Immediate versus conventional loading of variable-thread tapered implants supporting three- to four-unit fixed partial dentures in the posterior maxilla: 3-year results of a split-mouth randomised controlled trial.

PURPOSE: To compare the 3-year outcomes of immediately loaded and one-stage conventionally loaded variable-thread tapered implants in the posterior maxilla. MATERIALS AND METHODS: This study was designed as a split-mouth randomised controlled trial. Twenty-six patients attending the postgraduate Periodontics Department at the Lebanese University, and missing teeth bilaterally in the posterior maxilla were randomised. All patients received three to four implants in each of the posterior sextants. The implants on one side were immediately loaded with a provisional resin fixed partial denture on definitive multi-unit abutments regardless of their primary stability. The implants in the contralateral side received definitive multi-unit abutments according to the one-stage unloaded protocol. Three to 3.5 months following implant placement, the implants were restored with metal-ceramic fixed prostheses. Outcome measures were implant and prosthesis failure rates, complications, and peri-implant bone level changes up to 3 years following delivery of the definitive prosthesis. The clinical outcomes and radiographic measurements were performed by a single outcome assessor blinded to the type of interventions. RESULTS: Two patients dropped out prior to the delivery of definitive prostheses. The results were analysed using a per-protocol analysis and included 24 patients. Four implants supporting a four-unit immediately loaded prosthesis failed in one patient, 3 months following definitive prosthesis. In the same patient, the three contralateral conventionally loaded implants failed 14 months after definitive prosthesis. There were no significant differences in the proportions of implant and prosthesis failures at 3 years (difference = 0%; 95% CI 0.0% to 14.2%; P = 0.999). Peri-implantitis was diagnosed at two adjacent conventionally loaded implants in one patient at the 3-year examination. In the immediately loaded group, four early minor prosthetic complications occurred during the provisionalisation phase. Following delivery of the definitive prostheses, one minor ceramic fracture was observed in each of the implant groups. The difference in the rate of complications between the two interventions was not statistically significant at 3 years (difference = 13%; 95% CI 3.4% to 27.7%; P = 0.453). The 3-year peri-implant marginal bone level changes were evaluated in 23 patients (77 immediately loaded and 76 conventionally loaded implants). On average, patients lost 0.79 (0.62) mm at the immediately loaded and 0.91 (0.82) mm at the conventionally loaded implants, the difference being statistically not significant (difference = 0.12 mm; 95% CI -0.31 to 0.55 mm; P = 0.590). The 3-year marginal bone level changes were not significantly different between smokers (n = 12) and non-smokers (n = 11) (difference = 0.19 mm; 95% CI -0.24 to 0.62 mm; P = 0.382). CONCLUSIONS: Immediate loading of three- to four-unit fixed partial prostheses supported by variable-thread implants in the posterior maxilla can achieve similar 3-year results to one-stage conventionally loaded implants.

Effect of patient- and surgery-related factors on supracrestal tissue reestablishment after crown lengthening procedure.

OBJECTIVES: The standard application of a mean value of 2.04 mm for the biologic width has been demonstrated to result in inconsistent amounts of tooth extension following a crown lengthening procedure. Biologic width has been replaced by the supracrestal gingival tissue dimension, which includes the biologic width and sulcular depth. The question whether supracrestal gingival tissue dimension established at tissue maturation following a crown lengthening procedure is not significantly different from the presurgical dimension has not been fully answered. The primary objectives of the present prospective clinical study were to compare the preoperative and the 24-week dimensions of supracrestal gingival tissue following a crown lengthening procedure and assess the alterations in gingival margin position. A secondary objective was to assess selected patient- and surgery-related factors on supracrestal gingival tissue reestablishment. METHOD AND MATERIALS: Twenty adult systemically healthy patients requiring a crown lengthening procedure were recruited for the study. A crown lengthening procedure was performed at 33 teeth and the patients were followed up to 24 weeks. The following parameters were recorded using customized stents for measurement reproducibility: stent-gingival margin (baseline, immediately after surgery, and at 6, 12, and 24 weeks), stent-bottom of sulcus (baseline and at 6, 12, and 24 weeks), stent-bone crest (baseline, at completion of osseous resection, and at 24 weeks), bone thickness (baseline, postsurgery), buccal gingival thickness (baseline, 24 weeks), and radiographic interproximal bone width (baseline, 24 weeks). Supracrestal gingival tissue, crown extension, and distance between the immediate postoperative position of the gingival margin relative to the contoured bone crest (F) were calculated. RESULTS: There were no statistically significant differences between supracrestal gingival tissue measurements at baseline and at 24 weeks for any of the four tooth sides. Crown extension remained significantly increased at 24 weeks compared to baseline for all sides, with the largest amounts of gingival creeping mesially and distally. A highly significant positive correlation (r = 0.97, P < .001) was demonstrated between flap positioning and stability of the gingival margin during the healing period. The closer was the F measurement to baseline supracrestal gingival tissue dimension, the less change in gingival margin was observed. CONCLUSIONS: The preliminary results of this investigation suggest the following: The presurgical supracrestal gingival tissue dimension can be used as a guideline measurement in crown lengthening procedures as it is reestablished with a similar apico-coronal dimension 24 weeks postoperatively; and crown extension is stable when the distance between the sutured gingival margin and the contoured osseous crest is similar to the preoperative supracrestal gingival tissue dimension.

Insertion Torque of Variable-Thread Tapered Implants in the Posterior Maxilla: A Clinical Study.

PURPOSE: Primary stability is a key factor for successful implant osseointegration, especially in poor bone quality and early/immediate loading. In the immediate loading protocol, insertion torque values (ITVs) have been suggested to be the most valid prognostic factor for osseointegration of maxillary implants. The objectives of this study were to: (1) evaluate ITVs achieved by a variable-thread tapered implant in the posterior maxilla; and (2) assess the impact of bone quality, implant dimensions, bicortical anchorage, and implant location on ITVs. MATERIALS AND METHODS: Twenty-six adult, systemically healthy patients received 173 variable-thread tapered implants in maxillary premolar and molar healed edentulous sites with a minimum subsinus height of 8 mm. Implant sites were prepared using the bone-quality adjusted drilling sequence according to manufacturer's recommendations. Bone quality was recorded subjectively during drilling based on Misch criteria (D1-D4), and ITVs were measured with a manual torque wrench. Univariate and multivariate analyses were performed at the 0.05 significance level. RESULTS: First and second molar sites accounted for 46.8% of all implants. D4 bone was encountered in 61.3% of the sites. Most of the implants were 4.3 mm in diameter (59.5%), and lengths of 11.5 and 13 mm were most commonly used (75.2%). Approximately half of the implants were associated with apical cortical anchorage (51.4%). The overall mean ITV was 44.5 ± 23.0 Ncm, with 65.5 ± 15.6 Ncm, 55.5 ± 19.6 Ncm, and 36.6 ± 21.7 Ncm for D2, D3, and D4 bone, respectively. Bone quality and implant location significantly affected ITVs, while implant dimensions and apical cortical anchorage did not. CONCLUSIONS: ITVs of variable-thread implants were significantly influenced by variations in bone quality and implant position in the posterior maxilla. Despite the influence of bone quality on primary stability, the mean ITVs attained with variable-thread tapered implants in poor bone quality were within the recommended range for immediate loading.

Comparison of fit accuracy of pressed lithium disilicate inlays fabricated from wax or resin patterns with conventional and CAD-CAM technologies.

STATEMENT OF PROBLEM: The use of resin patterns to produce partial coverage restorations is poorly documented. PURPOSE: The purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass-ceramic inlays obtained from wax or resin patterns and fabricated with digital and conventional techniques. MATERIAL AND METHODS: A dentoform mandibular first molar was prepared for a mesio-occlusal ceramic inlay. Six groups of 15 inlays were obtained by conventional impression and manual wax (group CICW) or resin patterns (group CICR); conventional impression, laboratory scanning of the stone die, CAD-CAM milled wax (group CIDW), or polymethylmethacrylate (PMMA) blocks (group CIDR); and scanning of the master preparation with an intraoral scanner, CAD-CAM milled wax (group DSDW), or PMMA blocks (DSDR). The same design was applied to produce the wax and PMMA patterns in the last 4 groups. The replica technique was used to measure marginal and internal fit under stereomicroscopy. Mixed-model ANOVA was applied to assess differences according to the techniques, materials, and discrepancy location (α=.05). RESULTS: The results demonstrated significant effects of the technique (P<.001), material (P=.009), and discrepancy location (P<.001) on fit measurements. Marginal discrepancy was only affected by the technique (P<.001), with the digital approaches yielding the smallest marginal discrepancy (23.5 ±3.6 µm), followed by the conventional digital techniques (31.1 ±5.6 µm) and finally by the conventional (42.8 ±7.2 µm) techniques. Internal fit was significantly influenced only by the material with lower discrepancy in wax (75.2 ±9.0 µm) than in resin patterns (84.7 ±15.1 µm). The internal discrepancy was significantly larger than the marginal discrepancy in all groups (P<.001). CONCLUSIONS: Inlays generated from conventional wax and resin patterns tend to show higher marginal discrepancies than conventional digital and full digital patterns. Wax and resin materials yield similar marginal fit accuracies irrespective of the impression/manufacturing technique. Better internal fit was shown in wax than in resin patterns, regardless of the technique.

Marginal and internal fit of pressed lithium disilicate inlays fabricated with milling, 3D printing, and conventional technologies.

STATEMENT OF PROBLEM: The subtractive and additive computer-aided design and computer-aided manufacturing (CAD-CAM) of lithium disilicate partial coverage restorations is poorly documented. PURPOSE: The purpose of this in vitro study was to compare the marginal and internal fit accuracy of lithium disilicate glass-ceramic inlays fabricated with conventional, milled, and 3-dimensional (3D) printed wax patterns. MATERIAL AND METHODS: A dentoform mandibular first molar was prepared for a mesio-occlusal ceramic inlay. Five groups of 15 inlays were obtained through conventional impression and manual wax pattern (group CICW); conventional impression, laboratory scanning of the stone die, CAD-CAM milled wax blanks (group CIDW) or 3D printed wax patterns (group CI3DW); and scanning of the master preparation with intraoral scanner and CAD-CAM milled (group DSDW) or 3D printed wax patterns (group DS3DW). The same design was used to produce the wax patterns in the last 4 groups. The replica technique was used to measure marginal and internal adaptation by using stereomicroscopy. Mixed-model ANOVA was used to assess differences according to the groups and discrepancy location (α=.05). RESULTS: Group DSDW showed the smallest marginal discrepancy (24.3 µm) compared with those of groups CICW (45.1 µm), CIDW (33.7 µm), CI3DW (39.8 µm), and DS3DW (39.7 µm) (P<.001). No statistically significant differences were detected among groups CICW, CIDW, CI3DW, and DS3DW relative to the marginal discrepancy. The internal discrepancy was significantly larger than the marginal discrepancy within all groups (P<.001). CONCLUSIONS: Lithium disilicate glass-ceramic inlays produced from digital scans and subtractive milling of wax patterns resulted in better marginal and internal fit accuracy than either conventional impression/fabrication or additive 3D manufacturing. Three-dimensional printed wax patterns yielded fit values similar to those of the conventionally waxed inlays.

Healing Time for Final Restorative Therapy After Surgical Crown Lengthening Procedures: A Review of Related Evidence.

Focused Clinical Question In healthy patients who receive surgical crown lengthening, how much healing time should be allowed for the positional changes of the gingival margin before final restoration? Clinical Scenario A 59-year-old woman presented to the University of Alabama at Birmingham School of Dentistry in August 2011 for replacement of her existing porcelain-fused-to-metal crowns on the maxillary anterior teeth for esthetic reasons. Clinical examination revealed a diagnosis of developmental mucogingival deformity manifested by gingival excess in the maxillary anterior sextant. An esthetic evaluation was performed and identified excessive gingival display attributable to short clinical crowns and excluded vertical maxillary excess and short or hypermobile upper lip as etiologic factors. After signing a written informed consent, the patient underwent an esthetic crown lengthening procedure to correct this mucogingival deformity, followed by prosthodontic rehabilitation. The patient and restoring dentist were concerned with the healing time that should elapse before the teeth were permanently restored. Figures 1 through 5 illustrate the initial presentation of the patient, surgical crown lengthening procedure, and final restorations.