Factors that influence the outcomes of surgical endodontic treatment

Surgical endodontic treatment encompasses a broad spectrum of procedures, amongst which root-end cavity preparation and filling, retrograde root canal treatment and through-and-through endodontic surgery, may be classified under the umbrella term 'Root-end surgery'. This narrative review considers the available data on periapical healing, soft tissue healing, tooth survival and oral health-related quality of life (OHRQoL), following root-end surgery and the factors that affect its outcomes. The pooled periapical healed rate for the studies published up to 2021 was 69% (95% CI: 65%, 73%) but increased to 76% (95% CI: 66%, 86%) when only data from the 2020's studies were analysed. The prognostic factors consistently reported for periapical healing have included: pre-operative periapical lesion with complete loss of buccal plate, quality of root-end preparation, remaining thickness of apical root dentine and restorative status. Soft tissue healing of the reflected flap was found to have a positive association with periapical healing. The survival rates following root-end surgery range from 48% to 93%, with failure of periapical healing associated with root and crown fracture, being the predominant reasons for tooth extraction. The factors influencing impact of root-end surgery on patients' quality of life could not be adequately evaluated due to design flaws in the available studies. In conclusion, if root canal treatment failure due to leakage through cracks, fractures or restoration margin are excluded, the remaining cases may represent localized residual infection and inflammation at the periapex that should be amenable to predictable management with the aid of modern root-end surgery.

Morphotypes of the apical constriction of maxillary molars: a micro-computed tomographic evaluation

Objectives

The aim of this study was to evaluate and compare the apical constriction (AC) and apical canal morphology of maxillary first and second molars, using micro-computed tomography (micro-CT).

Materials and Methods

The anatomical features of 313 root canals from 41 maxillary first molars and 57 maxillary second molars of patients with known age and sex were evaluated using micro-CT, with a resolution of 26.7 µm. The factors evaluated were the presence or absence of AC, the morphotypes, bucco-lingual dimension, mesio-distal dimension, and the profile (shape) of AC and the apical root canal. The apical root canal dimensions, location of the apical foramen (AF), AC to AF distance, and presence of accessory canals in the apical 5 mm were also assessed. Descriptive and analytical statistics were used for data evaluation.

Results

AC was present in all 313 root canals. Patients’ age and sex did not significantly impact either AC or the apical canal dimensions. The most common AC morphotype detected was the traditional (single) constriction (52%), followed by the parallel (29%) morphotype. The mean AC dimensions in maxillary first molars were not significantly different from those in maxillary second molars. Sixty percent of AF were located within 0.5 mm from the anatomic apex.

Conclusions

The most common morphotype of AC detected was the traditional constriction. Neither patients’ age nor sex had a significant impact on the dimensions of the AC or the apical root canal. The majority of AF (60%) were located within 0.5 mm from the anatomic apex.

Proximity of maxillary molar apexes to the cortical bone surface and the maxillary sinus

Objectives

Materials and Methods

Results

Conclusions

Ex vivo comparison of antibacterial efficacy of conventional chemomechanical debridement alone and in combination with light-activated disinfection and laser irradiation against Enterococcus faecalis biofilm

BACKGROUND AND OBJECTIVES

Intracanal disinfection plays an important role in endodontic treatment success. Enterococcus faecalis (E. faecalis) is a resistant microorganism responsible for endodontic infections. We aimed to assess the bactericidal effects of three disinfection methods on E. faecalis biofilm.

MATERIALS AND METHODS

Fifty-five freshly extracted single-rooted human teeth were evaluated. A barbed broach was used to extract the pulp tissue. No further root canal preparation was performed. Specimens were sterilized with gamma radiation, and inoculated with E. faecalis suspension. They were then incubated for 4 days and 4 weeks. Biofilm formation was confirmed using a scanning electron microscope (SEM). The teeth were randomly assigned to three subgroups (n = 7) to assess the antimicrobial efficacy of the following three disinfection methods against immature (4-day) and mature (4-week) biofilms: the conventional chemomechanical debridement (CCMD), CCMD + light-activated disinfection (LAD; 810 nm, 0.3 W, 120 J/cm²) with indocyanine Green (EmunDo) as photosensitizer and CCMD + diode laser irradiation (810 nm, 2 W). The teeth were then longitudinally split into two halves and the colony count was reported as colony forming units (CFUs) to assess bacterial viability after each disinfection protocol.

RESULTS

None of the disinfection methods could completely remove the biofilm. CCMD + LAD caused the highest and CCMD + diode laser caused the lowest reduction in biofilm. Antibacterial efficacy was significantly lower against the mature (4-week) biofilm compared with immature (4-day) biofilm in all groups (P < 0.05).

CONCLUSION

All three disinfection methods were effective for partial elimination of E. faecalis biofilm. But CCMD + LAD was significantly more efficacious in decreasing both mature and immature biofilms.

Micro-CT evaluation of apical delta morphologies in human teeth

The apical delta is an intricate system within the root canal and incompletely debridement may affect the long-term prognosis of root canal therapy. The aim of the present study is to investigate the morphologic features of apical deltas in human teeth with micro-computed tomography (micro-CT) using a centreline-fitting algorithm. One hundred and thirty-six apical deltas were detected in 1400 teeth. Molars had more apical deltas (15.8%) than anterior teeth (6.3%). In maxillary molars, the mesiobuccal root had a significantly higher prevalence of apical delta than the palatal root or the distobuccal root. The median vertical distance of the apical delta was 1.87 mm with 13% more than 3 mm. The median diameter and length of the apical delta branches were 132.3 and 934.5 μm. Apical delta branches were not straight with cross-sectional shapes being non-circular. These morphological features of apical delta may complicate debridement of the infected root canal system.

Comparative evaluation of canal cleaning ability of various rotary endodontic filesin apical third: A scanning electron microscopic study

BACKGROUND

The purpose of this study was to evaluate the canal cleaning ability of three novel endodontic rotary instruments and compare with ProTaper files as a control in apical third of root canals under scanning electron microscopy (SEM).

MATERIALS AND METHODS

Eighty freshly extracted mandibular premolars were selected according to inclusion criteria. Buccal cusp tips were ground to ensure having a flat coronal reference point with a total tooth length of 16 mm for all samples. Teeth were divided equally into four groups: Group I (ProTaper group), Group II (ProTaper next group), Group III (variable taper group), and Group IV (self-adjusting file [SAF] group). Using SEM, the dentinal surfaces were observed and rated at apical thirds with a magnification of ×1000 for the presence/absence of smear layer and debris. Descriptive analysis was performed, and analysis of variance with Bonferroni post hoc test was carried out for comparison between the groups, at a significance level of 0.05.

RESULTS

There was statistically significant difference between Group II and Group IV for debris (P = 0.047) and smear layer (P = 0.037).

CONCLUSION

In apical third of root canal, SAF showed statistically significant canal cleaning ability due to combined effect of continuous streaming irrigation with effectively replacing the irrigant from the apical portion of the root canal, irrigants activation through the creation of turbulence, and its self-adapting design to root canal anatomy with a scrubbing motion on the canal walls.

Scanning electron microscopic examination of resected root apices obtained from endodontic microsurgery

This study was designed to examine the morphological features of the resected root apices obtained from endodontic microsurgery using a scanning electron microscope (SEM) as well as their anatomical effect on the clinical outcome of the surgical treatment. One-hundred-six resected root apices from 91 patients/surgeries were obtained by endodontic microsurgery, and fixed immediately for storage. The resected apices were prepared for SEM to examine their morphological features, such as the number and size of the apical foramina. The patients were periodically checked up at least 1 year and the clinical outcome of the microsurgery was judged as a success or failure according to the Molven's criteria. The SEM findings and the clinical outcome of apical surgery were evaluated to see any potential correlation between them. The SEM examination revealed that 60.4% of specimens had more than two portals of exit on the resected root apices and the size of the major foramen was at least 386 micrometer and 334 micrometer from maxillary and mandibular molar, respectively. With a recall rate of 72.9%, 91.9% of the surgical cases were decided to have successful outcomes. Based on this SEM study, a relatively high frequency of multiple portals of exit was existed and the sizes of major foramina were bigger than that were reported in previous reports. The clinical outcomes of endodontic microsurgery were not correlated with the anatomical features of resected apical root apices. SCANNING 38:455-461, 2016. © 2016 Wiley Periodicals, Inc.

Proximity of the mandibular molar root apex from the buccal bone surface: a cone-beam computed tomographic study

Objectives

The purpose of this study was to evaluate the proximity of the mandibular molar apex to the buccal bone surface in order to provide anatomic information for apical surgery.

Materials and Methods

Cone-beam computed tomography (CBCT) images of 127 mandibular first molars and 153 mandibular second molars were analyzed from 160 patients' records. The distance was measured from the buccal bone surface to the root apex and the apical 3.0 mm on the cross-sectional view of CBCT.

Results

The second molar apex and apical 3 mm were located significantly deeper relative to the buccal bone surface compared with the first molar (p < 0.01). For the mandibular second molars, the distance from the buccal bone surface to the root apex was significantly shorter in patients over 70 years of age (p < 0.05). Furthermore, this distance was significantly shorter when the first molar was missing compared to nonmissing cases (p < 0.05). For the mandibular first molars, the distance to the distal root apex of one distal-rooted tooth was significantly greater than the distance to the disto-buccal root apex (p < 0.01). In mandibular second molar, the distance to the apex of C-shaped roots was significantly greater than the distance to the mesial root apex of non-C-shaped roots (p < 0.01).

Conclusions

For apical surgery in mandibular molars, the distance from the buccal bone surface to the apex and apical 3 mm is significantly affected by the location, patient age, an adjacent missing anterior tooth, and root configuration.

Surgical endodontic management of infected lateral canals of maxillary incisors

This case report presents surgical endodontic management outcomes of maxillary incisors that were infected via the lateral canals. Two cases are presented in which endodontically-treated maxillary central incisors had sustained lateral canal infections. A surgical endodontic treatment was performed on both teeth. Flap elevation revealed vertical bone destruction along the root surface and infected lateral canals, and microscopy revealed that the lateral canals were the origin of the lesions. After the infected lateral canals were surgically managed, both teeth were asymptomatic and labial fistulas were resolved. There were no clinical or radiographic signs of surgical endodontic management failure at follow-up visits. This case report highlights the clinical significance and surgical endodontic management of infected lateral canal of maxillary incisor. It is important to be aware of root canal anatomy variability in maxillary incisors. Maxillary central incisors infected via the lateral canal can be successfully managed by surgical endodontic treatment.

Analysis of the cause of failure in nonsurgical endodontic treatment by microscopic inspection during endodontic microsurgery

INTRODUCTION

This study examined the clinical causes of failure and the limitation of a previous endodontic treatment by an inspection of the root apex and resected root surface at 26× magnification during endodontic microsurgery.

METHODS

The data were collected from patients in the Department of Conservative Dentistry at the Dental College, Yonsei University in Seoul, Korea between March 2001 and January 2011. All root-filled cases with symptomatic or asymptomatic apical periodontitis were enrolled in this study. All surgical procedures were performed by using an operating microscope. The surface of the apical root to be resected or the resected root surface after methylene blue staining was examined during the surgical procedure and recorded carefully with 26× magnification to determine the state of the previous endodontic treatment by using an operating microscope.

RESULTS

Among the 557 cases with periapical surgery, 493 teeth were included in this study. With the exclusion of unknown cases, the most common possible cause of failure was perceived leakage around the canal filling material (30.4%), followed by a missing canal (19.7%), underfilling (14.2%), anatomical complexity (8.7%), overfilling (3.0%), iatrogenic problems (2.8%), apical calculus (1.8%), and cracks (1.2%). The frequency of possible failure causes differed according to the tooth position (P < .001).

CONCLUSIONS

An appreciation of the root canal anatomy by using an operating microscope in nonsurgical endodontic treatment can make the prognosis more predictable and favorable.

An ex vivo investigation of the relationship between apical root impedance and canal anatomy

AIM

To investigate a possible relationship between apical root impedance and canal anatomy.

METHODOLOGY

Twenty-three roots from human extracted teeth with different apical anatomy (classified by number of apical canal exits) were selected. After impedance measurements, the root canals were stained and the teeth cleared to confirm their division into simple (S - Vertucci type 1; n=12) and complex (C - various Vertucci canal types with multiple exits; n=11) root types. Impedance measurements were taken using a frequency response analyser at seven apico-coronal levels in each root (0.0, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 mm short of the apical terminus) at 14 frequencies ranging from 1120 to 100,000 Hz. Potential confounding factors were controlled. The impedance characteristics of individual roots were compared with 37 equivalent circuits to select best fit. The association between impedance characteristic (described by the selected equivalent circuit) and canal anatomy (S/C) was investigated using logistic regression with robust standard error to account for multiple data-sets from the same root.

RESULTS

Canal anatomy had a significant (P= 0.046) effect on the equivalent circuit model. One circuit (model 10) occurred significantly more commonly in the simple canals. The odds of selecting circuit-model-10 were 2.2 times (odds ratio 2.17, 95% confidence interval 1.01-4.63) higher in canals with simple anatomy compared to those with complex anatomy.

CONCLUSION

Canal anatomy had a significant effect on the equivalent circuit describing its impedance characteristics. It is theoretically possible to use impedance spectroscopy to clinically predict and image apical canal complexities.

Incidence of accessory canals in Japanese anterior maxillary teeth following root canal filling ex vivo

AIM

To investigate the vertical and horizontal distribution and the incidence of accessory canals in Japanese maxillary anterior teeth following root filling.

METHODOLOGY

The study included maxillary teeth; 69 central incisors, 61 lateral incisors and 31 canines. After the canal systems had been dyed and root canal instrumentation had been carried out, all prepared canals were filled with gutta-percha without using sealer. Transparent specimens were then obtained and examined with a digital microscope for horizontal and vertical distributions of accessory canals.

RESULTS

The incidence of teeth with accessory canals in the apical 3 mm was 46%, 29% and 38% for the maxillary central incisors, lateral incisors and canines, respectively. The horizontal distribution was mainly buccal for central incisors, palatal for lateral incisors and distal and palatal for canines. There was a significant difference (P < 0.05) between the apical 3 mm and the rest of the root (16%, 20% and 19% for the maxillary central incisors, lateral incisors and canines, respectively) in terms of the presence of accessory canals.

CONCLUSIONS

A high percentage of accessory canals can be found in apical 3 mm of the root. The horizontal distribution of accessory canals differed amongst the tooth types studied.

Morphological assessment of dentine and cementum following apicectomy with Zekrya burs and Er:YAG laser associated with direct and indirect Nd:YAG laser irradiation

OBJECTIVES

This study aimed to assess the apical surface morphology of maxillary central incisors resected 3.0 mm from the tooth apex using Zekrya burs or Er:YAG laser, with or without subsequent direct Nd:YAG laser irradiation (apical and buccal surfaces) and indirect irradiation (palatal surface).

STUDY DESIGN

Forty maxillary central incisors were instrumented and obturated. The roots were divided into 4 groups according to the root resection method (Zekrya bur or Er:YAG laser - 1.8 W, 450 mJ, 4 Hz, 113 J/cm(2)) and further surface treatment (none or Nd:YAG laser - 2.0 W, 100 mJ, 20 Hz, 124 J/cm(2)). The teeth were prepared for SEM analysis. Scores ranging from 1 to 4 were attributed to cut quality and morphological changes. The data were analyzed by the Kruskal-Wallis test and by Dunn's test.

RESULTS

SEM images showed irregular surfaces on the apical portions resected with Zekrya burs, with smear layer and grooves in the resected dentine and slight gutta-percha displacement and plasticization. On the other hand, apicectomies carried out with Er:YAG laser showed morphological changes compatible with ablated dentine, with rough surfaces and craters. In spite of the presence of plasticized gutta-percha, with the presence of bubbles, an irregular adaptation of the filling material to the root walls was also observed. Direct Nd:YAG laser irradiation of the apical and buccal surfaces of the resected roots resulted in areas of resolidification and fusion in the dentine and cementum, with a vitrified aspect; indirect Nd:YAG laser irradiation of the palatal surfaces yielded a lower number of changes in the cementum, with irregular resolidification areas.

CONCLUSIONS

There were no differences in terms of cut quality between the use of burs and Er:YAG laser or between the 2 surfaces (apical and buccal) treated with Nd:YAG laser with direct irradiation. However, morphological changes were significantly less frequent on surfaces submitted to indirect irradiation (palatal) when compared with those directly irradiated.

A stereomicroscopy study of root apices of human maxillary central incisors and mandibular second premolars in an Iranian population

Mandibular second premolars and maxillary central incisors usually have one root, one canal, and one apical foramen. However, some studies have revealed anatomic variations in these teeth. The aim of the present study was to investigate such variations in canal configuration, foramina, lateral and accessory canals and apical deltas in the root apex of human maxillary central incisors and mandibular second premolars, using a clearing technique and stereomicroscopy. One hundred maxillary central incisors and 137 mandibular second premolars were collected, and India ink was injected into their canals. The teeth were then demineralized with 0.5 N nitric acid, cleared with methyl salicylate, and studied at x 5 and x 16 magnification. The incidence of one canal and one apical foramen was 100% for maxillary central incisors and 94.16% for mandibular second premolars. The main apical foramen was located in the center of the root apex in 21.89% and 17% of mandibular second premolars and maxillary central incisors, respectively. Lateral and accessory canals were found in 84.50% and 77.15% of maxillary central incisors and mandibular second premolars, respectively. Several foramina were found in 11% of maxillary central incisors and 24.08% of mandibular second premolars. Apical deltas were seen in 4.38% and 2% of mandibular second premolars and maxillary central incisors, respectively. The rate of anatomic variations in the apical part of the tooth, especially in posterior teeth, is thus considered to be high.

Endodontic re-treatment associated with the elimination of amalgam root-end filling through sinus tracts: a report of two cases

Two patients presented with complaints of recurrent drainage of purulent exudate from sinus tracts, inflammation and pain after endodontic re-treatment of the maxillary left (Case 1) and right (Case 2) lateral incisors. The periapical lesions persisted after apical curettage, apicectomy and root-end filling with silver amalgam. Radiographic examination exposed the poor quality of the endodontic treatments and the silver amalgam root-end fillings, which were associated with periapical radiolucent areas in both teeth. The sinus tract persisted after root canal cleaning and shaping, followed by a calcium hydroxide root canal dressing. The root-end fillings were periapically dislodged with endodontic K-files, and showed progressive displacement by sinus tracts up to elimination in the oral cavity. Follow ups of 42 and 65 months post procedure revealed clinical disappearance of the symptoms, sinus tracts and exudates, and radiographs revealed that the repair process of the periapical radiolucent areas was quite advanced.

Computer-assisted evaluation of microleakage after apical resection with laser and conventional techniques

The purpose of this in vitro study was to observe the morphological changes and apical dye penetration at apical dentin surfaces after apicoectomy with conventional techniques and laser beam. Sixty single-rooted extracted teeth were selected for the study. The crowns were resected below the cemento-enamel junction. Then, these teeth were treated endodontically and filled with gutta-percha using AH-26 root canal sealer. The teeth were randomly divided into four groups of 15 teeth in each. The roots were resected perpendicular to its long axis 3 mm from the apex using Er: yttrium-aluminium-garnet (YAG) laser irradiation in groups 1 and 2, and the resected root surfaces were lased with Nd:YAG laser in group 2. The apexes were resected by a high-speed handpiece in groups 3 and 4, and the resected root surfaces were lased with Nd:YAG laser in group 4. Ten teeth in each group were used for leakage studies, and the other five teeth were used for scanning electron microscopic examinations. Seven sections were obtained from each root to assess the microleakage, and the sections were analyzed in a computer-assisted manner. No statistically significant differences were observed between the leakage percentage of groups 1 and 3 and groups 2 and 4 (p>0.05). Morphological differences were observed between apical dentin surfaces resected with conventional techniques and laser beam.

Methods of experimental induction of periapical inflammation. Microbiological and radiographic evaluation

AIM

To evaluate the influence of coronal filling and apical perforation on the induction of periapical inflammation.

METHODOLOGY

Fifty-eight root canals in the teeth of dogs were divided into four groups. Groups I and II: root canals were exposed for 180 days; groups III and IV: root canals were exposed for 7 days and then the access cavity filled for 53 days. The root apices of groups I and III were perforated after the coronal opening, whilst those of groups II and IV remained intact. Standard radiographs were taken before and after the experimental periods. Digital images of the radiographs were created and then analysed by three examiners. After induction of periapical inflammation, the root canal contents were collected using paper points. Microbiologic evaluation of the type of microorganism was carried out by culture in different growth media. The radiographic and microbiologic data were statistically analysed using anova at a 5% significance level.

RESULTS

There were a greater total number of microorganisms in groups I and II (P < 0.05). The number of anaerobes was greater than the number of aerobes (P < 0.05). The size of the periapical radiolucencies were not significantly different between the experimental groups.

CONCLUSIONS

The different methods analysed induced similar areas of periapical radiolucency in dogs with predominantly anaerobic bacteria. However, the time required for induction was less when the method with coronal filling was used.

Frequency Of Transverse Anastomoses With And Without Apical Communication In Japanese Population Teeth

The aim of this study was to describe and measure the frequency of transverse anastomoses with and without an apical communication in Japanese population teeth. One hundred and twenty-three extracted teeth from Japanese people were used in this study. The sample consisted of: 63 mandibular first molars, 30 maxillary first molars and 30 maxillary first premolars. Access openings were made through the crowns to the pulp chamber and India ink was injected into the coronal pulp space and vacuumed from the apical end. The teeth were cleaned and digital micrographs taken from several angles to identify transverse anastomoses. Fourteen teeth had only one canal and 81 teeth out of 109 (74%) had transverse anastomoses including 6 teeth (5.5%) that had an apical communication. Most of the anastomoses (50) were located in the middle portion of the canal and 22 (20%) teeth showed multiple anastomoses. Special attention must be taken after resection of roots with apparent multiple canals. The potentially exposed exits and/or isthmuses should be taken into consideration during surgical endodontic treatment.

Periapical endodontic surgery: a 3-year follow-up study

AIM

To monitor the outcome of periradicular surgery in a group of teeth treated with microsurgical technology and ultrasonic root-end preparation.

METHODOLOGY

One hundred and twenty-eight teeth with failed conventional root canal treatment were included. The surgical procedure was completed using ultrasonic retrotips and a zinc oxide-EBA (Super Seal, Ogna Pharmaceuticals. Milan, Italy)-reinforced material was used to seal the root end cavities. Lesions were examined radiologically at 1. 3. 6. 12, 24 and 36-month intervals. Radiographs were independently analysed according to a previously published classification.

RESULTS

Eight teeth were extracted due to fracture or perforations undetected radiologically: these cases were excluded from the study. Of the 120 teeth examined. the overall success rate was 92.5%; 94 healed with complete bone filling of the surgical cavity, 17 were considered to have healed by apical scar formation, four demonstrated uncertain healing and five were considered failures. Eighty of 120 teeth examined had successfully healed from a radiological point of view within 12 months. No differences in outcome occurred between anterior, premolar and molar teeth. Although all failures occurred in teeth with posts, no statistically significant difference was noted (Mann-Whitney U-test, P = 0.37).

CONCLUSION

Modern surgical endodontic procedures associated and ERA (Super Seal, Ogna Pharmaceuticals, Milan, Italy) root end fillings were successful over 3 years in 92.5% of cases.

An in vitro comparison of the bactericidal efficacy of lethal photosensitization or sodium hyphochlorite irrigation on Streptococcus intermedius biofilms in root canals

AIM

To compare the bacterial killing of Streptococcus intermedius biofilms in root canals using lethal photosensitization with various combinations of photosensitizer concentration and laser light dose or 3% sodium hypochlorite (NaOCl) irrigation.

METHODOLOGY

Extracted teeth (n = 35) with single canals were selected and the canals prepared to apical size 25 with a 10% taper. The teeth were autoclaved and the canals inoculated with Streptococcus intermedius in brain heart infusion broth and were incubated for 48 h to allow a biofilm to form. The teeth were then subjected to 3% NaOCl irrigation (n = 4) or lethal photosensitization using combinations of a range of toluidine blue O (TBO) photosensitizer concentrations (12.5, 25, 50, 100 microgram/mL-1) and light doses (60, 90, 120, 300, 600 s equivalent to energy doses of 2.1-21 J) using a 35-mW helium-neon low power laser targeted at the access cavity (n = 4 for each combination). Controls consisted of laser light only (TBO = 0 microgram/mL-1) (n = 4), TBO only (light dose = 0 s) (n = 4), and no treatment (positive control n = 17). Following treatment the canal contents were sampled with sterile paper points, the sample was dispersed in transport medium, serially diluted and cultured on blood agar to determine the number of colony forming units (CFU).

RESULTS

The combination of 100 microgram/mL-1 TBO and 600 s (21 J) of laser energy achieved maximum reduction in recovered viable bacteria (5 log10 CFU). TBO at low concentrations (< or =50 microgram/mL-1) was not bactericidal but treatment with 100 microgram/mL-1 TBO alone reduced recovered viable bacteria by 3 log10 CFU. Laser light alone had limited bactericidal effect. No viable bacteria were recovered following treatment with 3% NaOCl.

CONCLUSIONS

The combined use of a photosensitizing agent and a low power laser directed at the access cavity was bactericidal to S. intermedius biofilms in root canals but was unable to achieve total kill, unlike 3% NaOCl.

Effect of access cavity location and design on degree and distribution of instrumented root canal surface in maxillary anterior teeth

AIM

The null hypothesis tested in this study was that in single-rooted anterior teeth with simple root canal anatomy, different access cavity designs ('lingual cingulum', 'lingual conventional', 'incisal straight-line') do not influence the ability of endodontic files to plane the walls of the root canals.

METHODOLOGY

Thirty extracted human maxillary anterior teeth were divided randomly into three groups for each access cavity. The access cavities were prepared according to predefined criteria and the roots embedded in individual polyvinyl-siloxane putty matrices. The matrices allowed these teeth to be split into buccal and palatal halves and to be reassembled. The split teeth enabled removal of pulpal remnants from the root canal system and the walls to be stained with an even layer of permanent black ink. Once dried, the split roots were reassembled in the putty matrices and a step-back filing technique was used to prepare the canals with water irrigation. The canal walls were examined for residual ink staining and scored by three independent assessors using an index devised for the purpose.

RESULTS

There was good agreement between the assessors. None of the access cavities allowed file contact with the entire root canal wall. The overall (palatal and buccal sections) scores showed significant differences (P < 0.01) between the access cavity groups in the extent to which the canal walls could be filed. The straight-line incisal access cavity had the greatest proportion of instrumented root canal surface. The lingual cingulum access cavity was the worst in this respect. The differences in residual ink scores between the access cavity types were significant for the buccal halves (P < 0.01) but not for the palatal halves (P > 0.05).

CONCLUSIONS

The null hypothesis was proven. Regardless of access cavity design, mechanical preparation did not allow instrumentation of the entire root canal wall. Straight-line access allowed the greatest proportion of the root canal wall to be instrumented and the lingual cingulum access the least.

Protective and destructive immune reactions in apical periodontitis

Apical periodontitis is initiated primarily by the mixed microflora of infected root canals. Continuous flow of bacteria and their products through the apical foramen induces influx, activation and coordinated interaction of immune-inflammatory cells within the periapical area. Successful mobilization of host defense mechanisms prevents abundant extraradicular bacterial invasion. However, anti-infective effector mechanisms are not restricted to killing the invading microorganisms but also destroy normal tissue components and induce bone absorption, resulting ultimately in the loss of the affected teeth. Moreover, autocrine and paracrine loops of stimulation may lead to the perpetuation of the local inflammatory lesion and may also alter the function of remote tissues and organs. This review attempts to summarize current knowledge about the pathogenic mechanism of apical periodontitis, focusing on the formation of a special granulation tissue that effectively fights bacteria originated from the infected pulp chamber and, by exerting this protective function, also contributes to harmful local and distant events. The dynamic equilibrium between defensive and destructive mechanisms may provide a pathobiological basis for better understanding of clinical signs and symptoms of various forms of apical periodontitis lesions and influence treatment strategy and practice.