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 group₁), 4.8 mm (test group₂) and 5.5 mm (test group₃), 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 group₁, 0.82 mm (SD=0.36 mm) for test group₂ and 0.56 mm (SD=0.31 mm) for test group₃. 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 group₂ (0.87 mm) and test group₃ (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. To cite this article:
Canullo L, Fedele GR, Iannello G, Jepsen S. Platform switching and marginal bone‐level alterations: the results of a randomized‐controlled trial.
Clin. Oral Impl. Res. 21 , 2010; 115–121.     

Influence of Implant Neck Surface and Placement Depth on Crestal Bone Changes Around Platform‐Switched Implants: A Clinical and Radiographic Study in Dogs

Background: The aim of this animal study is to analyze bone remodeling around platform‐switching (PS) implants with and without a machined (MACH) collar placed at different levels in relation to the crestal bone in a canine model. Methods: All mandibular premolars and first molars were extracted in five dogs. After 6 months, grit‐blasted acid‐etched (GBAE) PS implants with and without a MACH neck were randomly inserted in each hemimandible, positioning the implant‐abutment interface in either a supracrestal (+1.5 mm), equicrestal, or subcrestal (?1.5 mm) position, and healing abutments were connected. Implant abutments were dis/reconnected at 12, 14, 16, and 18 weeks after implant placement. After 6 months of healing, animals were sacrificed. Clinical parameters and periapical radiographs were registered on the day of implant placement, at 2 months, at every abutment dis/reconnection, and at sacrifice. Crestal bone changes were calculated and defined as the primary outcome variable. Results: When crestal bone changes from implant placement to 6 months were compared between MACH and GBAE groups, no significant differences were encountered except for implants placed in an equicrestal position (P = 0.04). However, multivariable regression analysis revealed no significant differences between MACH and GBAE implants placed in a supracrestal (β = ?0.08; P = 0.45), equicrestal (β = ?0.05; P = 0.50), or subcrestal (β = ?0.13; P = 0.19) position. Conclusion: Surface treatment of the implant neck had no significant influence on crestal bone changes around PS implants with and without a MACH collar.     

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     

Effect of interimplant distance (2 and 3 mm) on the height of interimplant bone crest: a histomorphometric evaluation

Background: Implants restored according to a platform‐switching concept (implant abutment interface with a reduced diameter relative to the implant platform diameter) present less crestal bone loss than implants restored with a standard protocol. When implants are placed adjacent to one another, this bone loss may combine through overlapping, thereby causing loss of the interproximal height of bone and papilla. The present study compares the effects of two interimplant distances (2 and 3 mm) on bone maintenance when bone‐level implants with platform‐switching are used. Methods: This study evaluates marginal bone level preservation and soft tissue quality around a bone‐level implant after 2 months of healing in minipig mandibles. The primary objective is to evaluate histologically and histomorphometrically the affect that an implant design with a horizontally displaced implant–abutment junction has on the height of the crest of bone, between adjacent implants separated by two different distances. Results: Results show that the interproximal bone loss measured from the edge of the implant platform to the bone crest was not different for interimplant distances of 2 or 3 mm. The horizontal position of the bone relative to the microgap on platform level (horizontal component of crestal bone loss) was 0.31 ± 0.3 mm for the 2‐mm interimplant distance and 0.57 ± 0.51 mm above the platform 8 weeks after implantation for the 3‐mm interimplant distance. Conclusions: This study shows that interimplant bone levels can be maintained at similar levels for 2‐ and 3‐mm distances. The horizontally displaced implant–abutment junction provided for a more coronal position of the first point of bone–implant contact. The study reveals a smaller horizontal component at the crest of bone than has been reported for non‐horizontally displaced implant–abutment junctions.     

Influence of various implant platform configurations on peri-implant tissue dimensions: an experimental study in dog

Aim: To evaluate the influence (i) of various implant platform configurations and (ii) of implant surface characteristics on peri‐implant tissue dimensions in a dog model. Material and methods: Mandibular premolars and first molars were extracted bilaterally in six Labrador dogs. After 3 months of healing, two implants, one with a turned and a second with a moderately rough surface, were installed on each side of the mandible in the premolar region. On the right side of the mandible, implants with a tapered and enlarged platform were used, while standard cylindrical implants were installed in the left side of the mandible. Abutments with the diameter of the cylindrical implants were used resulting in a mismatch of 0.25 mm at the tapered implant sites. The flaps were sutured to allow a non‐submerged healing. After 4 months, the animals were sacrificed and ground sections were obtained for histometric assessment. Results: All implants were completely osseointegrated. A minimal buccal bone resorption was observed for both implant configurations and surface topographies. Considering the animals as the statistical unit, no significant differences were found at the buccal aspect in relation to bone levels and soft tissue dimensions. The surface topographies did not influence the outcomes either. Conclusions: The present study failed to show differences in peri‐implant tissue dimensions when a mismatch of 0.25 mm from a tapered platform to an abutment was applied. The surface topographies influence a neither marginal bone resorption or peri‐implant soft tissue dimension. To cite this article:
Baffone GM, Botticelli D, Pantani F, Cardoso LC, Schweikert MT, Lang NP. Influence of various implant platform configurations on peri‐implant tissue dimensions: an experimental study in dog.
Clin. Oral Impl. Res. 22 , 2011; 438–444.     

Submerged and transmucosal healing yield the same clinical outcomes with two-piece implants in the anterior maxilla and mandible: interim 1-year results of a randomized, controlled clinical trial

Objectives: To test whether or not transmucosal healing at two‐piece implants is as successful as submerged placement regarding crestal bone levels and patient satisfaction. Material and methods: Adults requiring implants in the anterior maxilla or mandible in regions 21–25, 11–15, 31–35 or 41–45 (WHO) were recruited for this randomized, controlled multi‐center clinical trial of a 5‐year duration. Randomization was performed at implantation allowing for either submerged or transmucosal healing. Final reconstructions were seated 6 months after implantation. Radiographic interproximal crestal bone levels and peri‐implant soft tissue parameters were measured at implant placement (IP) (baseline), 6 and 12 months. Patient satisfaction was assessed by a questionnaire. A two‐sided t‐test (80% power, significance level α=0.05) was performed on bone‐level changes at 6 and 12 months. Results: One hundred and twenty‐seven subjects were included in the 12‐month analysis (submerged [S]: 52.5%, transmucosal [TM]: 47.2%). From IP to 6 months, the change in the crestal bone level was ?0.32 mm (P<0.001) for the S group and ?0.29 mm (P<0.001) for the TM group. From IP to 12 months, bone‐level changes were statistically significant in both groups (S ?0.47 mm, P<0.001; TM ?0.48 mm, P<0.001). The mean differences of change in the bone levels between the two groups were not statistically significant at either time point, indicating the equivalence of both procedures. For both groups, very good results were obtained for soft tissue parameters and for patient satisfaction. Conclusions: Transmucosal healing of two‐piece implants is as successful as the submerged healing mode with respect to tissue integration and patient satisfaction within the first 12 months after IP. To cite this article:
Hämmerle CHF, Jung RE, Sanz M, Chen S, Martin WC, Jackowski J, Ivanoff CJ, Cordaro L, Ganeles J, Weingart D, Wiltfang J, Gahlert M. Submerged and transmucosal healing yield the same clinical outcomes with two‐piece implants in the anterior maxilla and mandible: interim 1‐year results of a randomized, controlled clinical trial.
Clin. Oral Impl. Res 23 , 2012; 211–219.
doi: 10.1111/j.1600‐0501.2011.02210.x     

Peri-implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part I: a pilot study in dogs

Purpose: The aim of the present study was to evaluate bone remodeling and bone‐to‐implant contact (BIC) after immediate placement at different levels in relation to the crestal bone of Beagle dogs. Materials and methods: The mandibular bilateral second, third and fourth premolars of six Beagle dogs were extracted and six implants were immediately placed in the hemi‐arches of each dog. Randomly, three cylindrical and three tapered implants were inserted crestally (control group) and 2 mm subcrestally (experimental group). Both groups were treated with a minimal mucoperiosteal flap elevation approach. A gap from the buccal cortical wall to the implant was always left. Three dogs were allowed a 4‐week submerged healing period and the other three an 8‐week submerged healing period. The animals were sacrificed and biopsies were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out in order to compare buccal and lingual bone height loss, and BIC between the two groups. Results: All implants osseointegrated clinically and histologically. Healing patterns examined microscopically at 4 and 8 weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. The distance from the top of the implant collar to the first BIC in the lingual crest (A–Lc) showed a significant difference (P=0.0313): 1.91 ± 0.2 mm in the control group and 1.08 ± 0.2 mm in the experimental group. There was less bone resorption in subcrestal implants than crestal implants. The mean percentage of newly formed BIC was greater with the cylindrical implant design (46.06 ± 4.09%) than with the tapered design (32.64 ± 3.72%). Conclusion: These findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri‐implant tissue remodeling. However, less resorption of the Lc may be expected when implants are placed 2 mm subcrestally. To cite this article:
Negri B, Calvo‐Guirado JL, Pardo‐Zamora G, Ramírez‐Fernández MP, Delgado‐Ruíz RA, Muñoz‐Guzón F. Peri‐implant bone reactions to immediate implants placed at different levels in relation to crestal bone. Part I: a pilot study in dogs.
Clin. Oral Impl. Res. 23 , 2012; 228–235.
doi: 10.1111/j.1600‐0501.2011.02158.x     

Influence of placement depth on bone remodeling around tapered internal connection implant: a clinical and radiographic study in dogs

Background: The aim of this study is to evaluate the influence of placement depth on bone remodeling around implants with two different types of tapered internal implant–abutment interface (IAI): tapped‐in (TI) tapered internal IAI and screwed‐in (SI) tapered internal IAI in dogs. Methods: The second, third, and fourth premolars and the first molar in mandibles of six beagle dogs were extracted. After 8 weeks, two SI implants and two TI implants were placed in one side of the mandible. There were four experimental groups: 1) SI placed crestally (SIC); 2) TI placed crestally (TIC); 3) SI placed 1.5 mm subcrestally (SIS); and 4) TI placed 1.5 mm subcrestally (TIS). Healing abutments were connected 12 weeks after implant surgery. Implants and teeth were brushed every second day during the healing period. Clinical and radiographic parameters were recorded at 4, 10, and 16 weeks after second‐stage surgery. Results: Differences between SI and TI implants inserted in the same vertical position were not significant for peri‐implant probing depth (PD), clinical attachment level (CAL), or bone resorption (P >0.05). Subcrestal placement of both implants had greater PD and CAL compared to crestal groups. However, distance from IAI to the first bone–implant contact was lower in subcrestal groups compared to crestal groups (1.27 ± 0.42 mm for SIC versus 0.46 ± 0.26 mm for SIS, P <0.05; 1.36 ± 0.31 mm for TIC versus 0.78 ± 0.42 mm for TIS, P <0.05). Conclusions: Tapered internal IAI configuration had no significant effect on crestal bone resorption. Moreover, subcrestal placement of tapered internal IAI had a positive impact on crestal bone preservation around the cervix of the implant.     

Five‐year outcomes of a randomized clinical trial comparing bone‐level implants with either submerged or transmucosal healing

Aim

To evaluate the long‐term hard and soft tissue peri‐implant tissue stability of bone‐level implants using a different implant placement protocol (submerged versus transmucosal).

Materials and methods

This study was partly a subset analysis of a multicentre study where in 40 patients, a single bone‐level implant with platform switching and a conical implant‐abutment interface was placed either submerged or transmucosal in non‐molar sites. Changes in the peri‐implant tissues between implant placement and 5 years were assessed clinically and radiologically. Patient‐related outcomes were also recorded.

Results

Thirty patients completed the 5‐year follow‐up. Implant survival rate was 100%. The mean radiographic changes in crestal bone levels between baseline and 5 years were 0.59 (0.92) mm and 0.78 (1.03) mm for the submerged and the transmucosal groups, respectively. No statistical significant differences were found between the groups for any of the investigated variables. Peri‐implantitis, defined as changes in the level of crestal bone of ≥2 mm together with bleeding on probing, was only diagnosed in one patient. Patients in both groups were highly satisfied with the treatment received.

Conclusions

Bone‐level implants with submerged or transmucosal healing protocols demonstrated similar outcomes after 5 years. Both protocols yielded optimal clinical and radiographic results when bone‐level implants were placed in non‐molar positions for single tooth replacement.     

Influence of a machined collar on crestal bone changes around titanium implants: a histometric study in the canine mandible

Background: It has been shown that peri‐implant crestal bone reactions are influenced by both a rough–smooth implant border in one‐piece, non‐submerged, as well as an interface (microgap [MG] between implant/abutment) in two‐piece butt‐joint, submerged and non‐submerged implants being placed at different levels in relation to the crest of the bone. According to standard surgical procedures, the rough–smooth implant border for implants with a smooth collar should be aligned with the crest of the bone exhibiting a smooth collar adjacent to peri‐implant soft tissues. No data, however, are available for implants exhibiting a sandblasted, large‐grit and acid‐etched (SLA) surface all the way to the top of a non‐submerged implant. Thus, the purpose of this study is to histometrically examine crestal bone changes around machined versus SLA‐surfaced implant collars in a side‐by‐side comparison. Methods: A total of 60 titanium implants (30 machined collars and 30 SLA collars) were randomly placed in edentulous mandibular areas of five foxhounds forming six different subgroups (implant subgroups A to F). The implants in subgroups A to C had a machined collar (control), whereas the implants in subgroups D to F were SLA‐treated all the way to the top (MG level; test). Furthermore, the MGs of the implants were placed at different levels in relation to the crest of the bone: the implants in subgroups A and E were 2 mm above the crest, in subgroups C and D 1 mm above, in subgroup B 3 mm above, and in subgroup F at the bone crest level. For all implants, abutment healing screws were connected the day of surgery. These caps were loosened and immediately retightened monthly. At 6 months, animals were sacrificed and non‐decalcified histology was analyzed by evaluating peri‐implant crestal bone levels. Results: For implants in subgroup A, the estimated mean crestal bone loss (± SD) was ?0.52 ± 0.40 mm; in subgroup B, +0.16 ± 0.40 mm (bone gain); in subgroup C, ?1.28 ± 0.21 mm; in subgroup D, ?0.43 ± 0.43 mm; in subgroup E, ?0.03 ± 0.48 mm; and in subgroup F, ?1.11 ± 0.27 mm. Mean bone loss for subgroup A was significantly greater than for subgroup E (P = 0.034) and bone loss for subgroup C was significantly greater than for subgroup D (P <0.001). Conclusions: Choosing a completely SLA‐surfaced non‐submerged implant can reduce the amount of peri‐implant crestal bone loss and reduce the distance from the MG to the first bone–implant contact around unloaded implants compared to implants with a machined collar. Furthermore, a slightly exposed SLA surface during implant placement does not seem to compromise the overall hard and soft tissue integration and, in some cases, results in coronal bone formation in this canine model.     

Radiographic evaluation of marginal bone maintenance around tissue level implant and bone level implant: a randomised controlled trial. A 1‐year follow‐up

The etiologic factors associated with crestal bone loss have not been comprehensively clarified. Several theories exist as to the reason for the observed changes in crestal bone height following implant restoration. In the 1990s, the wide‐diameter implants were commercially introduced. Initially, the implants were restored with standard‐diameter abutments because of lack of matching prosthetic components. Long‐term radiographic follow‐up of these ‘platform‐switched’ restored wide‐diameter dental implants has demonstrated a smaller‐than‐expected vertical change in the crestal bone height around these implants that is typically observed around implants restored conventionally with prosthetic components of matching diameters. The aim of this randomised controlled study was to assess radiographically marginal bone level alterations in implants restored according to the platform‐switching concept compared with traditionally restored implants. Fifty‐four subjects to participate in this randomised controlled study were selected. Two groups were assigned at random: control group (56 implants were restored with standard matching‐diameter abutments) and test group (58 implants were restored with medialised abutments). X‐ray explorations were taken for peri‐implant bone level at the minute the last cementing of the prosthesis and at 1‐year follow‐up. NHI Image was used to digitally process and manipulate the radiographic images and perform the measurements. Mean of bone loss with platform‐switching implants was ?0·01 mm, and the mean of bone loss with standard platform implant was 0·42 mm. Outcomes of this study indicated that the platform‐switching design could preserve the crestal bone levels to 1‐year follow‐up. There was a statistically significant difference in marginal bone loss.     

Impact of Platform Switching on Peri‐Implant Bone Remodeling around Short Implants in the Posterior Region, 1‐Year Results from a Split‐Mouth Clinical Trial

Aim: To assess the effect of platform switching on peri‐implant bone remodeling around short implants (8.5 mm) placed in the resorbed posterior mandibular and maxillary region of partially edentulous patients. Materials and Methods: Seventeen patients with one or more missing teeth at both sides in the posterior region were, according to a split‐mouth design, randomly assigned to be treated with a platform‐matched (control) implant on the one side and a platform‐switched implant (test) on the other side. A total of 62 short implants (8.5 mm) with a dual‐acid etched surface with nanometer‐sized calcium phosphate particles was placed. Follow‐up visits were conducted one month and one year after placing the implant crown. Outcome measures were interproximal bone level changes, implant survival and clinical parameters. Results: One year after loading, peri‐implant bone remodeling around test implants (0.53 ± 0.54 mm) was significant less than around control implants (0.85 ± 0.65 mm; p = .003). With regard to implant survival and clinical parameters no significant differences were observed between test and control implants. Conclusions: This study suggested that peri‐implant bone remodeling is affected by platform switching. One year after loading, interproximal bone levels were better maintained at implants restored according to the platform switching concept.     

The effect of different implant neck configurations on soft and hard tissue healing: a randomized-controlled clinical trial

Objective: To compare the soft and hard tissue healing and remodeling around tissue‐level implants with different neck configurations after at least 1 year of functional loading. Material and methods: Eighteen patients with multiple missing teeth in the posterior area received two implants inserted in the same sextant. One test (T) implant with a 1.8 mm turned neck and one control (C) implant with a 2.8 mm turned neck were randomly assigned. All implants were placed transmucosally to the same sink depth of approximately 1.8 mm. Peri‐apical radiographs were obtained using the paralleling technique and digitized. Two investigators blinded to the implant type‐evaluated soft and hard tissue conditions at baseline, 6 months and 1 year after loading. Results: The mean crestal bone levels and soft tissue parameters were not significantly different between T and C implants at all time points. However, T implants displayed significantly less crestal bone loss than C implants after 1 year. Moreover, a frequency analysis revealed a higher percentage (50%) of T implants with crestal bone levels 1–2 mm below the implant shoulder compared with C implants (5.6%) 1 year after loading. Conclusion: Implants with a reduced height turned neck of 1.8 mm may, indeed, lower the crestal bone resorption and hence, may maintain higher crestal bone levels than do implants with a 2.8 mm turned neck, when sunk to the same depth. Moreover, several factors other than the vertical positioning of the moderately rough SLA surface may influence crestal bone levels after 1 year of function. To cite this article:
Tan WC, Lang NP, Schmidlin K, Zwahlen M, Pjetursson BE. The effect of different implant neck configurations on soft and hard tissue healing: a randomized‐controlled clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 14–19.
doi: 10.1111/j.1600‐0501.2010.01982.x     

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, T₁], 4.8 [Test group 2, T₂] and 5.5 mm [Test group 3, T₃]). 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 T₁ (SD: 2.91), 3.30 ng for T₂ (SD: 1.94) and 3.18 ng for T₃ (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.     

The effect of internal versus external abutment connection modes on crestal bone changes around dental implants: a radiographic analysis

Background: To the best of our knowledge, the influence of external versus internal implant–abutment connections on crestal bone remodeling has not been reported. The aim of the present study is to investigate the influence of the abutment connection on peri‐implant crestal bone levels (CBLs) using radiographic recordings. Methods: Radiographic recordings from 40 single‐tooth implants (20 external and 20 internal octagonal connections; one implant/patient) in 40 patients (15 males and 25 females; mean age: 54.3 years) were selected for analyses. The radiographic evaluation included the following: 1) linear bone change (LBC); 2) dimensional change (DC); and 3) angle between the implant and adjacent bone (AIB). Differences in LBC, DC, and AIB between implant placement and 1 year after loading for each system were evaluated using a paired t test. Comparison of LBC, DC, and AIB between systems at 1 year after loading was done using analysis of covariance. The significance level was set at P ≤0.05. Results: Radiographic CBLs (LBCs) were reduced at 1 year after loading compared to those at implant placement to reach statistical significance for the external connection (P = 0.000) but not the internal connection (P = 0.939). CBL changes were significantly greater for the external compared to the internal connection (P = 0.000). Similarly, the DC for the external connection was significantly greater compared to that for the internal connection (P = 0.004). Conclusion: Within the limitations of this study, the implant–abutment connection technology appears to have a significant impact on peri‐implant CBLs, with the external connection paralleled by a significant reduction of CBLs.     

Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs

Objectives: The aim of this study was to histomorphometrically evaluate the influence of interimplant distances (ID) and implant placement depth on bone remodeling around contiguous Morse cone connection implants with ‘platform‐shifting’ in a dog model. Material and methods: Bilateral mandibular premolars of six dogs were extracted, and after 12 weeks, each dog received 8 implants, four placed 1.5 mm subcrestally (SCL) on one side of the mandible and four placed equicrestally (ECL) on the other side, alternating the ID of 2 and 3 mm. The experimental groups were SCL with IDs of 2 mm (2 SCL) and 3 mm (3 SCL) and ECL with IDs of 2 mm (2 ECL) and 3 mm (3 ECL). Metallic crowns were immediately installed. After 8 weeks, the animals were euthanized and histomorphometric analyses were performed to compare bone remodeling in the groups. Results: The SCL groups' indices of crestal bone resorption were significantly lower than those of ECL groups. In addition, the vertical bone resorption around the implants was also numerically inferior in the SCL groups, but without statistical significance. No differences were obtained between the different IDs. All the groups presented similar good levels of bone‐to‐implant contact and histological bone density. Conclusion: The subcrestal placement of contiguous Morse cone connection implants with ‘platform shifting’ was more efficient in preserving the interimplant crestal bone. The IDs of 2 and 3 mm did not affect the bone remodeling significantly under the present conditions. To cite this article:
Barros RRM, Novaes AB Jr., Muglia VA, Iezzi G, Piattelli A. Influence of interimplant distances and placement depth on peri‐implant bone remodeling of adjacent and immediately loaded Morse cone connection implants: a histomorphometric study in dogs.
Clin. Oral Impl. Res. 21 , 2010; 371–378.
doi: 10.1111/j.1600‐0501.2009.01860.x     

Vertical augmentation with interpositional blocks of anorganic bovine bone vs. 7‐mm‐long implants in posterior mandibles: 1‐year results of a randomized clinical trial

Objectives: To evaluate whether 7‐mm‐long implants could be an alternative to longer implants placed in vertically augmented posterior mandibles. Materials and methods: Sixty patients with posterior mandibular edentulism with 7–8 mm bone height above the mandibular canal were randomized to either vertical augmentation with anorganic bovine bone blocks and delayed 5‐month placement of ≥10 mm implants or to receive 7‐mm‐long implants. Four months after implant placement, provisional prostheses were delivered, replaced after 4 months, by definitive prostheses. The outcome measures were prosthesis and implant failures, any complications and peri‐implant marginal bone levels. All patients were followed to 1 year after loading. Results: One patient dropped out from the short implant group. In two augmented mandibles, there was not sufficient bone to place 10‐mm‐long implants possibly because the blocks had broken apart during insertion. One prosthesis could not be placed when planned in the 7 mm group vs. three prostheses in the augmented group, because of early failure of one implant in each patient. Four complications (wound dehiscence) occurred during graft healing in the augmented group vs. none in the 7 mm group. No complications occurred after implant placement. These differences were not statistically significant. One year after loading, patients of both groups lost an average of 1 mm of peri‐implant bone. There no statistically significant differences in bone loss between groups. Conclusions: When residual bone height over the mandibular canal is between 7 and 8 mm, 7 mm short implants might be a preferable choice than vertical augmentation, reducing the chair time, expenses and morbidity. These 1‐year preliminary results need to be confirmed by follow‐up of at least 5 years. To cite this article:
Felice P, Pellegrino G, Checchi L, Pistilli R, Esposito M. Vertical augmentation with interpositional blocks of anorganic bovine bone vs. 7‐mm‐long implants in posterior mandibles: 1‐year results of a randomized clinical trial.
Clin. Oral Impl. Res 21 , 2010; 1394–1403.
doi: 10.1111/j.1600‐0501.2010.01966.x     

Long-term follow-up of turned single implants placed in periodontally healthy patients after 16-22 years: radiographic and peri-implant outcome

Objectives: Retrospectively evaluate the survival, radiographic and peri‐implant outcome of single turned Brånemark^? implants after at least 16 years. Materials and methods: From 134 patients (C‐group), 101 could be contacted concerning implant survival and 50 (59 remaining implants) were clinically examined (I‐group). Marginal bone level was radiographically measured from the implant–abutment junction at baseline (=within 6 months after abutment connection) and 1–4, 5–8 and 16–22 years post‐operatively. Probing depth, gingival and plaque index were measured. Marginal bone‐level changes were analyzed using Friedman's and Wilcoxon's signed ranks tests. Spearman's correlations between radiographic and clinical parameters were calculated. Results: In the C‐group, 13 out of 166 implants in 11 out of 134 patients failed (CSR=91.5%). In the I‐group (28 males–22 females; mean age 23.9 years at baseline; range 14–57), the mean follow‐up was 18.4 years (range 16–22). The mean bone level was 1.7±0.88 mm (range ?0.8 to 5) after 16–22 years. Changes in the mean marginal bone level were statistically significant between baseline and the second measuring interval (1–4 years). Thereafter, no significant differences could be demonstrated. The mean interproximal probing depth, gingival and plaque indices were 3.9±1.27 mm, 1.2±0.81 and 0.2±0.48, respectively. Probing depth was moderately correlated with gingival inflammation (r=0.6; P<0.001) but not with bone level (P>0.05). 81.4% of the implants had a bone level ≤2nd thread and 91.5% had a probing depth ≤5 mm. 76.3% had both bone level ≤2nd thread and probing depth ≤5 mm. Conclusions and clinical implications: The single turned Brånemark^? implant is a predictable solution with high clinical survival and success rates. In general, a steady‐state bone level can be expected over decades, with minimal signs of peri‐implant disease. A minority (5%), however, presents with progressive bone loss. To cite this article :
Dierens M, Vandeweghe S, Kisch J, Nilner K, De Bruyn H. Long‐term follow‐up of turned single implants placed in periodontally healthy patients after 16–22 years: radiographic and peri‐implant outcome.
Clin. Oral Impl. Res. 23 , 2012; 197–204. doi: 10.1111/j.1600‐0501.2011.02212.x     

Biologic width changes around loaded implants inserted in different levels in relation to crestal bone: histometric evaluation in canine mandible

Objectives: The aim of the present study was to evaluate histometric changes around dental implants inserted at different levels in relation to the crestal bone, under different loading conditions. Material and methods: Thirty‐six implants were inserted in the edentulous mandible of six mongrel dogs. Each implant was assigned to an experimental group according to the distance from the top of the implant to the crestal bone: Bone Level (at the crestal bone level), Minus 1 (1 mm below the crestal bone) or Minus 2 group (2 mm below the crestal bone). Each hemimandible was submitted to a loading protocol: conventional or immediate restoration. After 90 days, the animals were killed. Specimens were processed, and measurements were performed concerning the length of soft and hard peri‐implant tissues. Data were analyzed using ANOVA and Student's t test (α=5%). Results: Among conventionally restored sites, the distance from the most coronal position of soft tissue margin (PSTM) and first bone–implant contact (fBIC) was greater for Minus 2 than for Bone Level and Minus 1 sites (P=0.03), but significant differences were not observed among immediately restored sites. Differences among groups were not observed concerning the PSTM, and the distance from the implant–abutment junction to fBIC. Greater amounts of lateral bone loss were observed for conventionally than for immediately restored sites (P=0.006). Conclusions: These findings suggest that the apical positioning of the top of the implant may not jeopardize the position of soft peri‐implant tissues, and that immediate restoration can be beneficial to minimize lateral bone loss. Further studies are suggested to evaluate the clinical significance of these results in longer healing periods.     

Platform switching minimises crestal bone loss around dental implants: truth or myth?

The aim was to assess the role of platform switching (PS) in minimising crestal bone loss around dental implants through a systematic review of the currently available clinical evidence. To address the focused question ‘Does PS minimise crestal bone loss compared with non‐platform‐switched (NPS) implants?’, PubMed/Medline and Google Scholar databases were explored from 1986 up to and including December 2013 using the following key words in different combinations: ‘bone loss’, ‘dental implant’, ‘diameter’, ‘mandible’, ‘maxilla’ and ‘platform switching’. Letters to the Editor, unpublished data, historical reviews, case reports and articles published in languages other than English were excluded. Fifteen clinical studies were included. In seven studies, PS and NPS implants were placed in both the maxilla and mandible. In 13 studies, implants were placed at crestal bone levels whereas in one study, implants were placed supracrestally. Three studies reported the bucco‐lingual (or transversal) width of the alveolar ridge which ranged between 7–8 mm. Seven studies reported that implants placed according to the PS concept did not minimise crestal bone loss as compared with NPS implants. 3D‐Implant positioning, width of alveolar ridge and control of micromotion at the implant‐abutment interface are the more critical factors that influence crestal bone levels than PS.