André V. Ritter

Unique Enamel Phenotype Associated with Amelogenin Gene (AMELX) Codon 41 Point Mutation

Different mutations in the amelogenin gene (AMELX) result in the markedly different enamel phenotypes that are collectively known as amelogenesis imperfecta (AI). We hypothesize that unique phenotypes result from specific genetic mutations. The purpose of this study was to characterize the enamel compositional and structural features associated with a specific AMELX mutation in three families with X-linked AI. We performed mutational analysis by amplifying AMELX exons and sequencing the products. Permanent and primary affected (N = 6) and normal (N = 3) teeth were collected and examined by light, scanning, and transmission electron microscopy. Enamel proteins were evaluated by immunolocalization of amelogenin and amino acid analysis. AI-affected individuals all shared a common AMELX point mutation (C to A change at codon 41). The dental phenotypic findings were remarkably consistent in all affected individuals. The AI enamel was opaque, with numerous prism defects or holes encompassing the entire prism width. Affected crystallites appeared more radiolucent and morphologically less uniform, compared with that of normal enamel. Immunogold labeling with anti-amelogenin antibodies localized amelogenin to the crystallites but not to the inter-crystalline spaces. No immunogold labeling was seen in normal enamel. There was an increased and amelogenin-like protein content in AI enamel (0.95%) compared with normal enamel (0.13%). We conclude that this codon 41 C to A missense point mutation, in a highly conserved region of the AMELX gene, results in a remarkably consistent phenotype.

Reattachment of Anterior Teeth Fragments: A Conservative Approach

UNLABELLED Coronal fractures of the anterior teeth are a common form of dental trauma that mainly affects children and adolescents. One of the options for managing coronal tooth fractures when the tooth fragment is available and there is no or minimal violation of the biological width is the reattachment of the dental fragment. Reattachment of fractured tooth fragments can provide good and long-lasting esthetics (because the tooths original anatomic form, color, and surface texture are maintained). It also restores function, provides a positive psychological response, and is a relatively simple procedure. Patient cooperation and understanding of the limitations of the treatment is of utmost importance for good prognosis. This article reports on two coronal tooth fracture cases that were successfully treated using tooth fragment reattachment. CLINICAL SIGNIFICANCE Reattachment of fractured tooth fragments offers a viable restorative option for the clinician because ot restores tooth function and esthetics with the use of a very conservative and cost-effective approach.

Clinical Evaluation of an All-in-one Adhesive in Non-Carious Cervical Lesions with Different Degrees of Dentin Sclerosis

This randomized clinical trial compared the performance of an all-in-one adhesive (iBond) applied in sclerotic and non-sclerotic non-carious cervical lesions with that of a three-step etch-prime-bond adhesive (Gluma Solid Bond, SB). One-hundred and five lesions were randomly assigned to four groups according to adhesive, sclerosis scale and technique: 1) SB applied to lesions with sclerosis scale 1 and 2 (n=26); 2) iBond applied to lesions with sclerosis scale 1 and 2 (n=28); 3) iBond applied to lesions with sclerosis scale 3 and 4 (n=25) and 4) iBond applied with prior acid-etching to lesions with sclerosis scale 3 and 4 (n=26). A microfilled composite (Durafill VS) was used as the restorative material. The restorations were evaluated for retention, color match, marginal adaptation, anatomic form, cavosurface margin discoloration, secondary caries, pre- and post-operative sensitivity, surface texture and fracture at insertion (baseline), 6, 18 months and at 3 years using modified USPHS evaluation criteria (Alfa=excellent; Bravo=clinically acceptable; Charlie=clinically unacceptable). There was a high percentage of Bravo scores for marginal adaptation (4%-32%) and marginal discoloration (18%-60%) in Groups 2, 3 and 4, but all groups had <5% Charlie scores at 6 months and <10% Charlie scores at 18 months for retention and marginal discoloration, respectively. However, it should be noted that 13% of the restorations in Group 4 were not retained at three years.

Root caries risk indicators: a systematic review of risk models

OBJECTIVE To identify risk indicators that are associated with root caries incidence in published predictive risk models. METHODS Abstracts (n = 472) identified from a MEDLINE, EMBASE, and Cochrane registry search were screened independently by two investigators to exclude articles not in English (n = 39), published prior to 1970 (none), or containing no information on either root caries incidence, risk indicators, or risk models (n = 209). A full-article duplicate review of the remaining articles (n = 224) selected those reporting predictive risk models based on original/primary longitudinal root caries incidence studies. The quality of the included articles was assessed based both on selected criteria of methodological standards for observational studies and on the statistical quality of the modeling strategy. Data from these included studies were extracted and compiled into evidence tables, with information about the cohort location, incidence period, sample size, age of the study participants, risk indicators included in the model, root caries incidence, modeling strategy, significant risk indicators/predictors, and parameter estimates and statistical findings. RESULTS Thirteen articles were selected for data extraction. The overall quality of the included articles was poor to moderate. Root caries incidence ranged from 12% to 77% (mean ± SD = 45 ± 17%); follow-up time of the published studies was ≤ 10 years (range = 9; median = 3); sample size ranged from 23-723 (mean ± SD = 264 ± 203; median = 261); person-years ranged from 23 to 1540 (mean ± SD = 760 ± 556; median = 746). Variables most frequently tested and significantly associated with root caries incidence were (times tested; % significant; directionality): baseline root caries (12; 58%; positive); number of teeth (7; 71%; three times positive, twice negative), and plaque index (4; 100%; positive). Ninety-two other clinical and nonclinical variables were tested: 27 were tested three times or more and were significant between 9% and 100% of the times tested; and 65 were tested but never significant. CONCLUSIONS The root caries incidence indicators/predictors most frequently reported were root caries prevalence at baseline, number of teeth, and plaque index. This finding can guide targeted root caries prevention. There was substantial variation among published models of root caries risk in terms of variable selection, sample size, cohort location, assessment methods, incidence periods, association directionality, and analytical techniques. Future studies should emphasize variables frequently tested and often significant, and validate existing models in independent databases.

Optical properties and light irradiance of monolithic zirconia at variable thicknesses

OBJECTIVES The aims of this study were to: (1) estimate the effect of polishing on the surface gloss of monolithic zirconia, (2) measure and compare the translucency of monolithic zirconia at variable thicknesses, and (3) determine the effect of zirconia thickness on irradiance and total irradiant energy. METHODS Four monolithic partially stabilized zirconia (PSZ) brands; Prettau® (PRT, Zirkonzahn), Bruxzir® (BRX, Glidewell), Zenostar® (ZEN, Wieland), Katana® (KAT, Noritake), and one fully stabilized zirconia (FSZ); Prettau Anterior® (PRTA, Zirkonzahn) were used to fabricate specimens (n=5/subgroup) with different thicknesses (0.5, 0.7, 1.0, 1.2, 1.5, and 2.0mm). Zirconia core material ICE® Zircon (ICE, Zirkonzahn) was used as a control. Surface gloss and translucency were evaluated using a reflection spectrophotometer. Irradiance and total irradiant energy transmitted through each specimen was quantified using MARC® Resin Calibrator. All specimens were then subjected to a standardized polishing method and the surface gloss, translucency, irradiance, and total irradiant energy measurements were repeated. Statistical analysis was performed using two-way ANOVA and post-hoc Tukeys tests (p<0.05). RESULTS Surface gloss was significantly affected by polishing (p<0.05), regardless of brand and thickness. Translucency values ranged from 5.65 to 20.40 before polishing and 5.10 to 19.95 after polishing. The ranking from least to highest translucent (after polish) was: BRX=ICE=PRT<ZEN<KAT<PRTA (p<0.05). The ranking from least to highest total irradiant energy was: BRX<PRT<ICE=ZEN<KAT=PRTA (p<0.05). There was an inverse relationship between translucency, irradiant energy, and thickness of zirconia and the amount was brand dependent (p<0.05). SIGNIFICANCE Brand selection, thickness, and polishing of monolithic zirconia can affect the ultimate clinical outcome of the optical properties of zirconia restorations. FSZ is relatively more polishable and translucent than PSZ.

Tooth-surface-specific Effects of Xylitol: Randomized Trial Results

The Xylitol for Adult Caries Trial was a three-year, double-blind, multi-center, randomized clinical trial that evaluated the effectiveness of xylitol vs. placebo lozenges in the prevention of dental caries in caries-active adults. The purpose of this secondary analysis was to investigate whether xylitol lozenges had a differential effect on cumulative caries increments on different tooth surfaces. Participants (ages 21-80 yrs) with at least one follow-up visit (n = 620) were examined at baseline, 12, 24, and 33 months. Negative binomial and zero-inflated negative binomial regression models were used to estimate incidence rate ratios (IRR) for xylitol’s differential effect on cumulative caries increments on root and coronal surfaces and, among coronal surfaces, on smooth (buccal and lingual), occlusal, and proximal surfaces. Participants in the xylitol arm developed 40% fewer root caries lesions (0.23 D2FS/year) than those in the placebo arm (0.38 D2FS/year; IRR = 0.60; 95% CI [0.44, 0.81]; p < .001). There was no statistically significant difference between xylitol and control participants in the incidence of smooth-surface caries (p = .100), occlusal-surface caries (p = .408), or proximal-surface caries (p = .159). Among these caries-active adults, xylitol appears to have a caries-preventive effect on root surfaces (ClinicalTrials.gov NCT00393055).

Examiner Training and Reliability in Two Randomized Clinical Trials of Adult Dental Caries

OBJECTIVES This report describes the training of dental examiners participating in two dental caries clinical trials and reports the inter- and intra-examiner reliability scores from the initial standardization sessions. METHODS Study examiners were trained to use a modified International Caries Detection and Assessment System II system to detect the visual signs of non-cavitated and cavitated dental caries in adult subjects. Dental caries was classified as no caries (S), non-cavitated caries (D1), enamel caries (D2), and dentine caries (D3). Three standardization sessions involving 60 subjects and 3,604 tooth surface calls were used to calculate several measures of examiner reliability. RESULTS The prevalence of dental caries observed in the standardization sessions ranged from 1.4 percent to 13.5 percent of the coronal tooth surfaces examined. Overall agreement between pairs of examiners ranged from 0.88 to 0.99. An intra-class coefficient threshold of 0.60 was surpassed for all but one examiner. Inter-examiner unweighted kappa values were low (0.23-0.35), but weighted kappas and the ratio of observed to maximum kappas were more encouraging (0.42-0.83). The highest kappa values occurred for the S/D1 versus D2/D3 two-level classification of dental caries, for which seven of the eight examiners achieved observed to maximum kappa values over 0.90. Intra-examiner reliability was notably higher than inter-examiner reliability for all measures and dental caries classifications employed. CONCLUSION The methods and results for the initial examiner training and standardization sessions for two large clinical trials are reported. Recommendations for others planning examiner training and standardization sessions are offered.

Dentin and enamel bond strengths of dual-cure composite luting agents used with dual-cure dental adhesives §

OBJECTIVE The purpose of this in vitro study was to evaluate and compare dentin and enamel bond strengths obtained with dual-cure composite luting agents when used with dual-cure dental adhesives. METHODS Human molars were ground flat to expose enamel (n=80) or dentin (n=80). Specimens in each substrate group were randomly assigned to eight treatment sub-groups, according to four adhesive-luting agent combinations and two test conditions (with or without thermocycling). Pre-polymerized composite resin posts (TPH Spectrum) were luted to either the enamel or dentin surfaces with one of the following adhesive-luting agent combinations: (1) Xeno IV Dual Cure (dual-cure self-etch adhesive) and Calibra (dual-cure luting agent); (2) Prime & Bond NT Dual Cure (dual-cure total-etch adhesive) and Calibra; (3) OptiBond All-in-One Dual Cure (dual-cure self-etch adhesive) and Nexus 2 Dual Syringe (dual-cure luting agent); (4) OptiBond Solo Plus Dual Cure (dual-cure total-etch adhesive) and Nexus 2 Dual Syringe. For each treatment sub-group, half the specimens (n=10) were tested after 24h storage in water at 37 degrees C, and the other half (n=10) were tested after thermocycling for 1800 cycles between water baths held at 5 and 55 degrees C, with a dwell time in each bath of 30s, and a transfer time of 10s. Bond strengths were measured in shear mode, and expressed in MPa. The fracture mode (adhesive, cohesive, mixed) was examined. Data were analyzed for statistical significance with a factorial ANOVA and post hoc tests. RESULTS Mean enamel bond strengths ranged from 8.4MPa for non-thermocycled OptiBond All-in-One|Nexus 2 to 35.5MPa for non-thermocycled Prime & Bond NT|Calibra. Mean dentin bond strengths ranged from 14.5MPa for non-thermocycled OptiBond Solo Plus|Nexus 2 to 30.9MPa for thermocycled Xeno IV|Calibra. The fracture mode was predominantly adhesive for all groups. CONCLUSIONS On enamel, the total-etch adhesives performed better than their self-etch counterparts, while in dentin, the opposite was found, i.e., the self-etch adhesives performed better than their total-etch counterparts. Thermocycling for 1800 cycles did not affect the SBS of the materials tested to dentin and enamel.

Posterior Composites Revisited

Although resin-based composites have been used to restore posterior teeth since the early 1970s, 1–4 the posterior composite technique has not been fully accepted in our profession. Recent advances in polymer chemistry and light-initiated polymerization systems have improved adhesives, composites , and light-curing, but concerns with composite wear, less than ideal bonding to dentin, polymerization shrinkage and related stresses, postop-erative sensitivity, cost, and technique sensitivity still exist. Given that the posterior composite technique has improved substantially since its introduction, and that it presents many advantages over alternative direct restorative materials (e.g., esthetics, adhesive properties), posterior composites are not as widely taught as one would expect. A survey of 54 dental schools in North America revealed that only 67% of them teach three-surface Class II composites in premolars, whereas only 60% teach two-surface Class II composites in molars. 5 Similar results were reported by another study recently published. 6 In part, this reluctance to incorporate posterior composites in the undergraduate curriculum reflects the lack of unanimous acceptance of the technique. The purpose of this article is to briefly review the key aspects of the posterior composite technique, with emphasis on controversial, clinically related topics. The most recent American Dental Association (ADA) Statement on Posterior Resin-Based Composites 7 endorses the use of posterior composites in (1) small and moderately sized restorations, (2) conservative tooth preparations , and (3) areas where esthetics is important. These include Classes I and II, replacement of failed restorations, and primary caries (Figures 1–4).

Ceramic Inlays: A Case Presentation and Lessons Learned from the Literature

UNLABELLED Ceramic dental restorative materials offer an esthetic alternative to dental amalgam or gold. There is uncertainty relative to the longevity of ceramic inlay restorations. Recently published long-term research studies reveal general clinical performance trends. These trends are discussed while presenting a ceramic inlay case. Successful clinical use of ceramic inlay materials is absolutely dependent on the creation of an uncompromised adhesive tooth/ceramic interface. Ceramic inlay restorations perform well in terms of long-term retention, color match, and anatomic contour stability. These restorations all experience limited margin deterioration that does not predispose to marginal discoloration or secondary caries. Patients rarely suffer from postoperative sensitivity secondary to ceramic inlay placement. Ceramic inlays fail predominantly as a result of crack propagation from material flaws leading to bulk fracture. Some superficial ceramic defects may be repaired with composite resin. Internal material flaws are minimized by industrial production of indirect pressable glass-ceramic materials or ceramic blocks designed for computer-aided design/computer-assisted manufacturing (CAD/CAM). External surface flaws are limited by careful polishing techniques. Strategic placement of ceramic inlays in teeth that are not subject to heavy occlusal loading will result in more predictable long-term performance. Preparation design to prevent flexure of ceramic inlay materials is essential. CLINICAL SIGNIFICANCE Use of ceramic inlays to restore defects in posterior teeth requires careful attention to detail. Placement of ceramic inlay materials in high-stress areas may result in less predictable long-term performance. Ceramic inlays are advantageous for restoring moderately sized defects when optimal control of restoration contours and esthetics is desired.