Vital pulp therapy & Regeneration Flashcards
What is the success rate of direct pulp capping?
Bogen et al (JADA - 2008) showed a 98% success when MTA was used as a direct pulp capping material over a period of 9 years in 53 teeth.
Hilton et al (JDR - 2013) showed a success of 81% with MTA vs 68.5% with Ca(OH)2
Mente et al (JOE-2014) showed as success of 81% with MTA vs 59% with Ca(OH)2
What are the factors affecting the success rate of direct pulp capping procedure?
- Material: Mente et al (JOE - 2014) found that MTA was superior to Ca(OH)₂ (MTA 80% vs Ca(OH)₂: 60%) as a pulp capping material. Probably that applies to other calcium silicate materials as well. Similar results were showed by Hilton et al (JDR - 2013) and Cho et al (JOE - 2013)
- Hemorrhage control: Matsuo et al (JOE- 1996) found that ability to control bleeding was a determining factor for the success of direct pulp capping.
- Exposure site: Cho et al (JOE -2013) found that the exposure site being occlusal exposure site has a better success rate that axial exposure sites. They also showed that pulp capping was more successful in younger patients.
- Patients’ age: Younger patient has a higher success rate (Cho et al, JOE -2013)
- Time of placing the final restoration: (<2days) (Hilton et al, JDR - 2013)
Explain the pulp reaction to Ca(OH)2 or MTA as a direct pulp capping material?
Upon contact, Ca(OH)2 or MTA will cause liquefaction necrosis of the superficial layer of the pulp which will be neutralized in deeper layers resulting in coagulative necrosis. This will result in slight irritation of the adjacent pulp tissue and stimulation of vascular and inflammatory cell migration and proliferation (to control and eliminate the irritant). This will lead to migration and proliferation of undifferentiated mesenchymal stem cells to differentiation to odontoblast-like cells causing hard tissue formation (Schroder, J Dent Res - 1985)
Explain why a successful regenerative procedure with initial evidence of root maturation and resolution of periapical pathology may fail on the long run?
Reinfection (coronal leakage)
Trauma
Remaining bacteria inside the root canal space.
Over time, the number of bacteria inside the root canal space may increase resulting in activation of the immune system. This can lead to recruitment of inflammatory meditators and impairment of attachment, proliferation and differentiation of stem cells. This can result no further hard tissue deposition and bone resorption.
Liu et al (IEJ -2016) has shown that TNF alpha and IL-1B can Inhibited mineralization and osteogenic-/ dentinogenic-related gene expression
What are the current challenges of pulp revitalization/revascularization techniques used today?
1- No of stem/progenitor cells that we can attract to the root canal space
2- Migration competition between the different types of cells (SCAP, PDLSC, MSC, etc)
3- It’s difficult to clinical identify the presence of viable apical papilla
4- Generated tissues in the canal is not pulp/dentin-like but more bone-like or cementum like
5- Microbial control (achieving a sterile environment) to ensure success and sustainability of the treatment
What are the current limitations of outcome studies in regenerative endodontics?
1- Studies generally have small patient sample size
2- Criteria used to define success are inconsistent.
3- Studies generally have a short follow up time and the sustainability of the outcome may not be guaranteed
4- There is generally a focus on radiographic healing (goal 1) as the primary outcome measure in most of the outcome studies and minimal attention to increase in root thickness/ length (goal 2) and vitality testing (goal 3). Goal 2 and 3 are the main reason why a clinician attempt this procedure in the first place.
List the available sources for stem cell sources that can clinically aid in pulp revascularization/ revitalization?
- Dental pulp stem cells (DPSC) from remaining pulp tissue inside the root canal space
- Stem cells of the apical papilla (SCAP) if they are still surviving in the apical tissue
- Periodontal stem cells and mesenchymal stem cells (PDLSC, MSC) from the periapical tissue following stimulating apical bleeding
- (MSC) from the blood stream
Which of the following treatments have a higher success rate in managing necrotic teeth with open apex: regenerative endodontic procedures or apexification?
The existing literature lacks high quality studies with a direct comparison of outcomes of regenerative endodontic treatment and apexification as shown in a recent systematic review by Torabinejad et al (JOE - 2017).
Regen and apexification appear to achieve a comparable outcome in regard to the resolution of symptoms and apical healing (Alobaid et al, JOE 2014; Kahler et al, JOE 2017, Lin et al, JOE 2017). There can a potential benefit of renegerative endodontic treatment to further increase root length/width (Lin et al, JOE 2017). The procedure, however, has been associated with greater incidence of adverse events (pain, swelling, intervention etc.) was observed in the revascularization procedure (Alobaid et al, JOE 2014)
Why is MTA more superior to Ca(OH)2 as a pulp capping material?
MTA is non-absorbable and structurally stable compared with Ca(OH)2 products (Al Hezaimi et al, JOE - 2011)
Min et al (JOE - 2008) showed that the hard tissue barrier formed with MTA is thicker and occurred in 100% of the cases compared to Ca(OH)2 (60%). This increase the ability to resist the penetration of microorganism and improves the ability to maintain the integrity of the pulp tissue.
Less inflammation and less tunnel defects in the hard tissue barrier with MTA (Nair et al, IEJ- 2009)
The success rate of MTA was constant over the follow-up period whereas the Ca(OH)2 tended to show failures at 2-3 years (Mente et al, JOE - 2014).
What is the difference between “Cell homing” approach and “Cell Based” approach in pulp regeneration?
Cell homing: attracting stem cells in the body to the site of interest (root canal space)
Cell based: growing stem cells in-vitro and placing them directly into the root canal space.
What is the difference between reparative dentin and reactionary dentin?
Reparative dentin: the original odontoblasts are destroyed and newly differentiated odontoblast-like cells are formed by the underlying fibroblast. The hard tissue formed is generally less tubular or lacks dentinal tubules and more irregular (more bone-like than dentin-like).
Reactionary dentin: is formed by the original odontoblast. Dentin is more regular and tubular than reparative dentine. Tubules are usually not continuous with those of secondary dentin.
Explain why the current AAE protocol for pulp regeneration regenerative suggests a) Low conc of NaOCI in the first visit (1.5%) b) Ca(OH)2 or Low conc of triple or double antibiotic paste (TAP/DAP) as an intra canal medication c) The use of 17% EDTA as the final irrigation before stimulating bleeding d) The use of CHX is not recommended
A. Low conc of NaOCI in the first visit (1.5)
The use of low conc (1.5%) of NaOCI is based on the article of Martin et al (JOE-2014) which showed better survival of the stems cells of the apical papilla (SCAP) and greater dentin sialophosphoprotein (DSPP) expression with 1.5% NaOCI compared to other conc.
B. Ca(OH)2 or low conc TAP/DAP as an intra-canal medication
High conc of TAP/DAP has been shown to have a negative effect on the survival of SCAP. Low conc starting 1-6mg/ml has been shown to allow for SCAP survival (Ruparel et al, JOE - 2012). Ca(OH)2 has also been shown by Galler et al (JOE-2015) that it does not interfere with TGF beta release from dentin.
C. The use of 17% EDTA as the final irrigation before stimulating bleeding
EDTA facilitate the release of growth factors from Dentin and allows better survival of stem cells (Galler et al, JOE-2015,Martin et al, JOE-2014)
D. The use of CHX is not recommended
CHX has been shown to have a negative effect on the survival of SCAPs (Trevino et al, JOE-2011).
Describe the structure of the hard tissue barrier formed under direct pulp capping material (MTA or Ca(OH)2)?
- It has tunnel defects (Cox et al, Oper Dent- 1996, Al Hezaimi et al, JOE -2011).
- It resembles more bone than dentin (Andelin et al, JOE - 2003)
- Nair et al (IEJ, 2008) showed that the hard tissue barrier fromed under MTA is more compact with less pulpal inflammation compared to Ca(OH)2 that had more tunnel defect. Later Al Hezaimi et al (JOE, 2011) showed that there are tunnel defects in the hard tissue barrier in MTA as well, but the defects were more prominent with Ca(OH)2.
