The Frequency of Different Liners Usages in Upper and Lower Anterior Teeth at Dentistry Teaching Clinic Patients in Kabul, Afghanistan

Abstract

The use of liners to maintain the vitality and health of dental pulp is an effective method in operative dentistry, which involves placing a protective layer of liner on the exposed pulp to maintain the health of pulp and stimulate dentin cells to make reparative dentin. The use of liners for pulp vitality has been used for many years and is considered an essential part of restorative procedures in operative dentistry textbooks. Liners have traditionally been used to protect the pulp from the potentially toxic effects of different irritants. Liners are currently used for their therapeutic effects or for sealing dentinal tubules against the penetration of microorganisms or their by-products. Different types of materials have been introduced as liners to protect pulp tissue from irritants. Liner materials that have been used for many years include calcium hydroxide, glass-ionomer, and modified resin glass-ionomer. Therefore, this study, performed in the Dentistry Teaching Clinic of Kabul, Afghanistan, aims to present the most frequently clinically used liners in anterior teeth, to maintain pulp vitality.

1. Introduction

One of the main goals of operative dentistry is to protect the health of dental pulp, which can be provided by using liners. Liners are materials that have the healing ability and sealing properties of dentinal tubules, protect the pulp from chemical, mechanical, and thermal stimuli and stimulate the formation of reparative dentin. Liners are used as a specific thickness in preparing cavities on the pulp to maintain the pulp health. In the anterior teeth, the use of liners has particular importance to protect the dental pulp [1].

In this study, the different usage of liner in the anterior maxillary and mandibular teeth to preserve the pulp and prevent tooth extraction to evaluate the effectiveness of each liner in the future to obtain better clinical results.

The volume of the anterior teeth is smaller than the posterior teeth according to anatomical structure, and if there is caries or any defect that requires a dental filling, the size of the prepared cavity is small or with a preparing cavity, each cavity walls may near contact to the dental pulp or pulp horn. So, in such cases, the use of liners is mandatory and requires special technical care in the clinical procedure so that a certain size of the liner is placed in the cavity and the space prepared for permanent filling materials is not occupied by the liner to interfere with retention and resistance form of the cavity [1].

A study by Naji Ziad Arandi, in 2017, suggested that one of the goals of operative dentistry is, to maintain the health of the pulp in teeth with caries and defects. For the mentioned goal, liners are placed in a certain size in preparing cavities for maintaining the health of the pulp which is exposed or not exposed and stimulating the reparative dentin to make new dentin. The use of pulp preservative liners has been practiced in the field of dentistry for many years and is still considered an essential part of restorative procedures in operative dentistry textbooks [2].

Liners have previously been used to protect pulp tissue from the potentially toxic effects of different irritants. Currently, liners are used to treat and seal the dentinal tubules against the penetration of microorganisms or their toxic products into the teeth. Different liners introduced to protect pulp tissue from stimuli include Mineral Trioxide Aggregate (MTA), calcium hydroxide, Glass Ionomer (GI), Zinc Oxide Eugenol (ZOE), Modified Resin Glass-Ionomer (MRGI), and flowable composites [3].

Several liners have been proposed to protect the pulp. Interestingly, none of them has a significant advantage among doctors. In a survey of doctors, what kind of liners do they use, respondents mentioned four different substances, none of which are preferred by the majority of users [4].

Zinc oxide eugenol has been used in the dental sector for many years as a base, liner, cement, and temporary filling materials. Its use for direct pulp capping is questionable because the eugenol in its composition, is highly cytotoxic and shows ZOE interfacial leakage, but this leakage is not debatable because the eugenol released seals this leakage biologically and reduces bacteria [4].

A human clinical study using ZOE as a direct pulp capping agent showed in all teeth treated with ZOE as a liner, chronic pulp inflammation, without improving pulp tissue, and dentin bridge formation up to 12 weeks after the procedure was shown. Conversely, all control teeth lined with calcium hydroxide showed improvement within 4 weeks [4].

Glass Ionomer and Resin-Modified Glass Ionomer are not as cytotoxic as ZOE but become cytotoxic when in direct contact with cells. GI is less toxic than RMGI, but it is still not a good choice for pulp protection in deep cavities. GI binds chemically to the tooth structure to prevent the penetration of potentially toxic substances through the dentin into the pulp. Glass ionomer prevents bacteria to penetrate the pulp and has biocompatible properties but should not be in contact with pulp tissue. Direct pulp capping with RMGI showed chronic inflammation and no dentin bridge formation up to 300 days after the procedure, while calcium hydroxide control groups showed significantly better pulp healing [4].

Calcium hydroxide was introduced in the field of dentistry in 1921 and has been considered a direct pulp cap material for several decades as the “gold standard.” There are several benefits of calcium hydroxide known as the gold standard. Calcium hydroxide has excellent antibacterial properties, and a study showed a 100% reduction in microorganisms associated with pulp infection after 1 hour of exposure to calcium hydroxide. Most importantly, calcium hydroxide has a long history of clinical success as a direct pulp cap agent for up to 10 years. Calcium hydroxide also has some disadvantages. Its self-cure form is very soluble and dissolves over time. However, it has been noted that the formation of the dentin bridge occurs until calcium hydroxide is lost due to dissolution. Calcium hydroxide does not have adhesive properties and has poor sealing power. Another critique of calcium hydroxide is the term “tunnel defects” in reparative dentin, which forms under the pulp cap. The tunnel defect is described as a pathway from the pulp exposure and through reparative dentin to the pulp. Sometimes fibroblasts and capillaries are present inside the tunnel defect. Other researchers have found that the quality of reparative dentin improves with the thickening of the dentin bridge so that many cases of tunnel defects do not remain as a communication path to the pulp. Tunnel defect does not appear to be a common finding in human studies involving direct pulp capping with calcium hydroxide. There are fewer studies that indicate the existence of a tunnel defect and there are more studies that have not reported a tunnel defect [5, 6].

Calcium hydroxide is believed to have one or more mechanisms of action on the restorative effects of the pulp tissue. Calcium hydroxide has antibacterial properties and can minimize or eliminate bacterial infiltration into the pulp. It was previously believed that the high pH of calcium hydroxide stimulated pulp tissue, which in turn slowed down the healing process through some unknown mechanism. In recent years, this “unknown mechanism” has been explained by the release of bioactive molecules that combine different types of proteins with dentin matrix during dentinogenesis. At least two of these proteins, Bone Morphogenic Protein and Transforming Growth Factor-Beta One (TBF-β1), are important in the pulp cap process because they can stimulate pulp repair. Calcium hydroxide dissolves these proteins from dentin and, upon release of these bioactive molecules, acts as a significant mediator in pulp repair after pulp capping [6].

In recent years, MTA has been introduced as pulp cap material, which shows a significant interest of doctors in this new material. MTA consists of calcium oxide in the form of tricalcium silicate, dicalcium silicate, and tricalcium aluminate to which bismuth oxide has been added for radiopaque. MTA is compatible with tissues. Interestingly, the product of the initial reaction of MTA with water is calcium hydroxide, which the formation of calcium hydroxide provides the ability to be compatible with tissue in MTA. As a result, many of the potential benefits and mechanisms of action for MTA are similar to those of calcium hydroxide, including antibacterial properties, tissue compatibility properties, high pH, radiopaque, and the ability to release dentin bioactive proteins. There are differences between MTA and calcium hydroxide. First, MTA is available in two colors, white and gray, with a gray version due to the addition of iron. Another notable difference is that MTA provides the ability to seal tooth structures well. There are also several disadvantages of MTA, including its high solubility and 24% loss after 78 days of storage in water. The presence of iron in its gray form may indicate a darker tooth color. One of the significant disadvantages of MTA is its long-term hardening of about 2 hours and 45 minutes, which requires pulp capping with MTA in two stages, so placing a temporary filling on top of the MTA before placing a permanent filling or using a fast-hardening liner is essential to protect the MTA before permanent filling. The price of 1 gram of MTA powder is approximately 24 grams of calcium hydroxide, which can be considered one of its disadvantages [6].

In a review of animal pulp capping studies comparing MTA with calcium hydroxide, general improvement of pulp with MTA was generally reported. However, in most human studies, similar results have been shown with pulp capping as a result of the use of MTA and calcium hydroxide. Among the studies, only two showed superior performance of MTA over calcium hydroxide because MTA has a better ability to seal the exposed area of the pulp than calcium hydroxide. Studies show that MTA, as the only pulp-cap material without a control group, has shown success over periods of 6 months to 4 years [6].

Different theories are available when using liners. A study conducted by R. Weiner in 2011 at a dental school in North America did not agree on the use and timing of liners. In an amalgam-filled deep cavity, 46 percent of the 52 schools of dentistry supported the use of glass ionomer as a liner. This study considers cavities with 1 mm remaining dentin thickness as deep cavities. Similarly, recent surveys of liners in North American schools of medicine show no agreement on a standard pulp protection protocol. 38 percent of the 39 schools of dental medicine in the survey reported that calcium hydroxide liner was used for deep cavities filled with amalgam and 30.8% used glass ionomer. The study also reported that for deep composite fillings, the use of glass ionomer was 35.9%, followed by calcium hydroxide at 28.2% [5].

A study by Hilton and Thomas was conducted to examine methods to protect dental pulp among 500 dental students (stagers), young doctors, and doctors at various educational institutions in Pakistan and concluded that contemporary protocols for pulp conservation were not available. Donors respond to the institutions that participated in the survey. For example, approximately 89% of the respondents did not consider the remaining dentin thickness, while 82% of them considered the use of calcium hydroxide as a liner [7].

The objective of this study is, to find out how liners are used in the anterior teeth of the jaws to preserve pulp tissue in patients who have been referred to the dentistry teaching clinic due to dental caries in 2018.

2. Materials and methods

This study is done using the case series and retrospective data methods that were registered. As the patients’ registration book of 2018 was reviewed and related cases were recorded in the table prepared for data collection, which was later included in the excel sheet, and finally, the percentage and number of different liner usage, the percentage and number of anterior teeth, the number of liners used according to gender and age, and its figures were presented.

3. Results

This study was performed on 123 cases who were referred to the dentistry teaching clinic in 2018. The results of this study are as follows:

The percentage of liner usage in the age group of 16–30 years old is 73%, in the age group of 31–40 years old is 15%, in the age group of 41–50 years old is 8% and in the age group is 51–65 years is 4%, respectively (Figure 1).

Figure 1.

Shows the percentage of liner usage in the different age groups.

This study shows the percentage of liner users is 59.3% for women and 40.7% for men (Figure 2).

Figure 2.

Shows the use of liners percentage in anterior teeth of upper and lower teeth according to sex.

In this study, calcium hydroxide was used in 44.71% of cases, glass ionomer was used in 21.13% of cases, zinc oxide eugenol was used in 16.26% of cases, and a flowable composite was used in 11.38% of cases and MTA was used in 6.5% of cases (Figure 3).

Figure 3.

Shows how to use liners in terms of percentage.

The percentage of liner use in the maxillary anterior teeth is 67.12% and in the mandibular anterior teeth is 32.87% (Figure 4).

Figure 4.

Shows the percentage of liner use in the anterior of upper and lower teeth.

4. Discussion

In this study, the different usage of liners in the anterior teeth of the jaws in the dentistry teaching clinic was evaluated. In this study, liners such as Calcium Hydroxide, Glass Ionomer, Zinc Oxide Eugenol, Flowable Composite, and MTA were used in patients who received caries treatment. In this study, the use of liners was evaluated according to the anterior teeth of the upper and lower jaw, sex, and age. Therefore, here it is necessary to compare research findings with the literature. In this study, among the 123 cases that were referred to the dentistry teaching clinic in 2018, in 55 (44.71%) cases, calcium hydroxide was used as a liner, in 26 (21.13%) cases, glass ionomer was used, in 20 (16.26%) cases, zinc oxide eugenol was used, in 14 (11.38%) cases, the flowable composite was used, and in 8 (6.5%) cases, MTA was used as a liner.

The results of pulp cap studies using MTA are encouraging. The following example may help to illustrate this point: “According to the results of the present study and other related studies, MTA is superior to calcium hydroxide for pulp capping of mechanically exposed teeth.” In one study, the pulps of 14 teeth were intentionally exposed, half of which were capped with calcium hydroxide and the other half with MTA. The teeth were extracted after one, two, three, four weeks, and six months and evaluated histologically. During the final evaluation period (six months), only one tooth in each group was evaluated. Based on these results, it appeared that MTA was superior to calcium hydroxide [8].

MTA is promising material, but calcium hydroxide indicates a long history of clinical success that MTA cannot currently claim. A review of 14 clinical studies, including more than 2300 cases of calcium hydroxide pulp caps, reported a success rate of up to 90% by experienced physicians. In addition, calcium hydroxide is successful even when done under less-than-ideal clinical conditions. To better elucidate the relative advantages of MTA over calcium hydroxide, prospective clinical trials comparing MTA with calcium hydroxide are required for pulp cap. Research networks based on such a study are engaged [8].

In a human clinical trial, a pulp cap was performed using ZOE. In this study, all pulp capping teeth with ZOE showed chronic inflammation, without pulp healing and dentin bridge formation, up to 12 weeks after the procedure. Conversely, all calcium hydroxide-controlled teeth showed improvement within 4 weeks [8].

Similar to ZOE, a human study of direct pulp cap with glass ionomer showed chronic inflammation and no dentin bridge formation up to 300 days after pulp capping, while calcium hydroxide control groups showed significantly better pulp recovery [8].

In a study conducted by Andreea C Didilescu and colleagues in October 2018 according to Meta-Analysis, they compared the use of MTA and calcium hydroxide in the formation of hard tissue as a barrier (dentin bridge) and suggest that the positive effects of MTA on calcium Hydroxide is better to form hard tissue, and evidence suggests that MTA is more effective than calcium hydroxide in protecting the pulp if the pulp is mechanically exposed [8].

One study showed that the resin composite, as a pulp cap material, showed less pulp healing, chronic inflammation even in the absence of bacteria, and a reduced repair capacity for pulpitis due to dental caries [7].

A study was conducted about pulp capping carious exposures in adults, a randomized controlled trial investigating mineral trioxide aggregate versus calcium hydroxide. The Kaplan–Meier survival analysis showed a cumulative estimate rate of 85% for the MTA group and 52% for the calcium hydroxide group (P = 0.006). There was no significant association between the pulp capping material and postoperative pain. Mineral trioxide aggregate performed more effectively than a conventional calcium hydroxide liner as a direct pulp capping material with carious pulpal exposure in adult patients [9].

Mehmet Kemal and Calskan 2017 evaluated MTA pulp capped teeth and demonstrated a slightly higher success rate than calcium hydroxide, it can be recommended as a reliable direct pulp capping material. Direct pulp capping with MTA is a straightforward procedure with a favorable outcome of 24- to 72-month follow-ups in vital mature asymptomatic permanent teeth with carious exposed pulp [10].

A study was conducted about the treatment outcome of mineral trioxide aggregate or calcium hydroxide direct pulp capping for long-term results. The results of this study indicate that MTA provides better long-term results after direct pulp capping compared with calcium hydroxide placing a permanent restoration immediately after direct pulp capping is recommended (odds ratio = 3.18; 95% CI, 1.61–6.3; P = .004) [11].

A systematic review and meta-analysis result showed the effect of mineral trioxide aggregate and calcium hydroxide for direct pulp capping is different, as measured by the clinical and radiographic analysis. A statistically significant difference was found between the success rates of MTA and calcium hydroxide-treated teeth that needed direct pulp capping (P = 0.002). Clinical assessments of the MTA versus calcium hydroxide for direct pulp capping suggested that MTA was superior to calcium hydroxide in direct pulp capping resulting in a lower failure rate (risk difference 0.1 [95% CI 0.04 to 0.16]). MTA has a higher clinical success rate for direct pulp capping compared to calcium hydroxide and might be a suitable replacement for calcium hydroxide [12].

A study was conducted by Uzay Koc Vural et al. to compare the clinical performance of cavities with no lining and lining with resin-modified glass ionomer for the treatment of root surface carious lesions. The clinical performance of both unlined and RMGI-lined cavities at the 5-year post-restoration assessment was acceptable and there was no significant difference in the clinical performance of the lined and unlined restorations (P < 0.05) [13].

S Cushley et al. studied in 2021 the efficacy of direct pulp capping for the management of cariously exposed pulps in permanent teeth. The results were based on poor methodological quality studies. The effect size for MTA vs. calcium hydroxide, low-quality evidence suggests a high success rate for direct pulp capping in teeth with cariously exposed pulps with better long-term outcomes for MTA and Biodentine compared with calcium hydroxide [14].

A study was conducted about outcomes of direct pulp capping by using either ProRoot mineral trioxide aggregate or Biodentine in permanent teeth with carious pulp exposure in 6 to 18-year-old patients. The result shows that Biodentine was non-inferior to ProRoot MTA when used as a direct pulp cap material for cariously exposed permanent teeth of 6 to 18-year-old patients. However, Biodentine did not cause any gray discoloration in this study [15].

A study was conducted to assess the effectiveness of different direct pulp-capping (DPC) materials for human pulp-exposed teeth. An electronic search was performed on 20 February 2018. Long-term clinical and radiographic evaluations of the effectiveness of different DPC materials for use on human pulp-exposed teeth were included. Of the 496 identified articles, 15 met the eligibility criteria. Among the studies included in those articles, a total of 1322 teeth were treated with 12 types of DPC materials, and 1136 teeth were evaluated at a final follow-up examination. For mineral trioxide aggregate (MTA) and calcium hydroxide, the number of included studies, the number of treated teeth, and the mean follow-up period of studies were almost equal, and the success rates of MTA were superior to calcium hydroxide. Therefore, MTA is likely to be a more effective and predictable material for DPC compared to calcium hydroxide [16].

A randomized clinical trial about direct pulp capping with calcium hydroxide, MTA, and Biodentine in permanent young teeth with caries had done. At the follow-up examination at 1 week, the patients showed 100% clinical success. At 3 months, there was 1 failure in the calcium hydroxide group. At 6 months, there were 4 new failures (1 in the calcium hydroxide group and 3 in the MTA group). At 1 year, there was another failure in the calcium hydroxide group. There were no statistically significant differences among the experimental groups. Although no significant differences were found among the materials studied, Biodentine and MTA offered some advantages over calcium hydroxide [17].

Current philosophies and indications for use of cavity sealers, liners, and bases showed that traditional dental education has recommended the generous use of bases and liners under restorations, primarily to prevent postoperative sensitivity. However, new developments in bases and liners, as well as a better understanding of pulp biology, have changed the indications for the use of these materials. Understanding the properties of currently available materials and how they interact with pulpal tissues can help the practitioner decide when to use bases and liners and which products to choose [7].

However, the evaluation conducted in this study shows that the use of MTA liner in comparison to the literature review, in comparison to other liners and its clinical benefits, has been 6.5% (8 cases) in a year, which is very low, and few cases and it is due to the price of MTA that dentistry teaching clinic in Afghanistan as a governmental health sector cannot provide MTA for all cases that need MTA.

5. Conclusion

In this study, calcium hydroxide was used in more cases and MTA was used in fewer cases and it is due to MTA price. The liner usage in the younger age group is more than older age group. This study shows the usage of liners is higher in women than men. The modality liners usage in the maxillary anterior teeth is higher than in the mandibular anterior teeth.