Initial situation

A 76-year-old lady who complained of gum swelling and tooth mobility was a known case of hypertension and hyperlipidemia (Fig. 1). She was taking antihypertensives regularly (amlodipine 5 mg at night; losartan 50 mg QD). In addition, this patient had undergone a left hemithyroidectomy in 2018, as well as a spinal fusion many years ago. The patient was fit and ambulatory without any acute distress. Preoperative blood tests showed that she had mild vitamin D deficiency. Clinically, this patient suffered from multiple missing posterior teeth in her upper and lower jaws. The remaining teeth were diagnosed with secondary caries, chronic periodontal disease with clinical attachment loss, defective fillings and failing crown and bridgework (Fig. 2). Radiological examination further revealed that the three anterior mandibular implants had extensive peri-implant bone loss, which was consistent with a clinical diagnosis of severe peri-implantitis.

Treatment planning

After undergoing a CBCT scan, the patient’s DICOM files were exported for computer-aided implant planning (Figs. 3a,3b). Third-party software was used for segmentation and simulation. To respect the biology and biomechanics for optimal functional and esthetic outcomes, the treatment plan was formulated according to the principles of prosthetically driven implant planning (Figs. 4a,4b). Important planning considerations included the distribution of the dental implants in a wider arc, the placement of dental implants according to the future tooth position, and the elimination of a distal cantilever on the prosthesis.

Based on the clinical and radiological findings, this patient was found to have the following problems:

1. Terminal condition of the remaining upper and lower teeth,
2. Low-lying maxillary sinus floor bilaterally with limited residual bone volume,
3. Peri-implantitis of the anterior mandibular implants.

To solve the above-mentioned problems, the following treatment plan was explained and recommended to the patient and her family to consider:

1. Clearance of all remaining teeth,
2. Removal of the anterior mandibular implants,
3. Six conventional dental implants (Straumann® BLX, Basel, Switzerland) in the mandible for full-arch reconstruction,
4. Six dental implants in the maxilla for full-arch reconstruction including four conventional dental implants (Straumann® BLX, Basel, Switzerland) in the anterior maxilla and single zygomatic implants (Straumann® Zygomatic Implant, ZAGA™ round, Basel, Switzerland) bilaterally,
5. Immediate loading using abutment-level screw-retained provisional prostheses,
6. Surgery under general anesthesia.

Once the patient had made her decision and agreed with the proposed treatment plan, a written consent, a treatment schedule, and a quotation for the treatment fee were signed by the patient.

To prepare the patient for full-mouth implant reconstruction under general anesthesia, the patient was referred for anesthesia consultation. Blood tests and ECG examination were carried out by registered nurses, and the results were evaluated by the anesthetist in charge. The patient was classified as ASA II and was considered fit for general anesthesia.

Segmentation of the CBCT DICOM files were conducted and 3D printed jaw models were produced, and these real-size jaw models were used for visualization of anatomical structures and mental rehearsal of the surgical steps (Fig. 5). In addition to CBCT diagnostic imaging and computer-aided planning, 3D printing is an invaluable technology in the digital workflow of implant dentistry.

Implant Systems for Immediacy

Straumann implant systems (Basel, Switzerland) including BLX implants and ZAGA zygomatic implants were selected for this patient. BLX Implant System is designed for immediacy. Straumann Zygomatic Implants ZAGA flat and round (Basel, Switzerland) have been introduced to the market recently to provide implant surgeons with an extra tool to manage patients with severely atrophic maxilla. In this case report, ZAGA round implant was selected based on the current ZAGA Concept. According to the ZAGA classification 1, a zygomatic implant may take an intra-sinus path or extrasinus path depending on the lateral maxillary sinus wall configuration. When an intra-sinus path is anticipated, ZAGA round implant with threaded coronal portion is considered favorable.

Whether it is a BLX implant or a ZAGA zygomatic implant, they share the same prosthetic platform. The SRA abutments are available for both implant systems and these abutments are selected and connected immediately after implant placement to facilitate immediacy.

Surgical procedure

Surgery was performed under general anesthesia with naso-endotracheal intubation. After disinfection and draping, the patient underwent the following procedures:

1. Clearance of all the remaining teeth, excision and curettage of any granulation tissue,
2. Removal of the three implants in the anterior mandible,
3. Osseous reduction was conducted by using piezoelectric surgery in the upper and lower jaws to provide adequate restorative space and to create bone platform with sufficient width to support the chosen implants (Fig. 6),
4. Implant placement in the mandible was completed by free hand surgery (Fig. 7),
5. Implant placement in the anterior maxilla was performed by free hand surgery (Fig. 8),
6. Prior to zygomatic implant osteotomy, extended lateral window was cut on both sides for open sinus lift procedure (Fig. 9),
7. Elevation of the maxillary sinus membrane was carried out by leaving the bone window attached on the Schneiderian membrane (Fig. 10),
8. By locating the starting point and end point for the zygomatic implant placement zygomatic implant osteotomy was completed by sequential drilling (Fig. 11),
9. Grafting of the sinus floor with xenografts (Bio-Oss collagen, Geistlich, Switzerland) (Fig. 12),
10. Placement of ZAGA round zygomatic implant bilaterally (Fig. 13),
11. Grafting of the coronal portion of the ZAGA round zygomatic implant with xenografts (bio-Oss collagen, Geistlich, Switzerland) (Fig. 14),
12. Covering the grafted site with collagen membrane (Bio-Gide, Geistlich, Switzerland),
13. Connection and tightening of SRA abutments,
14. Closure of wound around the abutments and impression copings (Fig. 15),
15. Silicone impressions were made, and bite registration was taken for immediate prostheses.

Extended sinus lift is a technique introduced by Chow et al. 2 to eliminate the risk of maxillary sinusitis in zygomatic implant patients. In ZAGA type 0 and type 1 patients, extended sinus lift technique keeps the zygomatic implant external to the maxillary sinus despite that the implant has an intra-sinus trajectory. When extended sinus lift is performed, it is recommended to graft the sinus because of the following considerations:

1. To provide bone support around the coronal region of the zygomatic implant,
2. To increase the bone thickness to minimize the risk of development of an oral antral communication. 

Implants with sufficient insertion torque value were used for immediate loading (Table 1). In this case, except the BLX implant at the lower right first premolar location, all implants including the ZAGA round zygomatic implants were seated with insertion torque value not less than 30 Ncm. Since the BLX implant at the lower right first premolar location had a low insertion torque, it was submerged for healing.

The upper and lower working impressions and the bite registration were sent to the laboratory for fabrication of the screw-retained upper and lower acrylic prostheses. After the surgery, patient was kept under monitoring in the recovery room. When the patient was fully awake and her vital signs were stable, she was discharged home. Patient was prescribed with oral analgesics (Arcoxia 120 mg QD), oral antibiotics (Amoxicillin 250 mg TDS) and Chlorhexidine mouthwash for 5 days.

Immediate loading

Patient returned for a follow-up visit five days after surgery. She presented with moderate facial swelling and bruising without complaining of pain. Clinically, the oral wounds were clean and there was no bleeding nor any sign of infection. Provisional prostheses made of acrylic resin with metal reinforcement were delivered for immediacy (Fig. 16). All the prosthetic screws were tightened manually, and screw access holes were sealed with light-cure temporary composite resin (Fermit, Ivoclar Vivadent, Lichtenstein). OPG was taken after the delivery of the immediate prostheses (Fig. 17).

In this case, the following occlusal scheme for full-mouth implant reconstruction was adopted:

1. Prosthetically driven implant planning
2. Dental implants with moderately rough and hydrophilic surface
3. No cantilever in the prostheses
4. Even contacts in centric,
5. Shallow anterior guidance,
6. Group function on excursion,
7. Use of soft night guard.
   

Prosthetic procedure

Patient was scheduled for regular review for wound healing and occlusal adjustment. The definitive prostheses will be fabricated three to four months later.

Treatment outcomes

A significant proportion of patients for full-arch reconstruction are suffered from terminal dentition. Immediate implant placement and immediate loading protocol help these patients to go through the implant treatment by minimizing the stress and inconvenience related to edentulous phase. Meta-analyses have shown immediate implant placement is equally successful as delayed implant placement in full-arch reconstruction. Moreover, immediate loading is predictable with high implant survival rates as compare to conventional loading. Definitely, there are certain criteria for immediate loading, good primary stability is considered essential. The BLX implant is designed for immediacy and this implant system is indicated for all types of bone quality. The Straumann Zygomatic Implants ZAGA have been introduced recently with specific features to improve treatment outcomes and reduce complications in zygomatic implant patients. The ZAGA zygomatic implants have flat and round options available for extra-sinus or intra-sinus placement.

In this case of ZAGA type 0 classification, ZAGA round implant was chosen. In order to achieve a more distal location to eliminate cantilever, the starting point of the zygomatic implant is usually located around the zygomatic alveolar crest region. Before performing the zygomatic implant osteotomy, lateral sinus lift procedure with an extended window was opened from the sinus floor to the base of the Zygoma bone. The Schneiderian membrane was elevated with the bone wall of the lateral window attached. It was important to keep the integrity of the Schneiderian membrane. The purpose was to keep the zygomatic implant external to the maxillary sinus to reduce the risk of maxillary sinusitis. Grafting of the sinus floor and around the coronal portion of the zygomatic implant was performed. In principle, grafting increases the crestal bone support to the zygomatic implant and it is beneficial by distributing the functional loading more favorably compared to situation without bone. Moreover, the increased bone thickness surrounding the coronal portion of the zygomatic implant creates a more robust hard tissue barrier between the oral cavity and the sinus cavity. This may prevent the development of oral antral communication after zygomatic implant treatment. To investigate the sinus reaction after zygomatic implant treatment, CBCT examination is useful to evaluate the sinus membrane thickness and patency of the osteo-meatal complex. In this case, the CBCT taken 3 months after surgery showed that there was no sinus membrane thickening and no obstruction of the ostium (Fig. 18).