Search PubMed⌕ Search

Biomedical subjects

J B Summitt

Publications and source records attributed to J B Summitt.

At least 37 records · Page 2Linked to original sources
PubMed1992

The resistance to tensile, compression, and torsional forces provided by four post systems.

This study measured the force required to displace four different endodontic posts (an experimental, Para-Post, Flexi-Post, and V Lock) when tensile, torsion, or compressive forces were applied. Extracted mandibular premolars were decoronated at the cementoenamel junction, the roots were divided into groups of similar size, and the pulpal tissue was removed. The canals were enlarged, cleaned, and filled with gutta percha. Post preparations were made, and the posts were cut and cemented into the post spaces with resin cement. The roots were notched with a separating disc and lowered into a metal tube filled with acrylic resin. Two Minim pins were placed into the coronal dentin paralleling the post. Composite resin cores were made around the coronal 4 mm of the posts and the two pins for 10 specimens from each group. The specimens were placed into a standardized fixture and a load applied until failure. The tensile load required to pull the experimental post and resin was significantly less than the load required to remove the threaded posts. Flexi-Posts provided the greatest resistance to torsion and tensile loading. The compressive load required to fracture the core over the V-Lock post was significantly greater than the other post systems.

Dental Cements↗
PubMed1991

Comparison of resistance features for complex amalgam restorations.

This study evaluated the resistance provided to complex Dispersalloy amalgam restorations by pins (Group 1), amalgapins (Group 2), and a peripheral shelf or shoulder (Group 3) or in combinations of pins plus peripheral shelf (Group 4), or amalgapins plus peripheral shelf (Group 5). The occlusal surfaces of 50 extracted maxillary molar teeth were ground to a flat surface 2 mm occlusal to the CEJ, and the roots were matched and embedded in acrylic resin 2 mm apical to the CEJ. The greatest faciolingual and mesiodistal dimensions of each tooth at the level of preparation were recorded and these two measurements were multiplied to give a product for each specimen. The teeth were then sorted by tooth sizes and equally distributed among the five groups. Each group of flattened teeth received a different resistance form configuration. Amalgam was condensed using a matrix; the bands and excess amalgam were removed 24 hours later and each amalgam "occlusal" surface was ground flat to standardize the restoration at a 4 mm occlusal height. A 1 mm 45 degrees bevel was prepared on the facio-occlusal angle of the amalgam, and each specimen was loaded in compression at 45 degrees in an Instron at a crosshead speed of 1 mm/min. The groups and their mean (SD) failure loads in Newtons were: Group 1: 1515 (274); Group 2: 1521 (244); Group 3: 578 (175); Group 4: 1199 (229); and Group 5: 1691 (298). A one-factor ANOVA and a Tukey B post-hoc analysis showed no differences between Groups 1, 2 and 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1990

Adjacent-2 disjunction of a maternal t(9;22) leading to duplication 9pter----q22 and deficiency of 22pter----q11.2.

The proposita presented at birth with multiple congenital anomalies including craniofacial anomalies, bilateral cleft lip and palate, abnormalities of the urogenital system, talipes equinovarus, and the DiGeorge sequence. Cytogenetic investigation showed a 46,XX,-22,+der(9)t(9;22)(q22;q11.2) karyotype. The mother, maternal uncle, and maternal grandmother of the infant are carriers of a reciprocal balanced translocation involving chromosomes 9 and 22 at regions q22 and q11.2, respectively. The unbalanced karyotype seen in the proposita arose due to an adjacent-2 disjunction of the quadrivalent in the mother. Prenatal diagnosis of the second pregnancy of this woman showed a similar karyotype. Review of the literature shows that adjacent-2 disjunction may occur preferentially when certain chromosomes are involved in translocations.

Abnormalities, Multiple↗
PubMed1990

Fracture resistance of amalgam coronal-radicular restorations.

The effect of pulp chamber depth and extension into the root canal space on fracture resistance was examined on endodontically treated teeth with coronal-radicular amalgam restorations. Six groups of 10 mandibular molars were mounted in acrylic resin, and crowns were ground apically until the wall height of the pulp chamber was 2, 4, or 6 mm. Three millimeters of gutta-percha was removed from the three canals of one-half the teeth and amalgam was condensed into the canal space to a height 7.5 mm above the cementoenamel junction (CEJ). The remaining teeth had amalgam condensed from the floor of the chamber to 7.5 mm above the CEJ. The amalgam restorations were loaded with an Instron instrument (Instron Corp., Canton, Mass.) until failure. Amalgam extension into the root canal space contributed minimally to the fracture resistance of the amalgam coronal-radicular restoration with four or more millimeters of chamber wall. If less than 4 mm of chamber wall height remained, however, the fracture load was substantially increased. Amalgam extension into the root canal space should be confined to teeth with limited remaining pulp chambers.

Crowns↗
PubMed1990

Diagnosis of trisomy 18 using spontaneously dividing cells from fetal umbilical cord blood: a novel approach for rapid late second and third trimester prenatal diagnosis.

Cytogenetic methodology recently developed by us allows spontaneously dividing cells in fetal cord blood to be used for rapid (24 hours) chromosome analysis. We utilized this methodology to diagnose trisomy 18 and facilitate clinical management in a 32-week pregnancy characterized by multiple fetal anomalies and intrauterine growth retardation.

Abnormalities, Multiple↗
PubMed1990

Partial duplication of the long arm of chromosome 6: a clinically recognisable syndrome.

Reciprocal translocations involving the short arm of acrocentric chromosomes can segregate to produce partial duplications without associated deletions. We present a case of an infant with a 46,XY,-15,+der(15),T(6;15)(q23;p12)pat chromosome complement. The infant had multiple congenital abnormalities including cranial anomalies, facial dysmorphism, anterior webbing of the neck, cardiac anomalies, and joint contractures. From a comparison of the infant's phenotype with 20 other patients with a similar duplication, it is evident that partial duplication of the long arm of chromosome 6 is a clinically diagnosable syndrome.

Abnormalities, Multiple↗
PubMed1989

Retention and resistance features for complex amalgam restorations.

Although not absolute, there are indications for each of the retention and resistance features described. Amalgapins and circumferential slots have their greatest indication in teeth with short clinical crowns and in cusps that have been reduced 2-3 mm for coverage with amalgam. In these situations, slots provide more resistance than amalgapins and amalgam inserts. When amalgapins or slots are used as the only retention and resistance features, the restoration is susceptible to early fracture during matrix removal. When the technical requirements for placement of vertical pins can be met, they provide excellent retention and resistance form. Vertical pins should be placed at least 0.5 mm inside the dentinoenamel junction, at a depth of approximately 2 mm, and should protrude from the tooth approximately 2 mm. However, there are inherent risks involved with pin placement; these include crazing of tooth structure, perforation into the pulp or periodontium, and weakening of the amalgam restoration over the pins. The use of both vertical and horizontal pins may be limited by inadequate access; in these cases, alternate devices should be used. When a cusp has been reduced and increased resistance is needed, a ledge or peripheral step may be indicated. It must be remembered that this feature will result in a greater display of amalgam and may be esthetically unacceptable on a facial cusp. If esthetic appearance is a factor, horizontal pins may be used to reinforce a remaining facial cusp. Horizontal pins may also be used to splint or tie a remaining cusp to the restoration.(ABSTRACT TRUNCATED AT 250 WORDS)

Dental Amalgam↗
PubMed1988

Individuality of human palatal rugae.

Investigators have implied that palatal rugae are unique to each individual. However, these researchers have disagreed as to whether or not legal identification could be based solely on palatal rugae. Previous studies used poor duplicating materials and may not have considered the effects of growth, extractions, palatal expansion, or some combination of these. The inadvertent use of other features of the cast, such as teeth, edentulous ridge morphology, muscle attachments, vestibular depth, or some combination of these, to aid in the identification, may have influenced their results. The purpose of this investigation was to determine if palatal rugae can be relied upon for identification. Twenty-five orthodontic cases were selected with pre- and post-treatment casts; orthodontic treatment had taken eighteen to sixty months. One hundred casts were randomly selected as variables. All casts were trimmed so that all areas except for the rugae area of the hard palate were removed. The twenty-five post-orthodontic casts were dispersed within 100 randomly selected casts. Nine investigators were given the twenty-five pre-orthodontic casts and asked to compare them to the other one hundred and twenty-five casts for possible matches. Data were collected as to percentage of correct matches and time required for comparison. Each set of pre- and post-orthodontic casts was properly identified (100%) by 8 investigators, and the remaining investigator correctly matched 22 out of 25 casts (88%). These conclusions were drawn.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

The effects of two sharpening methods on the strength of a periodontal scaling instrument.

Several different techniques exist for sharpening periodontal scalers each of which will yield a relatively sharp instrument; however, some techniques may decrease the strength of the instrument more rapidly than others. The purpose of this study was to evaluate the effect of two different sharpening techniques on the strength of a periodontal scaler. Sixty McCall No. 13-14 scalers (SCI-DENT) were divided into groups of ten. Each group was reduced in size from 0 to 50% of a standard original size in increments of 10% by reducing the face of the instrument using an RX Honing Machine. A second set of 60 scalers was treated in a similar fashion by reducing the lateral surfaces of the instrument. Original angles and blade clearances were maintained on all instruments. Strength was measured by applying a force at a positive rake angle of 15 degrees in an Instron Testing Machine with a head speed of 50 cm/min. There were no significant differences in strength from grinding on the face vs. the lateral surfaces of the scaler in contrast to the observations of other investigators. Moreover, a 10 to 20% reduction can be accomplished before a significant drop in strength is observed by sharpening either the side or face of the instrument.

Dental Prophylaxis↗
PubMedDate not supplied

Evaluation of different methods for cleaning and preparing occlusal fissures.

The effectiveness of different methods for cleaning and preparing occlusal fissures before placing sealants was evaluated. Extracted mandibular molars received such treatments as brushing, pumicing, bur preparing, and air abrasion before application of fissure sealants. FluroShield fissure sealant was then applied to the occlusal fissures. Specimens were subjected to thermo-cycling and then immersed in a 10% solution of methylene blue, and finally sectioned. The sections were examined and photographed in a stereomicroscope, and the dye penetration was recorded using a scoring system. The results indicated that only the control (brushing with a dry brush) and the pumicing groups demonstrated dye penetration to the base of the sealant. Teeth prepared with the #1/4 round bur and air abrasion demonstrated a better seal in evaluated fissures. For this study, those three groups (occlusal fissures prepared with the #1/4 round bur and two air abrasion methods), demonstrated significantly better sealing (P < 0.01) than the control group and the other groups tested.

Air Abrasion, Dental↗
PubMedDate not supplied

The whitening effect of bleaching agents on tetracycline-stained rat teeth.

This study compared the whitening effect of three bleaching agents on the teeth of rats and demonstrated differences in bleaching where dentin was exposed or enamel was thin. Thirty Albino rats were peritoneally injected with tetracycline solution daily for two weeks. Thirty-two disc-shaped specimens were cut from the crowns of incisors removed from sacrificed rats and were irradiated with UV light for 16 hours. Sections were stored in saline. Eight sections served as controls and were not bleached. Three bleaching agents (Opalescence, Rembrandt and Nite White) were applied to eight specimens each, five times a day for two weeks, and images of the sections were recorded at the following times: before bleaching (baseline), day 1, day 3, day 5, day 7, day 9, day 11 and day 14. Mean colors to demonstrate any change (deltaE) from baseline for each time period were as follows: control-9.78 (baseline), 9.17, 9.36, 9.65, 9.40, 9.99, 10.57, 11.36; Opalescence-10.08, (baseline) 7.63, 6.72, 6.04, 5.10, 4.87, 4.89, 4.27; Rembrandt-9.83 (baseline), 11.27, 9.55, 8.36, 7.75, 6.94, 7.11, 7.04; Nite White-10.44 (baseline), 9.92, 7.58, 6.80, 5.45, 5.05, 4.73, 4.01. All bleached teeth were lightened (p<.01). Another 56 tetracycline-stained rat incisors were UV irradiated for three days. Three different penetration depths were tested: penetration through lingual dentin and labial enamel (DN group), penetration through labial enamel only (RE group) and penetration through labial enamel covered with 1.0 mm human enamel (HE group). Specimens were bleached with Opalescence for one hour five times a day for one week or four weeks. A control group of unbleached teeth was also examined. Results (deltaE) were as follows: control--11.67; 1-week DN--13.55; 1-week RE--12.80; 1-week HE--12.07; 4-week DN--7.48; 4-week RE--7.50; 4-week HE--11.69. The color change in the 4-week DN and the 4-week RE groups showed the greatest reduction (p<.01).

Analysis of Variance↗
PubMedDate not supplied

Pain perception and utility: a comparison of the syringe and computerized local injection techniques.

Thirty patients received maxillary infiltration and mandibular inferior alveolar nerve block injections with both a traditional syringe and a computerized system, the Wand. Patients noted their preference for either system and rated their injection pain and postoperative discomfort on a ten-point scale for each type of injection. Mean injection discomfort ratings with the Wand were lower than with the syringe but were not statistically significant. Reduced postoperative discomfort using the Wand for the inferior alveolar nerve block was significant. Both of the dentists in the study and those patients who stated a preference favored the Wand system.

Adult↗
PubMedDate not supplied

The use of dental amalgam in pediatric dentistry: review of the literature.

Dental amalgam is widely used as a restorative material even though it is not esthetic and there has been extensive anti-amalgam rhetoric. Although other materials have improved greatly, amalgam has the proven safety record and best cost-to-benefit ratio. Clinical evidence indicates that, in the posterior permanent dentition--where esthetics is not a primary concern--the small, minimally prepared, amalgam restoration, with its margins and any caries-susceptible fissures sealed with resin fissure sealant, is the restoration with the best survival. Amalgam also remains the best direct restorative option when larger restorations are required. In the primary dentition, the data indicates that resin-based composite and resin-modified glass-ionomer serve very well.

Child↗
PubMedDate not supplied

Effect of air/water rinse versus water only and of five rinse times on resin-to-etched-enamel shear bond strength.

This study compared the shear bond strength of composite resin bonded to etched, flattened enamel that had been rinsed for 0, 1, 2, 3, 5 or 20 seconds with either a water stream or an air/water spray. One hundred seventy-six molars were separated into mandibular and maxillary groups, then divided equally into 11 groups of 16 teeth each. The facial enamel surfaces were ground flat and etched for 20 seconds with 37% phosphoric acid gel. In one group, the etching gel was dried but not rinsed. In five groups the gel was rinsed with a direct stream of water at 22 psi. In the remaining five groups the gel was rinsed with an air/water spray (air at 53 psi, water at 22 psi). One tooth from each group was removed for scanning electron microscopy evaluation, leaving 15 specimens in each group for shear bond testing. Teflon tape with a 3 mm in diameter window was placed over each etched area, a light-curing liquid resin was applied and polymerized for 10 seconds, and a cylinder of light-curing composite resin was polymerized over the window. Specimens were thermocycled from 5 to 50 degrees C for 500 cycles (30-second dwell time). After 30 days' hydration at room temperature, the teeth were mounted and the composite resin cylinders were loaded in shear to failure with an Instron machine at a cross-head speed of 5 mm/min. Mean load to failure was calculated for each group. Specimens that were not rinsed had significantly (P < 0.001) less bond strength (mean 0.53 MPa) than any of the rinsed specimens (mean 18.7 MPa).(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗