Crestal (Axial / Screw)Implants
|Shape and structure
||Root form – designed to imitate roots of a tooth
||The implants look like an inverted T
||Screw shaped with machined / sandblasted / HA coated surfaces.
||Flat / blade like surfaces with spaces permitting bone in growth.
||Insertion thro’ crestal bone and communication with oral cavity much more than basal implants
||Insertion thro’ lateral aspect of basal bone. Load bearing area of implant has no communication with the oral cavity.
||Vertical bone – both crestal and rarely a small portion of basal bone.
||Basal bone is what is needed. Horizontal aspects of the bone are fully utilized along with the inner and outer cortices.
||A large set of instruments are necessary for procedures
||Instrumentation is completely different and are mostly surgery related
|Bone grafting procedures
||Essential in cases of deficiency in bone height. Grafting procedures give unpredictable results
||Considerable bone substance displacement / loss occurs and varies with size and length of implant. Crestal bone is more susceptible to resorption
||Displace upto 60% less bone substance. Bone integrity and perfusion are barely impaired. Basal bone – highly resistant to resorption
|Mucosal penetration diameter
||Larger. Chances of peri implantitis, vertical bone loss, crater like bone loss and infections are relatively high
||Smaller (1.9 – 2.3mm. only). The whole vertical implant part is polished – hence, chances of problems seen as in the case of crestal implants relatively very low.
|Anatomy – proximity to Maxillary Sinus & Inf.Alveolar Nerve
||Very important consideration and technique is to be modified accordingly. Bone augmentation essential in most cases.
||Overcoming unfavorably placed Maxillary Sinus and Inferior Alveolar Nerve is possible
||Two piece implants have to have pre-angulated abutments. KOS single piece implants provide angulated as well as bendable abutment provisions.
||All BOI implants have bendable abutments.
||Two piece implants often require delayed loading & two surgical phases at times
||Prolonged healing time – clinically significant
||Bone healing time not clinically significant
||Act in the vertical direction along the sides of the screw structure
||Transferred to the basal plate deep into the cortical bone areas which are able to accept large loads and have great capacity for regeneration.
|The Bone-Implant Relationship
|| The bone needs to be modified to suit the implant which is selected for the site of implantation
||The implant selected for the site can be modified to suit the available bone height and width
|Applications in destructive periodontitis & after multiple extractions of teeth
||Placement nearly impossible and success is unpredictable.
||Placement of implants very much possible and results are excellent.
||Failure rate is nearly 100%
||Best option for smoking patients
|Controlled diabetic patients
||Crestal implants always run a risk of failure in cases where there are blood sugar variations
||Blood sugar variations may not affect the survival of the implant at all.