Comparative Evaluation of Gingival Displacement and Patient Outcomes with Different Gingival Retraction Techniques: A Cross-over Clinical Trial

1. Student (Post Graduate), Department of Prosthodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India. 2. Professor, Department of Prosthodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India. 3. Assistant Professor, Department of Prosthodontics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India.

Abstract

Introduction: The success of fixed restorations depends on marginal integrity, particularly in subgingival areas. Gingival retraction facilitates proper placement of impression material in the displaced gingival sulcus; however, a lack of consensus on evaluation criteria hinders comparative studies of gingival retraction systems.

Aim: To evaluate the effectiveness of mechanical retraction cord and chemical gingival retraction paste compared to a control group with no retraction.

Materials and Methods: This study was a cross-over clinical trial conducted at Saveetha Dental College and Hospitals in Chennai, Tamil Nadu, India, involving 20 patients requiring single crowns from May 2024 and June 2024. Patients were allocated into three groups-no retraction, chemical retraction, and mechanical retraction-based on randomisation. Patients with healthy gingival and periodontal status, exhibiting no bleeding on probing, were included in the study. Impressions were taken at baseline, and subsequent gingival displacements on days 7 and 27 were performed using chemical and mechanical methods according to random allocation. A Visual Analogue Scale (VAS) score was used to analyse post-operative comfort. Gingival displacement was measured with a stereomicroscope, and results were tabulated. Data analyses were performed using Statistical Package for Social Sciences (SPSS) software (version 26.0). Statistical significance was set at a threshold of p<0.05, employing one-way analysis of variance and Tukey post-hoc tests for gingival retraction and Visual Analog Scale (VAS) scores.

Results: Among the 60 tested samples, significant differences in gingival retraction were noted (p<0.05). Both experimental groups (Mechanical gingival retraction=698.53±43.276 μm, Chemical retraction=509.33±29.405 μm) exhibited more gingival displacement than the control group (mean gingival retraction=164.8±15.725 μm), with mechanical retraction cord displaying the highest value. The mean gingival displacement rankings were as follows: mechanical retraction > chemical retraction > no retraction. For VAS scores, statistically significant results were observed for mechanical retraction compared to no retraction (0.9±0.052) and mechanical retraction (3.40±0.049), as well as between no retraction and chemical retraction (2.6±0.057) (p<0.05). However, the differences between mechanical and chemical retraction were not statistically significant (p>0.05).

Conclusion: Although there was a statistically significant difference in the amount of displacement between the chemical and mechanical systems, both were within the clinically acceptable range (220 microns). Hence, chemical retraction can be used as a substitute for mechanical retraction techniques.

Chemical retraction, Gingival sulcus, Mechanical retraction, Stereomicroscope, VAS score

The long-term success of fixed restorations relies heavily on maintaining optimal marginal integrity. Insufficient integrity can lead to periodontal inflammation and an increased risk of secondary caries. While capturing supragingival margins is straightforward, challenges arise with subgingival margins, especially when they are concealed or positioned below the gingival crest for aesthetic purposes (1). A clear field, free from blood, is crucial for a high-quality impression. Controlling sulcular bleeding before impression-making is essential. Adequate retraction in all subgingival areas ensures an accurate record of tissues. Gingival displacement, which involves the deflection of the marginal gingiva away from the tooth, is facilitated by gingival retraction. This process temporarily moves the gingival tissues to allow for proper material placement in the displaced gingival sulcus, ensuring accurate margin capture.

Numerous retraction materials have been introduced, with the gingival retraction cord being considered the gold standard method for gingival retraction in dentistry (2). However, its traditional use is not only time-consuming but also uncomfortable, posing potential harm to the tissues if not used with care. Non-medicated cords are considered safer but demonstrate limited efficacy in controlling haemorrhage, while medicated cords exhibit satisfactory effectiveness in haemorrhage control. Nevertheless, past research has highlighted both local and systemic adverse effects linked to the medications used for gingival retraction (3).

To address these issues, various new materials, such as gingival retraction pastes, have been introduced. These pastes serve as alternatives to retraction cords and are effective and tissue-friendly for gingival displacement and homeostasis. Astringent gingival retraction paste, a recently introduced option, offers a quick and easy method for sulcus retraction without causing trauma or consuming excessive time. It is comparatively easier to apply and minimises harm and discomfort to the patient (4),(5).

Despite these advancements, previous studies have only compared the clinical efficacy of traditional retraction materials. To the author’s knowledge, no studies have compared traditional methods with astringent retraction paste. This present study aims to assess the effectiveness of mechanical retraction cord and astringent gingival retraction paste compared to a control group with no retraction. The null hypothesis considered in the present study was that no significant difference exists in gingival retraction among these three approaches.

Material and Methods

This cross-over clinical trial was conducted at Saveetha Dental College and Hospitals, Chennai, Tamil Nadu, India, from May 2024 to June 2024. The study was approved by the Institutional Human Ethical Committee (SRB-IHEC) (approval number: IHEC/SDC/PROSTHO-2104/24/044) and registered in the Clinical Trial Registry, India, with the registration number CTRI/2024/05/067533.

The study was designed as a cross-over clinical trial to minimise the impact of inter-subject variability, as comparisons were made within the same individuals. A comparative assessment encompassing both mechanical and chemical retraction, along with a control group, was executed.

Sample size calculation: The study enlisted 20 patients requiring single crowns, and the sample size was determined using G Power calculation (G*Power 3.0.10), with an alpha level set at 0.05 and a power of 95% (0.95).

Inclusion criteria: Those patients aged between 20 and 35 years who are systemically healthy and in need of single crowns (Table/Fig 1). Additionally, participants with gingival index scores of ≤1 (Loe and Silness) (6) and plaque index scores of ≤1 (Silness and Loe) (7), as well as those exhibiting no periodontal pockets and no bleeding on probing, were included in the study.

Exclusion criteria: The periodontally compromised teeth, individuals who are pregnant or lactating, those with a history of systemic diseases or other debilitating conditions such as diabetes mellitus, haemophilia, hypertension, HIV/AIDS, and individuals on steroids, anticoagulants, aspirin, or other medications. Patients with harmful oral habits and those unwilling to provide consent for the study were also excluded.

A meticulous case history and intraoral examination, accompanied by written informed consent, preceded the initiation of the study.

The study involved 20 patients as case groups who required single crown treatments while 20 healthy individuals as control group. All the included subjects were categorised into three groups:

Group I (Case group) (n=20): No gingival retraction (Control, at baseline)

Group II (Case group) (Day 7): n=10, Chemical retraction with astringent retraction paste+n=10, Mechanical retraction using a retraction cord

Group III (Case group) (Day 27): n=10, Chemical retraction with astringent retraction paste + n=10, Mechanical retraction using a retraction cord

Allocation of participants: This study focused on patients who needed single crowns following endodontic treatment. Maxillary first premolars and mandibular lateral incisors were selected as the standard teeth for this investigation. To minimise bias as much as possible, impressions without gingival retraction were taken for the control group of the 20 patients (Table/Fig 1). Subsequently, both retraction systems were randomly assessed on the prepared teeth of the same 20 participants.

Intervention: Tooth preparations for all specimens followed the principles of tooth preparation. Impressions for the control group were made without any gingival retraction (Group I, n=20) using a custom tray. Provisional milled polymethylmethacrylate crowns, fabricated using the virtual tooth preparation technique, were made and cemented with temporary cement (3M RelyX Temp, 3M ESPE, Maplewood, Minnesota, USA) after the impression. On the seventh day, impressions were taken after gingival displacement facilitated by a chemical retraction agent, Smart Retract astringent paste (Safe Endo Dental, India Pvt. Ltd.) (Group II), or a mechanical retraction agent (UltraPak, Ultra-dent, Australia) (Group III). The test groups were then switched 20 days after the first session.

Utilising addition silicone impression material (Zhermack SpA Elite HD+, Italy) for all groups, the impressions were made, and the casts were poured with type IV die stone (Zhermack Stone, Italy).

Gingival Retraction using Astringent Gingival Retraction Paste

The prepared teeth underwent rinsing, drying, and isolation to ensure a dry working area. A retraction paste was used for the retraction process. The tip of the retraction paste was positioned in the gingival sulcus, and the retraction agent was injected. The astringent retraction paste was allowed to remain in the sulcus for two minutes, during which the blanching of the gingiva indicated compression by the paste. Subsequently, the paste was removed. The gingival sulcus was then dried, and an impression was made using addition silicone impression material.

Gingival Retraction using Retraction Cord

Isolation was achieved to create a dry working area on the prepared tooth surfaces. The size of the cord was selected based on the subject’s gingival biotype, with single cord packing employed in this study. The cord was cut to the required length and soaked in a 25% aluminium chloride solution (Haemostal, PrevestDenPro, USA). The retraction cord was then packed into the sulcus, starting from the mesial and progressing to the distal direction by gently inserting the cord into the gingival sulcus. After 5 minutes, the cord was carefully removed, and the impression was taken using addition silicone impression material with the single-stage impression technique. Knitted cords were chosen for this study due to their interlocking loops, which facilitate passive shaping and bending during placement in the gingival sulcus. This structure also effectively prevents cord displacement when inserting the other segment into the sulcus (8).

Sample Preparation

All impressions were poured with Type IV die stone to obtain casts. The mesiodistal width of each prepared tooth was measured on the cast using a Vernier caliper (Digimatic caliper, Japan), and the centre point of the tooth was marked on both the labial and lingual sides of the cast. The gingival displacement was calculated as the distance from the tooth to the crest of the gingiva in a transverse plane.

Outcome Assessment

Stereomicroscopic examination: The samples were examined under a stereomicroscope (SM) at a magnification of 40x (Leica M205C, Leica Microsystems, Danaher, Wetzlar, Germany). Images were captured and transferred to Keyence digital imaging software, which provided values for the amount of displacement. The vertical and horizontal gingival displacement values for all specimens on both the buccal and lingual sides were recorded in micrometres (μm), and the average of these values were tabulated.

Visual Analog Scale (VAS) Analysis

The VAS (9) was used to evaluate patient comfort after impression making with different retraction techniques. Participants were instructed to mark a 10 cm-long line on a VAS labeled from “no pain” (0) to “intolerable pain” (10) on three different occasions: day 1, day 7, and day 27 post-impression making.

Statistical Analysis

Descriptive statistics were computed using Microsoft Excel (Microsoft Corporation, 1985) and were subsequently transferred for further statistical analysis. The Kolmogorov-Smirnov normality test was employed to assess the distribution of the data. Statistical analyses of gingival displacement and VAS scores were conducted using pairwise comparisons with Tukey post-hoc tests. Data analyses were performed using Statistical Package for Social Sciences (SPSS) software (Version 26.0; SPSS, Inc., Chicago, IL, USA). Statistical significance was set at a threshold of p<0.05.

Results

A total of 60 samples were tested, including a control group with no retraction, as well as groups with chemical retraction and mechanical retraction.

Gingival Displacement

The amount of gingival displacement achieved by both intervention groups exceeded that of the control group (164.8±15.725 μm). The mechanical retraction cord (698.53±43.276 μm) demonstrated the highest value for gingival displacement, followed by chemical gingival retraction (509.33±29.405 μm) (Table/Fig 2),(Table/Fig 3).

After analysing the data, the mean gingival displacement of the materials was ranked as follows:

Mechanical retraction > Chemical retraction > No retraction. Pairwise analysis is presented in (Table/Fig 4).

(Table/Fig 5),(Table/Fig 6),(Table/Fig 7) show tooth preparation and impressions with stereomicroscopic images for the no retraction group, chemical retraction group, and mechanical retraction group.

Visual Analogue Scores (VAS)

The VAS measurements were taken on day 1, day 7, and day 27, immediately after recording impressions. The control group showed mean scores of 0.9±0.052 (indicating no pain), whereas the mechanical and chemical retraction methods had mean scores of 2.60±0.057 (indicating mild pain) and 3.40±0.049 (indicating mild to moderate pain) (Table/Fig 8),(Table/Fig 9).

Statistically significant results were observed between the no retraction group and the mechanical retraction group, as well as between the no retraction group and the chemical retraction group (p<0.05). However, the differences between the mechanical and chemical retraction methods were not statistically significant (p>0.05) (Table/Fig 10).

Discussion

The current study aimed to assess the effectiveness of mechanical retraction cords and astringent gingival retraction paste. Both mechanical and chemical retraction methods exhibited higher values than the control group, with statistically significant differences. This indicates that both materials are capable of producing some degree of displacement. The mechanical gingival retraction method demonstrated the highest amount of gingival displacement, measuring 698.53 μm, followed by the chemical retraction group with 509.33 μm of displacement. Therefore, the null hypothesis is rejected.

Using a retraction cord involves a mechanical method of gingival retraction, resulting in both physical and chemical retraction of the tissue (10). The advantages of a gingival retraction cord include its adaptability and flexibility, allowing for freedom in preshaping. Additionally, it offers good colour contrast with the surrounding tissue. Knitted cords were chosen for this study because of their interlocking loops, which facilitate passive shaping and bending during placement within the gingival sulcus. This structure also effectively prevents the cord from being displaced when inserting the adjacent segment into the sulcus (8),(10).

Astringents have gained favour as adjuncts in gingival tissue retraction due to their minimal systemic side effects. They not only achieve haemostasis but also induce retraction of tissues by reducing the elasticity of collagen fibres surrounding the tooth, aiding in keeping the sulcus open after the retraction cord is removed (11),(12). Among astringents, ferric sulphate (15.5-20%) is commonly used as a coagulant during gingival displacement. However, prolonged application may result in the removal of the smear layer, potentially leading to post-procedure sensitivity. Additionally, the residue of ferric sulphate can interfere with impression setting, lead to dentin discoloration due to its high iron content, and hinder composite bonding if not adequately removed after the cord is taken out. Although alum and aluminium sulphate are considered safer astringents with limited systemic effects, they are minimally effective in controlling bleeding, thereby limiting their utility in retraction methods. Zinc chloride and silver nitrate induce haemostasis and protein precipitation, but the potential for soft tissue injury associated with zinc chloride restricts its recommendation.

The astringent retraction paste used in the study comprises 20-25% aluminium chloride, along with antiseptic and gel-foaming agents. This formulation facilitates easy and time-saving retraction while also reducing bleeding after removal (13). Astringents, such as the metal salts found in the retraction paste used in this study, induce gingival retraction by precipitating proteins and inhibiting the capillary movement of proteins (14),(15). They work by decreasing cell permeability and drying the tissues (16). The inclusion of 20-25% aluminium chloride in the retraction material is advantageous because it is the least irritating to gingival tissues, making it suitable for use in the study.

In this study, all measurements were conducted by the same operator to prevent inter-operator differences. The washout period between each session of gingival displacement was set at 20 days to allow any potential gingival inflammation resulting from the previous displacement system to subside (17). The astringent gingival retraction paste was found to be relatively clinician-friendly compared to other gingival retraction materials. Furthermore, a single-step technique was utilised for impression making to prevent potential discrepancies arising from the use of two materials, tray positioning, and the gap in the two-stage process that occurs after the removal of the retraction material before making the impression.

The findings of this study align with those of Chaudhari J et al., who compared cords impregnated with tetrahydrozoline, aluminium chloride, and Expasyl retraction paste. They observed that the cord impregnated with aluminium chloride resulted in the highest amount of retraction, while the Expasyl paste showed the least amount of retraction (18).

This study indicates that both retraction systems are reasonably effective, as they achieve retraction exceeding the minimum required amount (220 microns) for fixed partial denture impressions (3),(19). The astringent gingival retraction paste demonstrated a significant difference in retraction compared to the control. This could be attributed to the material’s thick consistency, which resulted in greater displacement of the gingiva, along with the fine tip facilitating easy placement into the gingival sulcus. Within the limited scope of this study, the use of the astringent chemical paste was found to be painless, quick, and easy, thereby saving chairside time (20). VAS scores for both groups ranged from 2 to 4, indicating mild to moderate pain, which falls within the acceptable range for the usage of these materials.

Limitation(s)

The results of this study should be confirmed with a larger clinical sample size and in various situations, including both the anterior and posterior regions of the jaws, in both maxillary and mandibular arches, and across different gingival biotypes (thick and thin) as well as various age groups and genders. Future studies should focus on evaluating patient comfort, gingival injury during material application, and recession following material application. Additionally, further studies should involve direct clinical evaluation instead of laboratory procedures to achieve more accurate results.

Conclusion

Both mechanical retraction cords and chemical gingival retraction pastes showed significant differences compared to the control group in terms of gingival displacement and patient comfort. While the mechanical method achieved maximum retraction, the chemical paste was superior in terms of patient comfort. These findings highlight the importance of considering both clinical efficacy and patient experience when selecting gingival retraction techniques. Within the limits of this study, it can be inferred that, although there was a statistically significant difference in the amount of displacement between the two systems, they were both within the clinically acceptable range (220 microns). Therefore, chemical retraction systems can be used as a substitute for mechanical retraction techniques. Further clinical investigations are warranted to validate these results across diverse clinical scenarios.

DOI and Others

DOI: 10.7860/JCDR/2024/73545.19807

Date of Submission: Jun 13, 2024
Date of Peer Review: Jul 02, 2024
Date of Acceptance: Jul 22, 2024
Date of Publishing: Aug 01, 2024

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

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ETYMOLOGY: Author Origin

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