Philip L. Millstein

A comparative analysis of the accuracy of implant transfer techniques

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.

Effects of cement, cement space, marginal design, seating aid materials, and seating force on crown cementation

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.

Effect of eugenol and eugenol cements on cured composite resin.

Although the chemical nature of the reaction of eugenol and composite resin is not understood, this preliminary investigation indicates that eugenol and eugenol-containing cements alter the surface of cured composite resins.

Effect of surface roughness and cement space on crown retention

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.

Effect of design of prefabricated post heads on core materials

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.

Effects of temporary cementation on permanent cement retention to composite resin cores

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 method to determine occlusal contact and noncontact areas: Preliminary report

A new method for quantitative occlusal measurement is presented. This method allows for occlusal contacts and noncontact areas to be recorded, permanently referenced, and analyzed over time. The overall extent of application and refinement of the method is unknown. However, at present it provides a method for selectively recording occlusal positions and the surrounding spatial dimensions that occur on closure.

Differential accuracy of silicone-body and self-curing resin interocclusal records and associated weight loss

Abstract Two types of one brand of silicone-body impression material and two brands of self-curing resin were tested as interocclusal recording materials to evaluate their dimensional stability and associated weight losses due to volatiles. Silicone-body interocclusal records were shown to be more reliable than self-curing resin records. However, all of the materials tested exhibited some degree of weight loss and dimensional change over time.

Retention between a serrated steel dowel and different core materials.

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.

Differential accuracy of silicone-body interocclusal records and associated weight loss due to volatiles

Summary Three brands of silicone-body impression material were tested to evaluate dimensional stability and associated weight loss due to volatiles. The three materials displayed weight losses over time which were generally proportional to their respective dimensional changes.