phenotype of major affective, particularly bipolar, disease.

Adolescent↗
PubMed1993

Fracture strength of all-porcelain, resin-bonded bridges after testing in an artificial oral environment.

Twenty all-porcelain In-Ceram bridges were resin bonded to natural teeth on a study model. Ten of the test specimens were fixed on abutments placed directly in resin, and 10 were supported by an artificial periodontal membrane. Incisal forces of physiological magnitude and direction were applied in three bridges of both groups (test samples) in an artificial oral environment (1250,000 cycles). The fracture strength of the six test and 14 control specimens was tested in a universal testing instrument and the rupture strength measured. There was no significant difference between the fracture strength of the test and control samples. The artificial periodontal membrane around the abutment teeth did not reduce the fracture strength of the In-Ceram bridges.

Aluminum Oxide↗
PubMed1992

A large New England kindred with autosomal dominant neurogenic scapuloperoneal amyotrophy with unique features.

We describe a large New England kindred bearing an autosomal dominant syndrome of neurogenic amyotrophy with variable expression. Features include congenital absence of muscles, progressive scapuloperoneal atrophy, laryngeal palsy, and progressive distal weakness and atrophy. The pattern of expression and progression varies in different branches of the family. Males are more severely affected than females. Disease expression is more severe and progressive in succeeding (third and fourth) generations. This striking increase in severity and progressivity in succeeding generations may have genetic implications. The syndrome most resembles the Stark-Kaeser chronic scapuloperoneal amyotrophy, but is considered a distinct entity.

Abnormalities, Multiple↗
PubMed1992

A piezoelectric film transducer for dental occlusal analysis.

Occlusal load, contact sequence and location are necessary parameters for the study of dental biomechanics, simulation and clinical treatment planning. A piezoelectric film transducer for dental occlusal analysis was developed and in vitro evaluations of the transducer were conducted in a servohydraulically driven artificial mouth. The transducer is designed to provide occlusal contact force information. The transducer thickness (9 mum) minimizes interference with normal mandibular closure. Voltage outputs from the sensor as a result of occlusal contacts generated in the artificial mouth were sampled through a computer controlled data acquisition system. The transducer output recorded by the data acquisition system was calibrated to the applied load in the artificial mouth. The output of the piezoelectric film was evaluated during varying loads, cycling frequencies, surface areas of contact, and transducer surface areas. The preliminary studies indicate that the piezoelectric film holds out considerable promise and with further development may be well suited as a diagnostic tool in dental occlusal analysis.

Biomechanical Phenomena↗