Treatment of the atrophic edentulous maxilla: short ...

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RANDOMISED CONTROLLED CLINICAL TRIAL

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Pietro Felice, Elisa Soardi, Gerardo Pellegrino, Roberto Pistilli, Claudio Marchetti, Manlio Gessaroli, Marco Esposito

Treatment of the atrophic edentulous maxilla: short implants versus bone augmentation for placing longer implants. Five-month post-loading results of a pilot randomised controlled trial

Pietro Felice, MD, DDS, PhD Resident, Department of Periodontology and Implantology, University of Bologna, Bologna, Italy

Key words

Elisa Soardi, DDS

augmentation, RCT, short implants

Purpose: To evaluate whether short (5 to 8.5 mm) dental implants could be a suitable alternative to longer (>11.5 mm) implants placed in atrophic maxillae augmented with autogenous bone for supporting dental prostheses. Materials and methods: Twenty-eight patients with fully edentulous atrophic maxillae having 5 to 9 mm of residual crestal bone height at least 5 mm thick, as measured on computerised tomog raphy scans, were randomised into two groups either to receive 4 to 8 short (5 to 8.5 mm) implants (15 patients) or autogenous bone from the iliac crest to allow the placement of at least 11.5 mmlong implants (13 patients). Bone blocks and the windows at maxillary sinuses were covered with rigid resorbable barriers. Grafts were left to heal for 4 months before placing implants, which were submerged. After 4 months, provisional reinforced acrylic prostheses or bar-retained overdentures were delivered. Provisional prostheses were replaced, after 4 months, by definitive screw-retained metal-resin cross-arch fixed dental prostheses. Outcome measures were: prosthesis and implant failures, any complications (including prolonged postoperative pain) and patient satisfaction. All patients were followed for 5 months after loading. Results: All patients could be rehabilitated with implant-supported prostheses and none dropped out. One bilateral sinus lift procedure failed due to infection, though short implants could be placed. One implant failed in the augmented group versus 2 short implants in 2 patients. All failures occurred before loading. Significantly more complications occurred in augmented patients: 8 complications occurred in 5 augmented patients (all complained of pain 1 month after bone harvesting from the iliac crest). No complications occurred in the short implant group. All patients were fully satisfied with the treatment and would do it again. Conclusions: This pilot study suggests that short implants may be a suitable, cheaper and faster alternative to longer implants placed in bone augmented with autogenous bone for rehabilitating edentulous atrophic maxillae. However, these preliminary results need to be confirmed by larger trials with follow-ups of at least 5 years.

Eur J Oral Implantol 2011;4(3):191–202

Resident, Department of Periodontology and Implantology, University of Bologna, Bologna, Italy

Gerardo Pellegrino, DDS Resident, Department of Oral and Maxillofacial Surgery, University of Bologna, Bologna, Italy

Roberto Pistilli, MD Resident, Oral and Maxillofacial Unit, San Filippo Neri Hospital, Rome, Italy

Claudio Marchetti, MD Associate Professor, Department of Oral and Maxillofacial Surgery, University of Bologna, Bologna, Italy

Manlio Gessaroli, MD Resident, Oral and Maxillofacial Unit, Bufalini Hospital, Cesena, Italy

Marco Esposito, DDS, PhD Freelance researcher and Associated Professor, Department of Biomaterials, The Sahlgrenska Academy at Göteborg University, Sweden Correspondence to: Dr Marco Esposito Presso Ufficio Poste Italiane, Casella Postale 34, Via Gilera 8, Arcore (MB) 20862 Italy Email: espositomarco@ hotmail.com

Felice et al Augmentation versus short implants

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Introduction

pyrig No Co t fo rP ub lica tio The aim of this randomised controlled clinical trial n te se nc e of parallel group design was to compare the seffec-

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The rehabilitation of the fully edentulous maxilla is a relatively common clinical problem. The missing dentition can be replaced by dentures, which may not always be appreciated by patients due to their instability, discomfort and negative psychological impact. The ideal solution would be an implantsupported prosthesis, however the lack of sufficient bone volume to place at least four dental implants of ‘sufficient’ length due to advanced bone resorption is a common problem. Bone heights between 10 to 12 mm are generally considered the minimal amount of bone required to place implants of sufficient length (9 to 11 mm long) to be able to guarantee a good long-term prognosis. Unfortunately, often the residual amount of maxillary alveolar bone is less than 10 mm, especially below the maxillary sinuses, therefore implant-supported prostheses are considered at a higher risk of failure1. There are three main alternative options to provide implant-supported prostheses to patients with atrophic maxillae: i) augmenting the maxillary bone, and this could be done according to different techniques2,3; ii) using zygomatic implants4 (which can also be loaded immediately5); or iii) using short implants (8 mm or less). While the scientific literature is rather extensive on augmentation techniques for the maxilla, there is not a single randomised controlled clinical trial evaluating the effectiveness of zygomatic implants6 or short implants used in totally edentulous maxillae3. The definition of ‘short’ implants is controversial since some authors consider short all those implants with a length ranging from 7 to 10 mm1, whereas other authors consider ‘short’ those implants with a designed intra-bony length of 8 mm or less7. Nevertheless, it is commonly perceived that implants 7 mm or shorter do not have a good long-term prognosis when compared with longer implants. On the other hand, short implants could be a simpler, cheaper and faster alternative to augmentation procedures if they could provide similar success rates and be simpler to place than zygomatic implants. Preliminary findings suggest that short implants may be a better alternative to various bone augmentation procedures in posterior mandibles8-10 and maxillae9-11, though followups are still too short to draw definitive conclusions. Eur J Oral Implantol 2011;4(3):191–202

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tiveness of total maxillary prostheses supported by 5 to 8.5 mm short implants versus prostheses supported by long implants (at least 11.5 mm) placed in atrophic maxillae augmented with autogenous bone. The test hypothesis was that there were no differences between the two procedures against the alternative hypothesis of a difference. This report presents the preliminary data up to 5 months after loading. At protocol stage, it was planned to follow the patients up to 5 years after loading. The present article is reported according to the CONSORT statement for improving the quality of reports of parallel-group randomised trials (http:// www.consort-statement.org/).

Materials and methods Any fully edentulous patient with an atrophic maxilla, being 18 years or older and able to understand and sign an informed consent was eligible for inclusion in this trial. The maxilla should be able to receive 4 to 8 short (5 to 8.5 mm long) implants. The residual vertical bone height at the implant sites had to be of 5 to 9 mm and bone thickness of at least 5 mm measured on computerised tomography (CT) scans (Fig 1). Patients were not admitted in the study if any of the following exclusion criteria were present: 1) general contraindications to implant surgery, 2) subjected to irradiation in the head and neck area, 3) immunosuppressed or immunocompromised patients, 4) treated or under treatment with intravenous amino-bisphosphonates, 5) affected by untreated periodontitis, 6) poor oral hygiene and motivation, 7) severe intermaxillary discrepancies, 8) uncontrolled diabetes, 9) pregnant or lactating, 10) substance abuse, 11) psychiatric problems or unrealistic expectations, 12) lack of opposite occluding dentition/prosthesis, 13) acute/chronic infection/inflammation in the area intended for implant placement, 14) participating in other trials, if the present protocol could not be properly followed, 15) referred only for implant placement, 16) extraction sites with less than 3 months of healing. Patients were categorised into three groups according to what they declared: non-smoker,

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Fig 1 Preoperative radiographs used to evaluate the amount of residual bone for including patients in the study (5 to 9 mm of bone height at least 5 mm thick at the implant sites): a) dental computerised tomography scan, b) orthopantomograph, c) lateral radiograph.

oderate smoker (up to 10 cigarettes per day) or m heavy smoker (more than 10 cigarettes per day). Patients were recruited and treated at the Oral and Maxillofacial Unit, Sant’Orsola Malpighi Hospital, University of Bologna, Bologna, Italy (Dr Pietro Felice; 14 patients); and the San Filippo Neri Hospital in Rome (Dr Roberto Pistilli; 14 patients) using similar and standardised procedures. The principles outlined in the Declaration of Helsinki on clinical research involving human subjects were adhered to. All patients received thorough explanations and signed a written informed consent form prior to being enrolled in the trial. After consent was given, eligible patients were randomised according to a parallel group design to receive either 5- to 8.5 mm-long implants or autogenous bone from the iliac crest to allow placement of identical implants at least 11.5 mm long. Bone grafting procedures were performed according to the protocol that follows. Before being anaesthetised under general anaesthesia, patients rinsed with chlorhexidine mouthwash 0.2% for 1 minute. Patients received 2.2 mg of amoxicillin with clavulanic acid (Augmentin, GlaxoSmithKline, Brentford, UK) intravenously. Local anaesthesia was delivered using articaine with adrenaline 1:100,000. The iliac crest donor site was infiltrated with local anaesthesia (lidocaine 1%) and the non-scalpelbearing hand was used to displace the skin medially before the incision was made. A 3 cm-long incision was started 1 cm behind the anterior superior iliac spine and made through the displaced skin directly over the crest. Dissection was continued following the axis of the iliac crest through subcutaneous tissues, Scarpa’s fascia and periosteum, directly over the crest.

Then, the periosteum and the overlying muscles on the top of the crest and on the medial aspect of ilium were dissected. The corticotomy of the medial portion of the anterior iliac crest was performed with a fissure bur or a reciprocating saw: two vertical cuts defined a bone portion 5 to 7 cm long. These two vertical cuts (about 1 cm long) were connected by a horizontal cut along the medial portion of the top of iliac crest (above) and with a second horizontal cut (below) in the medial surface of the iliac bone. The osteotomy of the cancellous portion was completed with chisels, obtaining a monocortical cancellous rectangular block (Fig 2). A portion of the harvested block was reduced to particulate using a bone crusher (KLS Martin Group, Tuttlingen, Germany). The wounds were routinely drained for 2 days and the overlying soft tissues were closed with three layers of sutures. After crestal incision and flap elevation, all maxillae were augmented with bilateral sinus lifts and, if necessary, with onlay bone blocks (Fig 3) harvested from the iliac crest. First, the sinuses were lifted according to a lateral window technique. After internal displacement of a bony window prepared with a piezosurgery device (Mectron Piezosurgery Device™, Mectron S.p.a., Carasco Genoa, Italy), the maxillary membranes were carefully elevated and their integrity was assessed visually and with a blunt instrument. Any laceration or perforation was noted. Sinuses were then loosely packed with granular autogenous bone from the iliac crest. Once the sinus lift procedures were completed, the anterior portion of the maxillae was augmented. Bone blocks were adjusted with the aim to achieve the best adaptation on the maxilla. Blocks were trimmed with diamond disks and laboratory stainEur J Oral Implantol 2011;4(3):191–202


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Fig 2 a) A monocortical cancellous rectangular block of bone is prepared and b) harvested from the iliac crest and divided in smaller blocks as required.

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a Fig 3 Both sinuses were opened using a lateral widow technique to be filled with particulated autogenous bone from the iliac crest and, when needed, onlay cortical blocks were fixed with two titanium screws.

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less steel burs (Horico® Dental, Berlin, Germany) under profuse saline irrigation. It was ensured that the blocks had a sufficient width and allowed for sufficient vertical augmentation for, after healing, the placement of at least 11.5 mm-long implants. Several holes were made with a 0.9 mm diameter bur on the recipient sites to stimulate bleeding. The blocks were placed on the recipient bone and were fixed with two titanium screws (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) of 1.5 mm diameter. The screw heads were slightly submerged into the blocks to avoid their protrusion. After all blocks were fixed, they were ground to remove any sharp edges. Residual gaps between blocks and the recipient bony site were filled with particulated bone from the iliac crest. The bone blocks and the maxillary windows were then covered with resorbable bar riers (Inion GTR Biodegradable Membrane System, Inion, Tampere, Finland) (Fig 4). Inion membranes (30 x 40 mm) are rigid barriers, made of a synthetic co-polymer (trimethylene carbonate l-lactide polyglycolide), which become malleable after being immersed in a plasticising solution for 30 seconds and in a curing solution for 10 minutes as suggested by the manufacturer. This allowed the membranes to be cut and moulded to fit the space exactly, then the membranes stiffened in contact with water. Eur J Oral Implantol 2011;4(3):191–202

Periosteal incisions were made to release the flaps as coronally as needed and the flaps were sutured back with Vicryl 4.0 sutures (Ethicon FS-2, Ethicon, St-Stevens-Woluwe, Belgium) until the incisions were perfectly sealed. All patients remained hospitalised for 3 days and at the hospital they were given 2.2 mg amoxicillin plus clavulanic acid intravenously twice a day. On the first day, patients received betamethasone (Bentalan, Defiante Farmacêutica, Funchal, Portugal) 4 mg intravenously both in the morning and in the evening, the following day 4 mg in the morning only, and the last day at the hospital 2 mg in the morning only. As gastro-protector, patients received omeprazole (Antra, AstraZeneca, London, UK) 40 mg intravenously in the morning. At hospital discharge, patients were prescribed 1 g of amoxicillin with clavulanic acid twice a day for 4 days, and ibuprofen 600 mg 4 times a day during meals for 1 week, not to be taken in the absence of pain. Patients were instructed to use Corsodyl gel 1% (GlaxoSmithKline) twice a day and to have a soft diet for the following 2 weeks, avoiding brushing and trauma on the surgical sites. Dentures were not allowed for 1 month, after which they were rebased and given back to the patients. Patients were reviewed after 3 and 10 days when sutures were removed. All patients were recalled for additional postoperative reviews at

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Fig 4 The maxillary windows and the bone blocks were covered with rigid synthetic resorbable barriers.

Fig 5 After 4 months of healing, flaps were elevated, the screws were removed from the blocks, and 11.5 mm-long or longer implants were placed in the augmented group.

1, 2 and 3 months after the augmentation procedure. Four months after augmentation, a second CT scan was obtained to plan the implant placement operation. The implant placement and prosthetic procedures were identical for both groups. All patients received prophylactic antibiotic therapy: 2 g of amoxicillin + clavulanic acid 1 hour prior to the intervention and rinse with chlorhexidine mouthwash 0.2% for 1 minute. All patients were treated under local anaesthesia using articaine with adrenaline 1:100,000. No intravenous sedation was used. After crestal incision and flap elevation, and removal of the titanium screws holding the bone grafts of the augmented group, four to eight dental implants either 5 to 8.5 mm long (short implant group) or longer than 11.5 mm (augmented group), when possible, were inserted (Fig 5) under prosthetic guidance using a surgical template. The dental implants used for the short implant group were ExFeel and/or Rescue implants with external connection (MegaGen Implant, Gyeongbuk, South Korea). For ExFeel implants, operators were free to choose from lengths of 7 and 8.5 mm, and diameters of 4 and 5 mm according to clinical indications and their preferences. For Rescue implants, operators were free to choose from implant lengths of 5 and 6 mm, and diameters of 6, 7 and 8 mm according to clinical indications and their preferences. ExFeel implants with external connection were used in the augmented group. Operators were free to choose implant lengths (11.5 and 13 mm) and diameters (4 and 5 mm) according to clinical indications and their preferences.

Implant sites were slightly underprepared to increase the insertion torque and the motor was set with a torque of 25 Ncm. Implants were placed with the neck flush to the bone. A submerged technique was used, cover screws were placed and flap closure was obtained with Vicryl 4.0 sutures. Intraoral radiographs (baseline) were obtained with the paralleling technique. In cases where the bone levels around the study implants were hidden or difficult to be estimated, a second radiograph was obtained. Ibuprofen 400 mg was prescribed to be taken two to four times a day during meals, as long as required. Patients were instructed to use 0.2% chlorhexidine mouthwash for 1 minute twice a day for 2 weeks, to have a soft diet for 1 week, and to avoid brushing and trauma on the surgical sites. No denture was allowed for 1 month. Sutures were removed after 10 days. After 4 months of submerged healing, implants were exposed, manually tested for stability using a torque of 15 Ncm and impressions with the pickup impression copings were taken using a polyether material (Impregum, 3M/ESPE, St. Paul, MN, USA). The vertical dimensions were registered and models were made with class 4 precision plaster and mounted in a standard articulator. Patients scheduled to receive a one-piece bar-retained overdenture received their final prostheses at this time, otherwise they received a provisional screw-retained full acrylic reinforced restoration rigidly joining all of the implants on temporary abutments within 3 weeks (Fig 6). Intraoral radiographs and clinical pictures of the study implants were taken. Four months after Eur J Oral Implantol 2011;4(3):191–202

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Fig 6 Occlusal view of one of the provisional fixed dental prostheses delivered approximately 3 weeks after implant exposure.

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delivery of the provisional prostheses, implants were manually tested for stability using a torque of 15 Ncm and definitive screw-retained metal-resin cross-arch fixed dental prostheses, rigidly joining the implants, were delivered on definitive standard titan ium abutments (Fig 7). One month later, patients were recalled for a check-up and to evaluate their satisfaction. Patients were enrolled in an oral hygiene program with recall visits at least every 6 months for the entire duration of the study. Follow-ups were conducted by a single independent outcome assessor (ES) together with the surgical operators. This study tested the null hypothesis that there were no differences between the two procedures against the alternative hypothesis of a difference. Outcome measures were: • Prosthesis failure: planned prosthesis that could not be placed due to implant failure(s) and loss of the prosthesis secondary to implant failure(s). • Implant failure: implant mobility, removal of stable implants dictated by progressive marginal bone loss or infection, and implant fracture. Stability of individual implants was measured by tightening abutment screws with a torque of 15 Ncm at abutment connection (4 months after implant placement), at delivery of the provisional prostheses and at delivery of the definitive prostheses (4 months after delivery of the provisional prostheses). • Any biological or prosthetic complications at donor and recipient sites, including prolonged postoperative pain at the donor site. • Peri-implant marginal bone level changes evaluated on intraoral radiographs taken with the parEur J Oral Implantol 2011;4(3):191–202

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will be reported in a future publication describing the 1 year post-loading clinical results. • Patient satisfaction: five months after loading (1 month after delivery of the definitive prostheses for those who received provisional prostheses), the independent outcome assessor asked the patients the following questions: a) ‘are you satisfied with the function of your implant-supported prosthesis?’ Possible answers were ‘yes absolutely’, ‘yes partly’, ‘not sure’, ‘not really’, ‘absolutely not’; b) ‘are you satisfied with the aesthetic outcome of your implant supported prosthesis?’ Possible answers were ‘yes absolutely’, ‘yes partly’, ‘not sure’, ‘not really’, ‘absolutely not’; and c) ‘would you undergo the same therapy again?’ Possible answers were ‘yes’ or ‘no’. One dentist (ES) not involved in the treatment of the patients performed all clinical assessments without knowing group allocation, therefore the outcome assessor was blinded. The sample size was calculated for the primary outcome measures (implant failure): a two-group continuity corrected chi-square test with a 0.050 two-sided significance level will have 80% power to detect the difference between a proportion of 0.100 and a proportion of 0.300 for patients experiencing at least one implant failure (odds ratio of 3.857) when the sample size in each group is 72. However, it was decided to recruit only 14 patients in each group. A computer-generated restricted randomisation list was created. Only one of the investigators (ME), not involved in the selection and treatment of the patients, was aware of the randomisation sequence and could have access to the randomisation list stored in his password protected portable computer. The randomised codes were enclosed in sequentially numbered, identical, opaque, sealed envelopes. Envelopes were opened sequentially after eligible patients signed the informed consent form to be enrolled in the trial. Therefore, treatment allocation was concealed to the investigators in charge of enrolling and treating the patients. All data analysis was carried out according to a pre-established analysis plan. A biostatistician with expertise in dentistry analysed the data, without

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pyrig n 197 No Co t fo rP ub lica tio Fig 7 Definitive crossn te arch screw-retained ss e n c e n

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knowing the group codes. The patient was the statistical unit of the analyses. Differences in the proportion of patients with prosthesis failures, implant failures and complications (dichotomous outcomes) were compared between groups and centres using Fisher’s exact probability test. The Mann–Whitney U test was to be used to compare the medians of the two groups for patient satisfaction. All statistical comparisons were conducted at the 0.05 level of significance.

Results Twenty-eight patients were considered eligible and were consecutively enrolled in the trial. Each centre enrolled 14 patients, following the research protocol, who were to be randomised in two equal groups of 7 patients each. An additional 18 patients were screened for eligibility but 7 refused to participate in the trial since they were not willing to use their own bone from the iliac crest. Nine patients had an intermaxillary discrepancy judged by the operators to be too severe for receiving short implants and 2 patients were under treatment with intravenous amino-bisphosphonates. Fourteen patients should have been allocated in each group, but due to a communication mistake with the Rome centre, 15 patients received short implants and 13 were augmented for longer implants.

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prostheses: a) augmented group, b) short implant group, c) orthopantomograph showing a prosthesis supported by eight implants at least 11.5 mm long placed in augmented bone, d) orthopantomograph showing a prosthesis supported by seven short implants (5 to 8.5 mm long).

No patient dropped out and the data of all patients were evaluated in the statistical analyses. Only one deviation from the research protocol occurred: due to a communication error, one patient who should have been augmented received short implants instead. Patients were recruited and treated from June 2009 to April 2010. The follow-up of all patients was 5 months after implant loading. The main baseline patient characteristics are presented in Table 1. All 13 patients of the augmented group were treated with bilateral sinus lifts and 10 patients received additional onlay blocks. Ninetytwo implants were placed in the augmented group and 86 in the short implant group. With the exception of gender and number of implants, there were no apparent significant baseline imbalances between the two groups. Table 2 presents the frequencies of the implant lengths and diameters used by study group. The main results are summarised in Table 3. One augmentation procedure (bilateral sinus lift) was not successful and therefore it was not possible to place implants with the planned length of at least 11.5 mm. Implants 7 mm long had to be placed instead. All prostheses could be placed and were successful 5 months after loading. One implant failed in the augmented group versus two implants in two patients in the short implant group. All failures occurred prior to loading. The Eur J Oral Implantol 2011;4(3):191–202


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Table 1 Patient and intervention characteristics.

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Females

Augmented (n = 13)

Short implants (n = 15)

8 (62%)

4 (27%)

Mean age at implant insertion (range)

52 (29–65)

56 (41–65)

Smokers (all moderate smokers)

1 (8%)

4 (27%)

Total number of inserted implants

92

86

Average number of implants in each patient

7.1

5.7

Number of implants placed with less than 25 Ncm torque

67 (7 patients)

86 (15 patients)

Mean length of placed implants (SD)

11.6 (1.3) mm

7.6 (1.2) mm

Mean diameter of the placed implants (SD)

4.07 (0.25) mm

4.49 (0.76) mm

Number of overdentures

2 (15%)

9 (60%)

Number of metal-resin cross-arch fixed dental prostheses

11 (85%)

6 (40%)

Number of prostheses supported by 4 implants

1 (8%)

3 (20%)


0 (0%)

2 (13%)


3 (23%)

6 (40%)


2 (15%)

4 (27%)


7 (54%)

0 (0%)

ifferences in proportions of implant failures was d not statistically significant (Fisher’s exact test P = 1.00; difference in proportions = 0.06; 95% CI -0.28 to 0.17). The implant that failed in the augmented group (4 × 11.5 mm) was in position 26, was found not to be osseointegrated at abutment connection and was not replaced. One of the implants that failed Table 2 Length and diameters of the implants. Implant length

Augmented (n = 92)

Short (n = 86)

5 mm

0

10

6 mm

0

2

7 mm

5

23

8 mm

0

3

8.5 mm

0

48

10 mm

3

0

11.5 mm

61

0

13 mm

23

0

Implant diameter

Augmented (n = 92)

Short (n = 86)

4 mm

86

57

5 mm

6

17

6 mm

0

11

7 mm

0

1


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in the short implant group (4 × 7 mm) was in position 14, was found not to be osseointegrated at abutment connection and was replaced by a 5 × 8.5 mm implant. The other failed implant (4 × 8.5 mm) was in position 25 and was placed slightly supra crestally. It become exposed and was found mobile 2 months after its placement. It was painful at palpation and was probably lost because of the overload caused by the denture. It was replaced with another 4 × 8.5 mm implant. Three complications occurred in two patients of the augmented group: in one patient subjected to bilateral sinus lift alone, after 2 weeks 2 buccal dehiscences (one per side) appeared in the proximity of the sinus windows (Fig 8). The authors suspected an infectious aetiology and prescribed antibiotics (ceftriaxone, 1 mg intra-muscularly twice a day for 1 week), anti-inflammatory beclomethasone (ClenilA, 0.8 mg aerosol) twice a day for 15 days, antiseptic and decongestant (argotone nasal drops) twice a day for 15 days, and another decongestant xylo metazoline (Otrivine) nasal spray 3 times a day for 1 week. After 1 week, the particulated bone from both sinuses was removed, but after debridement both dehiscences worsened. Both dehiscences were still present at implant placement 4 months after sinus lifting, though the patient never had swell-

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Summary of the main results up to 5 months after loading.

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Table 3

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Augmented (n = 13)

Short implants (n = 15)

Prosthesis failures

0

0

Implant failures (all prior to loading)

1

2

Augmentation procedure failures

1

Not applicable

Complications before implant placement

3 (2 patients)

0

Complications after implant placement

0

0

Number of patients with postoperative pain at 1 week

13

0

Number of patients with postoperative pain at 1 month

5

0

Number of patients with postoperative pain at 2 months

2

0

ing, pain or symptoms from sinusitis. Five 7 mm and three 10 mm-long implants could be placed (Fig 9) and during the submerged healing periods of the implants both dehiscences healed (Fig 10). The other patient developed an early dehiscence in the palate, which spontaneously healed in 2 weeks. With regard to postoperative pain at the donor sites (the iliac crest), after 1 week all 13 patients complained of pain and were still taking analgesics. Five patients also complained 1 month after the grafting procedure and were still taking analgesics. Two months after grafting, two patients were still in pain and were taking analgesics. Considering as a complication the postoperative pain at donor sites 1 month after the harvesting procedure, five patients experienced eight complications in the augmented group versus none in the short implant group. There were significantly more patients experiencing complications in the augmented group (Fisher’s exact test P = 0.013; difference in proportions = 0.38; 95% CI 0.11 to 0.65). There were no differences for implant failures and complications between the two centres. Two implants failed in two patients in centre 1 versus one implant in centre 2. The difference in proportions of implant failures was not statistically significant (Fisher’s exact test P = 1.00; difference in proportions = 0.06; 95% CI -0.28 to 0.17). Three patients experienced six complications in centre 1 versus two patients experiencing one complication each in centre 2 (Fisher’s exact test P = 1.00; difference in proportions = 0.07; 95% CI -0.21 to 0.35) Five months after loading (1 month after delivery of the definitive prostheses for those who received provisional prostheses), all patients declared to the

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Fig 8 One of the bilateral dehiscences which developed 2 weeks after sinus lifting.

Fig 9 Orthopantomograph of the patient who developed a bilateral sinus infection. Five 7 mm and three 10 mm-long implants could be placed and were used to retain a cross-arch fixed dental prosthesis. Fig 10 During the implant submerged periods, both dehiscences healed.



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This pilot trial was designed to provide some preliminary data on which could be the most effective approach to rehabilitate totally edentulous atrophic maxillae with 5 to 9 mm of residual bone height using implant-supported prostheses. Five to seven 8.5 mm-long implants were compared with longer implants (at least 11.5 mm long) in bone augmented with autogenous bone from the iliac crest via sinus lift procedures and onlay bone blocks. Autogenous bone grafting is generally considered the gold standard procedure for augmenting atrophic jaws. These very preliminary results suggest similar clinical shortterm outcomes, however short implants achieved the same goal in half of the time (in approximately 5 months versus 9 months), at a cheaper cost (one less surgical procedure in general anaesthesia and fewer implants placed) and with less postoperative discomfort (all augmented patients in pain after 1 week versus none who received short implants, and about 40% of patients were still in pain 1 month after the augmentation procedure). All complications occurred in the augmented group (a bilateral sinus infection and a minor dehiscence) during the healing phase of the grafts. The augmentation procedure is also far more technically demanding than placing short implants, requiring a skilful maxillofacial surgeon and specialised auxiliary staff. The major drawback of short dental implants is the unknown medium and long-term prognosis when compared to longer implants, which are expected to have a better prognosis. In addition, on average, only 5.7 short implants were placed per patient versus 7.1 longer implants in the augmented group. This baseline imbalance was due to the fact that there was not sufficient bone to place more short implants, especially because the 5 mm-long implants commercially available for this study had a diameter of 6 mm, which is too large to be used in the anterior area and often even difficult to be used in the posterior areas9,10. This suggests that there is a clinical need

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Discussion

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independent outcome assessor to be highly satisfied with both the function and aesthetics of their implant-supported prostheses and that they would undergo the same therapy again.

pyrig No Co t fo rP ub lica tio to evaluate the outcome of 5 mm-long implants with n te ss e n c e diameters of 4 to 5 mm. In contrast, the augmenta-

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tion procedure was not only successful for allowing the placement of longer implants but also allowed for the placement of more implants. Only longer follow-ups will allow for an evaluation of the clinical relevance of placing additional implants in fully edentulous maxillae. Another interesting aspect is that 5 months after initial loading all patients, independent of the treatment received, were completely satisfied with both the function and aesthetics of their implant supported prostheses, and would undergo the same treatment again. This uniform response is surprising, especially for those two patients who had to take analgesics for 2 months after augmentation and for the patient who had a revision surgery at both sinuses because of infection. A possible explanation is that the satisfaction of having a fixed prosthesis obviated all the pain the patient had to go through to get it. It is difficult to compare the current results with those of other similar trials since there are no other trials investigating alternative options to treat a totally edentulous maxilla. While short-term data evaluating the effectiveness of short implants as an alternative to bone augmentation procedures in posterior partially edentulous mandibles has given some clear indications that, at least 1 year after loading, significantly better clinical outcomes can be obtained using short implants8-10,12, the situation in the posterior maxilla is less clear. This is because the only pilot trial testing this hypothesis found no significant differences or trends, though longer treatment periods were required when lifting sinuses9,10. It is an interesting observation that a minimal amount of residual bone height such as a mean of 4.5 mm (range from 3 to 6 mm) below the maxillary sinus seemed to be sufficient to ensure short-term high success rates of implants loaded just 45 days after their placement11. All of these indications suggest that small amounts of residual bone height are able to efficiently support dental implants up to 1 year after function. The real question now is whether these positive results for short implants can be maintained for decades of function, but only longer follow-ups can answer to this question. So what should one do in the meantime, when

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encountering patients with atrophic jaws requiring implant-supported prostheses? The possible therapeutic alternatives (short implants or longer implants in augmented bone) should be honestly discussed, explaining the potential advantages and disadvantages and leaving the final decision to the patient. The alternative of tilted implants13 in patients such as those included in this trial is not a viable option since the amount of residual bone was too scarce to allow placement of implants longer than 10 mm. However, some additional considerations could be made. For instance, in cases of sinus lift it is known that bone substitutes can be a valid alternative to autogenous bone3,14-17, which means less morbidity for the patient. In contrast, the possibility of using blocks of bone substitutes for reconstructing a maxilla is still largely anecdotal2. The main limitation of the present trial is the small sample size. This study was designed as a pilot study to provide an idea of the outcome of the comparison. Nevertheless, the sample size was big enough to disclose a significant difference in post-augmentation complications between the two procedures in favour of the less invasive approach. When the data from other trials are available, it could be possible to combine the present findings with those of similar trials in a meta-analysis to effectively obtain larger samples sizes and a more precise estimate of the reality. Curiously, there was an error in the present study with respect to patient allocation. Specifically, one patient erroneously received short implants when he should have been augmented. After an investigation, the present authors found that the error was a purely casual human mistake which occurred when the group allocation for that patient was communicated from the main centre where the envelopes where stored to the surgical unit in Rome. There are no serious consequences of this error on the validity of the study apart from a further reduction of the sample size. Both techniques were tested in real clinical conditions and patient inclusion criteria were rather broad, therefore the results of the present investigation can be generalised with confidence to a wider population with similar characteristics. However, both surgeons were experienced with both techniques and this factor might limit extrapolation of the results.

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Five months after loading, both techniques provided good and similar results, however, short implants might be a preferable choice in the short term since the treatment was faster, cheaper and associated with less morbidity than placing longer implants in augmented bone. These very preliminary results must be confirmed by larger trials with longer follow-ups.

Conflict of interest This trial was partially supported by MegaGen, Korea.

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