Immediate and early loading of Straumann implants with a chemically ...

Jeffrey Ganeles Axel Zo¨llner Jochen Jackowski Christiaan ten Bruggenkate Jay Beagle Fernando Guerra

Immediate and early loading of Straumann implants with a chemically modified surface (SLActive) in the posterior mandible and maxilla: 1-year results from a prospective multicenter study

Authors’ affiliations: Jeffrey Ganeles, Nova Southeastern University, Fort Lauderdale, FL, USA and Florida Institute for Periodontics and Dental Implants, Boca Raton, FL, USA Axel Zo¨llner, Jochen Jackowski, Universita¨t Witten-Herdecke, Witten, Germany Christiaan ten Bruggenkate, VU University Medical Center, Amsterdam and Rijnland Hospital, Leiderdorp, The Netherlands Jay Beagle, Private practice, Indianapolis, IN, USA Fernando Guerra, Faculdade de Medicina de Coimbra, Coimbra, Portugal

Key words: bone-level changes, early loading, immediate loading, implants, implant

Correspondence to: Dr Jeffrey Ganeles Florida Institute for Periodontics and Dental Implants 3020 North Military Trail, Suite 200 Boca Raton FL 33431 USA Tel.: þ 1 561 912 9993 Fax: þ 1 561 912 9883 e-mail: [email protected]

denture) out of occlusal contact either immediately (immediate loading) or 28–34 days later (early loading group), with permanent restorations placed 20–23 weeks after surgery.

survival, multicenter, radiographs, randomized Abstract Objective: Immediate and early loading of implants can simplify treatment and increase patient satisfaction. This 3-year randomized-controlled trial will therefore evaluate survival rates and bone-level changes with immediately and early loaded Straumann implants with the SLActive surface. Material and methods: Partially edentulous patients
18 years of age were enrolled. Patients received a temporary restoration (single crown or two to four unit fixed partial

The primary endpoint was change in crestal bone level from baseline (implant placement) to 12 months; the secondary variables were implant survival and success rates. Results: A total of 383 implants (197 immediate and 186 early) were placed in 266 patients; 41.8% were placed in type III and IV bone. The mean patient age was 46.3  12.8 years. Four implants failed in the immediate loading group and six in the early loading group, giving implant survival rates of 98% and 97%, respectively (P ¼ NS). There were no implant failures in type IV bone. The overall mean bone level change from baseline to 12 months was 0.77  0.93 mm (0.90  0.90 and 0.63  0.95 mm in the immediate and early groups, respectively; Po0.001). However, a significant difference in implantation depth between the two groups (Po0.0001) was found. After adjusting for this slight difference in initial surgical placement depth, time to loading no longer had a significant influence on bonelevel change. Significant influence was found for: center (Po0.0001), implant length (Po0.05) and implant position (Po0.0001). Bone gain was observed in approximately 16% of implants. Conclusions: The results demonstrated that Straumann implants with the SLActive surface are safe and predictable when used in immediate and early loading procedures. Even in poor-quality bone, survival rates were comparable with those from conventional or delayed loading. The mean bone-level change was not deemed to be clinically significant and compared well with the typical bone resorption observed in conventional implant loading.

Date: Accepted 3 July 2008 To cite this article: Ganeles J, Zo¨llner A, Jackowski J, ten Bruggenkate C, Beagle J, Guerra F. Immediate and early loading of Straumann implants with a chemically modified surface (SLActive) in the posterior mandible and maxilla: 1-year results from a prospective multicenter study. Clin. Oral Impl. Res. 19, 2008; 1119–1128 doi: 10.1111/j.1600-0501.2008.01626.x

The use of titanium as a biomedical material has been well documented in many applications, such as orthopedics and oral surgery. Currently, titanium is the standard material for dental implants due to its

 c 2008 The Authors. Journal compilation  c 2008 Blackwell Munksgaard

excellent biocompatibility and osseointegration properties (Adell et al. 1981; Bra˚nemark et al. 1983; Tengvall & Lundstro¨m 1992; Kasemo & Lausmaa 1994). From the outset, there have been constant efforts to

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improve osseointegration by modifying the surface properties of titanium, because this is where early interactions occur between the implant and the surrounding tissues following placement. Surface properties such as topography and chemistry can affect protein adsorption, cell-surface interaction and peri-implant tissue development, which are all relevant to the functionality of the implant or device (Ratner 1996) and have an influence on osseointegration, host response to the implant and subsequent treatment outcomes (Smith 1993; Brunette & Chehroudi 1999; Sykaras et al. 2000). In applications where integration of the implant in bone is of crucial importance (e.g., dental implants, artificial hip joints, osteosynthesis screws), surface modifications have been exploited successfully to influence expression of molecular factors and differentiation of osteoblasts (Kieswetter et al. 1996; Lincks et al. 1998; Schwartz et al. 1999; Boyan et al. 2003) and bone integration and long-term stability of the implants in both preclinical (Carlsson et al. 1988; Buser et al. 1991, 1999; Cochran et al. 1996; Li et al. 2002) and clinical studies of up to 5 years (Roccuzzo et al. 2001, 2008; Cochran et al. 2002; Barewal et al. 2003; Bornstein et al. 2003, 2005). Modifications may be additive [e.g. hydroxyapatite and titanium plasma-spraying (TPS)] or subtractive (e.g. sandblasting and acidetching) to produce roughened surfaces with improved osseointegration compared with smooth, machined surfaces (Suzuki et al. 1997; Piattelli et al. 1998; Buser et al. 1999; Cochran 1999; Cordioli et al. 2000; Grassi et al. 2006). More recent approaches have moved towards chemical modification of the implant surface to enhance osseointegration. These have included fluoride ion modification (Ellingsen et al. 2004; Cooper et al. 2006; Berglundh et al. 2007), biocoating with recombinant human bone morphogenetic protein-2 (Becker et al. 2006) and surface chemistry modification with hydroxy carbonate apatite (Zreiqat et al. 2005) or zinc (Petrini et al. 2006). Surface chemistry modification influences surface charge and wettability, i.e. the contact angle between a droplet of liquid on a horizontal surface. Wettability is largely dependent on surface free energy and affects the degree of contact between the

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implant surface and the physiologic environment. Greater wettability leads to greater interaction between the biomaterial and the host (Kilpadi & Lemons 1994). A new chemically modified titanium surface, SLActive (Straumann AG, Basel, Switzerland), has been developed, using the well-documented topography of the sandblasted, large-grit, acid-etched (SLA; Straumann AG) surface. Chemical modification of the surface is characterized by a hydroxylated/hydrated TiO2 film and is carried out under N2 conditions, maintained by storage in isotonic saline. The SLActive surface has a high surface free energy, reduced atmospheric hydrocarbon contamination and is strongly hydrophilic with a water contact angle of 01 compared with 139.91 for the standard SLA surface (Zhao et al. 2005; Rupp et al. 2006). Increased early cellular activity compared with the SLA surface has been shown, with enhanced osteoblast differentiation, increased production of osteocalcin and local growth factors such as PGE2 and TGF-b1 (Zhao et al. 2005). Greater gene expression of osteocalcin, alkaline phosphatase, type-I collagen, osteoprotegerin, glyceraldehyde3-phosphate dehydrogenase, TGF-1b and VEGF (Qu et al. 2007; Rausch-Fan et al. 2008) has also been observed. The osteoblast response appears to be much greater than would be expected from the sum of surface energy and topography effects independently, suggesting a synergistic effect (Zhao et al. 2007). Increased bone apposition to the SLActive surface in the early healing stages, with 60% greater bone formation at the SLActive compared with the SLA surface, was demonstrated in vivo, with earlier formation of more mature bone (Buser et al. 2004; Bornstein et al. 2008) and mean removal torque values consistently higher in the first 8 weeks (Ferguson et al. 2006). Histological and immunohistochemical evaluation has shown enhanced bone formation, significantly increased cellular activity and proliferation of vascular structures with SLActive compared with SLA (Schwarz et al. 2007a). Greater subepithelial connective tissue attachment, with well-organized collagen fibers and numerous blood vessels (Schwarz et al. 2007b) were also evident. Dental implants are traditionally left undisturbed or unloaded for a period of time following placement, based on the

theory that loading too soon would inhibit healing and compromise osseointegration (Bra˚nemark et al. 1977). In the case of Straumann SLA surface implants, the standard protocol is for loading after 6–8 weeks, with the exception of Lekholm & Zarb (1985) bone quality IV, where 3–4 months are recommended (Buser et al. 2000). It has been suggested that the SLActive surface can further reduce the loading time to 3–4 weeks (Oates et al. 2007). In recent years, immediate and early loading techniques have become more widely documented and accepted in many situations (Attard & Zarb 2005; Nkenke & Fenner 2006; Jokstad & Carr 2007). Early examples of immediate or early loading in the mandible include Babbush et al. (1986) and Schnitman et al. (1997). Immediate loading of implants in the edentulous mandible and maxilla was described by Tarnow et al. (1997), and immediate loading of SLA and TPS implants was described by Jaffin et al. (2000), with a success rate 495%. Early loading of Straumann SLA implants has demonstrated clinical outcomes equivalent to conventional loading (Cochran et al. 2002; Roccuzzo & Wilson 2002). Immediate or early loading of Straumann SLA implants in single-tooth replacement (Cornelini et al. 2004), splinted crowns and fixed prostheses (Bergkvist et al. 2005; Luongo et al. 2005; Tortamano et al. 2006), full-arch prostheses (Fischer & Stenberg 2006) and overdentures (Stricker et al. 2004) has demonstrated success and survival rates comparable with those obtained using standard delayed loading. Early or immediate loading can have several advantages, the most important of which is that it allows the patient to resume normal masticatory function as quickly as possible after surgery (Ganeles et al. 2001; Chee & Jivraj 2003). Immediate loading also avoids the requirement for a removable prosthesis, improves treatment efficiency and immediately enhances the esthetic appearance of the patient. The objective of this randomized-controlled study was to radiographically assess bone level-changes and evaluate the clinical survival of Straumann implants with the SLActive surface supporting single crowns or two to four unit fixed dental prostheses in immediate and early nonocclusal loading in the posterior maxilla and mandible.

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Ganeles et al . Immediate and early loading of SLActive implants

Materials and methods This is an ongoing prospective randomized 3-year study conducted at a total of 19 centers in 10 countries. The investigators placing the implants at all centers were experienced implant surgeons, each with between 10 and 25 years of clinical experience. The materials and methods for the study have been described in a previous publication (Zo¨llner et al. 2008), but will be outlined here. Patients and implants

The study enrolled patients aged
18 years who were missing at least one tooth in either the posterior maxilla (FDI positions 4–7, ADA positions 2–5 and 12–15) or the mandible (FDI positions 4–7, ADA positions 18–21 and 28–31) or both, and who desired an implant-supported restoration. Patients were randomized into immediate or early loading arms. Patients had to have fully healed implantation sites (teeth extracted/lost
4 months before implant placement), adequate bone quality and quantity, have natural teeth or a fixed prosthesis as opposing dentition and be committed to the study for the full duration. Exclusionary criteria included: conditions requiring chronic antibiotics or steroids; renal failure, severe or uncontrolled metabolic disorders; alcoholism or drug abuse, HIV infection or smoking 410 cigarettes (or cigar equivalents) per day, or chewing tobacco; local inflammation or mucosal diseases; and severe bruxing/clenching or persistent intraoral infection. Each patient received between one and four Straumann Standard dental implants with the SLActive surface, either 4.1 mm (Regular Neck, 2.8 mm machined surface transmucosal collar) or 4.8 mm (Wide Neck, 2.8 mm machined surface transmucosal collar) in diameter and 8, 10 or 12 mm in length. The only exception to this was the use of three Straumann Standard Plus (1.8 mm machined surface) implants, which were coincidentally placed in the immediate group. Randomization

The randomization list was generated for each center by an independent statistician using block sizes of 10; randomization

numbers were sequential, and each group (immediate or early) had an equal number in each block. The sequential randomization was placed in sealed envelopes for each center, which were opened before surgery after obtaining signed informed consent from the patient. Patients were consecutively enrolled by the investigators at each center, and each patient had a sealed treatment code envelope corresponding to their enrollment position. Pretreatment and surgical procedures

Eligible patients were assessed by clinical examination, medical and dental history and radiographs. In those selected for study participation, the intended implant site(s) and opposing dentition were examined and radiographs were evaluated. Intraoral photographs were obtained and the patients received oral hygiene instructions. All patient examination, radiographic and surgical procedures were agreed upon in investigator meetings and defined in a study protocol signed by all principal investigators. Study conduct and informed consent (received from all patients) was in accordance with the ‘Declaration of Helsinki’ (1964) and subsequent amendments and clarifications, and approval for the study was also obtained from the relevant Ethics Committees. Surgery was performed under local anesthesia under aseptic conditions in an outpatient environment, and the routine surgical techniques for each center were used, following the standard Straumann one-stage surgery protocol (Buser & von Arx 2000; Buser et al. 2000). Any patients with implants lacking primary stability, which was tested intra-operatively by hand, were excluded from further study participation but this situation did not constitute implant or treatment failure. Patients with inadequate bone at surgery were also excluded. Excluded patients were subsequently offered implant treatment using the conventional delayed protocol or another form of treatment. The day of surgery was defined as the baseline (day 0).

healing caps were placed following surgery, with abutments and provisional restorations placed 28–34 days later. All provisional restorations were placed out of occlusal contact in centric and excursive movements. In both groups, permanent fixed restorations were placed 20–23 weeks post-surgery. These were cement- or screw-retained and made of porcelain, ceramometal or acrylic resin on gold and fabricated according to each center’s usual dental technical laboratory and standard procedure. Radiographic evaluation

Standardized periapical radiographs, using a customized holder, were taken at the baseline and at the time of seating the permanent restoration. Radiographic and clinical evaluation was performed at 12 months, with further evaluations planned at 24 and 36 months. Standardized radiographs were taken using the same film holder-beam aiming device (e.g. Rinn System, RWT Window X-Ray System or similar) with the film placed parallel to the implants and the X-ray beam perpendicular to the implants. It was necessary to have at least two implant threads visible on the radiograph for analysis. Film holders were constructed to capture the cuspal indentations of the adjacent teeth with a suitable impression material whenever possible in order to maximize the reproducibility of the radiograph. The first radiographs after surgery were taken with the implant in situ but without the restoration, and subsequent radiographs with the restoration were standardized using a radiographic stent. These standardized radiographs were used to calculate the change in crestal bone level between the implant shoulder and the first visible bone-to-implant contact (BIC), measured at the mesial and distal aspects of each implant (Bra¨gger 1994). Measurements accounted for possible distortion based on changes on the radiograph from the true dimension of the implant. All radiographic analyses were performed by a single investigator blinded to the loading protocol at the University of Bern.

Prosthetic restoration and loading protocol

In the immediate loading group, implants received a provisional restoration [single crown or two to four unit fixed partial denture (FPD)] on the day of surgery. In the early loading group, mucosal height

 c 2008 The Authors. Journal compilation  c 2008 Blackwell Munksgaard

Primary and secondary objectives

The primary objective of the study was to evaluate the radiographic change in bone level from baseline to 12 months. The analysis included all patients who signed

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Statistical methods

Demographics and other baseline characteristics were reported descriptively. For continuous variables, means and standard deviations were calculated for each treatment group, with numbers and percentages calculated for categorical variables. Mean mesial and distal bone-level measurements were used to calculate bone-level change for each implant, and statistical analysis was by descriptive statistics and two generalized linear models, in each of which the patient was included as a random variable to consider possible correlations of implants within the same patient. All implants were assumed to have the same correlation to each other within the same patient, regardless of the position or the distance between them. Separate correlation coefficients were used for each treatment group. The Kenward–Roger method (Kenward & Roger 1997) was used to calculate the degrees of freedom in the denominator and type II tests were used to calculate P-values and confidence intervals. To evaluate significance, all independent parameters were included as fixed effects. The following were analyzed for a possible significant impact on bone loss: treatment group; center; center  treatment interaction; jaw; number of implants; sulcus bleeding index; diabetes; bone quality; and implant type.

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For analysis of the global difference of bone loss between the two groups, all identified significant effects were included as fixed effects, in addition to the treatment group. The observed distributions were used as coefficients to calculate the adjusted means and the difference between the groups. The risk for clinically relevant bone loss was analyzed and compared between the treatment groups by a generalized estimating equation model with treatment groups and jaw as fixed effects. Possible correlations between implants within a patient were considered as a repeating effect. The same correlation was used for both groups.

Results Patients and implants

The patient population (as defined above) included 266 patients: 138 (64 male and 74 female) and 128 (54 male and 74 female) in the immediate and early groups, respectively. A total of 383 implants were placed: 197 and 186 in the immediate and early groups, respectively. The mean age of patients at baseline was 46.3  12.8 years (46.1  13.3 in the immediate group and 46.6  12.4 in the early group). The female patients tended to be older than the male patients (mean age 55.6 years compared with 44.4 years). Patient recruitment began in April 2004 and the last patient was enrolled in August 2005; the 12month follow-up period was therefore from April 2005 to August 2006. The biggest reason for loss of the original tooth, or the reason for a gap to be filled by an implant, was dental caries (57.0%), followed by unsuccessful endodontic treat-

No. of patients

the consent form, received an implant and fulfilled the inclusion and exclusion criteria. Changes in crestal bone levels between the immediate and early loading groups were evaluated; bone loss 40.3 mm between the groups was deemed to be detectable on all X-ray assessments and was used as a non-inferiority margin for comparison of the two treatment groups. Secondary objectives included evaluations of implant survival and success, where success was defined as lack of mobility, absence of peri-implant radiolucency, recurrent peri-implant infection, continuous or recurrent pain or structural failure of the implant and 42 mm bone resorption between any two consecutive visits. A further secondary efficacy end point was clinically relevant bone loss of 42 mm, calculated as the mean between mesial and distal change in crestal bone level.

ment (16.8%), tooth fracture (10.5%) and periodontal disease (6.0%). Other reasons included trauma, agenesis, excessive internal tooth resorption and loss of a previous implant. In both groups, most patients (64.3%) received a single implant, while 30.1% received two implants, 3.0% received three implants and 2.6% received four implants (Fig. 1). Approximately two-thirds (67.9%; 260 implants) were placed in the mandible and one-third (32.1%; 123 implants) in the maxilla and the predominant implant site was the first molar position (FDI position 36/46, ADA positions 19/30), where 44.1% of the implants were placed (Fig. 2). There were no relevant differences between the groups for the number of implants placed or the implant position in each patient. Most implants were Regular Neck (Ø 4.1 mm; 64.2%) and the remainder were Wide Neck (Ø 4.8 mm; 35.8%). The number of implants placed according to length was 19.3% for 8 mm implants, 50.4% for 10 mm implants and 30.3% for 12 mm implants. Again, there were no relevant differences between the groups. Most prostheses were cement-retained (57.4%); 42.0% were screw-retained. Information on prosthesis retention was missing from two patients (0.5%), both in the immediate loading group. In the immediate loading group, 55.8% of prostheses were cement-retained and 43.2% were screw-retained; for the early loading group, the figures were 59.1% and 40.9%, respectively. Two hundred and twenty-three implants (58.2%) were placed in type I and II bone, according to the Lekholm & Zarb (1985) classification; 34.5% and 7.3% were

100 90 80 70 60 50 40 30 20 10 0

Immediate Early

1

2 3 No. of implants

4

Fig. 1. Number of implants per patient per group.

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Ganeles et al . Immediate and early loading of SLActive implants

60

placed in type III and IV bone, respectively. Slightly more implants were placed in type III and IV bone in the immediate group (36.5% and 8.1%) than in the early group (32.3% and 6.5%), but the differences were not significant (Table 1).

No. of implants

50

Implant success/survival and bone loss

Early

40 30 20 10 0 17 16 15 14 24 25 26 27 37 36 35 34 44 45 46 47 Position according to FDI scheme

Fig. 2. Implant distribution in the maxilla and mandible according to FDI position.

Table 1. Distribution of implants according to bone quality Treatment group

Total

Immediate

Maxilla Type I Type II Type III Type IV Mandible Type I Type II Type III Type IV Total Type I Type II Type III Type IV

Early

N

%

N

%

N

(%)

1 31 30 9

1.4 43.7 42.3 12.7

3 20 25 4

5.8 38.5 48.1 7.7

4 51 55 13

3.3 41.5 44.7 10.6

11 67 42 7

8.7 53.2 32.5 5.6

22 69 35 8

16.4 51.5 26.1 6

33 136 77 15

12.7 52.3 29.2 5.8

12 97 72 16

6.1 49.7 36 8.1

25 89 60 12

13.4 47.8 32.3 6.5

37 186 132 28

9.7 48.8 34.2 7.3

1.6 Immediate

Early

1.4 Mean bone loss (mm)

Of the 383 implants placed, 10 were lost by the 12-month follow-up analysis; four were lost in the immediate group and six were lost in the early group, yielding implant survival rates of 98% and 97%, respectively. None of the implant losses were in type IV bone. Only one implant (in the immediate group) was classified as unsuccessful at the 12-month follow-up due to the presence of continuous periimplant radiolucency based on radiographic findings. However, success rates were slightly lower than survival rates due to patient drop-out or the visit not being performed. No serious adverse events were noted in either group. Radiographs were available for comparison for both baseline (time of implant placement) and 12 months for 323 implants (168 and 155 in the immediate and early loading groups, respectively; 84.3% of all implants placed). Missing data were due to implant failures, non-analyzable radiographs or the follow-up visit not being performed. The total mean bonelevel change at 12 months was 0.77  0.93 mm, and bone gain was noted in approximately 16% of the implants. The mean bone level change was 0.90  0.90 mm for immediate loading and 0.63  0.95 mm for early loading, showing a significant difference between the treatment groups (Po0.001). Mean bone loss by implant position is shown in Fig. 3. The implantation depth (distance from implant margin to first bone contact) was also found to be significantly different between the two groups, with immediately loaded implants being placed deeper than early-loaded implants. The mean height from the top of the implant shoulder to the bone level was 1.22  0.74 mm for the immediate group, compared with 1.52  0.67 mm for the early group (Po0.0001), meaning that the immediately loaded implants were placed on average 0.3 mm deeper than early-loaded implants. Adjusting for this difference in implantation depth, statistical analysis

Immediate

1.2 1 0.8 0.6 0.4 0.2 0 Max. 4 Max. 5 Max. 6 Max. 7 Man. 4 Man. 5 Man .6 Man. 7 Implant position (maxilla and mandible) according to FDI scheme

Fig. 3. Mean bone loss according to implant position.

showed that the treatment group no longer had a significant influence on bone-level change. Further statistical analysis revealed a significant correlation with center (Po0.0001; Table 2), implant length (Po0.01) and implant position (Po0.0001). Sulcus bleeding also appeared to be significant (P ¼ 0.004), but the significance seemed

 c 2008 The Authors. Journal compilation  c 2008 Blackwell Munksgaard

to be caused by a single implant with a bone loss of 5.5 mm in the immediate group. Age, diabetes, bone quality and prostheses anchorage were not significant (Table 3). The frequency of bone loss 42 mm was low overall, but there was approximately a threefold increased risk of 42 mm bone loss in the immediate loading group from

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Ganeles et al . Immediate and early loading of SLActive implants

Table 2. Mean bone loss per center [mean bone loss in mm (95% CI)] Center

Immediate

Early

01 02 03 04 05 06 07 08 09 10 11 12 13 14 16 17 18 19 20

0.35 [  0.23–0.93] 0.48 [  0.07–1.03] 1.88 [0.92–2.83] 1.04 [0.13–1.95] 1.31 [1.03–1.59] 1.72 [1.19–2.24] 0.63 [  0.15–1.4] 0.25 [  0.36–0.86] 1.28 [0.58–1.98] 0.59 [  0.37–1.56] 1.76 [1.37–2.16] 0.28 [  0.21–0.76] 0.18 [  0.29–0.66] 1.1 [0.52–1.68] 0.74 [0.24–1.24] 0.58 [  0.27–1.43] 0.33 [  0.44–1.09]  0.65 [  1.49–0.19] 1.68 [0.71–2.65]

0.28 [  0.34–0.91] 0.51 [  0.05–1.08] 0.52 [  0.08–1.12] 0.92 [  0.02–1.87] 1.11 [0.83–1.38] 0.96 [0.46–1.46]  0.16 [  1.11–0.78] 0.06 [  0.56–0.68] 0.95 [0.3–1.6] 0.84 [0.1–1.58] 0.74 [0.36–1.13] 0.83 [0.41–1.24]  0.4 [  0.8–0] 0.42 [  0.13–0.97]  0.08 [  0.56–0.39] 0.87 [  0.48–2.21] 0.92 [0.24–1.59] 0.48 [  0.3–1.25] –

Table 3. Statistical modeling of change in mean bone level from surgery to 12 months – analysis for possible significant independent parameters using the Kenward–Roger method (Kenward & Roger 1997) Effect

P-Value

Treatment group 0.4054 Center o0.0001 Treatment  center interaction 0.0606 Implant length 0.0068 Implant depth o0.0001 No. implants per patient 0.0898 Sulcus bleeding index 0.004 Diabetes (yes/no) 0.9793 Bone quality 0.7519 Patient age 0.1866 Prosthesis anchorage 0.3138 Implant position o0.0001 Implant position  treatment 0.0829 interaction Center  implant position o0.0001 interaction

17.5

Number of implants 168 Mean 0.90 0.90 SD

12.5 %

Immediate

15.0

10.0 7.5

Treatment group

5.0 2.5 0 17.5

Number of implants 154 Mean 0.59 0.79 SD

15.0

%

Early

12.5 10.0 7.5 5.0 2.5 0 –3

–2.5

–2

–1.5

–1

–0.5

0 0.5 1 1.5 2.5 2 Change in mean bone level [mm]

3

3.5

4

4.5

5

5.5

Fig. 4. Change in mean bone level (from implant shoulder to first visible bone contact) by percentage of patients in each treatment group – frequency analysis. The dotted line denoted bone loss of 2 mm.

implant placement to 12 months [odds ratio (OR) 3.19, confidence interval (CI) 1.11–9.13 Po0.05]. The deeper implant depth may be one of the influential factors in this; 10.1% of the implants in the immediate group showed bone loss 42 mm, compared with 3.2% of the implants in the early group (Fig. 4). The risk of 42 mm bone loss was also greater in the maxilla vs. the mandible (OR 3.77, CI 1.49–9.53; Po0.01).

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Discussion Conventional implant loading protocols recommend a 12-week or longer period of undisturbed healing following implant placement, to minimize the risk of complications. Much shorter restoration times have become more widely accepted and practiced in recent years, especially due to reported success and patient demands for esthetics and function as soon as possible

after the surgery. Typically, with shortened loading times, provisional restorations in partially edentulous patients are placed out of occlusal contact. The current study was therefore designed to investigate the performance of Straumann dental implants with the new SLActive surface in early (4 weeks) and immediate (same day) non-occlusal loading protocols. Immediate and early loading with SLA implants in both the maxilla and the mand-

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Ganeles et al . Immediate and early loading of SLActive implants

ible with type I, II and III bone density, in both partially edentulous and fully edentulous patients, has demonstrated that early loading can be predictable with survival rates comparable to conventional or delayed loading (Jaffin et al. 2000; Cornelini et al. 2004; Nordin et al. 2004; Bergkvist et al. 2005; Luongo et al. 2005; Fischer & Stenberg 2006). Survival rates 495% with early loading have been well documented and are comparable with conventional delayed loading in good-quality bone. Examples of similar survival rates include Cornelini et al. (2004) for single-tooth implants in the molar region in 30 patients, and Salvi et al. (2004) for 67 early-loaded single-tooth implants in the posterior mandibles of 27 patients. Early loading of SLA implants with two splinted crowns or a three-unit fixed prosthesis in 40 patients (82 implants) also demonstrated comparable survival rates, with a mean bone loss o1 mm (Luongo et al. 2005). Bergkvist et al. (2005) also showed similar survival rates with immediate loading of full-arch prostheses and overdentures in 28 patients, although the mean change in marginal bone level was 1.6 mm. However, most studies of immediate/early loading involve relatively low patient numbers and few centers and focus on full-arch restorations rather than single crowns and two to four unit FPDs. To our knowledge, the present study, with over 260 patients recruited and over 380 implants placed, is the largest randomized-controlled clinical trial of its kind. The use of standardized radiographs is a significantly more sensitive, direct method to detect changes in bone levels adjacent to implants than fiduciary clinical indices such as probing depth or implant loss (Bra¨gger 1994, 1998). The combination of a large sample size, a randomized study design and sensitive analytical tools was designed to maximize the conclusive and statistical power of the study. The survival rates obtained at the 12month primary endpoint in this study with SLActive-surfaced implants (98% and 97% for immediate and early loading, respectively) are comparable to the those with SLA implants in conventional loading (e.g. Cochran et al. 2002; Pinholt 2003; Nedir et al. 2004), despite the more aggressive loading protocol. The survival and success rates also compare favorably with those from reviews of immediate and early load-

ing using pooled data including Del Fabbro et al. (2006) Ganeles & Wismeijer (2004), Attard & Zarb (2005) and Nkenke & Fenner (2006), who all suggested success rates of 493%. They are also similar to data with early loaded SLA implants reported by Bornstein et al. (2003) and Nordin et al. (2004). No implant failures were recorded in any of the implants placed in poor-quality (type IV) bone. There is no adequate explanation for this observation, but the authors’ speculation is that this may be a result of a number of factors. First, the study surgeons were highly skilled and experienced and may have been able to place implants to optimize stability by under-drilling the apical portions of the osteotomies, maximizing implant length and diameter (surface area) and attempting to engage cortical bone without encroaching on vital structures. The enhanced bioactivity of the SLActive implants may also improve the clinical success rate by accelerating BIC and bone maturation compared with SLA surface implants (Buser et al. 2004; Schwarz et al. 2007a). Using resonance frequency analysis, Oates et al. (2007) demonstrated enhanced earlier stability for SLActive surface implants compared with SLA implants during the critical first few weeks of healing. Clinically, the net effect of these factors combined could improve the success rate for implants in early or immediate loading in sites with poor bone quality. Additional investigations in poorquality bone with accelerated loading conditions are needed to confirm this theory. Shortening treatment times generally increases patient satisfaction and treatment efficiency, reducing time to restoration for patients, and the success of immediate and early loading in terms of function and predictability has been amply demonstrated, and it has been suggested as a realistic alternative to conventional delayed loading in many situations (Ganeles & Wismeijer 2004; Del Fabbro et al. 2006; Esposito et al. 2006, 2007; Glauser et al. 2006; Jokstad & Carr 2007). However, most articles cite strictly controlled clinical conditions and protocols (Szmukler-Moncler et al. 2000; Ganeles & Wismeijer 2004) and emphasize careful patient selection and screening to maximize the potential success of the procedure (SzmuklerMoncler et al. 2000; Tortamano et al.

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2006). The authors of many of the immediate loading publications in the literature are expert clinicians with extensive experience in the field, and so the data generally reported may not be representative of the experience of ‘average’ clinicians with ‘average’ patients (Ganeles & Wismeijer 2004). However, not all clinicians achieve optimal results with immediate loading (Esposito et al. 2007), indicating that the immediate loading procedure may be more technique sensitive than early or delayed loading. The radiographic results from the current study demonstrate a significant difference between immediate and early loading in terms of change in marginal bone level (mean bone-level change 0.90  0.90 and 0.63  0.95 mm for immediate and early loading, respectively; Po0.001). However, adjusting for the significant difference in initial implant depth meant that the treatment group no longer had a significant influence on bone-level change. In a systematic review of randomized-controlled trials, it was suggested that one of the prerequisites for successful immediate loading is a high degree of primary implant stability (Esposito et al. 2007). Because the randomization envelopes defining the restoration protocol were opened before implant placement, this may have introduced a selection bias; we therefore speculate that the implants for immediate loading may have been placed deeper in an attempt to maximize primary stability. This meant that the interface between the rough surface and the machined collar of the implant was placed deeper in the alveolar bone than in the early group. Several previous studies indicated that bone loss is greater the deeper the rough/smooth interface is placed (Ha¨mmerle et al. 1996; Hermann et al. 2000; Hartman & Cochran 2004; Alomrani et al. 2005). However, because loading protocols are generally decided before surgery in the normal clinical setting, we do not consider that this situation had any adverse affect on the study results. As with the interim analysis from this study (Zo¨llner et al. 2008), a significant center effect was also observed, indicating that differences in bone-level change between immediate and early groups are partially dependent on the center. The exact reason for this center effect has yet to be elucidated, but the results suggested

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that the immediate loading group was more heterogeneous, which tended to indicate that the procedure is more critical for immediate loading. The mean marginal bone loss in this study was not deemed to be clinically significant and was comparable with the bone resorption observed with other immediate and early loading studies (Grunder et al. 1999; Iban˜ez & Jalbout 2002; Degidi & Piattelli 2005; Luongo et al. 2005; Yoo et al. 2006). The mean bone loss was also lower than that observed in a recently published study with a similar protocol (Achilli et al. 2007). In this study, implants in the posterior maxilla or mandible in partially edentulous patients were also loaded with FPDs immediately or after 6 weeks, with minimal occlusion and definitive restorations placed after 6 months.

Results after 12 months showed a mean marginal bone resorption of 1.24  0.88 mm with immediate loading and 1.19  1.01 mm with early loading. The frequency of bone loss 42 mm was low overall and, as in the 5-month results, the phenomenon of bone gain was observed in approximately 16% of the implants in the current study (30 and 32 implants in the immediate and early loading groups, respectively). This phenomenon of bone gain with SLActive has also been observed in a preclinical study in dehiscence defects (Schwarz et al. 2007c), but the clinical significance of this phenomenon has yet to be elucidated. The 12-month endpoint results of this study demonstrate that Straumann implants with the chemically modified SLActive surface are safe and predictable in

Acknowledgements: The authors would like to thank Dr Klaus Freivogel (Analytica International, Lo¨rrach, Germany) for the statistical analysis of the study data, Professor Urs Bra¨gger and Dr Rigmor Persson (University of Bern, Switzerland) for the radiographic analysis, Dr Mariano Herrero Climent (private practice, Marbella, Spain) and Dr Kerstin Fischer (private practice, Falun, Sweden) for additional contributions to the manuscript and Institut Straumann AG, Basel, Switzerland, for supporting the study.

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early and immediate loading procedures, even in poor-quality bone, with results comparable with those achieved by conventional loading.

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