Premolar Root Research Articles

Cone-beam computed tomography and microscope-assisted endodontic management of maxillary first premolar with three roots

This study aims to report the endodontic management of the maxillary first premolar with three roots, using cone-beam computed tomography (CBCT) and an operating microscope. Most maxillary first premolars have two roots, buccal and palatal but it may rarely have three. The incidence of three separate roots in maxillary first premolars ranges between 0.5% and 6%. Variation in root anatomy makes root canal treatment challenging necessitating improved technology. CBCT imaging provides precise location and visualization of root morphology, and canal anatomy. Operating microscope provides better lighting, magnification, and visualization of the operative field that helps to recognize and locate additional roots canals. This article reports the endodontic management of a maxillary right first premolar with three separate roots.

Etidronic acid and ethylenediaminetetraacetic acid associated with sodium hypochlorite have limited effect on the compressive fracture resistance of roots ex vivo.

Aims:To assess the effect of etidronic acid (EA) mixed with sodium hypochlorite (NaOCl) and two ethylenediaminetetraacetic acid-containing preparations (EDTA and SmearClear) alternated with NaOCl, as a final rinse, on root fracture resistance to a compressive force.Materials and Methods:Seventy-two premolar roots were randomly allocated to the following groups according to the irrigant solutions. For the EA group, 9% EA + 2.5% NaOCl were used throughout the assays (n = 21). The remaining groups received 2.5% NaOCl during and immediately after chemo-mechanical instrumentation. Intermediately, the roots received 17% EDTA (n = 19), or SmearClear (n = 16), or no irrigation (control) (n = 16) plus a final rinse with 2.5% NaOCl. The specimens were subjected to a vertical compressive force loaded at a crosshead speed of 0.02 mm/s parallel to the long axis of the root until fracture occurred. The results were compared statistically using the one-way analysis of variance for intergroup comparisons.Results:The negative control presented with the highest values, whereas the SmearClear presented with the lowest values, though no significant differences were found when comparing the different groups (P = 0.82).Conclusions:The use of EA + NaOCl or two EDTA formulations in association with NaOCl does not affect the fracture resistance of previously chemo-mechanically prepared roots.

Causes of root canal treatment failure: A prospective study in Makkah City, Saudi Arabia

Aim: The aim of the study is to identify the causes of root canal treatment (RCT) failures in Makkah City. Materials and Methods: The study used a prospective cohort study design, using a clinical examination, treatment, and follow-up. The study summarized the data of 131 patients presented to the Endodontic Department in King Faisal Hospital, Makkah, in the Western region of Saudi Arabia and included patients with failed RCT aged 16 years or older without any systemic disorder. Results: Of the 131 patients, the most common factor for root canal failure was underfilling (71.0%), followed by coronal leakage (42.7%), overfilling (16.8%), missed canal (16.0%), iatrogenic (6.1%), leaked canal and anatomic (1.5%), and 3.1% for unknown causes. Fifty-two (39.7%) were female and 79 (60.3%) were male. One hundred and three (78.6%) were 18–40 years old, whereas 28 (21.4%) were 40 years old and older. For tooth type, 34 (26.0%) had an anterior root canal, 39 (29.8%) had a molar root canal, and 58 (44.3%) had a premolar root canal. Conclusion: Considering the limitations of the present study, it was determined that endodontic treatment failures mostly occurred in underfilled root canals, followed in number by coronal leakage. Premolars had a higher failure rate than did anterior and molar teeth.

The effect of silver nanoparticles, zinc oxide nanoparticles, and titanium dioxide nanoparticles on the push-out bond strength of fiber posts

BackgroundThis study was undertaken to investigate the effect of intraradicular dentin pretreatment with silver nanoparticles (SNPs), zinc oxide nanoparticles (ZNPs), and titanium oxide nanoparticles (TNPs) on the push-out bond strength (PBS) of fiber posts to root dentin using two types of resin cements. Material and MethodsEighty single-rooted human premolar roots were randomly divided into eight groups after endodontic treatment and post space preparation, according to the type of intraradicular dentin pretreatment with different nanoparticle solutions (n=20). The groups included no pretreatment (control) and pretreatments with SNPs, ZNPs, and TNPs. Each group was divided into 2 subgroups (n=10) according to cementation: Excite DSC/Variolink II and ED Primer II/Panavia F2.0. The PBS values were measured in different areas of the post space. The data were subjected to the three-way analysis of variance and Tukey tests (p=0.05). ResultsThe SNP-pretreated groups showed significantly higher PBS values than the other groups. No significant differences in PBS were noted among the control, ZNP-pretreated, and TNP-pretreated groups. There was no significant difference in the PBS of the fiber posts with respect to cement type. The PBS was significantly lower in the apical region than in the other two regions. There was no statistically significant difference between the PBSs of the cervical and middle thirds. ConclusionsIntraradicular dentin pretreatment with SNPs, TNPs, and ZNPs did not interfere with the PBS of the fiber posts. The best result was obtained for the SNP-pretreated groups for both types of cement. Also, the lowest PBS was found in the apical third of the root canal spaces. Key words:Fiber post, nanoparticles, push-out bond strength.

Bond strength of cemented fiber posts to teeth with simulated internal root resorption.

BackgroundTeeth with internal root resorption (IRR) have guarded prognosis, considering that IRR defect could influence on the post bond strength. The aim of this study was to evaluate the bond strength and the bond interface between different glass fiber-reinforced posts (FRP) after cementation in teeth with simulated internal root resorption (IRR). Material and MethodsForty-five (45) human premolar roots with simulated IRR were embedded in acrylic resin blocks and cross-sectioned into two segments, enabling them to be re-approximated by screws. Intracanal medication was inserted for 15-days, removed by passive ultrasonic irrigation (PUI) and examined by stereomicroscopy. The push-out bond strength of two fiber reinforced composite posts (Rebilda Post - RP) and Rebilda Post GT – GT, (VOCO) were evaluated at the cervical and IRR regions (n = 20). And, the bonded interface between resin cement and root dentine was analysed by scanning electron microscopy (SEM). Results62.5% of IRR were not completely cleaned by PUI. Bond strength values at the cervical region (9.8 and 14.6 MPa) were higher than the IRR region (6.3 and 4.2 MPa). Micrographies showed bubbles in the cement and spaces in the bonded interface. ConclusionsRP post showed better bond strength at the cervical region while GT had better bond strength at the IRR region. Key words:Endodontics, root canal filling materials, root resorption, X-Ray microtomography.

Evaluation of the effect of SmearOFF on Smear Layer Removal and Erosion of Root Canal Dentin An in Vitro Study

Background and Objectives: Root canal instrumentation produces a smear layer that covers the root canal walls and may have adverse effects on endodontic treatment. SmearOFF is a new endodontic irrigant, which proposes smear layer removal and microbial elimination in one step. The aim of the present study was to evaluate and compare the effect of SmearOFF with other final irrigants regarding smear layer removal and degree of erosion from the apical third of root canals. Methods: Forty mandibular premolar roots with single canals were selected. The teeth were randomly divided into 4 groups of 10 teeth each according to the type of final irrigants used during and after instrumentation: G1 6% NaOCl/ distilled water (control), G2 6% NaOCl/Qmix, G3 6% NaOCL/SmearOFF, G4 6% NaOCL/ 17% EDTA. All teeth were shaped by using ProTaper NEXT rotary system till X2. 6% NaOCl was applied with a 27-G side-vented syringe needle as an initial irrigant followed by the final irrigants. Endoultra ultrasonic device was used for irrigation activation. The samples were then submitted to scanning electron microscopy to evaluate the effectiveness of proposed treatments. Results: In smear layer variables score 2 was the most occurred value for G2 (QMIX) and G3 (SmearOFF), whereas in G1 (Distilled water) and G4 (17% EDTA) are 3 and 1 respectively. For erosion variable, erosion was most evident in G4 (6% NaOCL/ 17% EDTA). There were no significant differences between G2 and G3 and also between G3 and G4 in both smear layers and erosion. Conclusion: 17% EDTA, SmearOFF, and QMix using PUI can remove smear layer effectively from the apical third. In the future, SmearOFF may act as a promising chelating agent as well as an antimicrobial irrigant.

Structural analysis of premolar roots in Middle Pleistocene hominins from China

This study investigates permanent maxillary and mandibular premolar root structural organization in East Asian Middle Pleistocene hominins. In addition to reporting and analyzing the linear and volumetric properties of the roots, we used a landmark-free approach to both qualify and quantify in 3D premolar root shape variation of Middle Pleistocene hominins in East Asia. Moreover, we focus on some mid-to late East Asian Middle Pleistocene hominin specimens whose taxonomic attribution is unclear. We find considerable cementum in this sample of hominins, similar to other fossil groups, but clearly different from modern humans which have a very small amount of cementum. Additionally, a smaller root pulp cavity is found in later Homo (Neanderthals and modern humans). Our analyses on the crown-root surface area ratio show that East Asian Middle Pleistocene Homo erectus as well as one late Middle Pleistocene Homo sp. specimen (PA 81 P4 from Changyang site) are distinguished from other fossil and extant groups by a relatively larger root surface, stout root branches and thick cementum deposits. This may represent a distinct East Asian H. erectus dental pattern. Geometric morphometric analyses on the external root surface reveal a general trend of shape simplification along the Homo lineage examined here, and distinguish Early Pleistocene Homo, Middle Pleistocene H. erectus, Neanderthals and modern human morphologies. The late Middle Pleistocene teeth from Changyang site (PA 76 P3 and PA 81 P4) are close to East Asian H. erectus and Neanderthals, while the mid-Middle Pleistocene P3 from Panxian Dadong falls within the modern human distribution. Combined with dental crown morphology and root number/form reported in previous studies, our results show that the external root shape can be considered a taxonomically relevant indicator. In general, an evolutionary tendency towards modern human morphology is observed in part of the East Asian Middle Pleistocene specimens, while a retention of primitive, H. erectus-like features is expressed in some late Middle Pleistocene specimens, supporting a multi-lineage and discontinuous scenario of human settlements in East Asia.

Interfacial Characterization of Dentin Conditioned with Chitosan Hydroxyapatite Precursor Nanocomplexes Using Time-of-flight Secondary Ion Mass Spectrometry

IntroductionThe purpose of this study was to evaluate the effect of chitosan-hydroxyapatite precursor (C-HA) nanocomplex conditioning on the chemical modifications at the tricalcium silicate sealer-dentin interface using time-of-flight secondary ion mass spectrometry. MethodsDentin slabs from human premolar root dentin were prepared, demineralized, and randomly distributed between control and C-HA nanocomplex conditioned groups. Tricalcium silicate sealer was applied, and the slabs were allowed to set in 100% humidity for 10 days. The cross-sectional area was exposed, and the sealer-dentin interface was characterized for chemical/ultrastructural evaluation with time-of-flight secondary ion mass spectrometry and transmission electron microscopy, respectively. ResultsChemical analysis revealed the presence of an ion-rich layer constituted of abundant phosphates (PO2−, PO3−, and PO4−), hydroxide (OH−), and chitosan fragments (C2H4NO−, C3H4NO2−, C2H5O2+, C2H6NO+, C4H6NO2+, C5H6NO+, and C5H5O2+) on the dentin surface at the sealer-dentin interface and subsurface dentin after conditioning with C-HA nanocomplexes. In contrast, a decreased interfacial presence of calcium (Ca+) and calcium phosphates (CaPO2+, CaPO3+, CaPO4+, and Ca2PO3+) and the absence of phosphate fragments in the control were noted. Ultrastructural evaluation showed an interfacial layer (<1 μm) with interrupted mineral aggregates in the controls as opposed to a continuous (5 μm) mineral layer formation on the conditioned dentin. ConclusionsC-HA nanocomplex conditioning of dentin before tricalcium silicate sealer application resulted in a chemically modified dentin substrate with an ion-rich layer consisting of phosphate, calcium, calcium phosphates, and chitosan that chemically modified the dentin surface/subsurface.

Construction of swept source optical coherence tomography imaging system for root canal endoscopy and application in diagnosis of root fractures

To construct swept source optical coherence tomography (SS-OCT) imaging system for root canal endoscopy, and to evaluate the accuracy of diagnosing artificial root fractures. An ultra-high-speed (40 kHz) swept laser source was developed based on the piezoelectric tuning filter and the Fourier domain mode locking (FDML) swept laser technology (patent number: 200620135940.2). Ultra-miniature gradient index lens technology (patent number: 201320241218.7) was used to create a thin endoscopic probe with a diameter of 0.86 mm for real-time image transmission. The SS-OCT light source had a wavelength of 1 310 nm and a bandwidth of 100 nm. The axial and transverse image resolutions were 15 μm and 25 μm, respectively. Artificial fractures were created on human mandibular premolars with single root and the premolar roots were prepared to 41 horizontal sections (1 mm thick). 27 root sections with fractures (width: 52-284 μm) and 14 the sections without fractures were observed under an optical stereomicroscope with a cold light source as the gold standard. The horizontal root sections were scanned by self-developed SS-OCT imaging system for root canal endoscopy with a central wavelength of 1 310 nm and bandwidth of 100 nm. The data were reconstructed with 30 μm thick slices at an interval of 30 μm. Two observers, a radiologist and an endodontist, were trained and independently evaluated all the reconstructed images blindly. The diagnostic performance of SS-OCT imaging system was calculated, and statistical analysis was performed. SS-OCT root canal endoscopic imaging system composed of high-speed swept laser source, fiber coupler, endoscopic probe, reference arm and differential detector. Root sections could be scanned by SS-OCT and imaged in realtime at a depth of 1 to 2 mm. The kappa value for interobserver agreement was 0.792, and the intraobserver agreement was 1.000 and 0.709 for two observers respectively. All of 27 fractured root sections and 12 of 14 root sections without fractures were accurately diagnosed while 2 unfractured root sections were misdiagnosed. The sensitivity was 1.000 and the specificity was 0.857 for diagnosis of artificial root fractures by SS-OCT. The positive predictive value (PPV), negative predictive value (NPV) and the overall accuracy rate were 0.931, 1.000 and 0.951 respectively. The swept source optical coherence tomography imaging system for root canal endoscopy is a promising imaging method for observing root fractures．.

Comparative Assessment of Three Microimplant Assisted Biomechanical Strategies for the Simultaneous Intrusion and Retraction of Anterior Teeth in Relation to Alveolar Bone Stress and Change in Incisor Inclinations – A 3D Finite Element Analysis Study

Microimplants are widely used to provide absolute anchorage in cases with bimaxillary dentoalveolar protrusion especially in those that require simultaneous retraction and intrusion of anterior teeth. The position of the microimplant significantly affects the build up of stress in the alveolar bone as well as the incisor inclinations, and is therefore a critical factor in treatment plannning. Keeping this in mind, this finite element method(FEM) study was taken up to identify the most suitable combination of implant placement sites for cases in which en-masse anterior retraction is done along with intrusion. The geometric model was constructed from a CBCT scan of the maxilla of an adult patient with full permanent dentition.The images were saved as DICOM files and were later exported to the 3D image processing software (Mimics,version 17). The center of resistance for the 6 anterior teeth was 9 mm superiorly and 13.5 mm posteriorly from the midpoint of crown tip of central incisors. The working archwires were assumed to be 0.019 / 0.025-in stainless steel. The three mini-implant placement sites compared were – S1- Midline micro implant between the maxillary central incisors with two placed posteriorly between maxillary 2nd premolar 1st molar roots. S2 – Micro implant placed between the lateral incisor and canine along with posterior mini implants as above. S3- Micro implant placed high up between the maxillary second premolar and first molar roots. The amount of tooth displacement after finite element analysis was compared with central and lateral incisor and canine axis graphs. For the system S1, intrusive components were seen on the archwire mainly in the anterior region with maximum displacement between central incisors and gradually decreasing away from point of force application. In S2, the intrusive component of force was more evenly distributed. In S3, pattern of intrusive component was similar to S2 but the maximum displacement was slightly lower. Greatest value of minimal principal stress was seen on cervical and apical third of central incisors as well as apical third of lateral incisors in S1; and cervical third of lateral incisors and apical and cervical third of canines in S2. Maximum retraction of anterior teeth was seen in S3. In all of the three systems of force application, tooth inclinations were maintained. Maxillary anterior teeth showed more tendency towards retraction in the case where two micro implants were placed posteriorly high up above the roots of maxillary premolars and molars such that the force is directed diagonally having both horizontal and vertical components, and hence eliminating the need for anterior implants. Greater intrusion tendency was seen when implants were placed between the roots of maxillary central incisors.

A rare anatomic variation: Triple mental foramina

Multiple mental foramina (MF) are rarely found in the human mandible. We report on the case, as documented using cone beam computed tomography (CBCT), of the triple MF that were identified on the right hemimandible of a 28-year-old female patient. The distal foramen was located on the mandible between the apices of the second premolar root and the first molar mesiovestibular root, being reached by a thin canal that left the mandibular canal. A pair of mesial foramina were identified between the apices of the premolar teeth. Thus, the three foramina corresponded to a surface area of 23.49mm2 of the mandible. On the opposite side, a single mental foramen had a surface area of just 13.25mm2. On each side, retromolar canals that opened into the retromolar fossae were also found. The anatomic possibility of multiple MF increases the surface area at risk during surgical procedures, increases the risk of neurovascular damage and obscures the common tooth-related location of the mental foramen. Practitioners should, therefore, consider a personalised and imaging-documented approach so as to avoid treatment failure.

Distance and Bone Density between the Root Apex and the Mandibular Canal: A Cone-beam Study of 9202 Roots from a Brazilian Population

IntroductionAccidental damage to the inferior alveolar nerve is of concern during endodontic treatment of the posterior mandible teeth, and a careful evaluation of the relationship between the apices and the mandibular canal (MC) is mandatory to prevent iatrogenic complications. This study aimed to assess the distance between the root apices of posterior teeth and the MC and the bone density in such areas. MethodsOne thousand retrospective cone-beam computed tomographic scans were randomly selected from a private oral radiologic clinic database. The images were acquired with a limited field of view and analyzed by 2 evaluators who measured the shortest distance between the root apices and the upper cortical bone of the MC using Dental Slice software (Bioparts Biomedical Prototyping, Brasília, DF, Brazil). In addition, bone density was estimated using the tool “profile line of Hounsfield” and expressed in Hounsfield units. ResultsThe distal root of the right second molars was the closest to the MC (mean = 3.41 mm), and the right first premolar root was the farthest from the MC (mean = 5.87 mm), respectively. The root apices were closer to the MC in women than in men (P < .05). In 1.79% of the cases, the roots were in contact or invading the MC, whereas 8.35% of the root apices were close to the MC (<1.00 mm), and 89.85% were distant from the MC (>1.00 mm). In 85.55% of the cases, the bone was dense. ConclusionsThe results suggest that the risk of damage to the inferior alveolar nerve is higher for second molars, especially in female patients. The higher density of the adjacent bone may act as a protective factor against nerve damage arising from endodontic procedures.

Root growth and dental eruption in modern human deciduous teeth with preliminary observations on great apes

Recent studies of dental development have indicated that root growth rates are linked to the eruption of some permanent tooth types in modern humans and Pan troglodytes. Little is known about the potential links between these aspects of dental development in deciduous teeth of any primate species. This histology study calculates the rate at which roots extend in length for human deciduous maxillary teeth and a small sample of deciduous canines and premolars from P. troglodytes and Pongo pygmaeus. Links are sought between root extension rates and previously published data for deciduous tooth emergence in each of these species. Results reported here provide the first evidence that the roots of human deciduous incisors, canines, and premolars extend in length at an accelerated rate as these teeth emerge. Accelerated extension rates in a deciduous canine from Pan coincided with the age that this tooth type emerged in captive chimpanzees. High extension rates in a canine from Pongo preceded emergence age. Preliminary observations indicate that deciduous canine and premolar roots of Pan and Pongo extend in length rapidly when compared to these tooth types from modern human children. This study provides a starting point from which to investigate new links between the incremental development of deciduous roots and tooth emergence in primates.

Analysis of mandibular premolar root position in relation to adjacent cortical plates and mental foramen using cone beam computed tomography in the Saudi population.

Objectives:To evaluate the horizontal and vertical location of the mental foramen (MF), as well as the relationship of lower premolars to buccal and lingual cortical plates using cone beam computed tomography (CBCT).Methods:Retrospective cross-sectional study conducted using CBCT scans that were obtained between early 2014 and late 2016 from King Saud University Dental hospital database in Riyadh, Kingdom of Saudi Arabia; 94 patients (53 males and 41 females) were included. Three examiners independently performed one-sided measurements for each patient. Data analyzed statistically and a p<0.05 was considered significant.Results:The mean distances from the outer boundary of the buccal cortex to the first and second premolars (R1) were 1.55 mm and 1.98 mm. The mean distances from the outer boundary of the lingual cortical plate to the first and second premolars (R2) were 4.06 mm and 4.73 mm. The respective mean total bone thicknesses, including the roots of the first and second premolars (R3), were 9.32 mm and 10.08 mm. The mean distance between the MF and the mandibular second premolar apex was 3.13 mm.Conclusion:Mandibular premolars are in close proximity to MF especially mandibular second premolar. Presurgical assessment is essential when surgical treatment is planned at this area.

Comparative observations on the premolar root and pulp canal configurations of Middle Pleistocene Homo in China.

The aim of this study is to explore the root and root canal morphology of Homo fossil occupying China during the Middle Pleistocene period. Human occupation and evolutionary dynamics in East Asia during the Middle Pleistocene period is one of the most intriguing issues in paleoanthropology, with the coexistence of multiple lineages and regional morphs suggesting a complex population interaction scenario. Although premolar root and canal morphology has certain phylogenetic, taxonomic, and functional implications, its morphological diversity, possible evolutionary trend and characteristics regarding Middle Pleistocene hominins inhabiting East Asia are still insufficiently understood; where these populations fits within the Homo lineage (with respect to root and pulp canal structure) needs to be explored. Using microtomography, we directly observed and assessed the nonmetric variability of root and canal forms in maxillary and mandibular premolars of Chinese Middle Pleistocene Homo (N = 19), and compared our observed variations with Eurasian Early Pleistocene specimens from the Asia continent (N = 1) and Java (N = 2), as well as with Neanderthals (N = 28) and recent modern humans (N = 67). A total number of nine types of root-canal forms were recorded. As a whole, the Chinese Middle Pleistocene record shows an evolutionary trend toward a modern human-like condition (a reduction of root/canal number and a simplification of root surface structure). We documented primitive signals like high percentage of Tomes' root in lower premolars. A considerable occurrence of incompletely separated root branches and bifid root and canal apices, representing evolutionary transformation from multi-root to single-root condition was also noticed. The results were compared with previous publications on Early and Middle Pleistocene Homo in East Africa, North Africa, and Eurasia. This work provides new original data, incorporates the latest human fossil discoveries and suggests that analyzing the variation of premolar root structural organization, notably integrating together root/canal form and number, could possibly contribute to taxonomic and phylogenetic assessments. The mid-Middle Pleistocene populations, or "classic" Homo erectus, in our study show closer affinity to Early and Middle Pleistocene hominins in Eurasia, than to East African early Homo, which supports the suggestion that at least some of the Early Pleistocene hominin groups in Eurasia contribute to the later population; on the other hand, it is still difficult to clearly trace the evolutionary fate of those late Middle Pleistocene populations (roughly assigned as archaic Homo sapiens through a craniodental perspective). More comparable materials from the Early to Middle Pleistocene period as well as precise chronological framework is needed to further explore the evolutionary trends of archaic hominins in the Asian continent before the arrival of modern humans.

Effect of Different Adhesive Strategies on Bond Quality of Fiber Posts Cemented in Endodontically Treated Teeth.

The purpose of this in vitro study was to assess the effects of anatomic root levels, different adhesive strategies and cementation system on bond strength (BS), nano leakage (NL) and degree of conversion (DC) after fiber posts cementation. Sixty-six roots of human premolars were endodontically prepared and divided according to the combination of adhesive application technique (manual passive, manual active and active vibratory) and the cementation system (Adper Single Bond 2/RelyX ARC [SBAR] and Single Bond Universal/RelyX Ultimate [SBUL]). Specimens were transversally sectioned into six 1-mm-thick serial slices, which were subjected to BS testing (n=7), to NL analysis using scanning electron microscopy (SEM) after slice immersion in silver nitrate (n=2), and micro-Raman spectroscopy for DC (n=2). Data were analyzed using two-way ANOVA and Bonferroni post-hoc test (α=5%). Bond strength values significantly increased with active vibratory application technique (P<0.001), no significant difference was noted between adhesive systems. The cementation system Single Bond Universal/RelyX Ultimate demonstrated the lowest nano leakage values (P<0.05). The manual active and vibratory application techniques showed statistically higher degree of conversion values than the manual passive technique at the coronal and medium thirds (P<0.05); and the lowest results were observed with manual passive application to Single Bond Universal/RelyX Ultimate (P=0.016). The study concluded that techniques with active application (vibratory and manual) resulted in higher bond strength values. The mode of adhesive application influence the results.

Canine and Premolar Root Dimensions in Chinese. A Reference for Osteoodontokeratoprosthesis Surgery.

Osteoodontokeratoprosthesis (OOKP) surgery is used to restore vision in end-stage corneal disorders, where an autogenous tooth supporting an optical cylinder is implanted through the cornea under a buccal mucosal graft. The ideal tooth for OOKP is a healthy single-rooted permanent tooth with sufficient buccolingual/palatal root diameter to accommodate an optical cylinder. The aim of this study was to determine the buccolingual/palatal diameters of canine and premolar roots in Chinese, for selection of teeth for OOKP surgery. This was an anatomical study on root dimensions of extracted intact teeth. Extracted canine and premolar teeth (excluding maxillary first premolars) were collected and the buccolingual/palatal and mesiodistal diameters of the root at the cervical line and at 2-mm intervals below the cervical line were measured with Vernier calipers. Other measurements included total tooth length, crown buccolingual/palatal diameter, and root length. Mean and minimum buccolingual/palatal root diameters were compiled for each 2-mm interval. A total of 415 extracted teeth (198 male, 217 female) were collected and measured. Recorded dimensions of keratoprostheses in 55 previous OOKP surgeries were used to establish acceptable lamina dimensions to ascertain root size adequacy. Premolars in Chinese female patients were undersized in a small minority. Minimal dimensions of teeth were insufficient if at 6 mm root level, the buccolingual/palatal width was less than 5 mm, or the mesiodistal width was less than 3 mm. This was noted in female mandibular first premolars (5.6%), maxillary second premolars (4.5%), and mandibular second premolars (1.5%). Canines have adequate dimensions for OOKP surgery. However, premolars in Chinese females may be undersized in a small minority.

Fracture Resistance of Roots in Mandibular Premolars Following Root Canal Instrumentation of Different Sizes.

To measure the fracture resistance of mandibular premolar roots following root canal instrumentation with different sizes. A total of 100 human permanent mandibular premolars with a straight single canal were decoronated and assigned to 10 groups (n = 10) by block randomisation. In the control group, the roots were uninstrumented, whereas roots in the nine experimental groups were instrumented to different master apical files (MAF) and tapers (MAF/taper): 40/0.05, 45/0.05, 50/0.05, 55/0.05, 60/0.05, 40/0.10, 40/0.15, 45/0.10 and 45/0.15. All roots were subjected to vertical loading until fracture. Fracture load values for instrumented roots were lower than the intact roots of the control group. In 50/0.05, 55/0.05, 60/0.05, 40/0.15 and 45/0.15 groups, the fracture load values were significantly lower than the fracture load value for the control group (P < 0.05) with a 30% decrease. No significant differences in the fracture modes were detected among the 10 groups (P > 0.05). Mechanical instrumentation adversely affects the fracture resistance of roots. When the roots of mandibular premolars were instrumented to a MAF equal to or larger than 50 with a taper of 0.05 or to a MAF of 40 or 45 with a taper of 0.15, the fracture load values significantly decreased.

POSISI FORAMEN MENTALIS PADA MAHASISWA SUKU BATAK DITINJAU DARI RADIOGRAFI PANORAMIK DI FKG USU

The position of mental foramen is difficult to determine clinically. However, it can be seen using radiography. The position is generally located below mandibular second premolars, but these positions may vary in each individual. This study aims to know the position of the mental foramen on Bataknese students seen from panoramic radiography in Faculty of Dentistry USU. This research was descriptive with sample of 38 Bataknese students in Faculty of Dentistry USU aged 20-25 years old. The sample taken with purposive sampling methode. The research was conducted in Radiology Department, Faculty of Dentistry USU. The results of research showed that the position of mental foramen on Bataknese students varied, located between the anterior premolars one to first molar mesiobuccal root line. The conclution of this study is the position of the mental foramen on the Bataknese students at faculty of dentistry USU were lysed with second premolar root is equal to 42,1%.

Assessing surface characteristics of eroded dentine with optical coherence tomography: a preliminary in vitro validation study

We conducted the first pilot study to investigate the use of the attenuation coefficient from an optical coherence tomography (OCT) backscattered signal as a measure of surface roughness changes in eroded dentine at an early stage of the erosion process. Ten human premolar root samples were subjected to citric acid treatment before scanning by OCT. The extracted relative attenuation coefficient (μR) from backscattered OCT signals was shown to increase with the duration of acid challenge. Validated against roughness measurements (rSa) from scanning electron microscopy scans, μR is significantly correlated with rSa indicative of severity of erosion (p<0.01, r=0.9195). We conclude that the OCT attenuation coefficient of the immediate subsurface in eroded dentine is a potential surrogate measure for its surface roughness. However, further work should be performed to study how it relates to the surface and immediate subsurface changes effected by other mechanical wear before it could unequivocally be used as a surrogate measurement for surface roughness.