The International Journal of Prosthodontics, 06/1994

The etiology and treatment of occlusal tooth wear remain controversial. Longer tooth retention by the aging population increases the likelihood that clinicians will be treating patients with worn dentitions. A careful approach to interventional clinical procedures is advocated but should not curtail definitive management of patients having identifiable and potent causative agents that produce a rapid deterioration of the dentition. This article describes the epidemiology and etiology of occlusal wear and presents a conservative approach to its management.

A dental impression material must have sufficient strength to allow removal from a gingival sulcus without tearing; it must also have adequate elastic recovery. This study examined the tear energy, the permanent deformation upon extension, the energy absorbed to an estimated point of significant deformation, and the extent of permanent deformation at tear of polysulfide, polyether, and addition-reaction silicone impression materials. As expected, polysulfide material had a higher tear energy and strain at tear than either polyether or addition-reaction silicone materials. However, the more relevant clinical properties, such as energy absorbed per amount of deformation and tear at a point of minimal permanent deformation, favored the addition-reaction silicone material, followed by the polyether material.

During implant integration, it may be important to shield the implants from the possible detrimental effects of ionizing radiation. This paper offers a simple, effective method for shielding such areas while making radiographs of other areas of the mouth.

The use of osseointegrated implants is an accepted procedure for the treatment of total and partial edentulism and offers good predictability of long-term success. For the last several years, this procedure has also been used for single-tooth replacement following loss of teeth for traumatic, periodontal, and carious lesions. This paper reports the clinical experience of 47 patients treated for a single-tooth replacement. Sixty-seven screw-type standard, self-tapping implants and mini-implants were placed. The results were similar to those for complete and partial osseointegrated prostheses. The total implant survival rate was 94.4%. Two implants were lost as a result of suppuration caused by membrane exposure, while another was lost after loading. The results suggest that single-tooth replacement using osseointegrated implants provides predictable success.

This study compared the mechanical properties of machine-milled pure titanium and cast titanium. The metals were cast or milled to the dimensions of a standard tensile bar pattern. Each group was treated under three different conditions: as-cast (or as-milled), standard heat, and extended heat. Tensile testing found no difference in the mechanical properties of as-cast and as-milled titanium. Heat treatment significantly increased the ultimate tensile strength and the yield strength of cast titanium but had no such effects on milled titanium. There was no significant difference between the two metals in the modulus of elasticity or the percentage of elongation under the three treatment conditions.

This study compared the surface hardness, the effect of time on surface hardness, and the dimensional stability of various intermaxillary relationship registration materials. The Shore hardness values of one zinc oxide-eugenol material, one polyether, and seven poly(vinyl siloxane) materials were obtained at 30 minutes and 24 hours after the start of mixing. The dimensional stability of one polyether and seven poly(vinyl siloxane) materials was measured using a standard mold as described in American Dental Association (ADA) Specification No. 19. All materials exhibited relatively high surface hardness despite some statistical differences among them. Four materials possessed higher surface hardness at 24 hours than at 30 minutes. Although the polyether showed significantly lower dimensional stability than the other materials, all materials satisfied the minimum requirement for Type I elastomeric impression material.

This paper describes and compares the mandibular speech envelope and interocclusal dimensions, at the closest speaking and postural positions, for a group of 30 dentate subjects measured at separate data-collecting sessions. Mandibular movement was recorded by electrognathograph during recitation of a general phonetic articulation test containing all speech sounds. Comparison of the speech envelope and interocclusal dimensions between each recording session revealed no significant differences among them. An overall mean value calculated for the closest speaking space and postural interocclusal space from all recordings was significantly different (P > .05), with the closest speaking space the larger; however, considerable individual variation was noted.

The purpose of this study was to determine the stress corrosion fatigue characteristics of a heat-pressed ceramic material, IPS-Empress. Disks (1 mm thick, 12 mm in diameter) were prepared, polished, and subjected to dynamic loading at multiple constant stressing rates. Fatigue tests were conducted in a circulating bath using a biaxial flexure test. The inert strength of the samples was determined in oil. The mean fracture strength for the inert tests was 135.7 MPa. Linear regression analysis of log fracture strengths vs log time to failure was performed to obtain fatigue parameters. For IPS-Empress the n value was 31 (SE 3.5) and sigma f0 was 83.3 MPa (SE 1.3 MPa).

Indirect interim restorations have been traditionally fabricated on stone casts. Recently, flexible models fabricated from poly(vinyl siloxane) impression material have been suggested in place of stone casts. This study compared the marginal accuracy of indirect single-unit provisional restorations fabricated on stone casts with units made on poly(vinyl siloxane) impression material models. The mean marginal discrepancy of provisional restorations was compared for restorations fabricated from stone, low-viscosity poly(vinyl siloxane), and medium-viscosity poly(vinyl siloxane). Ten restorations were also fabricated directly on a master metal model (control). The mean marginal discrepancies were: control = 0.161 mm; stone model = 0.180 mm; low-viscosity poly(vinyl siloxane) = 0.245 mm; and medium-viscosity poly(vinyl siloxane) = 0.157 mm. The mean marginal discrepancy for the low-viscosity poly(vinyl siloxane) models was significantly higher than the other three groups. No significant difference was found between the control, stone cast, and medium-viscosity poly(vinyl siloxane) model groups.

The effect of the type of prosthodontic treatment on glove perforation and proteinaceous contamination of gloves was investigated for 364 prosthodontic treatments using poly(vinyl chloride) plastic (218 occasions) and latex gloves (146 occasions). The amount of protein contamination on plastic or latex gloves varied depending on the prosthodontic treatment performed and the patient treated. As determined directly, it averaged from approximately 800 to 1,500 micrograms per treatment, and the maximum value of protein contamination was more than 4,000 micrograms, corresponding to the amount of protein in 1.5 mL of saliva or 0.1 mL of serum. The perforation of plastic gloves was observed in 83.0% of the total occasions, and the perforation went unrecognized 96.1% of the time. In contrast, the proportion of glove perforation for latex gloves was 12.3% and the proportion of unrecognized perforation of latex gloves was 5.4%. The results suggest that latex gloves are effective in reducing the risk of cross-infection. Nevertheless, prosthodontists still have a potential risk of being exposed to bodily fluids, without being aware of glove perforation, at least once in every 20 treatments, even if latex gloves are worn.

This study examined the relationship between masticatory performance and oral stereognostic ability in 71 dentate individuals and 64 denture wearers. Stereognosis was evaluated in denture wearers with and without dentures in place. No significant differences (P > .05) were noted between the stereognostic scores of either group, with both groups correctly identifying approximately 68% of the items. This suggests that the receptors in the periodontal ligament are of minimal importance in the oral detection of shape and that the loss of teeth and placement of dentures does not diminish the perception of shape differences. Correlations between masticatory performance and stereognostic measures ranged in magnitude from 0.01 to 0.12 (P > .05). Further studies employing smaller test forms may be needed to assess the role of stereognosis on food manipulation during mastication.