Effect of Sparc knockout on the extracellular matrix of mouse periodontal ligament cells.

The periodontal ligament (PDL) is a critical component in maintaining tooth stability. It is composed of cells and an extracellular matrix (ECM), each with unique roles in tissue function and homeostasis. Secreted protein acidic and rich in cysteine (SPARC), a calcium-binding matricellular glycoprotein, plays a crucial role in regulating ECM assembly and turnover, alongside facilitating cellular-ECM interactions. In the present study, mass spectrometry-based proteomics was used to assess the impacts of Sparc-knockout (KO) on PDL-derived cells. Results demonstrated that Sparc-KO significantly reduces ECM production and alters its composition with increased levels of type I collagen. Despite this increase in Sparc-KO, type I collagen was not likely to be effectively integrated into the fibrils due to collagen cross-linking impairment. Furthermore, the pathway and process enrichment analyses suggested that SPARC plays a protective role against ECM degradation by antagonistically interacting with cell-surface collagen receptors. These findings provide detailed insights into the multifaceted role of SPARC in ECM organization, including its impact on ECM production, collagen regulation, and interactions with various cellular compartments. A better understanding of these complex mechanisms is crucial for comprehending the causes of periodontal disease and tissue regeneration, where precise control of ECM organization is necessary.

Bone heating and implant removal using a high-frequency electrosurgical device: An in vivo experimental study.

OBJECTIVES: Failed implant removal using a high-frequency electrosurgical device (HFED) has been reported to be less invasive than other surgical techniques. We sought to clarify the mechanism of removal torque reduction in an implant by heating with HFED. MATERIALS AND METHODS: Sixty-eight Wistar rats received titanium implants on the maxillary bone 4 weeks after extraction of the first and second molars. The control group was sacrificed 6 weeks after implant installation. In the experimental group, the implant was heated by HFED for 10 s using three different power outputs, and samples were collected at 3, 7, and 14 days after heating. Removal torque measurement and histological analysis were performed in the control and experimental groups. Implant surfaces were observed using an electron-probe microanalyzer (EPMA). Data were analyzed using Mann-Whitney U test at a significance level of 5%. RESULTS: The removal torque could not be measured in the control group due to fracture of the implant. After heating, the removal torque was measurable without fracture and decreased significantly at 14 days as compared with that at 3 days (p < .05). Heating with "min" power output resulted in a significantly smaller blank lacunae area and fewer osteoclasts at 14 days after heating (p < .05). EPMA revealed bone matrix adherence to outer surface of heated implant. CONCLUSIONS: After heating, an enlarged area of blank lacunae around the implant and an increased number of osteoclasts into the bone marrow cavity were observed, which may have contributed to the reduction in removal torque.

Peri-implant bone alterations under the influence of abutment screw preload stress. A preclinical vivo study.

OBJECTIVES: The study purpose was to examine peri-implant bone alternations around osseointegrated implants caused solely by abutment screw preload stress using different tightening torque values. MATERIALS AND METHODS: Twenty 20- to 22-week-old Japanese white rabbits received two implants each in right and left femurs. Implants were randomly assigned to one of three tightening torque groups or the control (Cont) group. After 8 weeks, 35 Ncm torque was delivered to abutment screws in the recommended torque (RT) group (n = 16). Other screws received 70 Ncm torque as the high torque (HT) group (n = 16). Temporary tightening (TT) groups (n = 8) received only 70 Ncm torque without preload stress as screws were untightened immediately. Cont group (n = 40) remained in situ. Animals were euthanized at 4, 6, 8, and 10 weeks after torque application. Micro-CT images were then taken, and undecalcified ground sections were stained with toluidine blue. RESULTS: Cross-sections of cortical bone showed remodeling activities adjacent to the implant in all groups. While bone marrow spaces appearance was relatively small in Cont and TT groups, RT and HT groups showed large bone marrow spaces and extensive remodeling activity. Bone-to-implant contact was significantly less in RT and HT groups compared with Cont and TT groups at different time points (p Ë‚ .05). Furthermore, RT and HT groups showed significantly less bone volume and area (p Ë‚ .05). CONCLUSION: Results suggested that preload stress without any occlusal loading might negatively affect peri-implant bone stability and initiate bone remodeling. This could alter bone mechanical properties, subsequently influencing long-term implant success.

Insulin-like growth factor binding Protein-3 suppresses osteoblast differentiation via bone morphogenetic protein-2.

Bone augmentation therapy is used in dental implantation. While techniques to induce bone formation are generally successful, the maintenance of bone mass is more difficult. Therefore, it is important to understand the mechanisms that regulate this process. Insulin-like growth factor-1 (IGF-1) is one of the most abundant growth factors that regulate bone mass, promote osteoblast differentiation, and accelerate bone formation. The activity of IGF-1 is regulated by IGF-binding proteins (IGFBPs). IGFBP-3 forms a ternary complex with IGF-1, extending its half-life in the circulating system. Therefore, IGFBP-3 acts as a stabilizer and transporter of IGF-1. Recent studies reported new IGF-1-independent functions of IGFBP-3 related with bone metabolism. In this study, we investigated the function of IGFBP-3 in osteoblast differentiation. Our results showed that IGFBP-3 decreases the expression of osteoblast differentiation markers, whose expression is enhanced by bone morphogenetic protein-2 (BMP-2). IGFBP-3 also reduced BMP-2 effect on ALP activity and mineral nodule formation. In addition, IGFBP-3 suppresses the activity of the Smad Binding Element (SBE) reporter, induced by BMP-2 signaling. These results suggest that IGFBP-3 inhibits osteoblast differentiation through the BMP-2 signal pathway, and that IGFBP-3 might play a role in bone mass maintenance in an IGF-1-dependent and -independent manner.

Correlation Between Stress Distributions and Biological Reactions in Bone Surrounding Implants That Support Cantilevers in Supraocclusal Contact in Rats.

PURPOSE: To investigate the relationship between stress distributions and peri-implant bone reactions around maxillary implants that support cantilevers in supraocclusal contact. MATERIALS AND METHODS: After molar extraction, 16 Wistar rats received a titanium implant unilaterally. After healing, 8 rats (control group) were killed and the others received implant-supported cantilever superstructures in supraocclusion (loaded group). After 5 days, they were killed. The maxillae of all rats were scanned by microcomputed tomography (µ-CT). Based on the µ-CT images, bone volumes were measured. For the loaded group, 3D finite element models were created and analyzed under 20-N vertical and 5-N lateral forces, successively. After µ-CT scanning, sections were prepared and observed histologically. RESULTS: When compared with the controls, the bone volume tended to decrease in the loaded group, but the difference was not statistically significant. On average, marginal bone resorption and stresses tended to be higher in 2 rats that occluded on the cantilever arm than in the others, which occluded right on the implant, nevertheless, calculated stress did not surpass the maximum elastic stress (yielding strength) of rat bone. However, at the implant-bone interface of these samples, partial bone resorption surrounded by signs of active resorption was histologically found. CONCLUSION: These findings suggest that in this occlusally loaded rat model, the stress distributions correlated to some extent with bone volume and morphological changes observed on µ-CT images and histological sections.

Association between gender and self-assessment skills amongst Japanese dental students.

Background/purpose: Self-assessment in dental education is considered a fundamental skill for proficient oral healthcare providers. While previous studies looked at self-assessment in education, few have done so at Japanese institutions. This study aimed to assess potential associations between gender and self-assessment skills in Japanese dental students. Materials and methods: Dental students from Niigata University (n = 301) completed preclinical prosthodontic exercises and self-assessed their practical exam performance. Three calibrated faculty evaluated students' work using the same rubric. The difference between student self-assessment score and mean faculty grade was defined as the student-faculty (S-F) gap, indicating how accurately students evaluated their work. The gap scores were stratified by quartiles by faculty grade and by gender. Regression analysis was used to investigate potential associations. Results: Students mean S-F gap was 2.9 ± 10.5 % with a significant negative association to faculty grades (coefficient, -0.32; P < 0.001). There was no significant difference between male and female students for faculty grades, self-assessment scores, and S-F gaps. When stratified by quartile, mean S-F gaps of bottom quartile students (5.7 ± 11.9 %) were significantly higher than the rest of the class (1.9 ± 9.8 %; P = 0.01), while the mean S-F gaps of students in the top quartile (-0.8 ± 10.2 %) were significantly lower than the rest of the class (4.2 ± 10.3 %; P < 0.001). Conclusion: Niigata University students generally overestimated their performance. Students with higher faculty grades self-assessed themselves more accurately than students with lower faculty grades. Gender did not influence S-F gaps, despite dentistry in Japan shifting toward a female-dominated field.

Acellular Extrinsic Fiber Cementum Is Invariably Present in the Superficial Layer of Apical Cementum in Mouse Molar.

The cementum is a highly mineralized tissue that covers the tooth root. The regional differences among the types of cementum, especially in the extrinsic fibers that contribute to tooth support, remain controversial. Therefore, this study used second harmonic generation imaging in conjunction with automated collagen extraction and image analysis algorithms to facilitate the quantitative examination of the fiber characteristics and the changes occurring in these fibers over time. Acellular extrinsic fiber cementum (AEFC) was invariably observed in the superficial layer of the apical cementum in mouse molars, indicating that this region of the cementum plays a crucial role in supporting the tooth. The apical AEFC exhibited continuity and fiber characteristics comparable with the cervical AEFC, suggesting a common cellular origin for their formation. The cellular intrinsic fiber cementum present in the inner layer of the apical cementum showed consistent growth in the apical direction without layering. This study highlights the dynamic nature of the cementum in mouse molars and underscores the requirement for re-examining its structure and roles. The findings of the present study elucidate the morphophysiological features of cementum and have broader implications for the maintenance of periodontal tissue health.

Evaluation of newly developed devices for denture placement and removal in the dependent elderly.

OBJECTIVE: The purpose of this study was to subjectively evaluate the utility of newly developed denture placement and removal devices. Objective observations were also made to support the evidence. MATERIALS AND METHOD: Twenty-one subjects were instructed to place and remove their dentures with and without the devices. We evaluated the device based on a questionnaire. Objective observations were based on a 2-D image analysis. We analysed three factors: the time, the area and the circumference required to insert and remove the dentures. RESULTS: Image analysis showed that the effectiveness and ease with which the subject used the device significantly improved with practice. The questionnaire data showed that a majority of the subjects appreciated the device after the first and second time. While there was no significant decrease in time required to place and remove dentures even with the device, the area and circumference of the movement on 2-D images were significantly reduced. CONCLUSION: In this study, the utility of denture placement and removal devices was evaluated both subjectively and objectively. Our data reveal that the device is effective in the elderly. Further minor improvement in the device might be required to increase its effectiveness.

Comparing dental student preclinical self-assessment in the United States and Japan.

PURPOSE/OBJECTIVES: Self-assessment is an essential skill for dental professionals. Understanding global trends in self-assessment can highlight the learning needs of students across a diversity of cultural backgrounds. The aim of this study is to compare the self-assessment ability of dental students in the United States and Japan, where cultural backgrounds may differ. METHODS: Students in the United States (n = 176) completed a typodont premolar and anterior Class II and Class III preparation and restoration. Students in Japan (n = 175) completed a typodont premolar crown preparation. Students and faculty then evaluated the student performance using rubrics for each respective procedure. The difference between the student's self-assessment score and the average faculty score (S-F gap) was calculated and the data were analyzed. RESULTS: The mean S-F gap was 2.8% in Japan and 7.6% in the United States. This indicates that Japanese students tended to assess themselves closer to their faculty graders than students in the United States. On average, students in both countries scored themselves higher than their faculty graders. Students in the United States more frequently overestimated their performance and students in Japan more frequently underestimated their performance. For students in the lower quartile, the mean S-F gap was 5.1% in Japan and 14.6% in the United States, indicating a large cultural discrepancy in the lower quartile groups. CONCLUSIONS: Although different preclinical procedures were compared, our findings demonstrated that Japanese students may score themselves more closely to their faculty assessors than students in the United States. Further investigation with more students completing the same preclinical activity will be needed.

The relationship between dental metal allergy, periodontitis, and palmoplantar pustulosis: An observational study.

PURPOSE: This study aimed to investigate the relationship between dental metal allergy, periodontitis, and palmoplantar pustulosis among patients from a dental metal allergy clinic over a period of 8 years. METHODS: This study included 436 patients who visited our dental metal allergy clinic between April 1, 2009 and March 31, 2016. Diagnoses of skin diseases, periodontal records, dental metal series patch test results, and electron probe microanalysis (EPMA) data were obtained from medical records. Relative risk (RR) values were estimated from these data. RESULTS: Of the 359 patients who underwent the patch test, 241 showed a positive reaction. Of the 187 patients who underwent EPMA, 113 had allergenic metals in their dental prostheses. These patients were suspected to have a dental metal allergy. Furthermore, 150 of the 436 patients were diagnosed with palmoplantar pustulosis (PPP). The RR of metal allergy between patients with PPP and healthy subjects was 3.88. The RR of periodontal disease between patients with PPP and PPP-negative patients in the national average was 2.54. CONCLUSION: In this study, both dental metal allergy and periodontitis showed a high RR for PPP.

Extracellular Matrix-Oriented Proteomic Analysis of Periodontal Ligament Under Mechanical Stress.

The periodontal ligament (PDL) is a specialized connective tissue that provides structural support to the tooth and is crucial for oral functions. The mechanical properties of the PDL are mainly derived from the tissue-specific composition and structural characteristics of the extracellular matrix (ECM). The ECM also plays key roles in determining cell fate in the cellular microenvironment thus crucial in the PDL tissue homeostasis. In the present study, we determined the comprehensive ECM profile of mouse molar PDL using laser microdissection and mass spectrometry-based proteomic analysis with ECM-oriented data curation. Additionally, we evaluated changes in the ECM proteome under mechanical loading using a mouse orthodontic tooth movement (OTM) model and analyzed potential regulatory networks using a bioinformatics approach. Proteomic changes were evaluated in reference to the novel second harmonic generation (SHG)-based fiber characterization. Our ECM-oriented proteomics approach succeeded in illustrating the comprehensive ECM profile of the mouse molar PDL. We revealed the presence of type II collagen in PDL, possibly associated with the load-bearing function upon occlusal force. Mechanical loading induced unique architectural changes in collagen fibers along with dynamic compositional changes in the matrisome profile, particularly involving ECM glycoproteins and matrisome-associated proteins. We identified several unique matrisome proteins which responded to the different modes of mechanical loading in PDL. Notably, the proportion of type VI collagen significantly increased at the mesial side, contributing to collagen fibrogenesis. On the other hand, type XII collagen increased at the PDL-cementum boundary of the distal side. Furthermore, a multifaceted bioinformatics approach illustrated the potential molecular cues, including PDGF signaling, that maintain ECM homeostasis under mechanical loading. Our findings provide fundamental insights into the molecular network underlying ECM homeostasis in PDL, which is vital for clinical diagnosis and development of biomimetic tissue-regeneration strategies.

Technical skill training and assessment in dental education.

Highly competent clinical practice requires cognitive, psychomotor and affective skills. Therefore, the ultimate goal of dental education is for practitioners to be competent in all of these domains. While many methods have been introduced to assess knowledge and non-technical skills, it is still very difficult for educators to assess technical skill. Assessment methods for technical skills are still not well established because it is very difficult to assure objectivity, validity and fairness. Nonetheless, technical skill is especially important in dental treatments, along with knowledge and attitude. The aim of this review was to summarize the methods of technical skill training in dental education and how they are assessed. This is a literature review. We searched PubMed MEDLINE using terms related to technical skill training and those assessment as of June 2020 and reviewed them. There have been many reports introducing methods of technical skill training and assessment, including the use of digital technology. However, no single assessment method had demonstrated validity of it. Technical skill training is very important in dental education and there are various ways of learning. The validity of current assessment methods is limited; therefore, a combination of several methods may achieve the best results.

Reducing bacterial counts around the abutment following professional mechanical plaque removal at the implant bridge: A randomized crossover comparison of removing or not removing the superstructure.

PURPOSE: The purpose of this study was to determine whether removing the superstructure of the implant bridge in cases of full-arch implant restorations for edentulous atrophic arches at the abutment level during professional mechanical plaque removal (PMPR) affects bacterial counts. METHODS: This crossover clinical trial included 20 patients who received screw-retained prostheses at the abutment level. Patients were randomly assigned to two groups and received PMPR with or without removal of the superstructure. After a three-month washout period, the type of treatment was reversed between the groups. Bacterial counts around the cylinder and abutment were measured and compared before and after PMPR. RESULTS: Bacterial numbers around the cylinder and abutment were significantly reduced after PMPR as compared with before PMPR regardless of whether the superstructure was removed (p <0.05). However the ratio of subjects with bacteria at 1.0 × 105 colony forming unit/ml (cfu/ml) or more after PMPR was significantly higher when the superstructure was not removed (p < 0.05). Among patients with bacterial counts of less than 10 × 105 cfu/ml, bacterial loads were reduced to less than 1.0 × 105 cfu/ml even when superstructures were not removed. Among patients with bacterial load of >10 × 105 cfu/ml, bacterial numbers were not reduced to <1.0 × 105 cfu/ml when PMPR was performed without removing the superstructure. CONCLUSIONS: Removal of the superstructure in cases of full-arch implant restorations for edentulous atrophic arches during PMPR reduces bacterial numbers around the implant bridge at the abutment level.

In vivo cell proliferation analysis and cell-tracing reveal the global cellular dynamics of periodontal ligament cells under mechanical-loading.

Periodontal ligament (PDL) is a uniquely differentiated tissue that anchors the tooth to the alveolar bone socket and plays key roles in oral function. PDL cells can respond rapidly to mechanical stimuli, resulting in accelerated tissue remodeling. Cell proliferation is an initial event in tissue remodeling and participates in maintaining the cell supply; therefore, analyzing cell-proliferative activity might provide a comprehensive view of cellular dynamics at the tissue level. In this study, we investigated proliferating cells in mouse molar PDL during orthodontic tooth movement (OTM)-induced tissue remodeling. Our results demonstrated that the mechanical stimuli evoked a dynamic change in the proliferative-cell profile at the entire PDL. Additionally, cell-tracing analysis revealed that the proliferated cells underwent further division and subsequently contributed to tissue remodeling. Moreover, OTM-induced proliferating cells expressed various molecular markers that most likely arise from a wide range of cell types, indicating the lineage plasticity of PDL cells in vivo. Although further studies are required, these findings partially elucidated the global views of the cell trajectory in mouse molar PDL under mechanical-loading conditions, which is vital for understanding the cellular dynamics of the PDL and beneficial for dental treatment in humans.

Biological reaction control using topography regulation of nanostructured titanium.

The micro- and nanosize surface topography of dental implants has been shown to affect the growth of surrounding cells. In this study, standardized and controlled periodic nanopatterns were fabricated with nanosized surface roughness on titanium substrates, and their influence on bone marrow stromal cells investigated. Cell proliferation assays revealed that the bare substrate with a 1.7 nm surface roughness has lower hydrophilicity but higher proliferation ability than that with a 0.6 nm surface roughness. Further, with the latter substrate, directional cell growth was observed for line and groove patterns with a width of 100 nm and a height of 50 or 100 nm, but not for those with a height of 10 or 25 nm. With the smooth substrate, time-lapse microscopic analyses showed that more than 80% of the bone marrow cells on the line and groove pattern with a height of 100 nm grew and divided along the lines. As the nanosized grain structure controls the cell proliferation rate and the nanosized line and groove structure (50-100 nm) controls cell migration, division, and growth orientation, these standardized nanosized titanium structures can be used to elucidate the mechanisms by which surface topography regulates tissue responses to biomaterials.

Histological evaluation on bone regeneration of dental implant placement sites grafted with a self-setting alpha-tricalcium phosphate cement.

This study aimed to evaluate the histological characteristics of the new bone formed at dental implant placement sites concomitantly grafted with a self-setting tricalcium phosphate cement (BIOPEX-R). Standardized defects were created adjacent to the implants in maxillae of 4-week-old male Wistar rats, and were concomitantly filled with BIOPEX-R. Osteogenesis was examined in two sites of extreme clinical relevance: (1) the BIOPEX-R-grafted surface corresponding to the previous alveolar ridge (alveolar ridge area), and (2) the interface between the grafting material and implants (interface area). At the alveolar ridge area, many tartrate-resistant acid phosphatase (TRAPase)-reactive osteoclasts had accumulated on the BIOPEX-R surface and were shown to migrate toward the implant. After that, alkaline phosphatase (ALPase)-positive osteoblasts deposited new bone matrix, demonstrating their coupling with osteoclasts. On the other hand, the interface area showed several osteoclasts initially invading the narrow gap between the implant and graft material. Again, ALPase-positive osteoblasts were shown to couple with osteoclasts, having deposited new bone matrix after bone resorption. Transmission electron microscopic observations revealed direct contact between the implant and the new bone at the interface area, although few thin cells could still be identified. At both the alveolar ridge and the interface areas, newly formed bone resembled compact bone histologically. Also, concentrations of Ca, P, and Mg were much alike with those of the preexistent cortical bone. In summary, when dental implant placement and grafting with BIOPEX-R are done concomitantly, the result is a new bone that resembles compact bone, an ideal achievement in reconstructive procedures for dental implantology.

Risk factors associated with post-loading implant loss of removable and fixed implant-supported prostheses in edentulous jaws.

PURPOSE: This study analyzed risk factors for post-loading implant loss in cases of implant-supported prostheses applied to edentulous jaws of Japanese patients. METHODS: In total, 245 dental implant fixtures placed in 54 edentulous jaws of 46 patients performed at Niigata University Hospital were retrospectively analyzed. Kaplan-Meier curves were used to estimate the cumulative survival rate (SR) of implants, and multiple Cox regression analysis was used to identify predictive factors of implant loss. The following risk factors for implant failure were examined: age, sex, survival time, implant length, implant location, smoking habit, bone density, bone augmentation, opposing dentition, loading period, and type of final restoration. The Cochran-Mantel-Haenszel test was used to examine difference in survival curves of the extracted predictors. RESULTS: Sixteen implants failed during the observation period (SR=92.8 %). Multiple Cox regression analysis revealed that male sex [hazard ratio (HR)=16.1; p=0.007] and use of maxillary removable restorations (HR=12.7; p<0.000) were risk factors for implant failure. Other factors had no significant effect on implant failure. The SR of implants for males (SR=86.9%) was significantly lower than that for females (SR=99.1%). The SR of implants for maxillary removable restorations (SR=76.4%) was significantly lower than for maxillary fixed restorations (SR=99.1%) and mandibular fixed restorations (SR=97.8%). CONCLUSIONS: Maxillary implants with removable restorations and male sex were risk factors for implant failure among Japanese edentulous patients.

Biological Evaluation of Implant Drill Made from Zirconium Dioxide.

PURPOSE: Zirconia is a good candidate material in the dental field. In this study, we evaluated biological responses against a zirconia drill using a bone cavity healing model. MATERIALS AND METHODS: Zirconia drills, stainless steel drills, and the drilled bone surface were observed by scanning electron microscopy (SEM), before and after cavity preparation. For the bone cavity healing model, the upper first and second molars of Wistar rats were extracted. After 4 weeks, cavities were prepared with zirconia drills on the left side. As a control, a stainless steel drill was used on the right side. At 3, 7, and 14 days after surgery, micro-CT images were taken. Samples were prepared for histological staining. RESULTS: SEM images revealed that zirconia drills maintained sharpness even after 30 drilling procedures. The bone surface was smoother with the zirconia drill. Micro-CT images showed faster and earlier bone healing in the zirconia drill cavity. On H-E staining, at 7 days, the zirconia drill defect had a smaller blank lacunae area. At 14 days, the zirconia drill defect was filled with newly formed bone. CONCLUSIONS: The zirconia drill induces less damage during cavity preparation and is advantageous for bone healing. (197 words).

[Regenerative medical therapy and prosthodontics].

The relation between prosthodontics and regenerative medical therapy was taken up as a theme at symposiums in the 112th and 113th scientific meeting of Japan Prosthodontic Society. In this article, these two symposiums are summarized, and academic conference presentations in the scientific meeting of Prosthodontic Society and the content of scientific papers published in the past 21 years are listed by theme, and how the academic society members had worked on themes such as basic medical research and regenerative medical therapy are verified. As a result, it is clarified that reports on biological research and research of regenerative medical therapy carried out from the prosthodontic viewpoint have increased in recent years. However, reports concerning biological findings on dental implants have not increased. It is shown that we have to think about the future direction again regarding the relations with recent regenerative medical therapy. In addition, the necessity of regenerative medical therapy in prosthodontic studies in the future is discussed including some personal opinions. The theme on which we have worked to date is not necessarily far from regenerative medical therapy, and research in the prosthodontic field will contribute to the development of regenerative medical therapy greatly if we appropriately adopt its concept and techniques. I hope that this article will have a good influence on the direction of research of academic society members, especially young members in the future.

The effect of electrical potential on the penetration of metal ions through radicular dentin.

PURPOSE: Electrical potential may facilitate the moving of corroded metal ions across radicular dentin to cause allergic reaction. This study was to investigate the effect of electrical potentials on the penetration of silver and copper ions through radicular dentin. MATERIALS AND METHODS: Eighty-eight dentin discs were prepared from intact premolar teeth and placed between two containers of the model. One container was filled with copper and/or silver solution. Another container was filled with 0.9% sodium chloride solution. Five levels of electrical potential were applied to the model at 37 degrees C for 1 and 24 hrs. Then silver and copper ions in sodium chloride solution were measured by ICP-ES. The data was analyzed by one-way ANOVA with Tukey comparison test and student's t-test (P< 0.05). RESULTS: The concentrations of metal ions significantly increased as the electrical potentials increased when above 250 mV were applied after 1 hr. The concentrations of silver ions were significantly greater than those of copper ions. Low concentrations of silver and copper ions were detected after 24 hrs at 125 mV level. CONCLUSIONS: These results suggest that the penetration of corroded silver and copper ions through radicular dentin caused by intraoral potential might be minimal.