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Tilted Implants in the Partially Edentulous Maxilla

December 27, 2023
Author
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Shankar Iyer, DDS, MDS
Tilted Implants in the Partially Edentulous Maxilla

The posterior maxilla can be a challenging area for implant placement due to the pneumatization of the maxillary sinus and the low density of remaining bone.1 Immediate loading in the posterior maxilla has shown a higher failure rate compared to implant loading in areas of better-quality bone.1 Sinus augmentation or overlay bone grafting may not provide the primary stability required for immediate function.2 Moreover, contraindications to sinus lift procedures — such as chronic sinusitis, tobacco use, pathologic lesions, odontogenic infections, anatomical abnormalities of the sinus and associated structures, and large prominent septa — pose challenging scenarios often associated with unpredictable outcomes.2,3,4,5

Use of short implants is a promising alternative, but caveats associated with biomechanics should be kept in mind. These issues include reduced bone-to-implant contact, especially in softer bone quality, and reduced force distribution, with more force concentration at the crest of the implant that can lead to greater resorption and greater risk of thread exposure.3,6,7,8,9

One alternative option enables treatment in a predictable and expeditious manner in the partially edentulous maxilla with reduced bone height. It involves using a combination of an axial implant in the anterior region and a tilted implant in the posterior region to support an implant-supported bridge. The placement of the posterior-tilted implant in partially edentulous situations should be in close proximity and parallel to the anterior wall of the maxillary sinus. The implant should be placed at an angle of 30 to 45 degrees, similar to completely edentulous scenarios of immediate loading.

Tilted implants have rendered predictable outcomes in completely edentulous scenarios for nearly 15 years.10,11,12 The benefits of tilted implants have also been noted in partially edentulous situations.13,14 There are several benefits associated with the use of tilted implants. Placing the implant at an angle enables placement of a longer implant. This provides greater implant engagement in the bone and increased bone-to-implant contact, which enhances the primary anchorage of the implant and enables immediate loading in many situations. This implant alignment often reduces bending moments by eliminating the need for a posterior cantilever. This in turn helps to attain a prosthetically favorable implant position while maintaining inter-implant distance.

This case report demonstrates how utilizing angled implants that bypass the maxillary sinus for immediate loading can result in successful quadrant restorations. Some key elements to note when considering tilted implants and immediate loading include:

1Good thread pitch to engage soft bone, which enhances primary fixation
2A tapered design for higher torques in soft bone
3A machined collar for adjusting depths when tilting the implants to avoid exposure of coronal threads
4A stable conical connection to enable a precise fit of the multi-unit abutments (MUAs)
5Wall thickness of the implant access channel to prevent crestal module fractures when the implant-abutment junction is loaded off axially

CASE REPORT

Figure 1a: 76-year old male patient's teeth #11-15
Figure 1b: 76-year old male patient's teeth #11-15

Figures 1a, 1b: A 76-year-old male patient reported with a failing posterior maxillary fixed dental prosthesis (FDP) from teeth #11–15. The abutment support for the failing maxillary FDP was compromised. Additionally, the root-to-sinus proximity and reduced available bone in the region were apparent. Teeth #11 & #14 were extracted because of their guarded prognosis. The patient objected to the use of a removable prosthesis and requested a fixed prosthesis for an esthetic and functional outcome.

Figure 2a: CBCT scans
Figure 2b: CBCT scans
Figure 2c: CBCT scans

Figures 2a–2c: Evaluation of the panoramic film and CBCT scans revealed sufficient bone at the prospective implant site in the region of tooth #11. However, bone height in the region of tooth #14 was insufficient for axial implant placement. The treatment plan included use of an implant-supported bridge with one axial and one tilted implant. For tooth #11, I decided to use an anterior, axial implant. For tooth #14, I selected a longer, tilted implant to avoid augmentation surgery.

Figure 3

Figure 3: After delivering the anesthesia with local infiltration, I exposed the surgical site with a mid-crestal incision and a vertical releasing incision distal to the lateral incisor. A full-thickness flap was then elevated on the buccal and palatal aspects of the ridge. Extensive reflection was obtained below the zygomatic buttress to gain access to the anterolateral wall of the sinus. The CBCT was correlated with the panoramic films to gauge the most accessible area to enter the sinus using a lateral approach.

Figure 4a: 2-mm round bur was used to create a pinpoint hole at the lateral wall
Figure 4b: 23 explorer was then used

Figures 4a, 4b: A 2-mm round bur was used to create a pinpoint hole at the lateral wall. A #23 explorer was then used to further delineate the anterior border of the sinus and the floor by using an indelible marker.

Figure 5: serial osteotomy was prepared for a 3.5 x 11.5 Hahn™ Tapered Implant

Figure 5: For the axial implant at the site of the canine, a traditional serial osteotomy was prepared for a 3.5 x 11.5 Hahn™ Tapered Implant (Glidewell Direct; Irvine, Calif.).

Figure 6a: area of tooth #14
Figure 6b: area of tooth #14

Figures 6a, 6b: In the area of tooth #14 and the selected exit site of the angled implant, serial osteotomies were prepared up to a depth of 14 mm at an angle of 45 degrees. This ensured that it would remain entirely in native bone and avoid engaging the sinus. Following that, the tapered osteotomy was prepared short of the final.

Figure 7a: A 3.5 x 11.5 mm Hahn implant was placed at the site of tooth #11 with 50 Ncm torque
Figure 7b: A 4.3 x 13 mm Hahn implant was inserted at the site of tooth #14 with 60 Ncm torque

Figures 7a, 7b: Both osteotomies were completed and followed by immediate implant placement. A 3.5 x 11.5 mm Hahn implant was placed at the site of tooth #11 with 50 Ncm torque, while a 4.3 x 13 mm Hahn implant was inserted at the site of tooth #14 with 60 Ncm torque.

Figure 8a: torque of 25 Ncm
Figure 8b: MUAs were placed on the implant fixtures

Figures 8a, 8b: At the exit site of the implants, MUAs were placed on the implant fixtures with a torque of 25 Ncm. The MUA for the axial implant was straight, while the MUA of the tilted implant was angled at 30 degrees.

Figure 9a: sutures placed
Figure 9b: radiograph taken to confirm position and placement of implants

Figures 9a, 9b: The flap was coapted, and intermittent sutures were placed to attain primary closure. A radiograph was then taken to confirm the position and placement of the implants.

Figure 10: Hahn Titanium Scan Bodies were placed on the MUAs

Figure 10: Hahn Titanium Scan Bodies were placed on the MUAs. A digital impression was captured with an intraoral scanner for a milled provisional interim bridge. After removal of the scan bodies, protective caps were placed on the MUAs to support the peri-implant mucosa while the provisional prosthesis was being fabricated.

Figure 11a: interim prosthesis with titanium cylinders
Figure 11b: interim prosthesis with titanium cylinders

Figures 11a, 11b: An interim prosthesis with titanium cylinders was fabricated by the lab. The ridge lap surface of the prosthesis was made convex with a self-cleaning design.

Figure 12a: patient's teeth after one week implant placement
Figure 12b: BioTemps® Provisionals

Figures 12a, 12b: One week after implant placement, the condition of the peri-implant tissues was assessed and the lab-fabricated BioTemps® Provisionals (Glidewell; Newport Beach, Calif.) were secured to the MUAs. After verifying the centric occlusion, all contacts were adjusted to achieve group function.

CONCLUSION

This case report demonstrates the use of a combination of axial and tilted implants to provide a graftless solution for a quadrant implant-supported restoration. The clinical indication for the use of tilted implants in the posterior maxilla is less than 5 mm of subantral residual bone height. Care should be taken that there is no severe alveolar ridge defect that would require major horizontal or vertical bone augmentation, and that a favorable interocclusal distance is present in such cases.1

Tilting the distal implant anterior to the maxillary sinus in this case led to achieving the emergence of the implant in the first molar region (#14) instead of the first premolar region (#13), where it would have emerged if axial implants were used in both sites. This achieved a longer span between the anterior and posterior implants, eliminating a cantilever design, while allowing for replacement of the optimal number of posterior teeth. The use of a tilted implant also rendered a stable biomechanical outcome by engaging a greater amount of bone than the alternative of using short implants. The engagement of bone enabled primary stability, which allowed me to immediately load the implants. The use of a tilted implant also eliminated the need for a sinus augmentation procedure, leading to a more efficient treatment with reduced surgical morbidity and expenses.

References

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  4. Jensen SS, Terheyden H. Bone augmentation procedures in localized defects in the alveolar ridge: clinical results with different bone grafts and bone-substitute materials. Int J Oral Maxillofac Implants. 2009;24 Suppl:218–36. 

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  10. Krekmanov L, Kahn M, Rangert B, Lindström H. Tilting of posterior mandibular and maxillary implants for improved prosthesis support. Int J Oral Maxillofac Implants. 2000 May–Jun;15(3):405–14.

  11. Maló P, Rangert B, Nobre M. “All-on-Four” immediate-function concept with Brånemark System implants for completely edentulous mandibles: a retrospective clinical study. Clin Implant Dent Relat Res. 2003;5 Suppl 1:2–9.

  12. Maló P, Nobre Md, Lopes A. Immediate loading of ‘All-on-4’ maxillary prostheses using trans-sinus tilted implants without sinus bone grafting: a retrospective study reporting the 3-year outcome. Eur J Oral Implantol. 2013 Autumn;6(3):273–83.

  13. Apaza Alccayhuaman KA, Soto-Peñaloza D, Nakajima Y, Papageorgiou SN, Botticelli D, Lang NP. Biological and technical complications of tilted implants in comparison with straight implants supporting fixed dental prostheses. A systematic review and meta-analysis. Clin Oral Implants Res. 2018 Oct;29 Suppl 18:295–308.

  14. Hämmerle CHF, Cordaro L, Alccayhuaman KAA, Botticelli D, Esposito M, Colomina LE, Gil A, Gulje FL, Ioannidis A, Meijer H, Papageorgiou S, Raghoebar G, Romeo E, Renouard F, Storelli S, Torsello F, Wachtel H. Biomechanical aspects: summary and consensus statements of group 4. The 5th EAO Consensus Conference 2018. Clin Oral Implants Res. 2018 Oct;29 Suppl 18:326–31.