Objective Measurement of Patient’s Dental Anxiety by Galvanic Skin Reaction
H. John Caprara, DMD, Paul D. Eleazer, DDS, MS, Robert D. Barfield, DMD, and Scott Chavers, PhD
An In Vivo Comparison of Two Frequency-based Electronic Apex Locators
Aaron R. Welk, DMD, J. Craig Baumgartner, DDS, PhD, and J. Gordon Marshall, DMD
Elimination of Candida albicans Infection of the Radicular Dentin by Intracanal Medications
Jośe F. Siqueira, Jr., DDS, MSc, PhD, Isabela N. Rôças, DDS, MSc, Hélio P. Lopes, DDS, LD, Fernando A. C. Magalhães, and Milton de Uzeda, DDS, MSc, PhD
The Effect of Insertion Rates on Fill Length and Adaptation of a Thermoplasticized Gutta-Percha Technique
Marc E. Levitan, DDS, Van T. Himel, DDS, and Jeffrey B. Luckey, BS
Analysis of Continuous-Wave Obturation Using a Single-cone and Hybrid Technique
Garrett M. Guess, DDS, Kevin R. Edwards, DDS, Ming-Lung Yang, DDS, Mian K. Iqbal, BDS, MS, and Syngcuk Kim, PhD, DDS
Crown-Down Tip Design and Shaping
Teresa Ponce de Leon Del Bello, DDS, Nancy Wang, DDS, and James B. Roane, BS, DDS, MS
Identification of Resected Root-end Dentinal Cracks: A Comparative Study of Visual Magnification
C. Cornelious Slaton, DMD, Robert J. Loushine, DDS, R. Norman Weller, DMD, MS, M. Harry Parker, DDS, MS, W. Frank Kimbrough, DDS, MS, and David H. Pashley, DMD, PhD
Patterns of Vertical Root Fracture: Factors Affecting Stress Distribution in the Root Canal
Veera Lertchirakarn, MDSc, PhD, Joseph E. A. Palamara, PhD, and Harold H. Messer, MDSc, PhD
Finite Element Analysis and Strain-gauge Studies of Vertical Root Fracture
Veera Lertchirakarn, MDSc, PhD, Joseph E. A. Palamara, PhD, and Harold H. Messer, MDSc, PhD
Objective Measurement of Patient’s Dental Anxiety by Galvanic Skin Reaction
H. John Caprara, DMD, Paul D. Eleazer, DDS, MS, Robert D. Barfield, DMD, and Scott Chavers, PhD
The purpose of this study was to determine if anxiety can be measured objectively by skin conductance of a weak electric current. Three measurements were taken. First, a standardized dental-anxiety questionnaire was given to determine anxiety. Second, galvanic skin conductance was measured. Third, polygraph responses were recorded to three key questions from the questionnaire. Questionnaire scores of these key questions were used to create two groups: anxious and not-anxious. The three key questions were subjected to polygraph verification. In the first analysis patients were excluded if the polygraph test disclosed lying on any of the three key questions. The second analysis excluded liars on a question-by-question basis. The third analysis disregarded the polygraph. A statistically significant correlation was found between skin conductance and dental anxiety in all cases. Data seem to indicate that fear of injection is the most anxiety-producing aspect of modern dentistry.
An In Vivo Comparison of Two Frequency-based Electronic Apex Locators
Aaron R. Welk, DMD, J. Craig Baumgartner, DDS, PhD, and J. Gordon Marshall, DMD
The purpose of this study was to compare the accuracy of a two-frequency (Root ZX) and a five-frequency (Endo Analyzer Model 8005) electronic apex locator under clinical conditions. Thirty-two teeth planned for extraction were used. The coronal portion of each canal was flared using Gates Glidden drills and Orifice Shapers. The canals were irrigated with 2.6% sodium hypochlorite. A K-type file was used to determine a separate working length in each canal using the electronic apex locators. The teeth were extracted and the apical 4 mm of each root canal was exposed along the long axis of the tooth. Photographic slides of each canal were projected and the file position in relation to the minor diameter was determined by two investigators. The mean distance between the electronic apex locator working length and minor diameter was 1.03 mm for the Endo Analyzer and 0.19 mm for the Root ZX. A paired sample t test showed that the Endo Analyzer had significantly longer readings beyond the minor diameter than the Root ZX (p < 0.0001). The ability to locate the minor diameter (+ 0.5 mm) was 90.7% for the Root ZX and 34.4% for the Endo Analyzer Model 8005.
Elimination of Candida albicans Infection of the Radicular Dentin by Intracanal Medications
Jośe F. Siqueira, Jr., DDS, MSc, PhD, Isabela N. Rôças, DDS, MSc, Hélio P. Lopes, DDS, LD, Fernando A. C. Magalhães, and Milton de Uzeda, DDS, MSc, PhD
Fungi have been associated with cases of secondary or persistent root canal infections. The purpose of this study was to evaluate the effectiveness of four intracanal medications in disinfecting the root dentin of bovine teeth experimentally infected with Candiba albicans. Infected dentin cylinders were exposed to four different medications: calcium hydroxide/glycerin; calcium hydroxide/0.12% chlorhexidine digluconate; calcium hydroxide/camphorated paramonochlorophenol/glycerin; and 0.12% chlorhexidine digluconate/zinc oxide. Specimens were in contact with the medications for 1 h, 2 days, and 7 days. The viability of C. albicans after exposure was evaluated by specimen incubation in culture medium to compare the effectiveness of the medications in disinfecting dentin. Results showed that the specimens treated with calcium hydroxide/camphorated paramonochlorophenol/glycerin paste or with chlorhexidine/zinc oxide paste were completely disinfected after 1 h of exposure. Calcium hydroxide/glycerin paste only consistently eliminated C. albicans infection after 7 days of exposure. Calcium hydroxide mixed with chlorhexidine was ineffective in disinfecting dentin even after 1 week of medication exposure. Among the medications tested, the calcium hydroxide/camphorated paramonochlorophenol/glycerin paste and chlorhexidine digluconate mixed with zinc oxide were the most effective in eliminating C. albicans cells from dentinal specimens.
The Effect of Insertion Rates on Fill Length and Adaptation of a Thermoplasticized Gutta-Percha Technique
Marc E. Levitan, DDS, Van T. Himel, DDS, and Jeffrey B. Luckey, BS
The purpose of this in vivo study was to determine the effect of the insertion rate of a thermoplasticized gutta-percha obturation technique (Thermafil Plus) on the quality of the root canal obturation. A calibrated practitioner obturated the tooth in each of three groups with insertion rates of 18, 6, and 3 mm/s, respectively. The quality of the obturation was assessed by measuring the length of fill and the replication of induced canal irregularities, consisting of dimples and grooves. All measurements were made on a single tooth, with a working length of 18 mm from the canal orifice, embedded in a split mold, with 20 measurements for each insertion rate. Measurements were made under a low-power microscope, with the images recorded on videotape. The length of fill decreased with decreasing the insertion rate, from a mean overextension of + 0.88 mm (SD 1.12 mm) for the 18 mm/s rate to a mean underfill of -0.13 mm (SD 1.03 mm) for the 3 mm/s rate. A trend of decreasing fill with decreasing insertion rate was observed, with the difference between the insertion rates of 18 mm/s and 3 mm/s being statistically significant at p < 0.05 using a single comparison test. Replication of dimples decreased with decreasing the insertion rate from a mean reproduction of 99% for the 18 mm/s rate to a mean reproduction of 90% for the 3 mm/s rate. The replication of grooves also decreased with decreasing the insertion rate from a mean reproduction of 100% for the 18 mm/s rate to a mean reproduction of 88% for the 12 mm/s rate. Statistical analysis of the data for both the dimples and the grooves using a paired comparison post hoc Scheffe test found these differences are significant at p < 0.05.
Analysis of Continuous-Wave Obturation Using a Single-cone and Hybrid Technique
Garrett M. Guess, DDS, Kevin R. Edwards, DDS, Ming-Lung Yang, DDS, Mian K. Iqbal, BDS, MS, and Syngcuk Kim, PhD, DDS
This study analyzed the adaptation of gutta-percha to prepared root canal walls using two obturation techniques and determined the influence of the System-B plugger depth on filling adaptation. Fifty-six extracted human mandibular molars were instrumented using Profile NiTi rotary instruments, stratified based on curvature, then randomly distributed into two groups. Group 1 was obturated using the single-cone continuous-wave technique. Group 2 was obturated with a hybrid technique: lateral condensation followed by a continuous-wave down-pack. Based on System-B plugger penetration, teeth were divided into three subgroups: (a) < 3.5 mm, (b) 3.5 to 4.5 mm, and (c) > 4.5 mm. Roots were horizontally sectioned at 1 mm and 3 mm coronal to the apical foramen, stained, and photographed. Four evaluators scored the adaptation of gutta-percha to the prepared canal walls. In 100% (n = 56) of the samples, no statistically significant difference existed between the two obturation methods at 1-mm (x = 1.80, SD + 0.69) or 3-mm (x = 1.804, SD + 0.69) sections. Best results were obtained with a plugger depth 3.5 to 4.5 mm from the working length.
Crown-Down Tip Design and Shaping
Teresa Ponce de Leon Del Bello, DDS, Nancy Wang, DDS, and James B. Roane, BS, DDS, MS
The shaping affects of three types of stainless-steel files that differ only in tip shape were studied using curved canals in acrylic blocks. Ninety curved canals were divided by degree of curvature into three equal groups of 30. The canals in each group were shaped using a crown-down technique and files possessing one of the three different tip shapes. The tip shapes were biconical tip (Flex-R), conical tip (Mor-Flex), and pyramidal tip (Flex-O). The canals were photographed before and after shaping and the finished shape analyzed. The incidences of transportation, ledging, and instrument damage were recorded during instrumentation. National Institutes of Health image software was used to measure the longitudinal cross-sectional areas and cross-sectional diameters at specified canal depths. Statistical analysis showed a significant difference in the preparations between the three tip shapes. Biconical tip files (Flex-R) produced the least transportation and no ledges. Pyramidal tip files (Flex-O) produced the most transportation, ledges, and damaged files. Only pyramidal-shaped tips developed ledges and experienced file separation. The participants reported less difficulty shaping with a biconical-tipped file and the greatest technical difficulty with a pyramidal-shaped tip. This study suggests that during crown-down rotational instrumentation, biconical file tips maintain the original canal curvature better and more frequently that do conical and pyramidal file tips.
Identification of Resected Root-end Dentinal Cracks: A Comparative Study of Visual Magnification
C. Cornelious Slaton, DMD, Robert J. Loushine, DDS, R. Norman Weller, DMD, MS, M. Harry Parker, DDS, MS, W. Frank Kimbrough, DDS, MS, and David H. Pashley, DMD, PhD
The purpose of this in vitro study was to evaluate and compare the effectiveness of visual enhancements as aids in identifying artificially created dentinal cracks in resected root ends. Fifty human maxillary central incisors were decoronated, and the root canals were instrumented to ISO size 50 at the working length. The apical 3 mm of the roots were resected, and cracks were artificially created in the apical dentin with an average load of 5.6 kg using a cylindrical wedge in a miniature drill press. A video microscope at x65 magnification was used to observe the cracks as they developed. Four independent examiners evaluated the root specimens using unaided/corrected vision (group 1), loupes at x3.3 magnification (group 2), a surgical operating microscope at x10 magnification (group 3), and the Orascope at x35 magnification (group 4). The examiners’ proficiency at correctly identifying root ends with and without cracks was evaluated. The data were compared to the predetermined standard (27 cracked, 23 not cracked) with a one-tailed Fisher’s exact test (χ = 0.05). Statistically, the Orascope (p = 0.02) was significantly superior, whereas using unaided/corrected vision (p = 0.99), loupes (p = 0.88), or the microscope (p = 0.14) was not significantly better than guessing. The accuracy of correct identification for unaided/corrected vision, loupes, the microscope, and the Orascope was 39%, 45%, 53%, and 58%, respectively. A two-way analysis of variance of the accuracy of crack identification showed a significant difference among the four visualization techniques (p = 0.0007) and also among the four evaluators (p = 0.006).
Patterns of Vertical Root Fracture: Factors Affecting Stress Distribution in the Root Canal
Veera Lertchirakarn, MDSc, PhD, Joseph E. A. Palamara, PhD, and Harold H. Messer, MDSc, PhD
Previous studies have indicated that vertical root fracture tends to occur in a buccolingual direction, where dentin thickness is greatest. Factors potentially influencing the location and direction of root fracture include root canal shape, external root morphology, and dentin thickness. In this finite-element study, simulated root sections were varied systematically with respect to canal size and shape, external root morphology, and dentin thickness to determine their relative contribution to vertical root fracture. Similar models were constructed based on cross-sections of human tooth roots that had been fractured clinically or experimentally. Finite-element models demonstrated that canal curvature seems more important than external root morphology, in terms of stress concentration, and that reduced dentin thickness increases the magnitude but not the direction of maximum tensile stress. Models based on actual root fractures showed a strong similarity between tensile-stress distribution and fracture patterns.
Finite Element Analysis and Strain-gauge Studies of Vertical Root Fracture
Veera Lertchirakarn, MDSc, PhD, Joseph E. A. Palamara, PhD, and Harold H. Messer, MDSc, PhD
Vertical root fracture seems to result from stresses generated within the root canal and typically occurs in a buccolingual direction through the thickest part of dentin. Because stresses in the canal wall are difficult to measure experimentally, we have attempted to correlate stress patterns derived from finite element models of maxillary and mandibular incisors with strain measurements on the root surfaces of extracted teeth. Finite element analysis indicated that circumferential tensile stresses were concentrated on the buccal and lingual surfaces of the canal wall, corresponding to areas of greatest canal wall curvature. Surface stresses were much lower and were consistently tensile on the proximal root surfaces. The measurement of root surface stresses does not provide a reliable picture of internal stresses in the root. Canal wall curvature is a major factor in stress concentration and hence in the pattern of fracture.