In the functional and esthetic rehabilitation of patients with atrophic maxilla or posterior maxillary defect, several options exist. These options include total/segmental bone onlays or inlays, Le Fort 1 osteotomy with interpositional bone grafts, grafting of the maxillary sinus with autogenous bone and/or bone substitutes, placement of implants without bone grafting in anatomical buttresses (frontomaxillary, frontozygomatic, palatal vault, pterygomaxillary buttress, etc.), use of short dental implants, and application of distraction osteogenesis technique. ¹ Bone grafting procedures to augment resorbed maxilla or posterior maxillary defects are associated with donor-site morbidity, and often involve a two-stage procedure with delayed implant placement. ² This translate to longer waiting time for the patient with regard to their rehabilitation, increased economic loss to the patient and their employer, and increased cost of treatment.

Zygomatic implants remain an important nongrafting option in the functional and esthetic rehabilitation of patients with atrophic maxilla or posterior maxillary defect following tumor ablative surgery or trauma. Since its first design by Nobel Biocare and its introduction by Brånemark in 1988, the use of zygomatic implants has reduced the number of surgeries and treatment time required for the successful rehabilitation of such patients. ³ Zygoma implants are used in situ ations where a posterior maxillary alveolar atrophy or defect exists but with adequate quantity and quality of bone in the anterior region to support conventional dental implants. ⁴ The classification system proposed by Misch and Jucan be used in patient selection, and class A or B in the anterior maxillary region existing with class C or D in the posterior maxillary region is ideal for the use of zygomatic implants. ⁵

The available length for zygoma implants range from 30 mm to 52.5 mm and anchorage is derived from the zygoma bone with either a palatal emergence or emergence at the center of the resorbed alveolar ridge. ⁶ , ⁷ The various anatomic-guided zygomatic implant pathways between the zygoma and the alveolar crest has been classified into group 04 with group 1 constituting about 49% of the reviewed implants. ⁸

However, despite the advantages of zygoma implant use when indicated in patients, certain disadvantages are associated with its use. Difficult surgical access that requires considerable expertise, risk of orbital injury, speech problems with palatal emergence, postoperative sinusitis, oroantral fistula, and periorbital and conjunctival hematoma are some of the documented problems associated with zygoma implant use. ⁶ , ⁹

Few studies on zygoma implants have previously been published in the literature. The aim of this retrospective study was to determine patient demographics, indications, success rate, and complications associated with zygoma implants placed in our department over a 16-year period.

Patients

Twenty-eight patients who had zygoma implants placed at the Department of Oral, Maxillofacial, and Plastic Surgery, Johannes Gutenberg University Medical Center, Mainz, Germany, between 1998 and 2013 were retrospectively assessed for implant outcome.

The case notes and radiographs of the patients from the time of treatment to the last follow-up were carefully studied. Parameters retrieved included age at implant insertion, indication, history of systemic disease, smoking, radiotherapy and chemotherapy, length/number/location of zygoma and regular dental implants, number of failed zygoma implants, and complications.

Preoperative assessment

Patients had clinical and radiological assessment to rule out the presence of uncontrolled systemic disease, local infections, and other pathologies, and to assess bone quantity and quality. Radiological assessment was achieved using the panoramic view and computed tomography.

Surgical and prosthetic protocol

All zygoma implants were placed under general anesthesia supplemented by local injection of adrenaline at the site of incision. Placement of zygoma implants was done according to the Brånemark protocol with bone preparation performed under copious saline irrigation. Delayed prosthetic protocol was used for all the patients, and the patients were rehabilitated with removable prosthetic appliances.

Criteria for success and statistical analysis

A zygoma implant was regarded as successful if it is in position in the mouth and functional (satisfactorily supporting a prostheses) in the absence of mobility, infection, pain, or fracture.

Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 16 (SPSS Inc., Chicago, IL, USA) and Microsoft Excel 2007 (Microsoft, Redmond, WA, USA). Results from descriptive statistics were represented in the form of tables and charts with test for significance (P) set at 0.05.

A total of 28 patients were rehabilitated with 42 zygoma implants under the period reviewed. The patients age range from 41 years to 83 years with a mean age of 60.3 ± 10.6 years. The age groups 51–60 and 61–70 years constituted the largest (28.6% each) population of the patients rehabilitated with zygoma implants. There were 22 females and 6 males, giving a male to female ratio of 1:3.7. Of these patients, 2 (7.14%) were active smokers, 4 (14.29%) had comorbid systemic conditions (hypertension in 2 patients, epilepsy in 1 patient, hyperparathyroidism in 1 patient, and a combination of diabetes, hypertension, and renal disease in 1 patient), and 5 (17.86%) had radiotherapy.

The indications for zygoma implant placement were maxillary defect following tumor resection - 9 (32.1%), and atrophic maxilla - 12 (42.9%) Figure 1. In 7 (25%) patients, the indication was not stated. Fourteen patients had unilateral zygoma implants insertion while an equivalent number had bilateral insertion. There was no statistically significant relationship between the age of the patients and number of zygoma implant placed (P = 0.454). The upper right first molar region was the most common site of implant insertion. The zygoma implant length used range from 35 mm to 50.4 mm with the implant length 45 mm (17.9%) been the most frequently used Table 1. There was no statistically significant relationship between the sex of the patients and zygoma implant length used (P = 0.513). A two-stage protocol was used for all zygoma implants placed. Assessment of marginal bone loss around zygoma implants over time was difficult due to implant orientation. Figure 1

Indications for zygoma implant placement.

Reduction in maxillary bone quantity may occur as a result of prolonged edentulism, tumor resection, trauma, or infection. Rehabilitation of the patients with reduced bone quantity can be quite challenging. The use of zygoma implants provides an acceptable nongrafting option in patient's rehabilitation.

In this retrospective study, the main indication for the insertion of zygoma implants was atrophic maxilla (42.9%). This is similar to findings from other studies. ² , ³ , ⁶ , ¹⁰ Zygoma implants were successfully used in patients of different age group in this analysis. Generally, the bone of elderly patients has been found to be less vascularized and to have reduced number of osteocytes; ¹¹ this may affect osseointegration. However, studies ¹² , ¹³ have shown success rates of implants in elderly patients that are comparable to that seen in younger patients. About 50% of the patients rehabilitated in this study were elderly (>60 years) and none of the implant failure occurred in this age group. Despite the presence of comorbid conditions in 4 of the patients reviewed, no implant failure was recorded in this group with systemic disease. The influence of comorbid conditions such as diabetes mellitus and epilepsy may be direct (from the disease itself) or indirect (as a result of medications such as phenytoin used in epilepsy and which is associated with gingival hyperplasia).

All implants were placed under general anesthesia supplemented by adrenaline containing local anesthesia at the surgical site to reduce hemorrhage (as a result of the local vasoconstricting property). General anesthesia has remained the major anesthetic technique for zygoma implant placement. ² , ¹⁴ This technique is safer and provides better comfort for the patient. ¹⁵ , ¹⁶ However, Zanette reported two cases of zygoma implants placed under regional anesthesia and conscious sedation without complications. Unlike general anesthesia, regional anesthesia can be performed in the dental office, but this technique requires appropriate patient selection, skill and experience, and maintenance of operating room standards to minimize complications. ¹⁷

In this retrospective analysis, the two-stage protocol was used for rehabilitation of all the patients. The two-stage protocol is the most frequently reported. ⁴ , ⁶ , ¹⁸ In the two-stage protocol, abutments are placed between 5 and 8 months after zygoma implant placement. ² The longer surgical step involved in the two-stage protocol before implant loading is a disadvantage both to the patient and the clinician in terms of cost and comfort. The one-stage protocol (immediate loading) has been reported in other studies. ⁵ , ¹⁹ , ²⁰ It has the advantages of reducing treatment time and patients discomfort, increasing masticatory function and improving the psychological condition of the patient. ²¹ Success with immediate loading requires careful patient selection and high initial primary stability. ⁵

A cumulative success rate of 88.1% reported in this study is lower than the reports from other studies. A cumulative survival rate of 96.3% was reported ⁴ in a 36 months follow-up review, while a cumulative success rate of 95.1% was reported ²² in a 10-year follow-up review. Similarly, a survival rate of 100% ¹⁰ has been documented. However, a lower survival rate of 82% ²³ compared to our findings has previously been reported. The difference in the various outcomes may be related to different criteria for assessment of survival/success rate and to the difference in the follow-up periods. No major complication was reported in this study. Other studies ² , ⁴ , ⁶ reported suborbital hematoma, sinusitis, fistula formation, and infraorbital nerve paresthesia as some of the complications encountered.

The use of zygoma implants provide a satisfactory nongrafting option for rehabilitation of the patients with maxillary atrophy or defect. However, there is a need to use a common well-defined terminology (survival rate or success rate) in assessing outcome following implant placement. This will allow for comparison of data more accurately.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declared that they have no conflicts of interest, real or perceived, and financial or nonfinancial in this article.