Isabel Tresguerres

Actions of melatonin mixed with collagenized porcine bone versus porcine bone only on osteointegration of dental implants

Abstract:  This study evaluated the effect of the topical application of melatonin mixed with collagenized porcine bone on the osteointegration on the rough discrete calcium deposit (DCD) surface implants in Beagle dogs 3 months after their insertion. In preparation for subsequent insertion of dental implants, lower molars were extracted from 12 Beagle dogs. Each mandible received two parallel wall expanded platform implants with a DCD surface of 4 mm in diameter and 10 mm in length. The implants were randomly assigned to the distal sites on each mandible in the molar area and the gaps were filled with 5 mg lyophilized powdered melatonin and porcine bone and collagenized porcine bone alone. Ten histological sections per implant were obtained for histomorphometric studies. After a 4‐wk treatment period, melatonin plus porcine bone significantly increased the perimeter of bone that was in direct contact with the treated implants (P < 0.0001), bone density (P < 0.0001), and new bone formation (P < 0.0001) in comparison with porcine bone alone around the implants. Melatonin plus collagenized porcine bone on DCD surface may act as a biomimetic agent in the placement of endo‐osseous dental implants and enhance the osteointegration. Melatonin combined with porcine bone on DCD implants reveals more bone in implant contact at 12 wk (84.5 ± 1.5%) compared with porcine bone alone treated area (67.17 ± 1.2%).

Effects of Local Melatonin Application on Implant Osseointegration

PURPOSE The aim of this study was to assess the effect of local melatonin administration on bone osseointegration around implants in rabbit tibiae. MATERIAL AND METHODS Ten female, 6-month-old New Zealand rabbits were randomly divided into two groups: the experimental group, where five rabbits were treated with local application of melatonin (3 mg) to implant sites when placed into the rabbit tibia, and the control group, those who where without additive materials. Four weeks later, animals were sacrificed; tibiae were dissected from soft tissues and fixed in buffered formaldehyde, and then included in methacrylate. Histological sections were performed to be studied under light microscopy and analyzed morphometrically to evaluate the amount of bone to implant contact (BIC), trabecular area density, and cortical area density. One-way analysis of variance test was used for statistical evaluation. p < .05 was considered to be significant. RESULTS Histological evaluation showed more trabecular reaction in the melatonin group. Morphometrical analysis showed a statistically significant increase in trabecular BIC in the melatonin group when compared with the control group (24.61% ± 2.87 vs 13.62% ± 1.44; p < .01). Cortical BIC was decreased in the melatonin group, without statistical significance (71.08 ± 3.63 vs 76.28 ± 2.57; p = 0.31). Trabecular area density was increased significantly in the melatonin group (8.68 ± 1.61 vs 4.02 ± 0.36; p < .05). Cortical area density was decreased significantly in the melatonin group (91.31 ± 1.6 vs 95.7 ± 0.5; p < .05). CONCLUSION Within the limitation of this animal study, local melatonin application at the time of implant placement might induce more trabecular bone at implant contact and higher trabecular area density.

Effect of Solely Applied Platelet-Rich Plasma on Osseous Regeneration Compared to Bio-Oss®: A Morphometric and Densitometric Study on Rabbit Calvaria

BACKGROUND The use of platelet-rich plasma (PRP) in bone augmentation procedures is well documented; however, the exact benefit of this material is not yet established. PURPOSE This study aimed to evaluate the benefits of using PRP, when only used, and compare it to Bio-Oss (Geistlich Biomaterials, Wolhusen, Switzerland) in vertical bone augmentation capacity. MATERIALS AND METHODS The study was performed in calvaria of eight adult female New Zealand rabbits using titanium bone conduction cylinder. Two titanium cylinders were fixed into perforated slits made on the parietal bone of each rabbit. On each rabbit, one chamber was grafted with Bio-Oss, and the contralateral was filled with PRP. Animals were sacrificed 4 weeks after intervention and biopsies were taken. Densitometric, histological, and histomorphometric analyses were performed to evaluate bone mineral density, vertical bone augmentation, and remaining graft volume, respectively. Statistical analyses were performed with Mann-Whitney test, using a significance level of p < .05. RESULTS Densitometric and histomorphometric data analysis revealed that mean bone mineral densities and bone augmentation were significantly lower in the cylinders treated with PRP (p < .0001) 4 weeks after implantation. CONCLUSION This study showed no beneficial effect of using PRP on osseous regeneration. In addition, it was emphasized that Bio-Oss presents good osteoconductive properties by achieving suitable bone volume values.

Monetite granules versus particulate autologous bone in bone regeneration

OBJECTIVE The aim of this study was to test bone tissue response to monetite granules in comparison with intramembranous autologous bone graft in a rabbit calvaria critical size defect model. MATERIALS AND METHODS Novel monetite granules were synthesized by thermal conversion of set brushite cement. Eight female New Zealand rabbits were used for this study. Two identical 10mm diameter bicortical cranial defects were created in each animal. One of the defects was grafted with monetite granules while the contralateral was grafted with granules of intramembranous autologous bone as control. Animals were sacrificed 8 weeks after surgery and biopsies were taken for histological and histomorphometrical evaluation under light microscopy. Wilcoxon test was used for statistical analysis. RESULTS The bone defects treated with either autologous bone or monetite granules were able to heal within the study period. Upon histological observation the defects treated with autologous bone granules resembled the adjacent intact calvaria, whereas the defects treated with monetite showed a high infiltration of new bone and only 13.4±8.4% of remaining granules. The percentage of bone volume in the defects of the control group (71±9%) was 16% higher than in the study group (55±10%) (p<0.05). The percentage of augmented mineralized tissue volume in the study group (68±18%) was not significantly different from the control group (p>0.05). CONCLUSION The amount of augmented mineralized tissue in the bone defects obtained with monetite granules was not significantly different from that obtained with autologous bone. This study confirms the potential of monetite based biomaterials as an alternative to autologous bone graft.

Local Application of Growth Hormone to Enhance Osseointegration in Osteoporotic Bones: A Morphometric and Densitometric Study

PURPOSE The aim of this study was to assess the effect of local application of growth hormone on osseointegration of dental implants inserted in osteoporotic bones. MATERIALS AND METHODS Twenty female New Zealand rabbits were used in this study. Ten were ovariectomized and fed a low-calcium diet for 6 weeks, and the others remained intact. A titanium implant was inserted into each tibia, in both groups. In half of the rabbits, 2 IU of growth hormone was placed into the ostectomy prior to the implant insertion. Two weeks after implant surgery, all animals were sacrificed. Tibiae were dissected from soft tissues, and included in methacrylate to be studied under light microscopy. Bone-to-implant contact (BIC) and bone mineral density (BMD) were measured by morphometric and densitometric analysis, respectively. Multifactorial analysis of variance (ANOVA) was used for statistical evaluation. P < .05 was considered to be significant. RESULTS Ovariectomy induced less BIC and BMD in regions closer to the implant compared with the control group. Local application of growth hormone was able to increase the BIC in the ovariectomized group, with statistically significant differences with respect to the control group (P < .01). Regarding the BMD, no statistically significant differences were found. CONCLUSION Within the limitations of this experimental study, local application of 2 IU of recombinant human growth hormone at the moment of titanium implant insertion in rabbit tibiae significantly enhanced the BIC around titanium implants 15 days after the implantation in this experimental osteoporotic animal model, without affecting the BMD.