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

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

A randomized clinical 1‐year trial comparing two types of non‐submerged dental implants

Objectives: This study compared the implant stability and clinical outcomes obtained with two types of non‐submerged dental implants that have different thread designs and surface treatments. Materials and methods: A randomized clinical trial with 1 year of follow‐up was performed on 56 participants with 75 implants (control group, 36 implants in 28 subjects; experimental group, 39 implants in 28 subjects). The experimental group received the Osstem SSII Implant system; the control group received the Standard Straumann^® Dental Implant System. The diameter and length of the fixture were uniform at 4.1 mm and 10 mm and all the implants restored the unilateral loss of one or two molars from the mandible. To compare implant stability, the peak insertion torque, implant stability quotient (ISQ), and periotest value (PTV) were evaluated during surgery, and at 4 and 10 weeks after surgery. To compare marginal bone loss, standard periapical radiographs were obtained during surgery, and at 10 weeks and 1 year after surgery. Results: This study showed statistically significant differences between the two groups in peak insertion torque (P=0.009) and ISQ (P=0.003) but not in PTV (P=0.097) at surgery. In contrast, there was no statistically significant difference in the pattern of change of ISQ during the 10 weeks after surgery (P=0.339). For marginal bone loss, no significant difference was observed between the control and the experimental groups before functional loading (P=0.624), but after 1 year of follow‐up, a borderline difference was observed (P=0.048). Conclusion: The success rate after 1 year of follow‐up was 100% for both implant system despite the presence of a significant difference in implant stability during surgery. There was a borderline difference in marginal bone loss after 1 year of follow‐up. To cite this article:
Park J‐C, Ha S‐R, Kim S‐M, Kim M‐J, Lee J‐B, Lee J‐H. A randomized clinical 1‐year trial comparing two types of non‐submerged dental implant.
Clin. Oral Impl. Res. 21 , 2010; 228–236.
doi: 10.1111/j.1600‐0501.2009.01828.x     

Relationship between the bone density estimated by cone-beam computed tomography and the primary stability of dental implants

Objectives: The aims of this study were to objectively assess bone quality with density values obtained by cone‐beam computed tomography (CBCT) and to determine the correlations between bone density and primary stability of dental implants. Material and methods: Eighteen Straumann implants were inserted into 18 fresh femoral heads of swine. The bone densities of implant recipient sites were preoperatively determined by the density value using CBCT. The maximum insertion torque value of each implant was recorded using a digital torque meter. Resonance frequency, which represented a quantitative unit called the implant stability quotient (ISQ), was measured using an Osstell^® Mentor immediately after the implant placement. Spearman's correlation coefficient was calculated to evaluate the correlations among density values, insertion torques, and ISQs at implant placement. Results: The density values ranged from 98 to 902. The mean density value, insertion torque, and ISQ were 591±226, 13.4±5.2 Ncm, and 67.1±8.1, respectively. Statistically significant correlations were found between the density values and insertion torque (r_s=0.796, P<0.001), density values and ISQ (r_s=0.529, P=0.024), and insertion torque and ISQ (r_s=0.758, P<0.001). Conclusions: The bone quality evaluated by specific CBCT showed a high correlation with the primary stability of the implants. Hence, preoperative density value estimations by CBCT may allow clinicians to predict implant stability. Whether the density values obtained by the CBCT device used in the present study could be applied to other devices requires further elucidation. To cite this article:
Isoda K, Ayukawa Y, Tsukiyama Y, Sogo M, Matsushita Y, Koyano K. Relationship between the bone density estimated by cone‐beam computed tomography and the primary stability of dental implants.
Clin. Oral Impl. Res. 23 , 2012; 832–836
doi: 10.1111/j.1600‐0501.2011.02203.x     

Peripheral quantitative computer tomographic,histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model

Objective: The objectives of this study were (1) to investigate the bone–tissue response to zirconia and titanium implants at the implant‐to‐bone interface and at the periosteal level and (2) to quantitatively measure the mineral density of the peri‐implant bone using peripheral quantitative computer tomography (pQCT). Material and methods: Ten 3.5 mm × 6.6 mm screw‐shaped threaded implants fabricated from titanium and zirconia were inserted into the mid‐tibial diaphysis of five male New Zealand white rabbits. Calcein green was administered at 4 weeks post‐implantation. The animals were sacrificed after 6 weeks and implants were retrieved and analyzed in terms of bone‐to‐implant contact (BIC), bone area (BA), mineralized surface (MS) percentage, inter‐thread calcein labels, removal torque (RT) values, as well as pQCT measurements. Findings: No statistically significant differences were detected between the zirconia and titanium implants in terms of BIC, RT, and pQCT. However, statistically significant higher BA and MS levels were found in the titanium group, while the higher amount of calcein labels occupying the threads were found in the zirconium group. Significant differences were also found in the quantity and the composition of bone at the bone–implant interfacial area vs. the region 1.5 mm away from the bone–implant interface, irrespective of the implant type. Conclusion: Zirconia implants demonstrated a lower bone remodeling activity in the periosteal region. The bone at the bone–implant interface shows a significantly lower cortical bone density, a higher trabecular density, and trabecular mineral content. Finally, zirconia and titanium implants showed similar bone–implant responses in terms of BIC and RT. To cite this article:
Shin D, Blanchard SB, Ito M, Chu T‐MG. Peripheral quantitative computer tomographic, histomorphometric, and removal torque analyses of two different non‐coated implants in a rabbit model.
Clin. Oral Impl. Res. 22 , 2011; 242–250.
doi: 10.1111/j.1600‐0501.2010.01980.x     

Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model

Objectives: The aim of the present study was to evaluate a Ca–P coated implant surface in a rabbit model. The Ca–P surface (test) was compared to the titanium porous oxide surface (control) in terms of bone‐to‐implant contact (BIC) and removal torque value. Materials and methods: Two hundred and sixteen dental implants were inserted in the tibia and in the femur of 36 rabbits. One hundred and eight were represented by Ca–P oxidized surface implant and other 108 were titanium porous oxide surface modified implants. Each rabbit received six implants. Animals were sacrificed after 2, 4 and 9 weeks of healing. Each group included 12 rabbits. The femoral implant and the proximal implant of the tibia of each animal were subjected to the histologic analysis and the distal implants of the tibia underwent removal torque test (RTQ). Results: Histological analysis in terms of BIC and RTQ did not revealed any significant difference between the Ca–P oxidized surface and the oxidized surface at 2 and 4 weeks. At 9 weeks, the oxidized surface demonstrated better results in terms of RTQ in the tibia. Conclusion: In conclusion, findings from the present study suggested that the Ca–P coating had no beneficial effect in improving bonding strength at the bone–implant interface either at 2, 4 and 9 weeks. To cite this article:
Fontana F, Rocchietta I, Addis A, Schupbach P, Zanotti G, Simion M. Effects of a calcium phosphate coating on the osseointegration of endosseous implants in a rabbit model
Clin. Oral Impl. Res. 22 , 2011; 760–766
doi: 10.1111/j.1600‐0501.2010.02056.x     

Mandibular single‐implant overdentures: preliminary results of a randomised‐control trial on early loading with different implant diameters and attachment systems

Objectives: To determine surgical and prosthodontic outcomes of mandibular single‐implant overdentures, opposing complete maxillary dentures, using a wide diameter implant and large ball attachment system compared with different regular diameter implants with standard attachment systems. Materials and methods: Thirty‐six edentulous participants (mean age 68 years, SD 9.2) were randomly assigned into three treatment groups (n=12). A single implant was placed in the mandibular midline of participants to support an overdenture using a 6‐week loading protocol. The control group received Southern regular implants and standard ball attachments. One group received Southern 8‐mm‐wide implants and large ball attachments. Another group received Neoss regular implants and Locator attachments. Parametric and non‐parametric tests of a statistical software package (SPSS) were used to determine between groups differences in marginal bone loss, implant stability, implant, and prosthodontic success (P<0.05). Results: Implant success after 1 year was 75% for Southern regular implant (control) group; and 100% for the Southern wide and Neoss regular implant groups (P=0.038). Mean marginal bone loss at 1 year was 0.19 mm (SD 0.39) without significant differences observed. Implant stability quotient (ISQ) at baseline was significantly lower for the Southern regular (control) group than the other two groups (P=0.001; P=0.009). At 1 year, no significant difference in implant stability was observed (mean ISQ 74.6, SD 6.1). The change in implant stability from baseline to 1 year was significant for the control group (P=0.025). Prosthodontic success was comparable between the groups but the maintenance (41 events overall, mean 1.2) was greater for the Locator and the standard ball attachments. Conclusions: Mandibular single‐implant overdentures are a successful treatment option for older edentulous adults with early loading protocol using implants of different diameters and with different attachment systems. To cite this article:
Alsabeeha NHM, Payne AGT, De Silva RK, Thomson WM. Mandibular single‐implant overdentures: preliminary results of a randomised‐control trial on early loading with different implant diameters and attachment systems.
Clin. Oral Impl. Res. 22 , 2011; 330–337.
doi: 10.1111/j.1600‐0501.2010.02004.x     

Single implants with different neck designs in the aesthetic zone: a randomized clinical trial

Objectives: To compare single implants in the aesthetic zone with different neck designs for marginal bone‐level changes and clinical outcome measures. Materials and methods: Ninety‐three patients with a missing anterior tooth in the maxilla were randomly assigned to be treated with an implant with a 1.5 mm smooth neck (“smooth group”), a moderately rough neck with grooves (“rough group”) or a scalloped moderately rough neck with grooves (“scalloped‐group”). Implants were installed in healed sites and were loaded after 3 months. Follow‐up visits were conducted at 6 and 18 months after implant placement. Results: The scalloped group showed significantly more radiographic bone loss from implant placement to 18 months (2.01 ± 0.77 mm) compared with the smooth group (1.19 ± 0.82 mm) and rough group (0.9 ± 0.57 mm). Furthermore the scalloped group showed significantly deeper pocket depths and a higher bleeding score. There were no between‐group differences in soft tissue levels. Survival rates were 97% for the smooth group and 100% for the rough and scalloped groups (P>0.05). No significant differences in outcome were found between the smooth group and rough group. Conclusion: For anterior tooth replacements, implants with a scalloped neck showed more marginal bone loss and less favourable clinical outcome compared with implants with a 1.5 mm smooth neck or implants with a rough neck. To cite this article:
den Hartog L, Meijer HJA, Stegenga B, Tymstra N, Vissink A, Raghoebar GM. Single implants with different neck designs in the aesthetic zone: a randomized clinical trial.
Clin. Oral Impl. Res. 22 , 2011; 1289–1297.
doi: 10.1111/j.1600‐0501.2010.02109.x     

Stability, marginal bone loss and survival of standard and modified sand-blasted, acid-etched implants in bilateral edentulous spaces: a prospective 15-month evaluation

Objectives: Chemical modification of the already proven sand‐blasted and acid‐etched (SLA) implant had increased its surface wettability and consequent early‐term osseointegration characteristics. The aim of this clinical trial was to compare the stability changes, success, survival, peri‐implant parameters and marginal bone loss (MBL) of the early‐loaded standard (SLA) and modified sand‐blasted, acid‐etched (modSLA) implants. Material and methods: A total of 96 SLA and modSLA implants were placed in a bi‐lateral, cross‐arch position to the jaws of 22 patients. Resonance frequency analysis (RFA) was used to measure the implant stability in the surgery and following healing after 1, 3 and 6 weeks. At the stage of loading, a panoramic X‐ray was obtained and RFA measurement was repeated for all implants. Implants were restored by metal–ceramic crowns and followed for 1 year to determine the success, survival rate, peri‐implant parameters and MBL. Results were compared by one‐ and two‐way ANOVA, log‐rank test and generalized linear mixed models (P<0.05). Results: One modSLA implant was lost after 3 weeks following the surgery yielding to a 100 and 97.91% success rate for SLA and modSLA implants, respectively (P=0.323). At the loading stage, modSLA implants showed significantly lower MBL (0.18 ± 0.05 mm) than SLA implants (0.22 ± 0.06 mm; P=0.002). In the loading stage, RFA value of the modSLA implants (60.42 ± 6.82) was significantly higher than the both implant types in the surgical stage (55.46 ± 8.29 and 56.68 ± 8.19), and following 1 (56.08 ± 7.01 and 55.60 ± 9.07) and 3 weeks of healing (55.94 ± 5.95 and 55.40 ± 6.50 for SLA and modSLA implants, respectively). Conclusions: modSLA implants demonstrated a better stability and a reduced MBL at the loading stage. Both SLA and modSLA implants demonstrated a favorable success and survival at the end of 15‐month follow‐up. To cite this article :
Karabuda ZC, Abdel‐Haq J. Arιsan V. Stability, marginal bone loss and survival of standard and modified sand‐blasted, acid‐etched implants in bilateral edentulous spaces: a prospective 15‐month evaluation.
Clin. Oral Impl. Res. 22 , 2011; 840–849
doi: 10.1111/j.1600‐0501.2010.02065.x     

Bone response of Mg ion‐implanted clinical implants with the plasma source ion implantation method

Objectives: This study examined the bone response of magnesium (Mg) ion‐implanted implants produced using a plasma source ion implantation method. Materials and methods: The surface characteristics were evaluated by scanning electron microscopy, Auger electron spectroscopy, X‐ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy. The screw‐type titanium implants were treated with resorbable blasting media (RBM) and divided into one control group (RBM implants) and three test groups (Mg ion‐implanted implants with different retained Mg doses). Twenty‐four implants from each group were placed into the tibiae of 24 New Zealand white rabbits. After allowing 6 weeks for healing, the removal torque (RTQ) was measured and the implants were subjected to histomorphometric analysis. Results: The surface roughness and surface morphology of the test groups were similar. The Mg ion‐implanted implants with a 2.3 × 10¹⁵ ions/cm² retained dose showed a significantly higher RTQ than the other implants. Histomorphometric analysis indicated that the bone contact of this group was superior to the other groups. Conclusion: The bone response of Mg ion‐implanted implant showed results superior or similar to an RBM‐treated implant. The optimal Mg ion concentration that induced the strongest osseointegration was approximately 9%. To cite this article:
Cho L‐R, Kim D‐G, Kim J‐H, Byon E‐S, Jeong Y‐S, Park C‐J. Bone response of Mg ion‐implanted clinical implants with plasma source ion implantation method.
Clin. Oral Impl. Res. 21 , 2010; 848–856.
doi: 10.1111/j.1600‐0501.2009.01862.x     

Osseointegration and stability of a modified sand-blasted acid-etched implant: an experimental pilot study in sheep

Objective: The aim of this pilot study was to compare the early‐term osseointegration characteristics of standard (SLA) and modified sand‐blasted and acid‐etched (modSLA) implants in an experimental animal model. Material and methods: A total of 30 SLA and modSLA implants were placed to the tibiae of three sheep and the insertion torque value (ITV) and resonance frequency analysis (RFA) measurements were performed. RFA measurement was repeated on 3 and 6 weeks healed implants after which the animals were sacrificed for histomorphometric analysis. Bone‐to‐implant contact was assessed on the non‐decalcified sections. Six weeks healed implants were also subjected to the reverse torque test (RTT). Results were analyzed by the Friedman test, Kruskal–Wallis test and Spearman rank correlation test. Results: All implants reached to a strong primary stability with a mean 36.13 ± 2.47 and 35.47 ± 2.85 N/cm ITV. In the surgical stage, RFA values for SLA and modSLA implants were found to be 72.27 ± 3.17 and 71.6 ± 2.87, respectively. After 3 weeks of healing, mean BIC% (80.64 ± 13.89%) and RFA value (76.8 ± 1.14) of modSLA implants were significantly higher (P=0.0002) than that of SLA implants (64.39 ± 21.2 BIC% and 74.2 ± 4.76 RFA). However, no statistically significant difference between SLA and modSLA implants was recorded after 6 weeks of healing. Both implants revealed similar results in the RTT test (115.2 ± 4.14 and 117 ± 4.47 N/cm for SLA and modSLA implants, respectively). No correlation was found between RFA and BIC%. Conclusion: Within the limits of this pilot study, it can be concluded that modSLA implants achieve a higher bone contact and stability at earlier time points when compared with SLA implants. To cite this article:
Abdel‐Haq J, Karabuda CZ, Arιsan V, Mutlu Z, Kürkçü M. Osseointegration and stability of a modified sand‐blasted acid‐etched implant: an experimental pilot study in sheep.
Clin. Oral Impl. Res. 22 , 2011; 265–274.
doi: 10.1111/j.1600‐0501.2010.01990.x     

Primary implant stability after maxillary sinus augmentation with autogenous mesenchymal stem cells: a biomechanical evaluation in rabbits

Objectives: To mechanically evaluate the effect of transplantation of precultured preosteoblasts derived from autogenic adult mesenchymal stem cells (aMSC) for experimental sinus floor augmentation on primary dental implant stability in comparison with conventional augmentation procedures in rabbits. Material and methods: After experimental sinus floor augmentation with a synthetic bone substitute, autogenous bone transplantation or osteoblast precursor cells, the primary stability of implants inserted in the edentulous part of the upper jaw of New Zealand White Rabbits was examined. Mechanical evaluation was performed by determination of insertion torque values (Osseocare^?), percussion testing (Periotest^?), resonance frequency analysis (Osstell^? and scanning laser Doppler vibrometer) and measurement of extraction forces. Results: Evaluation of mechanical properties with percussion testing and resonance frequency analysis with Osstell^? revealed slightly higher primary stability of the stem cell group whereas the scanning laser Doppler vibrometer and measurement of pull‐out forces showed no significant difference to the bone substitute group. Transplantation of autogenous bone graft resulted in the highest primary implant stability. Conclusions: The three examination modalities proved suitable for the determination of primary implant stability. The experimental maxillary sinus floor augmentation with precultured osteoblast precursor cells from autogenic stems cells clearly enhanced the primary stability of implants compared with the unaugmented sinus and lead to comparable primary mechanical properties to bone substitutes in rabbits. In comparison with the autogenous bone graft stability enhancement by stem cell transplantation declined. To cite this article:
Riecke B, Heiland M, Hothan A, Morlock M, Amling M, Blake FAS. Primary implant stability after maxillary sinus augmentation with autogenous mesenchymal stem cells – biomechanical evaluation in rabbits.
Clin. Oral Impl. Res. 22 , 2011; 1242–1246.doi: 10.1111/j.1600‐0501.2010.02043.x     

Effects of magnesium intake deficiency on bone metabolism and bone tissue around osseointegrated implants

Objectives: This study evaluated the effect of magnesium dietary deficiency on bone metabolism and bone tissue around implants with established osseointegration. Materials and methods: For this, 30 rats received an implant in the right tibial metaphysis. After 60 days for healing of the implants, the animals were divided into groups according to the diet received. Control group (CTL) received a standard diet with adequate magnesium content, while test group (Mg) received the same diet except for a 90% reduction of magnesium. The animals were sacrificed after 90 days for evaluation of calcium, magnesium, osteocalcin and parathyroid hormone (PTH) serum levels and the deoxypyridinoline (DPD) level in the urine. The effect of magnesium deficiency on skeletal bone tissue was evaluated by densitometry of the lumbar vertebrae, while the effect of bone tissue around titanium implants was evaluated by radiographic measurement of cortical bone thickness and bone density. The effect on biomechanical characteristics was verified by implant removal torque testing. Results: Magnesium dietary deficiency resulted in a decrease of the magnesium serum level and an increase of PTH and DPD levels (P≤0.05). The Mg group also presented a loss of systemic bone mass, decreased cortical bone thickness and lower values of removal torque of the implants (P≤0.01). Conclusions: The present study concluded that magnesium‐deficient diet had a negative influence on bone metabolism as well as on the bone tissue around the implants. To cite this article:
Belluci MM, Giro G, del Barrio RAL, Pereira RMR, Marcantonio E Jr, Orrico SRP. Effects of magnesium intake deficiency on bone metabolism and bone tissue around osseointegrated implants.

Clin. Oral Impl. Res. 22 , 2011; 716–721
doi: 10.1111/j.1600‐0501.2010.02046.x     

The effect of water pyrolysis on the removal torque of titanium implant inserted in rabbit tibias

Objective: The aim of this study is to examine the effect of oxidation with water pyrolysis (OWP) method on titanium (Ti) implants by comparing the bonding strength between bone and Ti implants that were inserted in the proximal tibia metaphysic of a rabbit for 12 weeks. The removal torque was measured to evaluate the bonding strength for different Ti implants with and without the OWP method. Material and methods: Nine sets of threaded Ti implants (ASTM grade 2) of diameter 3.75 mm and length 5 mm were prepared for the experiment. Each set was composed of four specimens; one was machine‐prepared (group D) and the other three were threaded followed by the OWP method at 300°C (group A), 600°C (group B), and 800°C (group C) for 10 min, respectively. Each set was used for each adult rabbit. To eliminate the effect of the sites or the legs, each rabbit received all four implants, two in the left and two in the right leg, inserted in the proximal tibia metaphyses of the left leg, using a fixed block randomization. After 12 weeks, removal torque tests were carried out. Results: The mean removal torque for the control group D was 16.19 N cm, while the mean removal torque values for the OWP groups A, B, and C were 26.75, 31.51, and 41.05 N cm, respectively. The removal torques obtained from the OWP groups B and C (showing the rutile oxide structure) were significantly greater than that for the control group by Bonferroni's‐corrected Wilcoxon's signed‐rank test (P<0.05). Conclusion: The strongest bonding between bone and group C (OWP method at 800°C) was confirmed by the comparison of removal torques. To cite this article:
S‐H Park, WB Song, KH Kim, DJ Soe, S‐A Cho. The effect of water pyrolysis on the removal torque of titanium implant inserted in rabbit tibias.
Clin. Oral Impl. Res. 22 , 2011; 157–164.
doi: 10.1111/j.1600‐0501.2010.01971.x     

Long-term outcomes of three types of implant-supported mandibular overdentures in smokers

Purpose: The aim of the study was to compare the differences in the long‐term clinical and radiologic effects for three different treatment strategies with implant‐supported overdentures in the edentulous mandible, with a special emphasis on smoking. Materials and methods: In a randomized‐ controlled clinical trial, 110 edentulous patients participated. Thirty‐six patients were treated with an overdenture supported by two implants with ball attachments (2IBA), 37 patients with an overdenture supported by two implants with a bar (2ISB) and 37 patients with an overdenture supported by four implants with a triple bar (4ITB). After a mean evaluation period of 8.3 years, the clinical and radiographic parameters were evaluated. Results: Ninety‐four out of the original 110 patients (=85%) were evaluated. In the 2IBA group, the plaque index was significantly lower (vs. 2ISB, P=0.013; vs. 4ITB, P=0.001) than in the other groups, but there was no correlation with the other peri‐implant parameters. In the 4ITB group, the marginal bone loss was significantly higher than that in the two implant groups. The maximal probing depth was correlated with peri‐implant bone loss (P=0.011). Smoking almost doubled marginal bone loss irrespective of the treatment strategy chosen. Conclusions: Patients with two implants show less marginal bone loss than those with four implants. Smoking is a risk factor for the survival of dental implants in the long run. To cite this article :
Stoker G, van Waas R, Wismeijer D. Long‐term outcomes of three types of implant‐supported mandibular overdentures in smokers.
Clin. Oral Impl. Res. 23 , 2012; 925–929
doi: 10.1111/j.1600‐0501.2011.02237.x     

Early Healing of Hydroxyapatite‐Coated Implants in Grafted Bone of Zoledronic Acid–Treated Osteoporotic Rabbits

Background: Resorption of grafted bone and delayed osseointegration of implants are main problems associated with alveolar bone augmentation in dental implantology, especially for patients with osteoporosis. The aim of this study is to investigate the early healing response of implants to systemic treatment of zoledronic acid (ZA) in autogenous grafted iliac bone of osteoporotic rabbits. Methods: Ovariectomy (OVX) or sham operation was performed in 46 rabbits, and osteoporotic changes were verified in animals receiving OVX 3 months later. The remaining animals were divided into three groups (n = 12): sham, OVX, and OVX with ZA treatment (ZA group). Autogenous iliac bone grafting was performed in bilateral tibiae, and hydroxyapatite‐coated titanium implants were simultaneously placed into the grafted bone. The animals were sacrificed 2 and 8 weeks later for examination. Results: At both time points, systemic treatment of ZA efficiently promoted bone healing of implants in grafted bone, and all histologic and microcomputed tomography bone indices, including mineralized bone volume, implant–bone contact ratio, connectivity density, trabecular thickness, and trabecular number, were significantly increased in the ZA group compared with the OVX‐only group (P <0.01); implant–bone contact rates in the ZA group were even restored to levels similar to those of sham‐operated animals (P >0.05). Furthermore, biomechanical testing demonstrated that removal torque of implants was significantly increased in the ZA group compared with the OVX group (P <0.01). Conclusion: Systemic treatment with ZA could efficiently promote early bone healing of implants in autogenous grafted bone of osteoporotic rabbits by increasing early osseointegration and fixation of implants.     

Primary stability,insertion torque and bone density of cylindric implant ad modum Branemark: Is there a relationship? An in vitro study

Objectives: Protocols of immediate loading have been reported in several studies. It has also been demonstrated that the cause of failure of immediate loaded implants is due to the micromotion on the bone–implant interface induced by immediate loading. There should be a minimum gap between the implant and the peri‐implant bone, without micromotions occurring above a definite threshold risk as they induce bone resorption and fibrosis around the implant. Measurement of the torque necessary to insert an implant in the bone is a parameter for measuring initial stability. The higher the implant insertion torque, the higher the initial stability attained. The aim of this study was to evaluate in vitro the correlation between the micromotion of cylindric screw implants ad modum Branemark and the insertion torque in bone of different densities. Material and methods: The test was carried out on 2 × 2 cm samples of fresh bovine bone of three different densities: hard (H), medium (M) and soft (S). One hundred and fifty hexa implants ad modum Branemark were used, 3.75 mm in diameter and 9 mm long. To screw in the implants, a customized manual key was used, controlled digitally to evaluate the peak insertion torques. Ten implants were prepared for each torque (20, 35, 45, 70 and 100 N/cm). The bone sample was then fixed on a loading device, which allowed evaluating the micromotion. On each sample, we applied a 25 N horizontal force. Results: The results indicate that the peak insertion torque and the implant micromotion are statistically correlated, and statistically significant differences in H and M bone were found compared with S bone. In S bone, we noted a micromotion significantly higher than the risk threshold, and it was not possible to reach peak insertion torque above 35 N/cm. In H and M bone, the micromotion is below the threshold of all insertion torques. Conclusions: Increasing the peak insertion torque, we can reduce the extent of the micromotion between the implant and the bone when submitted to lateral forces in vitro. In soft bone, the micromotion was always high; hence, immediate loading of implants in low‐density bone should be evaluated with care. To cite this article:
Trisi P, De Benedittis S, Perfetti G, Berardi D. Primary stability, insertion torque and bone density of cylindric implant ad modum Branemark: is there a relationship? An in vitro study.
Clin. Oral Impl. Res. 22 , 2011; 567–570
doi: 10.1111/j.1600‐0501.2010.02036.x     

Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits

Aim: To investigate bone‐to‐implant bonding for some novel surface modifications with a hierarchic structure and to correlate the in vivo results with surface roughness parameters. Materials and methods: Newly developed implants surfaces were tested in rabbits and compared with the commercially available OsseoSpeed^? (OS) implant. The blasted test samples were subjected to treatment in oxalic acid (AT‐II), followed by subsequent etching in hydrofluoric acid (AT‐I). Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to characterize the surface topography and chemical composition of the implants. Biomechanical testing after 6 weeks of healing was complemented with the quantification of fluorochromes and the results were subjected to a multivariate statistical analysis. Results: The results show, both with biomechanical‐ and with histomorphometrical tests, that the AT‐I implants with different surface roughness at the micro (blasting), submicro (shallow cavities) and nanolevels (precipitates) have a greater bone tissue integration compared with the AT‐II‐ and OS implants. The 2D bone‐to‐implant contact (BIC) data were in accordance with the 3D removal torque (RTQ) results even if the former were deduced from implants located in spongeous‐type bone and the latter in cortical bone. The increase in RTQ values for the test samples AT‐I and AT‐II compared with the reference complies with the slightly higher S_a values for these surfaces. Conclusions: Using a combination of conventional methods with novel quantification of florochrome and multivariate analysis, the influence of surface roughness on different levels could be discriminated. The RTQ and BIC values show that the most hierarchical structure with submicro cavities and nanoscale precipitates possesses the most favourable osseointegration properties. To cite this article:
Johansson CB, Gretzer C, Jimbo R, Mattisson I, Ahlberg E. Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits
Clin. Oral Impl. Res. 23 , 2012; 943–953
doi: 10.1111/j.1600‐0501.2011.02233.x     

Evaluation of implant osseointegration with different regeneration techniques in the treatment of bone defects around implants: an experimental study in a rabbit model

Aim: The aim of this study was to evaluate the osseointegration of implants placed in areas with artificially created bone defects, using three bone regeneration techniques. Material and methods: The experimental model was the rabbit femur (16), where bone defects were created and implants were placed. The peri‐implant bone defects were filled with a deproteinized bovine bone mineral, NuOss^? (N), NuOss^? combined with plasma rich in growth factors (PRGF) (N+PRGF), NuOss^? covered by an RCM⁶ membrane (N+M), or remained unfilled (control group [C]). After 4 and 8 weeks, the animals were euthanized and bone tissue blocks with the implants and the surrounding bone tissue were removed and processed according to a histological protocol for hard tissues on non‐decalcified ground sections. The samples were studied by light and electron scanning microscopy, histometric analysis was performed to assess the percentage of bone in direct contact with the implant surface and a statistical analysis of the results was performed. Results: In the samples analyzed 4 weeks after implantation, the percentage of bone tissue in direct contact with the implant surface for the four groups were 57.66±24.39% (N), 58.62±20.37% (N+PRGF), 70.82±20.34 % (N+M) and 33.07±5.49% (C). In the samples with 8 weeks of implantation time, the percentage of bone in direct contact was 63.35±27.69% (N), 58.42±24.77% (N+PRGF), 78.02±15.13% (N+M) and 40.28±27.32% (C). In terms of the percentage of bone contact, groups N and N+M presented statistically significant differences from group C in the 4‐week trial test (P<0.05; ANOVA). For the 8‐week results, only group N+M showed statistically significant differences when compared with group C (P<0.05; ANOVA). Conclusion: In conclusion, the NuOss^? granules/RCM⁶ membrane combination presented a percentage of bone contact with the implant surface statistically greater than in the other groups. To cite this article:
Guerra I, Branco FM, Vasconcelos M, Afonso A, Figueiral H, Zita R. Evaluation of implant osseointegration with different regeneration techniques in the treatment of bone defects around implants: an experimental study in a rabbit model.
Clin. Oral Impl. Res. 22 , 2011; 314–322.
doi: 10.1111/j.1600‐0501.2010.02002.x     

Primary stability measurements of single implants in the midline of the edentulous mandible for overdentures

Objectives: To determine the primary stability of the Southern wide diameter (8 mm) implants, Neoss regular diameter (4 mm) implants, and Southern regular diameter (3.75 mm) implants placed in the midline of edentulous mandibles for single‐implant overdentures. Variables related to host site and implant characteristics were investigated to determine their influence on the primary stability of the implants. Materials and methods: A total of 36 implants were placed in the midline symphysis of the edentulous mandibles of 36 participants. Their primary stability was then measured using the magnetic Osstell mentor device. Analysis of variance (ANOVA) was used to compare the mean implant stability quotient (ISQ) scores with one‐way ANOVA for multiple comparisons. Results: The highest measurement (ISQ) of primary stability was for the Southern 8 mm wide diameter implants (84.8, SD 9.8), followed by the Neoss 4 mm regular diameter (82.3, SD 4.8) implants and the Southern 3.75 mm regular diameter implants (75.3, SD 8.4), respectively. The Southern 3.75 mm regular diameter implants had a significantly lower mean ISQ value than the same system 8 mm wide diameter (P=0.004) and the Neoss 4 mm regular diameter implants (P=0.03). No significant differences were observed between the 8 mm and the 4 mm diameter implants (P>0.05). Conclusions: Host‐site variables such as age, gender, bone volume, and quality do not appear to influence the primary stability of the implants. No clear correlation was established between ISQ values and implant diameter. To cite this article:
Alsabeeha NHM, De Silva RK, Thomson WM, Payne AGT. Primary stability measurements of single implants in the midline of the edentulous mandible for overdentures.
Clin. Oral Impl. Res. 21 , 2010; 563–566.
doi: 10.1111/j.1600‐0501.2009.01890.x     

CBCT fractal dimension changes at the apex of immediate implants placed using undersized drilling

Objectives: To evaluate, on the base of cone beam computed tomography (CBCT) fractal dimension, bone quality changes surrounding the apical portion of immediate implants placed under higher insertion torque utilizing an undersized drilling technique. Materials and methods: Three patients were enrolled in this study. Single implants were placed into fresh extraction sockets in the anterior maxilla and provisionalized immediately. Adequate stability was ensured on all the implants by a 28.5% undersizing of the apical portion of the osteotomy. Bone quality at the most apical 1.15 mm peri‐implant bone portion were measured by CBCT at placement and after 6 months. This analysis was carried out by evaluating the box counting fractal dimension of 15 consecutive CBCT slices related to the most apical part of each implant. Results: All the three implants were successful after an 18‐month follow‐up period. The mean fractal dimension at the implant apex exhibited a 3% increase 6 months following placement. Conclusions: Within the limitations of an explorative study, an undersized drilling resulting in high insertion torque would seem to induce no adverse changes in radiographic bone quality after 6 months of follow‐up. The most favorable entity of drilling undersizing and its effect on peri‐implant bone remodeling, should be evaluated on a larger patient population. To cite this article :
González‐Martín O, Lee EA, Veltri M. CBCT fractal dimension changes at the apex of immediate implants placed using undersized drilling
Clin. Oral Impl. Res. 23 , 2012; 954–957
doi: 10.1111/j.1600‐0501.2011.02246.x