Crack Formation Following Root-End Preparation in Roots with the Butterfly Effect.

OBJECTIVE: To investigate apical cracks in roots that exhibit the butterfly effect and that have undergone apical resection and ultrasonic root-end cavity preparation. The effect of the obturation material was also studied. METHODS: Forty extracted single-rooted teeth were decoronated at the cemento-enamel junction. Roots were viewed under a light microscope and coded according to the presence or absence of the butterfly effect. Canals were prepared using ProTaper Next instruments to size X3 and assigned to two obturation groups (gutta-percha and AH Plus, and ProRoot MTA alone). Each contained twenty roots (10 with the butterfly effect and 10 without the butterfly effect). Roots were resected perpendicular to their long axis, 3 mm from the apex, and cavities were cut using ultrasonic retrotips. Resin replicas were used for crack imaging from scanning electron micrographs. Statistical analyses were performed using Stata 13.1 (StataCorp, College Station, TX, USA). RESULTS: Cracks occurred more frequently in teeth with the butterfly effect (80%), with this difference being significant (P=0.001). Most cracks (73%) ran buccolingually. Teeth obturated with MTA developed fewer cracks compared to those obturated with GP and sealer. CONCLUSION: Root-ends with the butterfly effect had a significantly higher number of buccolingual cracks following resection and ultrasonic root-end preparation. This might explain the development of some vertical root fractures, which usually run buccolingually. Canal obturation with MTA may be protective.

Eyesight: a study of the staff of a dental school.

OBJECTIVES/AIMS: The aim was to investigate the vision of all 90 dentally qualified staff at a dental school. MATERIALS AND METHODS: Ethical approval was obtained and a questionnaire-based survey conducted. Data were screened and analysed using Stata 13.1. The χ2 and Fisher's Exact tests were used to test for significance with an alpha level of 0.05. RESULTS: The participation rate was 95.6%. Most of the teachers (92%) considered their eyesight was satisfactory to practice dentistry. Of the 97% who had been tested at some stage, 15% had their eye examination due to sight deterioration with 22% needing correction. Almost two-thirds were myopic and a third were hyperopic. Forty-nine per cent wore spectacles only, with about a quarter of this group alternating between spectacles and contact lenses. Of those with corrected vision, 80% followed their optometrist's recall advice. Four participants reported that they were colour blind. While 4% had had laser-eye surgery, a further 27% were interested in this. Magnification was used by 72% with no significant differences between genders, age of staff member, place of qualification or registration status. Most of the staff (81%) thought that screening of dental student's eyesight should be mandatory, and regular eye examinations as a condition of dental practice was supported by 67%. DISCUSSION: The number of teachers reporting recent vision tests was encouraging; nevertheless, a worrying 8% surveyed were unsure if their eyesight was satisfactory for work. The commonest vision problem was myopia, with almost half of the teachers wearing spectacles. It is clear that visual standards for dentistry would be helpful. Magnification use was high, with many non-users indicating their intention to buy loupes. CONCLUSIONS: Within the limits of this study the teachers were conscientious regarding their eye care, irrespective of their training and age. There was strong support for the mandatory testing of vision for all dentists and especially dental students.

Root canal treatment and prevalence of apical periodontitis in a nigerian adult subpopulation: a radiographic study.

PURPOSE: To evaluate the frequency, distribution and quality of root canal treatment in an adult Nigerian subpopulation and to determine the prevalence of apical periodontitis. MATERIALS AND METHODS: The periapical status and length of root fillings of 756 patients attending Obafemi Awolowo University Teaching Hospital, Ile-Ife, Nigeria for the first time were evaluated using full mouth periapical radiographs. The length of the root canal filling was considered 'adequate' if it was ≤ 2 mm from the radiographic apex, 'under-filled' if it was > 2 mm short of the apex, and 'overfilled' if filling material extended beyond the radiographic apex. Periapical status was assessed using the periapical index (PAI) with teeth classified as having apical periodontitis if the score was over 2. RESULTS: Overall, 61.2% of the patients had root-filled teeth and 67.2% featured apical periodontitis. Of the 21,468 teeth examined, 12.2% had been root filled, and of these 41% exhibited apical periodontitis. The prevalence of root-filled teeth was higher in the younger patients, while the prevalence of apical periodontitis in root-filled teeth was similar between age groups. Root-treated teeth that were overfilled or were mandibular incisors had the highest prevalence of apical disease. Overfilled teeth were more prone to developing an apical radiolucency than were under-filled teeth (P < 0.001 and P < 0.05, respectively). CONCLUSIONS: The prevalences of endodontically treated teeth and apical periodontitis were within the range reported for other countries; however, a very large number of patients required treatment or retreatment.

Undergraduate endodontic teaching in New Zealand: students' experience, perceptions and self-confidence levels.

The aim was to investigate undergraduate students' experiences, perceptions of future practice and self-rated confidence levels across endodontic tasks. After ethical approval, a survey involved all fourth and fifth year students. Quantitative data were analysed in SPSS version 20.0. Qualitative data were analysed using a general inductive approach. The participation rate was 84% (n = 136 of 162). The mean number of canals completed was 2.6 by fourth years and 10.4 by fifth years. Maxillary premolars were the most common first tooth treated. Pulpal factors and root morphology were the most common reasons for experiencing difficulty. Self-rated confidence levels were lower for the more junior students and complex procedures. Students felt that an increased use of extracted natural teeth would be beneficial in their pre-clinical practice. A high level of interest was shown in future specialisation in endodontics. Students may benefit from further didactic teaching or pre-clinical instruction in selected topics.

Investigation of dentin hardness in roots exhibiting the butterfly effect.

INTRODUCTION: Most vertical root fractures occur in root canal treated teeth, and they usually run in a buccolingual direction. The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim was to investigate the microhardness of dentin in mesiodistal and buccolingual cross sections of roots exhibiting the effect. METHODS: Thirty extracted single-rooted teeth were allocated according to patient age: group 1, 15-24 years; group 2, 25-44 years; and group 3, 45 years and older. Roots were embedded in acrylic and cut into ten 1-mm-thick cross sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels featured the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (10) were selected. Two adjacent, consecutive cross sections were chosen from the middle of the roots. Vickers microhardness testing was carried out on the dentin walls. RESULTS: Mean hardness scores were highest mesiodistally (83.7 kgf/mm(2)) and lowest buccolingually (56.4 kgf/mm(2)), a significant difference (P = .028). This trend was found across all age groups. CONCLUSIONS: Root sections with the butterfly effect are harder mesiodistally. This might explain the high prevalence of vertical root fractures that run buccolingually.

Dentists make larger holes in teeth than they need to if the teeth present a visual illusion of size.

BACKGROUND: Health care depends, in part, on the ability of a practitioner to see signs of disease and to see how to treat it. Visual illusions, therefore, could affect health care. Yet there is very little prospective evidence that illusions can influence treatment. We sought such evidence. METHODS AND RESULTS: We simulated treatment using dentistry as a model system. We supplied eight, practicing, specialist dentists, endodontists, with at least 21 isolated teeth each, randomly sampled from a much larger sample of teeth they were likely to encounter. Teeth contained holes and we asked the endodontists to cut cavities in preparation for filling. Each tooth presented a more or less potent version of a visual illusion of size, the Delboeuf illusion, that made the holes appear smaller than they were. Endodontists and the persons measuring the cavities were blind to the parameters of the illusion. We found that the size of cavity endodontists made was linearly related to the potency of the Delboeuf illusion (p<.01) with an effect size (Cohen's d) of 1.41. When the illusion made the holes appear smaller, the endodontists made cavities larger than needed. CONCLUSIONS: The visual context in which treatment takes place can influence the treatment. Undesirable effects of visual illusions could be counteracted by a health practitioner's being aware of them and by using measurement.

The butterfly effect: an investigation of sectioned roots.

INTRODUCTION: The butterfly effect is an optical phenomenon seen in some sections of tooth roots. The aim of this work was to investigate the density of dentinal tubules in mesiodistal and buccolingual cross-sections of roots exhibiting the butterfly effect and to determine if the effect is featured throughout the length of roots and is age related. METHODS: Thirty extracted single-rooted teeth were allocated to the following groups according to patient age: group 1: 15-24 years, group 2: 25-44 years, and group 3: 45 years and over. The teeth were decoronated, and their roots were embedded in acrylic and cut into ten 1 mm-thick cross-sections. Sections were viewed under a light microscope and coded (1 or 2) according to presence or absence of the butterfly effect. A root scored 20 when all levels exhibited the butterfly appearance. The 2 teeth with the highest score from each group and 2 control teeth with the minimum score (of 10) were selected. Two adjacent, consecutive cross-sections were chosen with the most coronal cut mesiodistally and the other buccolingually. Scanning electron micrographs (×850) were taken of the central portion of their canal lumina and the density of the dentinal tubules determined. RESULTS: The butterfly effect was found at all levels in the roots of the affected teeth. The tubule density was highest in the buccolingual root sections (45,348 mm(-2)) and lowest mesiodistally (12,605 mm(-2)), a significant difference (P = .02). This trend was found across all age groups. CONCLUSIONS: Root sections with the butterfly effect have a lower density of dentinal tubules mesiodistally corresponding to the wings of the butterfly. The pattern was observed in teeth from all age groups and was absent in controls.

Avulsion and replantation of a primary incisor tooth.

Avulsion of a primary tooth is a serious dental trauma, and the guidelines of the International Association of Dental Traumatology and textbooks in paediatric dentistry do not recommend replantation. Such management can result in severe damage to the supporting structures, and together with avulsion itself is commonly associated with developmental disturbances of the permanent tooth. We report the case of replantation in a 9-month-old child with a successful outcome, in a unique situation where conditions were optimal and careful long-term follow up was possible.

Infection of apical dentin and root-end cavity disinfection.

INTRODUCTION: The purpose of this study was to assess Enterococcus faecalis penetration into the dentin of the apical 3 mm and bacterial death after the application of either chlorhexidine or laser to root-end cavities. METHODS: Root canals of 60 single-rooted teeth were prepared. In part 1, cementum was removed semicircumferentially from 21 roots, and the smear layer was removed from 15 roots using 17% EDTA/cetrimide. Teeth were inoculated and incubated with E. faecalis for 10 days, rinsed, and live/dead stained. The effect of cementum and smear on bacterial penetration was assessed by confocal laser scanning microscopy (CLSM). In part 2, 39 teeth had root ends resected and cavities ultrasonically prepared. Inoculated roots were assigned to 1 of the following 3 groups: (1) root-end cavities irrigated with 0.2 % chlorhexidine, (2) root-end cavities irradiated with a laser for 20 seconds at 1.5 W, or (3) root-end cavities that received no treatment. Roots were live/dead stained, sectioned, and examined by CLSM. The depth of the bacterial penetration and bacterial survival were compared using the Mann-Whitney U test. RESULTS: The presence of a smear layer and/or cementum did not significantly affect bacterial penetration. In root-end cavities, chlorhexidine was more effective than laser (P < .001), reducing bacterial viability by 93% versus 70% with a laser. CONCLUSIONS: E. faecalis invaded the entire width of dentin in the apical 3 mm irrespective of the smear layer and/or cementum. Chlorhexidine was more effective than laser in disinfecting root-end cavities.

Effect of the smear layer on a pulp proximity-indicating instrument.

The purpose of the study was to determine the effect of removing or modifying the smear layer on the indication provided by the Prepometer pulp proximity-indicating instrument. Third molars were prepared to produce flat surfaces in the coronal dentine, and control Prepometer LED readings were made. Group E was treated with 18% EDTA and Group T with Tubulicid. Prepometer readings were repeated. Dentine was removed in 0.5 mm increments, and readings repeated until a red LED appeared, indicating a danger of pulp exposure. Distances to the pulp were measured. t test, Wilcoxon signed ranks test (WSR) and ordinal regression (OR) analysis were performed, together with SEM examination. There were significant differences between both test groups and their untreated controls. OR showed that a red LED appeared further from the pulp with EDTA treatment than with no treatment. A red LED appeared closer to the pulp with Tubulicid treatment than with no treatment. SEM showed smear removal in Group E and occlusion of tubules in Group T. Prepometer performance was significantly influenced by treatment with EDTA and Tubulicid. Practitioners would be required to learn to interpret the display of the Prepometer instrument in the context of the tooth under treatment and the surface condition of the cut dentine.

New Zealand dentists' use of gingival retraction techniques for fixed prosthodontics and implants.

OBJECTIVE: To identify the techniques most commonly used in New Zealand for gingival retraction for impressions of natural teeth and implants in fixed prosthodontics. DESIGN: Postal survey of a random sample of dentists METHODS: A questionnaire was mailed to all members of the New Zealand Dental Association (NZDA). Data were analysed using SPSS. RESULTS: The response rate was 51%. Veneer, crown and bridge treatments were routinely carried out by 89% of respondents, while implant treatment and/or implant-supported prostheses were provided by 65%. Around natural teeth, gingival retraction was mainly achieved with surgery (including electrosurgery, laser and rotary curettage) and/ or cord, by 82% of dentists. Cord with chemicals was used by 63% and plain cord by 37%. Gingival retraction around implants was used by 18%. Among the latter, the most popular gingival retraction method for use around implants was plain cord (used by 31%), while 25% used cord with chemicals. Another 23% reported using surgery as their means of gingival retraction around implants, while 19% reported using Expasyl (Pierre-Roland), and 2% reported using Magic Foam Cord (Dentsply), both of which are injectable matrices for gingival retraction. CONCLUSION: Dentists in New Zealand undertake a considerable amount of fixed prosthodontic and implant work. Gingival retraction around natural teeth is used commonly, while only a small number of participants report using it for implants. A surprising finding was the relatively high number of participants who reported using surgery for gingival retraction around natural teeth.

A novel instrument to determine pulp proximity.

The aim was to determine whether extracted teeth could be used to test the Prepometer instrument, which indicates pulp proximity with green/amber/red light emitting diodes. Third molars were reduced to a plane in dentine and Prepometer readings made. Dentine was removed in 0.5 mm increments and readings made until only lights 9 or 10 (red) showed. The teeth were sectioned and the dentine thickness measured. Analysis permitted construction of a highly significant predictor-model (p < 0.01), the red/amber light boundary coinciding with a dentine thickness of 2.4 mm. The Prepometer was consistent in predicting pulp proximity but was more sensitive than specified.

Radiographic recognition and distribution of approximal carious lesions in New Zealand undergraduate dental students.

Bitewing radiographs are widely used to detect caries on the approximal surfaces of teeth. The aim of this study was to determine the prevalence of approximal caries in an educated young adult (New Zealand dental student) population, and to compare the diagnostic decisions of students and university teachers. A total of 123 students aged from 18 to 25 years (mean age 21 years) participated, having given their informed consent. Their bitewings were digitised and assessed for approximal carious lesions from the distal surface of the first premolars to the mesial surface of the second molars on the same computer screen. The following criteria were used: (0) no detectable radiolucency, (R1) lesion confined to the outer half of the enamel, (R2) lesion into the inner half of the enamel, (R3) lesion into the outer half of dentine along the amelodentinal junction, (R4) lesion beyond the outer part of the dentine. The views were assessed by two final-year dental students and two experienced university teachers, and results were compared. A total of 2710 surfaces were examined; restored and missing surfaces (tooth absent, off film or surface unreadable) were excluded. Carious lesions were found in 173 (6.38 percent) of the surfaces. Only 57 subjects presented with carious lesions radiographically, but 16 (13 percent) of subjects had 87 percent of all the lesions. Seventy-nine percent of the lesions were enamel lesions (R1 and R2), with 21 percent of the lesions having dentine involvement (R3 and R4). Inter-examiner agreement was high, Pearson's correlation coefficient r = 0.8237, and Cohen's kappa kappa = 0.76.

Comparison of two methods for the removal of root canal posts.

OBJECTIVE: To compare the application of ultrasound with the use of an engine-driven trephine bur to remove parallel-sided root canal posts. METHOD AND MATERIALS: Single-rooted human canine teeth were decoronated and prepared to receive preformed titanium posts. The posts were cemented with Panavia F resin cement. Ten teeth acted as controls, 10 had a 4-mm-deep gutter cut around the post using a Masserann trephining bur, and 10 were subjected to 10 minutes of ultrasound. The forces required to dislodge the posts were determined using a universal testing machine, and the data were analyzed using analysis of variance. RESULTS: The only significant difference was between the trephined and ultrasonically energized groups, with the ultrasonic group requiring greater forces for dislodgement. CONCLUSION: Resin composite cement could be removed from around the posts with the trephine bur but with considerable difficulty, and neither method of dislodging the posts was effective.

Effect of thermocycling on the retention of glass-fiber root canal posts.

OBJECTIVE: This study investigated the effects of thermocycling on the retention of glass-fiber and resin posts. METHOD AND MATERIALS: Forty premolar and canine tooth roots were embedded in acrylic blocks shaped to fit into a retention device. The roots were randomly assigned to two groups of 20 to receive either Lightposts or Luscent Anchors which were cemented into 9-mm-deep post spaces, with Panavia F resin cement. Each group was randomly divided into two equal subgroups: one for thermocycling, and the other to serve as a control. The thermocycled specimens were cycled 3,000 times between water baths at 5 degrees C and 55 degrees C, with a dwell time of 60 seconds in each. Control specimens were stored at 37 degrees C. The tensile force required to dislodge each post from its root was recorded and the data analyzed using Student's t tests. RESULTS: There were no significant differences in the forces required to cause post-retention failure between the control and thermocycled specimens. Lightposts were significantly more retentive than Luscent Anchors without thermocycling, but this distinction was not apparent in the thermocycled groups. CONCLUSION: Glass-fiber and resin posts cemented with resin cement offer acceptable levels of retention and are not susceptible to reduced retention from thermocycling. Thermocycling should be given less emphasis in tests for the retention of root canal posts cemented with resin cements.

Conventional versus storage phosphor-plate digital images to visualize the root canal system contrasted with a radiopaque medium.

The pulp tissue was removed from 20 mandibular first molar teeth using 2.5% NaOCl irrigation and hand files. The dried canals were infused with radiopaque contrast medium. Standardized conventional and Digora digital images were obtained of each tooth positioned in a dried mandible at 0- and 30-degree horizontal angulations. Three evaluators rated the image clarity of the 0- and 30-degree original, enhanced, three-dimensional, zoom, and reverse digital image modes as superior, equal, or inferior to corresponding 0- and 30-degree conventional radiographs. The ratings were compared using the Wilcoxon signed rank test. The original, three-dimensional, zoom, or reverse digital images were inferior to the conventional radiographs for clarity of canal anatomy. The enhanced digital images were not always inferior to the conventional radiographs and were the only images superior to the original digital images. Overall, evaluators rated the image clarity of root canal anatomy on conventional radiographs better than on Digora images. However, factors in the experimental design may have contributed to this result.

A comparison of the retention of tooth-colored posts.

OBJECTIVE: The aim of this in vitro study was to compare the retention of five different esthetic post systems of similar dimensions in extracted teeth using titanium posts as controls. METHOD AND MATERIALS: Sixty recently extracted single-rooted, caries-free teeth were sectioned horizontally and mounted in acrylic resin. The samples were randomly allocated into six groups of 10 for post preparation. Post space preparation was carried out according to the individual manufacturer's instructions. All posts were bonded using Panavia F. A 4-mm hollow, metal sleeve was luted over the free end of each post prior to mounting in a universal testing machine, and the forces required to dislodge the posts using a cross-head speed of 5 mm/min were recorded. RESULTS: It was found that the parallel-sided Lightposts were significantly more retentive than all of the other posts. Parapost Fibrewhite posts were more retentive than tapered Lightposts and Snowposts. There was no significant difference between the retention of stainless steel Paraposts and any of the other groups. CONCLUSIONS: Serrated parallel-sided stainless steel posts were no more retentive than either parallel-sided or tapered tooth-colored posts in this study. When all groups were considered, post dimension appeared to influence retention, with parallel-sided posts being more retentive than tapered posts.

A comparison of phosphor-plate digital images with conventional radiographs for the perceived clarity of fine endodontic files and periapical lesions.

OBJECTIVE: We sought to compare digital images with radiographs for the perceived clarity of small endodontic file tips at 2 different working lengths, as well as for the visualization of periapical bone lesions. STUDY DESIGN: Standardized conventional radiographic and phosphor-plate digital images were taken of 20 extracted permanent mandibular molars with 06 K-files placed in the distal root canal either 2 mm short or flush with the apical foramen. Similar images were obtained from mandibles with teeth that demonstrated large (n = 10) or small (n = 10) periapical lesions. Four evaluators ranked the clarity of the digital image with that of the radiograph. Results were analyzed by using the 2-sided sign test, ordinal logistic regression, and the kappa test. RESULTS: The perceived clarity of an endodontic file tip, at any position, and of a small or large periapical lesion was significantly (P < .01) less on all digital images compared with conventional films. CONCLUSION: Evaluator ratings indicated that the perceived clarity of fine endodontic files and periapical lesions was significantly less with phosphor-plate digital images than with conventional radiographs.

Electrical and dye leakage comparison of three root-end restorative materials.

OBJECTIVE: The purpose of this study was to assess three modern root-end restorative materials with electrical and dye leakage tests. METHOD AND MATERIALS: Thirty-three human canine teeth were prepared and filled with gutta-percha and sealer. Stainless steel rods were inserted into the root canals as anodes, and the teeth were varnished. The apical 3 mm of each tooth was resected, and 3-mm root-end preparations were made ultrasonically. Mineral trioxide aggregate, Super EBA, and IRM were used to restore 10 teeth each, and three teeth were varnished as controls. Following 24 hours' setting in blood, the specimens were placed in 1% potassium chloride electrolyte, and leakage was recorded electrically for 70 days. The teeth were then submerged in methylene blue dye for 72 hours, sectioned longitudinally, and scored for leakage by six examiners. RESULTS: In both tests, the mineral trioxide aggregate restorations leaked significantly less than the IRM and Super EBA restorations. Super EBA showed significantly less leakage than did IRM restorations in the electrochemical test but not in the dye leakage experiment. The teeth sealed with mineral trioxide aggregate performed similarly to the varnished negative control teeth. CONCLUSION: The results of this study indicated that mineral trioxide aggregate provides a superior seal in root-end-restorations.