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Journal of Oral Science & Rehabilitation Volume 2 | Issue 3/2016 59 I m m e d i a t e l o a d i n g u s i n g g u i d e d s u r g e r y duction. Since the data are digitized using X-ray technologyand since materialproperties orden- sities arevisualizedthroughvarious kinds ofgray value shades, the workflow is highly dependent on the gray values assigned to the scanned 3-D data from the DICOM files. More precisely, the workflow is dependent on the actual gray value that defines the radiographic guide’s borders. This grayvalue assignment to the DICOM files is unfortunately not standardized for CBCT scan- ners(almosteveryscannerassignsdifferentgray valuestodifferentobjectsandmaterials),making reliable default values for each scanner model almost impossible. This ultimately has implica- tions regarding the produced dimensions of the surgical template, as these dimensions are de- finedbythegrayvalueselectionrepresentingthe borders of the scanned radiographic guide. In order to automatically detect and automatically apply the correct settings needed for the soft- ware to define the actual physical borders ofthe scanned radiographic guide, NobelClinician (Nobel Biocare) is designed to work with the unique and innovative NobelGuide calibration procedure. The calibration object is a high- precision object, milled from a material that be- haves the same way when penetrated by X-rays as the resins typically used for the radiographic guide in combination with the scanner. This pro- cess ensures that each time the CBCT scanner is used with a known scanner the surgical templa- teproducedwillhavethesamefittingdimensions as the originally scanned radiographic guide. As a result, the procedure does not calibrate the scanner, but calibrates the full workflow, from an accurately fitting radiographic guide to an accurately fitting surgical template. Many factors are likely to affect the success of immediately loaded implants, including bone quality and quantity, the skill and experience of the clinician, implant design, implant primary stability, micro- and macromovement, aswellas occlusion.The qualityand quantityofbone atthe implant site have been shown to be important in determining the success of dental implants and are critical for ensuring the initial stability of the implant upon insertion.29 Primaryimplant stabil- ityand lack ofmicromovement are consideredto be two of the main factors necessary for achie- ving predictable high success rates for osseo- integrated oral implants.30 Thus, a high insertion torque value appears to be one of the prerequis- ites for a successful immediate or early loading procedure. The variable-thread tapered implant design with a moderately rough surface was in- troduced into the market to facilitate one-stage surgical procedures and to allow for immediate placement and anticipated loading protocols.31 According to the results of the present study, in which all of the patients included had failing maxillary dentition and refused interim comple- te removable dental prostheses, the major indi- cation for such implants is medium- or low- density bone sites in the maxilla. Nevertheless, a slight modification of the original drilling pro- tocol was adopted in that implant sites were underprepared according to the bone density. However, a guided screw tapping for half the depth of the osteotomy site was performed im- mediately before the implant placement. Great carewastakentoensureoptimalaccuracyduring implant placement because the implant mount had a smaller diameter than that of the sleeve. Nevertheless, this feature allowed the clinician to perceive the implant stabilitywithin the bone, without anyfriction betweenthe implant mount and the sleeve. Conclusion Withinthelimitationsofthisretrospectivestudy, variable-thread tapered design implants placed using computer-assisted template-guided sur- gery, in combination with a specially designed two-piece radiographic stent, can be considered a successfultreatment optionforimmediate im- plant placement and loading in the maxillae of completely edentulous patients, based on the results of up to five years of follow-up. Post- extraction implants showed statistically lower marginal bone remodeling compared with im- plantsplacedintohealedsites.Theresultsshould be interpreted with care and data should be investigated further in randomized controlled clinical trials. Competing interests The authorsdeclarethattheyhave nocompeting interests related to this study. No financial sup- port was received for this study. Volume 2 | Issue 3/201659