Comparison of various radiographic modalities to assess the bone height for implant placement

Introduction: The most advanced innovation in the last millennium was introduction of implants to dentistry. There were many advances from the onset to the current date in each and every aspect of implant dentistry. Among those advances some were a boon to the implant dentistry at the same time some were at the other side. However, implant success directly or indirectly relates when perfect pre-implant evaluation was made. Pre-implant evaluation can be done by several methods, of which radiography was widely used one because of its non-invasiveness. But the problem with radiography was the percentage of magnification. Aim and objectives: The aim of this study is to evaluate and compare the available bone height for placement of dental implant by using Orthopantomography (OPG) and Cone Beam Computed Tomography (CBCT). Methodology: 10 completely edentulous dry cadaver mandibles were selected for this study and radiographic markers i.e. gutta percha sticks were placed on the crest of the ridge bilaterally starting from a point just behind the mental foramen at mandibular 2nd premolar, 1st molar and 2nd molar regions and subjected to Orthopantomography (OPG) and Cone Beam Computed Tomography (CBCT). Then at all the 60 sites the mandibles were sectioned and anatomic length was measured from the crest of the ridge to the superior surface of the inferior alveolar canal by a digital caliper and the radiographic length was also measured with their respective software and finally the obtained values were statistically analyzed. Results: A measurement error i.e. magnification of 3.11% has been noted with CBCT and 22.08% with OPG. A safety margin that is followed till date to prevent the damage to the adjacent anatomical structures has to be increased from 2mm to 2.5 to 3mm while placing implant using OPG and can be reduced to 0.5mm while using CBCT. Conclusion: To conclude, when placing an implant taking CBCT as a guide the length of the implant can be almost the value obtained in CBCT, whereas in OPG the length of the implant should be 2.5mm less than that of the obtained value.