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Inaccuracies after underpinning of total prosthesis must be the responsibility of the technical laboratory in the first place. Six procedures were compared. Böcker's apparatus for underpinning gave the best results.
The detailed examination of the masticating apparatus of 18 skulls from the Middle Bronze Age in Pitten (Lower Austria) revealed numerous pathological findings of the teeth. Most remarkable were frequency and extent of dental abrasions. In addition to it, indications on inflammatory processes in the marginal parodontium were obtained, combined with partly immense formations of concrements on the surfaces of the teeth. The incidence of dental caries was relatively low. Abnormal positions of the teeth and pathological processes concerning the development of dentition as well as the eruption of the wisdom teeth could be observed repeatedly. Conclusions on insufficiences of the oral hygiene in this time follow especially from the concrement findings and from the inflammatory reactions of the marginal parodontium.
Perception of stability of the visual world and control of ocular fixation and tracking are altered in subjects submitted to high frequency vibration. Studies of the eye movements induced in man by passively rotating the head sinusoidally around a vertical axis show that beyond 8 Hz, the amplitude of the eye movements increases and reaches 2.5 times the amplitude of head movement at 30 hz. The high amplitude eye oscillation may, at least in part, explain the perception of visual world instability and the decrease of visuo-oculomotor system performance in man submitted to high frequency vibration. Two interpretations of this phenomenon have been proposed (9). High amplitude eye movements induced at high frequency may be due to either a non-linearity of the vestibulo-ocular reflex (VOR) or mechanical resonance oscillations of the orbital apparatus. To test these hypotheses, baboons were trained to fixate visual targets. Each animal's head was rigidly attached to a rotating frame through a block of dental cement bolted to the skull. Head rotation was produced by a servo-controlled vibrator. Rotations in the frequency range 1 to 20 Hz were successively applied with the animal in darkness or fixating a stationary target. The results showed that gain curves obtained with baboons are similar to those obtained with man. Paralysis of the muscles of one eye by injection of lidocaine disclosed a behavioral asymmetry of the two eyes at low frequency. The paralysed eye showed no movement below 8 Hz, while the normal eye behaved as in the normal situation. Beyond 8 Hz, the gain of the treated eye increased gradually so that beyond 12 Hz, the two eyes responded.(ABSTRACT TRUNCATED AT 250 WORDS)
To find out whether adhesive techniques could have a role in bone fixation in selected cases an in vitro comparison between the current 'Champy' miniplate system and bonded stainless steel was undertaken using cyanoacrylate or dental composite cement. 33 bovine ribs were sectioned to simulate fracture separation, divided randomly into three groups, and immobilised by one of the three treatments. Distraction across the 'fracture' was produced using a universal testing apparatus, and forces at failure were recorded in Newtons (N). Image analysis enabled the contact area of the adhesive to be determined in mm2, so the bond strength in N/mm2 was derived. The Champy system failed at a significantly greater force (N) than the adhesives (p = 0.000). There was no significant difference in bond strength between either of the adhesive systems tested.
Clear thermoplastic retainers are an alternative to fixed lingual retainers and removable Hawley appliances. However, thermoplastic retainers have demonstrated poor wear resistance and durability after only a few months of use. In this study, a simulated wear device was used to compare the wear of different thermoplastic materials used for orthodontic retainers. Three thermoplastic products were evaluated: C+ (Raintree Essix, New Orleans, La),.040-in Invisacryl C (Great Lakes Orthodontics, Towanda, NY), and.040-in TR sheet material (Bay Dental Direct, Bay City, Mich). Twenty specimens were fabricated for each group. The specimens were vacuum thermoformed according to the manufacturers' recommendations and subjected to wear for 1000 cycles in a wear apparatus with steatite ceramic abraders. Depth of wear was determined by surface profilometry. The maximum peak-to-valley measurement was recorded for each specimen. Mean wear (SD) in microns was as follows: C+, 5.9 (2.4); Invisacryl C, 6.1 (2.6); and TR, 1.6 (0.9). One-way analysis of variance detected a significant difference between groups (P <.001). TR material, a hard polyethylene terephthalate glycol copolymer (PETG), demonstrated greater resistance to wear than did the other 2 materials, which were softer, polypropylene-based thermoplastics. There was no evidence to suggest a difference in mean wear between the 2 polypropylene-based materials (P >.05).
The interface between oral tissues and ceramic endosteal dental implants was investigated in 36 experimental cases in dog jaws. Conventional electron microscopic modalities showed those tissues adjacent to the implants to be viable with no adverse cellular response to the biomaterial. A procedure to retrieve additional ultrastructural data from previously processed biological material was developed to expand upon these data. This included surface-etching with oxygen plasma of routinely processed electron microscopy specimens and formalin fixed histological specimens for scanning electron microscopy (SEM) study; and, cryofracturing of similar histological specimens for additional transmission electron microscopic (TEM) analysis. Results from these alternative protocols supported our observations from conventional studies of the direct association of bone and epithelia to the implant. In addition, they demonstrated a unique portrayal of the epithelial maturation patterns. Further, this alternative TEM method showed excellent retention of cellular integrity and demonstrated a hemidesmosomal-external basal lamina attachment apparatus at the junctional epithelial-implant interface. This latter composite attachment structure was not retained in our previous conventional microdissection procedures. Thus, the interface between oral tissues and the single crystal sapphire endosteal dental implant could be elucidated by these protocols.
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During cap enameloid formation in gars (Lepisosteus oculatus), the dental epithelial cells that constitute the enamel organ were observed by means of transmission electron microscopy and enzyme cytochemistry to detect the hydrolytic enzyme activities, alkaline phosphatase (ALPase), acid phosphatase (ACPase), calcium-dependent adenosine triphosphatase (Ca-ATPase) and potassium-dependent p-nitrophenylphosphatase (K-NPPase) (sodium, potassium-activated adenoshine triphosphatase (Na-K-ATPase)). The enameloid formation process in gars was divided into three stages: matrix formation, mineralisation and maturation. The enamel organ consisted of the outer dental epithelial (ODE) cells, stellate reticulum (SR), stratum intermedium (SI) and the inner dental epithelial (IDE) cells during the whole of the cap enameloid formation stages. During the matrix formation stage, many cisternae of rough endoplasmic reticulum and widely distributed Golgi apparatus, in which the procollagen granules containing cross-striations were often found, were remarkable elements in the IDE cells. During the stage of mineralisation, the IDE cells were tall columnar, and infoldings of distal plasma membrane of the IDE cells became marked. The most developed Golgi apparatus was visible at this stage, and large secretory granules containing fine granular or tubular materials were found in the distal cytoplasm that was close to the infoldings of the distal end. Many lysosomes that were ACPase positive were seen near the Golgi apparatus and in the distal cytoplasm of the IDE cells. ACPase positive granules often contained the cross-striation structure resembling procollagen, suggesting that the procollagen is degenerated in the IDE cells. During the maturation stage, the distal infoldings became unclear, and there were no large granules containing tubular materials, but many ACPase positive lysosomes were still present in the IDE cells. Non-specific ALPase was detected at the plasma membrane of the IDE cells at the mineralisation and maturation stages. K-NPPase was markedly detected at the plasma membrane of the IDE cells at the maturation stage. These results demonstrate that the IDE cells might be mainly involved in the removal of degenerated organic matrix from enameloid during the later formation stages. Strong Ca-ATPase activity was observed at the entire plasma membrane of the stratum intermedium cells, and there was slightly weak activity at the plasma membrane of the IDE cells during the mineralisation and maturation stages, implying that these cells are related to the active Ca transport to the maturing enameloid. It is likely that although the structure of the enamel organ is different, the function, especially at the mineralisation and maturation stages, is similar to other actinopterygians having well-mineralized cap enameloid.
It is probably true to say that the masticatory apparatus attracts proportionally greater attention than any other part of the body. Evidence that this is so is provided, not only by the degree of specialisation within the dental profession, but by the frequency with which references to teeth and dentistry crop up in literature. Generations of biographers, novelists, poets, playwrights and essayists have written about their dental experiences and included the dentition in describing the facial appearance of characters, factual and fictional. The literary extracts in this article, culled from an extensive collection, refer to orthodontics. They provide a fascinating insight into the patient's perspective on that speciality and make entertaining reading.
In many respects international sportsmen are trendsetters for the behaviour of recreational sportsmen. For this reason the attitude of international hockey players towards mouth protectors was studied. The possession and use of mouth protectors vary markedly between different countries. The incidence of dental-facial traumas among international field hockey players is high; 54% had sustained injuries necessitating a visit to a physician and/or a dentist. Of these victims 20% sustained serious dental damage at least once (women 16% and men 22%). Only 20% of the international players wear a mouth protector consistently during training and matches. Women use the apparatus almost twice as much as men. The main argument in rejecting a mouth protector is that it is not felt to be necessary.
The chief progress of maxillofacial surgery in recent years has been the preservation and the retention of functional tissue. The recent advances in microvascular and reimplantation surgery are examples. Similarly the preservation of the masticatory apparatus is best served by the retention of all viable components. Additional benefits derived from this approach include the facilitation with alignment of the bony fragments, proper occlusion of the teeth and maintenance of the vertical relationship between the upper and lower jaws; in addition to the restoration of appearance and the functions of mastication and speech. Although injuries of the teeth and their supporting stuctures at first glance may seem to be simple problems, frequently they turn out to be complicated. The most common injury is partial avulsion of the alveolar bone with loss of attached teeth, which may produce a severe defect in the jaw bone. During healing there is additional resorbtion of alveolar bone, which is quite a normal physiologic phenomenon. Therefore, the eventual defect is likely to be more severe yet. For this reason more concern should be shown for these lesser injuries.
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