Gap Magazine Implant Dentistry Today No 17

Implant Dentistry Today 25 on positions #13, #12, #11, #21, #22 and #23, with advanced chronic periodontitis and atrophic ridges on the posterior areas. On the other hand, in the lower jaw she presented an implant on position #43 supporting a failing partially removable prosthesis. The radiographic assessment depicted an extreme bilateral bone loss on both premolar and molar regions at the upper and lower jaws. Furthermore, a horizontal bone loss in the anterior area on both upper and lower arches was presented. The patient expectations were high, and she requested a short-lasting therapy avoiding large bone augmentations with an immediate fixed prosthesis at her upper and lower jaws. The decision was done in favour of the extractions of all remaining teeth which were considered hopeless and immediately followed by the complete rehabilitation of the upper and lower jaws with fixed prosthesis anchored on oral implants. Treatment planning The treatment decision-making process was based on impressions and casts from the upper and lower jaws using a SAM dental articulator, the radiographic assessment (X-rays & CBCT) and a digital planning software (Figs. 1- 4). Following a careful evaluation; it was planned to perform in the upper jaw a Hybrid Zygoma approach (4 dental- implants and 2 zygoma-implants), that included a ZAGA surgery with two ZAGA flat implants of 40 mm length on the right side and 42.5 mm length on the left side (advanced), four conventional dental implants, a periodontal plastic surgery (pediculated connective scarf graft) and an immediate fixed restoration consisted on a screwed retained provisional bridge. Moreover, in the lower jaw five conventional implants with an immediate screw-retained fixed restoration were planned. According to our standard protocol, the final restorations were delivered six months after surgery. Surgical procedure The whole procedure was conducted under full narcosis. The hopeless teeth were extracted and a mucoperiosteal flap was elevated by means of supracrestal and three vertical incisions in the tuberosity regions and the midline. These incisions enabled the flap mobilization beyond the infraorbital margin. The surgeon’s first act after raising the flap should be to mark with a surgical pencil the reference points for the alveolar and zygomatic bone entrances. Therefore, these coronal and the zygomatic entrance points on the left second premolar/first molar position were pointed according to the virtual planning (Figs. 5 & 6). As the alveolar thickness was less than 4 mm, a “tunnel” osteotomy was not recommended. The drilling protocol consisted on the use of the lateral cutting bur help to initiate a canal and where the next drill tail will slide. The canal diameter was still reduced at this stage in order to precisely embrace and guide the next bur tail. It is important to take into consideration that just the first part of the lateral drill is used to initially prepare a channel with a diameter congruent to the round bur tail (Fig. 7). The slight adaptation of the lateral bur allowed the use of a round bur, which was supported by the alveolar channel. In this stage; the direction, depth and the inclination of the future implant trajectory Figure 5 Figure 7 Figure 9 Figure 6 Figure 8 Figure 10 Fig. 5. Pencil Left Surgeon first act after raising the flap should be to mark the reference points for the alveolar and zygomatic bone entrances. Fig.6. Pencil Left 2 Clinical picture illustrating how the surgeon is marking the coronal and the zygomatic entrance points on the left second premolar/first molar position according to the virtual planning of Fig. 3. Fig.7. Channel left initial lateral cutting bur As the alveolar thickness is less than 4 mm a “tunnel” type osteotomy is not recommended. The lateral cutting bur helps to initiate a canal, were the next drill tail will slide. The canal diameter should still be reduced at this stage to precisely embrace and guide the next bur tail. Please note that just the first part of the drill is used in order to prepare a channel with a diameter congruent to the round bur tail. A slight adaptation of the step 7 allows for the use of a round bur (see steps 8 and 9) to precede the use of the lateral cutting bur. Considering that the hardness of the bone shall guide the decision, the presented sequence is adapted to this particular clinical case. Fig.8. Channel left, round bur The round bur tail being supported by the alveolar channel, this is the right time to evaluate the direction, the depth and the inclination of the future implant trajectory. Once the channel showed the desired depth, the floor surface shall become even, the round bur tail shall be able to gently slide up and down. The grinding with the round bur becomes more precise by gently touching the bone during the slide down movement. Fig.9. Channel left round bur2 With extreme precision the round bur has previously completed the channel grinding. The picture shows a notch marked at the zygomatic process of the maxillary bone. The round bur, sliding up and down, has penetrated on the zygomatic process of the maxillary bone. By a “grinding-back” movement the round bur would be able to eliminate channel floor irregularities. The goal being to prepare a smooth surface supporting the trajectory for the next drill. Fig.10. Channel left twist drill Once the notch is performed the channel would be double checked for uniform floor, desired inclination and depth. A twist drill of 2,9 mm diameter is advised as final drill diameter.