The Effects of Low-Intensity Pulsed Ultrasound Exposure on Gingival Cells

Osteogenic effect of low-intensity pulsed ultrasound on peri-implant bone: A systematic review and meta-analysis

Purpose This study aimed to evaluate the effect of low-intensity pulsed ultrasound (LIPUS) on promoting osseointegration around dental implants.Study selection A comprehensive search was performed on two databases, including MEDLINE (PubMed) and Web of Science to identify relevant studies published before June 1, 2022. Randomized controlled trials that met the inclusion criteria were selected for the study. The year of publication, study design, animal species, number of animals, number of implants, implant position, implant size, intervention, follow-up time, bone volume ratio (BV/TV), bone-implant contact ratio (BIC), and implant removal torque value (RTV) measurements, including mean and SD, were extracted.Results Ten randomized trials were included in this meta-analysis. The results showed that LIPUS significantly promoted osteogenesis around dental implants. Furthermore, in animal models of pre-existing diseases such as osteoporosis and diabetes, LIPUS had the same effect. The included data were divided into subgroups to explore the effects of different follow-up time, acoustic intensities, and frequencies. Results showed that higher acoustic intensities and frequencies significantly improve the osteogenic effects of LIPUS. There was some degree of heterogeneity owing to bias in the included studies. More high-quality randomized controlled trials are necessary in the future.Conclusions LIPUS can promote bone healing around dental implants and is an attractive option for edentulous patients, especially those with pre-existing diseases. Further clinical trials on the use of LIPUS in implant dentistry are warranted. Furthermore, future studies must pay more attention to acoustic intensity and frequency.

Evaluate the effects of low-intensity pulsed ultrasound on dental implant osseointegration under type II diabetes

Objective: The objective of this study is to assess the impact of low-intensity pulsed ultrasound (LIPUS) therapy on the peri-implant osteogenesis in a Type II diabetes mellitus (T2DM) rat model. Methods: A total of twenty male Sprague-Dawley (SD) rats were randomly allocated into four groups: Control group, T2DM group, Control-LIPUS group, and T2DM-LIPUS group. Implants were placed at the rats' bilateral maxillary first molar sites. The LIPUS treatment was carried out on the rats in Control-LIPUS group and T2DM-LIPUS group, immediately after the placement of the implants, over three consecutive weeks. Three weeks after implantation, the rats' maxillae were extracted for micro-CT, removal torque value (RTV), and histologic analysis. Results: Micro-CT analysis showed that T2DM rats experienced more bone loss around implant cervical margins compared with the non-T2DM rats, while the LIPUS treated T2DM rats showed similar bone heights to the non-T2DM rats. Bone-implant contact ratio (BIC) were lower in T2DM rats but significantly improved in the LIPUS treated T2DM rats. Bone formation parameters including bone volume fraction (BV/TV), trabecular thickness (Tb.Th), bone mineral density (BMD) and RTV were all positively influenced by LIPUS treatment. Histological staining further confirmed LIPUS's positive effects on peri-implant new bone formation in T2DM rats. Conclusion: As an effective and safe treatment in promoting osteogenesis, LIPUS has a great potential for T2DM patients to attain improved peri-implant osteogenesis. To confirm its clinical efficacy and to explore the underlying mechanism, further prospective cohort studies or randomized controlled trials are needed in the future.

Attenuation of orthodontically induced inflammatory root resorption by using low-intensity pulsed ultrasound as a therapeutic modality- a systematic review

Ultrasound is an effective tool for both diagnostic and therapeutic applications. As an imaging tool, ultrasound has mostly been used for real-time noninvasive diagnostic imaging. As ultrasound propagates through a material, a reflected radio-frequency (RF) signal is generated when encountering a mismatch in acoustic impedance. While traditionally recognized for its diagnostic imaging capabilities, the application of ultrasound has broadened to encompass therapeutic interventions, most notably in the form of Low-Intensity Pulsed Ultrasound (LIPUS). Low-Intensity Pulsed Ultrasound (LIPUS) is a form of mechanical energy transmitted transcutaneously by high-frequency acoustic pressure waves. The intensity of LIPUS (30 mW/cm2) is within the range of ultrasound intensities used for diagnostic purposes (1-50 mW/cm2) and is regarded as non-thermal, non-destructive, permeating living tissues and triggering a cascade of biochemical responses at the cellular level. The LIPUS device produces a 200 µs burst of 1.5 MHz acoustic sine waves, that repeats at a modulation frequency of 1 kHz and provides a peak pressure of 30 mW/cm2. Low-intensity pulsed ultrasound (LIPUS) forms one of the currently available non-invasive healing-enhancing devices besides electro-stimulation (pulsed electro-magnetic field, PEMF). This modality has been leveraged to enhance drug delivery, expedite injury recovery, improve muscle mobility, alleviate joint stiffness and muscle pain, and enhance bone fracture healing. Although LIPUS has been embraced within various medical disciplines, its integration into standard dental practices is still in its nascent stages, signifying an unexplored frontier with potentially transformative implications. Low-intensity pulsed ultrasound (LIPUS) has emerged as an attractive adjuvant therapy in various dental procedures, such as orthodontic treatment and maxillary sinus augmentation. Its appeal lies in its simplicity and non-invasive nature, positioning LIPUS as a promising avenue for clinical innovation. One particular area of interest is orthodontically induced inflammatory root resorption (OIIRR), an oftenunavoidable outcome of the orthodontic intervention, resulting in the permanent loss of root structure. Notably, OIIRR is the second most common form of root resorption (RR), surpassed only by root resorption related to pulpal infection. Given the high prevalence and potential long-term consequences of OIIRR, this literature review seeks to evaluate the efficacy of LIPUS as a therapeutic approach, with an emphasis on assessing its capacity to reduce the severity of OIIRR to a level of clinical significance. To conduct this systematic review, a comprehensive automated literature search was executed across multiple databases, including MEDLINE, Embase, PsycINFO, Web of Knowledge, Scopus, CINAHL, LILACS, SciELO, Cochrane, PubMed, trials registries, 3ie, and Google Scholar. Both forward and backward citation tracking was employed, encompassing studies published from database inception through January 2009 to April 2023. The review focused on randomized controlled trials (RCTs) that specifically evaluated the effects of low-intensity pulsed ultrasound therapy on orthodontically induced inflammatory root resorption (OIIRR), without restrictions of publication date. A stringent selection criterion was applied, and only studies demonstrating high levels of statistical significance were included. Ultimately, fourteen studies met the inclusion criteria and were subjected to further analysis. The overall quality of the included randomized controlled trials (RCTs) was rigorously assessed utilizing the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach. This analysis revealed certain methodological limitations that posed challenges in drawing definitive conclusions from the available evidence. Despite these constraints, the review offers invaluable insights that can inform and guide future research. Specifically, it delineates recommendations for targeted populations, necessary interventions, appropriate outcome measures, suitable study designs, and essential infrastructure to facilitate further investigations. The synthesis of these insights aims to enhance the development and application of low-intensity pulsed ultrasound therapy within the field of dentistry, thereby contributing to improved patient outcomes.

Low-intensity pulsed ultrasound promotes periodontal regeneration in a beagle model of furcation involvement

Objective: To evaluate the regeneration potential of periodontitis tissue treated by low-intensity pulsed ultrasound (LIPUS) combined with the guided tissue regeneration (GTR) technique in a beagle model of furcation involvement (FI).

Background: Achieving predictable regeneration remains a clinical challenge for periodontitis tissue due to the compromised regenerative potential caused by chronic inflammation stimulation. LIPUS, an FDA-approved therapy for long bone fracture and non-unions, has been demonstrated effective in the in vitro attenuation of inflammation-induced dysfunction of periodontal ligament stem cells (PDLSCs), the key cells contributing to periodontal regeneration. However, the in vivo effect of LIPUS on periodontitis tissue is rarely reported.

Methods: A beagle model of FI was established, and the experimental teeth were randomly assigned into three groups: control group, GTR group, and GTR+LIPUS group. Radiographic examinations were performed, and clinical periodontal parameters were recorded to reflect the periodontal condition of different groups. Histological analyses using H&E and Masson’s staining were conducted to evaluate the periodontal tissue regeneration.

Results: LIPUS could enhance new periodontal bone formation and bone matrix maturity in FI after GTR treatment. Moreover, clinical assessment and histomorphometric analyses revealed less inflammatory infiltration and superior vascularization within bone grafts in the LIPUS treatment group, indicating the anti-inflammatory and pro-angiogenic effects of LIPUS in FI.

Conclusion: Our investigation on a large animal model demonstrated that LIPUS is a promising adjunctive approach for the regeneration of periodontitis tissue, paving a new avenue for LIPUS application in the field of periodontal regenerative medicine.

Impact of photobiomodulation and low-intensity pulsed ultrasound adjunctive interventions on orthodontic treatment duration during clear aligner therapy: A retrospective study

OBJECTIVE

To assess the efficiency of low-intensity pulsed ultrasound (LIPUS) and photobiomodulation (PBM) interventions in accelerating orthodontic tooth movement during clear aligner therapy (CAT).

MATERIALS AND METHODS

This retrospective study was carried out on the records of 84 subjects who were treated using CAT. Twenty-eight patients were treated using CAT with a daily use of LIPUS for 20 minutes, 28 patients were treated using CAT with a daily use of PBM for 10 minutes, and 28 patients were treated using CAT alone. The total duration of treatment was recorded for all patients. One-way analysis of variance and post hoc Tukey test were used to assess whether there was any significant difference in total treatment duration among the three groups (P < .05).

RESULTS

The mean treatment durations in days were 719 ± 220, 533 ± 242, and 528 ± 323 for the control, LIPUS, and PBM groups, respectively. The LIPUS group showed a 26% reduction, on average, in treatment duration when compared with the control group, whereas the PBM group showed an average 26.6% reduction in the treatment duration when compared with the control group. The results showed that there were statistically significant differences among the groups (P = .011). Treatment durations were significantly reduced in the LIPUS and PBM groups as compared with the control (P = .027 and P = .023, respectively), with no statistically significant differences between the LIPUS and PBM groups (P = .998).

CONCLUSIONS

Daily use of LIPUS or PBM as adjunctive interventions during CAT could reduce the duration of orthodontic treatment.

Stimulation of oral mucosal regeneration by low intensity pulsed ultrasound: an in vivo study in a porcine model

PURPOSE

Many studies have shown the ability of low intensity pulsed ultrasound (LIPUS) to stimulate the bone, cartilage and tendon regeneration but only a few studied LIPUS interest in the regeneration of the oral mucosa. The purpose of this study is to assess the ability of LIPUS to stimulate the regeneration of the palatal mucosa in a porcine model.

METHODS

Ten adults mini-pigs were used. Two mucosal wounds were realised on the left and right side of the palate of each pig. The right side was treated with LIPUS at 1 MHz of frequency and 300 mW/cm2 of acoustic intensity. The left side was not treated. The morphology of the wound was evaluated using a polymer silicone molding.

RESULTS

The difference between two sides was significant from day 7 with a p value < 0.0001. At day 21, the wound is completely healed on all pigs with LIPUS. The control soft tissue defect exposed a healing of 80%.

CONCLUSIONS

The present study showed that the use of LIPUS on the oral mucosa accelerates the healing of the masticatory mucosa.

Effectiveness of low-intensity pulsed ultrasound on osteoarthritis of the temporomandibular joint: A review

Loading is indispensable for the growth, development, and maintenance of joint tissues, including mandibular condylar cartilage, but excessive loading or reduced host adaptive capacity can considerably damage the temporomandibular joint (TMJ), leading to temporomandibular joint osteoarthritis (TMJ-OA). TMJ-OA, associated with other pathological conditions and aging processes, is a highly degenerative disease affecting the articular cartilage. Many treatment modalities for TMJ-OA have been developed. Traditional clinical treatment includes mainly nonsurgical options, such as occlusal splints. However, non-invasive therapy does not achieve joint tissue repair and regeneration. Growing evidence suggests that low-intensity pulsed ultrasound (LIPUS) accelerates bone fracture healing and regeneration, as well as having extraordinary effects in terms of soft tissue repair and regeneration. The latter have received much attention, and various studies have been performed to evaluate the potential role of LIPUS in tissue regeneration including that applied to articular cartilage. The present article provides an overview of the status of LIPUS stimulation used to prevent the onset and progression of TMJ-OA and enhance the tissue regeneration of mandibular condylar cartilage. The etiology and management of TMJ-OA are explained briefly, animal models of TMJ-OA are described, and the effectiveness of LIPUS on cell metabolism and tissue regeneration in the TMJ is discussed.

Low-Intensity Pulsed Ultrasound Stimulates Osteogenic Differentiation of Periosteal Cells In Vitro

Adequate bone volume is required for osseointegrated implants to restore lost teeth and oral function. Several studies have demonstrated potential advantage of stem cells in regenerative medicine using osteoblasts. The periosteum is composed of osteoblasts, fibroblasts, and osteoprogenitor cells. It may be an alternative source for bone tissue engineering because of easy isolation and rapid proliferation in vivo and in vitro. Low-intensity pulsed ultrasound (LIPUS) has proved successful in recoveries from nonunions, delayed unions, and fracture of the bone in both animal experiments and clinical treatments. The study was to investigate the influence of LIPUS on the osteogenic differentiation in murine periosteum-derived cells (PDCs) and the underlying mechanism of LIPUS. PDCs were treated daily with LIPUS for 20 min up to 21 days with 3 MHz frequency, 30 mW/cm² intensity, and pulse repetition frequency of 1 kHz. The effects of LIPUS on cell proliferation and viability were investigated. Osteogenic differentiation was analyzed by alkaline phosphatase (ALP)-positive cell staining, ALP activity assay, mineralized nodule formation, real-time reverse transcription-polymerase chain reaction, as well as western blotting. The results indicated that ultrasound stimulation did not significantly affect the proliferation of PDCs. But LIPUS significantly increased ALP activity on day 7 and markedly promoted formation of mineralized nodules on day 21. mRNA expression of ALP and osteocalcin was significantly upregulated by stimulation with LIPUS. LIPUS enhanced gene expression of both bone morphogenetic protein-2 (BMP-2) and osterix only in the presence of osteogenic medium. LIPUS stimulation did not affect Smad 1 and Smad 5 protein expression, but significantly upregulated protein levels of BMP-2 and phosphor-Smad 1/5/9 in PDCs. Thus, LIPUS stimulation increased early osteogenic differentiation in a normal medium and further enhanced expression of BMP-2 and subsequent osterix expression through the canonical Smad-signaling pathway in an osteogenic medium, leading to mineral apposition. Therefore, LIPUS might have potential to promote osteogenesis in PDCs. Impact statement There are few studies on periosteum-derived cells (PDCs) because conventional methods of their isolation are relatively difficult to procure abundant cells for cell culture and the total cell numbers are limited. In this study, a modified isolation technique of murine calvarial PDCs using gelatin is described. PDCs were initiated to emerge as early as day 3 and showed increased proliferation, which can be used for further studies. Low-intensity pulsed ultrasound stimulation increased early osteogenic differentiation in a normal medium and further enhanced expression of bone morphogenic protein-2 and subsequent osterix expression through the canonical Smad-signaling pathway in an osteogenic medium, leading to mineral apposition.

Comparison of high-intensity laser therapy and combination of ultrasound treatment and transcutaneous nerve stimulation on cervical pain associated with cervical disc herniation: A randomized trial

The aim of the study was to compare the effect of high-intensity laser therapy (HILT) and a combination of transcutaneous nerve stimulation (TENS) and ultrasound (US) treatment on pain, range of motion (ROM) and functional activity on cervical pain associated with cervical disc herniation (CDH). A total of 40 patients (22 women and 18 men) affected by CDH were enrolled in this study. Patients were randomly divided into two groups. In group 1 (20 subjects), patients received 20 sessions of HILT plus exercise, while in group 2 (20 subjects), a combination of US, TENS and exercise were applied. The outcomes were cervical segment ROM, pain level measured by visual analogue scale (VAS), and functional activity measured by neck pain and disability scale (NPADS) before and after the therapy. The level of statistical significance was set as p < 0.05. There was no difference for cervical ROM, VAS and NPADS values between the groups at the baseline (p> 0.05). After the treatment, cervical ROM, VAS and NPADS values were significantly improved in both groups (p < 0.05). When the groups were compared in terms of post treatment VAS, NPADS and ROM values, no statistical significance was found between the two groups (p> 0.05). Both of therapeutic modalities demonstrated analgesic efficacy and improved the function in patients affected by CDH after 4 weeks of therapy (total 20 treatment sessions in 5 days a week). Both the HILT plus exercise program and the TENS / US plus exercise program were found to be effective in improving cervical range of motion and quality of life by reducing pain. These two treatment programs have similar effects in the treatment of cervical pain associated with CDH and can be used as an alternative to each other in clinical applications. However; It is clear that futher studies are needed to investigate the principles of application of HILT to painful areas or tissues (amount of area applied, dose applied, energy delivered, number of pulses, duration of session, frequency of sessions) and to exclude the effects of exercise treatment on the results of both treatment groups.

Effects of Ultrasound, Laser and Exercises on Temporomandibular Joint Pain and Trismus Following Head and Neck Cancer

OBJECTIVE

To compare the effects of low intensity ultrasound (LIUS), traditional exercise therapy (TET), low level laser therapy (LLLT) and TET on temporomandibular joint (TMJ) pain and trismus following recovery from head and neck cancer (HNC).

METHODS

Sixty participants following, who had experienced HNC, were randomly allocated to three groups of 20 people each. Each group received different therapy. Group A received LIUS and TET; group B received LLLT and TET; while group C received TET. All 60 participants were evaluated under the visual analog scale (VAS), the University of Washington Quality of Life questionnaire (UW-QOL) and the Vernier caliper scale (VCS) at the beginning of the therapies and after 4 weeks.

RESULTS

ANOVA test revealed significant improvements across all three groups with outcomes of p<0.05. The results of the UW-QOL questionnaire showed a significant difference between groups A, B and C in favor of group A (p<0.05). The VAS results showed a more improvement in group A as compared to group B (p<0.05), while there was no statistical difference between groups B and C (p>0.05). The VCS results showed more improvement for the individuals in group B as compared to those in group C (p<0.05), while there was minimal difference between groups A and B (p>0.05).

CONCLUSION

The LIUS and TET are more effective than LLLT and/or TET in reducing TMJ pain and trismus following HNC.

Possible reparative effect of low-intensity pulsed ultrasound (LIPUS) on injured meniscus

Menisci are a pair of crescent-shaped fibrocartilages, particularly of which their inner region of meniscus is an avascular tissue. It has characteristics similar to those of articular cartilage, and hence is inferior in healing. We previously reported that low-intensity pulsed ultrasound (LIPUS) treatment stimulates the production of CCN2/CTGF, a protein involved in repairing articular cartilage, and the gene expression of major cartilage matrices such as type II collagen and aggrecan in cultured chondrocytes. Therefore, in this present study, we investigated whether LIPUS has also favorable effect on meniscus cells and tissues. LIPUS applied with a 60 mW/cm² intensity for 20 min stimulated the gene expression and protein production of CCN2 via ERK and p38 signaling pathways, as well as gene expression of SOX9, aggrecan, and collagen type II in human inner meniscus cells in culture, and slightly stimulated the gene expression of CCN2 and promoted the migration in human outer meniscus cells in culture. LIPUS also induced the expression of Ccn2, Sox9, Col2a1, and Vegf in rat intact meniscus. Furthermore, histological evaluations showed that LIPUS treatment for 1 to 4 weeks promoted healing of rat injured lateral meniscus, as evidenced by better and earlier angiogenesis and extracellular matrix synthesis. The data presented indicate that LIPUS treatment might prevent meniscus from degenerative change and exert a reparative effect on injured meniscus via up-regulation of repairing factors such as CCN2 and that it might thus be useful for treatment of an injured meniscus as a non-invasive therapy.

Bone Texture Fractal Dimension Analysis of Ultrasound-Treated Bone around Implant Site: A Double-Blind Clinical Trial

Objectives

To evaluate the efficacy of bone texture fractal dimension (FD) analysis method in predicting implant stability from intraoral periapical radiographs using two implant protocols.

Materials and Methods

A double-blind clinical trial was conducted on 22 subjects who needed dental implants. The participants were randomized into two groups, the control group with standard implant protocol treatment and the intervention group with added low-intensity power ultrasound treatment (LIPUS) besides the standard implant protocol. The FD values of bone density were carried out on the mesial and distal sides of the implant on digital intraoral radiographs using the box-counting method. Both resonance frequency (RF) and fractal dimension (FD) were assessed in three time intervals: after surgery and before and after loading.

Results

FD on both the mesial and distal sides serve as very good-to-excellent tests with high validity (ROC area exceeding 0.8) in predicting high implant stability (ISQ ≥ 70). The mesial side measurements were consistently better than the distal side among the intervention groups. The optimum cutoff value for the FD-mesial side that predicts a highly stable implant (ISQ ≥ 70) is ≥1.505. At this optimum cutoff value, the mesial side FD is associated with a perfect sensitivity (100%) and fairly high specificity (86.5%).

Conclusion

The FD analysis could be recommended as an adjunctive quantitative method in prediction of the implant stability with very high sensitivity and specificity. This trial is registered with ISRCTN72648040.

Low-intensity pulsed ultrasound stimulation facilitates in vitro osteogenic differentiation of human adipose-derived stem cells via up-regulation of heat shock protein (HSP)70, HSP90, and bone morphogenetic protein (BMP) signaling pathway

Low-intensity pulsed ultrasound (LIPUS) has positive effects on osteogenic differentiation. However, the effect of LIPUS on osteogenic differentiation of human adipose-derived stem cells (hASCs) is unclear. In the present study, we investigated whether LIPUS could promote the proliferation and osteogenic differentiation of hASCs. hASCs were isolated and osteogenically induced with LIPUS stimulation at 20 and 30 mW cm^-2 for 30 min day^-1 Cell proliferation and osteogenic differentiation potential of hASCs were respectively analyzed by cell counting kit-8 assay, Alizarin Red S staining, real-time polymerase chain reaction, and Western blotting. The results indicated that LIPUS stimulation did not significantly affect the proliferation of hASCs, but significantly increased their alkaline phosphatase activity on day 6 of culture and markedly promoted the formation of mineralized nodules on day 21 of culture. The mRNA expression levels of runt-related transcription factor, osteopontin, and osteocalcin were significantly up-regulated by LIPUS stimulation. LIPUS stimulation did not affect the expression of heat shock protein (HSP) 27, HSP40, bone morphogenetic protein (BMP)-6 and BMP-9, but significantly up-regulated the protein levels of HSP70, HSP90, BMP-2, and BMP-7 in the hASCs. Further studies found that LIPUS increased the mRNA levels of Smad 1 and Smad 5, elevated the phosphorylation of Smad 1/5, and suppressed the expression of BMP antagonist Noggin. These findings indicated that LIPUS stimulation enhanced osteogenic differentiation of hASCs possibly through the up-regulation of HSP70 and HSP90 expression and activation of BMP signaling pathway. Therefore, LIPUS might have the potential to promote the repair of bone defect.

Low-intensity pulsed ultrasound reduces periodontal atrophy in occlusal hypofunctional teeth

OBJECTIVE

To clarify whether low-intensity pulsed ultrasound (LIPUS) exposure has recovery effects on the hypofunctional periodontal ligament (PDL) and interradicular alveolar bone (IRAB).

MATERIALS AND METHODS

Twelve-week-old male Sprague-Dawley rats were divided into three groups (n = 5 each): a normal occlusion (C) group, an occlusal hypofunction (H) group, and an occlusal hypofunction group subjected to LIPUS (HL) treatment. Hypofunctional occlusion of the maxillary first molar (M1) of the H and HL groups was induced by the bite-raising technique. Only the HL group was irradiated with LIPUS for 5 days. The IRAB and PDL of M1 were examined by microcomputed tomography (micro-CT) analysis. To quantify mRNA expression of cytokines involved in PDL proliferation and development, real-time reverse transcription quantitative PCR (qRT-PCR) was performed for twist family bHLH transcription factor 1 (Twist1), periostin, and connective tissue growth factor (CTGF) in the PDL samples.

RESULTS

Micro-CT analysis showed that the PDL volume was decreased in the H group compared with that of the C and HL groups. Both bone volume per tissue volume (BV/TV) of IRAB was decreased in the H group compared with that in the C group. LIPUS exposure restored BV/TV in the IRAB of the HL group. qRT-PCR analysis showed that Twist1, periostin, and CTGF mRNA levels were decreased in the H group and increased in the HL group.

CONCLUSION

LIPUS exposure reduced the atrophic changes of alveolar bone by inducing the upregulation of periostin and CTGF expression to promote PDL healing after induction of occlusal hypofunction.

Low-intensity pulsed ultrasound (LIPUS) treatment of cultured chondrocytes stimulates production of CCN family protein 2 (CCN2), a protein involved in the regeneration of articular cartilage: mechanism underlying this stimulation

OBJECTIVE

CCN family protein 2/connective tissue growth factor (CCN2/CTGF) promotes cartilage regeneration in experimental osteoarthritis (OA) models. However, CCN2 production is very low in articular cartilage. The aim of this study was to investigate whether or not CCN2 was promoted by cultured chondrocytes treated with low-intensity pulsed ultrasound (LIPUS) and to clarify its mechanism.

METHODS

Human chondrocytic cell line (HCS)-2/8, rat primary epiphyseal and articular cartilage cells, and Ccn2-deficient chondrocytes that impaired chondrocyte differentiation, were treated with LIPUS for 20 min at 3.0 MHz frequency and 60 mW/cm² power. Expressions of chondrocyte differentiation marker mRNAs were examined by real-time PCR (RT-PCR) analysis from HCS-2/8 cells and Ccn2-deficient chondrocytes at 30 min and 1 h after LIPUS treatment, respectively. CCN2 production was examined by Western blotting after 5 h of LIPUS treatment. Moreover, Ca²⁺ influx was measured by using a Fluo-4 probe.

RESULTS

The gene expression of chondrocyte differentiation markers and CCN2 production were increased in cultured chondrocytes treated with LIPUS. In addition, Ca²⁺ influx and phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK)1/2 were increased by LIPUS treatment, and the stability of TRPV4 and BK_ca channel mRNAs was decreased by siRNA against CCN2. Consistent with those findings, the LIPUS-induced the gene expressions of type II collagen (COL2a1) and Aggrecan (ACAN) observed in wild-type cells were not observed in the Ccn2-deficient chondrocytes.

CONCLUSION

These data indicate that chondrocyte differentiation represented by CCN2 production was mediated via MAPK pathways activated by LIPUS-stimulated Ca²⁺ influx, which in turn was supported by the induced CCN2 molecules in articular chondrocytes.

Effect of gingival fibroblasts and ultrasound on dogs' root resorption during orthodontic treatment

Objectives:

To investigate the effect of using osteogenic induced gingival fibroblasts (OIGFs) and low intensity pulsed ultrasound (LIPUS) on root resorption lacunae volume and cementum thickness in beagle dogs that received orthodontic tooth movement.

Materials and Methods:

Seven beagle dogs were used, from which gingival cells (GCs) were obtained and were induced osteogenically to produce OIGFs. Each third and fourth premolar was randomly assigned to one of the five groups, namely, LIPUS, OIGFs, bone morphogenetic protein-2 (BMP-2), OIGFs + LIPUS, and control. All groups received 4 weeks of bodily tooth movement, then LIPUS-treated groups received LIPUS for 20 min/day for 4 weeks, and OIGFs groups received an injection of OIGFs near the root apex. Microcomputed tomography analysis was used to calculate root resorption lacunae volume and histomorphometric analysis was performed to measure the cementum thickness of each root at 3 root levels on compression and tension sides.

Results:

There was no significant difference in resorption volume between the treatment groups. OIGFs + LIPUS increased cementum thickness (P > 0.05) in third premolars near the apex, and LIPUS increased cementum thickness (P > 0.05) in fourth premolars near the apex. Furthermore, BMP2 increased cementum thickness at the coronal third at the compression side.

Conclusion:

OIGFs, LIPUS, and BMP-2 can be potential treatments for orthodontically induced root resorption, however, improvements in experimental design and treatment parameters are required to further investigate these repair modalities.

Ultrasound: A Revenant Therapeutic Modality in Dentistry

An ultrasound (US) gives a visible image of the organs that are present inside the body. In medicine it serves for diagnosing and also its therapeutic benefits are well established for bone healing, osteointegration and soft tissue healing. In dentistry it is widely used for diagnostic purposes. When it was discovered it was introduced for therapeutic purposes, but due to lack of clinical studies its use as therapy was remittent in dentistry. The aim of the present paper was to establish the efficiency of therapeutic US in maxillofacial region for alleviating the pain and to see the other applications. Our search included the English terms like ultrasonography, applications, dentistry in Google search engine, PubMed and Medline from 1980 to 2015. We found very few articles showing the effects of therapeutic Ultrasound (US) in treatment of pain and healing in dentistry. We concluded that clinical benefits of in vivo studies were very little and demands further rigorous research to strive for the therapeutic success of US.

Ultrasound Stimulation of Different Dental Stem Cell Populations: Role of Mitogen-activated Protein Kinase Signaling

INTRODUCTION

Mesenchymal stem cells (MSCs) from dental tissues may respond to low-intensity pulsed ultrasound (LIPUS) treatment, potentially providing a therapeutic approach to promoting dental tissue regeneration. This work aimed to compare LIPUS effects on the proliferation and MAPK signaling in MSCs from rodent dental pulp stem cells (DPSCs) compared with MSCs from periodontal ligament stem cells (PDLSCs) and bone marrow stem cells (BMSCs).

METHODS

Isolated MSCs were treated with 1-MHz LIPUS at an intensity of 250 or 750 mW/cm2 for 5 or 20 minutes. Cell proliferation was evaluated by 5-bromo-2-deoxyuridine (BrdU) staining after 24 hours of culture following a single LIPUS treatment. Specific ELISAs were used to determine the total and activated p38, ERK1/2, and JNK MAPK signaling proteins up to 4 hours after treatment. Selective MAPK inhibitors PD98059 (ERK1/2), SB203580 (p38), and SP600125 (JNK) were used to determine the role of activation of the particular MAPK pathways.

RESULTS

The proliferation of all MSC types was significantly increased after LIPUS treatment. LIPUS at a 750-mW/cm2 dose induced the greatest effects on DPSCs. BMSC proliferation was stimulated in equal measures by both intensities, whereas 250 mW/cm2 LIPUS exposure exerted maximum effects on PDLSCs. ERK1/2 was activated immediately in DPSCs after treatment. Concomitantly, DPSC proliferation was specifically modulated by ERK1/2 inhibition, whereas p38 and JNK inhibition exerted no effects. In BMSCs, JNK MAPK signaling was LIPUS activated, and the increase in proliferation was blocked by specific inhibition of the JNK pathway. In PDLSCs, JNK MAPK signaling was activated immediately after LIPUS, whereas p-p38 MAPK increased significantly in these cells 4 hours after exposure. Correspondingly, JNK and p38 inhibition modulated LIPUS-stimulated PDLSC proliferation.

CONCLUSIONS

LIPUS promoted MSC proliferation in an intensity and cell-specific dependent manner via activation of distinct MAPK pathways.

Effect of low-intensity pulsed ultrasound on orthodontically induced root resorption caused by torque: A prospective, double-blind, controlled clinical trial

Objectives: 

To evaluate the effects of low-intensity pulsed ultrasound (LIPUS) on orthodontically induced tooth root resorption caused by torque in human subjects.

Materials and Methods: 

Ten healthy patients (12–35 years of age) who required extraction of all first premolars as a part of their routine orthodontic treatment were recruited. A 15° twist was applied in the arch wire using 0.019 × 0.025-inch TMA in a 0.022-inch bracket system (Synergy R) that produced a buccal root torque of approximately 5 N/mm at the bracket level. Using a split mouth design, randomization, and blinding, one side of the arch received LIPUS for 20 minutes per day for 4 weeks at an incident intensity of 30 mW/cm2 of the transducers’ surface area. The other side served as a self-control, which received a sham transducer. After 4 weeks, all first premolars were extracted and micro–computed tomographic analysis was performed on these extracted teeth. A linear mixed-model statistical analysis was used.

Results: 

LIPUS-treated teeth showed significantly less total volume of resorption lacunae compared to control teeth by a mean difference of (0.54 ± 0.09 mm3) (P &lt; .001) and percentage of root resorption by a mean difference of (0.33 ± 0.05 mm3) (P &lt; .001). In addition, significantly fewer resorption lacunae were found on all root surfaces in the LIPUS group compared to the control except in the instance of the distal surface.

Limitations: 

This study was performed on limited number of cases during a 4-week period.

Conclusions: 

LIPUS minimizes root resorption when applied during torque tooth movement over a 4-week period.

A Combination of Low-Intensity Pulsed Ultrasound and Nanohydroxyapatite Concordantly Enhances Osteogenesis of Adipose-Derived Stem Cells From Buccal Fat Pad

The osteogenic induction of adipose-derived stem cells (ADSCs) has been regarded as an important step in bone tissue engineering. In the present study, we focused on the buccal fat pad (BFP) as a source of adipose tissue, since BFPs are encapsulated by adipose tissue and are often coextirpated during oral surgery. Low-intensity pulsed ultrasound (LIPUS) is effective in the treatment of fractures, and nanohydroxyapatite (NHA) is known as a bone substitute material. Here we investigated the synergistic effects of LIPUS and NHA in the osteogenesis of ADSCs. A combination of LIPUS irritation and NHA as a scaffold significantly increased the osteogenic differentiation of ADSCs in vitro, and in our in vivo study in which ADSCs were transplanted into calvarial bone defects of nude mice, the combinational effect greatly enhanced the new bone formation of the margin of the defects. These results demonstrate that synergistic effects of LIPUS and NHA are capable of effectively inducing the differentiation of ADSCs into osteoblasts, and they suggest a novel therapeutic strategy for bone regeneration by the autotransplantation of ADSCs.

Low-intensity pulsed ultrasound in dentofacial tissue engineering

Oral and maxillofacial diseases affect millions of people worldwide and hence tissue engineering can be considered an interesting and clinically relevant approach to regenerate orofacial tissues after being affected by different diseases. Among several innovations for tissue regeneration, low-intensity pulsed ultrasound (LIPUS) has been used extensively in medicine as a therapeutic, operative, and diagnostic tool. LIPUS is accepted to promote bone fracture repair and regeneration. Furthermore, the effect of LIPUS on soft tissues regeneration has been paid much attention, and many studies have performed to evaluate the potential use of LIPUS to tissue engineering soft tissues. The present article provides an overview about the status of LIPUS stimulation as a tool to be used to enhance regeneration/tissue engineering. This review consists of five parts. Part 1 is a brief introduction of the acoustic description of LIPUS and mechanical action. In Part 2, biological problems in dentofacial tissue engineering are proposed. Part 3 explores biologic mechanisms of LIPUS to cells and tissues in living body. In Part 4, the effectiveness of LIPUS on cell metabolism and tissue regeneration in dentistry are summarized. Finally, Part 5 relates the possibility of clinical application of LIPUS in orthodontics. The present review brings out better understanding of the bioeffect of LIPUS therapy on orofacial tissues which is essential to the successful integration of management remedies for tissue regeneration/engineering. To develop an evidence-based approach to clinical management and treatment of orofacial degenerative diseases using LIPUS, we would like to be in full pursuit of LIPUS biotherapy. Still, there are many challenges for this relatively new strategy, but the up to date achievements using it promises to go far beyond the present possibilities.

Cellular and molecular actions of CCN2/CTGF and its role under physiological and pathological conditions

CCN family protein 2 (CCN2), also widely known as connective tissue growth factor (CTGF), is one of the founding members of the CCN family of matricellular proteins. Extensive investigation on CCN2 over decades has revealed the novel molecular action and functional properties of this unique signalling modulator. By its interaction with multiple molecular counterparts, CCN2 yields highly diverse and context-dependent biological outcomes in a variety of microenvironments. Nowadays, CCN2 is recognized to conduct the harmonized development of relevant tissues, such as cartilage and bone, in the skeletal system, by manipulating extracellular signalling molecules involved therein by acting as a hub through a web. However, on the other hand, CCN2 occasionally plays profound roles in major human biological disorders, including fibrosis and malignancies in major organs and tissues, by modulating the actions of key molecules involved in these clinical entities. In this review, the physiological and pathological roles of this unique protein are comprehensively summarized from a molecular network-based viewpoint of CCN2 functionalities.

Low-intensity pulsed ultrasound stimulation facilitates osteogenic differentiation of human periodontal ligament cells

Human periodontal ligament cells (hPDLCs) possess stem cell properties, which play a key role in periodontal regeneration. Physical stimulation at appropriate intensities such as low-intensity pulsed ultrasound (LIPUS) enhances cell proliferation and osteogenic differentiation of mesechymal stem cells. However, the impacts of LIPUS on osteogenic differentiation of hPDLCs in vitro and its molecular mechanism are unknown. This study was undertaken to investigate the effects of LIPUS on osteogenic differentiation of hPDLCs. HPDLCs were isolated from premolars of adolescents for orthodontic reasons, and exposed to LIPUS at different intensities to determine an optimal LIPUS treatment dosage. Dynamic changes of alkaline phosphatase (ALP) activities in the cultured cells and supernatants, and osteocalcin production in the supernatants after treatment were analyzed. Runx2 and integrin β1 mRNA levels were assessed by reverse transcription polymerase chain reaction analysis after LIPUS stimulation. Blocking antibody against integrinβ1 was used to assess the effects of integrinβ1 inhibitor on LIPUS-induced ALP activity, osteocalcin production as well as calcium deposition. Our data showed that LIPUS at the intensity of 90 mW/cm2 with 20 min/day was more effective. The ALP activities in lysates and supernatants of LIPUS-treated cells started to increase at days 3 and 7, respectively, and peaked at day 11. LIPUS treatment significantly augmented the production of osteocalcin after day 5. LIPUS caused a significant increase in the mRNA expression of Runx2 and integrin β1, while a significant decline when the integrinβ1 inhibitor was used. Moreover, ALP activity, osteocalcin production as well as calcium nodules of cells treated with both daily LIPUS stimulation and integrinβ1 antibody were less than those in the LIPUS-treated group. In conclusion, LIPUS promotes osteogenic differentiation of hPDLCs, which is associated with upregulation of Runx2 and integrin β1, which may thus provide therapeutic benefits in periodontal tissue regeneration.

Low-intensity pulsed ultrasound accelerates tooth movement via activation of the BMP-2 signaling pathway

The present study was designed to determine the underlying mechanism of low-intensity pulsed ultrasound (LIPUS) induced alveolar bone remodeling and the role of BMP-2 expression in a rat orthodontic tooth movement model. Orthodontic appliances were placed between the homonymy upper first molars and the upper central incisors in rats under general anesthesia, followed by daily 20-min LIPUS or sham LIPUS treatment beginning at day 0. Tooth movement distances and molecular changes were evaluated at each observation point. In vitro and in vivo studies were conducted to detect HGF (Hepatocyte growth factor)/Runx2/BMP-2 signaling pathways and receptor activator of NFκB ligand (RANKL) expression by quantitative real time PCR (qRT-PCR), Western blot and immunohistochemistry. At day 3, LIPUS had no effect on the rat orthodontic tooth movement distance and BMP-2-induced alveolar bone remodeling. However, beginning at day 5 and for the following time points, LIPUS significantly increased orthodontic tooth movement distance and BMP-2 signaling pathway and RANKL expression compared with the control group. The qRT-PCR and Western blot data in vitro and in vivo to study BMP-2 expression were consistent with the immunohistochemistry observations. The present study demonstrates that LIPUS promotes alveolar bone remodeling by stimulating the HGF/Runx2/BMP-2 signaling pathway and RANKL expression in a rat orthodontic tooth movement model, and LIPUS increased BMP-2 expression via Runx2 regulation.

Current status of low intensity pulsed ultrasound for dental purposes

Over the past few years, tissue engineering applied to the dental field has achieved relevant results. Tissue engineering can be described by actions taken to improve biological functions. Several methods have been described to enhance cellular performance and low intensity pulsed ultrasound (LIPUS) has shown to play an important role in cell metabolism. The present article provides an overview about the current status of LIPUS as a tissue engineering tool to be used to enhance tooth and periodontal regeneration.