Mid-root Region Research Articles

Effect of ultrasonic and Er,Cr:YSGG laser-activated irrigation protocol on dual-species root canal biofilm removal: An in vitro study.

The aim of the study was to investigate the disinfecting efficacy of a standardized irrigating solution activated by ultrasonics or laser irradiation on mature dual-species biofilms at different root levels in vitro. Conventional access cavity preparations were done on 160 single-rooted mandibular premolar teeth with single canals. Freshly extracted oral microbial strains of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Candida albicans after biochemical confirmation were used to generate two discrete dual-species microbial inoculums. The sterilized tooth samples were randomly segregated into two groups (n = 80) and inoculated with a mixed inoculum of S. aureus + E. faecalis strains (Group 1) and S. mutans + C. albicans strains (Group 2), respectively. Following the 21-day incubation period under aerobic conditions, the infected specimens in each group were divided into four subgroups (n = 20) and subjected to experimental treatment protocols. This included a positive control (no treatment of biofilms), syringe irrigation alone with TruNatomy needle, passive ultrasonically activated irrigation with 20# Irrisafe tip, and laser agitation of irrigant with Er,Cr:YSGG laser using RFT 2 laser tip. Root canals of experimental specimens (except the control samples) are instrumented with TruNatomy rotary file system using 1:1 mixture of 3% NaOCl and 18% etidronic acid as irrigants. The quantitative assessment of reduction in viable biofilm microbes after treatment was done using colony-forming unit counts and confocal laser scanning microscopy image analysis. The obtained data were analyzed statistically with a significant level set at 0.05. Laser-assisted irrigation has shown a considerably higher mean percentage reduction of microbes compared to ultrasonic agitation and the syringe irrigation showed the least microbial reduction (P = 0.001). No significant difference was noted between the three root regions of ultrasonic and laser groups (P > 0.05), whereas in the syringe groups, apical portions showed higher microbial counts compared to cervical and mid-root regions (P = 0.001). Erbium laser-assisted irrigation has performed superior to ultrasonic agitation against both the experimental dual-species biofilms, while the syringe irrigation showed the least microbial reduction specifically at apical root portions.

Fracture Strength of Tooth Roots Following Canal Preparation by Three Rotary File Systems: An In Vitro Study.

Since the beginning of modern endodontics, there have been many concepts, strategies, and techniques for root canal preparation. A mind-boggling variety of files have developed for negotiating and shaping them throughout the years. Today's most secure, most effective, and simplest file system combines the most reliable design elements of the past with the latest technological advances to create the most effective file system. So, the need for the study is to evaluate the fracture strength of tooth roots following canal preparation by three rotary file systems: ProTaper Universal file system (Dentsply, USA), ProTaper Next file system (Dentsply Sirona USA), and Neolix A1 nickel-titanium (NiTi) file system (Orikam Healthcare India Pvt Ltd., New Delhi, India). Ninety human mandibular molars were selected for the study. Inclusion criteria include human mandibular first and second molars and teeth removed for routine clinical reasons, and intact apices were selected, excluding cases with root surface caries, root surface fissures, teeth with immature root apex, mesial canal fusion, extremely short roots, thin roots, or curved roots. All teeth were preserved in a solution of 10% neutral buffered formalin for two weeks and then transferred to distilled water for examination. The teeth were randomly divided into three groups. Access cavities were created, and working lengths were determined. Groups 1, 2, and 3 underwent shaping using ProTaper Universal, ProTaper Next, and Neolix A1 (NiTi) file systems, respectively, following guidelines. Canals were irrigated with sodium hypochlorite and ethylenediaminetetraacetic acid (EDTA) and were obturated up to the mid-root region with AH Plus sealer. To facilitate fracture testing, obturation was performed to distribute the load from the spreader to the canal wall. The EndoSequence and Quick-Fill obturation system were utilized to fill the apical half of the canal with gutta-percha material. After obturation, the distal root of each tooth was cut, while the mesial root was securely positioned in a putty material. A universal testing machine was employed for the fracture tests, operating at a cross-head speed of 1 mm/min. The machine was equipped with a D11 hand spreader tip, which was inserted into the root canal to make contact with the gutta-percha. Gradual force was applied to the root canal until a fracture occurred, at which point the force application was stopped. The amount of force required to cause the fracture was measured in newtons. Data were collected and recorded using IBM SPSS Statistics for Windows, Version 17.0 (Released 2008; IBM Corp., Armonk, New York, United States) and then transferred to Microsoft Excel for analysis. Descriptive statistics, mean, and standard deviation were used for continuous data. The fracture resistance of dental roots treated with three types of files was compared using a one-way ANOVA. Graphs were generated using Excel and Word. A significance level of p<0.01 was chosen. ANOVA indicated significant differences in mean fracture resistance: Neolix A1 (NiTi) (95.3 N) > NEXT (91.0 N) > universal (86.6 N), with a p-value of 0.004 (<0.001), confirming statistical significance. The study concludes that the canal instrumented with Neolix A1 (NiTi) exhibits higher fracture resistance after canal instrumentation compared to ProTaper Next and ProTaper Universal.

Cone Beam Computed Tomography (CBCT) Evaluation of Alveolar Bone Thickness and Root Angulation in Anterior Maxilla for Planning Immediate Implant Placement.

This retrospective study aimed to measure the labial, palatal, mesial, and distal bone thickness around maxillary central and lateral incisors and canines and height from crest to apex, using cone beam computed tomography (CBCT) images and compare the results based on gender. The second objective of the study was to measure root angulation on CBCT images and its relation with the labial cortical thicknesses. Material and Methods:After the Institutional Review Board (IRB) approval, a total of 140 CBCT volumes were included in this study according to the set criteria. On each scan, right-side maxillary central, lateral incisors, and canine were selected for the measurements. All the measurements were done at three levels at the alveolar crest (L1), mid-root (L2), and apical region (L3) for each tooth. Results:The Student's t-test was performed to compare the result of buccal, palatal, mesial, and distal bone thickness,angulation, and height of all subjects. Buccal alveolar bone thickness was minimum at the mid-root region, and the palatal bone thickness was minimum at the crestal region. The mesial bone thickness was minimum at the mid-root level, and distalbone thickness was minimum at the crest level. The available bone height was maximum at the lateral incisor and equal for the central incisor and canine. The canine was the most angulated tooth. Cone beam computed tomography is a reliable imaging modality to evaluate pre-surgical immediate implant sites and measurealveolar bone thickness. The canine was the most angulated tooth with more buccal alveolar bone thickness.

Qualitative and Quantitative Assessments of Alveolar Bone Dimension and Its Correlation with Tooth Angulation in the Anterior Maxilla for Immediate Implant Placement

The aim of this paper is to ascertain the quantitative measurements of alveolar bone thickness at all maxillary anterior teeth and qualitatively demonstrate the relationship between tooth angulation (TA) and alveolar bone thickness. Cone-beam computed tomography (CBCT) images of 189 maxillary anterior teeth were collected. Sagittal view was selected to perform the measurement on alveolar bone wall at crestal, midlevel, and palatal. TA was measured along to the tooth long axis (TLA) related to the alveolar bone housing. Spearman's correlation coefficients were conducted to test the correlation between the variables. The facial alveolar bone (FAB) is predominantly thin (<1 mm) at the crestal and midroot region. A significant difference was recorded in the median thickness of FAB at the midroot and apical area (p = 0.001, p = 0.021). The FAB thickness was not gradual with midroot being thinner than crestal. For the palatal alveolar bone (PAB), the thickness was increased continuously toward the apex. At all apical levels of inspected teeth, a significant negative correlation existed between TA and FAB. A positive correlation of TA was only significant at the facial crest of lateral incisor (r = 0.308). However, the canines did not correlate with the FAB, but correlated with the PAB at the apical level (r = 0.478). The FAB wall crest of maxillary anterior teeth was generally thin and not gradual with the lateral incisor being the thinnest. A significant correlation of TA existed based on different types of maxillary anterior teeth and alveolar bone level. The maxillary anterior teeth with increased buccolingual angulation were correlated with thicker bone at the apical level. The quantitative assessment of FAB and TA in degree may serve as an anatomical index for ideal implant position.

The effect of micro-osteoperforations on orthodontic space closure investigated over 12 weeks: a split-mouth, randomized controlled clinical trial.

To evaluate the effects of minimally invasive micro-osteoperforations (MOPs) on orthodontic tooth movement and pain. Prospective, split-mouth, randomized controlled trial. Single-centre, university hospital. Twenty subjects requiring maxillary first premolar extractions were included. Right and left sides of the maxilla were randomly allocated into experimental and controls. Space closure was initiated following alignment on 0.20″ stainless steel archwires, using 150 g force, applied by coil springs on power arms. Nance-TPA was used for anchorage. On the experimental side, two 5 mm deep MOPs in vertical alignment on distal aspect of the maxillary canine mid-root region were performed prior to space closure. The primary outcome was the amount of tooth movement during space closure, measured every 4 weeks for 12 weeks (T1, T2, and T3). Secondary outcome was the pain levels related to MOP, measured using Visual Analogue Scale (VAS) questionnaires. Significance was set at P &lt; 0.01. Randomization was generated using a randomization table, and allocation was concealed in sequentially numbered, opaque, sealed envelopes. Blinding was not possible during the experiment but assessor was blinded during outcome assessment. All subjects completed the study, with tooth movement measurements available for all 20 patients for T0-T2. In three patients, space was closed on one side at T2. The average tooth movement between sides at three intervals (T0-T1, T1-T2, and T2-T3) were not significantly different. Overall difference following 12 weeks (T0-T3) was 0.69 mm higher on the experimental side (P &lt; 0.001). No harms were observed. Short-term study, cast measurements done with digital callipers. This 12-week randomized split-mouth controlled clinical trial showed two MOPs that are 5 mm deep, applied once prior to space closure, did not create clinically significant increase in maxillary premolar space closure. The protocol was not published before trial commencement. Trial was not registered. The Australian Society of Orthodontists Foundation for Research and Education.

Dislodgement resistance and adhesive pattern of different endodontic sealers to dentine wall after artificial ageing: an in-vitro study.

To compare the dislodgement resistance and the adhesive pattern of four different endodontic sealers to root dentine walls. Ninety lower premolars were assigned to five groups (n = 18), Group 1: no sealer (control); Group 2: EndoRez (ERZ); Group 3: Sealapex (SPX); Group 4: EndoSeal MTA (ESA) and Group 5: BioRoot RCS (BRS). They were instrumented up to size 30 taper 0.06 and obturated using single cone technique with matched-taper gutta-percha cones and one of the mentioned sealers. Six teeth from each group were then randomly subjected to 100, 1000 and 10,000 thermocycles, respectively. 1mm slice of mid root region, measuring 6mm from the apical foramen was prepared and subjected to push-out test under a Universal Testing Machine. Adhesive patterns of sealers were assessed using a stereomicroscope at 20 × magnification and classified using a new system. Statistical analyses were performed using two-way ANOVA, complemented by Tukey HSD and Chi-square tests. ESA and BRS showed significantly higher (p < 0.05) push-out bond strength, followed by SPX, ERZ and lastly the control, but no significant difference was noted between ESA and BRS (p > 0.05) at 100, 1000 and 10,000 thermocycles, respectively. Both ESA and BRS exhibited a significant higher rate (p < 0.05) of Type 3 and Type 4 adhesive patterns as the thermocycles increased. ESA and BRS demonstrated higher bond strength and better adhesive pattern to root dentine wall than SPX and ERZ, especially after artificial ageing.

Evaluation of Remaining Cementum Thickness Following the Use of Hand and Ultrasonic Curettes of Periodontally Diseased Root Surface - An in-vitro Study

Background: Scaling and root planing are the most predictable treatment outcomes for periodontal disease. However root planing with hand curettes removes excess of cementum as compared to ultrasonic curettes. Hence the purpose of this study was to evaluate the effectiveness of remaining cementum thickness following the use of ultrasonic and hand curettes. Aim: To evaluate the remaining cemental thickness following the use of hand and ultrasonic curettes on periodontally diseased root surface using a stereomicroscope. Materials and Methods: Thirty single rooted teeth were extracted due to advanced periodontitis and were randomly divided into two groups: Group 1 (SRP with hand curettes) and Group 2 (SRP with ultrasonic curettes). The proximal surfaces of the teeth (mesial and distal) were subjected to root planning. one surface served as a test site where instrumentation was done and no instrumentation was done on the other surface (control site). Following instrumentation, midroot region of instrumented specimen was cross-sectioned and prepared for stereomicroscopic study. The data gathered from stereomicroscopic study was subjected to statistical analysis by Mann Whitney test. Results: The results of our study showed that in both the groups, the mean cemental thickness in scaled group was significantly lower than unscaled group. Clinically, teeth treated with the ultrasonic scaler showed less tooth substance removal than hand curettes but the difference between the two groups were statistically non-significant. Conclusion: Both the therapies i.e. SRP with hand curettes and ultrasonic curettes seemed to be effective in the removal of diseased cementum.

Efficacy of smear layer removal by two Ayurvedic herbal irrigants, using continuous vs. syringe and needle irrigation

Introduction: A successful root canal therapy is largely dependent on thorough chemo-mechanical debridement of the root canal space. However, mechanical preparation inadvertently forms an amorphous layer, known as the “smear layer.” Traditionally used irrigants have a deleterious effect over root dentin and thus herbal alternatives can be a better option for smear layer removal with no action on root dentin. Aim: The purpose of the study was to compare the in vitro effectiveness of two potential herbal irrigants: 6% German chamomile extract (GCE) and 6% Morinda citrifolia juice (MCJ), in removal of smear layer. Materials and Methods: Eighty single-rooted human teeth were allocated into two equal groups: one to be instrumented with the self-adjusting file (SAF), while the other with WaveOne (WO). Four subgroups in each group were irrigated with 6% GCE, 6% MCJ, 17% ethylenediaminetetraacetic acid (EDTA) (positive control), and NS (negative control). Scanning electron microscopy (SEM) was used to evaluate the presence of smear layer. Statistical Analysis: As data for smear layer were categorical, Chi-square test was applied for data analysis. P Results: The most effective smear layer removal in the coronal part was observed with SAF-EDTA and SAF-GCE, followed by WO-EDTA. In the middle part, SAF-GCE was equivalent to that of SAF-EDTA, followed by WO-EDTA and WO-GCE. In the apical third, the most efficient smear layer removal was observed with SAF-EDTA, followed by some removal of smear layer by WO-EDTA and SAF-GCE. GCE was as effective as EDTA in removal of smear layer in the coronal and mid-root regions, when used with continuous irrigation.

Comparative CBCT analysis of the changes in buccal bone morphology after corticotomy and micro-osteoperforations assisted orthodontic treatment – Case series with a split mouth design

PurposeProcedures such as Periodontally Accelerated Osteogenic Orthodontics (PAOO) support the use of osteotomy to aid tooth movement and rapid distraction of the periodontal ligament by utilizing tissue engineering principles with periodontal regenerative surgery. The aim of this study was to evaluate and compare the amount of tooth movement and the associated changes in buccal bone morphology between corticotomy and flapless Micro-Osteoperforation (MOP) assisted orthodontic treatment. Material and methodsA total of ten healthy patients between 18 and 25 years of age requiring orthodontic treatment were recruited for this clinical trial with a split mouth design. After orthodontic and periodontal examinations, Cone Beam Computed Tomography scans (CBCT) were done pre- (T1) and post- (T2) operatively for each patient to evaluate radiographic parameters such as buccal bone thickness, root resorption and dehiscence. Amount of tooth movement was also evaluated and compared. ResultsThe canine-premolar distance, measured in a time interval of 3 months and over a follow-up period of 6 months, reduced significantly from T1 to T2 at both corticotomy and MOP sites. At the corticotomy site, there was a mean increase in bone thickness of 1.15 ± 0.3 mm at coronal region, 0.48 ± 0.1 mm at mid-root region and 0.15 ± 0.0 mm at apical region. This increase in bone thickness was statistically significant at coronal level (p = 0.001) and mid-root level (p = 0.02). Significant increase in bone thickness was observed at MOP site. While on intergroup comparison, the difference was statistically significant at coronal level (p = 0.01). ConclusionBoth the techniques cause an increase in canine retraction in short period of time with almost no harm to periodontal structures. MOP being a flapless procedure allow clinicians to deliver an efficient orthodontic care.

Effect of Smear Clear and Conventional Root Canal Irrigants on Push-Out Bond Strength of Resilon/Epiphany System.

The aim of the present study is to compare the effect of SmearClear and sodiumhypochlorite (NaOCl), chlorhexidine (CHX) and normal saline (NS) on the push-out bond strength of Resilon/Epiphany system to dentine. In this in vitro study; 48 single-rooted teeth were selected and decoronated from the CEJ. Then the specimens were divided into four groups (n=12). The roots were prepared by single length technique using MTwo rotary system. The final irrigations of the canals were done using 2% CHX, normal saline, 5.25% NaOCl or SmearClear. The canals were obturated by Resilon/Epiphany system. The teeth were cut perpendicular to their longitudinal axis and four 1-mm-thick sections were obtained from coronal and mid root regions. The push-out bond strength of Resilon/Epiphany system to dentin were calculated and bond failure patterns were assessed. The data were subjected to two-way analysis of variance and Tukey's tests. The highest bond strength values were reported for SmearClear and the lowest values for the NS solutions. The effects of irrigant type (P<0.05) and canal area (P<0.0001) on the bond strength of Resilon to dentin were significant (P<0.05). Higher bond strength values were obtained in the mid root areas compared to the coronal regions. In two-by-two comparisons, significant differences in bond strength were found between SmearClear and normal saline (P<0.05) while the other irrigants showed no significant differences (P>0.05). SmearClear solution was able to increase the push-out bond strength of Resilon to the dentin similar to other irrigants (NaOCl and CHX). Therefore, it can be used for the root canal irrigation and smear layer removal in the clinical situations.

Three-dimensional evaluation of alveolar bone thickness of mandibular anterior teeth in different dentofacial types.

The aim of this randomized study was to compare the alveolar bone thickness (ABT) of the mandibular incisor teeth of dental and skeletal Class I, II, and III adult patients at labial and lingual aspects of the bone and develop recommendations for the associated movements of teeth in this region, taking vertical facial type into consideration. : Sixty-two Class I, 74 Class II, and 63 Class III patients - aged between 20 and 45 - were assigned to three subgroups - high (H), low (L), and normal (N) growth patterns. On the axial slices of computerized tomographies, the measurements for the ABT on labial and lingual sides of the mandibular incisors were carried out at three levels. In Class I group, at apex region, ABT of subgroups N and L were greater than H, at labial side. In Class II, ABT of subgroups N and L were greater than H, at apex at both sides and cervical lingual region. Similarly, ABT of subgroup L of Class III group was greater than H, at labial and lingual apex, mid-root regions. In Class II, the ABT of subgroup H was greater than L, at lingual cementoenamel junction. ABT of mandibular incisors of Class I patients is not affected from vertical pattern except for apical region. There is not a thick bone on the lingual side of the Class II, high-angle patients. The ABT of the Class III, high-angle patients is thin as a risk factor for proclination.

In vitro Evaluation of the Efficacy of 2% Carbonic Acid and 2% Acetic Acid on Retrieval of Mineral Trioxide Aggregate and their Effect on Microhardness of Dentin

In this in vitro study, the efficacy of 2% carbonic acid and 2% acetic acid on the surface, microhardness of white mineral trioxide aggregate (MTA) and dentin after 1 day of setting and 21 days of setting of MTA is measured. Tooth molds were made using 60 single-rooted premolars by slicing them to 4 mm in the mid-root region. White MTA (Angelus) was mixed and packed in the molds. Three experimental groups were formed and exposed to 2% carbonic acid, 2% acetic acid, and saline for 10 minutes on 1 and 21 days of setting respectively. Vickers hardness test of white MTA and dentin was done before and after exposure. Data were subjected to analysis of variance (ANOVA) and post hoc tests. The results show that 2% acetic acid was significantly effective in reducing the microhardness of white MTA compared to 2% carbonic acid and saline on exposure for 10 minutes. The results of the present study indicate that 2% acetic acid has maximum efficacy in reducing the surface microhardness of partial and completely set MTA, followed by 2% carbonic acid. The following study will help find an adjunct for retrieval of MTA, which was found difficult with the existing methods.

Effectiveness of the GentleWave System in Removing Separated Instruments

IntroductionA separated instrument in a root canal system has the potential of severely affecting the outcome of endodontic therapy. This study evaluated the effectiveness of the minimally invasive GentleWave System (Sonendo Inc, Laguna Hills, CA) in removing separated stainless steel endodontic files from the apical and midroot regions of molar root canals. MethodsThirty-six extracted human molars were accessed, and the glide path was confirmed to the apex. ISO #10, #15, and #20 K-file fragments of 2.5-mm length were separated at the apical (n = 18) or midroot (n = 18) region of the molars by engaging a weakened file with downward pressure. During analysis, the teeth were divided into 2 curved groups based on the curvature of the root (<30° and >30°). The success rate of instrument removal and the treatment time were noted. Statistical comparison was done with the Fisher exact test and independent 2-sample t test (P < .05). ResultsThe overall success rate of instrument removal when the separated files were engaged in the apical region was 61%, and for the midroot region, it was 83%. Less curved canals (<30°) showed a 91% success rate (n = 24), whereas canals with an angle of curvature greater than 30° showed a 42% success rate (n = 12). The median treatment time for instrument retrieval was 10 minutes 44 seconds. ConclusionsThe results revealed that the GentleWave System is effective in retrieving separated instruments while conserving the dentinal structure.

Porosity distribution in root canals filled with gutta percha and calcium silicate cement

ObjectiveGutta percha is commonly used in conjunction with a sealer to produce a fluid-tight seal within the root canal fillings. One of the most commonly used filling methods is lateral compaction of gutta percha coupled with a sealer such as calcium silicate cement. However, this technique may result in voids and worse, the filling procedures may damage the root. MethodsWe compared the volume of the voids associated with two root canal filling methods, namely lateral compaction and single cone. Micro-computed tomography was used to assess the porosity associated with each method in vitro. An automated, observer-independent analysis protocol was used to quantify the unfilled regions and the porosity located in the sealer surrounding the gutta percha. ResultsSignificantly less porosity was observed in root canals filled with the single cone technique (0.445% versus 3.095%, p<0.001). Porosity near the crown of the tooth was reduced 6 fold, whereas in the mid root region porosity was reduced to less than 10% of values found in the lateral compaction filled teeth. SignificanceOur findings suggest that changing the method used to place the endodontic biomaterials improves the quality and homogeneity of root canal fillings.

Management of Invasive Cervical Resorption Involving the Pulp by Surgical and Restorative Therapy

ABSTRACT Invasive cervical resorption (ICR) is a form of external resorption which affects the cervical area of permanent teeth and may progress to involve the pulp. It can cause insidious loss of tooth structure, which often is undetected until late in the process. Two cases, both involving the maxillary left central incisor where cone-beam computed tomography (CBCT) revealed an invasive cervical resorptive lesion, extending from the cervical to mid root region and perforating the pulp chamber. The cases were managed surgically with the help of a dental operating microscope (DOM). Nine months follow-up revealed resolution of the lesion and restoration of the affected teeth to functional occlusion. This report emphasizes the restorability of advanced lesions of ICR, if adequate diagnostic and treatment equipment is used. How to cite this article Ranna V, Sayed A. Management of Invasive Cervical Resorption Involving the Pulp by Surgical and Restorative Therapy. Int J Experiment Dent Sci 2015;4(2): 130-133.

The effect of central incisor's root proximity to the cortical plate and apical root resorption in extraction and non-extraction treatment.

Aims:The present study was conducted to investigate the relevance of cortical plate proximity of maxillary central incisor root, maxillary alveolar bone width, and the apical root resorption in extraction and non-extraction orthodontically treated cases. Further, the correlation between the apical root resorption and the various parameters was investigated.Materials and Methods:A total of 80 lateral head cephalographs, 40 pre-treatment and 40 post-treatment, of orthodontic subjects with a mean age of 15 years treated with fixed standard edgewise appliance were obtained. All subjects were divided into two groups as extraction and non-extraction cases. Twelve linear and three angular parameters were measured and evaluated. The paired “t”-test, Pearson's correlation coefficient, and the stepwise regression analysis were done to test the relationship between the apical root resorption and the various parameters.Results and Conclusions:The study revealed slightly greater amount of apical root resorption in extraction subjects as compared to non-extraction subjects. However, no statistically significant difference was found between the two treatment modalities. In extraction subjects, the apical root resorption was directly proportional to the pre-treatment length of maxillary central incisor and inversely proportional to the root width in apical one-third region, though there was a weak correlation. In non-extraction subjects, the pre-treatment anteroposterior position of the root apex of maxillary central incisor in the alveolar bone, in combination with its root width in the apical one-third region formed the predictive factors for the variance in the amount of the apical root resorption, though there was a weak correlation. Furthermore, the changes in the alveolar widths at the root apex and mid-root region were considered as predictive factors for the amount of apical root resorption during extraction and non-extraction treatment, respectively.

Evaluation of stress on the periodontium induced by a fixed retraction screw appliance and an active tie-back: A 3-dimensional finite element study

Objectives: To evaluate the stresses and displacement induced in the periodontium by an active retraction screw device (hycon device) and an active tie back using the finite element analysis. Materials and Methods: A 3-dimensional model of the maxillary dentition was designed for the study. A retraction force of 410 and 200 g was applied to simulate the forces generated by the hycon device and an active tie back respectively. The stresses generated by these forces were evaluated on the periodontium at cervix, mid root and apical region. Results: In the present study, maximum amount of tensile stresses were found on the labio-cervical (0.4919 and 0.2945 MPa) aspects of canine, compressive stresses on the linguo-cervical (−0.1758 and −0.0679 MPa) aspect of the 2 nd premolar and the apical region of all teeth showed low magnitude compressive stresses, with both the loads. The displacement produced by the retraction screw was of the magnitude 0.172-0.183 mm (0.177 mm) in the anterior segment and 0.0065-0.007822 mm (0.0071 mm) in the posteriors (anchor loss). Active tie backs produce a displacement of 0.162-0.172 mm in the anterior segment and a negligible amount of displacement in the posteriors. Conclusions: Even though the stress level in the periodontium produced by hycon device was almost 2-3 times that of active tie backs, the displacement produced per activation was within the physiological limits and less than the width of the periodontium (0.20-0.25 mm), which in turn induces bone remodeling.

Physical properties of root cementum: Part 12. The incidence of physiologic root resorption on unerupted third molars and its comparison with orthodontically treated premolars: A microcomputed-tomography study

INTRODUCTION Root resorption can occur as a physiologic or a pathologic process, and it is an unwanted side effect of orthodontic treatment. No baseline studies have assessed this phenomenon in the absence of force variables such as mastication, parafunction, and soft-tissue pressure. In this study, we investigated the incidence and quantitative value of root resorption on unerupted third molars with normal development using microcomputed tomography. Nine unerupted, nonimpacted maxillary third molars were collected from 6 patients (ages, 19.47 plus /minus 1.89 years). The teeth were examined with microcomputed tomography and compared with teeth from other studies. (The other teeth had been treated with buccally directed light [25 g] or heavy [225 g] forces applied for 28 days, or light [25 g] or heavy [225 g] intrusion forces for 28 days.) Imaging and volumetric analyses showed resorption craters in many locations and with various magnitudes. Analysis of variance was completed by position (P = 0.04), surface (P = 0.07), height (P = 0.045), left or right side of the mouth (P = 0.85), and subject (P = 0.70). The midroot region on the mesial surfaces of the third molars, near the root structure of adjacent erupted second molars, had the greatest statistical significance. When compared with crater volumes of fully erupted first premolars, we found that the unerupted third molar sample had a slightly greater cube root volume per tooth than the erupted first premolars not subjected to orthodontic force and a similar cube root volume per tooth as did first premolars subjected to light (25 g) buccal and intrusive orthodontic forces. Root resorption as a consequence of orthodontic treatment might be added to a baseline level of root resorption. The elevated results suggest that resorption might occur as part of hard-tissue remodeling and turnover, eruption, or transmission of masticatory forces through the dentition to the alveolar bone.

Editor's Summary and Q&A: Physical properties of root cementum: Part 12. The incidence of physiologic root resorption on unerupted third molars and its comparison with orthodontically treated premolars: A microcomputed-tomography study

<h3>Introduction</h3> Root resorption can occur as a physiologic or a pathologic process, and it is an unwanted side effect of orthodontic treatment. No baseline studies have assessed this phenomenon in the absence of force variables such as mastication, parafunction, and soft-tissue pressure. In this study, we investigated the incidence and quantitative value of root resorption on unerupted third molars with normal development using microcomputed tomography. <h3>Methods</h3> Nine unerupted, nonimpacted maxillary third molars were collected from 6 patients (ages, 19.47 ± 1.89 years). The teeth were examined with microcomputed tomography and compared with teeth from other studies. (The other teeth had been treated with buccally directed light [25 g] or heavy [225 g] forces applied for 28 days, or light [25 g] or heavy [225 g] intrusion forces for 28 days.) <h3>Results</h3> Imaging and volumetric analyses showed resorption craters in many locations and with various magnitudes. Analysis of variance was completed by position (<i>P</i> = 0.04), surface (<i>P</i> = 0.07), height (<i>P</i> = 0.045), left or right side of the mouth (<i>P</i> = 0.85), and subject (<i>P</i> = 0.70). The midroot region on the mesial surfaces of the third molars, near the root structure of adjacent erupted second molars, had the greatest statistical significance. When compared with crater volumes of fully erupted first premolars, we found that the unerupted third molar sample had a slightly greater cube root volume per tooth than the erupted first premolars not subjected to orthodontic force and a similar cube root volume per tooth as did first premolars subjected to light (25 g) buccal and intrusive orthodontic forces. <h3>Conclusions</h3> Root resorption as a consequence of orthodontic treatment might be added to a baseline level of root resorption. The elevated results suggest that resorption might occur as part of hard-tissue remodeling and turnover, eruption, or transmission of masticatory forces through the dentition to the alveolar bone.

Cementum annulations and age determination

Background: Cementum is a hard tissue in the root, which is deposited around dentin in layers throughout life. Under the light microscope, root cementum is seen as alternate light and dark rings known as incremental lines of cementum. In paleontology and forensic medicine, the number of these incremental lines is used to derive the age at death of an individual. Objectives: The present study was undertaken to determine if any relation exists between incremental lines of cementum and age of the individual. Materials and Methods: Twenty-five teeth from patients of known ages and devoid of any pathology such as attrition or hypercementosis were selected for this study. Ground sections were prepared manually. Nineteen of them showed visible countable annulations, while six showed indistinct, invisible annulations and hence were excluded from the study. Half of the selected teeth were sectioned longitudinally and the remainder were cross-sectioned. The mid-root region was selected for counting the annulations. Cemental annulations were counted after taking a photograph and enlarging the mid-root area. Age was then determined by adding the eruption age of the tooth to the annulations counted. Results and Conclusions: It was observed that cemental annulations, when appreciated, can be used as a reliable guide to determine the age of the patient. The age thus determined varied by about 2−3 years from the actual age of the patient. The reliability of the method was found to be 94.73%. There was good interobserver agreement in counting annulations.