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.

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.

Three impression materials, Impregum, Permadyne, and Reprosil, were tested with three restorative materials, Lodestar, Dispersalloy, and Concise. Polished cylindrical samples of each restorative material with and without a collar design were used for impression retention testing. A pullout test using an Instron machine was used to test the samples that were individually submerged in the impression materials until set. Results show similar behavior for Lodestar and Dispersalloy with and without a collar. Permadyne and Impregum were significantly more retentive with resin composite than was Reprosil. Resin composite was significantly more retentive than the metals. Impression materials may bond with restorative materials, significantly increasing resistance to impression removal.

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.

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.

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 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 cement, but had no effect with zinc phosphate cement. Pretreatment with noneugenol cement did not reduce retainer 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.

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.

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.

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.