01/05/2011 Molar Incisor Hypomineralization: Review and Recommendations for Clinical Management

Resident: J. Hencler
Date: 01/05/2011

Article title: Molar Incisor Hypomineralization: Review and Recommendations for Clinical Management

Author: Williams et al.
Journal: Pediatric Dentistry-28:3 2006

Major topic: Molar incisor hypomineralization (MIH)
Type of Article: Lierature Review

Main Purpose:
Describe the diagnosis, prevalence, putative etiological factors, and features of hypomineralized enamel in MIH and present a sequential approach to management.

Background:
MIH was introduced in 2001 to describe the clinical appearance of enamel hypomineralization of systemic origin affecting one or more permanent first molars (PFMs) that are frequently associated w/ affected incisors. MIH is attributed to disrupted ameloblastic function during the transitional and maturational stages of amelogenesis. MIH’s clinical management is challenging due to the sensitivity and rapid development of caries in affected PFMs, the limited cooperation of a young child, difficulty in achieving anesthesia, and the repeated marginal breakdown of restorations.

MIH Diagnosis:
After a thorough prophy, the 4 PFMs and 8 erupted permanent incisors are examined wet for demarcated opacities, post eruption breakdown (PEB), and atypical restorations. Opacities are usually limited to the incisal or cuspal 1/3 of the crown, rarely involving the cervical 1/3. Restorations may not conform to typical caries pattern and frequently involve the cuspal or incisal 1/3 of the crown. Teeth with developmental defects of enamel may present similarly regardless of etiology and confused with MIH. For example, Enamel hypoplasia (EH) is a quantitative defect associated with a reduced localized thickness of enamel, following disruption of the secretory phase of amelogenesis. MIH and EH can be difficult to differentiate when affected molars have PEB due to caries or masticatory trauma.

Hypomineralized Enamel Characteristics:
Hypomineralization is thought to follow deposition of the full thickness of enamel matrix. The transitional ameloblast is considered most vulnerable and when these cells do not undergo complete maturation, full-thickness hypomineralization occurs. Hypomineralization is thought to be due to disturbed resorptive potential of ameloblasts and proteolytic enzyme inhibition, leading to protein retention and interference w/ crystal growth and enamel maturation. Also, conditions affecting matrix pH during enamel maturation and impaired calcium metabolism may predispose MIH.

Factors Associated With MIH:
Putative factors associated w/ disrupted amelogenesis of PFMs include systemic conditions and environmental insults influencing natal and early development. Although a number of etiological factors may contribute to MIH, the threshold needed to cause enamel defects at sensitive stages of amelogenesis is unknown and 2 or more concurrent conditions may act synergistically to produce a defect. Conditions common in the first 3 years, such as upper respiratory diseases, asthma, otitis media, tonsillitis, chicken pox, measles, and rubella, appear to be associated w/ MIH. Antibiotic usage has also been implicated but due to the concurrence of the disease and antibiotic therapy, it is difficult to determine whether MIH is associated with the disease, the antibiotic, or both. Systemic conditions implicated to date include nutritional deficiencies, brain injury and neurological defects, cystic fibrosis, syndromes of epilepsy and dementia (Kohlschutter-Tonz syndrome), nephritic syndrome, atopia, lead poisoning, repaired cleft lip and palate, radiation treatment, rubella embryopathy, epidermolysis bullosa, ophthalmic conditions, celiac disease, and GI disorders.

Prevalence of MIH:
Prevalence data is limited due to several diagnostic classifications but range from 4-25%

Risk Identification, Remineralization, and Preventaive Management:
Children at risk for MIH should be identified prior to PFM eruption if possible based on history of etiological factors in the first 3 years and careful radiographic exam of unerupted first molar crowns. Thorough OH should be instituted including desensitizing toothpaste. Remineralization therapy should commence as soon as the defective surface is accessible, aimimg to produce a hypermineralized surface layer and to desensitize the tooth. This can be accomplished with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) oral care products that enhance remineralization by creating a state of supersturation followed by deposition of calcium and phosphate ions at the enamel surface. OH strategies for sensitive, poorly mineralized affected molar should include brushing affected molars with fluoridated desensitizing toothpaste w/ a soft toothbrush, apply a CPP-ACP topical cream, and apply a low concentration fluoride treatment gel regularly. As remineralization and desensitization of the affect molars occurs, regular OH strategies can be instituted.

Restoring Hypomineralized First Permanent Molars:
Restoring affected PFMs is frequently complicated by difficulties in achieving anesthesia, managing the child’s behavior, determining how much affected enamel to remove, and selecting a suitable restorative material. The choice of material will depend on the defect severity and the age of the child. Restorative options include glass ionomer cements (GIC), resin-modified glass ionomer cements (RMGIC), polyacid modified resin composites (PMRC), resin composites (RC), amalgam, stainless steel crowns (SSCs), and indirect adhesive or cast onlays or crowns. Amalgam is the least durable due to poor retention in shallow cavity preps and inability to protect remaining tooth structure. Adhesive materials are usually chosen due to the atypical cavity outlines following removal of affected enamel. Removal of all defective enamel is recommended when bonding resin composite to hypomineralized PFMs due to the poor bond strength of resin adhesives to hypomineralized enamel.

Restoring Hypomineralized Permanenet Incisors:
Hypomineralized incisors commonly seen in MIH may present with esthetic concerns that can complicate treatment. A conservative approach includes etching lesion, bleach w/ 5% NaOCl, and re-etch the enamel prior to placing a sealant over the surface to occlude porosities and prevent re-staining. Little improvement was reported with acid/pumice micro-abrasion. Esthetic improvement was achieved when enamel reduction was combined with opaque resins then direct RC veneering.

Adhesion To Hypomineralized Enamel:
The limited literature on adhesion of dental materials to hypomineralized enamel has focused on case reports of Amelogenesis Imperfecta (AI). Bond strengths of RC to hypomineralized enamel of PFMs affected with MIH are significantly less than bond strengths to normal enamel for both single-bottle total etch and self-etching primer adhesives. After removing all discolored hypomineralized enamel, cavity margins should be placed on sound enamel and RC should be bonded w/ a self-etching primer adhesive.

Full Coronal Coverage Restorations:
When PFMs have moderate to severe PEB, SSCs are the treatment of choice. SSCs prevent further tooth deterioration, control tooth sensitivity, establish correct interproximal contacts and proper occlusal relationships, are not as technique sensitive or costly as cast restorations, and require little time to prepare and insert. If not adapted properly, however, SSCs may produce an open bite or gingivitis.

Extraction Of Severly Hypomineralized First Permanent Molars:
When PFMs are severely hypomineralized, restorations may be impossible and extraction must be considered. In such cases, early orthodontic assessment is recommended.

Summary of conclusions:
The prevalence of MIH appears to be increasing and managing affected children is now a common problem for pediatric dentists. Although the etiology is unclear and may be multifactorial, children born preterm and those w/ poor general health or systemic conditions in their first 3 years may develop MIH. The early identification of such children will allow monitoring of their PFMs so that remineralization and preventative measure can be instituted as soon as the affected surfaces are accessible.

Assessment of article:
Good review of MIH. More research needed. Because the prevalence of MIH is increasing it would helpful to know more info about the etiology and if in fact the condition is multifactorial.