Bone Defect Classification
Rud et al classified, clinically and radiologically, the healing patterns after endodontic surgery as complete, incomplete or scar, uncertain or unsatisfactory, and failure. They found that "apical marginal periodontitis" is one of the main reasons for failure, and incomplete bone healing was a standard result of the through-and-through osseous defect, due to ingrowth of connective tissue into the bone defect.
It has been reported that, when the apex of the root is totally surrounded by bone, the success rate is higher than when there is a lack of one cortical bone plate (success rate decreases down to 37%) or two cortical bone plates (down to 25%).
Hirsh et al found an association between the size of the former bone defect and the likelihood of full bone regeneration: the longer the bone defect, the less likely total bone regeneration will be, and lesion over a critical size defect (CSD) never heal completely.
Skoglund and Persson5 found that of all surgery performed on teeth with mesial and/or distal bone loss support, fewer than 50% were regarded as uncertain or failure. They also added that "it seems logical that a combined endodontic and periodontic treatment should be carried out when one is performing endodontic surgery on teeth with apicomarginal bone defects
As was said above, not all bone defects have the same size and location. A simple classification of the topography of bone defects that can preclude worsening the prognosis of a well-performed endodontic surgery are as follows.
Large Bone Defects
Large bone defects (LBDs) can cause periosteum collapse over the root surface; or, if they are close to the bone crest, invagination of the dentogingival junction in monoradicular teeth or into furca area in multiradicular teeth.
A through-and-through bone defect (TTBD) is normally produced by the pulp necrosis of maxillary lateral incisors; or when a maxillary molar root lesion perforates both the corticals to the sinus and the buccal bone plate.
Apicomarginal Bone Defects
An apicomarginal bone defect (AMBD) is a mix of two communicating bone defects: a periapical bone defect plus a total root dehiscence. Its prognosis depends on:
- the crown/root ratio
- the width of the dehiscence at the bone crest
- the thickness of the proximal bone margins
Although the diagnosis of apicomarginal defect can be easily made after reflection of the mucoperiapical flap, clinical and radiographic data obtained beforehand7 can advance us to this point and allow the patient to be informed about the special surgery, increased budget and longer surgery time. Regardless, a succesful treatment outcome depends more on the control of the epithelial downgrowth proliferation at the crestal level than on the management of the periapical defect.
Sometimes, there is a combination of two defects. A case study with TTBD and AMBD is presented later in the chapter as an example.