BONE VOLUME CLASSIFICATION

In addition to quality, bone can be classified according to volume. Misch classifies bone volume in to four groups, Division A, B ,C and D describing width and height. Bone volume and bone type quality have a direct influence on the success rate and drill protocol for Endosseous (Endosteal) implants as well as the esthetics and function of the final prosthesis. The patient's ambition and restorative needs in combination with the existing volume and bone quality conditions will dictate the plan of action to satisfied the patient's desires.

Division A

Division A bone can be described as abundant bone volume in height and width. The height is more than 10 mm and the width is greater than 5 mm. Bone modification procedures (grafting and or osteoplasty) may be avoided and result in less trauma to the bone and a reduced healing period.

Division B

Division B bone presents itself with moderate bone volume in height and width. The height is more than 10 mm but the width at the crest atrophied to 2.5 to 5 mm. Deficient width can be overcome by the use of narrow diameter implants, bone augmentation or osteoplasty. Small diameter implants (less than 4 mm) result in a reduced bone to implant contact (BIC) and less favorable stress distribution. Bone augmentation will delay implant placement and lengthen the treatment time frame but result in a more advantageous morphology for implant placement. Osteoplasty of the deficient ridge will allow the clinician to place the implant at the same time as the osteotomy but reduces the available bone height necessitating shorter implants. The cortical plate at the crest of the bone is also lost, reducing initial implant stability.

Division C

Division C bone is characterized by compromised bone volume in height and width. The height is less than 10 mm and the width atrophied to less than 2.5 mm. Either augmentation through block or sinus grafts before endosteal implant placement or the use of subperiostela implants is the preferred treatment modality. Extensive augmentation procedures will substantially increase cost, skill requirements and the treatment time frame.

Division D

Severely deficient bone volume in height and width indicates D4 bone. Extensive sinus grafting, block grafts and particulate grafts are necessary to achieve acceptable conditions for endosteal or subperiostela implant placement.