The Zygomatic Anatomy-Guided Approach, Zygomatic Orbital Floor Classification, and ORIS Criteria-A 10-Year Follow-Up

Abstract

Background: Presently, the management of patients with maxilla bone defects of the Cawood V or VI class is achieved using zygomatic or individual implants or through augmentation of the bone. For zygomatic implants, the ORIS criteria represent the most common factor in helping practitioners register success rates. The zygomatic anatomy-guided approach (ZAGA)and zygomatic orbital floor (ZOF) are factors that are crucial to examining the anatomy of a particular patient before the procedure. The aim of thisarticle is to find the statistical relationship between the abovementioned terms and other factors.

Methods: A total of 81 patients underwent zygomatic implant procedures in different configurations. The ORIS, ZAGA, and ZOF parameters were compared with other factors such as type of surgery, sex, age, and the anatomy of the zygomatic bone.

Results: Most patients in this article were classified as ZAGA Class 2. The relationships between type of surgery and ZAGA classification, and ZAGA and sinus/maxilla zygomatic implant localization were statistically significant.

Conclusions: The ZAGA and ZOF scales are practical and valuable factors that should be taken into account before surgery, whereas to date, criteria better than the ORIS scale have not been described in terms of the success of zygomatic implants. The ZOF scale might omit perforation of the orbit because this parameter warns a practitioner to be aware of the anatomy of the orbit.

Keywords: ORIS criteria; ZAGA classification; ZOF classification; zygomatic implants.

Figure 1

Some representative CBCT photos for each group: (a) Group 1—4 zygomatic implants + 1 or 2 conventional implants; (b) Group 2—4 zygomatic implants; (c) Group 3—2 zygomatic + 4 conventional implants; (d) Group 4—3 zygomatic + 1 or 2 conventional implants.

Figure 2

Depending on the type of surgery − Group 1: 4 zygomatic implants + 1 or 2 conventional implants; Group 2: 4 zygomatic implants; Group 3: 2 zygomatic + 4 conventional implants; Group 4: 3 zygomatic + 1 or 2 conventional implants ZAGA class was registered. In groups I and II, where the atrophy of the maxilla was the highest, the ZAGA classification was the lowest. The above relationship was statistically significant (p < 0.05). On (a) the right side and (b) the left side of the maxilla, the relationship between the type of surgery and the ZAGA class was statistically significant.

Figure 3

Despite the fact that there is a difference in face morphology in men and women, there is no statistical significance in ZAGA class and gender (p > 0.5) on the right side (a) and left side (b).

Figure 4

Box and whisker plots showing the relationship between age and ZAGA class on the right side (a) and left side (b). Neither show statistical significance (p > 0.5).

Figure 5

Simple regression proved no statistical significance between ORIS on zygomatic implants in Region 16 (a) and Region 26 (b) and age (p > 0.5).

Figure 6

Simple regression proved no statistical significance between ORIS and ZAGA class on the right side (a), and the squared model with the same parameters on the left side (b) also proved no statistical significance (p > 0.05).

Figure 7

Simple regression was made to check the height of the zygomatic bone on the left side and the zygomatic orbital floor (ZOF) (in mm). It was statistically significant (p < 0.05) (b). The same test proved a lack of statistical significance (p > 0.05) on the right side (a).

Figure 8

Box and whisker plots were used to check if ZOF classification depends on age (p > 0.05) on both sides (left—(a) and right—(b)). It was proved to have no statistical significance (p > 0.05).

Figure 9

Implants screwed too palatally in region 16 and 26. In (a) milled metal to check bite and (b) final prosthodontic restoration.

Figure 10

Implant in Region 26 screwed too buccally (a) resulted in implant removal 2 years aftersurgery (b)—lack of keratinized mucosa caused implant dehiscence.

Figure 11

16 months after surgery with immediate implantation and immediate loading. The 31-year-old patient has not come to a check-up visit since surgery. Lack of keratinized mucosa around the implant neck, bacteria plaque, and rough implant surface resulted in plural dehiscences; however, the stability of implants was high. Loss of zygomatic implants is just a matter of a few years.

Figure 12

(a) Intrasurgical implant placement legend: 1—pterygoid; 2—intramaxillary and intrasinus; 3—extramaxillary and extrasinus; 4—traditional endosseous; 5—intramaxillary and extrasinus; 6—intramaxillary and intrasinus. (b) The same patient on CBCT taken on the day of surgery.

Figure 13

2 zygomatic implants on the left side placed (a)intramaxillary and (b) intrasinus, and the same implant placement in the same patient on the right side.

Figure 14

During the screwing of the zygomatic implant block, the alveolar process of the maxilla was chipped out because the zygomatic implant transfer was wider than the zygomatic implant neck. Thanks to the osteosynthesis plate by means of 2.0 self-tapping screws, the alveolar process was preserved, and implants were registered as being placed intramaxillary. It has been healed successfully.

Figure 15

In severe maxilla defects, the placement of zygomatic intrasinus implants is a mistake for prosthodontic reasons. In the patient above, despite the extramaxillary approach, difficulties with speech and maintaining hygiene might occur.

Figure 16

Zygomatic Orbital Floor (ZOF) classification. The most lateral point (A) was in the lower wall of the orbit. Reference points in the frontal plane on CBCT were the lowest (B). Then, two simple parallel lines perpendicular to the basal line of the transversal plane were prolonged, and the distance between them (x). Thanks to ZOF classification the risk of orbital damage is significantly lower.