A study of the effects of chewing patterns on occlusal wear

Comparative Assessment of Compomers and Ormocers as Pit and Fissure Sealants in Permanent Molars among Children Aged 7-9 Years

Introduction

In recent years, the dental profession's focus has shifted from the therapeutic to the preventive aspect of dental caries. Pit and fissure sealants, optimal fluoridation, healthy dietary habits, and good oral hygiene have been recommended for caries prevention. Many sealant materials are available on the market. Compomers are hybrid dental materials that are modified composite resins with polyacids. The esthetic properties of traditional composite systems are combined with the fluoride-releasing and adhesive properties of glass ionomer cement (GIC). Organically modified ceramic (Ormocer) material has high abrasion resistance and better aesthetics, similar to natural teeth.

Aim

To compare the sealing ability of compomer and ormocer as pit and fissure sealants in permanent mandibular first molars of 7-9-year-old children.

Materials and methods

A cross-sectional study with a split-mouth design was conducted on 88 children aged 7-9 years who attended the Department of Pediatric and Preventive Dentistry. Children were selected based on the inclusion and exclusion criteria. By tossing a coin, the placement of sealant material was selected for the right permanent first molar. Rubber dam isolation was done. The tooth surface was etched and washed. The respective sealants were applied. Sealants were cured with visible light, and occlusion was checked with articulating paper. Subsequently, the second sealant was placed in the next appointment, following the same clinical procedure in the opposite quadrant. Clinical evaluation was done at 3, 6, and 9 months for retention, marginal integrity, color match, wear, and presence of caries. The criteria were graded and rated as alpha, beta, and charlie based on modified Ryge United States Public Health Service (USPHS) criteria. All the data were statistically analyzed using Statistical Package for the Social Sciences (SPSS) software 20.0.

Results

The retention rate of ormocer at the 9-month review interval was 88.3%. There was a statistically significant difference in retention rates between compomer and ormocer (p = 0.003). The marginal integrity and wear of ormocer at the 9-month review interval were 84.4% compared with compomer, which was statistically significant with p = 0.010 and p = 0.035, respectively. Children with the fewest caries belonged to the ormocer group (p = 0.010) compared to the compomer group.

Conclusion

Children with ormocer as a pit and fissure sealant showed good retention, remarkable marginal integrity, absence of wear, and fewer dental caries compared to compomer sealants. Hence, ormocer-based sealants can be used in pediatric dental practice to protect children's oral hygiene and promote a healthy lifestyle.

How to cite this article

Saravanan SM, Srinivasan D, AR SE, et al. Comparative Assessment of Compomers and Ormocers as Pit and Fissure Sealants in Permanent Molars among Children Aged 7-9 Years. Int J Clin Pediatr Dent 2024;17(7):742-747.

Comparison of wear and marginal fitness of 3D-printed deciduous molar crowns: An in vitro study

This study aimed to evaluate the wear resistance of primary tooth enamel and 3 kinds of 3D printing materials and to compare the marginal fitness and internal suitability of prefabricated all-ceramic crowns, computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns, and three 3D-printed deciduous molar crowns. Multifunctional friction wear testing machine was used to image the wear surface of the sample and calculate the maximum wear depth and volume loss value of each sample. The internal fit evaluation used the silicon replica method, The four points were measured using scanning electron microscopy (SEM). The obtained data were statistically analyzed using ANOVA and Tukey HSD-test with a fully randomized design (p<0.05). The results showed the wear resistance of E-Dent400 was better than that of PEEK and three different 3D printed materials have good wear resistance compared with the primary tooth enamel. The measured values at M1 and M4 of E-Dent400 were both the smallest.

Association between the Temporomandibular Joint Morphology and Chewing Pattern

This study aimed to investigate whether the morphology of the temporomandibular joint (TMJ) is associated with chewing patterns while considering skeletal morphology, sex, age, and symptoms of temporomandibular disorder (TMD). A cross-sectional observational study of 102 TMJs of 80 patients (age 16-40 years) was performed using pretreatment records of cone-beam computed tomography imaging of the TMJ, mandibular kinesiographic records of gum chewing, lateral and posteroanterior cephalometric radiographs, patient history, and pretreatment questionnaires. To select appropriate TMJ measurements, linear regression analyses were performed using TMJ measurements as dependent variables and chewing patterns as the independent variable with adjustment for other covariates, including Nasion-B plane (SNB) angle, Frankfort-mandibular plane angle (FMA), amount of lateral mandibular shift, sex, age, and symptoms of TMD. In multiple linear regression models adjusted for other covariates, the length of the horizontal short axis of the condyle and radius of the condyle at 135° from the medial pole were significantly (p < 0.05) associated with the chewing patterns in the frontal plane on the working side. "Non-bilateral grinding" displayed a more rounded shape of the mandibular condyle. Conversely, "bilateral grinding" exhibited a flatter shape in the anteroposterior aspect. These findings suggest that the mandibular condyle morphology might be related to skeletal and masticatory function, including chewing patterns.

Tooth Wear and Tribological Investigations in Dentistry

Dental or tooth wear is a physiological process in the life cycle of teeth. Loss of the occlusal surface may cause excessive tooth wear. Several factors may contribute to tooth wear with different intensities and duration in the oral cavity. The oral cavity is generally compared to a tribological system to determine the various types of wear between teeth and restorative materials and assess the amount of dental wear. However, it is challenging to investigate in vitro and in vivo wear owing to the complexity of tooth wear; thus, a clear correlation between in vitro and in vivo data could not be established. This review is aimed at providing an insight into the etiology of tooth wear and tribological investigations in dentistry.

Neurotic personality trait as a predictor in the prognosis of composite restorations: A 24-month clinical follow up study

The role of personality traits in modulating the incidence and progression of medical disease conditions are well documented, however, there is a paucity of information for its effects on dental health conditions and specifically on the prognosis of restorative dental materials. This study aims to evaluate the clinical performance of Micro-hybrid and Nano-ceramic composite restorations among patients with different personality traits. A total of 323 patients, indicated to receive operative treatment at a University Dental College Hospital, were invited to participate in this study. Consenting patients were requested to complete the Big Five Inventory (BFI-44 Item) personality questionnaire and were evaluated by a psychiatrist for categorizing the participants based on their personality traits. Out of the recruited patients, 124 patients falling in to the dominant trait of Agreeableness (n = 62) and Neuroticism (n = 62) were included in the study for further investigation. Next, patients from the Agreeableness (Group A) and the Neuroticism personality trait group (Group N) were randomly divided into two subgroups each—sub group Am (n = 44) and Nm (n = 48) for Micro-hybrid composite restorations and Sub group An (n = 42) and Nn (n = 47) for Nano-ceramic composite restorations. Two trained and calibrated dentists prepared the cavities according to previously published methodology. The restorations were evaluated at baseline (immediately after restoration), 6-months, 12-months and 24-months intervals by two blinded independent dental professionals for anatomical form, secondary caries, color match, retention, marginal adaptation, surface texture, marginal discoloration and post-operative sensitivity. There is no statistically significant difference noted in various parameters of restoration performance between Micro-hybrid composite and Nano-ceramic composite compared among ‘agreeableness’ personality group and among ‘neuroticism’ personality group after controlling the personality trait factor. Higher ‘Neuroticism’ individuals had higher restoration deterioration in color matching and surface texture when compared to higher ‘Agreeableness’ trait individuals. Regression analysis showed no effect of gender or cavity size on the outcome of results. Assessment of personality traits may serve as a useful tool during treatment planning which would aid clinicians in choosing suitable restorative dental material and prosthesis design according to individual patient’s physiological and functional needs, thereby overall improving the quality of treatment provided.

Wear of 3D printed and CAD/CAM milled interim resin materials after chewing simulation

PURPOSE

The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation.

MATERIALS AND METHODS

Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using one-way analysis of variance and Tukey's post-hoc test (α=.05).

RESULTS

The mean ± standard deviation values of wear volume loss (in mm³) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P<.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; μm) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P=.01).

CONCLUSION

The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin. The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.

Evaluation of the wear of glazed and polished zirconia crowns and the opposing natural teeth: A clinical pilot study

STATEMENT OF PROBLEM

Clinical studies on the wear properties of different zirconia surfaces are lacking. Selecting a surface that causes and undergoes minimal wear will help improve clinical outcomes.

PURPOSE

The purpose of this clinical study was to evaluate and compare the wear over 1 year use of glazed zirconia (GZ) and polished zirconia (PZ) crowns opposing natural enamel and the wear of natural enamel opposing PZ and GZ crowns.

MATERIAL AND METHODS

This prospective, split mouth, randomized clinical trial included 14 participants requiring complete coverage crowns on first molars, bilaterally, in a completely dentate mandibular arch. GZ and PZ crowns were cemented according to a randomization chart. Polyvinyl siloxane impressions were made immediately and 1 year after the cementation of the crowns. The respective casts were scanned by using a 3D scanner and a software program to measure the amount of linear wear of zirconia crowns and opposing natural teeth. Wear was observed in 8 groups: PZ crowns, GZ crowns, natural enamel opposing natural enamel in the molar and premolar regions (NE-M and NE-PM), natural enamel opposing PZ crowns in the molar region (NE-PZ-M), natural enamel opposing GZ crowns in the molar region (NE-GZ-M), natural enamel opposing PZ crowns in the premolar region (NE-PZ-PM), and natural enamel opposing GZ crowns in the premolar region (NE-GZ-PM). A descriptive analysis was followed by comparison between groups by using a repeated-measure ANOVA with post hoc adjustments (α=.05).

RESULTS

The mean wear (μm) observed was as follows (in ascending order): PZ crowns (13 ±3), NE-PM (13 ±1), GZ crowns (27 ±9), NE-M (34 ±3), NE-PZ-PM (44 ±18), NE-PZ-M (63 ±22), NE-GZ-PM (69 ±21), NE-GZ-M (113 ±33). Wear of GZ and PZ crowns was less than wear of NE-M. The difference was statistically significant when comparing PZ with NE-M (P<.001, CI=-17 to -24). Wear of NE-GZ-M and NE-PZ-M was higher than wear of NE-M, with a statistically significant difference (P<.001, CI=-49 to -107 and P =.004, CI=-8 to -49, respectively). Wear of NE-GZ-M was more than that of NE-PZ-M, and the difference was statistically significant (P<.001, CI=-68 to -32). Wear of NE-PZ-PM and NE-GZ-PM was also more than the wear of NE-PM, and the difference was statistically significant (P<.001, CI=-17 to -43 and P<.001, CI=-39 to -70).

CONCLUSIONS

PZ and GZ crowns wear substantially with time, with lesser wear observed in PZ crowns. PZ and GZ crowns also cause more wear in opposing natural enamel than natural enamel antagonists, with the highest wear caused by GZ crowns.

Masticatory Adaptation to Occlusal Changes

This review deals with the frequent wide variability of masticatory capacity/incapacity. Neither researchers nor clinicians have taken sufficient account of this variability despite its implications for nutrition. Mastication in normal healthy oral conditions is first described, followed by a short presentation of the mechanisms of masticatory adaptation in the nervous system. Capacity, incapacity, and successful compensatory adaptation of mastication are then defined, along with the different methods used for their evaluation. Examples of adaptation needs are given, such as those concomitant with dental wear or occlusal changes. Finally, given its vital importance for deeply impaired mastication/deglutition function, the impact of masticatory adaptation processes on nutrition is examined.

Evaluating the Wear of Resin Teeth by Different Opposing Restorative Materials

The aim of this study was to evaluate the wear properties of resin teeth with different opposing dental restorative materials. One type of resin tooth (Trubyte Biotone) was tested against six types of restorative materials including type III gold alloy (GO), monolithic zirconia (MZ), lithium disilicate glass ceramic (LD), nickel-chromium alloy (NC), feldspathic ceramic (FC), and steatite (ST). Two-body wear tests were performed under a vertical load of 5 kgf and thermo-cycling at 5/55 °C with a total of 120,000 cycles. The wear amount was quantified by measuring the volume loss of the resin teeth and the vertical substance loss of the opposing materials using three-dimensional images. The FC group showed a significantly greater amount of wear of the resin teeth, followed by the ST, NC, LD, MZ, and GO groups. The GO group showed significantly less wear of resin teeth than the other groups. There were no statistically significant differences in the wear of opposing restorative materials between groups. Within the limits of this study, it is recommended that zirconia, rather than feldspathic ceramic, should be used for restorations in the esthetic zone, and gold alloy should be used for areas with little or no esthetic demand.

A guide to the clinical management of attrition

Attrition is an enigmatic condition often found in older individuals and often as a result of bruxism which can take place as a result of either day bruxism, night bruxism or both. Various studies and systemic reviews clearly shown that tooth wear is an age-related phenomena and the last Adult Dental Health Survey showed that 15% of participants showed moderate wear and 3% severe wear with 80% of patients over 50 years of age showing signs of wear. This review examines current theories around the aetiological factors contributing to attrition together with the clinical management of attrition focusing on minimal intervention where possible.

In Vitro Investigation of Wear of CAD/CAM Polymeric Materials Against Primary Teeth

The aim of the study was to evaluate the effects of polymeric computer-aided design/computer-aided manufacturing CAD/CAM materials on antagonistic primary tooth wear. Five CAD/CAM polymeric materials were examined: Vipi Block Monocolor (VBM), Yamahachi polymethylmethacrylate (PMMA) (YAP), Mazic Duro (MZD), Vita Enamic (ENA), and Pekkton (PEK). All of the specimens were tested in a thermomechanical loading machine with the primary canine as the antagonist (50 N, 1.2 × 10⁵ cycles, 1.7 Hz, 5/55 °C). The wear losses of the antagonist tooth and the restorative materials were calculated using reverse modelling software and an electronic scale. VBM and ENA showed significantly higher antagonist tooth wear than PEK (p < 0.05), but there was no significant difference observed among VBM, YAP, MZD, and ENA (p > 0.05). PEK showed the largest value in both material volumetric and weight losses. In terms of material volumetric losses, there was no significant difference between all of the groups (p > 0.05). In terms of material weight losses, PEK was significantly larger than ENA (p < 0.05), but there was no significant difference between VBM, YAP, MZD, and ENA (p > 0.05). Volumetric and weight losses of materials showed similar wear behaviour. However, the wear patterns of antagonists and materials were different, especially in PEK.

Two Body Wear of Newly Introduced Nanocomposite Teeth and Cross Linked Four Layered Acrylic Teeth: a Comparitive In Vitro Study

STATEMENT OF PROBLEM

Wear of complete denture teeth results in compromise in denture esthetics and functions. To counteract this problem, artificial teeth with increased wear resistance had been introduced in the market such as nanocomposite teeth.

PURPOSE

The purpose of this study was to compare the amount of wear between nanocomposite teeth and acrylic teeth.

MATERIALS AND METHODS

Fifteen specimens were chosen from each group namely the nanocomposite teeth (SR_-PHONARES) and the acrylic teeth (ACRY PLUS). Maxillary premolar was only chosen for testing and the samples were customized according to the specifications of the pin on disc machine. Pin on disc machine is a two body tribometer which quantifies the amount of wear under a specific load and time. Test samples were mounted on to the receptacle of the pin on disc machine and tested under a load of 0.3 kg for 1,000 cycles of rotation against a 600 grit emery paper. The amount of wear is displayed from the digital reading obtained from the pin on disc machine.

RESULTS

After statistical analysis, it was found that, the amount of wear is more in four layered acrylic teeth. The p value obtained is 0.002 (<0.005) thus implies that the difference in wear between nanocomposite teeth and acrylic teeth is statistically significant.

CONCLUSION

Though the nanocomposite teeth has less amount of wear than the four layered acrylic teeth, the difference is very less and adds only to a little clinical significance but the cost of the nanocomposite is four times that of the acrylic teeth. Further clinical studies must be performed to confirm our results.

Functional analysis of the stomatognathic system in individuals infected with human immunodeficiency virus

PURPOSE

To understand the effects of HIV type 1 on the function of the masticatory muscles.

METHODS

Sixty individuals were selected from both genders, aged between 22 and 57years (mean 36.77±9.33years), and divided into two groups: Group HIVG, 30 individuals with HIV subtype 1, and Group CG, 30 healthy individuals (control group). The individuals were submitted to assessments of their masticatory muscle activity, biting strength and thickness of the masticatory muscles by means of electromyography, maximal molar bite force and ultrasound imaging, respectively. The resultant data were statistically analyzed by t-tests (p<0.05).

RESULTS

The HIVG normalized EMG data from a mandibular rest position, protrusion, right and left laterality movement of the jaw showed that HIVG presented a relative increase in EMG activity compared to the CG. The HIVG had a lower masticatory cycle ability while chewing Parafilm M®, Raisins and Peanuts when compared to CG. During rest conditions, the ultrasound images showed a greater average muscular thickness in the right and left temporal region compared to CG. Upon maximal voluntary contraction, an increased average thickness was seen in the temporalis muscles and left sternocleidomastoid muscle when compared to the CG.

CONCLUSION

Based on the results of this research, it can be concluded that individuals with acquired immunodeficiency syndrome showed muscular changes related to the stomatognathic system, especially concerning EMG activity and muscle thickness.

Are resin composites suitable replacements for amalgam? A study of two-body wear

OBJECTIVES

Wear resistance is an important property of the dental materials, particularly for large restorations in the posterior regions and for the patients suffering from parafunctional activities. Additionally, the wear resistance of flowable composite resin materials is a clinical concern, although they are popular among dentists because of their easy handling. The aims of the present study were to evaluate the wear resistance of nine composite resins both condensable (G-aenial posterior, Venus, GrandioSO, Tetric EvoCeram, Ceram X duo, Filtek Supreme XTE) and new-generation flowable resin composites (G-aenial Universal Flo, GrandioSO Flow and GrandioSO Heavy Flow) and to compare these results with amalgam.

MATERIALS AND METHOD

Eight specimens of each material were subjected to two-body wear tests, using a chewing simulator. The wear region of each material was examined under profilometer, measuring the vertical loss (μm) and the volume loss (mm(3)) of the materials. Additionally, SEM analysis was performed to assess surfaces irregularities.

RESULTS

The results showed significant difference of the vertical loss and the volume loss of the examined materials (p < 0.001). Although amalgam had the best wear resistance, two condensable resin composites (GrandioSO, Ceram X duo) and all flowable materials had no significant difference with amalgam. GrandioSO had the highest wear resistance and Filtek Supreme XTE the lowest wear resistance.

CONCLUSION

The majority of resin composites had good wear resistance and similar to amalgam.

CLINICAL RELEVANCE

Based on the in vitro measurements of two-body wear resistance, the new resin composites could replace amalgam for restorations placed in occlusal stress-bearing regions. New-generation flowable resin materials may also be used in occlusal contact restorations.

Wear of two pit and fissure sealants in contact with primary teeth

Objectives:

Wear simulations may provide an indication of the clinical performance of pit-and-fissure sealants when associated with primary teeth as counterbody, restricting the involved variables. The aim of this study was to evaluate wear of dental materials used as pit-and-fissure sealants in contact with primary teeth.

Materials and Methods:

A resinous sealant (Fluroshield^®) and a resin-modified glass ionomer cement (Vitremer^®) were selected in a post-plate design, using as counterbody primary tooth pins (4 × 4 × 2 mm) at 3 and 10 N vertical load, 1 Hz frequency, 900 wear cycles in artificial saliva (n = 15). Attrition coefficient values were obtained and the material and primary tooth volumes were analyzed. Data were analyzed statistically by ANOVA and Duncan's test (P < 0.05).

Results:

Fluroshield^® presented the highest attrition coefficient values for the 3 N but these values decreased significantly for the 10 N load. The means for volume loss (3 mm) of the different samples after the wear test were not statistically different for the materials. The volume loss values for the primary teeth were statistically different and there was an increase in volume loss with the increase of the load applied in the wear tests.

Conclusions:

Differences were also observed with regard to the surface deformation characteristics. The wear rates of primary tooth enamel vary according to the type of material and the load applied during mastication.

Two-body wear rate of CAD/CAM resin blocks and their enamel antagonists

STATEMENT OF PROBLEM

Computer-aided design and computer-aided manufacturing (CAD/CAM) resins exhibit good mechanical properties and can be used as long-term restorations. The wear rate of such resins and their enamel antagonists is unknown.

PURPOSE

The purpose of this study was to test and compare the 2-body wear rate of CAD/CAM resin blocks.

MATERIAL AND METHODS

Wear specimens (N=42, n=6) were made from 5 CAD/CAM resins: ZENO PMMA (ZP), artBloc Temp (AT), Telio CAD (TC), Blanc High-class (HC), CAD-Temp (CT); 1 manually polymerized resin: Integral esthetic press (negative control group, IEP); and 1 glass-ceramic: VITA Mark II (positive control group, VM2). The specimens for the wear resistance were aged in a thermomechanical loading machine (49 N, 1.67 Hz, 5/50°C) with human enamel antagonists. The material loss of all specimens before, during, and after aging was evaluated with a 3DS profilometer. The measured material loss data of all tested groups were statistically evaluated with linear mixed model analysis (a=.05).

RESULTS

Manually polymerized resin showed significantly higher material wear (P<.001) than all other tested groups. Glass-ceramic showed significantly lower wear values (P<.001) than CAD/CAM resins ZP, AT, HC, CT, and IES. CAD/CAM resin TC was not significantly different from the positive control group. Glass-ceramic showed the highest enamel wear values (P<.001) of all tested resins. No differences were found in the enamel wear among all resins. The glass-ceramic group showed damage in the form of cracks on the worn enamel surface in 50% of specimens.

CONCLUSIONS

CAD/CAM resins showed lower wear rates than those conventionally polymerized. Only one CAD/CAM resin, TC, presented material wear values comparable with glass-ceramic. The tested glass-ceramic developed cracks in the enamel antagonist and showed the highest enamel wear values of all other tested groups.

Two-body wear of monolithic, veneered and glazed zirconia and their corresponding enamel antagonists

OBJECTIVE

This study tested whether the two-body wear of monolithic zirconia and their corresponding enamel antagonists was higher compared to monolithic alloy and veneered zirconia.

MATERIALS AND METHODS

Cylindrical specimens (N = 36, n = 6) were prepared out of (A) veneered zirconia (VZ), (B) glazed zirconia using a glaze ceramic (GZC), (C) glazed zirconia using a glaze spray (GZS), (D) manually polished monolithic zirconia (MAZ), (E) mechanically polished monolithic zirconia (MEZ) and (F) monolithic base alloy (control group, MA). Wear tests were performed in a chewing simulator (49 N, 1.7 Hz, 5°C/50°C) with enamel antagonists. The wear analysis was performed using a 3D profilometer before and after 120,000, 240,000, 640,000 and 1,200,000 masticatory cycles. SEM images were used for evaluating wear qualitatively. The longitudinal results were analysed using linear mixed models (α = 0.05).

RESULTS

Materials (p < 0.001) and number of masticatory cycles (p < 0.001) had a significant effect on the wear level. The least enamel antagonist wear was observed for MAZ and MEZ (27.3 ± 15.2, 28 ± 11.1 μm, respectively). GZC (118 ± 30.9 μm) showed the highest wear of enamel antagonists. The highest wear rate in the material was observed in GZS (91.3 ± 38.6 μm). While in the groups of MA, VZ, GZC and GZS 50% of the specimens developed cracks in enamel, it was 100% in MAZ and MEZ groups.

CONCLUSION

Polished monolithic zirconia showed lower wear rate on enamel antagonists as well as within the material itself but developed higher rates of enamel cracks.

Tooth wear and wear investigations in dentistry

Tooth wear has been recognised as a major problem in dentistry. Epidemiological studies have reported an increasing prevalence of tooth wear and general dental practitioners see a greater number of patients seeking treatment with worn dentition. Although the dental literature contains numerous publications related to management and rehabilitation of tooth wear of varying aetiologies, our understanding of the aetiology and pathogenesis of tooth wear is still limited. The wear behaviour of dental biomaterials has also been extensively researched to improve our understanding of the underlying mechanisms and for the development of restorative materials with good wear resistance. The complex nature of tooth wear indicates challenges for conducting in vitro and in vivo wear investigations and a clear correlation between in vitro and in vivo data has not been established. The objective was to critically review the peer reviewed English-language literature pertaining to prevalence and aetiology of tooth wear and wear investigations in dentistry identified through a Medline search engine combined with hand-searching of the relevant literature, covering the period between 1960 and 2011.

Effect of surgically assisted rapid maxillary expansion on masticatory muscle activity: A pilot study

Background:

The aim of the present study was to analyze the electromyographic (EMG) activity of masseter and temporal muscles of adult patients submitted to surgically assisted rapid maxillary expansion (SARME) before and after the surgery.

Materials and Methods:

The sample consisted of 19 adults, with ages ranging from 20 to 47 years (mean 25.4 years), with bilateral posterior cross bite requiring SARME treatment. The electromyographic activity of masseter and temporal muscles was analyzed before treatment (T1) and after the surgical procedure (T2). The mean interval between the two electromyographic analyses was 15 days.

Results:

The muscular active was electromyographically analyzed during the clinical situation of habitual gum chewing (10 sec), dental clenching (4 sec), mouth opening and closing (10 sec), rest (10 sec), protrusion (10 sec), and right and left laterality (10 sec). The measured differences between T1 and T2 data were evaluated using the paired t-test (SPSS 17.0 for Windows). The electromyographic analysis showed that the activity of the masseter and temporal muscles decreased significantly after the SARME in all the clinical situations after the surgery.

Conclusion:

According to the results of the present study, individuals after SARME surgery presented patterns of electromyographic contraction similar to those developed by dentate individuals during the movements of mandibular excursion.

Three-body wear of resin denture teeth with and without nanofillers

STATEMENT OF PROBLEM

The wear behavior of newly developed denture teeth with nanofillers may be different from teeth with other chemical formulations.

PURPOSE

The purpose of this study was to examine the 3-body wear resistance of 11 different commercially available resin denture teeth.

MATERIAL AND METHODS

The materials tested were conventional (SR Orthotyp PE, Orthognath) and cross-linked acrylic resin teeth without inorganic fillers (Premium 8, SR Postaris DCL, Trubyte Portrait, Artiplus), composite resin teeth with inorganic fillers (SR Orthosit PE, Vitapan), and composite resin teeth (experimental materials) with inorganic nanofillers (NC Veracia Posterior, e-Ha, Mondial). Human enamel and a ceramic denture tooth (Lumin Vacuum) were used as reference materials. The 3-body wear test was performed in a wear machine developed by the Academic Center for Dentistry Amsterdam (ACTA), with millet suspension acting as an abrasive medium (n=10, test load: 15 N, slip rate: 20%, number of cycles: 100,000). Wear was determined with the aid of a profilometer. Data were analyzed with the Kruskal-Wallis test and Mann-Whitney U test using the closed testing approach (significance level for familywise error rate, alpha=.05).

RESULTS

None of the acrylic and composite resin materials tested in this study demonstrated the 3-body wear resistance of ceramic teeth or human enamel. Teeth with inorganic fillers demonstrated significantly lower wear values than conventional or cross-linked acrylic resin teeth without fillers. Composite resin teeth with traditional fillers showed significantly lower wear than composite resin teeth with nanofillers.

CONCLUSIONS

Denture teeth with and without inorganic fillers differed significantly with regard to the degree of wear generated in the ACTA wear simulator. The incorporation of nanofillers did not improve the wear resistance compared to teeth with traditional fillers.

Tooth-wear patterns in subjects with Class II Division 1 malocclusion and normal occlusion

INTRODUCTION

The aim of this study was to investigate the prevalence of tooth wear in adolescents with Class II malocclusion, compared with those with normal occlusion.

METHODS

The sample consisted of dental casts obtained from 310 subjects, divided into 3 groups: group 1, 110 subjects with normal occlusion (mean age, 13.51 years); group 2, 100 complete Class II Division 1 patients (mean age, 13.44 years); and group 3, 100 half-cusp Class II Division 1 patients (mean age, 13.17 years). Dental wear was assessed by using a modified version of the tooth-wear index. The 3 groups were compared by means of the Kruskal-Wallis and Dunn tests, considering the frequency and the severity of wear on each surface of each group of teeth. The level of statistical significance was set at 5%.

RESULTS

The normal occlusion group had statistically greater tooth wear on the palatal surfaces of the maxillary central incisors and the incisal surfaces of the maxillary canines than the corresponding surfaces in both Class II malocclusion groups. The complete and half-cusp Class II Division 1 malocclusion groups had statistically greater tooth wear on the occlusal surfaces of the maxillary second premolar and first molar, the occlusal surfaces of the mandibular premolars, and the buccal surfaces of the mandibular posterior teeth compared with the normal occlusion group. The half-cusp Class II Division 1 malocclusion group had significantly greater tooth wear on the incisal surfaces of the mandibular incisors compared with the complete Class II Division 1 malocclusion group.

CONCLUSIONS

Subjects with normal occlusion and complete or half-cusp Class II Division 1 malocclusions have different tooth-wear patterns. Tooth wear on the malocclusion subjects should not be considered pathologic but rather consequent to the different interocclusal tooth arrangement.

Masticatory process in individuals with maxillary and mandibular osteoporosis: electromyographic analysis

The masseter and temporal muscles of patients with maxillary and mandibular osteoporosis were submitted to electromyographic analysis and compared with a control group. In conclusion, individuals with osteoporosis did not show significantly lower masticatory cycle performance and efficiency compared to the control group during the proposal mastications.

INTRODUCTION

This study aimed to examine electromyographically the masseter and temporal muscles of patients with maxillary and mandibular osteoporosis and compare these patients with control patients.

METHODS

Sixty individuals of both genders with an average age of 53.0 +/- 5 years took part in the study, distributed in two groups with 30 individuals each: (1) individuals with osteoporosis; (2) control patients during the habitual and non-habitual mastication. The electromyographic apparel used was a Myosystem-BR1-DataHomins Technology Ltda., with five channels of acquisition and electrodes active differentials. Statistical analysis of the results was performed using SPSS version 15.0 (Chicago, IL, USA).

RESULTS

The result of the Student's t test indicated no significant differences (p > 0.05) between the normalized values of the ensemble average obtained in masticatory cycles in both groups.

CONCLUSION

Based on the results of this study, it was concluded that individuals with osteoporosis did not show significantly lower masticatory cycle performance and efficiency compared to control subjects during the habitual and non-habitual mastications. This result is very important because it demonstrates the functionality of the complex physiological process of mastication in individuals with osteoporosis at the bones that compose the face.

Wear of feldspathic ceramic, nano-filled composite resin and acrylic resin artificial teeth when opposed to different antagonists

The aim of this study was to evaluate the wear of denture teeth and their antagonists produced by two-body and three-body wear tests. Three types of denture teeth, namely feldspathic ceramic (FC), nano-filled composite resin (NCR), and experimental acrylic resin teeth (AR), were tested. For each type two groups of eight upper premolars each were prepared. The first group was tested against cusps from the same material and the second group was tested against human enamel cusps. Each group was loaded with a total of 200,000 chewing cycles (two-body wear 100,000 cycles and three-body wear 100,000 cycles). Wear was analyzed by measuring the maximum depth and volume loss of the denture teeth using a laser scanner and by measuring the vertical loss of the antagonists using an optical macroscope. Statistically, there was no significant difference between the following combinations: FC-FC and NCR-NCR regarding the vertical and volume loss; and FC-enamel and NCR-enamel regarding the total vertical substance loss. The combinations AR-AR and AR-enamel showed higher wear values than the other combinations. For complete dentures, composite resin and ceramic teeth showed similar vertical and volume loss, whereas composite resin teeth seemed to be more suitable for partial dentures opposing natural teeth in terms of wear of teeth and antagonists.

Attrition, occlusion, (dys)function, and intervention: a systematic review

OBJECTIVES

Attrition and occlusal factors and masticatory function or dysfunction are thought to be related. This study aims to systematically review the literature on this topic with the emphasis to find evidence for occlusion-based treatment protocols for attrition.

MATERIALS AND METHODS

Literature was searched using PubMed (1980 to 2/2006) and the Cochrane Library of Clinical Trials with the keywords 'tooth' and 'wear'. Five steps were followed. Exclusion was based on the following: (1) reviews, case-reports, studies on non-human tooth material, and studies not published in English and (2) historical or forensic studies. Included were (3) in vivo studies. Next, studies on (4) occlusal factors, function or dysfunction [temporomandibular disorders (TMD), bruxism], or intervention, and (5) attrition were included. Two investigators independently assessed the abstracts; measure of agreement was calculated using Cohen's kappa; disagreement was resolved by discussion. Full-text articles were obtained and correlation between outcomes on occlusal factors, (dys)function, treatment, and attrition were retrieved. References in the papers included in the final analysis were cross-matched with the original list of references to add references that met the inclusion criteria.

RESULTS

The search procedure revealed 1289 references on tooth wear. The numbers of included studies after each step were (1) 345 (kappa=0.8), (2) 287 (kappa=0.87), (3) 174 (kappa=0.99), (4) 81 (kappa=0.71), and (5) 27 (kappa=0.68). Hand searches through the reference lists revealed six additional papers to be included. Analysis of the 33 included papers failed to find sound evidence for recommending a certain occlusion-based treatment protocol above another in the management of attrition.

CONCLUSION

Some studies reported correlations between attrition and anterior spatial relationships. No studies were found suggesting that absent posterior support necessarily leads to increased attrition, though one study found that fewer number of teeth resulted in higher tooth wear index (on the remaining teeth). Attrition seems to be co-existent with self-reported bruxism. Reports on attrition and TMD signs and symptoms provide little understanding of the relationship between the two.

Age and gender-related differences in premolar and molar functional areas

The aim of the present study was to underline the difference in premolar-molar functional areas according to both age and gender in a human adult population. Premolar and molar series were marked manually on opposed casts with articulating paper and functional areas were evaluated by quantification of these markings. It was noticed that on average larger functional areas were displayed by the older group (19 individuals, mean age 71.2 years, minimum 68 years, maximum 73 years) in comparison with the younger one (24 individuals, mean age 27.4 years, minimum 22 years; maximum 33 years). It was also observed that the average total functional area (4 hemiarches) was larger in the male subgroup (n: 23; mean age 45; young adults, 14; old adults, 9) compared with the female one (n: 20; mean age 49; young adults, 10; old adults, 10). Nevertheless, this gender difference in premolar-molar functional areas was related to the individual occlusal areas. As a matter of fact, when the individual occlusal area was taken into account for each series in the form of a ratio (functional area/occlusal area), the values obtained were not different between both gender subgroups studied. When comparing premolar and molar functional ratios (functional area/occlusal area) between age groups, it appears that the values obtained were slightly higher for the premolar series (ratios for young and older adults, respectively: Premolar series: 23.6+/-7.5%, 30+/-6.5%; Molar series: 23.1+/-6.8%, 27.3+/-6.7%). This difference was interpreted in relation to the reference (occlusal area) chosen.

Changes in the masticatory cycle after treatment of posterior crossbite in children aged 4 to 5 years

INTRODUCTION

The aim of this study was to analyze the dynamics of the masticatory cycle after occlusal adjustment through coronoplasty on deciduous teeth (selective grinding) and composite resin occlusal guidance for posterior crossbite correction.

METHODS

Nineteen children, aged 4 to 5 years, with functional posterior crossbites diagnosed at their clinical examinations, were selected. Analyses of masticatory cycles, including lateral excursive movements, were performed before and after treatment by using kinesiographic examinations in the 3 reference planes (frontal, horizontal, and sagittal). The examinations were done during bubble-gum chewing. The data were submitted to sign, Mann-Whitney, and paired t tests concerning the variables: left maximum lateral movement, right maximum lateral movement, total lateral movement (LM), vertical movement (VM), anteroposterior maximum movement, maximum lateral movement (MLM), and total maximum lateral movement (TMLM).

RESULTS

The treatment produced increased TMLM, a significant increase of the MLM opposite the crossbite, no statistically significant difference of the crossbite side, and a significant decrease of LM. Left crossbite children showed significant decreases in the LM after treatment; right crossbite children showed significant increases in VM after treatment.

CONCLUSIONS

Functional crossbite treatment with selective adjustment and occlusal guiding changed masticatory cycle patterns, producing larger horizontal and vertical planes. The cycles became more symmetric in the frontal plane, increasing the tendency of bilateral alternate mastication.