Introduction
Tooth loss gives rise to gradual resorption of the alveolar process, with a change in bone and muscle relations and in facial morphology (Sutton et al. 2004). While most of this resorption occurs in the first year after tooth loss, it continues throughout life and can often give rise to severe bone atrophy both vertically and in width (Rossetti et al. 2010). Severe bone atrophy of the upper maxilla (Cawood and Howell class V and VI) is associated with certain problems such as reduced perioral tissue support, the impossibility of wearing com- plete dentures, chewing and speech alterations, and difficulties in placing dental implants due to the limited amount of available bone (Cawood and Howell 1988).
Many surgical techniques have been proposed for the rehabilitation of this type of patients. These methods can be classified into bone grafting techniques [i.e., guided bone regeneration (Urban et al. 2017), sinus floor augmentation (Wallace and Froum 2003; Pjetursson et al. 2008), onlay grafting with autogenous bone blocks (Sbordone et al. 2009; Aloy-Prósper et al. 2015), and inlay autogenous bone graft- ing (Nyström et al. 2009)], distraction osteogenesis (Jensen et al. 2011)], crestal expansion techniques [i.e., split crest (Jensen et al. 2009)], the use of special implants [i.e., short dental implants (<6 mm) or narrow dental implants (<3 mm) (Felice et al. 2011)], and the modification of the original implant insertion protocol to avoid bone grafting by using areas of residual bone or anatomical buttresses [i.e., zygo- matic implants (Branemark et al. 2004; Araújo et al. 2017), pterygoid implants (Candel et al. 2012), implant insertion in the maxillary tuberosity (Lopes et al. 2015), tilted implants (Testori et al. 2017), palatal implants (Peñarrocha et al. 2009; Peñarrocha-Oltra et al. 2013), and implants placed in the nasopalatine canal (Peñarrocha et al. 2014)].
The use of bone grafting to allow implant placement in atrophic maxillae is associated with more frequent complica- tions and higher morbidity, especially when an extraoral donor site is required (Nkenke and Neukam 2014). The asso- ciated increase in economic costs and a longer treatment time can lead, sometimes, to limit patient acceptance to treat- ment. Additionally, the use of extraoral grafts (i.e., iliac crest) has a non-predictable resorption pattern that can be of almost the entire graft, especially in the edentulous maxilla (Sbordone et al. 2012). The use of short and narrow implants is a promising alternative concept for the treatment of atro- phic maxilla, but the lack of trials for this specific situation with follow-ups of at least 5 years advises to take this result with caution (Esposito et al. 2015).
The use of anatomical buttresses and the residual bone is a predictable way to rehabilitate the atrophic maxilla with dental implants and fixed full-arch prostheses and several studies available for these techniques (Alzoubi et al. 2017a; Busenlechner et al. 2016a, b; Candel-Marti et al. 2015a; Fortin 2017; Maló et al. 2005; Peñarrocha et al. 2012). This approach avoids complications and morbidity associated with bone graft and reduces treatment cost and time and in overall has a high patient satisfaction (Candel-Marti et al. 2015b; Alzoubi et al. 2017b).
Rationale for Immediate Loading of Atrophic Jaws
Reduction treatment time is a goal in modern implant den- tistry. Increasingly, patients’ expectations go through a reduction between implant placement and the recovery of the function and esthetics with the installation of prosthesis as soon as possible (De Bruyn et al. 2014). Additionally, the adaptation to removable prosthesis is difficult, especially in elderly, what it entails and increasing demand of fixed pros- thesis (Allen and McMillan 2003). The efforts then must be placed to provide immediate loading prosthesis especially in fully edentulous patients that are the ones with more prob- lems to adapt to traditional dentures, and the treatment is very important to recover their function and social life (Muller et al. 2007).
The All-on-Four Treatment Concept
The “all-on-four” treatment concept was developed to maxi- mize the use of available remnant bone in atrophic jaws, allowing immediate function and avoiding regenerative pro- cedures that increase the treatment costs and patient morbid- ity, as well as the complications inherent to these procedures (Soto-Peñaloza et al. 2017).
Biomechanics of the All-on-Four Treatment Concept
The protocol uses four implants in the anterior part of com- plete edentulous jaws to support a provisional, fixed, and immediately loaded prosthesis. The two most anterior implants are placed axially, whereas the two posterior implants are placed distally and angled to minimize the can- tilever length and to allow the application of prostheses with up to 12 teeth, thereby enhancing masticatory efficiency (Maló et al. 2003a, b) (Fig. 1a, b). Several clinical studies have reported that tilting the implants represents a feasible treatment option (Krekmanov 2000; Krekmanov et al. 2000; Aparicio et al. 2001; Fortin et al. 2002; Maló et al. 2003a, 2005; Calandriello and Tomatis 2005; Capelli et al. 2007; Agliardi et al. 2008, 2009; Peñarrocha et al. 2010). Such technique is related to several surgical and prosthetic advantages, like the possibility of placing long implants with improvement of bone anchorage, the reduction of the need for bone grafting, the avoidance of long cantilevers, and the possibility of increasing the dis- tance between anterior and posterior abutments, with improvement of the load distribution. Additionally, no differ- ence in the marginal bone loss between tilted and axially placed implants, placed in either jaw, has been reported, sug- gesting that tilting of the implants causes no detrimental effect on the osseointegration process (Krekmanov 2000; Aparicio et al. 2001; Capelli et al. 2007; Koutouzis and Wennström 2007; Agliardi et al. 2009). A high degree of patient satisfaction was also reported as related to this clini- cal procedure (Capelli et al. 2007; Testori et al. 2008; Agliardi et al. 2009).
Branemark et al. in 1995 was the first who advocated for the use of a reduced number of implants in the treatment of edentulous patients (Branemark et al. 1995). This long-term study with a 10-year follow-up concluded that the use of only four implants is enough both in the maxilla and mandi- ble recommending avoiding the use of graft techniques (i.e., sinus augmentation) for the installation of more implants. From a biomechanical point of view, the rationale for the use of only four implants is that when the force is applied to the more distal part of the prosthesis, the 90% of the strength is absorbed by the more distal implants. The rest (10%) is absorbed by the two more anterior implants. The rest of the implants practically do not receive forces (Rangert et al. 1989). When six or four implants are spread out over the same arch length, there is no significant benefit in selecting six rather than four implants from a biomechanical point of view, because in this situation, the anterior and the posterior implants receive the forces with little to no contribution of the intermediate implants (Fig. 2). Additionally, tilting the posterior implants leads to more benefits as more reduce cantilever extension and a better spreading of the implants
Prognosis of the All-on-Four Treatment Concept
In the treatment of atrophy for full-arch implant-supported restorations, it is considered that four implants are enough for immediate loading and for the final prosthesis (Penarrocha-Diago et al. 2017). Immediate loading with the all-on-four concept provides high implant survival rates in the medium to long term (see Table 1). The all-on-four treat- ment concept offers a predictable way to treat the atrophic jaw in patients that do not prefer regenerative procedures, which increase morbidity and the treatment fees. The results obtained in a recent systematic review that assess results of 11,743 implants indicate a survival rate of 99.8% for more than 24 months (Soto-Peñaloza et al. 2017). For this chapter we reviewed the literature, and this approach showed implant survival rates around 93.8–100% up to 10 years for both jaws, based on a sample of 11,627 implants. Regarding the jaw, an implant survival rate of 95.4–100% is expected for the mandible up to 7 years. For the maxilla, an implant survival rate of 95.7–100% is expected up to 6 years. Regarding technical complications the most frequent is the fracture of the prosthesis or the veneering material followed by the loosening of the screws. Di et al. (2013) of 69 edentu- lous jaws reported the change of three fixed prostheses for removable overdentures after the loss of one or more implants and no replacement of it.
All-on-Four Clinical Procedures
Case 1 (Figs. 3a–e, 4a–g, 5a–j, and 6a–h), Case 2 (Figs. 7a–e, 8a–f, 9a–e, 10a–c, and 11a–f), Case 3 (Figs. 12a–i, 13a–f, 14a–e, 15a–g, and 16a–e), and Case 4 (Figs. 17a–g, 18a–l, 19a–g, and 20a–d) represent the clinical procedure to perform all-on-four.
Anesthesia
Local infiltrative anesthesia is applied at the buccal or labial and the lingual or palatal sides depending on the jaw with articaine chlorhydrate with 1:100,000 epinephrine.
In the case that the patient still has remnant teeth, the first step is their extraction.
Incision
With a 15 or 15C blade, a mid-crestal incision is made from the area of the first molar of one side to the contralateral first molar. Vertical-releasing incisions are made at the level of the first molars. In cases with little keratinized mucosa, the incision can be displaced slightly palatal or lingual to enhance the tissue in the buccal aspect. In cases with very little or no keratinized tissue, especially in the mandible, a connective tissue graft or free gingival graft, prior to defini- tive restoration, will be necessary to ensure comfort for the patient and to facilitate oral hygiene procedures.
Flap Elevation
A mucoperiosteal flap is elevated to expose the alveolar bone. In the mandible it is easier to start elevating the lingual flap because it is less firmly attached to the underlying bone. In the maxilla it is easier to start with the buccal flap for the same reason.
The key objective during flap elevation is to localize the mental foramina in the mandible and the anterior wall of the maxillary sinus, because these represent the posterior ana- tomical limits for the distal implants in this technique. Studying the preoperative CBCT can facilitate this by taking into account some anatomical references.
Evaluation of Anatomical Limits
It is very important to determine the trajectory of the inferior alveolar canal and determine if it follows a mesial loop before emerging through the mental foramen or not. Studying carefully the CBCT is very useful for this purpose. If it is not possible to determine this trajectory through radiological evaluation, we will have to probe the foramen with a peri- odontal probe to assess the extension and direction of the anterior loop. We will translate this extension and direction to the external wall of the bone to determine the position and angulation of the posterior implant. As a rule, it is necessary to ward off 2–3 mm from the mental foramen or the anterior loop of the alveolar canal for safety.
In the upper jaw, the position of the posterior implants is determined by the anterior wall of the maxillary sinus. Again, panoramic x-ray or panoramic view of CBCT is useful to determine it. In cases of doubt, it is necessary to create a little lateral window to the maxillary sinus and with a periodontal probe sound the anterior sinus wall and translate the mea- sures to the external side of the bone. In this way it is possi- ble to determine the limit of the posterior implant.
Bone Remodeling
After locating the posterior limits, the next step is to regular- ize the bone ridge to create a flat surface to position the implants. In post-extraction cases, careful debridement should be done to remove all granulation tissue. Bone remod- eling can be done with manual instruments (as Gubia or bone scrapers), burs mounted in a handpiece, or with a piezosur- gery device. The objective in the mandible is to obtain a 5 or 6 mm flat bone platform. When we have a narrow or knife- edge ridge, lowering the alveolar process will allow a greater buccolingual surface, eliminating the need of bone augmentation procedures and allowing the fabrication of a cleansable prosthesis.
In the maxilla when possible, we will do the same, and remodel the bone to obtain a wide flat platform before drill- ing the implant osteotomies. However, it is not necessary to obtain such a bone width because there is the possibility of inserting the implants in a palatal position.
In the maxilla, however, it is of capital interest for the final esthetic results of the rehabilitation to hide the transi- tion line of the prosthesis with the lip. For this reason in the preoperative assessment of maxillary cases, we must deter- mine if the patient shows the alveolar process when smiling
In these cases, we will measure how much alveolar process the patient shows. The final bone reduction will consider the amount of alveolar process shown by patient and 5 mm extra to ensure a final esthetic result.
Implant Placement
The next step will be to prepare the implant osteotomies and insert the fixtures. It is recommendable to start with the pos- terior ones. The literature supports the use of regular diame- ter implants—minimum width of 3.5–4 mm and 10 mm in length—to provide enough mechanical strength, prevent fractures of the components and achieve primary implant stability that allows immediate loading. A minimum inser- tion torque of 35–40 Nw is recommended. Depending on the quality of the bone, the underpreparation of implant bed, bicortical anchorage, the use of bone expanders, absence of tapping, or more aggressive implant designs can be advisable.
The tilting of the posterior implants will be between 30° and 45° mesio-distally, with the objective of increasing the arch length and reducing the distal cantilever. Depending on the anatomy of the patient (mental foram- ina and maxillary sinuses), distal implants emerge in the first or second premolar or first molar position. In cases with a wide pneumatization of the maxillary sinus that provoques an emergence of the posterior implant at the cuspid level, a change in the treatment plan is necessary, and a zygomatic implant is required to allow enough arch length.
The anterior implants are placed parallel to each other at the level of the lateral incisors both in the maxilla and man- dible. In the mandible the implants must follow the ridge angulation. This sometimes entails the use of angulated abut- ments because the implants have a backward angulation. In the maxilla if there is not enough bone width, a palatal posi- tion is recommended. Once implants are installed, if primary stability is suffi- cient, angulated abutments (30° or 17°; depending on the final implant angulation) are connected to the posterior implants, and standard straight abutments were connected to the anterior ones, screwed with the torque recommended by the manufacturer. After this, flaps are sutured
Prosthetic Procedure
Once the flaps are sutured, there are several alternatives to obtain an immediate loading fixed prosthesis. These alternatives are better explained in chapter “Immediate Loading with Fixed Full-Arch Prosthesis in the Edentulous Patient: Treatment Protocol.”
A first alternative is to use a laboratory-based or indirect technique, in which implant positions and inter-arch registra- tion are performed and sent to the laboratory. The dental technician will fabricate in 1–2 days the provisional full-arch acrylic restoration without cantilever extensions. Healing abut- ments are placed until provisional restoration is delivered. A second alternative is to use a chairside or direct technique, which consists in adapting a complete denture of the patient. Temporary titanium abutments are placed, and holes are made in the complete denture through which the abutments emerge. Care is taken in positioning accurately the denture in the mouth after cutting the temporary abutments to the correct height. After this, the abutments are fixed to the denture with acrylic resin. After hardening of the resin, the provisional restoration is unscrewed, polished, and adapted—the distal extensions eliminated as well as the buccal extension of the prosthesis and the palate.
When using either technique, a flat or convex base of the prosthesis is recommended to allow hygiene procedures.
In both cases a passive fit of the prosthesis is mandatory, and a panoramic x-ray is recommended to assess the adjust- ment. Occlusal contacts are checked, and a centric relation occlusion is provided with well-distributed contacts. The screws are tightened at approximately 15 Ncm or according to the manufacturer’s recommendation.
Postoperative Care
The patient receives postoperative instructions and pharma- cologic therapy that consist in antibiotic therapy (amoxicil- lin 500 mg, one capsule every 8 h for 7 days/or clindamycin 300 mg in cases of allergy), anti-inflammatory medication (ibuprofen 600 mg, one capsule every 8 h for 3 days), and 0.2% chlorhexidine mouthwash rinses (two to three times/ day). One week after the intervention, the sutures are removed and oral hygiene instructions explained to the patient. This must involve the use of interdental brushes, irrigator, and any device that can help the patient clean the area underneath the prosthesis. During the 2–3 months of the osseointegration period, the patient must follow a soft diet.
After a period of 3–6 months, the procedures to fabricate the definitive prosthetic rehabilitation can start.
Tooth loss gives rise to gradual resorption of the alveolar process, with a change in bone and muscle relations and in facial morphology (Sutton et al. 2004). While most of this resorption occurs in the first year after tooth loss, it continues throughout life and can often give rise to severe bone atrophy both vertically and in width (Rossetti et al. 2010). Severe bone atrophy of the upper maxilla (Cawood and Howell class V and VI) is associated with certain problems such as reduced perioral tissue support, the impossibility of wearing com- plete dentures, chewing and speech alterations, and difficulties in placing dental implants due to the limited amount of available bone (Cawood and Howell 1988).
Many surgical techniques have been proposed for the rehabilitation of this type of patients. These methods can be classified into bone grafting techniques [i.e., guided bone regeneration (Urban et al. 2017), sinus floor augmentation (Wallace and Froum 2003; Pjetursson et al. 2008), onlay grafting with autogenous bone blocks (Sbordone et al. 2009; Aloy-Prósper et al. 2015), and inlay autogenous bone graft- ing (Nyström et al. 2009)], distraction osteogenesis (Jensen et al. 2011)], crestal expansion techniques [i.e., split crest (Jensen et al. 2009)], the use of special implants [i.e., short dental implants (<6 mm) or narrow dental implants (<3 mm) (Felice et al. 2011)], and the modification of the original implant insertion protocol to avoid bone grafting by using areas of residual bone or anatomical buttresses [i.e., zygo- matic implants (Branemark et al. 2004; Araújo et al. 2017), pterygoid implants (Candel et al. 2012), implant insertion in the maxillary tuberosity (Lopes et al. 2015), tilted implants (Testori et al. 2017), palatal implants (Peñarrocha et al. 2009; Peñarrocha-Oltra et al. 2013), and implants placed in the nasopalatine canal (Peñarrocha et al. 2014)].
The use of bone grafting to allow implant placement in atrophic maxillae is associated with more frequent complica- tions and higher morbidity, especially when an extraoral donor site is required (Nkenke and Neukam 2014). The asso- ciated increase in economic costs and a longer treatment time can lead, sometimes, to limit patient acceptance to treat- ment. Additionally, the use of extraoral grafts (i.e., iliac crest) has a non-predictable resorption pattern that can be of almost the entire graft, especially in the edentulous maxilla (Sbordone et al. 2012). The use of short and narrow implants is a promising alternative concept for the treatment of atro- phic maxilla, but the lack of trials for this specific situation with follow-ups of at least 5 years advises to take this result with caution (Esposito et al. 2015).
The use of anatomical buttresses and the residual bone is a predictable way to rehabilitate the atrophic maxilla with dental implants and fixed full-arch prostheses and several studies available for these techniques (Alzoubi et al. 2017a; Busenlechner et al. 2016a, b; Candel-Marti et al. 2015a; Fortin 2017; Maló et al. 2005; Peñarrocha et al. 2012). This approach avoids complications and morbidity associated with bone graft and reduces treatment cost and time and in overall has a high patient satisfaction (Candel-Marti et al. 2015b; Alzoubi et al. 2017b).
Rationale for Immediate Loading of Atrophic Jaws
Reduction treatment time is a goal in modern implant den- tistry. Increasingly, patients’ expectations go through a reduction between implant placement and the recovery of the function and esthetics with the installation of prosthesis as soon as possible (De Bruyn et al. 2014). Additionally, the adaptation to removable prosthesis is difficult, especially in elderly, what it entails and increasing demand of fixed pros- thesis (Allen and McMillan 2003). The efforts then must be placed to provide immediate loading prosthesis especially in fully edentulous patients that are the ones with more prob- lems to adapt to traditional dentures, and the treatment is very important to recover their function and social life (Muller et al. 2007).
The All-on-Four Treatment Concept
The “all-on-four” treatment concept was developed to maxi- mize the use of available remnant bone in atrophic jaws, allowing immediate function and avoiding regenerative pro- cedures that increase the treatment costs and patient morbid- ity, as well as the complications inherent to these procedures (Soto-Peñaloza et al. 2017).
Biomechanics of the All-on-Four Treatment Concept
The protocol uses four implants in the anterior part of com- plete edentulous jaws to support a provisional, fixed, and immediately loaded prosthesis. The two most anterior implants are placed axially, whereas the two posterior implants are placed distally and angled to minimize the can- tilever length and to allow the application of prostheses with up to 12 teeth, thereby enhancing masticatory efficiency (Maló et al. 2003a, b) (Fig. 1a, b). Several clinical studies have reported that tilting the implants represents a feasible treatment option (Krekmanov 2000; Krekmanov et al. 2000; Aparicio et al. 2001; Fortin et al. 2002; Maló et al. 2003a, 2005; Calandriello and Tomatis 2005; Capelli et al. 2007; Agliardi et al. 2008, 2009; Peñarrocha et al. 2010). Such technique is related to several surgical and prosthetic advantages, like the possibility of placing long implants with improvement of bone anchorage, the reduction of the need for bone grafting, the avoidance of long cantilevers, and the possibility of increasing the dis- tance between anterior and posterior abutments, with improvement of the load distribution. Additionally, no differ- ence in the marginal bone loss between tilted and axially placed implants, placed in either jaw, has been reported, sug- gesting that tilting of the implants causes no detrimental effect on the osseointegration process (Krekmanov 2000; Aparicio et al. 2001; Capelli et al. 2007; Koutouzis and Wennström 2007; Agliardi et al. 2009). A high degree of patient satisfaction was also reported as related to this clini- cal procedure (Capelli et al. 2007; Testori et al. 2008; Agliardi et al. 2009).
Branemark et al. in 1995 was the first who advocated for the use of a reduced number of implants in the treatment of edentulous patients (Branemark et al. 1995). This long-term study with a 10-year follow-up concluded that the use of only four implants is enough both in the maxilla and mandi- ble recommending avoiding the use of graft techniques (i.e., sinus augmentation) for the installation of more implants. From a biomechanical point of view, the rationale for the use of only four implants is that when the force is applied to the more distal part of the prosthesis, the 90% of the strength is absorbed by the more distal implants. The rest (10%) is absorbed by the two more anterior implants. The rest of the implants practically do not receive forces (Rangert et al. 1989). When six or four implants are spread out over the same arch length, there is no significant benefit in selecting six rather than four implants from a biomechanical point of view, because in this situation, the anterior and the posterior implants receive the forces with little to no contribution of the intermediate implants (Fig. 2). Additionally, tilting the posterior implants leads to more benefits as more reduce cantilever extension and a better spreading of the implants
Prognosis of the All-on-Four Treatment Concept
In the treatment of atrophy for full-arch implant-supported restorations, it is considered that four implants are enough for immediate loading and for the final prosthesis (Penarrocha-Diago et al. 2017). Immediate loading with the all-on-four concept provides high implant survival rates in the medium to long term (see Table 1). The all-on-four treat- ment concept offers a predictable way to treat the atrophic jaw in patients that do not prefer regenerative procedures, which increase morbidity and the treatment fees. The results obtained in a recent systematic review that assess results of 11,743 implants indicate a survival rate of 99.8% for more than 24 months (Soto-Peñaloza et al. 2017). For this chapter we reviewed the literature, and this approach showed implant survival rates around 93.8–100% up to 10 years for both jaws, based on a sample of 11,627 implants. Regarding the jaw, an implant survival rate of 95.4–100% is expected for the mandible up to 7 years. For the maxilla, an implant survival rate of 95.7–100% is expected up to 6 years. Regarding technical complications the most frequent is the fracture of the prosthesis or the veneering material followed by the loosening of the screws. Di et al. (2013) of 69 edentu- lous jaws reported the change of three fixed prostheses for removable overdentures after the loss of one or more implants and no replacement of it.
All-on-Four Clinical Procedures
Case 1 (Figs. 3a–e, 4a–g, 5a–j, and 6a–h), Case 2 (Figs. 7a–e, 8a–f, 9a–e, 10a–c, and 11a–f), Case 3 (Figs. 12a–i, 13a–f, 14a–e, 15a–g, and 16a–e), and Case 4 (Figs. 17a–g, 18a–l, 19a–g, and 20a–d) represent the clinical procedure to perform all-on-four.
Anesthesia
Local infiltrative anesthesia is applied at the buccal or labial and the lingual or palatal sides depending on the jaw with articaine chlorhydrate with 1:100,000 epinephrine.
In the case that the patient still has remnant teeth, the first step is their extraction.
Incision
With a 15 or 15C blade, a mid-crestal incision is made from the area of the first molar of one side to the contralateral first molar. Vertical-releasing incisions are made at the level of the first molars. In cases with little keratinized mucosa, the incision can be displaced slightly palatal or lingual to enhance the tissue in the buccal aspect. In cases with very little or no keratinized tissue, especially in the mandible, a connective tissue graft or free gingival graft, prior to defini- tive restoration, will be necessary to ensure comfort for the patient and to facilitate oral hygiene procedures.
Flap Elevation
A mucoperiosteal flap is elevated to expose the alveolar bone. In the mandible it is easier to start elevating the lingual flap because it is less firmly attached to the underlying bone. In the maxilla it is easier to start with the buccal flap for the same reason.
The key objective during flap elevation is to localize the mental foramina in the mandible and the anterior wall of the maxillary sinus, because these represent the posterior ana- tomical limits for the distal implants in this technique. Studying the preoperative CBCT can facilitate this by taking into account some anatomical references.
Evaluation of Anatomical Limits
It is very important to determine the trajectory of the inferior alveolar canal and determine if it follows a mesial loop before emerging through the mental foramen or not. Studying carefully the CBCT is very useful for this purpose. If it is not possible to determine this trajectory through radiological evaluation, we will have to probe the foramen with a peri- odontal probe to assess the extension and direction of the anterior loop. We will translate this extension and direction to the external wall of the bone to determine the position and angulation of the posterior implant. As a rule, it is necessary to ward off 2–3 mm from the mental foramen or the anterior loop of the alveolar canal for safety.
In the upper jaw, the position of the posterior implants is determined by the anterior wall of the maxillary sinus. Again, panoramic x-ray or panoramic view of CBCT is useful to determine it. In cases of doubt, it is necessary to create a little lateral window to the maxillary sinus and with a periodontal probe sound the anterior sinus wall and translate the mea- sures to the external side of the bone. In this way it is possi- ble to determine the limit of the posterior implant.
Bone Remodeling
After locating the posterior limits, the next step is to regular- ize the bone ridge to create a flat surface to position the implants. In post-extraction cases, careful debridement should be done to remove all granulation tissue. Bone remod- eling can be done with manual instruments (as Gubia or bone scrapers), burs mounted in a handpiece, or with a piezosur- gery device. The objective in the mandible is to obtain a 5 or 6 mm flat bone platform. When we have a narrow or knife- edge ridge, lowering the alveolar process will allow a greater buccolingual surface, eliminating the need of bone augmentation procedures and allowing the fabrication of a cleansable prosthesis.
In the maxilla when possible, we will do the same, and remodel the bone to obtain a wide flat platform before drill- ing the implant osteotomies. However, it is not necessary to obtain such a bone width because there is the possibility of inserting the implants in a palatal position.
In the maxilla, however, it is of capital interest for the final esthetic results of the rehabilitation to hide the transi- tion line of the prosthesis with the lip. For this reason in the preoperative assessment of maxillary cases, we must deter- mine if the patient shows the alveolar process when smiling
In these cases, we will measure how much alveolar process the patient shows. The final bone reduction will consider the amount of alveolar process shown by patient and 5 mm extra to ensure a final esthetic result.
Implant Placement
The next step will be to prepare the implant osteotomies and insert the fixtures. It is recommendable to start with the pos- terior ones. The literature supports the use of regular diame- ter implants—minimum width of 3.5–4 mm and 10 mm in length—to provide enough mechanical strength, prevent fractures of the components and achieve primary implant stability that allows immediate loading. A minimum inser- tion torque of 35–40 Nw is recommended. Depending on the quality of the bone, the underpreparation of implant bed, bicortical anchorage, the use of bone expanders, absence of tapping, or more aggressive implant designs can be advisable.
The tilting of the posterior implants will be between 30° and 45° mesio-distally, with the objective of increasing the arch length and reducing the distal cantilever. Depending on the anatomy of the patient (mental foram- ina and maxillary sinuses), distal implants emerge in the first or second premolar or first molar position. In cases with a wide pneumatization of the maxillary sinus that provoques an emergence of the posterior implant at the cuspid level, a change in the treatment plan is necessary, and a zygomatic implant is required to allow enough arch length.
The anterior implants are placed parallel to each other at the level of the lateral incisors both in the maxilla and man- dible. In the mandible the implants must follow the ridge angulation. This sometimes entails the use of angulated abut- ments because the implants have a backward angulation. In the maxilla if there is not enough bone width, a palatal posi- tion is recommended. Once implants are installed, if primary stability is suffi- cient, angulated abutments (30° or 17°; depending on the final implant angulation) are connected to the posterior implants, and standard straight abutments were connected to the anterior ones, screwed with the torque recommended by the manufacturer. After this, flaps are sutured
Prosthetic Procedure
Once the flaps are sutured, there are several alternatives to obtain an immediate loading fixed prosthesis. These alternatives are better explained in chapter “Immediate Loading with Fixed Full-Arch Prosthesis in the Edentulous Patient: Treatment Protocol.”
A first alternative is to use a laboratory-based or indirect technique, in which implant positions and inter-arch registra- tion are performed and sent to the laboratory. The dental technician will fabricate in 1–2 days the provisional full-arch acrylic restoration without cantilever extensions. Healing abut- ments are placed until provisional restoration is delivered. A second alternative is to use a chairside or direct technique, which consists in adapting a complete denture of the patient. Temporary titanium abutments are placed, and holes are made in the complete denture through which the abutments emerge. Care is taken in positioning accurately the denture in the mouth after cutting the temporary abutments to the correct height. After this, the abutments are fixed to the denture with acrylic resin. After hardening of the resin, the provisional restoration is unscrewed, polished, and adapted—the distal extensions eliminated as well as the buccal extension of the prosthesis and the palate.
When using either technique, a flat or convex base of the prosthesis is recommended to allow hygiene procedures.
In both cases a passive fit of the prosthesis is mandatory, and a panoramic x-ray is recommended to assess the adjust- ment. Occlusal contacts are checked, and a centric relation occlusion is provided with well-distributed contacts. The screws are tightened at approximately 15 Ncm or according to the manufacturer’s recommendation.
Postoperative Care
The patient receives postoperative instructions and pharma- cologic therapy that consist in antibiotic therapy (amoxicil- lin 500 mg, one capsule every 8 h for 7 days/or clindamycin 300 mg in cases of allergy), anti-inflammatory medication (ibuprofen 600 mg, one capsule every 8 h for 3 days), and 0.2% chlorhexidine mouthwash rinses (two to three times/ day). One week after the intervention, the sutures are removed and oral hygiene instructions explained to the patient. This must involve the use of interdental brushes, irrigator, and any device that can help the patient clean the area underneath the prosthesis. During the 2–3 months of the osseointegration period, the patient must follow a soft diet.
After a period of 3–6 months, the procedures to fabricate the definitive prosthetic rehabilitation can start.
Case 2 (Figs. 7a–e, 8a–f, 9a–e, 10a–c, and 11a–f) 
Case 3 (Figs. 12a–i, 13a–f, 14a–e, 15a–g, and 16a–e)
Case 4 (Figs. 17a–g, 18a–l, 19a–g, and 20a–d)
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