Healing at implant sites prepared conventionally or by means of Sonosurgery (R): an experimental study in dogs

ObjectiveTo compare peri-implant tissue healing at implants installed in sites prepared with conventional drills or a sonic device.Material and methodsIn six Beagle dogs, the mandibular premolars and first molars were extracted bilaterally. After 3 months, full-thickness muco-periosteal flaps were elevated and recipient sites were prepared in both sides of the mandible. In the right side (control), the osteotomies were prepared using conventional drills, while, at the left side (test), a sonic device (Sonosurgery((R))) was used. Two implants were installed in each side of the mandible. After 8weeks of non-submerged healing, biopsies were harvested and ground sections prepared for histological evaluation.ResultsThe time consumed for the osteotomies at the test was more than double compared to the conventional control sites. No statistically significant differences were found for any of the histological variables evaluated for hard and soft tissue dimensions. Although not statistically significant, slightly higher mineralized bone-to-implant contact was found at the test (65.4%) compared to the control (58.1) sites.ConclusionsSimilar healing characteristics in osseointegration and marginal hard tissue remodeling resulted at implants installed into osteotomies prepared with conventional drills or with the sonic instrument (Sonosurgery((R))).

Sequential healing of the elevated sinus floor after applying autologous bone grafting: an experimental study in minipigs

AimTo describe the sequential healing after elevation of the maxillary sinus mucosa applying the lateral access technique with the use of autogenous bone grafting without membrane to occlude the osteotomy access.Material and methodsImmediately after the elevation of the maxillary sinus Schneiderian membrane, applying the lateral access technique in 10 minipigs, autologous bone was harvested from the lateral aspect of the mandibular molar region and ground into particles with a bone mill. The space under the Schneiderian membrane was filled with this graft. No membranes were placed onto the access osteotomy. The healing was evaluated after 15, 30, 90 and 180days. Paraffin sections were prepared and analyzed histologically.ResultsAfter 15days of healing, the elevated area was mainly filled with provisional matrix, newly formed bone and some remnants of bone chips, and appeared reduced in volume compared with that at the time of surgery. After 30days of healing, further shrinkage of the height of the elevated space was found, with similar percentages of the different tissue components. After 90 and 180days, the area underneath the Schneiderian membrane appeared reduced in volume and condensed toward the base of the sinus. The bone tissues appeared to be more mature, both for the mineralized and the non-mineralized portions, while connective tissue occupied 20% of the space, most likely related to the lack of the use of a membrane occluding the access at the time of surgery.ConclusionsSuboptimal healing outcomes with respect to augmentation of the space under the sinus floor membrane were documented when autologous bone chips were used as a filler and no membrane was applied to cover the access.

Healing at mandibular block-grafted sites: an experimental study in dogs

AimThe aim of this study was to evaluate the healing of autologous bone block grafts or deproteinized bovine bone mineral (DBBM) block grafts applied concomitantly with collagen membranes for horizontal alveolar ridge augmentation.Material and methodsIn six Labrador dogs, molars were extracted bilaterally, the buccal bony wall was removed, and a buccal box-shaped defect created. After 3months, a bony block graft was harvested from the right ascending ramus of the mandible and reduced to a standardized size. A DBBM block was tailored to similar dimensions. The two blocks were secured with screws onto the buccal wall of the defects in the right and left sides of the mandible, respectively. Resorbable membranes were applied at both sides, and the flaps sutured. After 3months, one implant was installed in each side of the mandible, in the interface between grafts and parent bone. After 3months, biopsies were harvested and ground sections prepared to reveal a 6-month healing period of the grafts.Results776.2% and 5.9 +/- 7.5% of vital mineralized bone were found at the autologous bone and DBBM block graft sites, respectively. Moreover, at the DBBM site, 63 +/- 11.7% of connective tissue and 31 +/- 15.5% of DBBM occupied the area analyzed. Only 0.2 +/- 0.4% of DBBM was found in contact with newly formed bone. The horizontal loss was in a mean range of 0.9-1.8mm, and 0.3-0.8mm, at the autologous bone and DBBM block graft sites, respectively.ConclusionsAutologous bone grafts were vital and integrated to the parent bone after 6months of healing. In contrast, DBBM grafts were embedded into connective tissue, and only a limited amount of bone was found inside the scaffold of the biomaterial.

Prevalence and possible risk factors of peri-implantitis: a concept review

The purpose of this review is to estimate the prevalence of peri-implantitis, as well as to determine possible risk factors associated with its development in patients treated with oral implants. Although implant therapy has been identified as a successful and predictable treatment for partially and fully edentulous patients, complications and failures can occur. Peri-implantitis is considered a biologic complication that results in bone loss around implants and may lead to implant treatment failure. A great variation has been observed in the literature regarding the prevalence of peri-implantitis according to the diagnostic criteria used to define peri-implantitis. The prevalence ranges from 4.7 to 43% at implant level, and from 8.9 to > 56% at patient level. Many risk factors that may lead to the establishment and progression of peri-implantitis have been suggested. There is strong evidence that presence and history of periodontitis are potential risk factors for peri-implantitis. Cigarette smoking has not yet been conclusively established as a risk factor for peri-implantitis, although extra care should be taken with dental implant in smokers. Other risk factors, such as diabetes, genetic traits, implant surface roughness and presence of keratinized mucosa still require further investigation. Peri-implantitis is not an uncommon complication following implant therapy. A higher prevalence of peri-implantitis has been identified for patients with presence or history of periodontal disease and for smokers. Until now, a true risk factor for peri-implantitis has not been established. Supportive maintenance program is essential for the long-term success of treatments with oral implants. The knowledge of the real impact of peri-implantitis on the outcome of treatments with oral implants as well as the identification of risk factors associated to this inflammatory condition are essential for the development of supportive maintenance programs and the establishment of prevention protocols.

Immunohistochemical, tomographic, and histological study on onlay bone graft remodeling. Part III: allografts

Objective In the last decades aroused the interest for bone tissue bank as an alternative to autogenous grafting, avoiding donor sites morbidity, surgical time, and costs reduction. The purpose of the study was to compare allografts (ALg) with autografts (AUg) using histology, immunochemistry, and tomographic analysis. Material and methods Fifty-six New Zealand White rabbits were submitted to surgical procedures. Twenty animals were donors and 36 were actually submitted to onlay grafting with ALg (experimental group) and AUg (control group) randomly placed bilaterally in the mandible. Six animals of each group were sacrificed at 3, 5, 7, 10, 20, and 60 postoperative days. Immunolabeling was accomplished with osteoprotegerin (OPG); receptor activator of nuclear factor-k ligand (RANKL); alkaline phosphatase (ALP); osteopontin (OPN); vascular endothelial growth factor (VEGF); tartrate-resistant acid phosphatase (TRAP); collagen type I (COL I); and osteocalcin (OC). Density and volume of the grafts was evaluated on tomography obtained at the surgery and sacrifice. Results The ALg and AUg exhibited similar patterns of density and volume throughout the experiments. The intra-group data showed statistical differences at days 7 and 60 in comparison with other time points (P = 0.001), in both groups. A slight graft expansion from fixation until day 20 (P = 0.532) was observed in the AUg group and then resorbed significantly at the day 60 (P = 0.015). ALg volume remained stable until day 7 and decreased at day 10 (P = 0.045). The light microscopy analysis showed more efficient incorporation of AUg onto the recipient bed if compared with the ALg group. The immunohistochemical labeling picked: at days 10 and 20 with OPG in the AUg group and at day 7 with TRAP in the ALg group (P = 0.001 and P = 0.002, respectively). Conclusions ALg and AUg were not differing in patterns of volume and density during entire experiment. Histological data exhibit more efficient AUg incorporation into recipient bed compared with the ALg group. Immunohistochemistry outcomes demonstrated similar pattern for both ALg and AUg groups, except for an increasing resorption activity in the ALg group mediated by TRAP and in the AUg group by higher OPG labeling. However, this latter observation does not seem to influence clinical outcomes.

Reconstruction of maxillary ridge atrophy caused by sequela of dentoalveolar trauma with autogenous bone graft harvested from mentum

Dentoalveolar traumatisms, particularly those that affect the anterior teeth, interfere adversely in the patient s life.Among them, tooth avulsion is pointed out because it is characterized as a complex injury that affects multiple tissues, andbecause there is no effective treatment available for its resolution with a stable long-term outcome.Aim/Hypothesis: The aim of the present study was to relate a clinical case of complete reconstruction of atrophy of the alveolarbone corresponding to tooth 11, lost by tooth resorption 10 years after the tooth reimplantation procedure.Material and methods: Reconstruction was performed with autogenous bone harvested from the mentum donor site. Surgicalaccess began in the receptor area with a Newman mucoperiosteal incision using a scalpel blade 15 mounted in a scalpel handlefor detachment and exposure of the receptor site. Extensive bone resorption was observed in the vestibular-palatine direction,proved by the thinness of the receptor bed. Decorticalization of the vestibular bone plate was performed. After preparing thereceptor bed, and incision was made in the mucosa in the depth of the anterior vestibular fornix, then a perpendicular muscleperiostealincision to detach and exposure the donor area. The bone graft necessary for reconstruction of the donor area wasdelimited, followed by monocortical osteotomy and the monocortical graft was removed. The next stage was to perform shapingfor passive graft accommodation and fixation by means of two bicortical screws. After fixation of the graft the sharp angles wererounded off in order to avoid possible exposure and/or fenestrations of the reconstructed area, then the receptor and donor areawere sutured. After the 6-month period to allow incorporation of the autogenous graft, an osseointegrated dental implant wasinserted. At the end of the 6-month period of waiting for osseointegration to occur, the process of fabricating the screw-retainedmetal ceramic

Bacterial leakage along the implant-abutment interface: culture and DNA Checkerboard hybridization analyses

Objective Bacterial species have been found harboring the internal surface of dental implants as consequence of their failed connections. The aim of the present study was to compare the detection frequency of bacterial leakage from human saliva through the implantabutment interface, under non-loading conditions, using either DNA Checkerboard or culture method. Materials and methods Thirty dental implants with hexagonal platforms were connected to pre-machined abutments according to the manufacturers specifications. The assemblies were individually incubated in human saliva under anaerobic conditions for 7 similar to days at 37 degrees C. Afterward, contents from the inner parts of the implants were collected and evaluated with either DNA Checkerboard (s similar to=similar to 15) or culture (n similar to=similar to 15). Subsequently, identification and quantitation of bacterial species from saliva and implants were carried out for the group evaluated with the DNA Checkerboard method. Results Both DNA Checkerboard and culture showed positive signals of bacterial leakage in 6 of the 15 evaluated samples. Capnocytophaga gingivalis and Streptococcus mutans were the most frequently detected species harboring the internal surface of the implants followed by Veillonella parvula. Conclusion Occurrence of bacterial leakage along the implantabutment interface is comparably detected with both DNA Checkerboard hybridization and conventional culture methods.

Torque removal evaluation of prosthetic screws after tightening and loosening cycles: an in vitro study

Objectives: The aim of this study was to evaluate the variation in removal torque of implant prosthetic abutment screws after successive tightening and loosening cycles, in addition to evaluating the influence of the hexagon at the abutment base on screw removal torque. Material and methods: Twenty hexagonal abutments were tightened to 20 regular external hex implants with a titanium alloy screw, with an insertion torque of 32 N cm, measured with a digital torque gauge. The implant/abutment/screw assemblies were divided into two groups: ( 1) abutments without hexagon at the base and ( 2) abutments with a hexagon at the base. Each assembly received a provisional restoration and was submitted to mechanical loading cycles. After this, the screws were removed and the removal torque was measured. This sequence was repeated 10 times, then the screw was replaced by a new one, and another cycle was performed. Linear regression analysis was performed. Results: Removal torque values tended to decrease as the number of insertion/removal cycles increased, for both groups. Comparisons of the slopes and the intercepts between groups showed no statistical difference. There was no significant difference between the mean values of last five cycles and the 11th cycle. Within the limitations of this in vitro study, it was concluded that ( 1) repeated insertion/removal cycles promoted gradual reduction in removal torque of screws, ( 2) replacing the screw with a new one after 10 cycles did not increase resistance to loosening, and ( 3) removal of the hexagon from the abutment base had no effect on the removal torque of the screws.

A study of effectiveness of midazolam sedation for prevention of myocardial arrhythmias in endosseous implant placement

Purpose: The study aimed to assess electrocardiographic alterations during oral implant placement surgeries under local anesthesia (lidocaine chlorhydrate with epinephrine), using 15 mg of midazolam as an anxiolytic premedication. Material and methods: The study randomly selected 20 patients, aged 21-50 years old, requiring bilateral mandibular dental implants. Each patient was assessed using placebo on one side and midazolam on the contralateral side, with random, double-blinded distribution. The electrocardiogram recorded 12 static leads every 2 min, while D2 derivations were recorded continuously. Results: No statistically significant differences were observed between the placebo and midazolam when analyzing the morphological behavior of the electrocardiographic wave and the presence of arrhythmias during the experiment. However, under sedation, assessment of the behavior of electrocardiographic parameters during different stages of the procedure revealed statistically significant differences (P<0.05) for heart rate, P-wave amplitude and duration of the RR and QTc intervals. The arrhythmias detected were considered low risk for patients without systemic alterations and were observed in 53.3% of patients. The most frequently occurring alterations were tachycardia, bradycardia, supraventricular and ventricular extrasystoles and blocked atrial extrasystole, which were similar for both placebo and midazolam, with the greatest incidence during the initial, incision and bone drilling stages. Conclusion: The use of 15 mg of midazolam made no difference compared with the placebo. The use of 15 mg of midazolam did not show an advantage in the incidence of arrhythmias The anxiolytic premedication does not prevent myocardial arrhythmias in endosseous implant placement. The clinical significance of the arrhythmias may not represent serious risks.

Biological monitoring of a promissory xenogenic pin for biomedical applications: a preliminary intraosseous study in rats

Objectives: Over the last years, it is known that in some cases metal devices for biomedical applications present some disadvantages suggesting absorbable materials (natural or synthetic) as an alternative of choice. Here, our goal was to evaluate the biological response of a xenogenic pin, derived from bovine cortical bone, intraosseously implanted in the femur of rats. Material and methods: After 10, 14, 30 and 60 days from implantation, the animals (n = 5/period) were killed and the femurs carefully collected and dissected out under histological demands. For identifying the osteoclastogenesis level at 60 days, we performed the immunohistochemisty approach using antibody against RANKL. Results: Interestingly, our results showed that the incidence of neutrophils and leukocytes was observed only at the beginning (10 days). Clear evidences of pin degradation by host cells started at 14 days and it was more intensive at 60 days, when we detected the majority of the presence of giant multinucleated cells, which were very similar to osteoclast cells contacting the implanted pin. To check osteoclastogenesis at 60 days, we evaluated RANKL expression and it was positive for those resident multinucleated cells while a new bone deposition was verified surrounding the pins in all evaluated periods. Conclusions: Altogether, our results showed that pins from fully processed bovine bone are biocompatible and absorbable, allowing bone neoformation and it is a promissory device for biomedical applications.

Effect of Si addition on Ca- and P-impregnated implant surfaces with nanometer-scale roughness: an experimental study in dogs

Objectives: To investigate the effect of Si addition on a nanometer-scale roughness Ca and P implant surfaces in a canine tibia model by biomechanical and histomorphometric evaluations. Material and methods: The implant surfaces comprised a resorbable media CaP microblasted (control) and a CaP resorbable media + silica-boost microblasted (experimental) surfaces. Surfaces were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and optical interferometry (IFM) down to the nanometric level. The animal model involved the bilateral placement of control (n = 24) and experimental surface (n = 24) implants along the proximal tibiae of six dogs, remaining in vivo for 2 or 4 weeks. After euthanization, half of the specimens were torquedto- interface failure, and the other half was subjected to histomorphologic and bone-to-implant contact (BIC) evaluation. Torque and BIC statistical evaluation was performed by the Friedman test at 95% level of significance, and comparisons between groups was performed by the Dunn test. Results: IFM and SEM observations depicted comparable roughness parameters for both implant surfaces on the micrometer and nanometer scales. XPS analysis revealed similar chemical composition, except for the addition of Si on the experimental group. Torque-to-interface failure and BIC mean values showed no significant differences (P = 0.25 and 0.51, respectively) at both 2- and 4-week evaluation points for experimental and control groups. Early bone healing histomorphologic events were similar between groups. Conclusions: The experimental surface resulted in not significantly different biomechanical fixation and BIC relative to control. Both surfaces were biocompatible and osseoconductive.

Use of a titanium device in lateral sinus floor elevation: an experimental study in monkeys

Aim: To evaluate the effect of a space-maintaining device fixed to the lateral wall of the maxillary sinus after the elevation of the sinus mucosa on bone filling of the sinus cavity. Material and methods: Immediately after the elevation of the maxillary sinus Schneiderian membrane accomplished through lateral antrostomy in four monkeys, a titanium device was affixed to the lateral sinus wall protruding into the sinus cavity to maintain the mucosa elevated without the use of grafting material. The healing of the tissue around the implants was evaluated after 3 and 6 months. Ground sections were prepared and analyzed histologically. Results: The void under the elevated sinus membrane, originally filled with the blood clot, was reduced after 3 as well as after 6 months of healing of about 56% and 40.5%, respectively. In seven out of eight cases, the devices had perforated the sinus mucosa. The formation of mineralized bone and bone marrow amounted to about 42% and 69% after 3 and 6 months, respectively. The connective tissue represented about 53% and 23% of the newly formed tissue after 3 and 6 months, respectively. Conclusions: New bone formation was found below the devices. However, shrinkage of the newly formed tissue was observed both after 3 and 6 months of healing. Hence, the space-maintaining function of the devices used in the present study has to be questioned.

Early peri-implant endosseous healing of two implant surfaces placed in surgically created circumferential defects. A histomorphometric and fluorescence study in dogs

Objective Several implant surfaces are being developed, some in the nanoscale level. In this study, two different surfaces had their early healing properties compared in context of circumferential defects of various widths. Material and methods Six dogs had the mandibular premolars extracted. After 8weeks, four implants were placed equicrestally in each side. One acted as control, while the others were inserted into sites with circumferential defects of 1.0, 1.5 and 2.0mm wide and 5mm deep. A nano-modified surface was used on one side and a micro-rough on the other. Bone markers were administered on the third day after implant placement and then after 1, 2, 4weeks to investigate the bone formation dynamic through fluorescence analysis. Ground sections were prepared from 8-week healing biopsies and histomorphometry was performed. Results The fluorescence evaluation of the early healing showed numerically better results for the nano-modified group; however this trend was not followed by the histomorphometric evaluation. A non-significant numerical superiority of the micro-rough group was observed in terms of vertical bone apposition, defect bone fill, bone-to-implant contact and bone density. In the intra-group analysis, the wider defects showed the worse results while the control sites showed the best results for the different parameters, but without statistical relevance. Conclusion Both surfaces may lead to complete fill of circumferential defects, but the gap width has to be considered as a challenge. The nano-scale modification was beneficial in the early stages of bone healing, but the micro-rough surface showed numerical better outcomes at the 8-week final period.

The effect of implant design on insertion torque and immediate micromotion

Objectives: To evaluate the effect of insertion torque on micromotion to a lateral force in three different implant designs. Material and methods: Thirty-six implants with identical thread design, but different cutting groove design were divided in three groups: (1) non-fluted (no cutting groove, solid screw-form); (2) fluted (901 cut at the apex, tap design); and (3) Blossomt (Patent pending) (non-fluted with engineered trimmed thread design). The implants were screwed into polyurethane foam blocks and the insertion torque was recorded after each turn of 901 by a digital torque gauge. Controlled lateral loads of 10N followed by increments of 5 up to 100N were sequentially applied by a digital force gauge on a titanium abutment. Statistical comparison was performed with two-way mixed model ANOVA that evaluated implant design group, linear effects of turns and displacement loads, and their interaction. Results: While insertion torque increased as a function of number of turns for each design, the slope and final values increased (Po0.001) progressively from the Blossomt to the fluted to the non-fluted design (M +/- standard deviation [SD] = 64.1 +/- 26.8, 139.4 +/- 17.2, and 205.23 +/- 24.3 Ncm, respectively). While a linear relationship between horizontal displacement and lateral force was observed for each design, the slope and maximal displacement increased (Po0.001) progressively from the Blossomt to the fluted to the non-fluted design (M +/- SD 530 +/- 57.7, 585.9 +/- 82.4, and 782.33 +/- 269.4 mm, respectively). There was negligible to moderate levels of association between insertion torque and lateral displacement in the Blossomt, fluted and non-fluted design groups, respectively. Conclusion: Insertion torque was reduced in implant macrodesigns that incorporated cutting edges, and lesser insertion torque was generally associated with decreased micromovement. However, insertion torque and micromotion were unrelated within implant designs, particularly for those designs showing the least insertion torque.