Horizontal Ridge Augmentation in Atrophic Posterior Mandible With Delayed Implant Placement

Clinically, the greatest loss of the alveolar ridge is usually in the horizontal dimension.1 Horizontal bone augmentation is a necessary and indispensable procedure for successful implant placement in a narrow alveolar ridge. A variety of reconstructive approaches have been introduced in order to obtain adequate bone volume prior to implant placement such as guided bone regeneration (GBR),2 ridge split/expansion,3 block grafting,4 tenting pole technique5 and tunneling technique.6

Autogenous block grafting or onlay bone grafts harvested either extraorally from the hip, tibia, clavarium and iliac crest or intraorally from maxillary tuberosity, symphysis of the chin, mandibular ramus and external oblique ridge. All these methods are associated with morbidity of donor sites, resorption of materials, and increased treatment costs. Hence various alternative procedures were developed to minimize this morbidity.3

On the other hand, splitting and expanding the edentulous ridge for bone augmentation and implant placement was considered as an innovative technique as it avoids the need for a second surgical site which further reduces the ailment of the patient.7 Historically bone splitting technique is used to increase the width of bone by splitting and expansion of the existing residual ridge.8 Bone splitting technique was developed by Simion et al.9 and Scipioni et al.8 In the early 1990s. Simion et al.9 aimed at originating a ''self-space making defect'' by separating the buccal cortical bone of narrow alveolar crests in two parts through a longitudinal greenstick fracture to create a gap for dental implants insertion.

GBR has demonstrated a predictable result in lateral augmentation and long-term implant success. To avoid shrinkage resulting from pressure after flap closure, several space-maintenance modalities were used to facilitate formation of reconstructed ridge such as tenting screws,10 titanium (Ti) meshes,11 and Ti-reinforced polytetrafluoroethylene (PTFE) membranes.12

Basically nonresorbable membranes have a high risk of exposure, necessitating removal in the re-entry stage.12 Incontrary, resorbable membranes have shown better biocompatibility and support of underneath bone growth.13 However, their lack of stiffness can lead to decreased bone volume gain. Therefore, the tent-pole technique, which combines resorbable collagen membrane and tenting screws, represents an effective approach, offering easy manipulation and low complication rates. 13

Tenting of mucoperiosteum has shown good potential in the rehabilitation of atrophied alveolar ridges. Expansion of the soft tissue with the use of titanium mini-screws and guided bone regeneration was introduced by Bash Le et al., 2010.10 They evaluated "the use of titanium screws in tenting fashion that was surrounded by particulate human mineralized allograft to reconstruct large mandibular defects before implant placement".

One of the techniques of guided bone regeneration is subperiosteal tunneling, suggested by Kent et al.14 In this technique, two vertical incisions are created in the ridge, and the area between them is totally detached, forming a tunnel. The graft material is positioned, and the area is sutured.15,16This allows the bone graft to be covered by an intact periosteum.17 Because of its minimal invasiveness, this technique has a shorter surgical time and lower postoperative morbidity.18-20

However, subperiosteal tunneling technique is a partially blind procedure that requires patience and delicate surgical maneuvers to develop the subperiosteal flap that could form a pocket for graft materials. Though this bone augmentation does not permit a direct view of the deficient ridge. Meanwhile, it has advantages of less postoperative complications such as less bleeding, discomfort, bone loss, and surgery recovery time. Moreover, augmentation without application of fixation is still controversial.21,22

According to forementioned data, this study will be directed to assess the clinical and radiographic outcomes of tenting pole technique versus modified tunneling technique used for horizontal augmentation of atrophied posterior mandibular ridge associated with delayed implant placement.