Histological Evaluation of Hard Tissue Formation After Direct Pulp Capping With RetroMTA
Condition: Dental Pulp Exposure
MeSH terms: Dental Pulp Exposure
Study type: Interventional

Summary: 
      This study presents a clinical and histological evaluation of human pulp tissue responses
      after direct capping using RetroMTA. Seven teeth were subjected to pulp exposure, direct
      capping with RetroMTA, and restoration with a composite resin. Seven months later, the teeth
      were clinically and radiographically evaluated. The teeth were then extracted and subjected
      to histological processing and evaluation.
    

Detailed description: 
      The study was conducted in accordance with the tenets of the World Medical Association
      Declaration of Helsinki. Seven caries-free, intact, maxillary, and mandibular third molars
      from humans, aged 30-37 years, which were scheduled for extraction for orthodontic or
      surgical purposes, were included in the study. The patients received a thorough explanation
      of the experimental rationale, clinical procedures, and possible complications. All
      experimental protocols were independently reviewed and approved by the Local Ethics Committee
      of Pomeranian Medical University, Szczecin, Poland (approval number KB-0012/27/13).

      Clinical protocol. For all included teeth, periapical radiographs were taken to exclude the
      presence of caries or periapical pathology. Tooth sensitivity was assessed by thermal testing
      (Kältespray; M&W Dental, Büdingen, Germany) and electric sensitivity testing (Vitality
      Scanner Pulp Vitality Tester; SybronEndo, Orange, CA, USA). These teeth were subjected to
      pulp exposure, direct capping with RetroMTA, and restoration with a composite resin. Seven
      months later, the teeth were clinically and radiographically evaluated. Clinical assessment
      was performed at 1 week and at 7 months after the procedure. During clinical interviews, the
      patients were asked about the presence of pain, and its type and duration. Reactions to
      thermal stimuli were classified into three categories: 1 = normal response (pain lasting up
      to 10 s); 2 = an extended response (pain > 10 s); 3 = no response. An electrical test was
      performed using a Vitality Scanner, and was repeated three times. Seven months after the
      procedure the teeth were extracted and subjected to histological processing and evaluation.

      Histological processing. Immediately after extraction, the teeth were immersed in a 10%
      neutral buffered formalin solution, and gently washed from blood and saliva. After brief
      prefixation (≤10 minutes), special precautions were taken to facilitate pulp tissue fixation.
      The roots were separated 5 mm apically to the cemento-enamel junction, using a diamond disk
      under copious water cooling. Then the teeth were grinded with a high speed cylindrical
      diamond bur under water spray in a mesio-distal or bucco-lingual plane until exposing one or
      more pulp horns. Photographs and radiographs were taken of each sample before successive
      steps. For demineralization, the specimens were immersed for 3 to 4 weeks in an aqueous
      solution consisting of a mixture of 22.5% (v/v) formic acid and 10% (w/v) sodium citrate,
      with radiographic determination of the end-point. Then all specimens were washed in running
      tap water for 24 hours, dehydrated using ascending grades of ethanol, cleared in xylene,
      infiltrated, and embedded in paraffin (melting point of 56 °C) following standard procedures.
      The paraffin blocks were trimmed. With the microtome set at 5 μM, serial sections were taken
      until exhausting the entire pulp tissue in the chamber. Six to eight sections were collected
      on each slide. Every fifth slide was stained with haematoxylin and eosin for screening and
      evaluation of mineralized tissue formation. These stained sections were used to locate the
      areas exhibiting the most severe inflammatory reactions, and those with less favourable
      bridging. Based on this initial evaluation, all slides adjacent to the location with the less
      favourable conditions were stained. In addition, the selected slides were subjected to a
      modified Brown and Brenn technique (Taylor 1966) for staining bacteria. Next, cover slips
      were placed on the slides, and the sections were examined using a light microscope. For each
      pulp, the worst histologic condition observed was recorded. If bacteria were observed on the
      cavity walls or in the area of exposure, the case was excluded from evaluation.

      Two intact teeth (one maxillary and one mandibular third molar) extracted for pericoronitis
      were used as control. To test the reliability of the bacterial stain, two teeth with deep
      caries were examined, extracted because deemed non-restorable. These teeth were processed
      using the same protocol as the experimental group.

      Slides were observed under a light microscope (Leica DMLB; Leica Microsystems, Wetzlar,
      Germany) and digital photographs were taken (Leica DFC420; Leica Microsystems, Wetzlar,
      Germany). Following aspects were observed with particular care: 1) Presence and type of
      mineralized tissues formed in the area of the surgical exposure; 2) Morphology of cells
      layering this mineralized tissue; 3) Presence and degree of inflammatory reactions in the
      pulpal area subjacent to the newly formed tissue; and 4) Presence of stainable bacteria in
      the experimental cavity or the area of pulp exposure.
    

Intervention name(s): direct pulp capping with RetroMTA
Intervention type(s): Procedure
Intervention description(s): The study included seven caries-free third molars from three adults. These teeth were subjected to pulp exposure, direct capping with RetroMTA, and restoration with a composite resin. Seven months later, the teeth were clinically and radiographically evaluated. The teeth were then extracted and subjected to histological processing and evaluation.
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: direct pulp capping, RetroMTA, histological evaluation