Steven A. Aquilino

Evaluation of three impression techniques for osseointegrated oral implants

The purpose of this in vitro investigation was to determine the accuracy of gypsum casts produced from impressions made with polyether, polyether and impression plaster, or polyether and acrylic resin for the fabrication of osseointegrated implant prostheses. Strain gauges were attached to a master framework to determine the passivity of fit of the framework to sample casts made by the three impression techniques. Strain values were statistically compared by one way analysis of variance and Duncans multiple range test. A statistically significant difference was found between the three impression techniques tested (p < 0.05). The results of this investigation revealed that none of the impression techniques resulted in an absolutely passive framework fit. However, of the techniques tested, the polyether alone resulted in the closest duplication of the master cast.

An evaluation of the bond strengths of four organosilane materials in response to thermal stress.

This study investigated the effect of thermal stress on the shear bond strength of four commercially available porcelain repair materials. Porcelain cylinders were made and embedded in acrylic resin. Composite resins were bonded to the porcelain samples by using the four organosilane systems. The specimens were aged in 37 degrees C distilled water for 24 hours. Ten specimens per system were then thermocycled for 48 hours. Ten specimens per system remained in 37 degrees C distilled water for 48 hours. All samples were loaded at the composite resin/porcelain interface by using an Instron machine. Results demonstrated cohesive porcelain failures for most of the nonthermocycled specimens. Thermocycling caused a significant decrease in the bond strengths of the Command Ultrafine, Enamelite 500, and Fusion materials. Only the Scotchprime system maintained consistently high shear strength values under the conditions tested.

Bond strengths of intraoral porcelain repair materials

This study investigated the in vitro shear strength of three porcelain repair systems. Glazed and roughened porcelain surfaces were evaluated. The repair systems tested were Fusion, Scotchprime, and Ultra-Bond. Porcelain cylinders were made. Half of the cylinders were wet-sanded to a flat, nonglazed surface and the remaining cylinders retained a smooth, glazed surface. Specimens were subjected to a shear force parallel to the composite/porcelain interface by use of an Instron Testing machine. Statistical analysis (at the 0.05 confidence level) showed significant differences in mean bond strengths related to the porcelain repair systems and the surface texture.

An evaluation of post length within the elastic limits of dentin

Posted teeth were evaluated to determine the reinforcement capabilities of various post lengths. The results suggest that as internal tooth structure is removed from the tooth the tooth becomes weaker, that teeth with posts do show more reinforcement than nonposted teeth with the same manipulation characteristics, and that some load transfer appears to exist with cemented posts.

Prosthodontic survey. Part I: Removable prosthodontic laboratory survey

A questionnaire was mailed to 488 dental laboratories in five midwestern states, of which 303 or 62% were returned after two mailings. The survey was conducted to discern what techniques are most frequently used by practicing dentists. The results indicate that dentists frequently use techniques that require a minimum of appointment time.

3D and 2D Marginal Fit of Pressed and CAD/CAM Lithium Disilicate Crowns Made from Digital and Conventional Impressions

PURPOSE This in vitro study evaluated the 3D and 2D marginal fit of pressed and computer-aided-designed/computer-aided-manufactured (CAD/CAM) all-ceramic crowns made from digital and conventional impressions. MATERIALS AND METHODS A dentoform tooth (#30) was prepared for an all-ceramic crown (master die). Thirty type IV definitive casts were made from 30 polyvinyl siloxane (PVS) impressions. Thirty resin models were produced from thirty Lava Chairside Oral Scanner impressions. Thirty crowns were pressed in lithium disilicate (IPS e.max Press; 15/impression technique). Thirty crowns were milled from lithium disilicate blocks (IPS e.max CAD; 15/impression technique) using the E4D scanner and milling engine. The master die and the intaglio of the crowns were digitized using a 3D laser coordinate measurement machine with accuracy of ±0.00898 mm. For each specimen a separate data set was created for the Qualify 2012 software. The digital master die and the digital intaglio of each crown were merged using best-fitting alignment. An area above the margin with 0.75 mm occlusal-gingival width circumferentially was defined. The 3D marginal fit of each specimen was an average of all 3D gap values on that area. For the 2D measurements, the marginal gap was measured at two standardized points (on the margin and at 0.75 mm above the margin), from standardized facial-lingual and mesial-distal digitized sections. One-way ANOVA with post hoc Tukeys honestly significant difference and two-way ANOVA tests were used, separately, for statistical analysis of the 3D and 2D marginal data (alpha = 0.05). RESULTS One-way ANOVA revealed that both 3D and 2D mean marginal gap for group A: PVS impression/IPS e.max Press (0.048 mm ± 0.009 and 0.040 mm ± 0.009) were significantly smaller than those obtained from the other three groups (p < 0.0001), while no significant differences were found among groups B: PVS impression/IPS e.max CAD (0.088 mm ± 0.024 and 0.076 mm ± 0.023), C: digital impression/IPS e.max Press (0.089 mm ± 0.020 and 0.075 mm ± 0.015) and D: digital impression/IPS e.max CAD (0.084 mm ± 0.021 and 0.074 mm ± 0.026). The results of two-way ANOVA revealed a significant interaction between impression techniques and crown fabrication methods for both 3D and 2D measurements. CONCLUSIONS The combination of PVS impression method and press fabrication technique produced the most accurate 3D and 2D marginal fits.

Development of the curve of Spee

INTRODUCTION Ferdinand Graf von Spee is credited with characterizing human occlusal curvature viewed in the sagittal plane. This naturally occurring phenomenon has clinical importance in orthodontics and restorative dentistry, yet we have little understanding of when, how, or why it develops. The purpose of this study was to expand our understanding by examining the development of the curve of Spee longitudinally in a sample of untreated subjects with normal occlusion from the deciduous dentition to adulthood. METHODS Records of 16 male and 17 female subjects from the Iowa Facial Growth Study were selected and examined. The depth of the curve of Spee was measured on their study models at 7 time points from ages 4 (deciduous dentition) to 26 (adult dentition) years. The Wilcoxon signed rank test was used to compare changes in the curve of Spee depth between time points. For each subject, the relative eruption of the mandibular teeth was measured from corresponding cephalometric radiographs, and its contribution to the developing curve of Spee was ascertained. RESULTS In the deciduous dentition, the curve of Spee is minimal. At mean ages of 4.05 and 5.27 years, the average curve of Spee depths are 0.24 and 0.25 mm, respectively. With change to the transitional dentition, corresponding to the eruption of the mandibular permanent first molars and central incisors (mean age, 6.91 years), the curve of Spee depth increases significantly (P < 0.0001) to a mean maximum depth of 1.32 mm. The curve of Spee then remains essentially unchanged until eruption of the second molars (mean age, 12.38 years), when the depth increases (P < 0.0001) to a mean maximum depth of 2.17 mm. In the adolescent dentition (mean age, 16.21 years), the depth decreases slightly (P = 0.0009) to a mean maximum depth of 1.98 mm, and, in the adult dentition (mean age 26.98 years), the curve remains unchanged (P = 0.66), with a mean maximum depth of 2.02 mm. No significant differences in curve of Spee development were found between either the right and left sides of the mandibular arch or the sexes. Radiographic measurements of tooth eruption confirm that the greatest increases in the curve of Spee occur as the mandibular permanent incisors, first molars, or second molars erupt above the pre-existing occlusal plane. CONCLUSIONS On average, the curve of Spee initially develops as a result of mandibular permanent first molar and incisor eruption. The curve of Spee maintains this depth until the mandibular permanent second molars erupt above the occlusal plane, when it again deepens. During the adolescent dentition stage, the curve depth decreases slightly and then remains relatively stable into early adulthood.

Effect of polyethylene fiber reinforcement on the strength of denture base resins polymerized by microwave energy

This study investigated the effect of addition of polyethylene fibers on the transverse strength, deflection, and elastic modulus of two denture base acrylic resins polymerized by microwave irradiation. Specimens of each resin, Lucitone 199 and Acron MC, were fabricated with 0.0%, 0.5%, 1.5%, and 3.0% fiber loading. Specimens were tested with use of a three-point flexure apparatus with an Instron universal testing machine after storage in water for 10 days at 37 degrees C. The results showed that polyethylene fibers significantly decreased the transverse strength of Acron MC resin and slightly increased the transverse strength of Lucitone 199 resin at a loading of 0.5% by weight. Fiber loading did not significantly affect the deflection and the elastic modulus of either material.

Prosthodontic survey. Part II: Removable prosthodontic curriculum survey

A removable prosthodontic curriculum questionnaire was mailed to 60 United States dental schools. Fifty-one were returned. The results were compared with those of Part I of the study, the removable prosthodontic laboratory survey. The comparisons and their implications were discussed.

Human Perception of Dental Porcelain Translucency Correlated to Spectrophotometric Measurements

PURPOSE This study evaluated the relationship between instrumental measurements and subjective visual assessment of differences in dental porcelain translucency. MATERIALS AND METHODS Unshaded feldspathic porcelain was used with controlled amounts of tin oxide to create two groups of 12-mm diameter disks with incremental changes in opacity. Contrast ratio (CR = Yb/Yw) was determined with a spectrophotometer, and used as a measure of porcelain translucency (Group A = 0.20 to 0.40; Group B = 0.6-0.8). Within each group, there were 14 specimens with 11 CRs. Three observer groups (first year dental students, residents, faculty with >10 years of shade matching experience) were recruited to assess the translucency between porcelain disks under two lighting conditions (reflected light, transmitted light). Each subjects ability to distinguish between specimens of differing translucency was determined. Descriptive statistics and three-way ANOVA followed by a post-hoc Tukey-Kramer test were used to evaluate the translucency perception threshold (TPT) of subjects (alpha= 0.05). RESULTS The overall mean TPT (DeltaC) was 0.07, while 50% of the subjects could perceive a 0.06 CR difference between porcelain specimens. Three-way ANOVA revealed a significant difference in translucency perception among the observer groups (p < 0.0001), whereas the main effects for porcelain opacity (p= 0.3038) and lighting condition (p= 0.0645) were not significant, and no significant interactions were found. Post-hoc Tukey-Kramer test indicated that the mean TPT observed in the faculty group (DeltaC = 0.04) was significantly lower than those observed in student (DeltaC = 0.09) and resident groups (DeltaC = 0.08), while there was no significant difference between students and residents. CONCLUSIONS The overall mean TPT of all subjects was 0.07, and 50% of the study population perceived a 0.06 CR difference in translucency. Increased shade matching experience (> or =10 years) significantly improved the ability to perceive differences in translucency; however, neither the viewing condition nor porcelain opacity affected the perceived translucency threshold.