The implant must be surrounded by an adequate amount of bone for fusion and long-term survival, as well as a thick envelope of healthy soft tissue (gum) around it. It is common for bone or soft tissue to be so deficient that the surgeon will need to reconstruct it either before or during implant placement.[30]
The use of bone implanted in the cavity of a dislocated canine to restructure the bony part
Bone reconstruction
See also: bone graft, maxillary sinus fundus lift
Bone grafting is necessary when there is a lack of bone as it helps to stabilize the implant in place in the long term and reduces bone loss in the margins. To achieve an adequate bone width and height, several bone grafting techniques have been developed. Bone grafting is done by filling the defect with either harvested natural bone or an artificial bone substitute, covered with a semi-permeable membrane and allowed to heal. During the healing phase, the natural bone replaces the bone used in the graft to form a new base for the implant.[31] While there are always new types of implants, such as short (lower diameter) implants, and techniques to allow compromises for implant placement, the general treatment goal is to have a minimum bone height of 10 mm, and a width of 6 mm.[32]
There are three common construction procedures which are:[33]
Sinus lift
Lateral enlargement (grafting)
Vertical augmentation (grafting)
There are also other more invasive procedures for larger bone defects. This involves stimulating the inferior alveolar nerve to allow placement of implants. Here, bone grafts are made using the iliac bone or another large source of bone such as the chin bone with microvascular bone where the blood supply to the bone is implanted with the source bone and reconnected. In general, the final decision on the best method of bone grafting depends on the assessment of the degree of bone loss present, both vertically and horizontally, which is categorized into either mild (2-3 mm bone loss), moderate (4-6 mm) or severe (loss greater than 6 mm).[35]
Soft tissue reconstruction
The black triangle on either side of the implant crown is due to bone loss between the implant and adjacent teeth.
The gingiva surrounding the tooth has a band of about 2–3 mm of bright pink, strong, strongly attached mucous membrane, and then a darker, larger area of unattached mucosa that folds into the cheeks. When replacing a tooth with an implant, a strip of strong gum is needed to maintain the health of the implant over the long term. This is particularly important for the continuity of blood supply to the gums, which are theoretically more susceptible to infection due to their longer attachment to the implant than to the tooth.[36] When an adequate band of attached tissue is absent, it can be recreated by soft tissue grafting. There are four methods that can be used for soft tissue transplantation. A roll of tissue adjacent to the implant (referred to as a palatal roll) can be taken and placed towards the lip. Gum can be transplanted from palatal tissue. Deep connective tissue can be transplanted from the palate. When a larger piece of palate is transplanted, larger tissue is needed. A finger can be repositioned from Tissue with blood vessels surrounding the palate.[37]
In addition, in order for the implant to look aesthetically pleasing, a strip of plump gum is needed to fill the space on either side of the implant. The most common soft tissue complication is known as the black triangle, in which the papilla (a small triangular piece of tissue between two teeth) shrinks back and leaves a three-way space between the implant and adjacent teeth. Dentists can only expect 2-4 mm of papilla height over the underlying bone. The black triangle can be expected if the distance between the place where the teeth touch the bone is greater than that.[38]
