Beng Choon, Keson Tan
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dentanbc@nus.edu.sg
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Publication Application of finite element analysis in implant dentistry: A review of the literature(2001-06) Geng, J.-P.; Tan, K.B.C.; Liu, G.-R.; RESTORATIVE DENTISTRY; MECHANICAL ENGINEERINGFinite element analysis (FEA) has been used extensively to predict the biomechanical performance of various dental implant designs as well as the effect of clinical factors on implant success. By understanding the basic theory, method, application, and limitations of FEA in implant dentistry, the clinician will be better equipped to interpret results of FEA studies and extrapolate these results to clinical situations. This article reviews the current status of FEA applications in implant dentistry and discusses findings from FEA studies in relation to the bone-implant interface, the implant-prosthesis connection, and multiple-implant prostheses.Publication Accuracy of Implant Analogs in 3D Printed Resin Models(WILEY, 2020-07-02) Maria, Rahmat; Tan, Ming Yi; Wong, Keng Mun; Lee, Bruce Chi Hong; Chia, Vanessa Ai Ping; Tan, Keson Beng Choon; Assoc Prof Beng Choon, Keson Tan; DENTISTRY; DEAN'S OFFICE (DENTISTRY)Purpose: To study the effect of implant analog system, print orientation, and analog holder radial offset on 3D linear and absolute angular distortions of implant analogs in 3D printed resin models. Materials and Methods: A sectional master model simulating a 2-implant, 3-unit fixed prosthesis in a partially edentulous jaw was fabricated. Three implant analog systems for 3D printed resin models—Straumann (ST), Core3DCentres (CD) and Medentika (MD)—were tested. The corresponding scan bodies were secured onto the implants and scanned using an intraoral scanner. Models were obtained with a Digital Light Processing printer. Each implant analog system had 2 print orientations (transverse [X] and perpendicular [Y] to the printer door) and 2 analog holder radial offsets (0.04 mm and 0.06 mm), for a total of 60 models. The physical positions of the implants in the master model and the analogs in the printed resin models were directly measured with a Coordinate Measuring Machine (CMM). 3D linear distortion (ΔR) and absolute angular distortion (Absdθ) defined the 3D accuracy of the analogs in the printed models. Univariate ANOVA was used to analyse data followed by post hoc tests (Tukey HSD, α = 0.05). Results: Mean ΔR for ST (–155.7 ± 60.6 µm), CD (124.9 ± 65.0 µm) and MD (–92.9 ± 48.0 µm) were significantly different (p < 0.01). Mean Absdθ was not significantly different between ST (0.57 ± 0.48°) and CD (0.41 ± 0.27°), but both were significantly different from MD (2.11 ± 1.14°) (p < 0.01). Print orientation had a significant effect on ΔR only but no discernible trend could be found. Analog holder radial offset had no significant effect on ΔR and Absdθ. Conclusions: Implant analog system had a significant effect on ΔR and Absdθ. Compared to the master model, CD produced greater mean interanalog distances, while ST and MD produced smaller mean interanalog distances. MD exhibited the greatest mean angular distortion which was significantly greater than ST and CD.Publication Three-Dimensional Static Articulation Accuracy of Virtual Models - Part I: System Trueness and Precision(WILEY, 2018-02-01) Yee, Sophia Hui Xin; Esguerra, Roxanna Jean; Chew, Amelia Anya Qin'An; Wong, Keng Mun; Tan, Keson Beng Choon; Assoc Prof Beng Choon, Keson Tan; DENTISTRY; DEAN'S OFFICE (DENTISTRY)Purpose: To evaluate the 3D static articulation accuracy of 3 model scanner-CAD systems (Ceramill Map400 [AG], inEos X5 [SIR], Scanner S600 Arti [ZKN]) using a coordinate measuring machine (CMM). Trueness and precision for each system will be reported in Part I. Materials and Methods: The master model simulated a single crown opposing a 3-unit fixed dental prosthesis. Five mounted stone cast sets were prepared, and one set was randomly selected. Reference values were obtained by measuring interarch and interocclusal reference features with the CMM. The stone cast set was scanned 5 times consecutively and articulated virtually with each system (3 test groups, n = 5). STL files of the virtual models were measured with CMM software. dRR, dRC, and dRL, represented interarch global distortions at right, central, and left sides, respectively, while dRM, dXM, dYM, and dZM represented interocclusal global and linear distortions between preparations. Results: For trueness values, mean interarch global distortions ranged from 13.1 to 40.3 μm for dRR, –199.0 to –48.1 μm for dRC, and –114.1 to –47.7 μm for dRL. Mean percentage error of interarch distortion did not exceed 0.6%. Mean interocclusal distortions ranged from 16.0 to 117.0 μm for dRM, -33.1 to 101.3 μm for dXM, 32.9 to 49.9 μm for dYM and –32.0 to 133.1 μm for dZM. ANOVA of trueness found statistically significant differences for dRC, dRL, dRM, dXM, and dZM. For precision values, absolute mean difference between the 10 superimposition combinations ranged from 25.3 to 91.0 μm for dRR, 21.5 to 85.5 μm for dRC, 24.8 to 70.0 μm for dRL. Absolute mean difference ranged from 49.9 to 66.1 μm for dRM, 20.7 to 92.1 μm for dXM, 86.8 to 96.0 μm for dYM, and 36.5 to 100.0 μm for dZM. ANOVA of precision of all test groups found statistically significant differences for dRR, dRC, dRL, dXM and dZM, and the SIR group was the least precise. Conclusion: The overall interarch global distortion of all three model scanner-CAD systems was low and did not exceed 0.6%. Variations in scanner technology, virtual articulation algorithm, and use of physical articulators contributed to the differences in distortion observed among all three groups.Publication Photomechanical studies on Non-Carious-Cervical-Lesions of the teeth(2005) Kishen, A.; Tan, K.B.C.; Asundi, A.; RESTORATIVE DENTISTRYThis study aims to examine the biomechanical factor underlying the origin of Non-Carious-Cervical-Lesions by examining the strain distribution in the enamel and dentine. A digital moiré interferometry was utilized for this purpose. It is observed from this study that the enamel displayed marked strains in the lateral direction, while the dentine experienced marked strains in the axial and lateral directions during compression. The strains in the enamel and the dentine displayed both normal and shear components. The shear strain in the lateral direction within the enamel and the normal and shear strains in the axial and lateral directions within the coronal dentine concentrated at the cervical region. These experiments highlights that the biting loads will contribute to the loss of hard tissue in the cervical region.Publication Load fatigue performance of a single-tooth implant abutment system: Effect of diameter(2006-11) Quek, C.E.; Tan, K.B.; Nicholls, J.I.; RESTORATIVE DENTISTRYPurpose: This study investigated the load fatigue performance of narrow-, regular-, and wide-diameter CeraOne (Nobel Biocare) single-tooth implants and abutments. Materials and Methods: Five samples of each implant-abutment combination in 3 different widths were tested at 3 applied screw torque levels (recommended torque, recommended torque +20%, and recommended torque -20%). A rotational load fatigue machine was used to apply a 21-N load, at an angle of 45 degrees to the long axis of the specimens. This loading produced an effective bending moment of 35 Ncm at the abutment-implant interface. An upper cyclic limit was set at 5 × 106 load cycles for all specimens. Results: Two-way analysis of variance revealed a significant difference between narrow-diameter and wide-diameter implant test groups but no significant difference between the 3 torque levels for each implant diameter. In the narrow-diameter group, 6 of the 15 specimens failed (5 abutment screw failures and 1 implant failure). In the regular-diameter group, 3 of the 15 specimens failed (2 implant failures and 1 abutment screw failure). There were no failures in the wide-diameter group. Discussion: The results of this study indicate that the abutment screw is not the only potential failure location. The possibility of implant fracture clinically has been previously reported for prostheses supported by both single- and multiple-implant prostheses. Conclusion: The wide-diameter CeraOne single-tooth implant system demonstrated superior load fatigue performance. For clinical situations with significant functional loading, the narrow-diameter implants would be at a greater risk of fatigue failure.Publication Relationships between depression/somatization and self-reports of pain and disability(2004) Yap, A.U.J.; Chua, E.K.; Tan, K.B.C.; Chan, Y.H.; RESTORATIVE DENTISTRYAims: To examine the relationship between depression and somatization and pain during muscle and joint palpation as well as limitations related to mandibular functioning (LRMF) in patients with temporomandibular disorders. Methods: The Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) data for Axes I and II for 196 consecutive patients (56 men and 140 women) with a history of facial pain were obtained. The mean age of the predominantly Chinese patient population (83.2%) was 33.4 years (range 18 to 55 years). A computerized diagnostic system was used to collect the RDC/TMD history data. The Symptom Check List (SCL-90) depression and somatization scales were generated on-line and archived. The mean muscle pain (MP), joint pain (JP), and LRMF scores were computed with depression and somatization as main effects. Data were subjected to analysis of variance (Scheffé test) and Pearson's correlation at a significance level of .05. Results: Depression scores ranged from 4.03 to 8.16 (MP), from 0.67 to 1.03 (JP), and from 0.30 to 0.38 (LRMF); somatization scores ranged from 2.64 to 7.75 (MP), from 0.58 to 1.00 (JP), and from 0.30 to 0.41 (LRMF). Interaction effects between depression and somatization were not significant. Patients with severe depression had significantly higher MP scores than normal patients or patients with moderate depression. Patients with moderate and severe somatization had significantly higher MP scores than normal patients. LRMF scores of patients with severe somatization were significantly greater than those who were normal or suffered from moderate somatization. No significant difference in JP scores was observed for depression and somatization scales. Correlations between depression/somatization and MP, JP, and LRMF scores were significant and positive but weak; coefficients ranged from 0.15 to 0.41. Conclusion: The results suggest that depression and somatization are related to the self-report of MP. In addition, severe somatization may be associated with an increase in jaw disability.Publication Depressive symptoms in Asian TMD patients and their association with non-specific physical symptoms reporting(2004) Yap, A.U.J.; Chua, E.K.; Tan, K.B.C.; RESTORATIVE DENTISTRYBACKGROUND: The expression of depression in Asian temporomandibular disorder (TMD) patients may differ from that of their Caucasian counterparts. This study examined the prevalence of depressive symptoms and their association with non-specific physical symptoms (NPSs) reporting in Asian patients. METHODS: Two hundred and fifty-five Asian TMD patients (68 males; 187 females) with a mean age of 33.0 years were selected for this study. Research diagnostic criteria (RDC)/TMD history questionnaire was input directly into computers by patients using the NUS TMDv.1.1 software. Symptom Checklist 90 (SCL-90) depression and NPS scales were generated online and automatically archived for statistical analysis. Data were subjected to ANOVA/Scheffe's test and Pearson's correlation at significance level 0.05 and 0.01, respectively. RESULTS: 43.1 and 50.6% of the patients scored moderate-to-severe on the depression and NPS scales, respectively. The percentage of patients with diffuse physical symptoms remained high (45.5%), even after pain items were excluded from the computation. NPS scores ranged from 0.34 to 1.64, while depression scores ranged from 0.27 to 1.21. A significant and positive correlation (r=0.74) was observed between depression and NPS scores. CONCLUSIONS: The prevalence of depressive symptoms and NPSs was lower in Asian TMD patients. Psychological distress experienced by female Asian TMD patients was comparable to their male counterparts. Results also suggest that depressive symptomatology is associated with the reporting of multiple NPSs.Publication Comparison of Three-Dimensional Accuracy of Digital and Conventional Implant Impressions: Effect of Interimplant Distance in an Edentulous Arch(QUINTESSENCE PUBLISHING CO INC, 2019-01-01) Tan, Ming Yi; Yee, Sophia Hui Xin; Wong, Keng Mun; Tan, Ying Han; Tan, Keson Beng Choon; Assoc Prof Beng Choon, Keson Tan; DENTISTRYPurpose: This study compared the three-dimensional (3D) accuracy of conventional impressions with digital impression systems (intraoral scanners and dental laboratory scanners) for two different interimplant distances in maxillary edentulous arches. Materials and Methods: Six impression systems comprising one conventional impression material (Impregum), two intraoral scanners (TRIOS and True Definition), and three dental laboratory scanners (Ceramill Map400, inEos X5, and D900) were evaluated on two completely edentulous maxillary arch master models (A and B) with six and eight implants, respectively. Centroid positions at the implant platform level were derived using either physical or virtual probe hits with a coordinate measuring machine. Comparison of centroid positions between master and test models (n = 5) defined linear distortions (d x , d y , d z ), global linear distortions (d R ), and 3D reference distance distortions between implants (ΔR). The two-dimensional (2D) angles between the central axis of each implant to the x- or y-axes were compared to derive absolute angular distortions (Absdθ x , Absdθ y ). Results: Model A mean d R ranged from 8.7 ± 8.3 μm to 731.7 ± 62.3 μm. Model B mean d R ranged from 16.3 ± 9 μm to 620.2 ± 63.2 μm. Model A mean Absdθ x ranged from 0.021 ± 0.205 degrees to -2.349 ± 0.166 degrees, and mean Absdθ y ranged from -0.002 ± 0.160 degrees to -0.932 ± 0.290 degrees. Model B mean Absdθ x ranged from -0.007 ± 0.076 degrees to -0.688 ± 0.574 degrees, and mean Absdθ y ranged from -0.018 ± 0.048 degrees to -1.052 ± 0.297 degrees. One-way analysis of variance (ANOVA) by impression system revealed significant differences among test groups for d R and ΔR in both models, with True Definition exhibiting the poorest accuracy. Independent samples t tests for d R , between homologous implant location pairs in model A vs B, revealed the presence of two to four significant pairings (out of seven possible) for the intraoral scanner systems, in which instances d R was larger in model A by 110 to 150 μm. Conclusion: Reducing interimplant distance may decrease global linear distortions for intraoral scanner systems, but had no effect on Impregum and the dental laboratory scanner systems. Impregum consistently exhibited the best or second-best accuracy at all implant locations, while True Definition exhibited the poorest accuracy for all linear distortions in both models A and B. Impression systems could not be consistently ranked for absolute angular distortions.Publication The use of multiplanar reformatted computerised tomography in the surgical-prosthodontic planning of implant placement.(1995) Tan, K.B.; RESTORATIVE DENTISTRYPresurgical planning and communication between the prosthodontist and the surgeon is essential to achieve optimal placement of functional implants. Besides the basic clinical examination and the use of mounted study models, radiographic imaging is an essential adjunctive aid in treatment planning. The latest imaging modality, multiplanar reformatted CT (MPR-CT) is the most comprehensive and accurate presently available. It allows precise assessment of the three-dimensional architecture and internal anatomy of the jaws. This enables accurate preoperative evaluation for planning implant fixture placement with maximal use of bone. It's widespread use would prevent unsuitable cases from ever reaching surgery. MPR-CT is described in detail and its usefulness in treatment planning the dental implant case illustrated. Indications, contraindications, advantages and disadvantages will be discussed. The use of radiographic stents derived from diagnostic wax-ups or set-ups is essential. The incorporation of suitable radiographic markers provide both the surgeon and prosthodontist with reference points to determine the available bone at the exact spatial location and orientation of the planned implant fixture at all primary and alternate sites. The same radiographic stent is then converted to a surgical guide stent for precise location of surgical implant sites.Publication Spectrophotometric and Visual Evaluation of Maxillary Anterior Implant Crowns and Peri-implant Soft Tissues: A Retrospective Study(QUINTESSENCE PUBLISHING CO INC, 2020-05-01) Wong, Jin Lin; Tan, Keson Beng Choon; Teoh, Khim Hean; Sim, Christina Poh Choo; Assoc Prof Beng Choon, Keson Tan; DEAN'S OFFICE (DENTISTRY); DUKE-NUS MEDICAL SCHOOLPurpose: To visually and spectrophotometrically determine the differences in the shades of maxillary anterior implant crowns and peri-implant soft tissues compared to a natural teeth control group. Materials and Methods: A total of 44 patients restored with single implant-supported restorations were assessed after at least 6 months in function. Images of the implant crowns, peri-implant soft tissues, and their controls were captured using a spectrophotometer (SpectroShade Micro, Medical High Technologies). Visual assessment of shade differences between the implant crowns and peri-implant soft tissues and their controls were performed by the patients and four dental professionals using a visual analog scale (VAS). Analysis of variance was applied to detect differences between groups. Results: The mean color differences (ΔE) between the implant crowns and peri-implant soft tissues and their respective controls were 4.8 ± 2.6 and 6.6 ± 2.7, respectively. A significant difference (P =.025)) in mean ΔE values was observed only at the cervical third of the implant crowns. The patient group showed the highest mean VAS scores for shade matching of the implant crowns (8.4 ± 1.2) and peri-implant soft tissues (7.8 ± 1.6) with their respective controls. Conclusion: Spectrophotometric analysis showed significant shade differences at the cervical third of the implant crowns. The patients were more satisfied with the shade matching of their implant restorations than the dental professionals. Int J Prosthodont 2020;33:277-284. doi: 10.11607/ijp.6526.