Ahmed A. Madfa

Determination the dental arch dimensions in human populations is necessary for various fields of dental sciences.
This study was designed to evaluate the maxillary dental arch dimensions of Yemeni children aged (10-12) years. The sample
was gathered from primary and intermediate school in Sana'a city, Yemen. Clinical examination was performed on 200 subjects
(100 males and 100 females) that fulfillment the criteria of this study. The examination was carried out for subjects that have
either normal occlusion or class I with anterior dental crowding. Pairs of studying models for the dental arch was constructed
and evaluated by special software for digitizing and analyzing the data. This study reported that class I with anterior dental
crowding is still high incidence, particularly for females, in Yemeni Population. Therefore, more prevention protocols and
dental health educational programs about orthodontics needs are essential in Yemen.

Health systems consist of all the people and actions whose primary purpose is to improve health. It is therefore
urgent to assess current performance and to judge how health systems can reach their potential. This cross sectional study was
conducted in Dhamar city, Yemen to assess the impression about level of the healthcare services. About 240 subjects agreed to
participate in this study but analysis was carried out on 194 subjects who provided complete data on the variables of interest to
this study. Participates satisfaction was measured using a semi-structured worker/patient judgments questionnaire. Participates
were asked to supply the following information about themselves: age, sex, marital status, occupation, level of education, types
of the hospital; employment, and monthly income. The overall level of satisfaction was assessed on a three point scale: 1= poor,
2= fair, 3= good. The results of the current study found that private hospitals have higher overall healthcare quality than public
hospitals. This study indicated that patient of private hospitals are more satisfied and feel more trust in healthcare service
provider than public hospitals. The result of the present study provided insights to both health care providers and hospital
managers to improve service quality and patient satisfaction in the hospital environment in Yemen.

Different dental post designs and materials affect the stability of restoration of a tooth. This study aimed to analyse and compare the stability of two shapes of dental posts (parallel-sided and tapered) made of five different materials (titanium, zirconia, carbon fibre and glass fibre) by investigating their stress transfer through the finite element (FE) method. Ten three-dimensional (3D) FE models of a maxillary central incisor restored with two different designs and five different materials were constructed. An oblique loading of 100 N was applied to each 3D model. Analyses along the centre of the post, the crown-cement/core and the post-cement/dentine interfaces were computed, and the means were calculated. One-way ANOVAs followed by post hoc tests were used to evaluate the effectiveness of the post materials and designs (p = 0.05). For post designs, the tapered posts introduced significantly higher stress compared with the parallel-sided post (p < 0.05), especially along the centre of the post. Of the materials, the highest level of stress was found for stainless steel, followed by zirconia, titanium, glass fibre and carbon fibre posts (p < 0.05). The carbon and glass fibre posts reduced the stress distribution at the middle and apical part of the posts compared with the stainless steel, zirconia and titanium posts. The opposite results were observed at the crown-cement/core interface.

Objectives: To evaluate the fracture resistance and failure mode of endodontically teeth restored with functionally graded structured (FGS) posts compared to titanium and cast posts. Methods: Single canals in 70 bovine incisors were instrumented, irrigated, obturated and divided into seven groups. They were then root restored with titanium, cast and 3 experimental FGS posts of different compositions; ZrO2-Ti-HA, Al2O3-Ti-HA and Ti-HA. Two control groups were also included; sound teeth and those root treated only. All posts were cemented with zinc phosphate cement and built up with composite core. Crowns margins of 1 mm chamfer finishing line were prepared to receive full metal crowns. The fracture resistance was evaluated using Universal Testing Machine. The failure mode was also evaluated as restorable or non-restorable. Data for fracture resistance were analyzed using one-way ANOVA and post-hoc test. Results: There is no significant difference in mean fracture resistance between cast (1398.58N±314.29), titanium (1408.65N±226.39) and FGS posts (ZrO2-HA-Ti; 1299.31N ±251.74, Al2O3-HA-Ti; 1242.53N±196.55 and Ti-HA-Ti; 1267.68N±173.00). However, cast, titanium and FGS posts groups showed significantly higher fracture resistance compared to those root treated only (1051.40N±207.78) and sound teeth (922.48N±261.59). For failure mode, FGS posts and root treated only showed high percentage of restorable cases compared to titanium, cast posts and sound teeth. Conclusions: There was no significant difference in mean fracture resistances among FGS, titanium and cast posts. Teeth restored using titanium and cast posts resulted in higher number of irreparable fracture whilst the FGS posts and root treated only had higher number of reparable fractures.

Objective: To analyse thermo-mechanical stress in endodontically treated teeth restored with Multilayered Structured Dental Posts (MSDPs) under cold and hot conditions using Finite Element Analysis (FEM). Methods: Three MSDPs of multilayer design of xTi-yHA composition added to a zirconia layer (model A), an alumina layer (model B) and a titanium layer (model C) were compared with zirconia (model D) and titanium (model E) posts. The fractions of Ti and HA was varied gradually. Changes in temperature of an endodontically restored tooth model were calculated as a result of hot and cold response. The resulting thermo-mechanical stresses were analysed and compared using FEM in models A, B, C, D and E. Results: It was noted that Models A, B and C returned to near body temperature better than that Models of D and E. There was no evident difference in all MSDPs models. The smallest Von Mises thermal stresses were observed in MSDPs (models A, B and C) compared to models D and E. There were no also differences in Von Mises thermal stresses for all MSDPs. The magnitude of interface of stresses in models D and E with the surrounding tooth structures were greater than those in MSDPs especially in area close to middle third of the dental posts. The peak stress by thermal irritant for models D and E are approximately three times higher than models A, B and C. Conclusion: The findings of this study showed that pure zirconia and titanium posts produced greater thermal stresses than MSDPs.

Objectives: This study compared warm vertical compaction with lateral compaction for obturating root canals with either a polymer-based resin system or gutta-percha. Quality of obturation was evaluated by (i) analysis of the canal area occupied by filling core materials, sealers and voids at three cross-sectional levels and (ii) SEM examination. Methods: Single canals in 64 mandibular premolars were instrumented, irrigated and divided into four equal groups. They were root filled as follows: lateral compaction/resin (RealSeal™, SybronEndo) (LC/R), lateral compaction/gutta-percha with AH Plus™ (LC/GP), warm compaction/resin (WC/R) and warm compaction/gutta-percha (WC/GP). One specimen from each group, randomly chosen for SEM examination, was longitudinally sectioned so that the dentine-filling interface could be evaluated. The remaining teeth were sectioned horizontally at 1 mm (L1), 3 mm (L3) and 6 mm (L6) intervals from the obturated canal terminus. Cross-sectional areas of filling core materials, sealers and voids were measured using a Leica Qwin Colour (RGB) image analysis system. Data were analyzed using independent sample t test and Mann-Whitney U test. Results: Techniques showed no significant differences for canal obturation with resin at L1 and L3 (p>0.05). However at L6, obturation quality was significantly better for warm compaction (p<0.05). For obturation with gutta-percha, there were no differences between the two techniques at L1 (p>0.05). However at L3 and L6, warm compaction was significantly better than lateral compaction (p<0.05). Under SEM, for gutta-percha obturation using both techniques, a uniform gap was observed between the sealer and gutta-percha and also between the sealer and dentine. However, for resin obturation, there was no evident gap. Conclusions: Both techniques showed comparable obturation quality at the apical level (L1). However, at more coronal levels of the canal, warm compaction was better than lateral compaction, especially for obturation with gutta-percha

Objective: This study compared the quality of root canal obturation in round and irregular-shaped canals at two cross-sectional levels by evaluating the canal area filled by two core materials using two obturation techniques. Methods: Single canals in 60 mandibular premolars were instrumented, irrigated and divided into four equal groups. They were root filled as follows: lateral compaction/RealSeal™ (LC/R), lateral compaction/gutta-percha (LC/GP), warm vertical compaction/RealSeal™ (WC/R) and warm vertical compaction/gutta-percha (WC/GP). The teeth were sectioned horizontally at 3 mm (L3) and 6 mm (L6) intervals from the obturated canal terminus. Shapes of canals in all cross-sections were examined using a Leica Qwin Colour (RGB) image analyzer. To determine whether the shape of each canal was round or irregular, the buccolingual and mesiodistal canal diameters were measured. The cross-sectional area of RealSeal™ and gutta-percha core materials were measured utilizing the same image analyzer. Data were analyzed using general linear model and independent sample t test. Results: Descriptively, at L3 and L6, the areas of both filling core materials were higher in round than in irregular canals. WC/R and WC/GP also showed higher areas than LC/R and LC/GP in irregular canals. Statistically, at L3, there were no significant differences in obturation quality between round and irregular-shaped canals (p>0.05). At L6, for techniques, there were no significant differences between the two shapes (p>0.05). For materials, at L6, WC/R showed a significantly higher area than WC/GP in irregular canals (p<0.05). However in round canals, there was no significant difference (p>0.05). For LC/R and LC/GP, there were also no significant differences between both shapes at L6 (p>0.05). Conclusions: Generally, obturation quality was better in round than in irregular canals. WC/R and WC/GP produced better adaptation than LC/R and LC/GP in irregular canals especially for WC/R at L6.

A multilayered titanium (Ti)–hydroxyapatite (HA) functionally graded material was produced via pressureless sintering at 1100°C. The initial and final porosities were determined via shrinkage measurements. The final porosity verification was carried out by the Archimedes method. The experimental porosity measurements were compared with two proposed models. The macroscopic and microstructure features and the measured porosities confirmed that the volume fraction porosity was associated with both matrix and reinforcing particles in all cases. The percolation threshold was observed at x = 0·75 in the xTi+(1−x)HA mixture

The present invention discloses a dental post fabricated of metal-ceramic functionally graded composite material. The dental post and method of fabrication and installation of the post were devised to enable a dental post to be prefabricated, utilizing materials that have structural and compositional compatibility with the natural tooth being restored. Using a metal-ceramic functionally graded composite material to fabricate the post, high modulus of elasticity at coronal part can be achieved which is approximately similar to the crown/s and bridge abutment/s and it gradually reduced towards the apical partof the tooth. Utilization of this post will increase the fracture resistance of endodontically treated teeth. It has also been shown that when failure occurs,the failed tooth is likely to be repairable thus making root treated teeth more durable.

The habit of chewing Qat is widely spread in Yemen. The adverse effects of
the chewing Qat habit on different human body systems, namely; CNS,
cardiovascular, digestive, genitourinary, and reproductive health systems
were broadly investigated. Furthermore, its effect on different oral tissues
including periodontal tissues, hard tissues of teeth, TMJ, muscles of
mastication and salivary glands were also comprehensively reported. Since,
this habit is recently highly prevalence among Yemeni Women,tTherefore,
this book covers the most oral manifestations that may be occurred among
Yemeni Woman due to chewing Qat.

Objectives: To study the stress distributions in maxillary central incisor restored with Ni-Cr custom-made, gold
custom-made, prefabricated titanium and prefabricated glass fibre dental posts subjected to oblique occlusal load at 100 N.
Materials and Methods: Four three dimensional finite element models of a maxillary central incisor restored with Ni-Cr
(Model I), gold custom-made (Model II), prefabricated titanium (Model III) and prefabricated glass fibre (Model IV) dental
posts were constructed and oblique loading of 100 N was applied. Stress analysing at the along the centre of the post and
post-surrounding structure interfaces were computed. Results: The result of this study indicates that the clinical
three-dimensional image provided information about the behaviour of teeth under function in all directions. The results
obtained from a finite element model on the restored system contain information about the stress distribution of each
component of the restoration. The maximum von Mises stress distribution at post center was recorded with Model I (38.6
MPa), followed by Model III (22.4 MPa) and Model II (20.8 MPa) respectively; whereas the minimum amount of stress was
noticed in Model IV (10.9 MPa). At post dentin interface, the highest von Mises stress distribution was noticed with Model I
(29.8 MPa), followed by Model III (18.9 MPa) and Model II (18.8 MPa) respectively; whereas the smallest amount of
stress was noticed in Model IV (10.16 MPa). Conclusions: Glass fibre posts generated the least amount of stress
concentration at middle and apical part of the posts compared to other dental posts.

Due to an increasing interest in esthetics and concerns about toxic and allergic reactions to certain alloys, zirconia was proposed as a new ceramic material in the later part of 20th century. It has become a popular alternative to alumina as biomaterial and is being used in dental applications for fabricating endodontic posts, crown and bridge restorations and implant abutments. It has also been applied for the fabrication of esthetic orthodontic brackets. This article presents a brief history, dental applications and new methods for fabrication of zirconia improving its mechanical properties. Additionally, the bonding between zirconia and resin cements as well as conventional cementation has been discussed. The methods of the improvement of the bonding strength have also been highlighted.

Calcium phosphate materials are similar to bone in composition and in having bioactive and osteoconductive properties. Calcium phosphate materials in different forms, as cements, composites, and coatings, are used in many medical and dental applications. This paper reviews the applications of these materials in dentistry. It presents a brief history, dental applications, and methods for improving their mechanical properties. Notable research is highlighted regarding (1) application of calcium phosphate into various fields in dentistry; (2) improving mechanical properties of calcium phosphate; (3) biomimetic process and functionally graded materials. This paper deals with most common types of the calcium phosphate materials such as hydroxyapatite and tricalcium phosphate which are currently used in dental and medical fields.

The emergence of Mineral Trioxide Aggregate (MTA) as endodontic repair filling material has generated a lot of interest due to its superior sealing ability and biocompatibility. Although MTA possesses superior sealing ability to traditional endodontic repair filling materials, such as calcium hydroxide, but it has poor handling characteristics. A novel endodontic repair filling materials with similar chemical composition, but improved handling characteristics, was recently developed. Recently, BioAggregate repair filling materials is claimed as biocompatible material and promotes cementogenesis and forms a hermetic seal inside the root canal. More recently, Biodentine and EndoSequence endodontic repair materials introduced to the market. Both materials have recommended for perforation repair, apical surgery, apical plug, and pulp capping. This article focused about physical properties of endodontic repair filling materials. - See more at: http://www.sciencedomain.org/abstract.php?iid=461&id=12&aid=3984#.U2X0_HZTV14

Alumina has received considerable attention and has been historically well-accepted as biomaterials for dental and medical applications. This article reviews the applications of this material in dentistry. It presents a brief history, dental applications and methods for improving the mechanical properties of alumina-based materials. It also offers perspectives on recent research aimed at the further development of alumina for clinical uses, at their evaluation and selection, and very importantly, their clinical performance. This article also stated about the Functionally Graded Materials (FGMs) which has been conceived as a new material design approach to improve performance compared to traditional homogeneous and uniform materials. This technique allows the production of a material with very different characteristics within the same material at various interfaces. The importance of the FGM concept in biological applications and functions was highlighted. Fundamentally, the combination of mechanical properties and biocompatibility are very important factors in application of any biomaterial to medical or dental fields. The characteristics of the surface govern the biocompatibility of the material, and the mechanical strength is determined by the average mechanical strength of the materials. However, the fabrication of FGMs is most often hindered by the variation of elastic, plastic, thermal, chemical, and kinetic properties within the composite. Across a material interface, these discontinuities in material properties lead to the formation of residual stresses. Despite these challenges, compositional gradient structures offer significant benefits. Notable research literature is highlighted regarding (1) applications of alumina in various fields in dentistry; (2) improvement of the mechanical properties of alumina by microstructural manipulation, FGM as well as composite formulations involving metallic, intermetallic elements and bioceramics.