Effect of curing regimes on physical properties of heat cure acrylic resin

This study was conducted to determine the effect of varying curing conditions on the residual monomer concentrations of heat cure acrylic denture resin

Sixty-four disc shaped acrylic resin specimens were processed at four powder-liquid ratios [2.22, 2.00, 1.80 and student-ratio] and cured in a heated water bath using 4 different curing regimes [two with a terminal boil and two without]. The residual monomer concentrations were determined at intervals of 24, 48 and 72 hours using a UV Spectrophotometer

The results indicated a decrease in residual monomer concentration with storage time. Group 4 [student-ratio] and curing by cycle 2B [placing the assembly in the water bath directly at 100°C] showed the highest overall residual monomer concentrations while group 1 [highest powder-liquid ratio] and curing by cycle 1A showed the least overall residual monomer concentrations It was concluded that students dispensing acrylic powder and liquid monomer without calculations would lead to higher residual monomers if a proper curing regime is not followed. Using a 60 minute terminal boil in the polymerization process is strongly recommended. Storing the acrylic denture bases for at least 24-48 hours in water before use will decrease residual monomers being leached into the oral environment

Effect of varying powder liquid ratios and curing conditions on the residual monomer concentration of heat cure acrylic resin

Objective of the study was to determine the effect of varying powder liquid ratios and curing conditions on the residual monomer concentrations of heat cure acrylic denture resin. Sixty four disc shaped acrylic resin specimens were processed at four powder-liquid ratios [2.22, 2.00, 1.80 and student-ratio] and cured in a heated water bath using 4 different curing regimes. Curing cycles 1A and 1B initiated curing of specimens at room temperature followed by a terminal boil for 60 and 30 minutes respectively. Cycles 2A and 2B initiated curing at 70°C and 100°C respectively, without any terminal boil. The residual monomer concentrations were determined at intervals of 24, 48 and 72 hours using a UV Spectrophotometer.Regression analysis indicated a moderately strong negative correlation [-0.515] between time and residual monomer concentration which suggests residual monomer concentration decrease with storage time. Group 4 [student-ratio] and curing by cycle 2B [placing the assembly in the water bath directly at 100 degree C] showed the highest overall residual monomer concentrations while group 1 [highest powder-liquid ratio] and curing by cycle 1A showed the least overall residual monomer concentrations. Independent t tests between groups however revealed mean residual monomer concentration of samples cured by cycle 2B [0.32 +/- 0.38] to be greater than the mean [0.06 +/- 0.07] of samples cured by Cycle 1A [p value= 0.02] suggesting that cycle 1A will produce less residual monomers irrespective of the powder-liquid ratio.It was concluded that students dispensing acrylic powder and liquid monomer without calculations would lead to higher residual monomers if a proper curing regime is not followed. Using a 60 minute terminal boil in the polymerization process is strongly recommended. Storing the acrylic denture bases for at least 24-48 hours in water before use will decrease residual monomers being leached into the oral environment

Effect of variations in buccal bone thickness, implant diameter and thread pitch on stress distributions upon implant placements at high insertion torques: a three-dimensional finite element analysis

The objective of this study was to investigative the influence of high insertion torques on the stress distribution around dental implants with variations in thread pitch and reductions in buccal cortical bone thickness. Two bone level dental implants [3.8mm and 5.0mm diameters and a standard length of 10mm] were modeled each having a thread pitch of 0.4mm and 0.65mm. Each implant was placed in two mandibular bone segments having buccal cortical bone thickness set at 2.0mm and 1.5mm. A total of 8 such models were created and discretized with hexahedral mesh elements with an average element size of 0.2mm. Implant-bone interface was simulated with non-linear contacts and friction. Static torque values from 50Ncm to 90Ncm were applied with an increment of 5Ncm on each fully inserted implant. Maximum von-Mises along with maximum frictional stresses were used to record stress distribution within each model. Maximum stresses seem to follow a linear relation with insertion torque showing an over-all increase in stress magnitudes with 1] a reduction in the diameter of the implants 2] decrease in thickness of the buccal cortical bone and 3] decrease in pitch of the dental implant threads from 0.65mm to 0.4mm. The maximum stress of 171.4 MPa was recorded at 90 Ncm for the 3.8mm diameter implant adjacent to a buccal bone thickness of 1mm with a thread pitch of 0.4mm. With an increase in insertion torque there is a corresponding increase in the magnitude of stress production. Maximum stresses are primarily distributed in the peri-implant region in particularly the buccal cortical bony plates. The use of profile drills to coronally flare the osteotomy especially in dense bone is highly recommended if the diameter of the final widening drills to place progressively tapered implants is narrower as compared to the diameter of the implants at the neck

Practical Utilization of Tooth and Implant Supported Prosthesis: a Critical Review of Literature

Connecting implants to natural teeth as a prosthetic treatment design for the restoration of partial edentulism has been subjected to significant clinical considerations. Several studies have reported complications associated with Tooth and Implant Supported Prosthesis [TISP], while others have shown favorable outcomes. The use of TISP had been discouraged previously due to the difference in the mobility patterns of implant and teeth which can subject the prosthesis to increased stresses potentially leading to failure. However, the complications associated with TISPs seem to have been overstated. This article reviews animal studies as well as human clinical trials over the past 25 years, which have shown favorable results with TISPs. The article also discusses the questionable data which has discouraged the use of TISP. Guidelines which would aid in attaining predictable service life and fewer complications with TISPs have also been mentioned

step by step guide to finite element analysis in dental implantology

As a consequence of dental implant treatment being considered effective, safe and predictable they are now a preferred solution for those who have lost teeth due to dental caries, periodontal disease, injuries or other reasons. The biomechanical performance of implants cannot be proven or tested in vivo due to difficulties in assessing or quantifying the level of osseointegration, the stability of the implant and various other factors. Finite element analysis [FEA] has been used extensively to examine intractable and inaccessible interfaces of the dental implant assembly and to predict biomechanical performance as well as the effect of clinical factors on implant success. Although an in depth under-standing of the theory, method, application and limitations of FEA in implant dentistry will help the clinician to interpret results of FEA studies and extrapolate these results to clinical situations, this article explains the basic practical steps involved in the utilization of FEA from a viewpoint of a researcher interested in conducting studies in dental implantology

Clinical Audit and Its Role in the Practice of Dentistry

Audit is the practice of ensuring good professional practice, which has been practiced in the various fields of professional world for a long time. The concept of clinical auditing which primarily ensures quality provision of equitable, ethical healthcare is still a new concept in the field of health sciences. In dentistry, this concept is even more recent, especially in the developing world. Many dental negligence cases go unaccounted for in various parts of the developing world. This article outlines the main concepts of clinical audit, explaining what exactly is clinical audit and how may it be implemented in the practice of dentistry

study to evaluate patient preferences in the decision making of dental treatment

The purpose of this study was to explore patient preferences in their dental treatment decision making and establish their role as active, passive or collaborative. Questionnaire based cross-sectional. Department of Prosthodontics and the Executive private clinics of the Islamic International Dental College, Hospital from the 1[st] of February till the 30th of March 2012. A convenience sample of 80 patients, 40 recruited from the Department of Prosthodontics and 40 from the executive clinics at the Islamic International Dental College were interviewed and their preferences for participation in treatment decision making were established using a measurement tool designed to elicit decision-making preferences. Patient preferences for participation in treatment decision making were established using a simplistic modification of the Control Preference Scale [CPS] tool. This study found that 45% clinic patients perceived active/semi-active roles in treatment decision making, 42.5% chose passive/semi-passive roles. 90% patients interviewed at the Department of Prosthodontics preferred passive/semi-passive roles. Over all, out of 80 patients, 53 chose the passive/semi-passive roles. Patients presenting at the private clinics prefer being actively involved in their treatments, having said that, majority of them choose to get treatment from private clinics because they expect better services and have more trust in their doctors

Incorporating implant dentistry into undergraduate dental curriculum: need, problems and a simplified implementation strategy

As a consequence of several paradigm shifts and the increasing need and demand for implant restorations by patients, these days' implant related procedures are more frequently performed by general dental practitioners [GDP]. The resulting lack of not following a team approach by the GDP has increased the rate of implants related complications. Thus dentists upon graduation need to be made competent by incorporating, in the curriculum, relevant concepts and procedure related to dental implants. This will enable local dental institutes not only to be in line with those in developed countries but they will also produce dental graduates competent for the practice of dental implants. The implant related curricular content shall comprise of learning and training of; indication of oral implants in overall treatment planning of patients, understanding of the basic aspects of healing and tissue integration, basic biomechanical andmaterial science principles, patients' evaluation, selection and identification of their treatment complexity, relevant ethical and moral considerations, surgical and prosthetic techniques, monitoring,maintenance and management of complications related to peri-implant tissues and implant prosthesis. This writing elaborates upon the strategy for overcoming the barriers to introducing dental implants in dental undergraduate studies and for ensuring desired learning and the acquisition of skills related to these issues of implant-supported dental restorations by graduating dentists

Repair of root perforation using mineral trioxide aggregate: two case reports

Root perforation repair has historically Seen an unpredictable treatment modality with an unacceptably high rate of clinical failure, Inadequacy of the repair materials has been a contributing factor to the poor outcome of repair procedures. Mineral trioxide aggregate [MTA] is a relatively new material that is being successfully used to repair perforations. This article reports the findings of research done on MTA used as a material to repair root perforations and presents two clinical cases where MTA was successfully utilized to repair root perforation

Two successful cases of root perforation repair using mineral troxide aggregate

Root perforation repair has historically been an unpredictable treatment modality with an unacceptably high rate of clinical failure. Inadequacy of the repair materials has been a contributing factor to the poor outcome of repair procedures. Mineral trioxide aggregate [MTA] is a relatively new material that is being successfully used to repair perforations. This article reports the findings of research done on MTA used as material to repair root perforations and presents two clinical cases where MTA was successfully utilized to repair root perforation

Writing a research proposal

As researchers in dentistry, we have a quest to learn more, to look beyond what is written and to contribute a little to the field we plan to dedicate our lives to. For a beginner, writing a research proposal is probably one of the most challenging and arduous tasks, especially since research is a new area for the majority of Pakistani dentists. This article provides the necessary guidelines for the inexperienced potential researcher to produce a standard research protocol. It is outlined in a comprehensible, easy-to-grasp and systematic manner. Obtaining a grant for a research project generally determines the academic and administrative success of any project. Therefore the quality of a research protocol is of paramount importance for viable competition. Despite the uphill daunting task of producing a protocol of high quality, it is nonetheless one of the most interesting and satisfying part of research. Conquering this arena opens the door to an exciting unending world of knowledge yet to be discovered

Tooth and mini-implant supported maxillary porcelain fused to metal bridge: a case report and 2 year follow up

Mini dental implants have been promulgated to be used for denture stabilization primarily in geriatric patients where bone is inadequate for conventional implants and surgery needs to be conservative The simple and straightforward modus operandi of this implant system along with its affordability has led to the use of larger sized mini-implants to be successfully utilized in single tooth replacements in non-stress bearing areas. The decision to employ mini-implants to replace posterior teeth should be experimented with caution Variables such as number and lengths of implants, time-span of the remodelling phase, height and width of abutments, design and occlusal scheme of prosthesis etc should be meticulously considered in the long term survival of the treatment. This article will discuss a case report of a female patient who was provided with a four unit porcelain fused to metal bridge supported by a natural canine and two maxillary square head mini-implants [2.4mm in diameter; 15mm and 10mm in length]. It will also give an evaluation of the prosthesis on completion of its 2 years of successful service

Mental supported telescopic acrylic based fixed and removable dentures: a case report

Providing a stable, long lasting, aesthetic and affordable prosthetic replacement to a patient having stringent and uncompromising requirements can be technically difficult, especially when such a patient presents with a series of previous unacceptable dentures. This article is a case report in which prosthetic replacements are reinforced with metal frame substructures which telescopically seat on metal copings cemented on the remaining abutments. The patient is an 82 year old male, concerned equally about restoring function and aesthetics, with a hypersensitive gag reflex and previous ill-fitting broken dentures

Effect of varying height and taper on the fatigue performance of full-coverage TESCERA ATL ceromer crowns

This study assessed the effects of varying crown preparation heights and tapers on the fatigue performance of full-coverage TESCERAATL ceromer crowns. Seven cobalt-chromium dies were fabricated to receive full-coverage crowns. The first four dies had heights measured at 4.0, 3.5, 3.0 and 2.5 mm from the lingual wall, each with a 6° taper and assigned as groups 1 to 4 respectively. The last three dies had tapers measured as 14°, 18° and 22°, with heights fixed at 4 mm and assigned as groups 5 to 7 respectively. All other variables were kept constant. Ten full-coverage TESCERAATL crowns were fabricated for each of the 7 dies, All 70 crowns were cemented with zinc phosphate onto their respective cobalt-chromium dies and secured on a metal repositioning jig, which standardized the load application point. The assembled specimens were subjected to a unidirectional cyclic loading of 210 N at a frequency of 4 Hz sequentially from group I to 7. Number of cycles to failure for each specimen was recorded once catastrophic failure occurred. Two electrical resistance strain gauges were used to indicate preliminary failure. One-way Analysis of Variance [ANOVA] and post hoc Tukey tests were conducted for groups 1-4 and 5-7. There is a statistical difference between groups 1-4 and 5-7 [p<0.05]. The means and standard deviations for the first four groups were 4.255 x105 [ +/- 0.486], 4.295 x l 05 [ +/- 0.689], 4.264 x 105 [ +/- 0.567] and 2.406 x 105 [ +/- 0.656] cycles to failure respectively. The means and standard deviations of groups 5, 6 and 7 were 4.12 x105 [ +/- 0.401], 3.583 x105 [ +/- 0.352] and 3.016 x105 [ +/- 0.246] cycles to failure respectively. Fatigue performance remains unaffected by reductions in height up to a particular value [3.0mm] and then suddenly drops. Fatigue performance follows a linear relationship with changes in taper, with fatigue life gradually decreasing with an increase in taper

Surface topography of titanium implants: which ones influence a better treatment outcome?

Since the early 1980s, oral implants have provided a new dimension to all fields of dentistry. Reliable procedures have developed rapidly and joined an important place in treatment planning. In periodontics, the usual, despairingly conservative treatment is moderated by a rational implant option. In prosthodontics, aesthetic and functional restorations have certainly benefited from implant therapy. In orthodontics, an implant abutment may be used to facilitate tooth movement in some situations. Successful implant treatment relies on a knowledge of anatomy, an understanding of tissue physiology, skillful surgical technique and a comprehensive understanding of all aspects of the implant system being used. The objective of this review is to enlighten the reader about the types of processed implant surfaces and as to which of these surfaces would influence a better treatment outcome

Advantages and disadvantages of porcelain fused to metal, all-ceramic and composite resin options: a practical overview

Demands for better performing, longer lasting, safer, more economical and more user friendly restorative materials with higher aesthetic values are constantly pushing the envelope of technological capabilities and dental practice. As a result, there is not only a plethora' of restorative materials already on the market, but more being swiftly manufactured and later superbly marketed with little research backing. With the current quantity and diversity of indirect restorative materials, dentists only after meticulous review of the capabilities, indications, advantages and limitations of each system can be in a favorable position of choosing restorative materials which can satisfy challenging clinical situations as well as the most discerning clientele. The following review provides a practical overview of the advantages and disadvantages of porcelain fused to metal, all-ceramic and composite resin options being used in today's dental laboratories. This is a review article