Novel Modifications to the Trephine Core/Osteotome Technique
An innovative alternative for implant site development
Anna M. Brunetti, DMD, MDS | Howard Drew, DMD | Andrew Sullivan, DDS | Joel Pascuzzi, DMD | Emil Cappetta, DMD
Inadequate bone height is often encountered in the posterior maxilla, complicating implant placement. The use of a combined trephine/osteotome technique has been introduced to increase bone height. This technique is less invasive than the lateral window and allows a relatively atraumatic implosion of autogenous bone displacing the floor of the sinus, increasing the amount of alveolar bone at the anticipated fixture site. The authors suggest novel modifications to make the technique more advantageous. Modifications include a two-stage procedure to place longer fixtures, use of the trephine and piezo tips when sinus floors are uneven, and multiple site sinus elevations. The following case presentations illustrate these novel modifications to maximize implant success in the posterior maxilla.
Sinus Augmentation Approaches
Common factors affecting implant success include the quantity and quality of bone, occlusal forces, and the anatomy of the maxillary posterior. Following tooth extraction, the rate of resorption is faster within the first 6 months, affecting the width and height of the ridge and compromising future implant placement.1 According to Lil and colleagues,2 the limiting factor for implant placement in this region is available bone height. According to previous studies, implant failures in the maxillary posterior region are attributed to type IV quality of bone.3-5
An absence of functional loading from tooth loss can result in severe bone resorption as the sinus walls gradually thin because of the increase in size of the maxillary sinus as pneumatization occurs.6 Thus, future implant placement is compromised, necessitating additional surgical procedures. Traditionally, lateral window and internal sinus augmentation procedures have been proposed to facilitate implant placement.7-10
Fugazzotto articulated an alternative approach to sinus augmentation, utilizing a trephine core plus osteotomes.11 When residual bone height was 4 to 5 mm in the posterior maxilla, he found utilization of a trephine created less trauma when compared to traditional internal sinus augmentations. In addition, the technique conserved autogenous bone and minimized the risk of membrane perforation by avoiding a 2-mm twist drill to begin the osteotomy sites.11-13 In his studies, Fugazzotto found 100% success rates in comparison to 97.3% success rate with the lateral approach.14
The trephine core technique can also be utilized to develop sites when simultaneous implant placement is not possible. Maxillary molar extraction sites were found to have a 96% to 97.8% success rate for implants in function for up to 3 years.15-17 In a clinical retrospective study, Kolerman and colleagues showed an 11-year 100% survival rate for implants placed in the maxillary posterior region using this technique.18
The proposed modifications to the trephine core technique allow for implant site development in the posterior maxilla in both single and multiple edentulous sites. Fugazzotto previously demonstrated the technique for immediate implant placement at a maximum length of 8.5 mm.11 The authors have attempted to further develop single and multiple sites to allow for longer length implants. In comparison to 8 mm long implants, implant lengths greater than 10 mm have had a more favorable cumulative success rate (88.9% versus 93.4%)19 with internal sinus lift procedures.
Preoperative radiographic measurements are made to evaluate residual bone height at the site of future implant placement. In edentulous sites, a palatal crestal incision is used. At the time of maxillary molar extractions, a palatal incision around the palatal root is utilized to allow membrane placement. Vertical releasing incisions are made buccally and full-thickness flaps are reflected in conjunction with periosteal releasing incisions to allow flap advancement. A calibrated trephine bur is then used to create a core. The interradicular bone of the maxillary molar usually serves as the core. The trephine core should be a minimum 2 mm less than the bucco-palatal width, ensuring 1 mm of bone on each side. Trephination is approximately 1 mm shy of the sinus membrane. To achieve good contact with the alveolar crest without “skipping of the bur,” the trephine is first used in reverse to engage bone, and then forward to continue cutting.18 Maximum cutting speed is 1200 rpm. Once the trephine core is completed, the lateral walls should be free from adjacent bone, while the core remains intact with the floor of the sinus. A calibrated osteotome is selected, which corresponds to the diameter of the trephine preparation. The osteotome is used with gentle malleting forces to implode the core to a depth of approximately 1 mm less than that of the prepared site. If cone-beam computed tomography confirms a thick schneiderian membrane, the authors have found that you can gently mallet beyond the overlapped area. Once the desired height is achieved, the osteotomy is gently packed with allograft material and covered with a resorbable membrane. In cases where primary closure is not attainable, a non-resorbable dense-PTFE membrane can be utilized.20
Once the membrane is stabilized, mucoperiosteal flaps are replaced and sutured to attempt primary closure. In regards to membrane stability, we have found for small sites, stability can be achieved through a fibrin clot adhesion. In larger sites, tacks can be added for additional stability.
The healing period ranges from 3 to 6 months. At the time of re-entry, implant placement is accomplished either by an additional osteotome internal lift or conventional drilling. A tapered implant design is preferred for increased stability,21 especially in areas where a cortical plate may be thin or missing due to type IV quality bone. The following case reports describe a technique of site development for future implant therapy.