**5.1 Lateral window approach**

This technique consists of preparing a window on buccal bone (also lateral wall of maxillary sinus) and elevating sinus membrane through the window. The superoinferior and anteroposterior borders of lateral window is determined depending on the location of maxillary sinus. Inferior border is usually 2 to 5 mm above the sinus floor to prevent any challenges during the infracturing. Once the lateral window is prepared and Schneiderian Membrane is elevated, various grafting materials can be added to the created space [49]. Barrier membranes are oftenly used to cover the bony window afterwards (**Figure 8**). Use of barrier membranes is reported to be more efficient than no membrane use in terms of implant survival rates [50]. In a clinical trial conducted by Garcia-Denche et al., no significant difference was found in lateral window approach with and without the use of membranes, though [51].

Lateral window approach is indicated when residual bone height is below 6 mm. Simultaneous implant placement may be applied when residual height is ≥4 mm. In cases presenting less than 4 mm of bone vertically, delayed implant placement is found to be safer [52]. Before proceeding to the surgery, a thorough medical examination is crucial to avoid possible complications. One of the most common complications in lateral window approach is bleeding during the flap elevation or preparation of lateral window. To avoid bleeding, inferior alveolar artery and posterior superior alveolar artery should be well examined, via radiographic images, in terms of location and possible anastomosis. Presence of septa should also be examined for a well-designed window preparation and for avoiding any membrane

#### **Figure 8.**

*Prepared lateral sinus access window (left) is closed by a resorbable barrier membrane (right) termed as the "open sinus lifting" or the "lateral window sinus lifting" technique.*

perforations. Separate windows can be prepared, if necessary. Healthy Schneiderian Membrane is usually 1 mm thick. Thickness of the sinus membrane should be examined and pathological conditions must be treated before the surgery if present. In the presence of active sinus infection, neoplasmic lesions, uncontrolled diabetes, recurrent chronic sinusitis this technique is contraindicated [5, 49].

The augmented site is very well vascularized through surrounding sinus walls and Schneiderian Membrane, therefore it shows high success rates in terms of bone volume gain. Grafting is possible with various bone graft types. Graftless approach and grafting the site with highly degradable materials like collagen sponges or PRF is also possible but pneumatization of maxillary sinus and the required period for bone regeneration should be considered well enough before these approaches, since it's possible for membrane to collapse and decrease the bone gain [2, 49, 53].

#### **5.2 Transalveolar approach**

Comparing to lateral window approach, this technique is considered to be less invasive. It's indicated in cases with ≥6 mm residual bone height. In a retrospective clinical study by Rosen et al., implant survival rates were found to be higher where residual bone height is greater than 4 mm. This rate, which is 96% when the residual bone height is over 4 mm, decreases to 85.7% in the presence of bone height less than 4 mm [54]. In this approach, a pilot implant slot is created with a drill narrower than the final diameter of the implant. The pilot implant slot is prepared to a depth 1–2 mm from the sinus floor. Different osteotomes of increasing diameters and lengths are used to prepare the slot. It's recommended that the final osteotome has a diameter 0.5 mm less than the planned implant diameter. After the final osteotomy, dental implant is placed in the slot [49]. A group of researchers modified the technique by introducing bone grafts to osteotomy site before implant placement. This modification aims to increase bone amount between the implant and the sinus floor. However, Si et al. reported similar implant survival rates and no significant difference between grafted sites and nongrafted sites [55].

There are various modifications of membrane elevation in transalveolar approach: antral membrane baloon elevation, hydraulic sinus lift, hydrodynamic ultrasonic cavitation sinus lift, trephine core sinus lift and osseodensification.

Transalveolar approach is minimal invasive. Graft and membrane use is not compulsory with this technique and simultaneous implant placement is possible in eligible cases. On the contrary, full visualization of the surgical site is not possible

#### **Figure 9.**

*Transcreastal osteotome technique used for the "closed sinus lifting" procedure. A bone graft was placed at the tip of the osteotome instrument for the prevention of the sinus membrane.*

**157**

**7. Conclusions**

*Alveolar Ridge Augmentation Techniques in Implant Dentistry*

maintained well enough and intra-operatively (**Figure 9**), [46].

therefore possible complications, such as membrane perforations, may not be

Distraction osteogenesis is based on creating two bone segments by controlled osteotomies and gradually separating the segments to induce bone regeneration mechanism in between. In the surgical procedure, after full-thickness flap elevation and proper visualization of the site, fixation plates are temporarily adapted to the cortical bone. In this way, borders of osteotomy is determined. Following osteotomies, the distractor is fixed in the final position. Mobility of the transport segment is checked, then the device is put to initial passive position. Post-operative activation period is divided into three phases: latency, distraction, consolidation [2, 46, 56].

*Latency:* This protocol takes 5 to 7 days for a proper soft tissue healing. Distractor

*Distraction:* Following latency, the distraction is activated by turning activation key at a rate of 0.5–1 mm per day. Transport segment is distracted from native bone vertically. Duration of distraction period depends on amount of bone needed. *Consolidation:* Once the distraction is finalized, maturation of newly formed bone between the segments is expected for 8–12 weeks. Then the device is removed

There is no need for additional bone grafts and membranes with this technique. Gradual distraction helps soft tissue increase along with bone regeneration. There is minimal infection risk and resorption levels are low in the newly formed bone. In sites regenerated with distraction osteogenesis, implant survival rates are comparable with other techniques. Alveolar ridge is regenerated by it's own osteogenic and regenerative potential, therefore autogenous bone transplant is not needed in distraction osteogenesis. Functional and esthetic discomfort of distraction device in oral cavity remains as one of the disadvantages, though. A wide range of complications with a high incidence up to %76 is reported with distraction osteogenesis [2, 46, 58]. Chiapasco et al. stated 'change of distraction vector' as the most frequent complication. Premature consolidation, insufficient distraction, resorption of transport segment and fractures of native bone, the transport segment or the device

This chapter reviewed various alveolar ridge augmentation techniques in implant dentistry in general aspect. Alveolar ridge augmentation procedures are advanced surgical interventions. Success of these interventions depend on many

is not activated during this period to reduce the risk of wound dehiscence.

Distraction osteogenesis can provide a bone gain of 5–15 mm vertically. Therefore it's safely indicated in vertical bone atrophies up to 15 mm [46]. In two clinical studies comparing autogenous bone block grafting and alveolar distraction osteogenesis (ADO), Bianchi et al. reported more bone gain in ADO group where Chiapasco et al. controversially reported no significant differences between the outcomes [56]. The procedure's contraindicated in cases presenting a thin knife-edge crest and insufficient bone amount to allow adequate anchorage. Patient co-operation during the distraction period is critical, treatment procedure should be thoroughly discussed with the patient before the initiation [46]. It is also a technique-sensitive procedure, therefore it is recommended for experienced

*DOI: http://dx.doi.org/10.5772/intechopen.94285*

**6. Distraction osteogenesis**

and implants are placed [2, 46].

surgeons to practice [57].

is among the possible complications [59].

therefore possible complications, such as membrane perforations, may not be maintained well enough and intra-operatively (**Figure 9**), [46].
