Sheep Mandibles Research Articles

The utilization of a commercial gloss spray in stabilization of incinerated dental structures

PurposeIncinerated human remains may require dental comparison to establish identity. The remains are often fragile and minor forces can damage teeth and facial bones, disrupting anatomical relationships, and impairing the ability to compare with antemortem records. This study evaluated the ability of a commercially available gloss spray to stabilize teeth in incinerated remains. MethodsLower anterior teeth of scavenged sheep mandibles were incinerated in a furnace at a temperature of 500 °C for 35 min. Before a series of vibration tests, the left side of each sample was treated with the spray, with the right side acting as a control. ResultsSignificant retention of dental data was achieved utilizing the spray in comparison to the non-stabilized sides. ConclusionThis study showed that a commercial clear gloss spray did not affect the ability to document or perform radiographic assessment of restorations, and statistically improved the stability and anatomical relationships of incinerated dental remains in scavenged sheep mandibles. Commercial products, such as the one tested in this study, are readily available and could be deployed at a mass disaster situation. However, the spray should not be used if there is any suspicion that accelerants might be involved at the scene.

Use of a non-volatile agent to stabilize severely incinerated dental remains.

The aim of this study was to identify volatile-free products that would be suitable for stabilizing incinerated dental remains at the scene of an incident, and that would not compromise any postmortem examination. The anterior mandibles of sheep were incinerated, sprayed unilaterally with stabilizing agents, vibrated for 30s, and assessed. The effect of the stabilizing solutions on radiographic examination was also recorded. Tests for volatility and the effect on human mandibles were also conducted. A flour/water mixture of one part flour to two parts water, and a paste mixture of one part Clag™ glue to one part water both produced significant stabilization results. The flour mixture left an opaque layer on the samples that it was applied to, which still allowed dental examination, but the glue paste mixture resulted in a clearer layer. Both solutions allowed radiographic examination and were free of volatiles. Diluted Clag™ paste, when sprayed on to incinerated remains, assists in their stabilization for transportation. When Clag™ paste is unavailable a mixture of two parts water to one part plain flour could be utilized for stabilization.

Anodisation Increases Integration of Unloaded Titanium Implants in Sheep Mandible.

Spark discharge anodic oxidation forms porous TiO2 films on titanium implant surfaces. This increases surface roughness and concentration of calcium and phosphate ions and may enhance early osseointegration. To test this, forty 3.75 mm × 13 mm titanium implants (Megagen, Korea) were placed into healed mandibular postextraction ridges of 10 sheep. There were 10 implants per group: RBM surface (control), RBM + anodised, RBM + anodised + fluoride, and titanium alloy + anodised surface. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) at surgery and at sacrifice after 1-month unloaded healing. Mean bone-implant contact (% BIC) was measured in undemineralised ground sections for the best three consecutive threads. One of 40 implants showed evidence of failure. RFA differed between groups at surgery but not after 1 month. RFA values increased nonsignificantly for all implants after 1 month, except for controls. There was a marked difference in BIC after 1-month healing, with higher values for alloy implants, followed by anodised + fluoride and anodised implants. Anodisation increased early osseointegration of rough-surfaced implants by 50–80%. RFA testing lacked sufficient resolution to detect this improvement. Whether this gain in early bone-implant contact is clinically significant is the subject of future experiments.

Morphometric Analysis of the Mandible of Tuj and Morkaraman Sheep

In the present study, it was aimed to determine morphometric differences of the mandible of Tuj and Morkaraman sheep having widespread breeding area in the Eastern Anatolia Region. In this study, 20 mandibles of the male Tuj and Morkara- man sheep were used. The 16- lenghts taken to the mandible were measured by electronic digital calliper. Furthermore, after the mandible were photographed and printed to milimetric paper, the 4-angles studied were measured with gonimeter. The results of this study proved that the means of the length and angle measurements obtained from Morkaraman sheep were mostly higher than Tuj sheep. The angle of margo ventralis mandibulae (A4) and the mandible height at the level of the rear alveolar edge with 3rd molar tooth (L14) had a significant statistical difference (p<0.05). According to the correlation values, it was seen that A2 values (the angle between the proc. condylaris and ramus mandibulae) of the both sheep breeds were in negative relation with the other mandible measurements. As a result, the obtained data indicate that genetic doesn't significantly affect the morphometry of the mandible of the Morkaraman and Tuj sheeps.

Effect of 50 to 60°C heating on osseointegration of dental implants in dense bone: an in vivo histological study.

To evaluate, in vivo, the effects of bone temperatures increased up to 60°C introduced before implant insertion on titanium implant osseointegration. Twenty-four acid etched and sandblasted implants (Cortex Dental Implants) were inserted in the inferior edge of sheep mandibles. Osteotomic sites were randomly divided into 3 groups before inserting the implant. In test 1 group and in test 2 group, implant sites were overheated, respectively, up to 50°C for 1 minute and 60°C for 1 minute, with an electronic controlled probe of 3 mm in diameter and 10 mm in length. Osteotomic sites in control group were not overheated. Implants were inserted according to standard procedures. After 2 months healing, % bone implant contact (%BIC) and infrabony pockets' depth were measured. Unpaired t test was applied to find statistical differences between groups. No implant failure occurred. No statistical significant difference in %BIC was found among groups. Histological analysis showed that mean infrabony pockets were statistically deeper in 60°C group than in other groups. Bone temperature up to 60°C for 1 minute does not seem to significantly impair titanium dental implant osseointegration. Bone damage signs evident in the 60°C group suggest that careful drilling procedure with sufficient irrigation is necessary to avoid periimplant infrabony pockets' formation. More in vivo evaluations are needed to identify what is the value of bone temperature increase for irreversible inhibition of implant osseointegration.

The impact of a modified cutting flute implant design on osseointegration

Information concerning the effects of the implant cutting flute design on initial stability and its influence on osseointegration in vivo is limited. This study evaluated the early effects of implants with a specific cutting flute design placed in the sheep mandible. Forty-eight dental implants with two different macro-geometries (24 with a specific cutting flute design – Blossom group; 24 with a self-tapping design – DT group) were inserted into the mandibular bodies of six sheep; the maximum insertion torque was recorded. Samples were retrieved and processed for histomorphometric analysis after 3 and 6 weeks. The mean insertion torque was lower for Blossom implants (P<0.001). No differences in histomorphometric results were observed between the groups. At 3 weeks, P=0.58 for bone-to-implant contact (BIC) and P=0.52 for bone area fraction occupied (BAFO); at 6 weeks, P=0.55 for BIC and P=0.45 for BAFO. While no histomorphometric differences were observed, ground sections showed different healing patterns between the implants, with better peri-implant bone organization around those with the specific cutting flute design (Blossom group). Implants with the modified cutting flute design had a significantly reduced insertion torque compared to the DT implants with a traditional cutting thread, and resulted in a different healing pattern.

Accuracy of linear measurement using cone-beam computed tomography at different reconstruction angles

PurposeThis study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT).Materials and MethodsForty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., 0°), +10°, +12°, -12°, and -10° with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant.ResultsThe differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of -12°, -0.66 to -0.11 at -10°, -0.51 to +0.19 at 0°, -0.64 to +0.08 at +10°, and -0.64 to +0.1 at +12°. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9.ConclusionChanging the slice orientation in the range of -12° to +12° reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.

Insufficient irrigation induces peri‐implant bone resorption: an in vivo histologic analysis in sheep

To measure in vivo impact of dense bone overheating on implant osseointegration and peri-implant bone resorption comparing different bur irrigation methods vs. no irrigation. Twenty TI-bone implants were inserted in the inferior edge of mandibles of sheep. Different cooling procedures were used in each group: no irrigation (group A), only internal bur irrigation (group B), both internal and external irrigation (group C), and external irrigation (group D). The histomorphometric parameters calculated for each implant were as follows: %cortical bone-implant contact (%CBIC) and %cortical bone volume (%CBV). Friedman's test was applied to test the statistical differences. In group A, we found a huge resorption of cortical bone with %CBIC and %CBV values extremely low. Groups B and C showed mean %CBIC and %BV values higher than other groups The mean %CBV value was significantly different when comparing group B and group C vs. group A (P < 0.05). Significant differences in %CBIC were found also between group C and group A (P < 0.05). Thermal injury, due to insufficient irrigation, of hard bone caused massive resorption of the cortical bone and implant failure. Drilling procedures on hard bone need an adequate cooling supply because the bone matrix overheating may induce complete resorption of dense bone around implants. Internal-external irrigation and only internal irrigation showed to be more efficient than other types of cooling methods in preventing bone resorption around implants.

Bone-Forming Capabilities of a Newly Developed NanoHA Composite Alloplast Infused with Collagen: A Pilot Study in the Sheep Mandible

Lateral or vertical bone augmentation has always been a challenge, since the site is exposed to constant pressure from the soft tissue, and blood supply only exists from the donor site. Although, for such clinical cases, onlay grafting with autogenous bone is commonly selected, the invasiveness of the secondary surgical site and the relatively fast resorption rate have been reported as a drawback, which motivated the investigation of alternative approaches. This study evaluated the bone-forming capability of a novel nanoHA alloplast infused with collagen graft material made from biodegradable polylactic acid/polyglycolic acid versus a control graft material with the same synthesized alloplast without the nanoHA component and collagen infiltration. The status of newly formed bone and the resorption of the graft material were evaluated at 6 weeks in vivo histologically and three dimensionally by means of 3D microcomputed tomography. The histologic observation showed that newly formed bone ingrowth and internal resorption of the block were observed for the experimental blocks, whereas for the control blocks less bone ingrowth occurred along with lower resorption rate of the block material. The three-dimensional observation indicated that the experimental block maintained the external geometry, but at the same time successfully altered the graft material into bone. It is suggested that the combination of numerous factors contributed to the bone ingrowth and the novel development could be an alternative bone grafting choice.

Effect of osteoblast cell culture on the bone implant contact

Purpose. The aim of this study is to acquire an ideal bone implant contact under the cover of osteogenic effect of osteoblasts derived from Mesenchymal Stem Cells (MSCs). Materials and methods. Thirty dental implants were used for this study. Implants were placed in sheep mandibles and defects were created 4 mm coronally in the dental implants. These defects were filled with Platelet Rich Plasma (PRP) in one group and with PRP + Osteoblast Cell Culture (OCC) in another group. No procedure was conducted on the control group defects (empty defect group). Eight weeks later, osseointegration was investigated with Bone Implant Contact (BIC) measurements histomorphologically. Data were checked statistically. Results. The variation of BIC rates between Empty Defect Group and PRP groups was significant (p <0.05). The BIC rate of the PRP group was higher than that of the Empty Defect Group. The variation of BIC rates between Empty Defect Group and PRP + OCC groups was significant (p <0.05). The BIC rate of the PRP + OCC group was higher than that of the Empty Defect Group. The variation of BIC rates between PRP and PRP + MSC groups was significant (p<0.05). The BIC rate of the PRP + OCC group was higher than that of the PRP group. At the end of the 8-week healing period, it was observed that the percentage of BIC was highest in the PRP + OCC group. Conclusions. Implant–bone connection was better in the OCC−PRP group compared with the PRP group and the empty defect group. The use of OCC-PRP combination was effective on healing. The BIC value was increased significantly by OCC.

Biomechanical in vitro evaluation of three stable internal fixation techniques used in sagittal osteotomy of the mandibular ramus: a study in sheep mandibles

Among the osteotomies performed in orthognathic surgery, the sagittal osteotomy of the mandibular ramus (SOMR) is the most common, allowing a great range of movements and stable internal fixation (SIF), therefore eliminating the need of maxillomandibular block in the postoperative period. Objectives: The purpose of this study was to evaluate the biomechanical resistance of three national systems used for SIF in SOMR in sheep mandibles. Material and methods: The study was performed in 30 sheep hemi-mandibles randomly divided into 3 experimental groups, each containing 10 hemi-mandibles. The samples were measured to avoid discrepancies and then subjected to SOMR with 5-mm advancement. In group I, 2.0x12 mm screws were used for fixation, inserted in an inverted "L" pattern (inverted "L" group). In group II, fixation was performed with two 2.0x12 mm screws, positioned in a linear pattern and a 4-hole straight miniplate and four 2.0x6.0 mm monocortical screws (hybrid group). In group III, fixation was performed with two 4-hole straight miniplates and eight 2.0x6.0 mm monocortical screws (mini plate group). All materials used for SIF were supplied by Osteosin - SIN. The hemimandibles were subjected to vertical linear load test by Kratos K2000MP mechanical testing unit for loading registration and displacement. Results: All groups showed similar resistance during mechanical test for loading and displacement, with no statistically significant differences between groups according to analysis of variance. Conclusion: These results indicate that the three techniques of fixation are equally effective for clinical fixation of SOMR.

The Effect of Slice Thickness on the Assessment of Bone Defect Volumes by the Cavalieri Principle Using Cone Beam Computed Tomography

The purpose of this study was to investigate the possible effects of section thickness on volume estimations obtained by cone beam computed tomography. Intraosseal cavities representing bone defects on vestibular sides of the two dry sheep mandibles were scanned by a cone beam computed tomography system. Consecutive sections at 0.2, 0.6, 1, 1.4, and 2.2 mm thickness were used to estimate the volumes of the cavities using the Cavalieri principle of stereological methods. Estimated volumes are then compared with the volumes obtained by the Archimedean principle. In 0.2-, 0.6-, and 1-mm-thick slices, the volumes estimated by the Cavalieri principle did not differ from the volumes by the Archimedean principle (p > 0.05). The 0.2 mm slice-thickness group had the highest asymptotic significance value (p = 0.6). Although the thinnest slice appears to provide the most accurate values, slice thickness up to 1 mm can be chosen for volume calculations on CBCT images.

A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy

Objectives: The objective this study is validate the use of nanoindentation tests in research and to assess the quality of newly formed bone in sheep mandibles submitted to Distraction osteogenesis (DO) and low-level laser therapy (LLLT) based on hardness and modulus of elasticity values. We also aim to determine the best moment for the application of laser therapy.

Evaluation of the Effects of Guided Bone Regeneration and Periosteum on Newly Formed Bone in a Distraction Gap

We determined the causes of bone resorption within a distraction gap and determined whether it could be prevented via guided bone regeneration during distraction. Another goal was to determine the effect of periosteum in bone healing in a distraction gap.Twelve sheep mandibles were bilaterally distracted. One side of the 6 sheep mandibles formed the control group; the other side was the study group, from which the periosteum was excised and distraction was performed. In the other 6 sheep, on the study side, guided bone regeneration was applied with distraction; on the other study side, guided bone regeneration was applied, and the periosteum was excised at the distraction. At the end of a 1-week latent period, all subjects were distracted 10 mm (1 mm/d), and we waited 3 months for consolidation. At the end of this period, all animals were killed, and radiologic evaluations of the newly formed bone within the distraction gap were conducted.The surface area of the regenerating bone in the membrane groups was significantly higher than in the groups without a membrane. However, no additional effect of the periosteum on the bone surface area was observed. No significant difference between the groups in densitometric values was observed.Concomitant use of guided bone regeneration with distraction osteogenesis may be the optimal way to generate a flat bone surface within a distraction gap.

A preliminary study of hardness and modulus of elasticity in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy

Objectives: To investigate the quality of newly formed bone in sheep mandibles submitted to distraction osteogenesis and low-level laser therapy (LLLT), based on hardness and modulus of elasticity values. The ideal moment for laser application (during the latency/activation period vs. during the bone consolidation period) was also evaluated. Computed tomography imaging was used to assess relapse as a result of early device removal. Study design: Extraoral distraction devices were placed in five sheep so as to achieve 1.5 cm of lengthened bone in 60 days. Distraction devices were removed 50, 40, and 33 days after surgery. Four animals were treated with LLLT, at different times, and one was used as control (no LLLT). Results: When applied during the bone consolidation period, LLLT caused an increase in hardness and modulus of elasticity values. On the other hand, animals irradiated with LLLT during the latency/activation period presented a delay in bone healing. A period of consolidation of 13 days (early device removal) was associated with relapse. Conclusions: Nanoindentation tests were able to detect slight abnormalities in bone metabolism and proved to be important tools for the assessment of bone quality following distraction osteogenesis. LLLT provided increased benefits when applied during the bone consolidation period, once it promoted an increase in hardness and modulus of elasticity values. According to our results, the bone consolidation period should be of at least 3 weeks, so as to prevent relapse. Key words: Osteogenesis distraction, low-level laser therapy, elastic modulus, hardness tests.

Biomechanical properties of the body and angle of the sheep mandible under bending loads

The aim of the study was to compare the body and angle of the sheep mandible in terms of bone density and biomechanical competence under bending load conditions. Nineteen sheep mandibles were used in this study. The mandibles were separated at the symphysis into two halves. Three regions of interest on the body and angle of the hemi-mandibles were selected for measurements of bone mineral density (g cm(-2) ) by dual energy X-ray absorbtiometry. Biomechanical properties of the left mandibular body and right mandibular angle were measured by three-point bending test using a material testing machine. The load and deformation were recorded, and the load-deformation curves were obtained. The values of failure load (FL), yield load (YL), yield deformation (YD), postyield deformation (PD), stiffness, energy to yield point (EY) and energy to failure point (EF) were calculated with the analysis of load-deformation curves. Groups were compared using independent samples Student's t-test. The mandibular angle exhibited the lower bone density (-64%) and biomechanical properties (FL; -45%, YL; -40%, PD; -7% stiffness, -40% EY; -48% and EF; -34%) than the mandibular body under bending loads, and there was no significant difference in values of YD between the two regions. Our results show that the mandibular angle is weaker than the mandibular body under bending loads.

The estimation of the volume of sheep mandibular defects using cone-beam computed tomography images and a stereological method

The Cavalieri principle of stereological methods is widely used to estimate the volume of structures. Recently in clinical practice, it has become common to use this approach for daily routine purposes. The Cavalieri principle provides quantitative and unbiased volume estimates which are independent of the observer. In the present study, the efficacy of using the Cavalieri principle to estimate the volume of sheep mandibular defects on cone beam CT (CBCT) scans was tested. 24 differently sized defects were created on 4 sheep mandibles. Before the defects were created, the outer boundaries of the defects were determined using plaster casts. CBCT scans of the defects were taken. The scans were reconstructed in the coronal plane and sections of 0.2 mm thickness with 0.2 mm and 0.4 mm intervals were obtained. The volume of each defect was estimated using the Cavalieri principle. The models were created using light-body silicone for the estimation of the actual volume of each defect. They were immersed in water using a pycnometer and the actual volumes were obtained on the basis of the Archimedean principle. The actual and estimated volumes of the defects were compared using the Wilcoxon signed-rank test. The results showed that the volumes from the Cavalieri estimates did not differ from the actual volumes of the defects (P > 0.05). We concluded that the volume of mandibular defects can be accurately estimated using the Cavalieri principle on images from a CBCT scan.

Influence of surface roughness and shape on microdamage of the osseous surface adjacent to titanium dental implants

To assess the relationship between smooth and roughened implant surfaces of straight and narrow configurations with respect to microdamage of the bone surface during placement of dental implants. Straight and tapered, rough and smooth surface Nobel Biocare implants were placed into sheep mandibles. Microdamage within the bone adjacent to the implant surface was quantitated using a semi-automated digitized histomorphometric method. Independent of implant type, microdamage, microcracks, cross-hatch damage and diffuse damage were significantly higher close to the implants compared with far from the implants. Microcracks and cross-hatch damage were higher for the rough cylindrical implants than all the other implant types. Insertion of a rough cylindrical implant type results in an increased fraction of microdamaged bone matrix in comparison to rough tapered, smooth cylindrical and smooth tapered implants.

The effect of hierarchical micro/nanosurface titanium implant on osseointegration in ovariectomized sheep

Hydrofluoric etching and anodized hierarchical micro/nanotextured surface titanium implant was placed in mandibles of ovariectomized sheep for 12 weeks, and it showed improved osseointegration by resonance frequency analysis (RFA), microcomputed tomography (micro-CT) evaluation, histomorphometry, and biomechanical test. This study aimed to investigate the effects of micro/nanotextured titanium implant on osseointegration in ovariectomized (OVX) sheep. The hierarchical micro/nanotextured surface of titanium implant was fabricated by acid in 0.5% (w/v) hydrofluoric (HF) and anodized in HF acid electrolytes with a DC power of 20 V, and the machined surface implants with no treatment served as control group. The implants were placed in mandibles of OVX sheep, respectively. Twelve weeks after implantation, RFA, microcomputed tomography, histomorphometry, and biomechanical tests were applied to detect the osseointegration of the two groups. The implant stability quotient (ISQ) values, the maximum pull-out forces, and the bone-implant contact (BIC) were 65.5 ± 6.3, 490.6 ± 72.7 N, and 58.31 ± 5.79% in the micro/nanogroup and 58.3 ± 8.9, 394.5 ± 54.5 N, and 46.85 ± 5.04% in the control group, respectively. There was no significant difference between the two groups in ISQ values (p > 0.05), but in the micro/nanogroup, the maximal pull-out force and the BIC were increased significantly (p < 0.05 or p < 0.01). Micro-CT analysis showed that the bone volume ratio and the trabecular number increased significantly (p < 0.01), and the trabecular separation decreased significantly (p < 0.05) in the micro/nanogroup. Implant modification by HF acid etching and anodization to form a hierarchical micro/nanotextured surface could improve titanium implant osseointegration in OVX sheep 12 weeks after implantation.

Stereologic Analysis of Bone Produced by Distraction Osteogenesis or Autogenous Bone Grafting in Mandible

To our knowledge, in the literature, any other investigation that numerically compared osteoblasts retrieved from transport distraction osteogenesis and bone grafting procedures using stereological methods is not reported. The purpose of this study was to compare the total number of osteoblast cells at 3 months in bone produced by distraction osteogenesis and that in autogenous bone graft. A total of 19 growing sheep (male aged 7 or 8 mo; weighing between 21 and 28 kg) were used in this study. Mandibular discontinuity defects created in mandibles of sheep were reconstructed by transport distraction osteogenesis and iliac crest bone graft and allowed to heal for 3 months. The animals were then killed, and the jaws were resected and prepared to be decalcified. Stereological and histologic examinations were performed. Intramembranous ossification and osteoid and trabecular formations were observed in both groups. In the distraction group, the mean +/- standard deviation (SD) numerical density of the osteoblasts was found to be higher (0.0004866 +/- [0.000044])when compared with those of both the graft (0.0003458 +/- [0.000030]) and control groups (0.0002714 +/- [0.000022]). Statistically significant differences were found among the groups (P < 0.05). Stereologic evaluation of bone in the sheep model demonstrated significantly greater osteoblast density in bone formed through transport distraction osteogenesis when compared with bone grafting and the control. Therefore, further studies should be conducted to evaluate the differences in both osteoblastic and osteoclastic cellular activities at different time points in distraction osteogenesis and autogenous bone grafting to assess the healing process of bone for clinical applications.