Evaluation of a New Titanium‐Zirconium Dental Implant: A Biomechanical and Histological Comparative Study in the Mini Pig

Background: Titanium zirconium alloy with 13–17% zirconium (TiZr1317) shows significantly better mechanical attributes than pure Ti with respect to elongation and fatigue strength. This material may be suitable for thin implants and implant components exposed to high mechanical constraints. Purpose: The aim of this study was to test the hypothesis that TiZr1317 and Ti implants show comparable osseointegration and stability. Materials and Methods: The mandibular premolars (P1, P2, P3) and the first molar (M1) in 12 adult miniature pigs were extracted 3 months prior to the study. Six specially designed implants made from Ti (commercially pure, Grade 4) or TiZr1317 (Roxolid®, Institut Straumann AG, Basel, Switzerland) with a hydrophilic sandblasted and acid‐etched (SLActive, Institut Straumann AG, Basel, Switzerland) surface were placed in each mandible; three standard implants modified for evaluation of removal torque (RT) in one side and three bone‐chamber implants for histologic observations in the contralateral side. RT tests were performed after 4 weeks when also the bone chamber implants and surrounding tissue were biopsied for histologic analyses in ground sections. Results: The RT results indicated significantly higher stability (p = 0.013) for TiZr1317 (230.9 ± 22.4 Ncm) than for Ti implants (204.7 ± 24.0 Ncm). The histology showed similar osteoconductive properties for both implant types. Histomorphometric measurements showed a statistically significant higher (p = 0.023) bone area within the chamber for the TiZr1317 implants (45.5 ± 13.2%) than did the Ti implants (40.2 ± 15.2%). No difference was observed concerning the bone to implant contact between the groups with 72.3 ± 20.5% for Ti and 70.2 ± 17.3% for TiZr1317 implants. Conclusion: It is concluded that the TiZr1317 implant with a hydrophilic sandblasted and acid‐etched surface showed similar or even stronger bone tissue responses than the Ti control implant     

Marginal Bone Level Changes and Prosthetic Maintenance of Mandibular Overdentures Supported by 2 Implants: A 5‐Year Randomized Clinical Trial

Background: Documentation of early loading of mandibular overdentures supported by different implant systems is scarce. Purpose: This study aimed to compare the biologic and prosthetic outcome of mandibular overdentures supported by unsplinted early‐loaded one‐ and two‐stage oral implants after 5 years of function. Materials and Methods: Twenty‐eight consecutive patients were screened following an inclusion and exclusion criteria, and randomly allocated to treatment groups. Ball‐retained mandibular overdentures were fabricated on two unsplinted Straumann® (Institut Straumann AG, Basel, Switzerland) and Brånemark® (Nobel Biocare AB, Göteborg, Sweden) dental implants and subjected to an early‐loading protocol. During the 5‐year period, prosthetic complications were recorded. At 5‐years of function, plaque, peri‐implant inflammation, bleeding, and calculus index scores were recorded, and standard periapical radiographs were obtained from each implant for measurement of marginal bone loss. Results: All implants survived during the observation period. The peri‐implant inflammation, bleeding, and calculus index scores around Straumann and Brånemark implants were similar (p > .05). The marginal bone loss around Brånemark implants (1.21 ± 0.1) was higher than Straumann implants (0.73 ± 0.06) at 5 years of function (p = .002). Kaplan–Meier tests revealed that 1‐ and 5‐year survival of overdentures on Straumann and Brånemark implants were similar (p = .85). Wear of the ball abutment in the Brånemark group was higher than in the Straumann group (p < .05). Complications regarding the retainer and the need for occlusal adjustments were higher in the Straumann group (p < .05). Chi‐square test revealed that the frequency of retightening of the retainer was higher in the Straumann group than in the Brånemark group (p < .05). Conclusions: Mandibular overdentures supported by unsplinted early‐loaded Straumann and Brånemark implants lead to similar peri‐implant soft tissue and prosthetic outcomes, although higher marginal bone loss could be observed around Brånemark implants after 5 years.     

Immediate and Early Loading of Chemically Modified Implants in Posterior Jaws: 3‐Year Results from a Prospective Randomized Multicenter Study

Background: There is a lack of well‐designed prospective, randomized clinical trials evaluating the efficacy of immediate and early loading of implants placed in the partially edentulous posterior maxilla or mandible. Purpose: The aim of this study was to evaluate crestal bone level changes over 3 years following immediate or early loading of Straumann implants with a chemically modified surface (SLActive®, Institut Straumann AG, Basel, Switzerland) placed in the posterior maxilla and mandible. Materials and Methods: Subjects received temporary restorations immediately or 28 to 34 days after surgery, with permanent restorations placed at 20 to 23 weeks. Bone level changes were measured by comparison of standardized radiographs taken on the day of implant placement and 5, 12, 24, and 36 months thereafter. Results: Two hundred thirty‐nine of two hundred sixty‐six patients (89.9%) completed the trial. Implant survival rates were 97.4% and 96.7% in the immediate and early loading groups, respectively (p = not significant). Over 36 months, the mean bone level change for immediately loaded implants was 0.88 ± 0.81 mm versus 0.57 ± 0.83 mm for the early‐loaded group (p < .001). After adjusting for a slight difference in initial placement depth, the time of loading had no significant influence on bone level change. Conclusions: Changes in crestal bone level occurred mostly during the first 5 months postloading. After this bone remodeling period, crestal bone level was stable up to 36 months. Implants with a chemically modified surface are safe and predictable for immediate and early loading in the posterior maxilla and mandible.     

Ridge alterations following immediate implant placement and the treatment of bone defects with Bio-Oss in an animal model

Background: Conflicting data exist on the outcome of placing Bio‐Oss® (Geitslich Pharm AG, Wolhausen, Switzerland) into extraction sockets. It is therefore relevant to study whether the incorporation of Bio‐Oss into extraction sockets would influence bone healing outcome at the extraction sites. Purpose: The aim of this study was to assess peri‐implant bone changes when implants were placed in fresh extraction sockets and the remaining defects were filled with Bio‐Oss particles in a canine mandible model. Materials and Methods: Six mongrel dogs were used in the study. In one jaw quadrant of each animal, the fourth mandibular premolars were extracted with an elevation of the mucoperiosteal flap; implants were then placed in the fresh extraction sockets and the remaining defects were filled with Bio‐Oss particles. After 4 months of healing, micro‐computed tomography at the implant sites was performed. Osseointegration was calculated as the percent of implant surface in contact with bone. Additionally, bone height was measured in the peri‐implant bone. Results: Average osseointegration was 28.5% (ranged between 14.8 and 34.2%). The mean crestal bone loss was 4.7 ± 2.1 mm on the buccal aspect, 0.4 ± 0.5 mm on the mesial aspect, 0.4 ± 0.3 mm on the distal aspect, and 0.3 ± 0.4 mm on the lingual aspect. Conclusion: The findings from this study demonstrated that the placement of implants and Bio‐Oss® particles into fresh extraction sockets resulted in significant buccal bone loss with low osseointegration.     

A Comparative Study of Crestal Bone Loss and Implant Stability between Osteotome and Conventional Implant Insertion Techniques: A Randomized Controlled Clinical Trial Study

Purpose: The aim of this prospective randomized controlled clinical study was to assess the crestal bone loss and the implant stability in implants that were placed by the osteotome technique compared with the conventional drilling technique. Materials and Methods: Forty‐six screw type Straumann SLA® oral implants (Straumann AG, Waldenburg, Switzerland) were inserted in the anterior segment of maxilla of 30 patients. The implant site was prepared randomly using either osteotome technique (test group) or the conventional drilling technique (control group). Radio frequency analysis (RFA) values at implant placement and after 3 months were recorded. The crestal bone loss was measured using digital subtraction radiography technique after 3, 6, and 12 months. Results: RFA demonstrated a statistically significant higher primary stability for implants in the osteotome group than that of the conventional group (p = .026) at the time of implant insertion. However, there was no statistically significant difference between both groups 3 months after the surgery (p = .06). At month 3, the osteotome group caused significantly more crestal bone loss than the conventional group (p = .04). At months 6 and 12, both groups had comparable bone levels (p = .29). Conclusion: Osteotome technique yielded higher primary stability than conventional drilling technique. However, this technique was not superior to conventional technique after 3 months.     

Marginal Bone Level Changes at Dental Implants after 5 Years in Function: A Meta‐Analysis

Background: It is important that peri‐implant bone breakdown caused by, for example, undue load and/or peri‐implantitis, is prevented or minimized. Some continuous loss of marginal bone is generally accepted, but the question remains as to what extent it must occur. Purpose: The purpose of this study was to compile and compare data on peri‐implant marginal bone level changes from prospective studies that have registered the peri‐implant marginal bone level radiographically at the time of prosthetic loading, and after 5 years of follow‐up for implant systems currently available on the market. Materials and Methods: A literature search was carried out to identify prospective studies on peri‐implant marginal bone level changes around dental implants. To be included in a meta‐analysis, the implant systems should have been subjected to at least two independent studies. Copycats without documentation were not accepted. Results: Forty prospective studies that presented with a 5‐year data were identified. Three implant systems met the inclusion criteria of having at least two independent studies; Astra Tech Dental Implant System® (Astra Tech AB, Mölndal, Sweden), Brånemark System (Nobel Biocare AB, Göteborg, Sweden), and Straumann Dental Implant System (Institute Straumann AG, Basel, Switzerland). The pooled mean marginal bone level change amounted to ?0.24 mm (95% CI ?0.345, ?0.135) for the Astra Tech Dental Implant System, 0.75 mm (95% CI ?0.802, ?0.693) for the Brånemark System, and 0.48 mm (95% CI ?0.598, ?0.360) for the Straumann Dental Implant System over 5 years, with a statistically significant difference (p < .01) between the systems. Conclusions: The identified implant systems showed an annual bone loss below or much below what hitherto has been set up as a limit for success. A careful documentation of marginal bone level changes should be mandatory for all implant systems before being marketed. It is also time for revision of existing success criteria to refine the basis for clinical quality judgment of implant treatment.     

Nonsubmerged and submerged implants in the treatment of the partially edentulous maxilla

Background: Dental implants vary in design and surfaces. In addition, different surgical techniques have been used for implant insertion. The ITI Dental Implant System (Straumann AG, Waldenburg, Switzerland) has always required a one‐stage technique, whereas the Brånemark System (Nobel Biocare AB, Gothenburg, Sweden) requires a two‐stage technique. Purpose: The aim of this study is to compare the outcome of fixed partial bridges in the maxilla supported by both ITI and Brånemark implants in a split‐mouth design. Materials and Methods: Twenty‐eight patients with a residual anterior dentition in the maxilla were included in this split‐mouth study. The Brånemark implants were used on one side and the ITI implants on the other side of the residual dentition according to a randomization procedure. A blocking size of four was used, giving equal probability of placing ITI or Brånemark implants in the right or left side of the jaw. The surgical and prosthetic procedures followed the guidelines given by the manufacturers. The prosthetic treatment with the two‐implant systems was performed at the same time, and for that reason the healing period was 6 months for both systems. The observation period for all patients was 1 year after loading. Results: Two Brånemark implants (in one patient) were lost before loading, and one ITI implant was lost 1 year after loading. There was no significant difference in survival rate. Radiographie examination of the bone level was performed at the time of delivery of the bridge and after 1 year. The mean marginal bone level at baseline was situated 1.9 mm from the reference point for the Brånemark implants and 1.5 mm for the ITI implants. With regard to the insertion depth used, these bone levels indicate that bone loss had taken place before baseline. However, between baseline and the 1‐year examination, there was no significant change of the marginal bone (0.2 ± 0.08 mm at the Brånemark implants and 0.1 ± 0.11 mm at the ITI implants). The difference between results with the two implants was not statistically significant. Crater‐form bone destructions were seen at some ITI implants, indicating periimplantitis. However, at only two implants were there clinical signs of periimplantitis. Conclusions: No significant difference in survival rate or in marginal bone change could be demonstrated between the two systems. At some ITI implants (18%), crater‐form bone loss was observed.     

Peri-implant tissue response to TiO2 surface modified implants

Objectives: The objective of this study was to evaluate peri‐implant soft tissue attachment and alveolar bone height on nanoporous TiO₂ thin film on commercial titanium dental implants compared with unmodified standard implants. Material and methods: In six adult beagle dogs, the mandibular premolars P2–P4 were extracted bilaterally. Sol–gel‐derived nanoporous TiO₂ thin film was produced on smooth coronal part of standard ITI^® Straumann implants (4.1 mm × 8.0 mm) by dip coating method. After 3 months healing period of the extraction sockets modified (n=24) and unmodified (n=11) control implants were placed bilaterally. The animals were killed after 8 weeks and the samples were retrieved and processed for histologic/histomorfometric and TEM/SEM evaluations. Results: Histological examination showed mild or absent inflammatory reaction in peri‐implant connective tissues around the surface modified implants. Further, junctional epithelium (JE)/connective tissue (CT) appeared to be in immediate contact with the experimental implants. Of the experimental implants, 22% were judged to be detached from the implant surface while 45% of the untreated control implants were detached. Dense plaques of hemidesmosomes were found in TEM evaluation of the JE cell membrane facing the surface‐treated implants. In the histomorfometric analysis, the distance between the implant margin and alveolar bone crest was significantly shorter in surface‐treated implants than in the control implants (P<0.02). Conclusion: Nanoporous sol–gel‐derived TiO₂ thin film on ITI^® Straumann dental implants improved soft tissue attachment in vivo.     

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

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 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. 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=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; P<0.001). However, a significant difference in implantation depth between the two groups (P<0.0001) was found. After adjusting for this slight difference in initial surgical placement depth, time to loading no longer had a significant influence on bone‐level change. Significant influence was found for: center (P<0.0001), implant length (P<0.05) and implant position (P<0.0001). 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.     

A three-year follow-up report of a comparative study of ITI Dental Implants and Brånemark System implants in the treatment of the partially edentulous maxilla

Background: Many longitudinal studies of different implant systems have been published but few controlled randomized investigations have been reported. A 1‐year report of a comparative study of ITI Dental Implant System® implants (Straumann AG, Waldenburg, Switzerland) and Brånemark System® implants (Nobel Biocare AB, Gothenburg, Sweden) has been published by the present authors. This paper is a 3‐year follow‐up of that randomized study. Purpose: The aim of the study was to compare the outcome of fixed partial prostheses supported by ITI or Branemark implants. The outcome was evaluated primarily in terms of survival rates and changes in marginal bone level. Material and Methods: The study group comprised 28 patients with anterior residual dentition in the maxilla. The patients were provided with two to four implants on each side of the dentition and were randomly allocated to Brånemark implants or ITI implants; 77 ITI implants and 73 Brånemark implants were inserted. After 6 months abutment connections were made to both ITI and Brånemark implants. All patients were provided with fked partial prostheses of gold‐ceramic. The patients were followed up annually with clinical and radiographic examinations for 3 years. Results: Two Brånemark implants and two ITI implants were lost. The Brånemark implants were lost before loading whereas the ITI implants were lost because of periimplantitis. The survival rate for both groups was 97.3%. The mean marginal bone level of the Brånemark implants was situated 1.8 mm from the reference point at both the baseline and the 3‐year examinations. The corresponding values for the ITI implants were 1.4 mm at baseline and 1.3 mm after 3 years. There was no significant difference between the implant systems with regard to bone level or bone level change. A steady state of the marginal bone level was calculated to have been reached after 3 years for 95.5% of the Brånemark implants and 87.1% of the ITI implants. Periimplantitis (infection including pus and bone loss) was observed with seven ITI implants but with none of the Brånemark implants. This difference was statistically significant. Conclusions: No statistically significant differences were found between the implants studied, except for the frequency of periimplantitis, which was higher for the ITI implants. The survival rates were high, and the marginal bone loss was small for both systems.     

In Vitro Assessment of Primary Stability of Straumann® Implant Designs

Background: Primary implant stability (PS) is one of the main factors influencing implant survival rate. Several methods to determine the PS have been used, such as Periotest values (PVs) and resonance frequency analysis (RFA) with implant stability quotient (ISQ) values. Purpose: The aim of this study was to compare different implant designs in regard to PS assessed by Periotest and RFA in vitro. Materials and Methods: A total of 90 implants were placed in freshly slaughtered cow ribs. The implants (Straumann®, Institute Straumann AG, Basel, Switzerland; length 10 mm, ø3.3 mm) had the following three designs: Bone Level (BL, 30 implants), Standard Plus (SP, 30 implants), and Tapered Effect (TE, 30 implants). Before implant placement, the investigator was calibrated for every design according to the manufacturer's instructions. An independent observer, blinded to the study, assessed the accuracy of placement. RFA based on the Osstell device and PVs were performed after abutment connection. One‐way analysis of variance and Tukey's post hoc test were used for statistical evaluation. Results: All implants were mechanically stable. The mean PV for BL was ?4.67(± 1.18), for SP, ?6.07(± 0.94), and for TE, ?6.57(± 0.57). The mean ISQ values were 75.02(± 3.65), 75.98(± 3.00), and 79.83(± 1.85), respectively. The one‐way ANOVA showed significant difference among three implant designs in PV (p < .0001) and for the ISQ between BL/TE or SP/TE implants (p < .0001). In addition, the Tukey's (pair‐wise comparison) test showed significant differences in PV and RFA between the BL/TE (p < .0001). Conclusion: Within the limitations of this study, higher implant stability was found for tapered designed implants.     

Nonsubmerged Implants in the Treatment of the Edentulous Lower Jaw: A 5-Year Prospective Longitudinal Study of ITI Hollow Screws

Background: Although most implant systems have been designed for a two‐stage surgical technique, a one‐stage surgical technique has always been advocated for the ITI Dental Implant System (Straumann AG, Waldenburg, Switzerland). A new generation of ITI implants was presented in 1988 and included a hollow cylinder, a hollow screw, and a solid screw. Purpose: The goal of this study was to evaluate the one‐stage surgical technique in connection with the ITI hollow screw in a longitudinal study over 5 years. Materials and Methods: Forty‐six patients with edentulous lower jaws were supplied with ITI hollow‐screw implants. Patients who requested an overdenture (n = 18) had four implants inserted; those who requested a fixed bridge (n = 28) had five to six implants. The patients have been followed annually for 5 years. There was a dropout of three patients (6.5%); one patient did not want to cooperate, one moved from the area, and one was deceased. The clinical examinations included bridge removal for evaluation of the individual implant stability in connection with the 1‐, 3‐, and 5‐year examinations. Radiographic examinations were performed with intraoral radiographs and the long‐cone technique. Results: The survival rate after 5 years was 95.7%. The success rate (in which implants undergoing treatment of peri‐implantitis were not counted as successes) was 91.4%. The mean marginal bone loss between the baseline and the 1‐year examination was 0.1 mm and between the 1‐ and 5‐year examinations was 0.1 mm. These changes in marginal bone level were not significant. Conclusions: The success rate of ITI hollow‐screw implants in the edentulous mandible was 91.4% after a 5‐year observation period. There was no significant change in mean bone level between the loading of the implants and the 5‐year examination. Peri‐implantitis was diagnosed in three patients with poor oral hygiene, and it affected six implants. Five of these failed in spite of treatment.     

Bone level alterations at implants placed in the posterior segments of the dentition: outcome of submerged/non-submerged healing. A 5-year multicenter, randomized, controlled clinical trial

Objective: To determine if longitudinal bone level change at Astra Tech^? implants placed in the posterior part of the dentition was influenced by the healing conditions provided following implant placement, i.e., submerged or non‐submerged healing. Material and methods: Eighty‐four patients and 115 fixed partial dentures (FPDs or cases) entered the study. The cases were randomized into two implant installation groups: initially non‐submerged (group A) or initially submerged (group B) implants. Three hundred and twenty‐four implants were installed (group A=153; group B=171): 145 in the maxilla and 179 in the mandible. Radiographs from the implant sites were obtained at FPD insertion (baseline) and subsequently every 12 months. In the radiographs, the position of the marginal bone at the mesial and distal aspects of the implants was determined and the radiographic (Rx) bone level change over time was calculated. Results: Seven implants failed to integrate (four in group A and three in group B). During the 5 years of monitoring, three implants had to be removed and 35 implants were lost to follow‐up. The Rx bone level alteration that occurred during year 1 was 0.02±0.38 mm in group A and 0.17±0.51 mm in group B. During the subsequent 4 years there was some further Rx bone loss in group B (0.02±0.62 mm), while in group A there was some gain of bone (0.07±0.5 mm). Conclusion: The peri‐implant bone level change and number of biological complications that took place during the 5 years was small and unrelated to the surgical protocol used for implant placement.     

Influence of bony defects on implant stability

Introduction: The purpose of this study was to analyze the evolution of implant mechanical stability in different types/sizes of bony defects using both Periotest and Osstell devices as “objective tools.” Materials and methods: Thirty‐two implants were randomly allocated to one of the four types of bone defects: marginal bone loss, peri‐apical bone defect, constant width dehiscence and constant length dehiscences. Periotest/Osstell measurements were completed before and during staged bone removal (to enlarge defect size). Results: Significant differences (P<0.05) with initial values were found after a 2 mm marginal bone removal (Osstell/Periotest); for a peri‐apical bone lesion, after removal of 5 mm (Osstell) or 8 mm (Periotest); for a 6‐mm‐long dehiscence, after removal up to 180° of the implant perimeter (Osstell/Periotest); for a 3‐mm‐wide dehiscence, after removal of 10 mm (Osstell) or 6 mm (Periotest). Conclusion: Periotest and Osstell are in general not very sensitive in the identification of peri‐implant bone destruction, except for marginal bone loss. To cite this article:
Merheb J, Coucke W, Jacobs R, Naert I, Quirynen M. Influence of bony defects on implant stability.
Clin. Oral Impl. Res. 21 , 2010; 919–923.
doi: 10.1111/j.1600‐0501.2010.01932.x     

Transmucosal healing around peri‐implant defects: crestal and subcrestal implant placement in dogs

Objective: This study was designed to evaluate the transmucosal healing response of implants placed with the junction of the smooth surfaces, either crestal or subcrestal, into simulated extraction defects after healing periods of 1 and 3 months. Materials and methods: A total of 23 Straumann SP ?3.3 mm NN, SLA^® 10 mm implants were placed in the mandibular premolar regions of three greyhound dogs 3 months after the teeth were removed. Five control implants were placed at the crestal bone level, and test implants with surgically created peri‐implant defects of 1.25 mm wide × 5 mm depth were placed either at the crestal (nine implants) or at the 2 mm subcrestal (nine implants) bone level. Implants on the right side were placed 1 month before the dogs were sacrificed, and implants on the left side were placed 3 months before sacrifice. All dogs had daily plaque control following surgery and were sacrificed 3 months after implant placement for histological and histometric analyses. Results: Mesial–distal ground sections of the control and test implant specimens showed a greater %BIC in the coronal defect region after 3 months of healing. This healing response was incomplete for the test implants compared with the control implants after a 1‐month healing period. The histometric measurements for test implants placed at the crestal bone level or 2 mm subcrestal with surgically created peri‐implant defects were more coronal or closer to the implant margin compared with the control implants. Additionally, the degree of osseointegration between the newly formed bone and the implant surface was similar between the test implants. Conclusion: Peri‐implant defects of 1.25 mm width healed with spontaneous bone regeneration around implants placed transmucosally at crestal or 2 mm subcrestal with a high degree of osseointegration after a 3‐month healing period. To cite this article:
Tran BLT, Chen ST, Caiafa A, Davies HMS, Darby IB. Transmucosal healing around peri‐implant defects: crestal and subcrestal implant placement in dogs.
Clin. Oral Impl. Res. 21 , 2010; 794–803.
doi: 10.1111/j.1600‐0501.2010.01911.x     

Microcomputed Tomographic Analysis of the Alveolar Ridge Alteration around Extraction Sites with and without Immediate Implants Placement: In Vivo Study

Background: The aim was to assess the alveolar ridge alteration around extraction sites with and without immediate implants according to extraction socket classification (ESC) using microcomputed tomography (micro‐CT). Material and Methods: Ten beagle dogs (mean age and weight: 24 ± 0.83 months and 13.8 ± 0.49 kg, respectively) were randomly divided into three groups according to the ESC. In Group 1 (ESC‐I), bilateral first and third premolars were extracted and replaced with immediate implants. In Group 2 (ESC‐II), two adjacent premolars were extracted with one immediate implant placement in the mesial socket in the maxilla and in the distal socket in the mandible. In Group 3 (ESC‐III), three adjacent teeth were extracted and an immediate implant was placed in the central socket. Primary closure was achieved using resorbable sutures. Buccal sites with dehiscence defects were excluded. After 4 months, subjects were sacrificed and alveolar ridge widths were measured at 1 mm interval in axial and sagittal views, using micro‐CT in sites with and without immediate implants. Results: In sites without immediate implant placement, alveolar ridge width was significantly higher in Group 1(6.1 ± 1.35 mm) than Group 3 (4.14 ± 1.53 mm) (p < .05). In sites with immediate implant placement, the alveolar ridge width was higher among sites in Group 1 (6.4 ± 3.8 mm) than Group 2 (4.8 ± 0.46 mm) (p < .05) and Group 3 (5.02 ± 0.84 mm) (p < .05). Overall, between each corresponding group in both sites with and without immediate implant placement at 1 mm thickness, there was no significant difference in the alveolar ridge widths. Conclusion: With the exception of Group 1 (ESC‐I), immediate implant placement did not prevent or minimize bone remodeling in extraction sites according to ESC.     

Clinical and radiographic characteristics of single‐tooth replacements preceded by local ridge augmentation: a prospective randomized clinical trial

Objectives: To assess in a randomized‐clinical trial the influence of three augmentation techniques (chinbone with or without a Bio‐Gide^® membrane and Bio‐Oss^® with a Bio‐Gide^® membrane) on the clinical and radiographic characteristics of hard and soft tissues around implants and adjacent teeth in the reconstructed maxillary anterior region, up to 1 year after functional loading. Materials and methods: Ninety‐three patients requesting single‐tooth replacement and presenting with a horizontal (bucco‐palatinal) bone deficiency were included. After augmentation, 93 ITI‐Esthetic^Plus implants were placed. Clinical variables, standardized photographs and radiographs were analysed to assess the impact on the levels of the marginal gingiva (MGL) and marginal bone (MBL) around implants and adjacent teeth, viz at pre‐augmentation, pre‐implantation (TPI) and 1 (T₁) and 12 (T₁₂) months after final crown placement. Results: Implant survival was 97.8%. No significant differences were observed in the treatment outcomes of the three augmentation modalities. Combining the three modalities, a slight but significant increase in the implants approximal pocket depth was found between T₁ and T₁₂. Approximal bone loss at the implant between T₁ and T₁₂ was 0.14 ± 0.76 mm (mesial) and 0.14 ± 0.47 mm (distal); the approximal MGL slightly increased (mesial: 0.24 ± 0.46 mm, distal: 0.25 ± 0.66 mm), and the buccal MGL decreased (0.11 ± 0.61 mm). Bone loss at the adjacent teeth, although minor, was significant between TPI and T₁. No correlations were observed in changes of MBL and MGL. Conclusions: None of the three applied augmentation technique procedures influenced the characteristics of the MGL and MBL or the implant survival of single‐tooth replacements. Peri‐implant hard and soft tissues were very stable in the first year after loading.     

Characterization of the surface properties of commercially available dental implants using scanning electron microscopy, focused ion beam, and high-resolution transmission electron microscopy

Background: Since osseointegration of the respective implant is claimed by all manufacturing companies, it is obvious that not just one specific surface profile including the chemistry controls bone apposition. Purpose: The purpose was to identify and separate out a particular set of surface features of the implant surfaces that can contribute as factors in the osseointegration process. Material and Methods: The surface properties of several commercially available dental implants were extensively studied using profilometry, scanning electron microscopy, and transmission electron microscopy. Ultrathin sections prepared with focused ion beam microscopy (FIB) provided microstructural and chemical data which have not previously been communicated. The implants were the Nobel Biocare TiUnite® (Nobel Biocare AB, Göteborg, Sweden), Nobel Biocare Steri‐Oss HA‐coated (Nobel Biocare AB, Yorba Linda, CA, USA), Astra‐Tech OsseoSpeed? (Astra Tech AB, Mölndal, Sweden), Straumann SLA® (Straumann AG, Waldenburg, Switzerland), and the Brånemark Integration Original Fixture implant (Brånemark Integration, Göteborg, Sweden). Results: It was found that their surface properties had differences. The surfaces were covered with crystalline TiO₂ (both anatase and rutile), amorphous titanium oxide, phosphorus doped amorphous titanium oxide, fluorine, titanium hydride, and hydroxyapatite, respectively. Conclusion: This indicates that the provision of osseointegration is not exclusively linked to a particular set of surface features if the implant surface character is a major factor in that process. The studied methodology provides an effective tool to also analyze the interface between implant and surrounding bone. This would be a natural next step in understanding the ultrastructure of the interface between bone and implants.     

Correlation between early perforation of cover screws and marginal bone loss: a retrospective study

Aim: This retrospective study aimed to determine the consequence of early cover screw exposure on peri‐implant marginal bone level. Material and Methods: Sixty Astra Tech^® MicroThread implants installed in partially edentulous jaws were compared: 20 implants were placed following a two‐stage procedure and were unintentionally exposed to the oral cavity (two‐stage exposed), 20 implants were placed following a two‐stage procedure and were surgically exposed after a subgingival healing time of 3–6 months (two‐stage submerged), and 20 implants were placed following a one‐stage surgical protocol (one‐stage). Digital radiographs were taken at implant placement for all implants, and after abutment surgery for the two‐stage exposed and two‐stage submerged groups or after 3 months for the one‐stage group. Bone loss mesially and distally was measured with an on‐screen cursor after calibration. Results: Mean bone re‐modelling was 1.96 mm (range: 0.2–3.2 mm) around the two‐stage exposed implants, 0.01 mm (range: 0.0–0.3 mm) around the two‐stage submerged implants and 0.14 mm (range: 0.0–1.2 mm) around the one‐stage implants. Conclusion: The unintentional perforation of two‐stage implants resulted in significant bone destruction, probably because the biological width was not considered.     

A retrospective analysis of early and delayed loading of full-arch mandibular prostheses using three different implant systems: clinical results with up to 5 years of loading

Background: Early loading of implant‐supported prostheses in the edentulous mandible is widely accepted, but do the clinical results replicate those of delayed loading? Purpose: The aim of this study was to evaluate clinical outcome and patient satisfaction with early or delayed loading in patients treated with fixed prostheses, using three different implant systems. Materials and Methods: One hundred and nine consecutively treated patients received 490 implants supporting fixed prostheses; 82 patients with Brånemark System® implants (Nobel Biocare AB, Göteborg, Sweden), 16 with Astra Tech® implants (Astra Tech AB Dental Implant system, Mölndal, Sweden), and 11 with ITI® MonoType® implants (ITI Dental Implant System®, Institute Straumann AG, Waldenburg, Switzerland). Prostheses were placed within 2 to 3 weeks in 55 patients; 54 patients underwent a two‐stage procedure. Data were collected from patient records and radiographs; 83 patients attended a clinical examination and received a questionnaire. Results: All patients had fixed prostheses at follow‐up with a mean observation time of 3.5 years. Cumulative survival rates (CSRs) were 92.5% of prostheses and 94.4% of implants for early loading, and 98.0 and 97.9% for delayed loading. The mean radiographic bone loss after the first year was small, and at 5 years less than 0.2 mm for both groups. With early loading, significantly more prostheses (p < .05) needed adjustment or replacement. Conclusion: Statistically significantly more prostheses needed adjustment or replacement in the early group. The present study suggested lower CSRs for prostheses and implants in the early loading group after 5 years; the difference was not statistically significant. Larger study samples are needed to verify statistically small differences between treatment techniques.