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Implant Tribune Italian Edition No.1, 2016

10 Implant Tribune Italian Edition - Marzo 2016 Speciale Digital Dentistry < < pagina 9 Materials & methods The research protocol was ap- proved by the ethics committee of Azienda Ospedaliera di Pado- va, Department of Neuroscienc- es, University of Padua (protocol #2629P; 10 April 2012). Patient selection In order to be recruited for the study, the patients had to meet the following inclusion criteria: willing to participate for the duration of the study and to provide informed consent, at least 18 years of age, in good general health, presence of a tooth to be extracted, willing to accept the immediate placement of an implant into the extraction socket, and presence of adjacent teeth both mesially and distally. The following exclusion criteria were adopted: pregnancy or un- treated dental disease. Smoking status was recorded, but was not considered a contraindication to treatment. Patients were advised that smoking is associated with an increased risk of implant failure. Ten consecutive subjects were recruited. Written consent was obtained from the patients. All patients received a careful den- tal and periodontal examination, followed by oral hygiene instruc- tions and dental and periodontal treatment, when necessary. All treatments and follow-ups were carried out in one clinic in Italy between September 2012 and Sep- tember 2014. An impression using polyvinyl siloxane (Sky Putty and Sky Light, Sweden & Martina, Due Carrare, It- aly) was taken before tooth extrac- tion (Time 0 = T0) and a gypsum cast was obtained (ORTOTYPO 4, LASCOD, Sesto Fiorentino, Italy). Subsequently, local anesthesia was administered and the tooth was extracted. An implant was imme- diately placed into the extraction socket and no filler material or membrane was used. Implants with a ZirTi surface (Premium TG, Sweden & Martina, Due Carrare, Italy) were placed. A cover screw was placed on top of the implant and resorbable sutures were pro- vided. No temporary prosthesis was seated. Antibiotics (amoxi- cillin 875 mg and clavulanic acid 125 mg b.i.d. for six days) and an- algesics if needed were prescribed and the patients were enrolled in a maintenance follow-up. A por- celain-fused-to-metal crown was provided to the patients approxi- mately three months after place- ment. Another impression was taken 12 months after implant placement (Time 1 = T1). 2-D digital analysis The casts obtained from the first and second impressions were dig- italized using a 3-D laser scanner (Dental Wings 7Series, Montre- al, Canada). The meshes (digital models) generated in this manner were imported into 3-D elabo- rating mesh software (Geomagic Studio and Geomagic Qualify, Geomagic, Berlin, Germany) and cleaned of defects. Figs. 1 & 2 - The two meshes (red T0 and purple T1) superimposed together were cut seven times vertically and six times horizontally using a Python script for Rhinoceros. Fig. 3 - A vertical 2-D cut was taken in the middle. In red is the section of the first mesh (T0) and in black the second mesh at (T1). The distance between two points was taken for the measurements in absolute values. Fig. 4 - The width of the alveolar process was also measu- red. The red line represents the width at T0 and the blue line at T1. The meshes were transformed from a surface to a solid. Subse- quently, teeth surfaces that co- incided on the meshes obtained from both casts were selected and the two digital models were su- perimposed, accepting values of average convergence distance of < 0.1 mm. The 2-D analysis was performed using the occlusal plane as the reference plane.7 From this ref- erence, a perpendicular plane in the lingual- or palatal-vestibular direction (cross-section) was cre- ated and the two meshes super- imposed were cut (Figs. 1 & 2). The grid used to section the mesh- es was made by taking the middle point of the vestibular marginal gingiva of the tooth to be extract- ed as the reference point (0) and creating vertical and horizontal planes starting from that point: Vertically: Seven vertical planes located at +3, +2, +1, 0, -1, -2 and -3 mm from the mesial (+3) to the distal aspect (-3); Horizontally: Six horizontal planes at 0 (vestibular marginal gingiva), -1, -2, -3, -4 and -5 mm from the most coronal (0) to the most apical (-5). The occlusal plane, the cutting procedure and the distance analysis were performed with automated Python scripts for Rhinoceros software (Robert McNeel & Associates, Seattle, Wash., U.S.) to reduce human er- ror during elaboration. A total of 42 points for horizontal var- iation for each side was tested: 42 at the buccal aspect and 42 at the lingual/palatal aspect. The vertical variation was measured at seven points at the buccal as- pect and seven points at the lin- gual/palatal aspect. Using the measures of the alveolar process at T0 and at T1, the dimensional variations (Δ) were expressed in absolute (Fig. 3) and relative (Fig. 4) values (in respect of the total alveolar width). 3-D digital analysis The 3-D analysis was performed by subtracting the volume of the second mesh (T1) from that of the first mesh (T0), generating a re- sulting volume that represented the difference between the two meshes (Boolean difference). > > pagina 11 Fig. 5 - The mesh-to-mesh deviation utility in Rhino Open Projects. The red area represents the volume loss. The area most a ected by resorption corresponds to about the vertical middle line of the two adjacent teeth. Fig. 6 - Palatal and buccal volumes, isolated from the rest of the model during 3-D elaboration. They represent the volume loss in the ROI and can be measured as absolute values in mm3 . Fig. 7 - ROI volume of the first mesh, which represents the volume of the alveolar process at T0, expressed in mm3 .

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