Biomedical subjects
Publications and source records attributed to P L Millstein.
Because the physical and mechanical properties of vital and devitalized teeth differ, a variety of complexities can occur during the reconstruction of endodontically treated teeth. The three products described are recommended to help overcome some of the shortcomings encountered in present-day rehabilitation.
Two hundred amalgam (Dispersalloy) cylinders, 3 mm high x 4 mm wide, were tested to determine the compressive and diametral tensile strength of amalgam treated with 1 and 3 mixed drops of Amalgambond resin and 1:1 and 3:3 drops of resin powder paste of Panavia Ex resin. Twenty samples of each group, including a control group, were tested with a 1 cm diameter testing rod in an Instron universal testing machine at 0.5 mm/minute speed. All samples tested for compressive strength were not statistically different from one another (ANOVA). ANOVA and Tukey HSD test indicated no significant difference in diametral tension between the Amalgam and Amalgambond 1X materials, but significant differences were demonstrated with the Amalgambond 3X and Panavia 1X and 3X materials.
This study compared the shear bond strength of resin-bonded amalgam with and without pins. The coronal third of 240 embedded posterior teeth was removed to expose a flat, nonretentive surface. Three Minikin pins were placed in the dentin in a triangular pattern 1 mm apart. Amalgam was condensed into a Delrin mold (4.2 mm in diameter and 3 mm in height) positioned over each tooth. The adhesives Amalgam-bond, All-bond, Amalgambond with high-performance additive, Panavia EX, and Panavia with Photobond were the materials used to bond the amalgam to the dentin. Half of the samples were immersed in normal saline solution for 7 days and the others for 30 days. Shear bond strengths were recorded as the maximum load per cross-sectional area of the bonded surface with a testing machine with 1 kN load cell and crosshead speed of 0.5 mm/min. A three-factor analysis of variance and Student-Newman-Keuls test (p = 0.05) identified Amalgambond with high-performance additive as the strongest adhesive in this study. The use of pins with or without adhesives increased the shear strength of amalgam samples significantly more than samples that used adhesives alone.
Six interocclusal recording materials: COE Bite Creme, Blu-Mousse, Correct Bite, Blue Velvet, Memosil C.D. and Ramitec brands, were studied for evaluation of their dimensional stability and associated weight change. The materials were divided into six groups of 10 samples and tested between metal dental casts on the hydroptic test and measurement system. Dimensional changes among the materials were not significantly different. Weight changes among materials were significantly different but did not exceed 0.1%. All 6 brands were highly accurate and dimensionally stable.
This study investigated post-core adaptation as it relates to core materials and post-head configuration. A total of 360 samples that consisted of three prefabricated post systems and three core materials of amalgam and composite resin of 1 and 3 mm post-head-covering thicknesses were made. Composite resin with a post-head covering of 3 mm was most resistant to compression, whereas amalgam was most resistant to retentive forces. The addition of titanium to composite resin as a reinforcement filler did not improve resistance to either compressive or tensile forces.
Four different implant transfer techniques using two master cast systems (solid cast and Zeiser system) were evaluated and compared with respect to the accuracy with which abutment positions were reproduced. A stainless steel experimental analogue with two anterior and two posterior fixtures and abutments was fabricated. Polyether impressions (14 each) were made by use of four techniques, (I) nonsplinted, (II) splinted with dental floss and acrylic resin, (III) splinted with orthodontic wire and acrylic resin, and (IV) splinted with acrylic resin alone. The fourteen impressions of each technique were divided into two equal groups: group 1, solid cast system, and group 2, Zeiser system. The abutments of each master cast were measured vertically and horizontally with a profile projector. Statistical analysis indicated no significant difference between the splinted and nonsplinted techniques. The Zeiser system provided more accurate interabutment relationships for the posterior region than the solid cast system.
This study compared the accuracy of three techniques used to fabricate master casts for implant prostheses. A metal model with six implants and standard abutments and a matching template were fabricated. Impressions of the model were made in Impregum and cast in Die Keen. The casts were divided into three groups of 15 casts: group A--solid casts; group B--Pindex; and group C--Zeiser system. Each cast was visually evaluated for fit of the template. Positional accuracy of the abutments was numerically assessed using an optical comparator. Visual analysis showed that only casts sectioned with the Zeiser system allowed a passive fit of the template. Statistical analysis of numerical findings indicated that casts made with the Zeiser system were significantly more accurate than solid casts, which in turn were more accurate than those made with the Pindex system.
The effects of varying luting agent space and internal surface roughness with different types of cores and cements were studied. One hundred eighty amalgam and 180 composite cores were cemented into standardized stainless steel retainers. Cores and retainers were divided into 12 groups according to core type, core diameter, and retainer roughness. Each group was further subdivided according to cement, A: zinc phosphate (ZOP); B: resin; and C: glass ionomer cement (GIC). Subgroups were divided into thermal-cycled and nonthermal-cycled groups. Thermal cycling was at 5 degrees to 55 degrees C, repeated 500 times. Cores were separated from their retainers with a compression rod in an Instron testing machine at a crosshead speed of 0.02 cm/minute. Results were as follows: Amalgam cores were most retentive. Resin and ZOP cements were equally retentive with amalgam cores, but GIC was less retentive. Resin cores cemented with resin cement were more than twice as retentive than those cemented with ZOP or GIC cements. Retainers with rough internal surfaces were most retentive. A reduced cement space between core and retainer was most retentive. Thermal cycling reduced retention.
An evaluation of the effects of a die spacer, the seating force, the marginal design, seating aid materials, and the cement type during cementation was conducted. Two stainless steel dies were used: one with a 1 mm shoulder and the other with a shoulder and a 65-degree bevel. Ten stone dies were produced from each metal die and half were painted with four layers of die spacer. The crowns were waxed on the dies and cast in a nonprecious alloy, and the seating of crowns was measured with a micrometer before and after cementation. Comparisons were made between zinc phosphate and glass ionomer cements under two seating forces of 5 and 30 lb using an orangewood stick or E-Z-bite seating aid. ANOVA and the Newman-Keuls test revealed that the use of a die spacer, a heavier force of 30 lb, and glass ionomer cement significantly improved crown seating. The beveled preparation led to superior crown seating when the heavier force or glass ionomer cement was used. The orangewood stick and bite device had a similar effect on crown seating.
This in vitro study compared the effects on retention of base metal cylindrical retainers placed on composite resin cores when pretreated with eugenol and noneugenol temporary cements. Sixty composite cores and base metal cylindrical retainers were tested. The cores were pretreated with eugenol and noneugenol temporary cements before eventual cementation with resin and zinc phosphate cements. Cemented core retention was measured by application of a compressive force to the cores in an Instron machine. Differences were found between the two permanent cements. Pretreatment with eugenol cement reduced retainer retention with resin cements, but had no effect with zinc phosphate cement. Pretreatment with noneugenol cement did not reduce retainer retention.
A study was conducted to evaluate the accuracy of casts made in Type IV dental stone. The results indicate that all casts distort, but that significant differences exist between various brands of die stone.
This in vitro study compared the retention of dowel posts using different core materials. Glass ionomer cements, composite resin, and amalgam core materials were combined with serrated dowel posts to form post and core assemblies. Individual post-core assemblies were mounted with a special jig in an Instron Universal testing machine. A tensile force was applied at a cross-head speed of 0.02 cm/min and the separation force was recorded. Glass ionomer cement core materials were weak in tension and metalized ionomers remained brittle and were not fracture resistant. Composite resin and amalgam were strong in tension and relatively fracture resistant.
Retention of restorations cemented with temporary cement varies. Some cements are adhesive and others are weak in retention. In addition, cement retention may vary over time. This study determined (1) the retentive properties of four temporary cements, and (2) the effects of aging on temporary cement retention. Cylindrical amalgam cores and mated stainless steel retainers with a 0.05 mm cement space were used in the study. Cores were cemented into the retainers and stored in 100% humidity at 37 degrees C until tested. Retention was measured by applying a compressive force to the cores through a rod in an Instron machine. Half the samples were tested after 1 week and half were tested after 6 weeks. The results indicate a significant difference in retentive value among the four cements, including a significant decrease in retention for one cement over the 6-week aging period.
Twelve articulators (Denar D5-A and Mark II) were calibrated using the Denar Field Inspection Gage device. Silicone interocclusal records and the split cast method were used to test the positional accuracy of mounted casts transferred from one articulator to another. The interchangeability was performed by three independent observers. The results indicate that calibrated articulators can be used to transfer casts between articulators without a loss of positional accuracy.
The use of a silicone fit-indicator significantly reduced crown cementation strength. Cleaning with a metal cleaner before cementation did not reverse the effect.
A study using a HunterLab colorimeter was conducted to determine the colour effect of denture base materials on denture tooth acrylics. The results show that denture base materials create a measurable change in the chroma of denture tooth acrylics and suggest that optimal shade selection of teeth should include a determination of the background effects of denture base materials.
Explore the source record for details and available documents.
Explore the source record for details and available documents.