Purpose <p>Surgical removal of impacted mandibular third molar (M3M) is the most commonly performed minor oral surgical procedure which may occasionally result in compromising the periodontal health of second molar. Proper seal of the soft tissue distal to second molar is critical to its periodontal health. The objective of this prospective split mouth clinical study was to compare the effectiveness of vertical mattress suturing versus simple interrupted suturing in preserving the periodontal health of the second molar after surgical removal of an impacted M3M.</p> Materials and Methods <p>The present study was conducted at Department of Dentistry, ESIC Medical College and Hospital, Hyderabad. This study included patients who had undergone surgical removal of bilateral symmetrically impacted M3M. The flap was closed with vertical mattress suture on one side and simple interrupted suture on the other side, with at least two months gap between the two procedures and the patients were reviewed for up to 6 months after surgery. Primary outcome variable was probing pocket depth (PPD) and secondary outcome variables were mouth opening and wound dehiscence.</p> Results <p>A total of 10 male and 20 female patients were included in the study. Vertical mattress suture sites showed significant reduction in PPD at both disto-lingual (<i>p</i> &lt; 0.001) and disto-buccal (<i>p</i> &lt; 0.001) sites compared to only disto-buccal sites in the simple interrupted suture sites (<i>p</i> &lt; 0.001). Shallow sites (PPD 0–3&#xa0;mm) and deep sites (PPD &gt; 3&#xa0;mm) showed significantly decreased PPD when vertical mattress suturing technique was used for closure of the flap (<i>p</i> &lt; 0.001).</p> Conclusion <p>Vertical mattress suture may be beneficial for preserving the periodontal health of second molar following the removal of impacted M3M.</p>