Early presentation of gingival squamous cell carcinoma (GSCC) is at times misdiagnosed as a benign inflammatory or reactive oral condition. Some misdiagnosed patients undergo unnecessary, invasive dental procedures, resulting in delayed cancer diagnosis and an increased risk of accelerated disease progression due to disruption of the periosteum and cortical bone. The records of 58 patients with biopsy-proven GSCC were retrospectively reviewed. The sample included 32 patients who underwent an invasive dental procedure (IDP) prior to cancer diagnosis and 26 patients who did not undergo an IDP (non-case group). Patients from both groups initially presented with similar symptoms. The median duration of symptoms at initial clinical presentation was 6 months for the IDP group and 2 months for the non-case group. In IDP patients, symptoms worsened after the IDP was rendered, with 37.5% presenting with a severe-grade symptom. In both groups, the majority of lesions were found on the posterior mandible and had a histologic grading of moderately differentiated GSCC. The odds of the IDP group having late-stage disease were 2.94 times greater than the odds for the control group. Stage T3/T4 malignancy was diagnosed in 77.4% of the IDP patients versus 53.8% of non-case patients. Disease-specific mortality was comparable; however, surgical treatment was significantly more extensive in the IDP group than in the non-case group. The disruption of alveolar periosteum in undiagnosed oral cancer patients results in significant delay in diagnosis, necessitating more complicated treatment regimens because of local tumor progression.