75 Years Ago: Discovery of Resin Adhesion to Acid-etched Enamel - A Comparison of the 1949 and 1955 Methods.

PURPOSE: This paper describes previously unknown details about the discovery of resin adhesion to acid-etched human enamel. MATERIALS AND METHODS: A literature review was performed through manual assessments. Primary sources revealing the discovery of resin curing on etched enamel were analyzed considering the research objectives and methodological procedure during that era, including the type of teeth used, preparatory measures, acid-etching process, type of resin and its application, and follow-up observations. Additionally, the political and economic contexts were examined. RESULTS: In 1949, acid etching was found to promote adhesion with acrylic resin, a finding described again in 1955. The 1949 studies utilized nitric acid for enamel etching and the acrylate resin Paladon from the Kulzer company (Germany). Conversely, the 1955 investigations employed phosphoric acid and an unnamed acrylate, likely a self-curing resin supported by Kulzer in the late 1930s. Disparities in the 1949 and 1955 findings can be ascribed to varying objectives and test conditions amidst a turbulent political backdrop, significantly impacting the Kulzer company. CONCLUSION: The discovery of resin adhesion to acid-etched enamel, approaching its 75th anniversary in 2024, is a landmark in 20th-century adhesive dentistry. Paladon represents a pioneering compound, exemplifying the influence of political, ideological, and economic factors on scientific advancements during that period.

New Methods for Replacing Single Missing Teeth with Non-prep Bridges (NPBs) - A Case Series.

PURPOSE: Newly developed non-invasive methods for replace a missing tooth and closing single-tooth gaps in the poster- ior region using resin composite are presented. MATERIALS AND METHODS: Four different non-invasive methods and the technical procedures, materials and instruments used are presented in a case series. These include the direct intraoral insertion of composite (with and without individual shaping aids) and indirect restorations, which are fabricated conventionally or digitally and bonded. RESULTS: The case series showed that all four methods can be used to replace single missing teeth in the posterior region, meeting current clinical requirements. Particular attention was paid to the design of the pontics, the dimension of the connector area, firm proximal contacts to the adjacent teeth, hygiene, and appearance of the non-prep bridges (NPBs). The advantages and disadvantages for both the direct and indirect techniques illustrated in this case series were com- pared in detail. CONCLUSIONS: Several direct and indirect non-invasive methods for single-tooth replacement are available today. Although the evidence is still limited, there is a potential for frugal dental interventions with NPBs. Further experimental and clinical studies are necessary to demonstrate that they reliably meet quality requirements (including sufficient survival rates), satisfy the criteria of cost-effectiveness (compared to treatment alternatives) and that there is a demand from the population.

New Options for Subgingival Oral Hygiene with a Flattened Interdental Brush Design - In Vitro Examination and Case Report.

PURPOSE: The subgingival area is only reached to a limited extent during home oral hygiene with the aids available to date. The question was investigated whether a newly developed, flattened cross-sectional design of interdental brushes (IDBs) can extend their subgingival reach. MATERIALS AND METHODS: In part I, the passage-hole diameters (PHD) of IDBs of different sizes and side-bristle lengths, with circular and flattened cross-sections, were compared according to the ISO standard 16409/2016. In part II, handling of flattened IDBs was described based on a case report of a patient with generalised stage 4, grade C periodontitis with locally persistent pockets. RESULTS: Depending on the brush's size, flattening of IDBs reduced the PHD by 1-18 intervals. IDBs with longer side bristles could thus be inserted into interdental spaces with equal force. This may increase the potential range of IDBs in the vertical dimension. Regular instruction and check-ups are necessary to enable correct handling, as the flattened brushes can only be used in two positions. The observations documented in the case report (duration: 1.5 years) showed that flattened IDBs were associated with reduced signs of inflammation (reduction of pocket depths from 6 to 3 mm, absence of bleeding on probing). CONCLUSION: IDBs with a flattened cross-sectional design have not been previously described in the literature. It was shown that flattening of IDBs leads to a size-dependent decrease in PHD. Based on a case report, it was hypothesised that the design change of the IDBs could be clinically relevant in the case of persistent deep pockets in narrow interdental spaces. However, this can only be verified or falsified by clinical studies.

The Origins of Acrylates and Adhesive Technologies in Dentistry.

PURPOSE: To examine the origins of acrylates and adhesive dentistry up to 1955. MATERIALS AND METHODS: A search of MEDLINE database and a manual literature search were conducted to find relevant articles. RESULTS: Acrylic acid was discovered in 1843, methacrylic acid in 1865. In 1880, light polymerization of acrylate compounds using glass prisms was introduced. In 1928, polymethyl methacrylate (PMMA) was industrially produced from methyl methacrylate (MMA). In 1930, PMMA moldings that could be adapted under heat and pressure were introduced into dentistry. The process was improved in 1936 by mixing pulverized PMMA and liquid MMA. In 1940, the intraoral polymerization of dental resins using UV light or catalysts was discovered. In the same year, the combined procedure (dual-curing) and addition of inorganic fillers to improve the material properties (precursors of composites) were proposed. Effects on the oxygen inhibition layer and intraoral bonding between several resin portions were also described. In 1942, direct restorations with self-curing resins (combined with a precursory version of cavity sealing) were described. These new resins were marketed in the late 1940s. Intraoral repair of restorations and cementation of crowns and bridges with resins were also described in 1942. In 1949, a glycerophosphoric acid-based sealer was marketed. In the same year, it was discovered that etching of the enamel (with nitric acid) caused an adhesion to thin layers of acrylic-based materials. In 1955, phosphoric acid etching of enamel was shown to improve adhesion. CONCLUSION: In the first half of the 20th century, important but little or unknown discoveries took place. These discoveries can improve our understanding of how adhesive dentistry evolved.

[Frugal dentistry-saving resources with a focus on core functions and patient needs]. / Frugale Zahnmedizin ­ Ressourceneinsparungen mit Fokussierung auf Kernfunktionen und Patientenbedürfnisse.

Frugal dentistry is derived from the term "frugal" (meaning simple, economical, usable, suitable). It focuses on dental interventions, which on one hand leads to a cost reduction compared to treatment alternatives and on the other hand focuses on dental core functionalities taking into account the patient's needs. In 2020, the World Health Organization (WHO) highlighted the urgency to prioritize cost-effective and affordable interventions.Against this background, a classification and review of frugal dentistry is carried out in this article. To what extent its objectives can be substantiated is investigated. Based on literature sources and an exemplary clinical presentation, options for frugal dentistry are shown. In addition, examples of potential frugal interventions and innovations are named and explained for a number of subject fields in dentistry. There are serious deficits in the systematic development and implementation of frugal dentistry. Numerous efforts in research, teaching, and patient care are therefore still required.

Mechanical plaque control of the interdental space with the "Heidelberg set".

At present, the most important criterion for the size selection of interdental brushes is the PHD-value (passage hole diameter) according to the ISO standard for interdental brushes ISO 16409:2016. The PHD size range of commercially available products currently lies between 0.6 and 5.2 mm. With the exceptions of special situations, a range between 0.7 and 2.9 mm is sufficient for clinical routine. As most products have longer filaments nowadays, one brush can often be applied for two PHD intervals. Consequently, adequate patient counseling and the individual selection of the appropriate interdental brushes can generally be achieved with an assortment of 12 systematically arranged interdental brush sizes. An application example is the "Heidelberg set" described herein. It is crucial that the correct choice of size is based upon continuously rising PHD-values, and not upon parameters such as stem size, outer diameter of filaments, or similar, as these do not allow for a reliable conclusion regarding the interdental passage. The usage of ISO sizes is also not recommendable due to their insufficient size differentiation. (Quintessence Int 2021;52: 176-186; doi: 10.3290/j.qi.b872241; Revised from an article originally published (in German) in Parodontologie 2020;31(1)37-49)

Mapping the Product Range of Interdental Brushes: Sizes, Shapes, and Forces.

PURPOSE: Preventive dentistry aims to improve oral hygiene, including the use of interdental cleansing aids. Clear and simple classifications may positively impact patient communication and motivate oral health behaviour. To date, there is no comparative analysis of interdental brush classifications and sizes. MATERIALS AND METHODS: A total of 2320 interdental brush samples by 24 manufacturers was examined regarding their passage hole diameter (PHD) according to the ISO standard for interdental brushes (ISO16409:2016), and their current classifications were evaluated. Inter- and intrarater reliability of the ISO size classification were determined based on 20 raters and 10 interdental brushes. The insertion force for these interdental brushes was analysed in vitro. RESULTS: Excellent intra- and interrater reliability was achieved (intraclass correlation coefficient (ICC) ≥ 0.973) overall, although greater variance was observed for bigger brush sizes. Insertion forces varied depending on size and form of the brushes, amounting to 1.58 N (SD = 1.27 N) for cylindric and tapered brushes, and to 2.31 N (SD = 0.81 N) for waist-shaped brushes. The size range of commercially available products was 0.6-5.2 mm PHD, 90% presenting with a PHD ≤ 2.0 mm. Size intervals were unsystematic. The ISO size was indicated by 33% of all manufacturers, the exact PHD by 25%. CONCLUSIONS: The determination of the PHD is a reproducible instrument for most brushes currently on the market. In vitro, forces developed based on this classification are mostly moderate, thus unlikely to cause periodontal trauma. Given the discontinuous range and unclear labelling of available products, the development of a simplified classification system by usage of the PHD may benefit the practitioner and patient alike by contributing to improve oral hygiene behaviours.

A New Restorative Method for the Closure of Single-Tooth Gaps - Technique Description and Case Series.

PURPOSE: To present a new method for the closure of single-tooth gaps using metal-, ceramic-, and glass-fiber-free direct composite cantilever restorations. MATERIALS AND METHODS: The new technique is described step by step in a case report, showing the creation and adhesive bonding of a single-retainer composite pontic. Furthermore, six cases are reported with radiological and clinical follow-up assessments over a period of one to three years after gap closure. RESULTS: Excellent outcomes were observed clinically and radiologically. No failures due to material properties (such as composite fractures, chipping) or esthetic limitations through discoloration were observed. Due to good oral hygiene, no periodontal complications were found during the observation period. CONCLUSIONS: This new minimally invasive procedure expands the therapeutic spectrum for the management of single-tooth gaps. It does not require laboratory-fabricated restorations and can be considered when conventional treatments, such as fixed dental prostheses or implants, are not options for medical reasons or due to special patient preferences.

Three-year randomized study of manual and power toothbrush effects on pre-existing gingival recession.

AIM: To compare long-term effects of brushing with an oscillating-rotating power toothbrush or an ADA reference manual toothbrush on pre-existing gingival recession. MATERIALS AND METHODS: In this controlled, prospective, single-blind, parallel-group study, healthy subjects with pre-existing recession were randomized and brushed with a power toothbrush (n = 55) or an ADA reference manual toothbrush (n = 54) for a 3-year study period. Subjects were required to brush their teeth twice daily for 2 min. using a standard fluoride toothpaste. During the study, subjects were assessed for clinical attachment loss and probing pocket depths to the nearest mm at six sites per tooth by the same calibrated examiner. Gingival recession was calculated at pre-existing sites as the difference between clinical attachment loss and probing pocket depths. Hard and soft oral tissues were examined to assess safety. RESULTS: After 35 ± 2 months, mean gingival recession did not differ significantly between groups, but was significantly reduced from baseline (p < 0.001), from 2.35 ± 0.35 mm to 1.90 ± 0.58 mm in the power and from 2.26 ± 0.31 mm to 1.81 ± 0.66 mm in the manual group. CONCLUSIONS: Gingival recession in subjects with pre-existing recession was significantly reduced after 3 years of brushing with either a power or manual toothbrush.

More conservative dentistry: clinical long-term results of direct composite resin restorations.

Current treatment protocols and recent developments in composite resin technology allow for extended indication of direct composite resin restorations. This article presents clinical longterm observations of direct composite resin restorations indicated for primary and replacement therapy, repair restorations, direct crowns, and composite buildups for the correction of tooth form.

Caries experience after periodontal treatment in aggressive and chronic periodontitis: results of a 10-year follow-up.

OBJECTIVE: To compare the increase of DMF-T and DMF-S in patients with aggressive periodontitis (AgP) and chronic periodontitis (ChP) after active periodontal therapy. MATERIALS AND METHODS: One hundred and thirty-six periodontally treated patients were re-examined after 10 years. Dental and periodontal status was assessed and patients' charts were screened for diagnosis, compliance to supportive periodontal treatment (SPT) and DMF-T/-S at baseline and re-examination. δDMF-T/-S was calculated and multi-level regression analyses were performed to identify factors contributing to increase of DMF-T/-S. RESULTS: Thirty patients with AgP, 37 with moderate ChP and 69 with severe ChP could be included. δDMF-T between first visit and re-examination was 2.07 (SD = 2.51, range = 0-14 teeth), mean δDMF-S = 14.66 (SD = 14.54, range = 0-83 surfaces). Patients with AgP showed a similar increase in DMF-T/-S to those with ChP. Regression analysis identified compliance as the only factor significantly accounting for preventing an increase of DMF-S (p = 0.017). No factor had a significant impact on DMF-T. CONCLUSIONS: DMF-T and DMF-S developed similarly in periodontally-treated patients with AgP and ChP during a follow-up of 10 years. SPT showed a positive influence on avoiding decline in DMF-S in periodontally compromised patients. No significant impact was detected for all other studied factors.

Analysis of the interdiffusion of resin monomers into pre-polymerized fiber-reinforced composites.

OBJECTIVES: The aim of the study was to analyze the dissolving depth of adhesive resin monomers into pre-polymerized fiber-reinforced composites (FRC) with either a semi-interpenetrating polymer network (semi-IPN) or a cross-linked polymer (CLP) matrix. METHODS: Five unidirectional FRCs were tested, including one semi-IPN FRC (everStick(®) C&B, StickTech, (ES)) and four CLP-FRCs (GrandTec(®), VOCO, (GT); Dentapreg(®), ADM, (DP); TenderFiber(®), Micerium, (TF); Splint-It(®), Pentron Clinical Technologies, (SI)). The FRCs were light-polymerized following manufacturers' instructions: the oxygen inhibition layers were removed and the adhesive resin (Optibond-FL(®), KerrHawe) was labeled with a fluorescent dye (Rhodamine-B-isothiocyanate), which was then applied to the FRCs (5 min) and light-polymerized (40s). Specimens were then prepared for confocal laser scanning microscopy. Three FRC strands per group were sectioned orthogonally to the direction of fibers, thus forming nine slices in each group. Four images were taken from each slice and the depths of adhesive penetration were measured in four sites per image (n=144 measurements per group). SIGNIFICANCE: Dissolving depths were 17.28 (3.04) µm (ES), 12.58 (2.94) µm (SI), 7.57 (1.91) µm (TF), 3.27 (0.73) µm (DP) and 2.55 (0.63) µm (GT). Samples were normally distributed. Differences between groups were analyzed by ANOVA (PostHoc Scheffé) showing four subgroups (p=0.05). The infiltration layers detected were either continuous/homogenous (ES, TF, DP GT) or discontinuous/insular (SI). CONCLUSION: The adhesive resin monomers were able to diffuse significantly deeper into pre-polymerized semi-IPN specimens than into CLP materials. Semi-IPN specimens showed a homogenous and comparatively deeper layer of infiltration. The diffusion capabilities of secondary-IPN formation might increase the opportunity to establish a good bond between pre-polymerized FRC and new resin.

Cyclosporine-induced gingival overgrowth correlates with NFAT-regulated gene expression: a pilot study.

OBJECTIVE: To determine whether incidence and severity of cyclosporine A (CsA)-induced gingival overgrowth (GO) is related to expression nuclear factor of activated T cells-regulated genes (NFAT-regulated genes). MATERIAL AND METHODS: Expression of NFAT-regulated genes was determined in 36 transplant patients medicated with CsA by real-time PCR before and 2 h after drug intake and residual NFAT activity was estimated as ratio of both measurements. Demographic, periodontal and pharmacologic parameters were recorded and GO assessed from models. Subjects were divided into two groups according to the degree of GO (responders: GO score≥10%). Groups were compared using parametric and non-parametric tests. The association of various CsA-specific and periodontal parameters on incidence and extent of GO were determined using regression analysis. RESULTS: Responders had a more than twofold lower residual NFAT activity than non-responders (7.9% and 18.1%, respectively; p<0.001). Multiple regression analysis revealed gingival inflammation, salivary CsA concentration, and residual NFAT activity to be significant factors influencing the expression of GO. Seventy-seven percent of the variability of GO could be explained by these parameters. CONCLUSIONS: This study showed that pharmacodynamic parameters such as residual NFAT activity may be promising prognostic indicators to identify patients with increased risk for GO.

Experimental study determining the mechanical properties of dental floss holders.

This study determined the mechanical properties of 19 dental floss holders. Eight single-use holders and 11 reusable ones were tested. An in vitro model with dental proximal contact strength of 8 N was created. Every device had to pass the proximal contact 30 times. We measured (1) the displacement of the floss [mm], (2) the force [N] necessary to pass the proximal contact after the 30th passage, (3) the loosening of the floss (offset [mm]), and (4) the change in the distance between the branches [mm]. Each measurement was repeated seven times. The results are displacement of the floss after 30 passages, 2.0 to 9.2 mm; passage force, 2.6 to 11 N; increases in branch distance, 0-2.9 mm; offset of the floss, 0-1.8 mm (all numbers are medians). Based on cleaning a full dentition (30 passages), we suggest introducing minimal requirements of <4 mm for the displacement of the floss, ≥11 N for the force, and <0.1 mm for the difference in branch distance and the offset. Only two products fulfilled our criteria. The tests show that dental floss holders vary extremely in their mechanical properties. Their effective use seems often impossible due to limited mechanical properties.

Fiber-reinforced composite fixed dental prostheses: a retrospective clinical examination.

PURPOSE: To obtain survival data on 32 fiber-reinforced fixed dental prostheses which were inserted in our department and to rate the quality of these restorations on the basis of esthetic, biological, and functional parameters. MATERIALS AND METHODS: Thirty-two patients with fiber-reinforced fixed dental prostheses were included in the study. The fiber frameworks were made of a polymer-monomer-preimpregnated continuous unidirectional glass fiber material. The survival times, failure events, and clinical parameters were recorded. Restorations in function without previous failure were classified as "Overall Survival". The classification "Functional Survival" was assigned in the event of minor failure and subsequent repair. Loss of the restoration was regarded as "Failure". The quality rating was performed using modified USHPS/Ryge criteria. RESULTS: The follow-up interval ranged from 2 to 64 months with a median follow-up time of 18.2 months. Twenty-four restorations were classified as "Overall Survival", seven were classified as "Functional Survival", and one was classified as "Failure". The overall survival at the median follow-up time was 74.4%. For the majority, the quality rating (USHPS/Ryge criteria) yielded clinically excellent results in all categories. No restoration was rated as insufficient or poor. CONCLUSION: Fiber-reinforced composite fixed dental prostheses provide sufficient stability and very good esthetic, biological, and functional performance in the case of specific clinical indications.

Full-mouth disinfection as a nonsurgical treatment approach for drug-induced gingival overgrowth: a series of 11 cases.

The treatment of drug-induced gingival overgrowth is compounded by the high recurrence rate resulting from chronic use of the medication and the persistence of other risk factors. In this case series, the treatment outcome of a nonsurgical periodontal therapy, according to the concept of full-mouth disinfection in 11 patients with drug-induced gingival overgrowth, is described. All clinical parameters improved significantly after therapy. Only 6% of teeth received further surgical treatment. The clinical situation remained stable during the recall. The present case series suggests that full-mouth disinfection might be a beneficial treatment concept for drug-induced gingival overgrowth, reducing the need for further surgical intervention.

Relationship between microtensile bond strength and submicron hiatus at the composite-dentin interface using CLSM visualization technique.

OBJECTIVES: "Submicron hiatus" represents a potential space between the base of the collagenous network and the mineralized dentin when it is acid etched for bonding. This study evaluated the relationship between microtensile bond strength (microTBS) and occurrence of submicron hiatus formations at the resin-dentin interface using the same specimens. METHODS: Resin-dentin bonded micro-specimens (sticks with a size of 300 microm x 300 microm x 8mm) were prepared using one of two material combinations (group I: Syntac Classic/Tetric Ceram Cavifil: n=51 group II: Prime & Bond NT/Tetric Ceram Cavifil: n=56). After labeling the primer component with a tiny amount of rhodamine-B-isothiocyanate, submicron hiatus formations were imaged nondestructively using a confocal laser scanning microscope (CLSM). Subsequently specimens were subjected to a microTBS test. RESULTS: For the influence of submicron hiatus formations on microTBS with the Syntac Classic group, the nonparametric Spearman's correlation was -0.329 at p=0.02. For the Prime & Bond NT group, the nonparametric Spearman's correlation was -0.356 at p=0.007. Analyzing the effect of submicron hiatus on without discriminating by group resulted in a Spearman's correlation coefficient of -0.341 at p=0.001; microTBS and quality of hybrid layer showed a correlation coefficient of 0.849 at p=0.001, and microTBS and quality of tag formation showed a correlation coefficient of 0.474 at p=0.001. SIGNIFICANCE: The degree of submicron hiatus formations had an influence on microtensile bond strength for both the Syntac Classic and the Prime & Bond NT group.

Relationship between microtensile bond strength and nanoleakage at the composite-dentin interface.

OBJECTIVES: This study evaluated the relationship between microtensile bond strength (microTBS) and occurrence of nanoleakage at the resin-dentin interface using the same specimens. METHODS: Resin-dentin-bonded micro-specimens (sticks with a size of 300 microm x 300 microm x 8mm) were prepared using one of two material combinations (group I: Syntac classic/Tetric Ceram Cavifil: n=57; group II: Prime & Bond NT/Spectrum TPH: n=52). After immersion of the micro-specimens in 0.1% rhodamine-B solution for 1h, nanoleakage was imaged nondestructively using a confocal laser scanning microscope (CLSM). Then the specimens were subjected to a microTBS test. RESULTS: For the influence of nanoleakage on microTBS with the Syntac classic/Tetric Ceram Cavifil group, the nonparametric Spearman correlation was 0.033 at p=0.805. For the Prime & Bond NT/Spectrum TPH group, the nonparametric Spearman correlation was 0.077 at p=0.584. SIGNIFICANCE: The degree of nanoleakage had no influence on microtensile bond strength for the Syntac classic/Tetric Ceram Cavifil or for the Prime & Bond NT/Spectrum TPH group.

Influence of the rubber dam on proximal contact strengths.

PURPOSE: The study tested the hypothesis that the application of a rubber dam influences the reconstruction of proximal contact strengths, while the corresponding contra-lateral teeth are not affected. METHODS: Seventy-four systemically and periodontally healthy subjects in need of a direct posterior composite restoration were treated with the use of a rubber dam. The proximal contact strengths (PCS) were electronically evaluated by measuring frictional forces during removal of a 50.0 +/- 5.0 microm-thick straight metal band. RESULTS: Proximal contact strengths significantly increased from 2.26 +/- 1.45N before to 3.83 +/- 2.34N after application of the rubber dam; whereas, the variation of PCS at the corresponding contacts in the contra-lateral quadrant remained within the intra-examiner variance of +/- 0.2N. Upon removal of the rubber dam, there was a statistically significantly drop in PCS from 3.54 +/- 1.87N to 2.31 +/- 1.35N. Again, there was only minimal change in the contra-lateral quadrant. It was concluded that application of the rubber dam affects proximal contact strengths.

Elevated levels of gene expression for collagen and decorin in human gingival overgrowth.

OBJECTIVES: It has been demonstrated that extracellular matrix molecules are involved in cyclosporine-induced gingival overgrowth (GO). However, for many of these molecules, it remains unclear whether their abundance is modulated on the protein and gene expression level. MATERIAL AND METHODS: To contribute to this clarification, we have analysed the protein and mRNA expression of type-I collagen (COL1) and decorin (DC) in native specimens obtained from five patients with GO, and matched normal tissue using indirect immunofluorescence (IIM), in situ hybridization (ISH) and quantitative polymerase chain reaction (PCR). RESULTS: IIF revealed a largely co-localized although remarkably increased abundance for COL1 and DC in GO. This increase coincided with an up-regulated gene expression observed for both molecules, as detected by ISH and quantitative PCR. CONCLUSIONS: Analysis of our data clearly demonstrates elevated levels for COL1 and DC and shows for the first time in native human tissue that involvement of these genes in GO is not confined to the protein level but also includes the transcriptional level.