Relationship between cortical bone thickness or computerized tomography‐derived bone density values and implant stability

Aims: To explore the relationship between primary implant stability and different parameters related to implant or bone properties. Materials and methods: Twenty‐four patients received a total of 136 Straumann SLActive implants. Resonance frequency analysis (RFA) was performed at implant placement, and RFA and Periotest (PTV) were scored at loading. Bone density [Hounsfield (HU) scores] and coronal cortical thickness at osteotomy sites were measured from pre‐operative computerized tomography scans. Results: Implant length, diameter or the presence of bony dehiscence did not have a significant effect on the mean RFA scores at implant insertion. Significant linear relations were found between RFA or PTV scores and HU values (P<0.05), or cortical bone thickness (P<0.05), both at insertion as well as at loading. Conclusion: RFA and PTV scores can be predicted based on implant and especially bone related factors. To cite this article:
Merheb J, Van Assche N, Coucke W, Jacobs R, Naert I, Quirynen M. Relationship between cortical bone thickness or computerized tomography‐derived bone density values and implant stability.
Clin. Oral Impl. Res. 21 , 2010; 612–617.
doi: 10.1111/j.1600‐0501.2009.01880.x     

Implant stability in relation to osseointegration: an experimental study in the Labrador dog

Objective: Resonance frequency analysis (RFA) is supposed to determine implant stability. The relation between RFA and the degree of bone-to-implant contact (BIC), however, is unclear. The objective of the present experiment was to evaluate RFA values in relation to osseointegration.
Material and methods: In 20 Labrador dogs, all mandibular premolars were extracted bilaterally. After 3 months, four transmucosal screw-shaped experimental implants were placed in each mandibular premolar region. The implants (12 mm length, Ø 4.1 mm, insertion depth 9 mm) were either SLA surface or turned surface implants. The animals were divided into four groups (five dogs in each group) to study healing following implant installation at 2 h, 4 days, 1, 2, 4, 6, 8 and 12 weeks. Two experimental implants of each type were installed in each edentulous premolar region. A plaque control program was initiated 2 weeks after each implant installation. RFA assessments were performed at the time of implant installation, at one to three occasions during the monitoring period and at the termination of the experiment. At the end of the experiment, the dogs were sacrificed and each implant site was dissected and processed for histological analysis. The results of the histological analysis, i.e. marginal bone level, degree of osseointegration (BIC%) and bone density, were compared with the corresponding Implant Stability Quotient (ISQ) values of the RFA assessment.
Results: No correlations between histological parameters of osseointegration and ISQ values could be identified. Marginal bone level changes, differences in BIC% and bone density were not reflected in the RFA at any time-point during the 12-week monitoring period.
Conclusion: The value of RFA to predict implant stability over time and to determine at which time-point an implant may be exposed to functional load has to be questioned.     

A comparative study on the initial stability of different implants placed above the bone level using resonance frequency analysis

PURPOSE

This study evaluated the initial stability of different implants placed above the bone level in different types of bone.

MATERIALS AND METHODS

As described by Lekholm and Zarb, cortical layers of bovine bone specimens were trimmed to a thickness of 2 mm, 1 mm or totally removed to reproduce bone types II, III, and IV respectively. Three Implant system (Brånemark System® Mk III TiUnite™, Straumann Standard Implant SLA®, and Astra Tech Microthread™-OsseoSpeed™) were tested. Control group implants were placed in level with the bone, while test group implants were placed 1, 2, 3, and 4 mm above the bone level. Initial stability was evaluated by resonance frequency analysis. Data was statistically analyzed by one-way analysis of variance in confidence level of 95%. The effective implant length and the Implant Stability Quotient (ISQ) were compared using simple linear regression analysis.

RESULTS

In the control group, there was a significant difference in the ISQ values of the 3 implants in bone types III and IV (P<.05). The ISQ values of each implant decreased with increased effective implant length in all types of bone. In type II bone, the decrease in ISQ value per 1-mm increase in effective implant length of the Brånemark and Astra implants was less than that of the Straumann implant. In bone types III and IV, this value in the Astra implant was less than that in the other 2 implants.

CONCLUSION

The initial stability was much affected by the implant design in bone types III, IV and the implant design such as the short pitch interval was beneficial to the initial stability of implants placed above the bone level.     

Evaluation of the primary stability in dental implants placed in low density bone with a new drilling technique,Osseodensification: an in vitro study

Background Primary stability is an important key determinant of implant osseointegration. We investigated approaches to improve primary implant stability using a new drilling technique termed osseodensification (OD), which was compared with the conventional under-drilling (UD) method utilized for low-density bones. Material and Methods We placed 55 conical internal connection implants in each group, in 30 low-density sections of pig tibia. The implants were placed using twist drill bits in both groups; groups Under Drilling (UD) and Osseodensification (OD) included bone sections subjected to conventional UD and OD drilling, respectively. Before placing the implants, we randomized the bone sections that were to receive these implants to avoid sample bias. We evaluated various primary stability parameters, such as implant insertion torque and resonance frequency analysis (RFA) measurements. Results The results showed that compared with implants placed using the UD technique, those placed using the OD technique were associated with significantly higher primary stability. The mean insertion torque of the implants was 8.87±6.17 Ncm in group 1 (UD) and 21.72±17.14 Ncm in group 2 (OD). The mean RFA was 65.16±7.45 ISQ in group 1 (UD) and 69.75±6.79 ISQ in group 2 (OD). Conclusions The implant insertion torque and RFA values were significantly higher in OD group than in UD. Therefore, compared with UD, OD improves primary stability in low-density bones (based on torque and RFA measurements). Key words:Osseodensification, primary stability, low density bone, RFA.     

Influence of surgical technique,implant shape and diameter on the primary stability in cancellous bone

Summary Achievement of primary stability during surgical placement of dental implants is one of the most important factors for successful osseointegration depending on various anatomical, surgical and implant‐related factors. Resonance frequency analysis (RFA) has been shown as a non‐invasive and objective technique for measuring the stability of implants. The aim of this study was to evaluate the effect of some surgical and implant‐related factors in enhancing primary stability and to estimate a correlation between RFA and insertion torque (IT) in proximal regions of cow ribs representing cancellous bone. Fifteen implant beds were prepared in the most proximal region of six fresh cow ribs. Ninety implants with three different shapes and two different diameters were placed with two different surgical techniques, and the primary stability was compared using RFA and IT. Significantly higher RFA and IT values were achieved when under‐dimensioned drilling was used as the surgical method (P < 0·01); significantly higher IT values were obtained with the use of wider implants (P < 0·01) and partially conical Astra Tech implants showed the highest IT values (P < 0·01). When all the implants were considered, significant correlations between the IT and RFA values were noted (%40·6, P < 0·05). Partially conical implants with a wide diameter to be placed with the modified surgical technique proposed appear to be useful in enhancing the primary stability in cancellous bone.     

Is the osseointegration of immediately and delayed loaded implants the same?—comparison of the implant stability during a 3‐month healing period in a prospective study

Objectives: The objectives of the present study were (1) to compare the stability of delayed loaded (DL) and immediately loaded (IL) ITI SLA implants during the first 3 months of the healing period using resonance frequency analysis (RFA) and (2) to determine the factors that affect implant stability during the healing period.
Materials and methods: To compare implant stability, RFA was performed on two groups of patients (12 patients received 25 IL implants and 47 patients received 79 DL implants) with a total 104 ITI SLA implants. Implant stability was measured directly by RFA at implant placement and consecutively once a week for 12 weeks. Statistical analyses were carried out to study implant stability differences between IL and DL groups.
Results: One of the 25 implants in the IL group failed, and no implant was lost in the DL group. Implant stability between the IL and DL groups showed a statistically significant difference ( P <0.05). The mean implant stability quotient of all measured implants from implant insertion to 12 weeks was 72.88 ± 5.39 for the DL and 75.86 ± 3.60 for the IL types. The lowest stability was at 4 weeks for DL implants (mean: 71.58 ± 5.11) and 2 weeks for IL implants (mean: 71.33 ± 2.97). In both groups, bone types I and II showed higher implant stability than bone type III ( P <0.05).
Conclusions: The findings of this study indicate that differences in osseointegration between IL and DL implants may be predicted according to differential implant stability.     

Five‐year outcomes of a randomized clinical trial comparing bone‐level implants with either submerged or transmucosal healing

Aim

To evaluate the long‐term hard and soft tissue peri‐implant tissue stability of bone‐level implants using a different implant placement protocol (submerged versus transmucosal).

Materials and methods

This study was partly a subset analysis of a multicentre study where in 40 patients, a single bone‐level implant with platform switching and a conical implant‐abutment interface was placed either submerged or transmucosal in non‐molar sites. Changes in the peri‐implant tissues between implant placement and 5 years were assessed clinically and radiologically. Patient‐related outcomes were also recorded.

Results

Thirty patients completed the 5‐year follow‐up. Implant survival rate was 100%. The mean radiographic changes in crestal bone levels between baseline and 5 years were 0.59 (0.92) mm and 0.78 (1.03) mm for the submerged and the transmucosal groups, respectively. No statistical significant differences were found between the groups for any of the investigated variables. Peri‐implantitis, defined as changes in the level of crestal bone of ≥2 mm together with bleeding on probing, was only diagnosed in one patient. Patients in both groups were highly satisfied with the treatment received.

Conclusions

Bone‐level implants with submerged or transmucosal healing protocols demonstrated similar outcomes after 5 years. Both protocols yielded optimal clinical and radiographic results when bone‐level implants were placed in non‐molar positions for single tooth replacement.     

Evaluation of Primary Stability of Self‐Tapping and Non‐Self‐Tapping Dental Implants. A 12‐Week Clinical Study

Purpose: The aim of this study was to investigate the relationship between surgical techniques and implant macro‐design (self‐tapping/non‐self‐tapping) for the optimization of implant stability in the low‐density bone present in the posterior maxilla using resonance frequency analysis (RFA). Materials and Methods: A total of 102 implants were studied. Fifty‐six self‐tapping BlueSkyBredent® (Bredent GmbH&Co.Kg®, Senden, Germany) and 56 non‐self‐tapping Standard Plus Straumann® (Institut Straumann AG®, Waldenburg, Switzerland) were placed in the posterior segment of the maxilla. Implants of both types were placed in sites prepared with either lateral bone‐condensing or with bone‐drilling techniques. Implant stability measurements were performed using RFA immediately after implant placement and weekly during a 12‐week follow‐up period. Results: Both types of implants placed after bone condensing achieved significantly higher stability immediately after surgery, as well as during the entire 12‐week observation period compared with those placed following bone drilling. After bone condensation, there were no significant differences in primary stability or in implant stability after the first week between both implant types. From 2 to 12 postoperative weeks, significantly higher stability was shown by self‐tapping implants. After bone drilling, self‐tapping implants achieved significantly higher stability than non‐self‐tapping implants during the entire follow‐up period. Conclusions: The outcomes of the present study indicate that bone drilling is not an effective technique for improving implant stability and, following this technique, the use of self‐tapping implants is highly recommended. Implant stability optimization in the soft bone can be achieved by lateral bone‐condensing technique, regardless of implant macro‐design.     

Experimental study on penetration of dental implants into the maxillary sinus in different depths

The exposing of dental implant into the maxillary sinus combined with membrane perforation might increase risks of implant failure and sinus complications.

Objective

The purpose of this study was to investigate the effects of the dental implant penetration into the maxillary sinus cavity in different depths on osseointegration and sinus health in a dog model.

Material and Methods

Sixteen titanium implants were placed in the bilateral maxillary molar areas of eight adult mongrel dogs, which were randomly divided into four groups according to the different penetrating extents of implants into the sinus cavities (group A: 0 mm; group B: 1 mm; group C: 2 mm; group D: 3 mm). The block biopsies were harvested five months after surgery and evaluated by radiographic observation and histological analysis.

Results

No signs of inflammatory reactions were observed in any maxillary sinus of the eight dogs. The tips of the implants with penetrating depth of 1 mm and 2 mm were found to be fully covered with newly formed membrane and partially with new bone. The tips of the implants with penetrating depth over 3 mm were exposed in the sinus cavity and showed no membrane or bone coverage. No significant differences were found among groups regarding implant stability, bone-to-implant contact (BIC) and bone area in the implant threads (BA).

Conclusions

Despite the protrusion extents, penetration of dental implant into the maxillary sinus with membrane perforation does not compromise the sinus health and the implant osseointegration in canine.     

Early functional loading of unsplinted roughened surface implants with mandibular overdentures 2 weeks after surgery

Background: Before early functional loading of unsplinted implants with mandibular overdentures can become widespread, more clinical studies are needed to investigate the success of the approach. Purpose: To evaluate the success rates of two types of roughened titanium surface implants with early 2‐week functional loading of paired mandibular interforaminal implants with overdentures. Materials and Methods: Random allocation divided 24 strictly selected edentulous participants into two groups, with each group to receive a different implant system (ITI Dental Implant System, Straumann AG, Waldenburg, Switzerland; or Southern Implant System, Southern Implants, Irene, South Africa). Two implants were placed in the anterior mandible of all participants using one‐stage standardized surgical procedures. Previously constructed conventional mandibular dentures (opposing maxillary complete dentures) were temporarily relined and worn by the participants for the first 2 weeks; participants used a soft diet. Two weeks after implant surgery and following some mucosal healing, the mandibular dentures had the tissue conditioner removed and the appropriate matrices included for an unsplinted prosthodontic design. Results: No implant from either group was lost. Resonance frequency analysis (RFA) indicated higher primary stability at surgery for the Southern group than for the ITI group, with a statistically significant difference between the groups throughout the study period. The drop in RF values between surgery and 6 weeks was significant and was greater for the Southern group. RFA also indicated stabilized osseointegration between 6 to 12 and 12 to 52 weeks, with no participant showing any decrease in those values over time. Participants with type 3 bone showed a significant improvement in RF values between 12 and 52 weeks, eventually matching those of participants with type 2 bone. There were no significant differences in marginal bone loss, periimplant parameters, or prosthodontic maintenance between the groups over the study period. Conclusions: Using only strict patient selection criteria, 1‐year follow‐up data indicate that early functional loading of ITI and Southern implants with mandibular two‐implant overdentures is possible as early as 2 weeks after implant surgery.     

Primary stability and self-tapping blades: biomechanical assessment of dental implants in medium-density bone

Aim: The aim of this biomechanical study was to assess the influence of self‐tapping blades in terms of primary implant stability between implants with self‐tapping blades and implants without self‐tapping blades using five different analytic methods, especially in medium‐density bone. Materials and methods: Two different types of dental implants (4 × 10 mm) were tested: self‐tapping and non‐self‐tapping. The fixture design including thread profiles was exactly the same between the two groups; the only difference was the presence of cutting blades on one half of the apical portion of the implant body. Solid rigid polyurethane blocks with corresponding densities were selected to simulate medium‐density bone. Five mechanical assessments (insertion torque, resonance frequency analysis [RFA], reverse torque, pull‐out and push in test) were performed for primary stability. Results: Implants without self‐tapping blades showed significantly higher values (P<0.001) in four biomechanical assessments, except RFA (P=0.684). However, a statistically significant correlation could not be detected between insertion torque values with the four different outcome variables (P>0.05). Conclusions: The outcomes of the present study indicate that the implant body design without self‐tapping blades has a good primary stability compared with that with self‐tapping blades in medium‐density bone. Considering the RFA, a distinct layer of cortical bone on marginal bone will yield implant stability quotient values similar to those in medium‐bone density when implants have the same diameter. To cite this article:
Kim Y‐S, Lim Y‐J. Primary stability and self‐tapping blades: biomechanical assessment of dental implants in medium‐density bone.
Clin. Oral Impl. Res. 22 , 2011; 1179–1184.
doi: 10.1111/j.1600‐0501.2010.02089.x     

Clinical evaluation of osseointegration using resonance frequency analysis

The stability of the implant at the time of placement and during the development of the osseointegration process are the two major issues governing the implant survival. Implant stability is a mechanical phenomenon related to local factors such as bone quality, quantity, type of placement technique and type of implant used. The application of a user-friendly, clinically reliable, non-invasive method to assess implant stability and the osseointegration process is considered highly desirable. Resonance frequency analysis (RFA) is one such method which shows almost perfect reproducibility and repeatability after statistical analysis. The aim of this paper is to review the various methods used to assess implant stability and on the currently used RFA method which is being highly accepted in the recent times.Key Words: Implant stability, resonance frequency analysis, RFA     

Micromotion analysis of different implant configuration,bone density,and crestal cortical bone thickness in immediately loaded mandibular full‐arch implant restorations: A nonlinear finite element study

Background

Excessive micromotion may cause failure of osseointegration between the implant and bone.

Purpose

This study investigated the effects of implant configuration, bone density, and crestal cortical bone thickness on micromotion in immediately loaded mandibular full‐arch implant restorations.

Materials and Methods

A finite element model of the edentulous mandible was constructed. Four implants were inserted in two different configurations, which were four parallel implants or tilted distal implants according to the all‐on‐four concept. Different cancellous bone densities and crestal cortical bone thicknesses were simulated. The framework was made of acrylic resin. A vertical load of 200 N was applied at the cantilever or on the distal implant (noncantilever loading).

Results

The maximum extent of micromotion was significantly influenced by the density of cancellous bone and to a lesser extent by implant configuration and the crestal cortical bone thickness. The all‐on‐four configuration showed less micromotion than the parallel implant configuration in some circumstances. The maximum micromotion detected with noncantilever loading was less than 1/3 of that with cantilever loading.

Conclusions

Implant configuration had a limited influence on micromotion. Avoiding cantilever loading during the healing period should effectively reduce the risk of excessive micromotion in patients with low‐density cancellous bone and thin crestal cortical bone.     

Integration of fluoridated implants in onlay autogenous bone grafts – An experimental study in the rabbit tibia

IntroductionBone augmentation before treatment with endosseous implants is a common procedure for rehabilitation of the edentulous jaw. Both machined and surface modified implants have been used in one-stage and two-stage surgery protocols with varying results and survival rates. The influence of surface modification on the integration of implants has been documented in both non-grafted and grafted bone. The aim of this study was to compare the integration and stability of surface modified fluoridated vs. machined implants when placed simultaneously with an onlay bone graft.Material and methodsEight rabbits were used in this study. A disc shaped bone graft was harvested from each side of the sagittal suture of the calvarial bone and fixed bi-cortically to the proximal tibial metaphysis by means of a dental implant, 9 mm long and 3.5 mm in diameter with a smooth machined surface as control and a blasted, fluoridated surface as test. Test and control sides were randomised. After a healing time of 8 weeks, the rabbits were sacrificed and the implants were removed en block for light microscopic analysis. Bone to implant contact (BIC) was registered as well as the amount of bone filling a rectangle indicating a region of interest (ROI) in the grafted area. Resonance frequency analysis (RFA) was conducted both at the time of surgery and at the end of the study.ResultsOur results showed statistically significant differences in BIC within the grafted area and the total bone to implant contact between the test and control sides in favour of the surface modified implants. The bone area filling the threads within a region of interest showed no statistically significant difference between the test and control sides. RFA showed higher implant stability with significant differences at the time of sacrifice in favour of the fluoridated implants.ConclusionSurface modified fluoridated implants showed a higher degree of osseointegration and stability in onlay bone grafts compared with control implants with machined surface texture.     

Impact of?crestal and subcrestal implant placement in peri-implant bone: A prospective comparative study

Background

To assess the influence of the crestal or subcrestal placement of implants upon peri-implant bone loss over 12 months of follow-up.

Material and Methods

Twenty-six patients with a single hopeless tooth were recruited in the Oral Surgery Unit (Valencia University, Valencia, Spain). The patients were randomized into two treatment groups: group A (implants placed at crestal level) or group B (implants placed at subcrestal level). Control visits were conducted by a trained clinician at the time of implant placement and 12 months after loading. A previously established standard protocol was used to compile general data on all patients (sex and age, implant length and diameter, and brushing frequency). Implant success rate, peri-implant bone loss and the treatment of the exposed implant surface were studied. The level of statistical significance was defined as 5% (α=0.05).

Results

Twenty-three patients (8 males and 15 females, mean age 49.8±11.6 years, range 28-75 years) were included in the final data analyses, while three were excluded. All the included subjects were nonsmokers with a brushing frequency of up to twice a day in 85.7% of the cases. The 23 implants comprised 10 crestal implants and 13 subcrestal implants. After implant placement, the mean bone position with respect to the implant platform in group A was 0.0 mm versus 2.16±0.88 mm in group B. After 12 months of follow-up, the mean bone positions were -0.06±1.11 mm and 0.95±1.50 mm, respectively - this representing a bone loss of 0.06±1.11 mm in the case of the crestal implants and of 1.22±1.06 mm in the case of the subcrestal implants (p=0.014). Four crestal implants and 5 subcrestal implants presented peri-implant bone levels below the platform, leaving a mean exposed treated surface of 1.13 mm and 0.57 mm, respectively. The implant osseointegration success rate at 12 months was 100% in both groups.

Conclusions

Within the limitations of this study, bone loss was found to be greater in the case of the subcrestal implants, though from the clinical perspective these implants presented bone levels above the implant platform after 12 months of follow-up. Key words:Immediate implants, tooth extraction, dental implants, single-tooth, crestal bone, placement level.     

Does bone mineral density influence the primary stability of dental implants? A systematic review

Objective: The aim of this systematic review was to investigate the influence of bone mineral density on the primary stability of dental implants. Material and methods: A search of health science databases (Cochrane Library, MEDLINE‐PubMed, ISI Web of Knowledge, EMBASE, LILACS) and grey literature was performed, including papers published until January 2011. The main key words used were “bone density” (MeSH/DeCS), “dental implant” (MeSH/DeCS), “implant stability”, “implant stability quotient”, “ISQ”, “resonance frequency analysis”, “RFA”, “Osstell”, “Periotest value”, “PTV”, “Periostest”, “insertion torque”, “placement torque”, “cutting torque”. The inclusion criteria comprised observational clinical studies performed in patients who received dental implants for rehabilitation; studies that evaluated the association between bone mineral density and implant primary stability; bone density assessment performed by measurement of Hounsfield units using cone beam computed tomography; and dental implant primary stability evaluated by ISQ value, PTV value or insertion torque measurement. The articles selected were carefully read and classified as low, moderate and high methodological quality, and data of interest were tabulated. Results: Ten articles met the inclusion criteria, but only seven were included because of overlapping patients. They were classified as low or moderate methodological quality and control of bias, and presented positive association between primary stability and bone density. Conclusions: There is a positive association between implant primary stability and bone mineral density of the receptor site. However, the methodological quality and control of bias of the studies should be improved to produce stronger evidences. To cite this article:
Marquezan M, Osório A, Sant'Anna E, Souza MM, Maia L, Does bone mineral density influence the primary stability of dental implants? A systematic review.
Clin. Oral Impl. Res. 23 , 2012; 767–774.
doi: 10.1111/j.1600‐0501.2011.02228.x     

The Effects of Cortical Bone Thickness and Trabecular Bone Strength on Noninvasive Measures of the Implant Primary Stability Using Synthetic Bone Models

Purpose: This study investigated how the primary stability of a dental implant as measured by the insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ) is affected by varying thicknesses of cortical bone and strengths of trabecular bone using synthetic bone models. Materials and Methods: Four synthetic cortical shells (with thicknesses of 0, 1, 2, and 3 mm) were attached to four cellular rigid polyurethane foams (with elastic moduli of 137, 47.5, 23, and 12.4 MPa) and one open‐cell rigid polyurethane foam which mimic the osteoporotic bone (with an elastic modulus 6.5 MPa), to represent the jawbones with various cortical bone thicknesses and strengths of trabecular bone. A total of 60 bone specimens accompanied with implants was examined by a torque meter, Osstell resonance frequency analyzer, and Periotest electronic device. All data were statistically analyzed by two‐way analysis of variance. In addition, second‐order nonlinear regression was utilized to assess the correlations of the primary implant stability with the four cortex thicknesses and five strengths of trabecular bone. Results: ITV, ISQ, and PTV differed significantly (p < .05) and were strongly correlated with the thickness of cortical bone (R² > 0.9) and the elastic modulus of trabecular bone (R² = 0.74–0.99). Conclusions: The initial stability at the time of implant placement is influenced by both the cortical bone thickness and the strength of trabecular bone; however, these factors are mostly nonlinearly correlated with ITV, PTV, and ISQ. Using ITV and PTV seems more suitable for identifying the primary implant stability in osteoporotic bone with a thin cortex.     

Biomechanical effects of the implant material and implant–abutment interface in immediately loaded small-diameter implants

Objective

Small-diameter implants have been available since the 1990s, but few studies have analyzed their mechanical properties. This study evaluated the effects of the implant material and the implant–abutment connection designs on the primary stability and the marginal bone strain of small-diameter implant subject to immediate loading.

Materials and methods

Insertion torque value (ITV), implant stability quotient (ISQ), and Periotest value (PTV) of three implant systems with four parameters (titanium, titanium alloy, internal and external hexagon connections) were measured after placing implants into artificial type 2 jaw-bone models. Specimens were tested under both vertical and oblique static loads at 190 N. Peak values of the principal bone strain were recorded and analyzed statistically by the Kruskal–Wallis test and multiple-comparisons Bonferroni test.

Results

PTV and ISQ were higher for the NIOSM311 (internal-hex and Ti alloy) and FOSM311 (external-hex and pure Ti) implants, respectively, than for the NOSM311 (external-hex and Ti alloy) implant. Under vertical loading the peak value of peri-implant bone strains did not differ significantly among these three implant systems. However, the peak bone strains were at least 32 % lower for the NIOSM311 and FOSM311 implants than for the NOSM311 implant under lateral loading.

Conclusions

The implant material and the implant–abutment connection design significantly influence the peri-implant bone strain of immediately loaded small-diameter implants, but barely affect their primary stability.

Clinical Relevance

A commercially pure titanium implant with an internal connection has the potential to reduce the risk of implant failure of small-diameter implant related to biomechanical complications.     

Reconstruction of the atrophic edentulous maxilla with free iliac crest grafts and implants: a 3-year report of a prospective clinical study

Purpose: The purpose of this study was to perform a longitudinal follow-up study of implant stability in grafted maxillae with the aid of clinical, radiological, and resonance frequency analysis (RFA) parameters. Materials and Methods: The atrophic edentulous maxillae in 29 patients were reconstructed with free iliac crest grafts using onlay/inlay or interpositional grafting techniques. The endpoint of the resorption pattern in the maxilla determined the grafting technique used. Endosteal implants were placed after 6 months of bone-graft healing. Implant stability was measured four times using RFA: when the implants were placed, after 6 to 8 months of healing, after 6 months and 3 years of bridge loading. Individual checkups were performed at the two later RFA registrations after removal of the supraconstructions (Procera® Implant Bridge, Nobel Biocare AB, Göteborg, Sweden). Radiological follow up of marginal bone level was performed annually. Results: Twenty-five patients remained for the follow-up period. A total of 192 implants were placed and with a survival rate of 90% at the 3-year follow up. Women and an implant position with a class 6 resorption prior to reconstruction were factors with significant increased risk for implant failure (multivariate logistic regression). Twelve of the 20 failed implants were lost before loading (early failures). The change in the marginal bone level was 0.3 ± 0.3 mm between baseline (bridge delivery) and the 3-year follow up. The implant stability quotient (ISQ) value for all implants differed significantly between abutment connection (60.2 ± 7.3) and after 6 months of bridge loading (62.5 ± 5.5) (Wilcoxon signed ranks test for paired data, p=.05) but were nonsignificant between 6 months of bridge loading and 3 years of bridge loading (61.8 ± 5.5). There was a significant difference between successful and failed implants when the ISQ values were compared for individual implants at placement (Mann-Whitney U test, p=.004). All 25 patients were provided with fixed implant bridges at the time of the 3-year follow up. Conclusion: This clinical follow up using radiological examinations and RFA measurements indicates a predictable and stable long-term result for patients with atrophic edentulous maxillae reconstructed with autogenous bone and with delayed placement of endosteal implants. The ISQ value at the time of placement can probably serve as an indicator of level of risk for implant failure.     

Comparison of implant stability by means of resonance frequency analysis for flapless and conventionally inserted implants

Background: Resonance frequency analysis (RFA) is a noninvasive technique for the quantitative assessment of implant stability. Information on the implant stability quotient (ISQ) of transmucosally inserted implants is limited. Purpose: The aim of this investigation was to compare the ISQ of conventionally inserted implants by raising a muco‐periostal flap with implants inserted using a flapless procedure. Materials and Methods: Forty elderly patients with complete edentulous maxilla were consecutively admitted for treatment with implant‐supported prostheses. A computer tomography was obtained for the computer‐assisted implant planning. One hundred ten implants were placed conventionally in 23 patients (flap‐group) and 85 implants in 17 patients by means of the flapless method (flapless‐group) using a stereolithographic template. RFA measurements were performed after implant placement (baseline) and after a healing time of 12 weeks (reentry). Results: All implants exhibited clinically and radiographically successful osseointegration. Bone level did not change significantly neither for genders nor type of surgical protocol. Mean ISQ values of the flapless‐group were significantly higher at baseline (p < .001) and at reentry (p < .001) compared with the flap‐group. The ISQ values were significantly lower at reentry compared with baseline for the flap‐group (p = .028) but not for the flapless‐group. This group showed a moderate, but insignificant increase. RFA measurements of males resulted in ISQ values that were thoroughly higher as compared with females at both time‐points in both groups. Correlation between RFA and bone level was not found. Conclusions: The flapless procedure showed favorable conditions with regard to implant stability and crestal bone level. Some changes of the ISQ values that represent primary (mechanical) and secondary (bone remodeling) implant stability were observed in slight favor of the flapless method and male patients. In properly planned and well‐selected cases, the minimal invasive transmucosal technique using a drill‐guide is a safe procedure.