In a constantly aging society, the need for maxillary implant rehabilitation is increasing. In fact, the regeneration of the physiological function of the dento-maxillary system is crucial for improvement in life quality.

Concomitantly, especially in elderly people, dental rehabilitation has a considerable effect on the overall morbidity and a resultant socioeconomic impact (Weyant et al. 2004). A successful implant therapy in senior citizens is directly linked with improved overall health and decreased health-care costs (Vogel et al. 2013). Thus, rehabilitation of edentulous patients with oral implants has become a routine treatment modality in the last decades, with reliable long-term results.

However, implant placement may become a challenging procedure in the presence of unfavorable local condition of the alveolar ridge. This problem is especially magnified in the posterior maxilla, where progressive ridge resorption in an apical direction is combined to the progressive sinus pneumatization (Garg 1999) as a consequence of intrasinus positive pressure (Smiler et al. 1992). Moreover, poor bone quality is also often encountered. Following tooth extraction, an initial bucco-palatal reduction of bone volume occurs because of the interruption of blood supply to the bone plate and to the absence of occlusal loads (Cawood and Howell 1991). As a result, the sinus floor is closer to the alveolar ridge. Based on the Cawood and Howell classification of bone loss, the residual bone crest may be classified in gradations of I (dentate) to VI (paper thin) (Cawood and Howell 1988).

The resulting alveolar bone atrophy may affect the ability to place implants of adequate size and length. Accordingly, decision-making challenge vastly depends on valid clinical evidence to assess the most favorable treatment modalities. Thus, several attempts have been made in the past years to develop new surgical procedures for the augmentation of the resorbed posterior maxilla to be convenient support for long-term predicable implants. Maxillary sinus floor elevation (SFE) procedure is nowadays the most frequently used bone augmentation technique prior to implant placement, in more of half of the cases (Seong et al. 2013).

Conventional lateral SFE has been developed over three decades ago, initially developed by Tatum (1986a) at the end of the 1970s (1977), and was first published in a clinical study in 1980 by Boyne and James (Boyne and James 1980).

Since, numerous successful techniques have been described to restore maxillary bone height (Smiler 1997). The 1996 Sinus Consensus Conference stated that SFE is a highly predictable and effective therapeutic modality (Jensen et al. 1998). Most publications feature a lateral approach to the sinus cavity. According to the “original technique,” a horizontal incision is made in the mucosa at the top of the alveolar crest or slightly palatally to raise a full-thickness flap that is deflected to expose the lateral antral wall of the maxillary sinus where an antrostomy is performed (modification of the Caldwell-Luc technique); access to the maxillary sinus is obtained by drilling a bone window in the lateral sinus wall using round burs, while ensuring that the Schneiderian membrane remains intact. The sinus membrane is then carefully elevated using sinus curettes, mobilized together with the attached bone window, and rotated medially. While rotary instruments are still used for window preparation, the recent development of piezoelectric ultrasonic devices may contribute to reduce intraoperative complications such as membrane perforation (Wallace et al. 2007).

Three variations of the basic SFE were described by Smiler (1997): the hinge osteotomy, the elevated osteotomy, and the complete osteotomy.

After a careful elevation of the sinus membrane from the walls of the sinus cavity, the resulting created space is ready for bone augmentation. The grafting material is steadily inserted in the cavity and subsequently the deflected gingival flap closes the sinus window. Several approaches involve classifications and treatments of membrane tearing as well as adaptations to the closure of the sinus (Vlassis and Fugazzotto 1999; Ardekian et al. 2006). Following SFE, a bone graft maturation time is required (from 5 to 10 months) depending on the grafting material.

Nowadays, the lateral SFE presents a clinically successful technique that offers good insight into the sinus cavity and leads to subsequent modifications in bone height (Chiapasco and Ronchi 1994). However, these advantages involve a secondary surgery site when placing dental implants and thus hold several drawbacks such as the potential for infections (Schwartz-Arad et al. 2004), particularly in smokers (Barone et al. 2006).

To address these drawbacks, Summers (1994a) described a modification of the original SFE technique, which is a codified transalveolar (crestal) approach, namely, the osteotome sinus floor elevation (OSFE), which was a called “new method” of placing implants into the maxillary bone without drilling. In this technique, the use of the tapered osteotomes with increasing diameter aims to preserve the residual bone tissue instead of loosing it while drilling through a conventional procedure. Moreover, they improve bone density around the implant in case of low bone density, which is often the case in the posterior maxilla. The author (Summers 1994a) concluded that the osteotome technique is superior to drilling for many applications in soft maxillary bone, capable to expand the bone.

The basic procedure involves a crestal incision at the planned implant site and a full-thickness flap that is prepared to expose the alveolar crest. After a preoperative careful measurement of the subsinus residual bone height, the initial osteotomy could be either created manually with osteotomes or by the use of a drill. The subsequent osteotomes are inserted into the implant socket by hand pressure or gentle malleting until the residual bone height (RBH) beneath the maxillary sinus floor is limited to about 2 mm. Then, osteotomes of increasing diameters are placed sequentially until the planned implant diameter is reached. Tapping on the last osteotome results in a greenstick fracture of the sinus floor and lifts the Schneiderian membrane without violating it. Finally, an implant is placed in the prepared site.

In fact, osteotome-mediated transcrestal SFE approach was first proposed by Tatum in the late 1970s who used at that time a crestal approach. His results using this transalveolar technique for SFE with simultaneous placement of implants were later published in 1986 (Tatum 1986).

In his original publication, a special instrument known as “socket former” was used to prepare the implant site leading to a controlled “greenstick fracture” of the sinus floor, moving it in a more apical direction. Root-formed implants were then simultaneously placed and allowed to heal in a submerged manner.

At the time, the author did not use any grafting material to increase and maintain the volume of the elevated area.

Later, an enhanced version of the OSFE in which a bone substitute is added to the osteotomy, namely, the “bone-added osteotome SFE” (BAOSFE) (Summers 1994c) was described. The space underneath the elevated floor is filled with particulate graft material via the implant bed to support the elevated membrane.

The author concludes that both the OSFE and the BAOSFE techniques are suitable solutions of altering the sinus floor so that longer implants can be inserted in a less invasive manner.

Later, to minimize the risk of membrane perforation, some clinicians used an inflatable device or fill the void with augmentation material prior fracturing the sinus wall (Stelzle and Benner 2011; Soltan and Smiler 2005).

Nowadays, several modifications of the original SFE technique have been described (Chen and Cha 2005) either through a lateral or a crestal approach. In both procedures, when it is possible, implant insertion is performed simultaneously after the desired augmentation height is reached. Most authors make their decision whether to use a simultaneous or staged approach according to the amount of residual bone height (RBH) (Zitzmann and Schärer 1998; Del Fabbro et al. 2013) essential for the initial implant stability. The consensus for selecting a simultaneous implant placement is applicable with a RBH of at least 4–5 mm. However, recent studies indicated successful one-stage approaches with only 1 mm RBH (Peleg et al. 1998; Winter et al. 2002). Taken together, the osteotome technique may provide lower morbidity and operational time but requires greater RBH.

Nevertheless, in SFE, membrane integrity is a primary condition for and measure of success. Furthermore, despite its predictability, the osteotome “blind” technique is associated with a higher possibility of membrane tearing, limited elevation of the sinus mucosa, and fewer control of the operation field.

Apart from the different surgical approaches providing adequate structure for primary implant stability, several additional parameters such as simultaneously or delayed implant placement, time of unloaded healing as well as the use of grafting materials or membranes significantly affect implant survival. The ideal graft material is described as a substance that will change into regular bone under functional loading without resorption and offers either osteoconductive or osteoinductive properties to promote new bone formation, able to support dental implants (Block and Kent 1997).

A broad variety of different grafting materials have been successfully applied in sinus augmentation, including autogenous bone (AB), allografts, xenografts, and alloplasts. AB has long been considered the “gold standard” for atrophic ridge regeneration because of its unique osteogenic, osteoinductive, and osteoconductive properties (Del Fabbro et al. 2004; Tong et al. 1998). AB can be harvested from various donor sites (i.e., ilium, symphysis, mandibular ramus). In the first publications (Boyne and James 1980), the grafting material was initially AB harvested from the iliac crest. Nevertheless, it was shown that AB is subject to high resorption (Wallace and Froum 2003), with up to 49.5 % of bone loss after 6 months. Additionally, the use of AB usually involves a second surgery site with the potential of donor site morbidity (Block and Kent 1997; Smiler and Holmes 1987).

Therefore, in order to avoid the drawbacks related to the use of AB, the development of alternative bone substitutes with osteoconductive properties can represent a valid alternative to AB, providing a scaffold for bone regeneration thus eliminating the need to harvest AB.

Allografts such as demineralized freeze-dried bone allograft (DFDBA) avoid a second surgical site and exhibit osteoinductive and osteoconductive properties (Block and Kent 1997; Hallman et al. 2005). However, it was stated that DFDBA generates unpredictable bone formation with newly-formed bone of low quality and quantity (Block and Kent 1997). The use of xenografts such as bovine bone mineral (Sauerbier et al. 2011; Bassil et al. 2013) and alloplasts such as hydroxyapatite (Mangano et al. 2003) alone or in combination with AB has increased over the past decade. Alloplastic materials are synthetic BS made of biocompatible, inorganic, or organic materials, not derived from a human or animal source. Their main advantage is that they have no potential for disease transmission.

Suchlike bone substitute materials vary in porosity and structure (particular pieces or blocks). Supplementary, some clinicians apply resorbable or non-resorbable membranes to protect the augmented area and prevent soft tissue encleftation in the grafted area.

Thus, membranes may promote guided bone regeneration (GBR) and increase the amount of newly-formed bone (Tarnow et al. 2000, Wallace et al. 2005