Occlusion Ash Ramfjord Pdf 58
Occlusion is a word that means closure, whether it be a door or a heart valve. Dental occlusion is the contact of the maxillary and the mandibular teeth when closed. It is 1 of 3 principle parts of the masticatory system (Figure 1), which Ramjford and Ash2 described as a functional unit composed of teeth; their supporting structures, the jaws; the TMJ, muscles of mastication, and tongue; and the innervation and vascularity supplying all of them.
Occlusion Ash Ramfjord Pdf 58
The results were disastrous! The American Dental Association's Council on Dental Education had recommended that dental schools establish coordinated teaching programs in occlusion, and from 1980 to 1981, 56% of the 51 US dental schools had separate departments dedicated to this subject.4 To my knowledge, not a single one exists today. Ironically, despite the change, Mohl4 continued to use the term masticatory system in which he detailed 9 mandibular positions, 16 types of mandibular movement, and 9 different occlusal concepts. If occlusion is a term that describes the system, how can we have 9 different occlusal concepts? It is reassuring to note that in the eighth edition of the Glossary of Prosthodontic Terms,5 the definition of occlusion is limited to the closure of teeth, whereas masticatory system correctly describes all the components of the system and the associated neurologic complex. The dual interpretation of the word is responsible for much of the confusion we are seeing today.
Ideally, how should teeth touch other in closure? Does it really matter if the patient is comfortable? Over the years, I've seen of hundreds of patients with unusual jaw relationships such as class II or III, many with crooked dentitions, and those who had anterior open bites occluding only on first and second molars, and they were comfortable because they were not affected with parafunction. However, if a patient were to clench, what would be the most ideal occlusion to embrace these powerful vertical forces (Figure 13)?
When the dentition is subjected to wear and the intra-incline space is lost, there is an increase of physical stress at the dentinal enamel junction (DEJ), causing sensitivity to temperature extremes and intense flavors. From an engineering point of view, these teeth would benefit from an equilibration (reducing the incline planes of the functional cusps to recreate the intra-incline space), but it may be detrimental to the patient. In my personal practice, I have performed equilibrations for patients with uncomfortable occlusions and often found comfort to be obtained within minutes; however, for some patients, it aggravated the problem. The difference was that certain patients, despite a flattened inefficient dentition, were quite comfortable, and the equilibration caused a change in their comfort zone, and they were not pleased. In my opinion, these patients should be left alone, and guard therapy should be discussed. What about equilibration as a treatment for TMJ disorders? If a newly placed restoration is uncomfortable and initiates parafunction, which in turn creates discomfort in the joints, it is good common sense to correct the morphology of that restoration. However, the National Institutes of Health has advised against equilibration as a treatment to treat TMJ, and they are correct in their prudence, as methods and goals for equilibration might vary depending on each dentist's philosophy.11
Engineering principles for endosteal implants should be the same as natural teeth regardless of the absence of a periodontal membrane. Because there may be compromises in the placement of implants due the availability of alveolar bone, it is extremely important that the restorative dentist manipulate the occlusal surfaces of the prostheses to avoid incline plane contacts. This would ensure vertical loading on closure and avoid harmful lateral influences on clenching. Recently, a colleague associated with full-mouth implant reconstructions expressed concern that there seemed to be a percentage of breakdown after 5 years for no apparent reason. A reasonable explanation is offered; in the restoration of a semiedentulous patient with implants, deformations or wear of the patient's remaining dentition should inspire a dialog as to the awareness and management of parafunctional activities. However, if the patient is totally edentulous, the focus may concentrate solely on the reconstruction and less on parafunction, namely clenching, which chronically and painlessly takes its toll. One must consider that DCS may have been responsible for the demise of the patient's dentition in the first place. Unfortunately, a percentage of implantologists believe that implant protected occlusion,12 which is derived from mutually protected articulation5 (MPA), will ensure longevity. With all due respect, we have to rethink this. What MPA is implying is that parafunction affecting one part of the dentition is acceptable because it will alleviate trauma to another part of the dentition. It defies common sense. If this were a valid concept, there would be no need for a guard. Longevity only comes with an educated patient, impeccable hygiene, and a proper guard.
The European light dosimeter network of over 40 stations has been established in Europe and other continents equipped with three-channel filter dosimeters to measure solar radiation in three channels, UV-B (280-315 nm), UV-A (315-400 nm) and photosynthetically active radiation (PAR). The recorded data have been evaluated, and the monthly doses in all three channels show a strong latitudinal dependence from northern Sweden to the Canary Islands. There are a few remarkable exceptions such as the data recorded at the high mountain station on the Zugspitze (German Alps) and unequal doses at stations at comparable latitudes which indicate the impact of local weather conditions and mean sunshine hours. While generally peak values are recorded in the months of June and July, the UV-B maxima are shifted later into the year, which is due to the antagonistic functions of decreasing solar angles and increasing transparency of the atmosphere as the total column ozone decreases in the second half of the year for the Northern Hemisphere. This is supported by comparison with modelled total column ozone and satellite-based measurements. Also the ratios of UV-B:UV-A and UV-B:PAR as well as UV-A:PAR peak during the summer months, with the exception of the northernmost station at Abisko (north Sweden) where the UV-A:PAR ratio peaks in the winter months which is due to the specific photoclimatic conditions north of the polar circle. The penetration of solar radiation into the water column was found to strongly depend on the transparency of the water column. In Gran Canaria more than 10% of the surface UV-B penetrated to 4-5 m depth. The path of the solar eclipse on 11 August 1999 could be followed in several stations with different degrees of occlusion of the sun disk. 350c69d7ab