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Cross-sectional morphology and minimum canal wall widths in C-shaped roots of mandibular molars

Chai WL, Thong YL

J Endod, 2004 Jul;30(7):509-12.
PMID: 15220648

The cross-sectional canal morphology and minimum widths of buccal and lingual canal walls were studied in 20 mandibular molars with C-shaped roots and canal orifices. The roots were mounted in clear resin blocks and sectioned transversely at 1-mm intervals. A total of 154 cross-sections were evaluated with an image analyzer. Twelve different longitudinal canal configurations were identified. The most prevalent were types 1-2 and 1-2-1 with each type occurring in four roots. Evaluation of the cross-sectional morphology showed that the configurations were complete "C" (27%), incomplete C (64%), and non-C (9%). The mean value for the minimum width of the lingual canal wall was 0.58 +/- 0.21 mm and the buccal wall was 0.96 +/- 0.26 mm. This suggests that there is a higher risk of root perforation at the thinner lingual walls of C-shaped canals during shaping and post canal preparation procedures. Both buccal and lingual canal walls were frequently narrower at mesial locations.
The clinical significance of the retromolar canal and foramen in dentistry

Ngeow WC, Chai WL

Clin Anat, 2021 May;34(4):512-521.
PMID: 32020669 DOI: 10.1002/ca.23577

The mandibular canal is nowadays acknowledged as a major trunk with multiple smaller branches running roughly parallel to it. Most of these accessory canals contain branches of the inferior alveolar neurovascular bundle that supplies the dentition, jawbone, and soft tissue around the gingiva and lower lip. This article reviews the prevalence, classification and morphometric measurements of the retromolar canal and its aperture. A retromolar canal is a bifid variation of the mandibular canal that divides from above this main canal, and travels anterosuperiorly within the bone to exit via a single foramen or multiple foramina into the retromolar fossa. This foramen, termed the retromolar foramen, allows accessory branches of the inferior alveolar neurovascular bundles to supply tissues at the retromolar trigone. Clinically, it is of the utmost importance to determine the exact location of the mandibular canal and to identify its retromolar accessory branches when surgery in the posterior mandible is to be performed.
The clinical anatomy of accessory mandibular canal in dentistry

Ngeow WC, Chai WL

Clin Anat, 2020 Nov;33(8):1214-1227.
PMID: 31943382 DOI: 10.1002/ca.23567

The mandibular canal is a conduit that allows the inferior alveolar neurovascular bundle to transverse the mandible to supply the dentition, jawbone and soft tissue around the gingiva and the lower lip. It is not a single canal but an anatomical structure with multiple branches and variations. The branches are termed accessory, bifid or trifid canals depending on their number and configuration. A bifid mandibular canal is an anatomical variation reported more commonly than the trifid variant. Because of these variations, it is of the utmost importance to determine the exact location of the mandibular canal and to identify any branches arising from it prior to performing surgery in the mandible. This article reviews the prevalence, classification and morphometric measurements of these accessory mandibular canals, emphasizing their clinical significance.
Fulltext Review on prophylactic antibiotics for dental patients with prosthetic joints

Chai WL, Yong CK, Ngeow WC

Ann Dent, 2003;10(1):22-26.
MyJurnal

Most prosthetic joint infections originate from wound contamination or haematogenous seeding from distant sites of infection. Bacteraemia may follow dental treatment but there is little evidence of it related to prosthetic joint infection. Nevertheless, controversy continues with regards to the effect of dental treatment in patients with prosthetic joints. This article reviews current English literature regarding the use of antibiotic prophylaxis in the dental management of patients with prosthetic joints. Routine antibiotic prophylaxis is not recommended for every patient with prosthetic joints when receiving dental treatments. However, antibiotic prophylaxis may be prescribed for high-risk groups with predisposing factors to infection when undergoing dental treatment with high risk of bacteraemia.
Fulltext Comment on: Medication-related osteonecrosis of the jaw in osteoporotic patients: prevention and management

Ngeow WC, Chai WL

Singapore Med J, 2019 01;60(1):52.
PMID: 30840997 DOI: 10.11622/smedj.2019006
Fulltext Comment on: Managing tooth pain in general practice

Ngeow WC, Chai WL

Singapore Med J, 2019 07;60(7):383.
PMID: 31378826 DOI: 10.11622/smedj.2019078
Transient loss of power of accommodation in 1 eye following inferior alveolar nerve block: report of 2 cases

Ngeow WC, Shim CK, Chai WL

J Can Dent Assoc, 2006 Dec;72(10):927-31.
PMID: 17187708

Unintended intravascular injection from inferior alveolar nerve blocks can result in frustrating distant complications affecting such structures as the middle ear and eyes. Possible complications affecting the eyes include blurring of vision, diplopia, mydriasis, palpebral ptosis and amaurosis (temporary or permanent). In this article, we present a complication that has been reported only rarely. Two patients developed transient loss of power of accommodation of the eye resulting in blurred vision after routine inferior alveolar nerve blocks on the ipsilateral side. Clear vision returned within 10-15 minutes after completion of the blocks. The possible explanation for this phenomenon is accidental injection into the neurovascular bundle of local anesthetic agents, which were carried via the blood to the orbital region. This resulted in paralysis of a branch of cranial nerve III, the short ciliary nerves that innervate the ciliary muscle, which controls accommodation.
Fulltext Three-dimensional cell culture at the frontiers of in vitro cancer research: present perspectives

Lee, Soo Leng, Zainal Ariff Abdul Rahman, Tsujigiwa, Hidetsugu, Takabatake, Kiyofumi, Nakano, Keisuke, Chai, Wen Lin, et al.

Ann Dent, 2016;23(1):13-22.
MyJurnal

In recent years, three-dimensional (3D) in vitro cell culture models have earned great attention, especially in the field of human cancer disease modelling research as they provide a promising alternative towards the conventional two-dimensional (2D) monolayer culture of cells with improved tissue organization. In 2D cell culture systems, the complexity of cells on a planar surface does not accurately reflects the in vivo cellular microenvironment. Cells propagated in 3D cell culture model, on the other hand, exhibit physiologically relevant cell-to-cell interactions and cell-to-extracellular matrix (ECM) interactions, important in maintaining a normal homeostasis and specificity of tissues. This review gives an overview on 2D models and their limitations, followed by 3D cell culture models, their advantages, drawbacks and challenges in present perspectives. The review also highlights the dissimilarities of 2D and 3D models and the applicability of 3D models in current cancer research
Managing complications of radiation therapy in head and neck cancer patients: Part II. Management of radiation-induced caries

Chai WL, Ngeow WC, Ramli R, Rahman RA

Singapore Dent J, 2006 Dec;28(1):4-6.
PMID: 17378334

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Where possible, pretreatment dental assessment shall be provided for these patients before they undergo radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally for radiation therapy. Because of this, they succumb to complicated oral complications after radiation therapy. The management of xerostomia has been reviewed in Part I of this series. In this article, the management of dental caries, a sequalae of xerostomia following radiation therapy is reviewed.
Managing complications of radiation therapy in head and neck cancer patients: Part I. Management of xerostomia

Ngeow WC, Chai WL, Rahman RA, Ramli R

Singapore Dent J, 2006 Dec;28(1):1-3.
PMID: 17378333

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Where possible, pretreatment dental assessment shall be provided for these patients before they receive radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally for radiation therapy. Because of this, they succumb to complicated oral adverse effects after radiation therapy. Part I of this series reviews the management of xerostomia. The management of the effect of xerostomia to the dentition/oral cavity is discussed in Part II.
Managing complications of radiation therapy in head and neck cancer patients: Part IV. Management of osteoradionecrosis

Ramli R, Ngeow WC, Rahman RA, Chai WL

Singapore Dent J, 2006 Dec;28(1):11-5.
PMID: 17378336

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Pretreatment dental assessment should be provided for these patients before they undergo radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally and, as a result, they succumb to complicated oral adverse effects after radiation therapy. Osteoradionecrosis (ORN) is a severe debilitating condition that impairs healing due to reduction in vascularity and osteocyte population in the affected bone. This article reviews methods of treatment used to treat ORN such as antibiotics, hyperbaric oxygen therapy, therapeutic ultrasound, surgery, and other modalities.
Managing complications of radiation therapy in head and neck cancer patients: Part III. Provision of dentures

Rahman RA, Ngeow WC, Chai WL, Ramli R

Singapore Dent J, 2006 Dec;28(1):7-10.
PMID: 17378335

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Pretreatment dental assessment should be provided for these patients before they undergo radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally and, as a result, they succumb to complicated oral adverse effects after radiation therapy. The management of radiation-induced caries, a sequelae of xerostomia has been reviewed in Part II of this series. In this article, the management of difficulty with dentures, another sequelae of xerostomia following radiation therapy is reviewed.
Managing complications of radiation therapy in head and neck cancer patients: Part VI. Management of opportunistic infections

Ngeow WC, Chai WL, Ramli R, Rahman RA

Singapore Dent J, 2006 Dec;28(1):19-21.
PMID: 17378338

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Where possible, pretreatment dental assessment shall be provided for these patients before they undergo radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally for radiation therapy. Because of this, they succumb to complicated oral adverse effects after radiation therapy. The last part of this series reviews the opportunistic infections that can occur to the perioral structure. Their management is briefly discussed.
Managing complications of radiation therapy in head and neck cancer patients: Part V. Management of mucositis

Ngeow WC, Chai WL, Rahman RA, Ramli R

Singapore Dent J, 2006 Dec;28(1):16-8.
PMID: 17378337

Head and neck cancer is becoming a more recognizable pathology to the general population and dentists. The modes of treatment include surgery and/or radiation therapy. Where possible, pretreatment dental assessment shall be provided for these patients before they undergo radiation therapy. There are occasions, however, whereby head and neck cancer patients are not prepared optimally for radiation therapy. Because of this, they succumb to complicated oral adverse effects after radiation therapy. The second last part of this series reviews and discusses the management of complication that commonly occur to the oral mucosa, i.e. mucositis.
Modified silk fibroin scaffolds with collagen/decellularized pulp for bone tissue engineering in cleft palate: Morphological structures and biofunctionalities

Sangkert S, Meesane J, Kamonmattayakul S, Chai WL

Mater Sci Eng C Mater Biol Appl, 2016 Jan 1;58:1138-49.
PMID: 26478414 DOI: 10.1016/j.msec.2015.09.031

Cleft palate is a congenital malformation that generates a maxillofacial bone defect around the mouth area. The creation of performance scaffolds for bone tissue engineering in cleft palate is an issue that was proposed in this research. Because of its good biocompatibility, high stability, and non-toxicity, silk fibroin was selected as the scaffold of choice in this research. Silk fibroin scaffolds were prepared by freeze-drying before immerging in a solution of collagen, decellularized pulp, and collagen/decellularized pulp. Then, the immersed scaffolds were freeze-dried. Structural organization in solution was observed by Atomic Force Microscope (AFM). The molecular organization of the solutions and crystal structure of the scaffolds were characterized by Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The weight increase of the modified scaffolds and the pore size were determined. The morphology was observed by a scanning electron microscope (SEM). Mechanical properties were tested. Biofunctionalities were considered by seeding osteoblasts in silk fibroin scaffolds before analysis of the cell proliferation, viability, total protein assay, and histological analysis. The results demonstrated that dendrite structure of the fibrils occurred in those solutions. Molecular organization of the components in solution arranged themselves into an irregular structure. The fibrils were deposited in the pores of the modified silk fibroin scaffolds. The modified scaffolds showed a beta-sheet structure. The morphological structure affected the mechanical properties of the silk fibroin scaffolds with and without modification. Following assessment of the biofunctionalities, the modified silk fibroin scaffolds could induce cell proliferation, viability, and total protein particularly in modified silk fibroin with collagen/decellularized pulp. Furthermore, the histological analysis indicated that the cells could adhere in modified silk fibroin scaffolds. Finally, it can be deduced that modified silk fibroin scaffolds with collagen/decellularized pulp had the performance for bone tissue engineering and a promise for cleft palate treatment.
Modified porous scaffolds of silk fibroin with mimicked microenvironment based on decellularized pulp/fibronectin for designed performance biomaterials in maxillofacial bone defect

Sangkert S, Kamonmattayakul S, Chai WL, Meesane J

J Biomed Mater Res A, 2017 Jun;105(6):1624-1636.
PMID: 28000362 DOI: 10.1002/jbm.a.35983

Maxillofacial bone defect is a critical problem for many patients. In severe cases, the patients need an operation using a biomaterial replacement. Therefore, to design performance biomaterials is a challenge for materials scientists and maxillofacial surgeons. In this research, porous silk fibroin scaffolds with mimicked microenvironment based on decellularized pulp and fibronectin were created as for bone regeneration. Silk fibroin scaffolds were fabricated by freeze-drying before modification with three different components: decellularized pulp, fibronectin, and decellularized pulp/fibronectin. The morphologies of the modified scaffolds were observed by scanning electron microscopy. Existence of the modifying components in the scaffolds was proved by the increase in weights and from the pore size measurements of the scaffolds. The modified scaffolds were seeded with MG-63 osteoblasts and cultured. Testing of the biofunctionalities included cell viability, cell proliferation, calcium content, alkaline phosphatase activity (ALP), mineralization and histological analysis. The results demonstrated that the modifying components organized themselves into aggregations of a globular structure. They were arranged themselves into clusters of aggregations with a fibril structure in the porous walls of the scaffolds. The results showed that modified scaffolds with a mimicked microenvironment of decellularized pulp/fibronectin were suitable for cell viability since the cells could attach and spread into most of the pores of the scaffold. Furthermore, the scaffolds could induce calcium synthesis, mineralization, and ALP activity. The results indicated that modified silk fibroin scaffolds with a mimicked microenvironment of decellularized pulp/fibronectin hold promise for use in tissue engineering in maxillofacial bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1624-1636, 2017.
Fulltext Expression of Interleukin-1β and Histological Changes of the Three-Dimensional Oral Mucosal Model in Response to Yttria-Stabilized Nanozirconia

Nasarudin NA, Razali M, Goh V, Chai WL, Muchtar A

Materials (Basel), 2023 Mar 01;16(5).
PMID: 36903142 DOI: 10.3390/ma16052027

Over the years, advancement in ceramic-based dental restorative materials has led to the development of monolithic zirconia with increased translucency. The monolithic zirconia fabricated from nano-sized zirconia powders is shown to be superior in physical properties and more translucent for anterior dental restorations. Most in vitro studies on monolithic zirconia have focused mainly on the effect of surface treatment or the wear of the material, while the nanotoxicity of this material is yet to be explored. Hence, this research aimed to assess the biocompatibility of yttria-stabilized nanozirconia (3-YZP) on the three-dimensional oral mucosal models (3D-OMM). The 3D-OMMs were constructed using human gingival fibroblast (HGF) and immortalized human oral keratinocyte cell line (OKF6/TERT-2), co-cultured on an acellular dermal matrix. On day 12, the tissue models were exposed to 3-YZP (test) and inCoris TZI (IC) (reference material). The growth media were collected at 24 and 48 h of exposure to materials and assessed for IL-1β released. The 3D-OMMs were fixed with 10% formalin for the histopathological assessments. The concentration of the IL-1β was not statistically different between the two materials for 24 and 48 h of exposure (p = 0.892). Histologically, stratification of epithelial cells was formed without evidence of cytotoxic damage and the epithelial thickness measured was the same for all model tissues. The excellent biocompatibility of nanozirconia, as evidenced by the multiple endpoint analyses of the 3D-OMM, may indicate the potential of its clinical application as a restorative material.
Contour Analysis of Three-Dimensional Peri-Implant Mucosal Model as an Endpoint Analysis of Photofunctionalization Effects on Implant Abutment Materials

Razali M, Chai WL, Omar RA, Ngeow WC

Materials (Basel), 2023 Aug 09;16(16).
PMID: 37629819 DOI: 10.3390/ma16165529

INTRODUCTION: The objective of this study was to examine the effect of photofunctionalization on the soft-tissue contour formed at the interface of various abutment materials using end-point analyses obtained from the three-dimensional oral mucosal model (3D-OMMs).
METHODS: Commercially pure titanium (CPTi), alumina-toughened zirconia (ATZ), and yttria-stabilized zirconia (YSZ) made into discs shapes were classified into two groups: UV-treated (PTx) and non-treated (NTx). The materials in PTx groups were exposed to UV light for 12 min. Human gingival fibroblasts and TR146 epithelial cell lines co-cultured on the acellular dermal membrane were used to construct the 3D-OMM. After 4 days of culture, the discs were inserted into the holes prepared within the membrane of 3D-OMMs. The contour formed by the tissue was evaluated after 14 days of culture.
RESULTS: The UV treatment of abutment materials resulted in the formation of more non-pocket-tissue types among the PTx group (p = 0.002). Of all materials tested, soft tissue contour around YSZ showed higher scores for the non-pocket type in both non- and UV-treated groups.
CONCLUSIONS: The non-pocket type of tissue attachment was frequently found in all surfaces modified by photofunctionalization, particularly zirconia. The 3D-OMM can be used to evaluate the biological endpoints of implant surface modifications.
Fulltext CRC14: Different Approaches to Morse Taper Abutment Fracture

Lim EL, Ngeow WC, Lim D, Chai WL

J Indian Prosthodont Soc, 2018 Oct;18(Suppl 1):S41.
PMID: 30532466 DOI: 10.4103/0972-4052.244669
The Management of Persistent Pain From a Branch of the Trifid Mandibular Canal due to Implant Impingement

Aljunid S, AlSiweedi S, Nambiar P, Chai WL, Ngeow WC

J Oral Implantol, 2016 Aug;42(4):349-52.
PMID: 27078072 DOI: 10.1563/aaid-joi-D-16-00011

The mandibular canal is a conduit that allows the inferior alveolar neurovascular bundle to transverse the mandible to supply the dentition, jawbone, and soft tissue around the lower lip. It is now acknowledged that the mandibular canal is not a single canal but an anatomical structure with multiple branches and variations. Iatrogenic injury to branches of the mandibular canal that carry a neurovascular bundle has been reported to cause injury to the main canal as severe as if the main canal itself is traumatized. These injuries include bleeding, neurosensory disturbance, or the formation of traumatic neuroma, and so far, they have involved cases with the bifid mandibular canal. This current report presents a case of neurosensory disturbance that resulted from the impingement of a branch of a trifid mandibular canal during implant insertion. Its management included analgesics, reexamination, and reinserting a shorter implant.

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