Correction to: The effect of magnesium on early osseointegration in osteoporotic bone: a histological and gene expression investigation.

This article was originally published under a CC BY-NC-ND 4.0 license, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the paper have been modified accordingly.

The effect of magnesium on early osseointegration in osteoporotic bone: a histological and gene expression investigation.

Magnesium has a key role in osteoporosis and could enhance implant osseointegration in osteoporotic patients. Titanium implants impregnated with Mg ions were installed in the tibia of ovariectomized rats. The release of Mg induced a significant increase of bone formation and the expression of anabolic markers in the peri-implant bone. INTRODUCTION: The success of endosseous implants is highly predictable in patients possessing normal bone status, but it may be impaired in patients with osteoporosis. Thus, the application of strategies that adjuvate implant healing in compromized sites is of great interest. Magnesium has a key role in osteoporosis prevention and it is an interesting candidate for this purpose. In this study, the cellular and molecular effects of magnesium release from implants were investigated at the early healing stages of implant integration. METHODS: Osteoporosis was induced in 24 female rats by means of ovariectomy and low-calcium diet. Titanium mini-screws were coated with mesoporous titania films and were loaded with magnesium (test group) or left as native (control group). The implants were inserted in the tibia and femur of the rats. One, 2 and 7 days after implantation, the implants were retrieved and histologically examined. In addition, expression of genes was evaluated in the peri-implant bone tissue at day 7 by means of quantitative polymerase chain reactions with pathway-oriented arrays. RESULTS: The histological evaluation revealed that new bone formation started already during the first week of healing for both groups. However, around the test implants, new bone was significantly more abundant and spread along a larger surface of the implants. In addition, the release of magnesium induced a significantly higher expression of BMP6. CONCLUSIONS: These results provide evidence that the release of magnesium promoted rapid bone formation and the activation of osteogenic signals in the vicinity of implants placed in osteoporotic bone.

Dental implant loss in older versus younger patients: a systematic review and meta-analysis of prospective studies.

The aim of this systematic review was to evaluate implant loss in younger and older patients. An electronic search of four databases (MEDLINE, EMBASE, SCOPUS and the Cochrane Library) was undertaken until May 2016 without time restriction and was supplemented by manual searching. Prospective cohorts were included if they met the following criteria: (i) presence of an exposed group (older subjects) with a minimum age of 60 years; (ii) presence of a control group (younger subjects) with a maximum age of 59 years; and (iii) outcome data considering implant survival or loss. Meta-analyses were performed to evaluate the impact of ageing on implant failure. Of 4152 potentially eligible articles, four were included in the qualitative analysis and quantitative synthesis. The pooled estimates suggest that the risk of implant loss in older patients is not significantly higher (RR = 0·92; 95% CI 0·43-1·96, P = 0·83) when compared to younger subjects. This systematic review suggests that age is not a limiting factor for dental implant therapy.

Turned versus anodised dental implants: a meta-analysis.

The aim of this meta-analysis was to test the null hypothesis of no difference in the implant failure rates, marginal bone loss (MBL)and post-operative infection for patients being rehabilitated by turned versus anodised-surface implants, against the alternative hypothesis of a difference. An electronic search without time or language restrictions was undertaken in November 2015. Eligibility criteria included clinical human studies, either randomised or not. Thirty-eight publications were included. The results suggest a risk ratio of 2·82 (95% CI 1·95-4·06, P < 0·00001) for failure of turned implants, when compared to anodised-surface implants. Sensitivity analyses showed similar results when only the studies inserting implants in maxillae or mandibles were pooled. There were no statistically significant effects of turned implants on the MBL (mean difference-MD 0·02, 95%CI -0·16-0·20; P = 0·82) in comparison to anodised implants. The results of a meta-regression considering the follow-up period as a covariate suggested an increase of the MD with the increase in the follow-up time (MD increase 0·012 mm year(-1) ), however, without a statistical significance (P = 0·813). Due to lack of satisfactory information, meta-analysis for the outcome 'post-operative infection' was not performed. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies.

Bruxism and dental implant failures: a multilevel mixed effects parametric survival analysis approach.

Recent studies have suggested that the insertion of dental implants in patients being diagnosed with bruxism negatively affected the implant failure rates. The aim of the present study was to investigate the association between the bruxism and the risk of dental implant failure. This retrospective study is based on 2670 patients who received 10 096 implants at one specialist clinic. Implant- and patient-related data were collected. Descriptive statistics were used to describe the patients and implants. Multilevel mixed effects parametric survival analysis was used to test the association between bruxism and risk of implant failure adjusting for several potential confounders. Criteria from a recent international consensus (Lobbezoo et al., J Oral Rehabil, 40, 2013, 2) and from the International Classification of Sleep Disorders (International classification of sleep disorders, revised: diagnostic and coding manual, American Academy of Sleep Medicine, Chicago, 2014) were used to define and diagnose the condition. The number of implants with information available for all variables totalled 3549, placed in 994 patients, with 179 implants reported as failures. The implant failure rates were 13·0% (24/185) for bruxers and 4·6% (155/3364) for non-bruxers (P < 0·001). The statistical model showed that bruxism was a statistically significantly risk factor to implant failure (HR 3·396; 95% CI 1·314, 8·777; P = 0·012), as well as implant length, implant diameter, implant surface, bone quantity D in relation to quantity A, bone quality 4 in relation to quality 1 (Lekholm and Zarb classification), smoking and the intake of proton pump inhibitors. It is suggested that the bruxism may be associated with an increased risk of dental implant failure.

The influence of statins on osseointegration: a systematic review of animal model studies.

Recent research data have suggested that the beneficial action of statins in bone tissue could improve osseointegration around titanium implants by increasing the bone implant contact (BIC), the expression of bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF). The aim of this systematic review was to evaluate the influence of statins on osseointegration of titanium implants in animal studies. Two reviewers searched independently four databases (MEDLINE, SCOPUS, WEB OF SCIENCE and the Cochrane Library), until March 15, 2016. The Cochrane Collaboration's Tool for Assessing Risk of Bias was used to assess the quality of the included studies. Papers that reported outcome data considering bone implant contact (BIC), mechanical tests or other histological evaluation were eligible for inclusion. 312 references were eletronically retrieved, 21 full-text papers were screened and 17 studies were included. Thirteen trials presented histomorphometry data on bone implant contact measures. All of them showed a significant improved BIC when using statins. Despite data from included studies point to beneficial effects, standardized studies and with less risk of bias, are needed to clarify the role of statins on osseointegration.

Dental implants inserted in male versus female patients: a systematic review and meta-analysis.

The aim of this meta-analysis was to test the null hypothesis of no difference in the failure rates, marginal bone loss (MBL) and post-operative infection for implants inserted in male or female patients, against the alternative hypothesis of a difference. An electronic search without time or language restrictions was undertaken in December 2014. Eligibility criteria included clinical human studies, either randomized or not. Ninety-one publications were included, with a total of 27,203 implants inserted in men (1185 failures), and 25,154 implants inserted in women (1039 failures). The results suggest that the insertion of dental implants in male patients statistically affected the implant failure rates (RR 1.21, 95% CI 1.07-1.37, P = 0.002). Due to the limited number of studies reporting results on MBL, it is difficult to estimate the real effect of the insertion of implants in different sexes on the marginal bone level. Due to lack of satisfactory information, meta-analysis for the outcome 'post-operative infection' was not performed. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies.

Photocatalytically induced hydrophilicity influences bone remodelling at longer healing periods: a rabbit study.

OBJECTIVES: Previously, we have reported that photocatalytically active hydrophilicity of the anatase titanium dioxide (TiO2) nanoparticles coated onto commercially pure titanium discs presented significantly improved hydrophilicity after ultraviolet irradiation. As hydrophilicity has shown enhancement of osseointegration, the in vivo responses were of great interest. The aim of this study was to evaluate whether or not the photo-activated hydrophilicity generated at the time of implant placement has an effect on the longer healing periods for osseointegration. MATERIALS AND METHODS: Photocatatytically active nanostructured TiO2 powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs and was heat-treated thereafter. These P25-coated discs were irradiated with ultraviolet (UV) light for the test (+UV) group, and non-irradiated discs were prepared for the control (-UV) group. Both groups of discs were placed in the rabbits' tibiae. After 12 weeks of healing period, histological analysis and gene expression analysis using real-time RT-PCR were performed. RESULTS: From the histological analyses, there were no specific differences between -UV and +UV groups. However, from the gene expression analysis, ALP, RUNX-2 and IL-10 were significantly upregulated for the +UV group compared with the -UV group. CONCLUSIONS: The biologically enhancing effect to photocatalytically activated surfaces remained even after 12 weeks of healing time in terms of genetic responses.

The osseointegration stimulatory effect of macrogeometry-modified implants: a study in the rabbit.

OBJECTIVE: To investigate the bone stimulatory effect of compression forces through histomorphometric analyses of macrothreaded implants with microthreads in between. MATERIAL AND METHODS: Two sets of turned implants with different macrogeometries were prepared. The test group possessed microthreads in between macrothreads, and the control group had macrothreads only. The two-implant groups were placed in both the femur and the tibiae of 10 rabbits. After 4 weeks, the animals were sacrificed and were subjected to histologic processing and histomorphometry. On the prepared stained sections, the total bone area (BA), new BA and bone-to-implant (BIC) were calculated. RESULTS: The mean new BA% (SD) for the test group in the femur presented significantly higher values compared with the control group, being 32.84 (32.5) ± 6.04 and 27.31 (28.19) ± 5.66, respectively (P = 0.04). There were no differences for the new BA in the tibia or the total BA% for both bone types (P = 0.86, P = 0.131, and P = 0.131, respectively). The mean BIC% (SD) in the femur was 13.66 (11.49) ± 6.86 for the test group and 8.48 (7.92) ± 3.31 for the control group and in the tibia, 11.4 (11.88) ± 4.21 for the test group and 13.91 (12.06) ± 6.07 for the control group, respectively. There was no statistical significance among the groups tested. CONCLUSION: The modified implant macrogeometry with microthreads in between promoted effect in the femur. However, no statistical differences could be seen in the tibia, suggesting that the modification may be more effective in bone with poor bone quality, such as in the maxillary bone.

Prophylactic antibiotic regimen and dental implant failure: a meta-analysis.

The aim of this meta-analysis was to investigate whether there are any positive effects of prophylactic antibiotic regimen on implant failure rates and post-operative infection when performing dental implant treatment in healthy individuals. An electronic search without time or language restrictions was undertaken in March 2014. Eligibility criteria included clinical human studies, either randomised or not. The search strategy resulted in 14 publications. The I(2) statistic was used to express the percentage of the total variation across studies due to heterogeneity. The inverse variance method was used with a fixed- or random-effects model, depending on the heterogeneity. The estimates of relative effect were expressed in risk ratio (RR) with 95% confidence interval. Six studies were judged to be at high risk of bias, whereas one study was considered at moderate risk, and six studies were considered at low risk of bias. The test for overall effect showed that the difference between the procedures (use versus non-use of antibiotics) significantly affected the implant failure rates (P = 0.0002), with a RR of 0.55 (95% CI 0.41-0.75). The number needed to treat (NNT) to prevent one patient having an implant failure was 50 (95% CI 33-100). There were no apparent significant effects of prophylactic antibiotics on the occurrence of post-operative infections in healthy patients receiving implants (P = 0.520). A sensitivity analysis did not reveal difference when studies judged as having high risk of bias were not considered. The results have to be interpreted with caution due to the presence of several confounding factors in the included studies.

Reasons for failures of oral implants.

This study reviews the literature regarding the factors contributing to failures of dental implants. An electronic search was undertaken including papers from 2004 onwards. The titles and abstracts from these results were read to identify studies within the selection criteria. All reference lists of the selected studies were then hand-searched, this time without time restrictions. A narrative review discussed some findings from the first two parts where separate data from non-comparative studies may have indicated conclusions different from those possible to draw in the systematic analysis. It may be suggested that the following situations are correlated to increase the implant failure rate: a low insertion torque of implants that are planned to be immediately or early loaded, inexperienced surgeons inserting the implants, implant insertion in the maxilla, implant insertion in the posterior region of the jaws, implants in heavy smokers, implant insertion in bone qualities type III and IV, implant insertion in places with small bone volumes, use of shorter length implants, greater number of implants placed per patient, lack of initial implant stability, use of cylindrical (non-threaded) implants and prosthetic rehabilitation with implant-supported overdentures. Moreover, it may be suggested that the following situations may be correlated with an increase in the implant failure rate: use of the non-submerged technique, immediate loading, implant insertion in fresh extraction sockets, smaller diameter implants. Some recently published studies suggest that modern, moderately rough implants may present with similar results irrespective if placed in maxillas, in smoking patients or using only short implants.

Characteristics of implant-CAD/CAM abutment connections of two different internal connection systems.

Titanium or zirconium computer-aided design/computer-aided manufacturing abutments are now widely used for aesthetic implant treatments; however, information regarding microscopic structural differences that may influence the biological and mechanical outcomes of different implant systems is limited. Therefore, the characteristics of different connection systems were investigated. Optical microscopic observation and scanning electron microscopy showed different characteristics of two internal systems, namely the Astra Tech and the Replace Select system, and for different materials. The scanning electron microscopic observation showed for the Astra Tech that the implant-abutment interface seemed to be completely sealed for both titanium and zirconium abutments, both horizontally and sagittally; however, the first implant-abutment contact was below the fixture top, creating a microgap, and fixtures connected with titanium abutments showed significantly larger values (23·56µm±5·44 in width, and 168·78µm±30·39 in depth, P<0·001). For Replace Select, scanning electron microscopy in the sagittal direction showed that the sealing of titanium and zirconium abutments differed. The seal between the implant-titanium and implant-zirconium abutments seemed to be complete at the butt-joint interface; however, the displacement of the abutment in relation to the fixture in the lateral direction was evident for both abutments with no statistical differences (P>0·70), creating an inverted microgap. Thus, microscopy evaluation of two commonly used internal systems connected to titanium or zirconium abutments showed that the implant-abutment interface was perfectly sealed under no-loading conditions. However, an inverted microgap was seen in both systems, which may result in bacterial accumulation as well as alteration of stress distribution at the implant-abutment interface.

Current challenges in successful rehabilitation with oral implants.

Very high survival/success rates have been reported for implant treatment, irrespective of the prosthetic type of reconstruction, be those full arcs, partial dentures, combined tooth implants or single crowns. However, survival/success is commonly reported in simple Cumulative Survival/Success Rate (CSR) tables only that may overestimate the true clinical outcome; furthermore, future challenges to clinical success may originate from too rapid launching of untested novelties or recommendations to apply too bold clinical procedures, potential problems that are summarised in the present paper.

Material degradation in implant-retained cobalt-chrome and titanium frameworks.

The purpose of the study was to estimate in vitro material degradation in implants and cobalt-chrome or titanium frameworks, before and after exposure to artificial saliva. Four full-arch implant frameworks were fabricated according to the Cresco™ method (Astra Tech AB, Mölndal, Sweden), two in a cobalt-chrome alloy and two in commercially pure (CP) titanium. They were cut vertically, and the three central sections of each framework were used. Element leakage into an artificial saliva solution was observed with mass spectrometry. Before artificial saliva exposure, three Brånemark System(®) implants (Nobel Biocare AB, Gothenburg, Sweden) were screw-retained to cobalt-chrome sections, and three to titanium sections. The contact surfaces with the implants of the framework sections and the corresponding surfaces of six implants were examined with optical interferometry before and after exposure to artificial saliva to evaluate material degradation. Conventional descriptive statistics were used to present the mass spectrometry and interferometry data. One-way anova and Dunnett's T3 post hoc test were used to identify and study differences between the groups. To highlight changes within the groups, the Student's t-test was used. The significance level was set at 5%. There was significantly more leakage of cobalt elements than of titanium and chrome (P < 0·05). After saliva exposure and framework connection, the implants roughened (P < 0·05). The titanium frameworks were generally rougher than the cobalt-chrome frameworks, both before and after saliva exposure (P < 0·05). The findings in this study suggest active material degradation processes for both implants and framework materials.

Dental implants in patients with Sjögren's syndrome: a case series and a systematic review.

The purpose of this study was to assess the clinical outcomes of dental implants in patients with Sjögren's syndrome (SS). The study consisted of two parts: report of a case series and a systematic review of the literature. The results of the clinical series revealed that 19 patients received 107 implants and were followed for a mean of 125months. Two patients lost three implants (failure rate 2.8%, 3/107). At the last follow-up, there was a mean marginal bone loss (MBL) of -2.190±1.384 mm; estimated MBL after 30 years was 4.39mm. The review identified 18 studies, resulting in 19 studies for analysis including the present clinical series. A total of 712 implants were placed in 186 patients; 705 implants were followed up for a mean of 72.5 months (failure rate 4.1%, 29/705; failed at a mean time of 12.9±31.7months). The probability of failure was 2.8% (95% confidence interval 1.6-4.1%). Primary SS patients had a lower implant failure rate (2.5%, 3/118) than secondary SS patients (6.5%, 12/184). In conclusion, dental implants should be considered by dentists as a viable treatment option for patients with SS, as the failure rate is fairly low. SS patients may, however, present a higher MBL around implants than patients from the general population.

Increased bone contact to a calcium-incorporated oxidized commercially pure titanium implant: an in-vivo study in rabbits.

The aim of this study was to evaluate the bone response to an oxidized titanium implant (Ox) and a calcium-incorporated oxidized titanium implant (Ca). A blasted titanium implant (Bl) was used as control. The implants were topographically characterized using an optical interferometer and placed: one in each distal femoral metaphysis and two in each proximal tibial metaphysis in rabbits. The rabbits were killed 12 weeks after implant insertion, and the implants and their surrounding tissues were removed en bloc for histomorphometrical evaluations. Topographical evaluation revealed three different surfaces: average height deviation (S(a), microm) values for Ca:Ox:Bl implants were 0.3:0.6:0.9, developed surface area ratios (%) 17:44:31, number of summits per microm(2) 208:136:118, and core fluid retention index values 1.33:1.33:1.38. The mean percentages of bone contact to the implants placed in the tibia (Ca:Ox:Bl) were 47:30:34 and to the implants placed in the femur (Ca:Ox) 32:20. The mean percentages of surrounding bone area for the implants placed in the tibia were 40:47:37 and for the implants placed in the femur 43:46. A significant increase in bone contact was found for smooth (S(a) <0.5 microm) but more densely peaked calcium-incorporated oxidized implants when compared to slightly rougher (S(a)=0.5-1.0 microm) oxidized or blasted implants.

Implants and/or teeth: consensus statements and recommendations.

In August 23-25, 2007, the Scandinavian Society for Prosthetic Dentistry in collaboration with the Danish Society of Oral Implantology arranged a consensus conference on the topic 'Implants and/or teeth'. It was preceded by a workshop in which eight focused questions were raised and answered in eight review articles using a systematic approach. Twenty-eight academicians and clinicians discussed the eight review papers with the purpose to reach consensus on questions relevant for the topic. At the conference the consensus statements were presented as well as lectures based on the review articles. In this article the methods used at the consensus workshop are briefly described followed by the statements with comments.

Inflammatory response to titanium surfaces with fibrinogen and catalase coatings: an in vitro study.

The aim of the present study was to evaluate the possibility to modulate the early inflammatory response in vitro by coating titanium surfaces with candidate proinflammatory (fibrinogen coated turned titanium "Fib") and antiinflammatory proteins (catalase on top of fibrinogen coated turned titanium "Cat"). Additionally, turned titanium surfaces (Ti) were used as controls. The discs were incubated with human mononuclear cells. Adhered cells were investigated with respect to number, viability, differentiation (acute marker 27E10 vs. chronic marker RM3/1), and cytokine production (TNF-alpha and IL-10), after 24 and 72 h. The results indicated that it is possible to modulate the inflammatory response with protein coatings. However, the strongest inflammatory response, indicated by increased number of adhered cells and release of pro and antiinflammatory mediators, was induced by Cat. Furthermore, the cytokine production on this surface was not sensitive to LPS stimulation. Differentiation measured as the expression of the chronic cell surface marker, dominated after 72 h for all surface modifications and Cat displayed an increased number compared to the others. A decrease in the total number of adhered cells and amounts of TNF-alpha were observed on all surfaces over time. The cell viability was, in general, high for all tested surfaces. In conclusion, the study proved it possible to influence the early inflammatory response in vitro by immobilizing protein coatings to titanium surfaces. However, the catalase surface demonstrated the strongest inflammatory response, and the possibility to selectively use the potent antiinflammatory capacity of catalase needs to be further evaluated.

Improved bone ingrowth and fixation with a thin calcium phosphate coating intended for complete resorption.

Bonit is claimed to be a resorbable electrochemically deposited calcium phosphate coating consisting mainly of brushite, which is a hydroxyapatite precursor. This study involved a comparison of Ti6Al4V screw-shaped implants with and without a 15 +/- 5 microm Bonit coating in rabbit tibia and femur, after 6 and 12 weeks of insertion. The biomechanical removal torque test showed significantly increased values for the coated implants after 12 weeks (p < 0.05) but not after 6 weeks of integration. Higher bone-implant contact was found for the coated implants in the tibia after 6 weeks and for both tibial and femoral screws after 12 weeks (p < 0.05). There was no difference in the inflammatory reaction around the implants, and possible grains of the coating could be detected after 6 weeks, but not after 12 weeks of follow-up. This unloaded short-term study has shown promising results for the easily applicable and resorbable coat (Bonit) compared to uncoated titanium-alloy implants.

Is the intake of selective serotonin reuptake inhibitors associated with an increased risk of dental implant failure?

The aim of this retrospective study was to investigate the association between the intake of selective serotonin reuptake inhibitors (SSRIs) and the risk of dental implant failure. Patients were included if they were taking SSRIs only and no other medication, did not present any other systemic condition or compromising habits (bruxism, smoking, snuff), and complied with the use of prophylactic antibiotics for implant surgery. The multivariate generalized estimating equation (GEE) method and multilevel mixed-effects parametric survival analysis were used to test the association between SSRI exposure (predictor variable) and the risk of implant failure (outcome variable), adjusting for several potential confounders (other variables). The total number of implants with information available and meeting the necessary eligibility criteria was 931 (35 failures). These were placed in 300 patients. The implant failure rate was 12.5% for SSRI users and 3.3% for non-users (P=0.007). Kaplan-Meier analysis showed a statistically significant difference in the cumulative survival rate (P<0.001). The multivariate GEE model did not show a statistically significant association between SSRI intake and implant failure (P=0.530), nor did the multilevel model (P=0.125). It is suggested that the intake of SSRIs may not be associated with an increased risk of dental implant failure.