Introduction

The rehabilitation of partially edentulous posterior maxillae represents a challenge, either due to the poor quality of the bone for implant placement¹, or due to important anatomical structures that need to be preserved². Technical difficulties can also arise in the ideal positioning for implant placement, added to the characteristics of the patients .

The implant angulation technique was developed to support the rehabilitation of atrophic full arches, and is well-documented in finite element studies⁴, clinical studies^5-7, and systematic reviews^8-12. The technique boasts success rates of over 95%, both for prostheses and implants, but depending on the extension of the arch to be rehabilitated, it can present extensive cantilevers , creating large lever arms. ^9,12 Some rehabilitation treatment options suitable for partially edentulous posterior maxillae can be more invasive (guided bone regeneration, sinus lifts) or less invasive (implants with reduced diameters and/or short implants,¹³ or even intentional implant angulation). Marginal bone loss rates, complications with peri-implant tissues, and patient satisfaction are independent of implant angulation for full-arch restorations¹⁰. Considering these results, we suggest a new concept to rehabilitate edentulous posterior maxillae with osseointegrated implants in an approach that reduces morbidity : NO SINUS LIFT CONCEPT.

Therefore, the aim of this case report is to show how the maxillary tuberosity region can be used to place angled implants for the rehabilitation of atrophic posterior maxillae within a total rehabilitation plan using the NO SINUS LIFT CONCEPT with immediate loading.

Case report

Clinical case 1.

Patient ACS , 57 years old, female, non-smoker, who presented to our practice in 2020, complaining of difficulty chewing as she had lost multiple teeth in both arches several years ago (Fig. 1). A computed tomography (CBCT) scan was performed and showed a mucosal retention cyst in the left maxillary sinus (Fig. 2A-2B). The patient was offered two treatment options: i) removal of the mucous cyst and elevation of the compromised maxillary sinus floor, placement of implants after graft healing within the sinus and finishing with implant-supported prostheses; ii) angled implants bypassing the maxillary sinus with immediate loading (NO SINUS LIFT CONCEPT). The patient chose option 2 because it was shorter and less invasive.

The reverse planning of the case began with intra and extra oral photos, impressions of both arches in addition silicone (Express™ XT Putty Soft. 3M®. São José do Rio Preto-SP. Brazil) and preparation of a study model in plaster (Snow Rock®. Premium Type 4. DK Mungyo Corp. South Korea) to maintain the patient's adequate vertical dimension of occlusion. Preoperative care, such as initial and surgical preparation, as well as postoperative care, were the same as previously described¹⁴.

In this case, to increase the precision of the surgery, both implant positioning and surgical template construction were performed in the CoDiagnostiX® software (Straumann® Basel, Switzerland) (Fig. 3). Two implants were selected in sextant C, positioned in the area of teeth 24 (Straumann® BLX Ø3.75x12 mm) and 28 (Straumann® BLX Ø10x5 mm). All edentulous areas that needed rehabilitation were included in these surgical guides to increase the precision of the surgeries during implant placement (Fig. 4). The technique used for the rehabilitation of this arch consisted of installing an implant anchored in the maxillary tubercle, angled so as to tangent the posterior wall of the maxillary sinus (Fig. 5) and another implant positioned in the premolar region, installed in the proper axial position, respecting the milling technique specified by the manufacturer (Fig. 6). In the same session, abutments with a gingival height of 3.5 mm were placed in the 24 position and 2.5 mm in the 28 position (Fig. 7-8). Open tray impression posts for fixed prostheses, were joined with resin (PATTERN RESIN™, GC AMERICA, Illinois,USA ), an impression was taken with addition silicone (Express™ XT Putty Soft, 3M®, São José do Rio Preto-SP, Brazil ) and sent to the prosthetic laboratory to fabricate the provisional fixed prosthesis in acrylic. These prostheses were installed 3 days after implant installation, remaining in position for 60 days, and then were replaced by conventional metal-ceramic definitive prostheses.

The sutures, when necessary, were removed at 15 days and no complications were observed. At the end of the rehabilitation (Fig. 9) the patient was enrolled in the periodontal/peri-implant control and maintenance program offered by our clinic (Fig. 10-11), as recommended in the literature15.

Clinical case 2.

Patient JT , male, 50 years old, smoker, complained of tooth loss and teeth/implants with mobility in the lower arch; in the upper arch softened teeth, hindering basic activities such as eating and speaking properly, as well as socializing (Fig. 12-13).

After clinical examination, the patient was asked for CBCT because the dental problems in the maxilla suggested the need for extractions with bilateral maxillary sinus lift and explantation of implants in the mandible and panoramic radiography. The CBCT confirmed that a bilateral sinus lift was required. The patient immediately rejected this treatment, as it is a lengthy procedure with a long postoperative follow-up. The patient did, however, readily accept an alternative technique, the NO SINUS LIFT CONCEPT, was suggested, with immediate loading in the upper arch and protocol prosthesis with immediate loading in the lower arch.

During the appointment to install the implants in the upper arch, teeth 15, 16, 17 (Fig. 14), 25, 26 and 27 were extracted. The implants positioned in the second molar areas were angled, tangential to the posterior wall of the maxillary sinuses, and the implants in the first premolar areas were positioned perpendicular to the occlusal plane, tangential to the medial wall of the maxillary sinuses bilaterally. BLX® (Straumann®, Basel, Switzerland) implants measuring Ø4.5 mm x 12 mm (positions 15 and 25), Ø3.75 x 12 mm (positions 17 and 27) with 3.5 mm high abutments were installed. The implant installation torques varied from 30 N/cm2 (position 25), 35 N/cm2 (positions 17 and 27) and 50 N/cm2 (position 15).

Four weeks later, the remaining teeth severely affected by periodontal disease were extracted from the lower arch, the implants were explanted due to peri-implantitis and mispositioning in the arch, followed by the installation of four implants (Fig. 15) (two measuring 4.0x12 mm, and two measuring 3.75x14 mm) for immediate loading (BLX® Straumann, Basel, Switzerland) with 3.5 mm high abutments. This full arch rehabilitation (Fig. 16) followed the same steps as the upper arch prosthesis (Fig. 17) and was installed 3 days after implant installation. The patient also received porcelain crowns on the anterosuperior teeth (Fig. 18).

Results

The postoperatively result of the two reported cases without significant changes. The patients' chief complaints were successfully addressed. The patients’ concerns regarding postoperative morbidity and treatment time were taken into account, and successfully addressed with less invasive techniques that offered greater treatment agility. In up to 18 months of follow-up, rehabilitation has been successful and no signs of mucositis/peri-implantitis, or active periodontal disease have been observed.

Discussion

After a follow-up of up to 18 months, these implants — placed in the region of the maxillary tuberosity, purposely tilted and splinted with axially placed implants, supporting fixed prostheses that received immediate loading — have shown satisfactory results, similar to those observed in the literature in cases of tilted implants supporting full-arch prostheses. Meta-analysis has suggested that there are no significant differences in terms of marginal bone loss, fracture, or survival between tilted and axial implants; however, in terms of patient comfort, treatment time, and cost, tilted implants appear to be a highly attractive alternative for patients.

The NO SINUS LIFT CONCEPT for fixed partial dentures advocates 1 implant placed in the region of the maxillary tuberosity, intentionally tilted and positioned tangentially to the posterior portion of the posterior wall of the maxillary sinus, with its apical portion facing the posterior face of the tuberosity, and another implant placed axially in the area anterior to the mesial wall of the maxillary sinus, supported by a rigid infra-structure of the fixed partial restoration. Some advantages of this approach can be listed, such as: I) lower biological cost, II) shorter treatment time, and III) lower financial cost. This concept allows the use of longer implants in the posterior region, facilitating the construction of prostheses and avoiding distal cantilevers as these can be related to greater bone loss3,4, unlike other implant angulation techniques. Care should be taken when drilling and placing implants in the tuberosity area, as the natural remodelling of the maxilla occurs from anterior to posterior and from buccal to palatal. These demands the use of long drills, often coupled to an extender, and implants should ideally be placed with a straight handle. In low-density bone, under-preparation of the surgical site is also recommended.

Maxillary sinus lift surgery remains an excellent treatment option when well indicated. Currently, however, there are several treatment options to avoid painful procedures that can also increase treatment morbidity, such as new alloys, short implants, stable connections, different surface treatments, mesio-distal angulation of implants and digital planning with guided surgery to achieve optimum angulation, all of which result in significantly lower morbidity.

The contraindications for tilted implants bypassing the maxillary sinus in the tuberosity area are the same as those considered for conventional implant placement, but it is necessary to carefully evaluate patients with a mouth opening of at least 40 mm , and cases where root/dental remnants may prevent the ideal angulation of implants; minimum maxillary bone height of 10 mm, combined with a minimum width of 5 mm; angulation can vary between 15º and 45º in relation to the occlusal plane; minimal placement torque value of 35 N/cm2.

Successful rehabilitation of the lower arch with immediate implants and immediate loading is already a reality in daily practice. In this case , implants with a surface design that allowed fewer implants to support immediate total prosthesis were used, following the same clinical protocol previously published¹⁷.

Conclusion

At the end of up to 18 months follow-up of these posterior maxillary partial rehabilitations with tilted implants in the maxillary tuberosity region receiving immediate loading, our results suggest that it is possible to successfully use implants and prostheses with this technique . Nevertheless, we consider the need for long-term clinical studies with larger case numbers to confirm our findings.

Jaques Luiz
Implantology – Private Practice, Curitiba/PR, Brazil.

Julia Helena Luiz
Periodontology – Private Practice, Curitiba/PR, Brazil

Flavia Sukekava
Periodontology – Private Practice, Curitiba/PR, Brazil

Christian Rado Jarry
Implantology - Instituto Praxis, Brasília/DF, Brazil / Straumann Headquarters, Switzerland