The philosophies of dowel diameter preparation: a literature review.

This article reviewed the literature regarding the diameter of dowels and identified three distinct philosophies of dowel space preparation. One group advocated the narrowest diameter for fabrication of a dowel to a desired length. Another recommended a dowel space with an apical diameter equal to one third of the narrowest dimension of the root at the terminus of the dowel. A third group advised that at least 1 mm of sound dentin should surround the entire surface of the dowel. A combination of the one third and 1 mm minimal philosophies yielded a practical guideline for dowel space preparation, particularly in aged teeth. Requiring a definite amount of tooth structure surrounding the dowel, while adhering to the one third proportion, indicated upper limits on both the diameter and length of the dowel. These calculated limits served as convenient starting points in selecting a specific style of dowel and assisted in determining whether additional measures are warranted to enhance dowel retention.

Nocturnal electromyographic evaluation of masseter muscle activity in the complete denture patient.

Nocturnal oral activity was evaluated in 12 complete denture wearers by means of EMG measurements of the masseter muscle. Patients who had worn dentures for at least 6 months were selected. EMG levels were compared when subjects slept with and without the dentures in the mouth. Three subjects appeared to have reduced EMG values when sleeping with the dentures. However, no overall group trends or significant differences were obtained. High variability in nightly EMG values could not be explained by a post hoc analysis of patient oral symptoms or denture characteristics. Efforts should be directed at improved methodology to study the specific mechanism of the effect of denture wearing on nocturnal muscle activity levels. Additional knowledge is needed on the occurrence and effects of parafunctional habits in the edentulous patients.

Accuracy of an earpiece face-bow.

The validity of the Hanau ear-bow to transfer an arbitrary hinge axis to a Hanau articulator was clinically compared with a Hanau kinematic face-bow. The study was conducted with 18 randomly selected patients. This investigation demonstrated a significant statistical difference between the arbitrary axis located with an ear-bow and the terminal hinge axis. This discrepancy was significant in the anteroposterior direction but not in the superior-inferior direction. Only 50% of the arbitrary hinge axes were within a 5 mm radius of the terminal hinge axis, while 89% were within a 6 mm radius. Furthermore, the ear-bow method was not repeatable statistically. Additional study is needed to determine the practical value of the arbitrary face-bow and to pursue modifications to improve its accuracy.

Duplicate casts in fabrication of temporary removable partial dentures.

The use of blocked-out duplicate casts in the fabrication of temporary removable partial dentures has been described. Temporary removable partial dentures produced in this controlled manner fit properly and aid in minimizing intraoral damage. Accuracy of fit is assured because all relief is accomplished by block out on the surveyor during the laboratory phase rather than by random grinding of the prosthesis at insertion. In addition, the original cast is salvaged and can be used as a meaningful reference during the finishing process in the laboratory (Fig. 5).

Separation and partial purification of acid phosphates of the enamel organ of rat molars.

At least two types of acid phosphatases with markedly different properties were separated from the enamel organ of rat molar tooth buds. One enzyme (A) bound weakly to the CM-cellulose column and was eluted with a combined linear salt and pH gradient; another enzyme (B) bound strongly to the column and was eluted with a second linear salt gradient at constant pH. Enzyme A was identified as a phosphomonoester hydrolase (3.1.3.2) similar to the lysosomal enzyme of soft tissues and the tartrate-sensitive enzyme of bone. Enzyme B did not hydrolyse aliphatic monophosphate ester substrates but, like enzyme A, it did split the aryl monophosphate ester substrate, para-nitrophenylphosphate, as well as the phosphate esters of casein and the acid anhydride substrates, ATP and inorganic pyrophosphate. This enzyme is similar to the low molecular weight tartrate-resistant acid phosphatases of bone and soft tissues.