Immediate occlusal loading of extrasinus zygomatic implants: A prospective cohort study with a follow-up period of 8 years

Abstract

The aim of this study was to evaluate the long-term success rate of immediate occlusal loading of extrasinus zygomatic implants after an 8-year follow-up. From 62 patients who needed implant treatment in 2003, 25 patients who presented with maxillary atrophy met the inclusion criteria and agreed to participate in the study. All patients received fixed dentures under immediate occlusal loading supported by extrasinus zygomatic implants associated with anterior standard implants. No bone grafting procedures were performed. During the 8-year follow-up period, 21 patients underwent clinical evaluation and radiographic examinations every 6 months. This study conforms to the STROBE guidelines regarding prospective cohort studies. 40 extrasinus zygomatic and 74 anterior standard implants were evaluated. All patients were clinically free of signs and symptoms of sinus disturbance at all follow-up appointments. After 8 years, the success rates of extrasinus zygomatic implants, standard anterior implants and definitive prostheses were 97.5%, 95.9% and 95.2%, respectively. Within the limits of this study, immediate occlusal loading of extrasinus zygomatic implants presents a predictable treatment option for the atrophic maxilla.

Edentulousness causes a reduction of masticatory function and changes in appearance that can lead to psychological issues, such as depression and poor self-esteem, as well as restriction of social activities. When edentulism occurs in the maxilla, the lack of labial support can be associated with premature aging. In general, the treatment of this condition consists of the placement of conventional dentures, implant-retained overdentures, or implant-supported fixed dentures, the latter being the option of choice for most patients.

The rehabilitation of edentulous subjects with extreme bone resorption with fixed dentures can be a challenge due to inadequate bone volume to anchor standard implants. To avoid complex grafting procedures of bone reconstruction, as well as discomfort, sensitivity and pain, zygomatic implants are proposed as an alternative to rehabilitate the atrophic maxilla.

The original zygoma anchored implant technique, proposed by Brånemark, recommends that these implants should be placed through the maxillary sinus and anchored apically in the zygomatic bone. The extrasinus zygomatic technique has been widely used to avoid the sinus access ( Fig. 1 ), which minimizes the risk of sinusitis. The prosthetic outcome of extrasinus zygomatic implants is improved by better positioning of the prosthetic platform.

Fig. 1
Original Brånemark technique for zygomatic anchoraging (A), and the extrasinus technique (B). Note the emergence of the extrasinus zygomatic implant closer to the top of the crest of the ridge.

Several studies have reported satisfactory success rates when performing the two-stage surgical technique, but during healing, the patients may associate chewing, phonetic and aesthetic problems with the transitional prosthesis. To avoid these issues, the immediate loading protocol has been proposed to improve patient comfort and masticatory function and to reduce treatment time.

Although extrasinus zygomatic implants have been widely used to rehabilitate atrophic maxilla with success, there is a lack of clinical data to support the use of immediate loading with extrasinus zygomatic implants. The aim of this study was to evaluate the long-term success rate of immediate occlusal loading of extrasinus zygomatic implants after an 8-year follow-up period.

Materials and methods

The STROBE guidelines were used to ensure the reporting of this prospective cohort study. From a total of 62 patients under treatment in a private dental office at Campinas city (São Paulo, Brazil) between January and December 2003, 25 were selected and agreed to participate in the study.

The primary inclusion criteria were: subjects presenting complete or partial edentulous maxilla, when the extraction of remaining teeth was indicated; impossibility of inserting 5–6 standard implants in the anterior region of the maxilla; presence of maxillary posterior bone height ranging from 1 to 3 mm in the premolar and molar regions; and anterior maxillary height of at least 10 mm to allow the placement at least of two standard implants. Exclusion criteria were: general contraindications for oral surgery; poor oral hygiene; pregnancy; and any history of chemotherapy or radiotherapy. Patients in whom the insertion torque was lower than 35 Ncm were also excluded.

Others treatment options, including bone grafting procedures or conventional prosthesis, were offered to all patients but all were rejected. All patients included in the study had to sign a written consent form and were followed-up for 8 years with radiographs and clinical examinations at 6 month intervals.

Cone beam computed tomography, study plaster models articulated in a semi adjustable articulator and clinical photographs were used for the rehabilitation planning of all selected patients.

All patients received 2 g of cephalexin intravenously 1 h before surgery and were instructed to wash their mouths with 2% chlorhexidine solution for 30 s immediately prior to surgery. The operations were carried out by same surgeon (RMM), using the surgical protocol for extrasinus implants ( Fig. 2 ) published in Miglioranca et al. in 2011. Osteotomies for the placement of the anterior standard implants (NobelReplace Tapered, Nobel Biocare, Yorba Linda, CA, USA) were performed, according to the manufacturer’s instructions, for the immediate occlusal loading protocol.

Fig. 2
Drilling access (A), preventing sinus membrane damage (B) for extrasinus zygomatic implant installation (C).

The platforms of the zygomatic implants emerged over or close to the top of the crest of the residual alveolar ridge. Straight abutments were tightened to the implants with 32 Ncm of torque. After the abutments were placed, the surgical wounds were sutured with polyglactin 4–0 (Vicryl, Ethicon, São José dos Campos, Brazil).

Postoperatively, all patients received 32 mg of methylprednisolone to prevent excessive facial swelling and 875 mg of amoxicillin antibiotic prophylaxis (500 mg ciprofloxacin for penicillin-allergic subjects) twice a day for 7 days. A combination of codeine phosphate (30 mg) and paracetamol (500 mg) was also administered to reduce postoperative pain. Patients were advised to rinse their mouths carefully with chlorhexidine solution after each meal for the next 14 days.

A provisional screw-fixed implant-retained denture was provided for all patients within 24 h of implant placement ( Fig. 3 ). To achieve this, impressions were made immediately after surgery with open-tray transfers and polyether impression material (Impregum, 3M ESPE, St. Paul, MN, USA). The transfers were splinted with a low shrinkage modelling resin (Pattern Resin, GC America, Alsip, IL, USA). Working plaster models were obtained (Durone IV, Dentisply, Petrópolis, RJ, Brazil) and an implant-screwed wax rim was fabricated.

Fig. 3
Occlusal view of provisional denture. Note the position of screw access openings placed on the occlusal/incisal surface mesial to the first molars.

The centric relation was recorded in the wax rim on the morning after surgery. Aesthetic and functional try-ins of the artificial teeth were performed, and as soon as they were approved, the provisional prostheses were finalized. The occlusion was verified and adjusted. All patients were instructed to use interdental brushes, dental floss and an oral hygiene system based on the use of a high-pressure water spray twice daily.

Patients were scheduled for check-up examinations on the tenth day after the installation of all acrylic prostheses, for suture removal and occlusion checking. Six months later the provisional prostheses were replaced by definitive, metal bar reinforced, prostheses with 10–12 units, and a cantilever length ranging from 8 to 14 mm.

Every 6 months during the 8 year follow-up period, all screw-retained prostheses were removed and the implants were evaluated. The implant success was assessed according to the following clinical and radiographic parameters : absence of pain; absence of progressive marginal bone resorption or peri-implant radiolucency; and absence of excessive bleeding during peri-implant probing or implant mobility. On reinsertion, the prostheses were polished and new screws were used.

Results

Among the 25 selected patients, 21 patients (8 men and 13 women) with a mean age of 55.14 ± 6.66 years were evaluated for 8 years post-implantation. Three patients were lost to follow-up and one died.

In the sample followed, 14 subjects smoked more than 10 cigarettes/day. The opposing arch exhibited natural dentition in three patients and implant-supported fixed dentures in 12. Five patients had a combination of natural dentition and implant-supported fixed prostheses and one patient had already presented with an overdenture in the opposing arch ( Table 1 ).

Table 1
Characteristics of patients treated with extrasinus zygomatic implants.
Patient Age Gender Smoking * Opposing dention Number of implants
Extrasinus zygomatic Standard anterior
1 56 M No IFP 2 4
2 49 M Yes ND 2 4
3 59 M No IFP 2 3
4 63 F Yes IFP 2 4
5 52 F Yes ND + IFP 2 4
6 69 M Yes OD 2 4
7 46 F No IFP 2 3
8 55 M Yes IFP 2 4
9 57 F No ND + IFP 2 2
10 51 F Yes ND + IFP 2 2
11 49 F Yes IFP 1 5
12 56 F No IFP 2 4
13 53 F No IFP 2 4
14 59 F Yes IFP 2 4
15 62 F Yes ND 2 4
16 43 F Yes ND + IFP 2 4
17 61 M Yes ND + IFP 1 3
18 54 F No IFP 2 4
19 62 F Yes IFP 2 2
20 44 M Yes ND 2 4
21 58 M Yes IFP 2 2
Only gold members can continue reading. Log In or Register to continue

Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Immediate occlusal loading of extrasinus zygomatic implants: A prospective cohort study with a follow-up period of 8 years
Premium Wordpress Themes by UFO Themes