Screw-type Implants Research Articles

Finite Element Analysis of the Influence of Implant Tilting and the Direction of Loading on the Displacement and Micromotion of Immediately Loaded Implants

ABSTRACT Objectives: To investigate the outcome of the loading direction and implant tilting on the micromotion and displacement of immediately placed implants with finite element analysis (FEA). Materials and Method: Eight blocks of synthetic bone were created. Eight screw-type implants were inserted, four axially and four slanted, each measuring 11 mm in length and 4.5 mm in diameter. The axial implants and the tilted implants were distally inclined by 30°. The top of the abutment was subjected to 180 N vertical and mesiodistal oblique (45° angle) loads, and the displacement of the abutment was measured. The abutment displacement and micromotion were estimated, and nonlinear finite element models simulating the in vitro experiment were built. In vitro studies and FEA data on abutment displacement were compared, and the reliability of the finite element model was assessed. Result: Under oblique stress, abutment displacement was larger than under axial loading, and it was also greater for tilted implants than for axial implants. The consistency of the in vitro and FEA data was satisfactory. Under vertical stress, the highest micromotion values in the axial and tilted implants were extremely near Conclusion: Under mesiodistal oblique stress, tilted implants may have a smaller maximum amount of micromotion than axial implants. The loading direction had a significant impact on the highest micromotion values. The abutment displacement values were not reflected in the maximum micromotion measurements.

Effect of Bilayer Nano-Micro Hydroxyapatite on the Surface Characteristics of Implanted Ti-6Al-4V ELI

Ti-6Al-4V ELI is a well-known, popular medical-grade titanium alloy due to its biocompatibility and excellent mechanical properties. However, like other metal implants, it is less bioactive that affects tissue regeneration around the implant, and may lead to implant failure. So, a bioactive substance such as hydroxyapatite (HA) has usually been coated on metal implants to improve its bioactive properties. However, a single layer of HA was reported to be dissolved into body fluid after a long time of exposure in the human body. In this study, bilayer HA was deposited on the surface of screw-type implants made of Ti-6Al-4V ELI through electrophoretic deposition (EPD method. The bottom layer consists of micro-size of HA, and the second layer contains nano-size HA. The suspension contains each micro and nano size of HA powder was homogenized for 1 h followed by sonication for 2 h using a magnetic stirrer. The coating layer was subsequently sintered at 700oC for 1 h. The bilayer-coated screw implant was then implanted into the proximal tibia of health rattus novergicus under proper surgical procedures. Some screws without HA deposition were also implanted into rattus novergicus for comparison. The implanted screws were then taken out via surgery after 2, 3 and 4 weeks, and they were subsequently observed by optical microscope, SEM and XRF. The results showed that organic material is found on each coated specimen, and few HA layer is disintegrated from the surface of the screw. The disintegrated HA remained in the surface of the screw, and the amount of HA increased with increasing implantation time, which indicates the increase of osseointegration between the bone and HA layer. XRF showed a significant difference in Ti and titanium oxide contents on the surface of the coated samples and the non-coted ones, where it is only 0.66%Ti (0.39% TiO2) on the surface of the screw with HA layer and 70%Ti (67% TiO2) for without HA. When TiO2 is formed as a fast self-healing reaction while the screw is exposed to body fluid, the HA acts as an interface against body fluid that may contain aggressive ions. So, HA layer is not only effective against corrosion attack but also inhibits the formation of TiO2 on the implant surface. The coated screws also revealed a strong bonding between the HA layer and the surface of the implant screw. Besides, the ratio between Ca and P elements on the screw surface is in the range of 0.58 – 2.04, which is in the range of bone characteristics.

Extramedullary Osseointegration-A Novel Design of Percutaneous Osseointegration Prosthesis for Amputees.

The percutaneous osseointegrated (OI) prostheses have greatly improved the overall quality of life for amputees. However, the long-term maintenance of the OI prostheses is still challenging. A major problem is bone resorption around the bone-implant-skin interface, which might cause implant loosening or osteomyelitis. Another problem is the breakage of connecting components between the intramedullary implant and external prosthesis due to excessive stress. We designed a novel osseointegration implant by changing the bone-implant contact from the inner cortex to the outer surface of cortical bone. In the current study, we compared the extramedullary cap-shaped implants with the intramedullary screw-type implants in rabbits. Osteointegration was confirmed at the interface of bone to implant contact (BIC) in both implant types. The external implant induced intramedullary bone regeneration in the medullary canal and increased the cortical bone density at the end of the stump. This study provides a new perspective on the design of osseointegration implants which might prevent the currently reported complications of the intramedullary OI systems.

Histomorphometric assessment of implant coated with mixture of nano-alumina and fluorapatite in rabbits

BackgroundThe application of nanoscale surface modification was found to be useful in the improvement of osseointegration of endosseous dental implants. The fluorapatite (FA)/alumina (Al2O3) mixture is recognized for its outstanding bioinertia and can significantly increase the biocompatibility and bioactivity of biomaterials. ObjectiveThe aim of the present work was to evaluate the bone response to nano-alumina- and fluorapatite-coated dental implants using rabbit tibiae. Material and MethodsThe coating was performed using the dip-coating method. Commercially pure titanium screw-type implants were used as a control group. The coated implants were the experimental group. Each group consisted of 12 screws that were surgically implanted in 6 healthy New Zealand rabbits. Histological and histomorphometric evaluations were performed at the bone to implant contact (BIC) interface, bone fraction area occupancy (BAFO) and fibrous tissue at 2 and 6 weeks of healing. ResultsThis analysis showed that the coated implants had more rapid osseointegration than the control group, with a significant difference after 2 and 6 weeks of healing for both groups. The histomorphometric evaluation demonstrated higher values for BIC% and BAFO% and lower values of fibrous tissue in the mixture-coated Ti implants than in the control group. ConclusionThe current study suggested that the nano-alumina and fluorapatite mixture coating is a favourable candidate for rapid osseointegration over uncoated implants.

Effect of platelet-rich and platelet-poor plasma on 3D bone-to-implant contact: a preclinical micro-CT study

BackgroundBone-to-implant contact ratio (BIC%) plays a critical role in secondary stability of osseointegrated dental implants. The aim of this study was to identify the correlation of 2D/3D micro-CT images with histology as a gold standard for evaluating BIC% and to investigate the influence of the platelet-rich plasma (PRP) and platelet-poor plasma (PPP) on 3D BIC% following delayed implant placement with delayed loading (DIP+DL).MethodsNine beagle dogs were recruited. Following bilateral extraction of mandibular 3rd premolar, 4th premolar, and 1st molar, 54 screw-type titanium implants were inserted and randomly divided into one control and two test groups based on a split-mouth design. The control group involved DIP+DL (n = 18) and both test groups included DIP+DL with local application of PRP (n = 18) and PPP (n = 18). A BIC analysis was performed utilizing 2D histomorphometry and 2D/3D micro-CT. Following identification of correlation between histology and 2D/3D micro-CT images, a 3D micro-CT assessment of the 3D BIC% at three follow-up time-points (1, 3, and 6 months) was carried out for observing the influence of PRP and PPP on BIC.ResultsThe 2D micro-CT BIC% values revealed a strong positive correlation with histology (r = 0.98, p < 0.001) and a moderate correlation existed with 3D micro-CT (r = 0. 67, p = 0.005). BIC levels at 1 month and combined influence of PPP and PRP irrespective of time-points revealed significantly higher 3D BIC% compared to the control. However, a reduction in 3D BIC% was observed at the 3rd and 6th month. No significant difference was observed between both PRP and PPP.ConclusionsBoth 2D and 3D micro-CT demonstrated a potential to be utilized as a complimentary method for assessing BIC compared to the histological gold standard. Overall, both PRP and PPP significantly facilitated bone healing and osseointegration with a higher 3D BIC at follow-up. However, their influence was reduced as the observation period was increased.

Survival rate of disk and screw-type implants used for the retention of extraoral prostheses

Statement of problemImplant-supported and implant-retained extraoral prostheses are reliable treatment options for patients with craniofacial defects. They provide stable retention and therefore enhance the patient's appearance and quality of life. Despite studies on survival rates of extraoral implants, little attention has been paid to the design of the implants used to support and retain extraoral prostheses. PurposeThe purpose of this longitudinal clinical study was to assess the long-term survival rate (1 to 12 years, mean 6 years) of 2 different designs of implants (disk: single, double, and triple and screw-type) used for extraoral epithesis anchorage. Material and methodsTwenty-six participants with orbital and nasal defects, 10 of whom had had radiation treatment, were included in the study. Disk implants and extraoral (EO) screw implants were used and placed in the periorbital (15 participants) and perinasal regions (11 participants). Data were analyzed by using the Chi-square test and the Fisher Exact test for qualitative variables and the Mann-Whitney U test for comparison of quantitative variables. Implant survival rates were calculated by Kaplan-Meier analysis. ResultsThe overall 12-year survival rate of all implants was 90.3% (mean=79 months), with 92.9% for nasal (mean=84 months) and 88.2% for orbital (mean=75 months) implants. Related to the implant design, survival rates were as follows: for single-disk implants, 90.2%; for double disks, 94.6%; for triple disks, 88.3%; and for screw implants, 83.3%. In nonradiated participants, the implant survival rate was 97.6%, and for radiated participants, 76.1%. ConclusionsSurvival rates for implant-retained craniofacial prostheses are limited. The nasal site seems to be a more predictable implant site than the orbital site, with a higher overall survival rate. Also, implants inserted in radiated tissues have lower survival rates for both anatomic sites, with statistically significantly lower results in the orbital region. The most reliable type of implant among the disk implants used was the double disk in the orbital site and the single disk in the nasal site, which may indicate the advantages of some designs in specific areas.

Nitrogen plasma immersion ion implantation treatment of Ti6Al7Nb alloy for bone-implant applications: Enhanced in vitro biological responses and in vivo initial bone-implant contact

Ti6Al4V alloy has been widely applied to orthopedic and dental implants; however, V ions release may have detrimental side effects. Ti6Al7Nb alloy provides mechanical characteristics similar to those of Ti6Al4V while with fewer potentially biological side effects. In the present investigation, nitrogen plasma immersion ion implantation (N-PIII) treatment was applied to Ti6Al7Nb alloy surfaces. N-PIII surface treatment formed a thin (< 100 nm) TiN-containing film on Ti6Al7Nb surface. A higher applied N-PIII voltage resulted in a higher TiN content on Ti6Al7Nb surface. Compared to the untreated Ti6Al7Nb surface, the N-PIII treated Ti6Al7Nb surface had higher surface roughness, hydrophilicity, hardness, corrosion resistance in simulated body fluid, protein (fibronectin) adsorption, and growth of human bone marrow mesenchymal stem cells, particularly Ti6Al7Nb surface with a higher TiN content. Initial bone-implant contact was investigated in vivo by implanting Ti6Al7Nb screw-type implants (with and without N-PIII treatment) in the femur of mini-pigs for two weeks. At two weeks of post-implantation, the N-PIII treated implant surface with a higher TiN content showed a higher initial bone-implant contact than other implants. Overall, the proposed N-PIII treatment of Ti6Al7Nb alloy surface (particularly with a higher TiN content) enhanced in vitro corrosion resistance, protein adsorption, and cell response as well as in vivo initial bone-implant contact.

Clinical Outcomes of Root-Analogue Implants Restored with Single Crowns or Fixed Dental Prostheses: A Retrospective Case Series.

The objective was to investigate clinical and radiological outcomes of rehabilitations with root-analogue implants (RAIs). Patients restored with RAIs, supporting single crowns or fixed dental prostheses, were recruited for follow-up examinations. Besides clinical and esthetical evaluations, X-rays were taken and compared with the records. Patients were asked to evaluate the treatment using Visual Analogue Scales (VAS). For statistical analyses, mixed linear models were used. A total of 107 RAIs were installed in one dental office. Of these, 31 were available for follow-up examinations. For those remaining, survival has been verified via phone. RAIs were loaded after a mean healing time of 6.6 ± 2.5 months. 12.1 ± 6.9 months after loading, a mean marginal bone loss (MBL) of 1.20 ± 0.73 mm was measured. Progression of MBL significantly decreased after loading (p = 0.013). The mean pink and white esthetic score (PES/WES) was 15.35 ± 2.33 at follow-up. A survival rate of 94.4% was calculated after a mean follow-up of 18.9 ± 2.4 months after surgery. Immediate installation of RAIs does not seem to reduce MBL, as known from the literature regarding screw-type implants, and might not be recommended for daily routine. Nevertheless, they deliver esthetically satisfying results.

A digital workflow for modeling of custom dental implants

Modern dental treatment with standard screw-type implants leave some cases unaddressed in patients with extreme jaw bone resorption. Custom-made subperiosteal dental implant could be an alternative treatment modality to sinus lift, nerve lateralization or zygomatic implant techniques. Subperiosteal dental implants were utilized for many years to treat such patients. A combination of traditional subperiosteal implant designs with current advancements in 3D imaging, design and printing allow to reduces treatment time and provides abutments for prostheses in cases where other techniques do not provide satisfactory results. The data manipulation and design software are important aspects in the manufacturing of custom implants. Programs that are specialized for industrial or medical design typically cost tens of thousands of US dollars. In this work I establish and test steps for design and production of a custom medical device (subperiosteal implant) from patient computed tomography (CT) data. Work stages to be defined are: selection of necessary software, CT data processing, 3D virtual model creation, modeling technique for custom implant and data file preparation for printing. Patient CT data was successfully converted into a watertight STL (Standard Tessellation Language) model of the maxilla. Error corrections and design were completed using freely available programs from Autodesk Inc.. The implant was produced in Ti64 (a type 5 titanium alloy) using three-dimensional (3D) printing DMLS (direct metal laser sintering) process. The avoidance of high cost software makes this treatment modality more accessible to smaller clinics or mid-size production facilities and subsequently more available to patients.

Clinical and Radiographic Evaluation of Early Loaded Maxillary Anterior Implants: Three-Year Follow-up.

The aim of this study was to evaluate clinical and radiologic results up to 3 years in patients treated with early loading of anterior implants supporting single-tooth all-ceramic restorations. Twenty-four patients were treated with 29 screw-type implants in the anterior maxilla. The implants were evaluated by clinical and radiographic parameters. Clinical parameters Plaque Index (PI), Sulcus Bleeding Index (BI), peri-implant probing depth (PD), and marginal bone loss (MBL) were recorded. At the recall examinations, all implants were successfully integrated, demonstrating healthy peri-implant soft tissues as documented by standard clinical parameters. No biologic complications were observed. There was no statistically significant increase in MBL between the baseline and recall stages (P > .05). Early loaded maxillary anterior implants supporting single-tooth restorations reveal successful clinical and radiographic outcomes when treatment steps were performed.

STRESS ANALYSIS EVALUATION OF COMBINING RESILIENT ATTACHMENTS WITH DIFFERENT CANTILEVER BAR LENGTH ON SUPPORTING STRUCTURES OF IMPLANT SUPPORTED OVERDENTURE IN-VITRO STUDY

Four screw type implants(Pitt-easy Implant System, SIS, Germany) were placed in the interforaminal region of mandibular acrylic model then the abutments(Titanium sleeve abutment,Pitt –easy, Germany) intimately fitted over the hex of the implant. Two bar-ball designs were constructed on single model; Design I: Bar with yellow colored clips(Vario- Soft bar- Pattern VSP) connecting four implants with 8 mm distal cantilever bar extension with distally placed ball attachment (Patrix VKS - SG,Bredent,Germany) Design II: Bar with yellow clips connecting four implants with 16 mm distal cantilever with distally placed ball attachment. Two bar-ball designs were constructed on single model as follow: The bar connecting the abutments were held with mandrel, so that it’s rounded surface facing occlusally and its flat surface facing to the ridge. The wires of the strain gauges(Kaywan, Electronic Instrument, Tokyo, Japan) were embedded in specially prepared channels in the base of the model. The straight load applicator bar of the universal testing machine(LLyod Instruments, Japan) was allowed to touch the denture teeth. Vertical unilateral loading was applied unilaterally at the central fossae of the left second premolar.All data of the study were collected and statistically analyzed. Using student T test to compare between two designs, it is found that there is statistically significant difference between design I and design II. The result obtained from this study showed that there is increase in the stresses applied to the nearby abutment this was due to the distal extension that act as hidden cantilever which add to bending moment and the fact that in design II the bending moment will decrease, thus decreasing the amount of force on the abutment.

A study on a pedicle-screw-based reduction method for artificially reduced artifacts

The purpose of this study is a quantitative analysis of the degree of the reduction of the artifacts that are induced by pedicle screws through the application of the recently developed iterative metallic artifact reduction (I MAR) software. Screw-type implants that are composed of 4.5 g/cm3 titanium (Ti) with an approximate average computed tomography (CT) value of 6500 Hounsfield units (HUs) that are used for the treatment of spinal diseases were placed in paraffin, a tissueequivalent material, and then dried. After the insertion, the scanning conditions were fixed as 120 kVp and 250 mA using multidetector computed tomography (MDCT) (Enlarge, Siemens, Germany). The slice thickness and the increment were set at the fields of view (FOVs) of 3 mm and 120 mm, respectively; the pitch is 0.8; the rotation time is 1 s; and the I MAR software was applied to the raw data of the acquired images to compare the CT-value changes of the posterior images. When the I MAR software was applied to animal vertebrae, it was possible to reduce the 65.7% image loss of the black-hole-effect image through the application of the I MAR software. When the I MAR image loss (%) was compared with the white-streak-effect image, the high-intensity image type with the white-streak effect could be reduced by 91.34% through the application of the I MAR software. In conclusion, a metal artifact that is due to a high-density material can be reduced more effectively when the I MAR algorithm is applied compared with that from the application of the conventional MAR algorithm. The I MAR can provide information on the various tissues that form around the artifact and the reduced metal structures, which can be helpful for radiologists and clinicians in their determination of an accurate diagnosis.

Comparative evaluation of topographical data of dental implant surfaces applying optical interferometry and scanning electron microscopy

ObjectiveComparability of topographical data of implant surfaces in literature is low and their clinical relevance often equivocal. The aim of this study was to investigate the ability of scanning electron microscopy and optical interferometry to assess statistically similar 3-dimensional roughness parameter results and to evaluate these data based on predefined criteria regarded relevant for a favorable biological response. MethodsFour different commercial dental screw-type implants (NanoTite Certain Prevail, TiUnite Brånemark Mk III, XiVE S Plus and SLA Standard Plus) were analyzed by stereo scanning electron microscopy and white light interferometry. Surface height, spatial and hybrid roughness parameters (Sa, Sz, Ssk, Sku, Sal, Str, Sdr) were assessed from raw and filtered data (Gaussian 50μm and 5μm cut-off-filters), respectively. Data were statistically compared by one-way ANOVA and Tukey–Kramer post-hoc test. For a clinically relevant interpretation, a categorizing evaluation approach was used based on predefined threshold criteria for each roughness parameter. ResultsThe two methods exhibited predominantly statistical differences. Dependent on roughness parameters and filter settings, both methods showed variations in rankings of the implant surfaces and differed in their ability to discriminate the different topographies. Overall, the analyses revealed scale-dependent roughness data. Compared to the pure statistical approach, the categorizing evaluation resulted in much more similarities between the two methods. SignificanceThis study suggests to reconsider current approaches for the topographical evaluation of implant surfaces and to further seek after proper experimental settings. Furthermore, the specific role of different roughness parameters for the bioresponse has to be studied in detail in order to better define clinically relevant, scale-dependent and parameter-specific thresholds and ranges.

Effects of implant tilting and the loading direction on the displacement and micromotion of immediately loaded implants: an in vitro experiment and finite element analysis.

PurposeThe purpose of this study was to investigate the effects of implant tilting and the loading direction on the displacement and micromotion (relative displacement between the implant and bone) of immediately loaded implants by in vitro experiments and finite element analysis (FEA).MethodsSix artificial bone blocks were prepared. Six screw-type implants with a length of 10 mm and diameter of 4.3 mm were placed, with 3 positioned axially and 3 tilted. The tilted implants were 30° distally inclined to the axial implants. Vertical and mesiodistal oblique (45° angle) loads of 200 N were applied to the top of the abutment, and the abutment displacement was recorded. Nonlinear finite element models simulating the in vitro experiment were constructed, and the abutment displacement and micromotion were calculated. The data on the abutment displacement from in vitro experiments and FEA were compared, and the validity of the finite element model was evaluated.ResultsThe abutment displacement was greater under oblique loading than under axial loading and greater for the tilted implants than for the axial implants. The in vitro and FEA results showed satisfactory consistency. The maximum micromotion was 2.8- to 4.1-fold higher under oblique loading than under vertical loading. The maximum micromotion values in the axial and tilted implants were very close under vertical loading. However, in the tilted implant model, the maximum micromotion was 38.7% less than in the axial implant model under oblique loading. The relationship between abutment displacement and micromotion varied according to the loading direction (vertical or oblique) as well as the implant insertion angle (axial or tilted).ConclusionsTilted implants may have a lower maximum extent of micromotion than axial implants under mesiodistal oblique loading. The maximum micromotion values were strongly influenced by the loading direction. The maximum micromotion values did not reflect the abutment displacement values.

One-Piece Implant-Retained Mandibular Overdentures By Pre-Fabricated Titanium Telescopic Attachments and Frictional Varnish: A Two-Year Prospective Study.

Clinical efficiency of one-piece screw-type implants with telescopic were attachments evaluated in this study. Twenty-four patients received a mandibular implant-supported overdenture and maxillary complete denture. Ninety-six one-piece implants were inserted in the inter-foraminal area. Implants were immediately loaded with an implant-retained overdenture and telescopic attachments which had frictional retention elements. There was 0.25±0.24 mm, 0.32±0.25 mm, 0.43±0.30 mm, 0.61±0.30 mm and of bone resorption after 3, 6, 12 and 24 months, respectively. The need to activate the frictional retention was the most common complication. Treatment outcomes for prefabricated telescopic retained overdentures on one-piece implants are similar to that obtained in cases of delayed loading.

Ligature induced peri-implantitis: tissue destruction and inflammatory progression in a murine model.

The aim of this study was to investigate tissue destruction and inflammatory progression of ligature-induced peri-implantitis in mice and to establish an alternative murine model of peri-implantitis. Sixty male C57BL/6NCrSlc mice (4-week-old) were used and the maxillary right first molars were extracted. Eight weeks after extraction, custom-made pure titanium machined screw type implants (0.8×1.5mm) were placed, one implant per animal. Four weeks later, 5-0 silk ligatures were applied around implant necks to induce peri-implantitis. Animals were sacrificed at 0 (before ligature), 7, 14, 21 and 28days after ligature. Half of the samples were analyzed radiologically and histologically to measure bone level change, osteoclast number, density, and distribution. The rest of the samples was used to determine the relative mRNA expression levels of IL-1 and TNF-α with RT-PCR analysis. Bone levels at all sites (buccal, palatal, mesial, distal) decreased 40-50% significantly 28days after ligature (P<0.01). Osteoclast number at all post-ligature time points increased significantly (P<0.05). However, their density at day 28 decreased significantly compared to that of day 21 (P<0.05). Accordingly, IL-1 and TNF-α mRNA expression increased significantly at the early time points but decreased significantly at day 28 after ligature (P<0.05). Inflammatory response followed by significant peri-implant bone resorption suggested 28days ligation is sufficient to successfully induce peri-implantitis in the current mice model. This model might open a new avenue to study the pathogenesis and mechanism of peri-implantitis.

UV-A and UV-C light induced hydrophilization of dental implants

ObjectivesWettability is increasingly considered to be an important factor determining biological responses to implant materials. In this context, the purpose of this study was to compare the dynamic wettability of dental implants made from different bulk materials and modified by different surface modifications, and to analyze the respective changes of wettability upon irradiating these implants by UV-A or UV-C light. MethodsFour original screw-type implants were investigated: One grit-blasted/acid-etched and one anodically oxidized titanium, one zirconia and one polyetheretherketone implant. Additionally, experimental, screwless, machined titanium cylinders were included in the study. Part of that cylinders and of blasted/etched implants were further modified by a magnetron-sputtered photocatalytic anatase thin film. Scanning electron microscopy was used to investigate the surface micro- and nanostructures. Samples were treated by UV-A (382nm, 25mWcm−2) and UV-C (260nm, 15mWcm−2) for entire 40min, respectively, and their wettability was quantified by dynamic contact angle (CA) analysis from multi-loop Wilhelmy experiments. ResultsAll implants are characterized by submicron- and nanosized surface features. Unexposed implants were hydrophobic (CA>90°). Upon UV-A, solely the implants with anatase coating became superhydrophilic (CA<5°). Upon UV-C, the blasted/etched implants turned superhydrophilic, the anodized titanium and the zirconia implants were considerably (CA=34° and 27°, respectively) and the PEEK implants slightly (CA=79°) hydrophilized. SignificanceThe wettability of implant surfaces can be improved by UV irradiation. The efficiency of UV-A and UV-C irradiation to lower the CA by photocatalysis or photolysis, however, is strongly dependent on the specific material and surface. Thus, attempts to photofunctionalize these surfaces by irradiation is expected to result in a different pattern of bioresponses.

The stability analysis of implants installed in osteotomies with different types of controlled bone defects

The stability parameters of implants (ITV, ISQ & PTV) according to different sizes of controlled bone defects made in implant osteotomies were analyzed and the correlation among the three kinds of implant stability parameters was tested in this study. 45 tapped screw-type dental implants were inserted in three types of implant osteotomies made in 8 fresh-frozen pig femoral bones: Type1 — without coronal bone defect, Type2 — with 3 mm coronal bone defects, and Type3 — with 6 mm coronal bone defects. The insertion torque values, ISQ & PTV of implants were measured and analyzed statistically. It is concluded that the circumferential coronal bone defects statistically influence the primary stability of implants; ITV, ISQ and PTV are suitable and available to detect the peri-implant coronal bone defects in 3 mm increments, and ITV and PTV are more sensitive to coronal cortical bone loss. There was a strong correlation between ITV and ISQ.

Buccal bone resorption around posterior implants after surgery: a 1-year prospective study.

This prospective study aimed to examine postoperative dimensional changes in the buccal bone and mucosa around single-stage implants placed in the posterior region. The dimensions of peri-implant tissue around screw-type implants placed in the posterior region were examined at surgery (baseline) and 6 months and 1 year after surgery. The lateral contour of the buccal bone and mucosa was horizontally measured at five vertical heights at 1-mm intervals (+1 to -3 mm from the implant platform) using custom-designed instruments. Bone resorption on the proximal sides was assessed on radiographs. Mucosal recession was measured on plaster casts of the dentition. Sixty-six implants placed in 30 patients were examined. All implants were clinically osseointegrated and stable throughout the study period. The buccal bone exhibited horizontal resorption throughout the study period, even at the most apical height measured. Assessed at each height, thicker bone (> 2 mm thick) tended to exhibit horizontal resorption during the first 6 months after surgery. However, the bone resorbed horizontally by approximately 0.4 mm during the final 6 months, irrespective of its contour. Vertical resorption of the buccal marginal bone was approximately 1 mm during the period from 6 months to 1 year. The bone-retaining group at the 1-year time point was found to have thicker bone walls at baseline compared with the bone-loss group. The thickness of the buccal mucosa showed little change. There was no obvious correlation between buccal bone resorption and mucosal recession. The buccal bone exhibited both horizontal and vertical resorption over the year after surgery. The initial contour of the bone was significantly associated with bone retention or loss at 1 year. However, mucosal recession was not directly affected by buccal bone resorption.

Long‐term analysis of osseointegrated implants in non‐smoker patients with a previous history of periodontitis

To evaluate long-term clinical and radiographic parameters of osseointegrated implants in non-smoker patients with a previous history of chronic periodontitis. Fifty-four screw-type implants with a moderately roughened surface and internal hexagonal implant-abutment connection were placed according to a two-phase protocol and 40 reference teeth were analysed at baseline, and after 5 and 10years. Pocket probing depth (PPD), clinical attachment level (CAL) and bleeding on probing were analysed 6x/tooth in all teeth, implants and reference teeth. Radiographic peri-implant bone level was measured on the mesial and distal surfaces. The prevalence of peri-implantitis and the survival rate of the implants were assessed at the patient and implant levels. Data were analysed using descriptive statistics, Mann-Whitney U-test, and Wald Z-test, at α=5%. In implants, the CAL at 5years was 0.3mm higher, and at 10years 1.2mm higher in comparison to baseline. The corresponding data for the reference teeth were 0mm and 0.5mm respectively. Multilevel testing showed statistical difference for PPD between implants and teeth over time. After 10years, the mean mesial bone loss was 0.63±0.26mm, and the mean distal bone loss was 0.56±0.25. The survival rates were 100% and 92.3% for the implants in the mandible and the implants in the maxilla respectively. Screw-type implants with internal hexagon placed in patients with a previous history of periodontitis attending a regular maintenance programme demonstrated stable clinical and radiographic results after 5 and 10years.