retinitis. The iris was completely dilated, and he had only light perception. The dental examination showed four impacted third molars, Nos. 19, 20, and 30 missing, and all the remaining teeth infected, except the lower cuspids and incisors. Extraction of the infected teeth. was performed, together with removal of infected. processes and curettage of cysts. Following this procedure there was rapid improvement in the condition of the eye. In 10 days large objects were discernible, and at the time of his discharge from the hospital he could count fingers at 5 feet.

TROPICAL DUTY AS PREDISPOSING TO GINGIVITIS.

By P. S. Tichey, Lieutenant, Dental Corps, United States Navy.

While stationed at Guantanamo, Cuba, during the late war I had occasion to observe an unusual condition of morbidity in the investing tissues of the teeth and gums of patients referred to me for treatment. This condition was so prevalent and so remarkably uniform in type that it served to interest me professionally to the extent of compiling certain records in an attempt to account for its presence. The clinical picture presented in these cases was somewhat similar to the advanced stages of pyorrhea alveolaris, but differed from the usual manifestations observable in pyorrhea in that there were no typical pockets, demonstrable as such, and pus and the débris of an active and destructive bacterial infection could not be as readily expressed by the usual methods.

The pronounced hypertrophy of the gum tissue and the fact that there was much pain while the tissues were relaxed served to distinguish the condition as unusual, and occasionally it was noted that the gum tissue was of a faint blue color but without apparent localized areas or any identifying lines.

The patients invariably complained of a puffiness of the gum that was extremely uncomfortable, and generally the teeth were loose while apparently retaining all fibrous and membranous attachments.

Microscopical examination of smears made revealed the presence of the usual organisms found in the mouth, and spirochetæ were sometimes demonstrated.

Had I been able to demonstrate the fusiform bacillus with any of the associate spirilla which are present in Vincent's angina the diagnosis and treatment of these cases would have been greatly simplified, as the clinical symptoms, particularly the fact that there was always a considerable amount of pain and fetor, would have supported this diagnosis. These, however, were absent, and there was also an absence of the typical lesions associated with this form of infection.

32 TICHEY-TROPICAL DUTY AS PREDISPOSING TO GINGIVITIS. Vol. XIX,

Pyorrhea was, of course, immediately considered, but was not thought sufficient to account for the apparent widespread nature of the infection, and as there was present always local pain without trauma and a lack of gingival pockets generally associated with the advanced stages of this disease this theory was not tenable.

The various oral infections with which my practice has made me familiar were reviewed in the light of the clinical evidence presented, coupled with symptoms and history of each case, and each was eventually discarded.

Proper laboratory facilities not being available for extensive investigation, I made attempts to clear up these cases by palliative methods designed to make the patients as comfortable as possible in the hope of arriving at some specific and regular technic. In this I was never wholly successful inasmuch as while I could do much to alleviate the condition in question I never could be sure just what specific effect my remedies had.

The possibility of rachitic conditions was given some thought in the light of the capillary bleeding complained of by the patients, and although there was a typical blue gum condition in some cases the diet served aboard ship would generally be considered as all that would be necessary to preclude the possibility of anything of this

nature.

It being my first experience in the Tropics, and not having observed this condition elsewhere, it seemed reasonable to me to assume that the climate may have had something to do with the matter. Particularly as all patients stated that they had experienced no discomfort until the arrival of their ship in warm waters, and men who had been in the Navy for some years informed me that this condition was not unfamiliar to them, generally clearing up on their return to colder climates and without medication.

This assumption that climatic conditions, if not primarily responsible for these cases, at least were a considerable factor in producing the conditions observed was forced upon me by the insistence of the patients themselves, the uniformity of the cases, and particularly the similarity of the history in each case.

In trying to seek justification for this assumption it occurred to me that it might be possible that climatic conditions might involve a change in the habits of the men aboard ship, particularly in respect to the diet, which fact might be the basic factor involved. I reasoned somewhat as follows:

In the main our men are of the Nordic branch of the white racemen whose natural environment has been for many generations the North Temperate Zone, with its changing seasons. These men are most active when they receive the external thermal stimulant brought

about by seasonal changes of temperature, and without which they become listless and lazy. A change of temperature is a muscular tonus, which brings tonicity to the blood vessels that ought surely to energize the most minute capillary found in the soft tissues of the mouth. On the other hand, in a constantly warm temperature the blood vessels, as well as the muscular structures, become flaccid, due to the lack of external stimuli, which I believe retards their tonicity, and it is possible that a degree of stasis may be established in the microscopical structures, thus lowering that structure's resistance to such an extent that if its environment contains both bacterial or mechanical irritants the structure succumbs to the bacterial invasion and becomes diseased.

Beside the depressing effects of a constantly warm climate upon the body of one who is accustomed to seasonal changes of temperature, we can view the cause and effect of diseased soft tissues of the mouth from the standpoint of an improperly balanced diet. Scientific research has made it clear to us why men like those in Dana's Two Years Before the Mast suffered from scurvy. The mouth conditions of men which I have examined were much the same but in milder form. Aside from good meats and plenty of that tuber which is so well known to every American, a sailor wouldn't walk athwartship for anything else except ice cream, cookies, and candy. He doesn't care for "trimmings" or "side dishes." He knows nothing about "fat soluble (A), water soluble (B) and (C)," etc., and it seemed likely that some of my patients suffered from a lack of vitamines, or antiscorbutic foods.

Men on board our vessels are not deprived of green vegetables, even in the Tropics, where they are procured at a great expense, but a great number of these men will not eat "hay." They demand beef and "spuds," and pork and beans; that is their diet. I have seen men go ashore after being aboard for months and order steak and eggs.

It is not that a balanced diet is not provided aboard ship-it is because the men choose from this diet what appeals to their fancythat it is possible to observe mouth conditions that are typical of an unbalanced ration. A nitrogenous equilibrium is an accident when the men consider only their personal likes and dislikes.

This, I think, accounts for the conditions which I have observed. Presumably other dental officers on tropical duty have observed it also and have been more successful in treating it than I have.

Lieutenant Daniels, while on duty in Pensacola, reports that the first 30 cases to report for dental treatment, each month for 12 months, an average of 9 were cases of gingival disturbance. (H. A. Daniels, lieutenant (DC), United States Navy: "Effect of Carbol

Fuchian Stain on Diseases of the Gingivae." U. S. Naval Medical Bulletin, January, 1923.)

A summary of my observations may be briefly noted as follows: That tropical service would seem to predispose certain unusual inflammatory conditions of the attaching tissues of the teeth.

That the diet may be a factor in controlling these conditions.

THE MANIPULATION OF MODELING COMPOUND AND SECTIONAL MODELING COMPOUND IMPRESSION TECHNIC.

By J. J. Haas, Lieutenant, Dental Corps, United States Navy.

The manipulation of modeling compound is not difficult when one has a knowledge of its properties or behavior under various circumstances. Compound if not properly heated can not be worked to advantage. It is generally heated by placing it in hot water or in a Bunsen flame. By softening compound in this way one is apt to obtain a compound that is not sufficiently soft to obtain an accurate detailed impression or so warm as to burn the mucous membrane. If compound is placed in a Bunsen flame and heated until its plastic properties are destroyed and it blisters or is scorched, it can not give an accurate impression.

An ideal impression material should have the following characteristics:

1. It should be composed of some material that will not be unduly disagreeable to the patient.

2. It should become plastic at a temperature the oral tissues can tolerate.

3. It should copy accurately the fine lines and irregular surfaces to which it is applied and retain the form so copied, without becoming distorted in removal from the mouth.

4. It should harden in a reasonably short time.

5. It should not expand, contract, or warp at ordinary temperatures to any appreciable degree.

6. One should be able to correct an impression by adding to or taking away from the original mass.

Various impression materials such as plaster of Paris, modeling compound, beeswax, paraffin, beeswax and paraffin combined, and gutta-percha are on the market. Of these, the first two only are of value.

Plaster of Paris has been discarded to a great extent because of its disagreeable taste and because one can not add to a plaster impression (full or partial) for correction. One of the greatest faults or disadvantages of plaster is its tendency to expand. Plaster expands thirty-two ten-thousandths of an inch 32 minutes after setting, and after 24 hours' setting it expands three times that amount. In

taking an impression for a partial case, in which we always have undercuts, the plaster breaks or the operator breaks it in removing the impression from the mouth. Sometimes it breaks clean, but usually it does not. It usually breaks and leaves small pieces at the gum margin and at the edentulous sections, which are needed in producing an accurate cast. If some of the small pieces are crushed, lost, or too small to be replaced, the operator usually tries to reproduce them by building up the deficit with wax, and in no way is he able to reproduce the lost section accurately. Modeling compound is the only material available at the present time which possesses the characteristics desirable in an ideal impression material.

In order to manipulate modeling compound successfully we must first understand its behavior and properties. Modeling compound at ordinary temperatures is a hard, brittle mass. It will break before it bends, and it breaks clean. Modeling compound, when heated to 120° F. in moist heat, will bend, hence the term "the bending stage." Compound at this temperature will not take a detailed impression. When compound is heated to a temperature of 150° F., it is soft and can be molded to take a detailed impression, hence the term "the working stage."

The oral tissues can withstand a temperature of 150° F. comfortably, and compound in this stage can be controlled by the operator. If the temperature is raised above 150° F., the compound becomes sticky, can not be adapted to the oral tissues, as it will scorch them, and it gets beyond the operator's control. Compound is best controlled by using a Supplee heating element, which keeps the upper half of the basin of water at a temperature of 150° F., and the lower half is about 20° cooler. The latter has advantages, because the compound will not adhere to the bottom of the basin at that temperature.

In taking any impression, full or sectional, a tray must be adapted to fit the case. A suitable amount of compound heated to a temperature of 150° F. is secured and seared on the tray. This is done by holding the compound in the Bunsen flame until it sputters and then attaching it to the dry tray. The modeling compound is then formed on the tray to suit the case and the tray and compound is immersed in ice water, tray side down. The compound is submerged half its thickness for 10 seconds. The reason for doing this is that we wish to have a supporting harder mass for the softer molding mass upon which the impression is made.

The mass is then introduced to the desired place in the mouth and the print is taken. The mass is then chilled in ice water, removed, and the water shaken off and the printed surface is glazed with a Tench mouth blowpipe flame. This glazing of compound is neces