AIM: To compare the stability of a non-cylindrical implant using piezoelectric drilling (Piezoimplant) with a cylindrical implant with conventional drilling (Nobel Biocare™). MATERIALS AND METHODS: Three adult female Gottingen miniature pigs were used for the surgical implantation. Three implants on each quadrant, randomized split-mouth design using cylindrical or non-cylindrical implants (n=36). Osteotomies were prepared using either conventional drilling technique as per manufacturer’s instruction (Nobel Biocare™) or using piezoelectric drilling (Piezotome® (P2) (Satelec Acteon, Merignac, France) with new implant prototype tips (Fraunhofer Center for Manufacturing Innovation). The minipigs were sacrificed at 4, 8 and 12-weeks. Stability tests (three per implant) using wireless Periotest® “M” were done at the start point and after euthanization. RESULTS: R-square (ANOVA) test was plotted comparing implant design, weeks 4, 8 and 12, and location (mandible and maxilla) for stability analysis. In this model, the R-square is only 0.51, which indicates only 51% of the response variability can be explained by the fitted model. Among all the 3 factors, group (experiment vs control) is the most significant one, followed by week. Location significance is the least among the three factors. CONCLUSION: In mandibular and maxillary sites in minipigs where non-cylindrical prototype implants (piezoimplant) were inserted by piezoelectric site preparation, statistically significant differences were found between control and test group stability measurements, but no differences in week (4, 8 or 12) and location among the two groups (mandible and maxilla). Stability was like the cylindrical implants. Meaning that Piezoimplants could be an alternative for narrow residual ridges. / 2020-03-14T00:00:00Z

BACKGROUND: The piezoelectric knife was developed for atraumatic bone surgery utilizing ultrasonic vibrations as an alternative to mechanical instruments in conventional oral surgery. Recently it has been used in surgically facilitated orthodontics with Piezocision™. This technique requires alveolar decortication with the piezoelectric knife that cuts through the cortical bone to reach the medullary space. We hypothesized that Its clinical effectiveness is “depth dependent” hence the need to reach the medullary bone and not rely on a “superficial scratch”. This study tested the hypothesis that the extent of the regional acceleratory phenomenon (RAP) following bone injury is depth dependent by comparing superficial and deep corticotomies on the rat tibia. MATERIAL & METHOD: Twenty-six, 9-10 week male Sprague-Dawley rats, weighing approximately 300g, were used in this study approved by the Boston University Medical Center Institutional Animal Care and Use Committee. The piezoelectric knife (Piezotome 2, Acteon, BSL1 insert) with a fixed D 1 power setting and a 30Hz modulation frequency was used to create a decortication on the tibia of the animal. This procedure was carried out with a 1mm penetration depth on the right tibia (deep corticotomy reaching the medullary space) and 0.5mm penetration depth on the left tibia (shallow corticotomy not reaching the medullary space). Tissue response was analyzed at day 1, 3, 7, 14, and 28 using Hematoxylin/Eosin, Masson trichrome, TRAP and picro sirus red stains. Untreated rats were used as controls. The samples were fixed in 4% formaldehyde and the location of the surgical defect underneath the soft tissue was confirmed using Computed Tomography (CT). RESULTS: The CT image analysis was used to cut the samples with extreme precision in the sagittal plane and prepare the tissues for histological analysis. Hematoxylin & Eosin staining highlighted the following sequence of events: 1) establishment of a fibrin clot and granulation tissue (activation phase) 2) increased osteoclastic activity at the site of decortication (resorption phase) 3) increased osteogenic activity (formation phase). Deep corticotomy sites showed extensive morphological changes for both soft and hard tissues. They were characterized by significant osteoclastic activity at day 7 and intense angiogenesis visible both at the entry and exit of the surgical wound. In contrast, the shallow sites showed none of these findings. The new bone that formed at the deep corticotomy site in the medullary space resorbed by at day 14, while the new that bone formed below the periosteum persisted at day 28. None of these phenomena were observed at the shallow sites, where repair had occurred at day 14 or earlier showing minimal RAP activity. CONCLUSION: The extent of the RAP following bone injury is depth dependent. The deep corticotomy sites showed more dramatic biological responses than the shallow osteotomy sites.

Corticotomies have been used to assist orthodontic treatment since the late 18th century. This review describes and compares different surgical techniques available to accelerate tooth movement: PAOO™, Corticision, Piezocision™ and Propel. All of the approaches described accelerate orthodontic tooth movement and may protect against root resorption. PAOO™ and Piezocision™ offer the option of bone and soft tissue grafting at time of surgery. Corticision, Piezocision™ and Propel are considered minimally invasive procedures thanks to the flapless approach, but the use of the mallet in Corticision could constitute a trauma for the patient. The piezoelectric knife creates a more intense Regional Accelleratory Phenomenon (RAP) at the site of injury due to the effect of high frequency vibrations. This suggests that Piezocision™ could create a greater effect on bone remodeling, hence producing faster tooth movement and extended RAP. The lack of randomized controlled clinical trials makes an effective comparison between these techniques difficult and future studies are needed to better evaluate the outcomes of each of these.

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