Primary Stability Of Implants Research Articles

Comparison of the Mechanical and Osseointegrative Performance of Porous Tantalum and Titanium for Acetabular Implantation in Total Hip Arthroplasty: A Literature Review

Introduction: Stability of the acetabular component is a critical factor in the success of primary and revision total hip arthroplasty (THA) procedures. As such, the identification of implant surface characteristics that maximize stability of the acetabular cup is an important research objective. While titanium has historically been the most commonly used implant material, the proportion of THA procedures utilizing porous tantalum (PTa) implants has increased in recent years. The objective of this review is to examine the comparative mechanical and osseointegrative performance of PTa and porous titanium (PTi) and interpret these results in the context of primary and secondary stability of acetabular implants in THA, as characterized by strength of initial mechanical attachment and successful interlocking at the bone-implant interface, respectively. Methods: A literature search using a predetermined protocol and inclusion criteria yielded 7 articles presenting results of comparative testing of mechanical performance or osseointegration of PTa and PTi in the context of THA. Results: Neither PTa nor PTi presented consistently superior results in mechanical tests designed to correlate to primary stability at the metallo-biological surface nor in measures of osseointegration intended to represent secondary stability in THA. Discussion: In comparing PTa and PTi, it appears that the characteristics of the implant coating's pores may have a more significant impact on factors affecting the stability of an acetabular cup implant than the metal selected. However, determining the ideal pore morphology for this application is complex; pore characteristics that would suggest mechanical compatibility may conflict with those that would encourage more effective osseointegration. Conclusion: When extrapolated to be indicators of hypothetical clinical success, the results of this review are consistent with those of recently released macro-analyses of clinical outcomes: PTa and PTi acetabular cups, as they are currently manufactured, produce clinically equivalent outcomes. In the development and comparison of coating options, pore morphology and its complex effects on stability must be adequately accounted for; only then can we reach a faithful conclusion regarding the ideal porous adhesion surface for acetabular implant in THA.

Determining primary stability for adhesively stabilized dental implants

ObjectivesTo examine factors influencing the primary stability of dental implants when stabilized in over-sized osteotomies using a calcium phosphate-based adhesive cement was the objective.MethodsUsing implant removal torque measurements as a surrogate for primary stability, we examined the influence of implant design features (diameter, surface area, and thread design), along with cement gap size and curing time, on the resulting primary implant stability.ResultsRemoval torque values scaled with implant surface area and increasing implant diameters. Cement gap size did not alter the median removal torque values; however, larger gaps were associated with an increased spread of the measured values. Among the removal torque values measured, all were found to be above 32 Ncm which is an insertion torque threshold value commonly recommended for immediate loading protocols.ConclusionThe adhesive cement show potential for offering primary implant stability for different dental implant designs. In this study, the primary parameters influencing the measured removal torque values were the implant surface area and diameter. As the liquid cement prevents the use of insertion torque, considering the relationship between insertion and removal torque, removal torque can be considered a reliable surrogate for primary implant stability for bench and pre-clinical settings.Clinical relevanceAt present, the primary stability of dental implants is linked to the quality of the host bone, the drill protocol, and the specific implant design. The adhesive cement might find applications in future clinical settings for enhancing primary stability of implants under circumstances where this cannot be achieved conventionally.

Influence of implant length and insertion depth on primary stability of short dental implants: An in vitro study of a novel mandibular artificial bone model

Background/purposeDental implants are a mainstream solution for missing teeth. For the improvement of dental implant surface treatment and design, short dental implants have become an alternative to various complex bone augmentation procedures, especially those performed at the posterior region of both the maxilla and mandible. The objective of this study was to evaluate the effect of various insertion methods on the primary stability of short dental implants. Materials and methodsCommercial dental implants were inserted into artificial mandibular bone specimens using various insertion methods (equicrestal position, subcrestal position 1.5 mm, and lateral cortical anchorage) in accordance with an implant surgical guide. Insertion torque value (ITV) curves were recorded while implant procedures were performed. Both maximum ITVs (MITVs) and final ITVs (FITVs) were evaluated. Subsequently, Periotest values (PTVs) and implant stability quotients (ISQs) were measured for all specimens. A Kruskal–Wallis test was conducted to analyze the results for four primary stability parameters, and the Dunn test was used for a post hoc pairwise comparison when a difference was identified. ResultsFor all groups, their mean MITVs ranged from 33.6 to 59.4 N cm, whereas their mean FITVs ranged from 17.5 to 43.5 N cm. Insertion torque value, ISQ, and PTV decreased significantly when implants were inserted into subcrestal positions. When implants were inserted in the lateral bicortical position, the four aforementioned parameters yielded greater values. ConclusionWhen 6-mm short implants were inserted in a lateral cortical anchorage position, high primary stability was yielded.

Configurations of implant threads: A Review

The dental implants are used for replacement of missing teeth, and it’s have been widely used for restore the function, esthetic, speech, and patient confidence. It forms the contact between the implant and the bone. The implant threads are altered to improve the initial contact, primary stability, increase the surface area, and facilitate dissipation of loads at the implant and bone surface. Implant thread design is one of the key factors it determines the primary stability and stress distribution during osseointegration, the threaded implants are reduced both stress on bone and sliding distance between the implant and bone. The primary stability is play a important role in less bone quality, double and triple threaded implant increases the primary stability than single threaded implant, the implant threads distribute mechanical stress equally at bone implant interface, lead to stability of dental implants and less bone resorption and also higher thread profile improve the primary stability, the success or failure of implants depend on the thread designs and quality of bone.

Correlation between CT - derived bone density and optimal bone densities acquired from CBCT scans.

It is of interest to explore the correlation between preoperative bone density, assessed via CBCTT, and primary stability of dental implants, assessed by torque ratchet. A total of 100 patients who had implant placed were taken a sample for this retrospective study. The Hounsfield units (HU) derived preoperative bone densities at implant sites that were acquired with the help of the CBCT and the primary stability was achieved during the day of surgery. Both were compared to optimum bone densities. Statistical correlation was done between the HU and Bone density. Data suggests that evaluating HU values, along with other parameters, before performing implant surgery could lead to better primary implant stability.

Comparison of insertion torque, implant stability quotient and removal torque, in two different implant designs with and without osseodensification. - An ex vivo bench top study.

Primary stability is an important factor in influencing the outcome of dental implants. Osteotomy modification techniques mentioned, include osteotomes for bone condensation, under-preparation of osteotomy and Osseodensification (OD). The objective of our twin arm study was to assess how two different implant designs respond to conventional osteotomy drilling and how these values obtained compare with OD. The study comprised a total of 80 implants inserted in pig tibia bone. Group 1a (n=20) consisted of tapered internal implants and group 1b (n=20) consisted of tapered pro implants, both inserted with conventional drilling. Group 2a (n=20) consisted of tapered internal implants and group 2b (n=20) consisted of tapered pro implants, both inserted with OD. Each implant inserted was measured for implant stability quotient (ISQ), insertion torque and removal torque. Group 1a showed a significantly lower ISQ, mean insertion and removal torque and as compared to Group 1b. Group 2a and 2b had comparable mean values for all the three parameters. Inter-group comparison showed a higher ISQ and insertion torque value for group 2 than group 1. Intra-group assessment showed a significantly lower value for all parameters for sub-group a than b. OD enhances primary stability of implants in bone; but when no OD is used, the tapered pro implant design offers a better primary stability. This may be attributed to the active thread design.

The Effect of Osseodensification on Ridge Expansion, Intraosseous Temperature, and Primary Implant Stability: A Pilot Study on Bovine Ribs.

Osseodensification is a novel technique based on nonsubtractive drilling to preserve and condense bone during osteotomy preparation. The aim of this ex vivo study was to compare osseodensification and conventional extraction drilling technique with regard to intraosseous temperatures, expansion of alveolar ridge width, and primary implant stability using different implant geometries: tapered and straight walled. A total of 45 implant sites were prepared in bovine ribs following osseodensification and conventional protocols. Changes in intraosseous temperatures were recorded at 3 depths using thermocouples, and ridge width was measured at 2 different depths before and after osseodensification preparations. The primary implant stability was measured using peak insertion torque and the implant stability quotient (ISQ) following placement of straight and tapered implants. A significant change in temperature was recorded during site preparation for all techniques tested but not at all depths. Osseodensification recorded higher mean temperatures (42.7°C) than conventional drilling, particularly at the midroot level. Statistically significant ridge expansion was observed at both the crestal and apical levels in the osseodensification group. The ISQ values were significantly higher only for tapered implants placed in osseodensification sites when compared with conventional drilling sites; however, there was no difference in the primary stability between tapered and straight implants within the osseodensification group. Within the limitations of the present pilot study, osseodensification was found to increase the primary stability of straight-walled implants without overheating the bone and significantly expanded the ridge width. However, further investigation is required to determine the clinical significance of the bone expansion created by this new technique.

NARROW AND EXTRA-NARROW IMPLANTS TO RETAIN MANDIBULAR OVERDENTURES: A SPLIT-MOUTH STUDY

The aim of this study was to evaluate the primary and secondary stability and success rates of narrow and extra-narrow implants as retainers’ mandibular overdentures. Twelve fully edentulous mandible patients participated of this split-mouth randomized controlled clinical trial. One narrow (G1: 3.5-mm) and one extra-narrow implant (G2: 2.9-mm) were placed in each patient. Data regarding anesthetics use, incision size, number of drills used, and surgery duration were obtained. Moreover, a satisfaction VAS (visual analog scale) questionnaire was answered by the surgeon to evaluate clinician satisfaction with respect to characteristics of the surgical procedure. The implants stability quotient (ISQ) was measured immediately after the implants placement (T0) and after four months of the surgical procedure (T4). Additionally, the success rates of the implants during the osseointegration period were recorded. Regarding the characteristics of the surgical technique, statistically significant difference between groups was found for incision length - which was significantly smaller for group G2 - and insertion torque - which was significantly greater for group G1 (P-value = 0.025 and 0.005, respectively). There was no statistically significant difference for ISQ values between T0 and T4 within the same group (G1, p=0.510 and G2, p=0.116). The implant success rate was 100% for both groups. Therefore, narrow, and extra-narrow implants showed good primary and secondary stability, as well as short-term implant success rates, without statistically significant differences between them, and thus seem to be suitable alternatives to retain immediately loaded mandibular overdentures.

In-vitro investigation of primary stability of orthodontic mini implants with different lengths using resonance frequency analysis

Out of various ways of gaining anchorage, mini implants are gaining attention due to its minimum compliance and maximum curative effects.Mini implants are considered successful if they have sufficient primary stability that comes from mechanical interlocking of mini implant with the bone.Factors which influence the implant stability are bone physiology, implant size, shape and surface characteristics. Considering all other factors within anatomic constraints, what may play a role in primary stability of mini implants is length. Literature search to correlate mini implant length with primary stability was found to be insufficient and hence this study was undertaken. In this study, two goat jaws were subjected to spiral 3D CT scan and the areas with D2 bone density were identified and marked. In these D2 density marked areas, 30 implants of 1.5 x 6mm (GROUP A) and 30 implants of 1.5 x8mm (GROUP B) were placed. Their stability was measured by Radio Frequency Analysis using Osstell ISQ device with its Smart Peg. A connector was fabricated to make the fit of smart peg compatible with the head of mini implant. Readings were made in 5 different directions for each implant and their average value was considered as final reading. It was noted that primary mini implant stability is significantly higher (p 0.034) with GROUP B implants than with GROUP A implants. The increased length of mini-implants positively affects its primary stability and should be taken into consideration when implants are used as anchorage devices.

Analysis of bone stress and primary stability of a dental implant using strain and torque measurements

IntroductionThe consensus among researchers is that early failure of dental implants is due to the lack of primary stability and compressive stress on the peri-implant bone that exceeds the physiological tolerance. ObjectiveThe objective of this work is to propose a new methodology to quantify bone stress during dental implant insertion and to correlate it with primary stability. Materials and MethodsTitanium dental implants with a diameter of 3.75 mm were inserted in a 3.35 mm hole of a synthetic bone of polyurethane (PU) foam with a density of 20 PCF (0.32 g/cm3). During insertion, the insertion torque was measured with a digital torque meter and the bone strain was measured with strain gages located at 2, 4, 6, 8, and 10 mm from the coronal region. ResultsThe tests showed that the compressive strain is maximum in the third coronal region and decreases in the apical direction. The data also showed that there is a relationship between strain, insertion torque, and the primary stability of dental implants. ConclusionThe stress and strain on the bone progressively decreased from the coronal to the apical third. The maximum compressive stress (0.42 MPa) during insertion of the implant did not exceed bone strength. Insertion of 3.75 mm implants in type D2 bone with a 3.35 mm hole provides adequate primary stability without excessive compression of the bone. Clinical SignificanceFor the implant-bone combination used in the present study, the compressive stress generated during implant insertion did not exceed the physiological limit of cortical and medullary bone to the point of impairing osseointegration.

Novel approach to assessing the primary stability of dental implants under functional cyclic loading in vitro: a biomechanical pilot study using synthetic bone.

This pilot study was conducted to develop a novel test setup for the in vitro assessment of the primary stability of dental implants. This was achieved by characterising their long-term behaviour based on the continuous recording of micromotions resulting from dynamic and cyclic loading. Twenty screw implants, each 11 mm in length and either 3.8 mm (for premolars) or 4.3 mm (for molars) in diameter, were inserted into the posterior region of 5 synthetic mandibular models. Physiological masticatory loads were simulated by superimposing cyclic buccal-lingual movement of the mandible with a vertically applied masticatory force. Using an optical 3-dimensional (3D) measuring system, the micromotions of the dental crowns relative to the alveolar bone resulting from alternating off-centre loads were concurrently determined over 10,000 test cycles. The buccal-lingual deflections of the dental crowns significantly increased from cycle 10 to cycle 10,000 (P<0.05). The deflections increased sharply during the first 500 cycles before approaching a plateau. Premolars exhibited greater maximum deflections than molars. The bone regions located mesially and distally adjacent to the loaded implants demonstrated deflections that occurred synchronously and in the same direction as the applied loads. The overall spatial movement of the implants over time followed an hourglass-shaped loosening pattern with a characteristic pivot point 5.5±1.1 mm from the apical end. In synthetic mandibular models, the cyclic reciprocal loading of dental implants with an average masticatory force produces significant loosening. The evasive movements observed in the alveolar bone suggest that its anatomy and yielding could significantly influence the force distribution and, consequently, the mechanical behaviour of dental implants. The 3D visualisation of the overall implant movement under functional cyclic loading complements known methods and can contribute to the development of implant designs and surgical techniques by providing a more profound understanding of dynamic bone-implant interactions.

Effect of Implant Length and Insertion Depth on Primary Stability of Short Dental Implant

Purpose: To evaluate the effect of insertion depth, bone type, and implant diameter on the primary stability of short implants. Materials and Methods: Commercial dental implants with different lengths (6 and 8 mm; BLX, Straumann) were inserted into artificial bone specimens of good and poor quality at three different depth positions: equicrestal, 1-mm subcrestal, and 2-mm subcrestal. Insertion torque values were recorded spontaneously during the implant procedure. Both maximum insertion torque values (MITVs) and final insertion torque values (FITVs) were recorded. Subsequently, Periotest values (PTVs) and implant stability quotients (ISQs) were measured for all specimens. Results: The mean MITVs of all groups ranged from 31.8 to 46.2 Ncm. However, the mean FITVs of all groups ranged from 8.8 to 29 Ncm. Torque values decreased significantly when the implants were inserted into their final positions. When insertion depth was increased, the PTV and ISQ decreased. Long implants and implants inserted into good-quality bone yielded greater primary stability, and bone quality appeared to have a greater effect on primary stability. Conclusion: When 6-mm short implants are inserted in a subcrestal position, low primary stability may be yielded, particularly in poor-quality bone.

Development and validation of an algorithm to determine the minimal factors needed for non-invasive measurement of the in vivo primary stability of cementless hip implants.

Aseptic loosening is a frequent cause for revision of endoprosthesis. X-ray examinations like Radio-Stereometry-Analysis (RSA) are among the most widely used in vivo methods for its detection. Nevertheless, this method is not used routinely because of bone marker and related radiation exposure. This work aims at creating a new in vivo concept to detect implant stability measuring micromotions without x-ray and to develop a corresponding algorithm. Based on the assumption of contactless measurement, the input parameters for the algorithm are the distances of each ultrasound sensor to the object (prosthesis and bone) and its position. First, the number of parameters necessary for a precise reconstruction and measurement of micromotions between objects had to be defined. Therefore, the algorithm has been tested with simulations of these parameters. Two experimental measurements, either using contact sensors or ultrasound, were used to prove the accuracy of the algorithm. Simulations indicate a high accuracy with three distances as initial parameters for each object. Contact measurements show precise representation of micromotion, and the contactless measurements show the possibility of detecting various materials with a high resolution. This work lays the foundations for non-invasive detection of micromotions between the implant-bone interface.

Efficacy of Three Different Photobiomodulation Therapies on Primary and Secondary Implant Stability in D3 and D4 Bone Type- A Research Protocol for Randomised Controlled Trial

Introduction: Osseointegration is considered one of the most important deciding factors to check for implant stability, which decides successful outcome of the implant. Photobiomodulation has been used to improve the implant stability by enhancing osseointegration. Photobiomodulation (PBM) or Low-level Laser Therapy (LLLT) causes an enhanced effect in the bone implant contact. Need for the Study: There are no definitive therapies/protocol of LLLT in cases of bone density of D3 and D4. Also There are no studies in literature which compares the different laser settings so that a standardised setting can be established. Therefore, there is need to generate evidence whether reducing the number of appointments and reducing the amount of energy given in D3 and D4(compromised) bone can help achieve early loading in patients. Aim: To evaluate and compare the effect of three different photobiomodulation therapies on primary and secondary implant stability in D3 and D4 bone type in comparison to control group to achieve early loading. Materials and Methods: This randomized controlled, double blinded study allocated 108 patients having D3 or D4 bone according to Misch classification into six groups. Three different PBM therapy which is either Therapy A, B or C(placebo) will be used. The implant stability will be measured by Ostell meter in Implant Stability Quotients (ISQ) scale, immediately after surgery, after 3 weeks, after 12 weeks and after 6 months of surgery. The bone density will be measured before surgery and 3 months after surgery. Expected Outcome: At the end of the study, an evidence will be generated whether reducing the number of appointments and reducing the amount of energy given in D3 and D4(compromised) bone can help achieve early loading in patients. Patients treated using PBM therapy either protocol A or protocol B may show enhanced implant stability.

Comparison of Primary Stability of Two Different Implants DesignsA Prospective Clinical Study

Introduction: Any implant treatment must begin with successful implant integration. The effectiveness of implant osseointegration is determined by various factors, including implant design, implant diameter and density, and surgical technique. Osseointegration is dependent on implant design. Aim: To assess the primary stability of tapered and cylindrical implants by using Resonance Frequency Analysis (RFA) and Insertion Torque Values (ITV). Materials and Methods: This in-vivo, prospective clinical study was conducted in the Department of Prosthodontics at Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India in the month of November 2019. Twenty patients were selected for the study. Tapered Bioline implants (Bioline Dental GmbH &amp; Co. KGGermany) were spaced in 10 patients (group 1) and cylindrical Bioline implants (Bioline Dental GmbH &amp; Co. KG-Germany) in the other 10 patients (group 2). For both implant designs, primary stability was assessed immediately after implant placement using RFA by Osstell Mentor and ITV by a torque wrench. KolmogorovSmirnov test, Shapiro-Wilk test were used for checking normality. Mann Whitney U test, Independent t tests, Spearman correlation tests were done by using software Statistical Package for Social Sciences (SPSS) Version 23.0. Results: The mean ISQ (Implant Stability Quotient) for tapered implants was 76.6±2.3, and for cylindrical implants mean ISQ is 59.75±4.2 (p-value &lt;0.001). The mean ITV for tapered implants was 43.5±2.58 Ncm, and for cylindrical implants, the mean ITV was 33±4.21 Ncm (p-value &lt;0.001). The correlation between ITV and RFA was 0.928 which was highly significant (p&lt;0.001**). Conclusion: Within the scope of this investigation, tapered implants showed better primary stability than cylindrical-shaped implants as determined by ISQ and insertion torque values. ITV and ISQ values showed a positive correlation in determining the primary stability of implants.

Investigation to Predict Primary Implant Stability Using Frictional Resistance Torque of Tap Drilling.

The purpose of this experimental study was to investigate the correlation between the frictional resistance torque of tap drilling prior to implant placement and the primary stability after implant placement. Solid rigid polyurethane bone blocks of four different densities were used in this study. A computerized surgical implant motor device was utilized to measure the frictional resistance torque of tap drilling. After the tap torque was measured, the dental implants were inserted at the prepared sites. During the implantation, the insertion torque was recorded, and resonance frequency analysis was performed, the value of which was calculated as the implant stability quotient. Thereafter, the correlation between the tap torque and the primary stability of the implant was evaluated and compared with the standard drilling protocol. A significant positive correlation was found between the tap torque and insertion torque (Pearson's r = 0.88, P < 0.0001). Similarly, there was a positive correlation between the tap torque and implant stability quotient (Pearson's r = 0.69, P < 0.0001). These results suggest that measurement of the frictional resistance torque of tap drilling prior to implant placement could provide helpful information for implant primary stability.

Placement accuracy and primary stability of implants in the esthetic zone using dynamic and static computer-assisted navigation: A retrospective case-control study

Statement of problemBoth the placement accuracy and primary stability of implants are important to implant therapy in the esthetic zone. The effect of dynamic and static computer-assisted navigation on the primary stability of implants in the esthetic zone remains uncertain. PurposeThe purpose of this case-control study was to investigate the effect of dynamic and static computer-assisted navigation on the placement accuracy and primary stability of implants in the esthetic zone. Material and methodsPartially edentulous participants who received at least 1 implant in the anterior maxilla using either fully guided static or dynamic computer-assisted implant surgery (s-CAIS, d-CAIS) from January 2020 to February 2022 were screened. Participant demographic information, timing of implant placement, primary stability represented by the insertion torque value (ITV) in Ncm, and implant survival were collected from the treatment record. Bone quality at the implant sites was determined according to the Lekholm and Zarb classification. The accuracy of implant placement represented by the linear (platform: Dpl, mm; apex: Dap, mm) and angular deviations (axis: Dan, degree) between the planned and placed implants was evaluated based on the preoperative surgical plan and postoperative cone beam computed tomography (CBCT) data. A statistical analysis of the data was completed by using the chi-squared, Fisher exact, Student t, and Mann-Whitney U tests (α=.05). ResultsA total of 32 study participants (38 implants) were included. The groups of s-CAIS (16 participants, 18 implants) and d-CAIS (16 participants, 20 implants) were statistically comparable in sex (P=.072), age (P=.548), bone quality (P=.671), and timing of implant placement (P=.719). All implants survived during an average follow-up period of 13 months. The d-CAIS group showed close linear deviations (Dpl 1.07 ±0.57 mm, Dap 1.26 ±0.53 mm) but lower angular deviation (Dan 2.14 ±1.20 degrees) and primary stability (ITV 25.25 ±7.52 Ncm) than the s-CAIS group (Dpl 0.92 ±0.46 mm, Dap 1.31 ±0.43 mm, Dan 3.31 ±1.61 degrees, ITV 30.56 ±11.23 Ncm, PDpl=.613, PDap=.743, PDan=.016, PITV=.028). ConclusionsComparable linear positioning accuracy and higher angular deviation were found for implants placed in the esthetic zone by using s-CAIS than when using d-CAIS. Higher primary stability of implants may be achieved by using s-CAIS, as s-CAIS seemed to have higher osteotomy accuracy than d-CAIS.

Preclinical study probing primary stability of dental implants in synthetic and natural bones

AbstractThe natural bone is a biological example of a polymer–ceramic composite with a higher volume fraction of nanosized ceramic (around 65% hydroxyapatite) dispersed in polymer (collagenous) matrix. The loading of a dental implant involves the biomechanical interactions of the implant with such natural composites in the jaw bones of human subjects. In particular, the insertion torque responses of the dental implant are related to the implant design, in particular the external thread morphology, which influences the primary stability of the implant. In this study, the effect of the bone properties (polyurethane‐based synthetic bone, porcine and human cadaver lumbar bone) and clinically relevant implant driving protocols on the insertion and removal torques of newly designed implant variants (hybrid threads with macro‐ and micro‐threads) were assessed, quantitatively and qualitatively. It was observed that torque response increased with an increase in bone density, irrespective of the implant designs. The torque response of the implants in both synthetic and natural bones was benchmarked with the commercially available implant. The implants with bone cutting partial macro‐threads at the apical end without inter thread gap exhibited comparable clinically relevant results with respect to control implants and were found to be most suitable for implantation into natural bone.

Measurement of bone damage caused by quasi-static compressive loading-unloading to explore dental implants stability: Simultaneous use of in-vitro tests, μ-CT images, and digital volume correlation

Primary stability of dental implants is the initial mechanical engagement of the implant with its adjacent bone. Implantation and the subsequent loading may cause mechanical damage in the peripheral bone, which ultimately reduces the stability of the implant. This study aimed at evaluating primary stability of dental implants through applying stepwise compressive displacement-controlled, loading-unloading cycles to obtain overall stiffness and dissipated energy of the bone-implant structure; and quantifying induced plastic strains in surrounding bone using digital volume correlation (DVC) method, through comparing μCT images in different loading steps. To this end, dental implants were inserted into the cylindrical trabecular bones, then the bone-implant structure was undergone step-wise loading-unloading cycles, and μCT images were taken in some particular steps, then comparison was made between undeformed and deformed configurations using DVC to quantify plastic strain within the trabecular bone. Comparing stiffness reduction and dissipated energy values in different loading steps, obtained from the force-displacement curve in each loading step, revealed that the maximum displacement of 0.16 mm can be deemed as a safe threshold above which damages in peri-implant bone started to increase considerably (p < 0.05). In addition, it was found here that peri-implant bone strain linearly increased with decreasing bone-implant stiffness (p < 0.05). Moreover, strain concentration in peri-implant bone region showed that the plastic strain in trabecular bone spread up to a distance of about 2.5 mm away from the implant surface. Research of this kind can be used to optimize the design of dental implants, with the ultimate goal of improving their stability, also to validate in-silico models, e.g., micro-finite element models, which can help gain a deeper understanding of bone-implant construct behavior.

Macrogeometric Differentiation of Dental Implant Primary Stability: An In Vitro Study

To evaluate an alternative cutting, progressive thread design to increase primary stability in low-density bone. Four different implants with different macrogeometries (Nobel Biocare Active [NA] Internal RP implants [4.3 × 11.5 mm], Straumann BLX Roxolid RB implants [4.5 × 10 mm], Astra Tech Implant EV implants [4.2 × 11 mm], and PrimeTaper [PT 4.2 × 11 mm]) were placed in simulated osteotomies and extraction sockets in synthetic bone (Sawbones) according to the manufacturers' protocol. Insertion torque and ISQ values were measured using Implantmed Plus motor and Ostell IDX, respectively. Insertion time was recorded. Average values were calculated and compared using ANOVA and Tukey test. Insertion torque (range: 5 to 44 Ncm) increased with increasing synthetic bone density for all implants. Different ISQ values in synthetic low-density bone were not observed in higher-density synthetic bone. Insertion torque of all implants was reduced when implants were placed in simulated sockets compared to simulated osteotomies. In both low-density and higher-density synthetic bone, the primary stability of PrimeTaper implants with cutting and progressive thread design was equivalent to that of the Nobel Biocare NobelActive implant with compressive thread design and greater than the BLX implant with compressive thread design. Different implant macrogeometries obtain relatively high primary stability in low-density bone when measured by ISQ. Doublethread implant designs reduce insertion times in higher-density bone. A cutting and progressive compressing thread design provides density-sensing performance compared to aggressive condensing thread designs. This macrogeometry can achieve high primary stability associated with modest insertion torque compared to aggressive threaded implant designs known to attain the highest insertion torque. The presence of multiple cutting threads may offer advantages in obtaining primary stability in low-density bone.