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 Table of Contents  
Year : 2018  |  Volume : 10  |  Issue : 6  |  Page : 299-302

Evaluation of different impression techniques for indirect E-max fixed dental prostheses. Randomized clinical trial

1 Dental Intern, Al-Farabi College, Jeddah, Saudi Arabia
2 Department of Fixed and Removable Prosthodontics, Oral and Dental Research Division, National Research Centre; Department of Fixed Prosthodontics, Faculty of Oral and Dental Medicine, Ahram Canadian University (ACU), Giza; Department of Fixed Prosthodontics, Al Nahda University (NUB), Beni Suef, Egypt
3 Department of Fixed and Removable Prosthodontics, Oral and Dental Research Division, National Research Centre, Giza, Egypt
4 Dentist, King Fahd Armed Forces Hospital, Jeddah, Saudi Arabia

Date of Web Publication24-Dec-2018

Correspondence Address:
Dr. Rami M. Galal Atia
59 4th, Touristic District, 6th of October, Giza
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jioh.jioh_191_18

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Background: Assessment of optical in comparison to traditional impressions is needed. The goal of this research is evaluating optical and traditional impressions regarding time, participant, and operators' preference. Materials and Methods: One optical and two traditional impressions were made in ten participants randomly. Optical scanner used is Omnicam of Cerec; traditional impression used closed mouth tray and other used one-step traditional tray. Time taking impression and occlusal relationship registration were evaluated. Participants and operators feeling about easiness of procedure were evaluated using visual analog scales. Paired t-test was applied detecting differences. Results: Mean time ± standard deviation was 336 ± 9.4 s using traditional closed mouth technique, 557 ± 8.2 for single step, and 397 ± 8.6 s for Omnicam. Timing of closed mouth technique was significantly lower than single-step and optical impression. Participant's assessment (very uncomfortable = 0 and comfortable = 100) measured 68 ± 9.7 for closed mouth, 79 ± 9.4 for optical, and 59 ± 9.7 for the single-step technique. There was statistical significance between differences except between closed mouth and single-step techniques; differences between them were not significant. Operators assessment (simple = 0 and very difficult = 100) was 21 ± 9.5 for closed mouth, 62 ± 9.2 for optical, and 46 ± 11.2 for single-step technique. There was statistical significance between the differences. Conclusions: Closed mouth took less time than optical and the single-step technique. Regarding comfort of participant, optical impression was the best. Operator's assessment favored optical impressions most as being the easiest.

Keywords: Impression techniques, optical impressions, traditional impressions

How to cite this article:
Linga SA, Atia RM, Hamza GE, Lanqa SA, Basheer DA, Alahmari MM. Evaluation of different impression techniques for indirect E-max fixed dental prostheses. Randomized clinical trial. J Int Oral Health 2018;10:299-302

How to cite this URL:
Linga SA, Atia RM, Hamza GE, Lanqa SA, Basheer DA, Alahmari MM. Evaluation of different impression techniques for indirect E-max fixed dental prostheses. Randomized clinical trial. J Int Oral Health [serial online] 2018 [cited 2022 Jan 28];10:299-302. Available from:

  Introduction Top

Nowadays, it is a new era in prosthetic dentistry, due to the use of digital impressions and new digital computer-aided methods for designing and manufacturing computer-aided design/computer-aided manufacturing (CAD/CAM). Now, we are trying to change all the old traditional methods to have better results. Some studies found that there is no significance between the overall survivals of the tooth supported and implant CAD CAM fabricated prostheses.[1],[2] In addition, there is no difference in accuracy.[3],[4] Making single crowns or short span bridges can be done efficiently with digital impressions.[5] In addition, it was found that digital impressions could be more reproducible.[6]

The digital procedures nowadays have a great level of attraction to the patients concerning its easiness, time-saving and of course, there is no annoying impression materials use. For the dentists, prostheses that are more accurate, easiness, and time-saving are great advantages of this technology.[7],[8] A study evaluated how accurate the digital impressions are in comparison to the traditional impressions and digitalization of full-arch stone casts; they found that the digital impressions are more time efficient and comfortable to the patient.[9] Other studies investigated the quadrant digital impressions in vivo in comparison to the conventional ones finding level of precision comparable with each other.[10] The time saving of the different digital impression systems was obvious, but the accuracy and precision vary from system to another. Digital impressions are suitable for different prosthetic indications. Furthermore, just quadrant scanning was suggested and found to be efficient and enough when using digital impressions.[11] Some studies compared between the digital impressions and traditional polyether impressions.[12],[13] The evaluation regarding the participant's preference was always in favor of the digital way. However, there is a need for randomized clinical studies to assess the time efficiency, efforts, subjective evaluation, and the final accuracy of the restorations. Our clinical study was designed to assess one digital impression and two traditional impressions for the construction of three units tooth supported all-ceramic fixed dental prostheses. The aim is to evaluate the time taken during taking the impressions, participants, and operators' evaluation of the easiness of the procedure.

  Materials and Methods Top

This randomized clinical study evaluated three impression techniques. The study was done in Al-Farabi College clinics and had the ethical approval by its ethical committee. The participants signed written consents and approved to be part of the study and to comply during the follow-up period. Ten participants demanding three units all-ceramic bridges were involved in the study. The inclusion criteria were from 18 to 60 years group age; the patient should have plaque score and bleeding score <25%, with good periodontal state, with one missing tooth in need to three units fixed dental prosthesis, with sound or properly restored neighboring and opposing teeth. Sequencing of the different impression techniques investigate is determined according to computer-generated randomization list. The sequence of the different impression techniques was concealed by sealed envelopes until the date of the participant clinical visit. Three operators (R.A, M.M, and R.G.) performed the impressions. The operators were well trained on the different impression techniques. Before beginning of the procedures, the operators gathered in a meeting to review standardize the techniques and methods of calibration. Abutments were prepared following the proper guidelines of preparation for receiving all ceramic retainers. Deep chamfer finish line was used, rounded point and line angles were evaluated and convergence for the opposing axial walls were assured to be 10°. Temporary fixed dental prosthesis fabrication. In the next visit, one optical impression and two traditional impressions were made in each of the ten patients. Randomization of the impressions sequence was computer generated. After removal of the provisional bridge and cleaning of the abutments, the sealed randomization envelopes were opened. The optical intraoral scanner used was the Cerec Omnicam (Sirona dental systems, GmbH) [Figure 1]. Scans were made according to manufacturer's guidelines. Traditional impressions were done using the closed mouth technique [Figure 2],[14] additional silicone impression material was used (fast set” Elite HD + putty soft and light body), the 3rd technique was the traditional prefabricated metal tray with one step putty and light bodied applied together [Figure 3]. The quality of the impression was checked by assessing the abutments, adjacent teeth, and occlusal surfaces. Impressions with low-quality were remade or rescanned. Timing of the traditional impression techniques were scored from the insertion of the tray till removal. The timing of the Omnicam scanning was recorded. After taking proper impressions, the participant and operator evaluation were rated by visual analog scales (VAS). The VAS is formed of 100 mm horizontal lines. Participants were asked to rate the easiness of the procedure (easy = 0, to difficult = 100). The operator rated the easiness of the procedure also (easy = 0, to difficult = 100). The VAS scores were converted into numerical format from 0 to 100 for statistical analysis. Statistics were computed with software SPSS 16.0 (IBM, New York, USA). Data were reported by means and standard deviation (SD). All results were normally distributed. The paired t-test was applied to detect the differences between groups.
Figure 1: Optical impression

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Figure 2: Closed mouth technique

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Figure 3: Traditional tray technique

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  Results Top

Almost 50% of the participants were male and the rest were female, with mean age 37.3 from range (from 20 to 50). Impressions were made to abutments of three units bridges.

The mean of the procedure time ± SD was 336 ± 9.4 s for closed mouth technique impressions, 557 ± 8.2 s for the single-step traditional metal tray technique, and 397 ± 8.6 s for the Omnicam [Table 1]. Differences between the procedures were statistically significant (P < 0.005). One traditional metal tray impression needed remake for only one patient. No additional scans were needed to any of the participants. Remake for one participant was needed with the closed mouth technique.
Table 1: Timing of the procedures

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Mean of participant evaluation of the easiness was 68 ± 9.7 for the closed mouth technique, 59 ± 9.7 for the traditional metal tray technique, and 79 ± 9.4 with the Omnicam [Table 2]. The difference between them was statistically significant (P < 0.05) except between the closed mouth technique and the traditional tray was not quite statistically significant P = 0.052.
Table 2: Impression procedure: participant and operator assessments

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Regarding operator assessment, it was 21 ± 9.5 for closed mouth technique, 46 ± 11.2 for the traditional tray, and 62 ± 9.2 for the Omnicam scanning. The differences were statistically significant (P < 0.05).

  Discussion Top

The studies testing the digital workflow in fixed prosthodontics are not enough.[15]

In this trial, the closed mouth technique was more time effective than the stock metal tray and the Omnicam optical scanning. However, concerning the participant assessments, they preferred Omnicam scanning to the closed mouth and the traditional metal tray techniques. The operator's assessment showed preference to the closed mouth technique followed by the custom metal tray then the Omnicam.

Our findings differed than that in a previous study regarding digital and conventional impressions. It was done by the evaluations of predoctoral operators taking optical and traditional impressions on an implant abutment on a cast.[16] The timing took by optical impression was less than the traditional attributed to more preparation time and remakes with the second one. The digital impressions were easier to the students. This difference is attribute to the use of the closed mouth technique in our study with both arches impressions taken together at the same time. Also, the procedures were done by experienced operators.

A trial to investigate the digital and traditional procedures was done also for single crowns and threeunit fixed partial dentures. The Lava optical impressions were used with polyether traditional impressions. For the single crowns, only quadrant impressions are taken with the opposite teeth and the view of the occlusion from the buccal view. However, for the three-unit bridges, the whole upper and lower jaws are scanned with the occlusion detection also. In case of traditional impressions, full-arch impressions were taken with separate step for interocclusal registration. The single crowns and the three unit bridges showed less timing in the digital procedures than the conventional ones using the traditional trays and this was in accordance with our study.

In other research, both students and experienced dentist evaluated the digital and conventional impressions difficulty.[16] Both students and dentists expressed the same assessments of difficulty.

Another study, where there was comparison between conventional and optical impressions in terms of timing and patient preference.[13] It was in approval with our study as the preference was in favor of the optical impressions but opposing our study regarding the timing that was less with conventional impressions. In another research,[12] the timing was less in the optical impressions than with the conventional ones, and the participant preference was also with the digital procedures as in our study results.

This study was also showing same results as that study[17] done to compare traditional impression with the triple-tray technique with the digital impressions, and they suggested more studies on multiple abutments' bridges as done in our study.

Our study is with a small sample size and this is a limitation.

  Conclusions Top

It was found in our research that the closed mouth technique is the fastest, with best patient acceptance and best operator easiness evaluation followed by the digital procedures, which are preferred over the conventional trays as approved by the previous studies in the literature.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Wittneben JG, Wright RF, Weber HP, Gallucci GO. A systematic review of the clinical performance of CAD/CAM single-tooth restorations. Int J Prosthodont 2009;22:466-71.  Back to cited text no. 1
Kapos T, Evans C. CAD/CAM technology for implant abutments, crowns, and superstructures. Int J Oral Maxillofac Implants 2014;29 Suppl: 117-36.  Back to cited text no. 2
3Ebeid K, Salah T, Nossair S. Accuracy and Reliability of Intraoral Scanners: Are they the better option? Curr Oral Health Rep 2017;4:209.  Back to cited text no. 3
Ahlholm P, Sipilä K, Vallittu P, Jakonen M, Kotiranta U. Digital versus conventional impressions in fixed prosthodontics: A Review. J Prosthodont 2018;27:35-41.  Back to cited text no. 4
Kim KR, Seo K, Kim S. Comparison of the accuracy of digital impressions and traditional impressions: Systematic review. J Korean Acad Prosthodont 2018;56:258-68.  Back to cited text no. 5
Kamimura E, Tanaka S, Takaba M, Tachi K, Baba K. In vivo evaluation of inter-operator reproducibility of digital dental and conventional impression techniques. PLoS One 2017;12:e0179188.  Back to cited text no. 6
Christensen GJ. Impressions are changing: Deciding on conventional, digital or digital plus in-office milling. J Am Dent Assoc 2009;140:1301-4.  Back to cited text no. 7
Reich S, Vollborn T, Mehl A, Zimmermann M. Intraoral optical impression systems – an overview. Int J Comput Dent 2013;16:143-62.  Back to cited text no. 8
Sfondrini MF, Gandini P, Malfatto M, Di Corato F, Trovati F, Scribante A, et al. Computerized casts for orthodontic purpose using powder-free intraoral scanners: Accuracy, execution time, and patient feedback. Biomed Res Int 2018;2018:4103232.  Back to cited text no. 9
Ender A, Zimmermann M, Attin T, Mehl A. In vivo precision of conventional and digital methods for obtaining quadrant dental impressions. Clin Oral Investig 2016;20:1495-504.  Back to cited text no. 10
Ahrberg D, Lauer HC, Ahrberg M, Weigl P. Evaluation of fit and efficiency of CAD/CAM fabricated all-ceramic restorations based on direct and indirect digitalization: A double-blinded, randomized clinical trial. Clin Oral Investig 2016;20:291-300.  Back to cited text no. 11
Joda T, Brägger U. Patient-centered outcomes comparing digital and conventional implant impression procedures: A randomized crossover trial. Clin Oral Implants Res 2016;27:e185-9.  Back to cited text no. 12
Wismeijer D, Mans R, van Genuchten M, Reijers HA. Patients' preferences when comparing analogue implant impressions using a polyether impression material versus digital impressions (Intraoral scan) of dental implants. Clin Oral Implants Res 2014;25:1113-8.  Back to cited text no. 13
Copoulos PC. The “check-bite” method in fixed prosthodontics. J Prosthet Dent 1969;21:333-7.  Back to cited text no. 14
Joda T, Zarone F, Ferrari M. The complete digital workflow in fixed prosthodontics: A systematic review. BMC Oral Health 2017;17:124.  Back to cited text no. 15
Lee SJ, Gallucci GO. Digital vs. conventional implant impressions: Efficiency outcomes. Clin Oral Implants Res 2013;24:111-5.  Back to cited text no. 16
Benic GI, Mühlemann S, Fehmer V, Hämmerle CH, Sailer I. Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part I: Digital versus conventional unilateral impressions. J Prosthet Dent 2016;116:777-82.  Back to cited text no. 17


  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2]


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