Introduction

Iatrogenic perforation of the maxillary sinus membrane during membrane elevation represents one of the most frequent intraoperative complications in 20% of sinus floor augmentation surgeries on average^3,4 and increases the chance of postoperative sinusitis owing to bacterial graft contamination or graft migration into the sinus cavity. Since various factors may contribute to a potential impact on membrane perforation and complication rates, including lack of proper surgical training, decreased membrane thickness^5,6 and the complex sinus morphology⁷, careful consideration of the treatment method is essential.

Sinus lift procedures are regularly indicated with the goal to have regular sized implants placed in the maxillary posterior region following axial positioning8. Early descriptions of implant placement in such a way as to create axial loading of the implant were derived from theories that were applicable to natural teeth, where the goal is to apply forces down the long axis of the teeth. With implants, this force application may be somewhat irrelevant because the complex forces of compression, tension, and shear exist macroscopically at each thread of the implant and microscopically at every undulation of the microscopic surface of the implant.⁹

In recent decades, the dental implant industry has invested heavily in research and development to allow less invasive treatment options in patients with poor bone quantity and quality. Based on long-term evidence, the use of short implants and tilted implant placement have been proposed as alternatives to avoid bone augmentation for the accommodation of standard implants . At the same time, more clinicians have recognized that the efforts, morbidity, increased cost and treatment time to allow a vertical osteotomy to house the implant in a similar way to that of the natural teeth are frequently perceived as over-treatment and have started adopting alternative options.^10,11,12

This case report describes a patient presenting with limited maxillary posterior bone availability who was successfully treated with the use of short implants and non-axial implant placement in the tuberosity area as a patient-centered alternative to a sinus lifting procedure.

Case Report

Initial situation:

A 49-year-old, non-smoking male patient with good general health and oral condition presented to the office with the main complaint of continuous pulsating pain on tooth 25 for over seven days and also the desire to replace the absent teeth 26 and 27 with dental implants. Intraoral examination revealed that tooth 25 was mobile and had been restored with a PFM crown whose porcelain layer was now considerably worn. After radiographic examination it was apparent that tooth 25 had an adequate crown adaptation and root canal with no previous endodontic treatment. Regions 26 and 27 presented pneumatization of the sinus floor with significantly reduced remaining vertical bone availability (Figs. 1,2)

Treatment planning:

The patient was presented with two scientifically and clinically validated treatment options:

Option 1 – Tooth 25: Removal of prosthetic crown, endodontic treatment, intra-radicular retentive post and manufacture of a new crown.
Regions 26 and 27: Sinus lift via lateral window and bone grafting (bovine sourced xenograft), (six months healing time for the grafted site)
Tooth 26: Implant placement
Tooth 27: Implant placement (twelve weeks healing time in the grafted area to initiate the prosthetic phase).

Option 2 – Tooth 25: Extraction with immediate implant placement.
Tooth 26: Placement of a short implant.
Tooth 27: Non-axial implant placement in the tuberosity area to maximize implant engagement.
After a healing period of six weeks, the prosthetic phase can be initiated.

Since the patient reported episodes of chronic and recurring sinusitis in the past, the option with the sinus lifting procedure was discarded. Moreover, after considering all the associated costs, surgical interventions, and the considerable amount of time needed to complete treatment, the patient opted for option 2.

Surgical phase:

Under local anesthesia, an intrasulcular incision was made on tooth 25 to minimize the trauma to the soft tissue contour during the extraction. A supracrestal incision followed from the distal part of tooth 25 to the end of the tuberosity, and a mucoperiosteal flap was elevated to expose the crestal bone.

At site 25, a periotome was used around the sulcus ligaments to minimize the need to apply lateral forces with the forceps during the extraction in the attempt to preserve as much surrounding bone as possible. In view of the lack of space apically to gain implant engagement in native bone without perforating the maxillary sinus floor, it was decided to place a Straumann® BLX Implant ∅ 5.0 mm × 12 mm directly into the socket without any osteotomy facilitated by the implant’s engaging thread design. The implant was initially inserted with the use of the handpiece at 25 rpm and taken to the final position with the use of the ratchet and torque control device, reaching a final torque value of 80 Ncm (Figs. 3,4).

At site 26, we performed a 6 mm depth osteotomy sequence according to the manufacturer’s step-by-step instructions for a soft bone type and a short implant. A Straumann® BLX Implant ∅ 5.0 mm × 6 mm was placed with final torque of 50 Ncm (Fig. 5).

For site 27, a non-axial osteotomy with apical orientation towards the distal was performed to by-pass the maxillary sinus and use the available tuberosity bone to an osteotomy depth of 14 mm. A Straumann® BLX Implant, ∅ 5.0 mm x 14 mm, was placed with a torque value of 50 Ncm. (Fig. 6)

All three sites received a transgingival healing abutment in a one-stage surgical approach without the need for a second surgical intervention to expose the implants. Continuous interlocking sutures were applied to bring the soft tissue in close contact with the healing abutments (Figs. 7,8).

Prosthetic Steps:

After six weeks, it was possible to verify an outstanding soft tissue healing response, and all implants were assessed for adequate osseointegration after radiographic examination (Figs. 9,10)

Open-tray impression posts were connected to the implants, and elastomer material was injected around the impression posts and the impression tray in a one-step impression taking. After the model was manufactured in the laboratory, a ceramic layer was applied to the milled framework, followed by a corresponding staining and glazing process. As a final step, the restoration was then seated directly onto the implants, when occlusion and proximal contacts were checked. The prosthesis was torqued to 35 Ncm on all screws, and they were then protected with PTFE tape and light-curing composite (Fig. 11).

Outcome:

In the final radiograph, we can see the complete osseointegration of all implants and the stable crestal preservation around the implant placed immediately after extraction and the short and non-axially placed implant positioned towards the tuberosity (Fig. 12).

The patient is completely satisfied with the esthetic and functional result and was impressed by the minimally invasive nature and the relative shortness of the entire treatment.

Discussion:

It is still important for the practitioner to learn and to perform surgical techniques for sinus lifting to serve the patients in whom this is absolutely indicated in the maxillary posterior region. Sinus augmentation requires a high degree of manual dexterity to avoid the most common complication, i.e. puncture or rupture of the sinus membrane. The recent scientific literature reports rates of between 25% and over 50% of all cases for sinus membrane perforations during sinus lift surgeries using a lateral window approach with consecutive loss of graft material and successive sinusitis¹².

In times of immediate gratification, patients expect efficient, low-trauma, affordable solutions based on the abundant information available in digital channels. Reducing the number and duration of visits, especially in times of ongoing pandemic, minimizing patient exposure and surgical interventions are of additional benefit and value.

The use of short implants and angulated placement in the tuberosity with splinted screw-retained prosthetics offers a reliable and predictable way to avoid a significant number of sinus lifting procedures¹³.

The percentage of sinus lift procedures and consequent complications that can be spared must be further investigated and guidelines defined.