Tissue Characteristics at Microthreaded Implants: An Experimental Study in Dogs

Comparative osseointegration of hydrophobic tissue-level tapered implants-A preclinical in vivo study

PURPOSE

To histometrically compare the osseointegration and crestal bone healing of a novel tapered, self-cutting tissue-level test implant with a standard tissue-level control implant in a submerged healing regimen.

MATERIALS AND METHODS

In a mandibular minipig model, implants were inserted and evaluated histometrically after a healing period of 3, 6, and 12 weeks. The primary outcome was the evaluation of bone-to-implant contact (BIC) and secondary outcomes were primary stability as per insertion torque and first BIC (fBIC). Outcomes for the test and control implants were compared using Wilcoxon signed-rank tests and mixed linear regression models.

RESULTS

Insertion torque values were significantly higher for the test (50.0 ± 26.4 Ncm) compared to the control implants (35.2 ± 19.7 Ncm, p = .0071). BIC values of test implants were non-inferior to those of control implants over the investigated study period. After 12 weeks, the corresponding values measured were 81.62 ± 11.12% and 90.41 ± 4.81% (p = .1763) for test and control implants, respectively. Similarly, no statistical difference was found for fBIC values, except for the 12 weeks outcome that showed statistically lower values for the test (-675.58 ± 590.88 μm) compared to control implants (-182.75 ± 197.40 μm, p = .0068).

CONCLUSIONS

Novel self-cutting tissue-level implants demonstrated noninferior osseointegration and crestal bone height maintenance to the tissue-level implants. Histometric outcomes between both implants demonstrated test implants were statistically noninferior to control implants, despite substantial differences in the bone engagement mechanism and resulting differences in insertion torque and qualitative bone healing patterns.

Relationship between dental implant macro-design and osseointegration: a systematic review

PURPOSE

This systematic review aimed to determine whether differences in the macro-geometry of titanium implants promote changes in osseointegration.

MATERIAL AND METHOD

SCOPUS, PubMed/Medline, Web of Science, and EMBASE databases were searched in June 2021. In addition, it was performed a manual search of the reference lists of the included articles. Eligibility criteria were in vivo studies that addressed the effect of titanium implant macro-geometry on osseointegration, studies that evaluated periodontally healthy models, and papers indexed in Journal Citation Reports.

RESULTS

The database search resulted in 1037 articles. Of the 19 articles selected for full reading, 16 remained in this systematic review. These had a high heterogeneity making it hard to perform statistical analysis of the data, so a descriptive analysis was performed.

CONCLUSIONS

Based on the studies included in this systematic review, implant macro-geometry provides influences on osseointegration. In this sense, the various isolated characteristics (thread type, thread pitch, thread depth, face angle) should be studied so that the implant geometry can balance the compressive stress and tensile stress and produce a minimum shear force.

Fibroblasts and osteoblasts behavior after contact with different titanium surfaces used as implant abutment: An in vitro experimental study

Background

The goal of this in vitro study was to compare three different surfaces: two types of implant surfaces commercially available ([a] smooth/machined and [b] acid-treated surface) versus (c) anodized surface. Discs were manufactured with commercially pure titanium (CP) grade IV, which were subsequently analyzed by scanning microscopy and fibroblastic and osteoblastic cell cultures.

Methods

Ninety-nine discs (5 × 2 mm) were manufactured in titanium grade IV and received different surface treatments: (i) Mach group: machined; (ii) AA group: double acid etch; and (iii) AN group: anodizing treatment. Three discs from each group were analyzed by Scanning Electron Microscopy (SEM) to obtain surface topography images and qualitatively analyzed by EDS. Balb/c 3T3 fibroblasts and pre-osteoblastic cells (MC3T3-E1 lineage) were used to investigate each group's biological response (n = 10/cellular type). The data were compared statistically using the ANOVA one-way test, considered as a statistically significant difference p < 0.05.

Results

The AA group had numerous micropores with diameters between 5 and 10 μm, while nanopores between 1 and 5 nm were measured in the AN group. The EDX spectrum showed a high titanium concentration in all the analyzed samples. The contact angle and wetting tension were higher in the AA, whereas similar results were observed for the other groups. A lower result was observed for base width in the AA, which was higher in the other two groups. The AN showed the best values in the fibroblast cells, followed by Mach and AA; whereas, in the culture of the MC3T3 cells, the result was precisely the opposite (AA > Mach > AN). There was similar behavior for cell adhesion for the test groups (Mach and AN), with greater adhesion of Balb/c 3T3 fibroblasts compared to MC3T3 cells; in the AA group, there was greater adherence for MC3T3 cells compared to Balb/c 3T3 fibroblasts.

Conclusions

The findings suggest that different surface characteristics can produce different biological responses, possibly cell-line dependent. These findings have important implications for the design of implantable medical devices, where the surface characteristics can significantly impact its biocompatibility.

Investigating the impact of diameters and thread designs on the Biomechanics of short implants placed in D4 bone: a 3D finite element analysis

BACKGROUND

Dental implants emerge as a dependable and efficacious alternative for patients experiencing partial or complete tooth loss. The stability of these implants is influenced by surface topography and macro-level design. In cases where the height of the maxillary posterior region is diminished, employing short implants can prove advantageous. With the aim of examining the distribution of von Mises stress, strain, and micromovement in D4 bone quality surrounding platform-switched short implants, measuring 6 mm in length and featuring diameters ranging from 4 to 6 mm, as well as different thread designs, an in-depth finite element analysis was conducted under immediate loading conditions.

METHODOLOGY

A 3D finite element model was constructed to simulate maxillary molar crowns, incorporating an implant with a length of 6 mm and varying diameters and thread designs. The diameters utilized were 4/3.6 mm, 5/4 mm, and 6/4.8 mm, while the thread designs included buttress, square, and triangle patterns. Each model underwent analysis with a 100 N force applied in two directions: vertical and oblique, relative to the long axis of the implant. Stress, strain, and micromovement in the peri-implant region were recorded, employing the Ansys Workbench R v.18.1 software for modelling and analysis.

RESULTS

When comparing all three diameters, the wide diameter (6 mm threads) exhibited the lowest values of peri-implant von Mises stresses (3.3 MPa and 35.1 MPa), strains (194 Ɛ and 484 Ɛ), and micromovements (0.7 μm and 1.3 Ɛ) subjected to axial and non-axial loading of a 100 N force. Notably, square microthreads yielded the most favorable stress parameters among the different thread shapes, manifesting the minimum values of stress, strains, and micromovements in their vicinity.

CONCLUSION

For the treatment of atrophic ridges or in scenarios necessitating extensive surgical preparation of the implant site, a combination of short implants, wide diameters, and platform switching can be employed. In situations with reduced bone height and the requirement for an implant-supported prosthesis to replace a missing permanent maxillary molar, the utilization of wide-diameter platform-switched short implants measuring 6 mm in length, featuring a square thread design, should be taken into consideration.

The Effect of Coronal Implant Design and Drilling Protocol on Bone-to-Implant Contact: A 3-Month Study in the Minipig Calvarium

Background: Stress concentrated at an implant’s neck may affect bone-to-implant contact (BIC). The objective of this study was to evaluate four different implant neck designs using two different drilling protocols on the BIC. Methods: Ninety-six implants were inserted in 12 minipigs calvarium. Implants neck designs evaluated were: type 1–6 coronal flutes (CFs), 8 shallow microthreads (SMs); type 2–6 CFs,4 deep microthreads (DMs); type 3–4 DMs; type 4–2 CFs, 8 SMs. Two groups of forty-eight implants were inserted with a final drill diameter of 2.8 mm (DP1) or 3.2 mm (DP2). Animals were sacrificed after 1 and 3 months, total-BIC (t-BIC) and coronal-BIC (c-BIC) were evaluated by nondecalcified histomorphometry analysis. Results: At 1 month, t-BIC ranged from 85–91% without significant differences between implant types or drilling protocol. Flutes on the coronal aspect impaired the BIC at 3 m. c-BIC of implant types with 6 CFs was similar and significantly lower than that of implant types 3 and 4. c-BIC of implant type 4 with SMs was highest of all implant types after both healing periods. Conclusions: BIC was not affected by the drilling protocol. CFs significantly impaired the -BIC. Multiple SMs were associated with greater c-BIC.

A novel fully tapered, self-cutting tissue-level implant: non-inferiority study in minipigs

Objectives

To assess the osseointegration and crestal bone level maintenance of a novel fully tapered self-cutting tissue-level implant for immediate placement (test) compared to a clinically established tissue-level implant (control) in moderate bone quality.

Materials and methods

Test and control implants were compared in 3 groups, i.e., small-, medium-, and large-diameter implants in an edentulous mandibular minipig model with moderate bone quality after 12 weeks of healing. Histometrically derived bone-to-implant contact (BIC) and first bone-to-implant contact (fBIC) were subjected to statistical non-inferiority testing. Maximum insertion torque values in artificial bone were assessed for comparison.

Results

BIC values for the tests and control implants for all 3 diameters were comparable and non-inferior: small diameter (61.30 ± 10.63% vs. 54.46 ± 18.31%) (p=0.99), medium diameter (60.91 ± 14.42 vs. 54.68 ± 9.16) (p=0.55), and large diameter (45.60 ± 14.67 vs. 52.52 ± 14.76) (p=0.31). fBIC values for test implants were higher and non-inferior compared to control implants in all three groups. Test implants further showed distinctly higher maximum insertion torque values compared to control implants.

Conclusion

The investigated novel tissue-level implant is able to achieve high levels of primary and secondary implant stability under simultaneous preservation of crestal bone levels. This qualifies the studied implant as an attractive candidate for immediate placement in bone of limited quality.

Clinical relevance

This pilot pre-clinical study investigated a novel tissue-level implant for immediate placement. With the aim of translating the studied prototype into clinical application pre-clinical models, procedures and controls have been chosen with the aim of reflecting its future clinical indication and use.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-03912-w.

Marginal Bone Loss around Machined Smooth Neck Implants Compared to Rough Threaded Neck Implants: A Systematic Review and Meta-Analysis

PURPOSE

The purpose of this meta-analysis was to assess the effect of rough threaded neck implants on marginal bone loss, compared to machined smooth neck implants.

MATERIALS AND METHODS

Literature searches were performed in the Cochrane Central Register of Controlled Trials (The Cochrane Library) (up to March 04, 2020), MEDLINE (PubMed) (1966 to March 04, 2020), and EMBASE (1980 to March 04, 2020), and reference lists of relevant manuscripts and relevant systematic reviews. Grey literature was sought using Grey Literature Net-Work Service (www.opengrey.eu) and The Grey Literature Report (www.greylit.org). Randomized controlled trials and controlled clinical trials that compared the effects of machined smooth neck implants versus rough threaded neck implants on marginal bone loss were included. Two review authors selected studies, assessed trial quality, and extracted data from included studies independently. The meta-analysis was carried out with Review Manager v5.3 software that compared marginal bone loss between rough threaded neck implants and machined smooth neck implants.

RESULTS

This review included 8 manuscripts (2 randomized controlled trials and 6 controlled clinical trials) from 6 clinical studies. The marginal bone loss around the rough threaded neck implants was significantly less than that around machined smooth neck ones (MD: -0.43 mm, 95% CI: -0.65 to -0.22 mm; p < 0.0001). In the subgroup with different platform connections, less marginal bone loss was observed around the rough threaded neck implants with platform switching (MD: -0.67 mm, 95% CI: -0.87 to -0.48 mm; p < 0.00001) or with regular platform (MD: -0.28 mm, 95% CI: -0.39 to -0.18 mm; p < 0.00001). The statistical analysis of the subgroups with functional loading for 3 or 6 months (MD: -0.39 mm; 95% CI: -0.61 to -0.18 mm; p = 0.0003) and 1 year or longer (MD: -0.43 mm, 95% CI: -0.65 to -0.22 mm; p < 0.0001) suggested that the rough threaded neck implants helped to reduce marginal bone loss.

CONCLUSIONS

The results of this review suggested that rough threaded neck implants may be helpful in maintaining the amount of marginal bone around implants. Larger sample size, longer follow-up periods and well-conducted randomized controlled trials are necessary to further prove the validity of the findings.

The effect of implant neck microthread design on stress distribution of peri-implant bone with different level: A finite element analysis

BACKGROUND/PURPOSE

Significant research has proposed that the implant with microthread in the neck can significantly reduce marginal bone loss, but whether it is consistent in the condition of marginal bone loss is still unknown. The objective of this study is to investigate the effect of microthread on stress distribution in peri-implant bone with different bone level using finite element analysis.

MATERIALS AND METHODS

A series of computational models of mandible segments with different bone resorption and implant models with or without microthread in the neck was installed by computer-aided design software. The simulated occlusal force of 150N was applied buccolingually on the top center point of implant. The FEA was performed, and the von Mises stress, principal stress and shear stress in peri-implant bone were recorded and analyzed.

RESULTS

In all models, the T-neck group exhibits higher von Mises stress and principal stress, as well as lower shear stress than S-neck group. Three types of stresses increase with the depth of bone resorption developed, but the differences of shear stress between two groups of implants were gradually decreased.

CONCLUSION

The micro-thread design in implant neck can reduce marginal bone loss by decreasing shear stress in peri-implant bone, but this effect is gradually weakened with the decline of the marginal bone level.

Effect of Rough Surface Platforms on the Mucosal Attachment and the Marginal Bone Loss of Implants: A Dog Study

The preservation of peri-implant tissues is an important factor for implant success. This study aimed to assess the influence of the surface features of a butt-joint platform on soft-tissue attachment and bone resorption after immediate or delayed implant placement. All premolars and first molars of eight Beagle dogs were extracted on one mandible side. Twelve-weeks later, the same surgery was developed on the other side. Five implants with different platform surface configurations were randomly inserted into the post-extracted-sockets. On the healed side, the same five different implants were randomly placed. Implants were inserted 1 mm subcrestal to the buccal bony plate and were connected to abutments. The primary outcome variables were the supracrestal soft tissue (SST) adaptation and the bone resorption related to the implant shoulder. The SST height was significantly larger in immediate implants (IC95% 3.9–4.9 mm) compared to delayed implants (IC95% 3.1–3.5 mm). Marginal bone loss tended to be higher in immediate implants (IC95% 0.4–0.9 mm) than in delayed implants (IC95% 0.3–0.8 mm). Linear-regression analysis suggested that the SST height was significantly affected by the configuration of the platform (0.3–1.9 mm). Roughened surface platforms resulted in higher SST height when compared to machined surface platforms. Marginal bone loss was less pronounced in roughened designs.

Crestal module design optimization of dental implants: finite element analysis and in vivo studies

The aim of this study was to evaluate the biomechanical behavior of Bone Level dental implants with four different neck designs in contact with cortical bone. Numerical simulations were performed using a Finite Element Method (FEM) based-model. In order to verify the FEM model, the in silico results were compared with the results obtained from histological analysis performed in an in vivo study with New Zealand rabbits. FEM was performed using a computerized 3D model of Bone Level dental implants inserted in the lower jaw bone with an applied axial load of 100 N. The analysis was performed using four different implant neck designs: even surfaced, screwed, three-ring design and four-ring design. Interface are of bone growth was evaluated by analyzing the Bone-Implant-Contact (BIC) parameter obtained from in vivo histological process and analyzed by Scanning Electron Microscopy (SEM). Bone Level implants were inserted in the rabbit tibia, placing two implants per tibia. The BIC was evaluated after three and six weeks of implantation. FEM studies showed that the three-ring design presented lower values of stress distribution compared to the other studied designs. The lower levels of mechanical stress were then correlated with the in vivo studies, showing that the three-ring design presented the highest BIC value after 3 and 6 weeks of implantation. In silico and in vivo results both concluded that the implants with three-ring neck design presented the best biomechanical and histological behavior in terms of new bone formation, enhanced mechanical stability and optimum osseointegration.

Influence of Implant Neck Design on Peri-Implant Tissue Dimensions: A Comparative Study in Dogs

This in vivo study assessed (hard and soft) peri-implant tissue remodeling around implants with micro-ring and open-thread neck designs placed in a dog model. Twenty histological sections corresponding to four different implant designs that were placed in America Foxhound dogs were obtained from previous studies. All the implants had been placed under identical conditions and were divided into four groups: Group A, micro-rings on implant neck plus 0.5 mm refined surface; Group B, micro-rings on implant neck; Group C, open-thread neck; and, Group D, double-spiral neck. Eight weeks after surgery, the integrated implants were removed and processed for histological examination. Crestal bone loss and bone-to-implant contact was greater for micro-ring necks than open-thread necks. Soft tissues showed significant differences on both buccal and lingual aspects, so that the distance from peri-implant mucosa to the apical portion of the barrier epithelium was smaller in the micro-ring groups. So, in spite of generating greater bone-to-implant contact, implants with micro rings produced more bone loss than open-thread implants. Moreover, the outcomes that were obtained IPX implants smooth neck design produced less bone loss in the cervical area, following by Facility implants when compared with the other open thread and microthreaded implant designs. Implant thread design can influence on bone remodeling in the cervical area, related to bundle bone preservation.

Immediate Implant Placement Into Fresh Extraction Sites Using Single-Drilling Bur and Two Loading Procedures: Follow-Up Results

Modern clinical protocols in implantology aim at shortening the treatment time and reducing duration and discomfort of the surgical phase, while maintaining optimal treatment outcomes. The purpose of this study was to evaluate clinical outcomes of implants immediately placed in extraction sites, using a single drilling step for implant site preparation. One-hundred thirty-three patients (mean age 55.3 ± 12.7 [SD] years, range 20-83 years) were treated at 2 clinical centers. Two-hundred sixty-one implants were inserted in fresh postextraction sockets. One-hundred sixty-five implants were immediately loaded (IL) and 96 underwent delayed loading (DL). Implant survival, peri-implant bone level change and patients' satisfaction were assessed after at least 3 years of function. No patient dropout occurred. The mean follow-up was 63.61 ± 11.52 months (range 39.71-85.71 months) from prosthesis delivery. Two IL and 1 DL implant failed in 3 patients. Implant survival was 98.8% and 99% for IL and DL group, respectively. The mean marginal bone loss after 1 year was 0.48 ± 0.40 mm and 0.52 ± 0.34 mm for IL and DL group. No biological nor mechanical complications occurred. All patients demonstrated full satisfaction. The present protocol with single burs for site preparation produced satisfactory clinical outcomes independent of the loading timing. Further long-term comparative studies are needed to confirm the present findings.

Evaluation of a New Dental Implant Cervical Design in Comparison with a Conventional Design in an Experimental American Foxhound Model

The aim of this study was to evaluate osseointegration and crestal bone height in implants with a triangular cervical design in comparison with a standard rounded cervical design. The control group consisted of 24 implants with a standard cervical design, and the test group of 24 implants with a triangular cervical design. The implants were inserted in healed bone in six American Foxhounds. Crestal bone height and tissue thickness in the cervical portion were measured after 12 weeks healing. Data analysis found mean crestal bone loss of: 0.31 ± 0.24 mm on the buccal side, 0.35 ± 0.14 mm on the lingual in the test group, and 0.71 ± 0.28 mm buccal loss, and 0.42 ± 0.30 mm lingual in the control group; with statistically significant differences on the buccal aspect (p = 0.0019). Mean tissue thickness in the test group was 1.98 ± 0.17 mm on the buccal aspect, and 2.43 ± 0.93 mm in the lingual; in the control group it was 2.48 ± 0.61 mm buccal thickness, and 2.88 ± 0.14 mm lingual, with significant differences on both aspects (p = 0.0043; p = 0.0029). The results suggest that greater thickness of peri-implant tissue can be expected when the triangular cervical implant design is used rather than the standard cervical design.

Does Oral Implant Design Affect Marginal Bone Loss? Results of a Parallel-Group Randomized Controlled Equivalence Trial

Objective

To test whether or not the modified design of the test implant (intended to increase primary stability) has an equivalent effect on MBL compared to the control.

Methods

Forty patients were randomly assigned to receive test or control implants to be installed in identically dimensioned bony beds. Implants were radiographically monitored at installation, at prosthetic delivery, and after one year. Treatments were considered equivalent if the 90% confidence interval (CI) for the mean difference (MD) in MBL was in between −0.25 and 0.25 mm. Additionally, several soft tissue parameters and patient-reported outcome measures (PROMs) were evaluated. Linear mixed models were fitted for each patient to assess time effects on response variables.

Results

Thirty-three patients (21 males, 12 females; 58.2 ± 15.2 years old) with 81 implants (47 test, 34 control) were available for analysis after a mean observation period of 13.9 ± 4.5 months (3 dropouts, 3 missed appointments, and 1 missing file). The adjusted MD in MBL after one year was −0.13 mm (90% CI: −0.46–0.19; test group: −0.49; control group: −0.36; p = 0.507).

Conclusion

Both implant systems can be considered successful after one year of observation. Concerning MBL in the presented setup, equivalence of the treatments cannot be concluded.

Registration

This trial is registered with the German Clinical Trials Register (ID: DRKS00007877).

Evaluation of bone stimulation by different designs of microthreaded implants in enhancing osseointegration: An in vivo animal study supported by a numerical analysis

BACKGROUND

An optimal shape of the thread design of the implants is required for equal distribution of stresses to the surrounding bone matrix and for stimulation and promotion of bone remodeling.

PURPOSE

The study was construed with the aim of histomorphometric evaluation of bone stimulation generated by different microthread designed implants in enhancing osseointegration, and to assess the pattern of stress dissipation through a two-dimensional finite element analysis.

MATERIALS AND METHODS

Computer Aided Designing of two type of microthreads, one V-shaped and the other Power-shaped microthreaded dental implants with only microthreads all along body of the implant from the neck to the apex was made and 30 implant prototypes were milled. Two-dimensional finite elemental analysis (FEA) was carried out to assess the pattern of stress distribution in the bone around these implant designs and for In vivo study 24 implant prototypes were placed in rabbits tibia and femur, out of which 12 were with V-shaped microthreads and the other 12 were with Power-shaped microthreads. Histomorphometric analysis was carried out of the sections obtained from the enbloc specimen retrieved from the sacrificed rabbits.

RESULTS

FEA showed less stress around the V-shaped microthreaded implant model when compared to Power-shaped microthreaded implant model. Hitomorphometry showed statistical significance difference in new bone volume (BV) and Total BV for V-shaped microthreaded prototype implant.

CONCLUSIONS

V-shaped microthreaded dental implant design can be preferred over Power-shaped microthreaded dental implant for proper stress distribution and for promoting osseointegration.

Comparison of in-vivo failure of single-thread and dual-thread temporary anchorage devices over 18 months: A split-mouth randomized controlled trial

INTRODUCTION

The purpose of this study was to compare the in-vivo failure rates of single-thread and dual-thread temporary anchorage device (TAD) designs over 18 months.

METHODS

Thirty patients with skeletal Class II Division 1 malocclusion requiring anchorage from TADs for retraction of maxillary incisors into the extracted premolar space were recruited in this parallel group, split-mouth, randomized controlled trial. A block randomization sequence was generated with Random Allocation Software (version 2.0; Isfahan, Iran) with the allocations concealed in sequentially numbered, opaque, sealed envelopes. A total of 60 TADs (diameter, 2 mm; length, 10 mm) were placed in the maxillary arches of these patients with random allocation of the 2 types to the left and the right sides in a 1:1 ratio. All TADs were placed between the roots of the second premolar and the first molar and were immediately loaded. Patients were followed for a minimum of 12 months and a maximum of 18 months for the failure of the TADs. Data were analyzed blindly on an intention-to-treat basis.

RESULTS

Four TADs (13.3%) failed in the single-thread group, and 6 TADs (20%) failed in the dual-thread group. The McNemar test showed an insignificant difference (P = 0.72) between the 2 groups. An odds ratio of 1.6 (95% confidence interval, 0.39-6.97) showed no significant associations among the variables. Most TADs failed in the first month after insertion (50%).

CONCLUSIONS

The failure rate of dual-thread TADs compared with single-thread TADs is statistically insignificant when placed in the maxilla for retraction of the anterior segment. Registration: The trial was not registered before commencement.

PROTOCOL

The protocol was not published before the trial.

Tapered Implants in Dentistry: Revitalizing Concepts with Technology: A Review

The most common approach to lessen treatment times is by decreasing the healing period during which osseointegration is established. Implant design parameters such as implant surface, primary stability, thread configuration, body shape, and the type of bone have to be considered to obtain this objective. The relationship that exists between these components will define the initial stability of the implant. It is believed implant sites using a tapered design and surface modification can increase the primary stability in low-density bone. Furthermore, recent experimental preclinical work has shown the possibility of attaining primary stability of immediately loaded, tapered dental implants without compromising healing and rapid bone formation while minimizing the implant stability loss at compression sites. This may be of singular importance with immediate/early functional loading of single implants placed in poor-quality bone. The selection of an implant that will provide adequate stability in bone of poor quality is important. A tapered-screw implant design will provide adequate stability because it creates pressure on cortical bone in areas of reduced bone quality. Building on the success of traditional tapered implant therapy, newer tapered implant designs should aim to maximize the clinical outcome by implementing new technologies with adapted clinical workflows.

Effect of microthreads on coronal bone healing of narrow-diameter implants with reverse-tapered design in beagle dogs

OBJECTIVES

The objective of this study was to investigate the effect of microthreads on the coronal bone healing of narrow-diameter implants with reverse-tapered design.

MATERIAL AND METHODS

A total of 52 implants were classified into two groups according to presence or absence of coronal microthreads, the reverse-tapered narrow-diameter implant (RTN) group, and the reverse-tapered narrow-diameter implant with microthreads (RTNM) group. The implants were installed in split-mouth design in the edentulous mandible of six dogs. Three animals were sacrificed at 4 weeks and three at 8 weeks. Resonance frequency analysis, bone measurement using microcomputed tomography (micro-CT), removal torque test, and histometric analysis were performed.

RESULTS

No significant differences in implant stability quotient value were observed between the groups at baseline, 4 weeks, or 8 weeks. Bone measurement using micro-CT showed that bone-implant contact volume (BICV) and bone-implant contact volume ratio (BICVR) in the coronal part of RTNM were statistically higher than those in RTN at 4 and 8 weeks. Histometric analysis showed statistically higher bone-implant contact length (BICL) in the coronal part of RTNM than in RTN at 4 weeks; however, bone-implant contact ratio (BICR) was not significantly different between the groups. At 8 weeks, the BICL and BICR did not differ significantly between the groups. Removal torque test showed no significant differences between the groups at 4 and 8 weeks.

CONCLUSIONS

The microthreads might facilitate more coronal bone-implant contact due to increased surface areas at an early healing phase; however, they did not significantly affect coronal bone healing at 8 weeks.

Influence of Implant Neck Design on Bone Formation Under Mechanical Repetitive Loading: Histomorphometric and Microcomputed Tomographic Studies in Rabbit Tibiae

PURPOSE

The aim of this study was to investigate effects of implant neck design on the original concept of osseointegration and bone formation when applying mechanical repetitive loading by bone-integrated implants.

MATERIALS AND METHODS

Twenty-eight anodized Ti-6Al-4V alloy implants with +60° or -60° grooves in the implant neck were placed in the proximal tibial metaphysis of 14 rabbits. Fourteen implants received mechanical repetitive loading along the long axis of the implant for 8 weeks at 12 weeks after implant placement. The remaining 14 implants received no loading. Histomorphometric and microcomputed tomographic analyses were then performed.

RESULTS

No effect of neck design was observed without mechanical loading, whereas osseointegration around the +60° grooves was upregulated with mechanical loading. Calculated load effects on bone structure around the implant neck with +60° grooves were larger when compared with the -60° grooves under mechanical loading.

CONCLUSIONS

These findings indicate that the establishment of osseointegration and bone formation around the implant neck with +60° grooves is superior to those with -60° grooves under loaded conditions.

Effect of Microthread Design on Marginal Bone Level Around Dental Implants Placed in Fresh Extraction Sockets

PURPOSE

This study was designed to compare radiographically the effect of microthread on the coronal portion of the fixture on marginal bone level (MBL) around immediately placed dental implants in human subjects.

MATERIAL AND METHODS

Forty-one roughened surface screw type Dentium oral implants (Dentium) were inserted in fresh extraction sockets of the anterior segment of maxilla of 30 patients. The implants were selected randomly using either microthread design on coronal portion of the fixture (Implantium) (test group) or without microthread thread design (Superline) (control group). MBL was measured using digital subtraction radiography technique after 3, 6, and 12 months.

RESULTS

At month 3, the microthread groups have been associated with more marginal bone loss than the control group (P = 0.04). At months 6 and 12, both groups had comparable bone levels (P = 0.21).

CONCLUSION

The microthread design of the implant collar could not have a positive effect in maintaining the MBL around implants placed in fresh extraction socket in anterior maxilla.

Optimally oriented grooves on dental implants improve bone quality around implants under repetitive mechanical loading

The aim was to investigate the effect of groove designs on bone quality under controlled-repetitive load conditions for optimizing dental implant design. Anodized Ti-6Al-4V alloy implants with -60° and +60° grooves around the neck were placed in the proximal tibial metaphysis of rabbits. The application of a repetitive mechanical load was initiated via the implants (50N, 3Hz, 1800 cycles, 2days/week) at 12weeks after surgery for 8weeks. Bone quality, defined as osteocyte density and degree of biological apatite (BAp) c-axis/collagen fibers, was then evaluated. Groove designs did not affect bone quality without mechanical loading; however, repetitive mechanical loading significantly increased bone-to-implant contact, bone mass, and bone mineral density (BMD). In +60° grooves, the BAp c-axis/collagen fibers preferentially aligned along the groove direction with mechanical loading. Moreover, osteocyte density was significantly higher both inside and in the adjacent region of the +60° grooves, but not -60° grooves. These results suggest that the +60° grooves successfully transmitted the load to the bone tissues surrounding implants through the grooves. An optimally oriented groove structure on the implant surface was shown to be a promising way for achieving bone tissue with appropriate bone quality. This is the first report to propose the optimal design of grooves on the necks of dental implants for improving bone quality parameters as well as BMD. The findings suggest that not only BMD, but also bone quality, could be a useful clinical parameter in implant dentistry.

STATEMENT OF SIGNIFICANCE

Although the paradigm of bone quality has shifted from density-based assessments to structural evaluations of bone, clarifying bone quality based on structural bone evaluations remains challenging in implant dentistry. In this study, we firstly demonstrated that the optimal design of dental implant necks improved bone quality defined as osteocytes and the preferential alignment degree of biological apatite c-axis/collagen fibers using light microscopy, polarized light microscopy, and a microbeam X-ray diffractometer system, after application of controlled mechanical load. Our new findings suggest that bone quality around dental implants could become a new clinical parameter as well as bone mineral density in order to completely account for bone strength in implant dentistry.

Microthreaded Implants and Crestal Bone Loss: A Systematic Review

This systematic literature review investigated the effect of microthreaded-neck dental implants on crestal bone loss. Using the participants, interventions, comparison groups, outcomes, and study design (PICO) system, we addressed the following focused question: Do microthreaded-neck dental implants positively affect the crestal bone level around dental implants? We searched 3 electronic databases to find articles published between January 1995 and June 2016 that contained any combination of the following keywords: dental implant, microthread, microthreaded, crestal bone level, crestal bone loss, and alveolar bone level. We excluded case reports, review articles, letters to the editor, commentaries, and articles published in a language other than English. We found a total of 70 articles. After eliminating duplicates and applying PICO eligibility criteria, we selected only articles that reported the results of randomized controlled trials, prospective or retrospective cohort studies, case control studies, cross-sectional studies, or other types of clinical trials that compared the microthreaded implant design with other implant designs. We were left with 23 articles for review. The 23 articles reported crestal bone loss ranging from .05 mm to .9 mm, with a range of 12 to 96 months of follow-up. Less crestal bone was lost with dental implants that had a microthreaded neck design than with machined-surface or conventional rough-surface dental implants. Thus, microthreaded dental implants are a better choice than are implants with other designs. Future studies should use standardized imaging techniques to evaluate the placement of these implants in bone-augmented sites.

Differences in crestal bone-to-implant contact following an under-drilling compared to an over-drilling protocol. A study in the rabbit tibia

OBJECTIVES

The objective of this study is to compare bone-to-implant contact (BIC) between implants inserted at high torque due to under-drilling of the crestal bone to those inserted at low torque due to over-drilling of the crestal bone.

MATERIALS AND METHODS

Forty implants with diameters of 3.75 mm (group A) or 3.55 mm (group B) were inserted in the proximal tibiae of NZW rabbits in two separate surgeries on day 0 or 21. Osteotomy of the crestal bone was finalized with a 3.65-mm drill. In group A, implants were inserted at torque ≥35 Ncm (under-drilling) and in group B with torque <10 Ncm (over-drilling). Implants and their surrounding bone were retrieved on day 42, thus creating 3- and 6-week observation periods, processed for non-decalcified histology and stained with toluidine blue. Crestal BIC (c-BIC) and total BIC (t-BIC) were measured. Wilcoxon test was used to evaluate differences between groups.

RESULTS

Three weeks post-surgery, the mean c-BIC in group A was 16.3 ± 3.3 vs 31.5 ± 3.4 % in group B (P < 0.05). At 6 weeks, a similar trend was observed (group A: 28.7 ± 3.6 %; group B: 38.4 ± 4.9 %) (P > 0.05). No differences in t-BIC were noted at 3 weeks and at 6 weeks between the groups.

CONCLUSIONS

Insertion of implants with an over-drilling protocol of the crestal aspect of the osteotomy resulted in increased short-term crestal bone-to-implant contact.

CLINICAL RELEVANCE

Insertion of implants with a high torque following an under-drilling protocol, commonly used for immediate loading, may reduce crestal bone-to-implant contact at early healing stages.

Early loading of splinted implants in the posterior mandible: a prospective multicentre case series

AIM

To evaluate the 12-months clinical and radiological outcomes with the OsseoSpeed(™) TX implant using an early loading protocol in patients with missing teeth in the posterior mandible.

MATERIAL AND METHODS

Forty-five subjects, with Kennedy class I or II edentulism in the mandible, were enrolled at three centres in China. Two or three implants were placed in one edentulous region using a one-stage procedure. Patients received a screw-retained splinted fixed permanent restoration in one edentulous region 6-8 weeks after surgery. Follow-up took place at 6 and 12 months after loading. Marginal bone level alteration, implant survival and clinical findings were assessed using descriptive statistics. The data were analysed on a patient level, implying that the mean overall implants by patient was used as the statistical unit. The data from the three centres were pooled in the statistical analyses.

RESULTS

A total of 107 implants were inserted in 45 patients. Twelve months after loading, the implant survival rate was 100%, with a mean (± std) marginal bone gain of 0.08 ± 0.411 mm and healthy soft tissue status.

CONCLUSIONS

Early loading of splinted OsseoSpeed(™) TX implants was an effective and safe treatment for partial edentulism of the posterior mandible. CLINICAL TRIAL REGISTRATION NUMBER ON CLINICALTRIALS.GOV: NCT01346683.

Effects of thread size in the implant neck area on peri-implant hard and soft tissues: an animal study

OBJECTIVES

The aim of this animal study was to examine the effects of thread size in the implant neck area on peri-implant tissues in terms of BIC and hard- and soft-tissue dimensions.

MATERIALS AND METHODS

Six Beagle dogs received experimental implants in the mandible 3 month after the removal of premolars and first molars (P2, P3, P4, and M1). Two different types of implants were installed in each animal: Anyone microthread(®) as Group 1 and Anyone(®) as Group 2. Resonance frequency test, intraoral radiography, micro-CT, and histomorphometry were used to evaluate peri-implant tissue after implantation periods of 4 and 8 weeks.

RESULTS

No remarkable complication was observed during the healing period in either group. Resonance frequency testing revealed no significant difference between groups. In radiographic evaluation, Group 2 showed more bone loss than Group 1. However, this difference was not statistically significant. In the micro-CT analysis, BIC and BIV values and soft-tissue height were not significant in both groups. Histological analysis revealed no significant difference in BIC ratio, bone density, or bone loss between groups. However, soft-tissue height was significantly greater in Group 2 than in Group 1 (P = 0.0004).

CONCLUSION

No difference in peri-implant hard or soft tissues was observed according to thread size in the implant neck area.

Decontamination methods using a dental water jet and dental floss for microthreaded implant fixtures in regenerative periimplantitis treatment

OBJECTIVE

This study evaluated decontamination methods using a dental water jet and dental floss on microthreaded implants for regenerative periimplantitis therapy.

MATERIALS AND METHODS

In 6 beagle dogs, experimental periimplantitis was induced, and decontamination procedures, including manual saline irrigation (control group), saline irrigation using a dental water jet (group 1) and saline irrigation using a dental water jet with dental flossing (group 2), were performed. After in situ decontamination procedures, some of the implant fixtures (n = 4 per group) were retrieved for analysis by SEM, whereas other fixtures (n = 4 per group) underwent regenerative therapy. After 3 months of healing, the animals were killed.

RESULTS

The SEM examination indicated that decontamination of the implant surfaces was the most effective in group 2, with no changes in implant surface morphology. The histological examination also revealed that group 2 achieved significantly greater amounts of newly formed bone (6.75 ± 2.19 mm; P = 0.018), reosseointegration (1.88 ± 1.79 mm; P = 0.038), and vertical bone fill (26.69 ± 18.42%; P = 0.039).

CONCLUSION

Decontamination using a dental water jet and dental floss on microthreaded implants showed positive mechanical debridement effects and positive bone regeneration effects.

2D FEA of evaluation of micromovements and stresses at bone-implant interface in immediately loaded tapered implants in the posterior maxilla

AIM

The aim of the study is to evaluate the influence implant length on stress distribution at bone implant interface in single immediately loaded implants when placed in D4 bone quality.

MATERIALS AND METHODS

A 2-dimensional finite element models were developed to simulate two types of implant designs, standard 3.75 mm-diameter tapered body implants of 6 and 10 mm lengths. The implants were placed in D4 bone quality with a cortical bone thickness of 0.5 mm. The implant design incorporated microthreads at the crestal part and the rest of the implant body incorporated Acme threads. The Acme thread form has a 29° thread angle with a thread height half of the pitch; the apex and valley are flat. A 100 N of force was applied vertically and in the oblique direction (at an angle of 45°) to the long axis of the implants. The respective material properties were assigned. Micro-movements and stresses at the bone implant interface were evaluated.

RESULTS

The results of total deformation (micro-movement) and Von mises stress were found to be lower for tapered long implant (10 mm) than short implant (6 mm) while using both vertical as well as oblique loading.

CONCLUSION

Short implants can be successfully placed in poor bone quality under immediate loading protocol. The novel approach of the combination of microthreads at the crestal portion and acme threads for body portion of implant fixture gave promising results.

Histological evaluation of bone formation adjacent to dental implants with a novel apical chamber design: preliminary data in the rabbit model

BACKGROUND

Wound healing events after implant placement will vary according to the extent of the necrotic zone.

PURPOSE

The goal of the present study was to evaluate bone healing around titanium implants with a novel apical chamber design.

MATERIALS AND METHODS

Titanium implants grade 4 were turned with different apex design. Control implants had a self tapping design with centric cutting grooves. Test implants exhibited eccentric cutting grooves interconnected by a hollow chamber. A total of 60 implants were installed in the femur/tibia of 10 rabbits for histological analysis.

RESULTS

After 1 week, immature bone formation started at the cortical level of the test implants associated to scalloped contours indicative of bone resorption. Control implants failed to show new bone formation, and the space within the threads was filled mainly by red blood cells and surgical debris. Bone contact values showed no difference after 1 week, and significant higher values for test implants showed likewise after 4 weeks compared with control implants in the tibia.

CONCLUSION

This experimental study verifies the beneficial effect of bone formation in the chamber at the apical part of the fixture coupled to a faster bone healing to implants placed in dense bone.

Effect of microthreads on removal torque and bone-to-implant contact: an experimental study in miniature pigs

Purpose

The objective of this study was to evaluate the effect of microthreads on removal torque and bone-to-implant contact (BIC).

Methods

Twelve miniature pigs for each experiment, a total of 24 animals, were used. In the removal torque analysis, each animal received 2 types of implants in each tibia, which were treated with sandblasting and acid etching but with or without microthreads at the marginal portion. The animals were sacrificed after 4, 8, or 12 weeks of healing. Each subgroup consisted of 4 animals, and the tibias were extracted and removal torque was measured. In the BIC analysis, each animal received 3 types of implants. Two types of implants were used for the removal torque test and another type of implant served as the control. The BIC experiment was conducted in the mandible of the animals. The P1-M1 teeth were extracted, and after a 4-month healing period, 3 each of the 2 types of implants were placed, with one type on each side of the mandible, for a total of 6 implants per animal. The animals were sacrificed after a 2-, 4-, or 8-week healing period. Each subgroup consisted of 4 animals. The mandibles were extracted, specimens were processed, and BIC was analyzed.

Results

No significant difference in removal torque value or BIC was found between implants with and without microthreads. The removal torque value increased between 4 and 8 weeks of healing for both types of implants, but there was no significant difference between 8 and 12 weeks. The percentage of BIC increased between 2 and 4 weeks for all types of implants, but there was no significant difference between 4 and 8 weeks.

Conclusions

The existence of microthreads was not a significant factor in mechanical and histological stability.

A 5-year prospective radiographic evaluation of marginal bone levels adjacent to parallel-screw cylinder machined-neck implants and rough-surfaced microthreaded implants using digitized panoramic radiographs

OBJECTIVE

The purpose of this split-mouth study was to compare macro- and microstructure implant surfaces at the marginal bone level over five years of functional loading.

MATERIALS AND METHODS

From January to February 2006, 133 implants (70 rough-surfaced microthreaded implants and 63 machined-neck implants) were inserted in the mandible of 34 patients with Kennedy Class I residual dentitions and followed until December 2011. Marginal bone level was radiographically determined at six time points: implant placement (baseline), after the healing period, after six months, and at two years, three years, and five years follow-up.

RESULTS

Median follow-up time was 5.2 years (range: 5.1-5.4). The machined-neck group had a mean crestal bone loss of 0.5 mm (0.0-2.3) after the healing period, 1.1 mm (0.0-3.0) at two years follow-up, and 1.4 mm (0.0-2.9) at five years follow-up. The rough-surfaced microthreaded implant group had a mean bone loss of 0.1 mm (-0.4 to 2.0) after the healing period, 0.5 mm (0.0-2.1) at two years follow-up, and 0.7 mm (0.0-2.3) at five years follow-up. The two implant types showed significant differences in marginal bone levels.

CONCLUSIONS

Rough-surfaced microthreaded design caused significantly less loss of crestal bone levels under long-term functional loading in the mandible when compared to machined-neck implants.

Effect of loading time on the survival rate of anodic oxidized implants: prospective multicenter study

PURPOSE

The purpose of this prospective study was to evaluate the effect of early loading on survival rate or clinical parameter of anodic oxidized implants during the 12-month postloading period.

MATERIALS AND METHODS

Total 69 implants were placed in 42 patients. Anodic oxidized implants (GS II, Osstem Cor., Busan, Korea) placed on the posterior mandibles were divided into two groups, according to their prosthetic loading times: test group (2 to 6 weeks), and control group (3 to 4 months). The implant survival rates were determined during one-year postloading period and analyzed by Kaplan-Meier method. The radiographic peri-implant bone loss and periodontal parameters were also evaluated and statistically analyzed by unpaired t-test.

RESULTS

Total 69 implants were placed in 42 patients. The cumulative postloading implant survival rates were 88.89% in test group, compared to 100% in control group (P<.05). Periimplant marginal bone loss (T: 0.27±0.54 mm, C: 0.40±0.55 mm) and periodontal parameters showed no significant difference between the groups (P>.05).

CONCLUSION

Within the limitation of the present study, implant survival was affected by early loading on the anodic oxidized implants placed on posterior mandibles during one-year follow-up. Early implant loading did not influence peri-implant marginal bone loss, and periodontal parameters.

A 5-year retrospective clinical study of the Dentium implants

PURPOSE

The aim of this retrospective study was to evaluate cumulative survival rate (CSR) of Implantium implants followed for 5 years and association between risk factors and the CSR.

MATERIALS AND METHODS

A total of two hundred forty-nine Implantium Implants System (Dentium, Seoul, Korea) placed in ninety-five patients from 2004 to 2009 were investigated with several identified risk factors (sex, systemic disease, smoking, alchohol, reason of tooth loss, length, arch (maxilla or mandible), replace tooth type (incisor, canine, premolar or molar) Kennedy classification, prosthodontic type, prosthodontic design, opposite dentition, abutment type, occlusal material, occlusal unit, splint to tooth, cantilever, other surgery). Clinical examination (mobility, percussion, screw loosening, discomfort, etc.) and radiographic examination data were collected from patient records including all problems during follow-up period according to protocols described earlier. Life table analysis was undertaken to examine the CSR. Cox regression method was conducted to assess the association between potential risk factors and overall CSR.

RESULTS

Five of 249 implants were failed. Four of these were lost before loading. The 5-year implant cumulative survival rate was 97.37%. Cox regression analysis demonstrated a significant predictive association between overall CSR and systemic disease, smoking, reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The screw related complication was rare. Two abutment screw fractures were found. Another complications of prosthetic components were porcelain fracture, resin facing fracture and denture fracture (n=19).

CONCLUSION

The 5-year CSR of Implantium implants was 97.37%. Implant survival may be dependent upon systemic disease, smoking reason of tooth loss, arch, Kennedy classification and prosthodontic design (P<.05). The presence of systemic diseases and combination of other surgical procedures may be associated with increased implant failure.

A short-term clinical study of marginal bone level change around microthreaded and platform-switched implants

PURPOSE

The marginal bone levels around implants following restoration are used as a reference for evaluating implant success and survival. Two design concepts that can reduce crestal bone resorption are the microthread and platform-switching concepts. The aims of this study were to analyze the placement of microthreaded and platform-switched implants and their short-term survival rate, as well as the level of bone around the implants.

METHODS

The subjects of this study were 27 patients (79 implants) undergoing treatment with microthreaded and platform-switched implants between October 2008 and July 2009 in the Dental Hospital of Yonsei University Department of Periodontology. The patients received follow-up care more than 6 months after the final setting of the prosthesis, at which time periapical radiographs were taken. The marginal bone level was measured from the reference point to the lowest observed point of contact between the marginal bone and the fixture. Comparisons were made between radiographs taken at the time of fixture installation and those taken at the follow-up visit.

RESULTS

During the study period (average of 11.8 months after fixture installation and 7.4 months after the prosthesis delivery), the short-term survival rate of microthreaded and platform-switched implants was 100% and the marginal bone loss around implants was 0.16±0.08 mm, the latter of which is lower than the previously reported values.

CONCLUSIONS

This short-term clinical study has demonstrated the successful survival rates of a microthread and platform-switched implant system, and that this system is associated with reduced marginal bone loss.

The effect of abutment dis/reconnections on peri-implant bone resorption: a radiologic study of platform-switched and non-platform-switched implants placed in animals

OBJECTIVES

The purpose of this animal study was to radiologically measure the influence of abutment disconnection on bone resorption and to compare this influence on platform-switched vs. non-platform-switched implants.

METHODS

The study design included extraction of all mandibular premolars in five canines . After 2 months, six implants were placed in each dog. Four of them were platform-switched (PS) implants and two were non-platform-switched (NPS) implants. Some or all of the abutments connected to the implants were disconnected at pre-ordained post-surgical intervals. Radiographs were taken at the time of implant placement and at every handling. The values for mesial (horizontal and vertical) and distal (horizontal and vertical) bone resorption were taken and compared for each implant at every abutment dis/reconnection.

RESULTS

The average vertical bone resorption around NPS implants after four dis/reconnections was 1.09 mm (SD 0.25 mm), and the average horizontal bone resorption was 0.98 mm (SD 0.27 mm). The average vertical bone resorption around PS implants after four dis/reconnections was 0.24 mm, (SD 0.08 mm) and the average horizontal bone resorption was 0.24 mm (SD 0.13 mm). The difference of the average horizontal and vertical bone resorption around NPS (site D) and PS (site A) implants was statically significant (P < 0.05). The average mesial and distal bone resorption values around PS (site A) implant adjacent to a tooth were compared, and statically significant differences were found (P < 0.05).

CONCLUSIONS

Implants with a PS design show less peri-implant bone resorption during the healing process and as their abutments are disconnected, than do comparably dis/reconnected NPS implants. The location of the PS implant next to a tooth may decrease radiographically visible peri-implant bone resorption significantly.

Osseointegration of commercial microstructured titanium implants incorporating magnesium: a histomorphometric study in rabbit cancellous bone

OBJECTIVE

Recent studies have suggested that magnesium (Mg) ions exert a beneficial effect on implant osseointegration. This study assessed the osseointegration of nanoporous titanium (Ti) surface incorporating the Mg produced by hydrothermal treatment in rabbit cancellous bone to determine whether this surface would further enhance bone healing of moderately rough-surfaced implants in cancellous bone, and compared the result with commercially available micro-arc oxidized Mg-incorporated implants.

MATERIAL AND METHODS

The Mg-incorporated Ti surfaces (RBM/Mg) were obtained by hydrothermal treatment using an alkaline Mg-containing solution on grit-blasted moderately rough (RBM) implants. Untreated RBM and recently introduced Mg-incorporated microporous Ti implants produced by micro-arc oxidation (M) were used controls in this study. The surface characteristics were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy and optical profilometry. Twenty-four threaded implants with a length of 10 mm (eight RBM implants, eight RBM/Mg implants and eight M implants) were placed in the femoral condyles of 12 New Zealand White rabbits. Histomorphometric analysis was performed 4 weeks after implantation.

RESULTS

Hydrothermally treated and untreated grit-blasted implants displayed almost identical surface morphologies and R(a) values at the micron-scale. The RBM/Mg implants exhibited morphological differences compared with the RBM implants at the nano-scale, which displayed nanoporous surface structures. The Mg-incorporated implants (RBM/Mg and M) exhibited more continuous bone apposition and a higher degree of bone-to-implant contact (BIC) than the untreated RBM implants in rabbit cancellous bone. The RBM/Mg implants displayed significantly greater BIC% than untreated RBM implants, both in terms of the all threads region and the total lateral length of implants (P<0.05), but no statistical differences were found between the RBM/Mg and M implants except BIC% values in total lateral length.

CONCLUSION

These results indicate that a nanoporous Mg-incorporated surface may be effective in enhancing the osseointegration of moderately rough grit-blasted implants by increasing the degree of bone-implant contact in areas of cancellous bone.