Fracture incidence of WaveOne Gold files: a prospective clinical study

AIM

This prospective clinical study evaluated the incidence of instrument fracture observed after single-file root canal treatment of molars using WaveOne Gold instruments.

METHODOLOGY

Three standardized, experienced and calibrated specialists treated 750 maxillary and mandibular molars with curvatures less than 45° (2691 root canals) over a 12-month period. All the treatments were performed in a single session. A total of 1104 WaveOne Gold instruments were used, including 38 small, 750 primary, 228 medium and 88 large instruments. Intracanal procedures were performed according to the manufacturer's recommendations, and each instrument was used in a single clinical case. The instruments were examined after their removal from the canal, under an operating microscope at 8× magnification.

RESULTS

No fractures were observed in any of the 1104 instruments used.

CONCLUSIONS

No fractures of WaveOne Gold reciprocating instruments occurred during root canal preparations performed in maxillary and mandibular molars with curvatures less than 45° when used strictly according to the manufacturer's recommendations and applied in a single clinical case.

Comparative accuracy of the Clearing Technique, CBCT and Micro-CT methods in studying the mesial root canal configuration of mandibular first molars

AIMS

To compare the accuracy of the clearing technique and cone beam computed tomography (CBCT) in the assessment of root canal configurations using micro-computed tomography (micro-CT) imaging system as the reference standard.

METHODOLOGY

Thirty-two mesial roots of mandibular first molars, selected on the basis of micro-CT scans (voxel size: 19.6 μm) and presenting several canal configurations, were evaluated using 2 CBCT scanners (voxels sizes: 120 μm and 150 μm) followed by the clearing technique. Two examiners analysed the data from each method and classified the anatomical configuration of the mesial canal according to Vertucci's system. Data were compared using Fisher's exact and chi-square tests. Reliability for each assessment was verified by the kappa test, and significance level was set at 5%.

RESULTS

Kappa value indicated a high level of agreement between the examiners. Detection of type I configurations was significantly lower in cleared teeth (P < 0.05), whilst type II root canals were detected in all specimens by both tests (P > 0.05). In mesial roots with variable anatomical configurations, CBCT and the clearing method were significantly less accurate than the reference standard (P < 0.05).

CONCLUSION

Within the tooth population studied, accuracy of identifying mesial root canal configuration was influenced greatly by the evaluation method and the type of anatomy. Detection of type I configurations in cleared teeth was significantly lower, whilst type II configurations were detected in all specimens by both methods. In mesial roots with variable anatomical configurations, neither CBCT nor clearing methods were accurate for detecting the actual root canal anatomy.

Alteration in the inherent metallic and surface properties of nickel-titanium root canal instruments to enhance performance, durability and safety: a focused review

The expanded use of nickel-titanium (NiTi) rotary instruments in root canal procedures has led to the development of a wide variety of shapes, designs and applications. Root canal anatomy has not changed, however, and the same challenges exist in both initial treatment and the revision of unacceptable treatment. These challenges include application with high levels of achievement and low to no levels of adverse effects, such as instrument fracture, root canal wall ledging, dentine wall perforation and so forth. To that end, many manufacturers have been seeking ways to alter the presently available and wide range of root canal instrument designs, with a focus on altering the surface of the alloy or altering the alloy microstructure with post-machining or post-twisting heat treatment. This focused review will address the impact that these modifications have had on instrument flexibility, resistance to cyclic fatigue and cutting efficiency.

Dislocation resistance of ProRoot Endo Sealer, a calcium silicate-based root canal sealer, from radicular dentine

AIM

To examine the dislocation resistance of three root canal sealers from radicular dentine with and without immersion in a simulated body fluid (SBF), using a modified push-out test design that produced simulated canal spaces of uniform dimensions under identical cleaning and shaping conditions.

METHODOLOGY

Sixty single-rooted caries-free human canine teeth were used. Standardized simulated canal spaces were created using 0.04 taper ProFile instruments along the coronal, middle and apical thirds of longitudinal tooth slabs. Following NaOCl/ethylenediamine tetra-acetic acid cleaning, the cavities were filled with ProRoot Endo Sealer, AH Plus Jet or Pulp Canal Sealer. After setting, half of the cavities were tested with a fibre-optic light-illuminated push-out testing device. The rest were immersed in SBF for 4 weeks before push-out evaluation. Failure modes were examined with stereomicroscopy and field emission (FE)-scanning electron microscopy.

RESULTS

Location of the sealer-filled cavities did not affect push-out strengths. ProRoot Endo Sealer exhibited higher push-out strengths than the other two sealers particularly after SBF storage (P < 0.001). Failure modes were predominantly adhesive and mixed for Pulp Canal Sealer and AH Plus Jet, and predominantly cohesive for ProRoot Endo Sealer. Spherical amorphous calcium phosphate-like phases that spontaneously transformed into apatite-like phases were seen in the fractured specimens of ProRoot Endo Sealer after SBF storage.

CONCLUSIONS

When tested in bulk without a main core, both 'sealer type' and 'SBF storage' were significant in affecting push-out results. The ProRoot Endo Sealer demonstrated the presence of spherical amorphous calcium phosphate-like phases and apatite-like phases (i.e. ex vivo bioactivity) after SBF storage.

Microscopic appearance and apical seal of root canals filled with gutta-percha and ProRoot Endo Sealer after immersion in a phosphate-containing fluid

AIM

To investigate the sealing quality of ProRoot Endo Sealer, a calcium silicate-based sealer and its morphologic characteristics after immersion in a phosphate-containing fluid (PCF).

METHODOLOGY

Single-rooted canals were filled with gutta-percha and either ProRoot Endo Sealer or two commercially available zinc oxide eugenol (ZOE)-based and epoxy resin-based sealers. The sealers were allowed to set for 6 days and the filled teeth were immersed in PCF for 24 h before fluid leakage evaluation. After initial leakage evaluation at the 7th day, each filled root was restored and reimmersed in PCF for 28 days before the second phase of leakage evaluation at 35 days. Cryofractured specimens of additional teeth filled with the three sealers were examined using scanning electron microscopy after immersion in PCF for the two periods.

RESULTS

One-way repeated measures anova and Tukey test revealed significant differences between the ZOE-based sealer at 35 days and the calcium silicate-based sealer at 35 days (P < 0.001), and between the ZOE-based sealer at 7 days and the calcium silicate-based sealer at 35 days (P = 0.001). No difference was found between the epoxy resin-based sealer and the calcium silicate-based sealer after both storage periods. Cryofractured calcium silicate-based sealer specimens demonstrated apatite-like crystalline deposits along the apical and middle thirds of the canal walls via transformation from amorphous calcium phosphate-like precursors.

CONCLUSIONS

ProRoot Endo Sealer is comparable in sealing quality to the epoxy resin-based sealer and seals better than the ZOE-based sealer after immersion in PCF. The calcium silicate-based sealer also demonstrates ex vivo bioactivity when it comes into contact with phosphate ions.

Biodegradable porous calcium polyphosphate scaffolds for the three-dimensional culture of dental pulp cells

AIM

To develop a three-dimensional culture model of human dental pulp cells (DPCs) with biodegradable porous calcium polyphosphate (CPP) scaffolds.

METHODOLOGY

Human DPCs were isolated from three donors. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of CPP compared with hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP). Values were analysed using unpaired t-tests. Cells were seeded onto porous CPP scaffolds with pore sizes in the range of 200-300 microm. The nature of cellular adaptation in the three-dimensional culture model was then evaluated visually by scanning electronic microscopy (SEM) and confocal laser scanning microscopy (CLSM). The apoptotic property of cells on the scaffolds was also assessed by DNA staining with CLSM.

RESULTS

The cytotoxicity assay indicated that there was no significant difference between CPP and HA for each donor's original cells (P>0.05). Calcium polyphosphate had no cytotoxic effect on DPCs, whilst SEMs showed that cells successfully adhered to CPP scaffolds and spread amongst pores. On the cell surface, fine processes and matrix secretory granules were found. Confocal laser scanning microscopy showed that cells took on a three-dimensional structure with signs of vitality.

CONCLUSION

Porous CPP scaffolds are promising for the establishment of a three-dimensional culture model of DPCs.

Evaluation of the accuracy of three electronic apex locators using glass tubules

AIM

To evaluate the accuracy of three different electronic apex locators (EALs) using glass tubules.

METHODOLOGY

Forty-eight glass tubules with different diameters and an agar model were used to mimic root canals. A size 15 stainless steel K-file was used as the measuring electrode. The Root ZX, Propex and Neosono Ultima EZ were used to measure the tubule length with tubules dry, or filled with 0.9% NaCl, 3% H(2)O(2), 2.5% NaOCl or 17% EDTA. The distance between the real length (RL) and measured length (ML) of the tubules was recorded. The range of RL +/- 0.5 mm and RL +/- 1 mm was used to evaluate the accuracy of the EALs. Results were subject to correlation analysis and Friedman's test.

RESULTS

In dry tubules, the accuracy of Root ZX was 75-91.7% for RL +/- 0.5 mm and 100% for RL +/- 1 mm, whilst the measurements of the other two EALs were all within the RL +/- 0.5 mm. No influence from the increase in tubule diameter on the accuracy of all three EALs was observed in dry tubules. In tubules filled with electrolyte, the accuracy of the Root ZX decreased as tubule diameter increased (R(d) > 0, P < 0.05). The RL-ML distance recorded by Propex was inversely related to the tubule diameter (R(d) < 0, P < 0.05). The accuracy of Propex was 75-100% for RL +/- 0.5 mm and 100% for RL +/- 0.5 mm when the tubule diameter was not more than 0.80 mm, but decreased in tubules with diameter over 0.80 mm and filled with 2.5% NaOCl or 17% EDTA. Nearly, all the measurements (except for six tubules) using Neosono Ultima EZ were within 1 mm shorter than RL despite the contents in tubules and the increase of tubule diameter.

CONCLUSIONS

The accuracy of the Root ZX decreased as the tubule diameter increased when tubules were filled with electrolytes. The electrolytes in the tubules decreased the accuracy of Propex when the tubule diameter was large. The electrolytes in tubules and tubule diameter had no influence on the accuracy of Neosono Ultima EZ. The Propex and Neosono Ultima EZ were more accurate than the Root ZX under various conditions in this laboratory study.

The efficacy of pain control following nonsurgical root canal treatment using ibuprofen or a combination of ibuprofen and acetaminophen in a randomized, double-blind, placebo-controlled study

AIM

To compare ibuprofen, to an ibuprofen/acetaminophen combination in managing postoperative pain following root canal treatment. It is hypothesized that the drug combination will provide more postoperative pain relief than the placebo or ibuprofen alone.

METHODOLOGY

Patients presenting at the Texas A&M Baylor College of Dentistry's graduate endodontic clinic, experiencing moderate to severe pain, were considered potential candidates. Fifty-seven patients were included based on established criteria. Following administration of local anaesthesia, a pulpectomy was performed. The patients were administered a single dose of either: (i) placebo; (ii) 600 mg ibuprofen; or (iii) 600 mg ibuprofen and 1000 mg of acetaminophen. Patients recorded pain intensity following treatment on a visual analogue scale and a baseline four-point category pain scale as well as pain relief every hour for the first 4 h then every 2 h thereafter for a total of 8 h. A general linear model (GLM) analysis was used to analyse the outcome.

RESULTS

Based upon the GLM analysis, there was a significant difference between the ibuprofen and the combination drug group, and between placebo and combination drug groups. There was no significant difference between the placebo and the ibuprofen.

CONCLUSION

The results demonstrate that the combination of ibuprofen with acetaminophen may be more effective than ibuprofen alone for the management of postoperative endodontic pain.

A comparison of instrument-centering ability within the root canal for three contemporary instrumentation techniques

AIM

To study and compare Great Taper (GT) hand files using a reversed balanced force technique, nickel-titanium (NiTi)flex files with a balanced force technique and stainless steel (SS) K-type files using a step-back technique.

METHODOLOGY

Forty-eight extracted mandibular premolar teeth with single root canals having curvatures between 15 and 45 degrees were prepared using a modified Bramante model and randomly divided into three groups. The teeth were cross-sectioned at 2, 6 and 10 mm from the working length. Preoperative images of canals at three levels were captured at 20x magnification using a stereomicroscope. Canals in each group were, respectively, prepared to an apical size.10 GT file with 0.2 mm tip diameter, size 30 NiTiflex file and size 30 SS K-file. The GT file was used in a reversed balanced force technique, the NiTiflex file was used in a balanced force technique, and the SS K-file was used in a step-back technique. Postoperative canals were imaged under the conditions same as those for the preoperative canals. The postoperative images were superimposed over the preoperative images using software photoshop 6.0. The ability to maintain the instrument in the central axis of the canal and the deviation from the central canal axis were determined and compared by statistical analysis, along with the assessment of the amount of dentine removed.

RESULTS

At apical level, the centering ratio, the distance of transportation and the dentine removed in GT and NiTiflex groups were significantly less than those in SS group (P < 0.01), but no statistical differences were found between the two NiTi groups. At other levels, there were no substantial differences amongst the groups.

CONCLUSIONS

Compared with SS K-files, GT hand files and NiTiflex files remain better centered and produce significantly less transportation in curved canals.

A clinical radiographic retrospective assessment of the success rate of single-visit root canal treatment

AIM

To determine retrospectively the clinical and radiographic success rate of single-visit root canal treatment performed in a busy endodontic practice using contemporary techniques of canal cleaning, shaping and obturation.

SUMMARY

Seven hundred and sixty-eight single-visit cases, of which 223 presented for a re-examination appointment ranging from 6 months to 4 years from the day of treatment, were considered. Four endodontists provided examinations for both root canal treatment and re-examinations. Clinical and radiographic data were used to form an overall impression of the outcomes for each case at the time of re-examination. Available demographics and treatment information of these 223 cases were compiled for comparison. The number of treatment visits was not determined by a pretreatment diagnosis or a re-assessment of the pulp status upon entry into the tooth; therefore both vital and necrotic cases, as well as those with and without periradicular pathosis, were included. Statistical analysis was carried out using Chi-square tests and considered variations in failure rates based on gender, provider, tooth type, position and arch. A t-test was used to evaluate data on age. The overall success rate was 89.2%. No statistically significant differences were seen based on gender, age, arch or provider. Statistically, anterior teeth were more successful than posterior teeth.

Osteoblasts and MG-63 osteosarcoma cells behave differently when in contact with ProRoot MTA and White MTA

AIM

To test the hypothesis that MG-63 osteosarcoma cells and primary osteoblasts react differently to ProRoot trade mark MTA (mineral trioxide aggregate) and White MTA by: (i) investigating the attachment of primary osteoblasts and MG-63 osteosarcoma cells to ProRoot trade mark MTA and White MTA; and (ii) comparing the osteogenic behaviour of both cell lines in contact with these endodontic materials.

METHODOLOGY

Primary osteoblasts were harvested from foetal rat calvaria by sequential digestion and MG-63 osteosarcoma cells were purchased. Cells were exposed to ProRoot trade mark MTA and White MTA prepared according to the manufacturer's instructions. All samples and controls were prepared in quadruplicate. After 6, 9 and 13 days exposure to MTA, the cells were fixed and prepared for SEM examination. In addition, both the cell types were grown to confluence and exposed to beta-glycerophosphate and dexamethasone to assess mineralized nodule formation as a function of osteogenic behaviour.

RESULTS

The number of cells on the surface of the culture dish and on top of the materials increased in all samples throughout the 3 time periods, except for White MTA where no primary osteoblasts were visible on top of the material by the end of 13 days. After exposing cells to differentiation medium nodules were observed in cultures of primary osteoblasts, but not of MG-63 osteosarcoma cells.

CONCLUSIONS

Under the conditions of this study, whilst primary osteoblasts initially bound to White MTA, they did not survive on the surface by the end of 13 days. Primary osteoblasts formed mineralized nodules when exposed to differentiation medium, whilst MG-63 cells did not form nodules. As MG-63 cells do not behave osteogenically by forming mineralized nodules, and primary osteoblasts are more sensitive than MG-63 osteosarcoma cells to White MTA in cell culture, primary osteoblasts are more appropriate than MG-63 cells for testing endodontic materials in cell culture.

Apoptosis: an introduction for the endodontist

Apoptosis plays an important role in many aspects of endodontics, yet there is a paucity of information in this regard in the endodontic literature. Apoptosis is a single deletion of scattered cells by fragmentation into membrane-bound particles that are phagocytosed by other cells. It is a key process in the embryological development of the tooth, periodontal ligament and supporting oral tissue in the progression of oral disease, bone resorption, immunological response and inflammation, and in wound healing and certain pharmacological effects. The understanding of the ability of clinical materials to induce or inhibit apoptosis and the investigation of apoptosis as it relates to the pathogenesis of pulpal and periradicular pathology may eventually lead to new treatment approaches for the endodontist. The purpose of this review is to familiarize the clinical endodontist with current knowledge on apoptosis as it relates to the pulp and periradicular tissues.

Comparison of Diaket and MTA when used as root-end filling materials to support regeneration of the periradicular tissues

AIM

The objective of this study was to evaluate on a comparative basis the potential for mineral trioxide aggregate (MTA) and Diaket to promote periradicular tissue regeneration when used as surgical root-end filling materials.

METHODOLOGY

Seven dogs weighing between 15 and 25 kg were anesthetized prior to having the root canals of their mandibular premolars accessed, cleaned, shaped and obturated. Coronal access cavities were restored with IRM. Surgical access to the root ends was established and the root ends were resected and prepared with ultrasonic tips. Root-end fillings of either MTA or thickly mixed Diaket were randomly assigned to the preparations. Reflected tissues were repositioned and sutured with 4-0 vicryl sutures. Sixty days postsurgery, the animals were killed, perfused with 10% neutral buffered formalin and the third and fourth premolars removed in block sections. The specimens were demineralized and sectioned at 6-microm intervals for histological assessment. Sections were stained with either haematoxylin and eosin or Gomori's one step trichrome stain and examined under the light microscope. All evaluations were made by two calibrated examiners and gradings were scored based on established criteria. The raw data was evaluated statistically using anova after adjusting for the animal block effect.

RESULTS

Statistical evaluation indicated that there were no statistical differences between the observed regenerative responses of the tissues to the two root-end filling materials.

CONCLUSIONS

Both Diaket and MTA can support almost complete regeneration of the periradicular periodontium when used as root-end filling materials in periradicular surgery on noninfected teeth.

The effect of FIV infection on CD4+ and CD8+ counts in periradicular lesions

AIM

The purpose of this study was to elucidate whether a decrease/increase in T-cell populations is present in the development of periradicular disease in the immunocompromised feline model.

METHODOLOGY

Eight cats were immunosuppressed with steroids prior to infection with feline immunodeficiency virus (FIV). Another eight cats, age and sex matched littermates, were monitored and tested at equivalent periods of time and served as uninoculated, seronegative controls. Periradicular lesions were induced using local bacterial inoculations into the pulp of the canine teeth and assessed after one- and four-week periods, corresponding to the acute and chronic stages of the periradicular disease. Block sections were obtained and specimens were prepared for H & E and immunohistochemical staining for CD4+ and CD8+ receptors. Cells were quantified using a computer imaging system and data analysed using generalized estimating equation (GEE) regression models.

RESULTS

Significantly lower CD4+ counts and CD4+/ CD8+ ratios were observed at all time periods in the periradicular region of the FIV group (P = 0.0006). No significant difference in CD8+ counts was observed between the two groups. In both groups there was a significant difference in the CD4+ counts between one week and baseline, and 1 week and 4 weeks. There was no significant difference between baseline and 4 weeks for either group.

CONCLUSION

FIV infection reflected decreased CD4+ counts at the periradicular level, however, inflammation and progression of the lesion, appeared to be comparable to the non-immunocompromised controls.

Interleukin-1beta production in periradicular lesions in a human immunodeficiency virus/acquired immune deficiency syndrome model compared with a noninfected host

This study elucidates the role of interleukin-1 (IL-1) in developing periradicular lesions in immunocompetent and immunocompromised (human immunodeficiency virus/acquired immune deficiency syndrome) hosts. Eight cats were immunosuppressed with steroids before infection with feline immunodeficiency virus (FIV). Eight uninoculated cats served as controls. Periradicular lesions were induced around the canine teeth. At 1 and 4 wk periradicular exudate was sampled via the root canals. IL-1beta levels were measured with ELISA. Data were analyzed using the Mann-Whitney U test and the Wilcoxon signed rank test. Statistically significant differences existed in cytokine levels between the FIV and non-FIV groups (p < 0.001). Cytokines were below detectable levels in the FIV group. A significant decrease in IL-1beta levels at 4 wk compared with 1 wk occurred in the non-FIV group (p < 0.05). In conclusion decreased IL-1beta production was obtained in the FIV group. In the non-FIV group decreases in IL-1beta levels were encountered at the chronic stage of the periradicular lesion compared with the acute stage.

Feline immunodeficiency virus model to study human immunodeficiency virus/acquired immune deficiency syndrome conditions

This study was designed to induce rapid progression of the feline immunodeficiency virus (FIV) infection in cats. Predictably inducing the FIV disease state in the cat would yield an excellent tool to study endodontic disease processes under immunosuppressed conditions. Eight cats were immunosuppressed with steroids before infection with FIV. Another eight cats, age- and sex-matched littermates, served as uninoculated seronegative controls. Complete blood counts were taken for 10 mo in the FIV group, and 10 wk in the control group, including lymphocyte subsets. ELISAs were used to detect FIV infection. Statistical analysis was performed with generalized estimating equation models. All cats were positive at one point in time. The FIV group had significantly lower peripheral blood CD4+ counts compared with the control group. Therefore the FIV model presented gives the desired outcome and simulates what occurs in human immunodeficiency virus infection.

Calcific metamorphosis: a challenge in endodontic diagnosis and treatment

Calcific metamorphosis (CM) is seen commonly in the dental pulp after traumatic tooth injuries and is recognized clinically as early as 3 months after injury. Calcific metamorphosis is characterized by deposition of hard tissue within the root canal space and yellow discoloration of the clinical crown. Opinion differs among practitioners as to whether to treat these cases upon early detection of CM or to observe them until symptoms or radiographic signs of pulpal necrosis are detected. In this review, the clinical, radiographic, and histopathologic appearance of CM is described; a review of the literature is presented to address these issues in an attempt to establish a sound rationale for treatment. Approximately 3.8% to 24% of traumatized teeth develop varying degrees of CM. Studies indicate that of these, approximately 1% to 16% will develop pulpal necrosis. Most of the literature does not support endodontic intervention unless periradicular pathosis is detected or the involved tooth becomes symptomatic. It may be advisable to manage cases demonstrating CM through observation and periodic examination.

Histologic assessment of healing after the use of a bioresorbable membrane in the management of buccal bone loss concomitant with periradicular surgery

Histological and morphometric assessment of periradicular wound healing was made after the use of a bioresorbable membrane over a buccal dehiscence. The third and fourth premolar teeth of nine dogs were resected and buccal defects created. Teeth were assigned randomly to the membrane or control group. One tooth in each quadrant received a membrane, covering both roots. The other tooth received no further treatment and served as a control. The animals were killed and specimens were assessed at two time periods: 9 wk and 27 wk. The 27-wk membrane group exhibited significantly more (p = 0.004) connective tissue height than the control group or either of the 9-wk groups. The amount of regenerated alveolar bone was significantly greater for the 27-wk membrane group than for the control (p = 0.001) and 9-wk groups. Mean junctional epithelium measurements were significantly greater (p = 0.012) for the control. The use of a bioresorbable membrane enhances bone regeneration when a buccal defect exists at the time of periradicular surgery.

The outcome of endodontic resurgery: a systematic review

AIM

The aim of this paper is to establish an outcome standard for the assessment of healing radiographically after resurgery of persistent periradicular lesions by systematically reviewing the results from published studies.

METHODOLOGY

The systematic review process requires the definition of predetermined criteria delineating the inclusion parameters of studies reviewed. Of 42 papers that were reviewed, eight qualified for inclusion. A weighted-average was calculated from the results taken from the eight eligible, peer-reviewed studies, published between 1970 and 1997.

RESULTS

Three hundred and thirty patients out of 2375 (14%) from the included studies underwent resurgery for failure of healing as determined radiographically. Of this population, 35.7% healed successfully after resurgery, 26.3% healed with uncertain results and 38% did not heal at the one-year follow-up.

CONCLUSIONS

Although there is nearly equal distribution of results between all categories, a 35.7% rate of healing as assessed radiographically is essentially equivalent to the 38% failure rate. This paper will allow an evaluation of current research results to establish an outcome standard and enable techniques and filling materials to be evaluated and compared. Furthermore, the outcome standard can assist in defining demographic and aetiological factors that contribute to the potential outcome of resurgery cases.

Restoring teeth that are endodontically treated through existing crowns. Part I: Survey of pulpal status on access

OBJECTIVE

The purpose of this study was to identify the pulpal findings encountered by practitioners when accessing complete-coverage crowns that require nonsurgical root canal treatment and the relevance of coronal leakage to the success of the RTC.

METHOD AND MATERIALS

The survey package consisted of a cover letter stating the instructions, rationale, and purpose for the questionnaire, a questionnaire with 8 short-answer questions, and a stamped, self-addressed envelope. A randomized sample of active dentists (300 general practitioners, 300 prosthodontists, and 300 endodontists) was selected. Collected data were analyzed with the chi-square test.

RESULTS

A 60% response rate was obtained. Statistically significant differences were found among the practitioner groups, depending on the question. General practitioners and endodontists obtain access through crowns and maintain these crowns as final restoration significantly more often than do prosthodontists. Practitioners responded that teeth with complete crowns require nonsurgical root canal treatment after 5 to 10 years.

CONCLUSION

Respondents believe that leakage must be addressed when endodontic access cavities in artificial crowns are restored after nonsurgical root canal treatment. General practitioners perform nonsurgical root canal treatment more frequently than do prosthodontists. Practitioners indicated that when teeth with complete crowns require nonsurgical root canal treatment, treatment is most often performed 5 to 10 years after placement of the crown.

Restoring teeth that are endodontically treated through existing crowns. Part II: Survey of restorative materials commonly used

OBJECTIVE

A survey was undertaken to categorize the materials used for the restoration of endodontic access openings through complete-coverage crowns after completion of nonsurgical root canal treatment.

METHOD AND MATERIALS

The survey package consisted of a cover letter stating instructions, rationale, and purpose for the questionnaire, a questionnaire of 8 short-answer questions, and a stamped, self-addressed envelope. A randomized sample of active dentists (300 general practitioners, 300 prosthodontists, and 300 endodontists), was selected. Collected data were analyzed with the chi-square analysis.

RESULTS

Most general practitioners (93%), endodontists (61%), and prosthodontists (75%) reported that they frequently or always permanently restore teeth after nonsurgical root canal treatment. Empress was the all-ceramic system used most commonly by prosthodontists (42%) and general practitioners (38%). A statistically significant difference in restorative material preference was found (P < 0.0001), depending on the type of crown used.

CONCLUSION

Amalgam alone and in combination with bonding agents are materials of choice for restoration of access openings through all-metal complete crowns, while resin composite is the choice for all types of complete crowns involving porcelain. Endodontists preferred "other" materials.

Effects of calcium hydroxide and transforming [correction of tumor] growth factor-beta on collagen synthesis in subcultures I and V of osteoblasts

Collagen protein synthesis by osteoblasts is influenced by transforming growth factor-beta (TGF-beta 1) and is essential to bone formation. The effectiveness of TGF-beta 1 depends on efficient delivery of the growth factor to target cells, adequate binding to cell surface receptors, and an optimum environment for promotion of collagen synthesis. The effects of calcium hydroxide (Ca(OH)2), TGF-beta 1, and Ca(OH)2/TGF-beta 1 co-administration on total protein, collagen protein, and noncollagen protein synthesis by early (subculture I) and late (subculture V) osteoblast cultures were tested. TGF-beta 1 significantly increased all protein synthesis in subculture I osteoblasts (p = 0.001; p < 0.001; p = 0.019). Ca(OH)2/TGF-beta 1 co-administration significantly increased total protein and collagen protein levels in subculture I osteoblasts as well (p = 0.048; p = 0.012). TGF-beta 1 increased total protein and collagen protein synthesis significantly in subculture V cells (p = 0.025; p = 0.01). These data indicate that co-administration of Ca(OH)2 and TGF-beta 1 enhances collagen synthesis by osteoblasts and may have implications for the clinical setting.

TGF-beta 1 alone and in combination with calcium hydroxide is synergistic to TGF-beta 1 production by osteoblasts in vitro

AIM

To examine the effects of calcium hydroxide (Ca(OH)2), transforming growth factor-beta (TGF-beta 1), and Ca(OH)2/TGF-beta 1 coadministration on TGF-beta 1 and interleukin-6 (IL-6) synthesis by early (subculture 1) and late (subculture 5) osteoblast cultures.

METHODOLOGY

Early and late cultures were established using bone cells harvested from 21-day-old fetal rat calvaria. Cell cultures of both early and late osteoblasts were divided into four groups: group 1, control; group 2, cells challenged with Ca(OH)2; group 3, cells challenged with TGF-beta 1; and group 4, cells challenged with Ca(OH)2 and TGF-beta 1 in combination. TGF-beta 1 and IL-6 levels for all groups were determined using ELISA methodology.

RESULTS

ANOVA and Tukey HS analyses revealed that osteoblasts of groups 3 and 4 significantly increased (P < 0.001) TGF-beta 1 synthesis in both early and late cultures of osteoblasts. IL-6 was not detected in any of the groups considered in this study.

CONCLUSIONS

Exogenous TGF-beta 1 has an autocrine effect on cell cultures of osteoblasts. Administration of TGF-beta 1 alone or in combination with Ca(OH)2 increases the synthesis of TGF-beta 1 in osteoblast cultures. Ca(OH)2 and TGF-beta 1 are compatible when placed in a culture of osteoblasts. Ca(OH)2 provides a favourable environment for the anabolic effects of TGF-beta 1.

In vitro evidence that lipopolysaccharide of an oral pathogen leaks from root-end filled teeth

AIM

The ability to achieve a complete apical seal of the root canal system is thought to be important in the success of non-surgical and surgical endodontics. The aim of this study was to establish whether or not root-end filled teeth allow leakage of lipopolysaccharide (LPS) from a known oral pathogen in vitro.

METHODOLOGY

Lipopolysaccharide (LPS) from a virulent strain of Prophyromonas gingivalis (P. gingivalis) (A7436 from patient with refractory periodontitis), was isolated by the Westphall and Jann technique, dialysed extensively, lyophilyzed, resuspended in distilled water and analysed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Root canals from 10 teeth were instrumented endodontically and the apical 3 mm of resected roots were filled with gutta-percha. The teeth were mounted in 12 mL polypropylene vials by using sticky wax and root surfaces were covered with two layers of nail varnish. Teeth were filled with 3.3 mg mL-1 LPS and the vials filled with 11 mL of Tris Buffered Saline (TBS) containing 0.05% sodium azide. Both positive and negative controls were run in parallel with the experimental specimens. Aliquots were removed each day and subjected to slot blot analysis to quantitate the amount of LPS that had leaked into the bottom of the vials. The density of slots was analyzed using a laser densitometer and regression analysis was used to generate a standard curve, confidence intervals and experimental values.

RESULTS

The data indicated that teeth obturated apically with gutta-percha leaked, whilst no LPS leakage was detected in teeth covered completely with nail varnish (P < 0.05).

CONCLUSIONS

In vitro teeth with gutta-percha root-end fills can permit leakage of LPS from an identified oral pathogen.

Comparative radiopacity of tetracalcium phosphate and other root-end filling materials

AIM

This study compared the radiopacity of tetracalcium phosphate (TTCP) and 11 root-end filling materials relative to human dentine.

METHODOLOGY

Specimens of 2 mm thickness and a graduated aluminium stepwedge were placed on dental X-ray films and exposed to an X-ray beam. The optical densities of the specimens and aluminium steps were measured. The optical densities of the specimens were correlated to the equivalent thickness of aluminium with a regression analysis equation. The equation was used to calculate the equivalent aluminium thickness of each of the specimens.

RESULTS

Nine of the materials were found to be of acceptable radiopacity (at least 2 mm Al more radiopaque than dentine). TCCP and two of the glass-ionomer compounds were found to have insufficient radiopacity to be radiographically distinguishable from human dentine.

CONCLUSIONS

All the materials were found to be distinguishable radiographically from dentine, except for Vitrebond, TTCP and Ketac-Fil. Amalgam was the most radiopaque material and Ketac-Fil was the least radiopaque material tested.

Prognosis in periradicular surgery: a clinical prospective study

AIM

The purpose of this prospective study was to evaluate the prognosis of periradicular surgery using well-defined case selection and a rigorous surgical protocol.

METHODOLOGY

Teeth to be treated surgically demonstrated a periradicular lesion of strictly endodontic origin with or without clinical signs and symptoms of inflammation. A total of 114 teeth were treated. Following the reflection of a full mucoperiosteal tissue flap, residual soft tissues were curetted, root ends were resected with a fine high-speed diamond bur, root-end cavities were prepared ultrasonically with diamond tips, and IRM root-end fillings were placed. Cases were followed clinically and radiographically for a period ranging from 1 to 4 years.

RESULTS

The results of this study showed 91.2% success out of a total of 102 teeth available for follow-up, based on accepted parameters of evaluation. Cases were considered successful if there were no clinical signs or symptoms present and there was radiographic evidence of complete or incomplete healing (scar tissue). Factors related to case selection, parameters of healing and surgical technique are discussed in relation to the success rate identified in this prospective study.

CONCLUSIONS

Adherence to a strict endodontic surgical protocol and the use of contemporary techniques and materials will result in a predictably successful outcome in a wide range of teeth.

Analysis of the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery

AIM

To analyse the healing response to gutta-percha and Diaket when used as root-end filling materials in periradicular surgery.

METHODOLOGY

Periradicular surgery was completed using the mandibular second, third and fourth premolar teeth from nine male mongrel dogs. The six roots on one side of the mouth were randomly allocated to one of the following groups: group A: a resected root end and a burnished gutta-percha root filling; group B: cavities were prepared to a depth of 4.0 mm, using ultrasonic root-end preparation and filled with Diaket. The response was evaluated histologically at 55 (nine specimens) and 150 (three specimens) days post operatively.

RESULTS

The data for the 55-day period was analysed statistically using Wilcoxon's Signed Ranks test. No statistical analysis was carried out on the 150-day group due to the small number of specimens. The level of significance was set at P < 0.05. No statistical significance was observed in the healing response between Diaket and gutta-percha in the following categories at 55 days: inflammatory response, angiogenesis, root-end resorption, and cementum deposition. Statistically significant differences were observed in the healing categories: bone apposition (P < 0.05) and periodontal ligament formation (P < 0.05).

CONCLUSIONS

At both time intervals, Diaket had a better healing response that was characterized by hard tissue formation adjacent to the root-end filling material bordered by occasional multinucleated giant cells. The nature of both the hard tissue formation and the adjacent cells, however, remains undetermined. Diaket displayed the best healing of either material used in this study.

Adaptation and sealability of two contemporary obturation techniques in the absence of the dentinal smear layer

AIM

The aim of this study was to evaluate the adaptation and short- and long-term sealability of two different thermoplastic techniques--a core carrier technique, Thermafil; and a warm vertical continuous wave of compaction technique, System B.

METHODOLOGY

Fifty-one mesial roots of mandibular molars with separate canals, patent canal orifices and curvature greater than 15 degrees were cleaned and shaped with Orifice Shapers and ProFile.04/.06 taper Ni-Ti rotary files using 5.25% NaOCl and 17% REDTA to a size 30.04 taper Profile at the apex to create a continuous tapered preparation. Canals were randomly obturated with Sealapex root canal sealer and either alpha-phase gutta-percha on a plastic Thermafil carrier, or nonstandardized beta-phase gutta-percha using the System B heat source. Proximal radiographs of roots were evaluated by three examiners based on established criteria for overall material adaptation, apical adaptation and filling material extrusion. Teeth were randomly separated into three groups of 17 each and placed in black India ink for 10 days, 24 h, or after 67 days storage in Hank's Balanced Salt Solution. All roots were demineralized and rendered transparent. Three examiners evaluated the apical leakage by the linear measurement of dye penetration under the stereo-microscope. The movement of filling material into canal irregularities was also evaluated.

RESULTS

Both obturation techniques were not significantly different in the overall canal obturation and in the apical third adaptation (P > 0.05). Significantly more filling material extrusion beyond the apex was noted with the Thermafil technique (P < 0.001). No significant difference was found amongst the 67-day, 10-day and 24 h System B groups (P > 0.05). The 67-day Thermafil group showed significantly more leakage than the 10-day and 24 h Thermafil groups. There was a significant difference in the degree of leakage between the 67-day Thermafil group and the 67-day System B group (P < 0.05), but not between the 10-day and 24 h groups (P > 0.05). Both obturation techniques produced substantial filling material movement into canal irregularities.

CONCLUSIONS

It was concluded that Thermafil demonstrated more filling material extrusion beyond the apex and significantly more long-term apical leakage.

Endodontic-orthodontic relationships: a review of integrated treatment planning challenges

Literature review There is a paucity of information on the concise relationship between endodontics and orthodontics during treatment planning decisions. This relationship ranges from effects on the pulp from orthodontic treatment and the potential for resorption during tooth movement, to the clinical management of teeth requiring integrated endodontic and orthodontic treatment. This paper reviews the literature based on the definition of endodontics and the scope of endodontic practice as they relate to common orthodontic-endodontic treatment planning challenges. Literature data bases were accessed with a focus on orthodontic tooth movement and its impact on the viability of the dental pulp; its impact on root resorption in teeth with vital pulps and teeth with previous root canal treatment; the ability to move orthodontically teeth that were endodontically treated versus nonendodontically treated; the role of previous tooth trauma; the ability to move teeth orthodontically that have been subjected to endodontic surgery; the role of orthodontic treatment in the provision for and prognosis of endodontic treatment; and, the integrated role of orthodontics and endodontics in treatment planning tooth retention. Orthodontic tooth movement can cause degenerative and/or inflammatory responses in the dental pulp of teeth with completed apical formation. The impact of the tooth movement on the pulp is focused primarily on the neurovascular system, in which the release of specific neurotransmitters (neuropeptides) can influence both blood flow and cellular metabolism. The responses induced in these pulps may impact on the initiation and perpetuation of apical root remodelling or resorption during tooth movement. The incidence and severity of these changes may be influenced by previous or ongoing insults to the dental pulp, such as trauma or caries. Pulps in teeth with incomplete apical foramen, whilst not immune to adverse sequelae during tooth movement, have a reduced risk for these responses. Teeth with previous root canal treatment exhibit less propensity for apical root resorption during orthodontic tooth movement. Minimal resorptive/remodelling changes occur apically in teeth that are being moved orthodontically and that are well cleaned, shaped, and three-dimensionally obturated. This outcome would depend on the absence of coronal leakage or other avenues for bacterial ingress. A traumatized tooth can be moved orthodontically with minimal risk of resorption, provided the pulp has not been severely compromised (infected or necrotic). If there is evidence of pulpal demise, appropriate endodontic management is necessary prior to orthodontic treatment. If a previously traumatized tooth exhibits resorption, there is a greater chance that orthodontic tooth movement will enhance the resorptive process. If a tooth has been severely traumatized (intrusive luxation/avulsion) there may be a greater incidence of resorption with tooth movement. This can occur with or without previous endodontic treatment. Very little is known about the ability to move successfully teeth that have undergone periradicular surgical procedures. Likewise, little is known about the potential risks or sequelae involved in moving teeth that have had previous surgical intervention. Especially absent is the long-term prognosis of this type of treatment. During orthodontic tooth movement, the provision of endodontic treatment may be influenced by a number of factors, including but not limited to radiographic interpretation, accuracy of pulp testing, patient signs and symptoms, tooth isolation, access to the root canal, working length determination, and apical position of the canal obturation. Adjunctive orthodontic root extrusion and root separation are essential clinical procedures that will enhance the integrated treatment planning process of tooth retention in endodontic-orthodontic related cases.

Assessment of apical and coronal root canal seals using contemporary endodontic obturation and restorative materials and techniques

AIM

The purpose of this study was to evaluate the sealing ability of two contemporary endodontic obturation and restorative techniques and materials.

METHODOLOGY

Seventy-nine extracted human single-rooted teeth were distributed randomly in two experimental groups of 36 and 37 specimens (groups 1 and 2, respectively), one group of three positive controls and one of three negative controls. The teeth were radiographed preoperatively, accessed, and instrumented. After smear layer removal, the teeth in group 1 were obturated using the System B and Obtura and were restored coronally with Core Paste using Tenure as a bonding agent. The teeth in group 2 were obturated using the Microseal technique and were restored coronally with amalgam using Panavia 21 as a bonding agent. All teeth in groups 1 and 2 were coated with three layers of nail varnish on all of their surfaces apart from the apical 4.0 mm and the coronal area above the cemento-enamel junction. The positive control teeth were obturated, restored coronally and completely coated with varnish, whereas the negative control teeth were not obturated, restored coronally, nor coated with varnish. The teeth were radiographed postoperatively and retained in saline solution for 10 days. For the next 10 days they were submerged in India ink. Subsequently all teeth were demineralized, dehydrated and rendered transparent. Dye penetration was measured using a stereomicroscope.

RESULTS

All materials and techniques provided minimal to zero dye penetration, apart from one specimen in the Core Paste group that showed 4.0 mm of dye penetration. The Wilcoxon rank sum test and t-test showed no statistically significant differences and all materials and techniques tested presented with a high degree of acceptability.

CONCLUSIONS

It was concluded that these contemporary techniques and materials provide equally good results, but long-term studies are needed for outright inferences to be drawn relative to their clinical performance.

Response of periradicular tissues to growth factors introduced into the surgical site in the root-end filling material

AIM

The objective of this study was to evaluate the healing of the periradicular tissues when exogenous growth factors were delivered to the respected root-end. The healing response was compared with that when Diaket was used as a control.

METHODOLOGY

Non-surgical root canal treatment was performed on mandibular teeth in mongrel dogs. Surgical treatment followed and included root-end resection and root-end cavity preparation. Insulin-like growth factor in combination with platelet-derived growth factor, or fibroblast growth factor alone, were then placed in the root-end preparations on a polylactic acid carrier (Atrisorb) with or without the incorporation of the carrier tetracalcium phosphate. The healing was evaluated at 60 days with regard to presence of inflammatory response, bone regeneration, periodontal ligament formation and cementum formation.

RESULTS

Osseous regeneration in the excisional would and periodontal formation were significantly greater when Diaket was used as the root-end filling material. Likewise, cementum deposition occurred significantly more frequently in the Diaket group (P < 0.05). The polylactic carrier Atrisorb remained in the surgical sites for the duration of the study.

CONCLUSIONS

The use of specific growth factors, FGF and a combination of IGF/PDGF, delivered to the prepared root end in a collagen carrier did not initiate the desired periradicular tissue response of regeneration. Diaket, as used in this study, did stimulate a periradicular tissue response compatible with regeneration.