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Biomedical subjects

P L Sadowsky

Publications and source records attributed to P L Sadowsky.

31 records · Page 2Linked to original sources
PubMed1989

Effects of phosphoric acid concentration and etch duration on the shear bond strength of an orthodontic bonding resin to enamel. An in vitro study.

The purpose of this in vitro study was to determine the effects of phosphoric acid (H3PO4) concentration and duration of etching on the shear bond strength of an orthodontic bonding resin to enamel. Nine bonding procedures, each involving 18 extracted human maxillary permanent canines, were used. Ground enamel surfaces were etched with a 37% H3PO4 solution, a 15% H3PO4 gel, or a 5% H3PO4 solution for 60, 30, and 15 seconds, respectively. Cylinders of an orthodontic bonding resin, Concise, were prepared in a special device. The test specimens were disassembled 15 minutes after preparation and stored in distilled water at 37 degrees C for 24 hours. A shear load was applied to the bonded cylinders at a crosshead speed of 0.02 in.min-1 in an Instron testing machine, and the shear bond strengths were calculated and expressed in MN.m-2. A two-factor analysis of the data showed that the H3PO4 concentration had no significant effect on the shear bond strength, but the duration of etching affected shear bond strength significantly. The enamel aspects of the fractured test specimens were examined microscopically and the percent failure within the bonding resin at the bonding sites estimated. The correlation between shear bond strength and percentage failure within the bonding resin was not significant. The effects of the nine etching procedures on ground and unground enamel surfaces were studied by scanning electron microscopy. The etching procedures produced well-defined etching patterns on both ground and unground enamel surfaces.

Acid Etching, Dental↗
PubMed1984

Variability in three morphologic features of the permanent maxillary central incisor.

Variability in tooth morphology can play a significant role in appliance design and the achievable results of orthodontic treatment. This investigation was undertaken to determine quantitatively the variation in three anatomic features of the maxillary central incisor. The three features are the crown-root angulation in a labiolingual direction, the angle formed by a tangent to the middle of the labial surface of the crown and the long axis of the crown from a proximal view, and the lingual curvature of the crown from a proximal view. Tracings of maxillary central incisors were made from two different sources. The first source consisted of radiograms of 98 extracted central incisors, and the second source was a group of 100 cephalometric radiograms which were part of pretreatment records of patients in the Orthodontic Department. The cephalometric radiograms included 25 Angle Class I, 25 Class II, Division 1, 25 Class II, Division 2, and 25 Class III malocclusions. The first measurement taken was the angle formed by the long axis of the crown and the long axis of the root. The second measurement was the angle formed by the long axis of the crown and a tangent to the midpoint of the labial surface of the crown. For the third measurement, the lingual curvature of the crown was described by a mathematical equation whose parameters were used for comparisons. The results revealed a wide range of variation in the three features measured. The mean crown-root angle for Class II, Division 2 malocclusions differed significantly from that for Class II, Division 1 and Class III malocclusions.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalometry↗
PubMed1983

Acid resistance of enamel exposed to fluoride-containing orthodontic cements.

In a previous study enamel fluoride uptake from fluoride-containing orthodontic cements was evaluated after a 21-day period. The enamel fluoride uptake from a zinc phosphate cement (A), a zinc phosphate cement containing 5 per cent stannous fluoride by weight (B), and a silicophosphate cement (C) was compared. The results indicated that there was a net loss of fluoride from enamel beneath the orthodontic bands cemented with A while the enamel beneath B and C acquired significant amounts of fluoride. The purpose of the present study was to evaluate enamel fluoride uptake after 12 weeks and the effect of the fluoride uptake or loss by the enamel on acid resistance. Five teeth each had bands cemented with cements A, B and C, respectively, and were individually suspended in synthetic saliva for 12 weeks at 37 degrees C. Following this period the bands were removed, the cements were carefully cleaned off the teeth, and the crowns of the teeth were individually suspended in a lactic acid buffer at pH 4 for 4 weeks. Each tooth crown was then sectioned longitudinally and examined microradiographically to study the degree of enamel demineralization. Characteristic subsurface enamel carieslike lesions were noted on all the specimens studied. The carieslike lesions in the enamel exposed to the fluoride-containing cements were considerably reduced. The enamel which had acquired fluoride from the fluoride-containing cements was apparently more resistant to artificial caries attack.

Acids↗
PubMed1981

Enamel fluoride uptake from orthodontic cements and its effect on demineralization.

This study was undertaken to determine the in vitro enamel fluoride uptake and distribution from fluoride-containing orthodontic cements after 21 days' exposure and the effect on acid demineralization. Three successive acid-etch biopsy specimens were taken from tne facial middle third of thirty maxillary central incisors. Orthodontic bands were cemented to these teeth, ten each with (A) zinc phosphate, (B) zinc phosphate containing 5 percent SnF2, and (C) silicophosphate cement, respectively. The teeth were suspended individually in synthetic saliva at 37 degrees C. in a shaking incubator for 21 days. The bands were removed, the cement was cleaned off, and three successive biopsies were carried out electrometrically and for calcium by atomic absorption spectroscopy. Fluoride concentrations were adjusted to depths of 10.0, 20.0, and 30.0 micron for the three biopsies, respectively. The acquired fluoride was calculated and the data were analyzed statistically. In addition, six teeth each with bands cemented with cements A, B, and C, respectively, were incubated in synthetic saliva for 21 days, after which the bands were loosened and the teeth were suspended for a further 3 months in a caries-producing medium. After careful cleaning, the enamel surfaces were examined by microradiography and scanning electron microscopy for demineralization. Results showed that acquired fluoride at the first depth was highest with cement C, followed by cement B, with cement A producing a net loss of fluoride. Further, the greater the fluoride uptake, the more resistant the enamel was to demineralization.

Dental Caries↗
PubMed1976

A comparative study of some dental cements used in orthodontics.

It is suggested that decalcification occurring beneath orthodontic bands is, among other factors, related to the tensile bond strength of the cement to the enamel surface, its marginal leakage at the enamel-cement interface, and its solubility and and disintegration. Under the laboratory conditions described in this study the composite cement exhibited the greatest tensile bond strength to both enamel and band material. The composite cement also displayed no marginal leakage at the enamel-cement interface and showed no solubility or disintegration under the experimental conditions. It could therefore be anticipated that, of the four cements evaluated in this study, the composite cement would have the greatest potential for eliminating pathologic enamel decalcification occurring beneath orthodontic bands.

Composite Resins↗
PubMed1975

Clinical experience with the acid-etch technique in orthodontics.

The acid-etch technique and the development of improved composite resin systems have made the direct bonding of orthodontic attachments an accepted clinical procedure. This technique can be used with confidence as an adjunct in the armamentarium of the orthodontist.

Adolescent↗