Comparison between stone and digital cast measurements in mixed dentition : Validity, reliability, reproducibility, and objectivity.

PURPOSE: To assess the validity, reliability, reproducibility, and objectivity of measurements on stone casts of patients with mixed dentitions compared to measurements on three-dimensional (3D) digital models derived from surface scans of the stone casts. METHODS: Pairs of stone casts of 30 young patients in their mixed dentition stage were included and processed into 3D digital models using an intraoral scanner (iTero Element 2; Align Technology, San Jose, CA, USA). Then an experienced and an inexperienced examiner independently performed measurements of five defined parameters, each in triplicate, both on the digital models with analysis software (OnyxCeph3™; Image Instruments, Chemnitz, Germany) and on the original casts with a vernier calliper. Paired t-tests were used for validity and interexaminer objectivity, Pearson correlation coefficients for intermethod reliability, and intraclass correlation coefficients (ICCs) for reproducibility testing. RESULTS: Significant (p < 0.05) intermethod differences were identified for four parameters, but only the differences for overbite and intermolar distance exceeded the threshold of clinical relevance (≥ 0.5 mm). Intermethod reliability was high and method error invariably lower for the digital measurements and for the experienced examiner. Both examiners achieved ICCs > 0.907 with both methods. Interexaminer variation involved significant differences for all parameters but one (intermolar distance) on the stone casts and for three parameters on the digital models. CONCLUSION: Measurements performed on digital models of mixed dentitions can yield clinically acceptable outcomes with OnyxCeph3™ software. Both the digital and the analogue measurements were highly reproducible and reliable. Objectivity of the measurements could not be confirmed, as operator experience did make a difference.

Impression material accuracy for palatal orthodontic miniscrews.

PURPOSE: This study investigates the accuracy of abutment transfer with current impression materials and provides a concise overview, including other relevant factors, in order to enable clinicians to make an informed decision about the optimal impression for this treatment procedure. METHODS: In all, 96 impressions of a cadaver head with two orthodontic miniscrews in place were taken with four common impression materials by two observers and using two methods of application. After pouring with a standard type IV stone and abutment transfer, all models and the upper jaw (which had been separated from the head) were scanned in a standard model scanner (Zirkonzahn® [Zirkohnzahn GmbH, Gais, Italy] S600 ARTI) and evaluated using a computer-aided design (CAD) program (GOM-Inspect [Gesellschaft für optische Messtechnik m.b.H., Braunschweig, Germany]). The deviations were measured at six points per screw and statistically evaluated with SPSS® (IBM, Chicago, IL, USA). RESULTS: Optimal values were obtained with biphasic polyvinylsiloxane, while monophasic polyvinylsiloxane, alginate and polyether also resulted in acceptable accuracy. Observer experience showed no effect and the method of application had only a minor effect on accuracy. CONCLUSIONS: Within the limitations of this study, it seems that all impression materials are suitable for miniscrew abutment transfer, provided that methods of intraoral adaptation of the orthodontic appliance can be employed. If higher accuracy is needed or for clinicians with less experienced, a biphasic polyvinylsiloxane impression with the putty-wash technique should be used as this combination reduces setting time. The most cost-effective version, alginate, can be used if the consequences of greater deviations can be handled. Caution is advised with polyether if undercuts are present.

Transfer accuracy of two indirect bonding techniques-an in vitro study with 3D scanned models.

Background and objectives: Indirect bonding (IDB) proved to be an effective method for appropriate bracket positioning in patients. Different methods and materials are available for fabricating transfer trays. This in vitro study was designed to measure and compare the transfer accuracy of two common IDB methods. Materials and methods: Sixty stone models were fabricated and separated in two groups of 30 models each (15 working models, 15 patient models). After placing brackets on the working models, 30 IDB trays were made: 15 silicone (method I) and 15 double-vacuum forms (method II). With these trays, the brackets were transferred to the patient models. The bracket positions were scanned before and after the IDB procedure with an intraoral scanner. The linear and angular discrepancies were then determined digitally by measuring six different dimensions: occluso-cervical, mesio-distal, bucco-lingual, tip, rotation, and torque. Results: The silicone trays showed fewer transfer discrepancies, on average, in all measured dimensions. There were significant differences between the methods in the occluso-cervical (P < 0.001), mesio-distal (P = 0.001), and torque (P = 0.044) dimensions. With both methods, 100 per cent of the horizontal and transversal measurements of both methods were within the clinically acceptable range of 0.25 mm. With method I, 98.5 per cent of the vertical and 95.9 per cent of the angular measurements were within the range of 0.25 mm and 1°, respectively. With method II, 94 per cent of the vertical and 84.8 per cent of the angular measurements were within the clinically acceptable range. Conclusions: Although both transfer methods showed a high precision, silicone trays scored better in terms of accuracy than double-vacuum forms.

Inter- and intraobserver variability in resonance frequency analysis of palatal implants--a technical note.

PURPOSE: To assess inter- and intraobserver variability in wireless resonance frequency analysis (RFA) stability measurements of palatal implants and to evaluate the influence of age, sex, time after implant insertion, and measurement direction on variability. MATERIALS AND METHODS: Three observers conducted wireless RFA stability measurements of palatal implants from 16 patients. Measurements were taken in anteroposterior and laterolateral directions and were repeated after 1 hour. RESULTS: Data showed a small interobserver variation (1.93) with intraobserver variation (1.77) as its largest component. Time after implantation showed a strong influence (P = .027) on the interobserver variation. CONCLUSIONS: The tested wireless RFA device can be considered a reliable instrument for measuring the stability of palatal implants. Multiple readings and observers could further improve measurement reliability.

Resonance frequency analysis: a new diagnostic tool for dental ankylosis.

Ankylosed teeth are considered in orthodontic treatment planning; however, diagnostic tools to quantify the rigidity of the tooth-to-bone connection are rare. Resonance frequency analysis (RFA) can quantify the rigidity of the dental implant-to-bone connection and thus may serve as a potential diagnostic tool to identify ankylosed teeth. To test this assumption, we examined 15 and 30 primary mandibular molars, with and without clinical signs of ankylosis, using the Osstell Mentor system. A cut-off implant stability quotient (ISQ) of 43 provided a specificity of 100% and a sensitivity of 53.3% when measured in the mesio-distal direction or a sensitivity of 20% when measured in the bucco-lingual direction. Based on a receiver-operating characteristic (ROC), the area under the curve (AUC) of 0.807 showed the mesio-distal direction of measurement to be a test of moderate discriminatory power. Given its non-invasiveness, RFA may serve as a quantitative diagnostic supplement to the clinical examination of potentially ankylosed primary molars.

Miniscrews in orthodontic treatment: review and analysis of published clinical trials.

INTRODUCTION: A systematic review of effects related to patient, screw, surgery, and loading on the stability of miniscrews was conducted. METHODS: Reports of clinical trials published before September 2007 with at least 30 miniscrews were reviewed. Parameters examined were patient sex and age, location and method of screw placement, screw length and diameter, time, and amount of loading. RESULTS: Fourteen clinical trials included 452 patients and 1519 screws. The mean overall success rate was 83.8% + or - 7.4%. Patient sex showed no significant differences. In terms of age, 1 of 5 studies with patients over 30 years of age showed a significant difference (P <0.05). Screw diameters of 1 to 1.1 mm yielded significantly lower success rates than those of 1.5 to 2.3 mm. One study reported significantly lower success rates for 6-mm vs 8-mm long miniscrews (72% vs 90%). Screw placement with or without a surgical flap showed contradictory results between studies. Three studies showed significantly higher success rates for maxillary than for mandibular screws. Loading and healing period were not significant in the miniscrews' success rates. CONCLUSIONS: All 14 articles described success rates sufficient for orthodontic treatment. Placement protocols varied markedly. Screws under 8 mm in length and 1.2 mm in diameter should be avoided. Immediate or early loading up to 200 cN was adequate and showed no significant influence on screw stability.

Osseointegration of a subperiosteal anchoring device in the minipig mandible.

INTRODUCTION: Onplants serve as subperiosteal anchorage in the maxilla to facilitate tooth movement. We determined the applicability of onplants and the process of osseointegration in the mandible of minipigs. METHODS: Thirty-six onplants (OnPlants, Nobel Biocare USA, Yorba Linda, Calif) were positioned in 9 adult animals, 2 on each side. At 3, 6, and 12 weeks after surgery, 3 minipigs were killed. Undecalcified ground sections were evaluated histologically and histomorphometrically. RESULTS: Nineteen onplants were lost during the observation period. Newly formed bone per tissue volume was 7% +/- 5% (n = 4), 21% +/- 9% (n = 5), and 22% +/- 13% (n = 8) at the 3 observation times. The corresponding percentages of bone-to-implant contact were 15% +/- 22%, 30% +/- 27%, and 44% +/- 35%. The number of bone-to-implant contacts remained stable over time at 1.0 +/- 0.9 contacts per millimeter. The average lengths of bone-to-implant contacts were 0.2 +/- 0.1 mm, 0.3 +/- 0.2 mm, and 0.5 +/- 0.3 mm. CONCLUSIONS: These results showed a low survival rate of onplants in the mandible and that the early stage of healing is central to the process of osseointegration. Stable placement is a prerequisite for onplant survival in the mandible.

Sagittal and vertical load-deflection and permanent deformation of transpalatal arches connected with palatal implants: an in-vitro study.

INTRODUCTION: The purposes of this laboratory investigation were to (1) measure the sagittal and vertical deflection of loaded transpalatal arches (TPAs) connected to a palatal implant, (2) measure the extent of permanent deformation of the connecting TPA in the sagittal and vertical directions, (3) test various wire dimensions in terms of deflection behavior, and (4) evaluate soldering vs laser welding vs adhesive bonding of TPAs in terms of load deflection behavior. METHODS: Stainless steel wires of 6 dimensions were tested: 0.8 x 0.8, 0.9, 1, 1.1, 1.2, and 1.2 x 1.2 mm. For each dimension, 10 specimens were soldered to the palatal implant abutment, 10 were laser welded, and 10 were adhesively bonded to the implant abutment (total, 180 specimens). The measuring device applied increments of force of 50 cN, from 0 to 500 cN. Then the specimens were unloaded. The values were statistically described and analyzed with ANOVA and Wilcoxon rank sum tests. RESULTS AND CONCLUSIONS: Absolute orthodontic anchorage without deformation of TPAs was not observed with the wire dimensions tested. To prevent loss of anchorage greater than 370 mum (sagittal deflection of 1.2 x 1.2 mm adhesively bonded TPA at 500 cN force level), wires thicker than 1.2 x 1.2 mm or cast anchorage elements must be considered for clinical practice. However, larger cross sections might cause more patient discomfort, and laboratory procedures increase costs.

Evaluation of the effects of rapid maxillary expansion in growing children using computer tomography scanning: a pilot study.

The principle of rapid maxillary expansion (RME) as a method to expand the transverse dimension of the palate and maxillary dental arch is by no means new, and previous studies have reported the effects of the method using a variety of radiographic methods. In the present study, the effect of a Hyrax splint appliance was studied in a group of nine growing children (six females, three males; mean age 8 years 1 month) undergoing orthodontic treatment. The changes were evaluated on pre- and post-treatment computer tomographic scans taken using a low-dosage protocol. The results demonstrated a clear appliance-induced effect in all patients, although the relative contribution of dental, alveolar, and skeletal changes varied from subject to subject. The average expansion, measured at the molar crowns, was 3.6 mm, whereas the actual sutural opening, the main aim of RME, was as low as 1.6 mm. The findings of this study raise doubts as to the efficiency of the Hyrax appliance and further comparative studies are recommended to evaluate other methods of maxillary expansion.

Nasal cavity perforation by palatal implants: false-positive records on the lateral cephalogram.

PURPOSE: Lateral cephalometric films were examined for their validity as a tool for the postoperative evaluation of palatal implant placement. MATERIALS AND METHODS: Cephalometric and histometric data of 20 partially edentulous human cadaveric maxillae were compared. Lateral cephalograms of the specimens were made, and the palatal complex was pencil traced. In addition, low-dose dental computerized tomography (CT) scans were obtained from every specimen. Based on the CT data, palatal implants (Orthosystem; Institut Straumann, Waldenburg, Switzerland) were placed. Postimplantation, another lateral cephalometric film was recorded. The specimens were prepared for histologic examination. The preoperative tracings were superimposed on the postoperative cephalometric films. RESULTS: Of 20 implants placed, 12 were 4 mm long and 8 were 6 mm long. The distance between the cranial end of the implants and the nasal floor on microscopy ranged from 0.3 to 9.3 mm. Perforation of the nasal floor was absent throughout on intraoperative probing, while 2 implants projected beyond the nasal floor on histologic analysis of the specimens. An analysis of the superimposed pre- and postoperative cephalograms showed 5 implants projecting beyond the nasal floor. Histologically, only 1 of these projecting implants had actually caused perforation of the palatal complex. A comparison between the histometric and the cephalometric data showed that cephalometry, on average, imaged the palatal complex 0.8 mm below the actual anatomic site. DISCUSSION AND CONCLUSIONS: Twenty percent of palatal implants projecting beyond the nasal floor were false-positive records on the postoperative lateral cephalograms. Despite CT scans, 10% of the implants placed caused fenestration of the nasal cavity by histologic evidence. If the palatal complex was perforated, intraoperative probing with a periodontal probe did not confirm the perforation. Bone perforations up to 1.3 mm did not necessarily result in frank perforation of the nasal mucosa. Two-dimensional images could not be related to actual penetrations into the nasal cavity.

Rectangular loops in inconsistent force systems: a laboratory investigation.

MATERIAL AND METHOD: [corrected] The force system delivered by the rectangular loop (R-loop) was the subject of this in-vitro investigation. The correction of a first-order irregularity was simulated in an inconsistent force system. Three types of R-loop made of 0.017" x 0.025" TMA wire but differing in length and insertion system were tested in a 3D strain gauge (Hottinger, Darmstadt, Germany). The buccal segment consisted of one molar and two bicuspids, with the first bicuspid as an active unit scheduled to be moved buccally into the dental arch. RESULTS: The first R-loop tested revealed too high a force magnitude to be recommended for clinical use. A loop connecting only two teeth and bypassing the second premolar delivered a favorable initial force of 85 cN with a drop of 20 cN per 1 mm deactivation. In order to achieve a translatory tooth movement, a buccal root torque must be bent in addition into the short horizontal leg of the R-loop. The use of a transpalatal arch is indispensable if adverse side effects are to be avoided.