The risk of the development of maxillary sinusitis associated with zygomatic implants installed using the original technique is reported to be low to moderate. Few data have been published regarding this risk in relation to the Stella and Warner’s technique. According to Peñarrocha et al., the small slot in the zygomatic-maxillary region diminishes the likelihood of maxillary sinusitis, reporting a 4.7 % rate of occurrence of this complication in 12 months of follow-up. In the present study, the implants had two position patterns: those that partially invaded the maxillary sinus and those that were positioned alongside but completely outside the sinus due to the anatomy of the zygomatic-maxillary region encountered. However, the slot that characterizes this technique was made in both cases. The clinical and imaging findings demonstrated no cases of maxillary sinusitis in the follow-up.

According to the Brazilian Guidelines for Sinusitis, the clinical exam has sensitivity and specificity of 69 and 79 %, respectively, which makes the use of complementary diagnostic tools necessary. A number of authors report the use of computed tomography for the diagnosis of sinusitis. Nakai et al. performed this exam 6 months following the placement of 15 zygomatic implants in nine patients and found an absence of signs and symptoms of sinusitis. Maló et al. evaluated the association between zygomatic implants and maxillary sinusitis using sinusoscopy on 14 patients and found no cases of infection or inflammation of the mucosa surrounding the implants, demonstrating that titanium implants are compatible with the health and normal function of the maxillary sinus. However, the studies cited employed the original technique.

In a systematic review, Chrcanovic and Abreu report that immobility of zygomatic implants is one of the main factors contributing to the homeostasis of the maxillary sinus. This immobility is accomplished by adequate anchorage of the implant in the zygomatic bone and, when possible, the maxillary bone as well as a firm connection with the overdentures. The rigorous selection of patients with no history of active sinus disease is another important factor and was confirmed in the present sample through preoperative computed tomography, following the normal routine of the hospital at which this study was carried out.

Computed tomography is currently the method of choice for the determination of sinusitis. A number of scoring systems have been proposed for this purpose, most of which are based on the presence and extent of inflammation in the interior of the paranasal sinuses. The Lund-McKay scoring system is an objective method for the evaluation of opacification of the sinuses on tomograms that eliminates the occurrence of false positives or negatives. A clinical exam and computed tomography performed by an otolaryngologist allows a precise diagnosis of sinus disease, which can present in a similar manner without necessarily being maxillary sinusitis. Moreover, a number of studies have demonstrated that cone-beam computed tomography (as employed in the present study) is a good imaging tool for the evaluation of sinus disease.

The prostheses supported by zygomatic implants have a special design due to the location and a more palatal emergence profile of the implants in position when compared to conventional implants. This situation can hinder the tongue position and hygiene of the prosthesis and interfere with function. Some studies conducted an assessment of the level of patient satisfaction on the prosthesis supported by zygomatic implants, demonstrating good levels of acceptance. Farzad et al. evaluated the satisfaction of patients undergoing placement of zygomatic implants by Stella and Warner’s technique and compared with a group rehabilitated with full fixed prosthesis without zygomatic implants also using VAS.

No statistically significant differences have been found considering the different aspects analyzed, except with respect to aesthetics. In our study, there were significant differences in both overall satisfaction as the specific items assessed showed better results in total fixed prosthesis without zygomatic implants, although group I, represented by the PTF with zygomatic implants, has achieved good averages, except in the ease of entry for cleaning the prosthesis.

Farzad et al. in their assessment of patient satisfaction after rehabilitation did not describe changes in speech. However, in our study three patients rehabilitated with zygomatic implants complained of difficulty in the ability to speak, especially when pronouncing words with the letter “s”. Nakai et al. also reported the presence of patients complaining about speech, one patient complained for 3 months and the other one for 2 weeks, both after installation of the prosthesis. Brånemark et al. and Nakai et al. correlated problems in speaking with the design of the installed prostheses in patients with zygomatic implants which differs from those who are treated with conventional implants with or without the need for grafting.

Hirsch et al. evaluated the satisfaction at the time of insertion of fixed prostheses and after 1 year of follow-up in 76 patients treated with 124 zygomatic implants. Complete satisfaction was observed with the cosmetic and functional results in 80 % of these patients, in both time frame analyzed. Farzad et al. also used a VAS to assess patients’ response to treatment with zygomatic implants, describing difficult to chew and less satisfaction with respect to aesthetics, that can be related to the subjectivity of the analyses. In our study, both groups of patients presented good results with respect to aesthetics and function, but the conventional implant group showed the highest rate for both questions. For the group with zygomatic implants, two patients in the cosmetic item reported that the prosthesis did not show the expected results, which may have been influenced by the individual’s subjective opinion.

Analyzing masticatory function and stability, the group without zygomatic implants showed better results that can be explained by the fact that 85.7 % of the total antagonists are fixed implant prostheses or natural dentition, against 57.14 % in group I.

The findings of our study showed that the technique of Stella and Warner allows the installation of zygomatic implant with high predictability, having achieved a high survival rate, and the absence of maxillary sinusitis, with a good level of satisfaction. These findings are important to confirm the efficacy and clinical applicability of the technique and demonstrate the low complication rate. However, the development of new studies with longer follow-ups and a larger number of patients involved in the sample is necessary to enhance the scientific evidence in this choice of treatment.