Clinical and radiographic evaluation of the Periodontium with biologic width invasion

Patients who attended at the clinics of the Department of Dentistry UFVJM were invited to participate in this research until complete the sample. They were clarified about the objective, risks and benefits of participating in the research.

The sample size was determined with the following parameters: significance level 95%, power of 80%, minimum difference to be detected between the groups of 0.1 mm, and the standard deviation of probing depth (0.18 mm) was obtained in a previous study [17]. It were added 20% to prevent losses. The calculations have determined that 61 teeth sites with invasion of biologic width would be sufficient to carry out the study.

The study included patients over 18 years of age, with good general health, with no distinction of gender, ethnicity or socioeconomic status. It were included restored teeth with biologic width invasion, on the mesial or distal sites, which was radiographically observed. It was considered as biologic width invasion when the distance between the restoration gingival margin and the alveolar bone crest was less than 3 mm [18].

Patients presenting periodontal disease, smokers or who had restorations with contact in eccentric movements, horizontal overcontour or secondary caries were excluded from the sample.

The radiographic parameters evaluated, in the test (biological width invasion) and control groups (adequate biological width), when there was intrabony defect were: (1) bone defect level (BDL), which is the distance between the restoration margin and the most apical portion of the defect where the space of the periodontal ligament presented normal width; (2) Bone crest level (BCL), measured between the margin of restoration and the projection of the most prominent portion of the alveolar bone crest on the root surface; (3) Vertical component (VC), defined by subtraction BDL - BCL; and, (4) horizontal component (HC), distance from bone crest to root surface (Fig. 1). The radiographs analyzed were those that were already present in the patient records who were attended at the UFVJM dental clinic.

These measurements were taken with a dry-tip compass and transformed in millimeters with the aid of a millimeter ruler, for greater accuracy and reliability, being obtained by a second duly calibrated researcher.

The sites with biological width invasion were considered test group. As control group, it were used sites of the analogous or antagonistic tooth to the one that presented biologic width invasion.

The clinical parameters evaluated, in the test and control groups, were: plaque index (PI) and bleeding on probing (BOP), both taken in percentage in relation to total number of sites, considering as positive the sites with visible plaque and with bleeding until 15 s after probing. The probing depth (PD) was determined by the distance from the gingival margin to the base of the gingival sulcus, performed with a computerized periodontal probe (Florida Probe). The gingival recession height (GRH) consists of the distance from the cement-enamel junction to the most apical extension of the gingival margin; gingival recession width (GRW), given by the distance from the right gingival margin to the left gingival margin at cement-enamel junction. Keratinized gingiva height (KGH), measured as the distance from the gingival margin to the mucogingival line. Clinical attachment loss (CAL) given by the sum of PD and GRH. The keratinized gingiva thickness (KGT) was measured by perforation of the gingival tissue with a thin digital endodontic spacer and a rubber stop in the half of the KGH under topical anesthesia. The GRH, GRW and KGH were taken with manual periodontal probe and measured in millimeters. The clinical evaluation was performed by four examiners (BASC, CABD, JFS and WWSB) previously calibrated, the inter-examiner ICC ranged from 0.799 to 0.890 and the intra-examiner ICC ranged from 0.842 to 0.903.

Statistical analyses were performed using the SPSS® (Statistical Package for the Social Sciences Inc.), version 22. Descriptive analysis of the data provided frequencies, means and standard deviations. Data normality was assessed by the Shapiro-Wilk test. The Spearman correlation and Wilcoxon test were used to verify, respectively, the correlation and the association between the clinical and radiographic parameters. The confidence interval of 95% was used, and the significance level adopted was 5%.

Periodontal health is a basic requirement for both the longevity of restoration and the aesthetics, as well as, function and maintenance of dentition. However, dental restorations presenting width invasion are a frequently problem in clinical practice and are capable of inducing gingival inflammation, loss of connective tissue and unpredictable bone loss [19, 20]. Also, the invasion of the biologic width may cause periodontal pocket which does not imply the diagnosis of periodontal disease.

It was observed that the first molar, in the test and control groups, showed greater invasion of biological space. According to Vacek et al. [5], there are variations in the dimensions of the supracrestal gingival tissue between teeth, as well as in their sites, with the average molar measurements being greater than in the other groups of teeth.

The gingival recession and inflammation were clinically observed in this study, in addition to the correlation between the presence of width invasion and the decrease in the level of the bone crest observed radiographically, these findings similar to those reported by Douglas-de-Oliveira et al. [17].

The relationship between width invasion and bleeding on probing found in the literature and in the present study can be explained by the fact that the placement of restorative margins within the width space often leads to gingival inflammation, loss of clinical attachment and bone loss. This is probably due to the destructive inflammatory response of the microbial located deeper into the gingival sulcus. These alterations were justified by studies that evaluated the histological and clinical response of periodontal tissues to the position of the restoration margins within the biologic width [21, 22].

In the present study, the negative correlation between keratinized tissue height and bone level was observed in the test group, which means that the higher the keratinized tissue, the lower the level of bone defect. In fact, according to Stetler and Bissada [23], teeth with subgingival restorations and narrow keratinized gingiva have worse gingival inflammation compared to a wide range of keratinized tissue.

A negative correlation was found between plaque index and bone crest level in teeth with biologic width invasion in the control group. This can happen due to the biofilm retention in the rough surface areas of restoration that was brought into the gingival sulcus, where the patient is unable to properly cleaning his/her tooth, aggravating biofilm accumulation [24]. Consequently, this condition could lead to progressive gingival inflammation followed by periodontal destruction with greater pocket depth, attachment loss and gingival recession, increasing vertical bone resorption and increasing the horizontal component [17].

A negative correlation was also found between the thickness of the keratinized gingiva and the level of the bone crest in the control group. This result is in agreement with studies that evaluated gingival phenotype [9] in which a greater distance from the supracrestal gingival tissue was found in thin phenotype compared to the thick phenotype.

Thus the use of radiographic data is important to diagnose the biologic width invasion. Interproximal radiographs are the most used one for this purpose, since it presents less distortion than the other techniques [25]. In addition to this technique, a recent study [26] has shown an innovative parallel-profile radiography technique for gauging the dimensions of biological space on the labial sites of anterior teeth.

In a patient with preserved biologic width, the measure up to the bone crest has an average of 3 mm [12]. Furthermore, in the comparison between clinical and radiographic parameters in patients with invasion of the biologic width, association was observed between bleeding on probing, gingival recession and bone defects. This association was not found in the teeth of the control group, confirming the deleterious aspect of overlap restorations. These findings corroborate the concept that apically placed restorations within the supracrestal connective tissues may be harmful to periodontal health [27, 28].