Prosto lec 4 IntroductionIn this lecture we are going to talk about the main principles of making and fabricating CD and they include: stability, support and retention. All of these we work to attain them to have the best fabricated denture we can make.SupportDef: It is the resistance of vertical forces of mastication, occlusal forces and other forces applied in a direction towards denture bearing area** bearing area differs for mandible than maxilla where the avg of bearing area in maxilla denture is 24 sq.cm but in mandible denture it is 14 sq.cm To increase the support there is things must be done and they are 1 to achieve the maximum coverage which will distribute the forces all the way over the bearing areas and reduce the amount of the forces and stress on the non bearing areas (snowshoe effect) but maintain the function and location of the supporting tissue 2 do a special physiological type of border molding to the patient 3 make a good space inside the tray for the final impression material 4 do a special relief by wax not complete one but the partial one for both upper and lower as u did in the lab while making the special tray 5 use the best impression material that you find it suitable to work with depend on the situation 6 insert the tray in a proper way inside the patient mouth to reach the best benefit in recording things 7 final impression material and the tray material must be stable and dont undergo any changes to help in making the best of the best 8 the final impression should be highly detailed coz the shape of it will be the same as the denture that will be fabricated 9 always in the final steps be accurate while fitting the trays and taking impression coz it is the final perfect steps that will denture will depend on itRetention Def: quality inherent in the denture that resists the vertical forces of dislodgement ** The forces that may affect retention of the CD are: 1force of gravity (especially maxillary) 2 the adhesiveness of food (sticky food that will remove CD from place)3 forces of the opining of the jaw (include muscle work and lips and other things)

The factors that affect the retention and make it more are 6 categories and they are:1 anatomical factors 2 physical factors 3 physiological factor 4 mechanical factors 5 surgical factor 6 psychological factor** Anatomical factors: things related to the anatomy of the upper and lower jaw either themselves or if there was anything to be done to them and they include:1 the maximum coverage of the basal seat area by extending the flanges of the denture to cover all the details but without disturbing the functional areas 2 quality of the denture bearing area means that you must look at the ridge if it was more pronounced, parallel and obvious it will be better than flat one3 oral and facial musculature it can supply supplementary retentive force by the properly polished surface that will apply the best ability to form retention 4 occlusal plane must be at the correct level 5 the arch form of the teeth must be in the neutral zone between the tongue and the cheek so no one of them can displace the denture from its place coz if u put it in one of these areas it will be dislocated by the movement of them 6 patients can control the denture by their muscle using the nerves so the younger patient will always have more controlling the old patient ** Physiological factors: it is mainly about the saliva and talking about the best type of saliva to retent any denture $$ saliva is either thick high mucin saliva that is more viscous than the watery saliva or watery serous saliva that can be interposed in a thinner film than the first one $$ excessive salivation is bad for retention also reduced salivation is bad too $$ well hydrated mucosa is better in retention than dry one ** Physical factors: it includes these things:1 adhesion: it is the attraction between the different types of molecules it depend on the saliva where it come between the denture and the tissue and it is increased when the distance between the denture and the tissue is decreased also increasing of saliva fluidity will increase it 2 cohesion: it is the attraction between the same type of molecules and mainly it is in the layer of saliva that separate the denture from the oral mucosa 3 interfacial surface tension: it is a thin layer of fluid that is present between two parallel surfaces of rigid materials and we must mention that denture has higher surface tension than oral mucosa but once coated by salivary pellicle tension is reduced4 capillarity: it is the state due to surface tension where there will be elevation or depression of the fluid surface which in contact with the solid so it's important come where saliva work as capillary and retention is formed between the surface of both mucosa and denture 5 atmospheric pressure: the source of it is the weight of the atmosphere 14.7 lb.sq inch ++ It will give us a power called suction that will result in resistance of the denture to be dislodged and removed from its place ++ It is also affected by 3 things: perfect peripheral seal, perfect border molding and selective pressure teqnique 6 gravity: not an important factor but it affect as a retentive force for lower denture and as a displacement force for the upper denture ((only when the patient is setting straight up))** Mechanical factors: includes (insertion pathways, undercuts, denture adhesives and parallel walls)1 undercuts: the resilience of the mucosa and sub mucosa overlying the basal bone allow for the existence of modest undercuts that can enhance retention ++ Undercuts that work as a retention factor are:((Less severe undercuts of the lateral tuberosities+ maxillary premolars areas +destolingual areas + lingual mandibular midbody areas))2 insertion pathways: provides resistance to vertical displacement 3 parallel walls: prominent alveolar ridge with parallel buccal and lingual walls; it works as a retention factor by increasing the surface area and maximing the interfacial and atmospheric forces 4 denture adhesives: non toxic material indifferent forms that is used by putting it on the tissue surface of the denture to enhance the retention of it ** Psychological factors: include both the patient tolerance; how much he can be corporative with you and patient education his knowledge and ability to work with u ** surgical factors: tuberoplasty + zygomaticoplasty + vestibuloplasty these are the main three features affecting the denture that we can do them and reach them by surgeries depending on the patient situation Stability We mean by this concept is the ability of the denture to be:1 firm2 stable an constant 3 resistance to displacement4 able to hold position when forces are applied ++ It is affected by several factors and they are:1 vertical height of the residual ridge: be aware that vertical ridge must be like a mountain and the more that it look like it the better effect coz if it got resorped then we will lose the stability that it gives 2 tissue covering the ridge: if the tissue is firmly attach and resilience then it is better than the flabby tissue in facing masticatory forces 3 impression quality: in here 3 things we concern about it which are (accurate detail recording + impression material stability to avoid 3d change + pouring time must be immediately 4 occlusal plane: it must be oriented in a way that maintain a good interocclusal space to increase stability 5 teeth arrangement it must be in an accurate occlusal way to reach the best stability also dont forget the neutral zone placement ***************************************************by this slides and book are all included you will find similarity and almost copy paste of the slides coz they have more things than the book