Effect on implant drills and postoperative reactions for pre-extraction interradicular implant bed preparation during the COVID-19 pandemic and beyond.

The aim of the present study was to observe the abrasion of implant drills and postoperative reactions for the preparation of the interradicular immediate implant bed during the COVID-19 pandemic and beyond. Thirty-two implant drills were included in four groups: blank, improved surgery, traditional surgery, and control. In the improved surgery group, a dental handpiece with a surgical bur was used to decoronate the first molar and create a hole in the middle of the retained root complex, followed by the pilot drilling protocol through the hole. The remaining root complex was separated using a surgical bur and then extracted. Subsequently, the implant bed was prepared. Implant drills were used in the traditional surgery group to complete the decoronation, hole creation, and implant-drilling processes. The tooth remained intact until the implant bed was prepared. The surface roughness of the pilot drill was observed and measured. Surgery time, postoperative reactions (swelling, pain, and trismus), and fear of coronavirus disease 2019 scale (FCV-19S) were measured and recorded, respectively. Statistical analysis revealed significant difference with surface roughness among blank group (0.41 ± 0.05 µm), improved surgery group (0.37 ± 0.06 µm), traditional surgery group (0.16 ± 0.06 µm), and control group (0.26 ± 0.04 µm) (P < .001). Significant differences were revealed with surgery time between improved surgery group (5.63 ± 1.77 min) and traditional surgery group (33.63 ± 2.13 min) (P < .001). Swelling, pain, and trismus (improved group: r ≥ 0.864, P ≤ .006; traditional group: r ≥ 0.741, P ≤ .035) were positively correlated with the FCV-19S. This study proved that a new pilot drill could only be used once in traditional surgery but could be used regularly in improved surgery. Improved surgery was more effective, efficient, and economical than the traditional surgery. The higher FCV-19S, the more severe swelling, pain, and trismus.

Visualization Experimental Study on Well Spacing Optimization of SAGD with a Combination of Vertical and Horizontal Wells.

For oil sand reservoirs, the steam-assisted gravity drainage (SAGD) technique is one of the most efficient thermal recovery technologies. However, the high oil viscosity and the severe heat loss seriously affect the production effect of SAGD in developing thin oil sand reservoirs by the traditional SAGD technology. Therefore, it is essential to improve the SAGD technology to enhance the recovery of the thin oil sand reservoir. In this paper, SAGD with a combination of vertical and horizontal well (VH-SAGD) technology was adopted, and the influence of different well spacings (horizontal distance between vertical steam injection wells and horizontal production wells) on the development of steam chambers was investigated. By the similarity criterion, the experimental parameters were obtained. After that, an improved 2D visualization physical model was designed with 9 × 9 high-precision thermocouples installed inside the device to monitor the real-time temperature. This experimental physical model can not only accurately capture the temperature distribution but also display the continuous change process of the chamber inside the model by the visible window. Finally, different well spacing cases (10, 15, and 20 cm) were tested to observe the development of the steam chamber and analyze the production data. Both the temperature distribution and visual window showed that the steam chamber has four obvious stages, and reasonable well spacing can promote the development of the steam chamber. When the well spacing is relatively small, the unswept area of the cold oil on both sides is large, and the area of the steam chamber overlaps more. When the well spacing is relatively moderate, the steam chamber is the most complete and the recovery factor is the highest. When the well spacing is relatively large, although the unswept area of the cold oil on both sides is small, the middle cold oil area is larger than the previous two groups. Therefore, the best well spacing for oil sand reservoirs of about 15 m thickness is 15-20 m, where the VH-SAGD method has a better displacement effect and higher oil recovery. The experimental conclusions can provide theoretical support for the production of thin oil sand reservoirs.

The Past, Present, and Future of Dentoalveolar Surgery in China.

Dentoalveolar surgery, formerly known as dental surgery or oral surgery, is one of the basic branches of oral and maxillofacial surgery. While it has a long history; however, there are great differences in its evolution globally. This article presents a brief review on the development of dentoalveolar surgery internationally. Furthermore, a systematic review on its development in China, is detailed in 6 stages. However, while its development in China since 2005 has been most profound, improvements are still needed in treatment concepts, instruments, treatment processes, attention to high-risk populations and cooperation with other dental/medical disciplines. Future projections based on present standards of care are also presented.

Gelatin microspheres containing calcitonin gene-related peptide or substance P repair bone defects in osteoporotic rabbits.

OBJECTIVES: To investigate the therapeutic effect of gelatin microspheres containing different concentrations of calcitonin gene-related peptide (CGRP) or substance P on repairing bone defects in a rabbit osteoporosis model. RESULTS: Gelatin microspheres containing different concentrations of CGRP or substance P promoted osteogenesis after 3 months in a rabbit osteoporotic bone defective model. From micro-computed tomography imaging results, 10 nM CGRP was optimal for increasing the trabecular number and decreasing the trabecular bone separation degree; similar effects were observed with the microspheres containing 1 µM substance P. Histological analysis showed that the gelatin microspheres containing CGRP or substance P, regardless of the concentration, effectively promoted osteogenesis, and the highest effect was achieved in the groups containing 1 µM CGRP or 1 µM substance P. CONCLUSIONS: Gelatin microspheres containing CGRP or substance P effectively promoted osteogenesis in a rabbit osteoporotic bone defect model dose-dependently, though their effects in repairing human alveolar ridge defects still need further investigation.

The influence of the sensory neurotransmitter calcitonin gene-related peptide on bone marrow mesenchymal stem cells from ovariectomized rats.

In order to explore the effects of calcitonin gene-related peptide (CGRP) on bone mesenchymal stem cells (BMSCs) from ovariectomized (OVX) rats, an OVX rat model was used. An ELISA was performed to examine the changes in CGRP level in the plasma and skeleton. The BMSCs from the sham rats were designated group A. The BMSCs from the OVX rats (groups B, C, D and E) were treated with different concentrations of CGRP (10-6, 10-8, 10-10 and 0 M) in vitro. The proliferation and osteogenic and adipogenic differentiation potential of the BMSCs were evaluated. BMSCs sheets and Bio-Oss® mixtures were transplanted into nude mice to observe the effects of CGRP on bone formation in vivo. The level of CGRP was decreased by almost 27 and 17 % in the plasma and bone, respectively, in OVX rats compared with sham rats (p < 0.05). Treatment with CGRP increased the proliferation and mineralization of BMSCs, and significantly decreased the lipid accumulation of BMSCs in a dose-dependent manner. The expression of Runx2 and Osterix was upregulated, but the expression of peroxisome proliferator-activated receptor γ was significantly downregulated in groups B, C and D compared with group E (p < 0.05). Micro computed tomography showed no difference between the images of the planted mixtures. Hematoxylin and eosin stain revealed the formation of slightly more hard bone-like structures in groups B and C. These results suggested that CGRP played a role in adjusting bone mass and strength by promoting the proliferation and osteogenic differentiation of BMSCs, as well as significantly suppressing the adipogenic differentiation of BMSCs.

Thorough documentation of the accidental aspiration and ingestion of foreign objects during dental procedure is necessary: review and analysis of 617 cases.

OBJECTIVES: To review the cases of accidental aspiration and ingestion of foreign objects during dental procedure, and to emphasize the importance of thorough documentation of the accidents. METHODS: A comprehensive search on (dental procedure/treatment/practice), (aspiration/inhalation), and (ingestion/swallow) was performed for all years before 1st October 2014 available. The statistic analysis was made on the variables including journals and reported year, patients' age, gender, general conditions, dental procedure and location for procedure, foreign objects, site of involvement, possible causes, anesthesia during procedure and treatment, symptoms, treatment time and treatment modality, follow-up, and so on. RESULTS: A total of 617 cases reported by 45 articles from 37 kinds of journals were included and analyzed. Most reports made detailed record. While some important variables were recorded incompletely, including patient's general conditions, location for procedure, clinical experience of the involving dentists, tooth position of procedure, possible causes, and anesthesia during procedure and treatment for the accident. CONCLUSIONS: Aspiration and ingestion of foreign objects are rare and risky complication during dental procedure. Each accident should have thorough documentation so as to provide enough information for the treatment and prevention.

In vitro and in vivo evaluation of puerarin-loaded PEGylated mesoporous silica nanoparticles.

Puerarin, which is extracted from Chinese medicine, is widely used in China and mainly used as a therapeutic agent for the treatment of cardiovascular diseases. Owing to its short elimination half-life in human beings, frequently intravenous administration of high doses of puerarin may be needed, which possibly leads to severe and acute side effects. The development of an effective sustained-release drug delivery system is urgently needed. In this study, PEGylated mesoporous silica nanoparticles (PEG-MSNs) had become a preferred way to prolong the half-life and improve the bioavailability of drugs. The release of puerarin from PEG-MSNs was pH dependent, and the release rate was much faster at lower pH than that at higher pH. Moreover, the PEG-MSNs exhibited improved blood compatibility over the MSNs in terms of low hemolysis, and it could also reduce the side effect of hemolysis induced by PUE. Compared with puerarin, PUE-loaded PEG-MSNs showed a 2.3-fold increase in half-life of puerarin and a 1.47-fold increase in bioavailability. Thus, the PEG-MSNs hold the substantial potential to be further developed as an effective sustained-release drug delivery system.

Influence of the lateral pterygoid muscle on traumatic temporomandibular joint bony ankylosis.

BACKGROUND: The pathogenesis of traumatic TMJ ankylosis remains unclear. This study aimed to verify the role of the lateral pterygoid muscle in the pathogenesis of traumatic temporomandibular joint (TMJ) bony ankylosis. METHODS: Eight 6-month-old male sheep were used in this study. Bilateral TMJ osteotomies were performed to induce sagittal fractures of the mandibular condyle. The lateral one-fourth segment of the disc was removed to establish a model of TMJ bony ankylosis. Subsequently, the function of the left and right lateral pterygoid muscles was blocked (experimental group) or maintained (control group), respectively. At 12 weeks postoperatively, animals were sacrificed and TMJ complex samples were evaluated by gross observation, spiral computed tomography (CT), micro-CT, and histological examinations. RESULTS: Gross observation revealed bony ankylosis in the control TMJs and fibrous adhesions in the experimental TMJs. Spiral CT and micro-CT demonstrated that, compared to the experimental group, the control group showed calcified callus formation in the joint space and roughened articular surfaces after new bone formation, which protruded into the joint space. Maximum mediolateral and anteroposterior condylar diameters were significantly larger in the control group than in the experimental group. Micro-CT also showed that the primary growth orientation of new trabeculae was consistent with the direction of lateral pterygoid traction in the control group, but not in the experimental group. Histological examination showed fibro-osseous ankylosis in the control group, but not in the experimental group. CONCLUSIONS: The lateral pterygoid simulates the effects of distraction osteogenesis, which is an important factor in the pathogenesis of TMJ bony ankylosis during the healing of sagittal condylar fractures.

Influence of preservation of the alveolar ridge on delayed implants after extraction of teeth with different defects in the buccal bone.

Our aim was to evaluate the influence of preservation of the alveolar ridge on delayed implants with different defects in the buccal bone. We enrolled 60 patients who had one posterior mandibular tooth extracted. Cone-beam computed tomography (CT) was used to measure the buccal bone defects in the alveolar ridge before the tooth was extracted (level A=3 to 5 mm, and level B=more than 5 mm). After the tooth had been extracted, the socket either had the alveolar ridge preserved (trial group) or it was left to heal spontaneously (control group). The changes in the dimensions of the alveolar ridge from preoperatively to 6 months postoperatively were evaluated by cone-beam CT. Suitable implants were inserted 6 months later, and their length and diameter recorded. The implant stability quotient was evaluated for the following 3 months. The dimensions of the bone in the alveolar ridge in the trial group were significantly less than those in the control groups in both levels. Fifty-seven patients required implants (except 3 in level B in the control group). There were more longer and wider implants in the trial group than in the control group in Level B. 3 months after implantation, there were no significant differences in implant stability quotients between the groups, though in the control group, Level B, the mean (SD) value was 69.50 (1.00) while in the other groups values were all above 70 at 3 months. We conclude that when the defect in the buccal bone was more than 5mm, the alveolar ridge preservation demonstrated a remarkable effect in preserving the alveolar ridge dimension and delayed implantation.

[Chemical Constituents of Ethyl Acetate Fraction from Hypericum ascyron].

Objective: To study the chemical consituents of Hypericum ascyron. Methods: The constituents were isolated and purified by chromatography on silica gel; the structure of the compound was determined by MS and NMR spectral analysis. Results: On the basis of spectroscopic analysis and comparison with the reported data, they were identified as hyperoside( 1),hypercalin B( 2),hypercalin C( 3),1,7-dihydroxyxanthone( 4),2,3-dimethoxyxanthone( 5),1-hydroxy-7-methoxyxanthone( 6),rutin( 7),kaempferol( 8),toxyloxanthone B( 9),quercetin( 10),quercitrin( 11),ß-daucosterol( 12) and ß-sitosterol( 13). Conclusion: Compounds 2,3,6 and 9 are obtained from this plant for the first time.

Evaluation of reference gene suitability for quantitative expression analysis by quantitative polymerase chain reaction in the mandibular condyle of sheep.

Reference genes are commonly used as a reliable approach to normalize the results of quantitative polymerase chain reaction (qPCR), and to reduce errors in the relative quantification of gene expression. Suitable reference genes belonging to numerous functional classes have been identified for various types of species and tissue. However, little is currently known regarding the most suitable reference genes for bone, specifically for the sheep mandibular condyle. Sheep are important for the study of human bone diseases, particularly for temporomandibular diseases. The present study aimed to identify a set of reference genes suitable for the normalization of qPCR data from the mandibular condyle of sheep. A total of 12 reference genes belonging to various functional classes were selected, and the expression stability of the reference genes was determined in both the normal and fractured area of the sheep mandibular condyle. RefFinder, which integrates the following currently available computational algorithms: geNorm, NormFinder, BestKeeper, and the comparative ΔCt method, was used to compare and rank the candidate reference genes. The results obtained from the four methods demonstrated a similar trend: RPL19, ACTB, and PGK1 were the most stably expressed reference genes in the sheep mandibular condyle. As determined by RefFinder comprehensive analysis, the results of the present study suggested that RPL19 is the most suitable reference gene for studies associated with the sheep mandibular condyle. In addition, ACTB and PGK1 may be considered suitable alternatives.

Alveolar ridge preservation with deproteinized bovine bone graft and collagen membrane and delayed implants.

To evaluate clinically and radiographically an alveolar ridge, preservation technique with deproteinized bovine bone graft and absorbable collagen membrane and then restoration with delayed implants were done. The study included 30 patients. The trial group's sockets were filled with deproteinized bovine bone graft (Bio-Oss) and covered with absorbable collagen membrane (Bio-Gide). The control group's sockets healed without any treatment. Panoramic radiograph and computed tomography were taken immediately after graft and 3 and 6 months later to evaluate the height, width, and volume change of the alveolar ridge bone. Dental implants were inserted in all sockets at 6 months, and osseointegration condition was evaluated in the following 12 months. All sockets healed uneventfully. In the trial group, the mean (SD) height reduction of the alveolar ridge bone was 1.05 (0.24) mm at 3 months and 1.54 (0.25) mm at 6 months. The width reduction was 1.11 (0.13) mm at 3 months and 1.84 (0.35) mm at 6 months. Bone volume reduction was 193.79 (21.47) mm at 3 months and 262.06 (33.08) mm at 6 months. At the same trend, in the control group, the bone height reduction was 2.12 (0.15) mm at 3 months and 3.26 (0.29) mm at 6 months. The width reduction was 2.72 (0.19) mm at 3 months and 3.56 (0.28) mm at 6 months. Bone volume reduction was 252.19 (37.21) mm at 3 months and 342.32 (36.41) mm at 6 months. There was a significant difference in alveolar ridge bone height, width, and volume reduction in the 2 groups. The osseointegration condition had no significant difference between the 2 groups. This study suggested that the deproteinized bovine bone graft and absorbable collagen membrane were beneficial to preserve the alveolar ridge bone and had no influence on the osseointegration of delayed implant.

Improved sedation for dental extraction by using video eyewear in conjunction with nitrous oxide: a randomized, controlled, cross-over clinical trial.

OBJECTIVE: The purpose of this study was to investigate the effect of a portable video eyewear entertainment system used in conjunction with nitrous oxide/oxygen sedation during the removal of impacted lower third molars. STUDY DESIGN: Thirty-eight patients had their bilateral third molars removed under local anesthesia and nitrous oxide/oxygen inhalation sedation in 2 visits. On one side, video eyewear was used (group NE). On the other side, the tooth was removed without the use of video eyewear (group N). Vital signs were monitored. Overall behavior and the outcome of treatment were assessed. RESULTS: All 38 patients completed the study. The mean scores on behavior rating in group NE were significantly higher than those in group N (P < .05). The majority of patients (92.1%) preferred nitrous oxide with video eyewear. CONCLUSIONS: The use of video eyewear appeared to augment the effectiveness of nitrous oxide sedation in dental extraction patients.

Secondary healing after removal of large keratocystic odontogenic tumor in the mandible: enucleation followed by open packing of iodoform gauze.

PURPOSE: The aim of this retrospective study was to present the findings of an open packing method after enucleation of large keratocystic odontogenic tumors (KCOTs) in the mandible. PATIENTS AND METHODS: We performed a retrospective case series study of 27 patients with KCOTs larger than 5 cm treated at our institution between September 2003 and September 2008. A conservative surgical treatment was applied, which involved enucleation of the primary lesion and open packing of the residual osseous defect with iodoform gauze for secondary healing. Bone regeneration, tumor recurrence, and surgical complications were observed and analyzed. We used the χ(2) test and Pearson correlation coefficient for statistical analysis. RESULTS: The postoperative follow-up time was 52.3 months on average (range, 24 to 84 months). The packing gauze was changed every 2 weeks after enucleation, and the total duration for packing was 10.2 months on average (range, 7-15 months). Bone regeneration and satisfactory secondary healing were observed clinically and radiographically after treatment. Only 1 case had a recurrence 6 months after initial treatment, which was attributed to insufficient bony unroofing during enucleation. The recurrent lesion was re-treated by the same method, and no recurrence occurred in the following 6 years. No serious complications from this method of treatment were observed. No significant variables were found to be related to the recurrence. CONCLUSIONS: Enucleation with subsequent open packing was shown to be a conservative and comfortable treatment for patients and appears to be an effective choice for the management of large KCOTs in the mandible.

The effect of low-intensity pulsed ultrasound on the osseointegration of titanium dental implants.

Our aim was to record the effect of low-intensity pulsed ultrasound (LIPUS) on the osseointegration of endosseous dental implants in 10 New Zealand rabbits. One titanium implant with screw was inserted into the metaphyseal region of each femur and tibia in the knee joints of each rabbit, making a total of 40 implants. The area of one lateral knee joint, including implants, was irradiated with LIPUS for 10 min twice a day for 21 days. The other side acted as control, having been given "sham" irradiation. Two rabbits were killed at each of 0, 2, 4, 6, and 8 weeks after irradiation. A micro-computed tomogram (µCT), histological examination, and implant pull-out test were used to judge the reactions of the bone to the titanium implant. Histological and µCT examinations showed that osseointegration of the implants on the LIPUS-treated side happened earlier and more effectively than on the control side. The mechanical test showed that the maximal axial pull-out strength of the implants on the LIPUS-treated side was greater than that on the control side. We conclude that LIPUS has the potential to accelerate the osseointegration of dental implants.

Prototyped flexible grafting tray for reconstruction of mandibular defects.

In our previous studies, prototyped individual bone-grafting trays have been used to restore discontinuous mandibular defects. However, the attempts have shown that the trays have shielded the graft from stress, which caused considerable resorption of bone. To eliminate the shielding, we designed a flexible tray. Finite element analysis was used to compare the distribution of strain on the bone grafts that were placed in flexible and conventional trays. The analogue computation suggested that most of the strain on the graft in the flexible tray resulted in a beneficial mechanical environment, while in the conventional tray more than half of graft was in the lowest class of strain (disuse - <50 µstrains). Animal experiments were conducted on hybrid dogs, and the prototype flexible tray was used to carry particles of autologous cancellous iliac bone to reconstruct a 40 mm defect in the mandibular body. Sequential radionuclide bone imaging was used to monitor the bone metabolism. Animals were killed at 4, 12 and 24 weeks, and specimens processed for quantitative histological examination. The data from the flexible trays were compared with those from the conventional trays, as in our previous study. The results showed that bone metabolism was more active in the flexible tray than in the conventional tray during the early stages. There was increased bony adaptation in the flexible tray. These results indicate that the flexible tray can efficiently eliminate the shielding from stress, and allow more occlusive force to be conducted on to the bone graft, which results in better remodelling of the graft.

Effects of capsaicin-induced sensory denervation on bone metabolism in adult rats.

Bone metabolism has recently been revealed to be under nerve regulation. In this study, the integrity of the sensory innervation contributing to bone metabolism was examined by capsaicin-induced sensory neuron lesions. Eight-week-old male Wistar strain rats in a modeling phase of skeletal growth were divided into four groups (8 rats per group) and treated with capsaicin at one of three different doses (37.5, 75, 150 mg/kg) or vehicle, subcutaneously. Five weeks later, high-dose (150 mg/kg) capsaicin treatment had reduced trabecular bone volume (BV/TV) due to increased trabecular separation (Tb.Sp) in the proximal tibia and the modification of mechanical properties such as strength, ductility, and toughness toward increasing bone fragility in the trunk of the sixth lumbar vertebrae (L6). Moderate-dose (75 mg/kg) capsaicin treatment had no significant effect on trabecular BV/TV or bone mechanical properties but increased Tb.Sp as seen high-dose capsaicin treatment. Bone histomorphometry showed osteoclast number (Oc.N/BS) and surface (Oc.S/BS) were increased in both the moderate-dose and high-dose capsaicin treatment groups. High-dose capsaicin significantly increased the level of tartrate-resistant acid phosphatase form 5b (TRAP 5b) in plasma, a systemic bone resorption marker, but had no influence on plasma osteocalcin concentration, a bone formation marker, suggesting that capsaicin-induced sensory nerve denervation increased bone resorption but had no influence on bone formation. Low-dose (37.5mg/kg) capsaicin had no influence on bone remodeling. These results suggest that sensory nerve innervation contributes to the maintenance of trabecular bone mass and its mechanical properties by inhibiting bone resorption.

The effect of chemical sympathectomy and stress on bone remodeling in adult rats.

OBJECTIVES: Bone remodeling has recently been revealed to be under sympathetic nerve control. The role of the sympathetic nerve system is not clearly understood. The present study aim to explore the effect of chemical sympathectomy and stress on bone remodeling in adult rats. METHODS: 24 twelve-month-old Wistar rats were divided into three group (sympathectomy, stress and control). The sympathectomy and stress group rats were administered 6-hydroxydopamine (150 mg/kg each day) and saline (1 ml/kg each day) intraperitoneal respectively for one week and exposed to stress procedure for another three weeks. The stress procedure was mild, unpredictable footshock, administered for one hour once daily. Analysis of serum chemistry, microcomputed tomography, dual energy X-ray absorptiometry, biomechanical testing and bone histomorphometry were employed. RESULTS: The stress group rats showed increased bone resorption in contrast to the sympathectomy and control group rats. The serum level of calcium and phosphorus cations and norepinephrine were enhanced, the cancellous bone volume and bone mineral density were reduced, bone mechanical property such as strength, ductility and toughness were weakened, the osteoclast counts and osteoclast surfaces were increased and the bone formatin rate were decreased significantly in the stress group rats in contrast to the other two groups rats. There was no significant difference of bone remodeling between the sympathectomy group and control group rats. CONCLUSION: Our study showed stress-increased sympathetic nerve system activity enhanced bone resorption while chemical sympathectomy inhibited bone resorption under stress. We postulate sympathetic neurotransmitter and neuropepitide may play a role in regulating bone remodeling.

99mTechnetium-methylene diphosphonate bone imaging using low-intensity pulsed ultrasound: promotion of bone formation during mandibular distraction osteogenesis in dogs.

Our objective was to assess the value of (99m)technetium-methylene diphosphonate ((99m)Tc-MDP) bone imaging in the use of low-intensity pulsed ultrasound to promote bony formation during mandibular distraction osteogenesis in dogs. The body of the mandibles in 7 dogs were cut between the first and the second premolar and were lengthened at the rate of 1mm/day, twice a day, for 20 days. During the period of distraction one lateral distraction gap was irradiated with low-intensity pulsed ultrasound (LIPUS) for 10min twice a day, and the other side was used as control. Serial radiographic inspections were made at different periods (0, 1, 2, 4, 6, 8, and 12 weeks) during the consolidation phase, followed by a plain radiograph and histological examination. The (99m)Tc-MDP imaging showed that the ratio of bone formation on the LIPUS-treated side was significantly higher than that on the control side during the early period of consolidation (before the 4th week), but later this was reversed and there were no significant differences between the two sides by the 12th week. Plain radiographs and histological examination showed that the new bone on the experimental side had matured earlier than that on the control side. Radionuclide bone imaging is a good way to assess the formation of bone after distraction osteogenesis.

Effect of low-intensity pulsed ultrasound on bone formation during mandible distraction osteogenesis in a canine model--a preliminary study.

PURPOSE: To make a preliminary study of the effect of low-intensity pulsed ultrasound on new bone formation during mandible distraction osteogenesis in dogs. MATERIALS AND METHODS: Bilateral surgical cuts were made in mandibles of 7 dogs between the first and second premolar regions. Anterior mandibles were lengthened by 20 mm at the rate of 1 mm/day twice a day. During the distraction period 1 lateral distraction gap was irradiated by low-intensity pulsed ultrasound for 10 minutes twice a day and the other side was sham irradiated as control. After distraction was completed, the dogs were sacrificed at 0, 1, 2, 4, 6, 8, and 12 weeks. Before sacrifice, dynamic bone imaging with technetium (99)m-methylene diphosphonate ((99)mTc-MDP) single-photon emission computed tomography was performed. Mandible samples were harvested. Then plain x-ray, dual-energy x-ray bone mineral density measurement, 3-dimensional computed tomography, and regular histologic examination were performed. RESULTS: The (99)mTc-MDP bone imaging showed that uptake of (99)mTc-MDP in the experimental side was higher than in the control side at the early period of the consolidation time, but the outcome was later reversed. Plain x-ray showed that new bone of the experimental side was mature sooner than that of the control side. Bone mineral density in the experimental side was higher than that of the control side. Volume of new bone of the 2 sides had no significant difference. Histologic examination showed that trabeculae of the experimental side were more numerous and thicker than those of the control side at the early period of the consolidation time. Endochondral bone formation was observed in the experimental side. CONCLUSION: Low-intensity pulsed ultrasound could accelerate bone formation during mandibular distraction osteogenesis and increase bone mineral density but had no effect on the volume of new bone.