Influence of the surgical technique and surface roughness on the primary stability of an implant in artificial bone with a density equivalent to maxillary bone: a laboratory study

Evaluation of a vibration modeling technique for the in-vitro measurement of dental implant stability

The Advanced System for Implant Stability Testing (ASIST) is a device currently being developed to noninvasively measure implant stability by estimating the mechanical stiffness of the bone-implant interface, which is reported as the ASIST Stability Coefficient (ASC). This study's purpose was to determine whether changes in density, bonding, and drilling technique affect the measured vibration of a dental implant, and whether they can be quantified as a change in the estimated BII stiffness. Stability was also measured using RFA, insertion torque (IT) and the pullout test. Bone-level tapered implants (4.1 mm diameter, 10 mm length) were inserted in polyurethane foam as an artificial bone substitute. Samples were prepared using different bone densities (20, 30, 40 PCF), drilling sequences, and superglue to simulate a bonded implant. Measurements were compared across groups at a significance level of 0.05. The ASC was able to indicate changes in each factor as a change in the interfacial stiffness. IT and pullout force values also showed comparable increases. Furthermore, the relative difference in ISQ values between experimental groups was considerably smaller than the ASC. While future work should be done using biological bone and in-vivo systems, the results of this in-vitro study suggest that modelling of the implant system with a vibration-based approach may provide a noninvasive method of assessing the mechanical stability of the implant.

Pre-implantation teriparatide administration improves initial implant stability and accelerates the osseointegration process in osteoporotic rats

PURPOSE

Osteoporotic individuals who have dental implants usually require a prolonged healing time for osseointegration due to the shortage of bone mass and the lack of initial stability. Although studies have shown that intermittent teriparatide administration can promote osseointegration, there is little data to support the idea that pre-implantation administration is necessary and beneficial.

METHODS

Sixty-four titanium implants were placed in the bilateral proximal tibial metaphysis in 32 female SD rats. Bilateral ovariectomy (OVX) was used to induce osteoporosis. Four major groups (n = 8) were created: PRE (OVX + pre-implantation teriparatide administration), POST (OVX + post-implantation administration), OP (OVX + normal saline (NS)) and SHAM (sham rats + NS). Half of rats (n = 4) in each group were euthanized respectively at 4 weeks or 8 weeks after implantation surgery, and four major groups were divided into eight subgroups (PRE4 to SHAM8). Tibiae were collected for micro-CT morphometry, biomechanical test and undecalcified sections analysis.

RESULTS

Compared to OP group, rats in PRE and SHAM groups had a higher value of insertion torque (p < 0.05). The micro-CT analysis, biomechanical test, and histological data showed that peri-implant trabecular growth, implants fixation and bone-implant contact (BIC) were increased after 4 or 8 weeks of teriparatide treatment (p < 0.05). There was no statistically difference in those parameters between PRE4 and POST8 subgroups (p > 0.05).

CONCLUSIONS

In osteoporotic rats, post-implantation administration of teriparatide enhanced peri-implant bone formation and this effect was stronger as the medicine was taken longer. Pre-implantation teriparatide treatment improved primary implant stability and accelerated the osseointegration process.

Fracture Resistance of a Two-Piece Zirconia Implant System after Artificial Loading and/or Hydrothermal Aging-An In Vitro Investigation

The purpose of the present study was to assess the fracture resistance of a two-piece alumina-toughened zirconia implant system with a carbon-reinforced PEEK abutment screw.

METHODS

Thirty-two implants with screw-retained zirconia abutments were divided into four groups of eight samples each. Group 0 (control group) was neither loaded nor aged in a chewing simulator; group H was hydrothermally aged; group L was loaded with 98 N; and group HL was subjected to both hydrothermal aging and loading in a chewing simulator. One sample of each group was evaluated for t-m phase transformation, and the others were loaded until fracture. A one-way ANOVA was applied to evaluate differences between the groups.

RESULTS

No implant fracture occurred during the artificial chewing simulation. Furthermore, there were no statistically significant differences (p > 0.05) between the groups in terms of fracture resistance (group 0: 783 ± 43 N; group H: 742 ± 43 N; group L: 757 ± 86 N; group HL: 740 ± 43 N) and bending moment (group 0: 433 ± 26 Ncm; group H: 413 ± 23 Ncm; group L: 422 ± 49 Ncm; group HL: 408 ± 27 Ncm).

CONCLUSIONS

Within the limitations of the present investigation, it can be concluded that artificial loading and hydrothermal aging do not reduce the fracture resistance of the investigated implant system.

Influence of different surgical techniques on primary implant stability in the posterior maxilla: a randomized controlled clinical trial

BACKGROUND AND OBJECTIVE

Primary stability (PS) is remarkable for secondary stability and implant success. Surgical technique modifications seem to improve primary stability, especially in poor quality bone. The aim of this study was to compare the insertion torque (IT) and implant stability quotients (ISQ) of implants placed with underpreparation, expanders, and standard surgical instrumentation in different bone types.

MATERIAL AND METHODS

This randomized controlled clinical trial enrolled 108 patients (n=108 implants) distributed in three study groups: group 1 (n=36) underpreparation technique, group 2 (n=36) expander technique, and group 3 (n=36) conventional drilling. IT was recorded with a torque indicator. ISQ was recorded with resonance frequency analysis immediately after surgery.

RESULTS

ISQ values were associated with the patient's bone quality and were higher in bone quality type II (76.65) and type III (73.60) and lower in bone quality type IV (67.34), with statistically significant differences (p<0.0001). Lower stability results were obtained when conventional drilling (69.31) was used compared to the use of underpreparation (74.29) or expanders (73.99) with a level of significance of p=0.008 and p=0.005, respectively.

CONCLUSIONS

The surgical technique influences the PS when there is low-quality bone. In low-quality bones, conventional drilling obtains lower ISQ values.

CLINICAL RELEVANCE

Replace the conventional drilling technique for an alternative, underpreparation or expanders, in low-quality bone in order to achieve greater primary stability.

In vivo osseointegration evaluation of implants coated with nanostructured hydroxyapatite in low density bone

OBJECTIVE

This in vivo study, aimed to biomechanically, histomorphometrically and histologically evaluate an implant surface coated with nanostructured hydroxyapatite using the wet chemical process (biomimetic deposition of calcium phosphate coating) when compared to a dual acid-etching surface.

MATERIAL AND METHODS

Ten sheep (2-4 years old) received 20 implants, 10 with nanostructured hydroxyapatite coating (HAnano), and 10 with dual acid-etching surface (DAA). The surfaces were characterized with scanning electron microscopy and energy dispersive spectroscopy; insertion torque values and resonance frequency analysis were measured to evaluate the primary stability of the implants. Bone-implant contact (BIC) and bone area fraction occupancy (BAFo) were evaluated 14 and 28 days after implant installation.

RESULTS

The HAnano and DAA groups showed no significant difference in insertion torque and resonance frequency analysis. The BIC and BAFo values increased significantly (p<0.05) over the experimental periods in both groups. This event was also observed in BIC value of HAnano group. The HAnano surface showed superior results compared to DAA after 28 days (BAFo, p = 0.007; BIC, p = 0.01).

CONCLUSION

The results suggest that the HAnano surface favors bone formation when compared to the DAA surface after 28 days in low-density bone in sheep.

Effect of cutting flute design features on primary stability of immediate implant placement and restoration: a dynamic experimental analysis

Self-tapping implants with self-cutting flutes may influence primary stability, especially for the immediate implant placement and restoration protocol in which implants are affixed to the bone in the apical portion. Screw geometry differs between brands, and the effect of apical design on its clinical outcomes remains unclear. This study is aimed at investigating the influence of cutting flute shape (spiral, straight, and without flute) on primary stability by using a dynamic experimental test. Six types of dental implants were designed using computer-aided design and computer-aided manufacturing technology, consisting of three types of cutting flute shapes along with two types of screw features. A dynamic mechanical test was performed using a cyclic loading scheme. The mechanical behaviors of resistance to lateral load (RLL), maximum force, and energy dissipation were compared between groups. In the dynamic test, implants without cutting flute also exhibited higher values in RLL, maximum force, and energy dissipation. The aggressive thread implant with straight flute displayed higher RLL and had a significantly higher values in RLL (p = 0.033) at the threshold point of bone-implant interface breakdown. The implants without cutting flutes exhibited higher primary stability. Straight flute design would improve RLL for aggressive thread implant.

Clinical Evaluation of Short Tuberosity Implants among Type 2 Diabetic and Non-Diabetic Patients: A 5 Year Follow-Up

Aim: To assess clinical and radiographic parameters including bleeding on probing (BoP); probing depth (PD), plaque index (PI) and crestal bone loss (CBL) around short tuberosity implants (STI) supporting fixed partial dentures in patients with Type 2 diabetes mellitus (T2DM) and non-diabetics. Material and Methods: Participants with T2DM and without T2DM with at least one STI (6 mm) posteriorly restored with a fixed partial denture splinting premolar implant were included. A questionnaire collected demographic details including gender, age, duration of diabetes, habits of brushing, the total number of dental implants and location, implant loading after placement, restoration type, and family history of DM. Clinical and radiographic assessment of peri-implant parameters, i.e., bleeding on probing (BoP), probing depth (PD), plaque index (PI), and crestal bone loss (CBL) was performed. The restorative success of STI was determined by no sensation of the foreign body, lack of pain and dysesthesia, lack of infection, no radiolucency around the implant, and no mobility. The Kruskal-Wallis test was used for statistical analysis. A p-value of less than 0.05 was considered statistically significant. Results: Twenty-five T2DM (19 males and 6 females) and 25 non-diabetic (18 males and 7 females) participants were included. The number of STIs in T2DM was 41, whereas in non-diabetic it was 38. At 1 year follow-up, mean PI% in T2DM participants was 18.9% (19.2-21.4%) and in non-diabetics it was 17.6% (16.3-18.5%). The mean PD was recorded in diabetics (1.3 ± 5.0 mm) and non-diabetics (1.1 ± 3.2 mm). The BoP value in diabetics was 44.9% (39.8-46.4%) and 28.2% in non-diabetics (17.2-24.6%). At 5 years of follow-up, the mean PI% range in T2DM participants was 26.18% (25.4-29.1%) and 24.42% in non-diabetic (20.1-25.5%). The mean PD in millimeters around STI in T2DM was observed to be 2.3 ± 4.8 mm and 1.4 ± 3.4 mm in non-diabetics. In addition, BoP in diabetic participants was 39.54% (27.7-42.1%) and 24.42% in non-diabetics (20.1-25.5%). A total of six STIs failed, i.e., two in the non-diabetic and four in the T2DM group. Conclusions: Patients with T2DM have poor periodontal (BoP, PD, CBL) and restorative peri-implant parameters around STIs when compared to healthy (non-diabetic) participants at five years of follow-up. For long-term stability, glycemic control is pivotal along with following good plaque control.

Does hyperbaric oxygen therapy pressure reduce mechanical stability of implants?

Hyperbaric oxygen therapy (HBOT) has beneficial effects for patients complaining of poor bone healing such as related to diabetes mellitus. However, it is known that changing pressure conditions might cause dental barotrauma in the oral cavity. The aim of this study was to evaluate implant mechanical stability under HBOT pressure. Thirty-five implants were placed in bone blocks divided into five groups as control, 1, 3, 5, 7 HBOT cycles. In one cycle, 2.4 bar 100% oxygen pressure was performed. Implants' stabilities were measured with resonance frequency analysis (RFA) and removal torque (RT) meter device. Data were analyzed using Shapiro Wilk, ANOVA, and Tukey HSD tests for RFA and RT values considering p < 0.05 as the statistical significance level. RFA and RT values were compared by Pearson correlation coefficiency. RFA values of 5 and 7 HBOT cycles were significantly lower than 1, 3 HBOT and control group (p < 0.001). There was no statistical difference between 5 and 7 HBOT cycles RFA values. HBOT pressure simulation slightly but statistically decreased the stability for the implants exposed to 5 and 7 HBOT cycles. Graphical abstract.

Stability of Dental Implants and Thickness of Cortical Bone: Clinical Research and Future Perspectives. A Systematic Review

Dental surgery implantation has become increasingly important among procedures that aim to rehabilitate edentulous patients to restore esthetics and the mastication ability. The optimal stability of dental implants is correlated primarily to the quality and quantity of bone. This systematic literature review describes clinical research focusing on the correlation between cortical bone thickness and primary/secondary stability of dental fixtures. To predict successful outcome of prosthetic treatment, quantification of bone density at the osteotomy site is, in general, taken into account, with little attention being paid to assessment of the thickness of cortical bone. Nevertheless, local variations in bone structure (including cortical thickness) could explain differences in clinical practice with regard to implantation success, marginal bone resorption or anchorage loss. Current knowledge is preliminarily detailed, while tentatively identifying which inconclusive or unexplored aspects merit further investigation.

Clinical, radiographic and restorative parameters for short tuberosity implants placed in smokers: a retrospective study with 5 year follow-up

This study aimed to estimate and compare the clinical, radiographic, and restorative parameters around short tuberosity implants (STIs) placed in cigarette smokers (CS) and never smokers (NS). In this 60-month follow-up retrospective study, a total of 50 (37 males + 13 females) individuals who had received 82 dental implants were included. These participants were categorized into two groups as follows: (i) Group-1: 25 self-reported systemically healthy CS with 43 STIs; and (ii) Group-2: 25 self-reported systemically healthy NS with 39 STIs. In both groups, peri-implant plaque index (PI), probing depth (PD), bleeding on probing (BOP), and crestal bone loss (CBL) and restorative parameters were measured at 12 and 60 months of follow-up. Group comparisons were performed utilizing the Kruskal-Wallis test. The significance level was set at p < 0.05. In CS and NS, the mean age of participants was 58.5 and 60.7 years, respectively. No statistically significant differences were observed in the overall mean levels of PD and CBL around STIs among CS and NS. However, a statistically significant increase was observed in the mean scores of BOP and PI around STIs in the NS and CS at 12 and 60 months follow-up, respectively. In both groups, the loosening of the implant was the most frequently encountered type of STI failure. The outcomes of the present study suggest that STIs placed in maxillary tuberosity can show reliable clinical, radiographic, and restorative stability among cigarettes smokers and non-smokers. However, the role of smoking status and oral hygiene cannot be disregarded in this scenario.

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.

Effect of macrogeometry and bone type on insertion torque, primary stability, surface topography damage and titanium release of dental implants during surgical insertion into artificial bone

This study investigated the influence of implant macrogeometry and bone type on insertion torque (IT), primary stability (ISQ), surface topography damage, and the amount of titanium (Ti) released during insertion. Forty implants with different macrogeometries (Facility - Cylindrical with spiral-shaped threads; Alvim - Tapered with buttress-shaped threads) were inserted into artificial bone types I-II and III-IV. Surface morphology was evaluated by Scanning Electron Microscope (SEM) and roughness parameters with Laser Scanning Confocal Microscopy (LSCM) before and after insertion (AI). Implant macrogeometry was characterized by LSCM. The chemical composition of bone beds was determined by SEM associated with Energy Dispersive X-Ray Spectroscopy. The amount of Ti released was analyzed with Energy Dispersive X-Ray Fluorescence. Alvim had greater IT and ISQ than Facility. Bone types I-II require higher IT of implants. Alvim also had greater internal threads angle, higher initial roughness, and significant reduction of roughness AI, compared to Facility. The functional surface height reduced AI, especially in flank and valley of threads. Height of surface roughness of Alvim and Facility implants was similar AI. Implants surface morphology changes and metallic particles on bone beds were observed after implant insertion, mainly into bone types III-IV. Implants inserted into bone types I-II showed less surface damage. Alvim implants released more Ti (37.52 ± 25.03 ppm) than Facility (11.66 ± 28.55 ppm) on bone types III-IV. The implant macrogeometry and bone types affect IT, ISQ, surface damage, and Ti amount released during insertion. Alvim implants were more wear susceptible, releasing higher Ti concentration during insertion into bone types III-IV.

Osseointegration of a novel injection molded 2-piece ceramic dental implant: a study in minipigs

OBJECTIVES

This study compared the osseointegrative potential of a novel injection molded zirconia dental implant (Neodent Zi ceramic implant, test) and a commercially available titanium implant (Neodent Alvim implant, control) in terms of histomorphometrically derived bone-to-implant contact (BIC), first bone-to-implant contact (fBIC), and the ratio of bone area to total area (BATA) around the implant.

MATERIALS AND METHODS

A total of 36 implants, 18 per individual test device, were implanted in a split-mouth arrangement in either side of the edentulous and fully healed mandible of 6 minipigs. Histomorphometric analysis of BIC, fBIC, and BATA were performed 8 weeks post implantation and subjected to statistical non-inferiority testing. Surface characteristics of both implant types were compared in terms of contact angle, surface topography, and elemental composition.

RESULTS

BIC, fBIC, and coronal BATA values of test and control implants were statistically comparable and non-inferior. BIC values of 77.8 ± 6.9% vs. 80.7 ± 6.9% (p = 0.095) were measured for the test and control groups. fBIC lingual values were - 238 ± 328 μm compared with - 414 ± 511 μm (p = 0.121) while buccal values were - 429 ± 648 μm and - 588 ± 550 μm (p = 0.230) for the test and control devices, respectively. BATA in the apical segment was significantly higher in the test group compared with the control group (67.2 ± 11.8% vs. 59.1 ± 11.4%) (p = 0.0103). Surface topographies of both implant types were comparable. Surface chemical analysis indicated the presence of carbonaceous adsorbates which correlated with a comparable and predominantly hydrophobic character of the implants.

CONCLUSION

The results demonstrate that the investigated zirconia implants, when compared with a commercially available titanium implant, show equivalent and non-inferior bone integration, bone formation, and alveolar bone level maintenance. This qualifies the investigated zirconia implant as a potential candidate for clinical development.

CLINICAL RELEVANCE

This study investigated the osseointegration of a novel zirconia 2-piece dental implant prototype intended for clinical development. With the aim of translating this prototype into clinical development preclinical models, procedures and materials within this study have been selected as close to clinical practice and human physiological conditions as possible.

Effect of insertion factors on dental implant insertion torque/energy-experimental results

Anchorage of dental implants is quantified with a mechanical engagement to insertion, for example maximum insertion torque (MIT) and insertion energy (IE). Good anchorage of dental implants highly correlates to positive clinical outcomes. However, it is still unclear how bone density, drill protocol, surface finish and cutting flute affect anchorage. In this study, effects of the insertion factors on both MIT and IE were investigated using a full-factorial experiment at two levels: bone surrogate density (0.32 g/cm³ versus 0.48 g/cm³), drill protocol (Ø2.4/2.8 versus Ø2.8/3.2 mm), implant surface finish (machined versus anodized surface) and cutting flute (with versus without). Osteotomies were prepared on rigid polyurethane foam blocks with dimensions of 40 × 40 × 8 mm. Screw shaped dental implants with variable tapered body were consecutively inserted into and removed from the polyurethane foam blocks three times under constant axial displacement and rotational speed. Axial force and torque were recorded synchronously. Insertion energy was calculated from the area under the torque-displacement curve. In this study, we found the main insertion mechanics were thread forming for the first insertion. For the second and third insertions, the main mechanics shifted to thread tightening. Maximum insertion torque (MIT) responded differently to the four insertion factors in comparison to IE. Bone surrogate density, drill protocol and surface finish had the largest main effects for first MIT. For the first IE, drill protocol, surface finish and cutting flute were significant contributors. These results suggest that MIT and IE are influenced by different mechanics: the first MIT and the first IE were sensitive to thread tighten and forming, respectively. Together MIT and IE provide a complete assessment of dental implant anchorage.

Effects of implant thread design on primary stability-a comparison between single- and double-threaded implants in an artificial bone model

Background

Primary implant stability is essential for osseointegration. To increase stability without changing the implant size, the thread length must be extended by reducing pitch, using a double-threaded implant, or reducing pitch/lead and lead angle to half that of a single-threaded implant.

Materials and methods

We tested the stabilities of these configurations using artificial bone. A 1.2-mm pitch, single-threaded implant (12S) was the control. We tested a 0.6-mm pitch/1.2-mm-lead double-threaded implant (06D) and a 0.6-mm pitch/lead single-threaded implant (06S). We compared stabilities by measuring insertion torque, removal torque, and the implant stability quotient (ISQ). Damage to bone tissue caused by the implants was evaluated using microscopy and morphometric analysis.

Results

We show that 06D and 06S significantly improved stability compared with the 12S reference. The stability of 06S was significantly greater compared with that of 06D, except for ISQ. The three implants were associated with bone tissue damage characterized by debris and voids surrounding the implant/bone interface. The 06D caused the most tissue damage, followed by 06S and then 12S.

Conclusion

These findings indicate that primary stability was significantly improved by changing the implant size, extending the thread length with reduced pitch/lead, and reducing the lead angle to half that of a single-threaded implant compared with a double-threaded implant.

Selected Nanomaterials' Application Enhanced with the Use of Stem Cells in Acceleration of Alveolar Bone Regeneration during Augmentation Process

Regenerative properties are different in every human tissue. Nowadays, with the increasing popularity of dental implants, bone regenerative procedures called augmentations are sometimes crucial in order to perform a successful dental procedure. Tissue engineering allows for controlled growth of alveolar and periodontal tissues, with use of scaffolds, cells, and signalling molecules. By modulating the patient's tissues, it can positively influence poor integration and healing, resulting in repeated implant surgeries. Application of nanomaterials and stem cells in tissue regeneration is a newly developing field, with great potential for maxillofacial bony defects. Nanostructured scaffolds provide a closer structural support with natural bone, while stem cells allow bony tissue regeneration in places when a certain volume of bone is crucial to perform a successful implantation. Several types of selected nanomaterials and stem cells were discussed in this study. Their use has a high impact on the efficacy of the current and future procedures, which are still challenging for medicine. There are many factors that can influence the regenerative process, while its general complexity makes the whole process even harder to control. The aim of this study was to evaluate the effectiveness and advantage of both stem cells and nanomaterials in order to better understand their function in regeneration of bone tissue in oral cavity.

De Aza P. Can changes in implant macrogeometry accelerate the osseointegration process?: An in vivo experimental biomechanical and histological evaluations

OBJECTIVES

The propose was to compare this new implant macrogeometry with a control implant with a conventional macrogeometry.

MATERIALS AND METHODS

Eighty-six conical implants were divided in two groups (n = 43 per group): group control (group CON) that were used conical implants with a conventional macrogeometry and, group test (group TEST) that were used implants with the new macrogeometry. The new implant macrogeometry show several circular healing cambers between the threads, distributed in the implant body. Three implants of each group were used to scanning electronic microscopy (SEM) analysis and, other eighty samples (n = 40 per group) were inserted the tibia of ten rabbit (n = 2 per tibia), determined by randomization. The animals were sacrificed (n = 5 per time) at 3-weeks (Time 1) and at 4-weeks after the implantations (Time 2). The biomechanical evaluation proposed was the measurement of the implant stability quotient (ISQ) and the removal torque values (RTv). The microscopical analysis was a histomorphometric measurement of the bone to implant contact (%BIC) and the SEM evaluation of the bone adhered on the removed implants.

RESULTS

The results showed that the implants of the group TEST produced a significant enhancement in the osseointegration in comparison with the group CON. The ISQ and RTv tests showed superior values for the group TEST in the both measured times (3- and 4-weeks), with significant differences (p < 0.05). More residual bone in quantity and quality was observed in the samples of the group TEST on the surface of the removed implants. Moreover, the %BIC demonstrated an important increasing for the group TEST in both times, with statistical differences (in Time 1 p = 0.0103 and in Time 2 p < 0.0003).

CONCLUSIONS

Then, we can conclude that the alterations in the implant macrogeometry promote several benefits on the osseointegration process.

Effect of implant design on the initial biomechanical stability of two self-tapping dental implants

BACKGROUND

This study evaluated the effect of two self-tapping implants on implant stability in immediate implantation.

METHODS

Two types of self-tapping implants, straight flute (STF) and spiral flute (SPF) designs, were studied. Two synthetic bone blocks with varying densities (0.32 g/cm³ and 0.16 g/cm³) were chosen to simulate the bone quality of the anterior maxilla. Insertion torque values were measured by a torque testing machine during implant insertion. Four biomechanical tests were performed: resonance frequency analysis was conducted using the Osstell device, and the strengths of screw push-in, lateral bending, and pull-out were evaluated using an MTS machine. The strength for each design feature was obtained by averaging the results of 10 trials. In total, 40 specimens were tested for each bone density. Statistical difference was determined by one-way analysis of variance followed by Bonferroni post hoc multiple tests between groups.

FINDINGS

The STF and SPF groups exhibited similar insertion torque values (p = 0.525 in low-density bone, and p = 0.99 in high-density bone). A significant difference (p < 0.001) was observed in the push-in test between the two groups when low-density bone was tested. The SPF group exhibited a significantly higher lateral bending force (p = 0.001) and a higher stiffness (p < 0.001) than the STF group in high-density bone. The SPF design attained higher (p < 0.001) ISQ numbers than the STF design, but all numbers were below 60.

INTERPRETATION

Implant stability can be influenced by the apical fixture design of self-tapping implants in immediate implantation.

Combined effect of undersized surgical technique and axial compression on the primary implant stability and host bone architecture

Aim

The aim of this study was to investigate the combined effect of the lateral-compression of host-bone (undersized-osteotomy-preparation) and axial-compression of host-bone (not drilling the full length of the implant) on the primary-implant-stability and the host-bone-architecture.

Materials and Methods

In this experimental-study, 44 dental implants (diameter-4.2 mm; length-10 mm; Dyna®) were installed in the femoral-condyles of four cadaver-goats using four different surgical approaches (11 implant/surgical approach; n = 11). Approach-1: Standard preparation according to the manufacturer's guidelines. The bone-cavity was prepared up to 10 mm in depth and 4 mm in diameter. Approach-2: Preparation up to 8 mm in depth and 4 mm in diameter. Approach-3: Preparation up to 10 mm in depth. Approach-4: The bone-cavity was prepared up to 8 mm in depth and 3.6 mm in diameter. Insertion torque (n = 11), removal torque (n = 7) and % bone-implant contact (n = 4) measurements were recorded. Bone architecture was assessed by micro-computer tomography and histological analysis (n = 4).

Results

For approaches 2, 3, and 4 (P < .05), insertion-torque values were significantly higher as compared to approach 1. Regarding the bone-implant-contact percentage (%BIC), approach 3 and 4 were significantly higher compared to approach 1 and 2 (P<.05). For approach 2, the %bone volume (%BV) was significantly higher as compared to approach 1 (P<.05) for the most the inner zone of host bone in proximity of the implant.

Conclusion

Lateral and axial compression improved the primary-implant-stability and therefore this new surgical-technique should be considered as an alternative approach especially for placing implants in low-density bone. Nevertheless, additional in vivo studies should be performed.

Evaluation of Peri-Implant Bone Grafting Around Surface-Porous Dental Implants: An In Vivo Study in a Goat Model

Dental implants with surface-porous designs have been recently developed. Clinically, peri-implant bone grafting is expected to promote early osseointegration and bone ingrowth when applied with surface-porous dental implants in challenging conditions. The aim of this study was to comparatively analyze peri-implant bone healing around solid implants and surface-porous implants with and without peri-implant bone grafting, using biomechanical and histomorphometrical assessment in a goat iliac bone model. A total of 36 implants (4.1 mm wide, 11.5 mm long) divided into three groups, solid titanium implant (STI; n = 12), porous titanium implants (PTI; n = 12) and PTI with peri-implant bone grafting using biphasic calcium phosphate granules (PTI + BCP; n = 12), were placed bilaterally in the iliac crests of six goats. The goats were sacrificed seven weeks post-operatively and then subjected to biomechanical (n = 6 per group) and histomorphometrical (n = 6 per group) assessment. The biomechanical assessment revealed no significant differences between the three types of implants. Although the peri-implant bone-area (PIBA%) measured by histomorphometry (STI: 8.63 ± 3.93%, PTI: 9.89 ± 3.69%, PTI + BCP: 9.28 ± 2.61%) was similar for the three experimental groups, the percentage of new bone growth area (BGA%) inside the porous implant portion was significantly higher (p < 0.05) in the PTI group (10.67 ± 4.61%) compared to the PTI + BCP group (6.50 ± 6.53%). These data demonstrate that peri-implant bone grafting around surface-porous dental implants does not significantly accelerate early osseointegration and bone ingrowth.

Short implants (≤6 mm) versus longer implants with sinus floor elevation in atrophic posterior maxilla: a systematic review and meta-analysis

OBJECTIVES

To compare the use of short implants (≤6 mm) in atrophic posterior maxilla versus longer implants (≥10 mm) with sinus floor elevation.

DESIGN

A systematic review and meta-analysis based on randomised controlled trials (RCTs).

DATA SOURCES

Electronic searches were conducted in PubMed, Embase and the Cochrane CENTRAL. Retrospective and prospective hand searches were also performed.

ELIGIBILITY CRITERIA

RCTs comparing short implants (≤6 mm) and longer implants (≥10 mm) with sinus floor elevation were included. Outcome measures included implant survival (primary outcome), marginal bone loss (MBL), complications and patient satisfaction.

DATA EXTRACTION AND SYNTHESIS

Risks of bias in and across studies were evaluated. Meta-analysis, subgroup analysis and sensitivity analysis were undertaken. Quality of evidence was assessed according to Grading of Recommendations Assessment, Development and Evaluation.

RESULTS

A total of seven RCTs involving 310 participants were included. No significant difference in survival rate was found for 1-3 years follow-up (RR 1.01, 95% CI 0.97 to 1.04, p=0.74, I²=0%, moderate-quality evidence) or for 3 years or longer follow-up (RR 1.00, 95% CI 0.97 to 1.04, p=0.79, I²=0%, moderate-quality evidence). However, short implants (≤6 mm) showed significantly less MBL in 1-3 years follow-up (MD=-0.13 mm, 95% CI -0.21 to 0.05; p=0.001, I²=87%, low-quality evidence) and in 3 years or longer follow-up (MD=-0.25 mm, 95% CI -0.40 to 0.10; p=0.001, I²=0%, moderate-quality evidence). In addition, short implant (≤6 mm) resulted in fewer postsurgery reaction (RR 0.11, 95% CI 0.14 to 0.31, p<0.001, I²=40%, moderate-quality evidence) and sinus perforation or infection (RR 0.11, 95% CI 0.02 to 0.63, p=0.01, I²=0%, moderate-quality evidence).

CONCLUSIONS

For atrophic posterior maxilla, short implants (≤6 mm) are a promising alternative to sinus floor elevation, with comparable survival rate, less MBL and postsurgery reactions. Additional high-quality studies are needed to evaluate the long-term effectiveness of short implants (≤6 mm).

TRIAL REGISTERATION NUMBER

The protocol has been registered at PROSPERO (CRD42018103531).

New Implant Macrogeometry to Improve and Accelerate the Osseointegration: An In Vivo Experimental Study

A new implant design with healing chambers in the threads was analyzed and compared with a conventional implant macrogeometry, both implants models with and without surface treatment. Eighty conical implants were prepared using commercially pure titanium (grade IV) by the company Implacil De Bortoli (São Paulo, Brazil). Four groups were performed, as described below: Group 1 (G1), traditional conical implants with surface treatment; group 2 (G2), traditional conical implants without surface treatment (machined surface); group 3 (G3), new conical implant design with surface treatment; group 4 (G4), new conical implant design without surface treatment. The implants were placed in the two tibias (n = 2 implants per tibia) of twenty New Zealand rabbits determined by randomization. The animals were euthanized after 15 days (Time 1) and 30 days (Time 2). The parameters evaluated were the implant stability quotient (ISQ), removal torque values (RTv), and histomorphometric evaluation to determine the bone to implant contact (%BIC) and bone area fraction occupancy (BAFO%). The results showed that the implants with the macrogeometry modified with healing chambers in the threads produced a significant enhancement in the osseointegration, accelerating this process. The statistical analyses of ISQ and RTv showed a significative statistical difference between the groups in both time periods of evaluation (p ≤ 0.0001). Moreover, an important increase in the histological parameters were found for groups G3 and G4, with significant statistical differences to the BIC% (in the Time 1 p = 0.0406 and in the Time 2 p < 0.0001) and the BAFO% ((in the Time 1 p = 0.0002 and in the Time 2 p = 0.0045). In conclusion, the result data showed that the implants with the new macrogeometry, presenting the healing chambers in the threads, produced a significant enhancement in the osseointegration, accelerating the process.

Primary and Secondary Stability of Single Short Implants

PURPOSE

This prospective cohort study assessed the effect of bone quality on the primary and secondary stability of single short implants placed in the posterior region.

MATERIALS AND METHODS

A total of 39 short implants (4.1 × 6-mm long) were placed in the posterior region of the maxilla or mandible in 18 patients. Bone quality was classified into type I, II, III, or IV as assessed intrasurgically. Primary implant stability was measured with insertion torque, damping capacity (PTV values), and resonance frequency analysis (ISQ values). Secondary stability was measured by ISQ and PTV at abutment installation. Data were analyzed by using repeated-measures ANOVA and Tukey's test, Kruskall-Wallis test, and Spearman correlation tests.

RESULTS

Implants placed in bone type IV had significant lower insertion torque and ISQ values as well as higher PTV values than in bone types I to II (P < 0.05). The mean ISQ values were higher at abutment installation than at implant placement (P < 0.05), regardless the bone type. The assessment methods of implant stability showed a moderate correlation.

CONCLUSIONS

Bone quality influences both the primary and secondary stability of single short implants in the posterior region.

Insertion Torque of Variable-Thread Tapered Implants in the Posterior Maxilla: A Clinical Study

PURPOSE

Primary stability is a key factor for successful implant osseointegration, especially in poor bone quality and early/immediate loading. In the immediate loading protocol, insertion torque values (ITVs) have been suggested to be the most valid prognostic factor for osseointegration of maxillary implants. The objectives of this study were to: (1) evaluate ITVs achieved by a variable-thread tapered implant in the posterior maxilla; and (2) assess the impact of bone quality, implant dimensions, bicortical anchorage, and implant location on ITVs.

MATERIALS AND METHODS

Twenty-six adult, systemically healthy patients received 173 variable-thread tapered implants in maxillary premolar and molar healed edentulous sites with a minimum subsinus height of 8 mm. Implant sites were prepared using the bone-quality adjusted drilling sequence according to manufacturer's recommendations. Bone quality was recorded subjectively during drilling based on Misch criteria (D1-D4), and ITVs were measured with a manual torque wrench. Univariate and multivariate analyses were performed at the 0.05 significance level.

RESULTS

First and second molar sites accounted for 46.8% of all implants. D4 bone was encountered in 61.3% of the sites. Most of the implants were 4.3 mm in diameter (59.5%), and lengths of 11.5 and 13 mm were most commonly used (75.2%). Approximately half of the implants were associated with apical cortical anchorage (51.4%). The overall mean ITV was 44.5 ± 23.0 Ncm, with 65.5 ± 15.6 Ncm, 55.5 ± 19.6 Ncm, and 36.6 ± 21.7 Ncm for D2, D3, and D4 bone, respectively. Bone quality and implant location significantly affected ITVs, while implant dimensions and apical cortical anchorage did not.

CONCLUSIONS

ITVs of variable-thread implants were significantly influenced by variations in bone quality and implant position in the posterior maxilla. Despite the influence of bone quality on primary stability, the mean ITVs attained with variable-thread tapered implants in poor bone quality were within the recommended range for immediate loading.

Role of Osteogenic Coatings on Implant Surfaces in Promoting Bone-To-Implant Contact in Experimental Osteoporosis: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the role of osteogenic coatings (placement of a thin film of organic and inorganic osteoinductive and osteoproliferative materials) on implant surfaces in augmenting bone-to-implant contact (BIC) in osteoporotic bone.

DATA SOURCES

To answer the focused question "Do osteogenic coatings on implant surfaces increase BIC in osteoporotic bone?" PubMed/MEDLINE, EMBASE, ISI Web of Knowledge, Scopus, and Google-Scholar databases were searched till June 2017 using different combinations of the following key words: bone-to-implant contact, coating, implant surface, osseointegration, and osteoporosis. Letters to the Editor, review articles, case-reports/case-series, and commentaries were excluded.

RESULTS

Six animal studies were included, in which osteoporosis was induced by bilateral ovariectomy. In all studies, implant surface roughness was increased by various osteogenic surface coatings including alumina, hydroxyapatite, calcium phosphate, and zoledronic acid. Five studies showed that bone volume and BIC are significantly higher around implants with coated surfaces than noncoated implants. In 1 study, there was no difference in BIC around coated and noncoated implants.

CONCLUSION

Although experimental studies have shown that osteogenic coatings are effective in enhancing BIC, their clinical relevance requires further investigations.

The effect of undersizing and tapping on bone to implant contact and implant primary stability: A histomorphometric study on bovine ribs

PURPOSE

Implant site preparation may be adjusted to achieve the maximum possible primary stability. The aim of this investigation was to study the relation among bone-to-implant contact at insertion, bone density, and implant primary stability intra-operatively measured by a torque-measuring implant motor, when implant sites were undersized or tapped.

MATERIALS AND METHODS

Undersized (n=14), standard (n=13), and tapped (n=13) implant sites were prepared on 9 segments of bovine ribs. After measuring bone density using the implant motor, 40 implants were placed, and their primary stability assessed by measuring the integral of the torque-depth insertion curve. Bovine ribs were then processed histologically, the bone-to-implant contact measured and statistically correlated to bone density and the integral.

RESULTS

Bone-to-implant contact and the integral of the torque-depth curve were significantly greater for undersized sites than tapped sites. Moreover, a correlation between bone to implant contact, the integral and bone density was found under all preparation conditions. The slope of the bone-to-implant/density and integral/density lines was significantly greater for undersized sites, while those corresponding to standard prepared and tapped sites did not differ significantly.

CONCLUSION

The integral of the torque-depth curve provided reliable information about bone-to-implant contact and primary implant stability even in tapped or undersized sites. The linear relations found among the parameters suggests a connection between extent and modality of undersizing and the corresponding increase of the integral and, consequently, of primary stability. These results might help the physician determine the extent of undersizing needed to achieve the proper implant primary stability, according to the planned loading protocol.

Methods to Improve Osseointegration of Dental Implants in Low Quality (Type-IV) Bone: An Overview

Nowadays, dental implants have become more common treatment for replacing missing teeth and aim to improve chewing efficiency, physical health, and esthetics. The favorable clinical performance of dental implants has been attributed to their firm osseointegration, as introduced by Brånemark in 1965. Although the survival rate of dental implants over a 10-year observation has been reported to be higher than 90% in totally edentulous jaws, the clinical outcome of implant treatment is challenged in compromised (bone) conditions, as are frequently present in elderly people. The biomechanical characteristics of bone in aged patients do not offer proper stability to implants, being similar to type-IV bone (Lekholm &amp; Zarb classification), in which a decreased clinical fixation of implants has been clearly demonstrated. However, the search for improved osseointegration has continued forward for the new evolution of modern dental implants. This represents a continuum of developments spanning more than 20 years of research on implant related-factors including surgical techniques, implant design, and surface properties. The methods to enhance osseointegration of dental implants in low quality (type-IV) bone are described in a general manner in this review.

Effect of Osteotomy Preparation on Osseointegration of Immediately Loaded, Tapered Dental Implants

The aim of the present preclinical in vivo study was to evaluate whether a modified "drill-only" protocol, involving slight underpreparation of the implant site, may have an effect on aspects of osseointegration of a novel bone-level tapered implant, compared with the "standard drilling" protocol involving taping and profiling of the marginal aspect of the implant socket. In each side of the edentulated and completely healed mandible of 11 minipigs, 2 tapered implants (8 mm long × 4.1 mm Ø, BLT; Institut Straumann AG, Basel, Switzerland) were installed either with the drill-only or the standard drilling protocol. Significantly lower average insertion torque values were recorded for the standard drilling protocol group (52 ± 29 Ncm) compared with the drill-only group (70 ± 27 Ncm) (t test, P ≤ 0.05); no significant difference was observed between the 2 groups regarding implant stability, by means of resonance frequency analysis (75 ± 8 vs. 75 ± 6, respectively). Half of the implants were immediately loaded and the rest were submerged, providing observation times of 8 or 4 wk, respectively. Non-decalcified histological and histomorphometric analysis of the implants with surrounding tissues showed no significant differences between the 2 drilling protocols regarding the distance from the implant platform to the first coronal bone-to-implant contact (f-BIC), the total bone-to-implant contact (BIC) as a percentage of the total implant perimeter, and the bone density in an area extending 1 mm laterally from the implant (BATA) within 2 rectangular regions of interest (ROIs) 4 mm in height, representing the coronal (parallel-walled) and apical (tapered) aspect of the implant (ROI 1 and ROI 2, respectively) in non-submerged implants. In general, marginal peri-implant bone levels were at or slightly apical to the implant platform, and large amounts of bone-to-implant contact were observed. In contrast, immediately loaded implants placed with the drill-only protocol showed statistically significantly lower BIC values (66% ± 13.7%) compared with those installed with the standard drilling protocol (74.8% ± 11.2%) (P = 0.018). In addition, although marginal bone levels were in most of the immediately loaded implants at or slightly apical to the implant platform, some of the implants installed with the drill-only protocol showed marginal bone loss and crater formation. Thus, in this model system, even slight underpreparation of the implant socket appeared to compromise osseointegration of immediately loaded bone-level tapered implants.

Primary stability of implants placed at different angulations in artificial bone

INTRODUCTION

The aim of this study was to evaluate the primary stability (PS) of titanium implants with a progressive thread design and more thread stability in the apical threads placed in artificial bone materials.

MATERIALS AND METHODS

A total of 120 implants were placed in commercially available polyurethane composite bone blocks. The angulations that were chosen to place the implants in bone types II and IV were 0, 10, and 20 degrees, respectively. The implant dimensions were 11 mm in length and 3.5 mm in diameter. Two clinicians placed all implants, and an independent examiner evaluated the PS using the Osstell (ISQ) and Periotest devices. The χ test was used to evaluate the statistical differences between the PS at different angulations.

RESULTS

This study showed that there was a statistically significant difference (P = 0.02) of the PS values, when measured using the Periotest values, among all 3 angulations in both bone qualities. Tilted implants with 10 degrees, angulation had a better stability than conventionally placed implants.

CONCLUSIONS

The PS of dental implants is higher for implants placed in type II when compared with type IV artificial bone. A higher stability was found for implants placed with 10-degree angulations.

Significance of osteogenic surface coatings on implants to enhance osseointegration under osteoporotic-like conditions

PURPOSE

The aim was to assess the significance of osteogenic surface coatings on implants to enhance osseointegration under osteoporotic-like (OP-like) conditions.

METHODS

To address the focused question "Do osteogenic surface coatings on implants enhance osseointegration under OP-like conditions?" PubMed/MEDLINE and Google-Scholar databases were searched from 1995 up to and including February 2014 using various keywords. Unpublished data, letters to the editor, review articles, and articles published in languages other than English were excluded.

RESULTS

Of the 28 studies identified, 11 experimental studies were included. These studies were performed on bilaterally ovariectomized animals. In all studies, implant surface roughness was increased by various osteogenetic surface coatings including alumina, hydroxyapatite, calcium phosphate, and zoledronic acid. Nine studies reported that compared with non-coated surfaces, osteogenic coatings on implant surfaces increases bone volume and bone-to-implant contact (BIC) under OP-like conditions. In 2 studies, there was no difference in BIC around hydroxyapatite-coated implants placed in animals with and without OP-like conditions.

CONCLUSION

Osteogenic coatings on implant surfaces enhanced osseointegration in animals with OP-like conditions. However, additional clinical studies are warranted to assess the role of osteogenic coatings in increasing osseointegration in patients with osteoporosis.

Effects on primary stability of three different techniques for implant site preparation in synthetic bone models of different densities

Preparation of implant sites affect the primary stability of implants that is necessary for osseointegration. We have investigated the effect on the primary stability of implants of three techniques used to prepare the site for implants in synthetic bone models of different densities. A total of 540 implants of varying diameters (3.3 (narrow), 4.1 (standard), and 4.8 (wide) mm) and lengths (8 or 12mm) were inserted into three artificial bone blocks (the density of which decreased from D2, D3, to D4), and we compared conventional, fully-guided, and condensing preparation of the site. After insertion, primary stability was measured using resonance frequency analysis. There were significant differences between conventional and condensing procedures (p <0.0001 in all cases) and between fully-guided and condensing procedures (p<0.01 in all cases), but there were no differences between fully-guided and conventional procedures when short implants were used, with a standard or wide diameter in low-density bone blocks (D3 and D4). In low-density bone blocks (D3 and D4) wide implants (4.8mm) compared with narrow (3.3mm) resulted in significantly better primary stability (p<0.0001 in all cases). Fully-guided preparation of the implant site is associated with increased primary stability, but is not an alternative to bone condensing. Use of longer or wider implants can increase primary stability, but the effect is less pronounced after bone condensing.

Inlay osteotome sinus floor elevation with concentrated growth factor application and simultaneous short implant placement in severely atrophic maxilla

Sinus floor elevation with simultaneous implant placement in severely atrophic maxilla is challenging. The aim of this retrospective study was to evaluate the short-term performance of modified osteotome sinus floor elevation (OSFE) with concentrated growth factor (CGF) application and concurrent placement of a short implant in cases with residual bone height (RBH) of 2-4 mm. Twenty-five short implants were installed in 16 patients with mean RBH of 3.23 mm using modified OSFE with CGFs from January 2012 to April 2014. Postoperatively, the implants were clinically evaluated, and vertical bone gain (VBG) was measured using cone beam computed tomography. The mean duration of follow-up was 19.88 months (12-32 months). All the implants were stable with an overall survival rate of 100%. The mean VBG immediately after surgery was 9.21 mm. Six months later, significant reduction of alveolar bone height (2.90 ± 0.22 mm) was found (P < 0.05). During the second 6-month period, further alveolar bone resorption (0.14 ± 0.11 mm) was noted but without significance (P > 0.05). Within the limits of this study, modified OSFE with CGF application and simultaneous short implant placement could yield predictable clinical results for severely atrophic maxilla with RBH of 2-4 mm.

Development and application of a direct method to observe the implant/bone interface using simulated bone

BACKGROUND

Primary stability after implant placement is essential for osseointegration. It is important to understand the bone/implant interface for analyzing the influence of implant design on primary stability. In this study rigid polyurethane foam is used as artificial bone to evaluate the bone-implant interface and to identify where the torque is being generated during placement.

METHODS

Five implant systems-Straumann-Standard (ST), Straumann-Bone Level (BL), Straumann-Tapered Effect (TE), Nobel Biocare-Brånemark MKIII (MK3), and Nobel Biocare-Brånemark MKIV (MK4)-were used for this experiment. Artificial bone blocks were prepared and the implant was installed. After placement, a metal jig and one side artificial bone block were removed and then the implant embedded in the artificial bone was exposed for observing the bone-implant interface. A digital micro-analyzer was used for observing the contact interface.

RESULTS

The insertion torque values were 39.35, 23.78, 12.53, 26.35, and 17.79 N cm for MK4, BL, ST, TE, and MK3, respectively. In ST, MK3, TE, MK4, and BL the white layer areas were 61 × 103 μm(2), 37 × 103 μm(2), 103 × 103 μm(2) in the tapered portion and 84 × 03 μm(2) in the parallel portion, 134 × 103 μm(2), and 98 × 103 μm(2) in the tapered portion and 87 × 103 μm(2) in the parallel portion, respectively.

CONCLUSIONS

The direct observation method of the implant/artificial bone interface is a simple and useful method that enables the identification of the area where implant retention occurs. A white layer at the site of stress concentration during implant placement was identified and the magnitude of the stress was quantitatively estimated. The site where the highest torque occurred was the area from the thread crest to the thread root and the under and lateral aspect of the platform. The artificial bone debris created by the self-tapping blade accumulated in both the cutting chamber and in the space between the threads and artificial bone.

Histological evaluation of two designs of shoulder surface replacement implants

AIMS

To assess the extent of osteointegration in two designs of shoulder resurfacing implants. Bony integration to the Copeland cylindrical central stem design and the Epoca RH conical-crown design were compared.

PATIENTS AND METHODS

Implants retrieved from six patients in each group were pair-matched. Mean time to revision surgery of Copeland implants was 37 months (standard deviation (sd) 23; 14 to 72) and Epoca RH 38 months (sd 28; 12 to 84). The mean age of patients investigated was 66 years (sd 4; 59 to 71) and 58 years (sd 17; 31 to 73) in the Copeland and Epoca RH groups respectively. None of these implants were revised for loosening.

RESULTS

Increased osteointegration was measured under the cup in the Copeland implant group with limited bone seen in direct contact with the central stem. Bone adjacent to the Epoca RH implants was more uniform.

CONCLUSION

This difference in the distribution of bone-implant contact and bone formation was attributed to the Epoca implant's conical crown, which is positioned in more dense peripheral bone. The use of a central stem may not be necessary provided there is adequate peripheral fixation within good quality humeral bone.

TAKE HOME MESSAGE

Poor osteointegration of cementless surface replacement shoulder prosthesis may be improved by implant design.

Influence of the implant diameter and bone quality on the primary stability of porous tantalum trabecular metal dental implants: an in vitro biomechanical study

OBJECTIVES

The aim of this study was to evaluate the primary, initial stability of Porous Tantalum Trabecular Metal^™ implants (TM) compared with Tapered Screw Vent^® implants (TSV) with different diameters, inserted in two bone densities.

METHODS

A total of 160 implants (80 TM and 80 TSV) with narrow (3.7 mm) and conventional (4.1 mm) diameters and the same length (10 mm) were placed in artificial bone blocks representing bone qualities II and IV. The implant stability was evaluated by insertion torque (IT) and Resonance Frequency Analysis. Statistical analysis was performed with non-parametric Kruskal-Wallis test with Dunn post-test for the differences between groups.

RESULTS

The results showed higher ISQ values in dense bone compared with soft bone for all the groups (P < 0.05). Conventional-diameter implants (TSV and TM) showed higher ISQ and IT values compared with narrow implants (TSV and TM) in dense and soft bone (P < 0.05). Tapered TSV implants showed higher stability in soft bone compared with TM implants (P < 0.05). In dense bone, differences were not observed between narrow TSV 3.7 mm and TM 3.7 mm implants (P > 0.05).

CONCLUSIONS

Within the limitations of this study, it can be concluded: In dense bone blocks, the wider diameter implants are more stable than narrow implants. In soft bone blocks, the tapered TSV implants are more stable than TM implants.

Influence of bone density and implant drill diameter on the resulting axial force and temperature development in implant burs and artificial bone: an in vitro study

PURPOSE

The aim of this study was to determine how the bone density affects the temperature development in artificial bone and drill.

METHODS

Ten single drills with diameters of 2.2, 2.8, 3.5, and 4.2 mm were used on four artificial bone blocks (density I-IV), with constant speed and external irrigation. Temperature measurement in blocks and drills was done by infrared camera. The resultant axial force was measured, and light microscopic examinations of the drills were performed before and after preparation.

RESULTS

The block density has a greater influence on resulting axial force than the drill diameter (D1 = 2.2 mm, 4.11 ± 0.64 N; 4.2 mm, 9.69 ± 0.78 N vs. D4 = 2.2 mm, 0.5 ± 0.18 N; 4.2 mm, 1.23 ± 0.08 N). For the narrowest drill, a decrease in bone density caused a significant temperature increase in the bone and drill. However, for the thickest drill, no thermal differences were found in the bone but were seen in the drill itself (D1 = 2.8 mm vs. D4 = 2.8 mm; bone p < 0.0001, drill p < 0.0001; D1 = 4.2 mm vs. D4 = 4.2 mm; bone p = 0.5366, drill p = 0.0411). An increase in the drill diameter in the highest bone density led to a significant thermal increase in the bone and drill. However, for the lowest bone density, thermal changes were observed only in the bone (D1 = 2.8 mm vs. D1 = 4.2 mm; bone p < 0.0001, drill p < 0.0001; D4 = 2.8 mm vs. D4 = 4.2 mm; bone p < 0.0102, drill p = 0.1784).

CONCLUSIONS

Thermal development depends on bone density with increasing density causing a temperature rise. However, this effect is reduced with increasing drill diameter. This may be important with regard to bone reactions and also in terms of tool wear.

Effect of implant design on primary stability using torque-time curves in artificial bone

Background

Primary stability following implant placement is essential for osseointegration and is affected by both implant design and bone density. The aim of this study was to compare the relationships between torque-time curves and implant designs in a poor bone quality model.

Methods

Nine implant designs, with five implants in each category, were compared. A total of 90 implants (Straumann: Standard RN, Bone Level RC, Tapered Effect RN; Nobel Biocare: Brånemark MKIII, MKIV) were placed in type IV artificial bone. Torque-time curves of insertion and removal were recorded at the rate of 1000 samples/s by a torque analyzer.

Results

The torque-time curves were divided into initial, parallel, tapered, and platform areas. The mean torque rise rate of the parallel area was smallest at 0.36 N · cm/s, with a significant difference from those of the other areas (p < 0.05). Values of 2.14, 2.33, and 2.65 N · cm/s were obtained for the initial, tapered, and platform areas, respectively. The removal torque for six of the implant designs (Bone Level RC 8, 10, and 12 mm; Tapered Effect RN 10 mm; Brånemark MKIII 10 mm, MKIV 10 mm) was significantly smaller than the corresponding insertion torque (p < 0.05). However, the removal torque for ST6, 8, and 10 was almost the same as or slightly greater than the corresponding insertion torque.

Conclusions

The insertion torque-time curves and design features of the implants were accurately transferred. Increasing implant taper angle appeared to increase the torque rate. Torque was mainly generated from the superior surface to the valley of the thread and the inferior and axial surfaces of the platform, while the inferior and axial surfaces of the thread did not significantly affect torque generation.

Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: a three-dimensional finite element analysis

OBJECTIVE

This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis.

MATERIALS AND METHODS

Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied.

RESULTS

Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%.

CONCLUSION

The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.

The effect of the thread depth on the mechanical properties of the dental implant

PURPOSE

This study aimed to evaluate the effect of implant thread depth on primary stability in low density bone.

MATERIALS AND METHODS

The insertion torque was measured by inserting Ti implants with different thread depths into solid rigid polyurethane blocks (Sawbones) with three different bone densities (0.16 g/cm³, 0.24 g/cm³, and 0.32 g/cm³). The insertion torque value was evaluated with a surgical engine. The static compressive strength was measured with a universal testing machine (UTM) and the Ti implants were aligned at 30° against the loading direction of the UTM. After the static compressive strength test, the Ti implants were analyzed with a Measurescope.

RESULTS

The Ti implants with deeper thread depth showed statistically higher mean insertion torque values (P<.001). Groups A and group B had similar maximum static compressive strengths, as did groups C and D (P>.05). After the static compressive strength, the thread shape of the Ti implants with deeper thread depth did not show any breakage but did show deformation of the implant body and abutment.

CONCLUSION

The implants with deeper thread depth had higher mean insertion torque values but not lower compressive strength. The deep threads had a mechanical stability. Implants with deeper thread depth may increase the primary stability in areas of poor quality bone without decreasing mechanical strength.

An experimental study to investigate biomechanical aspects of the initial stability of press-fit implants

Initial fixation of press-fit implants depends on interference fit, surface morphology, and bone material properties. To understand the biomechanical effect of each factor and their interactions, the pull-out strength of seven types of CoCrMo tapered implants, with four different interference fits, three different surface morphologies (low, medium and high roughness), and at two time points (0 and 30 min) were tested in trabecular bone with varying density. The effect of interference fit on pull-out strength depended on the surface morphology and time. In contrast with our expectations, samples with a higher roughness had a lower pull-out strength. We found a similar magnitude of bone damage for the different surface morphologies, but the type of damage was different, with bone compaction versus bone abrasion for low and high frictional surfaces, respectively. This explains a reduced sensitivity of fixation strength to bone mineral density in the latter group. In addition, a reduction in fixation strength after a waiting period only occurred for the low frictional specimens. Our study demonstrates that it is essential to evaluate the interplay between different factors and emphasizes the importance of testing in natural bone in order to optimize the initial stability of press-fit implants.