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.
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.
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.
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 .
|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|
|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|
|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|
|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|