Uneven Sinus Floor
Osteotomy starts with a 2 mm pilot drill (3 and 10 mm deep at the sites of #3 and 4, respectively); with a surgical stent, two parallel pins are fixed in place for PA (Fig.1). With the longer parallel pin at #4, a 4 mm trephine bur is used 2 mm; a piece of bone is removed (possible the oral cortex, Fig.2 black area). A 3.5 mm osteotome with a concave tip (Fig.5 pink outline) is used for sinus lift without success. A 2 mm osteotome with a pointed tip is used for further osteotomy for 1 mm (Fig.3). When a 3 mm osteotome is being tapped, it deviates distal (Fig.4). The 4 mm trephine bur is re-used for 4 mm (possibly penetrating the distal sinus floor (Fig.5 >), the 3.5 mm osteotome still cannot elevate the sinus floor. When the trephine bur extends 6 mm with possibly penetrating the mesial sinus floor (Fig.6 <), the 3.5 mm osteotome finally lifts the sinus floor (Fig.7 arrow) with perforation of the sinus membrane. Bone taps (5 and 6 mm) are used for further osteotomy (6 mm deep), gradually achieving stability. With placement of collagen membrane for repair (Fig.9 blue line), a 6.4x6 mm implant is placed with insertion torque ~ 55 Ncm (Fig.8 I). Placement of a 4.5x10 mm implant at #4 is accompanied with sinus lift (Fig.10 *). The incision is closed around the abutments placed immediately (Fig.11). Perio dressing is applied for wound protection. In brief, uneven sinus floor makes internal sinus lift difficult. Sinus Lift Master Kit may overcome this difficulty because of 2.8 and 3.6 mm round drills and stoppers.
Splinted provisional is fabricated 2 months postop. When the patient returns for impression 10 months postop (Fig.12), check occlusal contact of the provisional before removal. If it is off (in fact it is off), make it have normal contact after impression and encourage the patient to chew with it (a kind of progressive loading). The abutments change prior to impression (5.8x4(1 to 2), 4.8x4(2 to 3) mm). In 2 weeks, we can test whether these implants, especially the one at #14, have really osteointegrated. If not, continue to wear the provisional until the implant is functionally capable. In fact, the implants seem to be stable; the definitive crowns are cemented permanently.
The patient complains that an implant falls out 1.5 months post cementation. It must be #3 because of limited bone height (Fig.8-10,12). Models are studied to determine whether an implant should be placed at the same area or not (Fig.13,14). As a matter of fact, the implant crown dislodges at #14.
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Xin Wei, DDS, PhD, MS 1st edition 08/24/2015, last revision 08/29/2016