Pak Armed Forces Med J 2023; 73(2): 398 Intra-Observer Variation of Space Available in the Mandibular Dental Arch by Two Different Measuring Tools-Vernier Calliper and Brass Wire with a Millimetre Ruler Rooma Shahid, Abdullah Jan, Ayesha Fazal*, Alaina Tariq Mughal, Fareena Ghaffar, Sundas Mehmood Armed Forces Institute of Dentistry/National University of Medical Sciences (NUMS) Rawalpindi Pakistan, *Margalla Institute of Health Sciences Rawalpindi, Pakistan ABSTRACT Objective: To check the variation of space available in the mandibular dental arch using different tools, i.e., Vernier caliper and brass wire with a millimeter ruler. Study Design: Comparative cross-sectional study. Place and Duration of Study: Department of Orthodontics, Armed Forces Institute of Dentistry (AFID), Rawalpindi Pakistan, from Sep to Dec 2019. Methodology: Seventy-five dental casts of patients, with an age range between 12-25 years were included in the study. The variation of the space available using two different measuring tools (Vernier calliper and brass wire with millimetre ruler) in the mandibular arch was determined by the same observer to assess random and systematic errors. The examiner recorded the measurements, and then the same examiner repeated the measurements after ten days by taking two readings each using the blinding technique to minimize bias. Random and systematic errors were analyzed with the use of two methods. Results: Systematic errors were found to be significant with brass wire with millimetre ruler method only (p-value=0.02). For random errors, the Vernier calliper can be considered a better method to measure reproducibility and repeatability. However, brass wire with a millimetre ruler method can be considered better for measuring repeatability than reproducibility since the value to measure random errors was less than 1mm but in the upper limits (p-value=0.091). Conclusion: In the current study, it is concluded that the Vernier calliper is more precise in measuring the readings in orthodontics for arch space measurement than that of brass wire with a millimetre ruler. However, brass wire with a millimetre ruler method can also take the readings. Keywords: Brass wire, Intra observer, Space available, Systemic errors, Vernier calliper. How to Cite This Article: Shahid R, Jan A, Fazal A, Mughal AT, Ghaffar F, Mehmood S. Intra-Observer Variation of Space Available in the Mandibular Dental Arch by Two Different Measuring Tools-Vernier Calliper and Brass Wire with a Millimetre Ruler. Pak Armed Forces Med J 2023; 73(2): 389-401. DOI: https://doi.org/10.51253/pafmj.v73i2.5615 I NTRODUCTION Precise measurements of dental casts are essential for correctly detecting dental anomalies to plan ade- quate treatment. 1 According to the previous literature, three methods already used for space analysis of the mandibular arch discrepancy include visual inspec- tion, brass wire evaluation method, and contact point arch chart. 2,3 The latter was the most accurate; how- ever, this method includes a lot of technical com- petency and accuracy with the procedure. 4 Nic et al. defined repeatability as "the closeness of agreement between independent results obtained with the same method on identical test material under identical conditions" and reproducibility as "the close- ness of agreement between independent results obtained with the same method on identical test material, under different conditions”. 5 The readings obtained by the same observer are more reliable than those obtained by two different observers because readings by two different observers may induce sys- tematic errors more than the intra-observer measure- ment methods. 6,8 While taking multiple readings, there some errors might occur. These errors are either random or syste- matic. Random error occurs when different values are clustered around the true value. This may affect the precision of the results. Since random errors always exist, the average of multiple readings must be con- sidered. Random errors may occur due to taking measurements at different angles of the objects. In lieu of random errors, there are also systematic errors, which occur due to some error in the observer's obser- vation or some defect in the instrument. Systematic errors are predictable errors. Random errors will always exist in a study, while systematic errors can be eliminated by improving the measuring techniques. 9,10 Therefore, the study aims to check the repro- ducibility of intraobserver variation in the space available in mandibular arches has been assessed after This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Correspondence: Dr Rooma Shahid, Department of Orthodontics, Armed Forces Institute of Dentistry, Rawalpindi-Pakistan Received: 31 Oct 2020; revision received: 15 Feb 2021; accepted: 24 Feb 2021 mellowmelamiine@hotmail.com Original Article Open Access