3D Printed Surgical Simulation Models as educational tool by maxillofacial surgeons.

INTRODUCTION: The aim of this study was to evaluate whether inexpensive 3D models can be suitable to train surgical skills to dental students or oral and maxillofacial surgery residents. Furthermore, we wanted to know which of the most common filament materials, acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA), can better simulate human bone according to surgeons' subjective perceptions. MATERIALS AND METHODS: Upper and lower jaw models were produced with common 3D desktop printers, ABS and PLA filament and silicon rubber for soft tissue simulation. Those models were given to 10 blinded, experienced maxillofacial surgeons to perform sinus lift and wisdom teeth extraction. Evaluation was made using a questionnaire. RESULTS: Because of slightly different density and filament prices, each silicon-covered model costs between 1.40-1.60 USD (ABS) and 1.80-2.00 USD (PLA) based on 2017 material costs. Ten experienced raters took part in the study. All raters deemed the models suitable for surgical education. No significant differences between ABS and PLA were found, with both having distinct advantages. CONCLUSION: The study demonstrated that 3D printing with inexpensive printing filaments is a promising method for training oral and maxillofacial surgery residents or dental students in selected surgical procedures. With a simple and cost-efficient manufacturing process, models of actual patient cases can be produced on a small scale, simulating many kinds of surgical procedures.

An investigation of accessory foramina in furcation areas of human primary molars: Part 1. SEM observations of frequency, size and location of accessory foramina in the internal and external furcation areas.

Although the existence of accessory foramina in the furcation area and roots of permanent teeth has been demonstrated, the presence of accessory foramina in furcation areas of primary molars is less certain. This investigation was conducted to determine the presence or absence of accessory foramina in the furcation areas of human primary molars using the scanning electron microscope (SEM). Twenty extracted, carious and noncarious human primary molars were placed in fixative and then mounted in a hard tissue cutting machine: ten teeth were cut transversely 2.0mm coronal to the floor of the pulpal chamber and ten teeth were cut transversely 2.0mm apical to the external furcation. Both the internal and external furcation surfaces of these sectioned molars were debrided with sodium hypochlorite/hydrogen peroxide solutions to remove organic materials, which might obscure visibility of possible foramina and then rinsed in water and dried. The tissues were then prepared for and examined by SEM. Twenty percent of the molars examined by SEM on the internal furcation surface and 50% of the molars examined by SEM on the external furcation surface demonstrated accessory foramina.

An investigation of accessory canals in furcation areas of human primary molars: Part 2. Latex perfusion studies of the internal and external furcation areas to demonstrate accessory canals.

Four classes of accessory canals: "true," "blind," "looping" and "enclosed" canals have been suggested to exist in furcation areas of primary teeth. Although the existence of accessory canals in the furcation areas and roots of permanent teeth has been demonstrated, their presence in furcation areas of primary teeth is uncertain. This investigation was conducted to determine the presence or absence of accessory canals in the furcation areas of human primary molars using a variety of latex perfusion techniques. Twenty extracted, noncarious human primary molars were placed in fixative and then sectioned on a hard tissue cutting machine: ten teeth were cut transversely 2.0 mm coronal to the floor of the pulpal chamber and ten teeth were cut transversely 2.0 mm apical to the external furcation area. The internal and external furcation surfaces of these sectioned molars were debrided with sodium hypochlorite/hydrogen peroxide solutions, rinsed in water and dried to remove organic materials, which might obscure the existence of possible canals. Twenty of these extracted teeth were examined by SEM to detect the possible presence of accessory foramina in the internal and external furcation areas (Part 1). Twenty percent of the molars examined by SEM on the IFA and 50 percent of the molars examined by SEM on the EFA exhibited accessory foramina. Twenty molars were perfused with low viscosity latex using vacuum [negative] pressure (10 molars) and positive pressure (10 molars) to detect the possible existence of the patency and the extent of such accessory canals in the internal and external furcation areas (Part 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on focal alveolar bone healing with technetium (Tc)-99m labeled methylene diphosphonate and gold-collimated cadmium telluride probe.

The benefit of using a collimator for a miniaturized cadmium telluride probe was evaluated by monitoring the bone-healing processes for 13 weeks after the induction of small iatrogenic alveolar bone lesions in one side of the mandible in beagles. Technetium (Tc)-99m labeled methylene diphosphonate (200 to 300 MBq, 5.1 to 8.1 mCi, in a solution of 0.5 to 1 ml, intravenously) was used as a bone-seeking radiopharmaceutical. The radioactivity over the bone lesion (L) and the contralateral normal site (C) in the mandible were measured between 1.5 and 2 hours after injection of the tracer, and the activity ratio L/C served as an index of relative bone uptake. A study of six dogs revealed that the healing response to a hemispheric bone defect of 2 mm diameter in the cortical bone could not be detected by an uncollimated probe, and in a repeated study in two dogs the use of a gold collimator (5 mm in diameter, 5 mm in length) did not increase the L/C ratio significantly. A second study in six dogs with 5 mm lesions showed that although systematic trends in the time courses of the L/C ratio obtained both with and without the collimator could be demonstrated, the L/C ratio of collimated versus uncollimated measurements was significantly (p less than 0.005) increased. In three of the latter six dogs, abscesses developed after 9 weeks, leading to a second increase (p less than 0.05) of the L/C ratio with collimation compared with the noninflammation group; without collimation no significant (p greater than 0.15) difference between the two groups could be demonstrated.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy of dental radiographic practices: options for image receptors, examination selection, and patient selection.

Many technical factors and treatment philosophies affect the way dental radiology is practiced. Some, like minimum tube filtration, are legislated. Others, like proper darkroom techniques, are universally acknowledged as essential. Still others, like the selection of an image receptor and the selection of the type of examination, are the subject of much discussion and debate. This article addresses some of the more controversial options and choices facing dental practitioners by reviewing the standard assessment techniques available to help make appropriate decisions, by summarizing and analyzing available data, and by offering recommendations for practice.

Cephalometric norms for orthognathic surgery in black American adults.

Normal values for the Cephalometrics for Orthognathic Surgery (COGS) analysis for American black adults were developed in this study. The cephalometric radiographs of 33 black American adults with ideal dentitions were analyzed, and a statistical description of their hard and soft tissue cephalometric measurements is presented. In addition, mean values for black American adults were compared with those of white American adults. In black subjects, there was greater maxillary skeletal prognathism, skeletal lower face height, skeletal facial convexity, lower incisor proclination, anterior dental heights, upper and lower lip lengths, and soft tissue thickness of the lips and chin than in white subjects. There was less nasal depth and projection, less bony chin depth, and a smaller nasolabial angle in black subjects. The results of this study may be useful in providing racially specific cephalometric values for diagnosis and treatment planning for orthognathic surgery in American black adults.

Dental radiography: efficacy in the assessment of intraosseous lesions of the face and jaws in asymptomatic patients.

In this investigation the efficacy of dental radiography for the detection of occult intraosseous lesions of the face and jaws was evaluated. An analysis of 30 million health insurance records indicated that the period prevalence of malignant lesions was less than 5 cases/million/year, and for benign lesions approximately 100 cases/million/year. Data from a controlled observer-performance study showed that radiographic sensitivities ranged between 50% and 80%. The cost per true-positive finding was estimated to be +8.6 million per malignant case and +430,000 per benign case. An assessment of the dosimetric literature indicated that the benefits of radiographic screening as a means for early detection of a malignancy appear to be counterbalanced by the risk of causing a radiation-induced malignancy. Taken together, these data demonstrate that dental radiography is not efficacious for the purpose of detecting occult lesions.

Comparison of biodistribution of 3H, 32P and 99mTc labeled Gpp(NH)p in tumor bearing hamsters.

Biodistribution and tumor uptake studies were carried out with intravenously injected tracer doses of Gpp(NH)p labeled with 3H, 32P or 99mTc . Syrian golden hamsters with cheek pouch carcinomas, induced by repeated topical applications of DMBA, were used as a tumor model. The biodistributions of these three radionuclides were different, indicating significant molecular cleavage of this nucleotide analog. It was also apparent that this compound labeled with 99mTc may not be useful for tumor imaging due to low tumor-to-blood specific activity ratio. The cheek pouch carcinoma tumor model may be valuable for the evaluation of tumor localizing radiopharmaceuticals.