José Luis Calvo Guirado

Comparison of three hydroxyapatite/β‐tricalcium phosphate/collagen ceramic scaffolds: An in vivo study

Calcium-phosphate ceramics, which have a composition similar to bone mineral, represent a potentially interesting synthetic bone graft substitute. In the present study, three porous hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP)/collagen ceramic scaffolds were developed, characterized, and tested for their bone repairing capacity and osteoinductive potential in a New Zealand Rabbit model. The ratio of the ceramic components HA/-TCP/collagen varied from 40/30/30 to 50/20/30 and 60/20/20 (in wt %), respectively. None of the ceramic scaffolds succeeded in completely bridging the 6 mm calvarian defect with new bone after 60 days implantation. 60/20/20 ceramic scaffolds showed significantly more bone formation in the pores and in the periphery of the graft than the other two materials. Histomorphometric analysis revealed that the 40/30/30 scaffold produced best bone-to-implant contact (67.23 ± 0.34% with higher quality, closer contact) in comparison with 50/20/30 (54.87 ± 0.32%), and 60/20/20 (48.53 ± 0.31%). Both physicochemical and structural properties of the ceramic composites affected their in vivo behavior, either dependently or independently, emphasizing the importance of assessing bone repair parameters individually. The scaffolds may offer clinical applications in reconstructive surgery for treating bone pathologies.

Implants Placed in the Nasopalatine Canal to Rehabilitate Severely Atrophic Maxillae: A Retrospective Study With Long Follow-up

To assess the survival rate of implants placed in the nasopalatine canal for the rehabilitation of patients with atrophic maxillae and the level of satisfaction of these patients. A retrospective study was performed between 2000 and 2009 of patients with severe atrophy of edentulous maxillae (Cawood and Howells class V) rehabilitated with implant-supported prostheses with 1 implant placed in the nasopalatine canal. A preoperative computed tomography scan was obtained of all patients and all surgeries were performed by the same surgeon. The following parameters were assessed: neurosensory status of the anterior palate (using the pointed/blunt discrimination method); implant success rate according to criteria described by Albrektsson et al; patient satisfaction with the prosthetic treatment (using visual analogue scales). Thirteen patients with a mean age of 54.8 years were treated, 5 men and 8 women. Seventy-eight implants were placed: 13 in the nasopalatine canal, 6 in the zygomatic bone, 12 in the pterygomaxillary region, 2 in the frontomaxillary buttress and 45 in other locations. Six patients reported a slight decrease in sensitivity in the anterior palate after surgery, which disappeared in all cases within a few weeks. Two early failures (before prosthetic loading) and no late failures (after prosthetic loading) of nasopalatine implants were recorded, yielding a success rate for these implants of 84.6% after a mean follow-up of 70 months (range 24 to 132 months. High patient satisfaction with the prosthetic restoration was generally achieved in terms of comfort, stability, function, esthetics, and ease of cleaning. Residual bone is associated with the nasopalatine canal, even in patients with severe maxillary atrophy. This canal may be considered a possible location for an anterior implant when rehabilitating atrophic patients using implant-supported prostheses.

Peri‐implant tissue reactions to immediate nonocclusal loaded implants with different collar design: an experimental study in dogs

PURPOSE The aim of this study was to evaluate bone remodelling and soft tissue reactions around immediate nonocclusal loaded implants with different collar configuration in beagle dogs. MATERIAL AND METHODS The mandibular bilateral second, third and fourth premolars of six beagle dogs were extracted. After 3 months of healing, four implants were placed in the mandibles of each dog. Randomly, two implants with a 1.5 mm polished surface collar (TSA, control group) and two implants with a 0.7 mm polished surface collar and 2.5 mm microthreaded area (TSAA, test group) were inserted. Both groups were treated with a minimal mucoperiosteal flap elevation approach. Impressions were taken and two single screw-retained restorations were inserted in each hemi-mandible 2 days after the implant placement. The animals were sacrificed at 1, 2 and 3 months (two specimens each), and biopsies were obtained. Samples were processed for ground sectioning. Histomorphometric analysis was carried out to compare buccal and lingual bone height loss and soft tissue behaviour between the two groups. RESULTS Crestal bone resorption was significantly higher in the control group (P > 0.05). The establishment of the biological width showed similar outcomes for both groups. Only the distance from the top of the peri-implant mucosa to the apical portion of the barrier epithelium at lingual aspect was significantly more pronounced in the control group (P > 0.05). CONCLUSIONS The alterations that occurred in the peri-implant tissues were related to the adaptation that occurred after the loading conditions in both groups. The microthread design might have an effect in maintaining the marginal bone loss against loading.

Different configuration of socket shield technique in peri-implant bone preservation: An experimental study in dog mandible

The aim of this study was to evaluate the influence of the residual root and peri implant bone dimensions on the clinical success of the socket shield technique. Thirty-six dental implants were installed in 6 dogs. The clinical crowns of teeth P3, P4 and M1 were beheaded. Afterwards, the roots were worn down 2-3mm in apical direction until they were located at crestal level. Posterior implant beds were prepared in the center of the roots passing by 3mm apically forming 6 groups in accordance to the remaining root thickness. Radiography of the crestal bone level was performed on day 0 and after 12 weeks. Histomorphometric analyses of the specimens were carried out to measure the crestal bone level, the bone to implant contact and the buccal and lingual bone thickness at the implant shoulder portion. Correlations between groups were analyzed through nonparametric Friedman test, statistical significance was set as p<0.05. All 36 implants were osseointegrated, but 3 samples showed a clinical inflammatory reaction and some radicular fragments presented a small resorption process. On the buccal and lingual side, the radicular fragment was attached to the buccal bone plate by a physiologic periodontal ligament. In the areas where there was space between the implant and the fragment, newly formed bone was demonstrated directly on the implant surface. Within the limitations of an animal pilot study, root-T belt technique may be beneficial in preserving and protecting the bundle bone and preservation of soft tissues. If the thickness of the buccal bone is 3mm, and the thickness of the remaining root fragment is 2mm, the socket shield technique is more predictable and the bone contours can be maintained.

Comparison of the Accuracy of Cone Beam Computed Tomography and Medical Computed Tomography: Implications for Clinical Diagnostics with Guided Surgery

PURPOSE This study compared the accuracy of cone beam computed tomography (CBCT) and medical-grade CT in the context of evaluating the diagnostic value and accuracy of fiducial marker localization for reference marker-based guided surgery systems. MATERIALS AND METHODS Cadaver mandibles with attached radiopaque gutta-percha markers, as well as glass balls and composite cylinders of known dimensions, were measured manually with a highly accurate digital caliper. The objects were then scanned using a medical-grade CT scanner (Philips Brilliance 64) and five different CBCT scanners (Sirona Galileos, Morita 3D Accuitomo 80, Vatech PaX-Reve3D, 3M Imtech Iluma, and Planmeca ProMax 3D). The data were then imported into commercially available software, and measurements were made of the scanned markers and objects. CT and CBCT measurements were compared to each other and to the caliper measurements. RESULTS The difference between the CBCT measurements and the caliper measurements was larger than the difference between the CT measurements and the caliper measurements. Measurements of the cadaver mandible and the geometric reference markers were highly accurate with CT. The average absolute errors of the human mandible measurements were 0.03 mm for CT and 0.23 mm for CBCT. The measurement errors of the geometric objects based on CT ranged between 0.00 and 0.12 mm, compared to an error range between 0.00 and 2.17 mm with the CBCT scanners. CONCLUSIONS CT provided the most accurate images in this study, closely followed by one CBCT of the five tested. Although there were differences in the distance measurements of the hard tissue of the human mandible between CT and CBCT, these differences may not be of clinical significance for most diagnostic purposes. The fiducial marker localization error caused by some CBCT scanners may be a problem for guided surgery systems.

Bone healing at bicortically installed implants with different surface configurations. An experimental study in rabbits

OBJECTIVE To study the sequential healing at bicortically installed implants with surface modifications by the use of fluoroboric acid and/or H2 O2 . MATERIAL AND METHODS Twenty-eight albino New Zealand rabbits were used. Two recipient sites were prepared in the tibiae bilaterally, one in the metaphysis and the second in the diaphysis regions. Four implants with different surface characteristics were randomly installed with bicortical stabilization: (i) sandblasted and acid-etched; (ii) same surface as i, but with a substitution of the hydrofluoric acid with fluoroboric acid; (iii) same surface as i, additionally treated with H2 O2 ; and (iv) same surface modified as ii, additionally treated with H2 O2 . The animals were killed after 5, 8, 15, and 30 days. Ground sections were prepared for histological analyses. RESULTS No statistically significant differences in osseointegration were found among various surfaces at any of the healing periods. A higher degree of osseointegration was observed at the implants placed in the metaphysis compared to those placed in the diaphysis, especially during early healing. A higher degree of osseointegration was found at sites with proximity to compact (cortical) bone when compared to the middle portion of the implants, especially in the diaphysis region. CONCLUSIONS Surfaces modified with different acids or H2 O2 resulted in similar osseointegration compared to a standard sandblasted and acid-etched surface. The portion of the bicortically installed implants in close contact with the cortical compartment presented a higher percentage of osseointegration compared with the region in contact with the bone marrow compartment.

Biological width formation to immediate implants placed at different level in relation to the crestal bone: an experimental study in dogs

PURPOSE/AIM Evaluate differences in bone remodeling, soft tissue reactions and biological width formation around immediate implants placed at different level in relation to the crestal bone in beagle dogs. MATERIAL AND METHODS The mandibular second, third and fourth premolars of six beagle dogs were extracted, and three implants were placed in the right side of each dog. Healing abutments were adjusted (n = 18). After 4 weeks, the procedure was repeated on the left side of the mandible (n = 18). Randomly, three implants were placed at crestal level (control group), and three implants were placed 2 mm subcrestally (test group) in relation to the crestal bone in each animal. The dogs were sacrificed after 8 weeks from the first surgical procedure, and biopsies were obtained. Samples were processed for ground sectioning. Histometric analysis was carried out to compare buccal and lingual bone resorption, soft tissue behavior and biological width formation in both groups. RESULTS Crestal bone resorption was higher in the test group when considering the difference of 2 mms (IS-B = 2.05 ± 0.36 mm, control; 1.75 (+2) ± 0.38 mm, test). However, the dimensions of the biological width were similar for both groups (PM-C = 3.34 ± 0.53 mm, control; 3.13 ± 0.55 mm, test). CONCLUSIONS The alterations that occurred in the peri-implant soft tissues may be related to the hard tissue remodeling, showing similar quantitative findings in the biological width formation in both groups. Even though the subcrestal placement might reduce the distance from the implant shoulder to the first bone-to-implant contact and reestablish the biological width dimension in a most coronal position, it might not have any effect on minimizing the marginal bone loss.

Tilted Implants for the Restoration of Posterior Mandibles With Horizontal Atrophy: An Alternative Treatment

PURPOSE Horizontal atrophy in the posterior mandible presents serious limitations on conventional implant placement. The purpose of this study was to evaluate the use of tilted implants angled in a buccolingual direction for restoring atrophic posterior mandibular sectors. MATERIALS AND METHODS A cohort study was performed of 25 patients who had partial prostheses supported by more than 1 implant (≥ 1 tilted and 1 axial implant) to restore molar areas in the mandible. When the bone thickness was at least 5 mm, axial implants were placed; when the alveolar ridge was narrower, the implant was placed with tilted angulation. The beds for these tilted implants were prepared using a lingual approach, tipping the implant apex toward the vestibule. Twelve months after loading, bone loss was evaluated and the success rates of the tilted and axial implants were calculated. RESULTS The study included 20 women and 5 men (mean age, 54.8 yr) who received 67 implants in the posterior mandibular sectors. Thirty-nine implants were placed with a buccal angulation and 28 implants were placed vertically. Mean bone losses of 0.59 ± 0.26 mm among the tilted implants and 0.48 ± 0.34 mm among the axial implants were observed 1 year after loading. The success rate of the tilted implants was 94.9%, and that of the axial implants was 100%. No significant differences in success rates or in bone loss between the tilted and axial implants were found at 12 months after loading. CONCLUSIONS Twelve months after loading, tilted implants provided good results for the restoration of posterior mandibles with horizontal atrophy and no significant differences in success rates or marginal bone loss between tilted and axial implants were observed.

SEM-EDX Study of the Degradation Process of Two Xenograft Materials Used in Sinus Lift Procedures

Some studies have demonstrated that in vivo degradation processes are influenced by the material’s physico-chemical properties. The present study compares two hydroxyapatites manufactured on an industrial scale, deproteinized at low and high temperatures, and how physico-chemical properties can influence the mineral degradation process of material performance in bone biopsies retrieved six months after maxillary sinus augmentation. Residual biomaterial particles were examined by field scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) to determine the composition and degree of degradation of the bone graft substitute material. According to the EDX analysis, the Ca/P ratio significantly lowered in the residual biomaterial (1.08 ± 0.32) compared to the initial composition (2.22 ± 0.08) for the low-temperature sintered group, which also presented high porosity, low crystallinity, low density, a large surface area, poor stability, and a high resorption rate compared to the high-temperature sintered material. This demonstrates that variations in the physico-chemical properties of bone substitute material clearly influence the degradation process. Further studies are needed to determine whether the resorption of deproteinized bone particles proceeds slowly enough to allow sufficient time for bone maturation to occur.

Misfit of Three Different Implant-Abutment Connections Before and After Cyclic Load Application: An In Vitro Study

PURPOSE This study aimed to evaluate the misfit of three different implant-abutment connections before and after cycling load. MATERIALS AND METHODS One hundred twenty dental implants and correspondent prefabricated titanium abutments were used. Three different implant-abutment connections were evaluated: Morse taper (MT group), external hexagon (EH group), and internal hexagon (IH group). Forty implants and 40 abutments were used per group. The parameters for the mechanical evaluation were set as: 360,000 cycles, load of 150 N, and frequency of 4 Hz. Samples were sectioned in their longitudinal and transversal axes, and the misfit of the implant-abutment connection was evaluated by scanning electron microscopy analysis. One-way analyses of variance, Tukey post hoc analyses (α = .05), and t test (P < .05) were used to determine differences between groups. RESULTS At the longitudinal direction, all the groups showed the presence of microgaps before cycling load; after cycling load, microgaps were reduced in all groups (P > .05). Transversally, only the MT group showed full fitting after cycling load compared with the other groups (EH and IH) (P < .0001). CONCLUSION The application of cycling load produces an accommodation of the implant-abutment connection in internal, external, and Morse taper connections. In the longitudinal direction, the accommodation decreases and/or eliminates the gap observed initially (before load). In the horizontal direction, Morse cone implant-abutment connections experience a complete accommodation with the elimination of the gap.