Radiographic Blind Test of Curvature of the Posterior Border of the Mandibular Ramus as a Morphological Indicator of Gender.

PURPOSE: Curvature of the posterior border of the mandibular ramus at the occlusal plane has been described as a morphological trait for males. Controversy over the accuracy of this method remains among researchers; studies employing similar methods report accuracy rates for successful gender identification ranging from 59% to 99%. This blind study assessed evaluators' ability to determine gender based on the presence or absence of curvature of the posterior margin of the mandibular ramus through panoramic radiographs. MATERIALS AND METHODS: Randomly selected panoramic radiographs were obtained from The Ohio State University College of Dentistry for 413 adult male (M) and female (F) subjects. Two evaluators separately assigned ratings using a similar method to the Loth and Henenberg methodology to each subject on the right and left sides of mandibular rami. The ratings were based upon three criteria: (1) presence of curvature at the occlusal plane (M), (2) presence of curvature but not at the occlusal plane (F), and (3) lack of curvature (F). Pearson exact chi-squared test was used to evaluate the statistical strength of the ratings. RESULTS: The evaluators were only in agreement for both the right and left rami in roughly two-thirds (66.8%) of cases when there was no excessive tooth loss (ETL); however, the inter-observer agreement improved to 82.1% for those rami associated with ETL. Inter-observer agreement occurred in 72.9% of female rami and in only 64.4% of male rami. CONCLUSION: The results of this study indicated that assessment of posterior border curvature of  mandibular rami through panoramic radiographs was not a reliable indicator of gender and was further plagued by unacceptably high levels of inter-observer disagreement.

Mechanical properties of urethane and bis-acryl interim resin materials.

STATEMENT OF PROBLEM: The fracture or dislodgement of an interim prosthesis may result in additional appointments and could negatively affect the outcome of a fixed prosthodontic procedure. PURPOSE: The purpose of this study was to evaluate the flexural strength (FS), flexural modulus (FM), work-of-fracture (WOF), and Weibull parameters of 4 bis-acryl (Protemp Plus, Integrity, Turbo Temp 2, Temphase Fast-set) and 2 urethane (NuForm and Tuff-Temp) interim resins after being stored in distilled water for 1 hour and 24 hours. MATERIAL AND METHODS: Rectangular beam specimens (25 × 2 × 2 mm) of each resin (n=23) were prepared and stored in distilled water at 37°C. Then 3-point bending tests were performed on 1-hour and 24-hour (wet) and 24-hour (dry and wet) specimens in a universal testing machine at a cross-head speed of 1.0 mm/min. Stress/strain curves were generated and flexural strength, flexural modulus, and WOF values were calculated. Data were subjected to 3-way ANOVA and the Tukey-Kramer pairwise comparison test (α=.05). FS data were also subjected to a 2-parameter Weibull analysis. RESULTS: The 24-hour (wet) mean flexural strength and flexural modulus values were significantly higher than 1-hour values. The urethane Tuff-Temp, chemically and dual-polymerized, showed significantly higher (P<.05) 1-hour FS and FM, while the bis-acryl Protemp Plus showed significantly greater flexural strength and work-of-fracture than the other resins after 24 hours of wet storage. Protemp Plus, NuForm, and Turbo Temp 2 did not decrease in flexural strength and flexural modulus after 24 hours in dry and wet storage conditions. The Weibull modulus values of the flexural strengths of the interim resins at 1 hour and 24 hours ranged from 8.4 to 26.8. CONCLUSIONS: Postgelation polymerization plays an important role in the substantial increase in the flexural strength and flexural moduli of the interim resins between 1 and 24 hours. A wide variation in the mechanical properties of the interim resin materials was noted but was, for the most part, not category specific.

Linguoaxial wall and cervicoincisal dimension of anterior crown preparation: effect on retention.

This study sought to evaluate the effect of the linguoaxial wall, a lingual auxiliary groove, and the cervicoincisal dimension of the anterior tooth preparation on retention. A simulated maxillary central incisor was prepared following "ideal" guidelines. The linguoaxial wall of these preparations was modified and the samples were divided into three groups: preparations with a linguoaxial wall (Group 1), preparations with a linguoaxial wall and groove (Group 2), and preparations with no linguoaxial wall (Group 3). Ten metal dies and crowns were fabricated from each preparation group. A universal testing machine subjected cemented crowns to force along the long axis of the dies and load-to-dislodgement was measured. All preparations were shortened by 3.0 mm and crowns for the reduced-height groups were fabricated, cemented, and subjected to similar force. The preparations with the groove produced higher mean retention than the other groups. Among the reduced-height groups, the preparations with the groove also produced higher mean retention than the other groups. There were no differences in mean retention for the short and long preparation heights of each group.

Anterior deprogramming device fabrication using a thermoplastic material.

This article presents a simple and efficient technique to fabricate an anterior deprogramming device using a thermoplastic material. The material, softened by heating, is adapted to the maxillary incisors while moldable. The operator guides the mandible into closure as the material stiffens. The device is then trimmed, and a posterior centric relation record is made using the recording material of choice.

Effect of two types of latex gloves and surfactants on polymerization inhibition of three polyvinylsiloxane impression materials.

STATEMENT OF PROBLEM: Polymerization inhibition of polyvinylsiloxane impression materials has been reported when in sustained contact with some types of latex gloves. PURPOSE: This study examined the polymerization inhibition of 3 polyvinylsiloxane impression materials placed in contact with surfaces subjected to prior contact with gloves or commonly used surfactants. MATERIAL AND METHODS: A 2 x 3 x 4 x 2 design was used (n = 20), with 2 types of gloves (powdered and unpowdered), 3 types of polyvinylsiloxane impression materials (Aquasil, Extrude, and Affinis), 4 surfactant conditions (water, soap/water-rinse, alcohol, and unexposed), and 2 ambient temperatures of 22 degrees C and 36 degrees C. After glove exposure to surfactants, a glass surface was subjected to rubbing contact with the treated glove for a standardized time. After drying, automixed polyvinylsiloxane impression materials were dispensed onto the treated surface. Specimens were removed and evaluated for polymerization inhibition at the manufacturer's recommended polymerization time (36 degrees C), or after 15 minutes at 22 degrees C. Specimens were rated as polymerized, or as inhibited if any polyvinylsiloxane residue remained on the slab. A chi-square analysis was used to evaluate the results (alpha=.05). RESULTS: Setting inhibition was found only with one of the polyvinylsiloxane materials when alcohol was used as a surfactant. At 22 degrees C, the inhibition rate ranged from 95% to 100% for both glove types; at 36 degrees C inhibition ranged from 40% (unpowdered gloves) to 75% (powdered gloves), respectively. CONCLUSION: Under these in vitro conditions, glove exposure to alcohol resulted in polymerization inhibition of 1 of 3 tested polyvinylsiloxane impression materials (Extrude).