The International Journal of Prosthodontics, 03/1998

Purpose: The aim of this study was to evaluate the efficacy of three tooth conditioners in restoring the reduced bond strength between resin cement and teeth resulting from remaining temporary cement. Materials and Methods: Ethyl dihydrogen phosphate, methacryloxyethyl dihydrogen phosphate, and 2-methacryloxyethyl hydrogen maleate were evaluated as conditioners. After eliminating the temporary cement with a currette from the bovine dentin surface, the conditioners were applied onto the surface of the specimen and a resin cement was adhered. Stepwise scanning electron microscopic observation and tensile bond strength measurement were carried out. Results: Granular substances were present on the dentin surface even when the temporary cement was carefully eliminated with a curette. When primer and resin cement were applied on this surface without conditioner application, no resin tag or hybrid layer was observed and the mean bonding strength between tooth and adhesive resin cement was 1.8 MPa. In contrast, resin tag and hybrid layer were observed after primer and resin cement application when the dentinal surface was treated with conditioner. Mean tensile bone strength values increased to 6.2 MPa for specimens treated with 20% methacryloxyethyl dihydrogen phosphate for 60 seconds. Conclusion: The authors recommend methacryloxyethyl dihydrogen phosphate as it provides high tensile bond strength values and requires no additional rinse step.

Purpose: The aim of this prospective study was to present the results after 5 years of loading of 65 CeraOne (Nobel Biocare) crowns. Materials and Methods: Sixty-two implants in the maxilla and 3 implants in the mandible were placed in 57 patients. Sixty-two all-ceramic and three metal-ceramic crowns were cemented. The gruop comprised the first patients treated with the CeraOne prosthodontic concept. Results: Eight patients did not complete the study. Only one implant failed, giving a cumulative success rate for impla nts of 98.5%. The failed implant was replaced: a crown was cemented and then followed for 5 years without any complications. Four crowns were recorded as failures, giving a cumulative success rate for crowns of 93.7%. It should be observed that this result was very positive, as all crown failures were related to extraordinary causes and not one was a result of common bite forces or fatigue. The initial bone loss was in accordance with other studies on Branemark implants, and a stable situation was recorded after 2 years for the supporting bone around implants and adjacent teeth when the conical implants were excluded. Soft tissues around implants and adjacent teeth appeared healthy, and the cementation and the placement of the abutment shoulder in the peri-implant sulcus did not cause any recession of the peri-implant mucosa. Conclusion: CeraOne experienced virtually no complications and proved to be a highly predictable and safe prosthodontic concept. CeraOne also eliminated problems with abutment screw loosening and crated a platform for good esthetic results and satisfied patients.

Purpose: This study investigates the modulus of elasticity, yield strength, the strain at yield point, and the tear energy of nine elastomeric impression materials Materials and Methods: The values of the first three variables were computed from a tensile load test of 10 dumbbell-shaped specimens of each impression material. Results: A general descending order of modulus of elasticity (rigidity) follows: poly(vinyl siloxane) putty > polyether > polysulfides and the poly(vinyl siloxane) tray a nd syringeable materials. The descending order of yield strength was: poly(vinyl siloxane) putty > polyether and most poly(vinyl siloxane) tray and syringeable materails > one poly(vinyl siloxane) and the two polysulfides. The general descending order in strain at yield point (strain tolerance) was: two poly(vinyl siloxane) syringeable materials > four poly(vinyl siloxane) materails of various viscosities > polyether and the two polysulfides. Tear energy followed a general descending order of: polysulfies > polyether > poly(vinyl siloxane). Conclusion: The difficulty of removing impressions made of the putty or the polyether, and the increased risk of die breakage could be associated with the higher rigidity of these materials. The high strain tolderance of the poly(vinyl siloxane) impression materials allows their removal without distortion from appreciable tissue undercuts. The high tear energy of polysulfides indicates their superiority over other impression materials in their resistance to tear in thin sections.

Purpose: The purpose of the study were to evaluate the clinical performance of the Procera porcelain-fused-to-titanium crown system in general practice during a 2-year period, and to evaluate the performance of a new low-fusing porcelain as a veneering material on titanium. Materials and Methods: A number of consecutive complete-coverage crowns (40) in 25 patients (14 women and 11 men) with a mean age of 53.1 years (range 35 to 79 years) were made according to the Procera (Nobel Biocare) technique in a 3-month period. The titanium copings were fabricated from solid rods of pure titanium using spark erosion and copy-milling technique, whereafter they were veneered with a new type of low-fusing ceramic material. The crowns were evaluated using the CDA criteria at baseline and after 2 years. Results: The general failure rate was low and was restricted to one carious lesion, one porcelain fracture, and one loss of a crown resulting from failure of retention of a post and core. The most frequent single reason that the excellent color level was not recorded was a too-high value. A slightly dull or granular porcelain surface was observed both at baseline and after 2 years. Overall, the responses of the patients were positiv Conclusion: Within the limitations of the study it can be concluded that porcelain-veneered Procera titanium crowns can be used as an alterantive to other porcelain-fused-to-meta l systems. However, conclusions should be made with caution from the results of this study because of the limited number of patients and crowns and the short observation period.

Purpose: The main purpose of the present experimental study was to compare five different types of crowns, cemented on implant abutments, regarding their capability to withstand loads. Materials and Methods: Three types of all-ceramic crowns, a gold-foil-reinforced porcelain crown, and, as a control, a conventional metal ceramic crown were tested. Each crown was cemented onto an Astra Tech Single-Tooth implant. The five types of crowns, three of each type, and the titanium implants were subjected to loading in Lloyd test equipment until part of them was damaged, at which point the compression value was recorded and the deflection and bending moment were calculated. Comparisons were made on the basis of these data. Results: The results showed that the all-ceramic crowns fitted with a core should be able to withstand normally occurring biting forces without difficulty. The foil crown was also judged to be acceptable, while the bending moment of the cast all-ceramic crown without a core was considered unpredictable. The values for the metal ceramic design were as predicted, ie, they were clearly the highest in the study; the superior strength of metal ceramics should still be taken into account when deciding between all-ceramic colutions and the conventional metal ceramic crown. Conclusions: It was concluded that all-ceramic crowns are weak er than conventional metal ceramic crowns; however, based on estimated maximum clinical loadign (370 N in the incisor and premolar regions), In-Ceram and AllCeram crowns seem to function satisfactorily on implants.

Purpose: The purpose of this study was to facilitate the recognition of denture patients who are unable to adapt to conventional dentures and who are likely to benefit from treatment using implant-supported prostheses. Materials and Methods: Sixty-nine patients who were referred for postgraduate prosthetic treatment at Wits Dental School completed a self-report inventory of items related to their dentures in current use. Conventional dentures were fabricated for all subjects. Those patients who could not adapt to conventional complete denture treatment were referred for treatment with implant-su pported prostheses provided that they conformed with the recommended criteria for this treatment modality. Results: Analysis of the inventory of pretreatment denture complaints yielded variables that differentiated between the group who remained with conventional dentures and the group that was referred for implants. Significant variables we re the period that a mandibular denture was used before new dentures were requested (P = 0.025); the period that a maxillary denture was used before further treatment was sought (P = 0.03); the discarding of a mandibular denture (P = 0.035); and pain complaints related to maxillary dentures (P = 0.045). A logistic regression model was used to compare the clinical division of the sample with that determined by the mathematic model. Sixty-six percent of the subjects who accepted conventional treatment and 69% of implant patients corresponded for both classifications. Conclusion: The authors conclude that pretreatment denture complaints can be useful diagnostic aids for evaluating patients who are likely to benefit from implant-supported prostheses.

Purpose: The aim of the present investigation was to perform an international multicenter comparison of dental appearance as evaluated by dentists, dental technicians, and nondental subjects. Materials and Methods: The participants were drawn from three groups: 203 dentists, 197 dental technicians and 254 nondental subjects. The methods developed in a previous study in Sweden were applied again in seven centers located in six countries. A questionnaire, accompanied by five sets of comptuer-manipulated images portraying one man and one woman, was used to prompt and record responses to different aspects of dental appearance and function. Results: The questionnaire revealed that both the dental appearance and function of teeth were important to most of the participants, but three quearters of the participants did indicate that good dental function was more important than esthetics. More women (30%) than men (18%), however, placed greater importance on appearance. Age or gender did not influence judgments of the computer-manipulated images, although judgments did vary greatly within the three groups and between the centers. Nonetheless, lightly colored teeth were preferred more often by nondental subjects than be dentists or dental technicians. Conclusion: Computer-aided image manipulation shows promise as a method for investigating the significance of dental-related beliefs, especially those relating to esthetics, in different population groups. The evaluation of dental appearance and function in this study indicated that dental function is held in greater regard, and that the significance of dental appearance varies widely among dentists, dental technicians, and nondental subjects.

Purpose: The aim of this study was to investigate the influence of fatigue on the fracture strength of In-Ceram (Vita Zahnfabrik), Optimal Pressable Ceramics (Opc, Jeneric Pentron), and IPS Empress (Ivoclar-Vivadent) in both wet and dry environments. Materials and Methods: Twenty-six crown shapes measuring 8.0 mm in diameter and 8.5 mm in height were fabricated for each ceramic system. For each ceramic system, 10 specimens were tested for fracture strength without fatiguing. A second group (8 specimens) was submitted to a fatigue and fracture test in dry conditions, and a third group (8 specimens) was fatigued and fractured in a wet enviro nment using a mechanical testing machine (Instron). The results were statistically analyzed using a Mann-Whitney test. Results: The results indicated that: (1) The fracture strength for In-Ceram was significantly stronger than IPS Empress. No difference was found between In-Ceram and Opc, and Opc and IPS Empress. (2) The strength of the three ceramic systems decreased significantly after fatiguing in both dry and wet environments compared with the nonfatigued specimens. No difference was found between fatiguing in dry and wet environments. (3) For the three systems fatigued in a dry environment and then fracture tested, In-Ceram and Opc were significantly stronger than IPS Empress, but no difference was found between the three systems fatigued in a wet environment. Conclusion: Significant differences in the fracture strengths of the different systems investigated may be seen that result from both the nature of the system and the environment in which the specimens were fatigued.

Purpose: The purposes of this study were to compare changes in the condyle-fossa relationship in patients with temporomandibular disorders of arthrogenous origin treated with either a stabilization or a control appliance in a double-blind controlled study, and to compare the changes in the condyle-fossa relationship with the short-term treatment effect in the two treatment groups. The radiographic appearance of the temporomandibular joint was also studied. Materials and Methods: Fifty-eight patients with temporomandibular disorders of arthrogenous origin were assigned to two equally sized groups: a treatment group, given a stabilization appliance; and a control group, given a control appliance. The study covered 10 weeks. The treatment outcome regarding changes in severity of temporomandibular joint pain on a verbal scale was compared to changes in the condyle-fossa relationship in horiz ontally corrected oblique lateral transcranial radiographs taken with and without the appliance. Condyle-foss a relationship and structural bone changes were observed before treatment in corrected lateral tomogram Results: The group treated with a stabilization appliance showed a changed condylar position significantly more often (P = 0.004) than the control group. Of the patients reporting a successful treatment outcome, significantly more (P = 0.006) showed a changed condyle position in the group treated with a stabilization appliance than in the group treated with a control appliance. Conclusion: In patients with temporomandibular disorders of arthrogenous origin, the short-term occlusal appliance therapy resulting in a changed condylar position gave relief of symptoms more often than if the condylar position was unchanged

Purpose: The Periotest is an electronic instrument that has been advocated for the measurement of implant stability and osseointegration. The aims of this investigation were to establish the relationship between contact time and PTV values when the Periotest was used to assess implants in vivo and in vitro, and to investigate the influence of the striking height of the Periotest handpiece and the length of implant abutment. Materials and Methods: The accelerometer signal from a Periotest was captured and compared with the resulting PTV value. In vitro measurements of PTV and contact time were performed on a 3-mm abutment that had been attached to a 15-mm implant luted into an aluminum block, and were repeated on a patient in vivo. Further measurements were made of the abutments of six implants in turn in the maxilla of the same patient. The standard abutment lengths on the implants were 3, 4 (x 2), 5.5 (x 2), and 7 mm. Results: The results indicated that there was a linear relationship between contact time and PTV value for implants measured in vitro and in vivo. Greater scatter of the in vivo data was attributed to test and patient variables including striking position, distance, and damping as a result of the presence of soft tissues. There was a linear relationship between the PTV value and the striking height for implant measurements in vivo and in vitr Conclusion: It can be concluded that the sensitivity of the Periotest to clinical variables including striking height and handpiece angulation limit the application of the instrument as a clinical diagnostic aid to measure implant stability