Anatomical bases for the insertion of zygomatic implants

Purpose: The purpose of this study was to obtain anatomical information for installing four zygomatic implants, by measurements of maxillae and zygomata. Materials and Methods: Linear and angular measurements were obtained from the maxillae and zygomata of 40 dry skulls. Results: Based on mean and standard deviation values, the installation angle of the additional implant in the four zygoma technique was between 25° and 47°, and that of the conventional zygomatic implant was between 39° and 62°. The distance between the alveolar crest in the canine region and the lateral margin of the orbital socket was 53.42 mm, and between the alveolar crest in the premolar region and the area closest to the lateral margin of the orbital socket was 42.47 mm. Conclusions: When the angle of installation of the additional implant is less than 25° and that of the conventional zygomatic implant is less than 39°, perforation of the maxilla, zygoma, or the infratemporal fossa must be avoided. When the angle of installation of an additional implant is greater than 47° and that of the conventional zygomatic implant is greater than 62°, perforation of the orbital floor must be avoided. The length of an additional implant was greater than the length of a conventional zygomatic implant, and should be measured prior to drilling, because the greatest value found for this distance was 61.94 mm, while the maximum length of the zygomatic implants currently available on the market is 52.5 mm.     

A prospective clinical study on titanium implants in the zygomatic arch for prosthetic rehabilitation of the atrophic edentulous maxilla with a follow-up of 6 months to 5 years

Background Prosthetic rehabilitation with implant‐supported prostheses in the atrophic edentulous maxilla often requires a bone augmentation procedure to enable implant placement and integration. However, a rigid anchorage can also be achieved by using so‐called zygomatic implants placed in the zygomatic arch in combination with regular implants placed in residual bone. Purpose The aim of the present study was to report on the clinical outcome of using zygomatic and regular implants for prosthetic rehabilitation of the severely atrophic edentulous maxilla. Materials and Methods Sixty‐nine consecutive patients with severe maxillary atrophy were, during a 5‐year period, treated with a total of 69 fixed full‐arch prostheses anchored on 435 implants. Of these, 131 were zygomatic implants and 304 were regular implants. Fifty‐seven bridges were screw‐retained and 12 were cemented. The screw‐retained bridges were removed at the examination appointments and each implant was tested for mobility. In addition, the zygomatic implants were subjected to Periotest^® (Siemens AG, Bensheim, Germany) measurements. The patients had at the time of this report been followed for at least 6 months up to 5 years in loading. Results Two regular implants failed during the study period giving a cumulative survival rate of 99.0%. None of the zygomatic implants was removed. All patients received and maintained a fixed full‐arch bridge during the study. Periotest measurements of zygomatic implants showed a decreased Periotest values value with time, indictating an increased stability. Three patients presented with sinusitis 14–27 months postoperatively, which could be resolved with antibiotics. Loosening of the zygomatic implant gold screws was recorded in nine patients. Fracture of one gold screw as well as the prosthesis occurred twice in one patient. Fracture of anterior prosthetic teeth was experienced in four patients. Conclusions The results from the present study show that the use of zygomatic and regular implants represents a predictable alternative to bone grafting in the rehabilitation of the atrophic edentulous maxilla.     

The establishment of a protocol for the total rehabilitation of atrophic maxillae employing four zygomatic fixtures in an immediate loading system--a 30-month clinical and radiographic follow-up

Background: The existing approaches to the treatment of the atrophic maxilla are difficult and involve an element of risk. Purpose: The aim of the present study was to establish a new surgical/prosthetic protocol for the treatment of extremely atrophic maxillae using four zygomatic implants (ZIs) in an immediate loading system. Materials and Methods: Twelve patients were treated with the surgical placement of 48 ZIs, and the totally edentulous maxillae were rehabilitated with protocol‐type maxillary prostheses rigidly fixed to the ZIs in an immediate loading system. Follow‐up was conducted at 6 months and again at 30 months. Results: Of the 48 ZIs inserted, one implant failed to achieve osseointegration. The prosthetic components fitted well and no sinus pathology was detected in any of the patients. Conclusion: The surgical/prosthetic protocol showed that it was possible to insert four ZIs in an immediate loading system and achieve stability for up to 30 months.     

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.     

Reconstruction of the resorbed edentulous maxilla using autogenous rib grafts and osseointegrated implants

14 patients with severely resorbed edentulous maxillae underwent reconstruction by the use of autogenous rib graft on‐lays and osseointegrated Brånemark System® implants in a one‐stage procedure. 75 implants were installed. 16 (21.3%) failed to osseointegrate at the abutment connection. After a mean observation period of 5.2 years, 55 (73.3%) of the original implants were osseointegrated. 10 supplementary implants were inserted in 3 patients. At the end of the observation periods, 2 patients had overdentures and 12 had fixed prostheses. The mean marginal bone loss was 2.13mm (SD 0.47mm) the 1st year after grafting, and 2.92mm (SD 1.27mm) at the end of the follow‐up periods. Long‐term follow‐up did not show any persistent donor site discomfort. The results indicate that this technique is a conceivable alternative for patients with severe maxillary resorption.     

Maxillary bone grafting for insertion of endosseous implants: results after 12-124 months

Abstract: Insertion of endosseous implants in the atrophic maxilla is often complicated because of lack of supporting bone. Augmentation of the floor of the maxillary sinus with autogenous bone graft has been proven to be a reliable treatment modality, at least in the short term. The long‐term clinical and radiographic outcome with regard to the grafts, the implants and satisfaction of the patients with their implant‐supported overdenture was studied in 99 patients. The sinus floor was augmented with bone grafts derived from the iliac crest (83 subjects, 162 sinuses, 353 implants), the mandibular symphysis (14, 18, 37), or the maxillary tuberosity (2, 2, 2). Before implant installation, the width and height of the alveolar crest were increased in a first stage procedure in 74 patients, while in the other 25 patients augmentation and implant installation could be performed simultaneously (width and height of the alveolar crest >5 mm). Perforation of the sinus membrane occurred in 47 cases, which did not predispose to the development of sinusitis. Loss of bone particles and sequestration were observed in one (diabetic) patient only, in whom a dehiscence of the oral mucosa occurred. A second augmentation procedure was successful in this patient. Symptoms of transient sinusitis were observed in 3 patients. These symptoms were successfully treated with decongestants and antibiotics. 2 other patients developed a purulent sinusitis which resolved after a nasal antrostomy. In all cases, the bone volume was sufficient for implant insertion. 32 of 392 inserted Brånemark implants (8.2%) were lost during the follow‐up. After the healing period of the bone grafts, no sinus pathology was observed. The patients received implant‐supported overdentures (72 patients) or fixed bridges (27 patients). Overall, the patients were very satisfied with the prosthetic construction. We conclude that bone grafting of the floor of the maxillary sinus floor with autogenous bone for the insertion of implants is a reliable treatment modality with good long‐term results.     

Biologic outcome of single-implant restorations as tooth replacements: a long-term follow-up study

Background: The replacement of a single tooth or several teeth by means of single‐implant restorations is an increasingly used method that needs long‐term validation. Purpose: The goal of this study was to evaluate the outcome of single‐implant restorations by means of fixed restorations and to define the prognosis through marginal bone level estimations. Materials and Methods: From November 1986 to June 1998, 270 Brånemark implants (215 in the upper jaw) were installed in 219 patients (106 males). Both anterior and posterior sites were involved. Of the 263 single restorations, 28 were placed in private dental offices. The patients were followed until June 1999. Results: Twelve implants failed before or at abutment connection or within 6 months afterward. Only four implants failed later. The cumulative success rates were 93% for the implants and 96.5% for the restorations over a period of 11 years. The marginal bone loss during the first 6 months after abutment connection reached 0.71 mm and then dropped to 0.036 mm annually over a period of 10 years. Conclusions: Single‐implant restorations (Brånemark System) are a reliable treatment with a good long‐term prognosis. Failures were concentrated during the healing period and early loading phase.     

Clinical and radiographic evaluation of small-diameter (3.3-mm) implants followed for 1-7 years: a longitudinal study

Implants with a small diameter may be used where bone width is reduced or in single-tooth gaps with limited mesiodistal space, such as for the replacement of lateral maxillary or mandibular incisors. The purpose of the present longitudinal study was to compare the prognosis of narrow implants (3.3-mm-diameter) to standard (4.1-mm-diameter) implants. Over a 7-year period, 122 narrow implants were inserted in 68 patients to support 45 partial fixed prostheses (PFD) and 23 single-tooth prostheses (ST). Furthermore, 120 patients received 208 standard implants and were restored with 70 PFD and 50 ST, respectively. Clinical and radiographic assessment data were provided. Six (1.8%) out of 330 implants failed. Cumulative survival and success rates were calculated with life-table analyses processed by collecting clinical and radiographic data. For narrow implants, the cumulative survival rate was 98.1% in the maxilla and 96.9% in the mandible. The cumulative success rate was 96.1% in the maxilla and 92% in the mandible. Conversely, standard-diameter implants showed a cumulative survival rate of 96.8% in the maxilla and 97.9% in the mandible. The cumulative success rate was 97.6% in the maxilla and 93.8% in the mandible. Cumulative survival and success rates of small-diameter implants and standard-diameter implants were not statistically different (P > 0.05). Type 4 bone was a determining failure factor, while marginal bone loss was not influenced by the different implant diameters. The results suggest that small-diameter implants can be successfully used in the treatment of partially edentulous patients.     

Dental implants placed in grafted maxillary sinuses: a retrospective analysis of clinical outcome according to the initial clinical situation and a proposal of defect classification

Objective of the study: To present a classification of maxillary defects necessitating sinus floor elevation procedures (SFEPs) with two objectives: (a) to propose a standardization of surgical procedures according to initial type of atrophy and (b) to allow the evaluation of the success/survival rates of implants placed in the grafted areas according to the initial situation. Materials and methods: Nine‐hundred and fifty‐two consecutive SFEP were performed on 692 patients. Initial defects were classified according to a new classification, which considered not only residual bone height below the sinus but also the width of the alveolar crest and horizontal/vertical intermaxillary relationship. Results were evaluated according to the different classes. The sinuses were grafted with autogenous bone taken from intra‐oral or extra‐oral sites: 579 SFEP were associated with vertical and/or horizontal onlay grafts to correct concomitant alveolar ridge deficits. A total of 2037 implants were inserted into the grafted sinuses either immediately or 4–6 months later. Three to 6 months afterwards, implants were loaded. The mean follow‐up was 59 months (range: 12–144 months). Results: The success rate of the reconstructive procedures varied between 93.2% and 100%, according to class of atrophy; the overall survival and success rates of implants were 95.8% and 92.5%, respectively, whereas the survival and success rates according to class of atrophy varied between 90% and 97.6%, and between 85.4% and 95.5%, respectively. Lower success rates were found in classes presenting with more severe atrophy. Conclusion: The results obtained demonstrated that sinus floor elevation, alone or in association with reconstructive procedures with autogenous bone grafts, is a reliable procedure to allow implant placement in atrophic edentulous maxillae, irrespective of the initial clinical situation. However, it must be underlined that the success rates of reconstructive procedures and implants differ according to class of atrophy, showing lower success rates in classes presenting with more severe atrophy.     

Reconstruction of the atrophic edentulous maxilla with free iliac crest grafts and implants: a 3-year report of a prospective clinical study

Purpose: The purpose of this study was to perform a longitudinal follow-up study of implant stability in grafted maxillae with the aid of clinical, radiological, and resonance frequency analysis (RFA) parameters. Materials and Methods: The atrophic edentulous maxillae in 29 patients were reconstructed with free iliac crest grafts using onlay/inlay or interpositional grafting techniques. The endpoint of the resorption pattern in the maxilla determined the grafting technique used. Endosteal implants were placed after 6 months of bone-graft healing. Implant stability was measured four times using RFA: when the implants were placed, after 6 to 8 months of healing, after 6 months and 3 years of bridge loading. Individual checkups were performed at the two later RFA registrations after removal of the supraconstructions (Procera® Implant Bridge, Nobel Biocare AB, Göteborg, Sweden). Radiological follow up of marginal bone level was performed annually. Results: Twenty-five patients remained for the follow-up period. A total of 192 implants were placed and with a survival rate of 90% at the 3-year follow up. Women and an implant position with a class 6 resorption prior to reconstruction were factors with significant increased risk for implant failure (multivariate logistic regression). Twelve of the 20 failed implants were lost before loading (early failures). The change in the marginal bone level was 0.3 ± 0.3 mm between baseline (bridge delivery) and the 3-year follow up. The implant stability quotient (ISQ) value for all implants differed significantly between abutment connection (60.2 ± 7.3) and after 6 months of bridge loading (62.5 ± 5.5) (Wilcoxon signed ranks test for paired data, p=.05) but were nonsignificant between 6 months of bridge loading and 3 years of bridge loading (61.8 ± 5.5). There was a significant difference between successful and failed implants when the ISQ values were compared for individual implants at placement (Mann-Whitney U test, p=.004). All 25 patients were provided with fixed implant bridges at the time of the 3-year follow up. Conclusion: This clinical follow up using radiological examinations and RFA measurements indicates a predictable and stable long-term result for patients with atrophic edentulous maxillae reconstructed with autogenous bone and with delayed placement of endosteal implants. The ISQ value at the time of placement can probably serve as an indicator of level of risk for implant failure.     

Bone grafting and insertion of dental implants followed by Le Fort advancement for correction of severely atrophic maxilla in young patients

The atrophic maxilla often results in lateral, anteroposterior and vertical disproportion of the maxillary arches. This paper presents the case of a 40-year-old male with a severely atrophic maxilla who underwent oral rehabilitation. He was treated with onlay and inlay iliac bone grafts followed by vestibuloplasty and dental implant placement 170 days after initial bone grafting. The dental implants were uncovered after 4 months of healing. The patient also underwent orthognathic surgery for correction of the maxillary basal bone and to improve implant positioning. At the 48-month follow-up there were no complications.     

Clinical outcome of Screw Vent implants. A 7-year prospective follow-up study

The clinical results of 85 Screw Vent implants are described with respect to 7-year success, including radiographically detectable bone loss, survival and prosthetic quality. The 1-year results of the same material have been reported previously (De Bruyn et al. 1992). Implants were considered as successful when they were meeting with the success criteria proposed by the European Academy for Periodontology. From the 85 implants originally installed, 16 failed during the 7-year interval (18.8%), 6 were unaccounted for (7%), 21 (24.7%) did not meet the success criteria yet survived and 42 implants (49.4%) were successful. The success rate was 65.2% for the mandibular and 43.5% for the maxillary implants. Implant failures were irrespective of implant length, smoking habits, prosthetic quality or oral hygiene level. From 24 patients with a corresponding number of 60 implants, radiographs were available for bone loss analysis. The mean bone loss after 7 years was 2.92 mm (range -0.5 to 6.3) 18 out of 60 examined implants (30%) showed unacceptable radiological bone loss beyond the critical value of 2.7 mm. Implant material analysis and histomorphometric analysis of a retrieved implant are discussed. In the present clinical study, the Screw Vent implant system does not meet the success criteria proposed by the European Academy for Periodontology. The ongoing bone loss increases the risk for future implant failures and peri-implant disease.     

Complications related to zygomatic implants placement: A retrospective evaluation with 5 years follow-up

This retrospective study assessed zygoma implants in patients treated for upper maxilla extreme atrophy, trauma, cleft palate, or failed reconstruction.The implants were placed using Quad (4 zygoma implants) or mixed (zygoma and conventional implants in premaxilla) surgical technique, with intra-sinus or extra-sinus approach, followed by immediate or deferred loading. Clinical and radiographic evaluations were carried out at 5-year follow-up from loading. Implant survival, symptoms and signs of sinusitis, radiological alterations in terms of mucosal thickening or obliteration of the maxillary sinuses, oroantral communications, and peri-implant soft tissues were examined.A total of 42 patients, with 116 zygoma implants, were included in the study. The cumulative survival rate was 97.41%. One zygomatic bone fracture was assessed. Eight patients reported sinusitis, and two showed oro-antral communications. A comparison between mean pre- and post-operative Lund–Mackay scores showed a statistically significant increase of sino-nasal disease in the post-operative scores (p = 0.0019). Mucositis and gingival recession was observed in 21 and 8 implants respectively. Average recession was 2.52 ± 2.35 mm.According to our results, placement of zygoma implants has proved to be a predictable procedure, with a lower rate of severe complications compared to other treatment options in extreme upper jaw atrophy.