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Statement of Problem: Most faces are not symmetrical, and this complicates the task of aligning the anterior segment of the teeth for the restorative dentist, orthodontist, or oral and maxillofacial surgeon. The dental literature provides conflicting advice regarding guidelines for aligning the anterior teeth., Purpose: The purpose of this study was to determine the sensitivity of laypersons to variations in the alignment of the anterior segment within a symmetrical face, and to investigate which guidelines were preferred by laypersons and prosthodontists when aligning this segment., Material and Methods: Lay participants (21) were shown a series of 25 modified images of faces on a computer screen and asked to indicate 'noticeability' of tilt and, with another series of 19 images, preference for angulation of the anterior segment. Prosthodontists (14) were shown a further set of 7 images and asked to use a Clinometer to select an appropriate angle. Statistical comparisons were performed with multinomial goodness-of-fit tests and repeated measures ANOVA, followed by Sidak multiple comparisons tests (α=.05)., Results: The average angle at which the tilt of the anterior segment within a symmetrical face became noticeable to the laypersons was approximately 1 degree. No significant correlation (P=.15) was found between the laypersons' choice of angle for the anterior segment and the angle of the eyes, lips, or horizon, but an angle of 0 degrees was chosen significantly more often than the other angles offered (P<.001). The prosthodontists generally chose an angle close to zero., Conclusions: The results suggest that the threshold tilt within a symmetrical face, for noticeability by laypersons, is about 1 degree, and that for both laypersons and prosthodontists, the most important guideline is not any individual facial feature or the horizon but the face as a whole., (Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.)

Purpose: The determination of an acceptable occlusal plane is essential for the development of esthetic prosthodontic restorations. However, since most faces are not symmetric, a method was developed for measuring facial angular asymmetry, i.e., the divergence from the vertical or horizontal of the line joining the midpoint of the intercanthal line and the philtrum of the lip, the interpupillary line, the intermeatal line, the lip commissure line, and the intercuspid line., Materials and Methods: Standardized frontal images (mouth closed, smiling, and biting on a wooden spatula) of 100 subjects were taken using a digital camera. These images were downloaded into a computer, and the angles between the various facial lines and the horizontal were measured. The subjects were grouped by sex, age, and history of trauma and orthodontic treatment., Results: No statistically significant differences were found between the mean values for each group., Conclusion: Asymmetry of the face can be measured using digital camera imaging and computer analysis. A range of facial asymmetries that can influence the choice of occlusal plane during prosthodontic treatment exists. Thus, the use of an occlusal plane parallel to the ala tragus and interpupillary lines, as often advocated by prosthodontists, may result in less than ideal esthetics in the final restoration.

Objectives: The purpose of this study was to assess the effects of aging experimental dimethacrylate resin composites in water at 37 degrees C for periods up to 6 wk by measuring the variations in fracture toughness (K(c)), elastic modulus (E), fracture energy (G(c)), and water sorption., Methods: Six experimental resins were formulated from dimethacrylate resins, and were filled to 86 wt% (ca. 70 vol%) with treated inorganic filler to form six experimental composites. The fracture toughness was determined using a double torsion technique, the elastic modulus was measured in flexure, and the fracture energy was calculated from the fracture toughness and elastic modulus., Results: As a result of aging in water, K(c) and the G(c) increased, and the elastic modulus decreased, but all values approached a plateau near 6 wk. Water sorption also occurred during this period, mainly during the first 2 wk., Significance: Variations in the mechanical properties are interpreted as being due to plasticization of the resin matrix by water, which appears to lower the yield stress and increase in the size of the plastic zone ahead of the crack, thereby causing the observed increase in G(c) and K(c). After approximately 6 wk, no further changes in properties occurred.

This laboratory study compared the retention of prefabricated posts in well-fitting and loose-fitting post canals using different cement materials. Eighty-three human teeth were prepared for post placement. One of zinc phosphate cement, polycarboxylate cement, glass ionomer cement or resin cement was used to cement each post in place. A tensile force was applied to remove each post and the separation force was recorded. Posts cemented with the resin cement were the most difficult to dislodge. Posts cemented into loose-fitting canals exhibited greater resistance to dislodgment than posts cemented into well-fitting canals irrespective of the type of cements used.

Failures at composite resin/porcelain interfaces under shear-like loading were examined. Porcelain surfaces were treated with hydrofluoric acid and/or one of two silane coupling agents, using two different composite resin cements. The results showed that after seven days storage, bond strengths of specimens which had undergone porcelain surface treatment were greater than the cohesive strength of the porcelain itself, resulting in brittle fracture of the porcelain. The diluted restorative composite resin performed as well as the commercial composite resin cement. Silane pretreatment of porcelain was important as the bond strength of etched/silane primed specimens was significantly higher than the etched only specimens. However, one primer appeared to be more efficient than the other in bond promotion. Some explanations for the differences in bond strengths are offered.

Glutaraldehyde and hypochlorite solutions have been shown to be effective disinfectants for use in the dental surgery. However, their use in the disinfecting of alginate hydrocolloid impression materials must be open to question since these materials are dimensionally unstable when immersed in aqueous solutions for any length of time. This project investigated the dimensional changes noted in casts poured into alginate impressions which had been stored for up to 60 minutes in either hypochlorite or glutaraldehyde solutions. All changes measured were considered to be within clinical tolerance.

Specimens for the determination of adhesive bond strength to dentine were prepared using suitable surfaces of freshly extracted teeth from 15 patients who were having immediate dentures fitted. As soon as possible after extraction, shallow cavities were cut into the dentine to a depth of 1 mm using a high-speed round bur (diameter 4.2 mm) under water coolant. The cavities were restored using dentine bonding agents and single increments of light activated composite resin. The restored teeth were cut down to approximately 5 mm in diameter and 3 mm thick and were either placed in previously prepared sites in the buccal or occlusal surfaces of their respective dentures or in containers of tap water. Patients were instructed to remove their dentures only for cleaning with a soft nylon brush and toilet soap, while the laboratory specimens were stored at ambient temperature. After one week, the tensile force needed to dislodge each restoration from its cavity was determined using a universal testing machine. Previously reported laboratory methods for bond strength determination have usually employed a flat dentine surface. However, this study more closely resembled the clinical situation in that the smear layer was produced by a rotary cutting instrument, and the effects of polymerization shrinkage when curing the composite resin were simulated. Furthermore, it was easier to confine the bonding agent to the desired dentine surface.

Dental amalgam and porcelain control discs were implanted in the subcutaneous tissue of rats. Amalgam implants exerted a toxic effect caused by release of metal ions which was characterized by prolonged inflammation, delayed granulation and disordered collagen formation. Dental porcelain was found to be a suitable biocompatible control which provided a bulk similar to that of dental amalgam but induced only an uncomplicated granulation response.

The tensile bond strengths of three groups of adhesives to two electrolytically etched alloys were studied. It was found that the bis-GMA composite resins gave statistically similar bond strengths. The newer Japanese acrylics tested gave statistically higher results than the bis-GMA resins. The clinical significance of these results is discussed.

An attempt was made to develop a computer-assisted programme to aid in the positive identification of human remains. The first and second generations of a computer code and programme for entering ante-mortem and post-mortem records into a computer data bank are discussed. The initial code is presented along with the results following the computer evaluation of 50 record pairs. The self-evaluating aspects of the programme are discussed and the proposed second generation code is presented. The programme exhibits some promising characteristics but further refinement based on increased data banks is needed.

A survey of the attitudes of dentists in Victoria to various aspects of the treatment planning phase of removable partial denture prosthodontics was undertaken. Data were analysed and compared with those obtained from an identical study in South Australia. Those Victorian dentists who graduated in the 1960s, those who worked in multiple-practitioner practices, or non-rural areas, and those who had an added interest in removable prosthodontics were more likely to stress the importance of a greater number of attributes than those who graduated in the 1950s or 1970s, or those who worked alone, in rural areas, or had no particular interest in the discipline. Results indicated also that Victorian dentists tended to place greater emphasis on many of the concepts embraced by the questions asked than their interstate colleagues. It is suggested that, in addition to formal education, intraprofessional relationships and interest in a discipline are factors which might influence the concepts and attitudes of general practitioners.

Smooth stainless steel rods coated with silanes were embedded in acrylic resin dough. The strength of the bond between treated rods and polymerized resin was improved compared with that found in the untreated rods under all conditions of the tests. The strength increased with age when specimens were left in air; immersion in water lessened the increase in strength.