The International Journal of Prosthodontics, 03/1992

Eight intraoral porcelain repair systems, ie, Oral Ceram-Etch (Gresco), Scotchprime (3M), Rocatec (ESPE), Command Ultrafine (Kerr), Silistor (Kulzer), Clearfil Porcelain Bond (J Morita), All-Bond (Bisco), and Monobond S (Vivadent) were used in this study. The control specimens consisted of unetched porcelain surfaces onto which a resin composite was polymerized without the use of an adhesive. Load fatigue was used as the testing method to simulate the repetitive action of mastication. The peak stress applied to each test specimen was 1500 psi (10.34 MPa), and an upper limit on the number of load cycles applied to any specimen was set at 2,000,000 cycles. Statistical analysis revealed two significant subsets. Only Clearfil Porcelain Bond and All-Bond did not fail before reaching the 2,000,000-cycle upper limit.

The purpose of this investigation was to develop a new, in vitro bacteria-yeast denture colonization model. Candida albicans and Streptococcus mutans, organisms associated with denture stomatitis, reproducibly colonized denture blanks in high numbers. Both Efferdent and Super-Strength Polident were able to substantially reduce or eliminate colonizing S mutans. In sharp contrast, however, no significant decreases in adherent C albicans were observed with either denture soaking agent.

This study examined the extent to which denture satisfaction could be predicted by a measure of locus of control (the degree to which individuals feel that they control their destiny) and a questionnaire (designed to assess prior experiences, perceptions, and expectations relating to dentures). Prior to treatment, 29 patients (14 males; 15 females; mean age 70 ± 3.5 years) completed the Nowicke-Strickland Locus of Control Scale and a brief dental questionnaire. Approximately 10 days after denture placement, patients rated their degree of satisfaction. Correlational analyses were performed separately by gender, controlling for age. Locus of control scores were not significantly correlated with the degree of denture satisfaction for males or females. Responses to several questionnaire items were significantly correlated with denture satisfaction; however, different correlations emerged for males and females, suggesting that patient gender may be an important factor.

Prosthodontists surveyed preferred inverted V-shaped canine cingulum ledge rest seats located at the junction of the middle and cervical thirds of the lingual surface. Most respondents indicated that they preferred a ledge depth of at least 1.0 mm and indicated that their preparations usually did not extend into dentin. When the respondents evaluated various ledge depths, the mean depth of those judged adequate was 0.74 mm, which was less than the respondent and textbook recommendations. Premolar occlusal rest seats judged adequate generally met textbook size guidelines. The mean clinical incidence of dentin exposure with cingulum ledges and occlusal rest seats was 61%, close to the 55% exposure rate found on extracted teeth. Dentin Detector Gel effectively identified clinical dentin exposure but tooth sensitivity was not a good indicator of dentin exposure. Seventy-one of the 107 rest seats studied for incidence of caries and decalcification had exposed dentin but only two of the 71 had lesions. Ten of the 107 had small enamel fractures, primarily occurring on cingulum ledges.

One goal in metal ceramic substructure design is strengthening the restoration. This investigation compared the strength of four metal ceramic crown designs advocated in the dental literature. Metal ceramic crowns were fabricated, luted to a master die, and loaded to failure on a mechanical testing machine. Crowns with a facial veneer of porcelain covered occlusally with metal withstood significantly higher failure loads than did the other designs. These were followed by crowns having the porcelain extended to the central groove, crowns with facial porcelain veneers without occlusal metal coverage and, the weakest group, crowns with complete occlusal porcelain coverage. There were no significant differences between the latter three designs.

Patterns of incisal point movements during habitual and unilateral chewing of 35 complete denture wearers and a control group of 35 dentate subjects were analyzed using a Sirognathograph. The graphs of the lengths, angles, and envelopes of motion made during habitual chewing cycles by complete denture wearers were analyzed and found to be similar to those of dentate subjects. However, when analyzing the graphs of separate chewing cycles at the beginning of unilateral chewing, significant differences in the movement performance were found using the same parameters. The analysis of areas where some tooth contacts occurred defined the differences in performing contact movements during chewing.

This study compared the resistance to intermittent loading of teeth with tapered, individually cast posts and cores or prefabricated parallel-sided posts (Para-Post, Whaledent) and composite cores. Bovine teeth mounted in acrylic resin blocks with a simulated periodontium were used for the study. Two conditions were studied. One group received individually fabricated posts and cores, the second had titanium prefabricated posts and resin composite cores placed. All teeth receiving posts and cores had cast crown restorations placed. Teeth were intermittently loaded using a force of 250 N twice each second at an angle 45 degrees to the long axis until failure occurred. Teeth with prefabricated posts and resin composite cores showed a significantly higher resistance to intermittent loading than did teeth with tapered, individually cast posts and cores. Additional restored teeth were sectioned and the adaptation of the posts to the root were measured. The adaptation of the prefabricated posts was better than that of tapered, individually cast posts.

Nickel-chromium alloys were plated with tin and chromium to evaluate the effect on porcelain shear bond strength. Six plating methods were used. Additionally, the microstructure of the bond between the plated alloy and porcelain were studied using SEM and EPMA. Tin plating increased the bond strength of porcelain to a nickel-chromium alloy while chromium plating did not.

Wear of prosthodontic resin facings in 176 metal-resin canine crowns and retainers for fixed partial dentures was studied in clinical photographs and assessed using a graded scale. Four cross-sectional groups of restorations were studied according to length of clinical service (1, 3, 6, and 9 years). The criteria used during the examination described loss of substance in relationship to the metal cast framework. The method was tested for reliability and consistency. The results showed that the extent of wear increased with increasing time of clinical service (P less than .05). More severe wear scores were assigned to restorations in female patients than to those in male patients (P less than .05), to the mandibular facings compared to those in the maxillae (P less than .05), and the incisal areas of the facings compared to the cervical areas (P less than .05). Patients instructed

To gain more insight into the treatment strategies for edentulous patients with atrophic ridges, three groups of patients were evaluated: group 1, patients with atrophy of the mandible who needed preprosthetic surgery but who only received new dentures because surgery was contraindicated; group 2, patients in the same oral condition as those in group 1 who were treated with vestibuloplasty and lowering of the floor of the mouth before fabrication of new dentures; group 3, the control group of patients without residual ridge-related problems who were treated with new complete dentures. The differences between the three groups were evaluated 6.5 years after treatment. The results showed that the surface areas of the patients in group 2 were approximately 180% greater in the vestibular region and were 126% greater in the sublingual region, compared with the other groups. The stability of the mandibular dentures as well as the retention were better in group 2 than were those in group 1. Group 2 patients scored comparably or higher than the normal ridge group (group 3). The resistance against dislodgment of the denture was low in all three groups.

The phenomenon of occlusal wear has been generally reported, with no distinction being made between wear of the anterior or posterior teeth. This paper describes a group of patients without oral habits and exhibiting anterior tooth attrition or flaring with minimal posterior tooth attrition. The mandibular anterior movement patterns of the patients studied were evaluated using a Sirognathograph. These patterns appear to be the etiology for the anterior attrition or flaring present. A treatment mode allowing coexistence of this phenomenon with an anterior guidance that does not interfere with the mastication pattern is proposed. A hypothesis that might explain the clinical findings and a mode of treatment are described.