**5. Full arch rehabilitation in maxilla**

#### **5.1 Treatment of mild–moderate maxillary alveolar resorption**

The maxilla is a paired bone located in the middle third of the face. In its upper part is the orbital cavity, in its middle part the nasal cavity and in its lower part the oral cavity. Towards the oral cavity, there is the alveolar process, which houses the maxillary dental formula and is the main area affected by edentulism. Although the maxillary bone is voluminous, it is quite light due to the presence of the maxillary sinus. A cavity that is part of the respiratory system through which air passes, is heated, humidified and filtered to pass into the respiratory tract. In general, in the treatment of mild maxillary alveolar resorption, it is not necessary to lift the maxillary sinus membrane, allowing

the placement of axial implants. If bone resorption is moderate, consideration should be given to regenerative procedures, sinus lift, or placement of tilted implants [34].

The choice of implants will depend on bone availability and prosthetic planning. Although there is no statistically significant variation when choosing narrows versus regular platform implants, we prefer implant placement greater than 4.0 millimeters in diameter in full arch treatment [35]. This has several reasons. Mainly the thickness of the implant walls and prosthetic solutions such as angled abutments available for implants of this diameter or greater.

An important consideration during planning and implantation is that the implants are prosthetically guided achieving a polygonal emergence towards the prosthetic arch. Once the implantation is achieved, an adequate wound closure must be carried out and the patient should be offered immediate rehabilitation with which the healing process will continue.

#### **5.2 Treatment of severe maxillary alveolar resorption**

The rehabilitation of a patient with severe maxillary atrophy represents a significant challenge for the surgeon and the prosthetist. Often these patients have undergone multiple treatments that have not been able to meet their demands and their mentality regarding the treatment is expectant. In addition to this, patients with severe maxillary atrophy have suffered a total collapse of all their stomaognathic structures, suffering an aging of the face with loss of self-esteem, esthetics and function.

To achieve a successful rehabilitative treatment, we must consider all our therapeutic options and have an anatomical knowledge of the possible anchor points for the placement of osseointegrated implants. During planning, we must evaluate the advantages and disadvantages of regenerative treatment of lost bone versus using long implants with remote skeletal anchors. Sometimes, regenerating the bone with grafts and membranes entails a higher biological and economic cost for the rehabilitative treatment or could increase the times for the definitive rehabilitation.

When conventional implants are an unfeasible option due to the degree of maxillary atrophy or when multiple regenerative treatments must be performed prior to implantation, anchors with long implants in the buttresses have solved this situation. Zygomatic implants are a suitable option. Arch treatments can be performed on 4 zygomatic implants, two on each side or in combination with conventional implants. Zygomatic implants offer adequate insertion torque and can be used as a rescue when conditions are not ideal with conventional implants [36]. Posterior tilted implants, tuberosity implants and pterygopalatine implants are posterior implants that have reduced the distal cantiliever of the prosthesis and support the biomechanical demands of rehabilitation (**Figure 4B** and **C**) [37].
