OBJECTIVE: This study aims to determine the mean collum angle of maxillary central incisor and to compare it between high angle and low angle patients undergoing orthodontic treatment. METHODOLOGY: This cross-sectional, observational study was conducted using lateral cephalometric radiographs of 61 class II division 1 patients (comprised 32 males, 29 females, age range 13 to 30 years) from the record files of patients inducted for Orthodontic management from June 2020 till August 2020 at the Department of Orthodontics, Sindh Institute of Oral Health Science, Jinnah Sindh Medical University, Karachi, Pakistan. The sample was divided on the basis of Vertical Analysis (angulation of mandibular plane) into high and low angle cases. Collum angle was measured using the angulation of the Maxillary Central Incisor (MCI). Student t-test was used to compare the mean difference of the collum angle between skeletal vertical malocclusions. RESULTS: Mean value of the collum angle for high angle (Vertical Growth pattern) cases were mean ± standard deviation (4.35°±1.49°) while for low angle groups (Horizontal Growth pattern) were (2.41°±1.60°). CONCLUSION: There Collum angle of permanent maxillary central incisors differ significantly (p<0.001) among high angle and Low angle malocclusions cases (n=61) and showed pronounced axial bending in Class II division 1 incisors with high angle (4.35° ± 1.49°) as compared to low angle malocclusion (2.41° ± 1.60°). KEYWORDS: Collum Angle, Maxillary Central Incisor, Orthodontic Treatment, High Angle, Low Angle.

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Objective: To determine the awareness of regular orthodontic follow-up visits among the patients. The secondary objective was to assess patients’ perception towards orthodontic treatment needs and their psychological status during lockdown. Study Design and Setting: This cross-sectional study was conducted at Sindh Institute of Oral Health Sciences, (JSMU) from August, 2020 to January, 2021. Methodology: The questionnaire contained 15 questions divided into 3 categories. First category was about the awareness of routine checkup among patients Q1-Q5, second was to assess the impact of lockdown on patients’ visit to orthodontist Q6-Q12 and third was to assess the psycho-social effect of lockdown Q13-Q15. Three point likert scale was applied on each question with cut off value set as 70% for the 3 categories to get positive/negative response. SPSS version 22 was used for data entry and analyzing. Percentages and frequencies were calculated for qualitative variables like age, gender and educational level. Chi-square test was applied on all the three categories keeping the p-value <0.05 as significant. Results: The study included 115 subjects comprising of 21(18.3%) males and 94(81.7%) females, aged 12-30 years with mean age 19.15±3.96. Out of 115 patients 47(40.9%) patients met the 70 % cut off criteria for category 1.Similarly, for category 2, 73(63.5%) patients met the 70% cut off value. For category 3, 7(6.1%) patients met the 70% cut off value. Statistically significant difference was found for category 1 with age, gender and educational level at p-value<0.05. Similarly, in category 3, only educational level showed statistically significant association. Conclusion: The patients were quite aware of the need to visit orthodontists for regular follow ups during their treatment. The psychological status of the patients was the prime concern of the orthodontists as they had not sought orthodontic help during this time.

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OBJECTIVE: The study was conducted to evaluate the relationship of various cephalometric skeletal patterns in the vertical and anteroposterior planes with intercanine width in untreated orthodontic patients. METHOD AND MATERIAL: This study included dental cast and cephalometric radiographs of 100 patients (69 females and 31 males) of the age range 13 to 33 years. Skeletal parameters including SNA, SNB, SNMP angles were found from lateral cephalometric radiographs. Intercanine widths including upper intercanine widths (UICW) and lower intercanine widths (LICW) were measured by a digital caliper. RESULTS: The correlation of intercanine width with SNA, SNB, and SNMP angles was analyzed by applying Pearson correlation coefficient. According to statistical analysis, the only insignificant correlation was analyzed between UICW with SNB and LICW with SN-MP. CONCLUSIONS: The overall result showed statistically significant relationship of various cephalometric skeletal patterns in the sagittal and vertical planes with intercanine width.

SummaryThere are conflicting reports of the effect of nitrous oxide on the oxyhaemoglobin dissociation curve. We have therefore determined P~o of haemoglobin in the presence of either nitrous oxide or nitrogen and studied the upper portion of the curve in greater detail. No significant direrences in the oxyhaemoglobin dissociation curve were observed when nitrous oxide was substituted for nitrogen. The oxygen tensions measured in gas mixtures were not significantly direrent when determined simultaneously with a polarographic oxygen electrode and the mass spectrometer when nitrous oxide was used instead of nitrogen. . Key wordsBlood; oxyhaemoglobin dissociation, mass spectrometry. Gases; nitrogen, nitrous oxide. Measurement techniques; polargraphy.If the oxyhaemoglobin dissociation curve were shifted it would influence unloading of oxygen at the tissue level and might be sometimes clinically significant. Studies of the effects of nitrous oxide on oxyhaemoglobin dissociation have given inconsistent results. Smith and coworkers' studied this effect and showed a small rightward shift, which would improve oxygenation at the tissue level, whereas Fournier et aL2 recently reported a shift to the left in the oxyhaemoglobin dissociation curve of 9 mmHg, which could compromise unloading of oxygen at the tissue level. In the light of this recent report, we re-examined the effects of nitrous oxide on oxyhaemoglobin dissociation. Since Fournier et al. also reported systematically higher oxygen tension (Poz) readings with their Poz electrode in the presence of nitrous oxide, we also examined the effect of nitrous oxide on a polarographic oxygen electrode. MethodsVenous blood samples were obtained from five volunteers. Pairs of oxyhaemoglobin dissociation curves were plotted from each sample, using a Hem-0-Scan analyser (American Instrument Co., Silver Spring). This instrument continuously measures the oxygen tension and saturation of haemoglobin with oxygen, at 3 7 T , as a thin film of blood (2 x litre) equilibrates with a known gas mixture. A continuous oxyhaemoglobin dissociation curve is automatically plotted.A normal dissociation curve was plotted for each sample (the control curve) as follows. The blood was first deoxygenated by flushing the

OBJECTIVE: To assess the frequency of positive changes in orthodontic practice in Pakistani governmental and private workplaces after lifting of COVID-19 lockdown. METHODOLOGY: This cross sectional questionnaire-based study was carried out on 143 Pakistani orthodontic practitioners for the duration of 3 months. A well-constructed, computerized closed ended questionnaire was designed at an online website i.e., google drive and the link was circulated through social media and e-mail. Change in dental practice was assessed by comparing the results with CDC guidelines, keeping positive response cutoff 70%. Data was analyzed by using SPSS 22, Confounders, like educational qualification, gender and workplace were controlled through stratification. Post stratification Chi square Test was applied to assess the association of dentist's response with gender, educational level, age and workplace, keeping P value < 0.05. RESULTS: There were total 143 participants (80 female and 63 male) with age range from 23 to 56 years, with a mean age of 31.24 ± 6.82 years. Majority of the participants (75.52%) belonged to the age range of 23-33 years. Most of the orthodontists were post graduate trainees (66.4%). Out of all these participants, 67 were working at orthodontic OPD, 22 at private practice and 51 worked at both. 68.5% Implementation of positive modifications in dental practice were recorded. The chi square test results were significant (P <.05) for education and workplace of orthodontist. CONCLUSION: Most orthodontists have positively modified their dental practice post COVID-19 lockdown in Pakistan, by following WHO and CDC guidelines for Covid-19 to curtail spread of infection. KEYWORDS: Changes, Orthodontics, COVID