Detailed patient assessment, diagnostic wax up of the anticipated restoration in relation to the edentulous ridge, and CBCT with radiographic templates improves the assessment of edentulous site and are essential for treatment planning [12,13]. Recently, 3-D printing has become commercially available and the CBCT DICOM can be converted to a stereolithographic file which can then be used to construct a three dimensional true size cranial model [14]. Clinicians can familiarize themselves with a patient’s edentulous ridges and rehearse the planned procedure (Figure 1). Minimally invasive implant surgery is gaining popularity. The essence of minimally invasive procedures should not be one that sacrifices visibility for the perceived simplicity of surgery; but a procedure that encompasses an efficient and meticulous surgery with minimum intra-operative complication based on thorough pre-operative assessment and planning, which in turn leads to faster healing.

However, clinicians often do not have direct visualization of the defect topography or the anatomical landmark; resulting in risks of implant mal position, undetected fenestration, dehiscence, damages to vital structures or perforation of the Schneiderian membrane [15]. Accurate pre-operative assessment allows the planned procedure to be minimally invasive through avoidance of unexpected clinical findings, and reduction in surgical time, thereby improves patient comfort, and minimizes post-operative morbidity and complication.

Achieving an aesthetic restoration with harmonious hard and soft tissue topography in the anterior maxilla is not an easy task (Figure 2A-2C) [16]. A variety of different procedures for hard tissue augmentation have been described, like guided bone regeneration, onlay block bone graft, ridge split or ridge expansion technique and distraction osteogenesis [17]. However dehiscence, shortening or loss of the inter dental papillae remains a frequent post-surgical finding. Buser D and colleagues have illustrated maintenance of bone level and stable mid-buccal soft tissues using simultaneous implant placement with guided bone regeneration (GBR) in a 6-year follow up study [18].However, the inter dental papillae often appeared blunted following the GBR procedure. Cosyn J and colleagues showed that immediate implant treatment have better aesthetic outcomes than simultaneous implant placement with GBR, and staged implant treatment in grafted bone. Incomplete papilla fill were often associated with the latter two groups. The authors attributed this finding to the number of surgical interventions and repeated papilla elevation [19].

The vascularity of the papilla is supplied by the vascular anastomoses crossing the alveolar ridge [20]. The recurring disruption to the vascular supply through flap elevation can lead to scar tissue formation as a result of fibroblasts becoming prematurely activated and forming excess fibrotic scar tissue. A favorable soft tissue architecture and volume prior to large augmentation procedures is also important so that primary wound closure can be achieved. The soft tissue graft creates an advantageous blood supply bed for the boneaugmentation procedure resulting in higher predictability and setting a solid foundation for future implant success and an esthetically pleasing outcome [21].

Implant restorations in the posterior maxilla need to sustain functional loading. Improvements in implant surface technology have drastically improved the survival rate of dental implants in the posterior maxilla, which has inherently poorer bone quality [22]. The challenges associated with insufficient vertical bone volume are addressed with maxillary sinus augmentation, and non-inductive materials with slow resorption have been shown to be more superior in forming and maintaining bone than inductive materials [23,24].

Sinus augmentation can be performed directly through a lateral window or indirectly with a transcrestal approach [25]. The lateral window approach allows direct access and visualization of the sinus cavity for Schneiderian membrane elevation. While the direct technique has evolved into a predictable surgical modality, concerns over its technique-sensitivity and potential intra and post-operative complications have led to the introduction of the transcrestal osteotome technique for sinus augmentation [26]. It was presented as a less invasive and less time-consuming technique with a lower rate of post-operative complications [27]. However, the osteotome technique is a blind technique. The lack of visibility coupled with limited access during manipulation of the membrane can lead to perforation of the sinus membrane when using the twist drill or osteotomes. Moreover, the bone graft substitutes are blindly packed beneath the membrane, which increases the risk of membrane perforation. Despite the claim of minimum invasiveness, a systemic reviewed showed membrane perforation remains the most frequently reported complication, observed in 0% to 27% of indirect sinus floor elevation procedures [28]. The limited control over the operating site also reduces the volume of bone augmentation compared to that obtained with the lateral window technique. Furthermore, the trauma induced by percussion with the surgical hammer, along with hyperextension of the neck during the osteotome technique can lead to displacement of otoliths in the ears resulting in the appearance of benign paroxysmal positional vertigo and discomfort which can be a concern especially in the older population [29]. A case of early implant failure is shown in (Figure 3A-3C), where microfractures of the peri implant interfaces was likely the cause [30].

The osteotome technique may however improve initial implant primary stability on the premise that, condensing the cancellous bone of the maxillary alveolar process can increase the bone density.

Sinus augmentation has been demonstrated to be a reliable treatment modality for gaining vertical bone volume for implant placement in the posterior maxilla. The predictability of the sinus augmentation and implant placement procedure relies more on host factors, such as the health status of the sinus, size and location of the endosseous anastomosis, lateral wall and Schneiderian membrane thickness, and residual bone height, than the biomaterials used or techniques chosen [31,32]. Thorough pre-surgical assessment remains the key for success.

The absence of vital structures coupled with the frequently encountered type II/III bone quality makes the anterior region of the mandible suitable for implant placement [3]. Nevertheless, the thinning of the coronal region of the alveolar ridge is a common finding. Reduction of the ridge height until adequate bone width is obtained for subsequent apical implant placement may be a nongrafting option, but it is associated with increased crown length, which can compromise aesthetics and access for hygiene. Alternatively, GBR or ridge splitting has been shown to be predictable methods for increasing horizontal bone volume in the anterior mandible [7,8].

Insufficient mesial-distal distance is another concern for single mandibular incisor replacement. This problem can be addressed by the subcrestal placement of a platform switching implant, which has been shown to maintain bone level with 1 mm clearance from adjacent teeth, narrow diameter implants can also be used in such situations (Figures 4A and 4B) [33-35]. In addition, patients often present with more than one missing lower incisor. However, the reduced functional load and improved mechanical properties of the titanium alloy implants enable the use of long span bridges or cantilever restorations in the anterior mandible region [36].

The atrophic posterior mandible is often associated with high components of cortical bone, reduced vascular supply, superficial muscle attachment and lack of keratinized gingiva, moreover posterior mandible is subject to increased masticatory forces [5]. All these factors can complicate ridge augmentation procedures.

Distraction osseogenesis, autogenous onlay graft, and guided bone regeneration have been used to augment these defects with limited degrees of success and predictability, with vertical ridge augmentation remaining the most challenging and least predictable procedure [37-40]. An alternative to grafting bone coronally is to place the implants lateral to the inferior alveolar canal to engage the native residual bone (Figures 5A-5O) [41-44]. This maximizes the chances for successful osseointegration. This is possible because the inferior alveolar canal is closer to the lingual cortical bone, which usually leaves more available bone buccal to the canal for implant placement. However, the risk of violation of the neurovascular bundle remains a concern with implants placed lateral to the canal and careful execution of the planned implant position is needed.

The risks, biological complications, cost and prolonged treatment time associated with bone augmentation procedures have led to the increased popularity of short implants. However, implants with length ≤8 mm should be used with caution in the posterior jaw because their survival rates are reduced significantly when compared to standard implants >8 mm [45,46]. It is postulated that these unfavorable results occur from overload as shorter implants have less surface area in contact with the osseointegrated bone to dissipate the occlusal forces. More long term studies are needed to ascertain the validity of short implants in the posterior mandible.