Influences of microgap and micromotion of implant-abutment interface on marginal bone loss around implant neck

Comparative in vitro evaluation of microgap in titanium stock versus cobalt-chrome custom abutments on a conical connection implant: Effect of crown cementation and ceramic veneering

OBJECTIVE

To compare the implant-abutment connection microgap between computer-aided design and computer-aided manufacturing (CAD/CAM) milled or laser-sintered cobalt-chrome custom abutments with or without ceramic veneering and titanium stock abutments with or without crown cementation.

MATERIAL AND METHODS

Six groups of six abutments each were prepared: (1) CAD/CAM cobalt-chrome custom abutments: milled, milled with ceramic veneering, laser-sintered, and laser-sintered with ceramic veneering (four groups: MIL, MIL-C, SIN, and SIN-C, respectively) and (2) titanium stock abutments with or without zirconia crown cementation (two groups: STK and STK-Z, respectively). Abutments were screwed to the implants by applying 30 Ncm torque. All 36 samples were sectioned along their long axes. The implant-abutment connection microgap was measured using scanning electron microscopy on the right and left sides of the connection at the upper, middle, and lower levels. Data were analyzed using the Kruskal-Wallis test (p < .05).

RESULTS

Mean values (μm) of the microgap were 0.54 ± 0.44 (STK), 0.55 ± 0.48 (STK-Z), 1.53 ± 1.30 (MIL), 2.30 ± 2.2 (MIL-C), 1.53 ± 1.37 (SIN), and 1.87 ± 1.8 (SIN-C). Although significant differences were observed between the STK and STK-Z groups and the other groups (p < .05), none were observed between the milled and laser-sintered groups before or after ceramic veneering. The largest microgap was observed at the upper level in all groups.

CONCLUSIONS

Titanium stock abutments provided a closer fit than cobalt-chrome custom abutments. Neither crown cementation nor ceramic veneering resulted in significant changes in the implant-abutment connection microgap.

Marginal changes at bone-level implants supporting dental prostheses with or without intermediate standardised abutments after 36 months: Randomised controlled clinical trial

OBJECTIVE

The objective of this study is to evaluate the changes at marginal bone level at implants restored with screw-retained prosthesis connected directly to the implants or with an intermediate abutment, after 3-year follow-up.

MATERIAL AND METHODS

Thirty-six partially edentulous patients received 72 implants. Each patient received 2 implants and a 2-4-unit screw-retained implant-prosthesis. The test group implants received a screw-retained prosthesis connected directly to the implant shoulder, the control group prosthesis were connected through a 3-mm standardised intermediate abutment. Clinical and radiological data were recorded at baseline and at 6-, 12-, and 36-month follow-up.

RESULTS

At 36 months, the mean marginal bone loss was 0.13 ± 0.18 mm for the control group and 0.20 ± 0.24 for the test group, with no significant differences between groups (p > .05). Clinical variables (Probing Pocket Depth, Bleeding on Probing and Plaque Index) at 36 months also showed no significant difference between groups. Minor complications frequency was 6.7% in the control group and 5.3% in test group. None of the groups suffered from mayor complications. Patient Reported Outcomes (PROs) showed a General Satisfaction mean score in the control group of 9.40 (SD 0.82) and 9.37 (SD 1.06) in the test group with no significant differences between groups.

CONCLUSIONS

Bone-level implants restored with screw-retained partial prostheses with or without intermediate abutments showed similar radiographic and clinical outcomes after 3 years.

Fretting-corrosion at the Implant-Abutment Interface Simulating Clinically Relevant Conditions

OBJECTIVE

Implant treatment is provided to individuals with normal, idealized masticatory forces and also to patients with parafunctional habits such as grinding, clenching, and bruxing. Dental erosion is a common increasing condition and is reported to affect 32 % of adults, increasing with age. This oral environment is conducive to tribocorrosion and the potential loss of materials from the implant surfaces and interfaces with prosthetic components. Although several fretting-corrosion studies have been reported, until now, no study has simulated clinically relevant micromotion. Therefore, our aim is to investigate fretting-corrosion using our new micro-fretting corrosion system, simulating clinical conditions with 5 µm motion at the implant-abutment interface under various occlusal loads and acidic exposures.

METHODS

We simulated four conditions in an oral environment by varying the contact load (83 N and 233 N) and pH levels (3 and 6.5). The commonly used dental implant material, Grade IV titanium, and abutment material Zirconia (ZrO2)/ Grade IV titanium were selected as testing couple materials. Artificial saliva was employed to represent an oral environment. In addition, a standard tribocorrosion protocol was followed, and the pin was controlled to oscillate on the disk with an amplitude of 5 μm during the mastication stage. After the testing, 3D profilometry and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) were utilized to analyze the worn surfaces. Inductively coupled plasma mass spectrometry (ICP-MS) was also used to measure the metal ion release.

RESULTS

Energy ratios were below 0.2, indicating a fretting regime of partial slip for all groups. Open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were analyzed to compare the electrochemical behavior among groups. As a result, corrosive damage was observed to be more in the Ti4- Ti4 groups than in Zr-Ti4 ones, whereas more mechanical damage was found in the Zr-Ti4 groups than in the Ti4-Ti4 groups. Possible mechanisms were proposed in the discussion to explain these findings.

SIGNIFICANCE

The results observed from this study might be helpful to clinicians with implant selection. For example, for patients with bruxism, a titanium implant paired with a titanium abutment may be preferable, while patients with GERD may benefit more from a titanium implant paired with a zirconia abutment.

Comparative Analysis of Internal Tapered Implant-Abutment Connections: Evaluating the Morse Effect

The purpose of the present study was to evaluate the Morse effect of different internal tapered implant-abutment connections (ITCs) using a pullout test. Implants with different ITCs were selected: Short (Bicon, USA), G1; Novo Colosso (Medens, Brazil), G2; Epkut (SIN, Brazil), G3; Strong SW (SIN, Brazil), G4; Flash (Conexão, Brazil), G5 and Bone Level (Straumann, Switzerland), G6. The respective computer-aided design (CAD) files were loaded into the analysis software to measure each ITC's taper angle and implant-abutment contact area. Six implants from each group were embedded in acrylic resin blocks, and the respective universal abutments were fixed using a mallet (G1) or by applying 20 Ncm of torque (G2 to G6). After 10 minutes, each abutment's retention screw was removed, and the force necessary for abutment rupture was recorded using a universal testing machine at a crosshead speed of 0.5 mm/min. The groups were compared using a one-way analysis of variance and Tukey's test. Spearman's correlation was used to check the correlation of the taper angle and contacting area with the pullout strength. G1, a no-screw abutment with a 3° taper, and G2, a 10° tapered abutment tightened by 20 Ncm, presented the highest pullout strength (P < .05). The increased taper angle of G4, compared to G3, reduced the Morse effect despite their similar implant-abutment contacting areas (P < .05). The G5 and G6 abutments loosened after screw removal and did not exhibit pullout resistance. The closer the tapered angle (r = -.958) and the higher the implant-abutment contact area (r = .880), the higher the pullout strength (P < .001). Within the limits of this study, the Morse effect is different among tapered implant-abutment connections. The closer the tapered angle and the higher the interface area, the higher the Morse effect between the abutment and the implant.

Are healing abutments being reused in periodontics residency programs in the United States? A survey-based study

PURPOSE

Recent studies indicate that reusing healing abutments (HAs) may pose a risk of biomaterial cross contamination among patients. The intent is to investigate whether postgraduate periodontics residency programs in the United States are reusing dental implant HAs and determine if there is a standardization in the decontamination and sterilization protocol of used HAs.

METHODS

An electronic survey consisting of-seven multiple choice and/or short answer questions pertaining to the re-use of HAs among postdoctoral periodontics programs was sent to program directors of 57 accredited dental schools in the United States via an online survey system (Qualtrics). Three follow-up remainder emails were sent to programs that did not respond after over a 6-month period. Data were analyzed using descriptive statistics.

RESULTS

Of the 57 postdoctoral periodontics program directors contacted, only 14 responded with three programs (3/14, 21%) reported reusing HAs. Approximately, 46% stated their residents place dental implants in two stages, while ∼54% stated they used a one-stage protocol indicating varied time exposure of HA to the oral cavity. Even in a two-stage protocol, the extended time HA remained in situ varied from 4 weeks to 6 months. Each program reusing HAs employed a distinct decontamination approach highlighting a notable lack of standardization in practices.

CONCLUSION

The findings from our study suggest that a minority of residency programs in the United States are reusing HAs. However, the limited number of responses leaves uncertainty regarding whether our findings underestimate the prevalence of this practice and accurately reflect the reality. Among those re-using HAs, there seems to be a lack of standardization in their decontamination, potentially leading to cross-contamination of residual biomaterial among patients.

Clinical performance and risk factors of all-ceramic screw-retained implant crowns in the posterior region based on a retrospective investigation

OBJECTIVES

Clinical data on all-ceramic screw-retained implant crowns (SICs) luted on titanium base abutments (TBAs) over more than 3 years are sparse. This study aimed to evaluate the clinical performance and potential risk factors for these restorations.

MATERIALS AND METHODS

Analysis took place based on the medical patient-records of three dental offices. Implant survival and prosthetic complications over time were evaluated. The study included SICs in premolar and molar regions made from monolithic lithium disilicate ceramic (M_LiDi) or veneered zirconia (V_ZiO) luted on a TBA documented over an observation time of at least 3 years. Survival and complication rates were calculated and compared by a log-rank test. Cox-Regressions were used to check potential predictors for the survival (p < .05).

RESULTS

Six hundred and one crowns out of 371 patients met the inclusion criteria and follow-up period was between 3.0 and 12.9 (mean: 6.4 (SD: 2.1)) years. Over time, six implants had to be removed and 16 restorations had to be refabricated. The estimated survival rates over 10 years were 93.5% for M_LiDi and 95.9% for V_ZiO and did not differ significantly among each other (p = .80). However, V_ZiO showed significantly higher complication rates (p = .003). Material selection, sex, age, and implant diameter did not affect the survival of investigated SICs but crown height influences significantly the survival rate (hazard ratio, HR = 1.26 (95%CI: 1.08, 1.49); p = .043).

CONCLUSIONS

Screw-retained SICs luted on TBAs that were fabricated from monolithic lithium disilicate ceramic or veneered zirconia showed reliable and similar survival rates. Increasing crown heights reduced survival over the years.

Microbiological profile of peri-implantitis: Analyses of peri-implant microbiome

PURPOSE

To characterize the microbiome composition in peri-implant pocket of peri-implantitis and peri-implant sulcus controls using 16S rRNA gene sequencing.

MATERIALS AND METHODS

In this controlled clinical cross-sectional study, 23 subjects with control implants (n = 14) and diseased implants (peri-implantitis, n = 21) were included. The peri-implant pocket/sulcus was sampled and used to extract DNA and amplify the 16S rRNA gene using universal primers targeting the V3-V4 regions. The resulting 16S PCR amplicons were sequenced on Illumina MiSeq, and the sequences were processed using DADA2 and the Human Oral Microbiome Database (HOMD) as references. Alpha and Beta diversity, as well as core microbiome and differential abundance analyses, were performed using the MicrobiomeAnalyst workflow.

RESULTS

There were no significant differences in microbial diversity between control implants and implants with peri-implantitis (Shannon p = 0.82). Overall bacterial community structure assessed through beta diversity analysis was also not significantly different between the two groups (p = 0.18). However, high levels of Gram-negative bacteria were detected in peri-implant pockets compared to the control sulcus. Abundant species in peri-implantitis were Capnocytophaga leadbetteri, Treponema maltophilum, Peptostreptococcus, Neisseria, P. gingivalis, and Porphyromonas endodontali, Lactococcus lactis and Filifactor alocis (p < 0.05). Gram-positive bacteria such as Streptococcus salivaris, Prevotella melaninogenica, L. wadei, and Actinomyces spp. serve were more abundant in peri-implant control sulcus.

CONCLUSIONS

Peri-implant sulcus in control implants harbors predominantly Gram-positive bacteria, whereas pockets of implants with peri-implantitis harbor predominantly Gram-negative bacteria.

The relationship of peri-implant soft tissue wound healing with implant cover screw design: Cross-sectional study

INTRODUCTION

Dental implants are frequently preferred method for oral rehabilitation all over the world. The incidence of various complications such as incorrect prosthesis, peri-implant mucositis, and peri-implantitis is high; premature loss of implants is encountered due to osteointegration process not being completed for some unexplained reasons. However, there is no study in the literature examining the nonfunctional period of implants. Closure screws of different implant companies have different designs like surface properties, and areas, where closure screws sit, are important reservoirs for microorganism colonization. Our study aims to evaluate the inflammatory response, epithelial maturation, and epithelial-connective tissue interaction around closure screws.

METHODS

For this purpose, 52 implants belonging to five different implant companies were included in the study. Tissues removed over the cover screw during fitting of healing caps were used as biopsy material and for epithelial proliferation Ki-67, for epithelium-connective tissue interaction Syndecan-1, and for macrophage activation CD-68 expressions were evaluated by immunohistochemical analysis. Scanning electron microscopy (SEM) analyzes were performed to evaluate the presence of gap between the implant and the cover screw.

RESULTS

As a result of our study, intensity of subepithelial inflammation between groups wasn't statistically different. Differences in CD-68 and Syndecan-1 levels were obtained at the lamina propria level. H score of CD-68 was statistically significantly different in epithelium (p = 0.032), and H score of Syndecan-1 was different in lamina propria (p = 0.022). There wasn't a statistically significant difference between the groups for Ki-67 (p = 0.151).

CONCLUSION

Our study results indicate that in addition to the implant surface morphology, the design of the closure screws is important in the inflammatory response and epithelial maturation that develops during wound healing. Although the inflammatory response is required for healing, osteointegration, and implant survival, further investigation is needed to investigate the relationship between initial neck resorption and closure screws with radiographic and microbiological examinations.

Stress distribution on implant- supported zirconia crown of maxillary first molar: effect of oblique load on natural and antagonist tooth

This study evaluated the stress distribution on an implant-supported zirconia crown of a mandibular first molar subjected to oblique loading by occlusal contact with the natural maxillary first molar by using the 3D finite element method. Two virtual models were made to simulate the following situations: (1) occlusion between maxillary and mandibular natural first molars; (2) occlusion between zirconia implant-supported ceramic crown on a mandibular first molar and maxillary natural first molar. The models were designed virtually in a modeling program or CAD (Computer Aided Design) (Rhinoceros). An oblique load of 100 N was uniformly applied to the zirconia framework of the crown. The results were obtained by the Von Mises criterion of stress distribution. Replacement of the mandibular tooth by an implant caused a slight increase in stress on portions of the maxillary tooth roots. The crown of the maxillary model in occlusion with natural antagonist tooth showed 12% less stress when compared with the maxillary (model in occlusion with the) implant-supported crown. The mandibular crown of the implant show 35% more stress when compared with the mandibular antagonist crown on the natural tooth. The presence of the implant to replace the mandibular tooth increased the stresses on the maxillary tooth, especially in the region of the mesial and distal buccal roots.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study

The present study compared three different implant and abutment sets of type Morse taper (MT) connection, with- and without-index, were analyzed regarding their mechanical behavior without and with cyclic load application simulating the masticatory function. Ninety implant and abutment (IA) sets were used in the present study, divided into three groups (n = 30 samples per group): Group A, Ideale solid straight abutment (one piece) without index; Group B, Ideale abutment with an angle of 30-degree (two pieces) without index; Group C, Ideale abutment with an angle of 30-degree (two pieces) with index. The abutment stability quotient (ASQ) values, detorque value and rotation angle were measured before and after the cycling load. Twenty IA sets of each group were submitted to mechanical load at 360,000 cycles. The ASQ without load were 64.7 ± 2.49 for the group A, 60.2 ± 2.64 for the group B, 54.4 ± 3.27 for the group C; With load were 66.1 ± 5.20 for the group A, 58.5 ± 6.14 for the group B, 58.9 ± 2.99 for the group C. Detorque values were lower in groups B and C compared to group A (p < 0.05). In conclusion, the presence of the index did not influence the stability values. However, solid straight abutments (group A) showed higher values of stability compared to groups of angled abutments (groups B and C).

Misfit simulation on implant-supported prostheses with different combinations of engaging and nonengaging titanium bases: Part 3: A radiographic evaluation

STATEMENT OF PROBLEM

The fit of implant-supported prostheses plays an important role in their mechanical and biological stability. Clinically, the prosthetic fit is typically assessed radiographically, but this method relies on the operator's subjective evaluation. Whether available digital tools could optimize the evaluation of the prosthetic fit is uncertain.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of an image processing program on the radiographic detection of discrepancies in the active and passive fit of implant-supported prostheses. Two-implant-supported screw-retained prostheses were analyzed by simulating the vertical and horizontal misfits of 3 different implant abutment configurations.

MATERIAL AND METHODS

Seven casts were fabricated using 2 internal-connection titanium implants: 1 control; 3 with vertical (V) misfit of 50 µm, 100 µm, 150 µm; and 3 with horizontal (H) misfit of 35 µm, 70 µm, 100 µm. Thirty bar-shaped zirconia frameworks were fabricated and divided into 3 groups (n=10) according to their attachment to 2 engaging (E-E), 2 nonengaging (NE-NE), and engaging and nonengaging (E-NE) titanium bases. Digital parallel periapical radiographs were made of each specimen in the passive and active fit situation on each cast (1-screw test), except for the E-E specimens, which were only seated on the control, H35, and H70 casts because the fit on the remaining casts was poor. The mean gray value (MGV) was measured at the chosen regions of interest on the second implant (side B) using the ImageJ software program. Differences in the MGV measurements between the passive and active conditions were tested using a t test (α=.05) and compared the different misfit levels using analysis of variance (1-way ANOVA), followed by the Tukey HSD test (α=.05).

RESULTS

The highest values for the differences between passive and active fit were found for the V150 and H100 misfit simulations (P<.05). Statistical differences between the MGVs were found with some exceptions: the smallest simulated misfits (H35 and V50) revealed statistically significant MGV differences from the highest simulated misfits (V150, H100) and from the H70 in the groups where an engaging component was present (P>.05). In the horizontal misfit group of NE-NE abutment configuration, H70 revealed no significant difference from the control group cast (P>.05).

CONCLUSIONS

Measuring MGV differences between passive and active fit could be a promising alternative for detecting 70- to 150-µm gaps in the implant-abutment connection that result from the misfit. However, the procedure was not adequate for detecting <50 µm gaps, cannot be uniformly applied to all types of implant-abutment connections, and requires 2 exposures to X-radiation.

Evaluation of Vertical Misfit and Torque Loss of Different Abutments for Tri-Channel Type Internal Connection Dental Implants After Mechanical Cycling

The aim of this study was to evaluate the mechanical behavior of UCLA and Mini-conical abutments for implants with Tri-channel connections regarding torque loss and vertical misfit. Twenty 3-element metal-ceramic fixed partial dentures (FPD) supported by 2 implants were manufactured and divided into 2 groups (n = 10): UCLA (group 1) and Mini-conical Abutments (group 2). The evaluation of torque loss was carried out before and after mechanical cycling, while the vertical fit was evaluated throughout the different stages of manufacturing the prostheses, as well pre- and postcycling (300,000 cycles, 30 N). Statistical analyses of torque loss and vertical misfit were performed using the linear mixed effects model. Both groups showed torque loss after mechanical cycling (P < .05); however, there was no significant percentage differences between them (P = .795). Before cycling, the groups showed a significant difference in terms of vertical misfit values (P < .05); however, this difference was no long observed after cycling (P = .894). Both groups showed torque loss after the cycling test, with no significant difference (P > .05). There was no significant difference in vertical misfit after mechanical cycling; however, in group 1 (UCLA) there was accommodation of the implant-UCLA abutment interface, while group 2 (Mini-conical abutment) did not show changes in the interface with the implant after the test. Both groups behaved similarly regarding the torque loss of the prosthesis retention screws pre- and postmechanical cycling, with greater loss after the test.

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Less marginal bone loss around bone-level implants restored with long abutments: A systematic review and meta-analysis

The aim of this study was to investigate the biological outcomes of bone-level implants restored with long vs. short abutments, with regard to the 'one abutment at one time' protocol. The systematic search was performed in five databases: MEDLINE (PubMed), EMBASE, Web of Science, Scopus, and CENTRAL for randomized controlled trials up to January 14, 2023. Data were collected for marginal bone loss, bleeding on probing, and probing pocket depth by two reviewers. As effect size measure, mean difference (MD), and risk ratio (RR) were used for continuous and categorical outcomes, R-statistics software was used for conducting statistical analyses. For quality and certainty assessment, Risk of Bias Tool 2, ROBINS-I, and GRADE approach were used. The search resulted in 4055 records without any duplicates. After title, abstract, and full-text analysis, eight articles were found eligible for inclusion. Bone-level and platform-switched implants presented less marginal bone loss after 6 months and 1 year as well, when long abutments were used (MD 0.63, 95% CI: [-0.16; 1.42]) and (MD 0.26, 95% CI: [-0.02; 0.53]). However, subgroup analysis revealed no difference in marginal bone loss when applying 'one abutment at one time' protocol (p = 0.973). Bleeding on probing and probing pocket depth presented similarly good results in both groups without almost any differences (RR 0.97, 95% CI: [0.76; 1.23]) and (MD -0.05, 95% CI: [-1.11; 1.01]). Longer abutments on bone-level implants seem to be a favorable choice for decreasing early marginal bone loss, irrespective of connection timing.

Fatigue properties of plasma nitriding for dental implant application

STATEMENT OF PROBLEM

Fatigue failure of implant components is a common clinical problem. Plasma nitriding, an in situ surface-strengthening method, may improve fatigue properties of dental implants.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of plasma nitriding on the fatigue behavior of implant systems.

MATERIAL AND METHODS

The preload and friction coefficient of plasma nitrided abutment screws, as well as settlement of the implant-abutment interface, were measured. Then, the reverse torque values and pullout force were evaluated after cyclic loading. Finally, the fatigue properties of the implant system were investigated with static fracture and dynamic fatigue life tests, and the morphology of the fracture on the surface of the implant system was observed.

RESULTS

The plasma nitriding treatment reduced the friction coefficient; increased the preload, settlement value, reverse torque values, pullout force, and static fracture load; and prolonged fatigue life. Furthermore, abutment screws with plasma nitriding treatment showed a different fatigue fracture mode.

CONCLUSIONS

Plasma nitriding improved mechanical performance and may be a suitable way to optimize the fatigue behavior of dental implants.

Conometric Connection for Implant-Supported Crowns: A Prospective Clinical Cohort Study

BACKGROUND

Traditional screw or cemented connections in dental implants present limitations, prompting the exploration of alternative methods. This study assesses the clinical outcomes of single crowns and fixed partial prostheses supported by conometric connections after one year of follow-up.

METHODS

Twenty-two patients received 70 implants, supporting 33 rehabilitations. Biological responses and prosthodontic complications were evaluated at baseline, 6 months, and 12 months.

RESULTS

All implants exhibited successful osseointegration, with no losses or peri-implant inflammation. Marginal bone levels showed minimal changes, well below pathological thresholds. The difference in marginal bone loss (MBL) was -0.27 ± 0.79 mm between T0 and T1, and -0.51 ± 0.93 mm between T0 and T2. No abutment screw loosening or crown chipping occurred. However, coupling stability loss was observed in nine cases.

CONCLUSIONS

The conometric connection demonstrated successful integration and minimal complications after one year. This alternative shows promise, particularly in simplifying handling and improving marginal adaptation. Further research with larger sample sizes and longer follow-up is warranted for comprehensive validation.

Clinical and patient-centered outcomes following rehabilitation of atrophic edentulous maxilla using six implants placed simultaneously with bilateral maxillary sinus augmentation: A retrospective case series

OBJECTIVES

To evaluate treatment success, patient satisfaction, and oral health-related quality of life (OHRQoL) after rehabilitation of atrophic edentulous maxilla (AEM) with six implants placed simultaneously with bilateral maxillary sinus floor augmentation (MSFA).

MATERIALS AND METHODS

The selected patients were fully edentulous with atrophic maxillary posterior residual ridges and rehabilitated with six implants placed simultaneously with bilateral MSFA and immediate All-on-4 provisional fixed prosthesis (PFP). After 7-12 months of implant surgery, all patients have received an All-on-6 definitive fixed prosthesis (DFP). After at least one year of function with DFP, clinical and radiographic examinations were performed. Patient satisfaction was assessed through a visual analog scale (VAS). The OHRQoL before treatment (T0), during provisional (T1), and after definitive prosthesis (T2) was evaluated using OHI-14.

RESULTS

20 maxillary edentulous patients were rehabilitated with 120 implants, 20 immediate All-on-4 PFP, and 20 All-on-6 DFP. Of those, 12 patients have passed at least a year follow-up after DFP insertion and were eligible to be included in the assessment of treatment success. After a mean of 20 (12-36) months follow-up, the implant and prosthesis survival rates were 100%. The success rate at the implant level was 98.6%. The mean marginal bone loss (MBL) was 0.09 ± 0.06 mm. No prosthetic or postoperative complications, and the mean general satisfaction was (91.75 ± 7.06). There was a significant improvement in all OHIP-14 domains during the final All-on-6 prosthesis (T2) (P < 0.01).

CONCLUSIONS

Rehabilitation of atrophic edentulous maxilla using six implants with simultaneous bilateral MSFA and immediate All-on-4 PFP is a successful treatment approach associated with minimal postoperative complications and significant improvement in OHRQoL.

Clinical, Bacterial, and Prosthodontic Parameters After Implant Abutment Disinfection Using Nd:YAG, Er,Cr:YSGG, Chlorhexidine, and Conventional Steam Before Prosthesis Delivery

Objective: This 1-year prospective clinical trial was designed to assess the microbial, clinical, radiographic, and prosthetic parameters after disinfection of the implant abutment connection using Er,Cr:YSGG (erbium, chromium-doped: yttrium, scandium, gallium, and garnet) and Nd:YAG (neodymium-doped yttrium, aluminum, garnet). Materials and methods: All the patients were divided into four groups; Group I: Nd:YAG laser, Group II: Er,Cr:YSGG laser, Group III: 0.2% chlorhexidine (CHx), and Group IV: steam disinfection. Peri-implant parameters assessed included peri-implant bleeding scores (PIBS), peri-implant plaque scores (PIPS), peri-implant pocket depth (PIPD), and crestal bone loss (CBL). The peri-implant plaque samples were acquired to perform microbiological analysis to assess Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, respectively. All measurements were completed at baseline, 6 months, and 12 months postsurgery. Multiple groups were compared with the help of the Bonferroni post-hoc adjustment test (p < 0.01). Logistic regression models were utilized to assess the association between age, oral hygiene practices (brushing and flossing), and duration of implant function. Results: At the baseline level, there were no discernible differences in the peri-implant parameters between the study groups (p > 0.05). At the 6-month (p < 0.01) and 12-month (p < 0.001) follow-ups, all four study groups demonstrated a significant improvement in PIPS and PIBS, with no significant differences between the groups at baseline (p > 0.05). Based on an intergroup comparison, Group I (Nd:YAG) showed a significant decrease in PIBS when compared with the other groups. Group II showed a considerable decrease in PIPD and enhancements in CBL when compared with Groups I, III, and IV (p < 0.01). At the 6- and 12-month follow-up periods, P. gingivalis and T. denticola reduction were found to be statistically higher in Group II, whereas P. gingivalis and T. forsythia mean log CFU/mL were found to be statistically higher in Group I. Conclusions: Nd:YAG and Er,Cr:YSGG lasers both outperformed CHx and steam disinfection in terms of clinical, peri-implant, and prosthetic results when used to clean implant abutments.

Microbiological profile of peri-implantitis: Analyses of microbiome within dental implants

PURPOSE

To characterize the microbiome composition within dental implants of peri-implantitis subjects and healthy controls using 16S rRNA gene sequencing.

MATERIALS AND METHODS

Twenty-three subjects with healthy (n = 11 implants) and diseased (peri-implantitis, n = 21) implants were included in this controlled clinical cross-sectional study. Samples were obtained from internal surfaces of dental implants using sterile paper points for microbiological analysis. DNA was extracted, and the16S rRNA gene was amplified using universal primers targeting the V3-V4 regions. The resulting 16S polymerize chain reaction amplicons were sequenced on Illumina MiSeq, and the sequences were processed using DADA2 and the Human Oral Microbiome Database (HOMD) as references. Alpha and Beta diversity, as well as core microbiome and differential abundance analyses were then performed using the MicrobiomeAnalyst workflow.

RESULTS

A significant increase in microbial diversity was observed in the internal implant surface of healthy implants compared with the internal surfaces of peri-implantitis (Shannon p = 0.02). Bacterial community structure was significantly different among groups (p = 0.012). High levels of Gram-positive bacteria were detected inside implants with peri-implantitis compared to healthy implants, especially Enterococci.

CONCLUSIONS

There is a shift in bacterial diversity inside implants with peri-implantitis from the healthy control. The microbial colonization within that space might contribute to the etiology of peri-implant disease.

Accuracy of fit for cobaltchromium bar over two implants fabricated with different manufacturing techniques: an in-vitro study

OBJECTIVE

The purpose of the invitro research was to compare the fit of Cobalt Chromium customized bar fabricated with different manufacturing processes cast metal bar, milled bar and 3D printed bar using scanning electron microscope.

MATERIALS AND METHODS

Clear epoxy resin molds were prepared. In each mold two parallel implants with a 14 mm distance from each other were embedded. Thirty Co-Cr custom bars were constructed and were divided equally into three groups: Group (I) (Co-Cr conv), group (II) milled bar (Co-Cr milled), and group (III) printed bar (Co-Cr print). The marginal fit at implant-abutment interface was scanned using scanning electron microscope (SEM).

RESULTS

There was a significant difference between the three studied groups regarding marginal misfit the between implant and fabricated bars with p-value < 0.001. The highest value of micro-gap distance was found in Co-Cr conventional group (7.95 ± 2.21 μm) followed by Co-Cr 3D printed group (4.98 ± 1.73) and the lower value were found in Co-Cr milled (3.22 ± 0.75).

CONCLUSION

The marginal fit of milled, 3D printed and conventional cast for Co-Cr alloy were within the clinically acceptable range of misfit. CAD/CAM milled Co-Cr bar revealed a superior internal fit at the implant-abutment interface. This was followed by selective laser melting (SLM) 3D printed bar and the least fit was shown for customized bar with the conventional lost wax technique.

Influence of the Use of Transepithelial Abutments vs. Titanium Base Abutments on Microgap Formation at the Dental Implant-Abutment Interface: An In Vitro Study

This in vitro study aimed to assess the presence of microgaps at the implant-abutment interface in monolithic zirconia partial implant-supported fixed prostheses on transepithelial abutments versus Ti-base abutments.

METHODS

Sixty conical connection dental implants were divided into two groups (n = 30). The control group consisted of three-unit bridge monolithic zirconia connected to two implants by a transepithelial abutment. The test group consisted of monolithic zirconia three-unit restoration connected to two implants directly by a titanium base (Ti-base) abutment. The sample was subjected to thermocycling (10,000 cycles at 5 °C to 55 °C, dwelling time 50 s) and chewing simulation (300,000 cycles, under 200 N at frequencies of 2 Hz, at a 30° angle). The microgap was evaluated at six points (mesiobuccal, buccal, distobuccal, mesiolingual, lingual, and distolingual) of each implant-abutment interface by using a scanning electron microscope (SEM). The data were analyzed using the Mann-Whitney U tests (p > 0.05).

RESULTS

The SEM analysis showed a smaller microgap at the implant-abutment interface in the control group (0.270 μm) than in the test group (3.902 μm). Statistically significant differences were observed between both groups (p < 0.05).

CONCLUSIONS

The use or not of transepithelial abutments affects the microgap size. The transepithelial abutments group presented lower microgap values at the interface with the implant than the Ti-base group in monolithic zirconia partial implant-supported fixed prostheses. However, both groups had microgap values within the clinically acceptable range.

Biomechanical behavior of implants with different diameters in relation to simulated bone loss- an in vitro study

OBJECTIVES

Bone resorption around implants could influence the resistance of the implant abutment complex (IAC). The present in vitro study aimed to assess the stability to static fatigue of implants presenting different levels of bone losses and diameters.

MATERIALS AND METHODS

Ninety implants with an internal conical connection with 3 different implant diameters (3.3 mm (I33), 3.8 mm (I38), and 4.3 mm (I43)) and 3 simulated bone loss settings (1.5 mm (I_15), 3.0 mm (I_30), and 4.5 mm (I_45) (n = 10)) were embedded and standard abutments were mounted. All specimens were artificially aged (1,200,000 cycles, 50 N, simultaneous thermocycling) and underwent subsequently load-to-fracture test. For statistical analysis, Kolmogorov-Smirnov test, Kruskal-Wallis test, and Mann-Whitney U test (p < 0.05) were applied.

RESULTS

All test specimens withstood the artificial aging without damage. The mean failure values were 382.1 (± 59.2) N (I3315), 347.0 (± 35.7) N (I3330), 315.9 N (± 30.9) (I3345), 531.4 (± 36.2) N (I3815), 514.5 (± 40.8) N (I3830), 477.9 (± 26.3) N (I3845), 710.1 (± 38.2) N (I4315), 697.9 (± 65.2) N (I4330), and 662.2 N (± 45.9) (I4345). The stability of the IACs decreased in all groups when bone loss inclined. Merely, the failure load values did not significantly differ among subgroups of I43.

CONCLUSIONS

Larger implant diameters and minor circular bone loss around the implant lead to a higher stability of the IAC. The smaller the implant diameter was, the more the stability was affected by the circumferential bone level.

CLINICAL RELEVANCE

Preserving crestal bone level is important to ensure biomechanical sustainability at implant systems with a conical interface. It seems sensible to take the effect of eventual bone loss around implants into account during implant planning processes and restorative considerations.

Escherichia coli Cellular Activity and Frontal Trizonal Evaluation of Microspace Between Implants and Abutments Under Calibrated Cyclic Stress

AIM

To evaluate microspace and microleakage between implant and abutments subjected to pre- and post-calibrated cyclic stress.

MATERIALS AND METHODS

Twelve screw-retained implant prostheses with BioHPP polyetheretherketone (PEEK) abutment (Noris Dental Implant System Ltd., Nesher, Israel) (Group I) and 12 screw-retained implant prostheses with computer-assisted design/computer-assisted manufacturing (CAD/CAM) milled zirconia abutment (DentGallop, Houston, TX, USA) (Group II) were connected to their respective implant, and the prosthetic screw was torqued to 30N/cm (Noris). The microspace was evaluated using scanning electron microscopy (SEM; TeScan, Brno, Czech Republic). Twenty-four samples were then induced to cyclic stress (Lokesh Industries, Pune, India) simulating 180 days duration of oral stress. The microspaces (Group IA and Group IIB) were measured post-cyclic stress. Group I and II were again renamed into Group Ia and Group IIb for microbial study. Both implant assemblies were immersed in fresh soybean casein digest broth (SCDB) (Himedia, Mumbai, India) and subsequently inoculated with 1.0µL E. coli suspension (Himedia) at the open end and incubated at 37ºC for seven days. After the incubation period, cellular activity was determined by the spread plate method, and total colony-forming units (CFU) were calculated. The results were evaluated using independent T and Mann-Whitney tests.

RESULT

Average and microspace at the implant-abutment junction of Group I samples in the front right was 12.98µm, center 13.76µm, front left 13.22µm, and in Group II samples, the front right was 18.52µm, center 17.84µm, front left 18.58µm.After being subjected to cyclic loading, the mean levels of the vertical microgap for Group IA samples were: in the front right region 10.37µm, in the center 9.34µm, in the front left 10.51µm and in Group IIB samples front right was 14.59µm, center 13.39µm, front left 13.8µm. Independent t-tests showed insignificant differences between the two groups. The median value of microbial leakage of Group Ia samples after cyclic loading was 30 x 103 CFU/ml, and Group IIb samples were 42 x 103 CFU/ml and were significant.

CONCLUSION

There was minimal variation in the mean microspace between the BioHPP PEEK abutment and CAD/CAM milled zirconia abutment, and it was insignificant before and after cyclic stress. BioHPP PEEK abutment-titanium implant interfaces showed significantly decreased microbial leakage than CAD/CAM milled zirconia abutment-titanium implant interfaces after cyclic stress.

Assessment of Microgap and Microbial Leakage of Two Different Implant-abutment Interfaces: An In Vitro Study

AIM

The purpose of the current study was to evaluate Titanium and Bioneck TRI implant-abutment interfaces for microgaps and microbiological leakage.

MATERIALS AND METHODS

In this in vitro experiment, 40 dental implants were split into two groups, each of which had 20 samples. Group I: Titanium dental implant, group II: Bioneck TRI. E. coli strain was cultivated in MacConkey media for 24 hours at 37°C. To achieve a bacterial concentration of 1 × 108 colony-forming units per mL at 0.5 scale of MacFarland, the brain-heart infusion (BHI) broth was injected. The CFU count was done to evaluate the microbial leakage. The parts were first submerged, carefully cleaned in an ultrasonic bath, and then installed using a digital torque meter with a 20 N/cm preload. These were attached to a stub of approximately 13 mm using carbon tape, and the microgap evaluation was performed using a scanning electron microscope at a magnification of x1000. Unpaired t-test was used for the calculated data's statistical analysis. The p-value less than 0.05 was considered as statistically significant.

RESULTS

The maximum microbial leakage was in Bioneck TRI implants (10000 ± 0.01) followed by Titanium dental implants (8.60 ± 3.16). The mean difference was 9991.40 and there was a statistically significant difference found between the two different groups. The maximum microgap was found in the Bioneck TRI implants (9.72 ± 0.96), followed by Titanium dental implant (6.82 ± 1.10) and there was a statistically significant difference was found between the groups (p < 0.001).

CONCLUSION

The present study concluded that the microorganisms can infiltrate the microgap between the implant and abutment interface. When compared with Titanium dental implants, Bioneck TRI implants showed significantly higher levels of microbial leakage.

CLINICAL SIGNIFICANCE

A microgap between the implant and abutment connection might operate as a bacterial source, may produce inflammation, even osseointegration in danger, and subsequently alter clinical and histological parameters. Therefore, having an understanding of the compatible components aids in overcoming treatment planning challenges.

Influence of monolithic restorative materials on the implant-abutment interface of hybrid abutment crowns: An in vitro investigation

Purpose This in vitro study aimed to investigate the long-term performance, stability, and fracture mode of monolithic hybrid abutment crowns, and the effect of different materials on the implant-abutment interface (IAI).Methods Eighty monolithic hybrid abutment crowns luted on titanium bases were manufactured from 3Y-TZP zirconia (ZY3), "Gradient Technology" zirconia (ZY35), 5Y-TZP zirconia (ZY5), lithium disilicate ceramic (LDS), zirconia-reinforced lithium silicate ceramic (ZLS), polymer-infiltrated ceramic network (MHY), polymethylmethacrylate (PMA), and 3D-printed hybrid composite (PHC) (n = 10 for each material). Eighty implants (Camlog Progressive-Line, diameter: 3.8 mm) were embedded in accordance with ISO standard 14801, and crowns were mounted. After artificial aging (1.2 × 10⁶ cycles, 50 N, thermocycling), intact specimens were loaded 30° off-axis in a universal testing machine until failure.Results Seven specimens in the PHC group failed during artificial aging, and all the others survived. There were two subgroups based on the one-way analysis of variance and Dunnett's test (P < 0.05) of the mean fracture load values. The first comprised Z3Y, ZY35, Z5Y, and LDS, with mean fracture loads between 499.4 and 529.7 N, while the second included ZLS, MHY, and PMA, with values in the 346.2-416.0 N range. ZY3, ZY35, ZY5, and LDS exhibited irreversible, visible deformations of the implant shoulders with varying dimensions after load-to-fracture tests.Conclusions Crowns made of LDS, ZLS, MHY, and PMA may act as potential stress breakers, and prevent possible deformation at IAIs. Further clinical studies need to assess if these materials also withstand relevant loads in-vivo.

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.

Bacterial Detection, Deformation, and Torque Loss on Dental Implants with Different Tapered Connections Compared with External Hexagon Connection after Thermomechanical Cycling

The relationship between bacterial infiltration and internal conical Implant-Abutment Interfaces (IAIs) with different conicities still requires investigations that can offer valuable information in the clinical understanding of peri-implant health. The present study aimed to verify the bacterial infiltration of two internal conical connections with an angulation of 11.5° and 16° with the external hexagonal connection as a comparative after thermomechanical cycling using saliva as a contaminant. Test (n = 10) and control (n = 3) groups were set up. Evaluations were made on torque loss, Scanning Electron Microscopy (SEM), and Micro Computerized Tomography (MicroCT) after performing 2 × 10⁶ mechanical cycles (120 N) and 600 thermal cycles (5°-55° C) with 2 mm lateral displacement. The contents of the IAI were collected for microbiological analysis. There was a difference (p < 0.05) in torque loss of the groups tested; groups from the 16° IAI obtained a lower percentage of torque loss. All groups presented contamination and the analysis of the results shows that the microbiological profile of the IAI differs qualitatively from the profile found in the saliva used for contamination. The mechanical loading affects the microbiological profile found in the IAIs (p < 0.05). In conclusion, the IAI environment may favor a microbiological profile different from that of saliva and the thermocycling condition may alter the microbial profile found in the IAI.

Influence of buccal and palatal bone thickness on post-surgical marginal bone changes around implants placed in posterior maxilla: a multi-centre prospective study

BACKGROUND

Numerous clinical variables may influence early marginal bone loss (EMBL), including surgical, prosthetic and host-related factors. Among them, bone crest width plays a crucial role: an adequate peri-implant bone envelope has a protective effect against the influence of the aforementioned factors on marginal bone stability. The aim of the present study was to investigate the influence of buccal and palatal bone thickness at the time of implant placement on EMBL during the submerged healing period.

METHODS

Patients presenting a single edentulism in the upper premolar area and requiring implant-supported rehabilitation were enrolled following inclusion and exclusion criteria. Internal connection implants (Twinfit, Dentaurum, Ispringen, Germany) were inserted after piezoelectric implant site preparation. Mid-facial and mid-palatal thickness and height of the peri-implant bone were measured immediately after implant placement (T0) with a periodontal probe and recorded to the nearest 0.5 mm. After 3 months of submerged healing (T1), implants were uncovered and measurements were repeated with the same protocol. Kruskal-Wallis test for independent samples was used to compare bone changes from T0 to T1. Multivariate linear regression models were built to assess the influence of different variables on buccal and palatal EMBL.

RESULTS

Ninety patients (50 females, 40 males, mean age 42.9 ± 15.1 years), treated with the insertion of 90 implants in maxillary premolar area, were included in the final analysis. Mean buccal and palatal bone thickness at T0 were 2.42 ± 0.64 mm and 1.31 ± 0.38 mm, respectively. Mean buccal and palatal bone thickness at T1 were 1.92 ± 0.71 mm and 0.87 ± 0.49 mm, respectively. Changes in both buccal and palatal thickness from T0 to T1 resulted statistically significant (p = 0.000). Changes in vertical bone levels from T0 to T1 resulted not significant both on buccal (mean vertical resorption 0.04 ± 0.14 mm; p = 0.479) and palatal side (mean vertical resorption 0.03 ± 0.11 mm; p = 0.737). Multivariate linear regression analysis showed a significant negative correlation between vertical bone resorption and bone thickness at T0 on both buccal and palatal side.

CONCLUSION

The present findings suggest that a bone envelope > 2 mm on the buccal side and > 1 mm on the palatal side may effectively prevent peri-implant vertical bone resorption following surgical trauma.

TRIAL REGISTRATION

The present study was retrospectively recorded in a public register of clinical trials ( www.

CLINICALTRIALS

gov - NCT05632172) on 30/11/2022.

Biomechanical evaluation of abutment stability in morse taper implant connections in different times: A retrospective clinical study compared with an in vitro analysis

Objectives

Micromotion between a dental implant and abutment can adversely affect clinical performance and compromise successful osseointegration by creating a bacterial harbor, enabling screw loosening, and imparting disruptive lateral forces on the cortical bone. Thus, the aim of the present study was to measure the abutment stability evolution using resonance frequency analysis (RFA) in vivo at four different times (baseline, 3, 4, and 12 months), and compare these data obtained with the RFA measured after mechanical cycling (in vitro) corresponding to the proposed times in numbers of cycles.

Methods

To evaluate the abutment stability, RFA was performed in 70 sets of implant/abutment (IA) with a total of 54 patients (31 women, 23 men). These IA sets were divided into three groups, according to the abutment angulation: straight abutment (Abt1 group), 17-degree angled abutment (Abt2 group), and 30-degree angled abutment (Abt3 group). Abutment stability was measured immediately at implant placement and the abutment installation (T1), 3 (T2), 4 (T3), and 12 months (T4) later. For the in vitro analysis, ten sets of each group were submitted to mechanical cycling: T1 = 0 cycles, T2 = 90,000 cycles, T3 = 120,000 cycles, and T4 = 360,000 cycles. All data collected were statistically evaluated using the GraphPad Prism 5.01 software, with the level of significance was α = 0.05.

Results

In vivo, the overall data of implant stability quotient (ISQ) values obtained for all groups in each evaluation time were 61.5 ± 3.94 (95% CI: [60-63]) at T1, 62.8 ± 3.73 (95% CI, [61-64]) at T2, 63.4 ± 3.08 (95% CI: [61-64]) at T3, and 65.5 ± 4.33 (95% CI: [63-68]) at T4. Whereas in vitro, the ISQ were 61.5 ± 2.66 (95% CI: [59-63]) at T1, 63.2 ± 3.02 (95% CI, [61-65]) at T2, 63.9 ± 2.55 (95% CI: [62-66]) at T3, and 66.5 ± 2.97 (95% CI: [64-68]) at T4. In both evaluations (in vivo and in vitro), the data showed a significant difference (ANOVA test with p < 0.0001).

Conclusions

The RFA to measure the abutment stability used in this study showed that there was a progressive increase in stability among the predetermined times for the measurements, in both analysis (in vivo and in vitro). Furthermore, the values at each time point were similar, with no statistical difference between them.

A digital protocol for the fabrication of anatomic-contour implant zirconia crowns directly screwed on external hexagonal implant connections without the interposition of a Ti-base component

A straightforward and effective restorative option is proposed for implant-supported fixed prostheses with external connections by using monolithic zirconia without the interposition of a Ti-base component. The technique is based on a modification of the Brånemark connection used to link metal-ceramic or metal-composite resin restorations directly to the implant.

Same-Day Digital Dentistry Restorative Workflow for Single Immediate Provisionalization of Narrow-Diameter Implants: An Exploratory Prospective Study

This study evaluated the two-year clinical outcomes of 3.1 mm diameter dental implants, immediately provisionalized and later restored using same-day dentistry, in 10 patients receiving 11 narrow-diameter (3.1 mm) single implants. Each implant was placed and immediately restored with a provisional crown after placement. At least 2 months after placement, the implant was restored with a prefabricated titanium abutment and an all-ceramic crown using a same-day dentistry protocol. Clinical outcomes, including apical bone loss, probing depths, gingival index, and surgical and prosthetic complications, were documented. There was no implant failure over the course of two years. No surgical complications were reported. Two cases lost provisional crowns. One crown needed to be remade due to esthetic concern. The cumulative two-year survival rate of the implants was 100%. Implant bone loss after two years of functional loading was −0.56 ± 0.54 mm and −0.32 ± 0.68 mm for mesial and distal crestal bone, respectively. Two prosthetic complications included recementation of a crown and remaking of a crown. This exploratory study suggests that immediate provisionalization and a same-day restorative dentistry digital workflow protocol for narrow-diameter implants appear to be predictable clinical procedures with no reported surgical complications and minimal prosthetic complications.

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.

On Peri-Implant Bone Loss Theories: Trying To Piece Together the Jigsaw

This review aims to explore the plausibility of new theories on the etiopathogenesis of marginal bone loss (MBL) and peri-implantitis (PI) and to discuss possible underlying pathogenic mechanisms. The former concept of osteointegration of dental implants can now be conceptualized as a foreign body response histologically characterized by a bony demarcation in combination with chronic inflammation. Different risk factors can provoke additional inflammation and, therefore, pro-inflammatory cytokine release in soft tissues and bone, leading to an overpass of the threshold of peri-implant bone defensive and regenerative capacity. Progressive bone loss observed in MBL and PI is ultimately due to a localized imbalance in the receptor activator of nuclear factor kappaB ligand (RANKL)/Receptor activator of nuclear factor κ B (RANK)/osteoprotegerin (OPG) pathway in favor of increased catabolic activity. The genetic background and the severity and duration of the risk factors could explain differences between individuals in the threshold needed to reach an imbalanced scenario. MBL and PI pathogenesis could be better explained by the "inflammation-immunological balance" theory rather than a solely "infectious disease" conception. The link between the effect of biofilm and other risk factors leading to an imbalanced foreign body response lies in osteoclast differentiation and activation pathways (over)stimulation.

Evaluation of sealing efficacy and removal convenience of sealing materials for implant abutment screw access holes

Background

Sealing materials are used to fill abutment screw access holes (SAH) to prevent microleakage and protect the central screws in oral implant restoration. However, thus far, no consensus has been reached on sealing material selection. In this study, a comparison of the sealing efficacy and removal convenience of different sealing materials for cement-retained implant restoration was conducted.

Methods

Various sealing materials were classified into five groups, namely, gutta-percha (GP), temporary restorative paste (TRP), vinyl polysiloxane (VPS), polytetrafluoroethylene (PTFE) tape, and onlay resin (OR), and 35 sets of analog-abutments were allocated into five groups of seven specimens. A sealing efficacy test was conducted using a modified dye-penetration method, in which a lower absorbance indicated better sealing efficacy. For the removal-convenience test, the materials were removed from each SAH after solidification, and the retrieval time was recorded.

Results

On days 1 and 10, PTFE exhibited the highest absorbance value with significant differences compared to the other groups. On day 30, TRP and PTFE showed significantly higher absorbance values than GP, VPS, and OR, but no significant difference was detected between TRP and PTFE (p = 0.424). The absorbance values of TRP and PTFE from days 1, 10, and 30 showed significant intragroup differences, while those of the other groups did not. In terms of the removal convenience on days 1, 10, and 30, VPS achieved the best performance, followed by PTFE, OR, TRP, and GP.

Conclusion

Within the limitations of this experiment, VPS and OR showed better sealing efficacy against microleakage and a more convenient removal than the other materials; thus, VPS and OR are recommended for clinical use.

Current complications and issues of implant superstructure

The purpose of this review is to search for complications of dental implant superstructures and consider the issues involved. This narrative review was performed by searching through PubMed databases and review articles that were published after 1990. Misfitting of the superstructure can result in loosening of screws, reduced preload, and in some cases, significant stress around the implant. External connection modalities and single implant prostheses have been reported to have more loose or broken abutment screws. In addition, when zirconia abutment was used for platform shifting, the rate of fracture of the abutment was considered to be high. Additionally, it was reported that men were significantly at an increased risk of abutment fracture. As for the retention mechanism of implant overdenture, stud attachment (Locator type) should receive more attention to wear and damage of retention parts than other attachments. The causes of the complications of implant superstructures have not been clarified in some cases, and further verification is required. Verification of complications is considered important to obtain a long-term prognosis for superstructures of implants. It will be necessary to further verify complications of implants in the future.

Microleakage assessment of CAD-CAM Cobalt-Chrome and Zirconia abutments on a conical connection dental implant: A comparative in vitro study

Objective

To assess the marginal and bacterial microleakage in zirconia and CAD‐CAM or cast Co‐Cr implant abutments.

Methods

Sixty‐four conical connection implants with their respective abutments were divided into four groups (Co‐Cr (milled, laser‐sintered, and cast) and Zirconia (milled)). All specimens were subjected to a chewing simulation and thermocycling. After aging process, specimens were submerged in a 0.2% methylene blue solution with Porphyromonas gingivalis (P.g) for 48 h. The marginal microleakage was measured using a 40× optical microscopy at the internal part of the implant, and when positive microleakage was observed, a DNA isolation with a polymerase chain reaction (PCR) test was used. The microbiological assessment was based on colony forming units (CFUs).

Results

Thirty (47%) implant‐abutments presented microleakage and the PCR was performed on those specimens (1 Zirconia, 1 Co‐Cr milled, 14 Co‐Cr laser‐sintered and 14 cast). Seven specimens (1 Co‐Cr laser‐sintered and six cast) presented values below the PCR detection limit (< 100 CFUs). The lowest CFUs count occurred in the Co‐Cr milled group (5.17E+02 CFUs/ml) followed by zirconia (7.70E+03 CFUs/ml). The Co‐Cr cast (9.39E+03 CFUs/ml) and laser‐sintered (2.4E+05 CFUs/ml) groups had higher bacterial count. The CFU count comparison performed between Co‐Cr cast and laser‐sintered resulted in a statistically significant differences in favor of Co‐CrCL (p < .05).

Conclusions

The abutment material and fabrication technique affected the implant‐abutment microleakage. Although the CAD‐CAM abutments presented favorable results, all tested groups presented microleakage.

Passant Connection Screw of Dental Implants: An In Vitro SEM Preliminary Study

The use of dental implants in oral rehabilitations has become increasingly common, thanks to the safety and predictability of these rehabilitations. Unfortunately, dental implants, being alloplastic devices, are not free from biomechanical complications, especially in the case in which the connections are complex and involve several components. The aim of the study is to highlight what could be surface alterations using different screwing torques, or by repeating the screwing process several times. In this study, 40 passant screws (Osstem®, South Korea Dental Implant Ebony Gold®) were examined under a Zeiss EVO LS 10 scanning electron microscope (SEM), operating with an accelerating voltage of 20 kV. Passant screws were subdivided into 4 groups: 30 Nmm tightening torque; maximum tightening torque; 2 times 30 Nmm tightening torque; no screwing, new ones (control group). There are no significant differences in the surfaces of the passant screws in SEM images, and the 100% of the passant screws is free of defects or fractures. Surely, further studies and investigations will certainly be needed to allow improvement of these devices.

Influence of buccal emergence profile designs on peri-implant tissues: A randomized controlled trial

BACKGROUND

The prosthetic emergence profile design might be an important factor in postsurgical mucosal recession etiology. Therefore, a restorative buccal emergence profile designed correctly might reduce gingival margin recession.

PURPOSE

To compare the marginal gingival level and the width/height (W/H) ratio between two profile configurations of single implant-supported restorations at molar sites.

MATERIALS AND METHODS

Twenty-one patients requiring a single mandibular molar tooth replacement with supracrestal mucosal thickness ≥2 mm were recruited and randomly assigned to a prosthesis buccal emergence profile design based on the buccal mucosal W/H ratio (Test Group) or maintained the original emergence profile of the healing abutment (Control Group). Assessments were made before delivery of the definitive restoration (T0), at prosthesis placement (T1), one (T2), and 12 (T3) months after loading. The gingival margin level change (△GM), initial emergence angle, buccal mucosal W/H ratio, marginal bone loss (MBL), implant failure, and complications were assessed.

RESULTS

The gingival recession in the test group (0.13 ± 0.32 mm) was significantly lower than in the control group (0.63 ± 0.38 mm) at T3 (p = 0.006). The initial emergence angle in the test group (31.4 ± 7.22 degrees) was significantly lower than the control group (40.0 ± 7.60 degrees) (p = 0.025). The W/H ratio in the test group at T2 was significantly higher than at T0 but remained stable thereafter. The W/H ratio presented a continued rising trend in the control group.

CONCLUSIONS

When the initial supracrestal soft tissue thickness was ≥2 mm, a restorative emergence profile based on the W/H ratio significantly reduced gingival margin recession. An emergence angle of 32.4 degrees showed better behavior in maintaining the gingival margin than 40 degrees.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR190002210.

Success Factors of Additive Manufactured Root Analogue Implants

Dental implantation is an effective method for the treatment of loose teeth, but the threaded dental implants used in the clinic cannot match with the tooth extraction socket. A root analogue implant (RAI) has the congruence shape, which reduces the damage to bone and soft tissue. Additive manufacturing (AM) technologies have the advantages of high precision, flexibility, and easy operation, becoming the main manufacturing method of RAI in basic research. The purpose of this systematic review is to summarize AM technologies used for RAI manufacturing as well as the factors affecting successful implantation. First, it introduces the AM technologies according to different operating principles and summarizes the advantages and disadvantages of each method. Then the influences of materials, structure design, surface characteristics, implant site, and positioning are discussed, providing reference for designers and dentists. Finally, it addresses the gap between basic research and clinical application for additive manufactured RAIs and discusses the current challenges and future research directions for this field.

Titanium Base Abutments in Implant Prosthodontics: A Literature Review

Implant abutments are essential components in restoring dental implants. Titanium base abutments were introduced to overcome issues related to existing abutments, such as the unesthetic appearance of titanium abutments and the low fracture strength of ceramic abutments. This study aimed to comprehensively review studies addressing the mechanical and clinical behaviors of titanium base abutments. A search was performed on PubMed/MEDLINE, Web of Science, Google Scholar, and Scopus databases to find articles that were published in English until December 2020 and that addressed the review purpose. A total of 33 articles fulfilled the inclusion criteria and were included for data extraction and review. In vitro studies showed that titanium base abutments had high fracture strength, adequate retention values, particularly with resin cement, and good marginal and internal fit. Although the clinical assessment of titanium base abutments was limited, they showed comparable performance with conventional abutments in short-term evaluation, especially in the anterior and premolar areas. Titanium base abutments can be considered a feasible treatment option for restoring dental implants, but long-term clinical studies are required for a better assessment.

Microgap and bacterial microleakage during the osseointegration period: An in vitro assessment of the cover screw and healing abutment in a platform-switched implant system

STATEMENT OF PROBLEM

Microgap and bacterial microleakage at the implant-prosthetic abutment interface are recognized concerns for implant-supported restorations, leading to inflammation of the peri-implant tissues, with deleterious consequences for crestal bone levels. However, little is known regarding the interface established between the implant and the healing abutment or cover screw placed for the osseointegration phase.

PURPOSE

The purpose of this in vitro study was to characterize the implant-cover screw and implant-healing abutment interfaces of a platform-switched implant system to determine the microgap and bacterial microleakage of the system and evaluate the biological response and functionality of an interface sealing agent.

MATERIAL AND METHODS

The interfacial microgaps of the implant-healing abutment and implant-cover screw interfaces were characterized by scanning electron microscopy (n=10), and bacterial microleakage was evaluated after colonization with Enterococcus faecalis in a 30-day follow-up (n=10). The sealing efficacy and irritation potential of a silicone-based sealer were determined by using the hen's egg test on chorioallantoic membrane assay. The 2-sample t test was performed to compare means between groups, and data presented with the Kaplan-Meier method were compared statistically by using the log-rank test (α=.05).

RESULTS

The interfacial microgap was less than 2.5 μm for both systems. Bacterial microleakage was noted in approximately 50% of the specimens, particularly at early time points, at both the healing abutment and cover screw interfaces. The silicone-based sealer prevented bacterial leakage in the experimental setting.

CONCLUSIONS

The implant-healing abutment and implant-cover screw interfaces of the tested system, despite the low microgap, allowed for bacterial microleakage after internal colonization. The use of a nonirritating silicone-based sealing agent effectively sealed the system.

The Microbial Neck: A Biological Review of the Various Implant–Abutment Connections

Aim:

This study reviews the importance of selecting implant systems with connection designs that ensure better long-term prognosis of the prosthesis, thus placed.

Materials and Methods:

An electronic search on the PubMed database was done using MeSH keywords (“dental implant OR abutment OR connection AND microleakage OR bone loss”) to review English language articles published since the year 2011, which compared the crestal bone levels and microleakage around various implant–abutment connection designs (external hex, internal hex, and Morse taper). The search screened for articles on human trials and in vitro studies to be included within the review.

Results:

Based on the inclusion and exclusion criteria applied to the preliminary search, a total of four articles were included in the review for evaluating the influence of connection type on peri-implant bone loss, while nine articles were included to study the influence on bacterial leakage across the implant–abutment interface.

Conclusion:

Based on the studies reviewed, the conical connection design proved to be the most biologically stable junctional geometry because of the better microbial seal and the lesser micromovement observed in these types of implants during functional loading. Moreover, this review even emphasizes the need for more longitudinal clinical trials to assess the microbial seal of these connection designs within the actual oral environment to evaluate long-term changes in the peri-implant tissues, and subsequently even factor the prognosis of the planned prosthetic intervention.

Antimicrobial profile of a dental implant abutment coating to prevent adhesion and migration of bacteria and screw loosening

OBJECTIVE

Failure of dental implants treatment is frequently the result of bacterial colonization of implants followed by diseases like peri-implantitis. Recent studies have been made regarding the surface treatment of implants components, namely abutments that are in the interface of the living tissue with the implant. This work aimed at evaluating the antimicrobial profile of a silane-based coating with TiO₂ adapted to an abutment screw, that was also developed as an anti-loosening agent, to prevent adhesion and migration of Gram + and Gram-bacteria, Staphylococcus aureus, and Escherichia coli, respectively.

METHODS

Direct contact antimicrobial studies were conducted on coated and uncoated samples by resazurin fluorescent assay and cytotoxicity assessment was done via MTT indirect method on days 1 and 4. Sterilizations studies by FTIR analysis were also performed to understand the ideal balance between sterilization efficacy and coating functionality subjecting the samples to ethylene oxide, gamma irradiation, and autoclave sterilization, before antimicrobial testing. The implant system as a whole was also studied for its ability to block bacterial migration and preventing microleakage as well as an assessment of initial bacterial adhesion evaluated by scanning electron microscopy.

RESULTS

Direct contact studies performed on coated samples showed a very high antimicrobial activity, while cytotoxicity assays revealed the coating to be safe and non-leachable. Sterilizations studies showed that the antimicrobial features of the coating were preserved and interchangeable regardless of the sterilization method. The implant system migration studies demonstrated that the implant system works as an efficient barrier for the studied bacteria.

SIGNIFICANCE

The acquired results clearly show that it is possible to obtain a highly functional coating with obvious and marked antimicrobial features that together with an abutment that prevents bacterial migration and versatility in sterilization methodology has a very high potential in the dental implant field.

Microgap and microleakage of a hybrid connection platform-switched implant system in the absence or presence of a silicone-based sealing agent

The present study aims to characterize, for the first time, the microgap and bacterial microleakage of a platform-switched implant system with hybrid connection, screwed at distinct torque values (manufacturer recommended torque-25 N cm-and a reduced torque-5 N cm-mimicking the long-term functional use), in the absence or presence of a silicon-based sealing agent. Microgap was determined through scanning electron microscopy and bacterial microleakage was evaluated in vitro, upon Enterococcus faecalis colonization of the system. The sealing efficacy was evaluated in the absence or presence of a commercially available silicon-based sealer. The cytotoxicity of the sealer was further addressed in vitro, with a fibroblastic cell line, in accordance with reference standards. A low microgap of the implant system was verified, regardless of the applied torque load-maximal values ranged around 0.25 and 1.25 µm, for 25 and 5 N cm torques, respectively. No bacterial microleakage was reported at 25 N cm, while at 5 N cm, leakage was verified on 38% of the samples. The application of a silicon-based sealer-with an adequate cytocompatible profile-was effective on preventing the bacterial microleakage on the assayed experimental setting. The assayed platform-switched implant system with hybrid connection presented a low interfacial misfit and an effective sealing capability at manufacturer recommended torque. Despite the increased microleakage at low torque conditions, the application of a cytocompatible silicon-based sealing agent restored the sealing effectiveness of the system. The use of a silicon-based sealing agent can assist on the maintenance of the sealing effectiveness even at low torque conditions.

Effect of Fabrication Technique on the Microgap of CAD/CAM Cobalt-Chrome and Zirconia Abutments on a Conical Connection Implant: An In Vitro Study

The aim of this in vitro study was to investigate the microgaps at the implant-abutment interface when zirconia (Zr) and CAD/CAM or cast Co-Cr abutments were used.

METHODS

Sixty-four conical connection implants and their abutments were divided into four groups (Co-Cr (milled, laser-sintered and castable) and Zirconia (milled)). After chewing simulation (300,000 cycles, under 200 N loads at 2 Hz at a 30° angle) and thermocycling (10,000 cycles, 5 to 50 °C, dwelling time 55 s), the implant-abutment microgap was measured 14 times at each of the four anatomical aspects on each specimen by using a scanning electron microscope (SEM). Kruskal-Wallis and pair-wise comparison were used to analyze the data (α = 0.05).

RESULTS

The SEM analysis revealed smaller microgaps with Co-Cr milled abutments (0.69-8.39 μm) followed by Zr abutments (0.12-6.57 μm), Co-Cr sintered (7.31-25.7 μm) and cast Co-Cr (1.68-85.97 μm). Statistically significant differences were found between milled and cast Co-Cr, milled and laser-sintered Co-Cr, and between Zr and cast and laser-sintered Co-Cr (p < 0.05).

CONCLUSIONS

The material and the abutment fabrication technique affected the implant-abutment microgap magnitude. The Zr and the milled Co-Cr presented smaller microgaps. Although the CAD/CAM abutments presented the most favorable values, all tested groups had microgaps within a range of 10 to 150 μm.

Marginal bone loss and the risk indicators of fixed screw-retained implant-supported prostheses and fixed telescopic-retained implant-supported prostheses in full arch: A retrospective case-control study

OBJECTIVES

This study compared full-arch screw-retained implant-supported fixed dental prostheses (FSI-FDPs) and full-arch telescopic-retained implant-supported fixed dental prostheses with a professional retrieval system (FTI-FDPs) on marginal bone loss (MBL), the risk indicators and peri-implantitis rate after 7-13 years.

MATERIAL AND METHODS

Sixty five edentulous patients were treated with 86 prostheses and 592 implants. The FSI-FDP group comprised 26 patients (32 prostheses, 202 implants), and the FTI-FDP group comprised 39 patients (54 prostheses, 390 implants). MBL and the risk indicators of MBL ≥1 mm were assessed. Peri-implantitis rates at 13 years were also calculated.

RESULTS

Full-arch screw-retained implant-supported fixed dental prostheses and FTI-FDP implants exhibited comparable mean MBLs of 0.60 ± 0.51 and 0.41 ± 1.03 mm, respectively. MBL ≥1 mm was noted for 25% of FSI-FDP implants and 6.9% of FTI-FDP implants. Superstructure-abutment connection (screw retention:FSI-FDPs >telescopic retention:FTI-FDPs) and implant-abutment connection (External butt joint, Internal butt joint >Morse taper joint) were associated with MBL ≥1 mm. Peri-implantitis rates at the implant level were 3.99% (95%CI = 3.93-20.5) in FSI-FDP group and 3.85% (95%CI = 3.85-34.3) in FTI-FDP group with no significance.

CONCLUSIONS

It was concluded that FSI-FDP and FTI-FDP implants exhibited comparable MBL; however, the risk of MBL ≥1 mm in FTI-FDPs was lower than in FSI-FDPs. Besides, implant-abutment connection was the risk indicator of MBL ≥1 mm. In peri-implantitis rate, FSI-FDPs and FTI-FDPs behave similarly.

Evaluation of changes in mechanical properties of O-ring in one-piece and two-piece ball retained implant-supported overdentures: A three-year retrospective study

The o-rings in ball retained overdentures deteriorate with time and need replacement to restore the retentive quality. We evaluated retrospectively the mechanical properties of o-rings after 3 years in function in one and two-piece implant-supported overdentures. The o-rings were retrieved from one-piece (Myriad snap, Equinox-Straumann, 3.3 x 13mm) and two-piece (Neo Biotech, 3.3 x 13mm) implant-supported overdenture patients. A total of 16 pairs of matrices were tested for wear, type of damage and elasticity using Pin on Disc method, USB Digital Camera in 30x zoom and Universal Tensile Machine respectively. The statistical analysis for independent groups were done with the Mann-Whitney U test. Assessment of used O-rings showed 84% more wear in the two-piece system with an abrasive type of damage while 46% wear in the one-piece system with a compressive type of damage. The o-rings in one-piece system showed increase in elongation and maximum displacement to 2% and 7% respectively, while two-piece system showed decrease in elongation and maximum displacement by 13% and 6% respectively. In one-piece system, the loss of retention was more with slow wear rate and in two-piece system, the wear resistance of O-rings decreased due to increased stiffness. Further studies to evaluate the changes in O-ring with increased sample size and at interval 1 year will pave way for insight into the progressive changes in the mechanical properties of an O-ring.

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.