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Scientific Articles Dr Kenneth LEW 


We like to think we are a little bit different from the rest. Why? Because our clinical orthodontic treatment, diagnosis and process for our patients is enhanced by our Proprietary  Orthodontic Knowledge Store. To explain what it is, we, together with Dr Kenneth Lew’s Advanced Dentist Training Center, have collated a COLLECTION of Dr KENNETH LEW’S SCIENTIFIC ARTICLES ON ORTHODONTICS. These articles underpin Dr Kenneth Lew’s orthodontic strategy  for our patients –  Invisible Braces Center @ Tanglin dental Surgeons will always strive to your straighten your teeth, in relation to your E, your Esthetic line, ideal nose-lip/chin profile, and aim for a stable, functional result. Ours is a face and profile-driven orthodontic treatment, underpinned by our scientific research. We are humbled to note that many of Dr Lew’s articles, written in his decade long academic career lecturing in the Faculty of Dentistry, NUS, have been in turn cited by later textbooks and international articles.



I   ORTHOGNATHIC SURGERY

  1. CHANGES IN TONGUE AND HYOID BONE POSITIONS FOLLOWING ANTERIOR MANDIBULAR SUBAPICAL OSTEOTOMY IN PATIENTS WITH  CLASS III MALOCCLUSIONS by Dr Kenneth KK Lew
    In a sample of 28 Chinese adults (aged 24.2 +/- 3.1 years) who underwent anterior mandibular subapical osteotomy for the correction of Class III malocclusions, the interaction among the intermaxillary space, tongue position, and hyoid bone variables were quantified retrospectively using pretreatment and post-treatment lateral cephalograms. Lateral cephlograms taken at the early (5 to 7 days) postsurgical period showed that intermaxillary space decreased. The hyoid bone also moved inferiorly, while the tongue was displaced posteriorly and superiorly. The late (2 years) postsurgical lateral cephalograms showed that the hyoid bone and tongue position normalized to the pretreatment positions. These changes demonstrate the ability of the hyoid bone and the tongue structures to adapt to changes in the intermaxillary space following osteotomy. (International Journal of Adult Orthodontics and Orthognathic Surgery, USA, 1993 Vol8:123-128)

  2. THE REALIABILITY OF COMPUTERIZED CEPHALOMETRIC SOFT TISSUE PREDICTION FOLLOWING BIMAXILLARY ANTERIOR SUBAPICAL OSTEOTOMY by Dr Kenneth KK Lew
    The accuracy of predicting the results of orthodontic-surgical treatment following bimaxillary anterior subapical setback osteotomy was analyzed retrospectively. Comparison of pretreatment prediction tracings of the lateral cephalograms with the 6 months postsurgical cephalograms of 38 patients showed that there was no statistically significantly difference between the actual and predicted dentoalveolar setback in both arches. The computer generated soft tissues predictions were generally accurate, with the exception of the horizontal position of the lower lip, which was underestimated, and, to a lesser extent, the vertical position of the upper lip, which was also underestimated. Computerized cephalometric prediction following bimaxillary anterior subapical osteotomy is sufficiently accurate to be of value to be used routinely in treatment planning for the horizontal upper lip prediction, but some modifications are advisable to obtain a more accurate horizontal lower lip prediction. (Int J adult Orthod Orthognath Surg, USA, 1992 Vol7:97-101) 

  3. A COMPARISON OF PROFILE CHANGES BETWEEN RAMUS AND ANTERIOR MANDIBULAR SUBAPICAL OSTEOTOMIES IN CLASS III CHINESE PATIENTS. – Dr Kenneth KK Lew, Dr F.C Loh
    The purpose of this study was to compare cephalometrically the differences in soft tissue profile changes produced by intraoral ramus and anterior subapical osteotomies for the treatment of Chinese patients with class III malocclusion. Thirty-seven Chinese adults whose class III malocclusion was treated either with an intraoral ramus (Group A) or an anterior subapical (Group B) osteotomy were selected for the study. Serial lateral cephalograms taken pre-surgically (T1) and at least 6 months post-retention (T2), showed marked improvement in the soft tissue profile in both groups. Although the percentage response of soft – hard tissue movements was similar at lebrale inferius, the response at soft-tissue point B was found to be statistically less in group B than in group A (p < .05). Although the correlation between the upper lip response to mandibular ramus setback in group A was weak (r = 0.11), there appeared to be a relatively strong correlation between posterior movement of the upper lip and the magnitude of the lower segmental setback (r = 0.65). The difference in soft to hard tissue response with the two osteotomy procedures appear to vary with those reported in whites. This study emphasizes the need for different prediction ratios of soft to hard tissue movement in different racial types. (Journal of Oral Maxillofacial Surgery USA 49:831-837, 1991)

  4. ORTHODONTIC CONSIDERATIONS IN THE TREATMENT OF BIMAXILLARY PROTUSION WITH ANTERIOR SUBAPICAL OSTEOTOMY. – DR KENNETH KK LEW
    Severe bimaxillary dentoalveolar protusion, a dentofacial deformity prevalent among Asians, can be easily addressed with the use of anterior subapical osteotomies in conjunction with extraction of a tooth in each quadrant. Presurgical orthodontic preparation for anterior subapical osteotomy includes intra-arch (leveling, alignment and derotations) and interarch (sagittal, vertical, and transverse) objectives. The procedure requires careful attention to the use of segmental orthodontic mechanics and surgical arch wires, in conjunction with surgical splints and rigid osteosynthesis. The controlled use of training box and vertical elastics postsurgically and the proper choice of retainers have greatly facilitated the achievement of a good and stable end result. (Int J Adult Orthod Orthognath Surg  USA 1991; 6:113-122)

  5. A TEN YEAR FOLLOW UP CASE REPORT FOLLOWING SURGICAL CORRECTION OF ANTERIOR OPEN BITE. – DR KENNETH KK LEW AND H.S LOH
    A case is reported whereby an anterior open bite was treated with the Kole osteotomy in an adult Chinese girl. This study documents cephalometrically the post – treatment changes occuring in the dento – alveolar complex over a ten year follow up period and describes the possible mechanisms contributing to the remarkable stability of the open bite correction. (Australian Dental Journal 1991: 36 :139-142)

  6. EVALUATION OF SOFT TISSUE PROFILE FOLLOWING INTRAORAL RAMUS OSTEOTOMY IN CHINESE ADULTS WITH MANDIBULAR PROGNATISM by KKK LEW, FC LOH, JFYEO, HS LOH
    Twenty-five Chinese adults with mandibular prognathism were treated with either the intraoral vertical subcondylar osteotomy or the bilateral sagittal split ramus osteotomy. The patients were kept in maxillomandibular fixation for 6-8 weeks while osteosynthesis was achieved with the use of intraosseous wiring. Serial lateral cephalograms were taken presurgery and between 12-26 months postsurgery, and specific soft and hard tissue points were digitized on a computer. The mean mandibular setback postsurgically was 8.4 + 3.2mm, with a 5.2 degree reduction in point A-nasion-point B angle. Posterior movement of pogonion, point B and the mandibular incisal edge was accompanied by posterior movement of 95% at soft tissue pogonion (r = .96), 89% at soft tissue point B (r = .83), and 67% at labrale inferius (r = .81), respectively The correlation between changes in the labrale superius and mandibular setback appeared to be dependent on both the amount of mandibular setback and the degree of mandibular rotation during the setback of the surgery. The presently reported ratios of the soft tissue response to hard tissue movement vary from those reported in white patients by other researchers, which confirms the need for different ratios for different racial types. (The International Journal of Adult Orthodontics and Orthognathic Surgery  USA Volume 5. Number 3 1990 189-197)

  7. THE USE OF PSYCHOMETRIC TEST IN THE EVALUATION OF PATIENTS PRESENTING FOR ORTHOGNATHIC SURGERY – A PRELIMINARY REPORT  by DR KENNETH KK LEW, L.H PEH, A. YEOH & E.PANG
    Psychological evaluation in some orthognatic patients may be neccessary as the psychosocial stress of the deformity may lead to psychiatric morbidity such as depression or paranoid disorders. It is also possible for patients with underlying psychosis to present first to the dental surgeon for jaw correction. The use of several psychological test appropriate for patients presenting with dentofacial deformities is discussed. Nine patients with skeletal malocclusions who were referred for psychiatric assessment are reported here. Three case vignettes are included to give an impression of the type of clinical situations where such an assessment may be helpful. (Australian Orthodontic Journal 1990 11 :256-260)

  8. PROFILE CHANGES FOLLOWING ANTERIOR SUBAPICAL OSTEOTOMY IN CHINESE ADULTS WITH BIMAXILLARY PROTUSION by DR KENNETH KK LEW
    Nineteen adult Chinese patients, aged 18-28 years, who sought treatment for bimaxillary protusion were treated with combined maxillary and mandibular anterior subapical osteotomy and the extraction of one premolar in each quardrant. Intraoral cephalograms were taken pretreatment and an average of 19.8 months posttreatment. Significant cephalometric soft tissue changes (P < .01) included increased at the nasolabial angle, reduction of both the upper and lower lip protusions, lengthening of the upper lip, and decreased in the interlabial gap. The predictable success and the fact that these improvements in facial profile usually can be achieved in as little as 3-9 months make this mode of addressing bimaxillary protusion a viable alternative to orthodontic treatment of adult patients with bimaxillary protusion. (The International Journal of Adult Orthodontics and Orthognathic Surgery, USA, Volume 4, Number 3, 1989)

  9. BEGG ARCHWIRES FOR SURGERY CASES by KENNETH LEW
    The Begg technique has been criticised for its inability to provide adequate stability during inter-maxillary fixation. This is largely due to the fact that the Begg technique traditionally uses round wires in all stages of treatment commencing with 0.016 inch round Wilcock wires and finally terminating in 0.020 inch round Wilcock wires in stage III. Even in surgical cases, the heaviest wire used is usually 0.020 inch. Round wires in a Begg slot lack the ability to control bucco-lingual torque. The author prefers to use ribbon archwires*(TP Orthodontics Inc) or square archwires# ( Tomy International Inc) (0.020 inch x 0.020 inch) to control the torque in the premolars and anterior teeth. The use of ribbon archwires in conjunction with the surgical wafer ensures proper ‘rigid’ fixation at the occlusal and coranal level. The fixation at the dental level has to be adequate to complement the osseous fixation of our surgical colleagues. (March 1989, Australian Orthodontic Journal, 59-61)




II   TMJ ORTHODONTICS

  1. SUBMENTOVERTEX CEPHALOMETRIC NORMS IN MALE CHINESE SUBJECTS by DR KENNETH KK LEW AND DR D.K.L TAY
    Submentovertex (SMV) cephalograms of a random sample of 32 male Chinese subjects who were 20.1 + 1.9 years old and were free of temporomandibular joint symptoms were studied. A Submentovertex  cephalometric analysis comprised of 5 angular measurements and 10 linear parameters was developed for the purposes of establishing SMV cephalometric norms among our Chinese adult population for clinical usage. With the exception of condylar angulation, the lack of SMV cephalometric norms published in the literature for other parameters precluded comparison with information in the treatment of Dentofacial orthopedics and facilitate in the diagnosis of mandibular asymmetry. (American Journal of Orthodontics and Dentofacial  Orthopedics, USA 1993; 103:247-52)

  2. ORTHODONTIC FINALIZATION FOLLOWING THERAPY WITH AN ANTERIOR REPOSITIONING SPLINT by  DR KENNETH KK LEW
    After phase I splint therapy for the management of posterior condylar displacement, it is not unusual to find that a posterior open bite has been created. Finalization of a new occlusal position may be effected via occlusal equilibration, prosthodontics, orthodontics, orthognathic surgery, or a combination of these procedures. Stabilizing the occlusion with orthodontics in the new orthopedic jaw position requires a systemic approach. This article outlines a strategy for orthodontic finalization in phase II therapy. The splint-guided position is maintained while intra-arch and interarch malocclusion are corrected. The objective in treatment of posterior condylar displacement via splint therapy and orthodontics lies in the provision of a sound condylar position and the movement of the teeth and mandible into a stable and esthetic position. (International Journal of  Adult Orthodontics and  Orthognathic Surgery, USA, Vol 7, No 4, 1992: 251-264)



III   LINGUAL ORTHODONTICS

  1. CHANGES IN LIP CONTOUR FOLLOWING TREATMENT OF MAXILLARY PROTUSION WITH ESTHETIC ORTHODONTIC APPLIANCES by DR KENNETH KK LEW
    With the advent of acid etching techniques and the elimination of unesthetic band materials, direct bonding of orthodontic attachments kindled a desire for cosmetic appliances such as labial ceramic brackets and lingual orthodontics. Owing to the esthetic nature of our combination upper-lingual lower-ceramic orthodontic approach, adults who would have normally avoided orthodontic treatment are now seeking treatment. This study evaluated the cephalometric changes in the soft tissue lip profile following treatment of Class II Division 1 malocclusion with upper first bicuspid extractions with our esthetic orthodontic appliance approach. Serial lateral cephalograms (pretreatment and post treatment) of 16 adult patients with a mean age of 22.1 (+-) 3.2 years were studied. The mean upper incisor retraction, upper lip retraction, upper lip lengthening, and lower lip retraction were 5.75 (+-) 1.91mm, 2.8 (+-) 1.4mm, 1.5 (+-) 0.6mm and 1.4 (+-) 0.6mm, respectively. All these changes were statistically significant (p < 0.01). The nasolabial angle increase of 10.8 (+-) 3.0 degrees was also statistically significant (p < 0.01). The upper lip retraction to upper incisor retraction was 1:2:1, while the upper lip lengthening to upper incisor retraction was 1:3:8. The correlation coefficients (r) were 0.91 (p < 0.01) and 0.57 ( p < 0.01), respectively. This study shows that significant esthetic changes in lip profile are possible with this cosmetic orthodontic appliance approach. The treatment results in this study appear comparable to those published with labial metal brackets. With very few exceptions, patients were able to adapt within 2 weeks, with almost no trauma to the tongue. (Journal of Esthetic Dentistry, USA Volume 4 Number 1, 1992: 16 - 23)

  2. INITIAL ALIGNMENT WITH .008” PULSE STRAIGHTENED SUPREME WILCOCK WIRE IN LINGUAL ORTHODONTICS. – DR KENNETH KK LEW
    Owing to the smaller bracket span in the lingual technique (compared to fixed labial techniques), coupled with the need to form the mushroom arch wire, the use of the .008” pulse straightened Wilcock wire offers great promise in the lingual technique. We have found that the light forces generated from the .008” arch wire allows gentle alignment of teeth and therefore appears to be more comfortable in treatment for patients. The inclusion of the bite-opening bend just mesial to the molars complements the built-in bite plane in the Ormco Generation 7 brackets, thereby facilitating bite-opening. To minimize tongue soreness which may arise from the fine diameter of the .008” Wilcock arch wire, it is recommended that a length of plastic tubing is used in the section of arch wire adjacent to any edentulous spans (as a result of agenesis or extraction). (Australian Orthodontic Journal 1991: 12 (1) 53-54



IV   AESTHETICS

  1. ASSESMENT OF ORTHODONTIC TREATMENT NEEDS BY TEENAGERS IN AN ASIAN COMMUNITY IN SINGAPORE by  DR KENNETH KK LEW & DR GEORGE SOH
    The purpose of this study was to determine (1) the preference of dental occlusion types among teenagers and (2) their assessment of the necessity for orthodontic treatment. A total of 1189 teenagers (mean age 15.3 (+-) 3.2 years) were asked to rank a series of color photographs of seven occlusion types. Their ranking, in descending order of attractiveness, were as follow: Class I occlusion, anterior open bite, Class III occlusion, Class II occlusion, anterior spacing, anterior crowding and deep bite occlusion. The perceived need for treatment was found to be inversely correlated with the rank order of attractiveness. There appeared to be no statistical difference ( P < 0.05) in the perception for treatment among different racial and income groups. However, with the exception of anterior open bite and deep overbite occlusions, a statistically significant ( P<0.05) greater number of females than males perceived a  need for treatment. Assessment of occlusal disharmonies among teenagers could provide clinicians and health care personnel with an indication  of the relative attractiveness among occlusion types and hence the establishment of treatment priorities. (Community Dental Health USA (1992) 9, 57-62)

  2. SOFT TISSUE CEPHALOMETRIC NORMS IN CHINESE ADULTS WITH ESTHETIC FACIAL PROFILES by KENNETH  KK LEW, KK HO,  SB KENG, KH HO 
    Using a double selection process comprised of professionals and lay judges, the cephalometric tracings  on a final sample of 48 Chinese adults with esthetically pleasing profiles were analysed. The soft tissue cephalometric norms and standard deviations  of two widely accepted soft-tissue analyses, the Legan and Burstone analysis and the Holdaway analysis, were determined. In comparison with white norms, the Chinese profile was less prominent ( P<.01), the nasolabial angle was less obtuse (  (P< 0.01), both the upper and lower lips were more protrusive (P <..05), the upper lip curvature was greater (P<.01), and the soft tissue chin thickness was less ( P< .05). This variance between racial types  emphasizes the need to recognize that soft tissue cephalometric norms are specific for that racial type and cannot always be applied across different racial types . (J Oral  Maxillofacial Surgery 50 USA; 1184-1189, 1992, The American Association of Oral and Maxillofacial Surgeons)

  3. ESTHETIC ARCH BAR FOR MAXILLOMANDIBULAR FIXATION IN ORTHOGNATHIC SURGERY BY FC LOH, KENNETH KK LEW AND CHEE HWEE SIM
    Arch bars are well-known dental appliances for the management of fractures and orthognathic surgery. Traditionally both the commercially available, prefabricated arch bars as well as the custom made arch bars are made of metal so as to provide good rigidity. Each of these types of arch bars has its own advantages as well as drawbacks. This article looks at a type of custom made arch bar that is easy to construct and use. At the same time, it provides good rigidity, fit and esthetics. (Journal of Esthetic Dentistry  USA 35-37 Volume 4, 1992)

  4. RANKING OF FACIAL PROFILES AMONG ASIANS BY KKK LEW, G SOH, E LOH
    The purpose of this study was to determine the facial profile preferences in a sample of 1, 189 Asian teenagers (aged 15.3  (+-) 3.2 years. Five facial profile types were computer-generated by trained personnel (orthodontists and oral maxillofacial surgeons) to represent distinct facial types. Subjects were asked to rank the profiles in descending order of attractiveness. The ranking was as follows: orthognathic profile, bimaxillary retrusive profile, bimaxillary protrusive profile, mandibular retrognathic profile, and mandibular prognathic profile. The difference in rank scores between all the facial types  were statistically significant (P<.005). Assessment of the profile types  among lay personnel  could provide clinicians an indication into the relativve attractiveness among profile types and health care workers in treatment prioritization among dysmorphic facial types. (Journal of Esthetic Dentistry Vol 4 No 4, July/Aug 1992)

  5. A COMPARISON OF SHEAR BOND  STRENGTHS BETWEEN NEW AND RECYCLED CERAMIC BRACKETS BY KENNETH KK LEW, CL CHEW, KW LEE
    The recycling of ‘used’ ceramic brackets in the orthodontic surgery has been previously described. This present study investigates the shear bond strength of both recycled and  new ceramic brackets. The mean shear bond strengths of the new and recycled ceramic brackets were  259.7(+-) 88.2N and 187.2 (+-) 60.8N, respectively. Although significantly lower (P<0.01), the bond strength of recycled ceramic brackets appeared to be clinically adequate. There appeared to be little difference in the variation in bond strength  between the new and recycled ceramic bracket group. Our results showed that the site of bond failure depended on the magnitude of bond strength. Scanning electron micrograph examination of the failure sites showed enamel fracture in one sample where the bond strength was extremely high. (European Journal of Orthodontics 13 (1991) 306-310, European Orthodontic Society.

  6. TEMPORARY PONTICS IN AESTHETIC ORTHODONTICS – A NEW DESIGN BY KKK LEW
    A new and simple technique for aesthetic tooth replacement during orthodontic treatment, with a pontic using orthodontic wire mesh, is described and appears in the author’s clinical practice to be superior to other techniques reported previously. These pontics may be used in maxillary first bicuspid extraction cases, and with adaptation  where anterior teeth have to be replaced because of agenesis, extractions, or traumatic loss. This technique thus also provides the clinician with an aesthetic and dependable  space maintainer for anterior teeth whilst orthodontic treatment is being completed. (British Journal of Orthodontics Vol 17/1990/317-319, British  Society for the Study of Orthodontics)

  7. STAINING OF CLEAR ELASTOMERIC MODULES FROM CERTAIN FOODS  BY KENNETH KK LEW
    The use  of clear elastomeric modules to ligate ceramic and tooth colored plastic brackets have enhanced the aesthetic value of these appliances . However, the modules can be discolored  if patients eat certain foods between appointments. This double blind study was  undertaken to determine the in-vitro susceptibility of clear elastomeric modules  to staining from several common, colored food substances. (60 Alastik® modules were placed in seven capped glass bottles containing chocolate drink, coffee, Coca-cola, Lea&Perrins sauce, red wine,tea and tomato ketchup.) Teflon-coated ligature wires that do not discolor have been recently introduced (Rocky Mountain ®), but the greyish hues of these wires  make them aesthetically inferior to the clear elastomeric modules when first placed in the mouth. Furthermore, the author found that the Teflon coating can wear off after 2 to 3 weeks, exposing the metal surface of the wire. Even more color-stable and aesthetic ligatures may be developed to complement ceramic and plastic brackets. At present, it would be prudent for clinicians to advise their patients that although ceramic brackets are stain-resistant, the clear elastomeric modules are subject to discoloration from certain foods with high staining potential, such as coffee and tea. (Journal of Clinical Orthodontics, USA 1990: 472-474)

  8. RECYCLING OF CERAMIC BRACKETS BY KENNETH KK LEW AND SK DJENG
    Instruments such as the Transcend Debonding Instruments ® and improved techniques have made it possible to remove ceramic brackets without fracturing them. In addition, bond failures can occasionally occur, making it necessary either to rebond the dislodged bracket or to bond a new one. Recycling these debonded or dislodged brackets would provide a substantial savings in the expense of maintaining a bracket inventory. This method outlines a simple chairside method of recycling used ceramic brackets. Clinical experience with these recycled ceramic brackets has shown few bond failures. Further studies are needed to compare the shear bond strengths of recycled brackets with those of new brackets. (Journal of Clinical Orthodontics, Volume XXIV Number 1, 1990: 44-47)




V   SOFT TO HARD TISSUE LIP TREATMENT RESPONSE BY KENNETH LEW

  1. SOFT TISSUE PROFILE CHANGES FOLLOWING ORTHODONTIC TREATMENT OF CHINESE ADULTS WITH CLASS III MALOCCLUSIONS BY KKK LEW
    38 adult  Chinese patients  (24.3 (+/-) 3.2 years)  exhibiting true Class III dental and skeletal malocclusions were treated orthodontically with Edgewise  appliance and extractions of mandibular first premolars together with simultaneous anterior  expansion of the maxillary arch. A retrospective cephalometric study was undertaken to determine the soft tissue profile changes of at least 6 months postretention. Significant cephalometric changes included decrease in the mandibular incisor protrusiveness by 6.4mm (P<.oo1), and accompanying lower lip protrusiveness by 4.4mm (P< .01), together with a slight forward movement of the maxillary incisors by 1.7mm (P< .05) and consequently, a slight increase in upper lip protrusiveness by 1.2mm (P< .05), and decrease in nasolabial angle (P< .05). The overall improvement in lip profile provided by this mandibular arch expansion orthodontic approach  appears to be a viable  alternative in mild-to-moderate Class III patients who decline orthognathic surgery. (The International Journal of Adult Orthodontics and Orthognathic Surgery Volume 5 Number 1, 1990)

  2. PROFILE CHANGES FOLLOWING ORTHODONTIC TREATMENT OF BIMAXILLARY PROTRUSION IN ADULTS WITH THE BEGG APPLIANCE
    Thirty  eight oriental  patients aged 18-26 years  who sought treatment for their bimaxillary   protrusion were treated with Begg appliance following extraction of four first premolars.  A cephalometric study was undertaken to determine the soft tissue changes in lip profile following treatment.  Results show that upper incisors  were retracted by 5.6mm (+/-) 0.8mm and lower incisors by 4.4 (+/-)0.8mm on average. The nasolabial angle became more obtuse increasing from 80.7 degrees to 90.7 degrees. The upper lip and lower lip lengthened  by 1.9mm and 1.2 mm, respectively. The lower lip to “E” line reduced from 7.5mm to 3.7mm. All the previous changes  were statistically significant (P< 0.01). The upper lip to upper incisor retraction was 1:2.2 while the lower lower lip to lower incisor retraction was 1:1.4. The correlation coefficients (R) was 0.72 (P<0.01) and 0.80 (P< 0.01) respectively. The changes in the cants of the mandibular  and occlusal planes were statistically insignificant. This study shows that the Begg appliance has the ability to significantly reduce bimaxillary protrusions and thereby facial aesthetics. (European Journal of Orthodontics 11 (1989) 375-381, European Orthodontic Society)

  3. A COMPARISON OF ARCHWIRES USED FOR INITIAL ALIGNMENT IN BEGG TREATMENT BY KENNETH LEW
    Since the introduction of the Begg technique, the Wilcock 0.016”archwire® has been invariably used at the start of Stage! The recent past has witnessed advances in clinical orthodontic archwire metallurgy and with it, many flexible archwires have emerged. The impact of these wires, popular with the Edgewise operators, has yet to be felt in the Begg technique. The present study shows that flexible archwires such as the 0.016” Japanese Niti wire®, 0.016” Nitinol wire ®, 0.010” Supreme Wilcock wire can all significantly (p<0.001) decrease  the time taken for initial alignment of teeth as compared to the Wilcock 0.016” wire. Of the flexible archwires tested in this study, 0.016” Japanese Niti wire was most efficient in obtaining initial alignment (p<0.001). Therefore, in minimal to moderate anchorage cases where bite opening is not of a major concern, initiating Begg treatment with flexible archwires can shorten treatment time. The use of such flexible archwires is also consistent with the Begg philosophy of suing light forces to stimulate tooth movement. (Australian Orthodontic Journal, Melbourne, Australia, 10 (3) : 180-182



VI   EPIDEMIOLOGY BY DR KENNETH LEW

  1. HORIZONTAL SKELETAL TYPING IN AN ETHNIC CHINESE POLULATION WITH TRUE CLASS III MALOCCLUSIONS BY KKK LEW, WC FOONG
    Eighty Chinese adults with true Class III malocclusions were analysed cephalometrically to determine the percentage in each horizontal skeletal subtype. The maxillary and mandibular  skeletal bases for each subject were analysed using angular (SNA/SNB) as well as linear (point A/B to MaNamara’s line) criteria. Results indicated that mandibular hyperplasias with normal  maxillary position comprised the majority of true Class III malocclusions. Whilst the majority of Class III in males were due to hyperplastic mandibles and normal maxillary antero-posterior  relationship, most of the female Class III malocclusions were due to normal mandibles and hypoplastic maxillae. There was no significant difference between the  incidence of Class III subtypes when using either angular or linear criteria. (British Journal of Orthodontics Vol 20, 1993, 19-23)

  2. ATTITUDES AND PERCEPTIONS OF ADULTS TOWARDS ORTHODONTIC TREATMENT IN AN ASIAN COMMUNITY BY KENNETH KK LEW
    A retrospective study of 358 local Chinese adult orthodontic patients was undertaken to determine the motivating factors behind orthodontic treatment and the discomfort caused by fixed orthodontic appliances. From the completed questionnaires of 203 patients, the principle conclusions were that the improvement in dento-facial aesthetics following orthodontic treatment enhanced  their self confidence and self esteem in majority of cases; discomfort in oral soft tissues and  teeth were transient and did not exceed 7 days; transient pain from teeth was experienced by 91% of patients and  30% of these patients the discomfort to teeth was  experienced with each new archwire or elastic force application. The results may be useful in relating discomfort levels to prospective orthodontic patients. It was also evident in the study that several cross-cultural differences existed in the attitudes of our patients compared to those reported in Caucasians. (Community Dental Oral Epidemiol USA 1993: 21: 31-5)

  3. MALOCCLUSION PREVALENCE IN  ETHNIC CHINESE    BY KK LEW, WC FOONG, E LOH
    Population norms derived from one ethnic group  may not necessarily be valid and accurate for other ethnic groups. With the increasing number of ethnic Chinese immigrants in Australia, Europe and America,  it would be useful for dental practitioners to be informed about malocclusion prevalence amongst Chinese. This study was carried out on 1050 Chinese school children (aged 12 – 14 years) to assess both qualitatively and quantitatively certain occlusal features. The population was found to have  a high incidence of Class III malocclusions compared with Caucasians. However, the incidence of Class II malocclusions was quite similar to those reported in Caucasians. Normal occlusions occurred in about 7% of this population. Although this percentage was much lower than reported in blacks, it was similar to those reported in Caucasians. Crowding occurred in about 50% of the cases, which was slightly less than those reported for Caucasians, increased overbites were also less common in this Chinese population compared with Caucasians. Compared with Caucasians, cross bite was also less frequent in this Chinese population. (Australian Dental Journal 1993: 38:5) 


VII   BASIC SCIENCE (HISTOLOGICAL) STUDIES BY DR KENNETH LEW

  1. TOOTH EXTRUSION EFFECTS ON MICROVESSEL VOLUMES, ENDOTHELIAL AREAS, AND FENESTRAE IN MOLAR APICAL PERIODONTAL LIGAMENT BY KENNETH LEW AND PHILLIP L LEPPARD
    Extrusive tooth loads, simulating short term orthodontic movements, have not been previously used for transmission electron microscopic quantification of their effects  on the periodontal ligament vessels.  In this study, a continuous extrusive load of 1.0 N,  applied to the rat maxillary  first molar for  30 minutes,  produced statistically significant changes in the microvascular  bed of the tensioned apical periodontal ligament. This mean vascular volume, as a percentage of apical periodontal ligament volume, increased (p < 0.01) in post capillary sized venules, venous capillaries, arterial capillaries, and terminal arterioles from 16.6%  to 22.3%, 2.0% to 2.7%, 0.4% to 1.0%, and 1.0% to 2.5%, respectively. Mean endothelial surface area per cubic millimeter of apical periodontal ligament tissue increased (p < 0.01)  in post-capillary sized venules from 16.8 to 25.7 x 1000000 micromillimeter square/cubic mm), in venous capillaries  from 3.0 to 4.8 x 1000000micromillimeter/cubic millimeter, and in  arterial capillaries  from 0. 7 to 1.5 x 1000000 micromillimeter/cubic millimeter.

    The number of fenestrae per square micron of endothelium in post capillary sizes venules,  venous capillaries, and arterial capillaries showed a mean increase from 0.02 to 0.07, 0.11 to 0.31, and 0.02 to 0.21 fenestrae/micromillimeter square, respectively (p<0.01). Fenestrae per cubic millimeter of periodontal ligament tissue also demonstrated a statistically significant increase with extrusion (p< 0.01) in post capillary sized venules from 0.37 to 1.55 x 1000000 fenestrae/cubic millimeter, in venous capillaries from 0.27 to 1.34 x 1000000 fenestrae/cubic millimeter, and in arterial capillaries from 0.02 to 0.22 x 1000000 fenestrae/cubic millimeter.

    Fenestrae in control vessel had a  mean diameter of 54.2 (+/-) 0.56 nm (SE) compared with 61.1 (+/-)  0.7nm in tensioned vessels (p<0.01). This investigation demonstrates that multiple ultrastructural changes in the periodontal ligament microvascular bed after tooth extrusion. (AM J ORTHOD DENTOFAC ORTHOP 1989; 96:221-31, funded by the National Health and Medical Research Council, the Australian Society of Orthodontists Foundation for Research and Education, and the Australian Dental Research Fund, Inc).

  2. THE PERIODONTAL MICROVASCULATURE – A MORPHOLOGICAL AND MORPHOMETRIC STUDY  BY KENNETH KK LEW
    Various ultrastructural studies on the periodontal ligament ( PDL)  microvasculature have been reported. However, the laco of systematic classification  has led to much confusion in the terminology used  to define vessel types. On the basis of the morphological criteria, the author proposes that three vessel types  are present in the PDL; terminal arterioles (Type A vessels); capillaries (Types B-1 and B-2),  and postcapillary venules (Type C vessels). Morphometric analysis of the apical PDL revealed that the total vascular volume was 19.9 %. Type C vessels predominated with a vascular volume of  16.4 %, while the other two vessel types  made up the remainder of the vascular volume. The results of this study suggest that the apical PDL region is predominantly venous. (Journal of Nihon Dental JAPAN  Vol 20; 262-269, 1987)

  3. ORTHODONTICALLY INDUCED MICROVASCULAR INJURIES IN TENSION ZONE OF THE PERIODONTAL LIGAMENT BY KENNETH KK LEW
    A review of the literature pertaining to the histological and ultrastructural  changes related to orthodontic tooth movement reveals that  much attention has been devoted to the fibrillar and cellular components of the periodontal ligament ( PDL).  Although the vascular response to  experimental tooth movement has been investigated, specific morphological  and morphometric data on  changes in the tension zone of the PDL microvascular system are lacking.  The present investigation was conducted to study the ultrastructural vascular response  in the tension zone of the PDL following a short term extrusive force. Six 12-week old male Porton rats was anesthesized and cannulated  via the aorta  after applying a 1-N  extrusive force for 30 minutes to the right maxillary first molar. The contralateral molar  served as a control in all animals. The apical portion of both the control and experimental PDL were prepared for TEM examination. In the experimental PDL, degenerative changes  in the endothelial cell wall and incipient nuclear shrinkage were observed in  ab out 30% of the postcapillary venules  and 18% of the  capillaries, whereas the arterial components  were generally spared. Compared to the control PDL, these degenerative changes were significantly marked in the  experimental PDL (p < 0.01). The results of this study suggest that the postcapillary venules are the most vulnerable segment in the PDL microvasculature. (Journal NIHON DENT Ja[am VOL 31, 493 – 501, 1989)



VIII   CLINICAL ORTHODONTIC  INNOVATIONS BY DR KENNETH LEW

  1. ENAMEL STRIPPING AND THE SPRING ALIGNER APPLIANCE – AN UPDATE BY KENNETH K LEW 
    Irregularity of the mandibular incisors in an otherwise good occlusion is quite common in young adult patients. Through the use of enamel stripping in the incisor region it is possible to create sufficient space to align the teeth with a mandibular sectional removable appliance, commonly known as the spring aligner. This article reviews the methods of enamel stripping, and describes the author’s preferred technique of enamel stripping and the various modifications of the spring aligner  appliances that can be prescribed  by the general practitioner to correct mandibular crowding. (Quintessence International USA Vol 3 1-5, 1993)

  2. SHEAR BNOND STRENGTH OF ORTHODONTIC BRACKETS USING PANAVIA: AN IN-VITRO STUDY BY KENNETH KK LEW , JENNIFER NOE, AND CL CHEW
    In this study, Panavia (a phosphonated Bis -GMA resin which is known to  develop very high bond strengths with resin-bonded  bridges) is compared to a no-mix orthodontic Bis-GMA bracket adhesive. Results showed that  there was no statistically significant difference in the shear bond strengths between the two resins when used as adhesives for bonding orthodontic brackets. Coupled with the fact that Panavia requires an anaerobic environment for complete polymerization, its routine use as a bracket adhesive in direct bonding of orthodontic brackets is not indicated. (Clinical Materials USA 12 , 1993, 89-93)

  3. A REMOBAVLE APPLIANCE TO EXTRUDE TEETH BY KENNETH KK LEW
    A simple removable appliance to effect minor tooth extrusion of anterior teeth is described and its use illustrated.  This technique uses a labial bow in conjunction with a composite resign button bonded to the labial surface of the tooth or teeth to be extruded. (Quintessence Int USA 1993; 24:157-160)

  4. THE PREDICTION OF ERUPTION SEQUENCE FROM PANORAMIC RADIOGRAPHS BY KKK LEW
    The validity of using orthopantomograms in the prediction of eruption sequences of the permanent canines, premolars and second molars was found to be 95.8 percent accurate. The prediction was statistically (p< 0.01) more accurate for the mandibular arch than for the maxillary arch, Such prediction would be useful in case of arch length deficiencies.

    Determining the eruption sequence from orthopantomograms taken at a mixed dentition stage  would simplify the process of determining eruption sequences, as the eruption sequences can be determined without tedious longitudinal, periodic clinical examinations, Comparative data of eruption sequences between racial types can therefore be determined readily. Future studies will focus on the eruption sequences  in various ethnic types in our multiracial population. (Journal of Dentistry for Children, USA, 346-3491992)

  5. ANTERIOR CROWN DIMENSIONS AND RELATIONSHIP (BOLTON)  IN AN ETHNIC CHINESE POPULATION WITH NORMAL OCCLUSION BY KKK LEW, SB KENG
    Odontometric measurements of anterior tooth crown sizes in a Chinese sample of 85 Class 1 occlusions were  similar to those published in the white population except for the larger upper lateral incisors and smaller upper central incisors in Chinese. Sex differences in tooth sizes were seen only in the maxillary and mandibular  canines while differences between antimeres were not significant. The Bolton ratios of our Chinese  sample revealed a Bolton ratio of 77.89 (+/-)  1.62 for the combined mesio-distal widths of the six mandibular anterior teeth  as compared to the combined medio-distal widths of the six maxiallary anterior teeth. Surprisingly, the Bolton ratio in our sample compared favourably with those originally  published by Bolton  although the  interfacial angles, overbite and overjet relationships  were statistically different. (Australian Orthodontic Journal, Oct 1991, 105-109)

  6. LOWER INCISOR ANGULATION DIFFERENCES IN CLASS II DIVISION I  MALOCCLUSIONS WITH AND WITHOUT FULL ‘ LIP TRAP’ BY  KENNETH KK LEW
    A  cephalometric study was designed to investigate whether  a difference in lower incisor angulation  exists in Class II division I malocclusion subjects  with and without the presence of a lower lip trap.  Chinese  subjects (N=40)  with Class II division I malocclusions who demonstrated a complete lower lip trap were compared to an equal number  of subjects with a partial lip trap. Intergroup comparisons of several cephalometric parameters indicated the presence of statistically significant differences in both the degree of lower incisor proclination/retroclination (p<0.01) and the magnitude of the overjet (p <0.05). In the complete lip trap group, the lower incisor was more retroclined and the overjets were also statistically larger than the partial lip trap group. (March 1991, Australian Orthodontic Journal, 29-31)

  7. THE EFFECT OF VARIATIONS IN  THE MANDIBULAR PLANE ANGLE ON THE PONT’S INDEX BY DR KENNETH LEW
    The purpose of this study was to investigate whether a relationship existed between  Pont’s index and mandibular plane angle, in a group of  48 Chinese adult subjects with  orthodontically untreated excellent Class I dental occlusion and good facial balance.  Results of the study showed a weak  correlation between the combined  mesiodistal maxillary incisor widths and the interpremolar (r=0.27) and intermolar arch widths ( r=0.21). The correlation between mandibular plane angle and interpremolar arch widths (r=0.58) and intermolar (r=0.46) arch widths was fair. By taking into account the variations in the mandibular plane angle, the Pont’s index could be predicted with greater accuracy. The correlation between the combined mesiodistal maxillary incisor widths and the corrected interpremolar and intermolar archwidths was very strong ( r=0.85 and 0.82, respectively). For a given mesiodistal maxillary incisor widths, the interpremolar and intermolar arch widths in our Chinese sample  were smaller than those published by Ponts. This variation could be attributed by differences in the genetic inheritance in different racial types. (The Functional Orthodontist , USA 24-29, 1991)

  8. INTRUSION AND APICAL RESORPTION OF MANDIBULAR INCISORS IN BEGG TREATMENT: ANCHORAGE BEND OR CURVE? BY KENNETH LEW
    A statistical evaluation of apical root resorption in mandibular incisors following Begg treatment in one group with anchorage bends and another group with anchorage curves  showed no statistical difference. Although the overbite reduction in both groups was similar, the anchorage curve group was statistically more efficient incisor intrusion when compared to the anchorage bend group (p < 0.01) (Australian Orthodontic Journal, Melbourne,  March  1990, 164-167)

  9. ALIGNMENT OF BUCCALLY DISPLACED CANINES FOLLOWIING PREMOLAR EXTRACTIONS: ARCHWIRES OR NATURAL ALIGNMENT? BY KENNETH LEW
    The alignment times of the buccally  displaced maxillary canines following the first premolar extractions were studied in 2 groups. The control group (n= 28) comprised of cases where no appliances were sued  whilst the experimental group ( n= 28) had Begg brackets bonded on the upper teeth in conjunction with Sentalloy archwire. The imbrication indices (I.I) of all canines were recorded  for both groups prior to extraction and every 5 days after extractions until the canines aligned. The results indicated that there were no significant  difference in the alignment rate at 30 days and 60 days between the 2 groups. However, the alignment rates at 90 days and 120 days were both significantly faster  in the experimental group compared to the control group ( p < 0.01). Whilst the alignment rates at  30, 60, 90, 120 days  in the experimental group  followed a plateaued curve, the alignment rates in the control group followed a cusped curve. The results indicated that a 2 months self- alignment period following premolar extractions would be justified in most cases before banding. (Australian Orthodontic Journal,  Oct 1989, 85-88)

  10. THE ORTHODONTIC TOOTH POSITIONER – AN APPRAISAL  BY  KENNETH KK LEW
    The tooth positioner is a one-piece, resilient appliance  which may be used for finishing orthodontic cases. The appliance fills the free-way space, and covers the clinical crowns of all the teeth and about 3 mm of the buccal and lingual gingival mucosa. The positioner is constructed over a predetermined ‘setup’ and fabricated from either rubber or plastic. This article reviews the literature and describes the author’s method of manufacture and usage. (British Journal of Orthodontics, Vol. 16, 1989, 113-116, British Society for the Study of Orthodontics)

  11. EXTREMES IN SECOND MOLAR ERUPTION IN TWO ORIENTAL PATIENTS BY KKK LEW
    Two cases are presented where the maxillary second molars were just erupting.  The first was a Chinese boy of 8 years and 2 months, and the other, a Chinese boy of 17 years 4 months. These extremes in eruption time are unusual and do not appear to have been reported in literature. (British Dental Journal, 1989, 166; 415-418)

  12. CEPHALOMETRIC IDEALS  IN CHINESE , MALAY AND INDIAN ETHONIC GROUPS BY KKK LEW
    Cephalometric data from 105  female subjects (35 Chinese, 35 Malay, and 35 Indian) with good occlusion and aesthetically pleasing profiles (determined  by a trained clinician and endorsed by the lay public)  were analysed using the Steiner analysis. Statistical analysis of the date showed that while the cephalometric ideals of the Chinese  and Malay ethnic groups were rather similar, cephalometric differences existed between the Chinese and Indians as well as the Malay and Indians. Compared to the Chinese and Malays, the Indians appeared to have less prognathic mandibles and maxillae, less protrusive and proclined upper and  and lower incisors and also less protrusive upper and lower lips. The differences demonstrate intrinsic ethnic differences  and emphasize the need to treat patients of different ethnic groups using cephalometric norms which are peculiar to their own group. (Asian J Aesthetic Dent 1994; 2:35-38)

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