(12) along the marked line either to the entire depth of the socket or about half-way down. These holes are then connected with gradually deepening, running sweeps of the bur (13).

In a knife edge ridge, however, the groove approach is completely different. The knife edge ridge (14) is reduced with a round stone or the 700 XL bur in order to widen the occlusal table (15) . With a 700 XL bur a deep hole is made anywhere along the widened ridge (16) . The buried bur is then slightly lifted from its bony base in order to allow it to `spin in the bone' (17) while buried in it. The groove is then created during which time the bur is totally buried in bone (18). Thus the labial and lingual bone flanking the buried bur helps to support and guide the bur as the operator creates the groove.

In good bone, the depth of the channel or socket (19) equals the height of the blade, from its leading edge (20) to the bottom of its post (21) . The 700 XL bur, which is longer than the body of most blades is used to its entire depth. Often, the 700 XL bur must be substituted in maximum bone height to obtain the proper depth. If the channel is made deeper than necessary, there is little danger of the blade's sinking because its wedge shape (22) will brace it against the wall of the socket.

The socket should be no wider than the head of the bur. As injured bone cells whose processes have been disrupted by the drilling die, the socket will widen slightly. If the site has been properly pre-pared, the blade will not loosen. Also, the mechanical pressure on bone slightly stretched by a snugly fitting blade appears to hasten recovery of the site. A properly seated blade is tight upon insertion and should not loosen during the early catabolic changes.

When the socket appears finished, the bladevent is compared with it. The socket should be slightly longer than the bladevent on each end (23) or the same length, but not shorter. In many anterior cases, the implant socket curves to follow the arch (24) . The straight bladevent (25) must be bent to fit it passively.

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