The course in partial denture construction consists of an estimation of the indications and contraindications for partial dentures, means of retention, various materials used in their construction, sectional compound impression technic for partial dentures, the construction of partial dentures, selection of teeth, investing, packing, vulcanizing, and polishing. The partial denture course consists also of a consideration of the indications and contraindications for the use of clasps which include the hand-bent clasp, cast clasp, cast clasp with stop, Dresch attachment attached to cast clasp, wire-loop clasp, etc.

The crown and bridge course consists of various types of crowns and bridges. The indications and contraindications for crowns and bridges are carefully studied. The types of crowns which are made are the two-piece all-gold crown for bicuspids and molars, the castcusp crown, the whole-cast crown, various types of Carmichael crowns using a shoulder at the gingivæ or tapering it to a feather edge, the so-called half-cast crown for bridge abutments, the castbase Richmond crown, the cast-base Davis crown, and various others. The course in bridge work consists of fixed and removable bridges. On all fixed bridges a stress breaker of some sort is resorted to. Most bridges are constructed with tubular teeth, and those have porcelain facings; a root of porcelain is fused on the facing. Correct lingual anatomical contour is secured on all the ponts. Whenever possible and conditions permit, a sanitary bridge is constructed for the lower jaw. The removable-movable bridge work of Chayes's technic is also taught.

Special attention is given to anatomical tooth form by carving teeth in wax.

The cavity preparation taught for inlay and three-quarter crown abutments is the Black cavity preparation and the Carmichael, or modification of the Carmichael, preparation. All inlays and cast crowns are made indirect-direct. That is, a die is made from an accurate impression of the polished cavity preparation and the pattern is carved to suit the case. The pattern is then placed into the cavity for final adjustment and is never put back on the die. Careful attention is given to the manipulation of inlay wax, investing and burning out the wax from the flask, and casting.

The metallurgy course consists of a study of the metals used in dentistry, their properties and uses; also various alloys and amalgams and the recovery of precious metals from their alloys.

The student hospital corpsmen are being taught the manipulation of inlay wax, making amalgam dies, carving wax patterns to anatomical tooth form, investing, burning out the wax pattern, and

46457-23-2

casting. They are also being taught to box and pour impressions; set up the casts on a Gysi simplex articulator with the use of a face bow; anatomical articulation; festooning the trial dentures; investing, packing, vulcanizing, and polishing these dentures; various types of clasps are constructed; also the repairing of fractured dentures,

etc.

The corpsmen are given a course in elementary, nonmetallic chemistry which includes chemical laws, a study of the nonmetallic elements, their history, occurrence, preparation, properties, and uses. Also the most important compounds of these nonmetallic elements are studied.

The metallurgy course further consists of the study of the metals used in the laboratory, which includes their history, occurrence, preparation, properties, and uses of the various alloys and amalgams.

MINOR ORAL SURGERY.

The course in oral surgery has been designed to meet the general requirements of the naval dental surgeon with particular reference to his work in naval hospitals. It consists of a series of lectures in oral diagnosis supplemented by clinical demonstrations in minor surgery, the removal of impacted and nonerupted teeth, root resection, fractures, maxillary sinusitis, cysts, etc.

The importance of dentistry as a factor in group medicine is given thorough consideration, and it is one of the principal aims of this instruction to acquaint the dental surgeon with a knowledge of the value of his services in this respect. To this end methods of cooperation in general diagnosis and the relative importance of a thorough scientific knowledge in carrying out these methods is made one of the fundamental features of the course.

Careful attention is given to the general rules governing the treatnent of all fractures; and the comparative value of various types of appliances commonly employed in fracture reduction is reviewed with special consideration to those types accepted as of particular value in the treatment of fractures at sea. The construction and emplacement of splints is taught in connection with the course in prosthesis.

The so-called surgical removal of abscessed teeth, in contradistinction to ordinary surgical extraction, is discussed at length in an effort to arrive at the relative value of these operations and when they may be indicated.

The primary aim of the surgical course is to review the anatomy of the head as applied to such minor oral surgery as the dental officer may be called upon to perform, and supplement such instruction as is usually taught in the dental colleges of the country by such modern

methods of technique in the treatment of cases calling for surgical interference as recent developments in dental science have proved of advantage.

PATHOLOGY.

This subject is taught at the Navy Dental School in a joint lecture and laboratory course which consists of a review of general pathology, with particular attention to oral pathology.

Attention is directed largely to those neoplastic and systemic diseases commonly manifested in the mouth, such as syphilis, tuberculosis, malignancies, etc.

Dental pathology is so far differentiated from general pathology in this course as to place special emphasis on the study and treatment of diseases of the gingivæ and peridental membrane.

Special sections have been prepared for use in the study of the peridental tissues, and a thorough knowledge of the histology and functions of the pericemental membrane as a specialized organ is provided for.

The laboratory facilities of the medical school are at the disposal of the dental students, and microscopes and specially prepared slides are kept at the school for clinical comparison and supplementary study.

The technic of surgical elimination of all pyorrheal pockets and a study of the results of this treatment as applied to the tissues involved is a joint feature of this course with the instruction given in oral surgical demonstrations.

DENTAL RADIOLOGY.

The adoption of the X ray as an adjunct to diagnosis in diseases of the oral tissues has probably done more to revolutionize the practice of dentistry than any other phase of its development.

The course given in radiology is a combined lecture-recitationdemonstration course, embracing a study of the principles of the X ray, a thorough knowledge of the X-ray machine and its method of assembly and operation, the technic of exposure with an exhaustive study of angles and their importance, of tubes and tube technic.

As the most important work of the radiologist is the correct interpretation of X-ray pictures and a study of the structure and pathological changes which may be shown in an effort to arrive at the proper diagnosis in questionable cases, special emphasis is placed on this feature of the course as given to student officers.

Hospital corpsmen are given the same instruction in general principles of manipulation of the machine, with special consideration of its care and a thorough training in developing, mounting, and other accessory features of the work.

Both medical and dental arms of the X-ray machine are used, and all phases of the work are given the exacting care that radiology requires in order to make it of value.

FOREIGN BODIES OF DENTAL ORIGIN IN THE AIR AND FOOD PASSAGES.1 By Dr. Louis H. Clerf, Philadelphia, Pa.

8

With an increasing frequency in the recognition of foreign body cases there has been a relative increase in the number of foreign body cases of dental origin that have come to the bronchoscopic clinic. A recent summing up of these cases show a total of 40 foreign bodies. which include artificial dentures, teeth or fragments thereof, gold crowns, dental instruments,* amalgam fillings, orthodontic appliances, and one gold bridge.

An analysis of the circumstances attending the occurrence of these accidents shows an absence of carelessness on the part of the dentist, and they can be classed as purely accidental. When one reflects on the enormous numbers of patients that are examined and treated by dentists and the comparative infrequency of these accidents, it is, indeed, a great tribute to the skill of the dental profession.

Artificial dentures in most instances were defective or badly fitting, and the patient very carelessly continued to wear them in that condition. The denture may become dislodged during sleep, anesthesia, epileptic seizure, or any condition producing unconsciousness, or when eating, and is then either swallowed or aspirated. Of the 12 cases, 11 lodged in the esophagus and 1 in the left bronchus.

Case Fbdy. 887 was swallowed while the patient was asleep. The denture was defective, having broken three years previously, and was worn constantly in this condition. Case Fbdy. 965, originally supporting three upper teeth which had been broken off 25 years before, was swallowed while eating. The plate was worn to protect the gums. Case Fbdy. 937 was swallowed while the patient was sleeping. It was defective, one of the hooks to hold it in place having been lost. Case Fbdy. 669 was swallowed when the denture broke while in the patient's mouth. Case Fbdy. 1107, a badly fitting denture, was swallowed while the patient was eating. Cases Fbdys. 1032 and 1074, both badly fitting, were swallowed during epileptic seizures. Case Fbdy. 773 was aspirated in the left bronchus when the patient, falling unconscious, broke his tooth plate.

Aspiration of teeth.-Portions of a crushed tooth or even an entire tooth may be aspirated during exodontia, especially when a general

From the bronchoscopic clinic, Jefferson Hospital.

Formerly lieutenant, Medical Corps, United States Navy.

Jackson, Chevalier. Peroral Endoscopy and Laryngeal Surgery. Textbook, 1914. Laryngoscope Co., St. Louis.

Jackson, Chevalier. Observation on the Pathology of Foreign Bodies in the Air and Food Passages. Mutter Lecture. 1917. Surg., Gyn. and Obstet. March, 1919.