*2.1.1 Resorbable membranes*

Using resorbable membranes eliminates the second surgical intervention for membrane removal after healing and in this way decreases morbidity. Less complications occur with resorbable membranes compared to the non-resorbable ones. These membranes can easily be manipulated and adapted to the defect since they don't have any reinforcements with high elastic modulus. On the other hand, when compared to non-resorbable membranes they are more prone to collapse which lowers the maintained space. Bone graft substitutes and additional tools like tenting poles can be used along with resorbable membranes to increase stability. One major drawback of these membranes is varied and sometimes unpredictable resorption rates which directly affect new bone formation [13–15].

Resorbable membranes can be classified as natural and synthetic (**Figure 4**).

• *Non-cross-linking resorbable collagen membranes* are made of native collagen, have high levels of biocompability. They well-integrate into tissues and rapidly become vascularized. However, non-cross-linking resorbable membranes may resorp earlier than the required time for regeneration and lose their barrier functions. Cellular activity of host bone, membrane properties and possible exposures affect the biodegradation time. If any exposure occurs within the membrane, soft tissue spontaneously covers the exposed area in most cases. Bone grafts may resorp causing a decrease in the expected bone formation, though [3, 13].

#### **Figure 4.**

*Classification of barrier membranes used in guided bone regeneration procedures.*


## *2.1.2 Non-resorbable membranes*

When a bone defect lacks several supportive adjacent walls, utilized barrier membrane should provide additional strength to maintain space and stay stable during the regeneration process. To ensure stability and structural strength, different materials and compositions are used in production of non-resorbable membranes: titanium mesh, e-PTFE, d-PTFE and titanium reinforced PTFE membranes [3].

• **Expanded polytetrafluoroethylene (e-PTFE)** is the first generation of nonresorbable membranes used for guided bone regeneration. It's mostly preferred when a critical size defect is present and high amount of grafting is needed. Their stiff form makes them less compatible with soft tissues causing high rates of exposure. Once an exposure occurs with these membranes in use, infection develops and due to the porous structure, mechanical or chemical cleaning of infected site is almost impossible whether at early or late stage of healing. Recently, these membranes are rarely used in oral surgical interventions due to the high infection and irreversible complication rates [5, 7, 13].

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*Alveolar Ridge Augmentation Techniques in Implant Dentistry*

d-PTFE membranes 6 months post-operatively [18].

reported different exposure rates up to %50 [3, 17, 19].

Added framework results in higher rates of exposure [3, 20].

**2.2 Bone grafting materials**

*2.2.1 Osteogenesis*

vascular support [5, 13].

*2.2.2 Osteoinduction*

osteoinduction, osteoconduction [3, 5, 8].

• **Dense polytetrafluoroethylene (d-PTFE) membranes** are produced to overcome the disadvantages of e-PTFE membranes. These membranes have smaller pore size that they don't allow microorganism migration while oxygen diffusion is still possible in case of an exposure. With their low infection rates and additional mechanical strength, these micro-porous non-resorbable membranes are found to be effective in guided bone regeneration procedures [3, 13, 17]. Ronda et al. reported a mean defect fill of 5.49 mm in vertically augmented sites using

• **Titanium mesh membranes** are porous titanium plates used in guided bone regeneration. The pores in these membranes are large and do not interfere with blood supply. Ti mesh is highly biocompatible to the surrounding tissues. Infection rates are very low with these membranes. They have a wide range of properties like rigidity, elasticity, stability and plasticity which exceptionally make these membranes adaptable but rigid at the same time. Titanium mesh membranes are commonly used in large bone defects and when a resistance to the pressure of soft tissue is needed to avoid collapse. Main disadvantage of Ti mesh membranes is high exposure rates due to their stiffness, several studies

• **Titanium reinforced PTFE membranes** are modifications of PTFE membranes. There are titanium frameworks embedded in these membranes for additional strength and rigidity therefore they successfully maintain space during the healing period and do not collapse. They are mostly used for vertical bone augmentation where additional resistance to soft tissue collapse is crucial.

Various bone grafts and biomaterials can be used in guided bone regeneration. To choose the right material for predictable results in augmentation procedures, how these materials induce bone healing should be well-known. Healing properties of bone grafts and biomaterials are classified into three categories: osteogenesis,

Osteogenesis is defined as formation of new bone through viable osteoblast cells transferred to the site within grafting material. Autogenous bone grafts are transplanted from one site to another and the only type of grafting material with osteogenic features. Compared to cortical bone grafts, cancellous bone grafts contain higher amounts of osteoblast cells. To maintain the vitality of these cells and the dependent osteogenic process, angiogenesis is critically important. Therefore, once the autogenous bone graft is harvested it should be stored in sterile saline solution and placed in the recipient site as soon as possible. There are studies stating that autogenous bone grafts lose their osteogenic properties in 5 days without

Osteoinduction is a process where grafting material induces mesenchymal stem cells to migrate, proliferate and differentiate into osteoprogenitor cells. With

osteoprogenitor cells occuring in the site, new bone forms [5, 13].

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

*Alveolar Ridge Augmentation Techniques in Implant Dentistry DOI: http://dx.doi.org/10.5772/intechopen.94285*

*Oral and Maxillofacial Surgery*

**Figure 4.**

• *Cross-linked resorbable collagen membranes* are rich in cross-linking collagen fibrils so their degradation time is extended. Increased amount of collagen fibrils result in less biocompatibility and harder manipulation, still studies state good results in tissue integration and bone regeneration using these membranes [13–16].

• *Synthetic resorbable membranes*, mainly consisting of polyesters like polylactic acid or polyglycolic acid copolymers, are produced to achieve extended biodegradation period and increased biocompability. Derived from various origins, these membranes can offer various physical, chemical and mechanical properties. They also differ from natural resorbable membranes in terms of degradation pathways. Tatakis et al. demonstrated that synthetic resorbable membranes degrade via hydrolisis and alteration of degradation products through citric acid cycle causes an acidic enviroment. Therefore, using synthetic resorbable membranes result in higher inflammatory response and

When a bone defect lacks several supportive adjacent walls, utilized barrier membrane should provide additional strength to maintain space and stay stable during the regeneration process. To ensure stability and structural strength, different materials and compositions are used in production of non-resorbable membranes: titanium mesh, e-PTFE, d-PTFE and titanium reinforced PTFE membranes [3].

• **Expanded polytetrafluoroethylene (e-PTFE)** is the first generation of nonresorbable membranes used for guided bone regeneration. It's mostly preferred when a critical size defect is present and high amount of grafting is needed. Their stiff form makes them less compatible with soft tissues causing high rates of exposure. Once an exposure occurs with these membranes in use, infection develops and due to the porous structure, mechanical or chemical cleaning of infected site is almost impossible whether at early or late stage of healing. Recently, these membranes are rarely used in oral surgical interventions due to

the high infection and irreversible complication rates [5, 7, 13].

complications of soft tissue perforation [3, 13].

*Classification of barrier membranes used in guided bone regeneration procedures.*

*2.1.2 Non-resorbable membranes*

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## **2.2 Bone grafting materials**

Various bone grafts and biomaterials can be used in guided bone regeneration. To choose the right material for predictable results in augmentation procedures, how these materials induce bone healing should be well-known. Healing properties of bone grafts and biomaterials are classified into three categories: osteogenesis, osteoinduction, osteoconduction [3, 5, 8].

#### *2.2.1 Osteogenesis*

Osteogenesis is defined as formation of new bone through viable osteoblast cells transferred to the site within grafting material. Autogenous bone grafts are transplanted from one site to another and the only type of grafting material with osteogenic features. Compared to cortical bone grafts, cancellous bone grafts contain higher amounts of osteoblast cells. To maintain the vitality of these cells and the dependent osteogenic process, angiogenesis is critically important. Therefore, once the autogenous bone graft is harvested it should be stored in sterile saline solution and placed in the recipient site as soon as possible. There are studies stating that autogenous bone grafts lose their osteogenic properties in 5 days without vascular support [5, 13].

#### *2.2.2 Osteoinduction*

Osteoinduction is a process where grafting material induces mesenchymal stem cells to migrate, proliferate and differentiate into osteoprogenitor cells. With osteoprogenitor cells occuring in the site, new bone forms [5, 13].

#### *Oral and Maxillofacial Surgery*

Urist et al. performed the landmark study on osteoinductive grafting materials isolating bone morphogenetic protein (BMP), a growth factor from the transforming growth factor (TGF)-β family, and described it as the main inductive agent [5, 21, 22].
