One of the successful criteria for implant restorations is the stability of Osseo integration and bone to-implant contact (BIC). It is generally accepted that in physiological functional load can be expected to have a crestal bone loss of to 1.5 mm within the first year and less than 0.2 mm every successive year. According to Hingsammer et al. the ratio between the crown and the implant should not exceed 1.7 in order to avoid increased early bone loss". Prosthetic failure occurred at C/I ratio 1:1.75 and CHS 15 mm. Recent research carried out by Hammerle et al., where it was determined that from a biomechanical point of view, it is desirable for a crown-to-implant ratie to be in the range of 0.9 to 2.2 in single restorations. Increasing this marker above certain limits may lead to mechanical complications due to overloading occlusal forces upon the marginal part of the alveolar bone, crest module and implant body. With its increase, the size of the non axial forces rises, with which the crown acts as a lever arm. This creates a bending moment that carries stress to the marginal bone, It becomes clear that the crown-to-implant ratio should be subject to careful consideration in making the treatment plan in implant recovery. increase in its ratio leads to a proportional rise in the mean stress on the retained screw and peri-implant bone.

 B. Stoichkov, D.Kirov et al indicate that prosthetic restorations with higher crown to-implant ratio tend to cause higher marginal bone loss than those with lower one. in the mandibular molar area. Increasing the ratio of 1:1 to 1.25:1 leads to intensifying the stress in the implant crest module by 30.1%. respectively: in the ratio 1.5:1 the stress is grown by 51.5°%.

 OBJECTIVES OF THE STUDY 

 1. To evaluate the crestal bone levels and bone density around the dental implant for the crown-implant ratio of less than or equal to 1:1.5.

 2. To evaluate the crestal bone levels and bone density around the dental implant for the crown-implant ratio of more than 1:1.5. 

 3. Comparative evaluation of crestal bone levels and bone density between the crown implant ratios of less than or equal to 1:1.5 and more than 1:1.5.

Radiographic parameters to be assessed are:

 1. Edentulous area at implant site. (With CBCT)

 2. Marginal bone levels and bone density around implant with SIDEXIS 4 software with SICATSUITE version 2.0. (Dentsply Sirona; York, US) immediately after prosthesis placement, after I month of prosthesis placement, 3months of prosthesis placement. 

Method:

Marginal bone loss and bone density will be calculatcd by comparing bonc-to-implant contact levels to the radiographic bascline cxamination made with CBCT aken immediately after prosthesis placement.

The following linear measurements between landmarks are taken:  

1) crown height (CH) will be measured from the top of the restoration to the first bone-to implant contact (FBIC) on both mesial and distal sides

2) implant length (|L) will be measured from the apex to the FBIC on both mesial and distal sides. To obtain the mesial CII ratio, the mesial CH is divided by the mesial IL. The distal C/L ratio will also be determined. and mean mesiodistal C/1 ratio is then obtained for each implant. The periimplant marginal bone level will be measured from the reference point to the FBIC. The reference point is the fixture abutment interface. The mesial and distal values of the marginal bone loss are averaged to one value. The mean marginal bone loss will be calculated as the difference between the initial marginal bone level and the marginal bone level at the follow-up examination.