Implants in the zygomatic bone for maxillary prosthetic rehabilitation: a systematic review


The purpose of this systematic review was to evaluate clinical studies on the follow-up survival of implants inserted in the zygomatic bone for maxillary rehabilitation. A comprehensive search of studies published from 2000 to July 2012 and listed in the PubMed/MEDLINE, Embase, and Cochrane Library databases was performed in accordance with the PRISMA statement. Relevant studies were selected according to predetermined inclusion and exclusion criteria. The initial database search yielded 751 titles. After filtering, 313 abstracts were selected, culminating in 42 full text articles. Application of eligibility criteria led to the elimination of 17 articles. Hence 25 full-text articles were considered clinically relevant and were included. Calculations of the interval survival rates and cumulative survival rates of implants could be carried out on the data extracted from the final list of included studies for the different time intervals. These studies reported the insertion of a total of 1541 zygomatic implants and 33 implant failures. Failure generally occurred during the first year interval and was related to clinical complications, such as recurrent acute and chronic sinusitis. After a 36-month follow-up, the survival rate was 97.86%. Additional studies with longer follow-up periods, including the number of zygomatic implants inserted and details of the variations in the surgical techniques used and the impact of the maxillary morphology are still required.

Brånemark et al. and others have suggested that oral implants may be fixed in the zygomatic bone, alone or in combination with conventional implants, for the rehabilitation of an atrophic maxilla, or as an attachment system after a hemimaxillectomy. The zygomatic bone allows anchoring far from the occlusal level and presents regular and compact trabecular bone with 98% of bone density. For these reasons, some have suggested that zygomatic implants could be used as an alternative for fixed rehabilitation in edentulous patients. The use of zygomatic implants increases treatment success and decreases the use of bone grafts, the number of surgical steps, and the length of treatment. However, there are factors that are important to consider during the surgical–prosthetic planning of zygomatic implants, such as the size and extension of the nasal cavities, bone quantity, number and size of the implants, and the surgical technique. Clinical complications have been reported after implant insertion, including fracture of the prosthetic veneer and maxillary sinus infections requiring removal of the zygomatic implant.

The aim of this systematic literature review was to identify relevant clinical studies on zygomatic implants regarding their failure and clinical complications during follow-up. Two hypotheses were tested: (1) implant survival is reduced during the first year, and (2) the failure rate is not influenced by the number of zygomatic implants.


Search strategy

This systematic review was performed in accordance with the PRISMA statement and Cochrane guidelines. PubMed/MEDLINE, Embase, and Cochrane Library databases were searched for relevant articles published in English from 2000 to July 2011. The studies were grouped according to whether they evaluated zygomatic implants for maxillary rehabilitation. The search was updated in July 2012. A broad search strategy was pursued to capture relevant studies on zygomatic implants, grafting, bone resorption, techniques for the insertion of zygomatic implants, implant complications and failures, and patient satisfaction. The keywords ‘zygomatic implants’, ‘follow-up’, ‘clinical study’, ‘dental implants’, and ‘edentulous maxilla’ were used. Data from longitudinal studies were included, and article references were searched to identify additional relevant studies.

Study selection

The literature search was conducted by two independent individuals (AM and DMS). Studies were selected on the basis of their titles and abstracts according to the exclusion criteria for abstracts and full-text articles. Agreement between the readers was determined statistically, and any conflict was resolved by discussion or the analysis of a third reader (MCG). This procedure was applied at all selection stages. The full-text articles were evaluated by the readers using a pilot test form.

Inclusion and exclusion criteria

The inclusion criteria were: studies reporting clinical series of zygomatic implants with a follow-up period of at least 2 years; studies including patients with severely deficient edentulous maxillas, oro-nasal communication, and cases of tumour resection of the maxilla that could not be rehabilitated except with conventional dental implants due to a lack of bone; partially or totally edentulous patients; studies in which immediate or late function protocols were applied. Randomized controlled clinical trials (RCTs), cohort studies, case–control studies, and cross-sectional studies were included.

The exclusion criteria were: studies without an initial evaluation at 6–12 months after implant/prosthesis loading; case reports, comments, systematic reviews, and animal studies; non-oral implants (hip/knee). If necessary, the exclusion criteria were reviewed and the abstracts were reassessed until a complete definition of the exclusion criteria was determined.

Outcomes and variables

For each study included, the following information was extracted: year of publication; number of patients in whom zygomatic implants were placed; setting and country of the study; whether the patients used partial or complete dentures; implant manufacturer and instruments for measuring failure; whether the implant had a treated surface; type of implant loading; type of prosthesis installed; clinical complications reported before and after insertion of the final prosthesis, including other prosthetic complications reported during the follow-up period; whether the zygomatic/conventional implant was removed; length of the zygomatic implant; surgical protocol used; number of zygomatic implants placed and failed; number of conventional implants placed and failed; follow-up period range; and survival rate of the zygomatic implants.

Data synthesis

For selection of the references, the titles were evaluated and the kappa statistic was calculated to define agreement between the answers. Studies were evaluated regarding feasibility of data synthesis (qualitative and quantitative). All implants were classified into failure and survival groups. Failures included implants removed regardless of the cause, and survivals represented stable implants without signs of pathology, mobility, resistance to removal torque, pain, and peri-implantitis. Clinical and radiographic examinations evaluating peri-implant bone loss or a residual sinus disease, as well as the use of instruments for measuring zygomatic implant integrity, were also recorded. The results were summarized in tables and charts.

The survival of zygomatic implants was calculated by Kaplan–Meier method. The failure rate was determined as the percentage of implants lost relative to the number of implants inserted for each study. The statistical analysis was performed using IBM SPSS version 19.0 statistical software (IBM Corp., Armonk, NY, USA).


Study selection and characteristics

The search retrieved 751 references, including 382 from Medline, 264 from PubMed, 91 from Embase, and 14 from the Cochrane Library. After duplicate references had been removed, 292 studies were selected for the data synthesis ( Fig. 1 ). The search update resulted in 21 additional abstracts. After the 292 abstracts and 21 additional abstracts had been analyzed, 38 studies were selected (inter-reader agreement, kappa = 0.84). Reference tracking revealed an additional four papers, for a total of 42 full-text papers in the eligibility assessment. After the full-texts of these articles had been examined, 25 studies were included in the final review (inter-reader agreement, kappa = 0.70). The content of the articles is summarized for comparison in Tables 1–3 .

Fig. 1
Literature search and results.

Table 1
Summary of the sample sizes and characteristics of the implants inserted in the 25 selected studies.
Study Number (% female) Setting/country PE or CE maxilla Implant manufacturer * /postoperative exams Surface type Type of implant loading Type of prosthesis
Parel et al. (2001) 27 (–) Local/Sweden CE Late FP or OVD
Bedrossian and Stumpel (2002) 22 (–) Local/USA CE Nobel Biocare/C&R exams Late PP/FP or OVD
Boyes-Varley et al. (2003) 45 (–) Local/South Africa PE and CE Nobel Biocare/C&R examinations SLA Late FP or OVD
Vrielinck et al. (2003) 29 (69.0) Local/Belgium PE and CE Nobel Biocare/clinical and CT scan Late FP or OVD
Al-Nawas et al. (2004) 24 (–) Local/Germany CE –/Clinical exam and microbial analysis Late
Malevez et al. (2004) 55 (74.5) Local/Belgium CE Nobel Biocare/C&R exams Late FP
Schmidt et al. (2004) 9 (–) Local/USA CE –/Clinical examination and microbial analysis Late OVD
Becktor et al. (2005) 16 (62.5) Local/Sweden CE Nobel Biocare/C&R exams Late PP/FP
Aparicio et al. (2006) 69 (68.1) Local/Spain CE Nobel Biocare/C&R exams Late FP
Ahlgren et al. (2006) 13 (–) Local/Norway CE Nobel Biocare/C&R exams Late FP or OVD
Bedrossian et al. (2006) 14 (–) Local/USA CE Nobel Biocare/C&R exams Oxidized Immediate PP/FP
Aghabeigi and Bousdras (2007) 4 (–) Local/England CE Nobel Biocare/clinical and cranial radiographs Machined Late FP or OVD
Davo et al. (2007) 18 (66.7) Local/Spain CE Nobel Biocare/clinical and resonance frequency analysis Machined Immediate PP/FP
Duarte et al. (2007) 12 (–) Local/Brazil CE Nobel Biocare/orthopantomographic and Waters’ view posterior–anterior radiographs Machined Immediate PP/FP
Peñarrocha et al. (2007) 21 (52.4) Local/Spain CE Straumann/C&R exams Late FP
Kahnberg et al. (2007) 76 (75.0) Multicenter/Sweden, Australia, Italy, Finland, USA, Belgium, Germany, Spain PE and CE Nobel Biocare/clinical evaluation Late FP or OVD
Davó et al. (2008) 42 (54.8) Local/Spain PE and CE Nobel Biocare/C&R exams Immediate PP/FP
Mozzati et al. (2008) 7 (42.9) Local/Italy CE Nobel Biocare/C&R exams Oxidized (TiUnite) Immediate PP/FP
Pi Urgell et al. (2008) 54 (64.8) Local/Spain CE Nobel Biocare/C&R exams Machined Late FP or OVD
Balshi et al. (2009) 56 (51.8) Local/USA CE Nobel Biocare/C&R exams Oxidized (TiUnite) Immediate PP/FP
Davó (2009) 24 (66.7) Local/Spain CE Nobel Biocare/C&R exams Machined Late FP or OVD
Bedrossian (2010) 36 (61.1) Local/USA CE Nobel Biocare/C&R exams Oxidized (TiUnite) Immediate PP/FP
Chow et al. (2010) 16 (56.3) Local/China CE Nobel Biocare/clinical and CT scan Oxidized Immediate PP/FP
Stievenart and Malevez (2010) 20 (95.0) Local/Belgium CE Nobel Biocare/C&R exams Immediate PP/FP
Maló et al. (2012) 39 (76.9) Local/Portugal CE Nobel Biocare/C&R exams Oxidized (TiUnite) Immediate PP/FP
–, Condition not reported in the study; C&R exams, clinical and radiographic examinations; CE, completely edentulous; CT, computed tomography; FP, fixed prosthesis; PE, partially edentulous; OVD, overdenture; PP, provisional prosthesis; SLA, sandblasted, large-grit, acid-etched technique.

* Nobel Biocare: Nobel Biocare, Sweden; Straumann: Straumann, Basel, Switzerland.

Table 2
Summary of clinical complications and causes of implant loss in the 25 selected studies.
Study Clinical complications ( n ) ZI length (mm) Surgical protocol
Before FP insertion After FP insertion Prosthetic complications Removal of ZI/CVIs Other complications
Parel et al. (2001) No/– 25–60 Trans-sinus incision
Bedrossian and Stumpel (2002) 30–52.5 CI
Boyes-Varley et al. (2003) No/– 30–50 LFI
Vrielinck et al. (2003) Sinusitis (2); bucco-sinus fistula (1); chronic gingivitis around ZI abutments (2) Facial oedema; infra-orbital swelling and discomfort or pain symptoms in the zygoma 30–50 CI
Al-Nawas et al. (2004) OA fistula (1) Colonization with periodontal pathogens; colonization of corresponding cheek pouch; ZI bleeding on probing
Malevez et al. (2004) Sinusitis (1) Sinusitis (5) Wearing removable denture (3) No/yes 30–52.5 PI/LFI
Schmidt et al. (2004)
Becktor et al. (2005) Sinusitis (6) Sinusitis (1) Yes/yes Gingivitis; poor oral hygiene; fistulas and local infection surrounding the implant 30–50 Mucoperiosteal elevation
Aparicio et al. (2006) Sinusitis (3) Tooth fraction in incisal aspect in metal/resin (4) No/yes Facial oedema; moderate nasal bleeding 35–52.5 Trans-zygomatic incision
Ahlgren et al. (2006) Allergy to gold alloy Allergy to OVD gold bar supported by 4 implants (1) No/yes Facial haematoma/lip burning 11–50 PI/CI
Bedrossian et al. (2006) Partial fracture on surrounding denture (2) No/no 35–52.5 CI
Aghabeigi and Bousdras (2007) No/no 30–52.5 Mucoperiosteal elevation
Davo et al. (2007) Sinusitis (1) No/yes Slight discomfort at the palatal aspect of the ZI (1) 30–52.5 CI
Duarte et al. (2007) Peri-implant inflammation Changed prosthesis due to ZI loss (1) Yes/– CI
Peñarrocha et al. (2007) Sinusitis (2) No/yes 30–42.5 Sinus slot technique
Kahnberg et al. (2007) Fistula formation, sinus-related complications; sinusitis (1); paresthesia of the right infra-orbital nerve (1) Repair of fractured tooth and modification of prosthesis due to failed CVIs Yes/yes Inflammatory hyperplasia, infection, redness, and swelling tissue around the ZI abutments; pain at night; tenderness; symptoms in relation to cold, rhinitis, and in the sinus area CI
Davó et al. (2008) Sinusitis and intraoral fistula (1) No/yes Soft tissue oedema and pain in the zygomatic region 40–52 PI/LFI
Mozzati et al. (2008) No/no Slight difficulty pronouncing the letter ‘S’ with the PP (1) 35–50 CI
Pi Urgell et al. (2008) Sinusitis (4) Yes/yes Oedema and haematoma in the infra-orbital area 30–52.5 CI
Balshi et al. (2009) Yes/yes 30–52.5 CI
Davó (2009) Sinusitis (5) OVD removal after 1 year of function (1) Yes/yes 30–52.5 PI/LFI
Bedrossian (2010) Sinusitis (3) Yes/no 30–52.5 Mucoperiosteal elevation
Chow et al. (2010) No/– CI
Stievenart and Malevez (2010) Fixed denture loss due to loss of 3 implants (1) Yes/– Soft tissue inflammation, poor oral hygiene 30–52.5 CI
Maló et al. (2012) Sinusitis (3) Sinusitis (2); OA communication (1) No/no Extra-maxillary and extra-sinusal
–, Condition not reported in the study; CVI, conventional implant; CI, crestal incision; FP, final prosthesis; LFI, Le Fort I incision; OA, oro-antral; OVD, overdenture; PI, palatal incision; PP, provisional prosthesis; ZI, zygomatic implant.

Table 3
Summary of implant failures and follow-up intervals in the 25 selected studies.
Study Follow-up intervals of the study (months) No. of zygomatic/conventional implants Failures of zygomatic implants Survival rate (%) of zygomatic implants Failures of conventional implants
Parel et al. (2001) 12–144 65/– 0 100
Bedrossian and Stumpel (2002) 0–34 44/80 0 100 7
Boyes-Varley et al. (2003) 6–30 77/– 0 100
Vrielinck et al. (2003) 3–24 67/71 2 93.0 6
Al-Nawas et al. (2004) 11–30.5 37/– 1 97.0
Malevez et al. (2004) 6–48 103/194 0 100 16
Schmidt et al. (2004) 0–84 28/10 6 78.6 3
Becktor et al. (2005) 9–69 31/74 3 94.30 3
Aparicio et al. (2006) 6–60 131/304 0 100 2
Ahlgren et al. (2006) 11–49 25/30 0 100 5
Bedrossian et al. (2006) 12–34 28/55 0 100 0
Aghabeigi and Bousdras (2007) 9–24 8/14 0 100 0
Davo et al. (2007) 6–29 36/68 0 100 3
Duarte et al. (2007) 6–30 48/– 2 95.8
Peñarrocha et al. (2007) 12–45 40/89 0 100 2
Kahnberg et al. (2007) 1–36 145/– 5 96.3
Davó et al. (2008) 12–42 81/140 0 100 4
Mozzati et al. (2008) 1–24 14/34 0 100 0
Pi Urgell et al. (2008) 1–72 101/221 4 96.04 15
Balshi et al. (2009) 9–60 110/391 4 96.37 11
Davó (2009) 6–60 39/109 1 97.40 11
Bedrossian (2010) 6–84 74/98 2 97.2 0
Chow et al. (2010) 6–24 37/– 0 100
Stievenart and Malevez (2010) 6–40 80/– 3 96.0
Maló et al. (2012) 1–36 92/77 0 100 0
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Jan 19, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Implants in the zygomatic bone for maxillary prosthetic rehabilitation: a systematic review
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