Alveolar Bone Loss, Plaque Index, and Gingival Index among Non-Diabetics Treated with Class II Amalgam Restorations for Different Service Lives

Objective: The present study aimed to evaluate the influence of different service lives of class II amalgam restorations on periodontal health among patients without diabetes. Materials and Methods: Two hundred and twenty-five patients without diabetes were divided into five groups (G1–G5) based on the ages of their class II amalgam restorations, that is, 2, 4, 7, 10, and > 10 years, respectively. Each group had 45 patients, aged 45–60 years. They were assessed for the plaque index (PI), gingival index (GI), rate of overhangs (OH), and alveolar bone loss (ABL), (OH and ABL, using panoramic radiographs). The data were analysed using the Scheffé test and analysis of variance. Results: The periodontal parameters of the examined groups demonstrated low and intermediate scores that ranged from 25% to 41% for ABL, 1.1 to 1.5 for PI, and 1.2 to 1.5 for GI. G4 and G5 had the highest scores for the three parameters (PI, GI, and ABL); p<0.001. The rate of overhangs varied among groups considerably with G1 and G3 having the highest rate (p<0.037). Conclusion: two groups, while the participants of G1, G2, and G3 had relatively better periodontal status indicated by their low and intermediate periodontal scores.


Introduction
Periodontal disease is a chronic immunoinflammatory multifactorial illness of the oral cavity occurring owing to bacterial deposition and may cause several periodontal complications, such as alveolar bone destruction [1][2][3]. The origin and transmission of the periodontal disease occur via dysbacteriosis of the commensal oral microbiota, which then interacts with the immune defence of the host, leading to inflammation and disease [4,5]. It is one to a stage of inflammatory alteration in the oral tissues [16]. Such periodontal alteration can be quantified or diagnosed by examining basic clinical oral signs and assessing certain periodontal indices [17]. The most significant periodontal parameters that are routinely used to determine different stages of periodontal diseases are plaque index (PI), gingival index (GI), and alveolar bone loss (ABL).
The ongoing research has identified pertinent risk factors that play a significant role in the initiation and progression of periodontal inflammation. Many systemic and local factors are known to initiate and aggravate periodontal disease. A significant local factor is the quality of restorations performed in relation to the periodontal tissues. Faulty restorations are most likely to cause negative effects on the oral health status. This consistently present as an elucidation for the detrimental effects of restorations on periodontal status [18,19]. Certain essential restoration factors can negatively influence periodontal tissues, if not considered during restorative treatment. Some of these factors are 1) type of restoration, 2) marginal adaptation, 3) proximal relationships, 4) surface smoothness of the restoration, and 5) inflammation around the restored tooth. These factors not only dictate a relationship between restoration and the resultant periodontal diseases but also can play a significant role in the success and longer service life of a specific restoration [20].
A significant factor when designing proximal restorative treatment, such as class II restoration, is the overhanging margin.
In addition to disrupting the dynamic relationship that exists between a tooth and periodontium, overhanging margin promotes plaque accumulation, via providing an expedient site for diseaseassociated harmful organisms, eventually leading to a remarkable change in the ecological balance of the gingival sulcus region [21]. Moreover, this can be aggravated by a longer service life (age) of restorations. Older overhung restorations may encourage further growth of microbial dental plaque. This not only results in pathogenic multiplication but also gives rise to further periodontal destruction and ABL [22]. Hence, periodontal complications along with ABL, related to amalgam restoration overhang, were highly prevalent, as stated in previous research studies [22][23][24][25]. However, the size of the overhang and the affected site should also be relevant in this association. The most problematic restorations associated with massive ABL are those with larger overhangs, greater than 1 mm [22,23].
Many research studies were found in the literature that evaluates the effect of different restorative dental materials on periodontal health [20,[26][27][28][29][30]. However, no studies were found that appraise the effect of different service life (age) of class II amalgam restoration on periodontal health. Therefore, this study aimed to evaluate the effect of different service lives of class II amalgam restoration on periodontal health among patients without diabetes.
It was hypothesized that patients with older class II amalgam restorations would have worse periodontal parameters, PI, GI, and ABL, than those with shorter restorations' ages.

Sample Size and Sampling
The sample size was calculated using the formula that used for calculating sample size, in medical research, proposed by Crano et al, 2002 [31], as follows: n = Nn*/N+n* where n is the required sample size, N is the population size (total number of participants, 650), and n* is the first estimated sample. The first estimated sample (n*) was determined using the following formula: n*= P (1-P)/(SE) 2 Where P is the estimated proportion to participants, which was assumed as 0.5 for getting the maximum sample size. SE is the standard error, assumed as 0.05. Therefore, the first estimated sample, n* =100; consequently, the sample size (n) is 86.7. It should be noted that any further increment in the population size would have a limited effect on the results [31].

Inclusion and Exclusion Criteria
The inclusion and exclusion criteria for the selection of the participants adopted in the current study were as follows:

Study Population
Since this was an observational comparative cross-sectional study, the participants were clinically examined with their current dental status. Moreover, no dental treatment was provided to the participants before the clinical examination. Among a sample of 650 patients who presented at the specialized dental clinics, Faculty of Dentistry, Najran University, Kingdom of Saudi Arabia, 225 male patients without diabetes were selected. They were divided according to the age of class amalgam restorations into five groups, group 1 to group 5 (G1-G5). G1-G5 had their class II amalgam restorations for an approximate duration of the following service lives: 2, 4, 7, 10, and 12.5 years. Each group comprised 45 patients, aged 45-60 years. It is noteworthy that female participants were not included in the current study as the dentistry program of the current educational institution (University of Najran) is specified for male students only. Therefore, this study sample included only men.

Clinical Examinations
All participants were subjected to clinical oral examination including periodontal tissues status. The screening clinical examination included the state of periodontal tissues by assessing the amount of dental plaque, plaque index (PI), and gingival condition, and qualitative alterations of the gingiva, gingival index (GI) using the two scoring systems proposed by: 1) Silness and Löe, 1964, [32] for PI, and 2) Löe and Silness, 1963, [33] for GI. For PI evaluation, four sides per tooth (buccal, lingual, mesial, and distal) were examined for each participant (except for third molars), using William's periodontal probe. For GI assessment, certain teeth were chosen: 16, 12, 24, 32, 36, and 44.
Two periodontal investigators collected the periodontal parameters, PI and GI. Values obtained were compared, and the overall kappa score for intra-examiner reliability was calculated.

Radiographical Procedure
Panoramic radiography was used to measure ABL, and to locate sites of overhanging restorations. A panoramic X-ray unit (Planmeca Promax, Dent-R100, RPX253665, Helsinki, Finland) was used to produce the necessary images. The desired resolution of each radiographical procedure was selected, followed by adjusting the height of the X-ray according to patient height. The patient's chin was placed in the chin cup and the occlusal plane was set horizontally. The patient was directed to grasp the patient's handles tighten head support. The laser position was adjusted to correspond with the illustration on the touch screen. Final and fine adjustments were performed to volume location whenever needed.
All panoramic radiographs were digitized and analyzed using a computer-assisted system for linear measurements.
Panoramic radiographs and ABL measurements were recorded for all participants during regular daily dental practice visits between March 2018 and February 2020.

Panoramic Radiographs
Forty-five complete sets of panoramic radiographs were were measurable. At the end of the selection process for the set of images, radiographic images that did not fulfil the criteria were discarded. A computer screen was used to amplify and visualize images.
The distance between the CEJ and crest of the alveolar bone, and the crest of the alveolar bone and tooth apex, were used to identify the alveolar bone with bone loss. ABL was recorded when the distance between the CEJ and the ABC was > 2 mm. The ABL was presented as percentage bone loss [34].
Bone loss percentage was calculated using the following formula [34] ((CEJ-ABC)-2mm)/ ((CEJ-AP)-2mm) x100 Two periodontal investigators collected all clinical data. The collected data were grouped on Excel spreadsheets to record the percentage of alveolar bone level, root length, and bone loss in mm. The ABL assessments produced by the two investigators were compared, and the overall kappa score for intraexaminer reliability was calculated.

Statistical Analysis
Data were evaluated statistically using IBM SPSS version 25.
The variables were expressed as mean ± SD and analyzed using Scheffe test, and one-way analysis of variance (ANOVA). A p-value < 0.05 was considered statistically significant and p< 0.0001 was deemed extremely significant.

Results
The mean ages of participants of the examined groups G1-G5  (Table 2). Furthermore, statistical analysis showed that these service life durations significantly differed (p < 0.001). Regarding the overhanging class II amalgam restorations, the chi-square test showed that class II amalgam restorations differed significantly among all groups (p < 0.001). G1 had a significantly higher rate of overhanging restorations (60%) than those of the other groups (p < 0.001), whereas the lowest rate of overhanging restorations (40%) was recorded in G5 (p < 0.001).
The overhangs' rates among the examined groups are listed in Table 1.  Table 2: Mean plaque index, mean gingival index, and mean alveolar bone loss of the examined groups. The mean values of the PI and GI scores and the SD of all examined groups are listed in Table 2 Statistically, G5 had the highest two values of all groups (p < 0.001). Comparison of the assessment of the ABL made by the two investigators produced an overall kappa score of 0.85 for intraexaminer reliability.

Group Mean plaque index (SD) Mean gingival index (SD) Mean alveolar bone loss (SD)%
Representative ABL images for all examined groups are shown in Figures 1-4.    the whole effect of a dental restoration should not be extended beyond the restored area. Therefore, it can be speculated that PI and GI scores are independent of the effect of dental restorations as dental restoration can be responsible for the localized periodontal inflammation of the restored area, and its surroundings.
The prevalence of OH among the participants of the examined groups (G1-G5) ranged from 40% to 60%. The highest incidence of overhanging restorations, found among participants of G1, was accompanied by the lowest amount of ABL. G2 which had similar ABL to that of G1 had significantly a lower prevalence of OH. G4 and G5 demonstrated the highest amount of ABL despite their lower rate of OH than all other groups. These results indicated that the overhang's incidence did not correlate with ABL, which might be attributed to the effect of size of the restorations and/or size of overhangs' margins. It is well established that overhang's margin less than 0.2 mm should be harmless to the periodontal health. It is noteworthy that ABL correlated significantly with the service life of these restorations, but not with the incidence of overhanging restorations. Therefore, it can be speculated that longer service life (age) of overhanging restoration is more detrimental to periodontal health, and subsequently further ABL than merely the prevalence of overhanging restorations.
Another risk factor for the periodontal complications among the examined groups was the age of participants. It is well-known that there is a significant association between age, as a systemic risk factor, and periodontal health [35,36]. Therefore, when the age group is interrelated to the resultant periodontal parameters, two outcomes are equally conceivable. Firstly, participants with older ages will present with worse periodontal parameters as compared to younger ones. Secondly, participants with similar age groups will be accompanied by similar periodontal parameters. In the current study, the participants of the G4 and G5, the oldest among the examined groups presented with the worst periodontal parameters.
However, G1, G2, and G3, who had similar age groups, were shown to have different periodontal parameter values. Therefore, it is rational to speculate that periodontal outcomes are not necessarily stemming from the effect of a single risk factor, such as aging. Other risk factors should be relevant in this respect, such as oral hygiene status, the effect of dental restoration, and its related factors, such as service life, smoothness, overhang, and subgingival margin.
Therefore, it is anticipated that the synergistic action of these risk factors is detrimental to periodontal health. There are some limitations of the current study which might have biased the outcomes of the present study. Women were not included in this study. Hormonal changes in women were found to have an impact on periodontal health [38]. The fact that men have a higher rate of periodontal disease is true [39]. Moreover, there is still a necessity for research studies that evaluate the severity of periodontal disease among men and women. Although the effect of obesity on periodontal health, as a risk factor for the increased susceptibility of periodontal complications is inevitable [40]; it was not considered in the present study. Smoking is another important limitation of the present study. It is a well-known risk factor for numerous medical conditions, including periodontal disease [41].