Removable Prosthodontics

Abstract: This research was carried out on twenty patients of upper completely edentulous arch against mandibular bilateral distal extension ridges to study the effect of different torquing releasing clasps assemblies of mesially placed occlusal rest on alveolar bone height change of the abutment tooth. According to the type of the clasp assembly design used in this study the patients were classified into four groups. Where the mandibular distal extension removable partial denture frame work retained with RPI, RPL, RPA and, modified clasp assemblies design were constructed for group I, II, III and, IV respectively.After making an altered cast impression with selective pressure impression technique, jaw relation was registered and the dentures were processed with heat cure acrylic resin. Pre-apical x ray film of the abutment teeth was performed immediately, 6 months and 12 months of denture insertion. The results of this study revealed that all studied groups exhibited significant abutment alveolar bone resorption, along the follow up periods, after insertion of mandibular distal extension RPD. After sex months and 12 months follow up, abutment alveolar bone height change for mandibular distal extension RPD with RPI and modified clasp was ignificantly less than that of RPA clasp, on other hand comparing RPI, RPL and modified mandibular distal extension RPD wearer together was found insignificant in the abutment alveolar bone resorption the former and the latter exhibit an proximally equal amount of resorption. In conclusion, Modified and RPI clasps may be the clasp of choice because they exhibit less abutment alveolar bone resorption. RPL clasp is a substitute for the RPI clasp in distal extension cases

Abstract: The lack of a chemical bond between conventional denture base materials and framework elements represents a significant problem in removable prosthodontics. Poor chemical bonding of a denture base resin to cast metal frameworks often introduces adhesive failure and increases microleakage. Purpose. The purpose of this study
was to examine the shear bond strength of a denture base acrylic resin to commercially pure titanium alloy (CP Ti) and a cobalt-chromium alloy (Co-Cr) using a hybrid bonding system. Material And Methods. Square plates (of
different designs) were cast from the 2 alloys. The plates were grit-blasted with 50 μm of alumina and treated with
the Rocatec™ bonding system. A denture base heat-cured acrylic resin was then applied to the plates. Specimens without bonding were also prepared as controls. Both alloys were configured as frameworks with different retentive designs: flat plate, lattice retention, mesh retention and bead retention. Shear bond strength values were determined at a crosshead speed of 0.5 mm/min. Results. For CP Ti plates, shear bond strength was the highest for acrylic resin adhered with Rocatec™ to flat plates, followed by the bead, lattice and mesh designs. The shear bond strength for
different retentive Co-Cr frameworks, with or without Rocatec™, was the highest for bead retention, followed by mesh, flat plate and lattice. There was a statistically significant difference (P<.05) in bond strength between the 2 alloys for both flat plate and lattice retentive frameworks bonded with Rocatec™ to acrylic resin. Conclusion. The application of the Rocatec™ bonding system significantly improved the shear bond strength of denture base resin using both cast (CP Ti) and Co-Cr alloys.

Purpose: The objective of this study was radiographic assessment of the premolar teeth abutments alveolar
bone resorption in mandibular Kennedy Class I removable partial denture (RPD) utilizing the broad stress
distribution philosophy, either designed with multiple circlet clasp or compound Aker clasp.
Materials and Methods: Twelve patients were enrolled for this study with upper completely edentulous
arch against mandibular Kennedy Class I ridges posterior to the second premolar. The patients were divided
into two groups according to the type of the clasp assembly design used, where the mandibular Kennedy
Class I RPD was designed with multiple circlet clasp and compound Aker clasp assemblies for Groups I and
II, respectively. The abutment alveolar bone resorption was evaluated radiographically after 1st 6, 2nd 6, and
12 months of mandibular Kennedy Class I RPD insertion.
Results: Second premolar abutment interdental alveolar bone resorption was significantly increased as
compared to first premolar abutment along the interval periods of the study for Group I. The reverse was
observed for Group II. Along the interval periods of the study, the alveolar bone resorption at the first
premolar abutment of Group II was significantly increased compared to that of Group I while the reverse
was observed when comparing the second premolar of Group I with that of Group II.
Conclusion: Compound Aker clasp is better than the multiple circlet clasp assembly as it reduces abutment
alveolar bone resorption regards broad stress distribution philosophy is considered for distal extension cases.

Aims: Modifying heat cured denture base acrylic resin with new additives and the use of FT-IR spectroscopy to investigate and characterize the produced materials. Methods: Thermally activated Zinc Oxide (ZnO) and Zinc Diacrylate (ZDA) powders were synthesized. Heat cured acrylic resin denture base material had modified by adding inactivated ZnO powder with and without acrylic acid (AA), thermally activated ZnO powder, AA liquid, or ZDA powder in 5%by weight. FT-IR Spectrophotometer was used to assess the chemical conversion of the cured samples. Results: Both ordinary and thermally activated ZnO filler appear to have no chemical bonding with the cured resin structure. FT-IR analysis proved the successful synthesis of ZDA and its polymerization with MMA to form copolymer poly (methyl methacrylate-co-zinc acrylate) copolymer. The addition of AA resulted in a copolymer poly (methymathacrylate-co-acrylic acid) but failed to conjugate the ZnO to the resin matrix. Conclusion: The addition of an inactivated ZnO or a thermally activated ZnO powders appear to be just incorporation of a filler without changing the PMMA structure, while the addition of AA or ZDA result in copolymers with PMMA. The method in which the ZDA was added to the heat cured acrylic resin could be considered as a new way of chemical bonding or engagement of Zn ions to acrylic structure to produce a new enhanced denture bases.

The story of prosthodontics is quite unique and that status has been maintained for quite a long time. In dental history, Prosthodontics appeared second to oral surgery has a treatment modalities. 1918 saw the Professional emergence of this specialty when few dentists who were interested in the field of prosthetic dentistry assembled at Chicago and sought to learn the techniques and concepts which were popular then. Prosthodontics has pioneered the field of reconstruction compared to all other medical specialties. Over time, Rehabilitation techniques have changed considerably. Prosthodontics has a branch possesses a unique set of characteristics that have shaped much of dentistry. This article explores the relevance of prosthodontics through a careful journey from the profound past to the exciting futuristic frontiers

ABSTRACT
Background: metal bar splinted implants provide overdenture with good support and retentive quality. Besides, it is known to preserve marginal bone of corresponding dental implants. Reinforced composite bars offer less cost, time preserve, easy to construct and repair alternative.
Objective: Till now there is no clear research data comparing reinforced composite bar modality to conventional metal splinting in terms of implant marginal bone height changes.
Material and methods: twelve edentulous male patients were selected and assigned into two equal groups using balanced randomization. All patients received lower implant supported overdenture with either cast bar (group I) or infibra ribbon bar (group II). Radiographic evaluations were performed at the time of overdenture insertion then at 6, 12 and 18 months after overdenture insertion.
Results: The results were significant for all periods of study. (P=.006*, .039* and .000* for each period respectively) for group I compared to group II.
Conclusion: Within the limitation of this short clinical study it could be concluded that; mandibular two implant retained overdenture splinted with infibra ribbon bar reduces stress concentration in implant marginal bone compared to cast bar. As a consequence, bone level is better preserved, and implant survival is expected to be improved if all other clinical conditions were constant.

Abstract: In the clinical practice due to various factors we face with patients who have very few teeth left without prospective in the lower jaw. Due to reduced load capacity, they are loosening and soon are completely lost. Prosthodontics is a real magic that has great potential for a unique implant - prosthetic rehabilitation. The goal is to preserve the alveolar ridge and slow down its resorption. In the modern world trends, the conventional dentures are replaced by therapeutic methods and superstructures as modern prosthetic therapy for this problem. As an example of these restorations that are practically applied, we present multi unit system dentures with a single hybrid prosthesis. It is a conditionally mobile suprastructure fixed with screws on 4 implants. The combination of oral surgery with the placement of 4 implants and the hybrid prosthetic superstructure over them is known by a popular short name "all on four". There are many discussions and writings about this multidisciplinary concept in the professional world. Over the 4 implants, immediately is placed suprastructure with a maximum number of 12 teeth. The prosthetic construction circularly covers the entire toothless ridge. Bilaterally, the chewing center is mesialized in the area of the second premolar and first molar. The applied technique is a practical modern multi - combination for immediate rehabilitation and rapid restoration of the chewing function. The data obtained from the subjects with intact dentition indicate a difference in the development of the bite force in the chewing center. Significantly higher values were observed in subjects with a masseteric type of mastication with significant differences in the bite force in the molar region. Functional efficiency was significantly lower in subjects with total tooth loss with classic total dentures. This result is due to the gingival distribution of the load only to the masticatory gingiva and the alveolar ridge. The value of the bite strength in subjects with partial dentures with Kennedy I class of toothlessness according to the registration the performance in the chewing center is higher. There is a combination in the transmission of the pressure, some gingivally, some accept the remaining teeth. The functional efficiency is higher in hybrid denture subjects. The hybrid denture externally resembles a classical one, but unlike it, it is screwed in its base, fixed with nuts on the implants. It is retained exclusively on a minimum of 4 implants placed in the alveolar ridge, which later integrate with the bone during the chewing function. There is minimal mild tangential contact between it and the soft tissues of the alveolar ridge. It has the practical ability to be removed - unscrews for various needs such as perimplantitis treatment, additional plaque hygiene or any other adjustments and polishes. It is often used as immediate prosthetic therapy in patients who are in the transitional phase from partial - subtotal to total toothlessness. Namely, it is preventively applied to slow down the further atrophy of the supporting tissues and the resorption of the alveolar ridge.
Keywords: implant, denture, mastication, suprastructure.

Abstract
Background and Purpose:
Implant-retained mandibular overdentures have recently become a popular treatment alternative for edentulous patients desiring increased retention of complete dentures. Smoker patient’s are routinely excluded from this benefit, therefore the goal of this study was to evaluate marginal bone changes radiographically around implants placed in mandibular canine region for implant retained overdenture patients (smokers and non smokers) 18 months after loading.
Methods:
Forty patients received two implants in the mandibular canine region. 13 were nonsmokers and 27 were smokers and subdivided according to smoking ratio to smokers≤ 10cigaretts and smokers >10cigaretts. After three month submerging period healing abutments were connected. Ball abutments were mounted 4–6 weeks afterwards and the complete overdenture was constructed and delivered. Marginal bone level was assessed radio-graphically at time of loading, 6 month, 12 month and 18 month after overdenture insertion.
Results:
Two patients had unilateral implants were judged as failures at the second surgical appointment. Three patients with clinically successful implants were blindly selected for exclusion from the grouping for balancing the statistical analysis. After the drop outs, seventy two implants were evaluated. A statistically significant vertical bone loss was seen in the three groups after the first 6 months (average 0.733mm ) and after the 2nd 6 months (average .618mm), and after the 3rd 6 months (average .05 mm), with statistically significant differences among the three groups for all periods of study. Likewise, A statistically significant horizontal bone loss was seen in the three groups after the first 6 months (average 0.636mm) and after the 2nd 6 months (average .596mm), and after the 3rd 6 months (average .136 mm), with statistically significant differences among the three groups for all periods of study.
Conclusions:
With the limitation of this study it could be assured that smoking is a biological risk factor for osseointegration and the patient should be informed about its possible drawbacks. Also the effect of this bad habit is directly proportional to its rate, so the rate of smoking should be of diagnostic value during treatment planning stage.

Purpose: The loss of natural teeth leads to bone resorption and muscular hypotonicity, which may affect the structures involved in mastication.Atrophy of supporting tissues, poor adaptation, reduced masticatory efficiency, and psychosocial embarrassment are major complaints of edentulous patient wearing old/faulty denture. The need for this study is to examine the effect of old/faulty dentures and a new denture on the masticatory muscle efficiency with the help of electromyography.
Materials and methods: 15 edentulous patients wearing complete denture prosthesis selected as a subject for the investigation. Surface electrodes from electromyographic unit were placed in the region of right and left anterior Temporalis muscle and Masseter muscle, and the patients will be asked to perform maximum voluntary contraction. The muscle activity analyzed twice for each patient: (1) with the old/faulty dentures and (2) 5 month following insertion of new denture.
Results: The electrical activity during maximum voluntary contraction exhibited statistically significant improved muscle efficiency with new denture when compared to those with old dentures in place for 5 months.
Conclusion: New dentures or improvements in occlusion and vertical dimension produce a positive benefit to the patient by reducing the muscle effort during chewing without affecting masticatory performances. The reduction in muscle effort is likely to cause less tissue and in the end may minimize residual ridge resorption and new complete denture allows for neuromuscular reprogramming, which contributes to muscular balance of the masticatory system.

Purpose: The aim of this study was to evaluate the effect of cantilevered bar length on strain produced around two implants supporting a mandibular overdenture.
Materials and methods: Two root-form implants were placed bilaterally in the canine region of an edentulous acrylic resin mandibular cast and connected with a resilient bar/clip attachment. Four linear strain gauges were bonded to the acrylic resin at the mesial and distal surfaces of each implant. Each gauge was wired separately into a 1/4 Wheatstone bridge of a multichannel digital bridge amplifier. Strains were measured without cantilevered bar extensions (control group) and with the following lengths of cantilevered bars: 11 mm (group 1), 9 mm (group 2), and 7 mm (group 3). For each cantilevered bar length, strains were measured using clips placed on the cantilevers and attached to the overdenture (bar-clip contact) and without clips (bar-acrylic resin contact). Strain measurements were performed under central and unilateral loading using a loading device.
Results: The bar with cantilevers (either with or without clips) demonstrated a significant increase in strain compared to the bar without cantilevers. The 11-mm cantilever length generated the highest peri-implant strain values, while the 7-mm length recorded the lowest. For all cantilevered bar lengths, the strains significantly decreased with bar-clip contact compared to bar-acrylic resin contact. Under central loading, distal and mesial peri-implant strains were the highest and the lowest values, respectively, while under unilateral loading, the highest strain was recorded at distal sites of the loading side and the lowest was recorded at distal sites of the nonloading side. A positive correlation was found between the recorded strain and the cantilevered bar length.
Conclusion: The 7-mm cantilevered bar with clips placed on the cantilevers was recommended when two implants were used to support mandibular overdentures, as it demonstrated the lowest magnitude of strains with no significant differences between peri-implant sites.

The dimensional accuracy of four duplicating materials, including one brand of agar reversible hydrocolloid, one brand of polyether rubber, and two brands of polyvinyl siloxane (addition silicone) rubber was studied. A standard stainless steel specimen of 76 x 76 x 9.5 mm was made. Vertical and horizontal grooves were made on the specimen as reference marks. The horizontal grooves were in different depths and widths. The duplicating materials were prepared and poured over the standard die to make a negative likeness. These negatives were poured with the same investment material. Twelve investment specimens were measured for accuracy and detail reproduction with a Talysurf finish analyzer. Results of this study indicated that polyvinyl siloxane and polyether rubbers are superior in accuracy compared to the agar reversible hydrocolloid. No significant differences in detail reproduction were noted in any of the duplicating materials tested.

ABSTRACT
The aim of this 1-year study was to evaluate and compare crestal bone loss and clinical outcomes of immediate and delayed loaded implants supporting mandibular overdentures with Locator attachments. In a randomised controlled clinical trial, 36 completely edentulous patients (mean age 59•6 years) who desired to improve the stability of their mandibular dentures were randomly assigned into two groups. Each patient received two implants in the canine area of the mandible after a minimal flap reflection. Implants were loaded by mandibular overdentures either 3 months (delayed loading group, G1) or the same day (immediate loading group, G2) after implant placement. Locator attachments were used to retain all overdentures to the implants. Peri-implant vertical (VBL) and horizontal (HBLO) bone losses and clinical parameters [plaque scores (PI), gingival scores (GI), probing depths (PD) and implant stability (ISQ)] were assessed at time of overdenture insertion (T0), 6 months (T6) and 12 months (T12) after overdenture insertion. After 12 months of overdenture insertion, two implants (5•5%) failed in G2. Vertical bone loss was significantly higher in G2 compared with G1, while HBLO demonstrated insignificant differences between groups. All clinical parameters (PI, GI, PD and ISQ) did not differ significantly between groups. Vertical bone loss was significantly correlated with PD and HBLO. Immediately loaded two implants supporting a Locator-retained mandibular overdenture are associated with more vertical bone resorption when compared to delayed loaded implants after 1 year. Clinical outcomes do not differ significantly between loading protocols.

ABSTRACT
Purpose: This work was aimed to evaluate and compare the effect of early progressive and delayed loading of two implants retained mandibular overdentures regarding marginal bone changes and periotest values of implants supporting mandibular overdenture.

Material and Methods: 24 completely edentulous male patients were selected from department of prosthodontics, Faculty of dentistry, Mansoura University. All systemic and radiographic examinations needed for implant planning and placement were performed. All patients received two implants at the mandibular canine regions. Directly after implant placement, the patients were divided equally into two equal groups as follows; Group I: after 3 months submerging period, implants were exposed and overdentures were attached to ball abutments via direct pick-up technique of female socket attachments (delayed loading), Group II: after 4 weeks of implant installation the mandibular overdenture was attached to implant ball abutment via resilient liner and replaced after another 4 weeks by direct pick-up technique of female socket attachments (early progressive Loading). Follow-up records were done at 6, 12 and 18 months intervals after implant loading with overdentures. Study parameters were radiographic evaluation of marginal bone height changes and implant mobility using periotest.

Results: All implants were successful with respect to mobility test with no significant difference between both groups. Generally the mean marginal bone loss and heights changes, both vertically and horizontally, were comparable to the worldwide accepted range. In comparison of both groups, the means of vertical bone loss were higher for group I with no statistical significance. While the means of marginal bone heights were significantly reduced in group I after 6 months and 18 months of study. The means of horizontal bone level were significantly reduced in group I.

Conclusion: within the limitation of this short prospective clinical study it could be suggested that there is a promising radiographic finding of implant mean marginal bone status of patients treated with two implants retained mandibular overdentures loaded according to early progressive protocol. Results are comparable and even better to delayed loading protocol. A longitudinal study is recommended to compare both treatment regimes.

Background: The choice of the size of artificial teeth takes an important place in the removable
prosthodontic treatment. However, the standards or proportions commonly used as a guide have
been developed mainly on Caucasian populations.
Objectives: to investigate the relationship between intercanthal distance and the anterior maxillary
teeth size in Sudanese population.
Methods: This is a descriptive cross sectional study conducted in 114 subjects, (45 males - 69
females), from Khartoum and Juba Universities. The age range was from 18-46 years. The
intercanthal distance (I.C.D) was the measurement taken between the median angles of the
palpabral fissure. Maxillary intercanine distance was obtained by measuring a line from the tip of
the canine on one side, to the canine on the other side. An electronic digital caliper (Narex –
Czechoslovakia) was used for all measurements. Data were analyzed using Person chi–square test.
Results: a significant correlation is found between intercanthal distance and maxillary intercanine
distance in all subjects (P-value 0.015), and in females who had a (P-value of 0.006). Maxillary
intercanine distance may be estimated by dividing I.C.D by factor 0.9.
Conclusion: These results could be used as a helpful guide for selection of anterior teeth width in
the Sudanese population.

Objective: The aim was to compare two measurements of lower facial height (base of chin-subnasale and base of chin-tip of the nose) as related to different anthropometric measurements in dentate and completely edentulous subjects. Method and Materials: This cross-sectional study was conducted on 132 male subjects (group 1 [G1], 120 dentate subjects ; and group 2 [G2], 12 completely edentulous subjects). Base of chin-subnasale measurement (FM1), base of chin-tip of the nose measurement (FM2), Willis' measurement (FM3), glabella-subnasale measurement (FM4), length of the index finger measurement (AM1), and tip of thumb-tip of index finger measurement (AM2) of subjects of G1 and G2 were measured by using a modified caliper while the subjects in G1 closed in centric occlusion, and the subjects of G2 were asked to close the maxillary and mandibular complete dentures in centric relation. Statistical analysis was carried out by using paired t test, Pearson's correlation (PC), and regression analysis. Results: There were no significant differences between G1FM1 and G1FM3, G1FM1 and G1FM4, G1FM1 and G1AM2 (P > .05), and PCs were R = 0.74, R = −0.35, and R = −0.32 respectively. However, there were significant differences between G1FM2 and G1FM3, G1FM2 and G1FM4, G1FM2 and G1AM2 (P ≤ .05), and there were significant differences between G2FM2 and different measurements of G2 (P ≤ .05). Conclusion: The use of the linear equation to predict the possible base of chin-subnasale measurement through the Willis' measurement was recommended and could be used as a guide during restoration of the vertical dimension of occlu-sion when it has been lost.

Objective: To measure the effect of different contact time between the alginate impression and type III dental stone on cast model properties in the terms of dimension stability, hardness and surface details reproduction. Material and methods: Sixty-seven cast models were obtained from stainless steel cylinder using alginate impression material and type III dental stone. Thirty-seven cast models were separated after one hour (control group) and 30 cast models were separated from impressions after 9 hours. The samples were evaluated under light microscope for surface details, measured by digital caliper for dimension stability and hardness was tested by making indentation on the cast then measuring the depth using digital caliper. Results: The dimension stability of cast models was not affected by increasing contact time between type III dental stone and alginate impression while surface details decreased. In the meanwhile, hardness was improved with increasing contact time. Conclusion: According to the results of this study, pouring of impression up to 9 hours can negatively affect the cast model properties in the term of details richness.

Dental transposition is a form of ectopic eruption with change in position of normal adjacent teeth. Its prevalence is very low in general population and could be frequently missed on oral examination. We present a rare case of dental transposition between left mandibular canine and first premolar in a 22 year old Libyan male patient.

ABSTRACT
Purpose: This invitro study investigated and compared the effect of different retainer design on load transmission to abutments in asymmetrical distal extension removable partial denture (RPD) cases to verify the null hypothesis that; the use of different clasps in asymmetrical design has no effect on abutment teeth.
Materials and methods: A simulated Mandibular arch model with six-anterior teeth, two-first premolars and a left-second-premolar was fabricated. Six RPDs were constructed as follows; three RPDs designed with RPI clasp (mesial occlusal rest, proximal plate and I-bar retainer arm) on both sides (Group I) and the other three RPDs designed with RPI clasp on the longer side and a distal half T clasp (mesial occlusal rest, proximal plate and half T-bar retainer arm) on the shorter side. Linea strain gauges were bonded buccal, lingual and distal to the abutment teeth. Unilateral and central loading was applied and micro strains readings were collected, tabulated, and statistically analyzed
Results: The use of a distal half T clasp retainer decreases the micro strains on abutment of the shorter saddle in asymmetrical distal extension partial edentulous model. The use of RPI clasp in the shorter saddle increase strain of abutments (especially distal) upon central loading. Also thi increase strain of abutments (especially lingual) upon unilateral loading of longer RPD saddle.
Conclusion: The RPI clasp assembly was found to increase micro-strain versus the distal half T clasp under unilateral load and central loading conditions of asymmetrical bilateral distal extension RDPs.

Purpose:  This  study  was  aimed  to  evaluate  the  retentive  forces  of  acetal  resin  clasps  and  Cobalt-Chrome  (Co-Cr)  clasps  during
attachment/detachment cycles on abutment teeth with two different undercuts and at different intervals.
Materials and Method: Twenty models were constructed by placing either an upper 1 st  premolar or upper 1 st  molar inside an acrylic
rectangular block. Models were divided according to the abutment teeth into two groups (GI for 1 st  premolars group and GII for 1 st 
molars group), 10 each. Each group was divided into two subgroups according the framework material, SGA for acetal resin clasp
and SGC for Co-Cr clasp. Each testing models and its framework were mounted inside universal testing machine (Lloyd instruments
Ltd, England). Retention of each clasp at pre-test (0 cycle) and after cycling intervals (730 cycles, 1460 cycles, 2190 cycles, and 2920
cycles) were measured by applying withdrawal force to it using universal testing machine. The data of the retentive force magnitudes
at different intervals were collected and tabulated. The data were subjected to statistical analysis using 3-way-ANOVA test, student’s t
and paired t tests.
Results: After 730 cycles, 1460 cycles, 2190 cycles, and 2920 cycles there were non significant difference between SGIA and SGIC, and
SGIA and SGIIA at 95% confidence level (P > 0.05), however there were statistical significant difference between SGIIA and SGIIC, and
SGIC and SGIIC at 95% confidence level (P ≤ 0.05).
Conclusion: Acetal resin clasps (1.0 mm in cross section diameter) engage 0.25 mm provide sufficient retention nearly similar that of
Co-Cr clasps, The acetal resin clasps should be thicker more than 1.0 mm (in cross-sectional diameter) when engage a deeper undercut
(0.50 mm) to gain the stiffness of the cast Co-Cr clasps 1 mm in cross sectional diameter and to obtain clinically acceptable retention.

Objective: The aim of this study was to investigate the effect of adding different concentrations nanoparticles of silver on color stability of acrylic resin denture base material. Materials and Methods: A total of 20 discs were used in this study, divided into 4 groups (5 each) relative to percentage of nanoparticles of silver (NAg) adding (1%, 2%and 5%) and one group without additives (control group). A double beam ultraviolet visible spectrophotometer was used to obtain diffuse reflectance data at every 5nm between 400-700nm. An integrating sphere attachment was used for the measurement. The results were recorded using a computer color matching system (CCM) and tabulated for the statistical analysis of the data. Data analysis was performed by one way ANOVA. Post Hoc test (Scheffe) was used for pair-wise comparison between the means when ANOVA test is significant. Results: Heat-cured acrylic resin with 5% nanoparticles of silver (group D) showed significantly highest mean color differences (ΔE) followed by heat-cured acrylic resin with 2% nanoparticles of silver (group C) then heat-cured acrylic resin with 1% nanoparticles of silver (group B). Heat-cured acrylic resin without additives (control group) showed significantly lowest mean color differences (ΔE). The results of color differences (ΔE) showed significant difference (P<0.05) between groups (B, C and D) and group A. Conclusion: All Groups of heat-cured acrylic resin with addition of nanoparticles of silver (NAg) showed color differences (ΔE) values higher than that control group. From a clinical point of view, the silver nanoparticles incorporation within the acrylic denture base material can be improve its color stability. (Jul 2013)

Purpose: To assess the 3-year survival rates and the incidences of biological and technical complications of all-ceramic and metal-ceramic tooth-supported single crowns. Material and methods: An online research of literature on Pubmed was conducted independently by 3 reviewers to identify the clinical studies performed from 2000 up to 2017 and completed by a manual research. Keywords, inclusion and exclusion criteria were well-defined. Results: The research revealed 501 titles and led to a final analysis of 31 full text articles. Only 6 studies met the inclusion criteria and reported on 215 metal-ceramic and 501 all-ceramic TSSCs. The meta-analysis of the included studies indicated an estimated survival rate of metal-ceramic TSSCs of 90.14% (95% CI: 89.72%-91.35%) after 3 years. This was a little bit higher than the estimated 3-year survival rate of Lithium-disilicate (89.54%; 95% CI: 87.18%-91.89%). However the 3-year survival rate, of Zirconia TSSCs was statistically much higher (...

To assess the 3-year survival rates and the incidences of biological and technical complications of all-ceramic and metal-ceramic tooth-supported single crowns. Material and Methods: An online research of literature on Pub med was conducted independently by 3 reviewers to identify the clinical studies performed from 2000 up to 2017 and completed by a manual research. Keywords, inclusion and exclusion criteria were well-defined. Results: The research revealed 501 titles and led to a final analysis of 31 full text articles. Only 6 studies met the inclusion criteria and reported on 215 metal-ceramic and 501 all-ceramic TSSCs. The meta-analysis of the included studies indicated an estimated survival rate of metal-ceramic TSSCs of 90.14% (95% CI: 89.72%-91.35%) after 3 years. This was a little bit higher than the estimated 3-year survival rate of Lithium-disilicate (89.54%; 95% CI: 87.18%-91.89%). However the 3-year survival rate, of Zirconia TSSCs was statistically much higher (92.01%; 95% CI: 89.58-94.43%). When the outcomes in anterior and posterior regions were compared, Zirconia and Lithium-disilicate TSSCs exhibited survival rates of 91.64% and 91.12% respectively, in the posterior region, where metal-ceramic TSSCs exhibited only 90.14% as a 3-year survival rate. As for the anterior region, we could only compare the TSSCs made out of Lithium-disilicate and Zirconia as the metalceramic ones were all laid on the posterior regions. Zirconia performed the highest 3-year survival rate in the anterior region (93.54%; 95% CI: 91.08-96%) whereas Lithium-disilicate showed only 87.5%. This was due to the low level of the mechanical properties of such material, which clinically indicated by major chipping and tooth fracture. Conclusion: Survival rates of metal-ceramic crowns were nearly similar to those reported for most types of all-ceramic TSSCs in the posterior region. Weaker Lithium-disilicate-based ceramics should be limited to application in the anterior region, even if they expressed a higher survival rate in the anterior regions. Zirconia-based TSSCs should not be considered as a primary option due to their high incidence of technical problems.

BACKGROUND: The term decreased occlusal vertical dimension refers to the reduced distance between two anatomical points while the teeth are in a state of occlusion. The development of this situation is about some parafunctional activities of the masticatory system.

Obturators are the most common treatment modality compared to surgical reconstruction for Maxillectomy in oral cancer patients. The obturators frequently become bulky and need to be hollowed out properly in the defect area to decrease weight and make them comfortable for the patient. This case report describes the technique of using a hollow bulb obturator on an adult patient who had undergone a maxillectomy. An obturator was fabricated with the use of a self-cured acrylic resin shim filled with wax in the defect area during the packing procedure of the prosthesis, and the wax was eliminated after curing. It is a single step process for the closed-hollow bulb obturator fabrication as a single unit, with uniform wall thickness around the hollow space, ensuring the least possible weight of the hollow obturator. This technique attains the probable internal facet of the hollow space with a uniform wall thickness of the prosthesis.

Comparing the effect of two different types of attachments on mandibular overdenture abutments crestal bone height were studied and compared in twenty completely edentulous patients retaining their two remaining mandibular canines. Patients were randomly divided into two groups. Group I received magnetic attachment mandibular overdenture. Group II received ball and socket attachments mandibular overdenture, both groups, the mandibular overdentures opposed by conventional maxillary complete dentures. The results of this study showed no significant effect on bone height in both groups. Based on the results of the present study, it may be concluded that the use of magnet attachments may be valuable to solve a situation pushing the dentist to override the benefits of its use to prevent the dangerous effects of its horizontal stresses that may be transmitted to the overdenture abutments.

Purpose: To assess the effect of addition of different concentrations of nanodia-monds (NDs) on flexural strength, impact strength, and surface roughness of heat-polymerized acrylic resin. Materials and Methods: 120 specimens were fabricated from heat-polymerized acrylic resin. They were divided into a control group of pure polymethylmethacrylate (PMMA; Major.Base.20) and three tested groups (PMMA-ND) with 0.5%wt, 1%wt, and 1.5%wt of added ND to PMMA. Flexural strength was determined using the three-point bending test. Impact strength was recorded by using a Charpy type impact test. Surface roughness test was performed using a Contour GT machine. One-way ANOVA and Tukey's post-hoc analysis (p ࣘ 0.05) were used for statistical analysis. Results: Acrylic resin reinforced with 0.5% ND displayed significantly higher flexural strength than the unreinforced heat-polymerized specimens, acrylic resin reinforced with 1% ND and the 1.5% ND (p < 0.0001). The impact strength of unreinforced heat-polymerized specimens was significantly higher than all nano-composite materials (p < 0.0001) with no significant difference between 1% ND and the 1.5% ND (p > 0.05). The addition of 0.5% ND and 1% ND significantly decreased the surface roughness in comparison to both control and the 1.5% ND groups (p < 0.0001) while no significant differences between 0.5% ND and 1% ND (p > 0.05) were reported. Nano-composite material (0.5% ND) showed significantly lower surface roughness when compared to other specimens. Conclusions: The addition of NDs to acrylic denture base improved the flexural strength and surface roughness at low concentrations (0.5%), while the impact strength was decreased with ND addition. Computer-aided design/computer-aided manufacturing (CAD/ CAM) technology is now used in the fabrication of complete dentures. The dentures milled from blocks of pre-polymerized acrylic resin have shown improved properties. 1 Despite these advances, most dentures wordwide are still made with conventional heat-polymerized polymethylmethacrylate (PMMA). Although it presents many advantages, PMMA has poor mechanical properties such as low flexural and impact strength. 2,3 PMMA is a clear polymer liable to be modified to improve its physical properties. Several attempts have been made to upgrade mechanical features of acrylic resin by providing maximum bulk in the heavily stressed areas through cross-linking, copolymerization, and reinforcement. 4 Materials such as glass fibers, metal wires, and oxides (e.g., zirconium, aluminum, titanium) have been proposed to reinforce acrylic resin. 5-7 Addition of metal fillers (powdered silver, copper, and aluminum) to acrylic resin have been proposed and resulted in an increase in compressive and impact strengths with an improved fracture resistance of the resin. 8 Nanoparticles were also used as fillers in dental polymeric materials to upgrade some of the mechanical properties of the nanocomposites. 6-8 Similar to nanocomposites, nanodiamond powders' (NDs) unique properties of hardness and thermal conductivity allow them a wide range of applications. 9,10 ND particles are considered an effective reinforcing material to PMMA because of their strength, fine dispersion within the acrylic matrix, surface properties, and biocompatibility. 11 As the mechanical properties of the polymer-matrix composites depend on the efficient interaction between the polymer matrix and the filler material, the as-received ND has been

Purpose: The purpose of this in vitro study was to measure the loss of retention and wear of two clasp types (E-circlet, back action) against three abutment materials (enamel, composite, CAD/CAM ceramic) after 16,000 simulated cycles of attachment-detachment. Materials and Methods: Forty-eight models were constructed by placing either an upper first premolar or a metal die inside a metal rectangular block. Models were divided according to the abutment teeth into three groups. Group E consisted of 16 un-restored human premolars with sound enamel. Group R had 16 premolars recontoured buccally using composite resin. Group C had 16 metal dies (duplicated from a human premolar) covered by CAD/CAM all-ceramic crowns. On the models, E-circlet (E) and back-action (B) clasps were constructed to engage the model's teeth. Withdrawal and insertion cycling of clasps was carried out for 16,000 cycles by using a chewing simulator. The retention force of each clasp was measured after cycling. An acrylic replica was made for each abutment retention surface before and after cycling. Each replica was examined by SEM, and the wear areas were measured. The data were analyzed statistically using one-way ANOVA, two-way ANOVA, and Mann-Whitney tests. Results: There was no significant retention loss after 16,000 cycles (p ≥ 0.05) of both clasps (E, B) on the three abutment materials (E, R, C). The mean of wear areas in mm 2 were 1.83 ± 0.36, 0.85 ± 0.66, 2.37 ± 1.88, 1.7 ± 1.11, 0.6 ± 0.2, and 0.06 ± 0 for EE, BE, ER, BR, EC, and BC, respectively. There were significant differences among the wear areas of the abutment surface of the six subgroups (p ≤ 0.05). Conclusion: The composite resin contoured surfaces showed more wear than the enamel and ceramic surfaces. E-clasps caused more wear on the abutment materials than back-action clasps.

Purpose:  This  study  was  aimed  to  evaluate  the  fatigue  resistance  (amount  of  clasp  deformation)  of  acetal  resin  clasps
and cobalt–chromium (Co–Cr) clasps after attachment/detachment cycles on abutment teeth with two different undercuts.
Materials and Methods: Twenty models were constructed by placing either an upper first premolar or upper first molar inside
an acrylic rectangular block. Models were divided according to the abutment teeth into two groups (Group I for first premolar
group and Group II for first molar group), 10 each. Each group was divided into two subgroups according to the framework
material, SGA for acetal resin clasp and SGC for Co–Cr clasp. Each testing models and its framework were mounted inside
universal testing machine (Lloyd Instruments Ltd., England). Cycling was carried out for each specimen until 2920 cycles.
The data of the amount of clasp deformation after cycling were collected and tabulated. The data were subjected to statistical
analysis using student’s t and paired t-tests. Results: After 2920 cycles, the mean values and standard deviations of the clasp
deformation for SGIC, SGIA, SGIIC, and SGIIA were 0.0532 ± 0.006, 0.007 ± 0.003, 0.04323 ± 0.0048, and 0.0275 ± 0.004 mm,
respectively. Conclusions: Co–Cr clasps had significant clasp deformation more than acetal resin clasps. Increase the thickness
of cross-section of the acetal resin clasp more than 1 mm was recommended in case of engaging undercut more than 0.25 mm.

The immediate denture is a dental prosthesis constructed to replace the lost dentition, associated structures of the maxillae and mandible and inserted immediately following removal of the remaining teeth. The purpose of the present clinical report is to describe the use of a sectional impression tray technique that can prevent extraction of supporting teeth of patient’s extensive fixed prosthesis, where the teeth were hopeless and fabricating an interim immediate complete denture was a treatment option to prevent patient’s distress, anxiety and embarrassment. The present procedure was used to replicate the vertical dimension, phonetic and aesthetic of the existing fixed prostheses as part of an immediate denture and a final complete denture.

Objective: The objective was to investigate the effect of silver nanoparticles (AgNPs) incorporation on viscoelastic
properties of acrylic resin denture base material. Materials and Methods: A total of 20 specimens (60 × 10 × 2 mm)
of heat cured acrylic resin were constructed and divided into four groups (five for each), according to the concentration
of AgNPs (1%, 2%, and 5% vol.) which incorporated into the liquid of acrylic resin material and one group without
additives (control group). The dynamic viscoelastic test for the test specimens was performed using the computerized
material testing system. The resulting deflection curves were analyzed by material testing software NEXYGEN MT.
Results: The 5% nanoparticles of silver (NAg) had significantly highest mean storage modulus E’ and loss tangent
Tan δ values followed by 2% NAg (P < 0.05). For 1% nanosilver incorporation (group B), there were no statistically
significant differences in storage modulus E’, lost modulus E” or loss tangent Tan δ with other groups (P > 0.05).
Conclusion: The AgNPs incorporation within the acrylic denture base material can improve its viscoelastic properties.
Key words: Acrylic resin denture, nanoparticles, viscoelastic

Objective.To investigate the influence of reproduction of different thickness and palatal rugaematerials on complete dentures speech
usingComputerized Speech Lab (CSL) (spectrogram).Materials and Methods.Three completely edentulousmale patients (aged 50–
60 years) were selected for reading a paragraph. Twelve upper dentures were constructed, four for each patient. Thepatients’ speech
groups were divided into five groups, Group I: patients without dentures; Group II: patients rehabilitated with conventional acrylic
dentures; Group III: patients with conventional acrylic dentures with rugae reproduction; Group IV: patients with dentures with
metallic framework of minimal thickness and direct ragged metallic palatal surface at rugae area; Group V: patients with dentures
with palatal rugae constructed from resilient acrylic resin material with thickness less than conventional denture. Speech samples
were recorded after insertion of each denture for groups using Computerized Speech Lab (CSL) (spectrogram).The sounds selected
were lingopalatal /s/z/sh/t/d/ and /l/. Results. Group III produced highmean significant difference with /sh/t/ sound. For Group IV,
the difference was noticed with /s/z/sh/t/ and /d/ sounds, while for Group V the difference was shown with /z/l/ sound (𝑃 < 0.05).
Conclusion. It is recommended to reproduce the rugae area in complete denture because the phonetic quality of complete denture
with rugae is superior to the conventional denture.

Objectives: To evaluate the retention and wear behavior for different designs of precision attachments. Materials and Methods: Fifteen specimens of OT attachments castable system (Rhein83) with three different designs with plastic female parts and metal alloy male parts were selected. The specimens divided into three different designs groups; group I containing OT cap attachments, group II containing OT vertical attachments and group III containing OT strategy attachments. Each specimen subjected to 1200 wear cycle in a universal testing machine. Each cycle had performed full insertion/separation movement in an axial direction at a cross head speed of 50 mm/min in the presence of artificial saliva; and the retentive force had been measured at different thirteen intervals. Before and after testing, each one of the polymeric retentive female parts (caps and clips) had been individually weighted and scanned by SEM using low vacuum mode to detect loss of material and worn areas. Results: One-way ANOVA test revealed that there was a statistically significant difference between the groups (P<0.001). Pair-wise comparisons between the groups showed that; group II (OT vertical) showed the highest mean weight and retention loss followed by group I (OT cap) then group III (OT strategy). All designs subjected to wear but only OT vertical (group II) attachments have showed marked wear and retention loss. Conclusion: The designs of attachments have an important role in wear process. OT cap attachments and OT strategy attachments showed slight wear and material loss in comparison to OT vertical attachments.

Objective: The objective of this study was to evaluate and compare changes in the flexural strength of heat-cured denture base resins when treated using denture cleansers. Study design: A total of 40 specimens with dimension 65 mm length, 10 mm width, and 3 mm thickness were prepared as per ISO 1567 specification. A total of 10 specimens were immersed in distilled water to be used as control. Of the remaining 30 samples, 10 were treated with Clinsodent, 10 with VI-Clean, and 10 with Clanden denture cleansers. Specimens in each group were subjected to three-point flexural load in universal testing machine at a cross-head speed of 5 mm/min. The peak load (N) was recorded and flexural strength was calculated. The findings were analyzed using Kruskal–Wallis analysis of variance and Mann–Whitney test. Results: Heat-cured denture base resin selected for this study showed significant difference in flexural strength after immersion in denture cleansers Clinsodent, VI-Clean, and Clanden solutions, when compared with the control group. Conclusion: Findings of this study showed that denture cleansers altered the flexural strength of heat polymerized acrylic resins that endured soaking cycles which simulated 180 days of use. Hence, denture cleansers should be used with caution, once a day after brushing the dentures. It is advisable for patients to follow the manufacturer's instructions.

The purpose of this study was to compare the retention of circlet (E) clasps and back-action clasps against three abutment surface materials during long-term simulation of attachment and detachment. Forty-eight test models were constructed by placing premolars (natural abutments or metal dies) inside metal blocks to test different abutment retention surface materials (sound enamel, composite resin, and glass-ceramic; 16 each). The models were duplicated into investment models for construction of circlet (E) and back-action clasps. Removal and insertion cycling of clasps was carried out for 250, 500, 1000, 2000, 4000, 8000, and 16,000 cycles. The retention of each clasp was measured before cycling and after each interval. Data were analyzed using 1-way-ANOVA, 2-way-ANOVA, and Mann-Whitney U tests. No significant differences in retention of either clasp were found between the three abutment material surfaces; however, there was a significant decrease in retention force of the circlet (E) clasp between 1000 and 2000 cycles but not of the back-action clasp. (1) The back-action clasp maintains its retention force for a longer period than the circlet (E) clasp. (2) Composite resin contouring of teeth provided retention comparable to enamel and a ceramic material.

Restoring a single central incisor should aim at preserving the affected tooth as well as re-establishing function and esthetic. This clinical report describes a patient with compromised smile due to the fracture of the tooth number 11which was immediately restored by resin waiting for the healing process after the trauma. A zirconia based ceramic restoration was performed. Basic guidelines were followed to guarantee a natural mimicry of the restoration. The maxillary central incisors have an effect on the visual aspect of a person either positively or negatively. In fact achieving a natural mimicry of the single maxillary central incisor restoration with the adjacent  dentition  is  a  real  challenge.  Thus  an  accurate  match  of  a  single  incisor  crown  with  the  supporting  tissues  leads  to  a  near  mirror image [1]. When the central incisor is decayed or fractured, the  situation  is  complicated  as  it  needs  a  prior  reconstruction.  Currently, fiber posts and cores solve the problem thanks to their elastic  behavior.  Their  modulus  of  elasticity  is  similar  to  that  of dentin, unlike metal or ceramic posts [2,3]. The restoration will  be  instantly  compared  with  the  natural  counterpart.  Hence  the  slightest  differences  of  shape  and  color  will  be  immediately  perceived. Knowing that the patient’s expectations in this case are normally very high, this integration of the restored central tooth is more challenging for both the clinician and the ceramist.

Background: The purpose of this in-vitro study was to evaluate the effect of dynamic cyclic loading on screw loosening of retightened abutment screw versus new abutment screw in both narrow and standard implants. Methods: Separate acrylic resin blocks containing implant assembly (fixture, abutment, abutment screw, metal tube capping the abutment). Samples were divided into two main groups according to the diameter of implant: group 1 (GI 4.5-mm diameter) and group 2 (GII 3-mm diameter). Each group is subdivided into two subgroups according to the suggested option to manage screw loosening either by retightening (GIA, GIIA) or using new screws (GIB, GIIB). One hundred thousand cycles of eccentric dynamic cyclic loading (DCL) were applied before and after retightening or replacing the screw; then, removal torque loss (RTL) ratio was calculated, tabulated, and analyzed by t-student, ANOVA, pair wise Tukey's tests.

Purpose: The purpose of this study was to compare the retention of circlet (E) clasps
and back-action clasps against three abutment surface materials during long-term
simulation of attachment and detachment.
Material and Methods: Forty-eight test models were constructed by placing premo-
lars (natural abutments or metal dies) inside metal blocks to test different abutment
retention surface materials (sound enamel, composite resin, and glass-ceramic; 16
each). The models were duplicated into investment models for construction of cir-
clet (E) and back-action clasps. Removal and insertion cycling of clasps was carried
out for 250, 500, 1000, 2000, 4000, 8000, and 16,000 cycles. The retention of each
clasp was measured before cycling and after each interval. Data were analyzed using
1-way-ANOVA, 2-way-ANOVA, and Mann-Whitney U tests.
Results: No significant differences in retention of either clasp were found between
the three abutment material surfaces; however, there was a significant decrease in
retention force of the circlet (E) clasp between 1000 and 2000 cycles but not of the
back-action clasp.
Conclusions: (1) The back-action clasp maintains its retention force for a longer
period than the circlet (E) clasp. (2) Composite resin contouring of teeth provided
retention comparable to enamel and a ceramic material.