Biological complications and periimplant clinical and radiographic changes at immediately placed dental implants. A prospective 5-year cohort study

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1 Daniel Rodrigo Conchita Martin Mariano Sanz Biological complications and periimplant clinical and radiographic changes at immediately placed dental implants. A prospective 5-year cohort study Authors affiliations: Daniel Rodrigo, Mariano Sanz, Graduate Periodontology, Faculty of Odontology University Complutense of Madrid, Madrid, Spain Conchita Martin, Mariano Sanz, ETEP Research Group, Faculty of Odontology University Complutense of Madrid, Madrid, Spain Corresponding author: Prof. Mariano Sanz Facultad de Odontología Universidad Complutense de Madrid Plaza Ramón y Cajal Madrid, Spain Tel.: Fax: marianosanz@odon.ucm.es Key words: biological complications, immediate implant, periimplantitis Abstract Objectives: To evaluate clinically and radiographically immediate implants 5 years after insertion and to compare them with delayed-placed implants in the same subjects Material and methods: Twenty-two consecutive patients that needed at least two implants for replacing hopeless teeth, one immediately upon extraction and the other in a delayed fashion (at least 4 months post-extraction) were selected in this prospective cohort study. Post-extraction immediate implants (II) and delayed implants (DI) groups were defined. One and 5 years after implant loading, clinical and radiographical outcome variables were recorded and analysed both at site and at implant level. Intra-group and inter-group comparisons were performed. Results: The intergroup comparison did not show significant differences for plaque index, bleeding on probing and suppuration. These parameters worsen in both groups along the study. This trend was stronger for the plaque index in the group II, which increased from 15.6% at 1 year to 25.9% at 5 years (P < 0.04). One year after loading, the sites with probing depth 5 mm were higher for the group II compared to DI (2.5% vs. 0%; P = 0.049). At the end of the study, no significant statistical differences were found. Radiographically, bone crestal changes did not yield significant differences. During the follow-up period, 25% of the implants (26.4% in group II and 23.5% in DI) showed biological complications: mucositis (20%) and/or periimplantitis (5.8%). No differences between groups were found. Conclusions: Within the same patients, the implants placed with the immediate protocol demonstrated a higher tendency to crestal bone loss and to peri-implantitis, although these differences were not statistically significant. Date: Accepted 3 July 2011 To cite this article: Rodrigo D, Martin C, Sanz M. Biological complications and peri-implant clinical and radiographic changes at immediately placed dental implants. A prospective 5-year cohort study. Clin. Oral Impl. Res. 23, 2012, doi: /j x Oral implants have demonstrated a high predictability supporting fixed prosthetic restorations, provided certain conditions are met during their surgical installation and healing leading to osseointegration. In fact, the advances in implant surface micro-topography and the development of advanced surgical protocols have modified the original protocol described by Branemark et al. (1983). In recent years, immediate implant placement after tooth extraction (Type I placement; Hämmerle et al. 2004) has become a common clinical therapeutic approach, with the goal of counteracting the well-known ridge alterations that occur after tooth extraction (Schropp et al. 2003; Araujo & Lindhe 2005) and hence, preserving the hard and soft tissues and thus improving the outcomes of the implant therapy (Denissen et al. 1993; Watzek et al. 1995; Paolantonio et al. 2001). This hypothesis, however has not been validated in recent human clinical trials that have shown that also when the implants are placed immediately in fresh extraction sockets, there are marked ridge alterations both in the bucco-lingual as well as the apicocoronal dimensions (Botticelli et al. 2008; Ferrus et al. 2010; Sanz et al. 2010) These short-term changes may result in long-term compromised aesthetic outcomes (Kan et al. 2003; Evans & Chen 2008). Other investigations, however, have not reported any longterm differences in both hard and soft tissues, when immediately placed implants have been compared with implants placed with a delayed protocol (Cooper et al. 2010; van John Wiley & Sons A/S

2 Kesteren et al. 2010). On the other hand, the long-term outcome, in terms of implant survival of this immediate surgical protocol, has been reported as predictable as implant placement into healed alveolar sites (Chen et al. 2004). A systematic review evaluating this surgical protocol (Quirynen et al. 2007) identified only two prospective (Prosper et al. 2003; Covani et al. 2004) and four retrospective studies (Ashman et al. 1995; Huys 2001; Bianchi & Sanfilippo 2004; Schwartz-Arad et al. 2007) that included long-term data with a maximum follow-up period of 4 years. Although immediate implants exhibited a high survival rate, the efficacy could not be evaluated since there was a lack of long-term clinical and radiographic data. In a similar recent systematic review evaluating success, complications, aesthetics and patient satisfaction between immediate, immediate-delayed and delayed implants (Esposito et al. 2010), only two RCTs compared immediate versus delayed implants in 126 patients and found no statistically significant differences. The authors concluded that there is insufficient evidence to determine possible advantages or disadvantages of immediate, vs. delayed placement of implants, since these preliminary conclusions are based on few underpowered trials often judged to be at high risk of bias. A critical factor on the outcome of this technique seems to be the position of the implant in regard to the buccal bone and the width of the buccal bone crest (Tomasi et al. 2010). In situations of buccally placed implants or in cases of narrow buccal ridges, soft tissue recession of the buccal mucosa and exposure of the implant surface may be a frequent finding, which apart from the possible aesthetic consequences, represents a higher biological risk in a long-term basis, as these exposed rough titanium surfaces are more prone to bacterial colonization and contamination. This hypothesis has not yet been evaluated in long-term clinical studies and it was, therefore, the purpose of this 5-year prospective cohort study to evaluate the biological complications, as well as the clinical and radiographical outcomes of immediately placed implants, when compared with similar implants installed with a delayed protocol in the same patients. Material and methods Patients Twenty-two patients were selected for this study from a private clinic on the bases a thorough clinical and radiographic diagnosis and the fulfillment of the following criteria: Consecutive patients that needed to receive at least two implants for replacing teeth with hopeless prognosis. Patients were not included if presenting untreated periodontitis or with inappropriate periodontal maintenance. Similarly, patients with diabetes or any other systemic or local disease or condition that could compromise post-operative healing and/or osseointegration were not included. In each selected patient, an attempt was made to balance the implants by treatment group and by arch position. Experimental design This study was designed as a prospective cohort study. In each patient, two treatment groups were defined: post-extraction immediate implants (II) and delayed implants (DI). In both groups the same implants (sand-blasted and acid etched (SLA) cylindrical implants (Straumann, Dental Implant System; Straumann AG, Basel, Switzerland) were placed one immediately upon the extraction of the hopeless tooth and the other in a delayed fashion (4 months after the extraction). All patients were informed on the characteristics of the study and agreed to participate by signing an EC-approved informed consent and by agreeing to comply with the required follow-up and maintenance visits. The study was conducted in accordance with the Helsinki Declaration of 1975, as revised in Interventions Immediately before implant surgery the selected patients rinsed with 0.12% chlorhexidine (Perio-Aid ; Dentaid, Barcelona, Spain) and were locally anesthetized with articaine (Ultracain D-S forte; Aventis Pharma GnBh, Vienna, Austria). The implant placement followed the standard surgical protocol for this type of implants, although in situations of soft bone, under-drilling or ostetomes were utilized. Implants were placed immediately upon extraction when the extraction socket had a suitable anatomy for cylindrical implants and the implant placement could aimed towards the palatal bone wall. If the resulting gap between the buccal wall and the implant surface was >2 mm, it was filled with a xenograft (BioOss ; Geistlich Pharma, Wolhusen, Switzerland) or with an autologous bone graft collected during drilling. Once the implants were placed, its stability was checked manually and with resonance frequency analysis (RFA) using the Osstell Mentor device (Osstell AB, Gothenburg, Sweden). Healing abutments were then placed and flaps were approximated and sutured in place with 5-0 non-resorbable braided nylon interrupted single sutures. The implants were allowed to heal in a non-submerged environment in both treatment groups. Implants were not included in the study when there was an insufficient bone availability needing bone regenerative treatment and in cases were the implant was not fully stable (rotation movement upon manual screwing of the healing abutment). Post-treatment instructions As post-operative instructions, patients were prescribed systemic antibiotics (Clamoxyl 750 mg TID for 7 days; Glaxo-Smith-Kline AG, Munchenbuchsee, Switzerland) as well as anti-inflammatory medication (Ibuprofen 600 mg/tid for 3 days) and instructed to rinse with a 0.12% chlorhexidine mouthrinse (Perio-Aid ; Dentaid). Half of the implants from the group II and one-third from group DI were immediately loaded from 0 to 5 days after surgery. The rest of the implants had variable healing times between 2 and 4 months after insertion. The decision to load was based on the implant stability, the ISQ values and the occlusal situation of adjacent teeth. ISQ values were again registered before the placement of the prosthetic restoration. Once the final restorations were placed, the patients were asked to return for follow-up visits where clinical and radiographic examinations were carried out. Patients attended maintenance visits at least once a year. In patients with history of periodontal disease their recall appointments were scheduled according to their risk profile (i.e. smokers, plaque index, etc.). In these patients the recall frequency was always higher than once a year. Outcome measurements The primary endpoint of the study was to evaluate the occurrence of biological complications in both treatment groups. This outcome was evaluated both clinically and radiographically. Every patient had a full mouth periodontal examination at each year after the placement of the restoration, including the evaluation of the following clinical variables at six sites in each implant: Plaque Index (PI) (presence or absence of supragingival plaque) 2011 John Wiley & Sons A/S 1225 Clin. Oral Impl. Res. 23, 2012 /

3 Bleeding on probing (BOP) (presence or absence of bleeding after probing) Suppuration (presence or absence of suppuration after probing) Probing pocket depth (PPD), measured in mm using a periodontal probe. The occurrence of any surgical or followup complication. The changes between 1 and 5 years in these clinical variables were calculated for both groups. Similarly, 1 year after the placement of the prosthetic restoration and at the end of the study (5 years after loading) standardized periapical radiographs were taken with the parallel cone technique using a Rinn film holder (XCP instruments; Rinn Corporation Elgin, Elgin, IL, USA). One calibrated investigator, who was blind to the timing of implant placement, evaluated all the radiographs. The intra-examiner reproducibility of this investigator was attained prior to the start of the study by measuring the same 20 X-rays on five different days. The obtained X-rays were viewed on a light box placed in a dark room using 2.59 magnifying glasses. Changes in interproximal crestal bone levels were measured using an electronic digital caliper (Ceosa, Madrid, Spain) with a precision of 0.01 mm. Two methods were used to calculate the changes in bone crestal levels (Figs 1 and 2): method 1 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the first implant-bone contact (h1m/h1d), while method 2 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the closest homogeneous density area of implantbone contact (h2m/h2d). The neck of the implant (a-b) was used as a known dimension for calibrating the images and thus compensating for any possible magnification error in the X-rays. Radiographs with any damage during storage or radiographs from angulated implants that showed any distortion in their dimensions were excluded from the evaluation. In order to identify the occurrence of significant bone level changes in both treatment Fig. 1. Study diagram flow. Fig. 2. Landmarks used for the radiographical measurements. Cm: mesial portion of the rim; Cd: distal portion of the rim; h1m: first implant-bone contact at the mesial aspect; h1d: first implant-bone contact at the distal aspect; h2m: closest homogeneous density area of implant-bone contact at the mesial aspect; h2d: closest homogeneous density area of implant-bone contact at the distal aspect; a-b: neck of the implant used as a known dimension for calibration. groups, we used the tolerance method (Haffajee et al. 1983) where differences between pairs of bone level measurements were used to compare the mean change and the site-specific variability of that change. Significant bone loss was defined when surpassing the threshold calculated by multiplying three times the standard deviation of repeated measures. Biological complications were defined as mucositis when implant sites demonstrated PPD 4 mm that bled on probing but without significant bone loss. Periimplantitis sites had to demonstrate PPD 4 mm plus bleeding on probing plus significant bone loss. Statistical methods As each patient served as its own control, a convenience sample of consecutive patients fulfilling the pre-determined entrance criteria was selected. Descriptive statistics were used to present the demographics and other baseline characteristics using means, medians, 95% confidence intervals and ranges for continuous variables and frequency distributions for categorical variables. Clinical and radiographic outcome variables were analysed both at site and at implant level. Once the normal distribution of the data was confirmed (using the Kolmogorov-Smirnov and Shapiro-Wilk tests), an ANOVA test was chosen to compare the differences between the two types of implants (inter-group comparison) adjusted by patient. Intra-group comparisons of the categorical data were carried out using the McNemar test to compare the two timepoints (1- and 5-years). A two-sided P-value of 0.05 was considered to be statistically significant. Intra-examiner reliability of the radiographic ratings was tested using the intra-class correlation coefficient of total agreement. All analyses were conducted using SPSS version 19 (IBM Corporation, Somer, NY, USA). Results The study population consisted of 22 patients, 8 male and 14 female. Table 1 describes the demographic characteristics of this population. Their mean age was 59.3 years (range 33 76), 36% were smokers and 68% had been periodontally treated. In these patients 68 implants were placed, 34 belonging to group II (immediate implants) and 34 to group DI (delayed implants). The implant distribution in the two treatment groups is shown in Table 1 depicting the use of significantly longer implants in group II versus DI (P < 0.001). Clinical variables Table 2 shows the evolution in the clinical outcome variables between 1 and 5 years post-loading at site level. The intergroup comparison did not demonstrate any significant differences for plaque index, bleeding on probing and suppuration. These parameters worsen in both treatment groups along the study. This trend was more pronounced for the plaque index in the group II, which increased from 15.6% at 1 year to 25.9% at 5 years (P < 0.04). Probing pocket depths increased in both groups during the study. One year after loading, the number of sites with probing depth 5 mm was statistically higher for the group II compared to group DI (2.5% vs. 0%; P = 0.049). At the end of the study, however, no significant differences were found. Table 3 shows the changes at implant level of the clinical outcome variables between 1 and 5 years post-loading. At the 1 year evaluation more implants in the II group presented 1226 Clin. Oral Impl. Res. 23, 2012 / John Wiley & Sons A/S

4 Table 1. Demographic data and baseline characteristics of immediate and delayed implants. SD, standard deviation; 95% CI, confidence interval at 95% level; sig.: 2-sided P-value Implants (n = 64) Patients (n = 22) Immediate (34) Delayed (34) Sig. Age Mean (years) (95% CI) 59.3 ( ) Range Sex Male 8 (36.3%) Female 14 (63.7%) Periodontitis Yes 15 (68.1%) No 7 (31.9%) Smoking Yes 8 (36.3%) No 14 (63.6%) (13.6%) (13.6%) >20 2 (7.6%) Implant width (mm) (11.76%) 2 (5.88%) (67.64%) 31 (91.18%) (20.58%) 1 (2.94%) Implant length (mm) Mean/Median (95% CI) 11.7/12 (11.32 to 12.21) 10.5/10 (10.1 to 10.96) <0.001 RFA (ISQ) Osstell1 Mean/median (95% CI) 73.17/75 (70.96 to 75.39) 72.68/73 (70.13 to 75.22) Osstell2 Mean/median (95% CI) 76/78 (72.89 to 79.11) 77.3/79 (75.25 to 79.39) Gap (mm) Mean/median (95% CI) 1.88/2 (1.24 to 2.51) 0 <0.001 Graft 11 (32.3%) No Graft 23 (67.6%) 34 Immediate loading Yes 16 (47.1%) 12 (35.2%) No 18 (52.9%) 22 (64.7%) Table 2. Changes in clinical variables (site level) from 1 to 5 years after loading 1-year after loading 5-year after loading II 1 vs. 5 years DI 1 vs. 5 years II n = 204 DI n = 204 Sig. * II n = 204 DI n = 204 Sig. * Sig. Sig. Plaque Index 32 (15.6) 28 (13.7) (25.9) 41 (20) BOP 20 (9.8) 25 (12.2) (14.2) 28 (13.7) Sup 0 (0) 1 (0.4) 1 2 (0.9) 1 (0.5) PD = 4 mm 25 (12.2) 22 (10.7) (14.2) 32 (15.6) PD = 5 mm 5 (2.4) 0 (0) (2.4) 5 (2.4) PD >5 mm 0 (0) 3 (1.4) (0.5) 2 (0.9) PD >3 mm 30 (14.7) 25 (12.2) (17.1) 39 (19.1) PD >3 mm +BOP/sup 8 (3.9) 10 (4.9) (6.4) 15 (7.3) Values in parentheses are percentages. BOP, bleeding on probing; Sup, suppuration; PD, probing depth; Sig., 2-sided P-value. Comparisons for Immediate implants (II) and delayed implants (DI). * Inter-group comparisons. Intra-group comparisons. Number of sites per group: 6 sites 9 34 implants = 204. Table 3. Changes in clinical variables (at implant level with at least one of the sites presenting deep PD, BOP or suppuration) from 1 to 5 years after loading 1-year after loading 5-years after loading II 1 vs. 5 years DI 1 vs. 5 years II n = 34 DI n = 34 Sig. * II n = 34 DI n = 34 Sig. * Sig. Sig. PD = 4 mm 12 (35.3) 10 (29.4) (50) 15 (44.1) PD = 5 mm 5 (14.7) 0 (0) (8.8) 4 (11.8) PD >5 mm 1 (2.9) 3 (8.8) (2.9) 2 (5.8) PD >3 mm 14 (41.2) 9 (26.5) (32.4) 14 (41.2) PD>3 mm +BOP/sup 8 (23.5) 5 (14.7) (23.5) 11 (32.4) PD>3 mm buccal site 2 (5.9) 2 (5.9) 1 5 (14.7) 5 (14.7) Values in parentheses are percentages. PD, probing depth; BOP, bleeding on probing; Sup, suppuration; Sig., 2-sided P-value. Comparisons for immediate implants (II) and delayed implants (DI). * Inter-group comparisons. Intra-group comparisons. Number of implants per group: 34. at least on site with deep probing depths ( 5 mm) with BOP or suppuration (P = 0.053). At 5 years, however, more implants presented deep PD in the DI group than in the II group (6 vs. 4 implants), but these differences were not statistically significant. The number of implants in group DI with PD 3 mm plus bleeding on probing and/or suppuration increased from 5 to 11, while the figure in group II remained stable at 8. Differences between groups were not statistically significant for both intra-group 2011 John Wiley & Sons A/S 1227 Clin. Oral Impl. Res. 23, 2012 /

5 comparisons between 1 and 5 years and for the inter-group comparisons at 5 years. The incidence of surgical and post-surgical complications was low in both groups (Table 4) and they were all successfully treated without further consequences. Radiographic variables Table 5 shows the results from the intraexaminer reproducibility study carried out to ensure the reliability of the radiographic examination. From the 20 X-rays that were selected and measured on five different days, the intra-class correlation coefficient for total agreement was (95% CI ), hence demonstrating a high reproducibility. For the radiographic evaluation of the interproximal crestal bone changes, 19 patients and 26 implants in each group were used, since three patients had to be excluded due to non-fulfilling the radiographic inclusion criteria. Table 6 shows the results from the comparison between the two methods used to assess the bone crestal changes, which did not yield any statistically significant difference. With method 2, the mean difference of the radiographic bone levels between 1 and 5 years after loading at the mesial aspect was 0.4 mm for group II and 0.3 mm for group DI. Distally the respective figures were 0.8 mm for group II and 0.3 mm for group DI. This marked difference was due to the occurrence of peri-implantitis in an implant from group II that demonstrated a radiographic bone loss of 8 mm at the distal site. In spite of this difference, the intergroup comparisons were not statistically significant for either the mesial or distal sites. For calculating the threshold for significant change (tolerance method) we used the SD of the repeated measurements from the calibration study, which gave us value of 0.37 mm, which multiplied by three resulted in a value of 1.1 mm that we used as minimum threshold value for significant bone loss. Table 7 shows the distribution of sites demonstrating radiographic bone loss (>1.2 mm). In group DI there were no sites with bone loss, while in group II there were seven sites (13.4%). These differences were statistically different between both groups (P = 0.023). Table 7 also depicts the same analysis at implant level showing that five implants in group II (19.2%) lost more than 1.2 mm of crestal bone, and from these, two (8.2%) demonstrated more than 2.4 mm of bone loss. There were no implants in group DI losing significant bone. Biological complications During the follow-up period, in 25% of the implants (26.4% in group II and 23.5% in group DI) biological complications were diagnosed, being in 13 implants mucositis (20%) and in four implants periimplantitis (5.8%). From these, three implants belonged to group II (9%) and one to group DI (3%), being these differences without statistical significance. At the patient level, nine of the 22 participants (40%) were diagnosed of biological complications during the 5 years follow-up (Table 4). Table 4. Occurrence of short-term surgical and post-surgical implant complications and long-term (1 5 years) biological complications (mucositis and periimplantitis) and implant survival rates in immediate and delayed implants, at implant level and related to the total number of patients (n = 22) Surgical Post-surgical Mucositis Periimplantitis Total no. implants Mucositis+periimplantitis Total no. patients n = 22 Immediate (n = 34) 1 (2.9) 2 (5.8) 6 (17.6) 3 (8.8) 9 (26.4) 9 (40.9) 34 (100) Delayed (n = 34) 1 (2.9) 0 (0) 7 (20.5) 1 (2.9) 8 (23.5) 34 (100) Total implants (n = 68) 2 (2.9) 2 (2.9) 13 (19.1) 4 (5.8) 17 (25) 68 (100) Significance Values in parentheses are percentages. Survival Table 5. Radiographic measurements of 20 X-rays taken on 5 days. Intraclass correlation coefficient (ICC) of total agreement to test the intra-examiner reliability d d d d d ICC total agreement % CI to Table 6. Mean (mm) radiographic bone (loss) levels measured at the mesial and distal sites 1 and 5-years after loading using method 1 and 2. Comparison between immediate and delayed implants Method 1 Method 2 Immediate Delayed Sig. Inmediate Delayed Sig. Mesial Mean (SD) Mean (SD) Mean (SD) Mean (SD) 1-year 1.8 (0.9) 1.8 (1) 2 (0.9) 2 (0.8) 5-years 2.2 (0.9) 2.1 (1) 2.5 (1) 2.3 (0.8) Difference 0.4 (0.7) 0.4 (0.4) (0.6) 0.3 (0.4) Distal 1-year 1.9 (0.8) 2.3 (0.7) 2 (0.8) 2.3 (0.7) 5-years 2.4 (0.8) 2.6 (0.8) 2.8 (1.8) 2.7 (0.8) Difference 0.5 (0.5) 0.3 (0.5) (1.6) 0.3 (0.4) 0.06 Method 1 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the first implant-bone contact (h1m/h1d), while method 2 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the closest homogeneous density area of implant-bone contact (h2m/h2d) Clin. Oral Impl. Res. 23, 2012 / John Wiley & Sons A/S

6 Table 7. Stratified radiographic (rx) bone (loss) levels after 5 years, comparing the number of sites and the number of implants between immediate (II) and delayed (DI) implants, measured using both methods Number of sites Number of implants Method 1 Method 2 Method 1 Method 2 Rx bone loss II DI Sig. II DI Sig. II DI Sig. II DI Sig. <1.2 mm <2.4 mm mm Method 1 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the first implant-bone contact (h1m/h1d), while method 2 measured the distance from the mesial (Cm) and distal (Cd) portion of the rim of the implant to the closest homogeneous density area of implant-bone contact (h2m/h2d). When these biological complications were diagnosed, they were immediately treated with standard protocols (Lang et al. 2000). All implants were successfully treated except one implant in group II that at the end of the study continued with presence of deep probing depths and with progressing bone loss. Discussion The objective of this clinical study was to evaluate the incidence of biological complications as well as the clinical and radiographic changes at the peri-implant tissues of implants immediately placed upon tooth extraction, when compared with implants in the same patients placed in a delayed fashion. We purposely selected both implant treatments in the same patients in order to exclude patient-related factors that could influence the occurrence of biological complications, such as genetic factors (Alvim- Pereira et al. 2008), tobacco use, oral hygiene and history of a previous periodontal disease (Heitz-Mayfield & Huynh-Ba 2009). We tried to balance the two groups intrasurgically with the aim to place implants from both groups in symmetrical or contiguous positions, in order to avoid the implant location factor, which has also been reported to affect the incidence of biological complications (Fransson et al. 2009). We excluded implants placed in sites with limited bone availability, such as in narrow crests or in sites needing bone regeneration concomitant with the implant placement, since these sites have also been reported of being in higher risk of postoperative crestal bone loss (Strietzel et al. 2002; Felice et al. 2010). In spite of the efforts made to balance the implants between both groups, the mean implant length and width was different, being in group II slightly longer (1.2 mm) and wider than in group DI, although these macroscopic differences between implants have probably a limited significance in the treatment outcome (Renouard & Nisand 2006). Implants in the DI group were slightly longer and wider probably due to the need to stabilise the implants in the extraction sockets. In fact, we excluded all implants with rotational stability that could influence implant survival (Rodrigo et al. 2010) and when the measured primary stability (RFA values) was compared between both groups, there were no significant differences. In this study, more implants in group II were immediately loaded than in group DI (47.1% vs. 35.2%). Whether this difference might have influenced the results is difficult to ascertain. Recent clinical trials comparing immediately placed implants with and without immediate loading have not demonstrated significant differences in terms of crestal bone changes (Shibly et al. 2010; Blanco et al. 2011), although there seems to be an impact in the position of the soft tissues, both at the level of the gingival margin (De Rouk et al. 2008) as well as the interdental papilla (Kourkouta et al. 2009) with enhanced aesthetic outcomes in the immediately loaded implants. In terms of clinical outcome variables (probing depth, plaque, bleeding and suppuration) both implant groups did not show at baseline any significant difference, what assured similar soft tissue conditions at the beginning of the study. In spite of this, the health of the soft tissues worsened throughout the study and the incidence of sites with PD 3 mm was 17% for group II and 19% for group DI at the final 5-year evaluation. Similar results have been reported in other clinical investigations (Luterbacher et al. 2000; Roos-Jansaker 2007; De Boever et al. 2009). In the long-term study by Bianchi & Sanfilippo (2004) 116 single immediate implants were evaluated and the percentage of peri-implant sites with PPD 3 mm was more than 50% during the time interval between 3 and 6 years after implantation. Other authors, however, have reported maintained long-term soft tissue health around immediately placed implants (Cooper et al. 2010; van Kesteren et al. 2010). These differences may be attributable to the patient population in this study where 75% of the patients were either smokers or with a previous history of periodontitis, being both significant risk factors for the development of peri-implant pathology (Karoussis et al. 2007). With the goal of avoiding the bone remodelling changes that occur immediately after implantation (Matarasso et al. 2010) we used as radiographic baseline, the 1 year evaluation after implant loading. We have reported an average bone loss between 1 and 5 years of around 0.5 mm, similar in both treatment groups. These results are similar to other studies, both using the immediate placement protocol (Crespi et al. 2008; Cooper et al. 2010) and the delayed protocol (Wennstrom et al. 2004). When these radiographic results were stratified using the tolerance method to determine the threshold of significant bone loss (1.2 mm) (Haffajee et al. 1983) 19% of the implants (5/26) in the group II demonstrated significant bone loss, in contrast with no implants in the DI group. These differences have not been reported in other similar clinical investigations (Crespi et al. 2008; Cooper et al. 2010) and they could be explained, either because the immediate implant insertion approach leads to higher amounts of bone loss, or due to measurement errors. We used a standardised X-ray projection technique, although we did not individualise the Rinn-holders, what may have limited the accuracy of our linear measurements. In fact Bragger (1998) reported a variability of around 0.3 mm when the projections to be compared are not identical and Caulier et al. (1997) showed a mismatch of between 0.85 and 1 mm when comparing histological and radiographic measurements. In order to minimize measurement errors we used the known dimension of the implant collar to calibrate all the measurements and thus compensate for any possible distortion. The fact that this surgical approach leads to short-term crestal bone changes has been clearly shown both in animals (Araujo & 2011 John Wiley & Sons A/S 1229 Clin. Oral Impl. Res. 23, 2012 /

7 Lindhe 2005; Vignoletti et al. 2009) and in humans (Botticelli et al. 2004; Sanz et al. 2010), although the possible influence of these short-term changes on the long-term bone loss has not been previously reported. One possible factor in these higher shortterm crestal bone changes in the immediate group could be the more frequent use of wide implants in this group (one of each five implants). The use of wide implants reduces the horizontal gap between the implant surface and the bone crest and therefore, the available space for a stable blood clot conducive to horizontal bone formation, what leads to more pronounced horizontal crestal bone resorption (Schropp et al. 2003; Botticelli et al. 2004; Sanz et al. 2010). The evaluation of the incidence of biological complications (mucositis and periodontitis) was one the main objectives of this investigation. Our results reported that almost 6% of the implants suffered periimplantitis and 20% mucositis. These figures are similar to the systematic review published by Berglundh et al. (2002), although significantly lower than the ones reported in a more recent systematic review (Zitzmann & Berglundh 2008) where the prevalence of mucositis affected 50% of the patients and 80% of the implants, while the incidence of periimplantitis ranged between 28 56% of the subjects and 12 34% of the implants. This latter review included studies were large populations without supportive therapy, had been assessed long-term (Fransson et al. 2005; Roos-Jansaker et al. 2006). It is likely that the combination of longer evaluation times and the lack of systematic preventive and supportive programs in these populations would account for these high figures. In this investigation we detected a different incidence in peri-implantitis when both implant treatment groups were compared (9% in the immediate implant group vs. 3% in the delayed group), although these differences were not statistically significant. To this date, no other clinical investigation has reported that the immediate implant surgical approach would confer a higher long-term risk of suffering biological complications. The limited sample size in this study (34 patients) prevents us for making any valid assumptions, although this fact deserves further investigation in long-term cohort studies with large study populations. One explanation of these differences could be that the crestal changes on the buccal crest of immediately placed implants may lead to exposure of the implant surface, which may be subsequently colonised by subgingival biofilm leading to inflammatory changes and bone resorption (Quirynen et al. 2007). In this investigation we tried to prevent these resorptive changes by placing the immediate implants palatally and by grafting the resulting gap when this space was 2 mm. 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