A virtual reality dental simulator predicts performance in an operative dentistry manikin course

This study was designed to test the ability of a virtual reality dental simulator to predict the performance of students in a traditional operative dentistry manikin course. Twenty-six dental students were pre-tested on the simulator, prior to the course. They were briefly instructed and asked to prepare 12 class I cavities which were automatically graded by the simulator. The instructors in the manikin course that followed were unaware of the students' performances in the simulator pre-test. The scores achieved by each student in the last six simulator cavities were compared to their final comprehensive grades in the manikin course. Class standing of the students in the simulator pre-test positively correlated with their achievements in the manikin course with a correlation coefficient of 0.49 (P = 0.012). Eighty-nine percent of the students in the lower third of the class in the pre-test remained in the low performing half of the class in the manikin course. These results indicate that testing students in a dental simulator, prior to a manikin course, may be an efficient way to allow early identification of those who are likely to perform poorly. This in turn could enable early allocation of personal tutors to these students in order to improve their chances of success.     

Macrophages in periapical lesions

Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen-specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T-lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone-resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.     

Macrophages in periapical lesions

Abstract – Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen‐specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen‐activated T‐lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T‐lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone‐resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.     

Bone formation after sinus augmentation with engineered bone

Objectives: The aim of the following investigation was to quantify the resorption rate of tissue-engineered bone grafts in the maxillary sinus using volume measurements. MATERIAL AND METHODS: Sinus floor augmentation using autologous bone grafts from the iliac crest (n=17, group 1) was compared with commercially produced transplants of human cells seeded on polyglycolid-polylactid (PLGA) scaffolds (Oral Bone) (n=14, group 2). RESULTS: The total resorption rate for autologous transplants 3 months post operation was 29%, while the tissue-engineered bone showed a resorption rate of 90%. The autologous bone had a bone density of up to 266-551 Hounsfield units (HU), while sufficient mineralization of tissue-engineered bone was found in only one case (152 HU). CONCLUSION: In this clinical study, the use of autologous cancellous bone grafts in sinus augmentation was more reliable than scaffolds containing cultured osteoblasts. Further tissue-engineered bone transplants should be examined to draw general conclusions about the use of tissue-engineered grafts compared with autologous bone grafts for maxillary sinus augmentation.     

Local dexamethasone improves periodontal healing of replanted dogs' teeth

Abstract— The purpose of the present investigation was to evaluate histologically the effect of dexamethasone on root resorption in stored and replanted dogs' teeth. Twenty-nine roots from three beagle dogs were endodontically treated to prevent subsequent inflammatory root resorption of pulpal origin. The teeth were extracted and randomly assigned to three groups for 18-h storage. Group 1: control group teeth ( n = 13) were stored in vials containing ViaSpan only; Group 2: topical treatment teeth ( n =10) were stored in vials containing ViaSpan and dexamethasone (16 μg/ml); and Group 3: systemic treatment teeth ( n =6) were stored in bids containing ViaSpan without any additives. Dexamethasone was administered intramuscularly (0.5 mg/kg body weight) 2 days prior to, on the day of, and every other day after extraction and replantation for two administrations. After 12 weeks, the dogs were sacrificed, and the teeth histologically prepared and evaluated according to the analysis of Andreasen. Significant differences were found for complete healing ( P= 0.0583) and inflammatory root resorption ( P= 0.0568) but not for replacement resorption ( P= 0.1952). In addition, comparing local to systemic administration of dexamethasone (Group 2 vs. Group 3), statistically significant differences were found for healing, 85% (Group 2) vs. 67% (Group 3) ( P =0.0125) and inflammatory root resorption, 13% (Group 2) vs. 28% (Group 3) ( P =0.0126). This study indicated that topical use of dexamethasone enhances healing and results in fewer resorption complications.     

Epithelial-connective tissue interaction on the tooth surface: An in vitro model

In the present study, and in vitro system was developed and designed to examine the interaction between gingival fibroblasts (GF) and epithelial cells (EC) on the tooth surface. Porcine roots were cut transversely into 300 microns-thick root slices (RS). Gingival explants were placed on the upper RS surface and cultured in a defined medium permissive for the growth of EC. After 4 or 6 days, RS yielding EC were transferred onto confluent cultures of GF and further co-cultured for either 4 or 8 d. Cultures were then fixed and examined by SEM. The upper RS surfaces and the upper half of their peripheral aspect were covered by EC. The lower half of the peripheral RS surfaces were populated by GF originating from the confluent culture of GF. EC and GF made contact at approximately the middle of the side of the root slice. In cultures of epithelial components grown in defined medium for either 4 or 6 d and harvested 4 d after assembling the system, the EC-GF junction was located 117 +/- 45 and 271 +/- 82 microns, respectively from the upper RS aspect. Extending the co-culture period did not affect the EC-GF junction location. These results indicate that GF-EC contact stops the migration of these cells on root surfaces in vitro. The described system should be valuable for studying cellular events that may affect the formation of a new dentogingival junction following surgical periodontal therapy.     

From files to SAF: 3D endodontic treatment is possible at last

3D cleaning, shaping and obturation of root canals has always been the desired goal of endodontic treatment which in many cases is difficult to attain. The introduction of NiTi rotary files made a major change in endodontic practice, making treatment easier, safer and faster. Nevertheless, after 16 years of intensive development, most of these instruments still share several drawbacks, the major one being the inability to three-dimensionally clean and shape oval root canals. The Self-Adjusting File (SAF) System was designed to overcome many of the current drawbacks of rotary file systems. It is based on a hollow, highly compressible file that adapts itself three-dimensionally to the shape of a given root canal, including its cross section. The file is operated with vibratory in-and-out motion, with continuous irrigation delivered by a peristaltic pump through the hollow file. A uniform layer of dentin is removed from the whole circumference of the root canal, thus achieving the main goals of root canal treatment while preserving the remaining root dentin. The 3D scrubbing effect of the file, combined with the always fresh irrigant, result in unprecedentedly clean canals which facilitate in turn better obturation. More effective disinfection of flat-oval root canals is another goal which is simultaneously attained. The safety of the root-canal treatment is also greatly enhanced by the high mechanical stability of the SAF and by using a new concept of no-pressure irrigation. The SAF System gets the operator much closer to the long-desired goal of 3D root-canal treatment.     

End-of-life communication and adjustment: pre-loss communication as a predictor of bereavement-related outcomes

Although bereavement-related emotional distress usually remits on its own over time, approximately 20% of bereaved individuals experience chronic emotional difficulties following the loss (Prigerson & Jacobs, 2001). Although several factors have been shown to be associated with poor outcomes post-loss, few studies have examined the relationship between pre-loss communication and bereavement-related depression, and none have examined its relationship to complicated grief. The present study examined how pre-loss communication between the bereaved and the deceased is related to post-loss outcomes within a sample of 60 members of online bereavement support groups. Results indicated that developing acceptance of an expected loss is strongly associated with bereavement outcomes. This finding persists even after controlling for relationship closeness and time elapsed post-loss.