Evaluation of accuracy of casts of multiple internal connection implant prosthesis obtained from different impression materials and techniques: an in vitro study.

Movement of impression copings inside the impression material using a direct (open tray) impression technique during clinical and laboratory phases may cause inaccuracy in transferring the 3-dimensional spatial orientation of implants intraorally to the cast. Consequently, the prosthesis may require corrective procedures. This in vitro study evaluated the accuracy of 3 different impression techniques using polyether and vinyl polysiloxane (VPS) impression material to obtain a precise cast for multiple internal connection implants. A reference acrylic resin model with 4 internal connection implants was fabricated. Impressions of the reference model were made using 3 different techniques and 2 different impression materials. The study consisted of 24 specimens divided into 6 groups of 4 each. Impressions were poured with ADA type IV stone (Kalrock, Kalabhai Karson Pvt Ltd, Mumbai, India). All casts were evaluated for the positional accuracy (mm) of the implant replica heads using a profile projector. These measurements were compared to the measurements calculated on the reference resin model, which served as a control. Data were analyzed with 2-way analysis of variance (ANOVA) followed by Bonferroni multiple comparison procedures to evaluate group means. The results revealed significant difference for anterior implant distance between the 2 impression materials (P < .01) and also among the 3 different techniques (P < .05). The lowest mean variation was found with the polyether impression material and the splinted technique. For posterior implants, the results suggested no significant difference between the 2 impression materials (P ≥ .05). Although results were not statistically significant, the polyether impression material showed the lowest mean variation as compared to the VPS impression material. However, there was a significant difference among the 3 different techniques (P < .05). Among the 3 different techniques, the lowest mean variation between 2 posterior implants was found in the splinted technique. Casts obtained from impression techniques using square impression copings splinted together with autopolymerizing acrylic resin prior to the impression procedure were more accurate than casts obtained from impressions with nonmodified implant impression copings and with airborne particle-abraded, adhesive-coated copings. Casts obtained from polyether impression material were more accurate than casts obtained from vinyl polysiloxane impression material.

Retentiveness of various luting agents used with implant-supported prosthesis: an in vitro study.

Desired retrievability of cemented implant-supported fixed prosthesis makes the retentive strength of cementing agents an important consideration. The aim of the study was to evaluate the retentiveness of purposely designed implant cement and compare its retentiveness with dental cements that are commonly used with implant systems. Ten implant analogs were embedded in auto-polymerizing acrylic resin blocks and titanium abutments were attached to them. Fifty standardized copings were waxed directly on the abutment and casted. The cements used were: (1) resin-bonded zinc oxide eugenol cement, (2) purposely designed implant cement, (3) zinc phosphate cement, (4) zinc polycarboxylate cement, and (5) glass ionomer cement. After cementation, each sample was subjected to a pull-out test using universal testing machine and loads required to remove the crowns were recorded. The mean values and standard deviations of cement failure loads were analyzed using ANOVA and Bonferroni test. The mean values (± SD) of loads at failure (n = 10) for various cements were as follows (N): resin-bonded zinc oxide eugenol cement 394.62 (± 9.76), Premier implant cement 333.86 (± 18.91), zinc phosphate cement 629.30 (± 20.65), zinc polycarboxylate cement 810.08 (± 11.52), and glass ionomer cement 750.17 (± 13.78). The results do not suggest that one cement type is better than another, but they do provide a ranking order of the cements regarding their ability to retain the prosthesis and facilitate easy retrievability.

Retentiveness of various luting agents used with implant-supported prostheses: a preliminary in vitro study.

The aim of this preliminary in vitro study was to compare the retentiveness of a luting agent designed for use with dental implants to luting agents designed for use with tooth-retained restorations. The following luting agents were tested: (1) implant cement, (2) resin-bonded zinc oxide-eugenol cement, (3) zinc phosphate cement, (4) zinc polycarboxylate cement, and (5) glass-ionomer cement. After cementation, each sample was subjected to a pull-out test using a universal testing machine, and the loads required to remove the crowns were recorded. The mean values and standard deviations of cement failure loads were analyzed using analysis of variance and the Bonferroni test. The mean cement failure loads (N) were 333.86 ± 18.91 for implant cement, 394.62 ± 9.76 for resin-bonded zinc oxide-eugenol cement, 629.30 ± 20.65 for zinc phosphate cement, 810.08 ± 11.52 for zinc polycarboxylate cement, and 750.17 ± 13.78 for glass-ionomer cement. The retention provided by polycarboxylate cement was significantly greater than that of all other luting agents; the implant cement showed the lowest retention values. These preliminary in vitro observations need to be confirmed under conditions that more closely approximate the clinical environment.

Reconstruction of Exenterated Orbit using Combined Surgical and Prosthetic Approach.

Reconstruction of an exenterated orbit remains a challenge. Orbital prostheses are nowadays are made of silicone elastomers. A major limitation with silicone orbital prostheses is their relatively short life span. This case report describes the treatment of a patient with an exenterated orbit using a combined surgical and prosthetic approach. The upper and lower eyelids were reconstructed surgically using a deltopectoral flap. A sectional eye prosthesis was made and placed in the modified bottle-neck shaped defect to restore the patient's appearance and confidence.