e) Cementoenamel junction 11. In the progression and distribution of periodontal diseases, what is considered the most crucial factor? a) Social influences b) Environmental conditions c) Systemic health d) Genetic factors e) Composition of microbial dental plaque and its effects 12. Which tooth brushing technique involves a vertical sweeping brushing movement? a) Modified Bass brushing technique b) Stillman's brushing technique c) Charter's brushing technique d) Sulcular brushing technique e) Scrub brushing technique 13. Which of the following represents a major disadvantage of the Horizontal Scrub brushing technique? a) Gingival recession b) Incisor wear c) Cervical abrasion d) Lingual erosion e) Tooth sensitivity