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Introduction: Maintenance of mandibular pretreatment arch shape and size is important for long term orthodontic treatment stability. Will Andrews and Lawrence Andrews (WALA) ridge was proposed by Andrews as a clinical guide for the bucco-lingual position of mandibular teeth in the arch.
Objective: To determine the horizontal distance between WALA ridge and mandibular posterior teeth in individuals with normal occlusion.
Materials and Method: An analytical cross-sectional study was conducted from May to July 2020 at Kathmandu Medical College after getting ethical approval. The sample consisted of 130 dental casts of Nepali individuals (46 males and 84 females) with normal occlusion. WALA ridge and FA (facial axis) points of each mandibular posterior tooth except third molars were identified. FA to WALA ridge horizontal distance was determined using a modified digital Vernier caliper. Values were compared by arch side and gender using Student’s t-test in SPSS software v.20.
Result: Values for FA to WALA horizontal distance showed statistically significant gender variation for all teeth except for the first molar. Whereas, for arch side, there were no statistically significant differences for all teeth in both males and females. The mean FA to WALA ridge distance in males was 0.6 mm for first premolars, 1.16 mm for second premolars, 1.71 mm for first molars, and 2.41 mm for second molars. In females, it was 0.4 mm for first premolars, 0.88 mm for second premolars, 1.72 mm for first molars, and 2.1 mm for second molars.
Conclusion: In present study, mandibular posterior teeth showed progressively increasing horizontal distance to WALA ridge from anterior to posterior.

Mandibular posterior teeth; normal occlusion; WALA ridge.