Non-submerged Implants Research Articles

Crestal bone loss around submerged and non-submerged implants during the osseointegration phase with different healing abutment designs: a randomized prospective clinical study.

To evaluate peri-implant crestal bone loss during the osseointegration period, comparing submerged and non-submerged implants with healing abutments of different design. A total of 90 Avinent® dental implants (Avinent Implant System, Barcelona, Spain) were placed in 90 patients. All were sited in the posterior mandibular zone to replace teeth 3.6 or 4.6. Patients were divided randomly into three groups: submerged (n=30), non-submerged with anatomical healing abutment (n=30), and non-submerged with esthetic healing abutment (n=30). Peri-implant crestal bone loss was evaluated in intraoral radiographs taken at baseline, 1, and 3months after implant placement. Peri-implant crestal bone loss at the end of the (3-month) osseointegration period was lowest in the submerged group (0.11±0.14mm), followed by the esthetic non-submerged group (0.15±0.06mm), but without statistically significant difference between these groups (P=0.234). The greatest bone loss was produced in the non-submerged group with anatomical healing abutments (0.37±0.12mm), with significant differences between this group and the other two (P<0.001). On the basis of these findings, bone resorption during the osseointegration period using the non-submerged technique varied significantly depending on the morphology of the healing abutment used. The non-submerged technique with an esthetic healing post-produced an equally predictable outcome compared with the submerged technique.

Healing at implants placed in bone of different morphology: an experimental study in dogs.

To study osseointegration at implants installed using a standard bed preparation in sites of different bone morphology. In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4months of healing, flaps were elevated, and two recipient sites were prepared in each side of the mandible, one in the second premolar and the other in the molar regions. Bone morphology and final insertion torque were evaluated. Healing abutments were applied, and the flaps were sutured to allow a non-submerged healing. After 4months, the animals were sacrificed and ground sections were obtained for histomorphometric analyses. At the premolar sites, bone morphology Class 2 and at the molar regions Class 3 or 4 were identified. The final insertion torque was 50-55Ncm at the premolar and 30-35Ncm at the molar sites. Mean osseointegration in percentage reached 61.5±11.5% and 63.3±10.1% at the premolar and molar sites, respectively. Mineralized bone density evaluated from the implant surface up to a distance of about 0.6mm lateral to the implant surface was 63.0±7.4% and 65.4±17.7% at the premolar and molar sites, respectively. Similar implant bed preparations performed at premolar and molar sites with different bone morphology, yielding insertion torque values of about 30-35 and 50-55Ncm, respectively, did not affect osseointegration after 4months at non-submerged implants.

Effect of Osteotomy Preparation on Osseointegration of Immediately Loaded, Tapered Dental Implants.

The aim of the present preclinical in vivo study was to evaluate whether a modified "drill-only" protocol, involving slight underpreparation of the implant site, may have an effect on aspects of osseointegration of a novel bone-level tapered implant, compared with the "standard drilling" protocol involving taping and profiling of the marginal aspect of the implant socket. In each side of the edentulated and completely healed mandible of 11 minipigs, 2 tapered implants (8 mm long × 4.1 mm Ø, BLT; Institut Straumann AG, Basel, Switzerland) were installed either with the drill-only or the standard drilling protocol. Significantly lower average insertion torque values were recorded for the standard drilling protocol group (52 ± 29 Ncm) compared with the drill-only group (70 ± 27 Ncm) (t test, P ≤ 0.05); no significant difference was observed between the 2 groups regarding implant stability, by means of resonance frequency analysis (75 ± 8 vs. 75 ± 6, respectively). Half of the implants were immediately loaded and the rest were submerged, providing observation times of 8 or 4 wk, respectively. Non-decalcified histological and histomorphometric analysis of the implants with surrounding tissues showed no significant differences between the 2 drilling protocols regarding the distance from the implant platform to the first coronal bone-to-implant contact (f-BIC), the total bone-to-implant contact (BIC) as a percentage of the total implant perimeter, and the bone density in an area extending 1 mm laterally from the implant (BATA) within 2 rectangular regions of interest (ROIs) 4 mm in height, representing the coronal (parallel-walled) and apical (tapered) aspect of the implant (ROI 1 and ROI 2, respectively) in non-submerged implants. In general, marginal peri-implant bone levels were at or slightly apical to the implant platform, and large amounts of bone-to-implant contact were observed. In contrast, immediately loaded implants placed with the drill-only protocol showed statistically significantly lower BIC values (66% ± 13.7%) compared with those installed with the standard drilling protocol (74.8% ± 11.2%) (P = 0.018). In addition, although marginal bone levels were in most of the immediately loaded implants at or slightly apical to the implant platform, some of the implants installed with the drill-only protocol showed marginal bone loss and crater formation. Thus, in this model system, even slight underpreparation of the implant socket appeared to compromise osseointegration of immediately loaded bone-level tapered implants.

Marginal Bone Level Evaluation after Functional Loading Around Two Different Dental Implant Designs.

Purpose. To investigate peri-implant alveolar bone changes using periapical radiographs before and after prosthetic delivery in submerged and nonsubmerged dental implants. Methods. Digital periapical films of 60 ITI Straumann nonsubmerged dental implants and 60 Xive Dentsply submerged dental implants were taken before, immediately after, and 12 and 24 weeks after the prosthetic restoration was delivered. Results. The 60-nonsubmerged dental implant group showed mean marginal bone resorption at baseline of 0.10 ± 0.23 mm and 24 weeks later, marginal bone resorption was 0.16 ± 0.25 mm. The submerged dental implant group showed a significantly higher distal marginal bone resorption over the mesial side. Mean marginal bone resorption at baseline was 0.16 ± 0.32 on the mesial and 0.41 ± 0.56 on the distal side. Twenty-four weeks later, it was 0.69 ± 0.69 mm on the mesial and 0.99 ± 0.90 mm on the distal side. Conclusion. First, it was possible to determine that submerged implants had a higher mean marginal bone resorption and less bone-to-implant contact than nonsubmerged implants. And second, the distal side of submerged dental implants presented higher marginal bone loss than the mesial side.

Peri-implant crevicular fluid levels of cathepsin-K, RANKL, and OPG around standard, short, and mini dental implants after prosthodontic loading.

PurposeDespite the high success rates of endosseous dental implants, their placement is restricted according to the height and volume of bone available. The use of short or mini dental implants could be one way to overcome this limitation. Thus, this study aimed to compare standard, short, and mini dental implants with regard to associated clinical parameters and peri-implant crevicular fluid (PICF) levels of cathepsin -K (CTSK), RANK ligand (RANKL), and osteoprotegerin (OPG), after prosthodontic loading.MethodsA total of 78 non-submerged implants (Euroteknika, Aesthetica+2, Sallanches, France) were installed in 30 subjects (13 male, 17 female; range, 26-62 years) who visited the clinic of the Periodontology Department, Faculty of Dentistry, Selcuk University. Sampling and measurements were performed on the loading date (baseline) and 2, 14, and 90 days after loading. Assessment of the peri-implant status for the implant sites was performed using the pocket probing depth (PPD), modified plaque index, modified gingival index, modified sulcular bleeding index, and radiographic signs of bone loss. PICF samples collected from each implant were evaluated for CTSK, RANKL, and OPG levels using the ELISA method. Keratinized tissue and marginal bone loss (MBL) were also noted.ResultsClinical parameters statistically significantly increased in each group but did not show statistical differences between groups without PPD. Although implant groups showed a higher MBL in the upper jaw, only the standard dental group demonstrated a statistically significant difference. At 90 days, the OPG: sRANKL ratio and total amounts of CTSK for each group did not differ from baseline.ConclusionsWithin the limitations of this study, both short and mini dental implants were achieving the same outcomes as the standard dental implants in the early period after loading.

Long-term stability of soft tissues following alveolar ridge preservation: 10-year results of a prospective study around nonsubmerged implants.

The purpose of this study was to evaluate the long-term clinical outcomes around implants placed in sites previously augmented with demineralized bovine bone mineral with 10% collagen (Bio-Oss Collagen, Geistlich). In this prospective study, 36 consecutive, healthy patients, in need of a single-tooth extraction (incisors, canines, and premolars) and implant replacement, were included. After tooth extraction, Bio-Oss Collagen was inserted in the socket and covered either with a double layer of collagen membrane (test) or with a few drops of a flowable polylactide polymer (control). Following a healing period of 4 to 6 months, a single nonsubmerged implant surgery was performed. After cementation of a single ceramic crown, patients were asked to follow an individualized supportive periodontal therapy program. Clinical and radiographic data were obtained after prosthesis delivery (baseline) and at the 10-year follow-up visit. At the 10-year examination, two patients were lost to follow-up. All implants demonstrated healthy peri-implant soft tissues as documented by standard parameters (full-mouth plaque score, full-mouth bleeding score, local bleeding on probing) in both groups. Mean soft tissue recession (REC) was 0.39 ± 0.54 mm for the test group and 0.50 ± 0.33 mm for the control, with no significant difference between the two groups. The results of this prospective study confirmed the long-term stability of the peri-implant marginal soft tissues supported by regenerated bone by means of the described technique using Bio-Oss Collagen. If the patient is properly followed throughout time, the risk for mucosal recession is low, with < 1 mm of mean REC after 10 years.

Clinical evaluation of submerged and non-submerged implants for posterior single-tooth replacements: a randomized split-mouth clinical trial

The aim of this study was to evaluate clinical and radiographic results of submerged and non-submerged implants for posterior single-tooth replacements and to assess patient-based outcomes. Twenty patients were included in the study. A split-mouth design was used; implants inserted using a submerged technique were compared to those inserted with a non-submerged technique. Implants were restored with metal–ceramic crowns after 3 months. Reconstructions were examined at baseline, 6, 12, and 24 months. Standardized radiographs were made. Radiographic crestal bone level changes were calculated, as well as soft tissue parameters, including pocket probing depth, bleeding on probing, plaque index, and gingival index. Results were analyzed by two-way repeated measures of variance (ANOVA). To evaluate patient-based outcomes, patients were asked to complete a questionnaire at the 6-month follow-up; the Wilcoxon paired signed rank test was used to compare scores. The data of 18 patients were reviewed. During 24 months, non-submerged implants (0.57±0.21mm) showed significantly lower bone loss than submerged implants (0.68±0.22mm) (P<0.01). Patient satisfaction with non-submerged implants (median 87.5) was significantly higher than with submerged implants (median 81.5) (P<0.01). Non-submerged implants showed comparable clinical results to submerged implants and resulted in higher patient satisfaction due to decreased surgical intervention.

Marginal bone response of implants with platform switching and non‐platform switching abutments in posterior healed sites: a 1‐year prospective study

ObjectivesThis 1-year prospective study evaluated the implant success rate and marginal bone response of non-submerged implants with platform and non-platform switching abutments in posterior healed sites.Material and methodsNineteen patients (9 male, 10 female) with posterior partially edentulous spaces, between the ages of 23 and 76 (mean = 55.4 years), were included in this study. A total of 30 implants (15 implants restored with platform switching [PS] abutments [control] and 15 implants restored with non-platform switching [NPS] abutments [test]) were assigned between two groups using a randomization procedure. The definitive abutments with conical connections were placed at the time of surgery, and the definitive restorations were placed at 3 months. All patients were evaluated clinically and radiographically using standardized radiographs at time of implant placement (0), 3, 6 and 12 months after implant placement. Data were analyzed using Friedman test with post hoc pairwise comparisons, Mann–Whitney U-test, and Pearson's chi-square test at the significance level of α = 0.05.ResultsAt 12 months, all 30 implants remained osseointegrated corresponding to a 100% success rate. The overall mean marginal bone level change at 12 months was −0.04 ± 0.08 mm for PS group and −0.19 ± 0.16 mm for NPS group. Statistically significant difference in the marginal bone level change was observed between groups at 0 to 12 months and 3 to 12 months (P < 0.05).ConclusionsThis 1-year randomized control study suggests that when a conical implant–abutment connection is present, similar peri-implant tissue responses can be achieved with platform switching and non-platform switching abutments.

Implant–Buccal Plate Distance as Diagnostic Parameter: A Prospective Cohort Study on Implant Placement in Fresh Extraction Sockets

The aim of this study is to investigate contour changes around immediate implants in fresh extraction sockets when different grafting procedures are performed, based on the distance between the external implant collar and the bony surface on the buccal plate (I-BP). A secondary aim is to assess the esthetic outcome via the implant esthetic score (IAS). This prospective cohort study was performed in three centers. Suitable patients to undergo implant placement in fresh extraction sockets were selected. Periodontal biotype, horizontal and vertical peri-implant bone defects, and dehiscences were assessed. Depending on I-BP, two types of grafting procedures were performed. In group A (I-BP <4 mm), only the peri-implant gap was grafted during the surgical phase (internal grafting [IG]), whereas group B (I-BP ≥ 4 mm) received both internal and external grafting (IEG). Master casts of the sites, made before implant placement and after 1 year of loading, were optically scanned. A computerized analysis of the contour changes at the involved sites was performed by superimposing the scanned models. A total of 20 patients (eight males and 12 females) were recruited, and 20 non-submerged implants were placed in fresh extraction sockets. No implant failed during the observation period. The mean follow-up was 25 months (range: 12 to 37 months). After 1 year of loading, group A showed a slight decrease in mean buccal volume, whereas group B had an increase in volume (P = 0.02). IAS was higher for group B than group A. When implants are placed immediately after tooth extraction, I-BP may represent a useful diagnostic parameter in choosing the most appropriate grafting procedure (IG versus IEG). In clinical cases in which the distance between implant surface and the buccal plate is <4 mm, the combination of internal and external grafting (IEG) is recommended to maintain the volume and the contour of the ridge and achieve a successful esthetic outcome.

Soft Tissue Healing at One-Piece Zirconia Implants Compared to Titanium and PEEK Implants of Identical Design: A Histomorphometric Study in the Dog

This study aimed to histomorphometrically evaluate the soft tissue reactions of one-piece zirconia implants versus titanium implants in regard to their insertion depth. Four one-piece implants of identical geometry were inserted on each side of six mongrel dogs: an uncoated zirconia implant, a zirconia implant coated with a calcium liberating titanium oxide, a titanium implant, and an experimental implant made of a synthetic material. Using a split-mouth design, they were inserted in both submerged and nonsubmerged healing modes. After 4 months, dissected blocks were stained with toluidine blue to histologically assess the marginal portion of the implant mucosa, apical extension of the barrier epithelium, and margin level of bone-to-implant contact. The inflammation status at the crestal part of the implant was assessed as well. The histomorphology presented the typical soft tissue configuration of barrier epithelium and connective tissue near the bone-to-implant contact. Histomorphometrically, the length of the barrier epithelium did not differ significantly concerning material type or healing modality. Furthermore, the inflammation signs were higher with nonsubmerged implants. The submerged uncoated zirconia implants, however, showed few signs of inflammation. Within the limits of this study, it is concluded that uncoated and coated zirconia implants are capable of establishing sufficient soft tissue configurations that are comparable to those of titanium implants.

Impact of implant–abutment connection and positioning of the machined collar/microgap on crestal bone level changes: a systematic review

ObjectivesTo address the following focused question: What is the impact of implant–abutment configuration and the positioning of the machined collar/microgap on crestal bone level changes?Material and methodsElectronic databases of the PubMed and the Web of Knowledge were searched for animal and human studies reporting on histological/radiological crestal bone level changes (CBL) at nonsubmerged one-/two-piece implants (placed in healed ridges) exhibiting different abutment configurations, positioning of the machined collar/microgap (between 1992 and November 2012: n = 318 titles). Quality assessment of selected full-text articles was performed according to the ARRIVE and CONSORT statement guidelines.ResultsA total of 13 publications (risk of bias: high) were eligible for the review. The weighted mean difference (WMD) (95% CI) between machined collars placed either above or below the bone crest amounted to 0.835 mm favoring an epicrestal positioning of the rough/smooth border (P < 0.001) (P-value for heterogeneity: 0.885, I2: 0.000% = no heterogeneity). WMD (95% CI) between microgaps placed either at or below the bone crest amounted to −0.479 mm favoring a subcrestal position of the implant neck (P < 0.001) (P-value for heterogeneity: 0.333, I2: 12.404% = low heterogeneity). Only two studies compared different implant–abutment configurations. Due to a high heterogeneity, a meta-analysis was not feasible.ConclusionsWhile the positioning of the machined neck and microgap may limit crestal bone level changes at nonsubmerged implants, the impact of the implant–abutment connection lacks documentation.

Detection of predominant subgingival periopathogens around submerged and non-submerged hydroxy-apatite implants

Background: The microbiota associated with healthy peri-implant tissues has been studied in many cases. However, gram-negative anaerobic rods may also be found in small numbers and in low proportions around the endosseous dental implants. Objective: The purpose of this study was to investigate colonization of the peri-implant sulcus around two different types of implants by periopathogenic microbiota in a healthy patient. Materials and Methods: A patient with a healthy periodontium was selected. One hydroxy-apatite coated one-stage (AQB) implant was implanted at the site of the missing upper Right maxillary 1 st molar; the two units two-stage (PLATON) were implanted at the sites of the missing 1 st and 2 nd molars in the Left maxillary region. Saliva samples were collected from the peri-implant sulcus using paper points every 3 months for 9 months after implantation and fixation of porcelain crowns. Real-Time Polymerase Reaction (RT-PCR-Invader method) was used to detect periodontal pathogens. Results: Salivary periodontal pathogens were checked prior to implantation and Tannerella forsythia (0.06%) was detected. No periodontal pathogens were observed at 3 months. T. forsythia (0.06%) was detected at 6 months around the AQB implant; it was not detected in the PLATON implant. At 9 months, periopathogens increased in number around both types of implants; there was a major difference in numbers of Fusobacterium nucleatum (10.81%), and T. forsythia (0.057%) around the submerged and non-submerged implant systems. Conclusions: Submerged implants with screw-retained superstructures are more vulnerable to pathogenic microflora colonization than non-submerged implants.

What is the effect of initial implant position on the crestal bone level in flap and flapless technique during healing period?

PurposeThe level of the implant above the marginal bone and flap design have an effect on the bone resorption during the healing period. The aim of this study is to detect the relationship between the level of the implant at the implant placement and the bone level at the healing period in the mesial and distal side of implants placed with flapless (FL) and full-thickness flap (FT) methods.MethodsTwenty-two nonsubmerged implants were placed with the FL and FT technique. Periapical radiographs were taken of the patient at implant placement, and at 6 and 12 weeks. By using computer software, bone level measurements were taken from the shoulder of the healing cap to the first bone implant contact in the mesial and distal side of the implant surface.ResultsAt 6 weeks, the correlation between the crestal bone level at the implant placement and crestal bone level of the FT mesially was significant (Pearson correlation coefficient=0.675, P<0.023). At 12 weeks, in the FT mesially, the correlation was nonsignificant (Spearman correlation coefficient=0.297, P<0.346). At 6 weeks in the FT distally, the correlation was nonsignificant (Pearson correlation coefficient=0.512, P<0.107). At 12 weeks in the FT distally, the correlation was significant (Spearman correlation coefficient=0.730, P<0.011). At 6 weeks in the FL mesially, the correlation was nonsignificant (Spearman correlation coefficient=0.083, P<0.809). At 12 weeks in the FL mesially, the correlation was nonsignificant (Spearman correlation coefficient=0.062, P<0.856). At 6 weeks in the FL distally, the correlation was nonsignificant (Spearman correlation coefficient=0.197, P<0.562). At 12 weeks in the FL distally, the correlation was significant (Pearson correlation coefficient=0.692, P<0.018).ConclusionsA larger sample size is recommended to verify the conclusions in this preliminary study. The bone level during the healing period in the FT was more positively correlated with the implant level at implant placement than in the FL.

Clinical assessment of submerged vs non-submerged implants placed in pristine bone

The medium-long term success of osseointegrated dental implants is evaluated on the basis of the degree of osseointegration over time, assessed by radiographic or instrumental analysis (ISQ). Over the years, the question has always been which surgical technique can provide a better performance in the medium-long term and, thanks to literature studies, it has been evidenced that there are no differences between "one stage" and "two stage" interventions. The purpose of this study is to evaluate clinical and radiographic parameters, referring to interventions for the insertion of dental implants characterized by a new kind of implant surface (Synthegra® GEASS, Udine). The prospective study, not randomized and controlled, referred to the insertion of 18 implants on 9 patients with mono or bilateral edentulism, with measurements at 1, 3, 6 and 12 months and an overall follow-up at 3 years, in order to evaluate the different degree of crestal bone resorption using the submerged and transmucosal surgical technique. The results of our study show that there are no differences in the resorption of the two surgical techniques, with an average bone resorption of 2,05±0,16 mm, comparable with values reported in literature.

The Combined Use of rhBMP-2/ACS, Autogenous Bone Graft, a Bovine Bone Mineral Biomaterial, Platelet-Rich Plasma, and Guided Bone Regeneration at Nonsubmerged Implant Placement for Supracrestal Bone Augmentation. A Case Report

This case report presents the clinical application and outcomes of the use of a combined approach to treat a patient with a severe alveolar defect. Recombinant human bone morphogenetic protein-2 in an absorbable collagen sponge carrier, along with autogenous bone graft, bovine bone mineral, platelet-rich plasma, and guided bone regeneration, were used simultaneous with nonsubmerged implant placement. At 1 year postsurgery, healthy peri-implant soft tissues and radiographically stable peri-implant crestal bone levels were observed along with locally increased radiographic bone density. In addition, a cone beam computed tomography (CBCT) scan demonstrated apparent supracrestal peri-implant bone augmentation with the appearance of normal alveolar ridge contours, including the facial bone wall.

Inflammatory Implant Periapical Lesion Prior to Osseointegration: A Case Series Study

To report 20 cases with implant periapical pathology diagnosed during the osseointegration phase, evaluating retrospectively the efficacy of the treatment with implant periapical surgery. A retrospective chart review was conducted of all patients in whom implant periapical surgery was performed between 1996 and 2010. The criteria for diagnosing implant periapical pathology and, accordingly, performing implant periapical surgery were: (1) acute pain during the osseointegration period (8 weeks after implant placement) located in the area of the affected implant or presence of mucous fistula in relation with the implant apex; (2) absence of implant mobility; (3) non-dull percussion of nonsubmerged implants; and (4) presence or absence of implant periapical radiolucency. Twenty-two implants were diagnosed with periapical pathology in 20 patients (13 women and 7 men) with a mean age of 54.3 years (range, 32 to 70 years) and were consecutively treated by a surgical approach. In 19 implants, the diagnosis was acute apical peri-implantitis (nonsuppurated in 7 cases and suppurated in 12), as based on the symptoms and radiographic sign, and in 3 cases it was subacute apical peri-implantitis, as based on the presence of a fistula. After a minimum follow-up of 1 year, 20 implants remained functional, with no clinical or radiologic alterations; the survival rate of the treated implants was 91%. The early diagnosis of inflammatory implant periapical lesions during the osseintegration phase, and their prompt surgical treatment, led to a survival rate of the treated implants of 91%.

Primary Stability/Mobility of 1-Stage and 2-Stage Dental Implants

To evaluate the primary stability of 1-stage (nonsubmerged) and 2-stage (submerged) implants via newest wireless resonance frequency (RF) analyzer and newer wireless mobility measuring (MM) device. Six 1-stage dental implants with internal hex connection and six 2-stage dental implants, 4.1 mm in diameter and 11.5 mm in length, were inserted bilaterally into the first premolar, second premolar, and first molar regions of 6 standard mandibular transparent self-curing acrylic resin models. After that, the periimplant circular bone defects were created in millimeter increments ranging between 0 and 5 mm to the same extent on all implants. Implant stability quotient values significantly decreased at 1-stage and 2-stage implants when periimplant defects increased. Similar implant stability quotient values were found for both implant types; however, significantly lower MM values were noted for 2-stage implants. Irrespective of implant systems, the results indicated a significant association between wireless RF analyzer and wireless MM device. Both wireless RF analyzer and wireless MM device were adequate in assessing implant stability. There was no difference between 2-stage and 1-stage implant systems, except lower MM values were noted for nonsubmerged implants.

Bone anchoring of sutures for adequate repositioning of the soft tissue flaps in one stage dental implants

The choice of suture material and technique is important to optimize wound healing. If surgical wound edges are not properly approximated healing may be delayed because blood may accumulate under the flap and separate it from the underlying bone. The authors present an alternative suturing technique. They use a ‘C suture’ to fix and minimize mobilization of the soft tissues around non-submerged implants.

Influence of a Machined Collar on Crestal Bone Changes Around Titanium Implants: A Histometric Study in the Canine Mandible

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. 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. 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). 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.

Three‐dimensional finite element analysis of stress distribution in peri‐implant bone with relined dentures and different heights of healing caps

The purpose of this study was to evaluate the influence of height of healing caps and the use of soft liner materials on the stress distribution in peri-implant bone during masticatory function in conventional complete dentures during the healing period by using finite element analysis. Three-dimensional models of a severely resorbed mandible with two recently placed implants in the anterior region were created and divided into the following situations: (i) submerged implants, (ii) healing cap at gingival level and (iii) 1·5-mm supragingival. All these situations were also analysed for a conventional complete denture and a denture relined with a 3-mm-thick layer of soft liner material. The models were exported to mechanical simulation software that presented two simulations, one with load in the inferior right canine (35 N) and the other in the inferior right first molar (50 N). Data were evaluated using Maximum Principal Stress provided by the software. All models showed a stress concentration in the cortical bone corresponding to the cervical part of the implant. The simulations with non-submerged implants showed higher values of stress concentration than those that were submerged. Likewise, soft liner materials presented better results than when the denture base was not relined. The height of the healing caps seems to have a direct influence on the stress distribution in the peri-implant bone during the healing period. Considering the values obtained in this study, the use of soft liners with submerged implants seems to be the most suitable method to use during the period of osseointegration.