Periodontics. Fernando Suarez

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СКАЧАТЬ periodontium can be affected by the different types and surface characteristics (eg, surface free energy and roughness) of dental materials.^194–197 In a comparative study by Chan and Weber,¹⁹⁸ 150 crowns (50 porcelain crowns with aluminum-oxide framework, 68 porcelain-fused-to-metal [PFM] restorations, 13 cast gold crowns, 19 acrylic resin veneer crowns) and 242 intact natural teeth serving as controls were compared in terms of plaque retention using Löe and Silness¹⁹⁹ plaque index scores in a crown-to-quadrant ratio. Results showed that crowns with an aluminum-oxide base had minor plaque retention (32%), whereas PFM crowns (90%), natural teeth (110%), cast gold restorations (148%), and acrylic resin veneer crowns (152%) had substantially more plaque retention. Other material surfaces, like lithium disilicate and zirconia, have shown a superior resistance to surface roughness changes after instrumentation with stainless steel curettes, yet zirconia revealed a greater bacterial adhesion compared with gold alloy and lithium disilicate.²⁰⁰

      Despite differences in plaque retention and quality of the marginal fit, galvanic-ceramic crowns demonstrated significantly less clinical and inflammatory responses than metallic-ceramic crowns by means of plaque index, gingival index, gingival crevicular fluid flow rate, and levels of immunoglobulin G.²⁰¹ Nonetheless, these responses might differ when ceramic or metal restorations are compared with resin-bonded restorations. A study by van Dijken and Sjöström tested the effects of glass ionomer cement and composite filling materials for Class V subgingival cervical lesions and demonstrated that these materials present with no differences over time in term of the amount of plaque and degree of gingivitis when compared with enamel.²⁰² Konradsson et al noted a similar inflammatory biomarker response (interleukin [IL] 1α, IL-1β, and IL-1 receptor antagonist) with different materials when compared with enamel.²⁰³

      It has been proposed that a maximum roughness threshold of Ra less than 0.2 μm be recommended to reduce plaque accumulation.²⁰⁴ Moreover, periodontal therapy might have an impact in roughness changes, resulting in increased plaque accumulation. These changes are also dependent on each dental material and treatment modality.²⁰⁵ An in vitro study using gold alloy specimens showed that pre- and posttreatment Ra values significantly increased after instrumentation with stainless steel curettes and prophylactic cups.²⁰⁰ Interestingly, stainless steel curettes increase roughness levels nearly 13 times greater than prophylactic cups.

      Proceedings from the 2017 World Workshop on the classification of Periodontal and Peri-implant Diseases and Conditions concluded that dental materials act similar to enamel as plaque retentive factors to initiate gingivitis.¹⁹⁷

      LOCATION OF THE RESTORATIVE MARGIN

      The relationship between gingival health and the margin of the restoration has also been researched.^206–208 Newcomb showed in 51 subjects that the more apical the margin of the restoration, the more gingival inflammation was present according to a gingival index.²⁰⁹ Four groups were classified depending on the distance of the crown margin to the base of the crevice (CM-BC) and found that margins as close as 0.75 mm or less can induce gingival inflammation.

      A human histologic study²¹⁰ showed that restorations placed below the gingival margin were likely to accumulate plaque subgingivally, even when routine oral hygiene was performed. It was also noted that individual sites can re-form plaque as soon as 6 weeks on subgingival restorations, while others can be free of plaque for as long as 2 years.

      A 26-year longitudinal study examined the long-term effects of restorations with supra- and subgingival margins on periodontal health.²¹¹ It was concluded that subgingival margins exert a detrimental effect to gingival and periodontal health. Additionally, a “burn-out” effect was suggested as loss of attachment in teeth with subgingival margins was clinically detectable 1 to 3 years after the placement of the restoration.

      SUBGINGIVAL PLAQUE AND DENTAL RESTORATIONS

      The clinical and microbiologic effects of subgingival restorations have also been investigated. Lang et al found that placement of restorations with overhanging margins resulted in changes in subgingival microflora.¹⁹⁶ Also, increased proportions of gram-negative anaerobic bacteria, black-pigmented Bacteroides, and an increase in anaerobe:facultative ratio were noted. These changes may potentially initiate periodontal disease associated with iatrogenic factors. Similarly, the quality of plaque subjacent to bridge pontics from inflamed sites seems to harbor a higher proportion of periodontopathic bacteria (eg, Porphyromonas gingivalis, Prevotella intermedia, and Tannerrella forsythia) when compared with healthy sites.²¹²

      STATUS OF THE RESTORATIVE MARGIN

      The proper contour and adaptation of the restorative margins may also influence the presence of other factors such as overhangs, open contacts, food retention/impaction, recurrent caries, and plaque retention—and thus play a role in periodontal breakdown.^213,214 In this sense, Chan and Weber assessed crown margins and classified them into three groups based on the transition of the probe against the margin.¹⁹⁸ The classification proposed included grade I, grade II, and grade III for margins with a smooth transition from restoration to tooth substance, margins with a slight irregularity, and gross imperfections of the crown margin, respectively.

      OVERHANGING RESTORATIONS

      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

      OPEN INTERPROXIMAL CONTACTS

      The link between open contacts and periodontal breakdown has been a topic of debate. Open contacts can be measured by the visual assessment²²⁴ or through the resistance of dental floss within the СКАЧАТЬ