Periodontal evaluation of restorative and prosthodontic margins
Creators: name: FERRARI CAGIDIACO, EDOARDO
Publisher: name: Universit� degli Studi di Siena
Year: 2021

description: Prosthodontic and periodontal correlation on teeth
In the daily dental practice 3 fundamental/empiric/clinical parameters have a role to establish the clinical success of prosthodontic treatment: function, aesthetic and longevity of the restorations. But, from a scientific point of view, how do we rate the success of the restorations?
When analyzing the existing literature, it can be noted that many authors focus their attention on the precision of the margin, to pursuit a small gap between the abutment and the crown, and to achieve the clinical success. 
Christensen et al.1 and Mc Lean &amp; Von Fraunhofer2 investigated the margins? clinical acceptability by dentists and asked to measure the gap between the abutment and the crown to a number of practitioners: it was shown that a clinician can clinically appreciate a gap not lower than 120 microns using a sharp explorer. This result may end in a not sure and sufficient seal between the crown and abutment, and consequently leakage at the margins. 
This finding is not in agreement with the existing data coming from an in vitro study in which the acceptable marginal gap is lower than 50 microns3 Sorensen3 reported that small defects less or equal then 0,050 mm were associated with significantly less fluid flow and bone loss than defects exceeding this value.
Martignoni4-5 reported that there are variable definitions regarding what constitutes a margin that cab ne clinically acceptable, and there is no definite threshold for the maximum marginal discrepancy that is clinically acceptable. Many authors accept the criteria established by McLean and Von Fraunhofer2, they completed a 5-year examination of 1000 restorations and concluded that 120 microns should be considered the maximum marginal gap.
The adaptation, the precision and the quality of the restoration margin can be of greater significance in terms of gingival health, than the position of the margin6. 
According to Lang et al. 7 following the placement of restorations with overhanging margins, a subgingival flora was detected which closely resembled that of chronic periodontitis. Following the placement of the restorations with clinically perfect margins, a microflora characteristic for gingival health or initial gingivitis was observed.
In patients with suitable oral hygiene, tooth-supported and implant-supported crowns with intra-sulcular margins were not predisposed to unfavorable gingival and microbial responses8. 
Even among patients receiving regular preventive dental care, subgingival margins are associated with unfavorable periodontal reactions9. 
Ercoli and Caton10, in a systematic review, describe how placement of restoration margins within the junctional epithelium and supracrestal connective tissue attachment can be associated with gingival inflammation and, potentially, recession or periodontal pocket. The presence of fixed prostheses finish line within the gingival sulcus or wearing of partial, removable dental prostheses does not cause gingivitis if the patients are complaint with self-performed plaque control and periodic maintenance. Procedures adopted for the fabrication of dental restorations and fixed prostheses have the potential to cause traumatic loss of the periodontal supporting tissue. They concluded that restoration margins located within the gingival sulcus do not cause gingivitis if the patients are complaint with self-performed plaque control and periodic maintenance.
Tooth-supported and/or tooth-retained restorations and their design, fabrication, delivery, and materials, have often been associated with plaque retention and loss of attachment. Restoration margins placed within the junctional epithelium and supracrestal connective tissue attachment can be associated with inflammation and, potentially, recession. Factors related to the presence, design, fabrication, delivery and materials of tooth-supported prostheses seem to influence the periodontium, generally related to localized increase in plaque accumulation and, less often, to traumatic and allergic reactions to dental materials10.
Jansson showd that the influence of a marginal overhang on pocket depth and radiographic attachment decrease with increasing loss of periodontal attachment in periodontitis-prone patients, and the effect on pocket depth of a marginal overhang may act synergistically, potentiating the effect of poor oral hygiene11. 
Subgingival restorations with their apical borders still located subgingivally after periodontal treatment should be regarded as a risk factor in the progression of periodontitis12. Consequently, placement of the restoration margin supragingivally is recommended, especially in periodontitis-prone patients with an insufficient plaque control12. 
Dental restorations may be suggested as a risk indicator for periodontal disease and tooth loss. Routine SPT (Supportive Periodontal Therapy) was found to be associated with decrease in the prevalence of deep PPD over time, and it is of the utmost importance in maintaining periodontal health, especially adjacent to teeth with restorations. Finally, these findings may support the treatment of caries lesions and faulty restorations as part of a comprehensive cause-related therapy and should be followed by a regular maintenance program13. 
The relationship between dental restorations and periodontal status has been examined for some time. Research has shown that overhanging dental restorations and subgingival margin placement play an important role providing an ecologic niche for periodontal pathogens14. 
An overhanging dental restoration is primarily found in the class II restoration, since access for interdental finishing and polishing of the restoration, and cleansing is often difficult in these areas, even for patients with good oral hygiene. Many studies have shown that there is more periodontal attachment loss and inflammation associated with teeth with overhangs than those without. Presences of overhangs may cause an increase in plaque formation15-21 and a shift in the microbial composition from healthy flora to one characteristic of periodontal disease14. 
The location of the gingival margin of a restoration is directly related to the health status of the adjacent periodontium8. Numerous studies8-12-25
have shown that subgingival margins are associated with more plaque, more severe gingival inflammation and deeper periodontal pockets than supragingival ones. In a 26-year prospective cohort study, Schatzle et al. 25 followed middle class Scandinavian men for a period of 26 years. Gingival index, and attachment level were compared between those who did and those who did not have restorative margins greater than 1mm from the gingival margin. After 10 years, the cumulative mean loss of attachment was 0.5 mm more for the group with subgingival margins. This was statistically significant. At each examination during 26 years of the study, the degree of inflammation in the gingival tissue adjacent to subgingival restorations was much greater than in the gingiva adjacent to supragingival margins. This is the first study to document a time sequence between the placement of subgingival margins and periodontal attachment loss, confirming that the subgingival placement of margins is detrimental to gingival and periodontal health. 
Plaque at apical margin of a subgingival restoration will cause periodontal inflammation that may in turn destroy connective tissue and bone approximately, 1-2 mm away from inflamed area14. 
Determination of the distance between the restorative margin and the alveolar crest is often done with bitewing radiographs; however, it is important to remember that a radiograph is a 2-dimensional representation of 3-dimensional anatomy and structure. Thus, clinical assessment and judgment are important adjuncts in determining if, and how much, bone should be removed to maintain adequate room for the dento-gingival supra crestal connective tissue height attachment14. 
Although surface textures of restorative materials differ in their capacity to retain plaque26, all of them can be adequately maintained if they are correctly polished and accessible to patient care27. This includes underside of pontics. Composite resins are difficult to finish interproximally and may be more likely to show marginal defects than other materials28. As a result, they are more likely to harbor bacterial plaque29. Intra-subject comparisons of unilateral direct compositive ?veneers? showed a statistically significant increase in plaque and gingival indices adjacent to the composites, 5-6 years after placement28. In addition, when a diastema is closed with composite, the restorations are often overcontoured in the cervical-interproximal area, leading to increased plaque retention28. As more plaque is retained, this could pose a significant problem for a patient with moderate to poor oral hygiene14. 
For that, in absence of more specific prosthodontic parameters to evaluate the integration of crowns in to the periodontal environment, another way to determine the success and health of the restoration is to use the periodontal parameters such as: PPD (Periodontal Probing Depth) that is the measurement of the periodontal sulcus/pocket between the gingival margin and the bottom of the sulcus/pocket; REC (Recession) is the apical migration of the gingival margin measured with the distance between the gingival margin and the CEJ (Cement-Enamel Junction); PI (Plaque Index) the index records the presence of supragingival plaque; BOP (Bleeding On Probing) the presence or not of bleeding on surfaces of the teeth during the probing. 
The aim of this study/thesis was to propose a clinical procedure to evaluate single unit restorations and their relations with periodontal tissues by a new clinical score: the FIT ( Functional Index for Teeth). FIT, that is a novel index for the assessment of the prosthetic results of lithium disilicate crowns, based on seven restorative-periodontal parameters, that evaluate crowns placed on natural abutments, and want to be a reliable and objective instrument in assessing single partial crown success and periodontal outcome as perceived by patients and dentists.