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Chong Huat Siar

Publications and source records attributed to Chong Huat Siar.

17 recordsLinked to original sources
PubMed2006

Differential expression of basement membrane collagen-IV alpha1 to alpha6 chains during oral carcinogenesis.

This study aimed to resolve if basement membrane (BM) collagen alpha chains undergo remodeling during oral carcinogenesis. Using immunohistochemistry and transmission electron microscopy, we found that BMs in oral epithelial dysplasias (OED: mild, n=10; moderate, n=10; severe, n=10) and carcinoma in situ (CIS) (n=10) differed from normal mucosa (n=6) and oral epithelial hyperplasia (n=5) in showing: (1) excessive lamina densa-like material ultrastructurally, and (2) stronger immunoexpression for alpha5(IV) than for alpha1(IV), alpha2(IV), and alpha6(IV) chains-findings that implicate these molecules' role as an adhesive template for the attachment and persistence of basal dysplastic cells. Incipient loss of BM integrity in CIS, where alpha5(IV)/alpha6(IV) chains were more frequently absent than alpha1(IV)/alpha2(IV) chains, suggests that alpha(IV) network disruption is crucial for progression of dysplastic cells into the extracellular compartment, marking transition into the invasive phase. In carcinomatous BM, the disappearance of alpha(IV) chains was more severe in poorly differentiated oral squamous cell carcinoma (OSCC) (n=10) than in well-differentiated OSCC (n=10). In all samples examined, alpha3(IV) and alpha4(IV) chains were absent. These findings taken together suggest that BM collagen-IV alpha chains undergo remodeling where selective increase and loss of these molecules are probably early and late events, respectively, during progression of oral dysplasia to cancer.

Basement Membrane↗
PubMed2006

Microcystic adnexal carcinoma with mandibular bone marrow involvement: a case report with immunohistochemistry.

Microcystic adnexal carcinoma is a rare, locally aggressive cutaneous neoplasm with a high probability of persistence locally but a low probability of metastasis. We report a case of a 69-year-old female patient with an indurated plaque at the mental region. Histologically, the tumor cells invaded the subcutaneous tissue and mandibular bone. The tumor consisted mainly of squamous and basaloid epithelial nests and cords embedded in a desmoplastic stroma. A few keratin-filled microcysts and ductal structures were also observed. Perineural encroachment was also noted but there was no mitosis, cytologic features of malignancy, or metastasis. The epithelial nests were positive to various cytokeratins except for CK20 and the lumina of the ductal structures were positive to carcinoembryonic antigen. Our results indicate that microcystic adnexal carcinoma consists of tumor cells capable of both follicular and eccrine differentiation. It is locally aggressive, extends far beyond its clinical presentation and may involve the bone. It may persist and remain asymptomatic for so many years without metastasis. A lifetime postsurgery monitoring is mandatory to ensure early and proper management.

Aged↗
PubMed2005

Heparanase gene and protein expression in ameloblastoma: possible role in local invasion of tumor cells.

Ameloblastoma is the most common odontogenic neoplasm, particularized by its local invasiveness. Heparanase is the endo-glucuronidase enzyme that specifically cleaves heparan sulfate, the important modulator of extracellular matrix, and related to invasion of tumor cells. In this study, we addressed to show the gene expression and localization of heparanase in ameloblastoma. Immunohistochemistry and in situ hybridization of heparanase were carried out in 23 ameloblastomas. Strong expression of heparanase at both mRNA and protein levels was detected in all ameloblastomas studied. Small tumor nests and budding epithelial branches showed stronger staining pattern and the stromal tissues at the immediate vicinity of the tumor nests with strong heparanase expression were loose and edematous. Cystic areas and squamous metaplastic areas of the tumor showed intense staining with heparanase antibody proposing the implication of heparanase in these processes. These results suggest the possible contribution of heparanase in the local invasiveness and secondary morphologic changes of ameloblastoma.

Ameloblastoma↗
PubMed2005

Analysis of amelogenin gene (AMGX, AMGY) expression in ameloblastoma.

Although the amelogenin gene is expressed in ameloblastoma, the precise expression pattern of X and Y amelogenin genes (AMGX, AMGY) in this tumor has not yet been identified. In this study, we analyzed amelogenin gene expression in 19 samples (9 male, 10 female) of oral ameloblastomas by RT-PCR and detect the chromosomal origin of amelogenin mRNA by restriction enzyme digestion of the RT-PCR product. All tumor samples expressed amelogenin mRNA. We could detect increased level of AMGY expression in all male samples, higher than that of AMEX. It is an interesting finding as in normal male tooth development, the expression of AMGY is very much lower than that of AMGX. We postulate that epigenetic change of sex chromosomes may have some correlations with tumorigenesis of ameloblastoma. We also discuss the other possible mechanisms and points for future studies on this change in expression pattern.

Ameloblastoma↗
PubMed2004

Pseudo bilateral tonsilloliths: a case report and review of the literature.

Tonsilloliths are very rare concretions found in the tonsillar crypt. They are usually single and unilateral, but occasionally may be multiple or bilateral. Small concretions in the tonsils are common, but well formed giant unilateral or bilateral tonsilloliths are extremely uncommon. Only two cases of bilateral tonsilloliths have so far been reported in the literature. A case of unilateral tonsillolith, mimicking bilateral tonsilloliths taken with the orthopantogram (OPT) in a 57-year-old Malaysian Indian female with squamous cell carcinoma of the oral cavity is described. Although the OPT is a reliable and standard panoramic X-ray unit used in dentistry, superimposition of a lesion involving one side of the jaw creates a pseudo or ghost image on the contralateral side leading to a misdiagnosis of bilateral lesions. This report highlights that tonsilloliths, though rare, should be considered in the differential diagnosis of radiopaque masses involving the mandibular ramus, and that investigations such as CT scan or MRI may be required to differentiate pseudo or ghost images from true bilateral pathologies.

Calculi↗
PubMed2004

Cannon's disease: clinical and diagnostic implications: a case report.

Cannon's disease or white sponge naevus is a relatively rare genetically determined skin disorder. It is inherited as an autosomal dominant trait that displays a high degree of penetrance and expressivity. This article describes cases of Cannon's disease in a mother and her son.

Adult↗
PubMed2003

Odontogenic keratocyst with dentinoid formation.

Although rare, hard tissue deposits, namely dystrophic calcifications and cartilage, have been reported to occur in the connective tissue wall of the odontogenic keratocyst. However, dentinoid formation has not been previously documented. A case involving the left mandibular premolar-molar region in a 37-year-old Malay male is described here along with a brief review on the reported prevalence of hard tissue deposits in the odontogenic keratocyst. Differential diagnosis of this case from other dentinoid-forming odontogenic cysts and tumors-notably calcifying odontogenic cyst, odontoma, ameloblastic fibro-odontoma, central odontogenic fibroma and adenomatoid odontogenic tumor that may present with dentin/dentinoid formation-is discussed.

Adult↗
PubMed2003

Bone-implant interface around titanium implants under different loading conditions: a histomorphometrical analysis in the Macaca fascicularis monkey.

BACKGROUND: Bone healing around endosseous dental implants is associated with peri-implant loading conditions. Therefore, the aim of this study was to evaluate histomorphometrically the bone response around unloaded, delayed, and immediately loaded implants with a progressive thread design that were placed in the posterior regions of the lower jaw in monkeys. METHODS: Nine adult monkeys (Macaca fascicularis) were used in this study. After extraction of the second premolars and first and second molars in the mandible, the bone was allowed to heal for a period of 3 months. Forty-eight 8 mm long implants with a diameter of 3.5 mm were placed according to the following protocol. In two of the monkeys, six implants were placed and left to heal submerged for 3 months (group A). In seven monkeys, 21 implants were placed in one side of the mandible and loaded after 3 months of submerged healing (group B). The group B implants were loaded with temporary resin bridges at the same time as another 21 implants that were loaded immediately (group C) after placement in the contralateral side of the mandibles of the same monkeys. The occlusion of group B and C implants was checked for optimal relationship of the resin bridges that were replaced 1 month later with metal bridges and loaded for an additional 2 months. The group A animals were sacrificed after 3 months of submerged healing without loading; group B and C animals were sacrificed after 3 months of implant loading. Specimens were examined histologically and histomorphometrically. RESULTS: All implants osseointegrated without presenting any gap in the metal-bone interface. Compact cortical bone was found in contact with the implant surfaces. Group A implants demonstrated in the interface cancellous bone with loose connective tissue. Group B and C implants showed a thick cortical plate with extensive bone trabeculae formation. There was a significant difference in bone-to-implant contact (BIC) between the various loading conditions. No significant difference (P < 0.05) was found between groups B and C. There was an increased area of bone (BA) within the threads as well as around the apices of group B and C implants. CONCLUSIONS: Implant loading might have stimulated increased bone formation and thus may be a key factor in influencing positive osseointegration. In addition, immediately loaded implants may osseointegrate in a similar manner as delayed loaded implants.

Animals↗
PubMed2003

Peri-implant soft tissue integration of immediately loaded implants in the posterior macaque mandible: a histomorphometric study.

BACKGROUND: Today, one critical goal in implant placement is the achievement of optimal soft tissue integration. Reports thus far have demonstrated successful soft tissue preservation in delayed loaded implants placed in anterior jaws. The aim of this study was to histomorphometrically examine the soft tissues around immediately loaded implants placed in the macaque posterior mandible. METHODS: Splinted crowns on screw-shaped titanium implants (8 mm length, 3.5 mm diameter) were utilized. Three implants each were placed in the premolar-molar edentulous mandibular segments of 6 adult monkeys (Macaca fascicularis); one side served as the control (delayed loading) and the other as the test sites (immediate loading). The animals were sacrificed after 3 months of loading. Histomorphometry of 6 soft tissue indices including the sulcus depth (SD), junctional epithelium (JE), connective tissue contact (CTC), biologic width (BW = SD + JE + CTC), DIM (distance between the implant top and coronal gingiva), and DIB (distance between the implant top and first implant-to-bone contact) was performed on non-decalcified sections. RESULTS: No significant differences in the mean soft tissue scores (mm) between the test (SD = 0.68 +/- 0.63; JE = 1.71 +/- 1.04; CTC = 1.51 +/- 1.14; DIM = 2.27 +/- 1.18; DIB = 1.32 +/- 1.21; BW = 3.9) and control (SD = 0.88 + 0.57; JE = 1.66 + 0.77; CTC = 1.24 +/- 0.92; DIM = 2.38 +/- 0.81; DIB = 1.19 +/- 0.91; BW = 3.78) groups were observed (P > 0.01). CONCLUSION: These findings suggest that the dimensions of the peri-implant soft tissues were within the biologic range and were not influenced by immediate functional loading or posterior location of the implants in the macaque mandible.

Alveolar Process↗
PubMed2003

Oral candidosis in non-Hodgkin's lymphoma: a case report.

Though oral candidosis is an opportunistic fungal infection that commonly affects immunocompromised patients, little is known of its occurrence as a complication of Non-Hodgkin's lymphoma. This paper reports a case of oral candidosis in a 20-year-old Indonesian woman with this lymphoproliferative disease. She presented with acute pseudomembranous candidosis on the dorsum and lateral borders of the tongue, bilateral angular cheilitis and cheilocandidosis. The latter is a rare clinical variant of oral candidosis, and the lesions affecting the vermilion borders presented as an admixture of superficial erosions, ulcers and white plaques. Clinical findings were confirmed with oral smears and swabs that demonstrated the presence of hyphae, pseudohyphae and blastospores, and colonies identified as Candida albicans. A culture from a saline rinse was also positive for multiple candidal colonies. Lip and oral lesions were managed with Nystatin. The lesions regressed with subsequent crusting on the lips, and overall reduction in oral thrush. As Non-Hodgkin's lymphoma is a neoplastic disease that produces a chronic immunosuppressive state, management of its oral complications, including those due to oral candidosis, is considered a long-term indication.

Adult↗
PubMed2002

Differential expression of collagen IV alpha1 to alpha6 chains in basement membranes of benign and malignant odontogenic tumors.

Type IV collagen, the major component of basement membrane (BM), demonstrates a stage- and position-specific distribution of its isoforms during tooth development. To determine its localization in BM of odontogenic neoplasms, immunohistochemistry using six anti-alpha(IV) chain-specific monoclonal antibodies was performed. Results disclosed that BM demonstrated an irregular alpha(IV) chain profile in malignant odontogenic tumors as compared to benign odontogenic neoplasms. No alpha3(IV) chains were detected. Expression of alpha1(IV)/alpha2(IV) and alpha5(IV)/alpha6(IV) chains was stronger in desmoplastic ( n=3) than in ordinary (n=5) ameloblastomas. The adenomatoid odontogenic tumor ( n=2) distinctly expressed these chains in BM of cribriform areas and hyaline materials (which was also alpha4(IV)-positive), but weakly around epithelial whorls/rosettes/nests and mineralized foci. These five chains also stained BM and tumor cells of ameloblastic fibroma ( n=3) and ameloblastic fibro-odontosarcoma (n=1), but not the inductive hard tissues. Ameloblastic carcinoma ( n=2) showed specific alpha1(IV)/alpha2(IV) chain loss, while primary intraosseous carcinoma ( n=1) demonstrated a discontinuous alpha1(IV)/alpha2(IV) and alpha5(IV)/alpha6(IV) staining pattern. The present results suggest that modification and remodeling of BM collagen IValpha chains occur during odontogenic neoplasms' progression.

Animals↗
PubMed2002

Elemental sulphur and alkali elutable melanin detected in oral melanosis and malignant melanoma by energy-filtering transmission electron microscopy.

BACKGROUND: The morphology and contents of melanosomes are important features for differentiating melanocyte-derived melanotic lesions such as melanosis and malignant melanoma. METHODS: In this study, we attempted to elucidate the structure of melanin and sulphur content in oral melanosis and malignant melanomas by ultrastructural analysis. RESULTS: In oral melanosis, the essential pathological findings were overproduction of eumelanin and discharge of melanin into keratinocytes. In malignant melanoma in situ, pleomorphic and ellipsoid abnormal melanosomes with an increase in sulphur content and alkali elution rate were detected. In invasive malignant melanoma, the irregular ellipsoid and spheroid melanosomes existing either as discrete bodies or compound melanosomes with furtherly increased sulphur content and alkali elution were detected. CONCLUSIONS: Our findings suggest that abnormal melanosome morphology and high sulphur content are predictive markers for assessment of early or precancerous melanotic lesions and malignant melanoma.

Alkalies↗
PubMed2002

Distribution of basement membrane type IV collagen alpha chains in ameloblastoma: an immunofluorescence study.

BACKGROUND: Type IV collagen, a heterotrimeric molecule that exists in six genetically distinct forms, alpha1(IV)-alpha6(IV) is a major structural component of basement membrane (BM) and acts as a scaffold for other BM constituents. METHODS: Indirect immunofluorescence using alpha chain-specific monoclonal antibodies was employed to clarify basement membrane (BM) collagen IV distribution in two ameloblastoma, and for comparison, on oral mucosa and tooth germ. RESULTS: Ameloblastoma BM expressed five of six genetically distinct forms of collagen IV: alpha1(IV), alpha2(IV), alpha5(IV) and alpha6(IV) chains occurred as intense linear stainings without disruption around neoplastic epithelium, and this expression pattern was fundamentally similar to oral mucosa BM; alpha4(IV) expression was rare and occurred around nests of primitive tumor cells or potentially invasive sites. The tooth germ demonstrated a stage- and position-specific collagen IV distribution: the inner enamel epithelium BM expressed alpha1(IV), alpha2(IV), and alpha4(IV) except in the cuspal predentine region; and the outer enamel epithelium BM expressed alpha1(IV), alpha2(IV), alpha5(IV), and alpha6(IV) chains. CONCLUSIONS: Results suggest that collagen IV alpha chain distribution in ameloblastoma BM plays an important role in tumor cytodifferentiation and progression.

Ameloblastoma↗
PubMed1999

A preliminary study of healing of superpulsed carbon dioxide laser incisions in the hard palate of monkeys.

BACKGROUND AND OBJECTIVE: Prior studies of laser wound healing using different animal models have shown a delayed tissue response after carbon dioxide (CO2) laser application. This article reports on the preliminary findings of healing of superpulsed CO2 laser and scalpel incisions in the hard palate of monkeys. STUDY DESIGN/MATERIALS AND METHODS: Twelve parallel incisions using a superpulsed, continuous wave CO2 laser and a scalpel were performed in the hard palate of each of two adult monkeys at 3, 7, and 14 days time schedules. Power levels of 2.0, 4.0, and 6.0 Watts were used for the laser incisions. Wounds were harvested, fixed in 10% formalsaline for at least 48 hours and processed routinely. Each specimen was embedded in paraffin wax at 90 degrees to the surface epithelium and 5 microm thick sections prepared for staining with haematoxylin and eosin, Periodic acid Schiff and Masson-trichrome at a step-serial interval of 100 microm. Sections were evaluated independently. RESULTS: According to the clinical findings we showed a wound closure in all of the wounds (laser and scalpel incisions) at 3, 7, and 14 days of healing. Histologically, we showed that laser incisions at three and seven days demonstrated an increased, power setting-dependent tissue necrosis and marked inflammatory response with minimal organization compared to scalpel incisions. At 14 days both types of incisions exhibited complete wound healing of the epithelium and connective tissue. DISCUSSION AND CONCLUSIONS: According to these preliminary results, superpulsed CO2 laser tends to produce more pronounced changes (due to tissue thermal damage) with corresponding greater inflammatory reaction and delay in tissue organization only initially.

Animals↗
PubMed1996

An immunohistochemical study of two cases of either peripheral odontogenic fibroma (WHO type) or peripheral ameloblastoma.

Two cases of either peripheral odontogenic fibroma (POF) (WHO type) or peripheral ameloblastoma are reported. Their immunohistochemical characteristics were investigated in an attempt to clarify their histogenesis. The results showed that the epithelial component of this neoplasm tended to retain its distinct odontogenic character and expressed a keratin profile different from that of the overlying oral epithelium from which both cases most probably originated. The connective tissue element of these tumors was vimentin-positive and S-100 protein negative, confirming their mesodermal nature but precluding the possibility of ectomesenchymal derivation. No reactivity for desmin was noted.

Adult↗
PubMedDate not supplied

Histologic and histomorphometric evaluation of peri-implant bone subjected to immediate loading: an experimental study with Macaca fascicularis.

PURPOSE: Immediately loaded splinted implants can become osseointegrated when they are placed in the anterior part of the mandible. The concept of immediate loading has not been well examined in the posterior mandible. The aim of this study was to evaluate the hard tissue reactions around immediately loaded implants placed in the posterior mandible in the monkey model. MATERIALS AND METHODS: Six adult M. fascicularis monkeys were used in this study. Thirty-six Ankylos implants (Degussa Dental, Hanau-Wolfgang, Germany) were placed after extraction of the second premolar, first, and second molar teeth and complete healing of the sockets. Control (C) group implants were placed and, after osseointegration, were loaded for 1 month using temporary acrylic resin prostheses and later for 2 months using splinted metal crowns. In the contralateral region of the mandible, test (T) group implants were placed and loaded immediately with the same sequence as carried out for the C implants. After sacrifice of the animals, specimens were examined histologically and evaluated histomorphometrically. RESULTS: All implants were osseointegrated. Compact, cortical bone in contact with the implant surface without any gaps or connective tissue formation was demonstrated. DISCUSSION: Histomorphometric findings of the bone-implant-contacts showed no significant differences between the T and C group implants. Peri-implant mineralized bone areas presented statistically significant differences and showed a higher density of bone between the threads of immediately loaded implants (P < .05). CONCLUSIONS: Immediately loaded splinted implants in the posterior mandible can become osseointegrated with a hard tissue peri-implant response similar to that of delayed loaded implants. Moreover, immediate loading seems to increase the ossification of the alveolar bone around endosseous implants.

Alveolar Process↗