The accuracy measurement is always based on the STL files created by model scanning. We import the STL files into the Geomagic Control X software package, where we compare the STL files created with the tested intraoral scanner to the specific reference model. The reference for all 7 used samples is a highly accurate digital version of the original resin model, digitized with a high-precision lab scanner. It is essential to redigitize the sample with the reference scanner (3Shape E3 laboratory scanner) before each examination, as scientific studies have confirmed that resin materials can get deformed relatively quickly. In our study, we scan 7 models, the accuracy of which will determine the main indication area for the tested intraoral scanners. Based on this, we digitize a study model, a crowded dentition model, a prepared dentition model, a quadrant model, and 3 models with Straumann implant analogs. In the case of the study model, inexperienced dental students take digital impressions each time, modeling the situation when a dentist begins using a new intraoral scanner in their practice. With each tested scanner, 3 students are scanning, each producing 10 digital impressions. Dentists scan the other mentioned models with more than 3 years of experience in digital impression-taking. Each model is scanned by one dentist 10 times per model.
The measured parameters for each sample are as follows:
Study model:
- WHL (Whole Deviation): Average deviation of the entire dental arch.
Crowded model:
- WHL (Whole Deviation): Average deviation of the entire dental arch.
- Accuracy measurement performed on a segment cut from the right canine to the left canine.
Prepared model:
- WHL (Whole Deviation): Average deviation of the entire dental arch.
- Accuracy measurements include:
- Prepared abutment of the upper right central incisor.
- Distance between the upper right first premolar and second molar.
- Distance between the distobuccal cusps of the upper last molars represents a distortion of the entire dental arch.
Quadrant model:
- Accuracy measurement of the cavity prepared in the upper left first molar.
Implant model 1 (Upper jaw, with 6 Straumann implant analogs):
- WHL (Whole Deviation): Average deviation of the entire dental arch.
- Five distances measured between implant analogs: 16-14, 16-11, 16-21, 16-24, and 16-26 positions.
Implant model 2 (Upper jaw, with 3 Straumann implant analogs):
- WHL (Whole Deviation): Average deviation of the entire dental arch.
- Two small distances measured between implant analogs: 13-15 and 15-17 positions.
- One considerable distance measured between implant analogs: 13-17 position.
Implant model 3 (Lower jaw, with 4 Straumann implant analogs):
- WHL (Whole Deviation): Average deviation of the entire dental arch.
- Four distances measured between implant analogs: 33-43, 36-46, 33-36, and 43-46 positions.
The accuracy assessment was updated in September 2023 during our objective protocol/objective rating system revision/ renewal. Concerning the previous protocol, only one sample (prepared model) was measured regarding accuracy; however, the new protocol examines the accuracy of the 7 different samples described above. Therefore, the accuracy results are divided into previous (before September 2023) and new (after September 2023) accuracy results. The previous accuracy results include 27 intraoral scanner accuracy results, while currently, there are 2 intraoral scanner accuracy results based on the new protocol.