Clinical and radiological outcomes of implants with two different connection configurations: A randomised controlled trial.

Background: Peri-implant marginal bone loss is influenced by the interaction between tissues and the implant­abutment complex. The implant­abutment connection geometry is considered to be one of the factors that most affects peri-implant bone remodelling. Purpose: The primary purpose was to compare the clinical and radiographical differences between implants sharing the same macrogeometry but with two different connections. The secondary aims were to measure implant success and survival rate, primary and secondary stability, and the correlation between changes in marginal bone level and clinical variables. Additionally, a neural network was developed and tested to anticipate the impact of the insertion torque curve on marginal bone loss. Materials and methods: Patients requiring at least two implants in the posterior region were randomly divided into two groups. The implants presented the same micro- and macrotopography with different internal connections, conical standard (CS) and internal hex (IH). Upon implant surgery (T0), insertion torque, implant stability (implant stability quotient values were recorded by resonance frequency analysis), soft tissue height and the amount of keratinised gingiva were assessed. Stability was remeasured at the time of prosthetic connection (stage-two surgery) using a one-abutment one-time protocol and a fully digital workflow. At 6 months and 1 year after implant loading, periodontal parameters were assessed and periapical radiographs were taken. To study the differences between the two groups and the different variables, paired t test and generalised estimating equations models were adopted. Cluster analysis was used to assess the correlation between torque insertion/clinical profiles and changes in marginal bone level. Results: A total of 33 patients (17 men, 16 women, mean age 67.4 ± 14.5 years) were included in the study. No dropouts were reported. Fifty-three implants (26 CS and 27 IH) were inserted in the maxilla, and 15 (8 CS and 7 IH) in the mandible. No implants failed. Marginal bone loss at 6 months after prosthetic loading was 0.33 ± 0.34 mm for CS and 0.43 ± 0.37 mm for IH (P = 0.125), and after 1 year was 0.48 ± 0.18 mm for CS and 0.57 ± 0.24 mm for IH. A statistically significant difference between the implant stabilty quotient values for the test and control groups was demonstrated at T0 (P = 0.03) and at stage-two surgery (P = 0.000122). The generalised estimating equations model showed that soft tissue height (P = 0.012), keratinised gingiva (P = 0.05) and insertion torque (P = 0.042) had a significant effect on marginal bone loss, while the other variables did not play a statistically significant role. The neural network showed good sensitivity, accuracy, precision and specificity. Conclusions: The present research showed that different implant­abutment connections with the same implant macrogeometry have a significant effect on marginal bone loss. Better outcomes were observed in the CS group compared to the IH group. Marginal bone loss was found to be influenced by different individual and clinical factors.

Five-year cohort prospective study on single implants in the esthetic area restored using one-abutment/one-time prosthetic approach.

PURPOSE: This study was aimed to investigate, over 5 years, bone response to "one-abutment onetime" (OA-OT) protocol in the restoration of implants inserted in the anterior maxilla. Additionally, influence of soft tissue biotype in the bone remodeling was investigated. MATERIALS AND METHODS: From January 2011 to January 2012, all consecutive patients presented with a hopeless tooth in the maxillary area between canines were enrolled. Post-extraction ridge preservation was performed. After 6 months, implant was midcrestaly inserted and intraoperative impression was taken. Two months thereafter an immediate definitive abutment with a provisional crown was inserted. At final crown connection, patients underwent a standardized periapical radiograph (T0). At 12 (T1), 24 (T2), 36 (T3), 48 (T4), and 60 (T5) months, radiographic follow-up and clinical control were carried out. Independent sample t-test was conducted to compare bone loss at different times. To detect the potential role of biotype, groups (thick TK vs thin TH) were compared by analysis of variance with general linear model. RESULTS: Twenty-five patients were enrolled, but only 22 patients concluded the study. The radiographic analysis showed a stable longitudinal condition of bone levels after the first-year significant increasing (0.17 ± 0.25mm, 0.33 ± 0.25mm, 0.28 ± 0.27mm, 0.25 ± 0.26mm, 0.31 ± 0.35mm, and 0.31 ± 0.29mm, respectively at T1, T2, T3, T4, and T5). No statistical significant differences in bone loss among the two groups TH vs TK over the time (P = 0.952) were demonstrated. CONCLUSION: Results showed that the OA-OT approach allow to obtain stable bone levels.

Implant-abutment connection deformation after prosthetic procedures: an in vitro study.

This study tested the possible damage to the internal implant connection provoked by repeated disconnection and reconnection of prosthetic components. Using a light-structured scanner, connection deformation was inferred by threedimensional (3D) positional changes of a "reference" abutment before and after multiple dis- and reconnections. Measurements were taken after 1, 2, 5, 10, and 20 insertions of titanium abutments in 16 internal hexagon implants. Statistical analysis revealed that multiple dis- and reconnections could cause a deformation in the implant-abutment connection, proportional to the number of insertion procedures. However, below the threshold of 10 cycles, 3D deformation values were minimal.

Impact of plasma of argon cleaning treatment on implant abutments in patients with a history of periodontal disease and thin biotype: radiographic results at 24-month follow-up of a RCT.

BACKGROUND: A lack of evidence is present in literature regarding the clinical relevance of micropollution and bacterial contamination present on customized titanium abutments following laboratory stages and steaming cleaning procedures. To preserve abutments from such pollutants, plasma of argon cleaning of customized abutments was advocated. AIM: The aim of this prospective, randomized, match-paired, triple-blinded, controlled, clinical trial is to longitudinally assess radiographical marginal bone-level changes around implants restored according to the platform switching and "one-abutment-one-time" concepts, using commercially available abutments, with and without plasma of argon cleaning treatment after customization. MATERIALS AND METHODS: Thirty patients with thin gingival biotype, a history of periodontal disease, and in general good health received one implant in the anterior maxilla or premolar region. Patients were randomly assigned to control (abutment subjected only to usually adopted cleaning protocol by steam) and test group (abutment subjected to plasma of argon treatment). Periapical standardized digital radiographs were taken at the time of crown connection (T0), 6 (T1) and 24 months after the final restoration (T2). Average mesial-distal bone-level changes mean values with standard deviations (SD) were calculated. The Mann-Whitney U-test was selected to identify differences in bone-level changes between test and control groups. RESULTS: An average interproximal bone loss of 0.16 mm (SD: 0.17) and 0.07 mm (SD: 0.34) was revealed in the control and test group at 6 months (T1), respectively, while after 24 months, groups showed a mean bone-level changes of 0.38 mm (SD: 0.44) and 0.11 mm (SD: 0.14), respectively. Statistically significant differences among control and test groups were found at both time points. Intergroup comparison relived absence of statistically significant difference. CONCLUSION: Plasma-cleaning treatment of implant titanium abutments, together with platform switching and one-abutment-one-time concepts, could be favorable in terms of hard-tissue-level changes, also in critical conditions such as in patients with a history of periodontal disease, presenting thin gingival biotype.

Microscopical and microbiologic characterization of customized titanium abutments after different cleaning procedures.

AIM: To assess and characterize pollution micro-particles and bacterial growth on customized titanium abutments after steaming, ultrasonic and plasma cleaning treatments. MATERIALS AND METHODS: Thirty commercially available implant abutments, after customization, were randomly divided into 3 groups of 10 and cleansed by steam (considered as control group), ultrasonic cleaning (test group 1) and plasma of Argon (test group 2). For all specimens, SEM analysis and EDAX microanalysis were performed to count and characterize pollution micro-particles, both on the abutment surface and implant-abutment connection. For the control and test groups, mean values and standard deviations were calculated for number and density of micro-particles. Statistical differences were determined by one-way ANOVA with Scheffe multiple comparison test. The level of statistical significance was set at P ≤ 0.05. Additional microbiologic analysis was performed to detect bacterial contamination on the abutment surface. RESULTS: In the control group, the number of micro-particles on average was 117.5, and 14.1, respectively, on the abutment surface and connection. In the test groups, no pollution was revealed on the abutment (average of 1.09 and 1.13 spots, respectively, in test group 1 and test group 2) and connection (1.28 and 1.41, respectively, in test group 1 and test group 2). The analysis of variance (ANOVA) showed a statistically significant difference for all the variables examined. For each variable, at least one of the groups differs from the others. Scheffe multiple comparison test showed that all comparisons for every variables between the control group and both groups are significant, while there were some comparisons between test group 1 and test group 2 that were not significant. EDAX microanalysis identified micro-particles as residual of lubricant mixed with traces of Titanium and other metals. Microbiologic analysis demonstrated the presence of bacterial growth on the abutment surface only in the control group (111.5 ± 11.43 CFU/ml/implant-abutment as mean value). In the test groups, absence of growing microorganisms was found. CONCLUSIONS: This study confirmed that both plasma and ultrasonic treatments can be beneficially adopted for abutment cleaning process after laboratory technical stages, to supposedly favor soft tissue healing and implant-prosthetic connection stability.

Microscopical and chemical surface characterization of the gingival portion and connection of an internal hexagon abutment before and after different technical stages of preparation.

AIM: This study was aimed to assess contaminants on the abutment surface close to the implant-abutment interface and the connection, after common technical protocols. MATERIALS AND METHODS: A total of 40 abutments were divided into four groups: control group (abutment removed from the plastic envelop), test group1 (milled), test group2 (milled and polished), test group3 (milled, polished and steamed). Groups were subjected to scanning electron microscope (SEM) analysis. Pollution particles were counted and measured. Mean values and standard deviation (SD) were calculated. To evaluate any difference between groups Wilcoxon Signed Rank Test was conducted. In addition, contaminant chemical characterization was investigated by Energy-dispersive X-ray spectroscopy (EDX). RESULTS: Control group presented minimal amount of pollution (mean value of 2.1 spots [SD: 1.66] covering 0.004% of the surface). On the other hand, SEM analysis revealed on the abutment surface a mean value of 115.9 (SD: 32.27), 162 (SD: 21.17), and 32.5 (SD: 9.73) spots, respectively, in Test group 1, 2, and 3. Micro-particles covered the 0.025%, 0.057%, 0.0404% of the surface, respectively, in Test group 1, 2, and 3. On the connection, SEM analysis revealed a mean value of 61.9 (SD: 9.07), 39 (SD: 12.35), 42.1 (SD: 8.59) spots, respectively, in Test group 1, 2, and 3. Micro-particles covered the 0.0774%, 0.0869%, and 0.0392% of the surface, respectively, in Test group 1, 2, and 3. Spots were identified by EDX as micro-particles of lubricant and titanium smear layer. All differences were statistically significant. CONCLUSIONS: After technical procedures, presence of contaminants on the abutment surface in contact with the peri-implant tissues was confirmed. To prevent that such debris could interfere with biological stability of peri-implant tissues and, thus, enhance the implant-prosthesis integration, different cleaning protocols should be evaluated.

Crestal minimally-invasive sinus lift on severely resorbed maxillary crest: prospective study.

OBJECTIVES: This case series aimed to explore the clinical outcome of sinus floor elevation surgery using a crestal approach technique in case of severely resorbed maxillae. MATERIAL AND METHODS: Seventeen edentulous patients received 20 implants and sinus floor elevation in posterior maxillae with residual crestal height of 1.2-5.0 mm and >7 mm. Drilling perforation was performed until the sinus floor was felt; the sinus mucosa was then lifted and magnesium-enriched hydroxyapatite granules (Mg-e HAP) were placed; and implants were immediately inserted. Four months later, definitive crowns were cemented, and patients were followed up for 24 months. Implant failures and complications 24 months after prosthetic loading were noted, and radiographic regenerated bone height was measured. RESULTS: No patient dropped out, and all implants were successfully osseointegrated. There was minimal postoperative patient discomfort, and the only complication was a minimal perforation of the sinus membrane with no negative consequences. At the time of implant insertion, the residual crestal height mean value was 4.12 mm. After surgery and at the last follow-up, the mean heights of bone were 13.51 and 12.98 mm, respectively. CONCLUSION: The procedure was able to obtain sinus elevation and implant osseointegration.

Impact of implant diameter on bone level changes around platform switched implants: preliminary results of 18 months follow-up a prospective randomized match-paired controlled trial.

OBJECTIVE: This prospective randomized match-paired controlled trial aimed to evaluate the impact of implant platform diameter on marginal bone level around implants restored according to the platform switching (PS) concept. MATERIAL AND METHODS: A total of 24 implants were examined in 12 patients. All patients received two adjacent implants inserted at the crestal level: 4.3 mm (control group) and 4.8 mm (test group) in diameter. Mesio-distal implant position was randomly performed. According to the PS concept, for restoration, a 3.8 and 4.3 mm diameter abutment was used, respectively in the control and test groups, resulting, in both groups, with 0.25 mm of implant/abutment mismatching. Implant restorations were splinted. Eighteen months after final restoration, periapical standardized digital radiographs were taken to evaluate marginal bone level alterations after loading. The Wilcoxon Signed-Rank Test was selected to identify differences between groups. RESULTS: At the last follow-up, control implants exhibited a mean bone loss value of 1.10 mm (SD: 0.47 mm); the test group showed a mean value of 1.09 mm (SD: 0.08 mm). No statistically significant differences were found between test and control groups. CONCLUSIONS: Within the limits of this study, the present results suggest that bone resorption is mostly related to biologic (biologic width re-establishment) rather than to biomechanical factors (implant platform diameter). Furthermore long-term studies with a wider sample size are needed to confirm the platform diameter influence on hard tissue response around implants restored according to the PS concept.

Platform switching and matrix metalloproteinase-8 levels in peri-implant sulcular fluid.

OBJECTIVES: The concept of platform switching has been introduced to implant therapy, however long-term data are sparse. The aim of this study was to biochemically investigate the inflammatory response mediated by MMP-8 to platform switching after 3 years of loading, in order to understand the long-term effect of implant/abutment mismatching on peri-implant health. METHODS: A total of 70 implants had been inserted in the posterior maxilla in 26 patients and were randomly assigned to one of the four treatment regimens (implant diameter 3.8 [control group], 4.3 [Test group 1, T(1)], 4.8 [Test group 2, T(2)] and 5.5 mm [Test group 3, T(3)]). All implants were restored using a 3.8 mm abutment. In the test groups, this restoration resulted in a mismatching of 0.25-0.85 mm of implant-abutment diameters. RESULTS: Thirty-six months after prosthetic rehabilitation, peri-implant sulcular fluid samples were taken from two aspects of all implants and from periodontally healthy adjacent teeth. Samples were processed in a conventional ELISA using monoclonal antibodies recognizing the active entity of MMP-8. In the test groups, MMP-8 mean values were 2.76 ng for T(1) (SD: 2.91), 3.30 ng for T(2) (SD: 1.94) and 3.18 ng for T(3) (SD: 2.46). For the control group, MMP-8 mean value was 3.6 ng (SD: 2.23), whereas 3.38 ng (SD: 2.2) was recorded at the adjacent teeth. There were no statistically significant differences in MMP-8 values between the groups (P=0.113, Kruskal-Wallis). CONCLUSIONS: The presence of an implant/abutment mismatching specific for this prosthetic concept is compatible with long-term peri-implant health as demonstrated by analysis of a sensitive biomarker of the peri-implant inflammatory response.

A case series on crestal sinus elevation with rotary instruments.

PURPOSE: This case series aimed to evaluate the clinical outcome of a crestal approach technique in sinus floor elevation surgery with insertion of an alloplastic material. MATERIAL AND METHODS: A total of 50 edentulous patients received 64 implants and sinus floor elevation in posterior maxillae with residual crestal height 1.2 to 9.8 mm, and larger than 7 mm in width. Drilling perforation was performed until the sinus floor was felt. The sinus mucosa was then lifted. Hydroxyapatite granules were placed and implants were immediately inserted. Three months later, definitive crowns were cemented and patients were followed up for 18 months. Outcome measures were implant failures, complications and radiographic bone height gain measured 18 months after prosthetic loading. RESULTS: No patient dropped out and all implants were successfully osseointegrated. Only minimal postoperative patient discomfort was reported. Only one complication occurred: a minor perforation of the sinus membrane with no negative consequences. At the time of implant insertion, the residual bone height mean value was 6.20 mm (±2.22). After surgery and at the last follow-up, the mean height of bone was 15.26 (±3.19) and 15.40 mm (±4.21), respectively. CONCLUSION: The procedure was able to obtain sinus elevation and implant osseointegration.

The influence of individual bone patterns on peri-implant bone loss: preliminary report from a 3-year randomized clinical and histologic trial in patients treated with implants restored with matching-diameter abutments or the platform-switching concept.

PURPOSE: This study sought to determine whether there was a correlation between bone resorption and individual bone patterns in patients treated with implants restored conventionally or using the platform-switching concept. MATERIALS AND METHODS: Ten patients (24 implants) were randomly assigned to receive implants with different platform diameters (3.8, 4.3, 4.8, or 5.5 mm), all of which were restored with standard 3.8-mm-diameter abutments. Biopsy specimens were obtained prior to implant placement, and histologic and immunohistochemical analyses were performed. Standardized radiographs were made at each site after implant placement and at 36 months after prosthetic loading and bone levels were determined. RESULTS: One patient dropped out, resulting in a total of 9 patients and 22 implants. Mean bone resorption was 1.358 mm for non-platform-switched implants; mean resorption was 0.832, 0.486, and 0.375 mm for implant platforms of 4.3, 4.8, and 5.5 mm, respectively. After standardization of peri-implant bone remodeling values, a borderline direct correlation between peri-implant bone changes and levels of biglycans was found. At the same time, a borderline indirect correlation between bone changes and levels of tumor necrosis factor-a was found. CONCLUSIONS: Within the limit of this study, which was conducted in a small patient sample over a short observation period, an individual resorption trend was detected and paralleled by immunohistochemical findings. Individual local bone structure and quality seemed to be correlated to peri-implant bone resorption. Correlations between biglycan and tumor necrosis factor-a and bone resorption should be confirmed by a larger patient sample.

Replicative and transcriptional activities of hepatitis B virus in patients coinfected with hepatitis B and hepatitis delta viruses.

Hepatitis B virus (HBV) and hepatitis delta virus (HDV) interplay was investigated by examining liver and serum samples from 21 coinfected and 22 HBV-monoinfected patients with chronic liver disease. Different real-time PCR assays were applied to evaluate intrahepatic amounts of HBV DNA, covalently closed circular DNA (cccDNA), pregenomic RNA (pgRNA), pre-S/S RNAs, and HDV RNA. Besides HBV DNA and HDV RNA levels, HBsAg concentrations in the sera were also determined. HDV-coinfected cases showed significantly lower median levels of serum HBV DNA (-5 log), intrahepatic relaxed-circular DNA (-2 log), and cccDNA (-2 log) than those of HBV-monoinfected cases. Interestingly, pgRNA and pre-S/S RNA amounts were significantly lower (both -1 log) in HDV-positive patients, whereas serum HBsAg concentrations were comparable between the two patient groups. Pre-S/S RNA and HBsAg amounts per cccDNA molecule were higher in HDV-positive patients (3-fold and 1 log, respectively), showing that HBV replication was reduced, whereas synthesis of envelope proteins was not specifically decreased. The ratios of cccDNA to intracellular total HBV DNA showed a larger proportion of cccDNA molecules in HDV-positive cases. For these patients, both intrahepatic and serum HDV RNA amounts were associated with cccDNA but not with HBsAg or HBV DNA levels. Finally, HBV genomes with large deletions in the basal core promoter/precore region were detected in 5/21 HDV-positive patients but in no HDV-negative patients and were associated with lower viremia levels. These findings provide significant information about the interference exerted by HDV on HBV replication and transcription activities in the human liver.

Immediate positioning of a definitive abutment versus repeated abutment replacements in post-extractive implants: 3-year follow-up of a randomised multicentre clinical trial.

PURPOSE: The aim of this randomised clinical trial was to evaluate the influence of restoration on marginal bone loss (MBL) using immediately definitive abutments (one abutment­one time concept) versus provisional abutments later replaced by definitive abutments. MATERIALS AND METHODS: In three private clinics, 32 patients with 32 hopeless maxillary premolars were selected for post-extractive implant-supported immediate restoration and randomised to provisional abutment (PA) and definitive abutment (DA) groups, 16 sites in each group. After tooth extraction, 7 patients had to be excluded for buccal wall fracture at tooth extraction or lack of sufficient primary implant stability (< 35 Ncm). The remaining 25 patients (10 PA, 15 DA) received a post-extractive wide-diameter implant. Immediately after insertion, the PA group were immediately restored using a platform-switched provisional titanium abutment. In the DA group, definitive platform-switched titanium abutments were tightened. In both groups, provisional crowns were adapted, avoiding occlusal contacts. All implants were definitively restored after 3 months. In the PA group, a traditional impression technique with coping transfer was adopted, dis/reconnecting abutments several times; in the DA group, metal prefabricated copings were used and final restorations were seated, avoiding abutment disconnection. Digital standardised periapical radiographs using a customised film holder were recorded at baseline (T0 = implant insertion), final restoration (T1 = 3 months later), and at 18-month (T2) and 3-year (T3) follow-ups. The MBL was evaluated with a computerised measuring technique and digital subtraction radiography (DSR) software was used to evaluate radiographic density. RESULTS: At the 3-year follow-up a success rate of 100% in both groups was reported. In the PA group, peri-implant bone resorption was 0.36 mm at T1, 0.43 mm at T2, and 0.55 mm at T3. In the DA group, peri-implant bone resorption was 0.35 mm at T1, 0.33 mm at T2, and 0.34 mm at T3. Statistically significant lower bone losses were found at T2 (0.1 mm) and T3 (0.2 mm) for the DA group. At T3, significantly higher DSR values around implant necks were recorded in the DA group (72 ± 5.0) when compared with the PA group (52 ± 9.5). CONCLUSIONS: The current trial suggests that the 'one abutment­one time' concept might be a possible additional strategy in post-extraction immediately restored platform-switched single implants to further minimise peri-implant crestal bone resorption, although a 0.2 mm difference may not have any clinical effect. Additional clinical trials with larger groups of patients should be performed to better investigate this hypothesis.

Platform switching and marginal bone-level alterations: the results of a randomized-controlled trial.

OBJECTIVES: This randomized-controlled trial aimed to evaluate marginal bone level alterations at implants restored according to the platform-switching concept, using different implant/abutment mismatching. MATERIAL AND METHODS: Eighty implants were divided according to the platform diameter in four groups: 3.8 mm (control), 4.3 mm (test group(1)), 4.8 mm (test group(2)) and 5.5 mm (test group(3)), and randomly placed in the posterior maxilla of 31 patients. After 3 months, implants were connected to a 3.8-mm-diameter abutment and final restorations were performed. Radiographic bone height was measured by two independent examiners at the time of implant placement (baseline), and after 9, 15, 21 and 33 months. RESULTS: After 21 months, all 80 implants were clinically osseointegrated in the 31 patients treated. A total of 69 implants were available for analysis, as 11 implants had to be excluded from the study due to early unintentional cover screw exposure. Radiographic evaluation showed a mean bone loss of 0.99 mm (SD = 0.42 mm) for test group(1), 0.82 mm (SD = 0.36 mm) for test group(2) and 0.56 mm (SD = 0.31 mm) for test group(3). These values were statistically significantly lower (P<0.005) compared with control (1.49 mm, SD = 0.54 mm). After 33 months, five patients were lost to follow-up. Evaluation of the remaining 60 implants showed no difference compared with 21 months data except for test group(2) (0.87 mm) and test group(3) (0.64 mm). There was an inverse correlation between the extent of mismatching and the amount of bone loss. CONCLUSIONS: This study suggested that marginal bone level alterations could be related to the extent of implant/abutment mismatching. Marginal bone levels were better maintained at implants restored according to the platform-switching concept.

Short-term bone level observations associated with platform switching in immediately placed and restored single maxillary implants: a preliminary report.

PURPOSE: The aim of this study was to evaluate the short-term bone level response around immediately placed and provisionally restored implants using a platform switching concept. MATERIALS AND METHODS: Twenty-two implants with a platform diameter of 5.5 mm were immediately placed in healthy maxillary sites in 22 patients. Resultant circumimplant spaces were filled with a mixture of bovine bone matrix and collagen. The implants were randomly divided into two equal groups: 11 implants connected with 3.8-mm-diameter abutments (test group) and 11 with 5.5-mm-diameter ones (control). Provisional crowns were adapted and adjusted for nonfunctional immediate placement on each implant and the final crowns were constructed 2 months later. Posttreatment assessments were carried out by an independent trained observer at the time of implant placement (baseline), at definitive prosthesis insertion, and every 6 months thereafter. These assessments included periapical radiographs, pocket probing depths (PPD), bleeding on probing (BOP), and modified Plaque Index (mPII) on both implants and first proximal teeth. An image analysis software application was used to compare the bone crestal heights at the mesial and distal aspects of the implants. RESULTS: The mean follow-up observation period was 25 months and all implants were judged to be successfully osseointegrated. In the test group, radiographic analysis showed an average bone reduction level of 0.30 mm (SD = 0.16 mm). This mean value was statistically significantly different (P < or = .005) from the average reduction in the control group (mean = 1.19 mm, SD = 0.35 mm). No differences between the two groups in PPD, BOP, or mPII were found. CONCLUSION: This preliminary study suggests that immediate single implant restorations in specific maxillary sites with subsequent platform switching may provide peri-implant alveolar bone-level stability.

Double-blind randomized controlled trial study on post-extraction immediately restored implants using the switching platform concept: soft tissue response. Preliminary report.

AIM: To evaluate the soft tissue response to immediately placed implants using the platform switching concept. MATERIAL AND METHODS: In 22 patients, 22 implants of 5.5 mm platform diameter were placed immediately into fresh extraction sockets in maxillae without compromised bone tissue. Eventual post-extraction bone defects were filled using bovine bone matrix mixed with collagen. Immediately after insertion, implants were randomly divided: 11 implants were connected with a 3.8 mm diameter abutment (test group) and 11 with a 5.5 mm diameter abutment (control group). A provisional crown was adapted and adjusted for non-functional immediate positioning. Two months later, definitive prosthetic rehabilitation was performed. Periodontal parameter, buccal peri-implant mucosal changes (REC), mesial and distal papilla height (PH) and vertical height of jumping distance (VHG) were measured at the time of implant placement, of definitive prosthesis insertion and every 6 months thereafter. RESULTS: The mean follow-up was 25 months. All implants were clinically osseointegrated. The test group showed a +0.18 mm REC gain. PH gain was +0.045 mm on average. The mean values were statistically significant (P< or =0.005) compared with the control group (PH=-0.88 mm; REC=-0.45 mm). No difference between the two groups in periodontal parameters was found. The mean value of bone filling was 7.51 mm in the test group (97.4% of VHG) and 8.57 mm in the control group (95.2% of VHG). No statistically significant difference was found between the two groups. CONCLUSIONS: This study suggests that, in a limited time period of 2 years, immediately placed implants with subsequent platform switching can provide peri-implant tissue stability.