The effect of engaging the screw access channel of an implant abutment with a cement-retained restoration.

PURPOSE: Factors affecting the retention of fixed prostheses to natural abutments are well understood. In contrast, little is known concerning the factors influencing the retention of fixed prostheses cemented to implant abutments. The purpose of this study was to investigate the effect that extending a casting into the screw access channel of an implant abutment has on the retention when cemented using Temp Bond. MATERIALS AND METHODS: Replace Select Straight abutments received set modifications (buccal wall removal at 15 degrees , 22 degrees , and 30 degrees ) using a milling machine; controls were unmodified. Two castings were fabricated for each of the modified abutments, one with and one without an extension into the screw access channel. Following cementation with Temp Bond under standardized conditions, the castings were removed from the abutments using an Instron machine, and the peak removal force was recorded. RESULTS: Extending the casting into the screw access channel significantly (p < 0.001) increased the peak load of removal. Significant differences (p < 0.05) were found between no modification and 30 degrees modification, 15 degrees and 30 degrees modification, and 22 degrees and 30 degrees modification in the groups when the casting extended into the abutment. In the group where the casting did not extend into the abutment, all groups were significantly different (p < 0.001) with the exception of 22 degrees and 30 degrees modification. CONCLUSIONS: The increased load required to remove a casting that extends into the screw access channel of an implant abutment may compensate for loss in retention, which occurs through unfavorable modification of the abutment.

Chlorhexidine gluconate mouthwashes as a surfactant for addition-reaction silicone impressions.

Addition-reaction silicone impression (PVS) materials are hydrophobic. Hydrophobicity of the impression material may interfere with the wetting of the tooth, resulting in void formation. The study investigates whether conditioning teeth with Chlorhexidine-gluconate based mouthwashes can reduce the hydrophobicity and the number of voids on PVS impressions. Impression material contact angle specimens on bovine tooth surfaces were measured using a Reflex Microscope. PVS impressions (President) were made of untreated bovine teeth in three groups (1, 2 and 3) and fourth group used Impregum polyether impression material: Group I was used as a control group, and original and mint flavoured Corsodyl (Chlorhexidine) mouthwashes were used as clinical surfactants in Groups 2 and 3, respectively. Contact angle readings were recorded on each side of every impression in each of the four groups and compared by an analysis of variance. In the second part of the study, the numbers of air voids on impression surfaces were visually recorded. The proportions of air voids in the groups were compared using a Chi-squared test. The mean angle for Group 3 with mint flavoured Corsodyl mouthwash was significantly smaller than that of any of the other groups (P < 0.05). The only statistically significant (P < 0.01) comparisons of the proportions of air voids were between Group 4 and each of the other experimental groups, with the percentage of voids being significantly greater in Group 4. Although Corsodyl mint significantly reduced the mean contact angle it did not significantly reduce the percentage of voids on impression surfaces.

Effect of a laboratory surfactant on compatibility of type IV dental stones with addition-cured silicone impression materials.

This study compared the effect of a surfactant on surface detail reproduction between combinations of addition-cured silicone impression materials and type IV stones. Six hundred impressions were made of a ruled test block using; Examix-NDS, Doric-Es Flo-Light, Panasil Contact Plus, Extrude Wash and President Plus Jet. Half of the impressions were treated with a surfactant (Aurofilm). Impressions were poured with type IV dental stones; Silky Rock, Fuji Rock, Suprastone and Vel-Mix and the 20 mu line was scored. A laboratory surfactant (Aurofilm) significantly reduced (P<0.01) compatibility with; (i) Examix-NDS and Suprastone, (ii) Examix-NDS and Velmix, (iii) Extrude Wash and Fuji Rock.

A technique for post-orthodontic retention of maxillary anterior teeth in the restored dentition: A case report.

Retention is one of the most important factors in the long term success of orthodontic treatment. In the adult patient when orthodontic movement is part of an overall treatment plan involving other disciplines, the provision of permanent retention can he complicated. Several methods have been proposed in the literature to date, all with their own problems and risks. This case report presents a technique that may solve this problem for suitable patients in a way that is both non-invasive and has excellent long-term maintenance potential.

The effect of disinfection on irreversible hydrocolloid and type III gypsum casts.

Under standardised conditions, 80 impressions were made of a ruled stainless steel die (ISO Specification 1563) using irreversible hydrocolloid (alginate). The alginates were subsequently treated with 3 commercially available disinfectants, Perform-ID, ImpressiVand Dimenol and poured with type III gypsum. The alginates were evaluated for surface detail reproduction and the gypsum for surface detail reproduction and hardness. Disinfection with Perform ID significantly affected the surface detail reproduction of alginate while Dimenol and ImpressiV did not. Perform ID and Dimenol both significantly affect the hardness of poured type III gypsum casts while ImpressiV did not.

Type IV gypsum compatibility with five addition-reaction silicone impression materials.

STATEMENT OF PROBLEM: The compatibility of current addition-reaction silicone impression materials and Type IV gypsum products is not completely understood. PURPOSE: The purpose of this study was to compare surface detail reproduction between various combinations of contemporary addition-reaction silicone impression materials and Type IV gypsum products. MATERIAL AND METHODS: Under standardized conditions, 300 impressions were made of a ruled stainless steel die (ADA specification 19), using 5 addition-reaction silicones (Examix-NDS, Doric-ES Flo-Light, Panasil Contact Plus, Extrude Wash, and President Plus Jet). Fifteen impressions of each material were poured with each Type IV gypsum product (Silky-Rock, Fuji Rock, Suprastone, or Vel-Mix). Using x12 magnification, 2 independent examiners scored the reproducibility of a 20-microm line in both the impression and the resultant casts. Statistical analysis was performed using 2-way analysis of variance and post hoc Bonferroni testing (alpha = .05). RESULTS: All impression materials tested fully reproduced the 20-microm line. Different impression materials showed different compatibility with different Type IV gypsum products. Only 25% of the Type IV gypsum casts completely reproduced the resultant 20-microm line with fine margins, and 88% of the completely reproduced casts were made from Suprastone. CONCLUSION: Not all combinations of impression material and Type IV gypsum products used exhibited similar compatibility.