Interproximal Contact Research Articles

Duration of elastomeric separation and effect on interproximal contact point characteristics

The common protocol of a week-long duration of elastomeric separators to facilitate band placement usually causes discomfort. In this study, we examined the minimum separation time required to create an interproximal space >0.16 mm (band thickness), the interproximal changes over 24 hours after separator removal, and the mechanical characteristics of various separators. Thirty subjects, ages 28.1 +/- 2.8 years, had an elastomeric separator placed between the mandibular second premolar and first molar (CP5-6) for 1, 4, 12, and 24 hours. After separator removal, CP5-6 was measured for space and tightness of dental contact point (TDCP) changes up to 24 hours after separator removal. The mechanical behaviors of 6 manufacturers' separators were compared. After 12 and 24 hours of separation, all patients demonstrated space >0.16 mm (P <.001). A significant negative correlation (R = -0.59 to -0.63; P = .001) was found between baseline TDCP and the space measured at separator removal. A biphasic viscoelastic recovery (82%-95%) to baseline tightness level occurred within 24 hours. Variation between manufacturers was low (9%). Separators should be placed a day before banding. The patient should arrive 3 to 4 hours before the appointment for separator replacement if the separator is lost. Rapid recovery after separation removal implies the biological soundness of elastomeric separation regardless of the manufacturer used.

Existence of an electrically insulating layer in amalgam-containing galvanic couples

Objective Avoiding the placement of amalgam and noble metal restorations in interproximal contact is recommended due to anticipated galvanic corrosion of the amalgam. There is a similar concern for amalgam/amalgam galvanic couples. It was the objective of this study to determine if an electrically insulating layer forms in the contact area of these galvanic couples. The existence of an electrically insulating layer, which could reduce the galvanic corrosion rate, would be indicated by different corrosion potentials for the two restorations of the couple. Methods Using a convenience sample of 158 human subjects, corrosion potentials were measured on each restoration of three types of galvanic couples: amalgam/noble metal ( n = 8), amalgam/amalgam ( n = 93) and noble metal/noble metal ( n = 7). Measurements were made with a Ag/AgCl micro-reference electrode and a high impedance voltmeter. All restorations were at least 6 months old. Results Statistical analysis showed that the mean absolute corrosion potential differences and the simultaneous confidence intervals of the couples were, respectively, amalgam/noble metal: 62 (31) mV and (27, 99) mV, amalgam/amalgam: 11 (14) mV and (7, 15) mV and noble metal/noble metal: 7 (10) mV and (0, 19) mV. Significance The amalgam/noble metal couples had consistent and mostly large corrosion potential differences between their restorations, which indicated the presence of an electrically insulating layer. An electrically insulating layer was also indicated for the amalgam/amalgam and noble metal/noble metal couples. The layer is probably composed of non-metallic corrosion products, biofilms, and possibly, dental calculus, which could reduce galvanic corrosion rates to small or negligible values.

Interproximal dental caries detection using Photothermal Radiometry (PTR) and Modulated Luminescence (LUM)

Frequency-domain photothermal radiometry (FD-PTR or PTR) has been used to detect mechanical holes and demineralized enamel in the interproximal contact area of extracted human teeth. Thirty four teeth were used in a series of experiments. Preliminary tests to detect mechanical holes created by dental burs and 37% phosphoric acid etching for 20 s on the interproximal contact points showed distinct differences in the signal. Interproximal contact areas were demineralized by using a partially saturated acidic buffer system. Each sample pair was examined with PTR before and after micro-machining or treating at sequential treatment periods spanning 6 hours to 30 days. Dental bitewing radio graphs showed no sign of demineralized lesion even for samples treated for 30 days. μ-CT, TMR and SEM analyses were performed. Although μ-CT and TMR measured mineral losses and lesion depths, only SEM surface images showed visible signs of treatment because of the minimal extent of the demineralization. However, the PTR amplitude increased by more than 300% after 80 hours of treatment. Therefore, PTR has been shown to have sufficient contrast for the detection of very early interproximal demineralized lesions. The technique further exhibited excellent signal reproducibility and consistent signal changes in the presence of interproximal demineralized lesions, attributes which render PTR a reliable probe to detect early interproximal demineralization lesions. Modulated luminescence was also measured simultaneously, but it showed a lower ability to detect these interproximal demineralized lesions than PTR.

Time-related PDL: viscoelastic response during initial orthodontic tooth movement of a tooth with functioning interproximal contact—A mathematical model

Most anteroposterior orthodontic movements of posterior teeth have to overcome the “resistance” of adjacent teeth with functioning interproximal contacts. The aim of this study was to develop a mathematical model describing initial posterior tooth movement associated with functioning interproximal contacts in relation to the viscoelastic mechanical behavior of the human periodontal ligament (PDL). A linear viscoelastic 2D mathematical model was modified to depict tipping movement around the center of rotation ( C rot) of a premolar where tipping is restrained by adjacent teeth. Equilibrium equations were applied taking into account the sagittal moment developed around the C rot. The constants of the model were analyzed and applied to a numerical model that can simulate short-term tooth creep movement caused by a tipping force. Changes in force magnitude (0.5–3 N) and crown length (6–10 mm) were analyzed until no movement was observed (steady state). Premolar displacement in contact with adjacent teeth showed a non-linear progression over time with an initial sharp tipping movement followed by a transient period of 2.6–7.1 min. As tipping force increased the transient period increased. A similar but smaller effect was observed with an increase in crown length. The premolar initial displacement within the arch (3.2–19.5 μm) is about seven-fold smaller than retraction/protraction movement of an incisor. These suggest reduction in tooth displacement when functioning interproximal contact is present and clinically recommend establishing a space in the direction of tooth displacement before tooth movement.

Treatment outcomes in a graduate orthodontic clinic for cases defined by the American Board of Orthodontics malocclusion categories

The American Board of Orthodontics (ABO) discrepancy index (DI) quantifies the severity of a malocclusion. The ABO objective grading system (OGS) assesses the quality of orthodontic finishing. Indiana University's comprehensive clinical assessment (CCA) supplements the OGS to provide an instrument to determine clinical outcomes. The purposes of this article were to (1) determine whether treatment outcome is related to the type of malocclusion as defined by the ABO classification, (2) determine the fraction of finished orthodontic cases in the graduate orthodontics clinic that are within the ABO standards for passing the phase III clinical examination, (3) evaluate the contribution of each component of the OGS and the CCA to the total OGS and CCA scores, (4) determine the percentage of finished cases that meet the ABO case category specifications, and (5) identify problem areas to improve the quality of treatment for challenging malocclusions. Three hundred eighty-two cases that satisfied requirements for 8 of the ABO's malocclusion categories were selected from 989 consecutively finished cases from 1998 through 2003. They were evaluated by using the OGS, the CCA, and the DI. The average OGS score was 32.64, the average CCA score was 5.62, and the average DI score was 20.94. There was no significant difference in the OGS and the CCA scores among the categories. Categories 2, 5, 7, and 8 had a DI score that was significantly higher than the average for the entire sample. The OGS and CCA scores were positively correlated with the DI score, meaning that complex malocclusions are challenging to finish well. The most points lost for the OGS and the CCA were for occlusal contacts and treatment efficiency (length of treatment relative to the result), respectively. The fewest points lost were for interproximal contacts and vertical control, respectively. Furthermore, prematurely terminated cases (early debonds) had longer treatment times and higher (worse) OGS and CCA scores. This study demonstrates problems in treating complex malocclusions in a graduate orthodontics program and suggests methods for increasing the quality of clinical outcomes.

Bracket Placement in Lingual vs Labial Systems and Direct vs Indirect Bonding

To examine the ultimate accuracy of bracket placement in labial vs lingual systems and in direct vs indirect bonding techniques. Forty pretreatment dental casts of 20 subjects were selected. For each dental cast, four types of bracket placement were compared: labial direct (LbD), labial indirect (LbI), lingual direct (LgD), and lingual indirect (LgI). Direct bonding was performed with the casts held in a mannequin head. Labial brackets were oriented with a Boone gauge, and lingual brackets were oriented with the Lingual-Bracket-Jig System. Torque error (TqE) and rotation deviation (RotD) were measured with a torque geometric triangle and a toolmaker's microscope, respectively. Both torque and rotational measurements were evaluated statistically as algebraic and absolute numeric values, using analysis of variance with repeated measures. Absolute TqE and RotD were significantly (P < .001) higher in direct than in indirect bonding techniques higher in both the labial and lingual bracket systems by twofold and threefold, respectively (LbD = 7.26 degrees , 1.06 mm; vs LbI = 3.02 degrees , 0.75 mm; LgD = 8.42 degrees , 1.13 mm; vs LgI = 3.18 degrees , 0.55 mm). No statistically significant difference was found between labial and lingual systems for the same bonding technique. Maxillary incisors demonstrated the largest RotD angle (eg, right lateral: 12.04 degrees ). A distal off-center RotD was predominant in the mandibular dentition. Labial and lingual systems have the same level of inaccuracy. For both systems, indirect bonding significantly reduces absolute TqE and RotD. The TqE found can cause transverse discrepancy (scissors or crossbite) combined with disclusion with antagonist teeth. The RotD found can result in irregular interproximal contact points.

Detection of interproximal demineralized lesions on human teeth in vitro using frequency-domain infrared photothermal radiometry and modulated luminescence

Frequency-domain photothermal radiometry (FD-PTR or PTR) is used to detect mechanical holes and demineralized enamel in the interproximal contact area of extracted human teeth. Thirty-four teeth are used in a series of experiments. Preliminary tests to detect mechanical holes created by dental burs and 37% phosphoric acid etching for 20 s on the interproximal contact points show distinct differences in the signal. Interproximal contact areas are demineralized by using a partially saturated acidic buffer system. Each sample pair is examined with PTR before and after micromachining or treating at sequential treatment periods spanning 6 h to 30 days. Dental bitewing radiographs showed no sign of demineralized lesion even for samples treated for 30 days. Microcomputer tomography (micro-CT), transverse microradiography (TMR), and scanning electron microscopy (SEM) analyses are performed. Although micro-CT and TMR measured mineral losses and lesion depths, only SEM surface images showed visible signs of treatment because of the minimal extent of the demineralization. However, the PTR amplitude increased by more than 300% after 80 h of treatment. Therefore, PTR is shown to have sufficient contrast for the detection of very early interproximal demineralized lesions. The technique further exhibits excellent signal reproducibility and consistent signal changes in the presence of interproximal demineralized lesions, attributes that could lead to PTR as a reliable probe to detect early interproximal demineralization lesions. Modulated luminescence is also measured simultaneously, but it shows a lower ability than PTR to detect these interproximal demineralized lesions.

Assessing the American Board of Orthodontics objective grading system: Digital vs plaster dental casts

The purposes of this study were to determine whether the American Board of Orthodontics objective grading system (ABO OGS) can be assessed accurately from digital dental casts and whether there are statistical differences between digital and plaster dental casts in scoring the ABO OGS. Thirty posttreatment plaster dental casts were selected and scanned by OrthoCAD (Cadent, Carlstadt, NJ) to produce 30 corresponding digital dental casts. The plaster and digital casts were compared by using the criteria of the ABO OGS. Because the data were ordinal, a nonparametic statistical analysis was used. The Wilcoxon test for paired samples showed significant differences between the plaster and digital casts for occlusal contacts, occlusal relationships, and total scores (P <.05). No significant differences were found for alignment, marginal ridges, overjet, and interproximal contacts. Buccolingual inclination was not included in this study because of inability to perform proper measurements with the OrthoCAD program. Mean differences of points deducted ranged from .03 point for marginal ridges to 5.07 points for the total score. The variable with the most points deducted related to occlusal relationships, and the fewest points were deducted for interproximal contacts. Based on this study, the current OrthoCAD program (version 2.2) was not adequate for scoring all parameters as required by the ABO OGS.

The Subjective Image Quality of Conventional and Digital Panoramic Radiography Among 6 to 10 year old Children

To compare the diagnostic quality of orthopantomographs made with the conventional unit Orthophos Siemens and the direct digital unit Planmeca 2000 cc Proline among children 6-10 years old and to investigate possible diferences on image interpretation between oral radiologists and pediatric dentists. Study material included two independent groups of panoramic images (50 in each group) made with different panoramic modalities (digital conventional). Eight observers (four pediatric dentists and four oral radiologists) evaluated all images for diagnostic quality in 12 pre-determined areas using a 4-point rating scale. Digital and conventional panoramic radiography performed almost similarly as far as it concerns the specific diagnostic tasks rated with the exception of the interproximal contacts of mandibular molars where digital panoramic radiography was scored significantly higher and the periapical region of anterior mandible and anterior mandibular tooth germs where conventional panoramic radiography was found to be significantly better. Both oral radiologists and pediatric dentists graded similarly digital and conventional radiographs for a variety of diagnostic tasks. It can be concluded that diagnostic image quality obtained with the digital orthopantomograph unit Planmeca 2000 cc Proline was generally equal to image quality obtained with the conventional orthopantomograph unit Orthophos Plus CD. Image interpretation between oral radiologists and pediatric dentists was not substantially different

Preprosthetic Periodontal Surgery in the Proximal Area With Modification of the COL Area: Results Following the Reestablishment of the Contact Point

Anatomic characteristics of interproximal areas are dependent on the anatomy, position, and proximal contact of adjacent teeth. The objective of this study was to investigate the influence of the reestablishment of the interproximal contact following the restorative alveolar interface (RAI) procedure on the interproximal gingival COL and formation of the interdental gingival papilla. Six mongrel dogs received bilateral apically positioned flaps, crown lengthening, and the RAI procedure on the maxillary fourth bicuspid and first molar. After 2 weeks, in a randomized manner, one side was prepared to receive metallic crowns and the opposite side remained as the control. The crowns were cemented at the 4-week postoperative period, and the dogs were sacrificed after another 4 weeks, totaling a period of 4 weeks with the full crowns in position and a total of 8 postoperative weeks. Histologic specimens were stained with hematoxylin and eosin and Mallory dyes. Sections 6 micro m thick were obtained in a bucco-lingual plane allowing ample visualization of the interproximal area. Clinical measurements revealed that, in the restored sides, four animals had complete fill of the interdental spaces with gingival papilla, whereas the other two dogs had a distance from the contact point to the tip of papilla varying from 0.02 to 0.021 mm. In the control group, papillae were totally reepithelialized with keratinized epithelium and a convex form. The epithelium completely covered the connective tissue and showed both epithelial projections and surface desquamation. On the test group, despite the presence of the prosthesis, the COL morphology modified by preprosthetic surgery was not altered, presenting a convex papilla with a triangular form and with a keratinized epithelium. Additional histologic characteristics were the same as found in the control group. Based on the results of this study, the reestablishment of the contact point does not revert what was obtained with the RAI procedure; the interproximal tissues remain convex and keratinized.

Time-dependent corrosion potential of newly-placed admixed dental amalgam restorations

Objective It was the objective of this study to measure the corrosion potential over time of newly-placed admixed dental amalgam restorations as a possible indicator of corrosion activity. Methods The corrosion potentials of 271 amalgam restorations, 4-min to 24-month old were measured in a convenience sample of 81 subjects. The selected restorations had no occlusal or interproximal contact with other metallic restorations. Eighty-one percent of the restorations aged 4 min to 7 months were made from zinc-containing admixed high-copper amalgam. The remaining amalgams were an unknown mixture of admixed high-copper and single-composition-alloy amalgams. Results The data were fit to a mixed-effects model with random patient effects to allow for the correlation, using the maximum likelihood method. The early data best fit a quadratic model with an initially rapidly rising corrosion potential that leveled off to a constant mean value of −146 (60) mV (versus Ag/AgCl, 3 M KCl at 35 °C) by approximately 7 months. Most of the ennoblement occurred within the first 4 months after restoration placement. Significance This in vivo study observed a slower rate of corrosion potential ennoblement for admixed amalgam restorations than would be predicted from in vitro studies. The slower rate is believed due to the combination of mechanical, chemical and biological forces in the mouth that are generally absent using simulated conditions. The slower rate of ennoblement suggests a slower rate of achieving maximum corrosion resistance than would be predicted using in vitro studies.

Reprinting the classic article on USPHS evaluation methods for measuring the clinical research performance of restorative materials

The original article published by Cvar and Ryge in 1971 on the US Public Health Service (USPHS) Guidelines is virtually inaccessible to current scientists, despite its remarkable impact on clinical dental research. The original article described all the pilot studies that led to the choices for the final USPHS guidelines. However, many of the important basic ideas expressed in the original article, such as evaluator calibration, have been overlooked in recent years. Challenges for effective clinical testing of restorative procedures and materials that were emphasized by those authors are even more relevant today. Therefore, it is totally appropriate to republish the original article by Cvar and Ryge in this issue of Clinical Oral Investigations. This preface to the republication of the original article provides key background information and references to contributions by the many now-famous clinical investigators who were involved with pilot studies. In addition, the USPHS recommendations are critically reviewed. Clinical evaluation of restorative procedures requires (a) choices of clinically relevant criteria, (b) assessment using simple nominal scales, (c) calibration of evaluators, (d) two independent evaluations, and (e) nonparametric statistic analysis that recognizes the patient (and not the restoration) as the independent variable. Only portions of those procedures are being preserved in current clinical investigations. USPHS criteria continue in use until today as part of routine clinical evaluation and as components of standards programs such as the ADA acceptance program. However, in addition, USPHS-like criteria have been appended over the years to produce “modified USPHS guidelines.” These additional criteria include parameters such as postoperative sensitivity, fracture, interproximal contact, occlusal contact, and others. The combination of the original and modified USPHS criteria now have been accepted worldwide but are not necessarily uniformly applied. They constitute the foundation for current considerations of further development of clinical assessment methods for dental restorative procedures.

Evaluation of the accuracy of digital model analysis for the American Board of Orthodontics objective grading system for dental casts

In 1999, after 3 years of field testing, the American Board of Orthodontics (ABO) implemented a grading system for posttreatment orthodontic models and panoramic radiographs, to make the phase III examination both fair and objective. In the ABO's objective grading system, 7 occlusal criteria (tooth alignment, vertical positioning of marginal ridges, buccolingual inclination of posterior teeth, occlusal relationship, occlusal contacts, overjet, and interproximal contacts) are measured on plaster models to assess a patient's final occlusion. To date, no study has evaluated the ABO grading system for use on digital models. The purpose of this study was to determine whether digital models can be used with reasonable accuracy and reliability for assessing patients' final occlusions. Plaster and digital (OrthoCAD, Cadent Inc, Carlstadt, NJ) posttreatment models of 24 patients were gathered from the postgraduate orthodontic clinic at Columbia University School of Dental and Oral Surgery. The plaster models were scored by using the ABO measuring gauge and the 7 criteria of the ABO grading system. A second analysis was done on the digital models. To determine interexaminer error, a fourth-year dental student at Columbia University served as a second examiner and repeated all the analyses. The means of the total score and those for marginal ridges, occlusal contacts, occlusal relationships, overjet, and interproximal contacts were not significantly different between plaster and digital models. However, the means for alignment and buccolingual inclination were significantly different. In addition, the scorings of 2 examiners differed for the 2 methods. This finding suggests that alignment and buccolingual inclination should be reevaluated with both methods, and adequate calibration of the examiners is essential to achieve repeatability in both methods. Digital models might be acceptable for use in the ABO model examination.

Adjacent Implant-Supported Restorations in the Esthetic Zone: Understanding the Biology

Traditionally, whe n considering adjacent implants in the esthetic zone, clinicians have encountered problems associated with deficient interproximal soft tissues. These discrepancies were often solved either by fabricating restorations with long interproximal contacts or by adding pink ceramics, both of which represent an esthetic compromise in today's demanding standard of care for restorative dentistry. This challenge has led to the recent introduction of scalloped implants. An understanding of the biology of wound healing of bone and soft tissue around implants and the remodeling process with implant-supported restorations allows the dental team to offer patients an alternative restorative solution consisting of combining conventional flat prosthetic table implants and scalloped implants. This article illustrates the biologic behavior of wound healing associated with dental implants and shows a step-by-step clinical case in which a patient received four adjacent implants in the esthetic zone. It also describes key elements in laboratory communication when dealing with the aforementioned restorations.

Comparison of university and private-practice orthodontic treatment outcomes with the American Board of Orthodontics objective grading system

Treatment outcomes and duration of treatment for patients treated in university graduate orthodontic programs and private orthodontic practices were assessed and compared with the ABO objective grading system. The treatment records of 139 randomly selected adolescents who had received comprehensive orthodontic treatment were examined. Seventy-seven subjects had been treated in 3 postgraduate orthodontic clinics, and 62 had been treated in 3 private orthodontic practices. Pretreatment, all subjects had Class II Division 1 malocclusions and ANB angles equal to or greater than 4 degrees . All patients were treated with premolar extractions. Posttreatment dental casts were measured and scored with the ABO objective grading system. No significant differences were found between the groups in the alignment, buccolingual inclination, and overjet components. Patients treated in private practice had significantly lower scores for marginal ridge height and occlusal relationship. Patients treated in the university programs had significantly lower scores for occlusal contact and interproximal contact components. There was no significant difference in the overall score, thus no significant difference in the overall quality of orthodontic treatment outcome between patients treated in university programs and private practices. However, the university group had a significantly larger sample variance for the overall score. There was no significant difference in the duration of the treatment between patients treated in a university setting and in a private practice.

Long-term posttreatment changes measured by the American Board of Orthodontics objective grading system

The American Board of Orthodontics (ABO) developed the objective grading system (OGS) to evaluate cases submitted as part of the phase III examination for board certification. This study examines the long-term changes in 6 of the 8 criteria measured by the board, with an emphasis on the relationship between posttreatment results and subsequent improvement or worsening. One hundred subjects were randomly chosen from the postretention archives of the Department of Orthodontics at the University of Washington. Pretreatment peer assessment rating (PAR) scores and posttreatment and postretention OGS scores were measured on study casts. The ABO criteria studied were alignment, marginal ridges, buccolingual inclinations, occlusal contacts, occlusal relationships, and overjet. Interproximal contacts and root angulations were not scored. The mean overall OGS score at posttreatment was 21.5 points. At postretention, this score had improved significantly, by approximately 4 points. When comparing posttreatment scores and long-term changes, similar patterns were seen for all criteria, except alignment; increased posttreatment scores were associated with increased long-term improvement. Well-treated cases tended to deteriorate, and poorly finished cases tended to improve, illustrating a regression to the mean. Alignment was the only criterion associated with a mean long-term worsening, as well as a less predictable pattern of change. The results of this study indicate that settling occurs after orthodontic treatment, and that the attainment of perfect occlusal results does not ensure stability.

こう合接触関係が歯の近遠心的変化様相に及ぼす影響

To fabricate a prosthesis which is functionally harmonized with the stomatognathic system, the interocclusal relationship must be reproduced as accurately as possible. This study investigated the influence of the occlusal contacts upon tooth displacement and clarified the optimal occlusal contacts for the prosthesis. The displacement paths of six maxillary left first molars of six adults in good general health were measured in this study. We gave each test tooth eight patterns of artificial occlusal contacts by attaching platinum foil on the occlusal surface. Subjects were asked to perform clenching at the intercuspal position (= ICP) with medium occlusal forces, and 3-dimensional tooth displacement paths were measured by the Type M-3 tooth displacement transducer. The following conclusions were obtained. 1. Using the Student's t-test for statistical analysis, it was suggested that the difference of the buccolingual location of occlusal contacts influenced the direction of the tooth displacement. 2. The tooth which had occlusal contact in the buccal cusp displaced in the mesio-buccal direction, so this may create a wide dental arch and a slight discrepancy was generated at the distal interproximal contact area of the tooth. 3. It was shown that the tooth which had occlusal contact in the buccal cusp rotated in the buccoapical direction in reverse to the natural tooth.

The Effect of Different Lower Third Molar Conditions on the Re-Crowding of Lower Anterior Teeth in the Absence of Tight Interproximal Contacts One-Year Post Orthodontic Treatment: A Pilot Study

The role of lower third molars in lower incisor crowding is a debatable topic. Some believe the presence or eruption of lower third molars is associated with the crowding of mandibular incisors, others negate such association. Thirty-two newly debonded orthodontic patients, with ages ranging from 14-19 years, were randomly selected. No retainers were used for the lower dental arch. Removal of tight interproximal contacts of the lower anterior teeth was created and maintained by periodic abrasive stripping every 2-3 months, if needed. The cases were followed up for one year. Orthopantomographs (OPGs) and study casts were taken at debonding (post-treatment) and at the end of the one year follow up (post retention). Statistical analysis of the lower third molar conditions--erupted, unerupted, or missing with or without sufficient space for their eruption--versus re-crowding of lower incisors was evaluated using Fisher's Exact Test. The results of this pilot study revealed there was no significant correlation between the different conditions of the lower third molars versus lower anterior re-crowding in the absence of tight interproximal incisal contacts; however, a larger sample size is needed to verify such findings.

Use of a feeler gauge to measure the gap between adjacent teeth

The adjustment of the interproximal contact of a crown is generally accomplished in the laboratory 1 Rhoads J.E. Rudd K.D. Morrow R.M. Dental laboratory procedures fixed partial dentures. Vol 2. 2nd ed. Mosby, St. Louis1986 Google Scholar , 2 Shillingburg Jr, H.T. Hobo S. Whitsett L.D. Jacobi R. Brackett S.E. Fundamentals of fixed prosthodontics. 3rd ed. Quintessence Publishing Co, Chicago1997 Google Scholar and, subsequently, evaluated intraorally. Practical errors can result in a gap (Fig. 1) that must be repaired. If the gap is the same intraorally as on the cast, the contact may be restored using the cast as a guide. A transfer impression may be necessary when a gap is present and the adjacent tooth has been modified or the proximal contour of the cast has been damaged. This article describes a method using a feeler gauge to determine the exact width of the gap for correction.

Clinical use of the ABO-Scoring Index: reliability and subtraction frequency.

This study tested the reliability and subtraction frequency of the study model-scoring system of the American Board of Orthodontists (ABO). We used a sample of 36 posttreatment study models that were selected randomly from six different orthodontic offices. Intrajudge and interjudge reliability was calculated using nonparametric statistics (Spearman rank coefficient, Wilcoxon, Kruskal-Wallis, and Mann-Whitney tests). We found differences ranging from 3 to 6 subtraction points (total score) for intrajudge scoring between two sessions. For overall total ABO score, the average correlation was .77. Intrajudge correlation was greatest for occlusal relationships and least for interproximal contacts. Interjudge correlation for ABO score averaged r = .85. Correlation was greatest for buccolingual inclination and least for overjet. The data show that some judges, on average, were much more lenient than others and that this resulted in a range of total scores between 19.7 and 27.5. Most of the deductions were found in the buccal segments and most were related to the second molars. We present these findings in the context of clinicians preparing for the ABO phase III examination and for orthodontists in their ongoing evaluation of clinical results.