Constant Strain Rate and Peri‐Implant Bone Modeling: An In Vivo Longitudinal Micro‐CT Analysis

Background: Strain, frequency, loading time, and strain rate, among others, determine mechanical parameters in osteogenic loading. We showed a significant osteogenic effect on bone mass (BM) by daily peri‐implant loading at 1.600 µε.s^?1 after 4 weeks. Purpose: To study the peri‐implant osteogenic effect of frequency and strain in the guinea pig tibia by in vivo longitudinal micro‐computed tomography (CT) analysis. Material and Methods: One week after implant installation in both hind limb tibiae, one implant was loaded daily for 10′ during 4 weeks, while the other served as control. Frequencies (3, 10, and 30 Hz) and strains varied alike in the three series to keep the strain rate constant at 1.600 µε.s^?1. In vivo micro‐CT scans were taken of both tibiae: 1 week after implantation but before loading (v1) and after 2 (v2) and 4 weeks (v3) of loading as well as postmortem (pm). BM (BM (%) bone‐occupied area fraction) was calculated as well as the difference between test and control sides (delta BM) Results: All implants (n = 78) were clinically stable at 4 weeks. Significant increase in BM was measured between v1 and v2 (p < .0001) and between v1 and v3 (p < .0001). A significant positive effect of loading on delta BM was observed in the distal peri‐implant marrow 500 Region of Interest already 2 weeks after loading (p = .01) and was significantly larger (11%) in series 1 compared with series 2 (p = .006) and 3 (p = .016). Conclusions: Within the constraints of constant loading time and strain rate, the effect of early implant loading on the peri‐implant bone is strongly dependent on strain and frequency. This cortical bone model has shown to be most sensitive for high force loading at low frequency.     

The Peri‐Implant Sulcus Compared with Internal Implant and Suprastructure Components: A Microbiological Analysis

Purpose: A recent in vivo study has shown considerable contamination of internal implant and suprastructure components with great biodiversity, indicating bacterial leakage along the implant‐abutment interface, abutment‐prosthesis interface, and restorative margins. The goal of the present study was to compare microbiologically the peri‐implant sulcus to these internal components on implants with no clinical signs of peri‐implantitis and in function for many years. Checkerboard DNA‐DNA hybridization was used to identify and quantify 40 species. Material and Methods: Fifty‐eight turned titanium Brånemark implants in eight systemically healthy patients (seven women, one man) under regular supportive care were examined. All implants had been placed in the maxilla and loaded with a screw‐retained full‐arch bridge for an average of 9.6 years. Gingival fluid samples were collected from the deepest sulcus per implant for microbiological analysis. As all fixed restorations were removed, the cotton pellet enclosed in the intra‐coronal compartment and the abutment screw were retrieved and microbiologically evaluated. Results: The pellet enclosed in the suprastructure was very similar to the peri‐implant sulcus in terms of bacterial detection frequencies and levels for practically all the species included in the panel. Yet, there was virtually no microbial link between these compartments. When comparing the abutment screw to the peri‐implant sulcus, the majority of the species were less frequently found, and in lower numbers at the former. However, a relevant link in counts for a lot of bacteria was described between these compartments. Even though all implants in the present study showed no clinical signs of peri‐implantitis, the high prevalence of numerous species associated with pathology was striking. Conclusions: Intra‐coronal compartments of screw‐retained fixed restorations were heavily contaminated. The restorative margin may have been the principal pathway for bacterial leakage. Contamination of abutment screws most likely occurred from the peri‐implant sulcus via the implant‐abutment interface and abutment‐prosthesis interface.     

Reimplantation of Dental Implants following Ligature‐Induced Peri‐Implantitis: A Pilot Study in Dogs

Objectives: This preliminary investigation aimed to evaluate the potential of contaminated implants to reosseointegrate into pristine sites and, in addition, to assess the potential of osseointegration of new implants in peri‐implantitis sockets in a canine model. Methods: All mandibular premolars were bilaterally extracted from two mongrel dogs. Following 12 weeks of healing, two dental implants were inserted on each hemiarch. Forty‐five days following implant placement, a silk ligature secured with cyanoacrylate was placed around the implants' cervical region in order to induce peri‐implantitis. After another 45 days from ligature placement, the implants were mechanically removed using counter rotation with a ratchet and were reimplanted without any decontamination (neither rinsing nor chemical or mechanical cleaning) in adjacent pristine zones. In sites where implants were removed, new, wider‐diameter implants were placed in the infected sockets. Forty‐five days following reimplantation surgery, the dogs were sacrificed; nondecalcified specimens were processed and toluidine blue stained for morphologic and morphometric (bone‐to‐implant contact [BIC]) assessment under an optical microscope. In dog 1 all the implants (both in the pristine and in the infected sites) survived and osseointegrated while in dog 2, six out of eight implants failed to osseointegrate and exfoliated. Overall, the mean BIC of all implants was 51.08% (SD 20.54). The mean BIC for the infected implants placed into pristine sites was 51.48% ± 26.29% (SD) and the mean BIC for the new implants in peri‐implantitis socket was 50.58% ± 14.27% (SD). Conclusions: Within the limitations of this preliminary investigation, especially the small number of animals, osseointegration seems to be achievable both in infected sites and around contaminated implant surfaces.     

Microbial Colonization of the Peri‐Implant Sulcus and Implant Connection of Implants Restored With Cemented Versus Screw‐Retained Superstructures: A Cross‐Sectional Study

Background: The aim of this study is to investigate peri‐implant and intraconnection microflora of healthy implants restored with cemented and screwed superstructures. Methods: Patients with two to three implants restored with cemented or screwed restorations and 5 years of follow‐up were recruited. Samples were taken from peri‐implant sulci, adjacent teeth, and the inner portion of connections. Prevalence of positive sites and bacterial loads for 10 microorganisms were obtained with quantitative real‐time polymerase chain reaction. Implant connection permeability to the studied microorganisms was estimated using a standardized bacterial contamination index. Statistical analysis was performed using a generalized estimating equations model, Wald χ² test, and the least significant difference test. Results: The final sample consisted of 18 patients (55 implants) in the cemented group and 22 patients (46 implants) in the screw‐retained group. Regarding prevalence of positive sites, significant differences between groups were only found for Tannerella forsythia, which was 8.7 times more frequent at peri‐implant sulci of cemented than screw‐retained prostheses. Bacterial loads of Porphyromonas gingivalis, T. forsythia, Parvimonas micra, and total bacterial load were significantly higher at peri‐implant sulci for the cemented group; at the inner portion of connections, values were significantly higher for P. micra and Fusobacterium nucleatum for the screw‐retained group. Contamination index values demonstrated higher permeability to most microbes in the cemented group. Conclusions: Internal implant surfaces were microbiologically contaminated for both cemented and screw‐retained superstructures. Differences were found between the two methods of prosthetic retention: the cemented group presented significantly higher bacterial loads in the peri‐implant sulcus but significantly lower bacterial loads at the inner portion of the implant connection.     

Influence of Soft Tissue Thickness on Peri‐Implant Marginal Bone Loss: A Systematic Review and Meta‐Analysis

Background: Multiple variables have been shown to affect early marginal bone loss (MBL). Among them, the location of the microgap with respect to the alveolar bone crest, occlusion, and use of a polished collar have traditionally been investigated as major contributory factors for this early remodeling. Recently, soft tissue thickness has also been investigated as a possible factor influencing this phenomenon. Hence, this study aims to further evaluate the influence of soft tissue thickness on early MBL around dental implants. Methods: Electronic and manual literature searches were performed by two independent reviewers in several databases, including Medline, EMBASE, and Cochrane Oral Health Group Trials Register, for articles up to May 2015 reporting soft tissue thickness at time of implant placement and MBL with ≥12‐month follow‐up. In addition, random effects meta‐analyses of selected studies were applied to analyze the weighted mean difference (WMD) of MBL between groups of thick and thin peri‐implant soft tissue. Metaregression was conducted to investigate any potential influences of confounding factors, i.e., platform switching design, cement‐/screw‐retained restoration, and flapped/flapless surgical techniques. Results: Eight articles were included in the systematic review, and five were included in the quantitative synthesis and meta‐analyzed to examine the influence of tissue thickness on early MBL. Meta‐analysis for the comparison of MBL among selected studies showed a WMD of ?0.80 mm (95% confidence interval ?1.18 to ?0.42 mm) (P <0.0001), favoring the thick tissue group. Metaregression of the selected studies failed to demonstrate an association among MBL and confounding factors. Conclusion: The current study demonstrates that implants placed with an initially thicker peri‐implant soft tissue have less radiographic MBL in the short term.     

The Frequency of Peri‐Implant Diseases: A Systematic Review and Meta‐Analysis

Background: The peri‐implant diseases, namely peri‐implant mucositis and peri‐implantitis, have been extensively studied. However, little is known about the true magnitude of the problem, owing mainly to the lack of consistent and definite diagnostic criteria used to describe the condition. The objective of the present review is to systematically estimate the overall frequency of peri‐implant diseases in general and high‐risk patients. Methods: The systematic review is prepared according to the Meta‐analysis of Observational Studies in Epidemiology statement. Studies were searched in four electronic databases, complemented by manual searching. The quality of the studies was assessed according to Strengthening the Reporting of Observational Studies in Epidemiology, and the data were analyzed using statistical software. Results: Of 504 studies identified, nine studies with 1,497 participants and 6,283 implants were included. The summary estimates for the frequency of peri‐implant mucositis were 63.4% of participants and 30.7% of implants, and those of peri‐implantitis were 18.8% of participants and 9.6% of implants. A higher frequency of occurrence of peri‐implant diseases was recorded for smokers, with a summary estimate of 36.3%. Supportive periodontal therapy seemed to reduce the rate of occurrence of peri‐implant diseases. Conclusions: Peri‐implant diseases are not uncommon following implant therapy. Long‐term maintenance care for high‐risk groups is essential to reduce the risk of peri‐implantitis. Informed consent for patients receiving implant treatment must include the need for such maintenance therapy.     

Investigation of the Association Between Cement Retention and Prevalent Peri‐Implant Diseases: A Cross‐Sectional Study

Background: The aim of this study is to examine the association between retention type (cement‐retained versus screw‐retained restorations) and prevalence of peri‐implant diseases in a German university‐treated population. Methods: Data were analyzed from individuals that underwent clinical and radiographic peri‐implant examinations as part of a university‐based cross‐sectional study from September 2011 to October 2012. Results: Data from 139 individuals (mean age: 57.59 years) having 394 implants were analyzed: 192 implants supporting single crowns and 202 fixed partial dentures. Overall, 11.9% of the participants had peri‐implantitis, whereas 68.9% had peri‐implant mucositis. Crude odds ratios (95% confidence intervals) for peri‐implantitis and peri‐implant mucositis for cement‐ versus screw‐retained restorations were 1.43 (0.45, 4.60) and 0.89 (0.53, 1.48), respectively. Results remained non‐significant in multivariable models adjusting for type of restoration and smoking (all P values >0.50). There was also no effect of splinting restorations on disease prevalence in adjusted analyses (P values >0.32). Conclusions: In this university‐treated sample, there is no association between the type of prosthesis retention and peri‐implant diseases. Current findings show that, when appropriate selection and removal of cement is performed, cement retention is not a risk indicator for peri‐implant diseases.     

Comparison of Push‐In versus Pull‐Out Tests on Bone‐Implant Interfaces of Rabbit Tibia Dental Implant Healing Model

Purpose: This study aimed to investigate whether push‐in and pull‐out tests measure mechanical properties of the bone–implant interface differently, and which test is more sensitive to changes over the healing period. Materials and Methods: Two identical self‐threading dental implants (3.3 × 8.5 mm) were placed in medial surface of the proximal condyles of left and right tibias of 20 rabbits (40 implants total). Five rabbits each were sacrificed after 1, 4, 8, and 12 weeks of healing. Push‐in test was performed on one side's tibia implant and pull‐out on the other side's implant, at a rate of 6 mm/min. Primary and secondary implant stabilities and tibia weight were measured on all implants. Results: The push‐in test generated significantly higher failure load (p = .0001; 530 N vs 279 N), lower displacement at failure (p = .0003; 0.436 mm vs 0.680 mm), and higher interface stiffness (p < .0001; 1,641 N/mm vs 619 N/mm) than pull‐out test. Failure load, stiffness, and secondary implant stability were significantly higher for longer compared with shorter healing periods, while displacement, tibia weight, and primary stability were not. Failure load and stiffness differed significantly for four healing times for the push‐in but not for the pull‐out test. Failure load was significantly correlated with secondary implant stability for both push‐in (r = 0.66) and pull‐out (r = 0.48) tests, but stiffness was significantly correlated with secondary stability only for the push‐in test (r = 0.72; pull‐out test r = 0.40). Conclusion: The push‐in test appeared more sensitive than pull‐out to changes in mechanical properties at bone–implant interfaces during healing in rabbit tibia model.     

A Novel Approach for Enhanced Nanoparticle‐Sized Bone Substitute Adhesion to Chemically Treated Peri‐Implantitis–Affected Implant Surfaces: An In Vitro Proof‐of‐Principle Study

Background: The objective of this study is to evaluate micro and nano‐hydroxyapatite (NHA) blended clot adhesion to citric acid–conditioned peri‐implantitis–affected surfaces. Methods: Forty hopeless implants with peri‐implantitis designated for removal were included in this study. Implants were divided into eight groups of five each: group 1 (G1) test areas were coated with hydroxyapatite of a microparticle size (MHA); group 2 (G2) test areas were coated with NHA; group 3 (G3) implants were coated with MHA after surface conditioning using citric acid; group 4 (G4) samples were treated in the same manner as in G3 except for the use of NHA; group 5 (G5) samples were coated without surface treatment with MHA mixed with whole human blood; group 6 (G6) implant samples were treated in the same manner as in G5 except for the use of NHA; group 7 (G7) implant samples were treated in the same way as in G5 plus surface conditioning using citric acid; and group 8 (G8) samples were treated in the same manner as in G7 except for the use of NHA. All implants in all groups were agitated for 3 minutes in phosphate‐buffered saline. All samples were prepared for scanning electron microscopy evaluation. Results: G1 and G2 non‐etched implants coated with MHA or NHA sizes were devoid of any bone particle adhesion to the peri‐implantitis–affected surfaces. Contrary to the lack of microparticle adhesion to the root surface that was seen in G3, G4 acid‐treated and NHA‐coated samples revealed nearly complete coverage of the peri‐implantitis–affected parts by the graft material. G5 non‐etched, clot‐blended MHA showed some areas of clot‐blended graft adhesion covering 6.7% of the examined surfaces. G6 non‐etched, clot‐blended NHA showed NHA retention within the fibrin strands in areas where the implant surface pores were exposed (24.3%). G7 acid‐treated and clot‐blended MHA‐treated implant surfaces showed partial coverage of the implant surface with detached fibrin clot–blended graft material (31.4%). G8 acid‐treated and NHA clot‐blended graft‐coated implants showed complete coverage of the implant surface by the clot‐blended graft material (93.4%). Conclusion: Peri‐implantitis–affected surface conditioning with citric acid improves NHA‐blended clot adhesion to titanium implant surfaces.     

Peri‐Implant Endosseous Healing Properties of Dual Acid‐Etched Mini‐Implants with a Nanometer‐Sized Deposition of CaP: A Histological and Histomorphometric Human Study

Purpose: The aim of this histological and histomorphometric study was to compare the early peri‐implant endosseous healing properties of a dual acid‐etched (DAE) surface (Osseotite®, Implant Innovations Inc., Palm Beach Gardens, FL, USA) with a DAE surface modified with nanometer‐sized calcium phosphate (CaP) particles (NanoTite?, Implant Innovations Inc.) in grafted and mature maxillary bone. Materials and Methods: Fifteen patients received two mini‐implants, 1 with DAE surface (control) and 1 with a DAE + CaP surface (test), to fixate an iliac crest bone graft to the maxilla. A part of each mini‐implant was in contact with the grafted bone and a part extended into the native maxillary bone. After a healing period of 3 months, the specimens were harvested and analyzed. Results: Overall, a trend was seen for stronger bone response around the test mini‐implants in the native bone of the maxilla. However, only the old bone particles measured by percentages of bone‐to‐implant contact and bone area were statistically significant (p = .025 and p = .042, respectively). Conclusions: The NanoTite surface increases the peri‐implant endosseous healing properties in the native bone of the maxilla compared with the Osseotite surface, while this difference was not visible in the bone graft area. This might be a result of the lower remodeling process of the graft.     

The Peri‐Implantitis: Implant Surfaces,Microstructure, and Physicochemical Aspects

There are two ways of looking at secondary failures of osseointegration; one is to reflect on possible causes for the failure, the other focuses on the pathology per se. In the first case, background factors such as mechanical trauma (adverse loading) or inflammations/infections are being discussed as the cause of failure. Then peri‐implantitis is a term reserved for implant disturbance due to inflammation/infections only. However, irrespective of the original reason for the failure being adverse loading or inflammation/infection, the end result with bone resorption and inflammation may be very similar. Hence, in the present article, an alternative outlook has been chosen. Trigerring factors for peri‐implantitis are generally gathered under four categories: lesions of peri‐implant attachment, presence of aggressive bacteria, excessive mechanical stress, and corrosion. If only one of these factors would start a chain reaction leading to lesions, then the other factors may combine to worsen the condition. With other words, peri‐implantitis is a general term dependent on a synergy of several factors, irrespective of the precise reason for first triggering off symptoms.