Biomimetic mineralization: Long-term observations in patients with dentin sensitivity

Abstract

Objective

Cervical tooth erosion is increasingly observed among adults and frequently associated with dentin sensitivity (DS). This study evaluated the effectiveness on DS of a biomimetic mineralization system (BIMIN) in comparison to the current standard treatment (Gluma ® Desensitizer, Gluma).

Methods

In this single-blind, 2-arm study, 40 patients with confirmed cervical DS were randomized to either the test group or the positive control group. A Visual-Analog-Scale (VAS) was used to assess DS following stimulation of the exposed dentin with a 2-s air blast. Assessments were made at baseline (pre-treatment), 2 days, 4, 8 and 12 weeks, and 12 months after treatment. Two-stage replicas were obtained from the treated teeth and gold sputtered at baseline, and 2 days, 3 and 12 months after treatment. Surface topography of the treated cervical lesions and occlusion of dentinal tubules were investigated using scanning electron microscopy (SEM).

Results

Both treatments led to a statistically significant reduction ( P < 0.0001) in DS that persisted over the entire 12-month observation period. Differences in DS between the treatments were not statistically significant. SEM photomicrographs demonstrated that a mineral layer concealed the dentinal tubules in the test group. In contrast, numerous dentinal tubules remained visible in cervical defects that were treated with Gluma.

Significance

A biomimetic mineralization kit was successfully used to treat patients exhibiting DS. The effect was similar to using Gluma, and was likely the result of the deposition of an enamel-like layer on the exposed cervical dentin.

Introduction

Dentin sensitivity (DS) is observed frequently. Its prevalence has been reported to be between 4% and 69% among adults . DS has been associated with exposed dentin . Chronic trauma from tooth-brushing, acid erosion ( e.g. , as a result of environmental exposure, gastric regurgitation, or dietary substances), anatomical factors, and gingival recession caused by periodontitis and periodontal surgery have all been identified as etiological factors .

Several theories have been postulated to explain pain associated with DS . The widely accepted hydrodynamic theory of hypersensitivity describes the pathophysiological mechanisms and assumes that a stimulus applied to the dentin surface causes movement of tubular fluid; this leads to the activation of mechanoreceptors, eliciting pain and discomfort . The provoking stimulus can be tactile, osmotic, evaporative, thermal or chemical in nature . There are two main approaches to the treatment of DS, (i) tubule occlusion and (ii) blocking nerve activity via direct ionic diffusion through increased potassium ion concentration, thus reducing pulpal sensory nerve activity . There are many methods and products available for DS management. These products may be in the form of topically applied agents such as resins, varnishes, primers, dentin bonding agents, composite restorations as well as periodontal grafting techniques or laser application .

Tooth surface loss may be due to erosion , abrasion, or attrition . Exposure of tubules by erosion is probably the most frequent reason for DS . The deposition of enamel-like materials that substitute for lost tooth structure is therefore an important research area . Restorative materials that exhibit even greater biomimetic design features than current resin-composites could play a valuable role in this regard . Existing resin-composite restorative materials, are essentially inert space fillings for lost tooth structure. Currently available dental materials can be used to repair or replace lost or diseased tissue but they do not regenerate it. Furthermore, resin-composite materials and their associated dentin bonding agents are formulated with reactive chemical species. If the materials are optimally polymerized on placement then they are widely considered to be sufficiently safe, in accordance with the European Medical Device Directive and ISO Standards . However, recent research has drawn attention to the potential adverse consequences of inadequate cure of such materials . Therefore, if such potential hazards could be avoided in future formulations, that would be beneficial.

A recently introduced technique of guided formation of an enamel-like fluorapatite layer on a mineral substrate has the potential to enable remineralization of superficial enamel defects and/or exposed dentin. The technique, BIMIN, utilizes the diffusion of calcium ions from solution into a glycerine-enriched gelatine gel that contains phosphate and fluoride ions . When the conditioned gel is in direct contact with the exposed tooth surface, within 8 h, a firmly adhering mineral layer is formed on the tooth surface . Applying BIMIN in a clinical feasibility study, a deposition of fluorapatite mineral on dental enamel was recently demonstrated .

The aim of this study was to evaluate BIMIN in patients with moderate to severe DS. In a randomized controlled study, SEM analysis of the affected tooth surfaces, and the subjects’ perceptions of DS induced by a physical stimulus were used to compare BIMIN and Gluma.

Materials and methods

Subjects and study design

The “Guidelines for the design and conduct of clinical trials on dentin hypersensitivity” were followed in the planning and execution of the study . An examiner-blind, two-arm, randomized, controlled, 12-month study was conducted in 40 patients with DS. The differences in application protocols of the treatments did not permit blinding the patients. The study population was recruited from patients of the Department of Conservative Dentistry, Jena University Hospital, Germany. Inclusion criteria were presence of at least one sensitive tooth that resulted in a VAS score (details below) >50 mm, and exposed dentin in the cervical region (with or without wedge edge defects). Exclusion criteria were age <18 years, known allergies to materials used in the study, systemic diseases, pulpitis, and moderate or more severe gingival inflammation. Pregnant or lactating women were excluded from participation, too. In total, 48 subjects were recruited to the study. Forty subjects met all requirements, were enrolled, and completed the study.

The patients were randomized in blocks of 6 using a predetermined randomization table with balanced mean VAS score to either the test group (BIMIN, Heraeus Kulzer GmbH, Hanau, Germany) or the control group (Gluma ® Desensitizer, Heraeus Kulzer GmbH, Hanau, Germany). A total of 111 teeth (test group n = 58; control group n = 53) were treated. All treated teeth were free of cavities and dental fillings at the smooth surface sites.

Ethical approval was obtained from the ethics committee of the University of Jena (2391-10/08). Written informed consent was obtained from each subject prior to enrolment. The study was conducted in accordance with the principles of the Declaration of Helsinki (World Medical Association Declaration of Helsinki 2008).

Clinical protocol

The clinical protocol commenced with a dental prophylaxis. To remove the smear layer (non-collagenous proteins) from the exposed dentin, 24% EDTA solution (Pref Gel, Straumann, Freiburg, Germany) was applied to the surface for 2 min. The teeth were then washed with copious amounts of water and gently dried. Impressions were obtained for SEM analysis. After this procedure, the test group and the control group received the BIMIN treatment and Gluma treatment, respectively.

Treatment procedures

Test group

BIMIN consisted of (i) an alkaline pretreatment solution (pH 9) containing calcium ions, (ii) a gelatine gel film containing phosphate and fluoride ions, and (iii) a gelatine gel film containing calcium ions . The pretreatment solution increased the attractiveness of the tooth surface for mineralization, leading to greater thickness of the mineralized layer . Following pretreatment for 20 s, the gel-films were placed onto the tooth surface using a sandwich technique. As gelatine films would dissolve quickly in the mouth, individualized splints were constructed to protect them. The calcium-gelatine film was transferred into the splint first, before it was covered with the phosphate/fluoride-containing gel, ensuring the gel layers were in proper sequence. Immediately after the gels were combined, the splint was positioned into the mouth. To prevent saliva flowing under the splint and dissolving the gels, the splint was sealed against the teeth (VOCO pac, VOCO, Cuxhaven, Germany). Patients were advised not to eat or drink anything other than water and instructed to wear the splint overnight for a minimum of 8 h. The splint was removed the next morning. The application procedure was defined as successful when the gel was still visible inside the splint.

Control group

Gluma, a HEMA and glutaraldehyde containing primer, was applied according to the manufacturer’s instructions. After impressions for SEM analysis were taken, the teeth to be treated were isolated with rubber dam and air-dried. Next, Gluma was applied to the sensitive area (cervical region) and left for 30 s. Then, the treated teeth were dried for 5 s using an air spray followed by rinsing with a water spray for 5 s.

SEM-analysis

A replica technique was performed for evaluation of the cervical dentin using a modification of the method described by Absi et al. . The teeth were cleaned and pre-treated with EDTA. Polyvinyl siloxane impressions (President, Colténe/Whaledent, Altstätten, Switzerland) were obtained to investigate the characteristics of the tooth surface and exposed dentin. Additional impressions were obtained at 2 days, 3 and 12 months after treatment. The impressions were replicated with an epoxy resin (Glycidether 100, Serva, Heidelberg, Germany). The replicas were gold-sputtered and investigated with a scanning electron microscope (Philips SEM 515, Philips, Eindhoven, NL) ( Fig. 1 ). SEM-images obtained post-treatment were compared with those obtained before treatment.

Fig. 1
Workflow from clinical situation to SEM photomicrograph. The tooth surface (A) was cleaned and the smear layer removed using 24% EDTA. Next, an impression was obtained, and replicated with an epoxy resin. Gold-sputtered replicas (B) were then investigated with SEM (C).

Sensitivity assessment

DS was provoked using an air stimulation test and recorded on a Visual Analog Scale (VAS). A gentle 2-s air stream was directed perpendicularly to the test surface using a dental air syringe held at a distance of 1 cm. The air temperature and pressure were between 19 and 24 °C and 40 p.s.i., respectively. Immediately following each stimulus, patients were asked to place a vertical mark on a 100 mm line to indicate the intensity of the sensitivity or discomfort caused by the stimulus. The anchors of the VAS were labeled “no pain at all” (0 mm) and “unbearable pain” (100 mm). All measurements were made from the left anchor point to a precision of 1 mm. Sensitivity of the treated teeth was assessed before treatment (baseline), and 2 days, 4, 8 and 12 weeks, and 12 months after the single product application.

Statistical analysis

Comparative demographic information on the study population was analyzed using 2-sided t -tests for independent groups for continuous variables and Fisher’s Exact Test if the variables were categorical. VAS value (in mm) was the primary outcome variable of the study. For all examination time points, the patient VAS mean was calculated based on teeth that had a VAS > 50 mm at screening. The patient was the experimental unit for all statistical analyses.

Normality of data was tested before parametric tests were used. The statistical significance of the VAS difference between treatment groups overall and the VAS change over the 12-month study period were analyzed using a repeated measure ANOVA. Statistical significance was accepted at P ≤ 0.05. The statistical software package PASW 18.0 (SPSS, Chicago, IL, USA) was used for data analyses.

Materials and methods

Subjects and study design

The “Guidelines for the design and conduct of clinical trials on dentin hypersensitivity” were followed in the planning and execution of the study . An examiner-blind, two-arm, randomized, controlled, 12-month study was conducted in 40 patients with DS. The differences in application protocols of the treatments did not permit blinding the patients. The study population was recruited from patients of the Department of Conservative Dentistry, Jena University Hospital, Germany. Inclusion criteria were presence of at least one sensitive tooth that resulted in a VAS score (details below) >50 mm, and exposed dentin in the cervical region (with or without wedge edge defects). Exclusion criteria were age <18 years, known allergies to materials used in the study, systemic diseases, pulpitis, and moderate or more severe gingival inflammation. Pregnant or lactating women were excluded from participation, too. In total, 48 subjects were recruited to the study. Forty subjects met all requirements, were enrolled, and completed the study.

The patients were randomized in blocks of 6 using a predetermined randomization table with balanced mean VAS score to either the test group (BIMIN, Heraeus Kulzer GmbH, Hanau, Germany) or the control group (Gluma ® Desensitizer, Heraeus Kulzer GmbH, Hanau, Germany). A total of 111 teeth (test group n = 58; control group n = 53) were treated. All treated teeth were free of cavities and dental fillings at the smooth surface sites.

Ethical approval was obtained from the ethics committee of the University of Jena (2391-10/08). Written informed consent was obtained from each subject prior to enrolment. The study was conducted in accordance with the principles of the Declaration of Helsinki (World Medical Association Declaration of Helsinki 2008).

Clinical protocol

The clinical protocol commenced with a dental prophylaxis. To remove the smear layer (non-collagenous proteins) from the exposed dentin, 24% EDTA solution (Pref Gel, Straumann, Freiburg, Germany) was applied to the surface for 2 min. The teeth were then washed with copious amounts of water and gently dried. Impressions were obtained for SEM analysis. After this procedure, the test group and the control group received the BIMIN treatment and Gluma treatment, respectively.

Treatment procedures

Test group

BIMIN consisted of (i) an alkaline pretreatment solution (pH 9) containing calcium ions, (ii) a gelatine gel film containing phosphate and fluoride ions, and (iii) a gelatine gel film containing calcium ions . The pretreatment solution increased the attractiveness of the tooth surface for mineralization, leading to greater thickness of the mineralized layer . Following pretreatment for 20 s, the gel-films were placed onto the tooth surface using a sandwich technique. As gelatine films would dissolve quickly in the mouth, individualized splints were constructed to protect them. The calcium-gelatine film was transferred into the splint first, before it was covered with the phosphate/fluoride-containing gel, ensuring the gel layers were in proper sequence. Immediately after the gels were combined, the splint was positioned into the mouth. To prevent saliva flowing under the splint and dissolving the gels, the splint was sealed against the teeth (VOCO pac, VOCO, Cuxhaven, Germany). Patients were advised not to eat or drink anything other than water and instructed to wear the splint overnight for a minimum of 8 h. The splint was removed the next morning. The application procedure was defined as successful when the gel was still visible inside the splint.

Control group

Gluma, a HEMA and glutaraldehyde containing primer, was applied according to the manufacturer’s instructions. After impressions for SEM analysis were taken, the teeth to be treated were isolated with rubber dam and air-dried. Next, Gluma was applied to the sensitive area (cervical region) and left for 30 s. Then, the treated teeth were dried for 5 s using an air spray followed by rinsing with a water spray for 5 s.

SEM-analysis

A replica technique was performed for evaluation of the cervical dentin using a modification of the method described by Absi et al. . The teeth were cleaned and pre-treated with EDTA. Polyvinyl siloxane impressions (President, Colténe/Whaledent, Altstätten, Switzerland) were obtained to investigate the characteristics of the tooth surface and exposed dentin. Additional impressions were obtained at 2 days, 3 and 12 months after treatment. The impressions were replicated with an epoxy resin (Glycidether 100, Serva, Heidelberg, Germany). The replicas were gold-sputtered and investigated with a scanning electron microscope (Philips SEM 515, Philips, Eindhoven, NL) ( Fig. 1 ). SEM-images obtained post-treatment were compared with those obtained before treatment.

Nov 28, 2017 | Posted by in Dental Materials | Comments Off on Biomimetic mineralization: Long-term observations in patients with dentin sensitivity
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