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Objective: The aim of the study is to identify the normal vertical positions of sella (S) and nasion (N) points in subjects with a normal inclination of anterior cranial bases. Materials and Methods: Lateral cephalograms of 117 subjects who had a normal ∠SN-FH plane (7° ± 1°), ∠SN-palatal plane (9° ± 2°), ∠FH-palatal plane (1° ± 1°), and cranial base angles (131° ± 4°) were included in the study. Various linear and angular parameters and ratios were evaluated to determine the normal vertical positions of S and N points. An unpaired t-test was used to identify any significant differences between males and females. The P value of 0.05 was considered as the level of significance. Results: Among subjects with the normal inclinations of SN, FH, and palatal planes and cranial base angle, the mean values of ∠Ar-S-Ptm, ∠S-Ptm-Ar, and ∠S-Ar-Ptm were 59.38° ± 3.52°, 59.70° ± 3.21°, and 60.84° ± 3.56°, respectively, forming an almost equilateral triangle between S, Ar, and Ptm points. The mean values of ∠Ba-S-PNS, ∠S-PNS-Ba, and ∠S-Ba-PNS were 59.56° ± 3.17°, 59.72° ± 3.47°, and 60.76° ± 3.11°, respectively, forming another approximate equilateral triangle between S, Ba, and PNS points. The mean S-FH to N-FH ratio was 0.67 ± 0.06% for the whole sample, but it was significantly greater in males (0.69 ± 0.07%) compared to females (0.65 ± 0.06%) (P=0.002). Conclusions: Two approximate equilateral triangles were formed between S, Ar, and Ptm points; and S, Ba, and PNS points in subjects with normal inclinations of SN, FH, and palatal planes and cranial base angle. The S-FH to N-FH ratio was an excellent guide to locating the normal vertical position of S and N points.

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Background: Photobiomodulation has been gaining traction as a plausible therapy to control orthodontically induced root resorption. Aim: The aim of the present review was to systematically appraise randomized controlled trials conducted to study the influence of photobiomodulation on external root resorption during orthodontic movement in humans. Method: ology - A systematic search was carried out employing keywords in various electronic databases namely MEDLINE (Pubmed), Cochrane Library, Google Scholar, Semantic Scholar, ScienceDirect and Opengrey.eu for studies up to March 2020. Pre-defined inclusion and exclusion criteria were used to select the studies. Data extraction was carried out and the risk of bias was assessed using Cochrane Risk of Bias tool. Meta-analysis was conducted using random effects model for selected studies. Subgroup analysis was conducted for resorption on each axial surface of the tooth root viz. mesial, buccal, distal and palatal as well as for vertical thirds viz. cervical, middle and apical third. Summary of Findings was formulated according to GRADE Profile. Results: The search retrieved 1509 results out of which six studies were included for the systematic review. Two studies showed low overall risk of bias and the remaining four showed unclear risk of bias. The meta-analysis was conducted for three studies with an overall sample size of 120 teeth which showed a pooled mean difference of 0.08 (95% CI 0.15 - (-0.02) to 1.96, p=<0.0001) in favour of photobiomodulation group with respect to mean total resorption per tooth. I2 index revealed 88% heterogeneity. Conclusion: It is concluded that there is moderate grade of evidence to suggest beneficial effect of photobiomodulation on root resorption. Further high-quality randomized controlled trials with standardized intervention parameters are recommended. Registration: PROSPERO registration number - CRD42020167291.

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OBJECTIVE: The objective of the study was to compare external root resorption during orthodontic tooth movement between patients who were subjected to photobiomodulation and those who were not. MATERIALS AND METHODS: The study was designed as a split-mouth, single-blind randomized controlled trial conducted on twenty-two orthodontic patients requiring extraction of maxillary first premolars (age group 13-30years). A buccal force was applied to all the premolars using a 0.019″×0.025″ beta-titanium cantilever spring for 28days. The test group premolars were irradiated by indium-gallium-arsenide (InGaAs) diode laser (980nm, 100mW) 0, 3, 7, 11, 15 and 28days after force application. Each premolar was irradiated at ten locations on the buccal and palatal gingiva resulting in a total energy of 10J delivered per tooth. After 28days, the root surface of all the premolars were studied for the number and volume of resorption craters using three-dimensional optical profilometry by a blinded assessor. One-sample Kolmogorov-Smirnov test was used to ascertain normality and Mann-Whitney U test was applied for data analysis. RESULTS: All twenty-two patients enrolled completed the study. The root surface analysis showed formation of 32.78% less number of resorption craters (P<0.05) and 39.49% less volume of resorption craters (P<0.05) in the test group premolars relative to the control group premolars. CONCLUSIONS: The results of the present study, therefore, suggest that photobiomodulation reduces external root resorption during orthodontic tooth movement. TRIAL REGISTRATION/REGISTRATION NUMBER: CTRI/2018/04/013520.

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