A Technique Combining Straumann Zygomatic and BLX Implants for full arch rehabilitation PART 2
Digital Smile Design
Due to the absence of a natural occlusal stop it was important to establish and register the correct Occlusal Vertical Dimension in order for the laboratory to subsequently correlate the occlusion to the real life situation. This was achieved by construction an occlusal stop using composite material and bite registration using Coltene Jet Bite.
Using digitized pre-operative models and bite registration of the patients dentition the laboratory superimposed the digital smile design using full face photographs and digitally planned the ideal set up of teeth on planning software taking into account the patient’s aesthetic desires and open bite position.
The patient was provided with prescriptions according to the medication schedule ordinary used at our clinic.
The patient was treated under a General Anesthetic (TIVA) with a combination of propofol, midazolam, and remifentanil. Patients recover quickly using this technique, which is important for the subsequent try-in stage, which requires cooperation.
Dexamethasone 8mg, Cefazolin, IV Paracetamol
After administration of local anesthetic containing adrenaline (1:100,000), a flat incision was made across the ridge and buccal aspect of the teeth preserving the maximum bulk of keratinized tissue but excluding the scalloping of the gingival margins and papillae. This design helps facilitate neat closure and enhanced biotype.
A full thickness flap was raised and the lateral incisors were extracted. An alveolectomy was performed using rongers at first, followed by a surgical pear shaped bur (Fig. 8). The level of the alveolectomy was determined by the digital smile design with reference to the incisal edges of the temporarily retained central incisors.
The central incisors also served as positional references for the implant osteotomy. The positioning of the anterior implants is critical for aesthetics as well as speech and comfort, and this method helps ensure optimal positioning (Fig. 9).
The implant osteotomy for BLX implants requires varied instrumentation depending on the quality of the bone. In this case the trabecular bone density was low with a thin cortex. Selecting the widest implant whilst allowing for minimum 1.5mm buccal plate thickness helps to achieve the requisite stability for immediate loading. In this case the bone width after the alveolectomy allowed for a 5.5mm diameter in the 12 site (extraction socket) and 5mm in the 22 site (edentulous). This required 3 step drills to full length (2.2mm, 2.8mm and 3.5mm) and a 4.2mm drill at the coronal aspect to reduce coronal compression or fracture of the alveolar bone. Unlike instrumentation in soft bone that does not have a cortical ceiling, and where drilling to full length should be on the conservative side, if apical instrumentation is inadequate in the presence of a cortical ceiling (nasal floor), even a slight deviation in the implant path could miss the smaller osteotomy at the cortex, which will cause the implant to spin and lose stability without engaging he apical cortex.
In the anterior maxilla it is possible to achieve a higher stability in soft bone by having the implant apex engage the cortical bone at the nasal floor. Instrumentation through the nasal floor is required using a final full length drill with a tip diameter that lies in between the apical diameter of the implant threads (4mm for a 5.5mm BLX implant) and the apical diameter of the body (2.6mm for a 5.5mm BLX implant). This is why a 3.5mm drill was used to full length for the selected implants.
Before placing the implant any gaps that exist due to the residual tooth socked or any bony defect is repaired using bone collected using rongers during the alveolectomy (Fig. 10).
Two Straumann BLX implants were positioned in the 12 and 22 sites (Fig. 11). The implants were sunk 1.5mm below the ridge, and were fitted with 2.5mm straight SRA abutments (Fig. 12, 13).
Mid-surgery Reference Scan
Prior to removal of the remaining teeth and placement of the posterior implants, 6.5mm healing caps were fitted to the anterior implants and an open-flap digital scan was obtained picking up both the abutments and at least 3 reference points on the existing teeth and was sent to the laboratory.
The technician correlated these references to the same marks on the digitized pre-operative models, which were also correlated already to the smile design and digitized set up.
The remaining teeth were extracted, and bone levelled as predetermined in the planning phase. Due to a combination of sinus anatomy and low-density bone without an apical cortex to help stabilize standard implants in the posterior maxilla, Zygoma implants were chosen for more reliable posterior support (Fig. 14).
In order to preserve the Schneiderian membrane a Hockey Stick lateral anterostomy was used to allow simplified instrumentation to elevate the sinus lining and at the same time define the path with a slot towards the zygomatic bone (Fig. 15).
A suitable biomaterial known for its softness and membrane-like cohesiveness and documented success in the sinus space was used as a liner against the sinus mucosa. This was followed with a layer of an adapted bone substitute, which creates a firmer base for the Zygoma drilling process (Fig. 16, 17).
Once the sinus was protected with the aforementioned layers of grafting materials, a round bur was used to drill a mid-ridge pilot hole for the ideal mid-fossa emergence of the access hole (Fig. 18).
A round Zygoma pilot drill (Round Burr for Zygomatic, ∅2.9mm) was used from the pilot hole along the trajectory of the lateral slot and into the zygomatic bone where it curves internally within the sinus. This was followed with a single twist drill (Multi-use Twist Drill for Zygomatic, ∅2.9mm) until the tip of the drill protruded through the external of the zygomatic bone (Fig. 19).
Straumann Zygomatic ZAGA Flat implant was inserted to full depth, turned to the ideal orientation for the access hole, and fitted with a multi-unit abutment. The abutment is compatible with the BLX SRA abutment and provides a universal platform, which simplifies the restorative process as well as maintenance.
Finally the connective tissue of the palate was trimmed to allow adaptation of the keratinized palatal mucosa over the ridge for improve biotype and stability of the periimplant mucosa as well as to improve hygiene (below right).
Summary of Hardware and Torques
Site 15 – STRAUMANN Zygoma ZAGA Flat 4.3x40mm @45Ncm, fitted with straight 3.5mm abutment torqued to 35Ncm
Site 12 - STRAUMANN BLX WB 5.5x12mm @80Ncm, fitted with 2.5mm straight SRA abutment torqued to 35Ncm
Site 22 - STRAUMANN BLX WB 5.0x12mm @80Ncm, fitted with 2.5mm straight SRA abutment torqued to 35Ncm
Site 25 - STRAUMANN Zygoma ZAGA Flat 4.3x35mm @45Ncm, fitted with straight 3.5mm abutment torqued to 35Ncm
The advantages of the Straumann Zygomatic ZAGA Flat include:
- Low profile on the buccal and reduced infringement of the buccal sulcus;
- Narrow implant mount which improves the ability to drive the implant into its optimal position;
- 55º angle correction to facilitate optima emergence of the access hole;
- Smooth untreated surface improves hygiene and peri-implant health in the event of a dehiscence and exposure, thus reducing the progression of infection and complications;
- Solid and polished tip to reduce impact of protrusion through the Zygomatic bone as required for stability;
- Narrow profile reduced biologic infringement and allows improved separation in Quad Zygoma cases.
- (Fig. 18, 19, 20, 21)
After primary closure precise capture of implant positions was obtained digitally using PiC camera. The technician was then able to correlate the precise implant position to digitised set up by digitally superimposing the implant capture to the Mid-surgery Reference Scan via the anterior 2 implants.
Once all the information from the smile design right through to the precise implant position was digitally merged, the laboratory was able to design and produce a template of the set up to fit on the implants, and also to design a titanium frame for subsequent production of the final teeth.
The templates were tried in the mouth 3 hours after the surgery. Within this timeframe the patient is still in a relaxed state but the local anesthetic has worn off, and the post-operative swelling has not commenced. This creates the ideal conditions for assessing the aesthetics, phonetics vertical dimension and occlusion, and making the necessary adjustments before fabricating the final teeth. Once all adjustments were made, a bite registration was obtained, the teeth templates removed and sent to the lab. A duplicate set of the templates was then inserted and adjusted to eliminate premature contacts, and the patient was able to leave with same day teeth. (Fig. 22, 23, 24)
The laboratory used the adjusted templates to mount printed models, obtain keys, and then construct the final teeth in High Impact Acrylic over the titanium frame that was milled overnight. (Fig. 25)
On subsequent review at 3 months she was fitter, lost weight and stated that the treatment has changed her life on so many levels. She was confident and proud of her smile. (Fig. 26)