INTRAORAL SCANS FOR CAD / CAM APPLICATION
Original Article
CEREC , TRIOS ) were made from a PMMA model for comparison [ 17 ] ( Fig . 12 ).
4.1.2 . Time efficiency ( factor ) of digital impressions We have found numerous studies comparing the time needed for digital and conventional impressiontaking techniques . When investigating the whole treatment time an average of 260 s is needed for a digital impression and 620 s for a conventional one . Bite registration with intraoral scanner took five times less than with the conventional technique [ 18 ]. Although scanning time extends when there are abutment teeth in the arch . Scanning 1 abutment is 23 minutes , 2 abutments 22 minutes and the whole arch is 13 minutes faster than conventional impression-taking . As the number of prepared teeth increases , the time of the intraoral scanning gets closer to the conventional impression-taking time . In these studies participants had experience in taking conventional impressions [ 19 ]. In Lee and Galucci ’ s study dental students had no previous experience on taking impressions . Intraoral scanning took half the time of the conventional technique . Consequently , the study shows that without experience intraoral scanning is still a time saving technique . It seems that digital technology reduces patients ’ time spent in the dental office [ 20 ].
4.1.3 . Evaluation of the digital impression-taking procedure based on the dentist ’ s and the patient ' s subjective comfort In 2016 Joda et al . investigated digital and conventional implant impression procedures . They found the usability and the efficiency of intraoral scanners more favourable by students ( 88 %) and dentists ( 64 %) compared to conventional methods [ 21 ]. According the previous studies patients prefer digital impressions to conventional ones . During conventional impressions patients reported breathing difficulties and they felt vulnerable , especially when upper impressions were taken . They were afraid of repeating conventional impressions rather than repeating digital ones [ 22 ]. Overall both dentists and the patients found it less stressful when impressions were taken digitally .
4.2 . Intraoral scanning possibilities ; advantages and difficulties In the next session we would like to introduce the features of the new technology , which can be a benefit or an initial difficulty when we use an intraoral scanner [ 23 ].
4.2.1 . Difficulties of intraoral scanning Learning the process of intraoral scanning is not an easy task , it is important to follow the instructions given by the manufacturers . Digital impression taking is very different from conventional impression procedure . During scanning as the scanner-head goes above the surface of the tooth the software adds new data to the images that have already been taken . The inappropriate use leads to insufficient or inaccurate virtual model . For implant scanning scan bodies are used , which are supported by the manufacturers ( Fig . 13 ). These scan bodies should be compatible with the
Figure 11 . Fit of the final restoration depends on the quality of the impression . Accuracy consists of trueness and precision . Trueness shows how close is our data to the original true value . Precision shows the relative deviation of repeated measurements .
Figure 12 . Less time is needed for a full arch intraoral scan compared to the conventional impression taking procedure .
Figure 13 . Scan bodies are used for implant scanning , they provide the necessary information for designing the prosthetic appliance .
CAD software in order to plan the digital prosthetic appliance . Manufacturers have already faced the need to start production of hybrid scan bodies , which are compatible with different systems . If we are not properly informed about the scanners ’ features prior to the purchase , it may be an unpleasant surprise that some companies charge a data management fee . In such a case , after scanning the data , it is entered into the cloud operated by the company , from which it can only be sent to the laboratory after payment of the fee . However , most manufacturers provide an open system , which allows to export the STL files for free . Limitation of intraoral scanners is that they are very expensive , however the cost of equipment is expected
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Stoma Edu J . 2018 ; 5 ( 2 ): 110-117 http :// www . stomaeduj . com