The cause of most endodontic failures is leakage. This leakage can be from the root canal system to the periodontium
through the apical foraminas or through lateral canals. A lateroradicular lesion may or may not communicate to the cervical periodontium, but with no relation to the periapical region.
Lateroradicular microsurgery should be done when a lateroradicular lesion remains active after the tooth has been retreated, or when coronal access to the root is not possible. If this lateral canal has difficult surgical access, excessive bone removal must be avoided, and other options, like intentional replantation, should be considered.
The necessary armamentarium is the same as for periapical microsurgery, except that there is no fissure bur for apicoectomy.
Presurgical Bone Defect Evaluation
Finding the spatial location of the lateral canal in relation to the root (x, y, z) is the first step. If a fistula is present, inserting a guttapercha cone can give information of the point of origin (x). In the past, everything relied on standard radiographs. A radiograph provided a two-dimensional view, giving some information about the size of the lesion (x, y). Today, cone-beam computed tomography (CBCT) exploration provides a three-dimensional view of the lesion (x, y, z) and can in addition detect the presence of an apicomarginal bone defect. CBCT has become a useful tool for an accurate presurgical evaluation of the bone defect in order to plan ahead which technique and materials should be used.
In the evaluation of cervical bone using periodontal probing the location of an isolated deep periodontal probing defect is essential. These isolated pockets, called "tunnel probing" defects, provide clinical information regarding bone dehiscence and origin. If probing goes up to the lateral canal, then there is a lateromarginal bone defect (LMBD); if it goes up to the apex, then an apicomarginal bone defect (AMBD) will be present.
When facing these types of bone defect, the flap design (and especially the vertical releasing incisions) should be made further away than normal because more space under the soft tissues will be required at the end, in order to cover, without tension, the bone graft and membrane underneath.
Raising the flap together with an intact periosteum is an important issue, and it must be done with extreme care just in case there is some remaining small bone bridge underneath.
After retrocavity preparation and obturation of the exiting point of the lateral canal, if an LMBD, a guided bone regeneration (GBR) technique should be used.
If the flap is so small as to prevent the taking of bone graft chips from the neighboring area, then deproteinized bovine bone graft can be used as a space-maker underneath the membrane.
A fixed non-resorbable or a non-fixed resorbable membrane should cover 3 mm beyond the bone defect boundaries. A resorbable membrane should be used for a soft tissue perforation or a damaged flap edge, and when membrane early exposure is expected.