Jesús Torres

Craniofacial vertical bone augmentation: a comparison between 3D printed monolithic monetite blocks and autologous onlay grafts in the rabbit.

Onlay autografting is amongst the most predictable techniques for craniofacial vertical bone augmentation, however, complications related to donor site surgery are common and synthetic alternatives to onlay autografts are desirable. Recent studies have shown that the acidic calcium phosphates, brushite and monetite, are osteoconductive, osteoinductive and resorb faster in vivo than hydroxyapatite. Moreover, they can be 3D printed allowing precise host bone-implant conformation. The objectives of this study were to confirm that craniofacial screw fixation of 3D printed monetite blocks was possible and to compare the resulting vertical bone augmentation with autograft. 3D printed monolithic monetite onlay implants were fixed with osteosynthesis screws on the calvarial bone surface of New Zealand rabbits. After 8 weeks, integration between the implant and the calvarial bone surface was observed in all cases. Histomorphometry revealed that 42% of the monetite was resorbed and that the new bone formed within the implant occupied 43% of its volume, sufficient for immediate dental implant placement. Bone tissue within the autologous onlay occupied 60% of the volume. We observed that patterns of regeneration within the implants differed throughout the material and propose that this was due to the anatomy and blood supply pattern in the region. Rapid prototyped monetite being resorbable osteoconductive and osteoinductive would appear to be a promising biomaterial for many bone regeneration strategies.

Resorption of monetite granules in alveolar bone defects in human patients

Bone grafting is often required to restore mandibular or maxillary bone volume prior to prosthetic tooth root implantation. Preclinical animal models are often used to study the in vivo properties of new bone graft products designed for human use. Although animal studies may offer valuable data regarding bioperformance, materials do not necessarily perform the same in human patients. In this study we implanted bovine hydroxyapatite (BH), a widely used porous apatite granule, and dicalcium phosphate anhydrous (monetite) granules, bilaterally in human patients post extraction alveolar sockets. After six months, histomorphometrical analysis of the biopsies revealed that the amount of bone regenerated with monetite (59.5 +/- 13%) was significantly higher than that obtained with BH (33.1% +/- 4.9), while the amount of unresorbed graft was higher in the sockets treated with BH (37.8 +/- 6.1) than in those implanted with monetite (25.8 +/- 14.3). Resorption of calcium phosphate ceramics is discussed by applying the Hixon-Crowell dissolution model.

Effect of platelet-rich plasma on sinus lifting: a randomized-controlled clinical trial.

OBJECTIVE The combination of anorganic bovine bone (ABB) with platelet-rich plasma (PRP) has been widely used in bone regeneration procedures although its benefits are still unclear. The purpose of this study was to evaluate whether or not PRP improves the efficacy of ABB in sinus floor augmentation. In addition, we have investigated the effect of residual bone height and tobacco on implant survival in sinus augmentation procedures. PATIENT AND METHODS Eighty-seven patients recruited for this study underwent 144 sinus floor augmentation procedures using ABB alone or ABB plus PRP (ABB+PRP) in a randomized clinical trial. A total of 286 implants were placed in the augmented bone, and their evolution was followed up for a period of 24 months. In order to investigate on a histological level and any adjunctive effects, we performed an ancillary study in five edentulous patients with a symmetrical severely resorbed maxilla. In these patients, a bilateral sinus augmentation was randomly performed using ABB or ABB+PRP in a split-mouth design, and after 6 months, bone biopsies were taken from the implant sites for histological and histomorphometric analysis. RESULTS Overall, 96.2% of ABB and 98.6% of ABB+PRP implant success were obtained during the monitoring period and differences were not found between sites grafted with and without PRP in the 87 patients studied. Densitometry assessments and graft resorption were similar in both experimental groups. However, the histological and histomorphometrical analysis in the five edentulous patients revealed that bone augmentation was significantly higher in sites treated with ABB+PRP (p <or= 0.05). Another outcome from our study is that the lack of initial bone support (p <or= 0.05) and smoking (p=0.05) appeared to have a negative effect on the treatment success, which was accentuated when both circumstances coincided. CONCLUSIONS PRP is not a determining factor for implant survival in sinus lifting procedures. However, this study revealed that PRP can improve the osteoconductive properties of ABB by increasing the volume of new bone formed. Moreover, in sinus augmentation procedures the implants survival rate appears to be more influenced by the residual bone height or by tobacco than by the type of bone graft.

Bone regeneration in rabbit calvaria with novel monetite granules

The aim of this study was to evaluate whether local application of monetite granules would induce bone regeneration in critical size defects on rabbits calvaria. Novel monetite granules were synthesized by thermal conversion of preset brushite cement. Twelve female New Zealand rabbits were used for this study. Two identical 10-mm-diameter bicortical cranial defects were created in each animal. One of the defects was grafted with monetite granules while the contralateral was left unfilled as negative control. Animals were sacrificed at 4 and 8 weeks after surgery, and biopsies were taken for histological and histomorphometrical evaluation under light microscopy. Wilcoxon test was used for statistical analysis. The histological observations showed signs of graft resorption as newly formed bone tissue grew surrounding and penetrating the monetite granules. Histomorphometric evaluation showed that the augmented bone volume as well as the augmented mineral tissue was higher in the defects treated with monetite granules (p < 0.05) 8 weeks after the intervention. In this animal model, local application of the novel monetite granules in bone defects enhances bone healing significantly.

Minimally invasive maxillofacial vertical bone augmentation using brushite based cements

An ideal material for maxillofacial vertical bone augmentation procedures should not only be osteoconductive, biocompatible and mechanically strong, but should also be applied using minimally invasive procedures and remain stable with respect to the original bone surfaces. This way, implant exposure and infection might be reduced and good mechanical stability may be achieved. Calcium phosphate cements are proven biocompatible and osteoconductive materials that can be injected using minimally invasive procedures. Among these cements, brushite based cements have the added advantage of being biodegradable in vivo. Therefore, this material has the potential for use in the aforementioned procedures. An in vivo study was performed in rabbits to evaluate the potential use of brushite cements in minimally invasive maxillofacial vertical bone augmentation procedures. In this study, we injected self-setting brushite cements on the subperiosteal bone surface using a minimally invasive tunnelling technique. The cement pastes were stable on the bone surface and hardened soon after they were injected thereby negating the need for additional supports such as membranes or meshes. The animals were sacrificed 8 weeks after the intervention and histological observations revealed signs of successful vertical bone augmentation. Therefore, we have demonstrated a minimally invasive vertical bone augmentation procedure that is an attractive alternative to current surgical procedures in terms of increased simplicity, reduced trauma, and lower cost of surgery.

Platelet-rich plasma may prevent titanium-mesh exposure in alveolar ridge augmentation with anorganic bovine bone

OBJECTIVE Bone augmentation with the titanium-mesh (Ti-mesh) technique is susceptible to a large rate of complications such as morbidity of bone graft donor site, and mesh exposure to the oral cavity. The purpose of this study was to evaluate the effectiveness of anorganic bovine bone (ABB) in alveolar bone augmentation with the Ti-mesh technique. In addition, we investigated the effect of platelet-rich plasma (PRP) in preventing mesh exposure by using it to cover the Ti-mesh. PATIENTS AND METHODS Patients included in the clinical trial were randomly allocated by a blinded assistant into two groups. The 30 patients recruited for this study underwent 43 alveolar bone augmentation with the Ti-mesh technique using ABB as graft material in all of them. In 15 patients, the Ti-meshes were covered with PRP (PRP group) whereas in the other 15 the Ti-meshes were not (control group). After 6 months, patients were called for clinical, radiographic, and histological evaluation, and implant placement surgery. A total of 97 implants were placed in the augmented bone and their evolution was followed up for a period of 24 months. RESULTS Significant differences were found between the two study groups in terms of complications and bone formation. In the control group, 28.5% of the cases suffered from mesh exposure, while in the PRP group, no exposures were registered. Radiographic analysis revealed that bone augmentation was higher in the PRP group than in the control group. Overall, 97.3% of implants placed in the control group and 100% of those placed in the PRP group were successful during the monitoring period. We suggest that the positive effect of PRP on the Ti-mesh technique is due to its capacity to improve soft tissue healing, thereby protecting the mesh and graft material secured beneath the gingival tissues. CONCLUSIONS Alveolar bone augmentation using ABB alone in the Ti-mesh technique is sufficient for implant rehabilitation. Besides, covering the Ti-meshes with PRP was a determining factor in avoiding mesh exposure. Ti-mesh exposure provoked significant bone loss, but in most cases it did not affect the subsequent placement of implants.

Effect of silica gel on the cohesion, properties and biological performance of brushite cement

The cohesion of calcium phosphate cements can be improved by the addition of substances to either the solid or liquid phase during the setting reaction. This study reports the effect of silica gel on brushite cement cohesion. The cement was prepared using a mixture of beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate as the solid phase, while the liquid phase comprised carboxylic acids silica gel. This cement presents a shorter final setting time (FST), better cohesion and higher amount of unreacted beta-TCP than the cement prepared without silica gel. Furthermore, in vivo experiments using rabbits as an animal model showed that after 8 weeks of implantation cements modified with silica gel showed a similar new bone formation volume and more remaining graft in comparison with unmodified cements. Thus, the silica gel could be efficiently applied to reduce cement disintegration and to decrease the resorption rate of brushite cements.

The effect of hyaluronic acid on brushite cement cohesion

The improvement of calcium phosphate cement (CPC) cohesion is essential for its application in highly blood perfused regions. This study reports the effectiveness of hyaluronic acids of different molecular weights in the enhancement of brushite cement cohesion. The cement was prepared using a powder phase composed of a mixture of beta-tricalcium phosphate and monocalcium phosphate monohydrate, whereas the liquid phase was formed by 0.5M citric acid solution modified by the addition of hyaluronic acid of different molecular weights. It was found that medium and high molecular weight hyaluronic acid enhances the cement cohesion and scarcely affects the cement mechanical properties. However, concentrations >0.5% (w/v) were less efficient to prevent the cement disintegration. It is concluded that hyaluronic acid could be applied efficiently to reduce brushite cement disintegration.

The role of enamel crystallography on tooth shade.

OBJECTIVES Tooth shade is influenced by a combination of extrinsic-stains that are adsorbed to the enamel surface and by its intrinsic-shade resulting from the interaction of light with tooth structures. This study was designed to investigate how the variations in enamel ultrastructure may affect tooth optical properties. METHODS One-hundred extracted teeth were collected from adult patients attending McGill-Undergraduate Dental Clinics. Shade-spectrophotometry, FTIR and XRD were used to assess tooth shade, enamel chemical composition and crystallography. The data obtained was analysed for Pearson correlation analysis and multiple linear regression analysis. The statistical significance was set at P < 0.05. RESULTS Tooth shade parameters varied dramatically within the studied population. Pearson correlation analysis demonstrated that tooth hue was associated with enamel hydroxyapatite (HA) crystal size (R = -0.358; B = -0.866; P = 0.007), tooth chroma was associated with enamel HA carbonization (R = -0.419; B = -99.06; P = 0.005), and tooth lightness was associated with both enamel HA crystal size (R = -0.313; B = -1.052; P = 0.019) and the degree of HA carbonization (R = -0.265; B=-57.95; P = 0.033). Multiple linear regression analysis demonstrated that the size of enamel HA crystals and the relative content of mineral carbonate were the most important predictors for tooth shade lightness (P = 0.018) and chroma (P=0.008), respectively. In contrast, enamel organic content had no correlation with tooth shade. CONCLUSIONS In the present study we have revealed that the tooth shade is regulated by the size of their HA enamel crystals. On the other hand, variation in the degree of enamel HA carbonization can also affect the tooth shade. These findings are of great relevance in dentistry since it provides better understanding of tooth aesthetics.

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.