Effect of Ultraviolet Irradiation of the Implant Surface on Progression of Periimplantitis--A Pilot Study in Dogs.

OBJECTIVE: The objective of this study was to investigate morphologically the progression of periimplantitis around an ultraviolet (UV)-light-irradiated implant in dogs. MATERIALS AND METHODS: Pure titanium implants (3.3 mm in diameter and 8 mm long) were placed into dog jawbone bilaterally. Implants on one side were irradiated with UV light for 15 minutes using a photodevice immediately before placement (UV group), whereas those on the other side were not irradiated (non-UV group). Osseointegration was confirmed 90 days after implant placement by radiography. Experimental periimplantitis was induced by the application of dental floss over 90 days. Clinical and radiographic examination and micro-computed tomography (micro-CT) were performed after 90 and 180 days, and bone resorption was measured. The bone-implant interface in tissue sections was examined by light microscopy. RESULTS: Bone resorption around the UV-irradiated implant was less pronounced than around the non-UV-irradiated implant in the ligature-induced periimplantitis model. Tissue section images revealed no contact and partial destruction at the bone-implant interface. CONCLUSION: Within the limitations of this preliminary investigation, it is suggested that UV-light-irradiated implants suppress spontaneous progression of periimplantitis.

Contribution of nitrergic nerve in canine gingival reactive hyperemia.

Reactive hyperemia reflects a compensatory vasodilation response of the local vasculature in ischemic tissue. The purpose of this study is to clarify the mechanism of regulation of this response in gingival circulation by using pharmacological analysis of reactive hyperemia and histochemical analysis of gingival tissue. Application of pressure to the gingiva was used to create temporary ischemia, and gingival blood flow was measured after pressure release. Reactive hyperemia increased in proportion to the duration of pressure. Systemic hemodynamics remained unaffected by the stimulus; therefore, the gingival reactive hyperemia reflected a local adjustment in circulation. Gingival reactive hyperemia was significantly suppressed by nitric oxide (NO) synthase inhibitors, especially the neural NO synthase-selective antagonist 7-nitroindazole, but not by anticholinergic drugs, ß-blockers, or antihistaminergic drugs. Moreover, immunohistochemical staining for neural NO synthase and histochemical staining for NADPH diaphorase activity were both positive in the gingival perivascular region. These histochemical and pharmacological analyses show that reactive hyperemia following pressure release is mediated by NO-induced vasodilation. Furthermore, histochemical analysis strongly suggests that NO originates from nitrergic nerves. Therefore, NO may play an important role in the neural regulation of local circulation in gingival tissue ischemia.

Regeneration processes of alveolar bone and microvascular changes after the application of platelet-rich fibrin.

OBJECTIVES: Platelet-rich fibrin (PRF) is a promising agent for bone regeneration (BR). Platelets contain several growth factors that promote angiogenesis and BR. In this study, we observed the morphology of alveolar BR. METHODS: PRF (Advanced PRF: A-PRF) was prepared by extracting 10 mL of blood from each dog in a collection tube before tooth extraction. The samples were centrifuged at 200 × g for 8 min and incubated for 10 min to allow clotting. The alveolar socket on the dentition's right side was densely filled with PRF. The opposite side, which did not receive PRF, served as the control group. Different methods were used for specimen preparation and observation. Sections stained with hematoxylin and eosin were observed under a light microscope. Bone specimens were observed using stereoscopic microscopy. The resin cast models were examined using a scanning electron microscope. Moreover, bone formation ratio and height were measured. RESULTS: Fourteen days postoperatively, angiogenesis and bone deposition were more advanced in the PRF group than in the control group. Thirty days postoperatively, both groups developed porous bone. In the PRF group, new bone trabeculae (BT) and a network of blood vessels were formed in the bone marrow. Ninety days postoperatively, the resin cast showed a normal bone structure with BT and bone marrow. Thick BT were observed in the PRF group. CONCLUSIONS: Growth factors in PRF stimulate microcirculation and promote angiogenesis and bone deposition. The benefits of PRF include safety and increased bone formation.

Application of multi-directionally forged high-strength titanium to dental implants in beagle dogs.

Pure titanium is widely used as a material in dental implants. However, it possesses inferior mechanical strength. This study aimed to elucidate the efficacy of acid treated multi-directionally forged (MDF) pure titanium in vivo. We verified the temporal changes until osseointegration in beagle dogs. Using two types of experimental materials (conventional pure titanium or MDF pure titanium), new bone formation was assessed using morphological examinations, and the bone-to-implant contact (BIC) value was evaluated at each time point (14, 30, and 90 days after the operation). As such, new bone formation was observed around the acid-etched MDF group, in which the BIC value was highest, followed by that in the acid-etched pure titanium group. MDF pure titanium implants showed early promotion of new bone formation compared to conventional titanium implants. The new acid-treated MDF made of pure titanium could be applied to humans in the future to prove its practicality.

Advanced platelet-rich fibrin (A-PRF) has an impact on the initial healing of gingival regeneration after tooth extraction.

OBJECTIVES: Platelet-rich fibrin (PRF) is widely used in wound healing because it contains several growth factors, including vascular endothelial growth factor (VEGF). In this study, we investigated the effects of advanced PRF (A-PRF) in early-stage gingival regeneration after tooth extraction. METHODS: Blood sample was collected from females beagle dogs (age: 12 months) before tooth extraction for A-PRF preparation. All animals were sacrificed by perfusion-fixation on postoperative days 1, 3, and 7. The upper jaws were prepared for hematoxylin and eosin staining and immunostaining (for CD34 and VEGF). The lower jaw samples were prepared for scanning electron microscope observations. Blood flow in the gingiva before and after surgery was measured using laser Doppler flowmetry. RESULTS: In the A-PRF group, a large number of microvessels were observed in the gingival tissue on postoperative day 1. The microvessels in the control group were fewer and sparse. Regarding the vascular resin cast, a large number of new blood vessels were observed on postoperative day 1 in the A-PRF group. A stronger CD34-positive signal was obtained around the blood vessels in the A-PRF group than in the control group. Further, a strong VEGF-positive signal was observed in the perivascular tissue in the A-PRF group. Gingival blood flow was significantly higher in the A-PRF group after surgery. CONCLUSION: A-PRF had a positive impact on angiogenesis in the gingiva through the induction of VEGF expression. Thus, A-PRF may be beneficial for gingival tissue regeneration.

Double superior vena cava and anomaly of cardiovascular system with a review of the literature.

In a student course of gross anatomy dissection at Kanagawa Dental College in 2008, we found an extremely rare case of the double superior vena cava that has a shunt between the right and left atria of a 81-year-old Japanese male cadaver. The left superior vena cava passed through the space between the left cardiac auricle and the left pulmonary vein and entered the coronary sulcus. Then it opened near the opening of the inferior vena cava as the coronary venous sinus to the right atrium. The upper edge of the interatrial septum was located at the site where the right superior vena cava opened to the right atrium. Accordingly, the right atrium connected with left atrium through this site. We discuss the anatomy and etiology of these anomalous structures with a brief review of the literature.

Changes in the microcirculation in periodontal tissue due to experimental peri-implantitis.

OBJECTIVES: Peri-implantitis causes dislodgement of dental implants due to inflammation in the peri-implant tissue. The microcirculation in the periodontal tissue undergoes morphological and physiological changes due to inflammation. The immune mechanism of peri-implantitis differs from that of periodontitis. In this study, we examined the changes in the microcirculation in the peri-implant tissue with experimentally induced inflammation, using morphological and physiological techniques. METHODS: Six beagle dogs were used in the experiment. After extracting both mandibular premolars, three titanium screw implants were inserted on each side of the mandibular jaw. Dental floss was placed on the right side for 90 days in the study group but not in the control group. Microvascular resin cast models were created, and morphological changes were observed using scanning electron microscopy. Periodontal blood flow was measured using laser Doppler flowmetry. RESULTS: Ninety days after induction of inflammation, bone resorption was observed around the implant body. Osseointegration was impaired, and a gap at the implant-bone interface was observed. The resin cast models showed that inflamed gingival blood vessels had invaded the bone marrow through the resorbed apical margin of the alveolar bone. Analysis of the physiological data obtained using laser Doppler flowmetry showed a significant increase in blood flow around the implants with experimentally induced inflammation. CONCLUSIONS: Significant morphological and physiological changes occur in the gingival microcirculation of peri-implant tissue due to inflammation. Evaluating the vasculature and blood flow in the tissue surrounding the site of peri-implantitis may be helpful for pathologic analysis in clinical settings.

Application of deproteinized bovine bone mineral as proangiogenic scaffold for alveolar bone formation in beagle dogs.

Alveolar bone repair after tooth extraction is essential after oral surgeries. Various grafting materials are used to promote the regeneration of lost alveolar bone. This study analysed the morphological features of the tissue regeneration process using deproteinized bovine bone mineral (DBBM). DBBM was used to densely fill the extraction sockets in beagle dogs. Following resin casting of the vasculature, stereomicroscopy and scanning electron microscopy were used to observe blood vessels and hard tissues in haematoxylin and eosin-stained sections on postoperative days 14, 30 and 90 in conjunction with vascular endothelial growth factor (VEGF) immunostaining to evaluate alveolar bone vascularization. On day 14 post-operation, the DBBM granules tightly filled the extraction sockets, maintained alveolar margin height and formed a scaffold for aiding angiogenesis and new bone formation. On day 30, new bone formation was observed around the DBBM granules. By day 90, bone tissue regeneration progressed in both groups but was more pronounced in the DBBM group. Alveolar margin height was maintained in the DBBM group throughout the study. Furthermore, VEGF expression in the DBBM group was detected around newly formed bone. We conclude that DBBM acts as a suitable scaffold for new bone generation, as well as angiogenesis around healing alveolar bone, and that it has the potential to play a key role in vascularization and bone formation.

Vitamin C and eggshell membrane facilitate orthodontic tooth movement and induce histological changes in the periodontal tissue.

OBJECTIVES: Collagen remodeling of the periodontal tissue is an important mechanism that involves several biologically active substances to accelerate orthodontic tooth movement. It is known that Vitamin C (VC) enhances collagen production and induces tooth movement. Moreover, the eggshell membrane (ESM) is an integral component of various formulations used to promote wound healing. The purpose of our study was to determine the effects of combined treatment with VC and ESM on periodontal tissues during tooth movement. METHODS: Nine-week-old male osteogenic disorder Shionogi rats were randomized into four groups: control, VC, ESM, and VC + ESM. The control group was given tap water, and the VC, ESM, and VC + ESM groups were orally administered 0.1% VC solution, 1 wt% ESM solution, and a combination of 0.1 wt% VC and 1 wt% ESM solutions, respectively. A force of 25 or 75 g was applied for 10 days to produce orthodontic tooth movement. Distances of tooth movement were measured on days 3, 7, and 10 of treatment. Histological examination of the periodontal ligament was performed to determine the increase in type I and III collagen levels in response to treatment. RESULTS: Distances of tooth movement were significantly greater in the VC + ESM group than in the control group. The compression area of the alveolar bone showed increased osteoclastic activity and higher levels of bone resorption in the VC + ESM group. Expression levels of type I and III collagen in the tension area of the alveolar bone were higher in the VC + ESM group than in the control group. CONCLUSIONS: This study revealed that the combined administration of VC and ESM accelerated tooth movement by protecting the periodontal tissue during orthodontic treatment. The combined clinical application of VC and ESM could potentially shorten orthodontic treatment time.

Microcirculation changes in gingival tissue after ultrasonic tooth preparation in beagle dogs.

OBJECTIVE: Ultrasonic wave technology is widely used during dental treatments. We previously demonstrated that this method protects the gingival tissue. However, the physiological change on the gingival microvasculature caused by this method remains unclear. The aim of this study was to investigate the relationship between the morphological and physiological effects on gingival microcirculation when preparing teeth, using the conventional dental turbine or ultrasonic method. METHODOLOGY: The lower premolar teeth of beagle dogs were prepared along the gingival margin by using a dental turbine or ultrasonic wave instrument. Gingival vasculature changes were investigated using scanning electron microscopy for corrosion resin casts. Gingival blood flow at the preparation site was determined simultaneously by laser Doppler flowmetry. These assessments were performed immediately (Day 0), at 7 days and 30 days after tooth preparation. RESULTS: At day 0, in the turbine group, blood vessels were destroyed and some resin leaked. Furthermore, gingival blood flow at the site was significantly increased. In contrast, the ultrasonic group demonstrated nearly normal vasculature and gingival blood flow similar to the non-prepared group for 30 days after preparation. No significant alterations occurred in gingival circulation 30 days after either preparation; however, the turbine group revealed obvious morphological changes. CONCLUSIONS: Based on multiple approach analyses, this study demonstrated that ultrasonic waves are useful for microvascular protection in tooth preparation. Compared with a dental turbine, ultrasonic wave instruments caused minimal damage to gingival microcirculation. Tooth preparation using ultrasonic wave instruments could be valuable for protecting periodontal tissue.

Effect of physical stimulation (gingival massage) on age-related changes in gingival microcirculation.

The decline in circulatory function with aging may be alleviated by a combination of gingival massage (physical stimulation) and mechanical cleaning. Several studies have reported the systemic effect of physical stimulation on various parts of the body, including its therapeutic effect on pain in the neck and shoulders that becomes evident with age, and improvement in blood circulation. In contrast, few studies have reported on the changes in gingival microcirculation induced by gingival massage, while no previous study has evaluated the effect of gingival microcirculation on age-related changes in the hemodynamics of the oral cavity. This study aimed to investigate how gingival massage affects age-related changes in gingival microcirculation. Male Wistar rats (7-week, 6-month and 1-year old) were prepared for a gingival massage group and a control group. Mechanical stimulation was applied on the maxillary molar gingiva for 5 seconds twice a week for 4 weeks. Subsequently, gingival reactive hyperemia was measured using a laser Doppler flowmeter. In addition, morphological analyses were also performed by hematoxylin and eosin and Indian ink staining and a vascular resin cast model. Base Flow, maximum response (Peak), and time required for the maximum response to halve (T1/2) were reduced in 1-year-old rats compared with the other age groups. In the mechanical stimulated group, T1/2 was increased in 7-week, 6-month, and 1-year-old rats, and total blood flow (Mass) was increased in 6-month and 1-year-old rats. In addition, clear blood vessel networks and loop-like revascularization were only observed in the mechanical stimulated group. Changes in age-related decline in gingival microcirculatory function and vascular construction were reported in this study, and the results suggested that gingival massage activates both the functional and morphological aspects of gingival microcirculation and may be effective for maintaining oral health.

Effect of advanced platelet-rich fibrin on accelerating alveolar bone formation in dogs: a histological and immunofluorescence evaluation.

Several methods have been developed to regenerate lost alveolar bone. Platelet-rich fibrin (PRF) is a useful adjunct for new bone formation in dentistry. To elucidate the effect of advanced PRF (A-PRF) on bone formation, we inserted A-PRF clots in sockets after tooth extraction. Premolars were extracted from beagle dogs, and A-PRF was applied to the socket. New bone formation was assessed using histological and immunofluorescence examinations, and the bone formation ratio was evaluated 14 and 30 days postoperatively. Histological examination revealed newly formed bone filling the sockets up to the center in the A-PRF group at 14 days postoperatively, while thick and regular bone trabeculae were arranged in porous bone after 30 days. Higher expressions of osteocalcin and osteopontin were observed in newly formed bone in the A-PRF group, compared to the control group. The bone formation ratio was also higher in the A-PRF group than in the control group. Thus, A-PRF application may result in enhanced new bone formation and may aid in accelerating bone formation. A-PRF was more rapid than a self-limiting process during induction of bone formation by enhancing osteoblast activity and may be useful for bone formation in clinical medicine.

Effect of social isolation stress on saliva BDNF in rat.

Salivary glands produce various compounds, including brain-derived neurotrophic factor (BDNF), which serve as biomarkers of stress-related disorders. Social isolation-induced stress models a form of chronic mild stress that induces neurodegenerative changes in the brain and behavioral alterations. This study employed a rat model to determine whether social isolation stress affects BDNF levels in saliva. Male Sprague-Dawley rats were randomly allocated to social isolation stress (1 animal/cage) or control (3-4 animals/cage) groups and reared for 8 weeks. The concentration of BDNF was quantified in specific brain regions, blood, and saliva using enzyme-linked immunosorbent assay (ELISA). The levels of expression of Bdnf and tyrosine kinase B (TrkB) mRNA were quantified using reverse transcriptase-polymerase chain reaction. Behavioral alterations were analyzed using the open-field and elevated plus maze assays. The BDNF concentration was lower in the hippocampus, prefrontal cortex, blood, and saliva of the stress group than in those of the controls. Trkb expression in the hippocampus and prefrontal cortex was decreased by social isolation stress. Moreover, the social isolation stress group showed behavioral deficits in both tests. In conclusion, these findings indicate that social isolation stress may reduce the expression of BDNF protein in blood and saliva, thus providing a potentially valuable biomarker for diagnosis of stress-related disorders.

The retroesophageal right subclavian artery - A case report and review.

In a student course of gross anatomy dissection at Kanagawa Dental University in 2011, we encountered anomalous case of the right subclavian artery arising from the aortic arch as the last branch in an 84-year-old Japanese male cadaver. The anomalous artery ran obliquely upward, passed behind the esophagus and trachea, and ultimately ran toward right scalene gap. The area of distribution of the anomalous artery was normal. We report a case of retroesophageal right subclavian artery, and discuss its development, or relation with the thoracic duct, and its clinical importance. Despite this type of variation being relatively rare, reports on such a case have been accumulating. Owing to the recent development of CT and MRI, the number of clinical reports on this anomaly has been increasing.

Microcirculation alterations in experimentally induced gingivitis in dogs.

The present study aimed to morphologically examine the gingival microvascular network using a microvascular resin cast (MRC) technique, and to investigate how inflammatory disease functionally affects gingival microcirculation using laser Doppler flowmetry (LDF). We used four beagle dogs with healthy periodontal tissue as experimental animals. To cause periodontal inflammation, dental floss was placed around the cervical neck portions of the right premolars. The unmanipulated left premolars served as controls, and received plaque control every 7 days. After 90 days, gingivitis was induced in the experimental side, while the control side maintained healthy gingiva. To perform morphological examinations, we used an MRC method involving the injection of low-viscosity synthetic resin into the blood vessels, leading to peripheral soft-tissue dissolution and permitting observation of the bone, teeth, and vascular cast. Gingival blood flow was estimated using an LDF meter. The control gingival vasculature showed hairpin-loop-like networks along the tooth surface. The blood vessels had diameters of 20-40 µm and were regularly arranged around the cervical portion. On the other hand, the vasculature in the experimental group was twisted and gathered into spiral forms, with blood vessels that had uneven surfaces and smaller diameters of 8-10 µm. LDF revealed reduced gingival blood flow in the group with experimentally induced gingivitis compared to controls. The actual measurements of gingival blood flow by LDF were in agreement with the alterations that would be expected based on the gingivitis-induced morphological alterations observed with the MRC technique.

Microcirculation changes in gingival tissue after ultrasonic tooth preparation in beagle dogs

Abstract Ultrasonic wave technology is widely used during dental treatments. We previously demonstrated that this method protects the gingival tissue. However, the physiological change on the gingival microvasculature caused by this method remains unclear. Objective The aim of this study was to investigate the relationship between the morphological and physiological effects on gingival microcirculation when preparing teeth, using the conventional dental turbine or ultrasonic method. Methodology The lower premolar teeth of beagle dogs were prepared along the gingival margin by using a dental turbine or ultrasonic wave instrument. Gingival vasculature changes were investigated using scanning electron microscopy for corrosion resin casts. Gingival blood flow at the preparation site was determined simultaneously by laser Doppler flowmetry. These assessments were performed immediately (Day 0), at 7 days and 30 days after tooth preparation. Results At day 0, in the turbine group, blood vessels were destroyed and some resin leaked. Furthermore, gingival blood flow at the site was significantly increased. In contrast, the ultrasonic group demonstrated nearly normal vasculature and gingival blood flow similar to the non-prepared group for 30 days after preparation. No significant alterations occurred in gingival circulation 30 days after either preparation; however, the turbine group revealed obvious morphological changes. Conclusions Based on multiple approach analyses, this study demonstrated that ultrasonic waves are useful for microvascular protection in tooth preparation. Compared with a dental turbine, ultrasonic wave instruments caused minimal damage to gingival microcirculation. Tooth preparation using ultrasonic wave instruments could be valuable for protecting periodontal tissue.

Scanning electron microscopic observation of microvasculature in periodontium.

In this study, vascular resin cast models in the periodontium of beagle dogs were prepared and three-dimensional observation of the relationship between the gingiva and periodontal ligament (PDL) vascular network was performed. After the perfusion of Ringer's solution and fixative, synthetic resin was injected from the inferior alveolar arteries. Soft tissue was digested by proteinase solution and specimens were examined under scanning electron microscope (SEM). The gingival vascular network (GVN) in the region facing the teeth consisted of sulcular and junctional epithelium. The vascular network of the sulcular epithelium (SE) had a renal glomerulus-like form and the junctional epithelium (JE) consisted of squamous mesh. The gingival sulcular fluid exudated from the vascular network directly beneath the JE, and leukocytes permeated from the vascular network beneath the epithelium. Thus, we considered that the GVN performs an important function in the protection against the inflammation. Periodontal ligament had a polygonal mesh vascular network that was anastomosed to the venous plexus of alveolar bone through Volkmann's canals (VC). When occlusal force was applied, the blood in the periodontal vessels flowed out through VC into the bone marrow, and when the force was removed, it flowed backward into the PDL. This blood transfer acted as an absorber against occlusal force. Our findings suggest that the blood vessels of the gingiva perform an important function in defending against inflammation, while the blood vessels of the PDL play a key role in absorbing occlusal force.

Anatomical study of the coexistence of the postaortic left brachiocephalic vein with the postaortic left renal vein with a review of the literature.

In a student course of gross anatomy dissection at Kanagawa Dental University in 2009, we found an extremely rare case of the coexistence of the postaortic left brachiocephalic vein with the postaortic left renal vein of a 73-year-old Japanese male cadaver. The left brachiocephalic vein passes behind the ascending aorta and connects with the right brachiocephalic vein, and the left renal vein passes behind the abdominal aorta. These two anomalous cases mentioned above have been reported respectively. There have been few reports discussing coexistence of the postaortic left brachiocephalic vein with the postaortic left renal vein. We discuss the anatomical and embryological aspect of this anomaly with reference in the literature.

Morphological observation of the horseshoe kidney with circumaortic venous ring.

In a student course of gross anatomy dissection at Knagawa Dental College in 2010, we found an extremely rare case of the horseshoe kidney with circumaortic venous ring in a 43-year-old Japanese male cadaver. In this case, the kidney consisted of three parts: the original kidneys on both sides and an isthmus between them. The location of each kidney was lower than that of the normal kidney. The hili on both sides opened toward the ventral direction, and the ureters descended in front of the isthmus and entered the bladder normally. This horseshoe kidney had original left and right renal arteries that branched from the abdominal aorta. There were also two surplus arteries. There were three renal veins on the left side, and these renal veins formed the circumaortic venous ring. The anatomical and embryological significance of this anomaly and its associated vascular system are discussed. The anatomy and etiology of these anomalous structures are discussed with references in the literature.

Implications of cultured periodontal ligament cells for the clinical and experimental setting: a review.

The periodontal ligament (PDL) is a key contributor to the process of regeneration of the periodontium. The heterogeneous nature of the PDL tissue, its development during early adulthood, and the different conditions to which the PDL tissue is exposed to in vivo impart on the PDL unique characteristics that may be of consequence during its cultivation in vitro. Several factors affecting the in vivo setting influence the behaviour of PDL fibroblasts in culture. The purpose of this review is to address distinct factors that influence the behaviour of PDL fibroblasts in culture -in vivo-in vitro transitions, cell identification/isolation markers, primary PDL cultures and cell lines, tooth-specific factors, and donor-specific factors. Based on the reviewed studies, the authors recommendations include the use of several identification markers to confirm cell identity, use of primary cultures at early passage to maintain unique PDL heterogeneic characteristics, and noting donor conditions such as age, systemic health status, and tooth health status. Continued efforts will expand our understanding of the in vitro and in vivo behaviour of cells, with the goal of orchestrating optimal periodontal regeneration. This understanding will lead to improved evidence-based rationales for more individualized and predictable periodontal regenerative therapies.