Histologic Features of External Cervical Resorption Affecting Impacted Maxillary Canines: A Report of 2 Cases.

Reports on the histopathologic features of external cervical resorption (ECR) in unerupted teeth are scarce. This article reports on 2 maxillary impacted canines from different patients that showed ECR lesions and were surgically removed and histologically evaluated. Case 1 showed symptoms associated with oral communication of the dental follicle and pulpal exposure. Radiographs and cone-beam computed tomographic imaging showed that resorption affected a large part of the root and the crown. Case 2 was asymptomatic, and the resorption cavity was restricted to the tooth crown. Both teeth were extracted and subjected to histologic processing and analysis. In case number 1, the coronal pulp was necrotic and infected, showing areas of exposure to the resorption channels. The apical pulp was vital and uninflamed. The pulp space was surrounded by a continuous pericanalar resorption-resistant sheet. Part of the resorbed area of dentin was occupied by inflamed granulation tissue. More apically, a network of trabecular bone was present in the resorbed area. In case number 2, the pulp around the resorbed area was uninflamed and vital. A large fraction of the lost dentin was replaced by trabecular bone, closely adapted to the irregularly resorbed dentin surface, and no inflammatory cells. Our findings indicate that impacted teeth with ECR may remain asymptomatic until associated with infection. Histologic features of resorption in impacted teeth were similar to those in erupted teeth. In the case associated with infection, the resorbed area was occupied by inflamed tissue and newly formed bone. In the case with no infection, the resorption area was filled with bone undergoing a remodeling process.

Biomechanical perspectives on dentine cracks and fractures: Implications in their clinical management.

OBJECTIVES: The present review discussed the biomechanical properties of cracks and fractures in crown and root dentine and attempted to explain why cracked teeth and vertical root fractures are so frequent despite the existence of multiple crack toughening mechanisms in dentine. The implications of this knowledge were used to justify how these defects are managed clinically. DATA, SOURCES AND STUDY SELECTION: Literature search was conducted on PubMed, Web of Science, and Scopus for a narrative review on fracture mechanics of crown and root dentine as well as the clinical management of cracked teeth and teeth with vertical root fracture. CONCLUSIONS: Although dentine is tougher and less brittle than enamel, it's facture toughness is considerably lower than most ductile metals. Because the initiation toughness of dentine is very low, cracks initiate from incipient damage under low stress While crack toughening mechanisms exist that enable dentine to resist crack extension, these mechanisms are often inadequate for protecting dentine from crack propagation that ultimately leads to catastrophic failure. Additional factors such as ageing also reduces the resistance of dentine to crack growth. Because dentine cracks are eventually filled with bacteria biofilms upon exposure to oral fluids, they enable rapid bacteria ingress into the dental pulp via open dentinal tubules. To date, treatment options for cracked teeth are limited. While most teeth with vertical root fracture are recommended for extraction, new strategies have been reported that appeared to achieve short-term success in preserving these teeth. CLINICAL SIGNIFICANCE: Current strategies for the management for dentine cracks and fractures are limited and their long-term effectiveness remain uncertain. Understanding the characteristics, toughening mechanism and weakening factors of tooth cracks is helpful in designing better treatment.

Surgical management of a lateral lesion refractory to root canal retreatment caused by an extraradicular calculus. A case report.

This article describes the management of a root canal-treated maxillary central incisor displaying a radiographic lateral radiolucency and a sinus tract that persisted irrespective of root canal retreatment following high standards. Endodontic microsurgery was indicated and curettage of the pathologic tissue revealed a calculus-like material attached to the outer root surface around the exit of a large lateral canal. A non-conventional approach was chosen: No root-end resection was conducted. Instead, the calculus was removed and the apical surface was scaled and smoothed, conserving the apical structure. Retrocavities were prepared in both lateral and apical foramens and filled with a bioceramic material. Follow-up examination showed optimal soft tissue healing. One-year follow-up of radiographs revealed healing of the lateral lesion. The lesion was diagnosed as a cyst, with an infected lumen. An exuberant calculus-like material attached to the external root surface was the most likely cause of the recalcitrant lateral periradicular lesion.

Outcome of Direct Pulp Capping Using Calcium Hydroxide: A Long-term Retrospective Study.

INTRODUCTION: This retrospective study evaluated the long-term outcome of direct pulp capping in mature teeth using specific case selection and treatment procedures. METHODS: Teeth with pulp exposure due to advanced caries and clinical diagnosis of reversible pulpitis were treated by direct pulp capping. Treatments were conducted over a period of 15 years by a single operator. Under magnification, caries was completely removed, the exposed pulp examined, and capped with either pure calcium hydroxide or a calcium hydroxide-based cement. The cavity was restored and the long-term outcome evaluated from 1 to >35 years. Teeth that were asymptomatic, responded to sensibility pulp tests within normal limits, and showed no radiographic periapical changes were categorized as success. Teeth with no response to pulp tests and/or showing radiographic evidence of apical periodontitis were classified as failures. The effects of independent variables (sex, age, symptoms, number and size of pulp exposures, bleeding time, capping material, bases used over the capping material, and final coronal restoration) on the outcome were evaluated. RESULTS: In general, 225 teeth from 148 patients were available for follow-up examination in at least one of the evaluated periods. The success rate of the direct pulp capping procedure was 100%, 95%, 95%, 86%, and 89% at 1-, 5-, 10-, 20-, and 35-year follow-up examination, respectively. The main variable significantly affecting the treatment outcome in all follow-up periods was the quality/presence of coronal restoration (P < .001). Other isolated variables associated with the outcome included the size and number of pulp exposures at the 20-year follow-up, and the exposure size, capping material, and restoration type at the 35-year follow-up. Multiple regression analysis confirmed the results for exposure size (P < .05), and disclosed a higher proportion of failures at 5 years when varnish was used as the base. CONCLUSIONS: A very high success rate of the direct pulp capping with calcium hydroxide was observed, especially in the first 10 years following treatment. The main variable influencing the outcome was the quality of the coronal restoration.

Unusual Lesion Caused by Food Displacement Into the Oral Mucosa, Mimicking a Sinus Tract.

This article reports an unusual case of foreign body lesion on the oral mucosa. A 61-year-old man, with no previous traumatic episode, presented with a small swelling resembling a sinus tract on the mucosa in the anterior mandible, adjacent to the left central and lateral incisors. Because of a discrete drainage of serous/purulent exudate, the clinician initially suspected endodontic involvement; however, the adjacent teeth were caries-free, responded positively to pulp tests, and the periapical tissues were radiographically normal. Exploration of the lesion opening under an operating microscope revealed a small seed associated with a dark filamentous structure; both were removed and processed for histologic examination. The seed was from a fig, and was germinating under the mucosa conditions. Bacterial colonization of the vegetable structures and polymorphonuclear leukocyte accumulations were histologically observed. The mucosa healed completely and uneventfully over the following weeks.

Bacterial Invasion of Pulp Blood Vessels in Teeth with Symptomatic Irreversible Pulpitis.

INTRODUCTION: This study described the degenerative changes and infection patterns of the pulp tissue associated with symptomatic irreversible pulpitis. METHODS: The material consisted of 32 extracted teeth with untreated deep caries that were clinically and histologically diagnosed with irreversible pulpitis and were part of the histopathologic collection of 1 of the authors. The controls consisted of intact teeth with normal uninflamed pulps and teeth with reversible pulpitis. Teeth were processed for histopathologic and histobacteriologic analyses. RESULTS: All teeth with irreversible pulpitis showed areas of severe acute inflammation, necrosis, microabscesses, and bacterial infection in the pulp chamber. These areas were surrounded by a chronic inflammatory infiltrate, and, at the distance, the pulp tissue was often uninflamed. Bacteria were also observed in the areas surrounding the necrotic foci, both as scattered cells through the extravascular space and at varying numbers within the blood vessel lumen. The number of bacteria and the density of the intravascular bacterial aggregations varied considerably. In one third of the cases, bacteria occurred in the lumen of venules in areas at a considerable distance from the necrotic focus in the coronal third of the root. No intravascular bacteria were noted in the middle and apical segments of the canal. No bacteria were found in the pulps of any of the control specimens. CONCLUSIONS: Bacterial invasion and colonization of necrotic areas were observed in the pulp of all teeth with caries exposure and symptomatic irreversible pulpitis. Bacterial penetration of blood vessels occurred in all cases, suggesting that this may be an important mechanism of spread of bacterial infection through the pulp tissue in an endodontic infection.

Pulp Response to Periodontal Disease: Novel Observations Help Clarify the Processes of Tissue Breakdown and Infection.

INTRODUCTION: This study evaluated the pulp response to periodontal disease of increasing severity. METHODS: The material comprised human teeth affected by moderate (n = 16) to severe (n = 48) periodontal disease and no clinically identified caries lesions. Specimens were obtained by extraction and were processed for histopathologic and histobacteriologic methods. RESULTS: In 13 of 16 teeth with moderate periodontal disease and vital pulp, no frank accumulations of inflammatory cells were observed. In 22 of 32 teeth with severe periodontal disease and vital pulps, no distinct inflammatory cell accumulations were observed in any portion of the pulp when there was an intact or minimally damaged cementum layer in the corresponding areas. Intravascular bacterial aggregations were detected in pulp blood vessels in 6 teeth with symptomatic pulpitis and severe periodontal disease, which had not reached the root apex in 4 of them. Focal areas of infection and varying accumulations of acute and chronic inflammatory cells were observed throughout the pulp tissue and surrounding these infected blood vessels. When the periodontal pocket reached the apex of single-rooted teeth, the entire canal space was necrotic and colonized by bacteria, often forming biofilms. In multirooted teeth, the pulp response varied according to the root(s) affected. Intrapulpal calcifications were observed in 91% of the teeth. The pulp and cementum of the control teeth showed no pathologic changes or bacteria. CONCLUSIONS: The pulp showed a significantly detectable response when the cementum coverage was lost or when the periodontal pocket reached the root apex. In the former condition, the pulp response was usually discrete, whereas in the latter, severe reactions usually developed. In some teeth, vessels with a compromised blood flow may serve as avenues for bacteria to invade the pulp via apical or lateral foramina. This indicates that in some teeth the pulp may undergo severe inflammation and necrosis even before the periodontal disease reaches the apical root segment.

Mineral trioxide aggregate apexification: a 20-year case review.

Apexification strategies in traumatised non-vital immature permanent teeth can promote root-end closure and continued root development. However, traumatic injuries may compromise the integrity of generative cells of the apical papilla responsible for root maturation. This report describes the long-term treatment outcome of mineral trioxide aggregate (MTA) apexification managed with late-term surgical intervention. A seven-year-old male reported with swelling and suppuration associated with a traumatised maxillary left central incisor (#21). After palliative treatment and MTA apexification procedures, the incisor demonstrated normal function during a 14.5-year period with radiographic evidence of atypical radicular elongation. Seventeen years after initial treatment, the patient presented with mid-plate buccal swelling and surgical treatment was completed involving root resection, biopsy of a spherical mineralised tissue specimen and placement of MTA root-end filling. Periapical healing and normal tooth function was evident at the 20-year review.

Unusual Location of Dens Invaginatus Causing a Difficult-to-Diagnose Pulpal Involvement.

This article reports on an unusual case of dens invaginatus in a maxillary third molar that was causing severe symptoms of irreversible pulpitis. This malformation was not clinically or radiographically identified, and the occurrence of referred pain made the early identification of the responsible tooth difficult. Determination of the tooth that was the source of symptoms was only possible after an observation period and fast aggravation of the pathologic process to cause pulp necrosis and extreme tenderness to percussion. The diagnosis of dens invaginatus was made only after extraction and sectioning. Histopathologic and histobacteriologic features of this case are illustrated.

Pulp and dentine responses to selective caries excavation: A histological and histobacteriological human study.

OBJECTIVE: The present study investigated the histobacteriological condition of human carious dentine, and the histological response of dental pulps after selective caries excavation to firm dentine and cavity restoration with adhesive procedures. METHODS: Twelve vital teeth with medium/deep occlusal caries from 12 patients were scheduled for extraction. The patients gave consent to have caries removed selectively and the cavity restored with adhesive procedures prior to extraction. Caries excavation was achieved using burs and sharp hand excavators until "leathery" or "firm" dentine was encountered. After extraction, the teeth were completely-demineralised, processed for light microscopy, serial-sectioned and stained with haematoxylin and eosin staining for histological examination of dentine characteristics and pulpal responses. Additional sections were stained with Taylor-modified Brown and Brenn technique for histobacteriological examination of bacteria infiltration of the dentinal tubules and dental pulp. RESULTS: The 12 teeth showed varying degrees of tertiary dentine formation. Chronic inflammatory cell infiltrates were identified in the pulp of all specimens and appeared as scattered inflammatory cells or exiguous localised accumulations. Capillaries were heavily congested with erythrocytes and polymorphonuclear leukocytes. A large amount of stainable bacteria was observed in the dentine subjacent to the cavity floor in all specimens. CONCLUSIONS: The present study demonstrated that "leathery" or "firm" carious dentine is infected. The remnant bacteria in the dentine provoked subclinical pulpal inflammation over the entire evaluation period. The presence of potentially-arrested caries does not necessarily mean that bacterial infection is absent or under control. CLINICAL SIGNIFICANCE: Knowledge on the pulpal response to active caries and the inflammatory responses associated with bacteria ingress into dentine is paramount in helping clinicians make an informed, rational choice based on biologically-robust principles.

Bacteriologic status of non-cavitated proximal enamel caries lesions. A histologic and histobacteriologic study.

OBJECTIVES: This histologic and histobacteriologic study evaluated non-cavitated interproximal white spot lesions in human teeth for the 1) presence and morphology of bacterial aggregations at the enamel-dentinal junction (EDJ), and 2) reactions in the subjacent pulp tissue. METHODS: The material comprised 16 third molars diagnosed with early interproximal caries lesions obtained consecutively in a single clinical practice. Four third molars with clinically intact proximal surfaces served as controls. Caries activity was categorized as active or arrested. Teeth were prepared for histologic and histobacteriologic analyses. RESULTS: Control teeth exhibited normal tissue conditions with no bacteria. Macroscopic discoloration of the superficial dentin occurred in 14/16 teeth with early caries lesions. Bacterial aggregations resembling biofilms were observed in 10/16 teeth (six with active and four with arrested lesions). Bacterial cells were observed superficially in some of the underlying dentinal tubules, while in a few cases a deeper penetration was evident. Pathologic changes of varying degrees were observed in the pulps of all 16 teeth, regardless of the caries activity (active or arrested). Pulp reactions varied from disruption of the odontoblast layer, with loss of odontoblasts, to formation of tertiary dentin. CONCLUSIONS: Bacterial biofilms associated with white-spot caries lesions may traverse the enamel and reach the underlying dentin in both active and arrested lesions. In all teeth with early lesions, the pulps showed changes in response to the very superficial biofilm challenge. CLINICAL SIGNIFICANCE: In non-cavitated, active or arrested, enamel caries lesions, bacteria traverse the enamel and may establish structured biofilms at the enamel-dentinal junction, causing early pulp changes. These new findings may stimulate clinicians to rethink the rationale for treatment methods that are based on the assumption that bacteria are absent in white-spot lesions.

"True" Versus "Bay" Apical Cysts: Clinical, Radiographic, Histopathologic, and Histobacteriologic Features.

INTRODUCTION: This study compared the main clinical, radiographic, and histologic features of true and bay apical cysts. METHODS: The study material comprised 95 biopsy specimens of apical periodontitis lesions obtained attached to the root tip of both untreated and root canal-treated teeth. Clinical and radiographic data were recorded. Specimens were obtained by extraction or periradicular surgery and were meticulously processed for histopathologic and histobacteriologic methods. All cases diagnosed as apical cysts (n = 23) were divided into the true and bay types, which were then compared for tooth location, patient's sex, lesion size, severity of clinical symptoms, presence of a sinus tract, previous abscess episodes, and prevalence of bacteria in the main root canal lumen and ramifications, on the outer root surface, and within the cyst cavity. RESULTS: Eleven specimens were classified as true (48%) and 12 (52%) as bay cysts. Bacteria were found in all specimens, regardless of the histopathologic diagnosis. Planktonic bacteria were observed in the main root canal in all true cysts and in 11 of 12 (92%) bay cyst cases. Biofilms were detected in the main canal in 10 cases from each diagnostic group and were frequently observed in ramifications. Extraradicular biofilms occurred in a few specimens only. Bacteria were visualized within the cavity of both true (4/11, 36%) and bay (6/12, 50%) cyst specimens. The severity of histologic inflammation was always high. There were no significant differences between true and bay cysts for all the clinical, radiographic, histopathologic, and histobacteriologic parameters assessed. CONCLUSIONS: Except for the morphologic relationship of the cyst cavity with the root canal space, true and bay cysts exhibited no other significant differences in the various parameters evaluated. The 2 cyst types were always associated with an intraradicular infection and sometimes with an extraradicular infection. Findings question the need to differentiate true and bay cysts and do not support the assumption that true cysts are self-sustainable entities not maintained by infection.

Cleaning, Shaping, and Disinfecting Abilities of 2 Instrument Systems as Evaluated by a Correlative Micro-computed Tomographic and Histobacteriologic Approach.

INTRODUCTION: This study assessed the cleaning, shaping, and disinfection abilities of 2 instrumentation systems in molar root canals using a novel correlative analytical approach. METHODS: The root canals from extracted mandibular and maxillary molars with apical periodontitis were pair matched according to anatomic similarities as determined by micro-computed tomographic analysis and prepared with either XP-endo Shaper (FKG Dentaire, La Chaux-de-Fonds, Switzerland) (n = 16) or Reciproc Blue (VDW, Munich, Germany) (n = 16) instruments and 2.5% sodium hypochlorite irrigation. Pre- and postpreparation micro-computed tomographic scans were used to identify and calculate the unprepared surface areas (shaping), which were histobacteriologically evaluated for the presence of residual bacteria (disinfection) and pulp tissue remnants (cleaning) in each canal third. RESULTS: Unprepared canal surface areas for XP-endo Shaper and Reciproc Blue in the full canal length were approximately 26% and 19% (P < .05), respectively (30% and 23% in the apical part of the canal, P > .05). Preparation with Reciproc Blue resulted in 37.5% canals free of bacteria in all sections examined and 56% in the apical sections only. XP-endo Shaper resulted in 44% canals free of bacteria in all sections, and 56% in the apical part of the canal only. Pulp tissue remnants were not observed in 31% (all canal sections) and 50% (apical canal sections) of specimens from both instrument systems. No significant differences were observed between instruments when comparing the amount of pulp tissue remnants and the number of cases negative for bacteria and tissue remnants (P > .05). CONCLUSIONS: Although the Reciproc Blue instrument had superior shaping ability in comparison with XP-endo Shaper, both systems performed similarly in cleaning and disinfecting root canals. Irregular canals and difficult-to-reach areas were not thoroughly cleaned and disinfected by any of the tested systems.

An Unusual Case of a Large Periapical Cyst Mimicking a Nasopalatine Duct Cyst.

This article reports on the management of a large median symmetrical lesion of the anterior palate, which was clinically and radiographically diagnosed as an infected nasopalatine duct cyst. However, histopathology demonstrated it to be a radicular cyst of endodontic origin.

An Immunofluorescence Study to Analyze Wound Healing Outcomes of Regenerative Endodontics in an Immature Premolar with Chronic Apical Abscess.

INTRODUCTION: Limited studies have examined tissue formation via immunofluorescence in regenerative endodontic procedures (REPs) performed on infected human teeth. This report investigated the immunofluorescent histologic outcomes of REPs in which repeated canal disinfection was required. METHODS: An 11-year-old girl presented with a fractured dens evaginatus (#29) with a sinus tract. Three visits involving chemical and mechanical disinfection were required before the resolution of clinical signs and symptoms was achieved and the REP could be performed. Healing of the periapical lesion was noted by 12 months, although the tooth remained unresponsive to sensibility tests. At 18 months, the tooth underwent orthodontic extraction. Histology and immunofluorescent techniques were used to stain for dentin sialophosphoprotein (DSPP), osteopontin (OPN), periostin, and myelin basic protein. RESULTS: Histology did not reveal a newly formed pulp-dentin complex. Neomineralized tissues were seen interlocked into preexisting dentinal tubules. Non-odontoblast-looking cells expressed different proportions of OPN and DSPP according to their location. Cells nearer to mineral trioxide aggregate expressed DSPP and OPN, but cells found apically expressed predominantly OPN. Myelin basic protein was found centrally within new tissues and did not extend to the coronal third. Periostin was highly expressed throughout the entire canal space, suggesting active repair processes instead of regeneration. CONCLUSIONS: This study shows the clinical effectiveness of REP in a tooth with recalcitrant infection with histologic demonstration of a reparative phenotype. De novo pulp regeneration in a clinical scenario may be limited by a complex interplay of host response factors.

Atypically grown large periradicular cyst affecting adjacent teeth and leading to confounding diagnosis of non-endodontic pathology.

This article reports a case of a large osteolytic lesion in the mandible, mostly associated with the apices of the premolars, and suspected as having a non-endodontic origin because the 2 premolars responded positively to the cold sensibility test. The distal border of the lesion reached the mesial root of the first molar, which also had a small lesion in its distal aspect. Cone-beam computed tomography revealed that the large lesion communicated with the small molar lesion. Because the large lesion was suspected as having a non-endodontic origin, surgery was scheduled for enucleation and biopsy. The molar was root canal-retreated, and the 2 premolars treated. Histologic analysis of the premolar pulps showed vitality but advanced degenerative changes. The lesion was histologically diagnosed as an inflammatory periradicular cyst, which originated in the first molar and had an atypical growth to the premolar area. Follow-up revealed that the affected area healed uneventfully.

Histologic Response of Human Pulp and Periapical Tissues to Tricalcium Silicate-based Materials: A Series of Successfully Treated Cases.

Pulpal/periapical responses of human teeth that are treated successfully with tricalcium silicate-based materials are extremely difficult to obtain because of the typical unavailability of these teeth for histologic examination. The present case series reports histologic and histobacteriologic findings of 3 human teeth that had undergone pulpotomy, orthograde retreatment, and apicoectomy/root-end filling using tricalcium silicate-based endodontic materials. The teeth were extracted after 34 days, 7 weeks, and 20 months, respectively, because of unusual circumstances. The extracted teeth were processed, paraffin embedded, sectioned, stained with hematoxylin-eosin or the modified Brown and Brenn technique, and examined with light microscopy. The recurrent observation for the 3 cases presented was the absence of inflammatory or foreign body reactions of the host tissues in contact with tricalcium silicate-based materials after different observation periods despite the identification of bacteria in dentinal tubules close to the site of operation. Wound healing was rapid with repair/regeneration of lost tissues with cementum and new bone trabeculae. Although the level of evidence for a case series is low because of the anecdotal nature of the reported episodes, the histologic results reported in the present case series illustrate the highly biocompatible and bioactive nature of the tricalcium silicate-based materials used in treating these cases.

Vital pulp therapy of mature permanent teeth with irreversible pulpitis from the perspective of pulp biology.

The American Association of Endodontists (AAE) Consensus Conference Recommended Diagnostic Terminology states that mature permanent teeth clinically diagnosed with irreversible pulpitis are treated with pulpectomy and root canal filling because inflamed vital pulp is not capable of healing. Histological studies have demonstrated that clinically diagnosed irreversible pulpitis does not involve the entire pulp. A recent International Endodontic Journal Editorial suggested clinical diagnosis of pulp disease should be reassessed because of the poor correlation between clinical symptoms and pulp sensibility testing and the actual histological status of the pulp. This review identified studies in a PubMed search that provide evidence for vital pulp therapy (VPT) of mature permanent teeth with irreversible pulpitis is predictable if correctly diagnosed and properly treated. A narrative review was undertaken to outline the correlation between the clinical symptoms/signs and pulp sensibility testing and the histological findings of the pulp. Treatment procedures for permanent teeth are outlined.

Vital pulp therapy: histopathology and histobacteriology-based guidelines to treat teeth with deep caries and pulp exposure.

OBJECTIVES: Vital pulp therapy (VPT) encompasses distinct treatment modalities for deep caries that approximate the pulp chamber in vital teeth. Confusion exists in the literature in terms of the indication and rationale for each VPT approach. The objectives of the present study are to elucidate the indications for VPT and to present a set of histopathology and histobacteriology-based guidelines for VPT in teeth with deep caries. METHODS: Two hundred and sixty-four carious, unrestored and VPT-treated human teeth, which were extracted for reasons not related to the present study. The teeth were processed for histological and histobacteriological examination. Other 757 clinical cases that received different VPT procedures were followed-up to identify success rates, with the longest observational period of 30 years. RESULTS: Follow-up of the clinical cases indicated that direct pulp capping was successful in 73.2%, partial pulpotomy in 96.4% and full pulpotomy in 77.8% of the cases. Histological and histobacteriological examination showed a localised inflammatory response that commonly occurred in the subjacent pulp tissue as soon as the enamel was penetrated by caries. If the softened and infected dentine were completely excavated, without pulp exposure, and the cavity restored with an adequate restoration, pulp inflammation frequently subsided. In teeth showing pulp exposure, the extent of bacterial penetration varied and areas of infection presented severe pulp inflammation, including micro-abscesses. However, the pulp tissue apical to the infected/inflamed area was usually uninflamed and normal. Guidelines based on the present histopathological, histobacteriological and clinical findings are proposed for VPT and mainly involve direct examination of dentine and the exposed pulp tissue under deep caries for decision-making, and require strict asepsis during procedures. CONCLUSIONS: Vital pulp therapy following the guidelines proposed in the present article has the potential to improve the outcome of the conservative treatment of mature teeth with deep caries and in some occasions may be an alternative to pulpectomy. CLINICAL SIGNIFICANCE: A guideline for VPT in the treatment of deep caries is proposed, focusing on direct observation of dentine and the exposed pulp tissue under deep caries. Stringent aseptic techniques are mandatory for VPT procedures to be successful.

Histological evaluation of hard tissue formation after direct pulp capping with a fast-setting mineral trioxide aggregate (RetroMTA) in humans.

OBJECTIVES: To histologically evaluate the morphology of the newly formed mineralized tissue and of the adjacent cells, in intact human teeth subjected to mechanical pulp exposure and capping with a fast-setting mineral trioxide aggregate (RetroMTA). MATERIALS AND METHODS: Seven caries-free third molars from three adults 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, extracted, and subjected to histological processing and evaluation. RESULTS: All teeth were clinically and radiographically inconspicuous and showed no presence of severe inflammatory reactions. Bacteria were absent in all teeth. All cases exhibited some degree of mineralized tissue in the area of exposure to varying extent. This newly formed mineralized tissue was mostly atubular and did not display the features of regular dentine in any of the cases. No cells exhibiting the features of odontoblasts or odontoblast-like cells were observed. Instead, the cells exhibited a flat or cuboidal shape, resembling fibroblasts. CONCLUSIONS: When the exposed pulps were directly capped with RetroMTA, the new calcified hard tissue was not "regular dentine," and did not seem to be the product of genuine odontoblast differentiation. These results suggest that the formation of calcified tissues after direct pulp capping with RetroMTA may be more appropriately regarded as a reparative process than as a genuine regeneration response. CLINICAL RELEVANCE: This is the first histological study on humans showing that regular dentine was not regenerated when a bioactive pulp-capping material (RetroMTA) was placed over exposed pulp tissue. TRIAL REGISTRATION: NCT03631511.