An evaluation of the effects of two distal extension removable partial denture designs on tooth stabilization and periodontal health.

A 30-month follow-up study was conducted on 36 patients to evaluate the effects of the lingual plate as a major connector in distally extended removable partial dentures (RPDs) on tooth stabilization. At the same time, the study evaluated the effects of lingual plate-type RPDs and lingual bar-type RPDs on periodontal health. The most striking finding of the study was that, with the exception of gingival recession (GR), periodontal conditions improved with both types of RPDs. At the end of 30 months, there were significant differences in plaque index, GR and tooth mobility (TM) values between treatment groups (P < 0.05). Plaque accumulation was greater in the lingual plate treatment group; however, this did not result in periodontal breakdown. There were no statistically significant differences between treatment groups with respect to pocket depth, gingival index or attachment loss (P > 0.05). Moreover, patients treated with lingual plate-type RPDs demonstrated less TM when compared with patients treated with lingual bar-type RPDs at the end of 30 months follow-up. Overall study findings established that with adequate checks on oral and denture hygiene at regular intervals, patients with RPDs may even experience improved periodontal health. Moreover, the clinical interpretation of decreased TM observed in patients treated with lingual plate-type RPDs may be questionable as the plaque accumulation was greater in the lingual plate treatment group inspite of periodic recalls.

Time-related wettability characteristic of acrylic resin surfaces treated by glow discharge.

STATEMENT OF PROBLEM: Adhesion and cohesion have important roles in denture retention, and attempts have been made to improve the wettability of the acrylic resin material by surface treatments. PURPOSE: This study examined the initial and subsequent wettability of an acrylic resin denture base material treated under air or argon plasma atmosphere before and after exposure to air or distilled water. MATERIAL AND METHODS: Acrylic resin specimens were treated with plasma under air or argon atmosphere and were either exposed to air or distilled water for up to 60 days. Wettability characteristics of the acrylic resin specimens were determined by contact-angle measurements after 2 hours and after 60 days. Surface composition of the specimens also was analyzed with x-ray photoelectron spectroscopic (XPS) measurements. RESULTS: Statistically significant difference was found between control and each of the plasma treatment groups (P <.05). Although the storage condition and storage period caused statistically significant difference on contact angle values (P <.05), atmosphere type did not have any effect on the results (P >.05). XPS spectra of the plasma-treated specimens differed from control specimens only in the O1s region with a narrower and more intense peak that could be assigned to -COH groups. During 60 days of exposure, the O/C atomic ratios decreased within the first 2 weeks but settled to 0.40 and 0. 32 up to 60 days compared with 0.26 for untreated control specimens. CONCLUSION: Glow discharge plasma altered the surfaces of the acrylic resin and increased thc wettability as shown both by XPS and contact-angle measurements, and plasma treatment seemed to offer a durable (at least up to 60 days) wettability.

Retentive characteristics of different dental magnetic systems.

It is necessary to recognize the retentive capabilities of magnetic systems to assess their clinical performance. This study determined the retentive characteristics of one open-field and two closed-field commercial dental magnetic systems. The effect of speed of separation and the space between the magnet and its keeper on the retention force were evaluated. The magnets and their respective keepers, embedded in acrylic resin blocks, were tested with fast and slow speeds of separation. The maximum retention values of the magnetic systems were tested with slow speed of separation. The fast speed of separation was designed to reflect mandibular movement. Various spaces were developed between the magnets and their respective keepers, and magnetic systems were tested only in slow speed of separation. The fast speed of separation dramatically lowered the retention force of each magnetic system. As the space increased between the magnet and keeper, the retention values diminished rapidly. While closed-field systems demonstrated higher retentive forces than the open-field system, the open-field system was less affected by the various spaces.

Effect of surface treatments of porcelain on the shear bond strength of applied dual-cured cement.

The effect of different surface treatments of porcelain on the shear bond strength of the applied dual-cured cement was examined. Acid etching with hydrofluoric acid, roughening the porcelain surface by means of grinding with a diamond bur, and the use of silane coupling agent alone and with combinations of these surface treatments were used. Silane treatment resulted in a shear bond strength on roughened porcelain surfaces that was statistically significantly greater than all other treatment groups (p < 0.05). However the use of two mechanical bond systems together with a chemical bond did not improve the shear bond strength.