The effects of cortical bone thickness and trabecular bone strength on noninvasive measures of the implant primary stability using synthetic bone models

Anatomic variability of the human femur and its implications for the use of artificial bones in biomechanical testing

Aside from human bones, epoxy-based synthetic bones are regarded as the gold standard for biomechanical testing os osteosyntheses. There is a significant discrepancy in biomechanical testing between the determination of fracture stability due to implant treatment in experimental methods and their ability to predict the outcome of stability and fracture healing in a patient. One possible explanation for this disparity is the absence of population-specific variables such as age, gender, and ethnicity in artificial bone, which may influence the geometry and mechanical properties of bone. The goal of this review was to determine whether commercially available artificial bones adequately represent human anatomical variability for mechanical testing of femoral osteosyntheses. To summarize, the availability of suitable bone surrogates currently limits the validity of mechanical evaluations of implant-bone constructs. The currently available synthetic bones neither accurately reflect the local mechanical properties of human bone, nor adequately represent the necessary variability between various populations, limiting their generalized clinical relevance.

An In Vitro Evaluation of Periotest Implant Stability Measurements Taken on Implant Retained Crowns and Healing Abutments

OBJECTIVE

To assess the reliability of implant stability measurements recorded with the Periotest device and to investigate the differences in values when these measurements were taken on implant retained crowns and healing abutments.

MATERIALS AND METHODS

Fifty-six implants in eight synthetic bone blocks were used to carry out implant stability measurements using the Periotest device by two different operators. Each block constituted an example of bone of density D1, D2, D3, or D4, and two blocks of each density were used. The healing abutments placed were of a height to allow approximately 6 mm of the implant-abutment complex to be supracrestal and temporary crowns were made to match the dimensions of an average central incisor. Descriptive statistics were used to describe the perio test values (PTVs) at each of the different heights on the implant abutments and implant crowns. Means for each site were calculated and distribution of data assessed using the Kruskal Wallis test. The interclass correlation coefficient (ICC) was used to determine the relationship between the PTVs recorded on the implant abutments and implant crowns.

RESULTS

The mean PTV (±standard devidation) recorded across all sites was 5.57 ± 11.643 on the implant abutments, and 12.27 ± 11.735 on the temporary crowns. Excellent/good inter-operator ICCs were recorded for the mid-abutment site in all bone blocks D1-D4 (ICC = 0.814, p < 0.001, ICC = 0.922, p < 0.001, ICC = 0.938, p < 0.001, ICC = 776, p < 0.001). For mid crown sites, ICC between operators was excellent/good only for recordings in D2 bone (ICC = 0.897, p < 0.001).

CONCLUSIONS

Periotest device seems to be able to reliably measure implant stability across all types of bones when the implant stability is assessed at approximately 3 mm coronal to the implant platform for abutments and 4.5 mm for implant supported single crowns.

Preoperative assessment of bone density for dental implantation: a comparative study of three different ROI methods

BACKGROUND

Dental cone beam computed tomography (CBCT) is commonly used to evaluate cancellous bone density before dental implant surgery. However, to our knowledge, no measurement approach has been standardized yet. This study aimed to evaluate the relationship between three different regions of interest (ROI) methods on cancellous bone density at the dental implant site using dental CBCT images.

METHODS

Patients' dental CBCT images (n = 300) obtained before dental implant surgery were processed using Mimics (Materialise, Leuven, Belgium). At the potential implant sites, the rectangle, cylinder, and surrounding cylinder ROI methods were used to measure bone density. Repeated measures one-way analysis of variance was performed to compare the three ROI methods in terms of measurement results. Pearson correlation analysis was performed to identify the likely pair-wise correlations between the three ROI methods.

RESULTS

The density value obtained using the surrounding cylinder approach (grayscale value [GV],523.56 ± 228.03) was significantly higher than the values obtained using the rectangle (GV, 497.04 ± 236.69) and cylinder (GV,493 ± 231.19) ROI methods in terms of results. Furthermore, significant correlations were noted between the ROI methods (r > 0.965; p < 0.001).

CONCLUSIONS

The density measured using the surrounding cylinder method was the highest. The choice of method may not influence the trends of measurement results.

TRIAL REGISTRATION

This study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH111-REC3-205. Informed consent was waived by the Institutional Review Board of China Medical University Hospital, CMUH111-REC3-205, owing to the retrospective nature of the study.

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/purpose

Dental 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 methods

Commercial 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.

Results

For 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.

Conclusion

When 6-mm short implants were inserted in a lateral cortical anchorage position, high primary stability was yielded.

Bone density and proximal support effects on dental implant stability - Finite element analysis and in vitro experiments

OBJECTIVES

The application of dental implants presents the occurrence of implant failures associated with bone proximal support. This study aims to assess implant behavior, in particular implant stability and strain distribution in the bone at different bone densities, and the effect of proximal bone support.

MATERIAL AND METHODS

Three bone densities (D20, D15, and D10) were considered in the experimental in vitro study, represented by solid rigid polyurethane foam and two conditions of bone support in the proximal region. A finite element model was developed and validated experimentally and a Branemark model at a 3:1 scale was implanted in the experiments; the model was loaded and extracted.

RESULTS

The results of the experimental models validate the finite element models with a correlation R2 equal to 0.899 and NMSE of 7%. The implant extraction tests for the effect of bone properties in the maximum load were 2832 N for D20 and 792 N for D10. The effect of proximal bone support changes the implant stability was observed experimentally; at 1 mm less bone support decreases by 20% of stability and at 2 mm by 58% for D15 density.

CONCLUSIONS

Bone properties and bone quantity are important for the initial stability of the implant. A bone volume fraction of less than 24 g/cm3 exhibits poor behavior and is not indicated for implantation. Proximal bone support reduces the primary stability of the implant and the effect is critical in lower bone density.

Low Bone Density Predictability of CBCT and Its Relation to Primary Stability of Tapered Implant Design: A Pilot Study

Research regarding bone density assessment using cone beam computed tomography (CBCT) in low bone density regions is sparse. This in vitro study aimed to evaluate the predictability of CBCT for low bone density regions and its correlations with primary implant stability when placing tapered design implants with a stepped osteotomy. Eighteen porcine mandibular condyles were used as simulated low bone density regions. Hounsfield units (HU), obtained via multislice computed tomography, and gray values (GVs), obtained via CBCT, were measured 3 times at 1-month intervals. The maximum implant insertion torque (MIT) and implant stability quotient (ISQ) were recorded as the taper design implants were placed using a stepped osteotomy. Hounsfield units and GV were measured as 335.05-803.07 and 389.98-906.40, respectively. For repeated measurements of HU and GV, the intraclass correlation coefficients were 0.989 and 0.980; the corresponding value for mean HU and GV was 0.768. Bland-Altman plots showed a mean difference between HU and GV of -78.15. Pearson correlation coefficients revealed a strong correlation between HU and GV (r = 0.91, P < .01). The mean ± SD values for MIT and ISQ were 36.44 ± 6.64 Ncm and 80.85 ± 2.03, respectively, but no statistically significant correlations were found with GV and HU. Within the study's limitations, GV showed similar bone density estimation compared with HU in soft bones. Tapered implant placement with a stepped osteotomy achieved stable primary implant stability in soft bones. However, these in vitro results need to be approved in further clinical studies.

Evaluation of stresses on mandible bone and prosthetic parts in fixed prosthesis by utilizing CFR-PEEK, PEKK and PEEK frameworks

Fixed prostheses are appropriate treatment solutions for edentulous patients. In fixed prostheses, following "All on four", titanium frameworks are commonly used to support the implants. However, the limitations of titanium have prompted researchers to search for alternative materials (e.g. polymers). This study applied finite element investigation to evaluate the stress distribution in the parts of fixed prosthesis and the surrounding bone tissue, using polymeric frameworks in place of titanium, and different densities of spongy bone. As, the success of fixed prosthesis was predicted to be influenced also by bone quality, particularly spongy bone density. Fixed prosthesis was constructed on edentulous mandible, then different frameworks (CFR-PEEK 60%, CFR-PEEK 30%, PEKK, and PEEK) were stimulated instead of titanium, under 300N unilateral and bilateral forces. Three densities of spongy bone were stimulated which are normal, low and high. The choice of framework material depended on the density of spongy bone. Moreover, PEEK framework showed the lowest stress values on bone tissues and the highest stress values on mucosa. All frameworks could be used in the fixed prosthesis, in the cases of normal and high densities of spongy bone. In low-density case, soft frameworks (PEKK and PEEK) were recommended to reduce the stresses generated on bone tissues.

A three-year prospective cohort study evaluating implant stability utilising the osstell® and periotest™ devices

Objectives

To investigate implant stability measurements from two different devices and at three different time points in order to determine their level of correlation. To also evaluate the influence of a range of clinical characteristics on the values produced by the devices at these three time points.

Materials &amp; Methods

Measurements were recorded at implant placement (T1), implant exposure (T2) and at 3 years from implant placement (T3). A range of clinical data was collected including patient demographics and site characteristics. Stability measurements and clinical characteristics were recorded for 29 patients and 68 dental implants at T1, subsequent stability measurements were recorded for 67 implants at T2 and 58 implants at T3. Correlation testing between the Osstell® and Periotest™ devices was carried out utilising Spearman's rank correlation for each time point. Analysis of the difference between clinical factors and stability measurements was compared using Krushal-Wallis test for each variable and time point.

Results

A single dental implant failed shortly after 2nd stage surgery for an overall survival rate of 98% during the study timeline. The median ISQ value was 73.25 (IQR 67–75) at T1 and 74 (IQR 70.5–77) at T3. The median Periotest value was −4 (IQR −6, −2) at T1 and −6 (IQR −7, −5) at T3. The range of ISQ values observed was 50 (39–89) ISQ at T1 and decreased to 21 (61–82) ISQ at T3. The Periotest values ranged from 37 (29 to −8) at T1 and decreased to 6 (−2 to −8) at T3. A weak to moderate correlation was observed between mean ISQ and Periotest values across time-points T1, T2 and T3, (r = −0.26, p = 0.05), (r = −0.35, p &lt; 0.01) and (r = −0.28, p = 0.04) respectively.

Conclusions

Based on the results of this study there was a weak to moderate level of correlation between values recorded between the two measurement devices at implant placement, implant exposure and three years following placement. For both the Osstell® and Periotest™ a narrowing of the range of stability values was observed from T1 to T3. In general, Periotest™ seemed to be more sensitive in highlighting differences in measurements affected by local conditions.

Prediction of Bone Healing around Dental Implants in Various Boundary Conditions by Deep Learning Network

Tissue differentiation varies based on patients' conditions, such as occlusal force and bone properties. Thus, the design of the implants needs to take these conditions into account to improve osseointegration. However, the efficiency of the design procedure is typically not satisfactory and needs to be significantly improved. Thus, a deep learning network (DLN) is proposed in this study. A data-driven DLN consisting of U-net, ANN, and random forest models was implemented. It serves as a surrogate for finite element analysis and the mechano-regulation algorithm. The datasets include the history of tissue differentiation throughout 35 days with various levels of occlusal force and bone properties. The accuracy of day-by-day tissue differentiation prediction in the testing dataset was 82%, and the AUC value of the five tissue phenotypes (fibrous tissue, cartilage, immature bone, mature bone, and resorption) was above 0.86, showing a high prediction accuracy. The proposed DLN model showed the robustness for surrogating the complex, time-dependent calculations. The results can serve as a design guideline for dental implants.

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

Objectives

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.

Material and Methods

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.

Results

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).

Conclusions

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.

The Effects of Insertion Approach on the Stability of Dental Implants

Dental implant surgery involves the insertion of a dental implant into the alveolar bone; the success of the surgery depends on the initial stability of the implant. The objective of this study was to examine the effects of dental implant insertion approaches in clinical surgery and in accordance with the standards of American Society for Testing and Materials on initial implant stability. Three insertion approaches were used for dental implant placement (Branemark Systems NobelSpeedy Groovy, Nobel Biocare AB, Gothenburg, Sweden) in two types of artificial bone—good bone (GB) and poor bone (PB). The three insertion approaches were as follows: (1) continuous rotation insertion (CRI): using a torque testing machine to continuously screw in an implant to completion and (2 and 3) intermittent rotation insertion (IRI)_90 and IRI_80: using CRI to bury an implant to 90% and 80% of its full length followed by IRI to complete the implantation, respectively. The maximum insertion torque value (ITV), periotest value (PTV), and implant stability quotient (ISQ) were measured and compared. The results indicated that bone quality and insertion approach both affected implant stability. Insertion approaches affected all three implant stability indicators differently in the GB and PB groups (p = 0.008). In GB groups, the insertion approach primarily affected ITV, whereas in PB groups, it primarily affected PTV. The effect of the insertion approach was less apparent for ISQ. Overall, in both the GB and PB groups, the implant stability for IRI_80 was greater than that for IRI_90, and the implant stability for IRI_90 was greater than that for CRI. Future in vitro studies should adopt an insertion approach that complies with the clinical practice for dental implant surgery. Dentists should adjust the timing for IRI in dental implant surgery to achieve greater initial dental implant stability.

Mandibular Canal Location and Cortical Bone Thickness in Males and Females of Different Age Groups: A Cone-beam Computed Tomography Study

AIM: The purpose of the study was to measure and compare the prevalence of mandibular canal (MC) location variations in regard to mandibular first molars in both genders at different age groups. METHODS: A retrospective study was performed on 80 cone-beam computed tomography scans. Distance between MC and apical apices of first molars, buccal and lingual cortical plates was measured in both sides. RESULTS: 80 scans with 160 sides were analyzed. Distances was measured bilaterally for all scans with mean (5.22 ± 0.77) in men versus (4.1 ± 0.7) in women at group age 31–40 apical to apices of first molars. The mean was (3.77 ± 0.62) in men versus (2.81 ± 0.47) in women at same age group at buccal side, lingually the mean was (4.02 ± 0.67) in men versus (3.67 ± 0.26) in women in the same age group. CONCLUSION: Our study showed that there were decrease in measurements in older age group in both genders and in female groups more than male groups but with no statistical significant difference.

Can the design of the instruments used for undersized osteotomies influence the initial stability of implants installed in low-density bone? An in vitro pilot study

Objectives

The aims of this study were to compare the initial implant stability obtained using four different osteotomy techniques in low-density synthetic bone, to evaluate the instrument design in comparison to the implant design, and to determinate a possible correlation between the insertion torque and initial stability quotient (ISQ).

Materials and methods

Four groups were identified in accordance with the osteotomy technique used (n = 10 implants per group): group G1, osteotomy using the recommended drilling sequence; group G2, osteotomy using an undersized compactor drill; group G3, osteotomy using an undersized drill; and group G4, osteotomy using universal osseodensification drills. Two polyurethane blocks were used: block 1, with a medullary portion of 10 pounds per cubic foot (PCF 10) and with a 1 mm cortical portion of PCF 40, and block 2, with a medullary of PCF 15 and with a 2 mm cortical portion of PCF 40. Tapered implants of 4 mm in diameter and 11 mm in length were used. The insertion torque (IT) and ISQ were measured. The dimensions of the final instrument used in each group and the dimensions of the implant were used to calculate the total area of each part, and these data were compared.

Results

Differences between the four groups were found for IT and ISQ values depending on the technique used for the osteotomy in the two synthetic bone models (p < 0.0001). All groups showed lower values of initial stability in block 1 than in block 2.

Conclusions

Undersized osteotomies with instruments designed according to the implant body significantly increased the initial stability values compared to beds prepared with universal drills and using the drilling sequence standardized by the manufacturer.

An experimental study on the effects of the cortical thickness and bone density on initial mechanical anchorage of different Straumann® implant designs

Background

The aim of the current study was to comparatively assess the primary stability of different Straumann® implant designs (BLX, Straumann Tapered Effect, Bone Level Tapered, and Standard Plus) via resonance frequency analysis by using an implant insertion model in freshly slaughtered bovine ribs with and without cortical bone. Tapered Effect (4.1 × 10 mm), Bone Level Tapered (4.1 × 10 mm), Standard Plus (4.1 × 10 mm), and BLX (4.0 × 10 mm) implants were inserted into the distal epiphysis on the longitudinal axis of the freshly slaughtered bovine ribs. As a control, implants with the same sizes were inserted into the proximal diaphysis. The stability of the implants was examined with resonance frequency analysis.

Results

BLX and Tapered Effect implants showed higher implant stability quotient values in both study and control groups. All implant systems showed a significant decrease of mechanical anchorage in the study group. BLX and Bone Level Tapered designs had a significantly lower loss of mechanical anchorage in the lack of cortical bone.

Conclusion

Both Tapered Effect and BLX designs could ensure sufficient initial stability; however, BLX implants could be an appropriate option in the lack of cortical bone and poor bone quality at the implant recipient site.

Clinical relevance

BLX is a novel implant system, which could be especially beneficial in the presence of spongious bone type at posterior maxillae.

Evaluation of a metal artifact reduction algorithm and an adaptive image noise optimization filter in the estimation of peri-implant fenestration defects using cone beam computed tomography: an in-vitro study

OBJECTIVE

The aim of this study is to assess the effects of metal artifact reduction (MAR) and adaptive image noise enhancer (AINO) in CBCT imaging on the detection accuracy of artificially created fenestration defects in proximity to titanium and zirconium implants in sheep jaw.

METHODS

Six zirconium and 10 titanium implants were planted on mandibular jaws of three sheep, and artificial defects were created. All images were obtained with a standard voxel size (0.150 mm³) and with 4 scan modes: (1) without MAR/without AINO; (2) with MAR/without AINO; (3) without MAR/with AINO; and (4) with MAR/with AINO during CBCT scanning. A total of 60 CBCT scans were produced.

RESULTS

For all types of implants, intra- and inter-observer kappa values were the highest for MAR filter. The scan mode of with MAR filter was found to have the highest area under the curve (AUC), whereas the scan mode of without both MAR and AINO filters was found to have the lowest AUC values with statistical significance (p ≤ 0.05). Titanium implants were found to have higher AUC values than zirconium (p ≤ 0.05).

CONCLUSION

Both MAR module and AINO filters enhance the accuracy of the detection of peri-implant fenestrations; however, the use of MAR filter solely can be recommended for detection of peri-implant fenestrations.

Can Male Patient's Age Affect the Cortical Bone Thickness of Jawbone for Dental Implant Placement? A Cohort Study

Dental implants are among the most common treatments for missing teeth. The thickness of the crestal cortical bone at the potential dental implant site is a critical factor affecting the success rate of dental implant surgery. However, previous studies have predominantly focused on female patients, who are at a high risk of osteoporosis, for the discussion of bone quality and quantity at the dental implant site. This study aimed to investigate the effect of male patients’ age on the crestal cortical bone of the jaw at the dental implant site by using dental cone-beam computed tomography (CBCT). This study performed dental CBCT on 84 male patients of various ages to obtain tomograms of 288 dental implant sites at the jawbone (41 sites in the anterior maxilla, 95 in the posterior maxilla, 59 in the anterior mandible, and 93 in the posterior mandible) for measuring the cortical bone thickness. A one-way analysis of variance and Scheffe’s test were performed on the measurement results to compare the cortical bone thickness at implant sites in the four jaw areas. The correlation between male patient age and cortical bone thickness at the dental implant site was determined. The four jaw areas in order of the cortical bone thickness were as follows: posterior mandible (1.07 ± 0.44 mm), anterior mandible (0.99 ± 0.30 mm), anterior maxilla (0.82 ± 0.32 mm), and posterior maxilla (0.71 ± 0.27 mm). Apart from dental implant sites in the anterior and posterior mandibles, no significant correlation was observed between male patients’ age and the cortical bone thickness at the dental implant site.

Effects of Intrabony Length and Cortical Bone Density on the Primary Stability of Orthodontic Miniscrews

Miniscrews have gained recent popularity as temporary anchorage devices in orthodontic treatments, where failure due to sinus perforations or damage to the neighboring roots have increased. Issues regarding miniscrews in insufficient interradicular space must also be resolved. This study aimed to evaluate the primary stability of miniscrews shorter than 6 mm and their feasibility in artificial bone with densities of 30, 40, and 50 pounds per cubic foot (pcf). The primary stability was evaluated by adjusting the intrabony miniscrew length, based on several physical properties: maximum insertion torque (MIT), maximum removal torque (MRT), removal angular momentum (RAM), horizontal resistance, and micromotion. The MIT and micromotion results demonstrated that the intrabony length of a miniscrew significantly affected its stability in low-density cortical bone, unlike cases with a higher cortical bone density (p < 0.05). The horizontal resistance, MRT, and RAM were affected by the intrabony length, regardless of the bone density (p < 0.05). Thus, the primary stability of miniscrews was affected by both the cortical bone density and intrabony length. The effect of the intrabony length was more significant in low-density cortical bone, where the implantation depth increased as more energy was required to remove the miniscrew. This facilitated higher resistance and a lower risk of falling out.

Alveolar Bone Density and Width Affect Primary Implant Stability

Primary implant stability (PIS) depends on surgical technique, implant design, and recipient bone characteristics, among other factors. Bone density (BD) can be determined in Hounsfield units (HUs) using cone beam computerized tomography (CBCT). Reliable prediction of PIS could guide treatment decisions. We assessed whether PIS was associated with recipient bone characteristics, namely, BD and alveolar ridge width (ARW), measured preoperatively by CBCT. We studied a convenience sample of 160 implants placed in 48 patients in 2016 and 2017. All underwent CBCT with a radiologic/surgical guide yielding values for ARW and BD. PIS measures used were the implant stability quotient (ISQ) from resonance frequency analysis and insertion torque (IT). IT was most influenced by the HU value at 0.5 mm outside the implant placement area, followed by the value within this area, and ISQ by the HU value at 0.5 mm outside the placement area, followed by implant placement site and apical ARW. ISQ values were significantly related to ARW in coronal (P < .05), middle (P < .01), and apical (P < .01) thirds. ISQs were higher with larger-diameter implants (P < .01). ISQ and IT were strongly correlated (P < .001). PIS in terms of ISQ and IT is positively correlated with edentulous alveolar ridge BD measured by CBCT, implying that implant stability may be predicted preoperatively. Wide alveolar ridges favored lateral PIS but did not affect rotational PIS. The most significant predictor of lateral and rotational PIS in our patients was the HU value at 0.5 mm outside the implant placement area.

Relationship between Cortical Bone Thickness and Cancellous Bone Density at Dental Implant Sites in the Jawbone

Dental implant surgery is a common treatment for missing teeth. Its survival rate is considerably affected by host bone quality and quantity, which is often assessed prior to surgery through dental cone-beam computed tomography (CBCT). Dental CBCT was used in this study to evaluate dental implant sites for (1) differences in and (2) correlations between cancellous bone density and cortical bone thickness among four regions of the jawbone. In total, 315 dental implant sites (39 in the anterior mandible, 42 in the anterior maxilla, 107 in the posterior mandible, and 127 in the posterior maxilla) were identified in dental CBCT images from 128 patients. All CBCT images were loaded into Mimics 15.0 to measure cancellous bone density (unit: grayscale value (GV) and cortical bone thickness (unit: mm)). Differences among the four regions of the jawbone were evaluated using one-way analysis of variance and Scheffe's posttest. Pearson coefficients for correlations between cancellous bone density and cortical bone thickness were also calculated for the four jawbone regions. The results revealed that the mean cancellous bone density was highest in the anterior mandible (722 ± 227 GV), followed by the anterior maxilla (542 ± 208 GV), posterior mandible (535 ± 206 GV), and posterior maxilla (388 ± 206 GV). Cortical bone thickness was highest in the posterior mandible (1.15 ± 0.42 mm), followed by the anterior mandible (1.01 ± 0.32 mm), anterior maxilla (0.89 ± 0.26 mm), and posterior maxilla (0.72 ± 0.19 mm). In the whole jawbone, a weak correlation (r = 0.133, p = 0.041) was detected between cancellous bone density and cortical bone thickness. Furthermore, except for the anterior maxilla (r = 0.306, p = 0.048), no correlation between the two bone parameters was observed (all p > 0.05). Cancellous bone density and cortical bone thickness varies by implant site in the four regions of the jawbone. The cortical and cancellous bone of a jawbone dental implant site should be evaluated individually before surgery.

The clinical significance of implant stability quotient (ISQ) measurements: A literature review

Implant stability quotients (ISQ values) are obtained in dental clinical practice on a non-invasive basis by resonance frequency measurement rapidly after surgical placement of implants. The ISQ-values are used as indicator for mechanical implant stability, and are believed to have predictive power for clinical outcome. It is the aim of this review to provide a synopsis of all factors described in the literature that influence ISQ measurements by performing an exhaustive literature review; moreover, this review aims at elucidating the key factors relevant for a rapid clinical predictive assessment. We searched systematically and exhaustively all major databases for publications relating to ISQ measurement methodology and for ISQ-influencing factor analyses. The reports identified were ordered in experimental (preclinical) studies and in clinical publications. We were able to identify 13 basic factors influencing ISQ-measurements. Among these, local bone quality, playing a key role in such measurements, was subdivided in four specific subfactors; thus a total of 17 individual factors was identified and reported to influence ISQ-measurements. A comprehensive list of these factors is provided in Table-form. A critical analysis points out that only 6 of these factors are of a sound predictive power useful for a rapid clinical assessment; and only two of these factors appear to have a well-documented scientific basis.

Association between Age of Menopause and Thickness of Crestal Cortical Bone at Dental Implant Site: A Cross-Sectional Observational Study

Satisfactory host bone quality and quantity promote greater primary stability and better osseointegration, leading to a high success rate in the use of dental implants. However, the increase in life expectancy as a result of medical advancements has led to an aging population, suggesting that osteoporosis may become a problem in clinical dental implant surgery. Notably, relative to the general population, bone insufficiency is more common in women with post-menopausal osteoporosis. The objective of this study was to compare the thickness of the crestal cortical bone at prospective dental implant sites between menopausal and non-menopausal women. Prospective dental implant sites in the jawbone were evaluated in two groups of women: a younger group (<50 years old), with 149 sites in 48 women, and an older group (>50 years old) with 191 sites, in 37 women. The thickness of the crestal cortical bone at the dental implant site was measured based on each patient’s dental cone-beam computed tomography images. For both groups, one-way analysis of variance and Tukey’s post-test were used to assess the correlation between cortical bone thickness and the presence of implants in the four jawbone regions. Student’s t-test was further used to compare differences between the older and younger groups. From the retrospective study results, for both groups, thickness of the crestal cortical bone was the highest in the posterior mandible, followed by anterior mandible, anterior maxilla, and posterior maxilla. Compared with the younger group, the older group had a lower mean thickness of the crestal cortical bone. Among the four regions, however, only in the posterior maxilla was the crestal cortical bone significantly thinner in the older group than in the younger group.

Effect of bone quality and quantity on the primary stability of dental implants in a simulated bicortical placement

OBJECTIVES

Conventional dental implants inserted in the molar region of the maxilla will reach into the sinus maxillaris when alveolar ridge height is limited. When surgery is performed without prior augmentation of the sinus floor, primary stability of the implant is important for successful osseointegration. This study aimed at identifying the impact of bone quality and quantity at the implantation site on primary implant stability of a simulated bicortical placement.

MATERIALS AND METHODS

In our in vitro measurements, bone mineral density, total bone thickness and overall cortical bone thickness were assessed by micro-computed tomography (μCT) of pig scapulae, which resembled well the bicortical situation found in human patients. Dental implants were inserted, and micromotion between bone and implant was measured while loading the implant with an axial torque.

RESULTS

The main findings were that primary implant stability did not depend on total bone thickness but tended to increase with either increasing bone mineral density or overall cortical bone thickness.

CLINICAL RELEVANCE

Limited bone height in the maxilla is a major problem when planning dental implants. To overcome this problem, several approaches, e.g. external or internal sinus floor elevation, have been established. When planning the insertion of a dental implant an important aspect is the primary stability which can be expected. With other factors, the dimensions of the cortical bone might be relevant in this context. It would, therefore, be helpful to define the minimum thickness of cortical bone required to achieve sufficient primary stability, thus avoiding additional surgical intervention.

Assessment of Peri-implant Buccal Bone Thickness Using Digital Imaging Techniques: A Systematic Review and Meta-analysis

Objectives:

This systematic review aimed to answer the following focused question: Do the currently available imaging techniques provide accuracy in the assessment of peri-implant buccal bone thickness?

Methods:

A search strategy was conducted in eight electronic databases, followed by an additional manual search in grey literature and references of selected articles. Studies evaluating the accuracy of imaging techniques to measure peri-implant buccal bone thickness were included. Individual risk of bias was assessed by the Quality Assessment Tool for Diagnostic Accuracy Studies-2 (QUADAS-2). Meta-analysis was performed to evaluate CBCT accuracy. The overall effect size was determined by means of the Z-test. Q test was used to evaluate the homogeneity of effect sizes among studies and I2 was applied to determine the variance within studies.

Results:

After an initial screening, 83 studies were further selected for full reading and 13 of them were considered eligible for this review. In sum, the accuracy of Cone-beam Computed Tomography (CBCT), of ultrasound, and of computed tomography were assessed. There was no statistically significant difference between CBCT and the gold standard (p=0.81). The mean difference between measurements of bone thickness obtained by CBCT and the goldstandard was -0.0.3mm [95%CI -0.29;0.253mm].

Conclusion:

CBCT showed acceptable accuracy for assessing peri-implant bone. No meaningful conclusion could be drawn about other techniques.

Characterising the compressive anisotropic properties of analogue bone using optical strain measurement

The validity of conclusions drawn from pre-clinical tests on orthopaedic devices depends upon accurate characterisation of the support materials: frequently, polymer foam analogues. These materials often display anisotropic mechanical behaviour, which may considerably influence computational modelling predictions and interpretation of experiments. Therefore, this study sought to characterise the anisotropic mechanical properties of a range of commonly used analogue bone materials, using non-contact multi-point optical extensometry method to account for the effects of machine compliance and uneven loading. Testing was conducted on commercially available 'cellular', 'solid' and 'open-cell' Sawbone blocks with a range of densities. Solid foams behaved largely isotropically. However, across the available density range of cellular foams, the average Young's modulus was 23%-31% lower (p < 0.005) perpendicular to the foaming direction than parallel to it, indicating elongation of cells with foaming. The average Young's modulus of open-celled foams was 25%-59% higher (p < 0.05) perpendicular to the foaming direction than parallel to it. This is thought to result from solid planes of material that were observed perpendicular to the foaming direction, stiffening the bulk material. The presented data represent a reference to help researchers design, model and interpret tests using these materials.

The effect of ovariectomy and 2 antiresorptive therapeutic agents on bone response in rats: A 3-dimensional imaging analysis

OBJECTIVE

The aim of this study was to evaluate bone mineral density (BMD) and microarchitecture in femurs and maxillary bones of ovariectomized (OVX) rats treated or not treated with alendronate (ALD) or odanacatib (ODN).

STUDY DESIGN

Twenty rats were divided into groups: SHAM, OVX, OVX/ALD, and OVX/ODN. After 12 weeks, the femurs and maxillae were removed and subjected to 3-dimensional analysis by micro-computed tomography. Results were analyzed with 1-way analysis of variance and Tukey's post hoc test (α = 0.05).

RESULTS

OVX decreased maxillary and femoral BMD and altered femoral microarchitecture (P < .05). The drugs increased BMD of both types of bones, but only ALD maintained the phenotype similar to the SHAM group. The action of ALD was limited to the femoral trabecular separation (Tb.Sp). OVX and the drugs had no effect on the microarchitecture of the maxilla (P > .05).

CONCLUSIONS

ALD and ODN therapy increased BMD in both bones after ovariectomy. ALD was more successful than ODN in preserving the morphology of bone similar to the SHAM group. ALD maintained the phenotype for Tb.Sp in the femur, but ODN did not. In the maxillae, neither ovariectomy nor the 2 antiresorptive drugs had significant effects on microarchitecture.

Correlation between the thickness of the crestal and buccolingual cortical bone at varying depths and implant stability quotients

Background/purpose

Resonance frequency analysis (RFA) is clinically used in dentistry to access the stiffness of dental implants in surrounding bone. However, the clear advantages and disadvantages of this method are still inconclusive. The aim of this study was to investigate and compare implant stability quotient (ISQ) values obtained from RFA with parameters obtained from a cone beam computed tomography (CBCT) scan of the same region.

Materials and methods

Nineteen implants (Conelog) were inserted in the posterior maxillary and mandibular partially edentulous regions of 16 patients. At the time of implant placement, the ISQ values were obtained using RFA (Osstell). CBCT was used to measure the thickness of the crestal, cortical, buccolingual cortical, and cancellous bone at 3, 6, and 9 mm below the crestal bone level, as indicated by radiographic markers. The ratio of the thickness of the cortical to cancellous bone at varying depths was also calculated and classified into 4 groups (Group 1–4).

Results

There was a strong correlation between the crestal cortical bone thickness and ISQ values (P<0.001). The thickness of the buccolingual cortical bone and ratio of the cortical to cancellous bone thickness at 3 mm were significantly related to the ISQ (P = 0.018 and P = 0.034, respectively). Furthermore, the ISQs in Group 1 were the highest compared with those in Group 2 and Group 3, whereas the CBCT parameters at 6 and 9 mm did not have any specific correlation with the ISQ values.

Conclusion

This study showed that the ISQ values obtained from RFA highly correlated with the quantity and quality of bone 3 mm below the crestal bone level. The correlation between the ISQ and bone surrounding the implant site was dependent on the depth of measurement. Therefore, RFA can help to predict the marginal bone level, as confirmed in this study.

Effects of implant length and 3D bone-to-implant contact on initial stabilities of dental implant: a microcomputed tomography study

Background

The influences of potential bone-to-implant contact (BIC) area (pBICA), BIC area (BICA), and three dimensional (3D) BIC percentage (3D BIC%; defined as BICA divided by pBICA) in relation to the implant length on initial implant stability were studied. Correlations between these parameters were also evaluated.

Methods

Implants with lengths of 8.5, 10, 11.5, and 13 mm were placed in artificial bone specimens to measure three indexes of the initial implant stability: insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ). The implants and bone specimens were also scanned by microcomputed tomography, and the obtained images were imported into Mimics software to reconstruct the 3D models and calculate the parameters of 3D bone-to-implant contact including pBICA, BICA, and 3D BIC%. The Kruskal-Wallis test, Wilcoxon rank-sum test with Bonferroni adjustment, and Spearman correlations were applied for statistical and correlation analyses.

Results

The implant length affected ITV more than PTV and ISQ, and significantly affected pBICA, BICA, and 3D BIC%. A longer implant increased pBICA and BICA but decreased 3D BIC%. The Spearman coefficients were high (>0.78) for the correlations between the three 3D BIC parameters and the three indexes of the initial implant stability.

Conclusions

pBICA, BICA, and 3D BIC% are useful when deciding on treatment plans related to various implant lengths, since these 3D BIC parameters are predictive of the initial implant stability.

In Vitro Biocompatibility, Radiopacity, and Physical Property Tests of Nano-Fe₃O₄ Incorporated Poly-l-lactide Bone Screws

The aim of this study was to fabricate biodegradable poly-l-lactic acid (PLLA) bone screws containing iron oxide (Fe₃O₄) nanoparticles, which are radiopaque and 3D-printable. The PLLA composites were fabricated by loading 20%, 30%, and 40% Fe₃O₄ nanoparticles into the PLLA. The physical properties, including elastic modulus, thermal properties, and biocompatibility of the composites were tested. The 20% nano-Fe₃O₄/PLLA composite was used as the material for fabricating the 3D-printed bone screws. The mechanical performance of the nano-Fe₃O₄/PLLA bone screws was evaluated by anti-bending and anti-torque strength tests. The tissue response and radiopacity of the nano-Fe₃O₄/PLLA bone screws were assessed by histologic and CT imaging studies using an animal model. The addition of nano-Fe₃O₄ increased the crystallization of the PLLA composites. Furthermore, the 20% nano-Fe₃O₄/PLLA composite exhibited the highest thermal stability compared to the other Fe₃O₄ proportions. The 3D-printed bone screws using the 20% nano-Fe₃O₄/PLLA composite provided excellent local tissue response. In addition, the radiopacity of the 20% nano-Fe₃O₄/PLLA screw was significantly better compared with the neat PLLA screw.

Variations in crestal cortical bone thickness at dental implant sites in different regions of the jawbone

BACKGROUND

Dental implants have become reliable and predictable tools for treating missing teeth. The survival rate of dental implants is markedly influenced by the host bone quality and quantity of the jawbone. A better host bone provides higher initial stability of the dental implant, resulting in better osseointegration and a higher success rate. Host bone quality and quantity are determined by the crestal cortical bone thickness and inner cancellous bone density.

OBJECTIVE

The purpose of this study was to determine the crestal cortical bone thickness at dental implant sites in different regions of the jawbone through the use of dental cone-beam computed tomographic (CBCT) images.

MATERIALS AND METHODS

A total of 661 dental implant sites (81 in the anterior mandible, 122 in the anterior maxilla, 224 in the posterior mandible, and 234 in the posterior maxilla) were obtained from the jawbones of 173 humans. The data were subjected to statistical analysis to determine any correlation between crestal cortical bone thicknesses and jawbone regions using one-way analysis of variance with Tukey's post-test.

RESULTS

The crestal cortical bone thicknesses at dental implant sites in the four regions decreased in the following order: posterior mandible (1.07 ± 0.47 mm, mean ± SD) >anterior mandible (0.99 ± 0.36 mm) >anterior maxilla (0.82 ± 0.30 mm) >posterior maxilla (0.75 ± 0.35 mm).

CONCLUSION

The dental CBCT data demonstrate that crestal cortical bone thickness varies markedly between dental implant sites in the four regions of the jawbone.

Prospective randomized clinical trial of hydrophilic tapered implant placement at maxillary posterior area: 6 weeks and 12 weeks loading

PURPOSE

Early loading of implant can be determined by excellent primary stability and characteristic of implant surface. The implant system with recently improved surface can have load application 4-6 weeks after installing in maxilla and mandible. This study evaluated the effect of healing period to the stability of hydrophilic tapered-type implant at maxillary posterior area.

MATERIALS AND METHODS

This study included 30 patients treated by hydrophilic tapered-type implants (total 41 implants at maxilla) and classified by two groups depending on healing period. Group 1 (11 patients, 15 implants) was a control group and the healing period was 12 weeks, and Group 2 (19 patients, 26 implants) was test group and the healing period was 6 weeks. Immediately after implant placement, at the first impression taking, implant stability was measured using Osstell Mentor. The patients also took periapical radiographs after restoration delivery, 12 months after restoration and final followup period. The marginal bone loss around the implants was measured using the periapical radiographs.

RESULTS

All implants were survived and success rate was 97.56%. The marginal bone loss was less than 1mm after 1 year postoperatively except the one implant. The stabilities of the implants were not correlated with age, healing period until loading, insertion torque (IT), the diameter of fixture and the location of implant. Only the quality of bone in group 2 (6 week) was correlated with the stability of implant.

CONCLUSION

Healing period of 6 weeks can make the similar clinical prognosis of implants to that of healing period of 12 weeks if bone quality is carefully considered in case of early loading.

The effects of bone density and crestal cortical bone thickness on micromotion and peri-implant bone strain distribution in an immediately loaded implant: a nonlinear finite element analysis

Purpose

This study investigated the effects of bone density and crestal cortical bone thickness at the implant-placement site on micromotion (relative displacement between the implant and bone) and the peri-implant bone strain distribution under immediate-loading conditions.

Methods

A three-dimensional finite element model of the posterior mandible with an implant was constructed. Various bone parameters were simulated, including low or high cancellous bone density, low or high crestal cortical bone density, and crestal cortical bone thicknesses ranging from 0.5 to 2.5 mm. Delayed- and immediate-loading conditions were simulated. A buccolingual oblique load of 200 N was applied to the top of the abutment.

Results

The maximum extent of micromotion was approximately 100 μm in the low-density cancellous bone models, whereas it was under 30 μm in the high-density cancellous bone models. Crestal cortical bone thickness significantly affected the maximum micromotion in the low-density cancellous bone models. The minimum principal strain in the peri-implant cortical bone was affected by the density of the crestal cortical bone and cancellous bone to the same degree for both delayed and immediate loading. In the low-density cancellous bone models under immediate loading, the minimum principal strain in the peri-implant cortical bone decreased with an increase in crestal cortical bone thickness.

Conclusions

Cancellous bone density may be a critical factor for avoiding excessive micromotion in immediately loaded implants. Crestal cortical bone thickness significantly affected the maximum extent of micromotion and peri-implant bone strain in simulations of low-density cancellous bone under immediate loading.

Cortical Bone Morphological and Trabecular Bone Microarchitectural Changes in the Mandible and Femoral Neck of Ovariectomized Rats

Objective

This study used microcomputed tomography (micro-CT) to evaluate the effects of ovariectomy on the trabecular bone microarchitecture and cortical bone morphology in the femoral neck and mandible of female rats.

Materials and Methods

Twelve female Wister rats were divided into two groups: the control and ovariectomized groups. The rats in the ovariectomized group received ovariectomy at 8 weeks of age; all the rats were sacrificed at 20 weeks of age, and their mandibles and femurs were removed and scanned using micro-CT. Four microstructural trabecular bone parameters were measured for the region below the first mandibular molar and the femoral neck region: bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular separation (TbSp), and trabecular number (TbN). In addition, four cortical bone parameters were measured for the femoral neck region: total cross-sectional area (TtAr), cortical area (CtAr), cortical bone area fraction (CtAr/TtAr), and cortical thickness (CtTh). The CtTh at the masseteric ridge was used to assess the cortical bone morphology in the mandible. The trabecular bone microarchitecture and cortical bone morphology in the femoral necks and mandibles of the control group were compared with those of the ovariectomized group. Furthermore, Spearman’s correlation (r_s) was conducted to analyze the correlation between the osteoporosis conditions of the mandible and femoral neck.

Results

Regarding the trabecular bone microarchitectural parameters, the BV/TV of the trabecular bone microarchitecture in the femoral necks of the control group (61.199±11.288%, median ± interquartile range) was significantly greater than that of the ovariectomized group (40.329±5.153%). Similarly, the BV/TV of the trabecular bone microarchitecture in the mandibles of the control group (51.704±6.253%) was significantly greater than that of the ovariectomized group (38.486±9.111%). Furthermore, the TbSp of the femoral necks in the ovariectomized group (0.185±0.066 mm) was significantly greater than that in the control group (0.130±0.026mm). Similarly, the TbSp of the mandibles in the ovariectomized group (0.322±0.047mm) was significantly greater than that in the control group (0.285±0.041mm). However, the TbTh and TbN trends for the mandibles and femoral necks were inconsistent between the control and ovariectomized groups. Regarding the cortical bone morphology parameters, the TtAr of the femoral necks in the ovariectomized group was significantly smaller than that in the control group. There was no significant difference in the TtAr, CtAr, or CtTh of the femoral necks between the control and ovariectomized groups, and no significant difference in the CtTh of the mandibles between the control and ovariectomized groups. Moreover, the BV/TV and TbSp of the mandibles were highly correlated with those of the femurs (r_s = 0.874 and r_s = 0.755 for BV/TV and TbSp, respectively). Nevertheless, the TbTh, TbN, and CtTh of the mandibles were not correlated with those of the femoral necks.

Conclusion

After the rats were ovariectomized, osteoporosis of the trabecular bone microarchitecture occurred in their femurs and mandibles; however, ovariectomy did not influence the cortical bone morphology. In addition, the parametric values of the trabecular bone microarchitecture in the femoral necks were highly correlated with those of the trabecular bone microarchitecture in the mandibles.

Osstell Resonance Frequency Measurement Values as a Prognostic Factor in Implant Dentistry

Resonance frequency analysis (RFA) using the Osstell device (Osstell AB, Gothenburg, Sweden) has been advocated for quantifying implant stability on a relative scale of implant stability quotients (ISQ). It was the goal of this prospective clinical study to evaluate whether a certain ISQ level, at the time an implant is placed, correlates with successful osseointegration as some have claimed. Four hundred ninety-five implants (Straumann AG, Basel, Switzerland), varying in length and diameter, were placed in a private practice, strictly adhering to the implant manufacturer's surgical protocol. After placement and after healing periods of 42 days in the mandible and 56 days (implant manufacturer's protocol) in the maxilla, implant stability was measured using RFA. After healing, implants were torqued forward at 35 Ncm and allowed to heal further if the patients felt discomfort. Statistical analysis of the data obtained was based on Welch tests and Kolmogorov-Smirnow tests (level of significance α = 0.05). Results showed that 432 implants were osseointegrated after the predefined healing periods while 8 implants were lost and, in 55 cases, healing was prolonged. Both at insertion (P = .025) and after healing (P &lt; .001), successful implants showed significantly different ISQ values as compared to implant failures or implants with prolonged healing. However, overlapping ISQ distributions at implant insertion demonstrated that there was no correlation among the data that could be used to predict successful osseointegration. Within the limits of this study, the prognostic value of ISQ values appears to be ambiguous.

Assessment of the Correlation between the Implant Distance and Primary Stability by Resonance Frequency Analysis

Objective. The aim of this study was to assess the influence of the interimplant distance on the implant primary stability (ISQ) by Resonance Frequency Analysis (RFA). Method. Forty-five implants were placed in the mandible of human cadavers and 108 in artificial bone substrates in the form of polyurethane foam blocks. Primary implant stability was successively measured first by RFA immediately after the placement of the first implant (A) and then after two other implants (B and C) proximal and distal to the first implant. The interimplant distances were defined from 1 to 6 mm and the three primary stability values measured were compared. Results. On the mandibles, no correlation was observed between the interimplant distances and primary stability. On the polyurethane foam block, the primary stability of implant A increased significantly (p<0.001) after the placement of implant B but remained constant after placement of implant C. Conclusion. Reducing the interimplant distance does not affect the primary stability on dry bone or artificial substrate.

Associations of Resonance Frequency Analysis with Dynamic Mechanical Analysis of Dental Implant Systems

BACKGROUND

Resonance frequency analysis (RFA) has been introduced as a noninvasive method to clinically estimate the stability of dental implant systems.

PURPOSE

The objective of this study was to examine whether implant stability quotient (ISQ) values of RFA can account for mechanical stability of the dental implant system, which is assessed using dynamic mechanical analysis (DMA).

MATERIALS AND METHODS

Fifty-seven screw-type titanium dental implants were placed in artificial polyurethane foams with seven different thicknesses (3.5 to 12 mm) and eight edentulous mandibles of human cadavers (four men and four women, 79.11 ± 13.48 years). After the ISQ values, insertion torque, and static stiffness of each implant system were measured, the DMA was performed to assess dynamic stiffness and viscoelastic tan δ.

RESULTS

The ISQ value had strong positive correlations with thickness, insertion torque, static and dynamic stiffness, and a negative correlation with tan δ of implant systems in artificial bone blocks (r = 0.769 to 0.992, p < .043). However, the ISQ value was correlated with only the insertion torque of implant systems in human mandibles (p < .049).

CONCLUSION

The ISQ values could reflect mechanical stability of the dental implant system under the controlled condition of homogeneous density in simple dimensions.

Evaluation of local cancellous bone amelioration by poly-L-DL-lactide copolymers to improve primary stability of dental implants: a biomechanical study in sheep

OBJECTIVES

The aim of this study was to evaluate the clinical performance of local cancellous bone amelioration by a 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer with two different implant designs on primary stability and after 4 and 12 weeks of healing time.

MATERIAL AND METHODS

In six sheep, n = 36 implants (TH) with a conditioned, sandblasted, thermal acid-etched micro-rough surface and n = 36 implants (NB) with a highly crystalline and phosphate-enriched anodized titanium oxide surface were placed in the pelvic bone. Using an ultrasound-based process named Constant Amelioration Process (CAP), half of peri-implant trabecular bone structures were locally tested with 70:30 poly-(L-lactide-co-D,L-Lacide) copolymer in both implant groups, TH and NB. The CAP technology employs ultrasonic energy to liquefy 70:30 poly-(L-lactide-co-D,L-Lacide) which enters the inter-trabecular space, leading to local reinforcement of the cancellous bone structure after solidification of the copolymer. The CAP test group was compared with reference implants placed with the conventional site preparation according to the manufacturers' description. Primary stability was assessed by the measurement of torque-in values and implant stability quotient (ISQ; n = 18 per group). Secondary stability was analyzed by biomechanical removal torque testing after 4 and 12 weeks (n = 9 per group).

RESULTS

Insertion torque value (23.3 N cm ± 13.6) of reference TH implants demonstrated a statistically significant (P = 0.00) difference in comparison with test TH implants (41.9 N cm ± 19.5). Reference NB implants revealed a statistically significant (P = 0.03) lower insertion torque value (23.7 N cm ± 13.5) than test NB implants (39.7 N cm ± 18.6). ISQ values increased for all implants from initial implant placement until sacrifice at 12 weeks. Reference TH implants tended to result in an increase in torque values from 4 weeks (181.9 N cm ± 22.8) to 12 weeks (225.7 N cm ± 47.4). This trend could be also proven for implants of test sites (4 week: 176.8 N cm ± 24.1; 12 week: 201.5 N cm ± 53.4). For reference, NB implants a non-significant increase in removal torque values from 4 weeks (146. 7 N cm ± 18.0) to 12 weeks (170.2 N cm ± 40.4) was observed. Removal torque values of test NB implants did not increase from 4 weeks (153.3 N cm ± 21.5) to 12 weeks (146.1 N cm ± 37.5).

CONCLUSION

Biomechanical data proved significantly enhanced primary stability of dental implants after local amelioration without long-term sequelae and irrespective of implant design. After 4- and 12-week healing time, removal torque of locally test implants was as high as for control implants, and osseointegration was therefore not influenced by the CAP process. No correlation between ISQ values and torque values was found.

Trabecular bone structural parameters evaluated using dental cone-beam computed tomography: cellular synthetic bones

Objective

This study compared the adequacy of dental cone beam computed tomography (CBCT) and micro computed tomography (micro-CT) in evaluating the structural parameters of trabecular bones.

Methods

The cellular synthetic bones in 4 density groups (Groups 1–4: 0.12, 0.16, 0.20, and 0.32 g/cm³) were used in this study. Each group comprised 8 experimental specimens that were approximately 1 cm³. Dental CBCT and micro-CT scans were conducted on each specimen to obtain independent measurements of the following 4 trabecular bone structural parameters: bone volume fraction (BV/TV), specific bone surface (BS/BV), trabecular thickness (Tb.Th.), and trabecular separation (Tb.Sp.). Wilcoxon signed ranks tests were used to compare the measurement variations between the dental CBCT and micro-CT scans. A Spearman analysis was conducted to calculate the correlation coefficients (r) of the dental CBCT and micro-CT measurements.

Results and Conclusion

Of the 4 groups, the BV/TV and Tb.Th. measured using dental CBCT were larger compared with those measured using micro-CT. By contrast, the BS/BV measured using dental CBCT was significantly less compared with those measured using micro-CT. Furthermore, in the low-density groups (Groups 1 and 2), the Tb.Sp. measured using dental CBCT was smaller compared with those measured using micro-CT. However, the Tb.Sp. measured using dental CBCT was slightly larger in the high-density groups (Groups 3 and 4) than it was in the low density groups. The correlation coefficients between the BV/TV, BS/BV, Tb.Th., and Tb.Sp. values measured using dental CBCT and micro-CT were 0.9296 (p < .001), 0.8061 (p < .001), 0.9390 (p < .001), and 0.9583 (p < .001), respectively. Although the dental CBCT and micro-CT approaches exhibited high correlations, the absolute values of BV/TV, BS/BV, Tb.Th., Tb.Sp. differed significantly between these measurements. Additional studies must be conducted to evaluate using dental CBCT in clinical practice.

Location of the mandibular canal and thickness of the occlusal cortical bone at dental implant sites in the lower second premolar and first molar

The objective of this study was to evaluate the location of the mandibular canal and the thickness of the occlusal cortical bone at dental implant sites in the lower second premolar and lower first molar by using dental cone-beam computed tomography (CBCT). Seventy-nine sites (47 second premolar and 32 first molar sites) were identified in the dental CBCT examinations of 47 patients. In this study, 4 parameters were measured: (1) MC—the distance from the mandibular canal to the upper border of the mandible; (2) CD—the distance from the mandibular canal to the buccal border of the mandible; (3) MD—the distance from the mandibular canal to the lingual border of the mandible; (4) TC—the thickness of the cortical bone at the occlusal side. A statistical analysis was employed to compare the size and differences between these 4 parameters at the lower second premolar and lower first molar. Regarding the MC and MD, the experimental results showed no statistical difference between the first molar and second premolar. However, the TC for the second premolar was greater than that of the first molar. Thus, careful consideration is necessary in choosing the size of and operation type for dental implants.

Comparisons of maximum deformation and failure forces at the implant-abutment interface of titanium implants between titanium-alloy and zirconia abutments with two levels of marginal bone loss

Background

Zirconia materials are known for their optimal aesthetics, but they are brittle, and concerns remain about whether their mechanical properties are sufficient for withstanding the forces exerted in the oral cavity. Therefore, this study compared the maximum deformation and failure forces of titanium implants between titanium-alloy and zirconia abutments under oblique compressive forces in the presence of two levels of marginal bone loss.

Methods

Twenty implants were divided into Groups A and B, with simulated bone losses of 3.0 and 1.5 mm, respectively. Groups A and B were also each divided into two subgroups with five implants each: (1) titanium implants connected to titanium-alloy abutments and (2) titanium implants connected to zirconia abutments. The maximum deformation and failure forces of each sample was determined using a universal testing machine. The data were analyzed using the nonparametric Mann–Whitney test.

Results

The mean maximum deformation and failure forces obtained the subgroups were as follows: A1 (simulated bone loss of 3.0 mm, titanium-alloy abutment) = 540.6 N and 656.9 N, respectively; A2 (simulated bone loss of 3.0 mm, zirconia abutment) = 531.8 N and 852.7 N; B1 (simulated bone loss of 1.5 mm, titanium-alloy abutment) = 1070.9 N and 1260.2 N; and B2 (simulated bone loss of 1.5 mm, zirconia abutment) = 907.3 N and 1182.8 N. The maximum deformation force differed significantly between Groups B1 and B2 but not between Groups A1 and A2. The failure force did not differ between Groups A1 and A2 or between Groups B1 and B2. The maximum deformation and failure forces differed significantly between Groups A1 and B1 and between Groups A2 and B2.

Conclusions

Based on this experimental study, the maximum deformation and failure forces are lower for implants with a marginal bone loss of 3.0 mm than of 1.5 mm. Zirconia abutments can withstand physiological occlusal forces applied in the anterior region.

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.