2019 Volume 32 Issue 2 Pages 116-125
Dental implant rehabilitation is an established treatment for edentulous patients. Recently, treatment procedures have changed from the original protocols, towards a shorter treatment time. The achievement of greater primary stability, which is one of the prerequisites for osseointegration, is demanded in clinical situations, since there is a trend to load the implant immediately or in the early stages after implant placement. With this aim, several modifications have been introduced, such as more aggressive implant design, modified surfaces, and novel surgical techniques. Undersized drilling osteotomy is one of the most commonly adopted procedures for implant surgery. This technique creates an osteotomy that is substantially smaller than the implant diameter, so that a tight interfacial contact and compression are created. This is perceived by the surgeon with an increase of the insertion torque value (ITV).
Albeit commonly performed in clinical situations, several aspects of undersized drilling are still not well investigated. It was hypothesized that large compression at implant placement would cause tissue damage and may trigger a negative bone response during the healing time. This could lead to impaired bone material properties, decreased stability, marginal bone loss, and in the worst case, implant loss. The aim of our research was to gain a more consistent understanding of the effects of an undersized drilling osteotomy.
Our studies suggested that undersized drilling osteotomy can cause negative effects in cortical bone. The literature indicated that the undersized drilling technique is effective for increasing the ITV in low-density bone. However, ITV is mostly influenced by bone quality rather than drilling protocol. Furthermore, high ITV can induce greater bone resorption in dense bone. On the other hand, cortical bone has the capability to maintain high levels of rotational stability at undersized sites in the early healing period, despite the great amount of micro-damage. From a biological point of view, this procedure causes a reduced apposition of newly formed bone at the implant surface and initiates an intense bone resorption activity in the surrounding tissue. This creates a temporary porosity into cortical bone, reducing the volume of peri-implant mineralized tissue. Intra-cortical resorption cavities caused an impairment of material properties and compromised mechanical behavior. The model with bone resorption cavities was more prone to micro-damage and delayed healing process. Therefore, it is recommended to avoid the early loading protocol. Further studies are needed to establish the protocol for immediate and early loading with undersized drilling osteotomy.
