Clinical Implications and Microbiology of Bacterial Persistence after Treatment Procedures

Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes. Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans. 227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure. 3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost–effectiveness analysis.

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3D-printing techniques in a medical setting: a systematic literature review

Debridement of the root canal by instrumentation and irrigation is considered the most important single factor in the prevention and treatment of endodontic diseases. In clinical practice, instrumentation of the root canal(s) within the affected tooth is usually the most time consuming and technically demanding element of the treatment. The technical success of the treatment, as judged by the post-operative radiograph after the root filling, is based on optimized root canal instrumentation. Mounting evidence from epidemiological research is also indicating that the combination of high-quality coronal restoration and technically satisfactory root canal treatment is associated with the greatest long-term prognosis. Therefore, it is not surprising that for several decades of endodontic research, a substantial number of articles on instruments and instrumentation have been published in the scientific literature. Although interest in the effects of instrumentation on intracanal infection is not new, it is obvious that during the last few years a renewed focus of interest has appeared on the relationship between instrumentation and infection control in the root canal. The ongoing discussion in international endodontics about one-appointment therapy in the treatment of apical periodontitis has naturally further motivated the newly emerged research activities. The goal of this review is to gather the relevant and most recent literature and provide an updated analysis of the effect of preparation (instrumentation and irrigation) on the microbial infection in the necrotic root canal.

Eradication of endodontic infection by instrumentation and irrigation solutions

Objectives: The aim of this study was to investigate the root canal microbiota of primary and secondary root-infected canals and the association of constituent species with specific endodontic signs and symptoms.

Methods:  Microbial samples were taken from 60 root canals, 41 with necrotic pulp tissues (primary infection) and 19 with failed endodontic treatment (secondary infection). Strict anaerobic techniques were used for serial dilution, plating, incubation and identification.

Results:  A total of 224 cultivable isolates were recovered belonging to 56 different bacterial species. Individual root canals yielded a maximum of 10 bacterial species. Of the bacterial isolates, 70% were either strict anaerobes or microphilic. The anaerobes most frequently isolated were: Peptostreptococcus micros (35%), Fusobacterium necrophorum (23.3%), Fusobacterium nucleatum (11.7%), Prevotella intermedia/nigrescens (16.7%), Porphyromonas gingivalis (6.7%) and Porphyromonas endodontalis (5%). The root canal microflora of untreated teeth with apical periodontitis was found to be mixed, comprising gram-negative and gram-positive and mostly anaerobic microorganisms and usually containing more than 3 species per canal. On the other hand, facultative anaerobic and gram-positive bacteria predominated in canals with failed endodontic treatment, which harbored 1–2 species per canal. Suggested relationships were found between anaerobes, especially gram-negatives, and the presence or history of pain, tenderness to percussion and swelling (P < 0.05). In particular, associations were found between: a) pain (n = 29) and P. micros (P < 0.01), P. intermedia/nigrescens and Eubacterium spp. (both P < 0.05); b) history of pain (n = 31) and P. micros (P < 0.01) Porphyromonas and Fusobacterium spp. (P < 0.05); c) tenderness to percussion (n = 29) and Porphyromonas spp. (P < 0.01), Peptostreptococcus and Fusobacterium spp. (P < 0.001); d) swelling (n = 20) and Peptostreptococcus spp. (P < 0.01), Porphyromonas and Enterococcus spp. (P < 0.05); e) wet canals (n = 33) and Porphyromonas and Fusobacterium spp. (P < 0.05); f) purulent exudate (n = 20) and Porphyromonas, Peptostreptococcus and Fusobacterium spp. (P < 0.05); previous endodontic treatment and Enterococcus faecalis, Streptococcus spp., P. micros, F. necrophorum (P < 0.05).

Conclusions:  Our findings indicate potential complex interactions of species resulting in characteristic clinical pictures which cannot be achieved by individual species alone. They also indicate that the microbiota of primary infected canals with apical periodontitis differs in number and in species from the secondary infected canals by using the culture technique.

Microbiological examination of infected dental root canals

Current state of Fe-Mn-Al-C low density steels

Effect of grain size on tensile properties of fine-grained metastable β titanium alloys fabricated by stress-induced martensite and its reverse transformations

Objectives. Recent molecular approaches have revealed that fastidious organisms such as Bacteroides forsythus and oral treponemes were frequently found in root canals with apical periodontitis. The purpose of this study was to identify the isolates of oral spirochetes at the species level in endodontic infections and to determine their association with B forsythus and Porphyromonas gingivalis. Study design. Seventy-nine teeth with apical periodontitis were selected for this study. After sampling from the root canals aseptically, polymerase chain reaction amplification for the 16S rRNA gene was performed with eubacterial universal primers. Subsequently, dot-blot hybridization was performed with 8 species-specific oligonucleotide probes. The microbial associations were analyzed by using the odds ratio. Results. The most frequently found species was P gingivalis (27.4%), followed by Treponema maltophilum (26%), B forsythus (16.4%), and Treponema socranskii (2.7%). Other treponemes, including Treponema denticola, were not detected in our samples. Significant microbial associations were identified between T maltophilum, B forsythus, and P gingivalis by performing analysis with the odds ratio. Conclusion. Our results indicate that T maltophilum should be included in etiologic studies of endodontic diseases. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2001;92:329-34)

Identification of oral spirochetes at the species level and their association with other bacteria in endodontic infections

Objectives The purpose of this study was to compare the gutta-percha–filled area in oval canals while varying the temperature and penetration depth of the System B plugger. Study design Seventy-five resin blocks, with artificially created oval canals, were obturated by using a continuous wave technique. In groups 1, 2, and 3, the plugger was introduced to a depth of 4 mm from the apex at set temperatures of 100, 200, and 350°C, respectively. In group 4, the plugger was inserted to a depth of 2 mm from the apex at a set temperature of 200°C. Group 5 was obturated in the same way as group 2, and then an additional cold plugging was performed to a depth of 3 mm from the apex. The cross sections of the obturated canals were photographed, and the percentage of the gutta-percha–filled area (PGP) was measured. Results No significant differences were found between the 3 different temperature settings (P > .05). At 1 mm from the apex, group 4 showed the highest PGP (95.57% ± 6.86), followed by group 5 (84.72% ± 12.19), and group 2 (67.33 ± 13.03) (P Conclusion In artificially created oval canals, plugger temperature within the range used in this study did not affect the PGP. However, the penetration depth of the plugger was significantly related to PGP.

Effect of different temperatures and penetration depths of a System B plugger in the filling of artificially created oval canals.

Solidification behavior and solid-state transformation were investigated in Fe-Mn-Al-C lightweight steel. The solidification mode of the Fe-9.3Mn-5.6Al-0.2C (wt.%) lightweight steel was predicted to be the F mode (liquid → liquid + δ-ferrite → δ-ferrite → δ-ferrite + γ-austenite), according to the classification of the solidification modes of stainless steels. However, the microstructures of an ingot of the lightweight steel showed that the solidification occurred by the FA mode (liquid → liquid + δ-ferrite → liquid + δ-ferrite + γ-austenite → δ-ferrite + γ-austenite). To examine the difference between predicted and actual solidification modes, some specimens were annealed at various temperatures ranging from 1200°C to 1450°C for 10 min and then quenched. The microstructures of the annealed specimens exhibited that there were the narrow ranges of single δ-ferrite and solidification sections. This result indicates that the solidification mode of the present steel was the F mode, matching well with the predicted solidification mode. The reason for the FA mode, which was observed in the ingot, was because the liquid passed by a narrow solidification section and a single δ-ferrite region, and it directly entered the dual-phase region of δ-ferrite and γ-austenite during cooling.

The Solidification Mode of Fe-Mn-Al-C Lightweight Steel

The cariostatic effect of fluoride had been established by many epidemiologic and experimental studies. But, there are still different views on the mechnism of cariostasis and remineralization, especially about the proper fluoride concentration. The purpose of this study is to ascertain the remineralization of caries lesion and influence of fluoride concentration which affect remineralization by a study based on dynamic mechanism. The subjects, sound permanent teeth without demineralization or crack, were immersed in lactic acid buffered demineralization solution for 4 days. Dental caries with surface zone and subsurface lesion were artificially produced. All specimens were immersed in lactic acid buffered remineralization solution which had fluoride concentrations of 1 ppm, 2 ppm, 3 ppm for 10days. Final conclusions were obtained by observing the specimens for every 10 days under polarized microscopy. 1. Remineralization of caries lesion as well as demineralization of enamel were produced by changing the degree of saturation of lactic acid buffer solution. 2. Remineralization of caries lesion was facillitated by fluoride ion in lactic acid buffer solution. but, remineralization of the entire caries lesion was not increased as fluoride ion concentration increased.

The influence of fluoride on remineralization of artificial dental caries

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