Influence of intraoral conditions on the accuracy of digital and conventional implant impression techniques for two-implant-supported fixed dental prostheses

Abstract

Misfitting implant-supported fixed dental prostheses (FDPs) may lead to an increased rate of biological and mechanical complications and further influence the long-term success of implants [1,2]. As the first step in fabricating a passively fitting implant-supported FDP, accurate implant impressions obtained using either conventional (CITs) or digital impression techniques (DITs) are crucial [2][3][4].CITs are a reliable and standard approach for transferring the positions of dental implants [5]. However, certain limitations exist, including high complexity, time consumption, material costs, storage issues, and unpleasant patient experiences [6,7]. Over the past several decades, DITs using intraoral scanners have been considered an advantageous alternative to CITs because they improve comfort and are more efficient [8,9]. However, the accuracy of DITs remains inconclusive, and a wide range of values (5.38-810 µm) is documented [10].Most recent studies regarding the accuracy of implant impression techniques are limited to laboratory study designs [11][12][13][14][15][16][17], and only a few clinical studies have been reported [18]. As defined by ISO 5725-1, accuracy comprises trueness and precision. Trueness describes the deviation of the obtained results from true reference values. However, a standard method for intraoral acquisition of the actual reference positions of implants has not yet been developed [3]. Precision describes the closeness of agreement between the results of repeated measurements on the same object. Although the precision of impression techniques can be evaluated in clinical studies by measuring the difference between repeated intraoral impressions [19][20][21], previous precision studies regarding implant impression techniques mainly employed in vitro designs [22][23][24][25][26], and clinical data remain very limited [27]. Compared with extraoral conditions, intraoral conditions involve more complex factors associated with the impression removal pathway, including temperature, humidity, saliva, tongue movements, limited spaces, and different ambient light conditions, which may influence the accuracy of the J Prosthodont Res. 2023; **(**):

Intraoral digital implant scans: Parameters to improve accuracy

“…80 The in vivo study, compared the maxillary and mandibular anterior or posterior regions. 79 Results revealed significant differences between the implants located in the anterior or posterior regions, for both maxillary and mandibular intraoral digital implant scans. 79 In completely edentulous conditions, to the best authors' knowledge, only three in vitro studies have assessed the influence of implant position in the arch on intraoral scanning accuracy.…”

“…The dental literature analyzing the influence of the arch being scanned (maxillary vs. mandibular arch) when acquiring intraoral digital implant scans is scarce. 40,78,79 In these studies, contradictory results have been reported. Gómez-Polo et al 40 compared the accuracy of maxillary and mandibular complete-arch intraoral digital implant scans.…”

“…78 Additionally, another clinical study analyzed the extraoral and intraoral (Trios 2, v. 21.2.0; 3Shape A/S) scanning accuracy between maxillary and mandibular intraoral digital implant scans. 79 Six participants received a custom acrylic resin-made holder containing two implant analogs that fitted in the maxillary and mandibular anterior or posterior regions. Authors reported lower trueness in maxillary-posterior and mandibular-posterior regions compared with maxillary-anterior and mandibular anterior.…”

“…Authors reported lower trueness in maxillary-posterior and mandibular-posterior regions compared with maxillary-anterior and mandibular anterior. 79 One in vitro study compared the scanning accuracy of maxillary complete-arch intraoral digital implant scans (Trios 3; 3Shape A/S) with and without the inclusion of the palate. 80 The results revealed that the accuracy of digital scans of the edentulous maxillary arch with four implants when the palate was scanned compared with the scans that did not scan the palate was similar.…”

“…The implant position in the dental arch can also impact the accuracy of complete-arch intraoral digital implant scan of partially 63,79,81 and completely edentulous 45,79,82 patients with different numbers of implants placed. However, limited dental studies have considered this variable.…”