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Implant Tribune Italian Edition

25Implant Tribune Italian Edition - Novembre 2012 original article Letteratura internazionale Fig. 2.a-n - A paradigmatic case of transcrestal sinus floor elevation performed with the Smart Lift technique. Fig. 2.d - The Smart Lift Drill Ø 3.2, used at the surgical working length of 7 mm, trephined a bone core up to the sinus floor. Fig. 2.e - The bone core created by the Smart Lift Drill. Figg. 2.f, g - Additional biomaterial (biphasic calcium phosphate composed of hydroxyapatite (60%) and beta form of tricalcium phosphate (40%)**) was inserted into the implant site, to be grafted into the sinus. Fig. 2.c - The surgical working length was assessed at 6.5 mm throu- gh tactile perception of the sinus floor using the Probe Osteotome. Fig. 2.a - A 53 year-old male, former smoker patient presented with an edentulous lacuna in the maxillary left quadrant. The prosthetic rehabilitation plan of the patient included the placement of one implant-supported crown in the region of the left second premolar. << pagina 24 This intrusion osteotomy proce- dure elevates the sinus membrane, thus creating a space for blood clot formation. It is conceivable that the contribution of the bone core to the intra-sinusal bone formation may relate to the amount of residual bone at the implant site (i.e. the more the native bone pushed into the sinus, the more the newly for- med bone). When a limited amount of residual bone is present with re- spect to the amount of bone needed for proper implant placement, bone formation may be implemented by the additional use of a graft. Scientific evidence clearly indicates that the use of a graft biomaterial in association with tSFE may effec- tively sustain bone regeneration15-19 . Recently our research group20 com- pared the clinical effectiveness of a synthetic hydroxyapatite in a colla- gen matrix (S-HA) and DBBM when used in association with the Smart Lift technique and we demonstrated that both biomaterials may provide a predictable elevation of the ma- xillary sinus floor along with limi- ted post-surgical complications and post-operative pain/discomfort. At present, whether and to what extent the Smart Lift technique may benefit by the additional use of different graft biomaterials, and which biomaterial is the most sui- table to provide conditions for new bone formation still needs to be elu- cidated. In this context, we report a clinical case in which the Smart Lift technique was associated with biphasic calcium phosphate com- posed of hydroxyapatite (60%) and beta form of tricalcium phosphate (40%). Material And Methods Rationale and indications The Smart Lift technique was de- veloped by the Research Center for the Study of Periodontal and Peri-implant Diseases, Universi- ty of Ferrara, and the Department of Odontostomatology, Ospedale “Casa Sollievo della Sofferenza”, S. Giovanni Rotondo. The technique is characterized by a transcrestal ac- cess to the sinus cavity by means of specially-designed drills and osteo- tomes. The pristine bone at sites of implant placement is drilled up to the sinus floor with a trephine bur, and then used to fracture the sinus floor by hydraulic pressure through osteotomes. In this respect, the pro- cedure represents a modification of the technique proposed by Fu- gazzotto10 . The major novelty with previously described procedures resides in the fact that all manual and rotating instruments are used with adjustable stop devices which are selected in relation to the verti- cal amount of residual bone at sites where implants have to be placed (Fig. 1.a). These stop devices have a variable length, from 4 to 11 mm, and may be adapted to all manual and rotating instruments. The use of the stop device restricts the wor- king action of burs and osteotomes to the vertical amount of residual bone, thus preventing the acciden- tal penetration of instruments into the sinus cavity. The identification of the working length (i.e. the di- stance from the bone crest to the sinus floor) where the osteotome and burs should limit their working action is first diagnosed on periapi- cal x-ray or CT scan, and then intra- surgery assessed by means of a spe- cially-designed osteotome. The Smart Lift technique shares its clinical indications with any other proposed surgical procedures for si- nus floor elevation with a transcre- stal approach21, 22 . - indications for implant-suppor- ted prosthetic rehabilitation, based on accurate diagnosis and treatment planning; - systemic and local conditions which are compatible with im- plant placement and sinus floor elevation procedures; - residual bone height (i.e. the di- stance from the bone crest to the sinus floor) of at least 4 mm. The Smart Lift technique must not be performed when systemic and lo- cal conditions which contraindicate sinus floor elevation are present21, 22 . Surgical Technique According to the prosthetic tre- atment planning, the location for implant placement is established, and the residual bone height at such locations is first diagnosed by pro- per x-ray examination. The distan- ce from the bone crest to the sinus floor as assessed radiographically will provide the “radiographic wor- king length”. Surgical stents may be recommended for implant positio- ning, particularly when multiple implants have to be inserted. All instruments in the surgical set* are characterized by laser marks at 4-5-6-7-8-9-10-11 mm to allow for a precise control of the working length. The first drill, (Locator Drill) is designed to perforate the cor- tical bone to a depth of 3.5 mm at the site where the implant is to be placed (Fig. 1.b). A second drill (Pro- be Drill), with a diameter of 1.2 mm and cutting only at the top edge, is used to define the position and orientation of the implant. In order to minimize the risk of sinus floor perforation, this bur is used with an adjustable stop device which is set at least 1 mm shorter than the “ra- diographic working length” (Fig. 1.c). Then, the “Probe Osteotome” (Ø 1.2 mm) is carefully inserted into the site prepared by the Probe Drill, and gently forced in an apical direction through the cancellous bone until the cortical bone resistance of the sinus floor is met. Therefore, the Probe Osteotome will provide the “surgical working length”, which is the true anatomical distance from the bone crest to the sinus floor in the exact location where the im- plant should be placed (Fig. 1.d). Thus, the working action of all ma- nual and rotating instruments that will be used in subsequent surgical steps will be now set at the “surgical working length” by using the proper adjustable stop device. A Radiographic Pin (Ø 1.2 mm) can also be used to check the angula- tion and depth of the prepared site by means of a periapical x-ray (Fig. 1.e). The Radiographic Pin handle has a diameter of 4.0 mm, thus permitting to evaluate the spatial relationship between the prepared site and the bucco-lingual as well as mesio-distal dimensions of the alveolar ridge. This will help the cli- nicians to determine the diameter of the implant to be placed. Then, a “Guide Drill” of Ø 3.2 mm (implants Ø: 3.75 ÷ 4.5 mm) or Ø 4.0 mm (im- plants Ø: 4.8 ÷ 5.0 mm) can be used. This drill follows the Ø 1.2 mm site preparation and creates a crestal countersink, 2 mm deep, where the trephine bur (Smart Lift Drill) will be inserted (Fig. 1.f). Such countersink enables the trephine bur to centre the working action of the bur accor- ding to the desired direction. The “Smart Lift Drill” (Ø 3.2 or 4.0), set at the surgical working length, produ- ces a bone core up to the sinus floor (Fig. 1.g). Following the removal of the trephine bur, the bone core (Fig. 1.h) is then condensed and malleted to fracture the sinus floor by means of a calibrated osteotome (Smart Lift Elevator, Ø 3.2 or Ø 4.0) that corresponds to the diameter of the trephine preparation (Fig. 1.i, l). If the alveolar bone core is found to be inside the trephine, the bone core is gently removed from the trephine and replaced in the alveolar bone preparation. The osteotome is used under gently malleting forces to im- plode the trephined bone core over the sinus floor. <> pagina 26 Fig. 2.b - The pre-operatory periapical radiograph showed a residual bone height (i.e. radiographic working length) of 6.5 mm at location of the second upper premolar.