Comparative analysis of endodontic pathogens using checkerboard hybridization in relation to culture

Background/Aim:  The purpose of this study was to detect bacterial species and to quantify the total number of bacteria from samples of infected root canals before (S1) and after chemo-mechanical preparation using 2% chlorhexidine (CHX) gel as auxiliary chemical substance (S2) and after 7 days of intracanal dressing (S3) to compare microbial changes.
Method:  Twenty-four teeth were selected for this study. Chemo-mechanical preparation was performed using 2% CHX gel, then three different intracanal medicaments [M1: Ca(OH)₂ paste; M2: 2% CHX gel; and M3: Ca(OH)₂ paste plus 2% CHX gel] were used for 7 days. Checkerboard DNA–DNA hybridization was performed to detect 40 bacterial species. Aerobic and anaerobic culture techniques were used to determine the bacterial community by counting the colony-forming units (CFU).
Results:  The species most frequently identified by checkerboard in S1 were: Fusobacterium nucleatum ssp . polymorphum , Treponema socranskii ssp. socranskii , Parvimonas micra and Enterococcus faecalis. In S2 and S3 a total of eight different species were identified; and only one of them was gram-positive ( E. faecalis ). Microorganisms were not identified after use of M2 for 7 days. The quantification obtained on agar plates ranged from 4 × 10⁵ to 2.6 × 10⁶ CFU/ml in S1, mean CFU was reduced by 99.96% in S2, and there was no statistical difference between the CFU in S2 and S3.
Conclusion:  The antibacterial effect of the mechanical preparation supplemented by the use of an antibacterial auxiliary substance greatly reduced the microorganisms in the main root canal.     

Bacterial leakage along the implant-abutment interface of premachined or cast components

In recent clinical studies, contamination of the inner parts of dental implants through bacterial penetration along the implant components has been observed. The aim of the present in-vitro study was to investigate leakage of Fusobacterium nucleatum through the interface between implants and premachined or cast abutments. Both premachined (n=10) and cast (n=10) implant-abutment assemblies were inoculated with 3.0 microL of microbial inoculum. The assemblies were completely immersed in 5.0 mL of tryptic soy broth culture medium to observe leakage at the implant-abutment interface after 14 days of anaerobic incubation. Bacterial growth in the medium, indicative of microbial leakage, was found only in 1 out of 9 samples (11.1%) in each group. Both premachined and cast abutments connected to external hexagonal implants provide low percentages of bacterial leakage through the interface in in vitro unloaded conditions if the manufacturer's instructions and casting procedures are properly followed.     

Occlusion for fixed prosthodontics: a historical perspective of the gnathological influence

This article addresses the historical perspective of the gnathological influence upon the concepts of occlusion for fixed prosthodontics. A critical assessment and subsequent scientific validation of occlusal theories require an understanding of their evolution in the formative years and the subsequent development of effective models for clinical practice. While gnathological concepts offer a structured methodology for prosthodontic procedures, further research is needed to corroborate current occlusal treatment approaches. This review focuses on the "classic" fixed prosthodontic literature and the currently available scientific literature involving fixed prosthodontic dentate occlusion and gnathology. A MEDLINE search was performed to identify English-language peer-reviewed publications spanning the last 56 years, along with an extensive hand search for years prior. Electronic searches of the literature were performed in MEDLINE using the key words: case series, clinical trials, cohort studies, fixed partial denture occlusion, dental occlusion, dental occlusion research, centric relation, incisal guidance, maximal intercuspation, occlusal vertical dimension, and occlusion, in various combinations to obtain potential references for review. A total of 10,382 English-language nonduplicate titles were obtained for 1950-2006 for the key words "dental occlusion." Other key word searches produced smaller numbers of articles, many of which were duplicates due to multiple searches and were subsequently eliminated. Manual hand searching of the MEDLINE reference list and other journals of interest was performed to identify any articles missed in the original search. Articles were included for review if they contained emerging occlusal theories, new technologies, or occlusal studies that included multiple subjects in contrast to case reports.     

Systemic antibiotics and tooth loss in periodontal disease

Systemic antibiotics have been recommended for the treatment of destructive periodontal disease. Our goal was to relate antibiotic use for medical or dental reasons to subsequent tooth loss in a cohort of 12,631 persons with destructive periodontal disease. After adjustment for age, smoking, and other confounders, the dispensing of antibiotics for 1-13 days, 14-20 days, or 21 or more days was not associated with reduced tooth loss [Adjusted rate ratio (RR) = 1.0; 95% Confidence Interval (CI) = 0.8-1.1; RR = 1.2; 95% CI = 0.9-1.4, and RR =1.2, 95% CI =1.0-1.3, respectively]. Numerous subgroup analyses were consistent with these overall null findings, with two exceptions: Longer courses of tetracyclines were associated with reduced tooth loss among persons receiving periodontal care, and penicillin was associated with reduced tooth loss among persons with more severe disease. Long-term, larger randomized trials are needed to provide evidence that antibiotics reduce tooth loss when used in the management of destructive periodontal disease.     

Electric pulp testing: a review

Electric pulp testing (EPT) has been available for more than a century and used in dental practices worldwide. This article provides an overview of this diagnostic aid. The PubMed database from 1953 was used initially; the reference list for pulp testing featured 1071 articles, and for EPT identified 121 papers. A forward search was undertaken on these articles and using selected author names. Potentially relevant material was also sought in contemporary endodontic texts, while older textbooks on endodontics, operative dentistry and pain revealed historic information and primary research not found electronically. A short account of the innervation of the pulp is followed by an historic overview. Clinical considerations discussed include tooth isolation, glove wearing and tester electrode placement. Orthodontic treatment, pacemaker wearing and patient medications are considered. Research applications are also discussed. While EPT is valuable, no single pulp testing technique can reliably diagnose all pulp conditions. Careful collection of patient history regarding the problem tooth and prudent use of appropriate radiographs are also helpful. The shortcomings of electric tests, especially in the case of immature and concussed teeth, must be understood. The demeanour of the patient and the responses given by control teeth also require careful consideration.     

Temporomandibular joint adaptations following two-phase therapy: an MRI study

Authors – Wadhawan N, Kumar S, Kharbanda OP, Duggal R, Sharma R Aim – To document the alterations within the condyle‐glenoid fossa (C‐GF) complex and the positional changes of the glenoid fossa in the cranium after removable functional appliance therapy and after the completion of fixed appliance therapy. Setting and Sample – The Department of Orthodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India. The study sample consisted of 12 growing children (eight girls and four boys) between 10 and 14 years of age with skeletal Class II division 1 malocclusion selected on well defined criteria. Materials and Methods – All patients were treated with either the Twin Block or the Bionator appliance followed by fixed appliances. Mean total treatment duration was 28 months. The changes in and around the C‐GF complex were evaluated using MRI at pre‐treatment stage, after functional appliance therapy and at the completion of fixed mechanotherapy. Results – Forward condylar position within the glenoid fossa and articular disc retrusion with respect to the condylar head were statistically significant after functional appliance therapy. However, the condyles had a relatively concentric position within the glenoid fossa, while the articular disc resumed its pre‐treatment position at the end of the treatment. Linear measurements from the centre of the external auditory meatus to the post‐glenoid spine revealed a 1.3‐mm forward relocation of the post‐glenoid spine along the Frankfurt Horizontal plane. Conclusions – Forward relocation of the C‐GF complex seems to be one of the mechanisms of action of functional appliances, while the internal anatomic arrangement within the temporomandibular joint (TMJ) complex normalizes to its pre‐treatment position.     

Clinical, histological and microbiological study of hand-excavated carious dentine in extracted permanent teeth.

Changes in cultivable flora in dentine samples collected before and after hand excavation were examined in association with clinical status of the cavity surface, light microscopy and scanning electron microscopy (SEM). Thirty-five extracted permanent molar teeth with an occlusal caries lesion were excavated with hand instruments according to the atraumatic restorative treatment (ART) approach. Excavation pressure, dentine colour and consistency were recorded at the dentine-enamel junction (DEJ) prior to carious dentine removal and at the cavity floor after the final excavation; a microbiological sample of dentine was taken at both stages. Twelve restored teeth; six with positive and six with negative bacterial growth on the second sample, were selected for light microscopy and SEM. The hand-excavation removed tooth structure was soft, irreversibly damaged, dark and highly infected. Hand excavation reached dentine of increased hardness with a more normal colour to provide a sound structural base for restoration. Light and SEM examination of the cavity floor showed infected dentinal tubules in all 12 teeth examined. Linear logistic analysis showed a statistical association between light-yellow dentine on the cavity floor and an absence of bacterial growth (P = 0.006). This short-term in vitro study showed that caries-producing bacteria remained in dentine close to the cavity floor in 26/35 teeth despite clinical observations that indicated a suitably prepared cavity floor.     

Fracture strength of ceramic bracket tie wings subjected to tension

One of the most common areas of ceramic bracket fracture is within the tie-wing complex. When an archwire is ligated into position, tensile forces are placed under the tie wing. However, no study, to date, has focused specifically on the fracture resistance of the tie-wing complex. The aim of this study is to compare the tensile fracture strength of seven currently available ceramic brackets (Inspire, Fascination, Mystique, InVu, Clarity, Virage, and Luxi) as a function of bracket brand and bracket configuration, semitwin vs true-twin. Based on a power analysis of pilot data, 10 maxillary central incisor brackets per group were tested to failure with a tensile load placed directly under the distoincisal tie wing. The results ranged from a maximum mean fracture strength of 147.71 (5.87) MPa with Fascination brackets to a minimum mean fracture strength of 84.28 (7.01) MPa with Luxi brackets. The statistical analysis indicated a significant effect on fracture strength as a function of bracket brand (P < .05) and that semitwin brackets, Fascination, Mystique, and Virage, had significantly higher fracture strength than true-twin brackets, Clarity, lnVu, and Luxi (P < .05). Interestingly, the only monocrystalline bracket in the study, Inspire, could not be fractured using the investigation protocol. In fact, the steel ligature fixture wire would break before tie-wing fracture at a mean fixture failure of 198.65 MPa.