Quintessence International, 08/1991

This paper reports the management of a patient with severe localized periodontitis accompanied by drifting and extrusion of a central incisor. Although the traditional treatment approach to this condition often includes extraction and prosthetic replacement, the approach presented here provides an alterantive to extraction by combining periodontal and orthodontic treatment.

In cases of severe coronal destruction, conventional dentistry must resort to complex techniques and combinations of prosthetic materials. In addition, execution and placement of the restoration results in more destruction of sound dental tissue. This paper presents an alternative technique that utilizes the adhesive capabilities of new materials in combination with strategic placement of parts of extracted human teeth to achieve better esthetics and more conservation of sound dental tissue.

An in vitro study was conducted to examine the influence of the number of remaining cusps and the use of the amalgapin technique on the tensile resistance of complete cast crowns in posterior teeth. Results showed the number of amalgapins and remaining cusps to have no influence on the tensile strength. Failure occurred predominantly at the cemented area (ie, the crown was dislodged from the core

Interincisal point movements in 35 healthy, dentate subjects were investigated with an electognathic apparatus. The main focus of the study was to find the average values of determined point graphic assessment in frontal and sagittal planes during chewing of hard and soft foods. However, as this was insufficient to obtain information on areas where occlusal contacts were reached, border movement envelopes were also recorded to obtain indirect information in connection to the previous task. The results showed that the graphic assessment form of mandibular movements was dependent on the consistency of the food that was chewed.

Prior to cementation, a cast restoration must be clinically evaluated in a number of critical areas. The proximal contacts and internal surface of the casting, as well as centric and excursive occlusion, require assessment and generally require adjustment before cementation. The time necessary to accomplish these adjustments is not predictable. A technique is presented that permits the majority of these adjustments to be completed in the laboratory, thus minimizing the clinical time required to seat the casting.

This study investigated the use of iontophoresis in altering the sensitivity level of teeth that displayed thermal and tactile hypersensitivity. A total of 95 teeth were treated with an iontophoresis instrument. Forty-eight of these teeth were treated with a placebo of deionized water, and 47 were treated with a 2% sodium fluoride solution. Two of the 47 teeth receiving sodium fluoride had identical pretreatment and posttreatment sensitivity ratings, while 40 teeth (85.1%) demonstrated a reduction in sensitivity. Twenty-nine of the 48 teeth receiving the plac ebo demonstrated no change in sensitivity. All teeth receiving the placebo were re-treated with soidum fluoride. Forty-seven (97.9%) responded with reduced levels of sensitivity.

Nine maxillary premolars were restored with composite resin inlays involving large intracoronal cavity preparations. Buccal and lingual bonded strain gauges measured the cuspal flexure under a carefully controlled application of occlusal force. The intact tooth was compared with the corresonding preparation and final restoration. The preparation itself greatly reduced the coronal rigidity, but this was completely recovered in the restored tooth, within the functional force of 111 N. A stiffness ratio showed a 97% recovery. From the point of view of cuspal strength, this may mean that larger intracoronal restorations are feasible with this type of restoration. However, other factors, such as chairside time and complexity, and material properties, such as occlusal wear, have to be taken into consideration.

The present study was designed toe valuate the metallurgical proeprties of an experimental, low-cost copper-zinc-aluminum-nickel alloy for dental castings. Some specimens were subjected to heat treatment after induction csting. The extent of corrosion was determined by measuring weight loss of specimens stored in a sodium sulfite solution. In the as-cast specimens, tests demonstrated the presence of three phases: the first consisted of copper-zinc-aluminum, the second was similar but lower in copper and aluminum, and the third consisted of an intermetallic compound of manganese-nickel-phosphorus. A fter heat treatment, the first phase remained relatively constant, the second was converted to Cu3Al, and the third increased in volume. The weight loss from the as-cast specimens was eight times that of the heat-treated specimens. It was concluded that the heat treatment substantially changed the microstructure and improved the corrosion resistence of the xperimental alloy.

A technique, sensitive enough to determine both dentinal and enamel abrasion in vivo, is presented. Computer-aided profilometry was used to measure the surface of dentinal and enamel samples before the experiment. Samples were subsequently placed in the buccal flanges of the mandibular dentures of two test subjects, who then brushed these pieces with a soft, multitufted brush, and two different toothpastes. Results of these pilot studies showed that the samples brushed with Colgate BiFluor had markedly less enamel and dentinal abrasion than did those brushed with Smokers. In addition, surface roughness was greater in the specimens brushed with Smokers. However, person-to-person variation can have a great influence on the abrasion process; moreover, only two persons were involved in this pilot study, and no definitive statement can be made about the effect of the toothpastes.

The effectiveness of the Cavidrill baseplate in the training of second-year dental students in cavity preparations in primary ivorine teeth was assessed. The preclinical class of 112 students was divided into four groups: Cavidrill-only group, two groups combining Cavidrill training with traditional typodont training, and a typodont-only group. The Cavidrill baseplate was found not to improve the students' performance in cavity preparation when assessed on midterm and final examinations.