Gajanan V. Kulkarni

The effect of various storage methods and media on shear-bond strengths of dental composite resin to bovine dentine

A variety of media and methods have been used to store teeth used in bond-strength studies of resin restorative materials to dentine. This study examined the effect of 2 months of storage using 11 different methods and media on the shear-bond strength of Z100 resin composite to bovine dentine mediated by Scotchbond Multi Purpose adhesive. Freshly harvested teeth were used as controls. The results showed that 7 of the l1 storage methods or media were similar in shear-bond strengths and bond-failure characteristics. Four of the 11 methods (irradiation, or storage in thymol, methanol, and glutaraldehyde) resulted in significantly lower shear-bond strengths and atypical shear-bond failure, indicating that these are the least desirable methods of tooth storage for studies of this type. This study has further shown that if insufficient numbers of fresh teeth are available for studies of shear-bond strength, then freezing is the preferred method of storage for the registration of high shear-bond strengths. It is also apparent that further investigations are needed to examine what post mortem changes occur in dentine, whether these changes are modified by various storage conditions, and whether they have any significant effect on bonding of resin composites.

The influence of orthodontic bracket base design on shear bond strength

Many bracket base designs and adhesive materials are in clinical use today. Bases have evolved from perforated metal bases to the present foil mesh bases, and treatments range from none, to spraying metal alloy onto the base, to the most common treatment of microetching. The purpose of this study was to determine the effect of orthodontic bracket base design on mean shear bond strength 1 hour or 24 hours after bonding. For each time group, 12 specimens of 6 types of metal brackets were bonded to bovine incisors with Transbond XT (3M Unitek, Monrovia, Calif) light-cured composite resin. Brackets were debonded 1 hour or 24 hours later, and the shear bond strength was recorded. Six debonded brackets of each type from each time group were selected at random and sandblasted. All the teeth were cleaned, and half were rebonded with used brackets, and half were rebonded with new brackets. Bond strength was measured again, 1 hour or 24 hours later. Representative specimens were inspected under the scanning electron microscope. Bracket base design significantly affected mean shear bond strength. Speed (60-gauge, microetched foil-mesh base; Strite Industries, Cambridge, Ontario, Canada) had the highest bond strength at 1 hour; followed by Time (machined, integral, microetched base with mechanical undercuts; American Orthodontics, Sheboygan, Wis); American Master Series (80-gauge foil-mesh base; American Orthodontics); Ovation Roth (80-gauge layered onto 150-gauge, microetched foil-mesh base; GAC, Central Islip, NY); Orthos Optimesh XRT (100-gauge microetched foil-mesh base; Ormco, Orange, Calif); and, finally, the nickel-free brackets (injection molded, 100-gauge, microetched, foil-mesh base; World Class Technology, McMinnville, Ore). The 24-hour results were similar except that Time had the highest mean shear bond strength (ANOVA, P <.05). Chairside sandblasting significantly affected the 1-hour, but not the 24-hour, mean shear bond strengths (ANOVA, P <.05). Sandblasting appears to be an effective method of cleaning bracket bases before rebonding.

Promotion of selective cell attachment by the RGD sequence in dentine matrix protein 1

Dentine matrix protein 1 (DMP1) is an important component of the non-collagenous extracellular matrix of developing teeth and bones. Functions of DMP1 other than a putative role in the initiation of mineralization are largely unknown. A first report on the DNA and deduced amino acid sequence showed that DMP1 has a single Arg-Gly-Asp (RGD) sequence. Here, whether the RGD sequence functions as a cell-attachment domain was tested. Using site-directed mutagenesis, two mutant recombinant DMP1 proteins with specific alterations at the RGD site were created. In the first mutant protein the RGD sequence was altered to a RGE (RGE) sequence; in the second the RGD domain was deleted (DEL). Mutated proteins were confirmed to be DMP1 by partial protein sequencing and dot-blot analysis with an anti-DMP1 antibody. Attachment of RPC-C2A (dental pulp cells), MC3T3-E1 (calvarial cells) or CHO (Chinese hamster ovary cells) to non-tissue-culture plastic coated with either DMP1, RGE or DEL proteins was compared. Bovine serum albumin and fibronectin served as negative and positive controls, respectively. The RGD-containing native DMP1 protein effectively allowed cell attachment and spreading. The RGE and DEL proteins with the altered and deleted RGD sites were significantly less effective in promoting cell attachment than the recombinant DMP1. Both RPC-C2A pulp cells and MC3T3-E1 cells showed similar reductions in attachment to mutated proteins. Treatment of RPC-C2A cells with a RGD-containing peptide prior to plating on DMP1-coated chambers abolished DMP1-mediated cell attachment. In contrast to RPC-C2A and MC3T3-E1cells, CHO cells, which normally do not express DMP1, failed to attach to DMP1. These data demonstrate that DMP1 promotes cell attachment through the RGD domain and that the attachment is cell- and tissue-specific. A basis for these observations is proposed using computer-generated models of the polypeptides within the DMP1 protein containing the RGD, RGE or DEL sequences.

Resolution of Maxillary Sinus Mucositis after Endodontic Treatment of Maxillary Teeth with Apical Periodontitis: A Cone-Beam Computed Tomography Pilot Study

INTRODUCTION Apical periodontitis (AP) is an inflammatory response that can affect the maxillary sinus. This study characterized maxillary sinus mucositis adjacent to teeth with AP and assessed its resolution after endodontic treatment. METHODS Thirty maxillary sinuses in subjects (n = 29) who had AP associated with maxillary posterior teeth were imaged with cone-beam computed tomography (CBCT). When mucositis was detected, its resolution was assessed with CBCT scanning 3 months after treatment, and periapical healing was assessed using the periapical index (PAI) after 6 months. RESULTS Excluding 5 sinuses obscured by sinusitis, mucositis was detected in 14 of 25 sinuses (56%). Nonsignificant inverse association was observed between the mucosal lining thickness and the distance from the sinus to root apices with AP. Four noncompliant subjects were discontinued. Three months after treatment, mucositis was fully resolved in 3 of 10 subjects (30%), partially resolved in 3 of 10 subjects (30%), unchanged in 3 of 10 subjects (30%), and worsened in 1 subject (10%). Six months after treatment, 6 of 10 subjects (60%) had reduced PAI scores classified as healed or healing. The subject with expanded mucositis at 3 months was not healing at 6 months. CONCLUSIONS Within the limited sample of this pilot study, CBCT imaging revealed a lower-than-expected prevalence of mucositis adjacent to teeth with AP. Fully resolved mucositis was not common 3 months after endodontic treatment, suggesting that in specific cases it might linger beyond 3 months after the elimination of the endodontic infection. Because of the low statistical power, the association between the resolution of mucositis and periapical healing could not be explored.

An ultrasonographic investigation of cleft-type compensatory articulations of voiceless velar stops

Ultrasound imaging was used to investigate the articulation of the voiceless velar stop [k] in five speakers with compensatory articulation related to cleft palate. The perceptual evaluation of the acoustic realization and the visual assessment of the tongue movement for the target sound were made by three examiners. The analysis revealed a variety of different compensatory strategies that included glottal stops, pharyngeal stops, midpalatal stops and glottal and velar co-productions. One patient produced palatal click sounds together with a midpalatal stop. The ultrasound imaging also revealed covert articulatory movements that would have been missed in a purely perceptual analysis. The analysis of the ultrasound images points to subphonemic aspects of cleft-type compensatory articulation that are important to understand for speech therapy.

Perceptual, durational and tongue displacement measures following articulation therapy for rhotic sound errors.

ABSTRACT Outcomes of articulation therapy for rhotic errors are usually assessed perceptually. However, our understanding of associated changes of tongue movement is limited. This study described perceptual, durational and tongue displacement changes over 10 sessions of articulation therapy for /ɹ/ in six children. Four of the participants also received ultrasound biofeedback of their tongue shape. Speech and tongue movement were recorded pre-therapy, after 5 sessions, in the final session and at a one month follow-up. Perceptually, listeners perceived improvement and classified more productions as /ɹ/ in the final and follow-up assessments. The durations of VɹV syllables at the midway point of the therapy were longer. Cumulative tongue displacement increased in the final session. The average standard deviation was significantly higher in the middle and final assessments. The duration and tongue displacement measures illustrated how articulation therapy affected tongue movement and may be useful for outcomes research about articulation therapy.

Long-Term Effectiveness of Parent Education Using the “Baby Oral Health” Model on the Improvement of Oral Health of Young Children

Purpose. To determine the long-term effectiveness of comprehensive education given to parents and caregivers with respect to the incidence of preventable oral diseases, utilization of dental services, and retention of knowledge related to oral health. Methods. Group presentations on oral health were conducted for caregivers of infants (n = 161) using an interactive audio-visual aid. Followup occurred at 18 months. A comparison group (n = 181) was enrolled from the same community groups. Chi-square and Fishers exact tests were used to analyze findings. Results. There was a difference in caries incidence, knowledge levels of caregivers, and utilization of dental services (P < 0.05) when comparing the SGB to the SGFU. Conclusions. One-time exposure to parent education using a comprehensive interactive audio-visual aid has an effect on reducing caries incidence and increasing dental utilization. While most knowledge is retained by parents, there is some attrition in the information retained over an 18-month time period. This emphasizes the importance of repeated reinforcement of the same concepts over a shorter time span.

Production of Two Nasal Sounds by Speakers With Cleft Palate

Many speakers with cleft palate develop atypical consonant productions, especially for pressure consonants such as plosives, fricatives, and affricates. The present study investigated the nature of nasal sound errors. The participants were eight female and three male speakers with cleft palate between the ages of 6 to 20. Speakers were audio-recorded, and midsagittal tongue movement was captured with ultrasound. The speakers repeated vowel-consonant-vowel with the vowels /α/, /i/, and /u/ and the alveolar and velar nasal consonants /n/ and /η/. The productions were reviewed by three listeners. The participants showed a variety of different placement errors and insertions of plosives, as well as liquid productions. There was considerable error variability between and within speakers, often related to the different vowel contexts. Three speakers co-produced click sounds. The study demonstrated the wide variety of sound errors that some speakers with cleft palate may demonstrate for nasal sounds. Nasal sounds, ideally in different vowel contexts, should be included in articulation screenings for speakers with cleft palate, perhaps more than is currently the case.