Les Cahiers de prothese最新文献

Primary impressions in full dentures are too frequently considered of lesser importance. The method described in this article gives much credence to the precision of these impressions, the quality of which is largely guaranteed by the final success of the denture construction. Several steps are required: anatomical investigation of the area using a heavy silicone; making of personalized impression (PEP) with correction depending on the area and the clinical observation; primary impressions including impression of the physiological borders with an adapted silicone material; furthermore, pre-estimation of the intermaxillary relationships and recording of the lip line with a material designed for this purpose. Once this stage has been completed, the practitioner already has at his/her disposal particularly valuable information; the primary impressions with borders registration; approximative occlusal relationships; volume of the future denture and the lip line. Now, an individual tray can be made by the dental technician, which will be really adapted to the clinical case.

There are many differences between full dentures on Brånemark implants and fixed partial dentures built on the same type of implants: due to some more critical anatomical conditions, the choice of number, position and length of the implants is more delicate; the need of an harmonious crown-gingival tissue relationship; higher occlusal forces than in edentalous cases; difficulty in satisfying aesthetic requirements and ease of hygiene. The surgical treatment plan, a pre-requesite to any surgery, permits to determine the length of implants, their number, their position, their long axis direction and the design of the surgical guide, which will indicate to the surgeon the location and the axis for drilling. If this axis is nearly parallel to the sagittal plane for mandibular implants, it will be angulated to that same plane for maxillary implants. In the latter cases, it is often necessary to use angulated transepithelial abutments in order to prevent the abutment screw from having an occlusal access. In order to perform the prosthetis, an impression should be taken with the transepithelial abutments. The final reconstruction can be preceded by a temporary prosthesis, then (or) transitory to await gingival stabilization and not overload the implant immediately after it has been connected with the abutment. The fixed partial denture can be secured with screws or cemented when it is of small size and it must satisfy the functional and aesthetic requirements of the patient. The choice of the material used on the occlusal surface is very important and varies depending on the case. Aesthetics should not be prevent an in easy hygiene. These objectives are not reached at the time the prosthesis is made but during the course of the surgical and prosthetic treatment. Single restorations are subjected to the rules pertaining to any fixed partial denture on implants, but have particular characteristics, such as the almost systematic elimination of the abutment and the absolute necessity of the correct placement of the implant. The single units are more easily subject to unscrewing for mechanical reasons. Although the use of implants is a valuable aid in cases of partial fixed restoration, it requires particular attention with regard to precision.

During the last decade, the concept of an effective, even steep anterior guidance did evolve toward the description of a "kinder" or "softer" anterior guidance which, while ensuring the disclusion of the posterior teeth, leaves some anterior functional freedom. It then becomes necessary to determine more precisely the criteria for diagnosis, orthodontic treatment, prosthetic restoration of anterior functional surfaces. In order to reveal some functional agreement between an anterior and posterior guidance, the analysis of the functional morphology of antero-maxillar teeth in relation to their skeletal context was proposed, in a study of 33 cases, so as to correlate the condylar steepness measured by axiography. It should be noted that a decreasing gradient exists between the mean respective values of the functional slopes of the central incisors (S1 = 64.3 degrees), and lateral incisors (SF1 = 53.5 degrees) and the canine (Cf = 51.8 degrees). Although the cingular surface S1 does not appear to have any influence on the posterior guiding factor (r = 0.1), in fact the anterior functional surface which is stategic in mastication, is located on the occlusal surface of the palatol side (S2) of the antero-maxillary teeth. The correlation is significant (r = 0.325) when the anterior guidance (incisives and canines) is associated to the mean condylar value more than being correlated to the mean functional value of the central incisor alone. It thus appears logical that the functional modeling of the articular cavities be influenced by the overall anterior guidance and not by the single central incisor. It has also been possible to emphasise the influence of the orientation of the occlusal plane in the anterior functional relationship (r = 0.547); thus, the anterior guidance appears to have to be assessed over a "relative overall analysis": overall: meaning the overall anterior guidance, i.e. the six anterior maxillary teeth; relative: meaning measured in relation to the occlusal plane. This concept of relative overall analysis of the anterior guidance, developed using a simple computerised program, will allow the diagnosis and anterior prosthetic or orthodontic restoration to be facilitated.

The knowledge of the biomechanical principles of position, relation and function of the anterior teeth must be used in the study of their diagnosis and restoration. The method presented here allows the simple use of functional characteristics to propose a diagnosis and ensure the restoration of the anterior guidance. The instrument necessary to achieve this goal--the C.C.F.--is easy to use with any articulator whatsoever; the non-arcon instruments nonetheless require a particular adaptation. Mounting and use of the C.C.F. are shown. In addition, the essential stages of guidance wax-up is explained. It is important to be attentive to changes in anterior teeth long axis directions, in the case of dento-maxillary dysmorphosis.

Cases of multiple agenesia present some difficulties in the treatment planing. Three situations may be encountered: limited agenesia, restored by a fixed, bonded or cemented prosthesis, multiple uni- or bimaxillary agenesia without remaining of deciduous teeth, restored by a fixed, bonded or cemented prosthesis or the partial adjacent prosthesis, multiple uni- or bimaxillary agenesia with remaining of deciduous teeth, restored by means of a supra-dental prosthesis. The first two situations have been described in dental literature and are relatively easy to treat. The same is not true for the third situation, where the decision to keep the temporary teeth considerably increases the difficulty of prosthetic restoration. This subject will be illustrated by the presentation of a clinical case of multiple bi-maxillary agenesia. The patient has: on the maxilla: an absence of 9 permanent teeth (18, 15, 14, 12, 22, 23, 24, 25, 28) and the presence of 4 deciduous teeth (62, 63, 64, 65), on the mandible: an absence of all permanent teeth, with the exception of 36 and 46, and the remaining of 4 deciduous teeth (75, 73, 83, 84). The remaining of deciduous teeth and the presence of a very high inter-arch space led to opting for dental coverage so as to keep the deciduous teeth and a proper vertical dimension. The patient wished to solve his "problem" in the maxilla first, and is not wanting to undergo the extraction of his deciduous teeth. The following therapeutic proposal was adapted: On the maxilla, a three-step procedure: first step: building of metal copings on 13, 16 and 26 and metal-ceramic crowns on 11 and 21, second step: building of telescop crowns on 16 and 26 and clasps on 13, 11 and 21, third step: casting of the removable partial denture framework and soldering to the telescop crowns and clasps. On the mandible, a provisional restoration using a supra-dental resin removable partial denture with ceramic occlusal surfaces was adopted. The aesthetic and functional improvement, as well as the comfort provided to the patient due to this kind of mixed prosthesis, appeared to be satisfactory.

In elderly patients, recurrent fractures of the lower denture must raise the question of a neurological deficit as cause of the occluso-prosthetic imbalance. Hypotonicity of the peri-oral mastication musculature, especially the masseters, may explain the alteration of the prosthetic supporting surface due to shriveling of the mandibular arch, along with an osseogenesis at the point of flexion of the mandible. The rest and activity muscular imbalance, resulting from unilateral mastication, may cause lingual dysfunction and deviation of the tongue at rest. If this problem is not controlled within an acceptable period of time, one should expect psychological, biological and physiological consequences affecting the patient's physical condition. The restoration of the denture fracture is insufficient. Reconditioning must be performed in order to replace the existing prosthesis in the patient's function, allowing him/her to recover a normal psychological, biological and physiological balance. In conclusion, in geriatric dentistry, the objective of reconditioning is, not only to restore a functional occlusion, but also the psychological, biological and physiological balance of the patient. This is an unvaluable advantage, especially if this contributes to maintain or restore an often precarious health.

Implantology, very frequently presented under only the surgical angle, must in fact be approached from a biological and functional point of view. The analysis of the future prosthetic situation will allow an overall treatment scheme to be established, in which periodontics, surgery, prosthodontics and occlusal equilibration will follow each other in order to achieve the functional rehabilitation. In the first part of this article, the various steps which make up the treatment scheme are briefly and quickly described. It is imperative to approach them according to this chronological order when there is any treatment involving implants. While implantology involved only one surgical session a few years ago, it now involves two: the first, consisting of placing the implant in the living tissues, and the second, at some months interval from the first, allowing the endo-osseous portion to be attached to the future prosthesis. These two surgical acts are inter-dependent. Given the wide array of systems proposed and the quantity of "Implant-Prosthesis" connections produced in each system, the practitioner does not always know which kind of connection to choose or how to use it. The second part of the article is devoted to the study of the various connection possibilities between the Steri-oss implants and the prosthesis. The methods for lining up the cores in relation to the others are studied in detail, as are the different possibilities for stabilising removable prosthesis. Some of the methods described can be used with other implant systems.

Success in acid-etched dentistry essentially depends on the quality of the adhesion. The bonding session must be carried out with the upmost rigour. The operative field will permit good protection against humidity (saliva, bleeding, gingival fluid, breathing), as well as good instrumental and visual access for finishing. Three different methods are available: retraction (retraction cords), isolation (rubber-dam, "contour strip"), and retraction + combined isolation (thick rubber-dam + suture; mini rubber-dam + suture. The indications depend on the localization in the mouth and the kind of restoration. It is thus necessary to classify the methods so that the selection of the operative field will be simple to work in, quick and systematic. The impossibility of isolating the surfaces to be bonded and to have an access to the margins must be an absolute counter-indication of this technique.

The goal of any prosthesis should be to restore the function of the masticatory system with occlusal stability and good esthetics. Even with fixtures, the prosthetic achievement must tend toward the final goal: the position of the prosthetic teeth. Therefore the prosthodontist must indicate to the surgeon the optimal sites for the fixtures. The link between the prosthetic team and the surgical team is the surgical template used not only during the installation of the fixtures, but also during the C.T. scan examination and for the localization of the fixtures after the healing period. The fabrication of the resin surgical template made from a wax up of the future restoration, with, if necessary, titanium rings at the location of the teeth necks, is presented in this article. This type of surgical guide is a versatile device allowing a better approach of the optimal prosthetic tooth localization all along the different periods of the surgical treatment. A better result is then obtained by the collaboration of the surgical and prosthetic teams, for the benefit of the patient.