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An overhanging restoration that occupies the interproximal space might be conducive to periodontal breakdown and alveolar bone destruction.^215,216 Studies reporting the prevalence of overhangs are included in Table 5-12.^216–218

TABLE 5-12 Prevalence of overhanging restorations

Authors	Prevalence
Gilmore and Sheiman216	32%
Jeffcoat and Howell217	71%
Pack et al218	56%

The classic study by Jeffcoat and Howell randomly selected 100 periodontal patients to assess the effect of amalgam overhangs on the alveolar bone height and classified their size into small (< 20%), medium (20%–50%), and large (> 50%) based on the interproximal space occupied by the overhang²¹⁷ (Table 5-13). The authors showed that only medium and large overhanging restorations revealed significant bone loss when compared with control teeth.

TABLE 5-13 Classification of overhangs by Jeffcoat and Howell²¹⁷

Size	Percentage of interproximal space occupied by overhang
Small	< 20%
Medium	20%–50%
Large	> 50%

Pack et al evaluated 2,117 restored surfaces and reported that most of the overhangs were associated with pockets greater than 3 mm (64.3%) and bleeding on probing (32%).²¹⁸ Also, Jansson et al concluded that sites with overhangs were associated with deeper probing depths, radiographic bone loss, and worsened parameters among susceptible periodontal patients.²¹⁹

Removal of overhangs in combination with plaque elimination results in significant reduction of gingival inflammation,^220–222 and it is recommended during the initial phase of periodontal therapy.²²³