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Biomedical subjects

D A Curtis

Publications and source records attributed to D A Curtis.

At least 19 recordsLinked to original sources
PubMed1992

Incidence of various classes of removable partial dentures.

The purpose of a classification for removable partial dentures (RPDs) is to simplify identification and enhance its teaching. A classification also allows a longitudinal comparison of various classes of RPDs to determine whether the teaching of RPD design is consistent with the relative frequencies of RPD use. This study surveyed the types of removable partial dentures being fabricated in a regional dental laboratory and compared these findings with data from previous studies. Results indicate that mandibular RPDs are more common than maxillary RPDs and the class I mandibular RPD is the most common type of RPD for either dental arch. A palatal strap was the most frequently used maxillary major connector and a lingual bar was used three times more often than a lingual plate in the mandibular arch. Cast circumferential clasps were used twice as often as RPI clasp designs. The percentage of Kennedy class I RPDs was 40%, class II 33%, class III 18%, and class IV 9%. Comparisons with a previous study indicate the percentage of Kennedy class II has increased, whereas class I, class III and class IV RPDs have not changed significantly. Findings of the study indicate that the frequency of use of the various types of RPDs have changed in the past 30 years.

Chromium Alloys↗
PubMed1992

Vertical dimension increases in the adult rhesus monkey: a pilot study.

Tooth impaction, increased muscle activity, and histologic changes in the bone of the temporomandibular joint have been reported following attempts to increase the vertical dimension of occlusion. The purpose of this research was to study the effects of increases in the vertical dimension of occlusion on bone density at five levels of the mandible in the adult rhesus monkey, and to assess dentoalveolar changes by lateral cephalometric radiographs and mounted diagnostic casts. Mandibular cobalt chromium splints measuring 3 mm in height at the first molar, providing even occlusal contact to the maxillary anterior and posterior teeth, were cemented in place on two monkeys. Five similar monkeys without splints were used as controls. Computed tomograms were completed to evaluate bone density bilaterally at five levels of the mandible after 3 months of splint wear. Pretreatment and posttreatment lateral cephalometric radiographs and mounted diagnostic casts were completed to assess tooth impaction. Periodontal ligament (PDL) thickening and mobility of molars and premolars were evaluated before splint placement and after splint removal. There was no statistically significant difference in the bone density levels of the animals with splints compared with the controls. Minimal dentoalveolar changes were observed.

Animals↗
PubMed1991

Adaptability of the adult primate craniofacial complex to asymmetrical lateral forces.

The adaptability of the adult craniofacial skeleton to altered functional relationships has been reported. An experimental quantification of these changes is lacking, however, and the possible underlying mechanisms of the alterations have not been explained. The purpose of this investigation was to evaluate the effect that lateral displacement of the mandible has on the dentoalveolar, craniofacial, and neuromuscular system in the adult rhesus monkey. Ten adult monkeys were studied; five served as controls, three were fitted with bilaterally inclined mandibular splints designed to deviate the mandible toward the left on closure, and two animals had flat splints to provide even occlusal contact. Pretreatment and posttreatment assessment of dentoalveolar and craniofacial change was made from mounted study casts, cephalometric head films, electromyograms and computed tomograms. Axial computed tomographic scans were used to evaluate potential changes in bone density at the lower part of the mandible, the condyle, the coronoid process, the neck of the condyle, and the zygomatic arch by means of a one-way analysis of variance. Changes in the measured variables were not observed in the control animals or in the animals with flat splints. Animals with inclined splints, however, demonstrated attrition and intrusion of maxillary molars and mild proclination of the maxillary incisors. Posttreatment computed tomographic scans in these animals showed significantly increased bone density in the right coronoid process (p less than 0.05) and bilaterally at the necks of the condyles (p less than 0.005). Resting electromyographic activity remained low and was not significantly different among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1991

Histologic evaluation of hydroxylapatite-coated versus uncoated titanium blade implants in delayed and immediately loaded applications.

It has been suggested that the long-term success of blade implants could be improved by placing the implants using a two-stage surgical protocol to allow the implant to develop a direct bony interface instead of a fibrous tissue interface. This study compared the implant interfaces of delayed and immediately loaded blade implants in nonhuman primates. A second objective was to compare the effects of hydroxylapatite coating on delayed and immediate loading applications. The delayed loaded uncoated titanium and hydroxylapatite-coated blade implants did osseointegrate. This study also suggests that hydroxylapatite-coated blade implants may form a direct bony interface even when they are loaded immediately after implantation, provided that they are splinted to a firm natural tooth.

Animals↗
PubMed1990

Purification of PDGF-AB and PDGF-BB from human platelet extracts and identification of all three PDGF dimers in human platelets.

We have developed a panel of monoclonal antibodies to platelet-derived growth factor (PDGF) which have variable specificities for the three dimeric forms of the molecule (AA, AB, and BB). We have used these antibodies to detect and immunoaffinity purify the individual dimers from human platelet rich plasma. Extracts of outdated platelet preparations were initially chromatographed over CM-Sepharose and then passed over the Sepharose-coupled monoclonal antibodies in series in selectively isolate the three dimeric forms of PDGF. The PDGF eluted from the affinity columns was subsequently further purified by reversed-phase HPLC. From 300 units of outdated platelet preparations, we purified 58 micrograms of PDGF-BB and 140 micrograms of PDGF-AB. Using the monoclonal antibodies to develop PDGF dimer-specific ELISAs, it was observed that all three PDGF dimer forms are present in fresh human platelet extracts and that the ratios of the three dimer forms vary depending upon the extraction conditions used. The identification of all three PDGF dimer forms in human platelets point to the need to view PDGF isolated from human platelets by conventional techniques as a mixture of all three forms and not solely as PDGF-AB.

Amino Acid Sequence↗
PubMed1989

A comparison of lateral interocclusal records to pantographic tracings.

Many techniques exist to record patients' lateral jaw movements, but they have not been thoroughly investigated. This study compared recordings of immediate sideshift by using a pantograph and two intraoral registration materials. Pantographs were completed on 20 healthy participants by using chinpoint guidance and a kinematic hinge axis. Three lateral interocclusal records were completed on each participant and averaged for right and left sides. The average immediate sideshift recorded by a pantograph (0.54 mm) was less than that recorded by the two intraoral registration materials. The standard deviations were similar for all materials. An analysis of variance test identified significant statistical differences between a pantograph and one of the intraoral registration materials, but not between the pantograph and the other registration material. Immediate sideshift recorded with one material compared favorably with a pantograph recording when three records using the chinpoint guidance were averaged.

Adult↗
PubMed1989

A comparison of protrusive interocclusal records to pantographic tracings.

The rationale for recording protrusive mandibular movement is to accurately adjust an articulator. Techniques to record condylar inclination include radiographic interpretation, extraoral tracings, and intraoral recording materials. This study compared the protrusive settings on an articular adjusted by a pantograph to protrusive settings recorded by two intraoral recording materials, one a polyvinyl siloxane material and one a laminated, metalized wax. Pantographs were completed for 20 patients by using a kinematic hinge axis and conventional pantographic techniques. The patients also had three protrusive interocclusal records made with two intraoral registration materials completed and averaged. The average condylar inclination recorded with a pantograph (29.5 degrees) was greater than the recording by either intraoral registration material. Standard deviations ranged from 4.1 degrees to 6.6 degrees. An analysis of variance showed that the condylar inclination recorded by wax was statistically less than recorded with a pantograph. A comparison between the pantograph and the polyvinyl siloxane displayed no statistically significant difference in recording condylar inclination.

Adult↗
PubMed1989

Shear bond strength of visible-light-cured resin relative to heat-cured resin.

One promising clinical application of visible-light-cured (VLC) denture resin is for relining complete and partial dentures. Typically, a VLC resin would be used to reline an existing prosthesis fabricated from heat-cured resin (HCR). This study measured the shear bond strength of a VLC resin bonded to HCR specimens by different bonding agents. For comparison, we measured the shear bond strengths of VLC resin bonded to VLC resin specimens and of autopolymerizing resin (APR) to HCR specimens. Cylindrical specimens of HCR (n = 126) and VLC (n = 24) were thermocycled to simulate aging, and the bonding surfaces were prepared by being sanded to approximate clinical roughness. The specimens were divided into seven groups of approximately 20 each, and test materials were bonded by different bonding agents. Statistical analysis by ANOVA and the Student-Newman-Keuls test showed significant differences (p less than 0.05) among all groups except APR to HCR/no bonding agent, VLC to HCR/VLC bonding agent, or VLC to HCR/VLC and HCR bonding agent. The traditional bond of APR to HCR with HCR bonding agent was significantly stronger (p less than 0.05) than the strongest bond of VLC to HCR with HCR and VLC bonding agents.

Acrylic Resins↗
PubMed1988

Occlusal considerations for partially or completely edentulous skeletal Class II patients. Part II: Treatment concepts.

Four basic concepts must be considered when developing the prosthetic occlusion for skeletal class II patients: (1) Centric relation must be used as a reference position to relate the mandible to the maxillae; (2) the posterior denture teeth must be positioned close to their former positions; (3) freedom of movement must be created in eccentric movements; and (4) multiple occlusal contacts must be provided in centric and eccentric positions. We have described a method that incorporates these basic concepts and provides a harmonious occlusal arrangement for both edentulous and partially edentulous class II patients.

Dental Occlusion, Balanced↗
PubMed1988

Occlusal considerations for partially or completely edentulous skeletal class II patients. Part I: Background information.

Although approximately 15% of the population may be classified as having the skeletal class II relationship, this group of patients is far from homogeneous. Two prototypes were used to delineate various problems in the prosthodontic occlusion that dentists may encounter with these patients. A satisfactory occlusion is difficult to achieve because of skeletal discrepancies, limited space for occlusal contact, steep guidance factors, and the necessity for multiple eccentric occlusal contacts because of the significant range of mandibular motion.

Cephalometry↗
PubMed1987

Neurochemical changes in experimental African trypanosomiasis in voles and mice.

Dopamine, norepinephrine, serotonin and related metabolites were measured in the brain of meadow voles and mice after infection with Trypanosoma brucei gambiense with the goal of understanding the neurochemical changes accompanying infection with this parasite. Serotonin and 5-HIAA levels both fell by 26%, and HVA levels rose by 56%, in vole brains during infection. Dopamine, DHPG and norepinephrine levels, however, remained unchanged. In mice, serotonin levels dropped by 17 and 23%, respectively, in the pons-medulla and midbrain regions after infection; 5-HIAA and dopamine levels remained unaffected by infection in mice. The possible causes and the significance of these changes are discussed.

Animals↗