Effect of platform switching on peri-implant bone levels: a randomized clinical trial

Objective: The concept of platform switching has been introduced to implant dentistry based on observations of reduced peri‐implant bone loss. However, randomized clinical trials are still lacking. This study aimed to test the hypothesis that platform switching has a positive impact on crestal bone‐level changes. Material and methods: Two implants with diameters of 4 mm were inserted epicrestally into one side of the posterior mandibles of 25 subjects. After 3 months of submerged healing, the reentry surgery was performed. On the randomly placed test implant, an abutment 3.3 mm in diameter was mounted, resulting in a horizontal circular step of 0.35 mm (platform switching). The control implant was straight, with an abutment 4 mm in diameter. Single‐tooth crowns were cemented provisionally. All patients were monitored at short intervals over the course of 1 year. Standardized radiographs and microbiological samples from the implants' inner spaces were obtained at baseline (implant surgery), and after 3, 4, and 12 months. Results: After 1 year, the mean radiographic vertical bone loss at the test implants was 0.53±0.35 mm and at the control implants, it was 0.58±0.55 mm. The mean intraindividual difference was 0.05±0.56 mm, which is significantly <0.35 mm (P=0.0093, post hoc power 79.9%). The crestal bone‐level changes depended on time (P<0.001), but not on platform switching (P=0.4). The implants' internal spaces were contaminated by bacteria, with no significant differences in the total counts between the test and the control at any time point (P=0.98). Conclusions: The present randomized clinical trial could not confirm the hypothesis of a reduced peri‐implant bone loss at implants restored according to the concept of platform switching. To cite this article:
Enkling N, Jöhren P, Klimberg V, Bayer S, Mericske‐Stern R, Jepsen S. Effect of platform switching on peri‐implant bone levels: a randomized clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 1185–1192.
doi: 10.1111/j.1600‐0501.2010.02090.x     

Factors affecting soft tissue level around anterior maxillary single‐tooth implants

Background: Peri‐implant soft tissue recession is a major esthetic concern for the anterior implants. The aim of this study was to determine the factors that affected the facial marginal mucosal level and papilla level around single‐tooth implants in the anterior maxilla. Methods: Forty single‐tooth implants in the anterior maxilla were studied. Variables possibly associated with the soft tissue level were obtained from clinical measurements, study models, peri‐apical radiographs, and computerized tomograms. Fisher's exact test, analysis of variance, and binary logistic regression analysis were used to determine the influence of each factor on the facial marginal mucosal level and papilla level. Results: The majority of the implants (75%) replaced the upper central incisors. The facial mucosal margin of the implant was 0.5±0.9 mm more apical than that of the contralateral tooth. Half or more of papilla fill was observed in 89% of the samples. More apical level of the facial mucosal margin at the implant sites was significantly influenced by many factors including a thin peri‐implant biotype, a proclined implant fixture angle, more apical level of the facial bone crest, increased distance from the contact point to the bone crest, contact point to the platform, and contact point to implant bone. A thin biotype was the most significant factor in determining the facial marginal mucosal level. Increased distance from the contact point to the bone crest was the only factor significantly associated with less papilla fill. Conclusions: The papilla level around single‐tooth implants in the anterior maxilla was mainly influenced by the interproximal bone crest level of the adjacent tooth. Facial marginal mucosal level, on the other hand, was affected by multiple factors including the peri‐implant biotype, the facial bone crest level, the implant fixture angle, the interproximal bone crest level, the depth of implant platform, and the level of first bone to implant contact. To cite this article:
Nisapakultorn K, Suphanantachat S, Silkosessak O, Rattanamongkolgul S. Factors affecting soft tissue level around anterior maxillary single‐tooth implants.
Clin. Oral Impl. Res. 21 , 2010; 662–670.
doi: 10.1111/j.1600‐0501.2009.01887.x     

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.     

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     

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.     

Evaluation of a Variable‐Thread Tapered Implant in Extraction Sites With Immediate Temporization: A 3‐Year Multicenter Clinical Study

Background: The purpose of this clinical study is to evaluate the radiographic bone remodeling, survival rate, and soft tissue health surrounding a variable‐thread tapered implant immediately placed in extraction sites. Methods: Sixty implants were placed in 55 patients at six centers according to a predetermined protocol. All implants were placed in extraction sockets and were subjected to immediate temporization and function. Definitive prostheses (58 single crowns and one two‐unit fixed bridge) were placed within the first year. Clinical and radiographic examinations were performed at implant placement and after 3, 6, 12, 24, and 36 months. Measurements of implant stability, papilla index, plaque, peri‐implant mucosa, and marginal bone levels were recorded at each visit. Results: Thirty‐five implants were evaluated at both implant insertion and 3‐year follow‐up. Bone levels were observed at 6 months after surgery and yearly intervals thereafter and remained stable throughout the study. There was a slight decrease in mean bone level from ?0.68 mm at implant insertion to ?0.93 mm at the 6‐month recall and then an increase of bone to ?0.53 mm from the reference point at the 2‐year follow‐up (an average increase of 0.15 mm from implant insertion). Bone levels remained steady between the 2‐year recall and the 3‐year recall. Papilla scores increased significantly (P <0.001; Wilcoxon signed‐rank test) from insertion to the 3‐year follow‐up, with most of the increase occurring during the first year. Patient assessments of function, esthetics, feel of implant, speech, and self‐esteem also showed significant improvement over the course of the study. Conclusions: The results, over 36 months, indicate that the variable‐thread tapered implant can be used safely and effectively under demanding conditions as an immediate postextraction tooth replacement. Bone remodeling remained stable with a slight increase, and patients expressed high levels of satisfaction with the restorative results over the course of the study.     

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     

Stability of Contour Augmentation and Esthetic Outcomes of Implant‐Supported Single Crowns in the Esthetic Zone: 3‐Year Results of a Prospective Study With Early Implant Placement Postextraction

Background: Early implant placement is one of the treatment options after tooth extraction. Implant surgery is performed after a healing period of 4 to 8 weeks and combined with a simultaneous contour augmentation using the guided bone regeneration technique to rebuild stable esthetic facial hard‐ and soft‐tissue contours. Methods: In this prospective study, 20 patients were treated with an implant‐born single crown and followed for 3 years. Clinical, radiologic, and esthetic parameters were recorded to assess treatment outcomes. Results: At the 3‐year examination, all 20 implants were successfully integrated, demonstrating ankylotic stability and healthy peri‐implant soft tissues as documented by standard clinical parameters. Esthetic outcomes were assessed by the pink esthetic score (PES) and white esthetic score (WES) and confirmed pleasing results overall. WES values were slightly superior to PES values. Periapical radiographs showed minimal crestal bone loss around used bone‐level implants with a mean bone loss of 0.18 mm at 3 years. Only two implants revealed bone loss between 0.5 and 1.0 mm. One of these implants had minor mucosal recession <1.0 mm. Conclusions: This prospective study evaluates the concept of early implant placement and demonstrated successful tissue integration for all 20 implants and stable bone‐crest levels around implant–abutment interfaces according to the platform‐switching concept. The midterm 3‐year follow‐up revealed pleasing esthetic outcomes and stable facial soft tissues. The risk of mucosal recession was low, with only one patient showing minor recession of the facial mucosa. These encouraging results need to be confirmed with a 5‐year follow‐up examination.     

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.     

In-patient comparison of immediate and conventional loaded implants in mandibular molar sites within 12 months

Objectives: The aim of this prospective clinical study was to evaluate the clinical outcomes of dental implants placed in the mandibular molar sites and immediately functionally restored compared with conventionally loaded controls in an in‐patient study. Material and methods: Twenty‐four dental implants were placed in 12 patients who had first molar loss bilaterally in the mandibular area. One site of the patient was determined as immediately loaded (IL) and the other side was conventionally loaded (CL). Resonance frequency analyses for implant stability measurements, radiographic examinations for marginal bone levels and peri‐implant evaluations were performed during the clinical follow‐up appointments within 12 months. Results: During the 12‐month follow‐up period, only one implant was lost in the IL group. The mean implant stability quotient values were 74.18±5.72 and 75.18±3.51 for Groups IL and CL at surgery, respectively, and the corresponding values were 75.36±5.88 and 75.64±4.84 at 1‐year recall, respectively. The difference was not statistically significant between the two groups during the 12‐month study period (P>0.05). When peri‐implant parameters were evaluated, excellent peri‐implant health was demonstrated during the 1‐year observation period and all implants showed less than 1 mm of marginal bone resorption during the first year. Conclusions: In the present study, immediate functionally loading did not negatively affect implant stability, marginal bone levels and peri‐implant health when compared with conventional loading of single‐tooth implants.     

A prospective,multi‐center study assessing early loading with short implants in posterior regions. A 3‐year post‐loading follow‐up study

Background

Few prospective studies about early loading of short implant have been available and very little evidence exists on the outcomes longer than 3 years.

Purpose

To assess clinical and radiographic outcomes of 6 mm‐short implants placed in the posterior maxilla and mandible applying an early loading protocol.

Materials and methods

Ninety‐five short implants (6 mm‐short, Ø 4 mm) were placed in 45 subjects at 3 study sites, 2 or 3 implants per subject, using a one‐stage surgical procedure and loaded with a screw‐retained splinted fixed prosthesis 6 weeks later. Follow‐up took place at 6, 12, 24, and 36 months after loading. Marginal bone level changes, implant survival, clinical variables, and adverse events were assessed.

Results

The survival rate for all implants placed was 95.8%. From implant loading to 3 years follow‐up, mean marginal bone level changes were minimal (0.07 ± 0.49 mm) and the peri‐implant soft tissue status was healthy. No major technical or biological complications occurred except for the 4 early implant losses.

Conclusion

Three‐year data indicates that the use of splinted 6 mm‐short implants is a viable treatment in posterior regions with low marginal bone resorption. Early loading after 6 weeks should be taken cautiously in patients with known risk factors.     

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.     

Implants with an Oxidized Surface Placed Predominately in Soft Bone Quality and Subjected to Immediate Occlusal Loading: Results from a 7‐Year Clinical Follow‐Up

Purpose: The purpose of this clinical follow‐up was to document the 7‐year outcome of immediately loaded implants exhibiting an oxidized surface. Material and Methods: Thirty‐eight patients received a total of 51 implant‐supported fixed prostheses. The restorations were supported by 102 implants, the majority of which were placed in posterior regions (88%) and primarily in soft bone quality (76%). Radiographic examinations were performed at prosthesis insertion, at 1‐ and 6‐month follow‐ups, and annually at the 1‐ through 5‐year follow‐up visits. Marginal peri‐implant soft tissue evaluations were conducted at all these follow‐ups. This report presents the results after at least 7 years of loading. Results: After 7 years of prosthetic loading, the cumulative implant survival rate was 97.1% and the mean marginal bone remodeling was ?1.51 mm (SD 1.00, n = 73) with significantly more initial remodeling at sites having received marginal guided bone regeneration procedures. A low rate of biological and technical complications was detected after 7 years of function. The quantification of intrasulcular plaque sampling showed no significant difference between teeth and implants. Conclusion: The 7‐year follow‐up data indicate that the introduced immediate loading protocol is a successful treatment alternative also including regions exhibiting soft bone conditions.     

Narrow‐ and regular‐diameter implants in the posterior region of the jaws to support single crowns: A 3‐year split‐mouth randomized clinical trial

Objectives

The objective of this 3‐year split‐mouth randomized controlled clinical study was to compare narrow‐diameter implants (NDIs) to regular‐diameter implants (RDIs) in the posterior region of the jaws (premolars and molars) in regards to (i) the marginal bone level (MBL) and (ii) implant and prosthesis survival and success rates.

Material and Methods

A total of 22 patients were included in the study. Each patient received at least one implant of each diameter (Ø3.3 and Ø4.1 mm), placed either in the maxilla or mandible to support single crowns. A total 44 implants (22 NDIs and 22 RDIs) were placed and included in the study. Twenty‐one implants were placed in the premolar, whereas 23 were placed in molar areas. Radiographic evaluations to access the MBL were performed immediately after implant placement, 1 and 3 years after implant loading. Peri‐implant clinical variables including probing pocket depth (PPD) and bleeding on probing (BoP) were obtained after crown delivery, 1 and 3 years after loading. Furthermore, the survival and success rates of the implants and prosthesis were also evaluated.

Results

Twenty patients were able to complete the study. There was no statistically significant difference regarding MBL between groups at implant placement (p = .084), 1‐year (p = .794) and 3‐year (p = .598) time intervals. The mean peri‐implant bone loss at 3‐year follow‐up was ?0.58 ± 0.39 mm (95% CI: ?0.751 to ?0.409) and ?0.53 ± 0.46 mm (95% CI: ?0.731 to ?0.329) for NDIs and RDIs, respectively. BoP was present at 15% and 10% of NDIs and RDIs, respectively, at 3‐year follow‐up. PPD >5 mm was observed in 5% and 0% of the implants of NDIs and RDIs, respectively, at 3‐year follow‐up. At the 3‐year examination, the implant success rates were in the NDIs and RDIs sites, respectively, 95% and 100%. The corresponding values for prosthesis success rates were 90% for NDIs and 95% for RDIs.

Conclusion

The present study demonstrated that NDIs placed to support single crowns in the posterior region did not differ to RDIs in regards to MBL, implant survival, and success rates.     

A Retrospective Evaluation of the Survival Rates of Splinted and Non‐Splinted Short Dental Implants in Posterior Partially Edentulous Jaws

Background: The aim of the present study is to evaluate the survival rate and bone loss around short implants (≤10 mm) supporting splinted or non‐splinted posterior prostheses during a follow‐up period of 3 to 16 years. Methods: A total of 453 implants from 198 patients was divided into splinted or non‐splinted groups. Implant survival rate was calculated for each group, and potential risk was represented as odds ratio (OR). The final linear distance from implant platform level to the first bone‐to‐implant contact was compared to this same reference just after loading by digital periapical radiographs to determine the marginal bone loss (BL). Results: The splinted group comprised 219 implants in 86 patients, whereas the non‐splinted group included 234 implants from 112 patients. The mean follow‐up period was 9.7 ± 3.7 years. Although different success rates were found for splinted (97.7%) and non‐splinted (93.2%) groups, they exhibited similar BL (1.22 ± 0.95 mm and 1.27 ± 1.15 mm, respectively). The success of splinted implants was associated with no other variable, whereas non‐splinted implants exhibited higher risk of failure when placed in men (OR = 3.2) and when implants shorter than 10 mm were used (OR = 3.6 and 4.1 for 8.5 mm and 7 mm, respectively). Regardless of group, 71.4% of the unsuccessful implants failed before the end of the first year after loading. Conclusion: Non‐splinted posterior short implants had a somewhat lower success rate than splinted short implants, and the failure rate in non‐splinted short implants appeared to be greater in males as well as in implants ≤10 mm.     

Immediately restored one-piece single-tooth implants with reduced diameter: one-year results of a multi-center study

Objectives: The aim of the present multi‐center study was to evaluate the treatment outcome of immediately restored one‐piece single‐tooth implants with a diameter of 3 mm after 1 year. Material and methods: A total of 57 one‐piece implants (NobelDirect^® 3.0) were inserted in 47 patients (26 females, 21 males) with a mean age of 31 years (range: 17–76 years) at five different centers. The implants replaced maxillary lateral incisors and mandibular incisors. The implants were placed either in conjunction with tooth extraction or in healed sites, and all implants were immediately restored with a provisional resin crown. If needed, the abutment part of the implant was prepared before crown cementation. The permanent crown was placed after 1.9–14.5 months. Radiographs were taken at implant insertion as well as after 6 and 12 months to evaluate the peri‐implant marginal bone level and bone loss. Moreover, plaque, bleeding on probing and complications were assessed. Results: A total of 44 patients (23 females, 21 males) with 54 implants were available for the 1‐year follow‐up. One implant was lost, thus the 1‐year implant survival was 98%. A statistically significant mean marginal bone loss was observed between baseline and 6 months (1.1 mm, range: ?0.7 to 4.4 mm; n=49) and between baseline and 12 months (1.6 mm, range: ?0.8 to 4.6 mm; n=50). A total of 18% of the implants were characterized by a bone loss of more than 3 mm. No bleeding on probing was observed around 83% of the implants. Plaque was registered at 15% of the implants. The most common complications were related to the provisional crown, i.e. fracture (n=3) and loss of retention (n=3). Conclusions: A high 1‐year implant survival was observed in the present study. However, the excessive peri‐implant marginal bone loss around several implants indicates that this implant should be used with caution until further studies have been conducted. To cite this article:
Zembi? A, Johannesen LH, Schou S, Malo P, Reichert T, Farella M, Hämmerle CHF. Immediately restored one‐piece single‐tooth implants with reduced diameter: one‐year results of a multi‐center study.
Clin. Oral Impl. Res. 23 , 2012; 49–54.
doi: 10.1111/j.1600‐0501.2011.02174.x     

Implant Abutment Cleaning by Plasma of Argon: 5‐Year Follow‐Up of a Randomized Controlled Trial

Background: Contamination of implant abutments could potentially influence the peri‐implant tissue inflammatory response. The aim of the present study is to assess the radiographic bone changes around customized, platform‐switched abutments placed according to the “one‐abutment‐one‐time” protocol, with and without plasma of argon cleaning treatment. Methods: Thirty healthy patients with thin gingival biotype (<1 mm) and history of periodontal disease received one maxillary implant each. Immediately before abutment connection, patients were randomly assigned to control group (cleaning protocol by steaming) or test group (plasma of argon treatment). Outcome measures were: 1) success rate of implants and prostheses; 2) biologic and prosthetic complications; 3) peri‐implant marginal bone loss (MBL); 4) esthetic and periodontal parameters; and 5) patient satisfaction. Results: Neither implants nor prostheses were lost in either group at the 5‐year follow‐up examination. Overall, both groups showed a slight amount of peri‐implant bone loss from baseline to 5 years. A statistically higher mean MBL was found in the control group compared with the test group at 6, 24, and 60 months after crown connection. Nevertheless, during the entire follow‐up period, intragroup comparison demonstrated statistically significant mean MBL in the control group, but not in the test group. The test group showed a higher mean gain at the soft tissue margin, but not for the papilla. All implants showed good periodontal parameters, with no significant differences between groups. Conclusion: Plasma of argon could be used to disinfect implant abutments before insertion to minimize future peri‐implant bone resorption.     

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     

Maxillary implant‐supported overdentures opposed by (partial) natural dentitions: a 5‐year prospective case series study

The aim of this study was to assess the 5‐year treatment outcome of maxillary implant‐retained overdentures opposed by natural antagonistic teeth. Fifty consecutive patients received maxillary overdentures supported by six dental implants. Implants were placed in the anterior region, if enough bone was present (n = 25 patients) Implant were placed in the posterior region if implant placement in the anterior region was not possible (n = 25 patients). Variables assessed included survival of implants, condition of hard and soft peri‐implant tissues and patients' satisfaction. The five‐year implant survival rate was 97·0% and 99·3%, and mean radiographic bone loss was 0·23 and 0·69 mm in the anterior and posterior group, respectively. Median scores for plaque, calculus, gingiva, bleeding and mean scores for pocket probing depth were low and stayed low. Patients' satisfaction after treatment was high in both groups. Within the limits of this 5‐year study, it is concluded that six dental implants (placed in the anterior or posterior region) connected with a bar and opposed to natural antagonistic teeth result in acceptable results for clinical parameters and good outcomes for marginal bone level changes and patient satisfaction.     

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.