K. K. K. Lew

A clinical investigation of the efficacy of low level laser therapy in reducing orthodontic postadjustment pain

Low level laser therapy (LLLT) has been shown to produce analgesic effects in many clinical applications. The aim of this clinical study was to test the efficacy of LLLT in controlling orthodontic postadjustment pain. Thirty-nine volunteers were selected for this study that used a double-blind design with placebo control. Elastomeric separators were placed at the proximal contacts of one premolar in each quadrant of the dentition to induce orthodontic pain. The tip of a 30 mW gallium-arsenide-aluminium (830 nm) diode laser probe was then placed at the buccal gingiva and directed at the middle third of the root. Three different treatment durations of 15, 30, and 60 seconds and one placebo treatment of 30 seconds were tested within each subject. The study was conducted over 5 days, and the visual analogue scale (VAS) was used to quantify the pain experienced by the subjects before and after laser applications for each day. Analysis of the VAS median scores showed that teeth exposed to laser treatment had lower levels of pain as compared with those with the placebo treatment. However, nonparametric statistical analysis of the data showed that the differences between treatments and placebo within each subject were not statistically significant.

Attitudes and perceptions of adults towards orthodontic treatment in an Asian community

A retrospective survey 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 principal conclusions were that the improvement in dento-facial aesthetics following orthodontic treatment enhanced their self-confidence and self-esteem in a majority of patients; 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 in 39% of these patients the discomfort to teeth was experienced with each new archwire or elastic force application. These 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.

Horizontal Skeletal Typing in an Ethnic Chinese Population with True Class III Malocclusions

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 McNamaras line) criteria. Results indicated that mandibular hyperplasias with normal anteroposterior maxillary position comprised the majority of true Class III malocclusions. While 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 in Class III subtypes when using either angular or linear criteria.

Bending stiffness of two aesthetic orthodontic archwires: An in vitro comparative study

The aims of the study were to quantify the transverse stiffness of two aesthetic orthodontic archwires (0018 inch Teflon-coated stainless steel and 0017 inch Optiflex) in a simulated clinical setting and to assess the influence of deflection direction on the bending stiffness. The aesthetic archwires were randomly divided into three equal groups: group 1, lingual deflection; group 2, labial deflection; and group 3, occlusal deflection. Each group consisted of six archwires of the same type. The control group consisting of eighteen 0014 inch stainless steel archwires were also subjected to the same grouping. A total of 54 archwires were tested in the study. The deflection of the archwires was measured with a travelling microscope and the load measured with a calibrated strain gauge ring transducer. The mean stiffnesses of the archwires in the lingual, labial and occlusal deflection groups were found to be 29, 08 and 25 mN/mm respectively for 0017 inch Optiflex (r = 09, P less than 0001), 132, 105 and 245 mN/mm respectively for 0018 inch Teflon-coated stainless steel (r = 09, P less than 0001) and 266, 164 and 323 mN/mm respectively for the control (r = 09, P less than 0001). Springback was found to be poor for Optiflex and the archwire remained bent upon deactivation. ANOVA showed that the influence of arch curvature on the bending stiffness was significantly different for Optiflex (P less than 005), Teflon-coated stainless steel (P less than 0005) and the control group (P <0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Tooth extrusion effects on microvessel volumes, endothelial areas, and fenestrae in molar apical periodontal ligament

Extrusive tooth loads, simulating short-term orthodontic movements, have not previously been 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. The mean vascular volume, as a percentage of apical periodontal ligament volume, increased (p less than 0.01) in postcapillary-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 less than 0.01) in postcapillary-sized venules from 16.8 to 25.7 x 10(6) microns 2/mm3, in venous capillaries from 3.0 to 4.8 x 10(6) microns 2/mm3, and in arterial capillaries from 0.7 to 1.5 x 10(6) microns 2/mm3. The number of fenestrae per square micron of endothelium in postcapillary-sized 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/microns 2, respectively (p less than 0.01). Fenestrae per cubic millimeter of periodontal ligament tissue also demonstrated a statistically significant increase with extrusion (p less than 0.01) in postcapillary-sized venules from 0.37 to 1.55 x 10(6) fenestrae/mm3, in venous capillaries from 0.27 to 1.34 x 10(6) fenestrae/mm3, and in arterial capillaries from 0.02 to 0.22 x 10(6) fenestrae/mm3. Fenestrae in control vessels had a mean diameter of 54.2 +/- 0.56 nm (SE) compared with 61.1 +/- 0.7 nm in tensioned vessels (p less than 0.01). This investigation demonstrates multiple ultrastructural changes in the periodontal ligament microvascular bed after tooth extrusion.

Orthodontically induced microvascular injuries in the tension zone of the periodontal ligament.

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 were anesthetized and cannulated via the aorta after applying a 1-N extrusive force for 30 min 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 was prepared for TEM examination. In the experimental PDL, degenerative changes in the endothelial cell wall and incipient nuclear shrinkage were observed in about 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 less than 0.01). The results of this study suggest that the postcapillary venules are the most vulnerable segment in the PDL microvascular system.

Shear bond strength of orthodontic brackets using Panavia: An in-vitro study

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 conventional 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.

The periodontal microvasculature--a morphological and morphometric study.

Various ultrastructural studies on the periodontal ligament (PDL) microvasculature have been reported. However, the lack of a systematic classification has led to much confusion in the terminology used to define vessel types. On the basis of morphological criteria, the author proposes that 3 vessel types are present in the PDL: terminal arterioles (Type A vessels), capillaries (Types B-1 & 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 2 vessel types made up the remainder of the vascular volume. The results of this study suggest that the apical PDL region is predominantly venous. Introduction By use of the SEM methacrylate corrosion cast technique[1] and transmission electron microscopy[2,3] in a variety of animal models, various types of microvascular segments have been described in the periodontal ligament (PDL). These include arterioles, venules, sinusoids, lymphatics and capillaries. However, a feature common to these studies was the lack of a systematic classification of the PDL blood vessels. Furthermore, the authors have not always defined their criteria for categorization of vessel types. Estimates of the vascular volume in selected regions of the PDL range from 1-2%[4] to 22%[5]. It is generally agreed that the vascularization is densest in the apical region of the PDL[6,7]. However, the relative proportions of vascular types have not been reported. The objective of this study was to derive an ultrastructural classification system for the PDL microvasculature and to determine morphometrically the vascular volume of different vascular types using the rat molar periodontal ligament as a model. Faculty of Dentistry, National University of Singapore, National University Hospital, Lower Kent Ridge Road, Singapore 0511.

The Orthodontic Tooth Positioner—An Appraisal

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 authors method of manufacture and usage.

Temporary Pontics in Aesthetic Orthodontics—a New Design

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 authors clinical practise to be superior to the 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.