DIGITAL IMPLANT PLANNING: A BRIEF NARRATIVE REVIEW

Recently, the development of radiology, and software engineering, has led to the development of a new protocol called computer-assisted implantology (CAI) or guided implantology. CT / CBCT scanners allow the dentist to visualize a patient's anatomy in 3 dimensions. Define the precise measurement of bone for implant placement, soft tissue thickness, proximity and adjacent root anatomy. The exact location of the maxillary sinuses, and other relevant vital structures such as mandibular canal, mental and incisal foramen canal. Once the images are imported, to the software the clinician can then virtually begin treatment planning. The type and size of the planned implant, its position in the bone, its relationship to the restoration and adjacent teeth and/or implants, and its proximity to vital structures can be determined prior to surgery. Computer-generated surgical drill guides can then be manufactured from the virtual treatment plan.


ISSN: 2320-5407
Int. J. Adv. Res. 9(02), 869-873 870 projects it into a digital sensor with each pulse. The conical beam makes it possible to directly obtain the volume of the object by computer calculation from the multiple 2D projections acquired during the rotation of the device. [3] Both CT and CBCT are stored inthe universal format for "Digital Imaging and Communicationin Medicine" (DICOM-format). Amongst imagingdata, geometric and mathematical information, practicalinformation such as acquisition details and settings areincluded in the DICOM file.
Volumetric imaging data is displayed in 2D crosssectionalimages aligned to the prospective implant position.3D surface models of CT or CBCT data are displayedusing segmentation.CT or CBCT does not sufficiently display the tooth surfacefor the prosthetic set-up and for drill guide production.Especially in the presence of restorations, Therefore, CTor CBCT scans and a virtual dental model obtained eitherfrom an intraoral optical scan or an extraoral scan of impressionsor stone casts are aligned to each in implant planning software. [4] [5] Implant planning software : Recent Pre-implant simulation software are programs that provide clinicians excellent tools for pre-operative implant planning. to make digitally the placement of implants and different prosthetic components. These programs, for the most advanced ones, can also offer the possibility to design a surgical guide from the computer project, and even to foresee thedesign of the future prosthesis.
This software does not necessarily revolutionize the surgical procedure, but above all improves the conditions of reliability and security. They allow the practitioner to anticipate thepositioning of the implant and the resulting surgical procedure. [6] Most implant planning systems use CT or CBCT DICOM data for bone diagnostics. Three-dimensional reconstructions and multiplanar cross-sections oriented along the alveolar process in the implant region are available in all systems to review important parameters for the implant position. [7] imaging artefacts can occur distorting the tooth surface and bone volume. Implant planning software systems provide automatic segmentation of bone, teeth or soft tissues; however due to artifacts these default settings could not be used to display specific anatomical structures. Manual segmentation by limiting the window of grey values for the display of three-dimensional models is necessary and possible in all systems. [8] The importation, segmentation and pre-processing of radiographic data is crucial for the accurate transfer of the planned implant position to the surgical site. Radiographic data and virtual dental models are aligned with each other using either the tooth surface displayed both in CT or CBCT and in virtual dental models or with the help of reference markers in a radiographic splint. Incorrect matching between CT or CBCT and virtual models is known to happen after registration in relation to the number of existing metallic restorations. [9] It is possible to use either an intra-oral optical scan or an impression or model scan, respectively, to produce a virtual dental model if the data is imported in STL format.
Intra-oral optical scanning reduces the steps and thus the time required to produce virtual models. In addition to the promising efficiency of intra-oral scanners, the accuracy of intra-oral optical scanning is still not fully validated in vivo. On the other hand, extraoral optical scanning of stone casts has shown high accuracy (10 μm). [10] This means that depending on the implant system used, the drilling sequence and insertion of the implant is either performed in one step or through the drill guide. The software used in the examination has enabled guided implant placement for a number of integrated systems. The choice of implant planning software therefore depends on the specific implant systems used in daily routine.
The positioning of the drill guide on the teeth and mucosa, respectively, allows a more precise transfer of the implant position than the bone support. The operator is able to choose between the three support surfaces. The time required for the personal design and/or manufacture of the drill guide and the cost of the software must be taken into account by the user when using or selecting virtual implant planning software. [11] 871 It has to be considered that the user's experience plays an important role in any CAD software. According to the user's experience and affinity for digital products, the learning curve may vary. In conclusion, the authors find that one planning software is more intuitive than the other, which is very subjective. Before choosing a system, it is recommended to test as much as possible to find a satisfactory product.

Drilling guide:
Three types of computer-generated surgical guides are currently available: supported by teeth, mucosa and bone. Tooth-supported guides are used in cases of partial edentulism [12].
The surgical guide is conceived to rest on other teeth in the arch to ensure a precise fit of the guide. Mucosasupported guides are primarily used in fully edentulous cases and are designed to rest on the mucosa. Accurate registration of the occlusion between the arches is of critical importance when these guides are used to ensure accurate positioningof the surgical guide [13] and placement of screws or pins priorto implant placement. In addition, pins or provisional implants can be placed with all systems to facilitate fixation of the drill guide during the procedure.
The individual design of the drill guides allowed the user to choose the supporting surfaces according to the individual patient case. While most systems (NC, SIM, CDX, IST) suggest a closed design of the guide, an "open" design may be beneficial for more visibility, accessibility and less risk of interference with hard or soft tissue. Consequently, the insertion of windows in the closed design becomes important. Because of the centralized design and production of drill guides, the user must provide individual information for any design specialty before manufacturing. Bone supported guides can be used in partially toothless or fully edentulous cases, but are mostly used in fully edentulous cases where there is significant crestal atrophy and where the proper seating of a mucosasupported guide is doubtful. Such guides require the elevation of a thick flap to expose the bone in the intended implant sites and adjacent areas for a complete and stable seating of the guide on the bony ridge. [14] The placement of dental implants using CT-guided drill guides is known to improve safety over the freehand technique as well. Based on the NobelGuide protocol, when the guided abutment is used to secure the immediate restoration, the accuracy should be sufficient to insert a final prefabricated restoration at the time of implant surgery. However, no CT-guided drill guide technology exists today with absolute accuracy. The literature on stereolithographic guides shows errors in all dimensions between virtual planning and the resulting implant positions [16].
According to the literature, implants placed by bone-supported guides have the highest mean deviations, while implants placed by mucosa-supported guides have smaller deviations. Dental-supported guides have the smallest measured deviation. A single guide, using metal guide sleeves and rigid screw or pin fixation with specific drilling instrumentation, further minimizes the error. [15] Clinical case reporting the digital steps for implant planning using implaStation software:

Conclusion:-
The implant guided surgery can offer many advantages to this discipline, like precision, predictability of the results and more simple steps in the prosthetic steps, alearning curve must be conducted before facing complex cases,the clinician must understand the limitations and advantages associated with guided surgery so as to apply the benefits of this rapidly evolving technology when appropriately indicated.