Digital impressions in implant-prosthodontics

Dugoročna funkcijska i estetska stabilnost i uspješnost implantoprotetske terapije ovisi o pasivnom dosjedu suprastrukture na implantatima. Precizan prijenos trodimenzionalnog položaja implantata na radni model ključan je korak pri izradi restauracije s pasivnim dosjedom. Napretkom digitalizacije i 3D tehnologija razvijeni su dentalni skeneri (IOS) koji omogućuju zamjenu konvencionalnih otisnih tehnika digitalnim. Dentalni skeneri sastavni su dio CAD/CAM sustava, a dijelimo ih na intraoralne, koji se koriste u ordinaciji, i ekstraoralne, laboratorijske, kojima se skeniraju otisci ili izliveni radni modeli. Tehnologije koje se koriste u radu intraoralnih skenera najčešće su: triangulacija, paralelno konfokalno lasersko skeniranje i aktivno uzorkovanje valne fronte, a najbitnije karakteristike dentalnih skenera koje digitalni otisak čine vjerodostojnim su realnost i preciznost. Digitalni otisci se u implantoprotetici koriste pri planiranju terapije, pri računalno navođenoj implantaciji, za uzimanje otisaka i prikaz 3D lokacije implantata kao prvi korak pri digitalnom procesu izrade restauracija. Otisci uzeti dentalnim skenerima pokazuju brojne prednosti u usporedbi s konvencionalnim tehnikama otiskivanja. Vrijeme uzimanja otiska značajno se smanjuje, kao i broj faza rada, što uvelike reducira mogućnost nastanka pogrešaka. Osim smanjenja utroška vremena postoji i mogućnost arhiviranja radova, kao i olakšana komunikacija između ordinacije i laboratorija. Pojedinačne krunice i mostovi manjeg raspona nastali prema digitalnim otiscima pokazuju bolji dosjed i preciznost pred konvencionalnim metodama, dok se za veće konstrukcije nošene manjim brojem implantata ipak ne preporučuje upotreba IOS-a. Vjerodostojnost digitalnih otisaka veća je što je broj implantata veći, a udaljenost među njima manja.Passive fit is a primary factor for long term clinical success and survival of an implant-supported restoration. The precise transfer of three-dimensional intraoral implant relationship to the master cast is a critical step to achieve a passive fit. Advancements of 3D technology and digitalization enabled the development of dental scanners (IOS), which offer the possibility to replace conventional impression methods with optical impressions. Dental scanners are an integral part of CAD/CAM systems and are divided into intraoral scanners, which are used in-office, and laboratory scanners, which are used extra-orally for scanning the impression or master casts. Working principles most commonly used for intraoral scanners are triangulation, active wavefront sampling and parallel confocal laser scanning, and the most important characteristics of dental scanners, for verification of the reproducibility of an impression, are trueness and precision. In implant-prosthodontics, digital impressions are used for therapy planning, computer guided implant surgery, making impressions and presenting 3D location of implants as the first step of digital workflow in restoration making. Being compared with conventional impressions, digital impressions taken by dental scanners show numerous advantages. The time needed for impressions-making is significantly reduced and the number of work phases shortened, which greatly decreases the possibility of errors. Apart from reduced time consumption, digital impressions also provide the possibility of easy archiving, as well as improved communication between the office and the laboratory. Single crowns and smaller prosthetic restorations, made by IOS, achieve better fit and precision than classical impressions, however they are not recommended for scanning of implant-supported restorations with large range and small number of implants. Accuracy of optical impression increases as the number of placed implants increases and the distance between implant decreases. Ke