Abstract
Objectives The impression-taking technique is one of the most critical factors that not only prevents the shrinkage caused by polymerization but also enhances the accuracy of implant impressions. Also, choosing the right time of taking impressions after splinting implants is one of the important criteria that affects the impression-taking technique. Accordingly, the present study aimed to evaluate the accuracy of different splint methods for implant impressions made at different times. Methods In this in vitro study, a two-piece metallic index was prepared, and the patient's jaw was simulated by placing self-cured acrylic resin in the lower part of the index. Then, two holes were made in the acrylic resin at a specific distance from each other, and the analogs were placed in these holes. Splinting of impression copings was carried out with autopolymerized acrylic resin (GC Pattern resin LS, GC America Inc., USA), and an open tray impression approach was performed. Thirty-six casts in three groups (n = 12) were fabricated from the acrylic model. After scanning the casts, the impression accuracy was compared between the three study groups by measuring the distance between the outer portions of the scan bodies screw-retained on implant analogs inside the cast using the Exocad software (2015.07 version). Group 1: splinting impression copings with autopolymerized acrylic resin and impression making immediately after the setting time (4 minutes); group 2: splinting and impression procedure after 17 minutes with splint sectioning and reconnection; group 3: splinting and impression procedure after 24 hours with splint sectioning and reconnection. The data were analyzed using SPSS 17 using the Kruskal–Wallis test. Results The mean distance measured in group 1 was 19.14 ± 0.029 mm, which was significantly lower than the main model. The distances were 19.15 ± 0.039 and 19.159 ± 0.33 mm in groups 2 and 3, respectively. These two groups were not significantly different from the main model. Moreover, the mean distance measured in the three impression techniques was similar. Conclusions There was no significant difference in the measurements between group 2, group 3, and the main model. Therefore, dentists can make an impression after 17 minutes to reduce chair time.
Highlights
Dental implants are substitutes for conventional prostheses with favorable long-term outcomes in patients who have lost all or some of their teeth [1,2,3,4]. e success of an implant depends on the passive fit of the prosthesis and its components. erefore, accurate impressions and the correct transfer of implant position to the cast are of high importance [5], and the clinician will receive results of an accurate impression by good adaptation of final prosthesis and reducing chair time [6]
According to International Journal of Dentistry studies, misfit in the prosthesis effects the outline and amount of stress distribution in the prosthesis and surrounding bone which may cause adverse complications. ese adverse complications may include the fracture in the different sections of the implant system, framework break, or porcelain fracture, loosening of the abutment and retaining screws, marginal bone loss, and even pain or loss of osseointegration. erefore, diminishing the misfit and improving the passive fit over variation in impression methods and impression materials is an important goal in prosthesis knowledge and dental implants [11]
Due to the controversial findings of various studies concerning the effect of splinted impression copings during implant impressions, it is necessary to overcome the shrinkage caused by the polymerization and assess the impression timing after component splinting and the role of sectioning considering the availability of diverse splint techniques
Summary
Dental implants are substitutes for conventional prostheses with favorable long-term outcomes in patients who have lost all or some of their teeth [1,2,3,4]. e success of an implant depends on the passive fit of the prosthesis and its components. erefore, accurate impressions and the correct transfer of implant position to the cast are of high importance [5], and the clinician will receive results of an accurate impression by good adaptation of final prosthesis and reducing chair time [6]. Mixing the powder and liquid leads to unwanted “polymerization shrinkage,” affecting the accuracy of impression and distorting implant prostheses [16]. The splint technique affects distortion and polymerization shrinkage. Ey concluded that making an impression of splinted impression copings applying autopolymerized resin with sufficient time for polymerization (24 h) coupled with sectioning for compensating polymerization shrinkage is the most accurate splinting method [20]. E results of studies on the effect of splint impression copings during implant impressions are controversial. Due to the controversial findings of various studies concerning the effect of splinted impression copings during implant impressions, it is necessary to overcome the shrinkage caused by the polymerization and assess the impression timing after component splinting and the role of sectioning considering the availability of diverse splint techniques. If there is no significant difference between the impression accuracy at different times, dentists can apply the impression technique after 17 minutes. e latter method reduces chair time and results in higher treatment success by selecting the best technique with the highest accuracy and the least defects
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