Showing papers in "Journal of Prosthetic Dentistry in 1976"

The neutral zone in complete dentures.

Abstract: The neutral-zone philosophy is based upon the concept that for each individual patient, there exists within the denture space a specific area where the function of the musculature will not unseat the denture and where forces generated by the tongue are neutralized by the forces generated by the lips and cheeks. The influence of tooth position and flange contour on denture stability is equal to or greater than that of any other factor. We should not be dogmatic and insist that teeth be placed over the crest of the ridge, buccal or lingual to the ridge. Teeth should be placed as dictated by the musculature, and this will vary for different patients. Positioning artificial teeth in the neutral zone achieves two objectives. First, the teeth will not interfere with the normal muscle function, and second, the forces exerted by the musculature against the dentures are more favorable for stability and retention.

Measurement of personality traits and their relation to patient satisfaction with complete dentures.

Abstract: 1. There was a high incidence of the personality traits of hypochondriasis, depression, hysteria, and manifest anxiety in the 70 complete denture patients of this study. 2. Most patients in this study were satisfied with the complete dentures received. 3. There was no significant relationship between the personality traits of hypochondriasis, depression, hysteria, and manifest anxiety and the degree of patient satisfaction with dentures. 4. There was no significant relationship between the personality traits of hypochondriasis, depression, hysteria, and manifest anxiety and the techinical quality of dentures. 5. There was no significant relationship between the technical quality of complete dentures and the degree of patient satisfaction with the same dentures.

The remodeling of the edentulous mandible.

Abstract: In a sample of mandibles having complete or nearly complete loss of dentition, the left half of each mandible was serially sectioned. The entire perimeter of each section was analyzed for the distribution of resorptive and depository periosteal surfaces, and from this information, the fields of remodeling were mapped for the mandible as a whole. The most common patterns of combined resorption-deposition and the range of variations were then determined. The over-all distribution of remodeling fields in the edentulous mandible differs markedly from that in the young, growing mandible. In most of the edentulous specimens, the surface of the basal bone on both the medial and lateral sides of the corpus is of a depository nature. The overlying alveolar regions on both the lingual and buccal sides, however, are characteristically resorptive. Significantly, the placement of the reversal line between the alveolar resorptive and the basal depository areas is much lower (i.e., at the level of the mental foramen) on the buccal side. Except for its inferior part, the lateral side of the ramus tends to be largely resorptive in character, and the posterior half of the lingual side also tends to be resorptive. Unlike the child's mandible, the posterior border of the ramus is resorptive, and the posteroanterior dimension of the ramus (not the whole mandible) becomes reduced and narrowed in conjunction with resorption along the anterior border. However, the amount removed from the anterior ramus is actually added to the dimension of the corpus, which becomes longer. Further, removal from the posterior ramus border does not affect the over-all length of the mandible unless condylar reduction is also involved. Also, over-all arch length is not decreased, because the surface of the mental protuberance is retained as a depository type of field (or at least does not become actively resorptive). The corpus-ramus angle (not gonial angle) is increased in the antegonial region. Because of the opening of this angle, over-all mandibular length as well as arch length is increased. In about half of the specimens, arch width was not decreased, because the lateral side of the corpus is usually of a depository nature. Notching of the anterior side of the condylar neck and the inferior part of the anterior ramus border is associated with resorptive fields in these regions, changes that are presumed to be a consequence of pressure contacts made with the articular tubercle and the maxillary tuberosity, respectively, in conjunction with a forward rotation of the whole mandible. The inferior direction of corpus realignment relative to the basal part of the ramus also increases the notching effect in the antegonial region, an effect augmented by the presence of the resorptive field in the notch itself. Certain specific variations commonly occur in several major regions of the mandible on both the lateral and medial sides...

Abrasive wear, tensile strength, and hardness of dental composite resins—Is there a relationship?

Abstract: The in vitro abrasive wear resistance, tensile strength, and hardness of seven widely used composite restorative resins have been measured Findings indicate that the values of tensile strength and hardness are not related to the measured abrasion rates It is apparent that abrasive wear is a complex phenomenon and that materials which have high values for strength and/or hardness do not necessarily have high resistance to abrasive wear

Retentive properties of post and core systems

Abstract: An investigation was conducted in which different post and core systems were subjected to tensile, shear, and torque forces and their abilities to resist such forces were measured. The following conclusions can be drawn: (1) A post and core unit made of composite resin alone, without the additional retention provided by cemented posts or threaded pins, is the least retentive, and its use should be discouraged. (2) The retention of composite resin cores by four threaded pins compares favorably with other accepted techniques. (3) A round post retaining a composite resin core alone provides poor resistance to torque, but with the addition of threaded pins, its ability to resist displacement improves substantially. (4) The procedure in which composite resins are used to restore the coronal portion of pulpless teeth, with threaded pins and/or posts in the root canal, is reliable.

Self-image and its relation to denture acceptance.

Abstract: A study was initiated to determine whether a relationship exists in geriatric patients between self-image and the extent of their denture acceptance. Three assessing instruments were employed, namely, a "Focused Interview," the embedded-figures test, and projective figure drawings. Scores obtained were compared with scores on the Denture-Acceptance Rating Scale. The research results derived from the data follow: 1. Comparison of the degree of denture acceptance with the scores on all three assessing instruments showed significant relationships. Therefore, the hypothesis under study was accepted. 2. The "Focused Interview" appeared particularly well suited to a geriatric population, because it was nonthreatening, provided a communication outlet, and can be readily employed by a practitioner. 3. The embedded-figures test and the projective figure drawings appeared less appropriate for this population because of factors such as psychomotor retardation, perceptual difficulties, and diminution of ego strength which accompany the aging process. 4. The men in this study appeared to accept dentures more readily than the women, manifested higher morale, and were more field-independent. 5. Employed subjects, as compared to unemployed, showed significantly greater denture acceptance, higher morale and self-image, and a greater degree of field-independence. These factors appeared related to greater flexibility of adaptation. 6. Socioeconomic factors appeared to be significantly and positively related to morale factors. 7. Complaints regarding dentures were largely of a physical nature. They appeared to relate primarily to difficulties with adjustment to the new artifact which represented an alteration of body image for the subjects. 8. The study provided corroborative evidence of the need for the dentist to make an initial assessment of those personality factors in his patients which might limit his ability to provide adequate dental services.

The bonding properties of elastomer tray adhesives

Abstract: 1. The surface yielded by the acrylic resin formed against tinfoil provided better retention for the rubber base than any other surface tested. 2. Wax consistently gave the worst results in spite of careful boiling out. 3. The use of wax or asbestos spacers would not degrade the resin surface if tinfoil, or presumably the more easily obtainable aluminum foil, were used as a separating medium. 4. For drying times of between 15 minutes and 72 hours, no significant change was found in bond strength of elastomer to tray material. 5. Drying times of less than 15 minutes were found to be inadequate and to decrease bond strength; they are clinically inadvisable. 6. If, as a result of unavoidable delay, a tray is painted and then left for a number of days prior to making the impression, satisfactory bonding will still occur. However, if the dentist wishes to apply a second coat and dry it for 15 minutes, an increase in bond strength is likely to occur. 7. In the six systems tested, failure occurred at varied levels, from a low of 20 p.s.i. to a high of 80 p.s.i. 8. In the silicone and polyether systems, cohesive failure of the elastomer occurred before the adhesive bond between elastomer and tray failed. This finding correlates with the clinical observation that silicones and polyethers are more difficult to remove completely from acrylic resin trays when an impression has to be repeated.

A systematic approach to the control of esthetic form

Abstract: A systematic, orderly approach to the problem of establishing harmonious phonetics, esthetics, and function in fixed restorations has been described. The system requires an initial investment of time in performing an adequate diagnostic waxing, but recoups that time in many clinical and laboratory procedures. The method has proved a valuable asset in fixed prosthodontic care. The technique can be expanded and combined with other techniques with a little imagination and artistic bent.

Five-year cephalometric study of mandibular ridge resorption with different posterior occlusal forms. Part I. Denture construction and initial comparison

Abstract: The average 5 year reduction of the occluding vertical dimension (nasion to menton) for 45 patients was 3.2mm. (2.8 mm. for the anatomic group, 3.2 mm. for the semianatomic group, and 3.6 mm. for the nonanatomic group, each constituting 15 patients). Mandibular physiologic resting face height became foreshortened on the average only one third as much as the morphologic centric occlusion face height. Tabulation of adjustments for sore spots indicated that: the fewest postinsertion appointments were required for the anatomic group of patients; three fourths of 604 denture base alterations were on lower dentures; for upper and lower denture base alterations, one third were made on the borders and two thirds, on the basal seat; one sixth of all alterations were made at routine recall examinations; the fewest upper denture base alterations were for the nonanatomic patients; and the fewest adjustments of the lower denture base on the tissue surface and on the borders were done for the anatomic group of patients. This investigation has been underway for 18 years, and several more re

Significance of the Frankfort-mandibular plane angle to prosthodontics

Abstract: Cephalometric information, specifically, vertical facial types and the Frankfort-mandibular plane angle, pertinent to prosthodontics has been discussed. The Frankfort-mandibular plane angle (FMA) is formed by the intersection of the Frankfort horizontal plane and the mandibular plane. This angle can be traced and measured by means of a diagnostic overlay. An FMA of 25 +/- 5 degrees is within normal range. A high-angle patient has an FMA of 30 degrees or more, and a low-angle patient has an FMA of 20 degrees or less. A high FMA is characterized by open-bite skeletal patterns, and a low FMA by closed-bite skeletal patterns. The clinical manifestations pertinent to prosthodontics in high- and low-angle (FMA) patients are shown in Table I. However, not all clinical characteristics are present in a given patient. The classification in Table I is a beginning. The authors consider the prosthodontic study of cephalometrics an unexploited research tool. Hopefully, in the future, it will help to bridge the gap of the biological-technical interplay that is such an integral part of prosthodontics.

Articulator selection for restorative dentistry

Abstract: There are many types of articulators that can be used for making fixed restorations. While unquestionably the most accurate, the fully adjustable instrument is not feasible or necessary for many forms of simple occlusal treatment. The effects of tooth-hinge axis radius, intercondylar distance, and condylar inclination on occlusal morphology have been discussed. Guidelines have been proposed for matching the type of articulator with the extent of treatment anticipated. The use of small, nonadjustable hinge articulators is not recommended.

Radiation complications in edentulous patients

Abstract: Complete dentures were fabricated for 88 patients following completion of cancericidal doses of radiation therapy to the head and neck regions. All were followed for at least 6 months after delivery. All patients received dentures resting within the radiation field. Three patients developed osteoradionecroses directly attributable to their dentures. These three had been dentulous prior to therapy and had either pre- or posttreatment extractions. Of the 58 patients who had been edentulous prior to therapy, none developed osteoradionecrosis. Five patients developed soft tissue necroses secondary to the use of dentures.

Posterior bilateral condylar displacement: its diagnosis and treatment.

Abstract: One type of condylar displacement (posterior bilateral) was discussed as an etiologic factor in TMJ dysfunction. Joint noise, tenderness on muscle palpation, and acute TMJ pain are all considered signs of TMJ dysfunction. Any joint noise is considered to be an early dysfunctional symptom because of its higher incidence in association with palpable muscle pain or acute TMJ dysfunction. Sometimes the joint noise will immediately precede acute muscle pain and/or fluctuate with the painful symptoms. The treatment of bilateral posterior condyle displacement has been described. The mandibular anterior teeth were shortened and the maxillary posterior occlusion adjusted so that the mandible could be respositioned in an anterior position without increasing the vertical dimension of occlusion. A silver-plated maxillary cast was obtained and mounted on a semiadjustable articulator (Hanau) with a face-bow. The mandibular cast was mounted in the dysfunctional (retruded) centric relation. The articulator was moved into a protrusive position by the amount of anterior correction that is needed to reposition the condyles into the middle of the fossae symmetrically on both sides. The original TMJ radiographs provide the necessary information for this clinical judgment. Acrylic resin was placed in the space created between the condylar sphere and stop on the articulator. An acrylic resin temporary repositioning prosthesis constructed on the metal cast has two functions. It provides a therapeutic trial for the anterior condylar respositioning, and it holds the mandible in the therapeutic position while TMJ radiographs confirm the corrective position of the condyles in the fossae. After a successful 6 to 8 week trial period with remission of symptoms, a gold prosthesis was constructed on the same cast in the same therapeutic position. It remains to be seen whether, after several years, the condylar suspension system changes from a dysfunctional centric relation to a new functional centric relation in which the patient can no longer return to the posterior displaced condylar position in the fossa. Only with painstaking observations, accurate TMJ radiographs, complete documentation, and after-care can a more scientific approach to the diagnosis and treatment of TMJ dysfunctional pain syndrome be achieved.

Posterior accessory foramina of the human mandible.

Abstract: A study was performed on 150 dry, adult, human mandibles from cadavers of unspecified sex and unknown ethnic background, which had been imported from India. These mandibles were placed in the “standard basal position” and topographically divided into 11 bilateral areas posterior to the second bicuspid teeth. The accessory foramina in these areas were studied to determine their mean diameter, incidence of occurrence, and the areas in which they occurred. The medial surfaces of the mandibles exhibited foramina more frequently and in greater numbers than did the lateral surfaces. The right and left halves of the mandibles showed remarkable similarity. Much of the data obtained correlated with previous investigations, indicating that neurovascular components enter and leave the body on the mandible in the posterior region. Foramina 0.4 mm. or larger in diameter were evaluated separately. These larger foramina occur most often in the superior and middle thirds on the medial surface of the ramus (areas 6 and 7). They also occur fairly frequently in the retromolar area (area 11). This information can be usefully applied to future dissection studies concerning the soft-tissue components of these foramina. The data obtained reveal that these foramina occur frequently and in approximately the same locations. This suggests that these foramina are functionally important in supplying neural and/or vascular components to the mandible.

Excessive crown contours facilitate endemic plaque niches.

Abstract: Facial and lingual surfaces of teeth restored with complete metal and porcelain-fused-to-metal crowns exhibited greater mean plaque accumulation than did the contralateral teeth. This cross-sectional study showed greater facial-lingual width and plaque indices for restored teeth than for natural or unrestored teeth. This relationship between plaque and excessive contours must not be considered wholly dependent and conclusive. The multifactorial phenomenon influencing plaque accumulation no doubt could contribute to the findings of this study. However, until demonstrated otherwise, the creation of artificial crown contours that are greater than natural tooth convexities must be considered another parameter promoting endemic plaque niches. Sound application of principles with respect to the form of teeth and supporting tissue can preclude contouring of restorations beneficial to the accumulation of dental plaque.

The marginal integrity of the temporary acrylic resin crown

Abstract: A primary objective of the temporary crown is to maintain good gingival health prior to placement of the final restoration. Unless the temporary crown has a well adapted and well contoured margin, it may be difficult to achieve this goal. In addition to good gingival health, several other desirable ends are achieved by assuring well adapted margins on temporary crowns. One of these is decreased sensitivity, which is demonstrated when freshly prepared dentin is left exposed to the oral environment. Also, better esthetic values are obtained when margins of temporary crowns extend to the finishing lines of anterior preparations. It is desirable to construct temporary crowns which have well adapted margins at the finishing lines of the preparations to protect the prepared tooth.* This report describes a method which will predictably facilitate the construction of such well adapted margins. This technique was first performed on a Typodont and later applied to patients.

Scanning electron microscope study of the junction between restorations and gingival cavosurface margins.

Abstract: This study demonstrates a definite interfacial void between the cervical margins of the tooth preparation and gold inlay, composite resin, and amalgam restorations. In addition, these marginal defects permit plaque formation within them. Furthermore, microleakage may be a complicating factor in this lack of fit. Restorations which may be "clinically acceptable" may not, in fact, be ideal because of the properties of the restorative materials. It would seem desirable, therefore, to encourage the development of new restorative materials that will bond to the tooth surface.

Design and technique variables affecting fracture resistance of metal-ceramic restorations.

Abstract: An attempt was made in this study to make a clinically meaningful measure of fracture resistance in metal-ceramic restorations. Forty-four solid metal-ceramic crown forms were fabricated and subjected to compressive load testings. Variables included the presence or absence of a metal coating agent, the type of metal preparation (using stones of different abrasives), and three designs of the underlying metal. The following conclusions were arrived at: (1) The design of the underlying metal structure had a significant relation to the ultimate fracture strength. (2) A design with a definite acuteness of the underlying metal structure failed at significantly lower ultimate fracture strengths. (3) A metal conditioning agent did not decrease fracture resistance if applied properly. (4) Fracture strength was severely decreased when (a) improper thickness of the coating agent was used and (b) porcelain was fused to an unoxidized metal surface. (5) Bond strength, although a contributing factor, may not be as important as metal design and proper manipulation of materials during fabrication of the restoration.

Controlling anomalies of vertical dimension and speech

Abstract: In this article, definite ways and means have been discussed for controlling the vertical dimension of occlusion by using certain tooth-to-tooth and tooth-to-tissue relations that exist in normal speech. The primary emphasis is placed on managing the problems encountered in the most troublesome types of patients—those with Class II occlusions, the tongue thrusters, and those who lisp. It is not easy to identify those patients in whom these problems previously existed after they become edentulous. An Analytical Control Chart has been introduced which can be used to separate these problem patients from the normal ones, and a step-by-step procedure for their management can be followed. Also the phases of this approach which are beneficial in restorative dentistry are reviewed.

Pulp reaction to a temporary zinc oxide/eugenol cement.

Abstract: The pulpal irritation, such as inflammatory reaction and aspiration of pulpal cells, demonstrated after insertion of the zinc oxide/eugenol cement (Nobetec) seems to warrant the following recommendations: (1) A temporary restoration with a zinc oxide/eugenol base should not be inserted in deep cavities without a protective liner or a calcium hydroxide base covering the exposed dentinal tubules. (2) Before the temporary cementing of inlays and crowns with a zinc oxide/eugenol cement, not only should the dentin be properly cleaned and debris removed, but the prepared surfaces should be covered with a calcium hydroxide liner.

When to glaze—An electron microscope study

Abstract: 1. A smooth porcelain surface can be obtained by glazing after grinding. There is no need for sanding or polishing with a rubber wheel. 2. A low-fusing glaze gives a slightly smoother surface than a natural glaze. The low-fusing glaze may be added at any stage of polishing, and the results will be the same.

Prosthodontic aspects of palatal elevation and palatopharyngeal stimulation

Abstract: The prosthodontic aspects of palatal elevation and palatopharyngeal stimulation were discussed. Following are important factors that must be considered. (1) Elevation of the soft palate should be gradual to avoid placing pressure upon the teeth retaining the prosthesis and to reduce mucosal irritation. (2) Prosthetic stimulation should be initiated as soon as palatal paralysis is noted to prevent palatal disuse atrophy. (3) The palatal lift prosthesis may be used as a temporary or definitive treatment for palatal incompetency. When adequate elevation of the soft palate has been achieved, the prosthesis may be discarded. Otherwise, the patient would wear the prosthesis as a permanent supportive device. (4) The construction of the combined palatal lift/pharyngeal section prosthesis includes the gradual palatal elevation and molding of the pharyngeal section to reduce the gag reflexes and to increase palatopharyngeal muscle adaptation to the prosthesis. After the initial placement, adjustment to the pharyngeal section is easier for the patient. (5) Speech and myofunctional therapy should be instituted in conjunction with prosthetic treatment. (6) The palatal lift and combination prostheses are more effective for patients with less severe neurologic impairment and speech articulatory problems. (7) The palatal lift prosthesis is more effective for those patients with palatal incompetency who have no involvement of the other oropharyngeal muscles. The combination type of prosthesis is more effective for patients with palatopharyngeal insufficiency without marked speech articulatory disorders. There are still several questions which require further investigation. These include: (1) What is the relationship between the palatal stimulation and the degree of neuromuscular function and recovery? (2) What is the relationship between the palatal stimulation and the degree of palatal disuse atrophy? (3) What is the relationship between pharyngeal stimulation and muscle contraction? (4) What is the degree of stability of palatopharyngeal function and muscle contraction after stimulation?

The influence of fixed splints on mandibular flexure.

Abstract: The degree of mandibular flexure during forced opening of the jaws with various fixed splints in place was measured. Significant results indicate that: (1) all splints tested reduce the amount of mandibular flexure; (2) the reduction of measured mandibular flexure cannot be explained solely by tooth movement, rather it is indicative of a limitation of bony flexure by fixed splints; (3) extensive mandibular splints flex during forced opening; and (4) fixed prostheses involving many teeth do not completely inhibit mandibular flexure. Inhibition of mandibular flexure apparently increases as more teeth are splinted and more rigid attachments are used.

A histologic comparison of palatal mucosa before and after wearing complete dentures.

Abstract: A histologic investigation to study the tissue changes occurring under complete dentures was done. Biopsies were obtained from 40 patients from the area of left side of the hard palate at the first molar region, midway between the median raphe and the residual ridge. The same patients were examined 3 months after placement of well-fitted dentures. Thirty of the 40 patients responded. A second biopsy was taken from the same area on the right side of these patients. On the basis of the microscopic examination, the following conclusions were drawn. 1. The average thickness of the palatal epithelium of edentulous non-denture wearers was 0.222 mm. in the rete peg region. 2. There was a general increase in the thickness of the palatal epithelium following 3 months of wearing complete dentures. 3. The increase in the palatal epithelium was more marked in the rete peg region than in the inter-rete peg region. 4. There was an increase in the thickness of the keratin layer in most patients. 5. No significant changes were found in the granular-cell layer or the prickle-cell layer. 6. The oral mucous membrane responded favorably to well-fitted dentures.

The contact angles of die stone on impression materials.

Abstract: 0 bservations in the clinic at the Medical College of Georgia, School of Dentistry, indicated that certain impression materials appeared to yield casts that contained more entrapped air bubbles than appeared with other impression materials when the same die stone was used. As a result of these observations, an investigation was performed to determine the advancing contact angle of die stone on silicone, polysulfide, polyether, and colloidal impression materials. The rationale of this approach is that if the die stone forms an advancing contact angle with the impression material approximating or greater than 90 degrees, there is a high probability for entrapment of air bubbles during the pouring of the impression. If the contact angle is relatively low, there is less chance of air entrapment.

A magnetically retained interim maxillary obturator.

Abstract: A technique has been presented for the fabrication of a sectional interim maxillary obturator with retention augmented by a magnet A tonogram 9, 10 revealed a 32 per cent decrease in hypernasality during speech when the prosthesis was worn (Fig 12) The positive locking and continuous retentive quality of the prosthesis provided by the magnet permitted normal speech and mastication as well as an improved psychologic state during a very trying rehabilitation period

Prosthetic support for unilateral facial paralysis.

Abstract: Removable prostheses were used to determine that esthetics and speech could be improved for patients with permanent unilateral facial paralysis. Esthetics had to be compromised somewhat to obtain the maximum benefit for intelligible speech. This procedure can be beneficial in helping patients who are high surgical risks or for whom surgery, for various reasons, is unacceptable.

Periodontal considerations of restorative procedures

Abstract: M any years ago: G. V. Black recommended that cavity preparations be extended to self-cleansing areas or to areas with minimal susceptibility to caries.’ Thus, extending preparations below the gingival margin w’as suggested to reduce the incidence of recurrent caries. The “extension for prevention” concept was based on clinical experience which suggested that decay did not start in the subgingival portion of the clinical crown. In this report on periodontal considerations of restorative procedures, the following topics will be discussed : ( 1) placement of margins, (2) marginal fit, (3) interdental space and contour of restorations, and (4) surface texture of restorations.

A study of distortion and surface hardness of improved artificial stone casts

Abstract: 1. The single-pour technique is as accurate as the double-pour technique except for point 6 (palatal point). Here the double-pour technique has greater accuracy. Impression material thickness over point 6 was approximately 15 mm. 2. The double-pour technique produced specimens which had superficial hardness values significantly higher than those of casts produced by the single-pour technique. 3. Specimens made with slurry water showed no greater distortion than specimens from other techniques. Surfaces of the specimens made with slurry water were significantly harder than those of specimens made with distilled water. Both types of specimens were made with the single-pour technique. 4. No significant difference in distortion was found in specimens produced with varying thickness of irreversible hydrocolloid impression material over the occlusal pins.