STATEMENT OF PROBLEM
Macroscopic and especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Dental implants with modified surfaces have shown stronger osseointegration than implants which are only turned (machined). Advanced surface modification techniques such as anodic oxidation and Ca-P application have been developed to achieve faster and stronger bonding between the host bone and the implant.
The purpose of this study was to investigate the effect of surface treatment of titanium dental implant on implant stability after insertion using the rabbit tibia model.
MATERIAL AND METHODS
Three test groups were prepared: sandblasted, large-grit and acid-etched (SLA) implants, anodic oxidized implants, and anodized implants with Ca-P immersion. The turned implants served as control. Twenty rabbits received 80 implants in the tibia. Resonance frequencies were measured at the time of implant insertion, 2 weeks and 4 weeks of healing. Removal torque values (RTV) were measured 2 and 4 weeks after insertion.
The implant stability quotient (ISQ) values of implants for resonance frequency analysis (RFA) increased significantly (P < .05) during 2 weeks of healing period although there were no significant differences among the test and control groups (P > .05). The test and control implants also showed significantly higher ISQ values during 4 weeks of healing period (P < .05). No significant differences, however, were found among all the groups. All the groups showed no significant differences in ISQ values between 2 and 4 weeks after implant insertion (P > .05). The SLA, anodized and Ca-P immersed implants showed higher RTVs at 2 and 4 weeks of healing than the machined one (P < .05). However, there was no significant difference among the experimental groups.
The surface-modified implants appear to provide superior implant stability to the turned one. Under the limitation of this study, however, we suggest that neither anodic oxidation nor Ca-P immersion techniques have any advantage over the conventional SLA technique with respect to implant stability.
surface treatment; bone to implant contact; removal torque; dental implant
The objective of this study was to investigate the mechanical characteristics of implant–abutment interface design in a dental implant system, using nonlinear finite element analysis (FEA) method. This finite element simulation study was applied on three commonly used commercial dental implant systems: model I, the reduced-diameter 3i implant system (West Palm Beach, FL, USA) with a hex and a 12-point double internal hexagonal connection; model II, the Semados implant system (Bego, Bremen, Germany) with combination of a conical (45° taper) and internal hexagonal connection; and model III, the Brånemark implant system (Nobel Biocare, Gothenburg, Sweden) with external hexagonal connection. In simulation, a force of 170 N with 45° oblique to the longitudinal axis of the implant was loaded to the top surface of the abutment. It has been found from the strength and stiffness analysis that the 3i implant system has the lowest maximum von Mises stress, principal stress and displacement while the Brånemark implant system has the highest. It was concluded from our preliminary study using nonlinear FEA that the reduced-diameter 3i implant system with a hex and a 12-point double internal hexagonal connection had a better stress distribution, and produced a smaller displacement than the other two implant systems.
external hexagonal connection; finite element analysis; implant–abutment interface; internal hexagonal connection; nonlinear analysis
The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC).
Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants. Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals. The P1-M1 teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed.
No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks.
The existence of microthreads was not a significant factor in mechanical and histological stability.
Biomechanics; Dental implants; Osseointegration; Torque
Initial stability of the implant is, in effect, one of the fundamental criteria for obtaining long-term osseointegration. Achieving implant stability depends on the implant-bone relation, the surgical technique and on the microscopic and macroscopic morphology of the implant used. A newly designed parabolic screw-type dental implant system was tested in vivo for early stages of interface reaction at the implant surface.
A total of 40 implants were placed into the cranial and caudal part of the tibia in eight male Göttinger minipigs. Resonance frequency measurements (RFM) were made on each implant at the time of fixture placement, 7 days and 28 days thereafter in all animals. Block biopsies were harvested 7 and 28 days (four animals each) following surgery. Biomechanical testing, removable torque tests (RTV), resonance frequency analysis; histological and histomorphometric analysis as well as ultrastructural investigations (scanning electron microscopy (SEM)) were performed.
Implant stability in respect to the measured RTV and RFM-levels were found to be high after 7 days of implants osseointegration and remained at this level during the experimented course. Additionally, RFM level demonstrated no alteration towards baseline levels during the osseointegration. No significant increase or decrease in the mean RFM (6029 Hz; 6256 Hz and 5885 Hz after 0-, 7- and 28 days) were observed. The removal torque values show after 7 and 28 days no significant difference. SEM analysis demonstrated a direct bone to implant contact over the whole implant surface. The bone-to-implant contact ratio increased from 35.8 ± 7.2% to 46.3 ± 17.7% over time (p = 0,146).
The results of this study indicate primary stability of implants which osseointegrated with an intimate bone contact over the whole length of the implant.
STATEMENT OF PROBLEM
Primary stability at the time of implant placement is related to the level of primary bone contact. The level of bone contact with implant is affected by thread design, surgical procedure and bone quality, etc.
The aim of this study was to compare the initial stability of the various taper implants according to the thread designs, half of which were engaged to inferior cortical wall of type IV bone (Group 1) and the rest of which were not engaged to inferior cortical wall (Group 2) by measuring the implant stability quotient (ISQ) and the removal torque value (RTV).
MATERIAL AND METHODS
In this study, 6 different implant fixtures with 10 mm length were installed. In order to simulate the sinus inferior wall of type IV bone, one side cortical bone of swine rib was removed. 6 different implants were installed in the same bone block following manufacturer's recommended procedures. Total 10 bone blocks were made for each group. The height of Group 1 bone block was 10 mm for engagement and that of group 2 was 13 mm. The initial stability was measured with ISQ value using Osstell mentor® and with removal torque using MGT50 torque gauge.
In this study, we found the following results. 1. In Group 1 with fixtures engaged to the inferior cortical wall, there was no significant difference in RTV and ISQ value among the 6 types of implants. 2. In Group 2 with fixtures not engaged to the inferior cortical wall, there was significant difference in RTV and ISQ value among the 6 types of implants (P < .05). 3. There was significant difference in RTV and ISQ value according to whether fixtures were engaged to the inferior cortical wall or not (P < .05). 4. Under-drilling made RTV and ISQ value increase significantly in the NT implants which had lower RTV and ISQ value in Group 2 (P < .05).
Without being engaged to the inferior cortical wall fixtures had initial stability affected by implant types. Also in poor quality bone, under-drilling improved initial stability.
Thread design; Taper implant; Bicortical engagement; ISQ; Removal torque value
STATEMENT OF PROBLEM
A number of studies about the nano-treated surfaces of implants have been conducting along with micro-treated surfaces of implants.
The purpose of this study was to get information for the clinical use of nano-treated surfaces compared with micro-treated surfaces by measuring removal torque and analyzing histological characteristics after the placement of various surface-treated implants on femurs of dogs.
MATERIAL AND METHODS
Machined surface implants were used as a control group. 4 nano-treated surface implants and 3 micro-treated surface implants [resorbable blast media surface (RBM), sandblast and acid-etched surface (SAE), anodized RBM surface] were used as experimental groups. Removal torque values of implants were measured respectively and the histological analyses were conducted on both 4weeks and 8weeks after implant surgery. The surfaces of removed implants after measuring removal torque values were observed by scanning electron microscopy (SEM) at 8 weeks.
1. Removal torque values of the nano-treated groups were lower than those of micro-treated groups. 2. Removal torque values were similar in the anodized RBM surface groups. 3. On the histological views, there was much of bone formation at 8 weeks, but there was no difference between 4 and 8 weeks, and between the types of implant surfaces as well.
It is suggested that implant topography is more effective in removal torque test than surface chemistry. To get better clinical result, further studies should be fulfilled on the combined effect of surface topography and chemistry for the implant surface treatments.
removal torque; implant; surfaces characteristics; dog; histology; SEM
The aim of this study is to evaluate the short time aesthetic and functional outcome of a new implant system, the Nobel Active™. The Nobel Active™ features several innovations such as an extensive self-drilling capacity, axial and radial bone compression and an inward tapered collar allowing for marginal bone maintance an soft tissue stabilization. This design makes it possible to place the implant into narrower osteotomies, thus requiring less drilling, compared to conventional implants. The Nobel Active™ implants are available in two different prosthetic connections: Internal connection and external connection. The Nobel Active™ External connection is a 1.5 piece implant, with a primary abutment included with the implant. The Nobel Active™ internal connection is a two piece implant with a standard hexagonal internal connection. In this study we present a single tooth replacement with immediate loading of Nobel Active External connection.
osseointegration; immediate loading; Nobel Active™
To gain basic information regarding the biologic stability of plasma ion-implanted miniscrews and their potential clinical applications.
Sixteen plasma ion-implanted and 16 sandblasted and acid-etched (SLA) miniscrews were bilaterally inserted in the mandibles of 4 beagles (2 miniscrews of each type per quadrant). Then, 250 - 300 gm of force from Ni-Ti coil springs was applied for 2 different periods: 12 weeks on one side and 3 weeks contralaterally. Thereafter, the animals were sacrificed and mandibular specimens including the miniscrews were collected. The insertion torque and mobility were compared between the groups. The bone-implant contact and bone volume ratio were calculated within 800 µm of the miniscrews and compared between the loading periods. The number of osteoblasts was also quantified. The measurements were expressed as percentages and analyzed by independent t-tests (p < 0.05).
No significant differences in any of the analyzed parameters were noted between the groups.
The preliminary findings indicate that plasma ion-implanted miniscrews have similar biologic characteristics to SLA miniscrews in terms of insertion torque, mobility, bone-implant contact rate, and bone volume rate.
Orthodontic mini-implant; Surface treatment; Histology; Stability
Objective: To evaluate the vertical misfit between different brands of dental implants and prosthetic abutments, with or without mechanical torque, and to study their possible combination.
Study design: Five different brands of implant were used in the study: Biofit (Castemaggiore, Italy), Bioner S.A. (Barcelona, Spain), 3i Biomet (Palm Beach, U.S.A.), BTI (Alava, Spain) and Nobel Biocare (Göteborg, Sweden), with standard 4.1 mm heads and external hexagons, and their respective machined prosthetic abutments. The implant-to-abutment fit/misfit was evaluated at four points (vestibular, lingual/palatine, mesial and distal) between implants and abutments of the same brand and different brands, with or without mechanical torque, using SEM micrographs at 5000X. Image analysis was performed using NIS-Elements software (Nikon Instruments Europe B.V.).
Results: Before applying torque, vertical misfit (microgaps) of the different combinations tested varied between 1.6 and 5.4 microns and after applying torque, between 0.9 and 5.9 microns, an overall average of 3.46±2.96 microns. For manual assembly without the use of mechanical torque, the best results were obtained with the combination of the 3i implant and the BTI abutment. The Nobel implant and Nobel abutment, 3i-3i and BTI-BTI and the combination of 3i implant with BTI or Nobel abutment provided the best vertical fit when mechanical torque was applied.
Conclusions: The vertical fits obtained were within the limits considered clinically acceptable. The application of mechanical torque improved outcomes. There is compatibility between implants and abutments of different brand and so their combination is a clinical possibility.
Key words:Vertical fit, implant, prosthetic abutment, combination.
This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading.
MATERIALS AND METHODS
Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at 30° to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for 105 cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (α=0.05).
Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences.
The abutment types did not have a significant influence on short term screw loosening. On the other hand, after 105 cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not.
Computer-aided design; Dental implantation; Prosthesis failure; Removal torque; Screw loosening
To evaluate the R‐INJ‐04 soft‐tipped injector, a new injector with an integral round nozzle manufactured by Rayner Intraocular Lenses, England.
16 Rayner C‐flex intraocular lenses (IOLs; Rayner Intraocular lenses, England) ranging between +10 and +30 D (2 for each power) were tested. An ophthalmic viscoelastic device (Healon, AMO, Santa Ana, California, USA) was applied to the injectors. The IOLs were loaded according to the company injector's instructions for use and were injected into a Petri dish. After the injection, all the IOLs and nozzles were evaluated by gross (macroscopic) and microscopic analyses and photographed under a light microscope. One lens of each power and the cartridge used for the implantation were then sent for further analysis by scanning electron microscopy (SEM). The rest of the IOLs were tested for power and modulation transfer function (MTF).
All the injections were successful. No damage to the IOLs or to the injectors was found by gross examination, light microscopy and SEM. No deposits were found on the IOL optical surfaces or haptics. Power and MTF analysis showed a close match with the original measurements.
Our results suggest that the R‐INJ‐04 soft‐tipped injector is safe for the implantation of the C‐flex IOL with power range from 10 to 30 D. No structural damage to the IOLs or to the injectors was found, and the lens power and light transmission properties were not damaged in any way by the injection process.
The use of implants as anchorage for orthodontic forces seems to be a good alternative in partially edentulous patients needing orthodontic treatment.
This study is aimed at assessing the performance and behavior of microtextured surface endosseous implants obtained by means of a double acid etching against orthodontic forces, as well as their adequacy to be used first as anchorage and later as fixtures for the definitive prosthesis.
Materials and Methods:
A total of 93 double acid-etched surface parallel wall implants (Osseotite® Implants, Implant Innovations Inc., Palm Beach, Florida, USA) were inserted in 38 partially edentulous patients prior to orthodontic treatment This was carried out by following two-stage surgery protocols in the maxilla as well as in the mandible.
After a healing period of six months for the maxilla and four months for the mandible, the implants were used as anchorage for sliding, compression and traction orthodontic forces between 100 to 200 g by means of Ni-TI springs.
Bone level and Resonance Frequency Analysis (RFA) were measured before and after the introduction of the orthodontics forces.
After removal of the orthodontics appliances, all the implants remained stabile and served as support for prosthetic replacement of missing teeth. The bone level showed no variationeven when a positive difference 0.02 ± 0.38mm was noticed. The RFA scored a significant difference (p≤ 0.03) between the initial Implant Stability Quotient (ISQ) values (66) and the final ones (68).
These findings showed that Osseotite implants were able to support the orthodontic forces applied during this investigation, maintaining osseointegration without significant variation in bone level. Therefore, they can be used to support dental prosthesis once they have been used as orthodontic anchorage under the cited conditions.
Osseointegrated implants; orthodontic forces; absolute anchorage
Vertical bone loss evaluations in the Nobel Biocare Replace® Select Tapered ™ implant system in the human after one-year loading time.
Materials and Methods:
This retrospective cross-sectional study was performed on 31 patients (14 men, 17 women; mean age, 60.39 years) receiving 170 implants (mean, 5.48 for each patient) of Groovy and Non-groovy designs in the Nobel Biocare Replace® Select Tapered ™ system. The marginal bone loss was measured at mesial and distal aspects of the implants on OPG x-rays after one-year follow-up. The data regarding the patient’s gender, age, history of disease, smoking, bone type at implant location, loading time of prosthesis and implant, implant design, diameter and length were recorded by the patients’ records and interview. The data were subjected to multiple linear regression and Pearson coefficient ratio regarding different factors.
The mean (standard deviation) distal, mesial and overall bone loss was 0.688 mm (0.851), 0.665 mm (0.849) and 0.935 mm (0.905), respectively in the studied implants. No significant differences were found regarding implant location, bone quality at the implant region, implant design and bone graft reception. In addition, no significant correlation was found between the occurred bone loss and implant diameter, length and number of used splints.
Due to the criteria mentioned for implant success in term of bone loss values after one-year loading time, Noble Biocare Replace® Select Tapered ™ implant system is an acceptable treatment option for implant restorations in this regard.
Dental Implants; Data Interpretation, Statistical; Radiography, Panoramic; Alveolar Bone Loss
STATEMENT OF PROBLEM
Implant drivers are getting popular in clinical dentistry. Unlike to implant systems with external hex connection, implant drivers directly engage the implant/abutment interface. The deformation of the implant/abutment interface can be introduced while placing an implant with its implant driver in clinical situations.
This study evaluated the change of rotational freedom between an implant and its abutment after application of different insertion torques.
MATERIAL AND METHODS
Three kinds of internal connection implants were utilized for the current study (4.5 × 12 mm Xive, 4.3 × 11.5 mm Inplant Magicgrip, 4.3 × 12 mm Implantium MF). An EstheticBase, a 2-piece top, a Dual abutment was used for its corresponding implant system. The rotational freedom between an implant and its abutment were measured before and after applying 45, 100 Ncm insertion torque. Repeated measures ANOVA was used for statistical analysis.
Under 45 Ncm insertion torque, the rotational freedom between an implant and its abutment was significantly increased in Xive (P = .003). However, no significant change was noted in Inplant Magicgrip and Implantium MF. Under 100 Ncm torque, both in Xive (P = .0005) and Implatium MF (P = .03) resulted in significantly increased rotational freedom between the implant and its abutment.
The design of the implant/implant driver interface effectively prevented the deformation of implant/abutment interface. Little change was noted in the rotational freedom between an implant and its abutment, even though the insertion torque was far beyond clinical application.
The implant/abutment joint of internally connecting implants were quite stable under insertion torque in clinical situation.
Rotational freedom; Internal connection; Insertion torque; Implant driver
Owing to the complexity and magnitude of functional forces transferred to the bone-implant interface, the mechanical strength of the interface is of great importance. The purpose of this study was to determine the intraosseous torsional shear strength of an osseointegrated oral implant using 3-D finite element (FE) stress analysis implemented by in vivo failure torque data of an implant.
A Ø 3.5 mm × 12 mm ITI® hollow screw dental implant in a patient was subjected to torque failure test using a custom-made strain-gauged manual torque wrench connected to a data acquisition system. The 3-D FE model of the implant and peri-implant circumstances was constructed. The in vivo strain data was converted to torque units (N.cm) to involve in loading definition of FE analysis. Upon processing of the FE analysis, the shear stress of peri-implant bone was evaluated to assume torsional shear stress strength of the bone-implant interface.
The in vivo torque failure test yielded 5952 μstrains at custom-made manual torque wrench level and conversion of the strain data resulted in 750 N.cm. FE revealed that highest shear stress value in the trabecular bone, 121 MPa, was located at the first intimate contact with implant. Trabecular bone in contact with external surface of hollow implant body participated shear stress distribution, but not the bone resting inside of the hollow.
The torsional strength of hollow-screw implants is basically provided by the marginal bone and the hollow part has negligible effect on interfacial shear strength.
With the increase in joint revision surgery after arthroplasty, defects of hydroxyapatite (HA)-coated prostheses have been observed increasingly often. These defects adversely affect the prosthetic stability in vivo. This study has analyzed the potential effect of the adhesive strength of HA coating on the stability of HA-coated prostheses in vivo after its implantation.
Material and methods
Sixty experimental rabbits were divided into HA- and Ti-coated groups. HA-coated prostheses were implanted into the bilateral epicondyle of rabbits femurs. Ti-coated prostheses were implanted as control. At different time points(4, 9, and 15 weeks) after implantation, bone tissue samples were fetched out respectively for histomorphometric analysis. Push-out testing was used to detect the ultimate shear strength at the bone-prosthesis interface. Scanning electron microscope (SEM) observation and energy-dispersive X-ray spectroscopy (EDX) analysis were used to observe the changes in surface composition of the prostheses after the ultimate shear strength testing. The coating adhesive strength of two kinds of coatings were also examined by scratch testing.
Hydroxyapatite coating has an obvious advantage in facilitating osteogenesis and its plays a critical role in the stability of prostheses. However, the ultimate shear strength of HA-coated prostheses is much lower than that of Ti-coated implants (p < 0.01). Further study has demonstrated that the stability of HA-coated prostheses in vivo is affected by the relatively low adhesive strength between coating and substrate.
Obvious advantage in facilitating osteogenesis around HA-coated prostheses is not the only factor that determines the stability of prostheses in vivo.
hydroxyapatite coating; artificial joints; stability; biomechanical; adhesive strength
The aim of the study was to evaluate mechanical behavior of implants inserted in three substrates, by measuring the pullout strength and the relative stiffness. 32 implants (Master Porous-Conexao, cylindrical, external hexagon, and surface treatment) were divided into 4 groups (n = 8): pig rib bone, polyurethane Synbone, polyurethane Nacional 40 PCF, and pinus wood. Implants were installed with the exact distance of 5 mm of another implant. The insertion torque (N·cm) was quantified using the digital Kratos torque meter and the pullout test (N) was performed by an axial traction force toward the long axis of the implant (2 min/mm) through mount implant devices attached to a piece adapted to a load cell of 200 Kg of a universal testing machine (Emic DL10000). Data of insertion torque and maximum pullout force were submitted to one-way ANOVA and Bonferroni tests (α = 0.05). Polyurethane Nacional 40 PCF and pinus wood showed the highest values of insertion torque and pullout force, with significant statistical difference (P < 0.05) with other groups. The analysis showed stiffness materials with the highest values for primary stability.
STATEMENT OF PROBLEM
Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink.
In this study, Bicon® Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured.
MATERIAL AND METHODS
10 Bicon® implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length.
It was evident, that the amount of abutment sinking in Bicon® Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at 0.45 ± 0.09 mm.
Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location.
locking taper connection; abutment sinking; masticatory force; Bicon® Implant System
Tooth/implant supported fixed prostheses may present biomechanical design problems, as the implant is rigidly anchored within the alveolus, whereas the tooth is attached by the periodontal ligament to the bone allowing movement. Many clinicians prefer tooth/implant supported fixed prosthesis designs with rigid connectors. However, there are some doubts about the effect of attachment placement in different prosthesis designs. The purpose of this study was to examine the stresses accumulated around the implant and natural teeth under occlusal forces using three dimensional finite element analysis (3D FEA).
Materials and Methods:
In this study, different connection designs of tooth/implant fixed prosthesis in distal extension situations were investigated by 3D FEA. Three models with various connection designs were studied; in the first model an implant rigidly connected to an abutment, in the second and third models an implant connected to abutment tooth with nonrigid connector in the distal part of the tooth and mesial part of the implant. In each model, a screw type implant (5×11mm) and a mandibular second premolar were used. The stress values of these models loaded with vertical forces (250N) were analyzed.
There was no difference in stress distribution around the bone support of the implant. Maximum stress values were observed at the crestal bone of the implant. In all models, tooth movement was higher than implant movement.
There is no difference in using a rigid connector, non rigid connector in the distal surface of the tooth or in the mesial surface of an implant.
3D Finite Element Analysis; Fixed Prosthesis; Rigid Connection; Non- Rigid Connection
Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone.
Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bottom at 8 mm depth was reached. OMI designs were analyzed with a scan electron microscope (SEM).
Results: SEM images revealed a great variation in product refinement. In the whole sample, a cylindrical OMI shape was associated with higher POS (p<0.001) but lower IT (p=0.002) values. The outer and inner OMI diameters were design characteristics well correlated with POS, IT and TF values (ranging from 0.601 to 0.961). Greater thread depth was related to greater POS values (r= 0.628), although OMIs with similar POS values may have different IT values. Thread depth and pitch had some impact on POS. TF depended mainly on the OMI inner (r= 0.961) and outer diameters (r=0.892). A thread depth to outer diameter ratio close to 40% increased TF risk.
Conclusions: Although at the same insertion depth the OMI outer and inner diameters are the most important factors for primary stability, other OMI design characteristics (cylindrical vs. conical, thread design) may significantly affect primary stability and torsional fracture. This needs to be considered when selecting the appropriate OMI for the desired orthodontic procedures.
Key words:Orthodontic mini-implants, primary stability, insertion torque, pullout strength, torsional fracture.
The aim of this review paper is to define the fixation of the cemented stem. Polymethyl methacrylate, otherwise known as “bone cement”, has been used in the fixation of hip implants since the early 1960s. Sir John Charnley, the pioneer of modern hip replacement, incorporated the use of cement in the development of low frictional torque hip arthroplasty. In this paper, the concepts of femoral stem design and fixation, clinical results, and advances in understanding of the optimal use of cement are reviewed. The purpose of this paper is to help understanding and discussions on the thickness and the porosity of the cement mantle in total hip arthroplasty. Cement does not act as an adhesive, as sometimes thought, but relies on an interlocking fit to provide mechanical stability at the cement–bone interface, while at the prosthesis– cement interface it achieves stability by optimizing the fit of the implant in the cement mantle, such as in a tapered femoral stem.
Mechanical torque devices (MTDs) are one of the most commonly recommended devices used to deliver optimal torque to the screw of dental implants. Recently, high variability has been reported about the accuracy of spring-style mechanical torque devices (S-S MTDs). Joint stability and survival rate of fixed implant supported prosthesis depends on the accuracy of these devices. Currently, there is limited information on the steam sterilization influence on the accuracy of MTDs. The purpose of this study was to assess the effect of steam sterilization on the accuracy (±10% of the target torque) of spring-style mechanical torque devices for dental implants.
Materials and methods
Fifteen new S-S MTDs and their appropriate drivers from three different manufacturers (Nobel Biocare, Straumann [ITI], and Biomet 3i [3i]) were selected. Peak torque of devices (5 in each subgroup) was measured before and after autoclaving using a Tohnichi torque gauge. Descriptive statistical analysis was used and a repeated-measures ANOVA with type of device as a between-subject comparison was performed to assess the difference in accuracy among the three groups of spring-style mechanical torque devices after sterilization. A Bonferroni post hoc test was used to assess pairwise comparisons.
Before steam sterilization, all the tested devices stayed within 10% of their target values. After 100 sterilization cycles, results didn’t show any significant difference between raw and absolute error values in the Nobel Biocare and ITI devices; however the results demonstrated an increase of error values in the 3i group (P < 0.05). Raw error values increased with a predictable pattern in 3i devices and showed more than a 10% difference from target torque values (maximum difference of 14% from target torque was seen in 17% of peak torque measurements).
Within the limitation of this study, steam sterilization did not affect the accuracy (±10% of the target torque) of the Nobel Biocare and ITI MTDs. Raw error values increased with a predictable pattern in 3i devices and showed more than 10% difference from target torque values. Before expanding upon the clinical implications, the controlled and combined effect of aging (frequency of use) and steam sterilization needs more investigation.
accuracy; steam sterilization; mechanical torque devices; spring-style; dental implants
Background and aims. The aim of this study was to determine the stress patterns within an implant and the effect of different types of connections on load transfer.
Materials and methods. Three different types of implant-abutment connections were selected for this study. Sample A: 1.5-mm deep internal hex corresponding to a lead-in bevel; sample B: a tri-channel internal connection; and sample C: in-ternal Morse taper with 110 degrees of tapering and 6 anti-rotational grooves. Four types of loading conditions were simu-lated in a finite element model, with the maximum von Mises stress set as output variables.
Results. The maximum stress concentration at the inner surface of the fixtures was higher than the stress value in bone in all of the samples. Stress values in sample B were the lowest amongst all of the models. Any alterations in the amount and direction of the 100-N axial load resulted in an increase in fixture surfaces stress. Overall, the highest amount of stress (112 MPa) was detected in sample C at the inner surface of the fixture under a non-axial load of 300 N.
Conclusion. Stress concentration decreased when the internal surface area increased. Creating three or six stops in the internal surface of the fixtures resulted in a decrease in stress.
Biomechanics; dental implant/abutment; finite element; stress
The aim of this study was to investigate a comparison of implant bone bed preparation with Er,Cr:YSGG laser and conventional drills on the relationship between implant stability quotient (ISQ) values and implant insertion variables.
MATERIALS AND METHODS
Forty implants were inserted into two different types of pig rib bone. One group was prepared with conventional drills and a total of 20 implants were inserted into type I and type II bone. The other group was prepared with a Er,Cr:YSGG laser and a total of 20 implants were inserted into type I and type II bone. ISQ, maximum insertion torque, angular momentum, and insertion torque energy values were measured.
The mean values for variables were significantly higher in type I bone than in type II bone (P < .01). In type I bone, the ISQ values in the drill group were significantly higher than in the laser group (P < .05). In type II bone, the ISQ values in the laser group were significantly higher than in the drill group (P < .01). In both type I and type II bone, the maximum insertion torque, total energy, and total angular momentum values between the drill and laser groups did not differ significantly (P ≥ .05). The ISQ values were correlated with maximum insertion torque (P < .01, r = .731), total energy (P < .01, r = .696), and angular momentum (P < .01, r = .696).
Within the limitations of this study, the effects of bone bed preparation with Er,Cr:YSGG laser on the relationship between implant stability quotient (ISQ) values and implant insertion variables were comparable to those of drilling.
Er,Cr:YSGG laser; Titanium implant; Insertion torque resonance frequency analysis; Energy
Pink gingival esthetic especially on the anterior teeth has been an important success criterion in implant-supported restoration. Inter-implant papillae are a critical factor for implant esthetics, and various techniques for inter-implant papilla reconstruction have been introduced. The aim of this study is to suggest and evaluate a surgical technique for reconstructing inter-implant papillae.
A 28-year-old man had an implant placed on the #13 and #14 area. Four months after implant placement, a second stage surgery was planned for inter-implant papilla reconstruction. At the time of the abutment connection, I-type incisions were performed on the #13i & #14i area followed by full-thickness flap elevation and connection of a healing abutment on underlying fixtures without suture.
Two weeks after the second stage implant surgery, soft tissue augmentation between the two implants was achieved.
I-shaped incisions for papilla reconstruction performed during the second stage implant surgery were useful for inter-implant papilla reconstruction and showed a good esthetic result.
Dental esthetics; Dental implants; Dental papilla