*3.6. Mesh Exposure*

Except for Corinaldesi et al. [21] all the included studies evaluated the mesh exposure (N = 404), and it proved to be a highly prevalent complication, appearing in 115 cases out of 404 meshes (28%) (range 0% to 80%). Of these 115 exposed meshes, 25 were removed due to more severe complications, and 75 were stabilized and controlled through local hygiene measures.

According to the studies in which the implant was placed simultaneously [18,23,30,33,34] the mesh exposure rate was 14% (13 out of 87). In contrast, in the cases of guide bone regeneration (GBR) and delayed implant placement [17,19,21–25,27,29,31,32,37] the mean mesh exposure rate was 30% (58 out of 187).

## *3.7. Implant Placement*

Apart from performing the alveolar ridge augmentation, there were 16 studies in which dental implants were placed [18,19,21–25,27,29–34,37] (Table 4). The other five studies focused on the bone regeneration process without involving implant placement. The outcomes were studied and summarized in Table 5.

In total, 709 implants were placed and the total prevalence of implant failure in this review was 0.5% (4 implants were lost). The follow-up time after the implant placement was on average of 32 months (range 6 to 96).

In five studies, bone augmentation was performed simultaneously with implant placement (N = 145) [18,23,30,33,34], in the other studies, the implant placement was delayed after 7,1 months on average (N = 564) (range 3 to 10 months) [17,19,21–25,27,29,31,32,37].

The implant success rate was assessed considering at least 6 months from the prosthetic load. The survival rate of 145 simultaneous implants was 99.5%; the survival rate of 507 delayed implants was 99%. The success rate of 105 simultaneous implants was 97%; the success rate of 285 delayed implants was 95.1%. Proussaefs et al. [19] did not specify the survival and success rates and Corinaldesi et al. [21], Torres et al. [24], Zita et al. [30], and Ciocca et al. [32] did not specify the success rate.

The marginal bone resorption (MBR) was evaluated in 6 studies and it was on average of 0.75 mm [19,22–24,30,31,37] (N = 234). There were no statistically significant differences between de MBR observed in the simultaneous implants and delayed implants.


**Table 5.** Evaluation of characteristics of implant placement.

M: Mesial; D: Distal; MBR: Marginal bone resorption; V: Vertical; H: Horizontal.

#### **4. Discussion**

From the analysis of the recent published articles, few studies concerning GBR using titanium mesh were published. The present systematic review aimed to evaluate the results reported in the literature evaluating the following aspects: (a) the success rate of this technique regarding the quantity of augmented bone; (b) the complications rate by means of exposure; (c) the implants survival and success rate. The topic was focused on the presence of the titanium meshes used as a physical barrier for ridge reconstruction in partial or total edentulism, preventing soft tissue colonization and allowing osteoprogenitor cells to reach the site and form new bone.

#### *4.1. Bone Gain*

The use of non-resorbable titanium meshes allows maintaining the shape between the barrier and the bone defect. Furthermore, the pores allow to maintain vascularization both to the soft tissue and to the bone during the regeneration process and facilitates tissue nutrition [12,38]. Generally, the literature showed that the use of non-resorbable titanium meshes in GBR represent a safe and predictable technique to gain vertical and/or horizontal bone augmentation, in the treatment of small and medium-sized defects around dental implants and prevention of alveolar ridge after tooth extraction [9,20,30,35]. The analysis of the studies included in the present systematic review corroborates this statement, although only six included studies quantified both width and height bone gains [17,19,22,24,31,34]. The histological and histomorphometric analysis also demonstrates the effectiveness of GBR using the titanium mesh, and good capacity of the method to increase bone volume in the distal mandibular atrophies [19,21,31,33]. On the other hand, other authors like Uehara et al. [29] appear more doubtful about the success of this technique. According to their success criteria, only 13 sites were judged as successful with a success rate of 56.6%, emphasizing that, the greatest success rate was obtained at the sites with a shorter span of augmentation.

When comparing the success of this technique with other GBR techniques such as the use of PTFE membranes, results of bone gain did not differ much. Cucchi et al. [39] found that the height bone gain was 4.2 (range 2.7 to 5.8) mm when using PTFE and 4.1 (range 2.6 to 6.3) mm when using a titanium mesh. Sagheb et al. [40], found a height bone gain higher (4.16 and 5.5 mm).


**Table 6.** Incidence of membrane/barrier exposure in different techniques.

#### *4.2. Mesh Exposure*

From the analysis of the complications, the investigation was focused on mesh exposures which was the most usual complication when performing this technique. To prevent premature exposure of the augmented area, all the analysed studies highlighted the necessity to mobilize the flaps to obtain a primary wound closure without tensions. According to the results of this review, the mean rate of mesh exposure was 28%. Other reviews about membrane/mesh exposure were found in the literature (Table 6).

The prevalence of mesh exposure in the cases of GBR and delayed implant placement was higher than when simultaneous implant placement. The reason for this higher incidence might be correlated with "free-end" edentulism and severe vertical ridge resorption, as well as a low number of included cases in the simultaneous placement group.

Some authors propose that to reduce the rate of mesh exposure, consensus protocols are needed, but also more precise customized meshes. Also, the use of resorbable membranes and PRP to prevent the risk of early dehiscence [18,43,44].

Even though the most frequent complication associated with this device is its exposure, according to the results of this review, it is worth noting that this event does not necessarily compromise the final treatment outcome and further complications were avoided using topical application of chlorhexidine gel [19,25].

Comparing to other types of techniques, Garcia et al. [45] found that when GBR is associated with collagen membranes or e-PTFE, the exposure of the membrane may influence bone gain. The sites without exposure achieved 74% more horizontal bone gain than sites with membrane exposure. In all types of GBR, meticulous soft-tissue handling is mandatory to obtain flaps without tension over the membranes, in order that the regenerative tissue can be kept entirely covered. When a titanium mesh is exposed and the grafted bone had been sufficiently stabilized by newly formed bone, the integrity of the hole new bone regeneration can be mostly ensured and avoid superinfection. This is possible due to its pores since they play a crucial role in vascularization of the graft and allows its hygiene [19,23,25].

#### *4.3. Characteristics of the Mesh*

Regarding the thickness of the mesh most currently used is 0.2 mm (range 0.1–0.5 mm), since it provides sufficient rigidity to maintain space and protect the graft [34,37]. According to other authors, a titanium mesh should be sufficiently stiff to be able to resist the muscular tensions and the pressure of the surgical flap, but at the same quite manageable to be adapted to the bone defect [10–12,30,34,37].

The external form should be as round as possible to avoid damaging he flap and the surface as smooth as possible to avoid bacterial colonization or infection [10,12,37]. In most of the articles, the authors specify the devices were polished and rounded before placed, to avoid dehiscence and soft tissue ruptures.
