Gerald N. Graser

Bond strength and microleakage of porcelain repair materials

T he increased use of porcelain restorations engenders the need for a reliable porcelain repair system. Retention of restorative resins to dental porcelain is poor and difficult to attain. Commercial repair materials are used for all types of restorative materials, including porcelain, while others are specifically designed for porcelain fractures. Jochen and Caputo’ reported that the abrasion of the surface of the porcelain with a diamond rotary instrument increased the retention of the repair material. It is not known how important mechanical retention is compared with chemical retention of the resin. It seems that undercuts in the porcelain would enhance the bond of the repair material. Semmelman and Kulp’ evaluated silane as a bonding agent and concluded that silane increased the retention of porcelain denture teeth to acrylic resin. Newberg and Pameijer3 found that the use of a silane solution before bonding a composite resin to dental porcelain greatly increased the retention. Eames et a1.4~5 have also shown similar findings when using Fusion (George Taub Products, and Fusion Co., Jersey City, N.J.) before bonding restorative resins. They observed, after 1 year, that the retention was higher for all the materials and that with Fusion plus Concise (3M Co., Dental Products Div., St. Paul, Minn.) all the bond failures occurred in the porcelain. Highton and Caputo6 reported that Fusion, used with a composite resin, was superior to Den-Mat (Den-Mat Inc., Santa Maria, Calif.). Thirty-nine percent of the strength was regained after 3 months with the acrylic resin and 25% with the composite resin. Nowlin et al.’ reported that Fusion plus Concise was superior to Den-Mat and 18% of the original porcelain strength was regained.

Porosity of denture resin cured by microwave energy

This study compared porosity of denture resin cured by microwave energy to denture resin cured by the conventional heat method. Seven groups of 10 samples each were tested. The control samples of methyl methacrylate monomer were cured in a curing tank at 165 degrees F for 9 hours. Four of the six experimental groups, consisting of samples made from Micro Liquid monomer (H.D. Justi Co., Oxnard, Calif.), were cured by microwave energy at varying wattages and times. The other two experimental groups contained samples of methyl methacrylate monomer cured by microwave energy. No significant differences were found in mean porosity between the control group and the four groups of microwave-processed samples that used Micro Liquid monomer. The two groups of microwave-processed samples of methyl methacrylate monomer showed a significantly higher mean porosity.

Dimensional accuracy of denture resin cured by microwave energy.

Microwave processing has several time-saving advantages over conventional processing of denture base resins. Little is known about the adaptation of bases processed by microwave radiation to the cast and the mouth. Comparisons were made in five regions of the palate and ridge. The microwave-processed denture bases had equal or better dimensional accuracy than conventionally processed bases.

Long-term reinforced fixed provisional restorations

Extensive prosthodontic treatment often requires fabrication of long-term provisional restorations. Numerous materials and techniques have been described for prolonged insertion of interim restorations. This article describes a procedure for fabrication of long-term reinforced heat-processed provisional restorations based on a diagnostic wax-up. Reinforced heat-processed provisional restorations reduced flexure, which minimizes progressive loss of cement and diminished the possibility of recurrent decay. Occlusal stability and vertical dimension were maintained because of greater wear resistance. Occlusion, tooth contours, and pontic design developed in the provisional restoration were duplicated in the definitive restoration. The use of a matrix from a diagnostic wax-up facilitated fabrication of the prosthesis, and made the procedure less time-consuming and more predictable.

Completed bases for removable dentures

A technique for the fabrication of completed bases for removable dentures has been described. The artificial stone mounting casts and completed bases must be kept free of debris at all times to allow for accurate seating of the bases on the casts. The completed bases must be kept in water when not in use between patient appointments.

The relationship of drug use to denture function and saliva flow rate in a geriatric population.

This study investigated an old elderly population and the relationships between the use of hyposalivatory drugs and denture function, including saliva flow rates and denture-supporting structures and health. There was a high prevalence of drug use and medical problems. Hyposalivatory drugs were prescribed for more than half of the subjects. There was a significant relationship between increased hyposalivatory drug use and reduced saliva flow rates. Reduced values for denture-supporting structures were found to be related to increased medical problems and hyposalivatory drug use. Reduced values for denture-supporting tissue health were found to be related to masticatory performance and retention and stability. Bite force showed a strong positive relationship with masticatory performance. Some of the subjective evaluations by the subjects showed statistically significant relationship with their respective objective measures: perceptions of dry mouth were related to saliva flow rates, perceptions of denture rocking or looseness were related to retention and stability ratings, and reports of pain on chewing were related to masticatory performance. It may be concluded that the use of drugs with hyposalivatory side effects may have a deleterious influence on the denture-bearing tissue. Direct influence on denture function, however, was not found. These findings provide valuable insights into the effects of drug usage in old age and their impact on oral health and denture function. Diagnostic and treatment capabilities are thus enhanced in that physicians, pharmacists, and other health-related professionals can be alerted to the problems accompanying hyposalivatory drug use. This may permit alternatives in medication when possible, and dentists may more effectively plan and conduct prosthodontic care for these individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Tooth Preparation: A Study on the Effect of Different Variables and a Comparison Between Conventional and Channeled Diamond Burs

PURPOSEnThe purpose of this study was to evaluate the different variables involved in tooth cutting to characterize intrapulpal temperature generation, cutting efficiency, and bur durability when using conventional and channeled diamond burs.nnnMATERIALS AND METHODSnForty premolars and 60 molars were selected for the study. Four diamond burs were paired according to grit size: 125-microm grit: Brasseler Coarse (Control 1) and TDA System (Test 1) burs; and 180-microm grit: Brasseler CRF (Control 2) and NTI Turbo Diamond (Test 2) burs. Each bur was used twice when cutting the premolar teeth, whereas it was used for 60 cuts when cutting the molar teeth. The data were analyzed to compare the correlation of bur design, grit and wear, amount of pressure, advancement rate, revolutions per minute, cutting time and rate, and proximity to the pulp chamber with intrapulpal temperature generation, cutting efficiency, and bur longevity. The mean values of test and control burs in each group were compared using an ANOVA (p < 0.05 for significant differences) for temperature generation and an ANOVA and the Tukey multiple range test (p< or = 0.05) for cutting efficiency and bur longevity.nnnRESULTSnNo significant difference was found in intrapulpal temperature generation while cutting premolar and molar teeth with conventional and channeled diamond burs. In both groups, the mean temperature recorded during and after the cutting procedure was lower than the baseline temperature. For premolar teeth, no significant difference was established for control and test burs for the load required to cut into the tooth and the cutting rate. However, both test burs showed significantly fewer revolutions per minute when compared to their control counterparts. For the molar teeth, the Brasseler CRF bur required a significantly lower cutting load when compared to the NTI bur, whereas no difference was noted between the other pair of burs. The cutting rate was significantly higher for both control burs, whereas revolutions per minute (rpm) were greater for control coarser burs only. Overall, channeled burs showed a significantly lower cutting efficiency when compared to conventionally designed burs.nnnCONCLUSIONnWithin the limitations of this study, channeled burs showed no significant advantage over conventional diamond burs when evaluating temperature generation and bur durability. Moreover, the cutting efficiency of conventional burs was greater than that of channeled burs.

Face-bow record without a third point of reference: Theoretical considerations and an alternative technique

Accurate mounting of dental casts is achieved by transferring the tridimensional spatial relationship of the maxillary arch to an articulator. A face-bow is used to transfer this relationship to the articulator, usually by relating the face-bow to a plane of reference. The most common reference plane is the Frankfort plane, which has been assumed to be horizontal when the patient is in the natural head position. The axis-orbitale plane has also been considered horizontal and used as reference. However, it has been shown that both planes are not horizontal, and mounting a maxillary cast according to these planes can result in an inaccurate mounting. This article describes an alternative procedure for face-bow transfer without a plane of reference, and uses the angular relationship between the occlusal plane and the condylar path to mount the maxillary cast on the articulator. The elimination of a reference plane, to which relate the functional determinants of occlusion, avoids an additional source of error during the mounting procedure.

ALTERNATIVE PROCEDURE FOR MAKING A METAL SUPRASTRUCTURE IN A MILLED BAR IMPLANT-SUPPORTED OVERDENTURE

The predictability of implant-supported prostheses has been established. Although the original Brånemark design has been successfully used in the mandible, esthetic, speech, and hygiene-related problems have been reported in maxillary fixed prostheses. Implant-overdentures can overcome some of the problems encountered in maxillary fixed prostheses. Milled-bar implant-supported overdentures fabricated by electric discharge machining are characterized by stability similar to a fixed prostheses and are removable for hygiene procedures. However, the procedure is costly and requires highly trained technicians. An alternative procedure to produce an accurately fitting metal suprastructure is presented. This procedure does not require additional technical skills and uses instruments and materials that are readily available and relatively inexpensive. The use of simple and easy to replace attachments allows repairs to be performed in the dental office, thus reducing maintenance cost. The overall result is a prosthesis that incorporates the features of a spark erosion overdenture at a fraction of the cost and that is available to a broader patient population.

Resolving esthetic and phonetic problems associated with maxillary implant-supported prostheses. A clinical report

A technique has been presented for placement of an implant prosthesis without a visually detectable space between the prosthesis and soft tissue or visibility of the metal abutments. The prosthesis permits better phonetics and greatly improved esthetics including better lip support. Proper presurgical planning and careful assessment of the potential level of home care are especially important when this technique is used.