Rehabilitating patients with severe maxillary atrophy has remained a consistent challenge for clinicians. In select cases, a complete or partial dental rehabilitation anchored with zygomatic implants can be an excellent option. In practice, though, the historical long-term unpredictability of such procedures means that some clinicians still opt for conventional methods, even though they can be more complex, time-consuming, and costly for the patient. As is true of techniques for placing standard implants in different situations, zygomatic implant placement practices have evolved over the years, from the original Brånemark technique to the slot, extrasinus, and extramaxillary approaches, and now the zygoma anatomy-guided approach (ZAGA). As zygomatic implant placement systems have evolved, so have the implants, tools, technology, and thinking behind them.

Thirty years ago, zygomatic implants were uncharted territory for the vast majority of clinicians. Today, zygomatic implant therapy represents a milestone of progress in the genesis of oral implantology. As it has become more commonplace, a substantial body of evidence has grown to support it. The technique has been well documented over the long term, with success rates that compare favorably with conventional treatment using dental implants and bone grafting. Changes in zygomatic implant design have occurred over the past 20 years, and with these changes, surgical protocols have also evolved. This chapter examines the evolution of oral rehabilitation with zygomatic implant–supported prostheses, from its origins to the present.

Technique Evolution

Brånemark’s original technique: The beginning of the ZAGA story

In the early 1990s, several reports were published on the possibility of anchoring implants into the zygomatic bone for both nasofacial1 and dental prostheses.2 In 2004, Brånemark et al published a long-term follow-up study on onlay bone grafting and the simultaneous placement of zygomatic implants,3 and zygomatic implants were accepted into the scientific implantology community. In this study, 52 zygomatic implants and 106 conventional implants were placed across 28 patients. Bone grafting was performed in 17 patients. All patients were followed closely for 5 to 10 years. The procedure for placing the zygomatic implants consisted of performing a window antrostomy in the upper lateral quadrant of the anterior maxillary wall. The sinus mucosa was then reflected, and “no special effort was made to keep it intact.”3

According to Brånemark, “the direction of the zygoma fixture was selected to provide optimal stability against prosthetic requirements,” meaning the implant path had a more-or-less palatal point of entry, depending on the curvature of the maxillary wall.3 This implant path was said to achieve an intrasinus trajectory (Fig 1-1). Due to the palatal positioning of the zygomatic implants, the palatal flap had to be thinned and the fat tissue eliminated to prevent any soft tissue inflammation around the final abutments. However, despite the palatal positioning of the implant head, no patient discomfort or speech difficulties were reported in the initial study.

FIG 1-1 This clinical photograph shows some of the features of the original surgical technique, such as palatal entry and the opening of an anterior window to visualize the implant path.

The results

In the long term, there were three reported zygomatic implant failures, reflecting a survival rate of 94.2%. Overall, the prosthetic restoration success rate at 5 years was 96%. At least 96 conventional implants between 10 and 20 mm in length were placed. The success rate for the original conventional implants was about 71%. In 2 of the 28 patients, one of the two zygomatic implants installed was disconnected from the prosthesis due to suppuration at the palatal entry point of the implant combined with sinus infection. Recurrent sinusitis affected four patients within the follow-up time (Fig 1-2). The treatment of these four cases was identical: an antrostomy of the inferior meatus with satisfactory results. An additional four patients were found to have radiographically diagnosed sinusitis with clinically symptom-free maxillary sinuses. In those cases, no treatment was considered necessary. According to the definition of Lanza and Kennedy,4 the percentage of cases that developed clinical sinusitis was 21%. If we also apply the radiologic criteria of Lund and Mackay,5 the percentage of rhinosinusitis would rise to 35.7%.

FIG 1-2 (a) Tomographic section of the maxillary sinus taken 1 year after placement of the zygomatic implant through the thin palatal wall. Note the transparency of the maxillary sinus. (b) After a period of 3 years, the patient was diagnosed with rhinosinusitis with radiologic occupation of the sinus with no apparent cause.

In 2010, Bedrossian reported a retrospective follow-up of 36 patients treated with the immediate loading protocol over a period of 5 to 7 years. The survival rate was 97.2%.6 Following this in 2012, Aparicio et al reported on a prospective study with a minimum 10-year follow-up of 22 consecutive patients.7 In this study, the original Brånemark two-stage protocol was used along with the original titanium-turned zygomatic implants. In year 9, two stable zygomatic implants from one patient were removed due to a peri-implant infection in conjunction with recurrent sinusitis, resulting in a cumulative overall survival rate of 95.12% over 10 years.

Concerns with the original technique

When first marketed in 1998, the original Brånemark zygomatic implant was fully threaded and machined. Its head had a 45-degree angulation. The implant transporter and then the abutment were fixed to the implant with a screw that went completely through the head of the implant. The implant was initially designed with an external hex connection so that clinicians could effectively use the components of the Brånemark system. Passing the implant through the maxillary sinus via a palatal perforation did not appear to cause any serious negative sinus reactions, provided the implant was stable and the antral cavity was sealed, as evaluated in a sinuscopy study of 14 patients.8

However, Brånemark’s 2004 study found that 6 of 28 patients (21%) experienced clinical symptoms of acute sinusitis, 4 of whom experienced recurrent acute sinusitis.3 An additional four patients (14%) experienced only radiologic findings of sinusitis (chronic rhinosinusitis), resulting in an overall prevalence of sinusitis of 35%. The occurrence of a relatively high percentage of infectious sinus problems was initially attributed to causes such as poor sealing of the antrum near the palatal area caused by implant micromovement or imprecise surgical technique. Other clinicians attributed these infections to the design of the abutment and implant head screw attachment, through which bacterial microleakage and a consequent inflammatory response with bone destruction could have occurred.

Significantly, most of the studies that include follow-ups of zygomatic implants placed according to the original technique do not mention the prevalence of sinus problems or complications. When rhinosinusitis infections were reported, they appeared to occur at a rate similar to those obtained by Hirsch et al and Malevez et al in 2004, who reported the occurrence of sinusitis in 2.3% to 13.6% of all treated sinuses.9,10 This is in contrast to studies by Brånemark et al,3 Becktor et al,11 and Farzad et al,12 in which the incidences of sinusitis were 35%, 29%, and 31.8%, respectively. Becktor et al had to remove 3 of 31 implants due to recurrent sinusitis, although the implants were clinically stable.11 Again, the two explanations proposed for these problems were, first, that the internally threaded abutment screw chamber in the zygomatic implant head may have created an oroantral communication leading to sinusitis and, second, that there may have been a lack of osseointegration at the marginal level in the palatal area, resulting in transverse mobility of the zygomatic implant and a pump effect during function.

It is noteworthy that very few studies have been as detailed as Brånemark’s with respect to patient follow-up, especially sinus status. Additionally, at the time the original technique was first being performed, there was a lack of consensus on how to report a diagnosis of sinusitis in the dental literature, so information on the prevalence of sinus infection problems should be taken with caution. In most studies with a focus on zygomatic implants, the term used to describe sinus pathology is sinusitis, without clarifying the type, associated signs and symptoms, or whether CT or endoscopy was performed to confirm the diagnosis. Furthermore, sinusitis can be diagnosed years after zygomatic implant surgery.

In summary, oroantral fistulas and subsequent sinusitis are typical late complications associated with zygomatic implants,13 and there are different hypotheses for their etiology—one being lengthy resorption of the thin bone surrounding the neck of the implant when it crosses the palate. There may also be other factors affecting the resorption process, like overly extensive preparations, fracture of the thin alveolar ridge during implant placement, history of periodontitis, and oral hygiene procedures.

In 2016, the Nobel Zygoma with a TiUnite surface implant (Nobel Biocare) replaced the original Brånemark System Zygoma...