Preparation, characterization and biological properties of a novel bone block composed of platelet rich fibrin and a deproteinized bovine bone mineral.

Alveolar bone defects caused by tooth loss often lead to challenges in implant dentistry, with a need for development of optimal bone biomaterials to predictably rebuild these tissues. To address this problem, we fabricated a novel bone block using platelet-rich fibrin (PRF) and Deproteinized Bovine Bone Mineral (DBBM), and characterized their mechanical and biological properties. The bone block was prepared by mixing DBBM, Liquid-PRF, and Solid-PRF fragments in various combinations as follows: (1) BLOCK-1 made with Solid-PRF fragments + DBBM, (2) BLOCK-2 made with Liquid-PRF + DBBM, (3) BLOCK-3 made with Solid-PRF fragments + Liquid-PRF + DBBM. The time for solidification and the degradation properties were subsequently recorded. Scanning electron microscopy (SEM) and tensile tests were carried out to investigate the microstructure and mechanical properties of each block. The bioactivity of the three groups towards osteoblast differentiation was also evaluated by culturing cells with the conditioned medium from each of the three groups including cell proliferation assay, cell migration assay, alkaline phosphatase (ALP) staining, and alizarin red staining (ARS), as well as by real-time PCR for genes encoding runt-related transcription factor 2 (RUNX2), ALP, collagen type I alpha1(COL1A1) and osteocalcin (OCN). BLOCK-3 made with Solid-PRF fragments + Liquid-PRF + DBBM had by far the fastest solidification period (over a 10-fold increase) as well as the most resistance to degradation. SEM and tensile tests also revealed that the mechanical properties of BLOCK-3 were superior in strength when compared to all other groups and further induced the highest osteoblast migration and osteogenic differentiation confirmed by ALP, ARS and real-time PCR. PRF bone blocks made through the combination of Solid-PRF fragments + Liquid-PRF + DBBM had the greatest mechanical and biological properties when compared to either used alone. Future clinical studies are warranted to further support the clinical application of PRF bone blocks in bone regeneration procedures.

Incidence of COVID-19 Virus Transmission in Three Dental Offices: A 6-Month Retrospective Study.

The World Health Organization (WHO) declared COVID-19 a pandemic on March 11, 2020. SARS CoV-2, the virus that causes COVID-19, has shown the ability to become aerosolized with a potential airborne route of transmission. Dentists and dental hygienists are listed as two of the occupations in a nonhospital setting with the greatest risk of contracting the SARS-CoV-2 virus, as routine dental procedures involve aerosol generation. In a statement on interim guidance, WHO recommended that all routine dental procedures be delayed until COVID-19 transmission rates decrease from community transmission to cluster cases and until the risk of transmission in a dental office can be studied and evaluated. This prospective study involves 2,810 patients treated over a 6-month period (March 15 to September 15, 2020) in three different dental offices by two dentists and three hygienists during and shortly after the height of the pandemic in New York. By utilizing screening questionnaires, performing enhanced infection control, and having appropriate personal protective equipment, these dental offices were able to record no transmission of COVID-19 to the dental healthcare workers or patients during the study. In addition, 69% of the patients treated in these dental offices were recorded as having one or more high-risk comorbidities related to COVID-19 severity.

A Rationale for Postsurgical Laser Use to Effectively Treat Dental Implants Affected by Peri-implantitis: Two Case Reports.

Peri-implantitis is a biologic complication that can affect the survival of a dental implant. Most surgical and nonsurgical treatments have been relatively ineffective even when using targeted antimicrobial approaches. A growing number of reports are documenting the presence of titanium granules and/or cement in the soft tissues surrounding peri-implantitis-affected dental implants. Two case reports are presented demonstrating how the Nd:YAG or a carbon dioxide (CO2) laser used following regenerative surgeries changed failures into successes as measured by radiographic bone fill and improved clinical parameters. These cases suggest that successful peri-implantitis treatment may need to incorporate decontamination of the soft tissues in addition to the implant's surface. Further studies are warranted to determine if each of these lasers would be successful over a larger patient cohort.

Thermal Testing of Titanium Implants and the Surrounding Ex-Vivo Tissue Irradiated With 9.3um CO2 Laser.

PURPOSE: To measure the temperature rise and surface damage of titanium dental implants and the surrounding tissue in a pig jaw during 9.3-µm carbon dioxide (CO2) laser irradiation at various durations of time. MATERIALS AND METHODS: Thermal analysis tests were performed on 12 implants with the same surface. Twelve implants mounted alone or in pig jaws were laser-irradiated with a 9.3-µm CO2 laser using 3 different power settings. The temperature of the implant body and the proximal tissues was measured with a J-Type Thermocouple after being laser-irradiated with 3 different power setting for 30, 60 seconds, and 2 minutes. Scanning electron microscope (SEM) and digital microscope images were also taken of the all the implants before and after laser irradiation to detect the presence or absence of surface damage. RESULTS: Temperature analysis showed that in all cases the implant and the proximal tissue temperatures remained around the start temperatures of the implant and tissues with fluctuations of ±3°C but never reached the upper threshold of 44°C, the temperature at which thermal injury to bone has been reported. Digital and SEM images that were taken of the implants showed an absence of surface damage at the cutting speed of 20% (0.7 W); however, cutting speeds of 30% to 100% (1.0-4.2 W) did yield surface damage. CONCLUSIONS: Laser irradiation of titanium implant surfaces using a 9.3-µm carbon dioxide laser with an average power of 0.7 W showed no increase in thermal temperature of the implant body and tissue temperatures as well as no evidence of implant surface damage.

Retrospective Evaluation of Factors Related to the Outcomes of Regenerative Therapy for Implants Affected by Peri-implantitis.

The aim of this retrospective study was to examine the histories of 100 patients with 170 implants that were consecutively treated and reported in a previous study to identify which patient and implant factors might have affected the outcomes of therapy. Patient factors included history of periodontitis, hypertension, cardiac problems, rheumatoid arthritis, smoking, and penicillin allergy. Implant factors included whether the prosthesis was cemented or screw retained and initial bone loss (≤ 50% or > 50% of implant length). Frequency of maintenance visits (≤ 3 months or > 3 months) were recorded, as was patient age (≤ 60 years or > 60 years). On the patient level, only postoperative maintenance (≤ 3 months) showed a statistically significant effect on radiographic bone gain (RBG) compared to patients with > 3 months maintenance frequency. Nondiabetic patients showed a trend toward soft tissue gain. On an implant level, screw-retained prostheses demonstrated a statistically significant RBG compared to those with cement-retained prostheses. Significant favorable differences were seen in all outcomes when evaluating presurgical bone level loss (> 50% of the implant length). Further studies with larger groups of patients are necessary to substantiate the findings in this report.

A Regenerative Approach to the Successful Treatment of Peri-implantitis: A Consecutive Series of 170 Implants in 100 Patients with 2- to 10-Year Follow-up.

This article presents the results of a consecutive case series of 170 treated peri-implantitis-affected implants in 100 patients with follow-up measurements from 2 to 10 years. A total of 51 implants in 38 patients previously reported on were followed for an additional 2.5 years, and 119 additional implants in 62 additional patients were treated with the same protocol and monitored for at least 2 years posttreatment. The treatment consisted of flap reflection, surface decontamination, use of enamel matrix derivative (EMD) or platelet-derived growth factor (PDGF), and guided bone regeneration with mineralized freezedried bone and/or anorganic bovine bone combined with PDGF or EMD and covered with an absorbable membrane and/or subepithelial connective tissue graft. Maintenance and monitoring followed every 2 to 3 months. Two implants were lost 6 months posttreatment, for a 98.8% survival rate. Bleeding on probing was eliminated in 91% of the treated implants. Probing depth reduction averaged 5.10 mm, bone level gain averaged 1.77 mm, and soft tissue marginal gain averaged 0.52 mm. These outcomes were obtained with one surgical procedure on 140 implants, with two procedures on 18 implants, and with three procedures on 10 implants. The results to date with this layered/combined regenerative approach for the treatment of peri-implantitis appear to be encouraging.

The use of a xenogeneic collagen matrix at the time of implant placement to increase the volume of buccal soft tissue.

The purpose of this study was to evaluate the efficacy of Mucograft (MG; a porcine-derived purified collagen membrane) to increase the thickness and height of the buccal soft tissue when placed at the time of implant placement in patients with thin or deficient keratinized tissue (KT). The primary endpoint of the study was the change in thickness and height of the buccal KT. Secondary endpoints included stability of the midbuccal soft tissue level; clinician rating of color, texture, and contour of treatment site; probing pocket depths (PPDs); assessment of satisfaction outcome; and patient assessment of pain/discomfort. Thirty-two patients were enrolled and 31 patients completed the study. There were no statistically significant (SS) differences between the MG and control groups for height measures. There was no SS difference for KT thickness (P = .117) between the groups at the final measurement (3 months postsurgery). However, there was an SS difference (P = .009) in favor of the MG group when comparing the difference in presurgical KT thickness to that 3 months postsurgery. Thus, MG was successful (compared to the control) in increasing the buccal KT. There were no SS differences between the groups for any of the other endpoints, including color, texture, contour, and pain assessment at any visit or successful outcome between the treatment group and the control. More cases and longer follow-up of implants placed with MG are needed to verify the results of this randomized prospective study.

Radiographic comparison of different concentrations of recombinant human bone morphogenetic protein with allogenic bone compared with the use of 100% mineralized cancellous bone allograft in maxillary sinus grafting.

The purpose of this study was to radiographically evaluate, then analyze, bone height, volume, and density with reference to percentage of vital bone after maxillary sinuses were grafted using two different doses of recombinant human bone morphogenetic protein 2/acellular collagen sponge (rhBMP-2/ACS) combined with mineralized cancellous bone allograft (MCBA) and a control sinus grafted with MCBA only. A total of 18 patients (36 sinuses) were used for analysis of height and volume measurements, having two of three graft combinations (one in each sinus): (1) control, MCBA only; (2) test 1, MCBA + 5.6 mL of rhBMP-2/ACS (containing 8.4 mg of rhBMP-2); and (3) test 2, MCBA + 2.8 mL of rhBMP-2/ACS (containing 4.2 mg of rhBMP-2). The study was completed with 16 patients who also had bilateral cores removed 6 to 9 months following sinus augmentation. A computer software system was used to evaluate 36 computed tomography scans. Two time points where selected for measurements of height: The results indicated that height of the grafted sinus was significantly greater in the treatment groups compared with the control. However, by the second time point, there were no statistically significant differences. Three weeks post-surgery bone volume measurements showed similar statistically significant differences between test and controls. However, prior to core removal, test group 1 with the greater dose of rhBMP-2 showed a statistically significant greater increase compared with test group 2 and the control. There was no statistically significant difference between the latter two groups. All three groups had similar volume and shrinkage. Density measurements varied from the above results, with the control showing statistically significant greater density at both time points. By contrast, the density increase over time in both rhBMP groups was similar and statistically higher than in the control group. There were strong associations between height and volume in all groups and between volume and new vital bone only in the control group. There were no statistically significant relationships observed between height and bone density or between volume and bone density for any parameter measured. More cases and monitoring of the future survival of implants placed in these augmented sinuses are needed to verify these results.

Histomorphometric comparison of different concentrations of recombinant human bone morphogenetic protein with allogeneic bone compared to the use of 100% mineralized cancellous bone allograft in maxillary sinus grafting.

The purpose of this study was to histomorphometrically evaluate the percentage of vital bone after grafting of maxillary sinuses using two different concentrations of recombinant human bone morphogenetic protein/acellular collagen sponge (rhBMP-2/ACS) combined with mineralized cancellous bone allograft (MCBA) and to compare the results to a control sinus grafted with MCBA only. Thirty-six sinuses in 18 patients had two of three of the graft combinations including: (1) control, MCBA only; (2) test one, MCBA + 5.6 mL of rhBMP-2/ACS (containing 8.4 mg of rhBMP-2); or (3) test two, MCBA + 2.8 mL of rhBMP-2/ACS (containing 4.2 mg of rhBMP-2). Histologic cores were taken 6 to 9 month following sinus augmentation. The results showed no statistically significant differences in vital bone between the two test groups compared to the control sinus group treated with MCBA alone. Future studies involving more cases and evaluating survival of implants placed in these augmented sinuses are needed to verify the results of this randomized prospective study.

A histomorphometric comparison of Bio-Oss alone versus Bio-Oss and platelet-derived growth factor for sinus augmentation: a postsurgical assessment.

The purpose of this study was to assess vital bone formation at 4 to 5 months and 7 to 9 months following sinus augmentation with anorganic bovine bone matrix (ABBM) with and without recombinant human platelet-derived growth factor (rhPDGF). Twenty-four subjects received bilateral sinus elevation surgery with ABBM on one side and ABBM and rhPDGF on the contralateral side. Twelve patients had core sampling at 4 to 5 months and 12 patients at 7 to 9 months postoperatively. In subjects with cores taken at 4 to 5 months, mean vital bone, connective tissue, and residual graft were 11.8%, 54.1%, and 33.6%, respectively, with ABBM alone. Cores of sinuses filled with ABBM and rhPDGF showed mean 21.1% vital bone, 51.4% connective tissue, and 24.8% residual graft. Paired t test showed a statistically significant difference in vital bone. In cores taken at 7 to 9 months, the values for ABBM alone and ABBM + rhPDGF were 21.4% vs 19.5% vital bone, 28.4% vs 44.2% connective tissue, and 40.3% residual graft vs 35.5%. There was no statistically significant difference in vital bone at 7 to 9 months after surgery. Test and control groups showed clinically acceptable levels of vital bone both at 4 to 5 months and 7 to 9 months postsurgery. However, vital bone formation was significantly greater in the 4- to 5-month sections of ABBM + rhPDGF vs the Bio-Oss alone. In the 7- to 9-month specimens, this difference disappeared. More rapid formation of vital bone with the addition of rhPDGF may allow for earlier implant placement.

Successful management of peri-implantitis with a regenerative approach: a consecutive series of 51 treated implants with 3- to 7.5-year follow-up.

The results of a case series of 51 consecutively treated, peri-implantitis-affected implants in 38 patients with follow-up measurements from 3 to 7.5 years are presented. Each implant displayed bleeding on probing, probing depths ≥ 6 mm, and bone loss ≥ 4 mm prior to surgery. A successful regenerative approach including surface decontamination, use of enamel matrix derivative, a combination of platelet-derived growth factor with anorganic bovine bone or mineralized freeze-dried bone, and coverage with a collagen membrane or a subepithelial connective tissue graft was employed in all cases. Patients were divided into two groups. Group 1 included patients in which the greatest defect depth was visible on radiographs; group 2 included patients in which the greatest loss of bone was on the facial or oral aspect of the implant. Bone level changes in patients in group 2 were determined by probe sounding under local anesthesia. Probing depth reductions at 3 to 7.5 years of follow-up were 5.4 and 5.1 mm in groups 1 and 2, respectively. Concomitant bone level gain was 3.75 mm in group 1 and 3.0 mm in group 2. No implant in either group lost bone throughout the duration of the study. The results to date with this regenerative approach for the treatment of peri-implantitis appear to be encouraging.

The use of phentolamine mesylate to evaluate mandibular nerve damage following implant placement.

High success rates and long-term predictability of implant therapy have been well documented in the literature. However, complications in implant treatment can arise and include sensory disturbances, especially in the posterior mandible in areas close to the inferior alveolar nerve. Treatment efficacy of sensory disturbances caused by implant placement in this area relies on the expeditious diagnosis of an induced paresthesia. Recently, phentolamine mesylate has been introduced as a reversal agent of local anesthesia with the ability to decrease the requisite time for a patient to return to normal sensation. This article introduces a method for faster detection of a potential paresthesia induced by implant placement in the posterior mandible.

Trophic effects of platelets on cultured endothelial cells are mediated by platelet-associated fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF).

In addition to their role in primary hemostasis, platelets serve to support and maintain the vascular endothelium. Platelets contain numerous growth factors including the potent angiogenic inducers VEGF and FGF-2. To characterize the function of these two platelet-associated growth factors, the effects of the addition of purified platelets to cultured endothelial cells were examined. The survival and proliferation of endothelial cells were markedly stimulated (2-3-fold and 5-15-fold respectively) by the addition of gel-filtered platelets. Acetylsalicylic acid-treated or lyophilized fixed-platelets were ineffective in supporting endothelial cell proliferation. In Transwell assays, the stimulatory effect of platelets on endothelial cells was preserved, consistent with an effect mediated by secreted factors. The combined inhibition of VEGF and FGF-2 by neutralizing antibodies, in contrast to inhibition of either alone, abrogated both platelet-induced endothelial cell survival and proliferation. FGF-2 isoforms were detected in platelet lysates, as well as in the releases of agonist-stimulated platelets. Megakaryocytes generated by ex vivo expansion of hematopoietic progenitor cells with kit ligand and thrombopoietin were analyzed for expression of FGF-2. Punctate cytoplasmic staining but no nuclear staining was observed by immunocytochemistry consistent with possible localization of the growth factor to cytoplasmic granules. The addition of platelets to cultured endothelial cells activated extracellular signal-regulated kinase (ERK) in a dose and time-dependent manner. This effect was abrogated by both anti-FGF-2 and anti-VEGF antibody. Since FGF-2 and VEGF are potent angiogenic factors and known endothelial cell survival factors, their release by platelets provides a plausible mechanism for the platelet support of vascular endothelium.