Journal of Dentistry, 3, 163-l 66
Introducing a clinical flavour to prosthetic technique teaching R. M. Basker, MDS, LDS Department
of Dental Prosthetics, The Dental School, University of Birmingham
ABSTRACT
A description
is given of a full denture teaching programme built around a phantom head. This programme introduces some clinical techniques to the prosthetic laboratory course and has been shown to be of benefit in teaching dental students.
INTRODUCTION ONE commonly held view behind current prosthetic technique teaching programmes is that dental students should be instructed in laboratory procedures to such a level that they understand the correct way of constructing prosthetic appliances and, equally important, that they recognize the pitfalls when incorrect techniques are employed. As a result, knowledge gained in the teaching programme enables the newly qualified dental graduates to recognize the technical problems and be able to discuss them in a realistic manner with the technician. It is widely recognized that junior students respond well to the ‘clinical carrot’ and that the introduction of some clinical flavour to the laboratory course injects added interest into the work being done, as well as laying down useful groundwork for the future. Introducing a clinical slant to the partial denture section of the laboratory course is relatively straightforward. With the help of radiographs and models, a photographs, clinical case can be presented and the students asked to design partial dentures to meet the particular needs of the ‘patient’. When the designs have been discussed and any errors have been corrected, the students can progress
to construct the actual appliance which each has designed. Continuing this philosophy through to the full denture section of the teaching programme is more of a problem. However, the introduction of a recently designed phantom head to the teaching programme for junior students at the Birmingham Dental School has gone some way to bringing the clinical situation to the laboratory course. THE PHANTOM HEAD The internal structure of the phantom head* is shown in Fig. 2. The edentulous models are made of heat-cured acrylic resin and are secured to the upper and lower jaws. The centrally placed ball and socket joint A allows movement of the mandible in vertical and lateral directions. A degree of resistance to movement of the mandible in the horizontal plane is obtained from the springs situated either side of the joint. The mandible can be held in any desired position by tightening the locking nut B. Access to the locking nut is through an opening at the back of the cranium which fits on top of the assembly. The phantom head is free to rotate on the vertical metal support which is clamped to the bench. ‘Lips’ and ‘cheeks’ are provided by a latex rubber mask which is attached to screws on the cranium and on the base of the phantom head (Fig. 2).
The design
of mouth
opening
was
*Phantom head P2: Franz Sachs & Co., Tettnang, Western Germany. United Kingdom distributor: Kavo Dental Limited.
Journal of Dentistry,
164
Fig. I.-Internal
Fig. 3.-Reflection
structure of the phantom head.
of the cheek to allow insertion of the impression tray.
Fig. 2.-Phantom
Fig. I.-Judging
Vol. ~/NO. 4
head complete with rubbermask.
trial dentures in the phantom head.
Basker:
Prosthetic
Technique
Teaching
chosen after several trials. Although a slit aperture simulated the lips and cheeks quite satisfactorily, the mask hindered movement of the lower jaw and the corners of the mouth were readily torn. The opening shown in Fig. 2 still ensures that the students must reflect lips and cheeks when inserting an upper impression tray. However, the mask is less likely to be torn by inexperienced students and it does not influence the pattern of movement of the lower jaw. The upper margin of the mouth opening is so positioned that it produces a realistic upper lip line for the purpose of recording the occlusion and subsequently judging the appearance of the trial denture. The upper lip line on the mask provided by the manufacturer was positioned so high that realistic assessment of appearance was not possible. THE TEACHING PROGRAMME A teaching programme has been devised which allows the students to progress through all the clinical and laboratory stages of constructing full dentures. Special trays and impressions Having constructed special trays, the student takes the upper impression using alginate and the lower using zinc oxide impression paste. Elementary errors in mixing the impression materials and loading the trays can therefore be corrected. The presence of a rubber mask means that instruction in correct handling of the lips and cheeks and in seating the impression trays can be given (Fig. 3). The student is taught how to pack alginate into the sulcus prior to seating the special tray in order to avoid filling defects. One deviation from normal clinical technique is the need to apply a thin layer of separating medium, silicone grease, over the lower model to prevent the zinc oxide impression paste sticking to the acrylic. Record blocks and recording the occlusion Having cast models into the impressions, the student constructs a shellac base for the upper
165
record block and an acrylic base for the lower record block. Four items of information are given prior to recording the occlusion : 1. A measurement of the rest face height, between the tip of the nose and the middle of the central screw in the lower model. 2. The ala-tragal line. 3. The requirement that the incisal edge of the upper rim should be at the level of the upper lip. 4. That an Angle’s Class I incisal relationship should be provided. The student then progresses through the procedures of recording the jaw relationship. The articulation of the lower jaw is such that unless the lower jaw is manipulated with care, it is quite easy to produce a jaw relationship which is incorrect in the horizontal plane. This is additional useful training for subsequent clinical procedures. The trial dentures The student is taught a split-cast technique for mounting the models on a Rational articulator. Trial dentures are constructed and checked in the phantom head for such routine points as correct occlusal face height, even occlusal contact and satisfactory appearance (Fig. 4). Finishing and fitting the dentures The student processes the dentures and returns them to the articulator. In this way it is possible to demonstrate any increase in occlusal face height arising from processing errors. The dentures are finally fitted in the phantom head. Evaluation of the teaching programme A questionnaire was completed anonymously by 52 students after they had finished the laboratory course and had treated their first edentulous patients in the clinic. The following questions were asked : 1. Did you find that learning full denture techniques using a phantom head was more interesting than making full dentures purely as a technical exercise? 2. Do you consider that the phantom head exercise was of benefit when you subsequently
Journal of Dentistry, Vol. ~/NO. 4
166
undertook clinical work for an edentulous patient? 3. If ‘yes’ to question 2, did you find the experience beneficial when : u. Taking impressions for a patient. b. Recording the occlusion for a patient. The results of the questionnaire are given in Table I. Table I.--Results
of the questionnaire Answer
(% of students)
Question
1 2 3a 36
Yes
No
88 94 37 87
6 4
Don’t know 6 2
DISCUSSION The result of the questionnaire showed that the students favoured the phantom head teaching programme and valued the opportunity of familiarizing themselves with clinical procedures before commencing to treat patients. Furthermore, the response to question 1 illustrates the benefit of the ‘clinical carrot’ in laboratory teaching. The clinical techniques can be taught by one member of the clinical staff to a number of students at the same time, and initial instruction can be put over more easily in the absence of a patient. From the answer to question 3 it was apparent that the students found the previous experience of the phantom head more useful when recording the occlusion in the clinic than when taking impressions. This can perhaps be explained in terms of the amount of clinical realism produced by the exercise; although use of the phantom head teaches the student how to manipulate the lips and cheeks in order to
insert the tray into the mouth, it was not possible to devise a functional buccal and lingual sulcus so as to teach the all-important procedures of border-trimming the special tray. In contrast, the help given by the phantom head to the often perplexing procedure of recording the occlusion was quite apparent. Using the existing equipment, it is only possible to carry clinical simulation to a certain degree. In the absence of mobile musculature it is not possible to instruct the student in shaping the record rims relative to the neutral zone. Also, the teaching of the aesthetics of the dentures is limited to a consideration of individual tooth arrangement, midline and occlusal plane as it is not possible to illustrate the effect of the labial segment of the upper denture on lip support. However, the advantages of this teaching programme considerably outweigh the shortcomings. Not only are the students given an appreciation of the clinical situation, but they are also given the opportunity to use the impression trays, record blocks and dentures that they themselves have made. This factor helps to emphasize one of the aims in the prosthetic techniques course-that of teaching students to appreciate both right and wrong ways of making the various items needed for the construction of full dentures.
Acknowledgements I should like to express grateful thanks to my colleagues in the Department of Dental Prosthetics, University of Birmingham, who have been involved in the design and development of the teaching programme, and to Mr T. F. Stack and members of the Photographic Unit, Department of Oral Pathology, for the illustrations.
Introducing a clinical flavour to prosthetic technique teaching R. M. Basker, MDS, LDS Department
of Dental Prosthetics, The Dental School, University of Birmingham
ABSTRACT
A description
is given of a full denture teaching programme built around a phantom head. This programme introduces some clinical techniques to the prosthetic laboratory course and has been shown to be of benefit in teaching dental students.
INTRODUCTION ONE commonly held view behind current prosthetic technique teaching programmes is that dental students should be instructed in laboratory procedures to such a level that they understand the correct way of constructing prosthetic appliances and, equally important, that they recognize the pitfalls when incorrect techniques are employed. As a result, knowledge gained in the teaching programme enables the newly qualified dental graduates to recognize the technical problems and be able to discuss them in a realistic manner with the technician. It is widely recognized that junior students respond well to the ‘clinical carrot’ and that the introduction of some clinical flavour to the laboratory course injects added interest into the work being done, as well as laying down useful groundwork for the future. Introducing a clinical slant to the partial denture section of the laboratory course is relatively straightforward. With the help of radiographs and models, a photographs, clinical case can be presented and the students asked to design partial dentures to meet the particular needs of the ‘patient’. When the designs have been discussed and any errors have been corrected, the students can progress
to construct the actual appliance which each has designed. Continuing this philosophy through to the full denture section of the teaching programme is more of a problem. However, the introduction of a recently designed phantom head to the teaching programme for junior students at the Birmingham Dental School has gone some way to bringing the clinical situation to the laboratory course. THE PHANTOM HEAD The internal structure of the phantom head* is shown in Fig. 2. The edentulous models are made of heat-cured acrylic resin and are secured to the upper and lower jaws. The centrally placed ball and socket joint A allows movement of the mandible in vertical and lateral directions. A degree of resistance to movement of the mandible in the horizontal plane is obtained from the springs situated either side of the joint. The mandible can be held in any desired position by tightening the locking nut B. Access to the locking nut is through an opening at the back of the cranium which fits on top of the assembly. The phantom head is free to rotate on the vertical metal support which is clamped to the bench. ‘Lips’ and ‘cheeks’ are provided by a latex rubber mask which is attached to screws on the cranium and on the base of the phantom head (Fig. 2).
The design
of mouth
opening
was
*Phantom head P2: Franz Sachs & Co., Tettnang, Western Germany. United Kingdom distributor: Kavo Dental Limited.
Journal of Dentistry,
164
Fig. I.-Internal
Fig. 3.-Reflection
structure of the phantom head.
of the cheek to allow insertion of the impression tray.
Fig. 2.-Phantom
Fig. I.-Judging
Vol. ~/NO. 4
head complete with rubbermask.
trial dentures in the phantom head.
Basker:
Prosthetic
Technique
Teaching
chosen after several trials. Although a slit aperture simulated the lips and cheeks quite satisfactorily, the mask hindered movement of the lower jaw and the corners of the mouth were readily torn. The opening shown in Fig. 2 still ensures that the students must reflect lips and cheeks when inserting an upper impression tray. However, the mask is less likely to be torn by inexperienced students and it does not influence the pattern of movement of the lower jaw. The upper margin of the mouth opening is so positioned that it produces a realistic upper lip line for the purpose of recording the occlusion and subsequently judging the appearance of the trial denture. The upper lip line on the mask provided by the manufacturer was positioned so high that realistic assessment of appearance was not possible. THE TEACHING PROGRAMME A teaching programme has been devised which allows the students to progress through all the clinical and laboratory stages of constructing full dentures. Special trays and impressions Having constructed special trays, the student takes the upper impression using alginate and the lower using zinc oxide impression paste. Elementary errors in mixing the impression materials and loading the trays can therefore be corrected. The presence of a rubber mask means that instruction in correct handling of the lips and cheeks and in seating the impression trays can be given (Fig. 3). The student is taught how to pack alginate into the sulcus prior to seating the special tray in order to avoid filling defects. One deviation from normal clinical technique is the need to apply a thin layer of separating medium, silicone grease, over the lower model to prevent the zinc oxide impression paste sticking to the acrylic. Record blocks and recording the occlusion Having cast models into the impressions, the student constructs a shellac base for the upper
165
record block and an acrylic base for the lower record block. Four items of information are given prior to recording the occlusion : 1. A measurement of the rest face height, between the tip of the nose and the middle of the central screw in the lower model. 2. The ala-tragal line. 3. The requirement that the incisal edge of the upper rim should be at the level of the upper lip. 4. That an Angle’s Class I incisal relationship should be provided. The student then progresses through the procedures of recording the jaw relationship. The articulation of the lower jaw is such that unless the lower jaw is manipulated with care, it is quite easy to produce a jaw relationship which is incorrect in the horizontal plane. This is additional useful training for subsequent clinical procedures. The trial dentures The student is taught a split-cast technique for mounting the models on a Rational articulator. Trial dentures are constructed and checked in the phantom head for such routine points as correct occlusal face height, even occlusal contact and satisfactory appearance (Fig. 4). Finishing and fitting the dentures The student processes the dentures and returns them to the articulator. In this way it is possible to demonstrate any increase in occlusal face height arising from processing errors. The dentures are finally fitted in the phantom head. Evaluation of the teaching programme A questionnaire was completed anonymously by 52 students after they had finished the laboratory course and had treated their first edentulous patients in the clinic. The following questions were asked : 1. Did you find that learning full denture techniques using a phantom head was more interesting than making full dentures purely as a technical exercise? 2. Do you consider that the phantom head exercise was of benefit when you subsequently
Journal of Dentistry, Vol. ~/NO. 4
166
undertook clinical work for an edentulous patient? 3. If ‘yes’ to question 2, did you find the experience beneficial when : u. Taking impressions for a patient. b. Recording the occlusion for a patient. The results of the questionnaire are given in Table I. Table I.--Results
of the questionnaire Answer
(% of students)
Question
1 2 3a 36
Yes
No
88 94 37 87
6 4
Don’t know 6 2
DISCUSSION The result of the questionnaire showed that the students favoured the phantom head teaching programme and valued the opportunity of familiarizing themselves with clinical procedures before commencing to treat patients. Furthermore, the response to question 1 illustrates the benefit of the ‘clinical carrot’ in laboratory teaching. The clinical techniques can be taught by one member of the clinical staff to a number of students at the same time, and initial instruction can be put over more easily in the absence of a patient. From the answer to question 3 it was apparent that the students found the previous experience of the phantom head more useful when recording the occlusion in the clinic than when taking impressions. This can perhaps be explained in terms of the amount of clinical realism produced by the exercise; although use of the phantom head teaches the student how to manipulate the lips and cheeks in order to
insert the tray into the mouth, it was not possible to devise a functional buccal and lingual sulcus so as to teach the all-important procedures of border-trimming the special tray. In contrast, the help given by the phantom head to the often perplexing procedure of recording the occlusion was quite apparent. Using the existing equipment, it is only possible to carry clinical simulation to a certain degree. In the absence of mobile musculature it is not possible to instruct the student in shaping the record rims relative to the neutral zone. Also, the teaching of the aesthetics of the dentures is limited to a consideration of individual tooth arrangement, midline and occlusal plane as it is not possible to illustrate the effect of the labial segment of the upper denture on lip support. However, the advantages of this teaching programme considerably outweigh the shortcomings. Not only are the students given an appreciation of the clinical situation, but they are also given the opportunity to use the impression trays, record blocks and dentures that they themselves have made. This factor helps to emphasize one of the aims in the prosthetic techniques course-that of teaching students to appreciate both right and wrong ways of making the various items needed for the construction of full dentures.
Acknowledgements I should like to express grateful thanks to my colleagues in the Department of Dental Prosthetics, University of Birmingham, who have been involved in the design and development of the teaching programme, and to Mr T. F. Stack and members of the Photographic Unit, Department of Oral Pathology, for the illustrations.
