MyMedR

Ong ST, Ngeow WC

Dent Update, 1999 May;26(4):163-5.

Sinus on the chin can be the result of a chronic apical abscess due to pulp necrosis of a mandibular anterior tooth. The tooth is usually asymptomatic, and a dental cause is therefore not apparent to the patient or the unsuspecting clinician. Not infrequently, the patient may seek treatment from a dermatologist or general surgeon instead of a dentist. Excision and repair of the fistula may be carried out with subsequent breakdown because the dental pathology is not removed. This paper reports the presence of median mental sinus of dental origin in twins. One case healed following root canal therapy while the other required both root canal therapy and surgery to eliminate the infection.

Florid cemento-osseous dysplasia in a young Chinese man. Case report

Ong ST, Siar CH

Aust Dent J, 1997 Dec;42(6):404-8.

PMID: 9470284

Florid cemento-osseous dysplasia refers to a group of fibro-osseous lesions which are exuberant, multiquadrant and arise from the tooth-bearing area of the jaws. It is classically described as a condition occurring almost exclusively in middle-aged black women. A case of florid cemento-osseous dysplasia occurring in a young Chinese male is reported which was rare in regard to race and sex. This 20 year old Chinese man presented with huge symmetrical bony lesions in all four quadrants of the jaws. Clinical presentation, radiological findings and histological features of the excised specimens are described. Treatment of the lesions was unusual. Curettage was first done with minimal benefit and it was followed by mandibular recontouring to improve facial appearance. The outcome of these procedures will be discussed.

Fulltext Ameloblastic carcinoma: A case with cervical node and pulmonary metastases

Khoo SP, Ong ST

Ann Dent, 1998;5(1):49-52.

MyJurnal

Odontogenic carcinomas of the jaws are subclassified into malignant ameloblastoma, ameloblastic carcinoma and primary intraosseous carcinoma arising from within the bone. These may arise from residual islands of epithelium derived from dental lamina or epithelial lining of dental cysts. Ameloblastic carcinoma is extremely rare. An aggressive case of ameloblastic carcinoma occumng in a 59-year-old Malay man is presented. Wide excision of the primary lesion with radical neck dissection was carried out. He developed lung metastasis 4 months post-operatively. Despite chemotherapy upon discovery of lung metastasis, he expired 7 months following the initial diagnosis.

Chronic disseminated histiocytosis X: a case report

Ong ST, Lian CB

J Clin Pediatr Dent, 1992;17(1):33-5.

PMID: 1290758

A case of chronic disseminated histiocytosis X (Hand-Schuller-Christian Disease) of the mandible is presented. Multi-modal approach to management is discussed.

Removal of basic and reactive dyes using ethylenediamine modified rice hull

Ong ST, Lee CK, Zainal Z

Bioresour Technol, 2007 Nov;98(15):2792-9.

PMID: 17400446

Wastewaters from textile industries may contain a variety of dyes that have to be removed before their discharge into waterways. Rice hull, an agricultural by-product, was modified using ethylenediamine to introduce active sites on its surface to enable it to function as a sorbent for both basic and reactive dyes. The sorption characteristics of Basic Blue 3 (BB3) and Reactive Orange 16 (RO16) by ethylenediamine modified rice hull (MRH) were studied under various experimental conditions. Sorption was pH and concentration dependent. Simultaneous removal of BB3 and RO16 occurred at pH greater than 4. The kinetics of dye sorption fitted a pseudo-second order rate expression. Increase in agitation rate had no effect on the sorption of BB3 but increased uptake of RO16 on MRH. Decreasing particle size increased the uptake of dyes in binary dye solutions. Equilibrium data could be fitted into both the Langmuir and Freundlich isotherms. Maximum sorption capacities calculated from the Langmuir model are 14.68 and 60.24 mg/g for BB3 and RO16, respectively in binary dye solutions. This corresponds to an enhancement of 4.5 and 2.4 fold, respectively, compared to single dye solutions. MRH therefore has the potential of being used as an efficient sorbent for the removal of both dyes in textile wastewaters.

Adenomatoid odontogenic tumour: a case study with radiographic differential diagnostic considerations

Siar CH, Ong ST, Ng KH

Singapore Dent J, 1996 Jul;21(1):19-22.

PMID: 10597178

Adenomatoid odontogenic tumours (AOT) are benign, hamartomatous odontogenic lesions that not uncommonly mimic a dentigerous cyst radiographically. Such a case as found involving an unerupted left maxillary canine in a 19-year-old Chinese female is described. The differential diagnosis of some common odontogenic cysts and neoplasms occurring in Malaysians, that may present in a dentigerous relationship to an unerupted tooth is discussed. A brief review of the radiographic literature on AOT is also included.

Satisfaction of orthognathic surgical patients in a Malaysian population

Siow KK, Ong ST, Lian CB, Ngeow WC

J Oral Sci, 2002 Dec;44(3-4):165-71.

PMID: 12613507

Thirty-one patients treated at the Faculty of Dentistry, University of Malaya, were assessed for their satisfaction following orthognathic surgery. The female to male ratio was 22:9 with an age range of 17 to 36. Almost all patients (97%) listed appearance as one of their rationales for surgery. More males (78%) than females (59%) wanted functional improvement, while more females (91%) than males (33%) hoped for improvement in self-confidence. All patients reported esthetic improvement while 68% each reported improvement in mastication and self-confidence. Slightly more than half (52%) chose esthetic improvement as the single most important factor resulting in satisfaction. Almost ninety percent of male patients claimed satisfaction with functional improvement, while 68% of those who found satisfaction in improved self-confidence were females. Eighty-seven percent rated their post-surgical changes as being well accepted by their family. The impact of these findings on the success of the surgery and the need to reinforce verbal communication with printed pamphlets are emphasized.

Fulltext Orthognathic surgery in the University of Malaya

Ngeow WC, Ong ST, Siow KK, Lian CB

Med J Malaysia, 2002 Dec;57(4):398-403.

PMID: 12733163

This is the first review on orthognathic surgery in Malaysia. The records of a total of 84 patients seen between 1977 and 1999 in the Department of Oral and Maxillofacial Surgery of the Faculty of Dentistry, University of Malaya were analysed. Skeletal III deformity formed 85% of the sample with a female dominance of 2 to 1. The patients' age ranged from 17 to 36 years, with a mean of 25.3 years. The common surgical techniques used were combined bilateral sagittal split and Le Fort I osteotomy. The predominant ethnic group was Chinese (n = 58, 69%); followed by Malay (n = 14, 17%) and Indian (n = 12, 14%).

Osteosarcoma presenting as an aggressive nodular mass in the region of the mandible

Ong ST, Shim CK, Ng KH, Siar CH

J Oral Sci, 2004 Mar;46(1):55-9.

PMID: 15141725

Osteosarcomas are highly malignant neoplasms of bone that are challenging to diagnose. These neoplasms often show atypical behavior. In the initial phase they may present as nondescript bony swellings with an indolent growth rate, only to become overtly aggressive and malignant towards the later phase of the disease. Similarly, the histological growth pattern of this neoplasm can be quite diverse, presenting with areas that mimic benign myofibroblastic tumors, giant cell granulomatous conditions and partial encapsulation. The final diagnosis of an osteosarcoma is often reached after thorough sampling and examination of multiple biopsy specimens. All these clinical features and histological diagnostic difficulties were encountered in a case of osteosarcoma affecting the right mandible of a 62-year-old Chinese woman described here. The diagnostic lessons accrued from this case are discussed.

Purification and characterization of Nipah virus nucleocapsid protein produced in insect cells

Eshaghi M, Tan WS, Ong ST, Yusoff K

J Clin Microbiol, 2005 Jul;43(7):3172-7.

PMID: 16000431

The nucleocapsid (N) protein of Nipah virus (NiV) is a major constituent of the viral proteins which play a role in encapsidation, regulating the transcription and replication of the viral genome. To investigate the use of a fusion system to aid the purification of the recombinant N protein for structural studies and potential use as a diagnostic reagent, the NiV N gene was cloned into the pFastBacHT vector and the His-tagged fusion protein was expressed in Sf9 insect cells by recombinant baculovirus. Western blot analysis of the recombinant fusion protein with anti-NiV antibodies produced a band of approximately 62 kDa. A time course study showed that the highest level of expression was achieved after 3 days of incubation. Electron microscopic analysis of the NiV recombinant N fusion protein purified on a nickel-nitrilotriacetic acid resin column revealed different types of structures, including spherical, ring-like, and herringbone-like particles. The light-scattering measurements of the recombinant N protein also confirmed the polydispersity of the sample with hyrdrodynamic radii of small and large types. The optical density spectra of the purified recombinant fusion protein revealed a high A(260)/A(280) ratio, indicating the presence of nucleic acids. Western blotting and enzyme-linked immunosorbent assay results showed that the recombinant N protein exhibited the antigenic sites and conformation necessary for specific antigen-antibody recognition.

Fulltext An N-terminal extension to the hepatitis B virus core protein forms a poorly ordered trimeric spike in assembled virus-like particles

McGonigle R, Yap WB, Ong ST, Gatherer D, Bakker SE, Tan WS, et al.

J Struct Biol, 2015 Feb;189(2):73-80.

PMID: 25557498 DOI: 10.1016/j.jsb.2014.12.006

Virus-like particles composed of the core antigen of hepatitis B virus (HBcAg) have been shown to be an effective platform for the display of foreign epitopes in vaccine development. Heterologous sequences have been successfully inserted at both amino and carboxy termini as well as internally at the major immunodominant epitope. We used cryogenic electron microscopy (CryoEM) and three-dimensional image reconstruction to investigate the structure of VLPs assembled from an N-terminal extended HBcAg that contained a polyhistidine tag. The insert was seen to form a trimeric spike on the capsid surface that was poorly resolved, most likely owing to it being flexible. We hypothesise that the capacity of N-terminal inserts to form trimers may have application in the development of multivalent vaccines to trimeric antigens. Our analysis also highlights the value of tools for local resolution assessment in studies of partially disordered macromolecular assemblies by cryoEM.

Dimensional profile of oral mucosa around combined tooth-implant-supported bridgework in macaque mandible

Siar CH, Toh CG, Ali TB, Seiz D, Ong ST

Clin Oral Implants Res, 2012 Apr;23(4):438-46.

PMID: 21435011 DOI: 10.1111/j.1600-0501.2010.02145.x

A stable oral mucosa is crucial for long-term survival and biofunctionality of implants. Most of this evidence is derived from clinical and animal studies based solely on implant-supported prosthesis. Much less is known about the dimensions and relationships of this soft tissue complex investing tooth-implant-supported bridgework (TISB). The aim here was to obtain experimental evidence on the dimensional characteristics of oral mucosa around TISB with two different abutment designs.

Influence of abutment design on clinical status of peri-implant tissues

Taiyeb-Ali TB, Toh CG, Siar CH, Seiz D, Ong ST

Implant Dent, 2009 Oct;18(5):438-46.

PMID: 22129962 DOI: 10.1097/ID.0b013e3181ad8e7a

To compare the clinical soft tissue responses around implant tooth-supported 3-unit bridges using tapered abutments with those using butt-joint abutments.

Mutagenesis of the nucleocapsid protein of Nipah virus involved in capsid assembly

Ong ST, Yusoff K, Kho CL, Abdullah JO, Tan WS

J Gen Virol, 2009 Feb;90(Pt 2):392-397.

PMID: 19141448 DOI: 10.1099/vir.0.005710-0

The nucleocapsid protein of Nipah virus produced in Escherichia coli assembled into herringbone-like particles. The amino- and carboxy-termini of the N protein were shortened progressively to define the minimum contiguous sequence involved in capsid assembly. The first 29 aa residues of the N protein are dispensable for capsid formation. The 128 carboxy-terminal residues do not play a role in the assembly of the herringbone-like particles. A region with amino acid residues 30-32 plays a crucial role in the formation of the capsid particle. Deletion of any of the four conserved hydrophobic regions in the N protein impaired capsid formation. Replacement of the central conserved regions with the respective sequences from the Newcastle disease virus restored capsid formation.

Cloning and expression of the nucleocapsid protein gene of nipah virus in different strains of Escherichia coli

Ong ST, Tan WS, Hassan SS, Mohd Lila MA, Yusoff K

J. Biochem. Mol. Biol. Biophys., 2002 Oct;6(5):347-50.

PMID: 12385971

The coding region of the nucleocapsid (N) gene was amplified from the viral RNA and inserted into the bacterial expression vector, pTrcHis2, for intracellular expression in three Escherichia coli strains: TOP 10, BL 21 and SG 935. The N protein was expressed as a fusion protein containing the myc epitope and His-tag at its C-terminal end. The amount of the fusion protein expressed in strain SG 935 was significantly higher than the other two strains, and was detected by the anti-myc antibody, anti-His and swine anti-NiV serum. Hence, the N(fus) protein produced in E. coli could serve as an alternative antigen for the detection of anti-NiV in swine.

Solubility, immunogenicity and physical properties of the nucleocapsid protein of Nipah virus produced in Escherichia coli

Tan WS, Ong ST, Eshaghi M, Foo SS, Yusoff K

J Med Virol, 2004 May;73(1):105-12.

PMID: 15042656

The nucleocapsid (N) protein of Nipah virus (NiV) can be produced in three Escherichia coli strains [TOP10, BL21(DE3) and SG935] under the control of trc promoter. However, most of the product existed in the form of insoluble inclusion bodies. There was no improvement in the solubility of the product when this protein was placed under the control of T7 promoter. However, the solubility of the N protein was significantly improved by lowering the growth temperature of E. coli BL21(DE3) cell cultures. Solubility analysis of N- and C-terminally deleted mutants revealed that the full-length N protein has the highest solubility. The soluble N protein could be purified efficiently by sucrose gradient centrifugation and nickel affinity chromatography. Electron microscopic analysis of the purified product revealed that the N protein assembled into herringbone-like particles of different lengths. The C-terminal end of the N protein contains the major antigenic region when probed with antisera from humans and pigs infected naturally.

N-terminally His-tagged hepatitis B core antigens: construction, expression, purification and antigenicity

Yap WB, Tey BT, Ng MY, Ong ST, Tan WS

J Virol Methods, 2009 Sep;160(1-2):125-31.

PMID: 19433111 DOI: 10.1016/j.jviromet.2009.04.038

The core antigen of the hepatitis B virus (HBcAg) has been used widely as a diagnostic reagent for the identification of the viral infection. However, purification using the conventional sucrose density gradient ultracentrifugation is time consuming and costly. To overcome this, HBcAg particles displaying His-tag on their surface were constructed and produced in Escherichia coli. The recombinant His-tagged HBcAgs were purified using immobilized metal affinity chromatography. Transmission electron microscopy and enzyme-linked immunosorbent assay (ELISA) revealed that the displayed His-tag did not impair the formation of the core particles and the antigenicity of HBcAg.

Fulltext Antimicrobial quaternary ammonium organosilane cross-linked nanofibrous collagen scaffolds for tissue engineering

Dhand C, Balakrishnan Y, Ong ST, Dwivedi N, Venugopal JR, Harini S, et al.

Int J Nanomedicine, 2018;13:4473-4492.

PMID: 30122921 DOI: 10.2147/IJN.S159770

Introduction: In search for cross-linkers with multifunctional characteristics, the present work investigated the utility of quaternary ammonium organosilane (QOS) as a potential cross-linker for electrospun collagen nanofibers. We hypothesized that the quaternary ammonium ions improve the electrospinnability by reducing the surface tension and confer antimicrobial properties, while the formation of siloxane after alkaline hydrolysis could cross-link collagen and stimulate cell proliferation.

Materials and methods: QOS collagen nanofibers were electrospun by incorporating various concentrations of QOS (0.1%-10% w/w) and were cross-linked in situ after exposure to ammonium carbonate. The QOS cross-linked scaffolds were characterized and their biological properties were evaluated in terms of their biocompatibility, cellular adhesion and metabolic activity for primary human dermal fibroblasts and human fetal osteoblasts.

Results and discussion: The study revealed that 1) QOS cross-linking increased the flexibility of otherwise rigid collagen nanofibers and improved the thermal stability; 2) QOS cross-linked mats displayed potent antibacterial activity and 3) the biocompatibility of the composite mats depended on the amount of QOS present in dope solution - at low QOS concentrations (0.1% w/w), the mats promoted mammalian cell proliferation and growth, whereas at higher QOS concentrations, cytotoxic effect was observed.

Conclusion: This study demonstrates that QOS cross-linked mats possess anti-infective properties and confer niches for cellular growth and proliferation, thus offering a useful approach, which is important for hard and soft tissue engineering and regenerative medicine.

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