Les Cahiers de prothese最新文献

In this paper the occlusal reduction for a single crown is studied. After a brief description of the classical techniques and usual instruments, an analysis of the different malocclusions demonstrates that the reduction has to be made in accordance with each individual case. Afterwards, the author presents a new diamond with an original profile which shows a concave working side limited by two spherical parts. With this profile an ideal prepared occlusal surface can be obtained with only one passage of the bur. The preparation of the occlusal surface with this instrument is then analysed step by step, showing how a real sculpture of this surface can be achieved rapidly and with ease. A clinical case demonstrates the results.

The loss of a maxillary incisor is traditionally treated with a three-unit bridge. The progress made in dental implantology since the demonstration of osseointegration by Brånemark and al. allows the overall replacement of the missing tooth. Furthermore, the use of osseointegrated implants makes the replacement of a single maxillary incisor reliable and aesthetic, even in cases of moderate gingival and bone recession. In respect of the rules set forth by Brånemark and al., it is essential to make a wax-up and a surgical stents. For anterior teeth, the single tooth abutment marketed by Nobelpharma allows the aesthetic margins of the prosthesis to be placed in a sub-gingival position. Once this component is positioned on the fixture, the achievement of the prosthesis is practically identical to traditional metal ceramic crown. The abutment is maintained on the fixture by a screw which can be easily removed and avoids an excess of subgingival cement. Nonetheless, its diameter means that it is reserved for relatively wide teeth. This type of treatment involves the development of a reliable and proven surgical planning for bone grafts, especially in cases of facial traumatism.

Balanced occlusion is the occlusal concept used in full dentures. In this article, which describes the technique for mounting teeth according to LUDWIGS, the authors present a very typical equipment (guide punch, tooth guide, positioning and mounting plates...). This provides the dental technician with all the possibilities to create occlusal curves which are individualised for each case in order to achieve a balanced and rational mounting of artificial teeth.

In the technique described, the search for the peripheral joint and the final impressions are really functional and rely on adapted silicone impression materials. The vertical dimension is investigated physiologically (speech/swallowing). The recording of the centric relation is confirmed graphically with a centric pin. Thus, the patient transcribes his "occlusal signature" and provides both the practitioner and the dental technician with precise data for the mounting of denture teeth.

The complexity of this type of restoration comes from the numerous clinical and laboratory steps required. Achievement of these prosthodontic restoration is based on a careful clinical examination, models mounted on an articulator, in centered relation and adequate vertical dimension. The models allow the surveyor examination, the teeth set up and/or wax up. Duplication of the teeth set up in acrylic will reduce the number of patient's appointments, and thus, the potential errors will be minimized. This acrylic teeth set up (A.T.S.) will allow: to keep the decided occlusal relationships; to visualize the teeth grinding to be made; to guide the tooth preparation; to take the abutment impression, in occlusion. Therefore: the final model; the vertical dimension; occlusal relationship; the aesthetic; and, the removable partial denture design will be available for the dental technician. Furthermore, in close to full denture cases (class I and large class IV), the A.T.S. can be used to take the impression, to achieve the framework, and to transfer the occlusal registration.

Numerous core composites are used to reconstruct abutments for fixed partial dentures. The preparation is carried out with various type of burs. The purpose of this study is to facilitate the choice among them. Six chemical composites, one glass ionomer cement and two light cured composites have been selected. Calibrated samples have been made, divided into four series and prepared with six different burs used for fixed partial dentures, three of them as finishing burs. In the first part of the investigation, the samples were examined with a S.E.M., in order to visualize the surface texture. According to the materials used, variations may exist. In the second part of the investigation, a tridimensional study was performed using a mechanical scanner microscope which permitted the quantification of some roughness characteristics, thus, an objective comparison of the surfaces became possible. Due to the complementary nature of the two investigation techniques, a protocol is presented for the study of burs instrumentation and prepared tooth surface.

The purpose of this study is to compare the masticatory efficiency and the physiological activity of masticatory muscles among patients with removable partial dentures (R.P.D.) and patients with natural dentition. The masticatory efficiency is assessed from the duration of chewing sequences for various foods, from the first masticatory cycle to the swallowing. The physiological activity is tested by the duration of the inhibition reflex called the "silent period" (S.P.) obtained upon each muscle examined: 29 subjects are examined, 24 of them had a R.P.D.; they were divided into four groups according to the extent of their edentation; 5 control subjects have full natural dentition. The study is performed using global electromyography of the two masseter muscles and the two anterior temporal muscles. The mastication of the control subjects appears to have a regular alternance of working potential and periods of rest. The duration of the chewing sequences is determined by the nature of the food, brief for soft food, long for hard food. The mastication of patients with R.P.D. appears more irregular with a lengthening of active phases. The duration of chewing sequences is significantly longer for the control subjects. The duration of the S.P. is 19-21 milliseconds for the masseter muscles of the patients with dentures and the control patients, and 20-22 milliseconds for the temporal muscles for the same individuals. The differences of the S.P. durations between control subjects and patients with R.P.D. is never significant.(ABSTRACT TRUNCATED AT 250 WORDS)

The pre-surgical investigation may provide added information by the wearing of a detection cad-can indicating the axes of the future implants at the time of the cad-can examination. This stent is made, using a polymerised director mounting, equipped with radio-opaque detectors in aluminium or zinc oxyphosphate sealing cement. The resulted illustration facilitates the concentration between the surgeon and the prosthetist in the definitive choice of the site of implantation. The plaster model, used for the making of the detection cad-can, is used to transfer this information. In the clinic, the latter is supported by a surgical stent. This guide includes: an indexed stabilising portion on the remaining teeth or portions of edentated crest not involved in the surgery; guiding tubes with a diameter of 2.1 mm, made of infiltrated aluminium according to the INCERAM* procedure. The detection cad-can and surgical stent unit permit a correlation between the preimplant investigation phase and the surgery.

Further to some reminders concerning terminology and resorption, this article presents the full denture prosthetic treatment for two patients with total edentation and a prognathic malocclusion. The first case presents a tridimensional symptomatology, described by: a progeny; a voluminous mandibular terrain; a concave profile; a rather closed mandibular angle; a mandible ridge which circumscribes the upper jaw; The particularities of the prosthetic treatment in this case are: a lowering of the posterior occlusal plane; a mounting of the teeth in a limited external position, that is to say, the maxillary lingual cuspids and the mandibular mesio-distal groove on the inter-crest line; the mandibular incisors and cuspids placed with a lingual inclination to obtain an edge-to-edge occlusal contact. The second case is of vertical symptomatology type, described by: a macrogeny; a moderate concavity of the profile; a very marked increase of the vertical dimension; an open mandibular angle; a short ramus; a long mandibule; a very marked overjet between the anterior crests. The particularities of the prosthetic treatment for this case are: a posterior teeth placement, avoiding cross-bite position, taken into account the strong convergence of the intercrest lines; a strong lingual inclination of the mandibular incisors and cuspids, in order to obtain an edge-to-edge occlusal contact. In the light of these two specific cases, emphasis is placed on the particularities of the treatment and on the teeth placement proposed in order to avoid any cross-bite teeth mounting.

The long term success of any bonded prosthesis mainly depends on the quality of the marginal adaptation. Its degradation has been noted both at the clinical and the experimental levels. It may be due to biological, chemico-physical, mechanical and clinical factors. Improving the marginal gap closure is based on some principles: the type of preparations on which depends the stabilisation and the good positioning of the restorations; the quality of the clinical isolation which will avoid any humidity on the bonded surfaces (saliva, blood, gingival fluids); the chemical and physical type of the bonding polymer and the quality of its polymerisation; the finishing and final surface condition directly related to the kind of finishing burs used. The understanding and application of these few clinical principles enable the practitioner to expect a better clinical result as regards the bonding of aesthetic restorations.