According to the results of this study, no statistically significant differences were found among Groups A, B, and C in any of the factors regarding stability of the implant, complications, amount of marginal bone resorption, and diameter and length of the implant. These findings can be interpreted as excellent CA implant stability regardless of surgical modalities such as bone grafting, simultaneous implant placement with bone grafting, and delayed placement of implants after bone grafting.
Beginning in January 2013, only 7 of the 258 implants failed over an average of 5 years. Among the seven implants, two with initial complications were presumed to be caused by failure of initial osseointegration and combined apex lesions due to root invasion of adjacent teeth. The implants that failed to survive were immediately removed, and after a certain period of bone healing, implants were placed again through the submerged implantation method and have been well maintained without complications until now.
Sussman et al. reported that the prognoses of adjacent teeth and implant failures can be very poor due to traumatic damage to adjacent teeth caused by implant fixtures. He argued that if a patient complains of clinical symptoms due to traumatic damage to the adjacent tooth after implant placement or if periapical pathology is observed, the implant should be removed, and endodontic treatment for the tooth should be performed. In addition, it was argued that in situations where potential endodontic lesions of adjacent teeth might adversely affect implant osseointegration due to apex lesions after surgery, endodontic treatment of adjacent teeth should be performed prior to implant placement [13].
However, Yoon et al. reported that even if the implant fixture damages the roots of adjacent teeth, no harmful symptoms (for example, positive reactions with percussion test, tooth mobility, pulp necrosis) occur. If osseointegration of the implant is achieved, continuous use through follow-up is possible. They explained that no harmful symptoms occurred even when the implant fixture invaded the teeth, and reported that the reason was that it did not damage the cementum of the tooth root and thus did not cause pulpal damage [14]. In addition, Yi et al. reported that even if the surrounding natural teeth were damaged during implant placement, immediate extraction of adjacent teeth is not necessary, and that a conservative approach is sufficient to predict the prognosis of adjacent teeth. Osseointegration success rate and survival rate of the implant were high [15]. Although this study was conducted before digital dental implant technology was widespread, so all implantation was performed using conventional methods, one complication, in which the fixture invaded the adjacent root, is considered a problem that can be avoided if guided implantology and 3D-planning were used.
The remaining 5 of 7 implants that failed to survive all showed delayed complications, with peri-implantitis as the largest cause. As soon as symptoms of peri-implant mucositis or peri-implantitis were observed, peri-implant curettage, chlorhexidine solution irrigation, and minocycline ointment application were performed under local anesthesia as the primary treatment methods. If symptoms were not alleviated, open flap debridement, cleaning using a titanium brush, tetracycline application, and detoxification treatment using laser were performed as a secondary treatment method. If the amount of bone defect was severe, additional bone grafting was performed. Removal and re-implantation of the 5 implants was planned after the symptoms of peri-implantitis continued to worsen after treatment, eventually resulting in mobility of the implant fixture with inflammation. However, of the 8 cases of peri-implantitis, except for 5 of which failed to survive, the complications could be resolved through the above treatment. All prosthetic delayed complications, except peri-implantitis, such as screw loosening, screw fracture, food impaction, and occlusal disorders, were resolved through repair and remanufacture of the prosthesis.
Several studies have demonstrated the effectiveness of chlorhexidine and minocycline as non-surgical supportive treatment in peri-implant mucositis [16, 17]. However, if peri-implantitis develops beyond peri-implant mucositis and bone loss begins to progress, it is recommended to proceed with surgical treatment [18, 19].
Toma et al. reported that, when peri-implantitis occurs, curettage using a plastic curette, a method using an air-abrasive device, and a cleaning method using a titanium brush are very effective for removing inflammation. In addition, it was reported that the use of antibiotic therapy together with these physical methods could lead to more effective results [20]. In particular, John et al. reported that removing plaque using a titanium brush is more efficient than any other method using plastic or metal curettes [21]. In addition, in recent studies, physical methods such as curettage, titanium brushing, and implantoplasty have emerged as effective methods because they do not reduce the biocompatibility between the titanium surface of the implant fixture and osteoblasts [22].
In addition, when the prognosis of the implant is poor due to excessive marginal bone resorption, additional bone grafting around the implant fixture was performed as a reconstructive procedure. Bassi et al. reported that additional bone grafting at the end of long-term peri-implantitis management and treatment increased radiopacity around the implant and was able to effectively fill bone defects [23].
Two implants that did not survive due to osseointegration failure were considered early implant failures, and five implants that failed to survive due to peri-implantitis were considered delayed failures. Early implant failure typically is caused by disruption of the initial healing process due to formation of abnormal tissue between the surface of the implant and the bone due to infection, trauma during surgery, excessive load, or tissue necrosis. Delayed implant failure is attributed to a pathological phenomenon in which the biological equilibrium around the implant is disrupted due to inflammation around the prosthesis and implant fixture due to various factors [24,25,26,27,28,29].
In this study, implants with delayed implantation after a healing period from primary bone graft did not experience failure or showed a small amount of marginal bone resorption. Recently, the immediate implant placement method has received more attention than the delayed method to reduce patient discomfort and maintain soft-tissue morphology. However, in several papers comparing the long-term stability of implants, it has been argued that implants with delayed placement are more stable than immediately placed implants. Haas et al. reported that immediate implant placement was more time-efficient compared to delayed placement and could be a more aesthetic treatment option but did not show the same success rate as delayed placement [30]. In addition, Kunnekel et al. found that osseointegration in delayed implantation occurred much faster than did that of immediate implantation according to resonance frequency analysis [31].