Deformation of HyFlex CM instruments and their shape recovery following heat sterilization.

AIM: To assess the deformation of HyFlex CM instruments (Coltene Whaledent) when used in two instrumentation sequences and to assess their shape recovery after heat sterilization. METHODOLOGY: Simulated root canals with four different shapes were prepared with HyFlex CM instruments using a single-length technique (n = 40) or a crown down technique (n = 40). Pre-preparation, post-preparation and post-sterilization standardized images of each instrument were recorded. Assessment of instrument deformation and their subsequent shape recovery was carried out visually and by comparing the digitised images. Data analysis was carried out using chi-square tests. RESULTS: None of the 400 instruments fractured. Visual assessment of instruments post-preparation revealed that 30.5% had unwound and 0.5% had reverse winding. Following sterilization 8.5% remained unwound and 0.5% remained with reverse winding. When assessing instrument shape using digital images, 35.25% were unwound post-preparation, which reduced to 11% post-sterilization. Nine size 25, 0.08 instruments deformed, but none fully regained their original shape after sterilization; however, other sizes of deformed instruments did regain their shape (P < 0.001). CONCLUSION: Approximately one third of instruments became deformed as a result of use. However, two thirds of these fully recovered their shape following sterilization. The number of deformed instruments was underestimated when no magnification was used for assessment. Instrument size was related to incidence of deformation and shape recovery.

The confidence of undergraduate dental students when performing root canal treatment and their perception of the quality of endodontic education.

AIM: This article aims to gain understanding into the perception of undergraduate dental students in terms of their confidence and competence at performing root canal treatment and their perception of the quality of endodontic education. METHODS: An online questionnaire was distributed to all 3rd, 4th and 5th year dental students at Cardiff University via their academic e-mail addresses. The questionnaire utilised both scaled response and open questions to gain an insight into undergraduate opinion. RESULTS: Out of a possible 208 students, 98 responses were obtained (response rate = 47%). Perception of competence and confidence were significantly greater amongst the more senior year groups (P < 0.01). However, 49% (n = 38) of participants did not feel competent performing root canal treatment on anterior, single-rooted teeth, whilst 74% (n = 70) did not feel competent performing root canal treatment on posterior, multirooted teeth. Free comments from participants indicated that this was due to a lack of clinical experience. Approximately, 80% of participants ranked education in endodontics at Cardiff University as ≤5 on a Likert scale (1 = inadequate to 10 = good), indicating that improvement was required. Improvements that were suggested by the students included the provision of further information within lectures, a broader range of lecturers, an increased number of shorter, more organised practical sessions, additional training equipment, greater supervision and online reference guides to root canal treatment. CONCLUSION: Enhancing undergraduate education in endodontics is necessary to increase students' perception of their confidence and competence when performing root canal treatment.

The effect of pH on surface hardness and microstructure of mineral trioxide aggregate.

AIM: To evaluate the surface microhardness of mineral trioxide aggregate (MTA) specimens following exposure of their surface to a range of acidic environments during hydration. In addition, the morphological microstructure features of samples were studied by scanning electron microscopy (SEM). METHODOLOGY: White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Four groups, each of 10 specimens, were formed using a pressure of 3.22 MPa and exposed to pH 4.4, 5.4, 6.4 and 7.4, respectively, for 4 days. Vickers microhardness of the surface of each specimen was measured after exposure. Four groups of two specimens were prepared and treated in the same way prior to qualitative examination by SEM. Data were subjected to one-way anova and post hoc Tukey's test. RESULT: The greatest mean surface hardness values (53.19 +/- 4.124) were observed following exposure to pH 7.4 with the values decreasing to 14.34 +/- 6.477 following exposure to pH 4.4. The difference between these values at the 95% CI (33.39-44.30) was statistically significant (P < 0.0001). There were no distinct morphological differences between groups in terms of the internal microstructure. However, a trend was observed that the more acidic the solution, the more extensive the porosity of the specimens. CONCLUSION: Under the conditions of this study, surface hardness of MTA was impaired in an acidic environment.

Cardiac risk factors for dental procedures: knowledge among dental practitioners in Wales.

OBJECTIVES: To determine knowledge and educational needs of dental practitioners in Wales regarding congenital or acquired cardiac disease and the provision of antibiotic prophylaxis. DESIGN: Self-administered postal questionnaire. SETTINGS: Cardiff University Dental Hospital, district general hospitals (HDS), all general dental practices (GDP) and community dental service (CDS) clinics throughout Wales. Methods A questionnaire sent to 1,182 dentists in Wales in 2004-5. RESULTS: 528 questionnaires were returned (a response rate of 45%). These were analysed using one-way analysis of variance to compare summary scores between the occupation groups. Significant differences in knowledge of cardiac risk factors for infective endocarditis and for dental procedures requiring cover were observed between the occupation groups. The majority of dentists (92% GDPs, 94% CDS and 77% HDS) requested postgraduate education in cardiac risk factors and laminated flow diagrams for their surgeries as the preferred educational format. CONCLUSION: The knowledge of Welsh dentists regarding cardiac conditions or procedures which are risk factors for paediatric and adult patients varied according to place of work. The study identified potential for under- and over-prescription of antibiotic prophylaxis within the current guidance. There was confusion as to which patient groups and cardiac conditions required prophylaxis and for which particular dental procedures. Postgraduate education detailing advances in cardiology practice is necessary for dentists.

The effect of condensation pressure on selected physical properties of mineral trioxide aggregate.

AIM: To examine the effect of condensation pressure on surface hardness, microstructure and compressive strength of mineral trioxide aggregate (MTA). METHODOLOGY: White ProRoot MTA (Dentsply Tulsa Dental, Johnson City, TN, USA) was mixed and packed into cylindrical polycarbonate tubes. Six groups each of 10 specimens were subjected to pressures of 0.06, 0.44, 1.68, 3.22, 4.46 and 8.88 MPa respectively. The surface hardness of each specimen was measured using Vickers microhardness. Cylindrical specimens of 4 mm in diameter and 6 mm in height were prepared in polycarbonate cylindrical moulds for testing the compressive strength. Five groups of 10 specimens were prepared using pressures of 0.06, 0.44, 1.68, 3.22 or 4.46 MPa. Data were subjected to one-way anova. The microstructure was analysed using a scanning electron microscope (SEM) after sectioning specimens with a scalpel. RESULT: A trend was observed for higher condensation pressures to produce lower surface hardness values. A condensation pressure of 8.88 MPa produced specimens with significantly lower values in terms of surface hardness than other groups (P<0.001). A condensation pressure of 1.68 MPa conferred the maximum compressive strength; however, it was not statistically different. Higher condensation pressures resulted in fewer voids and microchannels when analysed with SEM. In specimens prepared with lower condensation pressures distinctive crystalline structures were observed. They tended to appear around microchannels. CONCLUSION: Condensation pressure may affect the strength and hardness of MTA. Use of controlled condensation pressure in sample preparation for future studies is suggested.

An audit of root canal treatment performed by undergraduate students.

AIM: The objective of this study was to audit the quality of root canal treatment performed by undergraduate students on adult patients. METHODOLOGY: All root canal treatment completed by first and second clinical year undergraduates over a 12-month period were included in the study. The availability and readability of pretreatment, diagnostic length, try-in point and postoperative radiographs were noted for each case. All readable postoperative radiographs of primary treatments were examined for quality of the root filling, categorized as complete, incomplete apical, incomplete apical and lateral or not assessable. The distance from the radiographic apex of the root to the apical extent of each root filling was measured to 0.1 mm precision. RESULTS: Undergraduates performed primary treatment on 157 teeth. A postoperative radiograph was available in 97% of cases. A try-in point radiograph was unavailable in one-fifth of cases. Twenty-seven teeth (13%) were categorized as satisfactory in terms of both radiographic quality and distance of the root filling from the radiographic apex. CONCLUSIONS: Overall, the technical quality of root canal treatment completed by undergraduate students was poor.

Canal shapes produced sequentially during instrumentation with Quantec SC rotary nickel-titanium instruments: a study in simulated canals.

AIM: The aim of this study was to determine the shaping ability of Quantec SC nickel-titanium rotary instruments in simulated root canals. METHODOLOGY: Forty simulated canals consisting of four different shapes in terms of angle and position of curvature were prepared with Quantec SC instruments. Sequential still images were taken of the canals using a video camera attached to a computer with image analysis software. Images were taken preoperatively, and then after instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06 taper), and instrument 10 (size 45, 0.02 taper) were taken to length. Each sequential postoperative image was superimposed individually over the preoperative image in order to highlight the amount and position of material removed during preparation. RESULTS: Overall, the mean preparation time to size 10 was 3.6 min with 12 mm canals taking on average less time than 8 mm canals. There was a highly significant difference between the canal types (P < 0.0001). No instruments fractured within the canal or deformed, although one instrument separated from the latch grip. All canals remained patent. Following preparation to size 10, 19 canals (48%) retained their length, eight (20%) lost length, and 13 (32%) gained length; the magnitude of the change in length was always 0.5 mm or below. Following preparation to size 7 instruments all canals showed aberrant shapes. Excess removal of material along the outer aspect of the curve between the beginning of the curve and the end-point (outer widening) was found in 26 canals (65%) after instrument 7. At the same stage of preparation six canals (15%) had zips, three (8%) had ledges and five (13%) had perforations. Following preparation to size 10, 27 (68%) canals were perforated. CONCLUSIONS: Under the conditions of the study, Quantec SC instruments consistently produced aberrations when canals were enlarged to size 7 (size 25, 0.05 taper) or above. Care should be exercised when using these instruments in real teeth.

The outcome of root canal treatment. A retrospective study within the armed forces (Royal Air Force).

OBJECTIVE: The objective of this study was to investigate the outcome of conventional root canal treatment in a general practice setting within the Royal Air Force dental service. Design Retrospective review. METHODS: Teeth that had been root-filled for 12 months or more by Royal Air Force dental practitioners in patients attending a large Royal Air Force dental centre were included in the study. Following clinical and radiographic review the root fillings were classified as 'definitely successful', 'probably successful' or 'failed' The effect on success of several variables on the outcome was investigated. RESULTS: Out of a total of 406 teeth, 59% were maxillary teeth and 41% were mandibular teeth. Sixty-nine per cent of the total sample had pre-existing periapical radiolucencies. Cold lateral condensation of gutta-percha was the most widely used filling technique (64% of all cases). Fifty per cent of the teeth had root fillings within 2 mm of the radiographic apex, 32% were greater than 2 mm from the radiographic apex and 18% were overfilled. Cold lateral condensation was the most successful (92% overall) filling technique. Maxillary anterior teeth had a better success rate (96%) than other tooth types. Teeth with pre-existing periapical radiolucencies had a higher success rate (87%) than those cases where there was no pre-existing periapical radiolucency (80%). Root fillings that were less than 2 mm from the radiographic apex of the tooth had a higher success rate (88% overall) than those that were greater than 2 mm from the radiographic apex (77% overall). Of the 406 cases, 57% (n=231) were classified as definitely successful, 28% (n=114) were classified as probably successful and 15% (n=62) were classified as failures. Thus, the overall success rate combining definitely successful and probably successful root fillings was 85% (n=344). CONCLUSIONS: Root fillings placed using cold lateral condensation of gutta-percha to within 2 mm of the radiographic apex of the tooth were associated with the best outcome.

Comparison of lateral condensation and thermomechanically compacted warm alpha-phase gutta-percha with a single cone for obturating curved root canals.

OBJECTIVE: To evaluate and compare the sealability and radiographic quality of root fillings in extracted teeth by using lateral condensation of gutta-percha or alpha-phase gutta-percha in conjunction with a single gutta-percha cone. STUDY DESIGN: A total of 108 single-rooted teeth were divided into 2 groups of 54 teeth based on canal shape. Canals were prepared to a minimum 0.055 taper and enlarged to a size 35 at the working distance. Irrigation was done with 17% EDTA and 2.5% sodium hypochlorite (NaOCl) to remove smear layer. One group was obturated by using cold lateral condensation of gutta-percha; the other group was obturated with thermomechanically compacted alpha-phase gutta-percha and a single cone of gutta-percha. Apical extrusion of sealer or gutta-percha was recorded. Sealability of each technique was assessed by dye penetration. The radiographic quality of obturation was also determined. RESULTS: Root canals filled with alpha-phase gutta-percha and a single cone had significantly more extrusion of sealer than canals filled by lateral condensation. Lateral condensation achieved significantly better scores for radiographic quality. There was no significant difference between the 2 filling techniques in terms of apical or coronal leakage. CONCLUSIONS: Thermomechanically condensed alpha-phase gutta-percha used in conjunction with a single gutta-percha cone had poorer radiographic quality than laterally condensed gutta-percha.

Canal shapes produced sequentially during instrumentation with Quantec LX rotary nickel-titanium instruments: a study in simulated canals.

AIM: The aim of this study was to determine the shaping ability of Quantec LX nickel-titanium rotary instruments in simulated root canals. METHODOLOGY: Forty simulated canals consisting of four different shapes in terms of angle and position of curvature were prepared with Quantec LX instruments. Sequential still images were taken of the canals using a video camera attached to a computer with image analysis software. Images were taken preoperatively; after, instrument 7 (Size 25, 0.05 taper), instrument 8 (size 25, 0.06 taper), and instrument 10 (size 45, 0.02 taper) were taken to length. Each sequential postoperative image was superimposed individually over the preoperative image in order to highlight the amount and position of material removed during preparation. Intra-canal impressions after preparation to size 10 were taken to evaluate three-dimensional canal form. RESULTS: Overall, the mean preparation time to size 10 was 4.7 min; canal shape did not have a significant effect on speed of preparation. No instruments fractured within the canal, but 7 instruments separated from the latch grip, and a further 3 instruments deformed. All canals remained patent. Following preparation to size 10, 29 canals (72%) retained their length, 7 (17%) lost length, and 4 gained length; the magnitude of the change in length was always below 1 mm. Zips were created in 3 canals (7%) after use of size 10 instruments, but no perforations or danger zones were produced. Excess removal of material along the outer aspect of the curve between the beginning of the curve and the end-point (outer widening) was found in 22 canals (55%) after instrument 7, in 30 (75%) canals after size 8 and in 35 canals (88%) after size 10. There was a significant difference (P < 0.0001) between canal shapes for the incidence of this aberration at all sizes. CONCLUSIONS: Under the conditions of the study, Quantec LX instruments tended to remove excess material from the outside of the curve between the beginning of the curve and the end-point. These aberrations increased in prevalence and severity following the use of larger instruments when they were taken to length. Size 8, 9 and 10 Quantec LX instruments should be used with care and short of length, especially in severely curved canals.

Comparison of cold lateral condensation and a warm multiphase gutta-percha technique for obturating curved root canals.

AIM: The aim of this project was to evaluate and compare the radiographic quality and sealability of root fillings in extracted human teeth using lateral condensation of gutta-percha or multiphase gutta-percha obturation (Alphaseal). METHODOLOGY: A total of 108 freshly extracted human, mature single-rooted teeth were divided into two identical groups of 54 teeth on the basis of root canal shape. The canals were prepared to a minimum 0.055 taper and enlarged to size 35 at the apex. All root canals were flushed with 17% EDTA solution and 2.5% NaOCl to remove the dentinal smear layer. The canals of one group were obturated using cold lateral condensation of gutta-percha and the canals of the other group were filled using a warm multiphase gutta-percha obturation technique. The extrusion of sealer and/or gutta-percha through the apex of the teeth was recorded using a simple yes/no scheme. The sealability of each technique was assessed by a dye penetration method. The radiographic quality of obturation was determined for each canal using a four-point scale. RESULTS: Root canals filled by multiphase obturation had significantly more extrusion of sealer (P < 0.001) and gutta-percha (P < 0.001) than canals filled by lateral condensation. Canals filled by multiphase gutta-percha obturation had significantly less apical dye leakage than those obturated by lateral condensation (P < 0.05). Lateral condensation achieved significantly better scores for radiographic quality than multiphase obturation from the bucco-lingual view (P < 0.01). CONCLUSIONS: Under laboratory conditions multiphase gutta-percha had better sealability but poorer radiographic quality than lateral condensation.

Shaping ability of .04 and .06 taper ProFile rotary nickel-titanium instruments in simulated root canals.

AIM: The aim of this study was to determine the shaping ability of ProFile .04 and .06 taper rotary nickel-titanium instruments in simulated canals. METHODOLOGY: A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared using the 'crowndown' approach recommended by the manufacturer. Pre-operative pictures of each canal were recorded on optical discs using an image analysis package. The simulated canals were prepared and postoperative pictures superimposed on the original images. RESULTS: No instrument fractures occurred and none deformed; none of the canals became blocked with debris. Change in working distance was, on average, 0.063 mm with 33 canals retaining the correct length. Overall, five zips (12.5%) were created and 24 (60%) canals demonstrated a widened area on the outer aspect of the canal between the end-point and the curve. Two danger zones (5%) were created and two perforations but no ledges were found. Between canal shapes there were highly significant differences (P < 0.0001) for the incidence of zips and elbows but not for the other aberrations. There were highly significant differences (P < 0.0001) for the total width of the canals between the various canal shapes at the apex of the curve, the beginning of the curve and half way to the orifice, and a significant difference (P < 0.05) at the end-point. There were highly significant differences (P < 0.0001) for the amount of resin removed from the outer aspect of the curve at the end-point and at the beginning of the curve, and significant differences (P < 0.05) at the apex of the curve and half way to the orifice. There were highly significant differences (P < 0.0001) for the amount of resin removed from the inner aspect of the curve at the beginning of the curve and half way to the orifice. Overall, transportation was towards the outer aspect of the canal except at the beginning of the curve. CONCLUSIONS: Under the conditions of this study the combined use of .04 and .06 taper ProFile instruments was rapid, effective and produced good canal shapes except in those specimens with short curves that began near the end-point.

Shaping ability of Profile rotary nickel-titanium instruments with ISO sized tips in simulated root canals: Part 1.

The aim of this study was to determine the shaping ability of ProFile 0.04 taper rotary nickel-titanium instruments with ISO sized tips in simulated canals. A total of 40 simulated root canal made up of four different shapes in terms of angle and position of curvature were prepared by ProFile instruments using the 'crown down' approach recommended by the manufacturer. Part 1 of this two-part report describes the efficacy of the instruments in terms of preparation time, instrument failure, canal blockages, loss of canal length and three-dimensional canal form. The time necessary for canal preparation was on average 5.2 min and was not influenced significantly by canal shape. Three instrument fractures occurred and a further 3 instruments deformed; size 35 instruments failed the most (4) followed by size 30 (2), four of the failures occurred in canals with 40 degrees curves. None of the canals became blocked with debris and change in working distance was minimal. Intra-canal impressions of canal form demonstrated that most canals had apical stops and smooth canal walls whereas all canals had good flow and taper. Under the conditions of this study, ProFile 0.04 taper rotary nickel-titanium instruments with ISO sized tips prepared simulated canals rapidly and created good three-dimensional form.

Shaping ability of ProFile rotary nickel-titanium instruments with ISO sized tips in simulated root canals: Part 2.

The aim of this study was to determine the shaping ability of ProFile 0.04 taper rotary nickel-titanium instruments with ISO sized tips in simulated canals. A total of 40 simulated root canals made up of four different shapes in terms of angle and position of curvature were prepared by ProFile instruments using the 'crown down' approach recommended by the manufacturer. Part 2 of this two-part report describes the efficacy of the instruments in terms of prevalence of canal aberrations, the amount and direction of canal transportation and the overall post-operative shape. Out of 37 completed specimens 9 zips (24%) and one ledge (3%) were created, but no perforations or danger zones were found. There were significant differences (P < 0.01) between canal shapes for the incidence of zips and elbows but not for their distance from the end-point of preparation. At specific positions along the canal length there were significant differences between the canal types in terms of their mean total width; overall, at the end-point of preparation and along the curved portion of the canals those specimens with 40 degrees curves were widest. This trend continued for the width of material removed from the outer aspect of the canal curves, whereas along the inner aspect of curves more material was removed in the 20 degrees canals. Overall, transportation was towards the outer aspect of the curve at the end-point of preparation and along the curved portion of canals but more balanced along the straight coronal section. Absolute transportation was small and below 0.1 mm at every position including the zips. Under the conditions of this study, ProFile nickel-titanium rotary instruments with ISO sized tips produced a larger number of zips than expected; however, the degree of zipping was limited and relatively minor.