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This study examined the changes seen on the submentovertex radiograph when the head is not extended sufficiently. A human dry skull supported on a cephalostat was used to simulate head extension. The range of rotation tested was an under-rotation of the skull of 30 degrees to an over-rotation of 10 degrees in intervals of 5 degrees. The measured variables were the intercondylar axis angles, corpus lengths and condylar widths. The relationships between skull rotation and changes in these variables were determined. Three selected landmarks, the spinosa points (right and left) and the pogonion point of each radiograph were located and compared spatially with the same points on the ideal radiograph. The results showed that variation in skull rotation affects both linear and angular measurements significantly (P < 0.01). Landmarks further away from the axis of rotation are affected by distortion more than those nearer to it.

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The effect of contamination by dietary oil on acid etching has not been reported in the literature. If dietary oil adversely affects acid etching, then a decrease in bond strength is expected. This in vitro study investigated the bond strength of brackets bonded to tooth surfaces that had been contaminated with dietary oil and on which prophylaxis was not carried out. The mean shear bond strengths for the control, teeth with oil contamination and teeth with oil contamination but no prophylaxis undertaken were 53.33 +/- 14.31 (SD), 61.76 +/- 19.32 and 64.12 +/- 17.90 N, respectively. An analysis of variance (ANOVA) test showed that there was no significant difference between the three groups. The power of the ANOVA was calculated for the minimum clinical change that would be worth detecting and was found to be approximately 1.0. It can therefore be concluded that the presence of dietary oil on the tooth surface does not adversely affect shear bond strength, even if prophylaxis is not carried out. Bond failures for all three groups occurred mainly at the tooth-adhesive interface.

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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.

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The search for an ideal enamel surface finishing method following bracket debonding has met with equivocal response. In this study, four other methods were assessed to determine their effectiveness against the slow speed tungsten carbide bur which is regarded as the established method of removing residual composite. Orthodontic brackets were bonded on 50 premolar teeth extracted for orthodontic purpose. After debonding with a standardized technique, the teeth were randomly divided into five equal groups. Samples in each group were subjected to different finishing procedures: Group A--Ormco band removing plier. Group B--Komet slow speed tungsten carbide bur. Group C--High speed ultrafine diamond bur. Group D--Jet high speed tungsten carbide bur. Group E--High speed white stone finishing bur. For consistency, the finishing procedures were limited to 15 seconds with each particular method. The composite remnants which then remained on the enamel surface were graded by four independent raters using the Composite Remnant Index (CRI). Subsequent to this, the enamel surface was examined in a Scanning Electron Miscroscope at x203 magnification. The photomicrographs were then graded by the same four independent raters using the Surface Roughness Index (SRI). Statistical analysis with the Friedman test indicated that there was no significant difference in inter-examiner variability in both the CRI and SRI assessment, but there existed significant difference among groups (P < 0.01) for both the CRI and SRI. It was found that no single absolute method was considered to be ideal for composite removal.(ABSTRACT TRUNCATED AT 250 WORDS)

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Cephalometric data from 105 female subjects (35 Chinese, 35 Malay and 35 Indian) with good occlusion and aesthetic pleasing facial profiles (determined by a trained clinician and endorsed by the lay public) were analysed using the Steiner analysis. Statistical analysis of the data showed that while the cephalometric ideals of the Chinese and the Malay ethnic groups were rather similar, cephalometric differences existed between the Chinese and Indians as well as the Malays and Indians. Compared to the Chinese and Malays, the Indians appeared to have less prognathic mandibles and maxillae, less protrusive and proclined upper and lower incisors and also less protrusive upper and lower lips. These 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.

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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)

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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 among 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 per cent of this population. Although this percentage was much lower than those reported in blacks, it was similar to those reported in caucasians. Crowding occurred in about 50 per cent of cases, which was slightly less than for those reported for caucasians. Increased overbites were also less common in this Chinese population compared with caucasians. Compared with caucasians, crossbites were also less frequent in this Chinese population.

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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 the results of our study. This new SMV cephalometric analysis can provide clinically relevant information in the treatment of dentofacial orthopedics and facilitate in the diagnosis of mandibular asymmetry.

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A simple removable appliance to effect minor tooth extrusion of anterior teeth is described and its use is illustrated. This technique uses a labial bow in conjunction with a composite resin button bonded to the labial surface of the tooth or teeth to be extruded.

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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.

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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 McNamara's 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.

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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 intermaxillary space, tongue position, and hyoid bone variables were quantified retrospectively using pretreatment and posttreatment lateral cephalograms. Lateral cephalograms taken at the early (5 to 7 days) postsurgical period showed that the 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 tongue structures to adapt to changes in the intermaxillary space following osteotomy.

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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.

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Irregularity of the mandibular incisors in an otherwise good occlusion is quite common in young adult patients. Through 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 anterior crowding.

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Using a double selection process comprised of professional and lay judges, the cephalometric tracings on a final sample of 48 Chinese adults with esthetically pleasing profiles were analyzed. 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 nose was less prominent (P < .01), the nasolabial angle was less obtuse (P < .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 lateral cephalometric norms are specific for the racial group and cannot always be applied across different racial types.

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The author tests the validity of predicting the eruption-sequence of permanent teeth from orthopantomograms taken during the early mixed dentition, based on criteria of root formation.

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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 differences in rank scores between all the profile types were statistically significant (p < 0.05). Assessment of profile types among lay personnel could provide clinicians an indication into the relative attractiveness among profile types and health care workers in treatment prioritization among dysmorphic facial types.

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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 colour photographs of seven occlusion types. Their ranking, in descending order of attractiveness, were as follows: 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 less than 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 less than 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.

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