Regeneration of the dentine-pulp complex with revitalization/revascularization therapy: challenges and hopes

The concept of regenerative endodontics has gained much attention in clinical endodontics in the past decade. One aspect of this discipline is the application of revitalization/revascularization therapies for infected and/or necrotic immature pulps in permanent teeth. Following the publication of a case report (Iwaya et al. ), investigators have been rigorously examining the types of tissues formed in the canals as well as exploring strategies to regenerate the pulp-dentine complex in revitalized teeth. This review will provide an update on the types of tissues generated in the canals after revitalization/revascularization therapy in both animal and human studies. The understanding of the role of stem cells and microenvironment in the process of wound healing resulting in either regeneration or repair will be thoroughly discussed. Stem cells and microenvironmental cues introduced into the canal during revitalization/revascularization procedures will be examined. In addition, requirement of a sterile microenvironment in the canal and vital tissue generation in revitalization/revascularization therapy will be emphasized. The challenges that we face and the hopes that we have in revitalization/revascularization therapy for regenerative endodontics will be presented.

Canal and isthmus debridement efficacies of two irrigant agitation techniques in a closed system

AIM

To compare canal and isthmus debris debridement efficacies of the manual dynamic irrigation (MDI) and apical negative pressure (ANP) techniques in the mesial root of mandibular first molars with narrow isthmi, using a closed canal design.

METHODOLOGY

Micro-computed tomography was employed to select 20 teeth, each containing a narrow isthmus. Each root was sealed at the apex with hot glue and embedded in polyvinylsiloxane to simulate a closed canal system. The teeth were submitted to a standardized instrumentation protocol. Final irrigation was performed with either the MDI or the ANP technique using the EndoVac system (N=10). Masson trichrome-stained sections were prepared from completely demineralized roots at 10 canal levels between 1 and 2.8mm of the anatomical apices. Areas occupied by canals and isthmus of each root and debris in the corresponding regions were digitized by the NIH Image J software and statistically analysed using two-way repeated measures anova.

RESULTS

For the instrumented canals, there were no differences between the two groups (P=0.131) in the area occupied by debris at all canal levels (P=0.343). Conversely, for the isthmus, less debris was found in the ANP group (P<0.001) but no differences were seen in each group with respect to the 10 canal levels (P=0.352).

CONCLUSION

Neither technique completely removed debris from the isthmus regions. However, the EndoVac system, which encompasses the ANP concept, removed considerably more debris from narrow isthmi in mandibular mesial roots.

Calculus-like deposit on the apical external root surface of teeth with post-treatment apical periodontitis: report of two cases

AIM

To report two cases in which calculus-like material was found on external root surfaces of (i) an extracted root and (ii) an apicected part of a root, both of which were removed due to post-treatment refractory apical periodontitis.

SUMMARY

In each case, there was a fistulous tract, which did not heal after conventional root canal treatment. The first case did not heal even after apical surgery, and subsequent tooth extraction revealed calculus-like material on a root surface of complex anatomy. The second case showed radiographic signs of healing after apicectomy. Histology of the apical biopsy revealed a calculus-like material on the external surface of the root apex. It is suggested that the presence of calculus on the root surfaces of teeth with periapical lesions may contribute towards the aetiology of failure.

KEY LEARNING POINTS

Biofilm on the external root surface has been implicated in the failure of apical periodontitis to heal, despite adequate root canal treatment. Calculus-like material was found, in two cases, on the root surface of teeth with post-treatment apical periodontitis, where the only communication externally was a sinus tract.

Apical limit of root canal instrumentation and obturation, part 1. Literature review

One of the major controversies in root canal therapy concerns the apical limit of instrumentation and obturation. The results of longitudinal prognostic studies, basic anatomical knowledge of the apical third of the root canal, and the histological pulp reaction to caries progression demonstrated the presence of a vital apical pulp remnant, even in the presence of a periapical lesion. Finally necrosis and bacteria establish themselves in the periapical lesion. All valid prognosis studies confirm the practice of staying short of the apex with a homogeneous obturation to obtain the highest success rate of 90-94% (when done by or under supervision of specialists; results in the general population had a failure rate greater than 50%). The location of the apical foramen(ina) related to root canal treatment most frequently ends short of the apex, often by several millimetres.

Bacterial status in root-filled teeth exposed to the oral environment by loss of restoration and fracture or caries - a histobacteriological study of treated cases

AIM

To describe histological and microbiological findings in teeth where root fillings had been exposed to caries and the oral environment for a prolonged period.

METHODOLOGY

For inclusion in the study, only teeth with a follow-up period of 3 years or more and those that had been without proper restoration for at least a period of 3 months were considered. Some root fillings had been without restoration for several years. In all, 39 roots representing 32 teeth were examined by histology.

RESULTS

The majority of the specimens were without a discernible periapical bone lesion as assessed by radiography. Osteolytic lesions were seen with five roots. Longitudinal tissue sections stained with a modified Brown/Brenn staining technique revealed presence of stainable bacteria in abundance at the canal entrance and in dentinal tubules but were absent mid-root and apically in all but two specimens. Soft tissue attached to the root tip and in apical ramifications displayed distinct inflammatory cell infiltrates, suggesting microbial exposure in 7 of the 39 roots examined. In all other specimens, inflammatory cell infiltrates were either nonexistent or sparse and then associated with extruded sealer material.

CONCLUSIONS

Well-prepared and filled root canals resist bacterial penetration even upon frank and long-standing oral exposure by caries, fracture or loss of restoration.

Apical limit of root canal instrumentation and obturation, part 2. A histological study

The results of an in vivo histological study involving apical and periapical tissues following root canal therapy after different observation periods demonstrated the most favourable histological conditions when the instrumentation and obturation remained at or short of the apical constriction. This was the case in the presence of vital or necrotic pulps, also when bacteria had penetrated the foramen and were present in the periapical tissues. When the sealer and/or the gutta-percha was extruded into the periapical tissue, the lateral canals and the apical ramifications, there was always a severe inflammatory reaction including a foreign body reaction despite a clinical absence of pain.

Periapical status of root-filled teeth exposed to the oral environment by loss of restoration or caries

OBJECTIVE

Studies in vitro carried out on extracted teeth have demonstrated that bacterial elements may penetrate root fillings from the coronal to the apical end after a period of exposure to artificial saliva or bacterial culture. To address the clinical significance of this so-called issue of coronal leakage, a retrospective cohort analysis was conducted of 55 patients with root fillings that had been exposed to the oral environment because of caries or absent restorations.

STUDY DESIGN

Cases were matched 1-to-1 with regard to initial pulpal and periapical diagnosis, period after completion of endodontic therapy, tooth type, age of the patient, and the technical quality of the root filling. Only cases with a follow-up period of 3 years or more were included. Radiographs taken at the last follow-up examination were subjected to a masked evaluation.

RESULTS

A total of 14 osteolytic lesions were recorded. In 43 of the 55 matched pairs (78%), there were identical periapical conditions. In 9 pairs, a periapical lesion was present in the "open" tooth category, whereas in 3 pairs, a periapical lesion was seen exclusively in the "intact" tooth. Though the odds-ratio for a lesion to be present in the "open group" was 3. 0, this was not a statistically significant result (P >.10).

CONCLUSIONS

Data suggest that the problem of coronal leakage may not be of such a great clinical importance as implicated by numerous studies in vitro, provided instrumentation and root fillings are carefully performed.

Incomplete calcium hydroxide removal from the root canal: a case report

This case demonstrates failure of root canal treatment of a maxillary central incisor following incomplete mechanical removal of a Ca(OH)2 intracanal dressing and subsequent resorption of the material from the apical portion of the root canal. Retreatment some 4 years later involved the removal of the contents of the root canal and permanent obturation by lateral condensation of cold gutta-percha with a sealer. Follow-up showed complete periradicular bone healing with a lamina dura evident. An explanation of the processes involved is offered, based upon histopathological and microbiological evidence in the literature.

Three independent canals in the mesial root of a mandibular first molar

Endodontic therapy was performed in a mandibular first molar with three canals in the mesial root. The mesiobuccal and the mesiolingual canals were found in their normal locations. The third was located in the middle of the distance between the other two. Radiographically, it ended in its own distinct foramen. Many reports deal with three orifices in the mesial root, but very few describe three independent canals, indicating a rare anatomical configuration. To locate the third possible intermediate canal it was suggested to reduce the mesial dentinal wall of the pulp chamber after instrumenting the main two canals.

Long-term follow-up on C-shaped mandibular molars

Three cases of mandibular second molars with C-shaped root canal morphology are described. Two of these molars did not radiographically show the usual anatomic configuration of two separated roots, but rather had a single conical root. Only two root canals orifices were observed in the pulp chamber floor: a mesial-lingual orifice in its normal position and a buccal C-shaped fissure that was continuous from the normal location of the mesiobuccal canal to that of the distal canal. The fissure became smaller in the apical third, ending in a distal direction. The third case, a second molar extracted because of severe periodontal involvement showed, after sectioning, a C-shaped root with connections between all three canals.

[New cement filled with hydroxyapatite. Preliminary clinical results]

After histological, scanning-electromicroscope, stereomicroscope and transillumination controls, the clearing technique definitively demonstrated that it's really impossible to empty and entirely fill the endodontic apical extremity inside the correct limit, without running the risk to cause iatrogenesis interferences against periodontal reparation processes. Then also the "tridimensional fill" conception, as a simple "seal by physical push", must be integrated with the conception of root canal sealer materials biocompatibility toward the periodontal tissues. "Bioseal" root canal sealer which is the subject of this research is certainly an example of progress about this objective.

[Pulpal-periapical response to canal medication with Ca(OH)2]

This study consisted of biopsies of teeth and root tips removed after Ca(OH)2 therapy. The teeth were clinically intact or exposed to caries, trauma, and/or iatrogenesis. Following the therapy most of the canal walls were clean, but the canals contained varying amounts of pulp tissues, debris and Ca(OH)2 particles. In one case microrganisms were present in the apical part of the canal, but not beyond the foramen. The Ca(OH)2 therapy was efficient for its purpose.