Comparison of the cutting efficiency of two ultrasonic units utilizing two different tips at two different power settings

The objective of this in vitro study was to set up a testing protocol and utilize it to evaluate and compare the cutting efficiency of ultrasonic units. Evaluation of two ultrasonic units utilizing two different tips was done by measuring the weght of a dentin specimen before and after ultrasonic treatment for set time periods. The difference in weight was the amount of dentin removed. The ultrasonic units tested were the P5 Booster (Staelec, France) and the Spartan (Obtura-Spartan, Fenton, MO) machines. The tips tested were the CPR-2D and ETD20 types. The units were tested at maximum and medium power. All the experimental variables, ultrasonic unit type, power setting and tip type were found to have an effect on the cutting efficiency (P<0.0001). The P5 ultrasonic unit was more effective at dentin removal than the Spantan ultrasonic unit at both power settings. The ETD-20 tip was more effective at dentin removal than the CPR-2D tip on both units at both power settings.     

The effectiveness of two sonic and two ultrasonic scaler tips in furcations

This study compared the effectiveness of two sonic and two ultrasonic scaler tips on artificial calculus removal from the furcations of mandibular first and second molars. Twenty-four extracted mandibular molars were cleaned and randomly assigned to one of four treatment groups. Teeth were split buccal lingually, artificial calculus was placed in the furcation areas, and the teeth were photographed with a stereo camera. Teeth were reconnected with bonding material and mounted in a typodont with simulated gingiva and attached to a dental chair. Teeth were instrumented with either a Cavitron TFI10 tip, Cavitron EWPP tip, Titan-S Universal tip, or Titan-S Sickle tip by a licensed dental hygienist until each tooth was judged calculus free to the touch with a CH3 explorer. Time for each instrumentation period was recorded. Following instrumentation, the teeth were again split and photographed. Stereophotogrammetry was used to produce tracings of the teeth with initial calculus and remaining calculus. Pre-instrumentation and post-instrumentation amounts of calculus on the surface area were computed using the Bioquant system. A two factor analysis of variance was conducted followed with a Newman-Keuls Multiple Comparison Technique to test for within and between differences. Significant differences (P less than or equal to 0.01) were found between pre- and post-amounts of calculus for all tips. No significant differences (P less than or equal to 0.05) were found between the four instrument tips with respect to percentage of furcation surface with calculus remaining. No differences were found between tips with regard to the time required to clean the test surfaces.     

Managed care--serving two masters

It is likely that enrollment in managed care dental plans will continue to increase. Dentistry can respond to this trend by resisting it; however, just as the health care marketplace drove medical care into managed care mechanisms, so too will these forces impact dentistry. For those who are participating in managed care dental plans, it is heartening that current data indicate that most types of patient care are not adversely affected by reimbursement mechanisms. Dentistry, however, should seek out opportunities to shape the managed care format and must be at the table to assure that ethical principles and conflicts of interest receive due consideration. Dentists who treat patients under a managed care reimbursement system must be certain that the plan does not require providers to sacrifice patient autonomy or compromise care in the process of serving two masters.     

Epignathus: two cases

Epignathus is a rare congenital nasopharyngeal tumour that is derived from the upper jaw, palate, and sphenoid bone. It usually protrudes through the mouth, leading to an appreciable risk of obstruction of the upper airway and death soon after birth. We report two cases of unusual presentations that illustrated some uncommon and similar characteristics. Although these tumours are not consistent in origin, number, and differentiation of tissues, both contained structures that were derived from all three layers of germ cells, including different anomalous tissues internally (dental bud, fat and muscular tissues, mucosal epithelium). Externally, they contained normal epidermis (skin with fine hairs). Imaging studies and operative findings showed that both tumours originated from the anterior portion of the sphenoid bone causing a sphenoidal sinus cleft without intracranial communication.     

Maxillary removable prostheses retained by telescopic crowns on two implants or two canines

Precision telescopic attachments allow for rigid connection between removable prostheses and abutments. However, it is still unknown whether implants can bear similar long-term loading forces as teeth when telescopic crowns are used as retention devices. It was the aim of this prospective clinical study to observe maxillary removable partial dentures that were retained by telescopic crowns on two endosseous implants in the canine regions. In a control group, identical dentures were fabricated that were retained by telescopic crowns on the maxillary canines. The implant group consisted of 14 patients, and the control group included 8 patients. Mean observation time of the prostheses was 25.6 months. Radiographic bone levels and periodontal parameters did not reveal specific differences between the two groups. However, five implants failed, and there were no failures in the control group. Survival rates were 48.9% for the implant group and 100% for the control group, with a significant difference between the two groups. Within the limits of this study, it is concluded that the telescopic connection might be too rigid (thus delivering overloading) for two single implants in the canine region of the maxilla supporting a removable denture.     

2种根管封闭剂对2种纤维桩剪切粘接强度的影响

目的 研究2种根管封闭剂对2种纤维桩固位力的影响.方法 将28颗完整离体上颌中切牙截冠、逐步后退法预备根管,按采用的根管封闭材料及纤维桩不同分为4组:Cortisomol封闭剂+Matchpost纤维桩(A组),Cortisomol封闭剂+Macrolock纤维桩(B组),Guttaflow封闭剂+Matchpost纤...     

Maxillary permanent incisors with two root canals: a report of two cases

The root canal treatment of permanent maxillary incisors with two root canals is reported. Two cases are presented, one success and one failure, with discussion regarding the different outcome, highlighting the need for careful radiographic investigation and patient management.     

Quantitative evaluation of marginal leakage of two resin composite restorations using two filling techniques

This in vitro study evaluated the marginal leakage of two light-cured resin composites used for posterior restorations using two filling techniques. Standardized Class V cavities were made on the enamel vestibular surface of 30 freshly extracted sound inferior bovine incisors. The teeth were randomly restored according to three experimental groups (Group 1--Z250 with 1 mm vertical increments; Group 2--Z250 with 1 mm horizontal increments; Group 3--SureFil with 1 mm horizontal increments). All samples were thermocycled (3000 cycles at 5 degrees C and 55 degrees C) with a dwell time of one minute at each temperature and immersed in a dye solution for 12 hours. After being ground into powder, the samples were individually immersed into glass tubes with absolute alcohol. The solution was centrifuged and the supernatant was analyzed using a spectrophotometer to quantify its dye concentration. Results showed that Group 2 exhibited the lowest leakage means, which was significantly different from Groups 1 and 3 (p<0.05). It was concluded that despite the lower leakage means exhibited by medium viscosity composites, no restorative material or filling technique was able to avoid leakage.     

Endodontic treatment of mandibular incisors with two root canals: report of two cases

The root canal anatomy of mandibular incisors can present a number of variations, including multiple canals. Two case reports are presented to illustrate the serendipitous discovery and successful non-surgical endodontic management of complex canal systems in mandibular incisors. In both cases, all four mandibular incisors had two canals each.     

Effect of two dentin bonding agents on microleakage in two different cavity designs.

Studies have shown that cavity design and dentinal bonding agents can affect composite resin microleakage. This study compared the microleakage at cementum-dentin margins of box- and Vshaped preparations restored with two different bonding agents. Twenty freshly extracted, human third molars were prepared with one box-shaped and one V-shaped preparation on the mesial or distal surface. Occlusal margins were terminated in etched enamel and gingival margins were in cementum-dentin. There was no statistically significant difference (p greater than 0.05) between Dual Cure Scotchbond and Scotchbond 2 samples restored in the box-shaped preparations, but Scotchbond 2 had statistically significantly less microleakage (p less than 0.05) than Dual Cure adhesive in V-shaped preparations. The sealing of dentinal bonding agents varied in different cavity designs.     

Bond strength of three porcelains to two forms of titanium using two firing atmospheres

STATEMENT OF PROBLEM: Problems with casting and porcelain bonding are encountered when titanium is used in metal-porcelain restorations. The oxidation characteristics of titanium are the main problem. The bonding mechanisms in titanium-porcelain systems are complex and poorly understood. PURPOSE: An in vitro investigation was performed to evaluate the bonding characteristics of 3 titanium-porcelain systems in various firing conditions. MATERIAL AND METHODS: This study evaluated the bonding strength of 3 commercial titanium porcelains fired in a vacuum and in an argon atmosphere to cast and noncast commercially pure titanium, using a 3-point bending test according to DIN 13927 and SEM with energy-dispersive spectrometry analysis. The results were compared with an Ni-Cr alloy and a conventional porcelain that was chosen as a control. RESULTS: The Ni-Cr-conventional porcelain system fired in an argon atmosphere had significantly higher bond strength than the other systems (P<.001). In addition, the bond strength of the titanium-spark erosion-Noritake Ti22 combination, fired in an argon atmosphere, was significantly higher than the other titanium-porcelain groups, which had results similar to those obtained with the vacuum-fired, Ni-Cr-conventional porcelain and argon-fired titanium-cast-Noritake Ti22 groups. On the other hand, the bond strength of the titanium-TiBond and titanium-Vita Titankeramik groups was below the lower limit value in the DIN 13927 standard for the 3-point bending test (25 MPa). Although the results of the Duncan multiple range test showed that firing in an argon atmosphere did not affect the bond strength of the titanium-Vita Titankeramik groups, the titanium-spark erosion-TiBond group, or the titanium-cast-Noritake Ti22 group, argon firing improved the bond strengths of the Ni-Cr-conventional porcelain group, the titanium-cast-TiBond group, and the titanium-spark erosion-Noritake Ti22 porcelain group. It was also found that there were no significant differences between the bond strengths of cast and non-cast titanium groups; an exception was the titanium TiBond groups in which the porcelain was fired in a vacuum. CONCLUSION: The oxide layer produced on titanium was considered to have a potentially adverse effect on titanium-porcelain bonding. It was also concluded that matching the titanium-porcelain combination is the main determinant for optimal bonding. Firing in an argon atmosphere that limited the oxidation of titanium improved the titanium-porcelain bond in some of the groups.     

下颌尖牙双根双根管1 例

下颌尖牙一般为单根单管,作者碰到1 例双根双根管型下颌尖牙.据观察,该牙颊、舌侧根的大小基本一致.测量其颊、舌侧根的长度,分别为24.5、 23.0 mm.想要成功施行牙髓病治疗,临床医师应意识到下颌尖牙解剖变异的可能.     

Talon cusp in two siblings

Talon cusps were observed in a 10-year-old boy and his 12-year-old sister. Although the sister's affected tooth was asymptomatic and free of any occlusal interference, the boy's tooth presented some problems. The affected tooth had displaced the occluding mandibular tooth lingually, and this had resulted in a mid-line shift. To overcome the problem, the talon cusp was ground off and a prophylactic odontotomy performed. Orthodontic treatment was later carried out.