Distal Roots Of Mandibular Molars Research Articles

Rehabilitation with Table-Top Restoration Post Bicuspidisation: An Interdisicplinary Case Report

The first teeth to erupt in the oral cavity are the mandibular molars which are more prone to endodontic and periodontal involvement. This may lead to significant issues like an increase in pocket depth, furcation involvement, loss of clinical attachment and mobility of teeth ultimately resulting in tooth loss. Thus, it necessitates cautious oral hygiene measures. Advances in dentistry have led to treatment modalities for preserving teeth which were earlier indicated for extraction. Hence, periodontally compromised tooth with severe furcation involvement, which may not be amenable for regeneration, may be retained by bicuspidisation. Bicuspidisation is a surgical technique which involves separation of mesial and distal roots of mandibular molars along with its crown portion, where both segments are then retained individually, followed by rehabilitation with fixed prosthesis of the individual segments. This not only eliminates furcation involvement but also facilitates effective oral hygiene maintenance. In the present case report, a 50-yearold male patient reported with the chief complaint of pain, sensitivity and food lodgement in left mandibular first molar. Clinical and radiographic examination revealed grade III furcation involvement, significant pocket depths, delayed electric pulp test response and bone loss in furcation area. Bicuspidisation was opted as the suitable treatment modality. Root canal treatment was done, followed by bicuspidisation and subsequent rehabilitation with novel prosthetic technique. The bicuspids were restored using combination of deep margin elevation, and non splinted Lithium Disilicate table-top restorations. Six month follow-up showed good healing of hard and soft tissues around the bicuspidized sections, which was indicative of a successful treatment outcome, and can be attributed to a careful case selection, choice of restorative materials and techniques as well as good oral hygiene compliance.

The shaping ability of WaveOne Gold, TRUShape and XP-endo Shaper systems in oval-shaped distal canals of mandibular molars: A microcomputed tomographic analysis.

To compare the shaping ability of a heat-treated centric reciprocating file system (WaveOne Gold), a heat-treated eccentric rotary multifile system (TRUShape 3D Conforming Files), and a heat-treated expandable one-file rotary system (XP-endo Shaper) extending its activation time, in preparing oval-shaped root canals in extracted mandibular molars by means of microcomputed tomography (micro-CT) analysis. Thirty moderately curved oval-shaped distal roots of mandibular molars were selected. The normality of canal length, curvature angle, volume, surface area, structure model index, and aspect ratio were confirmed. The samples were randomly divided into three groups (n=10). Micro-CT scans were taken before and after canals were instrumented using WaveOne Gold (size 35, .06 taper), or TRUShape (size 30, .06v taper), both following the manufacturer's instructions, or XP-endo Shaper following a new protocol with extended activation time. The mechanical preparation time for each sample was recorded. Pre- and postoperative images were analysed for the percentage of unprepared canal areas and the percentage of removed dentine. Data were compared between groups using the statistical analyses one-way ANOVA and Tukey tests (p<.05). The percentage of unprepared canal areas was significantly higher with WaveOne Gold (% 11.5±4.0) and TRUShape (% 12.4±5.8) compared with XP-endo Shaper (% 5.2±2.6) (p<.05). XP-endo Shaper removed significantly more dentine (3.3±1.5mm3 ) than WaveOne Gold (1.8±0.8mm3 ) and TRUShape (1.9±0.8mm3 ) (p<.05). No significant differences were seen for mechanical preparation time between WaveOne Gold (79±31s), TRUShape (104±41s) and XP-endo Shaper (71±23s) (p>.05). The comparison of three recognized root canal filing systems has shown that with similar preparation times, the XP-endo Shaper removed more dentine (mm3 ) leaving less unprepared canal wall area (%) than WaveOne Gold and TRUShape when preparing oval-shaped root canals of extracted mandibular molars.

Bond strength and quality of bond interface of multifilament fiberglass posts luted onto flat-oval root canals without additional dentin wear after biomechanical preparation

Statement of problemAn intraradicular retainer formed by multiple independent glass fiber filaments was developed aiming to allow better adaptation in flattened root canals; however, the performance of the new posts is unclear. PurposeThe purpose of this in vitro study was to compare the bond strength (BS) and adhesive interface quality achieved in flattened root canals restored with conventional glass fiber posts (CFPs) and multifilament glass fiber posts (MFPs). Material and methodsThe distal roots of mandibular molars with long oval root canals were endodontically treated, and the obturation material was removed and assigned to 2 groups (n=11) according to the type of retainer used: CFP (WhitePostDC#0.5; FGM) or MFP (CometTail#4; Synca). The posts were cemented with self-adhesive resin cement. The specimens were sectioned (2 slices per third). The most cervical slice in each third was used to evaluate the BS, while the adhesive interface in the apical slices was analyzed by scanning electron microscopy. BS data were analyzed by using a multilevel generalized linear model, and adhesive interface SEM data were analyzed by using a multilevel ordinal logistic regression model (α=.05). ResultsMultilevel regression showed a statistically significant difference for the “type of retainer” factor (P=.001; CFP 2.61 ±1.30>MFP 1.59 ±1.54). No statistically significant differences were found for the “root thirds” factor (P=.346) or for the interaction of both factors (P=.114). The failure pattern was predominantly mixed or adhesive for CFP and adhesive to dentin for MFP. A better adaptation of the restorative material was observed in the cervical third for CFP and in the apical third for MFP (P<.001). ConclusionsMFP resulted in lower BS values than CFP, with a higher prevalence of adhesive failures to dentin and better adaptation of the adhesive interface in the apical third.

Evaluation of two shaping systems and two sonic irrigation devices in removing root canal filling material from distal roots of mandibular molars assessed by micro CT

To compare two preparation systems and two sonic irrigation devices during the removal of root filling material from oval distal canals of extracted mandibular molars. The distal canals in 40 extracted mandibular molars were shaped using the ProTaper Next system (Dentslpy Sirona, Ballaigues, Switzerland), filled with Gutta Percha X2 (Dentsply Sirona), along with AH Plus sealer (Dentsply De Trey, Konstanz, Germany) and randomly divided into two groups (n=20) according to volume of initial filling, preparation diameter and working length. One group was retreated using the Reciproc system (VDW, Munich, Germany), and the other using the 2Shape system (Micro-Mega, Besançon, France). A micro-CT scan was taken after the initial root filling and after retreatment to evaluate the volume of filling material remnants. The teeth were divided into four groups to test the supplementary effect of two sonic irrigation devices on removing filling material: Eddy (VDW) and MM1500 (Micro-Mega). In the first and second groups, 2Shape was followed subsequently by MM1500 and Eddy; in the third and fourth groups, Reciproc was followed by MM1500 and Eddy. A third micro-CT was taken to compare the remaining root filling material in all groups. Wilcoxon's signed rank tests, Mann-Whitney and Kruskal-Wallis tests were used for statistical analysis. No significant difference was found for the volume of filling material removed between the Reciproc and 2Shape in the entire canal (P=0.355). The volume dropped significantly from its initial value after removing the bulk of the root filling by 95.8% (from 4.71 to 0.22mm3 ) with the 2Shape (P<0.001) and by 94.0% (from 5.05 to 0.33mm3 ) with the Reciproc (P<0.001). Sonic activation significantly decreased the residual volume of filling material remnants by 3.21% (P=0.013) in the first group, 1.38% (P=0.012) in the second group, 1.83% (P=0.008) in the third group and 1.83% (P=0.012) in the fourth group. At the end, the percentage of residual material was not significantly different among the groups in the entire canal (P=0.163). In the distal oval canals of extracted mandibular molar teeth, there was no significant difference between the 2Shape and Reciproc systems in removing gutta-percha/sealer. Sonic activation with MM1500 and Eddy significantly improved filling material removal.

Radiographic Indications of Vertucci Type V Configuration in the Distal Root of Mandibular Molars: A Case Series

Knowledge of the prevalent root canal anatomy and potential variations is necessary before the initiation of endodontic treatment. The purpose of this study was to aid in the detection and treatment of the Vertucci type V canal configuration when present in the distal root of the mandibular molars. This case series presents 3 radiographic indications of a type V configuration in the distal roots of the mandibular molars as revealed on conventional periapical radiographs: a “ghost” apex, a fast break canal, and eccentric canal tracing. Nonsurgical endodontic treatment was performed for 5 mandibular molars with the type V distal root canal. Four cases showed posttreatment resolution of symptoms and return of normal function. One case was classified as “failed” because of persistent symptoms and clinical signs. The tooth was surgically treated and subsequently healed. These case reports show the importance of visualizing and managing the anatomic variations of the canal system in distal roots of mandibular molars and incorporating these capabilities into clinical practice to enhance the occurrence of a successful outcome. Additionally, clinical guidelines are provided that can help clinicians overcome the challenges in diagnosing and treating such complex cases.

Evaluation of bond strength in single-cone fillings of canals with different cross-sections.

To evaluate the effect of root canal cross-sectional shape on single-cone root filling bond strength, as well as to determine the percentage of gutta-percha-filled areas (PGFA) and sealer-filled areas (PSFA), establishing a relationship between these variables. Distal roots of mandibular molars were selected using microcomputed tomography imaging and allocated into three groups (n=10) according to canal shape: round, oval and long oval. The canals were prepared with an R40 reciprocating instrument and filled with matching single-cone gutta-percha and AH Plus sealer. Two 1-mm-thick dentine slices were obtained from each third of each root. PGFA and PSFA were calculated in digital images (x25 magnification) of each slice. Next, the slices were subjected to a push-out test and the failure modes (adhesive, cohesive or mixed) were assessed. Data were analysed using parametric tests (P<0.05). In the coronal (2.17±0.56MPa) and middle thirds (1.78±0.45MPa), the round canals were associated with higher bond strength values (P<0.01), with no difference between the groups for the apical third (P>0.05). Adhesive and mixed failures predominated in round canals, whilst cohesive failures were more frequent in oval and long oval canals. Round canals had significantly higher PGFA and lower PSFA than all other groups (P=0.000). The PGFA and PSFA had a positive (r=0.521, P=0.000) and a negative (r=-0.523, P=0.000) correlation with bond strength, respectively. Bond strength values of gutta-percha and sealer were affected by canal shape. Higher percentage of gutta-percha-filled area resulted in higher bond strength to dentine.

Root and root canal morphology of third molars in a Jordanian subpopulation

Introduction: The aims of this study were to (1) investigate the root and root canal morphology of human third molars in a Jordanian subpopulation and (2) determine the effect of age, gender, and tooth location on the morphology of these teeth. Materials and Methods: A total of 159 maxillary and mandibular third molars were used in this study. After canal staining and tooth clearing, the specimens were examined, and the following morphological features were recorded: Number of roots and presence of roots fusion, number of canals and their configurations in each root, total number of canals per tooth, and incidence of lateral canals and intercanal communications. Results: The majority (74.2%) of maxillary molars had 3 roots and 3 (55.1%) or 4 (27%) canals while the majority (74.3%) of mandibular molars had 2 roots and 2 (38.6%) or 3 (45.7%) canals. Roots fusion was found in 70.1% of maxillary molars and 40.7% of mandibular molars. Type I canal configuration was the predominant type in distal roots of mandibular molars and distobuccal and palatal roots of maxillary molars. Multiple canals were evident in 36% of the maxillary mesiobuccal roots and 56% of mandibular mesial roots. Single/fused roots showed a wide range of canals number and configurations. The number of roots and canals in both molars did not differ with gender, age, and tooth location. Females had a higher incidence of roots fusion than males and this difference was significant in mandibular molars (P = 0.034). Conclusions: Third molars showed a range of root and canal morphologies. Careful preoperative assessment is essential before commencing root canal treatment on these teeth.

Histological evaluation of refinement influence in the cleaning efficacy of rotary nickel-titanium ProTaper® instruments in oval-shaped root canals

The aim of this in vitro study was to evaluate the cleaning and shaping efficacy of rotary nickel-titanium ProTaper® instrumentation in oval canals and the influence of ultrasonic irrigation on the final refinement. Material and methods: Twenty mandibular molars were accessed and divided in two groups. Only distal roots with oval canals were used. Group I was instrumented using only rotary nickel-titanium ProTaper® instruments. Group II received the same preparation followed by refinement with 3 minutes of ultrasonic passive irrigation. After preparation, the distal roots were sectioned for histological processing. Coronal, middle and apical thirds were analyzed. Uninstrumented perimeter in each third was measured by the software Image tool 3.0. Results: The percentage of uninstrumented perimeter was calculated for each third of each root and average percentage was calculated for each third in both groups. Statistical analysis was performed with t-test through the software SPSS 11.0.1 for Windows. The level of significance was set at 1%. Group I showed higher percentage of uninstrumented perimeter in all thirds. Group II, which received ultrasonic irrigation showed better results in all thirds (p &lt; 0.01). Comparing the three thirds in the same group, no statistically significant differences were found (p &gt; 0.05). Conclusion: Under the conditions of this ex vivo study, the three minutes use of ultrasonic irrigation after rotary instrumentation resulted in significantly more instrumented walls in the distal roots of mandibular molars.

Adhesion of resin‐based sealers to dentine: an atomic force microscopy study

To evaluate the effect of several final irrigants on the adhesion force (Fad) between dentine and resin-based sealers by means of atomic force microscopy (AFM). Twelve distal roots of mandibular molars were used. The roots were smoothened and cut to obtain 36 specimens. During chemomechanical preparation of the root canals, 5.25% NaOCl was used as the irrigant. The specimens were then divided into six groups according to the final irrigant used: control group - immersed in distilled water (DW) for 1min; chlorhexidine (CHX) group - in 2% CHX for 1min; NaOCl group - in 5.25% NaOCl for 1min; EDTA group - in 17% EDTA for 5min, EDTA/CHX group - in EDTA, followed by intermediate flushing with DW and then immersed in CHX; EDTA/NaOCl group - in EDTA, followed by intermediate flushing with DW and then immersed in NaOCl. After the treatments, all groups were washed with DW to remove all traces of the irrigants. Afterwards, the samples were dried and attached to a glass base. AFM tips containing AH Plus and Real Seal SE sealers were used to obtain force-distance curves with regard to dentine-treated surfaces. Data were analysed statistically using nonparametric tests with the significance level set at P<0.05. In the groups with smear layer, a final flush with CHX and NaOCl resulted in significantly higher Fad values than the control group for both sealers (P<0.001). When smear layer was removed, the highest Fad values associated with AH Plus occurred with a final flush of NaOCl, whilst in Real Seal SE, the highest values were found with a final flush of CHX (all results significant at P<0.001). Irrigants had a positive effect on the adhesion of the resin-based sealers, AH Plus and Real Seal SE, to dentine.

Mandibular second molar with 3 mesial canals and a radix paramolaris

Mandibular first molar commonly has two roots, the mesial and the distal root. Surprisingly in some mandibular first molar has an unusual extra third root in between mesial and distal root. This extra root is the most commonly seen in lingual side and is called as radix entomolaris. If this extra root is seen on the buccal side, it is termed as radix paramolaris (RP), which is a very rare phenomenon. Recently, various case report studies has shown the presence of third canal in the mesial and distal roots of mandibular molars. They are named as middle mesial and middle distal canal, respectively. Here, we present a case report of mandibular second molar showing three canals in the mesial root and a RP.

Management of periodontal furcation defects employing molar bisection; a case report with review of the literature

Introduction: The management and long-term retention of molars exhibiting furcation invasion have always been a challenge in dentistry. Latest innovations in dental sciences and higher patient's expectations have led to more conservative treatment approaches in saving the teeth with hopeless periodontal prognosis. When periodontal disease affects the furcation area of tooth, the chance of its exfoliation increase considerably. Here, authors have sought to discuss a comprehensive review of literature with case report for the management of decayed mandibular first molars (with furcation invasion) using bicuspidization procedure. Case Report: The furcation defect (in mandibular first molars) was clinically detected in a middle aged male, which was converted into two bicuspids by intentional bisection procedures. The definitive treatment included restoration with double crowns. Bicuspidization procedure with double metal crowns truly yielded a satisfactory result. Discussion: The treatment of furcations affected by periodontal disease is one of the most difficult problems for the general dentist and periodontist. An increase in the exposed root surface, anatomical peculiarities and irregularities of the furcation surface all favor the growth of bacteria. These problems make it harder for the patient to maintain hygiene, and impede adequate treatment. Bisection/bicuspidization of the decayed molars can be a practicable treatment option when there is vertical bone loss involving root/roots with furcation defect. In real terms, it is the separation of mesial and distal roots of mandibular molars along with its crown portion, where both segments are then retained individually.

Clinical management of multiple mesial and distal canals in mandibular first molars- A case report

Thorough cleaning and shaping and followed by three-dimensional obturation is secret to successful clinical endodontics. Therefore, it is imperative that aberrant anatomy should be identified before and during root canal treatment. Multiple case reports of aberrant canals morphology in the mesial root of mandibular first molar have been documented. However, fewer studies have discussed the occurrence of a third distal canal in distal root of mandibular molars. The incidence of middle distal canal is much lower than that of middle mesial canal. This article presents the two rare case reports describing of multiple canals in mandibular first molars i.e 3 distal canals in one case report and 3 mesial canals in another.

Efficacy of two rotary systems in removing gutta-percha and sealer from the root canal walls.

The aim of this in vitro study was to compare the efficacy of two retreatment rotary systems in removal of gutta-percha (GP) and sealer from the root canal walls with and without use of solvent. Sixty single-canalled distal roots of mandibular molars were prepared and root filled with gutta-percha and AH26. Each canal was randomly allocated to receive one of the retreatment techniques, Mtwo R or ProTaper. The groups were further divided into two subgroups: with or without the use of solvent. The cleanliness of canal walls was determined by stereomicroscope and scanning electron microscopy. The results showed that Mtwo R without the use of solvent was more efficient in material removal compared to ProTaper D (P<0.05). Most remnants were found in the apical third of the canals (P<0.05). Mtwo R seems to be an efficient rotary system for endodontic retreatment of root canal with GP.

Preparation of Oval-shaped Root Canals in Mandibular Molars Using Nickel-Titanium Rotary Instruments: A Micro-computed Tomography Study

IntroductionThis study evaluated the prepared surface areas of oval-shaped canals in distal roots of mandibular molars using four different instrumentation techniques. MethodsTeeth were prescanned and reconstructed using micro–computed tomography (MCT) scans at low resolution (68 μm). Forty-eight molars with ribbon-shaped/oval distal root canals were selected and randomly assigned to four groups. Distal canals (n = 12 each) were prepared by circumferential filing using Hedström files to apical size #40 (group H/CF); with ProTaper nickel-titanium rotaries to finishing file 4 (F4) considering the distal canal as 1 canal (group PT/1); ProTaper to F4 considering buccal and oral aspects of the distal canal as 2 individual canals (group PT/2); ProTaper to F4 in a circumferential filing motion (PT/CF). Before and after shaping, teeth were evaluated using MCT at 34-μm resolution. The percentage of prepared surface was assessed for the full canal length and the apical 4 mm. Statistical analysis was performed using analysis of variance and Bonferroni/Dunn multiple comparisons. ResultsPreoperatively, canal anatomy was statistically similar among the groups (p = 0.56). Mean (± standard deviation) untreated areas ranged from 59.6% (±14.9, group PT/2) to 79.9% (±10.3, PT/1) for the total canal length and 65.2% to 74.7% for the apical canal portion, respectively. Canals in group PT/1 had greater untreated surface areas (p < 0.01) than groups PT/2 and PT/CF. Among all groups, amounts of treated surface areas were statistically similar in the apical 4 mm. ConclusionsPreparations of oval-shaped root canals in mandibular molars left a variable portion of surface area unprepared regardless of the instrumentation technique used. However, considering oval canals as two separate entities during preparation appeared to be beneficial in increasing overall prepared surface.

Radiographic quality of root canal fillings performed in a postgraduate program in endodontics

The aim of this study was to evaluate the standard quality of 1,347 root fillings performed by postgraduate students in Endodontics according to 3 radiographic quality parameters. The analyzed quality parameters included apical extension (AE), taper (TA) and homogeneity (HO), which received scores S2 (ideal standard), S1 (slight deviation) or S0 (accentuated deviation). A perfect filling (PF) received S2 for all parameters. In the absence of one or two S2 score, the fillings were deemed as satisfactory (SF) or deficient (DF), respectively. The results showed 51.7%, 41.5% and 6.8% of PF, SF, and DF, respectively. AE, TA, and HO presented equivalent quality parameters in root-filled canals of mandibular incisors and mandibular premolars (p>0.05). Conversely, in maxillary incisors, canines and distal root of mandibular molars, significant differences (p<0.05) were found between 2 parameters. Besides, there were significant differences (p<0.05) among the measured parameters in root-filled canals of maxillary premolars, all root canals of the maxillary molars and mesial root of the mandibular molars. AE showed the lowest frequency of S2 score for all groups. In conclusion the prevalence of perfect, satisfactory and deficient fillings varied significantly according to the root canal group. The quality parameters categorized fillings in 3 complexity degrees. AE was the most critical parameter of quality in root canal fillings.

Root and canal morphology of the mesiobuccal and distal roots of permanent first molars in a Kuwait population – a clinical study

To identify the number of roots and canal configurations in permanent first molars of the indigenous Kuwaiti sub-population and compare them against a similar group of non-Kuwaiti population in different age groups and gender, and to determine the frequency of a second canal in the mesiobuccal root of maxillary first molars and distal root of mandibular first molars that could be located and treated in routine practice without using magnification or special lighting conditions. A total of 220 permanent first molar teeth of patients scheduled for root canal treatment over a period of 1 year were included. Patients were identified and grouped according to their nationality as Kuwaiti and non-Kuwaiti (which included Filipinos, Indonesian Indians, Srilankans, Egyptians, Saudi Arabians and Syrians). In both nationality groups, patients were successively distributed into four groups based on their age. The first age group included patients below 20 years, the second 21-30 years, the third 31-40 years and the fourth were over 40 years. The first three groups comprised of 15 male and 15 female patients whilst the fourth group had 10 patients of each gender. Teeth with open apices, resorptions and calcification were excluded from the study. The teeth included were both clinically and radiographically examined for number of roots, the canal configuration and the presence of the additional mesiobuccal and distal canals and recorded. The simplified classification of canal configurations proposed by Weine was utilized. The incidence of a second canal in the mesiobuccal (MB) root of maxillary first molars and the distal root of mandibular first molars was not influenced significantly by nationality and gender. All the 110 maxillary first molars treated had three roots; 58% of MB root had one canal and 42% had two canals. The majority of the mesial roots had Weine type II canal configuration when the second mesiobuccal canal was present. All distobuccal and palatal roots had a single or type I canal configuration. Of the 110 mandibular first molars that were treated, 96% had two roots and 4% had three roots. When present, the third root was located either buccal or lingual to the main distal root. Overall 51% of the single distal roots had one canal whilst 49% had two canals. The mesial root frequently had a Weine type II canal configuration as did the distal root when a second canal was present. Pearson's correlation analysis of both molars revealed a significant (P < 0.05) negative correlation (r = -0.274, r = -0.144) between age and number of canals as well as the type of canal. The incidence of a second canal in distal roots of permanent mandibular first molars was 49% in the Kuwaiti population and this was similar to other Asian ethnic populations. Adopting modified access and troughing procedures revealed a 42% frequency of MB2 canals in maxillary first molars. The incidence of a second canal in both mesiobuccal roots of maxillary molars and distal roots of mandibular molars decreased significantly with age; no differences were noticed amongst the nationalities and gender studied. The possibility of extra roots should be anticipated in mandibular molars.

Effects of an Intracanal Glass Ionomer Barrier on Coronal Microleakage in Teeth with Post Space

Bacterial microleakage of the remaining gutta-percha in teeth prepared for post space with and without the use of an intracanal glass ionomer barrier was evaluated. Forty distal roots of mandibular molars were instrumented, obturated with gutta-percha and AH Plus sealer, and post spaces created. Teeth were divided as follows: Group I, 3 mm of gutta-percha; group II, 4 mm of gutta-percha; group III, 2 mm of gutta-percha plus 1 mm of Vitrebond; and group IV, 3 mm gutta-percha plus 1 mm Vitrebond. The roots were suspended in Rogosa SL broth and Lactobacilli casei was used as a microbial marker. At the end of 92 days, the mean number of days for the broth to turn turbid was group I, 23.8; group II, 43.0; group III, 57.4, and group IV, 70.5. A two-way ANOVA showed differences between the groups and a post hoc Tukey HSD analysis revealed the following significant differences (p < 0.05): Group I leaked faster than groups III and IV and group II leaked faster than group IV. In clinical situations of teeth with compromised crown-root ratio that require a post and core, 1 mm of Vitrebond over 2 or 3 mm remaining gutta-percha could reduce the risk of recontamination of the apical gutta-percha.

The impact of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars

Posts frequently are used to retain buildups. The authors examined the effects of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars. The authors embedded 26 root-treated mandibular molars in endodontic cubes and sectioned them perpendicularly to their long axis at 1.8-millimeter intervals. They placed Gates-Glidden drills nos. 3, 4, 5 and 6 sequentially to 5 mm short of working length in the distal canals. After using each drill size, the authors measured the dentin thickness from light microscopic images of the tooth slices. The authors analyzed data to detect changes resulting from canal instrumentation. They performed statistical analysis by partitioning the variability in a nested analysis of variance. Strip perforations occurred with a no. 4 Gates-Glidden drill 7.3 percent of the time and more frequently with larger drills. After endodontic treatment alone, the canal wall on the furcal side was less than 1 mm thick 82 percent of the time and less than 0.5 mm thick 17.5 percent of the time. Dentin thickness correlates inversely to post space diameter. A no. 4 Gates-Glidden drill caused strip perforations in 7.3 percent of the canals studied, and therefore the authors recommend that Gates-Glidden drills larger than a no. 3 not be used in these roots. After endodontic treatment, the furcation-side dentin thickness was less than 1 mm in 82 percent of the teeth. Post space preparation in mandibular molars carries significant risk of perforation. Post space in such teeth should be limited to the endodontically prepared canal.

Efficiency of Hand and Rotary Instruments in Shaping Oval Root Canals

This study was designed to determine the efficiency of hand and rotary instruments in shaping oval root canals. Seventy-five oval canals were equally divided into three groups. The apical third was prepared with rotary LightSpeed instruments either to size 52.5 (mandibular incisors) or to size 57.5 (distal root of mandibular molars). The middle third with an oval cross-section was shaped with Hedström hand files using circumferential technique, with 6% taper rotary Hero files in a circumferential filing movement or with rotary LightSpeed instruments in a step-back technique. Instrumentation was performed under clinical conditions in a phantom head. The teeth were sectioned at two levels in the middle third of the root. An assembly technique allowed comparing the canal outline before and after instrumentation. The photographed root sections were superimposed and traced under a stereomicroscope. The ratio of prepared to unprepared canal outline was calculated for each section. The lowest values were observed in the LightSpeed group (mean: 0.42; 95% confidence interval (CI): 0.37; 0.47). Significantly higher values were recorded in the Hero group (mean: 0.58; 95% CI: 0.53; 0.64) and in the Hedström group (mean: 0.56; 95% CI: 0.49; 0.62). No instrumentation technique was capable of completely preparing dentin walls of oval root canals. Circumferential filing of the middle third of oval root canals with either 6% taper Hero files or conventional Hedström hand files gave comparable results.

Determinação do comprimento de dentes em função da posição da placa óptica do sistema de imagem digital Digora em relação ao eixo dentário

O objetivo deste trabalho foi avaliar a influência do posicionamento da placa óptica do Digora em relação ao eixo dentário na determinação do comprimento de dentes. Sessenta dentes humanos extraídos foram avaliados, divididos em: dez incisivos superiores, dez incisivos inferiores, dez pré-molares superiores, dez pré-molares inferiores, dez molares superiores e dez molares inferiores. Eles foram radiografados com placa óptica do sistema de imagem digital Digora em duas posições: com seu longo eixo paralelo ao comprimento da placa óptica e com seu longo eixo paralelo à largura da mesma. As medidas radiográficas digitais foram obtidas com recursos do programa Digora for Windows, utilizando-se as imagens padrão, negativa e 3D. Os resultados mostraram que não houve diferenças estatisticamente significantes entre as medidas radiográficas digitais obtidas nas duas posições, com exceção do grupo dos pré-molares superiores e da raiz distal dos molares inferiores, embora essa diferença não tenha sido clinicamente significante, ou seja, superior a 0,5 mm.