Is insertion torque correlated to bone-implant contact percentage in the early healing period? A histological and histomorphometrical evaluation of 17 human-retrieved dental implants

Bone quality affects stability of orthodontic miniscrews

The objective of this study was to evaluate the effect of bone–miniscrew contact percentage (BMC%) and bone quality and quantity on orthodontic miniscrew stability and the maximum insertion torque value (ITV). Orthodontic miniscrews of five different dimensions and several bovine iliac bone specimens were used in the evaluation. Miniscrews of each dimension group were inserted into 20 positions in bovine iliac bone specimens. The experiment was divided into three parts: (1) Bone quality and quantity were evaluated using cone-beam computed tomography (CBCT) and microcomputed tomography. (2) The 3D BMC% was calculated. (3) The ITVs during miniscrew insertion were recorded to evaluate the stability of the orthodontic miniscrews. The results indicated that longer and thicker miniscrews enabled higher ITVs. CBCT was used to accurately measure cortical bone thickness (r = 0.939, P < 0.05) and to predict the bone volume fraction of cancellous bone (r = 0.752, P < 0.05). BMC% was significantly influenced by miniscrew length. The contribution of cortical bone thickness to the ITV is greater than that of cancellous bone structure, and the contribution of cortical bone thickness to BMC% is greater than that of cancellous bone structure. Finally, the higher is BMC%, the greater is the ITV. This study concludes that use of CBCT may predict the mechanical stability of orthodontic miniscrews.

Bone stress and damage distributions during dental implant insertion: a novel dynamic FEM analysis

The objective of this research was to evaluate the stress and damage occurring on the bone model of D2 quality during implant insertion procedure using a novel dynamic finite element analysis (FEA) modeling. Three-dimensional finite element method was used to simulate the implant placement into the mandible. The cross-sectional model of the implant was created in SolidWorks 2007 software. The implant model was created to resemble a commercially available fine thread bone level dental implant (Bilimplant®, Turkey). 3 D bone models created with and without cortical bone drilling were specified according to D2 bone (Misch's Bone Classification) with a 1.5 mm cortical bone thickness. The stress patterns in both cancellous and cortical crestal bone were examined during implant insertion by using a novel dynamic FEA in ABACUS/Explicit (ABAQUS/Explicit version 6.14). According to the results of the dynamic FEA, it was reduced stress and damage significantly on the crestal bone region using the cortical drill before the implantation. Also, implant placement time was shorter when the cortical drill was used. The present research is a pilot study using a novel dynamic FEM to model and simulate the dental implant insertion process. This study showed that the use of cortical drills decreased the stress in the bone, especially crestal region, and shortened the whole implant insertion time.

3D full-field strain in bone-implant and bone-tooth constructs and their morphological influential factors

The biomechanics of bone-tooth and bone-implant interfaces affects the outcomes of several dental treatments, such as implant placement, because bone, tooth and periodontal ligament are living tissues that adapt to the changes in mechanical stimulations. In this work, mechanical testing coupled with micro-CT was performed on human cadaveric mandibular bone-tooth and bone-implant constructs. Using digital volume correlation, the 3D full-field strain in bone under implant loading and tooth loading was measured. Concurrently, bone morphology and bone-implant and bone-tooth contact were also measured through the analysis of micro-CT images. The results show that strain in bone increased when a tooth was replaced by a dental implant. Strain concentration was observed in peri-implant bone, as well as in the buccal bone plate, which is also the clinically-observed bone resorption area after implant placement. Decreasing implant stability measurements (resonance frequency analysis and torque test) indicated increased peri-implant strain, but their relationships may not be linear. Peri-implant bone strain linearly increased with decreasing bone-implant contact (BIC) ratio. It also linearly decreased with increasing bone-tooth/bone-implant contact ratio. The high strain in the buccal bone plate linearly increased with decreasing buccal bone plate thickness. The results of this study revealed 3D full-field strain in bone-tooth and bone-implant constructs, as well as their several morphological influential factors.

Mechanical testing of antimicrobial biocomposite coating on metallic medical implants as drug delivery system

Post-operative infection often occurs following orthopedic and dental implant placement requiring systemically administered antibiotics. However, this does not provide long-term protection. Over the last few decades, alternative methods involving slow drug delivery systems based on biodegradable poly-lactic acid and antibiotic loaded hydroxyapatite microspheres were developed to prevent post-operative infection. In this study, thermally anodised and untreated Ti6Al4V discs were coated with Poly-Lactic Acid (PLA) containing Gentamicin (Gm) antibiotic-loaded coralline Hydroxyapatite (HAp) are investigated. Following chemical characterization, mechanical properties of the coated samples were measured using nanoindentation and scratch tests to determine the elastic modulus, hardness and bonding adhesion between film and substrate. It was found that PLA biocomposite multilayered films were around 400nm thick and the influence and effect of the substrate were clearly observed during the nanoindentation studies with heavier loads. Scratch tests of PLA coated samples conducted at ~160nm depth showed the minimal difference in the measured friction between Gm and non Gm containing films. It is also observed that the hardness values of PLA film coated anodised samples ranged from 0.45 to 1.9GPa (dependent on the applied loads) against untreated coated samples which ranged from 0.28 to 0.8GPa.

Mechanical and Biological Advantages of a Tri-Oval Implant Design

Of all geometric shapes, a tri-oval one may be the strongest because of its capacity to bear large loads with neither rotation nor deformation. Here, we modified the external shape of a dental implant from circular to tri-oval, aiming to create a combination of high strain and low strain peri-implant environment that would ensure both primary implant stability and rapid osseointegration, respectively. Using in vivo mouse models, we tested the effects of this geometric alteration on implant survival and osseointegration over time. The maxima regions of tri-oval implants provided superior primary stability without increasing insertion torque. The minima regions of tri-oval implants presented low compressive strain and significantly less osteocyte apoptosis, which led to minimal bone resorption compared to the round implants. The rate of new bone accrual was also faster around the tri-oval implants. We further subjected both round and tri-oval implants to occlusal loading immediately after placement. In contrast to the round implants that exhibited a significant dip in stability that eventually led to their failure, the tri-oval implants maintained their stability throughout the osseointegration period. Collectively, these multiscale biomechanical analyses demonstrated the superior in vivo performance of the tri-oval implant design.

Retrospective radiographic observational study of 1692 Straumann tissue-level dental implants over 10 years: I. Implant survival and loss pattern

BACKGROUND

Implant dentistry is progressing based on extensive scientific results including preclinical and clinical studies. Researchers and clinicians have focused on implant designs and surface characteristics, which has resulted in various features being developed and introduced for enhancing osseointegration and reducing complications.

PURPOSE

The purpose of this study was to determine the cumulative survival rates of Straumann tissue-level dental implants over a 10-year period and identify the patterns of implant loss at a single research institution.

MATERIALS AND METHODS

In total, 1692 implants were installed in 881 patients who visited the Department of Periodontology, Dental Hospital, Yonsei University, Seoul from January 2003 to December 2009. Cases in which the implant was completely removed were defined as implant failures. Electronic or paper charts and radiographs were used to determine whether the implants failed. The survival rate of implants was analyzed using lifetime tables and Kaplan-Meier survival estimates. Log-rank test and Cox regression with shared frailty were used to analyze the risk factors and the types of implant failure.

RESULTS

The 10-year cumulative survival rates were 98.23% and 95.70% at the implant and patient levels, respectively. Before installing a prosthesis (defined as the early stage), 13 implants in 10 patients were removed, while eight implants in seven patients were removed after completing a prosthesis (defined as the late stage). The cumulative survival rate was related to the implant diameter, length, site, and insertion torque. Most implant failures within 1 year were attributable to osseointegration failure. There were several cases of failure in the late stage without apparent marginal bone loss.

CONCLUSION

Straumann tissue-level dental implants showed low failure rates and can be considered a useful long-term treatment option. The length, placement site, and insertion torque might affect implant survival.

Effects of Condensation on Peri-implant Bone Density and Remodeling

Bone condensation is thought to densify interfacial bone and thus improve implant primary stability, but scant data substantiate either claim. We developed a murine oral implant model to test these hypotheses. Osteotomies were created in healed maxillary extraction sites 1) by drilling or 2) by drilling followed by stepwise condensation with tapered osteotomes. Condensation increased interfacial bone density, as measured by a significant change in bone volume/total volume and trabecular spacing, but it simultaneously damaged the bone. On postimplant day 1, the condensed bone interface exhibited microfractures and osteoclast activity. Finite element modeling, mechanical testing, and immunohistochemical analyses at multiple time points throughout the osseointegration period demonstrated that condensation caused very high interfacial strains, marginal bone resorption, and no improvement in implant stability. Collectively, these multiscale analyses demonstrate that condensation does not positively contribute to implant stability.

Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

Background

This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA).

Material and Methods

Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]).

Results

The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p<0.05). However, no statistically significant differences were obtained between ISQ values at 10 or 12 mm drilling depths (p>0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p >0.05).

Conclusions

Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values.

Key words:Implant stability quotient, overdrilling, primary stability, resonance frequency analysis, torque.

Combined microcomputed tomography, biomechanical and histomorphometric analysis of the peri-implant bone: a pilot study in minipig model

OBJECTIVES

To present a practical approach that combines biomechanical tests, microcomputed tomography (μCT) and histomorphometry, providing quantitative results on bone structure and mechanical properties in a minipig model, in order to investigate the specific response to an innovative dental biomaterial.

METHODS

Titanium implants with innovative three-dimensional scaffolds were inserted in the tibias of 4 minipigs. Primary stability and osseointegration were investigated by means of insertion torque (IT) values, resonance frequency analysis (RFA), bone-to-implant contact (BIC), bone mineral density (BMD) and stereological measures of trabecular bone.

RESULTS

A significant positive correlation was found between IT and RFA (r=0.980, p=0.0001). BMD at the implant sites was 18% less than the reference values (p=0.0156). Peri-implant Tb.Th was 50% higher, while Tb.N was 50% lower than the reference zone (p<0.003) and they were negatively correlated (r=-0.897, p=0.006).

SIGNIFICANCE

μCT increases evaluation throughput and offers the possibility for qualitative three-dimensional recording of the bone-implant system as well as for non-destructive evaluation of bone architecture and mineral density, in combination with conventional analysis methods. The proposed multimodal approach allows to improve accuracy and reproducibility for peri-implant bone measurements and could support future investigations.

Evaluation of the insertion torque, implant stability quotient and drilled hole quality for different drill design: an in vitro Investigation

OBJECTIVE

The purpose of the present study was to compare the insertion torque and implant stability quotient between different drill design for implant site preparation.

MATERIALS AND METHODS

Synthetic blocks of bone (type I density) were used for drilling procedures. Three groups were evaluated: Group G1 - drilling with a single bur for a 4.2 mm conical implant; Group G2 and Group G3 - drilling with three consecutive burs for a 4.1 mm cylindrical implant and for a 4.3 mm conical implant respectively. For each group, 15 drilling procedures were performed without irrigation for 10-mm in-depth. The drilled hole quality (HQ) after the osteotomy for implant site preparation was measured in the five-first holes through a fully automated roundness/cylindricity instrument at three levels (top, middle, and bottom of the site). The insertion torque value (ITV) was achieved with a computed torquimeter and the implant stability quotient (ISQ) values were measured using a resonance frequency apparatus.

RESULTS

The single drill (group 1) achieved a significantly higher ITV and ISQ than the multiple drills for osteotomy (groups 2 and 3). Group 1 and 3 displayed significantly better HQ than group 2.

CONCLUSIONS

Within the limitations of the study, the results suggest that the hole quality, in addition to the insertion torque, may significantly affect implant primary stability.

Impact of Bone Quality and Implant Type on the Primary Stability: An Experimental Study Using Bovine Bone

The purpose of this in vitro study was to compare the primary stability and removal torque of bone level and tissue level implants in different bone qualities. Twenty tissue level and bone level implants (3.3 × 10 mm and 4.1 × 10 mm) were used for assessing the stability in type II and type IV bone. Forty bovine rib blocks were used in this study. The primary stability of the implant was measured by the resonance frequency using an Osstel device. The removal torque values (RTV) of the implants was assessed using a digital torque gauge instrument. The implant stability quotient (ISQ) values and the RTV showed a marginally higher stability with bone level implants as compared to tissue level implants. However, these differences were not statistically significant in both type of bone used (P &gt; 0.05). On the other hand, compared to type IV, type II bone showed significant differences in the ISQ (P &lt; 0.01) and RTV (P &lt; 0.001) of bone level and tissue level implants. The study concluded that bone quality is an important factor in establishing primary stability than the implant dimension. Bone level and tissue level implants of same dimensions can be selected based on the esthetic demands since they showed similar mechanical properties.

Biomechanical evaluation of resistance to insertion torque of different implant systems and insertion driver types

PURPOSE

The aim of this study was to quantify the resistance to torque of different implant systems and their connection devices using in vitro torsion tests.

MATERIALS AND METHODS

Three internal connection systems, 1 conventional system with internal torque and 1 conventional system with a mounting device used as a control group were tested on 5 groups.

RESULTS

Rupture torque (in newton meter): Biomet 3i Certain group 4 showed a statistically significant higher average (2.65 N·m), followed in order by Biomet 3i Osseotite group 5 (2.18 N·m), Bonelike group 2 (1.80 N·m). Angle deformation/rupture: all groups obtained similar values, without significant differences. Elastic limit (in newton meter): Bonelike group 2 (1.06 N·m) showed similar behavior to group 1 (1.39 N·m) (Nobel Biocare), without significant differences, whereas Bonelike group 3 showed a significantly lower value (0.93 N·m). Maximum torque (in newton meter): Biomet 3i Certain group 4 showed significantly higher values in relation to other groups (2.80 N·m).

CONCLUSIONS

The greater contact area the system is built on, the greater resistance against insertion torque, as internal hexagon implants with a greater contact area and external hexagon implants using a mounting device showed higher resistance to insertion torque.

Influence of surface treatment on osseointegration of dental implants: histological, histomorphometric and radiological analysis in vivo

OBJECTIVE

The aim of this article is to compare the influence of surface treatment on the integration (at 2, 4 and 8 weeks) of 120 dental implants inserted in 60 tibiae of rabbits.

MATERIALS AND METHODS

Four different surfaces were double-blind tested: blasted, acid-etched and discrete crystal deposition (DCD) (group A); blasted (group B); acid-etched (group C) and blasted and acid-etched (group D). Bone-to-implant contact plus reverse torque and bone level were measured at the time of implant insertion and at 14, 28 and 56 days of healing.

RESULTS

Group A showed the highest early and late bone-to-implant contact (BIC) values: 40.8 ± 2.3 % at 14 days decreasing to 27.7 ± 1.1 % after 28 days and 39.4 ± 1.4 % at 56 days. For group B, the average BIC values at 14, 28 and 56 days were 23.34 ± 2.1, 23.77 ± 1.9 and 29.47 ± 1.7 %, respectively. Group C showed a value of 25.72 ± 2.3 % after 14 days of integration, 34.92 ± 2.2 % at 28 days and 32.91 ± 1.6 % at 56 days. Group D showed a BIC value of 32 ± 2.5 % at 14 days, 32.85 ± 1.4 % at 28 days and 34.04 ± 2.3 % at 56 days. In the scanning electron microscopy (SEM) analysis, no statistically significant differences were found. The Ca/P ratio values were 1.762 for surface A, 1.625 for surface B, 1.663 for surface C and finally 1.722 for surface D.

CONCLUSIONS

Therefore, we conclude that even if there seems to be a tendency to obtain better BIC results with surface A (blasted-etched and covered with hydroxyapatite (HA)), no statistical differences were obtained in this study.

CLINICAL RELEVANCE

The study shows the influence of different implant surfaces in increasing osseointegation for immediate loading implants.

Resonance frequency analysis, insertion torque, and bone to implant contact of 4 implant surfaces: comparison and correlation study in sheep

INTRODUCTION

Primary stability is evaluated using resonance frequency analysis (RFA) and insertion torque (IT). Although there is a strong correlation between RFA and IT, studies failed to find a correlation between RFA and bone to implant contact (BIC) or IT and BIC.

OBJECTIVE

To compare RFA, IT, and BIC of SLA, SLActive, Euroteknika, and TiUnite implant surfaces and evaluate the correlation between them.

MATERIALS AND METHODS

Thirty-two implants were placed in 8 sheep. RFA and IT were recorded. Animals were killed at 1 and 2 months.

RESULTS

A significant difference was found in RFA between the 4 surfaces. No significant difference was found for IT. Mean BIC was different between all 4 surfaces. A significant positive correlation was found between RFA and IT with SLA. No significant correlation was found between RFA and BIC and between IT and BIC at 1 and 2 months.

CONCLUSIONS

Implants with 4 different surfaces have similar IT values but different RFA and BIC. Additionally irrespective of the implant surface, there is no correlation between IT and BIC and between RFA and BIC.

Understanding mechanisms and factors related to implant fixation; a model study of removal torque

Osseointegration is a prerequisite for achieving a stable long-term fixation and load-bearing capacity of bone anchored implants. Removal torque measurements are often used experimentally to evaluate the fixation of osseointegrated screw-shaped implants. However, a detailed understanding of the way different factors influence the result of removal torque measurements is lacking. The present study aims to identify the main factors contributing to anchorage. Individual factors important for implant fixation were identified using a model system with an experimental design in which cylindrical or screw-shaped samples were embedded in thermosetting polymers, in order to eliminate biological variation. Within the limits of the present study, it is concluded that surface topography and the mechanical properties of the medium surrounding the implant affect the maximum removal torque. In addition to displaying effects individually, these factors demonstrate interplay between them. The rotational speed was found not to influence the removal torque measurements within the investigated range.

Correlation between the bone density recorded by a computerized implant motor and by a histomorphometric analysis: a preliminary in vitro study on bovine ribs

PURPOSE

The purpose of the present preliminary in vitro study on bovine ribs was to validate a new intraoperative site-specific classification of bone Density Index (IDI), obtained by an innovative computerized implant motor, by correlating these data with the data obtained by the histomorphometrical evaluation of the same samples.

MATERIALS AND METHODS

Five segments of bovine ribs were used, and a total of 22 perforations were performed. A computerized implant motor ("Torque Measuring Motor") was used to evaluate the bone density, which was classified into four classes: ID1, ID2, ID3, and ID4. Histomorphometrical analysis of bone density, expressed as percentage of bony trabeculae over the total biopsy area, was also performed. The data of bone density obtained by the implant motor were statistically correlated with the histomorphometrical results.

RESULTS

A significant positive correlation was found between the bone density measured by the implant motor and the bone density assessed by histomorphometry (r = 0.89, p < .0001). Moreover, a significant positive correlation in D1, D2, and D4, whereas a negative, not significant correlation in D3 was found.

CONCLUSION

Within the limitations of this in vitro study, the intraoperative site-specific classification of bone density, obtained with this innovative system, could be helpful for the clinician to tailor the surgical protocol to the different situations in implant dentistry.

Evaluation of the correlation between insertion torque and primary stability of dental implants using a block bone test

PURPOSE

Implant stability at the time of surgery is crucial for the long-term success of dental implants. Primary stability is considered of paramount importance to achieve osseointegration. The purpose of the present study was to investigate the correlation between the insertion torque and primary stability of dental implants using artificial bone blocks with different bone densities and compositions to mimic different circumstances that are encountered in routine daily clinical settings.

METHODS

In order to validate the objectives, various sized holes were made in bone blocks with different bone densities (#10, #20, #30, #40, and #50) using a surgical drill and insertion torque together with implant stability quotient (ISQ) values that were measured using the Osstell Mentor. The experimental groups under evaluation were subdivided into 5 subgroups according to the circumstances.

RESULTS

In group 1, the mean insertion torque and ISQ values increased as the density of the bone blocks increased. For group 2, the mean insertion torque values decreased as the final drill size expanded, but this was not the case for the ISQ values. The mean insertion torque values in group 3 increased with the thickness of the cortical bone, and the same was true for the ISQ values. For group 4, the mean insertion torque values increased as the cancellous bone density increased, but the correlation with the ISQ values was weak. Finally, in group 5, the mean insertion torque decreased as the final drill size increased, but the correlation with the ISQ value was weak.

CONCLUSIONS

Within the limitations of the study, it was concluded that primary stability does not simply depend on the insertion torque, but also on the bone quality.

Human cadaver study evaluating a new measurement technique for graft volumes after sinus floor elevation

PURPOSE

Volumetric data can be used as complementary information to characterize grafting materials. The aim of this cadaveric study was to analyze a noncommercial measurement technique based on the novel concept of an "interactive rigid registration algorithm" (IRRA). Parameters analyzed included the reproducibility of IRRA measurements and their reliability in comparison with the established measurement technique of "region growing segmentation thresholding" (RGST).

MATERIALS AND METHODS

Three human skulls were used to simulate a total of 18 sinus grafts, using three incremental grafting procedures in each sinus (three skulls ×t wo sinuses × three grafting increments). Radiopaque impression material was used for the simulated grafts, whose volumes were recorded by computed tomography from three different tilt angles. The reproducibility of IRRA measurements and the reliability of volumetric results obtained with both the IRRA and RGST techniques were evaluated by appropriate intraclass correlation coefficient (ICC) and Bland-Altman analysis.

RESULTS

ICC greater than 0.9 indicated close to perfect agreement of the results obtained with both methods and good reproducibility of the IRRA measurements. Bland-Altman analysis demonstrated good inter-method and intramethod agreement.

CONCLUSIONS

The IRRA measurement technique can be recommended as a noninvasive tool to evaluate graft volumes in human maxillary sinuses.

Relation between insertion torque and bone-implant contact percentage: an artificial bone study

OBJECTIVES

The purpose of this study was to determine the correlation between the peak insertion torque value (ITV) of a dental implant and the bone-implant contact percentage (BIC%).

MATERIAL AND METHODS

Dental implants were inserted into specimens comprising a 2-mm-thick artificial cortical shell representing cortical bone and artificial foam bone representing cancellous bone with four densities (groups 1 to 4--0.32, 0.20, 0.16, and 0.12 g/cm(3)). Each specimen with an inserted implant was subjected to micro-computed tomography (micro-CT) scanning, from which the 3D BIC% values were calculated. Pearson's correlation coefficients (r) between the ITV and BIC% were calculated.

RESULTS

The ITVs in groups 1 to 4 were 56.2 ± 4.6 (mean±standard deviation), 45.6 ± 0.9, 43.3 ± 4.3, and 38.5 ± 3.4 N cm, respectively, and the corresponding BIC% values were 41.5 ± 0.5%, 39.0 ± 1.0%, 30.8 ± 1.1%, and 26.2 ± 1.6%. Pearson's correlation coefficient between the ITV and BIC% was r = 0.797 (P < 0.0001).

CONCLUSION

The initial implant stability, quantified as the ITV, was strongly positively correlated with the 3D BIC% obtained from micro-CT images.

CLINICAL RELEVANCE

The ITV of a dental implant can be used to predict the initial BIC%; this information may provide the clinician with important information on the optimal loading time.

Histological evaluation of the peri-implant tissues of three human-retrieved Straumann implants

The most frequently-used histological parameters to define dental implant osseointegration include bone-to-implant contact and quantitative and qualitative assessments of the surrounding tissue (rate of mineralized/non-mineralized tissue and proportion of lamellar and woven bone compared to soft tissue or bone marrow). The aim of this paper was to present the histological features of the bone tissue surrounding three well-functioning Straumann SLA and SLActive implants placed in two patients after 12 and 60 months of loading. The percentage of osseointegration ranged from 66.4% and 71.9% for SLA surfaces, to 88.3% for the SLActive implant. Such results confirm that osseointegration occurs with high rates of bone-to-implant contact in humans, and that implants can be similarly clinically successful, although they show different bone-to-implant contact values.

Implant insertional torque values predict outcomes

PURPOSE

To study the relationships between insertional torque values (ITVs) recorded during implant placement and implant healing times and cumulative survival rates.

MATERIALS AND METHODS

This retrospective study evaluated 174 Osseotite 6.0-mm-diameter, straight-wall, threaded dental implants (BIOMET 3i, Palm Beach Gardens, FL) placed in 172 consecutive patients by the primary author. All implants were placed immediately into mandibular first or second molar extraction sockets after extraction. ITVs were recorded at placement. Implants were evaluated 3 months after surgery before discharge to restorative dentists for restoration. The post-restorative follow-up ranged from 2 years 1 month to 4 years 8 months (median and mean of 3 years 1 month [SD, 4.95]).

RESULTS

Of the implants, 3% (n = 5) were removed at the time of surgical placement because of perceived clinical mobility of the implants within the osteotomies. The implants that were stable at the time of implant placement (n = 169) were placed into 1 of 3 groups relative to the specific ITVs at implant placement: group 1, low ITV, 29% (n = 49); group 2, medium ITV, 23% (n = 39); and group 3, high ITV, 48% (n = 81). Cumulative survival rates for each group were 86% for low ITV, 90% for medium ITV, and 96% for high ITV (P = .0302). At the scheduled 3 months' follow-up visit, 33% of the low ITVs, 21% of the medium ITVs, and 5% of the high ITVs required an additional 3 months of healing.

CONCLUSION

In this study ITVs measured through surgical handpieces during implant placement provided meaningful real-time feedback that aided the surgeon regarding implant survival and determining unloaded healing times on a case-by-case basis.

Influence of lateral pressure to the implant bed on osseointegration: an experimental study in dogs

AIM

To study osseointegration and bone-level changes at implants installed using either a standard or a reduced diameter bur for implant bed preparation.

MATERIAL AND METHODS

In six Labrador dogs, the first and second premolars were extracted bilaterally. Subsequently, mesial roots of the first molars were endodontically treated and distal roots, including the corresponding part of the crown, were extracted. After 3 months of healing, flaps were elevated and recipient sites were prepared in all experimental sites. The control site was prepared using a standard procedure, while the test site was prepared using a drill with a 0.2 mm reduced diameter than the standard one used in the contra-lateral side. After 4 months of healing, the animals were euthanized and biopsies were obtained for histological processing and evaluation.

RESULTS

With the exception of one implant that was lost, all implants were integrated in mineralized bone. The alveolar crest underwent resorption at control as well as at test sites (buccal aspect ∼1 mm). The most coronal contact of bone-to-implant was located between 1.2 and 1.6 mm at the test and between 1.3 and 1.7 mm at the control sites. Bone-to-implant contact percentage was between 49% and 67%. No statistically significant differences were found for any of the outcome variables.

CONCLUSIONS

After 4 months of healing, lateral pressure to the implant bed as reflected by higher insertion torques (36 vs. 15 Ncm in the premolar and 19 vs. 7 Ncm in the molar regions) did not affect the bone-to-implant contact.

Influence of high insertion torque on implant placement: an anisotropic bone stress analysis

The aim of this study was to evaluate the influence of the high values of insertion torques on the stress and strain distribution in cortical and cancellous bones. Based on tomography imaging, a representative mathematical model of a partial maxilla was built using Mimics 11.11 and Solid Works 2010 softwares. Six models were built and each of them received an implant with one of the following insertion torques: 30, 40, 50, 60, 70 or 80 Ncm on the external hexagon. The cortical and cancellous bones were considered anisotropic. The bone/implant interface was considered perfectly bonded. The numerical analysis was carried out using Ansys Workbench 10.0. The convergence of analysis (6%) drove the mesh refinement. Maximum principal stress (σmax) and maximum principal strain (εmax) were obtained for cortical and cancellous bones around to implant. Pearson's correlation test was used to determine the correlation between insertion torque and stress concentration in the periimplant bone tissue, considering the significance level at 5%. The increase in the insertion torque generated an increase in the σmax and εmax values for cortical and cancellous bone. The σmax was smaller for the cancellous bone, with greater stress variation among the insertion torques. The εmax was higher in the cancellous bone in comparison to the cortical bone. According to the methodology used and the limits of this study, it can be concluded that higher insertion torques increased tensile and compressive stress concentrations in the periimplant bone tissue.