Clinical audit of posterior three-unit fixed-movable resin-bonded fixed partial dentures - A retrospective, preliminary clinical investigation.

BACKGROUND: Two-unit cantilevered resin-bonded fixed partial dentures (RBFPDs) have higher retention rates over longer span fixed-fixed RBFPDs. It has been hypothesized that interabutment stresses associated with fixed-fixed designs cause prosthesis debonds therefore for the replacement of molar-sized and longer spans, non-rigid connectors have been used to allow independent movement between two abutment teeth. OBJECTIVES: This preliminary study evaluates the clinical longevity and subjects' satisfaction of three-unit fixed-movable (FM3) RBFPDs provided at a dental teaching hospital. MATERIALS AND METHODS: Subjects who had received FM3 RBFPD(s) in the posterior region were clinically reviewed for complications. History of any debonds and subjects' satisfaction to the prosthesis was recorded. Time-to-debond (retention rate) and time-to-loss (survival rate) of these prostheses were presented in life tables. RESULTS: Ninety-eight prostheses in 84 subjects were examined. Their mean service life was 31.8 months (SD 11.5, range 3-67 months). Twenty-two prostheses had a history of debond, resulting in a retention proportion of 77.6%; seventeen of these were rebonded and still present at the time of review. One prosthesis was lost after extraction of a periodontally-involved abutment tooth, giving a survival proportion of 93.9%. High subject satisfaction and no adverse outcome were reported. CONCLUSION: Three-unit fixed-movable RBFPDs have a shorter success than two-unit cantilevered RBFPDs. However, non-rigid connectors allow the possibility of rebonding giving satisfactory short-term survival rate. Further research is needed to investigate their long-term efficacy. CLINICAL SIGNIFICANCE: Three-unit fixed-movable RBFPDs incorporating non-rigid connectors may be a feasible option for replacement of molar-size pontic in the posterior region.

Coolant effectiveness in dental cutting with air-turbine handpieces.

OBJECTIVE: To establish a strategy for evaluating coolant effectiveness and to compare typical cooling conditions used in dental cutting. MATERIALS AND METHODS: A test system comprising a resistive heat source and an array of four type K thermocouples was used to compare the cooling effectiveness of air alone, water stream alone, and an air-water spray, as delivered by representative air-turbine handpieces. Mean temperature change at the four sites was recorded for a range of water flow rates in the range 10 to 90 mL min(-1), with and without air, and with and without the turbine running. The thermal resistance of the system, R, was calculated as the temperature change per watt (KW(-1)). RESULTS: For wet cooling (water stream and air-water spray), R was 5.1 to 11.5 KW(-1), whereas for air coolant alone the range was 18.5 to 30.7 KW(-1). R for air-water spray was lower than for water stream cooling at the same flow rate. CONCLUSIONS: The thermal resistivity approach is a viable means of comparative testing of cooling efficacy in simulated dental cutting. It may provide a reliable means of testing handpiece nozzle design, thus enabling the development of more efficient cooling.

Effect of contamination and decontamination on adhesion of a resin-modified glass-ionomer cement to bovine dentin.

PURPOSE: To determine the adhesion of resin-modified glass-ionomer cement to bovine dentin under contaminated and decontaminated conditions. MATERIALS AND METHODS: Forty-five bovine mandibular incisors were used. The surfaces of bovine dentin specimens were subjected to Temp-bond, dental handpiece lubricant (contamination), Hibiscrub, chlorhexidine or pumice (decontamination), as well as contamination followed by decontamination. From these, 14 test groups were created to investigate the effects of these variables on the microtensile bond strength of a resin-modified glassionomer cement to dentin. In addition, scanning electron microscopy was performed to examine the effects of contamination and decontamination procedures on the dentin surfaces. The data were analyzed by one-way ANOVA, Kruskal-Wallis, and Mann-Whitney tests. RESULTS: SEM examination showed visible differences between the control group and dentin contaminated with Temp-bond or handpiece lubricant. All the contamination and decontamination test agents when used alone - except Hibiscrub - showed significant reductions in bond strength when compared to the control (p < 0.001). All the test groups subjected to contamination followed by decontamination showed a significantly reduced bond strength (p < 0.001) when compared to the control, with the exception of the handpiece lubricant/Hibiscrub combination. CONCLUSION: Under the conditions tested, Temp-bond, handpiece lubricant, chlorhexidine, and pumice may have an adverse effect on the bonding of resin-modified glass ionomer to dentin. Hibiscrub was effective in decontaminating handpiece lubricant but not Temp-bond.

Vibration characteristics of dental high-speed turbines and speed-increasing handpieces.

OBJECTIVES: Vibrations of dental handpieces may contribute to symptoms of hand-arm vibration syndrome in dental personnel and iatrogenic enamel cracking in teeth. However, methods for measuring dental handpiece vibrations have previously been limited and information about vibration characteristics is sparse. This preliminary study aimed to use a novel approach to assess the vibrations of unloaded high-speed handpieces in vitro. METHODS: Maximum vibration displacement amplitudes of five air turbines and two speed-increasing handpieces were recorded whilst they were operated with and without a rotary cutting instrument (RCI) using a scanning laser vibrometer (SLV). RESULTS: RCI rotation speeds, calculated from frequency peaks, were consistent with expected values. ANOVA statistical analysis indicated significant differences in vibrations between handpiece models (p<0.01), although post hoc tests revealed that differences between most individual models were not significant (p>0.11). Operating handpieces with a RCI resulted in greater vibrations than with no RCI (p<0.01). Points on the head of the handpiece showed greater vibration displacement amplitudes than points along the body (p<0.01). CONCLUSIONS: Although no single measurement exceeded 4 microm for the handpieces in the current test setup (implying that these vibrations may be unlikely to cause adverse effects), this study has formed the basis for future work which will include handpiece vibration measurements whilst cutting under clinically representative loads.

Long-span, fixed-movable, resin-bonded fixed partial dentures: a retrospective, preliminary clinical investigation.

PURPOSE: Long-span, resin-bonded fixed partial dentures (FPDs) have been associated with higher debonding rates than short-span prostheses. The use of modified nonrigid connectors that allow movement between the abutments in long-span resin-bonded prostheses may reduce harmful interabutment forces that stress the metal framework and resin-bonded interface. This preliminary investigation aimed to evaluate the longevity of long-span resin-bonded FPDs of 4 or more units with a modified nonrigid connector and increased extension of the retainer framework around the major abutment. MATERIALS AND METHODS: Thirty-eight patients attended a clinical examination; each had been provided with 1 or more resin-bonded FPD of 4 or more units (43 prostheses). For each patient, the following data were recorded: gender, age, cementation date, and endodontic treatment, if performed. Data regarding the occurrence of any debondings and patient expectations were also recorded. RESULTS: The mean service life for the 43 prostheses was 46.9 months (SD 22.0), with a range of 12 days to 87 months. Three prostheses had debonded, resulting in a clinical retention rate of 92.2%. CONCLUSION: Long-span resin-bonded FPDs incorporating nonrigid connectors that allow independent movement between the major and minor retainer, combined with increased framework extension on the major abutment, appear successful in the short term. Further research is required to determine their long-term efficacy.

Oral health status of institutionalised elderly in Hong Kong.

OBJECTIVES: To describe the oral health status of institutionalized elderly in Hong Kong. METHODS: Older adults in 56 elderly homes were clinically examined in the institution by one of two calibrated dentists using standard methods recommended by the World Health Organization. Information on their perceived oral health status and behaviour was obtained from an interview. RESULTS: A total of 3153 elderly aged 65 years or above (mean = 79.8) were examined. Around 20% of them were edentulous. The mean DMFT score was 23.0 (DT = 2.6; MT = 20.1; FT = 0.3). The percentage of dentate subjects with healthy gingivae, bleeding on probing, calculus, shallow pockets, and deep pockets (according to the highest CPI score) were 1, 2, 41, 37 and 20 respectively. Two-thirds of the elderly reported having difficulties chewing, and over half had not visited a dentist for over 5 years. CONCLUSION: The oral health status of institutionalised elderly in Hong Kong is poor and needs to be improved.

Outreach dental service for persons with special needs in Hong Kong.

The authors describe the acceptance and efficiency of an outreach dental service, which provided oral health care to persons with special needs in Hong Kong. Portable dental equipment was transported to various institutions. Basic dental care including prevention, scaling, restoration, extraction, and denture repair was provided free of charge. Elderly adults living in institutions were the main service recipients, but other people with special needs, including physically disabled and persons with mental retardation were also reached. One-third of the patients had dental pain or sensitivity, and 70% had not visited a dentist for more than three years. Dental care was provided to 6,867 patients over four years. Feedback from the patients showed that more than 90% of them were satisfied with the service. These findings indicate that patients with special needs in Hong Kong are in great need of dental care. An outreach dental service appears to be both appropriate and efficient in providing care to these persons.