The cumulative effect of error in the digital workflow for complete-arch implant-supported frameworks: An in vitro study.

PURPOSE: To investigate the error accumulation and distribution through various stages of the digital workflow for complete-arch implant-supported framework fabrication. MATERIALS AND METHODS: A resin model of edentulous maxilla with 6 dental implants was scanned using an intraoral scanner for 10 times (Complete-digital group). Ten conventional gypsum casts were made and digitized by a laboratory scanner (Analogue-digital group). Five implant frameworks were designed and milled using CAD-CAM technique for each workflow. Inter-implant distances and angles of the resin model (reference) and frameworks were measured by a coordinate measuring machine, while the scans and virtual frameworks were examined by an inspection software. Effect of type of workflow and the individual stage on the accuracy of the frameworks were analysed by Two-way ANOVA. RESULTS: The expanded uncertainty of both workflows was ~150 µm and ~ 0.8°. The accuracy of the CAD stage was the highest. In the complete-digital workflow, the greatest distortion was found in the data acquisition stage, while in the analogue-digital workflow, it was found in the CAM stage. Compared with the analogue-digital group, the complete-digital group showed a significant higher precision in the first quadrant, but lower trueness in the second quadrant in data acquisition, and a significantly lower precision in the second quadrant at the CAD stage. CONCLUSIONS: Linear distortions of the complete-digital and analogue-digital workflows were clinically acceptable, while angular distortions were not. Distortions were generally derived from data acquisition and CAM stage. The CAD precision depended on the distortions derived from data acquisition. The complete-digital workflow was not as accurate as the analogue-digital in complete-arch implant rehabilitation.

Does the geometry of scan bodies affect the alignment accuracy of computer-aided design in implant digital workflow: An in vitro study?

OBJECTIVES: To compare 2 implant scan bodies with different geometry on the accuracy of the virtual alignment process in the digital workflow. MATERIALS AND METHODS: A master model of the edentulous maxilla with 6 implants and multiunit abutments (MUA) inserted was fabricated. Six dome-shaped and cuboidal scan bodies were mounted on the MUAs, respectively, and consecutively scanned by a laboratory scanner 10 times. The original scans were imported to a dental-specific CAD software and virtually aligned with the default CAD model in the implant library. Thus, 10 aligned models were created. Both the original scans and the aligned models were evaluated by an inspection software for deviation of the scan body surfaces, the centroids of scan body and MUA, the scan body center-axis, and the inter-MUA distances/angles. The two-sample T-test/Mann-Whitney U test were used to analyze the data with the level of significance set at 0.05. RESULTS: The cuboidal group showed significant greater deviations of the model surface (13.9 µm vs. 10.7 µm) and the MUA centroids (31.7 µm vs. 22.8 µm) but smaller deviation of the inter-MUA angle (0.047° vs. 0.070°) than those of the dome-shaped group (p < .05). No significant differences in the deviation of scan body centroids, center-axis, and the inter-MUA distances between the 2 groups were found. CONCLUSIONS: Virtual alignment of implant scan body affected the accuracy of the digital workflow for complete-arch implant-supported prostheses (up to ~30 µm/0.09°). Different geometries of the implant scan body could also influence the transfer accuracy in the CAD process.

Implant framework misfit: A systematic review on assessment methods and clinical complications.

BACKGROUND: The fit of implant-supported prostheses is of prime importance for the long-term success of implant therapy. PURPOSE: This systematic review aimed to evaluate recent evidence on current techniques for assessing implant-framework misfit, its associated strain/stress, and whether these misfits are related to mechanical, biological, and clinical consequences. MATERIALS AND METHODS: An electronic search for publications from January 2010 to October 2020 was performed using the Pubmed, Embase, Web of Science, and Cochrane Library databases with combined keywords on implant-framework misfit assessments and related clinical complications. Inclusion and exclusion criteria were applied. After full-text analyses, data extraction was implemented on current techniques of misfit assessment and the relationship between the misfit and the induced strain/stress. RESULTS: A total of 3 in vivo and 92 in vitro studies were selected, including 47 studies on quantifying the degree of implant-framework misfit with dimensional techniques, 24 studies measuring misfit-induced strain/stress with modeling techniques, and 24 studies using both methods. The technical details, advantages, and limitations of each technique were illustrated. The correlation between the implant-framework misfit and the induced strain/stress has been revealed in vitro, while that with the biological complications and implant/prostheses failure was weak in clinical studies. CONCLUSIONS: Dimensional and modeling techniques are available to measure the implant-framework misfit. The passivity of implant-supported fixed prostheses appeared related to the induced strain/stress, but not the clinical complications. Further studies combining three-dimensional (3D) assessments using dimensional and modeling techniques was needed.

A randomised controlled trial of two-unit cantilevered or three-unit fixed-movable resin-bonded fixed partial dentures replacing missing molars.

OBJECTIVE: To examine the short-term clinical performance and patient-reported outcomes of two-unit cantilevered (CL2) and three-unit fixed-movable (FM3) RBFPDs for replacement of single molar-sized spans. MATERIALS AND METHODS: Subjects with an 8-10 mm molar-sized edentulous span(s) and 12 pairs of occluding units were randomly assigned to receive either CL2 or FM3 RBFPD (ratio 1:1). The survival (retention of original prosthesis) and success (survival, complication-free) of RBFPDs at one-year were analysed. Patient-reported outcomes were assessed by prosthesis satisfactory questionnaire and Oral Health Impact Profile (OHIP-49). Data in mean, proportion and longevity were analysed by t-test/Mann-Whitney U test/Wilcoxon signed-rank test, chi-square and log-rank tests respectively at significance level α = 0.05. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT02239718. RESULTS: Ninety-eight RBFPDs (42 CL2 and 56 FM3) were delivered in eighty-three patients. Majority (n = 89) of the prostheses were provided by operators who have less than 2 years of clinical experience. Sixty-six patients with seventy-eight RBFPDs (35 CL2 and 43 FM3) were reviewed at one-year. One CL2 and one FM3 RBFPDs debonded, resulting in a success rate at 97.1 % and 97.7 % respectively (P > 0.05). Both RBFPDs were rebonded and the survival rate were 100 % for both designs. No significant difference in satisfactions and summary OHIP-49 scores were observed (P > 0.05). CONCLUSION: CL2 RBFPDs can be used for replacing molar-sized edentulous spans with minimal observable complications up to one-year. Longer-term data is being collected. CLINICAL SIGNIFICANCE: This clinical trial demonstrates CL2 RBFPDs have comparable clinical and patient-reported outcomes as the FM3 design. This challenges the current dogma in prosthodontics and expands the clinical use of CL2 design which is more conservative, simpler and easier for patients to maintain.

Impact of hypo-salivation on severe tooth wear: A ten-year cohort of patients received radiotherapy for nasopharyngeal carcinoma.

OBJECTIVES: This study was conducted to examine the tooth wear status of nasopharyngeal-carcinoma (NPC) patients who had received radiotherapy at least 5-year previously, and to investigate the salivary parameters that may be associated with the tooth wear. METHODS: Tooth wear status of NPC survivors were clinically assessed using the Exact Tooth Wear Index. A tooth was graded to have severe wear when more than one-third of its buccal/occlusal/lingual surface had dentine loss. At the subject-level, percentages of anterior/posterior/all teeth with severe wear were calculated. Age, number of teeth, flow-rate/buffering capacity/pH of stimulated whole (SWS) and parotid (SPS) saliva's were collected. Correlation and multiple-linear regression tests were performed at the significance level α = 0.05. RESULT: Sixty-eight participants (mean age of 60.0 ±â€¯8.9), 697 anterior and 686 posterior teeth were examined with a mean of 10-years post-radiotherapy. Severe tooth wear was found in 63 (92.6 percent) participants, 288 anterior and 83 posterior teeth. The mean percentage of anterior/posterior/all teeth with severe wear were 42.3 ±â€¯28.1, 14.5 ±â€¯19.9 and 30.0 ±â€¯21.7. Anterior teeth, particularly the incisal surface of central incisors were most affected. The mean flow-rate of SWS and SPS were 0.1 ±â€¯0.1 ml/min and 0.03 ±â€¯0.07 ml/min respectively. Thirty (44.1 percent) and 48 (70.6 percent) participants were found to have low/no buffering capacity of SWS and SPS respectively. Multiple-regression analyses revealed the SWS flow-rate was associated with the percentage of anterior teeth with severe wear (p=0.03). CONCLUSION: Anterior tooth wear is a significant dental problem among NPC survivors and was associated with hypo-salivation. CLINICAL SIGNIFICANCE: Patients with hypo-salivation should be being monitored for tooth wear particularly on the anterior teeth.

Reproducibility of laboratory scanning of multiple implants in complete edentulous arch: Effect of scan bodies.

OBJECTIVES: To evaluate the reproducibility of complete arch scanning with multiple implant scan bodies using a laboratory scanner. METHODS: A master model of edentulous maxillary arch with 6 implants was fabricated. PEEK scan bodies were inserted into the model and consecutively scanned using a dental laboratory scanner (N = 10, Group C). Another 10 scans were performed with each scan body detached and reinserted into the same site between each scan (Group CR). The last group of scanning was performed with the scan bodies detached and randomly repositioned between each scan (N = 10, Group RR). Virtual models were created and the inter-implant distances and angles were measured using an inspection software. Accuracy of the complete arch scans was calculated and compared using Two-Way ANOVA (⍺ = 0.05). RESULTS: Significant greater distance distortion was found in CR (27.6 ±â€¯18.9 µm) and RR (34.2 ±â€¯25.0 µm). No significant difference in angular distortion was found among 3 groups. The greatest distance distortion was found in the anterior and cross-arch region of the arch. The smallest angular distortion was found in the first scanned sextant, with increasing distortion along the scanning path of the arch. The distance precision was significantly reduced in group CR and RR, while the angular precision was significantly reduced in group RR only. CONCLUSION: Reproducibility of complete arch scanning was significantly affected by repositioning of the scan bodies using a laboratory scanner. Repeated and random repositioning of the scan bodies would decrease the reproducibility of the spatial position and angle of the virtual implant. The distortion appeared to be small and within the clinical tolerance. CLINICAL SIGNIFICANCE: High-precision transfer of the implant information from intra-oral environment to dental laboratory is a prerequisite for the success of implant-supported prosthesis. Although laboratory scanners seem to be accurate, their accuracy is also affected by the precision and attachment procedure of the implant scan bodies and that has always been overlooked.

The adverse effects of tungsten carbide grinding on the strength of dental zirconia.

OBJECTIVES: This study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP). METHODS: Two types of tungsten-carbide burs (TC), 6-blade (TC1) and 8-blade (TC2) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC1 + APA and TC2 + APA; and rubber polishing (RP): TC1 + RP and TC2 + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (Ra) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. One-way ANOVA, Kruskal-Wallis test and Weibull analysis were performed at α = 0.05. RESULTS: Groups TC1 and TC2 had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC2 grinding had significant higher mean BFS than those following TC1 grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding. SIGNIFICANCE: Tungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed micro-structural surface and subsurface damage.

Ten-year clinical evaluation of posterior fixed-movable resin-bonded fixed partial dentures.

OBJECTIVES: Two-unit cantilevered resin-bonded fixed partial dentures (RBFPDs) offer long-term retention for anterior and premolar-sized spans. At this center, molar and longer spans have been restored with fixed-movable (FM) RBFPDs to overcome the lower retention rates of fixed-fixed RBFPDs. This retrospective study aimed to evaluate the long-term longevity and the patient-reported outcomes of posterior FM-RBFPDs. METHODS: Posterior FM-RBFPDs that had been inserted at least five years were reviewed. Survival was "retention of the original prosthesis in mouth" and success was "survival of prosthesis and absence of complications requiring treatment intervention". Prosthesis location, number of units, insertion year, tooth/teeth replaced and operator experience were collected. Patients' acceptance to FM-RBFPDs were assessed using prosthesis satisfaction questionnaire and Oral Health Impact Profile (OHIP-49). Results were analyzed using log-rank and cox-regression tests at significance level α = 0.05. RESULTS: One-hundred-and-one prostheses were examined. The mean observation time was 126.4 ±â€¯32.2 months. Thirty-six (35.6%) and 63 (62.4%) FM-RBFPDs were rated as success and survival respectively. Prostheses inserted after year 2001 (n = 69) experienced 42.0% (n = 29) success and 75.4% (n = 52) survival, and its survival rate was significantly better than those inserted in or before 2001 (p = 0.01). Five- and ten-year cumulative survival probability of FM-RBFPDs inserted after year 2001 were 82.3% and 74.1% respectively. The most frequent complications were debonding among 34 (33.7%) prostheses. Patients' acceptance were high. CONCLUSIONS: More recently inserted prostheses showed improved longevity and patients' acceptance to posterior FM-RBFPDs were high. CLINICAL SIGNIFICANCE: Fix-Movable RBFPDs are a viable tooth replacement option in the posterior region.

Mapping intraoral photographs on virtual teeth model.

OBJECTIVES: Tooth shade is crucial to patient satisfaction in aesthetic dentistry. Two-dimensional (2D) clinical photographs have been widely used to record patients' tooth shade for creation of beautiful smile. However, in the digital workflow, 3D virtual teeth models in open file format contain only mesh information with no colour. This paper describes the mapping of colour information from the intraoral photographs onto the virtual teeth model. METHODS: Intraoral photographs of occlusal and buccal views were taken using digital single lens reflex (SLR) camera with macro lens and ring flash. Photographs were calibrated for its colour and white balance. Virtual models were generated by scanning teeth/stone casts using an intraoral/model scanner. Intraoral photographs were mapped onto the virtual model using the image-to-geometry registration method by locating corresponding feature points in the 2D and 3D images. RESULTS: Virtual teeth models of dentate (with and without crowding) and partially dentate patients were mapped with intraoral photographs. The resultant models are open file format and can be viewed and manipulated in dental or generic CAD/CAM software. Moreover, RGB (Red Green Blue) colour information and error of registration can be retrieved. CONCLUSION: Image-to-geometry registration allows mapping of colour information in the 2D intraoral photographs on 3D virtual teeth models. The proposed method is applicable across scanning systems and the coloured model can be generated from stone casts and intraoral photographs. CLINICAL SIGNIFICANCE: Virtual teeth model with colour information facilitates shade matching and creation of beautiful smile.

The effect of surface treatments on dental zirconia: An analysis of biaxial flexural strength, surface roughness and phase transformation.

OBJECTIVES: This study investigates the effect of selected surface finishing techniques on the biaxial flexural strength, surface roughness and phase transformation of a zirconia dental restorative material. MATERIALS AND METHODS: Fully-sintered zirconia discs (⌀19.5 mm × 0.85 mm) were treated on one side with a single or a combination of the following treatments: diamond and/or tungsten-carbide burs without water coolant in an air-turbine handpiece, air-particle abrasion, rubber-point polishing in a contra-angle handpiece, or no treatment (control). Biaxial flexural strength (BFS) (eleven groups, n = 10) was determined using a universal testing machine and surface roughness (thirteen groups, n = 6) was assessed using a profilometer. Results were analysed using one-way ANOVA and Student-Newman-Keuls Post-hoc test (α = 0.05) with Bonferroni correction. Specimens were observed under scanning electron microscopy (SEM) and x-ray diffraction (XRD) for their microstructure and crystalline phases respectively. RESULTS: Grinding with diamond burs did not weaken zirconia (p > 0.0045) but produced rougher surfaces than the control group (p < 0.0038). Tungsten-carbide burs smoothened diamond ground specimens (p < 0.0038) for both grits of diamond. Specimens ground by tungsten-carbide burs have significantly reduced mean BFS (p < 0.0045) by up to two-thirds and SEM revealed fine surface cracks. Air-particle abrasion restored the mean BFS of tungsten-carbide ground specimens to control levels (p > 0.0045) and surface cracks were not observed. Phase transformation was not detected by XRD. CONCLUSIONS: Dental zirconia ground dry with tungsten-carbide burs has a significantly reduced BFS and a smooth but defective surface. These defects may be removed and BFS restored by air-particle abrasion. CLINICAL SIGNIFICANCE: The use of tungsten-carbide burs for grinding dental zirconia should be cautioned. Diamond grinding does not weaken zirconia but requires further polishing.

A clinical technique for virtual articulator mounting with natural head position by using calibrated stereophotogrammetry.

Accurate articulator-mounted casts are essential for occlusion analysis and for fabrication of dental prostheses. Although the axis orbital plane has been commonly used as the reference horizontal plane, some clinicians prefer to register the horizontal plane with a spirit level when the patient is in the natural head position (NHP) to avoid anatomic landmark variations. This article presents a digital workflow for registering the patient's horizontal plane in NHP on a virtual articulator. An orientation reference board is used to calibrate a stereophotogrammetry device and a 3-dimensional facial photograph with the patient in NHP. The horizontal plane can then be automatically registered to the patient's virtual model and aligned to the virtual articulator at the transverse horizontal axis level. This technique showed good repeatability with positional differences of less than 1 degree and 1 mm in 5 repeated measurements in 1 patient.

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.

A 2-part facebow for CAD-CAM dentistry.

Converting the patient's clinical information into the virtual world is a prerequisite for the computer-aided design and computer-aided manufacturing (CAD-CAM) of dental restorations. This article describes a modified facebow which facilitates the radiation-free registration of the maxillary teeth to a 3-dimensional face image for transfer to a virtual articulator. This facebow can be easily fabricated with minimal materials and adjusted to fit different patients; its error in tooth registration was demonstrated to be less than 1 mm.

Long-term evaluation of cantilevered versus fixed-fixed resin-bonded fixed partial dentures for missing maxillary incisors.

OBJECTIVES: To evaluate the long-term longevity and patient-reported outcomes of two-unit cantilevered (CL2) and three-unit fixed-fixed (FF3) resin-bonded fixed partial dentures (RBFPDs) for the replacement of a maxillary permanent incisor. MATERIALS AND METHODS: Twenty-eight subjects were randomly assigned to receive either a CL2 or FF3 RBFPD placed by one operator. Prosthesis longevity was determined by clinical examination and history. Success was defined as absence of complications requiring intervention and survival as retention of the original prosthesis in mouth. Subjects' satisfaction was assessed using visual analogue scale (VAS) and oral health-related quality of life (OHRQoL) using Oral Health Impact Profile (OHIP-49). Outcomes were analysed with t-test/Mann-Whitney U test, chi-square and log-rank test at significance level α=0.05. RESULTS: Twenty-two subjects were reviewed. Thirteen of fifteen CL2 and ten of fourteen FF3 RBFPDs were examined (79.3 percent response rate) with a mean service life of 216.5±20.8months. All CL2 RBFPDs survived with no complications while only 10 percent of FF3 experienced no complications and only 50 percent of them survived (both P=0.000). CL2 had a significantly better success and survival rate than FF3 (P=0.000 and P=0.009, respectively). There was no significant difference in subjects' satisfaction and OHRQoL apart from CL2 group subjects had a higher satisfaction in cleaning of the prosthesis (84.1±13.6) than FF3 group (72.6±11.7) (P=0.05). CONCLUSIONS: Two-unit cantilevered RBFPDs were observed to have a significantly better success and survival than the FF3 design for the replacement of a maxillary incisor. Good patient-reported outcomes have been found for RBFPDs in single-tooth replacement in aesthetic zone.

A fixed movable resin-bonded fixed dental prosthesis--A 16 years clinical report.

PATIENTS: This report describes the case of a 48-year-old female patient who initially received a 4-unit fixed-fixed (FF) resin-bonded fixed dental prosthesis (RBFDP) for replacement of mandibular left second premolar and first molar. Twenty-one months later, debond of the RBFDP was found at one of retainers. A new fixed-movable RBFDPs with a modified non-rigid connector as well as increased resistance form features was placed and successfully retained at the 16-year clinical review. DISCUSSION: RBFDPs are a conservative tooth replacement option that requires minimum tooth preparation and retention by a resin cement to etched enamel. However debonding is the most frequently seen complication and has been attributed to the relative movement between abutment teeth during function that stress the bonding interface. This case report highlights the use of modified non-rigid connector which allows relative movement between abutment teeth and therefore a reduced stress on the bonding interface. CONCLUSION: It is proposed that the use of modified non-rigid connectors that allow independent movement between the abutment teeth during function was responsible for the long term clinical success of fixed-movable RBFDPs.

Rehabilitation of molar-incisor hypomineralization (MIH) complicated with localized tooth surface loss: a case report.

Molar-incisor hypomineralization (MIH) is a developmental enamel hypomineralized condition characteristically involving the first permanent molars and sometimes also the incisors. The affected teeth are predisposed to tooth surface loss (TSL) which may not only compromise the esthetics and function but also endanger the pulp and longevity of the teeth. This report describes the management of a patient with MIH complicated with localized TSL and lack of occlusal clearance due to dentoalveolar compensation. The atypical TSL pattern involved all anterior teeth and required the placement of Dahl appliances on both arches.

Impact of complications of single tooth restorations on oral health-related quality of life.

OBJECTIVE: To compare oral health-related quality of life (OHRQoL) among subjects who received implant-supported crowns (ISC) and 2-unit cantilevered resin-bonded bridges (cRBB) in a bounded single tooth space (BSTS) after at least 5 years and to investigate factors associated with their OHRQoL. METHODS: A case-control study among 78 subjects who received ISC or cRBB rehabilitation at a teaching hospital (39 ISCs and 39 cRBBs). OHRQoL was measured using the Oral Health Impact Profile (OHIP-49) and compared between treatment modality. Variations in OHIP scores with respect to "minor complications" (repair of the original "survived" restorations) and "major complications" (replacement of "failed" restorations); and number of complications were determined in bivariate and multivariate analyses (negative binominal regression) controlling for socio-demographic and clinical factors. RESULTS: Oral Health Impact Profile scores were similar among those who received ISC and cRBB (P = 0.53). Among subjects with complicated restorations, those with major complications reported significantly higher OHIP scores (poorer OHRQoL) than those with minor complications (P = 0.02). Subjects who experienced multiple complications had significantly higher OHIP scores (poorer OHRQoL) than those with a single complication (P = 0.04). In regression analyses (which considered OHIP scores of those with complications), the nature of complications (P < 0.01), treatment modality (P = 0.04), and gender (P = 0.02) emerged as significant factors. CONCLUSION: In the rehabilitation of a BSTS patients, OHRQoL was similar irrespective of treatment modality (ISC or cRBB). Among those who experienced complications their OHRQoL was associated with the nature of complications, treatment modality and gender.

Longevity of implant crowns and 2-unit cantilevered resin-bonded bridges.

OBJECTIVE: To compare "survival" and "success" of implant-supported crowns (ISC) and tooth-supported 2-unit cantilevered resin-bonded bridges (cRBB) in the rehabilitation of a bounded single tooth space (BSTS), after an observation period of ≥5 years. METHODS: A case-control study among subjects who received ISC or cRBB rehabilitation at a teaching hospital. The (i) survival (retention in mouth) and (ii) success (absence of complications requiring intervention) for the ISCs and cRBBs were compared (overall, supporting structures and that of the prostheses). Rates of survival and success were compared using log-rank statistics. Prevalence of survival and success (categories) were compared by chi-square/Fisher's exact test. RESULTS: Seventy eight subjects participated in this study (39 ISC and 39 cRBB cases). Both had a mean observation time exceeding 100 months, P > 0.05. ISCs and cRBBs had similar survival rates: overall (P = 0.96), supporting structures (P = 0.14) and prostheses (P = 0.44) There was a significant difference in the rate of overall success between ISCs and cRBBs (P = 0.03), specifically with respect to the success rate of the supporting structures (P = 0.03). There was also a significant difference in the prevalence of supporting structures categorized as a "success": ISCs (69.2%) and cRBBs (89.7%), P = 0.03. Biological complications of supporting structures were more common among ISCs (25.6%) compared with cRBBs (7.7%), P = 0.03. CONCLUSION: Implant-supported crowns and cRBBs in the rehabilitation of a BSTS survive similarly after at least 5 years. However, cRBBs had a higher success rate and were more frequently categorized as successful than ISCs. Notably, there were fewer biological complications of cRBBs supporting structures than ISCs.

Mealtime glucose regulation with nateglinide in healthy volunteers: comparison with repaglinide and placebo.

OBJECTIVE: This study was designed to compare the pharmacodynamic effects of single doses of nateglinide (A-4166), repaglinide, and placebo on mealtime insulin secretion and glycemic control in healthy subjects. RESEARCH DESIGN AND METHODS: Fifteen healthy volunteers participated in this open-label five-period crossover study. They received single 10-min preprandial doses of 120 mg nateglinide, 0.5 or 2 mg repaglinide, or placebo or 1 min preprandially of 2 mg repaglinide. Subjects received each dose only once, 48 h apart. Pharmacodynamic and pharmacokinetic assessments were performed from 0 to 12 h postdose. RESULTS: Nateglinide induced insulin secretion more rapidly than 2 and 0.5 mg repaglinide and placebo (10 min preprandial), with mean rates of insulin rise of 2.3, 1.3, 1.15, and 0.8 microU x ml(-1) x min(-1), respectively, over the 0- to 30-min postmeal interval. After peaking, insulin concentrations decreased rapidly in the nateglinide-treated group and were similar to placebo within 2 h postdose. After 2 mg repaglinide, peak insulin concentrations were delayed and returned to baseline more slowly than with nateglinide treatment. Nateglinide treatment produced lower average plasma glucose concentrations in the 0- to 2-h postdose interval than either dose of repaglinide and placebo (P < 0.05 vs. 0.5 mg repaglinide and placebo). Plasma glucose concentrations returned more rapidly to predose levels with nateglinide treatment than with either dose of repaglinide. Treatment with repaglinide produced a sustained hypoglycemic effect up to 6 h postdose. CONCLUSIONS: In this single-dose study in nondiabetic volunteers, nateglinide provided a more rapid and shorter-lived stimulation of insulin secretion than repaglinide, resulting in lower meal-related glucose excursions. If similar results are observed in diabetes, nateglinide may produce a more physiological insulin secretory response with the potential for a reduced risk of postabsorptive hypoglycemia.

Mealtime glucose regulation by nateglinide in type-2 diabetes mellitus.

OBJECTIVES: Pharmacodynamic effects of nateglinide, a novel antidiabetic agent, were investigated in patients with type-2 diabetes mellitus. METHODS: Ten patients participated in this single-center, double-blind, crossover study. Plasma glucose and insulin levels were measured over 24 h following five 7-day treatment periods with nateglinide (30, 60, or 120 mg) or placebo given three times daily before breakfast, lunch, and dinner. A fifth treatment consisted of 120 mg nateglinide four times daily, with the fourth dose given before an evening snack. RESULTS: Taken 10 min before meals, doses of 30-120 mg nateglinide caused dose-dependent increases in plasma insulin levels that were significantly greater than with placebo. Higher doses were more effective and had a longer duration of action than lower doses. Nateglinide was also significantly better than placebo in lowering plasma glucose levels; the 60-mg and 120-mg doses were similarly effective and superior to the 30-mg nateglinide treatment. Following the fourth 120-mg dose, the glucose-lowering effects of treatment were maintained through the night. No serious adverse events occurred during the study. There were no events of hypoglycemia and no clinically meaningful changes in safety parameters. CONCLUSIONS: Nateglinide produced rapid, short-lived, dose-related increases in plasma insulin that significantly lowered mealtime glucose excursions compared with placebo with no incidence of hypoglycemia. The decrease in mealtime glucose levels produced a significant improvement in overall 24-h glycemia.