Showing papers in "Journal of Prosthetic Dentistry in 1994"
TL;DR: Biomechanical problems are analyzed, and a recommended clinical approach is presented, suggesting that the post did not improve the resistance to fracture during occlusion and did not support the restoration.
Abstract: Various concepts for dental treatment have been established without appropriate documentation, such as restoration of endodontically treated teeth. Some researchers and dentists strongly recommend including a post with the restoration to strengthen the root. Other studies have indicated that posts may substantially weaken the roots and should be avoided. An additional approach suggested that the post did not improve the resistance to fracture during occlusion and did not support the restoration. Biomechanical problems are analyzed, and a recommended clinical approach is presented.
374 citations
TL;DR: The significance of tightening abutment screws and gold cylinders to osseointegrated fixtures with the correct torque is demonstrated, and a simple relationship between applied torque and screw preload is derived by use of mechanical engineering principles.
Abstract: The significance of tightening abutment screws and gold cylinders to osseointegrated fixtures with the correct torque is demonstrated, and a simple relationship between applied torque and screw preload is derived by use of mechanical engineering principles. The principles of a number of tightening methods are outlined and assessments made of their accuracy. The difference between optimum and design torque is highlighted. The necessity and means of achieving optimum torque to ensure a reliable joint in clinical practice is discussed.
266 citations
TL;DR: Sandblasting of all ceramic clinical restorations with feldspathic glass materials should be avoided, but for In-Ceram ceramic the volume loss was within an acceptable range and similar to that of noble metals.
Abstract: Silica coating can improve bonding of resin to glass-infiltrated aluminum oxide ceramic (In-Ceram), and sandblasting is a pretreatment to thermal silica coating (Silicoater MD system) or a tribochemical coating process (Rocatec system). This study evaluated the effects of sandblasting and coating techniques on volume loss, surface morphology, and surface composition of In-Ceram ceramic. Volume loss through sandblasting was 36 times less for In-Ceram ceramic compared with a feldspathic glass ceramic (IPS-Empress), and sandblasting of In-Ceram ceramic did not change its surface composition. After tribochemical coating with the Rocatec system, a layer of small silica particles remained that elevated the silica content to 19.7 weight percentage (energy-dispersive spectroscopy). Ultrasonic cleaning removed loose silica particles from the surface and decreased the silica content to 15.8 weight percentage, which suggested firm attachment of most of the silica layer to the surface. After treatment with the Silicoater MD system, the silica content increased only slightly from that of the sandblasted specimen. The silica layer created by these systems differs greatly in both morphology and thickness, which could result in different bond strengths. Sandblasting of all ceramic clinical restorations with feldspathic glass materials should be avoided, but for In-Ceram ceramic the volume loss was within an acceptable range and similar to that of noble metals.
255 citations
TL;DR: Porcelain surface treatment with aluminum oxide air abrasion followed by hydrofluoric acid, a silane coupling agent, and an unfilled resin produced a bond strength after 3 months' water storage and thermocycling that was significantly greater than the other nine porcelainsurface-treatment techniques.
Abstract: A laboratory study was conducted to evaluate the bond strength of composite resin bonded to porcelain surfaces by use of a variety of treatment regimens with the All-Bond 2 adhesive system. There were significant differences in the 24-hour bond strengths between several of the surface treatment methods. The mean shear bond strength after 24 hours of water storage ranged from 10.6 +/- 2.3 MPa to 25.0 +/- 4.4 MPa. Nine of the surface treatment methods showed a significant decrease (p < 0.05) in bond strengths after 3 months of water storage and thermocycling. After 3 months, the bond strengths ranged 0.1 +/- 0.1 MPa to 17.4 +/- 2.0 MPa. Porcelain surface treatment with aluminum oxide air abrasion followed by hydrofluoric acid, a silane coupling agent, and an unfilled resin produced a bond strength after 3 months' water storage and thermocycling that was significantly greater (p < 0.05) than the other nine porcelain surface-treatment techniques. Visual examination of the debonded specimens generally showed cohesive failures in porcelain for the treatment groups with a mean bond strength above 13 MPa.
234 citations
TL;DR: Data are reviewed in accordance with the concept that TMD is a chronic pain condition that shares many features with other common chronic pain conditions and the concept of chronic pain dysfunction, which has emerged as a critical consideration for chronic pain research and management.
Abstract: Temporomandibular disorders (TMD) are examined from a biopsychosocial or illness perspective. Data are reviewed in accordance with the concept that TMD is a chronic pain condition that shares many features with other common chronic pain conditions. TMD is placed within the same biopsychosocial model currently used to study and manage all common chronic pain conditions. The concept of chronic pain dysfunction, which has emerged as a critical consideration for chronic pain research and management, is also reviewed. Most chronic pain patients seem to bear their condition adequately and thus maintain adaptive levels of psychosocial function. By contrast, a psychosocially dysfunctional segment of the chronic pain population appears unable to cope as well and demonstrate higher rates of depression, somatization, and health care use, even though persons in this segment are not different from their functional peers on the basis of observable organic pathology. Finally, data are reviewed from longitudinal, epidemiologic, and experimental intervention studies that substantiate these two perspectives.
170 citations
TL;DR: The three methods of tooth preparation were statistically compared and revealed suitable dimensional stability during the firing and glazing process of In-Ceram alumina porcelain ceramic.
Abstract: This study evaluated the dimensional stability during firing of In-Ceram alumina porcelain ceramic and examined the marginal fit for three different configurations of tooth preparation. A stereomicroscope was used to measure the space between the margin of restorations and tooth preparations. The three methods of tooth preparation were statistically compared and revealed suitable dimensional stability during the firing and glazing process. A better marginal fit was recorded for artificial crowns fabricated on a chamfer or 50-degree shoulder tooth preparation.
170 citations
TL;DR: The results indicated that an increase in the amount of fibers enhanced the fracture resistance of the test specimens (p < 0.001).
Abstract: This study tested the effect on the fracture resistance of acrylic resin test specimens when different amounts of fibers were incorporated in the resin matrix. The fibers used included glass, carbon, and aramid fibers, with 30 test specimens of each concentration of fibers. Transverse sections of the specimens were studied by scanning electron microscope to establish how the fibers behave in the polymerization process. The results indicated that an increase in the amount of fibers enhanced the fracture resistance of the test specimens (p < 0.001). The SEM micrographs of transverse sections of test polymerized specimens revealed void spaces of different sizes inside the fiber roving.
164 citations
TL;DR: This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention that longer cantilevers lead to increased risk of failure.
Abstract: Various lengths of cantilevers for fixed implant-supported prostheses have been recommended in the literature. No scientific data are available for selecting specific lengths, and different views are reported. Authors contend that longer cantilevers lead to increased risk of failure. This study examined survival of fixed implant-supported prostheses using different cantilever lengths and offers clinical support for the contention.
157 citations
TL;DR: Immersion of acrylic resin dentures in hot water (50 degrees C) before insertion is recommended, especially for autopolymerized resins used either for rebasing or as denture base materials, to minimize the risk of adverse reactions in patients who wear acrylic resin Dentures.
Abstract: Acrylic resin dentures have the potential to elicit irritation, inflammation, and an allergic response of the oral mucosa. Studies of substances leachable from acrylic resins, their cytotoxicity to cultured cells, and means of reducing their leaching were systematically conducted. Under in vivo and in vitro conditions, formaldehyde and methyl methacrylate were significantly leached into human saliva and saliva-substitute buffer, especially from autopolymerized resins. Both leachable substances showed cytotoxic potentials in the range of their leaching concentrations. Formaldehyde was cytotoxic at lower concentrations than methyl methacrylate. Preleaching in water reduced subsequent leaching of both formaldehyde and methyl methacrylate, and the amount of reduction depended on an increase in the preleaching temperatures. Immersion of acrylic resin dentures in hot water (50 degrees C) before insertion is recommended, especially for autopolymerized resins used either for rebasing or as denture base materials, to minimize the risk of adverse reactions in patients who wear acrylic resin dentures.
157 citations
TL;DR: The high incidence of early repairs, and the greater potential for a removable ISP requiring adjustment and repair, should be considered both when discussing options with the patient and when estimating treatment and maintenance costs before the commencement of implant therapy.
Abstract: Prosthetic parameters for implant success have not been well defined but should include patient satisfaction and prosthesis maintenance, including adjustments and repairs. In addition, differences between fixed and removable implant-supported prostheses (ISPs) should be quantified. This study retrospectively evaluated both patient satisfaction and maintenance for 156 patients. Removable ISPs averaged almost three times as many adjustments per prosthesis (2.1 versus 0.8 per fixed ISP) and more than twice as many repairs (1.9 per removable ISP versus 0.9 per fixed ISP). The most common adjustments were to the contour of both types of prosthesis, and the most frequent repairs involved the retentive clips with removable ISPs and the gold screws with fixed ISPs. The incidence of repeat repairs was more than twice as high with removable prostheses compared with fixed prostheses. However, the repairs to opposing dentures most often needed were for conventional dentures opposing fixed ISPs. The vast majority of repairs were needed within the first year of service. Despite the high maintenance needed, patients were satisfied with both types of ISP, with the exception of limited satisfaction with cleansability, particularly with fixed restorations. The high incidence of early repairs, and the greater potential for a removable ISP requiring adjustment and repair, should be considered both when discussing options with the patient and when estimating treatment and maintenance costs before the commencement of implant therapy.
153 citations
TL;DR: It was concluded that for the short follow-up period, the state of connection did not influence the clinical success of implants and although splinted bar-retained overdentures scored better objectively, subjective satisfaction ratings did not differ.
Abstract: Thirty-six edentulous patients, each provided with two Brȧnemark implants in the mandible to anchor an overdenture, were selected for this study and randomly divided into three groups of 12 patients each. In each group a different attachment system was used: (1) magnets, (2) ball attachments, and (3) straight bars with clips (control). The mean loading time was 12.4 months (range 3 to 24 months). This study investigated (1) the clinical behavior of loaded implants by means of overdentures related to their connection system (splinted versus unsplinted) and (2) the clinical performance of prosthetic treatment. Preliminary results indicate no differences; no failures occurred and the level of marginal bone height, as well as the probing attachment level, changed similarly in the three groups. Although splinted bar-retained overdentures scored better objectively, subjective satisfaction ratings did not differ. It was concluded that for the short follow-up period, the state of connection did not influence the clinical success of implants. However, no definite conclusions may be drawn until long-term data become available.
TL;DR: It is suggested that proper wetting of the repair surface makes an important contribution to the strength of repaired acrylic resin.
Abstract: This study investigated the transverse strength of repaired test specimens of heat-cured acrylic resin The repair surfaces of the specimens were wetted with methyl methacrylate for various amounts of time before the autopolymerizing acrylic resin was applied to the joint space A three-point loading test was used to determine the transverse strength of the test specimens, and the morphologic changes in the methyl methacrylate-wetted repair surface was analyzed by scanning electron microscopy Visual inspection was used to determine whether the failures were adhesive or cohesive The results revealed that repaired test specimens were weaker than those unrepaired (p < 0001) The strength of the test specimens increased as the duration of methyl methacrylate wetting of the repair surfaces increased (p < 0001) Furthermore, the number of adhesive failures was small if the repair surfaces were adequately wetted with methyl methacrylate Scanning electron micrographs revealed that after 60- and 180-second wetting periods, the poly(methyl methacrylate) was noted to be dissolved with a smooth surface texture This study suggests that proper wetting of the repair surface makes an important contribution to the strength of repaired acrylic resin
TL;DR: The reinforcement effects from posts appeared limited in pulpless incisors when the tooth was subjected to masticatory and traumatic loads, and stress distributions in dentin were similar whether or not the post was present.
Abstract: A finite element analysis was conducted to study the influence of posts on dentinal stress in pulpless teeth. Three-dimensional models of an intact Chinese maxillary central incisor with and without post restoration were analyzed. When the tooth was subjected to masticatory and traumatic loads, stress distributions in dentin were similar whether or not the post was present. Maximal dentinal stresses were reduced by only 7% to 10% and 10% to 14.5%, respectively, with gold alloy and stainless steel posts. Thus the reinforcement effects from posts appeared limited in pulpless incisors.
TL;DR: A mouth guard with a stiffer insert, which softens at a higher temperature in the occlusal portion, is proposed as a more protective mouth guard.
Abstract: Mouth guards and materials were tested to provide information for a more protective yet more comfortable product. Ethylene-vinyl acetate copolymer materials varying in thickness and stiffness were tested for their mechanical, thermal, and water-absorption properties. Thickness was measured before and after fabrication of the mouth guard. During fabrication, thicknesses decreased from 25% to 50% for the custom-fabricated mouth guards and 70% to 99% for the mouth-formed (boil-and-bite), off-the-shelf, over-the-counter mouth guards. The thicker the material is, the greater the resulting energy absorption is. It is therefore essential that the thickness in the occlusal portion of the mouth guard remain optimal after fabrication. A mouth guard with a stiffer insert, which softens at a higher temperature in the occlusal portion, is proposed as a more protective mouth guard.
TL;DR: Investigation of the glazed porcelain surface showed that the glaze was removed in less than 2 hours of wear on the machine, and the amount of enamel wear produced by both glazed and unglazed Porcelain was similar; however, that produced by polished porcelains was substantially less.
Abstract: Abrasive wear tests were performed on unglazed, glazed, and polished porcelain stud specimens using human enamel as the opposing plate specimens. The wear tests were carried out on a wear machine that was specifically designed to simulate the masticatory cycle. The amount of enamel wear produced by both glazed and unglazed porcelain was similar; however, that produced by polished porcelain was substantially less. Investigation of the glazed porcelain surface showed that the glaze was removed in less than 2 hours of wear on the machine.
TL;DR: Cantilever lengths for fixed implant supported prostheses have been based largely on empirical judgment on load transfer to the mandible and curves describing the effect of cantilever length on maximal stress are presented.
Abstract: Cantilever lengths for fixed implant supported prostheses have been based largely on empirical judgment. This study determined the effects of cantilever length on load transfer to the mandible. A photoelastic model of a moderately resorbed edentulous human mandible with five 13 mm Branemark implants was constructed. Simulated occlusal loads at varying cantilever lengths were applied to the occlusal surface of a routinely fabricated fixed prosthesis. The highest stresses were located at the ridge crest on the distal surface of the distal implant for all cantilever lengths. Apical stresses at this implant developed in reciprocation to the effect of the distal tipping force on the cantilever. Curves describing the effect of cantilever length on maximal stress are presented. Little load transfer to adjacent implants was found. Disproportionate increases in maximum stress with increasing cantilever length occurred. Minor variations in implant angulation had a distinct effect on stress magnitude.
TL;DR: The findings indicate that ridge width decreases 25% within 3 years after primary molar extraction, and the rate of decrease diminishes to 4% over the next 3 years.
Abstract: This study investigated changes in ridge width over time in patients who were congenitally missing mandibular second premolars. Data were obtained from stone casts and radiographs of 35 edentulous sites on 22 patients representing three time periods: (1) before extraction of the primary mandibular second molar, (2) completion of orthodontic treatment, and (3) long-term evaluation. The findings indicate that ridge width decreases 25% within 3 years after primary molar extraction. The rate of decrease diminishes to 4% over the next 3 years. The change in ridge width had a weak association with the age of the patient at the time of the extraction but a small predictive value. No correlation was found between changes in ridge width and height and the time since the extraction or the age of the patient at the time of extraction.
TL;DR: Surface roughness resulting from five polishing systems on two ceramics was assessed and it was found that Feldspathic porcelain could be polished smoother than glazed and Dicor ceramic could be polish smoother than Ceramco II ceramic.
Abstract: Conventional and CAD-CAM ceramic restorations often require adjustments that result in a need to reduce surface roughness. Surface roughness resulting from five polishing systems on two ceramics was assessed. Disks of Ceramco II and Dicor MGC ceramic blocks were polished with five combinations of 45, 25, and 10 μm diamonds; a 30-fluted carbide; three silicon carbide-impregnated rubber points; 4 and 1 μm diamond gels; and an aluminum oxide point and two aluminum oxide pastes. Five profilometer average roughness measurements (Ra) were taken of five replications of each step in each sequence. Controls were autoglazed Ceramco II and Dicor MGC ceramic specimens milled with a Cerec diamond wheel. Feldspathic porcelain could be polished smoother than glazed. Dicor ceramic could be polished smoother than Ceramco II ceramic. Finishing diamond points followed by diamond gels produced the smoothest surface. A 30-fluted carbide did not improve smoothness as used. The aluminum oxide point followed by aluminum oxide pastes was equivalent to finishing diamonds and gels for Dicor ceramic.
TL;DR: According to the results, the ratio that caused only minor polymerization shrinkage of PMMA in the glass fiber roving improved the fracture resistance of the test specimens and seemed to increase the amount of PM MA inside the Fiber roving.
Abstract: This study determined the effect of polymerization shrinkage of polymethyl methacrylate (PMMA) coating of fiber roving on the transverse strength of an acrylic resin-glass fiber composite. The test specimens were heat-cured acrylic resin reinforced with glass fibers. The glass fiber rovings were treated with four PMMA-MMA mixtures (30 specimens per group) of various ratios assumed to have different amounts of polymerization shrinkage. A transverse strength test was used to determine the fracture resistance of the test specimens and the polymerization shrinkage of the PMMA-MMA mixtures was measured. After the specimens were fractured, single glass fibers used to reinforce the test specimens were'studied by SEM. The fracture resistance of the specimens was statistically different (p
TL;DR: The major findings were that the denture adhesive produced a statistically significant improvement in the retention and stability of the maxillary denture during the various chewing, swallowing, and speaking activities, for up to 8 hours; there were no statistically significant differences in improvement between a poorly fitting and well-fitting denture.
Abstract: This study used quantitative methods to measure the effects of a denture adhesive on the retention and stability of the maxillary denture. Denture movements were measured on 20 patients during standardized chewing, swallowing, and speaking activities, first with no adhesive, and then at 0, 2, 4, 6, and 8 hours after application of an over-the-counter cream adhesive. The major findings were that the denture adhesive produced a statistically significant improvement in the retention and stability of the maxillary denture during the various chewing, swallowing, and speaking activities, for up to 8 hours; there were no statistically significant differences in improvement between a poorly fitting and well-fitting denture; and patients were able to produce significantly greater levels of incisal bite force with the use of the adhesive.
TL;DR: Various components of denture cleansers and soft lining materials, particularly peroxides, in cleanser and gel formation components ofsoft liners play important roles in the deterioration of soft liners caused by cleansers.
Abstract: The deterioration of six commercial resilient denture lining materials immersed in seven groups of denture cleansers was investigated. Although the grades of deterioration of these soft liners were not related to the amount of peroxide content or the pH of denture cleansers, the effects of peroxide cleansers were, with few exceptions, more severe than those of the other types. For example, an enzyme cleanser caused severe changes of one soft liner. The grades of surface porosity were correlated well with the log of the gelation time of the tissue conditioners (except for one soft liner), in four kinds of peroxide cleansers. These results suggest that various components of denture cleansers and soft lining materials, particularly peroxides, in cleansers and gel formation components of soft liners play important roles in the deterioration of soft liners caused by cleansers.
TL;DR: This study investigated adhesive tag formation within dentinal tubules and the anastomosing of lateral canals observable with scanning electron microscopy to find the network of interconnected adhesive tags formed with these materials may be fundamental to the development of a stronger dentin/resin bond.
Abstract: This study investigated adhesive tag formation within dentinal tubules and the anastomosing of lateral canals observable with scanning electron microscopy. This mechanism of micromechanical bonding had not been studied previously. The following brands of adhesives were applied to the prepared dentin surface of unerupted human third molars: Scotchbond Multipurpose, C&B Metabond, All-Bond 2, both etched and unetched, Tenure Solution, and XR-Bond. The experimental specimens were decalcified and prepared for SEM examination. Many tubule resin tags with lateral branching were observed. The resin branches were the result of primer, adhesive, or both entering lateral canals and communicating with adjacent tubules. The polymerization of adhesive in lateral canals was more prevalent with Scotchbond Multipurpose, C & B Metabond, and etched All-Bond 2 adhesives. The network of interconnected adhesive tags formed with these materials may be fundamental to the development of a stronger dentin/resin bond.
TL;DR: Hydrated teeth exhibited less deformation than dehydrated teeth because of polymerization shrinkage and greater cuspal deformations were measured with the microscopic technique than with interferometry because of differences in experimental design.
Abstract: Polymerization shrinkage of two posterior composite resin restorative materials was measured by dilatometry. The results were compared with a decrease in cavity width of MOD preparations in extracted premolars restored with the composite resins. A highly filled hybrid composite exhibited greater free shrinkage and cuspal deformation than a hybrid composite with a lower filler content. Deformation of the cusps was less than the unrestricted shrinkage of the composite resins. Hydrated teeth exhibited less deformation than dehydrated teeth because of polymerization shrinkage. Greater cuspal deformations were measured with the microscopic technique than with interferometry because of differences in experimental design.
TL;DR: If the average occlusal loading levels were 10 MPa, there did not appear to be a risk of microfracture in dental cement because of mechanical loading and Fatigue analysis was based on estimated stress versus number of cycle curves for cements and resulted in stresses below the estimated endurance limit.
Abstract: Long-term clinical failures of complete veneer crowns are commonly attributed to microleakage of the cement. Excessive stress or fatigue cycling may create cement microfractures and promote microleakage. Two-dimensional (2D) finite element analysis (FEA) was selected to determine stress levels and distributions on dental cements resulting from 10 MPa occlusal loads on single-unit complete artificial veneer crowns during various clinical conditions. Sixteen 2D-FEA computer models were generated for a mandibular first premolar to study the effects of (1) marginal configuration (shoulder for all-ceramic crown versus chamfer for type III gold alloy crown), (2) four types of cement (zinc phosphate, polycarboxylate, glass ionomer, and composite resin), and (3) two thicknesses of cement (25 and 100 μm) for single-cycle loads and fatigue loading. There was almost no difference between a chamfer and shoulder marginal configuration except at the edge of the margin where the chamfer finish lines reached 2 to 8 times greater stresses. There were minimal effects for thickness of cement and marginal configurations. Stresses were slightly less for thicker cement. Fatigue analysis was based on estimated stress versus number of cycle curves for cements and resulted in stresses below the estimated endurance limit. If the average occlusal loading levels were 10 MPa, there did not appear to be a risk of microfracture in dental cement because of mechanical loading.
TL;DR: A well-constructed removable partial denture of either design, supported by favorable abutments and accompanied by a regular recall program offers a satisfactory treatment modality.
Abstract: A randomized clinical trial was undertaken to compare the effectiveness of two partial denture designs, one with I-bar (bar) and the other with circumferential retainers (circumferential), in 134 patients with Kennedy class I and class II edentulous conditions. A total of 30 partial dentures were considered failures, five because of abutment failures and 25 because of the lack of removable partial denture use for eating. The 5-year success rate of 71.3% for the circumferential design did not differ significantly from the 76.6% for the bar design (p > 0.05). There were no discernible changes in the nine periodontal health components of abutment teeth with either of the two designs after 60 months. The results indicate that the two designs do not differ significantly in terms of success rates, maintenance care, and effects on abutment teeth. A well-constructed removable partial denture of either design, supported by favorable abutments and accompanied by a regular recall program offers a satisfactory treatment modality.
TL;DR: Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive of cements, but no difference in retention was recorded between Ketac-Cem and Panavia cements.
Abstract: This investigation evaluated the retention of preformed posts with four different cements: C & B Metabond, Panavia, All-Bond 2, and Ketac-Cem. Sixty intact maxillary canines were selected for the study. The clinical crowns were removed and endodontic therapy done on each root, which was then prepared to receive prefabricated posts. The 60 samples were divided into four groups of 15, and the posts in each group were cemented with one of the four cements. The roots were mounted in acrylic resin blocks and the posts were separated from the canals with an Instron testing machine. Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive (p < 0.05). No difference in retention was recorded between Ketac-Cem and Panavia cements. All-Bond 2 cement was the least retentive of cements.
TL;DR: A clinical pilot study that monitored a group of 12 patients who have received 14 single tooth replacement experimental restorations made with prefabricated continuous fiber-reinforced composite (FRC) frameworks found the restoration with the longest service life was a mandibular molar replacement that has remained in service 24 months.
Abstract: This report describes a clinical pilot study that monitored a group of 12 patients who have received 14 single tooth replacement experimental restorations made with prefabricated continuous fiber-reinforced composite (FRC) frameworks. Because these restorations represent a purely adhesive restorative system, tooth preparation was not performed. The Kaplan-Meier survival probability at 12 months was approximately 50%. The restoration with the longest service life was a mandibular molar replacement that has remained in service 24 months. With improved survival times, bonded FRC definitive restorations should be plausible.
TL;DR: The intraoral use of hydrofluoric acid is no more effective than the less dangerous acidulated phosphate fluoride gel, and two common fluoride etchants yielded bond strengths that produced cohesive failure of all samples.
Abstract: Hydrofluoric acid etches porcelain to produce a porous surface visible under scanning electron microscopy when compared to an acidulated phosphate fluoride gel. Some investigators have suggested the greater porosity of the hydrofluoric acid etch produces a greater composite-to-porcelain bond. This investigation tested that assumption with two common fluoride etchants. The etched surfaces were first viewed under scanning electron microscopy to ensure that a characteristic etch was achieved. Both etchants yielded bond strengths that produced cohesive failure of all samples. This suggested that the intraoral use of hydrofluoric acid is no more effective than the less dangerous acidulated phosphate fluoride gel.
TL;DR: This technique records the planned and subsequently proven contours, which are then used to guide fabrication of the final prosthesis and produce a predictable esthetic result.
Abstract: Despite successful osseointegration of dental implants, patients can be dissatisfied with the definitive restoration because of a poor esthetic result. An esthetic implant restoration depends on correct implant placement and a well-designed and fabricated prosthesis that includes the prosthetic teeth and the surrounding whether it is acrylic resin or soft tissue. This article describes a technique to help predict, develop, and evaluate implant prostheses and their soft tissue contours at the provisional restoration stage. This technique records the planned and subsequently proven contours, which are then used to guide fabrication of the final prosthesis and produce a predictable esthetic result.
TL;DR: Standardized tooth preparations were completed on previously intact human molars in vivo, and castings were made with a precious metal ceramic alloy by conventional techniques, revealing that the zinc phosphate group leaked significantly more than other cement groups.
Abstract: Standardized tooth preparations were completed on previously intact human molars in vivo, and castings were made with a precious metal ceramic alloy by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate, composite resin-glass ionomer hybrid, and a composite resin-glass ionomer hybrid with a dentinal bonding agent and were cemented in a standardized manner to periodontally compromised molars. After 6 months the teeth were carefully extracted, stained, embedded, and sectioned, and the in vivo microleakage was measured. ANOVA disclosed significant differences between groups, and a multiple comparisons test revealed that the zinc phosphate group leaked significantly more than other cement groups.