Lars Bjørndal

A clinical and microbiological study of deep carious lesions during stepwise excavation using long treatment intervals.

Concern about the survival of microorganisms in deep carious lesions may often lead to unnecessary exposure of the pulp during final excavation. There are reasons, therefore, to initiate systematic studies on the alternative procedure known as stepwise excavation. Clinical evaluation of stepwise excavation was performed on 31 deep carious lesions considered to result in pulp perforation by traditional excavation. This study examines the clinical and microbiological alterations during the final excavation performed during long intervals (6-12 months) after the initial treatment that included peripheral dentine excavation and removal of the central cariogenic biomass and the superficial necrotic dentine. The dentine colour and consistency were assessed by means of standardized scales before application of a Ca(OH)2 compound and a temporary sealing for 6-12 months. Reassessments were performed before the after final excavation. Microbiological dentine samples were obtained in 19 randomly selected lesions by a sterile bur, transferred to and diluted in reduced transport fluid, and plated on tryptic soy agar. After anaerobic incubation at 37 degrees C for 7 days, total colony-forming units per millilitre were counted from (1) peripheral excavated and hard dentine (control), (2) central demineralized dentine before and final excavation, and (3) central dentine after the final excavation. Six samples of central demineralized dentine were without any cultivable flora increasing to 9 samples after the final excavation. The clinical dentine changes occurring during stepwise excavation were characterized by enhanced hardness of the dentine which was associated with a marked reduction in bacterial growth after the final excavation. Despite the presence of bacteria in the excavated dentine none of the carious lesions resulted in pulp perforation, suggesting that the initial removal of the cariogenic biomass appears to be essential for control of caries progression. Stepwise excavation is not only an appropriate treatment of deep carious lesions but is also considered a suitable model for microbiological studies to determine the bacteria persisting in clinically excavated lesions.

Treatment of deep caries lesions in adults: randomized clinical trials comparing stepwise vs. direct complete excavation, and direct pulp capping vs. partial pulpotomy

Less invasive excavation methods have been suggested for deep caries lesions. We tested the effects of stepwise vs. direct complete excavation, 1 yr after the procedure had been carried out, in 314 adults (from six centres) who had received treatment of a tooth with deep caries. The teeth had caries lesions involving 75% or more of the dentin and were centrally randomized to stepwise or direct complete excavation. Stepwise excavation resulted in fewer pulp exposures compared with direct complete excavation [difference: 11.4%, 95% confidence interval (CI) (1.2; 21.3)]. At 1 yr of follow-up, there was a statistically significantly higher success rate with stepwise excavation, with success being defined as an unexposed pulp with sustained pulp vitality without apical radiolucency [difference: 11.7%, 95% CI (0.5; 22.5)]. In a subsequent nested trial, 58 patients with exposed pulps were randomized to direct capping or partial pulpotomy. We found no significant difference in pulp vitality without apical radiolucency between the two capping procedures after more than 1 yr [31.8% and 34.5%; difference: 2.7%, 95% CI (-22.7; 26.6)]. In conclusion, stepwise excavation decreases the risk of pulp exposure compared with direct complete excavation. In view of the poor prognosis of vital pulp treatment, a stepwise excavation approach for managing deep caries lesions is recommended.

Changes in the Cultivable Flora in Deep Carious Lesions following a Stepwise Excavation Procedure

This study examined the cultivable microflora before and after stepwise excavation procedures in deep carious lesions in 9 permanent teeth, categorized according to degrees of proximal surface destruction. The final excavation was performed 4–6 months after the initial treatment, which included peripheral dentine excavation and removal of the central cariogenic biomass and the superficial necrotic dentine. Dentine colour and consistency were assessed by means of standardized scales before the application of a Ca(OH)2 compound and temporary sealing. Reassessments were performed before and after the final excavation. Microbiological samples of the central demineralized dentine were obtained with a sterile bur before and after the first excavation, as well as before and after the final excavation. After anaerobic cultivation on enriched non–selective tryptic soy agar, 30 colonies from a representative area were identified by standardized biochemical and physiological tests. Before temporary restoration, a yellowish and light brown demineralized soft dentine was typically observed, and gram–positive rods accounted for 70% and lactobacilli for 50% of the total colony–forming units. Lactobacillus casei subsp. rhamnosus and Actinomyces naeslundii dominated the lactobacilli and the other gram–positive rods, respectively. Gram–negative rods were the next most frequent isolates, followed by streptococci, each group accounting for about 20% of the colony–forming units in positive samples. Before the final excavation, which did not cause exposure of the pulp in any of the cases, the retained demineralized dentine had changed into a darker and harder tissue, and the total colony–forming units, as well as the frequency and proportions of lactobacilli were substantially reduced. Gram–negative rods also declined, and the flora was dominated by A. naeslundii and various streptococci. In conclusion, the cultivable flora detected following the treatment interval had declined substantially, and the distribution of bacterial species did not represent a typical cariogenic microbiota of deep lesions, confirming the clinical findings of arrested caries progression.

Managing Carious Lesions: Consensus Recommendations on Carious Tissue Removal

The International Caries Consensus Collaboration undertook a consensus process and here presents clinical recommendations for carious tissue removal and managing cavitated carious lesions, including restoration, based on texture of demineralized dentine. Dentists should manage the disease dental caries and control activity of existing cavitated lesions to preserve hard tissues and retain teeth long-term. Entering the restorative cycle should be avoided as far as possible. Controlling the disease in cavitated carious lesions should be attempted using methods which are aimed at biofilm removal or control first. Only when cavitated carious lesions either are noncleansable or can no longer be sealed are restorative interventions indicated. When a restoration is indicated, the priorities are as follows: preserving healthy and remineralizable tissue, achieving a restorative seal, maintaining pulpal health, and maximizing restoration success. Carious tissue is removed purely to create conditions for long-lasting restorations. Bacterially contaminated or demineralized tissues close to the pulp do not need to be removed. In deeper lesions in teeth with sensible (vital) pulps, preserving pulpal health should be prioritized, while in shallow or moderately deep lesions, restoration longevity becomes more important. For teeth with shallow or moderately deep cavitated lesions, carious tissue removal is performed according to selective removal to firm dentine. In deep cavitated lesions in primary or permanent teeth, selective removal to soft dentine should be performed, although in permanent teeth, stepwise removal is an option. The evidence and, therefore, these recommendations support less invasive carious lesion management, delaying entry to, and slowing down, the restorative cycle by preserving tooth tissue and retaining teeth long-term.

A LIGHT MICROSCOPIC STUDY OF ODONTOBLASTIC AND NON-ODONTOBLASTIC CELLS INVOLVED IN TERTIARY DENTINOGENESIS IN WELL-DEFINED CAVITATED CARIOUS LESIONS

This study examines cellular and microradiographic findings in thin, undemineralized sections of 46 cavitated lesions, that were clinically well–defined with respect to lesion activity and estimated lesion age at extraction time. The progressive stages of surface breakdown ranged from enamel cavitation to larger dentine exposures classified as closed and open lesion environments. Measurements of the following parameters were performed using computerized image processing software: (a) the cytoplasm:nucleus ratio of primary odontoblast cells; (b) the cell:dentinal tubule ratio; (c) the adjacent predentine area (μm2), and (d) the cytoplasm: nucleus ratio of non–odontoblastic cells, and secondary odontoblast–like cells, where estimation of these cell types were based on structural criteria. In active enamel cavitated lesions, reduced odontoblast–predentine regions and indistinct subodontoblastic regions were noted. During initial dentine exposures, non–odontoblastic cells along the pulp–dentinal interface were observed as well. The first indication of tertiary dentine was seen in old lesions with exposed dentine. The tertiary dentine appeared more atubular in the closed/active lesions than in the open/slow–progressing lesions. The involved odontoblastic cells in tubular tertiary dentine in small open/slow–progressing lesions were comparable to the primary odontoblast cells, however, new dentinal tubules were also noted presenting a mixture between reactionary and reparative dentinogenesis. In close/active lesions non–primary odontoblastic cells were aligning the atubular tertiary dentine, whereas well–defined signs of secondary odontoblast–like cells were first seen in larger open lesions, producing tubular tertiary dentine. In conclusion, a strong relationship between external lesion environments and corresponding different formations of tertiary dentine was noted in advanced cavitated lesions. It is additionally suggested that the stimulation of tubular tertiary dentine could be a closely related reaction when an active lesion complex changes into a slower progressing lesion environment.

A Quantitative Light Microscopic Study of the Odontoblast and Subodontoblastic Reactions to Active and Arrested Enamel Caries without Cavitation

This study describes cellular and microradiographic findings in thin undemineralized enamel-dentine sections from 36 enamel caries lesions from freshly extracted third molars. Lesions activity was determined by clinical examination and the estimated age of the lesion at extraction time. The cellular reactions to the enamel/dentine lesion complex were measured using computerized histomorphometry under the following conditions: (a) the cytoplasm:nucleus ratio of the odontoblast cell; (b) the odontoblast cell:dentinal tubule ratio, and (c) the adjacent predentine area (μm2). The first cellular reactions were observed beneath superficial enamel lesions before visible alterations in dentine mineralization. The cytoplasm:nucleus ratio of the odontoblast cells was markedly reduced, and only active lesions showed evidence of cellular proliferation into the cell-free zone. In more advanced active lesions the affected odontoblast cells had a significantly lower cytoplasm:nucleus ratio compared with the controls. Similar changes were not seen in arrested or slow-progressing lesions. Before onset of tertiary dentine formation there was a positive correlation between odontoblast cell size and predentine formation. Primary odontoblast cells were involved in early tertiary or reactionary dentine formation without odontoblast cell replacement. Reactionary dentine was only seen in active lesions, suggesting that reactions in the dentine/pulp complex are closely associated with the external environment.

Indirect Pulp Therapy and Stepwise Excavation

Various treatment concepts have been suggested to solve the deep carious lesion dilemma. Recent systematic reviews are presented. Their conclusions are based on very few studies, and the main message is that optimal randomized clinical studies are lacking. Observational studies on indirect pulp treatment and stepwise excavation demonstrate that these treatments avoid pulp exposures, but it cannot be said which approach is best. A less invasive modified stepwise excavation approach is described, focusing on changing an active lesion into an arrested lesion even without performing an excavation close to the pulp. In Denmark and Sweden a randomized clinical multi-center trial is currently taking place, the Caries and Pulp (CAP) trial. This trial is investigating the effects of stepwise excavation over 2 visits versus 1 complete excavation of deep caries in permanent teeth. Guidelines for treatment are presented.

Managing Carious Lesions: Consensus Recommendations on Terminology

Variation in the terminology used to describe clinical management of carious lesions has contributed to a lack of clarity in the scientific literature and beyond. In this article, the International Caries Consensus Collaboration presents 1) issues around terminology, a scoping review of current words used in the literature for caries removal techniques, and 2) agreed terms and definitions, explaining how these were decided. Dental caries is the name of the disease, and the carious lesion is the consequence and manifestation of the disease—the signs or symptoms of the disease. The term dental caries management should be limited to situations involving control of the disease through preventive and noninvasive means at a patient level, whereas carious lesion management controls the disease symptoms at the tooth level. While it is not possible to directly relate the visual appearance of carious lesions’ clinical manifestations to the histopathology, we have based the terminology around the clinical consequences of disease (soft, leathery, firm, and hard dentine). Approaches to carious tissue removal are defined: 1) selective removal of carious tissue—including selective removal to soft dentine and selective removal to firm dentine; 2) stepwise removal—including stage 1, selective removal to soft dentine, and stage 2, selective removal to firm dentine 6 to 12 mo later; and 3) nonselective removal to hard dentine—formerly known as complete caries removal (technique no longer recommended). Adoption of these terms, around managing dental caries and its sequelae, will facilitate improved understanding and communication among researchers and within dental educators and the wider clinical dentistry community.

The caries process and its effect on the pulp: the science is changing and so is our understanding.

The understanding of the caries process and its effect on the pulp is presented in the context that caries does develop in various rates of progression. Early in the caries process, the pulp reflects changes within lesion activity. Thus, the early pulp response is reversible. Later, the rate of caries progression is reflected by the quality of the tertiary dentin. Slowly progressing lesions create tertiary dentin resembling normal tubular dentin. Rapidly progressing lesions lead to the production of atubular dentin or complete absence of tertiary dentin, as well as pulp necrosis and apical pathology. Finally, the nature of the untreated deep carious lesion is an ecosystem that might undergo significant changes. The untreated lesion is temporarily converted from an active and closed lesion environment into one that is open and slowly progressing. The analysis of untreated carious lesions has transformed the treatment philosophy of deep carious lesions.

Micro-CT analyses of apical enlargement and molar root canal complexity

AIM To compare the effectiveness of two rotary hybrid instrumentation techniques with focus on apical enlargement in molar teeth and to quantify and visualize spatial details of instrumentation efficacy in root canals of different complexity. METHODOLOGY Maxillary and mandibular molar teeth were scanned using X-ray microcomputed tomography. Root canals were prepared using either a GT/Profile protocol or a RaCe/NiTi protocol. Variables used for evaluation were the following: distance between root canal surfaces before and after preparation (distance after preparation, DAP), percentage of root canal area remaining unprepared and increase in canal volume after preparation. Root canals were classified according to size and complexity, and consequences of unprepared portions of narrow root canals and intraradicular connections/isthmuses were included in the analyses. One- and two-way anova were used in the statistical analyses. RESULTS No difference was found between the two techniques: DAP(apical-third) (P = 0.590), area unprepared(apical-third) (P = 0.126) and volume increase(apical-third) (P = 0.821). Unprepared root canal area became larger in relation to root canal size and complexity, irrespective of the technique used. Percentage of root canal area remaining unprepared was significantly lower in small root canals and complex systems compared to large root canals. The isthmus area per se contributed with a mean of 17.6%, and with a mean of 25.7%, when a narrow root canal remained unprepared. CONCLUSIONS The addition of isthmuses did not significantly alter the ratio of instrumented to unprepared areas at total root canal level. Distal and palatal root canals had the highest level of unprepared area irrespective of the two instrumentation techniques examined.