A Stereophotogrammetry Face Study Between Dentate and Edentulous Adults Rehabilitated with Either a Conventional Complete or an Implant-Supported Fixed Complete Denture

Quantifying in edentulous patients the facial collapse and whether complete conventional denture (CCD) and implant-supported fixed complete denture (ISFCD) can restore the facial proportions to match those of a dentate patient (CG) is relevant for clinical dentists. One hundred and four participants were enrolled and divided into edentulous (n=56) and CG (n=48). The edentulous participants were rehabilitated with CCD (n=28) or ISFCD (n=28) in both arches. Anthropometric landmarks in the face were marked and captured by stereophotogrammetry. Linear, angular, and surface measurements were analyzed and compared among groups. The statistical analysis was performed by an independent t-test, the one-way ANOVA, and Tukey's test. The significance level was set at 0.05. The facial collapse was quantified as a significant shortening of the lower third of the face affecting facial aesthetics in all parameters evaluated and the same was observed in comparison among CCD, ISFCD, and CG. The CCD presented statistical differences with the CG group in the lower third of the face and labial surface, and the ISFCD showed no statistical differences with the CG and CCD. The facial collapse in edentulous patients could be restored through oral rehabilitation with an ISFCD similar to those of dentate patients.

What Are the Effects on Palate of Early Lip Surgery in Children With Cleft Lip and Palate? Cross-Sectional Evaluation From 5-Year-Old

This study aimed to evaluate the postsurgical effects from 5 years on the palate after surgical repair of the lip at 3 or 9 months of age in children with cleft lip and palate. Eighty-four digitized dental impressions were divided into the following groups: group 1 (G1): lip surgery at 3 months of life; group 2 (G2): lip surgery at 9 months of life; group 3 (G3): without orofacial cleft. Five angular (C'IC, ICM, IC'M', CMM', and C'M'M) and 3 linear parameters (C-C', c-c', and M-M') were evaluated. Statistical analysis was applied with α=5%. Intraclass Correlation Coefficient was significantly smaller in G1 than in G3 ( P =0.005), while IC'M' was significantly smaller in G3 than in G1 ( P <0.001). C'M'M was significantly smaller in G1 than in G2 and G3 ( P <0.001). The distances C-C' and c-c' were significantly smaller in G1 than in G2 and G3 ( P <0.001). There was a statistically significant difference in both G1 and G2 ( P <0.001, in all) in the analysis of palatal symmetry. Linear regression analysis showed that the, 11.2% of outcomes determined by c-c' distance can be explained by the age of lip repair ( P =0.013). In conclusion, lip surgery at 3 months of life showed a tendency toward more restriction in 5-year postsurgery palate development. The age of cheiloplasty is one of the factors that can influence palatal development; however, other factors may be associated and should be studied.

Sensitivity Treatments for Teeth with Molar Incisor Hypomineralization: Protocol for a Randomized Controlled Trial

Background

The sensitivity of teeth with molar incisor hypomineralization (MIH) can affect children’s quality of life and is a challenging problem for dentists. Remineralizing agents such as sodium fluoride varnish seem to reduce the sensitivity of teeth with MIH, but long-term clinical trials with large samples are still needed for more evidence about its effectiveness as a desensitizing agent before its clinical recommendation.

Objective

This randomized clinical trial aims to compare three treatment interventions for teeth with MIH and hypersensitivity.

Methods

A total of 60 children aged 6-10 years presenting with at least one first permanent molar with sensitivity and no loss of enamel will be randomly assigned to three groups: the control group (sodium fluoride varnish; Duraphat, Colgate); experimental group I (4% titanium tetrafluoride varnish); and experimental group II (a coating resin containing surface prereacted glass-ionomer filler; PRG Barrier Coat, Shofu). The sodium fluoride varnish and 4% titanium tetrafluoride varnish will be applied once per week for 4 consecutive weeks and the PRG Barrier Coat resin will be applied in the first session and the application will be simulated the following 3 weeks to guarantee the blinding of the study. The primary outcome will be sensitivity level measured at different moments (before each material application, immediately after application or simulation, and 1, 2, 4, and 6 months after the last application/simulation) by one examiner using the Wong-Baker FACES Pain Rating Scale, the Schiff Cold Air Sensitivity Scale, and the FLACC (Face, Legs, Activity, Cry, Consolability) scale. As secondary outcomes, parental satisfaction and child self-reported discomfort after the treatment will be measured with a questionnaire prepared by the researcher. The data will undergo statistical analysis and the significance level will be set at 5%.

Results

The project was funded in 2018, and enrollment was completed in November 2019. The recruitment of participants is currently underway and the first results are expected to be submitted for publication in 2022.

Conclusions

If found effective in reducing the patient’s sensitivity long term, these agents can be considered as a treatment choice, and the findings will contribute to the development of a treatment protocol for teeth with sensitivity due to MIH.

Trial Registration

Brazilian Registry of Clinical Trials Universal Trial Number U1111-1237-6720; https://tinyurl.com/mr4x82k9

International Registered Report Identifier (IRRID)

DERR1-10.2196/27843

Dental Plaque Disclosing as an Auxiliary Method for Professional Dental Prophylaxis in Early Childhood

Aim

This study aimed to clarify whether dental plaque disclosing before professional prophylaxis would improve the visualization of dental plaque, therefore optimizing the procedure.

Materials and methods

The sample comprised both the smooth and occlusal surfaces of the teeth of 25 children from 18 to 36 months. A randomized crossover clinical trial was conducted with two groups: GI—with disclosing and GII—without disclosing (washout/1 month). The teeth were stained with 1% malachite green solution to assess the amount of dental plaque on smooth and occlusal surfaces.

Results

Dental plaque removal was more effective and statistically faster (391.27 seconds ±142.2) in GI. The plaque index and the prophylaxis duration were inversely related in GI. The child's behavior did not affect the plaque removal effectiveness, regardless of plaque disclosure (p > 0.05).

Conclusion

Dental plaque disclosing in young children is an effective and less time-consuming method that improves the quality of the professional dental prophylaxis.

Clinical significance

Biofilm control is important for the success of programs for prevention of early childhood caries (ECC) and considering the particularities inherent to the dental care of infants, it is necessary that periodic professional prophylaxis is effective in eliminating the oral biofilm, ideally reducing chair time. Although dental plaque disclosing has been traditionally performed on educational basis during oral hygiene instruction, this resource can be safely employed to help professional prophylaxis in infants.

How to cite this article

de Alencar CRB, de Oliveira GC, et al. Dental Plaque Disclosing as an Auxiliary Method for Professional Dental Prophylaxis in Early Childhood. Int J Clin Pediatr Dent 2019;12(3):189–193.

Evaluation of Dentin-Pulp Complex Response after Conservative Clinical Procedures in Primary Teeth

Introduction

Although selective caries tissue removal decreases the number and diversity of bacteria, stops the caries process, and reduces the risk of pulp exposure, the studies on the minimally removal of caries tissue are limited and further clinical research is necessary in this field.

Aim

This study aimed to evaluate through clinical and radiographic assessments the in vivo response of the dentin-pulp complex of human deciduous teeth after either partial or total caries removal (TCR).

Materials and methods

A total of 49 deciduous molars of children aged between 5 and 9 years were carefully selected. The teeth were divided into two groups: Group I: Partial removal of caries; group II: Total removal of caries. Clinical and radiographic evaluations were performed during the period of 4 to 6 months after the procedure. The intraexam-iner reproducibility was determined by Kappa test. Fisher’s exact test was used to determine the statistical difference between groups.

Results

All teeth showed clinical success during the 4- to 6-month evaluation period. The radiographic evaluation showed 94.2 and 89.6% of success rate in groups I and II respectively. Radiographic results did not show statistically significant differences between the studied groups (p > 0.05).

Conclusion

The partial caries removal (PCR) showed satisfactory clinical and radiographic outcomes, suggesting that this minimally invasive approach might replace the TCR when correctly indicated.

How to cite this article: Mello B, Stafuzza TC, Vitor L, Rios D, Silva T, Machado M, Oliveira TM. Evaluation of Dentin-Pulp Complex Response after Conservative Clinical Procedures in Primary Teeth. Int J Clin Pediatr Dent 2018;11(3):188-192.

Immunolocalization of dentin matrix protein-1 in human primary teeth treated with different pulp capping materials

The aim of this study was to evaluate the immunolocalization of dentin matrix protein (DMP)-1 in human primary teeth treated with different pulp capping materials. Twenty-five primary molars were divided into the following groups: formocresol (FC), calcium hydroxide (CH), mineral trioxide aggregate (MTA), corticosteroid/antibiotic solution + CH (O + CH), and Portland cement (PC), and all received conventional pulpotomy treatment. The teeth at the regular exfoliation period were extracted for histological analysis and immunolocalization of DMP-1. Statistical analysis was performed using the χ(2) test (p < 0.05). Histological analysis revealed statistically significant differences in the comparison among the groups through the use of a score system regarding the presence of hard tissue barrier, odontoblastic layer, and internal resorption, but not regarding pulp calcification. Immunohistochemical analysis showed immunostaining for DMP-1 in groups CH, MTA, O + CH, and PC. Internal resorption was observed in the groups FC and CH. MTA and PC showed pulp repair without inflammation and with the presence of hard tissue barrier. DMP-1 immunostaining was higher for MTA and PC, confirming the reparative and bioinductive capacity of these materials.

The usefulness of cone beam computed tomography for treatment of complex odontoma

BACKGROUND

Odontomas are odontogenic tumours, resulting from epithelial growth and differentiated mesenchymal cells, clinically asymptomatic, and often associated with changes to the eruption of the permanent dentition. In recent years, cone beam computed tomography (CBCT) has been used in the diagnosis and treatment planning of this condition.

CASE REPORT

A 9-year-old male patient, with an unerupted permanent maxillary right central incisor (tooth 11) presented to our clinic. The panoramic radiograph showed impaction of tooth 11 with incomplete root development and the suspicion of an odontome and supernumerary tooth. CBCT was performed and enabled the visualisation of a radiopaque image compatible with an odontome, confirming the presence of an impacted supernumerary tooth on the palatal surface of tooth 11.

TREATMENT

Surgical excision of the odontome and the supernumerary tooth was performed.

FOLLOW-UP

Clinical and radiographic evaluations 2 months after the removal of the lesion showed lack of space for the eruption of tooth 11. The patient was referred for orthodontic treatment and a Hyrax appliance was fitted. The patient has been followed for 12 months.

CONCLUSION

CBCT is an important auxiliary tool, aiding in both correct diagnosis and accurate treatment planning. It is currently a technology accessible to most paediatric dentists and should be beneficial considering the diagnostic information provided as well as the cost-benefit ratio for the patient.

Reconstruction of bony facial contour deficiencies with polymethylmethacrylate implants: case report

Facial trauma can be considered one of the most serious aggressions found in the medical centers due to the emotional consequences and the possibility of deformity. In craniofacial surgery, the use of autologous bone is still the first choice for reconstructing bony defects or irregularities. When there is a shortage of donor bone or a patient refuses an intracranial operation, alloplastic materials such as polymethylmethacrylate (PMMA) can be used. The PMMA prosthesis can be pre-fabricated, bringing advantages such as reduction of surgical time, easy technical handling and good esthetic results. This paper describes the procedures for rehabilitating a patient with PMMA implants in the region of the face, recovering the facial contours and esthetics of the patient.

The low frequency of clinical resistance to PDGFR inhibitors in myeloid neoplasms with abnormalities of PDGFRA might be related to the limited repertoire of possible PDGFRA kinase domain mutations in vitro

Myeloproliferation with prominent eosinophilia is associated with rearrangements of PDGFR-A or -B. The most common rearrangement is FIP1L1-PDGFRA (FP). The majority of patients with PDGFR-rearranged myeloproliferation respond to treatment with imatinib. In contrast to BCR-ABL-positive chronic myelogenous leukemia, only few cases of imatinib resistance and mutations of the FP kinase domain have been described so far. We hypothesized that the number of critical residues mediating imatinib resistance in FP in contrast to BCR-ABL might be limited. We performed an established systematic and comprehensive in vitro resistance screen to determine the pattern and frequency of possible TKI resistance mutations in FP. We identified 27 different FP kinase domain mutations including 25 novel variants, which attenuated response to imatinib, nilotinib or sorafenib. However, the majority of these exchanges did not confer complete inhibitor resistance. At clinically achievable drug concentrations, FP/T674I predominated with imatinib, whereas with nilotinib and sorafenib, FP/D842V and the compound mutation T674I+T874I became prevalent. Our results suggest that the PDGFR kinase domain contains a limited number of residues where exchanges critically interfere with binding of and inhibition by available PDGFR kinase inhibitors at achievable concentrations, which might explain the low frequency of imatinib resistance in this patient population. In addition, these findings would help to select the appropriate second-line drug in cases of imatinib-resistant disease and may be translated to other neoplasms driven by activated forms of PDGFR-A or -B.

Pulpotomy of human primary molars with MTA and Portland cement: a randomised controlled trial

OBJECTIVE

This study compared the clinical and radiographic effectiveness of mineral trioxide aggregate (MTA) and Portland cement (PC) as pulp dressing agents in carious primary teeth.

METHODOLOGY

Thirty carious primary mandibular molars of children aged 5-9 years old were randomly assigned to MTA or PC groups, and treated by a conventional pulpotomy technique. The teeth were restored with resin modified glass ionomer cement. Clinical and radiographic successes and failures were recorded at 6, 12, 18 and 24-month follow-up.

RESULTS

All pulpotomised teeth were clinically and radiographically successful at all follow-up appointments. Six out of 15 teeth in the PC group and five out of 14 teeth in the MTA group exfoliated throughout the follow-up period. No statistically significant difference regarding dentine bridge formation was found between both groups throughout the follow-up period. As far as pulp canal obliteration is concerned, a statistically significant difference was detected at 6-month follow-up (p <0.05), since the beginning of mineralised material deposition could be radiographically detected in 100% and 57.14% of the teeth treated with PC and MTA, respectively.

CONCLUSIONS

PC may serve as an effective and less expensive MTA substitute in primary molar pulpotomies. Further studies and longer follow-up assessments are needed.

Clinical management for epidermolysis bullosa dystrophica

Epidermolysis bullosa (EB) consists of a group of genetic hereditary disorders in which patients frequently present fragile skin and mucosa that form blisters following minor trauma. More than 20 subtypes of EB have been recognized in the literature. Specific genetic mutations are well characterized for most the different EB subtypes and variants. The most common oral manifestations of EB are painful blisters affecting all the oral surfaces. Dental treatment for patients with EB consists of palliative therapy for its oral manifestations along with typical restorative and periodontal procedures. The aim of this article is to describe two dental clinical treatments of recessive dystrophic EB cases and their specific clinical manifestations. The psychological intervention required during the dental treatment of these patients is also presented.

Knowledge and attitude of parents or caretakers regarding transmissibility of caries disease

Dental caries is a transmissible infectious disease in which mutans streptococci are generally considered to be the main etiological agents. Although the transmissibility of dental caries is relatively well established in the literature, little is known whether information regarding this issue is correctly provided to the population. The present study aimed at evaluating, by means of a questionnaire, the knowledge and usual attitude of 640 parents and caretakers regarding the transmissibility of caries disease. Most interviewed adults did not know the concept of dental caries being an infectious and transmissible disease, and reported the habit of blowing and tasting food, sharing utensils and kissing the children on their mouth. 372 (58.1%) adults reported that their children had already been seen by a dentist, 264 (41.3%) answered that their children had never gone to a dentist, and 4 (0.6%) did not know. When the adults were asked whether their children had already had dental caries, 107 (16.7%) answered yes, 489 (76.4%) answered no, and 44 (6.9%) did not know. Taken together, these data reinforce the need to provide the population with some important information regarding the transmission of dental caries in order to facilitate a more comprehensive approach towards the prevention of the disease.

COX-2 inhibition decreases VEGF expression and alveolar bone loss during the progression of experimental periodontitis in rats

BACKGROUND

Vascular endothelial growth factor (VEGF) is a macromolecule of importance in inflammation that has been implicated in periodontitis. The aims of this study were to investigate VEGF expression during the progression of periodontal disease and to evaluate the effect of a preferential cyclooxygenase (COX)-2 inhibitor meloxicam on VEGF expression and alveolar bone loss in experimentally induced periodontitis.

METHODS

A total of 120 Wistar rats were randomly separated into groups 1 (control) and 2 (meloxicam, 3 mg/kg/day, intraperitoneally, for 3, 7, 14, or 30 days). Silk ligatures were placed at the gingival margin level of the lower right first molar of all rats. VEGF expression was assessed by reverse transcription-polymerase chain reaction (RT-PCR), Western blot (WB), and immunohistochemical (IHC) analyses. The hemiarcades were processed for histopathologic analysis. RT-PCR and WB results were submitted to analysis of variance, the Tukey test, and Pearson correlation analysis (P <0.05).

RESULTS

A reduction in alveolar bone resorption was observed in the meloxicam-treated group compared to the control group at all periods studied. There was a positive correlation between COX-2 mRNA and VEGF mRNA in the gingival tissues and periodontal disease (R = 0.80; P = 0.026). Meloxicam significantly reduced the increased mRNA VEGF expression in diseased tissues after 14 days of treatment (P = 0.023). Some alterations in VEGF receptor 1 mRNA expression were observed, but these were not statistically significant. VEGF protein expression in WB experiments was significantly higher in diseased sites compared to healthy sites (P <0.05). After 14 days of treatment with meloxicam, an important decrease in VEGF protein expression was detected in diseased tissues (P = 0.08). Qualitative IHC analysis revealed that VEGF protein expression was higher in diseased tissues and decreased in tissues from rats treated with meloxicam.

CONCLUSIONS

The present data suggest an important role for VEGF in the progression of periodontal disease. Systemic therapy with meloxicam can modify the progression of experimentally induced periodontitis in rats by reducing VEGF expression and alveolar bone loss.

The effectiveness of mineral trioxide aggregate, calcium hydroxide and formocresol for pulpotomies in primary teeth

AIM

To compare the effectiveness of mineral trioxide aggregate (MTA), calcium hydroxide (CH) and formocresol (FC) as pulp dressing agents in carious primary teeth.

METHODOLOGY

Forty-five primary mandibular molars with dental caries in 23 children [AUTHOR QUERY: How many children?] between 5 and 9 years old were treated by a conventional pulpotomy technique. The teeth were randomly assigned to the experimental (CH or MTA) or control (FC) groups. After coronal pulp removal and haemostasis, remaining pulp tissue was covered with MTA paste or CH powder in the experimental groups. In the control group, diluted FC was placed with a cotton pellet over the pulp tissue for 5 min and removed; the pulp tissue was then covered with zinc oxide-eugenol (ZOE) paste. All teeth were restored with reinforced ZOE base and resin modified glass-ionomer cement. Clinical and radiographic successes and failures were recorded at 3, 6, 12, 18 and 24 month follow-up.

RESULTS

Forty-three teeth were available for follow-up. In the FC and MTA groups, 100% of the available teeth were clinically and radiographically successful at all follow-up appointments; dentine bridge formation could be detected in 29% of the teeth treated with MTA. In the CH group, 64% of the teeth presented clinical and radiographic failures detected throughout the follow-up period, and internal resorption was a frequent radiographic finding.

CONCLUSIONS

Mineral trioxide aggregate was superior to CH and equally as effective as FC as a pulpotomy dressing in primary mandibular molars. Internal resorption was the most common radiographic finding up to 24 month after pulpotomies performed with CH.

Repair of furcal perforation treated with mineral trioxide aggregate in a primary molar tooth: 20-month follow-up

Furcal perforations may occur during access opening of the pulp chamber or cavity preparation. The perforation can cause an inflammatory reaction in the periodontal ligament. Management of these iatrogenic accidents can pose a significant clinical challenge, mainly when they occur in primary teeth. Current developments in the techniques and materials utilized for root perforation repair have enhanced this procedure's prognosis. Recently, mineral trioxide aggregate (MTA) has been used for several dental purposes. This biocompatible material promotes bone healing and elimination of clinical symptoms. The purpose of this case report was to describe the treatment of a furcal perforation using mineral trioxide aggregate (MTA) in a primary molar tooth. After 20 months, the tooth was asymptomatic. The radiolucent image had disappeared and bone formation at the furcation area had been observed, suggesting healing of the underlying periodontal tissues. Therefore, MTA may be considered an alternative option for the repair of furcal perforation in primary teeth, prolonging the longevity of these dental elements.

Surgical removal of an oral pyogenic granuloma and subsequent root coverage with a pedicle graft

Pyogenic granuloma (PG) is a lesion characterized by non-neoplastic proliferation of endothelial cells, occurring in gingival tissue and representing an excessive reaction of the connective tissue to stimuli or injuries. The purpose of this report was to describe the treatment of an oral pyogenic granuloma, with emphasis on clinical, histopathological, and radiographic aspects. The surgical therapy comprised lesion excision followed by pedicle graft to cover the exposed root surface. The patient's pyogenic granuloma has been under control for a year, and recurrence has not been observed. The permanent teeth erupted correctly and the gingival tissue of both the receptor and donor sites shows a satisfactory clinical appearance.

Knowledge and attitude of mothers with regards to emergency management of dental avulsion

Traumatic injuries to the teeth and their supporting structures are frequent in children. Among the traumatic injuries, dental avulsion results in the major functional and esthetic disturbances for patients.

PURPOSE

The present study's aim was to assess the mothers' level of knowledge and attitude concerning dental avulsion.

METHODS

A questionnaire contained 6 objective questions for the assessment of the mothers' knowledge and attitude regarding the management of dental avulsion and emergency procedures.

RESULTS

A total of 242 mothers participated in the study. A lack of technical information was observed among the mothers.

CONCLUSION

This study showed the need of a more effective communication between dental professionals and mothers to better handle dental emergencies. Educational campaigns and preventive programs on dental trauma must be organized to improve the emergency management of dental avulsion.

Mineral trioxide aggregate pulpotomy of a primary second molar in a patient with agenesis of the permanent successor

AIM

To describe a pulpotomy with mineral trioxide aggregate in a primary second molar with no permanent successor.

SUMMARY

Coronal pulpotomy was performed on a carious primary molar with no permanent successor in a 7-year-old child. Follow-up examinations 24 months later revealed that the treatment was successful in preserving the tooth and the vitality of its pulp.

KEY LEARNING POINT

Mineral trioxide aggregate might be considered as an alternative wound dressing for pulpotomy in primary molars, preserving pulp vitality and prolonging the useful life of the tooth.

HFE gene mutations in Brazilian thalassemic patients

Hereditary hemochromatosis is a disorder of iron metabolism characterized by increased iron intake and progressive storage and is related to mutations in the HFE gene. Interactions between thalassemia and hemochromatosis may further increase iron overload. The ethnic background of the Brazilian population is heterogeneous and studies analyzing the simultaneous presence of HFE and thalassemia-related mutations have not been carried out. The aim of this study was to evaluate the prevalence of the H63D, S65C and C282Y mutations in the HFE gene among 102 individuals with alpha-thalassemia and 168 beta-thalassemia heterozygotes and to compare them with 173 control individuals without hemoglobinopathies. The allelic frequencies found in these three groups were 0.98, 2.38, and 0.29% for the C282Y mutation, 13.72, 13.70, and 9.54% for the H63D mutation, and 0, 0.60, and 0.87% for the S65C mutation, respectively. The chi-square test for multiple independent individuals indicated a significant difference among groups for the C282Y mutation, which was shown to be significant between the beta-thalassemia heterozygote and the control group by the Fisher exact test (P value = 0.009). The higher frequency of inheritance of the C282Y mutation in the HFE gene among beta-thalassemic patients may contribute to worsen the clinical picture of these individuals. In view of the characteristics of the Brazilian population, the present results emphasize the need to screen for HFE mutations in beta-thalassemia carriers.

Complete spontaneous regression of congenital epulis in a baby by 8 months of age

BACKGROUND

This paper describes the case of a 7-day-old girl who was referred to a paediatric dentistry clinic because of the presence of a pedunculated mass protruding from the front of her mouth.

CASE REPORT

The mass was attached to the maxillary alveolus to the right of the midline, and was clinically diagnosed as a congenital epulis. The baby had no airway obstruction and was able to feed well. A conservative treatment was proposed, with monthly follow-up appointments to monitor the lesion.

CONCLUSION

After 8 months, the lesion had completely regressed, meaning that the girl did not have to be exposed to unnecessary surgical procedures in her first few days of life. The eruption of the upper anterior teeth was not affected.

An analysis of idiotype expression in a high-affinity, somatically mutated variant of a germline-encoded anti-p-azobenzenearsonate antibody

Using two polyclonal (rabbit) and two monoclonal anti-idiotype (anti-Id) reagents, we investigated structural correlates of the Id of mAb 36-71, a somatically mutated member of the CRIA Id family that has an exceptionally high affinity for the p-azobenzenearsonate (Ars) hapten. The two monoclonal anti-Ids reacted principally with the L chain of 36-71. The polyclonal anti-Ids interacted with both the H and L chain. The amino acid sequences of the VH and VL regions of 36-71 differ in eight and 11 positions respectively from those of the anti-Ars mAb 36-65, an unmutated prototype of the CRIA family. In the presence of 36-71L only three substitutions in 36-65 VH, introduced by mutagenesis, sufficed to restore full expression of the 36-71 Id. The same three substitutions had previously been shown to increase the affinity of 36-65 by a factor of 200, to a level equivalent to that of 36-71. X-ray crystallography had indicated that two of these substitutions introduce conformational changes consistent with the increase in affinity. We propose that these conformational changes may also account for the critical role of the three amino acids in Id expression. We also found that 36-65 is a very poor inhibitor of the interaction of 36-71 with its polyclonal anti-Ids, despite identity of the hapten-contacting residues in the two mAbs and evidence (from hapten inhibition) that the hapten-binding region is part of an important Id. Again, a difference in conformation at the binding site of the two mAbs could account for these observations.