Occlusal Surfaces Of Posterior Teeth Research Articles

Accuracy of Complete-Arch Scans Obtained by Intraoral Scanner and Smartphone Three-Dimensional Scanning Applications With Different Smartphone Position Setups: An In Vitro Study.

The high cost of intraoral scanners (IOS) for complete-arch scans makes them less accessible for many dental practitioners. As a viable alternative, smartphone scanner applications (SMP) provide comparable scanning capabilities at a significantly low cost. However, there is limited data on the accuracy of SMP, especially when used in various smartphone positions. This study aimed to compare the three-dimensional (3D) and linear accuracy of complete-arch scans acquired by an IOSand SMP (KIRI Engine, KIRI Innovations, Guangdong, China) at three shooting angles (0°, 45°, and 90° for SMP_3A) and two shooting angles (30° and 60° for SMP_2A). A stone dental cast was scanned with a laboratory scanner as a reference, with 11 scans performed by an IOS, SMP_2A, and SMP_3A. In 3D analysis, trueness and precision were evaluated through superimposition with the reference scanand within each group, respectively, using the best-fit algorithm of Geomagic Wrap software (3D Systems, Inc., Rock Hill, SC). Trueness in linear discrepancy was assessed by comparing the occlusal-cervical and mesiodistal dimensions of reference teeth (canine, premolar, and molar), intercanine width, and intermolar width on the digital casts to measurements of the stone cast, while precision was measured using the coefficient of variance. Differences between groups were analyzed using the Friedman test, followed by the Dunn-Bonferroni post hoc test with a significance level set at 0.05. IOS exhibited significantly lower trueness than SMP_2A (p = 0.003) with significantly greater width discrepancies on canines (p = 0.001) and molars (p < 0.001). Discrepancy patterns differed among the three scanning methods. The IOS showedgreater discrepancieson the occlusal surfaces of posterior teeth. While SMP_3A demonstrated higher variation on the palatal surfaces and interproximal areas of posterior teeth. For precision,SMP_3A (p = 0.028) and SMP_2A (p = 0.003) showed a significantly lower precision in 3D analysis, but a comparable reproducibility in linear measurement to IOS. TRIOS IOS (3Shape,Copenhagen, Denmark) exhibited lower trueness in 3D and linear accuracy analyses for complete-arch scans. The positions of the smartphonesignificantly enhanced trueness at the undercut region. SMP_2A and SMP_3A can be a potential alternative for precise linear measurement in complete-arch scans with selective use.

Conservative Dental Management of a Patient With Amelogenesis Imperfecta Under Oral Sedation: A Case Report

Amelogenesis imperfecta (AI) is a rare hereditary developmental disease that has a significant effect on the enamel structure. Both primary and permanent dentition could be affected by this condition. The pivotal characteristics are loss of the tooth structure, wear of enamel, and exposed dentinal areas at the occlusal surface of posterior teeth. AI may be inherited in autosomal dominant, autosomal recessive, or X‐linked types. Treatments of AI cases should be initiated in childhood and continue into adolescence. Considering that AI is a rare and heterogeneous condition, the dental team faces various difficulties regarding choosing the appropriate treatment plan. The oral rehabilitation of patients with AI is a challenging condition that needs a multidisciplinary approach. Many treatment options have been reported for solving cosmetic and restorative problems in AI cases. The conservative treatment plan in this hypoplastic-hypomature AI case included esthetic rehabilitation with a sequential method, innovative non-invasive pulp-therapy methods, and dental restorations under oral sedation. The written consent for the treatments was obtained after consultation with the child and his parents.

Pulp Polyp Exhibiting a Unique Worm-shaped Presentation in an Ectopic Deciduous Tooth: A Novel Case Report

Pulp polyp is a reactive lesion that occurs as a result of chronic long standing caries. Dental caries is common in children for a variety of reasons, including increased bacterial colonisation, frequent exposure to dietary sugars, improper bottle feeding technique, low community water fluoride levels, inadequate tooth brushing, and a lack of parental knowledge about oral health. Failure to treat such carious lesions during childhood will result in chronic long-term caries leading to pulpal necrosis or reactionary proliferations of pulpal tissue known as pulp polyp. Apart from caries, trauma can also lead to hyperplastic behaviour of the pulp. Pulp polyps are most commonly found in the molars due to their abundant blood supply, whereas their presence in the anterior teeth is considered uncommon. Pulp polyp can cause anxiety among parents when they spot it in their child’s oral cavity. This is due to the unique clinical appearance, discomfort while having food and occasional bleeding while irritated. This case report presents an unusual presentation of pulp polyp in an 11-years-old female patient with a chief complaint of pain, discomfort, and bleeding on irritation. Its peculiar worm-shaped clinical appearance in the anterior attached gingival region imposed a diagnostic dilemma which on histological examination was confirmed to be pulp polyp and was excised subsequently. Therefore, emphasises the fact that pulp polyps are not only limited to the occlusal surface of posterior teeth with a typical mushroom-shaped appearance but also have a wide range of presentations regardless of their location and appearance

Aesthetic restoration of posterior teeth using different occlusal matrix techniques.

The occlusal matrix technique appears as an alternative to the conventional restorative technique. The aim of this study is to present treatment options for the decayed occlusal surface of posterior teeth by means of an occlusal matrix made with different materials, for an accurate reproduction of the tooth surface. This paper presents five clinical cases using five different materials, such as Bite-Perf, flowable composite, self-curing acrylic resin, silicone and thermoforming foil. Before light-curing, the last layer of composite resin, the matrix, is repositioned and firmly pressed so the replication of the original occlusal anatomy can be achieved. When using an occlusal matrix, minimal or no finishing and polishing procedures are needed and the offered aesthetics are clearly an advantage. Moreover, this technique makes up for the additional chairside work time. The occlusal matrix technique is demonstrated to be effective for direct composite resin restorations in posterior teeth, allowing a reliable and predictable reproduction of the occlusal anatomy and clinical adjustment. For this purpose, a clear material is preferable since it allows light transmission.

Influence of Liquid on the Tooth Surface on the Accuracy of Intraoral Scanners: An In Vitro Study.

To assess the influence of liquid attached on the tooth surfaces on the accuracy (trueness and precision) of intraoral scanners and the effectiveness of the drying method (using compression air) to exclude the influence of liquid on the scanning results. A mandibular jaw model was scanned using an industrial computed tomography scanner to obtain a reference model. A scanning platform was designed to simulate three specific tooth surface states (dry, wet, blow-dry). Two kinds of liquids (ultra-pure water and artificial saliva) were used for the test. Two intraoral scanners (Trios 3 and Primescan) were used to scan the mandibular jaw model 10 times under each condition. All scanning data were processed and analyzed using dedicated software (Geomagic Control 2015). Trueness and precision comparison were conducted within the 12 groups of 3D models divided based on different intraoral scanners and liquids used under each condition. The root mean square (RMS) value was used to indicate the difference between the aligned virtual models. The color maps were used to evaluate and observe the deviation distribution patterns. The 3-way ANOVA (condition, intraoral scanner, liquid) followed by the Tukey test were used to assess precision and trueness. The level of significance was set at 0.05. The mean RMS values obtained from wet condition were significantly higher than those of the dry and blow-dry condition (p < 0.001, F = 64.033 for trueness and F = 54.866 for precision), which indicates less accurate trueness and precision for wet condition. For two different types of liquids, the mean RMS value was not significantly different on trueness and precision. The deviations caused by liquid were positive and mainly distributed in the pits and fissures of the occlusal surface of posterior teeth, the interproximal area of the teeth, and the margin of the abutments. Liquid on the tooth surface could affect intraoral scanning accuracy. Blow-drying with a three-way syringe can reduce scanning errors.

Accuracy of different tooth surfaces on 3D printed dental models: orthodontic perspective

BackgroundFew studies have been reported regarding the accuracy of 3D-printed models for orthodontic applications. The aim of this study was to assess the accuracy of 3D-printed dental models of different tooth surfaces.MethodsThirty volunteers were recruited from the hospital, and then their dental models were produced by means of oral scanning and a stereolithography-based 3D printer. Each printed model was digitally scanned and compared with the oral-scanned STL file via superimposition analysis. A color map was used to assess the accuracy of different surfaces (occlusal, buccal, lingual) of anterior and posterior teeth. The Tukey test was used to evaluate the differences between the superimposition.ResultsStatistically significant differences were found in the average deviations of different tooth surfaces (P < 0.05). The mean average absolute deviations of the occlusal surfaces of posterior teeth were greater than those of other surfaces. Percentages of points beyond the upper and lower limits of different tooth surfaces displayed the same results (P < 0.05).ConclusionsOcclusal surfaces, especially pits and fissures of posterior teeth on 3D printed maxillary dental models, showed greater distortions than those of other teeth and regions.

Prevalence of Occlusal Morphological Patterns of Permanent Mandibular First Molar

Teeth are informative indicators for the study of human populations, serving as markers and thebases for comparisons of genetic origin. Mandibular first molar is represented as 36 or 46 in the FDI system.The occlusal surfaces of posterior teeth occlude with the opposing occlusal surfaces of posterior teeth. Theocclusal morphology differs in each posterior tooth. The occlusal aspect of posterior teeth is developed intocusps ( 5 or 4 or 6 ) and grooves ( Y or + or X pattern ). These cuspal patterns and groove patterns help inforensic identification in cases like gender determination and also to identify the ethnic background of anindividual. Variation in degree of expression and frequency of teeth in dentitions of different populationsis different which may be helpful for forensic identification. The aim of the study was to determine theprevalence of different occlusal morphological patterns of permanent mandibular first molars. The studyincluded a predominantly South Indian population. Approval was received from the Institutional ReviewBoard. Study was conducted with 100 participants who were randomly selected. The occlusal morphologypatterns (number of cusps and groove pattern) of left and right permanent mandibular first molar wereassessed from the photographs of the oral cavity and the date was recorded. Results showed that the mostprevalent number of cusps in permanent mandibular first molar was 5 cusps ( 71% ) and Most prevalentgroove pattern in permanent mandibular first molar was Y pattern. It was also observed that the combinationof the 5Y pattern was more prominent in females than in males.

Is the inferior occlusal plane a reliable anatomic landmark for inferior alveolar nerve block? A study on dry mandibles of Brazilian adults

To investigate the relationship between the mandibular foramen (MF) and the inferior occlusal plane (IOP) of anatomic specimens, in order to guide clinicians in the inferior alveolar nerve block (IANB). Eighty-two dry mandibles (totally or partially toothed) of Brazilian adults were selected, totalizing 66left and 66right antimeres. A flat plate of rigid PVC plastic was placed on the occlusal surfaces of posterior teeth and pressure was then manually applied to simulate the IOP. Following, the perpendicular distance from the IOP to the lowest point of the MF was measured by the use of a digital caliper, adopting negative values inferiorly and positive values superiorly. Regarding the antimeres, the majority of the lowest limits of the MF was below the IOP (right: 86.4%, left: 81.8%) with a mean of -4.2mm (±4.8) in the right and -4.1mm (±4.8) in the left ones, without any statistical significance. Considering both sexes, no statistically significant difference was obtained between them. The IOP seems not to be a good anatomical landmark to localize the MF and, its turn, to guide clinicians during the IANB for Brazilian adults, given the marked topographic variations.

Evaluation of pre-alginate impression preparation methods in the surface accuracy of dental cast

ObjectiveThe aim of this study was to investigate the influence of pre-preparation technique (finger smearing and saliva ejection) of alginate impressions on the quality and accuracy of dental casts. Materials and methodsTwenty mandibular impressions from 20 patients (10 males, 10 females) with an age range of 20–40 years were recorded using stock trays. A standard impression and pre-preparation technique for alginate were employed. This included removal of saliva with saliva ejector, smearing of alginate on occlusal surfaces of posterior teeth and smoothing of the material in the tray (Group-1: Test) and no drying and smearing or smoothing of the material prior to impression (Group-2: Control). Standardized disinfection, storage, pouring and removal from die stone techniques were used for all samples. Surface defects (nodules/blebs) on the occlusal surface of casts as examined with digital microscope, were classified according to their sizes and surface area into; Type-A (<500); Type-B (>500 <100); Type-C (>1000) in micrometers (μm). Data was tabulated and analyzed by SPSS using Anova and Tukey’s test. ResultsDefects were significantly higher (p < 0.01) in samples in Group-2 (1225.51 ± 823.44 μm) as compared to Group-1 (783.68 ± 501.41 μm). All types of defects (Types A, B and C) were significantly higher in samples from Group-2 as compared to Group-1. ConclusionsUse of pre-preparation technique of finger smearing and saliva ejector prior to alginate impressions resulted in significant reduction of surface nodules/blebs and enhanced the quality and accuracy of fabricated casts. Therefore, the use of saliva ejector, finger smearing on the occlusal surface of teeth and smoothening of alginate impression, immediately prior to intra-oral placement is clinically recommended.

Preliminary study assessing remineralisation of early caries on posterior teeth using SoproLife®

PurposeThe aim of this study was to assess the effectiveness of minimal intervention via fluoride therapy in management of early caries lesion with the aid of SoproLife®. Materials and methodsA total of 40 patients were recruited, (mean age = 23 years) and were assigned to low and moderate caries risk groups (n = 20). Eighty occlusal surfaces of posterior teeth were examined for early caries lesion visually and using SoproLife® at baseline and at a recall visit six months later. At baseline visit, patients were given oral hygiene education, fluoridated toothpaste for homecare and topical fluoride application. SoproLife® images acquired were analysed using Image J software version 1.50. Difference in the mean value of intensity of the red wavelength spectrum between baseline and recall visits, (ΔI), were analysed for both risk groups. ΔI for upper and lower first molar teeth were also analysed. ResultsResults show no statistical difference for ΔI between low and moderate risk groups (p = 0.13). There is no statistical difference in ΔI within the low caries risk group (p = 0.42) but there is significant difference in the moderate risk group (p = 0.02). No statistically significant difference in ΔI value between upper first molars (UFM) (p = 0.80) and lower first molars (LFM) (p = 0.07) were detected. There was also no statistically significant difference in ΔI value within the upper and lower first molars (UFM: p = 0.31, LFM: p = 0.27). ConclusionSoproLife® generated images did not show significant differences in remineralisation of early caries between low and moderate caries risk patients and between the upper first and lower first permanent molars in these patients.

The The effect of different solutions and thermocycling on the vickers hardness of acrylic resin denture teeth

Aim: The aim of this study was to evaluate the effect of artificial saliva, disinfectant solution, distile water and thermocycling on Vickers hardness of 4 commercial brands of acrylic resin denture teeth.&#x0D; Methodology: Four different brands of acrylic resin denture teeth (Major Dent, Acry Lux, Acry Rock, Imident Lux) were evaluated. 15 anterior and 15 posterior teeth of each group embedded in autopolymerized acrylic resin. The occlusal surfaces of posterior teeth and the vestibule surfaces of anterior teeth were flattened by using silicone carbid paper. After polishing, microhardness measurements were repeated three times for each teeth. The teeth were submitted to different conditions: (1) storage in distilled water at 37±2°C for 7 days; (2) storage in artificial saliva at 37±2°C for 30 days and (3) storage in 1 % sodium hypochlorite. After, thermal cycling between 5 and 55 °C for 2500 cycles was made. The microhardness measurements were repeated. Data were analyzed with one-way analysis of variance (ANOVA) and Duncan test ( p&lt;0.05).&#x0D; Results: There was statistical significant differences between initial and final microhardness values of different barnds of acrylic resin denture teet. Anterior teeth showed lower microhardness values than posterior teeth.&#x0D; Conclusion: Storage in different solutions and thermal cycling significantly reduced the Vickers hardness of the acrylic resin denture teeth.

The Islamic Perspective of Lingual Dens Evaginatus in a Mandibular Left Second Premolar: A Case Report

Dens evaginatus (DE) is a developmental anomaly. It is an extra cusp or tubercle that protrudes from the occlusal surface of posterior teeth, as well as the lingual surface of anterior teeth. Tubercles are susceptible to pulp exposure from wear or fracture because of malocclusion;leading to pulpal complications early after eruption.DE may also complicate the process of daily routine oral health care. A 13-year-old girl presented to our polyclinic with sinus track at the posterior lower left buccal gingiva forthe past1 year. All 35 teeth were sound. At the lingual side, there was an accessory tooth in close relation to tooth 35 covered with supra-gingival inflammation. Electric pulp test (EPT) showed that tooth 35 was already non-vital. Intraoral periapical (IOPA) radiograph and cone beam computed tomography (CBCT) scan showed an abnormalappearing root which shows DE with radiolucency at the periapical area. Root canal treatment was performed using crown down pressureless (CDP) technique and obturation was done using lateral condensation technique. The tooth was restored using composite restoration. DE is a rare condition. It is quite a challenge for dental practitioner since the diagnosis is difficult and the treatment options are limited. In the case of DE with necrotic pulp and periapical abscess, root canal treatment is a treatment of choice. We have to accept and appreciate any gift from Allah SWT whether it is good or bad, no equal divine creation except from Allah SWT.Therefore we need to take care of our oral hygiene to prevent diseases. In every disease, there is a cure; we thus need to try to do the best to find the cure and to not easily get rid of the tooth and replace it with a denture. Early diagnosis of DE can lead to proper treatment which can result in high success rate if it is followed by adequate restoration.

A Simplified Approach for Restoration of Worn Dentition Using the Full Mock-up Concept: Clinical Case Reports.

Treatment of tooth wear has increased over the last two decades. However, the treatments involved have not been satisfactory to most patients, nor have they achieved the expected goal on some worn teeth. New approaches have emerged to reconstruct full arches in a minimally invasive way that take advantage of developments in the field of adhesive dentistry. These new concepts constitute a revolution in dentistry and their application requires adapted techniques and training. The purpose of this article is to suggest a precise and reproducible method that simplifies the treatment of worn dentition. A wax-up and a mock-up are primarily used to design the esthetic outcome and then used as a guide for the preparation of anterior teeth or the occlusal surfaces of posterior teeth. This not only provides the exact new vertical dimension of occlusion but serves as a guide for precisely controlling occlusal preparation simultaneously with buccal preparation. The classical cavity design for a partial bonded restoration on posterior worn dentition is also reviewed. The authors believe that during the preparation of the occlusal surfaces of the posterior teeth surfaces, the marginal ridges must be preserved to reduce the biologic cost and mechanical stress leading to fracture. A new type of thin and reduced restoration called tabletop is presented.

Fracture resistance of ceramic and polymer-based occlusal veneer restorations

ObjectivesThe purpose of this in vitro study was to evaluate the influence of thermodynamic loading on the durability and fracture resistance behavior of occlusal veneers fabricated from different biomedical dental CAD/CAM materials. MethodsThe occlusal surfaces of 64 extracted premolars were prepared in the enamel layer and restored with occlusal veneers with a fissure/cusp thickness of 0.5/0.8mm made from four different dental CAD/CAM materials: group LD lithium disilicate (e.max CAD), group LS zirconia-reinforced lithium silicate (Vita Suprinity), group PI polymer-infiltrated ceramic (Vita Enamic), and group PM polymethylmethacrylate PMMA (Telio CAD). The prepared teeth were etched with phosphoric acid. The occlusal veneers were then bonded using an adhesive luting system (Multilink Primer A/B and Multilink Automix luting resin). Half of the specimens were subjected to thermodynamic loading in a chewing simulator (1.2 million cycles at 98N). All specimens were quasi-statically loaded until fracture. The statistical analysis was made using the t-test and one-way ANOVA followed by the Tukey HSD test (α = 0.05). ResultsAll aged specimens survived the thermodynamic loading. Thermodynamic loading significantly raised the fracture resistance in groups LS, PI, and PM (P < 0.03). Occlusal veneers made from lithium disilicate and zirconia-reinforced lithium silicate recorded higher fracture resistance than those made from polymer-infiltrated ceramic and PMMA resin. ConclusionsAll tested dental CAD/CAM biomaterials exhibited a fracture resistance considerably exceeding the average occlusal force in the posterior dentition. Therefore, they might present a viable long-term treatment for restoring the occlusal surfaces of posterior teeth.

The minimally invasive management of early occlusal caries: a practical guide.

Pits and fissures on the occlusal surfaces of posterior teeth are sites affected commonly by demineralisation caused by the caries process. Clinicians face daily challenges in detecting these lesions, accurately diagnosing their activity and choosing from a range of management options. Traditionally, the detection of an active (or potentially active) occlusal lesion invariably resulted in the preparation of a standardised occlusal cavity, often extending beyond the confines of diseased tissue, followed by the insertion of a direct restorative material, most commonly dental amalgam. The overwhelming weight of contemporary evidence now favours minimally invasive (MI) operative management when required (usually after non-operative prevention has failed), and a wide range of equipment, materials and operative techniques is available to help operators to preserve the maximum amount of healthy/repairable tooth tissue and to allow restoration with more biologically respectful, tooth-preserving materials. This paper aims to provide clinicians with practical guidance in the prevention, early detection, predictable diagnosis and minimally invasive management of early occlusal carious lesions.

Finite element analysis of provisional structures of implant-supported complete prostheses.

The use of provisional resin implant-supported complete dentures is a fast and safe procedure to restore mastication and esthetics of patients soon after surgery and during the adaptation phase to the new denture. This study assessed stress distribution of provisional implant-supported fixed dentures and the all-on-4 concept using self-curing acrylic resin (Tempron) and bis-acrylic resin (Luxatemp) to simulate functional loads through the three-dimensional finite element method. Solidworks software was used to build three-dimensional models using acrylic resin (Tempron, model A) and bis-acrylic resin (Luxatemp, model B) for denture captions. Two loading patterns were applied on each model: (1) right unilateral axial loading of 150 N on the occlusal surfaces of posterior teeth and (2) oblique loading vector of 150 N at 45°. The results showed that higher stress was found on the bone crest below oblique load application with a maximum value of 187.57 MPa on model A and 167.45 MPa on model B. It was concluded that model B improved stress distribution on the denture compared with model A.

Current possibilities in occlusal caries management

Dental caries is a multifactorial disease that affects most populations throughout the world and it is still the primary cause of oral pain and tooth loss. The occlusal surfaces of posterior teeth are the most vulnerable sites for dental caries due to their anatomy. Therefore, the aim of the following article is to summarize current knowledge on occlusal caries development and the possibilities of its prevention. Although the overall caries rate today has fallen for populations in industrialized countries, the rate of occlusal surface caries has not decreased. This may be explained with fact that topically applied fluorides and their mode of action prevent caries better on smooth than on occlusal surfaces. As we know, tooth decay of first permanent molars causes a great deal of different short and long term difficulties for patients. Therefore, there is a continuous need for implementation of programs for caries prevention in permanent teeth. Nowadays, we like to treat our patients by minimally invasive methods. A very important step in our effective preventive treatment is sealing pits and fissures as a cornerstone of occlusal caries management. Reliable assessment of caries activity is also very important for defining treatment needs and plans. A very important decision, which should be made during occlusal caries management, is the selection of restorative material according to the treatment plan. Current possibilities in occlusal caries prevention and management are very effective. Therefore, dentists today do not have any excuse for avoiding the philosophy of Minimally Invasive Dentistry, especially when we talk about caries management of occlusal surfaces in permanent molars.

Reliability of electronically detection of fissure caries (by using a prototype device): An alternative diagnostic electronic caries monitor device

Objective: The purpose of this in vitro study was to investigate the reliability of a prototype electronic caries monitor (ECM) for diagnosis of the dental caries on the occlusal surfaces of posterior teeth and to compare using histological examination as gold standard. Materials and Methods: Data were obtained from 93 occlusal sites of 33 extracted human molars. Electrical resistance to alternative currency of 21 Hz and 24 Vpp of the teeth was measured with the ECM, which produced in Selcuk University. After obtaining electrical conductance values, each tooth was then sectioned into two pieces mesiodistally and examined histologically for occlusal caries under the stereomicroscope. Statistical evaluations were made using Pearson correlation test. Results: A statistically significant negative correlation was found between electrical resistance of the teeth and occlusal caries presence ( P < 0.05). Conclusion: As a result, it is suggested that ECM is a nondestructive and suitable method at detection of occlusal caries.

FINITE ELEMENT ANALYSIS OF PROVISIONAL STRUCTURES OF IMPLANT-SUPPORTED COMPLETE PROSTHESES.

The use of provisional resin implant-supported complete dentures is a fast and safe procedure to restore mastication and aesthetics of patients soon after surgery and during the adaptation phase to the new denture. This study assessed stress distribution of provisional implant-supported fixed dentures and the all-on-four concept using self-curing acrylic resin (Tempron) and bis-acrylic resin (Luxatemp) to simulate functional loads through the 3D finite element method. The Solidworks software was used to build 3D models, using acrylic resin (Tempron - A) and bis-acrylic resin (Luxatemp - B) for denture captions. Two loading patterns were applied on each model: 1) right unilateral axial loading of 150 N on the occlusal surfaces of posterior teeth; 2) oblique loading vector of 150 N at 45 degrees. The results showed that higher stress was found on the bone crest below oblique load application with maximum value of 187.57 MPa on model A and 167.45 MPa on model B. It was concluded that model B improved stress distribution on the denture compared to model A.

Hunter-Schreger Band patterns in human tooth enamel.

Using light microscopy, we examined Hunter-Schreger Band (HSB) patterns on the axial and occlusal/incisal surfaces of 160 human teeth, sectioned in both the buccolingual and mesiodistal planes. We found regional variations in HSB packing densities (number of HSBs per mm of amelodentinal junction length) and patterns throughout the crown of each class of tooth (maxillary and mandibular: incisor, canine, premolar, and molar) examined. HSB packing densities were greatest in areas where functional and occlusal loads are greatest, such as the occlusal surfaces of posterior teeth and the incisal regions of incisors and canines. From this it is possible to infer that the behaviour of ameloblasts forming enamel prisms during amelogenesis is guided by genetic/evolutionary controls that act to increase the fracture and wear resistance of human tooth enamel. It is suggested that HSB packing densities and patterns are important in modern clinical dental treatments, such as the bonding of adhesive restorations to enamel, and in the development of conditions, such as abfraction and cracked tooth syndrome.