Peri-implant Bone Defects Research Articles

Influence of blinded wound closure on the volume stability of different GBR materials: an in vitro cone‐beam computed tomographic examination

To test whether the use of (i) particulated bone substitute + collagen membrane used for guided bone regeneration (GBR) of peri-implant bone defects renders different results from (ii) particulated bone substitute + collagen membrane + fixation pins and from (iii) block bone substitute + collagen membrane with respect to the volume stability of the augmented region during suturing of mucosal flaps. Twenty peri-implant box-shaped bone defects were created in 10 pig mandibles. Every bone defect was augmented once with each of the following GBR procedures: Granulate (particulated xenograft + collagen membrane), Granulate + Pins (particulated xenograft + collagen membrane + fixation pins), and Block (block xenograft + collagen membrane). Cone-beam computed tomography scans were obtained prior and after blinded wound closure. The horizontal thickness (HT) of the augmented region (bone substitute + membrane) was assessed at the implant shoulder (HT0 mm ) and at 1-5 mm apical to the implant shoulder (HT1 mm -HT5 mm ). The changes of HT during flap suturing were calculated as absolute (mm) and relative values (%). Repeated-measures ANOVA was used for statistical analysis. Wound closure induced a statistically significant change of HT0 mm and of HT1 mm in all the treatment groups (P ≤ 0.05). The change in HT0 mm measured -42.8 ± 17.9% (SD) for Granulate, -22.9 ± 21.2% (SD) for Granulate + Pins, and -20.2 ± 18.9% (SD) for Block. The reduction in HT0 mm, HT1 mm , HT2 mm, and HT3 mm for the Granulate procedure was significantly higher as compared to the Granulate + Pins and the Block procedures (P ≤ 0.05). There were no statistically significant differences in the change of HT between the Granulate + Pins and the Block procedures (P > 0.05). Wound closure induced displacement of the bone substitute resulting in a partial collapse of the collagen membrane in the coronal portion of the augmented site. The stability of the bone substitute and collagen membrane was enhanced by the application of fixation pins and by the use of block bone substitute instead of particulated bone substitute.

Effect of parathyroid hormone (1-34) and coralline hydroxyapatite on bone regeneration of peri-implant bone defects

To evaluate the effect of parathyroid hormone (1-34) [PTH(1-34)] and coralline hydroxyapatite (CHA) on bone regeneration of peri- implant bone defects. Two implant sites were prepared on both sides of tibia in 8 mongrel dogs. The bone defect was created along one bone wall of each implant site. Implants were implanted into the implant sites, then CHA was grafted into the bone defects. After surgery, the animals were randomly divided into two groups. PTH (1-34) (40 µg/kg) was used for subcutaneous injection to the experimental group for three consecutive days, meanwhile the same amount of saline was given to the control group. Half of the animals of each group were sacrificed after 4 weeks and 8 weeks respectively. Specimens were subjected to implant pull- out strength tests, X-ray picture and histological observation. The bone density of bone defects in the experimental group were higher than that in the control group. No low-density images was observed between the implants and bone at 4 weeks and 8 weeks. The maximum pull-out force value of the experimental group (199.8 N, 411.5 N) was higher at 4 weeks and 8 weeks than that of the control group (100.1 N, 184.5 N) (P < 0.05). The pull-out force value of the experimental group at 4 weeks and the pull-out force value of the control group at 8 weeks were similar. The new bone trabecular around CHA of experimental group was thicker at 4 weeks. Implant surface contacted to the new bone directly without fiber. CHA granules of the experimental group at 8 weeks were fewer than that of the control group. New bone tissue of the experimental group was denser. The contact area between implant surface and new bone was wider in experimental group than in the control group. PTH (1-34) and CHA can promote bone regeneration of peri-implant bone defects, shorten the implants and bone healing cycle and improve the implants osseointegration.

The stability analysis of implants installed in osteotomies with different types of controlled bone defects

The stability parameters of implants (ITV, ISQ & PTV) according to different sizes of controlled bone defects made in implant osteotomies were analyzed and the correlation among the three kinds of implant stability parameters was tested in this study. 45 tapped screw-type dental implants were inserted in three types of implant osteotomies made in 8 fresh-frozen pig femoral bones: Type1 — without coronal bone defect, Type2 — with 3 mm coronal bone defects, and Type3 — with 6 mm coronal bone defects. The insertion torque values, ISQ & PTV of implants were measured and analyzed statistically. It is concluded that the circumferential coronal bone defects statistically influence the primary stability of implants; ITV, ISQ and PTV are suitable and available to detect the peri-implant coronal bone defects in 3 mm increments, and ITV and PTV are more sensitive to coronal cortical bone loss. There was a strong correlation between ITV and ISQ.

Effect on bone formation of the autogenous tooth graft in the treatment of peri-implant vertical bone defects in the minipigs.

BackgroundThe aim of this study was to evaluate the effect of autogenous tooth bone as a graft material for regeneration of bone in vertical bony defects of the minipigs.Material and MethodsSix minipigs were used in this study. Four molars were extracted in the right mandibular dentition and sent to the Korea Tooth Bank for fabrication of autogenous tooth bone. Ten days later, each extraction site was implanted with MS Implant Narrow Ridge 3.0x10mm fixture (Osstem, Seoul, Korea) after standardized 2mm-sized artificial vertical bony defect formation. Pineappleshaped Root-On type autogenous tooth bones were applied to the vertical defects around the neck area of the posterior three fixtures and the fore-most one was not applied with autogenous bone as a control group. Each minipig was sacrificed at 4, 8, 12 weeks after fixture installation and examined radiologically and histologically. Histological evaluation was done under light microscope with Villanueva osteochrome bone staining with semi-quantitative histomorphometric study. Percentage of new bone over total area (NBF) and bone to implant contact (BIC) ratio were evaluated using digital software for area calculation.ResultNBF were 48.15 ± 18.02%, 45.50 ± 28.37%, and 77.13 ± 15.30% in 4, 8, and 12 weeks, respectively for experimental groups. The control group showed 37.00 ± 11.53%, 32.25 ± 26.99%, and 1.33 ± 2.31% in 4,8,12 weeks, respectively. BIC ratio were 53.08 ± 19.82%, 45.00 ± 28.37%, and 75.13 ± 16.55% in 4,8,12 weeks, respectively. Those for the control groups were 38.33 ± 6.43%, 33.50 ± 29.51 %, and 1.33 ± 2.31% in 4, 8, 12 weeks, respectively.ConclusionAutogenous tooth bone showed higher score than control group in NBF and BIC in all the data encompassing 4,8,12 weeks specimens, but statistically significant only 12 weeks data in both NBF and BIC.

Use of buccal fat pad to repair post-extraction peri-implant bone defects in the posterior maxilla. A preliminary prospective study.

BackgroundExtensive literature exists about the use of the BFP in the treatment of oral defects but, to our knowledge, no article refers to the use of the BFP as a substitute of the membrane barriers for treatment of peri-implant bone defects. The aim was to evaluate the use of the buccal fat pad as a coating material for bone grafting in the peri-implant bone defect regeneration of immediate implants placed in the posterior maxilla.Material and MethodsA preliminary prospective study of patients involving immediate implants in which the buccal fat pad was used as a coating material to peri-implant bone defects was carried out. The outcome measures assessed were: postoperative pain and swelling, complications related to buccal fat pad surgery, implant survival and success rates and peri-implant marginal bone loss at 12 months of prosthetic loading.ResultsTwenty-seven patients (17 women and 10 men) with a mean age of 55.3 ± 8.9 years, and a total of 43 implants were included. Two-thirds of the patients reported either no pain or only mild intensity pain and moderate inflammation, two days after surgery. Post-operative period was well tolerated by the patients and no serious complications occurred. None wound dehiscence occurred. Implant survival and success rates were 97.6% and the average marginal bone loss 1 year after loading was 0.58 ± 0.27 mm.ConclusionsWithin the limits of this preliminary study, the use of the buccal fat pad as a coating material for bone grafting in peri-implant bone defects placed in the upper posterior maxilla was a well-tolerated technique by patients; high implant success rate was achieved with a minimal peri-implant marginal bone loss at 12 months of prosthetic loading. Key words:Buccal fat pad, immediate implant, peri-implant bone defect.

Dental implants with versus without peri-implant bone defects treated with guided bone regeneration.

Background The guided bone regeneration (GBR) technique is highly successful for the treatment of peri-implant bone defects. The aim was to determine whether or not implants associated with GBR due to peri-implant defects show the same survival and success rates as implants placed in native bone without defects. Material and Methods Patients with a minimum of two submerged dental implants: one suffering a dehiscence or fenestration defect during placement and undergoing simultaneous guided bone regeneration (test group), versus the other entirely surrounded by bone (control group) were treated and monitored annually for three years. Complications with the healing procedure, implant survival, implant success and peri-implant marginal bone loss were assessed. Statistical analysis was performed with non-parametric tests setting an alpha value of 0.05. Results Seventy-two patients and 326 implants were included (142 test, 184 control). One hundred and twenty-five dehiscences (average height 1.92±1.11) and 18 fenestrations (average height 3.34±2.16) were treated. At 3 years post-loading, implant survival rates were 95.7% (test) and 97.3% (control) and implant success rates were 93.6% and 96.2%, respectively. Mean marginal bone loss was 0.54 (SD 0.26 mm) for the test group and 0.43 (SD 0.22 mm) for the control group. No statistically significant differences between both groups were found. Conclusions Within the limits of this study, implants with peri-implant defects treated with guided bone regeneration exhibited similar survival and success rates and peri-implant marginal bone loss to implants without those defects. Large-scale randomized controlled studies with longer follow-ups involving the assessment of esthetic parameters and hard and soft peri-implant tissue stability are needed. Key words:Guided bone regeneration, peri-implant defects, dental implants, marginal bone level, success rate, survival rate.

Do Dual-Thread Orthodontic Mini-Implants Improve Bone/Tissue Mechanical Retention?

The aim of this study was to understand whether the pitch relationship between micro and macro thread designs with a parametrical relationship in a dual-thread mini-implant can improve primary stability. Three types of mini-implants consisting of single-thread (ST) (0.75 mm pitch in whole length), dual-thread A (DTA) with double-start 0.375 mm pitch, and dual-thread B (DTB) with single-start 0.2 mm pitch in upper 2-mm micro thread region for performing insertion and pull-out testing. Histomorphometric analysis was performed in these specimens in evaluating peri-implant bone defects using a non-contact vision measuring system. The maximum inserted torque (Tmax) in type DTA was found to be the smallest significantly, but corresponding values found no significant difference between ST and DTB. The largest pull-out strength (Fmax) in the DTA mini-implant was found significantly greater than that for the ST mini-implant regardless of implant insertion orientation. Mini-implant engaged the cortical bone well as observed in ST and DTA types. Dual-thread mini-implant with correct micro thread pitch (parametrical relationship with macro thread pitch) in the cortical bone region can improve primary stability and enhanced mechanical retention.

Tissue stability of implants placed in fresh extraction sockets: a 5-year prospective single-cohort study.

Several materials have been used for ridge preservation after tooth extraction. This 5-year prospective single-cohort study is aimed at evaluating the success rate, marginal bone level (MBL), soft tissue stability, and subjective patient evaluation of implants placed in fresh extraction sockets with the use of a flapless technique and a xenograft to treat the peri-implant bone defect. Patients requiring a single implant in fresh extraction sockets were selected. After flapless extraction and implant insertion, the peri-implant bone defect was grafted with porcine bone. Collagen membrane was used to stabilize the graft. Four months later, a second surgery and prosthetic procedures were performed. Clinical parameters (width of keratinized gingiva [WKG], facial soft tissue level [FST], papilla index, plaque index, and bleeding on probing) were measured, and periapical radiographs were taken at the time of implant placement (baseline) and then at 1, 3, and 5 years thereafter. Image analysis software was applied to measure changes in the marginal bone level (ΔMBL). Additionally, patient satisfaction regarding the implant treatment was evaluated. All analyses were collected and measured by an independent, trained observer. Together with descriptive statistics, for each of the outcome variables, pairwise comparisons were performed using the Wilcoxon signed-rank test for matched samples. The level of statistical significance was set at 0.01 for all analyses. Forty-seven consecutive patients were treated, with an implant survival rate at 5 years of 95.7%. ΔMBL showed statistically significant differences: mean values were -0.68 ± 0.39, -0.94 ± 0.44, and -1.08 ± 0.43 mm at the 1, 3, and 5-year follow-up, respectively. Changes in WKG (ΔWKG) and FST (ΔFST) decreased from the 1-year point of the survey (0.80 ± 0.79 and 0.71 ± 0.73 mm for ΔWKG and ΔFST, respectively) to the last follow-up check at 5 years (0.67 ± 0.74 and 0.56 ± 0.69 mm for ΔWKG and ΔFST, respectively), with no significant differences. The papilla indexes showed significant differences among the baseline and all the other time points. Concerning patient satisfaction, at the last survey time point, 74% ± 11.8% of patients were satisfied regarding the overall implant treatment, 73.0% ± 11.1% gave a favorable opinion regarding the appearance of the peri-implant soft tissues, and 80.5% ± 11.3% judged positively the finished appearance of the implant crown. No significant differences were obtained among the three follow-up times. The data of the present study suggest that the placement of a dental implant by means of a flapless technique in a fresh extraction socket filled with slowly resorbable graft biomaterial and with a delayed prosthetic restoration shows positive final esthetic outcomes. At the 5-year point of the survey, the changes in the bone level were minimal. Moreover, both midfacial tissue and the papillae maintained the early increase recorded before the first year of the follow-up.

Marginal bone loss evaluation around immediate non-occlusal microthreaded implants placed in fresh extraction sockets in the maxilla: a 3-year study.

To evaluate marginal bone loss over 3 years around immediate microthreaded implants placed in the maxillary anterior/esthetic zone and immediately restored with single crowns. Seventy-one implants (with microthreads up to the platform--rough surface body and neck, internal connection and platform switching) were placed in fresh extraction sockets in the maxillary arches of 30 men and 23 women (mean age 37.85 ± 7.09 years, range 27-60). All subjects had at least 3 mm of soft tissue to allow the establishment of adequate biologic width and to reduce bone resorption. Each patient received a provisional restoration immediately after implant placement with slight occlusal contact. Mesial and distal bone height was evaluated using digital radiography on the day following implant placement (baseline) and after 1, 2, and 3 years. Primary stability was measured with resonance frequency analysis. No implants failed, resulting in a cumulative survival rate of 100% after 3 years. Marginal bone loss from implant collar to bone crest measured at baseline (peri-implant bone defect at the fresh extraction socket) and after 3 years was 0.86 mm ± 0.29 mm. Mesial and distal site crestal bone loss ranged from 3.42 mm ± 1.2 mm at baseline to 3.51 mm ± 1.5 mm after 3 years (P = 0.063) and from 3.38 mm ± 0.9 mm at baseline to 3.49 mm ± 0.9 mm after 3 years, respectively (P = 0.086). This prospective study found minimal marginal bone loss and a 100% implant survival rate over the 3-year follow-up for microthreaded immediate implants subjected to immediate non-occlusal loading.

Preliminary evaluation of a three-dimensional, customized, and preformed titanium mesh in peri-implant alveolar bone regeneration

ObjectivesThe purpose of this preliminary study is to evaluate the effectiveness of a customized, three-dimensional, preformed titanium mesh as a barrier membrane for peri-implant alveolar bone regeneration.Materials and MethodsTen patients were recruited for this study. At the time of implant placement, all patients had fenestration or a dehiscence defect around the implant fixture. A mixture of particulate intraoral autologous bone and freeze-dried bone allograft was applied to the defect in a 1 : 1 volume ratio and covered by the preformed titanium mesh. A core biopsy specimen was taken from the regenerated bone four months postoperatively. Patients were followed for 12 months after the definitive prosthesis was placed.ResultsSatisfactory bone regeneration with limited fibrous tissue was detected beneath the preformed titanium mesh. Histologic findings revealed that newly formed bones were well-incorporated into the allografts and connective tissue. New growth was composed of approximately 80% vital bone, 5% fibrous marrow tissue, and 15% remaining allograft. All implants were functional without any significant complications.ConclusionThe use of preformed titanium mesh may support bone regeneration by maintaining space for new bone growth through its macro-pores. This preliminary study presents the efficacy of a preformed titanium mesh as a ready-to-use barrier membrane around peri-implant alveolar bone defect. This preformed mesh is also convenient to apply and to remove.

Implant–Buccal Plate Distance as Diagnostic Parameter: A Prospective Cohort Study on Implant Placement in Fresh Extraction Sockets

The aim of this study is to investigate contour changes around immediate implants in fresh extraction sockets when different grafting procedures are performed, based on the distance between the external implant collar and the bony surface on the buccal plate (I-BP). A secondary aim is to assess the esthetic outcome via the implant esthetic score (IAS). This prospective cohort study was performed in three centers. Suitable patients to undergo implant placement in fresh extraction sockets were selected. Periodontal biotype, horizontal and vertical peri-implant bone defects, and dehiscences were assessed. Depending on I-BP, two types of grafting procedures were performed. In group A (I-BP <4 mm), only the peri-implant gap was grafted during the surgical phase (internal grafting [IG]), whereas group B (I-BP ≥ 4 mm) received both internal and external grafting (IEG). Master casts of the sites, made before implant placement and after 1 year of loading, were optically scanned. A computerized analysis of the contour changes at the involved sites was performed by superimposing the scanned models. A total of 20 patients (eight males and 12 females) were recruited, and 20 non-submerged implants were placed in fresh extraction sockets. No implant failed during the observation period. The mean follow-up was 25 months (range: 12 to 37 months). After 1 year of loading, group A showed a slight decrease in mean buccal volume, whereas group B had an increase in volume (P = 0.02). IAS was higher for group B than group A. When implants are placed immediately after tooth extraction, I-BP may represent a useful diagnostic parameter in choosing the most appropriate grafting procedure (IG versus IEG). In clinical cases in which the distance between implant surface and the buccal plate is <4 mm, the combination of internal and external grafting (IEG) is recommended to maintain the volume and the contour of the ridge and achieve a successful esthetic outcome.

Silk Fibroin and 4-Hexylresorcinol Incorporation Membrane for Guided Bone Regeneration

The objective of this study was to demonstrate that a silk fibroin (SF) and 4-hexylresorcinol (4-HR) incorporation membrane could be used for a guided bone regeneration technique. Fourier transform infrared measurements were obtained to determine change of physical property of SF membrane by 4-HR incorporation. Two peri-implant defects, 3.0 × 5.0 mm (width × length), were prepared on the lateral side of the implant hole in the tibia of New Zealand white rabbits (n = 8). The peri-implant defect was left unfilled in the control group. Silk fibroin + 4-HR membrane was applied to the peri-implant defect in the experimental group. The 8 animals were killed at 8 weeks after implantation. Subsequently, removal torque test and histomorphometric evaluation were done. Fourier transform infrared spectroscopy showed no specific chemical interaction between 4-HR and SF. In the histomorphometric analysis, the mean bone regeneration was 18.3 ± 1.9 mm(2) in the experimental group and 9.3 ± 0.9 mm(2) in the control group (P = 0.004). In conclusion, the SF and 4-HR incorporation membrane successfully regenerated bone in the rabbit tibia peri-implant bone defect model.

Vertical Ridge Augmentation with a Collagen Membrane, Bovine Bone Mineral and Fibrin Sealer: Clinical and Histologic Findings

This study evaluated the treatment of alveolar bone deficiencies combined with dental implant placement. Thirty-five endosseous implants were inserted into 20 patients. After implant placement, the mean height of the supracrestal bone defects measured 4.25 ± 1.34 mm. Bone regeneration procedures were performed using a combination of a bovine bone-derived mineral stabilized with a fibrin-fibronectin sealing system and covered with a bilayered porcine collagen membrane. Healing was uneventful in all instances with maintenance of primary closure throughout the healing period. Stage-two surgery was performed after 6 months, and a hard bonelike tissue was detectable at the defect sites. Histologic examination confirmed the presence of newly formed bone with residual particles of xenograft. The mean bone gain was 3.95 ± 1.47 mm. The positive outcomes in terms of bone regeneration and low complication rate demonstrated the potential of this technique for the treatment of supracrestal ridge deficiencies. Bovine bone mineral combined with a fibrin sealer and protected by a collagen membrane should be considered as an alternative in the treatment of vertical peri-implant bone defects.

A new classification of peri‐implant bone morphology: a radiographic study of patients with lower implant‐supported mandibular overdentures

This study aimed to classify peri-implant bone defects (PIBDs) on the basis of their radiographic appearance in a cohort of patients with lower implant-supported overdentures. Eighty-three patients with lower implant-supported overdentures were recruited to participate in the study, which was approved by the ethics committee of Ignatius Teaching Hospital. Details about the patients' smoking habits were recorded. The participants had a total of 224 implants involving 3214 implant sites. The mean observation time of the subjects was 10.7 years. Panoramic radiographs of all sites were evaluated in duplicate (first evaluation [t1], second evaluation [t2]) during 2 weeks by one experienced observer. PIBDs were classified into the following types: saucer-shaped, wedge-shaped, flat, undercut, and slit-like bone defects. Intra-examiner agreement was tested using crosstabs and Cohen's kappa coefficient. The association of PIBD type with gender, time after implant placement, smoking, and treatment strategy was investigated using multivariate test of independence on the basis of spatial signs. Intra-observer reliability was moderate (κ = 0.51). Saucer-shaped defects were the most frequent (42.8% [t1] and 44.6% [t2]), followed by wedge-shaped (26.0% [t1] and 27.4% [t2]), flat (10.7% [t2] and 17.7% [t1]), undercut (8.8% [t1] and 11.9% [t2]), and finally slit-like defects (4.7% [t1] and 5.4% [t2]). Peri-implant bone defects morphology was significantly associated with gender, smoking, and treatment strategy. The morphology of PIBDs can be classified into five meaningful classes, as opposed to the two described in the literature.

A randomized controlled clinical multicenter trial comparing the clinical and histological performance of a new, modified polylactide‐co‐glycolide acid membrane to an expanded polytetrafluorethylene membrane in guided bone regeneration procedures

To compare the clinical and histological outcomes of a resorbable modified polylactide/polyglycolide acid (PLGA) test membrane and a titanium-reinforced expanded polytetrafluorethylene (ePTFE) control membrane used for guided bone regeneration (GBR) around dental implants. A total of 40 patients with peri-implant dehiscence-type defects were randomly allocated to a GBR procedure using either a modified PLGA test or an ePTFE control membrane. Soft tissue condition, implant integration, adverse events and quality of life were recorded during the 6-month healing period. At re-entry peri-implant bone defect dimensions were measured and compared with values recorded at implant/GBR surgery. A biopsy was retrieved for qualitative and quantitative histological analyses. A comparison between the groups was conducted using non-parametric statistical tests. Soft tissue complications were observed in five test patients and two control patients. Except for soft tissue complications and incomplete regeneration, no procedure- or device-related adverse events were observed. The vertical bone defect component was, in mean, reduced by-5.1 mm (95% CI -6.8, -3.3) in the test group and -6.9 mm (95% CI -8.2, -5.5 mm) in the control group. The mean residual vertical defect height measured 1.2 ± 2.4 mm in the test group and 0.3 ± 1.1 mm in the control group meaning a mean defect resolution of 81% in the test group and 96% in the control group (P = 0.161). The horizontal bone thickness at implant shoulder level decreased from a mean of 3.2 mm to 1.4 mm (-56%, mean -1.7 mm, 95% CI -2.3, -1.1) in the test group and from 3.3 mm to 2.5 mm (-24%, mean -0.8 mm, 95% CI -1.3, -0.3) in the control group (P = 0.022). Qualitative and quantitative histological analyses did not show significant differences in the tissue composition between groups. Peri-implant GBR was successfully performed using either of the membranes. The control membrane was able to better maintain the horizontal thickness of regenerated bone and revealed less soft tissue complications. No statistically valid evidence about the superiority of one membrane was found in any other parameters. Soft tissue dehiscences occur with both types of membranes and can impair the amount of regenerated bone.

Induction of Periimplantitis in Dental Implants

Development, progression, and therapy of periimplantitis are nonresolved emerging problems. The aim of this pilot study was to establish a model for periimplantitis in mice to have a base for tests with immune-deficient knockout organisms to improve the knowledge about development and progression of periimplantitis and to develop further therapeutic options.In 8 mice, titanium implants were inserted in the median of the palate. Four of these implants had ligatures (periimplantitis group). After 2 weeks, the animals received a special diet enriched with sugar and flavor. After 9 weeks, micro-computed tomography (micro-CT) examinations to evaluate the periimplant tissue and histologies were performed.Dental implant insertions within the oral cavity are possible in living mice. Implants with ligatures showed significantly larger periimplant bone defects than controls. The radiologic findings were confirmed by histology. At the end of the observation period, the portion of implants lost was higher in the ligature group.This is the first publication to describe the insertion of dental implants in living mice. In addition, it is the first time that periimplant infection could be induced in that species. This model will pave the way to study knockout mice with reduced or even enhanced resistance to periimplantitis.

The Effect of Platform Switching on Stress in Peri-implant Bone in a Condition of Marginal Bone Resorption: A Three-Dimensional Finite Element Analysis

The aim of the present study was to investigate the stress distribution in the bone around a platform-switched implant with marginal bone loss. Finite element models of an implant-supported crown on a mandibular first molar were constructed and included an osseointegrated implant, a metal crown, and cancellous and cortical bone. Two kinds of abutments, conventional and platform-switched, were imported into the model. A variety of different levels of conical marginal bone resorption, from 0 to 2.0 mm in height and width, was created around the implant neck. The stresses generated in the peri-implant bone tissue were analyzed under 200 N of vertical or oblique loading. The location of stress concentration extended from the implant neck toward the apex in association with increases in bone resorption depth. In the bone-resorbed models, the platform-switched implant showed lower maximum equivalent stresses in the peri-implant bone than the conventional abutment. The difference between the two implant models decreased as bone resorption increased. Within the limitations of this study, the results suggest a biomechanical advantage for platform switching in a condition of marginal bone resorption, but this advantage may be weakened when bone resorption is dramatic. Additional animal or clinical studies are necessary to better clarify the effects of peri-implant bone defects on the biomechanical features of a platform-switched configuration.

Primary Stability/Mobility of 1-Stage and 2-Stage Dental Implants

To evaluate the primary stability of 1-stage (nonsubmerged) and 2-stage (submerged) implants via newest wireless resonance frequency (RF) analyzer and newer wireless mobility measuring (MM) device. Six 1-stage dental implants with internal hex connection and six 2-stage dental implants, 4.1 mm in diameter and 11.5 mm in length, were inserted bilaterally into the first premolar, second premolar, and first molar regions of 6 standard mandibular transparent self-curing acrylic resin models. After that, the periimplant circular bone defects were created in millimeter increments ranging between 0 and 5 mm to the same extent on all implants. Implant stability quotient values significantly decreased at 1-stage and 2-stage implants when periimplant defects increased. Similar implant stability quotient values were found for both implant types; however, significantly lower MM values were noted for 2-stage implants. Irrespective of implant systems, the results indicated a significant association between wireless RF analyzer and wireless MM device. Both wireless RF analyzer and wireless MM device were adequate in assessing implant stability. There was no difference between 2-stage and 1-stage implant systems, except lower MM values were noted for nonsubmerged implants.

Current Knowledge and Perspectives for the Use of Platelet-Rich Plasma (PRP) and Platelet-Rich Fibrin (PRF) in Oral and Maxillofacial Surgery Part 2: Bone Graft, Implant and Reconstructive Surgery

Platelet concentrates for surgical use are innovative tools of regenerative medicine, and were widely tested in oral and maxillofacial surgery. Unfortunately, the literature on the topic is contradictory and the published data are difficult to sort and interpret. In bone graft, implant and reconstructive surgery, the literature is particularly dense about the use of the various forms of Platelet-Rich Plasma (PRP) - Pure Platelet-Rich Plasma (P-PRP) or Leukocyte- and Platelet-Rich Plasma (L-PRP) - but still limited about Platelet-Rich Fibrin (PRF) subfamilies. In this second article, we describe and discuss the current published knowledge about the use of PRP and PRF during implant placement (particularly as surface treatment for the stimulation of osseointegration), the treatment of peri-implant bone defects (after peri-implantitis, during implantation in an insufficient bone volume or during immediate post-extraction or post-avulsion implantation), the sinuslift procedures and various complex implant-supported treatments. Other potential applications of the platelet concentrates are also highlighted in maxillofacial reconstructive surgery, for the treatment of patients using bisphosphonates, anticoagulants or with post-tumoral irradiated maxilla. Finally, we particularly insist on the perspectives in this field, through the description and illustration of the use of L-PRF (Leukocyte- and Platelet-Rich Fibrin) clots and membranes during the regeneration of peri-implant bone defects, during the sinus-lift procedure and during complex implant-supported rehabilitations. The use of L-PRF allowed to define a new therapeutic concept called the Natural Bone Regeneration (NBR) for the reconstruction of the alveolar ridges at the gingival and bone levels. As it is illustrated in this article, the NBR principles allow to push away some technical limits of global implant-supported rehabilitations, particularly when combined with other powerful biotechnological tools: metronidazole solution, adequate bone substitutes and improved implant designs and surfaces (for example here AstraTech Osseospeed or Intra-Lock Ossean implants). As a general conclusion, we are currently living a transition period in the use of PRP and PRF in oral and maxillofacial surgery. PRPs failed to prove strong strategic advantages that could justify their use in daily practice, and the use of most PRP techniques will probably be limited to some very specific applications where satisfactory results have been reached. Only a few simple, inexpensive and efficient techniques such as the L-PRF will continue to develop in oral and maxillofacial surgery in the next years. This natural evolution illustrates that clinical sciences need concrete and practical solutions, and not hypothetical benefits. The history of platelet concentrates in oral and maxillofacial surgery finally demonstrates also how the techniques evolve and sometimes promote the definition of new therapeutical concepts and clinical protocols in the today's era of regenerative medicine.

A comparison of cone beam computed tomography and conventional periapical radiography at detecting peri‐implant bone defects

To compare the diagnostic accuracy of conventional periapical radiography and cone beam computed tomography (CBCT) at detecting peri-implant bone defects. Implants were placed in fresh bovine ribs in osteotomy sites of varying diameter (five with no peri-implant space, five with a 0.35 mm space, five with a 0.675 mm space) and imaged using (i) digital long cone periapical radiographs (LCPAs), (ii) limited volume CBCT using 3D Accuitomo 80(®) and (iii) large volume CBCT using i-CAT Next Generation(®). Images from each were randomly presented to nine examiners on two occasions. Confidence in diagnosing the presence or absence of a peri-implant radiolucency was recorded on a five-point scale. Receiver Operating Characteristic (ROC) analysis and Kappa tests were performed. Digital LCPAs were better at diagnosing a peri-implant bone defect when the peri-implant space was 0.35 mm (P < 0.02). As the peri-implant space increased to 0.675 mm, there was no significant difference in diagnostic accuracy between the three imaging methods. Sensitivity of LCPAs (100) and Accuitomo (97.8) was better than i-CAT (64.4) (P < 0.02). LCPAs and i-CAT had significantly better specificity and positive predictive value than Accuitomo. The negative predictive value of LCPA was significantly better than i-CAT. LCPAs showed better intra-examiner and inter-examiner agreement than CBCT. Within the limitations of this study, LCPAs are a reliable and valid method of detecting circumferential peri-implant bone defects and performed significantly better than CBCT.