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Biomedical subjects

Asgeir Sigurdsson

Publications and source records attributed to Asgeir Sigurdsson.

At least 19 recordsLinked to original sources
PubMed2024

Genome-Wide Association Study of Accessory Atrioventricular Pathways.

IMPORTANCE: Understanding of the genetics of accessory atrioventricular pathways (APs) and affiliated arrhythmias is limited. OBJECTIVE: To investigate the genetics of APs and affiliated arrhythmias. DESIGN, SETTING, AND PARTICIPANTS: This was a genome-wide association study (GWAS) of APs, defined by International Classification of Diseases (ICD) codes and/or confirmed by electrophysiology (EP) study. Genome-wide significant AP variants were tested for association with AP-affiliated arrhythmias: paroxysmal supraventricular tachycardia (PSVT), atrial fibrillation (AF), ventricular tachycardia, and cardiac arrest. AP variants were also tested in data on other heart diseases and measures of cardiac physiology. Individuals with APs and control individuals from Iceland (deCODE Genetics), Denmark (Copenhagen Hospital Biobank, Danish Blood Donor Study, and SupraGen/the Danish General Suburban Population Study [GESUS]), the US (Intermountain Healthcare), and the United Kingdom (UK Biobank) were included. Time of phenotype data collection ranged from January 1983 to December 2022. Data were analyzed from August 2022 to January 2024. EXPOSURES: Sequence variants. MAIN OUTCOMES AND MEASURES: Genome-wide significant association of sequence variants with APs. RESULTS: The GWAS included 2310 individuals with APs (median [IQR] age, 43 [28-57] years; 1252 [54.2%] male and 1058 [45.8%] female) and 1 206 977 control individuals (median [IQR] year of birth, 1955 [1945-1970]; 632 888 [52.4%] female and 574 089 [47.6%] male). Of the individuals with APs, 909 had been confirmed in EP study. Three common missense variants were associated with APs, in the genes CCDC141 (p.Arg935Trp: adjusted odds ratio [aOR], 1.37; 95% CI, 1.24-1.52, and p.Ala141Val: aOR, 1.55; 95% CI 1.34-1.80) and SCN10A (p.Ala1073Val: OR, 1.22; 95% CI, 1.15-1.30). The 3 variants associated with PSVT and the SCN10A variant associated with AF, supporting an effect on AP-affiliated arrhythmias. All 3 AP risk alleles were associated with higher heart rate and shorter PR interval, and have reported associations with chronotropic response. CONCLUSIONS AND RELEVANCE: Associations were found between sequence variants and APs that were also associated with risk of PSVT, and thus likely atrioventricular reentrant tachycardia, but had allele-specific associations with AF and conduction disorders. Genetic variation in the modulation of heart rate, chronotropic response, and atrial or atrioventricular node conduction velocity may play a role in the risk of AP-affiliated arrhythmias. Further research into CCDC141 could provide insights for antiarrhythmic therapeutic targeting in the presence of an AP.

Humans↗
PubMed2006

A common variant associated with prostate cancer in European and African populations.

With the increasing incidence of prostate cancer, identifying common genetic variants that confer risk of the disease is important. Here we report such a variant on chromosome 8q24, a region initially identified through a study of Icelandic families. Allele -8 of the microsatellite DG8S737 was associated with prostate cancer in three case-control series of European ancestry from Iceland, Sweden and the US. The estimated odds ratio (OR) of the allele is 1.62 (P = 2.7 x 10(-11)). About 19% of affected men and 13% of the general population carry at least one copy, yielding a population attributable risk (PAR) of approximately 8%. The association was also replicated in an African American case-control group with a similar OR, in which 41% of affected individuals and 30% of the population are carriers. This leads to a greater estimated PAR (16%) that may contribute to higher incidence of prostate cancer in African American men than in men of European ancestry.

Alleles↗
PubMed2005

Associations among four modalities of experimental pain in women.

UNLABELLED: The aim of this study was to investigate the associations among 4 measures of pain induction procedures in 244 healthy women. The procedures were (1) pressure pain threshold assessed over the temporalis muscles, masseter muscles, temporomandibular joints, and the wrists; (2) C fiber-mediated heat pain threshold/tolerance assessed on the skin over the forearm, cheek, and dorsal aspect of the foot; (3) temporal summation of C fiber-mediated heat pain; and (4) ischemic pain threshold/tolerance. Strong associations among pressure pain thresholds at the 4 sites examined (rho = 0.7 to 0.8, P values < or = .001) and among heat pain threshold/tolerance values at the 3 sites examined (rho = 0.6 to 0.9, P values < or = .001) were observed. Pressure pain threshold was moderately correlated with each of the heat pain threshold/tolerance values (rho = 0.2 to 0.4, P values < or = .001). Ischemic pain threshold/tolerance was moderately associated with each of the pressure and heat pain measures (rho = 0.2 to 0.3, P values < or = .05 to .001). Derived measures of the temporal summation of heat pain did not correlate strongly with threshold or tolerance measures of pressure, ischemic, or heat pain. We concluded (1) that for a specific pain modality, the correlation between threshold and tolerance values across anatomic sites is high, and (2) that measures of pressure, ischemic, and thermal pain threshold/tolerance are significantly correlated, although the strength of these associations is moderate. These findings demonstrate that a battery of pain-assessing procedures is required to determine an individual's pain sensitivity profile or phenotype. PERSPECTIVE: By investigating the relationship between pain sensitivity produced by different forms of stimuli, this study demonstrates that a battery of tests should be used to assess an individual's pain sensitivity and one should be careful in making inferences about an individual's sensitivity to pain by using only one pain modality.

Adolescent↗
PubMed2005

Reduction of intracanal bacteria using GT rotary instrumentation, 5.25% NaOCl, EDTA, and Ca(OH)2.

This study was conducted to determine the bacterial reduction using Profile GT files and a strict irrigation protocol utilizing 5.25% NaOCl and EDTA. The additive antibacterial effect of Ca(OH)2 was also evaluated. In addition, the study compared the bacterial reduction with the GT protocol versus larger instrumentation. Thirty-one subjects with apical periodontitis were recruited. Bacterial samples were taken upon access (S1), after instrumentation and a strict irrigation protocol (S2), and following >1 wk of Ca(OH)2 (SC). A log10 transformation of colony forming units was done since sample bacterial counts are not normally distributed. At S1, 93.55% of canals sampled bacteria. At S2, 52.72% of the cases sampled bacteria. At SC, 14% of the cases cultured bacteria. The McNemar test showed a significant reduction (p<0.0009) in bacteria between S1 and S2. This was also true between S2 and SC (p<0.0019). It was concluded the GT protocol significantly reduced the number of bacteria in the canal but failed to render the canal bacteria free in more than half of the cases Ca(OH)2 application significantly further reduced bacteria. Lastly, large apical instrumentation removed more bacteria than small apical instrumentation.

Bacteria, Anaerobic↗
PubMed2005

Disinfection of immature teeth with a triple antibiotic paste.

This study assessed the efficacy of a triple antibiotic paste in the disinfection of immature dog teeth with apical periodontitis. The canals were sampled before (S1) and after (S2) irrigation with 1.25% NaOCL and after dressing with a triple antibiotic paste (S3), consisting of metronidazole, ciprofloxacin, and minocycline. At S1, 100% of the samples cultured positive for bacteria with a mean CFU count of 1.7 x 10. At S2, 10% of the samples cultured bacteria-free with a mean CFU count of 1.4 x 10. At S3, 70% of the samples cultured bacteria-free with a mean CFU count of only 26. Reductions in mean CFU counts between S1 and S2 (p < 0.0001) as well as between S2 and S3 (p < 0.0001) were statistically significant. These results indicate the effectiveness of a triple antibiotic paste in the disinfection of immature teeth with apical periodontitis.

Animals↗
PubMed2004

Genetic basis for individual variations in pain perception and the development of a chronic pain condition.

Pain sensitivity varies substantially among humans. A significant part of the human population develops chronic pain conditions that are characterized by heightened pain sensitivity. We identified three genetic variants (haplotypes) of the gene encoding catecholamine-O-methyltransferase (COMT) that we designated as low pain sensitivity (LPS), average pain sensitivity (APS) and high pain sensitivity (HPS). We show that these haplotypes encompass 96% of the human population, and five combinations of these haplotypes are strongly associated (P=0.0004) with variation in the sensitivity to experimental pain. The presence of even a single LPS haplotype diminishes, by as much as 2.3 times, the risk of developing myogenous temporomandibular joint disorder (TMD), a common musculoskeletal pain condition. The LPS haplotype produces much higher levels of COMT enzymatic activity when compared with the APS or HPS haplotypes. Inhibition of COMT in the rat results in a profound increase in pain sensitivity. Thus, COMT activity substantially influences pain sensitivity, and the three major haplotypes determine COMT activity in humans that inversely correlates with pain sensitivity and the risk of developing TMD.

Adolescent↗
PubMed2004

Catastrophizing predicts changes in thermal pain responses after resolution of acute dental pain.

UNLABELLED: Substantial research suggests that coping strategies, especially catastrophizing, play an important role in shaping adjustment to chronic pain. Although laboratory and clinical studies both suggest that catastrophizing enhances pain, the interaction of catastrophizing and clinical pain on pain sensitivity has received little attention. The present study evaluated the extent to which catastrophizing influenced laboratory thermal pain responses during and after the resolution of acute dental pain. Thermal pain threshold and tolerance, as well as self-reported catastrophizing, were determined in 46 dental patients (15 men and 31 women) experiencing pain as a result of acute pulpitis. All subjects participated in 2 experimental sessions; the first took place immediately before endodontic treatment for relief of pulpal pain, and the second session occurred when patients were pain free, approximately 1 to 2 weeks later. Thermal pain thresholds increased on resolution of acute dental pain, whereas levels of catastrophizing did not change from pretreatment to post-treatment. Catastrophizing was unrelated to thermal pain responses in the presence of acute dental pain (ie, during the first session). Once patients were pain free, catastrophizing showed significant inverse associations with measures of thermal pain threshold and tolerance. In addition, catastrophizing was a robust predictor of changes in thermal pain responses across sessions, with higher baseline catastrophizing predicting reductions or relatively smaller increases in pain threshold and tolerance after successful treatment of acute pain. These data suggest that catastrophizing is prospectively associated with enhanced sensitivity to and reduced tolerance for thermal pain. The use of catastrophizing as a coping strategy might interfere with the resolution of sensitization after cessation of an acutely painful condition, or it might be associated with magnified experimental pain responses across time. PERSPECTIVE: The findings of the present study suggest that, in some instances, different ethnic groups and genders may use the same descriptors to report different levels of pain. In the context of clinical pain assessment, it may be important to consider the possibility that descriptions of painful sensations reflect, in part, demographic characteristics.

Adaptation, Psychological↗
PubMed2004

Effects of saliva contamination on resin-resin bond strength.

OBJECTIVE: The purpose of this study is to evaluate the effects of saliva contamination on microtensile bond strength (microTBS) between resin interfaces and to determine which decontamination methods best re-established the original resin-resin bond strength. MATERIALS AND METHODS: Ninety-six light-cured resin composite cylinders of Z-250, Renew, Clearfil APX, and Pertac II were randomly divided into six groups. For each material, one group of specimens was not contaminated, serving as the control. For the other specimens, the top surface of each block was treated with saliva that was slowly dried (Treatment 1); dried forcefully (Treatment 2); slowly dried, rinsed, and dried (Treatment 3); slowly dried, rinsed, dried, and bonded with Single Bond, One-Step, Clearfil SE Bond, or Prompt L-Pop (Treatment 4); or slowly dried, but not rinsed, and bonded using the same adhesives (Treatment 5). Two 2-mm increments of resin composite were applied and light-cured. After 24 h, the assemblies were trimmed for microtensile bond testing and were loaded to failure at 1 mm/min. Data were analyzed using two-way and one-way ANOVA and Fisher's PLSD (p<0.05). RESULTS: Control values ranged from 45.1 MPa for Pertac II to 71.5 MPa for APX. Treatment 1 caused significant reduction in resin-resin bond strength for all materials tested but for two of the materials in treatment 2. Pertac II was the only material that did not show a statistical difference from control group for treatment 3. Treatment 4 re-established the control values for Z-250 and Renew and treatment 5 was the only one to show no statistical difference for all materials tested. SEM observation revealed a smooth surface in treatment 1, but treatment 3 showed a few craters. Treatment 4 and 5 showed a mixture of cohesive failure in the composite and adhesive. SIGNIFICANCE: The most reliable method for decontaminating saliva from resin surfaces involves the application of adhesives.

Adhesiveness↗
PubMed2004

Effects of blood contamination on resin-resin bond strength.

OBJECTIVE: Incremental placement and curing of resin composites has been recommended. However, this requires longer operating time, and therefore, increased risk of contamination. The purpose of this study was to evaluate the effects of blood contamination on microtensile bond strengths (microTBS) between resin interfaces and to determine the best decontamination method to re-establish the original resin-resin bond strength. MATERIALS: The top surfaces of 64, 4-mm composite blocks (Z-250, Renew, APX, Pertac II) were untreated as the control, or were treated as follows: blood applied and dried on the surface (Treatment 1), blood applied, rinsed, dried (Treatment 2), blood applied, rinsed, and an adhesive applied (Single Bond, One-Step, Clearfil SE, Prompt L-Pop) (Treatment 3). Fresh composite was applied and light-cured in 2-mm increments. After 24 h storage in water, the specimens were sectioned into 0.7-mm thick slabs, trimmed to a cross-sectional area of 1 mm(2), and loaded to failure at a crosshead speed of 1 mm/min using an Instron universal testing machine. Data were analyzed using two-way ANOVA and Fisher's PLSD test (p<0.05). RESULTS: Control values ranged from 45.1 MPa for Pertac II to 71.5 MPa for APX. Untreated blood contamination resulted in resin-resin bond strengths of only 1.0-13.1 MPa. Rinsing raised bond strengths to over 40 MPa for each material. Use of an adhesive further increased bond strengths except for Pertac II. SIGNIFICANCE: Rinsing blood from contaminated surfaces increases the resin-resin bond strength significantly and the application of an appropriate adhesive increases the bond strength to control levels.

Analysis of Variance↗
PubMed2004

Pulp revascularization of replanted immature dog teeth after treatment with minocycline and doxycycline assessed by laser Doppler flowmetry, radiography, and histology.

This study investigated the effect of topical antibiotic treatment on pulp revascularization in replanted teeth. Thirty-four immature teeth were selected from three young dogs. Baseline radiographs and laser Doppler flowmetry (LDF) readings were obtained. Specimens were randomly divided into four groups: Thirty-eight teeth were extracted, kept dry for 5 min, and either (Group 1) covered with minocycline mixture (G1, n = 11), (Group 2) soaked in doxycycline (G2, n = 11), or (Group 3) soaked in saline (G3-negative control, n = 6), and replanted. Teeth in Group 4 were not extracted (positive control, n = 6). Postoperative radiographs and LDF readings were obtained for 2 months after replantation. After sacrifice, the jaws were collected and processed for light microscopy. Pre- and postreplantation LDF readings and radiographs, and histologic findings were analyzed to assess revascularization. Pulp revascularization occurred in 91% (G1), 73% (G2), and 33% (G3) of the specimens. In conclusion, minocycline facilitates pulp revascularization in replanted immature teeth after replantation.

Animals↗
PubMed2004

Incidence of cerebral concussions associated with type of mouthguard used in college football.

Controversy exists among sports dentists as to whether or not a 'custom made' mouthguard is more effective in reducing the incidence of cerebral concussion than the boil-and-bite 'non-custom made' mouthguard. While members on each side remain steadfast in their opinion, not a single epidemiological study has been conducted to investigate the effect of type of mouthguard worn on the incidence of cerebral concussion. The aim of this study was to determine if there was a difference between the type of mouthguard worn and the incidence of cerebral concussions among National Collegiate Athletic Association (NCAA) Division I-A football players. During the 15-week 2001 college football season, trainers entered, via an interactive web site, weekly data for each game and practice sessions for the preceding week. Eighty-seven (76%) out of a possible 114 Division I teams participated. A total of 506 297 athletic exposures were recorded; 369 brain concussions were reported. The incidence of cerebral concussions per 1000 exposures was 0.73. Utilizing a risk ratio with a 95% confidence interval, no statistical difference occurred in the incidence of cerebral concussions between football players wearing custom made versus non-custom made mouthguards (0.990,1.750). In this study, there was no advantage of wearing a custom made mouthguard over a boil-and-bite mouthguard to reduce the risk of cerebral concussion in football players.

Brain Concussion↗
PubMed2004

Success of an alternative for interim management of irreversible pulpitis.

BACKGROUND: Extraction and endodontic therapy are treatment options for irreversible pulpitis. Extraction often is chosen for financial reasons. The authors conducted a study to investigate an alternative interim therapy. METHODS: The authors recruited patients (N = 73) with irreversible pulpitis and whose teeth were restorable but who opted for extraction owing to financial reasons. After undergoing pulpotomy, the teeth were restored by random assignment with one of two intermediate restorative materials: Caulk IRM (Dentsply Caulk, Milford, Del.) (Group I, n = 38) or an IRM base with glass ionomer core (Fuji IX GP, GC America, Alsip, Ill.) (Group II, n = 35). The authors monitored the teeth over six and 12 months for pain, integrity of restoration and radiographic periapical status by densitometric analysis. RESULTS: By six months, 10 percent of subjects remaining in the study (Group I, n = 27; Group II, n = 25) reported pain; by 12 months, 22 percent (Group I, n = 22; Group II, n = 18) reported pain. A two-tailed Fisher exact test showed no significant difference (P > or = .05) between groups at either time interval. No apical radiographic change was noted in 49 percent of teeth at six months (Group I, n = 18; Group II, n = 19) and 42 percent at 12 months (Group I, n = 16; Group II, n = 15). Chi2 analysis demonstrated no significant differences (P > or = .05) between groups. Seven of 22 restorations in Group I and four of 18 in Group II required repair at 12 months with no statistical difference (chi2 analysis, P > or = .05). CONCLUSIONS: The interim treatment of eugenol pulpotomy using either restorative material reliably prevented pain for six months. For longer periods, both restorations may require repair. CLINICAL IMPLICATIONS: This option should preserve the integrity of the arch and extend the use of the tooth while the patient finds the means to finance complete endodontic treatment.

Absorptiometry, Photon↗
PubMed2003

Comparison of reporting systems to determine concussion incidence in NCAA Division I collegiate football.

OBJECTIVE: To determine the incidence of concussion during the 2001 Division I-A college football season through utilization of the Internet. DESIGN: Prospective Internet survey. SETTING: Internet Web site. PARTICIPANTS: Head athletic trainers from Division I-A collegiate football programs. MAIN OUTCOME MEASURES: During the 2001-2002 football season, head athletic trainers from 87 Division I-A football programs agreed to use an Internet Web site to submit weekly data on the number of athlete exposures and concussions. RESULTS: A total of 373 concussions were reported over the course of a season in both practices and games combined. Of these concussions, 256 (68.6%) occurred during games, and 117 (31.4%) occurred during practice. The injury rate per 1,000 athletic exposures was 5.56 in games and 0.25 in practices. There were 230 grade 1 (61.7%), 134 grade 2 (35.9%), and 9 grade 3 (2.4%) concussions reported. There was a significant (p < 0.01) difference found between the total concussion injury rate and game concussion injury rate when comparing the Internet and the NCAA injury data collection methods. CONCLUSIONS: The results of this study suggest an underreporting of concussions using the NCAA Injury Surveillance System and demonstrate that the Internet is a simple and effective tool for data collection.

Adult↗
PubMed2002

Group differences in pain modulation: pain-free women compared to pain-free men and to women with TMD.

Previously reported differences in sensitivity to experimental pain stimuli between the sexes, as well as between temporomandibular disorder (TMD) patients and healthy control subjects, may be attributable in part to group differences in two pain modulatory mechanisms: the baroreceptor reflex arc and the endogenous opioid system. Twenty-two pain-free (PF) men, 20 PF women and 20 women with TMD underwent two testing sessions in which heat pain and ischemic arm pain threshold and tolerance were measured during both sessions, but followed relaxation during one session and laboratory stress tasks during the other. Blood pressure (BP) and plasma -endorphin (E) concentration were measured during a baseline rest and during the stress or relaxation periods. PF men's threshold and tolerance for heat pain, but not for ischemic pain, exceeded that of PF women's during both sessions. PF women and TMD women did not differ in sensitivity to either pain modality; however, significantly lower ischemic pain threshold (IPTh) was linked to oral contraceptive use in PF women but not TMD patients. In the men alone, higher baseline systolic BP (SBP) was correlated with higher heat pain threshold on both days and heat pain tolerance on the stress day. Conversely, in TMD women, higher baseline SBP was correlated with lower ischemic pain tolerance (IPTol) on both days; BP and pain sensitivity were not related in PF women. In men, but not in PF or TMD women, stress systolic and diastolic BP were positively correlated with heat pain threshold and tolerance and higher diastolic reactivity to stress were correlated with higher heat pain and IPTh and tolerance. On the stress day, higher baseline E level was strongly associated with higher IPTol in PF women but marginally associated with lower IPTol in TMD women. Thus, it appears that a BP-related analgesic mechanism (probably baroreceptor-mediated) predominates in PF men, while an endogenous opioid mechanism predominates in PF women. Stress enhances the expression of these central mechanisms. Female TMDs appear unable to effectively engage normal pain-inhibitory systems; opioid receptor desensitization and/or downregulation are probably implicated, because TMDs' production of E appears normal.

Adult↗
PubMed2002

Trigeminal c-Fos expression and behavioral responses to pulpal inflammation in ferrets.

Injury to peripheral dental tissues evokes dynamic alternations in central sensory pathways. We have previously reported that transient stimulation of the dental pulp with noxious heat evokes the induction of the immediate early gene product Fos in the transitional region between subnucleus interpolaris and caudalis (Vi/Vc) and subnucleus caudalis (Vc). A question arises as to whether similar changes occur in response to inflammation to the tooth pulp. In this study, the effects of pulpal inflammation produced by bacterial lipopolysaccharide (LPS) on face-grooming behavior and trigeminal Fos expression were examined. Face-grooming behaviors were recorded daily for 3 days pre- and 24, 48 and 72 h post- LPS or saline application. All animals were perfused 72 h post- LPS or saline application. Brainstems were processed for Fos-like immunoreactivity (Fos-LI). Teeth were processed for H&E staining. Histological examination of LPS-treated teeth revealed features of an acute pulpitis. Moreover, LPS-treated animals showed greater face-grooming activity (i.e. tongue protrusions) directed to the injured tooth than the sham-operated group. The number of Fos-positive neurons was greater in the trigeminal subnucleus caudalis (Vc) and the transitional regions (Vi/Vc) in LPS-treated animals compared with sham-operated animals, and greater in the deeper laminae than the superficial laminae of each trigeminal region. LPS treatment did not evoke Fos expression in the rostral trigeminal regions above Vi/Vc. These results demonstrate that LPS-induced pulpal inflammation results in significant alterations in the Vi/Vc and Vc, and such changes may underlie the observed nociceptive behavioral responses and may play an important role in producing a symptomatic pulpitis in humans.

Animals↗
PubMed2002

Temporomandibular disorder and optimism: relationships to ischemic pain sensitivity and interleukin-6.

The current study examined patients with temporomandibular disorders (TMD) (n=20) and pain-free controls (n=28) under stress and relaxation conditions. Interleukin-6 (IL-6), norepinephrine and epinephrine (NE and E) were measured both before and during each of two conditions: a non-stressful relaxation period and a speech stressor. Ischemic pain sensitivity was also assessed after each of these conditions. Optimism (Life Orientation Test (LOT)), which has been associated with better outcomes in relationship to health and disease, was also evaluated in relationship to ischemic pain tolerance and unpleasantness ratings as well as to IL-6 levels under the two conditions. Regression analysis determined the unique contribution of each predictor and the interaction between Optimism and Group (TMD versus controls) after controlling for gender and blood pressure. During stress, IL-6 levels appeared to parallel NE with only controls displaying significant increases. After controlling for depressed mood, TMD patients as a whole showed a significantly blunted response in IL-6 levels produced during stress as compared to controls (beta=0.31*). Although TMD subjects as a whole did not show the expected greater pain sensitivity to the ischemic task, those displaying a less optimistic style did exhibit lower pain tolerance times (beta=-0.61*) and higher pain unpleasantness ratings (beta=0.48*), compared with low optimism controls and high optimism TMD patients. Less optimistic TMD patients also had higher NE and IL-6 levels during stress than other TMD patients, while optimism was unrelated to responses in controls (*P<0.05).

Adult↗
PubMed2002

The effectiveness of increased apical enlargement in reducing intracanal bacteria.

It has been suggested that the apical portion of a root canal is not adequately disinfected by typical instrumentation regimens. The purpose of this study was to determine whether instrumentation to sizes larger than typically used would more effectively remove culturable bacteria from the canal. Forty patients with clinical and radiographic evidence of apical periodontitis were recruited from the endodontic clinic. Mandibular cuspids (n = 2), bicuspids (n = 11), and molars (mesial roots) (n = 27) were selected for the study. Bacterial sampling was performed upon access and after each of two consecutive instrumentations. The first instrumentation utilized 1% NaOCI and 0.04 taper ProFile rotary files. The cuspid and bicuspid canals were instrumented to a #8 size and the molar canals to a #7 size. The second instrumentation utilized LightSpeed files and 1% NaOCl irrigation for further enlargement of the apical third. Typically, molars were instrumented to size 60 and cuspid/bicuspid canals to size 80. Our findings show that 100% of the cuspid/bicuspid canals and 81.5% of the molar canals were rendered bacteria-free after the first instrumentation sizes. The molar results improved to 89% after the second instrumentation. Of the (59.3%) molar mesial canals without a clinically detectable communication, 93% were rendered bacteria-free with the first instrumentation. Using a Wilcoxon rank sum test, statistically significant differences (p < 0.0001) were found between the initial sample and the samples after the first and second instrumentations. The differences between the samples that followed the two instrumentation regimens were not significant (p = 0.0617). It is concluded that simple root canal systems (without multiple canal communications) may be rendered bacteria-free when preparation of this type is utilized.

Bacteria↗