Novel Histopathological Findings of Micro Bone Fragments and Epithelial Response in the Oral Mucosa in Bisphosphonate-Related Osteonecrosis of the Jaw.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) occurs in the jawbone and interfacing oral mucosa of patients treated with bisphosphonates. Herein, we report novel histopathological findings in the oral mucosa of a surgical specimen obtained from a 61-year-old man with BRONJ. The resected jawbone and adjacent oral mucosa were separated for histological examination. The mucosal tissue was examined using Von Kossa staining and immunohistochemical (CK5/6, p63) staining of non-decalcified paraffin sections. Pseudoepitheliomatous hyperplasia (PEH), a microscopic feature of the mucosal epithelium in BRONJ, was observed in soft tissue specimens, concomitant with inflammatory cell infiltration. Von Kossa staining revealed small fragments of necrotic bone, tens to hundreds of micrometers in size, scattered within the connective tissues; the PEH forefront contacted some of the bone fragments. Immunohistochemical staining demonstrated that occasionally, the PEH not only contacted but also encompassed the bone fragments. To our knowledge, this is the first report of presence of micro bone fragments and their association with PEH in the oral mucosa in BRONJ.

Neutrophil-to-lymphocyte ratio as an early marker of outcomes in patients with recurrent oral squamous cell carcinoma treated with nivolumab.

The immune checkpoint inhibitor (ICI), nivolumab, has revolutionised the treatment of recurrent and metastatic oral cancer. However, the response rate to ICIs remains low, and identifying predictors of nivolumab response is critical. Although the neutrophil-to-lymphocyte ratio (NLR) has been suggested as a predictive marker of nivolumab response in patients with various types of cancer, its utility in oral squamous cell carcinoma (OSCC) has not been elucidated. In this retrospective multicentre cohort study, we evaluated the association between NLR and outcome of nivolumab treatment in 64 patients with OSCC treated between 2017 and 2020. The objective response and disease control rates were 25.1% and 32.9%, respectively. The rates for complete and partial responses were 15.7% (10/64) and 9.4% (6/64), respectively; stable and progressive disease rates were 7.8% (5/64) and 67.1% (43/64), respectively. Complete and partial responses were classified as responders, and stable and progressive diseases were classified as non-responders. The median (range) pre-treatment NLR among responders was 4.3 (2.8-8.0), which decreased to 4.0 (2.6-6.3) after nivolumab treatment, and the median (range) pre-treatment NLR among non-responders was 5.1 (2.7-7.9), which increased to 6.4 (4.0-14.0) with tumour growth. Moreover, overall survival was significantly worse in the group with a higher post-treatment NLR (≥5) than in the group with a lower NLR (<5). Patients with a post-treatment NLR of ≥6 had worse outcomes for salvage chemotherapy following nivolumab treatment. Thus, post-treatment NLR could be a useful marker for predicting the response to nivolumab treatment or salvage chemotherapy in patients with OSCC.

Clinical Application of Hyperdry Amniotic Membrane in Cleft Palate Repair.

OBJECTIVE: To examine the safety and efficacy of hyperdry amniotic membrane (HDAM) for wound closure after palatoplasty in cleft palate patients. METHODS: HDAMs were prepared by washing and drying under infrared rays and microwaves at temperatures less than 60°C using a hyperdrying device. A total of 16 cleft palate patients (8 males, 8 females), aged 1 to 3 years (mean age 1 year 9 months), received one-stage pushback palatoplasty. The remaining raw wound after surgery was covered by an HDAM and a plastic cover plate. The cover plate was removed 1 week after surgery and parameters including temperature, feeding, allergic reactions, postoperative bleeding, re-epithelialization, wound dehiscence, and infection were monitored during the follow-up period of 31.2 months. RESULTS: All patients could adequately ingest at 5 days postoperation and after removal of the cover plate. None of the patients had a persistent fever or allergic reactions. Ingestion was feasible immediately in all patients, and no postoperative bleeding was observed during ingestion. No secondary hemorrhages were observed during follow-up. No postoperative wound dehiscence on the midline of the palate was observed. No infections were observed after the removal of the cover plate. No patients suffered from severe scar formation or contracture of the wound in the follow-up period. Hemorrhage, undue epithelialization, and scar contracture did not occur in any patient. The mean evaluation score was 7.75 points. CONCLUSION: HDAM can be used safely and effectively for wound closure following palatoplasty in cleft palate infants. Future studies testing the safety of patient's own amnion for palatoplasty, are required.

Predictive Value of Neutrophil-Lymphocyte Ratio as a Marker in Antiresorptive Agent-Related Osteonecrosis of the Jaw: A Retrospective Analysis.

Antiresorptive agent-related osteonecrosis of the jaw (ARONJ), a multifactorial disease, can drastically affect a patient's quality of life. Moreover, disease progression to severe acute inflammation can hinder treatment. Therefore, we aimed to investigate the diagnostic value of the neutrophil−lymphocyte ratio (NLR) and platelet−lymphocyte ratio (PLR) in predicting the risk of acute inflammation in patients with ARONJ. In total, 147 patients with ARONJ were enrolled between 1 January 2011 and 31 December 2019. They were divided into two groups according to their baseline NLR (high NLR vs. low NLR) or PLR (high PLR vs. low PLR) to analyze the relationship between NLR and PLR and the outcomes of acute inflammatory events. An optimal NLR cut-off value of 2.83 was identified for hospitalization for an inflammatory event. Logistic regression analysis showed that NLR > 2.83 was associated with an increased risk of hospitalization for an inflammatory event. A PLR cut-off value of 165.2 was identified for hospitalization for an inflammatory event. However, logistic regression analysis showed that PLR > 165.2 was not significantly associated with hospitalization for an inflammatory event. Our study findings suggest that the NLR has diagnostic value in predicting the risk of hospitalization for inflammatory events among patients with ARONJ.

Clinical utility of oral management in allogeneic hematopoietic stem cell transplantation recipients: microbiological evidence based on molecular analysis of oral bacteria.

PURPOSE: This study aimed to clarify the clinical utility of oral management to prevent bloodstream infections by oral bacteria microbiologically in patients undergoing allogeneic hematopoietic stem cell transplantation (ASCT). METHODS: Ten consecutive patients with hematological malignancies undergoing ASCT were enrolled in this study. We implemented dental treatments before transplantation, if required, and carried out oral hygiene instructions and oral management every other day after transplantation. Molecular analysis of bacterial DNA for seven oral species using a polymerase chain reaction (PCR) assay was performed for oral samples and peripheral blood once a week for 3 weeks after transplantation. RESULTS: Periodontitis was found in all 10 patients (mild grade in 3 and middle grade in 7) for whom basic periodontal therapy was conducted. Necessary dental procedures, including tooth extraction were performed in 5 patients. After transplantation, oral mucositis occurred in 10 patients (grade 1 in 3, grade 2 in 2, and grade 3 in 5) for whom oral hygiene instruction and oral care were continued every other day. PCR-identified three to six bacterial species in oral samples from nine patients, but none in peripheral blood from any patient during the observation period. CONCLUSIONS: Our study suggests that oral management could prevent bloodstream infections by oral bacteria in ASCT recipients despite the existence of periodontitis or oral mucositis. Its utility was confirmed by microbiological evidence based on molecular data.

Oral Management of a Haematopoietic Stem Cell Transplant Recipient with Chédiak-Higashi Syndrome.

Chédiak-Higashi syndrome (CHS), a rare autosomal recessive disorder associated with leukocyte dysfunction, is characterised by partial skin and hair albinism, immunodeficiency, and abnormal bleeding. Furthermore, it may be associated with cognitive and neurological impairments. The long-term prognosis of patients is generally poor, and haematopoietic stem cell transplantation is a radical immunodeficiency treatment. Here, we report a case of successful oral management of an 18-year-old woman with CHS accompanied by aggressive periodontitis who underwent haematopoietic stem cell transplantation.

Role of Phosphodiesterase2A in Proliferation and Migration of Human Osteosarcoma Cells.

BACKGROUND/AIM: The prognosis of patients with osteosarcoma is poor; therefore, new treatment strategies are urgently needed. Phosphodiesterase 2 (PDE2) is one of the 11 families (PDE1-PDE11) of the phosphodiesterase superfamily that regulates the intracellular concentrations and effects of cAMP and cGMP. This in vitro study was performed to investigate the role of PDE2 in human oral osteosarcoma HOSM-1 cells. MATERIALS AND METHODS: PDE2 expression was measured by a cAMP-PDE assay and real-time-PCR. The effects of the PDE2-specific inhibitors, erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), 8-bromo-cAMP, and 8-bromo-cGMP on cell proliferation and migration were assessed. RESULTS: PDE2 activity and PDE2A mRNA expression were detected in HOSM-1 cells. Cell proliferation was inhibited by EHNA and 8-bromo-cAMP but not by 8-bromo-cGMP. Cell migration was stimulated by EHNA and 8-bromo-cGMP, but it was inhibited by 8-bromo-cAMP. CONCLUSION: Cell proliferation is regulated by PDE2-cAMP signaling and cell migration is regulated by PDE2-cGMP signaling in HOSM-1 cells.

Skeletal stability after maxillary step osteotomy compared with original Le Fort I osteotomy during one-year of follow-up.

The purpose of the current study was to compare the 1-year stability of skeletal after original Le Fort I osteotomy and maxillary step osteotomy. Fifty-two patients with prognathism underwent sagittal split ramus osteotomy with either original Le Fort I osteotomy or maxillary step osteotomy (26 patients each). Twelve cephalometric parameters were measured to evaluate postsurgical stability (lesser change was considered as enhanced stability) at 1 month (T1), 6 months (T2), and 1 year (T3) postoperatively. Only 3 parameters-vertical and horizontal distance of menton and vertical distance of point B-showed minimal but significant differences between the two groups. Lesser degrees of changes were observed after maxillary step osteotomy than after original Le Fort I osteotomy, and the differences were significant during the period between T1 and T2, but not from T1 to T3. Differences between the two groups were less in asymmetry cases required correction of the occlusal plane. In conclusion, differences between original Le Fort I osteotomy and maxillary step osteotomy were observed at the frontal points of the mandible; however, they were not clinically significant. It may be suggested that there is no significant difference in skeletal stability at 1 year after the two procedures.

Evaluation of a New Hydroxyapatite Nanoparticle as a Drug Delivery System to Oral Squamous Cell Carcinoma Cells.

BACKGROUND/AIM: Due to its abilities of substance adsorption and intracellular transportation, hydroxyapatite is a potential carrier in drug delivery systems (DDS). This in vitro study investigated whether newly-developed, highly-dispersive calcined hydroxyapatite nanoparticles with an average grain diameter of 20 nm (nano-SHAP) were suitable as a DDS for the drugs zoledronic acid (ZA), cisplatin, and carboplatin. MATERIAL AND METHODS: The effects of drug-bearing nano-SHAP on cell proliferation were assessed using three human oral squamous cell carcinoma cell lines (HSC-4, KOSC, and SAS) and one human breast cancer cell line (MCF-7). RESULTS: Nano-SHAP alone did not affect proliferation of any cell line until a concentration of 1 µg/ml was reached. Although the effective concentration of ZA in ZA-bearing nano-SHAP differed, it inhibited cell proliferation better than ZA alone. Cisplatin and carboplatin-bearing nano-SHAP had the same effect as these drugs alone. CONCLUSION: The nano-SHAP system is of potential use as a drug delivery system.

A novel approach to predict cetuximab-induced hypersensitivity reaction: detection of drug-specific IgE on basophils.

Cetuximab is remarkable for the relatively high rate and severity of hypersensitivity reactions (HR) being reported in the literature. Screening for cetuximab-specific IgE in serum via immunoassay has been found to be useful in preventing HR; however, these tests are known to have a low positive predictive rate. In an attempt to remedy this, we evaluated the interaction between cetuximab and IgE on basophils for predicting severe cetuximab-induced HR. Twelve head and neck cancer patients were enrolled in this single-institution study: four with a history of cetuximab-induced HR and eight with no such history. Cetuximab-specific and galactose-α-1,3-galactose (α-gal) specific IgEs in serum were measured in vitro using an enzyme-linked immunosorbent assay (ELISA). IgE-cetuximab binding on basophils was also analyzed to evaluate the decrease in cetuximab molecules on basophils after dissociation of IgE from FcεRI. The positive predictive value associated with the presence of cetuximab- or α-gal-specific IgE in serum was found to be only 0.67, whereas the negative predictive value was 1.00. On the other hand, in all four patients who developed HR, the cetuximab molecules on basophils were decreased significantly due to the dissociation of IgE from basophils (P < 0.05). However, this was not the case in patients who did not develop HR. In conclusion, our results strongly imply that the IgE-cetuximab interaction on basophils may be key to developing improved methods for predicting severe cetuximab-induced HR.

Extracellular Ca(2+)-dependent enhancement of cytocidal potency of zoledronic acid in human oral cancer cells.

Direct antitumor effects of bisphosphonates (BPs) have been demonstrated in various cancer cells in vitro. However, the effective concentrations of BPs are typically much higher than their clinically relevant concentrations. Oral cancers frequently invade jawbone and may lead to the release of Ca(2+) in primary lesions. We investigated the effects of the combined application of zoledronic acid (ZA) and Ca(2+) on proliferation and apoptosis of oral cancer cells. Human oral cancer cells, breast cancer cells, and colon cancer cells were treated with ZA at a wide range of concentrations in different Ca(2+) concentration environments. Under a standard Ca(2+) concentration (0.6mM), micromolar concentrations of ZA were required to inhibit oral cancer cell proliferation. Increasing extracellular Ca(2+) concentrations greatly enhanced the potency of the ZA cytocidal effect. The ability of Ca(2+) to enhance the cytocidal effects of ZA was negated by the Ca(2+)-selective chelator EGTA. In contrast, the cytocidal effect of ZA was less pronounced in breast and colon cancer cells regardless of whether extracellular Ca(2+) was elevated. In oral cancer cells incubated with 1.6mM Ca(2+), ZA up-regulated mitochondrial Bax expression and increased mitochondrial Ca(2+) uptake. This was associated with decreased mitochondrial membrane potential and increased release of cytochrome c. We suggest that ZA can specifically produce potent cytocidal activity in oral cancer cells in an extracellular Ca(2+)-dependent manner, implying that BPs may be useful for treatment of oral squamous cell carcinoma with jawbone invasion leading to the hypercalcemic state.

Role of phosphodiesterase 2 in growth and invasion of human malignant melanoma cells.

Cyclic nucleotide phosphodiesterases (PDEs) regulate the intracellular concentrations and effects of adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP). The role of PDEs in malignant tumor cells is still uncertain. The role of PDEs, especially PDE2, in human malignant melanoma PMP cell line was examined in this study. In PMP cells, 8-bromo-cAMP, a cAMP analog, inhibited cell growth and invasion. However, 8-bromo-cGMP, a cGMP analog, had little or no effect. PDE2 and PDE4, but not PDE3, were expressed in PMP cells. Growth and invasion of PMP cells were inhibited by erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), a specific PDE2 inhibitor, but not by rolipram, a specific PDE4 inhibitor. Moreover, cell growth and invasion were inhibited by transfection of small interfering RNAs (siRNAs) specific for PDE2A and a catalytically-dead mutant of PDE2A. After treating cells with EHNA or rolipram, intracellular cAMP concentrations were increased. Growth and invasion were stimulated by PKA14-22, a PKA inhibitor, and inhibited by N(6)-benzoyl-c AMP, a PKA specific cAMP analog, whereas 8-(4-chlorophenylthio)-2'-O-methyl-cAMP, an Epac specific cAMP analog, did not. Invasion, but not growth, was stimulated by A-kinase anchor protein (AKAP) St-Ht31 inhibitory peptide. Based on these results, PDE2 appears to play an important role in growth and invasion of the human malignant melanoma PMP cell line. Selectively suppressing PDE2 might possibly inhibit growth and invasion of other malignant tumor cell lines.

Gemcitabine chemotherapy induces phenotypic alterations of tumor cells that facilitate antitumor T cell responses in a mouse model of oral cancer.

OBJECTIVES: Gemcitabine (GEM) is a pyrimidine nucleoside analogue that is a new chemotherapeutic agent used for treating various cancers. Because accumulating evidence indicates that GEM may activate host immune responses, its potential as an immune modulator in cancer chemotherapy has generated considerable interest. MATERIALS AND METHODS: In the present study, we investigated the antitumor effects of GEM using a mouse oral cancer model using immunological analyses. We examined apoptotic cell death of tumor cells with GEM treatment both in vitro and in vivo. We also investigated whether in vivo administration of GEM affected the distributions of immune cells, tumor-cell surface expression levels of immune accessory molecules and T cell immune responses in tumor-bearing mice. RESULTS: GEM induced significant oral cancer-cell apoptosis in vitro, and in vivo GEM administration markedly attenuated established mouse tumor growth. In vivo GEM administration decreased the numbers of both myeloid-derived suppressor cells (MDSCs) and B cells in tumor-bearing mice and enhanced dendritic cell maturation. Moreover, GEM treatment upregulated tumor-cell surface expressions of several immune accessory molecules and adhesion molecules, including CD80, CD86, CD40, ICAM-1, VCAM-1, and P-selectin. Remarkably, these tumor cells augmented tumor specific T-cell responses. CONCLUSION: These results suggest that GEM can induce host antitumor immune responses, which would facilitate antitumor effects in the treatment of oral cancer.

Intraoral application of hyperdry amniotic membrane to surgically exposed bone surface.

Hyperdry amniotic membrane, a novel preservable material derived from the human amnion, has been introduced clinically in ophthalmology and other fields. This membrane is available as a wound dressing material for surgical wounds of the tongue and buccal mucosa but has not been used on wounds of the alveolar mucosa. This paper reports 2 cases in which intraoral alveolar wounds with bone exposure were successfully treated with the use of hyperdry amniotic membrane: a 74-year-old woman with gingival leukoplakia of the edentulous mandible, and a 43-year-old man who underwent vestibuloplasty of the reconstructed mandible. The results indicate that the hyperdry amniotic membrane is a useful dressing material, not only for soft tissue wounds, but also for exposed bone in the oral cavity.

CD44 and SSEA-4 positive cells in an oral cancer cell line HSC-4 possess cancer stem-like cell characteristics.

BACKGROUND: Cancer may be derived from cancer stem-like cells (CSCs), which are tumor-initiating cells that have properties similar to those of stem cells. Identification and isolation of CSCs needs to be improved further. MATERIALS AND METHODS: CSCs markers were examined in human oral cancer cell lines by flow cytometry. The stem cell properties of subpopulations expressing different markers were assessed further by in vitro sphere formation assays, expression of stemness genes, drug resistance assays, and the ability to form tumors in nude mice. RESULTS: We demonstrated that CSCs could be isolated by the cell surface markers CD44 and stage-specific embryonic antigen-4 (SSEA-4). CD44+SSEA-4+ cells exhibited cancer stem-like properties, including extensive self-renewal into the bulk of cancer cells. In vivo xenograft experiments indicated that CD44+SSEA-4+ cells exhibit the highest tumorigenic capacity compared with the remaining subpopulations and parental cells. Double-positive cells for CD44 and SSEA-4 exhibited preferential expression of some stemness genes and were more resistant to the anticancer drugs, cisplatin and 5-fluorouracil (5-FU). In addition, cells expressing CD44 and SSEA-4 were detected in all tumor specimens analyzed, while coexpression of CD44 and SSEA-4 was not detectable in normal oral mucosa. CONCLUSION: Our findings suggest that CD44+SSEA-4+ cells exhibit the characteristics of CSCs in oral squamous cell carcinoma and provide a target for the development of more effective therapies.

Clinical application of a hyperdry amniotic membrane on surgical defects of the oral mucosa.

PURPOSE: The aim of this study was to evaluate the usefulness of a hyperdry amniotic membrane (AM), a novel preservable human amnion, as a wound-dressing material for surgical defects of the oral mucosa. MATERIALS AND METHODS: A hyperdry AM was used in the treatment of 10 patients who had developed secondary defects in the tongue and buccal mucosa after the surgical removal of cancerous or precancerous lesions. The effectiveness of the hyperdry AM was assessed by scoring its operability during the surgical procedure and by the hemostatic status, pain relief, feeding situation, epithelialization, and scar contracture in the postoperative period. Its usefulness was evaluated by considering its effectiveness and safety based on the absence of wound infection and graft rejection. RESULTS: The membrane was found to be easy to handle as an oral-dressing material. It adhered well to the bare connective and muscular tissues. One lingual case showed slight postoperative bleeding, which astriction then stopped. No remarkable adverse effects were observed in the process of wound healing. The average score of the patients was 11.2 points (10 to 13 points) in the present evaluation, with 14 being the highest possible score. CONCLUSIONS: This study showed the clinical usefulness of the hyperdry AM as an intraoral wound-dressing material. Although the number of cases was small, the results suggested that the hyperdry AM is biologically acceptable to oral wounds and could be a suitable clinical alternative for the repair of the oral mucosa.

Silencing of autocrine motility factor induces mesenchymal-to-epithelial transition and suppression of osteosarcoma pulmonary metastasis.

Phosphoglucose isomerase (PGI) is a multifunctional enzyme that functions in glucose metabolism as a glycolytic enzyme catalyzing an interconversion between glucose and fructose inside the cell, while it acts as cytokine outside the cell, with properties that include autocrine motility factor (AMF)-regulating tumor cell motility. Overexpression of AMF/PGI induces epithelial-to-mesenchymal transition with enhanced malignancy. Recent studies have revealed that silencing of AMF/PGI resulted in mesenchymal-to-epithelial transition (MET) of human lung fibrosarcoma cells and breast cancer cells with reduced malignancy. Here, we constructed a hammerhead ribozyme specific against GUC triplet at the position G390 in the human, mouse, and rat AMF/PGI mRNA sequence. Mesenchymal human osteosarcoma MG-63, HS-Os-1, and murine LM8 cells were stably transfected with the ribozyme specific for AMF/PGI. The stable transfectant cells showed effective downregulation of AMF/PGI expression and subsequent abrogation of AMF/PGI secretion, which resulted in morphologic change with reduced growth, motility, and invasion. Silencing of AMF/PGI induced MET, in which upregulation of E-cadherin and cytokeratins, as well as downregulation of vimentin, were noted. The MET guided by AMF/PGI gene silencing induced osteosarcoma MG-63 to terminally differentiate into mature osteoblasts. Furthermore, MET completely suppressed the tumor growth and pulmonary metastasis of LM8 cells in nude mice. Thus, acquisition of malignancy might be completed in part by upregulation of AMF/PGI, and waiver of malignancy might also be controlled by downregulation of AMF/PGI.

Heparin induces apoptosis through suppression of AKt in oral squamous cell carcinoma cells.

BACKGROUND: Heparin is a polysulfated glycosaminoglycan that has been shown to have antiproliferative and apoptotic effects in addition to its anticoagulant effects. MATERIALS AND METHODS: The present work investigated the effects of unfractioned heparin (UFH) on cell growth and apoptosis in four oral squamous cell carcinoma (SCC) cell lines and the mechanism(s) underlying its actions using MTT assay, Annexin-V-FITC and Western blotting. RESULTS: Treatment with UFH resulted in significant reduction in cell viability and increase in apoptosis in three of the four tested cell lines. Further, such treatment resulted in a significant decrease in phosphorylated AKt, and consequently led to activation of the mitochondrial pathway in heparin-sensitive cells. Moreover, pretreatment with UFH significantly increased the apoptosis induced by cisplatin. CONCLUSION: These findings indicate that heparin induces apoptosis through suppression of AKt, and suggest a potential utility of heparin for development of less toxic chemotherapy in treatment of oral SCC.

[Incident and accident reports in Tokyo Medical and Dental University Dental Hospital (FY 2001-2002)].

In 2002, the Dental Hospital of Tokyo Medical and Dental University set up a working group for risk management. This working group analyzed 225 incident and accident reports submitted to the hospital in 2001 and 2002. Each report was analyzed with regard to "type," "place," "reporter," "severity," and "cause" in order to diagnose hospital safety and prevent future incidents and accidents. The cause of incidents and accidents was analyzed using the SHEL model, where S stands for Software, H for Hardware, E for Environment, and L for Liveware. The severity of the consequence was classified into 6 levels, where level 0 = "error not applied," level 1 = "not affected," level 2 = "watch and see or additional test," level 3 = "treatment," level 4 = "aftereffect," and level 5 = "death." The incidents and accidents judged to have potentially high risk were given a score of "+H," irrespective of the level. The results of the analyses revealed that most of the incidents and accidents happened in "wards," "operation rooms," and "oral surgery clinics." This is probably because the incident and accident reporting system is well established by nurses working in these clinics. Additional analysis revealed that most of the reports were written and submitted by nurses. The frequencies of "treatment procedure," "misuse of dental instruments," "mis-prescription," "falling down" and "needlestick" related incidents and accidents were the highest and were caused mainly by L and S. There were only 3 accidents above level 4, however, less severe cases were given a score of +H due to the high potential risk involved.