Role of the microgap between implant and abutment: a retrospective histologic evaluation in monkeys

Resistance to Torsion of Cement vs Screw-Retained Abutments Under a Tangential Load: A Pilot Study

The aim is to compare the resistance to torsion between 2 implant systems with internal hexagon connection: one using screw-retained abutments (Titanium Fix) and the other using cementable abutments (ITEC) under a tangential load. An in vitro experimental study was carried out. Fourteen implants, 7 implants from each system, were included in this study. The implants were placed at a 45° angle into metal blocks to simulate their position in the maxilla. Then, implants were subjected to a resistance test on a CMT5L universal testing machine, and the maximum load was applied to each sample. The maximum force with which the torsion was achieved in each sample was analyzed. The data were tested using the Shapiro-Wilk test and showed normal distribution. Student t test was used to examine statistical significance between the two groups, and the P value was set at P < .05. There was a statistically significant difference between the two groups (P = .001). ITEC implants with a cementable abutment showed greater flexural strength compared to the Titanium Fix with a screwed abutment implant system. The cemented abutment showed more resistance to torsion against a tangential load compared with the screwed abutment.

Effect of vertical implant position on marginal bone loss: a randomized clinical trial

OBJECTIVES

One of the most important factors that has influence on dental implants success rate is marginal bone loss. The purpose of this study is to investigate the effect of the implant's vertical position and the soft tissue's thickness on the rate of marginal bone loss of the dental implant.

MATERIALS AND METHODS

In this single-blind randomized clinical trial study, 56 implants placed in the posterior region of mandible of 33 patients (19 women, 14 men) were divided into two groups. The group of crestal (28 implants) and subcrestal (28 implants) implants, each group was divided into two sub-groups with soft tissue thickness of 2 mm and less than 2 mm (14 implants) and more than 2 mm (14 implants). The amount of marginal bone loss was measured by Scanora 5.2 program with radiographs Digital parallelism based on the effect of the vertical position of the implant, soft tissue thickness, three months after placement, and three months after loading implants (six months after implant placement).

RESULTS

The results showed that marginal bone loss in subcrestal implants is significantly more than crestal implants (p-value = 0.001), and also marginal bone loss in the soft tissue thickness group of 2 mm and less is significantly more than the group of soft tissue thickness more than 2 mm (p-value < 0.001). The amount of marginal bone loss three months after implant loading was significantly higher than three months after implant placement (p-value < 0.001).

CONCLUSION

The implant's vertical position and the soft tissue's thickness around the implant are effective factors in the amount of marginal bone loss. Marginal bone loss is more in subcrestal implants and in cases with less soft tissue thickness. The time factor significantly affects the amount of marginal bone loss.

TRIAL REGISTRATION

this clinical trial was registered at Iranian Registry of Clinical Trials, registration number IRCT20120215009014N415, registration date 20,220,110, (https//en.irct.ir/trial/60,991).

The Influence of History of Severe Periodontitis on Estimated Long-Term Marginal Bone Loss around Implants Restored with Fixed Segmented Full-Arch Rehabilitation

The aim of this study was to analyze the long-term marginal bone level (MBL) of implants supporting fixed full-arch restoration in patients who had previously lost their dentition due to severe periodontitis. This retrospective study included 35 patients in whom 342 implants with internal tapered conical connections were placed. MBL was analyzed radiographically over time and a long-term estimation of MBL was calculated. A mixed linear model with abutment height, graft, diameter and location (maxilla/mandible) as factors and gender, age, implant length and prosthetic variables as covariates was used to evaluate the influence on MBL. MBL in these patients showed an estimator of predictions at 4108 days after loading of -0.307 mm, SE = 0.042. Only 0.15% of implants were radiographically affected with MBL of 3 mm or more. The mixed linear model results showed a main effect of the type of opposing dentition, gender, implant diameter, and abutment height. Particularly, an abutment height of 1 mm had associated larger MBL than the remaining heights. Thus, it can be concluded that dental implants restored with fixed segmented full-arch rehabilitation in patients with a history of severe periodontal disease do not suffer important marginal bone loss if some specific factors are considered, mainly the use of long transmucosal abutments (≥2 mm).

Can radiomic features extracted from intra-oral radiographs predict physiological bone remodelling around dental implants? A hypothesis-generating study

AIM

The rate of physiological bone remodelling (PBR) occurring after implant placement has been associated with the later onset of progressive bone loss and peri-implantitis, leading to medium- and long-term implant therapy failure. It is still questionable, however, whether PBR is associated with specific bone characteristics. The aim of this study was to assess whether radiomic analysis could reveal not readily appreciable bone features useful for the prediction of PBR.

MATERIALS AND METHODS

Radiomic features were extracted from the radiographs taken at implant placement (T0) using LifeX software. Because of the multi-centre design of the source study, ComBat harmonization was applied to the cohort. Different machine-learning models were trained on selected radiomic features to develop and internally validate algorithms capable of predicting high PBR. In addition, results of the algorithm were included in a multivariate analysis with other clinical variables (tissue thickness and depth of implant position) to test their independent correlation with PBR.

RESULTS

Specific radiomic features extracted at T0 are associated with higher PBR around tissue-level implants after 3 months of unsubmerged healing (T1). In addition, taking advantage of machine-learning methods, a naive Bayes model was trained using radiomic features selected by fast correlation-based filter (FCBF), which showed the best performance in the prediction of PBR (AUC = 0.751, sensitivity = 66.0%, specificity = 68.4%, positive predictive value = 73.3%, negative predictive value = 60.5%). In addition, results of the whole model were included in a multivariate analysis with tissue thickness and depth of implant position, which were still found to be independently associated with PBR (p-value < .01).

CONCLUSION

The combination of radiomics and machine-learning methods seems to be a promising approach for the early prediction of PBR. Such an innovative approach could be also used for the study of not readily disclosed bone characteristics, thus helping to explain not fully understood clinical phenomena. Although promising, the performance of the radiomic model should be improved in terms of specificity and sensitivity by further studies in this field.

Micro-CT Evaluation of Microgaps at Implant-Abutment Connection

The assessment of microgaps at the implant-abutment interface is an important factor that may influence clinical success. Thus, the aim of this study was to evaluate the size of microgaps between prefabricated and customised abutments (Astra Tech, Dentsply, York, PA, USA; Apollo Implants Components, Pabianice, Poland) mounted on a standard implant. The measurement of the microgap was performed using micro-computed tomography (MCT). Due to 15-degree rotation of samples, 24 microsections were obtained. Scans were performed at four levels established at the interface between the abutment and the implant neck. Moreover, the volume of the microgap was evaluated. The size of the microgap at all measured levels varied from 0.1 to 3.7 µm for Astra and from 0.1 to 4.9 µm for Apollo (p > 0.05). Moreover, 90% of the Astra specimens and 70% of the Apollo specimens did not exhibit any microgaps. The highest mean values of microgap size for both groups were detected at the lowest portion of the abutment (p > 0.05). Additionally, the average microgap volume was greater for Apollo than for Astra (p > 0.05). It can be concluded that most samples did not exhibit any microgaps. Furthermore, the linear and volumetric dimensions of microgaps observed at the interface between Apollo or Astra abutments and Astra implants were comparable. Additionally, all tested components presented microgaps (if any) that were clinically acceptable. However, the microgap size of the Apollo abutment was higher and more variable than that of the Astra one.

Bridging the Gap with Nanoparticles: A Novel Approach

Two-piece implants unavoidably present a microgap between the implant and the abutment interface. Although numerous modalities have been attempted to overcome this situation, the implant abutment interface still remains a critical point for microbial colonization, which starts an inflammatory cascade of events eventually compromising the implants. Throughout our life, cells in all biological systems are unprotected to oxidative stress leading to the formation of Reactive oxygen species which is of concern when it comes to placing implants in patients who are periodontally compromised. This necessitates the development of alternative therapeutic modalities, which could counteract as well as prevent the microbial overload and ROS generation thereby improving the longevity of implants. To evaluate and assess the antibacterial, antioxidant and anti inflammatory effectiveness of quercetin-loaded titanium nanocomposites as coatings over healing abutments. Quercetin-loaded titanium nanocomposites were synthesized using green synthesis and confirmation was done using UV spectroscopy. Healing abutments were coated with the formulated nanocomposites, an intra-oral environment was simulated by thermocycling. Their antibacterial, antioxidant, anti-inflammatory, and cytotoxicity were assessed using standard tests. Healing abutments were coated with the formulated nanocomposites, an intra-oral environment was simulated by thermocycling. They showed potent antibacterial, antioxidant, and anti-inflammatory properties, which could prove beneficial in a variety of clinical scenarios in which there is a high risk for implant failure during early osseointegration.

Marginal bone changes around platform-switched conical connection implants placed 1 or 2 mm subcrestally: A multicenter crossover randomized controlled trial

INTRODUCTION

This study analyzes early marginal bone modifications occurring around platform-switched implants with conical connection placed 1 or 2 mm subcrestally.

METHODS

This crossover randomized controlled trial enrolled partially edentulous patients needing two implants in either the posterior maxilla or mandible. Each patient received two platform-switched implants with conical connection inserted 2 mm (Test) and 1 mm (Control) subcrestally. Definitive abutments were immediately connected and, after 4 months of unsubmerged healing, screwed metal-ceramic crowns were delivered. Radiographs were taken at implant placement (T0), prosthesis delivery (T1), and after 1 year of prosthetic loading (T2).

RESULTS

Fifty-one patients (25 males and 26 females; mean age 61.2 ± 12.1 years) totaling 102 implants were included in the final analysis. Mean peri-implant bone level (PBL) reduction from T0 to T2 was not significantly different around Test (0.49 ± 0.32 mm) and Control implants (0.46 ± 0.35 mm; p = 0.66). Multivariate linear regression models highlighted a significant positive correlation between history of periodontitis and PBL reduction. At T2, no Test group implant and 6 Control group implants exhibited PBL below the implant platform (11.8% of Control group implants).

CONCLUSION

No significant differences in peri-implant marginal bone changes were demonstrated after 1 year of prosthetic loading between platform-switched implants with conical connection inserted either 1 or 2 mm subcrestally. However, 2 mm subcrestal placement resulted in deeper implant positioning at T2, with no exposure of treated implant surface and potential preventive effect against subsequent peri-implant pathology.

Transmucosal abutments in the esthetic zone: Surgical and prosthetic considerations

OBJECTIVE

This article describes an updated step-by-step protocol for transmucosal abutment selection and treatment sequencing after immediate implant placement in the esthetic zone.

CLINICAL CONSIDERATIONS

Current surgical and prosthetic concepts strive to preserve hard and soft-tissues to provide optimal esthetics at the implant-abutment interface. Consequently, restoring implants in the esthetic zone with transmucosal abutments presents a great challenge and must take into consideration implant depth, angulation, and bucco-lingual position as well as transmucosal height and space for an optimized emergence profile of the restoration and the dimensions of the anterior tooth to be restored. The proper selection of the type, shape, and dimensions of implant components and connections, determined by the product portfolio offered by the implant manufacturer, play a critical role in the ability to adequately address these challenges. This article provides an update on surgical and prosthetic workflows for single implant restorations in the esthetic zone.

CONCLUSIONS

Following esthetic, mechanical, and biologic principles, the long-term success of implant-supported restorations in the esthetic zone is directly correlated to proper execution and sequencing of surgical and prosthetic treatment steps, especially after immediate implant placement. These steps must be critically assessed based on the current scientific evidence to achieve the desired clinical outcomes on a predictable and consistent basis.

CLINICAL SIGNIFICANCE

Selection of surgical and prosthetic treatment protocols to achieve ideal esthetic outcomes and emergence profiles in implant dentistry is often a great challenge, not only determined by technical and clinical skills of the provider but also by the type and dimensions of implant components and connections offered by the manufacturer. Following certain decision-making principles and workflows are key for clinical success with implant-supported restorations after immediate implant placement the esthetic zone.

Exploring the Importance of Corticalization Occurring in Alveolar Bone Surrounding a Dental Implant

Several measures describing the transformation of trabecular bone to cortical bone on the basis of analysis of intraoral radiographs are known (including bone index or corticalization index, CI). At the same time, it has been noted that after functional loading of dental implants such transformations occur in the bone directly adjacent to the fixture. Intuitively, it seems that this is a process conducive to the long-term maintenance of dental implants and certainly necessary when immediate loading is applied. The authors examined the relationship of implant design features to marginal bone loss (MBL) and the intensity of corticalization over a 10-year period of functional loading. This study is a general description of the phenomenon of peri-implant bone corticalization and an attempt to interpret this phenomenon to achieve success of implant treatment in the long term. Corticalization significantly increased over the first 5-year functional loading (CI from 200 ± 146 initially to 282 ± 182, p < 0.001) and maintained a high level (CI = 261 ± 168) in the 10-year study relative to the reference bone (149 ± 178). MBL significantly increased throughout the follow-up period—5 years: 0.83 ± 1.26 mm (p < 0.001), 10 years: 1.48 ± 2.01 mm (p < 0.001). MBL and radiographic bone structure (CI) were evaluated in relation to intraosseous implant design features and prosthetic work performed. In the scope of the study, it can be concluded that the phenomenon of peri-implant jawbone corticalization seems an unfavorable condition for the future fate of bone-anchored implants, but it requires further research to fully explain the significance of this phenomenon.

Influence of apico-coronal positioning of tissue-level implants on marginal bone stability during supracrestal tissue height establishment: A multi-center prospective study

INTRODUCTION

Supracrestal tissue height establishment is a crucial factor influencing peri-implant marginal bone modifications prior to prosthesis delivery. If mucosal thickness is insufficient, peri-implant marginal bone resorption occurs to allow appropriate supracrestal tissue height formation. This study evaluates if marginal bone resorption occurring around tissue-level implants before prosthetic loading could be compensated by adapting apico-coronal positioning to mucosal thickness.

METHODS

Patients requiring placement of one single implant in the posterior mandible were treated with tissue-level implants with a 3-mm high transmucosal machined component and moderately rough implant body. Based upon vertical mucosal thickness measured after buccal flap reflection, implants were placed with the treated part: (group 1) 2 mm below crestal level in presence of thin mucosa (<2.5 mm); (group 2) 1 mm below the crestal level in presence of medium mucosa (2.5-3.5 mm); (group 3) at equicrestal level in presence of thick mucosa (>3.5 mm).

RESULTS

Forty-nine implants, placed in 49 patients were included in final analysis (group 1: 18 implants; group 2: 16 implants; group 3: 15 implants). Mean marginal bone resorption after 5 months of healing was 0.66 ± 0.49 mm, 0.32 ± 0.41 mm, and 0.22 ± 0.52 mm in groups 1, 2, and 3, respectively. Inter-group analysis highlighted significant differences between the three groups after ANOVA test (p = 0.025). However, adaptation of apico-coronal implant positioning in relation to mucosal thickness, allowed to avoid early exposure of the treated surface in 100%, 93.7%, and 53.3% of the implants in groups 1, 2, and 3, respectively.

CONCLUSION

During supracrestal tissue height formation, tissue-level implants inserted adapting apico-coronal positioning in relation to mucosal thickness exhibited greater marginal bone resorption at sites with thin mucosa than at sites with medium or thick mucosa. However, anticipating supracrestal tissue height establishment by adapting apico-coronal implant positioning in relation to mucosal thickness may effectively prevent unwanted exposure of treated implant surface.

Assessing Microleakage at 2 Different Implant-Healing Abutment Interfaces

OBJECTIVES

This study aimed to evaluate implants from different manufacturers and determine whether implant-healing abutment interface has a significant impact on implant seal.

METHODS

An air-injection pressure measurement test was performed on implants with either line-contact (modified TSIII [TSM] and Bone Level Tapered [BLT]) or partial face-contact (BlueDiamond [BD], SuperLine [SL], ISII, and UFII) interface design from 6 different manufacturers. Forty implants per implant type were analysed. Pressure data were evaluated with Kruskal-Wallis test and Dunn's post hoc analysis (statistical significance was set at P < .05).

RESULTS

BLT implants leaked when the mean pressure was increased to 199.9 kPa. The following implants showed mean leakage pressures of 182.9 (TSM), 157.4 (BD), 112.9 (SL), 101.8 (ISII), and 30.6 (UFII). There was a significant difference between line-contact and partial face-contact implants (P < .001).

CONCLUSIONS

The implant interface design has a significant impact on implant microbial leakage. Implants with a line-contact interface exhibited a higher resistance to leakage than those with partial face-contact.

Clinical, radiographic, and biochemical evaluation of two-piece versus one-piece single implants with a laser-microgrooved collar surface after 5 years of functional loading

AIM

To compare the clinical and radiographic conditions and the expression of pro-inflammatory cytokines in peri-implant crevicular fluid (PICF) at two-piece/bone level (TP/BL) versus one-piece/tissue level (OP/TL) single implants with a laser-microgrooved collar after at least 5 years of loading.

MATERIALS AND METHODS

In total, 20 single TP/BL implants and 20 contralateral OP/TL implants, both with a laser-microgrooved collar surface, in 20 systemically and periodontally healthy subjects (12 males and 8 females, between the age of 36 and 64 [mean age of 49.7 ± 12.3 years]), were examined. Levels of IL-1β, IL-1RA, IL-6, IL-8, IL-17, b-FGF, G-CSF, GM-CSF, IFN, MIP-1β, TNF-α, and VEGF were assessed in PICF using the Bio-Plex 200 Suspension Array System. Plaque index (PI), probing depth (PD), bleeding on probing (BOP), and gingival recession (REC) were recorded. Radiographic crestal bone levels (CBL) were assessed at the mesial and distal aspects of the implant sites.

RESULTS

The mean PI, PD, BOP, and REC values had no significant differences in either group. A higher mean value of CBL with statistical difference was detected for TP/BL compared with OP/TL implants. The levels of IL-1β, IL-6, IL-8, GM-CSF, and MIP-1β and TNF-α were higher at TP/BL implants than at OP/TL implants. However, only IL-1β, IL-6, and TNF-α values presented significant differences between the groups.

CONCLUSIONS

Although after 5 years of loading single TP/BL and OP/TL implants with a laser-microgrooved collar surface presented similar good clinical conditions, a higher proinflammatory state and higher crestal bone loss were detected for TP/BL implants.

Influence of Bone-Level Dental Implants Placement and of Cortical Thickness on Osseointegration: In Silico and In Vivo Analyses

The purpose of this research is to study the biomechanical response of dental implants in bone-level type locations, 0.5 mm above and below the bone level. In addition, the influence of the thickness of the cortical bone on osseointegration is determined due to the mechanical loads transfer from the dental implant to the cortical and trabecular bone. The thicknesses studied were 1.5 mm and 2.5 mm. Numerical simulations were performed using a finite element method (FEM)-based model. In order to verify the FEM model, the in silico results were compared with the results obtained from a histological analysis performed in an in vivo study with 30 New Zealand rabbits. FEM was performed using a computerized 3D model of bone-level dental implants inserted in the lower jawbone with an applied axial load of 100 N. The analysis was performed using different distances from the bone level and different thicknesses of cortical bone. The interface area of bone growth was evaluated by analyzing the bone–implant contact (BIC), region of interest (ROI) and total bone area (BAT) parameters obtained through an in vivo histological process and analyzed by scanning electron microscopy (SEM). Bone-level implants were inserted in the rabbit tibiae, with two implants placed per tibia. These parameters were evaluated after three or six weeks of implantation. FEM studies showed that placements 0.5 mm below the bone level presented lower values of stress distribution compared to the other studied placements. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that this position presented the highest BIC value after three or six weeks of implantation. In this placement, vertical bone growth could be observed up the bone level. The smallest thickness of the study showed a better transfer of mechanical loads, which leads to a better osseointegration. In silico and in vivo results both concluded that the implants placed 0.5 mm below the cortical bone and with lower thicknesses presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Success of dental implant influenced by abutment types and loading protocol

Background:

Dental implants are considered better, latest, and most advanced technique of teeth replacement in present times with more teeth loss and increased related concerns.

Aims:

The present clinical trial was carried out to assess marginal bone loss and implant failure in immediate and delayed loading implants. The study also evaluated healing using Polymerase Chain Reaction (PCR) and the effect of risk factors on marginal bone loss.

Materials and Methods:

The 44 subjects were randomly divided into two groups with immediate loading and delayed loading protocols. Various soft-tissue parameters were seen clinically. Quantitative PCR was done to detect biomarkers. The collected data were subjected to statistical evaluation with a level of significance at P < 0.05 and the results were formulated.

Results:

Concerning marginal bone loss, it was seen that for delayed loading, the bone loss at the implant level was 1.52 ± 0.14, 0.19 ± 0.11, and 0.40 ± 0.12, respectively, at placement, 1 and 2 years. Plaque and mucosal bleeding scores were low at the time of placement with respective values of 0.96 ± 0.12 and 28.42 ± 3.15 for the delayed loading group and 0.98 ± 0.11 and 30.24 ± 3.15 for the immediate loading group. Tartrate-resistant acid phosphatase (TRAP) showing remodeling was high at 3 months in delayed loading (13.3 ± 8.5). Alkaline Phosphatase (ALP) was highest in delayed loading at 3 months (25.2 ± 7.7) and immediate loading at 2 days (32.6 ± 13).

Conclusion:

Both immediate loading and delayed loading implants show similar results in terms of bone loss, soft-tissue parameters, and biomarkers in sulcular fluids with relatively few and manageable complications.

Evaluation of customized cobalt-chromium abutments fabricated with different manufacturing process versus titanium stock abutments on the marginal misfit -An in vitro study

Aim

Accurate fit of the abutment to the implant is required for the uniform load distribution throughout the assembly. The study aims to compare the marginal misfit of titanium stock abutments with the cobalt-chromium (CoCr) customized abutments fabricated with the different manufacturing processes in internal hex implant-abutment connection using an appropriate scanning technique.

Setting and Design

In vitro comparative study.

Materials and Methods

A total of 40 abutments were included in the study. Ten titanium stock abutments were used as control (Group CN) and 30 CoCr abutments were fabricated and taken as the test group. Stock abutments were scanned and from obtained images test group abutments were fabricated as follows: Ten cast abutments (Group CA), 10 sintered abutments (Group SA), and 10 milled abutments (Group MA). Endosseous implanst having internal hex connections were matched with 10 stock abutments and 30 customized CoCr abutments. Implants were mounted in a clear epoxy resin block and the abutments were then fitted onto the implants with a torque of 30Ncm. The marginal discrepancy at implant-abutment connections was measured with confocal laser scanning microscope.

Statistical Analysis Used

One-way ANOVA and Tukey's post hoc test was done for statistical analysis.

Results

One-way ANOVA revealed a significant difference in marginal misfit of abutments. The mean marginal misfit was lowest for stock abutments (0.35 ± 0.009 μm). Among the customized abutments, the mean marginal misfit was highest for cast abutments (2.44 ± 0.445 μm) followed by sintered abutments (1.67 ± 0.232 μm) and least for milled abutments (0.65 ± 0.041 μm). A significant difference was found in marginal misfit with cast abutments and sintered abutments when compared to stock abutments (P < 0.001). The difference in marginal misfit was insignificant between stock abutments and milled abutments (P = 0.052).

Conclusion

Difference in marginal misfit exists between the titanium stock abutments and customized CoCr abutments. Among the customized abutments, milled CoCr abutments have the least marginal discrepancy and cast CoCr abutments have a maximum marginal discrepancy. Milled CoCr abutments can be used as an alternative to titanium stock abutments.

The Association of the One-Abutment at One-Time Concept with Marginal Bone Loss around the SLA and Platform Switch and Conical Abutment Implants

Objectives: Repeated abutment disconnection/reconnection may compromise the mucosal barrier and result in crestal bone level changes. The clinical significance of this phenomenon is not yet clear, as most studies on this topic are short-term. Therefore, the aim of the present study was to evaluate the influence of abutment disconnections and reconnections on peri-implant marginal bone loss over a medium-term follow-up period. Material and methods: Twenty-one patients (6 men and 15 women) with a mean age 66.23 ± 9.35 year at the time of implant placement were included. All patients who received two adjacent nonsubmerged implants were randomly assigned into one of the two groups: definitive multiunit abutments (DEFs) connected to the implant that were not removed (test group) or healing abutments (HEAs) placed at surgery, which were disconnected and reconnected 3–5 times during the prosthetic phase (control group). Peri-implant marginal bone levels (MBL) were measured through periapical X-rays images acquired immediately after the surgery (baseline), at 4–7 months immediately after prosthetic delivery, and at 1-year and 3-year follow-up visits. Results: No implant was lost or presented bone loss of more than 1.9 mm during the 3-year follow-up; thus, the survival and success rate was 100%. Peri-implant mucositis was noticed in 38.1% DEFs and 41.9% of HEAs at the 3-year follow-up assessment. At the end of 3 years, the MBL was −0.35 ± 0.69 mm for participants in the DEFs group and −0.57 ± 0.80 mm for the HEAs group, with significant statistical difference between groups. Conclusions: Immediate connection of the multiunit abutments reduced bone loss in comparison with 3–5 disconnections noted in the healing abutments 3 years after prosthetic delivery. However, the difference between the groups was minimal; thus, the clinical relevance of those results is doubtful.

Marginal Bone Loss around Implants with Internal Hexagonal and Internal Conical Connections: A 12-Month Randomized Pilot Study

The aim of this study was to analyze the differences in terms of the marginal bone level (MBL) around implants with either an internal conical or an internal hexagonal implant–prosthesis connection. A randomized clinical trial included patients in need of a single implant-supported restoration. The implant–prosthesis connection was either internal conical or internal hexagonal while maintaining the same type of implant macro- and microarchitecture. Clinical and radiographical variables were registered up to 12 months of follow-up, including MBL. A total of 30 patients were included in the study. The main outcome variable, MBL 12 months after prosthesis delivery, was statistically different in both groups: −0.25 (0.12) vs. −0.70 (0.43) (conical vs. hexagonal; p = 0.033). Differences were also observed at the 3- and 6-month follow-up visits as well as for the MBL change from prosthesis delivery to the 12-month follow-up (−0.15 (0.13) vs. −0.56 (0.44); conical vs. hexagonal; p = 0.023). Correlations between MBL around the implants and radiographic measurements on the adjacent teeth, buccal bone to implant, tissue thickness or keratinized tissue were not significant neither globally nor when analyzed independently by group. In view of such results, it can be concluded that single-unit restorations with internal hexagonal-connection implants induce higher marginal bone loss after 12 months of follow-up from prosthesis delivery than internal conical-connection implants.

The Vertical Soft Tissue Thickness and Subcrestal Implant Placement as Factors for Peri-implant Crestal bone Stability

Aim The aim of this prospective study was to determine the influence of vertical soft tissue thickness on bone level changes in platform-switched implants placed eqicrestally or subcrestally and restored with screw-retained or cement-retained restorations. Methods Platform-switched bone-level implants were placed in a single stage manner in the posterior mandibular region. Implant sites were divided into thick (control) and thin (test) vertical soft tissue groups. The implants in the control group were placed equicrestally. The implant sites from the control group were randomly allocated to receive equicrestally or subcrestally placed implants. Bone remodeling/loss was radiographically measured at baseline, three months postoperatively and six months after delivery of final prosthetic restoration. Results The mean crestal bone loss values three months postoperatively and six months post prosthetic restoration were higher in sites with thin versus sites with thick gingiva. In implant sites with thin gingiva, subcrestally placed implants presented less bone loss than eqicrestally placed implants. Conclusion Platform switched implants are prone to more bone loss when they are placed in sites with thin soft tissue, regardless of the type of final restoration (screw-retained or cement-retained). Subcrestal placement of platform-switched implants can prevent crestal bone loss in sites with vertical soft tissue thickness < 3 mm.    

Factors Influencing Marginal Bone Loss around Dental Implants: A Narrative Review

Implant supported dental prostheses are increasingly used in dental practice. The aim of this narrative review is to present the influence of transmucosal surface of prosthetic abutment and implant on peri-implant tissue. The article describes causes of bone loss around the dental implant. Moreover, properties of different materials are compared and discussed. The advantages, disadvantages, and biomechanical concept of different implant-abutment connections are presented. The location of connections in relation to the bone level and the influence of microgap between the abutment and implant are described. Additionally, the implant abutments for cemented and screwed prosthetic restorations are compared. The influence of implant and abutment surface at the transmucosal level on peri-implant soft tissue is discussed. Finally, the biological aspect of abutment-implant connection is analyzed.

Synchrotron-based micro computed tomography investigation of the implant-abutment fatigue-induced microgap changes

OBJECTIVE

This study evaluates the effect of dynamic-loading on the microgap of the IAC when different supratructure heights are applied.

MATERIALS AND METHODS

Forty-eight dental implants (24 each of butt-joint (H) and internal-conical connections (C)) were tested in this study. Each group was further divided into three groups (n = 8) according to the applied suprastructure height (H1, C1: 10 mm, H2, C2: 14 mm and H3, C3: 18 mm). All specimens were subjected to cyclic loading in a chewing-simulator with a load of 98 N for 5 × 10⁶ chewing cycles. The microgap at the IAC was inspected before and after loading, using synchrotron-based micro computed tomography (SRμCT) and light microscopy (LM).

RESULTS

SRμCT revealed an internal microgap range between 0.26 μm and 0.5 μm in the group C, whereas the group H exhibited a microgap range between 0.26 μm and 0.47 μm prior to loading. After chewing simulation, a smaller microgap size in all groups was detected ranging from 0.11 μm to 0.26 μm (group C: 0.11μm-0.26 μm; group H: 0.21μm-0.25 μm). The LM investigation showed mean microgap values at the outer IAC junction before loading from 5.8 μm to 11.3 μm and from 3.9 μm to 7.2 μm after loading. All specimens exhibited a vertical intrusion displacement of the abutment.

CONCLUSION

Regardless of the crown height, the microgap between the abutment and implant systematically decreased after loading in both butt-joint and internal-conical connections.

Crestal bone changes around early vs. conventionally loaded implants with a multi-phosphonate coated surface: A randomized pilot clinical trial

OBJECTIVES

To compare the marginal bone level around implants with a thin multi-phosphonate coated surface after either an early or conventional loading protocol.

MATERIAL AND METHODS

A randomized pilot clinical trial was conducted. Dental impressions were obtained after either 4 (test) or 8 weeks (control) and single crowns screwed-in 2 weeks later. Several variables were evaluated including radiographical marginal bone level (MBL), patient's level variables, and those related to the restoration and surrounding tissues. These data were obtained at several time points up to a 1-year follow-up.

RESULTS

Thirty-four patients were included in the study, 18 assigned to the test group. No differences at implant placement were detected for tissue thickness, keratinized mucosa, nor any other clinical or radiological variable. At the time of impressions, tissue was thinner in the test group (2.30 (0.46) versus 2.78 (0.66) mm, test versus control, respectively; p = .012) so shorter abutments were used in this group. Regardless, no significant changes in marginal bone level were detected neither within group along time nor between groups. The average MBL at the 1-year follow-up was -0.15 (0.32) versus -0.22 (0.37) (p = .443) (test versus control, respectively). None of the clinical or radiological variables evaluated had a determinant influence on the MBL at any visit nor group.

CONCLUSION

The use of implants with a multi-phosphonate coated surface for early loading offers successful radiographical outcomes 1 year after loading. MBL over time was not affected by taking the impressions 4 or 8 weeks after implant placement and loading them 2 weeks later.

Survival Rate of 1008 Short Dental Implants with 21 Months of Average Follow-Up: A Retrospective Study

This retrospective study evaluated the survival rate of short, sandblasted acid-etched surfaced implants with 6 and 8 mm lengths with at least 120 days of follow-up. Data concerning patient, implant and surgery characteristics were retrieved from clinical records. Sandblasted and acid-etched (SLA)-surfaced tissue-level 6 mm (TL6) or 8 mm (TL8) implants or bone-level tapered 8 mm (BLT8) implants were used. Absolute and relative frequency distributions were calculated for qualitative variables and mean values and standard deviations for quantitative variables. A Cox regression model was performed to verify whether type, length and/or width influence the implant survival. The cumulative implant survival rate was assessed by time-to-event analyses (Kaplan–Meier estimator). In all, 513 patients with a mean age of 58.00 ± 12.44 years received 1008 dental implants with a mean follow-up of 21.57 ± 10.77 months. Most implants (78.17%) presented a 4.1 mm diameter, and the most frequent indication was a partially edentulous arch (44.15%). The most frequent locations were the posterior mandible (53.97%) and the posterior maxilla (31.55%). No significant differences were found in survival rates between groups of type, length and width of implant with the cumulative rate being 97.7% ± 0.5%. Within the limitations of this study, the evaluated short implants are a predictable option with high survival rates during the follow-up without statistical differences between the appraised types, lengths and widths.

Soft tissue healing around platform-switching and platform-matching single implants: A randomized clinical trial

BACKGROUND

Implants with platform-switching (PS) design have been demonstrated to reduce marginal bone loss. However, the influence on peri-implant soft tissue healing is unclear. This study was designed to investigate its effect on peri-implant soft tissue healing after implant uncovery.

METHODS

Non-smokers needing two implants in different quadrants were recruited in this study. For each individual, one PS and one platform-matching (PM) implants were placed using two-stage protocol. Following 2 to 8 months of healing, all implants were uncovered and connected to the corresponding healing abutments. Clinical measurements and peri-implant crevicular fluid (PICF) were taken at 1-, 2-, 4-, and 6-week after 2nd stage surgery. The cytokine concentrations in PICF were analyzed. Peri-implant mucosa (1 × 2 × 2 mm) was harvested around the healing abutment for the analysis of gene expression at uncovery and 6-week post-uncovery.

RESULTS

Eighteen participants (nine males; 51.7 ± 14.9 years) were recruited. Compared to PM, PS showed significantly lower probing depth (PD) at 1- and 2-week as well as modified sulcus bleeding index (mSBI) at 1-, 4-, and 6-week (P < 0.05). Over time, a decrease in osteoprotegerin and interleukin-1β concentrations in PICF along with an increase in receptor activator of unclear factor kappa-B ligand, periostin, and peroxidasin gene expressions in peri-implant mucosa were noted within both groups (P < 0.05) without significant intergroup differences.

CONCLUSION

Within the limits, implants with PS design rendered significant benefits over PM design in PD and mSBI reduction during a 6-week healing. However, molecular changes within PICF and peri-implant mucosa as a response to PM and PS appear negligible.

Influence of implant mucosal thickness on early bone loss: a systematic review with meta-analysis

Purpose

Marginal bone loss (MBL) is an important clinical issue in implant therapy. One feature that has been cited as a contributing factor to this bone loss is peri-implant mucosal thickness. Therefore, in this report, we conducted a systematic review of the literature comparing bone remodeling around implants placed in areas with thick (≥2-mm) vs. thin (<2-mm) mucosa.

Methods

A PICO question was defined. Manual and electronic searches were performed of the MEDLINE/PubMed and Cochrane Oral Health Group databases. The inclusion criteria were prospective studies that documented soft tissue thickness with direct intraoperative measurements and that included at least 1 year of follow-up. When possible, a meta-analysis was performed for both the overall and subgroup analyses.

Results

Thirteen papers fulfilled the inclusion criteria. A meta-analysis of 7 randomized clinical trials was conducted. Significantly less bone loss was found around implants with thick mucosa than around those with thin mucosa (difference, −0.53 mm; P<0.0001). Subgroups were analyzed regarding the apico-coronal positioning, the use of platform-matched vs. platform-switched (PS) connections, and the use of cement-retained vs. screw-retained prostheses. In these analyses, thick mucosa was found to be associated with significantly less MBL than thin mucosa (P<0.0001). Among non-matching (PS) connections and screw-retained prostheses, bone levels were not affected by mucosal thickness.

Conclusions

Soft tissue thickness was found to be correlated with MBL except in cases of PS connections used on implants with thin tissues and screw-retained prostheses. Mucosal thickness did not affect implant survival or the occurrence of biological or aesthetic complications.

Trial Registration

International Prospective Register of Systematic Reviews (PROSPERO): CRD42018084598

Biological Responses to the Transitional Area of Dental Implants: Material- and Structure-Dependent Responses of Peri-Implant Tissue to Abutments

The stability of peri-implant tissue is essential for the long-term success of dental implants. Although various types of implant connections are used, little is known about the effects of the physical mechanisms of dental implants on the stability of peri-implant tissue. This review summarizes the relevant literature to establish guidelines regarding the effects of connection type between abutments and implants in soft and hard tissues. Soft tissue seals can affect soft tissue around implants. In external connections, micromobility between the abutment and the hex component of the implant, resulting from machining tolerance, can destroy the soft tissue seal, potentially leading to microbial invasion. Internal friction connection implants induce strain on the surrounding bone via implant wall expansion that translates into masticatory force. This strain is advantageous because it increases the amount and quality of peri-implant bone. The comparison of internal and external connections, the two most commonly used connection types, reveals that internal friction has a positive influence on both soft and hard tissues.

Impact of crestal and subcrestal implant placement upon changes in marginal peri-implant bone level. A systematic review

BACKGROUND

To systematically assess studies analyzing peri-implant bone loss in implants placed in crestal and subcrestal position.

MATERIAL AND METHODS

Following the recommended methods for systematic reviews and meta-analyses (PRISMA), an electronic search was conducted in the PubMed (MEDLINE), EMBASE and LILACS databases to identify all relevant articles published up until April 2017. The search included human studies comparing marginal bone loss (MBL) between a control group and a study group with a minimum of 10 patients and a minimum follow-up of 6 months after prosthetic loading with rough neck implants. Two independent reviewers assessed the risk of bias in the selected studies based on the Newcastle-Ottawa scale for observational studies and the Cochrane Collaboration for clinical trials.

RESULTS

Of 342 potentially eligible items, 7 complied with the inclusion criteria. One article was retrieved through the manual search. Eight articles were finally included: five experimental and three observational studies. The risk of bias assessed by the Cochrane Collaboration and Newcastle-Ottawa showed a high risk of bias. The mean follow-up period was 21 months (range 6-36 months). In four studies, implants placed in a crestal position presented higher MBL than subcrestal implants - the differences being significant in one study, while in three studies, implants placed in a subcrestal position presented greater MBL than crestal implants, with significant differences in only one study.

CONCLUSION

Despite its limitations, the present systematic review did not find better outcomes between crestal and subcrestal implant placement, however, new studies will be needed, involving improved designs and the standardization of protocols to allow statistical comparisons and the drawing of firm conclusions.

The Effect of Tapered Abutments on Marginal Bone Level: A Retrospective Cohort Study

Background: Early peri-implant bone loss has been associated to long-term implant-prosthetic failure. Different technical, surgical, and prosthetic techniques have been introduced to enhance the clinical outcome of dental implants in terms of crestal bone preservation. The aim of the present cohort study was to observe the mean marginal bone level around two-part implants with gingivally tapered abutments one year after loading. Methods: Mean marginal bone levels and change were computed following radiological calibration and linear measurement on standardized radiographs. Results: Twenty patients who met the inclusion criterion of having at least one implant with the tapered prosthetic connection were included in the study. The cumulative implant success rate was 100%, the average bone loss was −0.18 ± 0.72 mm, with the final bone level sitting above the implant platform most of the time (+1.16 ± 0.91 mm). Conclusion: The results of this cohort study suggested that implants with tapered abutments perform successfully one year after loading and that they are associated with excellent marginal bone preservation, thus suggesting that implant-connection macro-geometry might have a crucial role in dictating peri-implant bone levels.

A New Strategy Against Peri-Implantitis: Antibacterial Internal Coating

The bacterial biofilm formation in the oral cavity and the microbial activity around the implant tissue represent a potential factor on the interface between bone and implant fixture that could induce an inflammatory phenomenon and generate an increased risk for mucositis and peri-implantitis. The aim of the present clinical trial was to investigate the bacterial quality of a new antibacterial coating of the internal chamber of the implant in vivo at six months. The PIXIT implant (Edierre srl, Genova Italy) is prepared by coating the implant with an alcoholic solution containing polysiloxane oligomers and chlorhexidine gluconate at 1%. A total of 15 healthy patients (60 implants) with non-contributory past medical history (nine women and six men, all non-smokers, mean age of 53 years, ranging from 45-61 years) were scheduled to receive bilateral fixed prostheses or crown restorations supported by an implant fixture. No adverse effects and no implant failure were reported at four months. All experimental sites showed a good soft tissue healing at the experimental point times and no local evidence of inflammation was observed. Real-Time Polymerase Chain Reaction (PCR) analysis on coated and uncoated implants showed a decrease of the bacterial count in the internal part of the implant chamber. The mean of total bacteria loading (TBL) detected in each PCR reaction was lower in treated implants (81038 units/reaction) compared to untreated implants (90057 units/reaction) (p < 0.01). The polymeric chlorhexydine coating of the internal chamber of the implant showed the ability to control the bacterial loading at the level of the peri-implant tissue. Moreover, the investigation demonstrated that the coating is able to influence also the quality of the microbiota, in particular on the species involved in the pathogenesis of peri-implantitis that are involved with a higher risk of long-term failure of the dental implant restoration.

ESTABLISH A MECHANICAL DAMPING MODEL FOR EVALUATING THE SURROUNDING SOFT TISSUE OF DENTAL IMPLANT

Multiple variables have been shown to influence early marginal bone loss around dental implants. Among these factors, the location of the microgap related to the alveolar crest, occlusion, crest module and soft tissue thickness were reported to be important factors for deciding the final outcome of the implant treatment. The purpose of this study was to establish a damping model to simulate the mechanical function of dental implants in the oral cavity. The experimental implant model consisted of a screw-type implant (10[Formula: see text]mm). The implant was placed into epoxy resin which was used to simulate bone tissue. In this study, two kinds of epoxy resin were used: PL-1 (with elastic moduli of 2900[Formula: see text]MPa) and PL-2 (210[Formula: see text]MPa) were used to simulate cortical bone and cancellous bone, respectively. Above bone block, a soft lining material was used to simulate the soft tissue around implant. In addition, two-implant model with various distance between implants were established to discuss the effect of soft tissue effect on the damping factors (DF) of the implant system. A noninvasive impulse-forced vibration technique was used to detect the damping factors of the implant models as previous reported. Briefly, the signal excitation was detected through the micro-phone and sent to the spectrum analyzer. The frequency response was obtained from a vibration-time histogram using Fast Fourier Transform software. The DF value of the signal dental implant model was detected to be [Formula: see text]. This value is closed to the in vivo data that was reported previously. This result showed that the model established in this study is a validated model for damping analysis. Furthermore, the DF value of a dental implant surrounded with 3[Formula: see text]mm soft tissue ([Formula: see text]) is significantly higher than the implant with 2[Formula: see text]mm-surround soft tissue ([Formula: see text]). In addition, implant models with larger interval distance between implants showed higher DF values. According to the results of this study, it is reasonable to suggest that dental implant surrounded with higher amount soft tissue may reduce more vibration amplitude while an occlusal force was applied to a dental implant. This vibration reducing effect may be helpful to reduce alveolar bone resorption around implants.

Bone Loss in Implants Placed at Subcrestal and Crestal Level: A Systematic Review and Meta-Analysis

Background: To assess differences in marginal bone loss in implants placed at subcrestal versus crestal level. Methods: An electronic and a manual research of articles written in English from Jaunary 2010 to January 2018 was performed by two independent reviewers. Clinical trials comparing bone loss for implants placed at crestal and subcrestal level were included. Pooled estimates from comparable studies were analyzed using a continuous random-effects model meta-analysis with the objective of assessing differences in crestal bone loss between the two vertical positions. Results: 16 studies were included; 10 studies did not encounter statistically significant differences between the two groups with respect to bone loss. Three articles found greater bone loss in subcrestal implants; while 3 found more bone loss in crestal implants. A meta-analysis for randomized control trial (RCT) studies reported an average and non-statistically different crestal bone loss of 0.028 mm. Conclusions: A high survival rate and a comparable bone loss was obtained both for crestal and subcrestal implants’ placement. Quantitative analysis considering a homogenous sample confirms that both vertical positions are equally valid in terms of perimplant bone loss. However, with respect to soft tissue; in presence of a thin tissue; a subcrestal placement of the implant should be preferred as it may reduce the probability for the implant to become exposed in the future and thus avoid the risk of suffering from peri-implant pathologies.

One Abutment at One Time Concept for Platform-Switched Morse Implants: Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was to compare the peri-implant vertical bone loss of immediate loading of implant crowns using the one abutment at one time (AOT) protocol and implants with abutment removal (AR). This systematic review with meta-analysis was reported according to the PRISMA statement, with guidance from the Cochrane Collaboration Handbook. A total of 103 publications were identified in the PubMed database and reference lists of examined articles. After the screening of titles and abstracts, the eligibility of eight full-text articles was assessed. Five studies published between 2010 and 2015 were included in the meta-analysis. There was less peri-implant vertical bone loss at implants using an AOT protocol than at implants using AR protocol (WMD -0.19, 95% CI -0.26 to -0.13; p<0.0001; random-effects model). In conclusion, the use of the AOT protocol with platform-switched Morse implants results in less bone loss than do AR procedures, but this effect may not be clinically relevant. The preservation of marginal bone level achieved with the AOT protocol may not enhance the aesthetics. These results should be interpreted with caution.

One-Piece Implants with Smooth Concave Neck to Enhance Soft Tissue Development and Preserve Marginal Bone Levels: A Retrospective Study with 1- to 6-Year Follow-Up

Novel one-piece implants with concave smooth neck have been introduced to promote the formation of a thick mucosal layer and preserve marginal bone. A retrospective study on 70 patients with 1- to 6-year follow-up was carried out. Cumulative survival rates were assessed. Variations of marginal bone level were measured on periapical radiographs as distance of the implant-abutment junction from the bone crest. Influence of different variables on treatment outcome was evaluated. Cumulative success rate after 6 years was 99.4 % at implant level and 98.6 % at patient level. Marginal bone level changed in a significant way over time. After 4 months, an increase of radiographic bone level of 0.173 ± 1.088 mm at implant level and 0.18 ± 1.019 mm at patient level was recorded. Mean marginal bone loss after 5 years was 0.573 ± 0.966 mm at implant level and 0.783 ± 1.213 mm at patient level. Age, sex, smoking habits, implant sites, implant lengths and diameters, prosthetic retentions, and timing of loading did not influence marginal bone remodeling in a statistically significant way. At 4-year follow-up partial restorations lost a mean of 0.96 mm of more marginal bone compared with single restorations. This difference was statistically significant.

Soft-tissue esthetic outcome of single implants: Immediate placement in fresh extraction sockets versus conventional placement in healed sockets

Background:

Immediate implant placement has advantages such as requiring fewer surgical procedures and decreased treatment time; however, unpredictable soft- and hard-tissue outcome is a problem. This study aimed to compare the soft-tissue esthetic outcome of single implants placed in fresh extraction sockets versus those placed in healed sockets.

Materials and Methods:

This cross-sectional, retrospective study was performed on 42 patients who received single implants. Twenty-two patients with a mean age of 40.14 years received immediate implants while 18 patients with a mean age of 43.40 years were subjected to conventional (delayed) implant placement. The mean follow-up time was 14.42 ± 8.37 months and 18.25 ± 7.10 months in the immediate and conventional groups, respectively. Outcome assessments included clinical and radiographic examinations. The esthetic outcome was objectively rated using the pink esthetic score (PES).

Results:

All implants fulfilled the success criteria. The mean PES was 8.54 ± 1.26 and 8.10 ± 1.65 in the immediate and conventional groups, respectively. This difference was not statistically significant (P = 0.329). The two PES parameters, namely, the facial mucosa curvature and facial mucosa level had the highest percentage of complete score.

Conclusions:

Immediate and conventional single implant treatments yielded comparable esthetic outcomes.

Implant-Abutment Contact Surfaces and Microgap Measurements of Different Implant Connections Under 3-Dimensional X-Ray Microtomography

PURPOSE

The presence of a microgap between implant and abutment could produce a bacterial reservoir which could interfere with the long-term health of the periimplant tissues. The aim of this article was to evaluate, by x-ray 3-dimensional microtomography, implant-abutment contact surfaces and microgaps at the implant-abutment interface in different types of implant-abutment connections.

MATERIALS AND METHODS

A total of 40 implants were used in this in vitro study. Ten implants presented a screw-retained internal hexagon abutment (group I), 10 had a Morse Cone taper internal connection (group II), 10 another type of Morse Cone taper internal connection (group III), and 10 had a screwed trilobed connection (group IV).

RESULTS

In both types of Morse Cone internal connections, there was no detectable separation at the implant-abutment in the area of the conical connection, and there was an absolute congruity without any microgaps between abutment and implant. No line was visible separating the implant and the abutment. On the contrary, in the screwed abutment implants, numerous gaps and voids were present.

CONCLUSIONS

The results of this study support the hypothesis that different types of implant-abutment joints are responsible for the observed differences in bacterial penetration.

Implant-abutment leaking of replace conical connection nobel biocare® implant system. An in vitro study of the microbiological penetration from external environment to implant-abutment space

PURPOSE

The aim of our study is to value the microbial contamination in the implant-abutment connections (IAC) of a Nobel Replace Conical Connection implant system [Nobel Biocare®, Vimercate (MB), Italy].

MATERIALS AND METHODS

To identify the capability of the implant to protect the internal space from the external environment, the passage of genetically modified bacteria across IAC was evaluated. Four Nobel Replace Conical Connection implants (Nobel Biocare®, Vimercate (MB), Italy) were immerged in a bacterial culture for twenty-four hours and then bacteria amount was measured inside and outside IAC with Real-time PCR. Bacterial quantification was performed by Real-Time Polymerase Chain Reaction using the absolute quantification with the standard curve method.

RESULTS

In all tested implants, bacteria were found in the inner side, with a median percentage of 10.9%. The analysis revealed that in both cases (internally and externally), bacteria grew for the first 48 hours but subsequently they started to dye, probably as a consequence of nutrient consumption. Moreover, the difference between outer and inner bacteria concentration was statistically significant at each time point.

CONCLUSIONS

Implant's internal contamination shows that IAC is not sealing. The reported results are similar to those of previous studies carried out on different implant systems. Until now, no IAC has been proven to seal the gap between implant and abutment.

Peri-implant Inflammation Defined by the Implant-Abutment Interface

An implant-abutment interface at the alveolar bone crest is associated with sustained peri-implant inflammation; however, whether magnitude of inflammation is proportionally dependent upon interface position remains unknown. This study compared the distribution and density of inflammatory cells surrounding implants with a supracrestal, crestal, or subcrestal implant-abutment interface. All implants developed a similar pattern of peri-implant inflammation: neutrophilic polymorphonuclear leukocytes (neutrophils) maximally accumulated at or immediately coronal to the interface. However, peri-implant neutrophil accrual increased progressively as the implant-abutment interface depth increased, i.e., subcrestal interfaces promoted a significantly greater maximum density of neutrophils than did supracrestal interfaces (10,512 ± 691 vs. 2398 ± 1077 neutrophils/mm2). Moreover, inflammatory cell accumulation below the original bone crest was significantly correlated with bone loss. Thus, the implant-abutment interface dictates the intensity and location of peri-implant inflammatory cell accumulation, a potential contributing component in the extent of implant-associated alveolar bone loss.

Bone level changes around platform switching and platform matching implants: a systematic review with meta-analysis

The amount of marginal bone loss is considered an important criterion to evaluate the implant therapy outcome and to predict the prognosis of the implant rehabilitation. The purpose of this systematic review was to examine the available literature comparing clinical and radiological outcomes like the implant failure rates and marginal bone loss around platform switching dental implants versus platform matching ones. English randomized controlled human clinical trials, comparing one or more PS groups with one or more PM groups, with at least 12 months of follow-up after loading and 10 implants, providing carefully the number of PS- and PM- implants used as well as implant survival and data concerning bone level changes or marginal bone loss around implants, were included. Fifteen publications, involving a total of 1439 implants and 642 patients, were eligible. More studies showed less mean marginal bone loss around PS implants and none of them showed differences in terms of implant failure rates. This review confirmed a great effectiveness of platform switching technique to prevent marginal bone resorption. Nevertheless, this result should be interpreted cautiously because of the heterogeneity of the included studies.

Factors Influencing the Soft Tissue Changes Around Single Laser Microtextured Implants-Abutments in the Anterior Maxilla: A 5-Year Retrospective Study

PURPOSE

The aim of this study was to evaluate the possible factors that influenced the periimplant soft tissue changes around single implants-abutments with laser-microtextured surface (LMS) in the esthetic zone.

MATERIALS AND METHODS

Thirty-nine units, formed by implant-abutment with LMS were studied. Variables possibly associated with the periimplant soft tissue changes were obtained from clinical measurements (plaque [present/absent], periimplant biotype [thin/thick], and probing depth); intrasurgical measurements (vertical height in millimeters of the keratinized gingiva in the vestibular part of the implant site vestibular keratinized gingiva [VKG], implant vestibular crestal exposition, vestibular crestal level, and vestibular bone width); cast models (implant position [buccal/palatal], implant abutments angle); periapical radiographs (distance from the contact point to the interproximal bone crest of the adjacent tooth [CP-BC], distance from the contact point to the implant platform [CP-P], distance from the contact point to the first bone to implant contact [CP-IB]); and digital clinical photographs. Fisher exact test was used to determine the influence of each factor on the papilla level and on the facial marginal mucosal level.

RESULTS

The papillae level at the implant sites was significantly associated with the distance from the contact point to the alveolar bone crest, whereas no association was found with other variables. Periimplant biotype, differences in the VKG, CP-BC, and CP-IB were found associated with the different facial marginal mucosal level groups.

CONCLUSIONS

This study showed that the papilla level at single-tooth implants-abutments with LMS in the anterior maxilla was mainly influenced by the interproximal bone crest level of the adjacent tooth, whereas the marginal mucosal level was affected by periimplant biotype, facial bone crest level, and crestal implant exposition.

Evaluation of Implant Collar Surfaces for Marginal Bone Loss: A Systematic Review and Meta-Analysis

Background. It is important to understand the influence of different collar designs on peri-implant marginal bone loss, especially in the critical area. Objectives. The purpose of the present systematic review and meta-analysis was to compare dental implants with different collar surfaces, evaluating marginal bone loss and survival rates of implants. Methods. Eligibility criteria included clinical human studies, randomized controlled trials, and prospective and retrospective studies, which evaluated dental implants with different collar surface in the same study. Results. Twelve articles were included, with a total of 492 machined, 319 rough-surfaced, and 352 rough-surfaced microthreaded neck implants. There was less marginal bone loss at implants with rough-surfaced and rough-surfaced microthreaded neck than at machined-neck implants (difference in means: 0.321, 95% CI: 0.149 to 0.493; p < 0.01). Conclusion. Rough and rough-surfaced microthreaded implants are considered a predictable treatment for preserving early marginal bone loss.